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排序方式: 共有197条查询结果,搜索用时 31 毫秒
101.
102.
Vanessa A. Béland Zhiqiang Wang Dr. Charles L. B. Macdonald Dr. Tsun-Kong Sham Dr. Paul J. Ragogna 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(65):14790-14800
The reductive dehalogenation of a zwitterionic GeII species to make a zwitterionic GeI dimer with a 1,2-dicationic core is reported herein. To the root of the stability of this compound, the molecular and electronic structures were comprehensively characterized and investigated using crystallographic, spectroscopic, and computational methods. It was determined that the Ge centers are attracted because they are both electron-rich and positively charged. A comparison to the electronic structure in triphosphenium cations revealed varying degrees of covalent bonding and that this difference can be distinguished spectroscopically. 相似文献
103.
Kandhro GA Kazi TG Baig JA Sirajuddin Afridi HI Shah AQ Sheikh HR Kolachi NF Wadhwa SK 《Journal of AOAC International》2010,93(5):1589-1594
A simple and rapid cloud point extraction method was applied for preconcentration of trace quantities of zinc (Zn) and iron (Fe) in biological samples (serum and urine) of thyroid patients prior to determination by flame atomic absorption spectrometry. The metals in serum and urine samples were complexed with 1-(2-thiazolylazo)-2-naphthol and entrapped in the surfactant octylphenoxypolyethoxyethanol (Triton X-114). After centrifugation, the surfactant-rich phase was diluted with 0.1 M HNO3 in methanol. For optimum recovery of analytes, the influences of the analytical parameters, including pH and amounts of complexing and surfactant reagents, were investigated. Enrichment factors of 66.4 and 70.2 were obtained for the preconcentration of Zn(II) and Fe(III), respectively. The obtained results showed sufficient recoveries (>98%) for Zn(II) and Fe(III) in certified reference materials (CRMs). The proposed method was applied to the determination of Zn(II) and Fe(III) in biological (serum and urine) samples and CRMs. 相似文献
104.
Dr. Lidia Armelao Dr. Franziskus Heigl Dr. Sophie Brunet Dr. Ramaswami Sammynaiken Dr. Tom Regier Dr. Robert I. R. Blyth Dr. Lucia Zuin Dr. Rami Sankari Dr. Johannes Vogt Prof. Tsun‐Kong Sham 《Chemphyschem》2010,11(17):3625-3631
The distinct optical emission from ZnO materials, nanoneedles and microcrystallites synthesized with different sizes and morphologies by a flow deposition technique, is investigated with X‐ray excited optical luminescence (XEOL) and time‐resolved X‐ray excited optical luminescence (TR‐XEOL) from a synchrotron light source at the O K and Zn L3,2 edges. The innovative use of XEOL, allowing site‐specific chemical information and luminescence information at the same time, is fundamental to provide direct evidence for the different behaviour and the crucial role of bulk and surface defects in the origin of ZnO optical emission, including dynamics. XEOL from highly crystalline ZnO nanoneedles is characterized by a sharp band‐gap emission (~380 nm) and a broad red luminescence (~680 nm) related to surface defects. Luminescence from ZnO microcrystallites is mostly dominated by green emission (~510 nm) associated with defects in the core. TR‐XEOL experiments show considerably faster decay dynamics in nanoneedles compared to microcrystallites for both band‐gap emission and visible luminescence. Herein we make a fundamental step forward correlating for the first time the interplay of size, crystallinity, morphology and excitation energy with luminescence from ZnO materials. 相似文献
105.
We report a flow phenomenon in entangled polymer solutions that has never been described in the literature. A large-amplitude oscillatory shear was imposed on the polymer sample at a frequency higher than the overall chain relaxation rate. The resulting chain orientation led to a new environment in which the initially well-entangled chains managed to disentangle inhomogeneously in space. A layer lacking chain entanglement developed to take the load of the imposed strain. As a result of this nonlinearity, the rest of the sample avoided significant deformation and its chain entanglement remained intact. 相似文献
106.
