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1.
Determination of window size for analyzing DNA sequences   总被引:4,自引:0,他引:4  
Summary DNA sequences are generally not random sequences. To show such nonrandomness visually, DNA sequence data are often plotted as moving averages for a certain length of window slid along a sequence. Here a simple algorithm is presented for determining the window size and for finding a nonrandom region of sequence.  相似文献   

2.
Agricultural field crops differ in their vegetation height, coverage, and temporal development, affecting the abundances of bird species, which are often used as bioindicators. Although this relationship has been observed, no significant methodology exists to describe the dynamics of field crop growth on a landscape scale in connection with the abundance of indicator bird species that allows meaningful interpretation of bird abundance data with respect to crop vegetation parameters during the breeding season. In a field observation program, we monitored 2,900 ha of agricultural landscape to represent both the crop growth processes and the bird abundances. We measured these two parameters in the study area, dominated by winter wheat, winter rapeseed, maize, and fallow fields, and adapted the moving window approach to a new method of “moving window growth” to describe the dynamic development of height and coverage of the crops over time. Simultaneously, Skylarks (Alauda arvensis) territorial behavior was measured concurrently on the same fields and crops. Their dynamic abundance was documented over the breeding season. To test the relationship between crop growth and development and bird abundance, we applied a generalized linear model (GLM) in two ways: (a) without differentiation of crop species and (b) with differentiation of crop species. We found significant relationships between bird abundance and vegetation height and coverage with respect to both individual parameters and their interactions, even without differentiation of the agricultural crops. In general, increasing vegetation height and coverage, especially the interaction, led to decreasing bird abundance values. The model quality increased significantly by including differentiation of specific crops as an explanatory variable indicating a non‐homogenous situation between crops. Separate models for individual crop species revealed larger differences in model quality with best and least goodness of fit values for fallow fields and winter rapeseed, respectively. Because of the clear interactions between bird abundance, type of field crop, and vegetation height and coverage, it follows that both habitat suitability assessments of arable fields and the definition of favorable vegetation structures for farmland birds should be crop species‐specific.  相似文献   

3.
胚泡着床窗口的分子调控   总被引:5,自引:0,他引:5  
着床窗口是指当胚胎发育到胚泡阶段时,子宫也增殖和分化到可接受状态,二者相互作用使胚泡着床的短暂时间.雌激素和孕酮是该过程的综合调控分子,它们通过多种局部信号分子的介导,使子宫中的各种细胞类型增殖、分化,为着床窗口的开放做出相互协调的反应.子宫与胚胎在着床窗口通过前列腺素、组织胺、降钙素、多种细胞因子和生长因子的旁分泌作用进行分子对话,使胚泡滋养层与子宫内膜上皮发生附着反应.着床窗口一旦开放,即自动向非接受态转化.  相似文献   

4.
采用适宜的参数,从豚鼠园窗记录出一种新的听觉40Hz相关电位,它不同于Galambos提出的听觉中潜伏期40Hz相关电位。通过不同部位引导的对比观察,对该电位的基本特征、影响因素及其可能发生机理进行了初步探讨,结果显示40HzAERP-ELR波形稳定,振幅高,频率响应好,反应阈值低。在0.5kHz短纯音的反应阈值为13.75dBnHL,较颅顶的听觉中潜伏期40Hz相关电位低35dBnHL。  相似文献   

5.
目的:获取不同黑色素瘤发展阶段的荷瘤鼠的最佳治疗时间以及最佳用药量。方法:将肿瘤大小不等的雄性黑色素瘤荷瘤鼠进行内皮抑素分组对比治疗,在用药3、5、7天后处死荷瘤鼠,剥离瘤体,称瘤重,分析生长趋势,做病理切片并进行HE染色和免疫组化。在与对照组进行对照后,根据肿瘤的大小、恶性化的程度以及CD31和VEGF的表达情况,找出内皮抑素的用药最有效的治疗时间窗。然后通过进一步实验,在已经检测出的不同肿瘤大小的荷瘤鼠的恩度作用时间窗内,给荷瘤鼠使用用不同浓度梯度的药物,在不同肿瘤发展大小之后剥离瘤体,做与上述类似的操作并分析,确定在治疗时间窗时的恩度使用的最佳剂量。结论:5天为内皮抑素抗黑色素瘤血管新生时间窗,两个实验组中,中等剂量即15 mg/kg和20 mg/kg为恩度作用最佳剂量。  相似文献   

6.
寡聚蛋白质广泛地参与多种生命活动,对其预测研究有重要的意义。文章从蛋白质序列出发,提出多策略滑动伸缩窗特征提取方法,采用“ 一对一”的多类分类策略,对蛋白质同源寡聚体进行预测研究。结果表明,在Jackknife检验下,基于支持向量机的多策略滑动伸缩窗特征和氨基酸组成成分构成的特征集在加权情况下,其总分类精度最高达到了75.37%,比单纯的氨基酸组成成分法提高10.05%,比参考文献最好特征BG_Zhang提高了3.82%。 说明多策略滑动伸缩窗特征提取方法对于蛋白质同源寡聚体分类,是一种非常有效的特征提取方法。  相似文献   

