MHD oblique stagnation-point flow of a Newtonian fluid

The steady two-dimensional oblique stagnation-point flow of an electrically conducting Newtonian fluid in the presence of a uniform external electromagnetic field (E0, H0) is analyzed, and some physical situations are examined. In particular, if E0 vanishes, H0 lies in the plane of the flow, with a direction not parallel to the boundary, and the induced magnetic field is neglected, it is proved that the oblique stagnation-point flow exists if, and only if, the external magnetic field is parallel to the dividing streamline. In all cases it is shown that the governing nonlinear partial differential equations admit similarity solutions, and the resulting ordinary differential problems are solved numerically. Finally, the behaviour of the flow near the boundary is analyzed; this depends on the Hartmann number if H0 is parallel to the dividing streamline

Does residence time affect responses of alien species richness to environmental and spatial processes?

One of the most robust emerging generalisations in invasion biology is that the probability of invasion increases with the time since introduction (residence time). We analysed the spatial distribution of alien vascular plant species in a region of north-eastern Italy to understand the influence of residence time on patterns of alien species richness. Neophytes were grouped according to three periods of arrival in the study region (1500–1800, 1800–1900, and > 1900). We applied multiple regression (spatial and nonspatial) with hierarchical partitioning to determine the influence of climate and human pressure on species richness within the groups. We also applied variation partitioning to evaluate the relative importance of environmental and spatial processes. Temperature mainly influenced groups with species having a longer residence time, while human pressure influenced the more recently introduced species, although its influence remained significant in all groups. Partial regression analyses showed that most of the variation explained by the models is attributable to spatially structured environmental variation, while environment and space had small independent effects. However, effects independent of environment decreased, and spatially independent effects increased, from older to the more recent neophytes. Our data illustrate that the distribution of alien species richness for species that arrived recently is related to propagule pressure, availability of novel niches created by human activity, and neutral-based (dispersal limitation) processes, while climate filtering plays a key role in the distribution of species that arrived earlier. This study highlights the importance of residence time, spatial structure, and environmental conditions in the patterns of alien species richness and for a better understanding of its geographical variation

Magnitudes of V(xb) CKM matrix elements

We review the current status of the absolute values of the CKM matrix elements V(xb), with particular attention to latest determinations.Comment: 12 pages, no figs.; in Proceedings of the 14th International Conference on B-Physics at Hadron Machines, April 8-12, 2013, Bologna, Ital

An Analysis of Settlement Risk Contagion in Alternative Securities Settlement Architecture

This paper compares the so-called gross and net architectures for securities settlement. It studies the settlement risk arising from exogenous operational delays and compares the importance of settlement failures under the two architectures, as a function of the length of the settlement cycle and of different market conditions. Under both architectures, settlement failures are non-monotonically related to the length of settlement cycle. There is no evidence that continuous time settlement provides always higher stability. Gross systems appear to be more stable than net systems

Crossovers between epigenesis and epigenetics. A multicenter approach to the history of epigenetics (1901-1975)

The origin of epigenetics has been traditionally traced back to Conrad Hal Waddington's foundational work in 1940s. The aim of the present paper is to reveal a hidden history of epigenetics, by means of a multicenter approach. Our analysis shows that genetics and embryology in early XX century--far from being non-communicating vessels--shared similar questions, as epitomized by Thomas Hunt Morgan's works. Such questions were rooted in the theory of epigenesis and set the scene for the development of epigenetics. Since the 1950s, the contribution of key scientists (Mary Lyon and Eduardo Scarano), as well as the discussions at the international conference of Gif-sur-Yvette (1957) paved the way for three fundamental shifts of focus: 1. From the whole embryo to the gene; 2. From the gene to the complex extranuclear processes of development; 3. From cytoplasmic inheritance to the epigenetics mechanisms

MHD OBLIQUE STAGNATION-POINT FLOW OF A MICROPOLAR FLUID

The steady two-dimensional oblique stagnation-point flow of an electrically conducting micropolar fluid in the presence of a uniform external electromagnetic field (E0,H0) is analyzed and some physical situations are examined. In particular, if E0 vanishes, H0 lies in the plane of the flow, with a direction not parallel to the boundary, and the induced magnetic field is neglected. It is proved that the oblique stagnationpoint flow exists if, and only if, the external magnetic field is parallel to the dividing streamline. In all cases it is shown that the governing nonlinear partial differential equations admit similarity solutions and the resulting ordinary differential problems are solved numerically. Finally, the behaviour of the flow near the boundary is analyzed; this depends on the three dimensionless material parameters, and also on the Hartmann number if H0 is parallel to the dividing streamline

Complex networks analysis in socioeconomic models

This chapter aims at reviewing complex networks models and methods that were either developed for or applied to socioeconomic issues, and pertinent to the theme of New Economic Geography. After an introduction to the foundations of the field of complex networks, the present summary adds insights on the statistical mechanical approach, and on the most relevant computational aspects for the treatment of these systems. As the most frequently used model for interacting agent-based systems, a brief description of the statistical mechanics of the classical Ising model on regular lattices, together with recent extensions of the same model on small-world Watts-Strogatz and scale-free Albert-Barabasi complex networks is included. Other sections of the chapter are devoted to applications of complex networks to economics, finance, spreading of innovations, and regional trade and developments. The chapter also reviews results involving applications of complex networks to other relevant socioeconomic issues, including results for opinion and citation networks. Finally, some avenues for future research are introduced before summarizing the main conclusions of the chapter.Comment: 39 pages, 185 references, (not final version of) a chapter prepared for Complexity and Geographical Economics - Topics and Tools, P. Commendatore, S.S. Kayam and I. Kubin Eds. (Springer, to be published

Strategic environmental assessment implementation of transport and mobility plans. The case of italian regions and provinces

Transport and mobility plans imply strategies and actions that affect the environment. The European Union has introduced in 2001 the strategic environmental assessment (SEA) to take into account and mitigate adverse environmental effects in planning and decision-making. SEA limited implementation has attracted the interest of many scholars that have sought methods able to assess the quality of SEA processes by identifying vices and virtues in practice. In this paper, we measure the quality of eight SEAs for transport and mobility plans of regional and provincial administrations of Italy. Results show that the overall quality level of SEA reports is only barely sufficient, Abruzzo is among the virtuous and Piedmont among the critical administrations. We also stress that the determination of impact significance has received the worse quality score. We finally compare our results to other Italian and British homologous cases finding interesting and generally confirmative evidence