Effect of Abiotic and Biotic Factors on the Photo-Induced Production of Dissolved Gaseous Mercury

This study was conducted to evaluate the contribution of environmental factors such as solar radiation and dissolved organic matter (DOM) on the photo-induced dissolved gaseous mercury (DGM) production through laboratory experiments using field water samples collected from wetlands. DGM production was more significantly influenced by UVB intensity than UVA. DGM formation was also significantly affected by DOM chemical structure/composition rather than its concentration. Increasing NO ₃ ^? concentration limited DGM production, but photo-induced Hg oxidation stimulated by NO ₃ ^? would possibly occur when the NO ₃ ^? level is more than twice the DOC level. The addition of phosphorus into the field water samples induced a slight increase of DGM production; however, the addition of nitrogen decreased DGM formation, suggesting that an increase of limiting nutrients in water may promote biotic DGM production. Experiments using a Selenastrum capricornutum monoculture solution showed that cell density had a positive effect on DGM production. Moreover, the difference in DGM production between filtered and unfiltered samples showed that S. capricornutum significantly produced biotic DGM under UVA irradiation. Finally, our results imply that environmental factors such as light intensity, DOM sources, and site-specific microorganisms can significantly affect photo-induced Hg transformation.     

Chemical characterization of six mangrove species in Bangladesh

Lack of data especially pertaining to the chemistry of mangrove wood species makes it difficult to prepare successful plans for their conservation and to use mangroves as a source of wood fiber. In this paper, chemical characterizations of the six main mangrove species of Bangladesh [namely Keora (Sonneratia apetala), Geoa (Excoecaria agallocha), Bine (Avicennia alba), Sundari (Heritiera fomes) Pashur (Xyloccarpous mekongests), and Kakra (Bruguiera gymnorhiza)] were investigated. The chemical results revealed that these species contain high percentages of dichloromethane followed by methanol extractives. Methanol extracts in Pashur, Sundari, and Bine were higher than 10%, which indicates high percentage of tannin material. The total lignin content in these species was higher than 25%, except for Gewa (23.6%) and Pashur (21.3%), which is higher than that of the normal range of hardwood. The pentosan content in these six species was within the range of 19.4–22.8%. The α-cellulose content in Keora and Gewa was acceptable for pulp production, but the others were lower than the normal range of hardwood. Alkaline nitrobenzene oxidation showed that all these species had a very high syringaldehyde to vanillin (2.6–5.0) ratio except Keora (1.6). Surprisingly, rhamnose is the main constituent with xylose of hemicelluloses of these six mangrove species. The ash content in these six mangrove wood species was also higher than that in normal hardwood.     

Continuous hot pressurized solvent extraction of 1,1-diphenyl-2-picrylhydrazyl free radical scavenging compounds from Taiwan yams (Dioscorea alata)

This study investigates a semicontinuous hot pressurized fluid extraction process and the scavenging activity on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical of the extract from Taiwan yams (Dioscorea alata). Liquid-liquid extractions were preliminarily employed to generate six fractions, initially extracted by ethanol. Then, the aqueous solution of dried crude ethanol extract was sequentially fractionated by hexane, chloroform, ethyl acetate, and n-butanol. The EC50 value was defined as the UV absorption of DPPH concentrations sufficiently decreased to 50% of the original value. It was found that all peel portions have a better effect on scavenging of the DPPH free radical than meat portions, especially for the ethyl acetate partition of the peel portion of Tainung #2 yam. Its EC50 value (14.5 microg mL(-1)) was even lower than that of ascorbic acid (21.4 microg mL(-1)). Furthermore, semicontinuous hot pressurized ethanol was superior to hot pressurized water in extracting the compound scavenging the DPPH radical from the Purpurea-Roxb peel. The recovery of four unknown compounds corresponded to the scavenging ratio of DPPH free radical in the hot pressurized ethanol extract. Finally, three-level and four-factor experimental design revealed that ethanol ratio and temperature were the most effective factors in order. Conditions of 80% of aqueous ethanol, 20.0 kg/kg solid ratio, 180 psig (1.342 MPa), and 100 degrees C were preferred to extract those antioxidants from the yam peel.     

Influence of crossing-beam shoulder and wood species on moment-carrying capacity in a Korean traditional dovetail joint

This study investigated the interaction effects of a crossing beam on the moment-carrying capacity of a Korean traditional dovetail joint. In particular, the length of the crossing-beam shoulder (B _s ) and the wood species were varied as important factors. Clearly, the B _s acts as a fastener that improves the performance of timber joints by preventing splitting failure parallel to the grain. All the specimens experienced tension failure by tension force in the direction perpendicular to the grain; therefore, the tension strength perpendicular to the grain could be considered an important property, and standard values could be determined to develop a formula for predicting the structural behavior of the joints or the structural design codes of the joints. The results of the tests indicated that the moment resistance of the joints increased as the length of the crossing B _s and the density of the wood species increased. Joint stiffness results also indicated that the joints became stiffer when the crossing beam had shoulders, but the results were not affected by the length of the B _s . In addition, the joint stiffness was proportional to the density of the wood species.     

