Demagnetizing and hardening mechanisms in Nd-Fe-B and Sr-hexaferrite permanent magnets

In the first part of this work, the microstructural influence on magnetic properties Sr-hexaferrites is investigated. Using a Magnetic Force Microscope (MFM) the domain evolution during magnetization from the Thermally Demagnetized State (TDS) and DC field Demagnetized State (DCD) and during demagnetization was investigated in-situ. A surface magnetization was determined from the MFM contrast that quantitatively matched the bulk magnetization determined by Superconducting Quantum Interface Device (SQUID). For the surface magnetization it was found that smaller grains below the critical single domain size reversed their magnetization from Single Domain State (SDS) to the reversed SDS, while larger grains form an intermediate Multi Domain State (MDS). Using a series of minor loops it was determined that the presence of MDS in the bulk is neglectable. An in-depth analysis of core shell structured Nd-Fe-B grains was carried out using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), optical Kerr microscopy and MFM. While the core consisted of pure Nd2Fe14B the shell, the composition of the shell was (Nd1-xDyx)2Fe14B. The composition and morphology of the grain boundary was analyzed using TEM. Using MFM the magnetic contrast of core and shell due to the lower saturation magnetization of the Dy substituted species could be correlated to the chemical contrast observed by SEM. The demagnetization of core and shell was observed under in-situ condition using MFM and Kerr microscopy. The results show a uniform demagnetization across core and shell. The time resolution of the Kerr microscope of 43 frames per second is not large enough to resolve an intermediate domain state between SDS and stable MDS within the 23 ms between two frames. In a subsequent micromagnetic simulation the nucleation site was shown to lie either at the grain boundary or in the core depending on the magnetocrystalline anisotropy at the grain boundary defect layer. The texture dependency of the Grain Boundary Diffusion Process (GBDP) in sintered and hot-deformed Nd-Fe-B magnets was analyzed by creating a global and a local coercivity profile of the diffused samples. While the former method allows a conclusion on how the magnet acts as a whole, the latter allows a more precise resolution of local coercivity. In sintered magnets a slightly higher coercivity improvement was observed for the diffusion perpendicular to the texture axis. A pole hardening effect was observed for diffusion parallel to the texture axis that compensated the higher coercivity improvement for parallel diffusion. In hot deformed magnets on the other hand, no pole hardening effect was observed and a higher coercivity improvement was observed for parallel diffusion. A microstructural investigation showed that this effect could be attributed to the platelet shaped grains in hot deformed magnets. The in-situ demagnetization of hot-deformed magnets was analyzed for different Dy contents. The composition of different pilot batch Nd-Fe-B magnets by VACUUMSCHMELZE GmbH & Co. KG was determined by Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES). The grain size distribution and orientation was determined using Electron Back Scattered Diffraction (EBSD). The influence of Heavy Rare Earth Elements (HRE) and microstructure engineering on the intrinsic and extrinsic magnetic properties was investigated. A similar minor loop investigation was also done for Nd-Fe-B sintered magnets showing that the vast majority of grains display a single domain like behavior despite being approximately one order of magnitude larger than the critical single domain size. Furthermore the amount of MDS during the demagnetization could be reduced by the addition of HRE

Walk This Way: The Effects of Wearing a Knee Brace on Gait

Gait is defined as the way a person walks; the manner of his or her steps taken. Walking is a simple concept that can be taken for granted until it is lost. When a movement in the gait cycle is limited due to injury, changes in biomechanical and neurological factors occur. The purpose of this study was to measure and evaluate gait patterns of subjects walking with and without a Breg T Scope Premier Post-Op Knee Brace. Twenty-two Texas Lutheran University students were tested using the Dartfish Software program in the Kieffer Laboratory. Seven females and fifteen males, ranging in ages 18 to 28 years, completed two five meter walks. The first recording was of the subjects walking without the Post-Op Knee Brace and the second recording was of the subjects walking with the Post-Op knee brace. The knee brace was set to limit the subject twenty degrees of full knee extension, not allowing full range of motion. Each subject was recorded from the front view and from the side view; the videos were then analyzed through Dartfish Software. Eight reflective markers were applied to the subject prior to walking to distinguish boney landmarks for angle measurement. Using a Paired Two Sample t-Test, a significant difference was found for hip flexion and extension, hip abduction, dorsiflexion, and plantar flexion. Hip Flexion, hip extension, plantar flexion, and dorsiflexion decreased with the addition on the Post-Op Knee Brace and hip abduction increased, resulting in gait abnormalities

