1-(3-Bromo-2-thien­yl)ethanone

In the title compound, C6H5BrOS, the non-H and aromatic H atoms lie on a crystallographic mirror plane. In the crystal, mol­ecules are linked into chains propagating along the c axis by inter­molecular C—H⋯O hydrogen bonds

Yield loss Modeling for late Leafspot and Rust in Groundnut

Late leaf spot and rust diseases occur together and cause considerable yield loss in groundnut. Cultivation of resistant varieties is the best strategy to stabilize productivity under disease epidemics. Several varieties resistant or moderately resistant to LLS and rust have been developed in groundnut, but most of them differ in yield loss even at the same level of disease due to complex interrelationships between disease and yield loss. Crop loss models have been employed to gain insight into these relations and to plan sound breeding strategies. In the present study, different empirical models were tested for their explanatory value for yield loss among 10 groundnut genotypes with varying level of resistance to late !eafspot and/or rust. Towards yield loss modeling, disease severity at different growth stages and physiological traits viz., leaf area index (LAI), harvest index (HI), healthy leaf area duration (HAD), crop and pod growth rates(CGR and PGR) and partitioning coefficient (PC) were considered as independent variables, while yield loss as dependent variable in regression models. Single pOint models based on disease did not explain the variation in loss completely, but revealed pOd fill ing as the critical stage in determining yield loss. Multiple point models using disease at different stages marginally improved the explanatory value; Inclusion of physiological traits in stepwise regression models improved the R2 considerably, revealing their relevance to yield loss. Yield loss varied significantly among the genotypes resistant to both LLS and rust (9-17%), moderately resistant to LLS or rust (18-26%) and susceptible to LLS and rust (30-42%). Resistant genotype, GPBD-4 had high yield potential with minimum yield reduction due to Its high partitioning efficiency and pod growth rate. Though highly susceptible, TAG-24 showed tolerance by early cessation of vegetative growth and efficient translocation of photosynthates to pOds leading to high harvest index

A free volume microprobe study of water sorption in a contact lens polymer

The kinetics of moisture uptake in a rigid gas-permeable contact lens material, Fluoroperm60, has been investigated. The free volume changes accompanied by the sorption of water were monitored using the positron lifetime spectroscopy (PLS) technique. The positron results indicated swelling in the initial stages of sorption and the filling of vacant free volume sites with water in the later stages of sorption. The sorption curve suggests that the diffusion process in this polymer follows the dual-mode sorption model. Using this model, it was possible to separate Fickian-controlled diffusion and relaxation-controlled diffusion. Furthermore, the positron results combined with the sorption results indicated that Fujita's free volume theory does not seem to be valid for the diffusion process in the present sample under study. The variation of the permeability as a function of the free volume suggests that the amount of water in a contact lens is a measure of its permeability

Structural relaxation in polyethylene in the presence of silver oxide investigated by positron-lifetime spectroscopy

Structural relaxation in high-density virgin polyethylene and silver oxide doped polyethylene has been investigated using positron annihilation lifetime technique at 30 degreesC and 100 degreesC ageing temperatures. The ortho-positronium (o-Ps) pick-off lifetime and its intensity show no changes with isothermal ageing time for the virgin sample at 30 degreesC. In the case of the doped sample at 30 degreesC, the o-Ps intensity shows exponential relaxation in the short-time range. At 100 degreesC, the o-Ps lifetime remains almost constant, whereas the o-Ps intensity exhibits an exponential character in the virgin and doped samples, which can be fitted with exponential decay curves. The relaxation times have been evaluated from the structural relaxation function constructed using o-Ps intensity values, and the stretching exponent beta has been estimated using the Kohlrausch-Williams-Watts (KWW) function. Positron results indicate that the stretching exponent beta seems to be temperature dependent

A positron lifetime study of structural relaxation in UV irradiated poly (ethylene terephthalate)

Structural relaxation in UV irradiated poly (ethylene terephthalate) (PET-UV) has been investigated using positron lifetime techniques. Positron lifetime results show that the structural relaxation processes in PET-UV encompass three different time regimes, unlike the unirradiated poly (ethylene terephthalate) (PET) where only two relaxation times were observed. The relaxation functions constructed from the measured ortho positronium intensity, I3, exhibit non-exponential character that can be best fitted with two additive exponentials. To determine the extent of deviation from exponential relaxation, we have used the Narayanaswamy model (KWW function) and evaluated the stretching parameter β. From the relaxation times derived from the exponential decay curves, the activation energies have been calculated and from these activation energies it seems possible to label the different kinetic units of the UV irradiated poly (ethylene terephthalate) structure participating in the relaxation processes

Water sorption studies in a RGP contact lens polymer paraperm by positron lifetime technique

