Endocrine disrupting compounds and human fertility Essay Example for Free

Endocrine disrupting compounds and human fertility Essay In the past 100 years, humans have introduced several hundreds of new compounds into the environment, which actually have affected the physiology of both plants and animals including humans (Propper, 2005). In most cases these deleterious effects are unintended and it was not predicted before that these compounds could have such effects on organisms. Therefore the actual mechanisms by which these compounds affect physiological functions of other organisms are not yet properly researched. When such compounds affect the endocrine systems they are called endocrine disrupting compounds. These compounds would affect different hormonal pathways and physiological functions such as reproduction, development, metabolism and even the behavior of humans and other animals. The present essay is intended to identify some of the endocrine disrupting compounds that affect human fertility, the mechanism of affecting, to analyze the weight of different evidences available and to analyze the current investigation techniques. Endocrine disrupting compounds have been defined as an exogenous agent that interferes with the synthesis, secretion, transport, binding, action, or elimination of natural hormones in the body which are responsible for the maintenance of homeostasis, reproduction, development and/or behavior (Kavloc et al. , 1996). The United States Environmental Protection Agency (USEPA) has accepted this definition as the most appropriate one in the year 2004. These compounds are capable of interfering with normal signaling mechanisms of the endocrine system. Either they could block or make changes in the synthesis of hormones, or they could mimic some of the endocrine compounds, thereby affecting the target organs. They could also affect the release of these hormones from the concerned glands and its transportation. They could also bind with the specific molecules to which hormone binds. These compounds are usually seen in pesticides, industrial effluents, pharmaceutical compounds, etc. Heavy metals also could induce endocrine disruption. Wastewater effluents from cities as well as from agricultural fields are sources of such compounds. The neuro- endocrine system might also get affected by these compounds causing changes in the reproductive organs and associated behaviors in humans. Most of the researches in this filed are concentrated towards the effect of these compounds on estrogen and other steroids responsible for reproduction (Propper, 2005). According to Caserto et al. (2008) these compounds could affect human heath seriously even when present in very small amounts. This is especially because many such chemicals would be these affecting a single target. There are many studies which reveal that waste water discharge in to natural waters have resulted in the changes in reproductive organs of aquatic fauna. This is because of the presence of 17 beta estradiol, estrogens, androgens, etc, in wastewater. These compounds are highly stable and therefore could not be removed completely from wastewater by various treatment procedures to reclaim the water. Traces of these compounds would be present in the drinking water, which is prepared from these natural waters into which the wastewater has been disposed. Bioaccumulation of these compounds in humans is expected to affect fertility (Falconer, 2006). Wagner and Oehlmann (2009) have conducted a study to determine the level of endocrine disrupting compounds in usual food stuffs of humans and they selected bottled mineral water as one of the sources of this compounds. The effort was taken based on the fact that endocrine disrupting hormones reaches the body of human mainly through foodstuffs. They used estrogen receptor alpha for the identification. They found that the mineral waters in plastic bottles are seriously contaminated with phthalates that are getting leached into the water from plastic bottle. Thus it was proved beyond doubt that endocrine disrupting compounds are present in plastic wares and extensive use of plastic wares to store food would result in increased level of these compounds in the foodstuffs with a deleterious effect on fertility. According to Rhind (2005) there is an urgent need to study the effects of endocrine disrupting compounds on animals. Very little is known regarding the concentration of these compounds in the different tissues of animals, the concentration required to produce a deleterious effect on the animals, effect of prolonged exposure to an single compound, the effects of different classes of compounds, effect of the exposure to more than one compounds at a time etc. With the available information it is possible to establish that the endocrine disrupting compounds in the environment is affecting human health adversely with a high impact on fertility. The effect of these endocrine disrupting compounds on human reproduction is different for different compounds. Compounds such as diethylstilbestrol affect female reproductive system and cause abnormal follicular growth, ovulation, abnormal formation of corpus luteum and the overall maintenance of ovary would be affected. It would also affect the normal sexual differentiation in females. Pregnancy would be affected because of the negative effects on fertilization and implantation of the embryo in the uterus. Another pollutant called dioxin has been reported to cause endometriosis in women, which is a very painful disease that leads to infertility (Crisp et al. , 1998). There are some compounds, which are naturally occuring such as phytoestrogens produced by plant that could mimic the properties of estrogens produced by humans (Caserta et al. , 2008). Natural sex hormones are used extensively for different purposes in farms as well as in urban areas and there is every chance that these would become harmful to non-targeted organisms including humans because of the concentrating effect. There are many evidences, which prove that environmental contaminants are causing problems in female fecundity as well as fertility (Louis et al. , 2006). There are evidences to prove that puberty, menstruation, endometriosis, pregnancy, senescence period for reproduction etc are affected by exposure to these compounds. Diethyl stilbestrol was given to pregnant women during 1950’s to prevent miscarriage. But later on due to the adverse effects of these compounds most of the kids developed abnormalities. Finally the compound was withdrawn from the market. The female child produced in such cases developed menstrual abnormalities, vaginal hypoplasia, sudden abortion, premature delivery, uterine malformation and overall low fertility. If the child is a male, it was found to develop testicular dysgenesis syndrome (Milhan 1992). Maternal exposure during pregnancy and exposure to these compounds present in the mother’s milk during the prenatal period are believed to be the reasons for such defects. This occurs due to the lipophilic nature of these compounds, which in turn gets stored in the adipose tissues of the mother. This is one of the strongest evidences of the deleterious effect of these compounds on human reproductive system. There are reports that state that human sperm production has decreased in the past 50 years. Although accurate evidence is not there, the reasons for this decrease is attributed to the presence of endocrine disrupting compounds in the environment (Crisp, 1998). Leydig cells tumors are increasingly believed to be caused by this factor. Same is the case of prostrate cancer. Studies conducted in Coke-oven workers have revealed that there has been an increase of mortality among them due to prostrate cancer due to occupational exposure to these compounds. However more research is required to find out the actual cause of this cancer, whether it is due to endocrine disruption by any chemicals in the environment.

