Search

Little is known about the structures and chemistry of perovskites, occurring from the surface to the bulk, at high temperatures and ambient oxygen pressures. Changes in the composition and electronic structure of (001)-oriented La0.8Sr0.2CoO3-d (LSC) films were investigated by using in situ depth-resolved X-ray adsorption (XAS) under practical operating conditions of solid oxide fuel cells. Depth-resolved XAS spectra of LSC films, with a depth resolution of [?] 2 nm, revealed that the surface regions of [?]10 nm were considerably different from the film bulk. The surface regions were enriched in strontium, which can play an important role in governing the oxygen exchange kinetics at the surface.

Ruddlesden–Popper materials such as La2NiO4+δ(LNO) have high activities for surface oxygen exchange kinetics promising for solid oxide fuel cells and oxygen permeation membranes. Here we report the synthesis of the (100)tetragonal-oriented epitaxial LNO thin films prepared by pulsed laser deposition. The surface oxygen exchange kinetics determined from electrochemical impedance spectroscopy (EIS) were found to increase with decreasing film thickness from 390 to 14 nm. No significant change of the surface chemistry with different film thicknesses was observed using ex situ auger electron spectroscopy (AES). Increasing volumetric strains in the LNO films at elevated temperatures determined from in situ high-resolution X-ray diffraction (HRXRD) were correlated with increasing surface exchange kinetics and decreasing film thickness. Volumetric strains may alter the formation energy of interstitial oxygen and influence on the surface oxygen exchange kinetics of the LNO films.

Films of La0.8Sr0.2CoO3-d (LSC-82) with 45 and 90 nm thickness were grown epitaxially on (001) oriented single crystal yttria-stabilized zirconia with a thin gadolinium-doped ceria interlayer using pulsed laser deposition, and characterized using X-ray diffraction (XRD), depth-profile secondary mass spectrometry (DP-SIMS), and linear and nonlinear electrochemical impedance spectroscopy (EIS and NLEIS). The films were found to exhibit in-plane tensile strain and normal compressive strain (with overall increased lattice volume) relative to freestanding cubic LSC-82. The films also possess a compositional La/Sr gradient across their thickness, with enhanced Sr2+ composition (within the perovskite lattice) at the gas-exposed surface. The oxygen storage capacity of the films at 450-600degC (as measured using EIS capacitance) is greatly enhanced relative to freestanding cubic LSC-82, consistent with an apparent increase in oxygen-vacancy concentration at the gas-exposed surface of the films (as revealed by NLEIS). These results can be explained by a two-layer model in which a finite thickness of the perovskite lattice near the surface has an enhanced Sr dopant concentration, leading to a much higher concentration of oxygen vacancies than the underlying bulk material of nominal Sr composition. The nonlinear electrochemical response of the film is consistent with a dissociative adsorption rate law, provided the enhanced bulk vacancy concentration near the surface is included in the analysis.

Hetero-structured interfaces of oxides, which can exhibit reactivity characteristics remarkably different from bulk oxides, are interesting systems to explore in search of highly active fuel cell catalysts for oxygen electrocatalysis. (001)-oriented La0.6Sr0.4CoO3-d (LSC60-40113) thin films having thicknesses from tens to hundreds of nanometers were grown epitaxially on (001)-oriented yttria-stabilized zirconia (YSZ). Atomic force microscopy showed that all the film surfaces were of high quality with average surface roughness approximately one nanometer. The surface oxygen exchange kinetics of these films were determined by electrochemical impedance spectroscopy. While (001)-oriented LSC60-40113 thin films were found to have similar surface oxygen exchange coefficients to LSC60-40113 bulk, surface coverage of (001)-oriented (La0.5Sr0.5)2CoO4+-d (LSC214) on the LSC60-40113 thin films led to significant enhancement in the surface oxygen kinetics up to [?]3 orders of magnitude. Interestingly, LSC214-decorated LSC60-40113 films have comparable surface exchange kinetics ([?]1*10[?]5 cm*s[?]1 at 550degC) to similarly prepared LSC214-decorated La0.8Sr0.2CoO3-d films. Such high surface oxygen kinetics are among the most active SOFC cathode materials reported to date.

