Mineralogy of agricultural soil of selected regions of South Western Karnataka, Peninsular India

Agricultural soils of selected regions of Southwestern Karnataka, Peninsular India, were subjected to systematic mineralogical characterization along with the study of soil physical properties. Physical properties such as soil texture and micro porosity were studied using particle size analyses and positron annihilation lifetime analysis (PALS) technique, respectively. The latter was used to analyze micro porosity of agricultural soil. Both major and minor minerals were identified and confirmed by some analytical techniques like thin section study, powder X- ray diffraction, X-ray fluorescence spectroscopy and Fourier transform infrared spectroscopy

Free volume study of poly(chlorotrifluoroethylene) using positron annihilation spectroscopy as a microanalytical tool

Positron lifetimes and X-ray diffraction measurements were carried out on poly(chlorotrifluoroethylene) films annealed between 25 and 215 degrees C. The positron lifetime results were used to determine the free volume and XRD data were used to determine the apparent crystallite size and crystallinity. The glass transition temperature (T-g) of 52 degrees C obtained from positron results is in agreement with that obtained by thermal analysis. The average free volume cell size is 74 Angstrom(3) in films annealed below T-g, and increases to 84 Angstrom(3) in samples annealed above T-g. Although the observed changes in positron lifetime parameters as a function of annealing temperature are small, they are significant for the kind of material investigated. Our observations are explained in terms of thermally activated chain mobility, local relaxations and long-range motions. We further estimate, for the first time, the activation energies in the amorphous and crystalline regions of the polymer using the Goldanskii kinetic relations. Copyright (C) 1996 Elsevier Science Ltd

Physics Potential of the ICAL detector at the India-based Neutrino Observatory (INO)

The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) is designed to study the atmospheric neutrinos and antineutrinos separately over a wide range of energies and path lengths. The primary focus of this experiment is to explore the Earth matter effects by observing the energy and zenith angle dependence of the atmospheric neutrinos in the multi-GeV range. This study will be crucial to address some of the outstanding issues in neutrino oscillation physics, including the fundamental issue of neutrino mass hierarchy. In this document, we present the physics potential of the detector as obtained from realistic detector simulations. We describe the simulation framework, the neutrino interactions in the detector, and the expected response of the detector to particles traversing it. The ICAL detector can determine the energy and direction of the muons to a high precision, and in addition, its sensitivity to multi-GeV hadrons increases its physics reach substantially. Its charge identification capability, and hence its ability to distinguish neutrinos from antineutrinos, makes it an efficient detector for determining the neutrino mass hierarchy. In this report, we outline the analyses carried out for the determination of neutrino mass hierarchy and precision measurements of atmospheric neutrino mixing parameters at ICAL, and give the expected physics reach of the detector with 10 years of runtime. We also explore the potential of ICAL for probing new physics scenarios like CPT violation and the presence of magnetic monopoles.Comment: 139 pages, Physics White Paper of the ICAL (INO) Collaboration, Contents identical with the version published in Pramana - J. Physic

Physical ageing of poly(chlorotrifluoroethylene): A positron annihilation study

Isothermal annealing of poly(chlorotrifluoroethylene) (PCTFE) was carried out at a temperature of 70 degrees C (slightly above T-g) using the positron annihilation lifetime (PAL) technique. Both the o-Ps lifetime and intensity shows systematic variation with ageing time, and its intensity can be represented by two additive decay exponentials. The free volume which is estimated using the Nakanishi et al. equation developed from Tao's model, exhibits Doolittle type free volume relaxation. Physical ageing seems to yield close packing of polymer chains without crystallization. The relaxation time, and the nonexponentiality parameter, were estimated using a Kolrausch-Williams-Watt (KWW) function. (C) 1997 Elsevier Science Ltd

UV degradation of bivoltine silk fiber: A positron annihilation study

The effects of ultra-violet (UV) irradiation on the microstructure of semicrystalline bivoltine silk fibers have been investigated using the positron annihilation lifetime (PAL) technique. Lifetime results indicate that in the early stages of UV irradiation, chain scission leads to free radicals formation. Cross-linking is the main process at longer radiation time td UV. Present results also show that silk-I type with a low degree of molecular orientation changes to silk-II type on UV irradiation. (C) 1998 Elsevier Science Ltd. All rights reserved

