Building the analytical response in frequency domain of AC biased bolometers Application to Planck/HFI

Context: Bolometers are high sensitivity detector commonly used in Infrared astronomy. The HFI instrument of the Planck satellite makes extensive use of them, but after the satellite launch two electronic related problems revealed critical. First an unexpected excess response of detectors at low optical excitation frequency for {\nu} < 1 Hz, and secondly the Analog To digital Converter (ADC) component had been insufficiently characterized on-ground. These two problems require an exquisite knowledge of detector response. However bolometers have highly nonlinear characteristics, coming from their electrical and thermal coupling making them very difficult to modelize. Goal: We present a method to build the analytical transfer function in frequency domain which describe the voltage response of an Alternative Current (AC) biased bolometer to optical excitation, based on the standard bolometer model. This model is built using the setup of the Planck/HFI instrument and offers the major improvement of being based on a physical model rather than the currently in use had-hoc model based on Direct Current (DC) bolometer theory. Method: The analytical transfer function expression will be presented in matrix form. For this purpose, we build linearized versions of the bolometer electro thermal equilibrium. And a custom description of signals in frequency is used to solve the problem with linear algebra. The model performances is validated using time domain simulations. Results: The provided expression is suitable for calibration and data process- ing. It can also be used to provide constraints for fitting optical transfer function using real data from steady state electronic response and optical response. The accurate description of electronic response can also be used to improve the ADC nonlinearity correction for quickly varying optical signals.Comment: 20 pages, 10 figure

Identification en thérapie cellulaire des patrons d’expression transcriptomique de cellules souches utilisées pour traiter la défaillance cardiaque afin d’en améliorer le potentiel thérapeutique

La cardiopathie ischémique incluant l’insuffisance cardiaque est la deuxième cause de mortalité annuelle au Canada. Bien que de nombreuses stratégies préventives et des thérapies pharmacologiques retardent la progression de la maladie, il n’existe aucune solution qui module directement aux les remaniements pathologiques et la perte de cardiomyocytes. Au cours des 25 dernières années, de multiples progrès dans les domaines de la médecine régénérative et de la thérapie cellulaire ont annoncé des résultats prometteurs, mais les résultats d’études cliniques contemporaines demeurent plutôt mitigés. COMPARE-AMI, une étude randomisée-contrôlée de phase II, a évalué l’effet d’injections intracoronariennes de cellules souches hématopoïétiques CD133+ chez des patients souffrant d’infarctus aigu. IMPACT-CABG, une ÉRC de phase II a également évalué l’effet d’injections intramyocardiques de cellules CD133+ chez les patients souffrant de cardiomyopathie ischémique chronique nécessitant une revascularisation chirurgicale. Nous avons émis l’hypothèse que les cellules CD133+ utilisées dans des études cliniques de cardiomyopathies ischémiques aiguës et chroniques des patients répondant à la thérapie cellulaire exhibent des signatures transcriptomiques communes responsables de leur effet thérapeutique. En classant les patients en tant que répondants et non-répondants selon leur fonction cardiaque, nous avons évalué, a posteriori, ces patrons d’expression. Les cellules CD133+ autologues de patients jugés répondants expriment des signatures qui sont hautement conservées entre elles (incluant l’angiogénèse, la régulation de la réponse au stress et la survie cellulaire) et uniques d’un modèle à l’autre et qui pourraient, en partie, exprimer les issus cliniques des patients. Afin de maximiser les effets de la thérapie cellulaire aux cellules souches, nous avons par la suite tenté de reproduire ces phénotypes par stimulation pharmacologique avec des inhibiteurs d’HSP90 pour leurs effets qui semblent reproduire ces signatures. Ainsi, nous avons démontré qu’une stimulation de cellules souches mésenchymateuses humaines (CSMh) au Célastrol (inhibiteur HSP90) pouvait répliquer certains de ces phénotypes. Notamment, des CSMh conditionnées activent des voies de signalisation de type ‘RISK’ et augmentent leur sécrétion de protéines en lien avec la réponse au stress ainsi que d’exosomes contenant des molécules impliquées dans la communication intercellulaire sans être liées à un changement de type cellulaire. De plus, les CSMh traitées semblent améliorer la guérison de plaie par activité paracrine et sont plus résistante à la sénescence oxydative. Ces résultats encourageants nous permettent d’envisager des stratégies plus poussées de pré-conditionnement cellulaire ex vivo de cellules CD133+ avant leur implantation. À terme, cela pourrait mener à une optimisation de la thérapie cellulaire afin d’en maximiser les bénéfices cliniques et d’en exploiter leur plein potentiel.Ischemic cardiomyopathy and heart failure are the second annual cause of mortality in Canada. Despite rigorous prevention strategies and drug regimens preventing progression, no therapeutic modality can currently reverse the pathologic modifications of the disease. In the last quarter century, numerous advances in the field of regenerative medicine and cell therapy have demonstrated promising effects. COMPARE-AMI, a phase II randomized controlled trial (RCT), evaluated the effect of intracoronary injection of CD133+ cells in acute myocardial infarction following percutaneous intervention. IMPACTCABG, also a phase II RCT, evaluated the effect of intramyocardial injection of CD133+ hematopoietic stem cells in chronic ischemic cardiomyopathy at the time of surgical revascularization. That being said, we believe that the CD133+ cells used in therapy have shared transcriptomic signatures that are responsible for their clinical effects. By classifying patients into responders and non-responders according to an improvement in ejection fraction, we evaluated, a posteriori, those expression patterns. Autologous CD133+ cells of patients classified as responders expressed highly conserved transcriptomic signatures that could be responsible for the clinical outcomes of patients. Notably, these signatures were related to cardioprotective mechanisms including angiogenesis, stress response regulation and cell survival. In order to harness the full potential of stem cell therapy, we attempted to reproduce the identified phenotypes by pharmacological intervention with HSP90 inhibitors which are known to mimic some of these effets. Conditioned human mesenchymal stem cells (hMSC) activated ‘RISK’-type signaling pathways and augmented exosome and protein secretion relating to the response to cellular stress; this activation was unrelated to a switch of cell type. Furthermore, treated hMSC seemed to favour improved wound healing by paracrine activity and were more resistant to oxidative senescence. These encouraging results allow us to develop novel, more advance, strategies of ex vivo cell preconditioning before implantation, including of CD133+ cells. Ultimately, we hope that optimisation of cells through this mechanism and others will allow us to unleash the full potential of stem cell therapy

