中国北方沙尘天气原因探讨

我国是沙尘暴易发的国家,进入20世纪90年代以来,强沙尘暴有频率增加、强度加大、范围扩展、危害程度加剧的趋势。沙尘暴的发生危害范围亦逐渐从西北干旱经济落后区扩展到经济发达的北京、天津及华北平原区,近年来的沙尘暴造成了社会经济和人民生命财产的重大损失。受大气环流场和季风气候类型影响,中国冬、春盛吹西北风,强劲而干燥。发生沙尘暴的天数与大风日数和地面热力稳定程度相关,3-5月中国西北内陆地表增温大,是风力场和热力场极不稳定的季节,地表气候容易发生蠕动,沙尘暴便由此启动并易发。除自然要素外,不合理的人类活动也将诱发沙尘暴天气的发生,有些情况下还起到比自然要素更重要的作用。从生态地理区域的角度看,沙尘暴的源地在干旱和半干旱地区,由于大气环流的作用,影响到下风向的半湿润甚至湿润地区。无论何地干旱、半干旱地区都将存在沙尘暴发生的自然条件,而其下风向必将受到不同程度的影响,只是因为中国的季风气候,决定西北干旱、半干旱地区发生的沙尘暴必然影响东南部地区。在现有的科学技术条件下,人类所能做的就是调节自身的行为。因此,在沙尘暴源地实施生态建设是减缓沙尘暴发生的最重要措施,也是消除东部城市沙尘天气的主要途径。根据生态地理区域的特征,沙尘暴源地的干旱区、半干?     

沙尘物质的来源与防治途径

本文分析了沙尘暴形成的自然过程和危害特征,并探讨了内蒙古沙源区土壤颗粒物质的含量,指出沙尘暴的沙尘来源主要是退化草原、活化的沙地和裸露坡耕地等。同时根据风沙流运移规律及其和土壤颗粒的关系,提出了防治沙尘暴的关键技术原理,并探讨了有效控制沙尘暴的技术途径。     

采收时间对蜡蚧轮枝菌分生孢子的萌发及致病力的影响

将蜡蚧轮枝菌Vp菌株在PDA培养基上23℃黑暗培养,分别于第5、15、20、25、30天后采收。将不同时间采收的分生孢子置于2％葡萄糖培养液内培养,16 h后检测其萌发率,结果表明,采收于第5天和第15天的分生孢子萌发率分别达到89.76％和94.98％,显著高于采收于第25天(30.27％)和第30天(6.12％)的孢子的萌发率;在PDA培养基培养5 d和15 d的分生孢子在相同浓度下对温室白粉虱的致病力分别达到83.40％和74.44％,显著高于培养了30 d的分生孢子的致病力(8.76％)。     

Bone marrow mesenchymal stem cells are induced to differentiate into cardiomyocytes by hepatocyte growth factor in vitro

AIM: To explore a new method of hepatocyte growth factor (HGF) inducing bone marrow mesenchymal stem cells (MSC) to differentiate into cardiomyocytes. METHODS: Bone marrow MSC was cultured with DMEM media (10% fetal calf serum) 4-6 passages, and induced by HGF (10 μg/L) for 30 d. Automatical beating of the differentiated cells was observed daily with transverse microscopy, or under condition of 0.1% isoproterenol or cal-cium-deprived incubation. Specific cardiac myosin in the cells was indentified by immunochemistry. RESULTS: At 14-20 d of differentiation, bone marrow mesenchymal stem cells formed clones, in 10%-50% of which spontaneous beating cell-mass had come to continuously exist. Isoproterenol increased the beating rate and calcium-deprived media inhibited the beating. The cells were identified to be cardiomyocytes by expression of cardiac myosin heavy chain. CONCLUSION: HGF may induce bone marrow mesenchymal stem cells into cardiomyocytes with high efficiency, but the differentiating pathway of stem cells remains to be further studied.     

