怀化市鹤城区退耕还林工程生态效益计量评价

对怀化市鹤城区自2001年实施退耕还林工程以来十年间所取得的生态效益进行计量评价,估算了鹤城区退耕还林工程在保护水资源效益、固土保肥效益和固碳制氧效益3个方面所产生的生态效益。结果表明,鹤城区退耕还林工程所带来的生态效益十分显著,鹤城区退耕还林工程生态效益总价值为16645.36万元。     

Resistance at the TM-2 locus in the tomato to tomato mosaic virus

Summary There are three known tomato mosaic virus (TMV) resistance factors, Tm-1, Tm-2 and Tm-2 ², in the tomato. Tm-2 ² is currently the most widely utilised in glasshouse cultivars. Both Tm-2 and Tm-2² can induce systemic necroses in response to virus infection. These are considered to be hypersensitive resistance reactions in view of the low virus concentrations in affected plants and because sub-inoculation usually fails to infect all plants possessing the same resistance gene. The literature relating to TMV resistance at the Tm-2 locus in the tomato is reviewed.Virulent strains may readily establish when Tm-1 or Tm-2 are used, but Tm-2 ² confers more effective resistance. The possible development of aggressive isolates capable of affecting Tm-2 ²/Tm-2² plants is discussed. The establishment of virus types which cause systemic necrosis at normal growing temperatures is considered more likely than widespread infection from fully virulent strain 2² mutants. However, the growing of crops isolated from the TMV reservoirs in the soil considerably reduces the likelihood of even this occurring.     

Pathologic features of abdominal and thoracic paragangliomas in F344/N rats

Seventeen paragangliomas were identified in a retrospective review of 200 NTP/NCI carcinogenicity studies in F344/N rats that served either as control or treated animals. Most tumors were grossly visible and located in the retroperitoneum adjacent to the vertebrae and aorta near the kidneys. Three microscopically detected paragangliomas were found at the base of the heart. Microscopically, neoplastic cells were in nests separated by reticulin fibers and capillaries. Argyrophil granules were in the cytoplasm of the retroperitoneal and mediastinal paravertebral tumors. Dense granules were found in the one tumor examined ultrastructurally. Some tumors had areas of necrosis and tumor emboli were present in the lumen of the abdominal aorta and vena cava adjacent to the tumor with metastases present in pulmonary vessels. The incidence of retroperitoneal neoplasms was 3 times more frequent in male than in female F344/N rats.     

Coughing in horses--an historical aspect.

A brief historical review is given of the incidence and types of respiratory disease that occurred in Britain in the 18th and 19th centuries. The significance of poor stabling and overcrowding in the causation and spread of coughing is emphasised and its dramatic reduction by simple methods of hygiene and ventilation.     

黄河表层沉积物与稀土元素La~(3+)的交换吸附作用研究

采用现场采样及室内实验方法,研究了黄河表层沉积物与La^3 的交换吸附作用。结果表明,用Langmuir方程和Freundlich方程均能较好地反映La^3 在沉积物表面上的等温吸附过程,但以Langmuir方程拟合程度更好,黄河表层沉积物对La^3 的吸附强烈地受控于pH值在2-12这一宽广的pH范围内,La^3 黄河表层沉积物的交换吸附呈现随pH的增加而增大的总体趋势,在pH为2-7的范围内,随pH的增大,La^3 的吸附量逐渐增加,并在pH为6-7时达到最高值;当pH＞7时,随Ph的增大,La^3 的吸附量基本保持恒定,沉积物去除有机质后吸附能力下降了12.71%,与颗粒物中稀上元素有机物结合态所占比例相当.     

Cattle twins and freemartin diagnosis

Some cattle breeding improvement programmes particularly in continental Europe aim to reduce the costs of rearing calves by increasing the number suckled by each cow. This encourages the rearing of twins and an increase in the number of heifers born twin-to-bull. Many of these are offered in the market and bought on the assumption that they are single-born. A large proportion will be freemartins and therefore irremediably sterile. Theories of the aetiology of the freemartin condition are summarised. The anatomical, haematological and chromosomal characteristics are described. Diagnostic methods based on these characteristics are described and compared. The clinical method is recommended as reliable in all but a small proportion of cases. The clinical signs of the freemartin at age three to six weeks are the absence of the external os, and a vagina length of 5 inches (12 cm) or less. The veterinary surgeon is encouraged to make the diagnosis on these clinical signs alone.