Water activity in lamellar stacks of lipid bilayers: "Hydration forces" revisited

Water activity and its relationship with interactions stabilising lamellar stacks of mixed lipid bilayers in their fluid state are investigated by means of osmotic pressure measurements coupled with small-angle x-ray scattering. The (electrically-neutral) bilayers are composed of a mixture in various proportions of lecithin, a zwitterionic phospholipid, and Simulsol, a non-ionic cosurfactant with an ethoxylated polar head. For highly dehydrated samples the osmotic pressure profile always exhibits the "classical" exponential decay as hydration increases but, depending on Simulsol to lecithin ratio, it becomes either of the "bound" or "unbound" types for more water-swollen systems. A simple thermodynamic model is used for interpreting the results without resorting to the celebrated but elusive "hydration forces"Comment: 24 pages, 12 figures. Accepted for publication in The European Physical Journal

Classification of Triadic Chord Inversions Using Kohonen Self-organizing Maps

In this paper we discuss the application of the Kohonen Selforganizing Maps to the classification of triadic chords in inversions and root positions. Our motivation started in the validation of Schönberg´s hypotheses of the harmonic features of each chord inversion. We employed the Kohonen network, which has been generally known as an optimum pattern classification tool in several areas, including music, to verify that hypothesis. The outcomes of our experiment refuse the Schönberg´s assumption in two aspects: structural and perceptual/functional

Estratificação para a inclusão: enxergar as diferenças para uma efetiva rede de laboratórios.

A análise de conformidade da qualidade dos produtos alimentícios em face da legislação em vigor demanda conhecimento e deve também ser acompanhada de garantias dos resultados das análises laboratoriais. Amparados por normas nacionais e internacionais, os laboratórios de uma determinada rede credenciada podem, entre si, reduzir e controlar a geração de resultados inconsistentes ou contraditórios, ou não conformes, segundo a necessária padronização ? de meios e instrumentos, em um ou mais escopos do seu leque de análises. Este trabalho, fundamentado em alguns dos diversos fatores que permeiam a atual busca pela qualidade dos resultados analíticos nos laboratórios, contextualiza as exigências dos vários órgãos de credenciamento de laboratórios existentes no Brasil e no mundo. A abordagem restringe-se aos laboratórios que controlam determinados produtos de origem vegetal, mas, guardadas as proporções necessárias, pode ser ampliada para outros laboratórios

Consumers using social media: impact on companies’ reputation

This paper addresses the topic of the impact social networks on companies’ reputation. Before a consumer with new aptitudes, access to new technologies and, above all, to a wider and more dynamic range of alternative communication sources, companies must pay attention to all that is written about in social networks, and should be especially careful about what to publish and the answer they give to their customers' publications. Social networks have become, in recent time, one of the most developed, simple and accessible means of communication. Herewith, even more companies pay attention to their reputation because one simple comment or opinion about a product/service of a company/brand could influence the decision making of other users/consumers. With regard the work’s methodology, after a literature review, a questionnaire to the users/consumers was applied in order to analyse the use of social networks, the opinions transmitted and how the company’s reputation may get out impaired in order to raise awareness of the factors that can influence the reputation of companies on social networks. So it is important to plan and work effective business communication strategy in a radical marketing perspective.info:eu-repo/semantics/acceptedVersio

The Likelihood Ratio Test and Full Bayesian Significance Test under small sample sizes for contingency tables

Hypothesis testing in contingency tables is usually based on asymptotic results, thereby restricting its proper use to large samples. To study these tests in small samples, we consider the likelihood ratio test and define an accurate index, the P-value, for the celebrated hypotheses of homogeneity, independence, and Hardy-Weinberg equilibrium. The aim is to understand the use of the asymptotic results of the frequentist Likelihood Ratio Test and the Bayesian FBST -- Full Bayesian Significance Test -- under small-sample scenarios. The proposed exact P-value is used as a benchmark to understand the other indices. We perform analysis in different scenarios, considering different sample sizes and different table dimensions. The exact Fisher test for $2 \times 2$ tables that drastically reduces the sample space is also discussed. The main message of this paper is that all indices have very similar behavior, so the tests based on asymptotic results are very good to be used in any circumstance, even with small sample sizes

Spatial patterns and biodiversity in off-lattice simulations of a cyclic three-species Lotka-Volterra model

Stochastic simulations of cyclic three-species spatial predator-prey models are usually performed in square lattices with nearest neighbor interactions starting from random initial conditions. In this Letter we describe the results of off-lattice Lotka-Volterra stochastic simulations, showing that the emergence of spiral patterns does occur for sufficiently high values of the (conserved) total density of individuals. We also investigate the dynamics in our simulations, finding an empirical relation characterizing the dependence of the characteristic peak frequency and amplitude on the total density. Finally, we study the impact of the total density on the extinction probability, showing how a low population density may jeopardize biodiversity.Comment: 5 pages, 7 figures; new version, with new title and figure

Temperature effect on (2+1) experimental Kardar-Parisi-Zhang growth

We report on the effect of substrate temperature (T) on both local structure and long-wavelength fluctuations of polycrystalline CdTe thin films deposited on Si(001). A strong T-dependent mound evolution is observed and explained in terms of the energy barrier to inter-grain diffusion at grain boundaries, as corroborated by Monte Carlo simulations. This leads to transitions from uncorrelated growth to a crossover from random-to-correlated growth and transient anomalous scaling as T increases. Due to these finite-time effects, we were not able to determine the universality class of the system through the critical exponents. Nevertheless, we demonstrate that this can be circumvented by analyzing height, roughness and maximal height distributions, which allow us to prove that CdTe grows asymptotically according to the Kardar-Parisi-Zhang (KPZ) equation in a broad range of T. More important, one finds positive (negative) velocity excess in the growth at low (high) T, indicating that it is possible to control the KPZ non-linearity by adjusting the temperature.Comment: 6 pages, 5 figure