231 research outputs found
A characterization of particular symmetric (0,1) matrices
AbstractA characterization of a class of symmetric (0, 1) matrices A such that AP is a symmetric matrix too, where P is a permutation matrix, is given, and an application to double coverings of graphs is considered
Applications of Automata and Graphs: Labeling-Operators in Hilbert Space I
We show that certain representations of graphs by operators on Hilbert space
have uses in signal processing and in symbolic dynamics. Our main result is
that graphs built on automata have fractal characteristics. We make this
precise with the use of Representation Theory and of Spectral Theory of a
certain family of Hecke operators. Let G be a directed graph. We begin by
building the graph groupoid G induced by G, and representations of G. Our main
application is to the groupoids defined from automata. By assigning weights to
the edges of a fixed graph G, we give conditions for G to acquire fractal-like
properties, and hence we can have fractaloids or G-fractals. Our standing
assumption on G is that it is locally finite and connected, and our labeling of
G is determined by the "out-degrees of vertices". From our labeling, we arrive
at a family of Hecke-type operators whose spectrum is computed. As
applications, we are able to build representations by operators on Hilbert
spaces (including the Hecke operators); and we further show that automata built
on a finite alphabet generate fractaloids. Our Hecke-type operators, or
labeling operators, come from an amalgamated free probability construction, and
we compute the corresponding amalgamated free moments. We show that the free
moments are completely determined by certain scalar-valued functions.Comment: 69 page
Continuum limit of parton distribution functions from the pseudo-distribution approach on the lattice
Precise quantification of the structure of nucleons is one of the crucial
aims of hadronic physics for the coming years. The expected progress related to
ongoing and planned experiments should be accompanied by calculations of
partonic distributions from lattice QCD. While key insights from the lattice
are expected to come for distributions that are difficult to access
experimentally, it is important that lattice QCD can reproduce the well-known
unpolarized parton distribution functions (PDFs) with full control over
systematic uncertainties. One of the novel methods for accessing the partonic
-dependence is the pseudo-distribution approach, which employs matrix
elements of a spatially-extended nonlocal Wilson-line operator of length .
In this paper, we address the issue of discretization effects, related to the
necessarily nonzero value of the lattice spacing , which start at first
order in as a result of the nonlocal operator. We use twisted mass fermions
simulated at three values of the lattice spacing, at a pion mass of 370 MeV,
and extract the continuum limit of isovector unpolarized PDFs. We also test,
for the first time in the pseudo-distribution approach, the effects of the
recently derived two-loop matching. Finally, we address the issue of the
reliability of the extraction with respect to the maximal value of .Comment: 31 pages, 20 figure
Continuum limit of parton distribution functions from the pseudo-distribution approach on the lattice
Precise exploration of the partonic structure of the nucleon is one of the
most important aims of high-energy physics. In recent years, it has become
possible to address this topic with first-principle lattice QCD investigations.
In this talk, we focus on the so-called pseudo-distribution approach to
determine the isovector unpolarized PDFs. In particular, we employ three
lattice spacings to study discretization effects and extract the distributions
in the continuum limit, at a pion mass of around 370 MeV. Also, for the first
time with pseudo-PDFs, we explore effects of the 2-loop matching from pseudo-
to light-cone distributions.Comment: 10 pages, 6 figures, proceedings of the 39th International Symposium
on Lattice Field Theory LATTICE 2022, 8-13 August 2022, Bonn, German
Lattice continuum-limit study of nucleon quasi-PDFs
The quasi-PDF approach provides a path to computing parton distribution
functions (PDFs) using lattice QCD. This approach requires matrix elements of a
power-divergent operator in a nucleon at high momentum and one generically
expects discretization effects starting at first order in the lattice spacing
. Therefore, it is important to demonstrate that the continuum limit can be
reliably taken and to understand the size and shape of lattice artifacts. In
this work, we report a calculation of isovector unpolarized and helicity PDFs
using lattice ensembles with Wilson twisted mass fermions, a pion
mass of approximately 370 MeV, and three different lattice spacings. Our
results show a significant dependence on , and the continuum extrapolation
produces a better agreement with phenomenology. The latter is particularly true
for the antiquark distribution at small momentum fraction , where the
extrapolation changes its sign.Comment: 24 pages, 21 figures. v2: additional references, discussion of
systematics, and position-space comparison with phenomenology. v3: applied
workaround for problem affecting Greek symbols in figures with some PDF
viewer
Improving IBD diagnosis and monitoring by understanding preanalytical, analytical and biological fecal calprotectin variability
