Wireless Sensor Networks

1. Introduction The increasing interest in wireless sensor networks can be promptly understood simply by thinking about what they essentially are: a large number of small sensing self-powered nodes which gather information or detect special events and communicate in a wireless fashion, with the end goal of handing their processed data to a base station. Sensing, processing and communication are three key elements whose combination in one tiny device gives rise to a vast number of applications [A1], [A2]. Sensor networks provide endless opportunities, but at the same time pose formidable challenges, uch as the fact that energy is a scarce and usually non-renewable resource. However, recent advances in low power VLSI, embedded computing, communication hardware, and in general, the convergence of computing and communications, are making this emerging technology a reality [A3]. Likewise, advances in nanotechnology and Micro Electro-Mechanical Systems (MEMS) are pushing toward networks of tiny distributed sensors and actuators. 2. Applications of Sensor Networks Possible applications of sensor networks are of interest to the most diverse fields. Environmental monitoring, warfare, child education, surveillance, micro-surgery, and griculture are only a few examples [A4]. Through joint efforts of the University of California at Berkeley and the College of the Atlantic, environmental monitoring is carried out off the coast of Maine on Great Duck Island by means of a network of Berkeley motes equipped with various sensors [B6]. The nodes send their data to a base station which makes them available on the Internet. Since habitat monitoring is rather sensitive to human presence, the deployment of a sensor network provides a noninvasive approach and a remarkable degree of granularity in data acquisition [B7]. The same idea lies behind thePods project at the University of Hawaii at Manoa [B8], where environmental data (air temperature, light, wind, relative humidity and rain fall) are gathered by a network of weather sensors embedded in the communication units deployed in the South-West Rift Zone in Volcanoes National Park on the Big Island of Hawaii. A major concern of the researchers was in this case camouflaging the sensors to make them invisible to curious tourists. In Princeton’s Zebranet Project [B9], a dynamic sensor network has been created by attaching special collars equipped with a low-power GPS system to the necks of zebras to onitor their moves and their behavior. Since the network is designed to operate in an infrastructure-free environment, peer-to-peer swaps of information are used to produce redundant databases so that researchers only have to encounter a few zebras in order to collect the data. Sensor networks can also be used to monitor and study natural phenomena which intrinsically discourage human presence, such as hurricanes and forest fires. Joint efforts between Harvard University, the University of New Hampshire, and the University of North Carolina have recently led to the deployment of a wireless sensor etwork to monitor eruptions at Volcan Tungurahua, an active volcano in central Ecuador. A network of Berkeley motes monitored infrasonic signals during eruptions, and data were transmitted over a 9 km wireless link to a base station at the volcano observatory [B10]. Intel’s Wireless Vineyard [B11] is an example of using ubiquitous computing for agricultural monitoring. In this application, the network is expected not only to collect and interpret data, but also to use such data to make decisions aimed at detecting the presence of parasites and enabling the use of the appropriate kind of insecticide.Data collection relies on data mules, small devices carried by people (or dogs) that communicate with the nodes and collect data. In this project, the attention is shifted from reliable information collection to active decisionmaking based on acquired data. Just as they can be used to monitor nat ure, sensor networks can likewise be used to monitor human behavior. In the Smart Kindergarten project at UCLA [B12], wirelessly-networked, sensor-enhanced toys and other classroom objects supervise the learning process of children and allow unobtrusive monitoring by the teacher. Medical research and healthcare can greatly benefit rom sensor networks: vital sign monitoring and accident recognition are the most natural applications. An important issue is the care of the elderly, especially if they are affected by cognitive decline: a network of sensors and actuators could monitor them and even assist them in their daily routine. Smart appliances could help them organize their lives by reminding them of their meals and medications. Sensors can be used to capture vital signs from patients in real-time and relay the data to handheld computers carried by medical personnel, and wearable sensor nodes can store patient data such as identification, history, and treatments.With these ideas in mind, Harvard University is cooperating with the School of Medicine at Boston University to develop CodeBlue, an infrastructure designed to support wireless medical sensors, PDAs, PCs, and other devices that may be used to monitor and treat patients in various medical scenarios [B13]. On the hardware side, the research team has Martin Haenggi is with the Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN 46556; Fax +1 574 631 4393; [email  protected]@nd. edu. Daniele Puccinelli is also with the Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN 46556. reated Vital Dust, a set of devices based on the MICA21 sensor node platform (one of the most popular members of the Berkeley motes family), which collect heart rate, oxygen saturation, and EKG data and relay them over a medium-range (100 m) wireless network to a PDA [B14]. Interactions between sensor networks and humans are already judged controversial. The US has recently app roved the use of a radio-frequency implantable device (VeriChip) on humans, whose intended application is accessing the medical records of a patient in an emergency. Potential future repercussions of this decision have been discussed in the media.An interesting application to civil engineering is the idea of Smart Buildings: wireless sensor and actuator networks integrated within buildings could allow distributed monitoring and control, improving living conditions and reducing the energy consumption, for instance by controlling temperature and air flow. Military applications are plentiful. An intriguing example is DARPA’s self-healing minefield [B15], a selforganizing sensor network where peer-to-peer communication between anti-tank mines is used to respond to attacks and redistribute the mines in order to heal breaches, complicating the progress of enemy troops.Urban warfare is another application that distributed sensing lends itself to. An ensemble of nodes could be deploy ed in a urban landscape to detect chemical attacks, or track enemy movements. PinPtr is an ad hoc acoustic sensor network for sniper localization developed at Vanderbilt University [B16]. The network detects the muzzle blast and the acoustic shock wave that originate from the sound of gunfire. The arrival times of the acoustic events at different sensor nodes are used to estimate the position of the sniper and send it to the base station with a special data aggregation and routing service.Going back to peaceful applications, efforts are underway at Carnegie Mellon University and Intel for the design of IrisNet (Internet-scale Resource-Intensive Sensor Network Services) [B17], an architecture for a worldwide sensor web based on common computing hardware such as Internet-connected PCs and low-cost sensing hardware such as webcams. The network interface of a PC indeed senses the virtual environment of a LAN or the Internet rather than a physical environment; with an architecture based on the concept of a distributed database [B18], this hardware can be orchestrated into a global sensor system hat responds to queries from users. 3. Characteristic Features of Sensor Networks In ad hoc networks, wireless nodes self-organize into an infrastructureless network with a dynamic topology. Sensor networks (such as the one in Figure 1) share these traits, but also have several distinguishing features. The number of nodes in a typical sensor network is much higher than in a typical ad hoc network, and dense deployments are often desired to ensure coverage and connectivity; for these reasons, sensor network hardware must be cheap. Nodes typically have stringent energy limitations, which make them more failure-prone. They are enerally assumed to be stationary, but their relatively frequent breakdowns and the volatile nature of the wireless channel nonetheless result in a variable network topology. Ideally, sensor network hardware should be power-efficient, small, inexpensive, and reliable in order to maximize network lifetime, add flexibility, facilitate data collection and minimize the need for maintenance. Lifetime Lifetime is extremely critical for most applications, and its primary limiting factor is the energy consumption of the nodes, which need to be self-powering. Although it is often assumed that the transmit power associated with acket transmission accounts for the lion’s share of power consumption, sensing, signal processing and even hardware operation in standby mode consume a consistent amount of power as well [C19], [C20]. In some applications, extra power is needed for macro-scale actuation. Many researchers suggest that energy consumption could be reduced by considering the existing interdependencies between individual layers in the network protocol stack. Routing and channel access protocols, for instance, could greatly benefit from an information exchange with the physical layer. At the physical layer, benefits can be obtained wi th ower radio duty cycles and dynamic modulation scaling (varying the constellation size to minimize energy expenditure THIRD QUARTER 2005 IEEE CIRCUITS AND SYSTEMS MAGAZINE 21 External Infrastructure Gateway Base Station Sensing Nodes Figure 1. A generic sensor network with a two-tiered archi1 tecture. See Section 5 for a hardware overview. [D35]). Using low-power modi for the processor or disabling the radio is generally advantageous, even though periodically turning a subsystem on and off may be more costly than always keeping it on. Techniques aimed at reducing the idle mode leakage current in CMOS-based rocessors are also noteworthy [D36]. Medium Access Control (MAC) solutions have a direct impact on energy consumption, as some of the primary causes of energy waste are found at the MAC layer: collisions, control packet overhead and idle listening. Powersaving forward error control techniques are not easy to implement due to the high amount of computing power that they require a nd the fact that long packets are normally not practical. Energy-efficient routing should avoid the loss of a node due to battery depletion. Many proposed protocols tend to minimize energy consumption on forwarding aths, but if some nodes happen to be located on most forwarding paths (e. g. , close to the base station), their lifetime will be reduced. Flexibility Sensor networks should be scalable, and they should be able to dynamically adapt to changes in node density and topology, like in the case of the self-healing minefields. In surveillance applications, most nodes may remain quiescent as long as nothing interesting happens. However, they must be able to respond to special events that the network intends to study with some degree of granularity. In a self-healing minefield, a number of sensing mines ay sleep as long as none of their peers explodes, but need to quickly become operational in the case of an enemy attack. Response time is also very critical in control applications (sensor/actuator networks) in which the network is to provide a delay-guaranteed service. Untethered systems need to self-configure and adapt to different conditions. Sensor networks should also be robust to changes in their topology, for instance due to the failure of individual nodes. In particular, connectivity and coverage should always be guaranteed. Connectivity is achieved if the base station can be reached from any node.Coverage can be seen as a measure of quality of service in a sensor network [C23], as it defines how well a particular area can be observed by a network and characterizes the probability of detection of geographically constrained phenomena or events. Complete coverage is particularly important for surveillance applications. Maintenance The only desired form of maintenance in a sensor network is the complete or partial update of the program code in the sensor nodes over the wireless channel. All sensor nodes should be updated, and the restrictions on the size of the new code should be the same as in the case of wired programming.Packet loss must be accounted for and should not impede correct reprogramming. The portion of code always running in the node to guarantee reprogramming support should have a small footprint, and updating procedures should only cause a brief interruption of the normal operation of the node [C24]. The functioning of the network as a whole should not be endangered by unavoidable failures of single nodes, which may occur for a