INDURIMENTO SUPERFICIALE DI LEGHE DI TITANIO MEDIANTE TRATTAMENTI TERMICI DI DIFFUSIONE DI Ni

In questo lavoro sono stati ottenuti rivestimenti di Ni elettrolitico e NiB electroless su campioni di titanio puro e sulla lega Ti-6Al-4V. Questi campioni dopo la deposizione sono stati sottoposti a trattamenti termici di diffusione a temperature inferiori e superiori alla temperatura di trasformazione allotropica del titanio e della lega per la durata di 1 h. E’ stato quindi analizzato l’effetto della temperatura sulla diffusione del Ni e del B all’interno del substrato e sulla profondità di indurimento dei campioni mediante analisi al SEM, EDS, XRD, GDOS e prove di microdurezza. Dopo il trattamento di 1h a temperatura superiore alla temperatura ?-transus (1000° C) nel campione di titanio CP si ha la formazione di uno strato di intermetallici NiTi e NiTi2 per uno spessore 20 ?m con valori di durezza di 1000 HV0,1 ed una zona di diffusione di 300-400 ?m con valori di durezza di 300 HV0,1. Per quanto riguarda la lega Ti6Al4V i trattamenti termici al di sopra della ? transus permettono di raggiungere durezze 1000 HV0,1, dovute alla formazione degli intermetallici NiTi e NiTi2 . I migliori risultati, ottenuti, sia per il titanio puro che per la lega, con il trattamento termico effettuato a temperatura superiore alla ? transus, sono da attribuirsi alla maggiore velocità di diffusione indotta sia dalla temperatura che dalla struttura ccc che il titanio assume a temperature superiori alla ? transus

Indurimento superficiale di leghe di alluminio mediante diffusione di rame

Lo scopo di questo lavoro è quello di sviluppare un processo per incrementare la durezza superficialedelle leghe di alluminio 2024 e 7075 mediante trattamenti di diffusione di rame, depositato elettroliticamentesulla superficie. I trattamenti diffusivi sono stati effettuati in forno in atmosfera inerte a temperaturecomprese nell’intervallo 470-500 °C per un tempo massimo di 24 h, seguiti da trattamenti di solubilizzazionee invecchiamento. I campioni sono stati caratterizzati mediante analisi al microscopio ottico (OM),microscopia elettronica a scansione (SEM), diffrazione a raggi X (XRD) e misure di microdurezza Vickers.La lega 2024, in seguito ai trattamenti di diffusione del rame condotti a temperature prossime ai 495 °C,raggiunge una durezza superficiale di 500 HV0,1, contro 80 HV0,1 del cuore del campione.Ciò è dovuto alla formazione dell’intermetallico Al2Cu. Il trattamento di invecchiamento non influenzalo spessore di diffusione che rimane di circa 50 ?m, bensì modifica la durezza in maniera diversa a secondache l’invecchiamento sia naturale o artificiale. I trattamenti di diffusione condotti sulla lega 7075 atemperature prossime a 500 °C provocano la diffusione del rame fino ad una profondità di 600 ?m e causanouna parziale fusione degli intermetallici superficiali, non permettendo di ottenere un aumento significativodella durezza superficiale. Abbassando la temperatura del trattamento diffusivo (470 °C), la zona interessatadalla diffusione del rame è di circa 100 ?m con una durezza di 860 HV0,1, dovuta alla formazione diintermetallici Al-Cu e Zn-Cu. Anche in questo caso, il successivo invecchiamento artificiale non varia lospessore di diffusione, ma porta ad una diminuzione della durezza superficiale a valori attorno a 500 HV0,1

Metallurgical and mechanical characterization of Cu electrolytic coating on Aluminium alloys

Aluminium and its alloys are attractive for many applications in chemical, automotive and aerospace industries because of their excellent properties as height\u2013 to\u2013 weight ratio, high electrical and thermal conductivities and good formability. In this work, a surface hardening process based on Cu electrolytic coating and subsequent diffusion heat treatments was studied for 7075 and 2024 aluminium alloys. The effect of temperature and time on the microstructure and the depth of hardening was studied by SEM, EDS, XRD and HV tests. The increasing of hardness and depth of hardening have been correlated to formation of different intermetallic phases in the surface coatings

Allogeneic Serum and Macromolecular Crowding Maintain Native Equine Tenocyte Function in Culture

The absence of a native extracellular matrix and the use of xenogeneic sera are often associated with rapid tenocyte function losses during in vitro culture. Herein, we assessed the influence of different sera (equine serum and foetal bovine serum) on equine tenocyte morphology, viability, metabolic activity, proliferation and protein synthesis as a function of tissue-specific extracellular matrix deposition (induced via macromolecular crowding), aging (passages 3, 6, 9) and time in culture (days 3, 5, 7). In comparison to cells at passage 3, at day 3, in foetal bovine serum and without macromolecular crowding (traditional equine tenocyte culture), the highest number of significantly decreased readouts were observed for cells in foetal bovine serum, at passage 3, at day 5 and day 7 and without macromolecular crowding. Again, in comparison to traditional equine tenocyte culture, the highest number of significantly increased readouts were observed for cells in equine serum, at passage 3 and passage 6, at day 7 and with macromolecular crowding. Our data advocate the use of an allogeneic serum and tissue-specific extracellular matrix for effective expansion of equine tenocytes