Microbial diversity and activity in the Nematostella vectensis holobiont: insights from 16S rRNA gene sequencing, isolate genomes, and a pilot-scale survey of gene expression

We have characterized the molecular and genomic diversity of the microbiota of the starlet sea anemone Nematostella vectensis, a cnidarian model for comparative developmental and functional biology and a year-round inhabitant of temperate salt marshes. Molecular phylogenetic analysis of 16S rRNA gene clone libraries revealed four ribotypes associated with N. vectensis at multiple locations and times. These associates include two novel ribotypes within the ε-Proteobacterial order Campylobacterales and the Spirochetes, respectively, each sharing 99% 16S rRNA identity with Endozoicomonas elysicola and Pseudomonas oleovorans, respectively. Species-specific PCR revealed that these populations persisted in N. vectensis asexually propagated under laboratory conditions. cDNA indicated expression of the Campylobacterales and Endozoicomonas 16S rRNA in anemones from Sippewissett Marsh, MA. A collection of bacteria from laboratory raised N. vectensis was dominated by isolates from P. oleovorans and Rhizobium radiobacter. Isolates from field-collected anemones revealed an association with Limnobacter and Stappia isolates. Genomic DNA sequencing was carried out on 10 cultured bacterial isolates representing field- and laboratory-associates, i.e., Limnobacter spp., Stappia spp., P. oleovorans and R. radiobacter. Genomes contained multiple genes identified as virulence (host-association) factors while S. stellulata and L. thiooxidans genomes revealed pathways for mixotrophic sulfur oxidation. A pilot metatranscriptome of laboratory-raised N. vectensis was compared to the isolate genomes and indicated expression of ORFs from L. thiooxidans with predicted functions of motility, nutrient scavenging (Fe and P), polyhydroxyalkanoate synthesis for carbon storage, and selective permeability (porins). We hypothesize that such activities may mediate acclimation and persistence of bacteria in a N. vectensis holobiont defined by both internal and external gradients of chemicals and nutrients in a dynamic coastal habitat.Massachusetts Institute of Technology. Department of Civil and Environmental EngineeringNational Science Foundation (U.S.). Graduate Research FellowshipNational Research Foundation of Korea (Fellowship

Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets.

We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (∅ 5 μm) and planar (20 μm × 2 μm). In both cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. This is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions

A Structurally Precise Mechanism Links an Epilepsy-Associated KCNC2 Potassium Channel Mutation to Interneuron Dysfunction

De novo heterozygous variants in KCNC2 encoding the voltage-gated potassium (K+) channel subunit Kv3.2 are a recently described cause of developmental and epileptic encephalopathy (DEE). A de novo variant in KCNC2 c.374G \u3e A (p.Cys125Tyr) was identified via exome sequencing in a patient with DEE. Relative to wild-type Kv3.2, Kv3.2-p.Cys125Tyr induces K+ currents exhibiting a large hyperpolarizing shift in the voltage dependence of activation, accelerated activation, and delayed deactivation consistent with a relative stabilization of the open conformation, along with increased current density. Leveraging the cryogenic electron microscopy (cryo-EM) structure of Kv3.1, molecular dynamic simulations suggest that a strong π-π stacking interaction between the variant Tyr125 and Tyr156 in the α-6 helix of the T1 domain promotes a relative stabilization of the open conformation of the channel, which underlies the observed gain of function. A multicompartment computational model of a Kv3-expressing parvalbumin-positive cerebral cortex fast-spiking γ-aminobutyric acidergic (GABAergic) interneuron (PV-IN) demonstrates how the Kv3.2-Cys125Tyr variant impairs neuronal excitability and dysregulates inhibition in cerebral cortex circuits to explain the resulting epilepsy

Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets

We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (∅ 5 μm) and planar (20 μm × 2 μm). In both cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. This is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions

