Entropy and efficiency of a molecular motor model

In this paper we investigate the use of path-integral formalism and the concepts of entropy and traffic in the context of molecular motors. We show that together with time-reversal symmetry breaking arguments one can find bounds on efficiencies of such motors. To clarify this techinque we use it on one specific model to find both the thermodynamic and the Stokes efficiencies, although the arguments themselves are more general and can be used on a wide class of models. We also show that by considering the molecular motor as a ratchet, one can find additional bounds on the thermodynamic efficiency

Soils, Science and Community ActioN (SoilSCAN): a citizen science tool to empower community-led land management change in East Africa

Pastoralist communities worldwide face complex challenges regarding food and feed productivity. Primary production systems are under stress, nutritional choices are changing and the relationship between development and agriculture is undergoing profound transformation. Under increasing pressure from climate and land use change, East African agro-pastoral systems are approaching a tipping point in terms of land degradation. There is an urgent need for evidence-led sustainable land management interventions to reverse degradation of natural resources that support food and water security. A key barrier, however, is a lack of high spatial resolution soil health data wherein collecting such information for each individual community is beyond their means. In this context, we tested whether bridging such data gaps could be achieved through a coordinated programme at the boundary between participation and citizen science. Key outputs included a community-led trial of a hand-held soil scanner, which highlighted a range of positive benefits and practical challenges in using this technology in this context, with identification of some potential solutions; and a targeted soil organic matter and nutrient status dataset in a small catchment-based community setting. The results show that if the practical challenges can be resolved, use of portable soil scanner technology has the potential to fill key knowledge gaps and thereby improve resilience to the threat of land degradation through locally responsive farmer and community decision-making

Tracing the dominant sources of sediment flowing towards Lake Victoria using geochemical tracers and a Bayesian mixing model

PurposeLake Victoria has been increasingly silting over the past decades, impacting water quality and loss of biodiversity. Sediment control strategies require information on the relative and absolute contributions of sediment from different sources. However, to date, there is no continuous monitoring of sediment flux or water quality in any of the tributaries, prohibiting an assessment of the scale of the problem. The aim of this study was to trace the dominant sources of riverine sediment using geochemical fingerprinting, thereby generating a knowledge base for improving land management and reducing sediment yields in Simiyu River catchment, one of the main contributing rivers to Lake Victoria.Materials and methodsGeochemical tracer concentrations were analyzed in transported sediment from the main river and two tributaries (riverbed sediments) and from soils in five dominant land use types (agricultural land, bush land, forest land, channel banks, and main river banks). Dominant sources to the Simiyu main river sediment were attributed using the Bayesian MixSIAR model.Results and discussionThe mixing model outputs showed that the Simiyu tributary was the dominant source of sediment to the Simiyu main river with 63.2%, while the Duma tributary accounted for 36.8%. Cultivated land was shown to be the main land use source of riverine sediment, accounting for 80.0% and 86.4% in Simiyu and Duma sub-tributaries, respectively, followed by channel banks with 9.0% in both sub-tributaries. Direct unmixing of the Simiyu main river sediment to the land use sources yielded 64.7% contribution of cultivated land and 26.5% of channel banks.ConclusionThe demonstrated application of sediment source tracing provides an important pathway for quantifying the dominant sources of sediment in the rivers flowing towards Lake Victoria. Eroded soil from agricultural areas is the biggest contributor to transported sediment in the Simiyu River. This information is vital for the design of catchment wide management plans that should focus on reducing soil erosion and sediment delivery from farming areas to the river networks, ultimately supporting both food security and water quality in the Lake Victoria Basin

A meaningful expansion around detailed balance

We consider Markovian dynamics modeling open mesoscopic systems which are driven away from detailed balance by a nonconservative force. A systematic expansion is obtained of the stationary distribution around an equilibrium reference, in orders of the nonequilibrium forcing. The first order around equilibrium has been known since the work of McLennan (1959), and involves the transient irreversible entropy flux. The expansion generalizes the McLennan formula to higher orders, complementing the entropy flux with the dynamical activity. The latter is more kinetic than thermodynamic and is a possible realization of Landauer's insight (1975) that, for nonequilibrium, the relative occupation of states also depends on the noise along possible escape routes. In that way nonlinear response around equilibrium can be meaningfully discussed in terms of two main quantities only, the entropy flux and the dynamical activity. The expansion makes mathematical sense as shown in the simplest cases from exponential ergodicity.Comment: 19 page

Drivers, Impacts and Mitigation of Increased Sedimentation in the Hydropower Reservoirs of East Africa

Hydropower reservoirs are essential for the climate-neutral development of East Africa. Hydropower production, however, is threatened by human activities that lead to a decrease in water storage capacity of reservoirs. Land use/land cover and climatic changes are driving accelerated soil erosion in semi-arid East Africa, which ultimately increases reservoir sedimentation and decreases energy production. Sediment delivery dynamics at the catchment scale are complex, involving the interaction of multiple factors and processes on different spatial and temporal scales. A lack of understanding of these processes and their interactions may impede the efficiency of sediment mitigation and control strategies. A deep understanding of the processes of erosion and connectivity of the land to river channel, as well as storage of eroded material within hillslopes and floodplains, and sediment accumulation in the reservoirs supports selection of future dam locations and sustainable management of reservoirs. The sediment budget approach can provide such a holistic perspective by accounting for the various sediment sources, transport, sinks, and redistribution when the sediment is routed through that catchment. Constructing sediment budgets is challenging, but the potential for integrating a number of different techniques offers new opportunities to collect the required information. In East Africa, the spatial planning of dams is mainly dominated by political and financial motives, and impacts of land use and climate on the sediment transport dynamics are not adequately considered. Production of sediment budgets under different scenarios of land use and climate change should be an essential step when deciding the location and management strategies for dams. Selection of new hydroelectric reservoir sites must consider long-term scientific data on climate change, and the sediment budget components for sustainable land management planning, hydropower sustainability.</jats:p

