Can we model DNA at the mesoscale ? Comment on: Fluctuations in the DNA double helix: A critical review

Comment on "Fluctuations in the DNA double helix: A critical review" by Frank-Kamenetskii and Prakas

Discreteness effects on soliton dynamics: a simple experiment

We present a simple laboratory experiment to illustrate some aspects of the soliton theory in discrete lattices with a system that models the dynamics of dislocations in a crystal or the properties of adsorbed atomic layers. The apparatus not only shows the role of the Peierls-Nabarro potential but also illustrates the hierarchy of depinning transitions and the importance of the collective motion in mass transport.Comment: 9 pages, 4 Figures, to Appear in American Journal of Physic

Digital Mathematics Libraries: The Good, the Bad, the Ugly

The idea of a World digital mathematics library (DML) has been around since the turn of the 21th century. We feel that it is time to make it a reality, starting in a modest way from successful bricks that have already been built, but with an ambitious goal in mind. After a brief historical overview of publishing mathematics, an estimate of the size and a characterisation of the bulk of documents to be included in the DML, we turn to proposing a model for a Reference Digital Mathematics Library--a network of institutions where the digital documents would be physically archived. This pattern based rather on the bottom-up strategy seems to be more practicable and consistent with the digital nature of the DML. After describing the model we summarise what can and should be done in order to accomplish the vision. The current state of some of the local libraries that could contribute to the global views are described with more details

Determinants of Desired Career Paths among Canadian Engineers

The goal of this research is to study five career paths available to engineers and to understand what leads them to prefer the management path to other career path possibilities (i.e. the technical path, the project-based path, the entrepreneurial path, and the hybrid path). A questionnaire survey was conducted using a sample of 900 male and female engineers from a large Canadian province. The0501n results show that several determinants under study (mainly individual-related factors, such as career anchors and education) effectively distinguish engineers who want to pursue a management path from those who choose other career paths, especially technical ones Cette recherche vise à étudier six orientations que les ingénieurs peuvent vouloir donner à leur carrière et à comprendre ce qui les amène à privilégier certains choix de carrière. Les possibilités de carrière retenues sont la voie de gestion, la voie technique, la voie de projet, la voie entreprenieuriale, la voie hybride et une nouvelle carrière. Une enquête par questionnaire a été réalisée auprès de 900 ingénieurs à travers le Québec, dont 403 femmes. Les résultats démontrent principalement que plusieurs des facteurs étudiés (principalement les facteurs individuels comme les ancres de carrière et la scolarité) permettent de distinguer efficacement les ingénieurs qui désirent poursuivre une carrière en gestion de ceux qui aspirent à d'autres voies de carrière.Engineers, career, career path, entrepreneurial career, career anchor, Ingénieurs, carrière, voies de carrière, changement de carrière

Convergence and round-off errors in a two-dimensional eigenvalue problem using spectral methods and Arnoldi-Chebyshev algorithm

An efficient way of solving 2D stability problems in fluid mechanics is to use, after discretization of the equations that cast the problem in the form of a generalized eigenvalue problem, the incomplete Arnoldi-Chebyshev method. This method preserves the banded structure sparsity of matrices of the algebraic eigenvalue problem and thus decreases memory use and CPU-time consumption. The errors that affect computed eigenvalues and eigenvectors are due to the truncation in the discretization and to finite precision in the computation of the discretized problem. In this paper we analyze those two errors and the interplay between them. We use as a test case the two-dimensional eigenvalue problem yielded by the computation of inertial modes in a spherical shell. This problem contains many difficulties that make it a very good test case. It turns out that that single modes (especially most-damped modes i.e. with high spatial frequency) can be very sensitive to round-off errors, even when apparently good spectral convergence is achieved. The influence of round-off errors is analyzed using the spectral portrait technique and by comparison of double precision and extended precision computations. Through the analysis we give practical recipes to control the truncation and round-off errors on eigenvalues and eigenvectors.Comment: 15 pages, 9 figure

SPAD: a distributed middleware architecture for QoS enhanced alternate path discovery

In the next generation Internet, the network will evolve from a plain communication medium into one that provides endless services to the users. These services will be composed of multiple cooperative distributed application elements. We name these services overlay applications. The cooperative application elements within an overlay application will build a dynamic communication mesh, namely an overlay association. The Quality of Service (QoS) perceived by the users of an overlay application greatly depends on the QoS experienced on the communication paths of the corresponding overlay association. In this paper, we present SPAD (Super-Peer Alternate path Discovery), a distributed middleware architecture that aims at providing enhanced QoS between end-points within an overlay association. To achieve this goal, SPAD provides a complete scheme to discover and utilize composite alternate end-to end paths with better QoS than the path given by the default IP routing mechanisms