Multifragmentation of non-spherical nuclei : Analysis of central Xe + Sn collisions at 50 MeV/nucl

The influence of shape of expanding and rotating source on various characteristics of the multifragmentation process is studied. The analysis is based on the extension of the statistical microcanonical multifragmentation model. The comparison with the data is done for central Xe+Sn collisions at 50 A MeV as measured by INDRA Collaboration.Comment: 9 pages, 2 figures; Talk given at the XXVII International Workshop on Gross Properties of Nuclei and Nuclear Excitation, Hirschegg (Austria), January 17 - 23, 199

THE CANADA-FRANCE REDSHIFT SURVEY V: Global Properties of the Sample

The photometric and spectroscopic data of the CFRS survey of objects with 17.5 < I_{AB} < 22.5 are combined and analysed. The overall completeness is 85%. The redshift histogram of the sample is presented for 591 field galaxies with secure redshifts. The median redshift is z = 0.56, and the highest redshift observed is z = 1.3; 25 galaxies have z > 1 The distributions of magnitudes and colors demonstrate that galaxies at these high redshifts have very similar colors to those observed locally. The survey thus represents a major improvement in our knowledge of field galaxies at large look-back times. Only ~1% of the galaxies are as compact as stars (on images with FWHM ~ 0.9") and comparisons of the photometric and spectroscopic data show that only one galaxy was initially incorrectly classified spectroscopically as a star, and only two stars were misclassified as galaxies. It is demonstrated that the redshift distributions in the five fields are statistically consistent with each other, once the reduction in the effective number of independent galaxies due to small-scale clustering in redshift is taken into account. The photometric properties of the spectroscopically-unidentified objects indicate that most are likely to be galaxies rather than stars. At least half of these must have the same redshift distribution as the identified galaxies, and a combination of magnitudes, colors and compactness of the remaining unidentified galaxies is used to predict their redshifts. The majority are probably ordinary galaxies at the high redshift end of our sample, including some quiescent galaxies at z > 1.0, rather than some new or unusual population.Comment: 20 uuencoded postscript pages (first part) with 12 figures (second part). Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.html and coming soon on a CFRS homepage. Accepted June 19, scheduled for Dec 10 issue of Ap

The CANADA-FRANCE REDSHIFT SURVEY I: Introduction to the Survey, Photometric Catalogs and Surface Brightness Selection Effects

The Canada-France Redshift Survey has been undertaken to provide a large well-defined sample of faint galaxies at high redshift in which the selection criteria match as closely as possible those of samples of nearby galaxies. The survey is designed to have a median redshift of z ~ 0.6 corresponding to a look-back time of half the present age of the Universe for Omega ~ 1. Such a survey can then be used for studying many different aspects of the evolution of galaxies over the interval 0 < z < 1. In this paper we describe the selection of the fields, the multicolor imaging observations and the construction and validation of the photometric catalogs. Particular attention is paid to quantifying the unavoidable selection effects in surface brightness and their impact on the survey is assessed in the context of the properties of known populations of galaxies. The photometric catalogs contain several thousand objects brighter than I_{AB}< 22.5 and are essentially complete for central surface brightnesses as faint as $\mu_{AB}(I)$ $\sim$ 24.5 mag arcsec$^{-2}$. This should be sufficient to include both normal surface brightness galaxies and prototypes of extreme low surface brightness galaxies.Comment: 17 pages, 2 tables, 10 postscript figures (in 2 parts), uses aaspp.sty Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.html and coming soon on a CFRS homepag