number of reasons, from battery depletion to unpredictable external events, and may either be independent or spatially correlated [C25]. Faulttolerance is particularly crucial as ongoing maintenance s rarely an option in sensor network applications. Self-configuring nodes are necessary to allow the deployment process to run smoothly without human interaction, which should in principle be limited to placing nodes into a given geographical area. It is not desirable to have humans configure node s for habitat monitoring and destructively interfere with wildlife in the process, or configure nodes for urban warfare monitoring in a hostile environment. The nodes should be able to assess the quality of the network deployment and indicate any problems that may arise, as well as adjust to hanging environmental conditions by automatic reconfiguration. Location awareness is important for selfconfiguration and has definite advantages in terms of routing [C26] and security. Time synchronization [C27] is advantageous in promoting cooperation among nodes, such as data fusion, channel access, coordination of sleep modi, or security-related interaction. Data Collection Data collection is related to network connectivity and coverage. An interesting solution is the use of ubiquitous mobile agents that randomly move around to gather data bridging sensor nodes and access points, whimsically named dataMULEs (Mobile Ubiquitous LAN Extensions) in [C28]. The predictable mobility of the data sink can be used to save power [C29], as nodes can learn its schedule. A similar concept has been implemented in Intel’s Wireless Vineyard. It is often the case that all data are relayed to a base station, but this form of centralized data collection may shorten network lifetime. Relaying data to a data sink causes non-uniform power consumption patterns that may overburden forwarding nodes [C21]. This is particularly harsh on nodes providing end links to base stations, which may end up relaying traffic coming from all ther nodes, thus forming a critical bottleneck for network throughput [A4], [C22], as shown in Figure 2. An interesting technique is clustering [C30]: nodes team up to form clusters and transmit their information to their cluster heads, which fuse the data and forward it to a 22 IEEE CIRCUITS AND SYSTEMS MAGAZINE THIRD QUARTER 2005 sink. Fewer packets are transmitted, and a uniform energy consumption pattern may be achieved by periodic re-clustering. Data redundancy is minimized, as the aggregation process fuses strongly correlated measurements. Many applications require that queries be sent to sensing nodes.This is true, for example, whenever the goal is gathering data regarding a particular area where various sensors have been deployed. This is the rationale behind looking at a sensor network as a database [C31]. A sensor network should be able to protect itself and its data from external attacks, but the severe limitations of lower-end sensor node hardware make security a true challenge. Typical encryption schemes, for instance, require large amounts of memory that are unavailable in sensor nodes. Data confidentiality should be preserved by encrypting data with a secret key shared with the intended receiver. Data integrity should be ensured to revent unauthorized data alteration. An authenticated broadcast must allow the verification of the legitimacy of data and their sender. In a number of commercial applications, a serious disservice to the user of a sensor network is compromising data availability (denial of service), which can be achieved by sleep-deprivation torture [C33]: batteries may be drained by continuous service requests or demands for legitimate but intensive tasks [C34], preventing the node from entering sleep modi. 4. Hardware Design Issues In a generic sensor node (Figure 3), we can identify a power module, a communication block, a processing unit ith internal and/or external memory, and a module for sensing and actuation. Power Using stored energy or harvesting energy from the outside world are the two options for the power module. Energy storage may be achieved with the use of batteries or alternative devices such as fuel cells or miniaturized heat engines, whereas energy-scavenging opportunities [D37] are provided by solar power, vibrations, acoustic noise, and piezoelectric effects [D38]. The vast majority of the existing commercial and research platforms relies on batteries, which dominate the no de size. Primary (nonrechargeable) batteries are often chosen, predominantlyAA, AAA and coin-type. Alkaline batteries offer a high energy density at a cheap price, offset by a non-flat discharge, a large physical size with respect to a typical sensor node, and a shelf life of only 5 years. Voltage regulation could in principle be employed, but its high inefficiency and large quiescent current consumption call for the use of components that can deal with large variations in the supply voltage [A5]. Lithium cells are very compact and boast a flat discharge curve. Secondary (rechargeable) batteries are typically not desirable, as they offer a lower energy density and a higher cost, not to mention the fact that in most pplications recharging is simply not practical. Fuel cells [D39] are rechargeable electrochemical energy- conversion devices where electricity and heat are produced as long as hydrogen is supplied to react with oxygen. Pollution is minimal, as water is the main byproduct of the reaction. The potential of fuel cells for energy storage and power delivery is much higher than the one of traditional battery technologies, but the fact that they require hydrogen complicates their application. Using renewable energy and scavenging techniques is an interesting alternative. Communication Most sensor networks use radio communication, even if lternative solutions are offered by laser and infrared. Nearly all radio-based platforms use COTS (Commercial Off-The-Shelf) components. Popular choices include the TR1000 from RFM (used in the MICA motes) and the CC1000 from Chipcon (chosen for the MICA2 platform). More recent solutions use industry standards like IEEE 802. 15. 4 (MICAz and Telos motes with CC2420 from Chipcon) or pseudo-standards like Bluetooth. Typically, the transmit power ranges between ? 25 dBm and 10 dBm, while the receiver sensitivity can be as good as ? 110 dBm. THIRD QUARTER 2005 IEEE CIRCUITS AND SYSTEMS MAGAZINE 23 Base Station Critical Nodes F igure 2.A uniform energy consumption pattern should avoid the depletion of the resources of nodes located in the vicinities of the base station. Communication Hardware Power Sensors (? Actuators) ADC Memory Processor Figure 3. Anatomy of a generic sensor node. Spread spectrum techniques increase the channel reliability and the noise tolerance by spreading the signal over a wide range of frequencies. Frequency hopping (FH) is a spread spectrum technique used by Bluetooth: the carrier frequency changes 1600 times per second on the basis of a pseudo-random algorithm. However, channel synchronization, hopping sequence search, and the high data rate ncrease power consumption; this is one of the strongest caveats when using Bluetooth in sensor network nodes. In Direct Sequence Spread Spectrum (DSSS), communication is carried out on a single carrier frequency. The signal is multiplied by a higher rate pseudo-random sequence and thus spread over a wide frequency range (typical DSSS radios h ave spreading factors between 15 and 100). Ultra Wide Band (UWB) is of great interest for sensor networks since it meets some of their main requirements. UWB is a particular carrier-free spread spectrum technique where the RF signal is spread over a spectrum as large as several GHz.This implies that UWB signals look like noise to conventional radios. Such signals are produced using baseband pulses (for instance, Gaussian monopulses) whose length ranges from 100 ps to 1 ns, and baseband transmission is generally carried out by means of pulse position modulation (PPM). Modulation and demodulation are indeed extremely cheap. UWB provides built-in ranging capabilities (a wideband signal allows a good time resolution and therefore a good location accuracy) [D40], allows a very low power consumption, and performs well in the presence of multipath fading. Radios with relatively low bit-rates (up to 100 kbps) re advantageous in terms of power consumption. In most sensor networks, high data rates are not needed, even though they allow shorter transmission times thus permitting lower duty cycles and alleviating channel access contention. It is also desirable for a radio to quickly switch from a sleep mode to an operational mode. Optical transceivers such as lasers offer a strong power advantage, mainly due to their high directionality and the fact that only baseband processing is required. Also, security is intrinsically guaranteed (intercepted signals are altered). However, the need for a line of sight and recise localization makes this option impractical for most applications. Processing and Computing Although low-power FPGAs might become a viable option in the near future [D41], microcontrollers (MCUs) are now the primary choice for processing in sensor nodes. The key metric in the selection of an MCU is power consumption. Sleep modi deserve special attention, as in many applications low duty cycles are essential for lifetime extension. Just as in the case of the rad io module, a fast wake-up time is important. Most CPUs used in lower-end sensor nodes have clock speeds of a few MHz. The memory requirements depend on the pplication and the network topology: data storage is not critical if data are often relayed to a base station. Berkeley motes, UCLA’s Medusa MK-2 and ETHZ’s BTnodes use low-cost Atmel AVR 8-bit RISC microcontrollers which consume about 1500 pJ/instruction. More sophisticated platforms, such as the Intel iMote and Rockwell WINS nodes, use Intel StrongArm/XScale 32-bit processors. Sensing The high sampling rates of modern digital sensors are usually not needed in sensor networks. The power efficiency of sensors and their turn-on and turn-off time are much more important. Additional issues are the physical ize of the sensing hardware, fabrication, and assembly compatibility with other components of the system. Packaging requirements come into play, for instance, with chemical sensors which require contact with the envi ronment [D42]. Using a microcontroller with an onchip analog comparator is another energy-saving technique which allows the node to avoid sampling values falling outside a certain range [D43]. The ADC which complements analog sensors is particularly critical, as its resolution has a direct impact on energy consumption. Fortunately, typical sensor network applications do not have stringent resolution requirements.Micromachining techniques have allowed the miniaturization of many types of sensors. Performance does decrease with sensor size, but for many sensor network applications size matters much more than accuracy. Standard integrated circuits may also be used as temperature sensors (e. g. , using the temperaturedependence of subthreshold MOSFETs and pn junctions) or light intensity transducers (e. g. , using photodiodes or phototransistors) [D44]. Nanosensors can offer promising solutions for biological and chemical sensors while concurrently meeting the most ambitious miniaturiza tion needs. 5. Existing Hardware PlatformsBerkeley motes, made commercially available by Crossbow, are by all means the best known sensor node hardware implementation, used by more than 100 research organizations. They consist of an embedded microcontroller, low-power radio, and a small memory, and they are powered by two AA batteries. MICA and MICA2 are the most successful families of Berkeley motes. The MICA2 platform, whose layout is shown in Figure 4, is equipped with an Atmel ATmega128L and has a CC1000 transceiver. A 51-pin expansion connector is available to interface sensors (commercial sensor boards designed for this specific platform are available).Since the MCU is to handle 24 IEEE CIRCUITS AND SYSTEMS MAGAZINE THIRD QUARTER 2005 medium access and baseband processing, a fine-grained event-driven real-time operating system (TinyOS) has been implemented to specifically address the concurrency and resource management needs of sensor nodes. For applications that require a bet ter form factor, the circular MICA2Dot can be used: it has most of the resources of MICA2, but is only 2. 5 cm in diameter. Berkeley motes up to the MICA2 generation cannot interface with other wireless- enabled devices [E47]. However, the newer generations MICAz and Telos support IEEE 802. 15. , which is part of the 802. 