66 resultados para Factorizations of Groups
em Chinese Academy of Sciences Institutional Repositories Grid Portal
Resumo:
Habitat fragmentation usually results in alteration of species composition or biological communities. However, little is known about the effect of habitat fragmentation on the fig/fig wasp system. In this study, we compared the structure of a fig wasp community and the interaction between figs and fig wasps of Ficus racemosa L. in a primary forest, a locally fragmented forest and a highly fragmented forest. Our results show that, in the highly fragmented forest, the proportion of pollinator wasps is lower and the proportion of non-pollinator wasps is higher compared with the primary forest and locally fragmented forest. The proportion of fruits without pollinator wasps in mature fruits is also greatly increased in the highly fragmented forest. The proportion of galls in all female flowers increases in the highly fragmented forest, whereas the proportion of viable seeds does not change considerably. The disruption of groups of fig trees results in a decrease in pollinator wasps and even might result in the extinction of pollinator wasps in some extreme cases, which may transform the reciprocal interaction between figs and fig wasps into a parasite/host system. Such an effect may lead to the local extinction of this keystone plant resource of rain forests in the process of evolution, and thereby, may change the structure and function of the tropical rain forest.
Resumo:
The black-crested gibbon, Hylobates concolor, is one of the few species of gibbons that has not yet been the subject of a long term field study. Field observations in the Ai Lao and Wu Liang Mountains of Yunnan Province, China indicate that in this area the habitat and ecology of this species differ markedly from those of other gibbons that have been studied to date. These differences are correlated with some behavioral differences. In particular, these gibbons apparently have greater day ranges than other gibbons. It has also been suggested that this species lives in polygynous groups. To demonstrate this requires observation of groups with two or more females with young. Our own observations and those from other recent studies suggest that there are alternative explanations consistent with available data.
Resumo:
The thermosetting polyimide PMR-I5 and its blends with thermoplastic polyimides have been studied by dynamic mechanical analysis. The results obtained indicate that the level of beta relaxations in PMR-15 are increased with an increase in cross-linking density. This phenomenon is interpreted as a change of chemical structure during the cross-linking process. Addition of thermoplastic polyimide makes the magnitude of beta relaxations increase when PMR-15 is the major component. This might be due to the strong intermolecular charge-transfer interaction between PI and PI or PMR-15 and PMR-15 molecular chains being partly replaced by the weak intermolecular interaction between PI and PMR-15 in PMR-15/PI blends, resulting in some phenylene rings or imide groups in PIs and PMR-15 chains being able to participate in beta relaxation. However, this increment in beta relaxation magnitude can be reduced by heat treatment of the sample, as a result of phase separation. Hence, it is concluded that the beta relaxation magnitude is determined by the number of groups which can participate in relaxation per unit length, i.e. the magnitude of beta relaxation increases with decreasing interaction between the molecular chains. Copyright (C) 1996 Elsevier Science Ltd
Resumo:
In this work PTFE sheets irradiated with gamma-rays at 150-degrees-C and 200-degrees-C were studied using x-ray photoelectron spectroscopy (XPS). The main structural changes in PTFE due to radiation are the formation of CF3 and CF groups. An irradiation temperature dependence of the relative content of the three kinds of groups in irradiated PTFE was observed. The CF3 groups, especially when irradiation is carried out a lower temperatures, can defluorinate in the same manner as previosly reported for CF2 groups. The CF groups, on the other hand, are observed to increase with increasing irradiation dose and irradiation temperature; the latter was explained as due to an increase in branching structures.
Resumo:
Classical fracture mechanics is based on the premise that small scale features could be averaged to give a larger scale property such that the assumption of material homogeneity would hold. Involvement of the material microstructure, however, necessitates different characteristic lengths for describing different geometric features. Macroscopic parameters could not be freely exchanged with those at the microscopic scale level. Such a practice could cause misinterpretation of test data. Ambiguities arising from the lack of a more precise range of limitations for the definitions of physical parameters are discussed in connection with material length scales. Physical events overlooked between the macroscopic and microscopic scale could be the link that is needed to bridge the gap. The classical models for the creation of free surface for a liquid and solid are oversimplified. They consider only the translational motion of individual atoms. Movements of groups or clusters of molecules deserve attention. Multiscale cracking behavior also requires the distinction of material damage involving at least two different scales in a single simulation. In this connection, special attention should be given to the use of asymptotic solution in contrast to the full field solution when applying fracture criteria. The former may leave out detail features that would have otherwise been included by the latter. Illustrations are provided for predicting the crack initiation sites of piezoceramics. No definite conclusions can be drawn from the atomistic simulation models such as those used in molecular dynamics until the non-equilibrium boundary conditions can be better understood. The specification of strain rates and temperatures should be synchronized as the specimen size is reduced to microns. Many of the results obtained at the atomic scale should be first identified with those at the mesoscale before they are assumed to be connected with macroscopic observations. Hopefully, "mesofracture mechanics" could serve as the link to bring macrofracture mechanics closer to microfracture mechanics.
