Domain structure of cobalt whiskers

An experimental investigation is made into the domain structure of cobalt whiskers by the colloid technique. A new type of domain structure was found; the width of the domains is studied as a function of the thickness of the whisker. This dependence follows a two-thirds power law and does not agree with existing theories which predict a half power law.

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. . , .

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In conclusion the authors wish to thank V. Janovec and F. Kroupa for valuable remarks and A. Tahalová for help in growing the whiskers.     

The thickness dependence of the permittivity of barium titanate single crystals

A thickness dependence of the permittivity ofc-domain barium titanate single crystals was found. The experimental results were explained by means of a model of a dielectric with surface layers. The thickness of the layer and the permittivity of the surface layer and bulk of the crystal were determined.

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iO₃

iO₃, -. . , .

     

Anisotropy of the low temperature resistivity of hexagonal single crystalline spin glass systems

The impurity contribution to the resistivity in zero field (T) of dilute hexagonal single crystals of ZnMn, CdMn and MgMn has been studied in the mK range on samples cut parallel () and perpendicular () to thec-axis, using a SQUID technique for the measurements. Typical spin glass behavior is found in (T) as well as (T) for all alloys, with Kondo like logarithmic increases at higher temperatures and maxima atT _m at lower temperatures, indicating the influence of impurity interactions. The differences in the corresponding isotropic resistivity _poly(T) between the three systems can qualitatively be understood within the framework of a theoretical model by Larsen, describing (T) as a function of universal quantitiesT/T _K and _RKKY/T _K , where _RKKY is the RKKY-interaction strength andT _K the Kondo temperature. With respect to the two lattice directions studied, the behavior of (T and (T is anisotropic in the Kondo regime as well as in the range where ordering becomes important. While the anisotropy in the Kondo slope can be understood by an anisotropic unitarity limit, the understanding of the anisotropy in region where impurity interactions are important remains problematic.Dedicated to Prof. Dr. S. Methfessel on the occasion of his 60th birthday     

Time production and spatial distribution of macroscopic space charges in D-C discharge plasma

It is shown for a one-dimensional approximation that, around a disturbance in the ion concentrationn ₊(x, t) in the axial direction of a cylindrical plasma, a corresponding electron distributionn _–(x, t) is established with such a large velocity that under the usual conditions of a discharge plasma this electron distribution follows the relatively slow changes in ion concentration practically without delay. Relation (24) then holds for the electron concentration, the parametersl ₁,l _D being given by Eqs. (15) and (16). As long as the disturbance of the ions isn ₊(x) 0, a space chargeq ₀(n ₊-n_–) is produced and maintained in the plasma even if the disturbance of the equilibrium state of the plasma in the initial stage was electrically neutral (i.e.n ₊(x, t=0)==n _–(x,t=0)). The dimensions of these space charges can be many orders larger than the Debye characteristic lengthl _D ; this is shown on an example of a spatially periodic curven ₊(x). The unique (quasi-stationary) expression of the electron concentrationn _– by means of the deflection of the ion concentrationn ₊(x, t) permits a considerable simplification of the solution of the problems connected with axially disturbing the homogeneous state of a plasma, sincen _–(x, t) can be eliminated from the equations of continuity of the plasma by substituting from (24), and the problem becomes that of determining the curve of the ion concentrationn ₊ from the equations modified in this way.

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, ₊(, t) - _–(, t) , . (24), l ₁ l _D (15) (16). ₊() 0, q ₀(n₊ — n_–), , (..n ₊(x,0)=_–(, 0)). () _{– +}(, t) , , . . _–(, t) n ₊ .

     

ПЛОТНОСТЬ ТОКА В АНОД НЫХ ПЯТНАХ ИСКРОВЫХ РАЗРЯДОВ В ВОЗДУХЕ ПР И АТМОСФЕРНОМ ДАВЛЕН ИИ

annapamyp, . .     

The basic equations of the dynamics of the continuous distribution of dislocations III. special problems

The basic equations of the dynamics of the continuous distribution of dislocations analogical to Maxwell equations are derived in a series of papers [I, II, III]. The analogy of the elastic and electromagnetic fields is analyzed. In part [III] some special problems are discussed, such as the density of the forces acting on the dislocations, the energy dissipation during the movement of dislocations, which is expressed by an equation analogical to Ohm's law. The equations derived in the previous parts in four-dimensional symbolics are considered in the three-dimensional differential and integral form. It is found that in special cases the relations become the known ones of elastodynamics, hydrodynamics and the static theory of the continuous distribution of dislocations. It is found that Kröner's method of integrating the equations of the dislocation field by means of so-called incompatibility tensors is analogical to the integration of the Maxwell equations by means of Hertz vectors. The analogy between the elastic dislocation field and the electromagnetic field is discussed in detail.

