On the problem of the permittivity dispersion of barium titanate

The complex permittivity of multidomain single crystals of BaTiO₃ was measured in the decimetre and centimetre wave bands and it was proved that in this frequency region there is dispersion of the permittivity. Apparatus for measuring the permittivity of substances with a high is described and the influence of the inhomogeneity of the field in the sample on the characteristics of the cavity resonator is calculated. Present theories of the high-frequency properties of BaTiO₃ are discussed from the point of view of the experimental results.

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BaTiO₃ , . . BaTiO₃.

     

The distribution of ions and their valencies in manganese ferrites I. MnFe2O4+γ ferrites

A model for the distribution of cations in the spinel lattice of manganese ferrites MnFe₂O₄₊ was elaborated on the basis of the experimental studies of the basic magnetic quantities, electrical conductivity and magnetic relaxation of the given ferrites, taking into consideration their crystallographic properties. The conclusions following from this model are in good agreement with the experimental results obtained by us and by other authors both for stoichiometric manganese ferrite and for a ferrite where 0.

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I. MnFe₂O₄₊

, MnFe₂O₄₊ . , , , , , 0.

     

К КИНЕТИКЕ ФОТОПРОВОДИМОСТИ СЕ ЛЕНА

- 65 –150 °. 0,2 . - , .     

ЭЛЕКТРИЧЕСКИЕ И ТЕРМ ОЭЛЕКТРИЧЕСКИЕ СВОЙ СТВА АНТИМОНИДА ИНДИЯ

Qj , i 4 ISb, - N , –180° +400°C. , ISb zi, - ; -m _n =3,6. 10^–, n . menem , , - .eue . - - .     

The temperature vibrations of urea molecules

The structural and dynamic parameters of urea at 112°K and 295°K were determined by the least squares method. The characteristic temperature of the torsional optical vibrations of a molecule about a C-O bond was determined and is in good agreement with the value determined by Raman scattering. The fractional X-coordinate of the nitrogen atom corrected for torsional vibrations was determined and it was found that the magnitude of the projection of the C-N bond in the given temperature range changes only within the limits of observational errors. A new method, called temperature difference synthesis, is described and it is shown that it is suitable for rapid qualitative determination of the thermal anisotropy of the vibrations of atoms in a crystal lattice.

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112°K 295°K. C-O , , . X- , C-N . , , , .

     

On the problem of the phase shifts of reflected light

. , . , . .

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On the problem of the phase shifts of reflected light

The paper solves the topical question of phase shifts when light is reflected. By introducing the reflection tensor and its transformation it was found that all phase shifts hitherto given in the literature can be used. It was proved that when different phase shifts are used the corresponding unit vectors must be oriented. If an arbitrary coordinate system and the relations pertaining to it are used consistently it is not possible by calculation or experiment to arrive at contradictory results.

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. , , . .: , 1961. . 45–49 . . , .. . , .     

ВЫРАЩИВАНИЕ МОНОКРИСТАЛЛОВ ТИТА НАТА БАРИЯ

, .     

К ВОПРОСУ О ФОТОПРОВО ДИМОСТИ ФОТОГРАФИЧЕСКОЙ ЭМУ ЛьСИИ

) . , , , ; , , . . , .     

Определение дефекто в решетки третъего ро да и величины когерентн ых областей решетки у порошкооБразного в олъфрама

, . , , -, , , .     

Локалъная чувствите лъностъ фотокатодов фотоумножителей

. . .

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The local sensitivity of photo-multiplier photo-cathodes

The influence of the non-uniform distribution of the sensitivity of a photo-multiplier photo-cathode on the spectrum shape of the output pulses from a scintillation detector is studied. Methods of scanning the local sensitivity and determining its distribution function are described. The theory was compared qualitatively with measurement on a slow-neutron detector from a mixture of zinc sulphate and boric acid.

     

The distribution of ions and their valencies in manganese ferrites II. Mn1+xFe2-xO4+y ferrites

The influence of the oxygen content on the saturation magnetic moment and the Curie temperature was studied experimentally on non-stoichiometric manganese ferrites having a varying excess of manganese. Taking into consideration the results of studying the electrical conductivity and magnetic relaxation effects, a model was elaborated for the distribution of ions in these ferrites, which starts out from the distribution of ions in stoichiometric manganese ferrite. The experimental results obtained by us and those of other authors confirm the justification of this model.

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II. Mn_1+xFe_2-xO_4+y

. , . .

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In conclusion the authors thank members of their technological department for preparing the samples and M. Mikulá for carefully carrying out the chemical analyses.     

