714 research outputs found
Dusty spirals triggered by shadows in transition discs
Context. Despite the recent discovery of spiral-shaped features in
protoplanetary discs in the near-infrared and millimetric wavelengths, there is
still an active discussion to understand how they formed. In fact, the spiral
waves observed in discs around young stars can be due to different physical
mechanisms: planet/companion torques, gravitational perturbations or
illumination effects. Aims. We study the spirals formed in the gaseous phase
due to two diametrically opposed shadows cast at fixed disc locations. The
shadows are created by an inclined non-precessing disc inside the cavity, which
is assumed to be optically thick. In particular, we analyse the effect of these
spirals on the dynamics of the dust particles and discuss their detectability
in transition discs. Methods. We perform gaseous hydrodynamical simulations
with shadows, then we compute the dust evolution on top of the gaseous
distribution, and finally we produce synthetic ALMA observations of the dust
emission based on radiative transfer calculations. Results. Our main finding is
that mm- to cm-sized dust particles are efficiently trapped inside the
shadow-triggered spirals. We also observe that particles of various sizes
starting at different stellocentric distances are well mixed inside these
pressure maxima. This dynamical effect would favour grain growth and affect the
resulting composition of planetesimals in the disc. In addition, our radiative
transfer calculations show spiral patterns in the disc at 1.6 {\mu}m and 1.3
mm. Due to their faint thermal emission (compared to the bright inner regions
of the disc) the spirals cannot be detected with ALMA. Our synthetic
observations prove however that shadows are observable as dips in the thermal
emission.Comment: 15 pages, 11 figures, accepted for publication in A&
Mobilisation du bois et approvisionnement pour une filiĂšre bois Ă©nergie en Languedoc-Roussillon -
L'approche Ă©conomique est l'Ă©lĂ©ment clef de la rĂ©flexion sur le dĂ©veloppement du bois Ă©nergie en forĂȘt mĂ©diterranĂ©enne. Les outils d'analyse Ă©conomique sont indispensables pour permettre de juger de l'opportunitĂ© qu'offre le bois Ă©nergie. Des Ă©tudes mĂ©thodologiques existent qui permettent de prendre en compte l'ensemble des facteurs Ă©conomiques pour pouvoir juger de la mise en place durable de la filiĂšre dans un contexte local spĂ©cifique Ă chaque territoire, comme celle prĂ©sentĂ©e ici et rĂ©alisĂ©e en Languedoc-Roussillo
Recherche et caractérisation de sols résistants aux Pythium spp. en Amazonie brésilienne
Aux environs de la ville de Manaus (Amazonie brĂ©silienne), les sols sont localisĂ©s dans deux Ă©cosystĂšmes: âterra firmeâ recouverte de foret vierge ou cultivĂ©e et âvarzeaâ, zones submergĂ©es chaque annĂ©e et cultivĂ©es. 160 Ă©chantillons de sol ont Ă©tĂ© prĂ©levĂ©s dans ccs deux zones, puis analysĂ©s afin de dĂ©terminer leur capacitĂ© de fonte des semis, causĂ©e par les Pythium spp.; 76 de ces sols semblaient non infestĂ©s, ou ne l'Ă©taient que faiblement. Afin de dĂ©terminer leur rĂ©ceptivitĂ© visâĂ âvis des Pythium spp., les 76 sols ont Ă©tĂ© inoculĂ©s avec 10% d'un sol infestĂ© naturellement, et la capacitĂ© d'infection a Ă©tĂ©Ă©valuĂ©e aprĂ©s des incubations de 4, 8, 12 et 16 semaines par tests biologiques sur jeunes plants de concombre. L'aptitude Ă supprimer les Pythium spp. n'est apparue que dans les Ă©cosystĂšmes âterra firme'et non dans les âvarzeasâ submergĂ©s. La frĂ©quence des sols pouvant supprimer la maladie semblait dĂ©croitre en fonction de la mise en culture: 82% dans les sols de foret vierge; 67% dans les sols de pĂ©piniĂšres forestiĂ©res; 53% dans les forets gĂ©rĂ©es; 31% dans les sols forestiers mis en culture avec des cultures variĂ©es; 7% dans les sols forestiers mis en culture et portant des cultures maraichĂšres. On a constatĂ© trois types d'aptitude Ă supprimer les Pythium spp. aprĂ©s inoculation des sols: (1) rĂ©sistance apparaissant rapidement et se maintenant Ă un niveau Ă©levĂ© et constant (jusqu'Ă 16 semaines); (2) rĂ©sistance initiate Ă©levĂ©e, mais non durable; (3) rĂ©sistance initialement faible, mais croissante avec le temps. Une partie de cette dynamique semble etre sous controle microbien. Le dĂ©veloppement agricole autour de Manaus ainsi que les systĂšmes de culture intensifs peuvent rapidement modifier les Ă©cosystĂšmes microbiens des sols et nuire Ă leur capacitĂ© naturelle Ă supprimer les Pythium spp. Copyright © 1987, Wiley Blackwell. All rights reserve
Emotions and performance in rugby
Purpose: This study investigated emotion-performance relationships in rugby union. We identified which emotions rugby players experienced and the extent to which these emotions were associated with performance, considering how emotions unfold over the course of a game, and whether the game was played at home or away. Methods: Data were gathered from 22 professional male rugby union players using auto-confrontation interviews to help identify situations within games when players experienced intense emotions. We assessed the intensity of emotions experienced before each discrete performance and therefore could assess emotion-performance relationships within competition. Results: Players identified experiencing intense emotions at 189 time-points. Experts in rugby union rated the quality of each performance at these 189 time-points on a visual analog scale. A Linear Mixed Effects model to investigate emotion-performance relationships found additive effects of game location, game time, and emotions on individual performance. Conclusion: Results showed 7 different pre-performance emotions, with high anxiety and anger associating with poor performance. Future research should continue to investigate emotion-performance relationships during performance using video-assisted recall and use a measure of performance that has face validity for players and coaches alike