Structural modifications in bivoltine silk fiber under thermal treatment

The microstructural changes of semicrystalline bivoltine silk fibers annealed between 27 to 260 degrees C were measured using positron annihilation lifetime spectroscopy (PALS). Measured lifetime and intensity as a function of temperature reveals the removal of water molecules until 60 degrees C. Present results indicate a T-g of 140 degrees C, which is further confirmed by differential scanning calorimetry (DSC). The structural changes like random-coil to alpha and then to beta form are observed in the crystalline and amorphous domains at 100 and 205 degrees C, respectively. Degradation of the fibers occur around 240 degrees C. As an extension of the present measurements, we have estimated the activation energy of 8.0 KJ/mol in the disordered domain of the fiber, based on Goldanskii's kinetic relations. (C) 1997 John Wiley & Sons, Inc

Effect of stress on the free volume content of poly(chlorotrifluoroethylene)

The effect of stress (hydrostatic compression) on the free volume of poly(chlorotrifluoroethylene) has been investigated using the positron annihilation lifetime (PAL) technique in the pressure range of 0-14 kbar at room temperature. The variation of the annihilation parameters indicates that the free volume compression occurs at a higher pressure (>8 kbar) compared to molecular compression (4 kbar). The measured free volume size decreases from 95 to 73 Angstrom(3) under the influence of compression. The results also indicate a crystalline-amorphous transformation. The free volume compressibility (beta(f)) is found to be maximum around 9 kbar (10(-3) atm(-1)). (C) 1998 Elsevier Science Ltd. All rights reserved

Influence of vinylidenefluoride on the physical ageing of poly(chlorotrifluoroethylene)

The influence of vinylidenefluoride (3 composition) on the physical ageing of poly(chlorotrifluoroethylene) at 70 °C has been investigated using the positron annihilation lifetime technique. Both the ortho-positronium (o-Ps) pick-off lifetime and its intensity show a systematic variation with ageing time. The o-Ps intensity exhibits non-exponential character which can be fitted with two additive exponential decay curves and the free volume is found to exhibit the Doolittle type of free volume relaxation. The relaxation times were evaluated from the structural relaxation function and the non-exponentiality parameter was estimated using the Kohlrausch–Williams–Watts (KWW) function, which indicates the deviation from exponential relaxation. Based on the relaxation times, the activation energies calculated seems to label the different kinetic units/irregularity in the chain backbone of PCTFE structure participating in the relaxation process. Physical ageing seems to yield close packing of polymer chains

A positron annihilation study of the tensile behaviour of bivoltine silk fibers

The influence of longitudinal stress on the microstructure of bivoltine silk fibers has been investigated by the Positron Lifetime Technique (PLT). The variation of o-Ps (orthopositronium atom) pick-off lifetime and intensity as a function of stress (0-240 kPa) reveals that the free volume size and its number density remains unchanged within the elastic limit (60 kPa). Thereafter, the free volume size decreases from 67 to 57 Angstrom(3). Owing to the loose helix structure, the chain alignment in the crystalline regions starts prior to that in the amorphous regions, leading to a more ordered silk-II type. The estimated low activation energy in the disordered regions suggests a folded chain conformation for the more ordered silk-II type. (C) 1999 Elsevier Science Ltd. All rights reserved

Construction of concentration density profile across the interface in SAN/EVA immiscible blend from positron lifetime parameters

The interface width determination through the construction of composition density profile across the interface in an immiscible binary polymer blend using ortho-positronium lifetime parameters is described in this paper. The distribution of free volume and hence the hydrodynamic interaction parameter has been evaluated for this purpose making use of the CONTIN routine analysis of the lifetime spectra. The results showed the broad free volume distribution and narrow interface width were reminiscent of lack of interaction between SAN and EVA the constituents