Swimming using surface acoustic waves

Microactuation of free standing objects in fluids is currently dominated by the rotary propeller, giving rise to a range of potential applications in the military, aeronautic and biomedical fields. Previously, surface acoustic waves (SAWs) have been shown to be of increasing interest in the field of microfluidics, where the refraction of a SAW into a drop of fluid creates a convective flow, a phenomenon generally known as SAW streaming. We now show how SAWs, generated at microelectronic devices, can be used as an efficient method of propulsion actuated by localised fluid streaming. The direction of the force arising from such streaming is optimal when the devices are maintained at the Rayleigh angle. The technique provides propulsion without any moving parts, and, due to the inherent design of the SAW transducer, enables simple control of the direction of travel

PCR-RFLP analysis of Vitis, Ampelopsis and Parthenocissus and its application to the identification of rootstocks

Methodologies based on the analysis of DNA polymorphism were recently described to identify and study grapevine rootstocks and cultivars. We report here rapid RFLP analysis of 17 Vitis, 3 Ampelopsis and 2 Parthenocissus DNAs amplified by PCR with primers based on sequences from previously defined polymorphic DNA fragments of V. vinifera cv. Chardonnay. These primers can be used as a tool for phylogenetic studies in the genus Vitis and more generally within the Vitaceae family. The DNAs of 22 rootstocks could be identified by PCR using 4 pairs of Chardonnay-derived primers combined with RFLP analysis. However, it was impossible to discriminate between 9 clones of the rootstock 3309 C. This technique is rapid and well reproducible

Identification of sixteen grapevine rootstocks by RFLP and RFLP analysis of nuclear DNA extracted from the wood

Sixteen rootstocks of the Vitis genus have been identified by the RFLP analysis methodology with the restriction enzyme HinfI. Uniques or moderately repeated DNA sequences of the nuclear genome of the Chardonnay V. vinifera variety were used as probes. RFLP analysis of 5 clones of SO 4 (V. berlandieri x V. riparia) and of 3 clones of 41 B Mgt (V. berlandieri x V. vinifera) with 4 probes and HinfI did not lead to any polymorphism. This is not surprising because of the vegetative origin of the clones. A simple method of nuclear DNA extraction of wood is described for the grapevine. We propose now the RFLP analysis methodology to complement or to replace in certain cases the ampelographical methods of identification of the rootstocks. The extension of this application to the V. vinifera varieties is considered.Identification de 16 porte-greffes de vigne par analyse RFLP, et analyse RFLP d'ADN nucléaire extrait à partir du boisNous avons identifié 16 porte-greffes du genre Vitis par la méthodologie d'analyse du polymorphisme de longueur des fragments de restriction (RFLP) de l'ADN avec l'enzyme de restriction HinfI. Pour cela, nous avons utilisé comme sondes des fragments d'ADN uniques ou peu répétés du génome de la variete Chardonnay de Vitis vinifera. L'analyse RFLP de cinq clones de SO 4 (V. berlandieri x V. riparia) et de trois clones de 41 B Mgt (V. berlandieri x V. vinifera) avec quatre sondes RFLP et l'enzyme HinfI n'a pas permis de différencier les clones d'un même hybride, dont les genomes sont extrêmement proches puisqu'ils sont obtenus de façon végétative. Nous présentons aussi une méthode simple d'extraction d'ADN nucléaire à partir du bois de vigne. Les analyses RFLP de cet ADN ont donné des résultats identiques à ceux obtenus avec l'ADN des feuilles. Nous sommes maintenant en mesure de proposer que la méthodologie d'analyse RFLP complète ou remplace dans certains cas les méthodes ampélographiques d'identification des portegreffes du genre Vitis. L'élargissement de cette application est envisagé pour les varietes de Vitis vinifera

Substance use and its association with mental health among Swiss medical students: A cross-sectional study.

Studies on mental health and substance use among medical students indicated worrying prevalence but have been mainly descriptive. To evaluate the prevalence of substance use in a sample of medical students and investigate whether mental health variables have an influence on substance use. The data were collected as part of the first wave of the ETMED-L, an ongoing longitudinal open cohort study surveying medical students at the University of Lausanne (Switzerland). N = 886 students were included and completed an online survey including measures of mental health (depression, suicidal ideation, anxiety, stress, and burnout) and use of and risk related with several substances (tobacco, alcohol, cannabis, cocaine, stimulants, sedatives, hallucinogens, opioids, nonmedical prescription drugs, and neuroenhancement drugs). We evaluated the prevalence of use of each substance and then tested the association between mental health and substance use in an Exploratory Structural Equation Modeling framework. Statistical indices indicated a four-factor solution for mental health and a three-factor solution for substance use. A factor comprising risk level for alcohol, tobacco, and cannabis use - which were the most prevalent substances - was significantly associated with a burnout factor and a factor related to financial situation and side job stress. There was a significant association between a factor comprising depression, anxiety, and suicidal ideation and a factor related to the use of sedatives, nonmedical prescription drugs and neuroenhancement drugs. Although their use was less prevalent, a factor comprising the risk level of stimulants and cocaine use was significantly but more mildly related to the burnout factor. A factor comprising stress related to studies and work/life balance as well as emotional exhaustion was not related to substance use factors. In this sample of medical students, the prevalence of substance use was substantial and poorer mental health status was related with higher substance use risk levels

Core stories of physicians on a Swiss internal medicine ward during the first COVID-19 wave: a qualitative exploration.

