International Nuclear Information System (INIS)

Molar heat capacities have been measured for VHsub(n) and NbHsub(n) with n up to 1.93 at temperatures between 1.5 and 16 K. The height of the peak in plots of the electronic specific heat, indicating superconductivity, diminishes with increasing hydrogen content in the #alpha# + #beta# two-phase region, and can be taken as a measure of the fractional amount of #alpha#-phase present (lever-rule). In NbHsub(n) accordingly, the two-phase region presumably extends up to n = approximately 0.9 at helium temperatures. No hydride phase, including VH_2 and NbH_2, showed superconductivity above 1.5 K. The measured #gamma#-coefficients of the V/H-alloys agree with APW band-structure calculations for V metal in the range 5 =< nsub(e) =< 7 of band electron concentration. They coincide with the #gamma#-coefficients of V/Cr-alloys reported in the literature. Hence VHsub(n) represents another example of the ...

International Nuclear Information System (INIS)

The detailed electronic energy band structure of hexagonal close-packed #alpha#-zirconium, corresponding to the atomic configuration of 4d"25s"2 of its four outermost valence electrons, has been computed by the composite-wave variational version of the augmented-plane-wave(APW) method in conjunction with the X#alpha#(#alpha# = 0.70424) exchange approximation for obtaining the potentials. From these data the electronic density of states and its angular-momentum-decomposed components have been obtained by the Raubenheimer-Gilat method. These quantities are required in order to calculate the electron-phonon interaction parameter (lambda) and the superconducting transition temperature (Tsub(c)) within the framework of the theories of Gaspari and Gyorffy and McMillan. A study of the variation of Tsub(c) with the Coulomb pseudopotential (#mu#*) revealed that #mu#* = 0.1 yields the best agreement between theory and experiment for ...

Energy Technology Data Exchange (ETDEWEB)

The existence of a narrow peak in the electronic density of states in A-15 compounds is explained by a strong electron--phonon interaction that leads to the polaron narrowing of the band. An analytic expression relating the transition temperature T/sub c/ to the phonon spectrum is derived under the assumption of a weak and an intermediate-strength coupling. The model allows the explanation of the correlation of T/sub c/ with the number of electrons per atom, the temperature dependence of the resistance, the magnitude and temperature dependence of the magnetic susceptibility, and the electronic specific heat.

Energy Technology Data Exchange (ETDEWEB)

The electronic structure and properties of the cubic Laves phase (C15) compounds ZrZn/sub 2/ and ZrV/sub 2/ have been determined using our all-electron full-potential linearized-augmented-plane-wave (FLAPW) method for bulk solids. The computations were performed in two stages: (i) self-consistent warped muffin tin and (ii) self-consistent full potential. Spin-orbit coupling was included after either stage. The effects of the inclusion of the nonspherical terms inside the muffin tins on the eigenvalues is found to be small (of order 1 mRy). However, due to the fact that some of the bands near the Fermi level are flat, this effect leads to a much higher value of the density of states at E/sub F/ in ZnZr/sub 2/. The most important difference between the materials ZrZn/sub 2/ and ZrV/sub 2/ is the position of the d bands derived from the Zr and V atoms. Consequently, these materials have completely different Fermi surfaces. We ...

CERN Document Server

We report on the design, fabrication and testing of two superconducting passive microwave components, a quadrature hybrid and a 20 dB directional coupler. These components are designed to be integrated with superconducting qubits or Josephson parametric amplifiers and used in quantum information processing applications. For the coupler, we measure return loss and isolation > 20 dB, and insertion loss 20 dB and insertion loss < 0.3 dB in a 10% band around 6.5 GHz. These values are within the design specifications of our application; however, we find a 7% difference between the designed and measured center frequency for the hybrid.

International Nuclear Information System (INIS)

The correlation between superconductivity and structural transformation in the A-15 compounds are examined in a unified way on the basis of the Gor'kov three-dimensional model and the anisotropic pairing interaction. The temperature dependence of the elastic modulus, the strain order parameter and the energy gaps of superconductivity are obtained and compared with the experimental data. (auth.).

International Nuclear Information System (INIS)

We present accurate tight-binding parametrizations of the first-principles augmented-plane-wave or linear-augmented-plane-wave band structures of LaCuO_3, La_2CuO_4, Ba_2CuO_4, and the high-temperature superconductor YBa_2Cu_3O_7. We discuss the methodology and efficient application of these fits, including as an example our tight-binding coherent-potential-approximation (CPA) calculations of the effects of disorder on the electronic structure of La/sub 2-//sub x/Ba/sub x/CuO/sub 4-//sub y/. Our CPA calculations support the hypothesis of a rigid-band lowering of the Fermi level for La/sub 2-//sub x/Ba/sub x/CuO_4, enhancing the density of states there. However, for La_2BaCuO/sub 4-//sub y/ they yield the interesting result that oxygen vacancies also lower E/sub F/ and raise N(E/sub F/). This is a significant result for the theory of superconductivity in these materials. In addition ...

Energy Technology Data Exchange (ETDEWEB)

Improvements in critical current capacity for superconducting film structures are disclosed and include the use of a superconducting RE-BCO layer including a mixture of rare earth metals, e.g., yttrium and europium, where the ratio of yttrium to europium in the RE-BCO layer ranges from about 3 to 1 to from about 1.5 to 1.

Energy Technology Data Exchange (ETDEWEB)

A phenomenological simulation was carried out for 41 experimental crystal-field (CF) levels within the {sup 4}I{sub 9/2-15/2}, {sup 4}F{sub 3/2-9/2}, {sup 4}S{sub 3/2} and {sup 2}H{sub 9/2} J manifolds, including the available infrared (IR) data up to {approx}15 000 cm{sup -1} for the Nd{sup 3+} ions in the Nd{sub 2}CuO{sub 4} single crystals. The CF Hamiltonian for the tetragonal C{sub 4v} symmetry was diagonalized together with the free-ion Hamiltonian in a basis that spans the entire 4f{sup 3} configuration. A rms error of 9 cm{sup -1} between the calculated and experimental energy level schemes was obtained. A comparison of the spectra in the visible region between the insulating Nd{sub 2}CuO{sub 4} and the metallic Nd{sub 2-x}Ce{sub x}CuO{sub 4}, allowed identifying the absorption bands associated with the development of the charge-doping induced local structural distortions in the superconducting regime.

Energy Technology Data Exchange (ETDEWEB)

Band-structure studies of NbN and VN are reported. The results of angle-resolved photoemission experiments performed on NbN/sub 0.93/ and VN/sub 0.89/ are presented. The bulk-band structures calculated for stoichiometric NbN and VN using the linearized augmented-plane-wave method are presented and utilized in the interpretation of the experimental spectra. It is shown that most of the features in the spectra can be accounted for by direct bulk-band transitions. A fairly good agreement between experimental and calculated band locations and dispersions is obtained.

CERN Document Server

The controlled growth of nanowires (NWs) with dimensions comparable to the Fermi wavelengths of the charge carriers allows fundamental investigations of quantum confinement phenomena. Here, we present studies of proximity-induced superconductivity in undoped Ge/Si core/shell NW heterostructures contacted by superconducting leads. By using a top gate electrode to modulate the carrier density in the NW, the critical supercurrent can be tuned from zero to greater than 100 nA. Furthermore, discrete sub-bands form in the NW due to confinement in the radial direction, which results in stepwise increases in the critical current as a function of gate voltage. Transport measurements on these superconductor-NW-superconductor devices reveal high-order (n = 25) resonant multiple Andreev reflections, indicating that the NW channel is smooth and the charge transport is highly coherent. The ability to create and control coherent ...

International Nuclear Information System (INIS)

... deformed nuclei eigenvalues even-odd nuclei gold 195 hamiltonians iridium

International Nuclear Information System (INIS)

Augmented plane wave calculation of gadolinium electronic structure crystallized in a hexagonal close-packed lattice is carried out.

Energy Technology Data Exchange (ETDEWEB)

Development of useful high-critical-temperature (high-{Tc}) superconductors requires synthesis of superconducting compounds; fabrication of wires, tapes, and films from these compounds; production of composite structures that incorporate stabilizers or insulators; and design and testing of efficient components. This report describes technical progress of research and development efforts aimed at producing superconducting components based on the Y-Ba-Cu, Bi-Sr-Ca-Cu, Bi-Pb-Sr-Ca-Cu, and Tl-Ba-Ca-Cu oxides systems. Topics discussed are synthesis and heat treatment of high-{Tc} superconductors, formation of monolithic and composite wires and tapes, superconductor/metal connectors, characterization of structures and superconducting and mechanical properties, and fabrication and properties of thin films. Collaborations with industry and academia are also documented. 10 figs.

International Nuclear Information System (INIS)

In an attempt to enhance the electrical and mechanical properties of the high temperature superconducting oxides, high T(sub c) composites were prepared composed of the 123 compounds and AgO. The presence of extra oxygen due to the decomposition of AgO at high temperature is found to stabilize the superconducting 123 phase. Ag is found to serve as clean flux for grain growth and precipitates as pinning center. Consequently, almost two orders of magnitude enhancement in critical current densities were also observed in these composites. In addition, these composites also show much improvement in workability and shape formation. On the other hand, proper oxygen treatment of Y5Ba6Cu11Oy was found to possibly stabilize superconducting phase with T(sub c) near 250 K. I-V, ac susceptibility, and electrical resistivity measurements indicate the existence of this ultra high T(sub c) phase in this compound. Detailed ...

Energy Technology Data Exchange (ETDEWEB)

There is considerable interest in the use of silicon devices as qubits for quantum computing. The existence of nuclear spin in a silicon isotope and the complex band structure of silicon are unfavourable for this application of silicon devices. (viewpoint)

Energy Technology Data Exchange (ETDEWEB)

Motivated by the discovery of superconductivity in alkali and alkaline earth fullerides, this program was undertaken both to understand the nature of and expand the range of materials demonstrating superconductivity. The first approach involved attempts to modify the fullerene cage by incorporating heteroatoms in the structure and the preparation and photophysical properties of nitrogen and sulfur doped fullerenes were studied in detail. The second approach involved examining the stoichiometry and effect of preparative conditions on the behavior of alkali, alkaline earth, lanthanide and mixed ion fullerides. In particular, the authors have elaborated on a technique for making such salts using liquid ammonia or aliphatic amines as solvents. Thirdly, modeling studies were undertaken to predict the properties of heterohedral fullerines and metal - C60 complexes, and theoretical guidelines were developed for understanding the ...

International Nuclear Information System (INIS)

The influence of 3d-transition metal impurities on the superconducting properties of the A-15 compounds V_3Si and V_3Ga have been investigated. In the case of V_3Si, the Fe impurities replacing V were found to have a local moment. A compensation effect was found in this case, resulting in a 20KOe increase in the upper critical field at dilute concentrations of Fe. It was demonstrated that long range order V_3Ga possessed higher transition temperature and upper critical field than found hitherto. Investigations on Nb_3Ge/sub 1-x/Ga/sub x/ films obtained by chemical vapor deposition has clearly shown the relation between the transition temperature and structural characteristics. The influence of generalized defects on the superconducting properties in A-15 type Nb_3X compounds has been discussed.

International Nuclear Information System (INIS)

It has recently been shown that the superconducting properties of Nb-base A-15 compounds, A_3B, are severely degraded when exposed to high-energy (E>1 MeV) neutron irradiation at ambient reactor temperatures. In each case, superconducting transition temperatures, Tsub(c), and the Bragg Williams order parameters, S, were observed to decrease steadily with irradiations in excess of 10"1"8 nvt. During irradiation the A-15 structure is retained and subsequent isothermal annealing restores almost completely the compound's original Tsub(c) value. In this letter a correlation between B atom diameter and the recovery rates of Tsub(c) for the irradiated materials Nb_3Ge, Nb_3Ga, Nb_3Al and Nb_3Sn is reported. (Auth.).

Energy Technology Data Exchange (ETDEWEB)

It is pointed out that a recently claimed result regarding the removal of sharp structure in the electronic density of states N(E) of A-15 superconducting compounds at T approximately equal to Tsub(c) was in fact, shown earlier by one of the present authors (M.N.M.). Merely the variation of N(E) with energy in the vicinity of the Fermi level in these materials cannot explain their anomalous normal state properties and high values of lambda and Tsub(c). Rather a non-varying N(E) accompanied by phonon softening is in better agreement with experiment.

Energy Technology Data Exchange (ETDEWEB)

High-T/sub c/ superconductivity is due to the action of two mechanisms: (1) plasmon mechanism, i.e., exchange of two-dimensional (2-D) plasmons and (2) strong electron--phonon coupling. The low dimensionality and the small value of the carrier concentration make the plasmon mechanism favorable. The small value of the coherence length leads to a unique opportunity to observe a multigap structure. The proximity effect can be used in order to increase T/sub c/ of A-15 compounds.

Energy Technology Data Exchange (ETDEWEB)

The study is concerned with the combined effect of high pressure and shear strain on the properties of the A-15 intermetallics Nb3Sn and Nb3Al0.75Ge0.25. The properties discussed are the superconducting transition temperature, the width and intensity of the X-ray diffraction lines, and the width and shape of the Mossbauer absorption lines. It is shown that the combined effect of high pressure and shear strain leads to an intense generation of defects in polycrystalline specimens; the size of the ordered regions does not exceed 300 A even under the least severe conditions. 5 references.

International Nuclear Information System (INIS)

A theoretical study of structural and electronic properties of GeC, SnC and GeSn is presented using the full potential linearized augmented plane wave method. In this approach, the generalized gradient approximation was used for the exchange-correlation potential. Results are given for lattice constant, bulk modulus and its pressure derivative in both zinc-blende and rocksalt structures. Band structure, density of states and band gap pressure coefficients in zinc-blende structure are also given. The results are compared with previous calculations and with experimental measurements.

