Cryogenic characterization of Josephson junctions

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.Includes bibliographical references (p. 109-110).Cryogenic characterization is a crucial part of understanding the behavior of low-temperature quantum electronics. Reliable device testing provides the feedback to fabrication process development, facilitating the rapid development of quantum devices. The research presented in this thesis explores the cryogenic testing, analysis, and characterization of a superconducting quantum device, the Josephson junction. This thesis begins with a theoretical description of superconductivity and Josephson junctions, two superconductors separated by a thin insulating battier. Two models of Josephson barriers are presented for use in analysis. The effect of self-induced magnetic field is considered. A numerical simulation is performed to justify neglecting effects of self-induced magnetic field in junctions of diameter less than the Josephson penetration depth Aj. Lincoln Laboratory's Josephson junction fabrication effort is described along with the apparatus used to test junctions at 4.2 K. Custom software used to test these junctions is then presented. The analysis of 4.2 K data is shown with a simple model of a disc as the insulating barrier. 391 valid Josephson junctions are analyzed across 16 wafers in 3 runs.(cont.) The critical current density J is calculated to be 4.88 ± 2.81 ( ... ) for junctions with expected J of 5 ( ... ). The superconductive energy gap A is calculated to be 1.51 ± 0.31 meV. The process bias 60 is shown to be -0.35 i 0.12 ,tm. Analyzing the junctions with an alternate model taking into account pollution produces an upper bound for barrier pollution depth of approximately 60 nm. Discussion of a 300 mK apparatus is then presented. This apparatus is constructed and presently being incorporated in an existing 300 mK 3He refrigerator. Finally, the results are concluded with a discussion of advantages, and proposed initial experiments for the 300 mK apparatus.by Keith Andrew Brown.S.B

A Music index of periodicals for the first six months of 1948 /

Thesis (M.M.)--Boston Universit

High Voltage Dielectrophoretic and Magnetophoretic Hybrid Integrated Circuit / Microfluidic Chip

A hybrid integrated circuit (IC)/microfluidic chip is presented that independently and simultaneously traps and moves microscopic objects suspended in fluid using both electric and magnetic fields. This hybrid chip controls the location of dielectric objects, such as living cells and drops of fluid, on a 60 times 61 array of pixels that are 30 times 38 mum2 in size, each of which can be individually addressed with a 50-V peak-to-peak dc-to-10-MHz radio-frequency voltage. These high-voltage pixels produce electric fields above the chip's surface with a magnitude |oarrE| ap 1 V/ mum, resulting in strong dielectrophoresis (DEP) forces |oarrFDEP| ap 1 nN. Underneath the array of DEP pixels, there is a magnetic matrix that consists of two perpendicular sets of 60 metal wires running across the chip. Each wire can be sourced with 120 mA to trap and move magnetically susceptible objects using magnetophoresis. The DEP pixel array and magnetic matrix can be used simultaneously to apply forces to microscopic objects, such as living cells or lipid vesicles, that are tagged with magnetic nanoparticles. The capabilities of the hybrid IC/microfluidic chip demonstrated in this paper provide important building blocks for a platform for biological and chemical applications.Engineering and Applied Science

Integrated Circuit / Microfluidic Chips for Dielectric Manipulation

Engineering and Applied Science

Mechanical thrombectomy in patients with acute ischemic stroke: a cost-effectiveness and value of implementation analysis

Background: Recent clinical trials have demonstrated the efficacy of mechanical thrombectomy in acute ischemic stroke. Aims: To determine the cost-effectiveness, value of future research, and value of implementation of mechanical thrombectomy. Methods: Using UK clinical and cost data from the Pragmatic Ischemic Stroke Thrombectomy Evaluation (PISTE) trial, we estimated the cost-effectiveness of mechanical thrombectomy over time horizons of 90-days and lifetime, based on a decision-analytic model, using all existing evidence. We performed a meta-analysis of seven clinical trials to estimate treatment effects. We used sensitivity analysis to address uncertainty. Value of implementation analysis was used to estimate the potential value of additional implementation activities to support routine delivery of mechanical thrombectomy. Results: Over the trial period (90 days), compared with best medical care alone, mechanical thrombectomy incurred an incremental cost of £5207 and 0.025 gain in QALY (incremental cost-effectiveness ratio (ICER) £205,279), which would not be considered cost-effective. However, mechanical thrombectomy was shown to be cost-effective over a lifetime horizon, with an ICER of £3466 per QALY gained. The expected value of perfect information per patient eligible for mechanical thrombectomy in the UK is estimated at £3178. The expected value of full implementation of mechanical thrombectomy is estimated at £1.3 billion over five years. Conclusion: Mechanical thrombectomy was cost-effective compared with best medical care alone over a patient’s lifetime. On the assumption of 30% implementation being achieved throughout the UK healthcare system, we estimate that the population health benefits obtained from this treatment are greater than the cost of implementation. Trial registration: NCT01745692

