Spatial coherence properties of monochromatic electromagnetic beams and of laser modes

It is shown that, contrary to common belief, monochromatic light beams are, in general, not spatially completely coherent, i.e., they will, in general, not produce fringes of unit visibility in a Young's double pinhole interference experiment. We cite experiments with laser modes which confirm this result.     

Photoisomerization of AZO Aromatic Chromophobes in Polyvinyl Chloride

Abstract

The synthesis and characterization of new vinyl chloride-p-acryloyloxyazobenzene copolymers are reported. Kinetics of photoinduced trans-cis and thermal cis-trans isomerization of azo pendant groups in copolymer have also been investigated, and the kinetic parameters were evaluated. An azo acrylate model compound was used for comparison.     

Synthesis and Characterization of Partially Substituted at Lower Rim Phosphorus Containing Calix(4)arenes

The synthesis and characterization of several new phosphorus-containing partially lower rim substituted derivatives of 5,11,17,23-tetra(t-butyl) calix(4)arene (I) and 5,11,17,23-tetra(t-octyl)calix(4)arene (II), namely 5,11,17,23-tetra(t-butyl)-25,27-dihydroxy-26,28-bis(diphenylphosphinoyl-oxy) calix(4)arene (IV); 5,11,17,23-tetra(t-butyl)-25-hydroxy-26,27,28-tris(tetramethyldiamido-phosphinoyl-oxy) calix(4)arene (Vb); 5,11,17,23-tetra(t-butyl)-25,27-dihydroxy-26,28-bis(dimethyl-phosphinoyl-methoxy) calix(4)arene (VI); 5,11,17,23-tetra (t-octyl)-25,27-dihydroxy-26,28-bis(dimethyl-phosphinoyl-methoxy) calix(4)arene (VII) are reported. The structure of the synthesized calix(4)arene derivatives are identified and confirmed by elemental analysis, IR, ¹H, ¹³C, ³¹P{¹H} NMR spectroscopy and mass spectrometry as and X-ray crystallographic analysis of 5,11,17,23-tetra(t-butyl)-25,27-dihydroxy-26,28-bis(dimethyl-phosphinoyl-methoxy) calix(4)arene VI. According to the NMR spectra, all calix(4)arenes are in cone conformation.     

Continuous development of schemes for parallel computing of the electrostatics in biological systems: Implementation in DelPhi

Due to the enormous importance of electrostatics in molecular biology, calculating the electrostatic potential and corresponding energies has become a standard computational approach for the study of biomolecules and nano‐objects immersed in water and salt phase or other media. However, the electrostatics of large macromolecules and macromolecular complexes, including nano‐objects, may not be obtainable via explicit methods and even the standard continuum electrostatics methods may not be applicable due to high computational time and memory requirements. Here, we report further development of the parallelization scheme reported in our previous work (Li, et al., J. Comput. Chem. 2012, 33, 1960) to include parallelization of the molecular surface and energy calculations components of the algorithm. The parallelization scheme utilizes different approaches such as space domain parallelization, algorithmic parallelization, multithreading, and task scheduling, depending on the quantity being calculated. This allows for efficient use of the computing resources of the corresponding computer cluster. The parallelization scheme is implemented in the popular software DelPhi and results in speedup of several folds. As a demonstration of the efficiency and capability of this methodology, the electrostatic potential, and electric field distributions are calculated for the bovine mitochondrial supercomplex illustrating their complex topology, which cannot be obtained by modeling the supercomplex components alone. © 2013 Wiley Periodicals, Inc.     

House-of-security approach to measurement in analytical chemistry: quantification of human error using expert judgments

A new technique for quantification of human errors in chemical analysis using expert judgments is described. This technique is based on the house-of-security approach developed recently in the field of safety and security for prevention of terrorist and criminal attacks against an organization. The following relative quantification parameters (expressed in %) are proposed in the technique: (a) likelihood score of human error in a chemical analytical measurement/testing method, (b) severity score of human error for reliability of the test results, (c) importance score of a component of a laboratory quality system, and (d) effectiveness score of the quality system as a whole in preventing/blocking human error. As an example, 34 scenarios of human error in pH measurement of groundwater are discussed and quantified.     

