Belousov-Zhabotinskii Reaction with Acetone- Tartaric Acid & Acetone-Mandelic Acid as Organic Substrates

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On long-wavelength magnetic anomalies over Indian region

A data set composed of vector magnetic measurements obtained by MAGSAT and very accurate altitude determinations made using Sun sensors and star cameras was used to obtain data for very quiet days over the Indian region at 10 S to 40 N and 60 E to 110 E in an effort to determine the validity of quantitative estimates made from aeromagnetic data obtained by removing the core field. To further account for the external effects, the ring current contributions estimated using both X and Z variations were subtracted from the observed values. Before this, the core contribution was eliminated through a spherical harmonic expansion with terms up to N=13. Analysis of the residual measurements using Fast Fourier techniques indicates that the anomalies contain substantial power for wavelengths of about 1500 kms. Because the ring current effect has a spatial structure of this dimension over India, efforts are being made to exactly eliminate these two interfering effects from the data

Hexagonal columnar phase in 1,4-trans-polybutadiene: morphology, chain extension, and isothermal phase reversal

Morphol., lamellar thickening, and the transition between the crystal and the hexagonal columnar phase were studied in 1,4-trans-polybutadiene (I) by optical and electron microscopy, time-resolved synchrotron x-ray diffraction, and DSC. I could form several-thousand-.ANG.-thick lamellas of the extended or nearly extended chain type. These could form either by direct growth from the melt or through annealing of thinner chain-folded lamellas, provided they were in the columnar phase. Lamellar thickness increased by several hundred .ANG. in soln.-crystd. mats immediately upon heating above the crystal-columnar transition, which contrasted with some previous reports on single crystals of I. The low-temp. crystal phase reappeared spontaneously on annealing above the temp. of the initial transition to the high-temp. columnar phase. [on SciFinder (R)

Birefringence analysis of multilayer leaky cladding optical fibre

We analyse a multilayer leaky cladding (MLC) fibre using the finite element method and study the effect of the MLC on the bending loss and birefringence of two types of structures: (i) a circular core large-mode-area structure and (ii) an elliptical-small-core structure. In a large-mode-area structure, we verify that the multilayer leaky cladding strongly discriminates against higher order modes to achieve single-mode operation, the fibre shows negligible birefringence, and the bending loss of the fibre is low for bending radii larger than 10 cm. In the elliptical-small-core structure we show that the MLC reduces the birefringence of the fibre. This prevents the structure from becoming birefringent in case of any departures from circular geometry. The study should be useful in the designs of MLC fibres for various applications including high power amplifiers, gain flattening of fibre amplifiers and dispersion compensation.Comment: 18 page

Sehgal index and its comparison with Mentzer's index and Green and King index in assessment of peripheral blood smear with marked anisopoikilocytosis

Background: Mild microcytic hypochromic anaemias due to iron deficiency (IDA) and beta thalassemia trait(β-TT) continue to be a cause of significant burden to the society, particularly in the poorer developing countries. The objective of the present study was to study the RBC based indices in patients of marked anisopoikilocytosis in determining the etiology of it, to standardize few automated red cell parameters, and also objective grading of RBC morphology on peripheral smear and interpreting its utility in indicating a diagnosis. Also, to establish a relation between value of RBC indices with that of degree of anisocytosis.Methods: A total of 500 patients diagnosed with mild microcytic hypochromic anaemia on complete blood count and peripheral blood film were included in the study. Hb, RBC count, MCV, MCH and RDW obtained from the electronic cell counter were used to calculate discrimination indices by various mathematical formulae. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and Youden’s index (YI) were calculated.Results: Green and King index demonstrated the lowest sensitivity of 70.51%. Mentzer index demonstrated the highest specificity of 96.80%. The highest and lowest PPV were found for Mentzer index (97.09%) and Sehgal index (92.81%) respectively. Sehgal’s index demonstrated the highest NPV of 95.96% and lowest NPV was exhibited by G and K (87.9%). The highest and the lowest values for Youden’s index were shown by Sehgal’s index (87.82%) and G and K index (68.47%).Conclusions: Sehgal’s index followed by Mentzer index are highly sensitive and reasonably specific in differentiating β-TT from IDA and none of the indices is 100% sensitive and specific. Though HbA2 estimation is the gold standard for diagnosing β-TT, in developing countries, Sehgal index followed by Mentzer et al, index can be used to screen mild microcytic hypochromic anaemia cases to eliminate as many false positive cases as possible to reduce the financial cost

Critical behavior at de-pinning of a driven disordered vortex matter in 2H-NbS2

We report unusual jamming in driven ordered vortex flow in 2H-NbS2. Reinitiating movement in these jammed vortices with a higher driving force, and halting it thereafter once again with a reduction in drive, unfolds a critical behavior centered around the de-pinning threshold via divergences in the lifetimes of transient states, validating the predictions of a recent simulation study, which also pointed out a correspondence between plastic de-pinning in vortex matter and the notion of random organization proposed in the context of sheared colloids undergoing diffusive motion.Comment: Phys. Rev. B (in press, 2012). The paper has 14 pages of Text+ Refs. with 4 figures. (Note as some of the figure files are large in size, to enable faster download, the file size has been kept small and the figure resolution are low. The online version of the paper to appear in PRB will contain the higher resolution figures

Thermodynamic anomalies in the pressure-temperature phase diagram of poly-4-methyl pentene-1 : disordering of crystals on cooling

Highly unusual phase behavior, of general implication for condensed matter, is reported for the title polymer. In situ x-ray studies, at the prerequisite pressure and temp., reveal amorphization in this polymer, passing through a continuously varying sequence of mesomorphic states, at 2 widely sepd. temp. regions, the process being reversible. Present findings invoke the possibility of the reentrant, widely sepd. disordered phases with temp. Such possibility has risen for the 1st time in a single-component system. The pressure-induced disordered phase, obtained at room temp., converts into crystal with increasing temp. and reverts to a glassy disordered phase on lowering the temp. Other unexpected findings include a new pressure-induced modification of the polymer, with a 1-way entry only. A few aspects of similar features found in other materials are also stated. [on SciFinder (R)