4,037 research outputs found
Design and advancement status of the Beam Expander Testing X-ray facility (BEaTriX)
The BEaTriX (Beam Expander Testing X-ray facility) project is an X-ray
apparatus under construction at INAF/OAB to generate a broad (200 x 60 mm2),
uniform and low-divergent X-ray beam within a small lab (6 x 15 m2). BEaTriX
will consist of an X-ray source in the focus a grazing incidence paraboloidal
mirror to obtain a parallel beam, followed by a crystal monochromation system
and by an asymmetrically-cut diffracting crystal to perform the beam expansion
to the desired size. Once completed, BEaTriX will be used to directly perform
the quality control of focusing modules of large X-ray optics such as those for
the ATHENA X-ray observatory, based on either Silicon Pore Optics (baseline) or
Slumped Glass Optics (alternative), and will thereby enable a direct quality
control of angular resolution and effective area on a number of mirror modules
in a short time, in full X-ray illumination and without being affected by the
finite distance of the X-ray source. However, since the individual mirror
modules for ATHENA will have an optical quality of 3-4 arcsec HEW or better,
BEaTriX is required to produce a broad beam with divergence below 1-2 arcsec,
and sufficient flux to quickly characterize the PSF of the module without being
significantly affected by statistical uncertainties. Therefore, the optical
components of BEaTriX have to be selected and/or manufactured with excellent
optical properties in order to guarantee the final performance of the system.
In this paper we report the final design of the facility and a detailed
performance simulation.Comment: Accepted paper, pre-print version. The finally published manuscript
can be downloaded from http://dx.doi.org/10.1117/12.223895
The deepest X-ray look at the Universe
The origin of the X-ray background, in particular at hard (2-10 keV)
energies, has been a debated issue for more than 30 years. The Chandra deep
fields provide the deepest look at the X-ray sky and are the best dataset to
study the X-ray background. We searched the Chandra Deep Field South for X-ray
sources with the aid of a dedicated wavelet-based algorithm. We are able to
reconstruct the Log N-Log S source distribution in the soft (0.5-2 keV) and
hard (2-10 keV) bands down to limiting fluxes of 2x10^{-17} erg s^{-1} cm^{-2}
and 2x10^{-16} erg s^{-1} cm^{-2}, respectively. These are a factor ~5 deeper
than previous investigations. We find that the soft relation continues along
the extrapolation from higher fluxes, almost completely accounting for the soft
X-ray background. On the contrary, the hard distribution shows a flattening
below ~2x10^{-14} erg s^{-1} cm^{-2}. Nevertheless, we can account for >68% of
the hard X-ray background, with the main uncertainty being the sky flux itself.Comment: Accepted for publication on ApJL. Two figures, requires emulateapj5
(included
Statistical mechanics of budget-constrained auctions
Finding the optimal assignment in budget-constrained auctions is a
combinatorial optimization problem with many important applications, a notable
example being the sale of advertisement space by search engines (in this
context the problem is often referred to as the off-line AdWords problem).
Based on the cavity method of statistical mechanics, we introduce a message
passing algorithm that is capable of solving efficiently random instances of
the problem extracted from a natural distribution, and we derive from its
properties the phase diagram of the problem. As the control parameter (average
value of the budgets) is varied, we find two phase transitions delimiting a
region in which long-range correlations arise.Comment: Minor revisio
Dynamical charge density fluctuations pervading the phase diagram of a Cu-based high-Tc superconductor
Charge density waves are a common occurrence in all families of high critical
temperature superconducting cuprates. Although consistently observed in the
underdoped region of the phase diagram and at relatively low temperatures, it
is still unclear to what extent they influence the unusual properties of these
systems. Using resonant x-ray scattering we carefully determined the
temperature dependence of charge density modulations in
(Y,Nd)BaCuO for three doping levels. We discovered
short-range dynamical charge density fluctuations besides the previously known
quasi-critical charge density waves. They persist up to well above the
pseudogap temperature T*, are characterized by energies of few meV and pervade
a large area of the phase diagram, so that they can play a key role in shaping
the peculiar normal-state properties of cuprates.Comment: 34 pages, 4 figures, 11 supplementary figure
Mental health in migrants contacting the mental health operational unit of the National Institute for Health, Migration and Poverty (NIHMP): preliminary data
