Hydrocarbons frozen

We have used osmotic stress (4) to examine the effect of Mg2 and Ca2 on the interactions between dioleoylphospha-tidylcholine or dipalmitoyl phosphatidyl choline bilayers. From the net repulsive forces between bilayers we are able to infer electrostatic potentials and charge densities at the site of ion binding these quantities are sensitive to bilayer separation. We find that at any particular bilayer separation dioleoyl phosphatidyl choline bilayers (melted hydrocarbon chains) adsorb less charge than dipalmitoyl phosphatidyl choline bilayers (frozen hydrocarbon chains) and that the binding of Ca2 is greater than that of Mg2 for both kinds of bilayers. 

Mass spectrometry has even been used on space probes to analyse rocks on Mars and in 2005 a mass spectrometer was used to analyse the frozen hydrocarbon surface of Titan, one of Saturn s moons. The technique is also used to analyse the isotopes in the solar wind on board the Solar and Heliospheric Observatory (SOHO) satellite. 

An operator had to drain water from a 1,200-m spherical storage vessel nearly full of propane (Figure 8-1). He opened valves A and B. When traces of oil showed that the draining was nearly complete, he shut A and then cracked it to complete the draining. No flow came. He opened A fully. The choke—presumably hydrate, a compound of water and a light hydrocarbon with a melting point above 0°C—cleared suddenly, and the operator and two other men were splashed with liquid. The handle came off valve A, and they could not get it back on. Valve B was frozen and could not be moved. Access was poor because the drain valves were immediately below the tank, which was only 1.4 m above the ground. 

ScHANTZ MM, Porter BJ, and Wise SA (2000) The stability of polycyclic aromatic hydrocarbons in frozen mussel tissue. Polycyclic Aromat Compd (in press). 

Now and then, projectiles from outer space cause excitement and surprises, as in January 2000, when a meteorite impacted the frozen surface of Lake Targish in Canada. It was a new type of C-chondrite with a carbon concentration of 4-5%, and probably came from a D-type asteroid (Hiroi et al., 2001). More exact analysis of the Targish meteorite showed the presence of a series of mono- and dicarboxylic acids as well as aliphatic and aromatic hydrocarbons (Pizzarello et al., 2001). Aromatic compounds and fullerenes were detected in the insoluble fraction from the extraction this contained planetary helium and argon, i.e., the 3He/36Ar ratio was... 

The experimental procedure is outlined schematically in Fig. 13 a detailed description was given by Hartog et al. 37). Benzene vapor and deuterium gas, in the molar ratio of 1 18, were passed through a catalyst bed and then through a cold trap immersed in liquid nitrogen in which the hydrocarbons were frozen out. The temperature of the catalyst bed was... 

Hemandez JE, Machado LT, Corbella R, et al. 1995. w-Alkanes and polynuclear aromatic hydrocarbons in fresh-frozen and pre-cooked-lfozen mussels. Bull Environ Contain Toxicol 55 461-468. 

Sediment-solid and soil-solid samples can be treated in different ways prior to extraction depending on the purpose of the research program. Sediments or soils are stored more conveniently as dried powders. However, this technique is not appropriate if relatively volatile pollutants such as l-ring aryl hydrocarbons (e. g., alkylbenzenes, chlorohydrocarbons, chlorobenzenes), PAH (e.g., naphthalene) are to be determined. In such cases, the sediment or soil should remain frozen prior to analysis and extracted wet. 

Natural gas is a hydrocarbon of low molecular weight consisting of about 85% methane (CH ), which is recovered as an underground gas in areas where petroleum is found. It is also economically produced by conversion of crude oil to gas. Possible future sources of a hydro-gen-based fuel are large frozen methane deposits recently found on ocean bottoms. 

Blood samples for analysis of chlorinated hydrocarbons were obtained by glass and stainless steel syringes and transferred to prewashed centrifugal tubes. The samples were frozen immediately and stored at -25 °C until analyzed. 

Methyl Radicals. Yoshida and Ranby (41) have recently shown by ESR measurements that the methyl free radical is produced in polypropylene by irradiation with ultraviolet light at liquid nitrogen temperature but decays at that temperature. The reaction is slow at —196°C., which suggests that all other hydrocarbon free radicals of larger molecular weight than the methyl free radical can be frozen in and immobilized at that temperature. 

At low enough temperatures vibrational fine structure of aromatic chromophores may be well resolved, especially if they are embedded in a suitable matrix such as argon or N2, which is deposited on a transparent surface at 15 K. This matrix isolation spectroscopy77166 may reveal differences in spectra of conformers or, as in Fig. 23-16, of tautomers. In the latter example the IR spectra of the well-known amino-oxo and amino-hydroxy tautomers of cytosine can both be seen in the matrix isolation IR spectrum. Figure 23-16 is an IR spectrum, but at low temperatures electronic absorption spectra may display sharp vibrational structure. For example, aromatic hydrocarbons dissolved in n-heptane or n-octane and frozen often have absorption spectra, and therefore fluorescence excitation spectra, which often consist of very narrow lines. A laser can be tuned to excite only one line in the absorption spectrum. For example, in the spectrum of the carcinogen ll-methylbenz(a)anthrene in frozen octane three major transitions arise because there are three different environments for the molecule. Excitation of these lines separately yields distinctly different emission spectra.77 Likewise, in complex mixtures of different hydrocarbons emission can be excited from each one at will and can be used for estimation of amounts. Other related methods of energy-... 

Wilkinson has recently described a novel approach.113 It has long been known that solvents containing heavy atoms markedly quench the fluorescence of aromatic hydrocarbons, and it has been shown that this effect arises from an enhancement of the rate of intersystem crossing. Thus the ratio of phosphorescence to fluorescence for naphthalene irradiated at 77°K can be increased more than a hundredfold upon addition of some isopropyl iodide to the solvent.114 The same effect has been noted upon changing from hydrocarbon glasses to frozen krypton and xenon matrices.115 Wilkinson found that the decrease in fluorescence intensity from irradiated solutions of anthracene and some of its derivatives upon addition of bromobenzene is attended by an increase in T-T absorption intensity.116 The fluorescence quenching follows the Stern-Volmer law ... 

Absorption and fluorescence spectra of aromatic hydrocarbons are not greatly affected by change of solvent, except for small solvent shifts. At low temperatures the vibrational structure of the bands sharpens up, and some peculiar solvent effects have been noted. When frozen in solution of normal paraffins coronene shows doubling of some of its vibrational bands, and the separation of the components varies with the number of carbon atoms in the solvent molecule chain. The most probable cause is some size-relationship factor between solvent and solute molecules (7). 

Hydrocarbon and mineral resource development Icebergs and sea ice frozen ground duration and thickness... 

Solid solutions in metallic alloys are normally compositionally very uniform random variations of 5% would be unusual. Also, a two phase layer normally is found between two solid solutions. The sulfur distribution in coal seems not to behave this way. Apparently, the distribution pattern established at some early stage of coal formation is frozen-in and the organic sulfur is bound so tightly to its hydrocarbon sites that it cannot diffuse until the temperature of the coal is raised to 400°C or above (18). 

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