共查询到20条相似文献,搜索用时 11 毫秒
1.
Balance of correlations is an approach to build up quantitative structure–property/activity relationships (QSPR/QSAR). This
approach is based on a split into the subtraining, calibration and test sets instead of classic split into training and test
sets. The function of the calibration set is the preliminary check up of the model. In other words, the calibration set is
like a preliminary test set. Computational experiments (with the Monte Carlo method) have shown that the statistical characteristics
of the prediction for the toxicity to Tetrahymena pyriformis (the 50% growth inhibition concentration, IGC50) based on the balance of correlations are better than the statistical characteristics of the prediction based on the classic
scheme. 相似文献
2.
QSAR modelling of carcinogenicity by balance of correlations 总被引:1,自引:0,他引:1
3.
The possible effects of short-range dynamical nucleon-nucleon correlations on high-energy hadron scattering on 4He are examined. The Glauber theory of multiple scattering is used as the basis for the computations. The conclusion is that very small effects are to be expected for elastic and sum total inelastic scattering of commonly available projectiles. 相似文献
4.
The synthesis of high temperature superconducting phases in the NbGe, NbSn, VSi, VGe, VSn, NbC and MoC systems is described by method consisting in the thermolysis of volatile hydrides or organometallic compounds on resistively heated wires. For face-centred cubic NbC a higher transition temperature than previously reported was obtained. The A15 phase boundary of NbGe is extended towards the stoichiometric 3:1 composition, affording samples of Nb3 Ge with a Tc onset of 15.8°K. 相似文献
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6.
A. Eichenberger G. Genevès P. Gournay 《The European physical journal. Special topics》2009,172(1):363-383
The kilogram is the only base unit of the Système International d’unités (SI) still defined by a material artefact. Regarding
the past evolution of the SI and the poor knowledge of the stability of the international prototype, its definition is not
satisfactory. In the long term, it would be better to move to a definition based either on atomic properties or on fundamental
constants. Among the various researches in progress in metrology laboratories, one of the most promising ways seems to be
the watt balance. Its principle consists in comparing a mechanical power to an electromagnetic power. This comparison results
from a measurement performed in two steps: a static measurement during which the Laplace force acting on a coil driven by
a DC current and subjected to an induction field is compared to the weight of a standard mass, and a dynamic measurement where
the induced voltage at the terminals of the same coil is determined when it is moved in the same field at a known velocity.
The measurement of electrical quantities in terms of the Josephson and the quantum Hall effects then allows the mass unit
be linked to the Planck constant. Although the principle of the experiment remains simple and direct, obtaining sufficiently
low uncertainty ( 10-8) implies that devices relevant of various fields of physics must be implemented at their best level. In this paper, a review
of the present developments at international level is presented. 相似文献
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8.
D.J. Gates 《Physica A》1975,81(1):47-71
The k-particle, infinite-volume distribution functions and modified Ursell correlation functions of a classical system of particles with the two-body potential are considered. The limiting values of the functions and in the limit γ → 0 are calculated, under fairly weak conditions on q and K, by a method involving functional differentiation. These limiting functions are used to describe the molecular structure of the various states of the system both in the range of the potential q(r) and in the rage of the potential γνK(γr). The direct correlation function c? (r, γ) is also considered and it is shown that for , , for all one-phase states, where β is the reciprocal temperature. Special cases of our results confirm those of other authors, including the well-known results of Ornstein and Zernike. 相似文献
9.
Migration and clustering of lattice defects after implantation of111In in Al and subsequent annealing at temperatures in the range from 80 to 800 K were investigated applying the DPAC technique. The effects of implantation dose, implantation temperature, laser irradiation, and plastic deformation were studied. The measurements on plastically deformed Al were complemented by positron lifetime measurements. We observed four In-defect clusters that can be flagged by well-defined hyperfine interaction parameters, and we determined their symmetry properties by using single-crystal samples. Important conclusions are: (i) monovacancies are not trapped by In-atoms, (ii) small In-defect clusters are formed by direct trapping of divacancies and/or trivacancies, and (iii) extended In-defect clusters are very stable and anneal in the temperature range 600–700 K. Consequences for the interpretation of other measurements on dilute Al(In) alloys are discussed.On leave from Tata Institute of Fundamental Research, Homi Bhabha Road, Bombay 400 005, India. 相似文献
10.
