35 research outputs found
Reminiscences of a radio astronomer
No full textInternational audienceThe author belongs to the second generation of radio astronomers. He started observing in 1954 with a German Riese-Würzburg radar transformed into a radio telescope, then in 1959-1963 with a two- Würzburg variable-spacing interferometer. He participated in the construction of the Nançay Large Radio Telescope, and used the Owens Valley Observatory interferometer during a stay in Caltech (1968-1969). He was deeply involved in the genesis of the French-German-Spanish Institute of Radio Astronomy at Millimeter waves (IRAM). His contacts with radio astronomers worldwide are described. In recent years, he participated in a series of seven papers devoted to the history of radio astronomy in France, published in this journal
Does resting heart rate measured by the physician reflect the patient’s true resting heart rate? White-coat heart rate
No full textObjectives: In cardiology, resting heart rate (HR) and blood pressure (BP) are key elements and are used to adapt treatment. However HR measured in consultation may not reflect true resting HR. We hypothesize that there may be a “white-coat” effect like with BP and that there may be an association between HR variations and BP variations.
Methods: This prospective, monocentric, observational, pilot study (January-April 2016) included 57 consecutive ambulatory patients at Poitiers University Hospital, France (58% male, mean age 64 years). Patients’ resting HR and BP were recorded with the same automated blood pressure sphygmomanometer in consultation by the physician then with self-measurement at home.
Results: In the overall cohort, we found that HR was significantly higher in consultation (70.5bpm ± 12.6 vs. 68.1bpm ± 10.1, p = 0.034). HR also correlated with diastolic BP (r = 0.45, p = 0.001).
Patients were divided into three groups to look for associations with BP: masked HR, (higher HR at home, 38.6%), white-coat HR, (lower HR at home 52.6%) and iso HR, (no change between HR at home and consultation, 8.8%).
Although there was no difference between groups in diastolic BP measured in consultation, home diastolic BP was lower in the white-coat HR group (74.3 mmHg ± 9.8 vs. 77.9 mmHg ± 7.5, p = 0.016).
Conclusions: Our study brings to light an exciting idea that could have a major therapeutic and maybe prognostic impact in cardiology: resting HR measured by the physician in consultation does not reflect true resting HR. This must be taken into account to adapt treatment
Birth, evolution and death of stars
No full textIt has been known for a long time that stars are similar to our Sun. But it was only in 1810 that they were shown to be made of an incandescent gas. The chemical composition of this gas began to be determined in 1860. In 1940, it was demonstrated that the energy radiated by the stars is of thermonuclear origin. How stars form from interstellar matter and how they evolve and die was understood only recently, with our knowledge still incomplete. It was also realized recently that close double stars present a wide variety of extraordinary phenomena, which are far from being completely explored. This book explains all these aspects, and also discusses how the evolution of stars determine that of galaxies. The most interesting observations are illustrated by spectacular images, while the theory is explained as simply as possible, without however avoiding some mathematical or physical developments when they are necessary for a good understanding of what happens in stars. Without being a textbook for specialists, this book can be profitably read by students or amateurs possessing some basic scientific knowledge, who would like to be initiated in-depth to the fascinating world of stars. The author, an emeritus astronomer of the Paris Observatory, worked in various domains of astronomy connected with the subject of this book: interstellar matter and evolution of stars and galaxies. He directed the Marseilles observatory from 1983 to 1988 and served for fifteen years as Chief Editor of the professional European journal Astronomy & Astrophysics. He has written many articles and books about physics and astronomy at different levels
Atypical chemokine receptor 2 expression is directly regulated by hypoxia inducible factor-1 alpha in cancer cells under hypoxia
No full textAbstract Lack of significant and durable clinical benefit from anti-cancer immunotherapies is partly due to the failure of cytotoxic immune cells to infiltrate the tumor microenvironment. Immune infiltration is predominantly dependent on the chemokine network, which is regulated in part by chemokine and atypical chemokine receptors. We investigated the impact of hypoxia in the regulation of Atypical Chemokine Receptor 2 (ACKR2), which subsequently regulates major pro-inflammatory chemokines reported to drive cytotoxic immune cells into the tumor microenvironment. Our in silico analysis showed that both murine and human ACKR2 promoters contain hypoxia response element (HRE) motifs. Murine and human colorectal, melanoma, and breast cancer cells overexpressed ACKR2 under hypoxic conditions in a HIF-1α dependent manner; as such overexpression was abrogated in melanoma cells expressing non-functional deleted HIF-1α. We also showed that decreased expression of ACKR2 in HIF-1α-deleted cells under hypoxia was associated with increased CCL5 levels. Chromatin immunoprecipitation data confirmed that ACKR2 is directly regulated by HIF-1α at its promoter in B16-F10 melanoma cells. This study provides new key elements on how hypoxia can impair immune infiltration in the tumor microenvironment
The evolution of the mass-metallicity relation in SDSS galaxies uncovered by astropaleontology
No full textMarangoni destabilization of bidimensional-confined gas-liquid co-flowing streams in rectangular microfluidic channels
