Pressure induced transformations in condensed and molecular phases of C60

Solid C₆₀ is known to undergo dimerization under suitable conditions of temperature and pressure. We use a potential model (6-exponential potential) to study the changes leading to the formation of various dimers by hydrostatic pressure on C₆₀ solid at elevated temperatures. We have earlier shown, using Tersoff and Brenner potentials, that a system of two bucky-balls can form a dimer by bonding in different ways, when they start with different orientations at close distances. Based on this, we suggest the required preconditions (P-T curve) for the formation of different dimers from the pristine solid. Stability of the bucky-ball under internal or external pressure has also been studied using Tersoff and Brenner potentials. These two potentials have been compared for their applicability under high pressure conditions as well as for dimerization. We have also estimated the bulk modulus of the bucky-ball at several pressures (under which the molecule remains stable). The values of bulk modulus agree closely with those reported in earlier calculations around zero pressure. When the pressure inside the bucky-ball exceeds 116 GPa, it is seen to break open. This is in close agreement with the findings of molecular dynamics calculations.     

High Temperature Sliding Wear of Spray-Formed Solid-Lubricated Aluminum Matrix Composites

The present work describes the tribological study of the aluminum metal matrix composite manufactured by the spray atomization and deposition technique. The immiscible element Sn is added in the Al-Si alloy in different proportion to see its effect on wear behavior. The economical mineral zircon sand (8 vol.%) of size range 63-90 μm has been used as ceramic reinforcement. The microstructural features showed that Sn and reinforced particles were homogeneously dispersed in the matrix phase. The wear experiments were conducted at high temperature on pin-on-disk wear testing machine. The wear debris and worn surfaces are analyzed with the help of scanning electron microscope equipped with energy-dispersive spectroscopy facility. The Al-Si-10Sn/ZrSiO₄ composite offers higher wear resistance as compared to base alloy and other composites irrespective of the high temperature conditions of wear tests.     

An Improved Protocol for Agrobacterium-Mediated Transformation in Subterranean Clover (Trifolium subterraneum L.)

Subterranean clover (Trifolium subterraneum) is the most widely grown annual pasture legume in southern Australia. With the advent of advanced sequencing and genome editing technologies, a simple and efficient gene transfer protocol mediated by Agrobacterium tumefaciens was developed to overcome the hurdle of genetic manipulation in subterranean clover. In vitro tissue culture and Agrobacterium transformation play a central role in testing the link between specific genes and agronomic traits. In this paper, we investigate a variety of factors affecting the transformation in subterranean clover to increase the transformation efficiency. In vitro culture was optimised by including cefotaxime during seed sterilisation and testing the best antibiotic concentration to select recombinant explants. The concentrations for the combination of antibiotics obtained were as follows: 40 mg L⁻¹ hygromycin, 100 mg L⁻¹ kanamycin and 200 mg L⁻¹ cefotaxime. Additionally, 200 mg L⁻¹ cefotaxime increased shoot regeneration by two-fold. Different plant hormone combinations were tested to analyse the best rooting media. Roots were obtained in a medium supplemented with 1.2 µM IAA. Plasmid pH35 containing a hygromycin-resistant gene and GUS gene was inoculated into the explants with Agrobacterium tumefaciens strain AGL0 for transformation. Overall, the transformation efficiency was improved from the 1% previously reported to 5.2%, tested at explant level with Cefotaxime showing a positive effect on shooting regeneration. Other variables in addition to antibiotic and hormone combinations such as bacterial OD, time of infection and incubation temperature may be further tested to enhance the transformation even more. This improved transformation study presents an opportunity to increase the feeding value, persistence, and nutritive value of the key Australian pasture.     

Synthesis of tetrahydrofuran ring containing oligoethylene glycol ethers from the seed oil of Vernonia anthelmintica

A tetrahydrofuran ring containing oligoethylene glycol ethers has been synthesized from the seed oil of Vernonia anthelmintica. The seed oil was reacted with mono-, di-, and triethylene glycols in the presence of boron trifluoride etherate, followed by saponification and esterification (MeOH/H⁺). The oligoethylene glycol ethers thus obtained were epoxidized with perbenzoic acid. The 9,10-epoxy oligoethylene glycol ethers so formed were intramolecularly cyclized in dry benzene using boron trifluoride etherate as a catalyst to yield the tetrahydrofuran ring containing oligoethylene glycol ethers; methyl 9,12-epoxy, 10-hydroxy-13-[2-hydroxyethyl-1-oxy]; methyl 9,12-epoxy,10-hydroxy-13-[2-hydroxy-3-oxapentyl-1-oxy] and methyl 9,12-epoxy,10-hydroxy-13-[8-hydroxy-3,6-dioxaoctyl-1-oxy]octadecanoates, respectively.     