Moments of frequency spectrum and thermodynamic functions of crystals with defects

The method for calculating the vibrational frequencies of a perturbed crystal lattice, elaborated by the author earlier, is combined with the method of contour integral to calculate the additive functions of the frequencies (E. W. Montroll). This leads to a formula which can be used to calculate the changes caused by a defect in the even moments of the frequency spectrum without knowing the spectrum of the unperturbed or perturbed crystal. The changes in thermodynamic functions and specific heat can be approximated by means of these changes in moments. The author also calculates the change in the frequency spectrum of a monatomic chain, which is caused by one foreign atom, confining himself to the isotopic effect.

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(. . ). , , , . . , , , .

     

Choice of parameters of an X-ray monochromating unit

In recent papers a way of computing the monochromated wavelength distribution in some current experimental arrangements was presented. In this paper an application is shown for the Johansson monochromating unit. The conditions are indicated for attaining the desired breadth of the monochromated interval and for its maximum intensity. The analysis implies that it is not advantageous to use very narrow foci and that the crystals should be neither very perfect nor very imperfect. The optimum conditions must be found in each case separately.

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. Johansson. , , . , , , . .

     

К ВОПРОСУ O КРИТИЧЕСКО Й ЧАСТОТЕ ПРИ ПРЕРЫВИСТОМ ОСВЕ ЩЕНИИ

c , c n , n AgBr. .     

НИЗКОЧАСТОТНЫЕ КОЛЕ БАНИЯ ПОЛОЖИТЕЛЬНОЮ ГО СТОЛБА ТЛЕЮЩЕГО РАЗР ЯДА В ГАЗАХ

[6]- , - . - - . -mam .     

A contribution to the theory of X-ray monochromators

The characteristic function is introduced, describing completely the monochromating effect of monochromating units. Expressions for this function are presented for monochromating units frequently used. An example of computation for Johansson's unit shows the conditions in a special case. The curves indicating the shift of the wavelength centroid of monochromated radiation for crystals of different perfection allow conclusions to be drawn about the influence of the alignment of the crystal on precision measurements of lattice constants. The experiments verify the suggested model. The computations for a given experimental arrangement permit a simple determination of the effective breadth of the reflection curve, if a distance of two suitably chosen diffraction lines of a polycrystalline specimen is measured. Finally, it was found experimentally that a small elastic bending does not essentially alter the reflection curve of highly elastic and imperfect crystals unless macroscopic distortions are present.

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, . . . , , . . , . , , , .

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The author is deeply grateful to Prof. A. Kochanovská for her encouraging interest and wishes to express his thanks to Z. Hemanová for her careful computations.     

ИССЛЕДОВАНИЕ ЭРОЗИЙ НОГО ДЕЙСТВИЯ ИМПУЛЬ СНЯХ ЭЛЕКТРИЧЕСКИХ РАЗРЯ ДОВ С СЛАБЫМ ТОКОМ

50–100 , 1–2 1–10 . - . - . , , - . -.     

МЕТОД ДЛЯ ВЫЧИСЛЕНИЯ КОЛЕБАНИЙ НАРУШЕННО Й АТОМНОЙ ЦЕПОЧКИ

- . - , .     

Three variations in the intensity of cosmic radiation in the first half of 1958

The time courses are given of three variations in the intensity of cosmic radiation, which occurred in the first half of 1958. The measuring apparatus is described and the energies of the particles recorded a reestimated. The paper is the partial result of systematic measurements of the intensity of cosmic radiation carried out in Czechoslovakia in the International Geophysical Year.

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1958

, 1958 . . , .

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The authors heartily thank the Institute of Geomagnetism in Krasnaja Pachra, near Moscow, and especially its director, Prof. M. B. Pukov, and Dr Ju. M. Kopylov for the neutron counters.The authors wish to thank Prof. V. Petrílka, corresponding member of the Czechoslovak Academy of Sciences, and Prof. L. Jurkiewicz, from the Academy of Mining and Heavy Industry in Cracow for help in the work and Academician J. Novák, who made possible the numerical evaluation of the data in the Mathematical Institute of the Czechoslovak Academy of Sciences. Especial thanks go to F. Pilát and B. Slavík for their great help in setting up the apparatus and to all colleagues who took part in the measurements.     

К ТЕОРИИ СПОНТАННОЙ Н АМАГНИЧЕННОСТИ ТОНК ИХ СЛОЕВ. I. ЧАСТЬ

- - , - . - . -, - [6]. 1956 . , .