Leveling transparency via situated intermediary learning objectives (SILOs)

When designers set out to create a mathematics learning activity, they have a fair sense of its objectives: students will understand a concept and master relevant procedural skills. In reform-oriented activities, students first engage in concrete situations, wherein they achieve situated, intermediary learning objectives (SILOs), and only then they rearticulate their solutions formally. We define SILOs as heuristics learners devise to accommodate contingencies in an evolving problem space, e.g., monitoring and repairing manipulable structures so that they model with fidelity a source situation. Students achieve SILOs through problem-solving with media, instructors orient toward SILOs via discursive solicitation, and designers articulate SILOs via analyzing implementation data. We describe the emergence of three SILOs in developing the activity Giant Steps for Algebra. Whereas the notion of SILOs emerged spontaneously as a framework to organize a system of practice, i.e. our collaborative design, it aligns with phenomenological theory of knowledge as instrumented action

Shell closure effects studied via cluster decay in heavy nuclei

The effects of shell closure in nuclei via the cluster decay is studied. In this context, we have made use of the Preformed Cluster Model ($PCM$) of Gupta and collaborators based on the Quantum Mechanical Fragmentation Theory. The key point in the cluster radioactivity is that it involves the interplay of close shell effects of parent and daughter. Small half life for a parent indicates shell stabilized daughter and long half life indicates the stability of the parent against the decay. In the cluster decay of trans lead nuclei observed so far, the end product is doubly magic lead or its neighbors. With this in our mind we have extended the idea of cluster radioactivity. We investigated decay of different nuclei where Zirconium is always taken as a daughter nucleus, which is very well known deformed nucleus. The branching ratio of cluster decay and $\alpha$-decay is also studied for various nuclei, leading to magic or almost doubly magic daughter nuclei. The calculated cluster decay half-life are in well agreement with the observed data. First time a possibility of cluster decay in $^{218}U$ nucleus is predicted

Post-spinel transformations and equation of state in ZnGa2O4: Determination at high-pressure by in situ x-ray diffraction

Room temperature angle-dispersive x-ray diffraction measurements on spinel ZnGa2O4 up to 56 GPa show evidence of two structural phase transformations. At 31.2 GPa, ZnGa2O4 undergoes a transition from the cubic spinel structure to a tetragonal spinel structure similar to that of ZnMn2O4. At 55 GPa, a second transition to the orthorhombic marokite structure (CaMn2O4-type) takes place. The equation of state of cubic spinel ZnGa2O4 is determined: V0 = 580.1(9) A3, B0 = 233(8) GPa, B0'= 8.3(4), and B0''= -0.1145 GPa-1 (implied value); showing that ZnGa2O4 is one of the less compressible spinels studied to date. For the tetragonal structure an equation of state is also determined: V0 = 257.8(9) A3, B0 = 257(11) GPa, B0'= 7.5(6), and B0''= -0.0764 GPa-1 (implied value). The reported structural sequence coincides with that found in NiMn2O4 and MgMn2O4.Comment: 20 pages, 4 figures, 2 Table

Identification of blast resistance expression in rice genotypes using molecular markers (RAPD & SCAR)

Rice is the second most important cereal crop of developing countries and the staple food of about 65% of the world’s population. In this endeavor, it is important to identify resistant gene(s) with the help of markers. Once a gene is tagged with a molecular marker, it can be transferred selectively into different genetic backgrounds by marker assisted selection. For this purpose, 48 elite Indian and exotic rice genotypes were evaluated for resistance to blast disease under induced epiphytotic conditions obtained in the field. The disease severity (%) and AUDPC was less than 45% and 1000, respectively, in all the resistant genotypes, while it was around 85% and higher than 2000 in the case of susceptible genotypes, respectively. Substantial variability was present among rice genotypes for resistance toMagnaporthe grisea. Ten random amplified polymorphic DNAs (RAPD) and two sequence characterized amplified region (SCAR) primers were used to identify blast resistant genes. Markers OPA-05, OPF-06, OPF-09, OPF-17, OPG-17, OPG-18, OPG-19, OPH-18, OPK-12, P-265-550 and P-286-350 found linked to blast resistance in most of the resistant genotypes could be considered as potent molecular markers in the selection of blast resistant genotypes. Amplification with RAPD and SCAR primers revealed a nonallelic relationship among resistant genotypes and thus, there is a good possibility of obtaining enhanced resistance through gene pyramiding