The effect of the orientation of zinc single crystals and of the rate of growth on the direction of cell substructure

The effect of the orientation of zinc single crystals and the rate of growth on the direction of the formation of cellular substructure is observed. A model accounting for the observed dependences is proposed.

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. .

     

The interaction of foils activated by thermal neutrons

The interaction of foils lying in a plane during their activation by thermal neutrons has been calculated. Numerical values of functions are listed, which can be used in calculations, especially for graphite. The interaction was measured in the graphite column of the VVR-S reactor.

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, , . , , . VVR-S.

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We thank J. Frytacký, T. Kania and V. ervenka for their help in the numerical calculations and measurements.     

The application of the thermodynamics of irreversible processes to welding arcs

The self-regulation of an inert gas shielded metal welding arc is dealt with briefly. A thermodynamic equation is derived for the self-regulation of such an arc.

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. .

     

The classical theory of nuclear spin interaction in a ferromagnet

The Hamiltonian of nuclear spin interaction in a ferromagnet is derived by the classical method, which introduces the precession of nuclear spin into the equation of motion for magnetization. From this it is shown that the interaction Hamiltonian also depends on the magnitude and sign of nuclear precession frequency _N and the damping constant of ferromagnetic resonance A. The calculation of these parameters makes the Suhl [1] quantum mechanical derivation of the Hamiltonian of nuclear spin interaction in a ferromagnet more accurate. The influence of these parameters on the relaxation timeT ₂ is also discussed and is applied to the case of cubic cobalt.

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. , _N . , [1] - . ₂ .

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In conclusion the author thanks Dr. L. Valenta for significant remarks and valuable advice on this work. He also thanks J. Kvasnica and Z. roubek for suggestive discussions.     

Magnetization coils without iron core for high field intensities

A new theory of rectangular coils without an iron core is described which amends the old one of Fabry and Bitter. It enables us to compute field intensities in coils having very small openings, which the old theory could not do.

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, , , .

     

Основные соотношени я длн построения механических селект оров нейтронов

, . , , . . , , .     

Nonlinear Response of the Semiconductor Laser with Pump Current Modulation

The influence of tuning the lasing monochromatic radiation frequency _g within the amplification band on the nonlinear response of the semiconductor laser with harmonic modulation of pump current is investigated theoretically. It is established that the principal features of the behavior of the nonlinear amplitude-detuning characteristic (ADC) are determined by the relation between the current modulation frequency _m and the main resonance frequency of the laser _r. If _{m r}, then with increase in _g the response decreases monotonically mainly due to the decrease of its dynamic component. The exception is provided by the spectral regions where peaks on the ADC appear because of the explicitly nonlinear lasing regimes (period doubling, chaos, etc.) When _m < _r, the resonance conditions for induced oscillations are satisfied only for definite spectral intervals within the amplification band and a dip appears on the low-frequency side of the ADC. With decreasing _m, the dip boundary shifts to a more high-frequency region of the band corresponding to smaller local resonance frequencies. The peaks on the ADC corresponding to the radiation period doubling shift to the region of smaller values of _g on increase in _m.     

Some applications of the discrete fourier transform to problems of crystal lattice deformation I

The theory of the discrete Fourier transform [1], [2] is applied in solving a system of difference equations describing the positions of atoms in a deformed crystal lattice. The crystal lattice is approximated by the Born-Kármán model modified to include the internal energy of the undeformed crystal.

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, , , [1] [2]. - , , .

     

Влияние катодной обл асти на динамические свойства тлеющего разряда в во дороде

. . , , I-om 1957 .     

