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Recent behavioral genetic research has shown that genetic propensities are associated with individual differences in experiences, and thus, what may appear to be environmental effects can reflect genetic influence. This study examines passive genotype-environment correlations (GECs) for language-related abilities by comparing environment-child language associations in adoptive and nonadoptive families. The results provide evidence for the genetic mediation of the association between home environmental variables, such as the provision of toys and games, maternal involvement, and degree of intellectual/cultural orientation with children's language-related abilities. Developmental changes in passive GECs are considered, and the implications for typical and atypical learners are discussed. 相似文献
64.
The mechanism and criterion of crack initiation and propagation of rocks were investigated by many researchers,And the creep behaviour of rocks was also theoretically and experimentally studied by some scientists and engineers.The characteristics of crack initation and propagation of rocks under creep condition.however,are very improtant for rock engineering and still not paid enough attention by researchers,In this paper,the criterion and mechanism of crack initiation and propagation under creep condition were investigated using specimens collected from sandstone rock formations outcropping in the Emei Mountain,the Sichuan Province of China.Cuboid specimens under three point bending were used in this investigation.All specimens were classified into four sorts and used for Mode-I fracutre of creep frcture tests.The experimental result shows that due to creep deformation.rock crack will inevitably initialt and propagate under a load of KI,which is less than fracture toughness KIC but not less than a constant(marked as KIC2),KIC2 indicates the ability of rock to resist crack initiation and propagation under creep conditions and is less than fracture tough ness KIC.defined as creep fracture toughness in this paper,KIC2 should be considered as an importnat parameter on design and computation of rock engineering.The microstructureal mechanism for crack initiation and propagation of rock materials under creep condition was introduced based on competitive model between softening effect and hardening effect,and the validity of test result was explained.The test result was also verified in rheological theory.When KI is more than KIC2 but less than KIC,rock crack will initiate and propagate after a time interval of sustained loading under creep condition.In order to find the relation between duration of sustained lading.which can lead to crack initiation and propagation,and the initial stress intensity factor KI,an unequal0interval time sequence forecasting and predicting model was introduced,and the relation was obtained for homogeneous and isotropic fine-grained red sandstone.Finally a modified fracture toughness formula was given,in which the influence of fracture process zone(FPZ) was fully considered. 相似文献
65.
B. Z. Sandler 《European Journal of Engineering Education》2002,27(2):157-172
Engineering education has recently been going through a process of internal fighting between the tendency to introduce more and more information and skills in the fields of computerization and mathematics (mathematics for engineers), on the one hand, and the need to provide the student with pure empirical technical and design knowledge and experience, on the other hand. In most mechanical engineering departments, the outcome of this competition has been a reduction in the time allotted to teaching the empirical part of engineering information: there is often a psychological barrier to understanding the importance of this group of subjects, and the computer- and mathematics-associated subjects usually win out. As a result, the new graduate usually knows how to fight the computation struggle but he/she is not able to formulate his/her final engineering goal. This paper focuses on various aspects of this situation. In particular, we set out to defend the need for serious and in-depth teaching of the empirical information required in engineering design work. 相似文献
66.
PaulZ.PerJes 《中国现代教育装备》2004,(6):40-41
什么是教育装备?这个问题看似简单,却并不是那么容易回答.教育装备的使用者,制造者及其相关人员都有着见仁见智的想法.如何看待这一问题,无论对于企业还是教师、学生都有重要的意义.教育界的专家与教育装备有着亲密接触,下面就来听听他们的声音吧. 相似文献
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M. Shafi M. Zargar Z. A. Shah M. Salahuddin M. Siddiqi 《Indian journal of clinical biochemistry : IJCB》1998,13(2):106-110
Serum and urine samples from 513 patients clinically suspected of monoclonal gammopathies over a period of five years (1992–97)
were subjected to various immunological procedures viz, electrophoresis, immunoelectrophoresis and immunoglobulin estimations.
Laboratory investigations confirmed gammopathies in 10.33%. It was observed that overall age of incidence for monoclonal gammopathies
in both sexes was between 42–72 years with a male to female ratio of 1.4∶1. Predominant paraprotein detected was IgG type
(75.47%) followed by IgA (16.98%) and Bence Jones proteins (7.55%). Amongst positive patients, 64.16% were having kappa (k) type light chains and 35.84% lambda (δ) type light chains. 69.39% patients with serum M component (IgG and IgA) had Bence
Jones proteinuria. Densitometric scanning revealed that majority of IgG type paraprotein was found in the slow gamma globulin
region and majority of IgA type paraprotein was found equally distributed between beta and fast gamma globulin regions. Both
types had decreased albumin and alpha-2-globulin concentrations as compared to normal controls. Immunoglobulin levels in patients
with paraprotein had very high levels of serum IgG (6467.0 mg%) and IgA (2714.0 mg%) in respective types of monoclonal gammopathies;
the rest of immunoglobulin classes were either at normal or decreased levels. 相似文献
69.
The educational and developmental needs of children with disabilities in general, and of children with vision impairments in particular, have been ignored until recently in the Sultanate of Oman. However, the situation of special education and rehabilitation services is changing and there is progress to report. This article presents an overview of the prevalence and patterns of vision impairment, types of services offered, and priorities for future work. 相似文献
70.
D. VEKSTEIN A. MEHREZ Z. LASLO A. SOLOMON 《European Journal of Engineering Education》1999,24(1):95-104
This paper focuses on the current situation of engineering education in Israel, the debate over the ways to manage it, and the prospects that a balanced education policy can entail for socio-economic development. Two degrees in engineering, the BTech and BSc, are described. It transpired that the BTech failed to meet the expectations. From the on-going debate about the situation, the need for a balanced policy for engineering education has emerged. This policy is outlined and it is shown that it can not only improve the BTech situation, but also Israel's national innovation system by viewing ‘research’ and ‘applied’ engineers as complementary to, rather than competing with, each other. It is also suggested that this balanced policy should implement project-based instruction in the engineering curriculum, both in the BTech and BSc programmes. 相似文献