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Molecular reaction dynamics is the study of chemical and physical transformations of matter at the molecular level. The understanding of how chemical reactions occur and how to control them is fundamental to chemists and interdisciplinary areas such as materials and nanoscience, rational drug design, environmental and astrochemistry. This book provides a thorough foundation to this area. The first half is introductory, detailing experimental techniques for initiating and probing reaction dynamics and the essential insights that have been gained. The second part explores key areas including photoselective chemistry, stereochemistry, chemical reactions in real time and chemical reaction dynamics in solutions and interfaces. Typical of the new challenges are molecular machines, enzyme action and molecular control. With problem sets included, this book is suitable for advanced undergraduate and graduate students, as well as being supplementary to chemical kinetics, physical chemistry, biophysics and materials science courses, and as a primer for practising scientists.

This comprehensive handbook covers the diverse aspects of chemical vapor transport reactions from basic research to important practical applications. The book begins with an overview of models for chemical vapor transport reactions and then proceeds to treat the specific chemical transport reactions for the elements, halides, oxides, sulfides, selenides, tellurides, pnictides, among others. Aspects of transport from intermetallic phases, the stability of gas particles, thermodynamic data, modeling software and laboratory techniques are also covered. Selected experiments using chemical vapor transport reactions round out the work, making this book a useful reference for researchers and instructors in solid state and inorganic chemistry.

Bretherick's Handbook of Reactive Chemical Hazards is an assembly of all reported risks such as explosion, fire, toxic or high-energy events that result from chemical reactions gone astray, with extensive referencing to the primary literature.

Primary pyrolysis reactions and relative reactivities for depolymerization and condensation/carbonization were evaluated for various lignin model dimers with α-O-4, β-O-4, β-1, and biphenyl substructures by characterizing the tetrahydrofuran (THF)-soluble and THF-insoluble fractions obtained after pyrolysis at 400°C. Reactivity was quite different depending on the model structure: depolymerization: α-O-4 [phenolic (ph), nonphenolic (nonph)], β-O-4 (ph) > β-O-4 (nonph), β-1 (ph, nonph) > biphenyl (ph, nonph); condensation/carbonization: β-1 (ph) > β-O-4 (ph) > α-O-4 (ph) > β-O-4 (nonph), biphenyl (ph, nonph), α-O-4 (nonph), β-1 (nonph). Major degradation pathways were also identified for β-O-4 and β-1 model dimers: β-O-4 types: Cβ-O cleavage to form cinnamyl alcohols and phenols and Cγ-elimination yielding vinyl ethers; β-1 types: Cα-Cβ cleavage yielding benzaldehydes and styrenes and Cγ-elimination yielding stilbenes. Relative reactivities of these pathways were also quite different between phenolic and nonphenolic forms even in the same types; Cβ-O cleavage (β-O-4) and Cγ-elimination (β-1) were substantially enhanced in phenolic forms.

Recent studies have revealed that dietary flavonoids are potent radical scavengers, acting in a manner similar to ascorbate and alpha-tocopherol. However, it is still not clear whether flavonoids have a similar antioxidative function in plants. We examined the possibility that flavonoids could function as stress protectants in plant cells by scavenging H2O2. Two major flavonoids, quercetin and kaempferol glycosides, were isolated from leaves of the tropical tree Schefflera arboricola Hayata. Both glycosides and aglycones of isolated flavonols were oxidized by H2O2 in the presence of horseradish peroxidase and/or in a soluble fraction of S. arboricola leaf extract. The rates of oxidation were in the order quercetin kaempferol quercetin glycoside kaempferol glycoside. Judging from the effects of inhibitors such as KCN, p-chloromercuribenzoate, and 3-amino-1H-1,2,4-triazole, we conclude that guaiacol peroxidase in the soluble fraction catalyzes H2O2-dependent oxidation of flavonols. In the flavonol-guaiacol peroxidase reaction, ascorbate had the potential to regenerate flavonols by reducing the oxidized product. These results provide further evidence that the flavonoid-peroxidase reaction can function as a mechanism for H2O2 scavenging in plants

Polyphenols, including extractable polyphenols (EPP) and non-extractable polyphenols (NEPP), are natural and secondary metabolic substances in plants that have beneficial properties to human health. However, NEPP associated with dietary fiber and protein are not taken into account in most literature data. In this paper, NEPP were released from blueberries with acid or alkaline hydrolysis methods, and the related extraction conditions were determined and optimised by response surface methodology (RSM). The results showed that NEPP yield obtained with alkaline hydrolysis was much higher than that obtained with acid treatment. The NEPP yield in alkaline hydrolysis process was significantly affected by the NaOH concentration and liquid/solid ratio, while in the acid hydrolysis process, the NEPP yield was significantly affected by the temperature, time and liquid/solid ratio. The second order polynomial models were developed for predicting NEPP content in blueberries. The optimisation of the extraction process of NEPP in blueberries would provide a good idea and basis for the application of non-extractable fractions.

