1,720,966 research outputs found
Pituitary-adrenal axis and peripheral cortisol metabolism in obese patients
No full textBackground and aim: A close relationship between adiposity and increased cortisol levels is well established in patients with endogenous hypercortisolism. Nevertheless, hypothalamic-pituitary-adrenal (HPA) axis regulation in overweight subjects is still a matter of concern. We studied free cortisol (urinary free cortisol, UFC and late night salivary cortisol, LNSC), pituitary feedback (serum cortisol after 1 mg dexamethasone suppression test, 1 mg DST) and peripheral cortisol metabolism (urinary cortisol to cortisone ratio, F/Eratio) in a large series of overweight subjects without Cushing’s Syndrome. Materials and methods: We considered 234 patients divided in 5 BMI classes, matched for age and gender (BMI ≤ 25 kg/m2n = 38; 25–30 n = 58; 30–35 n = 52; 35–40 n = 52; >40 n = 34). UFC, LNSC and urinary F/Eratio were assessed with LC-MS. Results: We collected 183 LNSC, 176 UFC, 152 1 mg DST and 64 F/Eratio tests. UFC levels were higher in lean subjects, and they decreased according to the BMI classes (p = 0.022). Non-suppressed cortisol levels (>50 nmol/L) after 1 mg DST were observed especially in patients with normal weight or mild obesity. Patients with BMI ≥ 35 kg/m2 revealed a reduced F/Eratio (0.39 vs. 0.61, p = 0.006). The specificity of tests (false positive results) was higher considering 1 mg DST or UFC in obese patients, on the contrary impaired cortisol rhythm (LNSC above normality) was observed in 47 subjects, irrespective of weight. Conclusions: Overweight and obese subjects are characterised by an original regulation of HPA axis (reduced UFC levels, increased suppression after 1 mg DST) and peripheral cortisol metabolism (reduced F/Eratio), suggesting an effort to counteract hypercortisolism
Influence of additive manufacturing-induced anisotropy on tool wear in end milling of Ti6Al4V
No full textAdditive manufacturing induces a microstructural anisotropy in its components, that reflects on their mechanical properties, and, in turn, on their machinability. In this paper, the tool wear when milling laser powder bed fused Ti6Al4V parts with four different build-up orientations was evaluated. The tool wear was qualitatively and quantitatively examined, and assessed indirectly by analyzing the chip morphology and the machined surface quality. This study demonstrates that the tool life decreases gradually up to 40%, going from machining horizontally manufactured samples to vertically manufactured ones. Furthermore, a novel interpretation of the correlation between the tool life and the additive manufacturing-induced anisotropy of the part was given
Drillability of Magnesium-Based Fiber Metal Laminates Obtained via Hot Metal Pressing with Different Metal Surface Treatments
Full text linkThe demand for lighter and more performant aerospace and automotive components has resulted in a substantial surge in a recent interest in parts made of Fiber Metal Laminates (FMLs). For such components, drilling operations are crucial for permitting subsequent assembly. However, drillability of fiber metal laminates is critical due to the heterogeneous thermal and mechanical properties of the metal and composite that form the laminate. In this framework, the current research work aims at understanding how drilling operations can be affected by different surface treatments carried out on AZ31B magnesium alloy sheets joined with Glass Fiber Reinforced Polyamide 6 (PA6GFRP) via hot metal pressing to form the FML. To this end, the Mg/PA6-GFRP/Mg composites were first fabricated using AZ31B surfaces that were previously treated through sandblasting, annealing, and their combination. Dry drilling was then performed using twist and spur drill bits. The feed was also varied, using two levels...
Improving surface integrity and corrosion resistance of additive manufactured Ti6Al4V alloy by cryogenic machining
No full textAdditive manufacturing (AM) processes are rapidly growing, thanks to the chance they offer for the component customization in terms of both in-service performances and geometrical features. Nevertheless, AM products still need finishing operations to obtain suitable surface finish, which may introduce machinability issues on the basis of the different mechanical and microstructural characteristics AM metal alloys have compared with the wrought ones. This work presents the pivotal topic of surface integrity evaluation of electron beam melted (EBM) Ti6Al4V titanium alloy after finishing turning operations carried out under dry, flood, and cryogenic cooling conditions at different feed rates. For the sake of comparison, the same machining trials were conducted on the wrought alloy. The machining-induced effects were broadly studied in terms of microstructural and mechanical features, residual stress nature, surface topography, and defects. Moreover, the corrosion behavior of the machined surfaces in simulated physiological conditions was also tested, proving that the combination of the particular microstructure of the EBM Ti6Al4V alloy with cryogenic machining allowed for significant improvement of the corrosion performances
Anisotropy effect of additively manufactured Ti6Al4V titanium alloy on surface quality after milling
No full textThe microstructural and mechanical anisotropy of metallic additive manufactured parts is well-established as the nature itself of the process induces the formation of columnar grains along the build-up direction. However, the effect of this anisotropy on the alloy machinability is rarely considered and a deeper understanding is needed. In the current study, Ti6Al4V prisms were fabricated by laser powder bed fusion in both vertical and horizontal orientation. After heat treatment, the prisms were slot milled at different cutting parameters to assess the influence of the build-up orientation on the surface quality, focusing on the surface topography. The results show that the skewness parameter can distinguish the machined surface of differently oriented AM parts and that the horizontal orientation allows for better machinability when considering the burrs height and the chip morphology
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Is pasireotide-induced diabetes mellitus predictable? A pilot study on the effect of a single dose of pasireotide on glucose homeostasis
No full textIntroduction: Pasireotide (PAS) is an effective treatment for Cushing’s disease (CD) but its use is burdened by an associated high incidence of diabetes mellitus (DM). The aim of this study was to examine the effect of a single subcutaneous injection of PAS on glucose metabolism in CD, and to identify predictors of DM onset. Methods: Fifteen patients with CD (13 females, 2 males; median age 43 years [IQR 34–50]) were submitted to an acute PAS test (600 μg s.c.), measuring glucose, insulin, C-peptide, GIP, glucagon, GLP-1, ACTH, and cortisol at the baseline and every 30 min for 2 h. Then they were treated twice daily with PAS 600 μg, and followed up with clinical and hormone assessments for a median of 6 months [2–13]. Results: PAS prompted a significant decrease in all hormonal parameters considered except for glycemia, which increased (as expected), reaching the highest value at 120′ (p 34.5 mmol/mol, and a glucose peak after PAS administration > 9 mmol/L. CD patients with these features given PAS therapy should therefore be monitored more carefully
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