Основные соотношени я длн построения механических селект оров нейтронов

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ЛЮМИНЕСЦЕНЦИЯ КРИСТ АЛЛОВ AgCl

AgCl –180°. . , ( : =4640 Å, =5080 Å). , , . . - . –183°, =1,6. 10^–8%±10%.

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Luminescence of AgCl crystals

The luminescence of normal and deformed single crystals of AgCl of different thickness was measured at a temperature of –180°C. With deformed samples the decrease in intensity of the luminescence was measured. On the luminescence band of the above crystals we observed a fine structure for which the series rule could be used (edge of series =4640 Å, =5080 Å).The observed luminescence was explained by means of the exciton mechanism proposed by Matyá, i.e. annihilation of a localized exciton either on a cation vacancy or on a cation vacancy on a dislocation jog. The luminescence yield at –183°C, =1.6×10^–3%±10%, was measured by a photographic method.

     

How often do simple dynamical processes have infinitely many coexisting sinks?

This work concerns the nature of chaotic dynamical processes. Sheldon Newhouse wrote on dynamical processes (depending on a parameter )x _x+1=T(x _n ; ), wherex is in the plane, such as might arise when studying Poincaré return maps for autonomous differential equations in IR³. He proved that if the system is chaotic there will very often be existing parameter values for which there are infinitely many periodic attractors coexisting in a bounded region of the plane, and that such parameter values would be dense in some interval. The fact that infinitely many coexisting sinks can occur brings into question the very nature of the foundations of chaotic dynamical processes. We prove, for an apparently typical situation, that Newhouse's construction yields only a set of parameter values of measure zero.This research was supported in part by grants from the Air Force Office of Scientific Research AFOSR 81-0217, the Consiglio Nazionale delle Ricerche-Comitato per le Matematiche, and the National Science Foundation DMS 84-19110On leave from: Dipartimento di Matematica G. Castel nuovo Universita di Roma La Sapienza P. le Aldo Moro 5, I-00185 Rome, Italy     

ОПРЕДЕЛЕНИЕ ВРЕМЕНИ ЖИЗНИ μ-МЕЗОНОВ ПО АНОМАЛЬНОМУ ПОГЛ0Щ ЕНИЮ МЕТОДОМ ЯДЕРНЫХ ЭМУЛЬСИЙ

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The propagation of excitation energy in perturbed crystals

The process of the propagation of excitation energy in perturbed dielectric crystals with a weak bond between the atoms having zero permanent dipole moment is studied. It is shown that on certain assumptions this process of propagation can be regarded as the motion of a Frenkel exciton in the electrostatic field of the defect. Frenkel's exciton can be characterized in this case as a neutral polarizable particle having induced dipole moment equal to the change in the induced dipole moment of the crystal during the excitation of one of its atoms.

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An Approach to Linear Scalable DH-PHEMT Model for Millimeterwave Application

This paper describes a scalable small-signal equivalent circuit for 0.25 m gatelength Double Heterojunction delta-doped PHEMTs. The scaling rules for all elements except the pad capacitances and bondwire inductances have been determined. Good agreement is obtained between simulation results and measured results for 2 times 20 m , 2 times 40 m, 2 times 60 m, 2 times 100 m gate width (number of gate fingers times unit gate width) DH PHEMT.     

Current distributions in a two-dimensional random-resistor network

The current and logarithm-of-the-current distributionsn(i) andn(ln i) on bond diluted two-dimensional random-resistor networks at the percolation threshold are studied by a modified transfer matrix method. Thek th moment (–9k8) of n(ln i) i.e., ln i&^k, is found to scale with the linear sizeL as (InL)^(k). The exponents (k) are not inconsistent with the recent theoretical prediction (k)=k, with deviations which may be attributed to severe finitesize effects. For small currents, ln n(y)–, yielding information on the threshold below which the multifractality of (i) breaks down. Our numerical results for the moments of the currents are consistent with other available results.     

Zeros of partition functions via correlation inequalities

We show analyticity of the pressure for some classical ferromagnetic systems in the region ¦Im ¦ < Re of the external field. The proof, via correlation inequalities, is simpler than existing proofs for the Lee and Yang region {Re 0} and applies, without any approximation procedure, to more general continuous spin variables, e.g., distributed as , where _2n is an arbitrary real number and the other parameters are positive. It also applies directly to plane rotators in the region ¦Im ¦ ¦Re ¦ (Euclidean norms), but the proof will be given in a subsequent article, together with new inequalities between truncated correlation functions.     

Der Einfluss der Plastischen Verformung durch Kaltwalzen auf die Koerzitivkraft

Zusammenfassung Es werden die Ergebnisse der Messungen der Koerzitivkraft von Eisen, Nickel und einiger Fe-Ni-Legierungen in Abhängigkeit von der plastischen Verformung durch Kaltwalzen angegeben. Gemessen wurde in Richtung parallel und senkrecht zur Walzrichtung. Die Ergebnisse werden insbesondere vom Gesichtspunkt des Einflusses der Versetzungen und der einachsigen induzierten Anisotropie diskutiert.

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Für die wertvollen Diskussionen und das Durchlesen der Arbeit danken wir den Kollegen J. Kaczér und V. Janovec, für die wirkungsvolle Hilfe bei den Messungen Koll. J. Grolmus.     

