波涌灌溉的水流推进规律研究

根据大田波涌灌与连续灌的试验实测资料,分析讨论了二者在灌水方向上的水流推进的时间分布特征,结论为第一周期的水流推进过程和连续灌基本相同,且波涌灌在各周期的平均水流推进速度均大于连续灌,认为最佳灌溉方式是合适的停水时间和合适的灌水总时间相结合,还对水流推进过程进行了分段拟合,相关系数均令人满意。     

工商资本下乡促进了农地流转吗?——来自CLDS的经验证据

为实现小农户和现代农业发展有机衔接,加快农业现代化的进程,推进工商资本下乡从事农业生产经营具有重要意义。基于工商资本下乡行为异质性的视角,从租赁农地和提供机耕服务两个方面梳理工商资本下乡影响农户农地流转的可能路径,利用中国劳动力动态调查数据,运用双变量Probit模型,分析工商资本下乡对农户农地流转的影响,探讨其影响机制。结果表明,44.46%和25.01%的调查农户所在村有工商资本下乡租赁过农地和提供过机耕服务;21.17%和72.06%的调查农户所在村有工商资本不止一次下乡租赁过农地和提供过多元化惠农服务。工商资本下乡租赁农地显著降低了农户的农地转入概率,对农户的农地转出决策影响不显著;工商资本下乡提供机耕服务显著提高了农户的农地转入概率,降低了农户的农地转出概率。户主年龄、性别、家庭实际耕地面积和村居劳动力年龄结构等因素也能够促进农地流转。随着工商资本下乡租赁农地强度的增加,将降低农户农地转入和转出概率;若工商资本下乡提供多元化惠农服务,将显著提高农户的农地转入概率,降低农户的农地转出概率。因此,需加强对农地流转的监督和管理,警惕工商资本下乡过程中大量"圈地"导致的土地"非粮化"和"非农化"现象,加快建立工商资本与农户之间的利益联结机制。     

盛夏高原涡生成频数与初夏大气环流背景场的关系

基于ERA-interim再分析资料,通过客观识别法得到的高原低涡统计数据集,选取1986-2015年7月高原低涡生成频数的多发年与少发年,通过相关分析与合成分析等方法分析7月生成的高原低涡频数与6月的大气环流之间的关系.主要结果如下:(1) 7月高原低涡主要生成在28°-36°N纬带内, 90°E以西生成的高原涡数量占全部的74.68%;(2)高原低涡多发年,高原低层相对湿度大,尤其改则—申扎(30°-34°N, 84°-90°E)与左贡(约29°N, 97°E)地区;整层大气热源偏强, 90°E以西地区垂直方向上各层均表现为热源.高原低涡少发年, 6月32°N以南低层相对湿度小;整层大气热源弱,垂直方向上低层表现为热源,热源偏弱.(3)高原涡多发年,高原涡主要生成范围内低层被正相对涡度控制,并且相对涡度偏大;高原主体范围内基本为上升气流,低层上升速度偏大,气流低层辐合,高层辐散,强度偏强,但在高原90°E以西与90°E以东有一定差异.高原涡少发年,高原涡主要生成范围内低层被正相对涡度控制,但相对涡度偏小;高原主体范围内为上升气流,低层上升速度偏小,气流低层辐合,高层辐合,强度偏弱.     

甜樱桃流通过程中影响保鲜效果的主要因素及对策

甜樱桃采后容易腐烂变质失去商品价值,明确流通过程中影响甜樱桃保鲜效果的主要因素并针对性提出保鲜策略,对有效延长甜樱桃流通时间、保持货架期品质具有重要意义。本文从采收、商品化处理、冷链物流、流通模式四个方面分析影响我国甜樱桃保鲜效果的突出问题,结合甜樱桃保鲜研究成果及成功应用经验提出相应对策,为我国甜樱桃保鲜方面的研究和应用提供理论借鉴和实践参考。     

新疆天山极端干湿事件时空演变特征

基于新疆天山26个气象站1960—2017年的气象资料,采用FAO Penman-Monteith模型计算了各气象站月地表湿润指数,标准化后统计极端干湿事件频率.运用线性趋势分析法、反距离加权法探究了极端干湿事件频率的时空演变特征,并采用相关分析、偏相关分析及交叉小波分析分别探讨了气象因子和大气环流对极端干湿事件变化的...     

