Helium Induced Structural Disorder in Hydrogenated Nanocrystalline Silicon (nc-Si:H) Thin Films Prepared by HW-CVD Method

Structural, optical and electrical properties of hydrogenated nanocrystalline silicon (nc-Si:H) films, deposited from silane (SiH4) and helium (He) gas mixture without hydrogen by hot wire chemical vapor deposition (HW-CVD) method were investigated as a function of helium dilution of silane (RHe). We observed that the deposition rate is much higher (4-33 Å/s) compared to conventional plasma enhanced chemical vapour deposited (PE-CVD) nc-Si:H films. Raman spectroscopy revealed that the crystalline volume fraction decreases with increasing He dilution of silane whereas the crystallite size remains almost constant (~ 2 nm) for the entire range of He dilution of silane studied. Furthermore, an increase in the structural disorder in the nc-Si:H films has been observed with increasing He dilution of silane. The hydrogen content was ~ 9 at. % in the film deposited at 60 % RHe and decreases rapidly as RHe increases further. The photoresponse decreases by order of 1 with increasing helium dilution of silane from 60 to 97 %. It has been concluded that adding helium gas to the silane induces the structural disorders in the hydrogenated nanocrystalline silicon (nc-Si:H) thin films prepared by HW-CVD method. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2960

Universal computation by multi-particle quantum walk

A quantum walk is a time-homogeneous quantum-mechanical process on a graph defined by analogy to classical random walk. The quantum walker is a particle that moves from a given vertex to adjacent vertices in quantum superposition. Here we consider a generalization of quantum walk to systems with more than one walker. A continuous-time multi-particle quantum walk is generated by a time-independent Hamiltonian with a term corresponding to a single-particle quantum walk for each particle, along with an interaction term. Multi-particle quantum walk includes a broad class of interacting many-body systems such as the Bose-Hubbard model and systems of fermions or distinguishable particles with nearest-neighbor interactions. We show that multi-particle quantum walk is capable of universal quantum computation. Since it is also possible to efficiently simulate a multi-particle quantum walk of the type we consider using a universal quantum computer, this model exactly captures the power of quantum computation. In principle our construction could be used as an architecture for building a scalable quantum computer with no need for time-dependent control

Staphylococcus aureus nasal carriage among outpatients attending primary health care centers: a comparative study of two cities in Saudi Arabia and Egypt

AbstractEpidemiological and molecular data on community acquired methicillin resistant Staphylococcus aureus (CA-MRSA) are still scarce in both Egypt and Saudi Arabia. There is almost no data regarding methicillin resistant Staphylococcus aureus (MRSA) prevalence in both countries. This study was conducted to investigate the prevalence and molecular epidemiology of S. aureus and MRSA nasal carriage among outpatients attending primary health care centers in two big cities in both countries. A total of 206 nasal swabs were obtained, 103 swabs from each country. S. aureus isolates were characterized by antibiotic susceptibility, presence of mecA and PVL genes, SCCmec-typing and spa typing, the corresponding Multi locus sequence typing clonal complex was assigned for each spa type based on Ridom StaphType database. MRSA was detected in 32% of the Egyptian outpatients while it was found in 25% of the Saudi Arabian outpatients. All MRSA isolates belonged to SCCmec type V and IVa, where some isolates in Saudi Arabia remained nontypeable. Surprisingly PVL+ isolates were low in frequency: 15% of MRSA Egyptian isolates and 12% of MRSA isolates in Saudi Arabia. Two novel spa types were detected t11839 in Egypt, and t11841 in Saudi Arabia. We found 8 spa types among 20 isolates from Egypt, and 12 spa types out of 15 isolates from Saudi Arabia. Only two spa types t008 and t223 coexisted in both countries. Four clonal complexes (CC5, CC8, CC22, and CC80) were identified in both Egypt and Saudi Arabia. However, the data collected lacked a representation of isolates from different parts of each country as only one health center from each country was included, it still partially illustrates the CA-MRSA situation in both countries. In conclusion a set of control measures is required to prevent further increase in MRSA prevalence

