Effects of AlGaAs cladding layers on the luminescence of GaAs/GaAs1-xBix/GaAs heterostructures.

The structural and optical properties of GaAs1-xBix quantum wells (QWs) symmetrically clad by GaAs barriers with and without additional confining AlGaAs layers are studied. It is shown that a GaAs/GaAs1-xBix/GaAs QW with x ~ 4% and well width of ~ 4 nm grown by molecular beam epitaxy demonstrates efficient photoluminescence (PL) that becomes significantly more thermally stable when a cladding AlGaAs layer is added to the QW structure. The PL behavior for temperatures between 10 and 300 K and for excitation intensities varying by seven orders of magnitude can be well described in terms of the dynamics of excitons including carrier capture in the QW layer, thermal emission and diffusion into the cladding barriers. Understanding the role of these processes in the luminescence of dilute GaAs1-xBix QW structures facilitates the creation of highly efficient devices with reduced thermal sensitivity and low threshold current.

Trophic and spatial patterns of contaminants in fishes from the Republic of the Marshall Islands in the equatorial Pacific.

The Republic of the Marshall Islands (RMI) has been affected by marine pollution from militarization and urbanization. To address concerns raised by the Marshall Islands Marine Resources Authority, this study examined concentrations of dissolved contaminants in reef and pelagic fishes in the RMI and assessed potential associated risks. Metals, organochlorine pesticides, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) were examined in reef and pelagic fishes from six atolls: Kwajalein, Majuro, Jaluit, Utirik, Rongelap, and Wotje. Clear trophic patterns emerged for metals. Total arsenic was highest in higher trophic level reef fishes, particularly in the camouflage grouper (Epinephelus polyphekadion) (>100 µg g-1 total As), but inorganic arsenic was negligible in higher trophic levels and showed an inverse trend with the highest percentages present in parrotfishes and herbivores. Copper and mercury were elevated in higher trophic level reef and pelagic fishes, respectively, and the maximum mercury concentrations (6.45 µg g-1 in Gymnosarda unicolor) were among the highest reported in the Pacific. Conversely, cadmium and lead were highest in lower trophic levels, like surgeonfishes and parrotfishes. PCBs were more clearly linked to locations and were highest at two atolls with military history (Kwajalein and Jaluit) (>U.S. EPA Screening Value of 2.5 ppb). PAHs were ubiquitous across taxa (detected in 97% of samples), but the highest concentrations were in lower trophic levels. Organochlorine pesticides were detected at very low concentrations that do not likely pose a risk. We compare concentrations to established thresholds for human health and find that - for specific locations and species - contaminant concentrations may pose a risk to fish and other marine taxa, as well as human consumers. This study provides baseline information that aids the development of marine conservation and public health recommendations and addresses a data gap that persists for marine pollution throughout the Pacific Islands.

Optical evidence of a quantum well channel in low temperature molecular beam epitaxy grown Ga(AsBi)/GaAs nanostructure.

A Ga(AsBi) quantum well (QW) with Bi content reaching 6% and well width of 11 nm embedded in GaAs is grown by molecular beam epitaxy at low temperature and studied by means of high-resolution x-ray diffraction, photoluminescence (PL), and time-resolved PL. It is shown that for this growth regime, the QW is coherently strained to the substrate with a low dislocation density. The low temperature PL demonstrates a comparatively narrow excitonic linewidth of ∼ 40 meV. For high excitation density distinct QW excited states evolve in the emission spectra. The origins of peculiar PL dependences on temperature and excitation density are interpreted in terms of intra-well optical transitions.

Low rate of intracerebral hemorrhage after cardiac catheterization in patients with acute ischemic stroke in a large case series.

