DSMC simulations of Mach 20 nitrogen flows about a 70 degree blunted cone and its wake

Numerical results obtained with the direct simulation Monte Carlo (DSMC) method are presented for Mach 20 nitrogen flow about a 70-deg blunted cone. The flow conditions simulated are those that can be obtained in existing low-density hypersonic wind tunnels. Three sets of flow conditions are simulated with freestream Knudsen numbers ranging from 0.03 to 0.001. The focus is to characterize the wake flow under rarefied conditions. This is accomplished by calculating the influence of rarefaction on wake structure along with the impact that an afterbody has on flow features. This data report presents extensive information concerning flowfield features and surface quantities

Non-linear IVIV characteristics in two-dimensional superconductors: Berezinskii-Kosterlitz-Thouless physics vs inhomogeneity

One of the hallmarks of the Berezinskii-Kosterlitz-Thouless (BKT) transition in two-dimensional (2D) superconductors is the universal jump of the superfluid density, that can be indirectly probed via the non-linear exponent of the current-voltage $IV$ characteristics. Here, we compare the experimental measurements of $IV$ characteristics in two cases, namely NbN thin films and SrTiO$_3$-based interfaces. While the former display a paradigmatic example of BKT-like non-linear effects, the latter do not seem to justify a BKT analysis. Rather, the observed $IV$ characteristics can be well reproduced theoretically by modelling the effect of mesoscopic inhomogeneity of the superconducting state. Our results offer an alternative perspective on the spontaneous fragmentation of the superconducting background in confined 2D systems.Comment: Final version, as publishe

Chemical potential shift and gap-state formation in SrTiO3−δ_{3-\delta} revealed by photoemission spectroscopy

In this study, we report on investigations of the electronic structure of SrTiO$_3$ annealed at temperature ranging between 550 and 840$^\circ$C in an ultrahigh vacuum. Annealing induced oxygen vacancies (O$_{vac}$) impart considerable changes in the electronic structure of SrTiO$_3$. Using core-level photoemission spectroscopy, we have studied the chemical potential shift ($\Delta\mu$) as a function of annealing temperature. The result shows that the chemical potential monotonously increases with electron doping in SrTiO$_{3-\delta}$. The monotonous increase of the chemical potential rules out the existence of electronic phase separation in the sample. Using valence band photoemission, we have demonstrated the formation of a low density of states at the near Fermi level electronic spectrum of SrTiO$_{3-\delta}$. The gap-states were observed by spectral weight transfer over a large energy scale of the stoichiometric band gap of SrTiO$_3$ system leading finally to an insulator - metal transition. We have interpreted our results from the point of structural distortions induced by oxygen vacancies.Comment: 7 pages, 6 figures, 1 tabl

Benigne zystische Raumforderungen des Hodens: Eine Übersicht

Zusammenfassung: Hodenzysten werden im Rahmen der skrotalen Sonographie zunehmend diagnostiziert. Grund hierfür ist u.a. die flächendeckende Verfügbarkeit moderner, hochauflösender Ultraschallgeräte. Differentialdiagnostisch und ätiologisch sind benigne und maligne Erkrankungen mit testikulärer Zystenbildung voneinander zu unterscheiden. Benigne Krankheitsbilder mit zystischen Raumforderungen des Hodens sind die tubuläre Ektasie des Rete testis, die zystische Dysplasie, Epidermoidzysten, einfache intraparenchymatöse Hodenzysten und Zysten der Tunica albuginea. Die testikuläre Dermoidzyste, die lange Zeit zu Unrecht als potentiell maligne angesehen wurde, ist ebenfalls als benigne zu klassifizieren. Bei Diagnose einer benignen zystischen Raumforderung des Hodens kann in den meisten Fällen eine organerhaltende operative Therapie oder ein abwartendes, überwachendes Procedere empfohlen werde

Competition between electron pairing and phase coherence in superconducting interfaces

In LaAlO3/SrTiO3 heterostructures, a gate tunable superconducting electron gas is confined in a quantum well at the interface between two insulating oxides. Remarkably, the gas coexists with both magnetism and strong Rashba spin–orbit coupling. However, both the origin of superconductivity and the nature of the transition to the normal state over the whole doping range remain elusive. Here we use resonant microwave transport to extract the superfluid stiffness and the superconducting gap energy of the LaAlO3/SrTiO3 interface as a function of carrier density. We show that the superconducting phase diagram of this system is controlled by the competition between electron pairing and phase coherence. The analysis of the superfluid density reveals that only a very small fraction of the electrons condenses into the superconducting state. We propose that this corresponds to the weak filling of high- energy dxz/dyz bands in the quantum well, more apt to host superconductivity

Direct Monte Carlo Simulations of Hypersonic Low-Density Flows about an ASTV Including Wake Structure

Results of a numerical study concerning flow past a 70-deg blunted cone in hypersonic low-density flow environments are presented using the direct simulation Monte-Carlo method. The flow conditions simulated are those that can be obtained in existing low-density hypersonic wind tunnels. Results indicate that a stable vortex forms in the near wake at and below a freestream Knudsen number (based on cone diameter) of 0.01 and the size of the vortex increases with decreasing Knudsen number. The base region of the flow remains in thermal nonequilibrium for all cases considered herein

Effects of Chemistry on Blunt-Body Wake Structure

Results of a numerical study are presented for hypersonic low-density flow about a 70-deg blunt cone using direct simulation Monte Carlo (DSMC) and Navier-Stokes calculations. Particular emphasis is given to the effects of chemistry on the near-wake structure and on the surface quantities and the comparison of the DSMC results with the Navier-Stokes calculations. The flow conditions simulated are those experienced by a space vehicle at an altitude of 85 km and a velocity of 7 km/s during Earth entry. A steady vortex forms in the near wake for these freestream conditions for both chemically reactive and nonreactive air gas models. The size (axial length) of the vortex for the reactive air calculations is 25% larger than that of the nonreactive air calculations. The forebody surface quantities are less sensitive to the chemistry than the base surface quantities. The presence of the afterbody has no effect on the forebody flow structure or the surface quantities. The comparisons of DSMC and Navier-Stokes calculations show good agreement for the wake structure and the forebody surface quantities