318 research outputs found
On the Earth's tidal perturbations for the LARES satellite
Frame dragging, one of the outstanding phenomena predicted by General
Relativity, is efficiently studied by means of the laser-ranged satellites
LARES, LAGEOS and LAGEOS 2. The accurate analysis of the orbital perturbations
of Earth's solid and ocean tides has been relevant for increasing the accuracy
in the test of frame-dragging using these three satellites. The Earth's tidal
perturbations acting on the LARES satellite are obtained for the 110
significant modes of corresponding Doodson number and are exhibited to enable
the comparison to those of the LAGEOS and LAGEOS-2 satellites. For LARES we
represent 29 perturbation modes for l=2,3,4 for ocean tides.Comment: 14 pages, 9 figures, to appear in Eur Phys J Plus (subm. Sept 20,
2017
Measles among healthcare workers in Italy. Is it time to act?
Vaccination of healthcare workers (HCWs) against measles is strongly recommended in Europe. In this study, we examined the impact of measles on Italian HCWs by systematically and quantitatively analyzing measles cases involving HCWs over time and by identifying the epidemiological characteristics of the respective measles outbreaks. We retrieved data on measles cases from the Italian national integrated measles and rubella surveillance system from January 2013 to May 2019. Additionally, we performed a systematic review of the literature and an analysis of the measles and rubella aggregate outbreaks reporting forms from 2014 to 2018. Our review suggests that preventing measles infection among HCWs in disease outbreaks may be crucial for the elimination of measles in Italy. National policies aiming to increase HCW immunization rates are fundamental to the protection of HCWs and patients, will limit the economic impact of outbreaks on the institutions affected and will help achieve the elimination goal
Qualification tests on the optical retro-reflectors of LARES satellite.
LARES Satellite has been successfully launched on February 13th 2012 with the first flight of the new European Launcher VEGA. The passive, laser ranged satellite carries 92 cube corner reflectors (CCR). Due to its high density LARES represents the known orbiting object with the highest mean density in the solar system. This property makes it an almost perfect proof particle in the gravitational field of Earth. LARES is now operational and it is tracked by the International Laser Ranging Service stations. It will be used to test General Relativity and in particular the fact that the rotating Earth drags spacetime. The satellite design is quite innovative in the use of tungsten alloy as a structural material; indeed, the satellite body has been machined from a single piece of high density sintered alloy. The sintered alloy is characterized by a porous surface that shall be carefully cleaned before the integration of the optical components, in order to avoid contamination of the back faces of the CCR from the metal. Two cleaning procedures have been identified, to be performed on LARES. One procedure consisted in chemical cleaning with different solvents and cleaning agents; the second procedure consisted in a chemical cleaning followed by degassing in a high vacuum oven. The cleanness procedures have been tested on breadboards reproducing the satellite materials. The breadboards were tungsten alloy cylinders, carrying a cube corner reflector. The test was performed on two different breadbords each one for one of the two cleaning procedure. To simulate the operative space conditions the Thermal Vacuum Facility of Sapienza University of Rome has been used. The breadboards were maintained in simulated space environment to allow degassing of possible contaminants from the metal and possible detachment of contaminants from the metal to the back faces of the CCR. Visual inspection and Far Field Diffraction Patter tests have been performed to verify the possible presence and effect of contaminants on the of the CCR back faces. In the paper some detail on the LARES mission and on the scientific objectives will be described along with all the details on this qualification process
On the emergence of Lorentzian signature and scalar gravity
In recent years, a growing momentum has been gained by the emergent gravity
framework. Within the latter, the very concepts of geometry and gravitational
interaction are not seen as elementary aspects of Nature but rather as
collective phenomena associated to the dynamics of more fundamental objects. In
this paper we want to further explore this possibility by proposing a model of
emergent Lorentzian signature and scalar gravity. Assuming that the dynamics of
the fundamental objects can give rise in first place to a Riemannian manifold
and a set of scalar fields we show how time (in the sense of hyperbolic
equations) can emerge as a property of perturbations dynamics around some
specific class of solutions of the field equations. Moreover, we show that
these perturbations can give rise to a spin-0 gravity via a suitable
redefinition of the fields that identifies the relevant degrees of freedom. In
particular, we find that our model gives rise to Nordstrom gravity. Since this
theory is invariant under general coordinate transformations, this also shows
how diffeomorphism invariance (albeit of a weaker form than the one of general
relativity) can emerge from much simpler systems.Comment: 10 pages, revtex4. Replaced with the published versio
Two-year observations of the Jupiter polar regions by JIRAM on board Juno
We observed the evolution of Jupiter's polar cyclonic structures over two years between February 2017 and February 2019, using polar observations by the Jovian InfraRed Auroral Mapper, JIRAM, on the Juno mission. Images and spectra were collected by the instrument in the 5‐μm wavelength range. The images were used to monitor the development of the cyclonic and anticyclonic structures at latitudes higher than 80° both in the northern and the southern hemispheres. Spectroscopic measurements were then used to monitor the abundances of the minor atmospheric constituents water vapor, ammonia, phosphine and germane in the polar regions, where the atmospheric optical depth is less than 1. Finally, we performed a comparative analysis with oceanic cyclones on Earth in an attempt to explain the spectral characteristics of the cyclonic structures we observe in Jupiter's polar atmosphere