Quantum gas microscopy of an attractive Fermi-Hubbard system

The attractive Fermi-Hubbard model is the simplest theoretical model for studying pairing and superconductivity of fermions on a lattice. Although its s-wave pairing symmetry excludes it as a microscopic model for high-temperature superconductivity, it exhibits much of the relevant phenomenology, including a short-coherence length at intermediate coupling and a pseudogap regime with anomalous properties. Here we study an experimental realization of this model using a two-dimensional (2D) atomic Fermi gas in an optical lattice. Our site-resolved measurements on the normal state reveal checkerboard charge-density-wave correlations close to half-filling. A "hidden" SU(2) pseudo-spin symmetry of the Hubbard model at half-filling guarantees superfluid correlations in our system, the first evidence for such correlations in a single-band Hubbard system of ultracold fermions. Compared to the paired atom fraction, we find the charge-density-wave correlations to be a much more sensitive thermometer, useful for optimizing cooling into superfluid phases in future experiments

Probing quench dynamics across a quantum phase transition into a 2D Ising antiferromagnet

Simulating the real-time evolution of quantum spin systems far out of equilibrium poses a major theoretical challenge, especially in more than one dimension. We experimentally explore the dynamics of a two-dimensional Ising spin system with transverse and longitudinal fields as we quench it across a quantum phase transition from a paramagnet to an antiferromagnet. We realize the system with a near unit-occupancy atomic array of over 200 atoms obtained by loading a spin-polarized band insulator of fermionic lithium into an optical lattice and induce short-range interactions by direct excitation to a low-lying Rydberg state. Using site-resolved microscopy, we probe the correlations in the system after a sudden quench from the paramagnetic state and compare our measurements to exact calculations in the regime where it is possible. We achieve many-body states with longer-range antiferromagnetic correlations by implementing a near-adiabatic quench and study the buildup of correlations as we cross the quantum phase transition at different rates

Electronic and phononic Raman scattering in detwinned YBa2_2Cu3_3O6.95_{6.95} and Y0.85_{0.85}Ca0.15_{0.15}Ba2_2Cu3_3O6.95_{6.95}: s-wave admixture to the dx2−y2d_{x^2-y^2}-wave order parameter

Inelastic light (Raman) scattering has been used to study electronic excitations and phonon anomalies in detwinned, slightly overdoped YBa$_2$Cu$_3$O$_{6.95}$ and moderately overdoped Y$_{0.85}$Ca$_{0.15}$Ba$_2$Cu$_3$O$_{6.95}$ single crystals. In both samples modifications of the electronic pair-breaking peaks when interchanging the a- and b-axis were observed. The lineshapes of several phonon modes involving plane and apical oxygen vibrations exhibit pronounced anisotropies with respect to the incident and scattered light field configurations. Based on a theoretical model that takes both electronic and phononic contributions to the Raman spectra into account, we attribute the anisotropy of the superconductivity-induced changes in the phonon lineshapes to a small s-wave admixture to the $d_{x^2-y^2}$ pair wave-function. Our theory allows us to disentangle the electronic Raman signal from the phononic part and to identify corresponding interference terms. We argue that the Raman spectra are consistent with an s-wave admixture with an upper limit of 20 percent.Comment: accepted in Phys. Rev. B, 11 page

Lattice dynamical signature of charge density wave formation in underdoped YBa2Cu3O6+x

We report a detailed Raman scattering study of the lattice dynamics in detwinned single crystals of the underdoped high temperature superconductor YBa2Cu3O6+x (x=0.75, 0.6, 0.55 and 0.45). Whereas at room temperature the phonon spectra of these compounds are similar to that of optimally doped YBa2Cu3O6.99, additional Raman-active modes appear upon cooling below ~170-200 K in underdoped crystals. The temperature dependence of these new features indicates that they are associated with the incommensurate charge density wave state recently discovered using synchrotron x-ray scattering techniques on the same single crystals. Raman scattering has thus the potential to explore the evolution of this state under extreme conditions.Comment: 12 pages, 11 figure

Energy Efficient Buildings in Smart Cities: Biomimicry Approach

Smart cities are those using technologies to make life easier for their citizens and enhancing the quality of life and urban service in order to reduce consumption, especially of energy. Biomimicry is one of the tools of the 21st century toachieve an emotional smart city that has its own spirit and identity. Biomimicryhas three main levels: organism, behaviour and ecosystem level, in terms of form generation, material selection,construction process, and function establishing.A subcategory of biomimicry is building skin which forms the entire exterior envelope of the building. It is the boundary through which buildings interact with the environment and the whole city. The aim of this paper isto discussbiomimicry as a tool to reduce energy consumption in cities through buildingskins. It also discusses concepts of smart cities. It provides an overviewof biomimicry as a tool of achieving a perfect biomimetic skin of buildings in smart cities. In addition it analysescase studies of energy conservationusing concepts of biomimicry. Finally it would conclude guidelines for biomimicry design of building skinsas a tool for reducing energy consumption in smart citie