56 research outputs found
A new FSA approach for in situ -ray spectroscopy
An increasing demand of environmental radioactivity monitoring comes both
from the scientific community and from the society. This requires accurate,
reliable and fast response preferably from portable radiation detectors. Thanks
to recent improvements in the technology, -spectroscopy with sodium
iodide scintillators has been proved to be an excellent tool for in-situ
measurements for the identification and quantitative determination of
-ray emitting radioisotopes, reducing time and costs. Both for
geological and civil purposes not only K, U, and Th have
to be measured, but there is also a growing interest to determine the
abundances of anthropic elements, like Cs and I, which are used
to monitor the effect of nuclear accidents or other human activities.
The Full Spectrum Analysis (FSA) approach has been chosen to analyze the
-spectra. The Non Negative Least Square (NNLS) and the energy
calibration adjustment have been implemented in this method for the first time
in order to correct the intrinsic problem related with the
minimization which could lead to artifacts and non physical results in the
analysis.
A new calibration procedure has been developed for the FSA method by using in
situ -spectra instead of calibration pad spectra. Finally, the new
method has been validated by acquiring -spectra with a 10.16 cm x 10.16
cm sodium iodide detector in 80 different sites in the Ombrone basin, in
Tuscany. The results from the FSA method have been compared with the laboratory
measurements by using HPGe detectors on soil samples collected in the different
sites, showing a satisfactory agreement between them. In particular, the
Cs isotopes has been implemented in the analysis since it has been
found not negligible during the in-situ measurements.Comment: accepted by Science of Total Environment: 8 pages, 10 figures, 3
table
Corticosterone enhances CSD susceptibility via glucocorticoid receptor activation in familial hemiplegic migraine 1 Cacna1a knock-in mice
Paroxysmal Cerebral Disorder
Purkinje cell-specific ablation of CaV2.1 Channels is sufficient to cause cerebellar ataxia in mice
The Cacna1a gene encodes the α1A subunit of voltage-gated CaV2.1 Ca2+ channels that are involved in neurotransmission at central synapses. CaV2.1-α1- knockout (α1KO) mice, which lack CaV2.1 channels in all neurons, have a very severe phenotype of cerebellar ataxia and dystonia, and usually die around postnatal day 20. This early lethality, combined with the wide expression of CaV2.1 channels throughout the cerebellar cortex and nuclei, prohibited determination of the contribution of particular cerebellar cell types to the development of the severe neurobiological phenotype in Cacna1a mutant mice. Here, we crossed conditional Cacna1a mice with transgenic mice expressing Cre recombinase, driven by the Purkinje cell-specific Pcp2 promoter, to specifically ablate the CaV2.1- α1A subunit and thereby CaV2.1 channels in Purkinje cells. Purkinje cell CaV2.1-α1A-knockout (PCα1KO) mice aged without difficulties, rescuing the lethal phenotype seen in α1KO mice. PCα1KO mice exhibited cerebellar ataxia starting around P12, much earlier than the first signs of progressive Purkinje cell loss, which appears in these mice between P30 and P45. Secondary cell loss was observed in the granular and molecular layers of the cerebellum and the volume of all individual cerebellar nuclei was reduced. In this mouse model with a cell type-specific ablation of CaV2.1 channels, we show that ablation of CaV2.1 channels restricted to Purkinje cells is sufficient to cause cerebellar ataxia. We demonstrate that spatial ablation of CaV2.1 channels may help in unraveling mechanisms of human disease
Mapping of natural radioelements using gamma-ray spectrometry: Tuscany Region case of study.
http://www.fe.infn.it/u/mantovani/CV/Proceedings/Bezzon_11a.pd
A γ-Spectroscopy System for Atmospheric Radon Detection
Radon isotopes and their decay products cause most
of the natural radioactivity in atmosphere at ground level
(Jacobi, 1964; Altshuler et al., 1964; UNSCEAR, 1988,
1993; Porstendorfer, 1994; Kathren, 1998). 222Rn (Radon)
and 220Rn (Thoron) enter the atmosphere from the Earths
surface, where they are produced via radioactive decay of
the precursors 238U and 232Th respectively. The major
contribution to the natural radioactivity dose is from the
inhalation of the daughters of this gas. They are attached
to very fine particles (Bergamini et al., 1973; Porstendorfer,
1994; Mohammed et al., 2000) and deposit on the surface
of the different parts of the respiratory system with a
probability dependent on aerosol particle sizes (ICRP, 1994).
The dynamics of the gas could be similar to that
of the atmospheric particulate and the daily change in
concentration can be correlated to it. The γ-rays produced
by the Radon daughters come both from the earth surface
and from the radon contained in the air. For a detector
placed in a fixed position, the first contribution remains
constant over the time while the second follows the change
in gas concentration in air. In order to determine the two
contributions a system composed by three sodium iodide
detectors has been designed and installed on a tower at the
LNL (Laboratori Nazionali di Legnaro).