15 Wireless Personal Area Network (WPAN) standard being developed by IEEE. At this point, these devices represent a very good solution for generic sensing nodes, even though their unit cost is still relatively high (about $100–$200). The proliferation of different lowerend hardware platforms within the Berkeley mote family has recently led to the development of a new version of TinyOS which introduces a flexible hardware abstraction architecture to simplify multi-platform support [E48]. Tables 1 and 2 show an overview of the radio transceivers and the microcontrollers most commonly used in xisting hardware platforms; an overview of the key features of the pl atforms is provided in Table 3. Intel has designed its own iMote [E49] to implement various improvements over available mote designs, such as increased CPU processing power, increased main memory size for on-board computing and improved radio reliability. In the iMote, a powerful ARM7TDMI core is complemented by a large main memory and non-volatile storage area; on the radio side, Bluetooth has been chosen. Various platforms have been developed for the use of Berkeley motes in mobile sensor networks to enable investigations into controlled mobility, which facilitates eployment and network repair and provides possibilities for the implementation of energy-harvesting. UCLA’s RoboMote [E50], Notre Dame’s MicaBot [E51] and UC Berkeley’s CotsBots [E52] are examples of efforts in this direction. UCLA’s Medusa MK-2 sensor nodes [E53], developed for the Smart Kindergarten project, expand Berkeley motes with a second microcontroller. An on-board power management a nd tracking unit monitors power consumption within the different subsystems and selectively powers down unused parts of the node. UCLA has also developed iBadge [E54], a wearable sensor node with sufficient computational power to process the sensed data.Built around an ATMega128L and a DSP, it features a Localization Unit designed to estimate the position of iBadge in a room based on the presence of special nodes of known location attached to the ceilings. In the context of the EYES project (a joint effort among several European institutions) custom nodes [E55], [C24] have been developed to test and demonstrate energy-efficient networking algorithms. On the software side, a proprietary operating system, PEEROS (Preemptive EYES Real Time Operating System), has been implemented. The Smart-Its project has investigated the possibility of embedding computational power into objects, leading o the creation of three hardware platforms: DIY Smartits, Particle Computers and BTnodes. The DIY S mart-its [E56] have been developed in the UK at Lancaster University; their modular design is based on a core board that provides processing and communication and can be extended with add-on boards. A typical setup of Smart-its consists of one or more sensing nodes that broadcast their data to a base station which consists of a standard core board connected to the serial port of a PC. Simplicity and extensibility are the key features of this platform, which has been developed for the creation of Smart Objects.An interesting application is the Weight Table: four load cells placed underneath a coffee table form a Wheatstone bridge and are connected to a DIY node that observes load changes, determines event types like placement and removal of objects or a person moving a finger across the surface, and also retrieves the position of an object by correlating the values of the individual load cells after the event type (removed or placed) has been recognized [E57]. Particle Computers have been developed at the University of Karlsruhe, Germany. Similarly to the DIY platform, the Particle Smart-its are based on a core board quipped with a Microchip PIC; they are optimized for energy efficiency, scalable communication and small scale (17 mm ? 30 mm). Particles communicate in an ad hoc fashion: as two Particles come close to one another, THIRD QUARTER 2005 IEEE CIRCUITS AND SYSTEMS MAGAZINE 25 Oscillator 7. 3728-MHz DS2401P Silicon Serial No. Antenna Connector Connector LEDs Battery Connection 32. 768-kHz Oscillator 14. 7456-MHz Oscillator ATMEL ATMega 128L CPU CC1000 Transceiver ATMEL AT45DB041 Data Flash Figure 4. Layout of the MICA2 platform. they are able to talk. Additionally, if Particles come near a gateway device, they can be connected to Internet-enabled evices and access services and information on the Internet as well as provide information [E58]. The BTnode hardware from ETHZ [E47] is based on an Atmel ATmega128L microcontroller and a Bluetooth module. Altho ugh advertised as a low-power technology, Bluetooth has a relatively high power consumption, as discussed before. It also has long connection setup times and a lower degree of freedom with respect to possible network topologies. On the other hand, it ensures interoperability between different devices, enables application development through a standardized interface, and offers a significantly higher bandwidth (about 1 Mbps) ompared to many low-power radios (about 50 Kbps). Moreover, Bluetooth support means that COTS hardware can be used to create a gateway between a sensor network and an external network (e. g. , the Internet), as opposed to more costly proprietary solutions [E59]. MIT is working on the ? AMPS (? -Adaptive Multidomain Power-aware Sensors) project, which explores energy-efficiency constraints and key issues such as selfconfiguration, reconfigurability, and flexibility. A first prototype has been designed with COTS components: three stackable boards (processing, radio and power) and an ptional extension module. The energy dissipation of this microsensor node is reduced through a variety of poweraware design techniques [D45] including fine-grain shutdown of inactive components, dynamic voltage and frequency scaling of the processor core, and adjustable radio transmission power based on the required range. Dynamic voltage scaling is a technique used for active power management where the supply voltage and clock frequency of the processor are regulated depending on the computational load, which can vary significantly based on the operational mode [D36], [C20]. The main oal of second generation ? AMPS is clearly stated in [D46] as breaking the 100 ? W average power barrier. Another interesting MIT project is the Pushpin computing system [E60], whose goal is the modelling, testing, and deployment of distributed peer-to-peer sensor networks consisting of many identical nodes. The pushpins are 18 mm ? 18 mm modular devices with a power substrate, an in frared communication module, a processing module (Cygnal C8051F016) and an expansion module (e. g. , for sensors); they are powered by direct contact between the power substrate and layered conductive sheets. 26 MCU Max.Freq. [MHz] Memory Data Size [bits] ADC [bits] Architecture AT90LS8535 (Atmel) 4 8 kB Flash, 512B EEPROM, 512B SRAM 8 10 AVR ATMega128L (Atmel) 8 128 kB Flash, 4 kB EEPROM, 4 kB SRAM 8 10 AVR AT91FR4081 (Atmel) 33 136 kB On-Chip SRAM, 8 Mb Flash 32 — Based on ARM core (ARM7TDMI) MSP430F149 (TI) 8 60 kB + 256B Flash, 2 kB RAM 16 12 Von Neumann C8051F016 (Cygnal) 25 2304B RAM, 32 kB Flash 8 10 Harvard 8051 PIC18F6720 (Microchip) 25 128 kB Flash, 3840B SRAM, 1 kB EEPROM 8 10 Harvard PIC18F252 (Microchip) 40 32 K Flash, 1536B RAM, 256B EEPROM 8 10 Harvard StrongARM SA-1110 (Intel) 133 — 32 — ARM v. 4PXA255 (Intel) 400 32 kB Instruction Cache, 32 kB Data 32 — ARM v. 5TE Cache, 2 kB Mini Data Cache Table 2. Microcontrollers used in sensor node p latforms. Radio (Manufacturer) Band [MHz] Max. Data Rate [kbps] Sensit. [dBm] Notes TR1000 (RFM) 916. 5 115. 2 ? 106 OOK/ASK TR1001 (RFM) 868. 35 115. 2 ? 106 OOK/ASK CC1000 (Chipcon) 300–1,000 76. 8 ? 110 FSK, ? 20 to 10 dBm CC2420 (Chipcon) 2,400 250 ? 94 OQPSK, ? 24 to 0 dBm, IEEE 802. 15. 4, DSSS BiM2 (Radiometrix) 433. 92 64 ? 93 9XStream (MaxStream) 902–928 20 ? 114 FHSS Table 1. Radios used in sensor node platforms. IEEE CIRCUITS AND SYSTEMS MAGAZINE THIRD QUARTER 2005MIT has also built Tribble (Tactile reactive interface built by linked elements), a spherical robot wrapped by a wired skinlike sensor network designed to emulate the functionalities of biological skin [E61]. Tribble’s surface is divided into 32 patches with a Pushpin processing module and an array of sensors and actuators. At Lancaster University, surfaces provide power and network connectivity in the Pin&Play project. Network nodes come in different form factors, but all share the Pin&Play connector, a custom component that allows physical connection and networking through conductive sheets which re embedded in surfaces such as a wall or a bulletin board [E62]. Pin&Play falls in between wired and wireless technologies as it provides network access and power across 2D surfaces. Wall-mounted objects are especially suited to be augmented to become Pin&Play objects. In a demonstration, a wall switch was augmented and freely placed anywhere on a wall with a Pin&Play surface as wallpaper. For applications which do not call for the minimization of power consumption, high-end nodes are available. Rockwellis WINS nodes and Sensoria’s WINS 3. 0 Wireless Sensing Platform are equipped with more powerful rocessors and radio systems. The embedded PC modules based on widely supported standards PC/104 and PC/104-plus feature Pentium processors; moreover, PC/104 peripherals include digital I/O devices, sensors and actuators, and PC-104 products support almost all PC software. PFU Systems’ Plug-N-Run products, which feature Pentium processors, also belong to this category. They offer the capabilities of PCs and the size of a sensor node, but lack built-in communication hardware. COTS components or lower-end nodes may be used in this sense [C32]. Research is underway toward the creation of sensor nodes that are more capable than the motes, yet maller and more power-efficient than higher-end nodes. Simple yet effective gateway devices are the MIB programming boards from Crossbow, which bridge networks of Berkeley motes with a PC (to which they interface using the serial port or Ethernet). In the case of Telos motes, any generic node (i. e. , any Telos mote) can act as a gateway, as it may be connected to the USB port of a PC and bridge it to the network. Of course, more powerful gateway devices are also available. Crossbow’s Stargate is a powerful embedded computing platform (running Linux) with enhanced communication and sensor signal process ing capabilities based n Intel PXA255, the same X-Scale processor that forms the core of Sensoria WINS 3. 0 nodes. Stargate has a connector for Berkeley motes, may be bridged to a PC via Ethernet or 802. 11, and includes built-in Bluetooth support. 6. Closing Remarks Sensor networks offer countless challenges, but their versatility and their broad range of applications are eliciting more and more interest from the research community as well as from industry. Sensor networks have the potential of triggering the next revolution in information technology. The challenges in terms of circuits and systems re numerous: the development of low-power communication hardware, low-power microcontrollers, MEMSbased sensors and actuators, efficient AD conversion, and energy-scavenging devices is necessary to enhance the potential and the performance of sensor networks. System integration is another major challenge that sensor networks offer to the circuits and systems research community. We believ e that CAS can and should have a significant impact in this emerging, exciting area. 27 Platform CPU Comm. External Memory Power Supply WesC (UCB) AT90LS8535 TR1000 32 kB Flash Lithium Battery MICA (UCB, Xbow) ATMega128L TR1000 512 kB Flash AAMICA2 (UCB, Xbow) ATMega128L CC1000 512 kB Flash AA MICA2Dot (UCB, Xbow) ATMega128L CC1000 512 kB Flash Lithium Battery MICAz (UCB, Xbow) ATMega128L CC2420 512 kB Flash AA Telos (Moteiv) MSP430F149 CC2420 512 kB Flash AA iMote (Intel) ARM7TDMI Core Bluetooth 64 kB SRAM, 512 kB Flash AA Medusa MK-2 (UCLA) ATMega103L TR1000 4 Mb Flash Rechargeable Lithium Ion AT91FR4081 iBadge (UCLA) ATMega128L Bluetooth, TR1000 4 Mb Flash Rechargeable Lithium Ion DIY (Lancaster University) PIC18F252 BiM2 64 Kb FRAM AAA, Lithium, Rechargeable Particle (TH) PIC18F6720 RFM TR1001 32 kB EEPROM AAA or Lithium Coin Battery or RechargeableBT Nodes (ETHZ) ATMega128L Bluetooth, CC1000 244 kB SRAM AA ZebraNet (Princeton) MSP430F149 9XStream 4 Mb Flash Lithium Ion Pushpin (MIT) C8051F016 Infrared — Power Substrate WINS 3. 0 (Sensoria) PXA255 802. 11b 64 MB SDRAM, 32 MB + 1 GB Flash Batteries Table 3. Hardware features of various platforms. THIRD QUARTER 2005 IEEE CIRCUITS AND SYSTEMS MAGAZINE Acknowledgments The support of NSF (grants ECS 03-29766 and CAREER CNS 04-47869) is gratefully acknowledged. References General References [A1] I. F. Akyildiz, W. Su, Y. Sankarasubramaniam, and E. Cayirci, â€Å"A survey on sensor networks,† in IEEE Communications Magazine, pp. 02–114, Aug. 2002. [A2] L. B. Ruiz, L. H. A. Correia, L. F. M. Vieira, D. F. Macedo, E. F. Nakamura, C. M. S. Figueiredo, M. A. M. Vieira, E. H. B. Maia, D. Camara, A. A. F. Loureiro, J. M. S. Nogueira, D. C. da Silva Jr. , and A. O. Fernandes, â€Å"Architectures for wireless sensor networks (In Portuguese),† in Proceedings of the 22nd Brazilian Symposium on Computer Networks (SBRC’04), Gramado, Brazil, pp. 167–218, May 2004. Tutorial. ISBN: 85-8 8442-82-5. [A3] C. Y. Chong and S. P. Kumar, â€Å"Sensor networks: Evolution, opportunities, and challenges,† in IEEE Proceedings, pp. 1247–1254, Aug. 003. [A4] M. Haenggi, â€Å"Opportunities and Challenges in Wireless Sensor Networks,† in Handbook of Sensor Networks: Compact Wireless and Wired Sensing Systems, M. Ilyas and I. Mahgoub, eds. , Boca Raton, FL, pp. 1. 1–1. 