9 research outputs found

    Quantitative characterization of short-range orthorhombic fluctuations in FeSe through pair distribution function analysis

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    Neutron and x-ray total scattering measurements have been performed on powder samples of the iron chalcogenide superconductor FeSe. Using pair distribution function (PDF) analysis of the total scattering data to investigate short-range atomic correlations, we establish the existence of an instantaneous, local orthorhombic structural distortion attributable to nematic fluctuations that persists well into the high-temperature tetragonal phase, at least up to 300 K and likely to significantly higher temperatures. This short-range orthorhombic distortion is correlated over a length scale of about 1 nm at 300 K and grows to several nm as the temperature is lowered toward the long-range structural transition temperature. In the low-temperature nematic state, the local instantaneous structure exhibits an enhanced orthorhombic distortion relative to the average structure with a typical relaxation length of 3 nm. The quantitative characterization of these orthorhombic fluctuations sheds light on nematicity in this canonical iron-based superconductor

    Case report and literature analysis: Autoimmune cerebellar ataxia associated with homer-3 antibodies

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    ObjectiveWe present a case of autoimmune cerebellar ataxia (ACA) associated with Homer protein homolog 3 (Homer-3) antibodies. Then, a review of the literature was conducted to summarize its clinical spectrum to improve clinicians' understanding of this rare entity.Case presentationA 25-year-old man suffered from the subacute onset of cerebellar ataxia and psychiatric symptoms with abnormalities in the cerebellum on initial brain MRI and Homer-3 antibodies titers of 1:100 in the serum. His neurological symptoms did not improve after intravenous methylprednisolone but significantly improved following plasma exchange with a modified Rankin Scale (mRS) score of 1. However, 5 months later, he experienced relapse during oral prednisone tapering with enhanced cerebellar lesions and obvious cerebellar atrophy on repeated MRI. Various immunomodulatory approaches, including corticosteroids and plasma exchange, were utilized with no improvement. Then rituximab was given for the first time to treat Homer-3 autoimmunity with partial improvement of symptoms. However, the patient remained profoundly disabled with an mRS score of 4.ConclusionACA associated with Homer-3 antibodies may have a suboptimal response to corticosteroid therapy. More intense immunotherapy such as rituximab may contribute to the improvement of cerebellar syndrome. Relapsing courses and presentation of cerebellar atrophy may suggest a poor prognosis in this entity

    Submicronic calcite particles with controlled morphology tailored by polymer skeletons via carbonation route with compressed or supercritical CO2

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    The preparation of biominerals based on CO 2 fixation and regulatory effect of organic macromolecules has attracted more and more interests in recent years, inspired by the increase in technological interests in bio-inspired materials science and fabrication of useful products via an environmentally friendly process. In this paper, submicronic CaCO 3 particles with ellipsoidal morphology were synthesized using compressed or supercritical CO 2 with sodium salt of carboxymethyl cellulose (NaCMC) as a template. By regulating some experimental parameters, including the concentration and molecular weight of NaCMC, as well as the CO 2 pressure and temperature, the morphology and size of the CaCO 3 particles could be effectively controlled. Besides, in contrast to the effective results of another additive, Polyacrylic Acid (PAA), our research suggested that the morphology of the synthesized particles was strongly related to the flexibility of the polymer chains, namely, the relatively rigid chains induce the formation of ellipsoidal particles while the more flexible chains would result in the spherical ones. In addition, amorphous calcium carbonate was traced as an intermediate phase during the crystallization process. Based on the experimental results, we discussed the formation mechanism of such particles: the polymer chains serve as the skeletons, then the ions attach along the chains to grow. The final morphology of CaCO 3 aggregates is tailored by the flexibility of the polymer chain, while the size of the particles is related with the chain length of the polymer. In comparison with the traditional mineralization methods, here we provide a highly efficient and versatile approach to integrate the fixation of CO 2 and the regulating effect of different polymer chains, to produce submicroscopic CaCO 3 particles and further control their morphology and size distribution. Such an approach is facile and of potential importance as an environmentally benign industrial route to synthesize biomaterials, and it may also serve to shed light on the study of the mechanism of biomimetic mineralization

    Heterogeneity of Radiological Spectrum in Tacrolimus-Associated Encephalopathy after Lung Transplantation

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    Background. Tacrolimus-associated encephalopathy (TAC-E) is usually described under the term of posterior reversible encephalopathy syndrome (PRES). However, a large amount of data has suggested that TAC-E is not a homogenous entity: indeed, TAC-E which is often presented with atypical and potentially misleading imaging characteristics does not always correspond to PRES. Objective. We aimed to identify the spectrum of brain MR imaging of TAC-E and discuss the underlying pathophysiological features. Methods. From September 2008 to October 2010, the neurological statuses of 45 patients, who underwent lung transplantation with TAC as posttransplantation immunosuppressive therapy, were regularly assessed in a prospective study. MRI was repeatedly performed, until recovery, in patients who developed central neurological symptoms. Results. Symptoms suggestive of encephalopathy occurred in five out of 45 patients (11.1%). According to our MRI study, two patients presented with reversible bilateral and relatively symmetric subcortical white matter edema with proximal vasospasms on MRA; however, three other patients were characterized by coexistence of two different lesions including laminar cortical infarcts with hemorrhagic transformation not typically found in PRES and reversible deep white matter edema, associated with distal vasospasms on MRA. Conclusions. It is considered that the mechanism of TAC-E would be more heterogenous than commonly perceived
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