Scale-dependent habitat use in three species of prairie wetland birds

We evaluated the influence of scale on habitat use for three wetland-obligate bird species with divergent life history characteristics and possible scale-dependent criteria for nesting and foraging in South Dakota, USA. A stratified, two-stage cluster sample was used to randomly select survey wetlands within strata defined by region, wetland density, and wetland surface area. We used 18-m (0.1 ha) fixed radius circular-plots to survey birds in 412 semipermanent wetlands during the summers of 1995 and 1996. Variation in habitat use by pied-billed grebes (Podilymbus podiceps) and yellow-headed blackbirds (Xanthocephalus xanthocephalus), two sedentary species that rarely exploit resources outside the vicinity of nest wetlands, was explained solely by within-patch variation. Yellow-headed blackbirds were a cosmopolitan species that commonly nested in small wetlands, whereas pied-billed grebes were an area-sensitive species that used larger wetlands regardless of landscape pattern. Area requirements for black terns (Chlidonias niger), a vagile species that typically forages up to 4 km away from the nest wetland, fluctuated in response to landscape structure. Black tern area requirements were small (6.5 ha) in heterogeneous landscapes compared to those in homogeneous landscapes (15.4–32.6 ha). Low wetland density landscapes composed of small wetlands, where few nesting wetlands occurred and potential food sources were spread over large distances, were not widely used by black terns. Landscape-level measurements related to black tern occurrence extended past relationships between wetlands into the surrounding matrix. Black terns were more likely to occur in landscapes where grasslands had not been tilled for agricultural production. Our findings represent empirical evidence that characteristics of entire landscapes, rather than individual patches, must be quantified to assess habitat suitability for wide-ranging species that use resources over large areas.     

草莓快速繁殖技术的研究

本文探讨了利用茎尖离体培养法进行草莓快速繁殖的方法。主要摸索了激素对试管苗的分化、生根的影响及移栽成活的技术要点。     

分层供水施磷对冬小麦磷效率及产量的影响

研究分层供水施磷对冬小麦磷效率及产量的影响,为指导旱地施磷提供一定理论和实践依据。试验设整体湿润(W1)和上干下湿(W2) 2 种水分处理,不施磷(CK)、表施(SP)、深施(DP)3 种施磷处理,供试品种选用水分敏感型（‘小偃22’）和抗旱型（‘长旱58’）。研究结果表明：磷肥施用深度对冬小麦磷根效率比、磷肥利用效率、磷肥偏生产力(PFPP)及产量的影响随土壤水分和品种而异。2 种水分条件下,‘小偃22’DP较SP处理磷肥利用率、PFPp均显著降低(P＜0.05),磷根效率比及产量则差异不显著;W1 处理下,‘长旱58’DP较SP处理除磷根效率比外其他指标均显著降低(P＜0.05),W2 处理下则相反,上述指标均显著增加(P＜0.05)。本试验结果表明,土壤水分供应不足时,磷肥深施有利于提高抗旱性较强冬小麦品种对磷素的吸收利用能力,从而提高磷肥利用率及产量。     

1株野鸭源鸡贫血病病毒的分离鉴定及其编码区基因序列分析

利用MDCC细胞系从东北地区采集的死亡野生鸟类样品中分离获得1株禽类病毒,对该病毒进行特异性PCR、特异性间接免疫荧光法等系统鉴定后,证实该分离株为鸡贫血病病毒(CAV),命名为WDNE110501株.利用PCR方法克隆出其编码区基因片段,测序结果表明,WDNE110501株的编码区全长为1 823 bp,无碱基缺失或插入.并将该基因序列和推导的氨基酸序列与国内外已发表的34个CAV株编码区基因进行同源性和亲缘关系的比对分析,同源性为96.1％～99.8％;氨基酸的同源性为89.8％～99.7％,与国内毒株harbin的差异最小,与国外最近的是美国毒株98D02152.序列比较表明CAV的3个编码基因VP1、VP2和VP3均有一定程度变异,以VP1变异性最大,且在不同毒株间的这3个阅读框的氨基酸序列变异是互不相关的.这是首次在野生鸟类中分离出CAV病毒,提示了我们野生鸟类在鸡传染性贫血病病毒传播和分布中可能起到一定作用.     

牛烂蹄坏尾病致病弯角镰刀菌代谢产物分离鉴定

取金寨县耕牛烂蹄坏尾病致病弯角镰刀菌的玉米培养物，用丙酮提取，硅胶净化，制备型硅胶大板分离，得到无色针状结晶体，经质谱和红外光谱分析，并经相关谱图数据库联机检索、甄别，按其分子量、化学式及结构式确定为麦角甾醇，从而证实了致牛烂蹄坏尾病的弯角镰刀菌可产生麦角甾醇。     

Influence of storage time and processing on chemical composition and in vitro ruminal fermentation of olive cake

