Editors' Note - N.D.L.R.

We hope you will find this the 2002 fall edition of the CHA bulletin enjoyable and informative. It is our first for us (Peter and John). It has been a quick but rewarding learning experience, and we would like to thank Joanne Mineault for her enthusiasm and assistance.Nous avons l'intention de veiller à la continuité des rubriques qui ont par le passé établi la pertinence de ce bulletin : les conférences, les publications, les nouvelles des départements ( bien sûr! ), les historiens à la une, etc. Ce faisant nous comptons poursuivre l'excellent travail de notre prédécesseur Don Wright et de ses collaborateurs

“Traveling the country ‘round”: migrations et syndicalisme chez les mouleurs de l’Ontario et du Québec membres de l’Iron Molders Union of North America, 1860 à 1892

La mobilité géographique des populations au XIXe siècle a suscité un grand intérêt et de nombreux travaux chez les historiens canadiens. Néanmoins, du côté de l'histoire des travailleurs, ce champ d’investigation ne fait que commencer à se développer. Le présent article vise à élargir nos connaissances sur le sujet en montrant l’importance centrale de la mobilité professionnelle dans le développement de l'une des principales organisations ouvrières au Canada pendant la seconde moitié du XIXe siècle : les sections canadiennes de l’Iron Molders Union of North America.Aux prises avec une mobilité phénoménale de leurs effectifs, les mouleurs élaborent en effet une réglementation syndicale des migrations qui transforme I’influence potentiellement négative de leurs déplacements en une force pour défendre ou promouvoir le statut du métier. Le succès est tel que leur mobilité géographique favorise considérablement l’expansion géographique de l'organisation et conduit à la formation de ses plus puissantes sections dans les localités où existe précisément la plus grande mobilité de mouleurs.The geographic mobility of people during the nineteenth century has generated considerable interest among Canadian historians. Nevertheless, with regard to workers' history, this topic has only begun to be explored. This article seeks to expand our understanding of the subject by showing the pivotal importance of professional mobility in one of the workers' central organizations in Canada during the second half of the nineteenth century, the Canadian sections of the Iron Molders' Union of North America.Grappling with a remarkable degree of mobility among its membership, the union worked out what was, in effect, a set of regulations regarding mobility which translated a potentially harmful consequence of high levels of mobility into a force for defending or promoting the workers' status. The union's success was such that geographic mobility actually helped in the geographic expansion of the organization, and led to the establishment of the most powerful branches in those areas where the greatest geographic mobility among workers prevailed

The 'un-shrunk' partial correlation in Gaussian graphical models

Abstract Background In systems biology, it is important to reconstruct regulatory networks from quantitative molecular profiles. Gaussian graphical models (GGMs) are one of the most popular methods to this end. A GGM consists of nodes (representing the transcripts, metabolites or proteins) inter-connected by edges (reflecting their partial correlations). Learning the edges from quantitative molecular profiles is statistically challenging, as there are usually fewer samples than nodes (‘high dimensional problem’). Shrinkage methods address this issue by learning a regularized GGM. However, it remains open to study how the shrinkage affects the final result and its interpretation. Results We show that the shrinkage biases the partial correlation in a non-linear way. This bias does not only change the magnitudes of the partial correlations but also affects their order. Furthermore, it makes networks obtained from different experiments incomparable and hinders their biological interpretation. We propose a method, referred to as ‘un-shrinking’ the partial correlation, which corrects for this non-linear bias. Unlike traditional methods, which use a fixed shrinkage value, the new approach provides partial correlations that are closer to the actual (population) values and that are easier to interpret. This is demonstrated on two gene expression datasets from Escherichia coli and Mus musculus. Conclusions GGMs are popular undirected graphical models based on partial correlations. The application of GGMs to reconstruct regulatory networks is commonly performed using shrinkage to overcome the ‘high-dimensional problem’. Besides it advantages, we have identified that the shrinkage introduces a non-linear bias in the partial correlations. Ignoring this type of effects caused by the shrinkage can obscure the interpretation of the network, and impede the validation of earlier reported results

Improving efficiency and robustness of enhanced assumed strain elements for nonlinear problems

The enhanced assumed strain (EAS) method is one of the most frequently used methods to avoid locking in solid and structural finite elements. One issue of EAS elements in the context of geometrically nonlinear analyses is their lack of robustness in the Newton–Raphson scheme, which is characterized by the necessity of small load increments and large number of iterations. In the present work we extend the recently proposed mixed integration point (MIP) method to EAS elements in order to overcome this drawback in numerous applications. Furthermore, the MIP method is generalized to generic material models, which makes this simple method easily applicable for a broad class of problems. In the numerical simulations in this work, we compare standard strain‐based EAS elements and their MIP improved versions to elements based on the assumed stress method in order to explain when and why the MIP method allows to improve robustness. A further novelty in the present work is an inverse stress‐strain relation for a Neo‐Hookean material model

A detailed guideline for the fabrication of single bacterial probes used for atomic force spectroscopy

The atomic force microscope (AFM) evolved as a standard device in modern microbiological research. However, its capability as a sophisticated force sensor is not used to its full capacity. The AFM turns into a unique tool for quantitative adhesion research in bacteriology by using “bacterial probes”. Thereby, bacterial probes are AFM cantilevers that provide a single bacterium or a cluster of bacteria as the contact-forming object. We present a step-by-step protocol for preparing bacterial probes, performing force spectroscopy experiments and processing force spectroscopy data. Additionally, we provide a general insight into the field of bacterial cell force spectroscopy