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71.
A binary operation ⊕ is defined in any bounded symmetric domain D turning it into a groupoid with relaxed associative and commutative laws, called a gyrogroup. It is shown that the group Aut(D) of all holomorphic automorphisms of D has a gyrosemidirect product structure, a structure that generalizes the semidirect product one. More specifically, the group Aut(D) turns out to be the gyrosemidirect product of the (nongroup) gyrogroup (D, ⊕) and the isotropic group K of D. 相似文献
72.
An analytical, unifying approach to geometric properties of the Fermat-Torricelli point of four affinely independent points yields several characterizations of isosceles tetrahedra and, in particular, a characterization or regular tetrahedra within the set of isosceles tetrahedra by means of the solid angle sum.Dedicated to Professor N. Stephanidis on the occasion of his sixtyfifth birthday 相似文献
73.
Yaakov S. Kupitz 《Combinatorica》1993,13(3):249-258
A question of the following kind will concern us here: what is the minimal numbern, ensuring that any spanning set ofn points in 3-space spans a plane, every open side of which contains at least, say, 1000 points of the set. The answer isn=4001 (see Theorem 2.1 below).This is a part of a Ph.D. thesis, with the same title, supervised by Professor Micha A. Perles in the Hebrew University of Jerusalem 相似文献
74.
Tal Ben Uliel Laxman Gouda Hagit Aviv Anat Itzhak Yaakov R. Tischler 《Journal of Raman spectroscopy : JRS》2019,50(11):1672-1678
Low-frequency Raman (LFR) spectroscopy is a powerful, nondestructive method used for chemical and structural characterization of materials. Typically, the signal intensity of LFR is relatively low, resulting significantly longer signal acquisition duration. Here, we show a photonic structure based on a planar optical microcavity consists of two distributed Bragg reflectors that is capable of enhancing the LFR signal of the material placed in between the mirrors. CsPbI3 forms smooth and uniform thin films and has distinct LFR signatures; thus, we chose to use it for investigating the microcavity enhancement capabilities. By compromising the quality factor of the cavity, we achieved a broader transmission peak and essentially earned enhancement from the double-resonance effect. Measurements on a CsPbI3 thin film inside a cavity compared with a bare film spin coated on glass demonstrated two orders of magnitude enhancement. In addition, we fabricated the microcavity with a gradient in the resonance wavelength, in order to study the tuning effect on spectral features and on the enhancement factor. Our results show that microcavity is a promising device for enhancing LFR scattering signal and for sensitive characterization of nanomaterials. 相似文献
75.
Yaakov S. Kupitz Hagit Last Horst Martini Micha A. Perles Rom Pinchasi 《Journal of Graph Theory》2020,94(1):159-169
76.
Jonas Schtti Valentin Khler Marcel Mayor Yaakov Y. Fein Philipp Geyer Lukas Mairhofer Stefan Gerlich Markus Arndt 《Journal of mass spectrometry : JMS》2020,55(6)
Studies of neutral biomolecules in the gas phase allow for the study of molecular properties in the absence of solvent and charge effects, thus complementing spectroscopic and analytical methods in solution or in ion traps. Some properties, such as the static electronic susceptibility, are best accessed in experiments that act on the motion of the neutral molecules in an electric field. Here, we screen seven peptides for their thermal stability and electron impact ionizability. We identify two tripeptides as sufficiently volatile and thermostable to be evaporated and interfered in the long‐baseline universal matter‐wave interferometer. Monitoring the deflection of the interferometric molecular nanopattern in a tailored external electric field allows us to measure the static molecular susceptibility of Ala–Trp–Ala and Ala–Ala–Trp bearing fluorinated alkyl chains at C‐ and N‐termini. The respective values are and . 相似文献
77.
It is shown that the direct correlation function of a mixture of hard ions in the mean spherical approximation (MSA) can be expressed in terms of overlap functions of charged spherical shells. In particular, if the system is a mixture of pairs of ions of equal size and opposite charge, then the MSA direct correlation function is given by the electrostatic energy of a pair of charged shells, of radius equal to the radius of the hard ion plus 1/(2). This direct correlation function can be derived from a free energy functional, and a simple extension to nonuniform systems is given. 相似文献
78.
