Percolation-Modeling Comparison Between the Conductivities of Zinc-Graphene Quantum Dot Nanocomposite and Graphite during Extracellular Electron Transfer in Microbial Fuel Cell Electrodes

While promising as an energy production alternative through its sustainability and wastewater treatment utility, a microbial fuel cell is not widely used due to its low power output and high cost. The development of advanced electrode materials is currently being pursued to solve this problem. A zinc-graphene quantum dot nanocomposite was modeled using percolation theory as a prospective advanced electrode material. During extracellular electron transfer, the electrical conductivity properties of the material were studied through cellular percolation models, percolation probability functions, and electrical conductivity curves. These models were compared against those of the conventional graphite electrodes and the leading graphene electrodes. The nanocomposite was found to conduct at low probabilities of open sites and exhibit the highest electrical conductivity of the three materials for the longest duration across the interval. Based on the models, Zn-GQD was demonstrated to be an ideal MFC electrode material for its balance between the early onset of conduction and decently high electrical conductivity

A comprehensive overview of grain development in Brachypodium distachyon variety Bd21

A detailed and comprehensive understanding of seed reserve accumulation is of great importance for agriculture and crop improvement strategies. This work is part of a research programme aimed at using Brachypodium distachyon as a model plant for cereal grain development and filling. The focus was on the Bd21-3 accession, gathering morphological, cytological, and biochemical data, including protein, lipid, sugars, starch, and cell-wall analyses during grain development. This study highlighted the existence of three main developmental phases in Brachypodium caryopsis and provided an extensive description of Brachypodium grain development. In the first phase, namely morphogenesis, the embryo developed rapidly reaching its final morphology about 18 d after fertilization (DAF). Over the same period the endosperm enlarged, finally to occupy 80% of the grain volume. During the maturation phase, carbohydrates were continuously stored, mainly in the endosperm, switching from sucrose to starch accumulation. Large quantities of β-glucans accumulated in the endosperm with local variations in the deposition pattern. Interestingly, new β-glucans were found in Brachypodium compared with other cereals. Proteins (i.e. globulins and prolamins) were found in large quantities from 15 DAF onwards. These proteins were stored in two different sub-cellular structures which are also found in rice, but are unusual for the Pooideae. During the late stage of development, the grain desiccated while the dry matter remained fairly constant. Brachypodium exhibits some significant differences with domesticated cereals. Beta-glucan accumulates during grain development and this cell wall polysaccharide is the main storage carbohydrate at the expense of starch

Desorption of hot molecules from photon irradiated interstellar ices

We present experimental measurements of photodesorption from ices of astrophysical relevance. Layers of benzene and water ice were irradiated with a laser tuned to an electronic transition in the benzene molecule. The translational energy of desorbed molecules was measured by time-of-flight (ToF) mass spectrometry. Three distinct photodesorption processes were identified - a direct adsorbate-mediated desorption producing benzene molecules with a translational temperature of around 1200 K, an indirect adsorbate-mediated desorption resulting in water molecules with a translational temperature of around 450 K, and a substrate-mediated desorption of both benzene and water producing molecules with translational temperatures of around 530 K and 450 K respectively. The translational temperature of each population of desorbed molecules is well above the temperature of the ice matrix. The implications for gas-phase chemistry in the interstellar medium are discussed.Comment: 23 pages, including 4 figures; submitted to Ap

Helium trapping in apatite damage: insights from (U-Th-Sm)/He dating of different granitoid lithologies

Apatite (U-Th-Sm)/He (AHe) thermochronometry is widely used to constrain thermal histories and rates of tectonic, exhumation, and erosion processes. However, data interpretation is often challenging, especially when the thermal history includes extended residence time in the He partial retention zone (HePRZ), with highly dispersed dates revealing the complexity of diffusion processes in natural systems. This study investigates chemical and physical factors that may have impacted He diffusion in apatite over long timescales in a context of protracted residence in the HePRZ. Nine samples from the Ploumanac'h pluton and North Tregor (Armorican Massif, France) were collected in granitoids, differing in petrography and chemisty. This area was chosen because these samples underwent a similar thermal history since ~300 Ma. We report new (U-Th Sm)/He dates, along with apatite fission-track (AFT) data, as well as lithological and chemical characterization. The results show dispersed (U-Th-Sm)/He dates, ranging from 87 ± 7 to 291 ± 23 Ma, whereas central AFT dates vary from 142 ± 6 to 199 ± 9 Ma. Current predictive models for He diffusion and fission-track annealing in apatite could not reproduce the two datasets together. However, this apparent discrepancy gives insight into the parameters influencing He diffusion at geological timescales. The data confirm that radiation damage enhances He trapping, as the AHe dates are positively correlated to effective uranium (eU) concentration. The He age dispersion for constant eU content cannot be explained just by variations in grain size or chemical composition. To explore the potential influence of recoil damage trapping behavior and annealing kinetics on AHe dates, we tested a new diffusion model from Gerin et al. (2017). Given the expected model of the thermal history provided by AFT inversion, we investigated the influence of the trapping energy on AHe dates. The AHe date variations can be explained only if the trapping energy evolves from one crystal to another, increasing with the amount of damage. For a given trapping energy, minor variations in the recoil-damage annealing rate can consistently explain most of the remaining dispersion of the AHe dates

Antibiotic Transport in Resistant Bacteria: Synchrotron UV Fluorescence Microscopy to Determine Antibiotic Accumulation with Single Cell Resolution

A molecular definition of the mechanism conferring bacterial multidrug resistance is clinically crucial and today methods for quantitative determination of the uptake of antimicrobial agents with single cell resolution are missing. Using the naturally occurring fluorescence of antibacterial agents after deep ultraviolet (DUV) excitation, we developed a method to non-invasively monitor the quinolones uptake in single bacteria. Our approach is based on a DUV fluorescence microscope coupled to a synchrotron beamline providing tuneable excitation from 200 to 600 nm. A full spectrum was acquired at each pixel of the image, to study the DUV excited fluorescence emitted from quinolones within single bacteria. Measuring spectra allowed us to separate the antibiotic fluorescence from the autofluorescence contribution. By performing spectroscopic analysis, the quantification of the antibiotic signal was possible. To our knowledge, this is the first time that the intracellular accumulation of a clinical antibitiotic could be determined and discussed in relation with the level of drug susceptibility for a multiresistant strain. This method is especially important to follow the behavior of quinolone molecules at individual cell level, to quantify the intracellular concentration of the antibiotic and develop new strategies to combat the dissemination of MDR-bacteria. In addition, this original approach also indicates the heterogeneity of bacterial population when the same strain is under environmental stress like antibiotic attack

Autoantibodies against type I IFNs in patients with life-threatening COVID-19

Interindividual clinical variability in the course of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is vast. We report that at least 101 of 987 patients with life-threatening coronavirus disease 2019 (COVID-19) pneumonia had neutralizing immunoglobulin G (IgG) autoantibodies (auto-Abs) against interferon-w (IFN-w) (13 patients), against the 13 types of IFN-a (36), or against both (52) at the onset of critical disease; a few also had auto-Abs against the other three type I IFNs. The auto-Abs neutralize the ability of the corresponding type I IFNs to block SARS-CoV-2 infection in vitro. These auto-Abs were not found in 663 individuals with asymptomatic or mild SARS-CoV-2 infection and were present in only 4 of 1227 healthy individuals. Patients with auto-Abs were aged 25 to 87 years and 95 of the 101 were men. A B cell autoimmune phenocopy of inborn errors of type I IFN immunity accounts for life-threatening COVID-19 pneumonia in at least 2.6% of women and 12.5% of men