Reading a GEM with a VLSI pixel ASIC used as a direct charge collecting anode

In MicroPattern Gas Detectors (MPGD) when the pixel size is below 100 micron and the number of pixels is large (above 1000) it is virtually impossible to use the conventional PCB read-out approach to bring the signal charge from the individual pixel to the external electronics chain. For this reason a custom CMOS array of 2101 active pixels with 80 micron pitch, directly used as the charge collecting anode of a GEM amplifying structure, has been developed and built. Each charge collecting pad, hexagonally shaped, realized using the top metal layer of a deep submicron VLSI technology is individually connected to a full electronics chain (pre-amplifier, shaping-amplifier, sample and hold, multiplexer) which is built immediately below it by using the remaining five active layers. The GEM and the drift electrode window are assembled directly over the chip so the ASIC itself becomes the pixelized anode of a MicroPattern Gas Detector. With this approach, for the first time, gas detectors have reached the level of integration and resolution typical of solid state pixel detectors. Results from the first tests of this new read-out concept are presented. An Astronomical X-Ray Polarimetry application is also discussed.Comment: 11 pages, 14 figures, presented at the Xth Vienna Conference on Instrumentation (Vienna, February 16-21 2004). For a higher resolution paper contact [email protected]

PlGFMMP9-engineered iPS cells supported on a PEGfibrinogen hydrogel scaffold possess an enhanced capacity to repair damaged myocardium

Cell-based regenerative therapies are significantly improved by engineering allografts to express factors that increase vascularization and engraftment, such as placental growth factor (PlGF) and matrix metalloproteinase 9 (MMP9). Moreover, the seeding of therapeutic cells onto a suitable scaffold is of utmost importance for tissue regeneration. On these premises, we sought to assess the reparative potential of induced pluripotent stem (iPS) cells bioengineered to secrete PlGF or MMP9 and delivered to infarcted myocardium upon a poly(ethylene glycol)-fibrinogen scaffold. When assessing optimal stiffness of the PEG-fibrinogen (PF) scaffold, we found that the appearance of contracting cells after cardiogenic induction was accelerated on the support designed with an intermediate stiffness. Revascularization and hemodynamic parameters of infarcted mouse heart were significantly improved by injection into the infarct of this optimized PF scaffold seeded with both MiPS (iPS cells engineered to secrete MMP9) and PiPS (iPS cells engineered to secrete PlGF) cells as compared with nonengineered cells or PF alone. Importantly, allograft-derived cells and host myocardium were functionally integrated. Therefore, survival and integration of allografts in the ischemic heart can be significantly improved with the use of therapeutic cells bioengineered to secrete MMP9 and PlGF and encapsulated within an injectable PF hydrogel having an optimized stiffness

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

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

A CASE OF HELLP SYNDROME: THE IMPORTANCE OF ANGIOGRAPHY WITH INDOCIANINE GREEN FOR DIAGNOSIS OF RETINIC AND CHOROIDAL VASCULAR OCCLUSION.

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Sex-differences in the longitudinal recovery of neuromuscular function in COVID-19 associated acute respiratory distress syndrome survivors

Introduction: Patients admitted to the intensive care unit (ICU) following severe acute respiratory syndrome 2 (SARS-CoV-2) infection may have muscle weakness up to 1 year or more following ICU discharge. However, females show greater muscle weakness than males, indicating greater neuromuscular impairment. The objective of this work was to assess sex differences in longitudinal physical functioning following ICU discharge for SARS-CoV-2 infection. Methods: We performed longitudinal assessment of physical functioning in two groups: 14 participants (7 males, 7 females) in the 3-to-6 month and 28 participants (14 males, 14 females) in the 6-to-12 month group following ICU discharge and assessed differences between the sexes. We examined self-reported fatigue, physical functioning, compound muscle action potential (CMAP) amplitude, maximal strength, and the neural drive to the tibialis anterior muscle. Results: We found no sex differences in the assessed parameters in the 3-to-6-month follow-up, indicating significant weakness in both sexes. Sex differences emerged in the 6-to-12-month follow-up. Specifically, females exhibited greater impairments in physical functioning, including lower strength, walking lower distances, and high neural input even 1 year following ICU-discharge. Discussion: Females infected by SARS-CoV-2 display significant impairments in functional recovery up to 1 year following ICU discharge. The effects of sex should be considered in post-COVID neurorehabilitation