Catalase Prevents Maternal Diabetes–Induced Perinatal Programming via the Nrf2–HO-1 Defense System

We investigated whether overexpression of catalase (CAT) in renal proximal tubular cells (RPTCs) could prevent the programming of hypertension and kidney disease in the offspring of dams with maternal diabetes. Male offspring of nondiabetic and diabetic dams from two transgenic (Tg) lines (Hoxb7-green fluorescent protein [GFP]-Tg [controls] and Hoxb7/CAT-GFP-Tg, which overexpress CAT in RPTCs) were studied from the prenatal period into adulthood. Nephrogenesis, systolic blood pressure, renal hyperfiltration, kidney injury, and reactive oxygen species (ROS) generation were assessed. Gene expression of transforming growth factor-β1 (TGF-β1), nuclear factor erythroid 2p45–related factor-2 (Nrf2), and heme oxygenase-1 (HO-1) was tested in both in vitro and in vivo studies. Renal dysmorphogenesis was observed in offspring of Hoxb7-GFP-Tg dams with severe maternal diabetes; the affected male offspring displayed higher renal ROS generation and developed hypertension and renal hyperfiltration as well as renal injury with heightened TGF-β1 expression in adulthood. These changes were ameliorated in male offspring of diabetic Hoxb7/CAT-GFP-Tg dams via the Nrf2–HO-1 defense system. CAT promoted Nrf2 nuclear translocation and HO-1 gene expression, seen in both in vitro and in vivo studies. In conclusion, CAT overexpression in the RPTCs ameliorated maternal diabetes–induced perinatal programming, mediated, at least in part, by triggering the Nrf2–HO-1 defense system

VITAE : VIrTual brAin pErfusion

VITAE is an ERC funded software project aimed at providing full brain simulations of cerebral blood flow and solute exchange between blood and the neural tissue. The endgoal is to understand fine scale interactions between the architecture of the microvascular network in the brain and its functions (blood supply, oxygen and nutrient delivery, waste removal). This may indeed help unveil potential causes of cerebral disease like Alzheimer’s Disease. In the actual state of the art, full scale brain simulations are something new. First, acquiring input anatomical data of the blood vessel network is difficult and is an active domain of research. Next, simulation by itself is a CPU intensive Computational Fluid Dynamic problem requiring both inversion of large matrices and manipulation of large amounts of data. The current milestone is capable of running pressure resolution in a full mouse brain composed of about 5 millions of microvessels in one second on 1024 processor cores. The software written in C++ fully supports parallelized IO and graph partitioning to optimize the placement of vertices and reduce computing times. The next challenge is to run simulations taking the complex behavior of blood into account, which requires to run the pressure solver from one hundred to several thousand times. This will require to improve significantly the convergence time. Acknowledgements: ERC Funded Project: Proof of Concept (PoC), ERC-2018-PoC A. Sauvé, J.-D. Julien, M. Berg, M. Peyrounette, P. Elyakime, Y. Davit, M. Pigou, S. Lorthoi

Fake news : les bibliothécaires du Québec veulent faire partie de l’équation

Cette enquête présente les perceptions de la communauté des bibliothécaires professionnels du Québec face aux fake news et les initiatives que celle-ci a mis en place pour lutter contre la désinformation. Au moyen d’un questionnaire en ligne soumis durant l’été 2020, auquel 263 bibliothécaires provenant de divers milieux d’exercice ont répondu, la consultation révèle que la quasi-totalité des bibliothécaires se préoccupent de la présence des fake news dans le paysage médiatique. Pour freiner les fake news, l’éducation aux médias et à l’information est une solution qui fait consensus, mais le recours aux lois reçoit un accueil mitigé. Grâce aux commentaires reçus, l’enquête met en lumière de nombreuses initiatives locales et nationales visant à sensibiliser la population aux dangers de la désinformation et lui donner des outils pour éviter de tomber dans le panneau. En conclusion, les auteurs encouragent les bibliothécaires à intervenir davantage sur la place publique, notamment en faisant valoir leur expertise, car celle-ci peut être utile à l’ensemble des citoyens.This survey presents the perceptions of the Quebec professional library community regarding fake news and the initiatives it has put in place to combat misinformation. Through an online questionnaire submitted in the summer of 2020, to which 263 librarians from various practice settings responded, the consultation reveals that almost all librarians are concerned about the presence of fake news in the media landscape. There is a consensus that educating citizens in information literacy skills is one way to stop fake news, but the use of legislative change receives a mixed reception. Thanks to the comments received, the survey highlights numerous local and national initiatives aiming to raise awareness of the dangers of misinformation and give people tools to avoid falling into the trap. In conclusion, the authors encourage librarians to become more involved in the public arena because their expertise can be useful to all citizens