GANIL RF systems : feedback control system and electronics

http://accelconf.web.cern.ch/AccelConf/c81/papers/ep-10.pdfInternational audienc

Femtosecond time resolved CARS spectroscopy of H2-N2 mixtures in the Dicke regime: Experiments and modeling of velocity effects

International audienceIn this paper, we present measurements and modeling of femtosecond time resolved CARS signal in H2-N2 mixtures at low densities. Three approaches have been used to model the CARS response. The first is the usual sum of Voigt profiles. In the second approach, the speed dependent Voigt profile is used. In the last approach, a new model of the CARS signal is developed which takes into account the velocity changes induced by collisions and the speed dependence of the collisional parameters. The velocity changes are modeled using the Keilson and Storer memory function; the radiator speed dependences of the collisional parameters are determined from their temperature dependences. The results show that the changes of the velocity have important effects for the H2/N2 system at the Dicke density regime

Photon-avalanche upconversion of red light into blue light in a thulium-doped fluorozirconate fibre

We report the investigation of the photon-avalanche effect in heavily thulium-doped fluorozirconate fibre. Pumping at red wavelengths, which are not resonant with the ground-state absorption, gives blue emission at 450nm and 480nm

SN 2008S: A Cool Super-Eddington Wind in a Supernova Impostor

We present visual-wavelength photometry and spectroscopy of supernova SN2008S. Based on the low peak luminosity for a SN of M_R = -13.9 mag, photometric and spectral evolution unlike that of low-luminosity SNe, a late-time decline rate slower than 56Co decay, and slow outflow speeds of 600-1000 km/s, we conclude that SN2008S is not a true core-collapse SN and is probably not an electron-capture SN. Instead, we show that SN2008S more closely resembles a "SN impostor" event like SN1997bs, analogous to the giant eruptions of LBVs. Its total radiated energy was 1e47.8 ergs, and it may have ejected 0.05-0.2 Msun in the event. We discover an uncanny similarity between the spectrum of SN 2008S and that of the Galactic hypergiant IRC+10420, which is dominated by narrow H-alpha, [Ca II], and Ca II emission lines formed in an opaque wind. We propose a scenario where the vastly super-Eddington wind of SN2008S partly fails because of reduced opacity due to recombination, as suggested for IRC+10420. The range of initial masses susceptible to eruptive LBV-like mass loss was known to extend down to 20-25 Msun, but estimates for the progenitor of SN2008S (and the similar NGC300 transient) may extend this range to around 15 Msun. As such, SN2008S may have implications for the progenitor of SN1987A.Comment: 4.5 pages, 2 figs, ApJ Letters accepted, figs and text significantly revised, fig1 in colo

ICME international survey on teachers working and learning through collaboration

This article presents preliminary results from a survey commissioned for ICME 13 (2016) focusing on "Teachers Working and Learning Through Collaboration". It takes as a starting point a previous survey, commissioned for ICME 10 in 2004 that focused on Mathematics Teacher Education. The current survey focuses centrally on teachers involved in collaborations, sometimes in formal settings of professional development, but also in a more diverse range of collaborative settings including research initiatives. The roles of teachers involved in the collaboration, survey methods, decisions and limitations are described. While some of the findings to date resonate with those of the earlier survey, other findings highlight characteristics and issues relating to the differing ways in which teachers collaborate, either with other teachers or the various 'others', most notably mathematics teacher educator researchers. The roles and relationships that contribute to learning in such collaborations, as well as theories and methodologies found in survey sources, are a focus of the findings presented here. Studies rarely theorised collaboration, and few of those that did so reported explicitly on how their theoretical frame shaped the design of research methodologies/approaches guiding activities with teachers. One significant outcome has been the difficulty of relating teachers' learning to collaboration within a project, although many initiatives report developments in teaching, teacher learning and students' learning

