creep behaviour of 15 15ti si austenitic steel in air and in liquid lead at 550 c

Abstract: This work aims at studying the creep behaviour of 15-15Ti(Si) austenitic steel, under uniaxial stress and its interaction with liquid lead. Creep tests were performed at 550 °C in an engineering stress range of 300-560 MPa. The 15-15Ti(Si) stainless steel is one of the best candidates for the nuclear reactor components of IV generation Lead-cooled fast reactor (LFR) and was tested in air and in stagnant liquid lead to simulate its behaviour in operating thermal and mechanical stress conditions and to verify its sensitivity to Liquid Metal Embrittlement (LME). Only few data can be found in the literature on 15-15Ti(Si) characterization, therefore the performed tests provided important information to use this material in the nuclear field, allowing to obtain the characteristic curve simulating the creep behaviour in air at all stress values, based on the Norton law and experimental data. The results of the specimens in air were compared with those obtained in lead, providing important information on creep corrosion: the liquid metal embrittlement effect takes place in lead and it produces a decrease of creep-rupture time, a reduction of creep strain and then the loss of steel ductility. Moreover, Scanning Electron Microscope (SEM) micrographs highlighted that lead changes both the mode and the type of specimen fracture. In addition, it was analyzed the lead action time, as the time after which the corrosion appears with macroscopic effects. These tests are still in progress: up to the current value of time (800h), they showed similar creep behaviour of the specimens tested in air and in lead. It can be assumed that liquid metal embrittlement takes place after a long time of steel/lead contact. However, since these tests are ongoing, these results will be object of our future studies

15-15Ti(Si) austenitic steel: Creep behaviour in hostile environment

This work aims at studying the creep behaviour of 15-15Ti(Si) austenitic steel, under uniaxial stress (range of 300-560 MPa), and its interaction with liquid lead. The steel was tested to verify its sensitivity to Liquid Metal Embrittlement (LME) and to simulate its behaviour in operating thermal and mechanical stress conditions of the IV generation Lead-cooled fast reactor. The experimental results permitted to plot the time-strain creep curve and the characteristic Norton-based curve, simulating the creep behaviour at all stress values. The comparison between the creep curves in air and in lead showed that the LME produces a decrease of creep-rupture time, a reduction of creep strain and then the loss of steel ductility. Moreover, the raw material and fracture surfaces were analyzed by Optical Microscope and Scanning Electron Microscope (SEM). SEM micrographs highlighted that lead changes both the mode and the type of specimen fracture. In addition, it was analyzed the lead action time, as the time after which the corrosion appears with macroscopic effects. Although some tests are still ongoing, it can be assumed that at high stresses, LME takes place after a long time of steel/lead contact while at low stresses, LME tends to prevail on creep effect

Neuroendocrine carcinomas of the breast

INTRODUCTION: Neuroendocrine (NE) breast cancers encompass a heterogeneous group of tumours showing morphological features similar to those of NE neoplasms of the gut and lung and expressing one or more neuroendocrine markers (neuron specific enolase, chromogranins synaptophysin) in at least 50% of tumour cells. They are rare lesions representing about 2-3% of all breast cancers and affecting more frequently elderly patients. AIM: Prospective observational study is to analyse the clinico-pathological aspects of NE carcinomas of the breast undergone surgical resection compared to breast carcinomas with a minor neuroendocrine component and to conventional invasive ductal or lobular cancers. MATERIAL AND METHOD: Thirty-five consecutive breast carcinomas showing morphological features suggestive of an endocrine differentiation were selected among breast cancers undergone surgical treatment during the period of January 1979-December 2004. RESULTS: The 35 patients were divided into two categories: 13 neuroendocrine carcinomas (NECs) and 22 ductal carcinomas with a minor neuroendocrine component (DC-NE). The average follow-up was 60 months. The patients with CNE developed breast cancer in an advanced age compared to the patients with infiltrating ductal carcinoma NAS or infiltrating lobular carcinoma. We did not find recurrent disease in the NEC group, while it was observed in 2 patients (9%) with DC-NE, in 6 cases (17%) with infiltrating ductal carcinoma NAS and in 7 cases (20%) with infiltrating lobular carcinoma. DISCUSSION: The CNE compared with the infiltrating ductal and lobular carcinoma are statistically different in relation to the expression of the receptor of c-erb-B2, p53, progesterone, for the lymph node state at diagnosis and the risk of reappearance of breast tumour. Our study confirms the choice to consider the neuroendocrine carcinoma of the breast as a separate histological group and seems to suggest a less aggressiveness of this type of tumou

