Verwey transition in Fe3_{3}O4_{4} at high pressure: quantum critical behavior at the onset of metallization

We provide evidence for the existence of a {\em quantum critical point} at the metallization of magnetite Fe$_{3}$O$_{4}$ at an applied pressure of $p_{c} \approx 8$ GPa. We show that the present ac magnetic susceptibility data support earlier resistivity data. The Verwey temperature scales with pressure $T_{V}\sim (1-p/p_{c})^{\nu}$, with $\nu\sim 1/3$. The resistivity data shows a temperature dependence $\rho(T)=\rho_{0}+AT^{n}$, with $n\simeq 3$ above and 2.5 at the critical pressure, respectively. This difference in $n$ with pressure is a sign of critical behavior at $p_{c}$. The magnetic susceptibility is smooth near the critical pressure, both at the Verwey transition and near the ferroelectric anomaly. A comparison with the critical behavior observed in the Mott-Hubbard and related systems is made.Comment: 5 pages, 5 figure

Terahertz Conductivity at the Verwey Transition in Magnetite

The complex conductivity at the (Verwey) metal-insulator transition in Fe_3O_4 has been investigated at THz and infrared frequencies. In the insulating state, both the dynamic conductivity and the dielectric constant reveal a power-law frequency dependence, the characteristic feature of hopping conduction of localized charge carriers. The hopping process is limited to low frequencies only, and a cutoff frequency nu_1 ~ 8 meV must be introduced for a self-consistent description. On heating through the Verwey transition the low-frequency dielectric constant abruptly decreases and becomes negative. Together with the conductivity spectra this indicates a formation of a narrow Drude-peak with a characteristic scattering rate of about 5 meV containing only a small fraction of the available charge carriers. The spectra can be explained assuming the transformation of the spectral weight from the hopping process to the free-carrier conductivity. These results support an interpretation of Verwey transition in magnetite as an insulator-semiconductor transition with structure-induced changes in activation energy.Comment: 6 Pages, 3 Figure

Fast Non-Adiabatic Two Qubit Gates for the Kane Quantum Computer

In this paper we apply the canonical decomposition of two qubit unitaries to find pulse schemes to control the proposed Kane quantum computer. We explicitly find pulse sequences for the CNOT, swap, square root of swap and controlled Z rotations. We analyze the speed and fidelity of these gates, both of which compare favorably to existing schemes. The pulse sequences presented in this paper are theoretically faster, higher fidelity, and simpler than existing schemes. Any two qubit gate may be easily found and implemented using similar pulse sequences. Numerical simulation is used to verify the accuracy of each pulse scheme

Effectiveness of fecal-derived microbiota transfer using orally administered capsules for recurrent Clostridium difficile infection

BACKGROUND: Clostridium difficile infection (CDI), a complication of antibiotic-induced injury to the gut microbiome, is a prevalent and dangerous cause of infectious diarrhea. Antimicrobial therapy for CDI is typically effective for acute symptoms, but up to one third of patients later experience recurrent CDI. Fecal-derived microbiota transplantation (FMT) can ameliorate the underlying dysbiosis and is highly effective for recurrent CDI. Traditional methods of FMT are limited by patient discomfort, risk and inefficient procedures. Many individuals with recurrent CDI have extensive comorbidities and advanced age. Widespread use of FMT requires strategies that are non-invasive, scalable and applicable across healthcare settings. METHODS: A method to facilitate microbiota transfer was developed. Fecal samples were collected and screened for potential pathogens. Bacteria were purified, concentrated, cryopreserved and formulated into multi-layered capsules. Capsules were administered to patients with recurrent CDI, who were then monitored for 90 days. RESULTS: Thirteen women and six men with recurrent CDI were provided with microbiota transfer with orally administered capsules. The procedure was well tolerated. Thirteen individuals responded to a single course. Four patients were cured after a second course. There were 2 failures. The cumulative clinical cure rate of 89% is similar to the rates achieved with reported fecal-derived transplantation procedures. CONCLUSIONS: Recurrent CDI represents a profound dysbiosis and a debilitating chronic disease. Stable cure can be achieved by restoring the gut microbiome with an effective, well-tolerated oral capsule treatment. This strategy of microbiota transfer can be widely applied and is particularly appropriate for frail patients

The Frenet Serret Description of Gyroscopic Precession

The phenomenon of gyroscopic precession is studied within the framework of Frenet-Serret formalism adapted to quasi-Killing trajectories. Its relation to the congruence vorticity is highlighted with particular reference to the irrotational congruence admitted by the stationary, axisymmetric spacetime. General precession formulae are obtained for circular orbits with arbitrary constant angular speeds. By successive reduction, different types of precessions are derived for the Kerr - Schwarzschild - Minkowski spacetime family. The phenomenon is studied in the case of other interesting spacetimes, such as the De Sitter and G\"{o}del universes as well as the general stationary, cylindrical, vacuum spacetimes.Comment: 37 pages, Paper in Late

Dynamics of a small gap gas lubricated bearing with Navier slip boundary conditions

A gas lubricated bearing model is derived which is appropriate for a very small bearing face separation by including velocity slip boundary conditions and centrifugal inertia effects. The bearing dynamics are examined when an external harmonic force is imposed on the bearing due to bearing begin situated within a larger complex dynamical system. A compressible Reynolds equation is formulated for the gas film which is coupled to the bearing structure through an axial force balance where the rotor and stator correspond to spring-mass-damper systems. Surface slip boundary conditions are derived on the bearing faces, characterised by the slip length parameter. The coupled bearing system is analysed using a stroboscopic map solver with the modified Reynolds equation and structural equations solved simultaneously. For a sufficiently large forcing amplitude a apping motion of the bearing faces is induced when the rotor and stator are in close proximity. The minimum bearing gap over the time period of the external forcing is examined for a range of bearing parameters

A Proposal for Integrated Efficacy-to-Effectiveness (E2E) Clinical Trials

We propose an “efficacy-to-effectiveness” (E2E) clinical trial design, in which an effectiveness trial would commence seamlessly upon completion of the efficacy trial. Efficacy trials use inclusion/exclusion criteria to produce relatively homogeneous samples of participants with the target condition, conducted in settings that foster adherence to rigorous clinical protocols. Effectiveness trials use inclusion/exclusion criteria that generate heterogeneous samples that are more similar to the general patient spectrum, conducted in more varied settings, with protocols that approximate typical clinical care. In E2E trials, results from the efficacy trial component would be used to design the effectiveness trial component, to confirm and/or discern associations between clinical characteristics and treatment effects in typical care, and potentially to test new hypotheses. An E2E approach may improve the evidentiary basis for selecting treatments, expand understanding of the effectiveness of treatments in subgroups with particular clinical features, and foster incorporation of effectiveness information into regulatory processes.National Center for Research Resources (U.S.) (Grant UL1 RR025752)National Center for Advancing Translational Sciences (U.S.) (Grant UL1 TR000073