whose presence, abundance, and health reveal the general condition of its habitat. biomass - the total weight or volume of living matter in a given area or volume. carbon cycle - the term used to describe the exchange of carbon ( in various forms, e. g., as carbon dioxide ) between the atmosphere, ocean, terrestrial biosphere, and geological deposits. catchments - assemblages used to capture and retain rainwater and runoff ; an important water management technique in areas with limited freshwater resources, such as gibraltar. ddt ( dichloro - diphenyl - trichloro - ethane ) - a colorless, odorless insecticide that has toxic effects on most animals ; the use of ddt was banned in the us in 1972. defoliants - chemicals which cause plants to lose their leaves artificially ; often used in agricultural practices for weed control, and may have detrimental impacts on human and ecosystem health. deforestation - the destruction of vast areas of forest ( e. g., unsustainable forestry practices, agricultural and range land clearing, and the over exploitation of wood products for use as fuel ) without planting new growth. desertification - the spread of desert - like conditions in arid or semi - arid areas, due to overgrazing, loss of agriculturally productive soils, or climate change. dredging - the practice of deepening an existing waterway ; also, a technique used for collecting bottom - dwelling marine organisms ( e. g., shellfish ) or harvesting coral, often causing significant destruction of reef and ocean - floor ecosystems. drift - net fishing - done with a net, miles in extent, that is generally anchored to a boat and left to float with the tide ; often results in an over harvesting and waste of large populations of non - commercial marine species ( by - catch ) by its effect of " sweeping the ocean clean. " ecosystems - ecological units comprised of complex communities of organisms and their specific environments. effluents - waste materials, such as smoke, sewage, or industrial waste which are released into the environment, subsequently polluting it. endangered species - a species that is threatened with extinction either by direct hunting or habitat destruction. freshwater - water with very low soluble mineral content ; sources include lakes, streams, rivers, glaciers, and underground aquifers. greenhouse gas - a gas that " traps " infrared radiation in the lower atmosphere causing surface warming ; water vapor, carbon dioxide, nitrous oxide, methane, hydrofluorocarbons, and ozone are


glaciers, and underground aquifers. greenhouse gas - a gas that " traps " infrared radiation in the lower atmosphere causing surface warming ; water vapor, carbon dioxide, nitrous oxide, methane, hydrofluorocarbons, and ozone are the primary greenhouse gases in the earth ' s atmosphere. groundwater - water sources found below the surface of the earth often in naturally occurring reservoirs in permeable rock strata ; the source for wells and natural springs. highlands water project - a series of dams constructed jointly by lesotho and south africa to redirect lesotho ' s abundant water supply into a rapidly growing area in south africa ; while it is the largest infrastructure project in southern africa, it is also the most costly and controversial ; objections to the project include claims that it forces people from their homes, submerges farmlands, and squanders economic resources. inuit circumpolar conference ( icc ) - represents the roughly 150, 000 inuits of alaska, canada, greenland, and russia in international environmental issues ; a general assembly convenes every three years to determine the focus of the icc ; the most current concerns are long - range transport of pollutants, sustainable development, and climate change. metallurgical plants - industries which specialize in the science, technology, and processing of metals ; these plants produce highly concentrated and toxic wastes which can contribute to pollution of ground water and air when not properly disposed. noxious substances - injurious, very harmful to living beings. overgrazing - the grazing of animals on plant material faster than it can naturally regrow leading to the permanent loss of plant cover, a common effect of too many animals grazing limited range land. ozone shield - a layer of the atmosphere composed of ozone gas ( o3 ) that resides approximately 25 miles above the earth ' s surface and absorbs solar ultraviolet radiation that can be harmful to living organisms. poaching - the illegal killing of animals or fish, a great concern with respect to endangered or threatened species. pollution - the contamination of a healthy environment by man - made waste. potable water - water that is drinkable, safe to be consumed. salination - the process through which fresh ( drinkable ) water becomes salt ( undrinkable ) water ; hence, desalination is the reverse process ; also involves the accumulation of salts in topsoil caused by evaporation of excessive irrigation water, a process that can eventually render soil incapable of supporting crops. siltation - occurs when water channels and reservoirs