7.
提出一种新颖的方案使蛋白质结构信息可视化。在滑动窗口方法基础上,每一个天然氨基酸采用从氨基酸索引数据库中挑选的48种特性参数描述,在某一特定窗口下的所有氨基酸残基的参数就组成一个矩阵,通过矩阵变换得到一个方矩阵,再经过窗口的滑动就得到基于整个蛋白质的所有这些窗口矩阵的本征值矩阵。对本征值矩阵元素作图得到一系列的本征值曲线,这种曲线的轮廓不随窗口的变化而变化,这些曲线被称为蛋白质的特征曲线。为选择合适的窗口宽度、对同一类型蛋白质不同窗口宽度及不同类型蛋白质相同窗口宽度下的本征值矩阵进行了比较研究,对其潜在的用途进行了讨论。  相似文献   

8.
A newborn female with partial trisomy for the distal part of the long arm of the chromosome 14 (14q24 --> qter) resulting from a paternal balanced translocation (3;14) is described. We compare her phenotype with eight other individuals with trisomy 14q24 --> qter.  相似文献   

9.
Reddy KV  Mangale SS 《Tissue & cell》2003,35(4):260-273
Cell-cell and cell-extracellular matrix (ECM) interactions play a critical role in various developmental processes, including differentiation, proliferation and migration of cells. ECM proteins can influence cellular function thus creating a complex feedback mechanism. The adhesion of cells to each other, their ECM proteins and endothelial surfaces is mediated by a variety of membrane proteins collectively known as adhesion molecules. Adhesion molecules have been further divided into five subfamilies, the integrins, the selectins, the cadherins, the mucins and the immunoglobulin superfamily. Members of the integrin family of cell surface adhesion receptors are important mediators of cell-ECM contact. Integrin receptors are alpha beta heterodimers with a transmembrane segment, a short cytoplasmic domain and a large extracellular domain. The role of integrins in reproduction has been established. Several reasons make these molecules very attractive due to their constant involvement from egg to birth. They participate in sperm-egg interaction, fertilization, implantation and placentation in many species including humans. Integrins provide signals to individual cells essential for growth and development of different tissues. In the present review, we describe (1) the regulatory pathways for controlling expression of integrins in the endometrium, (2) various biomarkers and their role in endometrial function, (3) reproductive disorders in women related to aberrant integrin expression in the endometrium and (4) the functional significance of integrins available from gene knockout studies.  相似文献   

10.
11.
Robert Kr?ger 《生态学报》2010,30(5):280-287
Wetlands are major sources of habitat heterogeneity, with certain environmental variables controlling wetland structure and composition. There is very little information on the heterogeneity of ephemeral floodplain wetland patch mosaics and how hydrogeomorphic circumstance affects composition and structure. Structure (wetland size) and composition (herbaceous species) are two attributes of an ephemeral wetland that are easily quantifiable using a moving window analysis. The moving window analysis is a statistical technique that identifies significant changes in parameters (i.e., structure and composition) along gradients. An analysis of changes in wetland structure and composition longitudinally identified two hydrogeomorphic types and laterally delineated wetland boundaries. The wide–flat type had a wide (131.2 ± 50.4 m) wetland patch and a mean lateral slope of 0.008 ± 0.003, in contrast the narrow–deep type had a significantly smaller (80 ± 40.2 m) and steeper (0.048 ± 0.06) wetland patch. Changes in hydrogeomorphology had distinct effects on the species composition of the wetland. Facultative wetland species such as Sporobolus pyrimidalis and Ischaemum afrum were associated with the wide–flat type, while, the narrow–deep type was characterized by more obligate, flood dependent species such as Phragmites australis, Mariscus congestus, and Eriochloa meyeriana. Internally, the structure and composition of ephemeral wetlands on the northern plains of Kruger National Park were spatially heterogeneous and correlated to hydrogeomorphic conditions, that are identifiable when examined at the wetland scale. Results add knowledge to wetlands as sources of landscape heterogeneity and highlight how environmental variation can result in increases in wetland heterogeneity.  相似文献   

