22,772 research outputs found

    Carbonate Formation in Non-Aqueous Environments by Solid-Gas Carbonation of Silicates

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    We have produced synthetic analogues of cosmic silicates using the Sol Gel method, producing amorphous silicates of composition Mg(x)Ca(1-x)SiO3. Using synchrotron X-ray powder diffraction on Beamline I11 at the Diamond Light Source, together with a newly-commissioned gas cell, real-time powder diffraction scans have been taken of a range of silicates exposed to CO2 under non-ambient conditions. The SXPD is complemented by other techniques including Raman and Infrared Spectroscopy and SEM imaging.Comment: 5 pages, 3 figures. Contribution to the Proceedings of the First European Conference on Laboratory Astrophysics (ECLA

    Fermi-surface topology and the effects of intrinsic disorder in a class of charge-transfer salts containing magnetic ions: β" — (BEDT — TTF)₄ [(H₃O)M(C₂O₄)₃]Υ (M = Ga, Cr, Fr; Υ = C₅H₅N)

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    We report high-field magnetotransport measurements on β" — (BEDT — TTF)₄ [(H₃O)M(C₂O₄)₃]Υ, where M =Ga, Cr and Fe and Υ = C₅H₅N. We observe similar Shubnikov–de Haas oscillations in all compounds, attributable to four quasi-two-dimensional Fermi-surface pockets, the largest of which corresponds to a cross-sectional area ≈ 8.5% of the Brillouin zone. The cross-sectional areas of the pockets are in agreement with the expectations for a compensated semimetal, and the corresponding effective masses are ∼mₑ, rather small compared to those of other BEDT-TTF salts. Apart from the case of the smallest Fermi-surface pocket, varying the M ion seems to have little effect on the overall Fermi-surface topology or on the effective masses. Despite the fact that all samples show quantum oscillations at low temperatures, indicative of Fermi liquid behavior, the sample and temperature dependence of the interlayer resistivity suggest that these systems are intrinsically inhomogeneous. It is thought that intrinsic tendency to disorder in the anions and/or the ethylene groups of the BEDT-TTF molecules leads to the coexistence of insulating and metallic states at low temperatures. A notional phase diagram is given for the general family of β" — (BEDT — TTF)₄ [(H₃O)M(C₂O₄)₃]Υ salts

    Gender discourse, awareness, and alternative responses for men in everyday living

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    In this paper, the authors use examples from their experiences to explore the nuances and complexities of contemporary gender practices. They draw on discourse and positioning theories to identify the ways in which culturally dominant, and difficult to notice, gender constructions help shape everyday experiences. In addition, the authors share their view that there are benefits in developing skills in noticing contemporary practices made available by dominant gender constructions. Such noticing expands possibilities for ways of responding and relating that might produce outcomes for men and women that fit with their hopes for living

    Measurement of the SOC State Specific Heat in ^4He

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    When a heat flux Q is applied downward through a sample of liquid 4He near the lambda transition, the helium self organizes such that the gradient in temperature matches the gravity induced gradient in Tlambda. All the helium in the sample is then at the same reduced temperature tSOC = ((T[sub SOC] - T[sub lambda])/T[sub lambda]) and the helium is said to be in the Self-Organized Critical (SOC) state. We have made preliminary measurements of the 4He SOC state specific heat, C[del]T(T(Q)). Despite having a cell height of 2.54 cm, our results show no difference between C[del]T and the zero-gravity 4He specific heat results of the Lambda Point Experiment (LPE) [J.A. Lipa et al., Phys. Rev. B, 68, 174518 (2003)] over the range 250 to 450 nK below the transition. There is no gravity rounding because the entire sample is at the same reduced temperature tSOC(Q). Closer to Tlambda the SOC specific heat falls slightly below LPE, reaching a maximum at approximately 50 nK below Tlambda, in agreement with theoretical predictions [R. Haussmann, Phys. Rev. B, 60, 12349 (1999)]

    Multiplexable Kinetic Inductance Detectors

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    We are starting to investigate a novel multiplexable readout method that can be applied to a large class of superconducting pair-breaking detectors. This readout method is completely different from those currently used with STJ and TES detectors, and in principle could deliver large pixel counts, high sensitivity, and Fano-limited spectral resolution. The readout is based on the fact that the kinetic surface inductance L_s of a superconductor is a function of the density of quasiparticles n, even at temperatures far below T_c. An efficient way to measure changes in the kinetic inductance is to monitor the transmission phase of a resonant circuit. By working at microwave frequencies and using thin films, the kinetic inductance can be a significant part of the total inductance L, and the volume of the inductor can be made quite small, on the order of 1 µm^3. As is done with other superconducting detectors, trapping could be used to concentrate the quasiparticles into the small volume of the inductor. However, the most intriguing aspect of the concept is that passive frequency multiplexing could be used to read out ~10^3 detectors with a single HEMT amplifier

    Critical Temperature tuning of Ti/TiN multilayer films suitable for low temperature detectors

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    We present our current progress on the design and test of Ti/TiN Multilayer for use in Kinetic Inductance Detectors (KIDs). Sensors based on sub-stoichiometric TiN film are commonly used in several applications. However, it is difficult to control the targeted critical temperature TCT_C, to maintain precise control of the nitrogen incorporation process and to obtain a production uniformity. To avoid these problems we investigated multilayer Ti/TiN films that show a high uniformity coupled with high quality factor, kinetic inductance and inertness of TiN. These features are ideal to realize superconductive microresonator detectors for astronomical instruments application but also for the field of neutrino physics. Using pure Ti and stoichiometric TiN, we developed and tested different multilayer configuration, in term of number of Ti/TiN layers and in term of different interlayer thicknesses. The target was to reach a critical temperature TCT_C around (1÷1.5)(1\div 1.5) K in order to have a low energy gap and slower recombination time (i.e. low generation-recombination noise). The results prove that the superconductive transition can be tuned in the (0.5÷4.6)(0.5\div 4.6) K temperature range properly choosing the Ti thickness in the (0÷15)(0\div 15) nm range, and the TiN thickness in the (5÷100)(5\div 100) nm rang
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