BACKGROUND AND AIMS: Myocardial infarction complicating acute ischemic stroke (IS) is associated with high mortality, but evidence guiding the acute management is scarce. In particular, data on the risk of intracerebral hemorrhage (ICH) due to early cardiac catheterization including the peri-procedural application of antithrombotic drugs in patients with acute ischemic stroke are limited. Here, we aimed to evaluate the incidence and patient characteristics of ICH after cardiac catheterization in acute stroke patients to help to govern the risk of intracranial bleeding versus the benefits of myocardial reperfusion via cardiac catheterization. METHODS: We screened a consecutive cohort of n = 126 patients with acute ischemic stroke (IS) who underwent cardiac catheterization during the same hospital stay at a large German neurovascular center (LMU Munich). Eventually, we identified n = 42 patients with cardiac catheterization after acute stroke. N = 22/42 patients did not receive neuroimaging post cardiac catheterization and were discharged without any new neurological deficits, n = 20/42 had neuroimaging after cardiac catheterization and were included for final analysis. RESULTS: Cardiac catheterization was performed within a median of 3,6 days after ischemic stroke (No-ICH 7,3 days (IQR, 3,8-16,2) vs. ICH 1,1 days (IQR, 0,8-74,6), p = 0,40), One patient showed new neurological deficits after cardiac procedures (n = 1/42, 2,4 %). New or progressive ICH was ultimately found in 15 % (3/20) of cases. They were classified as HT1, PH1 and PH2 according to ECASS II criteria, respectively. With regards to the coronary catheterization, 85 % of all patients undergoing catheterization ultimately received percutaneous cardiac intervention. ICH was not significantly associated with any of the independent variables. Intrahospital death due to either ischemic stroke, ICH or cardiovascular events did not occur. CONCLUSION: The incidence of ICH in ischemic stroke followed by early cardiac catheterization and application of antithrombotic drugs was comparable to studies reporting on the incidence of ICH in ischemic stroke patients without catheterization. This study's results strengthen the hypothesis that in presence of both, acute myocardial infarction and acute ischemic stroke, the general risk for ICH is not prohibitive of cardiac catheterization.

Surface effects of vapour-liquid-solid driven Bi surface droplets formed during molecular-beam-epitaxy of GaAsBi.

Herein we investigate a (001)-oriented GaAs1-xBix/GaAs structure possessing Bi surface droplets capable of catalysing the formation of nanostructures during Bi-rich growth, through the vapour-liquid-solid mechanism. Specifically, self-aligned "nanotracks" are found to exist trailing the Bi droplets on the sample surface. Through cross-sectional high-resolution transmission electron microscopy the nanotracks are revealed to in fact be elevated above surface by the formation of a subsurface planar nanowire, a structure initiated mid-way through the molecular-beam-epitaxy growth and embedded into the epilayer, via epitaxial overgrowth. Electron microscopy studies also yield the morphological, structural, and chemical properties of the nanostructures. Through a combination of Bi determination methods the compositional profile of the film is shown to be graded and inhomogeneous. Furthermore, the coherent and pure zincblende phase property of the film is detailed. Optical characterisation of features on the sample surface is carried out using polarised micro-Raman and micro-photoluminescence spectroscopies. The important light producing properties of the surface nanostructures are investigated through pump intensity-dependent micro-PL measurements, whereby relatively large local inhomogeneities are revealed to exist on the epitaxial surface for important optical parameters. We conclude that such surface effects must be considered when designing and fabricating optical devices based on GaAsBi alloys.

Herpes simplex virus (HSV) DNA in microglial nodular brainstem encephalitis.

Thirty-four brains with microglial nodular brain stem encephalitis were retrospectively investigated for herpes simplex virus (HSV) and cytomegalovirus (CMV) by in situ hybridization (ISH) with biotinylated cDNA probes, and by immunocytochemistry with polyclonal and monoclonal antibodies on formalin fixed paraffin embedded serial tissue sections. In 16 cases (47%), HSV DNA was found by ISH in the nuclei of neurons in microglial nodules or in the adjacent parenchyma of the brainstem, and more rarely at various cerebellar and telencephalic sites. None of the 34 cases was labeled for CMV DNA and none revealed HSV or CMV antigens. Ten control brains without microglial nodules were not labeled. This study suggests an HSV etiology for many cases with microglial nodular brainstem encephalitis.