A search for gravitational lensing in 38 X-ray selected clusters of galaxies

We present the results of a CCD imaging survey for gravitational lensing in a sample of 38 X-ray-selected clusters of galaxies. Our sample consists of the most X-ray luminous (Lx>= 2x10^{44} erg s^{-1}) clusters selected from the Einstein Observatory Extended Medium Sensitivity Survey (EMSS) that are observable from Mauna Kea (dec > -40deg). The sample spans a redshift range of 0.15 0.5. CCD images of the clusters were obtained in excellent seeing. There is evidence of strong gravitational lensing in the form of giant arcs (length l > 8'', axis ratio l/w > 10) in 8 of the 38 clusters. Two additional clusters contain shorter arclets, and 6 more clusters contain candidate arcs that require follow-up observations to confirm their lensing origin. Since the survey does not have a uniform surface brightness limit we do not draw any conclusion based on the statistics of the arcs found. We note, however, that 60% (3 of 5) of the clusters with Lx > 10^{45} erg s^{-1}, and none of the 15 clusters with Lx < 4x10^{44} erg s^{-1} contain giant arcs, thereby confirming that high X-ray luminosity does identify the most massive systems, and thus X-ray selection is the preferred method for finding true, rich clusters at intermediate and high redshifts. The observed geometry of the arcs, most of which are thin, have large axis ratios (l/w > 10), and are aligned orthogonal to the optical major axes of the clusters, indicate the cluster core mass density profiles must be compact (steeper than isothermal). In several cases, however, there is also some evidence, in the form of possible radial arcs, for density profiles with finite core radii.Comment: Latex file, 17 pages, 7 jpeg figures, to be published in Astronomy and Astrophysics Supplement

THE CANADA-FRANCE REDSHIFT SURVEY IX: HST Imaging of High-Redshift Field Galaxies

HST B and I images are presented of 32 CFRS galaxies with secure redshifts in the range 0.5 < z < 1.2. These galaxies exhibit the same range of morphological types as seen locally, i.e., ellipticals, spirals and irregulars. The galaxies look far less regular in the $B$ images (rest-frame ultraviolet) than at longer wavelengths, underlining the fact that optical images of galaxies at still higher redshift should be interpreted with caution. Quantitative analyses of the galaxies yield disk sizes, bulge fractions, and colors for each component. At these redshifts, galaxy disks show clear evidence for surface brightness evolution. The mean rest-frame central surface brightness of the disks of normal late-type galaxies is mu_{AB}(B)=20.2 \pm 0.25 mag arcsec^{-2}, about 1.2 mag brighter than the Freeman (1970) value. Some degree of peculiarity is measurable in 10 (30%) of the galaxies and 4 (13%) show clear signs of interaction/mergers. There are 9 galaxies (30%) dominated by blue compact components. These components, which appear to be related to star formation, occur most often in peculiar/asymmetric galaxies (some of which appear to be interacting), but a few are in otherwise normal galaxies. Thus, of the galaxies bluer than present-day Sb, one-third are "blue nucleated galaxies", and half are late-type galaxies with disks which are significantly brighter than normal galaxies at z=0. Taken together, these two effects must be responsible for much of the observed evolution of the luminosity function of blue galaxies.Comment: uuencoded compressed postscript, 8 pages, 1 table + 5 figures in a separate part. Also available at http://www.astro.utoronto.ca/~lilly/CFRS/ . Accepted for publication in ApJ Letter

Somatic and cognitive stress management techniques: their effect on measures of stress and competency in managers