Current Efficiency,Corrosion and Structural Changes in SnO2-Sb2O3-CuO Inert Anodes for Aluminium Electrolysis

A systematic study was conducted on current efficiency （CE）, corrosion and structural changes in SnO2-based inert anodes （made of 96wt%SnO2＋2wt%Sb2O3＋2wt%CuO） on a laboratory Hall-Heroult aluminium cell. The influence of operating parameters and electrolyte composition on the CE and corrosion process were evaluated. The CE was found to be more than 90% and catastrophic corrosion took place at low percent of Al2O3, high percent of LiF, low cryolite ratio and high current densities. From all the structural changes that took place in the SnO2-based inert anodes, we assumed that the most important contribution was due to the migration of CuO towards the outer limits of the constituent grains of SnO2 based ceramic. The complex process occurred during the formation of various phases and their sintering ability both directly depended on Cu/Sb molar ratio.     

Hard porous chromium containing macrospheres as new catalysts for the esterification reaction of acetic acid with epichlorohydrin

This paper reports a systematic study on the preparation, characterization and testing of metallosilicate macrobeads that contain chromium ions as active catalytic centers. In order to obtain hard macrospheres, four metals (Cr, Al, Zr and Zn) were incorporated into the silica matrix using chitosan as a template and shape generator. Metallosilicate macrospheres were synthesized at room temperature using tetraethylorthosilicate as silicon source and chlorohydric acid as catalyst. The size of metallosilicate macrospheres was in the range 0.9 — 1.1 mm. The catalyst was characterised by means of water sorption technique, FTIR spectroscopy and SEM/EDX analyses. FTIR spectra put into evidence the presence of metallic ions within the silica framework. EDX analyses confirmed the efficient incorporation of metals within the silica matrix (the content of metals from the calcined catalyst is almost the same as that from the initial gel mixture). Porous structure of catalyst investigated by water sorption technique and by pycnometric methods (with n-heptan and mercury respectively) proved that the synthesized catalyst had micro, meso and macropores. Catalyst was tested in the esterification reaction of acetic acid with epichlorohydrin. The temperature and the amount of catalyst exerted a marked influence on reaction rate. This work opens new perspectives for heterogeneous catalysis encouraging the replacement of powder catalysts with macrospherical catalysts that are easy to recover and to reuse.      

Morpho-structural and luminescence investigations on yttrium silicate based phosphors prepared with different precipitating agents

Yttrium silicate doped with cerium (Y₂SiO₅:Ce) was obtained from Y-Ce-Si based precursors prepared by the simultaneous addition of reagents (SimAdd) technique. The synthesis of the precursors was done in well controlled conditions using ammonium oxalate, ammonium carbonate or urea as precipitating agents. Results regarding the influence of precipitating agents on the morpho structural and photoluminescent characteristics of Y₂SiO₅:Ce are reported. The TG analysis in correlation with EGA, FT-IR and XRD investigations reveals the formation of oxalate, hydroxy-carbonate or hydroxy-nitrate based compounds, the same as the conversion of the precursors to well crystallized yttrium silicate. XRD patterns show that the precursors are amorphous except for the sample prepared with ammonium oxalate. Depending on the precipitation conditions, the phosphors phase composition varies from single phase (X2-Y₂SiO₅) to a mixture of phases (X2-Y₂SiO₅, X1-Y₂SiO₅, Y₂O₃). Under UV excitation, phosphors exhibit the specific blue emission of cerium with an intensity that varies from 175.8% (urea) to 96.0% (ammonium carbonate) and to 78.5% (ammonium oxalate). The emission intensity depends on the phase purity and order degree of the phosphors. PACS Classification codes:78.55 Hx, 81.20Fw