Tracking the long-term decline and recovery of an isolated population     

RL Westemeier  JD Brawn  SA Simpson  TL Esker  RW Jansen  JW Walk  EL Kershner  JL Bouzat  KN Paige 《Science (New York, N.Y.)》1998,282(5394):1695-1698

Effects of small population size and reduced genetic variation on the viability of wild animal populations remain controversial. During a 35-year study of a remnant population of greater prairie chickens, population size decreased from 2000 individuals in 1962 to fewer than 50 by 1994. Concurrently, both fitness, as measured by fertility and hatching rates of eggs, and genetic diversity declined significantly. Conservation measures initiated in 1992 with translocations of birds from large, genetically diverse populations restored egg viability. Thus, sufficient genetic resources appear to be critical for maintaining populations of greater prairie chickens.  相似文献   

精密镗床旋转轴几何误差完备性测量与辨识     

郭世杰  丁强强  邹云鹤  萨日娜  唐术锋 《农业机械学报》2024,55(1):446-458

针对四轴卧式镗床旋转轴需测几何误差的数目不统一与完备性缺失的问题,提出了基于形状创成函数的四轴卧式镗床旋转轴PIGEs形成机理分析方法与旋转轴完备几何误差测量辨识方法。基于形状创成机理构建了卧式镗床几何误差创成函数,确定了旋转轴可通过误差补偿进行调整的最少与位置无关的几何误差(Position-independent geometric error, PIGEs)数目。建立了卧式镗床旋转轴4项PIGEs、6项与位置有关的几何误差(Position-dependent geometric error, PDGEs)、6项安装误差(Setup error, SEs)与球杆仪(Double ball bar, DBB)测量轨迹半径之间的完备性函数模型,设计了基于DBB的四轴联动Viviani曲线测量轨迹,构建了旋转轴6项PDGEs的NURBS表征与PIGEs、SEs辨识方法。开展了误差补偿对比实验验证,结果表明,利用几何误差完备性测量与辨识结果进行误差补偿,较仅单一补偿6项PDGEs可提升圆轨迹测量精度40.69%。  相似文献   

Migration,colonization and seedling growth of rhizobia with matrine treatment in alfalfa (Medicago sativa L.)     

Yang-yang Miao  Jian-guo Zhang  Osama Abdalla Mohamad 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2018,68(1):26-38

Purpose: The purposes of this study were to determine the effect of matrine on the migration and the colonization dynamics of the two fluorescent-tagged rhizobia in Gannong No.5 alfalfa (Medicago sativa L. Gannong No. 5) tissues, and also to determine the effect of the combination treatments on alfalfa seedlings’ growth.

Materials and methods: 0, 100, 200, 300 and 400 mg L^?1 matrine levels were added into two cyan fluorescent protein (CFP)-tagged rhizobia; Ensifer meliloti LZgn5f (gn5f) and Ensifer meliloti 12531f (12531f), respectively; and drenched the alfalfa root with the inoculants. Then the migration and colonization of the two rhizobia in alfalfa on D7, D14, D21 and D28, and subsequently seedling growth were investigated.

Results: The results showed that the optimum matrine level enhanced the colonization of both fluorescent-tagged rhizobia in alfalfa roots and the highest colonization densities of log 6.31 cfu g^?1 and log 5.87 cfu g^?1 were achieved by adding 300 mg L^?1 matrine into 12531f and adding 100 mg L^?1 matrine into gn5f, respectively. They could migrate to the aerial tissues and most colonize stems through the application of adding 300 mg L^?1 matrine into 12531f and 100 mg L^?1 matrine into gn5f, respectively. No fluorescent-tagged rhizobia were detected in the control treatment. Alfalfa seedling growth parameters like leaf chlorophyll content, seedling growth rate, root length, seedling biomass and total N percentage also increased the most when 300 mg L^?1 matrine was added into 12531f and 100 mg L^?1 matrine added into gn5f treatments.

Conclusions: Our results suggest that 300 mg L^?1 matrine added into 12531f and 100 mg L^?1 matrine added into gn5f might be exploited to promote the colonization of rhizobia in alfalfa tissue and positively impact growth and yield, indicating possible benefits for plant cultivation.  相似文献   

短期玉米秸秆还田对冷凉地区土壤真菌多样性的影响   总被引：1，自引：0，他引：1  

萨如拉  杨恒山  高聚林  张丽娟  张玉芹  范秀艳  李纯燕 《干旱地区农业研究》2018,36(3):120-124

在玉米吐丝期,利用传统涂布平板法和高通量测序技术,设置常规秸秆不还田(CK)、秸秆深翻还田(SF)和秸秆旋耕还田(XG)3个处理,研究0~10 cm、10~20 cm和20~30 cm土层真菌群落丰富度、多样性和群落结构变化,揭示冷凉地区玉米秸秆还田真菌群落结构及其差异。结果表明:冷凉地区玉米秸秆还田对土壤真菌多样性的影响较大,秸秆还田土壤中可培养真菌数为SFXGCK;秸秆还田后土壤真菌优势菌群发生变化,CK优势菌为马拉色氏霉菌属、被孢霉属和葡萄孢属,XG优势菌为被孢霉属;XG和SF表层土壤中耐冷酵母菌属和被孢霉属是优势菌;SF处理20~30 cm土层优势菌为葡萄孢属。真菌菌群Alpha多样性、群落组成丰度、RDA(Redundancy analysis)和菌群相似性综合分析可知,SF和XG 0~20 cm土层菌群差异小;SF和XG均能增加10~30 cm土层真菌群落丰度。  相似文献   

