Glassy dynamics in thin films of polystyrene

Glassy dynamics was investigated for thin films of atactic polystyrene by complex electric capacitance measurements using dielectric relaxation spectroscopy. During the isothermal aging process the real part of the electric capacitance increased with time, whereas the imaginary part decreased with time. It follows that the aging time dependences of real and imaginary parts of the electric capacitance were primarily associated with change in volume (film thickness) and dielectric permittivity, respectively. Further, dielectric permittivity showed memory and rejuvenation effects in a similar manner to those observed for poly(methyl methacrylate) thin films. On the other hand, volume did not show a strong rejuvenation effect.Comment: 7 pages, 7 figures. Phys. Rev. E (in press

Étude spectrographique de l’émission des fils explosés

On fait exploser un fil métallique en déchargeant une batterie de condensateurs de 2 millifarads chargée sous une tension de 1 kilovolt. Le spectre obtenu présente un fond continu sur lequel apparaissent des raies d’émission et des raies d’absorption. Ces dernières sont très nombreuses dans les multiplets de faible énergie. On a ensuite étudié le phénomène des « onduloïdes » par voie spectrographique. L’influence de la tension, du diamètre et de la longueur du fil sur la largeur des raies d’absorption est expliquée par la notion de puissance disponible par atome. On étudie ensuite le mécanisme de la volatilisation, on en déduit que dans certains cas au moment de l’explosion, la température au centre du conducteur est moins élevée qu’à la partie périphérique

Blue-Sisyphus cooling in cesium gray molasses and antidot lattices

We present an experimental study of the kinetic temperature of cesium atoms interacting with laser beams tuned on the blue side of the $6S_{1/2}(F=3)\rightarrow 6P_{3/2}(F'=2)$ transition. In the case of a three-dimensional four-beam molasses, temperatures as low as 800 nK were found. These low temperatures are compatible with a good capture efficiency. The influence of other hyperfine transitions on the temperature is significant. In the presence of a static magnetic field (antidot lattices), the temperatures are slightly higher but show a much weaker dependence on the other hyperfine transitions

Obstruktive Schlafapnoe: Klug entscheiden, das Richtige tun

<jats:title>Zusammenfassung</jats:title><jats:p>Die obstruktive Schlafapnoe (OSA) kann zu einer erheblichen Einschränkung der Lebensqualität führen, und eine nicht behandelte mittel- bis schwergradige OSA (Apnoe-Hypopnoe-Index ≥ 15/h) erhöht das Risiko vieler – überwiegend kardiovaskulärer – Erkrankungen deutlich. In Anbetracht der Häufigkeit des Krankheitsbilds und der damit verbundenen Beeinträchtigungen ist eine effektive Diagnostik und Therapie der OSA von besonderer Bedeutung.</jats:p><jats:p>Die Deutsche Gesellschaft für Schlafforschung und Schlafmedizin (DGSM) hat daher jeweils fünf praxisnahe Positiv- und Negativempfehlungen zusammengestellt, die das diagnostische und therapeutische Vorgehen bei OSA erleichtern sollen. Sie beziehen sich insbesondere auf die Indikationen zur schlafmedizinischen Diagnostik und zu spezifischen Therapieoptionen unter Berücksichtigung von Alter, Klinik, Risikofaktoren und Komorbiditäten.</jats:p><jats:p>Die Auswahl der Empfehlungen orientiert sich an der klinischen Relevanz, an bestehenden Defiziten im Sinne einer Über- oder Unterversorgung und an der Stärke der Empfehlungen in der aktuellen S3-Leitlinie der DGSM zu den schlafbezogenen Atmungsstörungen.</jats:p&gt

Mechanical bistability of atoms cooled in an optical lattice

The dynamics of an atom localized in a periodic potential and submitted to a probe wave is studied theoretically and experimentally in a cesium optical lattice. Because the optical potential is not harmonic, two solutions for the amplitude of motion in steady state are found in a certain range of parameters. The free oscillation following the forced excitation exhibits two peaks associated with these two amplitudes. The relative weight of the peaks depends on the probe frequency and on the lattice temperature

Pinball atom dynamics in an antidot optical lattice

The dynamics of atoms in an antidot optical lattice is investigated both through numerical simulations and experiments performed with cesium atoms. The calculated atomic trajectories display pinball-like bounces on the antidots. These bounces manifest themselves by broad resonances in probe transmission spectroscopy. The experimental spectra are in excellent agreement with theoretical predictions

Modeling and Experimental Study of an Ammonia-water Falling Film Absorber

International audienc

Sample size estimation in clinical trials using ventilator-free days as the primary outcome: a systematic review

Abstract Background Ventilator-free days (VFDs) are a composite endpoint increasingly used as the primary outcome in critical care trials. However, because of the skewed distribution and competitive risk between components, sample size estimation remains challenging. This systematic review was conducted to systematically assess whether the sample size was congruent, as calculated to evaluate VFDs in trials, with VFDs’ distribution and the impact of alternative methods on sample size estimation. Methods A systematic literature search was conducted within the PubMed and Embase databases for randomized clinical trials in adults with VFDs as the primary outcome until December 2021. We focused on peer-reviewed journals with 2021 impact factors greater than five. After reviewing definitions of VFDs, we extracted the sample size and methods used for its estimation. The data were collected by two independent investigators and recorded in a standardized, pilot-tested forms tool. Sample sizes were calculated using alternative statistical approaches, and risks of bias were assessed with the Cochrane risk-of-bias tool. Results Of the 26 clinical trials included, 19 (73%) raised “some concerns” when assessing risks of bias. Twenty-four (92%) trials were two-arm superiority trials, and 23 (89%) were conducted at multiple sites. Almost all the trials (96%) were unable to consider the unique distribution of VFDs and death as a competitive risk. Moreover, significant heterogeneity was found in the definitions of VFDs, especially regarding varying start time and type of respiratory support. Methods for sample size estimation were also heterogeneous, and simple models, such as the Mann–Whitney–Wilcoxon rank-sum test, were used in 14 (54%) trials. Finally, the sample sizes calculated varied by a factor of 1.6 to 17.4. Conclusions A standardized definition and methodology for VFDs, including the use of a core outcome set, seems to be required. Indeed, this could facilitate the interpretation of findings in clinical trials, as well as their construction, especially the sample size estimation which is a trade-off between cost, ethics, and statistical power. Systematic review registration PROSPERO ID: CRD42021282304. Registered 15 December 2021 ( https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021282304 )