Distortion and segregation in a dislocation core region at atomic resolution

The structure of an isolated, Ga terminated, 30 degree partial dislocation in GaAs:Be is determined by high resolution transmission electron microscopes and focal series reconstruction. The positions of atomic columns in the core region are measured to an accuracy of better than 10 pm. A quantitative comparison of the structure predicted by an ab initio electronic structure total energy calculation to the experiment indicates that theory and experiment agree to within 20 pm. Further analysis shows the deviations between theory and experiment appear to be systematic. Electron energy loss spectroscopy establishes that defects segregate to the core region, thus accounting for the systematic deviations.     

Synthesis of oxime bearing cyclophosphazenes and their reactions with alkyl and acyl halides

Two novel cyclophosphazenes containing oxime groups were prepared from the hexakis(4‐formylphenoxy)cyclotriphosphazene ( 2 ) and hexakis‐(4‐acetylphenoxy)cyclotriphosphazene ( 7 ). The reactions of these oximes with acetyl chloride, chloroacetyl chloride, methyl iodide, propyl chloride, mono‐ chloroacetone, and 1,4‐dichlorobutane were studied. Hexasubstituted compounds were obtained from the reactions of hexakis(4‐[(hydroxyimino)methyl]phenoxy)cyclotriphosphazene ( 3 ) with acetyl chloride ( 4 ) and chloroacetyl chloride ( 5 ); however, tetrasubstituted product was obtained from methyl iodide ( 6 ). Tetra‐ and trisubstituted products were obtained from the reactions of hexakis(4‐[(1)‐N‐hydroxyethaneimidoyl]phenoxy)cyclotriphosphazene ( 8 ) with acetyl chloride ( 9 ) and chloroacetyl chloride ( 10 ), respectively. All products were obtained in high yields. Pure and defined product could not be obtained from the reaction of 8 with methyl iodide, and could not be also obtained from the reactions of 3 and 8 with propyl chloride, monochloroacetone, and 1,4‐dichlorobuthane. The structures of the compounds were defined by elemental analysis, IR, ¹H, ¹³C, and ³¹P NMR spectroscopy. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:112–117, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20176     

Role of oxygen at screw dislocations in GaN

Here we report the first direct atomic scale experimental observations of oxygen segregation to screw dislocations in GaN using correlated techniques in the scanning transmission electron microscope. The amount of oxygen present in each of the three distinct types of screw dislocation core is found to depend on the evolution and structure of the core, and thus gives rise to a varying concentration of localized states in the band gap. Contrary to previous theoretical predictions, the substitution of oxygen for nitrogen is observed to extend over many monolayers for the open core dislocation.     

Normal coordinate analysis and crystal structure of N,N-dimethyl-N'-(2-chloro-benzoyl)thiourea

In the present paper, the crystal structural and vibrational analysis of the N,N-dimethyl-N'-(2-chloro-benzoyl)thiourea molecule is reported. The molecular structure of the title compound was determined by single crystal X-ray diffraction method. The compound crystallizes monoclinic, space group P2(1)/c with a=5.6601(13)A, b=10.748(2)A, c=17.778(4)A, beta=94.266(5) degrees , and V=1078.5(4)A(3) with Z=4 for d(calc)=1.495 g/cm(3). Calculations of the vibrational frequencies have been carried out on the basis of normal coordinate analysis using simple general valence force field in Wilson's GF matrix method with the SPSIM computer program. With the help of this modern technique we were able to complete the assignment of the vibrational spectrum of the title compound.     

Cobalt,Nickel and Copper Complexes of Benzylamino-p-chlorophenylglyoxime. Thermal and thermodynamic data

Vic-dioxime ligandsand their metal complexes are used in analytical, bio, pigment and medicinal chemistry. Complexes of nickel(II), copper(II), and cobalt(II) with benzylamino-p-chlorophenylglyoxime (BpCPG) are synthesised. Thermal behaviour of these complexes was studied in dynamic nitrogen atmosphere by DTA, DTG and TG techniques. GC-MS combined system was used to identify the products during pyrolytic decomposition. The pyrolytic end products were identified by X-ray powder diffraction. Thermoanalytical data of these complexes are presented in this communication. Interpretation and mathematical analysis of these data and evaluation of order of reaction, the energy and entropy of activation based on the integral method using the Coats-Redfern equation and the approximation method using the Horowitz-Metzger equation are also given. The metal complexes undergo decomposition in three stages and metal oxides remained as end products of the complexes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Potential Therapeutic Benefits of Honey in Neurological Disorders: The Role of Polyphenols

Honey is the principal premier product of beekeeping familiar to Homo for centuries. In every geological era and culture, evidence can be traced to the potential usefulness of honey in several ailments. With the advent of recent scientific approaches, honey has been proclaimed as a potent complementary and alternative medicine for the management and treatment of several maladies including various neurological disorders such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and multiple sclerosis, etc. In the literature archive, oxidative stress and the deprivation of antioxidants are believed to be the paramount cause of many of these neuropathies. Since different types of honey are abundant with certain antioxidants, primarily in the form of diverse polyphenols, honey is undoubtedly a strong pharmaceutic candidate against multiple neurological diseases. In this review, we have indexed and comprehended the involved mechanisms of various constituent polyphenols including different phenolic acids, flavonoids, and other phytochemicals that manifest multiple antioxidant effects in various neurological disorders. All these mechanistic interpretations of the nutritious components of honey explain and justify the potential recommendation of sweet nectar in ameliorating the burden of neurological disorders that have significantly increased across the world in the last few decades.     

