oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 5 )

2019 ( 222 )

2018 ( 278 )

2017 ( 279 )

Custom range...

Search Results: 1 - 10 of 219554 matches for " C. Fradin "
All listed articles are free for downloading (OA Articles)
Page 1 /219554
Display every page Item
A Comparison of Methods to Measure the Magnetic Moment of Magnetotactic Bacteria through Analysis of Their Trajectories in External Magnetic Fields
Rohan Nadkarni, Solomon Barkley, Cécile Fradin
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0082064
Abstract: Magnetotactic bacteria possess organelles called magnetosomes that confer a magnetic moment on the cells, resulting in their partial alignment with external magnetic fields. Here we show that analysis of the trajectories of cells exposed to an external magnetic field can be used to measure the average magnetic dipole moment of a cell population in at least five different ways. We apply this analysis to movies of Magnetospirillum magneticum AMB-1 cells, and compare the values of the magnetic moment obtained in this way to that obtained by direct measurements of magnetosome dimension from electron micrographs. We find that methods relying on the viscous relaxation of the cell orientation give results comparable to that obtained by magnetosome measurements, whereas methods relying on statistical mechanics assumptions give systematically lower values of the magnetic moment. Since the observed distribution of magnetic moments in the population is not sufficient to explain this discrepancy, our results suggest that non-thermal random noise is present in the system, implying that a magnetotactic bacterial population should not be considered as similar to a paramagnetic material.
Self-directed growth of AlGaAs core-shell nanowires for visible light applications
C. Chen,S. Shehata,C. Fradin,R. LaPierre,C. Couteau,G. Weihs
Physics , 2007, DOI: 10.1021/nl070874k
Abstract: Al(0.37)Ga(0.63)As nanowires (NWs) were grown in a molecular beam epitaxy system on GaAs(111)B substrates. Micro-photoluminescence measurements and energy dispersive X-ray spectroscopy indicated a core-shell structure and Al composition gradient along the NW axis, producing a potential minimum for carrier confinement. The core-shell structure formed during the growth as a consequence of the different Al and Ga adatom diffusion lengths.
Multiple Quantum Well AlGaAs Nanowires
C. Chen,N. Braidy,C. Couteau,C. Fradin,G. Weihs,R. LaPierre
Physics , 2008, DOI: 10.1021/nl0726306
Abstract: This letter reports on the growth, structure and luminescent properties of individual multiple quantum well (MQW) AlGaAs nanowires (NWs). The composition modulations (MQWs) are obtained by alternating the elemental flux of Al and Ga during the molecular beam epitaxy growth of the AlGaAs wire on GaAs (111)B substrates. Transmission electron microscopy and energy dispersive X-ray spectroscopy performed on individual NWs are consistent with a configuration composed of conical segments stacked along the NW axis. Micro-photoluminescence measurements and confocal microscopy showed enhanced light emission from the MQW NWs as compared to non-segmented NWs due to carrier confinement and sidewall passivation.
Microscopic measurement of the linear compressibilities of two-dimensional fatty acid mesophases
C. Fradin,J. Daillant,A. Braslau,D. Luzet,M. Alba,M. Goldmann
Physics , 1997, DOI: 10.1007/s100510050152
Abstract: The linear compressibility of two-dimensional fatty acid mesophases has determined by grazing incidence x-ray diffraction. Surface pressure vs molecular area isotherms were reconstructed from these measurements, and the linear compressibility (relative distortion along a given direction for isotropic applied stress) was determined both in the sample plane and in a plane normal to the aliphatic chain director (transverse plane). The linear compressibilities range over two orders of magnitude from 0.1 to 10 m/N and are distributed depending on their magnitude in 4 different sets which we are able to associate with different molecular mechanisms. The largest compressibilities (10m/N) are observed in the tilted phases. They are apparently independent of the chain length and could be related to the reorganization of the headgroup hydrogen-bounded network, whose role should be revalued. Intermediate compressibilities are observed in phases with quasi long-range order (directions normal to the molecular tilt in L_2 or L_2' phases, S phase), and could be related to the ordering of these phases. The lowest compressibilities are observed in the solid untilted CS phase and for 1 direction of the S and L_2'' phases. They are similar to the compressibility of crystalline polymers and correspond to the interactions between methyl groups in the crystal. Finally, negative compressibilities are observed in the transverse plane for L_2' and L_2'' phases and can be traced to subtle reorganizations upon untilting.
T2DM: Why Epigenetics?
Delphine Fradin,Pierre Bougnères
Journal of Nutrition and Metabolism , 2011, DOI: 10.1155/2011/647514
