Internal stresses in steel plate generated by shape memory alloy inserts

Neutron strain scanning was employed to investigate the internal stress fields in steel plate coupons with embedded prestrained superelastic NiTi shape memory alloy inserts. Strain fields in steel were evaluated at T = 21 °C and 130 °C on virgin coupons as well as on mechanically and thermally fatigued coupons. Internal stress fields were evaluated by direct calculation of principal stress components from the experimentally measured lattice strains as well as by employing an inverse finite element modeling approach. It is shown that if the NiTi inserts are embedded into the elastic steel matrix following a carefully designed technological procedure, the internal stress fields vary with temperature in a reproducible and predictable way. It is estimated that this mechanism of internal stress generation can be safely applied in the temperature range from −20 °C to 150 °C and is relatively resistant to thermal and mechanical fatigue. The predictability and fatigue endurance of the mechanism are of essential importance for the development of future smart metal matrix composites or smart structures with embedded shape memory alloy components

High-fat diets and seizure control in myoclonic-astatic epilepsy: A single center's experience

AbstractPurposeTo determine the efficacy of the Modified Atkins Diet (MAD) and Ketogenic Diet (KD) in seizure control within a population of myoclonic-astatic epilepsy (MAE) patients.MethodsThis was a retrospective, single center study evaluating the seizure control by high fat diets. Seizure diaries kept by the parents performed seizure counts. All patients met the clinical criteria for MAE.ResultsNine patients met the clinical criteria. We found that both the MAD and KD were efficacious in complete seizure control and allowed other medications to be stopped in seven patients. Two patients had greater than 90% seizure control without medications, one on the KD and the other on the MAD. Seizure freedom has ranged from 13 to 36 months, and during this time four patients have been fully weaned off of diet management. One patient was found to have a mutation in SLC2A1.ConclusionOur results suggest that strictly defined MAE patients respond to the MAD with prolonged seizure control. Some patients may require the KD for seizure freedom, suggesting a common pathway of increased requirement for fats. Once controlled, those fully responsive to the Diet(s) could be weaned off traditional seizure medications and in many, subsequently off the MAD or KD

A multiscale study of hot extruded CoNiGa ferromagnetic shape memory alloys

Ferromagnetic shape-memory CoNiGa alloys have attracted much scientific interest due to their potential alternative use as high-temperature shape-memory alloys, bearing a high prospect for actuation and damping applications at elevated temperatures. Yet, polycrystalline CoNiGa, due to strong orientation dependence of transformation strains, suffers from intergranular fracture. Here, two multi-grain CoNiGa samples were prepared by a novel hot extrusion process that can promote favourable grain-boundary orientation distribution and improve the material's mechanical behaviour. The samples were investigated by multiple methods and their microstructural, magnetic, and mechanical properties are reported. It is found that a post-extrusion solutionising heat treatment leads to the formation of a two-phase oligocrystalline homogeneous microstructure consisting of an austenitic parent B2 phase and γ-CoNiGa precipitates. Reconstruction of the full 3D grain morphology revealed large, nearly spherical grains with no low-angle grain boundaries throughout the entire sample volume. The presence of γ precipitation affects the transformation behaviour of the samples, by lowering the martensitic transformation temperature, while, in conjunction with the oligocrystalline microstructure, it improves the ductility. Controlling the composition of the B2 matrix, as well as the phase fraction of the γ phase, is thus crucial for the optimal behaviour of the alloys

Mental and substance use disorders from early adolescence to young adulthood among indigenous young people: Final diagnostic results from an 8-year panel study

Objective: Our objective was to investigate change in prevalence rates for mental and substance abuse disorders between early adolescence and young adulthood in a cohort of indigenous adolescents who participated in an 8-year panel study.Method: The data are from a lagged, sequential study of 671 indigenous adolescents (Wave 1) from a single culture in the Northern Midwest USA and Canada. At Wave 1 (mean age 11.3 years, Wave 4 (mean age 14.3 years), Wave 6 (mean age 16.2 years), and at Wave 8 (mean age 18.3 years) the tribally enrolled adolescents completed a computer-assisted personal interview that included DISC-R assessment for 11 diagnoses. Our yearly retention rates by diagnostic wave were: Wave 2, 94.7 %; Wave 4, 87.7 %; Wave 6, 88.0 %; Wave 8, 78.5 %.Results: The findings show a dramatic increase in lifetime prevalence rates for substance use disorders. By young adulthood, over half had met criteria of substance abuse or dependence disorder. Also at young adulthood, 58.2 % had met lifetime criteria of a single substance use or mental disorder and 37.2 % for two or more substance use or mental disorders. The results are compared to other indigenous diagnostic studies and to the general population.Conclusions: A mental health crisis exists within the indigenous populations that participated in this study. Innovations within current mental health service systems are needed to address the unmet demand of adolescents and families.Peer reviewedSociolog

SARS-CoV-2 infects the human kidney and drives fibrosis in kidney organoids

Kidney failure is frequently observed during and after COVID-19, but it remains elusive whether this is a direct effect of the virus. Here, we report that SARS-CoV-2 directly infects kidney cells and is associated with increased tubule-interstitial kidney fibrosis in patient autopsy samples. To study direct effects of the virus on the kidney independent of systemic effects of COVID-19, we infected human-induced pluripotent stem-cell-derived kidney organoids with SARS-CoV-2. Single-cell RNA sequencing indicated injury and dedifferentiation of infected cells with activation of profibrotic signaling pathways. Importantly, SARS-CoV-2 infection also led to increased collagen 1 protein expression in organoids. A SARS-CoV-2 protease inhibitor was able to ameliorate the infection of kidney cells by SARS-CoV-2. Our results suggest that SARS-CoV-2 can directly infect kidney cells and induce cell injury with subsequent fibrosis. These data could explain both acute kidney injury in COVID-19 patients and the development of chronic kidney disease in long COVID

Reorientation in Combined Stress Induced Martensite?

The thermoelastic martensitic transformation induced by independent external forces has been investigated in combined tension-torsion experiments with Cu-Al-Zn-Mn SMA hollow bar polycrystals. When the nonproportional change of the applied stress (reloading) occurs at low volume fraction of stress induced martensite phase, the shape of the experimental transformation path suggests, that the forward or reverse stress induced martensitic transformations take place, depending whether the mechanical energy is being supplied or released. At higher volume fraction of martensite, the deformation behavior upon reloading becomes more complex, suggesting a possible role of martensite to martensite transformations or reorientation processes

Stability of γ1' Martensite in Cu-Base Alloys

The analysis of the nonequilibrium σ-T diagrams constructed from the results of tension/compression thermomechanical tests with [001] Cu-based shape memory alloy/SMA/ single crystals was found to be a good way how to understand complex path dependent phenomena exhibited by SMA single crystals. Particularly, it has been shown that the γ1' martensite phase forming in Cu-based SMA may exist in much wider range of stress-temperature conditions than would be expected just from the results of thermal cycles or tensile loading-unloading tests with single crystals usually presented in the literature