Radiative characteristics of pulsed power driven Z-pinch aluminumplasmas

In this paper, we study the dynamics of a massive aluminum Z-pinch plasma load and evaluate its performance as a soft X-ray radiator. A radiation hydrodynamic model self-consistently driven by a circuit describes the dynamics. Comparisons are made for the K- and L-shell soft X-ray emission as a function of the ionization dynamic model. The ionization dynamic models are represented by: 1) a time-dependent nonequilibrium (NEQ) model, 2) a collisional radiative equilibrium (CRE) model, and 3) a local thermodynamic equilibrium (LTE) model. For all three scenarios the radiation is treated 1) in the free streaming optically thin approximation where the plasma is treated as a volume emitter and 2) in the optically thick regime where the opacity for the lines and continuum is self-consistently calculated online and the radiation is transported through the plasma. Each simulation is carried out independently to determine the sensitivity of the implosion dynamics to the ionization and radiation model, i.e., how the ionization dynamic model affects the radiative yield and emission spectra. Results are presented for the L- and K-shell radiation yields and emission spectra as a function of photon energy from 10 eV to 10 keV. Also, departure coefficients from LTE are presented for selected levels and ionization stages     

Finite-element calculation of the influence of interdiffusion on eigenstates in a GaAs/Al x Ga1-x As single-quantum-well structure

The influence of interdiffusion on eigenstates in an interdiffusion-induced GaAs/Al_xGa_1-xAs single-quantum-well structure is analysed numerically by the finite element method. In this approach, the confinement potential profile of the interdiffused quantum well structure is nonlinear and is modelled by an error function and, in particular, the nature of the effective mass of an electron is considered. The results show that the number of eigenstates and energy levels varies with the extent of the interdiffusion. Numerical results for the quasi-bound states in the quantum well structure with an applied electric field are also presented.     

Superconductivity and normal state resistivity of Ba0.6K0.4BiO3: an optical phonon approach

We discuss the nature of the pairing mechanism and the physical properties associated with the normal as well as the superconducting state of cubic perovskites Ba_0.6K_0.4BiO₃using the strong coupling theory. An interaction potential which includes the Coulomb, electron–optical phonon and electron–plasmon interactions is developed to elucidate the superconducting state. A model dielectric function is constructed with these interactions fulfilling thef-sum rule. The screening parameter (μ^* = 0.26) infers the poor screening of charge carriers. The electron–optical phonon strength (λ) estimated as 0.98 is consistent with an attractive electron–electron interaction and supports the moderate to strong coupling theory. The superconducting transition temperature of Ba_0.6K_0.4BiO₃is then estimated as 32 K. Ziman's formula of resistivity is employed to analyse and compare this with the temperature-dependent resistivity of a single crystal. The estimated contribution from the electron–optical phonon together with the residual resistivity clearly infers a difference when a comparison is made with experimental data. The subtracted data infer a quadratic temperature dependence in the temperature domain (30 ≤ T ≤ 200 K). The quadratic temperature dependence of ρ [ = ρ_exp − (ρ₀ + ρ_e–ph)] is understood in terms of 3D electron–electron inelastic scattering. The presence of these el–el and el–ph interactions allows a coherent interpretation of the physical properties. Analysis reveals that a moderate to strong coupling exists in the Ba_0.6K_0.4BiO₃system and the coupling of electrons with the high-energy optical phonons of the oxygen breathing mode will be a reason for superconductivity. The implications of the above analysis are discussed.     

Über die Bedeutung von Diffusionsgrenzschichten bei Ionenaustauschvorgängen

Based on NMR imaging results of the spatial and temporal development of ion exchange processes in alginate gels, the question of appropriate modelling of these processes is discussed. For rare earth and actinoid ions, the behaviour is found to correspond qualitatively to the expectations of Stefan’s model (shrinking core model, SCM). However, quantitative correspondence of the experimental data with the model can only be achieved when an additional diffusive layer at the surface of the ion exchange material is assumed. An extension of the SCM with respect to this problem is derived.     

