2,455 research outputs found
Observing transiting planets with JWST -- Prime targets and their synthetic spectral observations
The James Webb Space Telescope will enable astronomers to obtain exoplanet
spectra of unprecedented precision. Especially the MIRI instrument may shed
light on the nature of the cloud particles obscuring planetary transmission
spectra in the optical and near-infrared. We provide self-consistent
atmospheric models and synthetic JWST observations for prime exoplanet targets
in order to identify spectral regions of interest and estimate the number of
transits needed to distinguish between model setups. We select targets which
span a wide range in planetary temperature and surface gravity, ranging from
super-Earths to giant planets, and have a high expected SNR. For all targets we
vary the enrichment, C/O ratio, presence of optical absorbers (TiO/VO) and
cloud treatment. We calculate atmospheric structures and emission and
transmission spectra for all targets and use a radiometric model to obtain
simulated observations. We analyze JWST's ability to distinguish between
various scenarios. We find that in very cloudy planets such as GJ 1214b less
than 10 transits with NIRSpec may be enough to reveal molecular features.
Further, the presence of small silicate grains in atmospheres of hot Jupiters
may be detectable with a single JWST MIRI transit. For a more detailed
characterization of such particles less than 10 transits are necessary.
Finally, we find that some of the hottest hot Jupiters are well fitted by
models which neglect the redistribution of the insolation and harbor
inversions, and that 1-4 eclipse measurements with NIRSpec are needed to
distinguish between the inversion models. Wet thus demonstrate the capabilities
of JWST for solving some of the most intriguing puzzles in current exoplanet
atmospheric research. Further, by publishing all models calculated for this
study we enable the community to carry out similar or retrieval analyses for
all planets included in our target list.Comment: 24 pages, 7 figures, accepted for publication in A&
ModĂ©lisation environnementale rĂ©gionalisĂ©e Ă lâĂ©chelle mondiale de lâacidification terrestre et aquatique dans le cadre de lâĂ©valuation des impacts du cycle de vie
Lâacidification des milieux terrestres et aquatiques est principalement causĂ©e par des Ă©missions
de SO2, NOx et de NH3 Ă lâatmosphĂšre. Ces polluants, une fois Ă©mis, sont transportĂ©s sur de
longues distances, interagissent avec les composantes de lâatmosphĂšre avant de retomber au
niveau du sol causant un changement dâaciditĂ© dans les milieux rĂ©cepteurs (i.e. terrestres et/ou
aquatiques). Pour presque toute espĂšce vivante, il existe une plage de pH optimale pour le
maintien de la vie. Une déviation de cet optimum est dommageable pour cette espÚce et engendre
un changement de la biodiversité dans les écosystÚmes.
Lâanalyse du cycle de vie (ACV) est un outil dâaide de prise Ă la dĂ©cision qui permet dâĂ©valuer
les impacts potentiels dâun produit pour de nombreuses catĂ©gories dâimpacts (e.g. changement
climatique, toxicitĂ©, acidification). Pour ce faire, les mĂ©thodes dâĂ©valuation des impacts du cycle
de vie (ACVI) ont recours à des facteurs de caractérisation (FCs). Un FC se définit comme étant
la reprĂ©sentation mathĂ©matique de la chaine de cause Ă effet dâune catĂ©gorie dâimpact donnĂ©e. En
considĂ©rant le cadre dâĂ©valuation des impacts reliĂ©s aux Ă©missions atmosphĂ©riques (Udo de Haes
et al., 2002), les FCs de la catĂ©gorie dâimpact acidification ont Ă©tĂ© calculĂ©s par la somme des
produits des facteurs de devenir atmosphĂ©rique associĂ©s Ă un lieu dâĂ©mission, de facteurs de la
sensibilité des sols ou de facteur de devenir des milieux récepteurs (terrestres et aquatiques)
associĂ©s aux milieux rĂ©cepteurs et de facteurs dâeffet Ă©galement associĂ©s aux milieux rĂ©cepteurs.