a given year, plus income earned by its citizens abroad, minus income earned by foreigners from domestic production. the factbook, following current practice, uses gdp rather than gnp to measure national production. however, the user must realize that in certain countries net remittances from citizens working abroad may be important to national well - being. this category includes the entries dealing with the system for the adoption and administration of public policy. government - note this entry includes miscellaneous government information of significance not included elsewhere. this entry gives the basic form of government. definitions of the major governmental terms are as follows. ( note that for some countries more than one definition applies. ) : absolute monarchy - a form of government where the monarch rules unhindered, i. e., without any laws, constitution, or legally organized opposition. anarchy - a condition of lawlessness or political disorder brought about by the absence of governmental authority. authoritarian - a form of government in which state authority is imposed onto many aspects of citizens ' lives. commonwealth - a nation, state, or other political entity founded on law and united by a compact of the people for the common good. communist - a system of government in which the state plans and controls the economy and a single - often authoritarian - party holds power ; state controls are imposed with the elimination of private ownership of property or capital while claiming to make progress toward a higher social order in which all goods are equally shared by the people ( i. e., a classless society ). confederacy ( confederation ) - a union by compact or treaty between states, provinces, or territories, that creates a central government with limited powers ; the constituent entities retain supreme authority over all matters except those delegated to the central government. constitutional - a government by or operating under an authoritative document ( constitution ) that sets forth the system of fundamental laws and principles that determines the nature, functions, and limits of that government. constitutional democracy - a form of government in which the sovereign power of the people is spelled out in a governing constitution. constitutional monarchy - a system of government in which a monarch is guided by a constitution whereby his / her rights, duties, and responsibilities are spelled out in written law or by custom. democracy - a form of government in which the supreme power is retained by the people, but which is usually exercised indirectly through a system of representation and delegated authority periodically renewed. democratic republic - a state in which the supreme power rests in the body of citizens entitled to vote for officers and representatives responsible to them. dictatorship - a form


, but which is usually exercised indirectly through a system of representation and delegated authority periodically renewed. democratic republic - a state in which the supreme power rests in the body of citizens entitled to vote for officers and representatives responsible to them. dictatorship - a form of government in which a ruler or small clique wield absolute power ( not restricted by a constitution or laws ). ecclesiastical - a government administrated by a church. emirate - similar to a monarchy or sultanate, but a government in which the supreme power is in the hands of an emir ( the ruler of a muslim state ) ; the emir may be an absolute overlord or a sovereign with constitutionally limited authority. federal ( federation ) - a form of government in which sovereign power is formally divided - usually by means of a constitution - between a central authority and a number of constituent regions ( states, colonies, or provinces ) so that each region retains some management of its internal affairs ; differs from a confederacy in that the central government exerts influence directly upon both individuals as well as upon the regional units. federal republic - a state in which the powers of the central government are restricted and in which the component parts ( states, colonies, or provinces ) retain a degree of self - government ; ultimate sovereign power rests with the voters who chose their governmental representatives. islamic republic - a particular form of government adopted by some muslim states ; although such a state is, in theory, a theocracy, it remains a republic, but its laws are required to be compatible with the laws of islam. maoism - the theory and practice of marxism - leninism developed in china by mao zedong ( mao tse - tung ), which states that a continuous revolution is necessary if the leaders of a communist state are to keep in touch with the people. marxism - the political, economic, and social principles espoused by 19th century economist karl marx ; he viewed the struggle of workers as a progression of historical forces that would proceed from a class struggle of the proletariat ( workers ) exploited by capitalists ( business owners ), to a socialist " dictatorship of the proletariat, " to, finally, a classless society - communism. marxism - leninism - an expanded form of communism developed by lenin from doctrines of karl marx ; lenin saw imperialism as the final stage of capitalism and shifted the focus of workers ' struggle from developed to underdeveloped countries. monarchy - a government in which the supreme power is lodged in the hands of a monarch who reigns over a state


