Deformation of lamellar TiAl alloys by longitudinal twinning

© 2016 Elsevier Ltd. The occurrence of longitudinal twinning in the engineering alloy Ti-45Al-2Nb-2Mn (at.%)-0.8 vol.% TiB2 has been studied by measuring the changes in crystallographic orientation within individual lamellae during microcompression. Twinning in this alloy appeared to be a nucleation-limited process with the twins growing from lamellar boundaries at resolved shear stresses as low as 100 MPa, consistent with observations elsewhere. However, instead of forming twins ∼ 10-200 nm in thickness, as in polysynthetically twinned crystals, the longitudinal twins in this alloy were initiated at a lamellar boundary and then spread through the whole lamella.The work was supported by the EPSRC / Rolls-Royce Strategic Partnership (EP/H500375/1). Alberto Palomares Garcia, Claire Davis and Robert Jones are acknowledged for discussions and help with the TEM respectively

Obstructive Sleep Apnoea Syndrome, Endothelial Function and Markers of Endothelialization. Changes after CPAP

STUDY OBJECTIVES: This study tries to assess the endothelial function in vivo using flow-mediated dilatation (FMD) and several biomarkers of endothelium formation/restoration and damage in patients with obstructive sleep apnoea (OSA) syndrome at baseline and after three months with CPAP therapy. DESIGN: Observational study, before and after CPAP therapy. SETTING AND PATIENTS: We studied 30 patients with apnoea/hypopnoea index (AHI) >15/h that were compared with themselves after three months of CPAP therapy. FMD was assessed non-invasively in vivo using the Laser-Doppler flowmetry. Circulating cell-free DNA (cf-DNA) and microparticles (MPs) were measured as markers of endothelial damage and the vascular endothelial growth factor (VEGF) was determined as a marker of endothelial restoration process. MEASUREMENTS AND RESULTS: After three month with CPAP, FMD significantly increased (1072.26 ± 483.21 vs. 1604.38 ± 915.69 PU, p< 0.005) cf-DNA and MPs significantly decreased (187.93 ± 115.81 vs. 121.28 ± 78.98 pg/ml, p<0.01, and 69.60 ± 62.60 vs. 39.82 ± 22.14 U/μL, p<0.05, respectively) and VEGF levels increased (585.02 ± 246.06 vs. 641.11 ± 212.69 pg/ml, p<0.05). These changes were higher in patients with more severe disease. There was a relationship between markers of damage (r = -0.53, p<0.005) but not between markers of damage and restoration, thus suggesting that both types of markers should be measured together. CONCLUSIONS: CPAP therapy improves FMD. This improvement may be related to an increase of endothelial restoration process and a decrease of endothelial damage

On-site tests for the detection of potential induced degradation in modules

This paper presents different test alternatives which can be used on-site in a PV installation to detect potential induced degradation (PID) in modules. The testing procedures proposed are: thermal imaging; electroluminescence imaging; open circuit voltage measurements; operating voltage measurements; IV curve measurements; and dark IV curve measurements. Advantages and disadvantages of each test are reported

Temperature-dependent exchange stiffness and domain wall width in Co

The micromagnetic exchange stiffness is a critical parameter in numerical modeling of magnetization dynamics and reversal processes, yet the current literature reports a wide range of values even for such simple and widely used material as cobalt. Using the ab initio estimated Heisenberg parameters we calculate the low temperature micromagnetic exchange stiffness for hexagonal-close-packed (hcp) and face-centered-cubic cobalt. For hcp Co they are slightly different in the directions parallel and perpendicular to the c axis. We establish the exchange stiffness scaling relation with magnetization A(m)∼m1.8 valid for a wide range of temperatures. For hcp Co we find an anisotropic domain wall width in the range 24-29 nm which increases with temperature. The results form a critical input for large-scale temperature-dependent micromagnetics simulations and demonstrate the importance of correct parametrization for accurate simulation of magnetization dynamics

WEB MAPPING ARCHITECTURES BASED ON OPEN SPECIFICATIONS AND FREE AND OPEN SOURCE SOFTWARE IN THE WATER DOMAIN

The availability of water-related data and information across different geographical and jurisdictional scales is of critical importance for the conservation and management of water resources in the 21st century. Today information assets are often found fragmented across multiple agencies that use incompatible data formats and procedures for data collection, storage, maintenance, analysis, and distribution. The growing adoption of Web mapping systems in the water domain is reducing the gap between data availability and its practical use and accessibility. Nevertheless, more attention must be given to the design and development of these systems to achieve high levels of interoperability and usability while fulfilling different end user informational needs. This paper first presents a brief overview of technologies used in the water domain, and then presents three examples of Web mapping architectures based on free and open source software (FOSS) and the use of open specifications (OS) that address different users' needs for data sharing, visualization, manipulation, scenario simulations, and map production. The purpose of the paper is to illustrate how the latest developments in OS for geospatial and water-related data collection, storage, and sharing, combined with the use of mature FOSS projects facilitate the creation of sophisticated interoperable Web-based information systems in the water domain

Measuring crack initiation and the plastic deformation behaviour of titanium aluminides under compressive and tensile uniaxial loading

