超临界CO_2流体处理工艺对木材渗透性的影响     

肖忠平  陆继圣 《福建林业科技》2009,36(3)

以苯—乙醇为夹带剂,研究超临界CO2流体不同处理压力、温度、时间对福建产杉木、马尾松、檫木木材渗透性的影响。结果表明,在35 MPa内,处理压力的增大有利于3种木材渗透性的提高;杉木在处理温度为40℃时,渗透性的变化率达到最大,为493%,马尾松和檫木在处理温度为45℃时,渗透性的变化率达到最大,分别为479%和349%;较佳的处理时间为30 min。  相似文献   

Permeability of the endothelium and partitioning of the pulmonary blood flow resistance in isolated perfused pig lungs: Effects of breed and age     

P. Gustin  B. Urbain  A. Delaunois  K. Zeimes  M. Ansay 《Veterinary research communications》1992,16(1):69-82

The right and left lungs of 5 healthy Minipigs and of 13 healthy Landrace piglets were isolated, perfused at constant pressure and maintained in an isogravimetric state under zone III conditions (pulmonary venous pressure>alveolar pressure). By applying the double, arterial and venous, occlusion technique, the total blood flow resistance (R _t) was partitioned into four components: arterial (R _a), pre-(R _a) and post-capillary (R _v) and venous (R _v). The capillary filtration coefficient (K _f,c) was evaluated by measuring the weight gained by the lungs when the arterial and venous pressures were suddenly increased. In the youngest Landrace piglets (5 weeks old), there was an uncontrolled vasoconstriction which sometimes prevented perfusion of the lungs and induced a large increase inR _t. These high values ofR _t were decreased by tolazoline administration. The values ofR _t recorded in older pigs (12–13 weeks old) were lower in Minipigs (33.66±3.77 cmH₂O min L^–1 per 100 g of lungs;n=5) than in Landrace piglets (55.20±6.18 cmH₂O min L^–1 per 100 g;n=5). This breed difference was due to the differences inR _a andR _v. The mean values ofK _f,c were 0.193±0.015 and 0.202±0.029 ml min (cmH₂O)^–1 per 100 g of the lungs in Minipigs and Landrace piglets respectively. All these parameters were stable for the 3 hours following the equilibrium period. It was concluded that: (1) There is an age-related maturation of the control of the vasomotor tone in porcine lungs. (2) Pulmonary microvascular haemodynamics are influenced by the breed of the pigs. (3) There was no difference in theK _f,c values between both the breeds. (4) A comparison of the values reported for dogs and rabbits with our data shows that the pre- and post-capillary resistances and, to a lesser extent, the arterial and venous resistances are relatively high in pigs.  相似文献   

The basic mechanism of increased microvascular permeability     

ZHAO Ke-sen  HUANG Qiao-bing 《园艺学报》2003,19(4):549-553

The increased microvascular permeability appears mainly in venule during inflammation, shock, and burns. Endothelial cells play an important role in venule permeability enhancement. There are two kinds of pathway for macromolecule extravasation. One is paracellular pathway and another is transcellular pathway, which are related to the formation of endothelial gap or transcellular openings seperately. The alteration of intercellular related protein, such as occludin, claudin, zona occludens (ZO), junctional adhesion molecule (JAM), VE cadherin, catenin, integrin, etc, and the alteration of endothelial cytoskeleton, such as rearrangement of actin filament, formation of stress fiber and focal adhesion, etc, involve in the pathogenesis of increased microvascular permeability.  相似文献   

Mechanism of exogenous nitric oxide in attenuating endotoxin-induced increase of rat pulmonary microvascular permeability     

LIU Yan-mei  WANG Dian-hua  LING Yi-ling  ZHANG Jun-lan 《园艺学报》2002,18(4):385-388

AIM and METHODS:The animal model of acute lung injury (ALI) caused by intratracheal instillation of lipopolysaccharides(LPS) in vivo and human peripheral blood polymorphonuclear neutrophil (PMN) in vitro were used to study the effects of sodium nitroprusside (SNP), nitric oxide (NO) donor, on LPS-induced PMN accumulation, microvascular permeability and PMN apoptosis. RESULTS:①In vivo, PMN accumulation in lung, the protein content in bronchoalveolar lavage fluid (BALF) and the Evans blue dye and monastral blue dye extravasation in lung tissue of LPS group were markedly higher than those of both sham operation group and LPS+SNP group. ②In vitro, the apoptotic percentage of SNP group was much higher than that of control group, while compared with LPS group, SNP+LPS group has significantly higher apoptotic percentage. CONCLUSIONS:SNP intratracheal instillation attenuated LPS-induced microvascular permeability and alleviated ALI. PMN apoptosis induced by SNP may be one of the potential mechanisms underlying the decrease of PMN accumulation in lung tissue.  相似文献   