Aim: Migration can lead to an increase in stress rates and can impact mental health, especially in certain migrant groups. Nonetheless, mental health needs and the importance of public health are not well captured in most studies using national samples. This study aimed to show the correlation between mental disorders, socio-demographic and cultural aspects among migrants. Subject and methods: One hundred nineteen migrants, applying for assessment to the Mental Health Operational Unit of the National Institute for Health, Migration and Poverty (NIHMP) in Rome, were recruited. Results: Migrants frequently reported mood disorders (mainly women). Men reported PTSD, somatization and adjustment disorders. Conclusions: Over time, diverse factors may produce a decline in an initially healthy migrant status. The research unveils a new focus on the psychopathology of migrants accessing the NIHMP, with important implications for migrants\u2019 mental health treatment and prevention
The resolved fraction of the Cosmic X-ray Background
We present the X-ray source number counts in two energy bands (0.5-2 and 2-10
keV) from a very large source sample: we combine data of six different surveys,
both shallow wide field and deep pencil beam, performed with three different
satellites (ROSAT, Chandra and XMM-Newton). The sample covers with good
statistics the largest possible flux range so far: [2.4*10^-17 - 10^-11] cgs in
the soft band and [2.1*10^-16 - 8*10^{-12}]cgs in the hard band. Integrating
the flux distributions over this range and taking into account the (small)
contribution of the brightest sources we derive the flux density generated by
discrete sources in both bands. After a critical review of the literature
values of the total Cosmic X--Ray Background (CXB) we conclude that, with the
present data, the 94.3%, and 88.8% of the soft and hard CXB can be ascribed to
discrete source emission. If we extrapolate the analytical form of the Log
N--Log S distribution beyond the flux limit of our catalog in the soft band we
find that the flux from discrete sources at ~3*10^-18 cgs is consistent with
the entire CXB, whereas in the hard band it accounts for only 93% of the total
CXB at most, hinting for a faint and obscured population to arise at even
fainter fluxes.Comment: Accepted for publication in Ap
Developing a questionnaire evaluating knowledge, attitudes and behaviors on audit & feedback among general practitioners. A mixed methods study
Background: Audit and Feedback (A&F) is one of the most common strategies used to improve quality in healthcare. However, there is still lack of awareness regarding the enabling factors and barriers that could influence its effectiveness. The aim of this study was to develop a questionnaire to measure the knowledge, attitudes and behaviors of general practitioners (GPs) regarding A&F. The study was performed in the context of the EASY-NET program (project code NET-2016-02364191). Methods: The survey was developed according to two steps. Firstly, a scoping review was performed in order to map the literature on the existing similar instruments with the aim of identifying the sub-domains and possible items to include in a preliminary version of the questionnaire. In the second phase, the questionnaire was reviewed by a multidisciplinary group of experts and administrated to a convenience sample in a pilot survey. Results: Ten papers were included in the scoping review. The survey target and development methodology were heterogenous among the studies. The knowledge, attitudes and behaviors domains were assessed in six, nine and seven studies, respectively. In the first step, 126 pertinent items were extracted and categorized as follows: 8 investigated knowledge, 93 investigated attitudes, and 25 investigated behaviors. Then, 2 sub-domains were identified for knowledge, 14 for attitudes and 7 for behavior. Based on these results, a first version of the survey was developed via consensus among two authors and then revised by the multidisciplinary group of experts in the field of A&F. The final version of the survey included 36 items: 8 in the knowledge domain, 19 in the attitudes domain and 9 in the behaviors domain. The results of the pilot study among 15 GPs suggested a good acceptability and item relevance and accuracy, with positive answers totaling 100% and 93.3% in the proposed questions. Conclusions: The methodology used has shown to be a good strategy for the development of the survey. The survey will be administrated before and after the implementation of an A&F intervention to assess both baseline characteristics and changes after the intervention
Usefulness of panoramic 344°-viewing in Crohn's disease capsule endoscopy : a proof of concept pilot study with the novel PillCam™ Crohn's system
