‘Factors of ignorance’ and the rationalized M.K.S.A. system of units

An attempt is made, by means of an allusive (rather than a systematic) historical account of the development of the subject, to exhibit the essentially unique character of the rationalized M.K.S.A. system of units. The establishment of this system involved one arbitrary decision—the determination to retain unaltered the size of the previously accepted unit of current. Thereafter, any choice of derived units, other than the choice actually made, would have destroyed the basic symmetry of the formulation.     

List of Ya.A. Smorodinsky’s publications

A list of Ya. Smorodinsky’s articles published in science journals is presented. The text was submitted by the author in English.     

Free radicals in pyrimidines: E.S.R. of a γ-irradiated single crystal of 5-nitrouracil

Free radicals are observed in γ-irradiated single crystals of 5-nitrouracil with the unpaired electron showing hyperfine interaction with one nitrogen atom. The principal values of hyperfine coupling are A_x = 22·5 g, A_y = 25·2 g, and A_z = 40·0 g, and the principal values of the spectroscopic splitting factor are g_u = 2·0117, g_v = 2·0064 and g_w = 2·0027. The relationship of the directions of the corresponding principal axes to the molecular orientations show that the unpaired electron must be located in an sp ² orbital on either N₍₁₎ or N₍₅₎. Considerations of the mechanism of radical formation and comparison to radiation damage in other molecules make the N₍₁₎ location seem more probable. The π interaction of the nitro group on C₍₅₎ evidently prevents the formulation of free radicals with the unpaired electron on C₍₅₎. That carbon atom is the most common location of unpaired electron density in other pyrimidine free radicals.     

N.M.R. spectra of the XnAA′ Xn′ type

The method described previously for the calculation of the X spectrum for spin systems of of the X_nAA′X_n′ type is extended by means of magnetic equivalence factoring to cases in which the long-range coupling constant J_x is non-zero. This coupling is treated as a first-order perturbation to the energy levels obtained when J_x =0, and it is found that J_x may be measured directly from the separations between easily identified lines in the spectrum. A detailed account of the X ₃ AA′X ₃′ system is given, and the N.M.R. spectrum of fluoro-N,N′-dimethyl-1,3,2,4-diazadiphosphetidine is analysed. The spectral parameters obtained are discussed. A computer programme which calculates the spectra of systems involving magnetic equivalence is used to examine the validity of the approximations in the method.     

Second‐Order Dispersion Forces. I. Equations of Motion

Equations of motion for polarization on the S–P atomic transition in a weak resonance field have been derived taking into account the Van der Waals interaction between atoms. The case of two atoms is considered within the Wigner–Weisskopf formalism and generalized to the case of identical atoms in a weak resonance field, where the saturation is negligible. It is found that two equations of motion are necessary: one of them for the polarization and another one for an effective polarization relaxation rate.     

Yu. N. Denisyuk’s ideas in the development of holographic methods of obtaining and projection of images

The main investigations carried out by Yuri Nikolaevich Denisyuk at the Ioffe Institute of the Russian Academy of Sciences have been presented. His investigations were aimed at developing methods of recording and projecting three-dimensional images in order to reduce the volume of information contained in the images for use in optical computers, optical interconnections, and displays.     

On the occurrence of b.c.c.–h.c.p. structural phase transition in Mo under pressure

Abstract

To resolve the controversy on the occurrence of a b.c.c.–h.c.p. transition in shock as well as static measurements in Mo, we have done more accurate total energy electronic structure calculations. Our results show that this phasetransition should occur at much higher pressures than suggested by earlier calculations.     

Mössbauer and N.M.R. studies of ErFe2Hx

Hydrides of Intermetallic compounds have been the object of many studies because of their potential applications/1/. Recent papers were devoted to the problem of interstitial site occupation in connection with H-H exclusion rule (d_H–H > 2.1 A). The present work deals with ErFe₂H_X, which has been investigated both by⁵⁷Fe Mössbauer Effect and by¹⁶⁷Er N.M.R. Previous studies were limited to X 2, 3.5, 4.1. Here five values of x (1.45, 1.6, 1.84, 2.6, 3.3) are considered, in order to obtain information on hydrogen location, filling and diffusion as a function of x, and also on hydrogen contribution to the electric field gradient (E.F.G.) and crystalline field at the Rare Earth.     

Origin of the E.S.R. hyperfine anisotropy and the cos2 θ rule of the β-fluorine couplings

The origin of the hyperfine couplings of β-fluorine nuclei in free radicals has been studied using the hyperfine tensors determined for and in single crystals. The direction of the maximum principal element of the β-fluorine coupling tensor in was found to be very close to the direction of the maximum overlap of the fluorine 2p π orbital with the half-filled carbon 2p π orbital. This means that the spin density in the fluorine 2p π orbital is mainly due to the direct overlap with the carbon 2p π orbital and the contributions from the hyperconjugation and the spin polarization mechanisms are less important. The cos²θ rule, B ₀ + B cos²θ, for the β-fluorine coupling tensor was also derived from the conformational dependence of the overlap integral. Using the ratio of B/B ₀ calculated from the overlap integral together with the observed hyperfine tensor for , the absolute values of B ₂ and B were determined and results were applied to the β-fluorine coupling tensor of the rotating CF₃ group in . The calculated tensor is in very good agreement with the one observed.     