Examining The Sound Navigation Technique Of Sonar Engineering Essay

Examining The Sound Navigation Technique Of Sonar Engineering Essay Sonar means sound navigation and ranging is a technique that uses sound propagation (usually underwater, as in Submarine navigation) to navigate, communicate with or detect other vessels. Two types of technology share the name sonar: passive sonar is essentially listening for the sound made by vessels; active sonar is emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of targets in the water. Acoustic location in air was used before the introduction of radar. Sonar may also be used in air for robot navigation, and SODAR upward looking in-air sonar) is used for atmospheric investigations. The term sonar is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic). The study of underwater sound is known as underwater acoustics or hydro acoustics History Although some animals (dolphins and bats) have used sound for communication and object detection for millions of years, use by humans in the water is initially recorded by Leonardo Da Vinci in 1490: a tube inserted into the water was said to be used to detect vessels by placing an ear to the tube.[citation needed] In the 19th century an underwater bell was used as an ancillary to lighthouses to provide warning of hazards. The use of sound to echo locate underwater in the same way as bats use sound for aerial navigation seems to have been prompted by the Titanic disaster of 1912. The worlds first patent for an underwater echo ranging device was filed at the British Patent Office by English meteorologist Lewis Richardson a month after the sinking of the Titanic, and a German physicist Alexander Behm obtained a patent for an echo sounder in 1913. Canadian Reginald Fessenden, while working for the Submarine Signal Company in Boston, built an experimental system beginning in 1912, a system later tested in Boston Harbor, and finally in 1914 from the U.S. Revenue (now Coast Guard) Cutter Miami on the Grand Banks off Newfoundland Canada. In that test, Fessenden demonstrated depth sounding, underwater communications (Morse Code) and echo ranging (detecting an iceberg at two miles (3 km) range). The so-called Fessenden oscillator, at ca. 500 Hz frequency, was unable to determine the bearing of the berg due to t he 3 meter wavelength and the small dimension of the transducers radiating face (less than 1 meter in diameter). The ten Montreal-built British H class submarines launched in 1915 were equipped with a Fessenden oscillator. During World War I the need to detect submarines prompted more research into the use of sound. The British made early use of underwater hydrophones, while the French physicist Paul Langevin, working with a Russian immigrant electrical engineer, Constantin Chilowski, worked on the development of active sound devices for detecting submarines in 1915 using quartz. Although piezoelectric and magnetostrictive transducers later superseded the electrostatic transducers they used, this work influenced future designs. Performance factors The detection, classification and localization performance of a sonar depends on the environment and the receiving equipment, as well as the transmitting equipment in an active sonar or the target radiated noise in a passive sonar. Sound propagation Sonar operation is affected by variations in sound speed, particularly in the vertical plane. Sound travels more slowly in fresh water than in sea water, though the difference is small. The speed is determined by the waters bulk modulus and mass density. The bulk modulus is affected by temperature, dissolved impurities (usually salinity), and pressure. The density effect is small. The speed of sound (in feet per second) is approximately: 4388 + (11.25 ÃÆ'- temperature (in  °F)) + (0.0182 ÃÆ'- depth (in feet)) + salinity (in parts-per-thousand ). This empirically derived approximation equation is reasonably accurate for normal temperatures, concentrations of salinity and the range of most ocean depths. Ocean temperature varies with depth, but at between 30 and 100 meters there is often a marked change, called the thermo cline, dividing the warmer surface water from the cold, still waters that make up the rest of the ocean. This can frustrate sonar, because a sound originating on one side of the thermo cline tends to be bent, or refracted, through the thermo cline. The thermo cline may be present in shallower coastal waters. However, wave action will often mix the water column and eliminate the thermo cline. Water pressure also affects sound propagation: higher pressure increases the sound speed, which causes the sound waves to refract away from the area of higher sound speed. The mathematical model of refraction is called Snells law. If the sound source is deep and the conditions are right, propagation may occur in the deep sound channel. This provides extremely low propagation loss to a receiver in the channel. This is because of sound trapping in the channel with no losses at the boundaries. Similar propagation can occur in the surface duct under suitable conditions. However in this case there are reflection losses at the surface. In shallow water propagation is generally by repeated reflection at the surface and bottom, where considerable losses can occur. Sound propagation is affected by absorption in the water itself as well as at the surface and bottom. This absorption depends upon frequency, with several different mechanisms in sea water. Long-range sonar uses low frequencies to minimize absorption effects. The sea contains many sources of noise that interfere with the desired target echo or signature. The main noise sources are waves and shipping. The motion of the receiver through the water can also cause speed-dependent low frequency noise. Scattering When active sonar is used, scattering occurs from small objects in the sea as well as from the bottom and surface. This can be a major source of interference. This acoustic scattering is analogous to the scattering of the light from a cars headlights in fog: a high-intensity pencil beam will penetrate the fog to some extent, but broader-beam headlights emit much light in unwanted directions, much of which is scattered back to the observer, overwhelming that reflected from the target (white-out). For analogous reasons active sonar needs to transmit in a narrow beam to minimize scattering. Target characteristics The sound reflection characteristics of the target of an active sonar, such as a submarine, are known as its target strength. A complication is that echoes are also obtained from other objects in the sea such as whales, wakes, schools of fish and rocks. Passive sonar detects the targets radiated noise characteristics. The radiated spectrum comprises a continuous spectrum of noise with peaks at certain frequencies which can be used for classification. Countermeasures 1) Active countermeasures may be launched by a submarine under attack to raise the noise level, provide a large false target, and obscure the signature of the submarine itself. 