831 research outputs found
Signature of Energy Losses on the Cosmic Ray Electron Spectrum
We show that the fine structure of the electron spectrum in cosmic rays,
especially the excess claimed by AMS-02 at energies 42 GeV, is fully
accounted for in terms of inverse Compton losses in the photon background
dominated by ultraviolet, infrared and CMB photons, plus the standard
synchrotron losses in the Galactic magnetic field. The transition to the
Klein-Nishina regime on the ultraviolet background causes the feature. Hence,
contrary to previous statements, observations do not require the overlap of
different components. We stress that the feature observed by AMS-02 at energies
42 GeV is not related to the positron excess, which instead requires the
existence of positron sources, such as pulsars. Because energy losses are the
physical explanation of this feature, we indirectly confirm that the transport
of leptons in the Galaxy is loss-dominated down to energies of the order of
tens of GeV. This finding imposes strong constraints on the feasibility of
alternative theories of cosmic transport in which the grammage is accumulated
in cocoons concentrated around sources, requiring that electrons and positrons
become loss dominated only at very high energies.Comment: 5 pages, 3 figures, minor updates in the text, fixed a typo in Eq.
Progettazione di una cassa d’espansione e determinazione della riduzione del rischio idraulico con modellazione 2D
Nell’articolo si studia l’effetto di una cassa d’espansione posta a monte di un’area
fluviale soggetta a rischio idraulico. Lo strumento utilizzato è un software
bidimensionale sviluppato per simulare la propagazione delle piene fluviali. Il
dominio di calcolo è rappresentato da una mesh triangolare non strutturata con una
maggiore densità di elementi all’interno dell’alveo e nelle zone immediatamente
limitrofe. Per facilitare gli accumuli temporanei di parte dei volumi di piena, si
ipotizza la costruzione di un restringimento dell’alveo per mezzo di due pareti verticali che avvicinano le sponde fluviali. Durante la piena, il passaggio per lo stato critico nel restringimento provoca un rigurgito a monte, e quindi un agevole riempimento della cassa d’espansione. La perimetrazione di tale cassa è definita con la costruzione di un rilevato arginale di adeguata altezza. Per meglio simulare il rigurgito a monte della strozzatura, si introduce una scabrezza equivalente negli elementi della strozzatura, per riprodurre le perdite di carico nel restringimento e nel successivo risalto idraulico, malgrado l’ipotesi diffusiva utilizzata nel software di calcolo. La conoscenza delle aree allagate in due eventi di piena storici e dei due
relativi idrogrammi di piena, ha consentito la determinazione del coefficiente di
Manning quale misura della scabrezza in alveo e fuori alveo.
Mediante l’applicazione del modello proposto è possibile validare sia il posizionamento degli argini a monte del restringimento per il contenimento della piena, sia la riduzione delle aree di valle soggette a rischio idraulico
Galactic factories of cosmic-ray electrons and positrons
We present a novel calculation of the spectrum of electrons and positrons
from random sources, supernova remnants and pulsars, distributed within the
spiral arms of the Galaxy. The pulsar emissivity in terms of electron-positron
pairs is considered as time dependent, following the magnetic dipole spin-down
luminosity, and the temporal evolution of the potential drop is accounted for.