沙质草地、高平原草地牧草总糖与还原糖含量变化     

殷周梅  卫智军  微微  萨格萨 《中国草地学报》2009,31(2)

研究了沙质草地与高平原草地六种牧草的总糖含量与还原糖含量变化情况.结果表明:沙质草地与高平原草地供试牧草的总糖含量变化(除糙隐子草外)和还原糖含量变化不同;除羊草和寸草苔外,其余几种牧草的还原糖含量都是高平原草地高于沙质草地.  相似文献   

Are the Australian poultry industries vulnerable to large outbreaks of highly pathogenic avian influenza?   总被引：1，自引：1，他引：0  

SA Hamilton  IJ East  J-A Toribio  MG Garner 《Australian veterinary journal》2009,87(5):165-174

Objective   To describe the structure of the Australian poultry industry and discuss the potential for highly pathogenic avian influenza (HPAI) to spread between Australian poultry farms.
Procedure   High densities of poultry farms, frequent contacts between farms by service providers, the supply of live poultry markets (LPM) and the presence of free-range duck flocks in affected regions have been identified as risk factors for the spread of HPAI between flocks in outbreaks causing the death or destruction of over 1 million poultry overseas. Data on 1,594 commercial Australian chicken meat, chicken egg, duck and turkey farms were collected by a telephone questionnaire of farm managers to assess the risk of a HPAI outbreak in Australia.
Results and Discussion   Five regions of Australia had farm densities comparable to overseas regions that experienced widespread HPAI. Common service providers routinely contacted different classes and types of farms over wide geographic areas. However, no responding farms supplied LPM and the majority of duck farms did not produce free-range ducks.
Conclusion   Outbreaks of HPAI have the potential to cause serious impacts on the Australian poultry industry. The risk posted by LPM and free-range ducks is limited, but the movement of genetic stock and common service providers could spread infection between companies, industries or geographical regions. Biosecurity measures are therefore considered critical to limit the secondary spread of infection should an outbreak occur.  相似文献   

Socio-Economic and Scientific Impact Created by Whitefly-Transmitted,Plant-Virus Disease Resistant Tomato Varieties in Southern India          下载免费PDF全文

John Colvin  N Nagaraju  Carlos Moreno-Leguizamon  R M Govindappa  T B Manjunatha Reddy  SA Padmaja  Neena Joshi  Peter M Hanson  Susan E Seal  V Muniyappa 《农业科学学报》2012,11(2):337-345

Research carried out to assess the impact of open-pollinated Tomato leaf curl virus (ToLCV)-resistant tomatoes and hybrids on the livelihoods of resource-poor farmers in Southern India is described and discussed. Three high-yielding ToLCV-resistant tomato varieties were developed initially using conventional breeding and screening techniques involving inoculation by ToLCV-viruliferous whitefly, Bemisia tabaci. In 2003 and 2004, respectively, these varieties were released officially by the Karnataka State Seed Committee and the Indian Ministry of Agriculture through notification in the Gazette of India. From 2003 to 2005, eleven seed companies bought breeder seed of the ToLCV-resistant varieties and used them to begin breeding F₁ hybrids from them. Socio-economic studies carried out to assess the benefits obtained from growing the ToLCV-resistant varieties found that farmers could gain up to 10 times the profit by growing the ToLCV-resistant varieties compared to the pre-existing ToLCV-susceptible varieties. Adoption of ToLCV-resistant tomatoes was also associated with reduced pesticide use. Extra income from tomato sales was prioritised by farmers to pay for children's education, better nutrition and medicines. In a joint effort with the commercial seed sector in India, a promotional field day was organised in 2007. As well as the three ToLCV-resistant varieties, 62 ToLCV-resistant hybrid tomatoes were exhibited during a farmer-field day by 17 commercial seed companies and several public institutes. Tomatoes with ToLCV-resistance are now grown widely in South India and seeds of the three open-pollinated varieties have been distributed to more than 12 countries. In 2007, a conservative estimate of the financial-benefit to cost of the research ratio was already more than 837:1.  相似文献   

Pelvic limb kinematics in the dog with and without a stifle orthosis          下载免费PDF全文

Bryan T. Torres DVM  PhD  DACVS‐SA  Yang‐Chieh Fu PhD  Gabriella S. Sandberg BS  Steven C. Budsberg DVM  MS  DACVS 《Veterinary surgery : VS》2017,46(5):642-652

  相似文献   

Outcome of laparoscopic adrenalectomy for resection of unilateral noninvasive adrenocortical tumors in 11 cats          下载免费PDF全文

Jeffrey W. Mitchell DVM  Philipp D. Mayhew BVM&S  DACVS  William T. N. Culp VMD  DACVS  J. Brad Case DVM  MS  DACVS  Ameet Singh DVM  DACVS  Mark C. Fuller DVM  DACVS‐SA  Ann Della Maggiore DVM  DACVIM 《Veterinary surgery : VS》2017,46(5):714-721

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Aspiration of barium-impregnated polyethylene spheres by a dog     

V Greci  SA Bissett  CN Copple  EC Hawkins 《Australian veterinary journal》2010,88(5):166-168

This case report describes an 11-year-old Belgian Malinois dog with acute onset of cough caused by aspiration of barium-impregnated polyethylene spheres (BIPS) and pneumonia following an episode of suspected gastric dilation. Although bronchoscopic retrieval of the BIPS was largely unsuccessful, the dog recovered uneventfully, with most of the BIPS being coughed out and swallowed over a 1-month period. Aspiration of BIPS should be considered a potential complication of their administration. Furthermore, endoscopic removal of aspirated BIPS is challenging and may not be indicated because of their inert nature and possible self-clearance.  相似文献