2) Passive countermeasures include: There is a mounting noise-generating device on isolating devices. We use a sound-absorbent coating on the hulls of submarines, for example anechoic tiles. Active sonarà   Active sonar uses a sound transmitter and a receiver. When the two are in the same place it is monostatic operation. When the transmitter and receiver are separated it is bistatic operation. When more transmitters (or more receivers) are used, again spatially separated, it is multistate operation. Most sonars are used monostatically with the same array often being used for transmission and reception. Active son buoy fields may be operated multistatically. Active sonar creates a pulse of sound, often called a ping, and then listens for reflections (echo) of the pulse. This pulse of sound is generally created electronically using a sonar Projector consisting of a signal generator, power amplifier and electro-acoustic transducer/array. A beam former is usually employed to concentrate the acoustic power into a beam, which may be swept to cover the required search angles. Generally, the electro-acoustic transducers are of the Tonpilz type and their design may be optimized to achieve maximum efficiency over the widest bandwidth, in order to optimize performance of the overall system. Occasionally, the acoustic pulse may be created by other means, e.g. (1) Chemically using explosives (2) Air guns (3) Plasma sound sources. To measure the distance to an object, the time from transmission of a pulse to reception is measured and converted into a range by knowing the speed of sound. To measure the bearing, several hydrophones are used, and the set measures the relative arrival time to each, or with an array of hydrophones, by measuring the relative amplitude in beams formed through a process called beam forming. Use of an array reduces the spatial response so that to provide wide cover multibeam systems are used. The targets signal (if present) together with noise is then passed through various forms of signal processing, which for simple sonars may be just energy measurement. It is then presented to some form of decision device that calls the output either the required signal or noise. This decision device may be an operator with headphones or a display, or in more sophisticated sonar this function may be carried out by software. Further processes may be carried out to classify the target and localize it, as well as measuring its velocity. The pulse may be at constant frequency or a chirp of changing frequency (to allow pulse compression on reception). Simple sonars generally use the former with a filter wide enough to cover possible Doppler changes due to target movement, while more complex ones generally include the latter technique. Since digital processing became available pulse compression has usually been implemented using digital correlation techniques. Military sonars often have multiple beams to provide all-round cover while simple ones only cover a narrow arc, although the beam may be rotated, relatively slowly, by mechanical scanning. Particularly when single frequency transmissions are used, the Doppler effect can be used to measure the radial speed of a target. The difference in frequency between the transmitted and received signal is measured and converted into a velocity. Since Doppler shifts can be introduced by either receiver or target motion, allowance has to be made for the radial speed of the searching platform. One of the useful small sonar is similar in appearance to a waterproof flashlight. The head is pointed into the water, a button is pressed, and the device displays the distance to the target. Another variant is a fish finder that shows a small display with shoals of fish. Some civilian sonars approach active military sonars in capability, with quite exotic three-dimensional displays of the area near the boat. When active sonar is used to measure the distance from the transducer to the bottom, it is known as echo sounding. Similar methods may be used looking upward for wave measurement. Active sonar is also used to measure distance through water between two sonar transducers or a combination of a hydrophone (underwater acoustic microphone) and projector (underwater acoustic speaker). A transducer is a device that can transmit and receive acoustic signals (pings). When a hydrophone/transducer receives a specific interrogation signal it responds by transmitting a specific reply signal. To measure distance, one transducer/projector transmits an interrogation signal and measures the time between this transmission and the receipt of the other transducer/hydrophone reply. The time difference, scaled by the speed of sound through water and divided by two, is the distance between the two platforms. This technique, when used with multiple transducers/hydrophones/projectors, can calculate the relative positions of static and moving objects in water. In combat situations, an active pulse can be detected by an opponent and will reveal a submarines position. A very directional, but low-efficiency, type of sonar makes use of a complex nonlinear feature of water known as non-linear sonar, the virtual transducer being known as a parametric array. Project ARTEMIS Project ARTEMIS was one-of-a-kind low-frequency sonar for surveillance that was deployed off Bermuda for several years in the early 1960s. The active portion was deployed from a World War II tanker, and the receiving array was a built into a fixed position on an offshore bank. Transponder This is an active sonar device that receives a stimulus and immediately retransmits the received signal or a predetermined one. Passive sonar Passive sonar listens without transmitting. It is often employed in military settings, although it is also used in science applications, e.g., detecting fish for presence/absence studies in various aquatic environments see also passive acoustics and passive radar. In the very broadest usage, this term can encompass virtually any analytical technique involving remotely generated sound, though it is usually restricted to techniques applied in an aquatic environment. Identifying sound sources Passive sonar has a wide variety of techniques for identifying the source of a detected sound. For example, U.S. vessels usually operate 60 Hz alternating current power systems. If transformers or generators are mounted without proper vibration insulation from the hull or become flooded, the 60 Hz sound from the windings can be emitted from the submarine or ship. This can help to identify its nationality, as most European submarines have 50 Hz power systems. Intermittent sound sources (such as a wrench being dropped) may also be detectable to passive sonar. Until fairly recently, an experienced trained operator identified signals, but now computers may do this. Passive sonar systems may have large sonic databases, but the sonar operator usually finally classifies the signals manually. A computer system frequently uses these databases to identify classes of ships, actions (i.e. the speed of a ship, or the type of weapon released), and even particular ships. Publications for classification of sounds are provided by and continually updated by the US Office of Naval Intelligence. Noise limitations Passive sonar on vehicles is usually severely limited because of noise generated by the vehicle. For this reason, many submarines operate nuclear reactors that can be cooled without pumps, using silent convection, or fuel cells or batteries, which can also run silently. Vehicles propellers are also designed and precisely machined to emit minimal noise. High-speed propellers often create tiny bubbles in the water, and these cavitations have a distinct sound. The sonar hydrophones may be towed behind the ship or submarine