Colloid Transport in Porous Media: A Review of Classical Mechanisms and Emerging Topics

To celebrate the tenth anniversary of InterPore, we present an interdisciplinary review of colloid transport through porous media. This review aims to explore both classical colloid transport and topics that fall outside that purview and thus offer transformative insights into the physics governing transport behavior. First, we discuss the unique colloid characteristics relative to molecules and larger particles. Then, the classical advection?dispersion?filtration models (both conceptual and mathematical) of colloid transport are introduced as well as anomalous transport behaviors. Next, the forces of interaction between colloids and porous media surfaces are discussed. Fourth, applications that are interested in maximizing the transport of colloids through porous media are considered. Then the concept of motile, active biocolloids is introduced, and finally, colloid swarming as a newly recognized mode of transport is summarized.Fil: Molnar, Ian L.. York University; CanadáFil: Pensini, Erica. School Of Engineering; CanadáFil: Asad, Md Abdullah. York University; CanadáFil: Mitchell, Chven A.. Department Of Physics And Astronomy; Estados UnidosFil: Nitsche, Ludwig C.. College Of Engineering; Estados UnidosFil: Pyrak-Nolte, Laura J.. Department Of Physics And Astronomy; Estados UnidosFil: Miño, Gastón Leonardo. Universidad Nacional de Entre Ríos. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática; ArgentinaFil: Krol, Magdalena M.. York University; Canad

Demulsification mechanism of asphaltene-stabilized water-in-oil emulsions by a polymeric ethylene oxide-propylene oxide demulsifier

The demulsification mechanism of asphaltene-stabilized water-in-toluene emulsions by an ethylene-oxide-propylene oxide (EO-PO) based polymeric demulsifier was studied. Demulsification efficiency was determined by bottle tests and correlated to the physicochemical properties of asphaltene interfacial films after demulsifier addition. From bottle tests and droplet coalescence experiments, the demulsifier showed an optimal performance at 2.3 ppm (mass basis) in toluene. At high concentrations, the demulsification performance deteriorated due to the intrinsic stabilizing capacity of the demulsifier, which was attributed to steric repulsion between water droplets. Addition of demulsifier was shown to soften the asphaltene film (i.e., reduce the viscoelastic moduli of asphaltene films) under both shear and compressional interfacial deformations. Study of the macrostructures and the chemical composition of asphaltene film at the toluene-water interface after demulsifier addition demonstrated gradual penetration of the demulsifier into the asphaltene film. Demulsifier penetration in the asphaltene film changed the asphaltene interfacial mobility and morphology, as probed with Brewster angle and atomic force microscopy

Cloud Computing As a Tool for Enhancing Ecological Goals?

Cloud computing has been introduced as a promising information technology (IT) that embodies not only economic advantages in terms of increased efficiency but also ecological gains through saving energy. The latter has become particularly important in view of the rising energy costs of IT. The present study analyzes whether necessary preconditions for accepting cloud computing as a new infrastructure, such as awareness and perceived net value, exist on the part of the users. The analysis is based on a combined research framework of the theory of reasoned action (TRA) and the technology acceptance model (TAM) in a cloud computing setting. Two consumer surveys, the one to elicit beliefs and the second to gain insight into the ranking of the variables, are employed. This study uses structural equation modeling (SEM) to evaluate the hypotheses. The results indicate support for the proposed research framework. Surprisingly however, the ecological factor does not play a role in forming cloud computing intentions, regardless of prior knowledge or experience. Empirical evidence of this study suggests increasing efforts for informing actual and potential users, particularly in respect to possible ecological advantages through applying the new IT infrastructure

Collective guilt and attitudes toward recycling: data from a North Queensland sample

There is overwhelming evidence that environmental concerns currently facing the modern world are, at least partly, due to the unsustainable use of resources in developed countries. In this study, feelings of collective guilt in members of a developed nation, Australia, were investigated as a factor motivating individuals to recycle. Eighty-five participants from North Queensland (24 male, 61 female; aged 17 to 64, M = 24.16, SD = 8.42) completed self-report measures of collective guilt, social desirability, social norms, attitudes toward recycling and percentage of household rubbish recycled. As predicted, those accepting more collective guilt for the actions of their ingroup reported more favourable attitudes toward recycling. However, collective guilt failed to predict actual recycling behaviour. The same was found for social norms in that they predicted attitudes to recycling, but not the amount of rubbish recycled. Attitudes toward recycling were the only successful predictor of the amount of rubbish recycled. This study has demonstrated the role of the emotion of collective guilt and social norms in one environmentally relevant domain. Avenues for future research regarding the implications of collective guilt on ecological behaviour have been discussed

