Sub-MHz Linewidth at 240 GHz from an Injection-Locked Free-Electron Laser

Radiation from an ultra-stable 240 GHz solid-state source has been injected, through an isolator, into the cavity of the University of California Santa Barbara (UCSB) MM-wave free-electron laser (FEL). High-power FEL emission, normally distributed among many of the cavity's longitudinal modes, is concentrated into the single mode to which the solid state source has been tuned. The linewidth of the FEL emission is 0.5 MHz, consistent with the Fourier transform limit for the 2 microsecond pulses. This demonstration of frequency-stable, ultra-narrow-band FEL emission is a critical milestone on the road to FEL-based pulsed electron paramagnetic resonance spectroscopy.Comment: 3 pages including 3 figure

High-frequency electron paramagnetic resonance investigation of the Fe3+ impurity center in polycrystalline PbTiO3 in its ferroelectric phase

The intrinsic iron(III) impurity center in polycrystalline lead titanate was investigated by means of high-frequency electron paramagnetic resonance (EPR) spectroscopy in order to determine the local-environment sensitive fine structure parameter D. At a spectrometer frequency of 190 GHz, spectral analysis of a powder sample was unambiguously possible. The observed mean value D = +35.28 GHz can be rationalized if Fe3+ ions substitute for Ti4+ at the B-site of the perovskite ABO3 lattice forming a directly coordinated iron - oxygen vacancy defect associate. A consistent fit of the multi-frequency data necessitated use of a distribution of D values with a variance of about 1 GHz. This statistical distribution of values is probably related to more distant defects and vacancies.Comment: 6 pages, 3 figures, 1 table, to appear in J. App. Phys, 96 (2004

Genetic parameters for�resistance to the Salmonella abortusovis vaccinal strain Rv6 in sheep

An experimental population (1216 lambs from 30 sires) of the Inra401 sheep was created in an Inra flock to allow QTL detection for susceptibility to Salmonella infection, wool and carcass traits. The Inra401 is a sheep composite line developed from two breeds: Berrichon du Cher and Romanov. At 113 days of age on average, the lambs were inoculated intravenously with 10(8 )Salmonella abortusovis Rv6 (vaccinal strain). They were slaughtered 10 days after the inoculation. Several traits were measured at inoculation and/or slaughtering to estimate the genetic resistance of the lambs to Salmonella infection: specific IgM and IgG1 antibody titres, body weight loss, spleen and pre-scapular node weights and counts of viable Salmonella persisting in these organs. This paper presents a quantitative analysis of the genetic variability of the traits related to salmonellosis susceptibility. The heritabilities of the traits varied between 0.10 and 0.64 (significantly different from zero). Thus, in sheep as well as in other species, the determinism of resistance to Salmonella infection is under genetic control. Moreover, the correlations between the traits are in agreement with the known immune mechanisms. The genetic variability observed should help QTL detection

X-Band ESR Determination of Dzyaloshinsky-Moriya Interaction in 2D SrCu2_2(BO3_3)2_2 System

X-band ESR measurements on a single crystal of SrCu$_2$(BO$_3$)$_2$ system in a temperature range between 10 K and 580 K are presented. The temperature and angular dependence of unusually broad ESR spectra can be explained by the inclusion of antisymmetric Dzyaloshinsky-Moriya (DM) interaction, which yields by far the largest contribution to the linewidth. However, the well-accepted picture of only out-of-plane interdimer DM vectors is not sufficient for explanation of the observed angular dependence. In order to account for the experimental linewidth anisotropy we had to include sizable in-plane components of interdimer as well as intradimer DM interaction in addition to the out-of-plane interdimer one. The nearest-neighbor DM vectors lie perpendicular to crystal anisotropy c-axis due to crystal symmetry. We also emphasize that above the structural phase transition occurring at 395 K dynamical mechanism should be present allowing for instantaneous DM interactions. Moreover, the linewidth at an arbitrary temperature can be divided into two contributions; namely, the first part arising from spin dynamics governed by the spin Hamiltonian of the system and the second part due to significant spin-phonon coupling. The nature of the latter mechanism is attributed to phonon-modulation of the antisymmetric interaction, which is responsible for the observed linear increase of the linewidth at high temperatures.Comment: 17 pages, 4 figures, submitted to PR

Effects of Paramagnetic Ferrocenium Cations on the Magnetic Properties of the Anionic Single-Molecule Magnet [Mn12O12(O2CC6F5)16(H2O)4]-

The preparation and physical characterization are reported for several single-molecule magnet salts to investigate the effects of paramagnetic cations on the magnetization relaxation behavior of [Mn12]- anionic single-molecule magnets.Comment: 30 pages, 5 tables, 15 figure

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

Spectres d’absorption infrarouge de HCI et HBr solides jusqu’à 1,5 °K

Les spectres d’absorption infrarouge de HCl et HBr solides obtenus par condensation du gaz sur une fenêtre maintenue à basse température, ont été étudiés, jusqu’à 1,5 °I< dans la région des vibrations moléculaires fondamentales. La double bande d’absorption intense (2 710-2 752 cm-1) caractéristique de la phase orthorhombique est observée dans tout le domaine de température si la condensation a lieu au-dessus de 50 °K. Une condensation de HCl à 1,5 °K provoque l’élargissement de cette double bande qui devient très faible et l’apparition d’une nouvelle fréquence à 2 872 cm-1. Dans HBr condensé à 1,5 °K la double bande est seulement élargie, sans manifestation d’une fréquence nouvelle. Ces phénomènes ainsi que leur évolution avec la température sont étudiés et discutés.Dans HCl une fréquence de translation du réseau (88 cm-1) apparaît sous forme de combinaisons avec les vibrations moléculaires. Comme on peut le prévoir, les fréquences différence disparaissent réversiblement vers 40 °K alors que les fréquences somme ne présentent aucune évolution

RAMAN SPECTRA OF MATRIX-ISOLATED HYDROGEN AND DEUTERIUM CHLORIDE

Author Institution: Laboratoire de Chimie-Physique, Institut National des Sciences Appliqu\'{e}esMatrix-isolated hydrogen chloride has been extensively studied by infrared absorption techniques. Attention has been focused on the spectrum of both monomeric and polymeric species. We have obtained the Raman spectra of HC1 and DC1 in Ar, Kr, and Xe matrices down to $7^{\circ} K$ I. Monomers: The interest lies in the problem of the rotation of the guest molecule. The infrared absorption spectrum of HCl in Ar at $7^{\circ} K$ exhibits three principal lines at 2887, 2867, and $2852 cm^{-1}$ which, from temperature dependence intensity measurements, were assigned to the $R_{0}$, Q, and $P_{1}$ treansitions, respectively. In the Raman spectrum we observe an intense the absence of the $R_{0}$ peak the latter cannot be assigned to $P_{1}$. Thus we can conclude that the so-called $P_{1}$ infrared line is the result of two transitions, one vibrational-rotational and the other pure vibrational which may be due to guest molecules trapped at a different site or to non first nearest neighbor dimers. This conclusion applies for Kr matrices. The temperature dependence of the Q branch width has been studied and will be discussed. II. Polymers: With respect to polymeric species, we observe the characteristic features of dimers, trimers, and higher order aggregates. The dimer frequency has the same value in both the Raman and the infrared spectrum, and this observation reules out the conclusion of previous workers who, from far infrared experiments, claimed that the dimer should be cyclic. Our observations favor an open-chain structure. III. External modes: Two external modes are observed. One of them is a combination between a localized translational mode and a stretching mode. The other a host frequency induced by the impurity