The influence of inter-particle forces on diffusion at the nanoscale

Van der Waals and electrostatic interactions are the dominant forces acting at the nanoscale and they have been reported to directly influence a range of phenomena including surface adhesion, friction, and colloid stability but their contribution on nanoparticle diffusion dynamics is still not clear. In this study we evaluated experimentally the changes in the diffusion coefficient of nanoparticles as a result of varying the magnitude of Van der Waals and electrostatic forces. We controlled the magnitude of these forces by varying the ionic strength of a salt solution, which has been shown to be a parameter that directly controls the forces, and found by tracking single nanoparticles dispersed in solutions with different salt molarity that the diffusion of nanoparticles increases with the magnitude of the electrostatic forces and Van der Waals forces. Our results demonstrate that these two concurrently dynamic forces play a pivotal role in driving the diffusion process and must be taken into account when considering nanoparticle behaviour

Sindrome nefrosica e sepsi da Gram negativi in corso di strongiloidiasi: considerazioni su un caso in immigrato imunocompetente

Strongyloidiasis is caused by a small intestinal nematode with a complex life cycle. In Italy the infection is endemic in rural areas of the Po Valley. The clinical syndrome of S. stercoralis encompasses a broad spectrum of symptoms and signs and, in the immunocompromised host, larvae can migrate to different organs and tissues. Also immune response seems to play a role in the pathogenesis of the disease. We report a case of strongyloidiasis complicated by Gram-negative sepsis and nephrotic syndrome in an immigrant from South America with a normal immune response. Whereas sepsis cleared up quickly, parasitic clearance was obtained only after treatment with ivermectin and nephrotic syndrome was still present three months after the end of treatmen

Data from: Transition from fractional to classical Stokes-Einstein behaviour in simple fluids

An optical technique for tracking single particles has been used to evaluate the particle diameter at which diffusion transitions from molecular behaviour described by the fractional Stokes-Einstein relationship to particle behaviour described by the classical Stokes-Einstein relationship. The results confirm a prior prediction from molecular dynamic simulations that there is a particle size at which transition occurs and show it is inversely dependent on concentration and viscosity but independent of particle density. For concentrations in the range 510-3 to 510-6mg/mL and viscosities from 0.8 to 150 mPa s, the transition was found to occur in the diameter range 150 to 300nm

Rapporti fra ECG ed ematocrito: variazioni post-trasfusionali dei voltaggi di QRS e T

The influence upon the ECG of blood resistivity variations provoked by hematocrit changes has been studied in 40 patients affected by Cooley’s anemia undergoing transfusion with packed red celles. In each case two electrocardiograms (immediately before and after the transfusion) were perfomed. The voltages of the Q, R, S, and T waves and the € R, obtained by the sum of the R waves observed in all the leads, were measured in each recording. The R waves voltages fell remarkably in all the leads after the transfusion, as well as the Q waves voltages in II and III and the R, while the S wave increased in $V_6$ and the T wave did not show any post-transfuslonal change. A meaningful correlation between the variations of R and Ht was also observed particularly In the patients with Ht<30. These electrocardiographic changes have ben interpreted as due to hematocrit variations, according to Brody’s theory. It is well known that the cardiac forces transmission is affected by highly conductive intracavitary blood, which Increases the transmlssion of the radial forces and decreases that of the tangential ones (Brody effect). The blood resistivity increase induced by the post-transfusional Ht change diminishes then the left ventricular forces (R waves), radially di rected, and increases the right ventricular ones (S waves in lead $V_6$), tangentially directed

Farmacocinetica della digossina e della betametildigossina in pazienti con epatopatie croniche

La farmacocinetica di due glicosidi digitalici è stata studiata in pazienti con epatopatie croniche distinti in due gruppi secondo il grado di compromissione epatica (lieve e grave). In 8 pazienti epatopatici ed in 4 soggetti normali è stata studiata la curva digossinemica dopo dose unica di betametildigossina (0,4 mg) e digossina (0,5 mg) con disegno cross-over ed intervallo fra i trattamenti di 7 giorni. In un secondo gruppo di 8 epatopazienti e 8 normali sono state somministrate in sequenza randomizzata rispettivamente digossina (0,25 mg/die) e betametildigossina (0,2 mg/die) per un periodo di due settimane con determinazione della digitalemia al 14° e 15° giorno di trattamento. I valori della concentrazione oraria media digossinemica, di concentrazione massima e di tempo di picco nella prova acuta ed i livelli digossinemici nella prova cronica non sono risultati significativamente differenti nei pazienti con epatopatia lieve o grave rispetto ai normali con entrambi i glicosidi impiegati