Background source

Donald Nichol. Oct. 31, 1997, and private communication, Nov. 16, 1997. Background source for Muskie hearing. 

Radioactive contaminations of individual construction materials, as well as the laboratory environment, were measured and the impact on detector performance was determined by Monte Carlo computations [83], The background sources which were considered are ... 

The selection of the counter-ion and its concentration are important for the separation of ionic compounds in reversed-phase and ion-exchange liquid chromatography. The addition of hydrophobic ions is an especially powerful method and several surfactants can be used as hydrophobic counter-ions. The theoretical column efficiency of ion-pair liquid chromatography is much better than that of an ion-exchange column, and the regeneration of a column is much faster. Thus, if we can control ion-pair liquid chromatography, we can solve a separation problem. (The important background sources in this area are listed at the end of the chapter.)... 

This is a very broad conclusion, and additional measurements must be made. Some of this effort (which is current) should address the problem of other pollutants and condensation nuclei that accompany the nonurban oxidant. Interpretation of these measurements will increase the specificity of separating anthropogenic sources from natural background sources. Theoretical assessments of the existing observations will shed light on the relative roles played by stratospheric injection, plant emission, background methane, and diy deposition on surfaces in the natural portion of the tropospheric ozone cycle. 

Regarding styrene, the variety of controlled human oral and inhalation studies that relate dose to urinary concentration and the existence of a pharmacokinetic model (Droz and Guillemin 1983) could facilitate interpretation of mandelic acid concentration in urine. A caveat in this regard is that other chemical exposures can produce mandelic acid in urine, such as ethyl benzene, acetophenone, and phenylglycine (ACGIH 1991). Those background sources would be more likely to confound low-level general-population biomarker results than workplace end-of-shift results. 

Long range transport modelling studies of SO2 in Northern Europe have shown that a "background source of sulphate is required to explain a poor... 

Koch, M., and Rotard, W. (2001). On the contribution of background sources to the heavy metal content of municipal sewage sludge. Water Sci. Technol. 43(2), 67—74. 

Troe and his co-workers [27] have recently measured directly the lifetimes of excited molecules undergoing unimolecular decomposition, under essentially collision-free conditions. In these experiments, cyclo-heptatriene, 7-methylcycloheptatriene, 7,7-dimethylcycloheptatriene and 7-ethylcycloheptatriene were each excited electronically with a short pulse of laser radiation. This is followed by a rapid internal conversion to generate highly vibrationally excited, electronic ground state molecules which absorb in the ultraviolet, at longer wavelengths than the unexcited parent. Their decay (isomerisation to alkylbenzenes) was monitored directly with a continuous background source. 

Spectroscopy allows one to see not only the elements in the gas phase, but also those in the dust grains. Using bright X-ray binaries as background sources, Ueda et al. (2005) were able to determine the total abundances of the elements in the diffuse ISM and found that most of them are approximately solar, with the exception of oxygen. From the details of the X-ray absorption spectra it could be determined to some extent what fraction of the elements were in the solid phase and also to a lesser extent the lattice structure could be determined. From this, they found the silicates to be predominantly rich in magnesium and poor in iron, in agreement with the infrared absorption spectroscopic study of the diffuse ISM by Min et al. (2007). 

In all, we receive about 360 mrem/yr from background sources of radiation a dose that varies considerably in both directions depending on local geology, elevation, and other factors. It is worth noting that, even in areas with exceptionally high levels of natural radiation, inhabitants do not appear to suffer from any ill effects. This suggests that occupational exposure to moderately elevated radiation levels is not harmful. 

Now b is the modified Schmidt S rate (spontaneous star formation), a is the induced rate of cloud consumption, d is the rate of cloud destruction by background sources, and e is the rate of formation of clouds out of diffuse gas. 

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