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McGraw Hill Financial, Inc. is an American publicly traded corporation headquartered in Rockefeller Center in New York City. Its primary areas of business are financial, publishing, and business services.
Cholesterol is an essential component of mammalian cell membranes. (In general, cholesterol and structurally related compounds made by plants and fungi are collectively termed “sterols.” Virtually all eukaryotic organisms require some sort of sterol in their membranes, and the presence of sterols is evidence for the existence of eukaryotes in the fossil record.) Without sufficient cholesterol, membranes cannot work properly and cells die.
Conversely, too much cholesterol is also lethal to cells and organisms, and high levels of cholesterol in blood are a major cause of atherosclerosis in humans. Therefore, cells and organisms must maintain an exquisite balance between the cholesterol supply and cellular demand. This balancing act is regulated at just about every conceivable level, from gene transcription to enzyme activity. The global coordination of cellular cholesterol metabolism, however, is largely effected at the level of transcription of the genes of cholesterol synthesis and uptake (for example, the low-density lipoprotein (LDL) receptor, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, and HMG CoA synthase) through the action of the sterol regulatory element binding proteins (SREBPs).
In mammals, there are three different SREBPs encoded by two different genes. SREBP-1a and -1c result from the utilization of alternative transcription initiation sites of the <i>SREBF-1</i> (sterol regulatory element binding transcription factor-1) gene; SREBP-2 is encoded by the <i>SREBF-2</i> gene. In adult animals, SREBP-1c and -2 are the predominant species, with the former preferentially targeting genes of fatty acid metabolism and the latter preferentially targeting genes of cholesterol metabolism.
Industry:Science
Electronic computers, designed for durability in industrial environments, that are used for the control of machines and manufacturing processes through the implementation of specific functions such as logic, sequencing, timing, counting, and arithmetic. They are also known as programmable logic controllers (PLCs). Historically, process control of a single or a few related devices has been implemented through the use of banks of relays and relay logic for both the control of actuators and their sequencing.
The advent of small, inexpensive microprocessors and single-chip computers, or microcontroller units, brought process control from the age of simple relay control to one of electronic digital control while neither losing traditional design methods such as relay ladder diagrams nor restricting their programming to that single paradigm. The computational power of programmable controllers and their integration into networks has led to their having capabilities approaching those of distributed control systems, and plantwide control is now a mixture of distributed control systems and programmable controllers.
Applications for programmable controllers range from small-scale, local process applications in which as few as 10 simple feedback control loops are implemented, up to large-scale, remote supervisory process applications in which 50 or more process control loops spread across the facility are implemented. Typical applications include batch process control and materials handling in the chemical industry, machining and test-stand control and data acquisition in the manufacturing industry, wood cutting and chip handling in the lumber industry, filling and packaging in food industries, and furnace and rolling-mill controls in the metal industry.
Industry:Science
Gypsum (CaSO<sub>4</sub>·2H<sub>2</sub>O) is a common mineral in sedimentary environments. The crystal structure of this calcium sulfate dihydrate can be defined as alternating double-sheet layers of sulfates bound covalently by calcium ions and single-sheet layers of water molecules linked by weak hydrogen bonds. The mineral gypsum has several varieties that differ by the shape of the crystals and their textural arrangements. The variety called gypsum alabaster is made of fine-grained crystals and is used for craftworks. The satin spar variety is made of tiny fibrous crystals and has an attractive silky luster. The most famous variety of gypsum is called selenite, which is characterized by colorless and transparent crystals.
Large selenite crystals were very valuable in Roman times because they were used for covering windows, in therma (baths) and palaces. Roman stonemasons took advantage of a well-known physical property of transparent selenite crystals, namely cleavage, the ease with which some crystals split along definite planes where the atoms are weakly bonded to the adjacent layers of atoms, thus creating smooth surfaces. In the case of gypsum, that plane is pinacoid (010), which corresponds to the plane parallel to the layers of molecules in the crystal structure.
According to Pliny the Elder, the largest, high-quality selenite crystals were found in Segobriga, central Spain. This was the main source of crystals for window coverings until the introduction of the flat glass technology in the Roman Empire at the end of first century A.D. Amazing as these crystals were, they cannot be compared in size or quality with the crystal wonderland recently discovered in Naica, a mining town located 112 km (70 mi) SE of Chihuahua City in Northern Mexico.
Industry:Science
Both regional climate models and general circulation models include time-dependent partial differential equations and algebraic equations to represent the motion and physics of the atmosphere and surface properties in the climate system (such as wind, pressure, temperature, clouds, radiation, rainfall, and soil hydrology). Most regional climate models cover an area of 10<sup>5</sup>–10<sup>7</sup> km<sup>2</sup> (10<sup>4</sup>–10<sup>6</sup> mi<sup>2</sup>) with a typical resolution of 10–100 km (6–60 mi), compared to a few hundred kilometers resolution for most general circulation models, which cover the global atmosphere. Integration times for regional climate models range from a month to more than 10 years. Most regional climate models use the observed sea surface temperature or the mixed-layer ocean model for the ocean. The coupled climate model system, including the regional atmospheric model, ocean–sea ice model, and hydrology model, has also been successfully applied for studying some extreme weather events in Germany.