At temperatures of the order of 700 °C, suitable for the operation of low and intermediate pressure turbines and compressors in gas turbine engines, gamma titanium aluminides possess a higher specific strength than nickel superalloys. However, γ-TiAl suffers from a sufficiently reduced plasticity for a threshold approach to fatigue lifing to be necessary. Improving the fatigue behaviour of γ-TiAl requires an understanding of crack nucleation and how this is related to the detailed microstructure. Towards this, the monotonic compressive and tensile deformation behaviour of this two-phase lamellar composite alloy, Ti-45Al-2Nb-2Mn(at.%)-0.8vol%TiB2, currently undergoing engine tests by Rolls Royce, has therefore been measured at both room temperature and at 700°C. Both colony and lamellar-scale deformation features of the material have been investigated. Microstructural conditions with varying lamellar thicknesses were characterised by scanning electron microscopy and transmission Kikuchi diffraction. The near-surface plastic strain field and the build-up of local strains have been measured, using digital image correlation, with a remodelled gold speckle pattern, and compared with misorientation mapping using electron backscatter diffraction, both before and after testing. Temperature was found to have a significant impact on the active deformation mechanisms and their directions relative to the lamellae; this affects the ability of the material to provide compatible deformation. At high temperature, the shear generated upon twinning was found to be closely associated to debonding at colony boundaries. This is related to the possible accumulation of damage in cyclic loading

Microstructure of selective laser melted CM247LC nickel-based superalloy and its evolution through heat treatment

The selective laser melting of high temperature alloys is of great interest to the aerospace industry as it offers the prospect of producing more complex geometries than can be achieved with other manufacturing methods. In this study, the microstructure of the nickel-based superalloy, CM247LC, has been characterised following selective laser melting and after a post deposition heat-treatment below the γʹ solvus temperature. In the as-deposited state, scanning electron microscopy with electron backscatter diffraction revealed a fine, cellular microstructure with preferential alignment of along the build direction. A high dislocation density was seen at the periphery of the cells, indicating substantial localised deformation of the material. Fine primary MC carbides were also observed in the inter-cellular regions. High-resolution transmission electron microscopy identified the occurrence of very fine γʹ precipitates, approximately 5 nm in diameter, dispersed within the gamma phase. After heat treatment, the elongated cell colonies were observed to partially coalesce, accompanied by a decrease in dislocation density, producing columnar grains along the build direction. Cuboidal γʹ precipitates approximately 500 nm in diameter were observed to form in the recrystallised grains, accompanied by larger γʹ precipitates on the grain boundaries.The authors acknowledge funding from the EU under the Seventh Framework Programme (FP7) through the ASLAM project (CfP topic number: JTI-CS-2013-01-SAGE-06-006Project reference number: 619993). The authors would also like to acknowledge Rolls-Royce plc. for providing conventionally cast CM247LC.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.matchar.2016.02.00

Neuroprotective fragment C of tetanus toxin modulates IL-6 in an ALS mouse model

Neuroinflammation plays a significant role in amyotrophic lateral sclerosis (ALS) pathology, leading to the development of therapies targeting inflammation in recent years. Our group has studied the tetanus toxin C-terminal fragment (TTC) as a therapeutic molecule, showing neuroprotective properties in the SOD1G93A mouse model. However, it is unknown whether TTC could have some effect on inflammation. The objective of this study was to assess the effect of TTC on the regulation of inflammatory mediators to elucidate its potential role in modulating inflammation occurring in ALS. After TTC treatment in SOD1G93A mice, levels of eotaxin-1, interleukin (IL)-2, IL-6 and macrophage inflammatory protein (MIP)-1 alpha (ff) and galectin-1 were analyzed by immunoassays in plasma samples, whilst protein expression of caspase-1, IL-1β, IL-6 and NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) was measured in the spinal cord, extensor digitorum longus (EDL) muscle and soleus (SOL) muscle. The results showed reduced levels of IL-6 in spinal cord, EDL and SOL in treated SOD1G93A mice. In addition, TTC showed a different role in the modulation of NLRP3 and caspase-1 depending on the tissue analyzed. In conclusion, our results suggest that TTC could have a potential anti-inflammatory effect by reducing IL-6 levels in tissues drastically affected by the disease. However, further research is needed to study more in depth the anti-inflammatory effect of TTC in ALS

The interaction of borides and longitudinal twinning in polycrystalline TiAl alloys

In this paper the occurrence of twinning parallel to the lamellae during compression at 700 °C of a polycrystalline nearly lamellar commercial γ-TiAl alloy, Ti-45Al-2Nb-2Mn(at%)-0.8 vol% TiB2, has been studied and shown to lead to the formation of cracks at colony boundaries. However, the occurrence of this longitudinal twinning mode was less common by at least a factor of ten in tests at room temperature. Furthermore, the debonding of colony boundaries caused by the shear strain of longitudinal twinning is exacerbated when the same γ-TiAl variant favourably oriented for twinning occurs repeatedly in the lamellar structure. This effect was caused by the preferential nucleation of certain γ-TiAl variants in the presence of TiB2 boride reinforcement. It is shown that the boride additions increase the probability of double, triple or even higher order multiply stacked γ-variants. This increases the resulting shear strain that must be accommodated and hence the probability of crack nucleation.The work was supported by the EPSRC/Rolls-Royce Strategic Partnership (EP/M005607/1)