A theorem regarding families of topologically non-trivial fermionic systems

We introduce a Hamiltonian for fermions on a lattice and prove a theorem regarding its topological properties. We identify the topological criterion as a $\mathbb{Z}_2-$ topological invariant $p(\textbf{k})$ (the Pfaffian polynomial). The topological invariant is not only the first Chern number, but also the sign of the Pfaffian polynomial coming from a notion of duality. Such Hamiltonian can describe non-trivial Chern insulators, single band superconductors or multiorbital superconductors. The topological features of these families are completely determined as a consequence of our theorem. Some specific model examples are explicitly worked out, with the computation of different possible topological invariants.Comment: 6 page

Photodiode with nanocrystalline Si/amorphous Si absorber bilayer

This letter reports a near-ultraviolet/visible/near-infrared n(+)-n-i-delta(i)-p photodiode with an absorber comprising a nanocrystalline silicon n layer and a hydrogenated amorphous silicon i layer. Device modeling reveals that the dominant source of reverse dark current is deep defect states in the n layer, and its magnitude is controlled by the i layer thickness. The photodiode with the 900/400 nm thick n-i layers exhibits a reverse dark current density of 3nA/cm(2) at -1V. Donor concentration and diffusion length of holes in the n layer are estimated from the capacitance-voltage characteristics and from the bias dependence of long-wavelength response, respectively. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3660725

Análisis de los ciclos de congelación y descongelación en la capa activa en el entorno de la BAE JCI. Periodo 2000-2011

Close to the Spanish Antarctic Station our research team drilled, at the 1999-2000 Antarctic campaign, a 2,30 m shallow borehole in quartzite bedrock. This borehole was instrumented with temperature data loggers (Tinytag model) that have allowed us to register the gradient thermal in a continuous regime evolution during the 2000-2011 period. The analysis of the temperature data allows to describe the temporal evolution of the freezing and thawing cycles in the active layer, as well as the N-Factor variability, related with the soil surface thermal behavior and its energy balance. In this work we discuss the different freezing and thawing mechanisms in monthly and annual periods. The study shows a important freezing and thawing inter annual variability,, the annual cumulative index showed values in the following intervals: freezing index (-700, -300 ºC day) and thawing index (400, 700 ºC day)

Resazurin reduction-based assays revisited: guidelines for accurate reporting of relative differences on metabolic status

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).Cell viability and metabolic activity are ubiquitous parameters used in biochemistry, molecular biology, and biotechnological studies. Virtually all toxicology and pharmacological projects include at some point the evaluation of cell viability and/or metabolic activity. Among the methods used to address cell metabolic activity, resazurin reduction is probably the most common. At variance with resazurin, resorufin is intrinsically fluorescent, which simplifies its detection. Resazurin conversion to resorufin in the presence of cells is used as a reporter of metabolic activity of cells and can be detected by a simple fluorometric assay. UV–Vis absorbance is an alternative technique but is not as sensitive. In contrast to its wide empirical “black box” use, the chemical and cell biology fundamentals of the resazurin assay are underexplored. Resorufin is further converted to other species, which jeopardizes the linearity of the assays, and the interference of extracellular processes has to be accounted for when quantitative bioassays are aimed at. In this work, we revisit the fundamentals of metabolic activity assays based on the reduction of resazurin. Deviation to linearity both in calibration and kinetics, as well as the existence of competing reactions for resazurin and resorufin and their impact on the outcome of the assay, are addressed. In brief, fluorometric ratio assays using low resazurin concentrations obtained from data collected at short time intervals are proposed to ensure reliable conclusions.The project leading to these results has received funding from “la Caixa” Foundation and FCT, I.P. under the project code [LCF/PR/HR21/00605], BREAST-BRAIN-N-BBB.info:eu-repo/semantics/publishedVersio

Are circles isoperimetric in the plane with density er?

We prove that an isoperimetric region in R2 with density er must be convex and contain the origin, and provide numerical evidence that circles about the origin are isoperimetric, as predicted by the Log-Convex Density Conjecture

Perfil compósito para colector solar, respectivo método de produção e utilização

A presente invenção diz respeito a um perfil compósito para caixa modular utilizada em colectores solares para aquecimento de águas para uso doméstico ou industrial cujas principais vantagens passam pela: produção através de um processo de extrusão, redução das perdas energéticas do colector solar devido ao design com perfil alveolar, fácil portabilidade devido a redução do peso por metro quadrado de painel, utilização de compósitos recicláveis na sua composição usando entre outros: borracha de pneu usado reciclada, redução dos tempos de montagem dos colectores solares, eliminação da necessidade de colocação de isolantes adicionais à caixa modular e redução dos custos de produção

