159 research outputs found
The SPOrt Project: Cosmological and Astrophysical Goals
We present the cosmological and astrophysical objectives of the SPOrt
mission, which is scheduled for flying on the International Space Station (ISS)
in the year 2002 with the purpose of measuring the diffuse sky polarized
radiation in the microwave region. We discuss the problem of disentangling the
cosmic background polarized signal from the Galactic foregrounds.Comment: 10 pages; 5 PS figures; requires aipproc2.cls, aipproc2.sty,
epsfc.tex; to appear in Proc. of ``3K Cosmology'', Rome 5-10 Oct. 199
Radio monitoring of a sample of X- and gamma-ray loud blazars
In this paper we present the results of a 4-year (1996 - 1999) radio flux
density monitoring program for a sample of X- and -ray loud blazars.
Our program started in January 1996 and was carried out on monthly basis at the
frequencies of 5 GHz and 8.4 GHz with the 32-m antennas located in Medicina
(Bologna, Italy) and Noto (Siracusa, Italy). 22 GHz data collected in Medicina
from January 1996 to June 1997 will also be presented. The sample of selected
sources comprises most radio loud blazars with
characterised by emission in the X- and -ray regimes, and target
sources for the BeppoSAX X-ray mission. All sources in the sample, except
J1653+397 (MKN 501), are variable during the four years of our monitoring
program. We classified the type of variability in each source by means of a
structure function analysis. We also computed th for all
epochs with nearly simultaneous observations ate spectral index and found that
starts flattening at the very beginning o f a radio flare,
or flux density increase.Comment: 12 pages, 3 tables and 1 figure, in press on A&
Low energy high angular resolution neutral atom detection by means of micro-shuttering techniques: the BepiColombo SERENA/ELENA sensor
The neutral sensor ELENA (Emitted Low-Energy Neutral Atoms) for the ESA
cornerstone BepiColombo mission to Mercury (in the SERENA instrument package)
is a new kind of low energetic neutral atoms instrument, mostly devoted to
sputtering emission from planetary surfaces, from E ~20 eV up to E~5 keV,
within 1-D (2x76 deg). ELENA is a Time-of-Flight (TOF) system, based on
oscillating shutter (operated at frequencies up to a 100 kHz) and mechanical
gratings: the incoming neutral particles directly impinge upon the entrance
with a definite timing (START) and arrive to a STOP detector after a flight
path. After a brief dissertation on the achievable scientific objectives, this
paper describes the instrument, with the new design techniques approached for
the neutral particles identification and the nano-techniques used for designing
and manufacturing the nano-structure shuttering core of the ELENA sensor. The
expected count-rates, based on the Hermean environment features, are shortly
presented and discussed. Such design technologies could be fruitfully exported
to different applications for planetary exploration.Comment: 11 page
The Coaxial L-P Cryogenic Receiver of the Sardinia Radio Telescope
The design and characterization of the coaxial dual-band L-P radio astronomical receiver for the prime focus of the Sardinia radio telescope are presented. The main feature of this receiver is to allow simultaneous radio astronomical observations in the P (305-410 MHz) and L (1.3-1.8 GHz) frequency bands. This functionality, which has been requested by the Pulsar research group at the National Institute for Astrophysics to estimate, among the others, the ionospheric dispersion in Pulsar observation, is currently missing in any other radio astronomical facility throughout the world. Also, single band operation is ensured by the proposed design both in linear and circular polarization, making this L-P receiver an ideal instrument for a wide range of radio astronomical and space applications. Some components of the receiver chain have been housed inside a cryostat and refrigerated at 20 K to reduce the noise temperature, resulting in a good performance compared to the receivers of other large radio telescopes. Several challenging issues have been faced in the design, mainly due to the large dimension and weight of the overall structure to be mounted in the prime focus position. Moreover, the design of the cryostat was constrained by the limited space available in the direction of the optical axis inside the focal cabin of the radio telescope, requiring a compact and light realization of the components of the receiver chain. This called for a home-made design of several devices, requiring a strong collaborative effort by researchers, engineers, and astronomers
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Thermal H<sub>2</sub>O emission from the Herbig-Haro flow HH 54
The first detection of thermal water emission from a Herbig-Haro object is presented. The observations were performed with the LWS (Long Wavelength Spectrograph) aboard ISO (Infrared Space Observatory). Besides H2O, rotational lines of CO are present in the spectrum of HH 54. These high-J CO lines are used to derive the physical model parameters of the FIR (far-infrared) molecular line emitting regions. This model fits simultaneously the observed OH and H2O spectra for an OH abundance X(OH)=10-6 and a water vapour abundance X(H2O)=10-5.
