Growth and Self-Ejection of Single Condensate Droplet on Nanostructured Microcones

In the last decade, the phenomenon of coalescence-induced droplet jumping has been studied in depth because of the advantages it brings in applications such as anti-frosting, anti-icing, condensation heat transfer, water harvesting, thermal diodes for electronics cooling and self-cleaning [1]. In this work we theoretically and experimentally show that surfaces structured with micro truncated cones covered with highly hydrophobic nanostructures exhibit a recurrent self-ejection of single condensate droplets in addition to the common coalescence-induced jumps. We analytically modelled the external forces acting both on a droplet of condensate slowly growing in conical pores (a simplification of the growth between truncated cones) and during the following rapid transient for two possible cases of self-ejection: 1) rapid swelling out of the structures and 2) detachment from a pinning site (a less hydrophobic defect or the nucleation site). Viscous and adhesion dissipations were included in the modelling. We described the shape of the growing droplet as a function of the tapering (B) and of dynamic contact angles (vadv and vrec ). For both cases, the minimum requirement for self-ejection is that the receding angle of the walls (vrec ) and any pinning site (vpinningrec ) are greater than 90°+B. In the first case, as the volume increases, the upper meniscus moves towards the apex of the cones and the lower one follows it as soon as it reaches vrec; when the droplet reaches the apex of the structures it self-ejects because the superior meniscus expands rapidly and a Laplace pressure gradient is generated between the menisci. In the second case, the superior meniscus grows towards the apex and when the lower one recedes from the pinning site, the droplet self-ejects due to the Laplace pressure gradient generated by the abrupt change in wettability, as recently reported for relatively large droplets (radius > 50 μm) in diverging grooves [2]. Describing growth and self-ejection with a system of forces requires a careful distinction between external and internal forces. The modelling with forces, unlike the energetic one [2], allowed us to describe the ejection transient dynamics and to derive the ejection velocity while maintaining the dependence on the dynamic contact angles of the superhydrophobic walls and of an eventual pinning site, fundamental quantities for the design of real surfaces. The analytical results relative to the case of the pinning site foresee that, at a fixed contact angle hysteresis of the superhydrophobic walls and vpinningrec, the ejection velocity increases with B (until the limit B = vpinningrec − 90°, beyond which there cannot be ejection); in addition, the velocity is greater as the droplet size decreases if viscous dissipations are not considered while a peak trend is observed with the dissipations included. We fabricated silicon truncated micro cones arranged in square and hexagonal patterns and covered with nanostructures. Through condensation experiments in a controlled environmental chamber we observed for the first time the self-ejection of the drops that nucleate and grow between the cones (in the case in question the droplet diameter ≈ 11 um). By fabricating cones of different sizes, we have also studied the self-ejection rate per unit area as a function of the droplet size. Furthermore, we performed preliminary condensation frosting experiments. Future investigations of this new class of jumping droplet surfaces may show important advantages in the mentioned applications

Decreasing Prevalence of the Full Metabolic Syndrome but a Persistently High Prevalence of Dyslipidemia among Adult Arabs

A decade has passed since metabolic syndrome (MetS) was documented to be highly prevalent in the kingdom of Saudi Arabia. No follow-up epidemiologic study was done. This study aims to fill this gap. In this cross-sectional, observational study, a total of 2850 randomly selected Saudi adults aged 18–55 years were recruited. Subjects' information was generated from a database of more than 10,000 Saudi citizens from the existing Biomarkers Screening in Riyadh Program (RIYADH Cohort), Saudi Arabia. Anthropometrics included body mass index (BMI), blood pressure, as well as waist and hip circumferences. Fasting blood glucose and lipid profile were determined using routine laboratory procedures. The definition of ATP-III (NHANES III) was used for the diagnosis of the full MetS. The overall prevalence of complete MetS was 35.3% [Confidence-Interval (CI) 33.5–37.01]. Age-adjusted prevalence according to the European standard population is 37.0%. Low HDL-cholesterol was the most prevalent of all MetS risk factors, affecting 88.6% (CI 87.5–89.7) and hypertriglyceridemia the second most prevalent, affecting 34% (CI 32.3–35.7) of the subjects. The prevalence of the full MetS decreased from previous estimates but remains high, while dyslipidemia remains extremely high, affecting almost 90% of middle-aged Arabs. Screening for dyslipidemia among Saudi adults is warranted, especially among those most at risk. Scientific inquiry into the molecular causes of these manifestations should be pursued as a first step in the discovery of etiologic therapies

