Microstructure dependent dynamic fracture analyses of trabecular bone based on nascent bone atomistic simulations

Trabecular bone fracture is closely related to the trabecular architecture, microdamage accumulation, and bone tissue properties. Primary constituents of trabecular tissue are hydroxyapatite (HA) mineralized type-I collagen fibers. In this research, dynamic fracture in two dimensional (2-D) micrographs of ovine (sheep) trabecular bone is modeled using the mesoscale cohesive finite element method (CFEM). The bone tissue fracture properties are obtained based on the atomistic strength analyses of a type-I collagen + HA interfacial arrangement using molecular dynamics (MD). Analyses show that the presented framework is capable of analyzing the architecture dependent fracture in 2-D micrographs of trabecular bone.     

The Linear Rational Pseudospectral Method with Preassigned Poles

We present a linear rational pseudospectral (collocation) method with preassigned poles for solving boundary value problems. It consists in attaching poles to the trial polynomial so as to make it a rational interpolant. Its convergence is proved by transforming the problem into an associated boundary value problem. Numerical examples demonstrate that the rational pseudospectral method is often more efficient than the polynomial method.     

Differential pulse polarographic determination of trace amounts of vanadium and molybdenum in various standard alloys and environmental samples after preconcentration of their morpholine-4-carbodithioates on microcrystalline naphthalene or morpholine-4-dithiocarbamate cetyltrimethyl-ammonium bromide-naphthalene adsorbent

A highly selective, sensitive, and fairly rapid and economical differential pulse polarographic (DPP) method has been reported for the determination of trace amounts of vanadium and molybdenum in standard alloys and various environmental samples. The morpholine-4-carbodithioates of these metals were retained (>99% recovery) quantitatively on microcrystalline naphthalene in the pH range 4.5-6.9 for vanadium and 1.5-4.5 for molybdenum. These metals were determined by DPP after desorption with 10 ml of 1 M HCl. Vanadium and molybdenum may also be preconcentrated by passing their aqueous solutions under similar conditions on morpholine-4-dithiocarbamate CTMAB-naphthalene adsorbent packed in a column at a flow rate of 1-5 ml min(-1) and determined similarly. The detection limits are 0.20 ppm for vanadium and 0.04 ppm for molybdenum at minimum instrumental settings (signal to noise ratio=2). The linearity is maintained in the following concentration ranges, vanadium 0.50-10.0 and molybdenum 0.10-9.0 ppm, with a correlation factor of 0.9996 (confidence interval of 95%, slopes 0.0196 and 0.01497 muA mug(-1), intercepts 3.65x10(-3) and -1.92x10(-3) respectively) and relative standard deviation of 1.1% in the microcrystalline method, while in the column method, the linearity is maintained in the concentration ranges, 0.50-6.5 for vanadium and 0.10-5.5 ppm for molybdenum with correlation factor of 0.9994 (with confidence interval of 95%, slopes 0.0194, 0.015 muA mug(-1), intercepts 3.60x10(-3) and -1.90x10(-3) respectively) and relative standard deviation of 1.4%. Various parameters such as the effect of pH, reagent, naphthalene and CTMAB concentrations, volume of aqueous phase and interference of a large number of metal ions on the estimation of vanadium and molybdenum have been studied in detail to optimize the conditions for their voltammetric determination at trace level in various standard alloys and environmental samples.     

Interaction between photons, “trapped electron” and vibronic excitation

The role of “trapped electron,” photon, and vibronic state coupling has been worked out in relation to an aspect of cancer, namely, to the activity of an anticancer drug. The main emphasis for such study comes from the fact that in cancerous systems the participation of usual electronic states of the molecule may not be sufficient. Because of disorder in the cancer tumour, additional states, viz. trapped electron states, could be formed in the manner of localised states in solids. The drug activity of mitomycin C obtained in this way agrees with the experimental values. An additional feature of the study is that it shows that it will be effective mainly in the initial phases of cancer.     

