Exciton quantum confinement in nanocones formed on a surface of CdZnTe solid solution by laser radiation

The investigation of surface morphology using atomic force microscope has shown self-organizing of the nanocones on the surface of CdZnTe crystal after irradiation by strongly absorbed Nd:YAG laser irradiation at an intensity of 12.0 MW/cm². The formation of nanocones is explained by the presence of a thermogradient effect in the semiconductor. The appearance of a new exciton band has been observed after irradiation by the laser which is explained by the exciton quantum confinement effect in nanocones.     

Thermal aging of single-layer polymer light-emitting diodes composed of a carbazole and oxadiazole containing copolymer doped with singlet or triplet emitters

An electron-transporting monomer was synthesized that was structurally and energetically similar to the small molecule 2-biphenyl-4-yl-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD). The monomer was copolymerized with 2-(9H-carbazol-9-yl)ethyl 2-methylacrylate and the resulting copolymer was utilized in organic light emitting devices which employed fluorescent coumarin 6 (C6) or phosphorescent tris(2-phenylpyridine)iridium(III) [Ir(ppy)₃] emitters. The copolymer devices exhibited a mean luminance of ca. 400 and 3552 cd/m² with the C6 and Ir(ppy)₃ emitters, respectively, that was stable with thermal aging at temperatures ranging from 23 °C to 130 °C. Comparable poly(9-vinyl-9H-carbazole)/tBu-PBD blend devices exhibited more pronounced variations in performance with thermal aging.     

Acinetobacter baumannii K106 and K112: Two Structurally and Genetically Related 6-Deoxy-l-talose-Containing Capsular Polysaccharides

Whole genome sequences of two Acinetobacter baumannii clinical isolates, 48-1789 and MAR24, revealed that they carry the KL106 and KL112 capsular polysaccharide (CPS) biosynthesis gene clusters, respectively, at the chromosomal K locus. The KL106 and KL112 gene clusters are related to the previously described KL11 and KL83 gene clusters, sharing genes for the synthesis of l-rhamnose (l-Rhap) and 6-deoxy-l-talose (l-6dTalp). CPS material isolated from 48-1789 and MAR24 was studied by sugar analysis and Smith degradation along with one- and two-dimensional 1H and 13C NMR spectroscopy. The structures of K106 and K112 oligosaccharide repeats (K units) l-6dTalp-(1→3)-D-GlcpNAc tetrasaccharide fragment share the responsible genes in the respective gene clusters. The K106 and K83 CPSs also have the same linkage between K units. The KL112 cluster includes an additional glycosyltransferase gene, Gtr183, and the K112 unit includes α l-Rhap side chain that is not found in the K106 structure. K112 further differs in the linkage between K units formed by the Wzy polymerase, and a different wzy gene is found in KL112. However, though both KL106 and KL112 share the atr8 acetyltransferase gene with KL83, only K83 is acetylated.     

Collision cascade temperature

Interaction of a projectile with a solid has been considered in detail. It has been found that any collision cascade generated by a projectile can be characterized by the average kinetic energy of cascade atoms that represents an “instantaneous temperature” of the cascade during its very short lifetime (10⁻¹² s). We refer to this value as the “dynamic temperature” in order to emphasize the fact that cascade atoms are in a dynamic equilibrium and have a definite energy distribution. The dynamic temperature defines the electron distribution in the cascade area and, hence, the ionization probability of sputtered atoms. The energy distribution of cascade atoms and, as a consequence, the dynamic temperature can be found experimentally by measuring the energy distribution of sputtered atoms. The calculated dynamic temperature has been found to be in good agreement with the experimental data on ion formation in the case of cesium and oxygen ion sputtering of silicon. Based on the developed model we suggest an experimental technique for a radical improvement of the existing cascade sputtering models.     

Fracture of precipitated NiTi shape memory alloys

The fracture mechanisms in single crystal and polycrystalline Ti-50.8at%Ni shape memory alloys containing Ti₃Ni₄ precipitates are studied using the scanning electron microscope (SEM). Aged materials with three different precipitate sizes (50 nm, 150 nm, and 400 nm), which have interfaces ranging from semi-coherent to incoherent, are considered. The mechanisms of material fracture identified in the single crystal NiTi are: 1. Nucleation, growth, and coalescence of voids from the Ti₃Ni₄ precipitates, 2. Cleavage fracture on {100} and {110} crystallographic planes, 3. Nucleation, growth, and coalescence of voids from fractured Ti-C inclusions. Cleavage and ductile tearing mechanisms also operate in polycrystalline NiTi, however, since the Ti-C inclusions are an artifact of single crystal growth processes, mechanism 3 was not discovered in the polycrystalline materials. Cleavage fracture and ductile tearing are found to act in conjunction, with the relative dominance of one over the other depending on the local precipitate size and concentration. As the Ti₃Ni₄ precipitate size increases to about 400 nm, the overall fracture is dominated by failure mechanism 1, and the cleavage markings become diffuse. Finally, we assert that the high tensile ductility of drawn NiTi polycrystals is due partially to the fact that drawn bar and wire stock usually have a strong {111} fiber texture. Such a texture promotes the initiation of the transformation at low stresses and concurrently prevents primary cleavage on the {100} or {110} planes.     

Role of caustics in the formation of networks of amplitude zeros for partially developed speckle fields

The topology of a partially developed speckle field was studied by use of interference techniques through computer simulation. Amplitude and phase structures in the vicinity of caustics for a coherent radiation field scattered at a surface with large inhomogeneities were investigated. It was confirmed that the caustics are indispensible components of the procedure for the formation of networks of amplitude zeros for a coherent field scattered by a rough surface with large inhomogeneities. It is shown that the formation of interference forklets in the field gives evidence of changes in the field's topology, as these forklets are a diagnostic sign of transition from a caustic to a three-dimensional pattern of a diffraction catastrophe.     

Acoustic Echo Cancellation Using Frequency-Domain Spline Identification

Low-complexity delayless acoustic echo cancellation techniques based on frequency-domain spline-identification are proposed and investigated. Two methods of approximation of the acoustic frequency response, both using B-splines, are considered: the optimal-spline method and the local-spline method. The optimal-spline method seeks the solution of a least squares problem. The most computationally demanding part of the method, solution of the normal equations, is implemented by using the low-complexity dichotomous coordinate descent algorithm. The local-spline method avoids solving the normal equations, enabling further simplification; this is at the expense of a slight degradation in the cancellation performance. A novel efficient double-talk detector is also proposed, being an inherent feature of the frequency-domain identification. Open-loop and closed-loop identification schemes with cubic splines are studied by simulation and compared with the fast affine projection (FAP) algorithm. The proposed techniques provide cancellation performance better than that of the FAP algorithm, especially in double-talk and noisy environments, with a lower complexity     

Current transfer processes in a hydrated layer localized in a two-layer porous structure of nanosized ZrO2

Journal of Materials Science: Materials in Electronics - The current transfer through a two-layer structure saturated with absorbed water, each layer of which consists of pressed ZrO2 nanoparticles...