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Search Results: 1 - 10 of 352352 matches for " W. J. Weber "
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The Generalized Gutzwiller Method for n=>2 Correlated Bands: First Order Metal-Insulator Transitions
J. Buenemann,W. Weber
Physics , 1996,
Abstract: We have generalized the Gutzwiller method to the cases of n=>2 correlated bands and report studies on a degenerate two-band model with Hund's rule type on-site interactions. At half band filling the metal-insulator transitions are usually of first order.
The Generalized Gutzwiller Method for n=>2 Correlated Orbitals: Itinerant Ferromagnetism in eg-bands
J. Buenemann,W. Weber
Physics , 1996, DOI: 10.1016/S0921-4526(96)00596-0
Abstract: Using the generalized Gutzwiller method we present results on the ferromagnetic behavior of extended Hubbard models with two degenerate eg orbitals. We find significant differences to results obtained from Hartree-Fock theory.
Psychosocial outcomes for children receiving a kidney transplant: a 30 year follow-up of patients of the Centre for Paediatric Nephrology, Münster
J. Prüfe,W. Weber
Transplantationsmedizin , 2010,
Abstract: Aim/Background: The aim of this single-centre study is to assess the social development of children suffering from early onset chronic renal disease into adulthood. A focus is put on their education and professional life as well as on their family life and satisfaction with life. Material/Methods: 57 former patients of the centre for paediatric nephrology in Münster (Germany) who received a kidney-transplant during childhood and adolescence where asked to complete a postal questionnaire. The survey asked for information on family life, schooling, vocational qualification and employment. Furthermore the participants’ satisfaction with life was assessed by the standardized Questionnaire on Satisfaction in Life (FLZ)”.Results: 50 participants (87,7%) returned a fully completed questionnaire. The average age of participants was 30,7 years (SD: 7,3; range: 20,0-44,2). 38 (76%) of them had a functioning graft. All but 5 participants had a secondary school degree. 42 (84%) participants had completed a professional training or were still in education. At the time of assessment 25 participants (50%) were working. The level of education was lower compared to the general population. 30 participants (60%) lived on their own or with a partner. 5 women had given birth to a total of 6 children; 3 men had become fathers. The mean general and health-related satisfaction with life is not significantly reduced as compared to the age matched general population. However, there were subscores of significant difference showing that participants were dissatisfied with their “partnership/sexuality”, their “family life / offspring” and their “income” as well as with their “physical condition” and their “ability to relax”.Conclusions: In individual cases social development can be almost unimpaired. However in general there is a widely reported dissatisfaction concerning specific areas of general as well as health-related quality of life. Also the social development in regard to the domestic situation and employment is hindered. This indicates a negative impact of early onset chronic renal disease on the social development. A need for psychosocial support to allow for an improved development into adulthood can be stated.
Multi-band Gutzwiller wave functions for general on-site interactions
J. Bünemann,W. Weber,F. Gebhard
Physics , 1997, DOI: 10.1103/PhysRevB.57.6896
Abstract: We introduce Gutzwiller wave functions for multi-band models with general on-site Coulomb interactions. As these wave functions employ correlators for the exact atomic eigenstates they are exact both in the non-interacting and in the atomic limit. We evaluate them in infinite lattice dimensions for all interaction strengths without any restrictions on the structure of the Hamiltonian or the symmetry of the ground state. The results for the ground-state energy allow us to derive an effective one-electron Hamiltonian for Landau quasi-particles, applicable for finite temperatures and frequencies within the Fermi-liquid regime. As applications for a two-band model we study the Brinkman-Rice metal-to-insulator transition at half band-filling, and the transition to itinerant ferromagnetism for two specific fillings, at and close to a peak in the density of states of the non-interacting system. Our new results significantly differ from those for earlier Gutzwiller wave functions where only density-type interactions were included. When the correct spin symmetries for the two-electron states are taken into account, the importance of the Hund's-rule exchange interaction is even more pronounced and leads to paramagnetic metallic ground states with large local magnetic moments. Ferromagnetism requires fairly large interaction strengths, and the resulting ferromagnetic state is a strongly correlated metal.
