Experimental comparison between traditional and cryogenic cooling conditions in rough turning of Ti-6Al-4V

Titanium alloys, mainly because of their poor thermal conductivity, need to be cut at relatively low cutting speeds to avoid a severe diffusion wear, with obvious negative consequences on the profitability of machining. An important amount of research activities has been done in order to increase productivity in titanium machining operations and one of the most promising solutions is represented by the use of liquid nitrogen as a coolant during the machining operation. The aim of this paper is to compare traditional and cryogenic turning of Ti6Al4V in a region of cutting parameters particularly relevant to the aerospace industry where no previous data are available. The cutting parameters are those typical of titanium alloys rough machining which is considered, cost-wise, the most important operation because, for aerospace components, the so-called Buy-To-Fly ratio can reach values up to 20:1. The experiments have been performed using a full factorial design in order to statistically evaluate, using ANOVA and regression analyses, the significance of the input factors on the process most interesting outputs. The considered input factors are: type of cooling method, cutting speed and feed rate. The main analysed responses are: tool wear, surface roughness, cutting forces, coefficient of friction and chip morphology. The results show the significance of the cooling method on the tool life and that cryogenic machining is able to increase the tool life with respect to wet cutting. On the other hand, the beneficial effect of the liquid nitrogen cooling is reduced at high cutting speed and feed rate. Besides, the results showed that a small but significant reduction can be achieved for both the repulsion force and the coefficient of friction at the tool-workpiece interface

On the mechanics of chip formation in Ti-6Al-4V turning with spindle speed variation

"In order to enhance material removal rate (MRR), a strategy that relies on higher depths of cut could be chosen if vibrational issues due to regenerative chatter did not occur. A lot of research was done to suppress regenerative chatter without detrimental effects on productivity. One of the most interesting chatter suppression methods, mainly due to its flexibility and relative ease of implementation, is spindle speed variation (SSV), which consists in a continuous modulation of the nominal cutting speed. Sinusoidal spindle speed variation (SSSV) is a specific technique that exploits a sinusoidal law to modulate the cutting speed. The vast scientific literature on SSV was mainly focused on cutting process stability issues fully neglecting the study of the mechanics of chip formation in SSV machining. The aim of this work is to fill this gap: thus, finite element method (FEM) models of Ti-6Al-4V turning were setup to simulate both SSSV and constant speed machining (CSM). The models consider both the micro-geometry of the insert and the coating. Numerical results were experimentally validated on dry turning tests of titanium tubes exploiting the experimental assessment of cutting forces, cutting temperatures and chip morphology. Tool-chip contact pressure, tool engagement mechanism and the thermal distribution in the insert are some of the analysed numerical outputs because they cannot be easily assessed by experimental procedures. These quantities were useful to compare thermo-mechanical loads of the insert both in CSM and SSSV machining: it was observed that the loads significantly differ. Compared to CSM, the modulation of the cutting speed involves a higher tool-chip contact pressure peak, a higher maximum temperature and higher temperature gradients that could foster the main tool wear mechanisms. (C) 2013 Elsevier Ltd. All rights reserved.

Evolution of porosity and geometrical quality through the ceramic extrusion additive manufacturing process stages

Ceramic Extrusion Additive Manufacturing (CEAM) enables the die-less fabrication of small ceramic parts, with a process chain that includes four consecutive stages: the 3D printing, solvent de-binding, thermal de-binding, and sintering. The 3D printing process was implemented through Ephestus, a specially developed EAM machine for the manufacturing of parts from alumina feedstock. A test part was designed, and X-ray computed tomography (μ-CT) was used to quantify its characteristics through the processing stages of the EAM. The porosity distribution and the distribution of void size and shape were determined throughout the samples at each stage, using image analysis techniques. Furthermore, the evolution of some macroscopic quality properties was measured. The results show that both microscopic (porosity) and macroscopic (geometry, density) properties of the samples improve through the process stages. A vertical gradient of porosity is present in green and de-bound samples, with porosity decreasing with increasing sample height. After sintering, the vertical gradient of porosity disappears. The sphericity and the diameter of voids are negatively correlated and dispersed over a wide range in the green state. The sintering process has a homogenization effect on the void shape distribution. The geometrical deviation from the nominal designed dimensions and the surface quality of parts improves when moving from the green to the sintered state

