630 research outputs found
Almost-rigidity and the extinction time of positively curved Ricci flows
We prove that Ricci flows with almost maximal extinction time must be nearly
round, provided that they have positive isotropic curvature when crossed with
. As an application, we show that positively curved metrics on
and with almost maximal width must be nearly round
Issues on 3D Noncommutative Electromagnetic Duality
We extend the ordinary 3D electromagnetic duality to the noncommutative (NC)
space-time through a Seiberg-Witten map to second order in the noncommutativity
parameter (theta), defining a new scalar field model. There are similarities
with the 4D NC duality, these are exploited to clarify properties of both
cases. Up to second order in theta, we find that duality interchanges the
2-form theta with its 1-form Hodge dual *theta times the gauge coupling
constant, i.e., theta --> *theta g^2 (similar to the 4D NC electromagnetic
duality). We directly prove that this property is false in the third order
expansion in both 3D and 4D space-times, unless the slowly varying fields limit
is imposed. Outside this limit, starting from the third order expansion, theta
cannot be rescaled to attain an S-duality. In addition to possible applications
on effective models, the 3D space-time is useful for studying general
properties of NC theories. In particular, in this dimension, we deduce an
expression that significantly simplifies the Seiberg-Witten mapped Lagrangian
to all orders in theta.Comment: 15 pages, revtex4. v.2: We added a proof that the terms in (4.9) are
not surface terms, a new paragraph in our conclusion and new references. v.3:
improvements in our introduction and conclusions. v.4: Published version
(PRD): additional comments and reference
Rastall Cosmology and the \Lambda CDM Model
Rastall's theory is based on the non-conservation of the energy-momentum
tensor. We show that, in this theory, if we introduce a two-fluid model, one
component representing vacuum energy whereas the other pressureless matter
(e.g. baryons plus cold dark matter), the cosmological scenario is the same as
for the \Lambda CDM model, both at background and linear perturbative levels,
except for one aspect: now dark energy may cluster. We speculate that this can
lead to a possibility of distinguishing the models at the non-linear
perturbative level.Comment: 9 pages, 1 figure. Accepted for publication in Physical Review
A Simple Capacitive Method To Evaluate Ethanol Fuel Samples
Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Ethanol is a biofuel used worldwide. However, the presence of excessive water either during the distillation process or by fraudulent adulteration is a major concern in the use of ethanol fuel. High water levels may cause engine malfunction, in addition to being considered illegal. Here, we describe the development of a simple, fast and accurate platform based on nanostructured sensors to evaluate ethanol samples. The device fabrication is facile, based on standard microfabrication and thin-film deposition methods. The sensor operation relies on capacitance measurements employing a parallel plate capacitor containing a conformational aluminum oxide (Al2O3) thin layer (15 nm). The sensor operates over the full range water concentration, i. e., from approximately 0% to 100% vol. of water in ethanol, with water traces being detectable down to 0.5% vol. These characteristics make the proposed device unique with respect to other platforms. Finally, the good agreement between the sensor response and analyses performed by gas chromatography of ethanol biofuel endorses the accuracy of the proposed method. Due to the full operation range, the reported sensor has the technological potential for use as a point-of-care analytical tool at gas stations or in the chemical, pharmaceutical, and beverage industries, to mention a few.7CAPESCNPq [483550/2013-2]FAPESP [2013/22127-2, 2014/25979-2]Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP
ETDB-Caltech: a blockchain-based distributed public database for electron tomography
Three-dimensional electron microscopy techniques like electron tomography provide valuable insights into cellular structures, and present significant challenges for data storage and dissemination. Here we explored a novel method to publicly release more than 11,000 such datasets, more than 30 TB in total, collected by our group. Our method, based on a peer-to-peer file sharing network built around a blockchain ledger, offers a distributed solution to data storage. In addition, we offer a user-friendly browser-based interface, https://etdb.caltech.edu, for anyone interested to explore and download our data. We discuss the relative advantages and disadvantages of this system and provide tools for other groups to mine our data and/or use the same approach to share their own imaging datasets
Functional Analysis of the TAN-1 Gene, a Human Homolog of Drosophila Notch
The TAN-1 gene was originally discovered at the breakpoint of a recurrent (7;9)(q34;q34.3) chromosomal translocation found in a subset of human T-lymphoblastic leukemias (Reynolds et al. 1987; Smith et al. 1988; Ellisen et al. 1991). This translocation joins roughly the 3′ half of TAN-1 head-to-head with the 3′ portion of the β T-cell-receptor gene (TCRB) beginning at the 5′ boundary of one or the other J segment. Intact TAN-1 is normally transcribed into an 8.2-kb transcript that is present in many tissues, most abundantly in developing thymus and spleen (Ellisen et al. 1991). This tissue distribution and the apparent involvement of an altered version of the gene in T-cell cancers have suggested that TAN-1 normally has some special function in lymphocytes or their precursors
Thrombosis Is Reduced by Inhibition of COX-1, but Unaffected by Inhibition of COX-2, in an Acute Model of Platelet Activation in the Mouse
This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
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