Expression of major histocompatibility complex class I molecules on the different cell types in multiple sclerosis lesions.

Multiple sclerosis is considered to be an immune-mediated disease of the central nervous system, characterized by chronic inflammation, primary demyelination and axonal damage. The mechanisms of demyelination and axonal injury are heterogeneous and complex. One possible mechanism is direct damage of oligodendrocytes and neurons by Class I MHC restricted cytotoxic T-cells. In this study we analyzed the expression of functional MHC class I molecule complex, consisting of alpha-chain and beta2-microglobulin, in a large sample of human autopsy material, containing 10 cases of acute MS, 10 cases of chronic active MS, 10 cases of chronic inactive MS and 21 controls. To examine the expression of MHC class I and II molecules on the different cell-types in brain, we used quantitative immunohistochemical techniques, double staining and confocal laser microscopy scans on paraffin embedded sections. We found constitutive expression of MHC class I molecule on microglia and endothelial cells. A hierarchical up-regulation of MHC class I was present on astrocytes, oligodendrocytes, neurons and axons, depending upon the severity of the disease and the activity of the lesions. MHC class II molecules were expressed on microglia and macrophages, but not on astrocytes. These data indicate that in MS lesions all cells of the central nervous system are potential targets for Class I MHC restricted cytotoxic T-cells.

Altered expression of voltage-dependent calcium channel alpha(1) subunits in temporal lobe epilepsy with Ammon's horn sclerosis.

Voltage-dependent calcium channels, the initial components in the calcium signalling cascade, are increasingly being recognised as relevant factors in the pathology of epilepsy. To further characterise their role in temporal lobe epilepsy associated with Ammon's horn sclerosis, we investigated the immunohistochemical distribution of five different voltage-dependent calcium channel alpha(1) subunits (alpha(1A), alpha(1B), alpha(1C), alpha(1D), alpha(1E)) in 14 hippocampal specimens of patients with Ammon's horn sclerosis in comparison with eight autopsy control cases. In epilepsy specimens an increased immunoreactivity was observed for alpha(1A), alpha(1B), alpha(1D) and alpha(1E) in the neuropil of the dentate gyrus molecular layer. Dentate gyrus granule cells and residual CA3 pyramidal neurones showed enhanced immunoreactivity for alpha(1A), while labelling of these neurones was decreased for alpha(1C). Astrocytes in Ammon's horn sclerosis specimens were strongly immunoreactive for the alpha(1C) subunit contrasting with an absent astrocytic alpha(1C) labelling in controls. Our results suggest that the expression of calcium channels in neurones and glial cells is dynamically regulated in temporal lobe epilepsy, supporting the relevance of calcium signalling pathways for this disease.

Subacute diencephalic angioencephalopathy: an entity similar to angiodysgenetic necrotizing encephalopathy and Foix-Alajouanine disease.

A previously healthy 58-year-old man developed neurological illness with progressive dementia, hallucinations, central motor and vegetative impairment which led to death in 14 weeks. Autopsy revealed lesions in a symmetrical centrencephalic distribution. Inner cerebral veins and arteries were surrounded by extravasation of plasma and perivascular haemorrhage and were thickened by fibrous scarring and muscle fibre proliferation. Necrotized blood vessels were also found. The parenchyma was damaged by incomplete to complete necrosis. The age and sex of the patient, the progressive clinical course, the increase of cerebrospinal fluid protein, and the histopathology of the lesion show some similarities to angiodysgenetic necrotizing encephalopathy and spinal Foix-Alajouanine disease.

Serum melatonin levels: a new neurodiagnostic tool in pineal region tumors?