BACKGROUND: The appropriate clinical use of fecal calprotectin (fCal) might be compromised by incomplete harmonization between assays and within- and between-subjects variability. Our aim was to investigate the analytical and biological variability of fCal in order to provide tools for interpreting fCal in the clinical setting. METHODS: Experiments were conducted to investigate the effects of temperature and storage time on fCal. Thirty-nine controls were enrolled to verify biological variability, and a case-control study was conducted on 134 controls and 110 IBD patients to compare the clinical effectiveness of three different fCal assays: ELISA, CLIA and turbidimetry. RESULTS: A 12% decline in fCal levels was observed within 24 h following stool collection irrespective of storage temperature. Samples were unstable following a longer storage time interval at room temperature. Within- and between-subjects fCal biological variability, at 31% and 72% respectively, resulted in a reference change value (RCV) in the region of 100%. fCal sensitivity in distinguishing between controls and IBD patients is satisfactory (68%), and the specificity high (93%) among young (<65 years), but not among older ( 6565 years) subjects (ROC area: 0.584; 95% CI: 0.399-0.769). Among the young, assays have different optimal thresholds (120 \u3bcg/g for ELISA, 50 \u3bcg/g for CLIA and 100 \u3bcg/g for turbidimetry). CONCLUSIONS: We recommend a standardized preanalytical protocol for fCal, avoiding storage at room temperature for more than 24 h. Different cutoffs are recommended for different fCal assays. In monitoring, the difference between two consecutive measurements appears clinically significant when higher than 100%, the fCal biological variability-derived RCV
Combined Before-and-After Workplace Intervention to Promote Healthy Lifestyles in Healthcare Workers (STI-VI Study): Short-Term Assessment
Health care workers (HCWs) are prone to a heavy psycho-physical workload. Health promotion programs can help prevent the onset of chronic and work-related diseases. The aim of the STI-VI 'before-and-after' study, with assessments scheduled at 6 and 12 months, was to improve the lifestyle of HCWs with at least one cardiovascular risk factor. A tailored motivational counseling intervention, focusing on dietary habits and physical activity (PA) was administered to 167 HCWs (53 males; 114 females). BMI, waist circumference, blood pressure, and cholesterol, triglyceride, and blood glucose levels were measured before and after the intervention. The 6-month results (total sample and by gender) showed a marked effect on lifestyle: PA improved (+121.2 MET, p = 0.01), and diets became more similar to the Mediterranean model (+0.8, p < 0.001). BMI dropped (-0.2, p < 0.03), and waist circumference improved even more (-2.5 cm; p < 0.001). Other variables improved significantly: total and LDL cholesterol (-12.8 and -9.4 mg/dL, p < 0.001); systolic and diastolic blood pressure (-4.4 and -2.5 mmHg, p < 0.001); blood glucose (-1.5 mg/dL, p = 0.05); and triglycerides (significant only in women), (-8.7 mg/dL, p = 0.008); but HDL cholesterol levels dropped too. If consolidated at 12 months, these results indicate that our intervention can help HCWs maintain a healthy lifestyle and work ability
Self-interstitials injection in crystalline Ge induced by GeO 2 nanoclusters
The effect of O implantation in crystalline Ge on the density of native point defects has been investigated through transmission electron microscopy and B diffusion experiments. Annealing at 650 âą C following O implants produces a band of defects (âŒ5-10 nm), compatible with GeO 2 nanoclusters (NCs). A clear shape transformation from elongated to spherical forms occurs within 2 h, concomitant with a transient enhanced diffusion of B. A large injection of self-interstitials from GeO 2 NCs, giving a vacancy undersaturation, and a long-range migration of self-interstitials are evidenced and discussed
A comparison of echocardiography to invasive measurement in the evaluation of pulmonary arterial hypertension in a rat model
Pulmonary arterial hypertension (PAH) is a life-threatening condition characterized by progressive elevation in pulmonary artery pressure (PAP) and total pulmonary vascular resistance (TPVR). Recent advances in imaging techniques have allowed the development of new echocardiographic parameters to evaluate disease progression. However, there are no reports comparing the diagnostic performance of these non-invasive parameters to each other and to invasive measurements. Therefore, we investigated the diagnostic yield of echocardiographically derived TPVR and Doppler parameters of PAP in screening and measuring the severity of PAH in a rat model. Serial echocardiographic and invasive measurements were performed at baseline, 21 and 35 days after monocrotaline-induction of PAH. The most challenging echocardiographic derived TPVR measurement had good correlation with the invasive measurement (r = 0.92, P < 0.001) but also more simple and novel parameters of TPVR were found to be useful although the non-invasive TPVR measurement was feasible in only 29% of the studies due to lack of sufficient tricuspid valve regurgitation. However, echocardiographic measures of PAP, pulmonary artery flow acceleration time (PAAT) and deceleration (PAD), were measurable in all animals, and correlated with invasive PAP (r = â0.74 and r = 0.75, P < 0.001 for both). Right ventricular thickness and area correlated with invasive PAP (r = 0.59 and r = 0.64, P < 0.001 for both). Observer variability of the invasive and non-invasive parameters was low except in tissue-Doppler derived isovolumetric relaxation time. These non-invasive parameters may be used to replace invasive measurements in detecting successful disease induction and to complement invasive data in the evaluation of PAH severity in a rat model
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