India’s Nuclear Doctrine : Context and Constraints

Ever since India achieved independence in 1947, its response to global nuclear non-proliferation measures has been a dominant theme in the country’s overall evolution of nuclear policy. However, India conducted a nuclear test in 1974, which it termed a ‘peaceful nuclear explosion’ and in 1998, India conducted a full-scale nuclear test and subsequently claimed to have attained nuclear capability. The purpose of this article is to critically evaluate key elements of India’s draft nuclear doctrine. The draft was presented to the Prime Minister and the Cabinet in August 1999 and released later for public debate by the National Security Advisory Board

TYPES OF QUESTIONS TEACHERS ASK TO ENGAGE STUDENTS IN MAKING SENSE OF A STUDENT CONTRIBUTION

In the student-centered classroom, a teacher’s interpretation and response to student mathematical contributions plays an important role to shape and direct students’ opportunities for sense-making. This research used a scenario-based survey questionnaire to examine what types of questions middle and high school mathematics teachers indicate they would ask to engage students in making sense of a high-leverage student mathematical contribution and their reasoning about why particular questions are or are not productive. From the results, it could be concluded that teachers asked more productive questions after seeing a set of possible questions. Their beliefs about the productivity of the questions related to a variety of factors, including the specificity of the question, student participation, student ability and whether incorrect solutions should be discussed. The results could inform future work with teachers to productively use student thinking in their teaching

Nucleotide-dependent DNA gripping and an end-clamp mechanism regulate the bacteriophage T4 viral packaging motor.

ATP-powered viral packaging motors are among the most powerful biomotors known. Motor subunits arranged in a ring repeatedly grip and translocate the DNA to package viral genomes into capsids. Here, we use single DNA manipulation and rapid solution exchange to quantify how nucleotide binding regulates interactions between the bacteriophage T4 motor and DNA substrate. With no nucleotides, there is virtually no gripping and rapid slipping occurs with only minimal friction resisting. In contrast, binding of an ATP analog engages nearly continuous gripping. Occasional slips occur due to dissociation of the analog from a gripping motor subunit, or force-induced rupture of grip, but multiple other analog-bound subunits exert high friction that limits slipping. ADP induces comparably infrequent gripping and variable friction. Independent of nucleotides, slipping arrests when the end of the DNA is about to exit the capsid. This end-clamp mechanism increases the efficiency of packaging by making it essentially irreversible