Fluorescent visualization of a spreading surfactant

The spreading of surfactants on thin films is an industrially and medically important phenomenon, but the dynamics are highly nonlinear and visualization of the surfactant dynamics has been a long-standing experimental challenge. We perform the first quantitative, spatiotemporally-resolved measurements of the spreading of an insoluble surfactant on a thin fluid layer. During the spreading process, we directly observe both the radial height profile of the spreading droplet and the spatial distribution of the fluorescently-tagged surfactant. We find that the leading edge of spreading circular layer of surfactant forms a Marangoni ridge in the underlying fluid, with a trough trailing the ridge as expected. However, several novel features are observed using the fluorescence technique, including a peak in the surfactant concentration which trails the leading edge, and a flat, monolayer-scale spreading film which differs from concentration profiles predicted by current models. Both the Marangoni ridge and surfactant leading edge can be described to spread as $R \propto t^{\delta}$. We find spreading exponents, $\delta_H \approx 0.30$ and $\delta_\Gamma \approx 0.22$ for the ridge peak and surfactant leading edge, respectively, which are in good agreement with theoretical predictions of $\delta = 1/4$. In addition, we observe that the surfactant leading edge initially leads the peak of the Marangoni ridge, with the peak later catching up to the leading edge

Optically Clear Adhesives for OLED

Optically clear adhesives (OCA) have been used for more than a decade to bond rigid LCD and AMOLED displays for consumer electronics applications, offering optical, mechanical, and electrical performance benefits. The performance requirements of an OCA to bond cover window, touch sensors, and circular polarizers in a plastic OLED display to bent cover glass or a flexible, foldable OLED display are drastically different from a flat, rigid device. For plastic OLED to bent cover glass bonding, the adhesive needs to be strong enough to resist spring back of the flat, plastic OLED devices. For flexible, foldable OLED displays, the neutral plane needs to be managed during folding keeping strain to a minimum in critical layers of the device (e.g., touch sensor, TFT, TFE), and the OCA cannot deform (or cause other layers to deform) during the folding process. Folding also brings challenges to touch sensors that can no longer use conventional passivation layers. As a result, the OCA will be responsible for preventing corrosion of touch sensor materials such as metal mesh, silver nanowire, carbon nanotube, and graphene. The chapter will discuss OCA performance requirements for rigid, flexible, and foldable OLED bonding

A method for estimating the turbulent kinetic energy dissipation rate from a vertically pointing Doppler lidar, and independent evaluation from balloon-borne in situ measurements

A method of estimating dissipation rates from a vertically pointing Doppler lidar with high temporal and spatial resolution has been evaluated by comparison with independent measurements derived from a balloon-borne sonic anemometer. This method utilizes the variance of the mean Doppler velocity from a number of sequential samples and requires an estimate of the horizontal wind speed. The noise contribution to the variance can be estimated from the observed signal-to-noise ratio and removed where appropriate. The relative size of the noise variance to the observed variance provides a measure of the confidence in the retrieval. Comparison with in situ dissipation rates derived from the balloon-borne sonic anemometer reveal that this particular Doppler lidar is capable of retrieving dissipation rates over a range of at least three orders of magnitude. This method is most suitable for retrieval of dissipation rates within the convective well-mixed boundary layer where the scales of motion that the Doppler lidar probes remain well within the inertial subrange. Caution must be applied when estimating dissipation rates in more quiescent conditions. For the particular Doppler lidar described here, the selection of suitably short integration times will permit this method to be applicable in such situations but at the expense of accuracy in the Doppler velocity estimates. The two case studies presented here suggest that, with profiles every 4 s, reliable estimates of ϵ can be derived to within at least an order of magnitude throughout almost all of the lowest 2 km and, in the convective boundary layer, to within 50%. Increasing the integration time for individual profiles to 30 s can improve the accuracy substantially but potentially confines retrievals to within the convective boundary layer. Therefore, optimization of certain instrument parameters may be required for specific implementations

FACTORS RELATED TO SUBSEQUENT ADOLESCENT PREGNANCY IN THE DOMINICAN REPUBLIC

Objectives: Adolescents with subsequent pregnancies in the Dominican Republic represent a significant but poorly understood population with little available data to inform health care services. The objective of this exploratory study was to begin to characterize this important cohort. Methods: A survey of demographic items and a sexual and obstetrical history was administered to 50 adolescents with subsequent pregnancies in La Romana, Dominican Republic. Results: Most participants were married (78%) and exclusively economically dependent on their partner (72%) and nearly half (48%) stopped attending school. Twelve percent reported having intended their current pregnancy. Conclusions: Adolescents with subsequent pregnancies were dependent on partners in the form of living conditions and marriage, economic dependence and unemployment, and lack of education

African forest elephant movements depend on time scale and individual behavior.