Resumo:
IQ Structure, Psycholinguistic and Visual-motor Abilities Study on Children Learning Disability TONG Fang Directed by professor Zhu Liqi (Developmental and educational psychology) ABSTRACT Objective To comprehensive analyze the IQ structures, and relationships among IQ, psychometric characteristics and visual-motor integration on children disability. At same time, to probe into the family factors that influenced IQ, psycholinguistic abilities and behavior of LD children. Method (1) Downloading the papers on children learning disability from www.cqvip.com and www.wanfangdata.com, in which, the articles were collected by key words from 1985 to 2005. To conduct meta-analysis on IQ construction, compare the case group and the control group, including full IQ, verbal and practice IQ. (2) Designed with model compared and self-compared, 59 diagnosed learning disability children, tested themes with WISC, ITPA and Berry’s VMI. WISC included 10 items, 5 of which subtotal to verbal and practice IQ respectively. IPTA included 10 items, too, 5 process of which subtotal to auditory and visual perception. The first 3 items shared representation level, the other 2 of that shared automatic level.VMI had one score. Analyzed factors and levels with description and Pearson Correlation. To probe to linguistic internal alternately functions of LD children, and compare the scores of groups in different IQ. (3) Analyzed the perspective questionnaire filled by parents. Early development facts compared with model groups. Factors relationships analyzed with Kendall correlation, KOM and Bartlett’s test of sphericity, Promax Rotation. Results: (1) There have been 319 papers related with LD, in which 36 with IQ and 14 valid reports have been analyzed by Meta. FIQ’s 95%CI (confidence interval) is 2.418 ~ 0.172, VIQ between the difficulty and non- difficulty group. C-WISC-R reports were 10 papers, of which, 95%CI of FIQ is 2.424 ~ 0.676, of VIQ is 2.314 ~ 1.196, of PIQ is 2.176 ~ 0.176. The VIQ comparing the PIQ, 95%CI is 1.1 ~ -0.07 in difficulty group and 0.5 ~ -0.0046 in non-difficult group. Nevertheless, in the other 4 tests, FIQ’s 95%CI is 2.00 ~ -0.818 between LD and NLD. (2) Children psycholinguistic abilities had strong relation with Berry’s VMI test excluding auditory reception, and with perceptive factor of intelligence excluding verbal expression. Auditory reception and visual closure had strong relation with FIQ and PIQ. Grammatic closure, visual association and manual expression had strong relation with concept factor. The representational and automatic levels are depended on integration of auditory and visual procession. Lower verbal expression (VE) let to lower expression process and low scores on representational level. Lower visual sequential memory (VSM) let to lower memory process and influenced automatic level. Groups compared by IQ 90 show that LD children with under IQ 90 had lower scores on items of IPTA than with up IQ 90 excluded verbal expression. It was proved that IQ administrated the linguistic ability. Nevertheless, general abilities deficiency didn’t show influencing on the types of the perceptive delay. There was mutual function among linguistic ability on LD children. Auditory and visual level are overlapped each other. Not only show higher Decoding and lower Encoding on Auditory perception, lower Decoding and higher Encoding on Visual perception, in representation, but also higher Sequential remember, lower Closure on Audition, and lower Sequential member, higher Closure on Vision, in Automation. Nevertheless, there was no different between Representational and Automatic level, which may be the relationship of parallel or evolution. (3) Major family factors were father’s education, occupation. Lower auditory perception related to unconcerned, lower visual perception related to premature delivery and written slowly. Threatened–abortion, childbirth-suffocated were known as influencing children’s IQ and later linguistic abilities. It wasn’t shown that dosage relationship with the types of perceptive delay. Conclusion: (1) The FIQ, VIQ and PIQ of Children with LD is lower than that of NLD group. There is no significantly different between VIQ and PIQ in LD and NLD groups. (2) The objectives of ITPA and WISC tests are differently. The psycholinguistic abilities had strong relation with perceptive factor and VMI. Some facts of IPTA related with FIQ. IQ had strong administration on linguistic abilities. There was mutual function among linguistic internal abilities. (3) Family facts on IQ and psycholinguistic abilities were Father’s education, abnormal pregnant and abortion. It would be pre-show development delay in early period.
