Electrical and thermal generation of spin currents by magnetic bilayer graphene

Ultracompact spintronic devices greatly benefit from the implementation of two-dimensional materials that provide large spin polarization of charge current together with long-distance transfer of spin information. Here spin-transport measurements in bilayer graphene evidence a strong spin–charge coupling due to a large induced exchange interaction by the proximity of an interlayer antiferromagnet (CrSBr). This results in the direct detection of the spin polarization of conductivity (up to 14%) and a spin-dependent Seebeck effect in the magnetic graphene. The efficient electrical and thermal spin–current generation is the most technologically relevant aspect of magnetism in graphene, controlled here by the antiferromagnetic dynamics of CrSBr. The high sensitivity of spin transport in graphene to the magnetization of the outermost layer of the adjacent antiferromagnet, furthermore, enables the read-out of a single magnetic sublattice. The combination of gate-tunable spin-dependent conductivity and Seebeck coefficient with long-distance spin transport in a single two-dimensional material promises ultrathin magnetic memory and sensory devices based on magnetic graphene

Forum Report: Issues in the Evaluation of Diagnostic Tests, Use of Historical Controls, and Merits of the Current Multicenter Collaborative Groups

This forum report contains conclusions about 3 different issues relevant to conducting clinical trials in deep mycoses. (1) Trials of diagnostic tests for deep mycoses must define the population appropriate for testing and the clinical question being asked. The unanswered question for the serum Aspergillus galactomannan assay is whether knowledge of results can change use of empirical therapy to treat febrile patients at high risk of invasive aspergillosis. (2) Use of historical controls is suboptimal but offers a pragmatic solution for studying rare mycoses; use of contemporaneous controls, matched for critical variables and evaluated by a blinded data review committee using detailed criteria, appears optimal. (3) Established groups of independent investigators, such as the European Organization for Research on Treatment of Cancer's Invasive Fungal Infections Group and National Institute of Allergy and Infectious Diseases's Bacteriology and Mycology Study Group, provide a pool of experienced investigators, defined operating rules, impartiality, and specialized expertise. Considering the enormous investment required for adequately powered efficacy trials of antifungal agents and the importance of these trials to guide clinical practice, use of collaborative groups outweighs the extra administrative time that is sometimes require

Forum Report: Issues in the Design of Trials of Drugs for the Treatment of Invasive Aspergillosis

A recent trial of drugs for invasive aspergillosis was used as a background for discussing critical features in the design of antifungal trials. The study under discussion allowed stopping either drug without classifying the patient as having treatment failure, so the trial should be understood as a comparison of 2 treatment strategies, not just 2 drugs. Although the study was a noninferiority trial, the outcome permitted a claim of superiority. Use of the category of "probable” in addition to "proven” aspergillosis permitted inclusion of patients for whom the diagnosis was less certain but who were still early enough in the disease progression to respond to therapy. Different opinions still exist about some of the criteria for the diagnosis of "probable” aspergillosis. A blinded data review committee was helpful in evaluating efficacy in this unblinded trial but had limited value in assessing toxicity. An understanding of these features of design of antifungal drug trials is important in applying the results to clinical practic

Forum Report: Issues in Clinical Trials of Empirical Antifungal Therapy in Treating Febrile Neutropenic Patients

There is inferential evidence that some patients with prolonged neutropenia and fever not responding to antibacterial agents are at sufficient risk of deep mycoses to warrant empirical therapy, although superiority of an antifungal agent over placebo has not been conclusively demonstrated. Amphotericin B deoxycholate, liposomal amphotericin B, and intravenous itraconazole followed by oral itraconazole solution are licensed in the United States for this indication. Fluconazole and voriconazole have given favorable results in clinical trials of patients with low and high risk of deep mold infections, respectively. Design features that can profoundly influence outcome of empirical trials are (1) inclusion of low-risk patients, (2) failure to blind the study, (3) obscuration of antifungal effects by changing antibacterial antibiotics, (4) failure to balance both arms of the study in terms of patients with prior antifungal prophylaxis or with severe comorbidities, (5) the merging of end points evaluating safety with those of efficacy, and (6) choice of different criteria for resolution of feve

Biomass Production Potential of a Wastewater Alga Chlorella vulgaris ARC 1 under Elevated Levels of CO2 and Temperature

The growth response of Chlorella vulgaris was studied under varying concentrations of carbon dioxide (ranging from 0.036 to 20%) and temperature (30, 40 and 50°C). The highest chlorophyll concentration (11 μg mL–1) and biomass (210 μg mL–1), which were 60 and 20 times more than that of C. vulgaris at ambient CO2 (0.036%), were recorded at 6% CO2 level. At 16% CO2 level, the concentrations of chlorophyll and biomass values were comparable to those at ambient CO2 but further increases in the CO2 level decreased both of them. Results showed that the optimum temperature for biomass production was 30°C under elevated CO2 (6%). Although increases in temperature above 30°C resulted in concomitant decrease in growth response, their adverse effects were significantly subdued at elevated CO2. There were also differential responses of the alga, assessed in terms of NaH14CO3 uptake and carbonic anhydrase activity, to increases in temperature at elevated CO2. The results indicated that Chlorella vulgaris grew better at elevated CO2 level at 30°C, albeit with lesser efficiencies at higher temperatures