14, CRC Press, 2004. [A5] J. Hill, System Architecture for Wireless Sensor Networks. Ph. D. thesis, University of California at Berkeley, Spring 2003. Applications [B6] A. Mainwaring, J. Polastre, R. Szewczyk, D. Culler, and J. Anderson, â€Å"Wireless sensor networks for habitat monitoring,† in First ACM Workshop on Wireless Sensor Networks and Applications, Atlanta, GA, Sept. 002. [B7] A. Cerpa, J. Elson, D. Estrin, L. Girod, M. Hamilton, and J. Zhao, â€Å"Habitat monitoring: Application driver for wireless communications technology,† in ACM SIGCOMM Workshop on Data Comm unications in Latin America and the Caribbean, San Jose, Costa Rica, Apr. 2001. [B8] E. Biagioni and K. Bridges, â€Å"The application of remote sensor technology to assist the recovery of rare and endangered species,† International Journal of High Performance Computing Applications, vol. 16, pp. 315–324, Aug. 2002. [B9] P. Juang, H. Oki, Y. Wang, M. Martonosi, L. Peh, and D.Rubenstein, â€Å"Energy-efficient computing for wildlife tracking: Design tradeoffs and early experiences with ZebraNet,† in Proceedings of the 10th International Conference on Architectural Support for Programming Languages and Operating Systems (ASPLOS-X), San Jose, CA, Oct. 2002. [B10] G. Werner-Allen, J. Johnson, M. Ruiz, J. Lees, and M. Welsh, â€Å"Monitoring volcanic eruptions with a wireless sensor network,† in Proceedings of the Second European Workshop on Wireless Sensor Networks (EWSN’05), Jan. 2005. [B11] J. Burrell, T. Brooke, and R. Beckwith, â€Å"Vineyard comp uting: Sensor networks in agricultural production,† IEEE Pervasive Computing, vol. , no. 1, pp. 38–45, 2004. [B12] M. Srivastava, R. 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Karp, Y. Ke, S. Nath, and S. Seshan, â€Å"IrisNet: An architecture for a worldwide sensor web,† IEEE Pervasive Computing, vol. 2, no. 4, pp. 22–33, 2003. [B18] P. Gibbons, B. Karp, Y. Ke, S.Nath, and S. Seshan, â€Å"IrisNet: An Architecture for Enabling Sensor-Enriched Internet Service,† Tech. Rep. IRP-TR-03-04, Intel Research, Pittsburgh, PA, June 2003. Characteristic Features Lifetime [C19] A. Goldsmith and S. Wicker, â€Å"Design challenges for energy-constrained ad hoc wireless networks,† IEEE Wireless Communications Magazine, vol. 9, pp. 8–27, Aug. 2002. [C20] L. Yuan and G. Qu, â€Å"Energy-efficient Design of Distributed Sensor Networks,† in Handbook of Sensor Networks: Compact Wireless and Wired Sensing Systems, M. Ilyas and I. M ahgoub, eds. , Boca Raton, FL, pp. 38. 1–38. 19, CRC Press, 2004. [C21] M.Haenggi, â€Å"Twelve Reasons not to Route over Many Short Hops,† in IEEE Vehicular Technology Conference (VTC’04 Fall), Los Angeles, CA, Sept. 2004. [C22] M. Haenggi, â€Å"Energy-Balancing Strategies for Wireless Sensor Networks,† in IEEE International Symposium on Circuits and Systems (ISCAS’03), Bangkok, Thailand, May 2003. Coverage [C23] S. Meguerdichian, F. Koushanfar, M. Potkonjak, and M. Srivastava, â€Å"Coverage problems in wireless ad-hoc sensor networks,† in Proceedings of the 20th Annual Joint Conference of the IEEE Computer and Communications Societies (INFOCOM’01), vol. 3, Anchorage, AK, pp. 1380–1387, Apr. 001. Maintenance [C24] N. Reijers and K. Loangendoen, â€Å"Efficient code distribution in wireless sensor networks,† in Second ACM International Workshop on Wireless Sensor Networks and Applications, San Diego, CA, Sept. 2003. [C 25] D. Ganesan, R. Govindan, S. Shenker, and D. Estrin, â€Å"Highly resilient, energy efficient multipath routing in wireless sensor networks,† in Proceedings of the 2nd ACM International Symposium on Mobile Ad Hoc Networking and Computing (MobiHoc’01), Long Beach, CA, pp. 251–254, 2001. Localization and Synchronization [C26] M. Mauve, H. Hartenstein, H. Fuessler, J. Widmer, and W.Effelsberg, â€Å"Positionsbasiertes Routing fuer die Kommunikation zwischen Fahrzeugen,† it—Information Technology (formerly it + ti)—Methoden und innovative Anwendungen der Informatik und Informationstechnik, vol. 44, pp. 278–286, Oct. 2002. [C27] F. Sivrikaya and B. Yener, â€Å"Time synchronization in sensor networks: A survey,† IEEE Network, vol. 18, pp. 45–50, July–Aug. 2004. Data Collection, Routing, and Architectures [C28] R. C. Shah, S. Roy, S. Jain, and W. Brunette, â€Å"Data MULEs: Modeling and analysis of a three-tier arch itecture for sparse sensor networks,† in Ad Hoc Networks Journal, vol. 1, pp. 215–233, Elsevier, Sept. 2003. [C29] A.Chakrabarti, A. Sabharwal, and B. Aazhang, â€Å"Using predictable observer mobility for power efficient design of sensor networks,† in Information Processing in Sensor Networks (IPSN’03), Palo Alto, CA, Apr. 2003. [C30] O. Younis and S. Fahmy, â€Å"HEED: A Hybrid, Energy-Efficient, Distributed Clustering Approach for Ad-hoc Sensor Networks,† in IEEE Transactions on Mobile Computing, vol. 3, pp. 366–379, 2004. [C31] R. Govindan, J. Hellerstein, W. Hong, S. Madden, M. Franklin, and S. Shenker, â€Å"The Sensor Network as a Database,† Tech. Rep. 02–771, University of Southern California, 2002. ftp://ftp. usc. edu/pub/csinfo/ tech-reports/papers/02-771. df. [C32] M. Yarvis and W. Ye, â€Å"Tiered Architectures in Sensor Networks,† in Handbook of Sensor Networks: Compact Wireless and Wired Sensing Systems, M. Ilyas and I. Mahgoub, eds. , Boca Raton, FL, pp. 13. 1–13. 22, CRC Press, 2004. Security [C33] F. Stajano and R. Anderson, â€Å"The resurrecting duckling: Security issues for ad-hoc wireless networks,† in 7th International Workshop on Security Protocols, Cambridge, UK, Apr. 1999. [C34] T. Martin, M. Hsiao, D. Ha, and J. Krishnaswami, â€Å"Denial-of-service attacks on battery-powered mobile computers,† in Proceedings of the 2nd IEEE Pervasive Computing Conference, Orlando, FL, pp. 09–318, Mar. 2004. Hardware [D35] C. Schurgers, O. Aberthorne, and M. Srivastava, â€Å"Modulation scaling for energy aware communication systems,† in Proceedings of the 2001 International Symposium on Low Power Electronics and Design, 28 IEEE CIRCUITS AND SYSTEMS MAGAZINE THIRD QUARTER 2005 Huntington Beach, CA, pp. 96–99, Aug. 2001. [D36] A. P. Chandrakasan, R. Min, M. Bhardwaj, S. Cho, and A. Wang, â€Å"Power aware wireless microsensor systems,† in 28th European Solid- State Circuits Conference (ESSCIRC’02), Florence, Italy, 2002. [D37] S. Roundy, P. Wright, and J. Rabaey, â€Å"A study of low level vibrations as a power source for ireless sensor nodes,† Computer Communications, vol. 26, pp. 1131–1144, July 2003. [D38] J. Kymissis, C. Kendall, J. Paradiso, and N. Gershenfeld, â€Å"Parasitic power harvesting in shoes,† in Proceedings of the 2nd IEEE International Symposium on Wearable Computers (ISWC’04), Pittsburgh, PA, Oct. 1998. [D39] A. J. Appleby, Fuel Cell Handbook, New York, NY: Van Reinhold Co. , 1989. [D40] W. C. Chung and D. S. Ha, â€Å"An Accurate Ultra WideBand (UWB) Ranging for precision asset location,† in International Conference on UWB Systems and Technologies, Reston, VA, Nov. 2002. [D41] M. Vieira, D. da Silva Jr. C. C. Jr. , and J. da Mata, â€Å"Survey on wireless sensor network devices,† in Proceedings of the 9th IEEE International Conference on Emerging Techno logies and Factory Automation (ETFA’03), Lisbon, Portugal, Sept. 2003. [D42] B. A. Warneke and K. S. J. Pister, â€Å"MEMS for distributed wireless sensor networks,† in Proceedings of the 9th International Conference on Electronics, Circuits and Systems (ICECS’02), vol. 1, Dubrovnik, Croatia, pp. 291–294, 2002. [D43] Z. Karakehayov, â€Å"Low-Power Design for Smart Dust Networks,† in Handbook of Sensor Networks: Compact Wireless and Wired Sensing Systems, M.Ilyas and I. Mahgoub, eds. , Boca Raton, FL, pp. 37. 1–37. 12, CRC Press, 2004. [D44] B. Warneke, â€Å"Miniaturizing Sensor Networks with MEMS,† in Handbook of Sensor Networks: Compact Wireless and Wired Sensing Systems, M. Ilyas and I. Mahgoub, eds. , Boca Raton, FL, pp. 5. 1–5. 19, CRC Press, 2004. [D45] R. Min, M. Bhardwaj, S. Cho, A. Sinha, E. Shih, A. Wang, and A. P. Chandrakasan, â€Å"An Architecture for a Power-Aware Distributed Microsensor Node,† in IEEE Wor kshop on Signal Processing Systems (SiPS’00), Lafayette, LA, Oct. 2000. [D46] D. D. Wentzloff, B. H.Calhoun, R. Min, A. Wang, N. Ickes, and A. P. Chandrakasan, â€Å"Design considerations for next generation wireless power-aware microsensor nodes,† in Proceedings of the 17th International Conference on VLSI Design, Mumbai, India, pp. 361–367, 2004. Existing Platforms [E47] J. Beutel, O. Kasten, M. Ringwald, F. Siegemund, and L. Thiele, â€Å"Poster abstract: Btnodes—a distributed platform for sensor nodes,† in Proceedings of the First International Conference on Embedded Networked Sensor Systems (SenSys-03), Los Angeles, CA, Nov. 2003. [E48] V. Handziski, J. Polastre, J. H. Hauer, C. Sharp, A. Wolisz, and D. Culler, â€Å"Flexible hardware abstraction for wireless sensor networks,† in Proceedings of the 2nd International Workshop on Wireless Sensor Networks (EWSN 2005), Istanbul, Turkey, Jan. 2005. [E49] R. M. Kling, â€Å"Intel Mote: An En hanced Sensor Network Node,† in International Workshop on Advanced Sensors, Structural Health Monitoring and Smart Structures at Keio University, Tokyo, Japan, Nov. 2003. [E50] K. Dantu, M. Rahimi, H. Shah, S. Babel, A. Dhariwal, and G. Sukhatme, â€Å"Robomote: Enabling Mobility In Sensor Networks,† Tech. Rep.CRES-04-006, University of Southern California. [E51] M. B. McMickell, B. Goodwine, and L. A. Montestruque, â€Å"MICAbot: A robotic platform for large-scale distributed robotics,† in Proceedings of International Conference on Intelligent Robots and Systems (ICRA’03), vol. 2, Taipei, Taiwan, pp. 1600–1605, 2003. [E52] S. Bergbreiter and K. S. J. Pister, â€Å"CotsBots: An Off-the-Shelf Platform for Distributed Robotics,† in Proceedings of the 2003 IEEE International Conference on Intelligent Robots and Systems (ICRA’03), Las Vegas, NV, Oct. 2003. [E53] A. Savvides and M. B.Srivastava, â€Å"A distributed computation platform for wireless embedded sensing,† in 20th International Conference on Computer Design (ICCD’02), Freiburg, Germany, Sept. 2002. [E54] S. Park, I. Locher, and M. Srivastava, â€Å"Design of a wearable sensor badge for smart kindergarten,† in 6th International Symposium on Wearable Computers (ISWC2002), Seattle, WA, pp. 13. 1–13. 22, Oct. 2002. [E55] L. F. W. van Hoesel, S. O. Dulman, P. J. M. Havinga, and H. J. Kip, â€Å"Design of a low-power testbed for Wireless Sensor Networks and verification,† Tech. Rep. R-CTIT-03-45, University of Twente, Sept. 2003. [E56] M.Strohbach, â€Å"The smart-its platform for embedded contextaware systems,† in Proceedings of the First International Workshop on Wearable and Implantable Body Sensor Networks, London, UK, Apr. 2004. [E57] A. Schmidt, M. Strohbach, K. V. Laerhoven, and H. -W. Gellersen, â€Å"Ubiquitous interaction—Using surfaces in everyday environments as pointing devices,† in 7th ERCIM Wo rkshop â€Å"User Interfaces For All,† Chantilly, France, 2002. [E58] M. Beigl, A. Krohn, T. Zimmer, C. Decker, and P. Robinson, â€Å"Aware- Con: Situation aware context communication,† in The Fifth International Conference on Ubiquitous Computing (Ubicomp’03), Seattle, WA, Oct. 003. [E59] J. Beutel, O. Kasten, F. Mattern, K. Roemer, F. Siegemund, and L. Thiele, â€Å"Prototyping sensor network applications with BTnodes,† in IEEE European Workshop on Wireless Sensor Networks (EWSN’04), Berlin, Germany, Jan. 2004. [E60] J. Lifton, D. Seetharam, M. Broxton, and J. Paradiso, â€Å"Pushpin computing system overview: A platform for distributed, embedded, ubiquitous sensor networks,† in Proceedings of the Pervasive Computing Conference, Zurich, Switzerland, Aug. 2002. [E61] J. A. Paradiso, J. Lifton, and M. Broxton, â€Å"Sensate media—multimodal electronic skins as dense sensor networks,† BT Technology Journal, vol. 2, pp. 32â€⠀œ44, Oct. 2004. [E62] K. V. Laerhoven, N. Villar, and H. -W. Gellersen, â€Å"Pin&Mix: When Pins Become Interaction Components. . . ,† in Physical Interaction (PI03)— Workshop on Real World User Interfaces†Ã¢â‚¬â€Mobile HCI Conference, Udine, Italy, Sept. 2003. Daniele Puccinelli received a Laurea degree in Electrical Engineering from the University of Pisa, Italy, in 2001. After spending two years in industry, he joined the graduate program in Electrical Engineering at the University of Notre Dame, and received an M. S. Degree in 2005. He is currently working toward his Ph. D. degree.His research has focused on cross-layer approaches to wireless sensor network protocol design, with an emphasis on the interaction between the physical and the network layer. Martin Haenggi received the Dipl. Ing. (M. Sc. ) degree in electrical engineering from the Swiss Federal Institute of Technology in Zurich (ETHZ) in 1995. In 1995, he joined the Signal and Information Process ing Laboratory at ETHZ as a Teaching and Research Assistant. In 1996 he earned the Dipl. NDS ETH (post-diploma) degree in information technology, and in 1999, he completed his Ph. D. thesis on the analysis, design, and optimization of ellular neural networks. After a postdoctoral year at the Electronics Research Laboratory at the University of California in Berkeley, he joined the Department of Electrical Engineering at the University of Notre Dame as an assistant professor in January 2001. For both his M. Sc. and his Ph. D. theses, he was awarded the ETH medal, and he received an NSF CAREER award in 2005. For 2005/06, he is a CAS Distinguished Lecturer. His scientific interests include networking and wireless communications, with an emphasis on ad hoc and sensor networks. THIRD QUARTER 2005 IEEE CIRCUITS AND SYSTEMS MAGAZINE 29

