On the exactness of the Semi-Classical Approximation for Non-Relativistic One Dimensional Propagators

For one dimensional non-relativistic quantum mechanical problems, we investigate the conditions for all the position dependence of the propagator to be in its phase, that is, the semi-classical approximation to be exact. For velocity independent potentials we find that: (i) the potential must be quadratic in space, but can have arbitrary time dependence. (ii) the phase may be made proportional to the classical action, and the magnitude (``fluctuation factor'') can also be found from the classical solution. (iii) for the driven harmonic oscillator the fluctuation factor is independent of the driving term.Comment: 7 pages, latex, no figures, published in journal of physics

To address emerging infections, we must invest in enduring systems: The kinetics and dynamics of health systems strengthening

Clinical pharmacology uses foundational principles of pharmacokinetics (PK) and pharmacodynamics (PD) to address medication use spanning a continuum from molecules to the masses. In the realm of infectious diseases, PK/PD attributes are considered especially important, because subtherapeutic dosing of antibiotics has been associated with poorer clinical outcomes in patients and increased incidences of drug resistance in populations. In consideration of these PK/PD principles, we will describe the analogous relationship between health systems strengthening, including for educating healthcare providers about emerging infections, and the tenets of therapeutic drug monitoring

Aggregation Prediction in Therapeutic Protein Formulations for Excipient Design

Computational Infrastructure & Informatics Poster SessionA major concern in the development therapeutic protein formulations is protein aggregation. Proteins can interact to form bound groups of protein molecules or aggregates. Aggregates in protein formulations reduce effectiveness and can lead to severe immune responses in patients. Excipients are additive molecules that are not therapeutically active, but can increase the stability of protein formulations. An ideal excipient binds with aggregation prone regions on the protein to limit interaction of that region with another protein molecule. The goal of this project is to predict aggregation prone regions and design excipients to interact with these regions. Several tools exist to predict which regions on a protein will be most likely to initiate aggregation. Aggrescan (http://bioinf.uab.es/aggrescan/) and SAP (Spatial Aggregation Potential) were used to predict aggregation prone regions on proteins and the results were compared. Aggrescan uses experimental data to assign each amino acid an aggregation propensity score. An aggregation prone region is identified by a sequence of amino acids with high propensities. The three-dimensional structure is not used in the aggregation prediction. SAP uses molecular simulation to determine regions that are hydrophobic and solvent accessible. Each residue is scored and the results are mapped to the three-dimensional protein structure. A successful prediction tool must use parameters that correlate with aggregation potential for a folded protein. The aggregation prone regions predicted by Aggrescan and SAP were compared to experimental data on protein aggregation. Proteins with a high number of predicted regions or large predicted regions were found to have higher experimental percent aggregation. With the regions identified, molecular simulations were performed for protein-excipient systems. A protein and small molecule docking algorithm was used to determine which regions of the protein certain excipients interacted with. Trehalose, poly(vinylpyrrolidone), and guanadine hydrochloride were used. For an excipient to successfully stabilize a protein and prevent aggregation, the excipient should interact with the aggregation prone regions predicted by Aggrescan and SAP. The predicted regions were compared to the regions where the excipient docks in the molecular simulation. The simulation results were compared to experimental data on the percent aggregation observed in several protein-excipient formulations. The excipients that were found to interact with the predicted aggregation prone regions in simulations should also experimentally prohibit aggregation, leading to lower percent aggregation. Hydrogen-deuterium swapping along with FTIR analysis will be performed experimentally to determine exposed regions on the protein. Proteins with a high number of exposed regions are less stable. The exposed regions will be compared to the aggregation prone regions predicted by Aggrescan and SAP

Boundary and Coulomb Effects on Boson Systems in High-Energy Heavy-Ion Collisions

The boundary of a boson system plays an important role in determining the momentum distribution of the bosons. For a boson system with a cylindrical boundary, the momentum distribution is enhanced at high transverse momenta but suppressed at low transverse momenta, relative to a Bose-Einstein distribution. The boundary effects on systems of massless gluons and massive pions are studied. For gluons in a quark-gluon plasma, the presence of the boundary may modify the signals for the quark-gluon plasma. For pions in a pion system in heavy-ion collisions, Coulomb final-state interactions with the nuclear participants in the vicinity of the central rapidity region further modify the momentum distribution at low transverse momenta. By including both the boundary effect and the Coulomb final-state interactions we are able to account for the behavior of the $\pi^{-}$ transverse momentum spectrum observed in many heavy-ion experiments, notably at low transverse momenta.Comment: 15 pages Postscript uuencoded tar-comprssed file, 9 Postscript figures uuencoded tar-compressed fil

A simple mean field model for social interactions: dynamics, fluctuations, criticality