Developing fencing policies in dryland ecosystems

The daily energy requirements of animals are determined by a combination of physical and physiological factors, but food availability may challenge the capacity to meet nutritional needs. Western gorillas (Gorilla gorilla) are an interesting model for investigating this topic because they are folivore-frugivores that adjust their diet and activities to seasonal variation in fruit availability. Observations of one habituated group of western gorillas in Bai-Hokou, Central African Republic (December 2004-December 2005) were used to examine seasonal variation in diet quality and nutritional intake. We tested if during the high fruit season the food consumed by western gorillas was higher in quality (higher in energy, sugar, fat but lower in fibre and antifeedants) than during the low fruit season. Food consumed during the high fruit season was higher in digestible energy, but not any other macronutrients. Second, we investigated whether the gorillas increased their daily intake of carbohydrates, metabolizable energy (KCal/g OM), or other nutrients during the high fruit season. Intake of dry matter, fibers, fat, protein and the majority of minerals and phenols decreased with increased frugivory and there was some indication of seasonal variation in intake of energy (KCal/g OM), tannins, protein/fiber ratio, and iron. Intake of non-structural carbohydrates and sugars was not influenced by fruit availability. Gorillas are probably able to extract large quantities of energy via fermentation since they rely on proteinaceous leaves during the low fruit season. Macronutrients and micronutrients, but not digestible energy, may be limited for them during times of low fruit availability because they are hind-gut fermenters. We discuss the advantages of seasonal frugivores having large dietary breath and flexibility, significant characteristics to consider in the conservation strategies of endangered species

Ultraviolet Imaging Polarimetry of the Large Magellanic Cloud. II. Models

Motivated by new sounding-rocket wide-field polarimetric images of the Large Magellanic Cloud, we have used a three-dimensional Monte Carlo radiation transfer code to investigate the escape of near-ultraviolet photons from young stellar associations embedded within a disk of dusty material (i.e. a galaxy). As photons propagate through the disk, they may be scattered or absorbed by dust. Scattered photons are polarized and tracked until they escape to be observed; absorbed photons heat the dust, which radiates isotropically in the far-infrared, where the galaxy is optically thin. The code produces four output images: near- UV and far-IR flux, and near-UV images in the linear Stokes parameters Q and U. From these images we construct simulated UV polarization maps of the LMC. We use these maps to place constraints on the star + dust geometry of the LMC and the optical properties of its dust grains. By tuning the model input parameters to produce maps that match the observed polarization maps, we derive information about the inclination of the LMC disk to the plane of the sky, and about the scattering phase function g. We compute a grid of models with i = 28 deg., 36 deg., and 45 deg., and g = 0.64, 0.70, 0.77, 0.83, and 0.90. The model which best reproduces the observed polarization maps has i = 36 +2/-5 degrees and g ~0.7. Because of the low signal-to-noise in the data, we cannot place firm constraints on the value of g. The highly inclined models do not match the observed centro-symmetric polarization patterns around bright OB associations, or the distribution of polarization values. Our models approximately reproduce the observed ultraviolet photopolarimetry of the western side of the LMC; however, the output images depend on many input parameters and are nonunique.Comment: Accepted to AJ. 20 pages, 7 figure

Epigenetic memory in response to environmental stressors

Exposure to environmental stressors, toxicants, and nutrient deficiencies can affect DNA in several ways. Some exposures cause damage and alter the structure of DNA, but there is increasing evidence that the same or other environmental exposures, including those that occur during fetal development in utero, can cause epigenetic effects that modulate DNA function and gene expression. Some epigenetic changes to DNA that affect gene transcription are at least partially reversible (i.e., they can be enzymatically reversed after cessation of exposure to environmental agents), but some epigenetic modifications seem to persist, even for decades. To explain the effects of early life experiences (such as famine and exposures to other stressors) on the long-term persistence of specific patterns of epigenetic modifications, such as DNA methylation, we propose an analogy with immune memory. We propose that an epigenetic memory can be established and maintained in self-renewing stem cell compartments. We suggest that the observations on early life effects on adult diseases and the persistence of methylation changes in smokers support our hypothesis, for which a mechanistic basis, however, needs to be further clarified. We outline a new model based on methylation changes. Although these changes seem to be mainly adaptive, they are also implicated in the pathogenesis and onset of diseases, depending on individual genotypic background and types of subsequent exposures. Elucidating the relationships between the adaptive and maladaptive consequences of the epigenetic modifications that result from complex environmental exposures is a major challenge for current and future research in epigenetics.-Vineis, P., Chatziioannou, A., Cunliffe, V. T., Flanagan, J. M., Hanson, M., Kirsch-Volders, M., Kyrtopoulos, S. Epigenetic memory in response to environmental stressors

Detection of [O I] 63 <i>μ</i>m in absorption toward Sgr B2

A high signal-to-noise 52-90 μm spectrum is presented for the central part of the Sagittarius B2 complex. The data were obtained with the Long Wavelength Spectrometer on board the Infrared Space Observatory (ISO). The [O I] 63 μm line is detected in absorption even at the grating spectral resolution of 0.29 μm. A lower limit for the column density of atomic oxygen of the order of 1019 cm-2 is derived. This implies that more than 40% of the interstellar oxygen must be in atomic form along the line of sight toward the Sgr B2 molecular cloud