654 research outputs found
Crossover Scales at the Critical Points of Fluids with Electrostatic Interactions
Criticality in a fluid of dielectric constant D that exhibits Ising-type
behavior is studied as additional electrostatic (i.e., ionic) interactions are
turned on. An exploratory perturbative calculation is performed for small
ionicity as measured by the ratio of the electrostatic energy to the strength
of the short-range nonionic (i.e., van der Waals) interactions in the uncharged
fluid.
With the aid of distinct transformations for the short-range and for the
Coulombic interactions, an effective Hamiltonian with coefficients depending on
the ionicity is derived at the Debye-Hueckel limiting-law level for a fully
symmetric model. The crossover between classical (mean-field) and Ising
behavior is then estimated using a Ginzburg criterion. This indicates that the
reduced crossover temperature depends only weakly on the ionicity (and on the
range of the nonionic potentials); however, the trends do correlate with the,
much stronger, dependence observed experimentally.Comment: 25 pages, 4 figure; submitted to J. Chem. Phy
Global Stationary Phase and the Sign Problem
We present a computational strategy for reducing the sign problem in the
evaluation of high dimensional integrals with non-positive definite weights.
The method involves stochastic sampling with a positive semidefinite weight
that is adaptively and optimally determined during the course of a simulation.
The optimal criterion, which follows from a variational principle for analytic
actions S(z), is a global stationary phase condition that the average gradient
of the phase Im(S) along the sampling path vanishes. Numerical results are
presented from simulations of a model adapted from statistical field theories
of classical fluids.Comment: 9 pages, 3 figures, submitted for publicatio
Religiosity, depression, and quality of life in bipolar disorder: a two-year prospective study
Objective: Few quantitative studies have examined the effect of religious involvement on the course of bipolar disorder (BD). We investigated the effects of religious activity and coping behaviors on the course of depression, mania, and quality of life (QoL) in patients with BD. Methods: Two-year longitudinal study of 168 outpatients with BD. Linear regression was used to examine associations between religious predictors and outcome variables (manic symptoms, depression, QoL), controlling for sociodemographic variables. Results: Among the 158 patients reassessed after 2 years, positive religious coping at T1 predicted better QoL across all four domains: physical (β = 10.2, 95%CI 4.2 to 16.1), mental (β = 13.4, 95%CI 7.1 to 19.7), social (β = 10.5, 95%CI 3.6 to 17.33), and environmental (β = 11.1, 95%CI 6.2 to 16.1) at T2. Negative religious coping at T1 predicted worse mental (β = -28.1, 95%CI -52.06 to -4.2) and environmental (β = -20.4, 95%CI -39.3 to -1.6) QoL. Intrinsic religiosity at T1 predicted better environmental QoL (β = 9.56, 95%CI 2.76 to 16.36) at T2. Negative religious coping at T1 predicted manic symptoms (β = 4.1) at T2. Conclusion: Religiosity/spirituality (R/S) may influence the QoL of patients with BD over time, even among euthymic patients. Targeting R/S (especially positive and negative religious coping) in psychosocial interventions may enhance the quality of recovery in patients with BD.
Open-source software product line extraction processes: the ArgoUML-SPL and Phaser cases
Software Product Lines (SPLs) are rarely developed from scratch. Commonly, they emerge
from one product when there is a need to create tailored variants, or from existing variants
created in an ad-hoc way once their separated maintenance and evolution become challenging. Despite the vast literature about re-engineering systems into SPLs and related technical
approaches, there is a lack of detailed analysis of the process itself and the effort involved.
In this paper, we provide and analyze empirical data of the extraction processes of two open source case studies, namely ArgoUML and Phaser. Both cases emerged from the transition
of a monolithic system into an SPL. The analysis relies on information mined from the
version control history of their respective source-code repositories and the discussion with
developers that took part in the process. Unlike previous works that focused mostly on the
structural results of the final SPL, the contribution of this study is an in-depth characterization of the processes. With this work, we aimed at providing a deeper understanding of the
strategies for SPL extraction and their implications. Our results indicate that the source code
changes can range from almost a fourth to over half of the total lines of code. Developers
may or may not use branching strategies for feature extraction. Additionally, the problems
faced during the extraction process may be due to lack of tool support, complexity on managing feature dependencies and issues with feature constraints. We made publicly available
the datasets and the analysis scripts of both case studies to be used as a baseline for extractive
SPL adoption research and practice.This research was partially funded by CNPq, grant no. 408356/2018-9; FAPPR, grant no. 51435; and FAPERJ PDR-10 Fellowship 202073/2020.
