Radar array diagnosis from undersampled data using a compressed sensing/sparse recovery technique

A Compressed Sensing/Sparse Recovery approach is adopted in this paper for the accurate diagnosis of fault array elements from undersampled data. Experimental validations on a slotted waveguide test array are discussed to demonstrate the effectiveness of the proposed procedure in the failures retrieval from a small set of measurements with respect to the number of radiating elements. Due to the sparsity feature of the proposed formulation, the method is particularly appealing for the diagnostics of large arrays, typically adopted for radar applications

Energy characterization of Pixirad-1 photon counting detector system

This work is focused on the characterization of the Pixirad-1 detector system from the spectroscopic point of view. An energy calibration has been carried out using different X-ray sources such as fluorescence lines, synchrotron radiation and radioactive elements. The energy resolution has been measured as function of the energy and the results have been compared with theoretical estimation. Last, the charge sharing fraction has been evaluated by exploiting the monochromatic energy of the Elettra synchrotron beam

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

The imaging properties of the Gas Pixel Detector as a focal plane polarimeter

X-rays are particularly suited to probe the physics of extreme objects. However, despite the enormous improvements of X-ray Astronomy in imaging, spectroscopy and timing, polarimetry remains largely unexplored. We propose the photoelectric polarimeter Gas Pixel Detector (GPD) as an instrument candidate to fill the gap of more than thirty years of lack of measurements. The GPD, in the focus of a telescope, will increase the sensitivity of orders of magnitude. Moreover, since it can measure the energy, the position, the arrival time and the polarization angle of every single photon, allows to perform polarimetry of subsets of data singled out from the spectrum, the light curve or the image of source. The GPD has an intrinsic very fine imaging capability and in this work we report on the calibration campaign carried out in 2012 at the PANTER X-ray test facility of the Max-Planck-Institut f\"ur extraterrestrische Physik of Garching (Germany) in which, for the first time, we coupled it to a JET-X optics module with a focal length of 3.5 m and an angular resolution of 18 arcsec at 4.5 keV. This configuration was proposed in 2012 aboard the X-ray Imaging Polarimetry Explorer (XIPE) in response to the ESA call for a small mission. We derived the imaging and polarimetric performance for extended sources like Pulsar Wind Nebulae and Supernova Remnants as case studies for the XIPE configuration, discussing also possible improvements by coupling the detector with advanced optics, having finer angular resolution and larger effective area, to study with more details extended objects.Comment: Accepted for publication in The Astrophysical Journal Supplemen

Different somatic alterations of the HRPT2 gene in a patient with recurrent sporadic primary hyperparathyroidism carrying an HRPT2 germline mutation

Early onset of primary hyperparathyroidism (PHPT) and multiglandular involvement suggest a familial form in which germline mutation of a PHPT-related gene(s) and a somatic event at the same locus can be often demonstrated. We investigated the involvement of multiple endocrine neoplasia type 1 (MEN1) and HRPT2 genes in a 39-year-old man with recurrent PHPT. PHPT was firstly diagnosed at the age of 21 and the patient had two recurrences separated by extended periods of normocalcemia. This unusual history prompted us to investigate other family members and study the MEN1 and HRPT2 genes. An HRPT2 germline missense mutation in exon 3 (R91P) was found in the index case, which was associated with different HRPT2 somatic alterations in each of the three examined parathyroid tumors. These findings are consistent with Knudson's 'two hit' concept of biallelic inactivation of classical tumor suppressor genes. Screening of 15 asymptomatic relatives was negative for the R91P germline mutation. All the three abnormal parathyroid specimens showed cystic features at histology and were negative for parafibromin immunostaining. In one specimen, diffuse parafibromin staining was evident in a rim of normal parathyroid tissue surrounding the adenomatous lesion. Our study shows that different somatic genetic events at the HRPT2 locus are responsible for the asynchronous occurrence of multiple adenomas in a patient carrying an HRPT2 germline mutation. The finding of diffuse parafibromin staining in a rim of normal parathyroid tissue, but not in the contiguous adenomatous lesion, reinforces the concept that loss of parafibromin expression is responsible for the development of parathyroid tumors in this setting

