332 research outputs found
The X-ray cycle in the solar-type star HD 81809
(abridged) Our long-term XMM-Newton program of long-term monitoring of a
solar-like star with a well-studied chromospheric cycle, HD 81809 aims to study
whether an X-ray cycle is present, along with studying its characteristics and
its relation to the chromospheric cycle. Regular observations of HD 81809 were
performed with XMM-Newton, spaced by 6 months from 2001 to 2007. We studied the
variations in the resulting coronal luminosity and temperature, and compared
them with the chromospheric CaII variations. We also modeled the observations
in terms of a mixture of active regions, using a methodology originally
developed to study the solar corona. Our observations show a well-defined cycle
with an amplitude exceeding 1 dex and an average luminosity approximately one
order of magnitude higher than in the Sun. The behavior of the corona of HD
81809 can be modeled well in terms of varying coverage of solar-like active
regions, with a larger coverage than for the Sun, showing it to be compatible
with a simple extension of the solar case.Comment: In press, Astronomy & Astrophysic
Humor with backgrounded incongruity: Does more required suspension of disbelief affect humor perception?
Humorous stimuli, like jokes and cartoons, are assumed to contain a central incongruity in a specific constellation of opposition and overlap that is essential to their humorousness. Many stimuli also contain additional incongruities that the audience usually overlooks, but that may be needed to create the setup for the main incongruity, e.g., animals that talk, space aliens, an Italian, an American, and a Russian sharing a language. Two of the studies described in the present paper investigated the effect of such backgrounded incongruities by removing them from a set of jokes and cartoons and testing how this affects humor processing and appreciation. A third study investigated whether the elimination of a backgrounded incongruity influences the position of a humorous stimulus on the incongruity-resolution and nonsense humor continuum. Methods included computer-based stimulus rating and self-explanations by the participants. The results suggested that backgrounded incongruities influence humor appreciation because their elimination leads to lower funniness and higher aversion. Furthermore, the backgrounded incongruities contribute strongly to the perceived absurdity of a joke. When they are removed, the jokes are perceived less to be nonsense humor but more as incongruity-resolution humo
High-amplitude, long-term X-ray variability in the solar-type star HD 81809: the beginning of an X-ray activity cycle?
We present the initial results from our XMM program aimed at searching for
X-ray activity cycles in solar-type stars. HD 81809 is a G2-type star (somewhat
more evolved than the Sun, and with a less massive companion) with a pronounced
8.2 yr chromospheric cycle, as evident from from the Mt. Wilson program data.
We present here the results from the initial 2.5 years of XMM observations,
showing that large amplitude (a factor of approx. 10) modulation is present in
the X-ray luminosity, with a clearly defined maximum in mid 2002 and a steady
decrease since then. The maximum of the chromospheric cycle took place in 2001;
if the observed X-ray variability is the initial part of an X-ray cycle, this
could imply a phase shift between chromospheric and coronal activity, although
the current descent into chromospheric cycle minimum is well reflected into the
star's X-ray luminosity. The observations presented here provide clear evidence
for the presence of large amplitude X-ray variability coherent with the
activity cycle in the chromosphere in a star other than the Sun.Comment: Accepted for publication in A&
Were they really laughed at? That much? Gelotophobes and their history of perceived derisibility
The List of Derisible Situations (LDS; Proyer, Hempelmann and Ruch, List of Derisible Situations (LDS), University of Zurich, 2008) consists of 102 different occasions for being laughed at. They were retrieved in a corpus study and compiled into the LDS. Based on this list, information on the frequency and the intensity with which people recall being laughed at during a given time-span (12 months in this study) can be collected. An empirical study (N = 114) examined the relations between the LDS and the fear of being laughed at (gelotophobia), the joy of being laughed at (gelotophilia), and the joy of laughing at others (katagelasticism; Ruch and Proyer this issue). More than 92% of the participants recalled having been laughed at at least once over the past 12 months. Highest scores were found for experiencing an embarrassing situation, chauvinism of others or being laughed at for doing something awkward or clumsy. Gelotophobia, gelotophilia, and katagelasticism were related about equally to the recalled frequency of events of being laughed at (with the lowest relation to katagelasticism). Gelotophobia, gelotophilia, and katagelasticism yielded a distinct and plausible pattern of correlations to the frequency of events of being laughed at. Gelotophobes recalled the situations of being laughed at with a higher intensity than others. Thus, the fear of being laughed at exists to a large degree independently from actual experiences of being laughed at, but is related to a higher intensity with which these events are experience
Coronal activity cycles in nearby G and K stars - XMM-Newton monitoring of 61 Cygni and Alpha Centauri
We use X-ray observations of the nearby binaries 61 Cyg A/B (K5V and K7V) and
Alpha Cen A/B (G2V and K1V) to study the long-term evolution of magnetic
activity in weakly to moderately active G + K dwarfs over nearly a decade.
