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排序方式: 共有279条查询结果,搜索用时 0 毫秒
31.
50-kHz ultrasonic vocalizations emitted by male rats during a 5-min period before introduction of a female (precontact vocalizations [PVs]) were analyzed in the context of acquisition of sexual experience. Changes in the main copulatory parameters and their N-methyl-D-aspartate (NMDA) receptor dependence, the role of contact with either anestrous or estrous females, and conditioning to odor and background cues were also investigated. Mount latency (ML) and intromission latency (IL) decreased after the 1st copulatory session, but ejaculation latency (EL) changed significantly only starting from the 4th session onward. The number of PVs gradually increased during the first 3–4 sessions. Blocking of NMDA receptors affected PVs and EL but not ML or IL. After a 5-month break in copulatory sessions, ML remained unchanged, whereas EL increased and the number of PVs decreased significantly. PVs were most robustly elevated by contact with estrous females. Exposure to background cues resulted in a linear decrease in number of PVs during 10 subsequent sessions without exposure to a female. The results suggest that, in the course of acquisition of a sexual experience, PVs reflect a learning process that depends on a rewarding value of sociosexual contact. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
32.
The effects of alumina, silica and carbon on hydrogen adsorption on nickel were studied by the temperature-programmed desorption (TPD) method. The examinations were carried out in the flow system, starting TP measurement at 100 K, which resulted in the formation of complete characteristics of the interaction of hydrogen with supported nickel. The examinations have shown that each support modifies in its own way the state of hydrogen adsorbed on nickel. Alumina and silica insignificantly affect hydrogen strongly adsorbed on nickel, but significantly affect hydrogen weakly adsorbed; in particular, the effect of silica depends qualitatively on the way of preparation of the examined sample. Carbon affects significantly both strongly and weakly adsorbed hydrogen. 相似文献
33.
Sergio Brovelli Francesco Meinardi Gustaf Winroth Oliver Fenwick Giuseppe Sforazzini Michael J. Frampton Leszek Zalewski James A. Levitt Francesco Marinello Piero Schiavuta Klaus Suhling Harry L. Anderson Franco Cacialli 《Advanced functional materials》2010,20(2):272-280
Here, it is demonstrated that energy transfer in a blend of semiconducting polymers can be strongly reduced by non‐covalent encapsulation of one constituent, ensured by threading of the conjugated strands into functionalized cyclodextrins. Such macrocycles control the minimum intermolecular distance of chromophores with similar alignment, at the nanoscale, and therefore the relevant energy transfer rates, thus enabling fabrication of white‐light‐emitting diodes (CIE coordinates: x = 0.282, y = 0.336). In particular, white electroluminescence in a binary blend of a blue‐emitting, organic‐soluble rotaxane based on a polyfluorene derivative and the green‐emitting poly(9,9‐dioctylfluorene‐alt‐benzothiadiazole ( F8BT ) is achieved. Morphological and structural analyses by atomic force microscopy, fluorescence mapping, µ‐Raman, and fluorescence lifetime microscopy are used to complement optical and electroluminescence characterization, and to enable a deeper insight into the properties of the novel blend. 相似文献
34.
Andrzej Dziedzic Leszek J. Golonka Jaroslaw Kita Heiko Thust Karl-Heinz Drue Reinhard Bauer Lars Rebenklau Klaus-Jurgen Wolter 《Microelectronics Reliability》2001,41(5)
This paper presents systematic investigations of electrical and stability properties of various low temperature co-fired ceramics (LTCC) resistors. One of the goals of this work was to check the compatibility of LTCC materials (tapes, resistive and conductive inks) from various manufacturers. Three commercially available green tapes and three LTCC resistor/conductor systems were examined. The resistive inks with 1 kΩ/sq. nominal sheet resistance were used. Buried (inside) and surface resistors were laminated and fired according to the tape manufacturers’ recommendations. The influence of dimensional effect on sheet resistance and hot temperature coefficient of resistance, the temperature dependence of resistance in a wide temperature range (from −180°C to +130°C), long-term stability of thermally aged as-fired resistors (150°C, 500 h) and durability to high-voltage micro- or nanosecond pulses (50 ns pulses with 4000 V/mm maximum electric field or 10 μs ones with 700–1000 V/mm electrical field) were carried out for electrical and stability characterisation of LTCC resistors. Non-destructive scanning acoustic microscope diagnostics was applied for structure investigation and estimation of lamination and cofiring process quality of buried LTCC resistors. 相似文献
35.
The positive ion-molecule reactions in the mixtures of hydrogen sulfide and methane have been examined by means of quadrupole mass spectrometer with the high-pressure ion source. The concentration of hydrogen sulfide in mixtures ranged from 10% to 90% with 10% increment. For each mixture major bimolecular ion-molecule reactions have been identified in the total pressure range from 0.7 to 33.3 Pa. The electron energy for all measurements was fixed at 300 eV and the repeller potential was maintained at 5 V. Relative intensities of ion currents for the observed ions C+, CH+, CH2+, CH3+, CH4+, CH5+, C2H3+, C2H4+, C2H5+, S+, HS+, H2S+, H3S+, H334S+, CHS+, CH3S+, S2+, HS2+ and H2S2+ were determined as a function of total gas pressure inside the ion source collision chamber, repeller potential and concentration of methane in the mixture. 相似文献
36.
