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.     

Fluorine incorporation in silica glass by the MCVD process: Study of fluorine incorporation zone,evaluation of optical properties and structure of the glass

A theoretical approach was made to find out a complete fluorine incorporation zone on a ternary diagram which serves as a useful graphical representation to select the flows of the supplied reagents for incorporation of the suitable amount of fluorine into cladding glass of optical fiber preform made by the MCVD process using CCl₂F₂ as a source of fluorine under oxygen abundance, oxygen deficiency and intermediate oxygen state conditions. The possible mechanism for incorporation of fluorine into cladding glass of optical fiber is also evaluated on the basis of the thermodynamical data. The fluorine incorporation mechanism in silica glass by the MCVD process is found to be dependent on the CCl₂F₂/SiCl₄ ratio in the input gas mixture. Fluorine doping is found to be effective for removing the strained Si–O–Si bonds, which govern the optical transparency in deep ultra-violet (DUV) and vacuum ultra-violet (VUV) regions. The maximum refractive index depression of ?0.5 × 10^?3 is obtained with incorporation of fluorine into silica cladding glass by the MCVD process using CCl₂F₂ as a dopant precursor with suitable flow of SiCl₄ vapor along with O₂ through backward deposition pass. The structure of fluorine doped silica glass preform samples containing 1.70–1.79 mol% fluorine incorporated by the MCVD process based on the analyses of ¹⁹F MAS spectra done by high-resolution ¹⁹F NMR spectroscopy reveal the presence of two distinct types of fluorine environments. The majority of the fluorine environments are formed in SiO_1.5F polyhedral and less abundant species is observed to be highly unusual, yielding a fivefold coordinated silicon of the type SiO₂F polyhedral which become increased with increasing the fluorine content.     

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.     

Correlation between Site ll-Specific Human Serum Albumin (HSA) Binding Affinity and Murine in vivo Photosensitizing Efficacy of Some Photofrin Components

Human serum albumin (HSA) is one of the key components in human blood that may influence drug distribution. As such, it is important to know the affinity of any drug for albumin. Previously, Photofrina mixture of monomeric, dimeric and oligomeric porphyrins, has been subjected to HSA binding studies. However, due to its complex nature, binding studies on Photofrin or other hematoporphyrin derivatives with HSA are inconclusive. In this report, the binding properties of some components (dimers and trimers) of Photofrin® and the relationship between murine photosensitizing efficacy and those binding properties were investigated. The interaction of these porphyrins with HSA was investigated by direct ultrafiltration and fluorescent titration techniques with fluorescent probes such as dansyl-L-proline (DP), which is known to interact selectively with site II on HSA. Porphyrins also were tested for antitumor activity in a mouse model following intravenous administration and exposure to laser light. Together, the results suggest that the photosensitizers that were preferentially bound to site II of HSA were most effective at controlling murine tumor regrowth     

Lattice instability in Hf1-x Ta x V2 compounds

The temperature dependence of the electric quadrupole interaction frequency _l ^o , experienced by the¹⁸¹Ta probe occupying Hf site in the compounds Hf_1-xTa_xV₂ has been measured for x=0.06, 0.10 and 0.20 in the temperature region between 8.5 K to 296 K. The measurements show lattice transformation in all the three compounds below 120 K.     

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.