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991.
The surface properties of aluminosilicates (perlites and zeolites)—potential fillers in abrasive articles—have been examined by inverse gas chromatography. The dispersive component of the surface free energy ( $ \gamma_{\text{S}}^{\text{D}} $ ) and K A and K D describing the acidity and basicity, respectively, of the fillers were used to express the surface activity of examined materials. The Flory–Huggins parameter, $ \chi_{23}^{'} , $ characterized the interactions between polymer and filler, i.e., interactions between phenolic resin and filler. Zeolites were found to be materials with an active surface layer and relatively high ability to participate in filler–resin interactions. Therefore, they might be considered as potential “replacement material” for standard fillers. The IGC-derived values mentioned above provided useful information about the behavior of fillers during the manufacture and use of abrasive articles. 相似文献
992.
García Ruano JL Torrente E Alonso I Rodriguez M Martín-Castro AM Degl'Innocenti A Frateschi L Capperucci A 《The Journal of organic chemistry》2012,77(4):1974-1982
Phenylselenyl benzylcarbanion stabilized by an (S)-2-p-tolylsulfinyl group evolves in a highly stereoselective way in the reactions with (S)-N-(p-tolylsulfinyl)imines at -98 °C affording diastereomerically pure 1,2-selenoamino derivatives in good yields. The syn or anti relationship of the obtained compounds depends on the alkyl or aryl character of the imine. They are easily transformed into enantiomerically pure (1R,2S)-1-aryl[or (1S,2S)-1-alkyl]-2-(phenylseleno)-2-phenylethylamines by reaction with t-BuLi and subsequent methanolysis of the generated sulfinamide derivatives with TFA. 相似文献
993.
Williams KS Hooper JP Horn JM Lightstone JM Wang H Ko YJ Bowen KH 《The Journal of chemical physics》2012,136(13):134315
Negative-ion photoelectron spectroscopy and ab initio simulations are used to study the variation in magnetic structure in Mn(x)O(y) (x = 3, 4[semicolon] y = 1, 2) clusters. The ferrimagnetic and antiferromagnetic ground-state structures of Mn(x)O(y) are 0.16-1.20 eV lower in energy than their ferromagnetic isomers. The presence of oxygen thus stabilizes low-spin isomers relative to the preferred high-spin ordering of bare Mn(3) and Mn(4). Each cluster has a preferred overall magnetic moment, and no evidence is seen of competing states with different spin multiplicities. However, non-degenerate isomags, which possess the same spin multiplicity but different arrangements of local moments, do contribute additional features and peak broadening in the photoelectron spectra. Proper accounting for all possible isomags is shown to be critical for accurate computational prediction of the spectra. 相似文献
994.
Ambadas B. Rode Jinkwon Kim Sang-Ho Kim Gajendra Gupta In Seok Hong 《Tetrahedron letters》2012,53(20):2571-2574
A novel S,S′-diallyl carbohydrazonodithioate derivative 3 of rhodamine B hydrazone was developed as a chemodosimeter for selective detection of mercury ions based on Hg2+ promoted cyclization. The allyl groups of 3 play a key role in the binding and selection of Hg2+ ions. The probe responds selectively to Hg2+ over various other competitive cations with marked chromo- and fluorogenic changes. The formation of stable oxadiazole derivative 8 was a strong driving force for this high selectivity. Practically, this probe is more promising because of the remarkable high selectivity, faster response, low detection limit, and aqueous solubility of 3. 相似文献
995.
996.
de Oliveira EC Monteiro MI Pontes FV de Almeida MD Carneiro MC da Silva LI Alcover Neto A 《Journal of AOAC International》2012,95(2):560-566
Chemical analysts use analytical blanks in their analyses, but seldom is this source of uncertainty evaluated. Generally, there is great confusion. Although the numerical value of the blank, in some situations, can be negligible, its source of uncertainty cannot be. This article discusses the uncertainty contribution of the analytical blank using a numerical example of the copper content in waters by flame atomic absorption spectrometry. The results indicate that the uncertainties of the analytical blank can contribute up to 50% when the blank sample is considered in this analysis, confirming its high impact. This effect can be primarily observed where the analyte concentration approaches the lower range of the analytical curve. Even so, the blank is not always computed. Therefore, the relevance of the analytical blank can be confirmed by uncertainty evaluation. 相似文献
997.
