Nano-calcium carbonate reinforced polypropylene and propylene-ethylene copolymer nanocomposites: Tensile vs. impact behavior

Improvement of both the tensile and impact strength of the same polymeric material has always been a great challenge for the plastic industry. The study focuses on the effect of incorporation of calcium carbonate nanoparticles (0.3 wt% to 15 wt%) into three polypropylene (PP) based matrices viz. PP homopolymer, propylene-ethylene (PP-PE) copolymer and the blend of PP:PP-PE (30:70) to improve their impact behavior without hampering the tensile strength much. A loss in both the tensile and impact properties was observed in PP based nanocomposite. However, PP-PE based nanocomposites showed a significant improvement in impact strength (47 %) at 10 wt% loading with a loss of tensile strength by 22 %. To minimize this loss a blend of PP:PP-PE (30:70) was explored as a matrix. At 10 wt% loading, this matrix showed an improvement of 30 % in impact strength whereas the tensile loss was minimized to 10 %. Further, silane coupling agent which promoted good interfacial adhesion was used for best compositions. The variation of crystalline morphology of the nanocomposites with various formulations was analyzed using differential scanning calorimetry and X-ray diffraction.     

Studies on composite filaments from nanoclay reinforced polypropylene

The development of high tenacity, high modulus monofilaments from Polypropylene/Clay nanocomposite has been investigated. Pure sodium montmorillonite nanoclay was modified using hexadecyl trimethyl ammonium bromide (HTAB) via an ion exchange reaction. Pure and modified clay were characterized through X-ray diffraction, FTIR and TGA. The modified clay was melt blended with polypropylene (PP) in presence of a swelling agent. Composite filaments from PP/Clay nanocomposite were prepared at different weight percentages of nanoclay and the spinning and drawing conditions were optimized. The filaments were characterized for their mechanical, morphological and thermal properties. The composite PP filaments with modified clay showed improved tensile strength, modulus and reduced elongation at break. The composite filaments with unmodified clay did not show any improvement in tensile strength but the modulus improved. The sharp and narrow X-ray diffraction peaks of PP/nanoclay composite filaments indicate increase in crystallinity in presence of modified clay at small loadings (0.5%). The improved thermal stability was observed in filaments with modified as well as unmodified clays.     

Expression of iron regulatory proteins in full-term swine placenta

In swine, even though the pregnant sows were with iron abundance, the inborn iron reserve of piglets was compromised. This indicates the insufficiency of molecular machinery involved in local placental iron flux. Here, we investigated the expression of iron regulatory proteins like hepcidin and ferroportin and also their association with iron reserve, inflammation and oxidative stress in placenta of full-term pregnant sows (n = 6). Amplification and sequencing of placental DNA confirmed the presence of hepcidin (MN579557) and ferroportin (MN565887) sequences and their 100% identity with existing GenBank data. Real-time amplification of placental mRNA revealed significant higher expression of hepcidin (p < .05) than ferroportin. Western blot analysis of placental tissues revealed specific bands for both hepcidin (~8 kDa) and ferroportin (~62 kDa) molecules. Immunohistochemistry revealed the immunoreactivity for both proteins in the cytoplasm and membrane of trophoblastic cells of the placenta. Hepcidin and ferroportin expressions were positively associated with placental non-haem iron reserve (p < .0001; p = .033), lipid peroxidation (p = .0060; p < .0001) and reactive oxygen species level (p = .0092; p = .0292). Hepcidin expression was positively associated with interleukin – 6 (p = .0002) and interferon gamma (p < .0001) expressions but ferroportin expression was negatively associated with interleukin-6 (p = .0005), interleukin-1β (p = .0226) and interferon gamma (p = .0059) expressions. This indicates hepcidin and ferroportin may have a role in controlling the local placental iron flux by acting as a molecular bridge between iron trafficking and inflammation.     

Transmission dynamics and control of severe acute respiratory syndrome

Severe acute respiratory syndrome (SARS) is a recently described illness of humans that has spread widely over the past 6 months. With the use of detailed epidemiologic data from Singapore and epidemic curves from other settings, we estimated the reproductive number for SARS in the absence of interventions and in the presence of control efforts. We estimate that a single infectious case of SARS will infect about three secondary cases in a population that has not yet instituted control measures. Public-health efforts to reduce transmission are expected to have a substantial impact on reducing the size of the epidemic.     

Production and optimization of indole acetic acid by indigenous micro flora using agro waste as substrate

Indole Acetic Acid (IAA) producing bacterium was isolated from the Rhizosphere soil and identified as Rhizobium sp. and Bacillus sp., Optimization of Indole acetic acid production was carried out at different cultural conditions, such as pH, temperature and substrate with Rhizobium sp., Bacillus sp. and Rhizobium sp., produced higher amount of Indole acetic acid (6.1 mg mL(-1)) than the Bacillus sp., (4.4 mg mL(-1)) at pH 7 and 37 degrees C in the Bengal gram substrate. Partial purification of Indole acetic acid was done by Thin Layer Chromatography (TLC). In conclusion Rhizobium sp., appear to be a suitable soil microorganism for high level of IAA production.     

Toxicity of chlorpyrifos,carbofuran, mancozeb and their formulations to the tropical earthworm Perionyx excavatus

Effects of chlorpyrifos, carbofuran, mancozeb and their formulated products on survival, growth and reproduction of the tropical earthworm Perionyx excavatus were investigated in standard artificial soil. The toxicity of the three chemicals decreased in the order carbofuran > chlorpyrifos > mancozeb. In general, formulations were more toxic than the active ingredients, but differences in LC₅₀ and EC_x values were significant only in two cases and not more than a factor of 2.0. This could mainly be due to masking of the effects of additives in the soil. Comparison with available survival data revealed that P. excavatus is more sensitive than the standard test species Eisenia andrei or E. fetida. The use of tropical species in the risk assessment of pesticides in tropical regions should therefore be encouraged.     