The critically endangered African forest elephant (Loxodonta cyclotis) plays a vital role in maintaining the structure and composition of Afrotropical forests, but basic information is lacking regarding the drivers of elephant movement and behavior at landscape scales. We use GPS location data from 96 individuals throughout Gabon to determine how five movement behaviors vary at different scales, how they are influenced by anthropogenic and environmental covariates, and to assess evidence for behavioral syndromes-elephants which share suites of similar movement traits. Elephants show some evidence of behavioral syndromes along an 'idler' to 'explorer' axis-individuals that move more have larger home ranges and engage in more 'exploratory' movements. However, within these groups, forest elephants express remarkable inter-individual variation in movement behaviours. This variation highlights that no two elephants are the same and creates challenges for practitioners aiming to design conservation initiatives

Heatwave and health impact research : a global review

Background Observed increases in the frequency and intensity of heatwave events, together with the projected acceleration of these events worldwide, has led to a rapid expansion in research on the health impacts of extreme heat. Objective To examine how research on heatwaves and their health-related impact is distributed globally. Methods A systematic review was undertaken. Four online databases were searched for articles examining links between specific historical heatwave events and their impact on mortality or morbidity. The locations of these events were mapped at a global scale, and compared to other known characteristics that influence heat-related illness and death. Results When examining the location of heatwave and health impact research worldwide, studies were concentrated on mid-latitude, high-income countries of low- to medium-population density. Regions projected to experience the most extreme heatwaves in the future were not represented. Furthermore, the majority of studies examined mortality as a key indicator of population-wide impact, rather than the more sensitive indicator of morbidity. Conclusion While global heatwave and health impact research is prolific in some regions, the global population most at risk of death and illness from extreme heat is under-represented. Heatwave and health impact research is needed in regions where this impact is expected to be most severe

Author Correction: Additive manufacture of complex 3D Au-containing nanocomposites by simultaneous two-photon polymerisation and photoreduction

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper

Ligand-induced control of photoconductive gain and doping in a hybrid graphene-quantum dot transistor

In graphene devices decorated with a layer of near-infrared colloidal PbS quantum dots (QDs), the choice of the QD capping ligands and the integrity of the QD layer have a strong influence on the doping, carrier mobility, and photoresponse. By using short (<1 nm) capping ligands, the photoresponsivity of the graphene devices is enhanced up to 109 A W−1

The value of local heatwave impact assessment : a case-crossover analysis of hospital emergency department presentations in Tasmania, Australia

Heatwaves have been identified as a threat to human health, with this impact projected to rise in a warming climate. Gaps in local knowledge can potentially undermine appropriate policy and preparedness actions. Using a case-crossover methodology, we examined the impact of heatwave events on hospital emergency department (ED) presentations in the two most populous regions of Tasmania, Australia, from 2008–2016. Using conditional logistic regression, we analyzed the relationship between ED presentations and severe/extreme heatwaves for the whole population, specific demographics including age, gender and socio-economic advantage, and diagnostic conditions that are known to be impacted in high temperatures. ED presentations increased by 5% (OR 1.05, 95% CI 1.01–1.09) across the whole population, by 13% (OR 1.13, 95% CI 1.03–1.24) for children 15 years and under, and by 19% (OR 1.19, 95% CI 1.04–1.36) for children 5 years and under. A less precise association in the same direction was found for those over 65 years. For diagnostic subgroups, non-significant increases in ED presentations were observed for asthma, diabetes, hypertension, and atrial fibrillation. These findings may assist ED surge capacity planning and public health preparedness and response activities for heatwave events in Tasmania, highlighting the importance of using local research to inform local practice