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1.
The release of CO2 by soil microorganisms after the addition of nitrogen and glucose in excess and calibration additions of phosphorus has successfully
been used to assess microbial available P, assuming the native soil P pool is then limiting respiration. However, in P-fixing
soils and soils with high P content, carbon can be exhausted before the available soil P pool. It is not possible to simply
increase the amount of glucose as then the glucose concentration would be lethal for microorganisms. A modified method was
tested where soil is mixed with perlite. It was hypothesised that perlite, having a high water holding capacity, would dilute
the concentration of glucose, while maintaining the bioavailability of added nutrients, thus avoiding carbon limitation. Factorial
combinations of amount of soil and perlite (both adjusted to −25 kPa water potential) were tested to examine if perlite as
such had any effect on the respiration. Five tropical soil samples with a sharp gradient in P availability and one N-limited
compost material were used. The method successfully reduced the risk of carbon limitation. Microbial indices, such as basal
respiration, substrate-induced respiration and maximum P-limited respiration, were directly proportional to the amount of
soil in the experiments but unrelated to the amount of perlite, showing that perlite did not affect microbial measurements. 相似文献
2.
A concentration process occurring in the melt zone of the Greenland ice cap has produced the richest known deposit of cosmic dust on the surface of the earth. Extraterrestrial particles collected from this region are well preserved and are collectable in large quantities. The collected particles are generally identical to cosmic spheres found on the ocean floor, but a pure glass type was discovered that has not been seen in deep-sea samples. Iron-rich spheres are conspicuously rare in the collected material. 相似文献
3.
To analyze the dynamics of protein complexes during the yeast cell cycle, we integrated data on protein interactions and gene expression. The resulting time-dependent interaction network places both periodically and constitutively expressed proteins in a temporal cell cycle context, thereby revealing previously unknown components and modules. We discovered that most complexes consist of both periodically and constitutively expressed subunits, which suggests that the former control complex activity by a mechanism of just-in-time assembly. Consistent with this, we show that additional regulation through targeted degradation and phosphorylation by Cdc28p (Cdk1) specifically affects the periodically expressed proteins. 相似文献
4.
Enzymatic production of monoacylglycerols containing polyunsaturated fatty acids through an efficient glycerolysis system 总被引：7，自引：0，他引：7
The aim of the study was to develop an efficient glycerolysis system for the enzymatic production of monoacylglycerols (MAGs) containing polyunsaturated fatty acids. Glycerolysis has been widely applied in industry for the chemical production of food MAGs under high temperature. The enzymatic glycerolysis system at 40-70 degrees C is unfortunately a multiphase system, which leads to the lower reaction efficiency. A tert-butyl alcohol system was developed after careful evaluation and more than 20-fold of the reaction efficiency from this system was obtained compared to the solvent-free system. Novozym 435 was employed as a catalyst in the glycerolysis from the screening. In the batch reaction system with tert-butyl alcohol, temperature higher than 40 degrees C was favored. The glycerol/oil ratio was best in the study with 4.5 while the solvent weight ratio from 1 to 3 had little effect. In general, 60-70% yield can be obtained at 2 h in the stirred tank reactor. The continuous glycerolysis was conducted in a packed bed reactor. MAG yield up to 70% was reached at 30-40 min residence time. The continuous glycerolysis was more sensitive to the amount of tert-butyl alcohol, and in the weight ratio to oil more than 2 was favored. The continuous process was optimized with the assistance of response surface methodology. Optimal conditions for the packed bed reactor after all considerations were recommended as glycerol/oil 4:1 (mol/mol), temperature 40 degrees C, and residence time 45 min. The operation stability study showed that there was no slight reduction of reaction performance at more than 30 days, implying a high feasibility in practical applications. 相似文献
5.
The effect of trawling on fish size and on different quality parameters of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) was evaluated after conducting 16 valid hauls using two trawls in a double rig fitted with a traditional and a novel ‘T90’
codend, respectively. The total catch volume during the fishing period was 47.6 metric tons, with an average catch per codend
of 1.5 (range 0.5–2.9) tons. The mean haul duration was 5 h. The catch was assessed according to fish size, mortality, external
damage, initial white muscle pH and development of rigor mortis. Fillet quality (colour, blood spots, gaping) was assessed
after 1 week of freeze-storage. Our results showed there was no difference between the two types of nets in terms of catch
volume, but significantly slightly bigger fish were caught with T90 than with the traditional trawl net (p < 0.05). Haddock caught with the traditional trawl net had more external injuries related to the trawl gear than haddock
caught with the T90 gear (p < 0.05). The gaping frequency for cod caught with the traditional trawl net tended to be higher than cod caught with the
T90 gear, but the difference was not significant (p = 0.07). No other differences in fish quality between fish caught in the trawl nets were observed. 相似文献
6.
