Translational and rotational friction on a colloidal rod near a wall

We present particulate simulation results for translational and rotational friction components of a shish-kebab model of a colloidal rod with aspect ratio (length over diameter) $L/D = 10$ in the presence of a planar hard wall. Hydrodynamic interactions between rod and wall cause an overall enhancement of the friction tensor components. We find that the friction enhancements to reasonable approximation scale inversely linear with the closest distance $d$ between the rod surface and the wall, for $d$ in the range between $D/8$ and $L$. The dependence of the wall-induced friction on the angle $\theta$ between the long axis of the rod and the normal to the wall is studied and fitted with simple polynomials in $\cos \theta$.Comment: 8 pages, 8 figure

Acoustic radiation- and streaming-induced microparticle velocities determined by micro-PIV in an ultrasound symmetry plane

We present micro-PIV measurements of suspended microparticles of diameters from 0.6 um to 10 um undergoing acoustophoresis in an ultrasound symmetry plane in a microchannel. The motion of the smallest particles are dominated by the Stokes drag from the induced acoustic streaming flow, while the motion of the largest particles are dominated by the acoustic radiation force. For all particle sizes we predict theoretically how much of the particle velocity is due to radiation and streaming, respectively. These predictions include corrections for particle-wall interactions and ultrasonic thermoviscous effects, and they match our measurements within the experimental uncertainty. Finally, we predict theoretically and confirm experimentally that the ratio between the acoustic radiation- and streaming-induced particle velocities is proportional to the square of the particle size, the actuation frequency and the acoustic contrast factor, while it is inversely proportional to the kinematic viscosity.Comment: 11 pages, 9 figures, RevTex 4-

Échange international et distorsions internes:Comment gouverner la globalisation ?

La concurrence des pays émergents de la taille de la Chine ou de l’Inde fait resurgir avec force le débat qui oppose partisans et adversaires du libre-échange au sein même des pays développés. Pour les premiers, la croissance du commerce international est forcément bénéficiaire pour tous. Pour les seconds, elle est la cause de tous les maux et en particulier du chômage. Les choses sont pourtant bien différentes et beaucoup moins simples. Les changements dans le commerce international, comme d’ailleurs le progrès technique, créent inévitablement des distorsions qui perturbent le fonctionnement de l’économie. Ces distorsions ne sont pas réductibles à des dysfonctionnements des marchés des biens ou du travail. Elles ne peuvent donc pas être éliminées ab initio en choisissant des institutions optimales. Pour autant, des restrictions au commerce international ne sont pas une solution car elles risquent de créer d’autres distorsions qui viennent s’ajouter aux premières. Des distorsions avant tout intérieures appellent des solutions intérieures. Pour explorer ces solutions, il faut retenir une analyse conçue pour étudier, non les propriétés des positions d’équilibre avant et après l’ouverture à l’échange, mais les caractéristiques d’un processus de transition dont le succès n’est pas assuré. Ce type d’analyse permet de mettre en évidence la nécessité d’introduire une forme d’inertie dans les mécanismes d’ajustement. Si une relative flexibilité des salaires est encore possible quand l’intensité du changement est limitée, une certaine viscosité est requise dans le cas contraire, et un accès facilité aux ressources financières externes est nécessaire. Ce résultat pourrait aider à formuler les choix institutionnels et organisationnels à mettre en œuvre dans les économies qui veulent tirer avantage du commerce international et de la globalisation.Changes in the pattern of international trade inevitably create distortions that perturb the functioning of the economy. These distortions may not be reduced to malfunctioning goods or labour markets, and hence cannot be eliminated by simply choosing the optimal institutions. Domestic distortions call for domestic solutions. To explore these solutions it is useless to analyze the properties of equilibria before and after the opening to trade. Rather, we need to build an analytical framework suited to investigate the characteristics of a transition process whose success is not guaranteed ex ante. it appears that wage rigidity and an easy access to external financial resources are necessary in presence of fast pace of change, while if change is sufficiently slow the standard recipe of wage flexibility may be appropriate. These results may help in the institutional and organizational choices to be implemented in economies willing to profit from international trade and globalization

Inverse lift: a signature of the elasticity of complex fluids?