International Nuclear Information System (INIS)

The measurements obtained here indicate ways in which micro-Raman spectroscopy can be used to elucidate structural characteristics and distribution of carbon in meteorites and interplanetary dust particles (IDPs). Existing information about structurally significant aspects of Raman measurements of graphite is combined with structurally relevant findings from the present micro-Raman studies of carbons prepared by carbonization of polyvinylidine chloride (PVDC) at various temperatures and natural material, as well as several acid residues from the Allende and Murchison meteorites in order to establish new spectra-structure relationships. Structural features of many of the materials in this study have been measured by x ray analysis and electron microscopy: thus, their structural differences can be directly correlated with differences in the Raman spectra. The ...

International Nuclear Information System (INIS)

The electronic structures of BaSnO_3, BaSbO_3, and BaPbO_3, calculated using an extended general-potential linearized augmented-plane-wave method, are reported. The electronic structures of BaSnO_3 and its 6s analog BaPbO_3 are found to be very different, explaining the absence of superconductivity in the Ba(Sn,Sb)O_3 system. These differences are explained by a combination of the relativistic lowering of the 6s states and ion-size effects. Muffin-tin-approximation augmented-plane-wave calculations for BaSnO_3 are also reported and the utility of the muffin-tin approximation for this and similar materials is discussed in terms of the differences between the two sets of calculations.

UK PubMed Central (United Kingdom)

AbstractThe structural integrity of striated muscle is determined by extra-sarcomere cytoskeleton that includes structures that connect the Z-disks and M-bands of a sarcomere to sarcomeres...Full Text Available

International Nuclear Information System (INIS)

The structural instability in high temperature A-15 superconductors is examined from a phenomenological, Landau theoretic point of view, based on the picture of an electronically driven lattice instability. emphasis is given to lattice properties--in particular, the extended softening of phonons in k-pace and phonon linewidth. Implications of the extended softening on the microscopic picture of the transition, and the interplay between structural and superconducting instabilities in the A-15 compounds are discussed.

Energy Technology Data Exchange (ETDEWEB)

The purified integral membrane protein, band 3, from human erythrocytes was inserted into egg lecithin liposomes. The insertion of band 3 was determined from thermal transition data from the analysis of the C-H stretching region bands recorded at temperatures from 25 to -22[sup o]C. Raman spectra show that band 3 considerably broadens and lowers the thermal transition of egg lecithin liposomes, suggesting the insertion of band 3. The band 3-inserted liposomes were irradiated with gamma-rays (40 Gy) and the radiation target groups were determined by the analysis of the structural sensitive Raman bands in the 1600-1700 cm[sup -1] (amide I), 1200-1300 cm[sup -1] (amide III) and 550-1030 cm[sup -1] (side chain amino groups) regions. The radiation-sensitive groups as identified from Raman spectra in the region 550-1030 cm[sup ...

International Nuclear Information System (INIS)

The structural, electronic and optical properties of ZnX and CdX (X = Se, Te and S) are studied using density functional theory by the Wien2k package. The energy band gap, real and imaginary parts of the dielectric function, energy loss function, optical absorption coefficient and reflectivity spectra of these compounds are calculated. The Engel-Vosko approach improves the energy band gaps of ZnX and CdX compounds. The calculated optical parameters are in good agreement with available experimental results, particularly in the Engel-Vosko approach. Furthermore the effect of hydrostatic pressure on the energy band gap, the real and imaginary parts of the dielectric function of these compounds is studied. The first and second order pressure coefficient for the energy band gaps, the static dielectric function and the static reflectivity spectra are calculated.

CERN Document Server

Conceptual Design of Superconducting Quadrupole Arrays for the Heavy-Ion Fusion

International Nuclear Information System (INIS)

The influence of irradiation with 2.6 MeV H and He nuclei on the superconducting properties (critical temperature Tsub(c), critical current Isub(c)) of the intermetallic compound Nb_3Sn was studied. Irradiation led to a significant lowering of Tsub(c), while Isub(c) is increasing with the radiation dose. This is assumed to be due to the formation of active pinning centres in the lattice. There is a fast drop of Isub(c) after a peak value has been reached. Annealing of the samples (600-1,000"0C) led to an almost complete recovery of the initial value of Tsub(c). X-ray diffraction showed that irradiation causes considerable distortions of the lattice while the A15 crystal structure is retained. The causes of the radiation effects related to structural defects are discussed. (GSCH).

International Nuclear Information System (INIS)

The method of augmented plane wave (APW) is used to obtain the band structure of the SmS compound in the semiconductor and metal phases. The noncentral part of the Coulomb electron-electron interaction is taken into account in the first order perturbation theory. In this case the radial part of the wave APW-function is taken as a zero approximation function. A multiplet structure of the excited configuration f"5d, which provides a good description of the X-ray photoelectron spectrum and optical spectrum epsilon_2(#omega#), is obtained. The configuration fd is calculated for the interpretation of the optical absorption spectrum of the samarium monosulfide metal phase. (author).

Energy Technology Data Exchange (ETDEWEB)

The paper presents cloud structure models for Jupiter's Great Red Spot, Equatorial and North Tropical Zones, North and South Temperate Zones, and North and South Polar Regions. The models are based on images of Jupiter in three methane bands and nearby continuum radiative transfer calculations include multiple scattering and absorption from three aerosol layers. The model results include the transition in the upper-cloud altitude to 3 km lower altitude from the tropical zones to temperate zones and polar regions, a N/S asymmetry in cloud thickness in the tropical and temperature zones, and the presence of aerosols up to about 0.3 bar in the Great Red Spot and Equatorial Zone. It is concluded that polarization data are sensitive to aerosols in and above the upper cloud layer but insensitive to deeper cloud structure.

British Library Electronic Table of Contents (United Kingdom)

Plasma polymerization of aniline is carried out in a radiofrequency plasma reactor and the effect of polymerization time is examined in the structural, optical and optoelectronic properties of deposited films. Conjugated structures of polyaniline like films are obtained with unique and broad optical absorption band in the ultraviolet and entire visible region. The width of the absorption band increases and hence the optical band gap decreases with polymerization time. The optical constants are extracted by Swanepoel method and the optical dispersion parameters are determined by employing the Wemple-DiDomenico single oscillator model. The films exhibit similar thermal stability in air and argon atmosphere in the region of interest for optoelectronic applications. The photoluminescence study...

International Nuclear Information System (INIS)

The band offsets and subband levels in a double quantum well layer for a 660 nm-Ga_0_._4In_0_._6P/(Al_0_._5Ga_0_._5)_0_._5In_0_._5P quantum well laser are determined by photoreflectance using a 410 nm InGaN laser with current modulation at room temperature. The subband levels are analyzed by numerical calculation of the Schroedinger equation for the layer structure by varying the conduction band offset and compared with the measured photoreflectance spectra. The conduction band offset ratio is determined to be 0.5+0.03. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Energy Technology Data Exchange (ETDEWEB)

Using Gammasphere data on prompt gamma rays from spontaneous fission of 252Cf, we propose energy-level schemes for 110,111,112, & 113Rh (Z=45). The fission-gamma data complement earlier studies of others on beta decay of fission products in that prompt fission gammas mainly populate yrast or near-yrast levels, while beta decay populates lower-spin levels. For the odd-A rhodium nuclei studied here, their ground bands and collective sidebands are compared with model calculations using triaxial-shaped nucleus with one odd quasi-proton. The energies and E2 transition rates are best fit by a shape slightly to the prolate side of maximum triaxiality, namely, gamma = 28 deg. The model calculations also show a K=1/2+ band with energies not in good agreement with a corresponding experimental band. The experimental 1/2+ band is regarded as an intruder band from a prolate-driving proton ...

International Nuclear Information System (INIS)

It is shown that both the Tsub(c) and Tsub(m) dependences on the deformations and composition for the A-15 compounds can be described at least qualitatively in the quasi-one-dimensional model developed by the authors previously. The mechanism for the superconductivity is supposed to be the same as in the BCS theory. The upper critical field near Tsub(c) is obtained. (author).

British Library Electronic Table of Contents (United Kingdom)

The Wendelstein 7-X (W7-X) modular stellarator is under construction at the Max-Planck-Institut fur Plasmaphysik in Greifswald, Germany. The W7-X magnet system contains 70 coils made up from helium cooled superconducting cables in aluminium alloy (EN AW-6063) jackets. Several hundred connections of the jacket to the cable joints are made by aluminium-to-aluminium welds. Due to geometrical and thermal boundary conditions these welds cannot be accomplished free from defects. Microscopic analyses of the welds show that a variety of small flaws such as cracks and pores develop during welding. The welds have thus to be dimensioned accordingly, and appropriate weld qualification, investigation and testing has to be done in order not to jeopardise the structural integrity and leak tightness. The ...

Energy Technology Data Exchange (ETDEWEB)

High-spin states in {sup 177}Ta were produced using the {sup 170}Er({sup 11}B, 4{ital n}) reaction at 55 and 60 MeV. Considerable extensions have been made to the previously known level scheme, and new structures have been found. {ital B}({ital M}1)/{ital B}({ital E}2) ratios have been extracted for strongly coupled bands. The behavior of the different rotational cascades, in particular the anomalous crossing frequency observed in the [541]1/2{sup {minus}} proton {ital h}{sub 9/2} band and the occurrence of ``identical bands,`` is discussed. Comparisons are made with projected shell model calculations.

Science.gov (United States)

Generally the photonic band gap (PBG) is a multi-variable function of several parameters related to the shape and size of the dielectric columns of photonic crystals (PhCs), and a time-consuming step-by-step scanning process for each parameter has to be used to find their best combination yielding maximum PBG. In this letter, the widely used Nelder-Mead simplex algorithm is introduced to optimize these parameters simultaneously to find a larger PBG for a new kind of two-dimensional (2D) hexagonal GaAs-Air PhC. This structure can be conveniently produced by the single-exposure holographic lithography, and the specific holographic design is also systematically investigated. This study reveals that the band gaps of PhCs made by holographic lithography may be widened by introducing irregularity of the columns and lowering the symmetry of the structure.

International Nuclear Information System (INIS)

Data by Wiesmann et al. on the temperature coefficient of the upper critical field, dH/sub c/2(T)/dT, and the normal-state resistivity rho_0 near the superconducting transition temperature T/sub c/ are analyzed to estimate the bare density of states N (E/sub F/) as a function of structural disorder and T/sub c/ in various #alpha#-particle irradiated samples of A-15 Nb_3Ge and Nb_3Sn. By taking into account the change in the electron-phonon coupling strength with T/sub c/ and the effect of mass enhancement arising from the electron-phonon interaction, the results of the new analysis indicate that (i) the drop in N (E/sub F/) for Nb_3Ge is relatively small as T/sub c/ changes from approx. 21 to approx. 4 K, in agreement with a recent low-temperature specific-heat measurement; (ii) the value of N (E/sub F/) in Nb_3Sn decreases by a factor of approx. 4 as T/sub c/ varies from approx. 18 to approx. 3 K. The implication of these findings is discussed ...

CERN Document Server

The main LHC superconducting magnets (dipoles and quadrupoles) use Rutherford type cables, stabilized electrically and thermally with copper profiles. The portions of cables are connected to each other by a soft soldering technique (Sn96Ag4) with an overlapping length corresponding to one pitch of the superconducting strands. The splice constitutes a "composite" structure with the interchanging layers of Sn96Ag4 and NbTi superconductor, located inside a Cu cage. In order to ensure a high level of reliability (failure probability not exceeding 10-8) for some 10000 connections in the LHC, a non-destructive technique to check the quantity of solder in the joint is foreseen. The technique is based on a gamma ray source (241Am) and the detection is position-sensitive in the transmission mode. Scintillating detectors of gamma rays are used and their accumulated length corresponds to the length of the radioactive source (120 mm). ...

Energy Technology Data Exchange (ETDEWEB)

The electronic structure of the C15, or cubic-Laves-phase material, UAl/sub 2/ has been calculated using the linearized relativistic augmented-plane-wave method. The anomalous behavior of the electrical resistivity, specific heat, and magnetic susceptibility can be explained by the fine structure of the density of states near the Fermi energy alone, without the necessity of the introduction of drastic spin fluctuations or many-body effects.

Science.gov (United States)

Not Available

Science.gov (United States)

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International Nuclear Information System (INIS)

The isostructural #gamma#-#alpha# phase transition of Ce which occurs at 8 kbar has been studied by means of fully self-consistent (non-muffin-tin potential) linearized-augmented-plane-wave energy band calculations carried out for five different values of the lattice constant. In contradiction to the 4f electron promotional model of the transition, the results yield essentially one 4f electron to be occupied in each phase but with the 4f wave function somewhat less localized, and therefore more bandlike, in the ''collapsed'' #alpha# phase. A singly occupied 4f state is shown to be consistent with the available experimental data. These results strongly support the picture of a 4f localized bold-arrow-left-right itinerant transition at the #gamma#-#alpha# transition and conflict with the promotional model in which some fraction of 4f electrons are transferred to the sd conduction bands. The weaker bonding of the 4f electrons, compared to that of ...

International Nuclear Information System (INIS)

We studied the influence of alloying on the structural and electronic properties of the unrelaxed and relaxed Si_1_-_yC_y random alloys by means of ab initio theoretical calculations using two methods: (i) a supercell approach in connection with the plane-wave pseudopotential method; (ii) the full-potential augmented plane-wave plus local orbitals (APW+lo) method. The first method is used to obtain the relaxed atomic structure. The relaxed atomic positions obtained by pseudopotential calculations were used to calculate the band structure via the second method. The local density approximation was used for the exchange and correlation energy density functional. We investigated the lattice parameters and band gap energies. We found that a quite smaller gap appears in the neighborhood of y=0.03125 concentration of C atoms. The band gap shows a large anomalous bowing ...

Energy Technology Data Exchange (ETDEWEB)

The difficulty in making good Ohmic contact at the interfaces with p-doped ZnSe is an important problem hindering the realization of blue-light-emitting diode lasers based on the II-VI semiconductor technology. So far no metal or semiconductor material has been found to have a low enough barrier at the (001) interface with ZnSe. A possible solution to this problem is the insertion of a so-called {ital barrier-reduction layer} at the interface with ZnSe. We have investigated the interface formation energies and valence-band offsets at the (001) interface between Al{sub x}Ga{sub 0.5{minus}x}In{sub 0.5}P and ZnSe. The results of our calculations show the existence of a strong interdependence between the valence-band offset and the interface geometric structure. The interface is found to have structural and electronic similarities to the GaAs-ZnSe(001) system. The very low values obtained for the ...