Brynjar Skulason Ole Kim Hansen Ulrik Braüner Nielsen 《Scandinavian Journal of Forest Research》2018,33(3):222-232
A field test with 26 provenances of subalpine fir and corkbark fir was established at three sites in Denmark and one site in Iceland in 1999. Survival, growth and Christmas tree quality were assessed after 10 growing seasons in Denmark and 12 in Iceland. Provenances showed significant differences for all measured traits. The western-most subalpine fir provenances from Washington state and British Columbia showed the overall best results in Denmark with the highest survival (after 15 years), fastest growth in height and highest Christmas tree quality and profitability as well as both good postharvest needle retention and high resistance to pests. The corkbark fir provenances also showed high Christmas tree quality and the lowest frequency of fork formation, but corkbark fir provenances also exhibited the poorest postharvest needle retention. In Iceland, the corkbark fir provenances generally showed the highest survival rate and Christmas tree quality. The White River provenance from British Columbia is recommended for use in Denmark. The Mount Taylor provenance from the Cibola National Forest in New Mexico is recommended for use in Iceland. 相似文献
7.
The efficiency of composting to remove the pollutants DEHP, PAHs and LAS from organic waste products was investigated. Source separated MSW and sewage sludge, respectively, were composted at temperatures ranging from 35 to 70°C using a laboratory-scale reactor composting system. At regular intervals, compost samples were taken from the reactors for chemical analysis. DEHP disappeared rapidly during composting of MSW; 96 to 99% of the initial content was degraded within 25 days of composting regardless of process temperature. In sewage sludge, the highest degradation of 91% was reached at a composting temperature of 65°C. LAS degradation in sewage sludge was fastest at 55°C, but at both process temperatures tested 99% of the initial content had been removed within 25 days. Degradation of PAHs was less complete. However, in all composting experiments, with MSW as well as sewage sludge, the final PAH concentration was less than in the starting material. Further experiments suggested that less than 0.1% of the pollutants had evaporated. Thus, composting proved to be a promising technique to promote degradation of organic pollutants — especially DEHP and LAS — in MSW and sewage sludge. 相似文献
8.
The effectiveness of bees as vectors for microbial biological control agents has been demonstrated in greenhouses and some small-acreage crops. Less is known about the viability of this tactic for other cropping systems, or the effects of outfitting hives with dispensers on the bees. Experiments conducted in lowbush blueberry (Vaccinium angustifolium) fields indicated that home-made wooden, Koppert, and Enviroquest dispensers had no significant effects on foraging behavior or pollen loads of the bumble bee Bombus impatiens, but the presence of a dispenser did reduce the rate of workers exiting hives. Following exit of bees from dispensers, no difference was found in the quantity of the microbial agent Clonostachys rosea applied to the bees or blossoms, and distribution of product in the field was not influenced by dispenser design or distance from hives. However, the prevalence of the pathogen Botrytis cinerea in blossoms from cages that contained hives with dispensers with C. rosea was significantly less (10–20 %) than blossom infection in control plots, despite unseasonably inclement conditions and restricted foraging. These results suggest that C. rosea can be effectively delivered by commercial bumble bees for prevention of B. cinerea infection in V. angustifolium, but the efficacy of the technique will be limited during periods of poor weather that often occur in regions where lowbush blueberries are grown. Some technical issues with dispensers and commercial B. impatiens hives also need to be addressed before widespread use can be expected within commercial lowbush blueberry production. 相似文献
9.
We studied the nutrient limitations of microbial respiration over time after the addition of glucose (G), glucose+nitrogen (G+N) or glucose+phosphorus (G+P) to a phosphorus-fixing tropical acrisol down to a depth of 80 cm, compared with those from compost. In the acrisol, the initial rate of respiration increase was higher when P was added together with glucose than when P was excluded. Without N, respiration reached a plateau faster and at a lower level than when N was added in excess. With glucose alone, the respiration kinetics followed the lower of the curves with G+N or G+P at any given time. Thus, nitrogen limited the maximum level of microbial respiration in the acrisol if ample carbon was available, but the initial respiration rate was limited by phosphorus. In contrast, for compost respiration was always lowest when N was not added. In conclusion, microbial respiration depended on the P-fixing properties of the soil, the time scale and the carbon availability. 相似文献
10.
A reconstruction of Cr emissions in Sweden is presented. Estimations of total flows for 1920 in 1980 were based on trade statistics, production of goods and life-length of products in society. A simple model was used to calculate amounts of Cr accumulated in soil and sediment at different times. The importance of production emissions from tanneries and ferrochrome and steel plants is obvious, but, in the future, diffuse emissions of the same magnitude may occur from Cr products within urban areas. 相似文献