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排序方式: 共有62条查询结果,搜索用时 15 毫秒
21.
Carolin Fischer Olav A. Høibø Geir I. Vestøl Marius Hauglin Endre H. Hansen Terje Gobakken 《Scandinavian Journal of Forest Research》2018,33(6):603-612
Norway spruce structural timber is one of the most important products of the Norwegian sawmilling industry, and a high grade-yield of structural timber is therefore important for the economic yield. Presorting of logs suited for production of structural timber might be one option to increase the grade yield. In this study, dynamic modulus of elasticity (Edyn) of structural timber was predicted based on forest inventory data at site level and single-tree data from airborne laser scanning (ALS) and harvester. The models were based on 611 boards from 4 sites in southeastern Norway. Important variables at site level were elevation, site index (SI), and mean stand age. However, when combining data from all information sources, mean stand age and site index were the only significant variables at site level. Tree height and variables describing the crown, like crown length and crown volume, were important vaiables extracted from ALS data. Stem diameter measures and tapering were important variables measured by the harvester. The combined model with variables from all three information sources reduced the variance the most, especially when using individual tree age instead of average stand age. However, combining all these data requires accurate positioning of the trees by the harvester. 相似文献
22.
V Marius J P Gillet R L'Hospitalier M Guittet G Bennejean 《Comparative immunology, microbiology and infectious diseases》1983,6(2):115-134
The immunity to infectious bronchitis afforded by spray vaccination of mycoplasma free two days-old broilers with maternal antibodies to infectious bronchitis virus was tested by comparing zootechnical scores, clinical signs, macroscopical and microscopical changes, frequency of infectious bronchitis virus isolation following challenge at one, three and five weeks of age in vaccinated, unvaccinated, challenged and unchallenged birds. This vaccination gave a very good protection to infectious bronchitis for the most part of broiler economical life; growth delays were especially avoided. However, vaccinated and unvaccinated one-week-old birds were not protected enough. No correlation was observed between haemagglutinating antibodies titres and protection. At last this vaccination caused a notable reaction in specific pathogen free control birds of the same age. 相似文献
23.
Physico-chemical data from 258 Quebec lakes were collected during spring and summer 1980. These data are examined in order obtain a first general diagnosis of lake acidification in Quebec. The spatial variation of the mineralization of lakes is interpreted in relation to lithology and glacial deposits, allowing the identification of Shield areas particularly threatened by acid precipitation. A strong south-west to north-east gradient in sulphate concentration is observed and interpreted as a result of long range atmospheric transport of S and as an indication of increased sulphate levels in southern Quebec lakes. The frequency distribution of pH values and the relation between pH and sulphate are examined; the results obtained suggest that many Shield lakes are probably affected by acid precipitation. A comparison is made between spring and summer conditions; data obtained in spring show a substantial decrease in pH and alkalinity. 相似文献
24.
Smit A Cordero Otero RR Lambrechts MG Pretorius IS Van Rensburg P 《Journal of agricultural and food chemistry》2003,51(17):4909-4915
Phenolic acids, which are generally esterified with tartaric acid, are natural constituents of grape must and wine and can be released as free acids (principally p-coumaric, caffeic, and ferulic acids) by certain cinnamoyl esterase activities during the wine-making process. Some of the microorganisms present in grape can metabolize the free phenolic acids into 4-vinyl and 4-ethyl derivatives. These volatile phenols contribute to the aroma of wine. The Saccharomyces cerevisiae phenyl acrylic acid decarboxylase gene (PAD1) is steadily transcribed, but its encoded product, Pad1p, shows low activity. In contrast, the phenolic acid decarboxylase (PADC) from Bacillus subtilis and the p-coumaric acid decarboxylase (PDC) from Lactobacillus plantarum display substrate-inducible decarboxylating activity in the presence of phenolic acids. In an attempt to develop wine yeasts with optimized decarboxylation activity on phenolic acids, the padc, pdc, and PAD1 genes were cloned under the control of S. cerevisiae's constitutive phosphoglyceratekinase I gene promoter (PGK1(P)()) and terminator (PGK1(T)()) sequences. These gene constructs were integrated into the URA3 locus of a laboratory strain of S. cerevisiae, Sigma1278b. The overexpression of the two bacterial genes, padc and pdc, in S. cerevisiae showed high enzyme activity. However, this was not the case for PAD1. The padc and pdc genes were also integrated into an industrial wine yeast strain, S. cerevisiae VIN13. As an additional control, both alleles of PAD1 were disrupted in the VIN13 strain. In microvinification trials, all of the laboratory and industrial yeast transformants carrying the padc and pdc gene constructs showed an increase in volatile phenol formation as compared to the untransformed host strains (Sigma1278b and VIN13). This study offers prospects for the development of wine yeast starter strains with optimized decarboxylation activity on phenolic acids and the improvement of wine aroma in the future. 相似文献
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Weihofen A Binns K Lemberg MK Ashman K Martoglio B 《Science (New York, N.Y.)》2002,296(5576):2215-2218
Signal peptide peptidase (SPP) catalyzes intramembrane proteolysis of some signal peptides after they have been cleaved from a preprotein. In humans, SPP activity is required to generate signal sequence-derived human lymphocyte antigen-E epitopes that are recognized by the immune system, and to process hepatitis C virus core protein. We have identified human SPP as a polytopic membrane protein with sequence motifs characteristic of the presenilin-type aspartic proteases. SPP and potential eukaryotic homologs may represent another family of aspartic proteases that promote intramembrane proteolysis to release biologically important peptides. 相似文献
27.
Precision Agriculture - Many farmers hesitate to adopt new management strategies with actual or perceived risks and uncertainties. Especially in ornamental plant production, farmers often stick to... 相似文献
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29.
为实现城市的可持续发展,一个非常适用、经济可行的新理念——分散式或半集中式水处理系统正受到越来越多的关注。德国Fraunhofer IGB承担了DEUS 21研究项目,并将半集中式理念在柯尼特林根进行了示范应用研究。污水处理系统的核心单元是厌氧膜生物反应器(AnMBR),运行结果表明,装置出水COD浓度相对较低,无颗粒物,几乎没有致病菌,并且营养元素氮和磷的浓度相对较高,可回用于农业生产或绿化。这种半集中式水处理模式非常适合那些气候温暖、需要灌溉用水并且还没有污水处理设施的地区,能够实现水、营养元素和能量的几乎闭合循环 相似文献
30.
Habitats modify the population ecology of species. Here, we show how low water level influences abundance and size of adult anadromous brown trout (Salmo trutta) entering a small, South Norwegian stream for spawning. After smolting, the fish appear chiefly to feed within 10 km of the home stream. In the autumn, South Norwegian streams typically flood because of heavy rainfall, when the anadromous brown trout entered from the sea. Mean annual duration of the upstream migration period was 34 days and ended when the flooding ended and the water temperature dropped to below 4°C. During most of the migration period, on average two trout ascended the river per day. The sexes entered the spawning area concurrently, and the male:female ratio of the anadromous trout was 1.27. No fish entered when the water depth just downstream of the spawning area was below 5 cm, and mean number of fish increased with increasing water depth to ca. 30 cm, but not at higher flows when the ascent gradually decreased. Mean and maximum size of the entering spawners increased with water depth between 5 and 16 cm. Among those that had been to sea, most were recaptured in the home stream, 4% in other streams, but only two of the strays were caught close to spawning time. The present results illustrate that population traits of anadromous brown trout from a small stream differ from those in larger rivers, probably because of selection associated with water flow. 相似文献