223 research outputs found
The contribution of maternal serum markers in the early prenatal diagnosis of molar pregnancies
The aim of this study was to evaluate the usefulness of maternal serum markers in the early prenatal diagnosis of molar pregnancies. The ultrasound features, cytogenetic and histopathological findings of 10 cases of molar pregnancy diagnosed at 11-13 weeks of gestation were compared retrospectively with the maternal serum concentrations of human chorionic gonadotrophin (HCG), alpha fetoprotein (AFP), pregnancy-associated plasma protein A (PAPP-A) and pregnancy-specific β1-glycoprotein (SP1). Free β-HCG and intact HCG concentrations were very high [≥ISOdia≥2.5 multiples of the median (MoM)] in all cases. AFP concentrations were extremely low in all cases of singleton complete moles (≤ISOdia≤0.5 MoM) and were high in one case of twin complete mole, in one case of triploid partial mole and two cases of euploid partial mole (≥ISOdia≥2.5 MoM). Serum PAPP-A and SP1 were high in complete moles. The combined use of ultrasound features, maternal serum proteins and fetal cytogenetic findings should enable the early differential diagnosis in utero and perinatal management of those molar pregnancies presenting with an anatomically normal fetu
Calculation of the electron mobility in III-V inversion layers with high-kappa dielectrics
We calculate the electron mobility for a metal-oxide-semiconductor system with a metallic gate, high-kappa dielectric layer, and III-V substrate, including scattering with longitudinal-optical (LO) polar-phonons of the III-V substrate and with the interfacial excitations resulting from the coupling of insulator and substrate optical modes among themselves and with substrate plasmons. In treating scattering with the substrate LO-modes, multisubband dynamic screening is included and compared to the dielectric screening in the static limit and with the commonly used screening model obtained by defining an effective screening wave vector. The electron mobility components limited by substrate LO phonons and interfacial modes are calculated for In0.53Ga0.47As and GaAs substrates with SiO2 and HfO2 gate dielectrics. The mobility components limited by the LO-modes and interfacial phonons are also investigated as a function of temperature. Scattering with surface roughness, fixed interface charge, and nonpolar-phonons is also included to judge the relative impact of each scattering mechanism in the total mobility for In0.53Ga0.47As with HfO2 gate dielectric. We show that InGaAs is affected by interfacial-phonon scattering to an extent larger than Si, lowering the expected performance, but probably not enough to question the technological relevance of InGaAs. (C) 2010 American Institute of Physics. [doi:10.1063/1.3500553
Hard X-ray polarimetry with Caliste, a high performance CdTe based imaging spectrometer
Since the initial exploration of soft gamma-ray sky in the 60's, high-energy
celestial sources have been mainly characterized through imaging, spectroscopy
and timing analysis. Despite tremendous progress in the field, the radiation
mechanisms at work in sources such as neutrons stars and black holes are still
unclear. The polarization state of the radiation is an observational parameter
which brings key additional information about the physical process. This is why
most of the projects for the next generation of space missions covering the
tens of keV to the MeV region require a polarization measurement capability. A
key element enabling this capability is a detector system allowing the
identification and characterization of Compton interactions as they are the
main process at play. The hard X-ray imaging spectrometer module, developed in
CEA with the generic name of Caliste module, is such a detector. In this paper,
we present experimental results for two types of Caliste-256 modules, one based
on a CdTe crystal, the other one on a CdZnTe crystal, which have been exposed
to linearly polarized beams at the European Synchrotron Radiation Facility.
These results, obtained at 200-300 keV, demonstrate their capability to give an
accurate determination of the polarization parameters (polarization angle and
fraction) of the incoming beam. Applying a selection to our data set,
equivalent to select 90 degrees Compton scattered interactions in the detector
plane, we find a modulation factor Q of 0.78. The polarization angle and
fraction are derived with accuracies of approximately 1 degree and 5%. The
modulation factor remains larger than 0.4 when essentially no selection is made
at all on the data. These results prove that the Caliste-256 modules have
performances allowing them to be excellent candidates as detectors with
polarimetric capabilities, in particular for future space missions.Comment: 17 pages, 14 figures, 2 tables in Experimental Astronomy, 201
The Microchannel X-ray Telescope on Board the SVOM Satellite
We present the Micro-channel X-ray Telescope (MXT), a new narrow-field (about
1{\deg}) telescope that will be flying on the Sino-French SVOM mission
dedicated to Gamma-Ray Burst science, scheduled for launch in 2021. MXT is
based on square micro pore optics (MPOs), coupled with a low noise CCD. The
optics are based on a "Lobster Eye" design, while the CCD is a focal plane
detector similar to the type developed for the seven eROSITA telescopes. MXT is
a compact and light (<35 kg) telescope with a 1 m focal length, and it will
provide an effective area of about 45 cmsq on axis at 1 keV. The MXT PSF is
expected to be better than 4.2 arc min (FWHM) ensuring a localization accuracy
of the afterglows of the SVOM GRBs to better than 1 arc min (90\% c.l. with no
systematics) provided MXT data are collected within 5 minutes after the
trigger. The MXT sensitivity will be adequate to detect the afterglows for
almost all the SVOM GRBs as well as to perform observations of non-GRB
astrophysical objects. These performances are fully adapted to the SVOM science
goals, and prove that small and light telescopes can be used for future small
X-ray missions.Comment: 6 pages, 6 figures, proceedings of the conference "Swift: 10 years of
Discovery", Rome, December 2-5, 2014. To be published by Po
Spectral performance of the Microchannel X-ray Telescope on board the SVOM mission
The Microchannel X-ray Telescope (MXT) is an innovative compact X-ray
instrument on board the SVOM astronomical mission dedicated to the study of
