Search results for "Process Engineering"
showing 10 items of 931 documents
Determination of N -nitrosamines in cosmetic products by vortex-assisted reversed-phase dispersive liquid-liquid microextraction and liquid chromatog…
2018
A new analytical method for the simultaneous determination of trace levels of seven prohibited N-nitrosamines (N-nitrosodimethylamine, N-nitrosoethylmethylamine, N-nitrosopyrrolidine, N-nitrosodiethylamine, N-nitrosopiperidine, N-nitrosomorpholine, and N-nitrosodiethanolamine) in cosmetic products has been developed. The method is based on vortex-assisted reversed-phase dispersive liquid-liquid microextraction, which allows the extraction of highly polar compounds, followed by liquid chromatography with mass spectrometry. The variables involved in the extraction process were studied to obtain the highest enrichment factor. Under the selected conditions, 75 μL of water as extraction solvent …
Magnetic and structural properties of the nanostructured Fe 1–x Si x system with x = 0.1, 0.2 and 0.3, mechanical alloyed and sintered
2007
The magnetic and structural properties of the nanostructured system Fe1–xSix with x = 0.1, 0.2 and 0.3 were studied by X-Ray diffraction (XRD), SEM, and Mossbauer Spectrometry (MS). The samples were prepared by compacting and sintering at two temperatures, 900 and 1000 uC, from powders obtained by means of two procedures: by elemental mixing of Fe and Si powders and by mechanical alloying (MA). For samples obtained from mixed powders and sintered at 900 and 1000 uC, XRD and MS show the presence of pure iron and silicon, indicating that these conditions do not favor alloying, except for the sample with 30 at.% and 1000 uC, for which, besides of iron and silicon patterns, the DO3 and FeSi pha…
Microfluidic Synthesis of Highly Shape-Anisotropic Particles from Liquid Crystalline Elastomers with Defined Director Field Configurations
2011
In this article, we present the synthesis of highly shape-anisotropic, micrometer-sized particles from liquid crystalline elastomers, which have the ability to reversibly change their shape in response to a certain external stimulus. For their preparation, we utilized a microfluidic setup. We succeeded in preparing sets of particles with differing degrees of shape anisotropy in their ground state including highly anisotropic fiber-like objects. All samples produced movement during the phase transition from the nematic to the isotropic phase of the liquid crystal. Depending on the direction of this shape change, we classified the samples in two groups. One type showed a contraction, while th…
Analysis of hazardous chemicals by “stand alone” drift tube ion mobility spectrometry: a review
2020
Ion mobility spectrometry (IMS) is a widely used technique based on gas phase ion separation under an electric field by differences in ion mobilities. In the last decade, IMS techniques have received increased attention due to their high operational speed and sensitivity. Currently, there are different IMS devices focused on solving different analytical performances, mainly based on linear drift tube (DT IMS), traveling wave, and field asymmetric waveform ion mobility spectrometers. In this review we summarize the main applications of DT-IMS devices for the determination of semi-volatile hazardous chemicals such as: illegal drugs, pesticides, explosives, chemical warfare agents, and others,…
Adverse drug reactions in some African herbal medicine: literature review and stakeholders’ interview
2014
International audience; Background: In view of the large consumption of herbal medicine in Africa countries, it is likely that many adverse drugs reactions go unrecorded with either patients failing to present to health services, or no pharmacovigilance analysis being made, or the analysis not being reported centrally. This problem is of interest especially for those who are working in the general area of adverse drug reactions or stakeholders in the domain of herbal medicine for considering safety issues. Methods: We are particularly interested in the way that the use of very wellknown and highly valued plants is linked to the observation of adverse drug reactions in African countries. We …
Physicochemical and perceptual interactions between composition/texture, taste and aroma: A way to enhance saltiness in foods
2009
Diplôme : Ph. D.; Excessive salt in the human diet is a major risk factor for hypertension and cardiovascular diseases. So, the World Health Organisation (WHO) advocates sodium reduction of foods as a cost-effective strategy to improve public health. Because of important functionalities of salt (NaCl) – salty taste and flavour enhancement, solutions are being sought to lower the salt content of processed foods without altering their taste. In this PhD work, the approach proposed was to use sensory interactions between the senses, especially composition/texture – saltiness interactions (i) and aroma-saltiness interactions (ii). The first part of this work aimed to investigate food compositio…
La perception des accords aromatiques : un exemple d'interactions perceptives dans les mélanges odorants
2007
Diplôme : Dr. d'Université; Dans le monde de la parfumerie et de l'aromatique, il existe un terme particulier définissant la formation d'une nouvelle qualité odorante à travers le mélange et la fusion de plusieurs odeurs : l'accord. Ce terme, largement employée parmi ces experts, n'avait jamais donné lieu à des études scientifiques approfondies.L' objectif de cette thèse a été de démontrer la réalité de l'accord en olfaction et de montrer qu'il repose sur des interactions perceptives influençant la qualité de l'odeur. Nous avons en particulier étudié les déterminants physico-chimiques, perceptifs et cognitifs des accords aromatiques. Dans un premier temps, nous avons démontré que la percept…
Influence des pratiques d’allaitement et de diversification sur l’acceptation de flaveurs nouvelles chez le jeune enfant : variabilité intra- et inte…
2007
This thesis covers three separate but related studies. The first, a questionnaire survey of infant feeding practices in two nearby European regions (Dijon, France and Aalen, Germany) reports between- and withinregion differences in breastfeeding duration and variety of vegetables offered early in weaning. This survey identified the level and rate of vegetable variety and the specific foods to use in a second study. The 2nd study examined the effects of breast- or formula-feeding and different levels of vegetable variety (no, low or high) early in weaning on acceptance (intake and liking) of new foods. The foods were: (1) a first new vegetable offered immediately after the intervention; (2) …
Quality of dietary supplements in ophthalmology
2006
International audience; Purpose: A rising number of dietary supplements are available to prevent age–related ocular pathologies such as AMD or dry eye syndrome. The purpose of this work was to evaluate the quality of dietary supplements containing omega–3 polyunsaturated fatty acids in terms of lipid, vitamin E and heavy metals composition. Dietary supplements designed for improving mental well–being were included in this study since they should share some similarities.Methods: Twenty dietary complements were analyzed (6 for dry eye prevention, 4 for AMD prevention and 10 for improving mental well–being). Lipids and lipophilic vitamins were extracted. The distribution of the lipid classes w…
Sensitivity analysis and process optimization of a natural gas dehydration unit using triethylene glycol
2019
Abstract Dehydration of natural gas by absorption using triethylene glycol (TEG) is a common industrial offshore procedure to ensure the compliance with the required water dew point specifications for midstream transportation. Two thermodynamic models, the UMR-PRU and the TST/NRTL, are applied for the process simulation while a preliminary economic evaluation has been conducted revealing that both yield overall similar results as for the fixed capital cost which is found to be in good agreement with reported literature values. Moreover, sensitivity analysis of several operational parameters of the process has been performed and optimized values are suggested aiming to reduce its energy requ…