Design and simulation of zipping variable capacitors

Variable capacitors are essential for building tunable RF systems. We present here the design and simulation of novel zipping variable capacitors with a high permittivity dielectric layer. Two modelling techniques are presented: finite element simulation and variational analysis. A capacitance ratio greater than 40 can be obtained for a 100µm x 25µm device which has a high permittivity dielectric layer (εr = 200). By shaping either the top electrode beam or the bottom electrode, continuously variable capacitance is achieved at low bias voltages

Ab initio calculation of the KRb dipole moments

The relativistic configuration interaction valence bond method has been used to calculate permanent and transition electric dipole moments of the KRb heteronuclear molecule as a function of internuclear separation. The permanent dipole moment of the ground state $X^1\Sigma^+$ potential is found to be 0.30(2) $ea_0$ at the equilibrium internuclear separation with excess negative charge on the potassium atom. For the $a^3\Sigma^+$ potential the dipole moment is an order of magnitude smaller (1 $ea_0=8.47835 10^{-30}$ Cm) In addition, we calculate transition dipole moments between the two ground-state and excited-state potentials that dissociate to the K(4s)+Rb(5p) limits. Using this data we propose a way to produce singlet $X^1\Sigma^+$ KRb molecules by a two-photon Raman process starting from an ultracold mixture of doubly spin-polarized ground state K and Rb atoms. This Raman process is only allowed due to relativistic spin-orbit couplings and the absence of gerade/ungerade selection rules in heteronuclear dimers.Comment: 16 pages, 7 figure

A parallel meshless dynamic cloud method on graphic processing units for unsteady compressible flows past moving boundaries

This paper presents an effort to implement a recently proposed meshless dynamic cloud method (Hong Wang et al., 2010) on modern high-performance graphic processing units (GPUs) with the compute unified device architecture (CUDA) programming model. Within the framework of the meshless method, clouds of points used as basic computational stencils are distributed in the whole flow domain. The spatial derivatives of the governing equations are discretised by the moving-least square scheme on every cloud of points. Roe’s approximate Riemann solver is adopted to compute the convective flux. A dual-time stepping approach, which iterates in physical and pseudo temporal spaces, is employed to obtain the time-accurate solution. Simulation of steady compressible flows over a fixed aerofoil is firstly carried out to verify the GPU implementation of the method. Then it is extended to compute unsteady flows past oscillatory aerofoils. Numerical outcomes are compared with experimental and/or other reference results to validate the method. Significant performance speedup of more than an order of magnitude is verified by the numerical results. Systematic analysis shows that GPU is more energy efficient than CPU for solving aerodynamic problems. This demonstrates the potential of the proposed method to solve fluid–structure interaction problems

Prostate cancer and Hedgehog signalling pathway

[Abstract] The Hedgehog (Hh) family of intercellular signalling proteins have come to be recognised as key mediators in many fundamental processes in embryonic development. Their activities are central to the growth, patterning and morphogenesis of many different regions within the bodies of vertebrates. In some contexts, Hh signals act as morphogens in the dose-dependent induction of distinct cell fates within a target field, in others as mitogens in the regulation of cell proliferation or as inducing factors controlling the form of a developing organ. These diverse functions of Hh proteins raise many intriguing questions about their mode of action. Various studies have now demonstrated the function of Hh signalling in the control of cell proliferation, especially for stem cells and stem-like progenitors. Abnormal activation of the Hh pathway has been demonstrated in a variety of human tumours. Hh pathway activity in these tumours is required for cancer cell proliferation and tumour growth. Recent studies have uncovered the role for Hh signalling in advanced prostate cancer and demonstrated that autocrine signalling by tumour cells is required for proliferation, viability and invasive behaviour. Thus, Hh signalling represents a novel pathway in prostate cancer that offers opportunities for prognostic biomarker development, drug targeting and therapeutic response monitoring

First Sagittarius A* Event Horizon Telescope results. I. The shadow of the supermassive black hole in the center of the Milky Way

Galaxie

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Monitoring the setting and early hardening of concrete using an ultrasonic waveguide

The use of an embedded waveguide to monitor the setting and early hardening of concrete has been investigated. The technique uses measurements of the attenuation of a guided wave propagating along the waveguide to obtain the shear velocity, and hence shear modulus, of the concrete. Tests have been carried out on mortar and concrete specimens monitored continuously over 48 hours. Over the first few hours, while the mortar/concrete was still fluid, the absolute rate of increase in shear modulus was low. From around 5 hours to around 20 hours, shear modulus increased linearly. Thereafter, shear modulus increased, but at an ever-decreasing rate. The shear velocity of the mortar was calculated to be 1720 m/s after two days, corresponding to a shear modulus of 5.6 GPa, while the 48 hour-old concrete had a shear modulus of 16.5 GPa. Repeated tests showed similar end states, but some differences in hardening rate; these were attributed either to temperature variations or to differences in mould geometry. The technique worked equally well on mortar and concrete, indicating that the presence of the large aggregate particles in concrete does not adversely affect the results

Preparation and properties of sputtered nitrogen-doped cobalt silicide film

It is the purpose of this study to develop tough hinge material for the application of the torsional springs. Nitrogen-doped cobalt silicide (CoSixNy) film is sputtered from cobalt silicide (CoSi2) target in Ar/N-2 discharge. Stress and sheet resistance of CoSixNy film are two major properties to be evaluated. Taguchi method is practiced in reactive sputtering deposition of CoSixNy film. Process pressure is most critical to the CoSixNy film stress and the optimum condition of 1000 W, 0.8 Pa, and 20% N-2 flow ratio, indeed results in low tensile CoSixNy film stress, about 54. MPa. Reannealing process indicates that stability of CoSixNy film is attained after first annealing process. Stress hysteresis behaviors of CoSix and CoSixNy films resemble that of metal film with a complete elastic manner in the second stage of heating and cooling. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses suggest that toughness and strength of the film is achievable. It is concluded that CoSixNy film as a hinge material is feasible. (C) 2004 Elsevier B.V. All rights reserved

Fabrication and characterisation of resistive nanocrystalline graphite

This work demonstrates the feasibility of fabricating resistive nanocrystalline graphite (NCG) on a Si substrate. The NCG film thickness of 9 nm was deposited using metal-free plasma enhanced chemical vapour deposition (PECVD) on a 6-inch p-type silicon wafer. The surface and electrical properties of the resistors produced were investigated. The average grain size of the NCG thin film is 35 nm with 0.8 nm of surface roughness. The electrical characterization of the NCG strips show metal-like behaviour in which the resistance is proportional to the strip lengths. The sheet resistance is found to be 39 kohm/sq which is two orders of magnitude larger than graphene deposited using Chemical Vapour Deposition. This indicates the carrier transport across grain boundaries has a large influence on the overall resistance of the device. However, the nano-sized grains on the NCG material could be used to enhance the sensitivity of the material towards the environment