1,245 research outputs found
Physical Investigation of the Potentially Hazardous Asteroid (144898) 2004 VD17
In this paper we present the observational campaign carried out at ESO NTT
and VLT in April and May 2006 to investigate the nature and the structure of
the Near Earth Object (144898) 2004 VD17. In spite of a great quantity of
dynamical information, according to which it will have a close approach with
the Earth in the next century, the physical properties of this asteroid are
largely unknown. We performed visible and near--infrared photometry and
spectroscopy, as well as polarimetric observations. Polarimetric and
spectroscopic data allowed us to classify 2004 VD17 as an E-type asteroid. A
good agreement was also found with the spectrum of the aubrite meteorite Mayo
Belwa. On the basis of the polarimetric albedo (p_v=0.45) and of photometric
data, we estimated a diameter of about 320 m and a rotational period of about 2
hours. The analysis of the results obtained by our complete survey have shown
that (144898) 2004 VD17 is a peculiar NEO, since it is close to the breakup
limits for fast rotator asteroids, as defined by Pravec and Harris (2000).
These results suggest that a more robust structure must be expected, as a
fractured monolith or a rubble pile in a "strength regime" (Holsapple 2002).Comment: 32 pages, 7 figure, paper accepted for publication in Icaru
Spectroscopic survey of M--type asteroids
M-type asteroids, as defined in the Tholen taxonomy (Tholen, 1984), are
medium albedo bodies supposed to have a metallic composition and to be the
progenitors both of differentiated iron-nickel meteorites and enstatite
chondrites. We carried out a spectroscopic survey in the visible and near
infrared wavelength range (0.4-2.5 micron) of 30 asteroids chosen from the
population of asteroids initially classified as Tholen M -types, aiming to
investigate their surface composition. The data were obtained during several
observing runs during the years 2004-2007 at the TNG, NTT, and IRTF telescopes.
We computed the spectral slopes in several wavelength ranges for each observed
asteroid, and we searched for diagnostic spectral features. We confirm a large
variety of spectral behaviors for these objects as their spectra are extended
into the near-infrared, including the identification of weak absorption bands,
mainly of the 0.9 micron band tentatively attributed to orthopyroxene, and of
the 0.43 micron band that may be associated to chlorites and Mg-rich
serpentines or pyroxene minerals such us pigeonite or augite. A comparison with
previously published data indicates that the surfaces of several asteroids
belonging to the M-class may vary significantly. We attempt to constrain the
asteroid surface compositions of our sample by looking for meteorite spectral
analogues in the RELAB database and by modelling with geographical mixtures of
selected meteorites/minerals. We confirm that iron meteorites, pallasites, and
enstatite chondrites are the best matches to most objects in our sample, as
suggested for M-type asteroids. The presence of subtle absorption features on
several asteroids confirms that not all objects defined by the Tholen M-class
have a pure metallic composition.Comment: 10 figures, 6 tables; Icarus, in pres
Inhomogeneities on the surface of 21 Lutetia, the asteroid target of the Rosetta mission
CONTEXT: In July 2010 the ESA spacecraft Rosetta will fly-by the main belt
asteroid 21 Lutetia. Several observations of this asteroid have been so far
performed, but its surface composition and nature are still a matter of debate.
