Pyrolysis/GC/MS was utilized as an integrated reaction, separation and identification system to study the thermal degradation products of non-volatile Maillard flavor precursors. Model systems of scL-phenylalanine (aromatic amino acid), glycine and scL-alanine (aliphatic amino acids), scL-serine ($ beta$-hydroxy amino acids) and scL-methionine (sulphur containing amino acid) were investigated. Quartz tube pyrolysis of scD-glucose/amino acid or dicarbonyl/amino acid mixtures shortened the analysis time (from hours to minutes) and eliminated the need for extraction since the volatiles generated from the precursors are directly transferred into the GC column. / Phenylalanine Amadori product and different model systems containing phenylalanine and different reducing sugars were studied. Ribbon pyrolysis was used to study the effect of temperature (150, 200, 250$ sp circ$C) on the efficiency of formation of initial pyrolysis products from phenylalanine and Amadori phenylalanine. Quartz tube pyrolysis was used at 250$ sp circ$C to enhance the secondary reactions. These studies revealed the formation of pyridine and naphthalene derivatives such as 3,5-diphenylpyridine, 1(2)-naphthaleneamine, N-methyl-1(2)-aminonaphthalene, 1-aminoanthracene, 2$ sp prime$-phenyl-pyrrolo (4,5-A) dihydronaphthalene, 1(2)-(N-phenethyl)napthaleneamine and 1(2)-(N-phenethyl-N-methyl)naphthaleneamine. / Model studies using scD- ($ sp{13}$C) glucoses and a series of dicarbonyl compounds with labeled ($ sp{15}$N/$ sp{13}$C) glycines and ($ sp{15}$N/$ sp{13}$C) alanines identified a new chemical transformation of $ alpha$-dicarbonyls, that lead to the addition of alkyl groups from the amino acid to the $ alpha$-dicarbonyl compounds, instead of the amino group as in the case of the Strecker type interaction between the two reactants. Thus, glyoxal and pyruvaldehyde can be transformed into pyruvaldehyde and 2,3-butanedione respectively, by glycine and 2-ketobutanal and 2,3-pentanedione respectively, by scL-alanine. The labeled glycine model studies indicated that methyl substituted pyrazines and pyrazinones formed in the model systems, have a common intermediate. Two pathways of pyrazinone formation were distinguished based on the labeling experiments, one involving the reaction of three moles of glycine and the other the interaction of the dipeptide glycylglycine with an $ alpha$-dicarbonyl compound. / A major product of the reaction of scD-glucose with excess glycine was detected by Py/GC/MS analysis and subsequently synthesized and isolated using focused microwave irradiation at atmospheric pressure conditions. Spectroscopic analysis by NMR, FTIR, MS and UV in conjunction with labeling studies have indicated the unknown compound to be 5-hydroxy-1,3-dimethyl-2 (1H) -quinoxalinone. The labeling studies indicated the incorporation of ten carbon atoms (six from sugar, one C-1 atom of glycine, and three C-2 atoms of glycine) and two nitrogens. / scL-Serine was found to be a unique amino acid generating in the absence of sugar a variety of heterocyclic compounds. Under pyrolytic conditions scL-serine can be viewed as a potential mixture of glycine, alanine, serine, formaldehyde and dicarbonyl compounds. / Model studies with scL-methionine provided evidence that methional (Strecker aldehyde) generated under Quartz tube pyrolysis undergoes secondary reactions with amino compounds generating 1,3-thiazines or 3-substituted pyridine in a similar fashion to that of scL-phenylalanine systems where 3-substituted pyridines were also identified. (Abstract shortened by UMI.)

No description available.

The physicochemical parameters of fifteen honey samples from a wide range of botanical origins were characterized to identify the influence of composition on the formation of alpha-dicarbonyl compounds during heating. Color, pH, moisture content, water activity, hydroxymethylfurfural (HMF), sugar and amino acid content were determined before and after storage at various time and temperatures. The effects of storage time and temperature on the formation of Maillard reaction product were also investigated. Analysis of the data has indicated that they have a significant impact on the rate of production of Maillard related compounds such as alpha-dicarbonyls and HMF. The content of free amino acids was also decreased 'over time with concomitant increase in color intensity. Furthermore, nine alpha-dicarbonyl compounds were detected in honey samples. The analysis of these compounds after derivatization with o-diaminobenzene resulted in the identification of three previously unreported derivatives in honey such as 3-deoxypentulose, 1,4-dideoxyhexulose and 3,4dideoxyglucosone-3-ene. More importantly, the detection of 5-hydroxycyclohexane-1,2,4-trione was to our knowledge the first cyclic alpha-dicarbonyl compound ever reported in literature. Characterization of this molecule by different mass spectrometric techniques and spiking experiments provided evidence that supported the precursor, the structure and proposed mechanism of formation.

The study of the speed of human reactions is older than experimental psychology. Starting in the early 1800's as the study of the "personal equation" in astronomy, it became known as "mental chronometry" in psychological laboratories of the late 19th Century (Boring, 1950). The time elapsing between the presentation of a predetermined signal and the occurrence of a predetermined response served as a measure of reaction speed. This measure, reaction time or response latency, was studied in relation to several variables (e.g., preparation, attention, signal modality) by the early investigators. [...]

Due to increasing atmospheric carbon dioxide (CO2) concentration, energy sources that release to the atmosphere smaller amounts of CO2 are of interest. Initially, all the efforts were focused on increasing the system efficiency, now more attention is being paid recently on capturing and sequestering CO2 from combustion process and eliminating discharge to the atmosphere from the major source points. In these circumstances, the chemical-looping combustion (CLC) is a promising concept that can be used in power generation which integrates power production and CO2 capture. The aim of this work is to study reaction kinetics of Chemical-Looping Combustion. In order to come up with a suitable reactor design we should have a good knowledge of the reaction kinetics happening in the air and fuel reactor; then, to get such an information as will be mentioned later, reactivity investigation was carried out in thermogravimetric analysis (TGA).

No description available.

No description available.

No description available.

No description available.

No description available.