陕北榆树大量死亡原因探析

根据分离培养和接种试验结果，认为白榆死亡是由白榆干枯病感染流行造成，病原菌为茎点霉菌。其发展蔓延具有明显的流域特征：河谷台地、沟坝地、山坡基部发病较重；山顶、梁峁地和山坡中、上部发病轻。红足壮异蝽的危害能加重病害的流行和扩展。     

北京市房山区乡村旅游节事活动的SWOT分析及策略

采用SWOT分析方法,针对北京市房山区乡村旅游节事活动中存在的优势、劣势、机遇及挑战进行了分析,旨在为打造乡村旅游品牌、扩大知名度、传播民俗文化及提高经济效益起到重要的推动作用。     

Chemical Compositions of Volatile Oil from Fruiting Body of Armillaria luteo-virens

The chemical compositions of volatile oil from fruiting body of Armillaria luteo-virens in Qinghai Province were firstly analyzed with GC-MS and its relevant compositions were detected by calculating chromatographic peak area with normalized method.21 peaks were separated and 13 compositions were identified which were mainly unsaturated fatty acids,taking 97.1% of the total volatile oil.     

贵州微小牛蜱的检测与防制研究

微小牛蜱在贵州某些奶牛场、人工草场、养牛专业户及农户的牛群中存在,严重危害牛群的健康.对贵州微小牛蜱的危害、流行情况、监测及防制进行了探索,可为进一步开展微小牛蜱的防治研究提供参考依据.     

一串红的品种选择与栽培技术

一串红是目前最主要的一种花坛花卉。介绍了一串红的形态特征、生态习性,并对其品种选择、繁殖与栽培技术等三方面进行了详细的阐述。     

Effect of NS-398 on invasion of colon cancer HT-29 cells in vitro and its regulation by CD44v6 and nm23-H1 genes

AIM: To study the anti-invasive effect of NS-398 on colon cancer cell line HT-29 in vitro an its regulation by CD44v6 and nm23-H1 genes. METHODS: Flow cytometry was used to detect the expression of COX-2 and CD44v6 in HT-29 cells. MTT was used for cell survival rate tests. The modified Boyden chamber model was used for quantitative invasion assay. RT-PCR was used to detect the expression of nm23-H1 mRNA. RESULTS: Flow cytometry analysis showed that COX-2 was positive in HT-29 cells. NS-398 had significant inhibitory effects on invasion of HT-29 cells, which had no relation with its cytotoxicity. NS-398 down-regulated the expression of CD44v6 and up-regulated the expression of nm23-H1 mRNA. CONCLUSION: NS-398 has an anti-invasive effect on HT-29 cells in vitro. Down-regulation of CD44v6 and up-regulation of nm23-H1 may be its underlying mechanisms.     

水稻栽培因素对北方粳稻产量及米质的影响[Ⅵ]--穗肥追肥时间对产量及米质的影响

通过田间对比试验研究穗肥追施时间对水稻产量及米质的影响,结果表明,水稻的穗肥追施时间越晚,加工品质越好,而产量和食味品质明显降低.这种趋势以出穗前25 d为准,有跳跃式的质的变化.所以为了提高产量和增加食味品质,水稻的穗肥追肥时间不应晚于出穗前25 d.     

不同利用方式下短花针茅草原生物量的形成规律

在内蒙古包头市达茂联合旗哈雅教学牧场 ,采用随机区组法对短花针茅草原在不同刈割时期、次数和高度下的生物量形成规律进行了研究 ,旨在探索短花针茅草原的合理利用方式 ,为草原放牧畜牧业生产实践提供理论依据。研究结果表明 ,短花针茅草原对刈割高度较为敏感 ,适宜的刈割高度为 2 cm;短花针茅草原植物生长缓慢 ,再生能力差 ,不宜于频繁利用 ,一年适宜利用 1 -2次 ;考虑牧草产量和营养物质含量 ,一年两次利用的间隔期应为 2 -3个月 ;一年一次利用的最佳利用期为 8月中旬以后。     

Effects of chlorine gas exposure on lung haemodynamic and respiratory function in intact and isolated perfused rabbit lungs

AIM:To investigate the effect of high concentration of chlorine gas(Cl₂) exposure on lung haemodynamic and respiratory function in intact and isolated perfused rabbit lungs (IPLs). METHODS:8 intact and 10 IPLs were exposed to Cl₂ at high concentration(50×10^-4)for 20 min, as measured group, 8 additional intact and 9 IPLs, which were similarly treated but not exposed to Cl₂, served as controls. The changes of lung weigh of IPL(△W)、pressure of pulmonary artery(Pa)and venous pressure(Pv)、airway pressure and tidal volume(TV) were continuously measured and recorded simultaneously. RESULTS: In IPL group: While the perfusing blood flow was kept constant (133.3 mL/min), and Pv did not change, following the exposure, the Pa increased slightly, then the lung weight were increased significantly and the TV decreased . Hematocrit of perfusate of EIPL and parameters of lung water increased also. In intact group: Pa increased slightly, respiratory rate accelerated immediately, and TV decreased. CONCLUSION:Although mean Pa increased continuously and slightly in both intact and IPL group following the exposure to high concentration of Cl₂, the primary cause of edema was most likely to alter pulmonary capillary permeability. The respiratory rate accelerated and TV decreased due to exposure to Cl₂ enhanced hypoxia of intact rabbits.     

成对或不成对反转试验设计

本文系统探讨了反转试验（交叉设计）设计的数学模型。统计分析方法和原理以及设计要求，根据t-测验思想，给出了成对或不成对反转试验设计的原理和方法。