Le facteur de devenir atmosphérique évalue la relation entre la quantité de polluant émis et la
quantité déposée en un lieu donnée. La sommation de ces derniers représente la fraction totale
dâune Ă©mission transfĂ©rĂ©e Ă lâensemble des mileiux rĂ©cepteurs. Le facteur de sensibilitĂ© ou le
facteur de devenir des milieux récepteurs évalue la stabilité (mesurée, par exemple, par le pH) des
milieux récepteurs (terrestre et/ou aquatique) suivant les dépositions de substances acidifiantes.
Le facteur dâeffet Ă©value le changement de biodiversitĂ© (e.g. perte dâespĂšces) du au changement
de la qualitĂ© des milieux rĂ©cepteurs suite aux dĂ©positions acides. Ces facteurs sont calculĂ©s Ă
lâaide de plusieurs modĂšles mathĂ©matiques basĂ©s sur les sciences naturelles et dĂ©crivent la
succession de processus chimiques, physiques et biologiques de la chaine cause-effet. Il existe
deux approches de calculs pour les FCs : une approche dite problĂšme et une approche dite
dommage. Cette derniĂšre approche modĂ©lise lâensemble de la chaine cause-effet jusquâaux
dommages. La premĂšre approche (problĂšme) ne modĂ©lise quâune partie de la chaine cause-effet;
vii
liant, par exemple, lâĂ©mission jusquâĂ la dĂ©position dans les milieux rĂ©cepteurs ou jusquâau
changement de la qualité des écosystÚmes. En théorie, cependant, les FCs orientés problÚmes
sont définis comme un compromis maximisant la pertinence environnementale (pour la prise de
dĂ©cision) et minimisant lâincertitude du modĂšle de caractĂ©risation.
Plusieurs limitations ont été identifiées dans les méthodes ACVI actuelles. (i) La plupart des FCs
retrouvés dans les méthodes ACVI actuelles sont basés sur de la modélisation réalisée à une
échelle continentale et sont de types problÚmes. Cependant, ces FCs ne sont représentatifs que
dâun lieu gĂ©ographique circonscrit (i.e. Canada, Ătats-Unis, Europe ou Japon). Lors de la
caractĂ©risation des Ă©missions du cycle de vie, lâhypothĂšse implicite posĂ©e a pour consĂ©quence
que toutes les émissions sont considérées comme ayant lieux dans ce lieu géographique
circonscrit (e.g. une Ă©mission de 1 kg de SO2 en Chine est Ă©quivalent Ă 1 kg SO2 en Europe).
Avec la globalisation des marchĂ©s, cette hypothĂšse sâavĂšre inexacte. (ii) Le recours Ă la
modélisation basée sur une échelle continentale est problématique puisque les émissions
voyageant hors du contexte dâapplication ne sont pas considĂ©rĂ©es. Bien que cette dĂ©position
transcontinentale représente, probablement, une faible proportion de la déposition totale, il est
possible que les dépÎts acides choient sur des milieux récepteurs sensibles causant un impact
important. (iii) Il existe un manque de cohĂ©rence entre les FCs de lâacidification terrestre de types
problÚme et dommage. En effet, les FCs problÚmes sont basés sur un indicateur de type « charge
critique » qui, pour le moment, ne peut ĂȘtre liĂ© Ă une modĂ©lisation subsĂ©quente vers un indicateur
de la perte de biodiversitĂ©. (iv) Il nâexiste pas de FCs rĂ©gionalisĂ©s basĂ©s sur le devenir
atmosphĂ©rique, le devenir des milieux rĂ©cepteurs et lâeffet pour lâacidification aquatique. Par
consĂ©quent, les impacts potentiels de lâacidification aquatique sont nĂ©gligĂ©s en ACV. (v) Les
capacitĂ©s de modĂ©lisaiton de lâacidification terrestre sont limitĂ©s Ă lâĂ©chelle nationale et celles de
lâacidification aquatique sont inexistantes. (vi) Bien que la variabilitĂ© spatiale des FCs est
gĂ©nĂ©ralement Ă©valuĂ©e, lâincertitude inhĂ©rentes aux FCs ne lâest pas.
