Bhimrao Ramji Ambedkar was born in the British-founded town and military cantonment of Mhow in the Central Provinces (now in Madhya Pradesh). He was the 14th and last child of Ramji Maloji Sakpal and Bhimabai Murbadkar. His family was of Marathi background from the town of Ambavade in the Ratnagiri district of modern-day Maharashtra. They belonged to the Hindu Mahar caste, who were treated as untouchables and subjected to intense socio-economic discrimination. Ambedkar's ancestors had for long been in the employment of the army of the British East India Company, and his father served in the Indian Army at the Mhow cantonment. He had received a degree of formal education in Marathi and English, and encouraged his children to learn and work hard at school.
Fight against untouchability
As a leading Indian scholar, Ambedkar had been invited to testify before the Southborough Committee, which was preparing the Government of India Act 1919. At this hearing, Ambedkar argued for creating separate electorates and reservations for Dalits and other religious communities. In 1920, he began the publication of the weekly Mooknayak (Leader of the Silent) in Mumbai. Attaining popularity, Ambedkar used this journal to criticize orthodox Hindu politicians and a perceived reluctance of the Indian political community to fight caste discrimination. His speech at a Depressed Classes Conference in Kolhapur impressed the local state ruler Shahu IV, who shocked orthodox society by dining with Ambekdar. Ambedkar established a successful legal practice, and also organised the Bahishkrit Hitakarini Sabha to promote education and socio-economic uplifting of the depressed classes. By 1927 Dr. Ambedkar decided to launch active movements against untouchability. He began with public movements and marches to open up and share public drinking water resources, also he began a struggle for the right to enter Hindu temples. He led a satyagraha in Mahad to fight for the right of the untouchable community to draw water from the main water tank of the town. He was appointed to the Bombay Presidency Committee to work with the all-European Simon Commission in 1928. This commission had sparked great protests across India, and while its report was ignored by most Indians, Ambedkar himself wrote a separate set of recommendations for future constitutional reformers.
Architect of India's constitution.
Upon India's independence on August 15, 1947, the new Congress-led government invited Ambedkar to serve as the nation's first law minister, which he accepted. On August 29, Ambedkar was appointed chairman of the Constitution Drafting Committee, charged by the Assembly to write free India's new Constitution. Ambedkar won great praise from his colleagues and contemporary observers for his drafting work. In this task Ambedkar's study of sangha practice among early Buddhists and his extensive reading in Buddhist scriptures was to come to his aid. Sangha practice incorporated voting by ballot, rules of debate and precedence and the use of agendas, committees and proposals to conduct business. Sangha practice itself was modelled on the oligarchic system of governance followed by tribal republics of ancient India such as the Shakyas and the Lichchavis. Thus, although Ambedkar used Western models to give his Constitution shape, its spirit was Indian and, indeed, tribal.
The text prepared by Ambedkar provided constitutional guarantees and protections for a wide range of civil liberties for individual citizens, including freedom of religion, the abolition of untouchability and the outlawing of all forms of discrimination Ambedkar argued for extensive economic and social rights for women, and also won the Assembly's support for introducing a system of reservations of jobs in the civil services, schools and colleges for members of scheduled castes and scheduled tribes, a system akin to affirmative action. India's lawmakers hoped to eradicate the socio-economic inequalities and lack of opportunities for India's depressed classes through this measure, which had been originally envisioned as temporary on a need basis. The Constitution was adopted on November 26, 1949 by the Constituent Assembly. Speaking after the completion of his work, Ambedkar said:
Ambedkar resigned from the cabinet in 1951 following the stalling in parliament of his draft of the Hindu Code Bill, which sought to expound gender equality in the laws of inheritance, marriage and the economy. Although supported by Prime Minister Nehru, the cabinet and many other Congress leaders, it received criticism from a large number of members of parliament. Ambedkar independently contested an election in 1952 to the lower house of parliament, the Lok Sabha but was defeated. He was appointed to the upper house of parliament, the Rajya Sabha in March 1952 and would remain a member until his death.
