Systematic Perturbation Theory for Dynamical Coarse-Graining

We demonstrate how the dynamical coarse-graining approach can be systematically extended to higher orders in the coupling between system and reservoir. Up to second order in the coupling constant we explicitly show that dynamical coarse-graining unconditionally preserves positivity of the density matrix -- even for bath density matrices that are not in equilibrium and also for time-dependent system Hamiltonians. By construction, the approach correctly captures the short-time dynamics, i.e., it is suitable to analyze non-Markovian effects. We compare the dynamics with the exact solution for highly non-Markovian systems and find a remarkable quality of the coarse-graining approach. The extension to higher orders is straightforward but rather tedious. The approach is especially useful for bath correlation functions of simple structure and for small system dimensions.Comment: 17 pages, 5 figures, version accepted for publication in PR

The potential role of T-cells and their interaction with antigen-presenting cells in mediating immunosuppression following trauma-hemorrhage

Objective: Trauma-hemorrhage results in depressed immune responses of antigen-presenting cells (APCs) and T-cells. Recent studies suggest a key role of depressed T-cell derived interferon (IFN)-g in this complex immune cell interaction. The aim of this study was to elucidate further the underlying mechanisms responsible for dysfunctional T-cells and their interaction with APCs following trauma-hemorrhage. Design: Adult C3H/HeN male mice were subjected to trauma-hemorrhage (3-cm midline laparotomy) followed by hemorrhage (blood pressure of 35�5mmHg for 90 min and resuscitation) or sham operation. At 24 h thereafter, spleens were harvested and T-cells (by Microbeads) and APCs (via adherence) were Isolated. Co-cultures of T-cells and APCs were established for 48 h and stimulated with concanavalin A and lipopolysaccharide. T-Cell specific cytokines known to affect APC function (i.e. interleukin(IL)-2, IL-4 and granulocyte-macrophage colony-stimulating factor (GM-CSF)) were measured in culture supernatants by Multiplex assay. The expression of MHC class II as well as co-stimulatory surface molecules on T-cells and APCs was determined by flow cytometry. Results: The release of IL-4 and GM-CSF by T-cells was suppressed following trauma-hemorrhage, irrespective of whether sham or trauma-hemorrhage APCs were present. Antigen-presenting cells from animals subjected to trauma-hemorrhage did not affect T-cell derived cytokine release by sham T-cells. In contrast, T-cells from traumahemorrhage animals depressed MHC class II expression of CD11c(þ) cells, irrespective of whether APCs underwent sham or trauma-hemorrhage procedure. Surprisingly, co-stimulatory molecules on APCs (CD80, CD86) were not affected by trauma-hemorrhage. Conclusions: These results suggest that beside IFN-g other T-cell derived cytokines contribute to immunosuppression following trauma-hemorrhage causing diminished MHC II expression on APCs. Thus, T-cells appear to play an important role in this interaction at the time-point examined. Therapeutic approaches should aim at maintenance of T-cell function and their interaction with APCs to prevent extended immunosuppression following trauma-hemorrhage

A global synthesis of fire effects on pollinators

Understanding fire effects on pollinators is critical in the context of fire regime changes and the global pollination crisis. Through a systematic and quantitative review of the literature, we provide the first global assessment of pollinator responses to fire. We hypothesize that pollinators increase after fire and during the early postfire succession stages; however, high fire frequency has the opposite effect, decreasing pollinators. Location: Terrestrial ecosystems, excluding Antarctica. Time period: Data collected from 1973 to 2017. Major taxa studied: Insects (Coleoptera, Diptera, Hymenoptera and Lepidoptera) and a few bird species. Methods: We first compiled available studies across the globe that assessed fire effects on pollinator communities. Then, by means of hierarchical meta-analyses, we evaluated how different fire regime parameters (fire frequency, postfire time and fire type) and habitat characteristics affect the abundance and richness of animals that act as pollinators. We also explored to what extent the responses vary among taxa groups and life history traits of pollinators (sociality system, nest location and feeding specialization), and among biomes. The overall effect size of fire on pollinator abundance and richness across all studies was positive. Fire effect was especially clear and significant in early postfire communities, after wildfires, and for Hymenoptera. Taxonomic resolution influenced fire effects, where only studies at the species/genus and family levels showed significant effects. The main exceptions were recurrent fires that showed a negative effect, and especially wildfire effects on Lepidoptera abundance that showed a significant negative response. Main conclusions: Pollinators tend to be promoted after a wildfire event. However, short fire intervals may threat pollinators, and especially lepidopterans. Given the current fire regime changes at the global scale, it is imperative to monitor postfire pollinators across many ecosystems, as our results suggest that fire regime is critical in determining the dynamics of pollinator communities.Fil: Carbone, Lucas Manuel. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Tavella, Julia Rita. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Pausas, Juli G.. Universidad de Valencia; EspañaFil: Aguilar, Ramiro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin

Dynamic Potential Intensity: An improved representation of the ocean's impact on tropical cyclones

