Plate Tectonics and Europa’s Icy Shell     

Abhinaba Das 《Resonance》2018,23(6):669-681

A unique attribute of Earth is the presence of plate tectonics. Not only does it give rise to continents, mountain chains, and ocean basins but also promotes a high level of biodiversity. It is the reason for the formation of the so-called ‘Pacific Ring of Fire’ – a belt of intense volcanic activity and a large number of earthquakes surrounding the Pacific ocean. But what drives the plate motion? Did Earth always have plate tectonics? These are some fascinating geoscientific questions. In trying to answer these questions, an effort is made to impress upon the reader the vast ocean of uncertainty, and hence the opportunity, in the field of Earth and Planetary Sciences. To make it more engaging, the article provides a peek into the long process which culminated in the present-day theory of plate tectonics on Earth. While the first half of the article focuses on subduction and its cause, the second half summarizes a recent finding made on the surface of Europa. In view of readability across disciplines, the complex subject details are kept to bare minimum.  相似文献   

Middle School Teachers’ Use of Mathematics to Make Sense of Student Solutions to Proportional Reasoning Problems     

Erik Jacobson  Joanne Lobato  Chandra H. Orrill 《International Journal of Science and Mathematics Education》2018,16(8):1541-1559

Mathematics teacher education aims to improve teachers’ use of mathematical knowledge to support teaching and learning, an aspect of pedagogical content knowledge (PCK). In this study, we interviewed teachers to understand how they used mathematics to make sense of student solutions to proportional reasoning problems. The larger purpose was to find accurate ways of categorizing teachers’ ability to do this vital aspect of teaching and thereby to inform assessment, teacher education, and professional development. We conjectured that teachers’ PCK for proportional reasoning could be reliably described in terms of attention to quantitative meanings in story problem contexts and in terms of understanding naïve forms of proportional reasoning. Instead, our findings reveal that individual teachers used a variety of means to make sense of (1) cognitively similar student solutions to different tasks and (2) mathematically related steps of a student solution within a single task. These findings illustrate the complexity of PCK for the topic of proportional reasoning and suggest the limits of what can be inferred about teacher knowledge from teachers’ evaluations of student solutions. We discuss implications for teacher education and assessment.  相似文献   

Toxic effects of Litsea elliptica Blume essential oil on red blood cells of Sprague-Dawley rats     

Izatus Shima Taib  Siti Balkis Budin  Seri Maseran Siti Nor Ain  Jamaludin Mohamed  Santhana Raj Louis  Srijit Das  Sulaiman Sallehudin  Nor Fadilah Rajab  Othman Hidayatulfathi 《Journal of Zhejiang University. Science. B》2009,10(11):813-819

Litsea elliptica Blume leaves have been traditionally used as medicinal herbs because of its antimutagenicity, che-mopreventative and insecticidal properties. In this study, the toxic effects of L. elliptica essential oil against Sprague-Dawley rat's red blood cells (RBCs) were evaluated. L. elliptica essential oil was given by oral gavage 5 times per week for 3 treated groups in the doses of 125, 250, and 500 mg/(kg body weight), respectively, and the control group received distilled water. Full blood count, RBC osmotic fragility, RBC morphological changes, and RBC membrane lipid were analyzed 28 d after the treatment. Although L. elliptica essential oil administration had significantly different effects on hemoglobin (Hb), mean cell hemoglobin concentration (MCHC), mean cell volume (MCV), and mean cell hemoglobin (MCH) in the experimental groups as compared to the control group (P<0.05), the values were still within the normal range. L. elliptica induced morphological changes of RBC into the form of echinoeyte. The percentage of echinocyte increased significantly among the treated groups in a dose-response manner (P<0.001). The concentrations of RBC membrane phospholipids and cholesterol of all treated groups were significantly lower than those of control group (P<0.001). However, the RBC membrane osmotic fragility and total proteins of RBC membrane findings did not differ significantly between control and treated groups (P>0.05). It is concluded that structural changes in the RBC membrane due to L. elliptica essential oil administration did not cause severe membrane damage.  相似文献   

Epigallocatechin-3-gallate affects the growth of LNCaP cells via membrane fluidity and distribution of cellular zinc     

Jun-guo Yang  Hai-ning Yu  Shi-li Sun  Lan-cui Zhang  Guo-qing He  Undurti N. Das  Hui Ruan  Sheng-rong Shen 《Journal of Zhejiang University. Science. B》2009,10(6):411-421