Death / Mahaparinirvana
Since 1948, Ambedkar had been suffering from diabetes. He was bed-ridden from June to October in 1954 owing to clinical depression and failing eyesight. He had been increasingly embittered by political issues, which took a toll on his health. His health worsened as he furiously worked through 1955. Just three days after completing his final manuscript The Buddha and His Dhamma, it is said that Ambedkar died in his sleep on December 6, 1956 at his home in Delhi.
Since the Caste Hindus denied the cremation at Dadar crematorium, A Buddhist-style cremation was organised for him at Chowpatty beach on December 7, attended by hundreds of thousands of supporters, activists and admirers.
Ambedkar was survived by his second wife Savita Ambedkar and converted to Buddhism with him. His wife's name before marriage was Sharda Kabir. Savita Ambedkar died as a Buddhist in 2002. Ambedkar's grandson, Prakash Yaswant Ambedkar leads the Bharipa Bahujan Mahasangha and has served in both houses of the Indian Parliament.
Thursday, August 27, 2009
"I bequeathe myself to the dirt, to grow from the grass I love;
If you want me again, look for me under your boot-soles."
- Walt Whitman.
An ecosystem consists of the biological community that occurs in some locale, and the physical and chemical factors that make up its non-living or abiotic environment. There are many examples of ecosystems -- a pond, a forest, an estuary, a grassland. The boundaries are not fixed in any objective way, although sometimes they seem obvious, as with the shoreline of a small pond. Usually the boundaries of an ecosystem are chosen for practical reasons having to do with the goals of the particular study.
The study of ecosystems mainly consists of the study of certain processes that link the living, or biotic, components to the non-living, or abiotic, components. Energy transformations and biogeochemical cycling are the main processes that comprise the field of ecosystem ecology. As we learned earlier, ecology generally is defined as the interactions of organisms with one another and with the environment in which they occur. We can study ecology at the level of the individual, the population, the community, and the ecosystem.
Studies of individuals are concerned mostly about physiology, reproduction, development or behavior, and studies of populations usually focus on the habitat and resource needs of individual species, their group behaviors, population growth, and what limits their abundance or causes extinction. Studies of communities examine how populations of many species interact with one another, such as predators and their prey, or competitors that share common needs or resources.
In ecosystem ecology we put all of this together and, insofar as we can, we try to understand how the system operates as a whole. This means that, rather than worrying mainly about particular species, we try to focus on major functional aspects of the system. These functional aspects include such things as the amount of energy that is produced by photosynthesis, how energy or materials flow along the many steps in a food chain, or what controls the rate of decomposition of materials or the rate at which nutrients are recycled in the system.
Components of an Ecosystem
You are already familiar with the parts of an ecosystem. You have learned about climate and soils from past lectures. From this course and from general knowledge, you have a basic understanding of the diversity of plants and animals, and how plants and animals and microbes obtain water, nutrients, and food. We can clarify the parts of an ecosystem by listing them under the headings "abiotic" and "biotic".
ABIOTIC COMPONENTS
BIOTIC COMPONENTS
Sunlight Primary producers
Precipitation Carnivores
Water or moisture Omnivores
Soil or water chemistry (e.g., P, NH4+) Detritivores
etc. etc.
All of these vary over space/time
By and large, this set of environmental factors is important almost everywhere, in all ecosystems.
Usually, biological communities include the "functional groupings" shown above. A functional group is a biological category composed of organisms that perform mostly the same kind of function in the system; for example, all the photosynthetic plants or primary producers form a functional group. Membership in the functional group does not depend very much on who the actual players (species) happen to be, only on what function they perform in the ecosystem.
Processes of Ecosystems
This figure with the plants, zebra, lion, and so forth illustrates the two main ideas about how ecosystems function: ecosystems have energy flows and ecosystems cycle materials. These two processes are linked, but they are not quite the same.
