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.     

Die Kohlenstoffbestimmung in Chloroestern der Orthokiesels?ure und in Alkylchlorsilanen

Ohne Zusammenfassung     

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.     

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.     

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.     

Zur Schnellbestimmung von Wasser in Teig und in Geb?ck

Ohne Zusammenfassung     

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

Ohne Zusammenfassung     

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,…     

Zur Kupier- und Molybd?nbestimmung in Mineralien, in Molybd?nkonzentraten und in Ferromolybd?n

Ohne Zusammenfassung     

Tritium in surface waters, tap water and in precipitation in Poland during the 1994–1999 period

Concentrations of tritium in environmental waters (precipitation, rivers, lakes, tap water) have been determined using electrolytic enrichment and liquid scintillation counting. In waters of big rivers (the Vistula and the Odra rivers), lakes and tap water the annual average concentrations were similar to each other being from 1.4 to 1.9 Bq·dm^-3. These concentrations were similar to those in the precipitation in which they ranged from 1.7 to 2.2 Bq·dm^-3. The lowest tritium concentrations were found in waters of the Seashore Region rivers (average for 1994–1999 was 1.1 Bq·dm^-3). The tritium concentrations in surface waters and in precipitation are still higher than that of natural level. The data obtained show that tritium concentration in the water of rivers might depend on the size of drainage area. The observed seasonal variations of tritium concentration in the precipitation collected in Warsaw and at the Mount Sniezka indicate the stratospheric source of tritium. It was found that about 30% of tritium deposited with precipitation is removed to the Baltic Sea with river waters.     

Radon concentrations in kindergartens and schools in two cities: Kalisz and Ostrów Wielkopolski in Poland

Plastic PicoRad detectors with activated charcoal have been used for radon monitoring in local kindergartens and schools in two cities, Kalisz and Ostrów Wielkopolski, in the region of Greater Poland. Detectors were exposed for a standard time of 48 h during the autumn and winter of 2011 in 103 rooms (Kalisz) and 55 rooms (Ostrów Wlkp), respectively. The detectors were calibrated in the certified radon chamber of the Central Laboratory for Radiological Protection in Warsaw, Poland. The arithmetic and geometric means of indoor radon concentrations in the examined rooms were 46.0 and 30.3 Bq/m³ for Kalisz and 48.9 and 29.8 Bq/m³ for Ostrów Wlkp, respectively. The measured levels of the indoor radon concentrations were relatively low, since the main source of indoor radon for these low storey (max. three storeys) buildings is radon escaping from the underlying soil with a low ²²⁶Ra concentration (~15 Bq/m³). Therefore, the calculated annual effective doses from that source for the children in Kalisz and Ostrów Wlkp were also low 0.35 mSv.     

Elements in the Sera of Preschool Children Living in Central Taiwan

This study assessed elemental concentrations in the serum of 154 preschool children in central Taiwan via instrumental neutron activation analysis （INAA）. A total of eight elements, Br, C1, Fe, Na, Rb, Sc, Se and Zn of sera for Taiwanese preschool children living at four residential areas： Taichung city, Taichung urban townships and in a remote area inhabited by two groups of aborigines, Atayal and Bunun were determined. Standard reference materials （tomato leaves, NIST-SRM 1570a, and lichen, IAEA-336） were used as quality control standards to crosscheck the accuracy. Residential area, socioeconomic status and gender were shown to significantly influence serum levels of the eight trace elements. Statistical analysis revealed several different gender patterns via the two-tailed student＇s test. A quantified index of agreement （AT） was used to classify these elements. Small AT indicated a close consistency, while large AT indicated a larger fluctuation, or less agreement, such that the correlation between the elements could be interpreted using a series of quantified indices at the serum levels of preschool children.