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Philipp Schlotzhauer Alexander Ehrmann Susanne Bollmus Holger Militz 《Wood material science & engineering》2020,15(5):278-288
ABSTRACT Knowledge about perpendicular to grain tension behavior of wood is essential, since in construction tension stresses perpendicular to grain cannot be avoided completely. Especially for hardwoods, the data basis is scarce. EN 338 design values are with 0.6 N/mm² characteristic strength set very low. The US-American National Design Specifications even set this value to zero and make local reinforcements mandatory. This paper compares strength and stiffness values attained with newly-designed, little, prismatic specimens and EN 408 structural timber specimens to evaluate the current European design values. Little specimen’s characteristic strength values range from 7.2 to 10.6?N/mm² and are assumed to be real material properties. EN 408 specimen values are with approximately 4.0?N/mm² lower. These lower values are mainly due to stress peaks introduced by the force introduction. Strength values attained for the medium-dense European hardwoods beech, ash and maple exceed EN 338 design values by a factor of six to seven. Adaptation of the EN 338 design value is not recommended, though. The abundance of influencing factors makes clear that the design value and the ensuing design code have to be synchronized carefully by tedious testing in order to make use of the perpendicular to grain tension strength potential of the selected hardwoods. 相似文献
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Marco Antonio López-Torres & Marcial Leonardo Lizárraga-Partida 《Aquaculture Research》2007,38(7):671-680
The impact of shrimp larvae development, as well as water and food inputs upon the increase of bacterial populations within the bacterial community of hatchery tank biofilms, was studied. For this study, a total of 68 biofilm samples were collected from concrete tanks at three larvae production times in a commercial shrimp hatchery. Seventeen samples were taken at each larval development stage (Zoea I, Mysis I, postlarvae 1 and postlarvae 16), as well as 37 samples from water, shrimp nauplii and food, introduced into the shrimp hatchery tanks. Culturable and direct bacterial counts were performed and 16S‐rRNA‐targeted oligonucleotide probes were used to quantify the presence of specific bacterial groups. An average of 27–70% of DAPI total cell counts were detected with the EUB338 probe, while the GAM42a probe signal ranged from 1% to 11%. Vibrio‐like bacteria (VLB) counts in TCBS agar ranged from <10 to 101 VLB/cm−2, with a tendency to increase at the last postlarvae stage. The most significant external source of bacteria registered with GAM42a probe and TCBS agar were found in live Artemia nauplii, used as food; nevertheless, biofilms remain with low counts of these groups. 相似文献
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[目的]探讨EUB338探针对真菌的检测灵敏度。[方法]以16株常见真菌为材料,使用荧光原位杂交法进行分析。[结果]EUB338探针检测灵敏度的平均值为63.9%,改良方法可将检测灵敏度平均值提高到71.3%。[结论]该研究可为从分子生物学角度检测土壤真菌提供科学依据。 相似文献
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Rohana P. Dassanayake Thomas C. Truscott Dongyue Zhuang David A. Schneider Sally A. Madsen-Bouterse Alan J. Young James B. Stanton William C. Davis Katherine I. O'Rourke 《Journal of veterinary science (Suw?n-si, Korea)》2015,16(2):179-186
Scrapie is diagnosed antemortem in sheep by detecting misfolded isoforms of prion protein (PrPSc) in lymphoid follicles of the rectal mucosa and nictitating membranes. Assay sensitivity is limited if (a) the biopsy is collected early during disease development, (b) an insufficient number of follicles is collected, or (c) peripheral accumulation of PrPSc is reduced or delayed. A blood test would be convenient for mass live animal scrapie testing. Currently approved techniques, however, have their own detection limits. Novel detection methods may soon offer a non-animal-based, rapid platform with detection sensitivities that rival the prion bioassay. In anticipation, we sought to determine if diseased animals could be routinely identified with a bioassay using B lymphocytes isolated from blood sample volumes commonly collected for diagnostic purposes in small ruminants. Scrapie transmission was detected in five of six recipient lambs intravenously transfused with B lymphocytes isolated from 5~10 mL of blood from a naturally scrapie-infected sheep. Additionally, scrapie transmission was observed in 18 ovinized transgenic Tg338 mice intracerebrally inoculated with B lymphocytes isolated from 5~10 mL of blood from two naturally scrapie-infected sheep. Based on our findings, we anticipate that these blood sample volumes should be of diagnostic value. 相似文献
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An extract prepared from the culture of a marine-derived actinomycete Streptomyces sp. ZZ338 was found to have significant antimicrobial and antiproliferative activities. A chemical investigation of this active extract resulted in the isolation of three known bioactive actinomycins (1–3) and two new metabolites (4 and 5). The structures of the isolated compounds were identified as actinomycins D (1), V (2), X0β (3), 2-acetylamino-3-hydroxyl-4-methyl-benzoic acid methyl ester (4), and N-1S-(4-methylaminophenylmethyl)-2-oxo-propyl acetamide (5) based on their nuclear magnetic resonance (NMR) and high resolution electrospray ionization mass spectroscopy (HRESIMS) data as well as their optical rotation. This class of new compound 5 had never before been found from a natural resource. Three known actinomycins showed activities in inhibiting the proliferation of glioma cells and the growth of methicillin-resistant Staphylococcus aureus, Escherichia coli, and Candida albicans and are responsible for the activity of the crude extract. Actinomycin D (1) was also found to downregulate several glioma metabolic enzymes of glycolysis, glutaminolysis, and lipogenesis, suggesting that targeting multiple tumor metabolic regulators might be a new anti-glioma mechanism of actinomycin D. This is the first report of such a possible mechanism for the class of actinomycins. 相似文献
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为明确不同施氮量对“鲁棉338”生长发育及产量的影响,确定“鲁棉338”最佳施氮量,解决“鲁棉338”种植中氮肥投入量不合理等问题。研究以“鲁棉338”为试验材料,采用单因素随机区组试验设计,设置0kg/hm2、100kg/hm2、200kg/hm2、300kg/hm2和400kg/hm25个施氮(纯氮)水平处理,分别用N0、N100、N200、N300和N400表示,研究不同施氮水平对“鲁棉338”株高、叶片SPAD值和产量的影响。结果表明,随着棉花生育进程的推进,不同施氮处理下的株高呈现逐渐上升的趋势,施氮处理下的棉花功能叶片SPAD值显著高于不施氮处理,同时施氮还能减缓功能叶片SPAD值的下降,保障作物营养物质的转运与利用。施氮量能显著影响棉花单株铃数、单铃重、籽棉产量、皮棉产量和衣分(p＜0.05),N300和N400处理下的棉花单株铃数、籽棉产量和皮棉产量间无显著性差异,在“鲁棉338”种植生产中,施氮量控制在300kg/hm2最为适宜。 相似文献
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王晓丹 《（《农业科学与技术》）编辑部》2011,(10)
[目的]探讨EUB338探针对真菌的检测灵敏度。[方法]以16株常见真菌为材料,使用荧光原位杂交法进行了分析。[结果]EUB338探针检测灵敏度的平均值为63.9%,改良方法可将检测灵敏度平均值提高到71.3%。[结论]该研究可为从分子生物学角度检测土壤真细菌提供科学依据。 相似文献
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