International Nuclear Information System (INIS)

We give a theoretical design for a locally resonant two-dimensional cylindrical structure involving a pair of C-shaped voids in an elastic medium which we term as double 'C' resonators (DCRs) and imbedded thin stiff bars, that displays the negative refraction effect in the low frequency regime. DCRs are responsible for a low frequency band gap which hybridizes with a tiny gap associated with the presence of the thin bars. Using an asymptotic analysis, typical working frequencies are given in closed form: DCRs behave as Helmholtz resonators modeled by masses connected to clamped walls by springs on either side, while thin bars behave as a periodic bi-atomic chain of masses connected by springs. The discrete models give an accurate description of the location and width of the stop band in the case of the DCR and the first two dispersion bands for the periodic thin bars. We then combine our asymptotic ...

International Nuclear Information System (INIS)

Excited states in the T_z=(1/2) nucleus "8"5Mo have been observed for the first time with the reaction "5"8Ni("3"2S,#alpha#n#gamma#) at 105 MeV. #gamma#-ray transitions in this nucleus have been assigned unambiguously by combining the information from the GASP #gamma#-ray array, the ISIS silicon ball, and the n-Ring neutron detector. Two band structures have been observed in this nucleus; they continue the smooth evolution of the known bands from the lighter N=43 isotones and have been tentatively assigned spins and parity on this basis. After reaching a maximum of collectivity at "8"3Zr, the trend with increasing mass is reversed, showing a smaller collectivity at "8"5Mo. The rotational behavior of the observed bands is discussed on the basis of the projected shell model calculations.

International Nuclear Information System (INIS)

The #pi#g_9_/_2 band structure in "1"2"1Cs is obtained. The experiment was performed at the HI-13 MV tandem accelerator of China Institute of Atomic Energy. The excited states of "1"2"1Cs were populated via the reaction "1"1"2Sn("1"2C, p2n). The #gamma#-#gamma# coincidence data were taken with five BGO-AC HpGe detectors at beam energy of 60 Mev. The energy-level schemes of "1"2"1Cs is presented.

British Library Electronic Table of Contents (United Kingdom)

Abstract Electronic structures of two representative zigzag and armchair models of aluminum phosphide nanotube (AlPNT) were investigated by density functional theory calculations. The structures were optimized and the bond lengths, tip diameters, band gaps, and dipole moments were calculated. Moreover, the quadrupole coupling constants (CQ) were calculated for the Al-27 atoms of the optimized structures. The same values of AlP bond lengths were calculated for both models. The larger value of band gap of armchair model than the zigzag model indicated the stronger dielectric property for the former model. The values of CQ(27Al) were the largest for the Al atoms placed at the tips of both zigzag and armchair AlPNT than other Al atoms, which could reveal dominant role of the Al atoms placed at...

Energy Technology Data Exchange (ETDEWEB)

The large aggregating proteoglycan aggrecan is a major structural component of the extracellular matrix of articular cartilage. Recent cDNA cloning of the human aggrecan gene (AGC1) reveals a core protein of at least 2316 amino acids characterized by several distinct structural domains. Two globular domains, termed G1 and G2, are present at the amino terminus of the molecule and a third, termed G3, is present at the carboxy terminus. The G1 domain is homologous in structure to the cartilage link protein and accounts for the aggregating potential of aggrecan through its ability to interact with hyaluronic acid. The aggrecan gene is known to consist of 15 exons, with each exon encoding a distinct functional region of the mature protein. However, while the link protein gene is known to reside on chromosome 5 in the human, the location of the aggrecan gene is currently undetermined in any species. The probe (pAGG2) for the ...

International Nuclear Information System (INIS)

Calculations of the Compton profiles for the transition metals Ta and W are performed, using electron wave functions obtained from self-consistent augmented plane wave (APW) band structure calculations within the local density formalism of Hedin-Lundqvist. Relativistic effects are included except for the spin-orbit interaction. The observed structures of the Compton profiles in these metals are understood in terms of the topology of their Fermi surfaces. (author).

International Nuclear Information System (INIS)

The structural ordering of oxygen deficient and Co-doped YBCO (YBa_2Cu_3_-_yCo_yO_6_+_x) have been studied experimentally, and by computer simulations of the oxygen ordering in the basal plane of the structure. The calculations are based on the two-dimensional ASYNNNI model and its modifications. Good agreement is established between the ASYNNNI calculations and the experimentally observed structural properties of the double cell ortho-II structure and the oxygen disordering process from Co-doping into the basal plane. A model that relates the superconducting transition temperature T_c(x) of undoped YBCO and T_c(y) of Co-doped YBCO to the formation of specific domains of the two orthorhombic ordered oxygen phases, ortho-I and ortho-II, shows a close agreement with experimental T_c(x) and T_c(y) data of samples prepared under equilibrium conditions. The ...

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The authors introduce the single electron (Cooper-pair) tunneling junctions using c-axis Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+d} (Bi-2212) superconducting single crystal whiskers. Focused-ion-beam (FIB) etching patterned the Bi-2212 whiskers. The fabricated small stacked junctions have in-plane area S smaller than <1 {micro}m{sup 2}. The junctions showed the current-voltage (I-V) characteristics with the periodic structure of current peaks. The stacking layered structure of Bi-2212 works as multi-junctions array which decrease the effective capacitance, C{sub {Sigma}} = C{sub 0}/N, where C{sub 0} is the capacitance of junction and N is the layer number of elementary junctions. The period of current peaks of I-V curves corresponds to the charging energy of the single Cooper pair, 2Ec (=e{sup 2}/C{sub {Sigma}}).

CERN Document Server

The International Linear Collider Main Linacs are based on superconducting accelerator structures operating at 1.3 GHz. The basis for this design has been developed and tested at DESY and R&D is progressing at many laboratories around the world including DESY, Orsay, KEK, FNAL, SLAC, Cornell, and JLAB. The status of the TESLA-style cavities and rf system will be reviewed and parameters for the ILC linac will be described. The role of the different linac test facilities will discussed and the critical items and R&D program to support a Conceptual Design and Technical Design will be outlined.

International Nuclear Information System (INIS)

The effects of hydrostatic pressure on the electronic band structure of the semiconductor mineral iron pyrite FeS_2 have been investigated theoretically by an ab initio full-potential linearized-augmented plane wave (FPLAPW) method within a local approximation (LDA/GGA) to the density functional theory. The calculations predict that at a pressure of 94.1 GPa the indirect band gap of pyrite FeS_2 vanishes and the material becomes a metal. This is due to the presence of the S-S and Fe-S bonds, which provide novel energy band distortions in the process of attaining the metallic state. Analysis indicates that, under increasing high pressure, the conduction bands (3p_z of sulfur and 3d_x_"2_-_y_"2+3d_x_y of iron) intrude downwards into the valence bands, which are predominantly 3d in nature. At normal pressure, the lattice constant, the bulk modulus, sulfur position ...

International Nuclear Information System (INIS)

The electronic band structure, transport properties, and lattice dynamics in AuX_2 (X = Al, Ga and In) under high pressure have been extensively studied with full potential linearized augmented plane wave and pseudopotential plane wave methods. The theoretical results for the electronic band structure and Fermi surface reveal pressure-induced electronic topological transitions (ETTs) in AuGa_2 and AuIn_2, while they are absent in AuAl_2, in excellent agreement with the experimental observations. Moreover, calculations of the transport properties at different pressures reveal subtle changes in the band structure close to the Fermi surface of the three intermetallic compounds. It is clear that the anomalies in transport properties are due to ETTs. Interestingly, a pressure-induced soft transverse acoustic (TA) phonon mode is identified only in AuGa_2. The TA ...

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The expression C/sub FB/ = C/sub ox/ x ({element of}/sub si//L/sub D/)/(C/sub ox/ + ({Epsilon}/sub si//L/sub D/)) (where L/sub D/ is the Debye length), commonly used for the flat-band capacitance of the MOS structure, is invalid in the temperature range below 100 {Kappa}. Consequently, significant error may be encountered when the flat-band capacitance method is used to extract the flat-band voltage V/sub FB/, which is of considerable interest for both the modeling and characterization of MOS devices. To extend this method to low-temperature CMOS applications one has to use a more general model that can be obtained by applying Fermi-Dirac statistics and taking into account the impurity freezeout effect. The authors show that when the temperature dependence of V/sub FB/ is extracted using this approach, the experimental data for n/sup +/ polysilicon gate MOS capacitors are in a good agreement with a ...

International Nuclear Information System (INIS)

We report a detailed augmented-plane-wave energy-band study and wave-function analysis of stoichiometric PdH which shows that, even though the Fermi surface of PdH is qualitatively similar to that of silver, the simple ''proton model'' is not valid. Instead, the screening of the proton in PdH is found to be larger than in an isolated H atom due, in part, to the formation of a H-Pd bonding band below the bottom of the d-band complex. This result, which is in qualitative agreement with Switendick's earlier calculation, is confirmed by ultraviolet photoemission experiments. A partial density-of-states (DOS) analysis in the energy range spanned by the six valence and conduction bands reveals the quantitative details of the bonding mechanism between the Pd and H constituents. At the Fermi energy, the high Pd d to H s DOS ratio approx. 10.3 is found to be far higher than expected in silver, despite the fact ...

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The electronic structure of octahedral metal atom clusters Me/sub 6/ of 3d, 4d, and 5d transition metal atoms (V, Cr; Nb, Mo; Ta, W) has been calculated applying two different quantum-chemical approximation methods (Extended Hueckel (EH) method; SW-Xsub(alpha) method). Equilibrium structures, energy level schemes, Fermi energies and band widths as well as densities of states of clusters are discussed in detail.

International Nuclear Information System (INIS)

Isotropic Compton profiles of TaC and TaN have been measured for the first time, at an intermediate resolution, using 662 keV #gamma#-radiation. Energy bands, density of states and Fermi surface topology of TaC and TaN have been computed using linear combination of atomic orbitals with density functional theory and full potential linearised augmented plane wave method. Both band structure calculations predict the metallic character of TaC and TaN. The electron momentum densities calculated using various approaches of density functional theory are compared with the present measurements. On the basis of Mulliken's population, it is also seen that TaC has more covalent bonding than TaN. The optical properties computed using full potential linearised augmented plane wave method are explained in terms of intraband transitions.

International Nuclear Information System (INIS)

First-principles self-consistent band-structure calculations of potassium titanyl arsenate, KTiOAsO_4 (KTA), have been made using the full potential linearized augmented plane wave (FP-LAPW) method. Total and partial densities of states of the constituent atoms of KTA have been derived. The results obtained show that the valence band of KTA is dominated by contributions of the O 2p-like states, while the Ti 3d-like states are the main contributors into the conduction band of the compound. Additionally, the FP-LAPW calculations have revealed that potassium atoms are highly ionized in KTA. In the present work, the X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) methods were also employed to investigate experimentally the electronic structure of potassium titanyl arsenate. For the mentioned compound, the XES K Ll, Ti L#alpha#, As K#beta#_2 and O K#alpha# ...

International Nuclear Information System (INIS)

Superconductivity of binary alloys spanning the A-15 compounds V_3Si, V_3Ge, V_3Ga, and V_3Al and the pseudobinary derivatives of these stoichiometric compounds was surveyed by studying samples prepared by rf-sputtering from alloy cathodes. The possible formation of the hypothetical A-15 binaries ''V_3P,'' ''V_3B,'' and ''V_3C'' and their pseudobinary formation with V_3Si was also explored. Efforts to form these hypothetical alloys were not successful. The T/sub c/'s were measured resistively and the structure and lattice constants were determined by x-ray analysis. A maximum T/sub c/ of 11.7"0K was obtained for A-15 V_3Al, and the importance of a suitable deposition temperature and high sputtering pressures was examined. It is proposed that large variations of T/sub c/ among pseudobinary alloys imply a rapid variation of the density of states at the Fermi level.

British Library Electronic Table of Contents (United Kingdom)

A novel visible light sensitive photocatalyst, AgSbO3 was prepared by a conventional solid-state reaction method. This oxide belonging to a cubic-pyrochlore structure can absorb visible light with wavelength up to about 480nm. From the band structure calculation, we found that the top of the valence band consists of the hybridized Ag 4d and O 2p orbitals and the bottom of the conduction band mainly consists of the Ag 5s and the Sb 5s orbitals. Photocatalytic activities were evaluated using O2 evolution from an aqueous silver nitrate solution and decomposition of gaseous 2-propanol under visible light irradiation. We found that AgSbO3 shows a higher O2 evolution activity than WO3 and 2-propanol can be mineralized by the AgSbO3 photocatalysis under visible light irradiation.

International Nuclear Information System (INIS)

Fermi radii and velocities are determined by deconvoluting de Haas-van Alphen data. Comparison of these data with accurate augmented-plane-wave band-structure results establishes the reliability of the augmented-plane-wave calculations and allows a determination of the anisotropic many-body enhancement factor lambda(k). The Fermi-surface average of 1.33 suggests a large electron-electron contribution. Our anisotropic lambda(k) porvides a detailed test and guide for model calculations of many-body enhancement.

Science.gov (United States)

Based on our cryogenic FT-IR spectroscopic studies of hydrogen bonds in cholic acid, the two-dimensional FT-IR spectroscopy was applied to enhance our understanding of the hydrogen bonds. Fine spectral structures were revealed by asynchronous 2D FT-IR spectra. The co-relationship among various bands was discussed according to the synchronous 2D FT-IR spectra. .