S. I. Kantorovich 《Russian Physics Journal》1976,19(4):499-501
Representation of the causal two-body Green's function in the form of a double (with respect to the external fields and the trajectories) continuous integral with a subsequent density expansion and termwise integration with respect to the external fields is used to consider correlation corrections to the collision integral for charged quantum particles in the field of the compensating background. The first-order coupling approximation leads to a nonlinear dependence of the collision integral on the two-particle Green's function, and in developing different approximations for the latter, collision integrals associated with the ring and ladder diagrams of Silin and Balescu that allow for a slow time delay, as in [1, 2], are obtained, as is a collision integral with an exponential cutoff for small distances.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 118–121, April, 1976.The author is grateful to L. Ya. Kobelev for suggesting the topic and his interest in the work, and to B. N. Shalaev for useful discussions. 相似文献
11.
For the development of a low-cost MgB2 superconductor the “powder-in-tube” (PIT) technique is investigated. Mechanically alloyed MgB2 powder provides a favorable microstructure and phase composition for the low temperature preparation of MgB2 tapes with superconducting properties. The composition of sintered bulk samples and Fe-clad MgB2 tapes made of mechanically alloyed MgB2 has been investigated by Auger micro-analysis. Due to the process the samples contain about 15% oxygen. Pure MgB2 crystallites were investigated as standard for stoichiometry and peak shape analysis. 相似文献
12.
Y. Zhang W. M. Cleaver M. Stuke A. R. Barron 《Applied Physics A: Materials Science & Processing》1992,55(3):261-268
The gas phase ultraviolet (UV) excimer laser induced photolysis of the gallium-alkyls Ga(t-C4H9)
n
– (CH3)3–n
(n=0, 1, 2, 3) was studied, using photolysis wavelengths of 308, 248, and 193 nm. The photofragments Ga, GaH, and GaCH3 were detected by laser ionization time-of-flight mass spectroscopy, while the hydrocarbon products CH4, C2H6, HC(CH3)3 and H2C=C(CH3)2 were identified using Fourier transform infrared (FTIR) spectroscopy. The formation of the GaH photofragment, and a high olefin-to-alkane product ratio, for Ga(t-C4H9)2(CH3) and Ga(t-C4H9)3 are interpreted to indicate a -hydrogen elimination process. However, -hydrogen elimination only occurs after fission of the weakest Ga-C bond, thus no -hydride elimination is observed for Ga(t-C4H9)(CH3)2. Detection of C2H6 for Ga(CH3)3 and Ga(t-C4H9)(CH3)2, but not for Ga(t-C4H9)2(CH3), shows that under our experimental conditions the formation of ethane is as a result of the reductive elimination of the methyl groups, and is not due to the recombination of two free methyl radicals. 相似文献
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15.
D.A. Allison G. Johansson C.J. Allan U. Gelius H. Siegbahn J. Allison K. Siegbahn 《Journal of Electron Spectroscopy and Related Phenomena》1973,1(3):269-283
The B 1s binding energies of 23 compounds, including boron hydrides and carboranes have been measured in the vapor state. Correlations with Pauling charges and with shifts, calculated from the potential model using CNDO charges, are presented. The B 1s binding energies are subsequently discussed in terms of the chemical reactivity of the compounds. The iodomethanes have also been studied, and an electronegativity value for iodine suitable for ESCA correlations is given. 相似文献
16.
The nonlinear optical response of three new organometallic compounds was studied by z-scan method under picosecond excitation at 1064 and 532 nm. The compounds showed self-focus effect at both wavelengths, and effective reverse saturation absorption at 532 nm and strong two-photon absorption at 1064 nm occurred. Through calculating and comparing the nonlinear optical indexes of the compounds, we found that the third-order nonlinear susceptibility was enhanced by two-fold for one photon transition resonant effect, and incorporating different heavy metal atoms in the delocalized organic system slightly influenced the nonlinear optical indexes. 相似文献
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Ability for an induction of the antiferroelectric phase in compounds with a cyano group in a terminal position has been tested by comparison of phase diagrams of their mixtures. Most of the tested compounds do not cause the induction by themselves but they support an antiferroelectric ordering in mixtures. The core comprising biphenylate fragment has a higher tendency to support the antiferroelectric order. 相似文献
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G.M. Bancroft I. Adams H. Lampe T.K. Sham 《Journal of Electron Spectroscopy and Related Phenomena》1976,9(2):191-204
X-ray photoelectron spectra have been recorded for a number of solid and gaseous organotin compounds. Solid-state charging effects (such as differential charge broadening) can be large, though we have almost eliminated them by subliming very thin films onto platinum metal. In this way, we have obtained solid-state Sn 3d line widths that are within 10% of the analogous gas-phase values. The quality and reproducibility of the solid-state spectra likewise approach those of gases.The general correlation between ESCA Sn 3d line widths and Mössbauer quadrupole splittings indicates that the broadening of the Sn 3d lines is due to crystal-field splitting from the C20 term (the quadrupole term) in the crystal-field expansion. There is a general correlation between ESCA binding energies and Mössbauer isomer shifts for the solids. 相似文献