兰州市居住空间分布及其成因   总被引：1，自引：0，他引：1  

刘争光  张志斌  汪晓霞  达福文 《干旱区资源与环境》2014,(1):72-78

城市居住空间是城市空间的重要组成部分。兰州市是典型的河谷型城市,对其居住空间进行研究,有助于揭示该类城市居住空间分布规律,合理引导城市居住空间的发展,优化城市居住空间结构。基于统计资料并结合实地调查,运用Arcgis软件的空间分析功能,从定量分析角度揭示出兰州市居住空间呈现沿交通线集聚分布、区域布局不均衡以及居住空间分异现象初显的特点。并从自然地理环境、城市规划、住房制度、房地产业的发展以及交通建设方面分析了兰州市居住空间分布形成的原因。  相似文献   

母鼠妊娠期铅镉联合暴露对仔鼠脑损伤病理学变化的影响     

路浩  达剑森  梅莉  张英  刘宗平 《中国兽医学报》2011,31(1)

为探讨母鼠妊娠期铅镉联合暴露对新生鼠生长发育及脑组织病理学变化的影响,20只怀孕SD母鼠被随机分为4组,即A组为对照组(饮用蒸馏水)、B组为铅组(300mg/L)、C组为镉组(10mg/L)、D组为铅+镉组(300mg/L+10mg/L)。采用饮水染毒,期间记录母鼠体质量及临床症状,染毒结束后记录新生鼠体质量及脑质量,并采集新生鼠大脑皮质观察其病理组织学变化,染毒时间为21d。结果表明,与对照组比较,各染毒组母鼠体质量均低于对照组,但差异不显著(P>0.05);而新生鼠体质量均显著低于对照组(P<0.05),脑质量也明显下降,除C组无显著性差异外,其余各组差异显著(P<0.05);病理组织学变化显示,光学显微镜观察大脑皮质未见明显异常,透射电镜下可见各染毒组神经细胞核染色质浓缩,线粒体肿胀、嵴部分或完全消失。铅镉联合毒性明显强于铅镉单独作用,铅镉联合表现协同毒性效应,镉在铅镉联合毒性损伤中发挥主要作用。  相似文献   

基于属性一致度的属性约简算法     

达列雄  邓方安  刘杰 《湖南农业大学学报(自然科学版)》2015,(3):64-66

为了对广东省的能源需求进行准确的预测，首先分析了影响广东省能源需求的各种因素，构建了预测指标体系.在此基础上，针对能源系统非线性等复杂系统特征，结合粒子群算法和BP神经网络的优点，构建了改进的PSO-BP神经网络的预测模型，并通过主成分分析法对指标体系进行数据降维，以降低神经网络的规模和复杂程度.以广东省1985-2013年的能源需求数据进行模拟与仿真，并对2014-2018年的能源需求量进行预测，理论分析和实证研究表明，该方法能够很好的反映广东省能源需求的特征，预测结果较为准确合理.  相似文献   

Complications of the angularis oris axial pattern buccal flap for reconstruction of palatine defects in two dogs     

DA Cook  MJ Thomson 《Australian veterinary journal》2014,92(5):156-160

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植物提取液对黄瓜白粉病的抑菌活性筛选研究   总被引：10，自引：1，他引：10  

金素心  顾振芳  代光辉  陈晓斌 《上海交通大学学报(农业科学版)》2006,24(1):48-53

首先通过叶圆盘法用29种植物提取液对黄瓜白粉病菌的抑菌效果进行了生物活性测定,初步筛选出槐、黄檀、南瓜和石楠等4种植物的提取液对黄瓜白粉病有较好的预防效果。然后对这4种植物提取液进行预防性和治疗性的室内盆栽药效试验,结果表明黄檀提取液对黄瓜白粉病的预防效果达到72.97%,治疗效果达到91.28%,并且在处理12 d后仍保持42.60%以上的防效。而槐提取液的预防效果和治疗效果分别为79.73%和79.19%,处理12 d后也保持在50%以上的防效。这两种植物提取液均极显著优于对照药剂三唑酮。  相似文献   

Cu2+对中华倒刺鲃超氧化物歧化酶活性的影响     

孙翰昌  丁诗华  代梅  黄丽英  耿晓修 《西南大学学报(自然科学版)》2005,27(5):709-712

Cu2+是养殖水体的常见污染物,为了评估Cu2+对鱼类超氧化物歧化酶(SOD)的影响,将中华倒刺鲃暴露于含0.01～0.32 mg/L Cu2+的水体中饲养8 d,测定肌肉、血浆及肝脏中SOD活性的变化.实验结果显示,低浓度Cu2+(0.01 mg/L)对肌肉、血浆及肝脏的SOD有诱导作用,随着处理时间的延长而升高.但当浓度较高(0.04mg/L以上)时,SOD活性均呈现先诱导后抑制的趋势.Cu2+浓度越高,SOD活性上升越急剧,出现活性抑制的时间就越提前.此外,SOD在3种组织中的分布亦存在明显差异,肝脏的SOD活性最大.这些结果表明,肝脏SOD活性更宜作为Cu2+污染的生物标记.  相似文献   