Angiopoietin-1 and regulation of vascular permeability     

YUE Fei  JIN Hui-ming 《园艺学报》2004,20(10):1929-1932

Angiopoietin-1 (Ang-1) is a newly-found endothelium-specific proangiogenic factor and it had been proved essential roles in both vasculogenesis and angiogensis. Among them, its anti-leakage ability may have great potential applications in clinical treatment of vascular hyper-permeability in a variety of diseases such as cancer, diabetic retinopathy, rheumatoid arthritis, asthma. In this review, some research progresses focused on this aspect are discussed.  相似文献   

某高铁隧道小口径井抽水试验探讨     

谭茂兰  武兴龙  肖纲通  覃明彩  辛武 《绿色科技》2020,(6):209-211

指出了在某高铁隧道勘察中采用小口径抽水试验方法,具有操作简单便捷,成本低的优势。通过小口径井抽水试验查明场地的水文地质条件,得出了水文地质原始数据资料,根据单孔稳定流承压水非完整井的水文地质实际情况,选取合适的公式分别计算出了隧道岩层渗透系数及影响半径,为高铁隧道的勘察设计及顺利施工提供参考。  相似文献   

应用压力早期恢复资料确定低渗地层压力   总被引：3，自引：0，他引：3  

魏芳 《长江大学学报》2007,4(3):42-43,52

低渗透油藏的压力恢复曲线,不能用Horner外推压力求取地层压力。基于Horner方程的等轴双曲线形式,提出了应用压力早期恢复资料确定低渗地层压力的新方法。通过油井实际资料计算验证,用该方法计算的地层压力准确可靠,较好地解决了低渗透油藏求地层压力的问题。  相似文献   

Deformation of deep foundation pits due to excavation and dewatering considering the change of void ratio and permeability coefficient with current stress of soil     

Shao Yu  Jiang Jie  Ma Shaokun  Lyu Hai-bo  He Jianxing  Chen Junyu 《保鲜与加工》2015,(2):92-100

基于修正剑桥模型理论,推导了孔隙比e随土体当前应力变化的方程,同时比选了4组经典的描述渗透系数k随孔隙比变化的方程,选择了其中一组最佳的估算公式,编写ABAQUS用户子程序VOIDRI和USDFLD,以实现孔隙比和渗透系数随土体当前应力的变化。在此基础上,研究深基坑降水开挖所致的坑内外土体的变形、围护结构的变形及弯矩,得到以下结论：当考虑孔隙比随土体当前应力变化时,坑外地表沉降量、墙体的水平位移、地下连续墙的弯矩、坑底隆起量均大于孔隙比为定值时的情况;当考虑渗透系数随土体当前应力变化时,坑外地表沉降量、墙体的水平位移、地下连续墙的弯矩均小于渗透系数为定值时的情况,但同时考虑渗透系数和孔隙比变化情况时,其对坑底的隆起量的影响可以忽略不计。  相似文献   

Mathematical Model of Methane Transport in Coal Seam     

Zhang Guangyang  Tan Xueshu  Xian Xuefu  Du Yungui 《保鲜与加工》1994,(4):53-57

This paper studies the effects of ground stress and ground electrical field onmethane transpont in coal seam. A gas seepage equation is set up based on the principles of seepagetheory,which takes the ground stress and ground electrical field into considerationz  相似文献   

不同降解阶段填埋垃圾体的气体渗透特性研究   总被引：3，自引：0，他引：3  

彭绪亚  余毅  刘国涛 《中国沼气》2003,21(1):8-11

通过对不同降解阶段填埋垃圾体渗透系数的测定，研究了在不同压实密度、不同含水率条件下垃圾体渗透特性的变化情况，实验表明：1.对不同降解阶段的填埋垃圾体，新鲜垃圾及混和垃圾的渗透系数接近，腐熟垃圾明显高于前两者；随压实密度增加，其气体渗透系数均呈指数规律递减；2.随着垃圾体含水率的增加，腐熟与新鲜垃圾的渗透系数均呈线性规律递减，含水率对渗透系数的影响要远小于压实密度的影响；3.新垃圾、混合垃圾、腐熟垃圾均具有较显著的各向异性特征，在典型压实密度下，水平方向的气体渗透系数Kh为垂直方向渗透系数Kv的3.5-27.3倍。  相似文献