Development of polyurethane based conducting nanocomposite fibers via twin screw extrusion

In the present study, conducting nanofillers are incorporated in thermoplastic polyurethane (TPU) to produce nanocomposite fibers through melt compounding route using micro twin screw extruder attached to a fiber drawing device. Nanocomposite fibers using bulk graphite, nanographite and carbon nanofiber were produced using varying amounts of these nanofillers. Metal coated nanographite, new hybrid nanoparticle produced in house, were also used to impart conductivity to the TPU fiber. The process parameters such as processing temperature, mixing time and rpm of the screw have been optimized considering minimum change in TPU bulk properties. It has been found that the nanofillers can be melt mixed safely up to 4 min with the TPU at 180 °C and 100 screw rpm. These mixing conditions give reasonable amount of dispersion. The studies on such fibers in differential scanning calorimetry (DSC) and thermomechanical analyzer (TMA) reveals that the metal coated nanographite particles make the nanocomposite fibers more thermally stable. Both the D. C. conductivity and A. C. impedance of the nanocomposite fibers have reduced significantly even at very low loading of nanofillers, although the conductivity of the produced fibers are in antistatic range (D.C. conductivity ～10^?4 S/m).     

Chemical composition and antioxidant property of holy basil (Ocimum sanctum L.) leaves, stems, and inflorescence and their in vitro callus cultures

In this study, the chemical constituents and antioxidant property of holy basil (Ocimum sanctum Linn.) field-grown plant parts (leaves, stems, and inflorescence) were compared with those of respective callus cultures induced from each explant in in vitro. The callus cultures were successfully initiated on Murashige and Skoog (MS) medium supplemented with 2,4-dichlorophenoxy acetic acid (2,4-D) (1 mg/L) combined with different concentrations (0.1-0.5 mg/L) of kinetin as plant growth regulators. The distribution of phenolic compounds in these extracts was analyzed using reverse phase high-performance liquid chromatography with reference standards. Interestingly, rosmarinic acid (RA) was found to be the predominant phenolic acid in all callus extracts in comparison with field-grown plant parts. In this study, the antioxidant activity of the extracts was evaluated with six different in vitro antioxidant-testing systems. Their activities of scavenging superoxide anion radicals, 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH), hydroxyl radicals, hydrogen peroxide, chelating ferrous iron, and ferric ion reducing potential were assessed. The antioxidant activity was increased in all testing systems with increasing amounts of extract. However, at the same concentration, the callus extracts exhibited higher antioxidant activity in all of the testing systems than the extract obtained from field-grown plant parts. The data obtained from this study suggested the possibility of the isolation of a high content of RA from in vitro callus cultures rather than field-grown plant organs of holy basil.     

Casuarina Coastal Forest Shelterbelts in Hambantota City, Sri Lanka: Assessment of Impacts

Growing of Casuarina equisetifolia as a small shelterbelt on the beach in Hambantotota City was implemented to protect the beautiful natural sand dunes, preserve visual amenity and be a barrier to seawater salt spray. The casuarina shelterbelt has become popular because it was the only undamaged area in Hambantota City after the devastating 2004 tsunami. The objective of the study was to assess the impacts of the casuarina shelterbelt in economic, social and environmental terms. A survey was conducted to elicit observations and experiences of city dwellers close to the shelterbelt. Respondents did not consider that the shelterbelt reduced wind speed. Although the belt has increased the size of the sand dunes, the casuarina trees have suppressed the growth of native species as an under-storey. The belt has improved the aesthetic value of the beach. No impact of the shelterbelt has been identified in protecting agricultural crops and reducing the corrosion of household goods from seawater salt spray. The city dwellers have not recognized the economic importance of casuarina timber but are impressed with the increase of fuelwood supply from the shelterbelt. The shelterbelt has prevented illegal settlement, but facilitated anti-social and illegal activities among lawless city dwellers. The attractiveness of the beach for tourism has been enhanced. Empirical evidence reveals that the casuarina belt in Hambantota City has greater environmental and social impacts than economic impacts.     

New sources of resistance to Fusarium wilt and sterility mosaic disease in a mini-core collection of pigeonpea germplasm

Fusarium wilt (FW) and Sterility mosaic disease (SMD) are important biotic constraints to pigeonpea production worldwide. Host plant resistance is the most durable and economical way to manage these diseases. A pigeonpea mini-core collection consisting of 146 germplasm accessions developed from a core collection of 1290 accessions from 53 countries was evaluated to identify sources of resistance to FW and SMD under artificial field epiphytotic conditions during 2007–08 and 2008–09 crop seasons. Resistant sources identified in the field were confirmed in the greenhouse using a root dip screening technique for FW and a leaf stapling technique for SMD. Six accessions (originated from India and Italy were found resistant to FW (<10% mean disease incidence). High level of resistance to SMD was found in 24 accessions (mean incidence <10%). These SMD resistant accessions originated from India, Italy, Kenya, Nepal, Nigeria, Philippines and United Kingdom. Combined resistance to FW and SMD was found in five accessions (ICPs 6739, 8860, 11015, 13304 and 14819). These diverse accessions that are resistant to FW or SMD will be useful to the pigeonpea resistance breeding program.