1,224 research outputs found

    Curvature of a class of indefinite globally framed ff-manifolds

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    We present a compared analysis of some properties of indefinite almost S\mathcal{S}-manifolds and indefinite S\mathcal{S}-manifolds. We give some characterizations in terms of the Levi-Civita connection and of the characteristic vector fields. We study the sectional and Ď•{\phi}-sectional curvature of indefinite almost S\mathcal{S}-manifolds and state an expression of the curvature tensor field for the indefinite S\mathcal{S}-space forms. We analyse the sectional curvature of indefinite S\mathcal{S}-manifold in which the number of the spacelike characteristic vector fields is equal to that of the timelike characteristic vector fields. Some examples are also described.Comment: 17 pages, no figure

    Recognition of landslides in lunar impact craters

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    Landslides have been observed on several planets and minor bodies of the solar System, including the Moon. Notwithstanding different types of slope failures have been studied on the Moon, a detailed lunar landslide inventory is still pending. Undoubtedly, such will be in a benefit for future geological and morphological studies, as well in hazard, risk and suscept- ibility assessments. A preliminary survey of lunar landslides in impact craters has been done using visual inspection on images and digital elevation model (DEM) (Brunetti et al. 2015) but this method suffers from subjective interpretation. A new methodology based on polynomial interpolation of crater cross-sections extracted from global lunar DEMs is presented in this paper. Because of their properties, Chebyshev polynomials were already exploited for para- metric classification of different crater morphologies (Mahanti et al., 2014). Here, their use has been extended to the discrimination of slumps in simple impact craters. Two criteria for recognition have provided the best results: one based on fixing an empirical absolute thresholding and a second based on statistical adaptive thresholding. The application of both criteria to a data set made up of 204 lunar craters’ cross-sections has demonstrated that the former criterion provides the best recognition

    Spectroscopic characterization of Phoenician-Punic coins

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    Sardinia hosted many Phoenician and Punic communities, as integrated forms of pacific cohabitation with the Lebanese merchants or actual colonies for the exploitation of the rich mines and wealthy coastal emporia under the Carthaginians (750-250 B.C.). One of their most important settlements is that of Mount Sirai, in the south west of the island, whose excavation revealed a complex structure of the site and allowed the discovery of excellent finds, as steles, everyday-life objects and tools, grave goods, amulets and coins. Punic coins were made by gold, electrum or, more commonly, by bronze. The first coin mintage from Carthage dates back to the IV century B.C. Whether the mintage was exclusive to Carthage or permitted outside the city too is still a matter of debate. There is the possibility that mintages were allowed in Sardinia (320-238 B.C. as well as in 216), in Spain (237-209 B.C.) and Southern Italy (216-203 B.C.). We have analyzed ten of these bronze coins (Fig. 1) to unveil the secrets of their mintage, origins and inner structure. Some traditional spectroscopic techniques such as X-ray diffraction (XRD) and fluorescence (XRF) have been used for this purpose, allowing us to learn about their mineral content (XRD) and elemental composition (XRF) [1,2]. Here we report about these findings

    Age of Cosmic-Ray Protons Computed Using Simple Configurations of the Galactic Magnetic Field

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    The influence of various magnetic field structures of the Galactic disk on some fundamental properties of cosmic-ray protons has been investigated with a simulation program, which generates cosmic-ray trajectories in the disk volume. The regular component of the Galactic magnetic field has been approximated by three different geometrical configurations (circular, elliptical, and spiral). Ages, residence times, and grammages of cosmic protons in various conditions are calculated and discussed. These calculations indicate that the proton age is strongly influenced by the magnetic field configuration but weakly affected by the field strength. The age of cosmic-ray protons in the spiral field turns out to be 6.7 Ă— 106 yr, and the corresponding matter thickness 12 g cm-2

    Voriconazole treatment of Candida tropicalis meningitis: persistence of (1,3)-b-D-glucan in the cerebrospinal fluid is a marker of clinical and microbiological failure

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    Introduction: Infections are still the most common complications of cerebral shunt procedures. Even though fungal etiologies are considered to be rare, they are associated with significant morbidity and mortality. Due to their uncommonness, diagnostic procedures and optimal therapy are poorly defined. We report a case of Candida tropicalis infection of ventriculo-peritoneal cerebrospinal fluid (CSF) shunt in a 49-year-old immune competent male treated with voriconazole (VOR). Methods: Microbiological and CSF markers (1,3-b-D-glucan-BDG) of fungal infection, biofilm production capacity, sensitivity of serial isolates of the pathogen, and the concentration of the antifungal drug have been monitored and related to the clinical course of this infection. Results: Despite appropriate treatment with VOR, in terms of adequate achieved CSF drug concentrations and initial effective therapeutic response, loss of VOR susceptibility of the C tropicalis and treatment failure were observed. Conclusion: Biofilm production of the C. tropicalis isolate might have had a significant role in treatment failure. Of interest, clinical and microbiological unfavorable outcome was anticipated by persistence of BDG in CSF. Rising titers of this marker were associated with relapse of fungal infection
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