Energy enters the biological system as light energy, or photons, is transformed into chemical energy in organic molecules by cellular processes including photosynthesis and respiration, and ultimately is converted to heat energy. This energy is dissipated, meaning it is lost to the system as heat; once it is lost it cannot be recycled. Without the continued input of solar energy, biological systems would quickly shut down. Thus the earth is an open system with respect to energy.
Elements such as carbon, nitrogen, or phosphorus enter living organisms in a variety of ways. Plants obtain elements from the surrounding atmosphere, water, or soils. Animals may also obtain elements directly from the physical environment, but usually they obtain these mainly as a consequence of consuming other organisms. These materials are transformed biochemically within the bodies of organisms, but sooner or later, due to excretion or decomposition, they are returned to an inorganic state. Often bacteria complete this process, through the process called decomposition or mineralization (see previous lecture on microbes).
During decomposition these materials are not destroyed or lost, so the earth is a closed system with respect to elements (with the exception of a meteorite entering the system now and then). The elements are cycled endlessly between their biotic and abiotic states within ecosystems. Those elements whose supply tends to limit biological activity are called nutrients.
The Transformation of Energy
The transformations of energy in an ecosystem begin first with the input of energy from the sun. Energy from the sun is captured by the process of photosynthesis. Carbon dioxide is combined with hydrogen (derived from the splitting of water molecules) to produce carbohydrates (CHO). Energy is stored in the high energy bonds of adenosine triphosphate, or ATP (see lecture on photosynthesis).
The prophet Isaah said "all flesh is grass", earning him the title of first ecologist, because virtually all energy available to organisms originates in plants. Because it is the first step in the production of energy for living things, it is called primary production (click here for a primer on photosynthesis). Herbivores obtain their energy by consuming plants or plant products, carnivores eat herbivores, and detritivores consume the droppings and carcasses of us all.
which energy from the sun, captured by plant photosynthesis, flows from trophic level to trophic level via the food chain. A trophic level is composed of organisms that make a living in the same way, that is they are all primary producers (plants), primary consumers (herbivores) or secondary consumers (carnivores). Dead tissue and waste products are produced at all levels. Scavengers, detritivores, and decomposers collectively account for the use of all such "waste" -- consumers of carcasses and fallen leaves may be other animals, such as crows and beetles, but ultimately it is the microbes that finish the job of decomposition. Not surprisingly, the amount of primary production varies a great deal from place to place, due to differences in the amount of solar radiation and the availability of nutrients and water.
For reasons that we will explore more fully in subsequent lectures, energy transfer through the food chain is inefficient. This means that less energy is available at the herbivore level than at the primary producer level, less yet at the carnivore level, and so on. The result is a pyramid of energy, with important implications for understanding the quantity of life that can be supported.
Usually when we think of food chains we visualize green plants, herbivores, and so on. These are referred to as grazer food chains, because living plants are directly consumed. In many circumstances the principal energy input is not green plants but dead organic matter. These are called detritus food chains. Examples include the forest floor or a woodland stream in a forested area, a salt marsh, and most obviously, the ocean floor in very deep areas where all sunlight is extinguished 1000's of meters above. In subsequent lectures we shall return to these important issues concerning energy flow.
Finally, although we have been talking about food chains, in reality the organization of biological systems is much more complicated than can be represented by a simple "chain". There are many food links and chains in an ecosystem, and we refer to all of these linkages as a food web. Food webs can be very complicated, where it appears that "everything is connected to everything else", and it is important to understand what are the most important linkages in any particular food web.
Biogeochemistry
How can we study which of these linkages in a food web are most important? One obvious way is to study the flow of energy or the cycling of elements. For example, the cycling of elements is controlled in part by organisms, which store or transform elements, and in part by the chemistry and geology of the natural world. The term Biogeochemistry is defined as the study of how living systems influence, and are controlled by, the geology and chemistry of the earth. Thus biogeochemistry encompasses many aspects of the abiotic and biotic world that we live in.
There are several main principles and tools that biogeochemists use to study earth systems. Most of the major environmental problems that we face in our world toady can be analyzed using biogeochemical principles and tools. These problems include global warming, acid rain, environmental pollution, and increasing greenhouse gases. The principles and tools that we use can be broken down into 3 major components: element ratios, mass balance, and element cycling.