Abstract: Type 2 Diabetes Mellitus (T2DM) is a metabolic disorder influenced by interactions between genetic and environmental factors. Epigenetics conveys specific environmental influences into phenotypic traits through a variety of mechanisms that are often installed in early life, then persist in differentiated tissues with the power to modulate the expression of many genes, although undergoing time-dependent alterations. There is still no evidence that epigenetics contributes significantly to the causes or transmission of T2DM from one generation to another, thus, to the current environment-driven epidemics, but it has become so likely, as pointed out in this paper, that one can expect an efflorescence of epigenetic knowledge about T2DM in times to come.
Les adjectifs dérivés en -eux liés aux éléments du corps. Comment traiter des microvariations interprétatives ?
Fradin Bernard,Mathieu Yvette Yannick
SHS Web of Conferences , 2012, DOI: 10.1051/shsconf/20120100163
Abstract: La majorité des adjectifs en EUX du fran ais est dérivée à partir d’un nom comme orag-eux ← orage. Ceux qui ne le sont pas proviennent du latin par emprunt e.g. ligneux < lat lignosus, plus rarement du grec e.g. scléreux. Cette contribution examine un sous ensemble de ces adjectifs dont le nom base dénote un élément du corps (cartilagineux, osseux, tendineux, etc.), ou lié au corps (bronchiteux, cancéreux, migraineux, etc.), avec pour objectif de déterminer la relation sémantique qui s’instaure entre le nom base et le nom recteur. Après avoir établi une classification des adjectifs en fonction de leur nom base (donnée en annexe), nous montrons comment les propriétés sémantiques des noms bases et des noms recteurs déterminent les possibilités interprétatives. Cette analyse est resituée à l’intérieur du traitement plus large des adjectifs en -EUX et montre que les principes interprétatifs généraux à l’ uvre dans la construction de ces adjectifs opèrent dans le domaine de ceux liés au corps. Cette analyse montre surtout que les propriétés sémantiques des noms bases et des noms recteurs déterminent fortement les possibilités interprétatives, et que l’interprétation la moins dépendante de ces propriétés, l’interprétation spatiale, constitue logiquement la plus répandue. Cette étude éclaire, en retour, le classement sémantique des noms.
T2DM: Why Epigenetics?
Delphine Fradin,Pierre Bougnères
Journal of Nutrition and Metabolism , 2011, DOI: 10.1155/2011/647514
Abstract: Type 2 Diabetes Mellitus (T2DM) is a metabolic disorder influenced by interactions between genetic and environmental factors. Epigenetics conveys specific environmental influences into phenotypic traits through a variety of mechanisms that are often installed in early life, then persist in differentiated tissues with the power to modulate the expression of many genes, although undergoing time-dependent alterations. There is still no evidence that epigenetics contributes significantly to the causes or transmission of T2DM from one generation to another, thus, to the current environment-driven epidemics, but it has become so likely, as pointed out in this paper, that one can expect an efflorescence of epigenetic knowledge about T2DM in times to come. 1. Introduction The threatened epidemic of T2DM, largely driven by the increase in obesity, is projected to affect >400 million adults worldwide by 2030. Obesity and T2DM, beyond their definition as “diseases,” are becoming the “normal” metabolic fate of a large fraction of modern human populations, notably in those of Asian descent [1]. This human tendency to eat in excess of the needs, to gain fat, and not to have an unlimited insulin secretion capacity, certainly has a widespread genetic background in our species, but the recent epidemics obviously finds its main sources in environmental changes. Those environmental changes can affect phenotype directly or through epigenetic mechanisms that provide an interface with the genome. This is why, in the minds of many, epigenetics has become a leading causative candidate for the causation (and possibly inheritance) of obesity and T2DM. There is no smoke without fire: epigenetic mechanisms have great potential to contribute to the mechanisms and possibly the causes of many environmentally sensitive human diseases. But epigenomics and epigenetic epidemiology are yet at a stage where genomics was 30 years ago, when everyone was working on his part of the puzzle. The complete DNA sequence of an organism does not contain the information necessary to specify the organism. The outcome of developmental processes depends both on the genotype and on the temporal sequence of environments in which the organism develops. If the phenotype of the organism of a given genotype is plotted against an environmental variable, the function that is produced is called the norm of reaction of the genotype [2]; it is the mapping function of environment into phenotype for that genotype. Since norms of reaction of different genotypes are curves of irregular shape that cross each other, it
Investigating liquid surfaces down to the nanometer scale using grazing incidence x-ray scattering
C. Fradin,A. Braslau,D. Luzet,M. Alba,C. Gourier,J. Daillant,G. Gruebel,G. Vignaud,J. -F. Legrand,J. Lal J. -M. Petit,F. Rieutord
Physics , 1997, DOI: 10.1016/S0921-4526(98)00255-5
