2,333 research outputs found
"MADE IN ITALY" AND "MADE IN CHINA". EMPIRICAL ANALYSIS AND INDUSTRIAL POLICY IMPLICATIONS
quality, sectoral specialisation, international trade, price differentials
Advanced radar absorbing ceramic-based materials for multifunctional applications in space environment
In this review, some results of the experimental activity carried out by the authors on advanced composite materials for space applications are reported. Composites are widely employed in the aerospace industry thanks to their lightweight and advanced thermo-mechanical and electrical properties. A critical issue to tackle using engineered materials for space activities is providing two or more specific functionalities by means of single items/components. In this scenario, carbon-based composites are believed to be ideal candidates for the forthcoming development of aerospace research and space missions, since a widespread variety of multi-functional structures are allowed by employing these materials. The research results described here suggest that hybrid ceramic/polymeric structures could be employed as spacecraft-specific subsystems in order to ensure extreme temperature withstanding and electromagnetic shielding behavior simultaneously. The morphological and thermo-mechanical analysis of carbon/carbon (C/C) three-dimensional (3D) shell prototypes is reported; then, the microwave characterization of multilayered carbon-filled micro-/nano-composite panels is described. Finally, the possibility of combining the C/C bulk with a carbon-reinforced skin in a synergic arrangement is discussed, with the aid of numerical and experimental analyses
Spectral and polarimetric characterization of the Gas Pixel Detector filled with dimethyl ether
The Gas Pixel Detector belongs to the very limited class of gas detectors
optimized for the measurement of X-ray polarization in the emission of
astrophysical sources. The choice of the mixture in which X-ray photons are
absorbed and photoelectrons propagate, deeply affects both the energy range of
the instrument and its performance in terms of gain, track dimension and
ultimately, polarimetric sensitivity. Here we present the characterization of
the Gas Pixel Detector with a 1 cm thick cell filled with dimethyl ether (DME)
at 0.79 atm, selected among other mixtures for the very low diffusion
coefficient. Almost completely polarized and monochromatic photons were
produced at the calibration facility built at INAF/IASF-Rome exploiting Bragg
diffraction at nearly 45 degrees. For the first time ever, we measured the
modulation factor and the spectral capabilities of the instrument at energies
as low as 2.0 keV, but also at 2.6 keV, 3.7 keV, 4.0 keV, 5.2 keV and 7.8 keV.
These measurements cover almost completely the energy range of the instrument
and allows to compare the sensitivity achieved with that of the standard
mixture, composed of helium and DME.Comment: 20 pages, 11 figures, 5 tables. Accepted for publication by NIM
Optimal cutoff-value of Siemens cardiac troponin I assay in patients with kidney disease for the early diagnosis of acute myocardial infarction
Purpose: The recent introduction of more sensitive cardiac troponin (cTn) assays improved the early diagnosis of acute myocardial infarction (AMI). However, its diagnostic utility has never been tested in patients with kidney disease (KD), who are known to have elevated levels of cTn already in the absence of AMI, which may lead to a lower diagnostic value of more sensitive cTn in this high-risk subgroup. Methods: We conducted an international multicenter study to examine the diagnostic accuracy of the Siemens cTnI Ultra assay in 1997 consecutive patients presenting to the emergency department with symptoms suggestive of AMI, of whom 343 (17%) were determined to have KD (MDRD GFR <60ml/min/1.73m2) and to derive the optimal cutoff-value for the diagnosis of AMI in patients with KD. The diagnostic accuracy was further compared to a conventional cTn assay (Roche Troponin T fourth generation). The final diagnosis was adjudicated by two independent cardiologists based on hs-cTnT. Results: AMI was the final diagnosis in 35% (n=120) of all KD-patients as compared to 18% in patients with normal kidney function (p<0.001). Among KD-patients with other diagnoses than AMI, baseline hs-cTnI-levels were elevated above the 99thpercentile in 20%, In patients with KD the diagnostic accuracy at presentation, quantified by the area under the receiver-operator-characteristic curve (AUC), was significantly greater for Siemens cTnI as compared to the standard cTnT assay (AUC for cTnI, 0.88 vs. AUC for the standard assay, 0.82, p=0.013). In patients presenting within three hours after the onset of chest pain, the superiority of Siemens cTnI over conventional cTnT was even more pronounced (AUC 0.86 vs. 0.72, p=0.005). In KD, the optimal hs-cTnI cutoff derived from the ROC curve was 46 ng/l compared to 19 ng/l in patients with normal kidney function (standard 99th percentile 40 ng/l, provided by the manufacturer). Conclusions: The Siemens cTnI Ultra assay has a very high diagnostic accuracy also in KD-patients and is superior to a conventional cTnT-assay. Mild cTnI elevations are common in non-AMI patients. The optimal cutoff-level in KD-patients seems to be around the 99th percentile of a standard population, whereas the optimal cutoff-level in patients with normal kidney function tends to be only half of the suggested cutoff-value. ClinicalTrials.gov number, NCT0047058
HSP 27 aspossible prognostic factor in patients with oral squamous cell carcinoma.