1. Element ratios
In biological systems, we refer to important elements as "conservative". These elements are often nutrients. By "conservative" we mean that an organism can change only slightly the amount of these elements in their tissues if they are to remain in good health. It is easiest to think of these conservative elements in relation to other important elements in the organism. For example, in healthy algae the elements C, N, P, and Fe have the following ratio, called the Redfield ratio after the oceanographer who discovered it:
C : N : P : Fe = 106 : 16 : 1 : 0.01
Once we know these ratios, we can compare them to the ratios that we measure in a sample of algae to determine if the algae are lacking in one of these limiting nutrients.
2. Mass Balance
Another important tool that biogeochemists use is a simple mass balance equation to describe the state of a system. The system could be a snake, a tree, a lake, or the entire globe. Using a mass balance approach we can determine whether the system is changing and how fast it is changing. The equation is:
NET CHANGE = INPUT + OUTPUT + INTERNAL CHANGE
In this equation the net change in the system from one time period to another is determined by what the inputs are, what the outputs are, and what the internal change in the system was. The example given in class is of the acidification of a lake, considering the inputs and outputs and internal change of acid in the lake.
3. Element Cycling
Element cycling describes where and how fast elements move in a system. There are two general classes of systems that we can analyze, as mentioned above: closed and open systems.
A closed system refers to a system where the inputs and outputs are negligible compared to the internal changes. Examples of such systems would include a bottle, or our entire globe. There are two ways we can describe the cycling of materials within this closed system, either by looking at the rate of movement or at the pathways of movement.
1. Rate = number of cycles / time * as rate increases, productivity increases
2. Pathways-important because of different reactions that may occur
In an open system there are inputs and outputs as well as the internal cycling. Thus we can describe the rates of movement and the pathways, just as we did for the closed system, but we can also define a new concept called the residence time. The residence time indicates how long on average an element remains within the system before leaving the system.
1. Rate
2. Pathways
3. Residence time, Rt
Rt = total amount of matter / output rate of matter
(Note that the "units" in this calculation must cancel properly)
Controls on Ecosystem Function
Now that we have learned something about how ecosystems are put together and how materials and energy flow through ecosystems, we can better address the question of "what controls ecosystem function"? There are two dominant theories of the control of ecosystems. The first, called bottom-up control, states that it is the nutrient supply to the primary producers that ultimately controls how ecosystems function. If the nutrient supply is increased, the resulting increase in production of autotrophs is propagated through the food web and all of the other trophic levels will respond to the increased availability of food (energy and materials will cycle faster).
The second theory, called top-down control, states that predation and grazing by higher trophic levels on lower trophic levels ultimately controls ecosystem function. For example, if you have an increase in predators, that increase will result in fewer grazers, and that decrease in grazers will result in turn in more primary producers because fewer of them are being eaten by the grazers. Thus the control of population numbers and overall productivity "cascades" from the top levels of the food chain down to the bottom trophic levels.
So, which theory is correct? Well, as is often the case when there is a clear dichotomy to choose from, the answer lies somewhere in the middle. There is evidence from many ecosystem studies that BOTH controls are operating to some degree, but that NEITHER control is complete. For example, the "top-down" effect is often very strong at trophic levels near to the top predators, but the control weakens as you move further down the food chain. Similarly, the "bottom-up" effect of adding nutrients usually stimulates primary production, but the stimulation of secondary production further up the food chain is less strong or is absent.
Thus we find that both of these controls are operating in any system at any time, and we must understand the relative importance of each control in order to help us to predict how an ecosystem will behave or change under different circumstances, such as in the face of a changing climate.
The Geography of Ecosystems
There are many different ecosystems: rain forests and tundra, coral reefs and ponds, grasslands and deserts. Climate differences from place to place largely determine the types of ecosystems we see. How terrestrial ecosystems appear to us is influenced mainly by the dominant vegetation.
