Modular Invariant of Quantum Tori II: The Golden Mean

In our first article in this series ("Modular Invariant of Quantum Tori I: Definitions Nonstandard and Standard" arXiv:0909.0143) a modular invariant of quantum tori was defined. In this paper, we consider the case of the quantum torus associated to the golden mean. We show that the modular invariant is approximately 9538.249655644 by producing an explicit formula for it involving weighted versions of the Rogers-Ramanujan functions

Temporal variations in the understory photosynthetic photon flux density of deciduous stand: the effects of canopy development, solar elevation, and sky conditions

The effects of canopy development, solar elevation, and sky conditions on temporal variation in photosynthetic photon flux density (PPFD) were examined within a 9-year-old bigleaf maple stand on Vancouver Island (Canada). PPFD was measured every second and stored as 10-min averages from 18 May to 14 October 1996, at 52 microsites characterised according to their growing season %PPFD (GSP). PPFD and %PPFD variability was examined at three different temporal levels. Specific days in May, July, and September with clear and overcast sky conditions were selected to separate the effects of canopy development and solar elevation on diurnal and seasonal light variability. \ud Diurnal light variability expressed as the mean of the difference between two consecutive 10-min averages of PPFD and %PPFD decreased with increasing GSP on clear days in May. For clear days in July and September, variability was characterised by arc-shaped relationships with high variability for microsites receiving between 20 and 80% GSP and lower variability for microsites below 20 and above 80% GSP. On overcast days, diurnal variability in PPFD increased with increasing GSP while diurnal variability in %PPFD showed an arc-shape relationship. The coefficient of variation of PPFD and %PPFD decreased with increasing GSP on clear days and sunflecks decreased with decreasing GSP and from May to September. \ud Day-to-day light variability expressed as the mean difference between consecutive daily PPFD increased with increasing GSP while the mean difference between consecutive daily %PPFD was higher for microsites receiving between 20 and 80% GSP. The coefficient of variation for the daily PPFD and %PPFD was higher for microsites receiving <20% GSP compared to other microsites. Seasonal light variability showed that microsites with <50% GSP received up to eight times more light in May than in July on both clear and overcast sky conditions because of canopy development. From July to September in clear sky conditions, decrease in light was variable for microsites receiving <40% GSP; probably because of the position of microsites in relation to the solar track. On overcast days, mean daily PPFD above canopy and in the understorey was 2 to 3 times higher in July than in September while mean daily %PPFD remained stable. The possible effects of the types of diurnal and day-to-day light variability on physiological and morphological responses of understorey plants are discussed

Comparison of various methods for estimating the mean growing season percent photosynthetic photon flux density in forests

Five methods for estimating the mean growing season percent photosynthetic photon flux density (PPFD) were compared to continuous measurements of PPFD throughout the growing season within a young bigleaf maple stand on Vancouver Island (Canada). Measured PPFD was recorded continuously as 10-min averages over the growing season (May 18-October 14, 1996) using 52 gallium arsenide phosphide photodiodes in the understory and a LI-COR quantum sensor (LI-190SA) in the open. Photodiodes were randomly located on a systematic grid of points and represented a wide range of above canopy openings which were classified into three different types of light environments: closed canopy, gaps of various sizes, and open canopy. Objectives of this study were to compare different methods for estimating the growing season %PPFD and to determine the efficiency of these methods in the three light environments. At each photodiode location, instantaneous light measurements using a Ceptometer on sunny days around noon and a LAI-2000 Plant Canopy Analyzer were made and hemispherical canopy photographs were taken. 10-min averages recorded by the photodiodes during completely overcast sky conditions were used as surrogate values for a method that uses instantaneous measurements on overcast days. Finally, a new light model (LITE) developed to estimate growing season %PPFD in a deciduous canopy was tested. All these five methods provided estimates of growing season %PPFD and are much less time consuming than continuous measurements of %PPFD using photodiodes. The three most accurate (r2>0.89) methods to estimate the growing season %PPFD were the 10 min averages on overcast days, the diffuse non-interceptance calculated using the LAI-2000, and the gap light index (GLI) calculated from the hemispherical canopy photographs. These three methods performed similarly in each type of light environment. Although the relationship between the LITE model and the growing season %PPFD was good (r2=0.79), the model systematically underestimated light transmission. The instantaneous sunny days around noon method was the least efficient method (r2=0.68) for estimating the growing season %PPFD, although replacing instantaneous measures with the mean of two 10-min averages improved r2 to 0.84. Estimates on sunny days tended to be low in low light and high in high light. Practical considerations such as equipment availability, cost, sampling and processing time, sky conditions, and the number of microsites to be sampled should be taken into account in the selection of the suitable method for a particular study

Foucault, Baudrillard et Bourdieu dans la recherche comptable : apports théoriques, interdisciplinarité et problématisation

Bien que le paradigme positiviste constitue le principal segment de recherche en comptabilité, depuis les deux dernières décennies un certain nombre de chercheurs comptables anglo-saxons en sont venus à baser leurs travaux de recherche sur les œuvres de penseurs et sociologues français comme Michel Foucault, Man Baudrillard et Pierre Bourdieu. Qui sont-ils, ces penseurs et sociologues français ayant suscité un tel intérêt de la part de chercheurs anglophones en comptabilité ? Quelles sont certaines des idées qui sous-tendent leur œuvre ? Finalement, pourquoi leurs travaux en sont-ils venus à franchir les frontières disciplinaires de la communauté scientifique de langue anglaise en comptabilité ? Cet article vise à apporter certains éléments d'explication relativement à ces questions.interdisciplinarité ; Foucault ; Recherche comptable - Penseur français

North American Bioactive Plants for Human Health and Performance

Native and naturalized bioactive plants of the Canadian and American temperate biome are examined for their health and performance enhancement properties. Some of these plants are now being used as natural health products, and many have a long history as traditional foods and/or medicines with indigenous groups. This paper reviews the medicinal/cultural uses and bioactive properties of selected plant families: the Holly family (Aquifoliaceae) as stimulants, the Celery family (Apiaceae) as normoglycemic aids and analgesics, the Ginseng family (Araliaceae) as energy- boosting aids, the Sunflower family (Compositae) as anti-inflammatory aids, and the Legume family (Fabaceae) and Nightshade family (Solanaceae) as functional foods. These North American plants show promising avenues for innovative health and performance enhancement aids and it is concluded that they should be investigated further for their bioactive properties

Predicting and managing light in the understory of boreal forests

This paper reviews current information relating to the dynamics of light in northern and boreal forests and discusses factors affecting overstory light transmission, seasonality of light, sunflecks, canopy gaps, and understory development, particularly with regard to tree regeneration. Techniques for measurement of light in forests such as radiometers, photosensitive paper or chemicals, hemispherical canopy photographs, the plant canopy analyzer, or visual estimators of canopy density are each discussed in terms of their accuracy, costs, ease of use, and conditions required during measurement. Predictive models of light transmission based on canopy architecture are also described in terms of their assumptions, accuracy, and input data costs. Lastly the paper discusses the relationship among overstory and understory densities, ground-level light, and 'windows of opportunity' for regeneration of trees in the understory following management interventions