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

Surviving extrema for the action on the twisted SU(∞) one point lattice

We give a simplified construction of twist eating configurations, based on a theorem due to Frobenius. These configurations are defined through the equation:U U U ⁺ U ⁺ =exp(2in /N) withU SU(N), =1 tod andn an antisymmetric matrix with integer entries. In the (Twisted)-Eguchi-Kawai model they yield extrema some of which survive forN. Comparison is made with the Monte Carlo data of the internal energy in the small coupling region.     

Nonlinear two-photon interaction in a strong magnetic field

Sections of nonlinear photon-photon scattering processes and merger of photons in the nucleus (Ze) (Ze) in a strong magnetic field are computed by using a developed two-dimensional formalism. Closed expressions are obtained for the sections with a graphical illustration of the results and they are compared with the case of no external fields.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 16–19, June, 1988.     

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

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Feasibility of an experiment to determine the branching ratio for the emission of a heavy neutrino after muon capture in3He

The triton energy of the muon capture reaction ³He t+v, where ³ He is the ground state of muonic³He, has been measured in order to investigate a possible heavy v admixture into the flavour with high sensitivity. ³ He has been formed via the pd fusion reaction by stopping ^– in an ionization chamber (IC) filled with an H/D gas mixture of 3% D concentration at a pressure of 161 bar. In a first short experiment 650 triton events were observed yielding an upper limit for the -heavy v mixing strength of 2.3×10^–3 atE _0v=60 MeV.     

The paramagnetic state (μ+e−) in silicon and tellurium at high temperature

The paramagnetic state (⁺e^–) in Si and Te was observed in a longitudinal magnetic field. The mean lifetimes of these states were obtained: _Si = 1.45(3) s, _Te = 12.5(8) s at 290 K, _Te = 12(2) s at 250 K.     

Optical tuning of a tellurium cavity: optical modulation and bistability in the infrared region at room temperature

A new optical-optical modulator for the infrared region (4m < < 11m) is described. It is based on the tuning of the transmission of a plane parallel tellurium slab by free carriers created by multiphoton absorption of 10.6m and 5.3m radiation at room temperature. The operation of this device is described by a simple theory using the plane-wave approximation and the Drude-Zehner model. The assumptions of this theory were fulfilled by the experimental conditions, permitting a quantitative analysis of the registered modulations. Under certain working conditions pulse shortening (170 ns pulses of=5.3m were shortened by up to 20 ns) and fast switch-on of the device (switch-on time 2 ns) were observed. Moreover, the modulator exhibits limiter action and optical bistability which, for the first time, is observed in an intrinsic semiconductor device at room temperature.The substance of this paper was presented at the Conference on Ultrafast Phenomena in Spectroscopy at Reinhardsbrunn (GDR), in November 1980, and a preliminary account published in theProceedings of the meeting.     

ДЕФОКУСИРОВКА ДИФФР АКТОМЕТРА ШУЛЬЦА

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Microstructure of fiber-like SiC/Si3N4 composite particulate

The microstructure of fiber-like SiC/Si₃N₄ composite particulate was investigated using high-resolution transmission electron microscopy techniques. The SiC/Si₃N₄ composite particulate consisted of a-SiC core and a -Si₃N₄ outer shell. Two kinds of composite particulate were distinguished when the observed orientation of the SiC core was <110>. In one type of the SiC/Si₃N₄ composite particulate, a crystal relationship of (111)-SiC | (102) -Si₃N₄ and (111)-SiC (114) -Si₃N₄ was identified; in the other type of the SiC/Si₃N₄ composite particulate, a crystal relationship of (111)-SiC (001) -Si₃N₄, and (111)-SiC (101) -Si₃N₄ was observed.     

К СПЕКТРУ ПОГЛОЩЕНИЯ АМОРФНОГО СЕЛЕНА В ИНФРАКРАСНОЙ ОБЛАС ТИ

0,6 25 . , , . , 13,4 20,4 , , , . . , . .

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A contribution to the absorption spectrum of amorphous selenium in the infra-red region

The absorption spectrum of amorphous selenium was measured in the region of 0·6 to 25 on samples of high purity and homogeneity. The absorption bands of amorphous and liquid sulphur were also measured in the same wave-length region. The measurements showed that the absorption bands 13·4 and 20·4 , appearing in the spectrum of amorphous selenium, are its intrinsic absorption bands and are not caused by impurities, as some authors think. The similarity between the infra-red spectra of selenium and sulphur is shown.

     

Weak four-fermion interaction in terms of SU(3) invariants. II

A lepton octet is constructed by analogy with the baryon octet by the substitution p⁺N ₁e⁺,⁺₁ é⁺,^-₂^-, ^- N ₂^-, where ₁, ₂,N ₁,N ₂ are arbitrary constants. The neutral components are replaced by a linear sum of the electron and muon neutrinos with arbitrary coefficients. The constants are determined from the system of general conditions (normalization, absence of crossed terms of the type ( etc.). As a result, the lepton octet is determined to within a single constant, and this is shown to be identical with the Cabibbo angle. Calculations are also made of the weak decays of baryons of the octet in the case of both charged and neutral currents. In the case of charged currents, the results agree with Cabibbo's theory. Calculations are also made of the lepton-lepton weak interactions and the ratios of the corresponding constants are determined. The ratios are in qualitative agreement with the existing experimental data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 51–56, January, 1976.