1,193 research outputs found
The evolution of the orbit distance in the double averaged restricted 3-body problem with crossing singularities
We study the long term evolution of the distance between two Keplerian
confocal trajectories in the framework of the averaged restricted 3-body
problem. The bodies may represent the Sun, a solar system planet and an
asteroid. The secular evolution of the orbital elements of the asteroid is
computed by averaging the equations of motion over the mean anomalies of the
asteroid and the planet. When an orbit crossing with the planet occurs the
averaged equations become singular. However, it is possible to define piecewise
differentiable solutions by extending the averaged vector field beyond the
singularity from both sides of the orbit crossing set. In this paper we improve
the previous results, concerning in particular the singularity extraction
technique, and show that the extended vector fields are Lipschitz-continuous.
Moreover, we consider the distance between the Keplerian trajectories of the
small body and of the planet. Apart from exceptional cases, we can select a
sign for this distance so that it becomes an analytic map of the orbital
elements near to crossing configurations. We prove that the evolution of the
'signed' distance along the averaged vector field is more regular than that of
the elements in a neighborhood of crossing times. A comparison between averaged
and non-averaged evolutions and an application of these results are shown using
orbits of near-Earth asteroids.Comment: 29 pages, 8 figure
Identification of two divergent swine Noroviruses detected at the slaughterhouse in North East Italy
Norovirus (NoV) has emerged as one of the major causative agents of non-bacterial, food- and water-borne gastroenteritis in humans, with the main genogroup involved in human outbreaks (GII), which has been detected worldwide in different animal species including swine. A four-month investigation at the slaughterhouse aiming to examine the presence of NoV in the swine in North-Eastern Italy, enabled the detection of two divergent Noroviruses (NoVs) (GII.P11) in two swine farms. This represents the first study in the swine population of North-Eastern Italy, which has paved the way for future integrated virological and epidemiological investigations on swine NoVs
Measuring the relativistic perigee advance with Satellite Laser Ranging
One of the most famous classical tests of General Relativity is the
gravitoelectric secular advance of the pericenter of a test body in the
gravitational field of a central mass. In this paper we explore the possibility
of performing a measurement of the gravitoelectric pericenter advance in the
gravitational field of the Earth by analyzing the laser-ranged data to some
existing, or proposed, laser-ranged geodetic satellites. At the present level
of knowledge of various error sources, the relative precision obtainable with
the data from LAGEOS and LAGEOS II, suitably combined, is of the order of
. Nevertheless, these accuracies could sensibly be improved in the
near future when the new data on the terrestrial gravitational field from the
CHAMP and GRACE missions will be available. The use of the perigee of LARES
(LAser RElativity Satellite), in the context of a suitable combination of
orbital residuals including also LAGEOS II, should further raise the precision
of the measurement. As a secondary outcome of the proposed experiment, with the
so obtained value of \ppn and with \et=4\beta-\gamma-3 from Lunar Laser
Ranging it could be possible to obtain an estimate of the PPN parameters
and at the level.Comment: LaTex2e, 14 pages, no figures, 2 tables. To appear in Classical and
Quantum Gravit
Development, optimization, and comparison of different sample pre-treatments for simultaneous determination of vitamin e and vitamin K in vegetables
The absence of vitamin E from the diet can lead to cardiovascular disease, cancer, cataracts, and premature aging. Vitamin K deficiency can lead to bleeding disorders. These fat-soluble vitamins are important nutritional factors that can be determined in different methods in vegetables. In this work, the simultaneous determination of α-tocopherol, α-tocopheryl acetate, phylloquinone, and menaquinone-4 by gas chromatography-mass spectrometry (GC-MS) has been optimized using both direct injection and solid phase microextraction (SPME). Three different sample pre-treatment approaches based on: (A) solid-liquid-liquid-liquid extraction (SLE-LLE), (B) SLE, and (C) SPME were then applied to extract the target analytes from vegetables samples using menaquinone as internal standard. All the procedures allowed the determination of the target analytes in onion, carrot, celery, and curly kale samples. Similar results were obtained with the three different approaches, even if the one based on SPME offers the best performance, together with a reduced use of solvent, time consumption, and experimental complexity, which makes it the preferable option for industrial applications
Perception, knowledge and attitude towards childhood fever: A survey among final-year medical students
Aims: Undue concerns about the consequences of fever and its inappropriate management have been documented worldwide among physicians. However, no data exist on medical students. We investigated the perception, knowledge and attitude towards childhood fever among final-year medical students. Methods: Between June and September 2021, final-year medical students of six Italian universities were invited to complete an online survey on their conceptions and attitude towards pharmacological and non-pharmacological management of childhood fever. History of relevant personal or second-hand experience with childhood fever was also addressed. Both quantitative and qualitative approaches were used. Results: Of 1095 (69%) final-year medical students, 756 completed the survey. Many students believe that high fever might cause brain damage, would recommend physical methods and alternate two drugs for fever. Most students do not think that fever has mainly beneficial effects. In Northern Italy, students are less likely to believe that fever might lead to brain damage (OR 0.55, 95% CI 0.33-0.94), and in Southern Italy students are more likely to advise physical methods (OR 1.77, 95% CI 1.22-2.57) and less likely to believe that fever has mainly beneficial effects (OR 0.55, 95% CI 0.39-0.77). History of a relevant personal episode of fever during childhood was not associated with these outcomes. Conclusions: Misconceptions about fever are common among final-year medical students in Italy. Cultural factors rather than individually learned traits might underlie these beliefs. Medical students are a promising target for educational interventions to improve childhood fever management
Fertilidade de um argissolo sob pomar de pêssego em função da irrigação e posição de amostragem.