Balanço de nutrientes no braço sul do estuário do rio Mondego

Na sequência de estudos realizados no domínio da análise de vulnerabilidade da costa litoral portuguesa, entendeu-se pertinente desenvolver um programa de investigação sobre o braço sul do estuário do rio Mondego visando, fundamentalmente, os seguintes aspectos: caracterização das marés, caudais fluviais e descargas de fontes poluidoras; modelação hidrodinâmica do sistema; avaliação do balanço anual de nutrientes; análise da vulnerabilidade deste sistema à eutrofização. Neste trabalho procedeu-se à modelação do sistema utilizando um modelo de qualidade unidimensional (DUFLOW) e os dados existentes. A não adopção, nesta fase, dum modelo multidimensional deve-se não só à não simultaneidade das medições dos parâmetros nos vários pontos de amostragem, mas, sobretudo, ao objectivo do presente trabalho: estimar o balanço de nutrientes neste sistema estuarino

On the adaptation to non-individualized HRTF auralisations: A longitudinal study

Auralisations with HRTFs are an innovative tool for the reproduction of acoustic space. Their broad applicability depends on the use of non-individualised models, but little is known on how humans adapt to these sounds. Previous findings have shown that simple exposure to non-individualised virtual sounds did not provide a quick adaptation, but that training and feedback would boost this process. Here, we were interested in analyzing the long-term effect of such training-based adaptation. We trained listeners in azimuth and elevation discrimination in two separate experiments and retested them immediately, one hour, one day, one week and one month after. Results revealed that, with active learning and feedback, all participants lowered their localization errors. This benefit was still found one month after training. Interestingly, participants who had trained previously with elevations were better in azimuth localization and vice-versa. Our findings suggest that humans adapt easily to new anatomically shaped spectral cues and they are able to transfer that adaptation to non-trained sounds.(undefined

Exploring the high-temperature thermoelectric performance of la-substituted Ca3Co4O9 bulk ceramics

It is well-known that the electrical properties of the Ca3Co4O9 thermoelectric (TE) compound are strongly influenced by the valence of the substituting cation, while its solubility and “functional” impact depend largely on the preparation and/or processing methods used. Furthermore, this material’s hybrid crystal structure allows for different cation substitutions in/from different sublattices. This research work presents the relevant effects of different La substitutions for the Ca ions from the insulating rock salt type [Ca2CoO3] crystal component (considered as a “charge reservoir” for the conductive [CoO2] layers) for a series of bulk samples prepared and processed via a solid-state method, chosen for simplicity. The results show that the actual level of La substitutions does not exceed 0.03 (x < 0.03), in Ca3-xLaxCo4O9 samples with x = 0.01, 0.03, 0.05 and 0.07, and that beyond this limit, simultaneous Ca3Co4O9 phase decomposition and secondary Ca3Co2O6 and (La,Ca)CoO3 phase formation take place. The morpho-structural features were found to be quite moderate, with a negligible effect on the charge carries transport. The electrical measurements and average oxidation state of cobalt (~3.11) suggest that the substitutions with La have only a minor effect on the charge carrier concentration. The electrical resistivity of the samples with x = 0.01, 0.03 and 0.05 is found to be ~1.3 times lower than of pristine Ca3Co4O9, while the changes in the Seebeck coefficient values are only moderate in the whole measured temperature range. The highest power factor, representing the electrical counterpart of the TE performance, was found for the Ca2.99La0.01Co4O9 samples (~0.28 mW/K2m, at 800 C), being among the best found in the literature for similar materials. Our results suggest that low substitutions with rare-earth cations in the “charge reservoir” layers of the Ca3Co4O9 compound can be promising in designing and improving these p-type oxides, provided by the strongly correlated nature of their conduction mechanism.publishe

Pair approximation for the noisy threshold qq-voter model

In the standard $q$-voter model, a given agent can change its opinion only if there is a full consensus of the opposite opinion within a group of influence of size $q$. A more realistic extension is the threshold $q$-voter, where a minimal agreement (at least $0<q_0\le q$ opposite opinions) is sufficient to flip the central agent's opinion, including also the possibility of independent (non conformist) choices. Variants of this model including non-conformist behavior have been previously studied in fully connected networks (mean-field limit). Here we investigate its dynamics in random networks. Particularly, while in the mean-field case it is irrelevant whether repetitions in the influence group are allowed, we show that this is not the case in networks, and we study the impact of both cases, with or without repetition. Furthermore, the results of computer simulations are compared with the predictions of the pair approximation derived for uncorrelated networks of arbitrary degree distributions.Comment: 13 pages, 12 figure