Electron spin-orbit splitting in InGaAs/InP quantum well studied by means of the weak antilocalization and spin-zero effects in tilted magnetic fields

The coupling between Zeeman spin splitting and Rashba spin-orbit terms has been studied experimentally in a gated InGaAs/InP quantum well structure by means of simultaneous measurements of the weak antilocalization (WAL) effect and beating in the SdH oscillations. The strength of the Zeeman splitting was regulated by tilting the magnetic field with the spin-zeros in the SdH oscillations, which are not always present, being enhanced by the tilt. In tilted fields the spin-orbit and Zeeman splittings are not additive, and a simple expression is given for the energy levels. The Rashba parameter and the electron g-factor were extracted from the position of the spin zeros in tilted fields. A good agreement is obtained for the spin-orbit coupling strength from the spin-zeros and weak antilocalization measurements.Comment: Accepted for publication in Semiconductors Science and Technolog

New skeletal tuberculosis cases in past populations from Western Hungary (Transdanubia)

The distribution, antiquity and epidemiology of tuberculosis (TB) have previously been studied in osteoarchaeological material in the eastern part of Hungary, mainly on the Great Plain. The purpose of this study is to map the occurrence of skeletal TB in different centuries in the western part of Hungary, Transdanubia, and to present new cases we have found. Palaeopathological analysis was carried out using macroscopic observation supported by radiographic and molecular methods. A large human osteoarchaeological sample (n = 5684) from Transdanubian archaeological sites ranging from the 2nd to the 18th centuries served as a source of material. Spinal TB was observed in seven individuals (in three specimens with Pott's disease two of which also had cold abscess) and hip TB was assumed in one case. The results of DNA for Mycobacterium tuberculosis were positive in seven of the eight cases identified by paleopathology, and negative in the assumed case of hip TB. However, the molecular results are consistent with highly fragmented DNA, which limited further analysis. Based on the present study and previously published cases, osteotuberculosis was found in Transdanubia mainly during the 9th–13th centuries. However, there are no signs of TB in many other 9th–13th century sites, even in those that lie geographically close to those where osteotuberculous cases were found. This may be due to a true absence of TB caused by the different living conditions, way of life, or origin of these populations. An alternative explanation is that TB was present in some individuals with no typical paleopathology, but that death occurred before skeletal morphological features could develop

Effects of Magnetic Field on Josephson Current in SNS System

The effect of a magnetic field on Josephson current has been studied for a superconductor/normal-metal/superconductor (SNS) system, where N is a two-dimensional electron gas in a confining potential. It is found that the dependence of Josephson currents on the magnetic field are sensitive to the width of the normal metal. If the normal metal is wide and contains many channels (subbands), the current on a weak magnetic field shows a dependence similar to a Fraunhofer-pattern in SIS system and, as the field gets strong, it shows another type of oscillatory dependence on the field resulting from the Aharonov-Bohm interference between the edge states. As the number of channels decreases (i.e. normal metal gets narrower), however, the dependence in the region of the weak field deviates from a clear Fraunhofer pattern and the amplitude of the oscillatory dependence in the region of the strong field is reduced.Comment: 14 pages, 9 figure

Ascending aortic remodelling in Fabry disease after long-term enzyme replacement therapy.

Previous cross-sectional studies reported a high prevalence of ascending aorta dilations/aneurysms in male adults with Fabry disease, independently of cardiovascular risk factors. To characterise the remodelling of the ascending aorta in classic Fabry disease under long-term enzyme replacement therapy. Diameter of the ascending aorta was measured with magnetic resonance imaging at the sino-tubular junction (STJ), and proximal (pAsAo), and distal ascending aorta (dAsAo) at baseline, and after 5 and 10 years of enzyme replacement therapy in 15 adult Fabry patients (10 males; 5 females). Over a mean follow-up of 9.5 years, the annual expansion rates measured in 10 males with Fabry disease were 0.41 ± 0.16, 0.36 ± 0.25 and 0.41 ± 0.26 mm/y at the STJ, pAsAo and dAsAo, respectively. Expansion rate at the pAsAo level in male patients was significantly higher than the expected expansion projected from theoretical normal values: 0.36 ± 0.25 vs 0.13 ± 0.05, p = 0.017. In 5 females, the annual expansion rates at the STJ, pAsAo and dAsAo were 0.14 ± 0.11, 0.21 ± 0.18 and 0.26 ± 0.24 mm/y, respectively. There was no significant difference from the projected normal expansion rate at the level of the pAsAo: 0.21 ± 0.18 vs 0.13 ± 0.04, p = 0.39. Our data suggest that the remodelling of the ascending aorta is more pronounced in male patients with Fabry disease under long-term enzyme replacement therapy compared with the progression observed in a large population study