Simultaneous determination of lead and cadmium in various environmental and biological samples by differential pulse polarography after adsorption of their morpholine-4-carbodithioates onto microcrystalline naphthalene or morpholine-4-dithiocarbamate-CTMAB-naphthalene adsorbent

A highly selective, sensitive and rapid differential pulse polarographic method (DPP) has been developed for the simultaneous estimation of trace amounts of lead and cadmium in standard alloys, biological and environmental samples. The morpholine-4-carbodithioates of the samples were absorbed on microcrystalline naphthalene in the pH range of 5-10 for lead and 3.4-11 for cadmium. The metal complexes were desorbed with 10 ml of 1M HCl and determined simultaneously with a differential pulse polarograph. These metals can alternatively be quantitatively adsorbed on morpholine-4-dithiocarbamate-cetyltrimethylammonium bromide-naphthalene adsorbent packed in a column and determined similarly. The detection limits are 0.14 ppm for Pb and 0.014 ppm for Cd at minimum instrumental settings (signal-to-noise ratio = 2). The linearity is maintained in the concentration ranges of Pb, 0.7-15 ppm and Cd, 0.07-10 ppm with a correlation factor of 0.9997 and relative standard deviations of 0.95 and 0.81%, respectively. Various parameters such as the effect of pH, volume of aqueous phase, and interference of a number of metal ions on the estimation of lead and cadmium have been studied in detail to optimize the conditions for their simultaneous estimation in various biological and environmental samples.     

Effect of the rate of diffusion of ions on the periodic precipitation of silver chromate

The effect of the rate of diffusion on the formation ofLiesegang rings of silver chromate in gelatin and agar agar medium has been studied. The rate of diffusion of silver ions in the agar agar gel is much slower than that in gelatin gel during the formation of rings of silver chromate. If the rate of diffusion of silver ions in agar agar gel is increased, even then rings do not form. The only change brought about by the rate of diffusion is for the distance between the successive rings.

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Zusammenfassung Der Einflu\ der Diffusionsgeschwindigkeit auf die Bildung vonLiesegang-Ringen aus Silberchromat in Gelatine und Agar-Agar wurde untersucht. Die Diffusionsgeschwindigkeit der Silberionen in den Agar-Agar-Gelen ist viel niedriger als in den Gelatinegelen während der Bildung der Ringe von Silberchromat. Wenn die Diffusionsgeschwindigkeit der Silberionen in Agar-Agar-Gelen gesteigert wird, bilden sich schlie\lich überhaupt keine Ringe. Der einzige Einflu\, den die Diffusionsgeschwindigkeit hervorruft, ist also änderung des Abstandes aufeinanderfolgender Ringe.

     

Extractive spectrophotometric determination of uranium with Malachite Green

A sensitive spectrophotometric method based on the extraction of a uranium-benzoate-Malachite Green complex by chlorobenzene is described. The absorption maximum is at 635 nm and the molar absorptivity is 8.3 x 10(4) 1 mole(-1), cm(-1). A preliminary separation of uranium by extraction with methyl isobutyl ketone from acid-deficient aluminium nitrate solution is used to avoid interferences. An aliquot of the extract is then diluted with chlorobenzene and shaken with benzoate buffer containing Malachite Green (MG). The method has been applied for the determination of uranium in a synthetic leach solution. The complex extracted is probably [MG(2)(C(6)H(5)COO)(3)][MG(+)].     

Ion-exchange studies of <Superscript>110m</Superscript>Ag(I) using synthetic inorganic ion-exchanger

In the present investigation, the selective adsorption of silver on synthetic inorganic ion exchanger, zinc(II) ferrocyanide, has been established by batch method, under specific conditions, using ^110mAg as a tracer. The efficiency of adsorption has been determined by γ-ray spectrometry and was found to be greater than 96%. The Ag(I) uptake by the exchanger has also been evaluated. The selectivity of the method was checked by studying the adsorption of Ag(I) in the presence of a number of foreign ions using their corresponding tracers. The interfering ions were removed by washing the ion-exchanger with appropriate reagents, so that it could be applied for the determination of trace amount of Ag(I) in complex matrices, containing trace amount of other metal ions.     

Tetrahydroepoxides and diol epoxides of benz[c]acridine

The chemical synthesis and NMR characterization of the benzo ring tetrahydro- and diol epoxides of the carcinogen benz[c]acridine are described.