Yip YC Chu HS Chan KC Chan KK Cheung PY Sham WC 《Analytical and bioanalytical chemistry》2006,386(5):1475-1487
An inductively coupled plasma quadrupole mass spectrometer equipped with an octopole collision/reaction cell was used for
the determination of cadmium in oyster tissue samples using isotope dilution inductively coupled plasma mass spectrometry.
The oyster samples in question were found to contain Mo and Zr. In our feasibility study on a Cd standard solution (10 μg
L−1) containing a matrix of Mo (1000 μg L−1) or Zr (250 μg L−1), the potentially interfering species (MoO+ or ZrO+) present at the analytical mass of cadmium concerned (m/z 111, 112 or 114) was reduced effectively through the use of a mixture of He and H2 as cell gases. The accuracy of the method was validated by the analysis of a matrix-matched certified reference material
(CRM) of NIST SRM 1566b. The CRM was analyzed under the standard and He/H2 cell modes. Two isotopic pairs of 114Cd/111Cd and 112Cd/111Cd were selected for quantification purposes. The recoveries of cadmium obtained in the two cell modes were compared with
each other. The validated method was applied successfully to the APMP.QM-P5 pilot study for international comparability purposes. 相似文献
107.
Sham M. Sondhi Sandeep Kumar Reshma Rani Ajanta Chakraborty Partha Roy 《Journal of heterocyclic chemistry》2013,50(2):252-260
A series of bis‐acridine derivatives 3a – j and 5a – j have been synthesized by condensation of 9‐chloro‐2,4‐(un)substituted acridines (1a – e) and 9‐isothiocyanato‐2,4‐(un)substituted acridines (4a – e) with diamine 2a and 2b , respectively. These bis‐acridines were evaluated in vitro for activity against a panel of human cancer cell lines of lung (NCI H‐522), ovary (PA1), breast (T47D), colon (HCT‐15), and liver (HepG2). Several bis‐acridines were found to possess good anticancer activity against various cancer cell lines. Of these, compound 3h exhibited good anticancer activity against all cancer cell lines tested except liver (HepG2) cell line. In addition to this, these compounds were screened for anti‐inflammatory activity at a dose of 50 mg/kg p.o. Compound 3g exhibited 41% anti‐inflammatory activity, which is better than most commonly used standard drug ibuprofen, which showed 39% anti‐inflammatory (at 50 mg/kg p. o.) activity. 相似文献
108.
Si K-edge XAFS was used to characterize a stoichiometric SiC film prepared by pulsed KrF laser deposition. The film was deposited on a p-type Si(1 0 0) wafer at a substrate temperature of 250 °C in high vacuum with a laser fluence of ∼5 J/cm2. The results reveal that the film contains mainly a SiC phase with an amorphous structure in which the Si atoms are bonded to C atoms in its first shell similar to that of crystalline SiC powder but with significant disorder. 相似文献
109.
Sham M. Sondhi Reshma Rani Partha Roy S. K. Agrawal A. K. Saxena 《Journal of heterocyclic chemistry》2011,48(4):921-926
Heterocyclic amidine derivatives of benzothiazole ( 6a , 6b , 6c ), benzimidazole ( 6d , 6e , 6f ), benzoxazole ( 6g , 6h , 6i ), and bis‐amidine derivatives of pyrimidine, ( 7a , 7b ) & triazole ( 7c , 7d , 7e ) ring system have been synthesized by nucleophilic addition reaction. All these compounds were screened for anti‐inflammatory and anticancer activities. At a dose of 50 mg/kg p.o., compounds 6c (39%), 6e (39%), and 6f (39%) exhibited anti‐inflammatory activity comparable to standard drug ibuprofen, which showed 39% activity and compounds 6b , 6e , 7a , and 7c exhibited moderate anticancer activity against cervix (HELA); neuroblastoma (IMR‐32); breast (MCF‐7), leukemia (THP‐1); and cervix (HELA) human cancer cell lines, respectively. J. Heterocyclic Chem., (2011). 相似文献
110.