A Personal Story

In my essay I am going to share a personal story with you that will tell you how I had to face hardships in order to pursue my studies. It’s all basically related to my education.So my story starts off from the time when I was studying at school. I was an above average student in the junior classes but once I started getting promoted to higher classes, my grades were affected and they started declining.Things worsened for me when I reached the tenth grade. I was in my O-levels at that time and so I had to leave school as my family was also facing a financial crisis.Once I left school, I appeared for my O-levels exams as a private candidate and after completing my O-levels, I joined a local school as an English teacher.Teaching English was not my only subject, I was also assigned to teach some of the other English subjects such as General Knowledge, Geography, History, etc. along with mathematics to the students of grade two, three and four. Although I was not much satisfied wi th the compensation I was getting but it was indeed a good start as I did not have any previous experience of teaching before and even my qualifications were not much as I had just done my O-levels at that time.Side by side, I started preparing to sit for A-levels examinations for which I choose three subjects. However, teaching was a hard job but along with teaching I decided to prepare for my exams but mostly due to lack of time I could not study.Other than that, as it was my first experience of working anywhere, I had to learn a lot as to how to respond or react to certain situations as I am a kind of person who very frequently gets angry at things and gets irritated by any small thing but at work, I had to control my impatience.This was the time when I started taking things in a different way. Although I was still impatient and fussy about things but I had to accept things that I was being told by my seniors to do. Therefore, I learnt to be patient and how to respond to things. In the world outside it’s usually that you always cannot say the things in a way that you really feel. However, one has to be very much careful due to the persisting politics in an organization and same was for the school I was working at.Moreover, working here made me learn new things that were proved to be helpful for my career and for my future. During this time, I became fussy about some things and I did plan to resign but my resignation never used to be accepted as the principal wanted me to continue working for her. Months passed and the date of my A-levels examinations came nearer and nearer that created a tension for me.As I mentioned above, I am not a brilliant student who could understand the concepts just by reading the books once. Therefore, to prepare for my examinations, I talked to my employer and asked him for an early off every day so that I could go home early and I could study. There were just three months left for my examinations when I started studying fo r my examinations and that too along with the work load of the place I was working at.Finally, the date of my examination came and I appeared for my A-levels examinations. The result was supposed to be announced a couple of months later. Meanwhile, I was still working at the school and during that time I also started preparing for my entrance test for my bachelors degree that was to be held a month after my A-levels examinations.Therefore, I gave my entrance test and was glad to know that I had cleared it. A few days later, I had my interview at my university and I cleared that as well. This was the time when I finally resigned and left the job as my university was to start within a month. I worked at the school for more or less a year.Meanwhile, I prepared for my university that started soon. I used all my savings to pay my university tuition fee and in the end I was left with nothing. Therefore, to cope up with my financial expenses, I decided to give home tuitions to the students .These students basically used to be from primary level classes and the basic subjects that I used to give tuitions for were English and Mathematics. I kept on giving tuitions to different students throughout as I was supposed to pay my university tuition fees as still my family was facing a financial crisis. Therefore, to continue my studies, I had to continue giving tuitions to the students.At university, I was enjoying my life although studies at this level got a little tougher and I had to study hard in order to achieve good grades in the courses I appeared for. Besides the academics, I took part in the extra circular activities at my university such as in sports, declamation contests, drama, etc. and this was the fun part of the time I used to spend at the university besides the stress of the studies.