Determinants of Vitamin D Levels in Italian Children and Adolescents: A Longitudinal Evaluation of Cholecalciferol Supplementation versus the Improvement of Factors Influencing 25(OH)D Status

Objective. This paper aims to assess 25(OH)D levels in Italian children and adolescents identifying risk factors for 25(OH)D deficiency and to evaluate whether a normal 25(OH)D value can be restored in 25(OH)D-deficient patients. Methods. We evaluated 25(OH)D levels in 679 Italian children and adolescents (≤10, 11–20, 21–30, and >30 ng/mL were defined as severe deficiency, deficiency, insufficiency, and sufficiency, resp.). Of these, 365 25(OH)D-deficient were followed up for 1 year; 205 were treated with cholecalciferol (Arm A: 400 I.U.) and 160 by improving the environmental variables influencing 25(OH)D levels (Arm B). Results. At cross-sectional evaluation, 11.3% showed sufficiency, 30.0% insufficiency, and 58.7% 25(OH)D deficiency. Mean 25(OH)D was 19.08±8.44 ng/mL. At the enrollment time (T0), no difference was found between Arms A and B with respect to distribution and 25(OH)D levels. At end time (T1) 26.0% (29.7% in Arm A versus 20.6% in Arm B) showed sufficiency, 38.4% (42.0% versus 34.4%) insufficiency, and 35.6% (28.3% versus 45.0%) 25(OH)D deficiency. Mean 25(OH)D level was 23.71±6.83 ng/mL. Conclusions. Neither changes of lifestyle nor 400 I.U. cholecalciferol supplementation alone appears to be sufficient to restore adequate 25(OH)D levels

Pain associated with COVID-19 vaccination is unrelated to skin biopsy abnormalities

Previous clinical observations raised the possibility that COVID-19 vaccination might trigger a small-fibre neuropathy.Objectives:In this uncontrolled observational study, we aimed to identify small fibre damage in patients complaining of generalized sensory symptoms and pain after COVID-19 vaccination.Methods:We collected clinical data, including a questionnaire for assessing autonomic symptoms (Composite Autonomic Symptom Score-31), and investigated quantitative sensory testing (QST) and skin biopsy in 15 prospectively enrolled patients with generalized sensory symptoms and pain after COVID-19 vaccination. Nine patients complaining of orthostatic intolerance also underwent cardiovascular autonomic tests.Results:We found that all patients experienced widespread pain, and most of them (11 of 15) had a fibromyalgia syndrome. All patients had normal skin biopsy findings, and in the 9 patients with orthostatic intolerance, cardiovascular autonomic tests showed normal findings. Nevertheless, 5 patients had cold and warm detection abnormalities at the QST investigation.Conclusions:In our study, most patients complaining of generalized sensory symptoms and pain after COVID-19 vaccination had clinical and diagnostic test findings compatible with a fibromyalgia syndrome. Although the abnormal QST findings we found in 5 patients might be compatible with a small-fibre neuropathy, they should be cautiously interpreted given the psychophysical characteristics of this diagnostic test. Further larger controlled studies are needed to define precisely the association between small fibre damage and COVID-19 vaccination

Full-dose atorvastatin versus conventional medical therapy after non-ST-elevation acute myocardial infarction in patients with advanced non-revascularisable coronary artery disease

Aims: This study tested the hypothesis that the addition of full-dose atorvastatin (80 mg/day) to conventional medical treatment could reduce ischaemic recurrences after non-ST-elevation acute myocardial infarction (NSTE-AMI) in patients with severe and diffuse coronary artery disease (CAD) not amenable to any form of mechanical revascularisation. Methods and results: The study was an open-label, randomised, controlled, blinded end-point classification trial, employing the PROBE (Prospective Open Treatment and Blinded End Point Evaluation) design. A total of 290 patients (mean age 74.6 +/- 9.6 years) with NSTE-AMI and angiographic evidence of severe and diffuse CAD, not amenable to revascularisation by either coronary surgery or angioplasty, were randomised to atorvastatin 80 mg/day (n = 144) or conventional medical treatment (n = 146). A primary end point event (combination of cardiovascular death, non-fatal acute myocardial reinfarction and disabling stroke within 12 months of randomisation) occurred in 16.0% of patients treated with atorvastatin 80 mg/day and in 26.7% of patients receiving conventional treatment (HR 0.56; 95% CI 0.33-0.93, p = 0.027). The study was not blinded. Consequently, a bias in the assessment of clinical outcome cannot be completely excluded. Conclusions: In conclusion, when compared with a conventional treatment strategy, full-dose therapy with atorvastatin 80 mg/day provides greater protection against ischaemic recurrences after NSTE-AMI in patients with severe, diffuse, non-revascularisable CAD

