Large-scale bottleneck effect in two-dimensional turbulence

The bottleneck phenomenon in three-dimensional turbulence is generally associated with the dissipation range of the energy spectrum. In the present work, it is shown by using a two-point closure theory, that in two-dimensional turbulence it is possible to observe a bottleneck at the large scales, due to the effect of friction on the inverse energy cascade. This large-scale bottleneck is directly related to the process of energy condensation, the pile-up of energy at wavenumbers corresponding to the domain size. The link between the use of friction and the creation of space-filling structures is discussed and it is concluded that the careless use of hypofriction might reduce the inertial range of the energy spectrum

Negligible structural development and edge influence on the understorey at 16–17-yr-old clear-cut edges in black spruce forest

Questions: What is the distance of edge influence on the structure and understorey composition at 16–17-yr-old cut edges in black spruce boreal forest? How do these edges compare with more recent 2–5-yr-old cut edges in the same region?\ud \ud Location: Northwestern Quebec, Canada.\ud \ud Methods: Forest structure and understorey composition were sampled along\ud transects perpendicular to ten 16–17-yr-old clear-cut edges, and compared to published results from 2–5-yr-old cut edges. We used randomization tests to assess themagnitude and distance of edge influence, and to compare edge influence between different edge ages.\ud \ud Results: Black spruce forest next to the 16–17-yr-old cut edges was structurally and compositionally very similar to interior forest, with little edge influence from harvesting beyond 5 m into the forest. Edge influence on the understorey was weak (low magnitude) and not very extensive (short distance) at these edges, with no significant edge influence on the abundance of individual species. Logs peaked in abundance on the forest side of the edge, with values higher than in either adjacent ecosystem.\ud \ud Conclusions: Overall, 16–17-yr-old cut edges in black spruce forest showed little evidence of further structural change compared to the 2–5-yr-old cut edges. Structural development of these edges as well as regeneration of the disturbed areas also resulted in reduced edge influence on the understorey. Instead, clearcut edges in black spruce forest may experience more forest influence on the regenerating disturbed area

pH-sensitive liposomes as a carrier for oligonucleotides: a physico-chemical study of the interaction between DOPE and a 15-mer oligonucleotide in quasi-anhydrous samples

AbstractpH-sensitive liposomes made of dioleoylphosphatidylethanolamine (DOPE)/oleic acid (OA)/cholesterol (CHOL) mixtures were shown to be very promising carriers for oligonucleotides (ON). However, it appeared necessary to clarify the structural consequence of the interactions of ON with the liposome, and especially on DOPE, the lipid responsible for the pH sensitivity. The present study was carried out by differential scanning calorimetry and X-ray diffraction, at low hydration. In such a case, DOPE generally adopt a hexagonal phase. It could be shown that ON increased DOPE transition temperature and increased v/al, as a result of electrostatic interactions between ON and DOPE headgroups. OA was found to have exactly opposite effects, its presence between DOPE molecules inhibiting the formation of hydrogen bonds. The presence of both ON and OA allowed the system to organize in a lamellar phase below the solid/liquid transition, whereas above this temperature ON preferably interacted with DOPE in a hexagonal phase and led OA to separate

Forest structure and composition at fire edges of different ages: Evidence of persistent structural features on the landscape

Accepted versionBoreal forest landscapes are dynamic with stands in different stages of development following stand-replacing disturbances such as fire and insect outbreaks. Forest edges are an important component of these heterogeneous landscapes but there have been few studies on intermediate-aged forest edges which are needed for a comprehensive perspective on the spatiotemporal dynamics of forest edges. We described the structure, composition and extent of edge influence at 13, 25 and 39-year old fire edges in black spruce Boreal forest in northwestern Québec and northeastern Ontario to characterize their structural development and to assess effects of edge development on the understorey. Forest structure and understorey composition were sampled along transects perpendicular to edges of the fires. Edge influence was assessed using randomization tests. Black spruce forest was relatively unaffected by edge influence beyond 5 m into the forest at all ages of edges studied. Edge influence on the understorey was weak and not extensive at intermediate-aged edges with few consistent responses of individual species. Less decayed snags and logs at 13 and 25-year old edges peaked in abundance at or near the edge with values higher than in either adjacent ecosystem. Overall, intermediate-aged fire edges in black spruce forest showed little evidence of further changes in canopy structure with time. Structural development of these edges as well as the regeneration of the disturbed areas also resulted in reduced edge influence on the understorey. A new insight from our study is that intermediate-aged forest edges may contribute unique structural features to landscapes such as a reservoir of deadwood that may be important for wildlife species