Resumo:
The aggressive behavior and the violent crime of the Adolenscents have aroused social widespread attention. The Social Implicit Cognition Method could overcome the insufficiency of explicit research methods such as Self-Report Scale, and carry on the thorough discussion to the intrinsic mechanism of the Adolenscent’s aggressive behavior. In this research, Implicit Association Test and Explicit Questionnaire are synthetically applied to inspect the relations among the aggression, Evaluation of Emotion Regulation and the aggressive behavior of the normal middle-school students and the Adolenscent violent criminals under the explicit and implicit conditions, and have carried the supplement to the internal condition of the General aggression model (GAM). The result indicates, 1. The concept of implicit aggression exists independently and separates from explicit aggression. However the relations between implicit aggression and the groups are remarkable, i.e. both the implicit and explicit aggressions of the Adolenscent violent criminals are remarkably higher than those of the normal middle-school students, but not influenced by sex factors. 2. Implicit Evaluation of Emotion Regulation is suitable to Chinese Adolenscents. The correlation of groups and sex factors exist to Implicit Evaluation of Emotion Regulation, i.e. in the group of criminals, the female inclines to the mood control compared with the male in the aspect of Implicit Evaluation of Emotion Regulation; however, in the group of normal persons, the difference between male and female is not remarkable in the aspect of Implicit Evaluation of Emotion Regulation. 3. Under the explicit conditions, it is discovered that the remarkable explicit aggression can predict violent criminals. But it is adjusted by Explicit Evaluation of Emotion Regulation, i.e. the predicting function is not remarkable when the Explicit Evaluation inclines to expression. Meanwhile, when checking the functions and the effects of the implicit variables after the explicit conditions are under control, it is discovered that the predicting function of implicit aggression is still remarkable, and the predicting function of Implicit Evaluation of Emotion Regulation is remarkable at the edge and also adjusted by sex factors. These findings help us not only understanding thoroughly the intrinsic mechanism of the Adolenscent’s aggressive behavior, discovering the moderating role of Evaluation of Emotion Regulation on aggression, but also providing an academic foundation on the prevention and intervention of the Adolenscent’s aggressive behavior.
Resumo:
A series of zinc tellurite glasses of 75TeO(2)-20ZnO-(5-x)La2O3-xEr(2)O(3) (x=0.02, 0.05, and 0.1 mol%) with the different hydroxl groups were prepared by the conventional melt-quenching method. Infrared spectra were measured in order to estimate the exact content of OH- groups in samples. The observed increase of the fluorescence lifetime with the oxygen bubbling time has been related to the reduction in the OH- content concentration as evidenced by IR transmission spectra. Various nonradiative decay rates from I-4(13/2) of Er3+ with. the change of OH content were determined from the fluorescence lifetime and radiative decay rates were calculated on the basis of Judd-Ofelt theory. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
A series of five different concentration erbium-doped tellurite glasses with various hydroxl groups were prepared. Infrared spectra of glasses were measured. In order to estimate the exact content of OH- groups in samples, various absorption coefficients of the OH- vibration band were analyzed under the different oxygen bubbling times. The absorption spectra of the glasses were measured, and the Judd-Ofelt intensity parameters Omega(i) of samples with the different erbium ions concentration and OH- contents were calculated on the basis of the Judd-Ofelt theory. The peak stimulated emission cross-section of (I13/2 ->I15/2)-I-4-I-4 transition of the samples was finally calculated by using the McCumber theory. The fluorescence spectra of Er3+:I-4(13/2)->I-4(15/2) transition and the lifetime of Er3+:I-4(13/2) level of the samples were measured. The effects of OH- groups on the spectroscopic properties of Er3+ doped samples with the different concentrations were discussed. The results showed that the OH- groups had great influences on the Er3+ lifetime and the fluorescence peak intensity. The OH- group is a main influence factor of fluorescence quenching when the doping concentration of Er2O3 is smaller than 1.0 mol%, but higher after this concentration, the energy transfer of Er3+ ions turns into the main function of the fluorescence quenching. And basically, there is no influence on the other spectroscopic properties (FWHM, absorption spectra, peak stimulated emission cross section, etc.).
Resumo:
Because of the influence of OH groups in phosphate glasses on the radiation of rare-earth ions, the laser performance is degraded. The laser efficiency and the small signal gain experiment of several phosphate glass samples have been done, the concentration of OH groups in glasses was calculated from the measured absorption coefficient at 3.47 μm. It is shown that the concentration of OH groups in phosphate glasses can seriously influence the laser output characteristics, and the OH groups have worse influence on the laser amplifier than laser oscillator.
Resumo:
The 9-bp deletion in the COII/tRNA(Lys) intergenic region (region V) of human mitochondrial DNA was screened in 1521 Chinese from 16 ethnic groups and 9 Hen geographic groups. The highest frequency was found in populations of Miao (32.4%) and Bouyei (30.8
Resumo:
Previous studies have shown that there were extensive genetic admixtures in the Silk Road region. In the present study, we analyzed 252 mtDNAs of five ethnic groups (Uygur, Uzbek, Kazak, Mongolian, and Hui) from Xinjiang Province, China (through which the