International Nuclear Information System (INIS)

In this work we study the structural and electronic properties of Be chalcogenides (BeS, BeSe and BeTe) using two different methods: the full-potential linear augmented-plane wave (FP-LAPW) and the plane-wave pseudopotential (PPsPW). The exchange-correlation effects are treated in the local-density approximation (LDA) and the generalized-gradient approximation (GGA). We have evaluated the ground-state quantities such as equilibrium volume, bulk modulus and its pressure derivative as well as the elastic constants. Various structural phase transitions were considered here in order to confirm the most stable structure and to predict the phase transition under hydrostatic pressure. In addition we have studied the band structure and the density of states, which show a wide indirect band gap for these compounds. These results were in favourable agreement with previous ...

International Nuclear Information System (INIS)

The self-consistent relativistic linearized-augmented-plane-wave method is applied to local-density calculation of electronic structure of TmS. It is found that thulium monosulphide is a compound with a trivalent state of thulium. The influence of spin-orbital interaction is shown for different symmetry states of electrons. Calculated densities of states are used for the estimation of the electron-phonon coupling constant. And in conclusion it is shown that TmS is a high temperature Kondo-like system. (author).

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Cold deformation of YBa{sub 2}Cu{sub 3}O{sub 7-x}(phase 123, T{sub c} = 88.5-92 K) powders and strips causes partial decomposition of the 123 phase, a reduction in the degree of orthorhombicity of the structure up to almost complete degradation, and a decrease in T{sub c}. When they are deformed, yttrium high temperature superconductors acquire basal (001) (110) texture with high pole density (13-15 arbitrary units), low scattering angle ({+-} 6deg--7deg from the normal direction), and a weak preference for a, b or a + b in the rolling direction; traces of (139) orientations may also be found. This texture is known to be favourable for increasing j{sub k}. The combined effect of cold deformation and a carbon-containing binder leads, however, to a complete loss of superconductivity at 77 K or above. Depending on the regime of subsequent annealing, the following effects may be observed: degradation of the orthorhombic ...

International Nuclear Information System (INIS)

We have studied the ion-beam synthesis of GaSb nanocrystals in Si by high-fluence '' hot '' implantation of Sb and Ga ions followed by thermal annealing. The Rutherford backscattering, transmission electron microscopy/transmission electron diffraction, Raman spectroscopy and photoluminescence were used to characterize the implanted layers. It was found that the nanocrystal size increases from 5 to 60 nm in the samples annealed at 900"oC up to 20-90 nm in those annealed at 1100"oC. For the samples annealed at 900"oC a broad band in the region of 0.75-1.05 eV is registered in the photoluminescence spectra. The nature of this photoluminescence band is discussed. (author)

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Low power rf measurements, S11, of electro-discharge machined (EDM) diffusion bonded mm-wave traveling wave rf cavities were not in satisfactory agreement with electromagnetic simulations. During subsequent mechanical inspection, the cell-to-cell iris were found to be distorted. This led to a series of systematic experiments to study the mechanical properties of oxygen free high conductivity Copper (OFHC) and Glidcop AL-15. Results of these studies which include cell-to-cell iris distortion, EDM machining accuracies, surface quality, and the results of different bonding techniques are presented. The results of our mechanical studies are used to develop a set of mechanical design constraints for a second series of constant impedance W-Band structures that also used wire EDM and high temperature bonding for their manufacture.

British Library Electronic Table of Contents (United Kingdom)

We investigate quantum mechanical electron transport along the long axis of the DNA molecule using an effective tight-binding model. The overall contour plot of transmission, the current-voltage characteristics, and the differential conductance are examined for the variation of backbone onsite energy, the energy-dependent hopping strength, and the contact coupling between the leads and the DNA molecule. It is shown that as backbone asymmetry increases, the merging and collapse of the two mini-bands take place and an extra resonance peak in the transmission appears. In addition, we present the modulation of voltage threshold in the current-voltage curves and a double-peak structure in the differential conductance due to the disappearance of the merged mini-band. Finally, in the Coulomb bloc...

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We develop a continuum description for the axial segregation of granular materials in a long rotating drum based on the dynamics of the thin near-surface granular flow coupled to bulk flow. The equations of motion are reduced to the one-dimensional system for two local variables only, the concentration difference and the dynamic angle of repose, or the average slope of the free surface. The parameters of the system are established from comparison with experimental data. The resulting system describes both initial transient traveling wave dynamics and the formation of quasi-stationary bands of segregated materials. A long-term evolution proceeds through slow logarithmic coarsening of the band structure which is analogous to the spinoidal decomposition described by the Cahn-Hilliard equation. {copyright} {ital 1999} {ital The American Physical Society}

British Library Electronic Table of Contents (United Kingdom)

Teleost gut associated lymphoid tissue (GALT) consists of leucocyte populations located both intraepithelially and in the lamina propria with no structural organization. The present study aims to assess different protocols for the isolation of GALT cells from an important fish species in the Mediterranean aquaculture, the gilthead seabream. Mechanical, chemical and enzymatic treatments were assayed. Nylon wool columns and continuous density gradients were used for further separation of cell subpopulations. Light microscopy and flow cytometry showed that the highest density band (HD) consisted of a homogeneous lymphocytic population, whereas the intermediate density band (ID) corresponded to epithelial and secretory cells and some lymphocytes. Respiratory burst activity of total cell suspen...

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International Nuclear Information System (INIS)

A self-consistent pseudopotential method together with a mixed-basis set of plane waves and Gaussian orbitals are used to determine the electronic structure of the (001) surface of molybdenum. The pseudopotential is derived from a self-consistent calculation of the atomic levels and wave functions, and is tested for bulk molybdenum. The resulting bulk band structure and density of states are compared with existing augmented-plane-wave APW calculations. The same potential is applied to investigate the electronic structure of an uncontracted Mo (001) surface. A complete analysis of the surface states is given in terms of their distribution in the two-dimensional surface Brillouin zone, charge-density distribution, and the local density of states. The results are in very good agreement with recent photoemission measurements.

Science.gov (United States)

By using a model dielectric matrix in electron self-energy evaluations the computational effort of a quasiparticle band-structure calculation for a semiconductor is greatly reduced. Applications to various systems with or without inversion symmetry, having narrow or wide band gaps, and semiconductor alloys demonstrate the reliability and accuracy of the method. Calculations have been performed for thirteen semiconducting or insulating materials: Si, LiCl, AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, InSb, and the Al{sub 0.5}Ga{sub 0.5}As and In{sub 0.53}Ga{sub 0.47}As alloys. Excellent agreement with experimental results is obtained for the quasiparticle energies for these materials. The only three exceptions, {ital E}({Gamma}{sub 1{ital c}}) of AlP, {ital E}({ital L}{sub 1{ital c}}) of AlAs, and {ital E}({ital L}{sub 1{ital c}}) of AlSb are discussed and attributed to various experimental uncertainties. Several other ...

International Nuclear Information System (INIS)

GaAs1-xPx p-n junction structures were grown on the epi-ready n-type GaAs(100) substrate by solid source MBE system for different phosphor compositions. To obtain the lattice-match sample structure was applied graded growth procedure. The structural and optical properties of the sample structures with different P concentration were investigated by using X-ray diffraction (XRD), spectroscopic ellipsometry (SE). In addition, The range of lattice parameters in the graded epilayer and phosphorous composition were determined from the HRXRD rocking curve simulation. We analyse dielectric function spectra of disordered GaAs1-xPx junction structures measured using spectroscopic ellipsometry at room temperature in the 0.6-4.7 eV photon energy region. The critical energy points such as band gap energy and spin-orbit-split energy of these structures ...

International Nuclear Information System (INIS)

We have already developed three conventional and one periodic permanent (PPM) type 50-MW class klystrons, a smart modulator, and the first HOM-free accelerator structure (Choke-mode type, full-scale high power model). A very stable ceramic high voltage monitor was successfully tested up to 367-kV with a 4.5-#mu#sec pulse. A new C-band SiC type high power rf-load, advancing the power handling capability up to 50-MW is now being designed. It should have excellent mass production characteristics as it uses circularly symmetric TM_0_1_1 chained cavities. The first high power prototype of an rf compressor cavity made of a low thermal expansion material (super Invar) was designed to provide stable operation even with a very high Q of 200-k, it was successfully tested the output rf power up to 135-MW, 0.5-#mu#sec pulse width and 50-pps repetition rate. The C-band linac rf-system will be used for the SASE-FEL (SCSS) production ...

International Nuclear Information System (INIS)

The CaWO_4:Ln"3"+ SiO_2 (Ln=Tb, Dy and Ho) nanoparticles were synthesized via a combustion process at 800 "oC, using citric acid as chelating agent and fuel, ammonium nitrate as fuel, boric acid as flux material and silica as supports. The persistent phosphor nanoparticles were characterized by X-ray diffraction (XRD), reflectance UV-vis and fluorescence spectroscopy (PL) and transmission electron microscopy (TEM) techniques. XRD patterns indicated that crystalline calcium tungstate with scheelite structure was produced. The reflectance UV-vis spectra showed the broad absorption band of WO_4"2"- groups and the PL spectra showed the WO_4"2"- wide excitation band, broad emission band of WO_4"2"- and characteristic emissions of Ln"3"+ ions. The average particle sizes were determined by TEM, which are about 50 nm.

Energy Technology Data Exchange (ETDEWEB)

The deformation behavior and structure changes of magnesium alloy AZ31 were studied in compression at temperatures ranging from 523 K to 673 K and at a strain rate of 3 x 10{sup -3} s{sup -1}. They depend sensitively on deformation temperature. At high temperatures, grain fragmentation takes place due to frequent formation of kink bands initially at corrugated grain boundaries and then in grain interiors, followed by full development of new grains in high strain. At lower temperatures, in contrast, twinning takes place in rather coarse grains and kink bands are formed mainly in finer original ones in low strain. It is concluded that new grain evolution can be controlled by a deformation-induced continuous reaction resulting in grain fragmentation by kink bands, i.e. continuous dynamic recrystallization (cDRX). The latter is discussed comparing with conventional, i.e. discontinuous, DRX. (orig.)

CERN Document Server

Luminosity-driven channeling extraction has been observed for the first time in a 900 GeV study at the Fermilab Tevatron. This experiment, Fermilab E853, demonstrated that useful TeV level beams can be extracted from a superconducting accelerator during high luminosity collider operations without unduly affecting the background at the collider detectors. Multi-turn extraction was found to increase significantly the efficiency of the process. The beam extraction efficiency was about 25%. Studies of time dependent effects found that the turn-to-turn structure was governed mainly by accelerator beam dynamics. An investigation of a pre-scatterer using the accelerator flying wire system showed that a fiber could produce a significant extracted flux, consistent with expectations. Based on these results, it is feasible to construct a parasitic 5-10 MHz proton beam from the Tevatron collider.

International Nuclear Information System (INIS)

Interest to thin film of metals' silicides first of all is conditioned intrinsic al them unique physical properties. On their basis of it is possible to produce extremely sophisticated devices of solid-state electronics, production which needs the controlled change of physics, chemical and electrical properties with high-level of accuracy. On the present time most are in detail investigated composition, structure and properties of three-dimensional samples of metals' silicides. In the last years the intensive are led to researches in the direction of creation and study of physical-chemical properties thin (500-1000 Angstroms) and ultrafine (100-120 Angstroms) films silicides. It has information about composition, morphology of surface and emission of properties of thin film of silicides of barium, of cobalt and of palladium, was obtained in conditions of ultra-high vacuum. Low energy ion implantation and further annealing on composition, electronic and crystalline ...

British Library Electronic Table of Contents (United Kingdom)

The light-emitting properties of cubic silicon carbide films grown by vacuum vapor phase epitaxy on Si(100) and Si(111) substrates under conditions of decreased growth temperatures (T gr ? 900?700?C) have been discussed. Structural investigations have revealed a nanocrystalline structure and, simultaneously, a homogeneity of the phase composition of the grown 3C-SiC films. Photoluminescence spectra of these structures under excitation of the electronic subsystem by a helium-cadmium laser (?excit = 325 nm) are characterized by a rather intense luminescence band with the maximum shifted toward the ultraviolet (?3 eV) region of the spectral range. It has been found that the integral curve of photoluminescence at low temperatures of measurements is split into a set of Lorentzian components. Th...

British Library Electronic Table of Contents (United Kingdom)

Orthogonal frequency division multiplexing (OFDM) can fully use the frequency band and transmit data at high speeds. The ADSP-TS101 is a high performance digital signal processor (DSP) with good properties that include parallel processing and a high speed. Aimed at the real-time processing requirement of the OFDM algorithm, an underwater acoustic communication system with real-time processing capability is carried out. The system is mainly composed of multiple ADSP-TS101s, a multi-channel synchronous sample module and a field programmable gate array (FPGA) chip. The multiprocessor structure is made up of a cluster/data flow associated multiprocessing parallel processing structure as the operation kernel, and a multi-channel synchronous sample module is designed to realize no phase warp amo...

British Library Electronic Table of Contents (United Kingdom)

We report the first band structure calculations of the quasi-one-dimensional [MnTPP][TCNE] compounds (TPP?=?meso-tetraphenylporphyrinato, TCNE?=?tetracyanoethylene), based on Density Functional Theory (DFT) methods, in order to interpret the magnetic ordering in these prototypic systems. We compare and contrast the results of broken-symmetry DFT calculations for extended systems, with periodic boundary conditions, and for finite systems, magnetic dimers modeling the actual molecular magnets. By varying systematically the main angles, we are able to determine the geometry dependence of the exchange interaction. Structure?properties correlations in these charge-transfer salts reveal the determinant role of the Mn-(N?C)TCNE bond angle on the strength of the ferrimagnetic coupling between the ...

Energy Technology Data Exchange (ETDEWEB)

A-15 compounds are extremely brittle and difficult to process for practical applications. A novel processing technique was developed to greatly improve the mechanical and superconducting properties of A-15 alloys. The new processing technique can be described as follows: (1) to select compounds that can form the A-15 phase (the selected A-15 compounds in this research were Ti3Nb6Mo3Si4 and Nb99.5-(x + y)AlxSiyB0.5 alloys); (2) to rapidly solidify them into the amorphous state; (3) to anneal the quenched amorphous products into ultra fine-grained single A-15 phase. The extreme grain refinement greatly improved the flexibility and the critical current density of the alloys. The melt spinning technique was used to rapidly solidify Ti3Nb6Mo3Si4 and Nb99.5-(x + y)AlxSiyB0.5 alloys. Ti3Nb6Mo3Si4 alloys were relatively easily formed into the amorphous state. Nb3Al alloys required the addition of glass forming elements Si and B. It was found that, without boron, the ...