Surveying activated sludge changes during acclimation with artificial wastewater
Many processes in the chemical and pharmaceutical industries generate wastewater containing organic
toxic compounds and other kinds of xenobiotics. Usually, biological treatments are used to degrade a
great quantity of these substances. However, most of the time, the microorganisms are not adapted and
the treatment can be blocked. Therefore, the first step to make a continuous reactor operative is the
acclimation, i.e., the adaptation of the microorganisms to a specific substrate. During this particular step
of the process there is a selection and a multiplication of specialized microorganisms and physiological
transformations can occur in their metabolic system. Furthermore, combining image processing
techniques have already been successfully used to elucidate the activated sludge morphological changes
for both aggregated and filamentous bacteria contents, during such processes.
The experimental set-up is composed of an aerated reactor and a clarifier. The sludge is recycled from the
clarifier by a peristaltic pump. The complete mixing inside the reactor is guaranteed by the diffusion of
air from its bottom. The reactor was inoculated with biomass collected from a wastewater treatment plant
and fed with an artificial wastewater based on meat extract. During acclimation, chemical parameters
were measured in the influent, reactor and effluent, in order to verify the stability of the process. To
complete the evaluation of the process, microscopy acquisition and image processing and analysis
techniques were performed for aggregates and filamentous bacteria characterization for bright field, Gram
and poly-ÎČ-hydroxybutyrate (PHB) staining images. The information extracted from those images
allowed for aggregates and filamentous bacteria contents inspection, identification of PHB storing
microorganisms and, gram-positive and gram-negative filamentous bacteria recognition. Figure 1 presents
activated sludge samples at the beginning and at the end of the acclimation phase. It was found in this
study that biomass changes during the acclimation phase could be effectively monitored, combining
image analysis information and chemical parameters
Embryonic development of pleuropodia of the cicada, Magicicada cassini
In many insects the first abdominal segment possesses embryonic appendages called pleuropodia. Here we show the embryogenesis of pleuropodial cells of the periodical cicada, Magicicada cassini (Fisher 1851) (Insecta, Homoptera, Cicadidae). An antibody, anti-horseradish perioxidase (HRP), that is usually neuron-specific strongly marked the pleuropodial anlagen and revealed their ectodermal origin shortly after limb bud formation. Thereafter the cells sank into the epidermis and their apical parts enlarged. A globular part protruded from the body wall. Filamentous structures were marked at the stem region and into the apical dilation. In later embryonic stages the pleuropodia degenerated. Despite the binding of anti-HRP the cells had no morphological neuronal characters and cannot be regarded as neurons. The binding indicates that glycosylated cell surface molecules contribute to the adhesion between the presumably glandular pleuropodial cells. In comparison, anti-HRP does not mark the pleuropodia of Orthoptera
Gemcitabine and oxaliplatin (GEMOX) in gemcitabine refractory advanced pancreatic adenocarcinoma: a phase II study
Gemcitabine and oxaliplatin (GEMOX) are active as first-line therapy against advanced pancreatic cancer. This study aims to evaluate the activity and tolerability of this combination in patients refractory to standard gemcitabine (GEM). A total of 33 patients (median age of 57) were included with locally advanced and metastatic evaluable diseases, who had progressed during or following GEM therapy. The GEMOX regimen consisted of 1000âmgâmâ2 of GEM at a 100-min infusion on day 1, followed on day 2 by 100âmgâmâ2 of oxaliplatin at a 2-h infusion; a cycle that was given every 2 weeks. All patients received at least one cycle of GEMOX (median 5; range 1â29). Response by 31 evaluable patients was as follows: PR: 7/31(22.6%), s.d. â©Ÿ8 weeks: 11/31(35.5%), s.d. <8 weeks: 1/31(3.2%), PD: 12/31(38.7%). Median duration of response and TTP were 4.5 and 4.2 months, respectively. Median survival was 6 months (range 0.5â21). Clinical benefit response was observed in 17/31 patients (54.8%). Grade III/IV non-neurologic toxicities occurred in 12/33 patients (36.3%), and grade I, II, and III neuropathy in 17(51%), 3(9%), and 4(12%) patients, respectively. GEMOX is a well-tolerated, active regimen that may provide a benefit to patients with advanced pancreatic cancer after progression following standard gemcitabine treatment
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