2,116 research outputs found
Resampling-based confidence regions and multiple tests for a correlated random vector
We derive non-asymptotic confidence regions for the mean of a random vector
whose coordinates have an unknown dependence structure. The random vector is
supposed to be either Gaussian or to have a symmetric bounded distribution, and
we observe i.i.d copies of it. The confidence regions are built using a
data-dependent threshold based on a weighted bootstrap procedure. We consider
two approaches, the first based on a concentration approach and the second on a
direct boostrapped quantile approach. The first one allows to deal with a very
large class of resampling weights while our results for the second are
restricted to Rademacher weights. However, the second method seems more
accurate in practice. Our results are motivated by multiple testing problems,
and we show on simulations that our procedures are better than the Bonferroni
procedure (union bound) as soon as the observed vector has sufficiently
correlated coordinates.Comment: submitted to COL
Amici Curiae in Support of Appellant and Urging Reversal in the Case of Stephen Thaler v. U. S. Copyright Office in the U. S. Court of Appeals for the District of Columbia (Case No. 23-5233) (2024)
CO adsorption on Cu(111) and Cu(001) surfaces: improving site preference in DFT calculations
CO adsorption on Cu(111) and Cu(001) surfaces has been studied within
ab-initio density functional theory (DFT). The structural, vibrational and
thermodynamic properties of the adsorbate-substrate complex have been
calculated. Calculations within the generalized gradient approximation (GGA)
predict adsorption in the threefold hollow on Cu(111) and in the bridge-site on
Cu(001), instead of on-top as found experimentally. It is demonstrated that the
correct site preference is achieved if the underestimation of the HOMO-LUMO gap
of CO characteristic for DFT is correct by applying a molecular DFT+U approach.
The DFT+U approach also produces good agreement with the experimentally
measured adsorption energies, while introducing only small changes in the
calculated geometrical and vibrational properties further improving agreement
with experiment which is fair already at the GGA level.Comment: 15 pages, 3 figures, submitted to Surf. Sci., WWW:
http://cms.mpi.univie.ac.at/mgajdos
On-Sky Demonstration of a Linear Band-limited Mask with Application to Visual Binary Stars
We have designed and built the first band-limited coronagraphic mask used for
ground-based high-contrast imaging observations. The mask resides in the focal
plane of the near-infrared camera PHARO at the Palomar Hale telescope and
receives a well-corrected beam from an extreme adaptive optics system. Its
performance on-sky with single stars is comparable to current state-of-the-art
instruments: contrast levels of or better at 0.8" in after
post-processing, depending on how well non-common-path errors are calibrated.
However, given the mask's linear geometry, we are able to conduct additional
unique science observations. Since the mask does not suffer from pointing
errors down its long axis, it can suppress the light from two different stars
simultaneously, such as the individual components of a spatially resolved
binary star system, and search for faint tertiary companions. In this paper, we
present the design of the mask, the science motivation for targeting binary
stars, and our preliminary results, including the detection of a candidate
M-dwarf tertiary companion orbiting the visual binary star HIP 48337, which we
are continuing to monitor with astrometry to determine its association.Comment: Accepted to Ap
Transport Through Andreev Bound States in a Graphene Quantum Dot
Andreev reflection-where an electron in a normal metal backscatters off a
superconductor into a hole-forms the basis of low energy transport through
superconducting junctions. Andreev reflection in confined regions gives rise to
discrete Andreev bound states (ABS), which can carry a supercurrent and have
recently been proposed as the basis of qubits [1-3]. Although signatures of
Andreev reflection and bound states in conductance have been widely reported
[4], it has been difficult to directly probe individual ABS. Here, we report
transport measurements of sharp, gate-tunable ABS formed in a
superconductor-quantum dot (QD)-normal system, which incorporates graphene. The
QD exists in the graphene under the superconducting contact, due to a
work-function mismatch [5, 6]. The ABS form when the discrete QD levels are
proximity coupled to the superconducting contact. Due to the low density of
states of graphene and the sensitivity of the QD levels to an applied gate
voltage, the ABS spectra are narrow, can be tuned to zero energy via gate
voltage, and show a striking pattern in transport measurements.Comment: 25 Pages, included SO
The low pKa value of iron-binding ligand Tyr188 and its implication in iron release and anion binding of human transferrin
2D NMR-pH titrations were used to determine pKa values for four conserved tyrosine residues, Tyr45, Tyr85, Tyr96 and Tyr188, in human transferrin. The low pKa of Tyr188 is due to the fact that the iron-binding ligand interacts with Lys206 in open-form and with Lys296 in the closed-form of the protein. Our current results also confirm the anion binding of sulfate and arsenate to transferrin and further suggest that Tyr188 is the actual binding site for the anions in solution. These data indicate that Tyr188 is a critical residue not only for iron binding but also for chelator binding and iron release in transferrin. © 2004 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.postprin
First-principles extrapolation method for accurate CO adsorption energies on metal surfaces
We show that a simple first-principles correction based on the difference
between the singlet-triplet CO excitation energy values obtained by DFT and
high-level quantum chemistry methods yields accurate CO adsorption properties
on a variety of metal surfaces.