Sur la base de ces constats, les objectifs principaux ont été définis:
1. CrĂ©er un modĂšle de caractĂ©risation rĂ©gionalisĂ© pour lâacidification terrestre et aquatique
sur la base de modÚles sophistiqués de devenir atmosphérique, de la sensibilité/devenir
des milieux rĂ©cepteurs et dâeffet Ă une Ă©chelle mondiale.
viii
2. Générer des facteurs de devenir atmosphérique permettant de considérer la déposition
transcontinentale.
3. Générer des facteurs de sensibilité terrestre compatible avec une phase subséquente vers
un indicateur de la perte de biodiversité.
4. DĂ©velopper un modĂšle permettant dâĂ©valuer le devenir des milieux rĂ©cepteurs pour
lâacidification aquatique pouvant ĂȘtre combinĂ© aux courbes dose-rĂ©ponses, illustrant la
perte de biodiversité, existantes.
5. GĂ©nĂ©rer des FCs rĂ©gionalisĂ©s, de type dommage, Ă lâĂ©chelle globale pour lâacidification
terrestre et aquatique.
6. Ăvaluer lâincertitude et la variation spatiale reliĂ©es aux FCs dĂ©veloppĂ©s afin de dĂ©finir et
gĂ©nĂ©rer des FCs de type problĂšme Ă lâĂ©chelle globale et supporter lâinterprĂ©tation lors
dâĂ©tude ACV.
Pour ce faire, il fut nécessaire de créer un cadre méthodologique identifiant les indicateurs
couvrant lâintĂ©gralitĂ© de chaĂźne cause-effet et les Ă©tapes de modĂ©lisation Ă dĂ©velopper pour
obtenir des facteurs de devenir atmosphĂ©rique rĂ©gionaux reliant lâĂ©mission Ă la dĂ©position, des
facteurs de sensibilité des sols reliant une déposition atmosphérique à un changement de pH des
sols, des facteurs de devenir des milieux rĂ©cepteurs (pour lâacidification aquatique) reliant une
dĂ©position atmosphĂ©rique Ă un changement de pH dans les lacs et des facteurs dâeffet (terrestres
et aquatiques) afin de calculer des changements de biodiversité des espÚces biologiques en
fonction dâun changement de pH. Tous dĂ©veloppements ont Ă©tĂ© menĂ©s dans le but de calculer des
FCs rĂ©gionalisĂ©s dommages, Ă lâĂ©chelle globale, et dâen Ă©valuer la variabilitĂ© spatiale et
lâincertitude.
Un modÚle de dispersion et de chimie atmosphérique mondial a été sélectionné pour servir de
base Ă la gĂ©nĂ©ration de facteurs de devenir atmosphĂ©rique. Ă lâaide de bilans de masse, il a Ă©tĂ©
possible de créer une matrice source-récepteur, dont les éléments sont des facteurs de devenir.
Les résultats ont montré que la déposition transcontinentale représentait, en moyenne, prÚs de 4%
de la dĂ©position totale dâun continent.
Un modÚle simulant les processus géochimiques des sols a servi pour évaluer différents
indicateurs chimiques des sols en régime permanent. Pour ce faire, il fut cependant nécessaire de
ix
créer une base de données mondiale des paramÚtres de sols. Les résultats ont montrés que le pH
surlignait les zones les plus sensibles attendues et dĂ©montrait le moins de variation suite Ă
lâincertitude des paramĂštres de sols.
Un modĂšle a Ă©tĂ© crĂ©Ă©e afin dâĂ©valuer le pH des lacs Ă travers le monde. Le modĂšle considĂšre que
les lacs sont représentés par une série de réacteurs parfaitement mélangés (CSTR). Il considÚre
les entrĂ©es dâions H+ provenant de lâatmosphĂšre, des sols environnants ainsi que de lâeau en
amont des lacs. Il considĂšre Ă©galement les sorties dâions H+ suite au transport en aval des lacs et
Ă lâĂ©vaporation.
