Effetto dell'attacco chimico su leghe amorfe a base Au con formazione di fasi nanocristalline

L'interesse scientifico per le leghe preziose si è recentemente rinnovato in seguito alla scoperta di leghemulticomponenti a base oro che possono facilmente essere ottenute con una struttura amorfa. Ciò implica unmiglioramento delle proprietà meccaniche del materiale amorfo rispetto al corrispondente cristallino e implicaanche una migliore resistenza alla corrosione del vetro metallico prodotto.In questo lavoro concentreremo la nostra attenzione sulla produzione di leghe metalliche amorfe a base oro esul cambiamento della struttura superficiale di questi materiali sottoposti a prove di resistenza allacorrosione. Sono state individuate differenti composizioni (Au44Cu36Ti2Si18; Au44Cu37Ti1Si18; Au42Cu29Ti8Si21;Au49Cu26.9Ag5.5Pd2.3Si16.3), che mostrano una buona tendenza a formare vetri, di cui sono stati prodotticampioni in forma di nastro tramite solidificazione rapida. La struttura superficiale dei campioni, così comeprodotti, è stata studiata tramite diffrattometria di raggi X ad angolo radente, mettendo in evidenza lapresenza della sola fase amorfa per tutti i campioni presi in esame.È stato successivamente eseguito un trattamento in sudore artificiale (0.5 % NaCl, 0.1 % acido lattico, 0.1 %urea; pH= 6.5) per una settimana seguendo la direttiva europea UNI EN 1811 del 1998. L'incubazione insudore artificiale ha portato a modifiche della superficie, differenti a seconda dei campioni, che sono statemesse in evidenza tramite diffrattometria di raggi X ad angolo radente, microscopia elettronica in scansioneSEM, spettroscopia fotoelettronica XPS. Per alcune composizioni, in particolare per la legaAu49Cu26.9Ag5.5Pd2.3Si16.3, il trattamento ha portato alla formazione di nanocristalli di oro, aggregatisuperficialmente a SiO2 in particelle delle dimensioni dell'ordine del centinaio di nanometri. La dimensione equantità di particelle che si formano sulla superficie non risulta omogenea per tutti i campioni esaminati, maè influenzata dalla composizione della lega. La formazione di cristalli sulla superficie ha, come conseguenza,il cambiamento delle qualità estetiche della lega; in particolare si osserva un imbrunimento della superficie,tanto più marcato, tanto più alta è la quantità di precipitati formatisi in superficie

Heart rate variability and early recurrence of atrial fibrillation after electrical cardioversion

The study evaluated the role of the autonomic nervous system in atrial fibrillation (AF) recurrence

Amplitude measurements of Faraday waves

A light reflection technique is used to measure quantitatively the surface elevation of Faraday waves. The performed measurements cover a wide parameter range of driving frequencies and sample viscosities. In the capillary wave regime the bifurcation diagrams exhibit a frequency independent scaling proportional to the wavelength. We also provide numerical simulations of the full Navier-Stokes equations, which are in quantitative agreement up to supercritical drive amplitudes of 20%. The validity of an existing perturbation analysis is found to be limited to 2.5% overcriticaly.Comment: 7 figure

The risk stratification of adverse neonatal outcomes in women with gestational diabetes (STRONG) study

Aims: To assess the risk of adverse neonatal outcomes in women with gestational diabetes (GDM) by identifying subgroups of women at higher risk to recognize the characteristics most associated with an excess of risk. Methods: Observational, retrospective, multicenter study involving consecutive women with GDM. To identify distinct and homogeneous subgroups of women at a higher risk, the RECursive Partitioning and AMalgamation (RECPAM) method was used. Overall, 2736 pregnancies complicated by GDM were analyzed. The main outcome measure was the occurrence of adverse neonatal outcomes in pregnancies complicated by GDM. Results: Among study participants (median age 36.8 years, pre-gestational BMI 24.8 kg/m2), six miscarriages, one neonatal death, but no maternal death was recorded. The occurrence of the cumulative adverse outcome (OR 2.48, 95% CI 1.59–3.87), large for gestational age (OR 3.99, 95% CI 2.40–6.63), fetal malformation (OR 2.66, 95% CI 1.00–7.18), and respiratory distress (OR 4.33, 95% CI 1.33–14.12) was associated with previous macrosomia. Large for gestational age was also associated with obesity (OR 1.46, 95% CI 1.00–2.15). Small for gestational age was associated with first trimester glucose levels (OR 1.96, 95% CI 1.04–3.69). Neonatal hypoglycemia was associated with overweight (OR 1.52, 95% CI 1.02–2.27) and obesity (OR 1.62, 95% CI 1.04–2.51). The RECPAM analysis identified high-risk subgroups mainly characterized by high pre-pregnancy BMI (OR 1.68, 95% CI 1.21–2.33 for obese; OR 1.38 95% CI 1.03–1.87 for overweight). Conclusions: A deep investigation on the factors associated with adverse neonatal outcomes requires a risk stratification. In particular, great attention must be paid to the prevention and treatment of obesity

