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991.
Shan Zhao 《Information Sciences》2010,180(24):5115-5124
This paper deals with invertible matrices and semilinear spaces over commutative semirings. Some necessary and sufficient conditions for matrices to be invertible over commutative semirings are obtained. The condition under which the cardinality of each basis of semilinear space of n-dimensional vectors is n is given. In the end, the factor rank of matrices over semirings is investigated. 相似文献
992.
993.
Qi Hui Sam Hua Ling Wen Shan Yew Zhaohong Tan Sharada Ravikumar Matthew Wook Chang Louis Yi Ann Chai 《International journal of molecular sciences》2021,22(12)
Fatty acids are derived from diet and fermentative processes by the intestinal flora. Two to five carbon chain fatty acids, termed short chain fatty acids (SCFA) are increasingly recognized to play a role in intestinal homeostasis. However, the characteristics of slightly longer 6 to 10 carbon, medium chain fatty acids (MCFA), derived primarily from diet, are less understood. Here, we demonstrated that SCFA and MCFA have divergent immunomodulatory propensities. SCFA down-attenuated host pro-inflammatory IL-1β, IL-6, and TNFα response predominantly through the TLR4 pathway, whereas MCFA augmented inflammation through TLR2. Butyric (C4) and decanoic (C10) acid displayed most potent modulatory effects within the SCFA and MCFA, respectively. Reduction in TRAF3, IRF3 and TRAF6 expression were observed with butyric acid. Decanoic acid induced up-regulation of GPR84 and PPARγ and altered HIF-1α/HIF-2α ratio. These variant immune characteristics of the fatty acids which differ by just several carbon atoms may be attributable to their origins, with SCFA being primarily endogenous and playing a physiological role, and MCFA exogenously from the diet. 相似文献
994.
INTRODUCTIONTo accommodate the requirement of lightweight,for many machine systems, such as flexiblemanipulator, large solar array and flexible antennas ofspacecraft, flexibility has become an imPOrtantcharacteristic. But flexible vibration can degrade badlythe peforance and the precision of flexible systems.Control of vibration becomes very important asdesigners attempt to push the state of the art withfaster and lighter machines systems. Researchers haveexammed many different controlle… 相似文献
995.
AlCl3/TiCl4催化癸烯聚合制润滑油基础油的研究 总被引:1,自引:0,他引:1
以AlCl3/TiCl4为催化剂对癸烯聚合制润滑油基础油进行了研究。考察了催化剂用量、Al与Ti摩尔比、反应时间和反应温度等工艺条件对合成油性质的影响,并比较了不同催化剂、不同烯烃原料对聚α-烯烃(PAO)性质的影响。结果表明,癸烯聚合制备PAO,AlCl3/TiCl4是较适宜的催化剂。PAO收率随着AlCl3/TiCl4催化剂用量的增大、反应温度的升高以及反应时间的延长而提高,但随着Al与Ti摩尔比的增加而迅速下降;粘度指数在所考察的条件范围内均较高;100 ℃下的运动粘度随着Al与Ti摩尔比的变化而急剧变化,因此可以根据需求,通过调节Al与Ti摩尔比,可制备各种粘度等级的PAO产品。 相似文献
996.
997.
Cyanex 92 3 ,amixtureofstraightchainalkylphosphineoxide ,isonecommercialex tractantdevelopedbyCytecCanadaInc ..ComparedwithTOPO ,ithasseveraladvan tagessuchaslittleliablehydrolyzation ,lowsolubilityinaqueousphaseandlowextractionacidity .Moreover,thegreatestadv… 相似文献
998.
In this paper, the results from 3D numerical simulations of circular synthetic jets issued into a zero-pressure-gradient laminar boundary layer developing along a flat plate are reported. The simulations are undertaken using FLUENT at a wide range of actuator operating conditions. The formation and development of the coherent structures produced as a result of the interaction between the synthetic jets and the boundary layer were examined using the Q-criterion. Non-dimensional parameter space maps were established to illustrate the variations in the appearance of these resultant structures and their shear stress footprints upon the changes in the operating conditions of synthetic jets. Finally, the parameter boundary separating the two distinct types of vortical structures and surface shear stress patterns is identified. It is found that the location of this boundary correlates closely with the jet-to-freestream velocity ratio of VR = 0.4 when the Strouhal number (Str) is less than 1, whereas for Str > 1 the boundary deviates from this trend, approaching the line of dimensionless stroke length of L = 1.6. In order to investigate the potential impact of the synthetic jets on the boundary layer, the increase in the space- and time-averaged skin friction coefficient relative to the baseline case without the synthetic jets is calculated. It appears that in order to maximise the impact on the near-wall flow while keeping the energy expenditure down, it is wise to maximise the accumulated effect of hairpin vortices by keeping the spacing between consecutive hairpin vortices similar to the local boundary layer thickness upstream of the separated flow instead of producing stronger individual structures. 相似文献
999.
利用溶胶凝胶法在850℃合成了硅酸盐氧摹磷灰石CaxLa9.67-2x/3(SiO4)6O2.5(x=0,0.25,0.50,0.75和1.00).经X射线衍射、红外光谱和扫描电镜等表征所得样品为磷灰石相.以电化学阻抗谱研究了CaxLaq.67-2x/3(SiO4)6O2.5的导电性能,发现阳离了空位越多,体系的电导率越大,活化能却越小.700℃时,La9.67(SiO4)6O2.5的电导率为2.09×10-3 S/cm,是CaLa9(SiO4)6O2.5的3倍.离子迁移数和氧分压对电导率的研究表明:主要的电荷载体是O2-. 相似文献
1000.
Jiu‐Hong Li Yi‐Xin Guan Hai‐Qing Wang Shan‐Jing Yao 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(2):208-214
BACKGROUND: Arthrobacter simplex cells immobilised in sodium cellulose sulfate/poly‐dimethyl‐diallyl‐ammonium chloride microcapsules were used for the microbial dehydrogenation of 11α‐hydroxy‐16α,17‐epoxyprogesterone to 11α‐hydroxy‐16α,17α‐epoxypregn‐1,4‐diene‐3,20‐dione in an aqueous/organic solvent two‐liquid‐phase system, which is a key reaction in the production of glucocorticoid pharmaceuticals. The aim of the study was to establish a suitable aqueous/organic solvent two‐liquid‐phase system for performing semi‐continuous production in an airlift loop reactor by encapsulated A. simplex cells with the addition of suitable surfactants to achieve a higher yield of the product. RESULTS: n‐Hexane was selected as the most suitable organic solvent. In optimised Tween‐80 emulsion feed mode the conversion in the airlift loop reactor was as high as 97.54% when the time of reaction was 2 h, and the reaction time was greatly shortened. In semi‐continuous production the cultivation with immobilised cells was carried out for five batches in total. The conversion in each batch was above 95% and the enzymatic activity still remained quite high after five batches of biotransformation. CONCLUSION: The results showed that performing the conversion by this method shortened the reaction time and increased the productivity, thus demonstrating the great potential of the method for the dehydrogenation of 11α‐hydroxy‐16α,17‐epoxyprogesterone. Copyright © 2008 Society of Chemical Industry 相似文献