1,067 research outputs found
Valley symmetry breaking in bilayer graphene: a test to the minimal model
Physical properties reflecting valley asymmetry of Landau levels in a biased
bilayer graphene under magnetic field are discussed. Within the band
continuum model with Hartree-corrected self-consistent gap and finite damping
factor we predict the appearance of anomalous steps in quantized Hall
conductivity due to the degeneracy lifting of Landau levels. Moreover, the
valley symmetry breaking effect appears as a non-semiclassical de Haas-van
Alphen effect where the reduction of the oscillation period to half cannot be
accounted for through quasi-classical quantization of the orbits in reciprocal
space, still valley degenerate.Comment: 4 pages, 3 figure
A New Framework for Join Product Skew
Different types of data skew can result in load imbalance in the context of
parallel joins under the shared nothing architecture. We study one important
type of skew, join product skew (JPS). A static approach based on frequency
classes is proposed which takes for granted the data distribution of join
attribute values. It comes from the observation that the join selectivity can
be expressed as a sum of products of frequencies of the join attribute values.
As a consequence, an appropriate assignment of join sub-tasks, that takes into
consideration the magnitude of the frequency products can alleviate the join
product skew. Motivated by the aforementioned remark, we propose an algorithm,
called Handling Join Product Skew (HJPS), to handle join product skew
Densidad básica de la madera de Acacia melanoxylon R. Br en relación con la altura de muestreo, el árbol y el sitio
The aim of the work was to assess basic wood density variations of Acacia melanoxylon R.Br according to sample tree height, tree, and site. Twenty trees were selected from four sites in Buenos Aires Province, Argentine. Wood density was determined over two disc samples at four tree height (base, breast height, 30% and 50% of total tree height). According to determined ages, some trees were divided into two groups according to age (26-32 years and 9-12 years) and data were analyzed with an analysis of variance according to mixed model where tree was the random effecTrees represent 74 % of total random variance. Within tree, axial tendency of wood density was to decrease from the base toward breast height and then its value was stable to the top. This was consistent across all sites and age groups. Forest resource growing at Los Tuelches site presented the highest basic wood density.El objetivo del presente trabajo fue analizar las variaciones en la densidad básica de la madera de Acacia melanoxylon R.Br, según las alturas de muestreo en el fuste, los árboles y el sitio. Se seleccionaron 20 árboles en cuatro sitios de muestreo en la Provincia de Buenos Aires, Argentina. Se determinó la densidad de la madera sobre dos rodajas en cada una de cuatro alturas en el fuste (base, altura de pecho, 30% y 50% de la altura total). De acuerdo a la edad determinada, parte del material se reunió en dos grupos (26-32 años y 9-12 años) para los análisis de la varianza bajo modelos mixtos donde el árbol fue considerado como aleatorio. Asimismo, el árbol fue responsable del 74 % de la variación aleatoria total. Dentro del fuste se describió un descenso significativo de la densidad entre la base y la altura del pecho, región a partir de la cual la densidad mantuvo su valor hacia el extremo superior del fuste. Esta tendencia se manifestó en todos los sitios y agrupamientos por edades. El recurso implantado en la estación serrana Los Tuelches presentó las mayores densidades de la madera
Color space distortions in patients with type 2 diabetes mellitus
Color vision impairment was examined in patients with type 2 diabetes mellitus (DM2) without retinopathy. We assessed the type and degree of distortions of individual color spaces. DM2 patients (n = 32), and age-matched controls (n = 20)were tested using the Farnsworth D-15 and the Lanthony D-15d tests. In addition, subsets of caps
from both tests were employed in a triadic procedure (Bimler & Kirkland, 2004). Matrices of inter-cap subjective dissimilarities were estimated from each subject’s “odd-one-out” choices, and processed using non-metric
multidimensional scaling. Two-dimensional color spaces, individual and group (DM2 patients; controls), were reconstructed, with the axes interpreted as the R0G and B0Y perceptual opponent systems. Compared to controls, patient results were not significant for the D-15 and D-15d. In contrast, in the triadic procedure the residual distances were significantly different compared to controls: right eye, P 0.021, and left eye, P 0.022. Color
space configurations for the DM2 patients were compressed along the B0Y and R0G dimensions. The present findings agree with earlier studies demonstrating diffuse losses in early stages of DM2. The proposed method of testing uses color spaces to represent discrimination and provides more differentiated quantitative diagnosis, which
may be interpreted as the perceptual color system affected. In addition, it enables the detection of very mild color vision impairment that is not captured by the D-15d test. Along with fundoscopy, individual color spaces may serve for monitoring early functional changes and thereby to support a treatment strategy
Effects of exoplanetary gravity on human locomotor ability
At some point in the future, if mankind hopes to settle planets outside the
Solar System, it will be crucial to determine the range of planetary conditions
under which human beings could survive and function. In this article, we apply
physical considerations to future exoplanetary biology to determine the
limitations which gravity imposes on several systems governing the human body.
