Piezo-rotatory coefficients and stress-induced optical activity

This paper reports the methods of obtaining the components of the fourth rank axial piezo-rotatory tensor in different crystal classes. The methods of recovering the two piezo-rotatory coefficients R₁₁ and R₁₂ of isotropic optically active glasses, the three coefficients R₁₁, R₁₂ and R₄₄ of cubic crystals belonging to the point group 432 and the four coefficients R₁₁, R₁₂, R₁₃ and R₄₄ of crystals like NaClO₃ (point group 23) have been described in detail. The non-centrosymmetric class 43 m. which is not optically active has one non-vanishing piezo-rotatory coefficient, showing that stress induces optical activity in it. A method of retrieving this coefficient has also been described. In most of the other point groups, the difficulty of measuring optical activity in directions other than those of the optic axes severely limits the number of coefficients that can be extracted. The paper also touches upon some interesting methods of obtaining the components of the gyration tensor in non-enantiomorphic optically active crystals.     

Faraday rotation tensor-extraction of components

This paper reports methods of obtaining the components of Faraday rotation tenser in anisotropic crystals, using longitudinal and transverse Faraday rotation along the optic axis. It is found that in crystals belonging to triclinic, monoclinic and orthorhombic symmetry, one can get 6 out of 9, 3 or 4 out of 5, and 2 out of 3 components respectively. In the case of uniaxial crystals only 1 component can be obtained. By measuring Faraday rotation in a randomly oriented polycrystal one more component in all the above classes can be obtained.     

Thermoplastic starch nanocomposites reinforced with cellulose nanocrystals: effect of plasticizer on properties

The objective of this study was to characterize cellulose nanocrystals /TPS-based nanocomposites. Nanocrystalline cellulose was isolated from cotton linters using sonochemical method and characterized through WXRD, TEM, and FTIR. These nanocrystals were then dispersed in glycerol and sorbitol plasticized starch using a Fluko high shear homogenizer in varying proportions and films were cast. The films were characterized using WXRD, SEM, and mechanical properties. TEM images of nanocrystals revealed a diameter of 20–30 nm and length 200–300 nm. XRD results for nanocomposite films for both the plasticizers showed 2θ peaks at 14.8°, 16.7,° and 22.5°. Elastic modulus increased with addition of cellulose nanocrystals and tan δ shifted toward higher temperature for both the plasticizers. Mechanical properties improved more than 200% for both glycerol and sorbitol plasticized nanocomposites.     

2‐(3‐tert‐Butyldimethylsiloxy‐4‐methoxyphenyl)‐6‐methoxy‐3‐(3,4,5‐trimethoxybenzoyl)indole

In the crystal structure of the title compound, C₃₂H₃₉NO₇Si, all geometric parameters fall within experimental error of expected values. The analysis of molecular‐packing plots reveals an infinite two‐dimensional linear array running parallel to the b axis, formed by one N—H?O intermolecular hydrogen‐bonding interaction. Several potential C—H?O interactions are also present.     

8-Hydroxyquinoline anchored to silica gel via new moderate size linker: synthesis and applications as a metal ion collector for their flame atomic absorption spectrometric determination