Abstract: Grazing incidence x-ray surface scattering has been used to investigate liquid surfaces down to the molecular scale. The free surface of water is well described by the capillary wave model ( ~ q-2 spectrum) up to wavevectors > 10^8 m^-1. At larger wavevectors near-surface acoustic waves must be taken into account. When the interface is bounded by a surfactant monolayer, it exhibits a bending stiffness and the bending rigidity modulus can be measured. However, bending effects generally cannot be described using the Helfrich Hamiltonian and the characteristic exponent in the roughness power spectrum can smaller than 4. Finally, upon compression, tethered monolayers formed on a subphase containing divalent ions are shown to buckle in the third dimension with a characteristic wavelength on the order of 10^8 m^-1.
Procalcitonin levels in acute exacerbation of COPD admitted in ICU: a prospective cohort study
Cédric Daubin, Jean-Jacques Parienti, Astrid Vabret, Michel Ramakers, Sabine Fradin, Nicolas Terzi, Fran?ois Freymuth, Pierre Charbonneau, Damien du Cheyron
BMC Infectious Diseases , 2008, DOI: 10.1186/1471-2334-8-145
Abstract: We conducted a single center prospective cohort study in consecutive COPD patients admitted to the ICU for AECOPD between September 2005 and September 2006. Sputum samples or tracheal aspirates were tested for the presence of bacteria and viruses. PCT levels were measured at the time of admittance, six hours, and 24 hours using a sensitive immunoassay.Thirty nine AECOPD patients were included, 31 of which (79%) required a ventilator support at admission. The median [25%–75% interquartile range] PCT level, assessed in 35/39 patients, was: 0.096 μg/L [IQR, 0.065 to 0.178] at the time of admission, 0.113 μg/L [IQR, 0.074 to 0.548] at six hours, and 0.137 μg/L [IQR, 0.088 to 0.252] at 24 hours. The highest PCT (PCTmax) levels were less than 0.1 μg/L in 14/35 (40%) patients and more than 0.25 μg/L in 10/35 (29%) patients, suggesting low and high probability of bacterial infection, respectively. Five species of bacteria and nine species of viruses were detected in 12/39 (31%) patients. Among the four patients positive for Pseudomonas aeruginosa, one had a PCTmax less than 0.25 μg/L and three had a PCTmax less than 0.1 μg/L. The one patient positive for Haemophilus influenzae had a PCTmax more than 0.25 μg/L. The presence or absence of viruses did not influence PCT at time of admission (0.068 vs 0.098 μg/L respectively, P = 0.80).The likelihood of bacterial infection is low among COPD patients admitted to ICU for AECOPD (40% with PCT < 0.1 μg/L) suggesting a possible inappropriate use of antibiotics. Further studies are necessary to assess the impact of a procalcitonin-based therapeutic strategy in critically ill COPD patients.Acute exacerbations are a leading cause of severe respiratory failure in chronic obstructive pulmonary disease (COPD) patients [1]. In this setting, the use of antibiotics is recommended by the recent guidelines of the European Respiratory Society (ERS), and French Consensus Conference [2,3]. However, bacteria are isolated from the respiratory tract
Procalcitonin levels and bacterial aetiology among COPD patients admitted to the ICU with severe pneumonia: a prospective cohort study
Cédric Daubin, Jean-Jacques Parienti, Sabine Fradin, Astrid Vabret, Michel Ramakers, Nicolas Terzi, Fran?ois Freymuth, Pierre Charbonneau, Damien du Cheyron
BMC Infectious Diseases , 2009, DOI: 10.1186/1471-2334-9-157
Abstract: We conducted a prospective cohort study in an ICU of a University Hospital. All consecutive COPD patients admitted for pneumonia between September 2005 and September 2006 were included. Respiratory samples were tested for the presence of bacteria and viruses. Procalcitonin was sequentially assessed and patients classified according to the probability of the presence of a bacterial infection.Thirty four patients were included. The PCT levels were assessed in 32/34 patients, median values were: 0.493 μg/L [IQR, 0.131 to 1.471] at the time of admission, 0.724 μg/L [IQR, 0.167 to 2.646] at six hours, and 0.557 μg/L [IQR, 0.123 to 3.4] at 24 hours. The highest PCT (PCTmax) levels were less than 0.1 μg/L in 3/32 (9%) patients and greater than 0.25 μg/L in 22/32 (69%) patients, suggesting low and high probability of bacterial infection, respectively. Fifteen bacteria and five viruses were detected in 15/34 (44%) patients. Bacteria were not detected in patients with PCTmax levels < 0.1 μg/L. In contrast, bacteria were detected in 4/7 (57%) patients estimated unlikely to have a bacterial infection by PCT levels (PCTmax > 0.1 and < 0.25 μg/L).Based on these results we suggest that a PCT level cut off > 0.1 μg/L may be more appropriate than 0.25 μg/L (previously proposed for non severe lower respiratory tract infection) to predict the probability of a bacterial infection in severe COPD patients with pneumonia. Further studies testing procalcitonin-based antibiotic strategies are needed in COPD patients with severe pneumonia.Severe pneumonia is a common cause of acute exacerbations of chronic obstructive pulmonary disease (AECOPD) [1]. In this setting, a prompt initiation of antibiotics is recommended [2,3]. However, bacterial etiology is only found in approximately 50% of cases [1,4]. Other pathogens, such as respiratory viruses, have been reported in severe AECOPD requiring ventilation [5,6] and pneumonic AECOPD [1]. Moreover, in clinical practice, signs and symptoms of bacte
Page 1 /219554
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.