Hydrogen Motion in Magnesium Hydride by NMR

In coarse-grained MgH2, the diffusive motion of hydrogen remains too slow (<10^5 hops s^−1) to narrow the H NMR line up to 400 °C. Slow-motion dipolar relaxation time T1D measurements reveal the motion, with hopping rate ωH from 0.1 to 430 s^−1 over the range of 260 to 400 °C, the first direct measurement of H hopping in MgH2. The ωH data are described by an activation energy of 1.72 eV (166 kJ/mol) and attempt frequency of 2.5 × 10^15 s^−1. In ball-milled MgH2 with 0.5 mol % added Nb2O5 catalyst, line-narrowing is evident already at 50 °C. The line shape shows distinct broad and narrow components corresponding to immobile and mobile H, respectively. The fraction of mobile H grows continuously with temperature, reaching ∼30% at 400 °C. This demonstrates that this material’s superior reaction kinetics are due to an increased rate of H motion, in addition to the shorter diffusion paths from ball-milling. In ball-milled MgH2 without additives, the line-narrowed component is weaker and is due, at least in part, to trapped H2 gas. The spin−lattice relaxation rates T1^−1 of all materials are compared, with ball-milling markedly increasing T1^−1. The weak temperature dependence of T1^−1 suggests a mechanism with paramagnetic relaxation centers arising from the mechanical milling

NMR Studies of the Hydrogen Storage Compound NaMgH_3

Hydrogen and ^(23)Na NMR were performed to 400 °C on NaMgH3 powder produced by reactive ball-milling of NaH and MgH2. The H resonance shows narrowing already at 100 °C as a narrow line superimposed on the broad, rigid-lattice signal. With increasing temperature, the fraction of spins in the narrow component grows smoothly, approaching 100% near 275 °C. This heterogeneous narrowing suggests a wide distribution of H motion rates. After annealing at 400 °C, the narrow component intensity at temperatures below 200 °C was substantially reduced and both H and ^(23)Na relaxation rates 1/T_1 were decreased. Thus, it appears that the high rates of H motion, particularly on first heating, are due to regions with poorly organized crystal structure. If this disorder could be maintained, this might be an avenue toward improved reaction kinetics of this or other hydrides. In the annealed sample, the activation energy for H diffusion is approximately 95 kJ/mol

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Electron spin resonance studies of \u3csup\u3e199\u3c/sup\u3eHgH, \u3csup\u3e201\u3c/sup\u3eHgH, \u3csup\u3e199\u3c/sup\u3eHgD and \u3csup\u3e201\u3c/sup\u3eHgD isolated in neon and argon matrices at 4K: an electronic structure investigation

Various isotopomers of the mercury hydride radical (HgH) have been generated in a microwave discharge and trapped in neon and argon matrices at 4 K for electron spin resonance (ESR) investigations. Both the dipolar (Adip) and isotropic (Aiso) components of the nuclear hyperfine interactions have been directly measured for 199Hg, 201Hg, H and D. Electronic structure information for HgH in its X2Σ ground state obtained from the hyperfine data is compared with theoretical results from several different computational methods. The hyperfine interactions in HgH are unusually large with Aiso(199Hg) = 6859(3), Adip(199Hg) = 446(3), Aiso(H) = 730(2) and Adip(H) = 0(2) MHz. A standard analysis of the hyperfine interactions demonstrates the need for a more in-depth theoretical treatment of HgH that should include relativistic effects. An interesting shift in spin density is observed when deuterium replaces hydrogen in HgH. The decreased spin density on deuterium, which was demonstrated in earlier studies, can now be..

RARE GAS MATRIX ISOLATION ESR (ELECTRON SPIN RESONANCE) STUDIES OF HYDROGEN HALIDE ANION RADICALS (HI−,HBr−,HCl−,HF−)(HI^{-}, HBr^{-}, HCl^{-}, HF^{-}) GENERATED BY PLASMA DISCHARGE

Author Institution: Department of Chemistry, Furman UniversityThe $HF^{-}/DF^{-}, HCl^{-}/DCl^{-}, HBr^{-}$, and $HI^{-}$ ion radicals have been generated by photoionization, trapped in neon matrices at 4 K, and invesigated by ESR (electron spin resonance) spectroscopy. The nuclear hyperfine interactions (A tensors) were fully resolved for both the hydrogen and halide nuclei. All the radicals proved to be monomeric anions, except for HF$^{-}$, which exhibited a dimeric molecular arrangement. Detailed information on electronic structure trends and comparisons with theoretical calculations will be presented

