Critical behaviors identification

This work has demonstrated that organically bound sulfur forms can be distinguished and in some manner quantified directly in model compound mixtures, and in petroleum and coal. The use of third derivatives of the XANES spectra was the critical factor in allowing this analysis. The tentative quantitative identifications of sulfur forms appear to be consistent with the chemical behavior of the petroleum and coal samples. XANES and XPS analyses of the same samples show the same trends in relative levels of sulfide and thiophenic forms, but with significant numerical differences. This reflects the fact that use of both XPS and XANES methods for quantitative determinations of sulfur forms are in an early development stage. Work is currently in progress to resolve issues of thickness effects for XANES spectra and to define the possible interferences from pyritic sulfur in both approaches. In addition these techniques are being extended to other nonvolatile and solid hydrocarbon materials. 

At least two points should be especially emphasized, (i) From the solvent part, the parent radical cations exist in a non polar surrounding. Hence, the cations have practically no solvation shell which makes the electron jump easier in respect to more polar solvents. In a rough approximation the kinetic conditions of FET stand between those of gas phase and liquid state reactions, exhibiting critical properties such as collision kinetics, no solvation shell, relaxed species, etc. (ii) The primary species derived from the donor molecules are two types of radical cations with very different spin and charge distribution. One of the donor radical cations is dissociative, i.e. it dissociates within some femtoseconds, before relaxing to a stable species. The other one is metastable and overcomes to the nanosecond time range. This is the typical behavior needed for (macroscopic) identification of FET ... 

From the point of view of purification, occlusion presents a serious obstacle in rejecting the impurities and residual solvent. Since solvent and temperature can drastically affect crystallization behaviors, these variables can play critical roles. Therefore, systematic screening of solvent and identification of proper crystallization conditions for optimum rejection of impurities are desirable. In view of the rapid development of high-throughput screening devices for the measurement of solubility (see Section 2.1.6), it is expected that there will be signih-cant progress in this field in the near future as well. 

TLC can provide other information critical in compound identification. Colors from selective chemical detection reactions, behavior in ultraviolet light, absorbance and/or fluorescence spectra obtained directly on the chromatogram by use of a spectrodensitometer or in solution after elution and Rp values of derivatives prepared by reaction before, during, or after development can be combined with the R p values of the sample to increase the degree of probability of correct identification [67,68]. Infrared (IR) and mass spectrometry combined with chromatography can provide unequivocal identification if sufficient sample is available. This is often not the case in trace analysis where nanogram amounts of material may be separated and detected by TLC, whereas microgram quantities are needed for conventional IR spectrometric confirmation of the trace substances. 

It seems evident that to achieve pheromone identification, a clear biological assay relying upon unambiguous behavior coupled with a chemical identification strategy, testing each successive purification step, is critical. Additionally, the use of biologically relevant samples such as conditioned seawater that contains compounds released into the environment at biologically relevant concentrations should be used. 

Within the frame of the value approach a new numerical method is proposed for the identification and study of critical phenomena in branched chain reactions, according to their kinetic models. As a criterion for the critical states of a reaction system its state of extreme behavior is proposed. This allows to consider the initial conditions and parameters of the reaction system as controlling parameters, on the base of which the critical states of reactions are searched. Calcnlations are performed using the Maximum Principle with simultaneous revealing the value characteristics for individual steps and chemical species. With the help of value quantities the chemical content of critical states for nonbranching chain reactions are numerically illuminated. 

In [16, 23-25] as a criterion critical state of the reaction system the extremal behavior of the total concentration of reaction species is suggested. Such a description of the critical state has obvious advantages. It permits to use mathematical tools on finding the extremal conditions of a reaction. It is well-known that such mathematical approaches are well developed. In this case we have used the calculus of variations, namely the Pontryagin method of maximum with value identification of species and steps under critical conditions of a reaction. Thus, simultaneously two important tasks are solved ... 

We summarize our findings. It is suggested the criterion of critical condition, that is, the extremal behavior of the reaction species concentration, may be applied to reveal the critical conditions of nonlinear chemical dynamic systems. This is with the changeover of different dynamic modes of the reactions, such as the quasi-periodic and chaotic oscillations of the intermediate concentrations, as well as the steady-state mode. At the same time the Hamiltonian formalism makes it possible not only to have a successful numerical identification of the critical reaction conditions, but also to specify the role of individual steps of the reaction mechanism under different conditions. 

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