Spectroscopic characterization of porous nanohydroxyapatite synthesized by a novel amino acid soft solution freezing method

In this paper, we have reported a novel method to synthesize nanoporous hydroxyapatite (HAP) powders by freezing organic–inorganic soft solutions. The formation of porous and crystalline HAP nanopowder was achieved via calcining the samples at 600 °C followed by sintering at temperatures ranging from 900 °C to 1100 °C. The samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopic (SEM) techniques. The results showed the formation of a carbon free nanoporous hydroxyapatite powders due to the decomposition of organic template enclosing the precipitated HAP. It was also observed that the rapid grain growth with retainment of pores while the crystallinity of the HAP nanopowder increased with the increase in sintering temperature which is substantiated from the XRD and SEM results. Such organized porous materials can act as a better biomaterial for bone tissue engineering.     

Polarization mode dispersion in single mode optical fibers due to core-ellipticity

The variation of polarization mode dispersion (PMD) with V-parameter in single mode optical fibers due to core-ellipticity is studied by performing numerical simulations taking into account both geometrical and thermal-stress-induced birefringences as well as the variation of fiber refractive indices with wavelength. Simple empirical relations are given for calculating the mean PMD for any value of core-ellipticity and V-parameter of a standard single mode fiber. It is observed that the mean PMD saturates for V ? 1.8 leading to very small second order PMD.     

Near-tip out of plane displacement fields for dynamic crack propagation in functionally graded materials

Asymptotic expansion for the out of plane displacement field around a crack propagating along the gradient in a functionally graded material is developed. The irregular behavior of one of the terms in the expansion at low crack speeds is further examined and a remedial solution, which is well behaved at low crack speeds, is proposed. The developed out of plane displacement field is used to estimate stress intensity factor from quasi-static finite element solution. The results indicate that inclusion of the proposed nonhomogeneity specific terms gives estimates of stress intensity factor, which are consistent with existing analytical predictions.     

The influence of comonomer (2‐hydroxyethyl acrylate) and keto group on photocrosslinking property of arylidene polymers

Two types of arylidene compounds were synthesized by reacting p‐hydroxybenzaldehyde with acetone [1,5‐bis(4‐hydroxyphenyl)penta‐1,4‐dien‐3‐one] (PBHP) and cyclohexanone [2,6‐bis(4‐hydroxybenzylidene)cyclohexanone] (HBC). 1,4‐Pentadien‐3‐one‐1‐p‐hydroxyphenyl‐5‐p‐phenyl methacrylate (PHPPMA) and 4‐{[‐3‐(4‐hydroxybenzylidene)‐2‐oxocyclohexylidene]methyl}phenyl acrylate (HBA) were prepared by reacting PBHP and HBC with methacryloyl chloride and acryloyl chloride in the presence of triethylamine, respectively. Copolymerization of different feed compositions of PHPPMA and HBA with 2‐hydroxyethyl acrylate (HEA) was carried out using a free‐radical solution polymerization technique in ethyl methyl ketone (MEK) using benzoyl peroxide (BPO). All the monomer and polymers were characterized by IR and NMR (¹H/¹³C) spectroscopic techniques. The reactivity ratio of the monomers were obtained using Fineman–Ross (FR), Kelen–Tudos (KT), and extended Kelen–Tudos (exKT) methods. The photocrosslinking properties of the polymers were done using a UV absorption spectroscopy technique. Homopolymers of both the arylidene polymers shows similar trend towards the rate of photocrosslinking. The rate of photocrosslinking was enhanced when the cyclohexanone based arylidene monomer was copolymerized with HEA. Thermal stability and molecular weights (M_w and M_n) of the polymers were determined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3433–3444, 2004     

Cycloaddition approach to benzo-annulated indane-based α-amino acid derivatives

Synthesis of various benzo-annulated indane-based α-amino acid (AAA) derivatives are reported via a [4+2] and [2+2+2] cycloaddition reactions as key steps. Here, o-xylylene based AAA moiety has been used as a reactive intermediate and by adopting this strategy various indane-based constrained AAA derivatives are prepared.     

Testing of linear polarizer using photorefractive effect

A new method is developed to test linear polarizers using two-wave mixing in photorefractive Bi₁₂TiO₂₀ (Bismuth Titanium Oxide, BTO). The extinction ratios obtained from this method was comparable with the literature values and the method is also useful for qualitative analysis of linear polarizers. Detailed theoretical and experimental analysis is given in the paper.     

Study of physicochemical properties-antitubercular activity relationship of naphthalene-1,4-dione analogs: A QSAR approach

Enduring pandemic nature of tuberculosis urges to explore novel antimycobacterial agents with different mechanism of actions. Plant containing 1,4-naphthoquinone derivatives showed promising antitubercular activity with novel mode of action and their synthetic/semi-synthetic derivatives devoid of toxicity. Structural requirements of naphthalene-1,4-dione derivatives towards antitubercular activity and cytotoxicity were explored using a mathematical model in order to understand their physicochemical parameters. A quantitative structure activity relationship study furnished some important structural insights for antitubercular activity, i.e. average connectivity index, information content index of neighborhood symmetry, aromatic ratio, and path/walk 3 Randic shape index. Similarly it also provides drivers for the cytotoxicity of compounds. These drivers will be helpful in further development of safer and potent 1,4-naphthoquinone derivatives.     

Search for non-strange dibaryons

Inspite of tremendous interest there has been sporadic searches for dibaryon resonances in the past few decades. The main hurdle one faces in this search is their identification, their signature and practically no guide to their location. With the identification of the pentaquark-θ⁺ resonance one is encouraged to look for the discovery of strange dibaryons also. However where and how to look for non-strange dibaryons is not clear. The transition from a bipolar to a unipolar non-strange dibaryon may possibly be seen in the (p, 2p) reactions on heavy nuclei. The change of the finite size of thep-p interaction vertex can be identified as a sudden change in the extracted DWIA spectroscopic factor. The DWIA anomalies are to be searched for in the existing (p, 2p) reaction data for the identification of non-strange dibaryons     

Microscopic study of low-lying yrast spectra in <Superscript>100–108</Superscript>Mo isotopes

Variation-after-projection (VAP) calculations in conjunction with Hartree-Bogoliubov (HB) ansatz have been carried out for A=100−108 molybdenum (Mo) isotopes. In this framework, the yrast spectra with J _max ^π ≥10⁺, B(E2) transition probabilities, quadrupole (β₂) and hexadecapole (β₄) deformation parameters, moment of inertia (I) and square of cranking frequency (ω²) for even-even Mo isotopes have been obtained. The results of the calculation give an indication that it is important to include the hexadecapole-hexadecapole component of the two-body interaction for obtaining various nuclear structure quantities in these Mo isotopes.