Contribution structures

The invisibility of the individuals and groups that gave rise to requirements artifacts has been identified as a primary reason for the persistence of requirements traceability problems. This paper presents an approach, based on modelling the dynamic contribution structures underlying requirements artifacts, which addresses this issue. We show how these structures can be defined, using information about the agents who have contributed to artifact production, in conjunction with details of the numerous traceability relations that hold within and between artifacts themselves. We describe a scheme, derived from work in sociolinguistics, which can be used to indicate the capacities in which agents contribute. We then show how this information can be used to infer details about the social roles and commitments of agents with respect to their various contributions and to each other. We further propose a categorisation for artifact-based traceability relations and illustrate how they impinge on the identification and definition of these structures. Finally, we outline how this approach can be implemented and supported by tools, explain the means by which requirements change can be accommodated in the corresponding contribution structures, and demonstrate the potential it provides for "personnel-based" requirements traceability

INSDOC’S contribution to bibliometrics

Traces the history of bibliometric research, training and activities in INSDOC. Describes briefly the objectives, facilities, services, research activities, and publications of National Centre on Bibliometrics

Gravitational contribution to fermion masses

In the context of a nonlinear gauge theory of the Poincar\'e group, we show that covariant derivatives of Dirac fields include a coupling to the translational connections, manifesting itself in the matter action as a universal background mass contribution to fermions.Comment: revtex4, 9 pages, no figures, to be published in Eur.Phys.J.C, 200

Arc Statistics in Clusters: Galaxy Contribution

The frequency with which background galaxies appear as long arcs as a result of gravitational lensing by foreground clusters of galaxies has recently been found to be a very sensitive probe of cosmological models by Bartelmann et al. (1998). They have found that such arcs would be expected far less frequently than observed (by an order of magnitude) in the currently favored model for the universe, with a large cosmological constant $\Omega_\Lambda \sim 0.7$. Here we analyze whether including the effect of cluster galaxies on the likelihood of clusters to generate long-arc images of background galaxies can change the statistics. Taking into account a variety of constraints on the properties of cluster galaxies, we find that there are not enough sufficiently massive galaxies in a cluster for them to significantly enhance the cross section of clusters to generate long arcs. We find that cluster galaxies typically enhance the cross section by only $\lesssim 15$.Comment: 19 pages, 1 figure, uses aasms4.sty, submitted to Ap

Altered Expression of the CB1 Cannabinoid Receptor in the Triple Transgenic Mouse Model of Alzheimer's Disease

The endocannabinoid system has gained much attention as a new potential pharmacotherapeutic target in various neurodegenerative diseases, including Alzheimer's disease (AD). However, the association between CB1 alterations and the development of AD neuropathology is unclear and often contradictory. In this study, brain CB1 mRNA and CB1 protein levels were analyzed in 3 × Tg-AD mice and compared to wild-type littermates at 2, 6 and 12 months of age, using in-situ hybridization and immunohistochemistry, respectively. Semiquantitative analysis of CB1 expression focused on the prefrontal cortex (PFC), prelimbic cortex, dorsal hippocampus (DH), basolateral amygdala complex (BLA), and ventral hippocampus (VH), all areas with high CB1 densities that are strongly affected by neuropathology in 3 × Tg-AD mice. At 2 months of age, there was no change in CB1 mRNA and protein levels in 3 × Tg-AD mice compared to Non-Tg mice in all brain areas analyzed. However, at 6 and 12 months of age, CB1 mRNA levels were significantly higher in PFC, DH, and BLA, and lower in VH in 3 × Tg-AD mice compared to wild-type littermates. CB1 immunohistochemistry revealed that CB1 protein expression was unchanged in 3 × Tg-AD at 2 and 6 months of age, while a significant decrease in CB1 receptor immunoreactivity was detected in the BLA and DH of 12-month-old 3 × Tg-AD mice, with no sign of alteration in other brain areas. The altered CB1 levels appear, rather, to be age-and/or pathology-dependent, indicating an involvement of the endocannabinoid system in AD pathology and supporting the ECS as a potential novel therapeutic target for treatment of AD

Correlation energy contribution to nuclear masses

The ground state correlation energies associated with collective surface and pairing vibrations are calculated for Pb- and Ca-isotopes. It is shown that this contribution, when added to those predicted by one of the most accurate modern nuclear mass formula (HFBCS MSk7 mass formula), reduces the associated rms error by an important factor, making mean field theory, once its time dependence is taken into account, a quantitative predictive tool for nuclear masses.Comment: 4 pages, 2 figures, RevTeX

RVB Contribution to Superconductivity in MgB2MgB_2

We view $MgB_2$ as electronically equivalent to (non-staggered) graphite ($B^-$ layer) that has undergone a zero gap semiconductor to a superconductor phase transition by a large c-axis (chemical) pressure due to $Mg^{++}$ layers. Further, like the \ppi bonded planar organic molecules, graphite is an old resonating valence bond (RVB) system. The RVB's are the `preexisting cooper pairs' in the `parental' zero gap semiconducting $B^-$ (graphite) sheets that manifests themselves as a superconducting ground state of the transformed metal. Some consequences are pointed out.Comment: 4 pages, 2 figure, RevTex. Based on a talk given at the Institute Seminar Week, IMSc, Madras (12-16, Feb. 2001