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排序方式: 共有345条查询结果,搜索用时 15 毫秒
21.
S. Schwarz M. Block G. Bollen C. M. Campbell M. Facina R. Ferrer C. M. Folden III A. A. Kwiatkowski D. J. Morrissey G. K. Pang A. M. Prinke R. J. Ringle J. Savory P. H. Schury 《The European Physical Journal A - Hadrons and Nuclei》2009,42(3):323-326
The low-energy beam and ion trap facility LEBIT at NSCL/MSU is at present the only facility where precision experiments are performed with stopped rare isotope beams produced by fast-beam fragmentation. LEBIT combines high-pressure-gas stopping with advanced ion manipulation techniques to provide brilliant low-energy beams. So far these beams have mainly been used for mass measurements on short-lived rare isotopes with a 9.4T Penning trap mass spectrometer. Recent examples include 70m Br , located at the proton dripline, 32Si and the iron isotopes 63-65Fe . While the measurement of 32Si helps to solve a long-standing dispute over the validity of the isobaric multiplet mass equation (IMME) for the A = 32 , T = 2 multiplet, the mass measurements of 65m,g Fe marked the first time a nuclear isomeric state has been discovered by Penning trap mass spectrometry. 相似文献
22.
[reaction: see text] Treatment of 1,4-dilithio-1,3-butadiyne (1) with dichalcogenides RSSR or RSeSeR affords dithio- and diseleno-1,3-butadiynes (2, 3), perthio- and perseleno-[3]-cumulenes (4, 5), perthio- and perseleno-1,3-butadienes (6, 7), and/or perthio- and perseleno-but-1-ene-3-ynes (8, 9). The products can be controlled by stoichiometry and temperature, by the presence or absence of oxygen, and by choice of the "R" group. By X-ray crystallography, hexa(methylthio)-1,3-butadiene is highly twisted, with a torsion angle [Phi(CCCC)] of 84.7 degrees and an elongated C(2)-C(3) distance of 1.484(3) A. 相似文献
23.
Let f :X→X be a continuous map of a compact metric space to itself. We prove that f is topologically conjugate to an adding machine map if and only if X is an infinite minimal set for f and each point of X is regularly recurrent. Moreover, if X is an infinite minimal set for f and one point of X is regularly recurrent, then f is semiconjugate to an adding machine map. 相似文献
24.
Kurt Binder Benjamin Block Subir K. Das Peter Virnau David Winter 《Journal of statistical physics》2011,144(3):690-729
Excess contributions to the free energy due to interfaces occur for many problems encountered in the statistical physics of
condensed matter when coexistence between different phases is possible (e.g. wetting phenomena, nucleation, crystal growth,
etc.). This article reviews two methods to estimate both interfacial free energies and line tensions by Monte Carlo simulations
of simple models, (e.g. the Ising model, a symmetrical binary Lennard-Jones fluid exhibiting a miscibility gap, and a simple
Lennard-Jones fluid). One method is based on thermodynamic integration. This method is useful to study flat and inclined interfaces
for Ising lattices, allowing also the estimation of line tensions of three-phase contact lines, when the interfaces meet walls
(where “surface fields” may act). A generalization to off-lattice systems is described as well. The second method is based
on the sampling of the order parameter distribution of the system throughout the two-phase coexistence region of the model.
Both the interface free energies of flat interfaces and of (spherical or cylindrical) droplets (or bubbles) can be estimated,
including also systems with walls, where sphere-cap shaped wall-attached droplets occur. The curvature-dependence of the interfacial
free energy is discussed, and estimates for the line tensions are compared to results from the thermodynamic integration method.
Basic limitations of all these methods are critically discussed, and an outlook on other approaches is given. 相似文献
25.
