Preparation of Amino-Functionalized Graphene Sheets and their Conductive Properties

Amino-functionalized graphene sheets were prepared through chemical reduction by hydrazine hy-drate, amination or amidation of graphite oxide. For amination of graphite oxide were used polyamine such as ethylenediamine, diethylenetriamine and triethylenetetramine. Addition of amine groups to graphene is identified by Fourier transform infrared spectroscopy, Raman spectroscopy, elemental analysis and ther-mogravimetry. Scanning electron microscopy data indicate that the organic amine is not only as nitrogen sources to obtain the nitrogen-doped graphene but also as an important modification to control the assem-bly of graphene sheets in the 3D structures. The electrical conductivity of the materials obtained by amina-tion and amidation of graphene is much smaller than that of reduced graphite oxide. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3563

Hidden Symmetry from Supersymmetry in One-Dimensional Quantum Mechanics

When several inequivalent supercharges form a closed superalgebra in Quantum Mechanics it entails the appearance of hidden symmetries of a Super-Hamiltonian. We examine this problem in one-dimensional QM for the case of periodic potentials and potentials with finite number of bound states. After the survey of the results existing in the subject the algebraic and analytic properties of hidden-symmetry differential operators are rigorously elaborated in the Theorems and illuminated by several examples

Vacuum polarization by a global monopole with finite core

We investigate the effects of a $(D+1)$-dimensional global monopole core on the behavior of a quantum massive scalar field with general curvature coupling parameter. In the general case of the spherically symmetric static core, formulae are derived for the Wightman function, for the vacuum expectation values of the field square and the energy-momentum tensor in the exterior region. These expectation values are presented as the sum of point-like global monopole part and the core induced one. The asymptotic behavior of the core induced vacuum densities is investigated at large distances from the core, near the core and for small values of the solid angle corresponding to strong gravitational fields. In particular, in the latter case we show that the behavior of the vacuum densities is drastically different for minimally and non-minimally coupled fields. As an application of general results the flower-pot model for the monopole's core is considered and the expectation values inside the core are evaluated.Comment: 22 pages, 4 figures, misprint is corrected, discussion is added, figures are change

Transparent conductive oxide TCO buffer layer effect on the resistive switching process in metal TCO TiO2 metal assemblies

The effect of transparent conductive oxide TCO buffer layer on the insulator matrix and on the resistive switching process in the metal TiO2 TCO metal assembly was studied depending on the material of TCO ITO In2O3 0.9 SnO2 0.1 or SnO2 or ZnO . First time electro physical studies and near edge x ray absorption fine structure NEXAFS studies were carried out jointly and in the same point of the sample providing the direct experimental evidence that switching process influences strongly the lowest unoccupied bands and local atomic structure of the TiO2 layers. It was established that TCO layer in metal TiO2 TCO metal assembly is an additional source of oxygen vacancies for TiO2 film. The RL RH states are achieved presumably with formation rupture of electrically conductive path of oxygen vacancies. The inserting the Al2O3 thin layer between TiO2 and TCO layers restricts to some extent processes of migration of oxygen ions and vacancies and does not permit to realize the anti clockwise bipolar resistive switching in Au TiO2 Al2O3 ITO Au assembly. The greatest value of the ratio RH RL is observed for assembly with SnO2 buffer layer that will provide to implement the maximum set of intermediate states recording analog data and increases the density of information recording in this cas

Collectivity, Phase Transitions and Exceptional Points in Open Quantum Systems

Phase transitions in open quantum systems, which are associated with the formation of collective states of a large width and of trapped states with rather small widths, are related to exceptional points of the Hamiltonian. Exceptional points are the singularities of the spectrum and eigenfunctions, when they are considered as functions of a coupling parameter. In the present paper this parameter is the coupling strength to the continuum. It is shown that the positions of the exceptional points (their accumulation point in the thermodynamical limit) depend on the particular type and energy dependence of the coupling to the continuum in the same way as the transition point of the corresponding phase transition.Comment: 22 pages, 4 figure

On possibility of measurement of the electron beam energy using absorption of radiation by electrons in a magnetic field

