1,546 research outputs found
Internationalization and Financial Federalism: The United States and Germany at the Crossroads?
In this article, the authors examine some effects of economic internationalization on state structures, especially in regard to the distribution of power and authority within federalist systems. Using an institutional rational choice model, they analyze changes in financial regulation and market structures in Germany and the United States. The focus is on the financial realm because of its high degree of internationalization and because, in both countries, financial markets and regulation have historically exhibited federalist traits. The findings indicate that internationalization has led to significant convergence in financial market structures and regulation across the two countries and that in each case this convergence has been accompanied by centralization of financial regulatory authority. Although both the German type of cooperative federalism and the U.S. model of competitive federalism proved to be vulnerable to the growing international pressures, the two countries took different paths of change that reflected differences in domestic institutions. Thus, the authors conclude that convergence is, and will likely remain, of a limited nature
Drude weight and total optical weight in a t-t'-J model
We study the Drude weight D and the total optical weight K for a t-t'-J model
on a square lattice that exhibits a metallic phase-modulated antiferromagnetic
ground state close to half-filling. Within a suitable 1/N expansion that
includes leading quantum-fluctuation effects, D and K are found to increase
linearly with small hole doping away from the Mott metal-insulator transition
point at half-filling. The slow zero-sound velocity near the latter transition
identifies with the velocity of the lower-energy branch of the twofold
excitation spectrum. At higher doping values, D and K eventually saturate and
then start to decrease. These features are in qualitative agreement with
optical conductivity measurements in doped antiferromagnets.Comment: 7 pages, REVTEX file (3 Postscript figures). To appear in J. Phys.:
Condens. Mattte
Retinal glycoprotein enrichment by concanavalin a enabled identification of novel membrane autoantigen synaptotagmin-1 in equine recurrent uveitis.
Complete knowledge of autoantigen spectra is crucial for understanding pathomechanisms of autoimmune diseases like equine recurrent uveitis (ERU), a spontaneous model for human autoimmune uveitis. While several ERU autoantigens were identified previously, no membrane protein was found so far. As there is a great overlap between glycoproteins and membrane proteins, the aim of this study was to test whether pre-enrichment of retinal glycoproteins by ConA affinity is an effective tool to detect autoantigen candidates among membrane proteins. In 1D Western blots, the glycoprotein preparation allowed detection of IgG reactions to low abundant proteins in sera of ERU patients. Synaptotagmin-1, a Ca2+-sensing protein in synaptic vesicles, was identified as autoantigen candidate from the pre-enriched glycoprotein fraction by mass spectrometry and was validated as a highly prevalent autoantigen by enzyme-linked immunosorbent assay. Analysis of Syt1 expression in retinas of ERU cases showed a downregulation in the majority of ERU affected retinas to 24%. Results pointed to a dysregulation of retinal neurotransmitter release in ERU. Identification of synaptotagmin-1, the first cell membrane associated autoantigen in this spontaneous autoimmune disease, demonstrated that examination of tissue fractions can lead to the discovery of previously undetected novel autoantigens. Further experiments will address its role in ERU pathology
Detecting circumbinary planets using eclipse timing of binary stars - numerical simulations
The presence of a body in an orbit around a close eclipsing binary star
manifests itself through the light time effect influencing the observed times
of eclipses as the close binary and the circumbinary companion both move around
the common centre of mass. This fact combined with the periodicity with which
the eclipses occur can be used to detect the companion. Given a sufficient
precision of the times of eclipses, the eclipse timing can be employed to
detect substellar or even planetary mass companions.
The main goal of the paper is to investigate the potential of the photometry
based eclipse timing of binary stars as a method of detecting circumbinary
planets. In the models we assume that the companion orbits a binary star in a
circular Keplerian orbit. We analyze both the space and ground based photometry
cases. In particular, we study the usefulness of the on-going COROT and Kepler
missions in detecting circumbinary planets. We also explore the relations
binding the planet discovery space with the physical parameters of the binaries
and the geometrical parameters of their light curves. We carry out detailed
numerical simulations of the eclipse timing by employing a relatively realistic
model of the light curves of eclipsing binary stars. We study the influence of
the white and red photometric noises on the timing precision. We determine the
sensitivity of the eclipse timing technique to circumbinary planets for the
ground and space based photometric observations. We provide suggestions for the
best targets, observing strategies and instruments for the eclipse timing
method. Finally, we compare the eclipse timing as a planet detection method
with the radial velocities and astrometry.Comment: 9 pages, 15 figures, accepted for publication in MNRA
Recommended from our members
Biporous Metal-Organic Framework with Tunable CO2/CH4 Separation Performance Facilitated by Intrinsic Flexibility.
