Can rigidly rotating polytropes be sources of the Kerr metric?

We use a recent result by Cabezas et al. to build up an approximate solution to the gravitational field created by a rigidly rotating polytrope. We solve the linearized Einstein equations inside and outside the surface of zero pressure including second-order corrections due to rotational motion to get an asymptotically flat metric in a global harmonic coordinate system. We prove that if the metric and their first derivatives are continuous on the matching surface up to this order of approximation, the multipole moments of this metric cannot be fitted to those of the Kerr metric.Comment: LaTeX, 17 pages, submitted to CQ

Applications of low enthalpy geothermal energy: the case of the Faculty of Physical and Mathematical Sciences at the University of Chile

In recent decades, the industry has observed a significant shift towards the use of renewable energy, such as solar, wind and geothermal. The Chilean scenario has not been an exception, and much progress has been made in sustainable energy prospection and implementation, especially in the electricity sector, where solar and wind power amount 2300 MW, and since April 2017, the first geothermal power plant (48 MW) has come into operation. In the area of low enthalpy geothermal energy, the use is around 19 MW. The Faculty of Physical and Mathematical Sciences at the University of Chile has been contributing to this transformational process, with its Sustainable Campus initiative. The first step of this initiative is the introduction of renewable energy on site, which has been achieved through the installation of a solar photovoltaic plant of 15 kW. Along this line, the design and implementation of a geothermal air conditioning system (HAVC) is underway, which will serve the classrooms and offices in the traditional engineering building of the campus. The technology to be used in this project is the Ground Heat Pump (GHP). The present paper includes an introduction of the applications of low enthalpy geothermal energy in Chile, a description of the Office of Engineering for Sustainable Development at the Faculty of Physical and Mathematical Sciences, and the design of a geothermal HAVC system in the university campus, considering economic, environmental, technical and social aspects. Besides the operation of the GHP, the system will be used for teaching purposes to incorporate sustainable development in the curriculum of the university. The expected savings of the geothermal system versus an aerothermal design are 41,070 kWh annually, considering both cooling and heating.This research was partially funded by the Andean Geothermal Center of Excellence (CEGA) and the Complex Engineering Systems Institute, ISCI (Project CONICYT: FB0816)

One-shot domain adaptation in multiple sclerosis lesion segmentation using convolutional neural networks

In recent years, several convolutional neural network (CNN) methods have been proposed for the automated white matter lesion segmentation of multiple sclerosis (MS) patient images, due to their superior performance compared with those of other state-of-the-art methods. However, the accuracies of CNN methods tend to decrease significantly when evaluated on different image domains compared with those used for training, which demonstrates the lack of adaptability of CNNs to unseen imaging data. In this study, we analyzed the effect of intensity domain adaptation on our recently proposed CNN-based MS lesion segmentation method. Given a source model trained on two public MS datasets, we investigated the transferability of the CNN model when applied to other MRI scanners and protocols, evaluating the minimum number of annotated images needed from the new domain and the minimum number of layers needed to re-train to obtain comparable accuracy. Our analysis comprised MS patient data from both a clinical center and the public ISBI2015 challenge database, which permitted us to compare the domain adaptation capability of our model to that of other state-of-the-art methods. For the ISBI2015 challenge, our one-shot domain adaptation model trained using only a single image showed a performance similar to that of other CNN methods that were fully trained using the entire available training set, yielding a comparable human expert rater performance. We believe that our experiments will encourage the MS community to incorporate its use in different clinical settings with reduced amounts of annotated data. This approach could be meaningful not only in terms of the accuracy in delineating MS lesions but also in the related reductions in time and economic costs derived from manual lesion labeling

Plantas de cobertura de solo para sistema plantio direto.

