Results 1 - 10 of 635
Results 1 - 10 of 635. Search took: 0.02 seconds
|Sort by: date | relevance|
[en] Herein, an electrochemical method has been introduced and developed for the selective benzylic oxidation of alkylarenes. This work utilizes a simple redox mediator system, N-Hydroxyphthalimide (NHPI), with an inexpensive and innovatory modified graphite and nickel-based electrode using undivided cell setups to the selective oxidation of alkylarenes toward the aldehyde and ketone production. Since, the selective oxidation of alkylarenes toward aldehyde formation (in the aerobic conditions) is a prominent challenge, our method for alkylarenes oxidation with high yield and selectivity in the presence of oxygen under mild and metal free conditions is promising. (paper)
[en] Highlights: • Two unique histidine kinases repress a developmental process in a moss plant. • These kinases promote the same process when submerged under water. • Similarly, they promote the process in artificial hypoxic condition. • Thus, these kinases have dual and opposite functions depending on oxygen condition. • This study adds insight into flexibility and evolution of two-component systems. Two-component systems, versatile signaling mechanisms based on phosphate transfer between component proteins, must have played important roles in adaptation and diversification processes in land plant evolution. We previously demonstrated that two Per-Arnt-Sim (PAS)-histidine kinases, PHK1 and PHK2, repress gametophore formation in the moss Physcomitrella patens under aerobic conditions, and that, in eukaryotes, the presence of their homologs is restricted to early-diverging streptophyte linages. We assessed here whether or not PHKs play a role in oxygen signaling. When submerged under water, the double disruption line for PHK1 and PHK2 formed fewer gametophores than the wild-type line (WT) both under light-dark cycles or continuous light, indicating that PHKs promote gametophore formation under an aquatic environment, in contrast to aerobic conditions. Similarly, in an artificial low-oxygen condition, the double disruption line formed fewer gametophores than WT. These results indicate that PHKs exert dual and opposite effects on gametophore formation depending on oxygen status. This study adds important insight into functional versatility and evolutionary significance of two-component systems in land plants.
[en] In this study, we are interested in the effect of long time exposure of the microbial fuel cells (MFCs) to air on the electrochemical performance. Here, MFCs enriched using an effluent from a MFC operated for about eight months. After 30 days, the condition of these systems was reversed from aerobic to anaerobic and vice versa, and their effects were observed for 11 days. The results show that for anaerobic MFCs, power generation was reduced when the anodes were exposed to dissolved oxygen of 7.5 ppm. The long exposure of anodic biofilm to air led to poor electrochemical performance. The power generation recovered fully when air supply stopped entering the anode compartment with a reduction of internal resistance up to 53 %. The study was able to show that mixed facultative microorganism able to strive through the aerobic condition for about a month at 7.5 ppm oxygen or less. The anaerobic condition was able to turn these microbes into exoelectrogen, producing considerable power in relative to their aerobic state. (author)
[en] In this article the results of the investigation on the processes of adsorption, hydrolysis and consumption of COD (chemical oxygen demand) in both aerobic and anaerobic reactors to laboratory scale, their relationship with the conditions of illumination, half of support and concentration of oxygen, and their possible application in aerobic post-treatment of anaerobic leachates are presented. The investigation consists of an experimental assembly and a theoretical development of search of descriptor equations of the global process, and rates of occurrence of the particular processes. The experimental assembly was carried out with four reactors to laboratory scale subjected to different conditions of light, half of support and concentration of oxygen; it had two phases: one of evaluation of the effect of the different conditions in the efficiency of the reactors, and another of evaluation of the kinetic constants in the reactor of better acting and their application in aerobic treatment of anaerobic leachates
[en] Ground-water chemistry data from coastal plain environments have been examined to determine the geochemical conditions and processes that occur in these areas and assess their implications for aquifer susceptibility. Two distinct geochemical environments were studied to represent a range of conditions: an inner coastal plain setting having more well-drained soils and lower organic carbon (C) content and an outer coastal plain environment that has more poorly drained soils and high organic C content. Higher concentrations of most major ions and dissolved inorganic and organic C in the outer coastal plain setting indicate a greater degree of mineral dissolution and organic matter oxidation. Accordingly, outer coastal plain waters are more reducing than inner coastal plain waters. Low dissolved oxygen (O2) and nitrate (NO3-) concentrations and high iron (Fe) concentrations indicate that ferric iron (Fe (III)) is an important electron acceptor in this setting, while dissolved O2 is the most common terminal electron acceptor in the inner coastal plain setting. The presence of a wide range of redox conditions in the shallow aquifer system examined here underscores the importance of providing a detailed geochemical characterization of ground water when assessing the intrinsic susceptibility of coastal plain settings. The greater prevalence of aerobic conditions in the inner coastal plain setting makes this region more susceptible to contamination by constituents that are more stable under these conditions and is consistent with the significantly (p<0.05) higher concentrations of NO3- found in this setting. Herbicides and their transformation products were frequently detected (36% of wells sampled), however concentrations were typically low (<0.1 μg/L). Shallow water table depths often found in coastal plain settings may result in an increased risk of the detection of pesticides (e.g., alachlor) that degrade rapidly in the unsaturated zone
[en] This study evaluated the effect of the application of liquid aerobic treated manure (continuous liquid composting, CLC) on physical, chemical and biological soil properties, with the objective of monitoring changes induced by soil management with CLC as a biofertilizer. Colonia, Uruguay (lat. 34,338164 S, long. 57,222630 W). Soil’s chemical properties, including nitrogen mineralization potential (NMP) and 15 microbiological properties (microbial biomass carbon, MBC; mesophylic aerobic bacteria; actinobacteria; filamentus fungi; fluorescein diacetate hydrolysis; dehydrogenase; with NMP; acid and alkaline phosphatase; cellulolose degraders; P-solubilizing bacteria; nitrifying; denitrifying and free-living N-fixing microorganisms; glomalin; and soil-pathogenicity index, SPI) were evaluated in two sites with similar cropping history, with one and three years of respective CLC application. CLC application had significant effects on soil microbial biomass (p<0.05), soil enzyme (p<0.1) and functional groups activity (p<0.05). SPI decreased in both sites with CLC application. No significant variations were detected for the chemical variables, with the exception of NMP, which was significantly high (p<0.05) in soil treated with CLC at both sites. The improved biological soil properties analyzed (MBC, soil enzyme activities and SPI, together with NMP) emerged as reasonable indicators to assess and monitor the effects of CLC application.