We demonstrate a linear relationship between the CO adsorption energy and the
CO singlet-triplet splitting, similar to the linear dependence of CO adsorption
energy on the energy of the CO 2* orbital found recently {[Kresse {\em et
al.}, Physical Review B {\bf 68}, 073401 (2003)]}. Converged DFT calculations
underestimate the CO singlet-triplet excitation energy ,
whereas coupled-cluster and CI calculations reproduce the experimental . The dependence of on is used
to extrapolate for the top, bridge and hollow sites for the
(100) and (111) surfaces of Pt, Rh, Pd and Cu to the values that correspond to
the coupled-cluster and CI value. The correction
reproduces experimental adsorption site preference for all cases and obtains
in excellent agreement with experimental results.Comment: Table sent as table1.eps. 3 figure
Atomic structure of the translation regulatory protein NS1 of bluetongue virus
Bluetongue virus (BTV) non-structural protein 1 (NS1) regulates viral protein synthesis and exists as tubular and non-tubular forms in infected cells, but how tubules assemble and how protein synthesis is regulated are unknown. Here, we report near-atomic resolution structures of two NS1 tubular forms determined by cryo-electron microscopy. The two tubular forms are different helical assemblies of the same NS1 monomer, consisting of an amino-terminal foot, a head and body domains connected to an extended carboxy-terminal arm, which wraps atop the head domain of another NS1 subunit through hydrophobic interactions. Deletion of the C terminus prevents tubule formation but not viral replication, suggesting an active non-tubular form. Two zinc-finger-like motifs are present in each NS1 monomer, and tubules are disrupted by divalent cation chelation and restored by cation addition, including Zn2+, suggesting a regulatory role of divalent cations in tubule formation. In vitro luciferase assays show that the NS1 non-tubular form upregulates BTV mRNA translation, whereas zinc-finger disruption decreases viral mRNA translation, tubule formation and virus replication, confirming a functional role for the zinc-fingers. Thus, the non-tubular form of NS1 is sufficient for viral protein synthesis and infectious virus replication, and the regulatory mechanism involved operates through divalent cation-dependent conversion between the non-tubular and tubular forms
Redshift Dependence of the CMB Temperature from S-Z Measurements
We have determined the CMB temperature, , at redshifts in the range
0.023-0.546, from multi-frequency measurements of the S-Z effect towards 13
clusters. We extract the parameter in the redshift scaling
, which contrasts the prediction of the standard
model () with that in non-adiabatic evolution conjectured in some
alternative cosmological models. The statistical analysis is based on two main
approaches: using ratios of the S-Z intensity change, , thus taking
advantage of the weak dependence of the ratios on IC gas properties, and using
directly the measurements. In the former method dependence on the
Thomson optical depth and gas temperature is only second order in these
quantities. In the second method we marginalize over these quantities which
appear to first order in the intensity change. The marginalization itself is
done in two ways - by direct integrations, and by a Monte Carlo Markov Chain
approach. Employing these different methods we obtain two sets of results that
are consistent with , in agreement with the prediction of the
standard model.Comment: Accepted for publication in Ap
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