For long time Lutetia was supposed to have a metallic nature due to its high
IRAS albedo. Later on it has been suggested to have a surface composition
similar to primitive carbonaceous chondrite meteorites, while further
observations proposed a possible genetic link with more evolved enstatite
chondrite meteorites. AIMS: In order to give an important contribution in
solving the conundrum of the nature of Lutetia, in November 2008 we performed
visible spectroscopic observations of this asteroid at the Telescopio Nazionale
Galileo (TNG, La Palma, Spain). METHODS: Thirteen visible spectra have been
acquired at different rotational phases. RESULTS: We confirm the presence of a
narrow spectral feature at about 0.47-0.48 micron already found by Lazzarin et
al. (2009) on the spectra of Lutetia. We also find a spectral feature at about
0.6 micron, detected by Lazzarin et al. (2004) on one of their Lutetia's
spectra. More importantly, our spectra exhibit different spectral slopes
between 0.6 and 0.75 micron and, in particular, we found that up to 20% of the
Lutetia surface could have flatter spectra. CONCLUSIONS: We detected a
variation of the spectral slopes at different rotational phases that could be
interpreted as possibly due to differences in the chemical/mineralogical
composition, as well as to inhomogeneities of the structure of the Lutetia's
surface (e.g., the presence of craters or albedo spots) in the southern
hemisphere.Comment: 3 pages, 2 figures. Accepted for publication in Astronomy and
Astrophysics. Updated on 25 March 2010
Visualizing cellular heterogeneity by quantifying the dynamics of MAPK activity in live mammalian cells with synthetic fluorescent biosensors.
Mitogen-Activated Protein Kinases (MAPKs) control a wide array of cellular functions by transducing extracellular information into defined biological responses. In order to understand how these pathways are regulated, dynamic single cell measurements are highly needed. Fluorescence microscopy is well suited to perform these measurements. However, more dynamic and sensitive biosensors that allow the quantification of signaling activity in living mammalian cells are required. We have engineered a synthetic fluorescent substrate for human MAPKs (ERK, JNK and p38) that relocates from the nucleus to the cytoplasm when phosphorylated by the kinases. We demonstrate that this reporter displays an improved response compared to other relocation biosensors. This assay allows to monitor the heterogeneity in the MAPK response in a population of isogenic cells, revealing pulses of ERK activity upon a physiological EGFR stimulation. We show applicability of this approach to the analysis of multiple cancer cell lines and primary cells as well as its application in vivo to developing tumors. Using this ERK biosensor, dynamic single cell measurements with high temporal resolution can be obtained. These MAPK reporters can be widely applied to the analysis of molecular mechanisms of MAPK signaling in healthy and diseased state, in cell culture assays or in vivo
Postoperative pain and surgical time comparison using piezoelectric or conventional implant site preparation systems
Since its introduction, piezoelectric bone surgery has established an important role in oral surgery and dental implantology. Piezoelectric surgery is efficient at preparing implant site osteotomies due to its selective cut, micro-streaming and cavitational effects, which preserve and maintain the soft tissue. Several advantages have been outlined in patient\u2019s symptoms, both in terms of improved intraoperative comfort and postoperative course. The aim of this study was to compare implant insertion procedures using piezoelectric surgery or conventional drilling. Intra- and postoperative pain, implant site preparation time and learning curve were evaluated. Methods: A total of 13 (7 women/6 men, aged between 45 and 75 years) partially edentulous patients were rehabilitated with 40 titanium implants (n=20). Implant therapy consisted in the inclusion of at least two conical implants between 3.8 and 4.5 mm diameter with a maximum torque of 35 Ncm in randomised bilateral edentulous areas. First sites were prepared with piezodevice (test sites) and the contralateral ones with conventional drilling (control sites). Surgery was always performed by the same operator. Implant site preparation timing was measured from flap elevation until implant inclusion. Patients recorded their subjective intraoperative and postoperative pain daily for 7 days and at 15th day after surgery using a Visual Analog Scale (VAS). Results: Patients treated with piezoelectric technique presented a lower VAS, minor swelling and less recovery time compared to the conventional technique. No operative complications were reported and the implant survival rate