International Nuclear Information System (INIS)

In this study, free electron laser (FEL) with selective wavelength was used to induce structure changes of biomolecules, which were characterized by FTIR spectroscopy. For understanding of the interactions between FEL and biomolecules as well as biological tissues, the biomolecules investigated are ATP, ADP, AMP, t-RNA, D-ribose and the complex of SmCl_3-D-ribose. Their FTIR spectra before and after irradiation of FEL show molecular structure variations of the samples after irradiation of FEL, especially the rearrangement of their hydrogen bond networks. Along with the various irradiation wavelengths, irradiation time and molecular structures, the changes after irradiation are different for these molecules. In the FTIR spectra after irradiation, the phenomenon that the bands split into several peaks indicates the existence of several structures, conformations and configurations, ...

International Nuclear Information System (INIS)

The band structure (BS) of crystalline Bi_2Se_2Te both pure as well as deposited on Si or SiO_2 (substrates) was calculated for the first time. The calculation approach consists of an orthogonalization of the plane wave basis set with respect to the core-like orbitals and the application of the Perdew-Alder exchange-correlation scheme. In addition, a virtual crystal approach was applied. Experimental ellipsometric spectra were used as a criterion of the advantages of the different calculation techniques. The results of traditional one-electron methods of BS calculations, using norm-conserving pseudo-potential (NCPP), and full linear augmented plane wave (FLAPW), were compared with the experimental data. Better agreement with experiment is achieved when the NCPP wave functions are orthogonalized to the 4dBi core-like states. Concerning the LMTO and the FLAPW all-electron methods, only appropriate application of the virtual crystal approximation ...

Science.gov (United States)

Charge flow and valence/d-band behavior in ion-beam-mixed (IBM) Pd1-xAgx (x = 0.5-0.9) alloys have been studied by X-ray photoemission measurement of the valence bands and of core-level binding energy shifts and X-ray absorption near-edge structure. We correlated the observed Ag 3d5/2 core-level shifts in these IBM alloys, relative to the elemental Ag, with the White Line area changes at the Pd and Ag L3-edge to investigate the charge redistribution at the Ag site. The results indicate that there is a decrease in sp-like conduction electron and a negligible change in the number of d-electrons at the Ag site upon alloying. These results are in line with our previous results in which Pd gains d-charges and loses sp-type charges. This electron redistribution due to hybridization in the alloy leads small net charge transfer from the Ag site to the Pd site in accordance with electronegativity predictions. This result is ...

International Nuclear Information System (INIS)

Secondary-electron emission (SEE) spectra have been obtained with the Scanning Probe Energy Loss Spectrometer at a tip-sample distance of only 50 nm. Such short working distances are required for the best theoretical spatial resolution (<10 nm). The SEE spectra of graphite, obtained as a function of tip bias voltage, are shown to correspond to unoccupied states in the electronic band structure. The SEE spectra of thin gold films demonstrate the capability of identifying (carbonaceous) surface contamination with this technique.

International Nuclear Information System (INIS)

A methods is presented for an accurate numerical determination of eigenvalues of real symmetric para-p diagonal matrices. The method takes advantage of the band structure to break up the matrix into p x p blocks and performing algebraic operations including inversions on these blocks only, no matter what the size of the matrix is. The eigenvalues are determined independently one at a time. Thus any error in the determination of one eigenvalue does not affect the other eigenvalues. The method is ideally suited for the Schroedinger eigenvalue problem of the anharmonic potentials. (author).

International Nuclear Information System (INIS)

The experimental results of the components substitution effect on crystal structure, electronic transport properties, and Eu effective valence in solid solutions based on EuCu_2Si_2 and EuPd_2Si_2 ternary compounds are presented. It is shown, that when the Eu effective valence reaches the critical value #nu#"c"r_e_f_f=2.1, corresponding to degeneration of the 4f"7 and 4f"6 configurations, the condition of the concentrated Kondo system and an essential perturbation of the band electron spectrum near the Fermi level occur. (orig.).

International Nuclear Information System (INIS)

The variation in the superconducting properties of various binary alloys of transition metal-germanium systems was surveyed by studying sputter deposited samples prepared under various conditions. The primary interest has been to study the formation of the stoichiometric A-15 compounds T_3Ge.

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It is shown that calculation of the anomalous expectation values for the massless Gross-Neveu model in the Hartree-Fock approximation indicates the presence of an ordinary chiral phase transition if the coupling constant has the normal sign (g > 0) and of a different transition of the superconductivity type if g < 0.

International Nuclear Information System (INIS)

The phase transition behaviour of polyethylene-b-poly(ethylene oxide) (PE-b-PEO) diblock copolymer with relatively short chain lengths has been studied on the basis of temperature dependent infrared and Raman spectral measurements and synchrotron WAXD/SAXS simultaneous measurements, from which the concrete structural changes were deduced successfully from the various levels of molecular chain conformation, chain packing mode and higher-order structure. The higher-order structure has been found to transform between lamella, perforated lamella, gyroid, cylinder and sphere structures. The inner structural changes occurring in the polyethylene and poly(ethylene oxide) parts have been related with these morphological changes. The morphological transition from lamella to gyroid occurs with keeping the crystalline state of polyethylene parts. This apparently curious transition can be ...

International Nuclear Information System (INIS)

1974. 124 p. United States Johnson, GR Rochester Univ., NY (USA).

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A new class of one-dimensional active acoustic metamaterials (AAMMs) with programmable effective densities is presented. The proposed AAMM is capable of producing densities that are orders of magnitudes lower or higher than the ambient fluid. Such characteristics are achieved by using an array of fluid cavities separated by piezoelectric diaphragms that are controlled to generate constant densities over wide frequency bands. The piezodiaphragms are augmented with passive electrical components to broaden the operating frequency bandwidth and enable densities higher than the fluid medium to be generated. The use of these components is shown to be essential to maintain the closed-loop compliance of the piezodiaphragm away from the zone of elastic instabilities. The values of the passive components are selected on a rational basis in order to ensure a balance between the frequency bandwidth and control voltage. With this unique structure of the ...

International Nuclear Information System (INIS)

Moss-Schottky plots and photoelectrochemical measurements were made on films formed at different potentials on AISI 304 stainless steel in a borate/boric acid solution, pH 9.2. The results allowed the determination of the semiconductive properties and band structure of the films, which account for the existence of two kinds of films depending on the formation potential. For potentials below 0 V (SCE), the results point out for a film with an inverse spinel structure constituted by Cr-substituted magnetite with two donor levels. Above 0 V only one donor level is detected, which should be Fe"2 "+ on tetrahedral sites.

Energy Technology Data Exchange (ETDEWEB)

AZ31 magnesium alloy was friction-welded to AM60 and the microstructures and the friction welding process were studied. The microstructures changed near the weld interface. The AZ31 was refined to a grain size of several {mu}m near the weld interface. The nucleation occurred in the shear bands that were introduced during the welding process. On the other hand, the eutectic structure was deformed and the lamellar structure which was composed of {alpha}-Mg and Mg{sub 17}Al{sub 12} was formed near the weld interface in AM60 alloy. In the friction process, the adhesion and peel off occurred alternately between AZ31 and AM60. Eventually, bonding was completed during upset process. (orig.)

International Nuclear Information System (INIS)

O.K. Andersen has recently introduced a linear augmented plane wave method (LAPW) for the calculation of electronic structure that was shown to be computationally fast. A more general formulation of an LAPW method is presented here. It makes use of a freely disposable number of eigenfunctions of the radial Schroedinger equation. These eigenfunctions can be selected in a self-consistent way. The present formulation also results in a computationally fast method. It is shown that Andersen's LAPW is obtained in a special limit from the present formulation. Self-consistent test calculations for copper show the present method to be remarkably accurate. As an application, scalar-relativistic self-consistent calculations are presented for the band structure of FCC lanthanum. (author).

International Nuclear Information System (INIS)

Passive films formed on Alloy 690 in different pH solutions at high temperatures were studied by potentiodynamic polarization, Auger electron spectroscopy, thermodynamic diagrams and the Mott-Schottky relation. The chemical compositions and electronic structures of the passive films were found to be strongly pH-dependent. In alkaline solutions, a secondary passivation was clearly observed on potentiodynamic polarization curves. The passive films were a mixture of Cr2O3 and FeCr2O4 below the flat band potential of nickel oxide and were NiFe2O4 above this potential. Electronic structure models, describing the electrochemical properties of the passive films, are proposed and discussed.

Energy Technology Data Exchange (ETDEWEB)

The possibility of fabricating a superconductive vertex detector is discussed on the basis of a preliminary experiment. The experiment has shown that an indium strip 15 mm long, 20 ..mu..m wide and 0.1 ..mu..m thick is changed from the superconductive state to the normal state when struck by a single 5.4 MeV alpha particle.

International Nuclear Information System (INIS)

The Wendelstein 7-X (W7-X) modular stellarator is under construction at the Max-Planck-Institut fuer Plasmaphysik in Greifswald, Germany. The W7-X magnet system contains 70 coils made up from helium cooled superconducting cables in aluminium alloy (EN AW-6063) jackets. Several hundred connections of the jacket to the cable joints are made by aluminium-to-aluminium welds. Due to geometrical and thermal boundary conditions these welds cannot be accomplished free from defects. Microscopic analyses of the welds show that a variety of small flaws such as cracks and pores develop during welding. The welds have thus to be dimensioned accordingly, and appropriate weld qualification, investigation and testing has to be done in order not to jeopardise the structural integrity and leak tightness. The weld is mechanically loaded during cool-down due to the difference in thermal contractions between the GRP insulation and the aluminium, and during operation ...

Energy Technology Data Exchange (ETDEWEB)

A processing technique for A-15 compounds which has improved mechanical and superconducting properties has been developed. This technique consists of rapid solidification of the alloy by the chill block spinning machine (CBSM) to form amorphous ribbons and by subsequent annealing crystallizes the stable or metastable fine grain flexible A-15 structure. The CBSM has been modified so that all the processing parameters could be controlled and optimized for each alloy composition. By the improved CBSM it was possible to form amorphous Nb{sub 3}Si, Nb{sub 3}Ge and Nb{sub 3}(AlSi) ribbons with more than 80% reproducible rate. Critical current density measurements are limited by contact resistance. A Cu plating technique was introduced in this research that made the contact resistance three orders of magnitude lower than that obtained by other methods. This plated coating also gave an additional mechanical support to the sample and acted as a shunt ...

International Nuclear Information System (INIS)

K#beta#-to-K#alpha# X-ray intensity ratios of Ti, Cr, Fe and Co in pure metals and in Cr_0_._2_6Fe_0_._7_4, Cr_0_._8_0Co_0_._2_0 and Ti_0_._8_0Cr_0_._2_0 alloys have been measured following excitation by 59.54 keV #gamma#-rays from a 7400 MBq (200 mCi) "2"4"1Am point-source. The valence electronic structure of Ti, Cr, Fe and Co in the samples have been evaluated by the comparison of the measured K#beta#-to-K#alpha# intensity ratios with the results of multiconfiguration Dirac-Fock calculations performed for various electronic configurations of these metals. The 3d-electron populations obtained for pure metallic Ti, Cr, Fe and Co agree well with the results of band structure calculations of Papaconstantopoulos (Handbook of band structure of elemental solids, Plenum Press, New York, 1986). Our analysis indicates significant increase of 3d-electron population of Ti, Cr and Fe in the ...

International Nuclear Information System (INIS)

The [402]5/2 bands in "1"7"7Ta which are ''identical'' to the neighboring even-even "1"7"6Hf groundstate band have been extended to higher angular momentum. These bands in the two nuclei are seen to diverge from each other in the region of the first i_1_3_/_2 neutron alignment. The lower observed crossing frequency for the [402]5/2 bands indicates a lower deformation for these bands compared to "1"7"6Hf. Extensions to the h_9_/_2 [541]1/2 yrast band are also reported. (orig.).

International Nuclear Information System (INIS)

Electron-beam codeposition of the elements to form certain high critical temperature superconducting materials, in particular A-15 compounds, has proven to be very useful in research directed at understanding and improving their superconducting properties. This work has used the close control of three or more evaporant sources to reproducibly make specimens that permit studies across selected regions of composition and phase space. The effect of composition and phase, together with the temperature and rate of deposition, on the growth morphology and superconducting properties has been studied. The superconducting properties measured include the critical temperature, ac loss, critical current density, and tunnel junction characteristics. The particular compounds studied include Nb_3Sn, Nb_3Ge, and V_3Si.

International Nuclear Information System (INIS)

This thesis is devoted to the study and development of Heterojunction Bipolar Transistors (HBTs) designed for high voltage operation. The work concentrates on the use of wide bandgap III-V semiconductor materials as the collector material and their associated properties influencing breakdown, such as impact ionisation coefficients. The work deals with issues related to incorporating a wide bandgap collector into double heterojunction structures such as conduction band discontinuities at the base-collector junction and results are presented which detail, a number of methods designed to eliminate the effects of such discontinuities. In particular the use of AlGaAs as the base material has been successful in eliminating the conduction band spike at this interface. A method of electrically injecting electrons into the collector has been employed to investigate impact ionisation in GaAs, GaInP and AlInP which has used the ...

Energy Technology Data Exchange (ETDEWEB)

The Thai natural rubber economy is described in the context of the world rubber market. An econometric model is estimated for 15 structural equations; it includes the Thai, US, and rest-of-the-world rubber economies. Several simulation experiments are analyzed for the period from 1984 to 1995. Impact and dynamic multipliers are reported for major endogenous variables in response to changes in US GDP, world crude oil price, Thai replanting cess tax and Thai natural rubber production. A 1%, one-time increase in the US GDP has a positive effect on the Singapore natural rubber price. A world crude oil price decline shock has a negative effect in both the short-run and the long-run. The INRO buffer stock stabilization policy as well as alternative domestic Thai policies of market intervention are analyzed. The simulation results show that buffer stock management which allows a price band of +/-20% around the price target has the most stabilized ...