Alti e bassi della glicemia

L'andamento glicemico nel corso di test incrementali in atleti di alto livello non sembra essere influenzato dalla glicemia basale e dalla durata della prova, ma determinato dall'intensit\ue0 d'esercizio e dall'accumulo di acido lattico

Predictors of environmental behaviour: a comparison of known groups

Purpose – The purpose of this paper is to investigate how different community groups differ in the extent to which environmentally friendly behaviours are performed, as well as how they differ across a host of other psychologically relevant variables.\ud \ud Design/methodology/approach – The study was conducted via a self-report questionnaire delivered to four community samples (environmentalists; performance car enthusiasts; young and older people; n=124) assessing demographic information, ecological behaviour, and the psychological variables.\ud \ud Findings – Results showed that environmentalists engage in more ecological behaviour, are more cooperative, have stronger social and personal norms, a more internal locus of control, feel more collective guilt, and identify less with Australia than performance car enthusiasts. Differences in younger and older populations revealed that young people engage in less ecological behaviour, cooperate less, have a more external locus of control, and identify less with Australia.\ud \ud Practical implications – The study may provide a starting-point for future research and behaviour change campaigns aiming to develop methods for increasing ecological behaviour in specific segments of the community.\ud \ud Originality/value – The paper is important in understanding factors contributing to ecological behaviour, and differs from previous research in that it identifies that certain variables are represented differently in different community samples

Electrical and mechanical Hmax-to-Mmax ratio in power- and endurance-trained athletes

The aim of this study was to compare the mechanical and electromyographic (EMG) characteristics of soleus motor units activated during maximal H reflex and direct M response among subjects with different histories of physical activity. Power-trained athletes produced stronger twitches, with a higher rate of twitch tension buildup and relaxation, than their endurance counterparts for both maximal H-reflex and maximal M-wave responses. The maximal H-reflex-tomaximal M-wave ratios for both force output (twitch) and EMG wave amplitude were significantly lower in powertrained than endurance-trained athletes. However, powertrained athletes exhibited a significantly greater twitch-to-EMG ratio for the reflexly activated motor units with respect to the entire motor pool, whereas endurance-trained athletes had comparable twitch-to-EMG ratios for both reflexly and directly activated units. Power training increases the force output of the whole ensemble of the motor units, thereby compensating for the lower efficacy of the reflex transmission between Ia spindle afferent input and soleus a-motoneuron. On the other hand, the lower level of force evoked by the reflexly activated units in endurance-trained athletes is associated with a greater motor pool reflex excitability. Therefore, endurance-trained athletes produce the necessary force by recruitment of more slow-twitch units than do other subjects for comparable levels of force and type of task

Effect of ageing on the electrical and mechanical properties of human soleus motor units activated by the H reflex and M wave

This study was designed to investigate the effect of ageing on the mechanical and electromyographic (EMG) characteristics of the soleus motor units (MUs) activated by the maximal Hoffmann reflex (Hmax) and by the direct muscle compound action potential (Mmax). Eleven young (mean age 25 ± 4 years) and ten elderly (mean age 73 ± 5 years) males took part in this investigation. The senior group presented lower amplitudes of Mmax (−57 %, P < 0.001) and Hmax (−68 %, P < 0.001) waves compared to the younger population. These were associated with a depression of relative twitch torque of the plantar flexors. The average values of the Hmax/Mmax ratio did not statistically differ between the two populations, despite a tendency for lower values (∼23 %) in the senior group. However, the older adults showed a greater relative amplitude of the sub-maximal M wave evoked at Hmax (MatHmax) than did the younger males (young 5 % vs. elderly 29 % of the Mmax, P < 0.01). This finding suggests an increased homogeneity between the excitability threshold of sensory and motor axons. The twitch torque at Hmax (PtH–M) was subsequently calculated by subtraction from the total twitch torque of the mechanical contamination associated with MatHmax. The resulting PtH–M was significantly lower in the elderly (−59 %, P < 0.001). Despite a discrepancy of 20 % between the two groups, the mechanical ratio (PtH–M/PtM; PtM, twitch tension related to the Mmax compound action potential), like the EMG ratio, did not statistically differ between the young and older individuals. Nevertheless, the senior subjects exhibited a higher twitch/EMG ratio for the reflexively activated MUs (PtH–M/Hmax) than the younger individuals (+40 %, P < 0.05). This finding suggests an on-going neuromuscular remodelling, resulting in an increased innervation ratio. The neural rearrangement may be viewed as a compensatory adaptation of the motor system to preserve the mechanical efficiency of the surviving MUs, despite the age-related impairment of the segmental reflex system. This phenomenon is confirmed by the maintenance, with senescence, of the approximately constant values of the twitch/EMG ratio for the entire motor pool (PtM/Mmax)