At the lateral boundaries, a regional climate model is driven by atmospheric wind, temperature, and humidity generated from a general circulation model output or global meteorological reanalysis, which is derived from the combination of the general circulation model output and observations. A regional climate model is, in principle, similar to the operational limited-area numerical weather forecasting models. But a regional climate model is integrated continuously over time intervals much longer than those used in numerical weather forecasting are. Consequently, lateral and surface boundary conditions become dominant in a regional climate model, while limited-area numerical weather forecasting is more dependent on the initial data.
Industry:Science
Cloning, which occurs naturally in many tree species, is assuming a rapidly expanding role in commercial forestry. Cloning is the production of genetically identical copies (ramets) from an original, selected individual (ortet). Direct evidence of humans cloning woody plants dates to circa 1000 BCE. Indeed, such cloning probably occurred much earlier when some prehistoric person noticed that fresh branches stuck in the ground would sometimes take root and produce a new stem.
Cloning has long been the standard practice for producing many tree food crops, such as apples and bananas. It is also a main propagation technique in the woody ornamental field, to faithfully reproduce tree shapes, foliage color, lack of seed production, and other unique traits. Cloning specifically for producing improved plantations dates back at least to the 1800s with sugi (<i>Cryptomeria japonica</i>) in Japan and hybrid poplars (<i>Populus</i> spp.) in Europe. With the rapid growth of genetic improvement efforts in the 1950s, cloning became important as the basis of most seed orchards (plantations of trees established for the purpose of producing genetically improved seed). Until recently, the establishment of large plantations of cloned trees was limited to a few species that could be rooted inexpensively from stem cuttings. Now, all that is changing due to tissue culture and other biotechnology methods.
The ability to clone trees is one of the most important tools that will be used in constructing the highly productive, very specialized tree plantations the world will need to meet its future requirements for wood products, renewable energy, and some biological chemicals. However, indiscriminate cloning also carries significant risks for the long-term stability of plantations.
Industry:Science
Every day, thousands of people are killed and injured on the roads. In 2006, in the United States alone, there were an estimated 5,973,000 police-reported traffic crashes, in which 42,642 people were killed and 2,575,000 people were injured, with 4,189,000 crashes involving property damage only. An average of 117 people died each day in motor vehicle crashes in 2006; that is, about 1 every 12 minutes. Motor vehicle crashes are the leading cause of major brain and spinal injuries and the leading cause of death for every age from 2 through 34. The personal, social, and economic costs of motor vehicle crashes include pain and suffering; direct costs sustained by the injured persons and their insurers; indirect costs to taxpayers for health care and public assistance; and for many victims, a lower standard of living and quality of life.
During the past 20 years, motor vehicles accounted for over 90% of all transportation fatalities, and an even larger percentage of accidents and injuries. Our increasingly mobile society exposes all age groups to the risks of crashes, as passengers, drivers, and pedestrians. In contemporary society, automobiles play an indispensable role in transporting people and goods, and yet motor vehicle crashes remain a major public health problem. The health care cost of motor vehicle crashes is a national financial burden that must and can be reduced.
Overall, the impact of motor vehicle crashes on a society is enormous. The U.S. National Highway Traffic Safety Administration (NHTSA) estimates the cost of crashes at well over $500 million a day, totaling $230 billion annually. These costs include property damage, medical care, insurance administration, emergency services, legal and court costs, travel delay, productivity losses, and costs to employers.
Industry:Science
From the beginning of recombinant fungal biotechnology, the yeast <i>Saccharomyces cerevisiae</i> has been the most commonly used host organism for the production of heterologous proteins. Most developments of fungal biotechnology were initiated by work with this organism.
In recent years, other yeast species, such as <i>Kluyveromyces lactis</i>, <i>Hansenula polymorpha</i>, and <i>Pichia pastoris</i>, have become accessible for applications with recombinant proteins. Interestingly, in some instances, yeasts are unable to express eukaryotic genes which encode proteins that require posttranscriptional modifications (such as glycosylations). In contrast, filamentous fungi are able to synthesize some of these proteins in the fully functional form. Simultaneous with the development of molecular genetic techniques and gene transfer systems in yeast, comparable systems were established for filamentous fungi, making strain improvements feasible. Filamentous fungi have been used for decades as major producers in the pharmaceutical, food, and food-processing industries, leading to a high technical standard in fermentation processes with large-scale fermenters. This, together with the fact that many filamentous fungi possess the GRAS (“generally recognized as safe,” in terminology of the US. Food and Drug Administration) status, makes them ideal organisms for the production of recombinant proteins.