marx ; lenin saw imperialism as the final stage of capitalism and shifted the focus of workers ' struggle from developed to underdeveloped countries. monarchy - a government in which the supreme power is lodged in the hands of a monarch who reigns over a state or territory, usually for life and by hereditary right ; the monarch may be either a sole absolute ruler or a sovereign - such as a king, queen, or prince - with constitutionally limited authority. oligarchy - a government in which control is exercised by a small group of individuals whose authority generally is based on wealth or power. parliamentary democracy - a political system in which the legislature ( parliament ) selects the government - a prime minister, premier, or chancellor along with the cabinet ministers - according to party strength as expressed in elections ; by this system, the government acquires a dual responsibility : to the people as well as to the parliament. parliamentary government ( cabinet - parliamentary government ) - a government in which members of an executive branch ( the cabinet and its leader - a prime minister, premier, or chancellor ) are nominated to their positions by a legislature or parliament, and are directly responsible to it ; this type of government can be dissolved at will by the parliament ( legislature ) by means of a no confidence vote or the leader of the cabinet may dissolve the parliament if it can no longer function. parliamentary monarchy - a state headed by a monarch who is not actively involved in policy formation or implementation ( i. e., the exercise of sovereign powers by a monarch in a ceremonial capacity ) ; true governmental leadership is carried out by a cabinet and its head - a prime minister, premier, or chancellor - who are drawn from a legislature ( parliament ). presidential - a system of government where the executive branch exists separately from a legislature ( to which it is generally not accountable ). republic - a representative democracy in which the people ' s elected deputies ( representatives ), not the people themselves, vote on legislation. socialism - a government in which the means of planning, producing, and distributing goods is controlled by a central government that theoretically seeks a more just and equitable distribution of property and labor ; in actuality, most socialist governments have ended up being no more than dictatorships over workers by a ruling elite. sultanate - similar to a monarchy, but a government in which the supreme power is in the hands of a sultan ( the head of a muslim state ) ; the sultan may be an absolute ruler or a sovereign with constitutionally limited authority. theocracy - a form of government in which a deity is


in which the supreme power is in the hands of a sultan ( the head of a muslim state ) ; the sultan may be an absolute ruler or a sovereign with constitutionally limited authority. theocracy - a form of government in which a deity is recognized as the supreme civil ruler, but the deity ' s laws are interpreted by ecclesiastical authorities ( bishops, mullahs, etc. ) ; a government subject to religious authority. totalitarian - a government that seeks to subordinate the individual to the state by controlling not only all political and economic matters, but also the attitudes, values, and beliefs of its population. greenwich mean time ( gmt ) the mean solar time at the greenwich meridian, greenwich, england, with the hours and days, since 1925, reckoned from midnight. gmt is now a historical term having been replaced by utc on 1 january 1972. see coordinated universal time. gross domestic product gross national product gross world product this entry gives the gross world product ( gwp ) or aggregate value of all final goods and services produced worldwide in a given year. this entry gives the total number of heliports with hard - surface runways, helipads, or landing areas that support routine sustained helicopter operations exclusively and have support facilities including one or more of the following facilities : lighting, fuel, passenger handling, or maintenance. it includes former airports used exclusively for helicopter operations but excludes heliports limited to day operations and natural clearings that could support helicopter landings and takeoffs. hiv / aids - adult prevalence rate this entry gives an estimate of the percentage of adults ( aged 15 - 49 ) living with hiv / aids. the adult prevalence rate is calculated by dividing the estimated number of adults living with hiv / aids at yearend by the total adult population at yearend. hiv / aids - deaths this entry gives an estimate of the number of adults and children who died of aids during a given calendar year. hiv / aids - people living with hiv / aids this entry gives an estimate of all people ( adults and children ) alive at yearend with hiv infection, whether or not they have developed symptoms of aids. household income or consumption by percentage share data on household income or consumption come from household surveys, the results adjusted for household size. nations use different standards and procedures in collecting and adjusting the data. surveys based on income will normally show a more unequal distribution than surveys based on consumption. the quality of surveys is improving with time, yet caution is still necessary in making inter - country comparisons. this entry gives information on


