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排序方式: 共有152条查询结果,搜索用时 62 毫秒
51.
52.
Ion Sava Inga A. Ronova Maria Bruma 《Journal of Macromolecular Science: Physics》2013,52(10):1991-2002
Two series of aromatic polyimides differing by the bridging group between imide rings, polymers a, b, and c, having C?O linkages and polymers d, e, and f, having C(CF3)2 groups, have been obtained by polycondensation reaction of aromatic dianhydrides with aromatic diamines containing substituted azobenzene groups. These polymers with good solubility in polar amidic solvents, were able to form transparent flexible films and showed high thermal stability. Conformational parameters of the polymers were calculated by the Monte Carlo method with allowance for hindered rotation. Several physical properties of these polymers, such as solubility, glass transition temperature (Tg), and initial decomposition temperature (Tonset) were measured and discussed in relation to the volume factor of the macromolecular chains. The volume factor is equal to ratio of the Van der Waals volume of the pendent group to the Van der Waals volume of the repeating unit of the main chain. 相似文献
53.
C. Küppersbusch S. Pascu P. von Brentano D. Bucurescu Gh. C?ta-Danil D. Deleanu J. Endres M. Elvers D. Filipescu C. Frie?ner D. G. Ghi?? T. Glodariu C. Mihai N. M. M?rginean R. M?rginean A. Negre? T. Sava L. Stroe V. Werner N. V. Zamfir K. -O. Zell A. Zilges 《The European Physical Journal A - Hadrons and Nuclei》2012,48(1):1-15
The low-spin excitations of the nucleus 146Sm which is just two neutrons and two protons away from the N = 82 shell and Z = 64 subshell closures have been investigated by means of the 143Nd (??, n) and 144Nd (??, 2n) fusion-evaporation reactions. We established 47 hitherto unknown energy levels up to 4.7MeV and 75 new transitions. In addition, 7 spin assignments were possible from the ??-?? angular correlation analysis. The structure of the possible candidates for a 2+ ? 3? quadrupole-octupole multiplet are first discussed in terms of the harmonic vibrational model. A comparison of these states with the corresponding ones in the neighboring N = 84 isotones is also presented. Finally, the structure of the 146Sm nucleus is interpreted in terms of the IBA-spdf model. It is shown that the model is able to reproduce the experimental relative transition strengths of the 2+ ? 3? quadrupole-octupole multiplet and also a series of collective properties such as the proposed double-octupole excitations. 相似文献
54.
Cylindrical diffusion chamber for radon measurement equipped with nuclear track detector (CR-39) and electretis considered in this work. Electret is electrostatic analogous of permanent magnet which preserves constant and strong electric
field for long time period. Electrets were used to attract radon progeny formed in a cup where CR-39 was placed for radon
measurements. In this way the sensitivity of detector could be increased by bringing progeny just in front of detector in
more convenient measuring geometry.
Influence of distance between electret and detector on sensitivity of such equipment has been investigated theoretically.
Different geometrical setups of detector and electret were tested in order to optimize this kind of device. Some results are
presented in this report.
相似文献
55.
56.
Due to the increasing frequency of wildfires in recent years, there is a strong need for developing mitigation strategies to manage the impact of smoke exposure of vines and occurrence of ‘smoke taint’ in wine. One plausible approach would be to prevent or inhibit the uptake of volatile phenols from smoke into grape berries in the vineyard. In this study we describe a model system we developed for evaluating under controlled conditions the effectiveness of a range of surface coatings (including existing horticultural sprays) for reducing/preventing the uptake of volatile phenols and their subsequent conversion to phenolic glycosides. Grapes were coated with the materials to be tested and then exposed to gaseous phenols, via evaporation from an aqueous solution, in a semi-closed glass container. Analysis of volatile phenols and their glycosidic grape metabolites demonstrated that the treatments typically did not provide any significant protection; in fact, some resulted in higher concentrations of these compounds in the grapes. The highest concentrations of volatile phenols and their glycosides were observed after application of oily, hydrophobic materials, suggesting that these materials may enhance the adsorption or transfer of volatile phenols into grape berries. Therefore, it is important to consider the types of sprays that are being applied in the vineyard before and during smoke events to prevent the potential of exacerbating the uptake of smoke compounds by grape berries. 相似文献
57.
A new model is proposed for the structure of low atomic coordination chalcogenide glasses. The closed clusters model is based on the various types of clusters, packed by van der Waals forces in a molecular-type packing. Arguments are given to support the new model, taken as example the typical chalcogenide glass As2S3. 相似文献
58.
M. Crul H. J. G. D. van den Bongard M. M. Tibben O. van Tellingen G. Sava J. H. M. Schellens J. H. Beijnen 《Analytical and bioanalytical chemistry》2001,369(5):442-445
NAMI-A is a novel ruthenium-containing experimental anticancer agent. We have developed and validated a rapid and sensitive
analytical method to determine NAMI-A in human plasma, plasma ultrafiltrate and urine using atomic absorption spectrometry
with Zeeman correction. The sample pretreatment procedure is straightforward, involving only dilution with an appropriate
hydrochloric acid buffer-solution. Because the response signal of the spectrometer depended on the composition of the sample
matrix, in particular on the amount of human plasma in the sample, all unknown samples were diluted to match the matrix composition
in which the standard line was prepared (plasma-buffer 1 : 10 v/v). This procedure enabled the measurement of samples of different
biological matrices in a single run. The validated range of determination was 1.1–220 μM NAMI-A for plasma and urine, and
0.22–44 μM for plasma ultrafiltrate. The lower limit of detection was 0.85 μM in plasma and urine and 0.17 μM in plasma ultrafiltrate.
The lower limit of quantitation was 1.1 and 0.22 μM, respectively. The performance of the method, in terms of precision and
accuracy, was according to the generally accepted criteria for validation of analytical methodologies. The applicability of
the method was demonstrated in a patient who was treated in a pharmacokinetic phase I trial with intravenous NAMI-A.
Received: 1 September 2000 / Revised: 1 November 2000 / Accepted: 12 November 2000 相似文献
59.
Kerry Wilkinson Renata Ristic Imogen McNamara Beth Loveys WenWen Jiang Mark Krstic 《Molecules (Basel, Switzerland)》2021,26(24)
It has been well established that bushfire/wildfire smoke can taint grapes (and therefore wine), depending on the timing and duration of exposure, but the risk of smoke contamination from stubble burning (a practice employed by some grain growers to prepare farmland for sowing) has not yet been established. This study exposed excised bunches of grapes to smoke from combustion of barley straw and pea stubble windrows to investigate the potential for stubble burning to elicit smoke taint. Increased levels of volatile phenols (i.e., chemical markers of smoke taint) were detected in grapes exposed to barley straw smoke (relative to control grapes), with smoke density and the duration of smoke exposure influencing grape volatile phenols. However, the sensory panel did not perceive wine made from grapes exposed to low-density smoke to be tainted, despite the presence of low levels of syringol providing compositional evidence of smoke exposure. During the pea stubble burn, grapes positioned amongst the burning windrows or on the edge of the pea paddock were exposed to smoke for ~15–20 and 30–45 min, respectively, but this only resulted in 1 µg/kg differences in the cresol and/or syringol concentrations of smoke-affected grapes (and 1 µg/L differences for wine), relative to controls. A small, but significant increase in the intensity of smoke aroma and burnt rubber flavor of wine made from the grapes positioned amongst the burning pea stubble windrows provided the only sensory evidence of any smoke taint. As such, had vineyards been located immediately downwind from the pea stubble burn, it is unlikely that there would have been any smoke contamination of unharvested grapes. 相似文献
60.