Fluctuations and Pattern Formation in Fluids with Competing Interactions

One of the most interesting phenomena in the soft-matter realm consists in the spontaneous formation of super-molecular structures (microphases) in condition of thermodynamic equilibrium. A simple mechanism responsible for this self-organization or pattern formation is based on the competition between attractive and repulsive forces with different length scales in the microscopic potential, typically, a short-range attraction against a longer-range repulsion. We analyse this problem by simulations in 2D fluids. We find that, as the temperature is lowered, liquid-vapor phase separation is inhibited by the competition between attraction and repulsion, and replaced by a transition to non-homogeneous phases. The structure of the fluid shows well defined signatures of the presence of both intra- and inter-cluster correlations. Even when the competition between attraction and repulsion is not so strong as to cause microphase formation, it still induces large density fluctuations in a wide region of the temperature-density plane. In this large-fluctuation regime, pattern formation can be triggered by a weak external modulating field.Comment: To appear in the proceedings of the "International workshop on collective phenomena in macroscopic systems", 2006 Villa Olmo (Como), Ital

Relevance of the socio-cultural perspective in the discussion about critical thinking

This is the final version. Available on open access from the publisher via the DOI in this recordCritical thinking (CT) is considered a key skill for success in the 21st century. Worldwide educational policies advocate the promotion of CT, and scholars across different fields have been involved in a wide debate on its definition, without reaching an agreement. Currently, research has not adequately addressed CT assessment, nor the way in which it should be taught. In the present work, an overview of the topic is provided, as well as an evaluation of the practices, in order to provide researchers or practitioners (particularly those involved in primary school education) a reference for the development of further theories and methods about CT in edu-cation. CT is considered from the perspective of philosophy, cognitive psychology, and education sciences. In addition, we propose the inclusion of a fourth perspective, which could be referred as socio-cultural pedagogic perspective, due to its important implications in teaching and assessment practices

Microphase morphology in two dimensional fluids under lateral confinement

We study the effects of confinement between two parallel walls on a two dimensional fluid with competing interactions which lead to the formation of particle micro-domains at the thermodynamic equilibrium (microphases or microseparation). The possibility to induce structural changes of the morphology of the micro-domains is explored, under different confinement conditions and temperatures. In presence of neutral walls, a switch from stripes of particles to circular clusters (droplets) occurs as the temperature decreases, which does not happen in bulk. While the passage from droplets to stripes, as the density increases, is a well known phenomenon, the change of the stripes into droplets as an effect of temperature is rather unexpected. Depending on the wall separation and on the wall-fluid interaction parameters, the stripes can switch from parallel to perpendicular to the walls and also a mixed morphology can be stable.Comment: accepted by Physical Review E (rapid communications

Inter-individual differences in foraging tactics of a colonial raptor : consistency, weather effects, and fitness correlates

Background: Consistent inter-individual differences in behavioural phenotypes may entail differences in energy efficiency and expenditure, with different fitness payoffs. In colonial-breeding species, inter-individual differences in foraging behaviour may evolve to reduce resource use overlap among conspecifics exploiting shared foraging areas. Furthermore, individual differences in foraging behaviour may covary with individual characteristics, such as sex or physiological conditions. Methods: We investigated individual differences in foraging tactics of a colonial raptor, the lesser kestrel (Falco naumanni). We tracked foraging trips of breeding individuals using miniaturized biologgers. We classified behaviours from GPS data and identified tactics at the foraging trip level by cluster analysis. We then estimated energy expenditure associated to each tactic from tri-axial accelerometer data. Results: We obtained 489 foraging trips by 36 individuals. Two clusters of trips were identified, one (SF) characterized by more static foraging behaviour and the other (DF) by more dynamic foraging behaviour, with a higher proportion of flying activity and a higher energy expenditure compared to SF. Lesser kestrels showed consistent inter-individual differences in foraging tactics across weather condition gradients, favouring DF trips as solar radiation and crosswind intensity increased. DF trips were more frequent during the nestling-rearing than during the egg incubation stage. Nestlings whose tracked parent was more prone to perform DF trips experienced higher daily mass increase, irrespective of nestling feeding rates. Conclusions: Our study provided evidence that breeding lesser kestrels flexibly adopted different foraging tactics according to contingent weather landscapes, with birds showing consistent inter-individual differences in the tendency to adopt a given tactic. The positive correlation between the tendency to perform more energy-demanding DF trips and nestling growth suggests that individual differences in foraging behaviour may play a role in maintaining key life-history trade-offs between reproduction and self-maintenance

