548 research outputs found
Collinear versus non-collinear magnetic order in Pd atomic clusters: ab-initio calculations
We present a thorough theoretical assessment of the stability of
non-collinear spin arrangements in small palladium clusters. We generally find
that ferromagnetic order is always preferred, but that antiferromagnetic and
non-collinear configurations of different sorts exist and compete for the first
excited isomers. We also show that the ground state is insensitive to the
choice of atomic configuration for the pseudopotential used and to the
approximation taken for the exchange and correlation potential. Moreover, the
existence and relative stability of the different excited configurations also
depends weakly on the approximations employed. These results provide strong
evidence on the transferability of pseudopotential and exchange and correlation
functionals for palladium clusters as opposed to the situation found for the
bulk phases of palladium.Comment: 5 pages, 4 figure
Exact thermodynamics of a planar array of Ginzburg-Landau chains with nn and nnn interactions
The exact expression of the free energy of a planar array of a
Ginzburg-Landau chains with nn and nnn interaction is obtained. The critical
behaviour of the specific heat is not qualitatively modified by taking into
account the nnn interaction
Procesamiento De Imágenes Para La Identificación De Personas Como Sistema De Seguridad En Zonas Domiciliarias/Image Processing for identification of people as a security system in domiciliary zones
El objetivo fue la implementación de dos algoritmos de reconocimiento facial para la identificación de personas, bajo condiciones reales en este caso un domicilio, se examinó las investigaciones relevantes en la identificación facial como los métodos de Análisis de Componentes Principales (PCA) y el Análisis Lineal Discriminante (LDA), procesos matemáticos utilizadas por los algoritmos Eigenfaces y Fisherfaces, que son técnicas de aproximación estadÃstica para clasificar datos en este caso rostros, con mÃnima complejidad computacional. El sistema de identificación de personas propuesto, desarrolló algoritmos en Matlab, describiendo sus etapas principales de procesamiento como la adquisición de imágenes, pre procesamiento, extracción de caracterÃsticas faciales, entrenamiento o clasificador, éstos algoritmos se sometieron a evaluación de eficacia en la identificación de personas, utilizando una base de rostros públicas de AT&T conocida como ORL Database of Faces, con 400 imágenes de rostros de distintas personas con variadas expresiones, adicionalmente se elaboró un base de rostros domiciliar, con 48 imágenes para el entrenamiento del sistema. Como resultado de la evaluación bajo condiciones de laboratorio se obtuvo una eficiencia superior al 90%, mientras que, al ser evaluados en condiciones reales, los algoritmos presentan eficiencias de identificación que oscilan del 50 al 80%, factores que dependen de la distancia, cámara, calidad de imagen, e iluminación. Estableciéndose las condiciones mÃnimas de requerimientos para la implementación de un sistema de vigilancia domiciliar, con porcentajes de efectividad favorables en estos ambientes, proponiendo una innovación en el uso de la tecnologÃa e ingenierÃa actual respecto a video vigilancia.
The objective of the project is the implementation of two facial recognition algorithms for the identification of people, under real conditions, in this case, an address. Relevant investigations in facial identification have been explored, such as Principal Component Analysis (PCA) and Discriminant Linear Analysis (LDA) methods, mathematical processes used by the Eigenfaces and Fisherfaces algorithms, which are statistical approximation techniques for classifying data, in this case, faces, with minimum computational complexity. The proposed people identification system, developed its algorithms in Matlab, describing its main processing stages such as image acquisition, pre-processing, extractions of facial features, training or classifier, these algorithms will be evaluated of efficiency in the identification of people, used for this a base of public faces of AT & T known as ORL Database of Faces, with 400 images of different faces forgive with various expressions, in addition to this a base of faces domiciliary, with 48 images will be elaborated for system training. As a result of the evaluations under laboratory conditions they present an efficiency of over 90%, while when evaluated in real conditions, the algorithms show efficiencies ranging from 50 to 80% depending on the distances between the subject and the camera, as well as it also depends on the image quality that can be acquired with them. In this way, minimum requirements have been established for the implementation of a home surveillance system, in which favourable percentages of effectiveness will be obtained in these environments, proposing an innovation in the use of current technology in relation to video surveillance.
Palabras claves: PCA, Eigenfaces, LDA, Fisherfaces, Base de Datos Públicas, Algoritmo, Reconocimiento.
