Optimization of Conditions for Studies of Protein Unfolding by Hydrogen Exchange/Mass Spectrometry

Understanding the forces driving protein folding and aggregation is an essential step in developing means for controlling these important processes. Amide hydrogen exchange, coupled with mass spectrometry, has become an important method for studying protein unfolding and refolding. To extend procedures developed to study unfolding of relatively soluble proteins to less soluble, aggregation-prone proteins requires special considerations. This publication describes a general strategy developed using yeast transaldolase, which aggregates easily under conditions required to study its unfolding. Results presented here show that reducing the protein concentration to the nanomolar range is essential for managing aggregation of transaldolase. In addition, the present results point to use of relatively high concentrations of denaturants and short incubation times to, minimize aggregation. These results also show how amide hydrogen exchange, coupled with mass spectrometry, ran be used to study soluble aggregates

Radar studies of the vertical distribution of insects migrating over southern Britain: the influence of temperature inversions on nocturnal layer concentrations

Insects migrating over two sites in southern UK (Malvern in Worcestershire, and Harpenden in Hertfordshire) have been monitored continuously with nutating vertical-looking radars (VLRs) equipped with powerful control and analysis software. These observations make possible, for the first time, a systematic investigation of the vertical distribution of insect aerial density in the atmosphere, over temporal scales ranging from the short (instantaneous vertical profiles updated every 15 min) to the very long (profiles aggregated over whole seasons or even years). In the present paper, an outline is given of some general features of insect stratification as revealed by the radars, followed by a description of occasions during warm nights in the summer months when intense insect layers developed. Some of these nocturnal layers were due to the insects flying preferentially at the top of strong surface temperature inversions, and in other cases, layering was associated with higher-altitude temperature maxima, such as those due to subsidence inversions. The layers were formed from insects of a great variety of sizes, but peaks in the mass distributions pointed to a preponderance of medium-sized noctuid moths on certain occasions

Opening Open Universities: The Canadian Experience

This article examines, from an administrative/management perspective, the two open universities which have been created in Canada in the 1970's, Athabasca University in Alberta and the Te´le´-universite´ in Que´bec. A study of the initial planning reveals that effective planning requires balanced attention to means and ends. The new management structures required for this type of institution, coupled with the climate of acute uncertainty in which it operates in the early days, require particularly able and committed leadership. That both institutions have been rather successful argues for the importance of the open university concept itself.Le présent article étudie, d'une perspective de l'administration et de la gestion, les deux "universités ouvertes"créées au Canada au cours des années 70 - à savoir - Athabaska University en Alberta et la Télé-université au Québec. Une étude de la planification initiale révèle que, pour procéder de façon efficace, il faut accorder une attention équilibrée aux moyens et aux fins. Les nouvelles-structures de gestion requises pour ce genre d'institution, ainsi que le climat d'incertitude profonde qui marque leurs débuts, exigent la présence des responsables compétents et engagés. Le fait que les deux institu-tions ont été plus ou moinx couronnées de succès est un témoignage de l'importance du concept en soi de "l'université ouverte"

Radio Source Heating in the ICM: The Example of Cygnus A

One of the most promising solutions for the cooling flow problem involves energy injection from the central AGN. However it is still not clear how collimated jets can heat the ICM at large scale, and very little is known concerning the effect of radio lobe expansion as they enter into pressure equilibrium with the surrounding cluster gas. Cygnus A is one of the best examples of a nearby powerful radio galaxy for which the synchrotron emitting plasma and thermal emitting intra-cluster medium can be mapped in fine detail, and previous observations have inferred possible shock structure at the location of the cocoon. We use new XMM-Newton observations of Cygnus A, in combination with deep Chandra observations, to measure the temperature of the intra-cluster medium around the expanding radio cavities. We investigate how inflation of the cavities may relate to shock heating of the intra-cluster gas, and whether such a mechanism is sufficient to provide enough energy to offset cooling to the extent observed.Comment: To appear in the Proceedings of "Heating vs. Cooling in Galaxies and Clusters of Galaxies", August 2006, Garching (Germany), Eds. H. Boehringer, G.W. Pratt, A. Finoguenov, P. Schuecker, Springer-Verlag series "ESO Astrophysics Symposia", p.101, in press. 8 pages, 3 multiple figure

Description of inclusive scattering of 4.045 GeV electrons from D

We exploit a relationship between the Structure Functions of nucleons, the physical deuteron and of a deuteron, composed of point-nucleons to compute angular distributions of inclusive cross sections of 4.05 GeV electrons. We report general agreement with data and interpret the remaining discrepancies. We discuss the potential of the data for information on neutron structure functions $F_k^n(x,Q^2)$ and the static form factor $G_M^n(Q^2)$.Comment: 9 pages,1 Fig., PS fil

Symmetry breaking due to Dzyaloshinsky-Moriya interactions in the kagome lattice

Due to the particular geometry of the kagom\'e lattice, it is shown that antisymmetric Dzyaloshinsky-Moriya interactions are allowed and induce magnetic ordering. The symmetry of the obtained low temperature magnetic phases are studied through mean field approximation and classical Mont\'e Carlo simulations. A phase diagram relating the geometry of the interaction and the ordering temperature has been derived. The order of magnitude of the anisotropies due to Dzyaloshinsky-Moriya interactions are more important than in non-frustrated magnets, which enhances its appearance in real systems. Application to the jarosites compounds is proposed. In particular, the low temperature behaviors of the Fe and Cr-based jarosites are correctly described by this model.Comment: 6 (revtex4) twocolumn pages, 6 .eps figures. Submitted to Phys. Rev.