2,794 research outputs found
Lightning and charge processes in brown dwarf and exoplanet atmospheres
The study of the composition of brown dwarf atmospheres helped to understand
their formation and evolution. Similarly, the study of exoplanet atmospheres is
expected to constrain their formation and evolutionary states. We use results
from 3D simulations, kinetic cloud formation and kinetic ion-neutral chemistry
to investigate ionisation processes which will affect their atmosphere
chemistry: The dayside of super-hot Jupiters is dominated by atomic hydrogen,
and not HO. Such planetary atmospheres exhibit a substantial degree of
thermal ionisation and clouds only form on the nightside where lightning leaves
chemical tracers (e.g. HCN) for possibly long enough to be detectable. External
radiation may cause exoplanets to be enshrouded in a shell of highly ionised,
H-forming gas and a weather-driven aurora may emerge. Brown dwarfs enable
us to study the role of electron beams for the emergence of an extrasolar,
weather-system driven aurora-like chemistry, and the effect of strong magnetic
fields on cold atmospheric gases. Electron beams trigger the formation of
H in the upper atmosphere of a brown dwarf (e.g. LSR-J1835) which may
react with it to form hydronium, HO, as a longer lived chemical tracer.
Brown dwarfs and super-hot gas giants may be excellent candidates to search for
HO as an H product.Comment: 16 pages, accepted for publication in the Philosophical Transactions
A of the Royal Society, (some typos corrected
Exo-lightning radio emission: the case study of HAT-P-11b
Lightning induced radio emission has been observed on solar system planets.
Lecavelier des Etangs et al. [2013] carried out radio transit observations of
the exoplanet HAT-P-11b, and suggested a tentative detection of a radio signal.
Here, we explore the possibility of the radio emission having been produced by
lightning activity on the exoplanet, following and expanding the work of
Hodos\'an et al. [2016a]. After a summary of our previous work [Hodos\'an et
al. 2016a], we extend it with a parameter study. The lightning activity of the
hypothetical storm is largely dependent on the radio spectral roll-off, ,
and the flash duration, . The best-case scenario would
require a flash density of the same order of magnitude as can be found during
volcanic eruptions on Earth. On average, times larger flash
densities than the Earth-storms with the largest lightning activity is needed
to produce the observed signal from HAT-P-11b. Combined with the results of
Hodos\'an et al. [2016a] regarding the chemical effects of planet-wide
thunderstorms, we conclude that future radio and infrared observations may lead
to lightning detection on planets outside the solar system.Comment: Accepted to the Conference Proceedings of the 8th International
Workshop on Planetary, Solar and Heliospheric Radio Emissions (PRE 8), held
in Seggauberg near Leibnitz/Graz, Austria, October 25-27, 2016. 12 pages, 2
figure
Patterns of innovation and protection activities within service companies: Results from a German study on service-intensive companies
There is an increasing number of researchers conducting empirical and theoretical investigations to better understand innovation and protection activities of service companies. In fact, previous analyses reveal that the protection topic is difficult to study, particularly when using traditional measurement concepts like patents. Thus, a different analytical conceptual frame has been developed in order to investigate deeper knowledge about service innovation protection and corporate strategic behaviour. --Service innovation,Protection strategies,Service companies,Study,Germany
Jupiter as a Giant Cosmic Ray Detector
We explore the feasibility of using the atmosphere of Jupiter to detect
Ultra-High-Energy Cosmic Rays (UHECR's). The large surface area of Jupiter
allows us to probe cosmic rays of higher energies than previously accessible.
Cosmic ray extensive air showers in Jupiter's atmosphere could in principle be
detected by the Large Area Telescope (LAT) on the Fermi observatory. In order
to be observed, these air showers would need to be oriented toward the Earth,
and would need to occur sufficiently high in the atmosphere that the gamma rays
can penetrate. We demonstrate that, under these assumptions, Jupiter provides
an effective cosmic ray "detector" area of km. We predict
that Fermi-LAT should be able to detect events of energy eV with
fluence erg cm at a rate of about one per month. The observed
number of air showers may provide an indirect measure of the flux of cosmic
rays eV. Extensive air showers also produce a synchrotron
signature that may be measurable by ALMA. Simultaneous observations of Jupiter
with ALMA and Fermi-LAT could be used to provide broad constraints on the
energies of the initiating cosmic rays.Comment: 8 pages, 5 figures. Accepted for publication in the Astrophysical
Journal Letter
Frictional dissipation of polymeric solids vs interfacial glass transition
We present single contact friction experiments between a glassy polymer and
smooth silica substrates grafted with alkylsilane layers of different coverage
densities and morphologies. This allows us to adjust the polymer/substrate
interaction strength. We find that, when going from weak to strong interaction,
the response of the interfacial junction where shear localizes evolves from
that of a highly viscous threshold fluid to that of a plastically deformed
glassy solid. This we analyse as resulting from an interaction-induced
``interfacial glass transition'' helped by pressure
Approximating open quantum system dynamics in a controlled and efficient way: A microscopic approach to decoherence
We demonstrate that the dynamics of an open quantum system can be calculated
efficiently and with predefined error, provided a basis exists in which the
system-environment interactions are local and hence obey the Lieb-Robinson
bound. We show that this assumption can generally be made. Defining a dynamical
renormalization group transformation, we obtain an effective Hamiltonian for
the full system plus environment that comprises only those environmental
degrees of freedom that are within the effective light cone of the system. The
reduced system dynamics can therefore be simulated with a computational effort
that scales at most polynomially in the interaction time and the size of the
effective light cone. Our results hold for generic environments consisting of
either discrete or continuous degrees of freedom
Metabolite-mediated catalyst conversion of PFK and PFP
Metabolites known to occur in the cytosol of photosynthetic leaf cells were found to mediate the reversible conversion of pyrophosphate—D-fructose-6-phosphate 1-phosphotransferase (PFP) to phosphofructokinase (PFK) in partially purified preparations from spinach leaves. Preincubation of PFP with fructose 2,6-bisphosphate, ATP or fructose 6-phosphate converted PFP to PFK. The reverse reaction (PFK → PFP) was promoted by UDP-glucose plus pyrophosphate. These conversions in catalytic capability were accompanied by changes in molecular mass and charge. The results are in accord with the view that the alterations in PFP and PFK activity, provisionally called ‘metabolite-mediated catalyst conversion’, represent a regulatory mechanism to direct left cytosolic carbon flux in either the biosynthetic or degradatory direction
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