2,405 research outputs found
CD30, Th2 cytokines and HIV infection: a complex and fashinating link
No full textCD30 is a member of the tumor necrosis factor (TNF)/nerve growth factor (NGF) receptor superfamily, and was originally described as a marker of Hodgkin's and Reed-Sternberg cells in Hodgkin's lymphoma. CD30 is preferentially expressed on CD4+ and CD8+ T-cell clones that produce T helper 2 (Th2)-type cytokines, and is also released in a soluble form by these cells. Elevated serum levels of soluble (s)CD30 have been found in some conditions in which a pathogenic role for Th2 cells has been suggested, such as atopy, Omenn's syndrome, systemic lupus erythematosus, as well as following infection with measles virus or human immuno-deficiency virus (HIV). Here, Gianfranco Del Prete and colleagues suggest a complex and fascinating link between the expression and release of CD30, and the immunopathogenesis of HIV infection
Sviluppo di un sistema per il monitoraggio della qualità in linea di componenti stampati
No full textLe tecnologie che sfruttano metodi di rilevamento senza contatto sono sempre più utilizzate per migliorare l’efficienza dell’ispezione qualità in ambito manifatturiero. E’ evidente come, i recenti progressi dei sistemi di scansione laser e di visualizzazione hanno fatto si che sia possibile migliorare anche l’efficienza del controllo statistico dei processi di produzione. In questo articolo, gli autori presentano un sistema messo a punto per fornire in modo rapido misure di interesse delle features geometriche, che normalmente caratterizzano gli imbutiti da lamiere piane, integrato ad un modulo software di elaborazione delle misure per automatizzare l’ispezione della qualità e il controllo statistico di processo. Il sistema è costituito da componenti hardware e software appositamente sviluppati per le finalità di utilizzo della macchina messa a punto. La parte hardware è costituita da un’apparecchiatura a scansione laser e dall’attrezzatura che consente di riferire opportunamente i componenti al sistema durante la fase di misurazione. La parte software ha la finalità di generare part program di scansione ottimizzati in funzione della geometria del componente. Ciascuna scansione viene registrata e va a fare parte di un database che opportunamente organizzato consente di fornire informazioni utili per il controllo della qualità e il monitoraggio del processo di produzione preso in esame. Il sistema realizzato è stato progettato per consentire il rilevamento dei componenti a bordo linea. In questo articolo, gli autori, oltre a descrivere nello specifico le principali caratteristiche del sistema di acquisizione messo a punto, riportano i risultati del suo utilizzo su di un caso pratico dato dall’analisi di un lotto di produzione di un componente automobilistico ottenuto per imbutitura di lamiera piana
Complete subcutaneous rupture of the patellar tendon: Epidemiological and treatment problems in athletes
No full textE. Verni, F. Catani, R. Beluzzi, G. Del Prete, L. Prosperi, and R. Buda: Complete subcutaneous rupture of the patellar tendon: epidemiological and treatment problems in athletes. J. Sports Traumatol. rel. res. 19: 38, 1997. An account is given of 14 cases of patellar tendon rupture observed in 10 years with a minimum follow-up of 18 months. All athletes were treated with the same surgical technique. In addition to providing temporary protection for the tendon suture, cerclage is a sound means of securing the correct position of the patella. The results show that resumption of sport is a more selective criterion than modem clinical and instrumental investigations. The common epidemiological denominator was eccentric pliometric power training. In the absence of controlled scientific data concerning this form of functional overuse, careful selection and periodic monitoring is required of athletes whose explosive force is to be increased through previous stretching of a muscle
Development of customized physics-based predictive models for improved performance in turning of Ti6Al4V
No full textThis paper presents a combination of numerical and analytical models for selection of optimal parameters on turning Ti6Al4V. In particular, the work demonstrates the efficiency of the combined models to properly design the process tremendously reducing the time requested to verify the final product characteristics. The applied models include the prediction of surface integrity characteristics such as grain size, hardness changes and residual stresses but also fatigue life prediction based on surface characteristics. The above models have been modified and updated according to the material characteristics, centered on physics-based equations and assumptions, process and phenomena taken into consideration for the specific setup. In particular, the models follow the overall process starting from the cutting phase up to the final fatigue operational performance. The proposed approach demonstrates that it is possible to predict, with adequate accuracy, the influence of the machining process on surface state and final performance in terms of fatigue life. Thus, it is possible to drastically reduce the time and efforts to build up knowledge based on experimental trials including the proposed models into an industrial context
Orti Botanici storici e di nuova o recente istituzione in Italia: ruoli attuali, attività e impegni per il futuro
No full textA numerical procedure for machining distortions simulation on a SAF 2507 casting workpiece
No full textThe workpiece distortion that occurs during machining, can lead to a large increase in the number of the scrap parts. Residual stresses are the main cause of these distortions and they are generally present in both forging and casting products. In order to obtain the desired microstructure and mechanical properties, the workpiece is subjected to heat treatment before being worked. Quenching produces residual stresses that exist throughout a large percentage of the casting or forging part. Distortion occurs as a result of removing stressed material from the workpiece. The component will re-equilibrate and distort as each layer of stressed material is machined away. This paper describes a procedure development for distortions numerical analysis on a SAF2507 casting bulk workpiece. A solubilization heat treatment has been simulated, in order to predict the bulk residual stresses distribution. Different metal cutting processes have been considered to measure the numerical distortions induced in the workpiece
A physically based constitutive model of microstructural evolution of Ti6Al4V hard machining under different lubri-cooling conditions
No full textThe metallurgical phenomena taking place during machining processes affect the thermo-mechanical properties of the severely deformed materials, influencing, consequently, the process behavior. The microstructural modifications are difficult to be evaluated when the material is subjected to high speed deformations that are typical of material removal processes. Therefore, the microstructure-based numerical simulations can represent a useful tool able to properly predict their mechanics. Hard turning experiments were conducted on Ti6Al4V alloy, involving different process parameters and lubri-cooling conditions. The worked samples surfaces were assessed in terms of resulting microstructural changes and microhardness. The obtained results (cutting forces, temperature, and surface metallurgical modifications) were considered to develop and validate a physics-based model able to describe the microstructural phenomena occurring under large deformation processes, taking into account the influence of the physical phenomena that accommodate the material plastic strengthening and their resulting effects on the process variables. The dislocations reciprocal influence and their interaction with the material lattice were considered to understand the material viscoplastic flow. Moreover, also the recrystallization phenomena influencing the grain size related strengthening were considered to formulate the model. Then, the developed material model was implemented via user sub-routine in a commercial finite element (FE) software. The FE model was used to in-depth analyze the inner evolution of the processed material and to predict the variables of industrial interest. A good agreement was shown between the experimentally measured variables and the numerically predicted results. Moreover, the model was employed to investigate additional machining conditions via finite element analysis (FEA), demonstrating a huge capability to improve the manufacturing process performances, leading to a deeper knowledge of microstructural evolution and the material machinability under various process conditions
Tool Wear Characterization in Turning of a Nickel Superalloy Through Customized Pin-On-Disk Tests and Acoustic Emission Signals Analysis
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