Les facteurs dâeffet terrestre et aquatique ont Ă©tĂ© gĂ©nĂ©rĂ©s Ă partir de modĂšles de rĂ©gressions de
différents écosystÚmes à travers le monde liant le pH à la perte de biodiversité des plantes
vasculaires, pour lâacidification terrestre, ou des poissons, pour lâacidification aquatique.
Ces développements méthodologiques ont donné comme résultat 13104 FCs pour,
respectivement, lâacidification terrestre et aquatique. Chaque FC peut dĂ©terminer lâimpact
potentiel dâune Ă©mission ayant lieu dans un grillage dâune rĂ©solution Ă©quivalente Ă 2ox2.5o
partout sur la planĂšte. Des variations de 5 Ă 6 ordres de grandeurs et de 8 Ă 10 ordres de grandeurs
pour respectivement lâacidification terrestre et aquatique ont Ă©tĂ© observĂ©es selon le lieu
dâĂ©mission. Lâincertitude des FCs dommages a Ă©tĂ© Ă©valuĂ©e Ă plus dâun ordre de grandeurs
(facteur 32) et Ă prĂšs de 2 ordres de grandeurs pour lâacidification terrestre et aquatique,
respectivement.
De plus, les rĂ©sultats ont montrĂ© lâimportance de considĂ©rer la dĂ©position transcontinentale. En
effet, bien que cette derniÚre représente prÚs de 4% de la déposition totale, elle est responsable de
typiquement 15-17% et 44-58% de lâimpact potentiel total de, respectivement, lâacidification
terrestre et aquatique pour un lieu dâĂ©mission donnĂ©.
En évaluant la contribution des facteurs de devenir atmosphérique, de la sensibilité des sols ou du
devenir dans les milieux rĂ©cepteurs et des effets Ă la variabilitĂ© spatiale et Ă lâincertitude du
facteur de dommage, il a été possible de conclure que les FCs de type problÚme doivent
incorporer à la fois le devenir atmosphérique et la sensibilité des sols ou, respectivement, le
devenir des milieux récepteurs. En effet, le facteur de devenir atmosphérique contribue peu à la
variabilitĂ© spatiale alors que le facteur dâeffet contribue Ă typiquement plus de 90% de
lâincertitude totale. On en conclu quâun FC portant sur la sensibilitĂ© des sols ou, respectivement,
x
du devenir des milieux rĂ©cepteurs sâavĂšre ĂȘtre le meilleur compromis entre la minimisation de
lâincertitude et la maximisation de la pertinence environnementale et ce, tout en garantissant un
lien cohĂ©rent entre les FCs problĂšmes et dommages. Lâincertitude des FCs problĂšmes a Ă©tĂ©
Ă©valuĂ©e Ă un facteur 3 et un facteur 2 pour lâacidification terrestre et aquatique, respectivement.
De plus, il a Ă©tĂ© montrĂ© quâune Ă©valuation basĂ©e sur de la modĂ©lisation Ă une lâĂ©chelle nationale,
continentale ou mondiale engendrait une incertitude supplémentaire équivalente à un ou deux
ordres de grandeurs selon la résolution sélectionnée.
Ainsi, cette thĂšse a proposĂ© un modĂšle de caractĂ©risation rĂ©gionalisĂ© Ă lâĂ©chelle mondiale
permettant la génération de FCs pouvant différentier davantage (comparativement aux FCs
existants) les Ă©missions de substances acidifiantes tout en montrant lâimportance i) des impacts
potentiels provenant de la déposition transcontinentale, ii) de la variabilité spatiale et iii) de
lâincertitude et ce, pour lâacidification terrestre et aquatique. En ce sens, cette thĂšse permet
dâamĂ©liorer les pratiques courantes de lâĂ©valuation des impacts du cycle de vie de la catĂ©gorie
dâimpact acidification en ACV.----------Terrestrial and aquatic acidification are mostly caused by atmospheric emissions of SO2, NOx and
NH3. Once emitted, these pollutants are transported over long distances, react with the
atmospheric components before being deposited on receiving environments. Consequently,
changes in their acidity levels may then be observed. For nearly every living species, there is an
optimum pH. A serious deviation from this optimum can cause damages for this species and may
thus result in a change of the ecosystem biodiversity.
