Electron supersurface scattering on polycrystalline Au

Supersurface electron scattering, i.e., electron energy losses and associated deflections in vacuum above the surface of a medium, is shown to contribute significantly to electron spectra. We have obtained experimental verification (in absolute units) of theoretical predictions that the angular distribution of the supersurface backscattering probability exhibits strong oscillations which are anticorrelated with the generalized Ramsauer-Townsend minima in the backscattering probability. We have investigated 500-eV electron backscattering from an Au surface for an incidence angle of 70° and scattering angles between 37° and 165°. After removing the contribution of supersurface scattering from the experimental data, the resulting angular and energy distribution agrees with the Landau-Goudsmit-Saunderson (LGS) theory, which was proposed about 60 years ago, while the raw data are anticorrelated with LGS theory. This result implies that supersurface scattering is an essential phenomenon for quantitative understanding of electron spectra

Relativistic general-order coupled-cluster method for high-precision calculations: Application to Al+ atomic clock

We report the implementation of a general-order relativistic coupled-cluster method for performing high-precision calculations of atomic and molecular properties. As a first application, the static dipole polarizabilities of the ground and first excited states of Al+ have been determined to precisely estimate the uncertainty associated with the BBR shift of its clock frequency measurement. The obtained relative BBR shift is -3.66+-0.44 for the 3s^2 ^1S_0^0 --> 3s3p ^3P_0^0 transition in Al+ in contrast to the value obtained in the latest clock frequency measurement, -9+-3 [Phys. Rev. Lett. 104, 070802 (2010)]. The method developed in the present work can be employed to study a variety of subtle effects such as fundamental symmetry violations in atoms.Comment: 4 pages, 3 tables, submitte

CORRESPONDENCE BETWEEN GEOMETRIC PROPERTIES OF REAL OBJECTS AND THE HUYNEN PARAMETERS

This paper presents an approach to classify real objects, using polarimetric radar data, on the basis of the Huynen parameters (HUYNEN, 1970). For this purpose a computer pro- gram was developed to calculate and display the Huynen parameters from the polarimetric scattering matrix S, which is measured over a wide frequency range. It is demonstrated here that the Huynen theory is correct and applicable to electromagnetic inverse scattering problems to derive target classification operators

The electronic structure and the phases of BaVS3

BaVS3 is a moderately correlated d-electron system with a rich phase diagram. To construct the corresponding minimal electronic model, one has to decide which d-states are occupied, and to which extent. The ARPES experiment presented here shows that the behavior of BaVS3 is governed by the coexistence of wide-band (A_1g) and narrow-band (twofold degenerate E) d-electrons. We sketch a lattice fermion model which may serve as a minimal model of BaVS3. This serves foremost for the understanding of the metal-insulator in pure BaVS3 and its absence in some related compounds. The nature of the low temperature magnetic order differs for several systems which may be described in terms of the same electron model. We describe several recent experiments which give information about magnetic order at high pressures. In particular, we discuss field-induced insulator-to-metal transition at slightly subcritical pressures, and an evidence for magnetic order in the high-pressure metallic phase. The phase diagram of Sr-doped BaVS3 is also discussed. The complexity of the phases of BaVS3 arises from the fact that it is simultaneously unstable against several kinds of instabilities.Comment: Presented at the International Conference on Magnetism 2006 (Kyoto), 6 pages, 9 figure

Magnetic and Transport Properties of Fe-Ag granular multilayers

Results of magnetization, magnetotransport and Mossbauer spectroscopy measurements of sequentially evaporated Fe-Ag granular composites are presented. The strong magnetic scattering of the conduction electrons is reflected in the sublinear temperature dependence of the resistance and in the large negative magnetoresistance. The simultaneous analysis of the magnetic properties and the transport behavior suggests a bimodal grain size distribution. A detailed quantitative description of the unusual features observed in the transport properties is given

Factor H autoantibodies in atypical hemolytic uremic syndrome correlate with CFHR1/CFHR3 deficiency

