Limited Role for C. pneumoniae, CMV and HSV-1 in Cerebral Large and Small Vessel Atherosclerosis

Aims: To explore whether Chlamydia pneumoniae, Cytomegalovirus and Herpes Simplex Virus type 1 could be detected in large and small cerebral arteries, as well as in an area of brain parenchyma where white matter lesions (leukoaraiosis) can be found, in patients with clinically unmanifested cerebrovascular atherosclerosis. Methods and results( Arterial specimens from the basilar artery and middle cerebral artery, and brain samples from the basal ganglia and periventricular white matter were obtained. Neuropathological changes were assessed in Haematoxylin-Eosin stained sections. Polymerase chain reaction (PCR) was performed on paraffin embedded sections. Subsequently, we performed immunohistochemical staining on samples, which were found positive in PCR. We failed to detect C. pneumoniae, CMV, or HSV-1, in any of the cerebral large vessels. In the brain tissue, we found only one case positive for CMV, and one for C. pneumoniae. Conclusions (our findings suggest a limited role for C. pneumoniae, CMV and HSV-1 in cerebral large and small vessel atherosclerosis

Interplay between pulsations and mass loss in the blue supergiant 55 Cygnus = HD 198478

Blue supergiant stars are known to display photometric and spectroscopic variability that is suggested to be linked to stellar pulsations. Pulsational activity in massive stars strongly depends on the star's evolutionary stage and is assumed to be connected with mass-loss episodes, the appearance of macroturbulent line broadening, and the formation of clumps in the wind. To investigate a possible interplay between pulsations and mass-loss, we carried out an observational campaign of the supergiant 55 Cyg over a period of five years to search for photospheric activity and cyclic mass-loss variability in the stellar wind. We modeled the H, He I, Si II and Si III lines using the nonlocal thermal equilibrium atmosphere code FASTWIND and derived the photospheric and wind parameters. In addition, we searched for variability in the intensity and radial velocity of photospheric lines and performed a moment analysis of the line profiles to derive frequencies and amplitudes of the variations. The Halpha line varies with time in both intensity and shape, displaying various types of profiles: P Cygni, pure emission, almost complete absence, and double or multiple peaked. The star undergoes episodes of variable mass-loss rates that change by a factor of 1.7-2 on different timescales. We also observe changes in the ionization rate of Si II and determine a multiperiodic oscillation in the He I absorption lines, with periods ranging from a few hours to 22.5 days. We interpret the photospheric line variations in terms of oscillations in p-, g-, and strange modes. We suggest that these pulsations can lead to phases of enhanced mass loss. Furthermore, they can mislead the determination of the stellar rotation. We classify the star as a post-red supergiant, belonging to the group of alpha Cyg variables.Comment: 20 pages, 18 figures, 3 tables, accepted to Astronomy & Astrophysic

A Methodology to Evaluate Canada's Arctic Shipping Regulations.

Transport Canada has the responsibility for regulating Arctic shipping in Canada as part of the Arctic Shipping Pollution Prevention Regulations. A Zone-Date System (ZDS) is used North of the 60\ub0 latitude. The ZDS is based on historical data of ice conditions up to the early 1970\u2019s and on the premise that the ice conditions are consistent from year-to-year. The ZDS consists of sixteen of geographic regions (Zones) and an associated Table that indicates the dates that each class of vessel is allowed in each geographical region. The Arctic Ice Regime Shipping System (AIRSS) is used by vessels wishing to access the Arctic Control Zones outside permissible dates for the vessels. The AIRSS, in contrast, allows shipping based on the actual, not historical, ice conditions. The objective of this study was to find how climate change would influence the veracity of the Zones and Dates used in the ZDS. This paper presents a methodology to evaluate Canada\u2019s Arctic shipping Regulations. The methodology comprises of analyzing the ice conditions in the North West Passage (NWP) shipping lanes and the access routes to the Port of Churchill in Hudson Strait. The existing and potential changes to ice regimes in the NWP and Hudson Strait shipping lanes due to the seasonal temperature variations and due to impact of climate change are examined. The length of the shipping season in the NWP and Hudson Strait is analyzed for each Zone by both the ZDS and the AIRSS, and both systems are then compared.NRC publication: Ye

An Operational Model of Iceberg Drift

A new iceberg drift, deterioration and calving model has been under development at the Canadian Ice Service (CIS). The model includes several new features including the utilization of detailed environmental forcing input, and a robust implicit numerical solution method. In particular, the vertical distribution of water current is incorporated in calculations of water drag force on the iceberg keel. The model is also the first to include treatment of calving, prediction of calved ice piece size distribution and deterioration, as well as the drift of calved pieces. This paper gives a description of the drift model formulation, and verification tests that include comparisons of model predictions with field observations. Additionally, the paper presents the outcome of a parametric study aimed at examining the sensitivity of iceberg drift to input parameters and environmental forcing. Tests examined the role of water and air drag coefficients, water current, wind waves and the waterline length of the iceberg. A number of scenarios of input water current, and wind drag force were also considered. The results determine the impact of the input parameters and variables on predicted iceberg tracks.NRC publication: Ye

Flow of Ice through Long Converging Channels

This paper examines some issues of the flow of ice in long and converging channels which may affect navigation. The emphasis is on pressure distributions and the role of ice properties and tidal currents. The present work employs an ice dynamics model that is based on a viscous plastic constitutive model with an elliptical yield envelope, the thickness redistribution model of Savage (2007), and a Particle-In-Cell (PIC) advection approach. Pressure distributions are obtained for an idealized geometry and uniform wind forcing. The results indicate that zones of relatively low pressures develop along the centre of the channel. Increasing the shear strength of the ice cover leads to somewhat lower pressures within such zones along the centre of the channel. That reduction of pressure is caused by the increased transfer of wind forces to land boundaries. Tides are shown to generally decrease pressures. The tidal currents also increase the overall drift, although drift slows and even reverses direction during parts of the tidal cycle.NRC publication: Ye

Structure and Evolution of Nearby Stars with Planets. I. Short-Period Systems

Using the Yale stellar evolution code, we have calculated theoretical models for nearby stars with planetary-mass companions in short-period nearly circular orbits: 51 Pegasi, Tau Bootis, Upsilon Andromedae, Rho Cancri, and Rho Coronae Borealis. We present tables listing key stellar parameters such as mass, radius, age, and size of the convective envelope as a function of the observable parameters (luminosity, effective temperature, and metallicity), as well as the unknown helium fraction. For each star we construct best models based on recently published spectroscopic data and the present understanding of galactic chemical evolution. We discuss our results in the context of planet formation theory, and, in particular, tidal dissipation effects and stellar metallicity enhancements.Comment: 48 pages including 13 tables and 5 figures, to appear in Ap