Thiol‐ene photopolymerization of polymer‐derived ceramic precursors

The liquid, ceramic precursor monomer VL20 was copolymerized with a thiol monomer in a traditional radical thiol‐ene photopolymerization. Polymerization occurred via addition of the thiol functional group to the vinyl silazane functional group in a 1:1 ratio consistent with a step‐growth polymerization. Gelation occurred at a high conversion of functional groups (70%) consistent with an average molecular weight and functionality of 560 and 1.7, respectively, for VL20 monomers. Initiatorless photopolymerization of the thiol‐VL20 system also occurred upon irradiation at either 365 or 254 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1752–1757, 2004     

The growth and decay of sonic waves in a radiating gas at high temperature

The propagation of a sonic discontinuity in an optically thick gray gas at temperature 10⁵°K or higher has been studied. The effects of radiation pressure and radiation energy density have been taken into account, while the profiles structured by radiant heat transfer are imbedded in the discontinuities under high temperature conditions of an optically thick medium. When the sonic discontinuity is propagating into a gas at rest, its velocity of propagation is found to be a constant which is the effective speed of sound in a radiating gas. The fundamental differential equations governing the growth of the sonic discontinuity are obtained and solved. It is concluded that if the sonic discontinuity is a compressive wave of order 1, then it terminates into a shock wave after a critical timet _c which has been determined. But on the other hand, when the sonic discontinuity is an expansion wave of order 1, then it will decay and will vanish ultimately. Particular cases of interest have been studied in details.     

Simultaneous determination of calcium, magnesium and sulphate in gypsum by ethylenediamine tetraacetic acid

Conclusion The method proposed above is convenient for rapid analysis of many samples where extremely high accuracy is not required especially with sulphate determination.     

Titanium dioxide photocatalyzed oxidation of proteins in biocontaminated waters

The TiO2 photocatalyzed oxidation of the proteins serum albumin, ovalbumin and gamma globulin, is reported. All the amino acids were susceptible to photocatalytic oxidation. However, some were especially vulnerable. Tyrosine was particularly sensitive, as was the semiaromatic histidine, although to a lesser extent. The lack of an activating group on the aromatic ring in Phe, renders the system less amenable to degradation. The photocatalytic degradation of the aliphatic amino acids Gly and Asp, was particularly slow, like in the Fenton oxidation where production of glycine was observed during the cleavage of collagen induced by hydroxyl radicals. Intermediate degradation rate was noticed in Ser, Arg, Val, Cys and Phe.     

Chaotic Quantization of Classical Gauge Fields

We argue that the quantized non-Abelian gauge theory can be obtained as the infrared limit of the corresponding classical gauge theory in a higher dimension. We show how the transformation from classical to quantum field theory emerges, and calculate Planck's constant from quantities defined in the underlying classical gauge theory.     

Synthesis and crystal structure of hexaaquamagnesium hydrogen phosphododecatungstate tetrahydrate [Mg(H2O)6][HPW12O40]·4H2O

Crystals suitable for X-ray structure analysis were obtained after the slow evaporation of the reaction mixture containing equimolar quantities of magnesium chloride and dodecatungstophosphoric acid aqueous solution insuring pH of the solution between 1.0 and 1.2. This simple synthetic route yielded stability of Keggin anion and high quality [Mg(H₂O)₆][HPW₁₂O₄₀]·4H₂O single crystals. The obtained compound belongs to the group of heteropoly compounds and its structure is composed of Keggin [PW₁₂O₄₀]^3– anions, [Mg(H₂O)₆]²⁺ cations and lattice water molecules. Zigzag arrangement of Keggin anions along c-axis creates irregular channels occupied by [Mg(H₂O)₆]²⁺ cations and lattice H₂O molecules. The calculation of the total potential solvent volume indicated the presence of 4.1 lattice H₂O lattice molecules per formula unit, which is in agreement with the here presented structural model. The position of one lattice water molecule is well defined, while each of three other molecules is statistically distributed over two locations. Hydrogen bonds involve all coordinated and lattice H₂O molecules, as well as some oxygen atoms from the Keggin anion. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Selective identification of specific aptamers for the detection of non-typhoidal salmonellosis in an apta-impedimetric sensing format

Microchimica Acta - The authors report on an aptamer-based method for the detection of S. Typhimurium. The aptamers were identified by using a modified cell-based SELEX method (cell-SELEX) by...     

Co2?+? interaction with Azospirillum brasilense Sp7 cells: a 57Co emission M?ssbauer spectroscopic study

The Thylacine Hole–001 meteorite was recovered from the Nullarbor Desert (Australia) in 1977 and is an Ordinary Chondrite, Group H4/5br, which has undergone moderate to severe (B/C) weathering. We have characterised the Fe-bearing phases in Thylacine Hole–001 by ⁵⁷Fe M?ssbauer Spectroscopy at 300?K, 100?K, 50?K and 4?K. The spectrum at 300?K is dominated by the paramagnetic doublets of Olivine, Pyroxene and a Ferric component which is most likely nanoparticulate Goethite. Magnetically split sextets due to Maghemite or Magnetite are also present, consistent with the relatively advanced terrrestrial age of 28,500 yrs The nanoparticulate Goethite component shows a blocked, magnetically split sextet at low temperatures. We also observe the effects of magnetic ordering of the Olivine and Pyroxene below 50?K.     

Different sensing mechanisms in single wire and mat carbon nanotubes chemical sensors

Chemical sensing properties of single wire and mat form sensor structures fabricated from the same carbon nanotubes (CNT) materials have been compared. Sensing properties of CNT sensors were evaluated upon electrical response in the presence of five vapours as acetone, acetic acid, ethanol, toluene, and water. Diverse behaviour of single wire CNT sensors was found, while the mat structures showed similar response for all the applied vapours. This indicates that the sensing mechanism of random CNT networks cannot be interpreted as a simple summation of the constituting individual CNT effects, but is associated with another robust phenomenon, localized presumably at CNT–CNT junctions, must be supposed.