Young children's causal inferences   总被引：1，自引：0，他引：1  

P Das Gupta  P E Bryant 《Child development》1989,60(5):1138-1146

We report 2 experiments that show a striking development between the ages of 3 and 4 years in children's ability to make causal inferences about sequences of events. The task in the first experiment was to work out what had caused the change to an object that started out as odd (noncanonical) in 1 way and ended up as odd in 2 ways--starting, for example, as a broken cup and ending as a wet and broken cup. When asked to choose the instrument that had caused the change, 3-year-olds often selected the instrument that could have caused the initial state (a hammer, in our example) and not the instrument that would produce the change. 4-year-olds hardly ever made this mistake. In the second experiment, the 3-year-olds were able to make the correct choice when the change was from a canonical to a noncanonical state (cup-wet cup) but had much more difficulty when the change was from noncanonical to canonical (wet cup-dry cup). The difference was much smaller in the older group. The first of these tasks can be solved simply on the basis of knowledge that a particular instrument can cause a particular effect without reference to the initial state. The second task requires attention to the differences between initial and final state. We conclude that the ability to make genuine causal inferences develops between the ages of 3 and 4 years.  相似文献   

The madelung constant of the sodium chloride crystal lattice     

Sourav Das 《Resonance》2003,8(10):76-84

An analysis of the Madelung constant of the sodium chloride crystal lattice has been made, in an effort to supplement information available in undergraduate textbooks. A method of approximation of the constant using the personal computer is presented. An erratum to this article is available at .  相似文献   

What is a Species? An endless debate     

Uttam Saikia  Narayan Sharma  Abhijit Das 《Resonance》2008,13(11):1049-1064

Everybody is familiar with the ubiquitous term ‘species’. But what is a species? Undeniably, this is one of the most complex dilemmas in the history of biology. There is no other concept in biology as elementary yet controversial as the concept of species. In practice, a species is regarded as the fundamental unit of comparison in all biological disciplines like systematics, evolution, ecology, ethology, physiology, and genetics. However, little agreement exists in the scientific community regarding the nature of species, whether it is a real entity or a cultural artifact, its biological significance or how to delineate a species. This article is a review of the seemingly endless debate on the species concept and its implications.  相似文献   

Polymorphonuclear leukocytic sialic acid and sialidase activity in obesity     

Raj K. Das  M. G. Muddeshwar 《Indian journal of clinical biochemistry : IJCB》1997,12(2):114-118

The level of sialic acid in the obese polymorphonuclear leukocytes (PMNL) was found to be significantly reduced as compared to normal. Activity of sialic acid degrading enzyme, sialidase, was found to be increased in the obese state. Restoration in both sialic acid content and sialidase activity was also evidenced in the PMNL of treated obese patients.  相似文献   

注意:概念、测验和教师等级评定     

J.P.Das 《华东师范大学学报(教育科学版)》2002,20(3):68-76,96

本文的理论部分探讨注意的性质、注意的测验和测量，以及注意缺陷的鉴定。注意具有选择性，它包含着对冲动反应的抑制和对分心的克服。第二部分讨论三项经验研究，这些研究探索了注意等级评定量表的使用，该量表由教师对儿童在课堂情境下的注意情况进行等级评定。研究发现，教师的等级评定可以预测课外情境中儿童在注意测验上的表现。这些等级评定具有显著的预测性，正如该测验的结果所表明的，教师一直关注着儿童注意的一个重要方面，即对分心的抵制。在结论性评述中，讨论了可能导向注意缺陷改善的动态测试。第三部分是附录部分，例举了若干注意力测验。  相似文献   

Supporting Online PBL: Design Considerations for Supporting Distributed Problem Solving   总被引：1，自引：0，他引：1  

Chandra Hawley Orrill 《Distance Education》2002,23(1):41-57

This study considers how four groups of education graduate students worked in a distributed problem-based learning (PBL) environment using an asynchronous threaded discussion tool. The analyses consider how the students were able to interact with each other using the tool and how they worked together to define the problem and identify key issues to explore. The outcomes include some design considerations for tools to support these activities as well as insight about how students may work together to solve a problem in a distributed environment.  相似文献   

A cogenerative inquiry using postcolonial theory to envisage culturally inclusive science education     

Jennifer Adams  Bal Chandra Luitel  Emilia Afonso  Peter Charles Taylor 《Cultural Studies of Science Education》2008,3(4):999-1019

This forum constitutes a cogenerative inquiry using postcolonial theory drawn from the review paper by Zembylas and Avraamidou. Three teacher educators from African, Asian and Caribbean countries reflect on problems confronting their professional practices and consider the prospects of creating culturally inclusive science education. We learn that in Mozambique, Nepal and the Caribbean scientism patrols the borders of science education serving to exclude local epistemological beliefs and discourses and negating culturally contextualized teaching and learning. Despite the diverse cultural hybridities of these countries, science education is disconnected from the daily lives of the majority of their populations, serving inequitably the academic Western-oriented aspirations of an elite group who are “living hybridity but talking scientism.” The discussants explore their autobiographies to reveal core cultural values and beliefs grounded in their non-Western traditions and worldviews but which are in conflict with the Western Modern Worldview (WMW) and thus have no legitimate role in the standard school/college science classroom. They reflect on their hybrid cultural identities and reveal the interplay of multiple selves grounded in both the WMW and non-WMWs and existing in a dialectical tension of managed contradiction in a Third Space. They argue for dialectical logic to illuminate a Third Space wherein students of science education may be empowered to challenge hegemonies of cultural reproduction and examine reflexively their own identities, coming to recognize and reconcile their core cultural beliefs with those of Western modern science, thereby dissipating otherwise strongly delineated cultural borders.

