197 research outputs found
A match coefficient approach for damage imaging in structural components by ultrasonic synthetic aperture focus
Ultrasonic Synthetic Aperture Focus (SAF) techniques are commonly used to image structural defects. In this paper, a variation of SAF based on ideas borrowed from Matched Field Processing (MFP) is evaluated to reduce artifacts and sidelobes of the resulting images. In particular, instead of considering the full RF ultrasonic waveforms for the SAF time backpropagation, only selected features from the waveforms are utilized to form a “data vector” and a “replica” (expected) vector of MFP. These vectors are adaptive for the pair of transmitter-receiver and the focus point. The image is created as a matched filter between these two vectors. Experimental results are shown for an isotropic and homogenous metallic plate with simulated defects, probed by six piezoelectric patches used as receivers or transmitters
Expression and regulation of α-transducin in the pig gastrointestinal tract
Taste signalling molecules are found in the gastrointestinal (GI) tract suggesting that they participate to chemosensing. We tested whether fasting and refeeding affect the expression of the taste signalling molecule, a-transducin (Gatran), throughout the pig GI tract and the peptide content of Gatran cells. The highest density of Gatran-immunoreactive (IR) cells was in the pylorus, followed by the cardiac mucosa, duodenum, rectum, descending colon, jejunum, caecum, ascending colon and ileum. Most Gatran-IR cells contained chromogranin A. In the stomach, many Gatran-IR cells contained ghrelin, whereas in the upper small intestine many were gastrin/cholecystokinin-IR and a few somatostatin-IR. Gatran-IR and Gagust-IR colocalized in some cells. Fasting (24 h) resulted in a significant decrease in Gatran-IR cells in the cardiac mucosa (29.3 0.8 versus 64.8 1.3, P < 0.05), pylorus (98.8 1.7 versus 190.8 1.9, P < 0.0 l), caecum (8 0.01 versus 15.5 0.5, P < 0.01), descending colon (17.8 0.3 versus 23 0.6, P < 0.05) and rectum (15.3 0.3 versus 27.5 0.7, P < 0.05). Refeeding restored the control level of Gatran-IR cells in the cardiac mucosa. In contrast, in the duodenum and jejunum, Gatran-IR cells were significantly reduced after refeeding, whereas Gatran-IR cells density in the ileum was not changed by fasting/refeeding. These findings provide further support to the concept that taste receptors contribute to luminal chemosensing in the GI tract and suggest they are involved in modulation of food intake and GI function induced by feeding and fasting
A public early intervention approach to first-episode psychosis: Treated incidence over 7 years in the Emilia-Romagna region
AimTo estimate the treated incidence of individuals with first-episode psychosis (FEP) who contacted the Emilia-Romagna public mental healthcare system (Italy); to examine the variability of incidence and user characteristics across centres and years. MethodsWe computed the raw treated incidence in 2013-2019, based on FEP users aged 18-35, seen within or outside the regional program for FEP. We modelled FEP incidence across 10 catchment areas and 7 years using Bayesian Poisson and Negative Binomial Generalized Linear Models of varying complexity. We explored associations between user characteristics, study centre and year comparing variables and socioclinical clusters of subjects. ResultsThousand three hundred and eighteen individuals were treated for FEP (raw incidence: 25.3 / 100.000 inhabitant year, IQR: 15.3). A Negative Binomial location-scale model with area, population density and year as predictors found that incidence and its variability changed across centres (Bologna: 36.55; 95% CrI: 30.39-43.86; Imola: 3.07; 95% CrI: 1.61-4.99) but did not follow linear temporal trends or density. Centers were associated with different user age, gender, migrant status, occupation, living conditions and cluster distribution. Year was associated negatively with HoNOS score (R = -0.09, p < .001), duration of untreated psychosis (R = -0.12, p < .001) and referral type. ConclusionsThe Emilia-Romagna region presents a relatively high but variable incidence of FEP across areas, but not in time. More granular information on social, ethnic and cultural factors may increase the level of explanation and prediction of FEP incidence and characteristics, shedding light on social and healthcare factors influencing FEP
Archaeological and archaeometric study of the glass finds from the ancient harbour of Classe (Ravenna- Italy): new evidence
Current drive at plasma densities required for thermonuclear reactors
