Photocured characteristics of fast photocurable acrylic formulations and investigations by differential photo calorimeter

Nanofluids are obtained by suspending metallic or non-metallic nanoparticles in conventional base liquids and can be employed to increase heat transfer rate in various applications. In this study, the effects of adding three types of nanofluids on turbulent convective heat transfer at the entrance region of a constant wall heat flux tube were experimentally studied. The nanofluids were mixtures of aluminium oxide, copper oxide, and silicon carbide at various nanoparticle volume fractions ranging from 0.0002 to 0.002 in water. The convective heat transfer coefficient was measured at different Reynolds numbers of 10,000–50,000. At these concentrations and Reynolds numbers, a maximum of 11–18% of convection heat transfer coefficient was observed as compared to the base fluid, showing a 6–9% increase on average. In this study, it was observed that changes in the nanoparticle type had no considerable effect on heat transfer coefficient increase. According to the model proposed here, the dimensionless thickness of laminar sub-layer is specified as a functional equation of the volume fraction of nanoparticles for each material.

     

Independent measurement of the total active 8B solar neutrino flux using an array of 3He proportional counters at the Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) used an array of 3He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (nu_x) 8B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54_-0.31;+0.33(stat)-0.34+0.36(syst)x10(6) cm(-2) s(-1), in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields Deltam2=7.59_-0.21;+0.19x10(-5) eV2 and theta=34.4_-1.2;+1.3 degrees. The uncertainty on the mixing angle has been reduced from SNO's previous results.     

tert-Butyl nitrite induced radical dimerization of primary thioamides and selenoamides at room temperature

A simple and efficient method for the dimerization of primary thioamides into 1,2,4-thiadiazoles using tert-butyl nitrite is described. The optimized condition was also found to be suitable for the dimerization of benzoselenoamides into 1,2,4-selenadiazoles. All the reactions proceed smoothly at room temperature and gave the desired products in excellent yields in a short span of time.     

Effect of lattice oxygen on optical absorption, radiation hardness and thermally stimulated luminescence of BaF2 crystal

The influence of the presence of BaO impurity on the optical absorption, radiation hardness and thermally stimulated luminescence of BaF₂ has been investigated. The presence of oxygen impurity gives rise to three absorption bands in the UV region, peaking around 220, 280 and 335 nm. Further, the impurity is found to be detrimental to crystal hardness against ionizing radiations. The thermally stimulated luminescence (TSL) has been studied from gamma-irradiated crystals containing different fractions of BaO impurity. Four prominent glow peaks around 100°C (peak I), 150°C (peak II), 220°C (peak III) and 290°C (peak IV) are observed for crystals containing BaO impurity concentrations lower than 0.5% (by wt). For crystals containing higher impurity concentrations, two additional peaks around 75°C and 260°C are also observed. The kinetics of TSL emission is observed to be of first order, implying that the absorption and the emission centers responsible for TSL are the same. The normalized TSL output for peak I is found to vary linearly with the concentration of oxide impurity. This fact can be utilized to detect the presence of minute amounts of oxygen in BaF₂ lattice, which is crucial to the growth of crystals exhibiting high radiation hardness.     

Drug and surfactant transport in Cyclosporine A and Brij 98 laden p-HEMA hydrogels

Surfactants are commonly incorporated into hydrogels to increase solute loading and attenuate the release rates. In this paper we focus on understanding and modeling the mechanisms of both surfactant and drug transport in hydrogels. Specifically, we focus on Brij 98 as the surfactant, Cyclosporine A (CyA) as the hydrophobic drug, and poly-hydroxy ethyl methacrylate (p-HEMA) as the polymer. The models developed here are validated by experiments conducted with gels of different thicknesses and surfactant loadings. Also the model is compared with prior experimental studies in literature. The model predicts that the percentage surfactant as well as drug release scales as 1/(surfactant loading)(0.5), and thus a four fold increase in surfactant loading leads to a two fold reduction in percentage release for both drug and surfactant at a given time. The models for the surfactant and drug release are fitted to the experimental data to obtain values of 1.44 x 10(-14) m(2)/s for CyA diffusivity and 414.4 for the partition coefficient between drug concentration inside the micelle and that in the gel. These models can be very helpful in tuning the drug release rates from hydrogels by controlling the surfactant concentration. The results also show that Brij 98 loaded p-HEMA exhibit an extended release of CyA and so contact lenses made with this material can be used for extended ocular delivery of CyA, which is an immunosuppressant drug commonly used for treatment of various ocular ailments.     

Coupling Effects of Electrostatic Interactions and Salt Concentration Gradient in Polymer Translocation through a Nanopore: A Coarse-Grained Molecular Dynamics Simulations Study

We study the influence of polymer pore interactions and focus on the role played by the concentration gradient of salt in the translocation of polyelectrolytes (PE) through nanopores explicitly using coarse-grained Langevin dynamics simulations. The mean translocation time is calculated by varying the applied voltage, the pH, and the salt concentration gradient. Changing the pH can alter the electrostatic interaction between the protein pore and the polyelectrolyte chain. The polymer pore interaction is weakened by the increase in the strength of the externally applied electric field that drives translocation. Additionally, the screening effect of the salt can reduce the strong charge-charge repulsion between the PE beads which can make translocation faster. The simulation results show there can be antagonistic or synergistic coupling between the salt concentration-induced screening effect and the drift force originating from the salt concentration gradient thereby affecting the translocation time. Our simulation results are explained qualitatively with free energy calculations.     

