21 research outputs found
Investigation of Hamamatsu H8500 phototubes as single photon detectors
We have investigated the response of a significant sample of Hamamatsu H8500
MultiAnode PhotoMultiplier Tubes (MAPMTs) as single photon detectors, in view
of their use in a ring imaging Cherenkov counter for the CLAS12 spectrometer at
the Thomas Jefferson National Accelerator Facility. For this, a laser working
at 407.2nm wavelength was employed. The sample is divided equally into standard
window type, with a spectral response in the visible light region, and
UV-enhanced window type MAPMTs. The studies confirm the suitability of these
MAPMTs for single photon detection in such a Cherenkov imaging application
Test of the CLAS12 RICH large scale prototype in the direct proximity focusing configuration
A large area ring-imaging Cherenkov detector has been designed to provide
clean hadron identification capability in the momentum range from 3 GeV/c up to
8 GeV/c for the CLAS12 experiments at the upgraded 12 GeV continuous electron
beam accelerator facility of Jefferson Laboratory. The adopted solution
foresees a novel hybrid optics design based on aerogel radiator, composite
mirrors and high-packed and high-segmented photon detectors. Cherenkov light
will either be imaged directly (forward tracks) or after two mirror reflections
(large angle tracks). We report here the results of the tests of a large scale
prototype of the RICH detector performed with the hadron beam of the CERN T9
experimental hall for the direct detection configuration. The tests
demonstrated that the proposed design provides the required pion-to-kaon
rejection factor of 1:500 in the whole momentum range.Comment: 15 pages, 23 figures, to appear on EPJ
Explanation of the activity sensitivity of Mn I 5394.7 \AA
There is a long-standing controversy concerning the reason why the Mn I
5394.7 A line in the solar irradiance spectrum brightens more at larger
activity than most other photospheric lines. The claim that this activity
sensitivity is caused by spectral interlocking to chromospheric emission in Mg
II h & k is disputed.
Classical one-dimensional modeling is used for demonstration; modern
three-dimensional MHD simulation for verification and analysis.
The Mn I 5394.7 A line thanks its unusual sensitivity to solar activity to
its hyperfine structure. This overrides the thermal and granular Doppler
smearing through which the other, narrower, photospheric lines lose such
sensitivity. We take the nearby Fe I 5395.2 A line as example of the latter and
analyze the formation of both lines in detail to demonstrate and explain
granular Doppler brightening. We show that this affects all narrow lines.
Neither the chromosphere nor Mg II h & k play a role, nor is it correct to
describe the activity sensitivity of Mn I 5394.7 A through plage models with
outward increasing temperature contrast.
The Mn I 5394.7 A line represents a proxy diagnostic of strong-field magnetic
concentrations in the deep solar photosphere comparable to the G band and the
blue wing of H-alpha, but not a better one than these. The Mn I lines are more
promising as diagnostic of weak fields in high-resolution Stokes polarimetry.Comment: 12 pages, 8 figures, accepted by A&
Photospheric Dynamic Model of Magnetic Reconnection
We present a dynamic model of the atmospheric magnetic field in which magnetic loop footpoints are controlled by photospheric flows computed through a N-body algorithm. This simulation reproduces a system whose behaviour is characterized by small scale (e.g., granular) advection flows that interact to form large spatial organization scales (e.g., meso- and super-granulation). In this model the passive advection of magnetic footpoints through photospheric spatio-temporal correlated flows causes the magnetic field to reconfigure as a consequence of magnetic reconnection processes. This approach, based on the dynamic model of multiple magnetic loops tep{b8 Hu03} and on an advective-interaction model proposed by tet{b8 Ra03}, naturally accounts for the observed probability distribution functions and waiting time statistics of the emitted magnetic energy
MiR-203 controls proliferation, migration and invasive potential of prostate cancer cell lines
Prostate cancers show a slow progression from a local lesion (primary tumor) to a metastatic and hormone-resistant phenotype. After an initial step of hyperplasia, in a high percentage of cases a neoplastic transformation event occurs that, less frequently, is followed by epithelial to mesenchymal transition and invasion of healthy tissues (usually bones). MicroRNA-203 (miR-203) is a tumor suppressor microRNA often silenced in different malignancies. Here, we show that miR-203 is downregulated in clinical primary prostatic tumors compared to normal prostate tissue, and in metastatic prostate cancer cell lines compared to normal epithelial prostatic cells. Overexpression of miR-203 in brain or bone metastatic prostate cell lines (DU145 and PC3) is sufficient to induce a mesenchymal to epithelial transition with inhibition of cell proliferation, migration and invasiveness. We have identified CKAP2, LASP1, BIRC5, WASF1, ASAP1 and RUNX2 as new miR-203 direct target mRNAs involved in these events. Therefore, miR-203 could be a potentially new prognostic marker and therapeutic target in metastatic prostate cancer
MiR-203 controls proliferation, migration and invasive potential of prostate cancer cell lines
Prostate cancers show a slow progression from a local lesion (primary tumor) to a metastatic and hormone-resistant phenotype. After an initial step of hyperplasia, in a high percentage of cases a neoplastic transformation event occurs that, less frequently, is followed by epithelial to mesenchymal transition and invasion of healthy tissues (usually bones). MicroRNA-203 (miR-203) is a tumor suppressor microRNA often silenced in different malignancies. Here, we show that miR-203 is downregulated in clinical primary prostatic tumors compared to normal prostate tissue, and in metastatic prostate cancer cell lines compared to normal epithelial prostatic cells. Overexpression of miR-203 in brain or bone metastatic prostate cell lines (DU145 and PC3) is sufficient to induce a mesenchymal to epithelial transition with inhibition of cell proliferation, migration and invasiveness. We have identified CKAP2, LASP1, BIRC5, WASF1, ASAP1 and RUNX2 as new miR-203 direct target mRNAs involved in these events. Therefore, miR-203 could be a potentially new prognostic marker and therapeutic target in metastatic prostate cancer