The possibility of the precise measurement of the electron beam energy using absorption of radiation by electrons in a static and homogeneous magnetic field in a range up to a few hundred GeV energies, was considered in [1]. With the purpose of experimental checking of this method in a range of several tens MeV energies, the possibility of measurement of absolute energy of the electron beam energy with relative accuracy up to 10^{-4} is examined in details.Comment: 14 pages, 10 figure

Irradiation, Annealing, and Reirradiation Effects on American and Russian Reactor Pressure Vessel Steels

One of the options to mitigate the effects of irradiation on reactor pressure vessels (RPVs) is to thermally anneal them to restore the toughness properties that have been degraded by neutron irradiation. Even though a postirradiation anneal may be deemed successful, a critical aspect of continued RPV operation is the rate of embrittlement upon reirradiation. There are insufficient data available to allow for verification of available models of reirradiation embrittlement or for the development of a reliable predictive methodology. This is especially true in the case of fracture toughness data. Under the U.S.-Russia Joint Coordinating Committee for Civilian Nuclear Reactor Safety (JCCCNRS), Working Group 3 on Radiation Embrittlement, Structural Integrity, and Life Extension of Reactor Vessels and Supports agreed to conduct a comparative study of annealing and reirradiation effects on RPV steels. The Working Group agreed that each side would irradiate, anneal, reirradiate (if feasible ), and test two materials of the other. Charpy V-notch (CVN) and tensile specimens were included. Oak Ridge National Laboratory (ORNL) conducted such a program (irradiation and annealing, including static fracture toughness) with two weld metals representative of VVER-440 and VVER-1000 RPVs, while the Russian Research Center-Kurchatov Institute (RRC-KI) conducted a program (irradiation, annealing, reirradiation, and reannealing) with Heavy-Section Steel Technology (HSST) Program Plate 02 and Heavy-Section Steel Irradiation (HSSI) Program Weld 73W. The results for each material from each laboratory are compared with those from the other laboratory. The ORNL experiments with the VVER welds included irradiation to about 1 x 10{sup 19} n/cm{sup 2} (>1 MeV), while the RRC-KI experiments with the U.S. materials included irradiations from about 2 to 18 x 10{sup 19} n/cm{sup 2} (>l MeV). In both cases, irradiations were conducted at {approximately}290 C and annealing treatments were conducted at {approximately}454 C. The ORNL and RRC-RI experiments have shown generally good agreement for both the Russian and U.S. steels. While recoveries of the Charpy 41-J transition temperatures were substantial in all cases, significantly less recovery of the lateral expansion and shear fracture in some cases (no recovery in one case) deserves further attention. The RRC-KI results for the U.S. steels showed reirradiation embrittlement rates which are conservative relative to the lateral shift prediction based on Charpy impact energy

Fatal subarachnoid hemorrhage following ischemia in vertebrobasilar dolichoectasia.

Vertebrobasilar dolichoectasia (VBD) is a chronic disorder with various cerebrovascular and compressive manifestations, involving subarachnoid hemorrhage (SAH). Occurrence of SAH shortly after worsening of clinical VBD symptoms has occasionally been reported. The goal of the study was to examine this association, in particular its pathophysiology, clinical precursor signs, time course, and outcome.To this end, in a retrospective multicenter study, we analyzed 20 patients with VBD and SAH in regard to preceding clinical symptoms, presence of vertebrobasilar thrombosis and ischemia, outcome and neuropathological correlates.Median age of the 7 female and 13 male patients was 70 years (interquartile range [IQR] 18.3 years). Fourteen patients (70%) presented with new or acutely worsening posterior fossa signs at a median of 3 days prior to SAH (IQR 2, range 0.5-14). A thrombus within the VBD was detected in 12 patients (60%). Thrombus formation was associated with clinical deterioration (χ = 4.38, P = 0.04) and ponto-cerebellar ischemia (χ = 8.09, P = 0.005). During follow-up after SAH, 13 patients (65%) died, after a median survival time of 24 hours (IQR 66.2, range 2-264 hours), with a significant association between proven ponto-cerebellar ischemia and case fatality (χ = 6.24, P = 0.01).The data establish an association between clinical deterioration in patients with VBD, vertebrobasilar ischemia, and subsequent SAH. Antithrombotic treatment after deterioration appears controversial and SAH outcome is frequently fatal. Our data also indicate a short window of 3 days that may allow for evaluating interventional treatment, preferably within randomized trials