The word "biome" is used to describe a major vegetation type such as tropical rain forest, grassland, tundra, etc., extending over a large geographic area (Figure 3). It is never used for aquatic systems, such as ponds or coral reefs. It always refers to a vegetation category that is dominant over a very large geographic scale, and so is somewhat broader than an ecosystem .
We can draw upon previous lectures to remember that temperature and rainfall patterns for a region are distinctive. Every place on earth gets the same total number of hours of sunlight each year, but not the same amount of heat. The sun's rays strike low latitudes directly but high latitudes obliquely. This uneven distribution of heat sets up not just temperature differences, but global wind and ocean currents that in turn have a great deal to do with where rainfall occurs. Add in the cooling effects of elevation and the effects of land masses on temperature and rainfall, and we get a complicated global pattern of climate.
A schematic view of the earth shows that, complicated though climate may be, many aspects are predictable (Figure 4). High solar energy striking near the equator ensures nearly constant high temperatures and high rates of evaporation and plant transpiration. Warm air rises, cools, and sheds its moisture, creating just the conditions for a tropical rain forest. Contrast the stable temperature but varying rainfall of a site in Panama with the relatively constant precipitation but seasonally changing temperature of a site in New YorkState. Every location has a rainfall- temperature graph that is typical of a broader region.
We can draw upon plant physiology to know that certain plants are distinctive of certain climates, creating the vegetation appearance that we call biomes. Note how well the distribution of biomes plots on the distribution of climates (Figure 5). Note also that some climates are impossible, at least on our planet. High precipitation is not possible at low temperatures -- there is not enough solar energy to power the water cycle, and most water is frozen and thus biologically unavailable throughout the year. The high tundra is as much a desert as is the Sahara.
Global warming has been and is being caused due to a various number of factors. Global warming is basically a change in the climatic conditions of the earth. These climatic conditions vary due to various reason, external and internal. Changes to climatic conditions and therefore Global Warming can be caused to to natural or man-made circumstances also. Some of the factors causing global warming are volcanic emissions and solar activity.
According to the solar variation theory,the sun has been gaining strength and is at it's strongest since a sixty years. Therefore, it may now be acting as a cause of global warming. Sunspots are also said to be a cause or catalyst for Global Warming. Recent reports suggest that the number of sunspots in an area directly affects the amount of time the nearby earth takes to cool. The sun is the main source of energy to the earth. The earth absorbs about seventy percent of the earth's solar flux. This solar flux increases the temperature of the earth's atmosphere, land and oceans.
Orbital forcing is also said to be one of the natural causes of Global Warming. The reports show the effect of the slow tilting of the earth's axis on the climate of the earth.The greenhouse effect is said to be the most important factor regarding global warming. When infrared radiation from the atmosphere increases the temperature of the earth's surface, it is termed as the greenhouse effect. The greenhouse effect has increased the earth's temperature by about twenty four percent.
Carbon dioxide contributes about twelve percent of the greenhouse effect, while water vapor contributes thirty six percent of the greenhouse effect. Methane causes five to ten percent of Global Warming, while Ozone makes around three to seven percent of the greenhouse effect possible.
Solar variation is said to be another reason of Global Warming. The changes in the amount of radiant energy emitted by the Sun are known as solar variation. This solar variation has been correlated with the changes in the Earth's climate and temperature.
Along with the natural causes of Global Warming, scientists have also contributed rapid industrialization to the increase of Global Warming today.Humans had first affected global warming some eight thousand years ago, with the start of agriculture. Due to the clearing of the forests for agriculture, the amount of carbon dioxide in the atmosphere increased drastically.
Scientists are of the opinion that industrialization releases various gases like carbon-dioxide and methane which are known to contribute to Global Warming. Deforestation is also said to increase global warming. Trees contain a high level of carbon, and therefore their cutting creates an increase of carbon in the atmosphere. Humankind also contributes to the increase of carbon dioxide by the burning of fossil fuels. The contribution of humankind to global warming due to the burning of fossil fuels has increased by about eighty percent in the past twenty years.