The pineal hormone melatonin (MLT) is secreted in a circadian rhythm with high serum levels during nighttime and low serum levels during daytime. Several authors have reported an altered secretion pattern of MLT in patients with pineal tumors and have proposed that MLT may be used as a tumor marker. In nine patients, a pineal region tumor was diagnosed by computer-assisted tomography. Before and after surgical removal of the tumor, several day- and nighttime serum samples were collected and MLT concentrations were estimated by radioimmunoassay. Before operation, five patients presented a normal circadian pattern of MLT secretion. In the remaining four subjects, MLT levels were undetectable or at the limit of detection, with no signs of a circadian secretion pattern. Eight patients were reexamined after tumor resection, when all but one had undetectable or very low MLT levels. The remaining subject, with a pineomesencephalic pilocytic astrocytoma, dislocating but not involving the pineal gland, presented a normal circadian secretion pattern of MLT after operation; in this case, tumor resection was possible without damaging the pineal gland. Thus, before operation, MLT deficiency rather than exaggerated serum levels may be used as a marker for pineal tumors that destroy the pineal gland. After tumor resection, serum MLT may serve to demonstrate complete pinealectomy.

Glioblastoma developing at the site of a cerebellar medulloblastoma treated 6 years earlier. Case report.

The authors report the highly unusual development of a glioblastoma multiforme at the site of excision of a medulloblastoma 6 years earlier. The patient was operated on for a cerebellar medulloblastoma at the age of 13 years. Postoperative treatment included irradiation and chemotherapy. Six years later, a glioblastoma multiforme was found at the original site of the medulloblastoma. Intensive multimodality treatment is considered the likely cause for the later tumor development.

Neuroepithelial and ectomesenchymal differentiation in a primitive pineal tumor ("pineal anlage tumor").

A primitive tumor of the pineal region in a 9-year-old girl led to death after 5 months of increased intracranial pressure with occlusive hydrocephalus. Histological investigation including immunocytochemistry revealed a broad spectrum of neuroectodermal differentiation with neuroblastic, neuronal, ependymal and retinoblastomatous features. Melanotic epithelial formations were similar to those of the so-called retinal anlage tumor and of the developing pineal gland. Striated muscle fibers indicated additional ectomesenchymal differentiation reminiscent of the close topographical relationship between neural crest and neural tube on the prosencephalic level of the pineal anlage. This developmental situation seems to be neoplastically reflected by the differentiation features of this tumor.

Posterior ischemic optic neuropathy following bilateral radical neck dissection.

A patient is presented with posterior ischemic optic neuropathy (PION) after bilateral radical neck dissection, probably caused by hemodynamic hypotension, combined with other factors. A postmortem histologic study of the optic nerve was performed to analyze the pathogenic mechanism of blindness. To prevent this complication, one should favor a two-stage procedure, avoiding drug-induced hypotension, overtransfusion, and anemia. During the postoperative period, visual acuity should be monitored regularly, and proper positioning of the patient's head is necessary.

[Immunologic hormone detection in hypophyseal adenomas: correlation of serum hormone findings with immunocytochemical hormone levels in tumor tissue]. / Immunologischer Hormonnachweis bei Hypophysenadenomen: Korrelation von Serumhormonbefunden mit immunzytochemischem Hormonbefund am Tumorschnitt.

Forty-four out of 82 patients with neurosurgically removed pituitary adenomas showed preoperatively elevated plasma hormone levels of prolactin (PRL; 22 patients), of human growth hormone (hGH; 15 patients), and of adrenocorticotropic hormone (ACTH; 7 patients). Immunocytochemical detection of the hypersecreted hormone in paraffin sections of tumour tissue, was possible in all 7 patients (100%) with Cushing's disease, in 20 patients (90%) with hyperprolactinaemia, and in 10 patients (66%) with acromegaly. In a further 3 cases beta-TSH, in one case beta-LH, and in 8 cases alpha-HCG were demonstrated in sections of tumour tissue. No clinical evidence of endocrine disturbance was found in any of these latter cases. More than one anterior pituitary hormone was detected in sections of tumour tissue in 7 cases. An overall qualitative correlation of 85% was found between the elevated plasma hormone level and immunocytochemical hormone detection in tumour tissue sections. Since there is no correlation between conventional histological staining modalities (acidophilic, basophilic, chromophobic) on the one hand, and the level of plasma hormones or immunological hormone detection in tumour tissue on the other hand, modern histological diagnosis of a pituitary adenoma should include assessment of the functional state as found by immunocytochemical hormone determination.

