Novel Rubidium Poly-Nitrogen Materials at High Pressure

First-principles crystal structure search is performed to predict novel rubidium poly-nitrogen materials at high pressure by varying the stoichiometry, i. e. relative quantities of the constituent rubidium and nitrogen atoms. Three compounds of high nitrogen content, RbN_{5}, RbN_{2}, and Rb_{4}N_{6}, are discovered. Rubidium pentazolate (RbN5) becomes thermodynamically stable at pressures above \unit[30]{GPa}. The charge transfer from Rb to N atoms enables aromaticity in cyclo-N_{^{_{5}}}^{-} while increasing the ionic bonding in the crystal. Rubidium pentazolate can be synthesized by compressing rubidium azide (RbN3) and nitrogen (N2) precursors above \unit[9.42]{GPa}, and its experimental discovery is aided by calculating the Raman spectrum and identifying the features attributed to N_{^{_{5}}}^{-} modes. The two other interesting compounds, RbN2 containing infinitely-long single-bonded nitrogen chains, and Rb_{4}N_{6} consisting of single-bonded N_{6} hexazine rings, become thermodynamically stable at pressures exceeding \unit[60]{GPa}. In addition to the compounds with high nitrogen content, Rb_{3}N_{3}, a new compound with 1:1 RbN stoichiometry containing bent N_{3} azides is found to exist at high pressures

Energetic Materials at High Compression: First-Principles Density Functional Theory and Reactive Force Field Studies

We report the results of a comparative study of pentaerythritol tetranitrate (PETN) at high compression using classical reactive interatomic potential ReaxFF and first-principles density functional theory (DFT). Lattice parameters of PETN I, the ground state structure at ambient conditions, is obtained by ReaxFF and two different density functional methods (plane wave and LCAO pseudopotential methods) and compared with experiment. Calculated energetics and isothermal equation of state (EOS) upon hydrostatic compression obtained by DFT and ReaxFF are both in good agreement with available experimental data. Our calculations of the hydrostatic EOS at zero temperature are extended to high pressures up to 50 GPa. The anisotropic characteristics of PETN upon uniaxial compression were also calculated by both ReaxFF and DFT

Дифференцированный выбор малоинвазивного хирургического доступа в хирургическом лечении желчнокаменной болезни

In 2009 at the University Clinic of the Odessa National Medical University with minilaparoscopic and single-port technology we have operated 47 patients with cholelithiasis. 26 patients were performed minilaparoscopic cholecystectomy, 21 — laparoscopic cholecystectomy using a single laparoscopic access. All surgical interventions had no intraoperative complications. In 5 patients because of anatomic difficulties in removing the gallbladder, we were used to installing an additional trocar in the epigastric region. Time used for interventions ranged from 30 to 130 minutes. Patients were hospitalized after the surgery from 1 to 4 days. Technically, the performance of single-port laparoscopic cholecystectomy was more difficult than the traditional laparoscopic or minilaparoscopic operations due to lack of conditions for the quality triangulation, visualization of anatomical structures in the area of operation and the small angle between the operating instruments. Particular attention was devoted to adequate closure of the abdominal wall defect after installing the port. Pain after use minilaparoscopic surgery was significantly less than with traditional laparoscopic approach. The intensity of pain after single-port operations, was comparable with that of conventional traditional laparoscopy. At follow-up of patients during the first months after surgery separated complications were not observed, marked by a beautiful cosmetic effect. 8 months after surgery 1 patient was diagnosed trocar-site hernia after a single port laparoscopic cholecystectomy.С 2009 г. в клинике Одесского национального медицинского университета прооперировано 47 больных с желчнокаменной болезнью. У 26 больных выполнена минилапароскопическая холецистэктомия, у 21 – однопортовая. Все оперативные вмешательства прошли без интраоперационных осложнений. У 5 пациентов из-за анатомических сложностей мы вынуждены были прибегнуть к установке дополнительного троакара в эпигастральной области. Время, использованное для проведения вмешательств, варьировалось от 30 до 130 мин. Больные находились в стационаре от 1 до 4 сут. При наблюдении за пациентами в течение первых месяцев после операции отдаленных осложнений не наблюдалось, отмечен хороший косметический эффект. Спустя 8 месяцев после операции у 1 пациента после однопортовой лапароскопической холецистэктомии диагностирована троакарная грыжа в месте установки порта

Quick search and synchronization algorithm for wideband noise-like signals

In this regard, the article proposes the fast search and synchronization algorithm for high-orbit satellite telecommunication systems when they are used as the information carriers of broadband noise-like signals with linear frequency modulation. The developed algorithm is based on the consideration of development peculiarities for these signal

On the effect of ballistic overflow on the temperature dependence of the quantum efficiency of InGaN/GaN multiple quantum well light-emitting diodes

The dependences of the quantum efficiency of InGaN/GaN multiple quantum well light-emitting diodes on the temperature and excitation level are studied. The experiment is performed for two luminescence excitation modes. A comparison of the results obtained during photo- and electroluminescence shows an additional (to the loss associated with Auger recombination) low-temperature loss in the high-density current region. This causes inversion of the temperature dependence of the quantum efficiency at temperatures lower than 220–300 K. Analysis shows that the loss is associated with electron leakage from the light-emitting-diode active region. The experimental data are explained using the ballistic-overflow model. The simulation results are in qualitative agreement with the experimental dependences of the quantum efficiency on temperature and current density

The second Konus-Wind catalog of short gamma-ray bursts

In this catalog, we present the results of a systematic study of 295 short gamma-ray bursts (GRBs) detected by Konus-Wind (KW) from 1994 to 2010. From the temporal and spectral analyses of the sample, we provide the burst durations, the spectral lags, the results of spectral fits with three model functions, the total energy fluences and the peak energy fluxes of the bursts. We discuss evidence found for an additional power-law spectral component and the presence of extended emission in a fraction of the KW short GRBs. Finally, we consider the results obtained in the context of the Type I (merger-origin) / Type II (collapsar-origin) classifications.Comment: Accepted to the Astrophysical Journal Supplement Series (7 Figures, 8 Tables

Rectification Mechanism in Di-Block Oligomer Molecular Diodes

We investigated a mechanism of rectification in di-block oligomer diode molecules that have recently been synthesized and showed a pronounced asymmetry in the measured I-V spectrum. The observed rectification effect is due to the resonant nature of electron transfer in the system and localization properties of bound state wave functions of resonant states of the tunneling electron interacting with asymmetric molecule in an electric field. The asymmetry of the tunneling wave function is enhanced or weakened depending on the polarity of applied bias. The conceptually new theoretical approach, the Green's function theory of sub-barrier scattering, is able to provide a physically transparent explanation of this rectification effect based on the concept of the bound state spectrum of a tunneling electron. The theory predicts the characteristic features of the I-V spectrum in qualitative agreement with experiment