The Redner - Ben-Avraham - Kahng cluster system

We consider a coagulation model first introduced by Redner, Ben-Avraham and Krapivsky in [Redner, Ben-Avraham, Kahng: Kinetics of 'cluster eating', J. Phys. A: Math. Gen., 20 (1987), 1231-1238], the main feature of which is that the reaction between a j-cluster and a k-cluster results in the creation of a |j-k|-cluster, and not, as in Smoluchowski's model, of a (j+k)-cluster. In this paper we prove existence and uniqueness of solutions under reasonably general conditions on the coagulation coefficients, and we also establish differenciability properties and continuous dependence of solutions. Some interesting invariance properties are also proved. Finally, we study the long-time behaviour of solutions, and also present a preliminary analysis of their scaling behaviour.Comment: 24 pages. 2 figures. Dedicated to Carlos Rocha and Luis Magalhaes on the occasion of their sixtieth birthday

The Redner - Ben-Avraham - Kahng coagulation system with constant coefficients: the finite dimensional case

We study the behaviour as $t\to\infty$ of solutions $(c_j(t))$ to the Redner--Ben-Avraham--Kahng coagulation system with positive and compactly supported initial data, rigorously proving and slightly extending results originally established in [4] by means of formal arguments.Comment: 13 pages, 1 figur

Covariant Bardeen Perturbation Formalism

In a previous work we obtained a set of necessary conditions for the linear approximation in cosmology. Here we discuss the relations of this approach with the so called covariant perturbations. It is often argued in the literature that one of the main advantages of the covariant approach to describe cosmological perturbations is that the Bardeen formalism is coordinate dependent. In this paper we will reformulate the Bardeen approach in a completely covariant manner. For that, we introduce the notion of pure and mixed tensors, which yields an adequate language to treat both perturbative approaches in a common framework. We then stress that in the referred covariant approach one necessarily introduces an additional hyper-surface choice to the problem. Using our mixed and pure tensors approach, we were able to construct a one-to-one map relating the usual gauge dependence of the Bardeen formalism with the hyper-surface dependence inherent to the covariant approach. Finally, through the use of this map, we define full non-linear tensors that at first order correspond to the three known gauge invariant variables $\Phi$, $\Psi$ and $\Xi$, which are simultaneously foliation and gauge invariant. We then stress that the use of the proposed mixed tensors allows one to construct simultaneously gauge and hyper-surface invariant variables at any order.Comment: 15 pages, no figures, revtex4-1, accepted for publication in PRD, typos fixed, improved discussion about higher order gauge and foliation invarianc

Scalar Perturbations in Scalar Field Quantum Cosmology

In this paper it is shown how to obtain the simplest equations for the Mukhanov-Sasaki variables describing quantum linear scalar perturbations in the case of scalar fields without potential term. This was done through the implementation of canonical transformations at the classical level, and unitary transformations at the quantum level, without ever using any classical background equation, and it completes the simplification initiated in investigations by Langlois \cite{langlois}, and Pinho and Pinto-Neto \cite{emanuel2} for this case. These equations were then used to calculate the spectrum index $n_s$ of quantum scalar perturbations of a non-singular inflationary quantum background model, which starts at infinity past from flat space-time with Planckian size spacelike hypersurfaces, and inflates due to a quantum cosmological effect, until it makes an analytical graceful exit from this inflationary epoch to a decelerated classical stiff matter expansion phase. The result is $n_s=3$, incompatible with observations.Comment: 10 pages, 2 figures, accepted version to Physical Review D 7

Hinting at primary composition using asymmetries in time distributions

Evidence of azimuthal asymmetries in the time structure and signal size have been found in non-vertical showers at the Pierre Auger Observatory. It has been previously shown that the asymmetry in time distributions offers a new possibility for the determination of the mass composition. New studies have demonstrated that the dependence of the asymmetry parameter in the rise-time and fall-time distributions with sec(theta) shows a clear peak. Both, the position of the peak, X_asymax, and the size of the asymmetry at X_asymax are sensitive to primary mass composition and have a small dependence on energy. In this paper a study of the discriminating power of the new observables to separate primary species is presented.Comment: To be published in the Proceedings of 29th International Cosmic Ray Conference (ICRC 2005), Pune, India, August 3-10, 200

Effect of different excipients and processing conditions on casein micellar formulation for children

Poster presented at the AAPS Annual Meeting and Exposition (American Association of Pharmaceutical Scientists). October 25-29, 2015, Orlando (FL), USA"Purpose: Investigation of the potential of casein micellar formulations as drug vehicles in pediatrics."Fundação para a Ciência e a Tecnologia (PTDC/DTP-FTO/1057/2012