If the greenhouse effect didn't exist, the temperature of the earth would be around twenty seven Celsius less. Some scientists are of the opinion that human life would be impossible on planet earth if the temperature would be so less.
The average surface temperature of Earth is maintained by a balance of various forms of solar and terrestrial radiation. Solar radiation is often called “shortwave” radiation because the frequencies of the radiation are relatively high and the wavelengths relatively short—close to the visible portion of the electromagnetic spectrum. Terrestrial radiation, on the other hand, is often called “longwave” radiation because the frequencies are relatively low and the wavelengths relatively long—somewhere in the infrared part of the spectrum. Downward-moving solar energy is typically measured in watts per square metre. The energy of the total incoming solar radiation at the top of Earth’s atmosphere (the so-called “solar constant”) amounts roughly to 1,366 watts per square metre annually. Adjusting for the fact that only one-half of the planet’s surface receives solar radiation at any given time, the average surface insolation is 342 watts per square metre annually.
The amount of solar radiation absorbed by Earth’s surface is only a small fraction of the total solar radiation entering the atmosphere. For every 100 units of incoming solar radiation, roughly 30 units are reflected back to space by either clouds, the atmosphere, or reflective regions of Earth’s surface. This reflective capacity is referred to as Earth’s planetary albedo, and it need not remain fixed over time, since the spatial extent and distribution of reflective formations, such as clouds and ice cover, can change. The 70 units of solar radiation that are not reflected may be absorbed by the atmosphere, clouds, or the surface. In the absence of further complications, in order to maintain thermodynamic equilibrium, Earth’s surface and atmosphere must radiate these same 70 units back to space. Earth’s surface temperature (and that of the lower layer of the atmosphere essentially in contact with the surface) is tied to the magnitude of this emission of outgoing radiation according to the Stefan-Boltzmann law.
Earth’s energy budget is further complicated by the greenhouse effect. Trace gases with certain chemical properties—the so-called greenhouse gases, mainly carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)—absorb some of the infrared radiation produced by Earth’s surface. Because of this absorption, some fraction of the original 70 units does not directly escape to space. Because greenhouse gases emit the same amount of radiation they absorb and because this radiation is emitted equally in all directions (that is, as much downward as upward), the net effect of absorption by greenhouse gases is to increase the total amount of radiation emitted downward toward Earth’s surface and lower atmosphere. To maintain equilibrium, Earth’s surface and lower atmosphere must emit more radiation than the original 70 units. Consequently, the surface temperature must be higher. This process is not quite the same as that which governs a true greenhouse, but the end effect is similar. The presence of greenhouse gases in the atmosphere leads to a warming of the surface and lower part of the atmosphere (and a cooling higher up in the atmosphere) relative to what would be expected in the absence of greenhouse gases.
It is essential to distinguish the “natural,” or background, greenhouse effect from the “enhanced” greenhouse effect associated with human activity. The natural greenhouse effect is associated with surface warming properties of natural constituents of Earth’s atmosphere, especially water vapour, carbon dioxide
, and methane. The existence of this effect is accepted by all scientists. Indeed, in its absence, Earth’s average temperature would be approximately 33 °C (59 °F) colder than today, and Earth would be a frozen and likely uninhabitable planet. What has been subject to controversy is the so-called enhanced greenhouse effect, which is associated with increased concentrations of greenhouse gases caused by human activity. In particular, the burning of fossil fuels raises the concentrations of the major greenhouse gases in the atmosphere, and these higher concentrations have the potential to warm the atmosphere by several degrees.
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors — the transformer's coils. A varying current in the first or primary winding creates a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the "secondary" winding. This effect is called mutual induction.
If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of turns in the secondary (NS) to the number of turns in the primary (NP) as follows:
Transformers come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions of national power grids. All operate with the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for household ("mains") voltage. Transformers are essential for high voltage power transmission, which makes long distance transmission economically practical.
