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131.
The thermally irreversible photochromic compound dithia-dithienylethenophane was synthesized, which is the first example of a dithienylethene bridged with benzene ring and due to the fixation to the photoactive anti-conformation the quantum yield for the photocyclization reaction became higher than that of the corresponding nonbridged type dithienylethene. 相似文献
132.
A new method for the preconcentration and determination of trace amounts of lead at the μg/L level in natural waters has
been established based on the formation of the thenoyltrifluoroacetone (TTA) complex with dibenzo-18-crown-6 (DB18C6) by means
of synergistic extraction and back-extraction combined with atomic absorption spectrometry (AAS). The effect of various factors
(synergism with TTA and DB18C6, shaking time, preconcentration factor, composition of the extracted species, and foreign ions
etc.) on the extraction and back-extraction of lead has been investigated in detail. The lead-TTA chelate in o-dichlorobenzene forms a stable adduct with DB18C6 as Pb(TTA)2 DB18C6. The stability constant (β) of the adduct determined by curve fitting method was log β = 4.2. The amount of lead in
natural waters such as tap water (Kanazawa University) and Kakehashi river (Komatsu City) determined by the present method
was found to be 0.64 ± 0.02 μg/L and 5.10 ± 0.03 μg/L, respectively.
Received: 14 July 1997 / Revised: 3 November 1997 / Accepted: 20 January 1998 相似文献
133.
F. De Corte S. M. Hossain S. Jovanovič A. Dlabač A. De Wispelaere D. Vandenberghe P. Van den Haute 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(3):551-555
A study is made of the corrections that are needed in the evaluation of the annual radiation dose, for use in TL/OSL-dating, via NaI(Tl) field gamma-ray spectrometry (monitoring of K, Th and U), calibrated via voluminous blocks that are simulating the Auger hole measuring conditions. Two cases are considered: the Heidelberg granite calibration block, which was found to be quasi-infinite, and the Oxford concrete calibration blocks, for which effective concentrations of elements are reported so as to account for their non-infiniteness. The calculations, via the software package ANGLE, are based on the concept of effective solid angles for Marinelli geometries. 相似文献
134.
A 60kDa spider toxin binding protein from bovine brain was solubilized with digitonin and purified up to 5800-folds over starting crude homogenate. The purification procedure entailed DEAE-cellulose, concanavalin-A affinity, 1-naphthylacetyl spermine affinity and high performance liquid chromatography. The purified protein owned a very high affinity for ligand 125I-JSTX-3 binding Kd 15.6nM and Bmax 6.5nM. The amino acid composition of the protein was determined. The N-terminal amino acid sequence analysis yielded a unique sequence: NH2-X-Pro-X-Val-Tyr-Phe-Lys-Glu-Gln-Phe-Leu-Asp-Gly-Asp-X. 相似文献
135.
Surface phase behavior of n-hexadecyl phosphate (n-HDP) and its mixture with L-arginine (L-arg), which behaves as L-argininium cation (L-arg(+)) in aqueous solution, at a molar ratio 2:3 in Gibbs adsorption layers has been studied by film balance, Brewster angle microscopy (BAM) and surface tensiometry at 20 degrees C. The monolayers of n-HDP show three phases that are gas (G), intermediate (I) and liquid condensed (LC), and two phase transitions. A first-order G-I phase transition that is followed by a second-order I-LC phase transition is found in these monolayers. Although the monolayers of the mixtures containing n-HDP and L-arg show three phases, the nature of the middle phase is different from that of the n-HDP monolayers. The three phases observed for the mixed systems are G, liquid expanded (LE) and LC phases. A first-order G-LE phase transition is found at a low surface pressure at > or =10 degrees C. This transition is followed by another first-order LE-LC phase transition at a certain higher surface pressure. The first-order nature of the phase transitions for both the systems is confirmed by the presence of plateaus in the pi-t curves, which are accompanied by two surface phases. A second-order phase transition in the monolayers of n-HDP is indicated by a gradual change in the surface morphology, from a uniformly bright isotropic to an anisotropic mosaic textured phase, which is accompanied by a continuous change in the surface pressure. The domains formed during the first-order phase transition in the adsorption layers of n-HDP are circular and remain unaffected by changing the temperature. Although the domains of an LE phase are circular, those of an LC phase at the latter transition are fractal in the mixed system. A further branching of the arms of the fractal domains is found to occur by an increase in the temperature. All the results are explained by considering salt formation between anion from n-HDP and L-arg(+). 相似文献
136.
