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1.
The psychophysiological structure of the verbal and nonverbal intelligence of children differing from one another in academic progress has been studied at the initial (six to seven years of age) and the last (nine to ten years of age) stages of studying at primary school. The age-related characteristics of the development and formation of a system of cognitive functions determining the efficiency of verbal and nonverbal activities in schoolchildren differing in academic progress have been determined. It has been demonstrated that the psychophysiological structure of intelligence in six-to seven-year-old and nine-to ten-year-old schoolchildren may characterize the cognitive strategy of their activity and is a criterion for early prediction of learning difficulties and a basis for developing individually oriented approaches to teaching and effective correction programs.  相似文献   

2.
By means of neurohistological and histochemical methods using serial sections of the embryos at the age of 12-30 days of development, the premediatory and beginning of the mediatory stages in development of cholinergic and adrenergic neural plexuses have been studied in rabbit small pelvis. Appearance of catecholamine-containing cells at early mediatory stages and a gradual development and complication of the cholinergic and adrenergic neural plexuses structure are demonstrated. By birth in the rabbit small pelvis area, some elements of cholinergic and adrenergic structures begin to form.  相似文献   

3.
退化草原狼毒个体年龄判定方法及其种群年龄结构的研究   总被引:2,自引:1,他引:2  
邢福  郭继勋  魏春雁 《应用生态学报》2004,15(11):2104-2108
详细观察了内蒙古东部退化草原糙隐子草(Cleistogenes squarosa)群落内狼毒(Stellera chamaejasme)的根颈分枝形态及其生长发育特点,研究了狼毒种群的年龄结构.结果表明,狼毒个体实际年龄为“类二叉分枝(quasi-dichotomous branching)回数加2”;根颈上茎的残茬、枝痕和环状痕是确定根颈分枝回数的重要辅助特征.重牧、过牧、极牧3个放牧演替阶段内狼毒个体最大年龄依次为15、16和19龄.8龄级个体数最多,其年龄比分别为18.71%、24.20%和19.06%.重牧阶段缺失1和2龄个体;过牧和极牧阶段均缺失1龄个体.狼毒种群年龄结构为“初始衰退型”,存活曲线接近于“凸型”或DeeveyⅠ型.老龄组(13龄以上者)个体数在重牧、过牧、极牧演替阶段分别占4.83%、2.84%和14.02%.随着放牧干扰的加剧,狼毒种群年龄结构呈现老龄化趋势.  相似文献   

4.
More than 8,000 roentgenograms and electroroentgenograms of brachial, ulnar, radiocarpal, coxofemoral, knee, talocrural joints have been studied in persons of both sex at the age from birth up to 25 years. The synostosis degree is appreciated by the six-mark system. The roentgenological data are corroborate histologically. The method of appreciation applied makes it possible to reveal cases of initially forming synostosis long before puberty. Three stages of synostosis process are defined. The first stage--slow increase of the synostosis mark. The second--quick synostosis formation. The third--final stage. According to the stages defined, a comparative analysis of the synostosis process in all metaepiphyseal zones of all long tubular bones, peculiarities of the process depending on the sex are demonstrated. The data on the time, when the points of ossification appear, on the beginning and completion of synostosis process in all metaepiphyseal zones of the long tubular bones are presented.  相似文献   

5.
Electron microscopic study of an 18-day-old planulae and primary polyps of the sea pen, Ptilosarcus gurneyi, reveals 14 cell types: sustentacular cell A, sustentacular cell B, nerve cell, sensory cell, cnidoblast, interstitial cell, five types of gland cell (A, B, C, D and E), amoebocyte, style cell and endodermal cell. Of these, 9 are found in the planula, 12 in polyps and 7 are common to both stages. The fine structure of all cell types is described. Since the planulae and polyps in this study were identical in age of development, the gaining and losing of certain types of cells in the polyp are attributed to changes associated with settlement and metamorphosis. Modifications of the seven common cell types during metamorphosis can also be attributed to the change of life style from pelagic to benthic.  相似文献   

