Surface tailoring of an ethylene propylene diene elastomeric terpolymer via plasma‐polymerized coating of tetramethyldisiloxane

In the research presented here, we explore the use of a low‐energy plasma to deposit thin silicone polymer films using tetramethyldisiloxane (TMDSO) (H(CH₃)₂? Si? O? Si? (CH₃)₂H) on the surface of an ethylene propylene diene elastomeric terpolymer (EPDM) in order to enhance the surface hydrophobicity, lower the surface energy and improve the degradation/wear characteristics. The processing conditions were varied over a wide range of treatment times and discharge powers to control the physical characteristics, thickness, morphology and chemical structure of the plasma polymer films. Scanning electron microscopy (SEM) shows that pore‐free homogeneous plasma polymer thin films of granular microstructure composed of small grains are formed and that the morphology of the granular structure depends on the plasma processing conditions, such as plasma power and time of deposition. The thicknesses of the coatings were determined using SEM, which confirmed that the thicknesses of the deposited plasma‐polymer films could be precisely controlled by the plasma parameters. The kinetics of plasma‐polymer film deposition were also evaluated. Contact angle measurements of different solvent droplets on the coatings were used to calculate the surface energies of the coatings. These coatings appeared to be hydrophobic and had low surface energies. X‐ray photoelectron spectroscopy (XPS) and photoacoustic Fourier‐transform infrared (PA‐FT‐IR) spectroscopy were used to investigate the detailed chemical structures of the deposited films. The optimum plasma processing conditions to achieve the desired thin plasma polymer coatings are discussed in the light of the chemistry that takes place at the interfaces. Copyright © 2004 Society of Chemical Industry     

Effects of neutralization on the structure and properties of an ionomer

The structure, morphology, and properties of an ionomer, poly(ethylene‐acrylic‐acid) neutralized by zinc salts (PI) depend on the free carboxylic acid content. In this work, metal acetates (Na, Zn, and Al acetates) were used to control the neutralization levels. A wide range of techniques were used, such as spectroscopic Fourier transform infrared spectroscopy (FTIR), thermal [thermogravimetric analysis, modulated differential scanning calorimetry (MDSC), and dynamic mechanical analysis (DMA)], mechanical (tensile measurement), and small angle neutron scattering (SANS). The melt rheological properties of the samples were also examined. The results show that metal acetate neutralizes free acrylic acid in the ionomer, which has the primary role in controlling ionic association. The number of ionic groups in ionic domains and multiplets in the matrix is dependent on the neutralization level. Metal valence determines the ionic domain or multiplet structure (FTIR), further properties of PI. Dynamic mechanical properties, the ionic transition behaviour, and the mechanical properties are improved compared with PI using monovalent cation (Na⁺), but decreased using trivalent cation (Al³⁺) or shows less significant changes due to steric effects. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Interaction of Bacillus polymyxa with some oxide minerals with reference to mineral beneficiation and environmental control

Interaction of Bacillus polymyxa with calcite, hematite, corundum and quartz resulted in significant surface chemical changes not only of the cells but also in the minerals. Both the cell surfaces as well as quartz particles were rendered more hydrophobic after mutual interaction, whilst the rest of the minerals exhibited enhanced hydrophilicity after interaction with the bacteria. The bacteria were also observed to be capable of dissolving calcite, hematite and corundum and biosorbing the dissolved metal ions to varying extents. An excess of polysaccharides could be observed on biotreated calcite, hematite and corundum while the predominance of a protein-based metabolic product was evident on quartz surfaces. The utility of bioprocessing in the beneficiation of the above minerals through bioflotation and bioflocculation is demonstrated.     

An assessment by subsistence farmers of the risks to food security attributable to climate change in Makwanpur,Nepal

The potential impacts of climate change on the food security of subsistence farmers is a serious concern. This article explores the food security situations of two categories of subsistence farm households, vegetable- and cereal-based farming systems, in the Makwanpur district of Nepal in the context of climate change. Local climate data for the past 30 years were analyzed. Interviews with local farmers and key informants, and focus group discussions were carried out to collect the primary data. Empirical data showed that changes in climate variables for the study period were in line with farmers’ perceptions and that farming communities were negatively impacted. Perceived impacts were erratic rainfall, increased frequency of floods and droughts, soil degradation and insect pests, weeds and diseases. Farmers have modified traditional cropping patterns and calendar, changed crop varieties and increased fertilizer and pesticide applications in order to maintain crop yields. They have also sought off-farm employment. However, agricultural productivity in the area is declining and only one third of all households in the area were food secure. Household food insecurity was at mild to moderate levels, but vegetable-based households were more secure than cereal-based ones. At the household level, locally successful adaptive measures, such as rainwater harvesting, mulching, planting date adjustments, off-farm opportunities, including infrastructure and extension support, could increase production and contribute to reversing the impact of increased risk attributed to climate change.     

Use of low dose e-beam irradiation to reduce E. coli O157:H7, non-O157 (VTEC) E. coli and Salmonella viability on meat surfaces

This study determined the extent that irradiation of fresh beef surfaces with an absorbed dose of 1 kGy electron (e-) beam irradiation might reduce the viability of mixtures of O157 and non-O157 verotoxigenic Escherichia coli (VTEC) and Salmonella. These were grouped together based on similar resistances to irradiation and inoculated on beef surfaces (outside flat and inside round, top and bottom muscle cuts), and then e-beam irradiated. Salmonella serovars were most resistant to 1 kGy treatment, showing a reduction of ≤ 1.9 log CFU/g. This treatment reduced the viability of two groups of non-O157 E. coli mixtures by ≤ 4.5 and ≤ 3.9 log CFU/g. Log reductions of ≤ 4.0 log CFU/g were observed for E. coli O157:H7 cocktails. Since under normal processing conditions the levels of these pathogens on beef carcasses would be lower than the lethality caused by the treatment used, irradiation at 1 kGy would be expected to eliminate the hazard represented by VTEC E. coli.     

