Effect of electron beam irradiation on physico-chemical properties of pullulan

Many widely used polymers undergo main chain scission or crosslinking when exposed to radiation. Effects of electron beam irradiation at different doses up to 500?kGy on the biodegradable pullulan polymer films have been investigated by ultraviolet?Cvisible (UV?CVIS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) techniques. UV?CVisible study shows increase of optical absorbance with increase of doses, attributing to the formation some groups or radicals. FTIR and TGA results reveal the processes of both crosslinking and degradation of polymer taking place depending upon the dose of e-beam radiation. The surface morphology of the film is found to be altered by the e-beam radiation as indicated by SEM micrographs.     

Ultracold atoms in a tunable optical kagome lattice

We realize a two-dimensional kagome lattice for ultracold atoms by overlaying two commensurate triangular optical lattices generated by light at the wavelengths of 532 and 1064 nm. Stabilizing and tuning the relative position of the two lattices, we explore different lattice geometries including a kagome, a one-dimensional stripe, and a decorated triangular lattice. We characterize these geometries using Kapitza-Dirac diffraction and by analyzing the Bloch-state composition of a superfluid released suddenly from the lattice. The Bloch-state analysis also allows us to determine the ground-state distribution within the superlattice unit cell. The lattices implemented in this work offer a near-ideal realization of a paradigmatic model of many-body quantum physics, which can serve as a platform for future studies of geometric frustration.     

Turbulence measurements in a rectangular mesoscale confined impinging jets reactor

Mesoscale chemical reactors capable of operating in the turbulent flow regime, such as confined impinging jets reactors (CIJR), offer many advantages for rapid chemical processing at the microscale. One application where these reactors are used is flash nanoprecipitation, a method for producing functional nanoparticles. Because these reactors often operate in a flow regime just beyond transition to turbulence, modeling flows in these reactors can be problematic. Moreover, validation of computational fluid dynamics models requires detailed and accurate experimental data, the availability of which has been very limited for turbulent microscale flows. In this work, microscopic particle image velocimetry (microPIV) was performed in a mesoscale CIJR at inlet jet Reynolds numbers of 200, 1,000, and 1,500. Pointwise and spacial turbulence statistics were calculated from the microPIV data. The flow was observed to be laminar and steady in the entire reactor at a Reynolds number of 200. However, at jets Reynolds numbers of 1,000 and 1,500, instabilities as a result of the jets impinging along the centerline of the reactor lead to a highly turbulent impingement region. The peak magnitude of the normalized Reynolds normal and shear stresses within this region were approximately the same for the Reynolds numbers of 1,000 and 1,500. The Reynolds shear stress was found to exhibit a butterfly shape, consistent with a flow field dominated by an oblique rocking of the impingement zone about the center of the reactor. Finally, the spatial auto- and cross-correlations velocity fluctuations were calculated and analyzed to obtain an understanding of size of the coherent structures.     

Magnetization plateaus and sublattice ordering in easy-axis kagome lattice antiferromagnets

We study kagome lattice antiferromagnets where the effects of easy-axis single-ion anisotropy (D) dominates over the Heisenberg exchange J. For S> or =3/2, virtual quantum fluctuations help lift the extensive classical degeneracy. We demonstrate the presence of a one-third magnetization plateau for a broad range of magnetic fields J3/D2 < or = B < or = JS along the easy axis. The fully equilibrated system at low temperature on this plateau develops an unusual nematic order that breaks sublattice rotation symmetry but not translation symmetry; however, extremely slow dynamics associated with this ordering is expected to lead to glassy freezing of the system on intermediate time scales.     

Smectic translational order parameter in two liquid crystalline compounds

In this paper, we report translational order parameter in two liquid crystalline compounds, namely, p-cyanobenzylidene p-nonyloxyaniline and p-decyloxybenzylidene p-butylaniline at different temperatures in their smectic phase(s). Translational order parameter has been estimated using the recorded X-ray intensity data. The results obtained are compared and discussed.     