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III.

, . . : , , , , . , , . , , . , . .

     

Der Einfluss der positiven Ionen auf die Exoelektronenemission

Zusammenfassung Es werden die Ergebnisse der Messung des Einflusses der auf den Emitter bei der Messung der Exoelektronenemission mittels Geiger-Müller-ZÄhlers auffallenden positiven Ionen beschrieben und die möglichen Mechanismen der Beeinflussung der Emission diskutiert.

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, -. , .

     

Interpolating gauges and the importance of a careful treatment of ε-term

We consider the use of interpolating gauges (with a gauge function F[A;]) in gauge theories to connect the results in a set of different gauges in the path-integral formulation. We point out that the results for physical observables are very sensitive to the epsilon term that we have to add to deal with singularities and thus it cannot be left out of a discussion of gauge-independence generally. We further point out, with reasons, that the fact that we can ignore this term in the discussion of gauge independence while varying of the gauge parameter in Lorentz-type covariant gauges is an exception rather than a rule. We show that generally preserving gauge-independence as is varied requires that the -term has to be varied with . We further show that if we make a naive use of the (fixed) epsilon term (that is appropriate for the Feynman gauge) for general interpolating gauges with arbitrary parameter values [i.e. ], we cannot preserve gauge independence [except when we happen to be in the infinitesimal neighborhood of the Lorentz-type gauges]. We show with an explicit example that for such a naive use of an -term, we develop serious pathological behavior in the path-integral as is/are varied. We point out that correct way to fix the -term in a path-integral in a non-Lorentz gauge is by connecting the path-integral to the Lorentz-gauge path-integral with correct -term as has been done using the finite field-dependent BRS transformations in recent years.     

On the geometrization of electrodynamics

This paper develops the conjecture that the electromagnetic interaction is the manifestation of the torsion of spacetime. This conjecture is made feasible by the natural separation of the connection ^v into gravitational and electromagnetic parts ^v and ^v , respectively, related to the metric and to the torsion. When ^v is neglected in front of ^v , the affine geodesics are shown to become the equations of motion of charged particles with Lorentz force, for an appropriate choice of . Since ^v contains the factor q/m, neutral particles do not see the torsional part of the connection and behave as if were zero, i.e., as in Einstein's theory of gravity (the same effect is obviously obtained for charged particles when ^{v v} ).In addition to the factor q/m, the velocity of the test particle appears in . This indicates that the appropriate context for this problem is to be found in velocity-dependent connections. The velocities are now coordinates and become the actual velocities of the test particles only in the system of equations that one solves for obtaining the affine geodesics in connections of this type.When written with differential forms, the combination of Maxwell's equations and of the pertinent form of the torsion suggests geometric field equations for electrodynamics. As for the gravitational part of the connection, it can be made to obey equations similar in form to the Einstein field equations. A unified geometric theory of electrodynamics and gravitation spontaneously emerges. The present state of the theory does not yet permit us to ascertain whether the right-hand side of the fully geometric, gravitational field equations corresponds to the energy-momentum tensor.     

Ermüdungserscheinungen der infrarotbestrahlten Silber-Cäsium-Photokathoden

Zusammenfassung In dieser Arbeit werden die Erscheinungen der normalen und anomalen, durch Infrarotstrahlung verursachten und von uns schon früher an diesen Photokatoden beobachteten Ermüdung von Silber-Cäsium-Photokathoden untersucht. Diese Erscheinungen wurden an durchsichtigen sowie undurchsichtigen, durch verschiedene Technologien zubereiteten Photokathoden festgestellt. Es wurden Messungen der Strahlungsintensitäts-, Temperatur- und Spektralverteilungsabhängigkeit der normalen und anomalen Ermüdung durchgeführt. Es werden die Ursachen der Unübereinstimmigkeit im Vergleich mit Arbeiten von De Boer und Teves besprochen. Ferner wurden die Zeitverläufe der Ermüdung bei der Abwechslung der Bestrahlungs- und Dunkelzyklen studiert.

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, , . , . , . . .

     

ГАЛЬВАНОМАГНИТНЫИ Э ФФЕКТ В МАРГАНЕЦ-ЦИНК ОВЫХ ФЕРРИТАХ В ОКРЕСТНОС ТИ ТОЧКИ КЮРИ

. , . _c . , , . _c ; .

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The magnetoresistance in zinc-manganese ferrites in the vicinity of the Curie point

The paper describes an exact method for measuring the adiabatic and isothermal magnetoresistant effects in ferrites. It gives the results of studying the temperature dependence of the magnetoresistant effect, which is negative near the Curie point in ferrites and the temperature dependence of which has a maximum of absolute values inT _c . It is also shown that the pronounced maximum of the adiabatic magnetoresistant effect is to a certain extent caused by the magnetocaloric effect. When measuring the dependence of the magnetoresistant effect on the field strength for a temperature equal toT _c , certain small deviations from the theoretically assumed dependence were found; the influence of different factors on these deviations is discussed and a proposal for their explanation is given in analogy to the results known for metals.