in order to reduce the effect of noise generated by the watercraft itself. Towed units also combat the thermo cline, as the unit may be towed above or below the thermo cline. The display of most passive sonars used to be a two-dimensional waterfall display. The horizontal direction of the display is bearing. The vertical is frequency, or sometimes time. Another display technique is to color-code frequency-time information for bearing. More recent displays are generated by the computers, and mimic radar-type plan position indicator displays. Performance prediction Unlike active sonar, only one way propagation is involved. Because of the different signal processing used, the minimum detectable signal to noise ratio will be different. The equation for determining the performance of passive sonar is: SL à ¢Ã‹â€ Ã¢â‚¬â„¢ TL = NL à ¢Ã‹â€ Ã¢â‚¬â„¢ DI + DT where SL is the source level, TL is the transmission loss, NL is the noise level, DI is the directivity index of the array (an approximation to the array gain) and DT is the detection threshold. The figure of merit of passive sonar is: FOM = SL + DI à ¢Ã‹â€ Ã¢â‚¬â„¢ (NL + DT). Warfare Modern naval warfare makes extensive use of both passive and active sonar from water-borne vessels, aircraft and fixed installations. The relative usefulness of active versus passive sonar depends on the radiated noise characteristics of the target, generally a submarine. Although in WW II active sonar was used by surface craft-submarines avoided emitting pings which revealed their presence and position-with the advent of modern signal-processing passive sonar became preferred for initial detection. Submarines were then designed for quieter operation, and active sonar is now more used. In 1987 a division of Japanese company Toshiba reportedly sold machinery to the Soviet Union that allowed it to mill submarine propeller blades so that they became radically quieter, creating a huge security issue with their newer generation of submarines. Active sonar gives the exact bearing to a target, and sometimes the range. Active sonar works the same way as radar: a signal is emitted. The sound wave then travels in many directions from the emitting object. When it hits an object, the sound wave is then reflected in many other directions. Some of the energy will travel back to the emitting source. The echo will enable the sonar system or technician to calculate, with many factors such as the frequency, the energy of the received signal, the depth, the water temperature, the position of the reflecting object, etc. Active sonar is used when the platform commander determines that it is more important to determine the position of a possible threat submarine than it is to conceal his own position. With surface ships it might be assumed that the threat is already tracking the ship with satellite data. Any vessel around the emitting sonar will detect the emission. Having heard the signal, it is easy to identify the sonar equipment used and its position. Active sonar is similar to radar in that, while it allows detection of targets at a certain range, it also enables the emitter to be detected at a far greater range, which is undesirable. Since active sonar reveals the presence and position of the operator, and does not allow exact classification of targets, it is used by fast (planes, helicopters) and by noisy platforms but rarely by submarines. When active sonar is used by surface ships or submarines, it is typically activated very briefly at intermittent periods to minimize the risk of detection. Consequently active sonar is normally considered a backup to passive sonar. In aircraft, active sonar is used in the form of disposable son buoys that are dropped in the aircrafts patrol area or in the vicinity of possible enemy sonar contacts. Passive sonar has several advantages. Most importantly, it is silent. If the target radiated noise level is high enough, it can have a greater range than active sonar, and allows the target to be identified. Since any motorized object makes some noise, it may in principle be detected, depending on the level of noise emitted and the ambient noise level in the area, as well as the technology used. To simplify, passive sonar sees around the ship using it. On a submarine, nose-mounted passive sonar detects in directions of about 270 °, centered on the ships alignment, the hull-mounted array of about 160 ° on each side, and the towed array of a full 360 °. The invisible areas are due to the ships own interference. Once a signal is detected in a certain direction (which means that something makes sound in that direction, this is called broadband detection) it is possible to zoom in and analyze the signal received (narrowband analysis). This is generally done using a Fourier transform to show the different frequencies making up the sound. Since every engine makes a specific sound, it is straightforward to identify the object. Databases of unique engine sounds are part of what is known as acoustic intelligence or ACINT. Another use of passive sonar is to determine the targets trajectory. This process is called Target Motion Analysis (TMA), and the resultant solution is the targets range, course, and speed. TMA is done by marking from which direction the sound comes at different times, and comparing the motion with that of the operators own ship. Changes in relative motion are analyzed using standard geometrical techniques along with some assumptions about limiting cases. Passive sonar is stealthy and very useful. However, it requires high-tech electronic components and is costly. It is generally deployed on expensive ships in the form of arrays to enhance detection. Surface ships use it to good effect; it is even better used by submarines, and it is also used by airplanes and helicopters, mostly to a surprise effect, since submarines can hide under thermal layers. If a submarines commander believes he is alone, he may bring his boat closer to the surface and be easier to detect, or go deeper and faster, and thus make sounder. Examples of sonar applications in military use are given below. Many of the civil uses given in the following section may also be applicable to naval use. Anti-submarine warfare Variable Depth Sonar and its winch until recently, ship sonars were usually with hull mounted arrays, either amidships or at the bow. It was soon found after their initial use that a means of reducing flow noise was required. The first were made of canvas on a framework, and then steel ones were used. Now domes are usually made of reinforced plastic or pressurized rubber. Such sonars are primarily active in operation. An example of conventional hull mounted sonar is the SQS-56. Because of the problems of ship noise, towed sonars are also used. These also have the advantage of being able to be placed deeper in the water. However, there are limitations on their use in shallow water. These are called towed arrays (linear) or variable depth sonars (VDS) with 2/3D arrays. A problem is that the winches required to deploy/recover these are large and expensive. VDS sets are primarily active in operation while towed arrays are passive. An example of a modern active/passive ship towed sonar is Sonar 2087 made by Thales Underwater Systems. Torpedoes Modern torpedoes are generally fitted with active/passive sonar. This may be used to home directly on the target, but wake following torpedoes are also used. An