Etching effects during the chemical vapor deposition of (100) diamond

Current theories of CVD growth on (100) diamond are unable to account for the numerous experimental observations of slow-growing, locally smooth (100)(2×1)(100)(2×1) films. In this paper we use quantum mechanical calculations of diamond surface thermochemistry and atomic-scale kinetic Monte Carlo simulations of deposition to investigate the efficacy of preferential etching as a mechanism that can help to reconcile this discrepancy. This etching mechanism allows for the removal of undercoordinated carbon atoms from the diamond surface. In the absence of etching, simulated growth on the (100)(2×1)(100)(2×1) surface is faster than growth on the (110) and (111) surfaces, and the (100) surface is atomically rough. When etching is included in the simulations, the (100) growth rates decrease to values near those observed experimentally, while the rates of growth on the other surfaces remain largely unaffected and similar to those observed experimentally. In addition, the etching mechanism promotes the growth of smooth (100) surface regions in agreement with numerous scanning probe studies. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70606/2/JCPSA6-111-9-4291-1.pd

A New Chapter in the Treatment of Patients with Heart Failure. The Role of Sodium-Glucose Co-transporter Type 2 Inhibitors

Heart failure (HF) remains one of the major social and medical public health problems worldwide. Despite new advances in the treatment of patients with HF, the prognosis is still poor. According to the European Cardiology Society guidelines for the diagnosis and treatment of acute and chronic heart failure (CHF) 2021, a new class of drugs related to hypoglycemic has been confirmed to be effective in influencing the survival of patients with heart failure with low ejection fraction (HFpEF), regardless of the presence of disorders of carbohydrate metabolism. We are talking about inhibitors of the sodium-glucose co-transporter type 2 (iSGLT-2) or gliflozins. The article presents the results of the latest large clinical trials on the effective use of SGLT-2 in patients with HF, not only with low, but also with intact ejection fraction (HFpEF), for which there is no evidence base at the present stage. The review article presents the results of experimental studies that explored the potential mechanisms of action of gliflozins with an emphasis on new ones that are of fundamental importance for patients with heart failure, and also describes controversial and little-studied issues. Currently, there is no therapy that improves outcomes in patients with acute heart failure. The article presents the results of small analyzes of the use of iSGLT-2 in this category of patients, which are the basis for the hypothesis of their potentially effective and safe use in the case of acute decompensation of CHF, however, the role of gliflozins in this category of patients requires further in-depth study

A dynamical systems approach to the tilted Bianchi models of solvable type

We use a dynamical systems approach to analyse the tilting spatially homogeneous Bianchi models of solvable type (e.g., types VI$_h$ and VII$_h$) with a perfect fluid and a linear barotropic $\gamma$-law equation of state. In particular, we study the late-time behaviour of tilted Bianchi models, with an emphasis on the existence of equilibrium points and their stability properties. We briefly discuss the tilting Bianchi type V models and the late-time asymptotic behaviour of irrotational Bianchi VII$_0$ models. We prove the important result that for non-inflationary Bianchi type VII$_h$ models vacuum plane-wave solutions are the only future attracting equilibrium points in the Bianchi type VII$_h$ invariant set. We then investigate the dynamics close to the plane-wave solutions in more detail, and discover some new features that arise in the dynamical behaviour of Bianchi cosmologies with the inclusion of tilt. We point out that in a tiny open set of parameter space in the type IV model (the loophole) there exists closed curves which act as attracting limit cycles. More interestingly, in the Bianchi type VII$_h$ models there is a bifurcation in which a set of equilibrium points turn into closed orbits. There is a region in which both sets of closed curves coexist, and it appears that for the type VII$_h$ models in this region the solution curves approach a compact surface which is topologically a torus.Comment: 29 page

Asymptotics of Eigenvalues and Eigenfunctions for the Laplace Operator in a Domain with Oscillating Boundary. Multiple Eigenvalue Case

We study the asymptotic behavior of the solutions of a spectral problem for the Laplacian in a domain with rapidly oscillating boundary. We consider the case where the eigenvalue of the limit problem is multiple. We construct the leading terms of the asymptotic expansions for the eigenelements and verify the asymptotics

Observation of band structure and density of states effects in Co-based magnetic tunnel junctions

Utilizing Co/Al$_2$O$_3$/Co magnetic tunnel junctions (MTJs) with Co electrodes of different crystalline phases, a clear relationship between electrode structure and junction transport properties is presented. For junctions with one fcc(111) textured and one polycrystalline (poly-phase and poly-directional) Co electrode, a strong asymmetry is observed in the magnetotransport properties, while when both electrodes are polycrystalline the magnetotransport is essentially symmetric. These observations are successfully explained within a model based on ballistic tunneling between the calculated band structures (DOS) of fcc-Co and hcp-Co.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let