Integrating microalgae production with anaerobic digestion: a biorefinery approach

This is the peer reviewed version of the following article: [Uggetti, E. , Sialve, B. , Trably, E. and Steyer, J. (2014), Integrating microalgae production with anaerobic digestion: a biorefinery approach. Biofuels, Bioprod. Bioref, 8: 516-529. doi:10.1002/bbb.1469], which has been published in final form at https://doi.org/10.1002/bbb.1469. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingIn the energy and chemical sectors, alternative production chains should be considered in order to simultaneously reduce the dependence on oil and mitigate climate change. Biomass is probably the only viable alternative to fossil resources for production of liquid transportation fuels and chemicals since, besides fossils, it is one of the only available sources of carbon-rich material on Earth. Over recent years, interest in microalgae biomass has grown in both fundamental and applied research fields. The biorefinery concept includes different technologies able to convert biomass into added-value chemicals, products (food and feed) and biofuels (biodiesel, bioethanol, biohydrogen). As in oil refinery, a biorefinery aims at producing multiple products, maximizing the value derived from differences in biomass components, including microalgae. This paper provides an overview of the various microalgae-derived products, focusing on anaerobic digestion for conversion of microalgal biomass into methane. Special attention is paid to the range of possible inputs for anaerobic digestion (microalgal biomass and microalgal residue after lipid extraction) and the outputs resulting from the process (e.g. biogas and digestate). The strong interest in microalgae anaerobic digestion lies in its ability to mineralize microalgae containing organic nitrogen and phosphorus, resulting in a flux of ammonium and phosphate that can then be used as substrate for growing microalgae or that can be further processed to produce fertilizers. At present, anaerobic digestion outputs can provide nutrients, CO2 and water to cultivate microalgae, which in turn, are used as substrate for methane and fertilizer generation.Peer ReviewedPostprint (author's final draft

Strain Relaxation Mechanisms and Local Structural Changes in Si_{1-x}$Ge_{x} Alloys

In this work, we address issues pertinent to the understanding of the structural and electronic properties of Si_{1-x} Ge_{x}alloys, namely, (i) how does the lattice constant mismatch between bulk Si and bulk Ge manifests itself in the alloy system? and (ii) what are the relevant strain release mechanisms? To provide answers to these questions, we have carried out an in-depth study of the changes in the local geometric and electronic structures arising from the strain relaxation in Si_{1-x} Ge_{x} alloys using an ab initio molecular dynamics scheme. The optimized lattice constant, while exhibiting a general trend of linear dependence on the composition (Vegard's law), shows a negative deviation from Vegard's law in the vicinity of x=0.5. We delineate the mechanisms responsible for each one of the above features. We show that the radial-strain relaxation through bond stretching is responsible for the overall trend of linear dependence of the lattice constant on the composition. On the other hand, the negative deviation from Vegard's law is shown to arise from the angular-strain relaxation.Comment: 21 pages, 7 figure

Donor states in modulation-doped Si/SiGe heterostructures

We present a unified approach for calculating the properties of shallow donors inside or outside heterostructure quantum wells. The method allows us to obtain not only the binding energies of all localized states of any symmetry, but also the energy width of the resonant states which may appear when a localized state becomes degenerate with the continuous quantum well subbands. The approach is non-variational, and we are therefore also able to evaluate the wave functions. This is used to calculate the optical absorption spectrum, which is strongly non-isotropic due to the selection rules. The results obtained from calculations for Si/Si$_{1-x}$Ge$_x$ quantum wells allow us to present the general behavior of the impurity states, as the donor position is varied from the center of the well to deep inside the barrier. The influence on the donor ground state from both the central-cell effect and the strain arising from the lattice mismatch is carefully considered.Comment: 17 pages, 10 figure

Origin and evolution of water oxidation before the last common ancestor of the Cyanobacteria

Photosystem II, the water oxidizing enzyme, altered the course of evolution by filling the atmosphere with oxygen. Here, we reconstruct the origin and evolution of water oxidation at an unprecedented level of detail by studying the phylogeny of all D1 subunits, the main protein coordinating the water oxidizing cluster (Mn4CaO5) of Photosystem II. We show that D1 exists in several forms making well-defined clades, some of which could have evolved before the origin of water oxidation and presenting many atypical characteristics. The most ancient form is found in the genome of Gloeobacter kilaueensis JS-1 and this has a C-terminus with a higher sequence identity to D2 than to any other D1. Two other groups of early evolving D1 correspond to those expressed under prolonged far-red illumination and in darkness. These atypical D1 forms are characterized by a dramatically different Mn4CaO5 binding site and a Photosystem II containing such a site may assemble an unconventional metal cluster. The first D1 forms with a full set of ligands to the Mn4CaO5 cluster are grouped with D1 proteins expressed only under low oxygen concentrations and the latest evolving form is the dominant type of D1 found in all cyanobacteria and plastids. In addition, we show that the plastid ancestor had a D1 more similar to those in early branching Synechococcus. We suggest each one of these forms of D1 originated from transitional forms at different stages towards the innovation and optimization of water oxidation before the last common ancestor of all known cyanobacteria