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991.
The contribution of the population fluctuations of two-level systems in glasses to the dynamic structure factor
is calculated using the concept of elastic dipoles. Describing the two-level systems by the tunneling model, with reasonable assumptions about the distribution of tunneling frequencies an essentially logarithmic decay in time of
is obtained. 相似文献
992.
S. Büttgenbach R. Dicke H. Gebauer R. Kühnen F. Träber 《Zeitschrift für Physik A Hadrons and Nuclei》1978,286(4):333-340
The hyperfine interaction constantsA andB of six low-lying metastable fine structure states of the two iridium isotopes191Ir and193Ir and the electronicg-factors of these levels have been measured using the atomic-beam magnetic-resonance method. From the values of the magnetic-dipole interaction constantsA, corrected for off-diagonal perturbations, we extracted the hyperfine anomaly of a pure 6s-electron state:191 Δ s 193 =0.64(7)%. Using nonrelativistic approximations for the effective radial parameters the nuclear electric-quadrupole moments were obtained:Q(191Ir) = 0.81(21)b,Q(193Ir)=0.73(19)b 相似文献
993.
Erwin Brüning 《Communications in Mathematical Physics》1978,58(2):167-194
The problem of uniqueness of monotone continuous linear extensions of $$T_{(2N)} = \{ 1,T_1 ,...,T_{2N} \} \in E'_{(2N)} = \prod\limits_{n = 0}^{2N} {E'_n } $$ is solved. A characterization of a relativistic QFT in terms of finitely many VEV's is derived. All results are illustrated by an explicit discussion of the extension problem for special cases ofT (4)={1,0,T 2,T 3,T 4}. This discussion contains explicitly necessary and sufficient conditions onT (4) for the existence of minimal extensions and some convenient sufficient conditions. 相似文献
994.
In this work a novel graphical method is applied to the presentation of intercomparison results. This is demonstrated with
the results of a recent intercomparison in measuring the 137Cs, 40K, and 90Sr activity concentration in milk powder. The “PomPlot”, an intuitive graphical method, is used for producing a summary overview
of the participants’ results of a common measurand. The “PomPlot” displays (relative) deviations of individual results from
the reference value on the horizontal axis and (relative) uncertainties on the vertical axis. 相似文献
995.
Reaction of benzotriazol‐1‐yl acetone 1 with phenyl isothiocyanate followed with α‐chloroacetone or ethyl‐α‐chloroacetate afforded 2‐anilinothiophenes 3 or 4 , respectively. Treatment of 3 with malononitrile at different reaction conditions afforded 6 or 7 . Reaction of 1 with CS2 in DMF and phenacylbromide afforded S‐alkylated thiophene 10 . Reactions of the latter compound with different active methylene nitriles afforded thienylthiopyridine derivatives 14 and 15 . Condensation of 10 with hydrazine hydrate afforded hydrazon derivative 16 . Reaction of thiophene 17 with formamide in DMF afforded 19 which converted to N‐thienylpyrimidine 20 when treated with malononitrile. The structure of the newly synthesized compounds has been established on the basis of their analytical and spectral data. The compounds were also investigated for antibacterial and antifungal activities. 相似文献
996.
Responsive polymers have been the focus of many studies during the past decade because of their ability to change according to environmental stimuli. In this paper, we report on the development of a method to synthesize a pH/temperature‐sensitive linear copolymer, poly(N‐isopropylacrylamide‐ co‐acrylic acid)(poly(NIPAAm‐co‐AAc)), with a molecular weight of about 106–105 Da in water using azobisisobutyronitrile (AIBN) as the initiator. The effects of the following on the lower critical solution temperature (LCST) of the copolymer and homopolymer of NIPAAm were investigated: the type of buffer salts and pH changes of test solutions, molecular weight and concentration of homopolymer/copolymer solutions, and AAc monomer molar feed ratio (mol%). The effects of different synthesis methods on the molecular weight and on the AAc content were also evaluated. The mechanism of action in environments with different pH values is discussed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
997.