Summary. HSP27 belongs to the Heat shock protein
(HSP) family, which plays essential functions in cells
under physiological conditions and prevents stressinduced
cellular damage. The aim of this study was to
investigate the biological role of HSP27 in oral
tumorigenesis. Materials and methods: Seventy-nine
cases of oral squamous cell carcinoma and 10 cases of
normal mucosa were analysed for HSP27 expression by
immunohistochemistry. Moreover, the western blot
analysis was performed on two cases of normal mucosa
and five cases of OSCC. Results: Normal oral mucosa
showed a suprabasal expression of HSP27. Twenty-four
cases of SCC (30.7%) showed a diffuse staining for
HSP27, and 48 cases (60.3%) showed instead a decrease
in staining, which was diffuse, homogeneous, or with
alternation of positive and negative areas in a single
tumor (“mosaic” pattern). Only 7 cases of OSCC (7.5%)
were completely negative for HSP27. Frequency of
lymph node metastases was higher in HSP27-negative
tumours (3/7, 42.8%) than in HSP-reduced (16/48,
33.3%) or positive ones (5/26, 19.2%). Regard staging,
stages I and II had a higher score than stages III and IV
(stage I > stage II > stage III > stage IV). There was also
a statistically significant correlation between HSP27
expression and grade: HSP27 expression was reduced in
poorly differentiated tumours (P < 0.05). When analysed
for prognostic significance, patients with
negative/reduced HSP27 expression had poorer survival
rates than the group with positive HSP27 expression (P
< 0.05). The statistical analysis of these findings showed
no significant correlation between HSP27 expression,
sex, and tumour size. Conclusion: Cases with reduced
expression were more aggressive and poorly
differentiated. These data suggest that HSP27 expression may be useful in order to identify cases of oral squamous
cell carcinoma with more aggressive and invasive
phenotype providing novel diagnostic and prognostic
information on individual patient survival with oral
cancers
Low energy polarization sensitivity of the Gas Pixel Detector
An X-ray photoelectric polarimeter based on the Gas Pixel Detector has been
proposed to be included in many upcoming space missions to fill the gap of
about 30 years from the first (and to date only) positive measurement of
polarized X-ray emission from an astrophysical source. The estimated
sensitivity of the current prototype peaks at an energy of about 3 keV, but the
lack of readily available polarized sources in this energy range has prevented
the measurement of detector polarimetric performances.
In this paper we present the measurement of the Gas Pixel Detector
polarimetric sensitivity at energies of a few keV and the new, light, compact
and transportable polarized source that was devised and built to this aim.
Polarized photons are produced, from unpolarized radiation generated with an
X-ray tube, by means of Bragg diffraction at nearly 45 degrees.
The employment of mosaic graphite and flat aluminum crystals allow the
production of nearly completely polarized photons at 2.6, 3.7 and 5.2 keV from
the diffraction of unpolarized continuum or line emission. The measured
modulation factor of the Gas Pixel Detector at these energies is in good
agreement with the estimates derived from a Monte Carlo software, which was up
to now employed for driving the development of the instrument and for
estimating its low energy sensitivity. In this paper we present the excellent
polarimetric performance of the Gas Pixel Detector at energies where the peak
sensitivity is expected. These measurements not only support our previous
claims of high sensitivity but confirm the feasibility of astrophysical X-ray
photoelectric polarimetry.Comment: 15 pages, 12 figures. Accepted for publication in NIM
The imaging properties of the Gas Pixel Detector as a focal plane polarimeter
X-rays are particularly suited to probe the physics of extreme objects.
However, despite the enormous improvements of X-ray Astronomy in imaging,
spectroscopy and timing, polarimetry remains largely unexplored. We propose the
photoelectric polarimeter Gas Pixel Detector (GPD) as an instrument candidate
to fill the gap of more than thirty years of lack of measurements. The GPD, in
the focus of a telescope, will increase the sensitivity of orders of magnitude.
Moreover, since it can measure the energy, the position, the arrival time and
the polarization angle of every single photon, allows to perform polarimetry of
subsets of data singled out from the spectrum, the light curve or the image of
source. The GPD has an intrinsic very fine imaging capability and in this work
we report on the calibration campaign carried out in 2012 at the PANTER X-ray
test facility of the Max-Planck-Institut f\"ur extraterrestrische Physik of
Garching (Germany) in which, for the first time, we coupled it to a JET-X
optics module with a focal length of 3.5 m and an angular resolution of 18
arcsec at 4.5 keV. This configuration was proposed in 2012 aboard the X-ray
Imaging Polarimetry Explorer (XIPE) in response to the ESA call for a small
mission. We derived the imaging and polarimetric performance for extended
sources like Pulsar Wind Nebulae and Supernova Remnants as case studies for the
XIPE configuration, discussing also possible improvements by coupling the
detector with advanced optics, having finer angular resolution and larger
effective area, to study with more details extended objects.Comment: Accepted for publication in The Astrophysical Journal Supplemen
Progress on the development of the Stellar X-ray Polarimeter on board of the Spectrum-X-Gamma Satellite
We present the status of the Stellar X-ray Polarimeter at November’94 devoted to measure linear polarisation from cosmic X-ray sources between 2 keV and 15 keV which will be flown on the Spectrum-X-Gamma Satellite. In particular, we
focus on the performances of the engineering model after the calibrations at Lawrence Livermore Laboratories and on the improvements which have been introduced on the four flight model imaging proportional counters which are key
parts of the experiment
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