1,721,243 research outputs found
Eta and Rho invariants on manifolds with edges
Full text linkWe establish existence of eta-invariants as well as of the Atiyah–Patodi–Singer and the Cheeger–Gromov rho-invariants for a class of Dirac operators on an incomplete edge space. Our analysis applies in particular to the signature and the spin Dirac operator. We derive an analogue of the Atiyah–Patodi–Singer index theorem for incomplete edge spaces and their non-compact infinite Galois coverings with edge singular boundary. Our arguments are based on the microlocal analysis of the heat kernel asymptotics associated to the Dirac laplacian of an incomplete edge metric. As an application, we discuss stability results for the two rho-invariants we have defined
Piazza P. — Histoire de la carte nationale d'identité
No full textLévy Michel Louis. Piazza P. — Histoire de la carte nationale d'identité. In: Population, 59ᵉ année, n°6, 2004. pp. 1007-1010
STRATIFIED SURGERY AND K-THEORY INVARIANTS OF THE SIGNATURE OPERATOR
Full text linkIn the works of Higson-Roe the fundamental role of the signature as a homotopy and bordism invariant for oriented manifolds is the starting point for an investigation of the relationships between analytic and topological invariants of smooth orientable manifolds. The signature and related K-theory invariants, primary and secondary, are used to define a natural transformation between the (Browder-Novikov-Sullivan-Wall) surgery exact sequence and a long exact sequence of C*-algebra K-theory groups.In recent years the primary signature invariants have been extended from closed oriented manifolds to a class of stratified spaces known as L-spaces or Cheeger spaces. In this paper we showt hat secondary invariants, such as the rho-class, also extend from closed manifolds to Cheeger spaces. We give a rigorous account of a surgery exact sequence for stratified spaces originally introduced by Browder-Quinn and obtain a natural transformation analogous to that of Higson-Roe. We also discuss geometric applications
POSTERIOR PETROUS FACE MENINGIOMAS:AN ALGORITHM FOR SURGICAL MANAGEMENT.
No full textOtol Neurotol. 2007 Oct;28(7):942-50.
Posterior petrous face meningiomas: an algorithm for surgical management.
Sanna M, Bacciu A, Pasanisi E, Taibah A, Piazza P.
SourceGruppo Otologico, Piacenza-Rome, Italy. [email protected]
Abstract
OBJECTIVE: The objective of the present study was to report our surgical strategy in the management of 81 patients with posterior petrous face meningiomas.
STUDY DESIGN: Retrospective study.
SETTING: This study was conducted at a quaternary private otology and cranial base center.
PATIENTS: Of 139 patients with posterior fossa meningioma, 81 occurred on the posterior petrous face of the temporal bone and were the object of this study.
INTERVENTIONS: Thirty-one patients were approached by the enlarged translabyrinthine approach. The enlarged translabyrinthine approach with transapical extension Type II was performedin 29 patients. The combined retrosigmoid-retrolabyrinthine approach was chosen in 8 cases. The modified transcochlear approach Type A with permanent posterior transposition of the facial nerve (FN) was performed in 6 patients. Two patients underwent a retrolabyrinthine subtemporal transapical approach. One patient underwent a transpetrous middle cranial fossa approach. Four patients with intracanalicular meningiomas were operated on through the enlarged middle cranial fossa approach.
RESULTS: Total removal of the tumor (Simpson Grades I and II) was achieved in most patients (92.5%). The FN was anatomically preserved in 79 of the 81 (97.5%) patients. Five patients had less than 1 year follow-up, and 2 patients were lost to follow-up and were excluded in evaluation of the final FN outcome. At 1-year follow-up, 46 patients (63%) had Grade I to II, 19 (26%) had Grade III, 4 (5.4%) had Grade IV, 1 (1.3%) had Grade V, and 3 (4.1%) had Grade VI. Hearing-preserving surgery was attempted in 15 patients (18.5%) with preoperative serviceable hearing. Of these 15 patients, 11 had their hearing preserved at the same preoperative level, and 4 experienced postoperative deafness. Postoperatively, a new deficit of 1 or more of the lower cranial nerves was recorded in 3 patients. One patient experienced subcutaneous cerebrospinal fluid collection that required surgical management.
CONCLUSION: Total tumor removal (Simpson Grades I-II) remains our treatment of choice and takes priority over hearing preservation. Subtotal resection is indicated for older and debilitated patients with giant lesions to relieve the tumor compression on the cerebellum and brainstem. Subtotal removal is also preferred in the face of the absence of a plane of cleavage between the tumor and the brainstem, in the presence of encasement of vital neurovascular structures, in elderly patients with tumors adherent to preoperatively normal facial or lower cranial nerves
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Chondrosarcomas of the jugular foramen.
No full textLaryngoscope. 2008 Oct;118(10):1719-28.
Chondrosarcomas of the jugular foramen.
Sanna M, Bacciu A, Pasanisi E, Piazza P, Fois P, Falcioni M.
SourceOtology, Neurotology and Skull Base Surgery, Gruppo Otologico, Piacenza, Italy. [email protected]
Abstract
OBJECTIVES/HYPOTHESIS: Chondrosarcomas of the jugular foramen are extremely rare tumors. Our review of the literature revealed eleven previously reported cases. The aim of this study is to describe the presenting symptoms, radiographic findings, operative procedures, and postoperative outcome of five histologically confirmed cases of chondrosarcomas arising from the jugular foramen. A review of the literature is also presented.
STUDY DESIGN: Retrospective study of an quaternary referral otology and skull base private center.
METHODS: Five cases of surgically treated and pathologically confirmed jugular foramen chondrosarcomas were identified. The follow-up of the series ranged from 23 to 42 months (mean, 32.8 +/- 7.7 months).
RESULTS: A single stage procedure was adopted in all the cases. Two patients underwent type A infratemporal approaches, one patient underwent a transotic approach extending to the neck with ligature of the internal jugular vein, one patient underwent a petro-occipital transigmoid approach, and one patient underwent a combined petro-occipital transigmoid-transotic approach. Gross total tumor removal was achieved in all patients. The most common complications were lower cranial nerve deficits. To date, no recurrence or residual tumors have been observed at radiological controls.
CONCLUSIONS: We believe that the primary treatment for chondrosarcomas of the jugular foramen is gross total surgical resection of the tumor. It is our philosophy to reserve postoperative radiotherapy for patients with histologically aggressive tumors, as well as in cases with subtotal resection and recurrent tumors
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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