Surface mixing and biological activity in the four Eastern Boundary Upwelling Systems

Eastern Boundary Upwelling Systems (EBUS) are characterized by a high productivity of plankton associated with large commercial fisheries, thus playing key biological and socio-economical roles. The aim of this work is to make a comparative study of these four upwelling systems focussing on their surface stirring, using the Finite Size Lyapunov Exponents (FSLEs), and their biological activity, based on satellite data. First, the spatial distribution of horizontal mixing is analysed from time averages and from probability density functions of FSLEs. Then we studied the temporal variability of surface stirring focussing on the annual and seasonal cycle. There is a global negative correlation between surface horizontal mixing and chlorophyll standing stocks over the four areas. To try to better understand this inverse relationship, we consider the vertical dimension by looking at the Ekman-transport and vertical velocities. We suggest the possibility of a changing response of the phytoplankton to sub/mesoscale turbulence, from a negative effect in the very productive coastal areas to a positive one in the open ocean.Comment: 12 pages. NPG Special Issue on "Nonlinear processes in oceanic and atmospheric flows". Open Access paper, available also at the publisher site: http://www.nonlin-processes-geophys.net/16/557/2009

Electromagnetic Corrections in Partially Quenched Chiral Perturbation Theory

We introduce photons in Partially Quenched Chiral Perturbation Theory and calculate the resulting electromagnetic loop-corrections at NLO for the charged meson masses and decay constants. We also present a numerical analysis to indicate the size of the different corrections. We show that several phenomenologically relevant quantities can be calculated consistently with photons which couple only to the valence quarks, allowing the use of gluon configurations produced without dynamical photons.Comment: 11 page

An Investigation of the Large-scale Variability of the Apparently Single Wolf-Rayet Star WR 1

In recent years, much studies have focused on determining the origin of the large-scale line-profile and/or photometric patterns of variability displayed by some apparently single Wolf-Rayet stars, with the existence of an unseen (collapsed?) companion or of spatially extended wind structures as potential candidates. We present observations of WR 1 which highlight the unusual character of the variations in this object. Our narrowband photometric observations reveal a gradual increase of the stellar continuum flux amounting to Delta v = 0.09 mag followed by a decline on about the same timescale (3-4 days). Only marginal evidence for variability is found during the 11 following nights. Strong, daily line-profile variations are also observed but they cannot be easily linked to the photometric variations. Similarly to the continuum flux variations, coherent time-dependent changes are observed in 1996 in the centroid, equivalent width, and skewness of He II 4686. Despite the generally coherent nature of the variations, we do not find evidence in our data for the periods claimed in previous studies. While the issue of a cyclical pattern of variability in WR 1 is still controversial, it is clear that this object might constitute in the future a cornerstone for our understanding of the mechanisms leading to the formation of largely anisotropic outflows in Wolf-Rayet stars.Comment: 11 pages, 9 figures, accepted for publication in Astronomy & Astrophysic

The effect of patient, provider and financing regulations on the intensity of ambulatory physical therapy episodes: a multilevel analysis based on routinely available data.

BACKGROUND: Many studies have found considerable variations in the resource intensity of physical therapy episodes. Although they have identified several patient- and provider-related factors, few studies have examined their relative explanatory power. We sought to quantify the contribution of patients and providers to these differences and examine how effective Swiss regulations are (nine-session ceiling per prescription and bonus for first treatments). METHODS: Our sample consisted of 87,866 first physical therapy episodes performed by 3,365 physiotherapists based on referrals by 6,131 physicians. We modeled the number of visits per episode using a multilevel log linear regression with crossed random effects for physiotherapists and physicians and with fixed effects for cantons. The three-level explanatory variables were patient, physiotherapist and physician characteristics. RESULTS: The median number of sessions was nine (interquartile range 6-13). Physical therapy use increased with age, women, higher health care costs, lower deductibles, surgery and specific conditions. Use rose with the share of nine-session episodes among physiotherapists or physicians, but fell with the share of new treatments. Geographical area had no influence. Most of the variance was explained at the patient level, but the available factors explained only 4% thereof. Physiotherapists and physicians explained only 6% and 5% respectively of the variance, although the available factors explained most of this variance. Regulations were the most powerful factors. CONCLUSION: Against the backdrop of abundant physical therapy supply, Swiss financial regulations did not restrict utilization. Given that patient-related factors explained most of the variance, this group should be subject to closer scrutiny. Moreover, further research is needed on the determinants of patient demand