early example of an acoustic homer was the Mark 37 torpedo. Torpedo countermeasures can be towed or free. An early example was the German Sieglinde device while the Pillenwerfer was a chemical device. A widely used US device was the towed Nixie while MOSS submarine simulator was a free device. A modern alternative to the Nixie system is the UK Royal Navy S2170 Surface Ship Torpedo Defense system. Mines Mines may be fitted with a sonar to detect, localize and recognize the required target. Further information is given in acoustic mine and an example is the CAPTOR mine. Mine countermeasures Mine Countermeasure (MCM) Sonar, sometimes called Mine and Obstacle Avoidance Sonar (MOAS), is a specialized type of sonar used for detecting small objects. Most MCM sonars are hull mounted but a few types are VDS design. An example of a hull mounted MCM sonar is the Type 2193 while the SQQ-32 Mine-hunting sonar and Type 2093 systems are VDS designs. See also Minesweeper (ship) Submarine navigation Submarines rely on sonar to a greater extent than surface ships as they cannot use radar at depth. The sonar arrays may be hull mounted or towed. Information fitted on typical fits is given in Yoshiro class submarine and Swift sure class submarine. Aircraft Helicopters can be used for antisubmarine warfare by deploying fields of active/passive son buoys or can operate dipping sonar, such as the AQS-13. Fixed wing aircraft can also deploy son buoys and have greater endurance and capacity to deploy them. Processing from the son buoys or dipping sonar can be on the aircraft or on ship. Helicopters have also been used for mine countermeasure missions using towed sonars such as the AQS-20A Ocean surveillance For many years, the United States operated a large set of passive sonar arrays at various points in the worlds oceans, collectively called Sound Surveillance System (SOSUS) and later Integrated Undersea Surveillance System (IUSS). A similar system is believed to have been operated by the Soviet Union. As permanently mounted arrays in the deep ocean were utilized, they were in very quiet conditions so long ranges could be achieved. Signal processing was carried out using powerful computers ashore. With the ending of the Cold War a SOSUS array has been turned over to scientific use. Underwater security Sonar can be used to detect frogmen and other scuba divers. This can be applicable around ships or at entrances to ports. Active sonar can also be used as a deterrent and/or disablement mechanism. One such device is the Cerberus system. Hand-held sonar Limpet Mine Imaging Sonar (LIMIS) is hand-held or ROV-mounted imaging sonar designed for patrol divers (combat frogmen or clearance divers) to look for limpet mines in low visibility water. The LUIS is imaging sonar for use by a diver. Integrated Navigation Sonar System (INSS) is small flashlight-shaped handheld sonar for divers that display range. Intercept sonar This is sonar designed to detect and locate the transmissions from hostile active sonars. An example of this is the Type 2082 fitted on the British Vanguard class submarines. Uses in daily life Fisheries Fishing is an important industry that is seeing growing demand, but world catch tonnage is falling as a result of serious resource problems. The industry faces a future of continuing worldwide consolidation until a point of sustainability can be reached. However, the consolidation of the fishing fleets are driving increased demands for sophisticated fish finding electronics such as sensors, sounders and sonars. Historically, fishermen have used many different techniques to find and harvest fish. However, acoustic technology has been one of the most important driving forces behind the development of the modern commercial fisheries. Sound waves travel differently through fish than through water because a fishs air-filled swim bladder has a different density than seawater. This density difference allows the detection of schools of fish by using reflected sound. Acoustic technology is especially well suited for underwater applications since sound travels farther and faster underwater than in air. Today, commercial fishing vessels rely almost completely on acoustic sonar and sounders to detect fish. Fishermen also use active sonar and echo sounder technology to determine water depth, bottom contour, and bottom composition. Cabin display of fish finder sonar Companies such as Ray marine UK makes a variety of sonar and acoustic instruments for the deep sea commercial fishing industry. For example, net sensors take various underwater measurements and transmit the information back to a receiver onboard a vessel. Each sensor is equipped with one or more acoustic transducers depending on its specific function. Data is transmitted from the sensors using wireless acoustic telemetry and is received by a hull mounted hydrophone. The analog signals are decoded and converted by a digital acoustic receiver into data which is transmitted to a bridge computer for graphical display on a high resolution monitor. Echo sounding An echo-sounder sends an acoustic pulse directly downwards to the seabed and records the returned echo. The sound pulse is generated by a transducer that emits an acoustic pulse and then listens for the return signal. The time for the signal to return is recorded and converted to a depth measurement by calculating the speed of sound in water. As the speed of sound in water is around 1,500 meters per second, the time interval, measured in milliseconds, between the pulse being transmitted and the echo being received, allows bottom depth and targets to be measured. The value of underwater acoustics to the fishing industry has led to the development of other acoustic instruments that operate in a similar fashion to echo-sounders but, because their function is slightly different from the initial model of the echo-sounder, have been given different terms. Net location The net sounder is an echo sounder with a transducer mounted on the headline of the net rather than on the bottom of the vessel. Nevertheless, to accommodate the distance from the transducer to the display unit, which is much greater than in a normal echo-sounder, several refinements have to be made. Two main types are available. The first is the cable type in which the signals are sent along a cable. In this case there has to be the provision of a cable drum on which to haul, shoot and stow the cable during the different phases of the operation. The second type is the cable less net-sounder such as Marports Trawl Explorer in which the signals are sent acoustically between the net and hull mounted receiver/hydrophone on the vessel. In this case no cable drum is required but sophisticated electronics are needed at the transducer and receiver. The display on a net sounder shows the distance of the net from the bottom (or the surface), rather than the depth of water as with the echo-sounders hull-mounted transducer. Fixed to the headline of the net, the footrope can usually be seen which gives an indication of the net performance. Any fish passing into the net can also be seen, allowing fine adjustments to be made to catch the most fish possible. In other fisheries, where the amount of fish in the net is important, catch sensor transducers are mounted at various positions on the cod-end of the net. As the cod-end fills up these catch sensor transducers are triggered one by one and this