Quantum Inequalities on the Energy Density in Static Robertson-Walker Spacetimes

Quantum inequality restrictions on the stress-energy tensor for negative energy are developed for three and four-dimensional static spacetimes. We derive a general inequality in terms of a sum of mode functions which constrains the magnitude and duration of negative energy seen by an observer at rest in a static spacetime. This inequality is evaluated explicitly for a minimally coupled scalar field in three and four-dimensional static Robertson-Walker universes. In the limit of vanishing curvature, the flat spacetime inequalities are recovered. More generally, these inequalities contain the effects of spacetime curvature. In the limit of short sampling times, they take the flat space form plus subdominant curvature-dependent corrections.Comment: 18 pages, plain LATEX, with 3 figures, uses eps

Preliminary checklist of the Cerambycidae, Disteniidae, and Vesperidae (Coleoptera) of Peru

A preliminary checklist of the Cerambycidae, Disteniidae, and Vesperidae (Coleoptera) of Peru is presented. Within Cerambycidae, we record five subfamilies, 55 tribes, 345 genera and subgenera, and 714 species. Within Disteniidae, we record one tribe, six genera, and 11 species. We also record one subfamily, one tribe, one genus, and two species within Vesperidae. Four new country records are recorded: one species in the tribe Anacolini (Cerambycidae: Prioninae): Cycloprionus flavus Tippmann, 1953; and three species in the tribe Onciderini (Cerambycidae: Lamiinae): Cacostola simplex (Pascoe, 1859); Marensis simplex (Bates, 1865); Trachysomus cavigibba Martins, 1975. In addition, 161 species recorded are known only from Peru

Spatiotemporal Chaos, Localized Structures and Synchronization in the Vector Complex Ginzburg-Landau Equation

We study the spatiotemporal dynamics, in one and two spatial dimensions, of two complex fields which are the two components of a vector field satisfying a vector form of the complex Ginzburg-Landau equation. We find synchronization and generalized synchronization of the spatiotemporally chaotic dynamics. The two kinds of synchronization can coexist simultaneously in different regions of the space, and they are mediated by localized structures. A quantitative characterization of the degree of synchronization is given in terms of mutual information measures.Comment: 6 pages, using bifchaos.sty (included). 7 figures. Related material, including higher quality figures, could be found at http://www.imedea.uib.es/PhysDept/publicationsDB/date.html . To appear in International Journal of Bifurcation and Chaos (1999

On the relation between virial coefficients and the close-packing of hard disks and hard spheres

The question of whether the known virial coefficients are enough to determine the packing fraction $\eta_\infty$ at which the fluid equation of state of a hard-sphere fluid diverges is addressed. It is found that the information derived from the direct Pad\'e approximants to the compressibility factor constructed with the virial coefficients is inconclusive. An alternative approach is proposed which makes use of the same virial coefficients and of the equation of state in a form where the packing fraction is explicitly given as a function of the pressure. The results of this approach both for hard-disk and hard-sphere fluids, which can straightforwardly accommodate higher virial coefficients when available, lends support to the conjecture that $\eta_\infty$ is equal to the maximum packing fraction corresponding to an ordered crystalline structure.Comment: 10 pages, 6 figures; v2: discussion about hard-square and hard-hexagon systems on a lattice added; five new reference

Interaction of silver nanoparticles with HIV-1

The interaction of nanoparticles with biomolecules and microorganisms is an expanding field of research. Within this field, an area that has been largely unexplored is the interaction of metal nanoparticles with viruses. In this work, we demonstrate that silver nanoparticles undergo a size-dependent interaction with HIV-1, with nanoparticles exclusively in the range of 1–10 nm attached to the virus. The regular spatial arrangement of the attached nanoparticles, the center-to-center distance between nanoparticles, and the fact that the exposed sulfur-bearing residues of the glycoprotein knobs would be attractive sites for nanoparticle interaction suggest that silver nanoparticles interact with the HIV-1 virus via preferential binding to the gp120 glycoprotein knobs. Due to this interaction, silver nanoparticles inhibit the virus from binding to host cells, as demonstrated in vitro

Looking at b-learning and online experience in higher education during COVID-19

COVID-19 caused changes in teaching practices at various levels of education, namely in higher education. This study aims to present an analysis of an experience with higher education students in a b-learning pedagogical model, before and during the current pandemic and in different moments of the confinement measures. The curricular unit analyzed started with a blended-learning approach since 2018, considering the importance of innovative pedagogical models in student learning and became an essential resource during the pandemic period. This case study was composed of a sample of 269 students from a Portuguese public University who attended the curricular unit Methods and Study Techniques, as optional, in their 1st year of degree, between February 2018 and March 2021.The data were processed using SPSS v.27, seeking to analyze different moments, according to the different confinement measures decreed by the Portuguese Government. Participants are aged between 17 and 64 years old, 62.5% female and 24.5% worker-students. It was found that regardless of the context of confinement, students showed positive satisfaction with the online course, with its contents, with the platform and with the b-learning pedagogical method, especially during total confinement when classes were in distance learning. The most valued aspects in this modality were the flexibility of teaching the curricular unit and time management. The acquired tools were highly valued by the students, first for the adaptability that gave them, but mainly to face the distance learning challenge in their 1st year of degree, giving them planning and organizing skills for autonomous work. Most students did not point out a disadvantage in this modality, although they expressed the importance of face-to-face classes that were suspended in the context of a pandemic.info:eu-repo/semantics/acceptedVersio

Symmetric hyperbolic systems for Bianchi equations

We obtain a family of first-order symmetric hyperbolic systems for the Bianchi equations. They have only physical characteristics: the light cone and timelike hypersurfaces. In the proof of the hyperbolicity, new positivity properties of the Bel tensor are used.Comment: latex, 7 pages, accepted for publication in Class. Quantum Gra

Electron mean free path from angle-dependent photoelectron spectroscopy of aerosol particles

We propose angle-resolved photoelectron spectroscopy of aerosol particles as an alternative way to determine the electron mean free path of low energy electrons in solid and liquid materials. The mean free path is obtained from fits of simulated photoemission images to experimental ones over a broad range of different aerosol particle sizes. The principal advantage of the aerosol approach is twofold. Firstly, aerosol photoemission studies can be performed for many different materials, including liquids. Secondly, the size-dependent anisotropy of the photoelectrons can be exploited in addition to size-dependent changes in their kinetic energy. These finite size effects depend in different ways on the mean free path and thus provide more information on the mean free path than corresponding liquid jet, thin film, or bulk data. The present contribution is a proof of principle employing a simple model for the photoemission of electrons and preliminary experimental data for potassium chloride aerosol particles

Periostin increases migration and proliferation of human periodontal ligament fibroblasts challenged by tumor necrosis factor ‐α and Porphyromonas gingivalis lipopolysaccharides

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106894/1/jre12120.pd