落叶松人工林地位指数级导向曲线模型的研究

本文用约1000块样地资抖,系统地研究了黑龙江省落叶松人工林的地位指数级导向曲线模型。通过林业统计分析软件Statistica6.0对各落叶松人工林数据进行拟合、分析比较,结果为：从拟合精度、曲线走向与散点分布趋势、残差分布等综合考虑,舒马切尔曲线函数比较适合落叶松人工林地位指数级导向曲线模型的拟合。     

Optimal cultivar mixtures in focal plant diseases

This paper deals with a study on the effects of mixtures of partially resistant cultivars in focus forming plant diseases. The focus expansion velocity in a mixture of two partially resistant cultivars depends on four parameters, the focus expansion velocity in a crop of cultivar 1 only and in a crop of cultivar 2 only, the net-reproduction in a crop of cultivar 1 and of cultivar 2, respectively. An explicit equation is developed for the damage of a cultivar mixture where the crop is infected by two physiological races of the pathogen. It is shown that cultivar mixtures exist where damage is smaller than in crops of either of the two cultivars only. A simple explicit formula is given on the basis of which it can be decided whether an optimal mixture exists for a given pathosystem.     

Virus transmission by aphids in potato crops

This paper reviews the contribution of vector activity and plant age to virus spread in potato crops. Determining which aphid species are vectors is particularly important for timing haulm destruction to minimize tuber infection by potato virus Y (PVY). Alate aphids of more than 30 species transmit PVY, and aphids such asRhopalosiphum padi, that migrate in large numbers before flights of the more efficient vector,Myzus persicae, appear to be important vectors. Differences in methodology, aphid biotypes and virus strains prevent direct comparisons between estimates of vector efficiencies obtained for aphids in different countries in north western Europe. M. persicae is also the most efficient vector of potato leafroll virus (PLRV), but some clones ofMacrosiphum euphorbiae transmit PLRV efficiently toNicotiana clevelandii and potato test plants. The removal of infected plants early in the season prevents the spread of PLRV in cool regions with limited vector activity. The proportion of aphids acquiring PLRV from infected potato plants decreases with plant age, and healthy potato plants are more resistant to infection later in the season. Severe symptoms of secondary leafroll developed on progeny plants of cv. Maris Piper derived from mother plants inoculated with PLRV in June or July of the previous year. Progeny plants derived from mother plants inoculated in August showed only mild symptoms, but the concentration of PLRV in these plants was as high as that in the plants with severe symptoms.     

Bacterial diseases of potatoes: from classical phytobacteriology to molecular pathogenicity

Various bacterial pathogens attack potato plants and tubers. These pathogens includeErwinia, Corynebacterium (Clavibacter), Psuedomonas andStreptomyces. Over the past few years there have been significant advances in the molecular biological analysis of several of these pathogens and this is now helping us to understand the major aspects of virulence mechanisms. However, to date, such information is not sufficiently useful to allow us to intervene rationally in these potato diseases, except by the standard practises of good husbandry.     

New genes for disease resistances through somatic hybridization

Somatic hybridization, a process of combining protoplasts from different plants, can provide new sources of disease resistances for plants. In the case of wild and cultivatedSolanum species, the hybrids express resistances from each partner in the fusion and can often be crossed with cultivars to improve agronomic characteristics of the tubers. Restriction fragment length polymorphism (RFLP) analyses can provide a means for determining that the plants being investigated are actually hybrids as well as a means for following the introgression of DNA into progeny lines. These points are addressed in this paper with specific reference to somatic hybrids betweenSolanum brevidens and potato.     