Moreover each pulsar, with the magnetic field and initial spin period selected
at random from the observed distribution, is considered as a source of pairs
only after it leaves the parent supernova due to its birth kick velocity (also
selected at random from the observed distribution). We show that (i) the
spectrum of electrons is characterized by a feature at GeV that
proves that their transport is dominated by radiative losses. The flux
reduction at TeV is explained as a result of lepton transport from
sources in the spiral arms. (ii) The spectrum of positrons is very well
described by the contribution of pulsars and the rising positron fraction
originates naturally. The implications of pulsars as positron sources in terms
of positron fraction at very high energies are also discussed. (iii) The role
of fluctuations in the high-energy regime is thoroughly discussed and used to
draw conclusions on the possibility to single out the contribution of local
sources to the lepton spectrum with current and upcoming experiments
Stochastic nature of Galactic cosmic-ray sources
The precision measurements of the spectra of cosmic ray nuclei and leptons in
recent years have revealed the existence of multiple features, such as the
spectral break at GV rigidity seen by PAMELA and AMS-02 and more
recently confirmed by DAMPE and CALET, the softening in the spectra of H and He
nuclei at TV reported by DAMPE, confirming previous hints by NUCLEON
and CREAM, a tiny change of slope at GeV in the electron spectrum,
revealed by AMS-02, and the large spectral break at TeV reported by
indirect (HESS, MAGIC and VERITAS) and direct (DAMPE, CALET) measurements of
the total (electrons+positrons) lepton spectrum. In all these cases, the
possibility has been suggested that these features might reflect the occasional
presence of a local cosmic ray source, inducing a noticeable reshaping of the
average expected spectra. All these proposals have to face the question of how
likely it is for such a source to exist, a question that we address here in a
quantitative way. We study the statistical properties of random distribution of
sources in space and time, and the effect of the spiral structure of our Galaxy
for both the spectra of light nuclei (p and He) and leptons (electrons and
positrons) in different energy regions
Association of non-alcoholic fatty liver disease and cardiometabolic risk factors with early atherosclerosis in an adult population in Southern Italy
Aim. The prevalence of risk factors for cardiovascular and metabolic diseases was inves-tigated in an adult population of the city of Cittanova, Southern Italy. Methods. The study was conducted among 992 randomly selected adults aged 18-75 years, between April 2009 and January 2011. Â Results. Prevalence rates of non-alcoholic fatty liver disease (NAFLD), overweight, obe-sity, and metabolic syndrome (MS) were 24.8%, 41.5%, 27.1%, and 34.4%, respectively. For the components of MS, prevalence of central obesity was 47.4%, impaired fasting glucose (IFG) 34.7%; hypertension 53.7%, low high-density lipoprotein (HDL) choles-terol 34.2%, and hypertriglyceridemia 27.2%. Â Conclusions. Hypertension, central obesity, IFG, low HDL cholesterol, hypertriglyc-eridemia, MS, and increased carotid artery intima-media thickness (IMT) were sig-nificantly associated with NAFLD after adjustment for age and sex. With additional adjustment for body mass index (BMI), IMT and MS (depending on the prevalence ra-tio that was investigated), the positive association between the NAFLD and increased IMT lost statistical significance, while that with body mass index (BMI) and MS re-mained significant
Residual feed intake is related with metabolic and inflammatory response during the pre-weaning period in Italian Simmental calves
Residual Feed Intake (RFI) is defined as the difference between measured and predicted intake. Understanding its biological regulators could benefit farm
profit margins. The most-efficient animals (M-Eff)
have observed intake smaller than predicted resulting
in negative RFI, whereas the least-efficient (L-Eff)
animals have positive RFI. Hence, this observational
study aimed at retrospectively comparing the blood
immunometabolic profile in calves with divergent RFI
during the preweaning period. Twenty-two Italian Simmental calves were monitored from birth through 60
d of age. Calves received 3 L of colostrum from their
respective dams. From 2 to 53 d of age, calves were
fed a milk replacer twice daily, whereas from 54 to 60
d (i.e., weaning) calves were stepped down to only one
meal in the morning. Calves had ad libitum access to
concentrate and intakes were recorded daily. The measurement of BW and blood samples were performed at
0, 1, 7, 14, 21, 28, 35, 45, 54, and 60 d of age. Calves
were ranked and categorized as M-Eff or L-Eff according to the median RFI value. Median RFI was –0.06 and
0.04 kg of DMI/d for M-Eff and L-Eff, respectively. No
evidence for group differences was noted for colostrum
and plasma IgG concentrations. Although growth rate
was not different, as expected, [0.67 kg/d (95% CI =
0.57 ‒ 0.76) for both L-Eff and M-Eff) throughout the
entire pre-weaning period (0–60 d), starter intake was
greater in L-Eff compared with M-Eff calves (+36%).