the physics factbook™ edited by glenn elert - - written by his students an educational, fair use website topic index | author index | special index the purpose of this lab is to determine the fractal dimension of broccoli. a fractal is an object that has a fractional spatial dimension. the dimension of a point is 0, a line is 1, a plane is 2 and a cube is 3. the dimension of a fractal that can be drawn from a line is between 1 and 2 and has infinite points and finite length. the dimension of a fractal created from a shape on a plane has a fractal dimension between 2 and 3 and has infinite length and finite area. broccoli is a fractal because it branches off into smaller and smaller pieces, which are similar in shape to the original. the fractional dimension can be calculated by : where n is the number of closed balls of diameter s needed to cover the object. in this study, the fractal dimension of a broccoli is determined by calculating the slope of the graph of ln ( n ) / ln ( s ). broccoli is especially interesting for its fractal properties. you can explore the concept of self - similarity by chopping broccoli. the fractal dimension of broccoli is the magnitude of the slope of the graph of ln ( number ) vs. ln ( size ). according to the line of best fir, the slope is 1. 5. but wait, that doesn ' t make sense since broccoli exists in three dimensions, so the fractal dimension must be somewhere near 3. something must be wrong. what should we do? let ' s get rid of the first and last data points. they are outliers that don ' t fit with the remaining points. aha! now the slope is 2. 66, which is closer to 3 and thus makes more sense. the fractal dimension of a broccoli is 2. 66. adam kapelner, vitaliy schupack, max golomshtok, johnny alicea - - 2002 chaos project pages in the physics factbook™ | another quality webpage by | home | contact bent | chaos | eworld | facts | physics


nist technologies contribute to top science stories of 2011 from nist tech beat : january 10, 2012 contact : laura ost the top science stories of 2011, as selected by several science magazines, include two experiments and a famous computer, that relied on technology from the national institute of standards and technology ( nist ). physics world ' s top breakthrough of the year was an experiment that " shifted the morals of quantum measurement " by doing something previously thought to be impossible — tracking the paths of single particles of light ( photons ) passing through two closely spaced openings. led by a university of toronto physicist, the experiment used a nist - made quantum dot as the source of single photons. the physics world story can be found at http : / / physicsworld. com / cws / article / news / 48126 and the nist contribution is described at http : / / www. nist. gov / pml / newsletter / quantum _ dot. cfm. science news and physics today highlighted experiments at the atacama cosmology telescope in chile that measured " gravitational lensing " of the cosmic microwave background and verified the existence of dark energy, believed to make up most of the universe and to drive its expansion. more than a dozen institutions collaborate on the research. the telescope camera relies on superconducting sensors based on a nist design and superconducting amplifiers and electronics made at nist. gravitational lensing refers to distortions in the afterglow of the big bang caused by the gravitational force of matter distributed across the universe. physics today editors selected the research as one of seven highlights of the most important and interesting news in physics and related sciences : http : / / www. aip. org / pt / e - alerts / ptpicks / 2011 _ 12. html ( see " the demonstration of gravitational lensing of the cosmic microwave background " ). science news included the work in its roundup of 2011 science news of the year, as one of 18 items in the atom & cosmos category : http : / / www. sciencenews. org / view / feature / id / 336994 / title / 2011 _ science _ news _ of _ the _ year _ atom _ % 2b _ cosmos ( see " dark check " entry ). several groups, including new scientist, discover magazine and national public radio, also cited one of the most - watched technology events of the year : the february 2011 victory of the ibm supercomputer watson on the tv game show jeopardy


physicists create working transistor consisting of a single atom by - - sciencedaily added : mon, 20 feb 2012 22 : 14 : 58 utc thanks to sci _ guy _ bri in a remarkable feat of micro - engineering, an international team of researchers, including physicists at the university of new south wales in australia, have created a working transistor consisting of a single atom placed precisely in a silicon crystal. the tiny electronic device, described in a paper published in the journal nature nanotechnology, uses as its active component an individual phosphorus atom patterned between atomic - scale electrodes and electrostatic control gates. this unprecedented atomic accuracy may yield the elementary building block for a future quantum computer with unparalleled computational efficiency. until now, single - atom transistors have been realised only by chance, where researchers either have had to search through many devices or tune multi - atom devices to isolate one that works. " but this device is perfect, " says professor michelle simmons, group leader and director of the arc centre for quantum computation and communication technology at unsw. " this is the first time anyone has shown control of a single atom in a substrate with this level of precise accuracy. " the microscopic device even has tiny visible markers etched onto its surface so researchers can connect metal contacts and apply a voltage, says research fellow and lead author dr martin fuechsle from unsw. mat honan - wired comments meet mat honan. he just had his digital life dissolved by hackers. photo : ariel zambelich / wired. illustration : ross patton / wired the very four digits that amazon considers unimportant enough to display in the clear on the web are precisely the same ones that apple considers secure enough to perform identity verification. sean carroll - cosmic variance -... comments launched on november 26, 2011, the mission is scheduled to land on mars ’ s gale crater tonight / tomorrow morning : 5 : 31 utc, which translates to 1 : 30 a. m. eastern time or 10 : 20 p. m. pacific. megan scudellari - thescientist 7 comments next generation : sneaking into a cell a nanoscale device measures electrical signals inside cells without causing damage polly curtis - the guardian 26 comments photograph : peter dazeley / getty images can you really be addicted to the internet? sharon begley - reuters 10 comments ion torrent ceo and chairman jonathan rothberg holds a semiconductor sequencing chip that will be used in the new proton semi - conductor based genome sequencing machine in guilford, connecticut