To understand the mechanics of a complex fluid such as a foam we propose a model experiment (a bidimensional flow around an obstacle) for which an external sollicitation is applied, and a local response is measured, simultaneously. We observe that an asymmetric obstacle (cambered airfoil profile) experiences a downards lift, opposite to the lift usually known (in a different context) in aerodynamics. Correlations of velocity, deformations and pressure fields yield a clear explanation of this inverse lift, involving the elasticity of the foam. We argue that such an inverse lift is likely common to complex fluids with elasticity.Comment: 4 pages, 4 figures, revised version, submitted to PR

Мониторинг резистентности грамотрицательных возбудителей, выделенных у пациентов с хирургическими инфекциями кожи и мягких тканей

МЯГКИЕ ТКАНИХИРУРГИЧЕСКИЕ ИНФЕКЦИИГРАМОТРИЦАТЕЛЬНЫЕ БАКТЕРИИГРАМОТРИЦАТЕЛЬНЫЕ БАКТЕРИАЛЬНЫЕ ИНФЕКЦИИРЕЗИСТЕНТНОСТЬ БАКТЕРИЙ К АНТИБИОТИКАМНОЗОКОМИАЛЬНАЯ ИНФЕКЦИЯСИНЕГНОЙНАЯ ПАЛОЧКААЦИНЕТОБАКТЕ

A user-friendly risk-score for predicting in-hospital cardiac arrest among patients admitted with suspected non ST-elevation acute coronary syndrome – the SAFER-score

Aim: To develop a simple risk-score model for predicting in-hospital cardiac arrest (CA) among patients hospitalized with suspected non-ST elevation acute coronary syndrome (NSTE-ACS). Methods: Using the Swedish Web-system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies (SWEDEHEART), we identified patients (n = 242 303) admitted with suspected NSTE-ACS between 2008 and 2014. Logistic regression was used to assess the association between 26 candidate variables and in-hospital CA. A risk-score model was developed and validated using a temporal cohort (n = 126 073) comprising patients from SWEDEHEART between 2005 and 2007 and an external cohort (n = 276 109) comprising patients from the Myocardial Ischaemia National Audit Project (MINAP) between 2008 and 2013. Results: The incidence of in-hospital CA for NSTE-ACS and non-ACS was lower in the SWEDEHEART-derivation cohort than in MINAP (1.3% and 0.5% vs. 2.3% and 2.3%). A seven point, five variable risk score (age ≥60 years (1 point), ST-T abnormalities (2 points), Killip Class >1 (1 point), heart rate <50 or ≥100 bpm (1 point), and systolic blood pressure <100 mmHg (2 points) was developed. Model discrimination was good in the derivation cohort (c-statistic 0.72) and temporal validation cohort (c-statistic 0.74), and calibration was reasonable with a tendency towards overestimation of risk with a higher sum of score points. External validation showed moderate discrimination (c-statistic 0.65) and calibration showed a general underestimation of predicted risk. Conclusions: A simple points score containing five variables readily available on admission predicts in-hospital CA for patients with suspected NSTE-ACS

Effects of Peroral Omega-3 Fatty Acid Supplementation on Cerebrospinal Fluid Biomarkers in Patients with Alzheimer’s Disease: A Randomized Controlled Trial—The OmegAD Study

Background: Studies have suggested a connection between a decrease in the levels of polyunsaturated fatty acids (PUFAs) and Alzheimer’s disease (AD). We aimed to assess the effect of supplementation with omega-3 fatty acids (n-3 FAs) on biomarkers analyzed in the cerebrospinal fluid (CSF) of patients diagnosed with AD. / Objective: To investigate the effects of daily supplementation with 2.3 g of PUFAs in AD patients on the biomarkers in CSF described below. We also explored the possible correlation between these biomarkers and the performance in the cognitive test Mini-Mental State Examination (MMSE). / Methods: Thirty-three patients diagnosed with AD were randomized to either treatment with a daily intake of 2.3 g of n-3 FAs (n  =  18) or placebo (n  =  15). CSF samples were collected at baseline and after six months of treatment, and the following biomarkers were analyzed: Aβ 38, Aβ 40, Aβ 42, t-tau, p-tau, neurofilament light (NfL), chitinase-3-like protein 1 (YKL-40), acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), soluble IL-1 receptor type II (sIL-1RII), and IL-6. / Results: There were no significant differences between the groups concerning the level of the different biomarkers in the CSF at baseline. Within the treatment group, there was a small but significant increase in both YKL-40 (p = 0.04) and NfL (p = 0.03), while the other CSF biomarkers remained stable. / Conclusion: Supplementation with n-3 FAs had a statistically significant effect on NfL and YKL-40, resulting in an increase of both biomarkers, indicating a possible increase of inflammatory response and axonal damage. This increase in biomarkers did not correlate with MMSE score. / Trial registration: clinicaltrial.gov Identifier: NCT00211159

Simple Viscous Flows: from Boundary Layers to the Renormalization Group

The seemingly simple problem of determining the drag on a body moving through a very viscous fluid has, for over 150 years, been a source of theoretical confusion, mathematical paradoxes, and experimental artifacts, primarily arising from the complex boundary layer structure of the flow near the body and at infinity. We review the extensive experimental and theoretical literature on this problem, with special emphasis on the logical relationship between different approaches. The survey begins with the developments of matched asymptotic expansions, and concludes with a discussion of perturbative renormalization group techniques, adapted from quantum field theory to differential equations. The renormalization group calculations lead to a new prediction for the drag coefficient, one which can both reproduce and surpass the results of matched asymptotics