Management of syncope: clinical and economic impact of a Syncope Unit

Aims Aim of this observational study is to evaluate the clinical performance of a Syncope Unit, in order to assess whether the implemented organization really improves syncope management. Methods and results The study enrolled patients with unexplained syncope who were consecutively referred to our Syncope Unit, either as outpatients or during hospitalization, in a 2-month period. The design of this observational study consists in three phases: a retrospective analysis of their clinical. management in the 9 months prior to the first attendance at the Syncope Unit (phase one), their subsequent clinical management in the Syncope Unit (phase two) and a 9-month follow-up (phase three). The retrospective analysis of phase one showed that 25% of patients had already been hospitalized without diagnosis. After Syncope Unit evaluation, diagnosis was obtained in 82% of patients, with 15% of patients indicated to pacing. In the follow-up, 23% of patients experienced a syncopal recurrence. Our analysis indicated an 85% reduction of hospital costs in the follow-up period. Conclusion The clinical and economic analysis of the three phases of our study demonstrates that a Syncope Unit allows an improved management of patients with syncope

Smoking cessation interventions after acute coronary syndromes. Results of a cross-sectional survey in the Lazio Region of Italy.

Given the limited research on Italian hospital smoking care practices, a cross-sectional survey was undertaken in April-May 2011 to describe the current status of smoking cessation interventions for ACS patients in cardiovascular institutions of the Lazio Region of Italy. Lazio is a region of central Italy with a resident population of about 5,600,000. According to the data of the Regional Health Authority, about 10.000 patients are admitted for ACS every year in this region of Italy. Acute cardiac care in the region is currently provided by 33 Cardiology Divisions. All of these units were considered as eligible for the survey. The eligible respondent for each unit was the director. A self-report questionnaire was developed based on previous studies that examined the specific features of smoking cessation care provided to hospitalised patients. Questionnaires were forwarded by the Lazio Regional Section of the Italian National Association of Hospital Cardiologists (ANMCO). Completed questionnaires were received from 22 of the 33 eligible Divisions (66%). These 22 responding units currently provide acute care to about 70% of all ACS patients of the region. Responding units were more likely to represent public non-teaching hospitals (p=0.002), while non-responders were mostly from private non-teaching institutions (p=0.04). Response rates were not influenced by the presence of either interventional catheterization laboratory (Cathlab)or cardiac surgery within the hospitals. The survey suggest that most of cardiology units fail to provide recommended smoking care interventions to ACS patients. In particular, brief smoking cessation advice before discharge represents the only systematically implemented approach in clinical practice (22 units; 100%). Smoking cessation counselling is provided only in 9 units (40%). Specific pharmacotherapy is prescribed in selected case only in about one third of units (7 units; 32%), with varenicline being the preferred drug. Structural variables and organizational complexity have no influence on smoking care, as hospitals with Cathlab and cardiac surgery do not implement more effective strategies. Overall, this survey shows that the majority of smoking ACS inpatients may receive inadequate smoking care and that hospitals have considerable opportunity for improvement

La riparazione dell’ernia ombelicale nella donna in postmenopausa

Gli Autori riportano la loro esperienza sull’impiego della protesi dual-mesh in PTFEe per il trattamento delle ernie ombelicali nelle donne in postmenopausa. La riparazione protesica vs l’intervento classico di Mayo trova giustificazione nella maggior parte dei casi per i deficit biostrutturali delle strutture muscolo-fasciali delle donne in menopausa, deficit legati alla riduzione della funzione ovarica e aggravati da pregresse gravidanze. Una corretta valutazione del trofismo delle strutture della parete addominale e delle dimensioni delle ernie è comunque indispensabile nel porre indicazione alla chirurgia protesica. Nella nostra casistica la morbilità riferita a complicanze precoci è assolutamente trascurabile. A tutt’oggi, sebbene il follow-up sia ancora piuttosto breve, non abbiamo riscontrato casi di recidiva