Keywords: PCA, Eigenfaces, LDA, Fisherfaces, Public Database, Algorithm, Recognition
Human Segmentation In Funerary Practices. The Middle Neolithic Cemetery Cave Of Bom Santo (Montejunto Mountain Range, Portugal)
UID/ANT/04038/2019
IF/00127/2014Ongoing multidisciplinary studies of skeletonized human remains from the Middle Neolithic Bom Santo Cave (Lisbon, Portugal) is indicating a very heterogeneous population at various levels (diets, mobility and genetics). The current interpretation suggests that its socioeconomic and funerary territories encompassed the lower Tagus, its tributaries and the granitic sectors of the Mora–Pavia area in the Alentejo. Archaeothanatological analyses indicated mutually exclusive funerary practices: secondary depositions at Room A and primary and secondary depositions at Room B. Polished stone tools are evenly distributed in both rooms, while ornaments, pottery, flint blades and sheep/goat phalanges are almost restricted to Room A. Such distribution patterns reflects the coexistence of distinct funerary practices in which Room A is part of a much complex behaviour that included primary depositions, exhumation, transportation and re-deposition of human bone remains between different sectors of the cave and/or cemeteries (caves, dolmens) of the above-described territory. Thus, a more dynamic (in its rituals) and wider (in its geography) set of funerary practices than usually perceived — in which the intentional segmentation of human skeletons is attested — seems to have taken place at the onset of megalithism in central-southern Portugal.publishersversionpublishe
Mechanobiology of Colorectal Cancer
In this review, the mechanobiology of colorectal cancer (CRC) are discussed. Mecha-notransduction of CRC is addressed considering the relationship of several biophysical cues and biochemical pathways. Mechanobiology is focused on considering how it may influence epithelial cells in terms of motility, morphometric changes, intravasation, circulation, extravasation, and metastization in CRC development. The roles of the tumor microenvironment, ECM, and stroma are also discussed, taking into account the influence of alterations and surface modifications on mechanical properties and their impact on epithelial cells and CRC progression. The role of cancer-associated fibroblasts and the impact of flow shear stress is addressed in terms of how it affects CRC metastization. Finally, some insights concerning how the knowledge of biophysical mechanisms may contribute to the development of new therapeutic strategies and targeting molecules and how mechanical changes of the microenvironment play a role in CRC disease are presented.The authors are grateful to Ana Silva ([email protected]) for expert assistance with graphical design and to Portuguese Fundação para a Ciência e a Tecnologia (FCT) for funds in the framework of the project Instituto de Investigação e Inovação em Saúde (i3S), ref. ID/BIM/04293/2020
Effects of Fe doping in La1/2Ca1/2MnO3
The effect of Fe doping in the Mn site on the magnetic, transport and
structural properties of polycrystalline La1/2Ca1/2MnO3 was studied. Doping
with low Fe concentration (< 10%) strongly affects electrical transport and
magnetization. Long range charge order is disrupted even for the lowest doping
level studied (~2%). For Fe concentration up to 5% a ferromagnetic state
develops at low temperature with metallic like conduction and thermal
hysteresis. In this range, the Curie temperature decreases monotonously as a
function of Fe doping. Insulating behavior and a sudden depression of the
ferromagnetic state is observed by further Fe doping.Comment: 2 pages, presented at ICM2000, to appear in JMM
Structural and energetic properties of nickel clusters:
The four most stable structures of Ni clusters with from 2 to 150
have been determined using a combination of the embedded-atom method in the
version of Daw, Baskes and Foiles, the {\it variable metric/quasi-Newton}
method, and our own {\it Aufbau/Abbau} method. A systematic study of
energetics, structure, growth, and stability of also larger clusters has been
carried through without more or less severe assumptions on the initial
geometries in the structure optimization, on the symmetry, or on bond lengths.
It is shown that cluster growth is predominantly icosahedral with of
{\it fcc}, {\it tetrahedral} and {\it decahedral} growth. For the first time in
unbiased computations it is found that Ni is the multilayer (third
Mackay) icosahedron. Further, we point to an enhanced ability of {\it fcc}
clusters to compete with the icosahedral and decahedral structures in the
vicinity of N=79. In addition, it is shown that conversion from the {\it
hcp}/anti-Mackay kind of icosahedral growth to the {\it fcc}/Mackay one occurs
within a transition layer including several cluster sizes. Moreover, we present
and apply different analytical tools in studying structural and energetic
properties of such a large class of clusters. These include means for
identifying the overall shape, the occurrence of atomic shells, the similarity
of the clusters with, e.g., fragments of the {\it fcc} crystal or of a large
icosahedral cluster, and a way of analysing whether the -atom cluster can be
considered constructed from the -atom one by adding an extra atom. In
addition, we compare in detail with results from chemical-probe experiment.
Maybe the most central result is that first for clusters with above 80
general trends can be identified.Comment: 37 pages, 11 figure
Abrupt field-induced transition triggered by magnetocaloric effect in phase-separated manganites
The occurrence at low temperatures of an ultrasharp field-induced transition
in phase separated manganites is analyzed. Experimental results show that
magnetization and specific heat step-like transitions below 5 K are correlated
with an abrupt change of the sample temperature, which happens at a certain
critical field. This temperature rise, a magnetocaloric effect, is interpreted
as produced by the released energy at the transition point, and is the key to
understand the existence of the abrupt field-induced transition. A qualitative
analysis of the results suggests the existence of a critical growing rate of
the ferromagnetic phase, beyond which an avalanche effect is triggered.Comment: 6 pages, 4 figures included. Acepted for publication in Phys. Rev.
Epigallocatechin-3-gallate Delivered in Nanoparticles Increases Cytotoxicity in Three Breast Carcinoma Cell Lines
The anticancer act i v i t y of epigallocatechin-3-gallate (EGCG), orally administrated, is limited by poor bioavailabi l i t y , absorption, and unpredictable distribution in human tissues. EGCG charged nanoparticles may represent an opportunity to overcome these limitations. We assayed two different kinds of lipid nanoparticles (LNPs and LNPs functionalized with folic acid) charged with EGCG on three breast carcinoma cell lines (MCF-7, MDA-MB-231, and MCF-7TAM) and the human normal MCF10A mammary epithelial cells. Both LNPs loaded with EGCG, at low concentrations, induced a significant cytotoxicity in the three breast carcinoma cells but not in MCF10A cells. In view of a future application, both LNPs and LNPs-FA were found to be very suitable for in vitro studies and usef u l to improve EGCG administration in vivo. Since they are produced by inexpensive procedures using bioavailable, biocompatible, and biodegradable molecules, t h e y represent an applicable tool for a more rationale use of EGCG as an anti-cancer agent
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