transient phenomena such as gamma-ray bursts. During 3 weeks, we have tested
the MXT flight model at the Panter X-ray test facility under the nominal
temperature and vacuum conditions that MXT will undergo in-flight. We collected
data at series of characteristic energies probing the entire MXT energy range,
from 0.28 keV up to 9 keV, for multiple source positions with the center of the
point spread function (PSF) inside and outside the detector field of view
(FOV). We stacked the data of the positions with the PSF outside the FOV to
obtain a uniformly illuminated matrix and reduced all data sets using a
dedicated pipeline. We determined the best spectral performance of MXT using an
optimized data processing, especially for the energy calibration and the charge
sharing effect induced by the pixel low energy thresholding. Our results
demonstrate that MXT is compliant with the instrument requirement regarding the
energy resolution (<80 eV at 1.5 keV), the low and high energy threshold, and
the accuracy of the energy calibration (20 eV). We also determined the
charge transfer inefficiency (~) of the detector and modeled its
evolution with energy prior to the irradiation that MXT will undergo during its
in-orbit lifetime. Finally, we measured the relation of the energy resolution
as function of the photon energy. We determined an equivalent noise charge of
4.9 0.2 e- rms for the MXT detection chain and a Fano factor of 0.131
0.003 in silicon at 208 K, in agreement with previous works. This
campaign confirmed the promising scientific performance that MXT will be able
to deliver during the mission lifetime.Comment: 20 pages, 10 figures, accepted for publication in Experimental
Astronom
The Scientific Performance of the Microchannel X-ray Telescope on board the SVOM Mission
The Microchannel X-ray Telescope (MXT) will be the first focusing X-ray
telescope based on a "Lobster-Eye" optical design to be flown on Sino-French
mission SVOM. SVOM will be dedicated to the study of Gamma-Ray Bursts and more
generally time-domain astrophysics. The MXT telescope is a compact (focal
length ~ 1.15 m) and light (< 42 kg) instrument, sensitive in the 0.2--10 keV
energy range. It is composed of an optical system, based on micro-pore optics
(MPOs) of 40 micron pore size, coupled to a low-noise pnCDD X-ray detector. In
this paper we describe the expected scientific performance of the MXT
telescope, based on the End-to-End calibration campaign performed in fall 2021,
before the integration of the SVOM payload on the satellite.Comment: 22 pages, 12 figures, accepted for publication in Experimental
Astronom
The TRILL project: increasing the technological readiness of Laue lenses
Hard X-/soft Gamma-ray astronomy (> 100 keV) is a crucial field for the study
of important astrophysical phenomena such as the 511 keV positron annihilation
line in the Galactic center region and its origin, gamma-ray bursts, soft
gamma-ray repeaters, nuclear lines from SN explosions and more. However,
several key questions in this field require sensitivity and angular resolution
that are hardly achievable with present technology. A new generation of
instruments suitable to focus hard X-/soft Gamma-rays is necessary to overcome
the technological limitations of current direct-viewing telescopes. One
solution is using Laue lenses based on Bragg's diffraction in a transmission
configuration. To date, this technology is in an advanced stage of development
and further efforts are being made in order to significantly increase its
technology readiness level (TRL). To this end, massive production of suitable
crystals is required, as well as an improvement of the capability of their
alignment. Such a technological improvement could be exploited in stratospheric
balloon experiments and, ultimately, in space missions with a telescope of
about 20 m focal length, capable of focusing over a broad energy pass-band. We
present the latest technological developments of the TRILL (Technological
Readiness Increase for Laue Lenses) project, supported by ASI, devoted to the
advancement of the technological readiness of Laue lenses. We show the method
we developed for preparing suitable bent Germanium and Silicon crystals and the
latest advancements in crystals alignment technology.Comment: arXiv admin note: text overlap with arXiv:2211.1688
Durability of bioprosthetic aortic valves in patients under the age of 60 years - Rationale and design of the international INDURE registry
Background: There is an ever-growing number of patients requiring aortic valve replacement (AVR). Limited data is available on the long-term outcomes and structural integrity of bioprosthetic valves in younger patients undergoing surgical AVR. Methods: The INSPIRIS RESILIA Durability Registry (INDURE) is a prospective, open-label, multicentre, international registry with a follow-up of 5 years to assess clinical outcomes of patients younger than 60 years who undergo surgical AVR using the INSPIRIS RESILIA aortic valve. INDURE will be conducted across 20-22 sites in Europe and Canada and intends to enrol minimum of 400 patients. Patients will be included if they are scheduled to undergo AVR with or without concomitant root replacement and/or coronary bypass surgery. The primary objectives are to 1) determine VARC-2 defined time-related valve safety at one-year (depicted as freedom from events) and 2) determine freedom from stage 3 structural valve degeneration (SVD) presenting as morphological abnormalities and severe haemodynamic valve degeneration at 5 years. Secondary objectives include the assessment of the haemodynamic performance of the valve, all stages of SVD, potential valve-in-valve procedures, clinical outcomes (in terms of New York Heart Association [NYHA] function class and freedom from valve-related rehospitalisation) and change in patient quality-of-life. Discussion: INDURE is a prospective, multicentre registry in Europe and Canada, which will provide much needed data on the long-term performance of bioprosthetic valves in general and the INSPIRIS RESILIA valve in particular. The data may help to gather a deeper understanding of the longevity of bioprosthetic valves and may expand the use of bioprosthetic valves in patients under the age of 60 years. Trial registration: ClinicalTrials.gov identifier: NCT03666741 (registration received September, 12th, 2018)
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