Life cycle assessment (LCA) is a decision making tool that allows for the evaluation of potential
impacts of a product over numerous impact categories (e.g. climate change, toxicity,
acidification). To do so, life cycle impact assessment methods (LCIA) use characterization
factors (CFs). A CF is defined as a mathematical representation of the cause-effect chain of a
given impact category. Considering the impact assessment framework for atmospheric emitted
pollutants (Udo de Haes et al., 2002), acidificationâs CFs were generated from the multiplication
and subsequent sum of an atmospheric fate factor associated to a source location, a soil
sensitivity or receiving environment fate factor related to receiving environments (terrestrial or
aquatic, respectively) and effect factor also related to receiving environments. The atmospheric
fate factor evaluates the source-receptor relationship. The sum of these factors represents to total
fraction of the emission transferred to the receiving environments. The soil sensitivity or
receiving environment fate factor evaluates the stability (measured, for example, with pH) of the
receiving environment(s) following acid deposits. The effect factor evaluates the change in
biodiversity loss caused by the recorded (or not) change in ecosystem quality.
These factors are calculated from numerous mathematical models based on natural sciences and
describe the cause-effect chain succession of chemical, physical and biological processes. There
are two approaches to calculating CFs: a midpoint and an endpoint approach. Endpoint CFs
model the entire cause-effect chain. The midpoint CFs only model a part of the cause-effect
chain; linking for example, emission to atmospheric deposition or to changes in ecosystem
quality. In theory, however, midpoint CFs are defined as the trade-off between the maximisation
of environmental relevance and the minimisation of the characterization model uncertainties.
xii
Many limitations of the existing LCIA methods were identified. (i) Most CFs are based on
continental modeling and evaluated with a midpoint approach. However, current CFs are only
representative of a specific geographical context (i.e. Canada, United States of America, Europe
or Japan). When characterizing life cycle emissions, it is assumed implicitly that they all occur
within this geographical location (i.e. 1 kg of emitted SO2 in China is equivalent to 1 kg of
emitted SO2 in Europe). With the globalization of markets, this represents an erroneous
assumption. (ii) Continental scale modeling is problematic since emissions travelling in or from
the considered continent are not considered. Even though transboundary deposition represent, in
all likelihood, a small fraction of the total emissions, it is possible that acid deposits reach
sensitive receiving environments and thus cause important potential impacts. (iii) There is also a
lack of coherence between existing midpoint and endpoint terrestrial acidification CFs. Indeed,
most midpoint CFs are based on a critical load approach, which, for the time being cannot be
linked to a subsequent biodiversity loss modeling step. (iv) Spatially differentiated aquatic
acidification CFs based on atmospheric fate, receiving environment fate and effect are nonexistent.
Consequently, the potential impacts of acidifying emissions on aquatic environments are
currently ignored by LCA case studies. (v) The terrestrial acidification CFs highest resolution is
the country level while it is inexistent for aquatic acidification. (vi) While CFs spatial variability
is typically evaluated, the CFs inherent uncertainty remains unevaluated.
Consequently, the objectives of this project were defined:
1. Create a global scale characterization model for terrestrial and aquatic acidification based
on sophisticated environmental models of atmospheric fate, soil sensitivity or receiving
environment fate and effects.
2. Generate global scale fate factors enabling transboundary deposition evaluation.
3. Generate terrestrial sensitivity factors compatible with a subsequent biodiversity loss
assessment.
4. Develop a model to assess aquatic acidification receiving environment fate which can be
combined with existing biodiversity loss dose-response curves.
