Emissivity of CO2-H2O mixtures at temperatures up to 1000° K

The emissivity in the 2.7 m range is examined with a spectrometer having 25 cm^–1 for 2.5, ,7.5 cm·atm,4 8cm·atm, 400T1000° K; 150P730 mm Hg. It is found that relation (1) is obeyed to within /0.1, though the calculated transmission is usually less than the measured value. It is shown that the relation is obeyed on account of the mutual position of the CO₂ and H₂O lines in the band, i.e., one gas may be considered as unselective relative to the other.     

A Monomial Basis for the Virasoro Minimal Series M(p,p′) : The Case 1<p′/p<2

Quadratic relations are given explicitly in two cases of chiral conformal field theory, and monomial bases of the representation spaces are constructed by using the Fourier components of the intertwiners. The first case is the (2,1) primary fields for the (p,p)-minimal series M_r,s (1rp–1,1sp–1) for the Virasoro algebra where 1<p/p<2. We restrict ourselves to the case p3, for which the (2,1) primary field exists. The second case is the intertwiners corresponding to the two-dimensional representation for the level k integrable highest weight modules V() (0k) for the affine Lie algebra      

Electronic structure of amorphous Nb1-x Si x films studied by X-ray emission and X-ray photoelectron spectroscopy

We present valence band spectra of the amorphous system Nb_1–x Si _x (0.2x0.8), of bcc-Nb and of a-Si obtained by X-ray photoelectron spectroscopy (XPS, Al K) and X-ray emission spectroscopy (XES, Si K-emission bands). The samples were prepared as thin films by sputtering. The origin of all prominent spectral features was identified and consistently correlated to Si 3s-, Si 3p-and Nb 4d-derived states. The Nb4d-Si3p coupling is stable in binding energy over a wide concentration range. There is strong experimental evidence that the short range order changes considerably within the concentration interval 0.4x0.7, whereas the partial density of states of the Si 3p-electrons is clearly altered in the small concentration range 0.50x0.57.     

Recent results from the TCV tokamak

During the first two years of operation, the TCV tokamak has produced a large variety of plasma shapes and magnetic configurations, with 1.0B _tor1.46T,I _p800kA,k2.05, –0.71. A new shape control algorithm, based on a finite element reconstruction of the plasma current in real time, has been implemented. Vertical growth rates up to 1000s^–1 have been stabilized using the external coil system. Ohmic H-modes with Troyon factors ( _tor aB/I _p) up to two and densities up to 2.25×10²⁰m^–3, corresponding to the Greenwald limit, have been obtained in diverted discharges. Limiter H-modes with line averaged electron densities up to 1.7×10²⁰m^–3 have been obtained in elongated D-shaped plasmas with 360 kAI _P600 kA.Presented at 17^th Symposium Plasma Physics and Technology, Prague, June 13–16, 1995.This work was partly supported by the Fonds National Suisse de la Recherche Scientifique.     

Stable Ultracompact Objects

Ultra-Compact Objects (ucos) have been found tobe interesting astrophysical entities. The existence ofsuch a possible stable object has been discussed byconsidering the stability of Tolman's type VII solution which is one of the few physicallyrelevant exact solutions of Einstein's field equationsfor a static and spherically symmetric massdistribution. A distinctive feature of this solutionamong the others is that the surface density alsodrops to zero (i.e., the continuity of density, and therespective derivative of the metric parameter() is also assured at the surface of theconfiguration). The stability analysis of this solution,according to the variational method [20], as well as thebinding-energy criteria of fluid spheres shows that theconfiguration remains stable at least up to a central redshift, z₀ 5.09, and surfaceredshift, z_a 0.78 (i.e. up to a u mass/size) value 0.3428), thereby confirmingthe existence of an ultracompact object (uco) thatcorresponds to a mass to size ratio (u M/a) 1/3.     

ЭЛЕКТРИЧЕСКАЯ ЭКВИВ АЛЕНТНАЯ СХЕМА ЗАТУХАЮЩИХ КОЛЕБАНИ Й ИЗГИБА У ПБЕЗОЭЛЕКТРИЧЕСКИ Х СТЕРЖНЕЙ

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Structural stability properties of friedman cosmology

A dynamical system with Robertson-Walker symmetries and the equation of the statep=, 01, considered both as a conservative and nonconservative system, is studied with respect to its structural stability properties. Different cases are shown and analyzed on the phase space (x=R ^D , y=x).     