Disseminated infection due to Mycobacterium avium subsp. avium in an Asian elephant (Elephas maximus)

A disseminated infection caused by Mycobacterium avium subspecies avium (MAA) was diagnosed in a 57-yr-old male Asian elephant (Elephas maximus) housed at the Seoul Zoo, Gyeonggi, Republic of Korea. An apparent granulomatous inflammation with central caseous necrosis was evident in the lung sections. To confirm mycobacterial infection, polymerase chain reaction-restriction enzyme polymorphism analysis (PCR-RFLP) of the rpoB and hsp65 genes was performed from multiple organs and cultured bacteria. The PCR-RFLP revealed a M. avium subspecies. MAA was identified by multiplex PCR for detection of IS901 and IS1311. Thus, it is believed that MAA caused the disseminated infection in this case. Although the source of infection was not determined, the elephant may have become infected through contamination of soil and feed by free-living birds infected with MAA. This is the first reported case of disseminated infection due to MAA in a captive elephant in the Republic of Korea.     

Coexpression with Auxiliary β Subunits Modulates the Action of Tefluthrin on Rat Na(v)1.6 and Na(v)1.3 Sodium Channels

The erythrocyte, due to its role as O₂ and CO₂ transporter, is under the constant exposure to reactive oxygen species and oxidative stress. The objective of this study was to investigate the ability of 2,4-D to induce oxidative stress in blood of male wistar rats. Rats were randomly divided into four groups: a control group and three treated groups receiving by gavage 15, 75 and 150 mg, respectively, of 2,4-D/kg/BW/day for 28 days. Results showed that 2,4-D caused significant negative changes in the investigated biochemical parameters. In fact, 2,4-D exposition strongly increases LDH, by contrast, there is a statistically significant decrease in Hgb levels. The malondialdehyde level was significantly increased in 2,4-D treated groups. Fatty acid composition of the erythrocytes was also significantly changed with 2,4-D exposure, in favor of the peroxidation of polyunsaturated fatty acids. Furthermore, antioxidant enzyme (SOD, CAT, GPx, and GR) activities in erythrocytes were significantly decreased. Thus, our results indicated the potential effects of 2,4-D to cause oxidative stress in rat erythrocytes. Therefore, at higher doses, 2,4-D may play an important role in the development of vascular disease via lipid peroxidation and oxidative stress.     

Contact and fumigant toxicity of plant essential oils and efficacy of spray formulations containing the oils against B‐ and Q‐biotypes of Bemisia tabaci

BACKGROUND: The contact + fumigant toxicity of 92 plant essential oils and control efficacy of 18 experimental spray formulations containing nine selected essential oils (0.5 and 0.1% sprays) and six commercial insecticides to females from B‐ and Q‐biotypes of Bemisia tabaci were evaluated using vapour‐phase mortality and spray bioassays. RESULTS: Garlic and oregano (LC₅₀, 0.15 mL cm^?3) were the most toxic oils against B‐ and Q‐biotype females. Strong fumigant toxicity to both biotype females was also obtained from catnip, cinnamon bark, clove bud, clove leaf, davana, savory and vetiver Haiti oils (LC₅₀, 0.17–0.48 mL cm^?3). The 0.5% sprays of these oils (except for thyme red oil) resulted in 90–100% mortality against both biotype females. Only garlic applied as 0.1% spray provided 100% mortality. Spinosad 100 g L^?1 suspension concentrate (SC) treatment resulted in 92 and 95% mortality against both biotype females, whereas acetamiprid 80 g L^?1 wettable powder (WP), imidacloprid 80 g L^?1 SC, thiamethoxam 100 g L^?1 water‐dispersible granule (WDG) and pyridaben 200 g L^?1 WP treatments resulted in 89–100% mortality against B‐biotype females only. CONCLUSION: In the light of global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment, the essential oils described, particularly garlic, cinnamon bark and vetiver Haiti, merit further study as potential insecticides for the control of B. tabaci populations as fumigants with contact action. Copyright © 2011 Society of Chemical Industry     

Thermal decomposition kinetics of copolymers derived from<Emphasis Type="Italic">p</Emphasis>-dioxanone,L-lactide and poly(ethylene glycol)

The kinetic parameters, including the activation energyE, the reaction ordern, and the pre-exponential factorZ, of the degradation of the copolymers based on the poly(L-lactide) (PLLA) or poly(p-dioxanone-co-L-lactide) (PDO/PLLA) and diol-terminated poly(ethylene glycol) (PEG) segments have been evaluated by the single heating methods of Friedman and Freeman-Carroll. The experimental results showed that copolymers exhibited two degradation steps under nitrogen that can be ascribed to PLLA or PDO/PLLA and PEG segments, respectively. However, copolymers exhibited almost single degradation step in air. Although the values of initial decomposition temperature were scattered, copolymers showed the lower maximum weight loss rate and degradation-activation energy in air than in nitrogen whereas the higher value of temperature at the maximum rate of weight loss was observed in air.     

Synthesis and solid-state NMR structural characterization of 13C-labeled graphite oxide

The detailed chemical structure of graphite oxide (GO), a layered material prepared from graphite almost 150 years ago and a precursor to chemically modified graphenes, has not been previously resolved because of the pseudo-random chemical functionalization of each layer, as well as variations in exact composition. Carbon-13 (13C) solid-state nuclear magnetic resonance (SSNMR) spectra of GO for natural abundance 13C have poor signal-to-noise ratios. Approximately 100% 13C-labeled graphite was made and converted to 13C-labeled GO, and 13C SSNMR was used to reveal details of the chemical bonding network, including the chemical groups and their connections. Carbon-13-labeled graphite can be used to prepare chemically modified graphenes for 13C SSNMR analysis with enhanced sensitivity and for fundamental studies of 13C-labeled graphite and graphene.