Multiscale correlative tomography: an investigation of creep cavitation in 316 stainless steel

Creep cavitation in an ex-service nuclear steam header Type 316 stainless steel sample is investigated through a multiscale tomography workflow spanning eight orders of magnitude, combining X-ray computed tomography (CT), plasma focused ion beam (FIB) scanning electron microscope (SEM) imaging and scanning transmission electron microscope (STEM) tomography. Guided by microscale X-ray CT, nanoscale X-ray CT is used to investigate the size and morphology of cavities at a triple point of grain boundaries. In order to understand the factors affecting the extent of cavitation, the orientation and crystallographic misorientation of each boundary is characterised using electron backscatter diffraction (EBSD). Additionally, in order to better understand boundary phase growth, the chemistry of a single boundary and its associated secondary phase precipitates is probed through STEM energy dispersive X-ray (EDX) tomography. The difference in cavitation of the three grain boundaries investigated suggests that the orientation of grain boundaries with respect to the direction of principal stress is important in the promotion of cavity formation

Deciphering chemical order/disorder and material properties at the single-atom level

Correlating 3D arrangements of atoms and defects with material properties and functionality forms the core of several scientific disciplines. Here, we determined the 3D coordinates of 6,569 iron and 16,627 platinum atoms in a model iron-platinum nanoparticle system to correlate 3D atomic arrangements and chemical order/disorder with material properties at the single-atom level. We identified rich structural variety and chemical order/disorder including 3D atomic composition, grain boundaries, anti-phase boundaries, anti-site point defects and swap defects. We show for the first time that experimentally measured 3D atomic coordinates and chemical species with 22 pm precision can be used as direct input for first-principles calculations of material properties such as atomic magnetic moments and local magnetocrystalline anisotropy. This work not only opens the door to determining 3D atomic arrangements and chemical order/disorder of a wide range of nanostructured materials with high precision, but also will transform our understanding of structure-property relationships at the most fundamental level.Comment: 21 pages, 4 figure

Freehand three-dimensional ultrasound to assess semitendinosus muscle morphology

In several neurological disorders and muscle injuries, morphological changes of the m. semitendinosus (ST) are presumed to contribute to movement limitations around the knee. Freehand three-dimensional (3D) ultrasound (US), using position tracking of two-dimensional US images to reconstruct a 3D voxel array, can be used to assess muscle morphology in vivo. The aims of this study were: (i) to introduce a newly developed 3D US protocol for ST; and (ii) provide a first comparison of morphological characteristics determined by 3D US with those measured on dissected cadaveric muscles. Morphological characteristics of ST (e.g. muscle belly length, tendon length, fascicle length and whole muscle volume, and volumes of both compartments) were assessed in six cadavers using a 3D US protocol. Subsequently, ST muscles were removed from the body to measure the same morphological characteristics. Mean differences between morphological characteristics measured by 3D US and after dissection were smaller than 10%. Intra-class correlation coefficients (ICCs) were higher than 0.75 for all variables except for the lengths of proximal fascicles (ICC = 0.58). Measurement of the volume of proximal compartment by 3D US was not feasible, due to low US image quality proximally. We conclude that the presented 3D US protocol allows for reasonably accurate measurements of key morphological characteristics of ST muscle

Assessment of net knee moment-angle characteristics by instrumented hand-held dynamometry in children with spastic cerebral palsy children and typically developing children

Background: The limited range of motion during walking in children with spastic cerebral palsy (SCP) may be the result of altered mechanical characteristics of muscles and connective tissues around the knee joint. Measurement of static net knee moment-angle relation will provide insights into these alterations, for which instrumented hand-held dynamometry may be applied. The aims of this study were: (1) to test the measurement error of the estimated net knee moment-angle characteristics, (2) to determine the correlation between knee extension angle measurement at a standardized knee moment and popliteal angle from common physical examination and (3) to compare net knee moment-angle characteristics in SCP versus typically developing children. Methods: With the child lying in sideward position, the knee was extended by moving the lower leg by a hand-held force transducer on a low friction cart. Force data were collected for a range of knee angles. Data were excluded when activity (EMG) levels of knee extensor and flexor muscles exceeded the EMG level during rest by more than two standard deviations. The net knee flexion moments were calculated from recorded force data and measured moment arm. Reliability for knee angles corresponding with 0.5, 1, 2, 3, and 4 Nm knee net flexion moments was assessed by standard error of measurements (SEM) and smallest detectable difference (SDD). Results: For between day comparison, SEMs were about 5° and SDDs were below 14° for knee angles at 1-4 Nm net knee flexion moments. In SCP children, the knee angle measured at 4 Nm knee flexion moment was not related to the popliteal angle (r∈=∈0.52). The slope at 4 Nm of the knee moment-angle curve in SCP children was significantly higher than that in typically developing children. Conclusions: The presented knee hand-held dynamometry allows assessment of net knee flexion moment-knee angle characteristics in typically developing and SCP children and can be used to identify clinically relevant changes as a result of treatment. Overall stiffness of structures that contribute to the net knee flexion moment at the knee (i.e. muscles, tendons, ligaments) is elevated in SCP children

Semitendinosus muscle morphology and gait kinematics after medial hamstring lengthening in children with spastic diplegia