Background: A new capsule endoscopy (CE) system featuring two advanced optics for 344\ub0-viewing and a prolonged operative time has been recently developed for Crohn's disease (CD) patients. Hence, we evaluated, for the first time, the performance of this novel CE and the add-on value of the 344\ub0-viewing in a multi-center real-life setting. Methods: Consecutive patients with suspected or established CD received the PillCam\u2122 Crohn's System as supplementary diagnostic work-up focused on the small-bowel between June 2017 and June 2018. Technical and clinical data, including the panenteric CE diagnostic yield, the Lewis score and the impact of small-bowel findings on clinical management during a 6-months follow-up (new diagnosis, staging or treatment upgrade) were collected, thereby evaluating the added value of the 344\ub0 panoramic-view (lesions detected by camera A and B) over the standard 172\ub0-view (lesions detected by one camera only). Results: Among 41 patients (aged 43 \ub1 20 years), 73% underwent CE for suspected CD and 27% for established CD. The rate of complete enteroscopy was 90%. No technical failure or retention occurred. Compared to the standard 172\ub0 view, the panoramic 344\ub0-view revealed a greater number of patients with a relevant lesion (56.1% vs. 39.0%; P = 0.023), resulting in higher Lewis score (222,8 vs. 185.7; P = 0.031), and improved clinical management (48.8% vs. 31.7%, P = 0.023). Conclusions: The panoramic 344\ub0-view increases small-bowel CE accuracy, thereby improving the clinical management of CD patients with mild small-bowel active disease. This system should be regarded as a new standard for both small-bowel diagnosis and monitoring in inflammatory bowel diseases
Development, evaluation, and validation of machine learning models for COVID-19 detection based on routine blood tests
The rRT-PCR test, the current gold standard for the detection of coronavirus disease (COVID-19), presents with known shortcomings, such as long turnaround time, potential shortage of reagents, false-negative rates around 15-20%, and expensive equipment. The hematochemical values of routine blood exams could represent a faster and less expensive alternative. Three different training data set of hematochemical values from 1,624 patients (52% COVID-19 positive), admitted at San Raphael Hospital (OSR) from February to May 2020, were used for developing machine learning (ML) models: the complete OSR dataset (72 features: complete blood count (CBC), biochemical, coagulation, hemogasanalysis and CO-Oxymetry values, age, sex and specific symptoms at triage) and two sub-datasets (COVID-specific and CBC dataset, 32 and 21 features respectively). 58 cases (50% COVID-19 positive) from another hospital, and 54 negative patients collected in 2018 at OSR, were used for internal-external and external validation. We developed five ML models: for the complete OSR dataset, the area under the receiver operating characteristic curve (AUC) for the algorithms ranged from 0.83 to 0.90; for the COVID-specific dataset from 0.83 to 0.87; and for the CBC dataset from 0.74 to 0.86. The validations also achieved good results: respectively, AUC from 0.75 to 0.78; and specificity from 0.92 to 0.96. ML can be applied to blood tests as both an adjunct and alternative method to rRT-PCR for the fast and cost-effective identification of COVID-19-positive patients. This is especially useful in developing countries, or in countries facing an increase in contagions
Covid-19 vaccine: A survey of hesitancy in patients with celiac disease
(1) Background: COVID-19 vaccination campaigns offer the best hope of controlling the pandemic. However, the fast production of COVID-19 vaccines has caused concern among the general public regarding their safety and efficacy. In particular, patients with chronic illnesses, such as celiac disease (CD), may be more fearful. Information on vaccine hesitancy plays a pivotal role in the development of an efficient vaccination campaign. In our study, we aimed to evaluate COVID-19 vaccine hesitancy among Italian CD patients. (2) Methods: an anonymous questionnaire was sent to CD patients followed at our tertiary referral center for CD in Milan, Italy. Patients were defined as willing, hesitant and refusing. We evaluated the reasons for hesitancy/refusal and the possible determinants, calculating crude and adjusted odds ratios [AdjORs] with 95% confidence intervals [CIs]. (3) Results: the questionnaire was sent to 346 patients with a response rate of 29.8%. Twenty-six (25.2%) of the 103 respondents were hesitant, with a total refusal rate of 4.8%. The main reason was fear of adverse events related to vaccination (68.2%). Among hesitant patients, 23% declared that their opinion was influenced by their CD. The determinants positively influencing willingness to be vaccinated against COVID-19 were adherence to a GFD, perception of good knowledge about COVID-19 and its vaccines, and a positive attitude to previous vaccines (AdjOR 12.71, 95% CI 1.82–88.58, AdjOR 6.50, 95% CI 1.44–29.22, AdjOR 0.70, 95% CI 0.11–4.34, respectively). (4) Conclusions: CD patients should be vaccinated against COVID-19 and a specific campaign to address the determinants of hesitancy should be developed
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