Universal thermodynamic bounds on nonequilibrium response with biochemical applications

Diverse physical systems are characterized by their response to small perturbations. Near thermodynamic equilibrium, the fluctuation-dissipation theorem provides a powerful theoretical and experimental tool to determine the nature of response by observing spontaneous equilibrium fluctuations. In this spirit, we derive here a collection of equalities and inequalities valid arbitrarily far from equilibrium that constrain the response of nonequilibrium steady states in terms of the strength of nonequilibrium driving. Our work opens new avenues for characterizing nonequilibrium response. As illustrations, we show how our results rationalize the energetic requirements of two common biochemical motifs.Comment: 21 pages, 15 figure

Under Democratic presidents, minorities make economic gains – and so do whites

In the lead up to presidential elections in recent years, both Republicans and Democrats have claimed that their policy platforms are better at improving the economic situation for minorities. Zoltan Hajnal and Jeremy Horowitz take a close look at both parties’ records on improving the economic situation for minorities, and find that under Democratic presidents, blacks and other minority groups see rising wages, falling poverty and unemployment rates, and that they tend to lose ground under Republican administrations. They also find that whites make similar gains under Democratic presidents

Spontaneous fine-tuning to environment in many-species chemical reaction networks

A chemical mixture that continually absorbs work from its environment may exhibit steady-state chemical concentrations that deviate from their equilibrium values. Such behavior is particularly interesting in a scenario where the environmental work sources are relatively difficult to access, so that only the proper orchestration of many distinct catalytic actors can power the dissipative flux required to maintain a stable, far-from-equilibrium steady state. In this article, we study the dynamics of an in silico chemical network with random connectivity in an environment that makes strong thermodynamic forcing available only to rare combinations of chemical concentrations. We find that the long-time dynamics of such systems are biased toward states that exhibit a fine-tuned extremization of environmental forcing. Keywords: nonequilibrium thermodynamics; adaptation; chemical reaction networks; self-organization; energy seekingGordon and Betty Moore Foundation (Grant GBMF4343

Minimum energetic cost to maintain a target nonequilibrium state

In the absence of external driving, a system exposed to thermal fluctuations will relax to equilibrium. However, the constant input of work makes it possible to counteract this relaxation and maintain the system in a nonequilibrium steady state. In this article, we use the stochastic thermodynamics of Markov jump processes to compute the minimum rate at which energy must be supplied and dissipated to maintain an arbitrary nonequilibrium distribution in a given energy landscape. This lower bound depends on two factors: the undriven probability current in the equilibrium state and the distance from thermal equilibrium of the target distribution. By showing the consequences of this result in a few simple examples, we suggest general implications for the required energetic costs of macromolecular repair and cytosolic protein localization.Gordon and Betty Moore Foundation (GBMF4343

Dissipation Bounds All Steady-State Current Fluctuations

Near equilibrium, small current fluctuations are described by a Gaussian distribution with a linear-response variance regulated by the dissipation. Here, we demonstrate that dissipation still plays a dominant role in structuring large fluctuations arbitrarily far from equilibrium. In particular, we prove a linear-response-like bound on the large deviation function for currents in Markov jump processes. We find that nonequilibrium current fluctuations are always more likely than what is expected from a linear-response analysis. As a small-fluctuations corollary, we derive a recently conjectured uncertainty bound on the variance of current fluctuations.Gordon and Betty Moore Foundation (Grant GBMF4513)Gordon and Betty Moore Foundation (Grant GBMF4343

Civic Education and Democratic Backsliding in the Wake of Kenya’s Post-2007 Election Violence

This article examines two unexplored questions concerning the impact of civic education programs in emerging democracies: (1) whether such programs have longer-terms effects and (2) whether civic education can be effective under conditions of democratic “backsliding.” We investigate these questions in the context of a large-scale civic education program in Kenya just before the disputed 2007 election that sparked a wave of ethnic clashes and brought the country to the brink of civil war. Analysis of a survey of 1,800 “treatment” and 1,800 “control” individuals shows that the program had significant long-term effects on variables related to civic competence and engagement, with less consistent effects on democratic values. We also find that participants who subsequently were affected by the violence were less likely to adopt negative beliefs about Kenya’s political system, less likely to support the use of ethnic or political violence, and more likely to forgive those responsible for the post-election violence

Panel Discussion: Provost\u27s Open Educational Resource (OER) Fellows

While the adoption of open educational resources (OERs) in the undergraduate curriculum has the evident benefit of reducing cost to the student, thinking deeply about OER adoption reveals numerous questions: can OERs match the quality of traditional textbooks and other commercial educational resources? Are there problems associated with the current textbook landscape that OERs can solve? And how easily can OERs be integrated into classrooms with established modes of instruction? Each of the Provost’s OER Fellows will discuss briefly some of the most important conclusions from the current OER research literature and discuss these in the context of SUNY Albany and its students. They will be sharing their experiences adopting and adapting OER materials for courses in the humanities and the sciences