The aim of this project is to understand the behavior of γ
emissions from ground surface at different altitudes and also
to study the correlation between the atmospheric conditions,
like the altitude of the atmosphere inversion layer, and the
radon concentration in air. http://www.fe.infn.it/u/mantovani/CV/Proceedings/Bezzon_11b.pd
The worldwide NORM production and a fully automated gamma-ray spectrometer for their characterization
Materials containing radionuclides of natural origin, which is modified by
human made processes and being subject to regulation because of their
radioactivity are known as NORM. We present a brief review of the main
categories of non-nuclear industries together with the levels of activity
concentration in feed raw materials, products and waste, including mechanisms
of radioisotope enrichments. The global management of NORM shows a high level
of complexity, mainly due to different degrees of radioactivity enhancement and
the huge amount of worldwide waste production. The future tendency of
guidelines concerning environmental protection will require both a systematic
monitoring based on the ever-increasing sampling and high performance of gamma
ray spectroscopy. On the ground of these requirements a new low background
fully automated high-resolution gamma-ray spectrometer MCA_Rad has been
developed. The design of Pb and Cu shielding allowed to reach a background
reduction of two order of magnitude with respect to laboratory radioactivity. A
severe lowering of manpower cost is obtained through a fully automation system,
which enables up to 24 samples to be measured without any human attendance. Two
coupled HPGe detectors increase the detection efficiency, performing accurate
measurements on sample volume (180 cc) with a reduction of sample transport
cost of material. Details of the instrument calibration method are presented.
MCA_Rad system can measure in less than one hour a typical NORM sample enriched
in U and Th with some hundreds of Bq/kg, with an overall uncertainty less than
5%. Quality control of this method has been tested. Measurements of certified
reference materials RGK-1, RGU-2 and RGTh-1 containing concentrations of K, U
and Th comparable to NORM have been performed, resulting an overall relative
discrepancy of 5% among central values within the reported uncertainty.Comment: 21 pages, 4 figures, 6 table
Can environment or allergy explain international variation in prevalence of wheeze in childhood?
Asthma prevalence in children varies substantially around the world, but the contribution of known risk factors to this international variation is uncertain. The International Study of Asthma and Allergies in Childhood (ISAAC) Phase Two studied 8–12 year old children in 30 centres worldwide with parent-completed symptom and risk factor questionnaires and aeroallergen skin prick testing. We used multilevel logistic regression modelling to investigate the effect of adjustment for individual and ecological risk factors on the between-centre variation in prevalence of recent wheeze. Adjustment for single individual-level risk factors changed the centre-level variation from a reduction of up to 8.4% (and 8.5% for atopy) to an increase of up to 6.8%. Modelling the 11 most influential environmental factors among all children simultaneously, the centre-level variation changed little overall (2.4% increase). Modelling only factors that decreased the variance, the 6 most influential factors (synthetic and feather quilt, mother’s smoking, heating stoves, dampness and foam pillows) in combination resulted in a 21% reduction in variance. Ecological (centre-level) risk factors generally explained higher proportions of the variation than did individual risk factors. Single environmental factors and aeroallergen sensitisation measured at the individual (child) level did not explain much of the between-centre variation in wheeze prevalence
In chronic lymphocytic leukemia nurse-like cells are targeted by Hepatocyte Growth Factor produced by bone mesenchymal stromal cells
A comparative evaluation between new ternary zirconium alloys as alternative metals for orthopedic and dental prosthetic devices
Purpose: We assessed in vitro the corrosion behavior and biocompatibility of four Zr-based alloys (Zr97.5 Nb1.5VM1.0; VM, valve metal: Ti, Mo, W, Ta; at%) to be used as implant materials, comparing the results with grade-2 titanium, a biocompatible metal standard. Methods: Corrosion resistance was investigated by open circuit potential and electrochemical impedance spectroscopy measurements as a function of exposure time to an artificial physiological environment (Ringer's solution). Human bone marrow stromal cells were used to evaluate biocompatibility of the alloys and their influence on growth kinetics and cell osteogenic differentiation through histochemical and gene expression analyses. Results: Open circuit potential values indicated that Zr-based alloys and grade-2 Ti undergo spontaneous passivation in the simulated aggressive environment. High impedance values for all samples demonstrated improved corrosion resistance of the oxide film, with the best protection characteristics displayed by Zr97.5 Nb1.5Ta1.0. Cells seeded on all surfaces showed the same growth kinetics, although matrix mineralization and alkaline phosphatase activity were maximal on Zr97.5 Nb1.5Mo1.0 and Zr97.5 Nb1.5Ta1.0. Markers of ongoing proliferation, however, such as podocalyxin and CD49f, were still overexpressed on Zr97.5Mo1.0Nb1.5even upon osteoinduction. No relevant effects were noted for he CD146-expressing population of bone progenitors. Nonetheless, the presence of a more differentiated cell population on Zr97.5Nb1.5Ta1.0 samples was inferable by comparing mineralization data and transcript levels of osteogenic markers (osteocalcin, osteopontin, bone sialoprotein, and RUNX2). Conclusions: The combination of passivation, corrosion resistance and satisfactory biotolerance to bone progenitors make the Zr-based alloys promising implant materials. Among those we tested, Zr97.5Nb1.5Ta1.0 seems to be the most appealin
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