information is transmitted acoustically to display monitors on the bridge of the vessel. The skipper can then decide when to haul the net. Modern versions of the net sounder, using multiple element transducers, function more like sonar than an echo sounder and show slices of the area in front of the net and not merely the vertical view that the initial net sounders used. The sonar is an echo-sounder with a directional capability that can show fish or other objects around the vessel good Ship velocity measurement Sonars have been developed for measuring a ships velocity either relative to the water or to the bottom. Scientific applicationsà   Biomass estimation Detection of fish, and other marine and aquatic life, and estimation their individual sizes or total biomass using active sonar techniques. As the sound pulse travels through water it encounters objects that are of different density or acoustic characteristics than the surrounding medium, such as fish, that reflect sound back toward the sound source. These echoes provide information on fish size, location, abundance and behavior. Data is usually processed and analyzed using a variety of software such as Echo view. Wave measurement An upward looking echo sounder mounted on the bottom or on a platform may be used to make measurements of wave height and period. From this statistics of the surface conditions at a location can be derived. Water velocity measurem

American Women Leaving the Home and Going to Work Essay -- Working-Wom

One of the most significant sociological changes in the nation's history began in the last decade of the nineteenth century and the ramifications are still being felt today. This change consisted of the large numbers of women who entered the work force. This dramatic change in American society was accompanied by a great deal of controversy and prejudice directed towards women. It was predicted that female employment would bring about the downfall of society and the change of the American family. While a large portion of the public was appalled by the thought of independent young working women, they were also fascinated. Therefore, the attitudes of the public toward these women can be seen in the literature that was produced at that time. The works of Edith Wharton and Theodore Dreiser immediately come to mind as dramatizations of the life of women of this period. Slowly, attitudes began to change. The employment opportunities for women enlarged and women began to slowly gain their rights as full citizens, finally receiving the right to vote in 1920. The attitudes of the women in the work force also changed as time progressed. At first, they struggled for even the opportunity to work. As the century progressed, they became more active in union activities and, as newspapers from the period demonstrate, they fought to achieve better working conditions and better wages. By 1900, many poor and working-class young women, mostly of Northern white extraction, were leaving the confines and moral structures of their families and elders and venturing forth to the large industrial cities such as New York (Lunbeck 781). There they became enthusiastic participants of the new pleasures that were offered to consumers in the brand-new century. Essentially, these young women added a stage to the female life cycle that had not previously existed à ±adolescence (Lunbeck 781). In the 1890s, female factory workers were seen as a serious economic and social threat. Because women generally worked at the bottom of the pay scale, the theory was that they depressed the overall pay scale for all workers (Kessler-Harris 98). Many solutions were suggested at this time that all revolved around the idea of these women getting marriedà ³the idea being that a married woman would not work for wages. Although this idea seems ludicrous from a modern perspective, it should be noted that t... ...Times (1913): 12 January, p. 7. Connell, Eileen. "Edith Wharton joins the working classes : 'The House of Mirth' and The New York City Working Girls' Clubs," Women's Studies, v26 n6 (1997): November, pp. 557-604. Dreiser, Theodore. "Sister Carrie". Dover Publications, 2004. Fennell, Dorothy E. "Common Sense and a Little Fire: Women and Working-Class Politics in the United States, 1900-1965," Industrial and Labor Relations Review, v49 n4 (1996): July, pp. 773-774. Keep, Christopher. "The cultural work of the Type-Writer Girl," Victorian Studies, V40 n3 (1997): Spring, pp. 401-426. Web. 26 May 2015. http://www.jstor.org/stable/3829292?seq=1#page_scan_tab_contents Kessler-Harris, Alice. Out to work: a history of wage-earning women in the United States (New York: Oxford University Press, 1982). Web. 26 May 2015. http://www.jstor.org/stable/2150229?seq=1#page_scan_tab_contents Lunbeck, Elizabeth. "The 'girl problem': female sexual delinquency in New York, 1900-1930," Journal of American History; June 1996, Vol. 83 Issue 1 Web. 26 May 2015. http://connection.ebscohost.com/c/articles/48102053/the-girl-problem-female-sexual-delinquency-new-york-1900-1930

The First World War (WWI) - Trench Warfare :: World War 1 I One

  Ã‚  Ã‚  Ã‚  Ã‚  During World War I, trench warfare was very common. It was a newer technique in battles as in wars prior to the Great World War, fighting was less invasive and men merely marched at each other from opposite ends of fields and fought until only one side remained standing or a white flag was hung high in surrender. In fact in older wars, the fighting was far less dangerous to the point where battles were often times viewed by locals who watched from side lines with really no threat of getting hurt. In World War I however, the fighting had upscaled to the most sadistic type the world had ever experienced. With the industrialist wave that had overcome us in the late 1800s into the early 1900s, many technological advancements made the war a lot harsher of a scenario. Mass weaponry was being created in factories all across Europe to use for the war, and so the â€Å"old wars,† of much less casualties and danger were in the past, and the â€Å"new war,† or first World War was at the present, with heavy war machinery and severe casualties. The picture in the Stearns text book on page 808 displays a group of soldiers during World War I in the trenches, their homes and in most cases-their death beds during combat.   Ã‚  Ã‚  Ã‚  Ã‚  In this picture it is clear to see that life in the trenches was dismal and uncomfortable. Trenches were basically dug out pieces of land that soldiers fought from and sought refuge in upon returning attacks. They were not fun places to live and consisted of numbers of men packed tightly together in constant fear of their lives being taken from them before they could ever return home to their families, if they were lucky enough to reach that day! Through the expressions on these men’s faces in the picture, one can see that the trenches were very uncomfortable and unlively. The men look dirty and tired in their cave like surroundings. Disenchanted with the lives they led and the war they were there to fight, the soldiers do not look at ease or positive about their current situation. They sit cramped on the ground with no smiles or grins for the photographer of this picture. There is rubble all around them, somewhat signifying their lives as they miss their homes and families and watch their closest friends die or suffer from deadly battle wounds beside them.