Phenotypic and genetic spectrum of epilepsy with myoclonic atonic seizures

Objective: We aimed to describe the extent of neurodevelopmental impairments andidentify the genetic etiologies in a large cohort of patients with epilepsy with myoclonicatonic seizures (MAE).Methods: We deeply phenotyped MAE patients for epilepsy features, intellectualdisability, autism spectrum disorder, and attention-deficit/hyperactivity disorderusing standardized neuropsychological instruments. We performed exome analysis(whole exome sequencing) filtered on epilepsy and neuropsychiatric gene sets toidentify genetic etiologies.Results: We analyzed 101 patients with MAE (70% male). The median age of seizureonset was 34 months (range = 6-72 months). The main seizure types were myoclonicatonic or atonic in 100%, generalized tonic-clonic in 72%, myoclonic in 69%, absencein 60%, and tonic seizures in 19% of patients. We observed intellectual disability in62% of patients, with extremely low adaptive behavioral scores in 69%. In addition,24% exhibited symptoms of autism and 37% exhibited attention-deficit/hyperactivitysymptoms. We discovered pathogenic variants in 12 (14%) of 85 patients, includingfive previously published patients. These were pathogenic genetic variants inSYNGAP1 (n = 3), KIAA2022 (n = 2), and SLC6A1 (n = 2), as well as KCNA2,SCN2A, STX1B, KCNB1, and MECP2 (n = 1 each). We also identified three newcandidate genes, ASH1L, CHD4, and SMARCA2 in one patient each.Significance: MAE is associated with significant neurodevelopmental impairment.MAE is genetically heterogeneous, and we identified a pathogenic genetic etiologyin 14% of this cohort by exome analysis. These findings suggest that MAE is a manifestationof several etiologies rather than a discrete syndromic entity

Potential of Airborne LiDAR Derived Vegetation Structure for the Prediction of Animal Species Richness at Mount Kilimanjaro

The monitoring of species and functional diversity is of increasing relevance for the development of strategies for the conservation and management of biodiversity. Therefore, reliable estimates of the performance of monitoring techniques across taxa become important. Using a unique dataset, this study investigates the potential of airborne LiDAR-derived variables characterizing vegetation structure as predictors for animal species richness at the southern slopes of Mount Kilimanjaro. To disentangle the structural LiDAR information from co-factors related to elevational vegetation zones, LiDAR-based models were compared to the predictive power of elevation models. 17 taxa and 4 feeding guilds were modeled and the standardized study design allowed for a comparison across the assemblages. Results show that most taxa (14) and feeding guilds (3) can be predicted best by elevation with normalized RMSE values but only for three of those taxa and two of those feeding guilds the difference to other models is significant. Generally, modeling performances between different models vary only slightly for each assemblage. For the remaining, structural information at most showed little additional contribution to the performance. In summary, LiDAR observations can be used for animal species prediction. However, the effort and cost of aerial surveys are not always in proportion with the prediction quality, especially when the species distribution follows zonal patterns, and elevation information yields similar results

Representativeness of Eddy-Covariance flux footprints for areas surrounding AmeriFlux sites

Large datasets of greenhouse gas and energy surface-atmosphere fluxes measured with the eddy-covariance technique (e.g., FLUXNET2015, AmeriFlux BASE) are widely used to benchmark models and remote-sensing products. This study addresses one of the major challenges facing model-data integration: To what spatial extent do flux measurements taken at individual eddy-covariance sites reflect model- or satellite-based grid cells? We evaluate flux footprints—the temporally dynamic source areas that contribute to measured fluxes—and the representativeness of these footprints for target areas (e.g., within 250–3000 m radii around flux towers) that are often used in flux-data synthesis and modeling studies. We examine the land-cover composition and vegetation characteristics, represented here by the Enhanced Vegetation Index (EVI), in the flux footprints and target areas across 214 AmeriFlux sites, and evaluate potential biases as a consequence of the footprint-to-target-area mismatch. Monthly 80% footprint climatologies vary across sites and through time ranging four orders of magnitude from 103 to 107 m2 due to the measurement heights, underlying vegetation- and ground-surface characteristics, wind directions, and turbulent state of the atmosphere. Few eddy-covariance sites are located in a truly homogeneous landscape. Thus, the common model-data integration approaches that use a fixed-extent target area across sites introduce biases on the order of 4%–20% for EVI and 6%–20% for the dominant land cover percentage. These biases are site-specific functions of measurement heights, target area extents, and land-surface characteristics. We advocate that flux datasets need to be used with footprint awareness, especially in research and applications that benchmark against models and data products with explicit spatial information. We propose a simple representativeness index based on our evaluations that can be used as a guide to identify site-periods suitable for specific applications and to provide general guidance for data use