The kinetics of moisture uptake in a rigid gas permeable contact lens material Paraperm has been investigated. The free volume changes accompanied by the sorption of water have been monitored using Positron Lifetime Spectroscopy (PLS) technique. The positron results indicate the swelling in the initial stages of sorption which seems to be balanced by the rearrangement of chains in the presence of water molecules and filling of vacant free volume sites with water at the later stages of sorption. The sorption curve suggests that diffusion process in this polymer follows dual‐mode sorption model. Using this model we have been able to separate the Fickian controlled diffusion and relaxation controlled diffusion. Further, the positron results combined with sorption results indicate that Fujita's free volume theory seems to be not valid for the diffusion process in the present sample under study. The variation of permeability as a function of free volume suggests the amount of water in a contact lens is a measure of its permeability

Positron lifetime study of diffusion kinetics in electron irradiated polycarbonate

Positron lifetime and gravimetric measurements of iodine sorption and diffusion behaviour in electron-irradiated polycarbonate and un-irradiated polycarbonate are investigated. The increase in ortho-positronium lifetime on electron-irradiation shows that scission of carbonate groups in the main-chain and formation of free radicals is the predominant process. The UV absorption measurement supports this. The free volume in polycarbonate after electron-irradiation seems to be not composed of independent pores but of interconnected channels. The positron results on iodine diffusion in un-irradiated polycarbonate shows a slower diffusion rate, whereas in electron-irradiated polycarbonate faster diffusion is observed. The gravimetric measurement of iodine diffusion attains an early saturation in electron-irradiated polycarbonate as compared to un-irradiated polycarbonate although in both cases the diffusion is nearly Fickian. An exponential type of correlation has been observed between fractional free volume and diffusion coefficient validating Fujita's free volume theory for un-irradiated and electron-irradiated polycarbonate

Influence of gamma irradiation on the formation of methanol induced micro-cracks in polycarbonate

The effects of γ-irradiation on the methanol diffusion behaviour in polycarbonate have been investigated by UV-visible, Fourier Transform Infra-red (FTIR) Spectroscopy, Positron Annihilation Lifetime Spectroscopy (PALS), Differential Scanning Calorimetry (DSC), Sorption, and Optical Microscopy. Positron results show that the free volume size and its content decreases after γ-irradiation which is due to cross-linking of chains. The cross-linking process is further confirmed by DSC measurements, which indicate an increase in glass transition temperature (Tg) after γ-irradiation. Sorption results reveal that methanol diffuses faster in virgin polycarbonate as compared to cross-linked polycarbonate (after gamma irradiation) in agreement with the results of supplementary techniques. Interestingly, the optical microscopic examination of the sample surfaces provides clear evidence of decreased micro-crack formation in γ-irradiated polycarbonate as compared to the virgin sample. This decrease in crack formation can be related to the decrease in the rate of methanol diffusion

Influence of ion-irradiation on the free volume controlled diffusion process in polycarbonate—a positron lifetime study

Iodine sorption in un-irradiated and ion-irradiated polycarbonate (PC) has been investigated using positron lifetime spectroscopy. The decrease in positron lifetime parameters of ion-irradiated sample is attributed to the free volume modifications, and the formation of more stable free radicals on cross-linking. The difference UV absorption spectrum shows a strong absorption peak at 384nm which is due to 2,2′-dihydroxybenzophenone; this depicts the possibility of photo stabilisation of polycarbonate on ion-irradiation. A comparative study of sorption process is explained in terms of iodine diffusion in free volume holes in un-irradiated and ion-irradiated polycarbonates. The experimental results on iodine diffusion shows an early saturation of positron parameters in irradiated PC, which is due to an increase in the rate of diffusion as small number of bigger size free volume holes are formed on irradiation. The diffusion process follows Fick's law and, an exponential type of correlation has been observed between fractional free volume and diffusion coefficient which indicates that Fujita's free volume theory is valid before and after ion-irradiation

Ethyl 6-(4-chlorophenyl)-4-(4-fluorophenyl)-2-oxocyclohex-3-ene-1-carboxylate

The asymmetric unit of the title compound, C21H18ClFO3, contains two independent molecules. In one molecule (A), the 4-chlorophenyl, oxocyclohex-3-ene, carboxylate, and ethyl groups were refined as disordered over two sets of sites with a 0.684 (5):0.316 (5) ratio. The cyclohexene ring in the disordered molecule is in a slightly distorted envelope conformation for the major component (with the C atom bound to the carboxylate group being the flap atom) and in a screw-boat conformation for the minor component. In the ordered molecule (B), the cyclohexene ring is in a half-chair conformation. The dihedral angles between the mean planes of the fluoro- and chloro-substituted benzene rings are 89.9 (7) (only the major component is considered for A) and 76.4 (7)° (B). In the crystal, inversion dimers are observed along with weak C—H...O hydrogen bonds, which form chains along [100]