Atrazine biodegradation efficiency, metabolite detection, and trzD gene expression by enrichment bacterial cultures from agricultural soil     

Robinson David Jebakumar SOLOMON  Amit KUMAR  Velayudhan SATHEEJA SANTHI 《Journal of Zhejiang University. Science. B》2013,14(12):1162-1172

Atrazine is a selective herbicide used in agricultural fields to control the emergence of broadleaf and grassy weeds. The persistence of this herbicide is influenced by the metabolic action of habituated native microorganisms. This study provides information on the occurrence of atrazine mineralizing bacterial strains with faster metabolizing ability. The enrichment cultures were tested for the biodegradation of atrazine by high-performance liquid chromatography(HPLC) and mass spectrometry. Nine cultures JS01.Deg01 to JS09.Deg01 were identified as the degrader of atrazine in the enrichment culture. The three isolates JS04.Deg01, JS07.Deg01, and JS08.Deg01 were identified as efficient atrazine metabolizers. Isolates JS04.Deg01 and JS07.Deg01 produced hydroxyatrazine(HA) N-isopropylammelide and cyanuric acid by dealkylation reaction. The isolate JS08.Deg01 generated deethylatrazine(DEA), deisopropylatrazine(DIA), and cyanuric acid by N-dealkylation in the upper degradation pathway and later it incorporated cyanuric acid in their biomass by the lower degradation pathway. The optimum pH for degrading atrazine by JS08.Deg01 was 7.0 and 16S rDNA phylogenetic typing identified it as Enterobacter cloacae strain JS08.Deg01. The highest atrazine mineralization was observed in case of isolate JS08.Deg01, where an ample amount of trzD mRNA was quantified at 72 h of incubation with atrazine. Atrazine bioremediating isolate E. cloacae strain JS08.Deg01 could be the better environmental remediator of agricultural soils and the crop fields contaminated with atrazine could be the source of the efficient biodegrading microbial strains for the environmental cleanup process.  相似文献   

Student achievement conditioned upon school selection: Religious and secular secondary school quality in Bangladesh     

Mohammad Niaz Asadullah  Nazmul Chaudhury  Amit Dar 《Economics of Education Review》2007,26(6):648

In this paper we present new evidence on the impact of school characteristics on secondary student achievement using a rich dataset from rural Bangladesh. We deal with a potentially important selectivity issue in the South Asian context: the non-random sorting of children into madrasas (Islamic faith schools). We do so by employing a combination of fixed effects and instrumental variable estimation techniques. Our empirical results do not reveal any difference in test scores between religious and secular schools when selection into secondary school is taken into account. However, we document significant learning deficit by gender and primary school type: girls and graduates of primary madrasas have significantly lower test scores even after controlling for school and classroom-specific unobservable correlates of learning.  相似文献   

Some reflections on mathematics classroom notebooks and their relationship to the public and private nature of student practices     

Michael N. Fried  Miriam Amit 《Educational Studies in Mathematics》2003,53(2):91-112

This article considers students' classroom notebooks, their character and their role in learning. The results presented were found within the frame work of a broader international project, the Learners Perspective Study, whose goal is to identify classroom practice from the students' point of view. Two 8^thgrade classrooms were studied. In each,every lesson over the course of three weeks was videotaped. After each lesson, two students were interviewed and their notebooks entrees for that lesson were photocopied; once a week, the teacher was interviewed as well. From the analysis of the data it became apparent that the notebook in the classroom is a publicobject; it is ever open for inspection and contains only finished work. That it is not a private object in which the student may freely record preliminary ideas, musings, and reflections may affect student learning negatively. The categorization of public and private as a categorization of learning activities is discussed. The relationship between the findings on notebooks and research on writing and classroom journals is discussed; in particular, a connection is made between public and private domains and transactional and expressive writing,respectively. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Recurring patterns in the development of high school biology students’ system thinking over time     

Jaklin Tripto  Orit Ben Zvi Assaraf  Miriam Amit 《Instructional Science》2018,46(5):639-680

The goal of this study was to identify and understand the mental models developed by 67 high school biology students as they learn about the human body as a complex system. Using concept maps, it sought to find an external way of representing how students organize their ideas about the human body system in their minds. We conducted a qualitative analysis of four concept maps created by each student throughout the 3-year learning process, which allowed us to identify that student’s systems thinking skills and the development of those skills over time. The improvement trajectories of the students were defined according to three central characteristics of complex systems: (a) hierarchy, (b) homeostasis and (c) dynamism. A comparative analysis of all of our students’ individual trajectories together revealed four typical learning patterns, each of which reflects a different form of development for systems thinking: “from the structure to the process level”, “from macro to micro level”, “from the cellular level to the organism level,” and “development in complexity of homeostasis mechanisms”. Despite their differences, each of these models developed over time from simpler structures, which evolved as they connected with more complex system aspects, and each indicates advancement in the student’s systems thinking.  相似文献   

Wavelet transforms: Application to data analysis - II     

Jatan K. Modi  Sachin P. Nanavati  Amit S. Phadke  Prasanta K. Panigrahi 《Resonance》2004,9(12):8-13

