Contact Angle Hysteresis on Superhydrophobic Stripes

We study experimentally and discuss quantitatively the contact angle hysteresis on striped superhydrophobic surfaces as a function of a solid fraction, $\phi_S$. It is shown that the receding regime is determined by a longitudinal sliding motion the deformed contact line. Despite an anisotropy of the texture the receding contact angle remains isotropic, i.e. is practically the same in the longitudinal and transverse directions. The cosine of the receding angle grows nonlinearly with $\phi_S$, in contrast to predictions of the Cassie equation. To interpret this we develop a simple theoretical model, which shows that the value of the receding angle depends both on weak defects at smooth solid areas and on the elastic energy of strong defects at the borders of stripes, which scales as $\phi_S^2 \ln \phi_S$. The advancing contact angle was found to be anisotropic, except as in a dilute regime, and its value is determined by the rolling motion of the drop. The cosine of the longitudinal advancing angle depends linearly on $\phi_S$, but a satisfactory fit to the data can only be provided if we generalize the Cassie equation to account for weak defects. The cosine of the transverse advancing angle is much smaller and is maximized at $\phi_S\simeq 0.5$. An explanation of its value can be obtained if we invoke an additional energy due to strong defects in this direction, which is shown to be proportional to $\phi_S^2$. Finally, the contact angle hysteresis is found to be quite large and generally anisotropic, but it becomes isotropic when $\phi_S\leq 0.2$.Comment: 17 pages, 8 figure

Regimes of Wetting Transitions on Superhydrophobic Textures Conditioned by Energy of Receding Contact Lines

We discuss an evaporation-induced wetting transition on superhydrophobic stripes, and show that depending on the elastic energy of the deformed contact line, which determines the value of an instantaneous effective contact angle, two different scenarios occur. For relatively dilute stripes the receding angle is above 90$^\circ$, and the sudden impalement transition happens due to an increase of a curvature of an evaporating drop. For dense stripes the slow impregnation transition commences when the effective angle reaches 90$^\circ$ and represents the impregnation of the grooves from the triple contact line towards the drop center.Comment: 5 pages, 5 figure

Antidepressant drugs and the response in the placebo group: the real problem lies in our understanding of the issue

In a recent paper, Horder and colleagues (Horder et al., 2010, J Psychopharmacol 25: 1277–1288) have suggested that the mainproblem in the Kirsch analysis is methodological. We argue that the results are similar irrespective of the method used. In our opinion the data suggest that placebo and drug effects are non-additive: antidepressants act independently of depression severity, while the placebo effect is present only in milder cases. While the response in the placebo group is due to unstable ‘noise’ and ‘artefacts’, the medication effect is reliable, valid and stable

Modeling and Analysis Generic Interface for eXternal numerical codes (MAGIX)

The modeling and analysis generic interface for external numerical codes (MAGIX) is a model optimizer developed under the framework of the coherent set of astrophysical tools for spectroscopy (CATS) project. The MAGIX package provides a framework of an easy interface between existing codes and an iterating engine that attempts to minimize deviations of the model results from available observational data, constraining the values of the model parameters and providing corresponding error estimates. Many models (and, in principle, not only astrophysical models) can be plugged into MAGIX to explore their parameter space and find the set of parameter values that best fits observational/experimental data. MAGIX complies with the data structures and reduction tools of ALMA (Atacama Large Millimeter Array), but can be used with other astronomical and with non-astronomical data.Comment: 12 pages, 15 figures, 2 tables, paper is also available at http://www.aanda.org/articles/aa/pdf/forth/aa20063-12.pd

Team adaptation

We model an organization as a team choosing between a status quo project and a potentially superior alternative. We show that the members’ concern for each other’s motivation leads to a lack of communication, resulting in a failure to adapt (i.e. the status quo is maintained even when evidence for the alternative’s superiority has been observed). Adaptation failures are particularly severe when production exhibits strong complementarities. Improving the organization’s aggregate information has the adverse effect of reducing communication. In the long run, the organization can become “locked-in” with the status quo, in that adaptation is impaired for every adoptable alternative