Upper and lower bounds on subcarrier collision for inter-cell interference scheduler in OFDMA-based systems: Voice traffic

This study investigates upper and lower bounds on subcarrier collision for inter-cell interference (ICI) schedulers in orthogonal frequency division multiple access (OFDMA)-based wireless systems carrying voice traffic. It is shown that the amount of knowledge regarding the reserved resources in the neighboring cell plays a crucial role in the performance of ICI schedulers. Also, it is proven that the upper bound of subcarrier collision for ICI schedulers corresponds to the case which is driven by the absence of knowledge about the reserved resources in the neighboring cell. On the other hand, the lower bound of subcarrier collision for ICI schedulers corresponds to the case which is driven by the perfect knowledge about the reserved resources in the neighboring cell. Based on the lower bound analysis, a minimum expected number of collision scheduler is developed and its performance is investigated as well. Moreover, the impact of scheduling period on the performance of schedulers is examined. Numerical results are presented along with related discussions.     

Cobalt ion-doped polyaniline,poly(N-methylaniline), and poly(N-ethylaniline): electrosynthesis and characterisation using electrochemical methods in acidic solutions

Cobalt ion (Co²⁺)-doped polyaniline (PANI-Co), poly(N-methylaniline) (PNMA-Co), and poly(N-ethylaniline) (PNEA-Co) films were synthesised electrochemically on a pencil graphite electrode (PGE) and their electrochemical properties were investigated for supercapacitor applications. The polymer film-coated electrodes (PGE/PANI-Co, PGE/PNMA-Co, and PGE/PNEA-Co) thus obtained were characterised by scanning electron microscopy (SEM) and different electrochemical methods. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were employed in 0.1 M H₂SO₄ solution to calculate the specific capacitance (C _S) values of the electrodes. The maximum C _S of 192.94 F g^?1, 139.83 F g^?1, and 47.12 F g^?1 were achieved for PGE/PANI-Co, PGE/PNMA-Co, and PGE/PNEA-Co at 1 mV s^?1, respectively. On the other hand, the charge/discharge stability of the electrodes was analysed using the repeating chronopotentiometry (RCP) method. The RCP measurements indicate that the electrodes could be used as an electrode active material for low voltage supercapacitor applications.     

Vibrational spectrum and assignments of 2-(4-methoxyphenyl)-1H-benzo[d]imidazole by ab initio Hartree-Fock and density functional methods

The room temperature attenuated total reflection Fourier transform infrared spectrum of the 2-(4-methoxyphenyl)-1H-benzo[d]imidazole has been recorded with diamond/ZnSe prism. The conformational behaviour, structural stability of optimized geometry, frequency and intensity of the vibrational bands of the title compound were investigated by utilizing ab initio calculations with 6-311G** basis set at HF, B3LYP, BLYP, B3PW91 and mPW1PW91 levels. The harmonic vibrational frequencies were calculated and scaled values have been compared with experimental IR spectrum. The observed and the calculated frequencies are found to be in good agreement. The theoretical vibrational spectra of the title compound were interpreted by means of potential energy distributions using VEDA 4 program. Furthermore, the optimal uniform scaling factors calculated for the title compound are 0.9120, 0.9596, 0.9660, 0.9699, and 0.9993 for HF, mPW1PW91, B3PW91, B3LYP and BLYP methods, respectively.     

Determination of antimony by using tungsten trap atomic absorption spectrometry

An electrically heated tungsten coil was used as a trap in the determination of antimony. The technique consists of three steps. Initially, SbH₃ is formed by hydride generation procedure; then the analyte species in vapor form are transported to W-coil trap heated at 370 °C. Following the preconcentration step, the trap is heated to 895 °C; analyte species are revolatilized and transported to the flame-heated quartz atom cell where atomization and the formation of signal take place. The experimental parameters were optimized both for trap and no-trap studies. The most important experimental parameters are concentrations of HCl and NaBH₄ solutions, H₂ and Ar gas flow rates, and collection and revolatilization temperatures of W-coil. Accuracy was tested using a certified reference material, waste water EU-L-1. Limit of detection for the system is 16 ng l^− 1 using a sample of 36 ml collected in 4.0 min. Enhancement factor in sensitivity was 17.