On the way to a Gutzwiller density functional theory
W. Weber,J. Buenemann,F. Gebhard
Physics , 2001,
Abstract: Multi-band Gutzwiller-correlated wave functions reconcile the contrasting concepts of itinerant band electrons versus electrons localized in partially filled atomic shells. The exact evaluation of these variational ground states in the limit of large coordination number allows the identification of quasi-particle band structures, and the calculation of a variational spinwave dispersion. The study of a generic two-band model elucidates the co-operation of the Coulomb repulsion and the Hund's-rule exchange for itinerant ferromagnetism. We present results of calculations for ferromagnetic nickel, using a realistic 18 spin-orbital basis of $4s$, $4p$ and $3d$ valence electrons. The quasi-particle energy bands agree much better with the photo-emission and Fermi surface data than the band structure obtained from spin-density functional theory (SDFT).
Stress dependence of the critical currents in neutron irradiated (RE)BCO coated conductors
J. Emhofer,M. Eisterer,H. W. Weber
Physics , 2013, DOI: 10.1088/0953-2048/26/3/035009
Abstract: The application of HTS coated conductors in future fusion or accelerator magnets is currently of increasing interest. High Lorentz forces and therefore high hoop stresses act on the conductors in large coils. The conductor is furthermore exposed to neutron radiation in fusion or accelerator magnets. The expected neutron fluence over the desired lifetime of such magnets can be simulated by irradiation experiments in a fission reactor. The coated conductors were characterized in the pristine state and after irradiation to the ITER design fluence. The sensitivity of the critical currents to applied stress was measured in liquid nitrogen. The cold part of the set-up was positioned between a rotatable split coil electro-magnet for assessing the Ic-anisotropy up to 1.4T under maximum Lorentz force configuration. The Ic-sensitivity to applied stress changed significantly in the GdBCO/IBADconductors after irradiation, whereas nearly no change was observed in the YBCO/RABiTS-conductor. Furthermore, Ic and Tc were strongly reduced in the GdBCO/IBAD-sample after irradiation. The angular dependence of Ic changed for both samples in different ways after the irradiation, but no change in the angular dependence was observed upon applying stress. The high neutron capture cross-section of Gd and the resulting strong reduction of Tc seem to be responsible for the different stress dependence of Ic in irradiated Gd-123 coated conductors.
Thoraco-Lumbar Junction Disc Herniation and Tight Filum: A Unique Combination?  [PDF]
Erwin M. J. Cornips, Emile A. M. Beuls, Biene W. Weber, Johannes S. H. Vles
International Journal of Clinical Medicine (IJCM) , 2014, DOI: 10.4236/ijcm.2014.512094

Purpose: The incidence of both symptomatic thoraco-lumbar junction disc herniation (TLJDH) and tight filum (TF) may be underestimated. Both conditions have a complex clinical presentation that may involve the distal spinal cord, conus medullaris, and/or cauda equina, including upper and/or lower motor neuron impairment, sensory impairment, urological and sexual dysfunction. The coexistence of both conditions has not been previously reported and may be a diagnostic and therapeutic challenge. Methods: We report three teenage girls, a 24-year-old woman, and two middle-aged women who were diagnosed with both conditions and treated at our institution. Results: Disc herniation level was T11-T12 in 2, T12-L1 in 3, and L1-L2 in one. All patients had a fatty filum (n = 5) and/or a low-lying CM (at or above L1-L2 in 2, at or below L2-L3 in 4), and were treated with filum sectioning first. All patients noted marked improvement of preoperative complaints including back pain (n = 5), leg pain and fatigue (n = 4), urological complaints (n = 4), and toe gait (n = 1). One 16-year-old girl successfully underwent a thoracoscopic microdiscectomy for persisting pain at the thoraco-lumbar junction two years after filum sectioning. Conclusions: Thoraco-lumbar junction disc herniation and tight filum both act on the distal spinal cord close to the transition to the cauda equina. Both conditions may coincide and may even act synergistically, the disc herniation acting as a fulcrum, aggravating the deleterious effect of the tethering force (and vice versa). This might explain why both conditions combined may present at a younger age. We suggest filum sectioning as the primary treatment option in all patients, however, more cases and a longer follow-up are needed to better understand their unique combination and interaction. Nevertheless, when confronted with a symptomatic TLJDH especially in young patients we advise to rule out a coinciding TF by careful consideration of all clinical, radiological, and urological data.

