Empirical Study of Ground Proximity Effects for Small-scale Electroaerodynamic Thrusters

Electroaerodynamic (EAD) propulsion, where thrust is produced by collisions between electrostatically-accelerated ions and neutral air, is a potentially transformative method for indoor flight owing to its silent and solid-state nature. Like rotors, EAD thrusters exhibit changes in performance based on proximity to surfaces. Unlike rotors, they have no fragile and quickly spinning parts that have to avoid those surfaces; taking advantage of the efficiency benefits from proximity effects may be a route towards longer-duration indoor operation of ion-propelled fliers. This work presents the first empirical study of ground proximity effects for EAD propulsors, both individually and as quad-thruster arrays. It focuses on multi-stage ducted centimeter-scale actuators suitable for use on small robots envisioned for deployment in human-proximal and indoor environments. Three specific effects (ground, suckdown, and fountain lift), each occurring with a different magnitude at a different spacing from the ground plane, are investigated and shown to have strong dependencies on geometric parameters including thruster-to-thruster spacing, thruster protrusion from the fuselage, and inclusion of flanges or strakes. Peak thrust enhancement ranging from 300 to 600% is found for certain configurations operated in close proximity (0.2 mm) to the ground plane and as much as a 20% increase is measured even when operated centimeters away

Studying Leaders and Elites : The Personal Biography Approach

The last two decades have seen a revival in work that takes the role of individual leaders and elites seriously. This article surveys new research that explores how biographical factors influence their behavior. We call this literature the personal biography approach to political leadership. Our survey first lays out four mechanisms through which biographical characteristics might affect leader behavior. We then discuss the main findings, grouping them according to socializing experiences (e.g., education, military service, and prior occupation) and ascriptive traits (e.g., gender, race, and ethnicity). We also consider the methodological problems, especially endogeneity and selection effects, that pose challenges to this style of research. We conclude with an assessment of gaps in the literature and provide suggestions for future work in the biographical vein

The viscous slowing down of supercooled liquids as a temperature-controlled superArrhenius activated process: a description in terms of frustration-limited domains

We propose that the salient feature to be explained about the glass transition of supercooled liquids is the temperature-controlled superArrhenius activated nature of the viscous slowing down, more strikingly seen in weakly-bonded, fragile systems. In the light of this observation, the relevance of simple models of spherically interacting particles and that of models based on free-volume congested dynamics are questioned. Finally, we discuss how the main aspects of the phenomenology of supercooled liquids, including the crossover from Arrhenius to superArrhenius activated behavior and the heterogeneous character of the $\alpha$ relaxation, can be described by an approach based on frustration-limited domains.Comment: 13 pages, 4 figures, accepted in J. Phys.: Condensed Matter, proceedings of the Trieste workshop on "Unifying Concepts in Glass Physics

Effects of Isometric Handgrip Training in Patients With Peripheral Artery Disease: A Randomized Controlled Trial

BackgroundMeta‐analyses have shown that isometric handgrip training (IHT) can reduce brachial systolic and diastolic blood pressure (BP) by >6/4 mm Hg, respectively. However, whether IHT promotes these effects among patients with peripheral artery disease, who exhibit severe impairment in cardiovascular function, is currently unknown. This study aimed to evaluate the effects of IHT on the cardiovascular function of patients with peripheral artery disease. Methods and ResultsA randomized controlled trial with peripheral artery disease patients assigned to either the IHT or control group was conducted. The IHT group performed 3 sessions per week, for 8 weeks, of unilateral handgrip exercises, consisting of 4 sets of isometric contractions for 2 minutes at 30% of maximum voluntary contraction and a 4‐minute interval between sets. The control group received a compression ball in order to minimize the placebo effects, representing sham training. The primary outcome was brachial BP. The secondary outcomes were central BP, arterial stiffness parameters, cardiac autonomic modulation, and vascular function. The IHT program reduced diastolic BP (75 [10] mm Hg preintervention versus 72 [11] mm Hg postintervention), with no change in the control group (74 [11] mm Hg preintervention versus 74 [11] mm Hg postintervention), with this between‐group difference being significant (P=0.04). Flow‐mediated dilation improved in the IHT group (6.0% [5.7] preintervention versus 9.7% [5.5] postintervention), with no change in the control group (7.6% [5.5] preintervention versus 7.4% [5.1] postintervention), with this between‐group difference being significant (P=0.04). There was no change in other measured variables over the intervention period. ConclusionsIHT reduced brachial diastolic BP and improved local vascular function in patients with peripheral artery disease

Dialkylcarbamoyl Chloride Dressings in the Prevention of Surgical Site Infections after Nonimplant Vascular Surgery

© 2017 Elsevier Inc. Background Dressings coated with dialkylcarbamoyl chloride (DACC) are highly hydrophobic and irreversibly bind multiple types of bacteria, trapping them in the dressing and reducing the number of organisms at the wound surface. We aimed to assess the impact of DACC-coated postoperative dressings on the incidence of surgical site infection (SSI) in nonimplant vascular surgery patients. Methods Two hundred patients undergoing nonimplant vascular surgery were prospectively recruited at a single vascular center. The initial 100 patients had their operative wounds dressed with conventional dressings followed by 100 patients who received DACC-coated postoperative dressings. Wounds were reviewed at day 5 and day 30 to determine the presence of SSI using the ASEPSIS scoring system. The variation in outcomes between groups was assessed using chi-squared test and logistic regression analysis to assess the effects of other variables, which may affect healing. Results Between August 1, 2015 and February 29, 2016, a total of 120 men and 80 women were recruited. The mean age was 63 (range 27–97) years, 92% were current or ex-smokers and 45.5% were diabetic. Rate of SSI at 5 days was significantly lower in the DACC group compared with standard dressings (1% vs. 10%, P < 0.05). There was no difference in the rates of SSI at 30 days. Logistic regression suggested that the type of dressing used was the most prominent predictor variable for the presence of early SSI (P = 0.028, odds ratio = 0.09, 95% confidence interval: 0.01–0.77). Conclusions DACC-coated dressings were associated with a significant reduction in SSI rates in the early postoperative period