851 research outputs found
Congruences of lines in , quadratic normality, and completely exceptional Monge-Amp\`ere equations
The existence is proved of two new families of locally Cohen-Macaulay sextic
threefolds in , which are not quadratically normal. These
threefolds arise naturally in the realm of first order congruences of lines as
focal loci and in the study of the completely exceptional Monge-Amp\`ere
equations. One of these families comes from a smooth congruence of multidegree
which is a smooth Fano fourfold of index two and genus 9.Comment: 16 page
Nanosized patterns as reference structures for macroscopic transport properties and vortex phases in YBCO films
This paper studies the striking correlation between nanosized structural
patterns in YBCO films and macroscopic transport current. A nanosized network
of parallel Josephson junctions laced by insulating dislocations is almost
mimicking the grain boundary structural network. It contributes to the
macroscopic properties and accounts for the strong intergranular pinning across
the film in the intermediate temperature range. The correlation between the two
networks enables to find out an outstanding scaling law in the (Jc,B) plane and
to determine meaningful parameters concerning the matching between the vortex
lattice and the intergranular defect lattice. Two asymptotic behaviors of the
pinning force below the flux flow regime are checked: the corresponding vortex
phases are clearly individuated.Comment: 4 pages, 4 figure
A new apparatus for deep patterning of beam sensitive targets by means of high-energy ion beam
The paper reports on a high precision equipment designed to modify over
3-dimensions (3D) by means of high-energy gold ions the local properties of
thin and thick films. A target-moving system aimed at creating patterns across
the volume is driven by an x-y writing protocol that allows one to modify beam
sensitive samples over micrometer-size regions of whatever shape. The apparatus
has a mechanical resolution of 15 nm. The issue of the local fluence
measurement has been particularly addressed. The setup has been checked by
means of different geometries patterned on beam sensitive sheets as well as on
superconducting materials. In the last case the 3D modification consists of
amorphous nanostructures. The nanostructures create zones with different
dissipative properties with respect to the virgin regions. The main analysis
method consists of magneto-optical imaging that provides local information on
the electrodynamics of the modified zones. Features typical of non-linear
current flow hint at which pattern geometry is more functional to applications
in the framework of nanostructures across superconducting films.Comment: 7 page
Perazzo 3-folds and the weak Lefschetz property
We deal with Perazzo 3-folds in P4, i.e. hypersurfaces X = V(f) subset of P4 of degree d defined by a homogeneous polynomial f(x0, x1, x2, u, v) = p0(u, v)x0 +p1(u, v)x1 + p2(u, v)x2 + g(u, v), where p0, p1, p2 are algebraically dependent but linearly independent forms of degree d - 1 in u, v, and g is a form in u, v of degree d. Perazzo 3-folds have vanishing hessian and, hence, the associated graded Artinian Gorenstein algebra Af fails the strong Lefschetz Property. In this paper, we determine the maximum and minimum Hilbert function of Af and we prove that if Af has maximal Hilbert function it fails the weak Lefschetz Property while it satisfies the weak Lefschetz Property when it has minimum Hilbert function. In addition, we classify all Perazzo 3-folds in P4 such that Af has minimum Hilbert function.(c) 2023 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons .org /licenses /by -nc -nd /4 .0/)
CONTRACTING OVER PERSISTENT INFORMATION
We consider a dynamic principal-agent problem, where the sole instrument the
principal has to incentivize the agent is the disclosure of information. The principal aims at maximizing the (discounted) number of times the agent chooses the
principal’s preferred action. We show that there exists an optimal policy, where
the principal recommends its most preferred action and discloses information as
a reward in the next period, until either this action becomes statically optimal for
the agent or the agent perfectly learns the state
Confinement of fluxons by surface columnar defects in Bi1.8Pb0.33Sr1.87Ca2Cu3Oy tapes
We study the effects of surface columnar defects created along about 5% of the sample thickness by means of 0.25 GeV Au ions at different doses on Bi1.8Pb0.33Sr1.87Ca2Cu3Oy high-quality tapes on the vortex dynamics in the sample bulk. Strong phenomena of vortex localization inside the bulk are revealed by shifts of the irreversibility lines (IL's) as well as by their after-irradiation shape. The enhanced IL's exhibit specific characteristics, such as a Bose-glass-like behavior up to quite high fields, with a dose-dependent onset point. Moreover, the irreversible regime expands with decreasing defect density. Such results are consistent with the setting up of confined vortices morphologies. Experimental data concerning the IL with the field orthogonal to the columnar defect direction as well as critical current density enhancements are also reported and discussed
The Nuclear Ten Micron Emission of Spiral Galaxies
We examine the 10\m\ emission of the central regions of 281 spiral galaxies,
after having compiled all ground-based, small-aperture (5") broad-band
photometric observations at \l10\m\ (N magnitudes) published in the
literature. We evaluate the compactness of the 10\m\ emission of galaxy
nuclei by comparing these small-beam measures with the large-beam IRAS 12\m\
fluxes. In the analysis of different subsets of objects, we apply survival
analysis techniques in order to exploit the information contained in
``censored'' data (i.e., upper limits on the fluxes). Seyferts are found to
contain the most powerful nuclear sources of mid-infrared emission, which in
1/3 of cases provide the bulk of the emission of the entire galaxy; thus,
mid-infrared emission in the outer disc regions is not uncommon in Seyferts.
