Critical parameters for the partial coalescence of a droplet

The partial coalescence of a droplet onto a planar liquid/liquid interface is investigated experimentally by tuning the viscosities of both liquids. The problem mainly depends on four dimensionless parameters: the Bond number (gravity vs. surface tension), the Ohnesorge numbers (viscosity in both fluids vs. surface tension), and the density relative difference. The ratio between the daughter droplet size and the mother droplet size is investigated as a function of these dimensionless numbers. Global quantities such as the available surface energy of the droplet has been measured during the coalescence. The capillary waves propagation and damping are studied in detail. The relation between these waves and the partial coalescence is discussed. Additional viscous mechanisms are proposed in order to explain the asymmetric role played by both viscosities.Comment: 16 pages, 14 figures, submitted to Physical Review

Valence, arousal, and imagery ratings for 835 French attributes by young, middle-aged, and older adults: The French Emotional Evaluation List (FEEL)

Introduction and objective Attributes are used by young, middle-aged, and older adults to describe persons in everyday life. The current study asks whether attributes are perceived similarly by different age groups: for example, some attributes could be perceived as more positive or more negative in old age than in young adulthood. Method To address this question, we investigated age-related differences in emotional evaluations of French adjectives. Young, middle-aged, and older adults judged 835 French adjectives on valence, arousal, and imagery. Results Age groups agreed highly on the relative rank order but showed mean differences for a substantial number of attributes, especially for arousal and imagery ratings. Associations between dimensions differed as well between age groups: valence and arousal were negatively correlated and this correlation was stronger in older than in younger age groups. Conclusion The present study provided new evidence that the perception of emotionally toned material is affected by age. Several explanations to these age-related differences are discussed

Age-relevance of person characteristics: Persons' beliefs about developmental change across the lifespan

The authors investigated normative beliefs about personality development. Young, middle-aged, and older adults indicated the age-relevance of 835 French adjectives by specifying person characteristics as typical for any age decade from 0 to 99 years. With this paradigm, the authors determined age-relevance (How typical is a characteristic for a given age decade?). Most characteristics were ascribed to young adulthood. The pattern differed across the lifespan, however, for positive and negative person characteristics as well as for physical, cognitive, and personal/expressive characteristics. Whereas the total number of ascribed positive characteristics peaked in young adulthood and declined thereafter, the number of ascribed negative person characteristics peaked during adolescence, remained fairly low during middle adulthood, and increased slightly in old age (70+ years). As a consequence, the most positive profile was ascribed to young olds (60 to 69 years), whereas the most negative personality profiles were ascribed to the oldest age groups (70+ years) and to adolescence (10 to 19 years). The negative profiles are primarily due to more negative physical characteristics ascribed to older adults and more negative cognitive characteristics ascribed to adolescence. (PsycINFO Database Record (c) 2013 APA, all rights reserved). (journal abstract

Empathy for Pain from Adolescence through Adulthood: An Event-Related Brain Potential Study

Affective and cognitive empathy are traditionally differentiated, the affective component being concerned with resonating with another\u27s emotional state, whereas the cognitive component reflects regulation of the resulting distress and understanding of another\u27s mental states (see Decety and Jackson, 2004 for a review). Adolescence is a critical period for the development of cognitive control processes necessary to regulate affective processes: it is only in young adulthood that these control processes achieve maturity (Steinberg, 2005). Thus, one should expect adolescents to show greater automatic empathy than young adults. The present study aimed at exploring the neural correlates of affective (automatic) and cognitive empathy for pain from adolescence to young adulthood. With this aim, Event Related Potentials (ERPs) were recorded in 32 participants (aged 11-39) in a task designed to dissociate these components. ERPs results showed an early automatic fronto-central response to pain (that was not modulated by task demand) and a late parietal response to painful stimuli modulated by attention to pain cues. Adolescents exhibited earlier automatic responses to painful situations than young adults did and showed greater activity in the late cognitive component even when viewing neutral stimuli. Results are discussed in the context of the development of regulatory abilities during adolescence.