Energy Technology Data Exchange (ETDEWEB)

Using the transfer matrix method we calculate the omni-directional band gap of a 1-D photonic crystal consisting of alternating layers of two dielectric materials A and B with refractive index n{sub A} and n{sub B}, respectively. The refractive index of layer A is constant and the refractive index of layer B varies according to the envelope of a Gaussian function. We find that under certain circumstances it is possible to obtain 100% reflectivity for both polarizations and any value of the incident angle of the electromagnetic waves. Although the structure considered does not posses a higher omni-directional band gap than the periodic sequence of low and high constant refractive indexes, it can be used to produce a new type of omni-directional mirrors without abrupt interfaces. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

International Nuclear Information System (INIS)

Local-density-functional calculations of the energy bands, equilibrium lattice constant, bulk modulus, and cohesive energy have been performed using a newly developed self-consistent full-potential linearized augmented-plane-wave (LAPW) program. Scalar-relativistic effects are included for the band states, and the core-level states are treated fully relativistically in a central-field approximation. Excellent agreement is obtained with the experimental lattice constant and bulk modulus. Generally good agreement is obtained with the scalar-relativistic pseudopotential results of Bylander and Kleinman. In this context, the impact of various approximations used in including the core states is assessed, and these findings are related to the frozen-core and pseudopotential approximations, especially with regard to the treatment of the somewhat overlapping 5p semicore states and their effect on ground-state properties. Comparison with the recent LAPW ...

Energy Technology Data Exchange (ETDEWEB)

We used light confinement in optical microcavities to achieve a strong enhancement and a precise wavelength tunability of the electrical photoconductance of nanostructured porous silicon (PS). The devices consist of a periodic array of alternating PS layers, electrochemically etched to have high and low porosities - and therefore distinct dielectric functions. A central layer having a doubled thickness breaks up the symmetry of the one-dimensional photonic structure, producing a resonance in the photonic band gap that is clearly observed in the reflectance spectrum. The devices were transferred to a glass coated with a transparent SnO{sub 2} electrode, while an Al contact was evaporated on its back side. The electrical conductance was measured as a function of the photon energy. A strong enhancement of the conductance is obtained in a narrow (17nm FWHM) band peaking at the resonance. We present experimental results of the ...

Energy Technology Data Exchange (ETDEWEB)

A non-invasive, wide-band electromagnetic (EM) impedance difference system for shallow subsurface electrical structure characterization in environmental and engineering problems has been developed at the Lawrence Berkeley National Laboratory (LBNL). Electrical parameters of interest are electrical conductivity and dielectric permittivity that are deduced from the impedance difference data. The prototype system includes a magnetic loop transmitter, which operates between 0.1 MHz and 100 MHz, an electrical dipole antenna for observing the electric field, and a loop antenna for measuring the magnetic field.All antennas are mounted on a cart made of non-metallic material for easy movement of the whole array for profiling. Surface EM impedance difference is obtained by taking the difference of the ratios of the electric fields to the magnetic fields at selected frequencies at two different levels. Numerical simulations will be presented to verify ...

International Nuclear Information System (INIS)

In this study, WO3 thin films were grown on glass substrates using an aqueous solution containing tungstate (NH4)2WO4 as precursor. The substrate temperature incremented from 250 to 500 deg. C, by steps of 50 deg. C. The structural properties were investigated using XRD, atomic force microscopy and scanning electronic microscopy techniques. Microprobe analyses showed that a balanced stoichiometric composition was obtained for thin films prepared at Ts = 350 and 400 deg. C. The X-ray diffraction analyses showed different structure crystallography in function of the substrate temperature. Moreover, films deposited at 400 deg. C were annealed in air for 2 h at 450 and 500 deg. C, respectively and the structural changes due to heat treatment were studied. Finally, the optical properties of these films were carried out using optical measurements of transmittance T(?) and reflectance R(?) spectra in 300-1800 nm domain. The ...

Energy Technology Data Exchange (ETDEWEB)

High-spin states in the mirror pair nuclei {sup 49}Cr and {sup 49}Mn and their cross-conjugate partners, the mirror pair {sup 47}V and {sup 47}Cr have been investigated using experimental {gamma}-ray spectroscopic techniques. The combination of high-efficiency EUROBALL cluster Germanium detectors and clean exit-channel gating afforded by a 31-element silicon ball used in conjunction with a 15-detector neutron wall allowed a revision and extension to the energy level schemes of all four nuclei up to J{sup {pi}}=31{sup -}/2. The difference in excitation energy between states of equivalent spin in the parent nucleus and its analogue partner have thus been established for both mirror pairs up to the f{sub 7/2}-shell band terminating state for the first time. This difference is assumed to be due almost entirely to the Coulomb effect and is therefore called the Coulomb energy difference (CED). The variation in the CED with spin has been interpreted as reflecting the ...

International Nuclear Information System (INIS)

We present the results of a comprehensive study of the temperature dependences of the quantum efficiency for ultraviolet detectors based on GaAs, GaP and 4H--SiC Schottky structures, and on Si, GaAs p-n structures. For ultraviolet detectors based on Schottky structures, the quantum efficiency increases with increasing temperature for all photon energies, even including the semiconductor intrinsic absorption region. On the other hand, for ultraviolet detectors based on p-n structures, the quantum efficiency is practically temperature independent in the semiconductor intrinsic absorption region. The change in the quantum efficiency for the GaAs and Si detectors is less than 0.01% per degree. To explain the measurements, a variable trap occupancy model is presented. Subsurface imperfections of the semiconductor cause fluctuations in the profile of the conduction band and the valence ...

International Nuclear Information System (INIS)

The T/sub c/ behavior of vapor-deposited Nb_3Ge and Nb_3Sn is examined as a function of low-fluence alpha-particle irradiation. It is found that for Nb_3Sn with rho_0approx.15 #mu##OMEGA#-cm the T/sub c/ is insensitive to low doses of radiation, whereas Nb_3Ge with rho_0approx.50 #mu##OMEGA#-cm has its T/sub c/ depressed immediately with irradiation. It is suggested that the T/sub c/ behavior of A-15 superconductors in the regime of small dose is strongly influenced by the initial state of the sample. Furthermore, it is argued that the behavior of the T/sub c/ with dose can be qualitatively explained by considering a sharp structure in the density of states N(E), the smearing of which by defects leads to a depression in T/sub c/.

Energy Technology Data Exchange (ETDEWEB)

A generic reactor model is used to examine the economic viability of electricity generation by magnetic fusion. The simple model uses components which are representative of those used in previous reactor studies of deuterium-tritium burning tokamaks, stellarators, bumpy tori, reverse field pinches and tandem mirrors. Conservative costing assumptions are made. The generic reactor is not a tokamak but rather it is intended to emphasize what is common to all magnetic fusion reactors. The reactor uses a superconducting toroidal coil set to produce the dominant magnetic field. To this extent it is a less good approximation to systems, such as the reversed field pinch in which the main field is produced by a plasma current. The main output of the study is the cost of electricity as a function of the weight and size of the fusion core - blanket, shield, structure and coils. The model shows that a 1200 MW/sub e/ power plant with a fusion core weight of ...

Energy Technology Data Exchange (ETDEWEB)

This paper contains literature from American Power Conference Air Toxics Being Measured Accurately, Controlled Effectively NO{sub x} and SO{sub 2} Emissions Reduced; Surface Condensers Improve Heat Rate; Usable Fuel from Municipal Solid Waste; Cofiring Technology Reduces Gas Turbine Emissions; Trainable, Rugged Microsensor Identifies of Gases; High-Tc Superconductors Fabricated; High-Temperature Superconducting Current Leads; Vitrification of Low-Level Radioactive and Mixed Wastes; Characterization, Demolition, and Disposal of Contaminated Structures; On-Line Plant Diagnostics and Management; Sulfide Ceramic Materials for Improved Batteries; Flywheel Provides Efficient Energy Storage; Battery Systems for Electric Vehicles; Polymer-Electrolyte Fuel Cells for Transportation; Solid-Oxide Fuel Cells for Transportation; Surface Acoustic Wave Sensor Monitors Emissions in Real-Time; Advance Alternative-Fueled Automotive Technologies; Thermal & ...

International Nuclear Information System (INIS)

There are 173 three quasiparticle rotational bands, out of which 38 bands display signature splitting and sometimes a signature inversion also. The observed signature splitting is basically due to the higher order Coriolis coupling and calculation based on particle rotor model (PRM) are in progress

CERN Document Server

The existence of n-particle n-hole deformed yrare bands in the N=28 isotones is explored using full pf-shell diagonalizations and the Lanczos Strength Function method. We find different 2p-2h and 4p-4h collective bands that, when allowed to mix, more often disappear. Only the 2p-2h yrare band in Cr-52 and the 4p-4h yrare band in Ni-56 survive, and only in this latter case, due to the reduced density of 2p-2h states, can the band be seen as a gamma-cascade.

International Nuclear Information System (INIS)

Nonparabolicity of the heavy hole band in diamond-like semiconductors, which occurs within the framework of the three band model with the perturbation from the other bands taken into account according to the Loewdin procedure, is studied. A direct dependence of nonparabolicity on the band anisotropy (caused by the different effect of Gamma/sub 15c/ and Gamma/sub 12c/ bands) and the inverse dependence on the magnitude of the spin-orbit splittiing is established. A connection between the effective mass of heavy holes and their energy is obtained, which is valid for the majority of diamond-like semiconductors, except for materials with a very strong nonparabolicity of the band of silicon type.

International Nuclear Information System (INIS)

Three major monomeric hemoglobins have been isolated from the erythrocytes of Glycera dibranchiata. Their importance to structure-function studies of heme proteins lies in the fact that they have been shown to possess an exceptional amino acid substitution. In these proteins, the E-7 position is occupied by leucine rather than the more common distal histidine. This substitution alters the polarity of the heme ligand binding environment compared to myoglobin. Due to this, the G. dibranchiata monomer hemoglobins are attracting much attention. However, until now no purity criterion has been developed. Here the authors demonstrate that, for all of the Glycera momomer hemoglobins, multiple line patterns are shown on high-voltage isoelectric focusing (IEF) gels. Most of these lines are shown to be a consequence of heme-related phenomena and can be understood on the basis of changes in oxidation and ligation state of the heme iron. The multiple line pattern does not ...

Energy Technology Data Exchange (ETDEWEB)

The K{beta}-to-K{alpha} X-ray intensity ratio of Ni in Ni{sub 3}Si, Ni{sub 2}Si and NiSi has been determined by energy dispersive X-ray fluorescence technique. It is found that the intensity ratio of Ni decreases from pure Ni to Ni{sub 2}Si and then increases from Ni{sub 2}Si to NiSi, in good agreement with the electronic structure calculations cited in the literature. We have also performed band structure calculations for pure Ni in various atomic configurations by means of linear muffin-tin orbital method and used this data with the normalized theoretical intensity ratios cited in the literature to estimate the 3d-occupation numbers of Ni in Ni-Si alloys. It is emphasized that investigation of alloying effect in terms of X-ray intensity ratios should be carried out for the stoichiometric alloys in order to make reliable and quantitative comparisons between theory and experiment in transition metal alloys.

CERN Document Server

The recently measured experimental data of Argonne National Laboratory for high-spin states in neutron-rich $^{71,73,75,77}$Ga isotopes have been interpreted in the framework of large-scale shell model. Calculations have been performed in $f_{5/2}pg_{9/2}$ model space with two recent effective shell model interactions, JUN45 and jj44b. We also predict high-spin states for $^{79,81}$Ga, where very little is known experimentally. The calculated results show that existence of band structure built on top of the 3/2$^-$, 5/2$^-$ and 9/2$^+$ levels in $^{71-77}$Ga. The collective structure reflected in experimental data is not well reproduced in calculated values. The calculated positive parity states in $^{71,73,75}$Ga are higher in energy in comparison to experimental finding, while for $^{77,79}$Ga, the positive parity states are in better agreement. Both the interactions predict, leading configuration of $\\pi(f_{5/2}^3)$ and ...

International Nuclear Information System (INIS)

Excitonic transitions in metalorganic vapor phase epitaxially grown In_xGa_1_-_xP/In_0_._4_8(Al_0_._7Ga_0_._3)_0_._5_2P strained single quantum-well structures are characterized using low-temperature photoluminescence and photoluminescence excitation (PLE) spectroscopies. The structures consist of several uncoupled quantum wells with thicknesses between 1.2 and 11.3 nm, and compositions x of 0.48 (nominally lattice matched) and 0.56 (#approx#0.6% biaxial compressive strain). The photoluminescence spectra exhibit intense peaks over the wavelength range 550--650 nm, with linewidths between 7 and 23 meV depending on the well thickness. The PLE spectra reveal strong heavy-hole and light-hole transitions, as well as higher-order (n=2) transitions in the thicker wells. The heavy-hole/light-hole splitting shows little dependence on well thickness in the strained structures, indicating a relatively large conduction ...

Energy Technology Data Exchange (ETDEWEB)

The ortho-metalated Pt(II) complexes Pt(ppy)(CO)Cl (1), Pt(ptpy)(CO)Cl (2), and Pt(ppy)(Hppy)Cl (3) (where ppy and ptpy are respectively the ortho-C-deprotonated forms of 2-phenylpyridine and 2-p-tolylpyridine and Hppy is 2-phenylpyridine) have been prepared. The CO ligand is coordinated trans to the nitrogen atom of the ortho-metalated ligand and exerts a strong trans effect resulting in a relatively long Pt-N bond [2.114(19) {angstrom}]. This structure shows both the bidentate ppy ligand and the monodentate Hppy with the nitrogens of these ligands trans to each other. The UV/vis electronic absorption spectra of 1-3 have intense bands in the near-UV region ({approximately}375 nm) which have been assigned as metal to ligand charge transfer (MLCT) transitions, and higher energy bands were assigned as ligand-centered transitions. Each complex exhibits relatively long-lived structured emissions in the ...