Growth Pattern, Resting Energy Expenditure, and Nutrient Intake of Children with Food Allergies

Growth impairment has been reported in children with food allergies (FA). However, the available data on the dietary intake of FA children are controversial, and no data are available on their resting energy expenditure (REE). The aim of this study was to test whether REE differs between FA and healthy children. In this study, 30 FA children were matched by sex and age, with 31 healthy controls using coarsened exact matching (CEM). Their REE was measured by indirect calorimetry (IC). Energy and macronutrient intake were evaluated using a three-day dietary record. Between-group comparisons were performed by robust median regression using CEM-related weights. The association of REE with allergies was also evaluated using robust median regression models. Anthropometric measurements, REE, and nutrient intake were similar in FA children and matched controls. Taking into account the association of REE with gender and age, a statistically significant but biologically negligible association was detected between median REE and allergy status (+9% in FA children). In conclusion, we did not find any biologically relevant difference in REE, anthropometry, and dietary intake in children with FA compared to healthy children

Threonine utilization is high in the intestine of piglets

The whole-body threonine requirement in parenterally fed piglets is substantially lower than that in enterally fed piglets, indicating that enteral nutrition induces intestinal processes in demand of threonine. We hypothesized that the percentage of threonine utilization for oxidation and intestinal protein synthesis by the portal-drained viscera (PDV) increases when dietary protein intake is reduced. Piglets (n = 18) received isocaloric normal or protein-restricted diets. After 7 h of enteral feeding, total threonine utilization, incorporation into intestinal tissue, and oxidation by the PDV, were determined with stable isotope methodology [U-(13)C threonine infusion]. Although the absolute amount of systemic and dietary threonine utilized by the PDV was reduced in protein-restricted piglets, the percentage of dietary threonine intake utilized by the PDV did not differ between groups (normal protein 91% vs. low protein 85%). The incorporation of dietary threonine into the proximal jejunum was significantly different compared with the other intestinal segments. Dietary, rather than systemic threonine was preferentially utilized for protein synthesis in the small intestinal mucosa in piglets that consumed the normal protein diet (P < 0.05). Threonine oxidation by the PDV was limited during normal protein feeding. In protein-restricted pigs, half of the total whole-body oxidation occurred in the PDV. We conclude that, in vivo, the PDV have a high obligatory visceral requirement for threonine. The high rate of intestinal threonine utilization is due mainly to incorporation into mucosal protein

Measurement of thermophysical properties of liquid metallic alloys in a ground- and microgravity based research program. The Thermolab Project

An outline of the Thermolab Project is reported with the aim of informing on the wide range of properties which are becoming available for some industrial alloys. Selected examples of experiments and properties are provided

Modeling of Ti-W Solidification Microstructures Under Additive Manufacturing Conditions

Additive manufacturing (AM) processes have many benefits for the fabrication of alloy parts, including the potential for greater microstructural control and targeted properties than traditional metallurgy processes. To accelerate utilization of this process to produce such parts, an effective computational modeling approach to identify the relationships between material and process parameters, microstructure, and part properties is essential. Development of such a model requires accounting for the many factors in play during this process, including laser absorption, material addition and melting, fluid flow, various modes of heat transport, and solidification. In this paper, we start with a more modest goal, to create a multiscale model for a specific AM process, Laser Engineered Net Shaping (LENS™), which couples a continuum-level description of a simplified beam melting problem (coupling heat absorption, heat transport, and fluid flow) with a Lattice Boltzmann-cellular automata (LB-CA) microscale model of combined fluid flow, solute transport, and solidification. We apply this model to a binary Ti-5.5 wt pct W alloy and compare calculated quantities, such as dendrite arm spacing, with experimental results reported in a companion paper