Billion, meaning

For gas-phase species, the most commonly used units are parts per million (ppm), parts per hundred million (pphm), parts per billion (ppb), and parts per trillion (ppt). These units express the number of molecules of pollutant found in a million (10fi), a hundred million (10x), a billion (an American billion (109)), or a trillion (1012) molecules of air, respectively. It should be noted that, although these are commonly used, confusion may arise in that in some European countries a billion means 1012 and a trillion means 10l8. As a result, in some journals when these units are used, they are accompanied by a definition, e.g., ppb (parts in 109). Care must also be taken to ensure that ppt means parts per trillion and not parts per thousand. The latter unit is often used in isotope studies and is denoted parts per mille, or %o. 

United States, billion means a thousand million (prefix giga), but, in most other... 

Billion, meaning of 789-790 Biochemical oxygen demand (BOD), 87-88 Biodegradable synthetic detergenf manufacture of 23-34... 

Disregarding exceptional circumstances, we can list the relative concentration of gases found in the atmosphere (see table 26.1). Excluding water vapor, we see that only three gases—N, Oj, and Ar—make up almost 100 percent of the gases in the atmosphere. Carbon dioxide is the next most abundant gas, but even its concentration is relatively tiny compared to the first three. The concentrations of any other gases are so small that they are usually expressed in units of parts per million (ppm) or parts per billion (ppb), where a part per million means only one molecule of that gas per million air molecules, and a part per billion means only one molecule of a gas per billion air molecules. 

Media reporting of road trauma doesn t help matters, as only deaths are routinely reported, and deaths are merely the tip of the iceberg. There are well over 10 serious injuries for every death, and injuries, as we saw in Chapter 2, have impacts weU beyond the injured person. Occasionally we read of the financial burden of the road toll, but this number—currently in the billions of dollars per annum in Australia— does not resonate with the public, as lobby groups and politicians are continuously quoting big numbers for every cause they want to promote, and most folk have little concept of what billions means. 

The requirements placed on the performance and reliability of CVD coatings are continuously upgraded. For one thing, this means the need for an ever increasing degree of purity of the precursor materials since impurities are the maj or source of defects in the deposit. The purity of a gas is expressed in terms of nines, for instance, six nines, meaning a gas that is 99.9999% pure, which is now a common requirement. It is also expressed in ppm (parts per million) or ppb (parts per billion) of impurity content. 

The concentration of ozone in the stratosphere is lower than predicted from reactions 1-4. This is due to the presence of trace amounts of some reactive species known as free radicals. These species have an odd number of electrons and they can speed up reaction 4 by means of catalytic chain reactions. Nitrogen oxides, NO and NO2, which are naturally present in the stratosphere at levels of a few parts per billion (ppb), are the most important catalysts in this respect. The reactions, first suggested by Paul Crutzen (2) and by Harold Johnston (3) in the early 1970 s, are as follows ... 

Extrapolating exposure estimates to all urban cities In the world would Indicate that as many as 625 million people, mostly In developing countries, are exposed to unacceptable levels of 02 pollution and about 1.25 billion people live In urban areas where SPN levels exceed acceptable guidelines. This means that less than 20 percent of city dwellers live In environments that can be considered to have acceptable outdoor air quality levels. 

This means that if all of the TCDD were retained, the level of TCDD would be less than 1 part per billion (ppb) in the whole animal. The lowest reported limit of detection for TCDD in whole tissue is 50 ppb (6). Thus, a guinea pig could be killed with TCDD, and it would be impossible to establish this fact with the analytical procedures in current use. 

The life span of the normal red blood cell is 120 days this means that slightly less than 1% of the population of red cells (200 billion cells, or 2 million per second) is replaced daily. The new red cells that appear in the circulation still contain ribosomes and elements of the endoplasmic reticulum. The RNA of the ribosomes can be detected by suitable stains (such as cresyl blue), and cells containing it are termed reticulocytes they normally number about 1% of the total red blood cell count. The life span of the red blood cell can be dramatically shortened in a variety of hemolytic anemias. The number of reticulocytes is markedly increased in these conditions, as the bone marrow attempts to compensate for rapid breakdown of red blood cells by increasing the amount of new, young red cells in the circulation. 

The number of surface collisions at p=l bar and T = 300 K is thus rcoii-surf = 1-08 X 10 m s for hydrogen and 2.88 x 10 m s for nitrogen. Since there are typically 1.5 x 10 surface atoms per m, a surface atom will on average be hit a billion times per second under ambient conditions. This, however, does not necessarily mean that the gas molecule reacts, particularly if the reaction is an activated process. 

Most recently, PECO Energy and Commonwealth Edison s parent company Unicom announced plans to merge. Once finalized the nearly 32 billion deal will mean that the new company will own and operate 14 nuclear units...not counting AmerGen-PECO Energy s joint venture with British Energy—that is in the process of purchasing six additional nuclear units so far. 

The problem in its entirety can be characterised by means of analogies. Thus the chemist Leslie Orgel, who carried out successful experiments on chemical evolution for many years, compared the struggle to solve the biogenesis problem with a crime novel the researchers are the detectives looking for clues to solve the case . But there are hardly any clues left, since no relicts remain from processes which took place on Earth more than four billion years ago. 

It is assumed that the average heat generation due to the radioactive processes described above was around 8x 10 6 J/g of rock (Birch, 1954). If this value is extrapolated to the Earth s crust (to a depth of 35 km), the result is 53 J/cm2/year. It seems clear that the crust of the primeval Earth contained about four times as much 40K as today. The higher half-life of 238U means that the amount of this isotope present about four billion years ago was around twice today s value. The corresponding factor for 235U, with a half-life of 7x 108 years, is 64. Thus, the value of... 

The variety of life forms to be found near hydrothermal vents does not, of course, mean that life itself originated there these geological systems are much too unstable for that. The dynamics of tectonic plates cause the vents to disappear after some decades, or at most after a few hundred years. According to Nils Holm from the Department of Geology and Geochemistry at the University of Stockholm, the discovery of the hydrothermal vents led to intense, and in some cases controversial, discussions of the question as to whether hydrothermal systems were the birthplaces of life around four billion years ago. Many geologists believe that hydrothermal activity on the primeval Earth was probably stronger than it is today, as the thick... 

Taking a value of 107 for N would mean that in our galaxy (with its perhaps 100 billion stars), there could be several million planets with life forms capable of interstellar communication. However, if these were distributed statistically, the nearest would still be 200 light years away from Earth. One point is important the term probability used in the Drake equation is interpreted in the sense of subjective probability (a term from the nomenclature used by statisticians and probability theorists), as the numerical value of this probability is determined only by the experience of the scientist concerned (Casti, 1989). Casti also provides more information on the Drake factors (apart from the factor fs) in the chapter Where are they then In summary, we can say that the Drake equation is a first attempt to quantify the ETI problem in order to move from the area of science fiction and pure speculation to that of serious scientific debate. 

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