11,832 research outputs found
Putative spin liquid in the triangle-based iridate BaIrTiO
We report on thermodynamic, magnetization, and muon spin relaxation
measurements of the strong spin-orbit coupled iridate BaIrTiO,
which constitutes a new frustration motif made up a mixture of edge- and
corner-sharing triangles. In spite of strong antiferromagnetic exchange
interaction of the order of 100~K, we find no hint for long-range magnetic
order down to 23 mK. The magnetic specific heat data unveil the -linear and
-squared dependences at low temperatures below 1~K. At the respective
temperatures, the zero-field muon spin relaxation features a persistent spin
dynamics, indicative of unconventional low-energy excitations. A comparison to
the isostructural compound BaRuTiO suggests that a concerted
interplay of compass-like magnetic interactions and frustrated geometry
promotes a dynamically fluctuating state in a triangle-based iridate.Comment: Physical Review B accepte
Kondo screening in a Majorana metal
Kondo impurities provide a nontrivial probe to unravel the character of the
excitations of a quantum spin liquid. In the S=1/2 Kitaev model on the
honeycomb lattice, Kondo impurities embedded in the spin-liquid host can be
screened by itinerant Majorana fermions via gauge-flux binding. Here, we report
experimental signatures of metallic-like Kondo screening at intermediate
temperatures in the Kitaev honeycomb material {\alpha}-RuCl3 with dilute Cr3+
(S=3/2) impurities. The static magnetic susceptibility, the muon Knight shift,
and the muon spin-relaxation rate all feature logarithmic divergences, a
hallmark of a metallic Kondo effect. Concurrently, the linear coefficient of
the magnetic specific heat is large in the same temperature regime, indicating
the presence of a host Majorana metal. This observation opens new avenues for
exploring uncharted Kondo physics in insulating quantum magnets.Comment: published in Nature Communications, 37 pages, 10 figure
Hypernetwork functional image representation
Motivated by the human way of memorizing images we introduce their functional
representation, where an image is represented by a neural network. For this
purpose, we construct a hypernetwork which takes an image and returns weights
to the target network, which maps point from the plane (representing positions
of the pixel) into its corresponding color in the image. Since the obtained
representation is continuous, one can easily inspect the image at various
resolutions and perform on it arbitrary continuous operations. Moreover, by
inspecting interpolations we show that such representation has some properties
characteristic to generative models. To evaluate the proposed mechanism
experimentally, we apply it to image super-resolution problem. Despite using a
single model for various scaling factors, we obtained results comparable to
existing super-resolution methods
Cost-effective solutions and tools for medical image processing and design of personalised cranioplasty implants
Cranial defects which are caused by bone tumors or traffic accidents are treated by cranioplasty techniques. Cranioplasty implants are required to protect the underlying brain, correct major aesthetic deformities, or both. With the rapid develop-ment of computer graphics, medical image processing (MIP) and manufacturing technologies in recent decades, nowadays, personalised cranioplasty implants can be designed and made to improve the quality of cranial defect treatments. However, software tools for MIP and 3D modelling of implants are ex-pensive; and they normally require high technical skills. Espe-cially, the process of design and development of personalised cranioplasty implants normally requires a multidisciplinary team, including experts in MIP, 3D design and modelling, and Biomedical Engineering; this leads to challenges and difficulties for technology transfers and implementations in hospitals. This research is aimed at developing, in particular, cost-effective solutions and tools for design and modeling of per-sonalised cranioplasty implants, and to simplify the design and modelling of implants, as well as to reduce the design and modeling time. In this way, surgeons and engineers can con-veniently and easily design personalised cranioplasty implants, without the need of using complex MIP and CAD tools; and as a result the cost of implants will be minimised
Gauge Invariance in Chern-Simons Systems
We show explicitly that the question of gauge invariance of the effective
potential in standard scalar electrodynamics remains unchanged despite the
introduction of the Chern-Simons term. The result does not depend on the
presence of the Maxwell term in the Chern-Simons territory.Comment: 10 pages, Plain Tex, DF/UFPB-14/9
Gauge Invariant Effective Potential for Abelian Maxwell-Chern-Simons Systems
We investigate the effective potential for Abelian Maxwell--Chern--Simons
systems. The calculations follow an alternate approach, recently proposed as a
gauge invariant formulation of the effective potential, constructed in terms of
a gauge invariant order parameter. We compare the results with another
investigation, obtained within a standard route of calculating the effective
potential.Comment: 10 pages. Revtex. To appear in Phys. Rev.