Exponential decay near resonance,without analyticity

We consider a quantum mechanical model which displays the behaviour associated with having a resonance or metastable state. The Hamiltonian depends on a parameter . When =0, there is an eigenstate ₀; when 0, ₀ dissolves into the continuous spectrum, showing approximate exponential decay. We prove this result without using dilatation analyticity. The model describes a two-state atom coupled to the quantized radiation field. The state space of the field is truncated, so that only the vacuum and one-photon states are included.This work was partially supported by NSF Grant DMS-8922941     

Notes on the classical and the nonrelativistic limits in quantum mechanics

A method is presented which can be used to discuss both the classical and also the nonrelativistic limit of quantum mechanics. A one-to-one correspondence may be established between the asymptotic convergence of the resolvent and that of the timedependent solution. In so far as the question of dynamics is concerned we investigate the relation between families of nonrelativistic Hamiltonians and the corresponding Dirac-Hamiltonians when c± or when c±0. The nonrelativistic free theory formally shows the same pattern when ±0 (the classical limit) or when ±. The investigation finally shows how the asymptotic convergence of the relativistic theory can take place under some fairly general conditions of the radiation field.     

Electron microscope study of dislocations in slip bands of bent Fe-3·2% Si alloy single crystals

Dislocations in Fe-3·2% Si alloy single crystals deformed by bending are studied in this paper. The specimens were cut parallel to the slip plane into platelets, polished, and studied in places at various distances from the neutral plane with an electron microscope. A large number of jogs of various sizes was found on screw dislocations. Many loops are formed by the motion of dislocations with jogs and by the stopping of moving dislocations by obstacles. Some of them grow as a result of stress. The activity of sources on large jogs is stopped at an early stage by a cross slip. The formation and growth of loops increases the dislocation density and causes the growth of slip bands.

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Fe-3,2% Si

Fe-3,2% Si, , , . . , . . . .

     

К В. Ч. НАГРЕВУ РАЗРЕЖЕННОЙ ПЛАЗМЫ

[2]. . , . , . . . .     

The crystal structure of meta-zeunerite Cu(UO2)2(AsO4)2⋅8 H2O

The structure of the mineral zeunerite (deposits at Rotava near Kraslice, Ore Mountains) was determined. The tetragonal unit cell, having the dimensionsa=7.10₅Å andc=17.70₄Å, contains two structure units of Cu(UO₂)₂(AsO₄)₂8H₂O. The space group isP4₂/nmc. The distribution of the atoms in the unit cell was determined from the Patterson projectionP(vw) and by means of (F ₀-F _c) synthesis. Meta-Zeunerite has a layer type structure. The sheets [(UO₂)(AsO₄)] are separated by layers containing the cations (Cu(H₂O)₄)²⁺ and molecules of water. The uranium is coordinated octahedrally with six oxygen atoms at distances: U-O₁ 1.94 Å, U-O₂ 1.78 Å, U-O₃₍₄₎ 2.18 Å (4×). The uranyl radical O₁-U-O₂ is linear. In the tetrahedron AsO₄ the interatomic distances are As-O 1.77 Å and the bond angles 102°, 102°, 113° and 113°. Each oxygen atom of the tetrahedron AsO₄ is simultaneously bonded to the uranium atom. The bond angle As-O-U is 137°. The layers [(UO₂)₂(AsO₄)] are bonded together by the cations (Cu(H₂O)₄)²⁺. The distances Cu-O₁ and Cu-O₂ are 2.55 and 2.58Å respectively. The structural changes during hydration and dehydration are explaned.

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- Cu(UO₂)₂(AsO₄)₂8 H₂O

( , ). =7,10₅ Å,=17,70₄ Å Cu(UO₂)₂(AsO₄)₂8 ₂O. P4₂/nmc. P(v w) (F ₀-F _c) . . , [(UO₂)(AsO₄)], , [u(₂)₄]²⁺ . : U-O₁ 1,94 Å, U-O₂ 1,78 Å, U-O₃₍₄₎ 2,18 Å ( ). ₁-U-₂. AsO₄ As- 1,77 Å -102°, 102°, 113° 113°. AsO₄ . As--U 137°. [(UO₂)₂(AsO₄)] [u(₂O)₄]²⁺. u-O₁ 2,55 Å, u-O₂ 2,58 Å. .

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In conclusion the author thanks T. Veselská for assistance in the calculations and workers of the National Museum in Prague, and primarily Dr. ípek, for supplying the sample. The experimental work was carried out at the Department of Physics of the Natural Science Faculty of Komenský University.     