Characterization of the Myocardial Inflammatory Response in Acute Stress-Induced (Takotsubo) Cardiomyopathy

This work was supported by grants from NHS Grampian Endowments and British Heart Foundation Project Grant no. PG/15/108/31928 The authors have reported that they have no relationships relevant to the contents of this paper to disclose.Peer reviewedPublisher PD

Discovery of enhanced lattice dynamics in a single-layered hybrid perovskite

Layered hybrid perovskites have attracted much attention in recent years due to their emergent physical properties and exceptional functional performances, but the coexistence of lattice order and structural disorder severely hinders our understanding of these materials. One unsolved problem regards how the lattice dynamics are affected by the dimensional engineering of the inorganic frameworks and the interaction with the molecular moieties. Here, we address this question by using a combination of high-resolution spontaneous Raman scattering, high-field terahertz spectroscopy, and molecular dynamics simulations. This approach enables us to reveal the structural vibrations and disorder in and out of equilibrium and provides surprising observables that differentiate single- and double-layered perovskites. While no distinct vibrational coherence is observed in double-layer perovskites, we discover that an off-resonant terahertz pulse can selectively drive a long-lived coherent phonon mode through a two-photon process in the single-layered system. This difference highlights the dramatic change in the lattice environment as the dimension is reduced. The present findings pave the way for the ultrafast structural engineering of hybrid lattices as well as for developing high-speed optical modulators based on layered perovskites

In the dedicated pursuit of dedicated capital: restoring an indigenous investment ethic to British capitalism

Tony Blair’s landslide electoral victory on May 1 (New Labour Day?) presents the party in power with a rare, perhaps even unprecedented, opportunity to revitalise and modernise Britain’s ailing and antiquated manufacturing economy.* If it is to do so, it must remain true to its long-standing (indeed, historic) commitment to restore an indigenous investment ethic to British capitalism. In this paper we argue that this in turn requires that the party reject the very neo-liberal orthodoxies which it offered to the electorate as evidence of its competence, moderation and ‘modernisation’, which is has internalised, and which it apparently now views as circumscribing the parameters of the politically and economically possible

Characterisation of L-Type Amino Acid Transporter 1 (LAT1) Expression in Human Skeletal Muscle by Immunofluorescent Microscopy

The branch chain amino acid leucine is a potent stimulator of protein synthesis in skeletal muscle. Leucine rapidly enters the cell via the L-Type Amino Acid Transporter 1 (LAT1); however, little is known regarding the localisation and distribution of this transporter in human skeletal muscle. Therefore, we applied immunofluorescence staining approaches to visualise LAT1 in wild type (WT) and LAT1 muscle-specific knockout (mKO) mice, in addition to basal human skeletal muscle samples. LAT1 positive staining was visually greater in WT muscles compared to mKO muscle. In human skeletal muscle, positive LAT1 staining was noted close to the sarcolemmal membrane (dystrophin positive staining), with a greater staining intensity for LAT1 observed in the sarcoplasmic regions of type II fibres (those not stained positively for myosin heavy-chain 1, Type II—25.07 ± 5.93, Type I—13.71 ± 1.98, p < 0.01), suggesting a greater abundance of this protein in these fibres. Finally, we observed association with LAT1 and endothelial nitric oxide synthase (eNOS), suggesting LAT1 association close to the microvasculature. This is the first study to visualise the distribution and localisation of LAT1 in human skeletal muscle. As such, this approach provides a validated experimental platform to study the role and regulation of LAT1 in human skeletal muscle in response to various physiological and pathophysiological models