Soil saturation effects on forest dynamics: scaling across a southern boreal/northern hardwood landscape

Patch modeling can be used to scale-up processes to portray landscape-level dynamics. Via direct extrapolation, a heterogeneous landscape is divided into its constituent patches; dynamics are simulated on each representative patch and are weighted and aggregated to formulate the higher level response. Further extrapolation may be attained by coarsening the resolution of or lumping environmental data (e.g., climatic, edaphic, hydrologic, topographic) used to delimit a patch.Forest patterns at the southern boreal/northern hardwood transition zone are often defined by soil heterogeneity, determined primarily by the extent and duration of soil saturation. To determine how landscape-level dynamics predicted from direct extrapolation compare when coarsening soil parameters, we simulated forest dynamics for soil series representing a range of drainage classes from east- central Maine. Responses were aggregated according to the distribution of soil associations comprising a 600 ha area based on local- (1:12,000), county- (1:120,000) and state- (1:250,000) scale soil maps. At the patch level, simulated aboveground biomass accumulated more slowly in poorer draining soils. Different soil series yielded different communities comprised of species with various tolerances for soil saturation. When aggregated, removal of waterlogging caused a 20–60% increase in biomass accumulation during the first 50 years of simulation. However, this early successional increase and the maximum level of biomass accumulation over a 200 year period varied by as much as 40% depending on the geospatial data. This marked discrepancy suggests caution when extrapolating with forest patch models by coarsening parameters and demonstrates how rules used to rescale environmental data need to be evaluated for consistency.     

Expression of natural killer cell stimulatory receptor NKG2D and its ligand MICA in Tibetan patients with gastric cancer at Qinghai plateau

AIM: To investigate the expression of natural killer cell stimulation receptor D(NKG2D) in peripheral blood and the expression of major histocompatibility complex class I chain-related protein A(MICA) on the gastric carcinoma tissue and the neighboring non-cancerous tissue in Tibetan patients with gastric cancer at Qinghai plateau. METHODS: Samples of 33 patients and 20 healthy persons were collected to detect NKG2D in peripheral blood by Flow cytometry analysis. The expressions of MICA in part of the correspondent tissues were examined by RT-PCR and immunohistochemistry.RESULTS: The expression of NKG2D in the plateau of Tibetan patients with gastric cancer group (13.47 ±5.26)% was significantly lower than that in healthy groups (32.62±10.08)%. The mRNA level of MICA in gastric cancer was significantly higher than that in neighboring non-cancerous tissue (P<0.05). The expressions of MICA proteins showed a significant difference between the neighboring non-cancerous tissue (21.21%, 7/33) and the gastric carcinoma tissue (78.79%, 26/33), between the high differentiation (60.00%, 3/5) and the moderate (72.73%, 8/11), low differentiation (88.24%, 15/17). The expressions of MICA were not correlated with tumor size, sex, age, lymph node metastasis of the patients (P>0.05). Spearman rank correlation displayed that the expressions of MICA mRNA were positively correlated with the MICA protein level (r=0.903, P<0.01).CONCLUSION: The immune escape in Tibetan patients with gastric cancer at Qinghai plateau probably relates to the down-regulation of NKG2D and the up-regulation of its ligand MICA. The activity of NK cells and the anti-cancer cellular immunity level are descending in the plateau of Tibetan patients with gastric cancer. The decrease in the receptor NKG2D is a reason for the activity of NK cell descending.     

班主任工作浅析

班主任有一颗永不泯灭的童心；慈祥、体贴学生；诚实、公正、虚心、好学、博识、多才；严于律己,宽以待人.老师从内心里整个地接纳学生,跟学生做知心朋友,随时进行心灵的交流,替学生排忧解难,给学生指点人生道路上的迷津,帮学生树立信心,为学生规划美好的前程,使学生身心得到健康的发展.     

高校大学生党课教育科学化建设之路径探讨

着力推进高校大学生党课教育的科学化建设,是高校党建链条上的一项基础性的重要任务。本文作者以亲历者的视域,概览了高校大学生党课教育在授课内容、方式、师资、教材等方面从认识到实际操作上的诸多科学化诉求,指出高校中蕴藏着大学生党课教育的丰富资源,只要改变思路、整合队伍、改进方法,完全可以使高校党课教育的水平提升一个档次。在理性思考之后,作者提出就地取材,坚持可操作性强的实际举措,意欲打造具有高校品牌特色的大学生党课教育的精品课程。