Decoupled Lithospheric Folding, Lower Crustal Flow Channels, and the Growth of Tibetan Plateau
The growth mechanism of the Tibetan Plateau, postulated by a number of hypotheses, remains
under intense debate. Our analysis of recent satellite-based gravity model reveals that Tibetan lithosphere has
been decoupled and folded. It is further evidenced by the existence of crustal melts and channel flow that have
been observed by seismic and magnetotelluric explorations. Based on 3D geodynamic simulations, we elucidate
the exact buckling structures in the upper crust and lithospheric mantle: at mixed wavelengths between ∼240
and ∼400 km, the lower crustal viscosity is smaller than ∼10 19 Pa·s, implicating weak lower crustal flow
beneath the Plateau. This mixed wavelength is consistent with the result of our inverse gravity modeling. Our
results facilitate a new plausible hypothesis that the decoupled lithospheric folding mechanism can explain the
growth mechanism of the anomalously thick and wide Tibetan Plateau by conflating our idea and contemporary
hypothesized scientific findings
A novel scytalidium species : understand the cellulolytic system for biomass saccharification
In order to overcome the bottlenecks related to lignocellulosic-derived sugars, the search for more efficient enzymatic cocktails, containing a broad-spectrum of specific activities, relies on an important feature. This paper describes new enzyme activities derived from the novel strain of the Scytalidium genus isolated from the Amazonas rainforest. The production of the enzymatic cocktail was induced by delignifiedhydrothermal bagasse (DHB), and yeast extract was used to improve secretion activities, resulting in a positive influence on total cellulase activity. The enzymatic cocktail produced by this novel strain contains specific activities for biomass degradation, including FPAse, xylanase and β-glucosidase. Moreover, it is capable of hydrolyzing 62% of the alkaline pretreated bagasse, surpassing in 14% the hydrolytic capability achieved by the commercial cocktail Celluclast. To this extent, the strain described here emerges as a reliable alternative to other available enzymes and, consequently, amplification of available specific substrate activities3618597FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2010/51309-
Warped Riemannian metrics for location-scale models
The present paper shows that warped Riemannian metrics, a class of Riemannian
metrics which play a prominent role in Riemannian geometry, are also of
fundamental importance in information geometry. Precisely, the paper features a
new theorem, which states that the Rao-Fisher information metric of any
location-scale model, defined on a Riemannian manifold, is a warped Riemannian
metric, whenever this model is invariant under the action of some Lie group.
This theorem is a valuable tool in finding the expression of the Rao-Fisher
information metric of location-scale models defined on high-dimensional
Riemannian manifolds. Indeed, a warped Riemannian metric is fully determined by
only two functions of a single variable, irrespective of the dimension of the
underlying Riemannian manifold. Starting from this theorem, several original
contributions are made. The expression of the Rao-Fisher information metric of
the Riemannian Gaussian model is provided, for the first time in the
literature. A generalised definition of the Mahalanobis distance is introduced,
which is applicable to any location-scale model defined on a Riemannian
manifold. The solution of the geodesic equation is obtained, for any Rao-Fisher
information metric defined in terms of warped Riemannian metrics. Finally,
using a mixture of analytical and numerical computations, it is shown that the
parameter space of the von Mises-Fisher model of -dimensional directional
data, when equipped with its Rao-Fisher information metric, becomes a Hadamard
manifold, a simply-connected complete Riemannian manifold of negative sectional
curvature, for . Hopefully, in upcoming work, this will be
proved for any value of .Comment: first version, before submissio
COVID-19 therapy target discovery with context-aware literature mining
The abundance of literature related to the widespread COVID-19 pandemic is
beyond manual inspection of a single expert. Development of systems, capable of
automatically processing tens of thousands of scientific publications with the
aim to enrich existing empirical evidence with literature-based associations is
challenging and relevant. We propose a system for contextualization of
empirical expression data by approximating relations between entities, for
which representations were learned from one of the largest COVID-19-related
literature corpora. In order to exploit a larger scientific context by transfer
learning, we propose a novel embedding generation technique that leverages
SciBERT language model pretrained on a large multi-domain corpus of scientific
publications and fine-tuned for domain adaptation on the CORD-19 dataset. The
conducted manual evaluation by the medical expert and the quantitative
evaluation based on therapy targets identified in the related work suggest that
the proposed method can be successfully employed for COVID-19 therapy target
discovery and that it outperforms the baseline FastText method by a large
margin.Comment: Accepted to the 23rd International Conference on Discovery Science
(DS 2020
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