Esophageal varices in dogs: A retrospective case series

BackgroundEsophageal varices (EV) are abnormally dilated veins in the esophagus caused by alterations of blood flow or pressure. Esophageal variceal hemorrhage is a major complication of hepatic disease in humans, but a lack of information exists regarding associated adverse events in dogs.ObjectiveTo describe the clinical manifestations and associated etiologies and outcomes of dogs with EV.AnimalsTwenty‐five client‐owned dogs with EV diagnosed via computed tomography (CT), endoscopy, or fluoroscopy.MethodsRetrospective case series. Cases were identified by review of the hospital imaging records database between 2010 and 2020. Signalment, clinical signs, and outcomes were documented. When present, additional collateral vasculature was also recorded. Cases were subcategorized into suspected etiology based upon the anatomic location or absence of an attributable underlying disease process, as well as the direction of blood flow.ResultsTwenty‐four of 25 cases were identified via CT, with a prevalence of 0.012% (24/1950 total studies). Presenting clinical signs were nonspecific, and more likely because of the underlying cause as opposed to complications secondary to EV themselves. Etiologic anatomic locations were similar in occurrence between the abdomen (N = 14) and thorax (N = 11). All cases with an abdominal etiologic location had presumed or confirmed portal hypertension and 9/11 cases with a thoracic etiologic location had pulmonary, caval, or systemic hypertension. No cases died or were euthanized as a direct result of EV or associated hemorrhage.Conclusions and Clinical ImportanceEsophageal varices are rarely reported in dogs and commonly identified concurrently with portal, pulmonary, and caval hypertension. Hemorrhage is not a common clinical manifestation of EV.     

Plasma FITC-dextran exchange between the primary and secondary circulatory systems in the Atlantic cod, <Emphasis Type="Italic">Gadus Morhua</Emphasis>

Fluorescein isothiocyanate dextran (FITC-dextran) exchange between the primary (PCS) and secondary (SCS) circulatory systems in the Atlantic cod, Gadus morhua (Linnaeus, 1752), were studied using 20-kDa (n = 4) and 500-kDa (n = 4) FITC-dextran. In order to give a qualitative perspective of the general connection between the PCS and SCS, distribution of plasma-borne tracers (FITC-dextran) in the PCS and SCS were examined. In this study, a total of eight cod were cannulated in the ventral aorta (PCS) and dorsal cutaneous vessel (SCS), for investigation of FITC-dextran disappearance in the PCS and its subsequent appearance in the SCS. FITC-dextran of both sizes was found to be in equilibrium between the PCS and SCS in less than 20 min. This indicates a profound connection between the PCS and SCS in the Atlantic cod, and rapid mixing of tracers between the PCS and SCS. The destination of the injected 500-kDa FITC-dextran was also examined, and it was observed that of the 500-kDa FITC-dextran lost from the primary and secondary vascular systems, 63.0 ± 9.2% could be recovered from the liver     

基于低碳温室技术的居室园艺系统探究

随着现代城市进程越来越快,人们的生活水平逐渐提高,对高品质、安全和健康的生活方式追求也越来越高.该研究从空气质量、食品安全和低碳环保角度进行分析,提出了基于低碳温室技术的居室园艺系统概念.通过对低碳温室技术、微气候和居室园艺系统概念的解析来进行3大系统的设计,使基于低碳温室技术的居室园艺系统的设计更加具有整体性、科学性、合理性.     

平房仓横向通风系统分区环流熏蒸应用研究

通过对跨度大于30m的平房仓横向通风系统进行分区环流设计,与不分区横向通风系统平房仓进行磷化铝片剂自然潮解环流熏蒸对比试验,科学验证分区环流的可行性,为平房仓横向通风储粮成套新技术和新工艺的推广应用总结经验。     

高校图书馆流通部读者服务质量分析

高校图书馆流通部是直接面对读者的一线阵地,流通工作也是与读者打交道最频繁的工作之一。要讲求服务方法,正确处理与读者的冲突;创新服务思想,构建和谐的服务氛围;重视读者培训,推进主动服务。在工作中不断增进与读者的交流,营造积极向上的学习氛围与文明和谐的人文环境,提高服务质量与读者满意度。