Incompatible sets of gradients and metastability

We give a mathematical analysis of a concept of metastability induced by incompatibility. The physical setting is a single parent phase, just about to undergo transformation to a product phase of lower energy density. Under certain conditions of incompatibility of the energy wells of this energy density, we show that the parent phase is metastable in a strong sense, namely it is a local minimizer of the free energy in an $L^1$ neighbourhood of its deformation. The reason behind this result is that, due to the incompatibility of the energy wells, a small nucleus of the product phase is necessarily accompanied by a stressed transition layer whose energetic cost exceeds the energy lowering capacity of the nucleus. We define and characterize incompatible sets of matrices, in terms of which the transition layer estimate at the heart of the proof of metastability is expressed. Finally we discuss connections with experiment and place this concept of metastability in the wider context of recent theoretical and experimental research on metastability and hysteresis.Comment: Archive for Rational Mechanics and Analysis, to appea

Peripheral neuropathy secondary to a ‘domino’ liver transplant: a case report

Background: Peripheral neuropathy caused by amyloidosis is one of the well-recognised sequelae of mutations in the transthyretin gene (TTR).// Case presentation: We describe a case of peripheral neuropathy in a White British 74 year old man with wild-type TTR, 8 years following receipt of a ‘domino’ liver transplant (from a donor with a TTR mutation). The clinical phenotype and neurophysiology, coupled with presence of ATTR amyloid deposits on fat biopsy, established the diagnosis of ATTR amyloid neuropathy, as a consequence of receipt of a variant-TTR secreting liver. A nerve biopsy was not clinically appropriate for this patient. Such cases are rare since recipients of such livers are typically restricted to people whose natural lifespan is unlikely to stretch into the anticipated symptomatic period of ATTR amyloidosis. However, novel “gene silencing” therapeutics are now available which can dramatically alter the course of this disorder, by reducing the proportion of abnormal proteins.// Conclusions: This represents a rare but predictable iatrogenic side effect, and doctors should be aware of this eventuality occurring in a shorter time span than previously anticipated

Peripheral neuropathy secondary to a ‘domino’ liver transplant:a case report

Abstract Background Peripheral neuropathy caused by amyloidosis is one of the well-recognised sequelae of mutations in the transthyretin gene (TTR). Case presentation We describe a case of peripheral neuropathy in a White British 74 year old man with wild-type TTR, 8 years following receipt of a ‘domino’ liver transplant (from a donor with a TTR mutation). The clinical phenotype and neurophysiology, coupled with presence of ATTR amyloid deposits on fat biopsy, established the diagnosis of ATTR amyloid neuropathy, as a consequence of receipt of a variant-TTR secreting liver. A nerve biopsy was not clinically appropriate for this patient. Such cases are rare since recipients of such livers are typically restricted to people whose natural lifespan is unlikely to stretch into the anticipated symptomatic period of ATTR amyloidosis. However, novel “gene silencing” therapeutics are now available which can dramatically alter the course of this disorder, by reducing the proportion of abnormal proteins. Conclusions This represents a rare but predictable iatrogenic side effect, and doctors should be aware of this eventuality occurring in a shorter time span than previously anticipated

Revealing per-grain and neighbourhood stress interactions of a deforming ferritic steel via three-dimensional X-ray diffraction

The structural performance of polycrystalline alloys is strongly controlled by the characteristics of individual grains and their interactions, motivating this study to understand the dynamic micromechanical response within the microstructure. Here, a high ductility single-phase ferritic steel during uniaxial deformation is explored using three-dimensional X-ray diffraction. Grains well aligned for dislocation slip are shown to possess a wide intergranular stress range, controlled by per-grain dependent hardening activity. Contrariwise, grains orientated poorly for slip have a narrow stress range. A grain neighbourhood effect is observed of statistical significance: the Schmid factor of serial adjoining grains influences the stress state of a grain of interest, whereas parallel neighbours are less influential. This phenomenon is strongest at low plastic strains, with the effect diminishing as grains rotate during plasticity to eliminate any orientation dependent load shedding. The ability of the ferrite to eliminate such neighbourhood interactions is considered key to the high ductility possessed by these materials

