The planar-to-tubular structural transition in boron clusters from optical absorption

The optical response of the lowest energy isomers of the B_20 family is calculated using time-dependent density functional theory within a real-space, real-time scheme. Significant differences are found among the absorption spectra of the clusters studied. We show that these differences can be easily related to changes in the overall geometry. Optical spectroscopy is thus an efficient tool to characterize the planar to tubular structural transition, known to be present in these boron based systems

h-multigrid agglomeration based solution strategies for discontinuous Galerkin discretizations of incompressible flow problems

In this work we exploit agglomeration based $h$-multigrid preconditioners to speed-up the iterative solution of discontinuous Galerkin discretizations of the Stokes and Navier-Stokes equations. As a distinctive feature $h$-coarsened mesh sequences are generated by recursive agglomeration of a fine grid, admitting arbitrarily unstructured grids of complex domains, and agglomeration based discontinuous Galerkin discretizations are employed to deal with agglomerated elements of coarse levels. Both the expense of building coarse grid operators and the performance of the resulting multigrid iteration are investigated. For the sake of efficiency coarse grid operators are inherited through element-by-element $L^2$ projections, avoiding the cost of numerical integration over agglomerated elements. Specific care is devoted to the projection of viscous terms discretized by means of the BR2 dG method. We demonstrate that enforcing the correct amount of stabilization on coarse grids levels is mandatory for achieving uniform convergence with respect to the number of levels. The numerical solution of steady and unsteady, linear and non-linear problems is considered tackling challenging 2D test cases and 3D real life computations on parallel architectures. Significant execution time gains are documented.Comment: 78 pages, 7 figure

A Hybrid High-Order method for nonlinear elasticity

In this work we propose and analyze a novel Hybrid High-Order discretization of a class of (linear and) nonlinear elasticity models in the small deformation regime which are of common use in solid mechanics. The proposed method is valid in two and three space dimensions, it supports general meshes including polyhedral elements and nonmatching interfaces, enables arbitrary approximation order, and the resolution cost can be reduced by statically condensing a large subset of the unknowns for linearized versions of the problem. Additionally, the method satisfies a local principle of virtual work inside each mesh element, with interface tractions that obey the law of action and reaction. A complete analysis covering very general stress-strain laws is carried out, and optimal error estimates are proved. Extensive numerical validation on model test problems is also provided on two types of nonlinear models.Comment: 29 pages, 7 figures, 4 table

Excitonic effects in the optical properties of CdSe nanowires

Using a first-principle approach beyond density functional theory we calculate the electronic and optical properties of small diameter CdSe nanowires.Our results demonstrate how some approximations commonly used in bulk systems fail at this nano-scale level and how indispensable it is to include crystal local fields and excitonic effects to predict the unique optical properties of nanowires. From our results, we then construct a simple model that describes the optical gap as a function of the diameter of the wire, that turns out to be in excellent agreement with experiments for intermediate and large diameters.Comment: submitte

Reverberation Mapping of High-z, High-luminosity Quasars

We present Reverberation Mapping results after monitoring a sample of 17 high-z, high-luminosity quasars for more than 10 years using photometric and spectroscopic capabilities. Continuum and line emission flux variability is observed in all quasars. Using cross-correlation analysis we successfully determine lags between the variations in the continuum and broad emission lines for several sources. Here we present a highlight of our results and the determined radius--luminosity relations for Ly_alpha and CIV.Comment: Contributed talk at conference "Quasars at all cosmic epochs", held in Padova 2-7 April 2017, published in Frontiers in Astronomy and Space Science

Book review: why people (don’t) buy: the GO and STOP signals by Amitav Chakravarti and Manoj Thomas

Why People (Don’t) Buy: The GO and STOP Signals, authored by Amitav Chakravarti and Manoj Thomas, argues that successful marketing is dependent on understanding the circumstances in which consumers choose to buy and – just as crucially – not buy, with a focus on pricing decisions. Packed with engaging and managerially relevant examples, this book offers a clear set of guidelines through which readers can gain insight into the factors that determine marketing successes and failures, writes Simona Botti

La Iglesia vasca dividida. Cuestión religiosa y nacionalismo a la luz de la nueva documentación vaticana

L'articolo muove da un preliminare stato degli studi sulla questione. Presenta poi i pincipali momenti di snodo della guerra civile nei Paesi baschi in relazione alle posizione e alla condotta del clero, dei vescovi e della Santa Sede. Fonti privilegiate sono i rapporti che l'incaricato d'affari della Santa Sede, I. Antoniutti e poi Cicognani, inviarono al Segretario di Stato, Pacelli. L'articolo mostra le divisioni in seno al clero e particolarmente all'interno delle congregazioni religiose, tra nazionalisti baschi, nazionalisti spagnoli e quanti schierati su posizioni di equidistanza tra i due schieramenti

Caratterizzazione di cellule staminali adulte isolate da regione sottoventricolare (SVZ) di topi con mutazione vps54-L967Q (topi wobbler)

Il topo Wobbler (Wr) è portatore di una mutazione spontanea e recessiva in un gene che codifica per la “vesicular protein sorter 54” (Vps54), coinvolta nel traffico di membrana, e sviluppa una progressiva disfunzione motoria con perdita di motoneuroni e forte astrogliosi. Lo scopo del mio progetto di tesi è stato quello di determinare se il complemento di cellule staminali neurali adulte (ANSCs)/ precursori cellulari neurali adulti (ANPCs) isolato da regione sottoventricolare (SVZ) di topi Wr, fosse alterato e determinare se cellule ottenute dal differenziamento di ANSCs/ANPCs Wr mostrassero caratteristiche tipiche della malattia. ANSCs/ANPCs Wr sono capaci di generare neurosfere vitali e metabolicamente attive, di proliferare, di autorinnovarsi e sono multipotenti; tuttavia, la capacità proliferativa di ANSCs/ANPCs Wr è significativamente ridotta e la neurogenesi è aumentata rispetto ad ANSCs/ANPCs Ctr. Una sottopopolazione di astrociti fortemente immunoreattivi per la GFAP è maggiormente rappresentata nelle colture Wr. Gli astrociti Wr mostrano soma ipertrofico con processi cellulari corti e spessi ed esercitano un effetto neurotossico sulla sopravvivenza motoneuronale; tali alterazioni ricordano quelle osservate in colture primarie di astrociti Wr adulti. In conclusione,il complemento di ANSCs/ANPCs Wr è alterato. Tali alterazioni potrebbero dipendere sia cambiamenti patologici nel microambiente circostante la nicchia subventricolare, sia dalla presenza della mutazione vps54