related forms : a closer look albert einstein ' s two theories of relativity were the first successful revisions of newtonian mechanics — a mechanics so simple and intuitive that it was held to be a permanent fixture of physics. uniting the theories is the idea that two observers traveling relative to each other may have different perceptions of time and space, yet the laws of nature are still uniform, and certain properties always remain invariant. einstein developed the first theory, the theory of special relativity ( 1905 ), to explain and extend certain consequences of maxwell ' s equations describing electromagnetism, in particular, addressing a puzzle surrounding the speed of light in a vacuum, which was predicted always to be the same, whether the light source is stationary or moving. special relativity considers the laws of nature from the point of view of frames of reference upon which no forces are acting, and describes the way time, distance, mass, and energy must be perceived by observers who are in uniform motion relative to each other if the speed of light must always turn out the same for all observers. two implications of special relativity are space and time dilation. as speed increases, space is compressed in the direction of the motion, and time slows down. a famous example is the space traveler who returns to earth younger than his earth - dwelling twin, his biological processes proceeding more slowly due to his relative speed. these effects are very small at the speeds we normally experience but become significant at speeds approaching the speed of light ( known as relativistic speeds ). perhaps the best - known implication of special relativity is the equation e = mc2, which expresses a close relation between energy and mass. the speed of light is a large number ( about 300, 000 km per second, or 186, 000 mi per second ), so the equation suggests that even small amounts of mass can be converted into enormous amounts of energy, a fact exploited by atomic power and weaponry. einstein ' s general theory of relativity extended his special theory to include non - inertial reference frames, frames acted on by forces and undergoing acceleration, as in cases involving gravity. the general theory revolutionized the way gravity, too, was understood. since einstein, gravity is seen as a curvature in space - time itself.


s high - density nonvolatile memory technology and is compatible with the industry - standard 80c51 instruction set and pinout. the at89s52 provides the following standard features : 8k bytes of flash, 256 bytes of ram, 32 i / o lines, watchdog timer, two data pointers, three 16 - bit timer / counters, a six - vector two - level interrupt architecture, a full duplex serial port, on - chip oscillator, and clock circuitry. in addition, the at89s52 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes.. the idle mode stops the cpu while allowing the ram, timer / counters, serial port, and interrupt system to continue functioning. the power - down mode saves the ram con - tents but freezes the oscillator, disabling all other chip functions until the next interrupt. the hardware is driven by a set of program instructions, or software. once familiar with hardware and software, the user can then apply the microcontroller to the problems easily. the 8051 architecture consists of these specific features : 16 bit pc & data pointer ( dptr ) 8 bit program status word ( psw ) 8 bit stack pointer ( sp ) internal rom 4k internal ram of 128 bytes. 4 register banks, each containing 8 registers 80 bits of general purpose data memory 32 input / output pins arranged as four 8 bit ports0 - p3 two 16 bit timer / counters : t0 - t1 two external and three internal interrupt sources oscillator and clock circuits gallium arsenide is a direct - gap semiconductor with an energy gap of 1. 4ev at room temperature. a typical gaps led is made by solid - state impurity diffusion with zinc as the p - type impurity diffused into an n - type substrate doped with tin, tellurium or silicon. the external efficiency at room temperature is typically 5 percent. a gaas diode can also be fabricated by liquid - phase epitaxial with silicon as both its n and p dopants. if a silicon atom replaces a ga atom, it provides one additional electron, thus the resulting gaas in as n - type. if a silicon atom replaces arsenic atoms, an electron is missing and the resulting gaas is a p - type. in si doped gaas diode, the emission peak shifts down to 1. 32ev. since the emission is in infrared region, gaa