Revealing per-grain and neighbourhood stress interactions of a deforming ferritic steel via three-dimensional X-ray diffraction

The structural performance of polycrystalline alloys is strongly controlled by the characteristics of individual grains and their interactions, motivating this study to understand the dynamic micromechanical response within the microstructure. Here, a high ductility single-phase ferritic steel during uniaxial deformation is explored using three-dimensional X-ray diffraction. Grains well aligned for dislocation slip are shown to possess a wide intergranular stress range, controlled by per-grain dependent hardening activity. Contrariwise, grains orientated poorly for slip have a narrow stress range. A grain neighbourhood effect is observed of statistical significance: the Schmid factor of serial adjoining grains influences the stress state of a grain of interest, whereas parallel neighbours are less influential. This phenomenon is strongest at low plastic strains, with the effect diminishing as grains rotate during plasticity to eliminate any orientation dependent load shedding. The ability of the ferrite to eliminate such neighbourhood interactions is considered key to the high ductility possessed by these materials

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park, Wyoming, USA. III. An anion-exchange resin technique for sampling and preservation of sulfoxyanions in natural waters

A sampling protocol for the retention, extraction, and analysis of sulfoxyanions in hydrothermal waters has been developed in the laboratory and tested at Yellowstone National Park and Green Lake, NY. Initial laboratory testing of the anion-exchange resin Bio-Rad™ AG1-X8 indicated that the resin was well suited for the sampling, preservation, and extraction of sulfate and thiosulfate. Synthetic solutions containing sulfate and thiosulfate were passed through AG1-X8 resin columns and eluted with 1 and 3 M KCl, respectively. Recovery ranged from 89 to 100%. Comparison of results for water samples collected from five pools in Yellowstone National Park between on-site 1C analysis (U.S. Geological Survey mobile lab) and IC analysis of resin-stored sample at SUNY-Stony Brook indicates 96 to 100% agreement for three pools (Cinder, Cistern, and an unnamed pool near Cistern) and 76 and 63% agreement for two pools (Sulfur Dust and Frying Pan). Attempts to extract polythionates from the AG1-X8 resin were made using HCl solutions, but were unsuccessful. Bio-Rad™ AG2-X8, an anion-exchange resin with weaker binding sites than the AG1-X8 resin, is better suited for polythionate extraction. Sulfate and thiosulfate extraction with this resin has been accomplished with KCl solutions of 0.1 and 0.5 M, respectively. Trithionate and tetrathionate can be extracted with 4 M KCl. Higher polythionates can be extracted with 9 M hydrochloric acid. Polythionate concentrations can then be determined directly using ion chromatographic methods, and laboratory results indicate recovery of up to 90% for synthetic polythionate solutions using AG2-X8 resin columns

Abnormal neuromuscular transmission in an infantile myasthenic syndrome

A term infant required intubation for respiratory depression. Examination revealed hypotonia and areflexia with intact extraocular movements. Electrodiagnostic studies demonstrated defective neuromuscular transmission characterized by borderline low motor evoked amplitudes, profound decremental responses at all stimulation rates, and moderate facilitation (50 to 740%) 15 seconds after 5 seconds of 50 Hz stimulation. Repetitive muscle action potential responses were not recorded following stimulation of nerves by single shocks. Sensory evoked responses and needle electromyographic findings were normal, as were acetylcholine receptor antibody levels. Results of muscle histochemical analyses, including acetylcholinesterase stains, were normal. End-plate histometric analyses demonstrated only a slight reduction in mean synaptic vesicle diameter compared with that in an adult control subject. In vitro muscle contractile properties, stimulating the muscle directly, were normal. Anticholinesterase medications were ineffective. Guanidine produced clinical deterioration. The amplitude of motor evoked responses progressively declined, whereas the percentage of decrement and amount of post-tetanic facilitation increased. Although the nature of the transmission defect was not identified, the data are consistent with abnormal acetylcholine resynthesis, mobilization, or storage without abnormality of release or receptors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50308/1/410160107_ftp.pd