Negligible structural development and edge influence on the understorey at 16–17‐yr‐old clear‐cut edges in black spruce forest

Accepted VersionQuestions: What is the distance of edge influence on the structure and understorey composition at 16–17-yr-old cut edges in black spruce boreal forest? How do these edges compare with more recent 2–5-yr-old cut edges in the same region?Location: Northwestern Quebec, Canada.Methods: Forest structure and understorey composition were sampled along transects perpendicular to ten 16–17-yr-old clear-cut edges, and compared to published results from 2–5-yr-old cut edges. We used randomization tests to assess the magnitude and distance of edge influence, and to compare edge influence between different edge ages.Results: Black spruce forest next to the 16–17-yr-old cut edges was structurally and compositionally very similar to interior forest, with little edge influence from harvesting beyond 5 m into the forest. Edge influence on the understorey was weak (low magnitude) and not very extensive (short distance) at these edges, with no significant edge influence on the abundance of individual species. Logs peaked in abundance on the forest side of the edge, with values higher than in either adjacent ecosystem.Conclusions: Overall, 16–17-yr-old cut edges in black spruce forest showed little evidence of further structural change compared to the 2–5-yr-old cut edges. Structural development of these edges as well as regeneration of the disturbed areas also resulted in reduced edge influence on the understorey. Instead, clear-cut edges in black spruce forest may experience more forest influence on the regenerating disturbed area

Edge influence on vegetation at natural and anthropogenic edges of boreal forests in Canada and Fennoscandia

Although anthropogenic edges are an important consequence of timber harvesting, edges due to natural disturbances or landscape heterogeneity are also common. Forest edges have been well studied in temperate and tropical forests, but less so in less productive, disturbance-adapted boreal forests. We synthesized data on forest vegetation at edges of boreal forests and compared edge influence among edge types (fire, cut, lake/wetland; old vs. young), forest types (broadleaf vs. coniferous) and geographic regions. Our objectives were to quantify vegetation responses at edges of all types and to compare the strength and extent of edge influence among different types of edges and forests. Research was conducted using the same general sampling design in Alberta, Ontario and Quebec in Canada, and in Sweden and Finland. We conducted a meta-analysis for a variety of response variables including forest structure, deadwood abundance, regeneration, understorey abundance and diversity, and non-vascular plant cover. We also determined the magnitude and distance of edge influence (DEI) using randomization tests. Some edge responses (lower tree basal area, tree canopy and bryophyte cover; more logs; higher regeneration) were significant overall across studies. Edge influence on ground vegetation in boreal forests was generally weak, not very extensive (DEI usually < 20 m) and decreased with time. We found more extensive edge influence at natural edges, at younger edges and in broadleaf forests. The comparison among regions revealed weaker edge influence in Fennoscandian forests. Synthesis. Edges created by forest harvesting do not appear to have as strong, extensive or persistent influence on vegetation in boreal as in tropical or temperate forested ecosystems. We attribute this apparent resistance to shorter canopy heights, inherent heterogeneity in boreal forests and their adaptation to frequent natural disturbance. Nevertheless, notable differences between forest structure responses to natural (fire) and anthropogenic (cut) edges raise concerns about biodiversity implications of extensive creation of anthropogenic edges. By highlighting universal responses to edge influence in boreal forests that are significant irrespective of edge or forest type, and those which vary by edge type, we provide a context for the conservation of boreal forests. Edges created by forest harvesting do not appear to have as strong, extensive or persistent influence on vegetation in boreal as in tropical or temperate forested ecosystems. We attribute this apparent resistance to shorter canopy heights, inherent heterogeneity in boreal forests and their adaptation to frequent natural disturbance. Nevertheless, notable differences between forest structure responses to natural (fire) and anthropogenic (cut) edges raise concerns about biodiversity implications of extensive creation of anthropogenic edges. By highlighting universal responses to edge influence in boreal forests that are significant irrespective of edge or forest type, and those which vary by edge type, we provide a context for the conservation of boreal forests

Migrant health in French Guiana: Are undocumented immigrants more vulnerable?

