天津地区鸡大肠杆菌病病原分离及病原特性

从天津地区１０个区县、２３个养鸡场的２４１只疑似大肠杆菌病病例中,分离出病原菌９２株,所得菌株符合大肠杆菌的微生物学特性。致病性在各菌株间略有差异。分离菌对氟哌酸、庆大霉毒、氯霉素最为敏感。抗“Ｏ”血清型鉴定,结果表明,分离菌株分属２５个血清型,并以Ｏ１１１、Ｏ８９、Ｏ８６、Ｏ３０、Ｏ７８为主。从优势血清型中选取的菌株,均具有良好的抗原性。     

狐狸脑炎病毒的分离鉴定

通过ＭＤＣＫ传细胞从黑龙江某狐场疑似狐狸脑炎病狐的肝脏中分离到对本动物具有较强致病能力的强毒株,定名为ＦＥＶ－Ｈ。经系统鉴定,并与已知国内分离毒株狐狸脑炎病毒ＦＥＶ－８８０１,狐喉气管炎病毒ＦＡＶ－２比较,证实为狐狸脑炎病毒,属犬１型腺病毒（ＣＡＶ－１）。     

Optimum test period and associations between standard 140-day test period and shorter test periods for growth rate in station tested beef bulls

SUMMARY: The records of 2034 beef bulls representing 931 sire families from ten breeds tested at Ellerslie Test Station, Alberta, Canada, from 1974 to 1987 were analyzed to investigate the feasibility of selecting a shorter test period and study the associations between the growth rate in the standard 140-day test period and that in shorter test periods for accurate evaluation of growth potential of young beef bulls in test station. The results indicated that the period between day 28 and day 112 of the standard test was less affected by herd of origin compared with the standard 140-day test period and therefore could be considered as the short optimum test period. Average daily gain in this period was least affected by herd of origin, and had relatively high heritability which would ensure satisfactory selection response. In order to properly evaluate growth potential of beef bulls and economically make use of the testing facilities, it would be appropriate to have an adjustment period of 56 days (original 28 days plus the first 28-day period of the standard test) followed by a test period of 84 days (between day 28 and day 112 of the standard test). Such a test would result in reduction in management costs while providing a more accurate evaluation of growth potentials of young beef bulls. ZUSAMMENFASSUNG: Optimale Prüfperiode und Zusammenh?nge zwischen Standard-140-Tage- und kürzerer Prüfung für Wachstumsrate bei Stationsprüfung von Fleischrind-Bullen Leistungsangaben von 2034 Fleischbullen aus 931 Bullennachkommenschaften von 10 Rassen wurden auf der Allersly-Station Alberta, Kanada, von 1974 bis 1987 im Hinblick darauf analysiert, inwieweit Beziehungen zwischen Wachstumsrate in der Standard-140-Tage-Periode und der in kürzeren Zeitabschnitten existieren. Die Ergebnisse zeigen, da? die Prüfperiode zwischen den Tagen 28 und 112 des Standardtests weniger durch Herkunft tangiert wird als die Standard 140-Tagetest-Periode und daher als optimale Prüfperiode betrachtet werden kann. Durchschnittszunahmen waren in dieser Periode am wenigsten durch Herkunft beeinflu?t und haben relativ hohe Heritabilit?t, die hinreicht, um Selektionserfolg zu sichern. Um das Wachstumspotential von Fleischrindbullen zu bewerten und Testanlagen ?konomisch zu nutzen, w?re es angebracht, eine Anpassungsperiode von 56 Tagen (ursprüngliche 28 plus die ersten 28 Tage der bisherigen Testperiode) vor einer eigentlichen Testperiode von 84 Tagen erfolgen zu lassen. Hierdurch würden Managementkosten reduziert und eine genauere Sch?tzung des Wachstumspotentials der Fleischbullen gesichert sein.     