MATRIX ISOLATION ESR STUDIES OF Hg RADICALS: Hg+Hg^{+}, HgDHgD, HgHHgH, and Hg(CH3)2+Hg(CH_{3})_{2}^{+}

Author Institution: Furman University; University of Western AustraliaAtomic mercury vapor was passed through various rare gas plasma discharges and condensed in neon, argon, and krypton rare gas matrices at cryogenic temperatures for electron spin resonance (ESR) investigations. The first ESR spectrum of $Hg^{+}$, observed in Ne, Ar, and Kr matrices is presented, with determination of its magnetic parameters, which exhibited excellent agreement with gas phase values. The ratio of the $g_{n} (g_{n} = \mu_{I}/I)$ values for $^{199}Hg$ and $^{201}Hg$ is shown to vary slightly from $Hg^{+}$ to HgH/HgD. This variation can be attributed to electronic structure differences surrounding the mercury nucleus. Observation of $Hg^{+}$ in a Kr lattice also provides information on the required energy gap between the electron affinity of an isolated species and the ionization potential of the matrix host atom. HgH and HgD were observed in experiments where the plasma discharge was doped with a small percentage of $H_{2}/D_{2}$ gas. The HgH/HgD radicals were observed for the firs t time in a neon matrix, providing a comparison of the various magnetic parameters to earlier argon matrix results. The electronic structure and magnetic parameters of $Hg(CH_{3})_{2}^{+}$ will be analyzed based upon these new matrix results for $Hg^{+}$ and HgH

Matrix-isolation investigation of the diatomic anion radicals of aluminum and gallium (Al\u3csub\u3e2\u3c/sub\u3e\u3csup\u3e-\u3c/sup\u3e and Ga\u3csub\u3e2\u3c/sub\u3e\u3csup\u3e-\u3c/sup\u3e) An electron spin resonance and \u3cem\u3eab initio\u3c/em\u3e theoretical study

The diatomic aluminum and gallium anion radicals ( Al 2 − and Ga 2 − ) have been studied by electron spin resonance(ESR) as isolated ions in neon matrices near 4 K. Apparently no previous examples of purely metallic anions have been studied by the rare gas matrix isolation trapping technique with any type of spectroscopic method. Pulsed laser ablation of the metals was the experimental generation method which has enabled the first direct characterization of the ground electronic states of these anions. The X-Š 4 Σ assignment agrees with previous interpretations of photoelectron spectroscopic results. The analysis of fine structure and nuclear hyperfineinteractions has yielded a detailed description of the electronic structure in these seven-valence electron anion radicals, with comparisons to other isovalent X-Š 4 Σ radicals presented. Experimental values of the nuclear hyperfineinteractions (A tensors) were compared with theoretical results obtained from various ab initio computational methods, including configuration interaction and density functional theory. Reasonable agreement between these experimental results and theoretical predictions was observed

Integration of a (6)LilnSe(2) thermal neutron detector into a CubeSat instrument

We present a preliminary design for a neutron detection system that is compact, lightweight, and low power consuming, utilizing the CubeSat platform making it suitable for space-based applications. This is made possible using the scintillating crystal lithium indium diselenide ((LiInSe2)-Li-6), the first crystal to include Li-6 in the crystalline structure, and a silicon avalanche photodiode. The schematics of this instrument are presented as well as the response of the instrument to initial testing under alpha radiation. A principal aim of this work is to demonstrate the feasibility of such a neutron detection system within a CubeSat platform. The entire end-to-end system presented here is 10 x 10 x 15 cm(3), weighs 670 g, and requires 5 V direct current at 3 W. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)National Science Foundation [AST-0849736]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Neutron detector development for microsatellites

We present a preliminary design for a novel neutron detection system that is compact, lightweight, and low power consuming, utilizing the CubeSat platform making it suitable for space-based applications. This is made possible using the scintillating crystal lithium indium diselenide ((LiInSe2)-Li-6), the first crystal to include Li-6 in the crystalline structure, and a silicon avalanche photodiode (Si-APD). The schematics of this instrument are presented as well as the response of the instrument to initial testing under alpha, gamma and neutron radiation. A principal aim of this work is to demonstrate the feasibility of such a neutron detection system within a CubeSat platform. The entire end-to-end system presented here is 10 cm x 10 cm x 15 cm, weighs 670 grams and requires 5 V direct current at 3 Watts.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]