7,652 research outputs found
An ALMA Dynamical Mass Estimate of the Proposed Planetary-mass Companion FW Tau C
Dynamical mass estimates down to the planet-mass regime can help to
understand planet formation. We present Atacama Large Millimeter/submillimeter
Array (ALMA) 1.3 mm observations of FW Tau C, a proposed ~10
planet-mass companion at ~330 au from the host binary FW Tau AB. We spatially
and spectrally resolve the accretion disk of FW Tau C in CO (2-1). By
modeling the Keplerian rotation of gas, we derive a dynamical mass of ~0.1
. Therefore, FW Tau C is unlikely a planet, but rather a low-mass star
with a highly inclined disk. This also suggests that FW Tau is a triple system
consisting of three ~0.1 stars.Comment: Accepted for publication in ApJ
WL 17: A Young Embedded Transition Disk
We present the highest spatial resolution ALMA observations to date of the
Class I protostar WL 17 in the Ophiuchus L1688 molecular cloud complex,
which show that it has a 12 AU hole in the center of its disk. We consider
whether WL 17 is actually a Class II disk being extincted by foreground
material, but find that such models do not provide a good fit to the broadband
SED and also require such high extinction that it would presumably arise from
dense material close to the source such as a remnant envelope. Self-consistent
models of a disk embedded in a rotating collapsing envelope can nicely
reproduce both the ALMA 3 mm observations and the broadband SED of WL 17. This
suggests that WL 17 is a disk in the early stages of its formation, and yet
even at this young age the inner disk has been depleted. Although there are
multiple pathways for such a hole to be created in a disk, if this hole were
produced by the formation of planets it could place constraints on the
timescale for the growth of planetesimals in protoplanetary disks.Comment: 7 pages, 3 figures, 2 tables, accepted for publication in ApJ
Even Orientations and Pfaffian graphs
We give a characterization of Pfaffian graphs in terms of even orientations,
extending the characterization of near bipartite non--pfaffian graphs by
Fischer and Little \cite{FL}. Our graph theoretical characterization is
equivalent to the one proved by Little in \cite{L73} (cf. \cite{LR}) using
linear algebra arguments
Four Paradoxes Involving the Second Law of Thermodynamics
Recently four independent paradoxes have been proposed which appear to challenge the second law of thermodynamics [1-8]. These paradoxes are briefly reviewed. It is shown that each paradox results from a synergism of two broken symmetries - one geometric, one thermodynami
Response to ‘‘Comment on ‘A paradox involving the second law of thermodynamics’ ’’ [Phys. Plasmas 2, 1893 (1995)]
Casimir chemistry
It is shown that, at the nanoscale, the Casimir effect can be used to mechanically tune critical aspects of chemical reaction e.g., energies, equilibrium constants, activation energies, transition states, reaction rates by varying the spacing and composition of reaction vessel boundaries. This suggests new modalities for catalysts, nanoscale chemical manufacturing, chemical-mechanical engines, and biochemical processes in organisms
Limiting the Closely Regulated Business Exception to the Warrant Requirement: V-1 Oil Co. v. Wyoming, Department of Environmental Quality, 902 F.2d 1482
Nonequilibrium heterogeneous catalysis in the long mean-free-path regime
It is shown that a standard principle of traditional catalysis-that a catalyst does not alter the final thermodynamic equilibrium of a reaction-can fail in low-pressure, heterogeneous gas-surface reactions. Kinetic theory for this epicatalysis is presented, and two well-documented experimental examples are detailed: surface ionized plasmas and hydrogen dissociation on refractory metals. This phenomenon should be observable over a wide range of temperatures and pressures, and for a broad spectrum of heterogeneous reactions. By transcending some constraints of equilibrium thermodynamics, epicatalysis might provide additional control parameters and synthetic routes for reactions, and enable product streams boosted in thermochemical energy or desirable species
Energy, Entropy and the Environment (How to Increase the First by Decreasing the Second to Save the Third)
Energy is the lifeblood of civilization, but inexpensive, high energy density sources are rapidly being depleted and their exploitation is severely degrading the environment. This paper explores a radical solution to this energy-environmental dilemma. In the last 10–15 years, the universality of the second law of thermodynamics has fallen into serious theoretical doubt [1–3].Should it prove experimentally violable, this would open the door to a nearly limitless reservoir of ubiquitous, clean, recyclable energy. If economical, it could precipitate paradigm shifts in energy production, utilization and politics. In this paper, recent challenges to the second law are reviewed, with focus given to one for which laboratory experiments are planned. Possible consequences of its violation for technology, society and the environment are explored
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