Provable secure proxy signature scheme without bilinear pairings

Proxy signature is an active research area in cryptography. A proxy signature scheme allows an entity to delegate his or her signing capability to another entity in such a way that the latter can sign messages on behalf of the former. Many proxy signature schemes using bilinear pairings have been proposed. But the relative computation cost of the pairing is more than 10 times of the scalar multiplication over elliptic curve group. In order to save the running time and the size of the signature, we propose a proxy signature scheme without bilinear pairings and prove its security against adaptive chosen‐message attack in random oracle model. The security of our scheme is based on the hardness of the elliptic curve discrete logarithm problem. With the running time being saved greatly, our scheme is more practical than the previous related scheme for practical applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Efficient ID-based multiproxy multisignature without bilinear maps in ROM

Most of the previously proposed identity-based multiproxy multisignature (IBMPMS) schemes used pairings in their construction. But pairing is regarded as an expensive cryptographic primitive in terms of complexity. The relative computation cost of a pairing is approximately more than ten times of the scalar multiplication over elliptic curve group. So, to reduce running time, we first define a model of a secure MPMS scheme, then propose an IBMPMS scheme without using pairings. We also prove the security of our scheme against chosen message attack in random oracle model. Our scheme’s construction avoids bilinear pairing operations but still provides signature in the ID-based setting and reduces running time heavily. Therefore, proposed scheme is more applicable than previous schemes in terms of computational efficiency for practical applications.     

Role of surfacelet transform in diagnosing Alzheimer’s disease

Multidimensional Systems and Signal Processing - The clinical diagnosis of Alzheimer’s disease (AD) is based on the tedious questionnaire and prolonged tests, which require involvement of the...     

Compatibilization of natural rubber–polyolefin thermoplastic elastomeric blends by phase modification

Natural rubber–polyolefin (70/30) blends have been studied by incorporation of modified rubber and plastic phases with a view to make the heterogeneous phases compatible. The modified rubbers used were epoxidized natural rubber (ENR) and sulfonated ethylene–propylene diene rubber (S-EPDM) at a level of 20 parts. Other rubbers such as chlorinated polyethylene (CPE) and ethylene propylene diene rubbers (EPDM) were also used at a level of 20 parts in the natural rubber–polyethylene (NR/PE) systems. The plastic phase was chemically modified with maleic anhydride (MA) in presence of benzoyl peroxide (BPO) and used at a concentration of 10% of PE, i.e., PEm. The tensile properties such as the modulus, elongation at break, tensile strength, and hysteresis were studied. NR/ENR/PEm/PE shows the greatest improvement in tensile strength (45% over control NR/PE). NR/S-EPDM/PEm/PE also shows similar improvement, although the hysteresis loss decreases. The change in these properties could be related to the adhesive strength. This was found to be improved by the incorporation of modified rubber and modified plastic phases. The best adhesion values have been obtained with NR/ENR/PEm/PE and NR/S-EPDM/PEm/PE. Thus, a correlation between tensile and adhesive strength was obtained for all the systems. The increase in adhesive strength is due to chemical reactions between the various phases. Probable chemical reactions have been suggested. Morphological observations show that the phases are interpenetrating, and this is consistent with the increased tensile strength. The natural rubber–polypropylene (NR/PP) systems do not offer good strength properties with the modified PP and modified rubbers. The adhesive strength also decreases with the incorporation of the modified system. The hysteresis properties show some improvement.     

Studies on Adhesion Between Natural Rubber and Polyethylene and the Role of Adhesion Promoters

Studies on adhesion between natural rubber (NR) and polyethylene (PE) with different levels of interaction (physical and chemical) have been carried out. Ethylene propylene diene rubber (EPDM) and chlorinated polyethylene (CPE) were used as physical promoters and epoxidised natural rubber/modified polyethylene (ENR/PEm) and sulfonated ethylene propylene diene rubber/modified polyethylene (S-EPDM/PEm) were used as chemical adhesion promoters. The failure surfaces were examined with the help of scanning electron microscopy (SEM), optical photography and electron spectroscopy for chemical analysis (ESCA) techniques.

The peel strength between natural rubber and polyethylene as measured in this study is 140 J/m². With the incorporation of physical promoters such as EPDM, the peel strength increases twenty fold because of structural similarity of EPDM with PE and the rubbery nature of EPDM. Similarly, the other promoters show significant improvement in peel strength. At high temperature and low rate of peeling, the nature of failure is mainly “stick-slip” for joints with interaction promoters. The average peel strength increases with increase in test rate and decrease in test temperature for most of the joints. All the data could be shifted onto a master curve indicating that the increase in strength is a result of viscoelastic dissipation. NR/EPDM/PE and NR/CPE/PE systems, however, behave in a different way probably because they alter the nature of crack propagation at or near the interface. ESCA results of the peeled PE surface show a chemical shift of C_1S peak. SEM photographs also indicate interaction at the interface when modifiers are used. An increase in crystallinity of PE from 30% to 64% and modulus increase the peel strength of NR/PE joints by a factor of four. The results of peel strength measurement at 90° are lower than those at 180°. Lap shear results are in line with peel strength.