Nobel Prizes in the “light” of Vavilov–Cherenkov radiation. To the 125th anniversary of the birth of S.I. Vavilov

The objective of this paper is not a detailed review or an analysis of the studies in the field of high-energy physics initiated by the discovery of Vavilov–Cherenkov radiation, occurred more than 80 years ago at the Lebedev Physical Institute, and awarded Nobel Prizes. The paper is written to emphasize the historical significance of the discovery of the effect and its key role in further studies in high-energy physics, commended by the high award of the Nobel committee. In 1958, 24 years after the first publication about the new phenomenon, i.e., emission of electrons moving in matter with the superlight speed, discovered by P.A. Cherenkov under the supervision by S.I. Vavilov, the Nobel Prize was awarded to a group of scientists of the Lebedev Physical Institute, P.A. Cherenkov, I.M. Frank, and I.E. Tamm “for the discovery and explanation of the Cherenkov effect”. Since then, practical application of Vavilov–Cherenkov radiation is widely spread.     

Measurement of deuterium quadrupole coupling constants of CD3 groups by 1H−{2H} N.M.R. studies of nematic solutions

Analytical expressions have been derived for the transition frequencies and intensities of a partially oriented group of deuterium nuclei with symmetry of the permutation group. Using d ₃-acetone, CD₃COCH₃, dissolved in a nematic solvent, as an example, it is shown how ¹H?{²H} double resonance experiments can be used to determine the relative signs of dipolar and quadrupolar interactions. The magnitude of the quadrupole coupling constant of the ²H nuclei in CD₃COCH₃ is determined.     

E.S.R. spectrum of BH3 -· in gamma-irradiated tetramethylammonium borohydride

We have determined the vibrational band intensities of the ¹ A ₂←¹ A ₁ transition of formaldehyde by means of an ab initio calculation. The values obtained fit correctly the experimental evaluations. It is also found that confining the Herzberg-Teller type expansion to the first non-zero term is a poor approximation to the exact value.     

Dielectric loss of half-doped manganite Lao.sCao.sMnO3＊

The dielectric loss tanfi of half-doped manganite Lao.sCao.sMnO3 is investigated using Green＇s function technique. The Lao.sCao.sMnO3 is described by the Kondo-lattice model in the double exchange limit, taking into account the Jahn- Teller distortion and the super-exchange interaction between the localized electrons. It is found that the intensity of tans decreases with increasing [e]TI, V, and U. It is also observed that the transition temperature Tp rises as l eJTI and U increase. It is worth noting that Tp remains unchanged and the strength of tans increases with increasing g. The calculated dielectric loss results are explained theoretically, and these behaviors are in qualitative agreement with the experimental results.     

Frequency response of loudspeakers by measuring theinduced e.m.f

1IntroductionTheperformanceofadirectradiatorloudspeakerisdirectIyrelatedtothediaphragmdis-placement.AccuratemeasurementoftIlefreqllenc,responseoftheloudspeakerbydifferentmethodsreqlliresananechoicchamberandacalibratednlicrophone.AI1echoicchambersoper-atingdowntorequiredlowfrequenciesareveryexpensive,a11dopenspacesareinconvenient.ThemethodsuggestedbyK.ele[l]isbasedonthefactthat,withsomerestrictions,thefarfieldfrequencyresponseofthespeakerissimilartothatofitsnearfieldresponse.Sincethereflected…     

Self-Similarity of Volume Measures for Laplacians¶on P. C. F. Self-Similar Fractals

Our main goal in this paper is to obtain a precise analogue of Weyl's asymptotic formula for the eigenvalue distribution of Laplacians on a certain class of “finitely ramified” (or p.c.f.) self-similar fractals, building, in particular, on the work of [7, 9, 22, 24]. Our main result consists in precisely identifying (for the class of “decimable fractals”) the volume measures constructed by the second author in [24] for general p.c.f. fractals and showing that they are self-similar. From a physical point of view, our results should be relevant to the study of the density of states for diffusions and wave propagation in fractal media. Received: 6 September 1999 / Accepted: 7 October 2000     

The diffusion of hydrogen in b.c.c. VTi solid solutions

Recent data for the variation of the diffusivity of hydrogen in b.c.c. VTi solid solutions with Ti-concentration and temperature have been analyzed in terms of the cell model for such ternary solid solutions. The data have been shown to be compatible with this model and a simple cell energy spectrum involving H-metal interactions which are linearly dependent upon the Ti-concentration.It is shown that the interaction energies deduced from the kinetic behavior of the system are in good accord with thermodynamic data for the VH and TiH terminal solid solutions.     

From extensive air showers to the characteristics of primary cosmic rays. To the 120th Anniversary of the Birth of D. V. Skobel’tsyn

The works by D.V. Skobel’tsyn that laid the foundation of the contemporary physics of cosmic rays and the physics of high energies are considered. Skobel’tsyn demonstrated that cosmic rays contain particles whose energy substantially surpasses the energies that are typical of radioactive decay, discovered the existence of air showers, i.e., when several particles hit an array simultaneously, and performed a series of investigations into extensive air showers that resulted in the discovery of a nuclear-cascade process in the atmosphere. The results that Skobel’tsyn obtained were of primary importance for the further development of cosmic-ray physics.