Heavy quarkonium: progress, puzzles, and opportunities

A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the $B$-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K. Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D. Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A. Petrov, P. Robbe, A. Vair

Direct observation of oligomeric species formed in the early stages of amyloid fibril formation using mass spectrometry

Numerous debilitating human disorders result from protein misfolding and amyloid formation. Despite the grave nature of these maladies, our understanding of the structural mechanism of fibril assembly is limited. Of paramount importance is the need to identify and characterize oligomeric species formed early during fibril assembly, so that the nature of the initiating assembly mechanism can be revealed and species that may be toxic to cells identified. However, the transient nature of early oligomeric species, combined with their heterogeneity and instability, has precluded detailed analysis to date. Here, we have used electrospray ionisation mass spectrometry (ESI-MS), complemented by analytical ultracentrifugation (AUC) and measurements of thioflavin-T fluorescence, to monitor the early stages of assembly of amyloid-like fibrils formed from human beta-2- microglobulin (β2m) in vitro. We show that worm-like fibrils that form with nucleation-independent kinetics assemble by a mechanism consistent with monomer addition, with species ranging from monomer to ≥13-mer being identified directly and uniquely as transient assembly intermediates. By contrast, only monomers, dimers, trimers and tetramers are observed during nucleated growth, which leads to the formation of long straight fibrils. The results highlight the unique power of non-covalent ESI-MS to identify protein assembly intermediates in complex heterogeneous systems and demonstrate its great potential to identify and characterise individual species formed early during amyloid assembly. © 2006 Elsevier Ltd

Breeding and winter site fidelity among eleven Neotropical Austral migrant bird species

Very little information currently exists on site fidelity patterns among Neotropical Austral migratory birds, which migrate wholly within South America. We banded migratory birds at three sites in South America, one located in the tropics and two at south temperate latitudes. We document breeding site fidelity among seven species and winter site fidelity among four species. Knowledge of patterns of site fidelity among migratory birds in South America is important for understanding the constraints affecting their populations throughout the annual cycle and ultimately for conservation planning. Accepted 8 April 2009. © The Neotropical Ornithological Society.Fil:Cueto, V.R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Sagario, M.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:De Casenave, J.L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

On the Maximum Principle for Impulsive Hybrid Systems

Hybrid systems consist of dynamical systems where both continuous and discrete event dynamics are interacting. These are widely accepted as realistic models of diverse technical systems and processes, for instance, industrial electronics, power systems, maneuvering aircrafts, automotive control systems, chemical processes and communication networks. Recently optimization problems and variants of the Maximum Principle (MP) for hybrid systems have attracted a great deal of attention. Both theoretical results and computational techniques were developed see e.g.,[1]-[14]. These results are extended here to a general class of hybrid systems with state jumps and the corresponding constrained optimal control problems. The family of hybrid optimization problems under consideration (called Impulsive Hybrid Optimal Control Problems IHOCP) include dynamical systems with internally forced switchings and continuous control signals. The discrete state transitions are triggered by the continuous state and are accompanied by a discontinuous change in the latter variable. This class captures phenomena arising e.g., in cyclically operated batch processes and certain epidemic propagation models. Using the mathematical techniques of distributional derivatives and impulsive differential equations, we extend the necessary optimality conditions to the above class of problems (IHOCPs). We obtain specific elements of the Impulsive Hybrid MP (IHMP), namely, the corresponding boundary-value problem and some additional relations. As in the classical case, the proposed IHMP provides a basis for diverse computational algorithms for the treatment of IHOCPs