Predicting crystal structures: the Parrinello-Rahman method revisited

By suitably adapting a recent approach [A. Laio and M. Parrinello, PNAS, 99, 12562 (2002)] we develop a powerful molecular dynamics method for the study of pressure-induced structural transformations. We use the edges of the simulation cell as collective variables. In the space of these variables we define a metadynamics that drives the system away from the local minimum towards a new crystal structure. In contrast to the Parrinello-Rahman method our approach shows no hysteresis and crystal structure transformations can occur at the equilibrium pressure. We illustrate the power of the method by studying the pressure-induced diamond to simple hexagonal phase transition in a model of silicon.Comment: 5 pages, 2 Postscript figures, submitte

INTEGRATION AND COMPARISON OF CLOSE-RANGE SFM METHODOLOGIES FOR THE ANALYSIS AND THE DEVELOPMENT OF THE HISTORICAL CITY CENTER OF BETHLEHEM

Abstract. The present paper illustrates a part of the methodological process of image-based acquisition developed for the documentation of the historical city center of Bethlehem, in the Middle East territory. The first mission of research activities, developed inside the international cooperation project "Management and control of urban growth for the development of heritage and improvement of life in the city of Bethlehem" (2018–2021), coordinated by University of Pavia in collaboration with the Municipality of Pavia and financed with the contribution of AICS (Italian Agency for Cooperation and Development), has been carried on through combined application of digital instruments, TLS and UAV, with the aim of developing "smart", low-cost and rapid execution procedures for the production of a reliable three-dimensional model of the historic city center. The paper shows the application of different photogrammetric survey campaigns in a portion of the historical town, acquisition problems and tests of morphometrical reliability of each output, in order to develop a general SfM database consisting of different definition levels of the photogrammetric models of historical city center.</p

Soft Covariant Gauges on the Lattice

We present an exploratory study of a one-parameter family of covariant, non-perturbative lattice gauge-fixing conditions, that can be implemented through a simple Monte Carlo algorithm. We demonstrate that at the numerical level the procedure is feasible, and as a first application we examine the gauge dependence of the gluon propagator.Comment: 11 pages, Latex, epsf.sty included + 5 PostScript picture

In vitro release of lectins by Phallusia mamillata hemocytes

α-Lactose specific lectins are released from Phallusia mamillata hemocytes during short-term cultures. The molecular weight of the subunits, the immunological cross-reaction and the sugar specificity suggest that the released lectins are similar to those isolated from the sonicated hemocytes. Because lectin release appears to take place independently of active protein synthesis, the possibility exists that lectins are pre-formed, stored in hemocytes and released when in vitro conditions stimulate the cells. © 1991

easySTORM: a robust, lower-cost approach to localisation and TIRF microscopy

TIRF and STORM microscopy are super-resolving fluorescence imaging modalities for which current implementations on standard microscopes can present significant complexity and cost. We present a straightforward and low-cost approach to implement STORM and TIRF taking advantage of multimode optical fibres and multimode diode lasers to provide the required excitation light. Combined with open source software and relatively simple protocols to prepare samples for STORM, including the use of Vectashield for non-TIRF imaging, this approach enables TIRF and STORM imaging of cells labelled with appropriate dyes or expressing suitable fluorescent proteins to become widely accessible at low cost