Droplet Impingement and Wetting Hysteresis on Textured Hydrophobic Surfaces

We study the wetting energetics and wetting hysteresis of sessile and impacting water droplets on superhydrophobic surfaces as a function of surface texture and surface energy. Detailed experiments tracking contact line motion simultaneously with contact angle provides new insights on the wetting hysteresis, stick-slip behavior and dependence on contact line velocity. For sessile drops, we find three wetting regimes on these surfaces: equilibrium Cassie at small feature spacing, equilibrium Wenzel at large feature spacing, and an intermediate state at medium feature spacing. We observe minimum wetting hysteresis not on surfaces that exhibit Cassie wetting but rather on surfaces in the intermediate regime. We argue that droplets on these surfaces are metastable Cassie droplets whose internal Laplace pressure is insufficient to overcome the energy barrier required to homogeneously wet the surface. These metastable Cassie droplets show superior roll-off properties because the effective length of the contact line that is pinned to the surface is reduced. We develop a model that can predict the transition between the metastable Cassie and Wenzel regimes by comparing the Laplace pressure of the drop to the capillary pressure associated with the wetting-energy barrier of the textured surface. In the case of impacting droplets the water hammer and Bernoulli pressures must be compared with the capillary pressure. Experiments with impacting droplets show very good agreement with this simple pressure-balance model.GE Global Research Center. Nanotechnology Progra

Automated murmurs: the social mobile tourist application

The popularity of mobile devices and their increased computing power has given rise to surge in mobile computing technologies. Users are increasingly turning to mobile devices for information relating to their activities and location while on the move. Independent of this, the world has seen a huge uptake in the social web, which has fueled the production of applications where users are the sole providers of valuable information. In this work we present a mobile platform which leverages the popularity of mobile and social computing to produce a location sensitive messaging system which delivers user generated content to the public in the context of their physical location

Free energy and configurational entropy of liquid silica: fragile-to-strong crossover and polyamorphism

Recent molecular dynamics (MD) simulations of liquid silica, using the ``BKS'' model [Van Beest, Kramer and van Santen, Phys. Rev. Lett. {\bf 64}, 1955 (1990)], have demonstrated that the liquid undergoes a dynamical crossover from super-Arrhenius, or ``fragile'' behavior, to Arrhenius, or ``strong'' behavior, as temperature $T$ is decreased. From extensive MD simulations, we show that this fragile-to-strong crossover (FSC) can be connected to changes in the properties of the potential energy landscape, or surface (PES), of the liquid. To achieve this, we use thermodynamic integration to evaluate the absolute free energy of the liquid over a wide range of density and $T$. We use this free energy data, along with the concept of ``inherent structures'' of the PES, to evaluate the absolute configurational entropy $S_c$ of the liquid. We find that the temperature dependence of the diffusion coefficient and of $S_c$ are consistent with the prediction of Adam and Gibbs, including in the region where we observe the FSC to occur. We find that the FSC is related to a change in the properties of the PES explored by the liquid, specifically an inflection in the $T$ dependence of the average inherent structure energy. In addition, we find that the high $T$ behavior of $S_c$ suggests that the liquid entropy might approach zero at finite $T$, behavior associated with the so-called Kauzmann paradox. However, we find that the change in the PES that underlies the FSC is associated with a change in the $T$ dependence of $S_c$ that elucidates how the Kauzmann paradox is avoided in this system. Finally, we also explore the relation of the observed PES changes to the recently discussed possibility that BKS silica exhibits a liquid-liquid phase transition, a behavior that has been proposed to underlie the observed polyamorphism of amorphous solid silica.Comment: 14 pages, 18 figure

Spatial and Temporal Occurrence of Preformed Nitrate Anomalies in the Subtropical Ocean