Mechanical Properties of non-accreting Neutron Star Crusts

The mechanical properties of a neutron star crust, such as breaking strain and shear modulus, have implications for the detection of gravitational waves from a neutron star as well as bursts from Soft Gamma-ray Repeaters (SGRs). These properties are calculated here for three different crustal compositions for a non-accreting neutron star that results from three different cooling histories, as well as for a pure iron crust. A simple shear is simulated using molecular dynamics to the crustal compositions by deforming the simulation box. The breaking strain and shear modulus are found to be similar in the four cases, with a breaking strain of ~0.1 and a shear modulus of ~10^{30} dyne cm^{-2} at a density of \rho = 10^{14} g cm^{-3} for simulations with an initially perfect BCC lattice. With these crustal properties and the observed properties of {PSR J2124-3358} the predicted strain amplitude of gravitational waves for a maximally deformed crust is found to be greater than the observational upper limits from LIGO. This suggests that the neutron star crust in this case may not be maximally deformed or it may not have a perfect BCC lattice structure. The implications of the calculated crustal properties of bursts from SGRs are also explored. The mechanical properties found for a perfect BCC lattice structure find that crustal events alone can not be ruled out for triggering the energy in SGR bursts.Comment: 10 pages, 6 figures, accepted for publication in Monthly Notices of the Royal Astronomical Societ

Quality Assessment of Meteorological Data for the Beaufort and Chukchi Sea Coastal Region using Automated Routines

Meteorological observations from more than 250 stations in the Beaufort and Chukchi Sea coastal, interior, and offshore regions were gathered and quality-controlled for the period 1979 through 2009. These stations represent many different observing networks that operate in the region for the purposes of aviation, fire weather, coastal weather, climate, surface radiation, and hydrology and report data hourly or sub-hourly. A unified data quality control (QC) has been applied to these multi-resource data, incorporating three main QC procedures: the threshold test (identifying instances of an observation falling outside of a normal range); the step change test (identifying consecutive values that are excessively different); and the persistence test (flagging instances of excessively high or low variability in the observations). Methods previously developed for daily data QC do not work well for hourly data because they flag too many data entries. Improvements were developed to obtain the proper limits for hourly data QC. These QC procedures are able to identify the suspect data while producing far fewer Type I errors (the erroneous flagging of valid data). The fraction of flagged data for the entire database illustrates that the persistence test was failed the most often (1.34%), followed by the threshold (0.99%) and step change tests (0.02%). Comparisons based on neighboring stations were not performed for the database; however, correlations between nearby stations show promise, indicating that this type of check may be a viable option in such cases. This integrated high temporal resolution dataset will be invaluable for weather and climate analysis, as well as regional modeling applications, in an area that is undergoing significant climatic change.Des observations météorologiques provenant de plus de 250 stations des régions côtières, intérieures et extracôtières de la mer de Beaufort et de la mer des Tchouktches ont été recueillies pendant la période allant de 1979 à 2009, puis elles ont fait l’objet d’un contrôle de la qualité. Ces stations relèvent de plusieurs réseaux d›observation différents qui existent dans la région à des fins d›aviation, de météorologie forestière, de météorologie côtière, de climat, de rayonnement de surface et d’hydrologie, et elles fournissent des données horaires ou subhoraires. Un contrôle de la qualité (CQ) unifié des données a été appliqué à ces données provenant de sources multiples en faisant appel à trois méthodes principales de CQ, soit le test d’acceptabilité (qui a permis de déterminer dans quels cas une observation ne faisait pas partie de la gamme normale); le test de la variation discrète (qui a permis de détecter les valeurs consécutives qui sont excessivement différentes); et le test de la persistance (qui a permis de repérer les cas de variabilité excessivement élevée ou basse). Les anciennes méthodes de CQ des données quotidiennes ne donnent pas de bons résultats dans le cas des données horaires parce qu’elles se trouvent à signaler un trop grand nombre d’entrées de données. Des améliorations ont été apportées afin d’obtenir les bonnes limites en vue du CQ des données horaires. Ces méthodes de CQ permettent de repérer les données douteuses et produisent beaucoup moins d’erreurs de type I (le signalement erroné de données valables). La fraction de données signalées pour l’ensemble de la base de données illustre que le test de persistance a échoué le plus souvent (1,34 %), suivi du test d’acceptabilité (0,99 %) et des tests de la variation discrète (0,02 %). Des comparaisons effectuées avec les données de stations avoisinantes n’ont pas été effectuées pour la base de données. Cependant, des corrélations entre les stations annexes s’avéraient prometteuses, ce qui a laissé entendre que ce type de vérification pourrait présenter une option viable dans de tels cas. Cet ensemble de données intégrées à haute résolution temporelle aura une très grande valeur pour l’analyse météorologique et climatique ainsi que pour les applications de modélisation régionale dans une région où le changement climatique est important