AMS Acta
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Repository of the University of Bologna.

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Mostrando recursos 221 - 240 de 318

221.
Serial entrepreneurship and born-global new ventures. A case study. - Presutti, Manuela; Onetti, Alberto; Odorici, Vincenza
Based on a longitudinal case study, we aim to understand how serial entrepreneurs can foster the development of born-global ventures. We consider a born-global start-up as the final stage of the learning process for a serial entrepreneur, advancing propositions regarding the importance of prior entrepreneurial experience for born-global venture creation and growth. We suggest that the serial entrepreneur’s previous entrepreneurial experiences could substitute for the lack of knowledge, opportunity recognition and social networks of a born-global start-up. Thus, we recognize the necessity of a shift in the unit of analysis, from born-global start-up to a global serial entrepreneur, suggesting to...

222.
Sleep Disturbance and Daytime Sleepiness in Patients with Cirrhosis: a Case Control Study - Mostacci, Barbara; Ferlisi, Monica; Baldi Antognini, Alessandro; Sama, Claudia; Morelli, Cristina; Mondini, Susanna; Cirignotta, Fabio
Objective: Sleep disturbance and excessive daytime sleepiness have been reported in patients
with hepatic cirrhosis. The objective of this study was to evaluate daytime somnolence and
sleep complaints in a group of 178 patients with cirrhosis compared to a control group.
Method: Sleep features and excessive daytime sleepiness were evaluated by the Basic Nordic
Sleep Questionnaire (BNSQ) and the Epworth Sleepiness Scale (ESS). We collected clinical
and laboratory data, neurological assessment and EEG recording in cirrhotic patients.
Results: Patients with cirrhosis complained of more daytime sleepiness (p<0.005), sleeping
badly at least three times a week (p<0.005), difficulties falling asleep (p<0.01) and frequent
nocturnal awakening (p<0.005) than controls. We...

226.
The CMC Dynamics Theorem in homogeneous n-manifolds - Meeks, William H.; Tinaglia, Giuseppe
In this paper we generalize the Dynamics Theorem for nonzero CMC surfaces in R^3 to a new Dynamics Theorem for nonzero CMC hyper-surfaces in a homogeneous manifold. In this case, the role of translations of R^3 is played by a subgroup, G, of the isometry group of N which acts transitively on N.

227.
The isometric deformability question for constant mean curvature surfaces with topology - Smyth, Brian; Tinaglia, Giuseppe
The paper treats the isometric deformability of non-simply-connected constant mean curvature surfaces which are neither assumed embedded nor complete. We prove that if a smooth oriented surface M immersed in R^3 admits a nontrivial isometric deformation with constant mean curvature H then every cycle in M has vanishing ﬂux and, when H is not zero, also vanishing torque. The vanishing of all ﬂuxes implies the existence of such an isometric deformation when H = 0. Our work generalizes to constant mean curvature surfaces a well-known rigidity result for minimal surfaces.

228.
Comparing continuous treatment matching methods in policy evaluation - Adorno, Valentina; Bernini, Cristina; Pellegrini, Guido
The paper evaluates the statistical properties of two different matching estimators in the case of continuous treatment, using a Montecarlo experiment. The traditional generalized propensity score matching estimator is compared whit a new two steps matching estimator for the continuous treatment case, recently developed (Adorno, Bernini, Pellegrini, 2007). It compares treatment and control units similar in terms of their observable characteristics in both selection processes (the participation decision and the treatment level assignment), where the generalized propensity score matching estimator collapses the two processes into one single step matching. The results show that the two steps estimator has better finite...

229.
Portfolio choice, behavioral preferences and equity home bias - Magi, Alessandro
We provide a plausible explanation of aggregate portfolio behavior, in a framework where economic agents have behavioral (narrow framing) preferences. The representative agent derives utility not only from consumption (standard models) but also from risky financial wealth fluctuations. Moreover, the investor frames the stock market risk narrowly and has loss averse preferences. We numerically solve, for the foreign equity share, a simple model of international portfolio choice, providing a possible explanation for the equity home bias puzzle. Only economic agents able to process correctly information deriving from stock markets exploit the diversification opportunities provided by international financial markets.

230.
The Eulerian distribution on self evacuated
involutions - Barnabei, Marilena; Bonetti, Flavio; Silimbani, Matteo
We present an extensive study of the Eulerian distribution on
the set of self evacuated involutions, namely, involutions corresponding to
standard Young tableaux that are fixed under the Sch¨utzenberger map. We
find some combinatorial properties for the generating polynomial of such distribution,
together with an explicit formula for its coefficients. Afterwards,
we carry out an analogous study for the subset of self evacuated involutions
without fixed points.

231.
The signed Eulerian numbers on involutions - Barnabei, Marilena; Bonetti, Flavio; Silimbani, Matteo
We define an analogue of signed Eulerian numbers fn;k for involutions
of the symmetric group and derive some combinatorial properties
of this sequence. In particular, we exhibit both an explicit formula and a
recurrence for fn;k arising from the properties of its generating function.