6.
阿尔泰狗哇花为根蘖型菊科多年生无性系草本植物.采用主根芽区的繁殖世代数划分分株和芽龄级的方法,研究了松嫩平原杂类草草甸阿尔泰狗哇花无性系种群不同构件的年龄结构.结果表明:分株构件和芽构件均由4个龄级组成.在孕蕾期,分株构件中1龄级占22.6%、2龄级44.8%、3龄级28.8%、4龄级3.8%,呈稳定型年龄结构.在乳熟期,生殖分株构件以2龄级比重最大,占45.6%,4龄级最小,占0.8%,为稳定型年龄结构;而营养分株构件以1龄级比重最大,占47.5%,4龄级最小,占1.1%,为增长型年龄结构.分株主根的生活年限最多为5年.不同生育期分株构件的生产力均以2龄级最高.在乳熟期,1龄级分株具有较大的生产潜力,4龄级分株的生产力已普遍减弱.芽库中潜在种群呈增长型年龄结构.  相似文献   

7.
The purpose of this study is to provide standard echocardiographic and morphometric data for normal mouse valve structure and function from late fetal to aged adult stages. Cross-sectional, two-dimensional and Doppler transthoracic echocardiography was performed in C57BL6 mice anesthetized with 1% to 2% isoflurane at embryonic day 18.5 (late fetal), 10 days (neonate), 1 mo (juvenile), 2 mo (young adult), 9 mo (old adult), and 16 mo (aged adult). Normal annulus dimensions indexed to age or weight, and selected flow velocities, were established by echocardiography. After echocardiographic imaging, hearts were harvested and histological and morphometric analyses were performed. Morphometric analysis demonstrated a progressive valve thinning and elongation during the fetal and juvenile stages that plateaued during adult stages (ANOVA, P < 0.01); however, there was increased thickening of the hinge of the aortic valve with advanced age, reminiscent of human aortic valve sclerosis. There was no age-related calcification. The results of this study provide comprehensive echocardiographic and morphometric data for normal mouse valve structure and function from late fetal to aged adult stages and should prove useful as a reference standard for future studies using mouse models of progressive valve disease.  相似文献   

8.
濒危植物大果木莲种群格局及濒危原因分析   总被引:1,自引:0,他引:1  
采用径级结构代替年龄结构以及方差均值比率法对木兰科(Magnoliaceae)木莲属(Manglietia Bl.)濒危植物大果木莲(Manglietia grandis Hu et Cheng)种群的年龄结构和种群格局进行了研究,并编制了大果木莲种群的特定时间生命表和存活曲线;结合生殖生物学特征以及遗传多样性研究结果,分析了导致大果木莲濒危的主要原因.根据株高和胸径可分别将大果木莲种群的年龄结构分为5级、高度结构分为6级;在大果木莲的5个年龄结构分级中,成年个体较多,幼年个体较少;其高度结构完整,个体高度主要在20 m以下.种群的方差均值比率为0.838 3,其空间分布格局属于随机分布.根据特定时间生命表可将大果木莲种群的发育分为3个阶段:幼树阶段(年龄级为Ⅱ~Ⅲ级)、成树阶段(年龄级为Ⅲ~Ⅳ级)、老树阶段(年龄级为Ⅳ~Ⅴ级),其中成树阶段个体死亡率最低.大果木莲种群存活曲线接近Deevey Ⅰ型,属于衰退型种群.种群自我更新能力差、种子生产力低下、有性生殖困难、生境片断化导致的基因流受限以及人为干扰是大果木莲濒危的主要原因.针对大果木莲濒危现状和致危原因,提出了相应的保护对策和建议.  相似文献   

9.
杨树林带生长阶段与林木分级的研究   总被引:2,自引:0,他引:2  
依据林带的特殊性,结合树木生长发育和林带结构变化规律,将林带生长阶段划分为幼龄期、中龄期(速生期)和防护成熟期3个时期;采用径级离散度、防护成熟龄、更新龄等量化指标,以杨树林带为例,将3个生长时期定量化;同时依据林带树木对防护效益的贡献和树木的生长状况,将林带树木划分为4级;并给出各生长发育时期的相应的经营措施.  相似文献   

