53 research outputs found
Crackling Noise, Power Spectra and Disorder Induced Critical Scaling
Crackling noise is observed in many disordered non-equilibrium systems in
response to slowly changing external conditions. Examples range from Barkhausen
noise in magnets to acoustic emission in martensites to earthquakes. Using the
non-equilibrium random field Ising model, we derive universal scaling
predictions for the dependence of the associated power spectra on the disorder
and field sweep rate, near an underlying disorder-induced non-equilibrium
critical point. Our theory applies to certain systems in which the crackling
noise results from avalanche-like response to a (slowly) increasing external
driving force, and is characterized by a broad power law scaling regime of the
power spectra. We compute the critical exponents and discuss the relevance of
the results to experiments.Comment: 27 Latex Pages, 14 eps figure
Universal relations in the finite-size correction terms of two-dimensional Ising models
Quite recently, Izmailian and Hu [Phys. Rev. Lett. 86, 5160 (2001)] studied
the finite-size correction terms for the free energy per spin and the inverse
correlation length of the critical two-dimensional Ising model. They obtained
the universal amplitude ratio for the coefficients of two series. In this study
we give a simple derivation of this universal relation; we do not use an
explicit form of series expansion. Moreover, we show that the Izmailian and
Hu's relation is reduced to a simple and exact relation between the free energy
and the correlation length. This equation holds at any temperature and has the
same form as the finite-size scaling.Comment: 4 pages, RevTeX, to appear in Phys. Rev. E, Rapid Communication
Quenching of chlorophyll fluorescence induced by silver nanoparticles
The interaction between chlorophyll (Chl) and silver nanoparticles (AgNPs) was evaluated by analyzing the optical behavior of Chl molecules surrounded by different concentrations of AgNPs (10, 60, and 100 nm of diameter). UVâVis absorption, steady state and time-resolved fluorescence measurements were performed for Chl in the presence and absence of these nanoparticles. AgNPs strongly suppressed the Chl fluorescence intensity at 678 nm. The Stern-Volmer constant (KSV) showed that fluorescence suppression is driven by the dynamic quenching process. In particular, KSV was nanoparticle size-dependent with an exponential decrease as a function of the nanoparticle diameter. Finally, changes in the Chl fluorescence lifetime in the presence of nanoparticles demonstrated that the fluorescence quenching may be induced by the excited electron transfer from the Chl molecules to the metal nanoparticles
Redes epóxi/amina alifåticas com perspectivas para aplicaçÔes cardiovasculares. Propriedades biológicas in vitro
Este trabalho descreve as propriedades biolĂłgicas in vitro de trĂȘs redes epoxĂdicas Ă base do Ă©ter diglicidĂlico do glicerol (DGEG) curadas com poli(oxipropileno) diamina (D230), isoforona diamina (IPD) e 4,4'-diamino-3,3'-dimetil-diciclohexilmetano (3DCM). As interaçÔes biolĂłgicas entre os polĂmeros e o sangue foram estudadas por ensaios biolĂłgicos in vitro. Estudos de adsorção de proteĂnas, adesĂŁo de plaquetas, atividade do lactato desidrogenase (LDH) e propriedades de tromboresistĂȘncia estĂŁo apresentados. Os ensaios de adsorção de proteĂnas na superfĂcie dos polĂmeros mostrou que as redes epoxĂdicas adsorvem mais albumina do que fibrinogĂȘnio. Os resultados relacionados Ă adesĂŁo de plaquetas, atividade do lactato hidrogenase e propriedades de tromboresistĂȘncia indicaram que as redes DGEG/IPD e DGEG/3DCM exibem comportamento hemocompatĂvel. Desta maneira, assumimos que estes polĂmeros epoxĂdicos sĂŁo materiais compatĂveis com o sangue
Emotional, hyperactivity and inattention problems in adolescents with immunocompromising chronic diseases during the COVID-19 pandemic
Objective: To assess factors associated with emotional changes and Hyperactivity/Inattention (HI) motivated by COVID-19 quarantine in adolescents with immunocompromising diseases.
Methods: A cross-sectional study included 343 adolescents with immunocompromising diseases and 108 healthy adolescents. Online questionnaires were answered including socio-demographic data and self-rated healthcare routine during COVID-19 quarantine and validated surveys: Strengths and Difficulties Questionnaire (SDQ), Pittsburgh Sleep Quality Index (PSQI), Pediatric Quality of Life Inventory 4.0 (PedsQL4.0).
Results: The frequencies of abnormal emotional SDQ scores from adolescents with chronic diseases were similar to those of healthy subjects (110/343 [32%] vs. 38/108 [35%], p = 0.548), as well as abnormal hyperactivity/inattention SDQ scores (79/343 [23%] vs. 29/108 [27%], p = 0.417). Logistic regression analysis of independent variables associated with abnormal emotional scores from adolescents with chronic diseases showed: female sex (Odds Ratio [OR = 3.76]; 95% Confidence Interval (95% CI) 2.00â7.05; p < 0.001), poor sleep quality (OR = 2.05; 95% CI 1.08â3.88; p = 0.028) and intrafamilial violence during pandemic (OR = 2.17; 95% CI 1.12â4.19; p = 0.021) as independently associated with abnormal emotional scores, whereas total PedsQL score was inversely associated with abnormal emotional scores (OR = 0.95; 95% CI 0.93â0.96; p < 0.0001). Logistic regression analysis associated with abnormal HI scores from patients evidenced that total PedsQL score (OR = 0.97; 95% CI 0.95â0.99; p = 0.010], changes in medical appointments during the pandemic (OR = 0.39; 95% CI 0.19-0.79; p = 0.021), and reliable COVID-19 information (OR = 0.35; 95% CI 0.16â0.77; p = 0.026) remained inversely associated with abnormal HI scores.
Conclusion: The present study showed emotional and HI disturbances in adolescents with chronic immunosuppressive diseases during the COVID-19 pandemic. It reinforces the need to promptly implement a longitudinal program to protect the mental health of adolescents with and without chronic illnesses during future pandemics
Salinomycin and virginiamycin for lactating cows supplemented on pasture
Animals on pasture generally show higher feed efficiency as a result of the use of antibiotics. This study evaluated the effect of the antimicrobials salinomycin and/or virginiamycin on production and the ruminal parameters of supplemented dairy cows grazing on Panicum maximum cv. Tanzania. Twelve Holstein/Zebu multiparous cows were used, distributed in three Latin squares, one for the evaluation of ruminal parameters, and the others for production parameters. Cows on pasture were fed 50 % of their estimated intake with corn silage and concentrate supplements containing salinomycin, virginiamycin or a combination of additives, in doses of 120 and 150 mg kgâ1, respectively. There were no differences in milk production and composition, energy and nitrogen balance, dry matter digestibility and feeding behavior. However, salinomycin and virginiamycin each reduced pasture and total dry matter intake by about 14 % and 10 %, with a consequent improvement in feed efficiency
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