A Turning Point

Walking past the corridor, I saw a student being punished, and I couldn't help but be filled with nostalgia, bad memories. I too was once caught up in such an embarrassing situation, being punished and disgraced in front of my entire class just because of my â€Å"brilliant† idea which went wrong. While I was in high school Year 10, like everyone else, I was in a celebrative mood jumping for joy, as it was the last week of school before the long school break. However, our laughter and happiness came to an abrupt halt as the form teacher of our class Mr Mann entered the classroom. The entire class groaned and became tense on seeing the stack of red report cards he was carrying. My stomach churned as I already knew that I did not excel in my exam, having failed most of my science subjects as I really detest being in a science stream class instead of arts. Reluctantly, I dragged my heavy feet to the front and took my report card when my name was called out. † I knew it,† I said and gave out a loud sigh when I saw my far from impressive results. Mostly were inked in red. Old fashion type of school but yes, my teacher insisted on our parent's signature on the report card for every exam and I could smell the trouble burning awaiting me at home. I knew I would be punished therefore, overwhelmed with fear, I came out with this â€Å"brilliant† idea which is to forge out my parent's signature. â€Å"Everything should be fine if I play my cards right,† I said to myself. Next day came D-day, trying to stop trembling like a leaf while handing up my report card, Mr Mann glared at me. Everything was over when he twitched his eyebrows and questioned me, I was caught red handed. He firmly admonished me in front of my whole class. Drama was unfolding before me just like in TV shows. He was hell bent on making a lesson to be learnt to the entire class out of me. â€Å"Well, do you have anything to say?† asked Mr Mann, in his mild and calm manner. I blushed and stood sheepishly as my classmates roared in laughter merciless. Helplessly I stared at the floor fully embarrassed, with eyes filled with tears hoping it to end as soon as possible. Yet that wasn't the end of the horror, my parents were called and now it is a total game over for me. Well, I had to face the music. My parents are loving and kind but once in a blue moon, like a volcano, they erupt! â€Å"You are grounded for a month!† said mother. â€Å"Your allowance is also going to be deducted!† added father. I'm sorry, that's all I could afford to say while tearing up. Looking back at this though it is just two years back, I saw how much this incident had taught me. It taught me that honesty is always the best policy no matter what happens. Putting aside my studies just because it is not something which I prefer over sports do not benefit me in anyway. Cheating does not bring nor benefit me but only brings out more trouble. I also realized that my parents always wanted what's best for me. Giving me loads of education in terms of academic, sports, music and even computer lessons, I never knew it could be that useful in building up a strong character and confidence in me. Most importantly my future, in who I want to be and what would make them proud. The lessons I learned from this incident has enriched my life and made it much more meaningful in which I promise to strive in studies and also sports. As saying goes, it's always never too late.

The Spectacle of Terror Essay Example | Topics and Well Written Essays - 1500 words

The Spectacle of Terror - Essay Example Now a day, violence on television has become concrete representation of class conflict in the society. The easy accessibility to the media technology helped quickly revealing many significant events across the country. For instance, the police trial and consequent unrest in Los Angeles, the Rodney King beating, and the 9/11, together with the alarming revelation of the country’s vulnerability towards international terrorist attacks. The media has become an integral part of the real and essential assemblies of various social institutions like, hospitals, schools, political, administrative and military systems, even in religions. The media has the power to lead gathering and transmitting news, advertising, conducting campaigns. In the same way, there is a widely accepted belief that â€Å"those who make the headlines have the power.† Moreover, the media plays significant role for successfully conducting and executing wars, educational programs, entertainment, and socializ ation. The influences the media have on such social enterprises are legitimate points for evaluating the impacts of saturation too. Even though the general individual homicide rates in U.S. have been steady for many years, there is an increase in the number of school-aged children towards homicidal attitudes. Since 1980s, there have been a sudden rise in the gun-related homicides among the teens and several publicized murders have taken place in schools making the issue too complicated to handle. The violence among youth is attributed to the permutation of various factors, which impede their emotional ad social developments. Obviously, visual media has played a great role in creating such drastic situation. Today, visual media has become an invasive element of American family life, and symbolic violence illustrated in such medium has become a significant social issue. Therefore, such obvious revelation underlines the question of media’s ability to form awareness and attitude within the mass, especially the youth. We find it too hard to form counterbalancing factors to the violent death themes exemplified by the media. Moreover, the ability to discrete between fantasy and reality is very less in the children, adversely affecting them by creating misconception of death in their mind. Hence, consequences are getting enlarged in an age of media modernization, expansion, and saturation. When the media content is in progress with technology and culture, it influences the method in which reality is comprehended. The modern perceptive and assessment of violence at the hands of government representatives and terrorists are customized and memorized by the present media technologies. In the same way, visual media often undergoes a phenomenon called â€Å"disaster marathons,† days and weeks of intense and continuous media coverage of massive tragedies such as, the 9/11 and its aftermath. In the opinion of Fischoff (2005), it creates all kind of possible dest ructive consequences on viewers and on journalists’ ethics due to the emotionally saturated over coverage of these traumatizing events. Undoubtedly, the media passes on entertainment and related diversions to all segments of people. The foremost audio-visual medium that

The Cultural Dominance of the Christians Essay Example | Topics and Well Written Essays - 500 words

The Cultural Dominance of the Christians - Essay Example Historically, they are almost a blank, we only know that at the end of this period of rapine and death the region now called Europe was utterly changed† (Doren cited in Riley). It was fundamentally the cultural dominance of the Christians that had enabled Europe to survive through this political instability. Another reason they are remembered as the dark ages is the fact that little if any, first-hand account of that period could ever be found. That was so because owing to the lack of education, reading and writing were not the virtues of the people of that era. It was the Christian church that learned during the Dark Ages. After the fall, instead of Rome’s City of Man, people accepted Augustine’s City of God. The converts had little concern with the materialistic world. They could sacrifice their status to attain spiritual wellbeing. The limited academic progress of society was the consequence of Christians’ lack of interest in science. Ans. Before explaining who the Historical Jesus was, it is advisable to mention that the Jesus Christ and the Historical Jesus was the same person. Some people consider the Jesus of Nazareth different from the historical Jesus. â€Å"The general consensus among non-evangelical scholars has been that the Jesus presented in the Bible, and the one who actually walked on the earth are two distinctly different people. The Bias of the Gospel and Epistles authors is often cited as the problem† (â€Å"The Historical Jesus†). The historical Jesus was provided with certain powers by God Almighty like he could bring a dead person back to life with due permission from God.

A View from the Bridge by Cherokee McDonald & Two Ways of Seeing a Essay

A View from the Bridge by Cherokee McDonald & Two Ways of Seeing a River by Mark Twain - Essay Example 2. Comparative Analysis Although the two essays deal with two different subject matters and themes yet there are some similarities in the thematic concerns and symbolism incorporated by the two authors. However the technique or the style of narration utilized and the depiction of the theme and symbols highlight their individualistic writing styles. 2.1. Narration Technique Mark Twain in his treatise uses the technique of third person narration which provides the readers with a chance to draw their personal conclusions as he acts as a mediator between the reader and the text. On the other hand McDonald employs the first person narration technique. Although generally it is assumed that first person narration limits a text’s interpretations for the readers since it is a first hand account of a writer’s explication of a situation. Yet the incorporation of the dialogues can be inferred as a technique employed in order to establish a close connection between the action of tak ing place in the essay and the readers. The use of dialogues also camouflages the presence of the writer or the narrator in the text. However a major similarity that is observed in the depiction of writing style is that both authors illustrate detailed descriptions. As observed that McDonald says, â€Å"He was a lumpy little guy with baggy shorts, and a faded T-shirt and heavy sweat socks falling down over old sneakers† (). Similarly Twain states, â€Å"A broad expanse of the river was turned to blood; in the middle distance the red hue brightened into gold†¦ in another the surface was broken by boiling, tumbling rings, that were as many-tinted as an opal; where the ruddy flush was faintest, was a smooth spot that was covered with graceful circles...high above the forest wall a clean-stemmed dead tree waved a single leafy bough that glowed like a flame in the unobstructed splendor that was flowing from the sun† (). Hence both the writers pay special attention to t he minute details. 2.2. Thematic Concern A major common theme that both the authors deal with in their respective pieces of work is the theme of innocence although the manner in which they project it is different. It is stated in Two Ways of Seeing a River that, â€Å"Now when I had mastered the language of this water and had come to know every trifling feature that bordered the great river as familiarly as I knew the letters of the alphabet, I had made a valuable acquisition†¦ All the grace, the beauty, the poetry had gone out of the majestic river† (). This line can be interpretted as, that the writer believes it is better to retain an aura of mystery or innocence and all the secrets should not be revealed so that it can stimulate human curiosity and interest. Since when all the mysteries are unveiled as is the case with the river than it becomes monotonous and even stifling because the newness fades away. Moreover in terms of human beings and their behavior it can be perceived that Overanalyzing of people or even ones self can result in the loss of beauty (however bittersweet) of humanity. A similar theme is used by McDonald in his essay. He emphasizes the importance of innocence through the actions of the blind child i.e. since his lack of sight hinders his quest for knowledge the

Case Studies Essay Example | Topics and Well Written Essays - 1500 words - 1

Case Studies - Essay Example It is understood that the recent wave of expansion that has hit the European travel market has been an application of strategic tools and techniques in order to achieve the organizational objectives of profit maximization, increased customer base and cost efficiency. According to the information presented by Page and Connell (2006: p129) the vast scope of the European travel market is such that 53% of the population residing in the continent were reportedly away on holiday with most holiday goers belonging to the western region of the continent which essentially represents the differences in incomes and savings of individuals residing in various parts of Europe. As per the guidelines set by strategic management, major tour operators in Europe have benefitted from various modes of integration in order to obtain a larger share of the overall market. Page and Connell (2006: p130) identify that due to the adoption of such practices of horizontal and vertical integration the landscape of the travel market in Europe is dominated by certain key players in the industry of which TUI AG and Thomas Cook AG are standout contenders on the list. As highlighted earlier, aspects of strategic management are pivotal to an organization’s success and this statement is also applicable within the context of major European tour operators. The tools, techniques and procedures that are involved in the assessment of a company’s internal analysis are used to define its value creating process and uncover its strategic capabilities. The implementation of these techniques consequently defines the optimal distribution of resources in an organization so that the achievement of economic advantages may guide the business towards prosperity and success (Bensoussan and Fleisher 2012). The purpose of this paper is to effectively utilize the tools of internal analysis which are, Value Chain Analysis and Balanced Scorecard with regards to the European tour operators TUI AG and Thomas C ook AG respectively. Accordingly, the concluding section of the paper examines the key aspects of the internal analysis to provide suitable suggestions and recommendations in the light of the discussion. 2. Value Chain Analysis According to Bensoussan and Fleisher (2012) the procedure which follows the implementation of a Value Chain Analysis can be described as a series of activities that are undertaken to guide products from the stage of inception till they are delivered to the final customers. Henceforth, the division of the Value Chain Analysis is based on the categories of primary activities and support activities which must be initiated for the achievement of various organizational objectives. This section of the paper focuses on the Value Chain Analysis for TUI AG on the basis of the aforementioned categories. The primary activities of the business can be examined on the basis of several categories that are classified as inbound logistics, operations, outbound logistics, mark eting and sales and service. The inbound logistics of TUI AG include: aircrafts, hotels, cruise ships and cruise liners. Accordingly, the operations of the business can be defined under the categories of tourism, travel and hospitality services. Outbound logistics of TUI AG are highly extensive which reflects the vast scope of its global operations, infrastructures comprising of the outbound facilities are travel agencies, airlines, retail stores, high street