To incorporate the effects of tropical cyclone (TC)-induced upper ocean mixing and sea surface temperature (SST) cooling on TC intensification, a vertical average of temperature down to a fixed depth was proposed as a replacement for SST within the framework of air-sea coupled Potential Intensity (PI). However, the depth to which TC-induced mixing penetrates may vary substantially with ocean stratification and storm state. To account for these effects, here we develop a “Dynamic Potential Intensity” (DPI) based on considerations of stratified fluid turbulence. For the Argo period 2004–2013 and the three major TC basins of the Northern Hemisphere, we show that the DPI explains 11–32% of the variance in TC intensification, compared to 0–16% using previous methods. The improvement obtained using the DPI is particularly large in the eastern Pacific where the thermocline is shallow and ocean stratification effects are strong.United States. Department of Energy. Office of Science (part of the Regional and Global Climate Modeling Program)Atlantic Oceanographic and Meteorological Laboratory (base funds

The effect of uncertain river forcing on the thermohaline properties of the North West European Shelf Seas

Modeling studies and observations show that the thermohaline properties of the North West European Shelf Seas (NWESS) are sensitive to surface wind and heat flux forcing, as well as river outflows that transport fresh water from land to the ocean. In previous studies, it was assumed that the variability of the thermohaline properties in response to river outflow could be adequately sampled with a high-resolution, submesoscale permitting, long-term (i.e., 30-year) deterministic hindcast. In this study, we assume that the statistical distribution of the river forcing, rather than the time series of forcing itself, is adequately constrained by a 28-year history (1991 to 2018) of river forcing created specifically for our domain. In this way, we created an ensemble of 10 lower-resolution ( 7-km), short-term (i.e., 2.5 years) hindcast models that are forced with randomly perturbed river outflows and an ensemble of surface fluxes from the 10-member ECMWF ERA5 reanalysis (the ‘Test’ ensemble) as well with a companion ensemble that is forced with the ERA5 surface forcing fluxes but unperturbed river outflows (the ‘Base’ ensemble) for the June 2016 through December 2018 time period. In both ensembles, the modeled evolution of 25-hour averaged (to partially filter out tides) temperature and salinity is realistic with peaks in summer for sea surface temperature and in winter for salinity, and annual amplitudes that are comparable to those found in other studies of the NWESS. The increased mean and standard deviation of the sea surface and bottom salinity in the Test ensemble are partly an artifact of the assumption that the errors in river forcing have a log-normal distribution that mimics the episodic nature of river outflow with a positive mean and an asymmetrical shape with a long tail towards large values. For surface density, the standard deviation in the Test ensemble was below 0.5 kg/m3, covering an areal extent larger than that for the Base ensemble throughout the year. The annual cycle of the areal extent of density in that range had a peak in summer and minima in winter, in phase with that of the river outflow forcing. Overall, the effect of uncertain river forcing on the thermohaline properties in this study is small. In order to understand the true impact of river forcings, better temporal and spatial observations of river outflow are needed

Advocating For Science: Amici Curiae Brief Of Wetland And Water Scientists In Support Of The Clean Water Rule

The Trump administration has proposed replacing the Clean Water Rule, a 2015 regulation that defined the statutory term waters of the United States to clarify the geographic jurisdiction of the Clean Water Act. Since its promulgation, the Clean Water Rule has been subjected to numerous judicial challenges. We submitted an amici curiae brief to the United States Court of Appeals for the Sixth Circuit, explaining why the Clean Water Rule, and its definition of waters of the United States, is scientifically sound. The definition of waters of the United States is a legal determination informed by science. The best available science supports the Clean Water Rule\u27s categorical treatment of tributaries because compelling scientific evidence demonstrates that tributaries significantly affect the chemical, physical, and biological integrity of traditional navigable waters (primary waters). Similarly, the best available science supports the Clean Water Rule\u27s categorical treatment of adjacent waters based on geographic proximity. Compelling scientific evidence demonstrates that waters within 100ft of an ordinary high water mark (OHWM) significantly affect the chemical, physical, and biological integrity of primary waters, as do waters within 100-year floodplains and waters within 1500ft of high tide lines of tidally influenced primary waters or OHWMs of the Great Lakes. This review article is adapted from that amici brief

Restoration of Ailing Wetlands

The science of ecological restoration involves building the technical understanding needed to restore damaged ecosystems, such as wetlands, which provide critical services needed to support human health and economic well-being

Illusions and Cloaks for Surface Waves

Open access articleEver since the inception of Transformation Optics (TO), new and exciting ideas have been proposed in the field of electromagnetics and the theory has been modified to work in such fields as acoustics and thermodynamics. The most well-known application of this theory is to cloaking, but another equally intriguing application of TO is the idea of an illusion device. Here, we propose a general method to transform electromagnetic waves between two arbitrary surfaces. This allows a flat surface to reproduce the scattering behaviour of a curved surface and vice versa, thereby giving rise to perfect optical illusion and cloaking devices, respectively. The performance of the proposed devices is simulated using thin effective media with engineered material properties. The scattering of the curved surface is shown to be reproduced by its flat analogue (for illusions) and vice versa for cloaks.Engineering and Physical Sciences Research Council (EPSRC