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81.
Travis J. Herbranson Richard F. Deckro James W. Chrissis Jonathan Hamill 《European Journal of Operational Research》2013
Given a network, G = [N, E] the Isolation Set Problem (ISP) finds the set of arcs, D ⊆ E, that when removed will separate a predefined set of r distinguished nodes [2]. This involves eliminating connections from a specific set of nodes to the rest of a network. In our increasingly interconnected network-centric world, this might be isolating various units from Headquarters; isolating a portion of a computer network to disrupt communications or to quarantine a virus or some other form of cyber attack; or isolating a cell or sub-group in a terrorist or “dark” network, for example. 相似文献
82.
针对开关滤波器组中超导滤波器的应用,文中探讨了极低温微波单刀八掷开关的研制,制作了一种微波PIN管SP8T开关。开关在77K温度下的插损≤1.6dB,隔离度≥70dB,开关速度9ns。对低温对开关性能的影响进行了分析。 相似文献
83.
海地瓜蛋白水解物中ACE抑制肽的分离纯化及合成 总被引:2,自引:0,他引:2
采用Sephadex G-25凝胶柱层析、SP Sephadex C-25 阳离子交换层析和反相高效液相色谱等方法对海地瓜水解产物进行分离纯化, 得到了一种新的强活性ACE抑制肽, 其氨基酸序列为MEGAQEAQGD, IC50值为15.9 μmol/L. 采用逐步缩合和片段缩合的方法对该抑制肽进行了设计合成. 合成肽的纯度为99.72%, 分子量与序列结构均与理论值相符. 研究发现, 抑制肽与胃蛋白酶和糜蛋白酶水解反应后, 活性增强了3.5倍. 动物实验结果表明, 剂量为3 μmol/kg的抑制肽对大鼠自发性高血压具有明显的降压效果. 相似文献
84.
Ivan Mukhin Alexandr Voitovich Oleg Palashov Efim Khazanov 《Optics Communications》2009,282(10):1969-4797
A Faraday isolator with one magneto-optical element providing 31 dB isolation ratio for 330 W average power lasers was produced and investigated in an experiment. These remarkable parameters were achieved by increasing the magnetic field and using a [0 0 1] oriented TGG crystal. 相似文献
85.
Five novel metabolites, acremines H-N, have been isolated from malt extract-peptone-glucose agar cultures of a strain of Acremonium byssoides. Their structures and stereochemistry were elucidated using a combination of 13C and 1H homo and heteronuclear 2D NMR experiments. Acremines H-N inhibited the germination of sporangia of Plasmopara viticola. 相似文献
86.
Alternaria sp. ND-16, a bacterium isolated from soil sample, was identified as a strain of Alternaria mali based on the morphology and comparison of internal transcribed spacer rDNA gene sequence studies. Furthermore, it is demonstrated that this strain has xylanase activity, and the activity can be optimized
under suitable growing conditions where wheat bran and urea are the primary sources of carbon and nitrogen. Partially purified
xylanase from Alternaria sp. ND-16 is shown to have an optimal pH of 6.0 and optimal temperature of 50 °C, making this enzyme potentially suitable
for industrial applications. It is also demonstrated that Na+ and Mn2+ show strong inhibition of the xylanase while K+, Li+, Fe2+, Cu2+, and Zn2+ have no significant effect on the activity. 相似文献
87.
Rapid Screening and Isolation of a Fungus for Sitosterol to Androstenedione Biotransformation 总被引:1,自引:0,他引:1
Androstenedione (AD) is a steroid intermediate used in the pharmaceutical industry for the production of several important
anabolic drugs. An important route for producing AD is by the microbial transformation of sterols. Microbes capable of efficiently
transforming sterols to AD are few and newer strains need to be isolated. Conventional procedures for screening and isolation
are time consuming. A new procedure was used for screening and isolation of fungal microorganisms capable of biotransformation
of sitosterol to androstenedione. In this procedure, Basic Alignment Search Tool (BLAST) and Position-Specific Iterative BLAST
were employed to obtain a parent set of candidate microorganisms. The parent set was reduced using heuristics and constraints
to obtain a manageable number of microorganisms that may be tested experimentally. For this work, screening of the entire
NCBI database yielded a parent set containing 64 microorganisms. Among these, only two microorganisms, Aspergillus oryzae and Aspergillus nidulans FGSC A4, qualified to the experimental stage. Sitosterol biotransformation experiments were carried out using A. oryzae and the production of AD in culture medium was confirmed. 相似文献
88.
Devender Goud Arjun Cherevotan Raghu Maligal‐Ganesh Bitan Ray S. D. Ramarao Jithu Raj Sebastian C. Peter 《化学:亚洲杂志》2019,14(24):4819-4827
Intermetallic compounds (IMCs) composed of transition metals and post‐transition metals function as superior heterogeneous catalysts in comparison to their monometallic and bimetallic alloy counterparts. Rendering IMCs in their nanomaterial iterations further enhances their efficiency. Herein, we demonstrate the role of PdIn as well‐dispersed intermetallic nanoparticles (IMNPs) for the semihydrogenation of phenylacetylene selectively to styrene at ambient conditions. Higher selectivity of PdIn was explained with the help DOS calculations. We have explored the role of a few well‐known silica‐based supports such as SBA‐15 and MCM‐41, providing insight into how they affect catalysis. As an additional support we have explored previously reported JNC‐1, a mesoporous carbon material obtained via a templated strategy using SBA‐15. PdIn supported on SBA‐15 and JNC‐1 displayed the best dispersion, while also exhibiting the most catalytic activity due to the unique nature of the porous structure. 相似文献
89.
90.
白术多糖的分离纯化与结构表征 总被引:1,自引:0,他引:1
采用UV, IR, NMR, GC-MS, 高碘酸氧化和Smith降解等物理化学方法对从白术根茎提取的白术多糖的纯度、理化性质和结构进行了表征. 以中药白术的根茎为原料, 通过热水(80 ℃)浸提和乙醇醇沉得到粗多糖, 再经DEAE-52阴离子交换柱层析分离和Sephadex G-200凝胶柱层析纯化, 得到一种水溶性的白术多糖(WAM). 经高效液相色谱(HPLC)分析, 多糖WAM是分子量约为3263的均一多糖. GC分析表明, WAM是由葡萄糖和半乳糖以摩尔比3.01:1构成的杂多糖. 甲基化分析、高碘酸氧化、Smith降解、部分酸水解、NMR和IR等分析结果表明, WAM具有多分支结构, 主链由β-D-1→3和β-D-1→3,6吡喃葡萄糖构成, 每个重复单元具有一个支链, 支链由β-D-半乳糖构成, 连接在主链葡萄糖的6位碳原子上. 相似文献