Chronic relapsing polyradiculoneuropathy in IgG lambda monoclonal gammopathy of undetermined significance (MGUS)--complete remission following carmustine treatment.

A previously healthy 43 year-old female developed IgG lambda monoclonal gammopathy of undetermined significance (MGUS) and ascending sensorimotor polyradiculoneuropathy which relapsed 11 times within 2 years. Marked improvement was noted repeatedly after plasmapheresis. However, on each occasion symptoms and signs of polyradiculoneuropathy recurred almost exactly 3 weeks after plasma-pheresis. Following 6 weeks of treatment with carmustine (70 mg/week), nearly complete recovery was established, which has persisted up to now (82 months after the end of therapy). The close temporal correlation between clinical relapse and recurrence of the IgG paraprotein and its permanent absence in stable clinical remission after carmustine treatment suggest a causal relationship between the paraprotein and the polyradiculoneuropathy. However, further studies are required to confirm this observation, as well as the efficacy of carmustine therapy.

[Stereotaxic biopsy of intracranial processes: validity of histologic diagnosis]. / Stereotaktische Biopsie intrakranieller Prozesse: Validität der histologischen Diagnostik.

The diagnostic validity of stereotactic intracranial biopsies was investigated in 70 patients retrospectively. In 56 cases (80%) the presence of a neoplastic lesion as well as its grade of malignancy was proved by cytological, histological and immunohistochemical techniques. An inflammatory or vascular lesion was found in 8 patients (11.4%). In 6 patients (8.6%) the nature of the lesion remained unclear because of nonspecific histological findings. In 27 cases a correlation was found between the biopsy specimens and corresponding material obtained during open surgery or autopsy. 24 concordant results were found (88.9%). In one case a malignant tumour was classified only according to the findings obtained at operation. In two cases subsequently diagnosed as glioblastoma biopsy reported a higher differentiated astrocytoma and a non-neoplastic lesion, respectively. These results confirm stereotactic biopsy of intracranial lesions as a method with low complication rate and high diagnostic validity.

X-ray diffraction from nonperiodic layered structures with correlations: analytical calculation and experiment on mixed Aurivillius films.

X-ray diffraction from films consisting of layers with different thicknesses, structures and chemical contents is analysed. The disorder is described by probabilities for different sequences of layers. Closed analytical expressions for the diffracted X-ray intensity are obtained when the layers form a stationary Markov chain. The proposed model is applied to the diffraction data from epitaxial sodium bismuth titanate thin films with Aurivillius structure possessing such one-dimensional disorder. In this case, the disorder is caused by a random stacking of three and four perovskite units separated by bismuth oxide interlayers. The results of analytical calculations are in good agreement with the experimental data and indicate that the incorporation of sodium in the Bi(4)Ti(3)O(12) phase causes the formation of a fourth perovskite unit.

A novel multi-detection technique for three-dimensional reciprocal-space mapping in grazing-incidence X-ray diffraction.

A new scattering technique in grazing-incidence X-ray diffraction geometry is described which enables three-dimensional mapping of reciprocal space by a single rocking scan of the sample. This is achieved by using a two-dimensional detector. The new set-up is discussed in terms of angular resolution and dynamic range of scattered intensity. As an example the diffuse scattering from a strained multilayer of self-assembled (In,Ga)As quantum dots grown on GaAs substrate is presented.