Growth of hair and the trace element profile a study by sectional analysis

Correlations between the growth of hair and the trace element profile have been investigated by non-destructive neuron activation analysis through gamma-ray speetrometry using NaI(Tl) as well as Ge(Li) detectors. After preliminary investigations to establish the experimental errors, the effect of washing procedures and in-person variations, hair samples belonging to ladies with known case histories, particularly with regard to dietary habits, health and profession, were examined. Scalp-hair samplex 50–100 cm in length, representing an average time span of ∼5–10 years were collected by combing. Samples in their non-anagen phase, differentiated by their roots, were analysed in 10 cm sections. The concentrations of the following elements were determined: Na, Cl, Mn, Co, Cu, Zn, As, Se, Ag, I, Au and Hg. Absolute values for the concentrations are reported for most of the elements, while for the rest relative values for the various sections are given. The values for the different sections vary by large factors for many elements although for some elements, like Cu and Mn, the variations are not appreciable. The unusually large concentrations of elements like Se ang Hg are in broad agreement with the case histories. However, detailed examination of the results with regard to time-dependent variations seem to pose serious problems in the applications to forensic science.     

Use of cyclotron-produced isotopes for analytical investigation: Determination of vanadium in gallium

The extraction of the V(V)-BPHA complex into chloroform and benzene was investigated using⁴⁸V tracer produced from the⁴⁵V reaction using the Variable Energy Cyclotron, Calcutta. A neutron activation analysis procedure for the estimation of vanadium in gallium metal samples based on the extraction of V(V)-BPHA complex into benzene is given.     

Formation of a crosslinked POSS network by an unusual hydrosilylation: Thermo‐oxidative stabilization of the α‐cristobalite phase in its amorphous regions

A semicrystalline inorganic–organic hybrid crosslinked network containing polyhedral oligomeric silsesquioxane (POSS) cores was constructed by the unusual hydrosilylation of the terminal vinyl groups of an internal acetylene‐containing silane linker by a POSS monomer. Products from the thermal treatments of this network in either argon or air at 250, 550, and 1000 °C, respectively, were characterized by Fourier transform infrared, Solid‐state ¹³C and ²⁹Si magic angle spinning NMR, X‐ray diffraction and XPS analyses. The highly symmetrically functionalized POSS silica clusters, in the fluorite silica phase, in the network were found to remain unchanged on thermal treatment possibly due to the shielding of the silica core by the functionalities and a cancellation of thermal stresses on the silica core. Stabilization of the metastable α‐cristobalite phase, which is typically formed on cooling by a β‐ to α‐transition of the β‐cristobalite phase formed above 1400 °C, was observed in the amorphous regions in the network sample treated only to 1000 °C in air. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Hybrid inorganic–organic poly(carborane‐siloxane‐arylacetylene) structural isomers with in‐chain aromatics: Synthesis and properties

Structural isomers of thermo‐oxidatively stable poly(carborane‐siloxane‐arylacetylene) (PCSAA), namely, m‐PCSAA and p‐PCSAA, were synthesized by the reaction of the dimagnesium salts of m‐diethynylbenzene or p‐diethynylbenzene with 1,7‐bis(chlorotetramethyldisiloxyl)‐m‐carborane. The developed polymers have exceptional thermo‐oxidative properties similar to their diacetylene counterpart poly(carborane‐siloxane‐acetylene), PCSA. Thermal treatment of either of the PCSAAs results in a fully crosslinked thermoset by 500 °C resulting from the cycloaddition reactions involving the acetylene and aryl functionalities and subsequent formation of bridging disilylmethylene entities as discerned from Fourier transform infrared, ¹³C and ²⁹Si solid‐state NMR, and XPS studies. X‐ray diffraction analysis revealed that the thermosets obtained from p‐PCSAA possess enhanced crystallinity when compared to that obtained from m‐PCSAA possibly due to more efficient packing interactions of the p‐diethynylbenzene groups during thermoset formation. The presence of the aryl groups in the backbone of the PCSAAs' chains appeared to have enhanced the storage and bulk moduli of their thermosets when compared to the thermoset of PCSA. Dielectric studies of m‐PCSAA and p‐PCSAA revealed segmental relaxation peaks, α, above their glass transition temperatures with p‐PCSAA exhibiting a broader peak with a slower relaxation rate than m‐PCSAA. © 2013 Wiley Periodicals, Inc.^? J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2638–2650     

Electro catalytic generation of reactive species at diamond electrodes and applications in microbial inactivation