In this work, we report the synthesis of SION-8, a novel metal-organic framework (MOF) based on Ca(II) and a tetracarboxylate ligand TBAPy4- endowed with two chemically distinct types of pores characterized by their hydrophobic and hydrophilic properties. By altering the activation conditions, we gained access to two bulk materials: the fully activated SION-8F and the partially activated SION-8P with exclusively the hydrophobic pores activated. SION-8P shows high affinity for both CO2 ( Qst = 28.4 kJ/mol) and CH4 ( Qst = 21.4 kJ/mol), while upon full activation, the difference in affinity for CO2 ( Qst = 23.4 kJ/mol) and CH4 ( Qst = 16.0 kJ/mol) is more pronounced. The intrinsic flexibility of both materials results in complex adsorption behavior and greater adsorption of gas molecules than if the materials were rigid. Their CO2/CH4 separation performance was tested in fixed-bed breakthrough experiments using binary gas mixtures of different compositions and rationalized in terms of molecular interactions. SION-8F showed a 40-160% increase (depending on the temperature and the gas mixture composition probed) of the CO2/CH4 dynamic breakthrough selectivity compared to SION-8P, demonstrating the possibility to rationally tune the separation performance of a single MOF by manipulating the stepwise activation made possible by the MOF's biporous nature
CoRoT 101186644: A transiting low-mass dense M-dwarf on an eccentric 20.7-day period orbit around a late F-star
We present the study of the CoRoT transiting planet candidate 101186644, also
named LRc01_E1_4780. Analysis of the CoRoT lightcurve and the HARPS
spectroscopic follow-up observations of this faint (m_V = 16) candidate
revealed an eclipsing binary composed of a late F-type primary (T_eff = 6090
+/- 200 K) and a low-mass, dense late M-dwarf secondary on an eccentric (e =
0.4) orbit with a period of ~20.7 days. The M-dwarf has a mass of 0.096 +/-
0.011 M_Sun, and a radius of 0.104 +0.026/-0.006 R_Sun, which possibly makes it
the smallest and densest late M-dwarf reported so far. Unlike the claim that
theoretical models predict radii that are 5%-15% smaller than measured for
low-mass stars, this one seems to have a radius that is consistent and might
even be below the radius predicted by theoretical models.Comment: Accepted for publication in Astronomy & Astrophysics, 8 pages, 10
figure
Ground-based photometry of space-based transit detections: Photometric follow-up of the CoRoT mission
The motivation, techniques and performance of the ground-based photometric
follow-up of transit detections by the CoRoT space mission are presented. Its
principal raison d'\^{e}tre arises from the much higher spatial resolution of
common ground-based telescopes in comparison to CoRoT's cameras. This allows
the identification of many transit candidates as arising from eclipsing
binaries that are contaminating CoRoT's lightcurves, even in low-amplitude
transit events that cannot be detected with ground-based obervations. For the
ground observations, 'on'-'off' photometry is now largely employed, in which
only a short timeseries during a transit and a section outside a transit is
observed and compared photometrically. CoRoT planet candidates' transits are
being observed by a dedicated team with access to telescopes with sizes ranging
from 0.2 to 2 m. As an example, the process that led to the rejection of
contaminating eclipsing binaries near the host star of the Super-Earth planet
CoRoT-7b is shown. Experiences and techniques from this work may also be useful
for other transit-detection experiments, when the discovery instrument obtains
data with a relatively low angular resolution.Comment: Accepted for the A&A special issue on CoRo
Linear response within the projection-based renormalization method: Many-body corrections beyond the random phase approximation
The explicit evaluation of linear response coefficients for interacting
many-particle systems still poses a considerable challenge to theoreticians. In
this work we use a novel many-particle renormalization technique, the so-called
projector-based renormalization method, to show how such coefficients can
systematically be evaluated. To demonstrate the prospects and power of our
approach we consider the dynamical wave-vector dependent spin susceptibility of
the two-dimensional Hubbard model and also determine the subsequent magnetic
phase diagram close to half-filling. We show that the superior treatment of
(Coulomb) correlation and fluctuation effects within the projector-based
renormalization method significantly improves the standard random phase
approximation results.Comment: 17 pages, 7 figures, revised versio
Searching For Transiting Circumbinary Planets in CoRoT and Ground-Based Data Using CB-BLS
Aims. We search for transiting circumbinary (CB) planets around eclipsing
binaries (EBs).
Methods. CB-BLS is a recently-introduced algorithm for the detection of
transiting CB planets around EBs.We describe progress in search sensitivity,
generality and capability of CB-BLS, and detection tests of CB-BLS on simulated
data. We also describe an analytical approach for the determination of CB-BLS
detection limits, and a method for the correct detrending of
intrinsically-variable stars.
Results. We present some blind-tests with simulated planets injected to real
CoRoT data. The presented upgrades to CB-BLS allowed it to detect all the blind
tests successfully, and these detections were in line with the detection limits
analysis. We also correctly detrend bright eclipsing binaries from observations
by the TrES planet search, and present some of the first results of applying
CB-BLS to multiple real light curves from a wide-field survey.
Conclusions. CB-BLS is now mature enough for its application to real data,
and the presented processing scheme will serve as the template for our future
applications of CB-BLS to data from wide-field surveys such as CoRoT. Being
able to put constraints even on non-detection will help to determine the
correct frequency of CB planets, contributing to the understanding of planet
formation in general. Still, searching for transiting CB planets is still a
learning experience, similarly to the state of transiting planets around single
stars only a few years ago. The recent rapid progress in this front, coupled
with the exquisite quality of space-based photometry, allows to realistically
expect that if transiting CB planets exist - then they will soon be found.Comment: A&A accepted. Presented at the 1st CoRoT symposium. Note table 3 is
too wide in this version, but omitted data is of minor significance. 10
pages, 10 figures, 3 table
- …