Ductile ordered intermetallic alloys

Many ordered intermetallic alloys have attractive high-temperature properties; however, low ductility and brittle fracture limit their use for structural applications. The embrittlement in these alloys is mainly caused by an insufficient number of slip systems (bulk brittleness) and poor grain-boundary cohesion. Recent studies have shown that the ductility and fabricability of ordered intermetallics can be substantially improved by alloying processes and control of microstructural features through rapid solidification and thermomechanical treatments. These results demonstrate that the brittleness problem associated with ordered intermetallics can be overcome by using physical metallurgical principles. Application of these principles will be illustrated by results on Ni(3)Al and Ni(3)V-Co(3)V-Fe(3)V. The potential for developing these alloys as a new class of high-temperature structural materials is discussed.     

苹毒蛾核多角体病毒观察初报

苹毒蛾病毒是典型的核型多角体病毒结构,对苹毒蛾幼虫有较强的致死能力,对于开展苹毒蛾的生物防治有一定意义;在病毒分类上根据形态鉴别,可能属于杆状病毒属(Baculovirus)亚组(A)的一个种。     

A Fluorite Isotype of SnO2 and a New Modification of TiO2: Implications for the Earth's Lower Mantle

The existence of a cubic fluorite-type SnO(2) and a hexagonal TiO(2) (which may be related to the fluorite structure) have been demonstrated by an in situ x-ray diffraction study in which a diamond-anvil pressure cell was used after the samples had been heated by a continuous yttrium-aluminum-garnet laser. At room temperature, the lattice parameter for SnO(2) (fluorite) is a = 4.925 +/- 0.005 angstroms and those for TiO(2) (fluorite-related) are a = 9.22 +/- 0.01 angstroms and c = 5.685 +/- 0.006 angstroms at about 250 kilobars. The volume change associated with the transition from rutile to fluorite (or related structure) is about -8 percent for SnO(2) and -10.5 percent for TiO(2) at transition. Upon release of pressure, both the fluorite-type SnO(2) and the TiO(2) reverted to the alpha-PbO(2) structure at room temperature. The hypothesis that the earth's lower mantle is composed of oxide phases might be feasible if it were possible for SiO(2) to possess the fluorite structure or its related forms at high pressure, as shown for SnO(2) and TiO(2) in this study. The oxide hypothesis proposed here differs from that postulated by Birch in that the primary coordination of silicon is 6 for Birch's hypothesis and 8 for the hypothesis presented here.     

应用灰色关联度分析法综合评价高羊茅品种初探

应用灰色关联度分析法,对2000～2002年本院引进的13个高羊茅品种的适应性鉴定结果进行评估,其评估结果与品种的实际表现基本一致,说明应用关联度分析法综合评价草坪品种是可行的。分析结果:皇后、贝克、上南都的关联系数与理想品种最接近,是种植高羊茅草坪的首选品种。     

Effect of infections with barley yellow dwarf virus and Fusarium spp. on assimilation of 14CO2 by flag leaves and translocation of photosynthates in wheat

Journal of Plant Diseases and Protection - The effects of infections of Barley yellow dwarf virus (BYDV), Fusarium culmorum and F. graminearum alone as well as double infections of BYDV and...     

5种国兰( Cymbidium ) 的光合特性

 通过气体交换和叶绿素荧光分析等方法研究了5种国兰(Cymbidium ) 的光合特性。其光饱和点、光补偿点、CO₂ 补偿点和CO₂ 饱和点表明它们具有C3 植物特征; 光合速率在3.0 ～5.9 μmol·m^{- 2} ·s^{- 1}之间, 在低于2 000 μmol·mol^{- 1} CO₂ 浓度下, 光合速率受CO₂ 浓度影响较大; 5种国兰的光合能力、表观量子效率、羧化效率等都有所差异; 光饱和点在350～650μmol·m^{- 2} ·s^{- 1}之间, 属于喜阴植物,其中春兰、建兰耐阴性相对较低, 墨兰、春剑耐阴性相对较高, 蕙兰居中。从暗处暴露到强光下, 5种国兰的光化学反应启动差异较大, 启动后的光化学效率差异也较大, 这可能与国兰不同种起源地的生态环境,适应性及进化有关。