Use of robust and safe water disinfection technologies which are inexpensive and energy-efficient are need of the hour to combat the problem of inadequate access of safe and clean drinking water. Energy and chemically intensive water treatment technologies warrant the need for a safe and environmentally sound treatment technology. Electrochemical disinfection or electrodisinfection (ED) is experiencing a great resurgence among the scientific communities owing to its novel use of electrode materials and electric current in an inexpensive and energy-efficient way for achieving the inactivation of microorganisms. Among the various electrodes used in the ED, boron-doped diamonds emerge as a sustainable alternate for their ability to electro generate strong potent oxidants which result in effective pathogen control in drinking water. ED for disinfecting waters occurs via generation of the reactive species which act in the bacterial inactivation mechanisms. In this mini-review, a critical discussion on the fundamentals and applications of promising electrochemical methods using boron-doped diamond anodes (namely electrochemical oxidation), evidencing their advantages for the remediation of drinking water infected with waterborne agents, is given.     

Evidence for superconductivity in fluorinated La2CuO4 at 35 K: Microwave investigations

In the fluorinated La₂CuO_4−x prepared using a solid state reaction with NH₄HF₂ as a fluorinating agent at 550 K at ambient pressure, superconductivity was detected by microwave and EPR techniques with aT _c of 35 K.     

Photochemistry of S-phenacyl xanthates

Various synthetically readily accessible S-phenacyl xanthates are shown to undergo photoinitiated homolytic scission of the C-S bond in the primary step. The resultant fragments, phenacyl and xanthic acid radicals, recombine to form symmetrical 1,4-diketones and xanthogen disulfides, respectively, in high to moderate chemical yields in chemically inert solvents. They can also be efficiently trapped by a hydrogen-atom-donating solvent to give acetophenone and xanthic acid derivatives. The latter compound is in situ thermally converted to the corresponding alcohol in high chemical yields. S-Phenacyl xanthates could thus be utilized as synthetic precursors to the above-mentioned compounds or as photoremovable protecting groups for alcohols in which the xanthate moiety represents a photolabile linker. The photochemically released phenacyl radical fragments efficiently but reversibly add to the thiocarbonyl group of the parent xanthate molecule. The kinetics of this degenerative reversible addition-fragmentation transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) mechanism was studied using laser flash photolysis (LFP) and density functional theory (DFT) calculations. The rate constants of the RAFT addition step, k(add) ～ 7 × 10(8) M(-1) s(-1), and phenacyl radical addition to a double bond of 1,1-diphenylethylene, k(add) ～ 10(8) M(-1) s(-1), in acetonitrile were experimentally determined by LFP. In addition, photoinitiation of the methyl methacrylate polymerization by S-phenacyl xanthate is demonstrated. The polydispersity index of the resulting poly(methyl methacrylate) was found to be ～1.4. We conclude that S-phenacyl xanthates can serve simultaneously as photoinitiators as well as RAFT/MADIX agents in polymerization reactions.     

Synthesis of several intercalating spinel cathode materials for secondary lithium cells by a simple low temperature procedure

Although several methods are available to prepare spinel cathode materials, a simple thermal method of low temperature inorganic procedure has been developed to synthesize these compounds of high purity, small particle size and good reversible behaviour on cycling. By this procedure, lithium based oxides, phosphates and boride materials were developed and these compounds can be used as secondary cathode electrodes for lithium cells. The procedure is very simple and novel. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

High-contrast imaging for weakly diffracting specimens in coherent diffraction imaging

Coherent diffraction imaging (CDI) and ptychography techniques bypass the difficulty of having high-quality optics in X-ray microscopy by using a numerical reconstruction of the image that is obtained by inverting the diffracted intensity recorded by a charge-coupled device array. However, the reconstruction of the image from the intensity data obtained from a weakly diffracting specimen is known to be difficult because of the obvious reduction in signal-to-noise ratio (SNR). In this case, the specimen only slightly modifies the probe diffraction pattern, resulting in difficulty in the identification of the detailed structure of the specimen from the reconstructed image because of the poor contrast and sharpness of the image. To address this situation, a modification in the image retrieval algorithms used in the iterative reconstruction of the image is suggested. This modification should double the presence of high spatial frequencies in the diffraction pattern to enhance the contrast and edge detection in existing imaging techniques.     

Simple model for frozen-in viscoelastic stress in optical fibers

We have measured residual stress in a commercial single mode optical fiber and observed its relaxation in an annealing process with a polariscopic stress measurement method. After annealing the fiber for an hour at various high temperatures in a specially made image furnace we have measured the temperature dependent relaxation of frozen-in viscoelastic stress in the fiber. We have proposed a simple physical model to explain recently observed relaxation of frozen-in viscoelastic stress in optical fibers based on the Kelvin-Voigt model of viscoelastic materials. The experimental results are explained with our model of frozen-in viscoelastic stress by introducing simplified four-step procedures for fiber drawing.