Mesomorphism of azo-esters and chalcone-esters

One chalcone-ester homologous series of mesogens α-4-[4^/-n-alkoxybenzoyloxy phenyl β-4^//methoxy benzoyl ethylenes (A) and one azo-ester homologous series of mesogens p-(p^/-n-alkoxybenzoyloxy) phenyl azo-p^//-methoxy benzene (B) being structurally similar are discussed. Both series (A) and (B) differ in respect of central bridges linking two phenyl rings. Mesomorphic properties start from 6th and 1st member of series (A) and (B) respectively. In series (A), 6th to 12th members show both smectogenic and nematogenic properties, and the 14th and 16th members show only nematogenic property. While in series (B), 1st to 10th members show nematogenic properties, 11th member shows both smectogenic and nematogenic properties, while 12th member shows only smectogenic property. Thermal stability of series (A) is relatively high as compared to series (B). Transition temperatures are observed through hot stage polarizing microscope by the miscibility method. Analytical data support the structure of molecules. Textures of series (A) in nematic are threaded and Schlieren in SmecticSmectic A type, while that of series (B) in nematic are threaded in SmecticSmectic A and smectic C.     

Stannoxane capping derived from chiral tridentate NNO donor ligand for nickel and copper macrocycles: Comparative binding studies of stannoxane moiety and its modulated copper complex with CTDNA

Novel stannoxane type dinuclear tin complex C₁₆H₁₃N₄O₂Sn₂Cl₇ (1) and its modulated macrocyclic complexes [C₂₄H₃₆N₁₀O₃Sn₂CuCl₇] ClO₄ (2) and [C₂₄H₃₄N₁₀O₂Sn₂NiCl₇] ClO₄ (3) were synthesized and characterized by elemental analysis and various spectroscopic techniques (IR, ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-MS, EPR and UV-Vis). ¹¹⁹Sn NMR shows the presence of two tin metal centers in different environment. The proposed pseudo-octahedral geometry of copper in complex 2 and square pyramidal geometry of nickel in complex 3 were established by the analysis of spectroscopic data. Absorption and fluorescence spectral studies and viscosity measurements have been carried out to assess the comparative binding of dinuclear stannoxane complex 1 and its modulated copper complex 2 with calf thymus DNA. The intrinsic binding constants K_b of the complex 1 and 2 were determined as 4.4 × 10⁴ M⁻¹ and 7.5 × 10⁴ M⁻¹, respectively. Cyclic voltammetric studies have also been employed to ascertain the binding of complex 2 with CTDNA. The results suggest that the complex 2 binds to CTDNA twice in the order of magnitude compared to complex 1. Interaction studies of complex 2 with guanosine 5′-monophosphate further confirm the binding via N₇ position of guanine and phosphate moiety.     

Quantum chemical and nuclear magnetic resonance spectral studies on molecular properties and electronic structure of berberine and berberrubine

The structural and electronic properties of berberine and berberrubine have been studied extensively using density functional theory (DFT) employing B3LYP exchange correlation. The geometries of these molecules have been fully optimized at the B3LYP/6-311G** level. The chemical shift of 1H and 13C resonances in NMR spectra of these molecules have been calculated using the gauge invariant atomic model (GIAO) method as implemented in Gaussian 98. One- and two-dimensional HSQC (1H-13C), HMBC (1H-13C) and ROESY (1H-1H) spectra were recorded at 500 MHz for the berberine molecule in D(2)O solution. All proton and carbon resonances were unambiguously assigned, and inter-proton distances obtained from ten observed NOE contacts. A restrained molecular dynamics (RMD) approach was used to get the optimized solution structure of berberine. The structure of berberine and berberrubine molecules was also obtained using the ROESY data available in literature. Comparison of the calculated NMR chemical shifts with the experimental values revealed that DFT methods produce very good results for both proton and carbon chemical shifts. The importance of the basis sets to the calculated NMR parameters is discussed. It has been found that calculated structure and chemical shifts in the gas phase predicted with B3LYP/6-311G** are in very good agreement with the present experimental data and the measured values reported earlier.     

Thermo and mechanoluminescence studies of BZT phosphor

Mechanoluminescence (ML) and thermoluminescence (TL) in barium zirconium titanate (BZT) is reported for the first time. The BZT powder sample, belonging to perovskite category is synthesized using solid state reaction technique. The sample is prepared at a temperature of 1200 °C. The obtained specimen is thoroughly characterized paying particular attention to their structure, composition, morphology and optical properties. The surface morphology and structural properties are analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns confirm the formation of crystalline perovskite type cubic structure. Also, highly agglomerated, porous and regular shaped particles are seen by SEM. The optical properties of as prepared sample is presented and discussed in terms of ML and TL. The ML intensity is found to be maximum for the sample irradiated for 10 min. More than one maxima in TL glow curve reveals that the traps are distributed in separate groups at different depths and corresponding values are calculated using initial rise method.