~(27)Al+~(27)Al耗散反应截面涨落的角度关联测量

在2 7Al+ 2 7Al(Elab≈ 1 2 0MeV)耗散反应激发函数涨落的实验研究中 ,首次在较大的角度范围内获得截面涨落的角度关联系数和角度关联函数 .实验结果表明 ,角度关联函数的形状呈现明显的非对称性 ,角度相干宽度至少为 4 0°;截面涨落在前后角区表现出明显不同的角度相关性 .

Negative differential resistance and multilevel memory effects in organic devices

Negative differential resistance ( NDR) and multilevel memory effects were obtained in organic devices consisting of an anthracene derivative, 9,10-bis-{ 9,9-di-[ 4-(phenyl-p-tolyl-amino)-phenyl]-9H-fluoren-2-yl}-anthracene ( DAFA), sandwiched between Ag and ITO electrodes. The application of a negative bias voltage leads to negative differential resistance in current-voltage characteristics and different negative voltages produce different conductance currents, resulting in the multilevel memory capability of the devices. The NDR property has been attributed to charge trapping at the DAFA/Ag interface. This opens up a wide range of application possibilities of such organic-based NDR devices in memory and logic circuits.

Loosely packed self-assembled monolayer of N-hexadecyl-3,6-di(p-mercaptophenylacetylene)carbazole on gold and its application in biomimetic membrane research

Dithiols of N-hexadecyl-3,6-di(p-mercaptophenylacetylene)carbazole (HDMC) have been synthesized and employed to form self-assembled monolayers (SAMs) on gold. One characteristic of the HDMC molecule is its peculiar molecular structure consisting of a large and rigid headgroup and a small and flexible alkyl-chain tail. HDMC adsorbates can attach to gold substrates by a strong Au-S bond with weak van der Waals interactions between the alkyl-chain tails, leading to a loosely packed hydrophobic SAM. In this way we can couple hybrid bilayer membranes (HBMs) to gold surfaces with more likeness to a cell bilayer than the conventional HBMs based on densely packed long-chain alkanethiol SAMs. The insulating properties and stability of the HDMC monolayer as well as the HDMC/lipid bilayer on gold have been investigated by electrochemical techniques including cyclic voltammetry and impedance spectroscopy. To test whether the quality of the bilayer is sufficiently high for biomimetic research, we incorporated the pore-forming protein a-hemolysin) and the horseradish peroxidase into the bilayers, respectively.

Enzymatic activities in constructed wetlands and di-n-butyl phthalate (DBP) biodegradation

The bioaccumulation of phthalate acid esters (PAEs) from industrial products and their mutagenic action has been suggested to be a potential threat to human health. The effects of the most frequently identified PAE, Di-n-butyl phthalate (DBP), and its biodegradation, were examined by comparison of two small scale plots (SSP) of integrated vertical-flow constructed wetlands. The influent DBP concentration was 9.84 mg l(-1) in the treatment plot and the control plot received no DBP. Soil enzymatic activities of dehydrogenase, catalase, protease, phosphatase, urease, cellulase, beta-glucosidase, were measured in the two SSP after DBP application for 1 month and 2 months, and 1 month after the final application. Both treatment and control had significantly higher enzyme activity in the surface soil than in the subsurface soil (P < 0.001) and greater enzyme activity in the down-flow chamber than in the up-flow chamber (P < 0.05). In the constructed wetlands, DBP enhanced the activities of dehydrogenase, catalase, protease, phosphatase and inhibited the activities of urease, cellulase and beta-glucosidase. However, urease, cellulase, beta-glucosidase activities were restored 1 month following the final DBP addition. Degradation of DBP was greater in the surface soil and was reduced in sterile soil, indicating that this process may be mediated by aerobic microorgansims. DBP degradation fitted a first-order model, and the kinetic equation showed that the rate constant was 0.50 and 0.17 d(-1), the half-life was 1.39 and 4.02 d, and the r(2) was 0.99 and 0.98, in surface and subsurface soil, respectively. These results indicate that constructed wetlands are able to biodegrade organic PA-Es such as DBP. (c) 2005 Elsevier Ltd. All rights reserved.