Evaluation of the ability of powdered milk to produce mini-tablets to deliver paracetamol in pediatrics

Paper presented at the 7th International Granulation Workshop. 1-3 July 2015, University of Sheffield, UK"This work aims to evaluate the usefulness of powdered milk as a vehicle of drugs for direct compression into mini-tablets specifically designed for the pediatric population. A 23 full factorial design was carried out to identify the effect of selected variables and their interactions (paracetamol to milk ratio, fraction of disintegrant and compression force), on selected responses (weight variation, thickness and tensile strength of minitablets and dissolution time of paracetamol) of the mini-tablets. Tablets were manufactured according to a matrix design resulting in eight combinations of four different tableting formulations compacted at two distinct forces. Each batch of tablets was evaluated for thickness (n=6), uniformity of weight (n=20), diametric crushing strength and tensile strength (σ) (n=6) and dissolution testing (n=12). A stepwise multiple linear regression was used to identify and quantify the relationships between each response and the variables studied and their interactions. Results were analyzed by ANOVA to identify the significant variables and variable interactions responsible for the effects observed.The increase on milk fraction in the formulation improved the compressibility of paracetamol with a decrease on weight variation. Thinner and harder compacts with slower paracetamol releases were also obtained. These observations were not surprising if powdered milk composition is taken into consideration: milk proteins, lactose (widely used as diluent) and lipids (often used as binders, lubricants and taste masking agents), which individually or in combination contribute to easier the production of tablets. A marked decrease on the dissolution time was observed as sodium croscarmellose was added to the milk rich formulations, as anticipated. The increase of the compression force was reflected by the production of thinner compacts with slightly higher tensile strengths but little effect on the dissolution median time. At high forces it was often observed a higher crushing strength and an increase of the importance of particle deformation in disintegration time.The study has proved the viability of using powdered milk on the production of minitablets to the delivery of drugs. The experimental design and statistical analysis enabled the identification of the most significant variables and their interactions affecting the properties of the mini-tablets, particularly the milk/paracetamol ratio which proved to be critical for the proprieties of the final product."Fundação para a Ciência e Tecnologia (FCT

How can the land managers and his multi-stakeholder network at the farm level influence the multifunctional transitions pathways?

The changing role of agriculture is at the core of transition pathways in many rural areas. Productivism, post-productivism and multifunctionality have been targeted towards a possible conceptualization of the transition happening in rural areas. The factors of change, including productivist and post-productivist trends, are combined in various ways and have gone in quite diverse directions and intensities, in individual regions and localities. Even, in the same holding, productivist and post-productivist strategies can co-exist spatially, temporally, structurally, leading to a higher complexity in changing patterns. In south Portugal extensive landscapes, dominated by traditionally managed agro-forestry systems under a fuzzy land use pattern, multifunctionality at the farm level is indeed conducted by different stakeholders whose interests may or not converge: a multifunctional land management may indeed incorporate post-productivist and productivist agents. These stakeholders act under different levels of ownership, management and use, reflecting a particular land management dynamic, in which different interests may exist, from commercial production to a variety of other functions (hunting, bee-keeping, subsistence farming, etc.), influencing management at the farm level and its supposed transition trajectory. This multistakeholder dynamic is composed by the main land-manager (the one who takes the main decisions), sub land-managers (land-managers under the rules of the main land-manager), workers and users (locals or outsiders), whose interest and action within the holding may vary differently according to future (policy, market, etc.) trends, and therefore reflect more or less resilient systems. The goal of the proposed presentation is to describe the multi-stakeholder relations at the farm level, its spatial expression and the factors influencing the land management system resilience in face of the transition trends in place

Development of casein micellar pediatric formulations

Poster presented at the 1st European Conference on Pharmaceutics. 13-14 April 2015, Reims, France."The current need for medicines specifically designed for children, which consider ease of administration, dose flexibility, palatability, safety of excipients, stability and therapeutic equivalency of pediatric dosage forms, has driven the development of pediatric drug formulations. In the present work casein (CN) based micellar formulations are evaluated as vehicles for the oral delivery of pediatric drugs, since caseins are nontoxic, biodegradable, GRAS materials and nanoencapsulation of drugs can improve their bioavailability. Chemical crosslinking of casein by carbodiimide (EDC) has been studied as an approach to improve the stability of the CN micelles and to tailor drug release."Fundação para a Ciência e a Tecnologia, Portugal (Research grant PTDC/DTPFTO/1057/2012