ECCC TEST PROGRAMME AND DATA ASSESSMENT ON GTD111 CREEP RUPTURE, STRAIN AND DUCTILITY

GTD111, a creep resistant Ni-based superalloy developed by GE, is widely used in land-based gas turbine first stage blades. However, there is little published information on its creep properties and microstructure. The European Creep Collaborative Committee (ECCC) Working Group 3C consequently selected GTD111 as a model material for testing and complementary data assessment. The aim of this paper is to present the results from the ECCC test program and data assessment, and to compare equiaxed (EA) and directionally solidified (DS) material performance. Testing and metallographic laboratories from six European nations collaborated to produce strain monitored creep rupture data on four EA and DS materials out to beyond 10,000 hours within a wide range of temperatures, 850-950°C, and stresses, 293-99 MPa. Available (generally short term) results from other sources were also included in the compiled, small but viable, 51-test data set. Assessment was carried out by three different assessors using different tools and adopting different prediction models. Conventional ECCC post-assessment techniques and novel “back-fitting” methods were used to identify a preferred model. It was shown that assessing all the EA and DS data together can lead to non-conservative predictions for EA materials, but separating the two classes creates small data subsets which cannot be modelled effectively. As a pragmatic compromise, the DS data and those EA data which also showed good ductility were included in a final "ductile GTD111" assessment. The resulting creep rupture material models and rupture strength predictions are presented up to 3 times the longest test duration. It was then shown that the performance of lower ductility EA materials can also be predicted effectively with the "ductile" model by truncating the rupture time at the measured fracture strain. For this exercise, a creep strain model based on rupture and time to strain data was fitted. In parallel, microstructural examination was performed to characterize the damage modes involved in the low ductility failures. It was thereby shown that the creep rupture strength shortfall of an EA material compared to its DS equivalent is not a constant factor, but is primarily governed by the reduced creep ductility. Hence, the shortfall varies between different EA casts, and tends to become greater in the longer term.JRC.F.4-Innovative Technologies for Nuclear Reactor Safet

Insights into non-Fickian solute transport in carbonates

[1] We study and explain the origin of early breakthrough and long tailing plume behavior by simulating solute transport through 3‐D X‐ray images of six different carbonate rock samples, representing geological media with a high degree of pore‐scale complexity. A Stokes solver is employed to compute the flow field, and the particles are then transported along streamlines to represent advection, while the random walk method is used to model diffusion. We compute the propagators (concentration versus displacement) for a range of Peclet numbers (Pe ) and relate it to the velocity distribution obtained directly on the images. There is a very wide distribution of velocity that quantifies the impact of pore structure on transport. In samples with a relatively narrow spread of velocities, transport is characterized by a small immobile concentration peak, representing essentially stagnant portions of the pore space, and a dominant secondary peak of mobile solute moving at approximately the average flow speed. On the other hand, in carbonates with a wider velocity distribution, there is a significant immobile peak concentration and an elongated tail of moving fluid. An increase in Pe , decreasing the relative impact of diffusion, leads to the faster formation of secondary mobile peak(s). This behavior indicates highly anomalous transport. The implications for modeling field‐scale transport are discussed

Very low prevalence of ultrasound detected tenosynovial abnormalities in healthy subjects throughout the age range: OMERACT ultrasound minimal disease study

Objectives: This study aimed to determine the prevalence of ultrasound detected tendon abnormalities in healthy subjects (HS) across the age range. / Methods: Adult HS (age 18 to 80 years) were recruited in 23 international Outcome Measures in Rheumatology (OMERACT) ultrasound centres and clinically assessed to exclude inflammatory diseases or overt osteoarthritis before undergoing a bilateral ultrasound examination of digit flexor (DF) 1-5 and extensor carpi ulnaris (ECU) tendons to detect the presence of tenosynovial hypertrophy (TSH), power Doppler (TPD) and tenosynovial effusion (TEF), usually considered ultrasound signs of inflammatory diseases. A comparison cohort of Rheumatoid Arthritis (RA) patients was taken from the Birmingham BEACON early arthritis inception cohort. / Results: 939 HS and 144 RA patients were included. The majority of HS (85%) had grade 0 for TSH, TPD and TEF in all DF and ECU tendons examined. There was statistically significant difference in the proportion of TSH and TPD involvement between HS and RA subjects (HS vs RA p<0.001). In HS there was no difference in the presence of ultrasound abnormalities between age groups. / Conclusions: Ultrasound detected TSH and TPD abnormalities are rare in HS and can be regarded as markers of active inflammatory disease in newly presenting suspected RA

Mathematical analysis of the Escherichia coli chemotaxis signalling pathway

We undertake a detailed mathematical analysis of a recent nonlinear ordinary differential equation (ODE) model describing the chemotactic signalling cascade within an {\it Escherichia coli} cell. The model includes a detailed description of the cell signalling cascade and an average approximation of the receptor activity. A steady-state stability analysis reveals the system exhibits one positive real steady-state which is shown to be asymptotically stable. Given the occurrence of a negative feedback between phosphorylated CheB (CheB-P) and the receptor state, we ask under what conditions, the system may exhibit oscillatory type behaviour. A detailed analysis of parameter space reveals that whilst variation in kinetic rate parameters within known biological limits is unlikely to lead to such behaviour, changes in the total concentration of the signalling proteins does. We postulate that experimentally observed overshoot behaviour can actually be described by damped oscillatory dynamics and consider the relationship between overshoot amplitude, total cell protein concentration and the magnitude of the external ligand stimulus. Model reductions of the full ODE model allow us to understand the link between phosphorylation events and the negative feedback between CheB-P and receptor methylation, as well as elucidate why some mathematical models exhibit overshoot and others do not. Our manuscript closes by discussing intercell variability of total protein concentration as means of ensuring the overall survival of a population as cells are subjected to different environments

Monotone and near-monotone biochemical networks

Monotone subsystems have appealing properties as components of larger networks, since they exhibit robust dynamical stability and predictability of responses to perturbations. This suggests that natural biological systems may have evolved to be, if not monotone, at least close to monotone in the sense of being decomposable into a “small” number of monotone components, In addition, recent research has shown that much insight can be attained from decomposing networks into monotone subsystems and the analysis of the resulting interconnections using tools from control theory. This paper provides an expository introduction to monotone systems and their interconnections, describing the basic concepts and some of the main mathematical results in a largely informal fashion

Deoxynivalenol and its toxicity

Deoxynivalenol (DON) is one of several mycotoxins produced by certain Fusarium species that frequently infect corn, wheat, oats, barley, rice, and other grains in the field or during storage. The exposure risk to human is directly through foods of plant origin (cereal grains) or indirectly through foods of animal origin (kidney, liver, milk, eggs). It has been detected in buckwheat, popcorn, sorgum, triticale, and other food products including flour, bread, breakfast cereals, noodles, infant foods, pancakes, malt and beer. DON affects animal and human health causing acute temporary nausea, vomiting, diarrhea, abdominal pain, headache, dizziness, and fever. This review briefly summarizes toxicities of this mycotoxin as well as effects on reproduction and their antagonistic and synergic actions