Hans E. Miltner Christophe Block Guy Van Assche Kurt Van Durme Bogdan Bogdanov 《European Polymer Journal》2010,46(5):984-996
A comprehensive overview of available methods for assessing nanofiller dispersion is presented for a wide range of layered silicate-based poly(ε-caprolactone) (PCL) nanocomposites. Focusing on their respective strengths and weaknesses, rheological, mechanical and thermal characterization approaches are evaluated in direct relation to morphological information. Pronounced changes in the rheological and mechanical properties of the materials are only observed for nanocomposites displaying the highest nanofiller dispersion levels, as confirmed by an innovative and highly reliable thermal analysis approach based on quasi-isothermal crystallization. As such, the data obtained from the different methods also allow a detailed investigation of the crucial factors affecting nanofiller dispersion, evidencing the importance of specific matrix/filler interactions and the need for proper melt processing conditions when targeting significant property enhancements. Finally, the wide potential of the developed methodologies for the characterization of polymeric nanocomposites in general is illustrated by an extension to carbon nanotube-based PCL composites, unambiguously demonstrating their complementarity and broad applicability. 相似文献
26.
We develop a simple theory of André-Quillen cohomology for commutative differential graded algebras over a field of characteristic zero. We then relate it to the homotopy groups of function spaces and spaces of homotopy self-equivalences of rational nilpotent CW-complexes. This puts certain results of Sullivan in a more conceptual framework. 相似文献
27.
Crystal Structure,Magnetism, 89Y Solid State NMR,and 121Sb Mössbauer Spectroscopic Investigations of YIrSb 下载免费PDF全文
Christopher Benndorf Lukas Heletta Theresa Block Hellmut Eckert Rainer Pöttgen 《无机化学与普通化学杂志》2017,643(4):294-298
The ternary antimonide YIrSb was synthesized from the binary precursor YIr and elemental antimony by a diffusion controlled solid‐state reaction. Single crystals were obtained by a flux technique with elemental bismuth as an inert solvent. The YIrSb structure (TiNiSi type, space group Pnma) was refined from single‐crystal X‐ray diffractometer data: a = 711.06(9), b = 447.74(5), c = 784.20(8) pm, wR2 = 0.0455, 535 F2 values, 20 variables. 89Y solid state MAS NMR and 121Sb Mössbauer spectra show single resonance lines in agreement with single‐crystal X‐ray data. YIrSb is a Pauli paramagnet. 相似文献
28.
M.M. Block F. Halzen G. Pancheri 《The European Physical Journal C - Particles and Fields》2002,23(2):329-335
Using an eikonal structure for the scattering amplitude, Block and Kaidalov [1] have derived factorization theorems for nucleon-nucleon,
and scattering at high energies, using only some very general assumptions. We present here an analysis giving experimental confirmation
for factorization of cross sections, nuclear slope parameters B and -values (ratio of real to imaginary portion of forward scattering amplitudes), showing that:
– the three factorization theorems [1] hold,
– the additive quark model holds to ,
– and vector dominance holds to better than .
Received: 6 November 2001 / Revised version: 29 November 2001 / Published online: 8 February 2002 相似文献
29.
Buffer gas beam coolers may become excellent beam preparation devices for high-resolution mass separation. The small beam
emittance provided makes efficient isobar resolution a realistic goal. In order to fulfill the needs of future facilities
providing high-intensity beams of rare isotopes, it is desirable to increase the beam intensity limit of such devices from
typically several tens of nanoamperes to microamperes. This requires the usage of high-voltage radiofrequencies in a low-pressure
gas environment. A buffer gas beam cooler, dedicated to this purpose, is under development at the NSCL. The study of voltage
breakdowns under such conditions and the design of an electrode system minimizing them is mandatory.
相似文献
30.
M. Maghrebi Melliti R. Chtourou J. Block V. Thierry-Mieg 《Physica E: Low-dimensional Systems and Nanostructures》2005,30(1-2):17-20
Polariton linewidths have been measured in a series of microcavities with different excitonic and cavity inhomogeneous broadening in the weak-disorder regime. We show experimentally that the behaviour of the polariton linewidths as a function of the detuning depends on the asymmetric line shape of an inhomogeneously broadened exciton line and particularly the disorder effect can be modulated and cancelled around resonance. When the disorder contribution is minimal, the behaviour of the cavity polariton linewidths tends to one of the homogeneous broadening system. 相似文献