2,352 research outputs found
Career situation of female astronomers in Germany
We survey the job situation of women in astronomy in Germany and of German
women abroad and review indicators for their career development. Our sample
includes women astronomers from all academic levels from doctoral students to
professors, as well as female astronomers who have left the field. We find that
networking and human support are among the most important factors for success.
Experience shows that students should carefully choose their supervisor and
collect practical knowledge abroad. We reflect the private situation of female
German astronomers and find that prejudices are abundant, and are perceived as
discriminating.We identify reasons why women are more likely than men to quit
astronomy after they obtain their PhD degree. We give recommendations to young
students on what to pay attention to in order to be on the successful path in
astronomy.Comment: published in Astronomical Note
Careers in astronomy in Germany and the UK
We discuss the outcomes of surveys addressing the career situation of
astronomers in Germany and the UK, finding social and cultural differences
between communities as well as gender bias in both.Comment: Astronomy and Geophysics. 13 page pdf with colour image
Hybrid propulsion system with a gyro component for economic and dynamic operation
The design of a hybrid drive with gyro components is described and its drive components for a medium class private car are discussed. The gyro component affects the short-period output of the drive by accelerating and slowing down and -- because of the mechanical transfer of kinetic energy between the gyro and the vehicle -- it affects also the energy balance in the case of intermittent operation. Energy can be taken in as desired either in the form of fuel or as fuel and current. A high energy recovery efficiency as well as the favorable operating range of the interval combustion engine makes it possible to reduce the fuel consumption per unit distance travelled to almost half that for a private car with a traditional engine
Hybrid propulsion systems for motor vehicles with predominantly intermittent modes of operation
A small delivery vehicle was equipped with a flywheel-hybrid drive and compared in test stand and driving tests with a conventional drive vehicle. It turned out that with the hybrid drive, energy can be saved and exhaust emissions can be reduced
The Influence of Dust Formation Modelling on Na I and K I Line Profiles in Substellar Atmospheres
We aim to understand the correlation between cloud formation and alkali line
formation in substellar atmospheres.We perform line profile calculations for Na
I and K I based on the coupling of our kinetic model for the formation and
composition of dust grains with 1D radiative transfer calculations in
atmosphere models for brown dwarfs and giant gas planets. The Na I and K I line
profiles sensibly depend on the way clouds are treated in substellar atmosphere
simulations. The kinetic dust formation model results in the highest
pseudo-continuum compared to the limiting cases.Comment: 5 pages, Accepted for publication in MNRA
Groups of Fibonacci type revisited
This article concerns a class of groups of Fibonacci type introduced by Johnson and Mawdesley that includes Conway?s Fibonacci groups, the Sieradski groups, and the Gilbert-Howie groups. This class of groups provides an interesting focus for developing the theory of cyclically presented groups and, following questions by Bardakov and Vesnin and by Cavicchioli, Hegenbarth, and Repov?s, they have enjoyed renewed interest in recent years. We survey results concerning their algebraic properties, such as isomorphisms within the class, the classification of the finite groups, small cancellation properties, abelianizations, asphericity, connections with Labelled Oriented Graph groups, and the semigroups of Fibonacci type. Further, we present a new method of proving the classification of the finite groups that deals with all but three groups
Hamiltonian and physical Hilbert space in polymer quantum mechanics
In this paper, a version of polymer quantum mechanics, which is inspired by
loop quantum gravity, is considered and shown to be equivalent, in a precise
sense, to the standard, experimentally tested, Schroedinger quantum mechanics.
The kinematical cornerstone of our framework is the so called polymer
representation of the Heisenberg-Weyl (H-W) algebra, which is the starting
point of the construction. The dynamics is constructed as a continuum limit of
effective theories characterized by a scale, and requires a renormalization of
the inner product. The result is a physical Hilbert space in which the
continuum Hamiltonian can be represented and that is unitarily equivalent to
the Schroedinger representation of quantum mechanics. As a concrete
implementation of our formalism, the simple harmonic oscillator is fully
developed.Comment: 19 pages, 2 figures. Comments and references added. Version to be
published in CQ
Did Fomalhaut, HR 8799, and HL Tauri Form Planets via the Gravitational Instability? Placing Limits on the Required Disk Masses
Disk fragmentation resulting from the gravitational instability has been
proposed as an efficient mechanism for forming giant planets. We use the planet
Fomalhaut b, the triple-planetary system HR 8799, and the potential protoplanet
associated with HL Tau to test the viability of this mechanism. We choose the
above systems since they harbor planets with masses and orbital characteristics
favored by the fragmentation mechanism. We do not claim that these planets must
have formed as the result of fragmentation, rather the reverse: if planets can
form from disk fragmentation, then these systems are consistent with what we
should expect to see. We use the orbital characteristics of these recently
discovered planets, along with a new technique to more accurately determine the
disk cooling times, to place both lower and upper limits on the disk surface
density--and thus mass--required to form these objects by disk fragmentation.
Our cooling times are over an order of magnitude shorter than those of Rafikov
(2005),which makes disk fragmentation more feasible for these objects. We find
that the required mass interior to the planet's orbital radius is ~0.1 Msun for
Fomalhaut b, the protoplanet orbiting HL Tau, and the outermost planet of HR
8799. The two inner planets of HR 8799 probably could not have formed in situ
by disk fragmentation.Comment: 5 pages, 1 figure, accepted for publication in ApJ
M dwarf stars in the light of (future) exoplanet searches
We present a brief overview of a splinter session on M dwarf stars as planet
hosts that was organized as part of the Cool Stars 17 conference. The session
was devoted to reviewing our current knowledge of M dwarf stars and exoplanets
in order to prepare for current and future exoplanet searches focusing in low
mass stars. We review the observational and theoretical challenges to
characterize M dwarf stars and the importance of accurate fundamental
parameters for the proper characterization of their exoplanets and our
understanding on planet formation.Comment: 4 pages, 1 figure. Summary of the splinter session "M dwarf stars in
the light of (future) exoplanet searches" held at the 17th Cambridge Workshop
on Cool Stars, Stellar Systems, and the Sun, June 28th 2012, Barcelona,
Spain. Submitted for publication in Astronomische Nachrichten - Astronomical
Notes (AN) 334, Issue 1-2, Eds Klaus Strassmeier and Mercedes L\'opez-Morale
Structure Space of Model Proteins --A Principle Component Analysis
We study the space of all compact structures on a two-dimensional square
lattice of size . Each structure is mapped onto a vector in
-dimensions according to a hydrophobic model. Previous work has shown that
the designabilities of structures are closely related to the distribution of
the structure vectors in the -dimensional space, with highly designable
structures predominantly found in low density regions. We use principal
component analysis to probe and characterize the distribution of structure
vectors, and find a non-uniform density with a single peak. Interestingly, the
principal axes of this peak are almost aligned with Fourier eigenvectors, and
the corresponding Fourier eigenvalues go to zero continuously at the
wave-number for alternating patterns (). These observations provide a
stepping stone for an analytic description of the distribution of structural
points, and open the possibility of estimating designabilities of realistic
structures by simply Fourier transforming the hydrophobicities of the
corresponding sequences.Comment: 14 pages, 12 figures, Conclusion has been modifie
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