Photoelectric characteristics of materials Pb1-xSnxTe?In? subject to microwave and infrared emission

Current/voltage (CV) characteristics of solid solutions Pb_1–xSn_xTeln (with D. 22x3. 24 and 0.2N_In1.0 atomic percent) were studied at He temperatures, in presence of background at 300K. Also the photoconductivity of these materials was measured in conditions of background screening and illumination at wavelengths 100µm and 2mm.CV-characteristics are interpreted within a model of two-electron capturing by Jahn-Teller centers. Photoconductivity in millimeter and submillimeter wavebands, having relaxation times less than 10^–5 sec, is related with heating of electronic gas in process of electromagnetic power absorption by the free carriers.     

Mössbauer spectroscopy,X-ray diffraction and magnetic measurements of iron-nickel ultrafine particles

Iron-nickel ultrafine particles with a composition in the Invar region (38–50% Ni) were prepared by the gas-evaporation-coalescence technique. The chemical composition was checked by electronprobe microanalysis, while X-ray diffraction Rietveld refinement was used to characterize the structure as well as to estimate the particle size. The temperature and field dependence of the magnetizationM(B, T) was measured for 0B25 kOe in the temperature range 4.2 KT400 K. Transmission Mössbauer spectra were taken at room temperature and at liquid helium temperature. The results obtained show that the predominant phase is a disordered Ni-rich alloy.On leave from Physics Department, University of Khartoum, P.O. Box 321, Khartoum, Sudan.     

Four-parametric regular black hole solution

We present a regular class of exact black hole solutions of the Einstein equations coupled with a nonlinear electrodynamics source. For weak fields the nonlinear electrodynamics becomes the Maxwell theory, and asymptotically the solutions behave as the Reissner–Nordström one. The class is endowed with four parameters, which can be thought of as the mass m, charge q, and a sort of dipole and quadrupole moments and , respectively. For 3, 4, and |q|2s _c m the corresponding solutions are regular charged black holes. For = 3, they also satisfy the weak energy condition. For = = 0 we recover the Reissner–Nordström singular solution and for = 3, = 4 the family includes a previous regular black hole reported by the authors.     

Mössbauer study of the perovskite series Sr(Fe1−xTix)Oy

⁵⁷Fe Mssbauer effect in the perovskite series Sr(Fe_1–xTi_x)O_y (0.0x0.99; y3) at RT and 78K has been analyzed. The influences of the Ti composition on the coexitence of Fe⁴⁺ and Fe³⁺, the ratio of Fe⁴⁺ to the total Fe, and the Y value have been studied. When 0x0.6 the ratio of Fe³⁺ (II) doublet to the total Fe increases as the final firing temperature increases, agreeing with the result obtained from the positron lifetime measurements. When x0.7, the Fe³⁺ (II) doublet disappears. In the range of x=0.9 and x=0.99, there still exists a considerable content of Fe⁴⁺ in samples, disagreeing with the result obtained from the chemical analysis by Clevenger. The relations between the electrical resistivity and the thermistor material constant B of negative temperature characteristic varying with Ti composition have been discussed.     

Logic of likelihood

The notion of probability is generalized to that of likelihood, and a natural logical structure is shown to exist for any physical theory which predicts likelihoods. Two physically based axioms are given for this logicai structure to form an orthomodular poset, with an order-determining set of states. The results strengthen the basis of the quantum logic approach to axiomatic quantum theory.     

Влияние сильного выс окочастотного поля на расслоение положи тельного столба постоянного тлеющег о разряда

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The influence of a strong high-frequency field on the stratification of the positive column of a D-C glow discharge

An experimental study is made of the damping of moving striations in a d-c glow discharge by a strong high-frequency field. The results of measurement are in agreement with existing conceptions on the production and mechanism of propagation of moving striations. Apart from the process of damping the paper also describes the standing stratification of the positive column of a d-c discharge as a result of a superposed high-frequency discharge.

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Temperature dependence of the electric field gradient in Er metal

The method of perturbed angular distributions was used to measure the temperature dependence of the electric field gradient in Er single crystal for 98 KT156 K. The I=11^– isomer in Er¹⁵⁴) was used as a probe. ₀ increases monotonically for 98 KT259 K and then decreases. A possible cause for this effect may be short range interactions between the f electrons above the Neel point.Visitor from the Weizmann Institute, Rehovoth, Israel.     