Science.gov (United States)

Basic research of the structure and electronic properties of a-Si:H is reported with particular emphasis on the role of defects. The main findings are as follows: (1) low defect density material can be deposited at a high rate using SiH/sub 4/ diluted in He or Ne. Using Ar or Kr results in a high defect density and columnar material; (2) an electrical bias during deposition modifies the band gap, hydrogen concentration and structure; (3) the clustering of hydrogen in the regions between the columns is confirmed; (4) hydrogen diffusion is observed by NMR; (5) the oxidation of an a-Si:H surface results in approx. 3 x 10/sup 11/ cm/sup -2/ dangling bonds at the interface; (6) auger recombination of photoexcited carriers is a significant non-radiative mechanism at low temperatures; (7) non-radiative recombination by diffusion and capture at dangling bonds is observed at temperatures above 50 to 100/sup 0/K; (8) the defect ...

International Nuclear Information System (INIS)

We present results from the first studies of electric-field effects on optical transitions in visible-band-gap InGaP/InAlGaP multiple-quantum-well (MQW) structures. These structures, grown at 775 degree C by metalorganic vapor phase epitaxy on (100) GaAs substrates misoriented 6 degree towards P(111)right-angle left-angle 111 right-angle A, consist of nominally undoped MQWs surrounded by doped In_0_._4_9Al_0_._5_1P cladding layers to form p-i-n diodes. The Stark shifts of various allowed and forbidden quantum-well transitions were observed in bias-dependent electroreflectance spectra of In_0_._4_9Ga_0_._5_1P/In_0_._4_9(Al_0_._5Ga_0_._5)_0_._5_1P MQW samples with 10-nm-thick layers. We find the magnitude of these shifts to depend on the details of the Mg doping profile, confirming the importance of Mg diffusion and unintentional background doping in these materials. Our results show that (InAlGa)P materials are promising for ...

Science.gov (United States)

Space Network Ku-band service. ... Completed GLAST mission schedule and budget assessment .... Utilize Ku band SN link (TDRSS) for science data return ...

Energy Technology Data Exchange (ETDEWEB)

A micellar method has been used to prepare silver-coated cobalt (Co-Ag) nanoparticles. The synthesized particles have been deeply characterized by several methods, i.e., XRD, UV-Vis, TEM, XPS, and electrochemical techniques. There is every indication that the obtained particles show a truly core-shell structure. All the nanoparticles obtained under different conditions are in the size range 3-5 nm. High-resolution TEM (HRTEM), Fast Fourier Transformation (FFT), and Selected Area Electron Diffraction (SAED) indicated that the presence of hcp-Co and fcc-Ag, in which cobalt is located in the central area; meanwhile silver is at the edges of the nanoparticle. The absorption band of the Co-Ag colloid shifts to a longer wavelength and broadens relative to that of pure silver colloid. Voltammetric characterization allowed to determine the coverage of the cobalt core.

DEFF Research Database (Denmark)

We suggest and study designed defects in an otherwise periodic potential modulation of a two-dimensional electron gas as an alternative approach to electron spin based quantum information processing in the solid-state using conventional gate-defined quantum dots. We calculate the band structure and density of states for a periodic potential modulation, referred to as an antidot lattice, and find that localized states appear, when designed defects are introduced in the lattice. Such defect states may form the building blocks for quantum computing in a large antidot lattice, allowing for coherent electron transport between distant defect states in the lattice, and for a tunnel coupling of neighboring defect states with corresponding electrostatically controllable exchange coupling between different electron spins.

CERN Document Server

We present mid-infrared spectro-imagery and high-resolution spectroscopy ofthe Orion bar and of a region in the Orion nebula. These observations have beenobtained in the Guaranteed Time with the Circular Variable Filters of the ISOcamera (CAM-CVF) and with the Short Wavelength Spectrometer (SWS), on board theEuropean Infrared Space Observatory (ISO). Our data shows emission fromamorphous silicate grains from the entire HII region and around the isolatedO9.5V star Theta2 Ori A. The observed spectra can be reproduced by a mixture ofinterstellar silicate and carbon grains heated by the radiation of the hotstars present in the region. Crystalline silicates are also observed in theOrion nebula and suspected around Theta2 Ori A. They are probably ofinterstellar origin. The ionization structure and the distribution of thecarriers of the Aromatic Infrared Bands (AIBs) are briefly discussed on thebasis of the ISO observations.

Science.gov (United States)

Homogenous Al{sub x}Ga{sub 1{minus}x}P liquid phase epitaxial layers have been obtained with the temperature difference method under controlled vapor pressure (TDM-CVP). Very clear fine structures near band edge in photoluminescence spectra have been observed at 77 K for the first time. Photoluminescence measurement results confirmed that the free exciton recombination without phonon assistance plays an important role in the luminescence at 77 K and becomes dominant at room temperature. It is considered that Zero-phonon assisted free exciton recombination is intensified by some local perturbations to electrical potentials against carriers or excitons introduced by Al atoms in Al{sub x}Ga{sub 1{minus}x}P layers, which can give momentum change necessary for recombination.

International Nuclear Information System (INIS)

Photocurrent and capacitance measurements of semiconductor passive films formed on metals and alloys can be used to study the electronic properties and reveal indirect information about structure and composition. The current work used these techniques to investigate the electronic properties of the passive films formed on three austenitic stainless steels, types 304L, 316L and 254SMO, in borate. Evidence was found for the existence of a large number of localised mid bandgap states, consistent with amorphous oxides. However, the flat-band potentials of the austenitic stainless steel passive films were found to be independent of both composition and measuring frequency. The most credible explanation for the bandgap values determined from photocurrent measurements is that the passive films are formed as dual layers, iron oxide outer layer and chromium oxide inner layer. This model does not need to evoke the potential dependent bandgaps used by ...

British Library Electronic Table of Contents (United Kingdom)

Abstract High-crystallinity hierarchical anatase TiO2 hollow spheres were prepared by a high-temperature (350 C) and non-aqueous solvothermal method in the absence of water, templates, or additives. The hollow structures were assembled from highly crystallized TiO2 nanoparticles and exhibit superior photocatalytic properties relative to those of Degussa P25 TiO2 under irradiation with UV light. The influence of reaction temperature on the crystallinity, morphology, crystallite shape and size, band gap, specific surface area, and pore size distribution of TiO2 has been studied in detail. It is evident that reaction temperature is the most important factor to increase the crystallinity of TiO2 in order to improve its charge transfer and transport properties, which are important in photocatal...

British Library Electronic Table of Contents (United Kingdom)

A two-dimensional (2D) lattice model with anisotropic resonant microstructures is found to provide an anisotropic band gap structure. A 2D continuum with anisotropic effective mass density is introduced to represent this lattice system. Two methods are proposed to derive the equivalent continuum. In the first method, the effective mass density of the equivalent continuum is obtained by matching the dispersion relations for harmonic waves propagating in the principal directions. The second approach employs an approximate estimation of the effective mass density by volume-averaging an effective mass that represents the resonant microstructure. For both equivalent continuum models, the effective mass density is frequency-dependent and may become negative in certain frequency ranges. Subsequen...

International Nuclear Information System (INIS)

Intermediate products of the conversions of 6-aminophenalenone in ethanol were investigated by pulse radiolysis. In alkaline medium the main product is the 6-aminophenalenone radical cation, the optical absorption spectrum of which contains two bands with maxima at 355 and 400 nm. The precursors of this particle are e_s, CH_3CHOH and CH_3CHO"- radicals. In neutral and acid medium, radical cations are protonated in reactions with alcohol and hydrogen ions. The H-adduct of 6-aminophenalenone that arises has optical absorption maxima at 350 and 390 nm. The presence of two maxima is due to two different structures of the product. The molar extinction coefficients of the radical anions and H-adducts of 6-aminophenalenone and the rate constants of the reactions involving them were estimated. 6 refs., 4 figs., 2 tabs.

CERN Document Server

The hyperfine interactions at the uranium site in the antiferromagnetic USb2 compound were calculated within the density functional theory (DFT) employing the augmented plane wave plus local orbital (APW+lo) method. We investigated the dependence of the nuclear quadruple interactions to the magnetic structure in USb2 compound. The investigation were performed applying the so called band correlated LDA+U theory self consistently. The self consistent LDA+U calculations were gradually added to the performed generalized gradient approximation (GGA) including scalar relativistic spin orbit interactions in a second variation scheme. The result, which is in agreement with experiment, shows that the 5f-electrons have the tendency to be hybridized with the conduction electrons in the ferromagnetic uranium planes.

CERN Document Server

We study the ground state of an ideal coupled two-component gas of ultracold atoms in a one dimensional optical lattice, either bosons or fermions. Due to the internal two-level structure of the atoms, the Brillouin zone is twice as large as imposed by the periodicity of the lattice potential. This is reflected in the Bloch dispersion curves, where the energy bands regularly possess several local minima. As a consequence, when the system parameters are tuned across a resonance condition, a non-zero temperature topological first order phase transition occurs which arises from an interplay between initernal and kinetic atomic energies. It is shown that these phenomena are also captured for two and three dimensional optical lattices.

Science.gov (United States)

Using Pd and Ag L3,2-edge x-ray-absorption near edge structures (XANES) and x-ray photoemission spectroscopy, we have investigated the charge distribution in a series of Pd-Ag alloys (Pd3Ag, PdAg, and PdAg3) from a local perspective. It is found that, relative to the pure element, both Pd and Ag gain d and lose non-d (s and p) charge upon alloying. The results are discussed in terms of band filling, rehybridization, electronegativity, and electroneutrality considerations. The possibility of using the L3,2-edge XANES white line to circumvent the need of an appropriate volume for charge transfer discussions and for other applications are noted.

Energy Technology Data Exchange (ETDEWEB)

The low-power operation of a semiconductor buried-heterostructure Raman laser is reported. We are developing these devices for very wide-band optical communication in the terahertz frequency region. It has a structure with a GaP active layer and Al{sub {ital x}}Ga{sub 1{minus}{ital x}}P cladding layers, which are grown by the temperature-difference method under controlled vapor pressure. By making the stripe width 30--40 {mu}m, we have obtained a threshold pump power of 500 mW. A low-threshold semiconductor Raman laser can be pumped by semiconductor injection lasers. We have measured the optical loss of the waveguide and detected the contribution from scattering and leakage at heterointerfaces.

British Library Electronic Table of Contents (United Kingdom)

In the present study the optical properties of co-evaporated indium sulfide thin films are investigated. Before being optically characterized, the composition as well as the crystalline properties of the film have been checked with the help of energy dispersive spectroscopy (EDX) and X-Ray diffraction (XRD) analyses. The optical absorption coefficient ? of this indium sulfide film has been deduced from reflectivity R(?) and transmission T(?) measurements. The fit of the curve representing ?(h?) suggests that the ?-In2S3 has an indirect bandgap of 2.01?eV. Density functional theory (DFT) calculations are performed on this indium sulfide compound, using TB-LMTO code. Through these band structure investigations, an indirect bandgap is predicted as observed experimentally. The top of the valen...

International Nuclear Information System (INIS)

Oxide superconducting thin films were irradiated with X-rays and ultra-violet (UV) light, and induced radiation effects on electrical and chemical properties were examined by transport measurement, X-ray diffraction analysis (XRD), diamagnetization measurement and X-ray photoemission spectroscopy (XPS). After irradiation for ErBa_2Cu_3O_x films with X-rays emitted from a Rh tube for 100 hours, superconductivity was remarkably damaged, destroying the zero-resistance state. The UV-light irradiation for Bi_2Sr_2CaCu_2O_x films was performed in He gas of about 500 Pa with a low pressure mercury lamp. The superconductivity was gradually degraded with the UV irradiation time up to 70 minutes. In both cases, adequate oxygen-annealing treatments restored superconductivity. The X-ray photoemission spectra showed that the mean Cu valence of the films was decreased approximately from +2 to +1 by the irradiation. ...

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In order to fabricate high temperature superconducting tapes for power applications, the authors have analyzed different buffer layer architectures grown on textured Ni substrates suitable for YBCO deposition. Due to its optimal lattice matching the studied structures present as top layer a CeO{sub 2} film. The deposition of CeO{sub 2} on Ni substrates was performed by pulsed laser ablation and by e-beam evaporation at different temperatures. The films obtained by the two deposition techniques have not optimal structural properties, having a polycrystalline component. The misorientation of CeO{sub 2} is probably due to the formation of NiO at the interface between the film and the substrate during the deposition process even if no oxygen is introduced. In order to prevent Ni oxidation an intermediate 2000 {angstrom} Pd thick film was deposited by e-beam. Furthermore, the lattice mismatch between Pd and CeO{sub 2} is smaller ...

International Nuclear Information System (INIS)

Raman scattering measurements of the Esub(g) and Tsub(2g) optical phonons in V"3Si, Nb"3Sn, V"3Ge, Cr"3Si, V"3Pt, and Nb"3Pt are presented and discussed in terms of interaction with interband electronic excitations. Data on superconducting Nb"3Sn is presented and modifications to the phonon spectral function and the spectrum of Raman active interband electronic excitations in the superconducting state are discussed. (orig.).

Science.gov (United States)

The results of this research centered on the experimental studies of a single superconducting persistent current qubit, the implementation of type-II algorithms using these qubits, and the proposal for adiabatic quantum computing using these qubits. The m...

International Nuclear Information System (INIS)

The magnetic ordering temperature of some rare-earth-based heavy-fermion compounds is strongly pressure dependent and can be completely suppressed at a critical pressure, p_c, making way for novel correlated electron states close to this quantum critical point. We have studied the clean heavy-fermion antiferromagnets CePd_2Si_2 and CeIn_3 in a series of resistivity measurements at high pressures up to 3.2 GPa and down to temperatures in the mK region. In both materials, superconductivity appears in a small window of a few tenths of a GPa on either side of p_c. We present detailed measurements of the superconducting and magnetic temperature-pressure phase diagram, which indicate that superconductivity in these materials is enhanced, rather than suppressed, by the closeness to magnetic order. (author)

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... MPS) Advanced Liquid Crystalline Optical Materials Superconductivity Computation and Visualization ... Cement-Based Materials Synthesis, Growth, and Analysis of Electronic Materials Photoinduced Charge ...