Jennifer AdamsEmail:

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Reconvene and Reconnect the Antioxidant Hypothesis in Human Health and Disease     

Singh PP  Chandra A  Mahdi F  Roy A  Sharma P 《Indian journal of clinical biochemistry : IJCB》2010,25(3):225-243

The antioxidants are essential molecules in human system but are not miracle molecules. They are neither performance enhancers nor can prevent or cure diseases when taken in excess. Their supplemental value is debateable. In fact, many high quality clinical trials on antioxidant supplement have shown no effect or adverse outcomes ranging from morbidity to all cause mortality. Several Chochrane Meta-analysis and Markov Model techniques, which are presently best available statistical models to derive conclusive answers for comparing large number of trials, support these claims. Nevertheless none of these statistical techniques are flawless. Hence, more efforts are needed to develop perfect statistical model to analyze the pooled data and further double blind, placebo controlled interventional clinical trials, which are gold standard, should be implicitly conducted to get explicit answers. Superoxide dismutase (SOD), glutathione peroxidase and catalase are termed as primary antioxidants as these scavenge superoxide anion and hydrogen peroxide. All these three enzymes are inducible enzymes, thereby inherently meaning that body increases or decreases their activity as per requirement. Hence there is no need to attempt to manipulate their activity nor have such efforts been clinically useful. SOD administration has been tried in some conditions especially in cancer and myocardial infarction but has largely failed, probably because SOD is a large molecule and can not cross cell membrane. The dietary antioxidants, including nutrient antioxidants are chain breaking antioxidants and in tandem with enzyme antioxidants temper the reactive oxygen species (ROS) and reactive nitrogen species (RNS) within physiological limits. Since body is able to regulate its own requirements of enzyme antioxidants, the diet must provide adequate quantity of non-enzymic antioxidants to meet the normal requirements and provide protection in exigent condition. So far, there is no evidence that human tissues ever experience the torrent of reactive species and that in chronic conditions with mildly enhanced generation of reactive species, the body can meet them squarely if antioxidants defense system in tissues is biochemically optimized. We are not yet certain about optimal levels of antioxidants in tissues. Two ways have been used to assess them: first by dietary intake and second by measuring plasma levels. Lately determination of plasma/serum level of antioxidants is considered better index for diagnostic and prognostic purposes. The recommended levels for vitamin A, E and C and beta carotene are 2.2–2.8 μmol/l; 27.5–30 μmol/l; 40–50 μmol/l and 0.4–0.5 μmol/l, respectively. The requirement and recommended blood levels of other dietary antioxidants are not established. The resolved issues are (1) essential to scavenge excess of radical species (2) participants in redox homeostasis (3) selective antioxidants activity against radical species (4) there is no universal antioxidant and 5) therapeutic value in case of deficiency. The overarching issues are (1) therapeutic value as adjuvant therapy in management of diseases (2) supplemental value in developing population (3) selective interactivity of antioxidant in different tissues and on different substrates (4) quantitative contribution in redox balance (5) mechanisms of adverse action on excess supplementation (6) advantages and disadvantages of prooxidant behavior of antioxidants (7) behavior in cohorts with polymorphic differences (8) interaction and intervention in radiotherapy, diabetes and diabetic complications and cardiovascular diseases (9) preventive behavior in neurological disorders (10) benefits of non-nutrient dietary antioxidants (11) markers to assess optimized antioxidants status (12) assessment of benefits of supplementation in alcoholics and heavy smokers. The unresolved and intriguing issues are (1) many compounds such as vitamin A and many others possessing both antioxidant and non-antioxidant properties contribute to both the activities in vivo or exclusively only to non-antioxidant activity and (2) since human tissues do not experience the surge of FR, whether there is any need to develop stronger synthetic antioxidants. Theoretically such antioxidants may do more harm than good.  相似文献   

Protective Role of <Emphasis Type="SmallCaps">l</Emphasis>-Arginine Against Free-Radical Mediated Oxidative Damage in Patients with Unstable Angina     

Tripathi P  Chandra M  Misra MK 《Indian journal of clinical biochemistry : IJCB》2010,25(3):302-306

Unstable angina is a critical condition of heart resulting from narrowing of vessels supplying blood to heart. Ischemia of the myocardium leads to oxidative stress and severe tissue damage. The objective of the present study was to determine the effect of l-arginine administration on the oxidant–antioxidant homeostasis which otherwise gets imbalanced in patients with cardiovascular diseases. The results obtained, show improvement in the oxidant–antioxidant levels of the subjects upon incorporation of l-arginine. Our findings suggest that supplementation of l-arginine along with regular anti-anginal therapy may be beneficial to the patients of unstable angina.  相似文献   

Systems biology     

Karthik Raman  Nagasuma Chandra 《Resonance》2010,15(2):131-153

Systems biology seeks to study biological systems as a whole, contrary to the reductionist approach that has dominated biology. Such a view of biological systems emanating from strong foundations of molecular level understanding of the individual components in terms of their form, function and interactions is promising to transform the level at which we understand biology. Systems are defined and abstracted at different levels, which are simulated and analysed using different types of mathematical and computational techniques. Insights obtained from systems level studies readily lend to their use in several applications in biotechnology and drug discovery, making it even more important to study systems as a whole.  相似文献