[en] Increased aerobic exercise capacity appears to reduce both all-cause mortality and cardiovascular disease mortality. Physical exercise to improve maximal oxygen consumption (VO/sub 2max/) is thus strongly recommended, however evidence regarding the most efficient training intensity for patients with coronary artery disease (CAD) is still lacking. The purpose of this randomized study was to assess the effects of aerobic exercise for increasing VO/sub 2max/ in stable CAD-patients. Thirty stable CAD-patients were randomized to supervised walking 30 min three times a week for 10 weeks. Before and after training VO/sub 2max/ was predicted from Bruce treadmill test. Before training VO/sub 2max/ was 35.2+-4.32 ml/kg/min and after training the mean VO/sub 2max/ was 43.1+-3.4 ml/kg/min. This difference was significant (p<0.05). Aerobic exercise is effective for increasing VO/sub 2max/ in stable CAD-patients. As VO/sub 2max/ seems to reflect a continuum between health and cardiovascular disease and death, the present data may be useful in designing effective training programmes for improved health in the future. (author)
[en] The present study deals with comprehensive analysis of the main factors like the effects of pH, influent substrate concentration and hydraulic retention time (HRT) driving simultaneous anaerobic sulfide and nitrate removal process. The analysis involved a multi-factorial orthogonal experiment. The results of range and variance analyses showed that decreasing influent substrate concentration might improve the effluent quality. Consequent to controlling the reaction pH at 7.0+-0.1, the effluent quality was the best keeping influent sulfide concentration of 220 mgL/sup -1/ and HRT of 10 h. Influent substrate concentration and HRT had significant bearing on the substrate removal rate, while pH had no significant effect. Decreasing HRT was a better option to increase substrate removal rate. Controlling the reaction pH around 7.0+-0.1, feeding influent sulfide concentration of 520 mgL/sup -1/ at HRT of 4h resulted in the optimum substrate removal rate. (author)
[en] The biomass was taken from a 3 m3 pilot scale acido-genesis bioreactor in Hsin Chu, Taiwan, for a batch study of the biochemical potential of hydrogen production. Six different food-microbial (S0/X0) ratios were conducted in batch biodegradation tests. In the first 30 hours, hydrogen was significantly produced with an initial food-microbial ratio as 10.87 g COD/g MLVSS. The maximum hydrogen production was 60 mL H2/ 80 mL mixed liquid in the serum bottle, and the maximum hydrogen production rate was 3.12 mL H2/ g-VSS-hr. A small amount of methane was also produced due to hydrogen-re-utilizing methano-genesis. A laboratory scale hydrogen fermentor is also established. The reactor volume is 3 liters, with fill-and-draw operation. In the first 20 days during the acclimation period, a corn starch is added as the auxiliary substrate. The kitchen waste loading rate is 10 kg COD/m3/day, and corn starch loading rate is also 10 kg COD/m3/day. It gives a hydrogen producing rate of 1 L H2/L/day. At run 2, the kitchen waste at the full loading, 20 kg COD/m3/day, was fed to the bioreactor. After a 20-day operation, the hydrogen producing rate is 0.8 mL/L/day. And the methane production is 16 mL CH4/L/day. The biogas consists mainly of carbon dioxide. The daily reactor operation profile is detected. The total carbohydrate is about 4000 mg/L, only 2000 mg/L of which can be degraded in the first six hours. To improve the hydrogen producing performance, the kitchen waste loading rate for this fermentor will be increased, and the influent operation strategy will be improved in the future. (authors)
[en] Radurization was investigated as a technique in the shelf life extension of ground beef. Although radurization does not necessarily kill off all meat spoilage bacteria, this process may be used for extending the bacteriological keeping quality of fresh meat. The materials and methods used in the investigation are also discussed