76,522 research outputs found

    Titanium reinforced boron polyimide composite

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    Program involves development of process technique for boron-polyimide prepeg, lay-up and curing procedures for prepegs when processed under vacuum bag pressure, and development and evaluation of titanium hard points for smooth transition of loads from titanium attach points into boron reinforced body of structure

    Entanglement and entropy engineering of atomic two-qubit states

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    We propose a scheme employing quantum-reservoir engineering to controllably entangle the internal states of two atoms trapped in a high finesse optical cavity. Using laser and cavity fields to drive two separate Raman transitions between metastable atomic ground states, a system is realized corresponding to a pair of two-state atoms coupled collectively to a squeezed reservoir. Phase-sensitive reservoir correlations lead to entanglement between the atoms, and, via local unitary transformations and adjustment of the degree and purity of squeezing, one can prepare entangled mixed states with any allowed combination of linear entropy and entanglement of formation.Comment: 4 pages, 5 figures, REVTe

    Metal alloy resistivity measurements at very low temperatures

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    High speed, automated system accurately measures to approximately one percent in three minutes. System identifies materials having constant thermal or electric conductivity, predicts new material properties, develops alloys in accordance with desired specifications, and develops nondestructive devices for measuring precipitation hardening

    A survey of compatibility of materials with high pressure oxygen service

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    The available information on the compatibility of materials with oxygen as applied to the production, transport, and applications experience of high pressure liquid and gaseous oxygen is compiled. High pressure is defined as about 2000 to 3000 psia. Since high pressure projections sometimes can be made from lower pressure data, some low pressure data are also included. Low pressure data are included if they are considered helpful to a better understanding of the behavior at high pressures

    Symmetry-constrained electron vortex propagation

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    Electron vortex beams hold great promise for development in transmission electron microscopy, but have yet to be widely adopted. This is partly due to the complex set of interactions that occur between a beam carrying orbital angular momentum (OAM) and a sample. Herein, the system is simplified to focus on the interaction between geometrical symmetries, OAM and topology. We present multiple simulations, alongside experimental data to study the behaviour of a variety of electron vortex beams after interacting with apertures of different symmetries, and investigate the effect on their OAM and vortex structure, both in the far-field and under free-space propagation.Comment: 11 page

    Quantitative measurement of orbital angular momentum in electron microscopy

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    Electron vortex beams have been predicted to enable atomic scale magnetic information measurement, via transfer of orbital angular momentum. Research so far has focussed on developing production techniques and applications of these beams. However, methods to measure the outgoing orbital angular momentum distribution are also a crucial requirement towards this goal. Here, we use a method to obtain the orbital angular momentum decomposition of an electron beam, using a multi-pinhole interferometer. We demonstrate both its ability to accurately measure orbital angular momentum distribution, and its experimental limitations when used in a transmission electron microscope.Comment: 6 pages, 5 figure

    Ephedrine requirements are reduced during spinal anaesthesia for caesarean section in preeclampsia

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    Part of the Portfolio Thesis by Geoffrey H. Sharwood-Smith: The inferior vena caval compression theory of hypotension in obstetric spinal anaesthesia: studies in normal and preeclamptic pregnancy, a literature review and revision of fundamental concepts, available at http://hdl.handle.net/10023/1815Background: Despite controversy over the haemodynamically safest blockade for caesarean section in women with severe preeclampsia, an increasing number of anaesthetists now opt for spinal anaesthesia. In a previous study we found that spinal compared to epidural anaesthesia offered an equally safe but more effective option for these patients. The current study was designed to compare the hypotension induced by spinal anaesthesia, as measured by ephedrine requirement, between 20 normotensive and 20 severely preeclamptic but haemodynamically stabilised women. Method: Standardised spinal anaesthesia was instituted and ephedrine was given in boluses of 6 mg if the systolic pressure fell >20% from the baseline, or if the patient exhibited symptoms of hypotension. Results: The mean ephedrine requirement of the normotensive group (27.9 ± 11.6 mg) was significantly greater (P < 0.01) than that of the preeclamptic group (16.4 ± 15.0 mg). Conclusion: This suggests that the hypotension induced by spinal anaesthesia in women with severe but haemodynamically stabilised preeclampsia, is less than that of normotensive patients.Publisher PD

    Comparison of boiler feed pumps for cesium and potassium Rankine cycle systems

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    Comparison of electromagnetic and centrifugal pumps for cesium and potassium Rankine cycle system

    Neighborhood Diversity and the Appreciation of Native- and Immigrant-Owned Homes

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    This paper examines the effect of neighborhood diversity on the nativity gap in homevalue appreciation in Australia. Specifically, immigrant homeowners experienced a 41.7 percent increase in median home values between 2001 and 2006, while the median value of housing owned by the native-born increased by 59.4 percent over the same period. We use a semi-parametric decomposition approach to assess the relative importance of the various determinants of home values in producing this gap. We find that the differential returns to housing wealth are not related to changes in the nature of the houses or the neighborhoods in which immigrants and native-born homeowners live. Rather, the gap stems from the fact that over time there were differential changes across groups in the hedonic prices (i.e., returns) associated with the underlying determinants of home values.International migration, home-ownership, decomposition analysis

    A critical appraisal of WinEcon and its use in a first‐year undergraduate Economics programme

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    This is an extended review of WinEcon, a CAL package for introductory economics. Our comments are based on a survey of staff and students involved in the first large‐scale (n = 300+) attempt to integrate WinEcon into a teaching and assessment programme
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