Admission Essy Essay Example | Topics and Well Written Essays - 500 words

Admission Essy - Essay Example I realize success in this Doctoral Program requires me to apply a financial plan with efficient time management skills. I held a full-time job as a pilot while studying to receive my Master of Arts in English as a Second Language from the University of Phoenix. This combination of work and school challenged my time management skills, allowing me to successfully meet my financial obligations to the University and graduate on schedule. The difference between this program and my M.A. program is the online environment. I am experienced with the UOP learning model and appreciate its advantages for timely completion of projects. It was instrumental as a support system and the collaborative knowledge I gained was outstanding. The team approach exposed me to new ideas and perspectives in a non-threatening environment. I have an appreciation for constructive criticism as an essential learning tool and the pragmatic knowledge the UOP learning model facilitates. For many years it has been my goal to pursue a Doctorate, but until discovering the Education Specialist program there wasnt a program I felt passionate enough about to devote the time and energy. The Education Specialist program will enhance my educational background, further develop my intellectual capabilities, and prepare me to provide effective leadership in my diversified

Characteristics of a Learning Organization Research Paper

Characteristics of a Learning Organization - Research Paper Example These organizations also end up repeating the same mistakes over and over again. The best example is situation whereby an organization spends a lot of time restructuring and repeating initiatives because the previous initiatives did not lead to the desired results (Boranmoon, 2005). My preferred learning organization is Social Care Institute for Excellence (SCIE). In addition, the Social Care Institute for Excellence is able to promote learning and leadership in its operations at all levels. The type of leadership promoted by the Social Care Institute for Excellence is able to promote accountability in various levels of leadership. Leaders as well as individuals are made accountable for their actions whenever they engage in decisions that do not contribute to the success of the organization. Organizations that encourage responsibility and accountability often become clearer and stronger in their dealings. These organizations also realize that they are able to produce good leaders of tomorrow who can bring change in the society in which they live in. creating responsible individuals is also important because they help in achieving the common goal to the organization. The Social Care Institute for Excellence’s vision, mission and values can fit well into an overall strategic direction. Learning organizations can only ensure that there is responsibility among individuals if they work through strong network of relationships and helping one another in correcting their weaknesses, rather that creating a working environment in which individuals work under pressure to achieve their objective (Boranmoon, 2005). The Social Care Institute for Excellence also ensures that there is a conducive learning environment for all individuals. The organization should take advantage and use the available intelligent resource within the organization to improve in their service delivery. This can only be achieved if every individual is given a chance to develop their skills and talents. Further, social Care Institute for Excellence engages both internal and external stakeholders in the decision making process. They them respond with adequate measures towards the issues generated by stake holders. Stakeholders must always be included in the decision making process for any learning organization to achieve their objectives. Lack of concern towards the views of the stakeholders can only lead to more complications in the process of implementing certain projects. Success in the implementation of all projects and activities of a learning organization depends upon the cooperation among all stakeholders (Boranmoon, 2005). Social Care Institute for Excellence ensures that there is sustainability thinking within the organization’s culture. Each and every individual within the organization should be made to think that they are very important to the sustainability of the organization. When individuals within the learning organization feel that they are very insi gnificant in the progress, the productivity may be affected thus affecting the ability to meet the set objectives. Every individual within the learning organization must feel a sense of worth in the operations and management of the organization (Boranmoon, 2005). Social Care Institute for Excellence incorporates the efforts of several individuals. It is more that just one person and it arises from the collaboration of individuals in groups

Anorexia Research Paper Example | Topics and Well Written Essays - 3250 words

Anorexia - Research Paper Example Anorexia nervosa may be characterized as when a person refuses to maintain his body weight of at least 85% of the expected weight that he should have according to his body mass index. Individuals tend to display a great sense of fear of putting on weight and literally have a phobia of ‘getting fatter’. They may also exhibit a much-distorted image of what is a perfect body type to them and reduce their intake of food to an alarming extent in order to stay thin. Moreover, in many young girls, an irregular menstrual cycle or an absence of the same can be a characteristic of anorexia or even reduced appetite and eating. Many people suffering from anorexia eat in front of other people in order to not let their problem out in the open, but often vomit out their food, exhibiting signs of bulimia, or abuse themselves by taking laxatives to take out the food from their body. Extreme weight loss accompanied with fainting and an abnormal blood count is the first symptoms of the eat ing disorder and if parents see these signs in their children then they should be alarmed and take necessary recourse in order to counter the problem.There are societies where it is alright to be thin and anorexia as an eating disorder is not given much thought to because parents think it alright for their children to lose weight and look good in society. Losing weight by exercising while eating necessary healthy foods is a perfectly viable option for a young adult but in no society should suffering from an eating disorder be considered okay.

Genetically Modified Food Essay Example for Free

Genetically Modified Food Essay Genetically modified (GM) foods are ethically unacceptable. GM foods are food product derived in whole or part from a genetically modified organism by human intention. It is a special set of technologies that concerns the alteration, deletion, or addition of the genetic makeup of living organisms such as animals, plants, or bacteria. This is an important issue because GM foods have been dubbed as the Food of the Future and although studies have shown that genetically modified foods may bring about many benefits to mankind, we must also look into the ethical issues involved in producing such food before we even consider accepting it as the way of the future. First, we must understand that the word ethical is defined as having to do with ethics or morality; or of conforming to moral standards. There will be 3 parts to this essay. Firstly, I will be presenting and defending 2 arguments that support my stand. Following that, Ill take into consideration some common objections against my thesis. Lastly, I will summarize the main points in this essay before drawing to a conclusion. The essays argument takes the form of Modus Ponens: If GM is X, GM is unethical GM is X GM is unethical My main argument is that it is unethical to tamper with nature by mixing genes among the different species. By doing so, it may actually lead to a violation of natural organisms intrinsic values. There is a very delicate balance that links this world together and this is the balance that makes things work. GM foods might actually give rise to more complications such as the disturbance of natures food pyramid. For example, the pesticide produced in the crop may unintentionally harm other creatures while producing a benefit to others. The introduction of pest-resistant genes into crops could lead to the death of the pests and other animals causing an imbalance in the food chain that could possibly lead to the extinction of some species especially if they are only localized in one particular area. In Britain, a native farm bird, the Skylark, was indirectly affected by the introduction of GM sugar beets that were designed to resist herbicides. The result in planting this crop was that weeds were reduced substantially. However, since the birds rely on the seeds of this weed in autumn and winter, researchers expect that up to 80% of the Skylark population would have to find other means of finding food. Another issue brought up is that GM crops may also pose a health risk to native animals that eat the plants and may be poisoned by the built-in pesticides. Although others might also argue that the cutting down of trees to construct buildings might also be a way of tampering with nature, GM food not just tampers with physical nature but with the foundation of nature genes. Every organism, no matter how small, is made up of genes. These genes control the physical development and behavior of the organism and are passed down from parent to offspring. The word genes (comes from the Greek word genos meaning origin) actually defines natures origin and the production of GM food would mean to change the origin of nature. Furthermore, religious communities Christians, Hindus, Jews and Muslims Ââ€" also share such concerns regarding GM products. According to Bishop Jeff Davies from the SA Council of Churches, With genetic engineering, we are tampering with the structures of life that have taken millions of years to evolve and we have the arrogance to think that we can improve on them in 10 years to transfer a gene from one species into another. Different religious communities have different believes and one of them would be their food such as kosher and halal food. But with the introduction of animal genes into plants how will they define a tomato with a fish gene? This will also be a major concern to vegetarians. All in all, I believe that people should be happy with what nature has to give and not play God and try to control nature. It is unethical to sacrifice other creatures and meddle with the delicate balance of nature. Furthermore, there will be potential chain reactions that may be unstoppable. One other argument is how GM products can affect our health especially in the long run. The unpredictable changes in our food could lead to negative reactions that are not detected by research techniques until much later. A quick acceptance of GE foods without proper testing could show corporate profitability to be very influential but that would be too dangerous because there has been no adequate safety testing to ensure that using other organisms genes is going to have the same useful effects if inserted into a totally unrelated species. Furthermore, testing has only been done on a small scale currently and its hard to predict what will happen when its used on a wider ecology. In 1989, dozens of Americans died and several thousands were afflicted and impaired by a genetically altered version of the food supplement L-tryptophan. Studies have been done to show how viruses can mix with genes of other viruses to give rise to more deadly viruses. To mass market the use of GM food when it has not been properly tested for safety issues would mean that businesses are gaining at the expense of consumers health and is therefore ethically unacceptable. On the other hand, some organizations insist that GM technology is the solution to solving the problem of world hunger. However, I feel that it is simply a ploy of corporations and countries that are using the plight of the developing world as a marketing strategy to gain acceptance of GE foods. GM technology is not an economical method that can be easily implemented by most countries. In fact, genetic engineering techniques are currently being applied to crops important to the industrialized world and not on crops which the worlds hungry depend on. GM foods could actually reduce developed countries reliance on crops from developing countries, resulting in loss of trade and severe economic damage for them and intensifying their problem of poverty. This would mean that theres a conflict of interest. Furthermore, an important factor that Friends of the Earth has pointed out is that many people in the world are suffering from malnutrition and hunger because they cannot afford to buy food, not because it is unavailable. Therefore, even with GM food, people would still not be able to afford it or have it distributed appropriately. Most of the causes of hunger are found in global politics, rather than issues of agriculture and technology. As a result, a variety of groups and people are questioning the motives behind GM foods as the political causes of hunger appear to be ignored. An article from Food First observed that most innovations in agricultural biotechnology have been profit-driven rather than need-driven and it questions whether GE technology can really ensure food security, protect the environment and reduce poverty in the developing world or is it produced simply because its patentable and thus, profitable to businesses. In some cases, as reported by The Institute for Science, pesticide usage is actually increasing, and GE crop actually yield less than conventional crops. In this essay, I have come up with several valid reasons why Genetically Modified Foods are ethically unacceptable. GM foods tamper with the origin of nature which is the genes and there is inadequate safety testing to prove that GM food is safe for human consumption. Therefore, businesses are mass marketing GM food at the expense of consumers health and proclaiming that GM Food is the solution to world hunger when it might not be true. Although there might be potential and benefits in GE technology, there are still many unknown areas that might prove to be more harmful then beneficial. Furthermore, there are still too many important ethical issues that have been ignored and that reason by itself makes it ethically unacceptable.