First orbital solution for the non-thermal emitter Cyg OB2 #9

After the first detection of its binary nature, the spectroscopic monitoring of the non-thermal radio emitter Cyg OB2 #9 (P=2.4yrs) has continued, doubling the number of available spectra of the star. Since the discovery paper of 2008, a second periastron passage has occurred in February 2009. Using a variety of techniques, the radial velocities could be estimated and a first, preliminary orbital solution was derived from the HeI5876 line. The mass ratio appears close to unity and the eccentricity is large, 0.7--0.75. X-ray data from 2004 and 2007 are also analyzed in quest of peculiarities linked to binarity. The observations reveal no large overluminosity nor strong hardness, but it must be noted that the high-energy data were taken after the periastron passage, at a time where colliding wind emission may be low. Some unusual X-ray variability is however detected, with a 10% flux decrease between 2004 and 2007. To clarify their origin and find a more obvious signature of the wind-wind collision, additional data, taken at periastron and close to it, are needed.Comment: 15 pages, 4 figures, accepted by Ap

Recherches écologiques sur une savane sahélienne du Ferlo septentrional, Sénégal : influence de la sécheresse de l’année 1972-1973 sur l’avifaune

Comparaison de l’avifaune dans une savane sahélienne (Fété Olé, Sénégal, 16° N, 15° W) en année « normalement » pluvieuse (303 mm de pluies, groupées entre juin et octobre) et en année anormalement sèche (33 mm de pluie). Inventaire des espèces recensées, analyses mensuelles de la structure de la population, de l’indice de diversité et de dominance pour les effectifs et les biomasses. L’avifaune s’est appauvrie en qualité et en quantité : moins d’espèces, chacune représentée par peu d’individus. L’effectif annuel moyen à l’hectare est passé de 6,3 à 2,9 et la biomasse moyenne annuelle, en grammes de poids frais à l’hectare, de 402 à 186 pour ces deux mêmes années. Alors qu’en 1969-70, les Tourte relles, oiseaux granivores buvant tous les jours, représentaient au moins le tiers des effectifs en saison sèche, celles-ci ont complète ment disparu en 1972-73, laissant la place à des oiseaux ne buvant pas (insectivores et frugivores), ou à des granivores capables de faire de longs vols pour boire (Gangas). La diminution de la population s’explique par les conditions trophiques du milieu : absence de renouvellement du tapis gra- minéen et de mares temporaires après les pluies. Ceci a contraint beaucoup d’espèces à migrer. D’autre part, les populations ont été soumises au seul facteur de la mortalité, puisque aucune espèce n’a été capable de se reproduire.A comparison was made of the bird populations of a dry thornbush savanna at Fété Olé, Senegal (16°N, 15°W) over two years ; one with normal rainfall (303 mm from June to October) and an exceptionnally dry one (33 mm). A check-list, a monthly analysis of the population structure, the diversity and dominance indices of the birds numbers and biomass, are given. A decrease of the number of different species, as well as total bird population, was observed on the IBP quadrat. The annual average number of birds per ha dropped from 6.3 to 2.9, and the annual average biomass from 402 g to 186 g. Seed eaters (doves), which need to drink daily, contributed at least one third of the dry season population in 1969-70, whereas they completely disappeared in 1972-73. Species that do not need to drink regularly (insectivores and fruit-eaters), or species which can fly long dis tances to water holes (sandgrouse) were able to stay. In 1972-73 the decrease in population numbers can obviously be related to the shortage of food : the very low rainfall did not allow the germination of seeds and no water was able to accumu late in the hollows after the rains. Many species were thus compelled to move away. No breeding took place in 1972-73 and the bird population was unable to compensate for the losses due to mortality

The Kaon B-parameter from Quenched Domain-Wall QCD

We present numerical results for the kaon B-parameter, B_K, determined in the quenched approximation of lattice QCD. Our simulations are performed using domain-wall fermions and the renormalization group improved, DBW2 gauge action which combine to give quarks with good chiral symmetry at finite lattice spacing. Operators are renormalized non-perturbatively using the RI/MOM scheme. We study scaling by performing the simulation on two different lattices with a^{-1} = 1.982(30) and 2.914(54) GeV. We combine this quenched scaling study with an earlier calculation of B_K using two flavors of dynamical, domain-wall quarks at a single lattice spacing to obtain B_K(MS,NDR,mu=2GeV)=0.563(21)(39)(30), were the first error is statistical, the second systematic (without quenching errors) and the third estimates the error due to quenching.Comment: 77 pages, 44 figures, to be published in Phys. Rev.