Energy balance for ethyl alcohol production from crops     

DA Silva JG  Serra GE  Moreira JR  Conçalves JC  Goldemberg J 《Science (New York, N.Y.)》1978,201(4359):903-906

Energy requirements to produce ethyl alcohol from three different crops in Brazil (sugarcane, cassava, and sweet sorghum) were calculated. Figures are presented for the agricultural and industrial phases. The industrial phase is always more energy-intensive, consuming from 60 to 75 percent of the total energy. Sugarcane is the more efficient crop for ethyl alcohol production, followed by sweet sorghum and cassava from a net energy viewpoint. The utilization of sweet sorghum stems might increase the total energy gain from this crop to almost the same level as sugarcane. Cassava has a lower energy gain at the present state of agriculture in Brazil.  相似文献   

Coelioscopic-assisted prefemoral ovariosalpingectomy in a d`Orbigny slider (Trachemys dorbigni) using a digital otoscope     

Bernardo Nascimento ANTUNES  Diego DA COSTA  Michelli Westphal DE ATAIDE  Allana Valau MOREIRA  Luis Fernando PEDROTTI  Francisco Schulz JÚNIOR  Cassiano Schmitz NHOATO  Renan Alves STADLER  Marco Augusto Machado SILVA  Maurício Veloso BRUN 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2020,82(12):1802

The purpose of this study was to assess the unilateral prefemoral coelioscopic-assisted approach for ovariosalpingectomy in a d`Orbigny slider (Trachemys dorbigni) using a digital otoscope. Twenty healthy turtles were randomly assigned to one of two groups, for right (GR; n=10) or left (GL; n=10) prefemoral access, for coelioscopic-assisted ovariosalpingectomy. Anesthesia and surgery times, body weight, and ovary/oviduct weight data were recorded. Anesthesia and surgery times did not differ significantly between the groups. Wound closure was the most time-consuming surgical step. Ovary and body weights significantly affected the exposure time of the ipsilateral and contralateral ovaries, respectively. Two intraoperative complications were reported. All the animals recovered uneventfully. The digital otoscope can be safely and effectively used for coelioscopic-assisted single-access, unilateral prefemoral ovariosalpingectomy in d`Orbigny slider.  相似文献   

黍族植物的叶片扩张和蒸腾作用对土壤水分亏缺的响应特征     

M. ESMAEILZADE-MORIDANI  B. KAMKAR  S. GALESHI  F. GHADERIFAR  J. A. TEIXEIRA DA SILVA 《土壤圈》2015,25(6):834-843

Plant processes, such as leaf expansion, stomatal conductance and transpiration, are affected by soil water, particularly in water-stressed environments. Quantifying the effects of soil water on plant processes, especially leaf expansion and transpiration, could be useful for crop modeling. In order to quantify the leaf expansion and transpiration in response to soil water deficit in three millet species, common (Panicum miliaceum L.), pearl (Pennisetum glaucum L.) and foxtail (Setaria italica L.) millets, a pot experiment was performed at the Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran. The soil water status was characterized by the fraction of transpirable soil water (FTSW). Leaf area and transpiration were measured daily. Relative leaf area expansion (RL) and relative transpiration (RT) data were plotted against FTSW. Finally the FTSW thresholds for RL and RT were calculated using linear-plateau and logistic models. The results showed that the thresholds for RL and RT were 0.68 and 0.62, respectively, based on all measured data of the three millet species using the linear-plateau model, indicating that RL and RT were constant when FTSW decreased from 1 to the threshold point. Thereafter, until FTSW = 0, RL and RT declined linearly with a slope of 1.48 and 1.43, respectively. Although millet is cultivated as a resistant crop in arid, semiarid and marginal lands, it showed an early response to soil water deficit at high FTSW thresholds. As leaf expansion and transpiration can be considered morphological and physiological variables, respectively, the results in this study indicate that millet has strong morphological flexibility when faced with soil water deficit.  相似文献   

西藏核桃休眠及萌芽特性研究   总被引：1，自引：0，他引：1  

曲芬霞  姚霞珍  郭建斌  李文博  达瓦次仁  索朗桑姆 《种子》2011,30(3)

利用浓硫酸浸泡处理西藏核桃种子,通过种子吸水率、不同层积方法和内源抑制物对小白菜萌发影响试验等方面来研究西藏核桃的休眠及萌芽特性.结果表明:用浓硫酸处理种吸水率大于对照,种壳并不是引起休眠的主要原因,外壳、内种皮、种仁可能均含有抑制种子发芽物质.用浓硫酸浸泡90 min,变温层积萌动时间早,且萌动率高;低温层积160 d,再在22℃恒温条件下发芽率高,为68%.  相似文献