5. Generate terrestrial and aquatic regionalised endpoint CFs at a global scale.
xiii
6. Evaluate the generated CFs spatial variability and the uncertainty to define and generate
worldwide regionalised midpoint CFs and support the interpretation of impact assessment
results in LCA case studies.
To do so, we created a methodological framework i) specifying the required indicators to
evaluate the entire cause-effect chain of terrestrial and aquatic acidification at a global scale and
ii) listing the required modeling steps to obtain regional atmospheric fate factors, terrestrial
sensitivity factors (linking an atmospheric deposition to a change in soil pH), receiving
environment fate factors (linking an atmospheric deposition to a change in lake(s) pH) and effect
factors (terrestrial and aquatic) to calculate changes in biodiversity loss according to a change in
the receiving environment pH. Every development aimed to calculate regionalised endpoint CFs
at a global scale and to evaluate both spatial variability and uncertainty.
A global scale atmospheric chemistry model was selected to serve as a basis for the generation of
atmospheric fate factors. With iterative mass balance calculations, we were able to generate
source-receptor matrices whose elements are atmospheric fate factors. The results showed that
transboundary deposition typically represented 4% of a continent total deposition.
A model simulating soil geochemical processes served as a basis to evaluate steady-state soil
chemical indicators. To do so, however, we needed to create a worldwide soil input parameter
database. Results showed that pH highlighted expected sensitive areas and demonstrated less
variations to soil input parameter uncertainty.
A model was created to evaluate worldwide lakes pH. This model considers lakes as a series of
interconnected continuously stirred reactor tanks (CSTR). It considers the H+ inputs from the
atmosphere, from the surrounding soils and from upstream transport and considers the H+ outputs
from downstream transport and evaporation.
The terrestrial and aquatic effect factors were calculated from different model regressions,
representing different ecosystems, linking pH to vascular plants (terrestrial acidification) or fishes
(aquatic acidification) biodiversity loss.
These methodological developments resulted in 13104 CFs for both terrestrial and aquatic
acidification. Each CF can assess the potential impacts of the acidifying emissions from any
worldwide 2ox2.5o grid. CFs can vary, across emission grids, by 5 to 6 orders of magnitude and 8
to 10 orders of magnitude for terrestrial and aquatic acidification, respectively. The endpoint CFs
xiv
uncertainty was established to more than an order of magnitude (factor 32) and about 2 orders
of magnitude for terrestrial and aquatic acidification, respectively.
Results also showed the importance of considering transboundary deposition. Indeed, while
transboundary deposition only represented a share of 4% of a continent total deposition, the
potential impacts of transboundary deposition represented, for an emission location, a share
typically equal to 15-17% and 44-58% of the terrestrial and aquatic acidification total potential
impacts, respectively.
By analysing the contributions of the atmospheric fate, soil sensitivity or the receiving
environment fate and effects factors to the endpoint CFs spatial variability and uncertainty, we
defined midpoint CFs. These midpoints CFs consider the evaluation of both atmospheric fate and
soil sensitivity or receiving environment fate for terrestrial and aquatic acidification, respectively.
Indeed, the atmospheric fate factor did little to explain the endpoint CFs spatial variability and
effect factors typically contributed to more than 90% of the total uncertainty. We thus concluded
that a CF based on soil sensitivity or receiving environment fate represented the best trade-off
between maximising environmental relevance and minimising uncertainty. These midpoint CFs
also ensure a consistent link to endpoint CFs. The midpoint uncertainty was approximated by a
factor 3 and a factor 2 for terrestrial and aquatic acidification, respectively.
Furthermore, it was shown that an evaluation based on worldwide, continental or country
resolutions CFs created an additional uncertainty equivalent to one or two orders of magnitude
depending on the chosen resolution.
Conclusively, this thesis presented a worldwide regionalised characterization model which
generated CFs capable of greater (comparatively to existing CFs) acidifying emissions
differentiation while showing the importance of i) the potential impacts from transboundary
deposition, ii) spatial variability and iii) uncertainty for both terrestrial and aquatic acidification.