Registration between DCT and EBSD datasets for multiphase microstructures

The ability to characterise the three-dimensional microstructure of multiphase materials is essential for understanding the interaction between phases and associated materials properties. Here, laboratory-based diffraction-contrast tomography (DCT), a recently-established materials characterization technique that can determine grain phases, morphologies, positions and orientations in a voxel-based reconstruction method, was used to map part of a dual-phase steel alloy sample. To assess the resulting microstructures that were produced by the DCT technique, an EBSD map was collected within the same sample volume. To identify the 2D slice of the 3D DCT reconstruction that best corresponded to the EBSD map, a novel registration technique based solely on grain-averaged orientations was developed -- this registration technique requires very little a priori knowledge of dataset alignment and can be extended to other techniques that only recover grain-averaged orientation data such as far-field 3D X-ray diffraction microscopy. Once the corresponding 2D slice was identified in the DCT dataset, comparisons of phase balance, grain size, shape and texture were performed between DCT and EBSD techniques. More complicated aspects of the microstructural morphology such as grain boundary shape and grains less than a critical size were poorly reproduced by the DCT reconstruction, primarily due to the difference in resolutions of the technique compared with EBSD. However, lab-based DCT is shown to accurately determine the centre-of-mass position, orientation, and size of the large grains for each phase present, austenite and martensitic ferrite. The results reveals a complex ferrite grain network of similar crystal orientations that are absent from the EBSD dataset. Such detail demonstrates that lab-based DCT, as a technique, shows great promise in the field of multi-phase material characterization.Comment: 15 pages, 11 figures. Preprint submitted to Materials Characterizatio

Design, Implementation and First Measurements with the Medipix Neutron Camera in CMS

The Medipix detector is the first device dedicated to measuring mixed-field radiation in the CMS cavern and able to distinguish between different particle types. Medipix2-MXR chips bump bonded to silicon sensors with various neutron conversion layers developed by the IEAP CTU in Prague were successfully installed for the 2008 LHC start-up in the CMS experimental and services caverns to measure the flux of various particle types, in particular neutrons. They have operated almost continuously during the 2010 run period, and the results shown here are from the proton run between the beginning of July and the end of October 2010. Clear signals are seen and different particle types have been observed during regular LHC luminosity running, and an agreement in the measured flux rate is found with the simulations. These initial results are promising, and indicate that these devices have the potential for further and future LHC and high energy physics applications as radiation monitoring devices for mixed field environments, including neutron flux monitoring. Further extensions are foreseen in the near future to increase the performance of the detector and its coverage for monitoring in CMS.Comment: 15 pages, 16 figures, submitted to JINS

Strategies to reduce attrition in managing paediatric obesity:A systematic review

OBJECTIVE: To conduct a systematic review of the literature for strategies designed to reduce attrition in managing paediatric obesity. METHODS: We searched Ovid Medline (1946 to May 6, 2020), Ovid Embase (1974 to May 6, 2020), EBSCO CINAHL (inception to May 6, 2020), Elsevier Scopus (inception to April 14, 2020), and ProQuest Dissertations & Theses (inception to April 14, 2020). Reports were eligible if they included any obesity management intervention, included 2 to 18 year olds with overweight or obesity (or if the mean age of participants fell within this age range), were in English, included experimental study designs, and had attrition reduction as a main outcome. Two team members screened studies, abstracted data, and appraised study quality. RESULTS: Our search yielded 5,415 original reports; six met inclusion criteria. In three studies, orientation sessions (n = 2) and motivational interviewing (MI) (n = 1) were used as attrition-reduction strategies before treatment enrollment; in three others, text messaging (n = 2) and MI (n = 1) supplemented existing obesity management interventions. Attrition-reduction strategies led to decreased attrition in two studies, increased in one, and no difference in three. For the two strategies that reduced attrition, (a) pre-treatment orientation and (b) text messaging between children and intervention providers were beneficial. The quality of the six included studies varied (good [n = 4]; poor [n = 2]). CONCLUSION: Some evidence suggests that attrition can be reduced. The heterogeneity of approaches applied and small number of studies included highlight the need for well-designed, experimental research to test the efficacy and effectiveness of strategies to reduce attrition in managing paediatric obesity