At a distance of 250pc, the total CO, OH and H2O rotational line cooling rate is estimated to be 1.3x10-2 L⊙, which is comparable to the mechanical luminosity generated by the 10km s-1 shocks, suggesting that practically all of the cooling of the weak-shock regions is done by these three molecular species alone
Synergistic interaction between the type III secretion system of the endophytic bacterium <i>Pantoea agglomerans</i> DAPP-PG 734 and the virulence of the causal agent of olive knot <i>Pseudomonas savastanoi pv. savastanoi</i> DAPP-PG 722
The endophytic bacterium Pantoea agglomerans DAPP-PG 734 was previously isolated from olive knots caused by infection with Pseudomonas savastanoi pv. savastanoi DAPP-PG 722. Whole-genome analysis of this P. agglomerans strain revealed the presence of a Hypersensitive response and pathogenicity (Hrp) type III secretion system (T3SS). To assess the role of the P. agglomerans T3SS in the interaction with P. savastanoi pv. savastanoi, we generated independent knockout mutants in three Hrp genes of the P. agglomerans DAPP-PG 734 T3SS (hrpJ, hrpN, and hrpY). In contrast to the wildtype control, all three mutants failed to cause a hypersensitive response when infiltrated in tobacco leaves, suggesting that P. agglomerans T3SS is functional and injects effector proteins in plant cells. In contrast to P. savastanoi pv. savastanoi DAPP-PG 722, the wildtype strain P. agglomerans DAPP-PG 734 and its Hrp T3SS mutants did not cause olive knot disease in 1-year-old olive plants. Coinoculation of P. savastanoi pv. savastanoi with P. agglomerans wildtype strains did not significantly change the knot size, while the DAPP-PG 734 hrpY mutant induced a significant decrease in knot size, which could be complemented by providing hrpY on a plasmid. By epifluorescence microscopy and confocal laser scanning microscopy, we found that the localization patterns in knots were nonoverlapping for P. savastanoi pv. savastanoi and P. agglomerans when coinoculated. Our results suggest that suppression of olive plant defences mediated by the Hrp T3SS of P. agglomerans DAPP-PG 734 positively impacts the virulence of P. savastanoi pv. savastanoi DAPP-PG 722
The Sport Project: an Experimental Overview
The Sky Polarization Observatory (SPOrt) is presented as a project aimed to measure the diffuse sky polarized emission, from the International Space Station, in the frequency range 20-90 GHz with 7 degrees of HPBW. The SPOrt experimental configuration is described with emphasis on the aspects that make SPOrt the first European scientific payload operating at microwave wavelengths
Comparison of EV-free fraction, EVs, and total secretome of amniotic mesenchymal stromal cells for their immunomodulatory potential: a translational perspective
Amniotic mesenchymal stromal cells (hAMSCs) have unique immunomodulatory properties demonstrated in vitro and in vivo in various diseases in which the dysregulated immune system plays a major role. The immunomodulatory and pro-regenerative effects of MSCs, among which hAMSCs lie in the bioactive factors they secrete and in their paracrine activity, is well known. The mix of these factors (i.e., secretome) can be either freely secreted or conveyed by extracellular vesicles (EV), thus identifying two components in the cell secretome: EV-free and EV fractions. This study aimed to discern the relative impact of the individual components on the immunomodulatory action of the hAMSC secretome in order to obtain useful information for implementing future therapeutic approaches using immunomodulatory therapies based on the MSC secretome. To this aim, we isolated EVs from the hAMSC secretome (hAMSC-CM) by ultracentrifugation and validated the vesicular product according to the International Society for Extracellular Vesicles (ISEV) criteria. EVs were re-diluted in serum-free medium to maintain the EV concentration initially present in the original CM. We compared the effects of the EV-free and EV fractions with those exerted by hAMSC-CM in toto on the activation and differentiation of immune cell subpopulations belonging to both the innate and adaptive immune systems.We observed that the EV-free fraction, similar to hAMSC-CM in toto, a) decreases the proliferation of activated peripheral blood mononuclear cells (PBMC), b) reduces the polarization of T cells toward inflammatory Th subsets, and induces the induction of regulatory T cells; c) affects monocyte polarization to antigen-presenting cells fostering the acquisition of anti-inflammatory macrophage (M2) markers; and d) reduces the activation of B lymphocytes and their maturation to plasma cells. We observed instead that all investigated EV fractions, when used in the original concentrations, failed to exert any immunomodulatory effect, even though we show that EVs are internalized by various immune cells within PBMC. These findings suggest that the active component able to induce immune regulation, tested at original concentrations, of the hAMSC secretome resides in factors not conveyed in EVs. However, EVs isolated from hAMSC could exert actions on other cell types, as reported by others
The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
The Photodetector Array Camera and Spectrometer (PACS) is one of the three
science instruments on ESA's far infrared and submillimetre observatory. It
employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16x25
pixels, each, and two filled silicon bolometer arrays with 16x32 and 32x64
pixels, respectively, to perform integral-field spectroscopy and imaging
photometry in the 60-210\mu\ m wavelength regime. In photometry mode, it
simultaneously images two bands, 60-85\mu\ m or 85-125\mu\m and 125-210\mu\ m,
over a field of view of ~1.75'x3.5', with close to Nyquist beam sampling in
each band. In spectroscopy mode, it images a field of 47"x47", resolved into
5x5 pixels, with an instantaneous spectral coverage of ~1500km/s and a spectral
resolution of ~175km/s. We summarise the design of the instrument, describe
observing modes, calibration, and data analysis methods, and present our
current assessment of the in-orbit performance of the instrument based on the
Performance Verification tests. PACS is fully operational, and the achieved
performance is close to or better than the pre-launch predictions
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