Consequently, this thesis improves the LCIA current practices when assessing the potential
impacts related to the acidification impact category
L'écriture par gestes-piliers dans ma démarche compositionnelle
Tableau dâhonneur de la FacultĂ© des Ă©tudes supĂ©rieures et postdoctorales, 2010-2011Ce mĂ©moire porte sur trois musiques de concert que j'ai composĂ©es entre 2006 et 2009. Il traite plus spĂ©cifiquement de l'Ă©criture par gestes-piliers dans la dĂ©marche compositionnelle qui a menĂ© Ă leur rĂ©alisation. Au dĂ©part, ma rĂ©flexion sur la genĂšse de ces oeuvres - Ă propos des Ăźles de lumiĂšres, Cinq pamphlets pour ailleurs et Les fatras du contre-jour - a mis au jour l'importance du concept d'art dans ma dĂ©marche. J'ai aussi notĂ© que des notions comme intuition, intention, technique, imaginaire et projet esthĂ©tique sont essentielles Ă la comprĂ©hension de ce concept. Je me suis Ă©galement penchĂ© plus spĂ©cifiquement sur ma mĂ©thode de composition : l'Ă©criture par gestes-piliers s'est rĂ©vĂ©lĂ©e comme l'axe principal de cette mĂ©thode. Je me suis alors questionnĂ© sur l'origine de ces gestes-piliers et j'ai identifiĂ© plusieurs sources d'influence, soit les musiques de VarĂšse, Scelsi, Sciarrino et Berio. Outre l'introduction et la conclusion, ce mĂ©moire est construit en deux parties : chapitre 1, l'Ă©noncĂ© des diffĂ©rents concepts nĂ©cessaires Ă la comprĂ©hension de ma dĂ©marche compositionnelle et chapitre 2, l'illustration et l'analyse de l'Ă©criture par gestes-piliers dans les oeuvres Ă l'Ă©tude
ĂpidĂ©miologie de la maladie de Crohn au QuĂ©bec
Mémoire numérisé par la Direction des bibliothÚques de l'Université de Montréal
A new experimental set-up for the study of the formation and dissociation of methane hydrate in sediments
methane hydrates ; sediments ; kinetics ; modelling ; heat transfer ; mass transfer ;International audienceIn this paper, we give a short presentation of the project ForDiMHyS which consists of experimental studies and model establishment (or development) of the kinetics of FORmation and Dissociation of Methane Hydrates in Sediments. We focus on the details of the experimental set-up which is newly, specially designed for this study in the preliminary step of the project. The four French academic teams and two PhD thesis are involved in the ForDiMHyS project on the period 2000-2004. The financial support is given by the five French Partners. The project consists of two-step programs; firstly the data acquisition from the laboratory experimental set-up and secondly simulation of methane production from methane hydrate fields
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International audienceTolerating byzantine faults on a large scale is a challenge: in particular, Desktop Grid environments sustain large numbers of faults that range from crashes to byzantine faults. Solutions in the literature that address byzantine failures are costly and none of them scales to really large numbers of nodes. This paper proposes to distribute task scheduling on trusted nodes in a Cloud network and to have these nodes assess the reliability of worker nodes by means of a reputation system. The resulting architecture is built for scalability and adapts costs to the workload associated with client requests
Risk Score, Causes, and Clinical Impact of Failure of Transradial Approach for Percutaneous Coronary Interventions
ObjectivesTo study the causes of and to develop a risk score for failure of transradial approach (TRA) for percutaneous coronary intervention (PCI).BackgroundTRA-PCI failure has been reported in 5% to 10% of cases.MethodsTRA-PCI failure was categorized as primary (clinical reasons) or crossover failure. Multivariate analysis was performed to determine independent predictors of TRA-PCI failure, and an integer risk score was developed.ResultsFrom January to June 2010, TRA-PCI was attempted in 1,609 (97.3%) consecutive patients, whereas 45 (2.7%) had primary TRA-PCI failure. Crossover TRA-PCI failure occurred in 30 (1.8%) patients. Causes of primary TRA-PCI failure included chronic radial artery occlusion (11%), previous coronary artery bypass