The silica gel modified with (3-aminopropyl-triethoxysilane) was reacted with 5-formyl-8-hydroxyquinoline (FHOQ_x) to anchor 8-quinolinol ligand on the silica gel. It was characterised with cross polarisation magic angle spinning (CPMAS) NMR and diffuse reflectance infrared Fourier transformation (DRIFT) spectroscopy and used for the preconcentration of Cu(II), Pb(II), Ni(II), Fe(III), Cd(II), Zn(II) and Co(II) prior to their determination by flame atomic absorption spectrometry. The surface area of the modified silica gel has been found to be 227 m² g⁻¹ and the two pKa values as 3.8 and 8.0. The optimum pH ranges for quantitative sorption are 4.0–7.0, 4.5–7.0, 3.0–6.0, 5.0–8.0, 5.0–8.0, 5.0–8.0 and 4.0–7.0 for Cu, Pb, Fe, Zn, Co, Ni and Cd, respectively. All the metals can be desorbed with 2.5 mol l⁻¹ HCl or HNO₃. The sorption capacity for these metal ions is in range of 92–448.0 μmol g⁻¹ and follows the order Cd3, NaCl, NaBr, Na₂SO₄ and Na₃PO₄, glycine, sodium citrate, EDTA, humic acid and cations Ca(II), Mg(II), Mn(II) and Cr(III) in the sorption of all the seven metal ions are reported. The preconcentration factors are 150, 250, 200, 300, 250, 300 and 200 for Cd, Co, Zn, Cu, Pb, Fe and Ni, respectively and t_1/2 values <1 min except for Ni. The 95% extraction by batch method takes ≤25 min. The simultaneous enrichment and determination of all the metals are possible if the total load of the metal ions is less than sorption capacity. In river water samples all these metal ions were enriched with the present ligand anchored silica gel and determined with flame atomic absorption spectrometer (R.S.D.≤6.4%). Cobalt contents of pharmaceutical samples (vitamin tablet) were preconcentrated with the present chelating silica gel and estimated by flame AAS, with R.S.D.1.4%. The results are in the good agreement with the certified value, 1.99 μg g⁻¹ of the tablets. Iron and copper in certified reference materials (synthetic) SLRS-4 and SLEW-3 have been enriched with the modified silica gel and estimated with R.S.D.<5%.     

New nonlinear optical processes in liquid crystals

We have worked out some consequences of the optical nonlinearities due to laser induced changes in the order parameter of a liquid crystal. The change in the order parameter can be affected by laser induced suppression of the director fluctuations in liquid crystals and or changes in the tilt angle of smectic liquid crystals. Both the processes lead to well known nonlinear optical effects like self-focusing, self-divergence, self-phase modulation, wave mixing, and so on. In addition, we predict some new phenomena like self-iridescence and new types of optical spatial solitons. In the case of chiral liquid crystals in the short wavelength limit the laser beam induces a change in the twist and at the long wavelength edge of the Bragg band it leads to temporal oscillations in the twist and the transmitted intensity. In smectic liquid crystals interesting periodic structures in a standing laser wave are to be expected.     

Characteristics of field-effect transistors based on undoped and B- and N-doped few-layer graphenes

Field-effect transistor characteristics of few-layer graphenes prepared by several methods have been investigated in comparison with those of single-layer graphene prepared by the in situ reduction of single-layer graphene oxide. Ambipolar features have been observed with single-layer graphene and n-type behaviour with all the few-layer graphenes, the best characteristics being found with the graphene possessing 2–3 layers prepared by arc-discharge of graphite in hydrogen. FETs based on boron and nitrogen doped graphene show n-type and p-type behaviour respectively.     

Novel Indole‐Quinazolinone Based Amides as Cytotoxic Agents

Indole‐quinazolinone hybrids with active amides were synthesized, characterized, and assessed for their cytotoxicity. Two molecules displayed substantial activity in sulphorhodamine B assay method.     

Effects of preferential and differential diffusion on the mutual annihilation of two premixed hydrogen–air flames

The unsteady process of upstream head-on quenching of two laminar premixed hydrogen–air flames at different equivalence ratios in one dimension is investigated numerically in the presence of preferential and differential diffusion effects. Important chemical and transport characteristics of the mutual annihilation process are studied during the two primary stages of upstream mutual annihilation, preheat layers' and reaction layers' interactions. Because of the diffusive mobility of the fuel, hydrogen, relative to heat and the oxidizer, preferential and differential diffusion effects result in a shift in the equivalence ratio in the reaction zone to leaner conditions. This shift, in turn, affects the subsequent reaction layers' interactions through qualitative and quantitative changes in the rates of reactants' consumption and radicals' production. Another consequence of this shift is the presence of excess and ‘unburnt’ fuel or oxidizer at the end of the mutual annihilation process. The process of mutual annihilation occurs over time scales that are significantly shorter than characteristic residence times associated with flames.