Alien Registration- Searles, Gerald M. (Portland, Cumberland County)

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Fluctuation Theorems

Fluctuation theorems, which have been developed over the past 15 years, have resulted in fundamental breakthroughs in our understanding of how irreversibility emerges from reversible dynamics, and have provided new statistical mechanical relationships for free energy changes. They describe the statistical fluctuations in time-averaged properties of many-particle systems such as fluids driven to nonequilibrium states, and provide some of the very few analytical expressions that describe nonequilibrium states. Quantitative predictions on fluctuations in small systems that are monitored over short periods can also be made, and therefore the fluctuation theorems allow thermodynamic concepts to be extended to apply to finite systems. For this reason, fluctuation theorems are anticipated to play an important role in the design of nanotechnological devices and in understanding biological processes. These theorems, their physical significance and results for experimental and model systems are discussed.Comment: A review, submitted to Annual Reviews in Physical Chemistry, July 2007 Acknowledgements corrected in revisio

Equilibrium binding energies from fluctuation theorems and force spectroscopy simulations

Brownian dynamics simulations are used to study the detachment of a particle from a substrate. Although the model is simple and generic, we attempt to map its energy, length and time scales onto a specific experimental system, namely a bead that is weakly bound to a cell and then removed by an optical tweezer. The external driving force arises from the combined optical tweezer and substrate potentials, and thermal fluctuations are taken into account by a Brownian force. The Jarzynski equality and Crooks' fluctuation theorem are applied to obtain the equilibrium free energy difference between the final and initial states. To this end, we sample non--equilibrium work trajectories for various tweezer pulling rates. We argue that this methodology should also be feasible experimentally for the envisioned system. Furthermore, we outline how the measurement of a whole free energy profile would allow the experimentalist to retrieve the unknown substrate potential by means of a suitable deconvolution. The influence of the pulling rate on the accuracy of the results is investigated, and umbrella sampling is used to obtain the equilibrium probability of particle escape for a variety of trap potentials.Comment: 21 pages, 11 figures, To appear in Soft Matte

Doping Effects on the Performance of Paired Metal Catalysts for the Hydrogen Evolution Reaction

Metal heteroatoms dispersed in nitrogen-doped graphene display promising catalytic activity for fuel cell reactions such as the hydrogen evolution reaction (HER). Here we explore the effects of dopant concentration on the synergistic catalytic behaviour of a paired metal atom active site comprised of Co and Pt atoms. The metals are coordinated to six atoms in a vacancy of N-doped graphene. We find that HER activity is enhanced with increasing N concentration, where the free energy of hydrogen atom adsorption ranges from 0.23 to -0.42 eV as the doping changes from a single N atom doped in the pore, to fully doped coordination sites. The results indicated that the effect of N is to make the Co atom more active towards H adsorption and presents a means through which transition metals can be modified to make more effective and sustainable fuel cell catalysts

Plant response to solar ultraviolet-B radiation in a southern South American Sphagnum peatland

1. Plant growth and pigmentation of the moss Sphagnum magellanicum and the vascular plants Empetrum rubrum, Nothofagus antarctica and Tetroncium magellanicum were measured under near-ambient (90% of ambient) and reduced (20%) ultraviolet-B (UV-B) radiation for three growing seasons in a Sphagnum peatland in Tierra del Fuego, Argentina (55°S). 2. Reduction of solar UV-B increased height growth but decreased volumetric density in S. magellanicum so that biomass production was not influenced during the 3 years. The morphology of vascular plants tended not to respond to UV-B reduction. 3. A 10-20% decrease in UV-B-absorbing compounds occurred in T. magellanicum under solar UV-B reduction. No effects were seen on chlorophyll or carotenoids in S. magellanicum, although, for UV-B-absorbing compounds, a significant interaction between UV-B and year suggests some response to solar UV-B reduction. 4. The climate-related growth of the dwarf shrub E. rubrum was assessed retrospectively by correlating an 8-year record of annual stem elongation with macroclimatic factors including solar UV-B and visible radiation, precipitation and temperature. 5. No significant negative correlations were found between annual E. rubrum stem elongation and ambient solar UV-B, the ratio of UV-B: visible radiation, or the 305-nm: 340-nm irradiance ratio for an 8-year record (1990-91 to 1997-98), nor was stem elongation affected by solar UV-B reduction in our experimental field plots after 3 years. 6. The role of solar UV-B radiation on plant growth in Sphagnum peatlands in Tierra del Fuego, Argentina, is likely to depend on the severity of stratospheric ozone depletion over the next several decades. The increases in ambient solar UV-B associated with ozone depletion over the last 20 years are less than the difference between our radiation treatments. Therefore, providing that the ozone layer substantially recovers by the middle of this century, only modest effects of increased solar UV-B on plant growth may be expected.Fil: Searles, Peter Stoughton. State University of Utah; Estados UnidosFil: Flint, Stephan D.. State University of Utah; Estados UnidosFil: Diaz, Susana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Rousseaux, Maria Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Ballare, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Caldwell, Martyn M.. State University of Utah; Estados Unido