The Waiting Time for Inter-Country Spread of Pandemic Influenza

BACKGROUND: The time delay between the start of an influenza pandemic and its subsequent initiation in other countries is highly relevant to preparedness planning. We quantify the distribution of this random time in terms of the separate components of this delay, and assess how the delay may be extended by non-pharmaceutical interventions. METHODS AND FINDINGS: The model constructed for this time delay accounts for: (i) epidemic growth in the source region, (ii) the delay until an infected individual from the source region seeks to travel to an at-risk country, (iii) the chance that infected travelers are detected by screening at exit and entry borders, (iv) the possibility of in-flight transmission, (v) the chance that an infected arrival might not initiate an epidemic, and (vi) the delay until infection in the at-risk country gathers momentum. Efforts that reduce the disease reproduction number in the source region below two and severe travel restrictions are most effective for delaying a local epidemic, and under favourable circumstances, could add several months to the delay. On the other hand, the model predicts that border screening for symptomatic infection, wearing a protective mask during travel, promoting early presentation of cases arising among arriving passengers and moderate reduction in travel volumes increase the delay only by a matter of days or weeks. Elevated in-flight transmission reduces the delay only minimally. CONCLUSIONS: The delay until an epidemic of pandemic strain influenza is imported into an at-risk country is largely determined by the course of the epidemic in the source region and the number of travelers attempting to enter the at-risk country, and is little affected by non-pharmaceutical interventions targeting these travelers. Short of preventing international travel altogether, eradicating a nascent pandemic in the source region appears to be the only reliable method of preventing country-to-country spread of a pandemic strain of influenza

The influence of farmers' mental models on an agroforestry extension program in the Philippines

The influence of farmers' mental models on the success of an agroforestry extension program on Leyte Island in the Philippines was investigated. Knowledge of farmers' mental models and hence the likely acceptance of technology was used to inform the design of a hypothetically expanded program. To gain an insight into the reasons behind differing acceptance of extension assistance, data were collected and analysed from formal interviews, translated conversations and visual observations. The data provided a chain of evidence and triangulation between farmers' stated intentions and their actions. Farmers had little prior knowledge of nursery technology and were highly receptive to extension assistance which enabled them to develop high self-efficacy in seedling production. However, farmers' rejection of silvicultural advice to thin and prune existing plantations was predicated by existing attitudes to forest resource management. Farmers also expressed a strong preference for a low-cost and low-input approach to establishing timber trees. Visual observations of farmers' tree establishment practices indicated the existence of gaps in their knowledge of tree growth processes. This investigation illustrates the need to elicit farmers' mental models as a parallel enquiry to extension activities. If agroforestry extension is to be constructivist and participatory, accommodation of farmers' mental models and modification of program goals may be necessary. Relatively little is known about the reasons for farmers' acceptance or rejection of silviculture in Leyte and these results indicate that further research into the way that farmers' mental models filter and guide acceptance of advice may be worthwhile

Erratum. Blood and Islet Phenotypes Indicate Immunological Heterogeneity in Type 1 Diabetes. Diabetes 2014;63:3835–3845

The article to which this is the erratum is available in ORE at: http://hdl.handle.net/10871/17968In the article, there are two errors in the research design and methods section. In the section with the heading “Studies on Islet-Infiltrating Leukocytes,” the antibody listed as #M0701 should be attributed to Dako and not to Abcam and the Abcam rabbit anti-CD8 catalogue number should read #ab4055 and not #GR404-4. The online version reflects these changes

Can Antiviral Drugs Contain Pandemic Influenza Transmission?

Antiviral drugs dispensed during the 2009 influenza pandemic generally failed to contain transmission. This poses the question of whether preparedness for a future pandemic should include plans to use antiviral drugs to mitigate transmission

Dual-gated bilayer graphene hot electron bolometer

Detection of infrared light is central to diverse applications in security, medicine, astronomy, materials science, and biology. Often different materials and detection mechanisms are employed to optimize performance in different spectral ranges. Graphene is a unique material with strong, nearly frequency-independent light-matter interaction from far infrared to ultraviolet, with potential for broadband photonics applications. Moreover, graphene's small electron-phonon coupling suggests that hot-electron effects may be exploited at relatively high temperatures for fast and highly sensitive detectors in which light energy heats only the small-specific-heat electronic system. Here we demonstrate such a hot-electron bolometer using bilayer graphene that is dual-gated to create a tunable bandgap and electron-temperature-dependent conductivity. The measured large electron-phonon heat resistance is in good agreement with theoretical estimates in magnitude and temperature dependence, and enables our graphene bolometer operating at a temperature of 5 K to have a low noise equivalent power (33 fW/Hz1/2). We employ a pump-probe technique to directly measure the intrinsic speed of our device, >1 GHz at 10 K.Comment: 5 figure