Open access funding provided by Johannes Kepler University Lin
Charge Fluctuations and Counterion Condensation
We predict a condensation phenomenon in an overall neutral system, consisting
of a single charged plate and its oppositely charged counterions. Based on the
``two-fluid'' model, in which the counterions are divided into a ``free'' and a
``condensed'' fraction, we argue that for high surface charge, fluctuations can
lead to a phase transition in which a large fraction of counterions is
condensed. Furthermore, we show that depending on the valence, the condensation
is either a first-order or a smooth transition.Comment: 16 pages, 1 figure, accepted to be published in PR
Achromatic Ellipsometry: Theory and Applications
In the present chapter, the theory and some applications of Achromatic Ellipsometry, including transmittance, absorbance, and emission, are presented. The new methodology introduced here comprises the calculation of Stokes parameters using Fourier series analysis. Light polarization was determined by calculating the polarization degree, anisotropy, asymmetry parameters, and rotational and ellipsometry angles. The nematic liquid crystal E7â„¢ doped with 4,7-bis{2-[4-(4-decylpiperazin-1-yl) phenyl]ethynyl}-[2,1,3]-benzothiadiazole (5A) within twisted and parallel structures, was used to illustrate the applications for this technique, that has been shown to be an innovative and versatile tool to correlate the photophysics with materials structure
Counterion Condensation and Fluctuation-Induced Attraction
We consider an overall neutral system consisting of two similarly charged
plates and their oppositely charged counterions and analyze the electrostatic
interaction between the two surfaces beyond the mean-field Poisson-Boltzmann
approximation. Our physical picture is based on the fluctuation-driven
counterion condensation model, in which a fraction of the counterions is
allowed to ``condense'' onto the charged plates. In addition, an expression for
the pressure is derived, which includes fluctuation contributions of the whole
system. We find that for sufficiently high surface charges, the distance at
which the attraction, arising from charge fluctuations, starts to dominate can
be large compared to the Gouy-Chapmann length. We also demonstrate that
depending on the valency, the system may exhibit a novel first-order binding
transition at short distances.Comment: 15 pages, 8 figures, to appear in PR
Primeiro relato e colonização diferencial de espécies de Passiflora pelo biótipo B de Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) no Brasil
This note is the first report of Bemisia tabaci (Gennadius) biotype B colonizing passionvine in Brazil. We examined the colonization of nine Passiflora species by a wild B type population under greenhouse conditions. P. amethystina Mikan was the most preferred species for oviposition and colonization, whereas P. suberosa L., P. coriacea Juss. and two commercially cultivated species, P. alata Curtis and P. edulis Sims f. flavicarpa Degener, were mostly uncolonised. P. morifolia Mast., P. cincinnata Mast., P. foetida L. and P. caerulea L. showed intermediate levels of colonization. Such differential colonization might suggest some degree of resistance by certain Passiflora species or oviposition preference by B. tabaci.Esse trabalho descreve pela primeira vez a ocorrência do aleirodÃdeo Bemisia tabaci (Gennadius) biótipo B colonizando maracujazeiros no Brasil. Também foi examinada a colonização de nove espécies de Passiflora pelo inseto em condições de telado. P. amethystina Mikan foi a espécie de maior preferência para oviposição e colonização, enquanto P. suberosa L., P. coriacea Juss. e duas espécies cultivadas comercialmente, P. alata Curtis e P. edulis Sims f. flavicarpa Degener, foram pouco colonizadas pelo aleirodÃdeo. P. morifolia Mast., P. cincinnata Mast., P. foetida L. e P. caerulea L. exibiram nÃveis intermediários de colonização. Esses resultados sugerem que certas espécies de Passiflora exibem diferentes graus de resistência à colonização ou preferência para oviposição de B. tabaci biótipo B
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