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

Validation of the 3-under-2 principle of cell wall growth in Gram-positive bacteria by simulation of a simple coarse-grained model

The aim of this work is to propose a first coarse-grained model of Bacillus subtilis cell wall, handling explicitly the existence of multiple layers of peptidoglycans. In this first work, we aim at the validation of the recently proposed "three under two" principle.Comment: Revised introduction, results unchange

Dopamine Receptors in Parkinson's Disease: A Meta-Analysis of Imaging Studies

AbstractDopamine receptors are abundant along the central nigrostriatal tract and are expressed as 5 subtypes in two receptor families. In PD, compensatory changes in dopamine receptors emerge as a consequence of the loss of dopamine nerve terminals or dopaminergic pharmacotherapy. We performed a systematic review and meta‐analysis of the available PET and single‐photon emission computed tomography studies that have investigated dopamine receptors in PD, PSP and MSA. The inclusion criteria were studies including human PET or single‐photon emission computed tomography imaging; dopamine receptor tracers (D1‐like or D2‐like) and idiopathic PD, PSP, or MSA patients compared with healthy controls. The 67 included D2‐like studies had 1925 patients. Data were insufficient for an analysis of D1‐like studies. PD patients had higher striatal binding early in the disease, but after a disease duration of 4.36 years, PD patients had lower binding values than healthy controls. Striatal D2R binding was highest in unmedicated early PD patients and in the striatum contralateral to the predominant motor symptoms. PSP and MSA‐P patients had lower striatal D2R binding than PD patients (14.2% and 21.8%, respectively). There is initial upregulation of striatal D2Rs in PD, which downregulate on average 4 years after motor symptom onset, possibly because of agonist‐induced effects. The consistent upregulation of D2Rs in the PD striatum contralateral to the predominant motor symptoms indicates that receptor changes are driven by neurodegeneration and loss of striatal neuropil. Both PSP and MSA patients have clearly lower striatal D2R binding values than PD patients, which offers an opportunity for differential diagnostics. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Societ

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

Optical, near-IR and XX-ray observations of SN 2015J and its host galaxy

SN 2015J was discovered on April 27th 2015 and is classified as a type IIn supernova. At first, it appeared to be an orphan SN candidate, i.e. without any clear identification of its host galaxy. Here, we present the analysis of the observations carried out {by the VLT 8-m class telescope with the FORS2 camera in the R band and the Magellan telescope (6.5 m) equipped with the IMACS Short-Camera (V and I filters) and the FourStar camera (Ks filter)}. We show that SN 2015J resides in what appears to be a very compact galaxy establishing a relation between the SN event and its natural host. We also present and discuss archival and new $X$-ray data centred on SN 2015J. At the time of the supernova explosion, Swift/XRT observations were made and a weak X-ray source was detected at the location of SN 2015J. Almost one year later, the same source was unambiguously identified during serendipitous observations by Swift/XRT and $XMM$-Newton, clearly showing an enhancement of the 0.3-10 keV band flux by a factor $\simeq 30$ with respect to the initial state. Swift/XRT observations show that the source is still active in the $X$-rays at a level of $\simeq 0.05$ counts s$^{-1}$. The unabsorbed X-ray luminosity derived from the {\it XMM}-Newton slew and SWIFT observations, $L_{x}\simeq 5\times10^{41}$ erg s$^{-1}$, places SN 2015J among the brightest young supernovae in X-rays.Comment: The Astrophysical Journal, Volume 850, Number

Combustion and performance characteristics of air-fuel mixtures ignited by means of photo-thermal ignition of Nano-Energetic Materials

Abstract This work presents an experimental investigation to determine the performance and characteristics of the combustion process triggered by a new ignition system based on photo-thermal effect, observed when nano-Energetic Materials are exposed to a flash light. The resulting combustion process has been compared with the one obtained using the spark-plug traditionally used in spark ignition engines. Results showed that the photo-thermal ignition determines higher combustion pressure gradient, peak pressure, total heat released, fuel combustion efficiency, and a shorter ignition delay and combustion duration compared with the spark ignition, for all the tested fuels and air-fuel ratios

The infrared emission of carbonaceous particles around C-rich IRAS sources

The IRAS spectra of 23 carbon-rich sources have been fitted by means of an improved theoretical model based on the Leung-Spagna radiative transfer code and using extinction data obtained in our laboratory for different types of amorphous carbon and silicon carbide submicron particles. The agreement between observations and theoretical spectra is rather good. However, a comparison between the IRAS spectrum of the object 1244710425 (RU Vir) and that recently obtained at UKIRT, for the same object but with higher resolution, seems to open new problems

HP Cet and Swift J0820.6-2805: two candidate intermediate polars observed by XMM-Newton

We report on the XMM-Newton observation of HP Cet and Swift J0820.6-2805, two X-ray photon sources that are candidates to be members of the intermediate polar class of cataclysmic variables. If the historical optical light curve of HP Cet shows a periodic feature at $\simeq 96$ minutes, a clear identification of such a signature in the high energy band (apart for a variability on a time scale of $\simeq 8$ minutes as detected by the ROSAT satellite) is lacking. By using XMM-Newton archive data, we clearly identify a feature (at $\simeq 88$ minutes) which is marginally consistent with one of the binary system orbital periods reported in the literature. We also found a signature of a periodic features on the time scale of $\simeq 5.6$ minutes. In the case of Swift J0820.6-2805, the intermediate polar nature was previously unclear and the orbital and the white dwarf spin periods were unknown. Here, the 0.3-10 keV data undoubtedly reveal an orbital period and a white dwarf spin of $\simeq 87.5$ minutes and $\simeq 27.9$ minutes, respectively. The spectral analysis showed that both HP Cet and Swift J0820.6-280 are members of the under-luminous IP subclass since their luminosity in the $0.3-10$ keV band is estimated to be $\simeq 5\times 10^{30}$ erg s$^{-1}$ and $\simeq 3.8\times 10^{29}$ erg s$^{-1}$, respectively.Comment: Accepted for publication on MNRAS, main journal, 2020. 9 Pages. 9 Figure