M. Sakhawat Hussain Abdul Rahman Al-Arfaj M. Latif Hossain 《Transition Metal Chemistry》1990,15(4):264-269
Summary Novel mixed-ligand copper(I) complexes of general formula [TPP–Cu–(L)Cl] or [TPPhos–Cu–(L)Cl], where TPP=triphenylphosphine, TPPhos=triphenylphosphate and L=imidazolidine-2-thione [Imt],N-propylimidazolidice-2-thione [PrImt],N-i-propylimidazolidine-2-thione [iPrImt], and 1,3-diazinine-2-thione [Diaz] and bis coniplexes of formula [(L)2CuCl] where L=[PrImt] and [iPrImt] have been prepared and characterized by electronic, vibrational and n.m.r. spectroscopy. The spectral data are consistent with S-donation of thiones. The magnitude of upfield shift in13Cn.m.r. of the thionreide carbon on complexation has been interpreted in terms of coordination geometry around the metal stoms. X-ray structure analysis agrees with the conclusions from the spectroscopic measurements. The structure of [(PrImt)2CuCl] revealed three-coordinated copper(I) with crystal data:a=14.106(4),b=14.380(2),c=19.024(3) A, =108.8(2)°,z=8 and space group P2/c. 相似文献
137.
M. Sakhawat Hussain M. Latif Hossain Abderehman Al-Arfaj 《Transition Metal Chemistry》1990,15(2):120-125
Summary Novel mixed-ligand complexes of Ag1 and Au1 containing triphenylphosphine (TPP) and heterocyclic thiones, of general formula [TPP–M–L]Cl and [(TPP)2–M–L]Cl, where L=imidazolidine-2-thione (Imt), 1,3-diazinine-2-thione (Diaz) or N-isopropylimidazolidine-2-thione (iPrImt) have been prepared. The spectroscopic data are consistent with S-donation in all complexes. The magnitude of high-field shift in carbon-13 n.m.r. of the thioureide carbon on complexation is interpreted in terms of coordination geometry around the metal atoms. The mixed-ligand complexes are structurally similar to some of the commonly used antiarthritic Au1 drugs and are thus potentially useful in chemotherapy. 相似文献
138.
Mohammad Abul Hossain Mikio Kumita Yoshimasa Michigami Shigeru Mori 《Adsorption》2005,11(5-6):561-568
Dynamic characteristics of Cr(VI) sorption on used black tea leaves (UBTLs) as a low-cost adsorbent are studied. Batch experiments
were conducted to evaluate the effects of Cr(VI) concentration, solution pH and temperature on the removal process. Both of
adsorption and reduction, involved in the process, are affected by the processing parameters. The adsorption kinetics is described
successfully using pseudo-second order rate equation and the rate constant decreases with increasing the initial concentration
of Cr(VI) up to 150 mg/L (for 0.1 g/L UBTLs) then becomes slow. Experimental and calculated kinetic data for equilibrium are
well expressed by Langmuir isotherm. The solution pH has a profound effect on the adsorption rate. The rate constant increases
linearly with an increase in temperature, and the low value of activation energy of adsorption, 16.3 kJ/mol, indicates that
Cr(VI) is easily adsorbed on UBTLs. The maximum Cr(VI) adsorptive conditions, with a minimum reduction, were achieved from
the dynamics of operational parameters: the initial Cr(VI) concentration < 150 mg/L (for 0.1 g/L UBTLs); the initial solution
pH = 1.54–2.00 and the processing temperature < 50 ∘C, for the possibility of its practical application. 相似文献
139.
Borophosphosilicate glass (BPSG) has been used for its improved reflow properties compared to low temperature oxide (LTO) in planar technology. Thin films of BPSG were deposited by a low-pressure chemical vapor deposition process. The boron content was determined by NDP. In addition from the NDP spectrum the depth profile of boron and the thickness of the film were also determined. In the NDP technique, samples, typically silicon wafers with 500 nm thick BPSG film, were exposed to a highly-thermalized neutron beam. Generated by the10B(n,)7 Li reaction, isotropically emitted monoenergetic particles of 1.47 MeV were counted in an evacuated in-beam analysis setup. The energy loss of the -articles in the film was proportional to the depth at which the nuclear reaction took place. The energy spectrum of the -articles, therefore, was a direct result of the boron depth profile, and the area under the curve was a measure of the total number of boron atoms in the film. This unique nuclear technique provided an excellent method for optimizing the composition of the BPSG film for device processing. 相似文献
140.
Md. Delwar Hossain 《Tetrahedron》2006,62(29):6955-6960
Diaryliodonium triflates have been directly prepared by reaction of some iodoarenes with aromatic substrates in good yields by using K2S2O8/CF3COOH/CH2Cl2. Treatment of a variety of iodoarenes with iodobenzene under the same conditions resulted in ligand transfer, and (4-iodophenyl)(phenyl)iodonium triflate was obtained. This procedure avoids the use of high temperature and severe reaction conditions. 相似文献