Why Are Mares with Pneumovagina Susceptible to Bacterial Endometritis? A Personal Opinion     

John R. Newcombe BVet Med  MRCVS   《Journal of Equine Veterinary Science》2011,31(4):174-179

Pneumovagina is the abnormal presence of air in the vagina, which may lead to pneumometra and endometritis. Predisposing factors are abnormal perineal conformation and weakness of the vestibulovaginal sphincter. This report examines why ponies and some other breeds are less susceptible to pneumovagina than Thoroughbreds and consequently less susceptible to endometritis. Observations on vaginal ballooning during vaginoscopic examination led to the conclusion that there is a fundamental difference in intra-abdominal pressures between horses and ponies, and between mares with high or low body condition scores. This difference in the extreme cases, for example, a small fat pony versus a large thin Thoroughbred, means that the pressure gradient in the former is from the uterus through the vagina to the exterior, whereas the case is reversed in the latter. Although the uterus is at a negative pressure relative to the exterior, evacuation of fluids is seriously disadvantaged, leading to an inability to resolve uterine infections.  相似文献   

Associations Between Oil and Gas Wells and Arthropod and Vegetation Communities in the Southern Plains     

Cameron A. Duquette  Craig A. Davis  Samuel D. Fuhlendorf  R. Dwayne Elmore 《Strength and Conditioning Journal》2019,72(5):749-756

Understanding how energy infrastructure affects local biodiversity and soil characteristics is important for informing restoration and management. However, the rapid rate of modern oil and gas development is beyond the limit of current knowledge and mitigation strategies. In a mixed-grass prairie in western Oklahoma, we assessed the presence and directionality of biodiversity and environmental gradients associated with energy development in an observational framework. Specifically, we sampled arthropods, vegetation, soil temperature, and soil moisture on the edge of active oil well pads and at 1 m, 10 m, and 100 m away from the well pad. Though variable, the abundance and biomass of most arthropod orders was lower on the pad and 1 m away compared with 10 m and 100 m away, suggesting that the pad itself negatively influenced arthropods but that these effects were limited in spatial extent. However, vegetation structure and composition varied more extensively. Vegetation height, shrub cover, and warm season grass cover increased sixfold, threefold, and fourfold, respectively, from on the oil pad to 100 m away. Forb cover was 5 × higher at 10 m from the well pad than on the pad, 1 m away, and 100 m away from the pad. Soil surface temperature was lower at sites farther from well pads, but we found no relationship between soil moisture and distance from well pad. Well pad effects on arthropods and soil temperature appear to be limited to the pad itself, though long-term changes in vegetation structure extend significantly beyond the well footprint and demand a better understanding of the effectiveness of restoration activities around well pads.  相似文献   

The use of gradient analysis studies in advancing our understanding of the ecology of urbanizing landscapes: current status and future directions   总被引：5，自引：3，他引：2  

Mark J. McDonnell  Amy K. Hahs 《Landscape Ecology》2008,23(10):1143-1155

Over the past decade, the urban–rural gradient approach has been effectively used to study the ecology of cities and towns around the world. These studies have focused on understanding the distribution of plants and animals as well as ecosystem processes along gradients of urbanization that run from densely urbanized inner city to more rural exurban environments. We reviewed 300 papers investigating urbanization gradients that were published in peer-reviewed journals between 1990 and May 2007. Sixty-three percent of the papers investigated the distribution of organisms along urbanization gradients. Only five papers addressed the measures used to quantify the urbanization gradient itself. Within the papers addressing the distribution of organisms, 49% investigated the responses of birds to urbanization gradients, and <10% of the papers investigated more cryptic organisms. Most of these studies utilized a variety of broad measures of urbanization, but future advances in the field will require the development of some standardized broad measures to facilitate comparisons between cities. More specific measures of urbanization can be used to gain a mechanistic understanding of species and ecosystem responses to urbanization gradients. While the gradient approach has made a significant contribution to our understanding of the ecology of cities and towns, there is now a need to address our current knowledge gaps so that the field can reach its full potential. We present two examples of research questions that demonstrate how we can enhance our understanding of urbanization gradients, and the ecological knowledge that we can obtain from them.  相似文献   

不同海拔野生金露梅叶的主要成分分析   总被引：1，自引：1，他引：1  

白东亚 《陕西林业科技》2007,(2):1-5,41

金露梅灌木林是青海最大的灌木林区之一。目前对金露梅叶片的研究仅限于解剖结构、灌丛地上部分生物量和黄酮类物质的研究,对青海野生金露梅叶成分整体研究较少。2005年7月在海拔2 840m和2 510 m处采野生金露梅叶作为样品进行成分分析,结果表明:样品在海拔2 840 m处黄酮的含量高于样品在海拔2 510 m处的含量,单宁的含量相当;样品在海拔2 840 m处还原糖的含量高于样品在海拔2 510 m处的含量,粗蛋白的含量低于样品2 510 m处的含量。  相似文献   

Effects of opening size and stand characteristics on light transmittance and temperature under young trembling aspen stands   总被引：2，自引：0，他引：2  

Janet M. Pritchard  Philip G. Comeau   《Forest Ecology and Management》2004,200(1-3):119-128

