Search results for "oxygen concentration"

Relevance of Oxygen Concentration in Stem Cell Culture for Regenerative Medicine

2019

The key hallmark of stem cells is their ability to self-renew while keeping a differentiation potential. Intrinsic and extrinsic cell factors may contribute to a decline in these stem cell properties, and this is of the most importance when culturing them. One of these factors is oxygen concentration, which has been closely linked to the maintenance of stemness. The widely used environmental 21% O2 concentration represents a hyperoxic non-physiological condition, which can impair stem cell behaviour by many mechanisms. The goal of this review is to understand these mechanisms underlying the oxygen signalling pathways and their negatively-associated consequences. This may provide a rationale…

Body size variability across habitats in the Brachionus plicatilis cryptic species complex

2020

AbstractThe body size response to temperature is one of the most recognizable but still poorly understood ecological phenomena. Other covarying environmental factors are frequently invoked as either affecting the strength of that response or even driving this pattern. We tested the body size response in five species representing the Brachionus plicatilis cryptic species complex, inhabiting 10 brackish ponds with different environmental characteristics. Principal Component Analysis selected salinity and oxygen concentration as the most important factors, while temperature and pH were less influential in explaining variation of limnological parameters. Path analysis showed a positive interclo…

Thermo-oxidative ageing of an organo-modified clay and effects on the properties of PA6 based nanocomposites

2013

a b s t r a c t In this work a careful investigation on the degradation of an organically modified montmorillonite sample (Cloisite 15A) thermal treated under different atmospheres, namely nitrogen, air and oxygen enriched atmosphere was performed. The exposure time of the thermal treatment ranged between 5 and 300 min. The chemical composition evolution as function of the thermal treatment conditions of the clay organic modifier was monitored by means of combined thermogravimetry/Fourier transform infrared spectroscopy (TGA-FTIR). Moreover, the morphological behaviour of treated Cloisite 15A sam- ples as function of the time and of the decomposition atmosphere was investigated by X-ray dif…

High-resolution characterization of the diffusion of light chemical elements in metallic components by scanning microwave microscopy

2014

International audience; An original sub-surface, high spatial resolution tomographic technique based on scanning microwave microscopy (SMM) is used to visualize in-depth materials with different chemical compositions. A significant phase difference in SMM between aluminum and chromium buried patterns has been observed. Moreover this technique was used to characterize a solid solution of a light chemical element (oxygen) in a metal lattice (zirconium). The large solubility of the oxygen in zirconium leads to modifications of the properties of the solid solution that can be measured by the phase shift signal in the SMM technique. The signal obtained in cross-section of an oxidized Zr sample s…

Tungsten oxide thin films sputter deposited by the reactive gas pulsing process for the dodecane detection

2015

International audience; The DC reactive magnetron sputtering of a metallic tungsten target was performed in an argon + oxygen atmosphere for depositing tungsten oxide thin films. In order to control the oxygen concentration in the films, the reactive gas pulsing process, namely RGPP, was implemented. Rectangular pulses were used with a constant pulsing period T = 16 s whereas the duty cycle α (time of oxygen injection to pulsing period T ratio) was systematically changed from 0 to 100% of T. This pulsing injection of the reactive gas allowed a gradual evolution of the films composition from pure metallic to over-stoichiometric WO3+ɛ’ compounds. These WOx films were sputter deposited on comm…

Hypoxia and anoxia in insects: microcalorimetric studies on two species (Locusta migratoria and Manduca sexta) showing different degrees of anoxia to…

1995

Abstract Microcalorimetry was used to study the effects of graded hypoxia and anoxia on two species of insects that differ in their tolerance of anoxia. Locusts (Locusta migratoria) can survive an atmosphere of pure nitrogen for not more than 4 h (at room temperature), whereas hawk moths (Manduca sexta) can recover from more than 24 h of anoxia. To produce graded hypoxia, air and pure nitrogen were mixed and this mixture was passed through the cells of a twin calorimeter equipped with circulation cells. A gas flow containing 2% or more of oxygen had no significant effect on behaviour (as observed in parallel experiments using transparent cells) or heat flow rate. If oxygen content was reduc…

1976

A radical mechanism is proposed for the formation of the 1,2-polymer 2 in the “spontaneous” polymerization of 4-vinylpyridinium salts 4-VP.HX (X=NO3, ClO4, HSO4, I) in aqueous solution on the basis of strong inhibition by oxygen and other radical inhibitors. Quantitative investigation of the influence of oxygen on the formation of the 1,2-polymer allowed the derivation of a formal kinetic scheme for the initiation and polymerization steps which is consistent with a free radical mechanism. Dependence of the average molecular weight of 2 on monomer concentration is in agreement with this model. Dependence of the inhibition time on the oxygen concentration as well as an acceleration of the fin…

Pyrene-Capped CdSe@ZnS Nanoparticles as Sensitive Flexible Oxygen Sensors in Non-Aqueous Media**

2014

A flexible, highly sensitive sensor of oxygen in non-aqueous solvents is described. It consists of CdSe/ZnS nanoparticles decorated with a considerable number of pyrene units, thus making the formation of the pyrene excimer possible. The emission of the pyrene excimer and that of the nanoparticle are suitably separated from each other and also from the excitation wavelength. This sensor can be applied as a ratiometric oxygen sensor by using the linear response of the pyrene excimer lifetime combined with the linear response of the nanoparticle excited state lifetime. This nanohybrid has been assayed in seven media with different dielectric constants and viscosities over the whole oxygen con…

Effect of gases on biochemical stabilization

2019

International audience; Lipid or protein are sensitive to peroxidation and inert gas limit or stop adulterations. Unsaturated lipids are peroxided by ground state dioxygen in presence of catalysts (iron, enzymes) or after thermal dissociation of C=C bond, and by excited state dioxygen without any assistance (photo-oxidation). Inerting fragile oils by bubbling with dinitrogen or carbon dioxide that are soluble gas in oil slows oxidation process during storage or frying. In a same way, limit the oxidation of the tryptophan residues of protein is possible by reducing oxygen content. Oxidation leads also to oxidation of thiol in disulfide, which induced protein cross-linked and decay of functio…

Does Oxygen Concentration Used for Resuscitation Influence Outcome of Asphyxiated Newly Born Infants Treated With Hypothermia?

2006

To the Editor. — In a recent article, Rutherford et al1 describe the neuroprotective effect of whole-body cooling and selective head cooling in newly born infants suffering from hypoxic-ischemic encephalopathy. MRI studies of infants receiving either of these therapies showed a lesser degree of basal ganglia and thalamic lesions than nontreated controls, which correlates with a better neurologic prognosis. However, no description of the resuscitation maneuvers used is present in the article's “Patients and Methods” section. Thus, the authors do not include details on how many infants were given positive pressure ventilation and, especially, what concentration of oxygen was used, if oxygen s…