Elastohydrodynamic Scaling Law for Heart Rates.

Animal hearts are soft shells that actively pump blood to oxygenate tissues. Here, we propose an allometric scaling law for the heart rate based on the idea of elastohydrodynamic resonance of a fluid-loaded soft active elastic shell that buckles and contracts axially when twisted periodically. We show that this picture is consistent with numerical simulations of soft cylindrical shells that twist-buckle while pumping a viscous fluid, yielding optimum ejection fractions of 35%-40% when driven resonantly. Our scaling law is consistent with experimental measurements of heart rates over 2 orders of magnitude, and provides a mechanistic basis for how metabolism scales with organism size. In addition to providing a physical rationale for the heart rate and metabolism of an organism, our results suggest a simple design principle for soft fluidic pumps.

Airway stent current practices evaluation: Survey among French bronchoscopy practitioners.

BACKGROUND: Airway stenting (AS) is performed for the treatment of benign or malignant central airway stenosis. In France, more than 30 centers practice AS. The aim of this survey was to evaluate the current practice around airway stenting among French bronchoscopy practitioners. METHOD: We performed an online survey sent to the GELF group (Groupe d'Endoscopie de Langue Française) mailing list. The first part comprised 10 questions about the different attitudes before AS and the second part included 10 questions about the management after AS. RESULTS: Thirty-six participants answered to the first part of the questionnaire and thirty-three to the second. There were some similarities, for example the absence of prophylactic antibiotic treatment before procedure (86%), use of saline nebulization, and removing or replacing the airway stent in case of persistent chest congestion or infection (73%). We also noted an important heterogeneity of the practices with several differences concerning systematic endoscopic control, bacteriological sampling before procedure (44%) and systematically AS replacement. CONCLUSION: This survey shows that AS management in France varies between practitioners. Respondents agreed on a few points, but disagreed on several important aspects of the management. These results emphasize the need of expert recommendations to improve AS management.

[SaO2 and PaO2 mismatch: Do not forget hemoglobinopathy]. / Discordance entre SaO2 ­ PaO2 : ne pas oublier les hémoglobinopathies.

INTRODUCTION: Different clinico-biological parameters are used to estimate the amount of oxygen available for the organism. Oxygen saturation measured with pulse oxymetry (SpO2), oxygen saturation of arterial blood (SaO2) and oxygen partial pressure of the arterial blood (PaO2) are the most commonly used. CASE REPORT: We report the case of a patient admitted for investigation of respiratory failure in the context of chronic dyspnea of effort. SpO2 and SaO2 were decreased, though the PaO2 was normal. This mismatch between oxygen saturation and PaO2 led to the diagnosis of hemoglobinopathy (Bassett hemoglobin). CONCLUSION: The diagnosis of hemoglobinopathy should be considered in cases of oxygen desaturation with normal respiratory and cardiac investigations. There are no reasons to prescribe long-term oxygen to these patients.

Publisher's Note: Critical wind speed at which trees break [Phys. Rev. E 93, 023001 (2016)].

This corrects the article DOI: 10.1103/PhysRevE.93.023001.

Critical wind speed at which trees break.

Data from storms suggest that the critical wind speed at which trees break is constant (≃42m/s), regardless of tree characteristics. We question the physical origin of this observation both experimentally and theoretically. By combining Hooke's law, Griffith's criterion, and tree allometry, we show that the critical wind speed indeed hardly depends on the height, diameter, and elastic properties of trees.

Reply to "Comment on 'Critical wind speed at which trees break' ".

In the preceding comment [A. Albrecht et al., Phys. Rev. E 94, 067001 (2016)10.1103/PhysRevE.94.067001], Albrecht et al. argue that important biomechanical ingredients are missing in our model about the wind speed at which trees break [Phys. Rev. E 93, 023001 (2016)10.1103/PhysRevE.93.023001]. Here we wish to emphasize that our model is an idealization, which primarily aims at evidencing the dominant ingredients of the problem. Since it captures both observed trends and orders of magnitude, we believe that the essential parameters in tree breakage have been identified, a useful step to make further progress and more detailed descriptions.