Comparative experimental and Density Functional Theory (DFT) study of the physical properties of MgB2 and AlB2

In present study, we report an inter-comparison of various physical and electronic properties of MgB2 and AlB2. Interestingly, the sign of S(T) is +ve for MgB2 the same is -ve for AlB2. This is consistent our band structure plots. We fitted the experimental specific heat of MgB2 to Debye Einstein model and estimated the value of Debye temperature (theta) and Sommerfeld constant (gamma) for electronic specific heat. Further, from gamma the electronic density of states (DOS) at Fermi level N(EF) is calculated. From the ratio of experimental N (EF) and the one being calculated from DFT, we obtained value of Lembda to be 1.84, thus placing MgB2 in the strong coupling BCS category. The electronic specific heat of MgB2 is also fitted below Tc using pi-model and found that it is a two gap superconductor. The calculated values of two gaps are in good agreement with earlier reports. Our results clearly demonstrate that the superconductivity of MgB2 is due to very large phonon contribution from its stretched lattice. The same two effects are obviously missing in AlB2 and hence it is not superconducting. DFT calculations demonstrated that for MgB2 the majority of states come from Sigma and Pi 2p states of boron on the other hand Sigma band at Fermi level for AlB2 is absent. This leads to a weak electron phonon coupling and also to hole deficiency as Pi bands are known to be of electron type and hence obviously the AlB2 is not superconducting. The DFT calculations are consistent with the measured physical properties of the studied borides, i.e., MgB2 and AlB2Comment: 16 pages Text + Figs: comments/suggestions welcome ([email protected])/www.freewebs.com/vpsawana

Dynamics of an atom cavity field system in interacting Fock space

In this paper, we investigate one-time passing of a $V$-type three-level atom through a single-mode interacting field in a cavity. We extend the idea of elementary Jaynes-Cummings model by assuming that the field vector belongs to interacting Fock space. In the process, we arrive at a state vector which will be analyzed to study the nonclassicality of the evolved state of the system.Comment: 14 pages, 5 figure

Strategic metrics for product development at Ford Motor Company

Thesis (S.M.)--Massachusetts Institute of Technology, System Design & Management Program, 2000.Includes bibliographical references (leaves 78-80).This thesis aims at developing a practical method to adjust product development metrics, which will enable effective management of the product development (PD) process. A set of good metrics is crucial to the success of a product, as metrics direct the development process by driving the actions and decisions of the PD team members which in turn define the product. Emphasizing or "weighting" certain metrics more than others can make the difference between success and failure. Through empirical exploration of metrics we seek to determine the weights, and the impact of different metrics on product success. Unlike its use in the engineering literature, the management use of the term "metric" includes both quantitative and qualitative measures which the PD team members can influence through their efforts. The theory used to determine the correct weight of a metric has its roots in the principles of Agency Theory and has been developed by "engineering" the theory to obtain two key parameters which define the weight of a metric. These two parameters are "leverage" and "risk discount factor" (RDF). Leverage is the amount by which a metric can impact the profitability of a product and RDF takes into account the inherent risk averse nature of the PD team members that influence their decisions. In order to evaluate the PD metrics and their weights within a firm, data was collected for a set of metrics across 17 programs at Ford Motor Company. The values for each metric were assigned based on information obtained through program documentation and interviews with multiple team members across various functions within the organization. Different success measures were collected and the impact and leverage of each metric was determined through empirical exploration of the various relationships. The key findings to date include: * Cronbach's Alpha for metrics regrouped using factor analysis average 0.7 demonstrating internal reliability. * Customer satisfaction correlates significantly with the rigor of the PD process, and internal coordination and communication between the core team and the other members of the value chain. * Time to market shows consistent correlation with profit and profit residuals. " The calculated weights suggest higher emphasis on capturing manufacturing need and using robust design practices, technology, and differentiation will increase profitability. " The measured RDF does not change the relative weightings of the metrics as obtained through the leverage calculation.by Arpita Majumder.S.M

Hydrologic modelling

Advances in computational tools and modeling techniques combined with enhanced process knowledge have, in recent decades, facilitated a rapid progress in hydrologic modeling. From the use of traditional lumped models, the hydrologic science has moved to the much more complex, fully distributed models that exude an enhanced knowledge of hydrologic processes. Despite this progress, uncertainties in hydrologic predictions remain. The Indian contribution to hydrologic science literature in the recent years has been significant, covering areas of surface water, groundwater, climate change impacts and quantification of uncertainties. Future scientific efforts in hydrologic science in India are expected to involve better, more robust observation techniques and datasets, deeper process-knowledge at a range of spatio-temporal scales, understanding links between hydrologic and other natural and human systems and integrated solutions using multidisciplinary approaches

Population dynamics of mycorrhizal fungi in rhizosphere of pigeon pea [Cajanus cajan (L.) Millsp.]

Soil samples collected from the rhizosphere of Pigeon pea [Cajanus cajan (L.) Millsp.] to evaluate the population dynamics of vesicular arbuscular mycorrhizae (VAM). Root colonization by native VAM fungi was recorded minimum in early stages of plant growth which significantly increased with the age of plants and became highest at maturity. Maximum VAM colonization in different blocks of the district ranged between 71-86% during both the years. Spore population was recorded maximum in soil samples collected at early stage of plant growth which significantly decreased of VAM fungi belonging 4 genera (Glomus sclerocystis, Acaulospora endogen) were identified. Among these Glomus mosseae and Sclerocystis rubiformis were found most dominating and widely distributed in all the blocks followed by Acaulospora longula  and Sclerocystis clavispora  which were distributed only in 12 blocks of the district. Acaulospora spinosa and Glomus diaphanum were recorded only from two blocks and their prevalence were least. Colonization per cent have negative correlation with spore density at different crop growth stages

Synthesis of SmFeAsO by an Easy and Versatile Route and its Physical Property Characterization

We report synthesis, structure, electrical transport and heat capacity of SmFeAsO. The title compound is synthesized by one-step encapsulation of stoichiometric FeAs, Sm, and Sm2O3 in an evacuated (10-5 Torr) quartz tube by prolong (72 hours) annealing at 1100oC. The as synthesized compound is crystallized in tetragonal structure with P4/nmm space group having lattice parameters a = 3.93726(33) A and c = 8.49802(07) A. The resistance (R-T) measurements on the compound exhibited ground state spin-density-wave (SDW)-like metallic steps below 140 K. Heat capacity CP(T) measurements on the title compound, showed an anomaly at around 140 K, which is reminiscent of the SDW ordering of the compound. At lower temperatures the CP(T) shows a clear peak at around 4.5 K. At lower temperature below 20 K, Cp(T) is also measured under an applied field of 7 Tesla. It is concluded that the CP(T) peak at 4.5 K is due to the anti-ferromagnetic(AFM) ordering of Sm3+ spins. These results are in confirmation with ordering of Sm in Sm2-xCexCuO4.Comment: 9 pages Text + Figs Contact Author ([email protected]