Glial plasticity in the dorsal vagal complex in response to western diet in rodents

International audienceGrowing evidence indicates that glial plasticity plays a role in feeding control, by adapting neuronal transmission to metabolic needs. Astroglial morphological changes and microglial activation occurs in response to feeding, in the hypothalamus and in other brain area involved in feeding regulation such as the olfactory bulb. Glial plasticity seems to evolve to glial activation in response to high-fat-high-sugar western diets (WD) consumption generating pro-inflammatory/obesogenic states. There is an abundant glial population in the dorsal vagal complex (DVC), a brainstem area involved in the integration of digestive signals. A thick border of astrocytes delineates the area postrema (AP), a circumventricular organ with permeable blood barrier, from the nucleus of the tractus solitarius (NTS) homing neuronal species involved in satiety, and astrocytes. Microglia are also abundant in the AP and NTS, where pro-inflammatory signals may arrive from the gut in response to dietary load and digestion. However, little isknown about the involvement of these glial populations in the satietogenic signals from the DVC.Our aim was to evaluate astrocytes and microglial changes in response to chronic or repeated episodes of western diet in the DVC of rats or mice.We have analysed the extent of the astrocyte spreading and the number and morphological phenotype of microglia in the AP and NTS by immunohistochemistry, on two rodent models: rats submitted to a high-fat/high-sugar diet (WD), and mice submitted to several 1-week-episodes of WD. Brainstems were taken after killing, fixed in formalin, and cryostat-cut coronal sections were labelled and analysed for astrocytes (GFAP) and microglia (Iba1). We found an increase in the astrocyte spreading (GFAP labelled area and thickness) between the AP and the NTS (but not in the astrocytes within the NTS) after one month of WD in rats as well as in mice after the repeated episodes of WD, as compared to control animals. We did not observe any increase in the microglial number or morphology within the AP in WD fed animals whereas we found an increased number of microglial cells in the NTS of WD fed rats as compared to controls. These glial changes were associated with several digestive markers alteration.These results show morphological changes enlarging the astroglial barrier between the AP and NTS in the DVC of rodents receiving a western diet. This was observed after a chronic exposition in rats or repeated expositions in mice, suggesting a persistence of the influence of the diet on the size of the astroglial barrier. Such an astroglial morphological plasticity in the DVC, between the AP and the NTS, may play a role in the adaptation of the satietogenic activity of the neurons to the type of diet

Natural history, diagnosis, treatment and outcome of medullary thyroid cancer: 37 years experience on 157 patients

Aim: The analysis of a 37-year retrospective study on diagnosis, prognostic variables, treatment and outcome of a large group of medullary thyroid cancer (MTC) patients was conducted, in order to plan a possible evidence-based management process. Methods: Between Jan 1967 to Dec 2004, 157 consecutive MTC patients underwent surgery in our centre: 60 males and 97 females, mean age 47.3 years (range 6-79). Total thyroidectomy was performed in 143 patients (91.1%); central compartment (CC) node dissection (level VI) in 41 patients; central plus lateral compartment (LC) node dissection (levels II, III, and IV) in 82 patients. Subtotal thyroidectomy was initially performed in 14 cases: 10 of them were re-operated because of persistence of elevated serum calcitonin levels. Results: After a median post-surgical follow-up of 68 months (range 2-440 months), 42.9% of patients were living disease-free, 39.8% were living with disease, 3.1% were deceased due to causes different from MTC, and 3.2% were deceased due to MTC. The overall 10-year survival rate was 72%. At uni-variate statistical analysis (a) patient's age at initial treatment (>45 years; ≥45 years), (b) sporadic vs. hereditary MTC, (c) disease stage, and (d) the extent of surgical approach resulted as significant variables. Instead, at multivariate statistical analysis, only (a) patient's age at initial diagnosis, (b) disease stage, and (c) the extent of surgery resulted as significant and independent prognostic variables influencing survival. Conclusion: The presence of lymph node and distant metastases at first diagnosis significantly worsened prognosis and survival rate in our series. Early diagnosis of MTC is very important, allowing complete surgical cure in Stages I and II patients. Due to the relatively bad prognosis of MTC, especially for disease Stages III and IV, it appears reasonable to recommend radical surgery including total thyroidectomy plus CC lymphoadenectomy as the treatment of choice, plus LC lymphoadenectomy in patients with palpable and/or ultrasound enlarged neck lymph nodes. © 2006 Elsevier Ltd. All rights reserved