Di-nuclear systems studied with the velocity filter SHIP

Various nuclear reactions like quasi-fission, fusion-fission or particle and cluster evaporation from excited compound nuclei were studied in heavy-ion reactions at the velocity filter SHIP of GSI. The velocity filter offers the possibility to detect all reaction products under zero degree relative to the beam direction. Together with the measurement of the product velocity distribution this allows for an identification of the underlying reaction mechanism. This article is focussed on reactions of Mg-25 and Ni-64 beams on Pb-206,Pb-207 targets at energies of 5.9 x A MeV and 8.7 x A MeV. Besides evaporation residues from Mg-25 + Pb-206 collisions we found evidence for rotation and quasi-fission of nuclear molecules formed in the entrance channel after the capture stage. The break-up of the systems showed a preferred clustering leading to isotopes in the region 84 <= Z <= 88 and 122 <= N <= 127 of the chart of nuclei.

Azimuthal di-hadron correlations in d plus Au and Au plus Au collisions at root s(NN)=200 GeV measured at the STAR detector

Yields, correlation shapes, and mean transverse momenta p(T) of charged particles associated with intermediate-to high-p(T) trigger particles (2.5 < p(T) < 10 GeV/c) in d + Au and Au + Au collisions at root s(NN) = 200 GeV are presented. For associated particles at higher p(T) greater than or similar to 2.5 GeV/c, narrow correlation peaks are seen in d + Au and Au + Au, indicating that the main production mechanism is jet fragmentation. At lower associated particle pT < 2 GeV/c, a large enhancement of the near- (Delta phi similar to 0) and away-side (Delta phi similar to pi) associated yields is found, together with a strong broadening of the away-side azimuthal distributions in Au + Au collisions compared to d + Au measurements, suggesting that other particle production mechanisms play a role. This is further supported by the observed significant softening of the away-side associated particle yield distribution at Delta phi similar to pi in central Au + Au collisions.

Rare earth metal alkyl complexes bearing N,O,P multidentate ligands: Synthesis, characterization and catalysis on the ring-opening polymerization of L-lactide

Alkane elimination reactions of rare earth metal tris(alkyl)s, Ln(CH2SiMe3)3(THF)2 (Ln = Y, Lu) with the multidentate ligands HL1-4, afforded a series of new rare earth metal complexes. Yttrium, complex I supported by flexible amino-intino phenoxide ligand HL1 was isolated as homoleptic product. In the reaction of rigid phosphino-imino phenoxide ligand HL 2 with equintolar Ln(CH2SiMe3)3(THF)2, HL 2 was deprotonated by the metal alkyl and its imino C=N group was reduced to C-N by intramolecular alkylation, generating THF-solvated mono-alkyl complexes (2a: Ln = Y; 2b: Ln = Lu). The di-ligand chelated yttriurn complex 3 without alkyl moiety was isolated when the molar ratio of HL 2 to Y(CH,SiMe3)3(THF)2 increased to 2: 1. Reaction of steric phosphino beta-ketoiminato ligand HL 3 with equimolar Ln(CH2SiMe3)3(THF)2 afforded di-ligated mono-alkyl complexes (4a: Ln = Y; 4b: Ln = Lu) without occurrence of intramolecular alkylation or formation of homoleptic product. Treatment of tetradentate methoxy-amino phenol HL 4 with Y(CH2SiMe3)3(THF)2 afforded a monomeric yttrium bis-alkyl complex of THF-free. The resultant complexes were characterized by IR, NMR spectrum and X-ray diffraction analyses.All alkyl complexes exhibited high activity toward the ring-opening polymerization Of L-lactide to give isotactic polylactide with controllable molecular weight and narrow to moderate polydispersity.