Preformed nitrate (PreNO3) was formulated to act as a conservative tracer of oceancirculation after accounting for the stoichiometry of marine biochemical reactions involving oxygen and nitrate. However, PreNO3 anomalies have been identified within the shallow subtropical ocean, that describe the biological consumption or production of oxygen without assumed stoichiometric changes in nitrate, which still have yet to be fully explained. The mechanisms proposed to drive the formation of PreNO3 anomalies are: vertically migrating phytoplankton (VMP), the export and subsequent remineralization of N-deficient transparent exopolymer particles (TEP, e.g. marine gels), and the remineralization of N-poor dissolved organic matter (DOM). Observations from the subtropical Pacific and Atlantic oceans taken by twenty Biogeochemical Argo (Bio-Argo) profiling floats which collectively span from 2007 to 2019 have been used to answer two questions related to PreNO3 anomalies. What is the seasonality and geographic extents of subsurface negative PreNO3 anomalies and euphotic zone positive PreNO3 anomalies in the global subtropical ocean? What biogeochemical processes capable of generating PreNO3 anomalies are consistent with the seasonality and spatial extents found in the Bio-Argo float records? Euphotic zone positive PreNO3 anomalies are consistently observed between 30˚S and 50˚N, whereas subsurface negative PreNO3 anomalies are absent in parts of the Equatorial West Pacific Ocean. The remineralization of N-poor DOM has been shown to contribute to PreNO3 anomaly formation by previous studies and has been accounted for in this study. The geographic extents of the remaining PreNO3 anomalies are consistent with previous observations of VMP taxa throughout the global subtropical ocean. The seasonal timing of euphotic zone positive PreNO3 anomalies in relation to subsurface negative PreNO3 anomalies indicates that both VMP and the export and remineralization of N-deficient TEP contribute to the formation of PreNO3 anomalies. Since VMP include large diatoms that produce ballasted organic matter while TEP may only sink slowly before remineralization, further investigation into the mechanisms generating PreNO3 anomalies is needed to assess their roles in the future biological carbon pump in an expanding subtropical ocean ecosystem

Spatial and Temporal Occurrence of Preformed Nitrate Anomalies in the Subtropical Ocean

Preformed nitrate (PreNO3) was formulated to act as a conservative tracer of oceancirculation after accounting for the stoichiometry of marine biochemical reactions involving oxygen and nitrate. However, PreNO3 anomalies have been identified within the shallow subtropical ocean, that describe the biological consumption or production of oxygen without assumed stoichiometric changes in nitrate, which still have yet to be fully explained. The mechanisms proposed to drive the formation of PreNO3 anomalies are: vertically migrating phytoplankton (VMP), the export and subsequent remineralization of N-deficient transparent exopolymer particles (TEP, e.g. marine gels), and the remineralization of N-poor dissolved organic matter (DOM). Observations from the subtropical Pacific and Atlantic oceans taken by twenty Biogeochemical Argo (Bio-Argo) profiling floats which collectively span from 2007 to 2019 have been used to answer two questions related to PreNO3 anomalies. What is the seasonality and geographic extents of subsurface negative PreNO3 anomalies and euphotic zone positive PreNO3 anomalies in the global subtropical ocean? What biogeochemical processes capable of generating PreNO3 anomalies are consistent with the seasonality and spatial extents found in the Bio-Argo float records? Euphotic zone positive PreNO3 anomalies are consistently observed between 30˚S and 50˚N, whereas subsurface negative PreNO3 anomalies are absent in parts of the Equatorial West Pacific Ocean. The remineralization of N-poor DOM has been shown to contribute to PreNO3 anomaly formation by previous studies and has been accounted for in this study. The geographic extents of the remaining PreNO3 anomalies are consistent with previous observations of VMP taxa throughout the global subtropical ocean. The seasonal timing of euphotic zone positive PreNO3 anomalies in relation to subsurface negative PreNO3 anomalies indicates that both VMP and the export and remineralization of N-deficient TEP contribute to the formation of PreNO3 anomalies. Since VMP include large diatoms that produce ballasted organic matter while TEP may only sink slowly before remineralization, further investigation into the mechanisms generating PreNO3 anomalies is needed to assess their roles in the future biological carbon pump in an expanding subtropical ocean ecosystem

Post awakening salivary cortisol secretion and trait well-being: The importance of sample timing accuracy