Combinatorial Characterizations of Authentication Codes II

For any authentication code for k source states and v messages having minimum possible deception probabilities (namely, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9qq-f0-yqaqVeLsFr0-vr% 0-vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGqbWaaS% baaSqaaiaadsgaaeqaaOWaaSbaaSqaaiaaicdaaeqaaOGaeyypa0Za% aSGbaeaacaWGRbaabaGaamODaaaaaaa!3F28!\[P_d _0 = {k \mathord{\left/ {\vphantom {k v}} \right. \kern-\nulldelimiterspace} v}\] and % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9qq-f0-yqaqVeLsFr0-vr% 0-vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGqbWaaS% baaSqaaiaadsgaaeqaaOWaaSbaaSqaaiaaigdaaeqaaOGaeyypa0Ze% xLMBb50ujbqeguuDJXwAKbacfaGae8hkaGIaam4AaiabgkHiTiaaig% dacqWFPaqkcqWFVaWlcqWFOaakcqWF2bGDcqGHsislcaaIXaGae8xk% aKIae8xkaKcaaa!4CD1!\[P_d _1 = (k - 1)/(v - 1))\], we show that there must be at least v encoding rules. (This can be thought of as an authentication-code analogue of Fisher's Inequality.) We derive several properties that an extremal code must satisfy, and we characterize the extremal codes for equiprobable source states as arising from symmetric balanced incomplete block designs. We also present an infinite class of extremal codes, in which the source states are not equiprobable, derived from affine planes.Dedicated to Gus Simmons     

Cylindrical spike model for the formation of diamondlike thin films by ion deposition

T /n_S of n_T rearrangements and n_S atoms in the spike volume as the crucial parameter characterizing the ability of a given ion–target combination to achieve complete rearrangement of the spike volume. n_T/n_S>1 is the optimum condition for diamondlike film growth. For aC films the ion energy dependence of n_T/n_S agrees well with the measured sp³ bond fraction. For Ar⁺-ion-assisted deposition of aC we find n_T/n_S>1 above 50 eV with no pronounced ion energy dependence. Furthermore, our model predicts optimum conditions for the formation of cubic boron nitride between 50 eV and 3 keV. Accepted: 14 October 1997     

Recurrent solar wind streams

A new approach to investigating the statistical relationship between certain solar features and recurrent wind streams is presented. This approach is based, on a comparative analysis of the distributions of lifetimes of a set of solar features, recurrent geomagnetic disturbances, and geomagnetic “calms.” Correlation coefficients of 0.81, 0.85, 0.79, and 0.77 are found for the distributions of several solar features—filaments, large-scale magnetic fields, coronal features, and coronal holes, respectively—and recurrent geomagnetic disturbances. A correlation factor of 0.97 between the distributions of geomagnetic “calms” and active regions is found. The combined evidence indicates that no specific type of solar feature is responsible for the recurrent stream activity. Rather, the configuration of the large-scale magnetic field of the Sun appears to control the permanently existing corpuscular activity. Since prominences trace polarity division lines of the large-scale magnetic field structure of the Sun, they have been checked as a possible general predictor of recurrent corpuscular activity; their parameters could present the most reliable indices that relate closely with trends in geomagnetic disturbances. A comparative analysis of cyclic variations of sunspot numbers, the total number of prominences, the relative number of low-height (<-20″) prominences, and recurrent geomagnetic storms is made for solar cycle N16. The relative number of low-height prominences is found to correlate broadly (0.83) with recurrent wind streams. P. K. Shternberg State Astronomical Institute, Moscow, Russia; National Solar Observatory, Sacramento Peak, U.S. Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 2, pp. 145–151, February, 1998.     

Carbon thin films through laser ablation

Thin carbon films were deposited on silicon substrates at room temperature using a 0.355 μm Nd:YAG laser wavelength at low irradiance in the presence of argon gas. Various techniques including scanning electron microscopy, X-ray diffraction and Raman spectroscopy were used to analyze the film quality. The influence of the argon gas pressure on the properties of the films is demonstrated and a correlation with the optical emission data is presented.     

Scanning capacitance microscopy and spectroscopy applied to local charge modifications and characterization of nitride-oxide-silicon heterostructures

We have combined a home-built capacitance sensor with a commercial scanning force microscope to obtain a Scanning Capacitance Microscope (SCM). The SCM has been used to study Nitride-Oxide-Silicon (NOS) heterostructures which offer potential applications in charge storage technology. Charge writing and reading on a submicrometer scale is demonstrated with our SCM setup. In addition, SCM appears to be very useful for the characterization of subsurface defects in semiconductor devices which are inaccessible by most of the other scanning probe microscopies. Finally, we introduce a novel spectroscopic mode of SCM operation which offers combined voltage-dependent and spatially resolved information about inhomogeneous charge distributions in semiconductor devices.     

Antimicorbial effects of newly synthesized organotin(IV) and organolead(IV) derivatives

Triorganotin(IV) and triorganolead(IV) derivatives of the types Me₃Sn(SCZ) and Ph₃Pb(SCZ) (where SCZ^? is the anion of a semicarbanzone ligand) have been synthesized by substitution reactions of trimethyltin chloride and triphenyl-lead chloride with semicarbazones derived from heterocyclic ketones. The resulting complexes have been characterized by elemental analyses, molecualr weight determinations and conductivity measurements. The mode of bonding has been established on the basis of infrared and ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopic studies. Some respresentative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria; the results of these investigations have been reported in the present paper.