Homogenität,Kovarianz und Relativität

Zusammenfassung Es werden zwei Begriffe: Homogenität des Raumzeitkontinuums und Kovarianz der Gleichungen, wie sie in der Relativitätstheorie gebraucht werden, definiert und erläutert. Es wird gezeigt, doss die beiden Begriffe wesentlich verschieden sind und in Form nichtäquivalenter mathematischer Bedingungen ihren Ausdruck finden. Trotzdem werden beide Begriffe sowohl von Einstein, als auch in der Literatur über Relativitätstheorie mit einem und demselben Wort Relativität bezeichnet. Der Missgebrauch des Wortes Relativität bedeutet nicht nur einen terminologischen Fehler, sondern spricht auch von einem ungenügenden Verständnis der Grundidee der Relativitätstheorie, besonders der sog. allgemeinen Relativitätstheorie. Versteht man unter Relativität Homogenität des Raumes, so ist in der sog. allgemeinen Relativitätstheorie überhaupt keine Relativität vorhanden. Versteht man dagegen unter Relativität Kovarianz der Gleichungen, so steckt in jener Theorie nicht mehr Relativität, wie z. B. in den unrelativistischen Bewegungsgleichungen, welche ebensogut eine allgemein-kovariante Formulierung gestatten (Lagrangesche Gleichungen 2-ter Art). Die Bezeichnung allgemeine Relativitätstheorie ist daher irrefuhrend. Die geniale Theorie Einsteins ist eine reine Gravitationstheorie. , No 4, . 131, 1955. (RhilosophischeFragen No 4, S. 131, Moskau 1955. Ins Deutsche über setzt vom Verfasser).     

Periodic Motion of Atoms Near a Charged Wire

We study the classical motion of an atom in the vicinity of an infinite straight wire which carries an oscillating uniform charge. This system has been proposed as a mechanism for trapping cold neutral atoms. The parameters of the problem are the magnitude Q and frequency of oscillation of the charge, the mass M and polarizability of the atom, and the angular momentum L of the atom about the wire. For 0 and 2MQ ² greater than, but close to, L ², we prove that the atom's radial motion is periodic (with period 2/), and that the atom moves in a helical path around the wire. For 2MQ ² L ² we prove that the atom must either collide with the wire or else escape to infinity in the radial direction.     

The motion of 90° wedge domains in BaTiO3 in an alternating electric field

The paper deals with the motion of 90° wedge domains in BaTiO₃ in an alternating field of 50 c/s. The critical field, the positional hysteresis loops with double asymmetry, the production of wedges with polarization perpendicular to the field and 180° substructure in the wedges were studied. The differences between the behaviour of the wedges and the individual 90° walls are pointed out which are caused by differences in the energy balance of these formations and by different interactions with 180° processes. The upper limit of contribution of the wedge motion to the initial permittivity is estimated. The results are discussed from the phenomenological point of view.

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90° BaTiO₃

90° BaTiO₃ , 50 Hz. , , , , , , 180° . 90° , 180° . , . .

     

The influence of oscillations on ionization in a discharge path

The paper solves the problem of gas ionization in a discharge path in a very dilute gas, where the free path of the electrons is much larger than the dimensions of the path and the transit time of the electrons between the electrodes is of the order of the period of the applied h-f voltage. It was found that for a certain ratio of the transit time of the electrons between the electrodes in the discharge path to the period of the h-f oscillation, resonance occurs when the wattless current component is zero. The electron density rises in the path and thus also the gas ionization.

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, , , . , , . , .

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In conclusion, the author would like to thank F. Benda for preparing the equipment, M. Kivánek for preparing the equipment and some of the measurements, and A. Hrdá for the measurements and for working out the case with equally large a-c and d-c voltages within the framework of her thesis.     

О СУЩЕСТВОВАНИИ ОТРИ ЦАТЕЛЬНОГО ЯВЛЕНИЯ БАРКГАУЗЕНА

. . , . , . , . coo , 13. 5. 1954 . - .     

Спектралъный метод о пределения изотонно го состава свинца. Частъ I

, . , . - . PbI4058 Å . , . 1000000. , , . - , .