Philosophy Statement :: Philosophy of Education Teaching Essays

Philosophy Statement Throughout my entire life there has always been one thing that has remained constant—there has always been some sort of teacher in my life. During my academic career, there have been teachers that I have liked and a few that I have disliked, but I have always respected them for what they accomplish on a day-to-day basis. It never occurred to me until my second year of college that I could also be a teacher. I have always participated in activities that stressed leadership, I have been a mentor for numerous children through 4-H and other youth programs. In a way I have been teaching my entire life, but I had never realized it until now. My classroom will be a place to learn and a place to develop social skills. It will include brightly colored and informational bulletin boards and seating that will depend on the classroom activity at the time. There will hopefully be at least three computers in the classroom and lots of resource and research materials available not only for me, the teacher, but also for the students. Throughout the school year projects will be assigned that will be relevant to the topic being studied at that time. As the school year progresses, projects will also be displayed around the room. Hopefully these will serve to inspire the students to learn and research new ideas on their own. The philosophy that I believe I am most similar too is John Dewey’s philosophy of Progressivism. Like Dewey I also believe that â€Å"one constant truth about the universe is the existence of change†. This is something that is not uncontrollable. As humans change their relationship with the environment that is being changed, they will change and be made different, and theoretically better, by the experience. I believe that change is very important in a classroom because one class of students is very dissimilar from another class. The teacher should be flexible so they are able to effectively teach all types of children. One of my goals would be to have my students be free-thinking and intellectual members of society. Education is a chance to utilize past experiences and to apply it to a new experience.

Describe the Main Features of the Fulling Industry in Pompeii.

Describe the main features of the fulling industry in Pompeii. The fulling industry was extremely important in Pompeii. We know this as there have been at least four fulleries found in Pompeii, the most famous of these fulleries is the Fullery of Stephanus. The Fullery of Stephanus is situated on the Via Dell Abbondanza. This Fullery was a dwelling with accommodation for the slaves working at the Fullery.Throughout the transformation of the dwelling into a Fullery the existence of the house was not lost, as the rooms were unchanged. I know that the fulling industry was important because of where the fulleries were situated, the Fullery of Stephanus was positioned on one of the main streets of Pompeii; this was important because it was surrounded by other small businesses and was next to a textile business, showing there was a strong chance that this industry was likely to be linked to other businesses especially in the cloth trade.From the evidence that has been found we know that cl oth was brought there to be washed and treated in a mixture of urine and soda, (and then trampled on which released the grease and then was bleached), we are told this by the elaborate red paintings on the walls. It also suggests that urine was collected in large pots in the streets which were used by passing pedestrians as it was a valuable resource.For the fulling industry you need good supplies of water and from the evidence of lead piping found, there was a good supply of water to the industry, this mainly would be because they could afford it; however there is also evidence that there were people and businesses were illegally taking water from the official supplies.As previously said the fulling industry was important to the Economic status of Pompeii, this is because the Eumachia building in the forum was built and paid for by family which were linked to the Fulling industry, many people believe they paid for this because of how vital it was to the cloth trade, and the wool in dustry. We also know that this industry was an important part to the city because it was involved in local politics, and fullers were believed to of stood for election. What evidence is there for the baking of bread in Pompeii?There is evidence for around 35 bakeries, and most of these in North side of town, close to the necessary supplies of grain. From the number of bakeries found archaeologists believe that bread was a staple to the Pompeian’s diet, and they would rather buy it than make it themselves. At the largest bakeries they had the facilities to grind their own wheat for the flour, as they had the mills, the bakery of Modesto being a prime example. They believe at Modesto the mills made of volcanic rock were turned by animal power.They added the grain at the top of mill which was then turned and filtered through to the bottom where it was collected on a stone tray. At Modesto there were also large ovens with the serving hatches nearby for the use of the public. We a lso know that the dough used for the bread was normally mixed by hand but on industrial scale wooden paddles were used. Once the dough was mixed it was shaped and marked by the baker. We know things were done on industrial scale because 85 carbonised loaves were found in one oven, this also shows there was a large demand for bread.The ovens found were fuelled by olive logs and large chimneys and flumes took away the smoke and some of the heat. There is evidence that there was a list of what was available on the wall, and all these were found in the oven carbonised from the eruption of Mt Vesuvius. There is also evidence that some of these loaves were sold on the street, we know this because there is a message scratched into the wall of the temple of Apollo that ‘bread is sold here’.What purpose did the Forum have in Pompeii? The Forum was not just a one building wonder; it had many functions. Not only was it the towns trading centre it was a place of religious statues a nd included a law court as well as places for business meetings. In the open space they think markets would have been held, this space was raised to the pavements and they think the road may have been closed to wheeled traffic whilst the markets were taking place.At the north end of the forum was the Temple of Jupiter and honorary arches dedicated to Drusus and to Tiberius to Germanicus. The south end of the forum was bordered by three municipal buildings. On the west side was situated the Basilica, the Temple of Apollo, the grain market and warehouse. On the east side stood the covered food market or Macellum, the sanctuary of Lares Publici, the Temple of Vespasian, and the Building of Eumachia and the Comitium. They believe the building of Eumachia possibly served as a wool market.The basilica was the main court of Law in Pompeii and was where legal business including trials would have taken place. The Temple of Apollo was next to the Basilica was a large imposing building surroun ded by 48 columns, this was paid by the local councillors which shows the wealth of Pompeii and its citizens. The Macellum, Eumachia and grain market show that Pompeii was a centre of trade in the religion and that the forum lay at the heart of this trade.The public weights and measures table at the northern end of the forum would have been used by public officials to check that sellers were being fair to their customers and selling the correct weights, which also shows that the people earned their money fairly. However at the times of the eruption the forum didn’t contain any of the statues of important citizens as they are presumed to be in safe keeping or in repair after the damages that Pompeii suffered in the earthquake of AD62 which contributed to Pompeii being a lost city.