Indices of post awakening cortisol secretion (PACS), include the rise in cortisol(cortisol awakening response: CAR) and overall cortisol concentrations (e.g. area under the curve with reference to ground: AUCg) in the first 30—45 min. Both are commonly investigated in relation to psychosocial variables. Although sampling within the domestic setting is ecologically valid, participant non-adherence to the required timing protocol results in erroneous measurement of PACS and this may explain discrepancies in the literature linking these measures to trait well-being (TWB). We have previously shown that delays of little over 5 min(between awakening and the start of sampling) to result in erroneous CAR estimates. In this study, we report for the first time on the negative impact of sample timing inaccuracy (verified by electronic-monitoring) on the efficacy to detect significant relationships between PACS and TWB when measured in the domestic setting.Healthy females (N = 49, 20.5 ± 2.8 years) selected for differences in TWB collected saliva samples (S1—4) on 4 days at 0, 15, 30, 45 min post awakening, to determine PACS. Adherence to the sampling protocol was objectively monitored using a combination of electronic estimates of awakening (actigraphy) and sampling times (track caps).Relationships between PACS and TWB were found to depend on sample timing accuracy. Lower TWB was associated with higher post awakening cortisol AUCg in proportion to the mean sample timing accuracy (p 5 min between awakening and collection of sample 1 (median = 8 min delay), negatively impacts on the sensitivity of analysis to detect associations between PACS and TWB

Ageing, physical function, and the diurnal rhythms of cortisol and dehydroepiandrosterone

The present study examined the relationship between ageing, physical function and the diurnal rhythms of cortisol and dehydroepiandrosterone (DHEA). Participants were 36 community dwelling older adults aged between 65-86 years old. Salivary cortisol and DHEA were measured over the course of one day: immediately upon awakening, 30 min later, and then 3 h, 6 h, 9 h and 12 h post-awakening. Participants completed the Nottingham extended activities of daily living index, the Berg Balance Scale and their handgrip strength was assessed. Older participants had a significantly higher cortisol area under the curve (AUC), lower overall DHEA levels, lower DHEA AUC, a decreased diurnal slope of decline and increased cortisol:DHEA ratio. Lower diurnal cortisol levels were associated with poorer performance on the Berg Balance Scale and lower handgrip strength, and those with a flattened DHEA diurnal profile reported less independence in carrying out daily tasks. These associations withstood adjustment for age. In conclusion, this study suggests an association between cortisol, DHEA, ageing and physical function

Assessment of the cortisol awakening response: expert consensus guidelines

The cortisol awakening response (CAR), the marked increase in cortisol secretion over the first 30–45 min after morning awakening, has been related to a wide range of psychosocial, physical and mental health parameters, making it a key variable for psychoneuroendocrinological research. The CAR is typically assessed from self-collection of saliva samples within the domestic setting. While this confers ecological validity, it lacks direct researcher oversight which can be problematic as the validity of CAR measurement critically relies on participants closely following a timed sampling schedule, beginning with the moment of awakening. Researchers assessing the CAR thus need to take important steps to maximize and monitor saliva sampling accuracy as well as consider a range of other relevant methodological factors. To promote best practice of future research in this field, the International Society of Psychoneuroendocrinology initiated an expert panel charged with (i) summarizing relevant evidence and collective experience on methodological factors affecting CAR assessment and (ii) formulating clear consensus guidelines for future research. The present report summarizes the results of this undertaking. Consensus guidelines are presented on central aspects of CAR assessment, including objective control of sampling accuracy/adherence, participant instructions, covariate accounting, sampling protocols, quantification strategies as well as reporting and interpreting of CAR data. Meeting these methodological standards in future research will create more powerful research designs, thus yielding more reliable and reproducible results and helping to further advance understanding in this evolving field of research

Aquaculture operation Bulletin: Weather window nowcast/forecast Bulletin tool for offshore aquaculture operators

Use Case Title: Offshore aquaculture siting Environmental matrix of interest (Air, Ice, Mar. Water, etc.): Marine Study Regions: Shelf Seas in Norway, Ireland and Spain Dissemination Method: Web We will develop a weather window tool to give developers real-time access to observations and model forecasts of seas state to plan day to day operation