We address unifying features of fragmentation channels driven by long-range Coulomb or pseudo-Coulomb forces in clusters, nuclei, droplets, and optical molasses. We studied the energetics, fragmentation patterns, and dynamics of multicharged (A+)n (n=55, 135, 321) clusters. In Morse clusters the variation of the range of the pair-potential induced changes in the cluster surface energy and in the fissibility parameter X=E(Coulomb)2E(surface). X was varied in the range of X=1-8 for short-range interactions and of X=0.1-1.0 for long-range interactions. Metastable cluster configurations were prepared by vertical ionization of the neutral clusters and by subsequent structural equilibration. The energetics of these metastable ionic clusters was described in terms of the liquid drop model, with the coefficients of the volume and surface energies depending linearly on the Morse band dissociation energy. Molecular-dynamics simulations established two distinct fragmentation patterns of multicharged clusters that involve cluster fission into a small number of large, multicharged clusters for X<1 and Coulomb explosion into a large number of individual ions and small ionic fragments for X>1. The Rayleigh instability limit X=1 separates between spatially anisotropic fission and spatially isotropic Coulomb explosion. Distinct features of the fragmentation energetics and dynamics were unveiled. For fission of n=55 clusters, large kinetic and internal energies of the large fragments are exhibited and the characteristic fragmentation time is approximately 700 fs, while for Coulomb explosion the major energy content of the small fragments involves kinetic energy and the characteristic fragmentation time of approximately 300 fs is shorter. The Rayleigh (X=1) limit, leading to isotropic Coulomb explosion, is transcended by a marked enhancement of the Coulomb energy, which is realized for extremely ionized clusters in ultraintense laser fields, or by a dramatic reduction of the surface energy as is the case for the expansion of optical molasses. 相似文献
79.
The complexity of the mechanisms by which proteins fold has been shown by many studies to be governed by their native-state topologies. This was manifested in the ability of the native topology-based model to capture folding mechanisms and the success of folding rate predictions based on various topological measures, such as the contact order. However, while the finer details of topological complexity have been thoroughly examined and related to folding kinetics, simpler characteristics of the protein, such as its overall shape, have been largely disregarded. In this study, we investigated the folding of proteins with an unusual elongated geometry that differs substantially from the common globular structure. To study the effect of the elongation degree on the folding kinetics, we used repeat proteins, which become more elongated as they include more repeating units. Some of these have apparently anomalous experimental folding kinetics, with rates that are often less than expected on the basis of rates for globular proteins possessing similar topological complexity. Using experimental folding rates and a larger set of rates obtained from simulations, we have shown that as the protein becomes increasingly elongated, its folding kinetics becomes slower and deviates more from the rate expected on the basis of topology measures fitted for globular proteins. The observed slow kinetics is a result of a more complex pathway in which stable intermediates composed of several consecutive repeats can appear. We thus propose a novel measure, an elongation-sensitive contact order, that takes into account both the extent of elongation and the topological complexity of the protein. This new measure resolves the apparent discrimination between the folding of globular and elongated repeat proteins. Our study extends the current capabilities of folding-rate predictions by unifying the kinetics of repeat and globular proteins. 相似文献
80.
Kahan A Nahmias O Friedman N Sheves M Ruhman S 《Journal of the American Chemical Society》2007,129(3):537-546
Sub-10-fs laser pulses are used to impulsively photoexcite bacteriorhodopsin (BR) suspensions and probe the evolution of the resulting vibrational wave packets. Fourier analysis of the spectral modulations induced by transform-limited as well as linearly chirped excitation pulses allows the delineation of excited- and ground-state contributions to the data. On the basis of amplitude and phase variations of the modulations as a function of the dispersed probe wavelength, periodic modulations in absorption above 540 nm are assigned to ground-state vibrational coherences induced by resonance impulsive Raman spectral activity (RISRS). Probing at wavelengths below 540 nm-the red edge of the intense excited-state absorption band-uncovers new vibrational features which are accordingly assigned to wave packet motions along bound coordinates on the short-lived reactive electronic surface. They consist of high- and low-frequency shoulders adjacent to the strong C=C stretching and methyl rock modes, respectively, which have ground-state frequencies of 1008 and 1530 cm-1. Brief activity centered at approximately 900 cm-1, which is characteristic of ground-state HOOP modes, and strong modulations in the torsional frequency range appear as well. Possible assignments of the bands and their implication to photoinduced reaction dynamics in BR are discussed. Reasons for the absence of similar signatures in the pump-probe spectral modulations at longer probing wavelengths are considered as well. 相似文献