Progress in thermonuclear fusion energy research based on deuterium plasmas magnetically confined in toroidal tokamak devices requires the development of efficient current drive methods. Previous experiments have shown that plasma current can be driven effectively by externally launched radio frequency power coupled to lower hybrid plasma waves. However, at the high plasma densities required for fusion power plants, the coupled radio frequency power does not penetrate into the plasma core, possibly because of strong wave interactions with the plasma edge. Here we show experiments performed on FTU (Frascati Tokamak Upgrade) based on theoretical predictions that nonlinear interactions diminish when the peripheral plasma electron temperature is high, allowing significant wave penetration at high density. The results show that the coupled radio frequency power can penetrate into high-density plasmas due to weaker plasma edge effects, thus extending the effective range of lower hybrid current drive towards the domain relevant for fusion reactors
Corrigendum: Current drive at plasma densities required for thermonuclear reactors
Nature Communications 1: Article number: 55 (2010); Published: 10 August 2010; Updated:19 September 2013. In Fig. 3 of this Article, the colours of the blue and green curves were accidentally interchanged while the manuscript was being revised. In addition, the x axis labels on Fig. 4 should have read 'Frequency (MHz)'
The number and profile of reactive NADH-d and NADPH-d neurons of myenteric plexus of six-month-old rats are different in the cecum portions
Minimum variance imaging in plates using guided wave mode beamforming
This paper presents improvements to ultrasonic imaging of solid plate-like structures using the minimum variance distortionless response (MVDR) beamforming processor. The primary application of this work is the nondestructive testing of plate-like components that are widely used in aerospace, marine, and civil structures. The study proposes a new set of weights, or MVDR replica vectors, that are based on the physics of the propagating Lamb modes, including the symmetric mode S0, the antisymmetric mode A0, and the shear horizontal mode SH0. Numerical results show that these wave mode weights, combined with geometrical spreading, improve the focus of the array by increasing dynamic range and spatial resolution of the image. Additionally, quite dramatic improvements in image quality are achieved by combining, or compounding, the multiple Lamb modes naturally present in the plate in both transmission and reflection. As shown in recent work applied to bulk waves in 3D solids, the compounding of Lamb modes in plates increases the array gain without increasing its physical aperture
Ultrasonic guided wave imaging of plates containing defects and inclusions
This paper addresses the nondestructive testing of platelike structural components that are widely used in aerospace, marine, and civil structures. The objective is not only to detect and localize possible defects, but to reconstruct a picture of the plate in terms of weakened areas, considering cases with multiple defects of different depths. To do so, the minimum-variance distortionless response (MVDR) beamforming processor is applied, using a new
set of weights, that improve the focus of the array by increasing the dynamic range and the spatial resolution of the image. These weights are based on the physics of the propagating Lamb modes, including the symmetric mode S0, the antisymmetric mode A0, and the shear horizontal mode SH0, taking advantage of their compounding too. The beamforming processor intensity enables to distinguish stiffer from weaker areas of the plate
Extraction of thermal Green's function using diffuse fields: A passive approach applied to thermography
In the field of non-destructive evaluation, defect detection and visualization can be performed exploiting different techniques relying either on an active or a passive approach. In the following paper the passive technique is investigated due to its numerous advantages and its application to thermography is explored.In previous works, it has been shown that it is possible to reconstruct the Green's function between any pair of points of a sensing grid by using noise originated from diffuse fields in acoustic environments. The extraction of the Green's function can be achieved by cross-correlating these random recorded waves. Averaging, filtering and length of the measured signals play an important role in this process. This concept is here applied in an NDE perspective utilizing thermal fluctuations present on structural materials. Temperature variations interacting with thermal properties of the specimen allow for the characterization of the material and its health condition. The exploitation of the thermographic image resolution as a dense grid of sensors constitutes the basic idea underlying passive thermography. Particular attention will be placed on the creation of a proper diffuse thermal field, studying the number, placement and excitation signal of heat sources. Results from numerical simulations will be presented to assess the capabilities and performances of the passive thermal technique devoted to defect detection and imaging of structural components
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