Investment Banking Interview Essay

Standard Questions: 1. Walk me through the highlights of your resume. What is your story, walk through the decisions you have made, and how that relates to your current interest in Investment Banking.. 2. Why investment banking? Why our bank? 3. How do you value a company? 4. To what extent have you created and used financial models before? Discuss your excel modeling skills. 5. Why did you choose McCombs? 6. What other firms are you interviewing with and why? Are you interviewing with consulting firms also? What career opportunities are you exploring other than I-Banking? 7. What were your grades in college? What were your grades for the first semester at McCombs? What was your GMAT score? 8. What qualities would you consider most important for a career in I-Banking? What are your greatest strengths? What are your weaknesses? 9. What do you understand the responsibilities of an associate/summer associate to be? 10. Describe a current event in the market (i.e., LTCM at the end of 1998)? 11. What questio ns do you have for me? Always have at least two questions prepared per bank. Resume-and personality questions: †¢ Why should I take you instead of someone from Wharton? †¢ Why should I pick you over the other qualified candidates at McCombs? †¢ What made you choose your undergraduate institution? Why did you pursue a major in _____? †¢ What was your favorite class at McCombs so far? Why? †¢ What classes are you currently taking to get ready for the summer? †¢ What are your 5-10 year long term career plans? †¢ What are your proudest accomplishments? What is your most challenging professional experience? †¢ Are you a leader or a follower? Give me an example where you were successful in both roles? †¢ What do you do to relax? †¢ Tell me a joke. †¢ Who has influenced you the most, besides family members? †¢ Say you are at a meeting with a client and your MD is giving a presentation. You suddenly notice a mistake in some of the calculations, which you have prepared. Do you mention it? When? What do you say? †¢ What is one skill that you think is most relevant to Banking? †¢ You seem to like marketing, why are you interested in finance? †¢ What is one word that describes you best? †¢ How would your groupmates describe you? How would you characterize yourself in the group dynamic? If I spoke with your groupmates, what would they say you needed to improve? †¢ Highlight your quantitative accomplishments. †¢ Describe an ethical decision you had to make? †¢ What do you read? What’s your favorite book? †¢ As an associate, what tasks would you like to spend most of your time doing? What percent of each day do you see yourself spending on those tasks? †¢ What is in a pitch book? †¢ What’s been your greatest challenge since beginning McCombs? Greatest accomplishment? †¢ Describe a time you failed, why did you fail, what did you learn? †¢ Describe a time you had to work with someone you didn’t like, or with a difficult person. Finance questions: †¢ What is a LBO? Why lever up a firm? †¢ What makes an attractive LBO? †¢ From a Private Equity firm’s perspective and from a modeling perspective: What are the 3 inputs that matter for an LBO Model? o Answer: Leverage Ratio, Equity Contribution, Estimated Returns, †¢ Why might a company choose to issue debt vs. equity? †¢ What could a company do with excess cash on the balance sheet? †¢ How would you calculate a firm’s WACC? What would you use it for? †¢ What does Beta mean? Where would you find a firm’s Beta? How and why would you unlever a Beta? †¢ What is the CAPM? †¢ How do you calculate the firm value for the following firm? †¢ What would greater impact a firms valuation, a 10% reduction in revenues or 1% reduction in discount rate? †¢ What major factors affect the yield on a corporate bond? †¢ How would you evaluate the creditworthiness of manufacturer with three factories in different locations throughout the US? †¢ Company A trades at a P/E of 20. Company B trades at a P/E of 10. Both are considering acquiring Company C, which trades at a P/E of 15. For which of the two acquiring companies would the deal be dilutive. For which would it be accretive? Explain why for each. †¢ Suppose you are buying a new fixed asset – part cash and part debt. Talk through how it affects all the financial statements. Financial market questions: †¢ Where is the market going? Bond, equity and foreign exchange? Where do you think interest rates will be in the next 12 months? †¢ What happened in the markets in the past three months? †¢ Do you read the Wall Street Journal everyday? What’s on the front page today? †¢ What industry do you follow and what numbers do you look at to determine if a firm is doing well in the industry. Accounting questions: †¢ What are deferred taxes? How do they arise? †¢ What is working capital? How would you calculate it? †¢ What is EBITDA? Why is it so widely used as a proxy for Operating CF in the financial sector? †¢ Say you knew a company’s net income. How would you figure out its cash flows? †¢ Walk me through the 3 major financial statements o What are the major line items of a Cash Flow Statement. o What is the difference between the balance sheet and the income statement? †¢ What is goodwill? How does it affect net income? †¢ A firm is using LIFO, and the COGS start decreasing. What are effects on I/S, BS and CFS? †¢ What is the difference between Purchase and Pooling accounting? Under what circumstances would you use one or the other? Questions on Investment Banks: †¢ Do you understand the lifestyle issues associated with this proffesion? Why don’t you have an problem with these issues? †¢ What is your greatest concern about investment banking? †¢ Why I-Banking vs. Consulting? Sales & Trading? Research? Finance in Industry? †¢ How does your past career qualify you for a position in investment banking? Why are you not going back to prior career? †¢ What do you hope to accomplish over the summer? †¢ What department do you want to work for inside I-banking and why? †¢ Who is in the bulge bracket? †¢ Rank firms on Wall Street and where do we fit? Who is our competition (in the major categories)? What differentiates our firm? What are our firm’s strengths? Weaknesses? †¢ If you were the CEO of our firm, what major changes would you implement? †¢ Describe a typical day of an investment banking associate? Technical Questions: †¢ What makes a proposed acquisition accretive? †¢ Suppose a proposed acquisition is accretive, how would you make it less accretive? †¢ What are the main factors in determining if a deal will be accretive or dilutive? †¢ Walk me through how the purchase of equipment effects the 3 statements. †¢ Walk me through the effects on the 3 statements given that a firm has to retroactively change the method of depreciation for last year’s financial statements. Previously, the firm’s fixed assets carrying value was $100M, with no salvage value, an estimated useful life of 10 years, and straight line depreciation. The salvage value has been determined to be $50M, but the useful life of the asset and method of depreciation has not changed. o Effect on Cash? Cash Flow Statement? †¢ What is the different factors to consider when choosing between Enterprise Value and Equity Value Comps? †¢ When you are trying to scale down the number of firms in your selected Comp universe, what would you look at to decide which Comps to include and which to pull out of the Comp universe? †¢ What types of discounts/premiums would you apply after determining valuation based on a Comp valuation? Why?