Effect of interface bonding on spin-dependent tunneling from the oxidized Co surface

We demonstrate that the factorization of the tunneling transmission into the product of two surface transmission functions and a vacuum decay factor allows one to generalize Julliere's formula and explain the meaning of the ``tunneling density of states'' in some limiting cases. Using this factorization we calculate spin-dependent tunneling from clean and oxidized fcc Co surfaces through vacuum into Al using the principal-layer Green's function approach. We demonstrate that a monolayer of oxygen on the Co (111) surface creates a spin-filter effect due to the Co-O bonding which produces an additional tunneling barrier in the minority-spin channel. This changes the minority-spin dominated conductance for the clean Co surface into a majority spin dominated conductance for the oxidized Co surface.Comment: 7 pages, revtex4, 4 embedded eps figure

Laplaciens de graphes infinis I Graphes m\'etriquement complets

We introduce the weighted graph Laplacian and the notion of Schr\"odinger operator on a locally finite weighted graph . Concerning essential self-adjointness, we extend Wojciechowski's and Dodziuk's results for graphs with vertex constant weight. The main result in this work states that on any metrically complete weighted graph with bounded degree, the Laplacian is essentially self-adjoint and the same holds for the Schr\"odinger operator provided the associated quadratic form is bounded from below. We construct for the proof a strictly positive and harmonic function which allows us to write any Schr\"odinger operator as a weighted graph Laplacian modulo a unitary transform

On metric-connection compatibility and the signature change of space-time

We discuss and investigate the problem of existence of metric-compatible linear connections for a given space-time metric which is, generally, assumed to be semi-pseudo-Riemannian. We prove that under sufficiently general conditions such connections exist iff the rank and signature of the metric are constant. On this base we analyze possible changes of the space-time signature.Comment: 18 standard LaTeX 2e pages. The packages AMS-LaTeX and amsfonts are require

Influence of s-d interfacial scattering on the magnetoresistance of magnetic tunnel junctions

We propose the two-band s-d model to describe theoretically a diffuse regime of the spin-dependent electron transport in magnetic tunnel junctions (MTJ's) of the form F/O/F where F's are 3d transition metal ferromagnetic layers and O is the insulating spacer. We aim to explain the strong interface sensitivity of the tunneling properties of MTJ's and investigate the influence of electron scattering at the nonideal interfaces on the degradation of the TMR magnitude. The generalized Kubo formalism and the Green's functions method were used to calculate the conductance of the system. The vertex corrections to the conductivity were found with the use of "ladder" approximation combined with the coherent-potential approximation (CPA) that allowed to consider the case of strong electron scattering. It is shown that the Ward identity is satisfied in the framework of this approximation that provides the necessary condition for a conservation of a tunneling current. Based on the known results of ab-initio calculations of the TMR for ballistic junctions, we assume that exchange split quasi-free s-like electrons with the density of states being greater for the majority spin sub-band give the main contribution to the TMR effect. We show that, due to interfacial inter-band scattering, the TMR can be substantially reduced even down to zero value. This is related to the fact that delocalized quasi-free electrons can scatter into the strongly localized d sub-band with the density of states at the Fermi energy being larger for minority spins compared to majority spins. It is also shown that spin-flip electron scattering on the surface magnons within the interface leads to a further decrease of the TMR at finite temperature.Comment: REVTeX4, 20 pages, 9 figures, 1 table, submitted to Phys.Rev.B; In Version 2 the text is substantially improved, the main results and conclusions left the sam

ECFA Detector R&D Panel, Review Report

Two special calorimeters are foreseen for the instrumentation of the very forward region of an ILC or CLIC detector; a luminometer (LumiCal) designed to measure the rate of low angle Bhabha scattering events with a precision better than 10$^{-3}$ at the ILC and 10$^{-2}$ at CLIC, and a low polar-angle calorimeter (BeamCal). The latter will be hit by a large amount of beamstrahlung remnants. The intensity and the spatial shape of these depositions will provide a fast luminosity estimate, as well as determination of beam parameters. The sensors of this calorimeter must be radiation-hard. Both devices will improve the e.m. hermeticity of the detector in the search for new particles. Finely segmented and very compact electromagnetic calorimeters will match these requirements. Due to the high occupancy, fast front-end electronics will be needed. Monte Carlo studies were performed to investigate the impact of beam-beam interactions and physics background processes on the luminosity measurement, and of beamstrahlung on the performance of BeamCal, as well as to optimise the design of both calorimeters. Dedicated sensors, front-end and ADC ASICs have been designed for the ILC and prototypes are available. Prototypes of sensor planes fully assembled with readout electronics have been studied in electron beams.Comment: 61 pages, 51 figure