Gamma Photon Exposure Buildup Factors for Some Spin Ice Compounds Using G-P Fitting Method

Exposure buildup factors(EBF) for some spin ice compounds such as Dysprosium Titanate (Dy2Ti2O7), Dysprosium Stannate (Dy2Sn2O7), holmium Titanate (Ho2Ti2O7) and holmium Stannate (Ho2Ti2O7) useful in nuclear engineering have been computed for photon energy range 0.015 to 15 MeV upto penetration depth of 40 mean free path. The eBF for these compounds were found to be the largest at photon energy 15 MeV excepts in low energy. The eBF for the compounds containing tin were found to be the largest as well as shown a peak at 30 keV photon energy

Molecular tailoring of thermoreversible copolymer gels: some new mechanistic insights

We earlier reported the role of hydrophobic and hydrogen bonding interactions on the transition temperatures of thermoreversible copolymer gels. We show here that the chemical structure of the hydrophobe and its concentration determine the transition temperatures [lower critical solution temperature (LCST)] and the heat of transition of new hydrophobically modified poly(N-isopropyl acrylamide) [PNIPAm] copolymer gels. The gels, prepared by copolymerizing NIPAm monomer with hydrophobic comonomers containing increasing lengths of alkyl side groups and a terminal carboxyl acid group, showed lower LCST and lower heat of transition when compared to pure PNIPAm gel. The experimental results were also compared with theoretical calculations based on a lattice-fluid-hydrogen-bond [LFHB] model. We show experimentally and theoretically that a linear correlation exists between the transition temperature and length of the hydrophobic alkyl side group. Also, in apparent contradiction to previous work, we found a reduction in the heat of transition with increasing hydrophobicity. We propose that the presence of the terminal carboxyl acid group on the hydrophobic side chain of the comonomer prevents the association of water molecules around the hydrophobe, thereby causing a reduction in the heat of transition. The LFHB model supports this argument

The Top 100 questions for the sustainable intensification of agriculture in India’s rainfed drylands

India has the largest area of rainfed dryland agriculture globally, with a variety of distinct types of farming systems producing most of its coarse cereals, food legumes, minor millets, and large amounts of livestock. All these are vital for national and regional food and nutritional security. Yet, the rainfed drylands have been relatively neglected in mainstream agricultural and rural development policy. As a result, significant social-ecological challenges overlap in these landscapes: endemic poverty, malnutrition and land degradation. Sustainable intensification of dryland agriculture is essential for helping to address these challenges, particularly in the context of accelerating climate change. In this paper, we present 100 questions that point to the most important knowledge gaps and research priorities. If addressed, these would facilitate and inform sustainable intensification in Indian rainfed drylands, leading to improved agricultural production and enhanced ecosystem services. The horizon scanning method used to produce these questions brought together experts and practitioners involved in a broad range of disciplines and sectors. This exercise resulted in a consolidated set of questions covering the agricultural drylands, organized into 13 themes. Together, these represent a collective programme for new cross- and multi-disciplinary research on sustainable intensification in the Indian rainfed drylands

Applications of biochar in sulfate radical-based advanced oxidation processes for the removal of pharmaceuticals and personal care products

Recently, biochar (BC) has been increasingly used as a catalyst for the degradation of ‘emerging pollutants’ (EPs). Pharmaceuticals and personal care products (PPCPs), which come under ‘EPs’, can be harmful to the aquatic ecosystem despite being present in very low concentrations (ng/L–μg/L). Advanced oxidation processes (AOPs), which produce sulfate radical (SR-AOPs), show a great potential to degrade PPCPs effectively from wastewater. It is mainly due to the higher stability, long half-lives and better non-selectivity of SO4• - compared with AOPs with •OH generation. Furthermore, research focus is now given on AOPs coupled with BC-supported catalyst to enhance the degradation of PPCPs because of quicker generation of radicals (•OH, SO4•−) by the activation of persulfate (PS) and peroxymonosulfate (PMS). This article sheds light on the catalytic ability of BC after its physical and chemical modifications such as acid/alkali treatment and metal doping. The role of persistent free radicals (PFRs) in the BC for effective removal of PPCPs has been elaborated. Its potential applications in synthetic as well as real wastewater have also been discussed. HIGHLIGHTS Advanced oxidation processes coupled with sulfate radical (SR-AOPs) for degradation of PPCPs have been introduced.; Implementation of biochar as a catalyst in SR-AOPs has been explained.; The mechanism and pathways of biochar-added catalyst for PPCP degradation have been summarized.; A potential application of biochar catalyst with SR-AOPs in real wastewater and sewage water has been discussed.

