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Chemistry in stars. The chemical composition of most stars is dominated by hydrogen, with helium in second place and the remaining elements a long way behind. The relative proportions (or abundances) of the elements are quantified either by the number of atoms or the mass involved. In terms of mass, average material from outer layers of the Sun and the rest of the Solar System contain 70.7% hydrogen, 27.4% helium and 1.6% of all the other elements. These three quantities are called mass fractions and are conventionally labelled X, Y and Z. In terms of the number of atoms, hydrogen dominates even more, with 92.0% hydrogen, 7.8% helium, and all the rest just 0.12%. Elements other than hydrogen and helium are often termed the HEAVY ELEMENTS. These figures, which are representative compositions throughout the Universe, are changed by NUCLEOSYNTHESIS reactions inside stars. Thus at the centre of the Sun, the abundance of hydrogen has currently fallen to 38% by mass, and that of helium...

  Branch of astronomy that uses the laws of physics to understand astronomical objects and the processes occurring within them. The terms ‘astronomy’ and ‘astrophysics’ are however often used as synonyms. Astrophysics effectively dates from the first applications of the SPECTROSCOPE to study astronomical objects. Sir William HUGGINS’ identification of some of the chemical elements present in the Sun and stars in the 1860s was the first major result of astrophysics. Today, the use of computers for data processing, analysis and for modelling objects and processes is an integral part of almost all aspects of astrophysics.  SPECTROSCOPY is the most powerful technique available in astrophysics. Individual atoms, ions or molecules emit or absorb light at characteristic frequencies (or ‘lines’, from their appearance in a spectroscope) and can thus be identified and their quantity assessed. Information on the physical and chemical state of an object can be obtained from an analys...

Traditionally physical systems have been designed by engineers using complex collections of rules and principles. The design process is top-down in nature and begins with a precise specification. This contrasts very strongly with the mechanisms which have produced the extraordinary diversity and sophistication of living creatures. In this case the ‘‘designs’’ are evolved by a process of natural selection. The design starts as a set of instructions encoded in the DNA whose coding regions are first transcribed into RNA in the cell nucleus and then later translated into proteins in the cell cytoplasm. The DNA carries the instructions for building molecules using sequences of amino acids. Eventually after a number of extraordinarily complex and subtle biochemical reactions an entire living organism is created. The survivability of the organism can be seen as a process of assembling a larger system from a number of component parts and then testing the organism in the environment in whi...

INTRODUCTION The word biometrics comes from the Greek words “bios” (life) and “metrikos” (measure). Strictly speaking, it refers to a science involving the statistical analysis of biological characteristics. Thus, we should refer to biometric recognition of people, as those security applications that analyze human characteristics for identity verification or identification. However, we will use the short term “biometrics” to refer to “biometric recognition of people”. MAIN FOCUS OF THE ARTIClE This article presents an overview of the main topics related to biometric security technology, with the central purpose to provide a primer on this subject. Biometrics can offer greater security and convenience than traditional methods for people recognition. Even if we do not want to replace a classic method password or handheld token) by a biometric one, for sure, we are potential users of these systems, which will even be mandatory for new passport models. For this reason, it is u...

1)On January 2, 2006, a coal mine exploded in Sago, West Virginia, trapping thirteen miners for nearly two days. All but one of the miners died. A series of subsequent mine disasters in 2006 claimed forty-seven more lives.   2)Workplace injuries come at a high cost to employers. According to a 2007 Workplace Safety Index from Liberty Mutual Insurance, the most disabling injuries cost U.S. employers over $48.3 billion in workers’ compensation claims. 3) In Japan, suicide resulting from overwork, or karojisatsu, is an officially recognized and compensated occupational hazard. By some estimates, 5 percent of all suicides in Japan are “company related.  4)From 2001 to 2002, Japan saw a record 690 claims of karoshi—death by overwork. Of these, 143 were confirmed cases: 96 from stroke and 47 from sudden heart attack. The numbers were even higher in 2003, with 819 claims, 160 of which were compensated.   5)Claims of karoshi jumped after Japan modified a rule ...

1)Falling from the roof is a specific concern at construction sites. Roof falls were the most prevalent type of deadly falls in 2007, and resulted in 686 fatalities from 2003 to 2007. Because of this, the Department of Labor recommends that construction workers avoid falling accidentally, especially from roofs.  2)A 2006 government study named agriculture, forestry, fishing and hunting as the most dangerous occupations in the United States, with an average of 30 deaths each per 100,000 workers.  3)In 2007, a laundry employee at Cintas Corp. in Oklahoma was killed when he fell into an industrial dryer while attempting to free a wad of clothes that had jammed a conveyor belt. 4) In its 2008 Death on the Job Report, the AFL-CIO ranked commercial fishing as the occupation with the highest fatality rate, with almost 150 deaths on the job per 100,000 workers . The fatality rate for the fish is even higher.  5)In a 2004 survey, 17 percent of men said they had been ...

1) In 1976, the typical CEO earned thirty-six times the salary of his average worker. Today, the average CEO makes 369 times what an average worker makes.  2)There were over 600 workplace homicides in this country in 2007. I wonder how many of those were CEOs.  3)One study suggests that Californians are more likely to be murdered at work than in a motor vehicle accident while commuting to work.  4) Fatalities at construction sites are most frequently caused by falls, accounting for one–third of constructionrelated deaths each year. The Bureau of Labor Statistics reports no fewer than 442 construction workers were killed by accidental falls on the job in 2007.   5)Almost 6,000 Americans— about seventeen per day— suffered fatal injuries on the job in 2006. Some people will do anything to get out of work.