Objective: To evaluate effects of epigallocatechin-3-gallate (EGCG) on the viability, membrane properties, and zinc distribution, with and without the presence of Zn2+, in human prostate carcinoma LNCaP cells. Methods: We examined changes in cellular morphology and membrane fluidity of LNCaP cells, distribution of cellular zinc, and the incorporated portion of EGCG after treatments with EGCG, Zn2+, and EGCG+Zn2+. Results: We observed an alteration in cellular morphology and a decrease in membrane fluidity of LNCaP cells after treatment with EGCG or Zn2+. The proportion of EGCG incorporated into liposomes treated with the mixture of EGCG and Zn2+ at the ratio of 1:l was 90.57%, which was significantly higher than that treated with EGCG alone (30.33%). Electron spin resonance (ESR) studies and determination of fatty acids showed that the effects of EGCG on the membrane fluidity of LNCaP were decreased by Zn2+. EGCG accelerated the accumulation of zinc in the mitochondria and cytosol as observed by atomic absorption spectrometer. Conclusion: These results show that EGCG interacted with cell membrane,decreased the membrane fluidity of LNCaP cells, and accelerated zinc accumulation in the mitochondria and cytosol, which could be the mechanism by which EGCG inhibits proliferation of LNCaP cells. In addition, high concentrations of Zn2+ could attenuate the actions elicited by EGCG.  相似文献   

Perspective: Flicking with flow: Can microfluidics revolutionize the cancer research?     

Tamal Das  Suman Chakraborty 《Biomicrofluidics》2013,7(1)

According to the World Health Organization, cancer is one of the leading causes of death worldwide. Cancer research, in its all facets, is truly interdisciplinary in nature, cutting across the fields of fundamental and applied sciences, as well as biomedical engineering. In recent years, microfluidics has been applied successfully in cancer research. There remain, however, many elusive features of this disease, where microfluidic systems could throw new lights. In addition, some inherent features of microfluidic systems remain unexploited in cancer research. In this article, we first briefly review the advancement of microfluidics in cancer biology. We then describe the biophysical aspects of cancer and outline how microfluidic system could be useful in developing a deeper understanding on the underlying mechanisms. We next illustrate the effects of the confined environment of microchannel on cellular dynamics and argue that the tissue microconfinement could be a crucial facet in tumor development. Lastly, we attempt to highlight some of the most important problems in cancer biology, to inspire next level of microfluidic applications in cancer research.  相似文献   

Inborn Errors of Metabolism: Challenges and Management     

Subir Kumar Das 《Indian journal of clinical biochemistry : IJCB》2013,28(4):311-313

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The counseling needs of foreign students     

Ajit K. Das  Stephen Y. Chow  Bruce Rutherford 《International journal for the advancement of counseling》1986,9(2):167-174

This paper reports the findings of three studies of the counseling needs of international students at a medium sized University in the Midwestern region of USA. The studies were conducted over a period of five years (1977–83), and provide an historical perspective on the changes in student needs as well as in the programs designed to respond to these needs.  相似文献   

The earth’s changing climate     

P. K. Das 《Resonance》1996,1(3):54-65

Various human activities have contributed to an increase in the levels of greenhouse gases. The contribution that these make to global warming requires further investigation, because there are several negative feedback mechanisms which inhibit the warming process.  相似文献   

Establishing the overall service quality of engineering education: fuzzy logic approach     

N. Chandra Shekhar  K. Venkatasubbaiah  N. R. Kandukuria 《European Journal of Engineering Education》2012,37(6):575-591

Measuring overall service quality (OSQ) is gaining prominence in higher education due to the increased competition among engineering education institutions (EEIs) and growing awareness about value for money among the public. Determination of OSQ on certain institutional aspects is done by various agencies throughout the world. Each system uses a different set of weighted indicators to measure the overall service quality of institutions. Five service quality factors, namely professionalism, integrated education, facilities, responsiveness and empathy are considered in the study. Trapezoidal fuzzy numbers are used to determine the aggregate weights of the factors to handle the vagueness present in the linguistic values of the stakeholders’ subjective opinions. Final weights of the factors are assessed by taking the distances of each factor between Fuzzy Positive Ideal Rating and Fuzzy Negative Ideal Rating. An illustrative study is presented to determine the OSQ of EEIs. The results help to focus on the factors which need immediate attention to enhance the quality of EEIs.  相似文献   

Policy versus ground reality: secondary English language assessment system in Bangladesh     

Sharmistha Das  Prithvi Shrestha  Arifa Rahman  Rubina Khan 《Curriculum Journal》2014,25(3):326-343

Any policy reform in education is highly effective when it is planned and implemented ‘holistically’ and yet, it is the most challenging way forward. Many countries in Asia have reformed their English language policies and syllabi in the last two decades due to the increasing value of the language worldwide. Motivated by a ‘communicative approach’ to English language teaching, Bangladesh was one of the countries that launched such a reform in the 1990s. However, this reform has been criticised for imposing the changes on teachers without preparing them sufficiently. More importantly, there is limited evidence as to how much the secondary English language assessment system is aligned with the changes introduced in the curriculum. In order to explore this gap, a medium-scale study was conducted in 38 secondary schools in Bangladesh, following a mixed methods approach. The findings highlighted a ‘mismatch’ between the intended English language learning outcomes and current assessment practices, including the resulting challenges faced by the teachers. This paper argues that language education reform is likely to fail if the assessment system is not aligned with the curriculum.  相似文献