232.
Combinatorial properties of the numbers of
tableaux of bounded height - Barnabei, Marilena; Bonetti, Flavio; Silimbani, Matteo
We introduce an infinite family of lower triangular matrices ¡(s), where
°s
n;i counts the standard Young tableaux on n cells and with at most
s columns on a suitable subset of shapes. We show that the entries
of these matrices satisfy a three-term row recurrence and we deduce
recursive and asymptotic properties for the total number ¿s(n) of
tableaux on n cells and with at most s columns.

233.
Arriving at equivalence. Making a case for comparable general reference corpora in Translation Studies. - Philip, Gill
When multilingual corpora are used in translation studies, it is usually assumed that they are either translated (parallel) or comparable, or both; and that their size and text composition are analogous. As general reference corpora become more widely available, it is inevitable that these too should be used to compare and contrast SL norms, thus extending the definition of comparability to include text collections whose size and content may vary considerably, and which are nevertheless considered representative of their languages. This paper addresses the contribution of comparable reference corpora to the identification of translation equivalence. Focusing in particular on native-speaker...

234.
GIT quotients of projective spaces - Incensi, Francesca
We study the quotients for the diagonal action of SL3(C) on the product of n-fold of P^2(C): we are interested in describing how the quotient changes when we vary the polarization (i.e. the choice of an ample linearized line bundle).
We illustrate the different techniques for the construction of a quotient, in particular the numerical criterion for semi-stability and the “elementary transformations” which are resolutions of precisely described singularities (case n = 6).

235.
The CMC Dynamics Theorem in R^3 - Meeks, William H.; Tinaglia, Giuseppe
In this paper, we develop some new tools and theory that are useful in describing the
geometry of properly embedded, constant mean curvature surfaces in R^3 with bounded
second fundamental form. More precisely, we prove dynamics type results for the space
of translational limits of such a surface. As a consequence of our main theorems, in
subsequent papers we obtain rigidity results for certain properly embedded, constant
mean curvature surfaces in R^3, as well as derive curvature estimates for complete,
embedded, constant mean curvature surfaces in complete locally homogeneous three-
manifolds.

236.
Adverb use in EFL student writing: from learner dictionary to text production - Philip, Gill
Adverbs, especially those occurring in adverb+adjective collocations, play a central role in the language that advanced learners are expected to produce in their argumentative writing. However submodifying adverbs of degree such as ‘closely’, ‘deeply’, ‘strongly’ and ‘widely’ have been identified as being problematic for learners of English: Italian learners over-use very and really to the virtual exclusion of any other adverb (Philip 2007). This situation is due in part to the EFL curriculum, but monolingual and bilingual learner’s dictionaries appear to do little to address the issue. This contribution examines the treatment of lexical adverbs of degree in the five...

237.
On the Characteristic Direction of Real Hypersurfaces in C^(N+1) and a Symmetry Result - Martino, Vittorio; Montanari, Annamaria
In this paper we show the following property of a non
Levi flat real hypersurface in C^(n+1): if the unit characteristic
direction T is a geodesic, then it is an eigenvector of the second
fundamental form and the relative eigenvalue is constant. As an
application we prove a symmetry result, of Alexandrov type, for
compact hypersurfaces in C^(n+1) with positive constant Levi mean
curvature.

238.
Integral Formulas for a Class of Curvature PDE'S and Application to Isoperimetric Inequalities and to Symmetry Problems - Martino, Vittorio; Montanari, Annamaria
We prove integral formulas for closed hypersurfaces in C^(n+1); which
furnish a relation between elementary symmetric functions in the eigenvalues of
the complex Hessian matrix of the defining function and the Levi curvatures of
the hypersurface. Then we follow the Reilly approach to prove an isoperimetric
inequality. As an application, we obtain the "Soap Bubble Theorem" for star-
shaped domains with positive and constant Levi curvatures bounding the classical
mean curvature from above.

239.
Self-evaluation test for student guidance: the case of the University of Bologna - Matteucci, Mariagiulia; Mignani, Stefania; Ricci, Roberto
In this work, the theme of student guidance in the university context is outlined. In order to introduce the competence evaluation for student guidance, a new guidance project based on self-evaluation tests of the University of Bologna (Italy) is presented. In the paper, the issues of item specification and test calibration are explored, with reference to item response theory models. Models are for multiple-choice and binary items and they assume that a single ability is responsible for the student performance in the test. The test calibration is conducted for the Statistics Faculty and the results are discussed, together with the...

240.
Adverb use in EFL student writing - Philip, Gill
Adverbs, especially those occurring in adverb+adjective collocations, play a central role in the language that advanced learners are expected to produce in their argumentative writing. However submodifying adverbs of degree such as ‘closely’, ‘deeply’, ‘strongly’ and ‘widely’ have been identified as being problematic for learners of English: Italian learners over-use very and really to the virtual exclusion of any other adverb (Philip 2007). This situation is due in part to the EFL curriculum, but monolingual and bilingual learner’s dictionaries appear to do little to address the issue. This contribution examines the treatment of lexical adverbs of degree in the five...