Overall, M-Eff calves had a greater gain-to-feed ratio
compared with L-Eff calves (+16%). Plasma ceruloplasmin, myeloperoxidase, and reactive oxygen metabolite concentrations were greater in L-Eff compared with M Eff calves. Compared with L-Eff, M-Eff calves had an
overall greater plasma concentration of globulin, and
γ-glutamyl transferase (indicating a better colostrum
uptake) and Zn at 1 d. Retinol and urea were overall
greater in L-Eff. The improved efficiency in nutrient
utilization observed in M-Eff was paired with a lower
grade of oxidative stress and systemic inflammation.
L-Eff may have had greater energy expenditure to sup port the activation of the immune system.
Keywords: Residual feed intake, Growth performance,
Metabolic profile, Simmental calves.peer-reviewe
XIPE: the X-ray Imaging Polarimetry Explorer
X-ray polarimetry, sometimes alone, and sometimes coupled to spectral and
temporal variability measurements and to imaging, allows a wealth of physical
phenomena in astrophysics to be studied. X-ray polarimetry investigates the
acceleration process, for example, including those typical of magnetic
reconnection in solar flares, but also emission in the strong magnetic fields
of neutron stars and white dwarfs. It detects scattering in asymmetric
structures such as accretion disks and columns, and in the so-called molecular
torus and ionization cones. In addition, it allows fundamental physics in
regimes of gravity and of magnetic field intensity not accessible to
experiments on the Earth to be probed. Finally, models that describe
fundamental interactions (e.g. quantum gravity and the extension of the
Standard Model) can be tested. We describe in this paper the X-ray Imaging
Polarimetry Explorer (XIPE), proposed in June 2012 to the first ESA call for a
small mission with a launch in 2017 but not selected. XIPE is composed of two
out of the three existing JET-X telescopes with two Gas Pixel Detectors (GPD)
filled with a He-DME mixture at their focus and two additional GPDs filled with
pressurized Ar-DME facing the sun. The Minimum Detectable Polarization is 14 %
at 1 mCrab in 10E5 s (2-10 keV) and 0.6 % for an X10 class flare. The Half
Energy Width, measured at PANTER X-ray test facility (MPE, Germany) with JET-X
optics is 24 arcsec. XIPE takes advantage of a low-earth equatorial orbit with
Malindi as down-link station and of a Mission Operation Center (MOC) at INPE
(Brazil).Comment: 49 pages, 14 figures, 6 tables. Paper published in Experimental
Astronomy http://link.springer.com/journal/1068
Quantitative MRI Harmonization to Maximize Clinical Impact: The RIN-Neuroimaging Network
Neuroimaging studies often lack reproducibility, one of the cardinal features of the scientific method. Multisite collaboration initiatives increase sample size and limit methodological flexibility, therefore providing the foundation for increased statistical power and generalizable results. However, multisite collaborative initiatives are inherently limited by hardware, software, and pulse and sequence design heterogeneities of both clinical and preclinical MRI scanners and the lack of benchmark for acquisition protocols, data analysis, and data sharing. We present the overarching vision that yielded to the constitution of RIN-Neuroimaging Network, a national consortium dedicated to identifying disease and subject-specific in-vivo neuroimaging biomarkers of diverse neurological and neuropsychiatric conditions. This ambitious goal needs efforts toward increasing the diagnostic and prognostic power of advanced MRI data. To this aim, 23 Italian Scientific Institutes of Hospitalization and Care (IRCCS), with technological and clinical specialization in the neurological and neuroimaging field, have gathered together. Each IRCCS is equipped with high- or ultra-high field MRI scanners (i.e., ≥3T) for clinical or preclinical research or has established expertise in MRI data analysis and infrastructure. The actions of this Network were defined across several work packages (WP). A clinical work package (WP1) defined the guidelines for a minimum standard clinical qualitative MRI assessment for the main neurological diseases. Two neuroimaging technical work packages (WP2 and WP3, for clinical and preclinical scanners) established Standard Operative Procedures for quality controls on phantoms as well as advanced harmonized quantitative MRI protocols for studying the brain of healthy human participants and wild type mice. Under FAIR principles, a web-based e-infrastructure to store and share data across sites was also implemented (WP4). Finally, the RIN translated all these efforts into a large-scale multimodal data collection in patients and animal models with dementia (i.e., case study). The RIN-Neuroimaging Network can maximize the impact of public investments in research and clinical practice acquiring data across institutes and pathologies with high-quality and highly-consistent acquisition protocols, optimizing the analysis pipeline and data sharing procedures