Atypical hemolytic uremic syndrome (aHUS) is a severe renal disease that is associated with defective complement regulation caused by multiple factors. We previously described the deficiency of factor H-related proteins CFHR1 and CFHR3 as predisposing factor for aHUS. Here we identify in an extended cohort of 147 aHUS patients that 16 juvenile individuals (ie, 11%) who either lacked the CFHR1/CFHR3 completely (n = 14) or showed extremely low CFHR1/CFHR3 plasma levels (n = 2) are positive for factor H (CFH) autoantibodies. The binding epitopes of all 16 analyzed autoantibodies were localized to the C-terminal recognition region of factor H, which represents a hot spot for aHUS mutations. Thus we define a novel subgroup of aHUS, termed DEAP HUS (deficiency of CFHR proteins and CFH autoantibody positive) that is characterized by a combination of genetic and acquired factors. Screening for both factors is obviously relevant for HUS patients as reduction of CFH autoantibody levels represents a therapeutic option

Anti-factor B autoantibody in dense deposit disease

Dense deposit disease (DDD), also known as membranoproliferative glomerulonephritis type II, is a rare kidney disorder that is associated with dysregulation of the alternative pathway of complement. Autoantibodies against the C3bBb convertase termed C3 nephritic factor are common in DDD patients. Here we report an autoantibody that binds to complement factor B in a DDD patient who was negative for C3 nephritic factor. This anti-factor B autoantibody recognized an epitope within the Bb fragment and was able to bind to the C3bBb convertase. Upon binding, the anti-factor B autoantibody stabilized the convertase against both intrinsic and factor H-mediated extrinsic decay and thus enhanced C3 consumption. Functional analyses demonstrated that, in contrast to C3 nephritic factor, the anti-factor B autoantibody inhibited complement-mediated lysis in vitro due to inhibition of the C5 convertase and the terminal complement pathway. Analysis of C5a plasma levels indicated that not all C5 convertases are inhibited by the autoantibodies in the patient in vivo. Antigen array experiments confirmed the presence of anti-factor B autoantibodies and also revealed complement activating anti-C1q antibodies in the patient's plasma. In summary, the present report describes a new autoantibody in DDD that binds to factor B and to the alternative pathway C3 convertase and alters the kinetics of complement activation and regulation. (C) 2010 Elsevier Ltd. All rights reserved

Quantum rings with time dependent spin-orbit coupling: Rabi oscillations, spintronic Schrodinger-cat states, and conductance properties

The strength of the (Rashba-type) spin-orbit coupling in mesoscopic semiconductor rings can be tuned with external gate voltages. Here we consider the case of a periodically changing spin-orbit interaction strength as induced by sinusoidal voltages. In a closed one dimensional quantum ring with weak spin-orbit coupling, Rabi oscillations are shown to appear. We find that the time evolution of initially localized wave packets exhibits a series of collapse and revival phenomena. Partial revivals -- that are typical in nonlinear systems -- are shown to correspond to superpositions of states localized at different spatial positions along the ring. These "spintronic Schrodinger-cat sates" appear periodically, and similarly to their counterparts in other physical systems, they are found to be sensitive to environment induced disturbances. The time dependent spin transport problem, when leads are attached to the ring, is also solved. We show that the "sideband currents" induced by the oscillating spin-orbit interaction strength can become the dominant output channel, even in the presence of moderate thermal fluctuations and random scattering events.Comment: 11 pages, 9 figures, submitted to PR

Kondo Behavior of U in CaB6_6

Replacing U for Ca in semiconducting CaB$_6$ at the few at.% level induces metallic behaviour and Kondo-type phenomena at low temperatures, a rather unusual feature for U impurities in metallic hosts. For Ca$_{0.992}$U$_{0.008}$B$_6$, the resistance minimum occurs at $T$ = 17 K. The subsequent characteristic logarithmic increase of the resistivity with decreasing temperature merges into the expected $T^2$ dependence below 0.8 K. Data of the low-temperature specific heat and the magnetization are analyzed by employing a simple resonance-level model. Analogous measurements on LaB$_6$ with a small amount of U revealed no traces of Kondo behavior, above 0.4 K.Comment: 4 pages, 4 figures, submitted for publication to Europhysics Letter

Anomalous Hall effect in (In,Mn)Sb dilute magnetic semiconductor

High magnetic field study of Hall resistivity in the ferromagnetic phase of (In,Mn)Sb allows one to separate its normal and anomalous components. We show that the anomalous Hall term is not proportional to the magnetization, and that it even changes sign as a function of magnetic field. We also show that the application of pressure modifies the scattering process, but does not influence the Hall effect. These observations suggest that the anomalous Hall effect in (In,Mn)Sb is an intrinsic property and support the application of the Berry phase theory for (III,Mn)V semiconductors. We propose a phenomenological description of the anomalous Hall conductivity, based on a field-dependent relative shift of the heavy- and light-hole valence bands and the split-off band