Optimization of the extraordinary magnetoresistance in semiconductor-metal hybrid structures for magnetic-field sensor applications

Semiconductor-metal hybrid structures can exhibit a very large geometrical magnetoresistance effect, the so-called extraordinary magnetoresistance (EMR) effect. In this paper, we analyze this effect by means of a model based on the finite element method and compare our results with experimental data. In particular, we investigate the important effect of the contact resistance $\rho_c$ between the semiconductor and the metal on the EMR effect. Introducing a realistic $\rho_c=3.5\times 10^{-7} \Omega{\rm cm}^2$ in our model we find that at room temperature this reduces the EMR by 30% if compared to an analysis where $\rho_c$ is not considered.Comment: 4 pages; manuscript for MSS11 conference 2003, Nara, Japa

Marked variation in venous thromboprophylaxis management for abdominal aortic aneurysm repair; results of survey amongst vascular surgeons in the United Kingdom

Objectives: We aimed to survey the current management of venous thromboprophylaxis in patients undergoing elective surgery for abdominal aortic aneurysm (AAA) by vascular surgeons in the United Kingdom. Design: A questionnaire was designed to investigate anticoagulation strategies in the perioperative period of elective AAA repair, both open and endovascular. This included both chemical and mechanical prophylaxis. A total of 395 questionnaires was posted to the members of the Vascular Society of Great Britain and Ireland. Results: One hundred and seventy-two (44%) valid responses were received. Half of the respondents administered pre-operative chemical prophylaxis at a mean of 13 h prior to AAA surgery. There was a high level of concordance in administration of heparin during surgery and in thromboprophylaxis post-operatively, with 97% giving some form of thromboprophylaxis. However there was a variation in the dose and timing, if administered, of chemical and mechanical prophylaxis. Conclusion: The survey revealed diversity in perioperative thromboprophylaxis strategies among vascular surgeons. This suggests that standardisation of pre-operative and post-operative mechanical and chemical thromboprophylaxis may be required which could potentially improve the outcomes in elective management of AAA in the UK

Bilinear and quadratic Hamiltonians in two-mode cavity quantum electrodynamics

In this work we show how to engineer bilinear and quadratic Hamiltonians in cavity quantum electrodynamics (QED) through the interaction of a single driven two-level atom with cavity modes. The validity of the engineered Hamiltonians is numerically analyzed even considering the effects of both dissipative mechanisms, the cavity field and the atom. The present scheme can be used, in both optical and microwave regimes, for quantum state preparation, the implementation of quantum logical operations, and fundamental tests of quantum theory.Comment: 11 pages, 3 figure

Experimental approximation of the Jones polynomial with DQC1

We present experimental results approximating the Jones polynomial using 4 qubits in a liquid state nuclear magnetic resonance quantum information processor. This is the first experimental implementation of a complete problem for the deterministic quantum computation with one quantum bit model of quantum computation, which uses a single qubit accompanied by a register of completely random states. The Jones polynomial is a knot invariant that is important not only to knot theory, but also to statistical mechanics and quantum field theory. The implemented algorithm is a modification of the algorithm developed by Shor and Jordan suitable for implementation in NMR. These experimental results show that for the restricted case of knots whose braid representations have four strands and exactly three crossings, identifying distinct knots is possible 91% of the time.Comment: 5 figures. Version 2 changes: published version, minor errors corrected, slight changes to improve readabilit

Nonadiabatic coherent evolution of two-level systems under spontaneous decay

In this paper we extend current perspectives in engineering reservoirs by producing a time-dependent master equation leading to a nonstationary superposition equilibrium state that can be nonadiabatically controlled by the system-reservoir parameters. Working with an ion trapped inside a nonindeal cavity we first engineer effective Hamiltonians that couple the electronic states of the ion with the cavity mode. Subsequently, two classes of decoherence-free evolution of the superposition of the ground and decaying excited levels are achieved: those with time-dependent azimuthal or polar angle. As an application, we generalise the purpose of an earlier study [Phys. Rev. Lett. 96, 150403 (2006)], showing how to observe the geometric phases acquired by the protected nonstationary states even under a nonadiabatic evolution.Comment: 5 pages, no figure

Interplay between hormones, the immune system, and metabolic disorders

No abstract available