Positron annihilation studies on the electronic structure of Pd−Ag−H system

Angular Correlation of Annihilation Radiation (ACAR) is shown to be useful to examine the electronic structure of -phase Pd_1–y Ag _y H _x system. Hydrogen absorption by Pd_1–y Ag _y alloys results in the increase of both nearly free andd-localized electron numbers in compliance with the KKR-CPA calculation outcomes. The investigation of -phase systems, PdH _x hydrides as well as Pd_1–y Ag _y H _x materials, failed because of a high concentration of lattice defects.     

Frequency discrimination near the spectral edge of simultaneous and forward maskers

The effects of the presence of an amplitude discontinuity in the spectrum of a noise masker on frequency discrimination performance were examined. First, detection thresholds as a function of masker level were obtained for pure-tone signals masked by either simultaneous or forward white and low-pass maskers. Then frequency discrimination thresholds were obtained using four masker levels that were chosen to yield predetermined masked thresholds, with signal levels corresponding to each of three sensation levels above these masked thresholds. The principal results indicate that frequency discrimination is poorer in simultaneous low-pass noise than in simultaneous white noise, and that this difference in performance increases with increasing sensation level and with increasing masker level. These results are inconsistent with an explanation based on the pitches generated at spectral edges ("edge pitch"), pitch shifts, or disruption of phase-locking information, but are generally consistent with an explanation based on lateral suppression. It is proposed that a release from suppression may occur in filtered noise backgrounds at high noise levels and at high sensation levels. The reduced suppression may result in poorer frequency discrimination due, in part, to reduced signal detectability.     

Windmill polynomials over fields of characteristic two

Chambers andSmeets [3] have designed a windmill arrangement of linear feedback shift registers (LFSRs) to generate pn-sequences overGF(2) with high speed. When the windmill hasv vanes, the associated minimal feedback polynomial (having degreen, relatively prime tov) can be taken to have the shapef ₁(x ^v )+x ⁿ f ₂(x ^–v ), where the polynomialsf ₁ andf ₂ have degree [n/v]. Their numerical evidence, whenv is divisible by 4, suggests that, surprisingly, there areno such windmill polynomials which are irreducible ifn±3 (mod 8), while about twice as many irreducible and primitive windmill polynomials as they expected occur ifn±1 (mod 8). A discussion of this behaviour is presented here with proofs. The brief explanation is that the Galois group of the underlying generic windmill polynomial overGF (4) is equal to the alternating groupA _n .     

Structure of a nonequilibrium high-frequency discharge

The problem for a one-temperature plasma is considered with allowance for the finite ionization rate. It is shown that in the developed nonequilibrium case the leading effect of ambipolar electron diffusion and ionization lag lead to a qualitatively different picture as compared with the equilibrium case. In particular, the heat release zone covers only a relatively small leading part of the ionization zone with a relatively low (n_e n_ef) electron concentration.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 161–169, May–June, 1989.The authors thank A. A. Barmin and A. G. Kulikovskii for useful discussions.     

Anticancer agent development: X-ray crystal structure and keto-enol tautomerism of dimethyl 1-hydroxy-6,7-methylenedioxy-4-(3′,4′,5′-trimethoxyphenyl-trans-3,4-dihydronaphthalene-2,3-dicarboxylate

Structural and conformational information obtained from the crystal structure and solution¹H nmr investigations of the title compound are compared. The 4-aryltetralone, C₂₄H₂₄O₁₀, crystallizes as a chloroform solvate in the monoclinic space group, P2₁/n, witha=12.519(4),b=17.938(6),c=12.534(9)Å,=111.90(5)°, and D_calc=1.51 g cm^–3 forZ=4. The data for this compound were collected at –150°C. Least-squares refinement of 2796 observed [F _o5(F _o)] reflections led to the final agreement index ofR=0.062. A threefold static disorder was observed for one of the carboxyl groups. The second carboxyl group participates in an intramolecular hydrogen bond and is thus ordered. The¹H nmr spectrum revealed the title compound to exist as a keto-enol tautomeric mixture in solution. Vicinal hydrogen coupling constant analysis proved reliable in ascertaining B-ring stereochemistry of 2,3-disubstituted-4-aryltetralones.     

Impossibility of centrally symmetric shock waves in vacuum in the relativistic theory of gravitation

Burevestnik Scientific-Industrial Union, Leningrad. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 79, No. 3, pp. 473–480, June, 1989.     

Variation of the instability index on stationary curves of elliptic equations depending on a parameter

The set of solutions of the equation A(u, )=0 in the case of general position consists of smooth curves. Solutions of a quasilinear elliptic equation with large instability index are constructed and an estimate obtained for the number of turning points of the solution curves.Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 12, pp. 47–58, 1987.     

Spectrum of the algebra of pseudodifferential operators in a halfspace

One considers C*-algebras, generated by pseudodifferential operators in a halfspace. The operators act in functional spaces with weighted norms. One describes the set of all classes of equivalent irreducible representations of algebras and reveals the topology on the spectrum. One investigates, in particular, the dependence of the spectrum on the choice of the weighted functional space.Translated from Problemy Matematicheskogo Analiza, No. 10, pp. 160–180, 1986.     

Spectral asymptotics for the Schrödinger operator with potential which steadies at infinity

We consider the discrete spectrum of the selfadjoint Schrödinger operatorA _h =–h ² +V defined inL ²(^m) with potentialV which steadies at infinity, i.e.V(x)=g+|x|^– f(1+o(1)) as |x| for>0 and some homogeneous functionsg andf of order zero. Let _h (),0, be the total multiplicity of the eigenvalues ofA _h smaller thanM–, M being the minimum value ofg over the unit sphereS ^m–1 (hence,M coincides with the lower bound of the essential spectrum ofA _h ). We study the asymptotic behaviour of ₁() as0, or of _h () ash0, the number0 being fixed. We find that these asymptotics depend essentially on the structure of the submanifold ofS ^m–1, where the functiong takes the valueM, and generically are nonclassical, i.e. even as a first approximation (2) ^m _h () differs from the volume of the set {(x, )^2m:h ²||²+V(x)<M–}.Partially supported by Contract No. 52 with the Ministry of Culture, Science and Education