CSM-178 - Learning to Recognise Human Faces

Recognition of human faces is an ambitious problem, being currently attacked by psychologists, cognitive scientists, and - to a limited extent - also by AI-community. Nevertheless, computer programs solving this task are still rare. Most of them rely on the artificial neural nets, which are not used in our approach to the problem. The presented paper reports a successful attempt to extract a reliable set of stable intrinsic features from the images by using edge-detection, boundary grouping, and boundary characterisation. Particular attention is paid to the local properties of the boundaries at junction points. No attempt to attach high-level meaning to the individual features is made. The resulting symbolic descriptions are processed by a simple Machine-Learning program constructing a recognition scheme in the form of a decision tree. In spite of some constraints - frontal head-on view, limited training set - the results, as measured by predictive accuracy, are promising for dealing with larger numbers of individuals

X-ray emission from hydrodynamical simulations in non-LTE wind models

Hot stars are sources of X-ray emission originating in their winds. Although hydrodynamical simulations that are able to predict this X-ray emission are available, the inclusion of X-rays in stationary wind models is usually based on simplifying approximations. To improve this, we use results from time-dependent hydrodynamical simulations of the line-driven wind instability (seeded by the base perturbation) to derive the analytical approximation of X-ray emission in the stellar wind. We use this approximation in our non-LTE wind models and find that an improved inclusion of X-rays leads to a better agreement between model ionization fractions and those derived from servations. Furthermore, the slope of the L_x-L relation is in better agreement with observations, however the X-ray luminosity is underestimated by a factor of three. We propose a possible solution for this discrepancy.Comment: 9 pages, accepted for publication in Astronomy and Astrophysic

Hybrid GIS and Remote Sensing in Environmental Applications

Geographical information systems (GIS) are a relatively new and rapidly developing class of computer applications. They show considerable potential in a growing number of application domains, regional and environmental planning and management being one of them. The integration of GIS methods adds a key technology for spatial analysis to the set of tools of applied systems analysis, and environmental systems analysis in particular. The two papers presented in this volume address the use of GIS and satellite imagery in environmental applications. Hybrid GIS, that combine both vector and raster information, are the topics of the first report that was presented at the "EARSel Workshop on Relationship of Remote Sensing and Geographical Information Systems" which took place in Hannover, Germany in September 1991. The integration of satellite imagery in a global change information system that also uses rule-based expert systems methods, together with GIS data structures and tools, is the theme of the second part. This paper was presented at the "25th International Symposium - Remote Sensing and Global Environmental Change, Tools for Sustainable Development," held in Graz, Austria, in September 1993

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

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