The 10\m\ emission of Seyferts appears to be unrelated to their X-ray emission.
HII region-like nuclei are stronger mid-infrared sources than normal nuclei and
LINER nuclei (whose level of emission is not distinguishable from that of
normal nuclei). Interacting objects have, on average, greater 10\m\
luminosities than non-interacting ones and exhibit more compact emission.
Early-type spirals have stronger and more compact 10\m\ emission than late-type
ones. Barred spirals are brighter at 10\m\ than unbarred systems,
essentially because they more frequently contain HII region-like nuclei. The
results of our detailed comparison between the behaviour of various categories
of objects stress that the 10\m\ emission of spiral nuclei is closely linked to
the (predominantly non-thermal synchrotron) radioComment: 20 pages, Latex, SISSA preprint, 8 figures and 4 tables available
upon reques
Estimating metabolic rate for butadiene at steady state using a Bayesian physiologically-based pharmacokinetic model
In a study of 133 volunteer subjects, demographic, physiologic and pharmacokinetic
data through exposure to 1,3-Butadiene (BD) were collected in order to
estimate the percentage of BD concentration metabolized at steady state, and to determine
whether this percentage varies across gender, racial, and age groups. During the
20 min of continuous exposure to 2 parts per million (ppm) of BD, five measurements
of exhaled concentration were made on each subject. In the following 40 min washout
period, another five measurements were collected. A Bayesian hierarchical compartmental
physiologically-based pharmacokinetic model (PKPB) was used. Using prior
information on the model parameters, Markov Chain Monte Carlo (MCMC) simulation
was conducted to obtain posterior distributions. The overall estimate of the
mean percent of BD metabolized at steady state was 12.7% (95% credible interval:
7.7–17.8%). There was no significant difference in gender with males having a mean
of 13.5%, and females 12.3%. Among the racial groups, Hispanic (13.9%), White
(13.0%), Asian (12.1%), and Black (10.9%), the significant difference came from
the difference between Black and Hispanic with a 95% credible interval from −5.63
to −0.30%. Those older than 30 years had a mean of 12.2% versus 12.9% for the younger group; although this was not a statistically significant difference. Given a
constant inhalation input of 2 ppm, at steady state, the overall mean exhaled concentrationwas
estimated to be 1.75ppm (95% credible interval: 1.64–1.84).An equivalent
parameter, first-order metabolic rate constant, was also estimated and found to be consistent
with the percent of BD metabolized at steady state across gender, race, and age
strata
The Effect of Cromolyn Sodium and Nedocromil Sodium Administered by A pressurized Aerosol with A spacer Device on Exercise-Induced Asthma in Children
To compare the effectiveness of cromolyn sodium (CS)
(10 mg) and nedocromil sodium (NS) (4 mg) administered
by a metered dose inhaler (MDI) with a spacer
device in preventing exercise-induced asthma (EIA), eight
asthmatic children with EIA were studied in a
randomized double-blind, cross-over, placebo-controlled
study, CS and NS provided significant, comparable protection
from EIA and both were better than placebo. We
conclude that CS and NS administered by a pressurized
aerosol with a spacer device provide equal protection
against EIA in children
Slow Proton Production in Semi-Inclusive Deep Inelastic Scattering off Deuteron and Complex Nuclei: Hadronization and Final State Interaction Effects
The effects of the final state interaction in slow proton production in semi
inclusive deep inelastic scattering processes off nuclei, A(e,e'p)X, are
investigated in details within the spectator and target fragmentation
mechanisms; in the former mechanism, the hard interaction on a nucleon of a
correlated pair leads, by recoil, to the emission of the partner nucleon,
whereas in the latter mechanism proton is produced when the diquark, which is
formed right after the visrtual photon-quark interaction, captures a quark from
the vacuum. Unlike previous papers on the subject, particular attention is paid
on the effects of the final state interaction of the hadronizing quark with the
nuclear medium within an approach based upon an effective time-dependent cross
section which combines the soft and hard parts of hadronization dynamics in
terms of the string model and perturbative QCD, respectively. It is shown that
the final state interaction of the hadronizing quark with the medium plays a
relevant role both in deuteron and complex nuclei; nonetheless, kinematical
regions where final state interaction effects are minimized can experimentally
be selected, which would allow one to investigate the structure functions of
nucleons embedded in the nuclear medium; likewise, regions where the
interaction of the struck hadronizing quark with the nuclear medium is
maximized can be found, which would make it possible to study non perturbative
hadronization mechanisms.Comment: 35 pages, 12 figures, accepted for pubblication in Phys. Rev.
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