No full textInternational audienceIn microchannels, the stability of a fluid jet injected into another immiscible fluid strongly depends on its degree of geometric confinement. When the width of the jet, w, is larger than the channel height, H, the surface tension driven Rayleigh-Plateau instability is suppressed so that the 2D (bidimensional)-confined jet is absolutely stable and never collapses into bubbles (or drops) in contrast to what occurs when w ≤ H [Dollet et al., "Role of the channel geometry on the bubble pinch-off in flow-focusing,"Phys. Rev. Lett. 100(3), 034504 (2008); Guillot et al., "Stability of a jet in confined pressure-driven biphasic flows at low Reynolds number in various geometries,"Phys. Rev. E 78(1), 016307 (2008)]. We here demonstrate both experimentally and theoretically that this picture is, indeed, no longer valid when Marangoni effects are considered. We experimentally show that the addition of small length alcohol molecules into the liquid phase destabilizes a 2D-confined gas-water microfluidic stream (w > H), leading to the generation of steady non-linear waves and further to the production of bubbles. Using a simple hydrodynamic model, we show through a linear analysis that the destabilization of the gas stream may result from a Marangoni instability due to the fast adsorption of the alcohol molecules, which occurs on a timescale comparable to that of the microfluidic flow. © 2023 Author(s)
Synthesis of Near-Infrared-Emitting, Water-Soluble CdTeSe/CdZnS Core/Shell Quantum Dots
No full textApplications of near-infrared (NIR) emitting CdTe-based QDs have been hampered by their sensitivity to oxidation. Here, we describe a synthetic method for the growth of CdTeSe/CdZnS core/shell QDs emitting in the NIR range (700−800 nm). We first synthesize high-quantum-yield zinc-blende CdTeSe cores with gradient composition and tunable emission up to 800 nm. The CdZnS shell growth is performed with cadmium and zinc carboxylate and trioctylphosphine sulfur precursors in trioctylamine solvent, and yields thick shell with controlled zinc blende crystalline structure. The presence of a high-band-gap, oxidation-resistant shell considerably improves the quantum yield and stability of these QDs when solubilized in saline buffers, making them promising fluorescence probes for NIR biological imaging
171 T wave variability (TWV): circadian variations in patients after acute coronary syndrome (ACS)
No full textIntroductionRisk stratification is a major challenge in ischemic cardiomyopathy. The prognostic significance of TWV measured by amplitude variance of T wave amplitude has been proved. But, short-term and midterm circadian variations of TWV are unknown.ObjectivesWe measured TWV during 24 hours in pts with normal or moderately altered LVEF at day 7 (D7) and after cardiac rehabilitation at day 40 (D40), after an ischemic event.MethodsStudy population consisted in 48 pts after ACS (45 males, aged 59±11, LVEF 53±10%, treated by angioplasty (88%), CABG (8%) or medically (4%). All pts have had 24h Holter recording (Sorin group, sampling at 1000Hz) divided in 30min-periods of measurement of TWV; we compared daytime (8am–8pm) and nighttime TWV (11pm–6am). Holters have been performed at D7 and D40 (90±54). We also compared TWV at rest during the first 30min-period at D7 and D40. There were no changes in LVEF and coronary status between both Holters.ResultsAt D7 and D40, circadian analysis showed maximum values from noon to 4 pm followed by a down sloping with a nadir between 6 and 7 am and an increase between 7 and 9 am. On the short term curve (D7), the daytime TWV amplitude was lower. At D7, TWV did not differ significantly between day and night (20.3±4.2μV vs 18.4±7.7μV, p=0.072, decrease of 9.35%). At D40, TWV was significantly higher during day period (21.1±55.4μV vs 18.4±6.9μV, p=0.009, decrease of 12.79%).Between D7 and D40, TWV at rest during a 30 min-period were not significantly different (18.3±5.4μV vs 18.2±6.8μV, p=0.885)ConclusionTWV has circadian variations, as shown for blood pressure and heart rate. The TWV was significantly higher during daytime than in sleeping period. These findings lead to recommend measuring TWV after cardiac rehabilitation but further studies are needed to precise the best study period during daytime.Circadian evolution of TWV at D7 and D40 after AC
Evolução química e história de formação estelar no universo local
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2010Analisamos as galáxias do Sloan Digital Sky Survey com o nosso código de síntese espectral Starlight. O Starlight acha a combinação de populações estelares simples de diferentes idades e metalicidades que melhor modela o espectro de uma galáxia. Ele permite derivar vários parâmetros associados a uma galáxia, como a massa em estrelas, a história de formação estelar e a evolução química. A partir do espectro residual puramente nebular (subtraindo do espectro observado o modelado), medimos as linhas de emissão, das quais derivamos propriedades do gás dentro das galáxias. Estudamos a evolução das galáxias com formação estelar. Constatamos que as galáxias de maior massa formaram suas estrelas e seus metais mais rapidamente. A evolução da metalicidade das estrelas é estudada diretamente. Calibramos também a taxa de formação estelar atual medida pela síntese com a medida pela luminosidade de Halfa. Derivamos a relação massa estelar-metalicidade estelar (M*-Z*) em diferentes redshifts. Esta é a primeira vez que a relação M*-Z* é calculada para o mesmo conjunto de galáxias. Observamos que a metalicidade estelar observada tem uma evolução compatível com um modelo simples de evolução química de caixa fechada. Para as galáxias classificadas como LINERs, encontramos que a luminosidade observada em Halfa é compatível com o número de fótons ionizantes emitidos pelas populações estelares velhas dessas galáxias. Este resultado implica em uma profunda revisão da taxa de atividade nuclear nas galáxias do Universo local