A report on the synthesis and characterization of nanoscale zero-valent iron in the presence of natural zeolite as a stabilizer is presented. This novel adsorbent (Ze-nZVI) was synthesized by the sodium borohydride reduction method. The scanning electron microscopy (SEM) images revealed that the stabilized nZVI particles were uniformly dispersed across the zeolite surface without obvious aggregation. The synthesized Ze-nZVI material was then tested for the removal of nitrate from aqueous solution. The effect of various parameters on the removal process, such as initial concentration of nitrate, contact time, initial pH, and Ze-nZVI dosage, was studied. Batch experiments revealed that the supported nZVI materials generally have great flexibility and high activity for nitrate removal from aqueous solution. The nitrogen mass balance calculation showed that ammonium was the major product of nitrate reduction by Ze-nZVI (more than 84% of the nitrate reduced); subsequently the natural zeolite in Ze-nZVI removed it completely via adsorption. The kinetic experiments indicated that the removal of nitrate followed the pseudo-second-order kinetic model. The removal efficiency for nitrate decreased continuously with an increase in the initial solution pH value and Ze-nZVI dosage but increased with the increase in the initial concentration of nitrate. The overall results indicated the potential efficacy of Ze-nZVI for environmental remediation application.

Land plants suffer from dehydration or water stress not only under drought and high-salt-concentration conditions but also under low-temperature conditions. They respond and adapt to water stress to survive these environmental stress conditions. Water stress induces various biochemical and physiological responses in plants. Under water-stress conditions plant cells lose water and decrease turgor pressure. The plant hormone ABA increases as a result of water stress, and ABA has important roles in the tolerance of plants to drought, high salinity, and cold. A number of genes that respond to drought, salt, and cold stress at the transcriptional level have recently been described (for review, see Ingram and Bartels, 1996; Shinozaki and Yamaguchi-Shinozaki, 1996; Bray, 1997). The mRNAs of water-stress-inducible genes decrease when the plants are released from stress conditions, which is consistent with evidence that shows that these genes respond to water stress or dehydration. The functions of some gene products have been predicted from sequence homology with known proteins and are thought to have a role in protecting the cells from water deficit (Ingram and Bartels, 1996; Bray, 1997). Expression patterns of dehydration-inducible genes are complex. Some genes respond to water stress very rapidly, whereas others are induced slowly after the accumulation of ABA. Most of the genes that respond to drought, salt, and cold stress are also induced by exogenous application of ABA (for review, see Shinozaki and Yamaguchi-Shinozaki, 1996; Bray et al., 1997). It appears that dehydration triggers the production of ABA, which in turn induces various genes. Several genes that are induced by water stress are not responsive to exogenous ABA treatment. These findings suggest the existence of both ABA-independent and ABA-dependent signal transduction cascades between the initial signal of drought or cold stress and the expression of specific genes (Shinozaki and Yamaguchi-Shinozaki, 1996; Bray et al., 1997). Promoter analysis of drought- and cold-inducible genes has identified several cis-acting elements that are involved in ABA-dependent and ABA-independent responses to conditions of water stress. Details of molecular mechanisms regulating responses of plant genes to water stress remain to be discovered, and there are many questions to be examined at the molecular level. These include the sensing mechanisms of water stress or osmotic stress, modulation of the stress signals to cellular signals, transduction of the cellular signals to the nucleus, transcriptional control of stress-inducible genes, and the function and cooperation of stress-inducible genes allowing water-stress tolerance. This Update focuses on recent progress toward understanding the signal transduction cascades leading to expression of water-stress-inducible genes. Possible sensors of osmotic stress in plants are discussed based on our knowledge of yeast and bacterial sensors. A glossary of terms is included to facilitate the reading.