623 research outputs found

    Distributional energy momentum tensor of the extended Kerr geometry

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    We generalize previous work on the energy-momentum tensor-distribution of the Kerr geometry by extending the manifold structure into the negative mass region. Since the extension of the flat part of the Kerr-Schild decomposition from one sheet to the double cover develops a singularity at the branch surface we have to take its non-smoothness into account. It is however possible to find a geometry within the generalized Kerr-Schild class that is in the Colombeau-sense associated to the maximally analytic Kerr-metric.Comment: 12 pages, latex2e, amslatex and epsf macro

    Spontaneous Dural Carotid-Cavernous Fistula Treated with Microcoil Insertion

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    This report includes a case of a 65-year-old woman presenting with a spontaneous dural carotid-cavernous fistula. Biomicroscopic examination of the anterior segment showed significant conjunctival chemosis, dilatation of the episcleral vessels, narrow anterior chamber, and a proptosis of the right eye, whereas the fellow eye was unremarkable. Retinal examination revealed an impaired arteriovenous ratio (A/V) from 1-4 to 1-2 and two extensive cotton exudates. An ultrasound scan (US) demonstrated congestion of the upper ophthalmic vein. Selective brain angiography through right femoral catheterization revealed a dural fistula of the wall of the cavernous right sinus. The patient underwent surgery on the superior ophthalmic vein and insertion of a micro-catheter in the cavernous sinus under CT guidance. Furthermore, a trans-femoral catheter was placed in the carotid artery on the same side as the fistula to allow arteriographic controls after micro coil positioning and embolization. Angiographic follow-up immediately after positioning the coils showed the occluded fistula and a regular flow circulation between the internal and the external carotid arteries. After treatment, the patient presented a complete resolution of symptoms. Conservative management is effective and safe in treating patients with carotid-cavernous fistula and mild clinical features because of a good chance of spontaneous or secondary thrombosis after arteriographic occlusion

    Concomitant Small Cell Neuroendocrine Carcinoma of Gallbladder and Breast Cancer

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    The neuroendocrine carcinoma is defined as a high-grade malignant neuroendocrine neoplasm arising from enterochromaffin cells, usually disposed in the mucosa of gastric and respiratory tracts. The localization in the gallbladder is rare. Knowledge of these gallbladder tumors is limited and based on isolated case reports. We describe a case of an incidental finding of small cell neuroendocrine carcinoma of the gallbladder, observed after cholecystectomy for cholelithiasis, in a 55-year-old female, who already underwent quadrantectomy and sentinel lymph-node biopsy for breast cancer. The patient underwent radiotherapy for breast cancer and six cycles of chemotherapy with cisplatin and etoposide. Eighteen months after surgery, the patient was free from disease. Small cell neuroendocrine carcinoma of the gallbladder has poor prognosis. Because of the rarity of the reported cases, specific prognostic factors have not been identified. The coexistence of small cell neuroendocrine carcinoma of the gallbladder with another malignancy has been reported only once.The contemporary presence of the two neoplasms could reflect that bioactive agents secreted by carcinoid can promote phenotypic changes in susceptible cells and induce neoplastic transformation

    Semi-invariants of symmetric quivers of finite type

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    Let (Q,σ)(Q,\sigma) be a symmetric quiver, where Q=(Q0,Q1)Q=(Q_0,Q_1) is a finite quiver without oriented cycles and σ\sigma is a contravariant involution on Q0Q1Q_0\sqcup Q_1. The involution allows us to define a nondegenerate bilinear form on a representation $V$ of $Q$. We shall call the representation orthogonal if is symmetric and symplectic if is skew-symmetric. Moreover we can define an action of products of classical groups on the space of orthogonal representations and on the space of symplectic representations. For symmetric quivers of finite type, we prove that the rings of semi-invariants for this action are spanned by the semi-invariants of determinantal type cVc^V and, in the case when matrix defining cVc^V is skew-symmetric, by the Pfaffians pfVpf^V

    Sub-clinical effects of chronic noise exposure on vestibular system

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    Aim: to investigate the effect of chronic noise exposure on vestibular function of subjects without clinical evidence of vestibular disorders and with documented cochlear damage from noise. Subjects and methods: 25 patients with chronic noise- induced hearing loss (NIHL) and without vestibular complaints (group A) and 25 matched controls with sensorineural hearing loss without noise exposure (group B), underwent audiological and vestibular test including caloric and cervical vestibular-evoked myogenic potentials tests (cVEMPs). Results: In subjects chronically exposed to noise, similarly to that of the auditory threshold, an increase in the evocation threshold of VEMPs has been documented, statistically significant (p<0,05) and independent of the performance of the auditory threshold. p1-n1 amplitude values showed a significant difference between group A and group B. No significant difference for p1-n1 latencies between the two groups was found. Conclusion: We have documented the possibility of vestibular lesion, along with cochlear damage, related to chronic acoustic trauma

    Voltammetric Study for the Determination of Diclofenac in Aqueous Solutions Using Electro-Activated Carbon Electrodes

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    Diclofenac (DCF) is a nonsteroidal anti-inflammatory drug to treat pain and inflammatory diseases. The high consumption of the drug leads to a significant change in the ecosystem. With the aim of optimizing a fast screening analysis for DCF detection on many samples with a sensitive and cheap procedure, we considered electrochemical methods using carbon-based electrodes as sensors. The electrochemical behavior of the DCF was studied on glassy carbon electrodes (GCE) and on screen-printed carbon electrodes (SPCEs) from two different suppliers after an anodic activation. The surface of the SPCEs was analyzed by scanning electron microscope (SEM) and Energy Dispersive Spectrometry (EDS). On all the activated electrodes, the voltammetric procedure (Differential Pulse Voltammetry) for the determination of DCF was optimized by the Experimental Design method, and the linearity range of the response, as well as the calibration and limit parameters (limits of detection—LoD; limit of quantification—LoQ), were defined. Analyses on SPCEs were performed both by immersing the electrode in the solution and by deposing a drop of solution on the electrode. DCF signals are stabilized by the polishing process and enhanced by the anodic activation and acid pH. The electrochemical response of DCF is not reversible, and its by-products tend to be adsorbed on the surfaces, particularly on GCE. The lowest limit parameters were obtained using the GCE (LoD = 1.6 µg L−1) and the SPCE, having the smallest surface, immersed in solution (LoD = 7 µg L−1)
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