Effect of domestic processing on flatus producing factors in ricebean (Vigna umbellata)

The effect of various processing treatments viz., soaking, pressure cooking, open pan cooking, germination followed by pressure cooking and roasting of whole ricebean and pressure cooking, open pan cooking and fermentation and frying of fermented batter of dehulled ricebean flour was assessed for total sugars and oligosaccharide contents. Dehulling caused a significant reduction in the raffinose and stachyose contents. Pre-soaking of ricebean caused appreciable losses in the oligosaccharide content. Germination (48 h) followed by pressure cooking and fermentation (18 h) followed by frying caused the maximum losses in the raffinose and stachyose contents.     

Differential sensitivity of Desi (small‐seeded) and Kabuli (large‐seeded) chickpea genotypes to water stress during seed filling: effects on accumulation of seed reserves and yield

Water stress during the reproductive phase, especially during seed development, is considered detrimental for chickpea yield. In the present study, the relative sensitivity of Desi and Kabuli chickpea types to water stress during seed filling was assessed in terms of effects on quantitative and qualitative aspects of seed yield. Leaves of both types experienced stress injury (evaluated as electrolyte leakage) to the same extent and possessed almost similar values of water potential at the end of 14 days of water stress. The stressed plants of Kabuli type lost more chlorophyll and had less photosynthesis than Desi type. At maturity, Desi type showed more diminution of vegetative dry matter due to stress over control than Kabuli type. On the other hand, Kabuli type showed a proportionally greater reduction in seed weight per plant, average seed weight, average seed size, number of pods (single‐ and double‐seeded) and harvest index. The stressed seeds of Kabuli type showed 48 and 46% reduction over control in starch and protein content compared with 25 and 40%, respectively in Desi type. The accumulation of soluble sugars was relatively greater due to stress in Kabuli (47%) than Desi type (23%). Fat and fiber content declined by 39 and 35% over control in Desi seeds because of stress whereas Kabuli type showed 46 and 67% decreases, respectively. Protein fractions, namely albumins, globulins, glutelins and prolamins, decreased in stressed seeds of Kabuli by 32, 40, 16 and 15% over control relative to 40, 48, 30 and 28%, respectively, in Kabuli type. The activities of sucrose synthase, invertase and soluble starch synthase were inhibited to a higher extent in Kabuli seeds than Desi seeds under stress. Kabuli seeds showed significantly more reduction in the accumulation of amino acids such as phenylalanine + tyrosine, tryptophan, valine, alanine and histidine and minerals (Ca, P, Fe) due to stress compared with Desi type. Copyright © 2006 Society of Chemical Industry     

Use of statistical methods for estimation of total number of charges in a mass spectrometry experiment

Estimation of the number of ions in a mass spectrometry experiment is needed to determine instrumentation parameters such as ionization efficiency, collision-induced dissociation efficiency, ion-transfer efficiency, ion trapping efficiency, and preamplifier detection limit. This work aims at analyzing the statistical characteristics (primarily variance) in the intensities of the isotopic distributions, which depend on the number of ions in the cell. A mathematical derivation was developed based on the maximum likelihood estimation method, which estimates the most likely number of ions in the cell using a method known as nonrandom parameter estimation. The performance of the method improves with increase in the number of observed distributions. The method works well provided the spectra show isotopic resolution and is independent of the instrument or method used to arrive at the spectra.     

Crystallization kinetics of bulk amorphous Se-Te-Sn system

In the present work crystallization kinetics of the amorphous Se_80–xTe₂₀Sn_x (0 x 9) system have been investigated using Differential Scanning Calorimetry. From the heating rate dependence of the glass transition temperature and the crystallization temperature the activation energy for the glass transition and that for crystallization have been determined using the Kissingers equation and Matusitas equation for non-isothermal crystallization of materials. The effect of addition of Sn to the Se-Te system on the dimentionality of crystal growth has been investigated. An increase in the glass transition temperature with increase in Sn content suggests that Sn plays a role in cross-linking the already existing Se-Te chains which causes an increase in the thermal stability of the material.     

Permeation enhancers for transdermal drug delivery

The transdermal route has been recognized as one of the highly potential routes of systemic drug delivery and provides the advantage of avoidance of the first-pass effect, ease of use and withdrawal (in case of side effects), and better patient compliance. However, the major limitation of this route is the difficulty of permeation of drug through the skin. Studies have been carried out to find safe and suitable permeation enhancers to promote the percutaneous absorption of a number of drugs. The present review includes the classification of permeation enhancers and their mechanism of action; thus, it will help in the selection of a suitable enhancer(s) for improving the transdermal permeation of poorly absorbed drugs.