Thermal-oxidation of epoxy/amine followed by glass transition temperature changes

Thermal oxidation of three epoxy resins differing by the nature of prepolymer (bisphenol A diglycidyl ether and 1,4-butanediol diglycidyl ether) and hardener (isophorone diamine and 4,7,10-Trioxa-1,13-tridecanediamine) was studied by monitoring changes in glass transition temperature using DSC. Results were discussed using the DiMarzio's approach in which parameters are estimated from an additive group contribution. This theory allowed a fair assessment of Tg values for unaged networks. During oxidation, epoxy networks were shown to undergo chain scissions occurring in great part in hydroxypropyl ether and isophorone groups. However, the exploitation of Tg changes showed the coexistence and even the predominance of crosslinking in materials having linear aliphatic segments. The DiMarzio's approach was used to discuss the possibility of intramolecular cyclization or intermolecular crosslinks which were shown to predominate. Crosslinks were tentatively justified from a mechanistic point of view and quantified depending on experimental conditions

Numerical methods for the pricing of Swing options: a stochastic control approach

International audienceIn the natural gas market, many derivative contracts have a large degree of flexibility. These are known as Swing or Take-Or-Pay options. They allow their owner to purchase gas daily, at a fixed price and according to a volume of their choice. Daily, monthly and/or annual constraints on the purchased volume are usually incorporated. Thus, the valuation of such contracts is related to a stochastic control problem, which we solve in this paper using new numerical methods. Firstly, we extend the Longstaff–Schwarz methodology (originally used for Bermuda options) to our case. Secondly, we propose two efficient parameterizations of the gas consumption, one is based on neural networks and the other on finite elements. It allows us to derive a local optimal consumption law using a stochastic gradient ascent. Numerical experiments illustrate the efficiency of these approaches. Furthermore, we show that the optimal purchase is of bang-bang type

Prediction of stress induced by heterogeneous oxidation: Case of epoxy/amine networks

A methodology to predict the formation of superficial stress during the diffusion-limited oxidation of thick epoxy/amine samples is proposed. This quantitative methodology is based on the understanding of mechanisms responsible for this stress lead to superficial micro-cracks. The first step consists of simulating the homogeneous oxidation on the surface of thick samples. The extent of oxidation is assessed through the concentration of oxidation products as amide groups measured using Fourier-transform infrared spectroscopy (FTIR). These experimental results are compared to simulations obtained from a kinetic model based on a close loop mechanistic scheme in chain oxidation. Shrinkage and tensile behavior changes are correlated with an oxidation tracer, being amide groups in our case. The second step considers diffusion-limited oxidation in thick samples where the gradients of oxidation products characterized through thickness by micro-FTIR are simulated by coupling the previous kinetic model with oxygen diffusion. Finally, the gradient of strain and stress induced by oxidation of a thick epoxy/amine sample is simulated by inserting the mechanical behavior modifications and shrinkage gradient associated with the amide gradient in finite element code (Abaqus®). As a result, it is shown that it is possible to predict the superficial stress level as a function time/temperature of exposure and sample geometry.ANRT (CIFRE No 2013/0356

Caracterización psicosocial de estudiantes universitarios: relación entre autoestima, autoeficacia y locus de control

Research has shown that psychosocial factors affect the emotional state and social relations of teachers and should therefore be taken into account to ensure the quality of educational processes. This research is carried out with the aim of characterizing the Self-esteem, Self-efficacy and Locus control of students newly entering the education career. For this purpose, using a quantitative method with correlational and explanatory treatment, a questionnaire was applied containing questions about the students' background and the following scales: the Rosenberg (1989) Self-Esteem Scale, the Baessler and Schwarcer (1966) Self-Efficacy Scale and the Moena (2012) Control Locus Scale. The sample consisted of 744 incoming students from a teacher training college, selected through random sampling from the population that passed the entrance exam. The results show that there is a correlation between Self-confidence and Self-efficacy. Similarly, it was found that the dimension of control locus called internality, has positive correlation with self-efficacy.Las investigaciones han demostrado que los factores psicosociales afectan el estado emocional, las relaciones sociales de los docentes y, por lo tanto, se deben tomar en cuenta para asegurar la calidad de los procesos educativos. Esta investigación se realiza con el objetivo de caracterizar la Autoestima, Autoeficacia y Locus control de los estudiantes de nuevo ingreso de la carrera de educación. Para ello, empleando un método cuantitativo con tratamiento correlacional y explicativo, se aplicó un cuestionario que contenía preguntas sobre los antecedentes de los estudiantes y las siguientes escalas: la escala de Autoestima de Rosenberg (1989), la escala de Autoeficacia de Baessler y Schwarcer (1966) y la escala de Locus de control de Moena (2012). La muestra estuvo integrada por 744 estudiantes de nuevo ingreso de una universidad de formación de docentes, seleccionados a través de un muestreo aleatorio entre la población que aprobó el examen de admisión. Los resultados demuestran que existe correlación entre Autoconfianza y Autoeficacia. De igual manera, se encontró que la dimensión de locus de control denominada internalidad, presenta correlación positiva con la Autoeficacia