Ullrich congenital muscular dystrophy (UCMD) is caused by mutations in the three genes coding for the alpha chains of collagen VI and characterized by generalized muscle weakness, striking hypermobility of distal joints in conjunction with variable contractures of more proximal joints, and normal intellectual development. The diagnosis is supported by abnormal immunoreactivity for collagen VI on muscle biopsies. As patients with UCMD show clinical characteristics typical of classical disorders of connective tissue such as Ehlers–Danlos syndromes (EDS), we investigated the ultrastructure of skin biopsy samples from patients with UCMD (n=5). Electron microscopy of skin biopsies revealed ultrastructural abnormalities in all cases, including alterations of collagen fibril morphology (variation in size and composite fibers) and increase in ground substance, which resemble those seen in patients with EDS. Our findings suggest that there is a true connective tissue component as part of the phenotypic spectrum of UCMD and that there is considerable clinical as well as morphological overlap between UCMD and classic connective tissue disorders. © 2004 Wiley‐Liss, Inc.

We present the clinical findings, radiological aspects, operative results, and histopathological features of four typical primitive neuroectodermal tumors (PNET) located in the pontine region in children. All the tumors had an endophytic intra-axial growth pattern. All the children had a short history of severe neurological deficits with involvement of the cranial nerves and pyramidal tract. MRI did not reveal any common feature of malignancy. Compared to our successful experience in operations of intra-axial endophytic brainstem tumors in a total of 32 children, the outcome was poor: all 4 children died within 13 months. We conclude that PNET occurring in the pons is not as rare as was believed, and, compared to PNET in other areas the prognosis is worse.

For patients who suffer from hydrocephalus that is difficult to treat because of impaired intracranial compliance, a programmable shunt system may be a helpful alternative. However, especially during the first weeks after implantation, many radiological follow-up studies are necessary to achieve the optimum pressure level. The authors present the case of a 7-year-old boy who suffered from posthemorrhagic hydrocephalus and did not respond to conventional shunt valve systems. After implantation of a programmable shunt system, achieving the optimum craniospinal fluid (CSF) pressure level was difficult because the symptoms of over-and under-drainage were similar. Using transcranial real-time ultrasonography for evaluation of the diameter of the intracranial CSF spaces, we were able to adjust the correct pressure level without long-term intracranial pressure monitoring or daily computed tomography, which otherwise would have been necessary because of the ambiguous symptomatology. Transcranial real-time ultrasonography (TCUS) displays an image of the intracranial parenchyma and CSF spaces through the intact temporal bone and is a valuable, serially applicable bedside monitoring technique for patients requiring close imaging follow-up

The brain morphology and chemistry of seven children with late infantile (4/7) and juvenile (3/7) forms of metachromatic leukodystrophy (MLD) were investigated by magnetic resonance imaging (MRI) and localized proton magnetic resonance spectroscopy (MRS). Patients who were examined at least 6 months after the onset of symptoms (6/7) had severe leukodystrophic changes on MRI. Proton MRS revealed a marked reduction of the neuronal markerN-acetylaspartate in white and grey matter and elevated lactate in demyelinated areas. In contrast to other leukodystrophies MLD patients showed a generalized increase of brainmyo-inositol (2- to 3-fold in white matter), indicating a specific role in the pathophysiology of demyelination in MLD.

The expression of the c-erbB-2 oncogene was studied in childhood medulloblastoma to evaluate its prognostic value, which has been claimed previously.

Children are more likely than adults to be bitten by ticks and thus more likely to be infected by Borrelia burgdorferi. In a serosurvey the infection rate measured by immunoglobulin G (IgG) antibodies was 2.6%. In a prospective hospital-based multicentre study 169 children with Lyme neuroborreliosis were examined; the infection was diagnosed by detection of specific immunoglobulin M (IgM) antibodies in the cerebrospinal fluid (CSF) using an IgM capture ELISA. The yearly incidence of Lyme neuroborreliosis was 5.8 cases per 100 000 children aged 1-13. Facial palsy and lymphocytic meningitis account for nearly 90% of all cases with neuroborreliosis indicating striking differences in the clinical spectrum between children and adults. Lyme borreliosis proves to be the most frequently verifiable cause of acute peripheral facial palsy in children, causing every second case of this disorder in the summer and autumn. In cases of facial palsy, nearly all patients with a positive history of tick bite or erythema migrans in the head and neck region show ipsilateral subsequent facial nerve palsy, suggesting a direct invasion via the affected nerve by Borrelia burgdorferi. Lyme borreliosis is the third most frequent cause of lymphocytic meningitis in childhood. Inflammatory changes of the cerebrospinal fluid along with the presence of specific antibodies are mandatory for the diagnosis of Lyme neuroborreliosis. High-dose intravenous penicillin G as well as third-generation cephalosporins prove to be effective in paediatric Lyme neuroborreliosis.

