48 research outputs found
Advancements and Challenges in Gridded Precipitation Datasets: Bias Correction and Downscaling Techniques for Enhanced Modeling in Sicily
No full textSpatial-temporal resolution advantages of Satellite Precipitation Products are limited by biases compared to ground observations. Various bias adjustment methods exist, from scaling methods to sophisticated techniques like Quantile Mapping (QM). However, many assume stationarity, leading to inaccuracies in variable climates. Alternative methods, instead, including Equidistant CDF
Matching (ECDFM), CDF transferring (CDFt), Quantile Delta Mapping (QDM), aim to address non-stationarity. Also, recent advancements in deep learning offer new methods, such as Convolutional Neural Networks (CNNs) and Long Short-Term Memory (LSTM) networks, promising good performances in capturing spatial-temporal dependencies of climate phenomena.
Our study proposes a two-stage bias adjustment framework integrating multiple methodologies and advanced deep learning techniques to mitigate systematic bias in Global Precipitation Measurement (GPM) Integrated Multi-satellitE Retrievals for GPM (IMERG) satellite estimatesfor the Sicily, Italy.
Also, to tackle one of the most important issues that affects semiarid regions as Sicily, i.e., precipitation datasets with zero-inflation, it exists different methods varying from Singularity Stochastic Removal (SSR) to complex zero-truncated models
Comprehensive Hydrological Modeling Tool for Flood Discharge Estimation in Sicilian Watersheds
No full textDesigning hydraulic infrastructures and/or carry out a flood risk assessment analysis, as mandated by Directive 2007/60/EC of the European Parliament regarding the assessment and management of flood risk, needs estimating flood discharges for different return periods. In the current era, Geographic Information Systems (GIS) make more efficient the integration of spatially distributed data and advanced analytical tools for hydrological applications.
This work introduces a Python-based tool that merges GIS functionalities (i.e., open-source geospatial libraries, such as native QGIS plugins, GDAL, SAGA) with hydrological modeling techniques, providing a comprehensive framework for watershed analysis aimed to derive synthetic flood hydrographs for specified return periods. The tool is composed of different modules, performing different operations: following the delineation of the watershed based on a user-specified outlet, the tool uses a regionalized approach to establish Depth-Duration-Frequency (DDF) curves and derives the synthetic Chicago hyetographs for specified return periods. The tool comprises a module for calculating runoff depths using the Curve Number method and another module where flow hydrographs are derived by using distributed unit hydrograph (D-UH) through
a spatial representation of times of concentration, accounting for varying flow velocities within the watershed. Additionally, the tool allows for the simulation of the basin response to historical precipitation. In the present study, the tool underwent testing on catchments of Sicily (Italy) even if it is worth noting that the tool can be customized for application in various regions worldwide
Reconstruction of Maximum and Minimum Temperature Time Series for the Mediterranean’s Largest Island
No full textAnalyzing potential indicators of climate change necessitates access to extensive historical datasets.
However, measurement gauges are subject to frequent replacement or upgrades, resulting in spatial and/or
temporal inconsistencies that undermine the reliability of these datasets. This is the case of Sicily, the largest
island in the Mediterranean Sea, which is characterized by the presence of two different monitoring networks,
spanning partially different periods. By using a spatial interpolation method, we merge the information from
these networks and obtain continuous daily maximum and minimum temperature series for the 1980-2023
period in a 2x2 km grid
Varieties of superalgebras of polynomial growth
No full text2010 Mathematics Subject Classification: 16R10, 16W55, 16P90.Let V^gr be a variety of associative superalgebras over a field F of characteristic zero. It is well-known that V gr can have polynomial or exponential growth. Here we present some classification results on varieties of polynomial growth. In particular we classify the varieties of at most linear growth and all subvarieties of the varieties of almost polynomial growth.∗ The author was partially supported by MIUR of Italy
Codimension growth of algebras with superautomorphism
No full textLet A be a finite dimensional algebra endowed with a superautomorphism over a field of characteristic zero. In this paper we study the asymptotic behavior of the sequence of phi-codimensions c phi / n(A), n = 1, 2, .... More precisely, we shall prove that limn ->infinity n c phi n(A) always exists and it is an integer related in an explicit way to the dimension of a suitable semisimple subalgebra of A. This result gives a positive answer to a conjecture of Amitsur in this setting. In the final part of the paper we characterize the algebras whose exponential growth is bounded by 2. (c) 2025 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Rashkova, T. The Robson cubics for matrix algebras with involution (Acta Univ. Apulensis Math. Inform.).
No full textLet R be the free associative algebra over a field K on
generators and let be the free
associative -algebra in one further indeterminate Consider
the set of polynomials in which are satisfied by
the matrix Such polynomials are
called laws over of the matrix Robson in [Robson, J.
