First-principles prediction of redox potentials in transition-metal compounds with LDA+U

First-principles calculations within the Local Density Approximation (LDA) or Generalized Gradient Approximation (GGA), though very successful, are known to underestimate redox potentials, such as those at which lithium intercalates in transition metal compounds. We argue that this inaccuracy is related to the lack of cancellation of electron self-interaction errors in LDA/GGA and can be improved by using the DFT+$U$ method with a self-consistent evaluation of the $U$ parameter. We show that, using this approach, the experimental lithium intercalation voltages of a number of transition metal compounds, including the olivine Li$_{x}$MPO$_{4}$ (M=Mn, Fe Co, Ni), layered Li$_{x}$MO$_{2}$ ($x=$Co, Ni) and spinel-like Li$_{x}$M$_{2}$O$_{4}$ (M=Mn, Co), can be reproduced accurately.Comment: 19 pages, 6 figures, Phys. Rev. B 70, 235121 (2004

Spontaneous Follicular Exclusion of SHP1-deficient B Cells Is Conditional on the Presence of Competitor Wild-type B Cells

Engagement of antigen receptors on mature B lymphocytes is known to block cell entry into lymphoid follicles and promote accumulation in T cell zones, yet the molecular basis for this change in cell distribution is not understood. Previous studies have shown that follicular exclusion requires a threshold level of antigen receptor engagement combined with occupancy of follicles by B cells without equivalent receptor engagement. The possibility has been raised that follicular composition affects B cell positioning by altering the amount of available antigen and the degree of receptor occupancy. Here we show that follicular composition affects migration of mature B cells under conditions that are independent of antigen receptor occupancy. B cells deficient in the negative regulatory protein tyrosine phosphatase, SHP1, which have elevated intracellular signaling by the B cell receptor, are shown to accumulate in the T zone in the absence of their specific antigen. Follicular exclusion of SHP1–deficient B cells was found to be conditional on the presence of excess B cells that lack elevated intracellular signaling, and was not due to a failure of SHP-1–deficient cells to mature and express the follicle-homing chemokine receptor Burkitt's lymphoma receptor 1. These findings strongly suggest that signals that are negatively regulated by SHP1 promote B cell localization in T cell zones by reducing competitiveness for follicular entry, and provide further evidence that follicular composition influences the positioning of antigen-engaged B cells

A functional bacteria-derived restriction modification system in the mitochondrion of a heterotrophic protist

The overarching trend in mitochondrial genome evolution is functional streamlining coupled with gene loss; therefore, gene acquisition by mitochondria is considered to be exceedingly rare. Selfish elements in the form of self-splicing introns occur in many organellar genomes, but the wider diversity of selfish elements, and how they persist in the DNA of organelles, has not been explored. In the mitochondrial genome of a marine heterotrophic katablepharid protist, we identify a functional type II restriction modification (RM) system originating from a horizontal gene transfer (HGT) event involving bacteria related to flavobacteria. This RM system consists of an HpaII-like endonuclease and a cognate cytosine methyltransferase (CM). We demonstrate that these proteins are functional by heterologous expression in both bacterial and eukaryotic cells. These results suggest that a mitochondrial-encoded RM system can function as a toxin-antitoxin selfish element and that such elements could be co-opted by eukaryotic genomes to drive biased organellar inheritance.Peer reviewe

Symmetry breaking in crossed magnetic and electric fields

We present the first observations of cylindrical symmetry breaking in highly excited diamagnetic hydrogen with a small crossed electric field, and we give a semiclassical interpretation of this effect. As the small perpendicular electric field is added, the recurrence strengths of closed orbits decrease smoothly to a minimum, and revive again. This phenomenon, caused by interference among the electron waves that return to the nucleus, can be computed from the azimuthal dependence of the classical closed orbits.Comment: 4 page REVTeX file including 5 postscript files (using psfig) Accepted for publication in Physical Review Letters. Difference from earlier preprint: we have discovered the cause of the earlier apparent discrepancy between experiment and theory and now achieve excellent agreemen

Are We Missing an Opportunity? Prediabetes in the U.S. Military

INTRODUCTION: The prevalence of prediabetes is estimated to be one-third of Americans with approximately 80% of these individuals unaware of the diagnosis. In the active duty military population, the prevalence of prediabetes is largely unexplored. The purpose of this study was to investigate the prevalence of prediabetes in military service members by quantifying those meeting prediabetes screening criteria, those actually being screened, and those being appropriately diagnosed. MATERIALS AND METHODS: Data were analyzed from calendar years 2014 to 2018 for active duty service members 18 years of age or older. Vitals records were collected to obtain body mass index values. Composite Health Care System laboratory data were queried for hemoglobin A1c (HbA1c) results as well as fasting plasma glucose (FPG) and oral glucose tolerance test (OGTT) results. The percentage of active duty service members meeting criteria for prediabetes screening was determined by totaling members age 45 and older with members age 18- to 44-year old with a body mass index ≥25.0 kg/m2, then dividing by the total number of members for each respective military branch. The percentage of active duty service members actually screened for prediabetes was determined based on members meeting prediabetes screening criteria who in fact had FPG, OGTT, or HbA1c labs. The total number of labs meeting prediabetes criteria was determined based on those aforementioned labs with results in the prediabetes range (FPG between 100 and 125 mg/dL, OGTT between 140 and 199 mg/dL, or HbA1c range of 5.7%-6.4%). The total number of service members with appropriate prediabetes International Classification of Disease (ICD) code was determined by identifying members with ICD-9 and ICD-10 codes 790.21, 790.22, and R73.01-R73.03 in their medical record. RESULTS: From 2014 to 2018, 53.9% of 332,502, 56% of 543,081, and 47.3% of 531,313 active duty service members in the Air Force, Army and Navy, respectively, met criteria for prediabetes screening. The rates of actually screening for prediabetes were similar across the Air Force (4.8%), Army (6.7%), and Navy (5.5%). The percentage with labs meeting prediabetes criteria ranged from 17.9% to 28.4% in the Air Force, 24.2% to 30.3% in the Army, and 24.2% to 30.9% in the Navy. The rate of ICD coding for prediabetes increased from 2014 to 2018 across all branches (29.8%-65.3% for the Air Force, 24.6%-46.8% for the Army, and 40.0%-45.5% for the Navy). CONCLUSION: Screening for prediabetes in the active duty military population is grossly inadequate, and even of those screened, diagnosing those meeting prediabetes criteria is similarly inadequate. Although this scenario is not unique to the Military Health System, but reflective of a larger national problem, efforts should be made within the Military Health System to increase the screening for this common disorder. Identifying service members with prediabetes enables opportunities for targeted interventions to delay or prevent the progression to diabetes mellitus

Microscopic Calculation of Total Ordinary Muon Capture Rates for Medium - Weight and Heavy Nuclei

Total Ordinary Muon Capture (OMC) rates are calculated on the basis of the Quasiparticle Random Phase Approximation for several spherical nuclei from 90^Zr to 208^Pb. It is shown that total OMC rates calculated with the free value of the axial-vector coupling constant g_A agree well with the experimental data for medium-size nuclei and exceed considerably the experimental rates for heavy nuclei. The sensitivity of theoretical OMC rates to the nuclear residual interactions is discussed.Comment: 27 pages and 3 figure