Qualitative properties of the free-boundary of the reynolds equation in lubrication

The hidrodynamic lubrication of a cylindrical bearing is governed by the Reynolds equation that must be satisfied by the preassure of lubricatiog oil. When cavitation occurs we are carried to an elliptic free-boundary problem where the free-boundary separates the lubricated region from the cavited region. Some qualitative properties are obtained about the shape of the free-boundary as well as the localization of the cavited region

Trade-offs Between Water Transport Capacity and Drought Resistance in Neotropical Canopy Liana and Tree Species

In tropical forest canopies, it is critical for upper shoots to efficiently provide water to leaves for physiological function while safely preventing loss of hydraulic conductivity due to cavitation during periods of soil water deficit or high evaporative demand. We compared hydraulic physiology of upper canopy trees and lianas in a seasonally dry tropical forest to test whether trade-offs between safety and efficiency of water transport shape differences in hydraulic function between these two major tropical woody growth forms. We found that lianas showed greater maximum stem-specific hydraulic conductivity than trees, but lost hydraulic conductivity at less negative water potentials than trees, resulting in a negative correlation and trade-off between safety and efficiency of water transport. Lianas also exhibited greater diurnal changes in leaf water potential than trees. The magnitude of diurnal water potential change was negatively correlated with sapwood capacitance, indicating that lianas are highly reliant on conducting capability to maintain leaf water status, whereas trees relied more on stored water in stems to maintain leaf water status. Leaf nitrogen concentration was related to maximum leaf-specific hydraulic conductivity only for lianas suggesting that greater water transport capacity is more tied to leaf processes in lianas compared to trees. Our results are consistent with a trade-off between safety and efficiency of water transport and may have implications for increasing liana abundance in neotropical forests

Gene flow risk assessment in centres of crop origin and diversity

Poster presented at Plant Biology & Botany Join Congress. Chicago (USA), 7-11 Jul 200

A Change of Variables to the Dual and Factorization of Composite Anomalous Jacobians

Changes of variables giving the dual model are constructed explicitly for sigma-models without isotropy. In particular, the jacobian is calculated to give the known results. The global aspects of the abelian case as well as some of those of the cases where the isometry group is simply connected are considered. Considering the anomalous case, we infer by a consistency argument that the `multiplicative anomaly' should be replaceable by adequate rules for factorization of composite jacobians. These rules are then generalized in a simple way for composite jacobians defined in spaces of different types. Implimentation of these rules then gives specific formulas for the anomally for semisimple algebras and also for solvable ones.Comment: 15 pages, no figures, Latex file, A treatment of the global aspects of the abelian and of semisimple duality groups are added. General formulas for the mixed anomaly are derive

Polynomial algebras and exact solutions of general quantum non-linear optical models I: Two-mode boson systems

We introduce higher order polynomial deformations of $A_1$ Lie algebra. We construct their unitary representations and the corresponding single-variable differential operator realizations. We then use the results to obtain exact (Bethe ansatz) solutions to a class of 2-mode boson systems, including the Boson-Einstein Condensate models as special cases. Up to an overall factor, the eigenfunctions of the 2-mode boson systems are given by polynomials whose roots are solutions of the associated Bethe ansatz equations. The corresponding eigenvalues are expressed in terms of these roots. We also establish the spectral equivalence between the BEC models and certain quasi-exactly solvable Sch\"ordinger potentials.Comment: 20 pages, final version to appear in J. Phys. A: Math. Theor

Learning from Phase I: A Survey of Project Leaders and Staff

IN response to an on-line survey, 76 project leaders and staff gave CPWF Phase 1 a generally favorable review. Respondents came from 68 CPWF projects in 45 countries on three continents. The survey sought to help learn what went well in Phase 1, what did not go so well and can be improved in Phase 2. Nearly three-quarters of respondents felt that they had achieved different research results, outcomes and impacts as a result of participation in the CPWF than otherwise possible from ‘business as usual’ research approaches. Most (84%) agreed that they had worked with more and different partners in the CPWF. Three-quarters agreed that this had contributed to different science and outcomes. Most respondents (80%) also valued the platform the CPWF provides for communicating project results. In areas to be improved, nearly half pointed to shortcomings in the scientific support provided to projects, in part due to lack of resources available to enable theme leaders to follow-up on project activities. Most respondents were generally happy with the way the CPWF Secretariat (60%) and CGIAR Lead Centres (70%) had managed their projects. One quarter felt that CPWF technical reporting requirements had not been useful. Respondents expressed frustration that reporting formats changed during the course of the project, but more so that they were not conceived as a cumulative process. There were expectations that periodic technical reports would have been structured to be amalgamated into the final report at the end of the project, yet this was not so. Respondents also commented on lack of feedback by CPWF (Secretariat, Theme Leaders & Basin Coordinators) to project leaders after report submission. Bi-annual reporting, as opposed to quarterly reporting, was suggested as more appropriate. Respondents were happier with financial reporting requirements and two thirds felt that financial disbursements had been timely. Several comments indicated problems early on that were resolved by the CPWF and partners. One recurring theme was the different accounting systems of various partners, which created delays in compiling and submitting reports in the required CPWF format. Given the emphasis put on capacity building during Phase I, the survey assessed respondent’s perceptions of the investment. Over 75% of respondents agreed that the CPWF provided valuable capacity building. A large majority (85%) agreed that student researchers were helpful and productive and comments were generally very positive on the role of student researchers. One respondent suggested student researchers had contributed more to project outputs than some of the professional researchers. However comments were also made about the time, money, and energy required to adequately supervise and monitor students to ensure their contributions to project teams and outputs