The effect of pressure on the elastic constants of Cu, Ag and Au: a molecular dynamics study

This paper describes the effect of pressure on some the mechanical properties of transition metals Cu, Ag, and Au, such as elastic constants and bulk modulus. Using molecular dynamics (MD) simulation, the present study was carried out using the modified many-body Morse potential function expression in the framework of the Embedded Atom Method (EAM). The effect of pressure on equilibrium volume, elastic constants, and bulk modulus were determined, and found to be in agreement with other theoretical calculations and experimental data.     

The alignment of nematic liquid crystal by the Ti layer processed by nonlinear laser lithography

It is well known that the alignment of liquid crystals (LCs) can be realised by rubbing or photoalignment technologies. Recently, nonlinear laser lithography (NLL) was introduced as a fast, relatively low-cost method for large area nano-grating fabrication based on laser-induced periodic surface structuring. In this letter for the first time, the usage of the NLL as a perspective method of the alignment of nematics was presented. By NLL, nanogrooves with about 0.92 μm period were formed on Ti layer. The nanostructured Ti layer (NSTL) was coated with oxidianiline-polyimide film with annealing of the polymer followed without any further processing. Aligning properties of NSTLs were examined with combined twist LC cell. The dependencies of the twist angle of LC cells and azimuthal anchoring energy (AE) of layers on scanning speed and power of laser beam during processing of the Ti layer were the focus of our studies as well. The maximum azimuthal AE, obtained for pure NSTL, is comparable with photoalignment technology. It was found that the deposition of polyimide film on NSTL leads to the gain effect of the azimuthal AE. Also, atomic force microscopy (AFM) study of aligning surfaces was carried out.     

Synthesis and characterization of a pyridine-containing Schiff base oligomer

The oligomer of 4-(4-pyridylmethylideneimino)phenol was formed during oxidative polycondensation in aqueous alkaline medium using oxygen as the oxidant. Optimum conditions of the oxidative polycondensation and the main parameters of the process were found. The maximum yield of the oligomer was 52.4%. The product was characterized by elemental analysis, FT-IR spectroscopy, UV-Vis spectroscopy, and ¹H NMR spectroscopy. The molecular weight distribution was determined by size exclusion chromatography. Thermogravimetric and differential thermal analyses were carried out for 4-(4-pyridylmethylideneimino)phenol and its oligomer. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1785–1788, October, 2006.     

238U and 222Rn activity concentrations and total radioactivity levels in lake waters

The concentrations and distributions of natural radioactivity, uranium and radon in lake waters from around Van, Turkey were investigated with an aim of evaluating the environmental radioactivity. Fourteen lake waters were collected from different six lakes around Van (Turkey) to determine ²³⁸U, ²²²Rn and total alpha and total beta distributions in 2009. The total α and total β activities were counted by using α/β counter of the multi-detector low background system (PIC-MPC-9604) and the ²³⁸U concentrations were determined by inductively coupled plasma-mass spectrometry (Thermo Scientific Element 2) and radon concentrations were measured with the solid state nuclear track detector technique. The activity concentrations ranging from ND to 0.039 Bq L^?1 and from 0.026 to 3.728 Bq L^?1 for total alpha and beta, respectively, and uranium concentrations ranging from 0.083 to 3.078 μg L^?1, and radon concentrations varying between 47.80 and 354.86 Bq m^?3 were observed in the lake waters.     

Evidence for correlation effects: −√T behaviour in the low temperature electrical resistance of disordered metals

It is found that the electrical resistance for several metal-metalloid amorphous alloys decreases with increasing temperature as ?√T from about 20 mK to several K. The form and magnitude of this temperature dependence is in agreement with recent predictions from interaction theories.     

Ring-expanded iridium and rhodium N-heterocyclic carbene complexes: a comparative DFT study of heterocycle ring size and metal center diversity

A new series of ring-expanded six- and seven-membered N-heterocyclic carbene precursors (re-NHCs) and their transition metal complexes were synthesized. The basic properties of the synthesized materials were investigated by density functional theory (DFT). The six- and seven-membered re-NHCs were synthesized in good yield via reaction of the corresponding alkyldibromides or alkyldiiodides with N,N′-bis-(2-phenylbenzene)formamidine in the presence of K₂CO₃ under aerobic conditions. Complexes, represented by the formula [ML_1,2(COD)Cl] (where M = Ir or Rh and L is a ring-expanded N-heterocyclic carbene ligand), were synthesized in the presence of the corresponding free carbene and iridium or rhodium metal precursors in tetrahydrofuran. All new re-NHC complexes were characterized by different analytical techniques, including NMR spectroscopy, X-ray diffraction, UV spectroscopy and elemental analysis. According to molecular electrostatic potential calculations, the electrophilic properties of the complexes were aligned, from highest to lowest, as Ir-6-DiPh, Rh-6-DiPh and Ir-7-DiPh. The HOMO, LUMO and energy gaps of the complexes were calculated by DFT. On the basis of the DFT analysis, it can be predicted that Rh-6-DiPh is the most stable complex and Ir-7-DiPh is more reactive than Ir-6-DiPh.     

Universality of sol--gel phase transition of κ-carrageenan in various salts: a steady state fluorescence study

Thermal phase transitions of κ-carrageenan in NaCl, KCl and CaCl₂ solutions were studied using steady state fluorescence (SSF) technique. Pyranine was introduced as a fluorescence probe for studying sol--gel phase transitions. Scattered light, I _sc and fluorescence intensity, I was monitored against temperature to determine the sol--gel (T _sg) phase transition temperatures. It was observed that T _sg values are strongly correlated to NaCl, KCl and CaCl₂ contents. The weight average degree of polymerization, DP _w and gel fraction G, exponents (γ and β) were measured and found to be in accord with the classical Flory--Stockmayer model, i.e., γ and β were found to be close to 1.0, independent of salt content.     

Optical characterisation of CuInSe2 thin films prepared by two-stage process

Optical absorption spectra of CuInSe₂ chalcopyrite semiconductor films prepared using a two-stage technique were investigated. In addition to absorption measurements, energy-dispersive analysis of X-rays (EDAX) and X-ray diffraction measurements (XRD) were also performed. Direct bandgap energy values for the CuInSe₂ films were derived from the variation of (αhν)² with energy. All the measurements were performed on samples with various Cu/In ratios. It was determined from the absorption measurements that the materials have strong absorption at the fundamental band edge. The E_g values showed an increasing trend with decreasing Cu/In ratios. Received: 26 May 2000 / Accepted: 31 October 2000 / Published online: 10 January 2001