716 research outputs found

    Geometry of contours and Peierls estimates in d=1 Ising models

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    Following Fr\"ohlich and Spencer, we study one dimensional Ising spin systems with ferromagnetic, long range interactions which decay as ∣x−y∣−2+α|x-y|^{-2+\alpha}, 0≤α≤1/20\leq \alpha\leq 1/2. We introduce a geometric description of the spin configurations in terms of triangles which play the role of contours and for which we establish Peierls bounds. This in particular yields a direct proof of the well known result by Dyson about phase transitions at low temperatures.Comment: 28 pages, 3 figure

    Corporate ownership and internationalization: the effects of family, bank and institutional investor ownership in the UK and in Continental Europe

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    While the role of corporate governance has been increasingly analysed during recent years, it is only very recently that the effects of corporate governance features on firm international strategies have been also considered. Using the Osiris database by Bureau van Djik we consider the potential role played by different kind of shareholders among the determinants of firm international level, distinguishing between the firms quoted in the UK from those listed in countries of Continental Europe (France, Germany, Italy, Poland and Spain). Overall our results confirm that different kind of ownerships affect with different degree of intensity the overall level of firm'sinternationalization. First, we find that ownership matter. Second, our results show that theeffects of ownership over firm's international strategies depend also on the context of analysis

    Entrepreneurial and market orientations: the moderating role of social networks on post-entry performance of international new ventures

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    This paper investigates whether entrepreneurial and marketing orientations (respectively EOs and Mos) impact – individually or collectively – international new ventures’ (INVs’) post-entry performance growth. Furthermore, we investigate whether such relations are moderated by the foreign social networks, both formal and informal, of international new ventures. Using a survey, we test our hypotheses on a sample of Italian high-tech INVs located in a cluster near Rome. A quantitative analysis is used to test the hypotheses. We found that EOs and MOs positively impact the post-entry international performance growth of INVs. Moreover, while informal foreign social network ties significantly moderate the impact of EOs and MOs, formal foreign social network ties do not have a significant moderating effect. Many theoretical and practical contributions are discussed in the paper

    The endoscopic anatomy of the cochlear hook region and fustis: Surgical implications

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    The cochlear hook region can be considered as the interface between the middle and inner ear. The identification of surgically-relevant endoscopic landmarks of this anatomical entity and assessment of their clinical value is still lacking in the literature. Procedures like cholesteatoma surgery and minimal invasive endoscopic approaches to the lateral skull base may particularly benefit from these considerations. We hypothesize that the spatial orientation of anatomical landmarks in the cochlear hook can be expressed in angles and are reproducibly identifiable by transcanal otoendoscopy. Therefore, endoscopic dissection of the cochlear hook region was performed in 32 temporal bone specimens. Topographic anatomy was documented and analysed. We performed computed tomography of 28 specimens to assess the region in three-dimensional reconstructions. The mean angle between the round window and the basal scala tympani was assessed 25.9\ub0 in endoscopic and 28.2\ub0 in three-dimensionally reconstructed models. The fustis was recognised as a reliable landmark for the basal turn. A mean angle of 155.4\ub0 to the basal scala tympani was assessed. A slight bulging without obstruction of the basal turn was observed in 5 cases. The utility of the revealed anatomical details was assessed in minimal invasive endoscopic lateral skull base approaches. In conclusion, we described the angles between anatomical landmarks of the cochlear hook region. Moreover, the angle as recorded through an endoscope was found to be reliable compared to three-dimensional reconstructions from computed tomography

    Endoscopic transcanal approach to geniculate ganglion hemangioma and simultaneous facial nerve reinnervation: A case report

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    Hemangioma of the facial nerve (FN) is a very rare benign tumor whose origin is the vascular plexi that surround the nerve. The transpetrous, retrosigmoid, and middle cranial fossa (MCF) routes are the traditional and most widely used approaches to reach these lateral skull base neoformations. However, this very complex region can be reached through an exclusive transcanal endoscopic procedure in selected cases. One of these was a 42-year-old patient who had been presenting a worsening left FN paralysis (grade VI according to the House-Brackmann scale at the time of visit) for 22 months without a history of trauma or infection. Radiological studies showed a lesion in the region of the geniculate ganglion. A suprageniculate endoscopic approach was performed to remove the lesion, with the sacrifice of the FN and a simultaneous hypoglossal-facial anastomosis. The aim of this minimally invasive surgery is the complete excision of the disease, maintaining the hearing function intact and restoration of facial function, whenever possible, avoiding more invasive approaches

    Current reservoirs in the simple exclusion process

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    We consider the symmetric simple exclusion process in the interval [−N,N][-N,N] with additional birth and death processes respectively on (N−K,N](N-K,N], K>0K>0, and [−N,−N+K)[-N,-N+K). The exclusion is speeded up by a factor N2N^2, births and deaths by a factor NN. Assuming propagation of chaos (a property proved in a companion paper "Truncated correlations in the stirring process with births and deaths") we prove convergence in the limit N→∞N\to \infty to the linear heat equation with Dirichlet condition on the boundaries; the boundary conditions however are not known a priori, they are obtained by solving a non linear equation. The model simulates mass transport with current reservoirs at the boundaries and the Fourier law is proved to hold

    Use of Foley catheter in control of internal carotid hemorrhage during endoscopic endonasal surgery

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    Internal carotid artery (ICA) injuries during endoscopic endonasal surgery (EES) are rare life-threatening events. We describe a technique to manage ICA injuries based on the use of Foley catheters.A 26-year-old female underwent endoscopic transnasal trans-sphenoidal removal of pituitary adenoma. Cerebrospinal fluid leak occurred 4 days postoperatively. During repair procedure, accidental injury of ICA occurred. Emergency nasal packing through positioning of four Foley urologic catheters was successfully performed to stop bleeding. The patient did not report neurologic deficits.In author's opinion, Foley catheters are suitable to obtain immediate bleeding control since they are rapidly available and easily usable
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