Cryptotomography: reconstructing 3D Fourier intensities from randomly oriented single-shot diffraction patterns

We reconstructed the 3D Fourier intensity distribution of mono-disperse prolate nano-particles using single-shot 2D coherent diffraction patterns collected at DESY's FLASH facility when a bright, coherent, ultrafast X-ray pulse intercepted individual particles of random, unmeasured orientations. This first experimental demonstration of cryptotomography extended the Expansion-Maximization-Compression (EMC) framework to accommodate unmeasured fluctuations in photon fluence and loss of data due to saturation or background scatter. This work is an important step towards realizing single-shot diffraction imaging of single biomolecules.Comment: 4 pages, 4 figure

Space-time evolution of electron cascades in diamond

Here we describe model calculations to follow the spatio-temporal evolution of secondary electron cascades in diamond. The band structure of the insulator has been explicitly incorporated into the calculations as it affects ionizations from the valence band. A Monte-Carlo model was constructed to describe the path of electrons following the impact of a single electron of energy E 250 eV. The results show the evolution of the secondary electron cascades in terms of the number of electrons liberated, the spatial distribution of these electrons, and the energy distribution among the electrons as a function of time. The predicted ionization rates (5-13 electrons in 100 fs) lie within the limits given by experiments and phenomenological models. Calculation of the local electron density and the corresponding Debye length shows that the latter is systematically larger than the radius of the electron cloud. This means that the electron gas generated does not represent a plasma in a single impact cascade triggered by an electron of E 250 eV energy. This is important as it justifies the independent-electron approximation used in the model. At 1 fs, the (average) spatial distribution of secondary electrons is anisotropic with the electron cloud elongated in the direction of the primary impact. The maximal radius of the cascade is about 50 A at this time. As the system cools, energy is distributed more equally, and the spatial distribution of the electron cloud becomes isotropic. At 90 fs maximal radius is about 150 A. The Monte-Carlo model described here could be adopted for the investigation of radiation damage in other insulators and has implications for planned experiments with intense femtosecond X-ray sources.Comment: 26 pages, latex, 13 figure

Orbital Magnetism and Current Distribution of Two-Dimensional Electrons under Confining Potential

The spatial distribution of electric current under magnetic field and the resultant orbital magnetism have been studied for two-dimensional electrons under a harmonic confining potential V(\vecvar{r})=m \omega_0^2 r^2/2 in various regimes of temperature and magnetic field, and the microscopic conditions for the validity of Landau diamagnetism are clarified. Under a weak magnetic field (\omega_c\lsim\omega_0, \omega_c being a cyclotron frequency) and at low temperature (T\lsim\hbar\omega_0), where the orbital magnetic moment fluctuates as a function of the field, the currents are irregularly distributed paramagnetically or diamagnetically inside the bulk region. As the temperature is raised under such a weak field, however, the currents in the bulk region are immediately reduced and finally there only remains the diamagnetic current flowing along the edge. At the same time, the usual Landau diamagnetism results for the total magnetic moment. The origin of this dramatic temperature dependence is seen to be in the multiple reflection of electron waves by the boundary confining potential, which becomes important once the coherence length of electrons gets longer than the system length. Under a stronger field (\omega_c\gsim\omega_0), on the other hand, the currents in the bulk region cause de Haas-van Alphen effect at low temperature as T\lsim\hbar\omega_c. As the temperature gets higher (T\gsim\hbar\omega_c) under such a strong field, the bulk currents are reduced and the Landau diamagnetism by the edge current is recovered.Comment: 15 pages, 11 figure