The first COVID-19 wave (2020), W1, will remain extraordinary due to its novelty and the uncertainty on how to handle the pandemic. To understand what physicians went through, we collected narratives of frontline physicians working in a Swiss university hospital during W1. Physicians in the Division of Internal Medicine of Lausanne University Hospital (CHUV) were invited to send anonymous narratives to an online platform, between 28 April and 30 June 2020. The analysed material consisted of 13 written texts and one audio record. They were examined by means of a narrative analysis based on a holistic content approach, attempting to identify narrative highlights, referred to as foci, in the texts. Five main foci were identified: danger and threats, acquisition of knowledge and practices, adaptation to a changing context, commitment to the profession, and sense of belonging to the medical staff. In physicians' narratives, danger designated a variety of rather negative feelings and emotions, whereas threats were experienced as being dangerous for others, but also for oneself. The acquisition of knowledge and practices focus referred to the different types of acquisition that took place during W1. The narratives that focused on adaptation reflected how physicians coped with W1 and private or professional upheavals. COVID-19 W1 contributed to revealing a natural commitment (or not) of physicians towards the profession and patients, accompanied by the concern of offering the best possible care to all. Lastly, sense of belonging referred to the team and its reconfiguration during W1. Our study deepens the understanding of how physicians experienced the pandemic both in their professional and personal settings. It offers insights into how they prepared and reacted to a pandemic. The foci reflect topics that are inherent to a physician's profession, whatever the context. During a pandemic, these foundational elements are particularly challenged. Strikingly, these topics are not studied in medical school, thus raising the general question of how students are prepared for the medical profession

Right Handed Weak Currents in Sum Rules for Axialvector Constant Renormalization

The recent experimental results on deep inelastic polarized lepton scattering off proton, deuteron and $^{3}$He together with polari% zed neutron $\beta$-decay data are analyzed. It is shown that the problem of Ellis-Jaffe and Bjorken sum rules deficiency and the neutron paradox could be solved simultaneously by assuming the small right handed current (RHC) admixture in the weak interaction Lagrangian. The possible RHC impact on pion-nucleon $\sigma$-term and Gamow-Teller sum rule for $(p,n)$ nuclear reactions is pointed out.Comment: to be published in Phys. Rev. Lett. LaTeX, 8 pages, 21 k

Semileptonic decay constants of octet baryons in the chiral quark-soliton model

Based on the recent study of the magnetic moments and axial constants within the framework of the chiral quark-soliton model, we investigate the baryon semileptonic decay constants $(f_1,f_2)$ and $(g_1, g_2)$. Employing the relations between the diagonal transition matrix elements and off-diagonal ones in the vector and axial-vector channels, we obtain the ratios of baryon semileptonic decay constants $f_2/f_1$ and $g_1/f_1$. The $F/D$ ratio is also discussed and found that the value predicted by the present model naturally lies between that of the Skyrme model and that of the nonrelativistic quark model. The singlet axial constant $g^{(0)}_A$ can be expressed in terms of the $F/D$ ratio and $g^{(3)}_A$ in the present model and turns out to be small. The results are compared with available experimental data and found to be in good agreement with them. In addition, the induced pseudotensor coupling constants $g_2/f_1$ are calculated, the SU(3) symmetry breaking being considered. The results indicate that the effect of SU(3) symmetry breaking might play an important role for some decay modes in hyperon semileptonic decay.Comment: 16 pages, RevTeX is used. No figure. Accepted for publication in Phys. Rev.

Evidence for SU(3) symmetry breaking from hyperon production

We examine the SU(3) symmetry breaking in hyperon semileptonic decays (HSD) by considering two typical sets of quark contributions to the spin content of the octet baryons: Set-1 with SU(3) flavor symmetry and Set-2 with SU(3) flavor symmetry breaking in HSD. The quark distributions of the octet baryons are calculated with a successful statistical model. Using an approximate relation between the quark fragmentation functions and the quark distributions, we predict polarizations of the octet baryons produced in $e^+e^-$ annihilation and semi-inclusive deeply lepton-nucleon scattering in order to reveal the SU(3) symmetry breaking effect on the spin structure of the octet baryons. We find that the SU(3) symmetry breaking significantly affects the hyperon polarization. The available experimental data on the $\Lambda$ polarization seem to favor the theoretical predictions with SU(3) symmetry breaking. We conclude that there is a possibility to get a collateral evidence for SU(3) symmetry breaking from hyperon production. The theoretical errors for our predictions are discussed.Comment: 3 tables, 14 figure

Critical Analysis of Baryon Masses and Sigma-Terms in Heavy Baryon Chiral Perturbation Theory

We present an analysis of the octet baryon masses and the $\pi N$ and $KN$ $\sigma$--terms in the framework of heavy baryon chiral perturbation theory. At next-to-leading order, ${\cal O}(q^3)$, knowledge of the baryon masses and $\sigma_{\pi N}(0)$ allows to determine the three corresponding finite low--energy constants and to predict the the two $KN$ $\sigma$--terms $\sigma^{(1,2)}_{KN} (0)$. We also include the spin-3/2 decuplet in the effective theory. The presence of the non--vanishing energy scale due to the octet--decuplet splitting shifts the average octet baryon mass by an infinite amount and leads to infinite renormalizations of the low--energy constants. The first observable effect of the decuplet intermediate states to the baryon masses starts out at order $q^4$. We argue that it is not sufficient to retain only these but no other higher order terms to achieve a consistent description of the three--flavor scalar sector of baryon CHPT. In addition, we critically discuss an SU(2) result which allows to explain the large shift of $\sigma_{\pi N}(2M_\pi^2) - \sigma_{\pi N}(0)$ via intermediate $\Delta (1232)$ states.Comment: 18 pp, TeX, BUTP-93/05 and CRN-93-0