Wave attenuation at a salt marsh margin: A case study of an exposed coast on the Yangtze estuary

To quantify wave attenuation by (introduced) Spartina alterniflora vegetation at an exposed macrotidal coast in the Yangtze Estuary, China, wave parameters and water depth were measured during 13 consecutive tides at nine locations ranging from 10 m seaward to 50 m landward of the low marsh edge. During this period, the incident wave height ranged from <0.1 to 1.5 m, the maximum of which is much higher than observed in other marsh areas around the world. Our measurements and calculations showed that the wave attenuation rate per unit distance was 1 to 2 magnitudes higher over the marsh than over an adjacent mudflat. Although the elevation gradient of the marsh margin was significantly higher than that of the adjacent mudflat, more than 80% of wave attenuation was ascribed to the presence of vegetation, suggesting that shoaling effects were of minor importance. On average, waves reaching the marsh were eliminated over a distance of similar to 80 m, although a marsh distance of >= 100 m was needed before the maximum height waves were fully attenuated during high tides. These attenuation distances were longer than those previously found in American salt marshes, mainly due to the macrotidal and exposed conditions at the present site. The ratio of water depth to plant height showed an inverse correlation with wave attenuation rate, indicating that plant height is a crucial factor determining the efficiency of wave attenuation. Consequently, the tall shoots of the introduced S. alterniflora makes this species much more efficient at attenuating waves than the shorter, native pioneer species in the Yangtze Estuary, and should therefore be considered as a factor in coastal management during the present era of sea-level rise and global change. We also found that wave attenuation across the salt marsh can be predicted using published models when a suitable coefficient is incorporated to account for drag, which varies in place and time due to differences in plant characteristics and abiotic conditions (i.e., bed gradient, initial water depth, and wave action).

Factors underlying male and female use of violent video games

Research has consistently shown that males play violent video games more frequently than females, but factors underlying this gender gap have not been examined to date. This approach examines the assumption that males play violent video games more because they anticipate more enjoyment and less guilt from engaging in virtual violence than females. This may be because males are less empathetic, tend to morally justify physical violence more and have a greater need for sensation and aggression in video game play than females. Results of a path model based on survey data of 444 respondents and using multi-step multiple mediation analyses confirm these assumptions. Taken together, the findings of this study shed further light on the gender gap in violent video game use

Field-testing of the revised, draft South African Paediatric Food-Based Dietary Guidelines among Siswati-speaking mothers/caregivers of children aged 0–36 months in Kabokweni, Mpumalanga province, South Africa

Objectives: To determine the appropriateness and understanding of the revised, draft South African Paediatric Food-Based Dietary Guidelines (SA-PFBDG) among siSwati speaking mothers/caregivers of children aged 0–36 months. Previous exposure to guidelines with similar messages, barriers and enablers to following the guidelines were also assessed. Design: A descriptive, cross-sectional qualitative research approach was followed. Purposive and snowball sampling were used to recruit a total of 75 participants. Data were collected by means of focus-group discussions from 12 groups. Setting: Kabokweni, Mpumalanga, South Africa. Subjects: The study population included mothers/caregivers older than 18 years who provided informed consent. Results: The participants were generally aware of messages similar to those contained in the revised, draft SA-PFBDG. They reported exposure to these messages at clinics/hospitals, radio/television, and the Road-to-Health booklet. Participants showed good understanding of guidelines on breastfeeding, complementary feeding, inclusion of protein-rich and starchy foods as well as fruit and vegetables in the diets of young children as well as hygiene practices. The guidelines on avoiding tea, coffee and sugar drinks and high-sugar, high-fat salty snacks, being active and providing five small meals were less well understood. Enablers to following the guidelines were its perceived importance and positive impact on children’s health. Barriers included misinterpretation of the guidelines and lack of money and resources. Conclusion: The revised, draft SA-PFBDGs are appropriate for the age group 0–36 months. A degree of rewording is suggested to aid understanding. The guidelines can be used as an educational tool to improve the nutritional status of children in South Africa