Boston beer case Essay Example for Free

Boston beer case Essay Boston Beer Company’s main growth strategy was focused by differentiation. The sources of its competitive advantage can be classified as a company that provides high quality beer with unique flavors, a market driven approach, and a very efficient contract brewing strategy. Unfortunately, by the 1990’s, their initial public offering of $30 went as low as to $8 per share. Since the easy of entry into the microbrewery business is low, that resulted in about 3000 new microbrewers into the market. When there became too many options available for the consumer, Jim Koch should have approached the situation and avoided the risks of the company’s shares from falling, right when they saw stocks going down. He could have also approached having a more aggressive growth approach when the company went IPO. They could have avoided the company from becoming part of the niche market, which is still the case today. If he would have been a little more aggressive when they went IPO, they could have invested money into a brewery where they can meet their demands, not over exuberate the expansion. Also, they could have invested in finding the right marketing campaign like using celebrities or just advertising the beer to capture consumer’s attention. They really needed to create a type of quote or motto people would remember, just like Dos Equis and Coors light. Boston Beer Company has failed to that and for that reason their growth is still at a steady pace where is still not part of the big dogs yet. Since they focus so much on differentiation as their strategy, why couldn’t they capture consumer’s attention quicker and faster? In the 1990’s, Jim Koch should have changed his company from getting into a niche market into a general market, so that today he still does not need to prove or go bar to bar, to ask them to carry their beer. It should be a first option when someone is opening a bar to have Samuel Adams beer because the consumers love it. He failed to do so by not taking advantage in the 1990s and he will still have to do the same beer pitch to bars, because of his mistake.

Structure of DNA: An Overview

Structure of DNA: An Overview The structure of DNA Deoxyribonucleic acid or DNA is generally found in all organisms as well as humans. DNA is an inherited material that every person has, and is set up in both the cell nucleus and the mitochondria. A higher percentage of human DNA comprise of nuclear DNA because it is found in the nucleus. (Berger, 1998). DNA comprises of numerous properties, the most significant being; that it can copy itself. In the occurrence of this process, the twofold helix strands of DNA are employed as a model for replicating the base sequences. (Watson, 2011). This is an important process in the event of cell division due to the vital requirement for each new cell to carry an accurate DNA copy found in the mature cell. Adenine (A), guanine (G), thymine (T), cytosine (C) and uracil (U) are major five chemical bases that accumulate DNA’s coded information (Watson Crick, 2003). There are over three billion of such chemicals. More than 99% of these bases have been proved to be reliable in all humans (Buch ini Leumann, 2003). As a result of the complexity and association of the entire DNA structure, an in-depth look of each part; DNA is the genetic information of nearly all living organisms. It can be copied over age brackets of cells; it can be converted into proteins; and can be mended when required. DNA is a polymer, composed of nucleotides (Watson Crick, 2003) Hydrogen bonds: bases pairing The (hydrophobic) bases are piled on the in the interior, their level surface are vertical to the axis of the double helix (Berger, 1998). The exterior (phosphate and sugar) is hydrophilic. Hydrogen limits between the bases of one strand and that of the other strand grip the two strands together (dashed lines in the drawing). A purine on one strand links to a pyrimidine on the other strand. Consequently, the number of purines deposits matches the number of pyrimidine deposits (Watson, 2011). A binds T (with 2 hydrogen bounds), while G binds C (with 3 hydrogen bounds: more stable link: 5.5 kcal vs 3.5 kcal) (Rà ¤dler Safinya, 1997). Thus, the substance in A in the DNA is equal to the one in T, and the substance in G equals the one in C. The complement of the 2 strands is as a result of this (AT and GC) correspondence. One serves as a template of the other, and vice versa. This feature allows exact replication (â€Å"semi-conservative replication: one strand -the template- is conserved, another is newly synthesized, same with the second strand, conserved, allowing another one to be newly synthesized†) (Buchini Leumann, 2003). The model of Watson and Crick above described sometimes differs from the Hydrogen bounds in base pairing from using the N7 atom of the purine instead of the N1 (Hoogsteen model). Figure 1 Major groove and minor groove The double helix is a rather inflexible and thick molecule of a huge extent and a small diameter. It presents both major groove and a minor groove (Patil, Rhodes Burgess, 2004). The major groove is profound and broad; the minor groove is thin and shallow. DNA-protein connections are essential procedures in the life of the cell life. Proteins connect at the ground of the DNA grooves, using a precise binding: hydrogen bounds, and distracted binding: van der Waals exchanges. Proteins recognize H-bond donors, H-bond acceptors, methyl groups (hydrophobic), which are later in the major groove (Rà ¤dler Safinya, 1997). The major groove involves 4 likely patterns of recognition, and 2 with the minor groove. A few proteins bind DNA in its major groove, some other in the minor groove, and some need to bind to both. The minor groove of double helical B-DNA is a sector of great attention for rising new drugs because of its non-covalence high succession specific connections for a huge number of tiny molecules (Berger, 1998). Minor groove binding lies among the broadly studied class of agents exemplified by, an advanced succession specificity and possessing diverse biological actions. A number of them display antiviral, antibacterial, and antiprotozoal properties. However, others have shown antitumor activity. Figure 2 H-DNA or triplex DNA Inverted repeats (palindromes) of polypurine/polypyrimidine DNA stretches can structure triplex structures (triple helix) (Watson Crick, 2003). A triple-stranded together with a single stranded DNA are formed. H-DNA may have a function in practical regulation of gene appearance as well as on RNAs (e.g. repression of transcription). Figure 3 Triplex Forming Nucleotides Triplex forming oligonucleotides (TFOs) have attained significant focus as a possible therapeutic agent to aim gene expression (Patil, Rhodes Burgess, 2004). They are a group of DNA oligonucleotides which are capable of fusing with other main groove of the duplex DNA creating triple helix (Buchini Leumann, 2003). The creation of a triplex beside the main groove leads to competition with the fusing of transcription factors and the proteins essential for transcription. TFOs provide specificity sequence and hence can be used to aim and inhibit appearance of specific genes which are associated with a particular disease state. In addition TFOs can also be used as diagnostic agents for identification of a foreign DNA (viral or bacterial) or any diseases associated to mutations. Binding of Triplex Forming Oligonucleotides TFOs, in the span of approximately 20 bases, can bind in the major groove via Hoogsteen hydrogen bonds to the purine (A and G) bases on the double stranded DNA, already in the structure of the Watson-Crick helix. The binding can take place at the extent of pyrimidines of one DNA strand and the opposite purines on the other. TFOs bind to the strand with purines. Respective of their base composure, TFOs can bind to the double helix in either parallel or antiparallel direction to the purine-bearing strand (Buchini Leumann, 2003). TFOs made of pyrimidines (C and T) bind to the purine-rich strand of the objective double helix via Hoogsteen hydrogen bonds in a parallel manner. TFOs comprised of purines (A and G), or mixed purine and pyrimidine (G and T) bind to the same purine-rich strand through reverse Hoogsteen bonds in an anti-parallel style (Rà ¤dler Safinya, 1997). Oligonucleotides with modified structural features Oligonucleotides hauling other compound moieties besides the normal bases are called â€Å"modified oligonucleotides†. The modifications can be situated at the 3’- or 5’-end of the oligonucleotide, or within the sugar-phosphate stamina or at the nucleobases. Mainly all PCR applications are still potential if the modification is close to the 5’- end of the oligonucleotide. Contrary, modifications at the 3’- end typically wedge this end for extra enzymatic response. In order to achieve an absolute blocking, an inverted end or C3-Spacer modification is recommended (Patil, Rhodes Burgess, 2004). Chemically synthesized oligonucleotides bear free hydroxy (OH) collection at their relevant 3’- and 5’- ends (Berger, 1998). Besides, some biological tests need the presence of the natural structure of an oligonucleotide. This modification requires being ordered explicitly (Rà ¤dler Safinya, 1997). Structure and Limitations DNA triple helices figure in a sequence-specific way on polypurine:polypyrimidine tracts (1–3), which are extensive in mammalian genomes (4–6). The third thread recline in the major groove of an integral duplex and is calmed by two Hoogsteen hydrogen bonds between third strand bases and the purines in the duplex (3, 7) (Buchini Leumann, 2003). The third strand may comprise of pyrimidines, or purines, respective of the character of the target succession. In the pyrimidine (or Y.R:Y) motif, a homopyrimidine oligonucleotide binds in a trend parallel to the purine strand in the duplex, with canonical base triplets of T.A:T and C.G:C. In the alternate purine motif (R.R:Y), a homopurine strand binds antiparallel to the purine strand, with base triplets of A.A:T and G.G:C (8, 9) (Buchini Leumann, 2003). The development of TFOs could involve sequence-specific gene targeting reagents in live cells (12–17) (Berger, 1998). Despite this, several obstacles still need to be overcome. Triplex chemistry and biochemistry inflict essential limitations to TFO action in the nuclear setting, and target choices are inadequate to polypurine:polypyrimidine sequences (Watson, 2011). Additionally, it is evident that nucleosomes can inhibit triplex formation (18–20). As a result, ease of access to genomic targets is an important issue. Potential applications of TFOs-gene targeting Potential applications of TFOs embrace gene targeting treatment particularly for cancer and the study of gene expressions. TFOs can hush a gene record by aiming the dictation initiation sites, (i.e., the promoter region), or by targeting recording of elongation by striking at the triplex binding sites. Specifity of sequence is the answer to efficient genetic targeting. With the use of specificity, genes that are targeted can be changed in many ways. Gene therapy agents change into loose cannons inside the cells without it. Triplex forming oligonucleotides (TFOs) fuse into main groove of the duplex DNA with high affinity and specificity (Watson, 2011). Due to these properties, TFOs have been thought as host devices for the genetic manipulation. Recent researches have shown that TFOs have the ability to mediate targeted gene success in mice, establishing the basis for the possible application of those molecules in a human being’s gene therapy. Molecules that fuse with the DNA double helix might interfere with gene appearance and, to add to the potential therapeutic applications, it can be useful for the research of DNA processing, package of chromatin, or related biological processes. The Triplex-forming oligonucleotides (TFOs) fuse with specific sequences in DNA double helix through hydrogen bonding interactions. The TFOs have been revealed to down-regulate the expression of the gene, to induce aimed genomic DNA modifications, so as to fasten DNA combination, and also to regulate chromatin organization. In addition to this, they can be used as transporting agents to place DNA-modifying agents into selected sequences (Patil, Rhodes Burgess, 2004). Something important regarding TFO technologies are the creation of fresh oligonucleotide analogues which have improved fusing affinity, sufficient stability and better target selectivity, in intracellular environment. References Watson, J. D, Crick, F. H, 2003, The structure of DNA. In Cold Spring Harbor Symposia on Quantitative Biology, Vol. 18, pp. 123-131, Cold Spring Harbor Laboratory Press. Berger, J. M. (1998). Structure of DNA topoisomerases. Biochimica et Biophysica Acta  (BBA)-Gene Structure and Expression, 1400(1), 3-18. Rà ¤dler, J. Safinya, C. R., 1997, Structure of DNA-cationic liposome complexes: DNA  Intercalation in Multilamellar Membranes in Distinct Interhelical Packing Regimes, Science, 275(5301), 810-814. Watson, J. D, 2011, The double helix: A personal account of the discovery of the structure of DNA, Simon and Schuster. Buchini, S., Leumann, C. J, 2003, Recent improvements in antigene technology, Current opinion in chemical biology, 7(6), 717-726. Patil, S. D., Rhodes, D. G., Burgess, D. J, 2004, Anionic liposomal delivery system for DNA transfection, The AAPS journal, 6(4), 13-22.