694 research outputs found
Critical sets of nonlinear Sturm-Liouville operators of Ambrosetti-Prodi type
The critical set C of the operator F:H^2_D([0,pi]) -> L^2([0,pi]) defined by
F(u)=-u''+f(u) is studied. Here X:=H^2_D([0,pi]) stands for the set of
functions that satisfy the Dirichlet boundary conditions and whose derivatives
are in L^2([0,pi]). For generic nonlinearities f, C=\cup C_k decomposes into
manifolds of codimension 1 in X. If f''0, the set C_j is shown to be
non-empty if, and only if, -j^2 (the j-th eigenvalue of u -> u'') is in the
range of f'. The critical components C_k are (topological) hyperplanes.Comment: 6 pages, no figure
Girdling, gibberellic acid, and forchlorfenuron: effects on yield, quality, and metabolic profile of table grape cv. Italia
Among the various vineyard treatments adopted in recent years for table-grape cultivation, there has been a significant use of plant growth regulators (PGRs) and girdling to increase berry size and yield. In particular, an increase in the application of forchlorfenuron (CPPU) and gibberellic acid (GA3) for many seeded and seedless table-grape cultivars has been registered in several countries. In this two-year study, girdling at berry set, gibberellic acid (10 mg/L) applied at berry diameter of 10 to 11 mm, and forchlorfenuron (9.75 mg/L) applied at berry diameter of 11 to 12 mm were investigated to verify their effects on berry size, yield, and chemical and metabolic characteristics of Italia grapes. In general, at harvest all treatments significantly increased berry diameter, length, and weight and consequent cluster weight and yield/vine compared to an untreated control. The treatments showed significant differences for the colorimetric parameters, in particular a higher value of hue for berries treated with GA3 and CPPU, thus shifting the skin color from yellow toward yellow-green. Metabolomic study carried out by nuclear magnetic resonance spectroscopy combined with principal component analysis indicated that metabolic profile depends on the year and, in each year, the effect of treatments consisted of a slight variation of amino acid content. Treatments effects were more pronounced in the year characterized by a cooler summer
VALSE: A Task-independent benchmark for Vision and Language models centered on linguistic phenomena
We propose VALSE (Vision And Language Structured Evaluation), a novel benchmark designed for testing general-purpose pretrained vision and language (V&L) models for their visio-linguistic grounding capabilities on specific linguistic phenomena. VALSE offers a suite of six tests covering various linguistic constructs. Solving these requires models to ground linguistic phenomena in the visual modality, allowing more fine-grained evaluations than hitherto possible. We build VALSE using methods that support the construction of valid foils, and report results from evaluating five widely-used V&L models. Our experiments suggest that current models have considerable difficulty addressing most phenomena. Hence, we expect VALSE to serve as an important benchmark to measure future progress of pretrained V&L models from a linguistic perspective, complementing the canonical task-centred V&L evaluations
VALSE: A Task-independent benchmark for Vision and Language models centered on linguistic phenomena
We propose VALSE (Vision And Language Structured Evaluation), a novel benchmark designed for testing general-purpose pretrained vision and language (V&L) models for their visio-linguistic grounding capabilities on specific linguistic phenomena. VALSE offers a suite of six tests covering various linguistic constructs. Solving these requires models to ground linguistic phenomena in the visual modality, allowing more fine-grained evaluations than hitherto possible. We build VALSE using methods that support the construction of valid foils, and report results from evaluating five widely-used V&L models. Our experiments suggest that current models have considerable difficulty addressing most phenomena. Hence, we expect VALSE to serve as an important benchmark to measure future progress of pretrained V&L models from a linguistic perspective, complementing the canonical task-centred V&L evaluations
Measurement of boron and carbon fluxes in cosmic rays with the PAMELA experiment
The propagation of cosmic rays inside our galaxy plays a fundamental role in
shaping their injection spectra into those observed at Earth. One of the best
tools to investigate this issue is the ratio of fluxes for secondary and
primary species. The boron-to-carbon (B/C) ratio, in particular, is a sensitive
probe to investigate propagation mechanisms. This paper presents new
measurements of the absolute fluxes of boron and carbon nuclei, as well as the
B/C ratio, from the PAMELA space experiment. The results span the range 0.44 -
129 GeV/n in kinetic energy for data taken in the period July 2006 - March
2008
Trapped proton fluxes at low Earth orbits measured by the PAMELA experiment
We report an accurate measurement of the geomagnetically trapped proton
fluxes for kinetic energy above > 70 MeV performed by the PAMELA mission at low
Earth orbits (350-610 km). Data were analyzed in the frame of the adiabatic
theory of charged particle motion in the geomagnetic field. Flux properties
were investigated in detail, providing a full characterization of the particle
radiation in the South Atlantic Anomaly region, including locations, energy
spectra and pitch angle distributions. PAMELA results significantly improve the
description of the Earth's radiation environment at low altitudes placing
important constraints on the trapping and interaction processes, and can be
used to validate current trapped particle radiation models.Comment: 22 pages, 5 figure
Time dependence of the electron and positron components of the cosmic radiation measured by the PAMELA experiment between July 2006 and December 2015
Cosmic-ray electrons and positrons are a unique probe of the propagation of
cosmic rays as well as of the nature and distribution of particle sources in
our Galaxy. Recent measurements of these particles are challenging our basic
understanding of the mechanisms of production, acceleration and propagation of
cosmic rays. Particularly striking are the differences between the low energy
results collected by the space-borne PAMELA and AMS-02 experiments and older
measurements pointing to sign-charge dependence of the solar modulation of
cosmic-ray spectra. The PAMELA experiment has been measuring the time variation
of the positron and electron intensity at Earth from July 2006 to December 2015
covering the period for the minimum of solar cycle 23 (2006-2009) till the
middle of the maximum of solar cycle 24, through the polarity reversal of the
heliospheric magnetic field which took place between 2013 and 2014. The
positron to electron ratio measured in this time period clearly shows a
sign-charge dependence of the solar modulation introduced by particle drifts.
These results provide the first clear and continuous observation of how drift
effects on solar modulation have unfolded with time from solar minimum to solar
maximum and their dependence on the particle rigidity and the cyclic polarity
of the solar magnetic field.Comment: 11 pages, 2 figure
Search for anisotropies in cosmic-ray positrons detected by the PAMELA experiment
The PAMELA detector was launched on board of the Russian Resurs-DK1 satellite
on June 15, 2006. Data collected during the first four years have been used to
search for large-scale anisotropies in the arrival directions of cosmic-ray
positrons. The PAMELA experiment allows for a full sky investigation, with
sensitivity to global anisotropies in any angular window of the celestial
sphere. Data samples of positrons in the rigidity range 10 GV R
200 GV were analyzed. This article discusses the method and the results of the
search for possible local sources through analysis of anisotropy in positron
data compared to the proton background. The resulting distributions of arrival
directions are found to be isotropic. Starting from the angular power spectrum,
a dipole anisotropy upper limit \delta = 0.166 at 95% C.L. is determined.
Additional search is carried out around the Sun. No evidence of an excess
correlated with that direction was found.Comment: The value of the dipole anisotropy upper limit has been changed. The
method is correct but there was a miscalculation in the relative formul
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