We study the dynamics of a spin-flip model with a mean field interaction. The system is non reversible, spacially inhomogeneous, and it is designed to model social interactions. We obtain the limiting behavior of the empirical averages in the limit of infinitely many interacting individuals, and show that phase transition occurs. Then, after having obtained the dynamics of normal fluctuations around this limit, we analize long time fluctuations for critical values of the parameters. We show that random inhomogeneities produce critical fluctuations at a shorter time scale compared to the homogeneous system.Comment: 37 pages, 2 figure

Fitness benefits of prolonged post-reproductive lifespan in women

Most animals reproduce until they die, but in humans, females can survive long after ceasing reproduction. In theory, a prolonged post-reproductive lifespan will evolve when females can gain greater fitness by increasing the success of their offspring than by continuing to breed themselves. Although reproductive success is known to decline in old age, it is unknown whether women gain fitness by prolonging lifespan post-reproduction. Using complete multi-generational demographic records, we show that women with a prolonged post-reproductive lifespan have more grandchildren, and hence greater fitness, in pre-modern populations of both Finns and Canadians. This fitness benefit arises because post-reproductive mothers enhance the lifetime reproductive success of their offspring by allowing them to breed earlier, more frequently and more successfully. Finally, the fitness benefits of prolonged lifespan diminish as the reproductive output of offspring declines. This suggests that in female humans, selection for deferred ageing should wane when one's own offspring become post-reproductive and, correspondingly, we show that rates of female mortality accelerate as their offspring terminate reproduction

Arctic air pollution: Challenges and opportunities for the next decade

The Arctic is a sentinel of global change. This region is influenced by multiple physical and socio-economic drivers and feedbacks, impacting both the natural and human environment. Air pollution is one such driver that impacts Arctic climate change, ecosystems and health but significant uncertainties still surround quantification of these effects. Arctic air pollution includes harmful trace gases (e.g. tropospheric ozone) and particles (e.g. black carbon, sulphate) and toxic substances (e.g. polycyclic aromatic hydrocarbons) that can be transported to the Arctic from emission sources located far outside the region, or emitted within the Arctic from activities including shipping, power production, and other industrial activities. This paper qualitatively summarizes the complex science issues motivating the creation of a new international initiative, PACES (air Pollution in the Arctic: Climate, Environment and Societies). Approaches for coordinated, international and interdisciplinary research on this topic are described with the goal to improve predictive capability via new understanding about sources, processes, feedbacks and impacts of Arctic air pollution. Overarching research actions are outlined, in which we describe our recommendations for 1) the development of trans-disciplinary approaches combining social and economic research with investigation of the chemical and physical aspects of Arctic air pollution; 2) increasing the quality and quantity of observations in the Arctic using long-term monitoring and intensive field studies, both at the surface and throughout the troposphere; and 3) developing improved predictive capability across a range of spatial and temporal scales

Closed-flavor pi + J/psi and pi + Upsilon Cross Sections at Low Energies from Dipion Decays

The scale of low energy c-cbar and b-bbar cross sections on light hadrons is of great importance to searches for the quark gluon plasma using the heavy-quarkonium suppression signature. Unfortunately, little is known about these near-threshold cross sections at present, and recent theoretical estimates span many orders of magnitude. Here we use experimental data on the four observed closed-flavor heavy quarkonium hadronic decays psi' -> pi pi J/psi, Upsilon' -> pi pi Upsilon, Upsilon'' -> pi pi Upsilon and Upsilon'' -> pi pi Upsilon', combined with simple models of the transition amplitudes, to estimate the pion scattering cross sections of c-cbar and b-bbar mesons near threshold. Specifically we consider the closed-flavor reactions pi J/psi -> pi psi', pi Upsilon -> pi Upsilon', pi Upsilon -> pi Upsilon'' and pi Upsilon' -> pi Upsilon'' and their time-reversed analogues. Our results may be useful in constraining theoretical models of the strong interactions of heavy quarkonia, and can be systematically improved through future detailed studies of dipion decays, notably psi' -> pi pi J/psi and Upsilon'' -> pi pi Upsilon.Comment: 6 pages, 6 figure

Report of the ICES\NAFO Joint Working Group on Deep-water Ecology (WGDEC), 11–15 March 2013, Floedevigen, Norway.

On 11 February 2013, the joint ICES/NAFO WGDEC, chaired by Francis Neat (UK) and attended by ten members met at the Institute for Marine Research in Floedevi-gen, Norway to consider the terms of reference (ToR) listed in Section 2. WGDEC was requested to update all records of deep-water vulnerable marine eco-systems (VMEs) in the North Atlantic. New data from a range of sources including multibeam echosounder surveys, fisheries surveys, habitat modelling and seabed imagery surveys was provided. For several areas across the North Atlantic, WGDEC makes recommendations for areas to be closed to bottom fisheries for the purposes of conservation of VMEs