Concentration of macromolecules from aqueous solutions: a new swellex process

A new swellex process (extraction through swelling polymers) to concentrate macromolecules from aqueous solutions has been demonstrated. Dilute solutions of biological macromolecules such as proteins have been concentrated with good recoveries and high selectivity. The selectivity was controlled by the extent of crosslinking in the gels. Electrolyte solution when pulsed through the column, causes the collapse of the gel. The reversible volume phase transition has been exploited for the regeneration of the gels

Response of TLD badges and cards for measurement of the operational quantity

The operational quantity, Hp(10), for strongly penetrating radiation was measured by a dosimeter placed on a phantom surface for individual external dose monitoring. Measurement of Hp(10) was carried out with a 137Cs source using CaSO4:Dy Teflon-based TLD badges and cards placed on the surface of a PMMA as well as water phantom at a depth of 10 mm. The ratio of response of the TLD discs to TLD badges and that of the TLD cards under similar conditions were identical for different experimental conditions. This experiment quantified the impact of the cassette on the dose measurement. Minor changes in the PMMA phantom thickness beyond 15 cm showed an insignificant impact on the dosimeter response

Swelling and phase transitions in deforming polymeric gels

Deformation of physically cross-linked gels is shown to increase their swelling capacity significantly and induce new volume phase transitions in the gels. Both of these phenomena are novel and are demonstrated here for the first time. The physical origin of the increased swelling lies in the breakage of some of the physical cross-links in the gel due to deformation. A phenomenological kinetic model is developed to describe the rate of breakage of physical cross-links in the gel due to shearing deformation. Coupling this model with the thermodynamics of swelling of polymeric networks gives quantitative predictions for the time evolution of the increase in the swelling capacity of such a gel. The enhanced swelling capacity of the gels due to deformation is also shown to be retained in the "memory" of the gel during further swelling-collapse cycles, a somewhat surprising result, which needs further elucidation

Core-shell morphology in poly(N-isopropyl acrylamide) copolymer gels induced by restricted diffusion of surfactant

In this paper, we report on the synthesis of copolymer gels of poly(N-isopropyl acrylamide) and poly(acryloyl aminoacids) and their interaction with anionic surfactant, namely, sodium dodecyl sulfate (SDS). While we were studying the swelling behavior of these copolymer gels in SDS solutions, we observed core-shell morphology in the swollen gels along with two discontinuous volume transitions. Such morphologies have potential applications in drug delivery systems. We provide a mechanistic interpretation of these new observations on the basis of electrostatic charge repulsion and restricted diffusion of surfactant into the gel

Thermoreversible hydrogel based on radiation induced copolymerisation of poly(N-isopropyl acrylamide) and poly(ethylene oxide)

Thermoreversible copolymer hydrogel based on poly(ethylene oxide) and poly (N-isopropyl acrylamide) has been prepared by γ-radiation technique. The utility of 13C n.m.r. spectroscopy in elucidating the structure and copolymer composition has been demonstrated. The volume transition as a function of temperature in these copolymers has been studied by swelling ratio measurements. Unlike poly(ethylene oxide) homopolymer gel, the copolymer gels show first order volume transition in the temperature range of 35-40°C. These gels are easy to synthesise in any shape and size and are found to be having good mechanical strength even in the fully swollen state. They can have potential applications in controlled drug delivery, bioseparations and biomedical fields

Characterization of chaotic dynamics-II: topological invariants and their equivalence for an autocatalytic model system and an experimental sheared polymer solution

Characterization of strange attractors exhibiting chaotic dynamics may be carried out through computation of metric, dynamical and topological invariants. The last of these are robust even under control parameter variations and hence have certain distinct advantages. In the present work, we carry out the topological analysis of the observed dynamics from a model autocatalytic reacting system and an experimental polymer solution subjected to shear. Low dimensional chaotic dynamics are observed in both these systems. The results show the global characterization and classification of the dynamics for both systems based on topological invariants, viz., linking numbers and relative rotational rates, is possible. The analyses of these invariants yield the template and the Markov transition matrix that contain in them valuable topological information about the system dynamics. The results obtained show that the two systems possess similar topological characteristics and follow the horseshoe mechanism. This information should help in developing design and control algorithms for these systems