Many filamentous fungi with the GRAS status are standard organisms for large-scale fermentation, able to secrete large amounts of proteins, and therefore are ideal host organisms for the production of recombinant proteins. Included in this category are <i>Aspergillus niger, Aspergillus oryzae, Acremonium chrysogenum, Penicillium chrysogenum</i>, and <i>Trichoderma reesei</i>, among others.
Industry:Science
Differential global positioning systems (DGPS) improve the positioning accuracy of GPS users who are equipped to receive correction messages broadcast over radio links from a GPS reference receiver or a network of receivers at a fixed, known location or locations. The method exploits the fact that the leading error sources for civil GPS receivers will be highly correlated at the reference receiver and at nearby user receivers. These errors include the propagation delay of radio signals through the ionosphere and the troposphere as well as errors that are characteristic of the satellite broadcast signals. The latter include satellite timing (clock) errors and errors in the broadcast satellite ephemerides (which provide precise satellite positions at any given time). A reference station estimates the combined effect of these errors as the difference between the measured value of the line-of-sight range to each satellite and the value of that range predicted from the known locations of a satellite and the reference station.
Public-use DGPS transmit the current value of these ranging errors for all satellites that are in view. Some systems separate out the individual error contributions attributable to satellite clock offsets, ephemeris errors, and propagation errors, whereas others transmit only the composite line-of-sight errors. These two approaches are generally characteristic of wide- and local-area DGPS respectively. An intermediate approach whereby each station transmits local, scalar corrections but a weighted average of corrections from multiple transmitters is used in the user receiver, is called regional DGPS. This concept is used in the Northwest European LORAN (NELS) Eurofix system, where DGPS corrections are transmitted by pulse-position modulation of the LORAN signal.
Industry:Science
From weather phenomena, to population dynamics, to the orbits of Jupiter's moons, chaos appears everywhere around us. All chaotic systems exhibit an extreme sensitivity to tiny changes in initial conditions that has come to be popularly illustrated by the butterfly effect: The flapping of a butterfly's wings can trigger the eventual development of a tornado half a world away. A majority of real-world phenomena, natural or human-made, are governed by nonlinear equations of motion that can lead to chaos, and this circumstance has inspired a systematic study of nonlinear dynamics and chaos theory over many decades.
Recent advances in optics, solid-state physics, and nanoscience are now making it possible to control systems at the level of individual atoms and photons. At this microscopic level governed by the laws of quantum mechanics, the concept of nonlinear dynamics and chaos becomes ambiguous and difficult to characterize. The problem arises from the uncertainty principle, which forbids exact knowledge of initial conditions, and from the Schrödinger equation, which appears to forbid nonlinear dynamics. The study of how chaos manifests itself at the quantum level is therefore crucial for understanding the fundamental connections between the quantum world and our macroscopic classical world, and also for developing a toolbox of useful quantum control techniques.
Quantum control of nonlinear systems is important for a variety of future applications, including control of molecular processes for chemical and biological purposes, controlling electron transport in solid-state devices, and performing high-precision measurements. Furthermore, due to the ever-increasing miniaturization of transistors on a computer chip, quantum chaos has gained new relevance in the field of quantum computation.
Industry:Science
Conservation paleobiology is a new, pragmatic, socially relevant discipline within paleobiology. Its emergence stems from the growing realization that the fossil record of the very recent past (the last centuries to millennia) can serve as an unprecedented baseline for studying rates and causes of ecological changes over time scales not accessible by studying modern conditions alone. Such a unique, multicentennial perspective can provide rigorous criteria for evaluating the current extent of ecosystem deterioration, enabling a realistic evaluation of the long-term context of anthropogenic disturbances and a critical assessment of the effectiveness of restoration efforts.
For example, in a recent study of coastal ecosystems, an extensive compilation of paleontological and archeological data was used to show that ecological deterioration often has deep historical roots. The compiled studies represented a wide range of time scales, from projects reaching back only a few decades to those spanning hundreds of thousands of years. In addition, they encompassed a wide spectrum of ecosystems, from high-latitude kelp forests of Alaska to tropical reefs of the Caribbean Sea.
Despite the great variety of ecosystems included in the compilation, virtually all cases revealed similar patterns: marine ecosystems were first altered by overfishing, an activity that invariably predated other anthropogenic disturbances by decades, centuries, or even millennia. Overfishing, which removes key members of marine ecosystems and often dramatically reduces total biomass, represents—most likely—a necessary precondition for various secondary disturbances such as eutrophication (overstimulation of algae and plant growth in aquatic systems due to natural or anthropogenic addition of excess nutrients), outbreaks of diseases, or species introduction.
Industry:Science