XANES spectroscopy for the clinician

XANES spectroscopy, which uses synchrotron radiation as a probe, offers substantial information about the local structure of biological samples, encompassing those without long range order such as Pt anticancer molecules, and nanometre scale or amorphous particles of calcium phosphate. Its subcellular spatial resolution, as well as its capacity to operate at room temperatures and pressures represent major advantages for medical research. Moreover, paraffin embedded biopsy samples can be analysed without any further preparation, Key publications which illustrate these capacities are presented

XANES spectroscopy for the clinician

XANES spectroscopy, which uses synchrotron radiation as a probe, offers substantial information about the local structure of biological samples, encompassing those without long range order such as Pt anticancer molecules, and nanometre scale or amorphous particles of calcium phosphate. Its subcellular spatial resolution, as well as its capacity to operate at room temperatures and pressures represent major advantages for medical research. Moreover, paraffin embedded biopsy samples can be analysed without any further preparation, Key publications which illustrate these capacities are presented

Stem Cell Res

Primary hyperoxaluria type 1 (PH1) is a rare autosomal recessive disorder of the liver metabolism due to functional deficiency of the peroxisomal enzyme alanine:glyoxylate aminotransferase (AGT). AGT deficiency results in overproduction of oxalate which complexes with calcium to form insoluble calcium-oxalate salts in urinary tracts, ultimately leading to end-stage renal disease. Currently, the only curative treatment for PH1 is combined liver-kidney transplantation, which is limited by donor organ shortage and lifelong requirement for immunosuppression. Transplantation of genetically modified autologous hepatocytes is an attractive therapeutic option for PH1. However, the use of fresh primary hepatocytes suffers from limitations such as organ availability, insufficient cell proliferation, loss of function, and the risk of immune rejection. We developed patient-specific induced pluripotent stem cells (PH1-iPSCs) free of reprogramming factors as a source of renewable and genetically defined autologous PH1-hepatocytes. We then investigated additive gene therapy using a lentiviral vector encoding wild-type AGT under the control of the liver-specific transthyretin promoter. Genetically modified PH1-iPSCs successfully provided hepatocyte-like cells (HLCs) that exhibited significant AGT expression at both RNA and protein levels after liver-specific differentiation process. These results pave the way for cell-based therapy of PH1 by transplantation of genetically modified autologous HLCs derived from patient-specific iPSCs

How to assess the role of Pt and Zn in the nephrotoxicity of Pt anti-cancer drugs?: An investigation combining μXRF and statistical analysis. Part II: Clinical application

International audienceIn this contribution, an approach developed previously for mice is used for human biopsy. In the case of patient 1, Pt detection is performed 6 days after the last oxaliplatin infusion, while for patient 2, the biopsy was performed more than 15 days after his first platin infusion and several dialysis. Even for these biological samples, experiments show that synchrotron mediated mXRF is a suitable tool to detect Pt in kidney biopsy, and thus probably for any organ exposed to Pt. Therefore, mXRF could also be of major interest to decipher the mechanism beyond Pt induced neurotoxicity, ototoxicity on human biopsy. Pharmacoavailability of chemotherapies is a major concern because some treatment failures are explained by poor tumor penetration of the active molecule. mXRF could be an elegant way to map the distribution of Pt inside cancerous cells at the micrometer scale. Pt and Zn are only two of the numerous trace elements that mXRF can detect; heavy metal intoxication diagnosis and the toxicity mechanism probably could also benefit from this innovative technique

Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome : Insights from the LUNG SAFE study

Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Methods: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 ≥ 0.60 during hyperoxemia). Results: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). Conclusions: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. Trial registration: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073publishersversionPeer reviewe