1H NMR-Based Protocol for the Detection of Adulterations of Refined Olive Oil with Refined Hazelnut Oil

A (1)H NMR analytical protocol for the detection of refined hazelnut oils in admixtures with refined olive oils is reported according to ISO format. The main purpose of this research activity is to suggest a novel analytical methodology easily usable by operators with a basic knowledge of NMR spectroscopy. The protocol, developed on 92 oil samples of different origins within the European MEDEO project, is based on (1)H NMR measurements combined with a suitable statistical analysis. It was developed using a 600 MHz instrument and was tested by two independent laboratories on 600 MHz spectrometers, allowing detection down to 10% adulteration of olive oils with refined hazelnut oils. Finally, the potential and limitations of the protocol applied on spectrometers operating at different magnetic fields, that is, at the proton frequencies of 500 and 400 MHz, were investigated

Fluid-fluid demixing transitions in colloid--polyelectrolyte star mixtures

We derive effective interaction potentials between hard, spherical colloidal particles and star-branched polyelectrolytes of various functionalities and smaller size than the colloids. The effective interactions are based on a Derjaguin-like approximation, which is based on previously derived potentials acting between polyelectrolyte stars and planar walls. On the basis of these interactions we subsequently calculate the demixing binodals of the binary colloid--polyelectrolyte star mixture, employing standard tools from liquid-state theory. We find that the mixture is indeed unstable at moderately high overall concentrations. The system becomes more unstable with respect to demixing as the star functionality and the size ratio grow.Comment: 24 pages, 9 figures, submitted to Journal of Physics: Condensed Matte

Sex-mediated changes in foraging behaviour according to breeding stage in a monomorphic seabird adapted to rural habitats

In contrast to sexually size-dimorphic species, monomorphic ones rarely show sexual differences in foraging behaviour as such variations have been primarily attributed to dissimilar body size. To investigate this aspect, we analysed foraging behaviour in breeding gull-billed terns, Gelochelidon nilotica, a monomorphic seabird adapted to rural habitats. We equipped 19 breeding birds with GPS devices and assessed differences in foraging behaviour and habitat use according to sex and breeding stage. Foraging trip distance and duration and daily frequencies were influenced by both breeding stage and sex, with females, but not males, performing closer, more frequent and shorter duration trips during chick rearing than incubation. Females, but not males, increased the repeatability of foraging metrics from incubation to chick rearing, while both sexes increased individual foraging site fidelity between the two breeding stages. Agricultural fields were the most exploited habitat for both sexes, but females made more use of aquatic habitats than males, especially during chick rearing. By foraging in different ways and in different habitats, the breeding pair can provide a wider range of prey types to their offspring, maximizing the chances of delivering high quantity and quality of food items under different environmental conditions. Our work provides new additional evidence of sex differences in foraging behaviour of monomorphic species, while highlighting the need to better understand underlying mechanisms driving foraging niche divergence and the consequences for fitness

Theranostics in Boron neutron capture therapy

Boron neutron capture therapy (BNCT) has the potential to specifically destroy tumor cells without damaging the tissues infiltrated by the tumor. BNCT is a binary treatment method based on the combination of two agents that have no effect when applied individually:10B and thermal neutrons. Exclusively, the combination of both produces an effect, whose extent depends on the amount of10B in the tumor but also on the organs at risk. It is not yet possible to determine the10B concentration in a specific tissue using non-invasive methods. At present, it is only possible to measure the10B concentration in blood and to estimate the boron concentration in tissues based on the assumption that there is a fixed uptake of10B from the blood into tissues. On this imprecise assumption, BNCT can hardly be developed further. A therapeutic approach, combining the boron carrier for therapeutic purposes with an imaging tool, might allow us to determine the10B concentration in a specific tissue using a non-invasive method. This review provides an overview of the current clinical protocols and preclinical experiments and results on how innovative drug development for boron delivery systems can also incorporate concurrent imaging. The last section focuses on the importance of proteomics for further optimization of BNCT, a highly precise and personalized therapeutic approach