Stress management interventions (SMIs) are increasingly used by organisations across both private and public settings. Such interventions are employed with the expectation that they will be effective in reducing levels of stress in participants and in turn, will provide a return to the organisation by way of increased productivity through performance improvements of those employees whose stress has been reduced. Despite the increasing popularity of SMIs, there exists a lack of evidence on whether they have any effect on the performance of users, and on the relative effectiveness of the components that often make up SMIs. Although the literature addressing SMIs and their effects is increasing, relatively few studies directly compare different techniques, and even fewer employ randomised controlled designs or follow-up measures. The assumed relationship between the reduction of stress and improvement of managerial performance does not appear to have been tested with a randomised controlled trial. The term “stress” as used in this study specifically denotes the concept of “distress” as defined by Selye (1956; 1987). To support this use of the term, the evolution of current terminology in the field of occupational stress is briefly discussed with specific reference to the development and influence in the wider literature of the Yerkes Dodson Law (Yerkes, 1909). The aims of this thesis were to (1) compare the relative effectiveness of two component techniques often used in SMIs (somatic and cognitive techniques) in the reduction of stress, and (2) to examine the effect of the use of these techniques on the performance of managers in their workplace. Study One was a randomised controlled trial assessing the effect of the use of somatic and cognitive stress management interventions on stress and performance in managers. Participants were 112 corporate managers who were randomly assigned to one of two intervention groups (somatic or cognitive technique training) or to a wait list control group. The intervention groups were trained in their respective techniques over a 4 week period in brief (20-30 minute) face-to-face workshop sessions. Participants were provided with recordings of the techniques to assist practice between training sessions. At baseline, stress was assessed using the Occupational Stress Inventory – Revised Edition (OSI-R, Osipow, 1998), and managerial performance was assessed with the Personal Qualities Competency from the Inventory of Management Competencies (IMC, Saville Holdsworth Ltd., 1993). In the case of the IMC, self, colleague, and subordinate assessments were used. On completion of the 4 week intervention, the OSI-R was readministered, and then at week 12 and week 24, follow-up assessments of stress and managerial performance took place. At the week 12 follow-up, MANOVA for the OSI-R showed no significant difference between the somatic and cognitive interventions in their effect on stress, although both interventions did reduce stress relative to the wait list control group, as measured by the OSI-R. A significant intervention effect was also shown (ηp2 = 0.089, p = 0.002) for the combined intervention groups (cognitive and somatic). MANOVA for the Personal Qualities Competency showed a significant intervention effect for the self (ηp2 = 0.077, p = 0.008) and colleague (ηp2 = 0.064, p = 0.013) assessments, and a no significant effect (ηp2 = 0.032, p = 0.063) for the subordinate assessment at the week 12 follow-up point. Unfortunately, withdrawal and attrition reduced the sample size below that required for analysis at the week 24 follow-up point. Study Two was designed as a follow-up qualitative study that aimed to gather information on participants’ perceptions of the effects of the interventions on their stress and performance, and of their reasons for completion or no completion of the SMI. In this study, 14 participants from Study One took part in semi-structured interviews after the final follow-up assessment (week 24) for that study. The interviews were structured to elicit responses concerning participants’ perceptions of the demands of their workplace and their stress, their experience of using the stress management techniques (including perceived benefits or behavioural changes from that use), their reasons for completion or no completion of the intervention, and their own definitions of stress. Several important findings emerged from this study. First, participants described their workplace as characterised by high pressure and demand with rapid change and a perceived lack of personal control. Second, participants who continued to use the techniques they had learned after the formal intervention was completed did so because they perceived personal benefits in terms of their ability to relax and in terms of their perceptions of workload and demand. For those who did not complete the intervention, the predominant reasons reported for no completion were workplace task demands, lack of top management commitment to an intervention of this nature, and lack of personal gain once the techniques had been learned. In relation to defining stress, participants did not have agreement, but rather reported definitions reflecting a multifaceted complex amalgam of physiological, psychological, and emotional aspects. Research such as this is important in terms of its contribution to the general field of occupational stress and its alleviation. It addresses a long-standing need to assess the relative effectiveness of some of the subcomponents commonly employed as part of more complex multifaceted approaches to SMIs, and the effect of the techniques on both stress and performance. This thesis makes several contributions to existing knowledge. First, this thesis clarifies the origin of the Yerkes Dodson Law and its relevance to current stress management thinking. In management texts distress has come to be regarded as too much stress or pressure. This is coupled with the idea that some stress has a positive impact on performance due to an earlier and erroneous interpretation of the Yerkes Dodson Law. Second, Study One provides evidence of the relative effectiveness of two different SMI components in the reduction of individuals’ occupational stress, as well as evidence for the effectiveness of individual focussed SMIs in the reduction of stress in corporate managers. Third, Study One provides evidence for a positive effect on managers’ performance consequent to their use of stress management techniques. This thesis also sheds light on managers’ definitions of stress, and their reasons for completion or no completion of SMIs. In summary, individual focussed (or secondary) SMIs have the potential to reduce stress and to improve performance in corporate managers as perceived by both the individual and others in the workplace