at 1 year was 100% for both the techniques. VAS significant differences were found for the test sites as intraoperative symptoms (p = 0.009), after 1 day (p = 0.010), 2 days (p = 0.016), 3 days (p = 0.017), 5 days (p = 0.015), 6 days (p = 0.018) and 7 days (p = 0.039). The average surgical times of implant sites preparation were: 10 (\ub1 1.4) minutes for the test sites, and 7.00 (\ub1 1.7) minutes for the control sites. In 69.2% of cases (9 of 13 patients) the operator has found advantages in terms of better access to the posterior sites, enhanced intraoperative visibility and insertion axis maintenance using the piezoelectric technique. The learning curve with piezodevice has seen a decrease in timing (rho = -0827, p = 0.001) from the first to the last intervention; whereas no significant difference was evaluated with the traditional method. Conclusion: Compared to traditional methods, piezoelectric technique enables optimal healing because it reduces the postsurgery swelling and discomfort. The average time necessary for the piezoelectric implant site osteotomy was approximately 3 minutes more than conventional technique
Thermal infrared observations of near-Earth asteroid 2002 NY40
We obtained N-band observations of the Apollo asteroid 2002 NY40 during its
close Earth fly-by in August 2002 with TIMMI2 at the ESO 3.6 m telescope. The
photometric measurement allowed us to derive a radiometric diameter of
0.28+/-0.03 km and an albedo of 0.34+/-0.06 through the near-Earth asteroid
thermal model (NEATM) and a thermophysical model (TPM). The values are in
agreement with results from radar data, visual and near-IR observations. In
this first comparison between these two model approaches we found that the
empirical NEATM beaming parameter =1.0 corresponds to a thermal inertia
values of about 100 for a typical range of
surface roughness, assuming an equator-on viewing angle. Our TPM analysis
indicated that the surface of 2002 NY40 consists of rocky material with a thin
or no dust regolith. The asteroid very likely has a prograde sense of rotation
with a cold terminator at the time of our observations. Although both model
approaches can fit the thermal spectra taken at phase angles of 22
and 59, we did not find a consistent model solution that describes
all pieces of photometric and spectroscopic data. In addition to the 2002 NY40
analysis, we discuss the possibilities to distinguish between different models
with only very few photometric and/or spectroscopic measurements spread over a
range of phase angles.Comment: 6 pages, 4 figures, A&A accepte
Absence of class 1 and class 2 integrons among Campylobacter jejuni and Campylobacter coli isolated from poultry in Italy
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Occurrence and characterization of Salmonella strains isolated from animals involved in animal assisted interventions (AAIs)
Low delta-V near-Earth asteroids: A survey of suitable targets for space missions
In the last decades Near-Earth Objects (NEOs) have become very important
targets to study, since they can give us clues to the formation, evolution and
composition of the Solar System. In addition, they may represent either a
threat to humankind, or a repository of extraterrestrial resources for suitable
space-borne missions. Within this framework, the choice of next-generation
mission targets and the characterisation of a potential threat to our planet
deserve special attention. To date, only a small part of the 11,000 discovered
NEOs have been physically characterised. From ground and space-based
observations one can determine some basic physical properties of these objects
using visible and infrared spectroscopy. We present data for 13 objects
observed with different telescopes around the world (NASA-IRTF, ESO-NTT, TNG)
in the 0.4 - 2.5 um spectral range, within the NEOSURFACE survey
(http://www.oa-roma.inaf.it/planet/NEOSurface.html). Objects are chosen from
among the more accessible for a rendez-vous mission. All of them are
characterised by a delta-V (the change in velocity needed for transferring a
spacecraft from low-Earth orbit to rendez-vous with NEOs) lower than 10.5 km/s,
well below the Solar System escape velocity (12.3 km/s). We taxonomically
classify 9 of these objects for the first time. 11 objects belong to the
S-complex taxonomy; the other 2 belong to the C-complex. We constrain the
surface composition of these objects by comparing their spectra with meteorites
from the RELAB database. We also compute olivine and pyroxene mineralogy for
asteroids with a clear evidence of pyroxene bands. Mineralogy confirms the
similarity with the already found H, L or LL ordinary chondrite analogues.Comment: 9 pages, 7 figures, to be published in A&A Minor changes by language
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