首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   22篇
  国内免费   1篇
  完全免费   4篇
  2018年   1篇
  2016年   1篇
  2015年   1篇
  2014年   2篇
  2013年   3篇
  2012年   3篇
  2011年   6篇
  2010年   1篇
  2009年   1篇
  2008年   2篇
  2006年   1篇
  2005年   2篇
  2004年   1篇
  2003年   1篇
  2002年   1篇
排序方式: 共有27条查询结果,搜索用时 109 毫秒
1.
Soft sensors for on-line biomass measurements   总被引:4,自引:0,他引:4  
One of the difficulties encountered in control and optimisation of bioprocesses is the lack of reliable on-line sensors for their key state variables. This paper investigates the suitability of using on-line recurrent neural networks to predict biomass concentrations. Input variables of the proposed recurrent neural network are feed rate, liquid volume and dissolved oxygen. Experimental results revealed that the proposed neural network is able to predict biomass concentrations with an accuracy of ±11%.  相似文献
2.
Effect of steam explosion on biodegradation of lignin in wheat straw   总被引:4,自引:1,他引:3  
The effect of steam explosion pretreatment on biodegradation of lignin in wheat straw was studied in this paper. Through experiments and analysis, 0.8MPa operation pressure and 1:20 wheat straw to water ratio are optimum for destroying lignin and the maximum of lignin loss rate is 19.94%. After steam explosion pretreatment, the wheat straw was retted by Trametes versicolor for 40 days. Biodegradation rate of lignin was tested and the maximum of 55.40% lignin loss rate was found on day 30. During the whole process of both steam explosion pretreatment and biodegradation, 75.34% lignin was degraded, without steam explosion the biodegradation of raw material the degradation rate of lignin was 31.23% only. FT-IR spectroscopy, TGA and SEM were used for further validating the results of biodegradation.  相似文献
3.
Microbacterium oxydans strain NJ 6 isolated from soil samples converted puerarin into two novel compounds, puerarin-7-O-glucoside and puerarin-7-O-isomaltoside, via an unreported O-glycosylation of the phenolic hydroxyl group at the 7-position of puerarin. Sucrose, maltotriose, and maltose could be used as glucosyl donors for glycosylation of puerarin, but uridine-diphosphate glucose, glucose, fructose, lactose, cyclodextrin, and starch could not. Regardless of the position of B-ring in the (iso)flavonoids core structure, the glycosylation of the phenolic hydroxyl group at the 7-position of (iso)flavonoids was governed by the presence or absence of a glucosyl residue at 8-C. The apparent solubility of puerarin-7-O-glucoside and puerarin-7-O-isomaltoside was approximately 18 and 100 times that of natural puerarin, respectively. Like parent puerarin, puerarin-7-O-glucoside maintained its physiological ability to relax the contractions of isolated rat thoracic aortic rings in vitro induced by phenylephrine. However, puerarin-7-O-glucoside was able to maintain higher plasma concentrations and have a longer mean residence time in the blood than the parent puerarin.  相似文献
4.
土地利用/覆被变化与景观服务:评估、制图与模拟   总被引:1,自引:0,他引:1  
从景观尺度上探讨生态系统服务功能的研究越来越引起国内外学者的重视.相比生态系统尺度,景观尺度是探索人类活动对土地利用/覆被变化影响、探究可持续景观演变机理和过程的最佳尺度.基于对当前国际学界对景观服务研究进展的系统梳理与分析,本文探讨了景观服务的内涵与分类,并对景观服务价值评估、制图与模拟等研究方法进行归纳与分析,并对景观服务的未来研究趋势进行展望.景观服务研究的未来方向应进一步明确景观服务的内涵及其分类体系,不断完善和发展景观服务评估、制图与模型模拟方法,重点开展景观格局-过程-服务-尺度长期综合研究,继续加强景观生态学及景观经济学等理论与方法在景观服务研究领域中的应用.  相似文献
5.
九种海滨沙生植物解剖构造及其生态适应性研究   总被引:1,自引:0,他引:1       下载免费PDF全文
利用常规石蜡制片法,对生长于北戴河海滨沙地的9种沙生植物的营养器官的形态结构进行比较观察。结果表明:(1)叶结构出现各种旱生和盐生植物特征,如一些植物叶的栅栏组织发达,海绵组织退化;多数植物的叶片较小;多数植物支脉和侧脉多等;(2)轴器官具有发达的表皮和机械组织,有异常结构的出现。说明北戴河海滨沙滩生长的9种植物的营养器官存在一系列的旱生结构特征,这些结构在减少蒸腾作用,增强光合作用,储存水分,增强器官的机械强度方面具有积极的作用。  相似文献
6.

Background  

Recently there has been an explosion of new data sources about genes, proteins, genetic variations, chemical compounds, diseases and drugs. Integration of these data sources and the identification of patterns that go across them is of critical interest. Initiatives such as Bio2RDF and LODD have tackled the problem of linking biological data and drug data respectively using RDF. Thus far, the inclusion of chemogenomic and systems chemical biology information that crosses the domains of chemistry and biology has been very limited  相似文献
7.