graft (27%), and cardiogenic shock (20%). Causes for crossover TRA-PCI failure included: inadequate puncture in 17 patients (57%); radial artery spasm in 5 (17%); radial loop in 4 (13%); subclavian tortuosity in 2 (7%); and inadequate guide catheter support in 2 (7%) patients. Female sex (odds ratio [OR]: 3.2; 95% confidence interval [CI]: 1.95 to 5.26, p < 0.0001), previous coronary artery bypass graft (OR: 6.1; 95% CI: 3.63 to 10.05, p < 0.0001), and cardiogenic shock (OR: 11.2; 95% CI: 2.78 to 41.2, p = 0.0011) were independent predictors of TRA-PCI failure. Risk score values from 0 to 7 predicted a TRA-PCI failure rate from 2% to 80%.ConclusionsIn a high-volume radial center, 2.7% of patients undergoing PCI are excluded from initial TRA on clinical grounds, whereas crossover to femoral approach is required in only 1.8% of the cases. A new simple clinical risk score is developed to predict TRA-PCI failure
Risk of neonatal hypothyroidism in newborns from mothers exposed to CTPA during pregnancy: Ancillary data from a prospective outcome study
Background: Neonatal hypothyroidism is often raised as a potential concern for the use of computed tomography pulmonary angiography (CTPA) in pregnant women with suspected pulmonary embolism (PE).
Objectives: To assess the incidence of neonatal hypothyroidism among newborns from mothers exposed to CTPA.
Patients/methods: Pregnant women with clinically suspected PE were included in a multicenter, multinational prospective diagnostic management outcome study, based on pretest clinical probability assessment, high-sensitivity D-dimer testing, bilateral lower limb venous compression ultrasonography, and CTPA. Results of Guthrie tests were systematically collected for newborns of all women who required CTPA as part of the diagnostic strategy. A thyroid-stimulating hormone (TSH) level above 15 U/ml was used to define hypothyroidism.
Results: Out of the 166 women included in the Swiss participating centers, 149 underwent a CTPA including 14 with twin pregnancies. Eight women suffered a pregnancy loss and results of the Guthrie test could not be retrieved for four newborns. All TSH levels were reported as being below 15 U/ml. The incidence of neonatal hypothyroidism was 0/151 (0.0%, 95% confidence interval: 0.0%-2.5%).
Conclusions: We did not identify any cases of neonatal hypothyroidism in our cohort of 149 pregnant women investigated for suspected PE using a CTPA. Along with previous literature data, this provides further reassuring data regarding the use of CTPA in this indication.
Keywords: Guthrie test; diagnosis; hypothyroidism; pregnancy; pulmonary embolism
Novel Insights into the Bovine Polled Phenotype and Horn Ontogenesis in Bovidae
Despite massive research efforts, the molecular etiology of bovine polledness and the developmental pathways involved in horn ontogenesis are still poorly understood. In a recent article, we provided evidence for the existence of at least two different alleles at the Polled locus and identified candidate mutations for each of them. None of these mutations was located in known coding or regulatory regions, thus adding to the complexity of understanding the molecular basis of polledness. We confirm previous results here and exhaustively identify the causative mutation for the Celtic allele (PC) and four candidate mutations for the Friesian allele (PF). We describe a previously unreported eyelash-and-eyelid phenotype associated with regular polledness, and present unique histological and gene expression data on bovine horn bud differentiation in fetuses affected by three different horn defect syndromes, as well as in wild-type controls. We propose the ectopic expression of a lincRNA in PC/p horn buds as a probable cause of horn bud agenesis. In addition, we provide evidence for an involvement of OLIG2, FOXL2 and RXFP2 in horn bud differentiation, and draw a first link between bovine, ovine and caprine Polled loci. Our results represent a first and important step in understanding the genetic pathways and key process involved in horn bud differentiation in Bovidae
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