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61.
We show, based on some results from classical analysis, that time-dependent perturbations can either increase or decrease the tunneling probability. The results depend on the form of the function T(√V), where T is the transmission coefficient and V the potential. If T(√V) is convex, the perturbation will always result in a decrease of the tunneling; if T(√V) is concave, both increase as well as decrease occur. 相似文献
62.
Wojciech Jaworski 《Monatshefte für Mathematik》2008,336(4):135-144
Given a locally compact group G, let
J(G){\cal J}(G)
denote the set of closed left ideals in L
1(G), of the form J
μ = [L1(G) * (δ
e
− μ)]−, where μ is a probability measure on G. Let
Jd(G)={\cal J}_d(G)=
{Jm;m is discrete}\{J_{\mu};\mu\ {\rm is discrete}\}
,
Ja(G)={Jm;m is absolutely continuous}{\cal J}_a(G)=\{J_{\mu};\mu\ {\rm is absolutely continuous}\}
. When G is a second countable [SIN] group, we prove that
J(G)=Jd(G){\cal J}(G)={\cal J}_d(G)
and that
Ja(G){\cal J}_a(G)
, being a proper subset of
J(G){\cal J}(G)
when G is nondiscrete, contains every maximal element of
J(G){\cal J}(G)
. Some results concerning the ideals J
μ in general locally compact second countable groups are also obtained. 相似文献
63.
Artur J. Jaworski Xiaoan Mao Xuerui Mao Zhibin Yu 《Experimental Thermal and Fluid Science》2009,33(3):495-502
This paper considers an entrance flow into the channels formed by a stack of parallel plates, placed in an acoustic resonator that provides oscillatory flow forcing. Interesting complex flow phenomena around the extremity of the stack are observed, essentially due to the introduction of cross-sectional discontinuities: vortex formation and shedding during the fluid ejection from the channels and development of an entrance flow during the suction phase, when the fluid enters the channels from outside. It is the latter that is of particular interest in this study. Particle image velocimetry (PIV) is used to investigate the flow structures in the “entrance region”. Velocity profiles are measured as a function of phase angle within an oscillation period and the distance from the stack end into the channel. Using the data obtained, an “entrance length” defined by analogy with existing fluid mechanical definitions, is estimated. The experiments are supplemented by CFD calculations to improve the understanding of such entrance flows. 相似文献
64.
65.
Zdzislaw Latajka Henryk Ratajczak W.J. Orville-Thomas Emil Ratajczak 《Journal of Molecular Structure》1974,21(2):299-303
CNDO/2 molecular orbital calculations have been carried out on the Dewar structures of pyridine to determine the configurations of minimum energy. 相似文献
66.
Wilds CJ Wawrzak Z Krishnamurthy R Eschenmoser A Egli M 《Journal of the American Chemical Society》2002,124(46):13716-13721
(L)-alpha-Threofuranosyl-(3'-->2')-oligonucleotides (TNA) containing vicinally connected phosphodiester linkages undergo informational base pairing in an antiparallel strand orientation and are capable of cross-pairing with RNA and DNA. TNA is derived from a sugar containing only four carbon atoms and is one of the simplest potentially natural nucleic acid alternatives investigated thus far in the context of a chemical etiology of nucleic acid structure. Compared to DNA and RNA that contain six covalent bonds per repeating nucleotide unit, TNA contains only five. We have determined the atomic-resolution crystal structure of the B-form DNA duplex [d(CGCGAA)Td(TCGCG)](2) containing a single (L)-alpha-threofuranosyl thymine (T) per strand. In the modified duplex base stacking interactions are practically unchanged relative to the reference DNA structure. The orientations of the backbone at the TNA incorporation sites are slightly altered in order to accommodate fewer atoms and covalent bonds. The conformation of the threose is C4'-exo with the 2'- and 3'-substituents assuming quasi-diaxial orientation. 相似文献
67.
Tayfun Hüyük Antonio Di Nitto Grzegorz Jaworski Andrés Gadea José Javier Valiente-Dobón Johan Nyberg Marcin Palacz Pär-Anders Söderström Ramon Jose Aliaga-Varea Giacomo de Angelis Ayşe Ataç Javier Collado Cesar Domingo-Pardo Francisco Javier Egea Nizamettin Erduran Sefa Ertürk Gilles de France Rafael Gadea Vicente González Vicente Herrero-Bosch Ayşe Kaşkaş Victor Modamio Marek Moszynski Enrique Sanchis Andrea Triossi Robert Wadsworth 《The European Physical Journal A - Hadrons and Nuclei》2016,52(3):55
68.
Abstract Two high pressure X-band ESR resonators for sensitive measurements are described. Both systems have 100 kHz internal modulation coils and can cooperate with any standard ESR spectrometer. These cavities operate in two different temperature and pressure ranges: 77–400 K, up to 0.8 GPa and liquid helium temperature range, up to 1 GPa, respectively. Additionally, the cavity operating in the 77–400 K temperature range enables Photo-ESR measurements to be carried out. 相似文献
69.
This paper investigates the feasibility of using commercially available loudspeakers as low-cost linear alternators for thermoacoustic applications, to convert acoustic power to electricity. The design of a purpose built experimental apparatus, in which a high intensity acoustic wave is induced by using a high power woofer, is described. The rig is used to excite loudspeakers (referred here as “alternators”) under test, while a pair of microphones and a laser displacement sensor are used to enable acoustic power measurements. The paper presents a case study in which characteristics of acoustic-to-electric energy conversion of a candidate loudspeaker (alternator) – selected from the viewpoint of general performance, as well as parameters such as: high force factor, low electrical resistance and low mechanical loss – are measured. The measurements of acoustic power absorbed by the alternator and the electric power extracted from it by the load resistor, which allow estimating acoustic-to-electric efficiencies, are presented. The alternator has been tested at different operating frequencies, cone displacements and load resistance values. The measurement results are discussed and compared in detail with the calculations based on the linear acoustics model. 相似文献
70.
The possibility of considerably changing the conditions for the proton transfer reaction in 3-hydroxyflavone molecules in
polyvinyl alcohol (PVA) polymer matrices by stretching deformations is demonstrated. Samples of this kind are traditionally
used to obtain ensembles of fluorophore molecules oriented along a chosen axis and for polarization measurements. The fluorescence
spectrum of 3-hydroxyflavone in PVA has two characteristic bands in the violet and green spectral regions, which indicates
excited-state proton transfer. Stretching leads to a strong reduction in the violet band, whose contribution in undeformed
samples is comparable to the contribution of green fluorescence. Even twofold stretching of PVA films strongly decreases the
violet band intensity, which is more pronounced in the case of sixfold stretching. In the latter case, the fluorescence spectrum
behavior is very close to the pattern observed in nonpolar and aprotic solvents, in which the violet fluorescence intensity
is very low. The data obtained indicate that mechanical stretching allows one to eliminate the main intermolecular factors
that slow down the proton transfer between the active groups in PVA. 相似文献