Differential diagnosis of neurodegenerative dementias with the explainable MRI based machine learning algorithm MUQUBIA
Biomarker-based differential diagnosis of the most common forms of dementia is becoming increasingly important. Machine learning (ML) may be able to address this challenge. The aim of this study was to develop and interpret a ML algorithm capable of differentiating Alzheimer's dementia, frontotemporal dementia, dementia with Lewy bodies and cognitively normal control subjects based on sociodemographic, clinical, and magnetic resonance imaging (MRI) variables. 506 subjects from 5 databases were included. MRI images were processed with FreeSurfer, LPA, and TRACULA to obtain brain volumes and thicknesses, white matter lesions and diffusion metrics. MRI metrics were used in conjunction with clinical and demographic data to perform differential diagnosis based on a Support Vector Machine model called MUQUBIA (Multimodal Quantification of Brain whIte matter biomArkers). Age, gender, Clinical Dementia Rating (CDR) Dementia Staging Instrument, and 19 imaging features formed the best set of discriminative features. The predictive model performed with an overall Area Under the Curve of 98%, high overall precision (88%), recall (88%), and F1 scores (88%) in the test group, and good Label Ranking Average Precision score (0.95) in a subset of neuropathologically assessed patients. The results of MUQUBIA were explained by the SHapley Additive exPlanations (SHAP) method. The MUQUBIA algorithm successfully classified various dementias with good performance using cost-effective clinical and MRI information, and with independent validation, has the potential to assist physicians in their clinical diagnosis
Colorectal Cancer Stage at Diagnosis Before vs During the COVID-19 Pandemic in Italy
IMPORTANCE Delays in screening programs and the reluctance of patients to seek medical
attention because of the outbreak of SARS-CoV-2 could be associated with the risk of more advanced
colorectal cancers at diagnosis.
OBJECTIVE To evaluate whether the SARS-CoV-2 pandemic was associated with more advanced
oncologic stage and change in clinical presentation for patients with colorectal cancer.
DESIGN, SETTING, AND PARTICIPANTS This retrospective, multicenter cohort study included all
17 938 adult patients who underwent surgery for colorectal cancer from March 1, 2020, to December
31, 2021 (pandemic period), and from January 1, 2018, to February 29, 2020 (prepandemic period),
in 81 participating centers in Italy, including tertiary centers and community hospitals. Follow-up was
30 days from surgery.
EXPOSURES Any type of surgical procedure for colorectal cancer, including explorative surgery,
palliative procedures, and atypical or segmental resections.
MAIN OUTCOMES AND MEASURES The primary outcome was advanced stage of colorectal cancer
at diagnosis. Secondary outcomes were distant metastasis, T4 stage, aggressive biology (defined as
cancer with at least 1 of the following characteristics: signet ring cells, mucinous tumor, budding,
lymphovascular invasion, perineural invasion, and lymphangitis), stenotic lesion, emergency surgery,
and palliative surgery. The independent association between the pandemic period and the outcomes
was assessed using multivariate random-effects logistic regression, with hospital as the cluster
variable.
RESULTS A total of 17 938 patients (10 007 men [55.8%]; mean [SD] age, 70.6 [12.2] years)
underwent surgery for colorectal cancer: 7796 (43.5%) during the pandemic period and 10 142
(56.5%) during the prepandemic period. Logistic regression indicated that the pandemic period was
significantly associated with an increased rate of advanced-stage colorectal cancer (odds ratio [OR],
1.07; 95%CI, 1.01-1.13; P = .03), aggressive biology (OR, 1.32; 95%CI, 1.15-1.53; P < .001), and stenotic
lesions (OR, 1.15; 95%CI, 1.01-1.31; P = .03).
CONCLUSIONS AND RELEVANCE This cohort study suggests a significant association between the
SARS-CoV-2 pandemic and the risk of a more advanced oncologic stage at diagnosis among patients
undergoing surgery for colorectal cancer and might indicate a potential reduction of survival for
these patients
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