Accumulation mechanism

Although the sediments in these systems accumulate Se over time, the small isotopic contrast suggests that dissimilatory reduction is not the dominant accumulation mechanism. If dissimilatory reduction of Se(VI) and/or Se(IV) to Se(0) by bacteria were the dominant mechanism, one would expect the accumulated Se(0) to be enriched in the lighter isotope. In the San Francisco Estuary case, this assumes that the isotopic fractionations measured by Ellis et al. (2003) can be extrapolated to much lower concentrations. Incorporation of Se into algae and macrophyte tissues, followed by decay of some material and conversion of its Se to Se(0), is more consistent with the observed Se isotope data. Notably, the mean Se isotope composition of the Se(0) in the sediments of the Herbel et al. (2002) study was identical to that of the macrophytes. 

Ultra fine or Aitken nuclei Accumulation Mechanically generated... 

Multiple accumulation mechanisms. These data and other published reports (I) indicated that partitioning of PCBs to phytoplankton involves adsorption to the cell surface and incorporation into the cell matrix. However, there is no indication whether the processes operate in parallel or serial. 

Michibata, H., T. Uyama, and K. Kanamori. 1998. The accumulation mechanism of vanadium by ascidians. In Vanadium compounds. Chemistry, biochemistry and therapeutic applications, A.S. Tracey and D.C. Crans (Eds.), American Chemical Society, Washington, D.C., pp. 248-258. 

The main questions raised at the very beginning of the studies can be briefly formulated as follows. Can the potential energy accumulated in the mechanically nonequilibrium matrix of a frozen sample of reactants be released by its brittle fracture Will the accumulated mechanical energy transform into chemical energy, and will a chemical conversion take place in this case ... 

Only the features of vanadium biochemistry relevant to understanding the accumulation mechanism in vanadocytes are presented here. More extensive coverage of this subject may be found in two recent reviews51 525. 

Volatile aldehydes, and (E)-2-nonenal in particular, had already been identified as the cause of "rancid odors" in beer (7,8). These substances result firom the oxidation of unsaturated fatty acids. The direct precursor of (E)-2-nonenal and others carbonyl components is linoleic acid (Ci8 2 A 9,12) (9). Volatile aldehydes may be derived firom fatty acids in various manners. Chemical auto-oxidative factors would seem to provide the most likely explanation for the presence of these components in oak stave wood after seasoning in the open air. On the other hand, enzymatic factors may explain the presence of ese components while the tree is still standing or immediately after it has been cut. Additional research is necessary to pinpoint the exact formation and accumulation mechanisms of these molecules in the wood. 

Use of Polysaccharide-Mediated Biofilm Accumulation Mechanisms in Prevention... 

The predominant mechanism of biofilm accumulation in staphylococci involves polysaccharide intercellular adhesin (PIA) [60-66], S. epidermidis strains lacking this adhesin are also regularly isolated from biomaterial-related infections, a fact which prompted a search for an alternative, PIA-independent accumulation mechanism [51, 52, 60-62, 67, 68], The responsible molecule was identified as accumulation associated protein, Aap [69-71], and there may also be a role for additional proteinaceous intercellular adhesins [52], Aap has a similar-acting homolog, SasG, in S. aureus [72], adding to the accumulating evidence that proteinaceous intercellular adhesins are also of importance in S. aureus biofilm formation and device-related infection [52, 72-74],... 

Transient Nuclei or I Accumulation Mechanically Generated Aitken Nuclei Range I Range Aerosol Range... 

Inhibition patterns of [ N]ammonia accumulation by strains JL907 and JB822 (GDH") are shown in Figure 4. It is clear that assimilation plays an important role in [ N] ammonia accumulation in these strains. Strain JB822 is resistant to methionine sulfoximine due to a defect in methionine transport (data not shown). The inhibition by metabolic inhibitors (Figure 4) was not unexpected, since assimilation and all possible accumulation mechanisms (Table II) are energy-dependent. It is presently unclear whether N-ethylmaleimide inhibition was due to inactivation of a sulfhydryl-containing surface receptor or to inhibition of electron transport. 

The conclusion one can draw from this work is that rhizosphere mechanisms involved in the release of metals from soil colloids may differ between metals as well as between willow clones with different properties of metal accumulation. Most of these mechanisms are found in low accumulators. Mechanisms involving pH seem to be important for both Cd and Cu accumulation. High pH decreases Cd release in soil with low Cd content and an increase in pH decreases the release of Cu from soil with high Cu level by low-Cu-accumulating clones. 

Modified secondary metabolites have different solubility and other physical properties than the parental compounds and may be involved in transport and accumulation mechanisms in plants (Wink, 1987). Nonetheless, there is little evidence to support the notion that most or all secondary metabolites once had primary roles (Williams et al., 1989). 

In order to correctly interpret the experimental information provided by EIS, conveyed in either Nyquist or Bode plots, the use of a sound physical model describing the relevant biophysicochemical processes taking place in the system is essential. A simple strategy to deal with the experimental information involves the implementation of the model into an equivalent circuit, which contains all the information of charge transport. In the equivalent circuit, the resistances and capacitances describe the charge loss and accumulation mechanisms that can take place in the system. In the following section, we first describe the most common circuit elements used in EIS data analysis, followed by the most common equivalent circuits used to describe typical electrochemical cells. 

Information on cellular metabolic organization of caffeine biosynthesis and catabolism links to purine nucleotide metabolism, intercellular translocation, and accumulation mechanisms at specific cellular sites, such as chloroplasts and vacuoles, have yet to be fully revealed. Cell-, tissue-, and organ-specific synthesis and possibly catabolism of purine alkaloids may be regulated by unique and unknown developmental- and environmental-specific control mechanisms. A great deal of fascinating purine alkaloid biology in plants still remained to be discovered. 

At present, only a few membrane compartments, transporters and channels are known to have a defined role in alkaloid transport and compartmentation. One major challenge for research is the high individuality in the cellular organization that rests on the species-specific localization of biosynthetic enzymes and the opportunistic use of transporters, metabolite pools, storage sites and accumulation mechanisms even between taxonomically related genera. 

Fig. 16. Accumulation of free glutamic acid within Staph, aureus incubated with curve 1, diethyl glutamic ester 2, iV-phosphorylglutamic acid 3, as 2 with a second addition of A -phosphorylglutamic acid at time indicated by arrow 4, IV-phosphoryl-glutamic acid and glucose 5, glutamic acid and glucose. Sources added to the external medium at concentrations sufficient to saturate the accumulation mechanism in all cases falling of rate in curve 2 is due to decomposition of the iV-phosphorylglutamic acid.

Char forming mechanisms are thus complementary of the clay layer accumulation mechanism proposed by Gilman. A schematic representation is reported in Fig. 10.2. Heat transfer from an external source or from the flame... 

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