20 research outputs found
Two-dimensional Einstein manifolds in geometrothermodynamics
We present a class of thermodynamic systems with constant thermodynamic
curvature which, within the context of geometric approaches of thermodynamics,
can be interpreted as constant thermodynamic interaction among their
components. In particular, for systems constrained by the vanishing of the
Hessian curvature we write down the systems of partial differential equations.
In such a case it is possible to find a subset of solutions lying on a
circumference in an abstract space constructed from the first derivatives of
the isothermal coordinates. We conjecture that solutions on the characteristic
circumference are of physical relevance, separating them from those of pure
mathematical interest. We present the case of a one-parameter family of
fundamental relations that -- when lying in the circumference -- describe a
polytropic fluid
Light propagation through optical media using metric contact geometry
In this work, we show that the orthogonality between rays and fronts of light
propagation in a medium is expressed in terms of a suitable metric contact
structure of the optical medium without boundaries. Moreover, we show that
considering interfaces (modeled as boundaries) orthogonality is no longer
fulfilled, leading to optical aberrations and in some cases total internal
reflection. We present some illustrative examples of this latter point.Comment: 8 pages, 7 figure
The Circumstellar Disk and Asymmetric outflow of the EX Lup Outburst System
We present Atacama Large Millimeter/submillimeter Array (ALMA) observations
at 0.3 arcsec-resolution of EX Lup, the prototype of the EXor class of
outbursting pre-main sequence stars. The circumstellar disk of EX Lup is
resolved for the first time in 1.3mm continuum emission and in the =2--1
spectral line of three isotopologues of CO. At the spatial resolution and
sensitivity achieved, the compact dust continuum disk shows no indications of
clumps, fragments, or asymmetries above 5-sigma level. Radiative transfer
modeling constrains the characteristic radius of the dust disk to 23 au and a
total dust mass of 1.010 M (33 M_earth), similar to
other EXor sources. The CO and CO line emission trace the disk
rotation and are used to constrain the disk geometry, kinematics, and a total
gas disk mass of 5.110 M. The CO emission extends
out to a radius of 200 au and is asymmetric, with one side deviating from
Keplerian rotation. We detect blue-shifted, CO arc-like emission located
0.8 arcsec to the north-west, and spatially disconnected from the disk
emission. We interpret this extended structure as the brightened walls of a
cavity excavated by an outflow, which are more commonly seen in FUor sources.
Such outflows have also been seen in the borderline FU/EXor object V1647 Ori,
but not towards EXor objects. Our detection provides evidence that the outflow
phenomenon persists into the EXor phase, suggesting that FUor and EXor objects
are a continuous population in which outflow activity declines with age, with
transitional objects such as EX Lup and V1647 Ori
A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)
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Resolving the Polarized Dust Emission of the Disk around the Massive Star Powering the HH 80-81 Radio Jet
Here we present deep (16 μJy beam), very high (40 mas) angular resolution 1.14 mm, polarimetric, Atacama Large Millimeter/submillimeter Array (ALMA) observations toward the massive protostar driving the HH 80-81 radio jet. The observations clearly resolve the disk oriented perpendicularly to the radio jet, with a radius of ≃0.″171 (∼291 au at 1.7 kpc distance). The continuum brightness temperature, the intensity profile, and the polarization properties clearly indicate that the disk is optically thick for a radius of R ≲ 170 au. The linear polarization of the dust emission is detected almost all along the disk, and its properties suggest that dust polarization is produced mainly by self-scattering. However, the polarization pattern presents a clear differentiation between the inner (optically thick) part of the disk and the outer (optically thin) region of the disk, with a sharp transition that occurs at a radius of ∼0.″1 (∼170 au). The polarization characteristics of the inner disk suggest that dust settling has not occurred yet with a maximum dust grain size between 50 and 500 μm. The outer part of the disk has a clear azimuthal pattern but with a significantly higher polarization fraction compared to the inner disk. This pattern is broadly consistent with the self-scattering of a radiation field that is beamed radially outward, as expected in the optically thin outer region, although contribution from non-spherical grains aligned with respect to the radiative flux cannot be excluded.© 2018. The American Astronomical Society. All rights reserved..This paper makes use of the following ALMA data: ADS/ JAO.ALMA#2015.1.00480.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan) and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. J.M.G., R.E., G.A., N.A.L., G.B., J.F.G., M.O., and J.M.T. are supported by the MINECO (Spain) AYA2014-57369-C3 and AYA2017-84390-C2 coordinated grants. S.C. acknowledges support from DGAPA, UNAM, and CONACyT, Mexico. H.Y. is supported in part by ALMA SOS, and Z.L.Y. by NASA NNX14AB38G and NSF AST-1313083 and 1715259. M.P. acknowledges funding from the European Unions Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 664931. I.J.S. acknowledges financial support from STFC through an Ernest Rutherford Fellowship (ST/L004801). J.M. acknowledges support from MINECO (Spain) AYA2016-76012-C3-3-P grant