Towards classical geometrodynamics from Group Field Theory hydrodynamics
We take the first steps towards identifying the hydrodynamics of group field
theories (GFTs) and relating this hydrodynamic regime to classical
geometrodynamics of continuum space. We apply to GFT mean field theory
techniques borrowed from the theory of Bose condensates, alongside standard GFT
and spin foam techniques. The mean field configuration we study is, in turn,
obtained from loop quantum gravity coherent states. We work in the context of
2d and 3d GFT models, in euclidean signature, both ordinary and colored, as
examples of a procedure that has a more general validity. We also extract the
effective dynamics of the system around the mean field configurations, and
discuss the role of GFT symmetries in going from microscopic to effective
dynamics. In the process, we obtain additional insights on the GFT formalism
itself.Comment: revtex4, 32 pages. Contribution submitted to the focus issue of the
New Journal of Physics on "Classical and Quantum Analogues for Gravitational
Phenomena and Related Effects", R. Schuetzhold, U. Leonhardt and C. Maia,
Eds; v2: typos corrected, references updated, to match the published versio
COVID-19 and the impact on the cranio-oro-facial trauma care in Italy: An epidemiological retrospective cohort study
The coronavirus disease 2019 (COVID-19) has deeply modified the organization of hospitals, health care centers, and the patient’s behavior. The aim of this epidemiological retrospective cohort study is to evaluate if and how the COVID-19 pandemic has determined a modification in cranio-oro-facial traumatology service. Methods: The dataset included hospital emergency room access of a six-month pre-pandemic period and six months into pandemic outbreak. The variables collected were: patient age, gender, type of emergency access with relative color code, Glasgow Coma Scale Score, type of discharge. Results: 537 vs 237 (pre-pandemic vs pandemic) patients accessed the hospital emergency room and the mean age decreased from 60.79 ± 25.34 to 56.75 ± 24.50 year. Yellow and green code access went from 28.9% and 66.1% to 37.5% and 57.7% (pre-pandemic vs pandemic). Glasgow Coma Scale (GCS) shows an increase of 16.6% vs 27.8% of 15 grade score, a 28.7% vs 28.5% of the 14 grade score and reduction of 13 and 12 grade 40.2% and 14.5% vs 37.1 and 9.7% (pre-pandemic vs pandemic). Conclusions: Since the COVID-19 outbreak continues, epidemiological data are still necessary to perform public health intervention strategies and to appropriately predict the population needs, in order to properly manage the COVID-19 related to oral pathologies as well as the most common health problems
Toward a One Percent Measurement of Frame Dragging by Spin with Satellite Laser Ranging to LAGEOS, LAGEOS 2 and LARES and GRACE gravity models
none8During the past century Einstein’s theory of General Relativity gave rise to an experimental triumph; however, there are still aspects of this theory to be measured or more accurately tested. Today one of the main challenges in experimental gravitation, together with the direct detection of gravitational waves, is the accurate measurement of the gravitomagnetic field generated by the angular momentum of a body. Here, after a brief introduction on frame-dragging, gravitomagnetism and Lunar Laser Ranging tests, we describe the past measurements of frame-dragging by the Earth spin using the satellites LAGEOS, LAGEOS 2 and the Earth’s gravity models obtained by the GRACE project. We demonstrate that these measurements have an accuracy of approximately 10%.
We then describe the LARES experiment to be launched in 2010 by the Italian Space Agency for a measurement of frame-dragging with an accuracy of a few percent.
We finally demonstrate that a number of claims by a single individual, that the error budget of the frame-dragging measurements with LAGEOS-LAGEOS 2 and LARES has been underestimated, are indeed ill-founded.IGNAZIO CIUFOLINI; Antonio Paolozzi; Erricos C. Pavlis; John C. Ries; Rolf Koenig; Richard A. Matzner; Giampiero Sindoni and Hans NeumayerCiufolini, Ignazio; Antonio, Paolozzi; Erricos C., Pavlis; John C., Ries; Rolf, Koenig; Richard A., Matzner; Giampiero, Sindoni; Hans, Neumaye
Malignant struma ovarii harboring a unique NRAS mutation: case report and review of the literature
Struma ovarii (SO), a rare tumor containing at least 50% of thyroid tissue, represents approximately 5% of all ovarian teratomas; its malignant transformation rate is reported to occur in up to 10% of cases and metastases occur in about 5-6% of them. We describe a 36-year old woman who underwent laparoscopic left annessectomy two years earlier because of an ovarian cyst. Follow-up imaging revealed a right adnexal mass, ascitis and peritoneal nodes that were diagnosed as comprising a malignant SO with peritoneal secondary localizations at histopathology performed after intervention. Restaging with F-18-FDG-PE T/CT scan, abdominal CT and ultrasonography showed abnormalities in the perihepatic region and presacral space and left hypochondrium localizations. The patient underwent thyroidectomy, hepatic nodulectomy and cytoreductive peritonectomy: histopathological examination did not show any malignant disease in the thyroid and confirmed the presence of peritoneal localizations due to malignant SO; molecular analysis detected NRAS Q61K mutation in exon 3, whereas no mutations were identified on the BRAF gene. The patient underwent radioiodine treatment: serum Tg was decreased at first follow-up after three months of I-131-therapy. We believe that our case raises some interesting considerations. First, pathologists should be aware of this entity and should check for the presence of point mutations suggesting an aggressive disease behavior, which could be beneficial for an optimal therapeutic approach. Second, although most of the knowledge in this field comes from case reports, efforts should be made to standardize the management of patients affected by malignant SO, including use of practice guidelines
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