Singular Lagrangian Systems on Jet Bundles

The jet bundle description of time-dependent mechanics is revisited. The constraint algorithm for singular Lagrangians is discussed and an exhaustive description of the constraint functions is given. By means of auxiliary connections we give a basis of constraint functions in the Lagrangian and Hamiltonian sides. An additional description of constraints is also given considering at the same time compatibility, stability and second-order condition problems. Finally, a classification of the constraints in first and second class is obtained using a cosymplectic geometry setting. Using the second class constraints, a Dirac bracket is introduced, extending the well-known construction by Dirac.Comment: 65 pages. LaTeX fil

Knudsen Effect in a Nonequilibrium Gas

From the molecular dynamics simulation of a system of hard-core disks in which an equilibrium cell is connected with a nonequilibrium cell, it is confirmed that the pressure difference between two cells depends on the direction of the heat flux. From the boundary layer analysis, the velocity distribution function in the boundary layer is obtained. The agreement between the theoretical result and the numerical result is fairly good.Comment: 4pages, 4figure

Free Thermal Convection Driven by Nonlocal Effects

We report and explain a convective phenomenon observed in molecular dynamics simulations that cannot be classified either as a hydrodynamics instability nor as a macroscopically forced convection. Two complementary arguments show that the velocity field by a thermalizing wall is proportional to the ratio between the heat flux and the pressure. This prediction is quantitatively corroborated by our simulations.Comment: RevTex, figures is eps, submited for publicatio

The unit cell parameters and electrical conduction of some new solar cell materials

New materials are being investigated that could yield solar energy conversion efficiency comparable in device production cost to the standard electric power generators. Continuing with this effort, in recent years solar cells with efficiency close to 20 %, prepared with alloys of CuIn1-xGaxSe2 has been reported. It is shown that the normalized values of the unit cell parameters a and c of the ordered defect compounds with respect to their corresponding 1:1:2 phase, that are formed on the In(Ga)-rich side of the pseudo-binary phase diagram of [Cu2(Se,Te)]X–[(In2,Ga2)(Se3,Te3)]1-X, vary linearly with the effective cation radius reff for the tellurides and selenides of Cu-In and Cu-Ga systems. This universal relationship has important significance. The unit cell dimensions of other chalcopyriterelated ordered defect compounds of these systems that have not been synthesized so far can be estimated. Because of the presence of shallow donor and acceptor levels due to the presence of cation-cation disorders in Cu(In,Ga)Se2 and ordered defects in Cu(In,Ga)3(Se,Te)5, the impurity band in these compounds starts to form between liquid helium and nitrogen temperatures. This permits to study the variable range hopping (VRH) conduction in the impurity band over a much wider temperature range

Nuclear Activity and the Conditions of Star-formation at the Galactic Center

The Galactic Center is the closest galactic nucleus that can be studied with unprecedented angular resolution and sensitivity. We summarize recent basic observational results on Sagittarius A* and the conditions for star formation in the central stellar cluster. We cover results from the radio, infrared, and X-ray domain and include results from simulation as well. From (sub-)mm and near-infrared variability and near-infrared polarization data we find that the SgrA* system (supermassive black hole spin, a potential temporary accretion disk and/or outflow) is well ordered in its geometrical orientation and in its emission process that we assume to reflect the accretion process onto the supermassive black hole (SMBH).Comment: 11 pages, 4 figures, 1 table; published in PoS-SISSA Proceedings of the: Frontier Research in Astrophysics - II, 23-28 May 2016, Mondello (Palermo), Ital

Clinical efficacy of β-lactam/β-lactamase inhibitor combinations for the treatment of bloodstream infection due to extended-spectrum β-lactamase- producing Enterobacteriaceae in haematological patients with neutropaenia: a study protocol for a retrospect observational study (BICAR).

Introduction: Bloodstream infection (BSI) due to extended-spectrum β-lactamase-producing Gram- negative bacilli (ESBL-GNB) is increasing at an alarming pace worldwide. Although β-lactam/β- lactamase inhibitor (BLBLI) combinations have been suggested as an alternative to carbapenems for the treatment of BSI due to these resistant organisms in the general population, their usefulness for the treatment of BSI due to ESBL-GNB in haematological patients with neutropaenia is yet to be elucidated. The aim of the BICAR study is to compare the efficacy of BLBLI combinations with that of carbapenems for the treatment of BSI due to an ESBL-GNB in this population. Methods and analysis: A multinational, multicentre, observational retrospective study. Episodes of BSI due to ESBL-GNB occurring in haematological patients and haematopoietic stem cell transplant recipients with neutropaenia from 1 January 2006 to 31 March 2015 will be analysed. The primary end point will be case- fatality rate within 30 days of onset of BSI. The secondary end points will be 7-day and 14-day case- fatality rates, microbiological failure, colonisation/ infection by resistant bacteria, superinfection, intensive care unit admission and development of adverse events. Sample size: The number of expected episodes of BSI due to ESBL-GNB in the participant centres will be 260 with a ratio of control to experimental participants of 2. Ethics and dissemination: The protocol of the study was approved at the first site by the Research Ethics Committee (REC) of Hospital Universitari de Bellvitge. Approval will be also sought from all relevant RECs. Any formal presentation or publication of data from this study will be considered as a joint publication by the participating investigators and will follow the recommendations of the International Committee of Medical Journal Editors (ICMJE). The study has been endorsed by the European Study Group for Bloodstream Infection and Sepsis (ESGBIS) and the European Study Group for Infections in Compromised Hosts (ESGICH).Ministerio de Economía y Competitividad REIPI RD12/001

Evidence of topological superconductivity in planar Josephson junctions

Majorana zero modes are quasiparticle states localized at the boundaries of topological superconductors that are expected to be ideal building blocks for fault-tolerant quantum computing. Several observations of zero-bias conductance peaks measured in tunneling spectroscopy above a critical magnetic field have been reported as experimental indications of Majorana zero modes in superconductor/semiconductor nanowires. On the other hand, two dimensional systems offer the alternative approach to confine Ma jorana channels within planar Josephson junctions, in which the phase difference {\phi} between the superconducting leads represents an additional tuning knob predicted to drive the system into the topological phase at lower magnetic fields. Here, we report the observation of phase-dependent zero-bias conductance peaks measured by tunneling spectroscopy at the end of Josephson junctions realized on a InAs/Al heterostructure. Biasing the junction to {\phi} ~ {\pi} significantly reduces the critical field at which the zero-bias peak appears, with respect to {\phi} = 0. The phase and magnetic field dependence of the zero-energy states is consistent with a model of Majorana zero modes in finite-size Josephson junctions. Besides providing experimental evidence of phase-tuned topological superconductivity, our devices are compatible with superconducting quantum electrodynamics architectures and scalable to complex geometries needed for topological quantum computing.Comment: main text and extended dat