An HPTLC Method for the Evaluation of Two Medicinal Plants Commercially Available in the Indian Market Under the Common Trade Name Brahmadandi

Brahmadandi is an important medicinal plant used in the Indian system of medicine (Ayurveda) for the treatment of numerous diseases. A literature search revealed that different plants are available on the market under the trade name Brahmadandi viz., roots of Echinops echinatus Roxb, and the aerial parts of Tricholepis glaberrima DC which are sold either in their crude or in powdered form. Currently, no analytical procedures appear to be available for quality control purposes. In the present communication, we report a simple HPTLC method for the quantification of the lupeol content in the aforementioned plant species. The method was validated for precision, repeatability and accuracy. Instrument precision and repeatability of the method were found to be 0.56 and 2.87 %RSD, respectively. Intra-day and inter-day precision of the method was determined to be in the ranges of 0.71–2.02 and 1.03–2.02 %RSD, respectively. Accuracy of the method was evaluated by a recovery study conducted at three different levels. The mean percentage recovery was found to be 100.85%. The developed HPTLC method for estimation of lupeol was found to be simple, precise and accurate and may be useful for routine quality control of the commercial samples of Brahmadandi.     

Conductometric and ph studies on cobalt tellurite

Summary Conductometric and p_H titration procedures for the determination of cobalt over a wide range of concentrations of cobalt solutions are described. Direct, as well as reverse titration procedure are shown to be possible and the effect of varying ethanol concentrations is reported. Both conductometric and p_H studies lend support to the 11 molar ratio of Co and Te.Sincere thanks of the authors are due to Prof. S. S. Joshi, D. Sc. (London), Head of the Chemistry Department for keen interest and facilities. The award of a scholarship to one of us (V.D.A.) by the Ministry of Scientific Research and Cultural Affairs is also acknowledged.     

Rapid titrimetric and spectrophotometric assay methods for the determination of lamivudine in pharmaceuticals using iodate and two dyes

One titrimetric and two spectrophotometric methods, which are simple, sensitive and rapid, are described for the assay of lamivudine in bulk drug and in tablet dosage forms using potassium iodate and two dyes, methyl orange and indigocarmine, as reagents. In titrimetry, an aqueous solution of lamivudine is titrated directly with iodate in an acidic medium, and in the presence of an excess of bromide using methyl orange as an indicator. After the decoloration of the red color of methyl orange, the residual bromine is titrated iodometrically to a starch endpoint. Spectrophotometric methods involve the addition of a known excess of iodate in an acidic medium and in the presence of an excess of bromide followed by the determination of residual bromine by the reaction with a fixed amount of either methyl orange and measuring the absorbance at 520 nm (method A), or indigo carmine and measuring the absorbance at 610 nm (method B). In all methods, the amount of iodate which reacted corresponds to the amount of lamivudine content. The titrimetric method is applicable over the 1.5–8.0 mg range. The systems obey Beer’s law for 0.5–5.0 μg/mL (method A) and 1.25–12.5 μg/mL (method B). The calculated apparent molar absorptivity values are found to be 3.3 × 10⁴ and 9.3 × 10³ L mol⁻¹ cm⁻¹, for method A and method B, respectively, and the corresponding Sandell sensitivity values are 6.94 and 24.62 ng/cm². The limits of detection and quantification are also reported for both spectrophotometric methods. Intra-and interday precision and accuracy for the developed methods have been evaluated. The methods were successfully applied to the assay of lamivudine in tablet form and the results were compared with those of a reference method by applying the Student’s t-test and F-test. No interference was observed from common tablet adjuvants. The accuracy and reliability of the methods were further ascertained by recovery experiments using the standard addition technique. The text was submitted by the authors in English.     

Orientational Order of Some Nematogenic Compounds

The paper discusses the results of the calculation of the orientational order parameters in the case of five nematogenic compounds. The order parameters are compared with the Maier-Saupe theoretical curve. The calculated values of characteristic absorption wavelength in each case corresponds to the conjugated bridge of the molecule.