An autotransformer has only a single winding with two end terminals, plus a third at an intermediate tap point. The primary voltage is applied across two of the terminals, and the secondary voltage taken from one of these and the third terminal. The primary and secondary circuits therefore have a number of windings turns in common. Since the volts-per-turn is the same in both windings, each develops a voltage in proportion to its number of turns. An adjustable autotransformer is made by exposing part of the winding coils and making the secondary connection through a sliding brush, giving a variable turns ratio. Such a device is often referred to as a variac.
For three-phase supplies, a bank of three individual single-phase transformers can be used, or all three phases can be incorporated as a single three-phase transformer. In this case, the magnetic circuits are connected together, the core thus containing a three-phase flow of flux. A number of winding configurations are possible, giving rise to different attributes and phase shifts. One particular polyphase configuration is the zigzag transformer, used for grounding and in the suppression of harmonic currents.
the below are some other transformers. Leakage transformers Resonant transformers Audio transformers Instrument transformers Voltage transformers current transformer
The first successful light bulb filaments were made of carbon (from carbonized paper or bamboo), later replaced with tungsten. improve the efficiency of the lamp, the filament usually consists of coils of fine wire, also known as a 'coiled coil.' For a 60-watt 120-volt lamp, the uncoiled length of the tungsten filament is usually 22.8 inches or 580 mm , and the filament diameter is 0.0018 inches (0.045 mm).
The advantage of the coiled coil is that evaporation of the tungsten filament is at the rate of a tungsten cylinder having a diameter equal to that of the coiled coil. Due to the coils creating gaps, such a filament has a lower surface area than the perceived surface area of the filament, and so evaporation is reduced. If the filament is then run hotter to bring back evaporation to the same rate, the resulting filament is a more efficient light sou
There are several different shapes of filament used in lamps, with differing characteristics. Manufacturers designate the types with codes such as C-6, CC-6, C-2V, CC-2V, C-8, CC-88, C-2F, CC-2F, C-Bar, C-Bar-6, C-8I, C-2R, CC-2R, and Axial.
Filaments is a library package that can be used to create architecture-independent parallel programs---that is, programs that are portable efficient across vastly different parallel machines. Filaments virtualizes the underlying machine in terms of the number of processors and the interconnection. This simplifies parallel program design in two ways. First, programs can be written (or generated) with the focus on the parallelism inherent in the application, not the architecture.
1. Outline of Glass bulb 2. Low pressure inert gas (argon, neon, nitrogen) 3. Tungsten filament 4. Contact wire (goes out of stem) 5. Contact wire (goes into stem) 6. Support wires 7. Stem (glass mount) 8. Contact wire (goes out of stem) 9. Cap (sleeve) 10 Insulation (vitrite) 11 Electrical contact
Second, programs can be written that use familiar shared-variable communication. Furthermore, Filaments uses a carefully designed API along with machine-specific runtime libraries and preprocessing that allow programs to run unchanged on both shared- and distributed-memory machines. Most importantly, applications programmed in Filaments run efficiently, achieving a speedup of over 4 on 8 processors or nodes in almost all tests that have been performed.
When the earth formed some 4.6 billion years ago, it was a lifeless, inhospitable place. A billion years later it was teeming with organisms resembling blue-green algae.
How did they get there?
How, in short, did life begin?
This long-standing question continues to generate fascinating conjectures and ingenious experiments, many of which center on the possibility that the advent of self-replicating RNA was a critical milestone on the road to life.
Before the mid-17th century, most people believed that God had created humankind and other higher organisms and that insects, frogs and other small creatures could arise spontaneously in mud or decaying matter. For the next two centuries, those ideas were subjected to increasingly severe criticism, and in the mid-19th century two important scientific advances set the stage for modern discussions of the origin of life.
Repeated generation after generation, natural selection could thus lead to the evolution of complex organisms from simple ones. The theory therefore implied that all current life-forms could have evolved from a single, simple progenitor - an organism now referred to as life's last common ancestor. (This life-form is said to be "last" not "first" because it is the nearest shared ancestor of all contemporary organisms; more distant ancestors must have appeared earlier.)