L. Fuks E. Gniazdowska P. Koźmiński I. Herdzik-Koniecko 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(1):395-399
The radiosynthesis of [99mTc]-phenformin ([99mTc]-1-phenethylbiguanide) complex and its suitability as precursor of the radiopharmaceuticals for the tumor imaging was assessed.
Radiochemical purity of the [99mTc]-complex was determined using radio-TLC and was studied by the HPLC with radiochemical detection, while its stability in
challenge experiments. The results show, that due to the sufficient stability and lipophilicity of the complex, it fulfills
our expectations for promising radiopharmaceutical precursor not only for the diagnostic agent, but also for the drug suitable
for the oncological Auger electron therapy. 相似文献
998.
Kyung-Seok Ko Jae Gon Kim Kyoochul Ha Kil Yong Lee 《Journal of Radioanalytical and Nuclear Chemistry》2012,294(2):229-235
The objective of this research is to trace the sources of stream sediments in a small watershed influenced by anthropogenic and lithogenic origins identified by the spatial distributions and temporal variations of stream sediments using geochemical interpretation of the stable and radiogenic isotopes, major components, and heavy metals data and principal component analysis. To know the effects of both present and past mining, the stream sediments were sampled at the stream tributaries and sediment coring work. The spatial distributions of heavy metals clearly showed the effects of Cu and Pb?CZn mineralization zones at the site. Anthropogenic Pb was elevated at the downstream area by the stream sediments due to an active quarry. The results of principal components analysis also represent the effects of the stream sediments origins, including anthropogenic wastes and the active quarry and lithogenic sediment. Anomalous Cu, indicating the effect of past Guryong mining, was identified at the deep core sediments of 1.80?C5.05?m depth. The influence of active quarry was shown in the recently deposited sediments of <1.50?m depth, which was proved by the profiles of radioactive 210Pb and stable Pb and Sr isotopes. This study suggests that the chemical studies using radiogenic and stable isotopes and heavy metals and multivariate statistical method are useful tools to discriminate the sources of stream sediments with different origins. 相似文献
999.
K. H. Kim H. -J. Ko K. Kim Y. -S. Jung S. -H. Oh K. -J. Cho 《Journal of Engineering Thermophysics》2012,21(1):1-15
The transient thermal behavior in the cryogenic oxidizer tank for the liquid propulsion system of the KSLV-I satellite launching
space vehicle is theoretically investigated for the pressurization process by gaseous helium injection followed by the readiness
check stage. The numerical model is established using the transient mass and energy conservation of oxygen/helium mixtures
both in ullage and liquid regions. At the liquid-gas interface, various modes of heat and mass transfer are considered, including
the liquid evaporation and the helium absorption. The present study focuses on the effects of the increasing pressurization
level on some of important properties that should be considered in the propulsion system design, such as tank pressure, ullage
gas temperature, and evaporation of liquid oxygen. Particularly, the tank pressure drop after the pressurization is investigated
in the proposed design of propulsion system. Also, the effect of the initial loading of liquid oxygen in the oxidizer tank
is studied and discussed. As for the helium absorption into the liquid region, its mass is negligibly small and it should
not be the concern in design and operation of the oxidizer tank system. 相似文献
1000.
The dynamic response of viscoelastic fluids under large amplitude oscillatory shear (LAOS) has been a subject of long history. In the LAOS flow, the analysis has been mostly focused on shear stress, possibly due to the lack of accurate measurement of normal stress. However, the normal stress may become larger than shear stress at high-strain amplitudes, and thus it is important that we have a good understanding of the normal stress behavior. Furthermore, with the advancement in the instrumentation, it has become possible to get more reliable data. The purpose of this paper is to develop a research platform to analyze and to understand the normal stress behavior of complex fluids under LAOS flow. In this study, we utilized the Giesekus model as a representative constitutive model, and investigated its diverse responses. We defined the dynamic properties corresponding to normal stress, in a similar way to define dynamic moduli from shear stress, and examine their behavior with various analyzing tools. Experimental data were also compared with model predictions. Despite the fact that it is not yet possible to compare all of the predictions because of instrumental limitation, the prediction has been found to fit well with the experimental data. This study is expected to provide a useful framework for further understanding the nonlinear behavior of complex fluids at large deformation. 相似文献