Bi-Hamiltonian Aspects of a Matrix Harry Dym Hierarchy

We study the Harry Dym hierarchy of nonlinear evolution equations from the bi-Hamiltonian view point. This is done by using the concept of an S-hierarchy. It allows us to define a matrix Harry Dym hierarchy of commuting Hamiltonian flows in two fields that projects onto the scalar Harry Dym hierarchy. We also show that the conserved densities of the matrix Harry Dym equation can be found by means of a Riccati-type equation.Comment: Revised version, 22 pages; a section on reciprocal transformations added. To appear in J. Math. Phys

Halloysite formation through in situ weathering of volcanic glass from trachytic pumices, Vico's volcano, Italy

L'étude minéralogique et pétrographique d'une ponce trachytique provenant des coulées pyroclastiques du volcan de Vico (Italie centrale) montre que l'altération des verres produit essentiellement une halloysite bien cristallisée avec conservation de leur texture. Les auteurs discutent les caractéristiques minéralogiques et structurales de cette argil

Suelos volcanicos endurecidos

In the sedimentary basin of Rieti (Central Italy) a Mollic Fragiudalf was studied in order to verify, through the analysis of differential dissolution kinetics of Si and Al, wether the presence of this two elements could be involved in determining the fragic characters of its deep horizons. The reuslts of the main physico-chemical analysis confirmed the fragic features of the deep horizons Bt3x and Ctgx which have been already observed in the field study. Differential dissolution of Si and Al was performed using 0,5 N NaOH at 25°C, and the values of silica and alumina obtained after each of ten consecutive extractions were cumulated to trace the cumulative curves of dissolution. Slope changes of the curves, which indicate changes in dissolution rate, allowed os to recognize three mineralogical phases with different degree of solubility. The total quantity of SiO2 and Al2O3 dissolved in all the extractions and relative to each of these three phases was estimated, by a graphic method, together with SiO2(Al2O3 molar ratio. This one was indicative of the mineralogical composition and behaviour of each horizon. This study showed an accumulation of free silica which could be present in the form of phytoliths or diatoms as well as a fine precipitate of opal-A and silica-gel in the whole soil, mainly in teh Ap and Ctgx horizons. Moreover neogenesis of clay was more evident in Bt3x horizon. The volcanic origin of the parent material, a trachytic ash fall, probably deposited in a lacustrine environment, could have favoured the availability of Si and the authigenic formation of halloysitic clay from the weathering of galss and feldspars. Our study therefore corroborates the findings of previous studies by Chadwick et al. (1987) and Karathanasis (1989) indicating the important role played by silica, probably as bonding agent, in contributing to produce characteristics of a fragipan. (Résumé d'auteur)

A 3-component extension of the Camassa-Holm hierarchy

We introduce a bi-Hamiltonian hierarchy on the loop-algebra of sl(2) endowed with a suitable Poisson pair. It gives rise to the usual CH hierarchy by means of a bi-Hamiltonian reduction, and its first nontrivial flow provides a 3-component extension of the CH equation.Comment: 15 pages; minor changes; to appear in Letters in Mathematical Physic

Digital Machines, Space, And Time: Towards A Behavioral Perspective Of Flexible Manufacturing

Recently, the diffusion of digital machines has further enhanced firms’ manufacturing flexibility, but also opened questions on potential challenges and implications in the production process. To respond to these timely issues, we adopt a behavioral perspective and comparatively explore how four different types of digital machines—characterized by increasing degrees of manufacturing flexibility—affect the perception and use of space and time for routines within the production plant. We qualitatively observe and compare 45 digital manufacturing machines, sampled across 14 firms in the British and Italian motorsport industry. A model emerges where four key mechanisms reshape the ‘space-machine’ and ‘time-machine’ routines. Such mechanisms mediate the relationship between manufacturing flexibility and firm performance. Further, we show how increasing digitalization in the manufacturing process enhances the establishment of new routines as flexible machines get introduced in the production. Finally, we discuss the theoretical and practical implications related to fostering a behavioral perspective in innovation and operations management studies

Flat bidifferential ideals and semihamiltonian PDEs

In this paper we consider a class of semihamiltonian systems characterized by the existence of a special conservation law. The density and the current of this conservation law satisfy a second order system of PDEs which has a natural interpretation in the theory of flat bifferential ideals. The class of systems we consider contains important well-known examples of semihamiltonian systems. Other examples, like genus 1 Whitham modulation equations for KdV, are related to this class by a reciprocal trasformation.Comment: 18 pages. v5: formula (36) corrected; minor change

COVID-19 Vaccination Status among Adults Admitted to Intensive Care Units in Veneto, Italy

: This cohort study examines admissions to intensive care units for COVID-19–associated acute respiratory distress syndrome by COVID-19 vaccination status among adults in the Veneto region of Italy from May to December 2021