Investigating the effect of a stress-based uniaxial anisotropy on the magnetic behaviour of La_0.7Sr_0.3MnO₃ elements

We investigate the interplay between shape anisotropy and a stress-based uniaxial anisotropy on the magnetic domain structure of La<sub>0.7</sub>Sr<sub>0.3</sub>MnO<sub>3</sub> nanoelements as a function of aspect ratio, using micromagnetic simulations. We show that a direct competition between the anisotropies gives rise to high energy multi-domain flux closure configurations, whilst an alignment of the anisotropies can modify the effective element dimensions and act to stabilise a single domain configuration. Our results demonstrate the ability to control the spin state of La<sub>0.7</sub>Sr<sub>0.3</sub>MnO<sub>3</sub> elements in addition to tailoring the domain wall width by controlling the anisotropy of the material, which is key for spintronic applications that require a high spin-polarization and stable magnetic configurations

Pixelated detectors and improved efficiency for magnetic imaging in STEM differential phase contrast

The application of differential phase contrast imaging to the study of polycrystalline magnetic thin films and nanostructures has been hampered by the strong diffraction contrast resulting from the granular structure of the materials. In this paper we demonstrate how a pixelated detector has been used to detect the bright field disk in aberration corrected scanning transmission electron microscopy (STEM) and subsequent processing of the acquired data allows efficient enhancement of the magnetic contrast in the resulting images. Initial results from a charged coupled device (CCD) camera demonstrate the highly efficient nature of this improvement over previous methods. Further hardware development with the use of a direct radiation detector, the Medipix3, also shows the possibilities where the reduction in collection time is more than an order of magnitude compared to the CCD. We show that this allows subpixel measurement of the beam deflection due to the magnetic induction. While the detection and processing is data intensive we have demonstrated highly efficient DPC imaging whereby pixel by pixel interpretation of the induction variation is realised with great potential for nanomagnetic imaging

Dupuytren's Disease: Anatomy and Surgical Treatment

The principal aim of this written account is to describe the evolution of a surgical approach to the treatment of Dupuytren's Disease based on current knowledge of pathogenesis and precise description of the anatomy. The historical record of the life and works of Baron Guillaume Dupuytren, together with those of his contemporaries, pupils and critics have been reviewed to clarify the understanding of the condition at that time and to uncover wisdom which has been forgotten. The disease process is considered by analysis of studies of incidence, aetiological factors, pathology and related fibromatous lesions. Series of dissections of the palm and digits in fresh and preserved cadaveric hands have been performed to establish a new perspective on the micro-anatomy of the normal ligamentous components of the hand. The lesions of Dupuytren's Disease - palmar nodules, pits and cords, distortion of palmar creases and knuckle changes - have been examined by observations of clinical signs and operative dissections. New clinical signs -the "blanching" sign in the palm, and knuckle changes -have been described. A new classification of operative interventions is described according to the approach to a) the skin, b) the fascia and c) the joints. The operative experience and long term results, using an evolution of techniques, have been reviewed in a series of 100 patients. Dupuytren's Disease is viewed as a process akin to wound healing which involves not only the palmar fascia, as described by Dupuytren, but many of the connective tissues of the hand including the dermis of the skin. The distribution of the pathological tissue is not random, but dictated by lines of tension or stress concentrations transmitted through certain anatomical pathways. Movement of the hand may be the stimulus to the propagation of the contracture once it has commenced. Treatment has been found to be generally not curative, but affording only temporary release. A less extensive and more precise operative approach has been developed. The values of minimal surgery and maximal rehabilitation are stressed

Nanocharacterisation of precipitates in austenite high manganese steels with advanced techniques: HRSTEM and DualEELS mapping

To achieve optimal mechanical properties in high manganese steels, the precipitation of nanoprecipitates of vanadium and niobium carbides is under investigation. It is shown that under controlled heat treatments between 850°C and 950°C following hot deformation, few-nanometre precipitates of either carbide can be produced in test steels with suitable contents of vanadium or niobium. The structure and chemistry of these precipitates are examined in detail with a spatial resolution down to better than 1 nm using a newly commissioned scanning transmission electron microscope. In particular, it is shown that the nucleation of vanadium carbide precipitates often occurs at pre-existing titanium carbide precipitates which formed from titanium impurities in the bulk steel. This work will also highlight the links between the nanocharacterisation and changes in the bulk properties on annealing

Sub-100 nanosecond temporally resolved imaging with the Medipix3 direct electron detector

Detector developments are currently enabling new capabilities in the field of transmission electron microscopy (TEM). We have investigated the limits of a hybrid pixel detector, Medipix3, to record dynamic, time varying, electron signals. Operating with an energy of 60keV, we have utilised electrostatic deflection to oscillate electron beam position on the detector. Adopting a pump-probe imaging strategy we have demonstrated that temporal resolutions three orders of magnitude smaller than are available for typically used TEM imaging detectors are possible. Our experiments have shown that energy deposition of the primary electrons in the hybrid pixel detector limits the overall temporal resolution. Through adjustment of user specifiable thresholds or the use of charge summing mode, we have obtained images composed from summing 10,000s frames containing single electron events to achieve temporal resolution less than 100ns. We propose that this capability can be directly applied to studying repeatable material dynamic processes but also to implement low-dose imaging schemes in scanning transmission electron microscopy.Comment: 11 pages, 6 figures; improve ref formatting + revise tex

3D sub-nanoscale imaging of unit cell doubling due to octahedral tilting and cation modulation in strained perovskite thin films