Real-time earthquake monitoring for tsunami warning in the Indian Ocean and beyond
W. Hanka,J. Saul,B. Weber,J. Becker
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2010, DOI: 10.5194/nhess-10-2611-2010
Abstract: The Mw = 9.3 Sumatra earthquake of 26 December 2004 generated a tsunami that affected the entire Indian Ocean region and caused approximately 230 000 fatalities. In the response to this tragedy the German government funded the German Indonesian Tsunami Early Warning System (GITEWS) Project. The task of the GEOFON group of GFZ Potsdam was to develop and implement the seismological component. In this paper we describe the concept of the GITEWS earthquake monitoring system and report on its present status. The major challenge for earthquake monitoring within a tsunami warning system is to deliver rapid information about location, depth, size and possibly other source parameters. This is particularly true for coast lines adjacent to the potential source areas such as the Sunda trench where these parameters are required within a few minutes after the event in order to be able to warn the population before the potential tsunami hits the neighbouring coastal areas. Therefore, the key for a seismic monitoring system with short warning times adequate for Indonesia is a dense real-time seismic network across Indonesia with densifications close to the Sunda trench. A substantial number of supplementary stations in other Indian Ocean rim countries are added to strengthen the teleseismic monitoring capabilities. The installation of the new GITEWS seismic network – consisting of 31 combined broadband and strong motion stations – out of these 21 stations in Indonesia – is almost completed. The real-time data collection is using a private VSAT communication system with hubs in Jakarta and Vienna. In addition, all available seismic real-time data from the other seismic networks in Indonesia and other Indian Ocean rim countries are acquired also directly by VSAT or by Internet at the Indonesian Tsunami Warning Centre in Jakarta and the resulting "virtual" network of more than 230 stations can jointly be used for seismic data processing. The seismological processing software as part of the GITEWS tsunami control centre is an enhanced version of the widely used SeisComP software and the well established GEOFON earthquake information system operated at GFZ in Potsdam (http://geofon.gfz-potsdam.de/db/eqinfo.php). This recently developed software package (SeisComP3) is reliable, fast and can provide fully automatic earthquake location and magnitude estimates. It uses innovative visualization tools, offers the possibility for manual correction and re-calculation, flexible configuration, support for distributed processing and data and parameter exchange with external monitoring
Photoenergy: Progress in Si-Related Solar Cells for a Low Cost and High Efficiency
J. Yi,Eicke R. Weber,C. W. Lan,Stephen Bremner
International Journal of Photoenergy , 2012, DOI: 10.1155/2012/486706
Observing single quantum trajectories of a superconducting qubit
K. W. Murch,S. J. Weber,C. Macklin,I. Siddiqi
Physics , 2013, DOI: 10.1038/nature12539
Abstract: The length of time that a quantum system can exist in a superposition state is determined by how strongly it interacts with its environment. This interaction entangles the quantum state with the inherent fluctuations of the environment. If these fluctuations are not measured, the environment can be viewed as a source of noise, causing random evolution of the quantum system from an initially pure state into a statistical mixture-a process known as decoherence. However, by accurately measuring the environment in real time, the quantum system can be maintained in a pure state and its time evolution described by a quantum trajectory conditioned on the measurement outcome. We employ weak measurements to monitor a microwave cavity embedding a superconducting qubit and track the individual quantum trajectories of the system. In this architecture, the environment is dominated by the fluctuations of a single electromagnetic mode of the cavity. Using a near-quantum-limited parametric amplifier, we selectively measure either the phase or amplitude of the cavity field, and thereby confine trajectories to either the equator or a meridian of the Bloch sphere. We perform quantum state tomography at discrete times along the trajectory to verify that we have faithfully tracked the state of the quantum system as it diffuses on the surface of the Bloch sphere. Our results demonstrate that decoherence can be mitigated by environmental monitoring and validate the foundations of quantum feedback approaches based on Bayesian statistics. Moreover, our experiments suggest a new route for implementing what Schrodinger termed "quantum steering"-harnessing action at a distance to manipulate quantum states via measurement.
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