Introduction: To improve gait in children with spastic diplegia, the semitendinosus muscle (ST) is frequently lengthened amongst other medial hamstring muscles by surgery. Side effects on gait due to weakening of the hamstring muscles and overcorrections have been reported [1]. How these side effects relate to ST morphology is unknown. Research question: Howdo ST morphology and gait kinematics change after medial hamstring lengthening in children with spastic diplegia? Methods: ST morphology and gait kinematics were determined in five children with spastic diplegia (2 boys; age at surgery: 14.4 2.4 years; GMFCS II&III) selected for medial hamstring lengthening to counteract limited knee range of motion and improve gait, before and 8–20 months after surgery. Muscle belly length, tendon length, muscle-tendon unit (MTU) length as well as muscle volume of ST at the knee angle corresponding to 4 N m knee moment in an imposed hip position of 708 flexion were assessed by freehand 3D ultrasound [2]. 3Dgait analysis was performed using an optoelectronic marker tracking system. For each participant, pelvic, hip and knee angles of the right leg were determined in the sagittal plane at midstance (MSt (30% gait cycle (GC))) and late swing (LSw (99% GC)) over three successful strides. Results: The knee angle corresponding to 4 N m knee moment was 57.2 14.98 (pre) and 35.2 12.28 (post) (p = 0.068). After surgery, muscle belly length normalized for femur length was 34 5% lower (p = 0.001), tendon length was 83 34% higher (p = 0.003) and MTU length was 10 7% higher (p = 0.044) (Fig. 1). Muscle volume was 39.6 17.6 cm2 before surgery and 21.3 17.2 cm2 after (p = 0.054). Kinematic results showed significantly improved knee extension but also increased pelvic anterior tilt, and no differences in hip angle (Table 1). Discussion: Our results show that medial hamstring lengthening leads to a longer ST MTU with a longer tendon, but a reduced muscle belly length. Differences in gait kinematics indicate that the longer ST MTU after surgery mainly leads to more knee extension during gait, while we did not find an increase in hip flexion. The increased pelvic tilt seems to be an effect of the changed knee kinematics through the femur kinematics during gait. Preoperative pelvic tilt needs to be considered when medial hamstring lengthening is indicated. References [1] Dreher J. Bone Joint Surg. Am. 2012;94:121–30. [2] Haberfehlner H. J. Anat. 2016 (in press)

Ready for handwriting? A reference data study on handwriting readiness assessments.

INTRODUCTION: Early evaluation of writing readiness is essential to predict and prevent handwriting difficulties and its negative influences on school occupations. An occupation-based measurement for kindergarten children has been previously developed: Writing Readiness Inventory Tool In Context (WRITIC). In addition, to assess fine motor coordination two tests are frequently used in children with handwriting difficulties: the modified Timed Test of In-Hand Manipulation (Timed TIHM) and the Nine-Hole Peg Test (9-HPT). However, no Dutch reference data are available. AIM: To provide reference data for (1) WRITIC, (2) Timed-TIHM and (3) 9-HPT for handwriting readiness assessment in kindergarten children. METHODS: Three hundred and seventy-four children from Dutch kindergartens in the age of 5 to 6.5 years (5.6±0.4 years, 190 boys/184 girls) participated in the study. Children were recruited at Dutch kindergartens. Full classes of the last year were tested, children were excluded if there was a medical diagnosis such as a visual, auditory, motor or intellectual impairment that hinder handwriting performance. Descriptive statistics and percentiles scores were calculated. The score of the WRITIC (possible score 0-48 points) and the performance time on the Timed-TIHM and 9-HPT are classified as percentile scores lower than the 15th percentile to distinguish low performance from adequate performance. The percentile scores can be used to identify children that are possibly at risk developing handwriting difficulties in first grade. RESULTS: WRITIC scores ranged from 23 to 48 (41±4.4), Timed-TIHM ranged from 17.9 to 64.5 seconds (31.4± 7.4 seconds) and 9-HPT ranged from 18.2 to 48.3 seconds (28.4± 5.4). A WRITIC score between 0-36, a performance time of more than 39.6 seconds on the Timed-TIHM and more than 33.8 seconds on the 9-HPT were classified as low performance. CONCLUSION: The reference data of the WRITIC allow to assess which children are possibly at risk developing handwriting difficulties

Attainment of personal goals in the first year of intrathecal baclofen treatment in dyskinetic cerebral palsy: a prospective cohort study

PURPOSE: To assess attainment of individual treatment goals one year after intrathecal baclofen (ITB) pump implantation in individuals with dyskinetic cerebral palsy (CP). MATERIALS AND METHODS: A multi-center prospective cohort study was conducted including 34 non-walking individuals with severe dyskinetic CP, classified as Gross Motor Function Classification System (GMFCS) IV/V, aged 4-24 years, 12 months after pump implantation. The main outcome measure was Goal Attainment Scaling (GAS). Predictors of GAS results were analyzed. Complications were registered systematically. RESULTS: Seventy-one percent of individuals with dyskinetic CP fully achieved one or more treatment goals. One or more treatment goals were partially achieved in 97% of individuals. Two factors were found to be associated with attainment of goals: Dyskinesia Impairment Scale (DIS) score at baseline and the difference in pain score between baseline and follow-up. These two variables explain 30% of the variance in the outcome. CONCLUSIONS: Intrathecal baclofen is effective in achieving individual treatment goals in children and young adults with dyskinetic CP after nine to 12 months of ITB treatment. A positive outcome on treatment goals is, for a small part, associated with higher severity of dystonia at baseline and with improvement of pain during treatment. CLINICAL TRIAL REGISTRATION NUMBER: Dutch Trial Register, number NTR3642.Implications for rehabilitationIntrathecal baclofen treatment is effective in attainment of personal treatment goals, one year after pump implantation in patients with dyskinetic cerebral palsy.A positive outcome on treatment goals is, for a small part, related to higher severity of dystonia at the start and on improvement of pain during treatment