Neurologic infections represent a major problem in child neurology. Recent research on this issue has had important implications for diagnosis and pathophysiology of infectious diseases of the child's brain, resulting in new therapeutic approaches. A better understanding of the molecular pathophysiology of bacterial meningitis has developed, and therapeutic interventions focus on the host's inflammatory response. Therapeutic trials with dexamethasone in addition to antibiotic treatment have yielded promising results in reducing morbidity and long-term neurologic sequelae in bacterial meningitisr The detection of Lyme borreliosis in 1977 substantially influenced the differential diagnosis of inflammatory central nervous system diseases. Lyme neuroborreliosis proved a main cause of acute peripheral facial palsy and aseptic meningitis in children. An effective antibiotic treatment has become available for a large number of patients with these illnesses.

Abstract: Between July 1987 and June 1994 we operated upon 30 consecutive children suffering from endophytic intra-axial tumors located in the pons and/or medulla oblongata. The 25 children operated on between July 1987 and October 1993 whose postoperative course could be assessed for a minimum of 2 years after operation were included in this study. Operability of a brain stem tumor was shown to be independent of its size. A gross tumor resection between 80% and 100% could be performed in half these cases, and subtotal or partial resection in the other half. The radicality of resection was not influenced by tumor histopathology, but was dependent on intraoperative findings relating to its consistency, infiltration, and visibility. On follow up, 15 of the 25 children were found to have died within the period of 2 years. Two children died in the immediate postoperative period (at 2 days and 2 weeks after surgery), of acute brain stem swelling and an unsuspected bleeding disorder, respectively. The other 13 of these 15 children died of tumor progression between 1 and 19 months after operation, with a median survival time of 9 months. In the group of the surviving 10 children the histopathology was grade I astrocystoma in 6 cases, angioma in 2 cases, and grade II oligodendroglioma and grade II ependymoma in 1 case each. Postoperatively, most of the children showed some increase in their preoperative deficits, but recovered after 2–3 months. After 2 years, 10 of the 25 children who were followed up are alive and 9 of them attend regular school or kindergarten.

Abstract: Between August 1987 and June 1994 we operated upon 30 consecutive children suffering from endophytic intra-axial tumors located in the pons and/or medulla oblongata. We present the clinical findings, neuroradiological aspects and histopathological results recorded in these cases. Diagnostic tests included clinical examinations, neurophysiological tests and neuroradiological imaging [magnetic resonance tomography (MRT) in all cases, often combined with cranial computer tomography (CCT)]. The diagnosis was confirmed by histopathological examination of the tumor material obtained by open surgical exploration in all cases. We conclude that a short history and more horizontal growth within the pons are more valuable predictors of the histopathology than dif-ferentiation between focal or diffuse growth patterns. MRT has little predictive value for histopathological diagnosis in intra-axial brain stem tumors.

Abstract: Malignant rhabdoid tumors (MRT) are characterized by a typical light microscopic morphology with uniformly round tumor cells, vacuolated cytoplasm with occasional round, hyaline intracytoplasmic, periodic acid-Schiff-positive inclusions, vesicular nuclei with prominent nucleoli and positive immunoreactivity for vimentin. The histogenesis of MRT is controversial. Five cases of primary central nervous system (CNS) rhabdoid tumors in children are presented. Immunohistochemical, light and electron microscopic features are compared with primary CNS malignant rhabdoid tumors reported in the literature. Expression of various neurofilaments in our cases of primary CNS rhabdoid tumors was prominent and we therefore favor a neural differentiation of extrarenal intracerebral rhabdoid tumors.

1. Die embryologische Untersuchung verschiedener Pflanzen von Rubus idaeus zeigte vollkommen normale Archespor- und Embryosackentwicklung.