Serum KL-6 could represent a reliable indicator of unfavourable outcome in patients with COVID-19 pneumonia

KL-6 is a sialoglycoprotein antigen which proved elevated in the serum of patients with different interstitial lung diseases, especially in those with a poorer outcome. Given that interstitial pneumonia is the most common presentation of SARS-CoV2 infection, we evaluated the prognostic role of KL-6 in patients with COVID-19 pneumonia. Patients with COVID-19 pneumonia were prospectively enrolled. Blood samples were collected at the time of enrolment (TOE) and on day 7 (T1). Serum KL-6 concentrations were measured by chemiluminescence enzyme immunoassay using a KL-6 antibody kit (LUMIPULSE G1200, Fujirebio) and the cut-off value was set at > 1000 U/mL. Fifteen out of 34 enrolled patients (44.1%) died. Patients with unfavourable outcome showed significantly lower P/F ratio and higher IL-6 values and plasmatic concentrations of KL-6 at TOE compared with those who survived (median KL-6: 1188 U/mL vs. 260 U/mL, p 1000 U/mL resulted independently associated with death (aOR: 11.29, p 1000 U/mL resulted independently associated with death and showed good accuracy in predicting a poorer outcome. KL-6 may thus represent a quick, inexpensive, and sensitive parameter to stratify the risk of severe respiratory failure and death

Awake fiberoptic intubation in patients with stenosis of the upper airways. Utility of the laryngeal nerve block

Awake fiberoptic intubation (AFOI) is mandatory to manage difficult airways. Superior laryngeal nerve block (SLNB) could reduce risks and improve patient comfort. The aim of this study is to assess the procedural comfort of SLNB during AFOI in a population of patients undergoing upper airway oncological surgery. Forty patients were randomized into two groups and were treated with continuous infusion of remifentanil, topic anesthesia and intercricoid block. In the study group (=20), SLNB was performed with lidocaine (L-SLNB); in the control group (n=20) SLNB was performed using saline (S-SLNB). AFOI was more comfortable in the L-SLNB group compared to S-SLNB patients [FOICS ≤ 1 in 18 patients (90%) L-SLNB; 2 (10%) S-SLNB (P<0.001)]. Intubation was faster in L-SLNB (47.45 ±15.38 sec) than S-SLNB (80.15 ±37.91 sec) (p<0.001). The SLNB procedure during AFOI is a safe and comfortable procedure in a population of patients undergoing upper airways surgery. Time to intubation was shorter in L-SLNB than in S-SLNB

XPOL-III: a New-Generation VLSI CMOS ASIC for High-Throughput X-ray Polarimetry

While the successful launch and operation in space of the Gas Pixel Detectors onboard the PolarLight cubesat and the Imaging X-ray Polarimetry Explorer demonstrate the viability and the technical soundness of this class of detectors for astronomical X-ray polarimetry, it is clear that the current state of the art is not ready to meet the challenges of the next generation of experiments, such as the enhanced X-ray Timing and Polarimetry mission, designed to allow for a significantly larger data throughput. In this paper we describe the design and test of a new custom, self-triggering readout ASIC, dubbed XPOL-III, specifically conceived to address and overcome these limitations. While building upon the overall architecture of the previous generations, the new chip improves over its predecessors in several, different key areas: the sensitivity of the trigger electronics, the flexibility in the definition of the readout window, as well as the maximum speed for the serial event readout. These design improvements, when combined, allow for almost an order of magnitude smaller dead time per event with no measurable degradation of the polarimetric, spectral, imaging or timing capability of the detector, providing a good match for the next generation of X-ray missions.Comment: accepted for publication at Nuclear Inst. and Methods in Physics Research Section