秦巴山区养羊户适度经营规模的研究

通过对秦巴山区陕西省西乡县15个典型陕南白山羊养殖专业户的资金投入、羊群结构、草地资源、经济效益等情况的调查，分析了养羊户的资源利用和生产经营状况，确定了与山羊生产密切相关的12个变量，即种公羊数、基础母羊数、后备母羊数、育肥羊数、羊舍面积、草地补种及施肥费用、医杂费、氨化或青贮饲料量、补饲精料量、工作日、投资额，并确定了各变量的参数值，以利润最大为目标函数，然后运用线性规划模型，计算出不同投资、不同人力及草地资源等条件下的适度经营规模。结果表明，养羊户的投资额是决定适度规模的主要因素。根据投资和羊群基础母羊数量设计的三种典型经营条件下，基础母羊全部留种的经营方式可获最大投资收益率(140．1％)；基础母羊数量达到20只以上，自繁种公羊的经营方式的最大投资收益率为74．0％；资金有限，人工授精配种的经营方式的投资收益率最低，为73．1％。     

二丁酰环腺苷酸对猪胴体组成和肉品质的影响

通过皮下注射和饲料添加不同剂量dbcAMP进行饲养试验 ,研究其对肥育猪胴体组成和肉品质的影响。结果表明 :皮下注射 1.0mg/kg和饲料添加 2 0mg/kg对改善肥育猪的胴体组成和肉品质效果最好 ,眼肌面积分别提高31.99%和 36 .39% (P <0 .0 5 ) ;瘦肉率分别提高 12 .4 2 %和 11.94 % (P <0 .0 5 ) ;背膘厚分别降低 19.95 %和 2 0 .97%(P <0 .0 5 )。肌肉粗蛋白含量分别提高 10 .87%和 16 .5 4 % (P <0 .0 5 )。     

三江白猪线粒体DNA-RFLP的分析

采用22种限制性内切酶分析了三江白猪线粒体DNA的多态性。结果表明：在60头个体中检出30种限制性态型．归结为7种基因单倍型；其间的差异来自少数限制性位点的突变。单倍型间平均遗传距离为0．35%，群体遗传多态程度为0．044％。三江白猪遗传多样性非常贫乏，说明三江白猪与地方种猪起源于一个共同祖先，在品种形成早期受到创立者效应的制约。     

Preliminary results of an anticircumsporozoite DNA vaccine trial for protection against avian malaria in captive African black-footed penguins (Spheniscus demersus).

Captive juvenile African black-footed penguins (Spheniscus demersus) housed in an outdoor enclosure at the Baltimore Zoo have an average 50% mortality from avian malarial (Plasmodium sp.) infection each year without intense monitoring for disease and chemotherapeutic intervention. During the 1996 malaria transmission season, the safety and efficacy of an anti-circumsporozoite (CSP) DNA vaccine encoding the Plasmodium gallinaceum CSP protein against P. relictum were studied. The goal was to reduce clinical disease and death without initiating sterile immunity after release into an area with stable, endemic avian malaria. The birds were monitored for adverse clinical signs associated with vaccination, the stimulation of an anti-CSP antibody response, and protection afforded by the vaccine. The presence of P. relictum in trapped culicine mosquitoes within the penguin enclosure was monitored to assess parasite pressure. Among the vaccinated penguins, the parasitemia rate dropped from approximately 50% to approximately 17% despite intense parasite pressure, as determined by mosquito infection rate. During the year of the vaccine trial, no mortalities due to malaria occurred and no undesirable vaccination side effects occurred. This is the first trial of an antimalarial vaccine in a captive penguin colony.     

捕食线虫性真菌18S rDNA基因序列与种系发生关系研究

对捕食线虫性真菌——少孢节丛孢菌A1分离株(Arthrobotrys oligospora A1)的18S rDNA基因序列进行了研究。结果表明：其18S rDNA全基因序列为1769bp，在进化树上与同种国外分离株A．oligospora var oligospora 1最为接近，同源性为94．7％。这与二者都具有捕食性结构—菌网的特点相一致。证实捕食线虫性真菌的捕食性结构与捕食线虫性真菌种系发生有关。从少孢节丛孢菌3个分离菌株(Arthrobotrys oligospora A1、A．oligospora 1、A．oligospora2)的进化树及同源性来看。不同国家地区的丛孢菌属(Arthrobotrys)分离株确实存在差异。     

四川省2种生境条件下黑麦草种子生产性能的研究

对四川省的丘陵区(洪雅)和中山地区(汉源)2种生境条件下的黑麦草种子生产性能进行了研究分析,结果表明,试验两地的种子产量和质量均有显著差异.其中,洪雅点种子产量为244.0 kg/hm2,汉源点的种子产量为532.8 kg/hm2.两样地的种子质量相比,汉源点的发芽势、发芽率、四唑染色数和四唑脱氢酶均高于洪雅点.两地的种子产量与其构成因素的相关性基本一致,均呈显著相关;相关性强弱依次为:每生殖枝种子数>生殖枝数>每生殖枝小花数>分蘖数>每生殖枝小穗数>千粒重.每生殖枝种子数对种子产量贡献最大.