Initially, we examine the ultimate limits at which the human skeleton breaks
and muscles become unable to lift the body from the ground. We also produce a
new model for the energetic expenditure of walking, by modelling the leg as an
inverted pendulum. Both approaches conclude that, with rigorous training,
humans could perform normal locomotion at gravity no higher than 4
.Comment: 12 pages, 4 figures, to be published in The Physics Teache
Novel insights on the population genetic structure of the Coffee Leaf Rust pathogen Hemileia vastatrix
Comunicação OralN/
Orbital quantization in the high magnetic field state of a charge-density-wave system
A superposition of the Pauli and orbital coupling of a high magnetic field to
charge carriers in a charge-density-wave (CDW) system is proposed to give rise
to transitions between subphases with quantized values of the CDW wavevector.
By contrast to the purely orbital field-induced density-wave effects which
require a strongly imperfect nesting of the Fermi surface, the new transitions
can occur even if the Fermi surface is well nested at zero field. We suggest
that such transitions are observed in the organic metal
-(BEDT-TTF)KHg(SCN) under a strongly tilted magnetic field.Comment: 14 pages including 4 figure
Early Permian Conodont Fauna and Stratigraphy of the Garden Valley Formation, Eureka County, Nevada
The lower part of the Garden Valley Formation yields two distinct conodont faunas. One of late Asselian age dominated by Mesogondolella and Streptognathodus and one of Artinskian age dominated by Sweetognathus with Mesogondolella. The Asselian fauna contains the same species as those found in the type area of the Asselian in the southern Urals including Mesogondolella dentiseparata, described for the first time outside of the Urals. Apparatuses for Sweetognathus whitei, Diplognathodus stevensi, and Idioprioniodus sp. are described. The Garden Valley Formation represents a marine pro-delta basin and platform, and marine and shore fan delta complex deposition. The fan-delta complex was most likely deposited from late Artinskian to late Wordian. The Garden Valley Formation records tremendous swings in depositional setting from shallow-water to basin to shore
Gender Artifacts in Visual Datasets
Gender biases are known to exist within large-scale visual datasets and can
be reflected or even amplified in downstream models. Many prior works have
proposed methods for mitigating gender biases, often by attempting to remove
gender expression information from images. To understand the feasibility and
practicality of these approaches, we investigate what exist within large-scale visual datasets. We define a
as a visual cue that is correlated with gender,
focusing specifically on those cues that are learnable by a modern image
classifier and have an interpretable human corollary. Through our analyses, we
find that gender artifacts are ubiquitous in the COCO and OpenImages datasets,
occurring everywhere from low-level information (e.g., the mean value of the
color channels) to the higher-level composition of the image (e.g., pose and
location of people). Given the prevalence of gender artifacts, we claim that
attempts to remove gender artifacts from such datasets are largely infeasible.
Instead, the responsibility lies with researchers and practitioners to be aware
that the distribution of images within datasets is highly gendered and hence
develop methods which are robust to these distributional shifts across groups.Comment: ICCV 202
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