10.
A growing requirement exists to determine the ages of the larger African mammals, concomitant with increasing management. Teeth offer the most practicable means of age determination, but no wholly reliable method, based on teeth, has been demonstrated. Tooth structure, growth and function, are considered, and related to methods of age determination. Methods are divided into those separating groups, and those for determining the chronological ages of groups. The various methods used in these two procedures are evaluated. It is pointed out that studies on the most promising method, cementum line counts, have been neglected in Africa, while methods of determining the ages of large carnivores are virtually uninvestigated, and there is a lack of basic studies describing tooth growth and changes for most large African mammals.  相似文献   

11.
黄山松种群结构与动态研究   总被引:1,自引:0,他引:1  
以“空间代替时间”的方法,以种群径级结构代替年龄结构,采用静态生命表和生存分析的方法,探讨了天柱山国家森林公园黄山松种群结构和动态规律。结果表明,随海拔升高,黄山松种群密度增大,径级分布范围减小,种群存活曲线由Deevey-Ⅱ型之间过渡到Deevey—Ⅰ型,种群由稳定型过渡为增长型。表明由低海拔向高海拔,黄山松种群处于不同的演替和发展阶段。  相似文献   

12.
The ovary of the tick Amblyomma triste is classified as panoistic, which is characterized by the presence of oogonia without nurse and follicular cells. The present study has demonstrated that the oocytes in all developmental stages (I-IV) are attached to the ovary through a pedicel, a cellular structure that synthesizes and provides carbohydrate, lipids and proteins supplies for the oocytes during the vitellogenesis process. The lipids are deposited during all oocyte stages; they are freely distributed as observed in stages II, III and IV or they form complexes with other elements. The proteins are also deposited in all stages of the oocytes, however, in lower concentration in the stage IV. There is carbohydrate deposition from oocytes in the stage II as well as in stages III and IV. In addition, the present work has demonstrated that the oocyte yolk of A. triste has a glycolipoprotein nature and the elements are deposited in the following sequence: firstly the lipids and proteins, and finally the carbohydrates.  相似文献   

13.
确定野生动物活体年龄是动物种群生态学研究的一项重要基础工作,然而,迄今为止,没有一种传统方法能高效精准地完成这项任务。岩羊角形态复杂且终身生长,其角形随年龄增长和观察角度变化极大。野外条件下,高效获取岩羊个体年龄信息的唯一方法就是拍摄其角的清晰照片。本研究旨在提出一种利用角形几何特征和计算机视觉技术确定野生岩羊活体年龄的新方法,其原理和操作如下:首先建立覆盖全部年龄段(1.5~15.5岁)的已知年龄羊角实体标本的3D模型(左、右角各22个);再在R程序控制下使其在3D空间中旋转,每旋转1°输出一张角形图片;最后计算每张角形输出图片与待定年龄角照片的形状相似性,找出相似性最高的角形图片对应的3D模型,该3D模型的年龄即为待定年龄羊角的实际年龄。30张已知年龄羊角照片的实验验证结果表明,上述年龄鉴定方法能高效地获得精准结果(准确率达100%)。  相似文献   

14.
The analysis of morphological and morphometrical data of the muscular membrane and its blood microcirculatory bed has demonstrated that their development during the postnatal ontogenesis advances unevenly. An intensified growth and development of the muscular membrane morphological structures, including its blood microcirculatory bed occurs from 3 up to 30 years of life. Their maximal growth is noted from 12 up to 30 years of age. The stages of intensified development of the muscular membrane and its blood microcirculatory bed change into stages of retarded growth, where processes of involutive character preponderate. This is especially noticeable from 60 and more years of age. The stages noticed in the muscular membrane development and its blood microcirculatory bed are characterized both by general and topographical morphofunctional peculiarities specific for every stage of organogenesis.  相似文献   