C. Polynomials satisfied by matrices. J. Algebra 55 (1978), no.
2, 509--520; MR523471 (80j:15012)] proved that such laws are a
``consequence" of a finite set of laws and for he exhibited
generators called Robson cubics.
Here the author considers the special case when is a
symmetric or skew-symmetric matrix under the transpose
or symplectic involution and gives an explicit form of the Robson
cubics. Some other results are also given in case $n=3.
Some results on ∗-minimal algebras with involution
No full textLet be an associative algebra with involution over a field
of characteristic zero, the ideal of -polynomial
identities of and , the
corresponding sequence of -codimensions. Recall that
is the dimension of the space of multilinear polynomials in
variables in the corresponding relatively free algebra with
involution of countable rank.
\par
When is a finite dimensional algebra, Giambruno and Zaicev [J.
Algebra 222 (1999), no. 2, 471–484; MR1734235 (2000i:16046)] proved
that the limit exists and is an integer
called the -exponent of
\par
Among finite dimensional algebras with the same -exponent a
prominent role is played by the so called -minimal algebras. This
notion was introduced by Di Vincenzo and La Scala in [J. Algebra 317
(2007), no. 2, 642–657; MR2362935 (2008j:16095)]. Recall that a
finite dimensional algebra is -minimal if for any
finite dimensional algebra with involution such that
we have that
\par
In this paper the authors review recent results of the first author
et al regarding -minimal algebras and prove further properties
towards a complete classification of -minimal algebras
Metabolic parameters and adipokine profile during GH replacement therapy in children with GH deficiency
No full textObjective: GH replacement therapy in children with GH deficiency (GHD) mainly promotes linear
growth. Not only have very few studies fully analyzed the metabolic consequences of GH therapy, but
also the question as to whether GH may affect adipokine secretion has been insufficiently investigated.
Our aim was to study the effects of GH replacement therapy on auxological data, lipid and glycemic
profiles, insulin homeostasis (HOMA-IR) and serum adipokines in children.
Methods: This was a 1-year prospective study. Thirty-four GHD children (11.6G2.6 years) and thirty
healthy matched controls were enrolled. Children affected by GHD were studied both before beginning
continuous GH replacement therapy and again at 12 months.
Results: At the beginning of the study, total and LDL cholesterol were higher in GHD children than in
controls (P!0.001), whereas HDL cholesterol, triglycerides, insulin, HOMA-IR, leptin, and
adiponectin were similar. At 12 months of continuous GH replacement therapy in the GHD group,
there was a significant increase in both auxological data and IGF-I (P!0.001); total cholesterol
(P!0.001), LDL (P!0.001), triglycerides (P!0.005), and leptin (P!0.001) decreased significantly;
HDL (P!0.003), insulin (P!0.001), HOMA-IR (P!0.001) increased while adiponectin was
unmodified. Furthermore, IGF-ID showed an inverse correlation with leptin D (rZK0.398, PZ0.02).
Conclusions: In GHD children, the evaluation of metabolic parameters proves to be a useful tool for the
evaluation of auxological parameters during GH replacement therapy. In our study, GH replacement
therapy in GHD children improved final height, restored IGF-I levels, reduced leptin levels, and
improved the lipid profile, without producing any unfavorable effects on glucose metabolism
Para-perirenal distribution of body fat is associated with reduced glomerular filtration rate regardless of other indices of adiposity in hypertensive patients
No full textObesity is a well-known risk factor for the development and progression of chronic kidney disease. Recently, para-perirenal ultrasonographic fat thickness (PUFT) has shown to correlate with both total and visceral fat better than body mass index (BMI), waist circumference (WC), and other indices of obesity. Moreover, a local paracrine and mechanical action of the PUFT on kidney has been described in recent studies. Aim of our study was to assess the relationship between glomerular filtration rate (GFR) and PUFT in comparison with other anthropometric and ultrasonographic indices of adiposity. Two hundred and ninety-six hypertensive patients were enrolled. PUFT, cutis-rectis thickness and rectis-aorta thickness were obtained by ultrasonography. Anthropometric measures of adiposity were also measured. Estimated GFR was calculated using the CKD-EPI equation. Higher PUFT values were observed in patients with impaired renal function (P < 0.001), whereas no differences in BMI and WC were shown between groups divided by GFR. PUFT significantly correlated with GFR in all patients (r = −0.284; P < 0.001), with no differences in groups divided by sex, diabetes, or BMI. This association held in multivariate analyses also after correction for confounding factors, including other adiposity indices (P < 0.001). When receiver operating characteristic curves were built to detect a eGFR < 60 mL/minutes per 1.73 m2, a PUFT value ≤3.725 cm showed a negative predictive value of 94.0%, with the largest area under the curve (AUC: 0.700) among the variables considered. In conclusion, the relationship between PUFT and GFR seems to be more accurate and less influenced by the bias affecting traditional indices of adiposity
