On Observing Top Quark Production at the Tevatron

A technique for separating top quark production from Standard Model background events is introduced. It is applicable to the channel in which one top quark decays semi-leptonically and its anti-quark decays hadronically into three jets, or vice versa. The method is shown to discriminate dramatically between Monte Carlo generated events with and without simulated top quarks of mass around 120 GeV and above. The simulations were performed with CDF detector characteristics incorporated, showing that the method is applicable to existing data.Comment: 8 pages, TUFTS-TH-92-G01 (Two minor TeX mistakes corrected

Pregnancy and cardiac disease

PKMedical disorders in pregnancy are one of the top five causes of maternal mortality in South Africa (SA), cardiac disease (CD) being the main contributor to this group. In developed countries, surgically corrected congenital heart disease (CHD) comprises the greater proportion of maternal deaths from CD. In SA and other developing countries, acquired heart disease such as rheumatic heart disease and cardiomyopathies are the major causes, although CHD remains significantly represented. Both congenital and acquired cardiac lesions may present for the first time during pregnancy. CD may also occur for the first time during or after pregnancy, e.g. peripartum cardiomyopathy. The risk to both the mother and the fetus increases exponentially with the complexity of the underlying disease. Generally, the ability to tolerate a pregnancy is related to: (i) the haemodynamic significance of any lesion; (ii) the functional class – New York Heart Association classes III and IV have poorer outcomes; (iii) the presence of cyanosis; and (iv) the presence of pulmonary hypertension. While the ideal time to assess these factors is before conception, women frequently present when already pregnant. This review discusses risk assessment and management of CD in pregnant women and the role of a combined cardiology and obstetric clinic

Planar multilayer circuit quantum electrodynamics

Experimental quantum information processing with superconducting circuits is rapidly advancing, driven by innovation in two classes of devices, one involving planar micro-fabricated (2D) resonators, and the other involving machined three-dimensional (3D) cavities. We demonstrate that circuit quantum electrodynamics can be implemented in a multilayer superconducting structure that combines 2D and 3D advantages. We employ standard micro-fabrication techniques to pattern each layer, and rely on a vacuum gap between the layers to store the electromagnetic energy. Planar qubits are lithographically defined as an aperture in a conducting boundary of the resonators. We demonstrate the aperture concept by implementing an integrated, two cavity-modes, one transmon-qubit system

Blood pressure measurements in the ankle are not equivalent to blood pressure measurements in the arm

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The reconfigurable Josephson circulator/directional amplifier

Circulators and directional amplifiers are crucial non-reciprocal signal routing and processing components involved in microwave readout chains for a variety of applications. They are particularly important in the field of superconducting quantum information, where the devices also need to have minimal photon losses to preserve the quantum coherence of signals. Conventional commercial implementations of each device suffer from losses and are built from very different physical principles, which has led to separate strategies for the construction of their quantum-limited versions. However, as recently proposed theoretically, by establishing simultaneous pairwise conversion and/or gain processes between three modes of a Josephson-junction based superconducting microwave circuit, it is possible to endow the circuit with the functions of either a phase-preserving directional amplifier or a circulator. Here, we experimentally demonstrate these two modes of operation of the same circuit. Furthermore, in the directional amplifier mode, we show that the noise performance is comparable to standard non-directional superconducting amplifiers, while in the circulator mode, we show that the sense of circulation is fully reversible. Our device is far simpler in both modes of operation than previous proposals and implementations, requiring only three microwave pumps. It offers the advantage of flexibility, as it can dynamically switch between modes of operation as its pump conditions are changed. Moreover, by demonstrating that a single three-wave process yields non-reciprocal devices with reconfigurable functions, our work breaks the ground for the development of future, more-complex directional circuits, and has excellent prospects for on-chip integration