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[1].

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., ., . . . , . . , . . . . .     

Problems in the interpretation of cosmic ray nuclear interactions

Difficulties in the interpretation of high-energy nuclear interactions are discussed and explanations suggested on the basis of successive or composite nucleon-nucleus collisions, the first predominant below a few 10 ¹¹ eV,the second for higher energies. In the energy region up to about 10 ¹¹ eVsome discrepancies in the frequency of production of strange particles, the small interaction cross-section of iron etc. are explained, taking into account secondary intranuclear collisions. The tunnel model of Heitler and McCusker is replaced by assuming a cone-shaped interaction volume (funnel) even at the highest primary energies. A number of consequences concerning the energies of the primary particles, the multiplicity and asymmetry in the angular distribution of secondaries, coefficient of inelasticity etc. are discussed.

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, , 10¹¹ eV, — . 10¹¹ eV , ., , . () . , , , .

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This paper contains a condensed summary of some of the material presented in a series of lectures given by the author on the occasion of his visit to Prague in December 1957/January 1958. Its publication in this form is intended as an expression of thanks to the Czechoslovak Academy of Sciences and its leading Officers, in particular Prof. V. Procházka, Prof. J. Novák, and Prof. V. Petrílka, whose kind invitation made this visit possible.     

ВЛИЯНИЕ ПОЛНОГО ОТРА ЖЕНИЯ НА ДИАФРАГМЕ СОЛЛЕРА НА РАЗРЕШАЮШ УЮ СИЛУ РЕНТГЕНОВСКО ГО СПЕКТРОГРАФА

- - , , , . - , -.     

ЗАТУХАНИЕ КОЛЕБАНИЙ ЧАСТИЦ В ОБЩЕМ ПОЛЕ С ПЕРИОДИЧЕСКОЙ СТРУКТУРОЙ I

, , . , . .

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The damping of particle oscillations in a general field with periodic structure I

A liner theory is derived, discussing the dynamics of particles in the region of an equilibrium orbit in a general electromagnetic field, which forms a periodic system. The total particle damping is determined from the Hamiltonian found and from dissipative forces brought out by a classical reaction radiation. Relations for the damping of the synchrotron oscillations are derived from the study of the appropriate phase space.

     

Измерение некоторых нейтронных спектров методом ядерных эмулъсий

. Ra+Be . , , . 8.     

Study of magnetic after-effect in magnesium manganese ferrites

The magnetic after-effect caused by the diffusion of electrons was studied in detail in MnMg ferrites of the series Mg _x Mn_1.15–x Fe_1.85O₄₊ ; the comparative measurements were also carried out on a sample of MgFe₂O₄₊₍<0). By combining the two methods, (a) investigation of the disaccommodation of initial permeability at different temperatures and (b) measurement of the displacement of the maximum of the temperature dependence tan with the frequency, it was possible to study the relaxation processes whose time constants lay between 0.5 sec and several hours, or between 10^–4 to 10^–7 sec. It was found that the processes taking place at low temperatures and studied by method (a) differ from those observed at high temperatures by method (b), particularly in the lower activation energies and greater dispersion of the time constants. In addition to these two main relaxation processes a weak relaxation superposed over the main disaccommodation was found in ferrites with non-zero content of manganese. An analysis of the intensity of different relaxation effects showed the participation of Mn ions in these relaxation effects and it was found that both main relaxations are probably equivalent as regards the final steady state, to the creation of which they lead; they differ however in the mechanism of electron diffusion by which this state is realized. The main features of the different diffusion mechanisms are discussed.

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, , MnMg Mg _x Mn_1.15–x Fe_1.85O₄₊ . MgFe₂O_{4+ (}<0). ()- , () tg , , 0,5 sec , 10^–4–10^–7 sec. , , () , , (), , , . , . Mn , , , , , ; , , , . .

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In conclusion the author thanks Dr. J. Bro and K. Závta for valuable discussion and F. Vilím for carefully carrying out the measurements.     

К ВОПРОСУ О ФОТОПРОВО ДИМОСТИ ФОТОГРАФИЧЕСКОЙ ЭМУ ЛьСИИ

) . , , , ; , , . . , .     

On longitudinal vibrations of thin cylindrical tubes

The method of variable coupling parameters is used for approximatively calculating the frequencies of longitudinal vibrations of isotropic homogeneous tubes. For thin-walled tubes we arrive at the same formula for frequencies as in Love's classical theory.

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. , .