Seung‐Chul Choi Jaejung Ko Sang Ook Kang Won‐Sik Han Ki‐Young Choi 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(3):m85-m87
The copper(II) ion in the syn–anti carboxylate‐bridged one‐dimensional zigzag chain title complex, {[Cu(C16H18N3O2)]ClO4}n, exhibits a distorted trigonal–bipyramidal environment. Two N atoms and one carboxylate O atom of the ligand form the basal plane, while the axial positions are filled by an N atom of the ligand and one O atom belonging to the carboxylate group of an adjacent molecule. The crystal packing is enhanced by C—H⋯O(perchlorate) hydrogen bonds. 相似文献
998.
T. K. Ikäheimonen V. P. Vartti E. Ilus J. Mattila 《Journal of Radioanalytical and Nuclear Chemistry》2002,252(2):309-313
Liquid discharges of 99Tc from the Sellafield nuclear facilities increased largely in the mid 90"s. These releases are transported to the Nordic sea areas by the ocean currents. Results of the 99Tc activities along the Norwegian coastal areas and in the North Sea have been reported but then again, the spreading of 99Tc into Baltic Sea has not been studied thoroughly. Fucus vesiculosus and seawater samples were collected in the summer 1999 from the Finnish coastal areas for measuring 99Tc in the Baltic Sea area. A modified analytical method for measuring 99Tc in the environmental samples was developed at that time. The method based on extraction chromatography and liquid scintillation measurement of 99Tc. The 99Tc concentration in the Fucus vesiculosus in the Finnish coast of the Baltic Sea varied from 1.6 to 11.6 Bq/kg (dry weight) being highest at the most northern sampling sites. These values were considerable lower than those in the Danish and Norwegian coasts. The variation in the concentrations observed are probably due to biological factors. The 99Tc concentration in the Baltic Sea water studied was below 0.2 Bq/m3. 相似文献
999.
Guey‐Sheng Liou Sheng‐Huei Hsiao 《Journal of polymer science. Part A, Polymer chemistry》2002,40(15):2564-2574
A new N‐phenylated amide (N‐phenylamide) unit containing aromatic diamine, N,N′‐bis(3‐aminobenzoyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine, was prepared by the condensation of N,N′‐diphenyl‐1,4‐phenylenediamine with 3‐nitrobenzoyl chloride, followed by catalytic reduction. Two series of organosoluble aromatic poly(N‐phenylamide‐imide)s and poly(N‐phenylamide‐amide)s with inherent viscosities of 0.58–0.82 and 0.56–1.21 dL/g were prepared by a conventional two‐stage method and the direct phosphorylation polycondensation, respectively, from the diamine with various aromatic dianhydrides and aromatic dicarboxylic acids. All polyimides and polyamides are amorphous and readily soluble in many organic solvents such as N,N‐dimethylacetamide and N‐methyl‐2‐pyrrolidone. These polymers could be solution cast into transparent, tough, and flexible films with high tensile strengths. These polyimides and polyamides had glass‐transition temperatures in the ranges of 230–258 and 196–229 °C, respectively. Decomposition temperatures of the polyimides for 10% weight loss all occurred above 500 °C in both nitrogen and air atmospheres. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2564–2574, 2002 相似文献
1000.
Chong‐Hyeak Kim Sueg‐Geun Lee 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(7):m421-m423
The title compound, [Ni(C3H10N2)2(H2O)2](C6H6NO3S)2, contains alternating layers of sulfanilate anions and diaquabis(1,3‐propanediamine)nickel(II) cations. The Ni atom lies on an inversion centre and is hexacoordinated by the 1,3‐propanediamine ligands, which function as N,N′‐bidentate ligands, and the water molecules, which are in a trans arrangement. The sulfanilate anions are arranged in layers, with the sulfonate and amine groups directed towards opposite sides of the layer. The structure is stabilized by a network of hydrogen bonding between the O and N atoms of the sulfanilate anions, the water molecules, and the N atoms of the 1,3‐propanediamine ligands. 相似文献