Drop Impact on Liquid Surfaces: Formation of Lens and Spherical Drops at the Air-Liquid Interface

Droplets at the air-liquid interface of immiscible liquids usually form partially-submerged lens shapes (e.g. water on oil). In addition to this structure, we showed that droplets released from critical heights above the target liquid can sustain the impact and at the end maintain a spherical ball-shape configuration above the surface, despite undergoing large deformation. Spherical drops are unstable and will transform into the lens mode due to slight disturbances. Precision dispensing needles with various tip diameter sizes were used to release pendant drops of deionized water onto the surface of fluorocarbon liquid (FC-43, 3M). A cubic relationship was found between the nozzle tip diameter and the released droplet diameter. Drop impact was recorded by a high speed camera at a rate of 2000 frames per second. In order for the water drops to sustain the impact and retain a spherical configuration at the surface of the target liquid pool, it is required that they be of a critical size and be released from a certain height; otherwise the commonly observed lens shape droplets will form at the surface

Retrieving Learning Resources over the Cloud

Reusing resources has been on the rise recently in the ICT sector. In fact, this trend is expanding into other areas such as the educational sector. Learning objects have made it possible to create digital resources that can be reused in various didactic units. These resources are stored in repositories, and thus require a search process that allows them to be located and retrieved. The present study proposes the AIREH tool, which was deployed into a cloud environment and facilitates the retrieval of learning objects by integrating virtual organizations and agents with CBR systems that implement collaborative filtering techniques

Multiple-length-scale elastic instability mimics parametric resonance of nonlinear oscillators

Spatially confined rigid membranes reorganize their morphology in response to the imposed constraints. A crumpled elastic sheet presents a complex pattern of random folds focusing the deformation energy while compressing a membrane resting on a soft foundation creates a regular pattern of sinusoidal wrinkles with a broad distribution of energy. Here, we study the energy distribution for highly confined membranes and show the emergence of a new morphological instability triggered by a period-doubling bifurcation. A periodic self-organized focalization of the deformation energy is observed provided an up-down symmetry breaking, induced by the intrinsic nonlinearity of the elasticity equations, occurs. The physical model, exhibiting an analogy with parametric resonance in nonlinear oscillator, is a new theoretical toolkit to understand the morphology of various confined systems, such as coated materials or living tissues, e.g., wrinkled skin, internal structure of lungs, internal elastica of an artery, brain convolutions or formation of fingerprints. Moreover, it opens the way to new kind of microfabrication design of multiperiodic or chaotic (aperiodic) surface topography via self-organization.Comment: Submitted for publicatio

Wettability-independent bouncing on flat surfaces mediated by thin air films

The impingement of drops onto solid surfaces1, 2 plays a crucial role in a variety of processes, including inkjet printing, fog harvesting, anti-icing, dropwise condensation and spray coating3, 4, 5, 6. Recent efforts in understanding and controlling drop impact behaviour focused on superhydrophobic surfaces with specific surface structures enabling drop bouncing with reduced contact time7, 8. Here, we report a different universal bouncing mechanism that occurs on both wetting and non-wetting flat surfaces for both high and low surface tension liquids. Using high-speed multiple-wavelength interferometry9, we show that this bouncing mechanism is based on the continuous presence of an air film for moderate drop impact velocities. This submicrometre ‘air cushion’ slows down the incoming drop and reverses its momentum. Viscous forces in the air film play a key role in this process: they provide transient stability of the air cushion against squeeze-out, mediate momentum transfer, and contribute a substantial part of the energy dissipation during bouncing

Patient perspectives on informed decision-making surrounding dialysis initiation

Careful patient–clinician shared decision-making about dialysis initiation has been promoted, but few studies have addressed patient perspectives on the extent of information provided and how decisions to start dialysis are made