840 research outputs found
A difference analogue of the Davey-Stewartson system: discrete Gram-type determinant solution and Lax pair
No full textWe consider a difference-difference Davey-Stewartson system together with its bilinear structure. We write some new Gram-type determinantal solutions taking into account a set of Jacobi identities for determinants. A bilinear Backlund transformation is constructed and consequently a Lax pair for the discrete system is derived
On a discrete Davey-Stewartson system
No full textWe propose a differential difference equation in R-1 x Z(2) and study it by Hirota's bilinear method. This equation has a singular continuum limit into a system which admits the reduction to the Davey-Stewartson (DS) equation. The solutions of this discrete DS system are characterized by Casorati and Grammian determinants. Based on the bilinear form of this discrete DS system, we construct the bilinear Backlund transformation which enables us to obtain its Lax pair
First synthesis of bridged and double calixsugars
No full textBridged and double calixarene-trehalose molecular architectures have been assembled through ester and amide linkages between the sugar and the macrocycle units; the double calixsugar showed selective receptor properties toward imidazole. © 2001 Elsevier Science Ltd
A phantom study on the behavior of Acuros XB algorithm in flattening filter free photon beams
No full textTo study the behavior of Acuros XB algorithm for flattening filter free (FFF) photon beams in comparison with the anisotropic analytical algorithm (AAA) when applied to homogeneous and heterogeneous phantoms in conventional and RapidArc techniques. Acuros XB (Eclipse version 10.0, Varian Medical Systems, CA, USA) and AAA algorithms were used to calculate dose distributions for both 6X FFF and 10X FFF energies. RapidArc plans were created on Catphan phantom 504 and conventional plans on virtual homogeneous water phantom 30 × 30 × 30 cm3, virtual heterogeneous phantom with various inserts and on solid water phantom with air cavity. Dose at various inserts with different densities were measured in both AAA and Acuros algorithms. The maximum % variation in dose was observed in (−944 HU) air insert and minimum in (85 HU) acrylic insert in both 6X FFF and 10X FFF photons. Less than 1% variation observed between −149 HU and 282 HU for both energies. At −40 HU and 765 HU Acuros behaved quite contrarily with 10X FFF. Maximum % variation in dose was observed in less HU values and minimum variation in higher HU values for both FFF energies. Global maximum dose observed at higher depths for Acuros for both energies compared with AAA. Increase in dose was observed with Acuros algorithm in almost all densities and decrease at few densities ranging from 282 to 643 HU values. Field size, depth, beam energy, and material density influenced the dose difference between two algorithms
Glycoside-Clustering Round Calixarenes toward the Development of Multivalent Carbohydrate Ligands. Synthesis and Conformational Analysis of Calix[4]arene <i>O</i>- and <i>C</i>-Glycoconjugates
No full textBis- and tetra-O- and C-glycosyl calixarenes (calixsugars) have been prepared by tethering carbohydrate moieties to a tetrapropoxycalix[4]arene scaffold through alkyl chains. Two methodologies have been employed. One consisted of the stereoselective multiple glycosylation of upper rim calix[4]arene polyols leading to calix-O-glycosides; the other involved a multiple Wittig olefination of upper rim calix[4]arene-derived polyaldehydes by the use of sugar phosphoranes and reduction of the alkene double bonds affording calix-C-glycosides. The NMR spectra and NOE experiments of bis-glycosylated products indicate that compounds bearing sugar-protected residues exist preferentially in solution in a flattened cone arrangement (far conformation) whereas deprotected derivatives adopt a close conformation. Calculations by molecular mechanics of the latter compounds point to a close conformation as well in gas phase
Width of the exotic Xb (5568) state through its strong decay to Bs0 π+
No full textAzizi, Kazem (Dogus Author)The width of the newly observed exotic state Xb(5568) is calculated via its dominant strong decay to Bs0π+ using the QCD sum rule method on the light cone in conjunction with the soft-meson approximation. To this end, the vertex XbBsπ is studied and the strong coupling gXbBsπ is computed employing for Xb(5568) state the interpolating diquark-antidiquark current of the [su][bd] type. The obtained prediction for the decay width of Xb(5568) is confronted and a nice agreement found with the experimental data of the
New geometric formalism for gravity equation in empty space
No full textIn this paper, a complex daor field which can be regarded as the square root of space-time metric is proposed to represent gravity. The locally complexified geometry is set up, and the complex spin connection constructs a bridge between gravity and SU(1, 3) gauge field. Daor field equations in empty space are acquired, which are one-order differential equations and do not conflict with Einstein's gravity theory.Astronomy & AstrophysicsSCI(E)1ARTICLE61009-10221
Optical properties of boron-doped Si nanowires
No full textRaman scattering and photoluminescence (PL) of boron-doped silicon nanowires have been investigated. Raman spectra showed a band at 480 cm(-1), indicating that the crystallinity of the nanowires was suppressed by boron doping. PL taken from B-doped SiNWS at room temperature exhibited three distinct emission peaks at 1.34, 1.42. and 1.47 eV and the PL intensity was much stronger than that of undoped SiNWS. The increased PL intensity should be very profitable for nano-optoelectronics. (C) 2004 Elsevier B.V. All rights reserved
AMPS modeling of light J-V characteristics of a-Si based solar cells
No full textAMPS (Analysis of microelectronic and photonic structures) mode,which was developed by Pennsylvania State University, has been used to module the light J-V characteristics of a-Si solar cells with a structure of TCO/p-a-SiC:H/i-a-Si:H/n-a-Si:H/ metal. The effects of valence band offset and contact barriers at p/i and TOC/p, n/metal interfaces on the light J-V characteristics have been examined. The modeling has qualitatively categorized and explained the non-ideal J-V behaviors (rollover, crossover, Voc shift,and rollunder) observed in a-Si based solar cells
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