On the Aging Dynamics in an Immune Network Model

Recently we have used a cellular automata model which describes the dynamics of a multi-connected network to reproduce the refractory behavior and aging effects obtained in immunization experiments performed with mice when subjected to multiple perturbations. In this paper we investigate the similarities between the aging dynamics observed in this multi-connected network and the one observed in glassy systems, by using the usual tools applied to analyze the latter. An interesting feature we show here is that the model reproduces the biological aspects observed in the experiments during the long transient time it takes to reach the stationary state. Depending on the initial conditions, and without any perturbation, the system may reach one of a family of long-period attractors. The pertrubations may drive the system from its natural attractor to other attractors of the same family. We discuss the different roles played by the small random perturbations (noise) and by the large periodic perturbations (immunizations)

Study of the magnetic and structural properties of Mn-, Fe-, and Co-doped ZnO powder

AbstractA study of the magnetic and structural properties of Zn1−xMxO powder (where x=0 or 0.01, and M=Mn, Fe or Co) produced by the proteic sol–gel process was undertaken. The sample crystal structure was analyzed by XRD and magnetic measurements were carried out in a SQUID magnetometer. Of the XRD analysis, all samples had hexagonal wurtzite crystal structure with P63mc space group, and no secondary phase was observed. It is observed of the M(H) measures at 2K, that the Co- and Mn-doped ZnO displayed saturation magnetizations (Ms) of approximately 2 and 3.2emu/g, respectively, and no remanence (Mr) was observed, indicating a superparamagnetic behavior in these samples. However, the Fe-doped sample showed a ferromagnetic behavior with Ms∼0.34emu/g, Mr∼0.05emu/g, and coercivity (Hc)∼1090Oe. Already at room temperature, the M(H) measurements reveal a purely paramagnetic behavior for Mn- and Fe-doped ZnO, indicating that the Curie temperature (Tc) is below 300K. However, a weak superparamagnetic behavior was observed in the Co-doped sample, indicating that Tc>300K

Examining Portuguese High School Students’ Attitudes Toward Physical Education

Portugal ranks fourth among countries with the highest rate of overweight population, considering that 67.6% of the Portuguese population over the age of 15 is overweight or obese. To our knowledge, limited studies have investigated students' attitudes toward physical education in Portugal. Such research is necessary because it can provide valuable insights for policy and application in the curriculum development for physical education, which may eventually increase participation in physical and sports activities. This study analyzed students' attitudes toward physical education (PE) according to sociodemographic variables, including grade level, socioeconomic status, and gender, and their participation in extracurricular sports activities and respective PE grades. The sample comprised 476 high school students (from the 7th, 8th, and 9th-grade levels) from five public schools located in Portugal. The Students' Attitudes toward Physical Education Questionnaire was adapted and validated for use with Portuguese students as a two-factor model. Findings show that students generally have a moderately positive attitude toward PE. However, students' positive attitudes tend to decrease throughout high school, which is particularly significant in the 9th grade. Furthermore, students' attitudes are influenced by gender, extracurricular sports practice, and grades. These findings may help stakeholders reflect on how to frame PE in a more meaningful way to create a solid foundation for maintaining an active lifestyle throughout life. Implications for further research and practice are discussed.info:eu-repo/semantics/publishedVersio

Portuguese Students’ Perceptions About the Motivational Climate in Physical Education

info:eu-repo/semantics/acceptedVersio

Destruction of Superconductivity by Impurities in the Attractive Hubbard Model

We study the effect of U=0 impurities on the superconducting and thermodynamic properties of the attractive Hubbard model on a square lattice. Removal of the interaction on a critical fraction of $f_{\rm crit} \approx 0.30$ of the sites results in the destruction of off-diagonal long range order in the ground state. This critical fraction is roughly independent of filling in the range $0.75 < \rho < 1.00$, although our data suggest that $f_{\rm crit}$ might be somewhat larger below half-filling than at $\rho=1$. We also find that the two peak structure in the specific heat is present at $f$ both below and above the value which destroys long range pairing order. It is expected that the high $T$ peak associated with local pair formation should be robust, but apparently local pairing fluctuations are sufficient to generate a low temperature peak

Method to obtain nonuniformity information from field emission behavior

Copyright © 2010 American Vacuum Society / American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Vacuum Science and Technology Part B: Microelectronics and Nanometer Structures, 28(3), Article number 441 and may be found at http://scitation.aip.org/content/avs/journal/jvstb/28/3/10.1116/1.3327928.This article describes the characterization of field emission from a planar cathode to a spherical anode with the approach curve method (ACM). In such a diode configuration the electric field strength at the cathode surface is nonuniform. This nonuniformity gives an extra degree of freedom and it allows the interpretation of the current-voltage and voltage-distance (V×d) curves in terms of nonuniformity. The authors apply the ACM to Cu emitters to explain the nonlinearity of the V×d curve in ACM measurements. This analysis provides a good insight into field emission phenomena, supporting a method for nonuniformity characterization based on field emission behavior