On the Possibility of Measuring the Gravitomagnetic Clock Effect in an Earth Space-Based Experiment
In this paper the effect of the post-Newtonian gravitomagnetic force on the
mean longitudes of a pair of counter-rotating Earth artificial satellites
following almost identical circular equatorial orbits is investigated. The
possibility of measuring it is examined. The observable is the difference of
the times required to in passing from 0 to 2 for both senses of
motion. Such gravitomagnetic time shift, which is independent of the orbital
parameters of the satellites, amounts to 5 s for Earth; it is
cumulative and should be measured after a sufficiently high number of
revolutions. The major limiting factors are the unavoidable imperfect
cancellation of the Keplerian periods, which yields a constraint of 10
cm in knowing the difference between the semimajor axes of the satellites,
and the difference of the inclinations of the orbital planes which, for
, should be less than . A pair of spacecrafts
endowed with a sophisticated intersatellite tracking apparatus and drag-free
control down to 10 cm s Hz level might allow to meet
the stringent requirements posed by such a mission.Comment: LaTex2e, 22 pages, no tables, 1 figure, 38 references. Final version
accepted for publication in Classical and Quantum Gravit
Reduced basis isogeometric mortar approximations for eigenvalue problems in vibroacoustics
We simulate the vibration of a violin bridge in a multi-query context using
reduced basis techniques. The mathematical model is based on an eigenvalue
problem for the orthotropic linear elasticity equation. In addition to the nine
material parameters, a geometrical thickness parameter is considered. This
parameter enters as a 10th material parameter into the system by a mapping onto
a parameter independent reference domain. The detailed simulation is carried
out by isogeometric mortar methods. Weakly coupled patch-wise tensorial
structured isogeometric elements are of special interest for complex geometries
with piecewise smooth but curvilinear boundaries. To obtain locality in the
detailed system, we use the saddle point approach and do not apply static
condensation techniques. However within the reduced basis context, it is
natural to eliminate the Lagrange multiplier and formulate a reduced eigenvalue
problem for a symmetric positive definite matrix. The selection of the
snapshots is controlled by a multi-query greedy strategy taking into account an
error indicator allowing for multiple eigenvalues
Risk factors for abnormally invasive placenta: a systematic review and meta-analysis.
Purpose of the article. To explore the strength of association between different maternal and pregnancy characteristics and the occurrence of abnormally invasive placenta (AIP). MATERIALS AND METHODS: Pubmed, Embase, CINAHL databases were searched. The risk factors for AIP explored were: obesity, age > 35 years, smoking before or during pregnancy, placenta previa, prior cesarean section (CS), placenta previa and prior CS, prior uterine surgery, abortion and uterine curettage, in vitro fertilization (IVF) pregnancy and interval between a previous CS and a subsequent pregnancy. Random-effect head-to-head meta-analyses were used to analyze the data. RESULTS: Forty-six were included in the systematic review. Maternal obesity (Odd ratio, OR: 1.4, 95% CI 1.0-1.8), advanced maternal age (OR: 3.1, 95% CI 1.4-7.0) and parity (OR: 2.5, 95% CI 1.7-3.6), but not smoking were associated with a higher risk of AIP. The presence of placenta previa in women with at least a prior CS was associated with a higher risk of AIP compared to controls, with an OR of 12.0, 95% CI 1.6-88.0. Furthermore, the risk of AIP increased with the number of prior CS (OR of 2.6, 95% CI 1.6-4.4 and 5.4, 95% CI 1.7-17.4 for two and three prior CS respectively). Finally, IVF pregnancies were associated with a high risk of AIP, with an OR of 2.8 (95% CI 1.2-6.8). CONCLUSION: A prior CS and placenta previa are among the strongest risk factors for the occurrence of AIP
The central role of Italy in the spatial spread of USUTU virus in Europe
USUTU virus (USUV) is an arbovirus maintained in the environment through a bird-mosquito enzootic cycle. Previous surveillance plans highlighted the endemicity of USUV in North-eastern Italy. In this work, we sequenced 138 new USUV full genomes from mosquito pools (Culex pipiens) and wild birds collected in North-eastern Italy and we investigated the evolutionary processes (phylogenetic analysis, selection pressure and evolutionary time-scale analysis) and spatial spread of USUV strains circulating in the European context and in Italy, with a particular focus on North-eastern Italy. Our results confirmed the circulation of viruses belonging to four different lineages in Italy (EU1, EU2, EU3 and EU4), with the newly sequenced viruses from the North-eastern regions, Veneto and Friuli Venezia Giulia, belonging to the EU2 lineage and clustering into two different sub-lineages, EU2-A and EU2-B. Specific mutations characterize each European lineage and geographic location seem to have shaped their phylogenetic structure. By investigating the spatial spread in Europe, we were able to show that Italy acted mainly as donor of USUV to neighbouring countries. At a national level, we identified two geographical clusters mainly circulating in Northern and North-western Italy, spreading both northward and southward. Our analyses provide important information on the spatial and evolutionary dynamics of USUTU virus that can help to improve surveillance plans and control strategies for this virus of increasing concern for human health
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