Synthesis,spectroscopic characterization,crystal structures,and theoretical studies of (<Emphasis Type="Italic">E</Emphasis>)-2-(2,4-dimethoxybenzylidene)thiosemicarbazone and (<Emphasis Type="Italic">E</Emphasis>)-2-(2,5-dimethoxybenzylidene)thiosemicarbazone

Two thiosemicarbazones, (E)-2-(2,4-dimethoxybenzylidene)thiosemicarbazone (24-MBTSC (1)) and (E)-2-(2,5-dimethoxybenzylidene)thiosemicarbazone (25-MBTSC (2)), derived from 2,4-dimethoxybenzaldehyde and 2,5-dimethoxybenzaldehyde, respectively, with thiosemicarbazide have been synthesized and their structures were characterized by elemental analyses, FT-IR, ¹H NMR spectroscopy, and X-ray single-crystal diffraction analysis. Molecular orbital calculations have been carried out for 1 and 2 by using an ab initio method (HF) and also density functional method (B3LYP) at 6-31G basis set. Compound 1 crystallizes in the monoclinic system, space group P2₁/c, with a = 8.1342(5) Å, b = 18.1406(10) Å, c = 8.2847(6) Å, β = 109.7258(17)°, V = 1150.75(12) Å³, and Z = 4, whereas compound 2 crystallizes in the orthorhombic system, space group Pbca, with a = 11.0868(6) Å, b = 13.1332(6) Å, c = 15.9006(8) Å, V = 2315.2(2) Å³, and Z = 8. The compounds 1 and 2 displays a trans-configuration about the C=N double bond.     

Optical time-domain analog pattern correlator for high-speed real-time image recognition

The speed of image processing is limited by image acquisition circuitry. While optical pattern recognition techniques can reduce the computational burden on digital image processing, their image correlation rates are typically low due to the use of spatial optical elements. Here we report a method that overcomes this limitation and enables fast real-time analog image recognition at a record correlation rate of 36.7 MHz--1000 times higher rates than conventional methods. This technique seamlessly performs image acquisition, correlation, and signal integration all optically in the time domain before analog-to-digital conversion by virtue of optical space-to-time mapping.     

Time-stretch oscilloscope with dual-channel differential detection front end for monitoring of 100 Gb/s return-to-zero differential quadrature phase-shift keying data

Optical performance monitoring of high-capacity networks is one of the enabling technologies of future reconfigurable optical switch networks. In such networks, rapid performance evaluation of data streams becomes challenging due to the use of advanced modulation formats and high data rates. The time-stretch enhanced recording oscilloscope offers a potential solution to monitoring high-rate data in a practical time scale. Here we demonstrate an architecture with a differential detection front end for simultaneous I/Q data monitoring of a 100 gigabits/s return-to-zero differential quadrature phase-shift keying signal. This demonstration shows the potential of this technology for rapid performance monitoring of high-rate optical data streams that employ advanced modulation formats.     

Crystal structure of dinuclear azide-bridged copper(II) complex [Cu2((3,4-MeO-Ba)2En)2(μ1,1-N3)2(N3)2]{(3,4-MeO-Ba)2En=N,N′-Bis(3,4-dimethoxybenzylidene)-1,2-ethanediamine}

New dinuclear copper(II)-azido complex [Cu₂((3,4-MeO-Ba)₂En)₂(μ_1,1-N₃)₂(N₃)₂] (I) ((3,4-MeO-Ba)₂En = N,N′-bis(3,4-dimethoxybenzylidene)-1,2-diaminoethane) has been synthesized and characterized by elemental analyses, FT-IR spectroscopy, and X-ray single-crystal diffraction. Complex I consists of a dinuclear unit that represents a new example of a copper(II)-azido compound and the Cu²⁺ ions are bridged by two azido ions in a double end-on fashion, consisting of two terminally bonded azido ligands. The Schiff base ligand (3,4-MeO-Ba)₂En is chelated by two imino nitrogen atoms.     

Monsterwellen aus Licht

Seit Jahrhunderten berichten Seefahrer von gigantischen Wellen, die scheinbar aus dem Nichts und ohne Vorwarnung auftauchen. Erst Mitte der 1990er‐Jahre hat sich die Erkenntnis durchgesetzt, dass es sie wirklich gibt und sie für eine größere Zahl katastrophaler Schiffsunglücke verantwortlich waren. In Experimenten an der University of California in Los Angeles haben wir vor kurzem überraschenderweise in Lichtleitfasern Monsterwellen aus Licht nachgewiesen. Ursache hierfür ist eine Nichtlinearität der Faser.     

Seeded supercontinuum generation with optical parametric down-conversion

The transition between modulation instability gain and induced soliton fission in nonlinear fiber is experimentally investigated by coherent seeding with the two-color output of an optical parametric oscillator. This approach produces supercontinuum spectra displaying persistent, fine modulation from seeding-induced noise reduction. Numerical simulations support the findings.     

Enhancing electrooptic modulators using modulation instability

As electronic operating frequencies increase toward the terahertz regime, new electrooptic modulators capable of low‐voltage high‐frequency operation must be developed to provide the necessary optical interconnects. This Letter presents a new concept that exploits modulation instability to compensate for the intrinsically weak electrooptic effect, χ⁽²⁾. Simulations demonstrate more than 50 times enhancement of electrooptic effect at millimeter wave frequencies leading to a substantial reduction in the required modulation voltage.

     

Application of copper oxide–thermal oil (CuO-HTO) nanofluid on convective heat transfer enhancement in inclined circular tube

Journal of Thermal Analysis and Calorimetry - The influence of using copper oxide–thermal oil on convective heat transfer and pressure drop in an upward flow in an inclined smooth tube is...     

On near-wall effects in hard disk packing between two concentric cylinders

Monodisperse packing of disks in confined geometries is rarely addressed in the literature. We present some theoretical aspects of the microstructural properties of 2D static packing of disks between two concentric cylinders. In the core of the geometry, the packing is intact, while it is dilated in the vicinity of the walls as a result of the removal of overlapping disks. We have derived the formula for average packing density in concentric cylinders geometry with given ratio of the particle diameter to the gap between cylinders. It is verified and analyzed further by constructing ordered and disordered packs of monodisperse disks in computer. In this context, Voronoi tessellation is performed for the resulting packs to demonstrate the thickness of the static boundary layer where the packing is influenced by the presence of cylindrical walls.