15.
The structure of variation in human mortality patterns is explored using a five-parameter competing hazards model and standard multivariate taxonomic procedures. The data consist of 281 national life tables representing a wide range of environmental and cultural regions of the world. A general or average age pattern of mortality was generated for the entire sample using multiple regression procedures. A K mean cluster analysis conducted on the residuals of the regression analysis identified seven distinct models of mortality that differ in characteristic ways from the general pattern. Four of the seven clusters have age patterns of mortality similar to the north, east, south, and west regions of the Coale and Demeny model life tables. The remaining three clusters represent regions of the world and age patterns of mortality that are not represented in the Coale and Demeny model life tables.  相似文献   

16.
A method is presented that uses beta-strand interactions to predict the parallel right-handed beta-helix super-secondary structural motif in protein sequences. A program called BetaWrap implements this method and is shown to score known beta-helices above non-beta-helices in the Protein Data Bank in cross-validation. It is demonstrated that BetaWrap learns each of the seven known SCOP beta-helix families, when trained primarily on beta-structures that are not beta-helices, together with structural features of known beta-helices from outside the family. BetaWrap also predicts many bacterial proteins of unknown structure to be beta-helices; in particular, these proteins serve as virulence factors, adhesins, and toxins in bacterial pathogenesis and include cell surface proteins from Chlamydia and the intestinal bacterium Helicobacter pylori. The computational method used here may generalize to other beta-structures for which strand topology and profiles of residue accessibility are well conserved.  相似文献   

17.
A revised method for estimating adult age at death using the auricular surface of the ilium has been developed. It is based on the existing auricular surface aging method of Lovejoy et al. ([1985] Am. J. Phys. Anthropol. 68:15-28), but the revised technique is easier to apply, and has low levels of inter- and intraobserver error. The new method records age-related stages for different features of the auricular surface, which are then combined to provide a composite score from which an estimate of age at death is obtained. Blind tests of the method were carried out on a known-age skeletal collection from Christ Church, Spitalfields, London. These tests showed that the dispersion of age at death for a given morphological stage was large, particularly after the first decade of adult life. Statistical analysis showed that the age-related changes in auricular surface are not significantly different for males and females. The scores from the revised method have a slightly higher correlation with age than do the Suchey-Brooks pubic symphysis stages. Considering the higher survival rates of the auricular surface compared with the pubic symphysis, this method promises to be useful for biological anthropology and forensic science.  相似文献   

18.
Since fluid dynamics plays a critical role in vascular remodeling, quantification of the hemodynamics is crucial to gain more insight into this complex process. Better understanding of vascular development can improve prediction of the process, and may eventually even be used to influence the vascular structure. In this study, a methodology to quantify hemodynamics and network structure of developing vascular networks is described. The hemodynamic parameters and topology are derived from detailed local blood flow velocities, obtained by in vivo micro-PIV measurements. The use of such detailed flow measurements is shown to be essential, as blood vessels with a similar diameter can have a large variation in flow rate. Measurements are performed in the yolk sacs of seven chicken embryos at two developmental stages between HH 13+ and 17+. A large range of flow velocities (1 µm/s to 1 mm/s) is measured in blood vessels with diameters in the range of 25–500 µm. The quality of the data sets is investigated by verifying the flow balances in the branching points. This shows that the quality of the data sets of the seven embryos is comparable for all stages observed, and the data is suitable for further analysis with known accuracy. When comparing two subsequently characterized networks of the same embryo, vascular remodeling is observed in all seven networks. However, the character of remodeling in the seven embryos differs and can be non-intuitive, which confirms the necessity of quantification. To illustrate the potential of the data, we present a preliminary quantitative study of key network topology parameters and we compare these with theoretical design rules.  相似文献   

19.
The F7(1) and F7(2) P-fimbriae of Escherichia coli are encoded by the fso (F seven one) and fst (F seven two) gene clusters, respectively (Van Die et al., 1984; 1985). With the immunocytochemical gold-labelling technique it was demonstrated that both the FsoE and FstE proteins are non-adhesive minor fimbrial subunits located at the tip of the fimbrial structure. The FsoF and FstFG proteins play an important role in the initiation of polymerization of the minor and major subunits into the fimbrial structure.  相似文献   

20.
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