Determining the 3-dimensional crystallography of a material with sub-nanometre resolution is essential to understanding strain effects in epitaxial thin films. A new scanning transmission electron microscopy imaging technique is demonstrated that visualises the presence and strength of atomic movements leading to a period doubling of the unit cell along the beam direction, using the intensity in an extra Laue zone ring in the back focal plane recorded using a pixelated detector method. This method is used together with conventional atomic resolution imaging in the plane perpendicular to the beam direction to gain information about the 3D crystal structure in an epitaxial thin film of LaFeO3 sandwiched between a substrate of (111) SrTiO3 and a top layer of La0.7Sr0.3MnO3. It is found that a hitherto unreported structure of LaFeO3 is formed under the unusual combination of compressive strain and (111) growth, which is triclinic with a periodicity doubling from primitive perovskite along one of the three directions lying in the growth plane. This results from a combination of La-site modulation along the beam direction, and modulation of oxygen positions resulting from octahedral tilting. This transition to the period-doubled cell is suppressed near both the substrate and near the La0.7Sr0.3MnO3 top layer due to the clamping of the octahedral tilting by the absence of tilting in the substrate and due to an incompatible tilt pattern being present in the La0.7Sr0.3MnO3 layer. This work shows a rapid and easy way of scanning for such transitions in thin films or other systems where disorder-order transitions or domain structures may be present and does not require the use of atomic resolution imaging, and could be done on any scanning TEM instrument equipped with a suitable camera.Comment: Minor fixes, especially in reference

Identification of novel keloid biomarkers through Profiling of Tissue Biopsies versus Cell Cultures in Keloid Margin specimens Compared to adjacent Normal Skin

Objective: Keloid disease (KD) is a benign fibroproliferative skin tumor that results from abnormal wound healing and has no single definitive treatment. This study aims to identify KD biomarkers, which are cellular mediators that can serve as indicators of normal, pathological, and therapeutic processes. Methods: Bioinformatics analytic approaches, including comprehensive literature searches and DAVID Bioinformatics Resources 2008, were performed on the established KD linkage and previously reported microarray data to identify potential candidate genes for the study. Keloid margins and unaffected skin were obtained from KD patients (n = 4). RNA was extracted from the biopsies and second-passage culture equivalents. Reverse-transcriptase quantitative polymerase chain reactions were used to determine the gene expression levels. Student t tests were used to analyze the statistical significance in differential gene expressions. Results: Nineteen candidate genes were initially selected by bioinformatics analysis. Of the 19 genes, 10 were significantly (P < .05) upregulated in keloid margin biopsy specimens. The top-5 fold changes range from 10-fold to 175-fold, including aggrecan; asporin; inhibin, beta A; tumor necrosis factor-α inducible protein 6; and chromosome 5 open reading frame 13. There was no significant differential gene expression between the fibroblasts established using keloid margin or internal control sites. Conclusions: The transcriptomic data generated from cultures did not consistently correlate to the biopsy equivalents. This study has demonstrated 10 genes that are significantly upregulated in biopsy samples of keloid margin, 5 of which have a fold change higher than 10-fold. Importantly these genes may serve as a potential biomarker for KD

Magnetic microscopy of topologically protected homochiral domain walls in an ultrathin perpendicularly magnetized Co film

Next-generation concepts for solid-state memory devices are based on current-driven domain wall propagation, where the wall velocity governs the device performance. It has been shown that the domain wall velocity and the direction of travel is controlled by the nature of the wall and its chirality. This chirality is attributed to effects emerging from the lack of inversion symmetry at the interface between a ferromagnet and a heavy metal, leading to an interfacial Dzyaloshinskii-Moriya interaction that can control the shape and chirality of the magnetic domain wall. Here we present direct imaging of domain walls in Pt/Co/AlO$_x$ films using Lorentz transmission electron microscopy, demonstrating the presence of homochiral, and thus topologically protected, N\'{e}el walls. Such domain walls are good candidates for dense data storage, bringing the bit size down close to the limit of the domain wall width

Grayson Ligament:A Revised Description of its Anatomy and Function

PURPOSE: Grayson ligament has been described as a common pathway for digital contracture in Dupuytren disease. Its anatomical descriptions in the literature are, however, inconsistent. METHODS: We have performed a microsurgical dissection study in 20 fresh-frozen and thawed digits to revisit the anatomy of Grayson ligaments. We also performed dissections in Thiel-preserved hands to be able to study the changes in tension of the ligaments during flexion and extension of the finger. RESULTS: We found the ligaments originally described by Grayson to be the best developed part of a trabecular network of fibers, originating in continuity with the outer adventitial layer of the flexor tendon sheath and running toward their insertions into the skin in multiple planes, all volar to the neurovascular bundle. The most dorsal fibers, which cover the neurovascular bundles, form a chevron shape with its midline apex pointing distally in an extended finger. During flexion, the fibers become more transversely oriented. CONCLUSIONS: We found Grayson ligament comprises a trabecular network of fibers, instead of a ligament, with a dynamic fiber orientation on the volar side of the finger. The main function of this network of fibers seems to be the stabilization of the skin and fat pad in digit extension while the relaxation in flexion allows the skin and volar fat pad to adapt optimally to the form of the object that is held. CLINICAL RELEVANCE: The new insights in the anatomy of Grayson trabecular network of fibers may be of importance in the understanding of the pathological anatomy of Dupuytren disease