Problems in Chemistry

利用数学方法解决化学问题是化学及相关专业学生必备的技能之一。作者Daley,H.O.针对这一需要,为大学学习普通化学的学生编写了这本习题集。通过解题学生可以检验自己对化学原理掌握的深浅程度。     

News in Brief

About 200 billion yuan (24.3 billion US dollars) of investment was spent in infrastructure projects in west China region in 2003, occupying 55.2 percent of the country's total annual investment to the region. According to a leading group conducting the west development strategy, China plans to invest 363.5 billion yuan (44 billion US dollars) to the west in 2003, including 76 key projects.     

Intermediate Filaments in Higher Plant Cells and Their Reconstitution in vitro

Delicate networks of 10-nm filaments were found to exist widely in suspension cells of cultured carrot and root tip cells of pea by selective extraction combined with whole mount and diethylene glycol distearate plastic embedment-free section for electron microscopy. These filament components are polypeptides of 52, 58, 62—64 and 50kD using Western blot analysis. A relatively uniform 10-nm filaments, as well as bundle of such filaments could be reconstituted in vitro. The reconstituted filaments were indistinguishable from native plant intermediate filaments in morphology and protein components. Thus the intermediate filaments are actually present in cytoplasm of higher plants. We also found no obvious specificity in tissues and species by comparison of the proteins among various types of plant cells.     

C-C activation in the solid state in an organometallic σ-complex

Herein is reported the synthesis, by a solid-state reaction from [Ir(NBD)(2)(P(i)Pr(3))][BAr(F)(4)], of the first example of a C-C σ-complex with iridium, [Ir(BINOR-S)(P(i)Pr(3))][BAr(F)(4)]. This compound is unique in that in the solid state it undergoes reversible activation of the C-C single bond that interacts with the metal center, establishing a temperature-dependent equilibrium between Ir(III) C-C σ/Ir(V) bis-alkyl complexes. This process has been interrogated by variable-temperature X-ray diffraction, NMR spectroscopy, and DFT calculations.     

Die Kohlenstoffbestimmung in Chloroestern der Orthokiesels?ure und in Alkylchlorsilanen

Ohne Zusammenfassung     

Development of X-ray fluorescence analysis in Russia in 1991–2010

A review attempted to examine the results of studies in X-ray fluorescence (XRF) analysis performed by Russian authors for the period from 1991 to the present time is given. This proved to be quite a challenge, since the number of articles published only on the theory and practice of XRF (excluding the development of equipment) exceeded 500. Therefore, the author had to limit himself to a more detailed presentation of only several important achievements. Further information, if necessary, can be found in the cited reviews.     

Eiwei? in Magermilch

Ohne Zusammenfassung     

Progress in oscillographic chronopotentiometry

The investigation on oscillographic chronopotentiometry after 2000 is reviewed. The development course of oscillographic chronopotentiometry is looked back. Some new instrumentations and new methods about oscillographic chronopotentiometry as well as applications of chemometrics in oscilloanalysis are introduced. The prospects of oscillographic chronopotentiometry development are also discussed in this paper.     

Dissolved oxygen in aeration-driven piezo-catalytic for antibiotics pollutants removal in water

The misuse of antibiotics and oxygen-lacking in aquaculture causes serious water environmental problems. Herein, a piezoelectic odd-layered Mo S2is prepared and applied to piezo-catalytic remove tinidazole(TNZ) and other antibiotic pollutants with aeration as a piezo-driving force. About 89.6% of TNZ can be degraded by Mo S₂ under aeration in the presence of dissolved oxygen with a reaction rate constant of0.15 min^-1, which is 2.4 times higher than that under N₂ ...     

Zur Bestimmung des in Wasser aufl?sbaren Calciums in Gips

Ohne Zusammenfassung     

Stabilization of Water‐Soluble Antioxidant in Water‐in‐Oil‐in‐Water Double Emulsions

Abstract

In this study, we are introducing a method that can effectively stabilize antioxidants in water‐in‐oil‐in‐water (W/O/W) double emulsions. Preliminarily, stable W/O/W double emulsions were produced by manipulating the characteristics of internal aqueous phase via two‐stage emulsification, resulting consequently in the formation of fine internal water droplets in the dispersed oil droplets. From conductivity measurements that can determine the elution amount of internal aqueous phase, it was confirmed that the double emulsion stability could be improved by treating the internal aqueous phase with a hydroxypropyl‐beta‐cyclodextrin. In this study, kojic acid, 5‐hydroxy‐2‐(hydroxymethyl)‐4‐pyrone was selected as a model antioxidant. The stabilization of kojic acid was attempted by locating it in the internal water droplets of the stable W/O/W double emulsions. The stability of kojic acid in the double emulsion system could be maintained at 90% for 10 weeks at high temperature. We believe that these stable W/O/W double emulsions could be used meaningfully as a carrier for many unstable antioxidants.     

Quasi-fluid state in gabbro

Usually, the matter state is divided into three kinds: solid state, fluid state and gas state. But under the normal temperature and pressure, the phenomenon of natural oscillation, similar to fluid property, happening on the surface of the solid-state materials, such as steel, Cu-Zn-Al alloy, and silicon single crystal, can be observed[1—3]. In the metal materials of the Cu-Zn-Al alloy and pure silver, the natural oscillation may lead to generation of alloy nanostructure as shown in fig. 1,…     

Die Polarographie von Blei in Hydroxyd- und in Cyanidl?sung

Ohne Zusammenfassung     

Zur Schnellbestimmung von Wasser in Teig und in Geb?ck

Ohne Zusammenfassung     

Antioxidant activity of β-carotene compounds in different in vitro assays

β-Carotene (BC) is the most abundant carotenoid in human diet, almost solely as(all-E)-isomer. Significant amounts of (Z)-isomers of BC are present in processed food as well as in mammalian tissues. Differences are described for the activity of various BC isomers in forming retinal and protecting against cancer and cardiovascular diseases. Eccentric cleavage of BC leads to degradation products such as carotenals. A variety of negative consequences were published for the non-vitamin A active BC metabolites, such as inducing the carcinogenesis of benzo[a]pyrene, impairing mitochondrial function, or increasing CYP activity. To increase the knowledge on the antioxidant activity, a variety of BC isomers and metabolites were tested in various in vitro assays. In the present study, no ferric reducing activity (FRAP assay) was observed for the BC isomers. Between the major BC isomers (all-E, 9Z, and 13Z) no significant differences in bleaching the ABTS●+ (αTEAC assay) or in scavenging peroxyl radicals (ROO●) generated by thermal degradation of AAPH (using a chemiluminescence assay) were detected.However, the (15Z)-isomer was less active, maybe due to its low stability. The degradation to β-apo-carotenoids increased FRAP activity and ROO● scavenging activity compared to the parent molecule. Dependence on chain length and character of the terminal function was determined in αTEAC assay with following order of increasing activity: β-apo-8'-carotenal < β-apo-8'-carotenoic acid ethyl ester < 6'-methyl-β-apo-6'-carotene-6'-one (citranaxanthin). The results indicate that BC does not lose its antioxidant activity by degradation to long chain breakdown products.