1,239 research outputs found
Polycapillary optics for soft X-ray imaging and tomography
Magnetic plasmas are extended volumetric sources of X-rays, and these emissions could reveal a lot of information about the processes occurring into the plasmas. Unfortunately, the constraints posed by these toroidal devices (high
neutron flux, gamma and hard-X background, extremely high radiofrequency powers, high magnetic fields, optical limitations and so on) are very severe and limit strongly the possibility to install X-ray detectors directly into or close to the machine. Soft X-ray diagnostics are meant both as tomography and imaging. We started, therefore, to investigate the feasibility of using polycapillary optics for these purposes, in collaboration between Istituto Nazionale di Fisica Nucleare (INFN)- Frascati, Ente per le Nuove tecnologie, lâEnergia e lâAmbiente (ENEA)-Frascati and
the Commissariat de lâEnergie Atomique (CEA)-Cadarache. The first tests were performed in order to characterize the polycapillary lenses (convergence, divergence, efficiency, spectral dispersion, etc.) for distances much larger than the optical focal length of the lenses, both for the detector and for the source. A silicon-based C-MOS imager (Medipix 2) has been used as a detector and the micro focus X-ray tubes as point-like sources. Results of these preliminary tests are presented, and the imaging capabilities of a polycapillary lens as well
MicroRNA Signature in Human Normal and Tumoral Neural Stem Cells
MicroRNAs, also called miRNAs or simply miRâ, represent a unique class of nonâcoding
RNAs that have gained exponential interest during recent years because of their determinant
involvement in regulating the expression of several genes. Despite the increasing number of
mature miRNAs recognized in the human species, only a limited proportion is engaged in the
ontogeny of the central nervous system (CNS). miRNAs also play a pivotal role during the
transition of normal neural stem cells (NSCs) into tumorâforming NSCs. More specifically,
extensive studies have identified some shared miRNAs between NSCs and neural cancer stem cells
(CSCs), namely miRâ7, â124, â125, â181 and miRâ9, â10, â130. In the context of NSCs, miRNAs are
intercalated from embryonic stages throughout the differentiation pathway in order to achieve
mature neuronal lineages. Within CSCs, under a different cellular context, miRNAs perform tumor
suppressive or oncogenic functions that govern the homeostasis of brain tumors. This review will
draw attention to the most characterizing studies dealing with miRNAs engaged in neurogenesis
and in the tumoral neural stem cell context, offering the reader insight into the power of next
generation miRNAâtargeted therapies against brain malignancies
Experimental results of crystal-assisted slow extraction at the SPS
The possibility of extracting highly energetic particles from the Super
Proton Synchrotron (SPS) by means of silicon bent crystals has been explored
since the 1990's. The channelling effect of a bent crystal can be used to
strongly deflect primary protons and eject them from the synchrotron. Many
studies and experiments have been carried out to investigate crystal
channelling effects. The extraction of 120 and 270 GeV proton beams has already
been demonstrated in the SPS with dedicated experiments located in the ring.
Presently in the SPS, the UA9 experiment is performing studies to evaluate the
possibility to use bent silicon crystals to steer particle beams in high energy
accelerators. Recent studies on the feasibility of extraction from the SPS have
been made using the UA9 infrastructure with a longer-term view of using
crystals to help mitigate slow extraction induced activation of the SPS. In
this paper, the possibility to eject particles into the extraction channel in
LSS2 using the bent crystals already installed in the SPS is presented. Details
of the concept, simulations and measurements carried out with beam are
presented, before the outlook for the future is discussed.Comment: 4 pages, 7 figures, submitted to to International Particle
Accelerator Conference (IPAC) 2017 in Copenhagen, Denmar
Production and performance of LHCb triple-GEM detectors equipped with the dedicated CARDIAC-GEM front-end electronics
The production of the triple-GEM detectors for the innermost region of the first muon station of the LHCb experiment has started in February 2006, and is foreseen to be completed by the end of July. The final design of the detector and the construction procedure and tools, as well as the quality controls are defined. The performances of each detector, composed by two triple-GEM chambers equipped with dedicated CARDIAC-GEM front-end electronics, are studied with a cosmic ray telescope. The cosmic ray telescope has been set up including all the final off-detector components
Aging measurements on triple-GEM detectors operated with CF4-based gas mixtures
We present the results of a global irradiation test of full size triple-GEM detectors operated with CF 4 -based gas mixtures. This study has been performed in the framework of an R&D activity on detectors for the innermost region of the first muon station of the LHCb experiment. The prototypes have been irradiated at the Calliope facility of the ENEA-Casaccia with a high intensity 1.25 MeV Îł 60 Co source. After the irradiation test the detectors performances have been measured with X-rays and with a 3 GeV pion beam at CERN. A SEM analysis on several samples of the detectors has been performed to complete the understanding of the physical processes occurring in a GEM detector during a strong irradiation
A complete simulation of a triple-GEM detector
Since some years the gas electron multipliers (GEM)based detectors have been proposed for many different applications, in particular, in high-energy physics and astrophysics experiments and medical imaging. Many experimental measurements and tests have been performed to investigate their characteristics and performances. To achieve a better understanding of the behavior of this kind of detector the computer simulation is a very important tool. In this paper, a complete and detailed simulation of a triple-GEM-based detector is described. A method has been developed to take into account all the processes from the ionization mechanism up to the signal formation and electronic response. The results obtained are compared with experimental data and a very good agreement is achieved
A triple GEM gamma camera for medical application
Abstract A Gamma Camera for medical applications 10 Ă 10 cm 2 has been built using a triple GEM chamber prototype. The photon converters placed in front of the three GEM foils, has been realized with different technologies. The chamber, High Voltage supplied with a new active divider made in Frascati, is readout through 64 pads, 1 mm 2 wide, organized in a row of 8 cm long, with LHCb ASDQ chip. This Gamma Camera can be used both for X-ray movie and PET-SPECT imaging; this chamber prototype is placed in a scanner system, creating images of 8 Ă 8 cm 2 . Several measurements have been performed using phantom and radioactive sources of Tc 99 m ( 140 keV ) and Na 22 ( 511 keV ) . Results on spatial resolution and image reconstruction are presented
Nestin expression associates with poor prognosis and triple negative phenotype in locally advanced (T4) breast cancer
Nestin, an intermediate filament protein, has traditionally been noted for its importance as a neural stem cell marker. However, in recent years, expression of nestin has shown to be associated with general proliferation of progenitor cell populations within neoplasms. There is no reported study addressing nestin expression in T4 breast cancer patients. Thus, the aim of the present study was to investigate, through immunohistochemistry, the expression and distribution of nestin in T4 breast cancer, in order to determine its association with clinical and pathological parameters as well as with patients' outcome. Nestin was detectable in tumoral cells and in endothelial cells of blood microvessels, and it is significantly expressed in triple-negative and in inflammatory breast cancer (IBC) subgroups of T4 breast tumours. The Kaplan-Meier analysis showed that the presence of nestin in tumoral cells significantly predicted poor prognosis at 5-years survival (P=0.02) and with borderline significance at 10-years of survival (P=0.05) in T4 breast cancer patients. On the basis of these observations, we speculate that nestin expression may characterize tumours with an aggressive clinical behavior, suggesting that the presence of nestin in tumoral cells and vessels may be considered an important factor that leads to a poor prognosis. Further studies are awaited to define the biological role of nestin in the etiology of these subgroups of breast cancers
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