目的比较慢性难愈合创面细菌菌种及药物敏感性差异,以指导临床合理使用抗生素.方法选取1989~2003年间中山大学附属第一医院488例慢性难愈合创面住院患者中行创面分泌物细菌培养者100例作为研究对象,对创面细菌培养及药敏结果进行回顾性分析.结果(1)慢性难愈合创面最常见细菌为铜绿假单胞菌(30.1%)、金黄色葡萄球菌(15.0%)、大肠埃希菌(10.6%).(2)革兰阴性杆菌对亚胺培南的敏感率为92.7%,对头孢哌酮/舒巴坦为84.2%,阿米卡星为76.9%,环丙沙星为61.2%;革兰阳性杆菌对万古霉素、氯霉素和复方新诺明敏感率依次为94.7%、52.9%和80.0%.(3)慢性难愈合创面铜绿假单胞菌对亚胺培南、头孢他啶和替卡西林/克拉维酸的敏感率依次为95.7%、72.7%和70.0%;金黄色葡萄球菌对药物的敏感率分别为氯霉素100%、万古霉素90.9%、甲氧苄啶/磺胺甲噁唑90.0%.结论(1)慢性难愈合创面革兰阳性菌对万古霉素高度敏感,革兰阴性菌对亚胺培南高度敏感.(2)耐万古霉素菌株出现,合理用药意义重大.  相似文献
8.
One pathogenesis of the obesity-associated complications is that consistent with increased body fat mass, the elevation of adipose tissue-derived cytokines inflicts a low-grade chronic inflammation, which ultimately leads to metabolic disorders. Adipocytes and macrophages in visceral adipose (VA) have been confirmed to contribute to the chronic inflammation; however, the role of the resident fibroblasts is still unknown. We established one VA fibroblast cell line, termed VAFC. Morphological analysis indicated that there were large numbers of pits at the cell plasma membrane. In vitro VAFC cells promoted bone marrow cells to differentiate into macrophages and protected them from apoptosis in the serum-free conditions. Additionally, they also interfered in lymphocytes proliferation. On the basis of these results, this cell line might be an in vitro model for understanding the role of adipose-derived fibroblasts in obesity-associated chronic inflammation.  相似文献
9.
Biglycan is a Class I Small Leucine Rich Proteoglycans (SLRP) that is localized on human chromosome Xq28-ter. The conserved nature of its intron-exon structure and protein coding sequence compared to decorin (another Class I SLRP) indicates the two genes may have arisen from gene duplication. Biglycan contains two chondroitin sulfate glycosaminoglycan (GAG) chains attached near its NH2 terminus making it different from decorin that has only one GAG chain. To determine the functions of biglycan in vivo, transgenic mice were developed that were deficient in the production of the protein (knockout). These mice acquire diminished bone mass progressively with age. Double tetracycline-calcein labeling revealed that the biglycan deficient mice are defective in their capacity to form bone. Based on this observation, we tested the hypothesis that the osteoporosis-like phenotype is due to defects in cells critical to the process of bone formation. Our data shows that biglycan deficient mice have diminished capacity to produce marrow stromal cells, the bone cell precursors, and that this deficiency increases with age. The cells also have reduced response to tranforming growth factor- (TGF-), reduced collagen synthesis and relatively more apoptosis than cells from normal littermates. In addition, calvaria cells isolated from biglycan deficient mice have reduced expression of late differentiation markers such as bone sialoprotein and osteocalcin and diminished ability to accumulate calcium judged by alizerin red staining. We propose that any one of these defects in osteogenic cells alone, or in combination, could contribute to the osteoporosis observed in the biglycan knockout mice. Other data suggests there is a functional relationship between biglycan and bone morphogenic protein-2/4 (BMP 2/4) action in controlling skeletal cell differentiation. In order to test the hypothesis that functional compensation can occur between SLRPs, we created mice deficient in biglycan and decorin. Decorin deficient mice have normal bone mass while the double biglycan/decorin knockout mice have more severe osteopenia than the single biglycan indicating redundancy in SLRP function in bone tissue. To further determine whether compensation could occur between different classes of SLRPs, mice were generated that are deficient in both biglycan (class I) and fibromodulin, a class II SLRP highly expressed in mineralizing tissue. These doubly deficient mice had an impaired gait, ectopic calcification of tendons and premature osteoarthritis. Transmission electron microscopy analysis showed that like the decorin and biglycan knockouts, they have severely disturbed collagen fibril structures. Biomechanical analysis of the affected tendons showed they were weaker compared to control animals leading to the conclusion that instability of the joints could be the primary cause of all the skeletal defects observed in the fibromodulin/biglycan knockout mice. These studies present important new animal models for musculoskeletal diseases and provide the opportunity to characterize the network of signals that control tissue integrity and function through SLRP activity. Published in 2003.  相似文献
10.
Extracellular matrix glycoproteins and proteoglycans bind a variety of growth factors and cytokines thereby regulating matrix assembly as well as bone formation. However, little is known about the mechanisms by which extracellular matrix molecules modulate osteogenic stem cells and bone formation. Using mice deficient in two members of the small leucine-rich proteoglycans, biglycan and decorin, we uncovered a role for these two extracellular matrix proteoglycans in modulating bone formation from bone marrow stromal cells. Our studies showed that the absence of the critical transforming growth factor-beta (TGF-beta)-binding proteoglycans, biglycan and decorin, prevents TGF-beta from proper sequestration within the extracellular matrix. The excess TGF-beta directly binds to its receptors on bone marrow stromal cells and overactivates its signaling transduction pathway. Overall, the predominant effect of the increased TGF-beta signaling in bgn/dcn-deficient bone marrow stromal cells is a "switch in fate" from growth to apoptosis, leading to decreased numbers of osteoprogenitor cells and subsequently reduced bone formation. Thus, biglycan and decorin appear to be essential for maintaining an appropriate number of mature osteoblasts by modulating the proliferation and survival of bone marrow stromal cells. These findings underscore the importance of the micro-environment in controlling the fate of adult stem cells and reveal a novel cellular and molecular basis for the physiological and pathological control of bone mass.  相似文献
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号