Olive oil extraction generates olive cake (OC) that could be used in ruminant feeding. However, the chemical composition of OC is affected by multiple factors, being therefore highly variable. The objective of this study was to analyse the influence of storage time and further processing: crude, exhausted (subjected to a second oil extraction) and cyclone (obtained from a cyclone separator) on nutritive value of OC samples. Twelve samples (six crude and six exhausted) were obtained monthly from the same pond from 1 to 6 storage months, and nine samples (three crude, three exhausted and three cyclone) were obtained monthly from a different pond from 6 to 9 months storage. Chemical composition was analysed, and OC samples were fermented in vitro with sheep rumen fluid. Increasing storage time up to 6 months decreased sugars and total soluble polyphenols content but increased fibre content in OC. Dry matter effective degradability (DMED) decreased linearly (p < 0.001) by 35.9 and 45.5% as storage time augmented from 1 to 6 months for crude and exhausted OC, respectively. Crude OC had lower DMED values than exhausted OC (averaged values 0.255 and 0.294 g/g, respectively). Both potential production and rate of gas production were lower (p ≤ 0.018) in crude compared with exhausted OC, which was attributed to the high fat content of crude OC (≥86 g/kg dry matter). For samples stored longer than 6 months, cyclone had greater (p < 0.05) DMED than crude and exhausted OC (averaged values 0.207, 0.164 and 0.164 g/g, respectively). The results indicate that ruminal degradability of OC is reduced with advancing storage time, but only subtle changes were observed during the first two months. Cyclone showed greater degradability than crude and exhausted OC, but differences between crude and exhausted OC became negligible after five storage months.     

Multiple amino acid substitutions are involved in the adaptation of H9N2 avian influenza virus to mice

To explore adaptation of avian influenza virus to mice we previously performed serial lung-to-lung passages of the influenza A/Chicken/Jiangsu/7/2002 (H9N2) strain, resulting in the isolation of a variant influenza strain lethal for mice. We now report that virulence correlates with improved growth characteristics on mammalian cells and extended tissue tropism in vivo. Sequencing of the complete genomes of the wild-type and mouse-adapted viruses revealed 25 amino acid substitutions. Some were found to reiterate known substitutions in human and swine H9N2 influenza isolates. Functions affected include nuclear localization signals and sites of protein and RNA interaction, while others are known determinants of pathogenicity and host specificity such as the viral polymerase PB2 E627K substitution. These observations suggest that enhanced growth characteristics and modified cell tropism may contribute to increased virulence in mice. We conclude that multiple amino acid substitutions are likely to be involved in the adaptation of H9N2 avian influenza virus to mice.     

牛体外受精时老化卵对受精率与染色体异常发生的影响

通过延长体外培养时间得到牛老化卵，对其体外受精率与染色体的异常发生进行了研究，体外受精48h后的受精率，46h培养组与22h和34h培养组之间差异显著（P＜0．05），随着老化时间的延长，受精率及胚胎发育速度明显降低。染色体分析结果表明，46h组的受精卵的染色体异常发生率为61．6％，22h组44．6％，2组之间差异显著（P＜0．05），单倍体（n=31)的发生率也随着老化时间的延长而增加，这些单倍体的性染色体的构成表明，含有X－性染色体的胚的出现率显著高于含有Y－染色体的胚的出现率（P＜0．05）。单倍体的发生是由卵的老化而引起单一配子的孤雌发生，体外培养时间的延长对正常的2倍体的性别无明显影响。     

不同生长期金荞麦营养成分含量及消化率测定研究

为系统地测定分析不同生长期金荞麦的常规营养成分、氨基酸、微量元素含量及其回肠末端消化率, 本研究用3头安装“T”型瘘管, 并做回-直肠吻合切除盲肠的巴克夏-驯养野猪-高坡黑猪(巴-野-高)三元杂交生长猪作为试验动物, 采用3×3拉丁方试验设计开展消化试验。结果表明, 分枝期、孕蕾期和初花期金荞麦OM、CP、EE、Ca、P、CF含量分别为88.59%、22.72%、2.34%、1.05%、0.39%、13.51%, 89.10%、20.57%、1.69%、1.25%、0.42%、15.50%和89.63%、17.54%、1.37%、1.29%、0.46%、19.75%;EAA、NEAA和TAA含量分别为9285、7982、6244 mg/100 g, 14334、10810、9320 mg/100 g和23619、18792、15564 mg/100 g。随着生长期的后延, 营养成分含量显著降低, 在体和离体消化率也随着生长期的后延而显著降低。分枝期与孕蕾期间营养成分含量差异显著(P<0.05), 分枝期与初花期间营养成分含量差异极显著(P<0.01), 孕蕾期与初花期间营养成分含量差异显著(P<0.05)。从分枝期到孕蕾期, 金荞麦CP、EE、EAA及TAA下降较慢, CF含量升高较慢, 营养成分消化率下降也较慢;从孕蕾期到初花期, 金荞麦CP、EE、EAA及TAA下降较快, CF含量升高也较快, 营养成分消化率下降也较快。以分枝期、孕蕾期和初花期体外法测定常规营养成分及微量元素消化率值为自变量, 以对应的动物饲养试验回肠末端表观消化率值为因变量建立的回归方程拟合度好,可用于推算对应的回肠末端表观消化率。本实验证明, 金荞麦营养丰富、消化率高, 必需氨基酸比例高、适合动物消化吸收。孕蕾期为金荞麦适宜收割期, 在适宜收割期内, 收割时间点应选择孕蕾后期。     

《天净沙·秋思》英译本之我见——与黄国文、金春笙先生商榷

《中国翻译》上刊登了黄国文和金春笙先生对《天净沙.秋思》英译本的分析和研究。针对金先生和黄先生相驳的两种观点,文章首先从语言学角度审视了“形式对等”的真正内涵、实用性以及可接受性;然后从文学角度——音律、情感逻辑、意象虚实等来探讨《天净沙.秋思》的Schlepp和翁显良两种英译本孰优孰劣;最后建议运用语言学的分析方法来理性思考,结合文学的印象式、感悟式和经验式的翻译批评可以使得译文更富艺术魅力。