We illustrate here, the use of wavelets both in one and two dimensions. We outline the procedure to construct wavelet transform in two dimensions. The method of forward transform, reconstruction and the various steps involved are explained pictorially.  相似文献   

A Synergistic Role of Myeloperoxidase and High Sensitivity Troponin T in the Early Diagnosis of Acute Coronary Syndrome     

Mihir D. Mehta  Simbita A. Marwah  S. Ghosh  Hitesh Shah  Amit Trivedi  N. Haridas 《Indian journal of clinical biochemistry : IJCB》2016,31(1):75-80

Aim of this study was to evaluate the role of Myeloperoxidase (MPO) and high sensitive Troponin T in the early diagnosis of acute coronary syndrome (ACS). This was a cross sectional study that comprised of 120 individuals of which 75 were cases and 45 healthy controls. On the basis of clinical history and 12 lead electrocardiogram initial diagnosis of ACS was made in the cases. MPO and high sensitive Troponin T (hs-cTnT) was measured in all the individuals. Levels of MPO were significantly higher in patients of ACS as compared to those in control group [medians: 15.40 (95 % CI 11.06–20.84) vs 5.84 (95 % CI 5.50–6.44)]. By taking the cut off as >11.87 U/mL for MPO, its sensitivity was 87 % (95 % CI 73.7–95.1), specificity was 97.3 % (95 % CI 90.6–99.7), positive predictive value was 94.6 % and negative predictive value was 92.6 %. Positive likelihood ratio was 33.0 while negative likelihood ratio was 0.13, whereas the corresponding values in case of hs-cTnT were 95.6 % (95 % CI 85.2–99.5), 61.3 % (95 % CI 49.5–72.6), 59.7 %, 95.8 %, 2.47 and 0.07 by taking cut off as >14 pg/ml. The area under the ROC curves (AUC) of MPO and hscTnT at 0–6 h were 0.971 (95 % CI 0.92–0.99, P < 0.001) and 0.797 (95 % CI 0.71–0.86, P < 0.001) respectively. The logistic model combining the two markers yielded sensitivity, specificity, positive predictive value and negative predictive value of 95.7, 97.3, 98.2 and 93.7 % respectively. It was concluded that MPO and hs-cTnT may be useful tools for risk stratification of ACS and can be used together with better accuracy in the early diagnosis of ACS.  相似文献   

Asymptotic stability in a flexible-joint robot with model uncertainty and multiple time delays in feedback     

Amit Ailon 《Journal of The Franklin Institute》2004,341(6):519-531

This study considers the stability problem of a flexible-joint robot in case time delays are involved in the feedback loop. We assume in our analysis that the controller uses only position measurements. The single and multiple time-delay cases, are considered. By using some useful structural properties of the robot model, sufficient conditions for asymptotic (exponential) stability of the system under consideration have been established. An estimate to the system rate of convergence is given and a procedure for evaluating the region of attraction, is given.  相似文献   

Therapy in Parkinson’s disease: Some recent developments     

Amit Krishna De 《Resonance》1999,4(5):78-87

Even though research is going on throughout the world, it is clear that at the present time there is really no cure for Parkinson’s disease. Treatment with drugs, with physiotherapy can slow down the progress of this disease. Treatment through brain grafting or reparative therapy using different nerve growth factors may be the only alternative for this disease. Researchers are still hoping that the newly discovered substances could one day help doctors treat this invincible disease and possibly cure it also.  相似文献   

The (amorphous) anatomy of an invention: the case of magnetic resonance imaging (MRI)     

Prasad A 《Social studies of science》2007,37(4):533-560

The priority dispute between Raymond Damadian and Paul Lauterbur over the 'invention' of magnetic resonance imaging (MRI) has attracted the attention of social and natural scientists for more than 30 years. In this paper, I have used this priority dispute to analyze the complex socio-epistemic processes through which a claim for an invention is made and strengthened. I argue that a tension exists because techno-scientific practices are embedded within a particular disciplinary regime of authorship: even though techno-scientific practices occur through distributed cognition and are contingent upon particular socio-epistemic contexts, a claim for an invention requires assigning authorship to a particular person, company, or institution in order to clearly define the origin and the novelty of that particular techno-scientific event. Nevertheless, the outcomes of socio-epistemic practices for making and strengthening priority claims are shifting, open-ended, and contingent upon particular socio-epistemic contexts.  相似文献   

Great experiments in physics     

Amit Roy 《Resonance》2000,5(11):4-13

In 1965, Arno Penzias and Robert Wilson of Bell Telephone Laboratories in USA discovered weak microwave radiation coming from all directions which was soon realised to be a relic from a hot dense early phase of our Universe—the ‘big bang’. This article focuses on the key experimental techniques and innovations which made this momentous—and accidental!—discovery possible. Amit Roy is at the Nuclear Science Centre, New Delhi, building a superconducting linac booster for the pelletron accelerator. He spent over two decades at the Tata Institute of Fundamental Research, Mumbai investigating nuclei using accelerators and probing symmetries in physics. His hobbies are books and music.  相似文献