<p>Abstract</p> <p>Background</p> <p>Few data exist on the health status of the immigrant population in French Guiana. The main objective of this article was to identify differences in its health status in relation to that of the native-born population.</p> <p>Methods</p> <p>A representative, population-based, cross-sectional survey was conducted in 2009 among 1027 adults living in Cayenne and St-Laurent du Maroni. Health status was assessed in terms of self-perceived health, chronic diseases and functional limitations. The migration variables were immigration status, the duration of residence in French Guiana and the country of birth. Logistic regression models were conducted.</p> <p>Results</p> <p>Immigrants account for 40.5% and 57.8% of the adult population of Cayenne and St-Laurent du Maroni, respectively. Most of them (60.7% and 77.5%, respectively) had been living in French Guiana for more than 10 years. A large proportion were still undocumented or had a precarious legal status. The undocumented immigrants reported the worst health status (OR = 3.18 [1.21-7.84] for self-perceived health, OR = 2.79 [1.22-6.34] for a chronic disease, and OR = 2.17 [1.00-4.70] for a functional limitation). These differences are partially explained by socioeconomic status and psychosocial factors. The country of birth and the duration of residence also had an impact on health indicators.</p> <p>Conclusion</p> <p>Data on immigrant health are scarce in France, and more generally, immigrant health problems have been largely ignored in public health policies. Immigrant health status is of crucial interest to health policy planners, and it is especially relevant in French Guiana, considering the size of the foreign-born population in that region.</p

Admission criteria and management of critical care patients in a pandemic context: position of the Ethics Commission of the French Intensive Care Society, update of April 2021.

Intensive care unit professionals have experience in critical care and its proportionality, collegial decision-making, withholding or withdrawal of treatment deemed futile, and communication with patients' relatives. These elements rely on ethical values from which we must not deviate in a pandemic situation. The recommendations made by the Ethics Commission of the French Intensive Care Society reflect an approach of responsibility and solidarity towards our citizens regarding the potential impact of a pandemic on critical care resources in France, with the fundamental requirement of respect for human dignity and equal access to health care for all

Epidemiology and outcome predictors in 450 patients with hanging-induced cardiac arrest: a retrospective study

BackgroundCardiac arrest is the most life-threatening complication of attempted suicide by hanging. However, data are scarce on its characteristics and outcome predictors.MethodsThis retrospective observational multicentre study in 31 hospitals included consecutive adults admitted after cardiac arrest induced by suicidal hanging. Factors associated with in-hospital mortality were identified by multivariate logistic regression with multiple imputations for missing data and adjusted to the temporal trends over the study period.ResultsOf 450 patients (350 men, median age, 43 [34–52] years), 305 (68%) had a psychiatric history, and 31 (6.9%) attempted hanging while hospitalized. The median time from unhanging to cardiopulmonary resuscitation was 0 [0–5] min, and the median time to return of spontaneous circulation (ROSC) was 20 [10–30] min. Seventy-nine (18%) patients survived to hospital discharge. Three variables were independently associated with higher in-hospital mortality: time from collapse or unhanging to ROSC&gt;20 min (odds ratio [OR], 4.71; 95% confidence intervals [95%CIs], 2.02–10.96; p = 0.0004); glycaemia &gt;1.4 g/L at admission (OR, 6.38; 95%CI, 2.60–15.66; p &lt; 0.0001); and lactate &gt;3.5 mmol/L at admission (OR, 6.08; 95%CI, 1.71–21.06; p = 0.005). A Glasgow Coma Scale (GCS) score of &gt;5 at admission was associated with lower in-hospital mortality (OR, 0.009; 95%CI, 0.02–0.37; p = 0.0009).ConclusionIn patients with hanging-induced cardiac arrest, time from collapse or unhanging to return of spontaneous circulation, glycaemia, arterial lactate, and coma depth at admission were independently associated with survival to hospital discharge. Knowledge of these risk factors may help guide treatment decisions in these patients at high risk of hospital mortality

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)