International Nuclear Information System (INIS)

This paper reports that only a few years ago superconducting magnetic separation was viewed as the next major market for superconducting magnets. The first commercial units had been installed, worked flawlessly, and demonstrated real economic viability. The potential market was seen as quite large, and many people believed that superconducting magnetic separation would soon show the same rapid growth that MRI had demonstrated after its initial success. These hopes even prompted IGC, one of the top MRI magnet builders, to form a separate division devoted to magnetic separation. Despite the existence of Magstream, IGC has not been overly active in the market. As a technology that has applications from the clay on the Earth to the soil on the moon, superconducting magnetic separation has yet to become widely used.

CERN Document Server

In these lecture notes we derive a generic holographic string theory realization of a p-wave superconductor and superfluid. For this purpose we also review basic D-brane physics, gauge/gravity methods at finite temperature, key concepts of superconductivity and recent progress in distinct realizations of holographic superconductors and superfluids. Then we focus on a D3/D7-brane construction yielding a superconducting or superfluid vector-condensate. The corresponding gauge theory is 3+1-dimensional N=2 supersymmetric Yang-Mills theory with SU(N) color and SU(2) flavor symmetry. It shows a second order phase transition to a phase in which a U(1) subgroup of the SU(2) symmetry is spontaneously broken and typical superconductivity signatures emerge, such as a conductivity (pseudo-)gap and the Meissner-Ochsenfeld effect. Condensates of this nature are comparable to those recently found experimentally in p-wave superconductors ...

International Nuclear Information System (INIS)

(15 Jul 1974). United States Sweedler, AR Schweitzer, DG Webb, GW

Science.gov (United States)

Ab initio lattice dynamics based on linear response method are performed for high pressure phase of yttrium to describe electron-phonon coupling and subsequent superconducting behavior. The critical temperature Tc in fcc-Y increases monotonically with pressure up to 9.25 K at 31 GPa, which is quantitatively in excellent agreement with two quasihydrostatic experiments and is qualitatively compatible with recent experiments. The excellent agreement with experiments gives us a better understanding of the effective pseudopotential ?* as well as spectral function ?2(?)F(?) in yttrium. These results demonstrate that there exists strong electron-phonon coupling in Y within the studied pressure regime, and for lower pressure electron correlation becomes stronger. Generally, it is found that superconductivity in yttrium under pressure can be described quantitatively within standard theory of phonon-mediated superconductivity.

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Energy Technology Data Exchange (ETDEWEB)

Lifetimes have been measured for dipole bands in {sup 142}Gd using DSAM. The deduced B(M1) and B(E2) values as well as B(M1)/B(E2) ratios are compared with calculations in the framework of the TAC (Tilted Axis Cranking) and SPAC (shears mechanism with Principal Axis Cranking) models. The dipole bands DB1 to DB4 can be interpreted as magnetic rotational bands. (orig.)

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KoreaScience (Korea)

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CERN Document Server

We examine the star clusters in the irregular galaxy NGC 4449. We use a near-infrared spectrum and broad-band images taken with the HST to place a limit of 8--15 Myrs on the age of the bright central ojbect in NGC 4449. Its luminosity and size suggest that it is comparable to young super star clusters. However, there is a peculiar nucleated-bar structure at the center of this star cluster, and we suggest that this structure is debris from the interaction that has produced the counter-rotating gas systems and extended gas streamers in the galaxy. From the images we identify 60 other candidate compact star clusters in NGC 4449. Fourteen of these could be background elliptical galaxies or old globular star clusters. Of the star clusters, three, in addition to the central object, are potentially super star clusters, and many others are comparable to the populous clusters found in the LMC. The star clusters span a large range in ...

CERN Document Server

The stellar disc kinematics in a sample of fifteen intermediate- to late-type edge-on spiral galaxies are studied using a dynamical modeling technique. The sample covers a substantial range in maximum rotation velocity and deprojected face-on surface brightness and contains seven spirals with either a boxy- or peanut-shaped bulge. Dynamical models of the stellar discs are constructed using the disc structure from $I$-band surface photometry and rotation curves observed in the gas. The differences in the line-of-sight stellar kinematics between the models and absorption line spectroscopy are minimized using a least-squares approach. The modeling constrains the disc surface density and stellar radial velocity dispersion at a fiducial radius through the free parameter $\\sqrt{M/L}$ $(\\sigma_{\\rm z}/\\sigma_{\\rm R})^{-1}$, where $\\sigma_{\\rm z}/\\sigma_{\\rm R}$ is the ratio of vertical and radial velocity dispersion and $M/L$ the disc ...

International Nuclear Information System (INIS)

The /sup 40/Ca(p,n)/sup 40/Sc reaction was studied at 134 MeV. Neutron energy spectra were measured by the time-of-flight technique with resolutions of 220 keV at angles from 0"0 to 41"0 and 415 keV out to 62"0. The 2"-,3"-,4"-,5"- band of states based on the (f/sub 7/2/,d/sub 3/2//sup -1/) 1p1h structure was observed at low excitation energies, in good agreement with known analog states in /sup 40/Ca and /sup 40/K. The shapes of the cross-section and analyzing-power angular distributions are in good agreement with distorted-wave impulse-approximation calculations using simple 1p1h (Tamm-Dancoff approximation) shell-model wave functions. A relatively strong transition to a state at E/sub x/ = 2.3 MeV with L = 3 is identified tentatively as a 4"- state with the predominant 1p1h structure (1f/sub 7/2/,2s/sub 1/2//sup -1/).

International Nuclear Information System (INIS)

A scalar-relativistic procedure for calculating the valence-electron contribution to the total energy of bulk and thin-film solids has been developed and applied to the fcc and bcc phases of the group-VIB transition elements Cr, Mo, and W. This approach, which is based on the linear augmented-plane-wave method and local-density-functional theory, contains no shape approximations for either the charge density or potential. The formulation adopts a rigid-core approximation and incorporates an exact treatment of the core-charge tails that extend beyond the muffin-tin spheres. The application of this procedure to bcc Cr, Mo, and W yields calculated lattice parameters and bulk moduli that are in good (Cr) to excellent (Mo and W) agreement with experiment. The present calculated properties also agree quite well with the results of previous calculations involving a variety of band-structure methods. The calculated fcc-bcc energy difference for Cr, Mo, and W increases in a ...

International Nuclear Information System (INIS)

A tri-functional polyhedral oligomeric silsesquioxane (POSS) based silane precursor R_xR_yR_z(SiO_3_/_2)_n (x + y + z = n = 6, 8, 10, ...) bearing 3-(N-(3-triethoxysilylpropyl)ureido)propyl, isooctyl and perfluoropropyl groups was synthesized and investigated as corrosion protective coating for AA 2024 alloy. Infrared reflection-absorption (IR RA) combined with X-ray photoelectron spectroscopy and atomic force microscopy provided information about partial self-assembling of coatings having a fluorine enriched upper layer with a low surface energy (#gamma#"t"o"t = 12.37 mN/m). The structural changes that accompanied corrosion produced under chronocoulometrical conditions were assessed from ex-situ IR RA spectra. A new band at 1690-1700 cm"-"1 appeared above the corrosion potential, and was assigned to the formation of amidonium ions and consequent relaxation of urea-urea associations.

International Nuclear Information System (INIS)

The authors compared unenhanced and contrast-enhanced fast MRI and Computerized Tomography in the detection of liver metastases. Eleven patients with single or multiple hepatic lesions (42 in all) were submitted to V and magnetic resonance studies; T1- and T2- weighted TSE, T2-weighted TSE with fat suppression, unenhanced breath-hold TFE and early or delayed enhanced breath-hold TFE images were acquired with a 1.5 T superconductive magnet (Philips NT). The quantitative analysis of all magnetic resonance images was performed for contrast/noise ratio (CNR) and number of detected lesions; magnetic resonance and Computerized Tomography images were also compared qualitatively for lesion conspicuity, anatomical structure identification and artifacts. The results were compared with Student's test. Early enhanced breath-hold TFE was statistically superior to T1-weighted TSE (p = .0009), T2-weighted TSE (p = .01) and Computerized Tomography ( p = .0004) ...

International Nuclear Information System (INIS)

A simple model is used to explain the decrease in superconducting critical temperature with damage observed for irradiated A-15 compounds. A truncated t-matrix approximation is used to describe the disorder along the one-dimensional transition metal chains. Three dimensionality is introduced by the inclusion of interaction between transition metal atoms on different chains. Numerical fits to experiment are discussed in the conclusion. (author).

International Nuclear Information System (INIS)

The defect-induced effect on superconducting transition temperature T_c of A-15 compounds is examined. T_c is found from the Eliashberg equations which take into account the defect-induced changes in the electron-phonon spectral function and electron density of states. The dependence of T_c on the defect type in the superconductor is obtained.

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The concept of the minimum propagating zone (MPZ) is used to examine the causes of quenches in ISABELLE cosine theta superconducting dipole magnets. The size of disturbances large enough to exceed the MPZ and initiate quenches is estimated and compared with the size of disturbances which may be produced in the magnets. A suggestion for reducing the size of these disturbances through individual support of the coil block is outlined.

Energy Technology Data Exchange (ETDEWEB)

A brief article gives an update on the commercial exploitation of superconductivity by the American Superconductor Corporation. Potential applications include transmission and distribution, motors, magnetic storage systems, current limiters and transport. The company have produced a kilometre long, ''wrappable'' cable capable of carrying thousands of amps when operating at a temperature of below -140[sup o]C. (UK)

CERN Multimedia

This 5-cell superconducting cavity, made from bulk-Nb, stems from the period of general studies, not all directed towards direct use at LEP. This one is dimensioned for 1.5 GHz, the frequency used at CEBAF and also studied at Saclay (LEP RF was 352.2 MHz). See also 7908227, 8007354, 8209255, 8210054, 8312339.

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Experimentally it is found that at constant temperature the order-parameter relaxation time, tausub(..delta..), decreases with increasing power of the microwaves, coupled into a superconducting strip. If the same increase in critical current, that corresponds with a given power of the microwaves, is obtained by lowering the temperature, the decrease in tausub(..delta..) is smaller. This reflects the fact that quasiparticles are removed more efficiently from the gap edge by microwaves than by lowering the temperature in equilibrium. A modified time-dependent Ginzburg-Landau equation is shown to describe these results adequately.

International Nuclear Information System (INIS)

Electron microscopic observations of neutron irradiated Nb_3Sn revealed the presence of highly disordered regions of size approximately 35 A in a much less disordered matrix. This observation is shown to provide a means of explaining quantitatively many superconducting properties of irradiated A-15 compounds. In particular Tsub(c) of the irradiated materials could be easily predicted using the mathematical formulations developed for the proximity effect. (Auth.).

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(12/11)CASSCF and (12/11)CASPT2 ab initio electronic structure calculations with both the cc-pVDZ and cc-pVTZ basis sets find that there is a barrier to the very exothermic hydrogen shift that converts singlet methylnitrene, CH{sub 3}N, to methyleneimine, H{sub 2}C{double{underscore}bond}NH. These two energy minima are connected by a transition structure of C{sub s} symmetry, which is computed to lie 3.8 kcal/mol above the reactant at the (12/11)CASPT2/cc-pVTZ//(12/11)CASSCF/cc-pVTZ level of theory. The (12/11)CASSCF/cc-pVTZ value for the lowest frequency vibration in the transition structure is 854 cm{sup {minus}1}, and CASPT2 calculations concur that this a{double{underscore}prime} vibration does indeed have a positive force constant. Thus, there is no evidence that this geometry is actually a mountain top, rather than a transition structure, on the global potential energy surface or that a C{sub 1} ...

Energy Technology Data Exchange (ETDEWEB)

Because of the equivalence principle, a global measurement is necessary to distinguish gravity from acceleration of the reference frame. A gravity gradiometer is therefore an essential instrument needed for precision tests of gravity laws and for applications in gravity survey and inertial navigation. Superconductivity and SQUID (superconducting quantum interference device) technology can be used to obtain a gravity gradiometer with very high sensitivity and stability. A superconducting gravity gradiometer has been developed for a null test of the gravitational inverse-square law and space-borne geodesy. Here we present a complete theoretical model of this instrument. Starting from dynamical equations for the device, we derive transfer functions, a common mode rejection characteristic, and an error model of the superconducting instrument. Since a gradiometer must detect a very weak differential gravity ...

International Nuclear Information System (INIS)

The lasing of the first free-electron laser (FEL) in the world was successfully carried out in 1977, so the history of FELs as a light source is not so long. But FELs are now utilized for research in many scientific and engineering fields owing to such characteristics as tunability of the wavelength, and short pulse and high peak power, which is difficult utilizing a common light source. Research for industrial applications has also been carried out in some fields, such as life sciences, semiconductors, nano-scale measurement, and others. The task for the industrial use of FEL is the realization of high energy efficiency and high optical power. As a means of promoting realization, the combining of an FEL and superconducting linac is now under development in order to overcome the thermal limitations of normal-conducting linacs. Further, since tuning the wavelength is carried out by changing the magnetic density of the undulator, which is now induced by moving part ...

Science.gov (United States)

The spread spectrum acquisition and tracking performance for the Shuttle S-band and Ku-band communication links are analyzed and compared to test results. The S-band link requirements are more severe than those of the Ku-band links, hence, different despreader designs were developed for the two systems. The S-band despreader acquires pseudonoise code lock by examining all possible code phases in half chip steps while the Ku-band despreader acquires pseudonoise code lock by continuously sweeping a tau-jitter loop. Both despreaders employ a tau-jitter loop for code tracking. The code tracking performance is computed for the tau-jitter loop and compared to that of the more complex delay lock loop.