On the role of hardy spaces in form factor bounds

Functions of the space H ^p (1p) of the unit disc and upper half-plane are characterized by their distributional boundary values and asymptotic behaviour.     

Critical exponents for numbers of differently anchored polymer chains on fractal lattices with adsorbing boundaries

We study the problem of polymer adsorption in a good solvent when the container of the polymer-solvent system is taken to be a member of the Sierpinski gasket (SG) family of fractals. Members of the SG family are enumerated by an integerb (2b), and it is assumed that one side of each SG fractal is an impenetrable adsorbing boundary. We calculate the critical exponents ₁, ₁₁, and _s , which, within the self-avoiding walk model (SAW) of the polymer chain, are associated with the numbers of all possible SAWs with one, both, and no ends anchored to the adsorbing impenetrable boundary, respectively. By applying the exact renormalization group (RG) method for 2b8 and the Monte Carlo renormalization group (MCRG) method for a sequence of fractals with 2b80, we obtain specific values for these exponents. The obtained results show that all three critical exponents ₁, ₁₁, and _s , in both the bulk phase and crossover region are monotonically increasing functions withb. We discuss their mutual relations, their relations with other critical exponents pertinent to SAWs on the SG fractals, and their possible asymptotic behavior in the limitb, when the fractal dimension of the SG fractals approaches the Euclidean value 2.     

Mössbauer study of mixed valent silicides Eu(Ir1−x Pd x )2Si2

The solid solutions Eu(Ir_1–x Pd _x )₂Si₂, which exist for 0x0.125 and 0.75x1. cristallize with the tetragonal ThCr₂Si₂-type structure. The variation of the europium valence with composition has been thoroughly studied at temperatures 4.2T293 K by¹⁵¹Eu Mössbauer resonance. For 0x0.125 the europium valence at room temperature decreases asx increases. For 0.75x1 the valence transition temperature Eu³⁺Eu²⁺ increases asx increases.     

Vibrational property of the slow N 2 + ions deposited SiNx films

We have investigated vibrational properties of silicon-nitride films, SiN_x (0.3×1.33), produced by a non-thermal method using high-resolution electron energy loss spectroscopy. The results, based on a continuous random network model assuming a planar XY₃ vibrational bond unit, show that the Si-N bonds in the films closely resemble those in typical thermal silicon nitride although nitrogens occupy some metastable binding sites. We estimate force constants of the restoring forces for a Si₃N bond unit, which tend to increase gradually with increasing nitrogen content x. In particular, the central force constant k₁ for the in-plane stretching mode of silicon atoms varies with x in the range 297k331 N/M, larger than the theoretical value for a nitrogen atom imbedded in a pure Si crystal.     

The MPE/UCB far-infrared imaging Fabry-Perot interferometer (FIFI)

FIFI is an imaging spectrometer with two or three Fabry-Perot interferometers (FPI) in series for airborne astronomical observations in the far-infrared range (=40...200m). It employs 5×5 arrays of photoconducting detectors and offers spectral resolutions as small as 2km/s. Resolution and bandwidth can be set over a wide range to match a variety of astronomical sources. Cryogenic optics minimizes thermal background radiation and provides for in-flight step tunable spatial resolution. At 158 m wavelength the background-limited NEP is 3 × 10^-15W/Hz at 40 km/s resolution and with two FPI's; with three FPI's the expected NEP is 10^-15WHz at 5 km/s resolution.The frequency-chopping mode of the high-resolution Fabry-Perot allows for line detection in extended objects. Absolute internal flux calibration ensures adequate flat fielding of the array elements.     

Intensity measurement for Kβ η satellites in the radiative auger effect

Calculations have been performed on the integral shapes of the K lines, which are long-wave satellites of the K ₁ lines, for Cl, Ti, and Fe, where allowance has been made for interference between states in the 2p^–1 and 3p^–2p configurations. The calculations show that these satellites represent short-wave branches of the K lines strengthened by the 3p-1s transition with simultaneous M electron ejection. The strong interference between the amplitudes of these processes in the final state means that it is in principle quite impossible to speak of the intensities of the K satellites without stating how they are isolated from the measured spectrum.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 34–39, September, 1984.