J. Tinsley Oden Serge Prudhomme Leszek Demkowicz 《Archives of Computational Methods in Engineering》2005,12(4):343-389
Summary The main purpose of this paper is to review a posteriori error estimators for the simulation of acoustic wave propagation
problems by computational methods. Residual-type (explicit and implicit) and recovery-type estimators are presented in detail
in the case of the Helmholtz problem. Recent work on goal-oriented error estimation techniques with respect to so-called quantities
of interest or output functionals are also accounted for. Fundamental results from a priori error estimation are presented
and issues dealing with pollution error at large wave numbers are extensively discussed. 相似文献
37.
Leszek Gasiński Nikolaos S. Papageorgiou 《Dynamical Systems: An International Journal》2014,29(2):190-207
We consider a generalized logistic equation of superdiffusive type, driven by a non-homogeneous nonlinear differential operator, which incorporates the p-Laplacian, the (p, q)-differential operator and the generalized p-mean curvature differential operator. Using variational methods coupled with truncation and comparison techniques, we prove a bifurcation-type theorem describing the dependence of positive solutions on the parameter λ > 0. 相似文献
38.
Leszek Zalewski Sergio Brovelli Massimo Bonini Jeffrey M. Mativetsky Michael Wykes Emanuele Orgiu Thomas Breiner Marcel Kastler Florian Dötz Francesco Meinardi Harry L. Anderson David Beljonne Franco Cacialli Paolo Samorì 《Advanced functional materials》2011,21(5):834-844
A comparative study of the self‐assembly at a variety of surfaces of a dithiophene rotaxane 1 ?β‐CD and its corresponding dumbbell, 1, by means of atomic force microscopy (AFM) imaging and scanning tunneling microscopy (STM) imaging on the micrometer and nanometer scale, respectively. The dumbbell is found to have a greater propensity to form ordered supramolecular assemblies, as a result of π–π interactions between dithiophenes belonging to adjacent molecules, which are hindered in the rotaxane. The fine molecular structure determined by STM was compared to that obtained by molecular modelling. The optical properties of both rotaxane and dumbbell in the solid state were investigated by steady‐state and time‐resolved photoluminescence (PL) experiments on spin‐cast films and diluted solutions. The comparison between the optical features of the threaded and unthreaded systems reveals an effective role of encapsulation in reducing aggregation and exciton migration for the rotaxanes with respect to the dumbbells, thus leading to higher PL quantum efficiency and preserved single‐molecule photophysics for longer times after excitation in the threaded oligomers. 相似文献
39.
Irena Roterman Katarzyna Stapor Leszek Konieczny 《International journal of molecular sciences》2023,24(1)
The amyloid structures and their wild type forms, available in the PDB database, provide the basis for comparative analyses. Globular proteins are characterised by a 3D spatial structure, while a chain in any amyloid fibril has a 2D structure. Another difference lies in the structuring of the hydrogen bond network. Amyloid forms theoretically engage all the NH and C=O groups of the peptide bonds in a chain with two hydrogen bonds each. In addition, the hydrogen bond network is highly ordered—as perpendicular to the plane of the chain. The β-structure segments provide the hydrogen bond system with an anti-parallel system. The folds appearing in the rectilinear propagation of the segment with the β-structure are caused by just by one of the residues in the sequence—residues with a Rα-helical or Lα-helical conformation. The antiparallel system of the hydrogen bonds in the β-structure sections at the site of the amino acid with a Rα- or Lα-helical conformation changes into a parallel system locally. This system also ensures that the involvement of the C=O and H-N groups in the construction of the interchain hydrogen bond, while maintaining a perpendicular orientation towards the plane of the chain. Conformational analysis at the level of the Phi and Psi angles indicates the presence of the conditions for the structures observed in the amyloids. The specificity of amyloid structures with the dominant conformation expressed as |Psi| = |Phi| reveals the system of organisation present in amyloid fibrils. The Phi, Psi angles, as present in this particular structure, transformed to form |Psi| = |Phi| appear to be ordered co-linearly. Therefore, the calculation of the correlation coefficient may express the distribution around this idealised localisation on the Ramachandran map. Additionally, when the outstanding points are eliminated, the part of amyloid chain can be classified as fulfilling the defined conditions. In addition, the presentation of the chain structure using geometric parameters, V-angle—the angle between the planes of the adjacent peptide bonds (angle versus the virtual axis Cα-Cα) and the radius of the curvature R, depending on the size of the angle V, allows for a quantitative assessment of changes during amyloid transformation. 相似文献
40.