While aspen (Populus tremuloides Michx.) cover provides protection from growing season radiative frosts, reduced light levels can limit growth of understory white spruce (Picea glauca (Moench) Voss). The creation of openings around individual spruce can provide more light, but the chance of radiative frost damage increases as gaps become larger. We examined the relationship between opening size and light and temperature levels in the center of circular gaps created in young aspen stands ranging from 1.8 to 8 m tall. Models for predicting transmittance as a function of sky view factor and transmittance under intact stands are presented. Results indicated a strong relationship between light levels and opening size after considering pre-treatment light levels. The relationship between opening size and temperature was weak with minimum temperatures being more affected by the height and density of the surrounding stand than opening size.  相似文献   

A New Heuristic Evolutionary Programming and Its Application in Solution of the Optimal Power Flow     

Shi Libao Hua Zhiming Xu Guoyu 《保鲜与加工》1997,(6):67-72

A new algorithm,based on the combination of the evolutionary programming with the traditional gradient adjustment technique,is presented for solving the optimal power flow problem which describes some technical problems(representations of candidate solutions,evaluation function,mutation operator).Its efficiency is higher than that of general evolutionary programming.  相似文献   

水分梯度对三江平原典型湿地植物小叶章地上生物量的影响   总被引：12，自引：8，他引：4  

王丽  胡金明  宋长春  杨涛 《草业学报》2008,17(4)

通过野外调查,研究不同水分梯度下三江平原典型湿地植物小叶章个体地上生物量季节动态、干鲜比(DW/FW)及生物量在构件中的分配特征.结果表明,小叶章个体地上生物量在小叶章群落中最大;各水分带小叶章地上生物量的时间动态呈双峰型变化特征,峰值出现时间随积水深度的增加而提前.生长季内,DW/FW随水分的增加而具有波动性,小叶章群落变化最大;灌丛一小叶章群落总体较低;常年积水的3个群落,不同生长期波动变化.小叶章地上生物量分配比:茎>叶>鞘;茎生物量比重,无常年积水群落大于常年积水群落;叶和鞘的生物量比重与茎相反.而水分梯度的直接作用以及各水分梯度下土壤环境条件是不同水分梯度带小叶章生长分异的主要原因.  相似文献   

卧龙自然保护区油竹子（Fargesia angustissima）生理生态特征的海拔变化     

潘红丽  田雨  刘兴良  蔡小虎  何飞  李迈和 《四川林业科技》2011,32(1):25-30

全球气候变化（如温度升高）迅速而强劲地影响着高海拔地区的生态环境,致使植物生长发生变化,因此高山地区成为研究植物环境适应性及其对全球气候变化响应的理想区域。为了认清气候变化如何影响竹子的生长和生理生态特性,本文系统调查研究了卧龙自然保护区内大熊猫典型主食竹种油竹子（Fargesia angustissima（Mitford）T.P.Yi）,从其天然分布下限至上限,在卧龙自然保护区沿海拔梯度研究了分株的比叶面积（SpecificLeaf Area,SLA）、基于单位叶面积和单位叶质量的叶氮含量（Narea,Nmass）,以及组织非结构性碳水化合物（NSC）含量及其组分。研究结果表明,各调查因子对海拔的响应均是非线性的,表现为随着海拔升高,各调查值先降后升,高峰值出现在分布上限区域（1 810 m）,而最低值出现在中海拔区域（1 620 m）,反映了环境因子随海拔的非线性变化。分析认为,油竹子的生长受不同海拔环境影响较大。  相似文献   

中密度纤维板微波预热后板坯内水分和温度的分布     

余妙春  饶久平  谢拥群 《东北林业大学学报》2011,39(6):47-48,64

研究了微波预热对中密度纤维板板坯中水分和温度分布规律的影响.结果表明:微波预热处理使板坯形成表层含水率高,芯层含水率低的含水率梯度,减小预压高度、增加微波预热时间、适当调高板坯初含水率有利于在板坯中形成表层含水率略高于芯层的含水率梯度;微波预热处理使板坯形成芯层温度高,表层温度低的温度梯度,形成了驱动内部水分向表层渗透...  相似文献   

闽东引种巨柏育苗试验初报   总被引：3，自引：1，他引：2  

李乾振  李朝晖 《林业科学》2003,(Z1)

巨柏 (Cupressusgigantea)系柏科柏木属高大常绿乔木 ,为西藏特有树种 ,是我国重点保护的珍稀树种。该树种具有树冠挺拔苍翠 ,树干圆满通直 ,单位面积生物产量高 ,单株材积大 ,材质优良 ,结构细密 ,纹理美观 ,芳香持久 ,耐腐防蛀等特点 ,树龄在 2 0 0 0a以上尚无空心腐朽现象。西藏林芝地区有一株树龄约 2 5 0 0a的巨柏 ,树高 5 0m ,胸径 475cm ,材积约 2 4 0m3 ,为我国现存柏科树种中树龄最大、胸径最大的巨树。可与我国陕西黄陵的侧柏 (Platycladusorientalis)、昆明黑龙潭的宋柏 (以及台湾阿里山的红桧(Chamaecyparisformosensis)相媲美。巨柏木材是建筑、车船、桥梁、雕刻、高档家具和高档装修的优良用材。种子可榨油 ,供医药之用。巨柏树形美观 ,也是园林绿化的优良树种之一。从巨柏的分布状况和生物特性来看 ,它具有喜温、喜光、趋湿的特性 ,说明它具有一定生态可塑性。将其引种到福建 ,进行驯化 ,使其适应福建某些地区的生态环境和立地条件 ,从而丰富福建省具有高价值的用材树种 ,增加生物多样性 ,保护珍稀树种 ,具有积极意义...  相似文献