ENDF-6 compatible evaluation of neutron induced reaction cross sections for 106,108,110,111,112,113,114,116Cd

An ENDF-6 compatible evaluation for neutron induced reactions in the resonance region has been completed for 106,108,110,111,112,113,114,116Cd. The parameters are the result of an analysis of experimental data available in the literature together with a parameter adjustment on transmission and capture data obtained at the time-of-flight facility GELINA. Complete evaluated data files in ENDF-6 format have been produced by joining the evaluations in the resonance region with corresponding files from the JEFF-3.1.2 nuclear data library (or with the JEFF-Beta-CAD proposed evaluation in case of 113Cd). These files were produced for use in the JEFF32T2 library. For neutron induced reactions in the unresolved resonance region the JENDL-4.0 evaluation for 111Cd and 113Cd was adopted. The evaluated files have been processed with the latest updates of NJOY.99 to test their format and application consistency as well as to produce a continuous-energy data library in ACE format for use in Monte Carlo codes. The ACE files have been utilized to study the effect of the evaluated resonance parameters on results of integral experiments. The evaluated files will be implemented in the next release of the JEFF-3 library which is maintained by the Nuclear Energy Agency of the OECD.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Nonequilibrium Linear Response for Markov Dynamics, II: Inertial Dynamics

We continue our study of the linear response of a nonequilibrium system. This Part II concentrates on models of open and driven inertial dynamics but the structure and the interpretation of the result remain unchanged: the response can be expressed as a sum of two temporal correlations in the unperturbed system, one entropic, the other frenetic. The decomposition arises from the (anti)symmetry under time-reversal on the level of the nonequilibrium action. The response formula involves a statistical averaging over explicitly known observables but, in contrast with the equilibrium situation, they depend on the model dynamics in terms of an excess in dynamical activity. As an example, the Einstein relation between mobility and diffusion constant is modified by a correlation term between the position and the momentum of the particle

Predicting COVID-19 prognosis in the ICU remained challenging: external validation in a multinational regional cohort

Objective: Many prediction models for Coronavirus Disease 2019 (COVID-19) have been developed. External validation is mandatory before implementation in the Intensive Care Unit (ICU). We selected and validated prognostic models in the Euregio Intensive Care COVID (EICC) cohort. Study design and setting: In this multinational cohort study, routine data from COVID-19 patients admitted to ICUs within the Euregio Meuse-Rhine were collected from March to August 2020. COVID-19 models were selected based on model type, predictors, outcomes, and reporting. Furthermore, general ICU scores were assessed. Discrimination was assessed by area under the receiver operating characteristic curves (AUCs) and calibration by calibration-in-the-large and calibration plots. A random-effects meta-analysis was used to pool results. Results: 551 patients were admitted. Mean age was 65.4±11.2 years, 29% were female, and ICU mortality was 36%. Nine out of 238 published models were externally validated. Pooled AUCs were between 0.53 and 0.70 and calibration-in-the-large between -9% and 6%. Calibration plots showed generally poor but, for the 4C Mortality score and SEIMC score, moderate calibration. Conclusion: Of the nine prognostic models that were externally validated in the EICC cohort, only two showed reasonable discrimination and moderate calibration. For future pandemics, better models based on routine data are needed to support admission decision-making

Neutron capture cross section measurements for 197Au from 3.5 to 84 keV at GELINA

Cross section measurements have been performed at the time-of-flight facility GELINA to determine the average capture cross section for 197Au in the energy region between 3.5 keV and 84 keV. Prompt gamma-rays, originating from neutron induced capture events, were detected by two C6D6 liquid scintillators. The sample was placed at about 13 m distance from the neutron source. The total energy detection principle in combination with the pulse height weighting technique was applied. The energy dependence of the neutron flux was measured with a double Frisch-gridded ionization chamber based on the 10B(n,alpha)reaction. The data have been normalized to the well-isolated and saturated 197Au resonance at 4.9 eV. Special care was taken to reduce bias effects due to the weighting function, normalization, dead time and background corrections. The total uncertainty due to normalization, neutron flux and weighting function is 1.0%. An additional uncertainty of 0.5% results from the correction for self-shielding and multiple interaction events. Fluctuations due to resonance structures have been studied by complementary measurements at a 30 m flight path station. The results reported in this work deviate systematically by more than 5% from the cross section that is recommended as a reference for astrophysical applications. They are about 2% lower compared to an evaluation of the 197Au(n,gamma) cross section, which was based on a least squares fit of experimental data available in the literature prior to this work. The average capture cross section as a function of neutron energy has been parameterized in terms of average resonance parameters. Maxwellian average cross sections at different temperatures have been calculated.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Current fluctuations in stochastic systems with long-range memory

We propose a method to calculate the large deviations of current fluctuations in a class of stochastic particle systems with history-dependent rates. Long-range temporal correlations are seen to alter the speed of the large deviation function in analogy with long-range spatial correlations in equilibrium systems. We give some illuminating examples and discuss the applicability of the Gallavotti-Cohen fluctuation theorem.Comment: 10 pages, 1 figure. v2: Minor alterations. v3: Very minor alterations for consistency with published version appearing at http://stacks.iop.org/1751-8121/42/34200