A camada de palha, sobre o solo, e essencial para o sucesso do Sistema Plantio Direto (SPD). Cria um ambiente extremamente favoravel as condicoes fisicas, quimicas e biologicas do solo contribuindo para o controle de plantas daninhas, estabilizacao da producao e recuperacao ou manutencao da qualidade do solo. O sistema de rotacao e sucessao de culturas deve ser adequado para permitir a manutencao de uma cobertura minima do solo com palha. Na escolha destas plantas, e fator decisivo conhecer a sua adaptacao a regiao e sua habilidade em crescer num ambiente menos favoravel, uma vez que as culturas comerciais sao estabelecidas nas epocas mais propicias. Isto e especialmente verdade nas condicoes de Brasil Central, onde o inverno e seco, ao passo que na regiao Sul, de inverno umido, nao existe essa limitacao e ha maior opcao de plantas adaptadas as condicoes do inverno. Existem muitas plantas de cobertura para as diferentes regioes edafoclimaticas do Brasil, e a experiencia local e decisiva nesta selecao. Em qualquer situacao, deve-se ter sempre em mente que nao existe uma planta milagrosa e que o ideal e ter mais de uma dessas especies no sistema de producao, onde busca-se aliar renda a preservacao ambiental

Theoretical insight on the LK-99 material

Two recent preprints in physics archive (arXiv) have called the attention as they claim experimental evidence that a Cu-substituted apatite material (called LK-99) exhibits superconductivity at room temperature and pressure. If this proves to be true, LK-99 will be the holy grail of superconductors. In this work, we used Density-Functional Theory calculations to elucidate some key features of the electronic structure of LK-99. Although some aspects of our calculations are preliminary, we found that: i) in the ground state of the material the ferromagnetic and antiferromagnetic configurations are practically degenerated, ii) the material is metallic, iii) the Cu atoms seem to be hosts in the lattice with not covalent bonds to other atoms and supporting almost flat bands around the Fermi level, and iv) the electron-phonon coupling of these flat bands seems to be dramatically large

Dental Education Required for the Changing Health Care Environment

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153648/1/jddjde017022.pd

Determinants of Non-Mining Exports: A Regional Perspective

The Chilean non-mining export sector has experienced a substantial increase over the last years, although exports to the main regions have evolved with different patterns. This work analyzes the role of the real exchange rate and world economic activity during the 1990-2001 period, after performing an extensive refinement and cleaning of export bundles by region. Based on a multivariate cointegration analysis, we find different effects of the real exchange rate and world output on the exported quantum. The long-run elasticity of the real exchange rate goes from 0.2 to 0.8 percent for Europe, Asia and United States, and it is non significant for Aladi countries, for which a lower effect of this latter variable is found as a determinant of regional exports. On the other hand, elasticity with respect to world output ranges between 2.3 and 4 percent for the United States, and between 1.2 and 2 percent for the other regions. A panel analysis supports the view that world output plays a significant role,while the real exchange rate is less important. Finally, our preliminary evidence suggests that foreign country tariff reductions may increase regional exports.

The effect of inoculum source and fluid shear force on the development of in vitro oral multispecies biofilms

AimsSaliva has been previously used as an inoculum for in vitro oral biofilm studies. However, the microbial community profile of saliva is markedly different from hardâ and softâ tissueâ associated oral biofilms. Here, we investigated the changes in the biofilm architecture and microbial diversity of in vitro oral biofilms developed from saliva, tongue or plaqueâ derived inocula under different salivary shear forces.Methods and ResultsFour inoculum types (saliva, bacteria harvested from the tongue, toothbrush and curetteâ harvested plaque) were collected and pooled. Biofilms (n ⠥ 15) were grown for 20 h in cellâ free human saliva flowing at three different shear forces. Stained biofilms were imaged using a confocal laser scanning microscope. Biomass, thickness and roughness were determined by image analysis and bacterial community composition analysed using Ion Torrent. All developed biofilms showed a significant reduction in observed diversity compared with their respective original inoculum. Shear force altered biofilm architecture of saliva and curetteâ collected plaque and community composition of saliva, tongue and curetteâ harvested plaque.ConclusionsDifferent intraoral inocula served as precursors of in vitro oral polymicrobial biofilms which can be influenced by shear.Significance and Impact of the StudyInoculum selection and shear force are key factors to consider when developing multispecies biofilms within in vitro models.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136333/1/jam13376-sup-0001-FigS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136333/2/jam13376-sup-0002-TableS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136333/3/jam13376_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136333/4/jam13376.pd

Association Between Dental Studentâ Developed Exam Questions and Learning at Higher Cognitive Levels

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153610/1/jddj0022033720157911tb06025x.pd