Specifically we search for X-ray activity cycles and related coronal changes
and compare them to the solar behavior. For 61 Cyg A we find a regular coronal
activity cycle analog to its 7.3 yr chromospheric cycle. The X-ray brightness
variations are with a factor of three significantly lower than on the Sun, yet
the changes of coronal properties resemble the solar behavior with larger
variations occurring in the respective hotter plasma components. 61 Cyg B does
not show a clear cyclic coronal trend so far, but the X-ray data matches the
more irregular chromospheric cycle. Both Alpha Cen stars exhibit significant
long-term X-ray variability. Alpha Cen A shows indications for cyclic
variability of an order of magnitude with a period of about 12-15 years; the
Alpha Cen B data suggests an X-ray cycle with an amplitude of about six to
eight and a period of 8-9 years. The sample stars exhibit X-ray luminosities
ranging between Lx < 1x10^26 - 3x10^27 erg s^-1 in the 0.2-2.0 keV band and
have coronae dominated by cool plasma with variable average temperatures of
around 1.0-2.5 MK. We find that coronal activity cycles are apparently a common
phenomenon in older, slowly rotating G and K stars. The spectral changes of the
coronal X-ray emission over the cycles are solar-like in all studied targets.Comment: 11 pages, 9 figures, accepted by Astronomy and Astrophysic
Sustainable Electrochemical Depolymerization of Lignin in Reusable Ionic Liquids
Lignin’s aromatic building blocks provide a chemical resource that is, in theory, ideal for substitution of
aromatic petrochemicals. Moreover, degradation and valorization of lignin has the potential to generate
many high-value chemicals for technical applications. In this study, electrochemical degradation
of alkali and Organosolv lignin was performed using the ionic liquids 1-ethyl-3-methylimidazolium
trifluoromethanesulfonate and triethylammonium methanesulfonate. The extensive degradation of
the investigated lignins with simultaneous almost full recovery of the electrolyte materials provided
a sustainable alternative to more common lignin degradation processes. We demonstrate here that
both the presence (and the absence) of water during electrolysis and proton transport reactions had
significant impact on the degradation efficiency. Hydrogen peroxide radical formation promoted certain
electrochemical mechanisms in electrolyte systems “contaminated” with water and increased yields of
low molecular weight products significantly. The proposed mechanisms were tentatively confirmed by
determining product distributions using a combination of liquid chromatography-mass spectrometry
and gas-chromatography-mass spectrometry, allowing measurement of both polar versus non-polar as
well as volatile versus non-volatile components in the mixtures
Ages for illustrative field stars using gyrochronology: viability, limitations and errors
We here develop an improved way of using a rotating star as a clock, set it
using the Sun, and demonstrate that it keeps time well. This technique, called
gyrochronology, permits the derivation of ages for solar- and late-type main
sequence stars using only their rotation periods and colors. The technique is
clarified and developed here, and used to derive ages for illustrative groups
of nearby, late-type field stars with measured rotation periods. We first
demonstrate the reality of the interface sequence, the unifying feature of the
rotational observations of cluster and field stars that makes the technique
possible, and extends it beyond the proposal of Skumanich by specifying the
mass dependence of rotation for these stars. We delineate which stars it cannot
currently be used on. We then calibrate the age dependence using the Sun. The
errors are propagated to understand their dependence on color and period.
Representative age errors associated with the technique are estimated at ~15%
(plus possible systematic errors) for late-F, G, K, & early-M stars. Ages
derived via gyrochronology for the Mt. Wilson stars are shown to be in good
agreement with chromospheric ages for all but the bluest stars, and probably
superior. Gyro ages are then calculated for each of the active main sequence
field stars studied by Strassmeier and collaborators where other ages are not
available. These are shown to be mostly younger than 1Gyr, with a median age of
365Myr. The sample of single, late-type main sequence field stars assembled by
Pizzolato and collaborators is then assessed, and shown to have gyro ages
ranging from under 100Myr to several Gyr, and a median age of 1.2Gyr. Finally,
we demonstrate that the individual components of the three wide binaries
XiBooAB, 61CygAB, & AlphaCenAB yield substantially the same gyro ages.Comment: 58 pages, 18 color figures, accepted for publication in The
Astrophysical Journal; Age uncertainties slightly modified upon correcting an
algebraic error in Section
Natural Language Watermarking and Tamperproofing
Two main results in the area of information hiding in natural language text are presented. A semantically-based scheme dramatically improves the information-hiding capacity of any text through two techniques: (i) modifying the granularity of meaning of individual sentences, whereas our own previous scheme kept the granularity fixed, and (ii) halving the number of sentences affected by the watermark. No longer a "long text, short watermark" approach, it now makes it possible to watermark short texts like wire agency reports. Using both the above-mentioned semantic marking scheme and our previous syntactically-based method hides information in a way that reveals any non-trivial tampering with the text (while re-formatting is not considered to be tampering---the problem would be solved trivially otherwise by hiding a hash of the text) with a probability 1--2 , n being its number of sentences and a small positive integer based on the extent of co-referencing
Dynamics, cation conformation and rotamers in guanidinium ionic liquids with ether groups
Ionic liquids are modern materials with a broad range of applications, including electrochemical devices, the exploitation of sustainable resources and chemical processing. Expanding the chemical space to include novel ion classes allows for the elucidation of novel structure-property relationships and fine tuning for specific applications. We prepared a set of ionic liquids based on the sparsely investigated pentamethyl guanidinium cation with a 2-ethoxy-ethyl side chain in combination with a series of frequently used anions. The resulting properties are compared to a cation with a pentyl side chain lacking ether functionalization. We measured the thermal transitions and transport properties to estimate the performance and trends of this cation class. The samples with imide-type anions form liquids at ambient temperature, and show good transport properties, comparable to imidazolium or ammonium ionic liquids. Despite the dynamics being significantly accelerated, ether functionalization of the cation favors the formation of crystalline solids. Single crystal structure analysis, ab initio calculations and variable temperature nuclear magnetic resonance measurements (VT-NMR) revealed that cation conformations for the ether- and alkyl-chain-substituted are different in both the solid and liquid states. While ether containing cations adopt compact, curled structures, those with pentyl side chains are linear. The Eyring plot revealed that the curled conformation is accompanied by a higher activation energy for rotation around the carbon-nitrogen bonds, due to the coordination of the ether chain as observed by VT-NMR
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