12.
Robert Krö  ger 《农业工程》2010,30(5):280-287
Wetlands are major sources of habitat heterogeneity, with certain environmental variables controlling wetland structure and composition. There is very little information on the heterogeneity of ephemeral floodplain wetland patch mosaics and how hydrogeomorphic circumstance affects composition and structure. Structure (wetland size) and composition (herbaceous species) are two attributes of an ephemeral wetland that are easily quantifiable using a moving window analysis. The moving window analysis is a statistical technique that identifies significant changes in parameters (i.e., structure and composition) along gradients. An analysis of changes in wetland structure and composition longitudinally identified two hydrogeomorphic types and laterally delineated wetland boundaries. The wide–flat type had a wide (131.2 ± 50.4 m) wetland patch and a mean lateral slope of 0.008 ± 0.003, in contrast the narrow–deep type had a significantly smaller (80 ± 40.2 m) and steeper (0.048 ± 0.06) wetland patch. Changes in hydrogeomorphology had distinct effects on the species composition of the wetland. Facultative wetland species such as Sporobolus pyrimidalis and Ischaemum afrum were associated with the wide–flat type, while, the narrow–deep type was characterized by more obligate, flood dependent species such as Phragmites australis, Mariscus congestus, and Eriochloa meyeriana. Internally, the structure and composition of ephemeral wetlands on the northern plains of Kruger National Park were spatially heterogeneous and correlated to hydrogeomorphic conditions, that are identifiable when examined at the wetland scale. Results add knowledge to wetlands as sources of landscape heterogeneity and highlight how environmental variation can result in increases in wetland heterogeneity.  相似文献   

13.
14.
围堤式颅窗大鼠软脑膜微循环观察方法   总被引:5,自引:0,他引:5  
本文介绍了本室建立的围堤式颅窗软脑膜微循环观察方法。大鼠暴露颅骨,顶骨钻孔后,固定一根4号头皮针于骨孔边缘,将牙托粉、牙托水调匀后于骨孔周围围一个环形堤,根据需要硬脑膜可以保持完整或剥去。经头皮针持续向颅窗内输恒温人工脑脊液(aCSF),并维持颅窗内aCSF的pH值和Pco2于正常水平。颅窗内数毫米厚的aCSF将外界隔开,使脑组织和软脑膜处于较好的生理环境。围堤式颅窗简便易行,并可达到与密闭颅窗相似的效果。  相似文献   

15.
16.

1. 1. Two-dimensional numerical analysis is carried out on the thermal structure in an empty heated room of actual size under a steady state.

2. 2. Three types of heater, floor heating, side-wall heating and hot-air heating were used.

3. 3. The thermal structure in a room formed by each heating type is investigated in consideration of the energy transfer through the window of the room.

4. 4. The results indicate that floor heating is most suitable in a room without window from a viewpoint of the thermal comfort.

5. 5. In a windowed room, it is desirable that a heater should be located by the side of the window to prevent the cold draft.

Author Keywords: Heating; numerical analysis; room thermal environment; window  相似文献   


17.
脑梗死是一种常见的神经系统疾病,具有高发病率、高死亡率和高致残率的特点,给患者及家庭带来巨大的痛苦和经济负担,它已成为当代医学界重要的研究课题。脑梗死的治疗直接影响患者的预后,因此寻找最有效的治疗药物及方法是非常重要的。目前,在急性脑梗死溶栓治疗方面国内外已经开展了大量的实验研究,取得了良好的实验结果。本文就急性脑梗死溶栓治疗的时间窗、溶栓方法、溶栓药物及影响因素等方面进行了总结及展望。  相似文献   

18.
19.
The transportation sector, particularly the road and the railway sectors, is an important source of CO2 emissions in China. This study combines the non-radial data envelopment analysis (DEA) model with window analysis to measure the energy-environment efficiency of the road and railway sectors of 30 provinces in China, then uses the Tobit regression model to analyze the factors affecting the energy-environment efficiency. The findings suggest that, first of all, although these two sectors are both with high energy-environment efficiency, there is a higher probability for railway sector to improve its energy-environment efficiency than that of road sector, with the average energy-environment efficiency 0.9307 and 0.9815, respectively. Second, the road sector in eastern China with the highest average energy-environment efficiency, lower in the western region, and lowest in the central region. As for the railway sector, the western region has the highest average energy-environment efficiency, followed by the central and the eastern regions. Third, the relationship between energy-environment efficiency and income level in the road and railway sectors follow the U-shaped and inverted U-shaped curves, respectively.  相似文献   

20.
目的:通过经胸超声心动图获取胸骨右缘升主动脉长短轴切面观察Stanford A型主动脉夹层患者的升主动脉结构,探讨对该类患者进行检查时该切面的应用价值。方法:31例经CTA或手术证实为A型主动脉夹层的连续性患者,超声心动图检查除常规通过胸骨左缘切面观察升主动脉结构外,均做胸骨右缘切面以进一步观察升主动脉结构,包括最大内径,有无撕脱内膜及内膜活动情况,同时应用常规胸骨左缘切面和胸骨右缘切面对A型主动脉夹层能够清晰显示出的病例比例加以比较。结果:胸骨左缘切面能够清晰显示升主动脉结构9例,占比例29%。胸骨右缘切面能够清晰显示升主动脉结构20例,比例65%。将两种切面结合能够清晰显示升主动脉结构的比例升高到74%。胸骨右缘肋间切面测得的升主动脉最大径线数值与CTA结果的一致性更好。结论:胸骨右缘肋间切面对A型主动脉夹层显示的清晰度更好,有助于临床诊断,具有重要的参考价值,值得临床广泛推广。  相似文献   

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