Elements Nature

Sulfur is a reactive, nonmetallic element naturally found in nature in a free or combined state. Large deposits of elemental sulfur are found in various parts of the world, with some of the largest being along the coastal plains of Louisiana. In its combined form, sulfur is naturally present in sulfide ores of metals such as iron, zinc, copper, and lead. It is also a constituent of natural gas and refinery gas streams in the form of hydrogen sulfide. Different processes have been developed for obtaining sulfur and sulfuric acid from these three sources. 

Element Natural rate (10 tonnes/yr) Anthropogenic rate (10 tonnes/yr) Anthropogenic/natural ratio... 

Element Natural anthropogenic P Natural weathering Municipal wastes... 

Mercury is a naturally occurring element. Natural emissions of mercury, e.g. from ore deposits and from volcanic activity, are variously estimated at amounts between 2500 and 5500 tonnes/year and are thus similar in magnitude to anthropogenic emissions, which are currently estimated at some 3600-4100 tonnes/year world-wide. Some 30000 tonnes of mercury are readily available in the environment, i.e. in the atmosphere or in the mixing zone of the oceans, with tens of millions of tonnes in the upper layers of the continental masses and still more in the deep oceans (see Table 2.1). 

Ogston, A.G. (1948). Interpretation of experiments on metabolic processes using isotopic tracer elements. Nature, London, 162, 963. 

Several elements naturally exist in two isotopes. Within the context of mass spectrometry it is useful to deal with them as a class of their own. Nevertheless, the term di-isotopic element is not an official one. These elements can even be subclassified into those having one isotope that is 1 u heavier than the most abundant isotope and those having one isotope that is 2 u heavier than the most abundant isotope. (For the unit u cf. Chap. 3.1.4.2). The first group has been termed A-rl or Xh-1 elements, the latter ones have been termed Ah-2 or Xh-2 elements, respectively. [2,3] If we do not restrict our view to the elements typically encountered in organic mass spectrometry, the class of X-1 elements with one minor isotope of 1 u lower mass than the most abundant one should be added. 

Pilpel Y. 2001. Identifying regulatory networks by combinatorial analysis of promoter elements. Nature Genetics 29 153. 

Some of these particles eventually sink to the seafloor, thus removing metals from the ocean. This process of surface adsorption followed by settling is referred to as particle scavenging. The rate and degree to which a dissolved metal is scavenged from the ocean depends on (1) its elemental nature, (2) the abimdance of particulate matter, (3) the concentrations of other solutes that can compete fc>r adsorption sites, and (4) the depth of the water column. Metal scavenging rates have been inferred from the concentrations of naturally occurring radionuclides, such as " Th, Th, and Th. 

The sample surface is bombarded with a beam of around 1 keV ions of some gas such as argon and neon. The action of the beam sputters atoms from the surface in the form of secondary ions, which are detected and analyzed to produce a characterization of the elemental nature of the surface. The depth of the analysis is usually less than a nanometer, making this process the most suitable for analyzing extremely thin films. 

Paneth, F. A., Tile making of the missing chemical elements, Nature,... 

Hahn WC, Counter CM, Lundberg AS et al. Creation of human tumour cells with defined genetic elements. Nature 1999 400 464 68. 

Bromine.—Of the three halogens, chlorine, bromine, and iodine, bromine has the least eventful history. Its elemental nature and its relation to chlorine and iodine were recognized from the very first. While studying the mother-liquid which remains after the crystallization of salt from the water of the salt-marshes of Montpellier, A. J. Balard was attracted by the intense yellow coloration developed when chlorine water is added to the liquid. A. J. Balard digested the yellow liquid with ether decanted off the supernatant ethereal soln. and treated this with potassium hydroxide. The colour was destroyed. The residue resembled potassium chloride but unlike the chloride, when heated with manganese dioxide and sulphuric acid it furnished red fumes which condensed to a dark brown liquid with an unpleasant smell. 

Standard states. The standard or reference state of each of the elemental substances is taken to be that physical state (or one of them, if there are two or more) in which the element naturally exists at a pressure, or a fugacity, of one atmosphere and at a temperature of 18°. The isotopic composition of each element in its standard state is understood to be the naturally existing one. For the element carbon, we have selected its form as diamond, C (c, diamond), as the standard state because no other form of solid carbon is at present a reproducible and invariable one. 

There are several factors which make neutron activation analysis (NAA) an appropriate technique for investigating potential pollutants in coal and the combustion process. First, the multi-element nature of NAA is useful because of the large number of potential elemental pollutants, such as Se, Hg, As, Zn, Ni, Sb, and Cd. Also, the use of elemental ratios made possible by the multi-element capability facilitates the understanding of chemical behavior during the combustion process. Elemental ratios have been used previously in urban (15) and upper atmospheric (26) studies. Secondly, the sensitivity and selectivity of NAA allows determination of many elements present at very low concentrations (ppm or lower), and the results are unaffected by matrix interferences. This sensitivity also allows analysis of very small samples. Finally, the cost of NAA when conducted as a multi-element analytical tool is competitive with more conventional and less sensitive techniques on the cost-per-element-per-sample basis. 

Falkner, F.G., Zachau, H.G. (1984). Correct transcription of an immunoglobulin K gene requires an upstream fragment containing conserved sequence elements. Nature 310,71-74. 

Montange, R. K., and Batey, R. T. (2006). Structure of the S-adenosylmethionine riboswitch regulatory mRNA element. Nature 441, 1172-1175. 

G. Hevesy and H. Levi, Artificial radioactivity of dysprosium and other rare earth elements, Nature 136 (1935) 103. G. Hevesy and H. Levi, Action of slow neutrons on rare earth elements, Nature 137 (1936) 185. 

Carbon dioxide and silicon dioxide are chemically very similar to each other in that both form weak acids, that of silicon, the heavier element, naturally being the weaker acid. On the other hand, these oxides are very dissimilar in their physical properties, one being a gas, and the other a solid with an extremely high melting point. 

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