The Steady State Fluctuation Relation for the Dissipation Function

We give a proof of transient fluctuation relations for the entropy production (dissipation function) in nonequilibrium systems, which is valid for most time reversible dynamics. We then consider the conditions under which a transient fluctuation relation yields a steady state fluctuation relation for driven nonequilibrium systems whose transients relax, producing a unique nonequilibrium steady state. Although the necessary and sufficient conditions for the production of a unique nonequilibrium steady state are unknown, if such a steady state exists, the generation of the steady state fluctuation relation from the transient relation is shown to be very general. It is essentially a consequence of time reversibility and of a form of decay of correlations in the dissipation, which is needed also for, e.g., the existence of transport coefficients. Because of this generality the resulting steady state fluctuation relation has the same degree of robustness as do equilibrium thermodynamic equalities. The steady state fluctuation relation for the dissipation stands in contrast with the one for the phase space compression factor, whose convergence is problematic, for systems close to equilibrium. We examine some model dynamics that have been considered previously, and show how they are described in the context of this work.Comment: 30 pages, 1 figur

Validation of a Parkinson disease predictive model in a population-based study

Parkinson disease (PD) has a relatively long prodromal period that may permit early identification to reduce diagnostic testing for other conditions when patients are simply presenting with early PD symptoms, as well as to reduce morbidity from fall-related trauma. Earlier identification also could prove critical to the development of neuroprotective therapies. We previously developed a PD predictive model using demographic and Medicare claims data in a population-based case-control study. The area under the receiver-operating characteristic curve (AUC) indicated good performance. We sought to further validate this PD predictive model. In a randomly selected, population-based cohort of 115,492 Medicare beneficiaries aged 66–90 and without PD in 2009, we applied the predictive model to claims data from the prior five years to estimate the probability of future PD diagnosis. During five years of follow-up, we used 2010–2014 Medicare data to determine PD and vital status and then Cox regression to investigate whether PD probability at baseline was associated with time to PD diagnosis. Within a nested case-control sample, we calculated the AUC, sensitivity, and specificity. A total of 2,326 beneficiaries developed PD. Probability of PD was associated with time to PD diagnosis (p<0.001, hazard ratio = 13.5, 95% confidence interval (CI) 10.6–17.3 for the highest vs. lowest decile of probability). The AUC was 83.3% (95% CI 82.5%–84.1%). At the cut point that balanced sensitivity and specificity, sensitivity was 76.7% and specificity was 76.2%. In an independent sample of additional Medicare beneficiaries, we again applied the model and observed good performance (AUC = 82.2%, 95% CI 81.1%–83.3%). Administrative claims data can facilitate PD identification within Medicare and Medicare-aged samples

Does evidence influence policy? Resource allocation and the Indigenous Burden of Disease study

Objective The Indigenous Burden of Disease (IBoD) report is the most comprehensive assessment of Indigenous disease burden in Australia. The aim of the present study was to investigate the potential effect of the IBoD report on Australian Indigenous health policy, service expenditure and research funding. Findings have significance for understanding factors that may influence Indigenous health policy. Methods The potential effect of the IBoD report was considered by: (1) conducting a text search of pertinent documents published by the federal government, Council of Australian Governments and the National Health and Medical Research Council of Australia (NHMRC) and observing the quantity and quality of references to IBoD; (2) examining data on government Indigenous healthcare expenditure for trends consistent with the findings and policy implications of the IBoD report; and (3) examining NHMRC Indigenous grant allocation trends consistent with the findings and policy implications of the IBoD report. Results Of 110 government and NHMRC documents found, IBoD was cited in 27. Immediately after publication of the IBoD report, federal and state governments increased Indigenous health spending (relative to non-Indigenous), notably for community health and public health at the state level. Expenditure on Indigenous hospital separations for chronic diseases also increased. These changes are broadly consistent with the findings of the IBoD report on the significance of chronic disease and the need to address certain risk factors. However, there is no evidence that such changes had a causal connection with the IBoD study. After publication of the IBoD report, changes in NHMRC Indigenous research funding showed little consistency with the findings of the IBoD report. Conclusions The present study found only indirect and inconsistent correlational evidence of the potential influence of the IBoD report on Indigenous health expenditure and research funding. Further assessment of the potential influence of the IBoD report on Indigenous health policy will require more targeted research, including interviews with key informants involved in developing health policy. What is known about the topic? There are currently no publications that consider the potential effed of the IBoD study on Indigenous health expenditure and research funding. What does this paper add? This paper offers the first consideration of the potential effect of the IBoD report. It contains analyses of data from readily available sources, examining national expenditures on Indigenous health and NHMRC Indigenous research, before and after the publication of the IBoD report. What are the implications for practitioners? The paper is relevant to analysts interested in drivers of Indigenous health policy. Although it finds correlations between the release of the IBoD report and some subsequent health spending decisions, other factors should be investigated to better understand the complexity of processes that drive government efforts to improve Indigenous health