Performance et réponses ventilatoires lors d'épreuves d'effort à puissance constante ou décrémentée visant à maintenir une consommation d'oxygène maximale

L’endurance aérobie est rarement mesurée à des intensités maximales, mais plutôt sous-maximales, principalement via des protocoles à puissance ou à durée constante. Or, les conditions réelles d’une épreuve sportive en compétition sont mieux représentées par le maintien de la plus haute puissance métabolique possible, et ce, le plus longtemps possible. Cela implique une autogestion de la puissance de travail de la part du participant – qui peut donc varier tout le long de l’épreuve – ainsi que l’atteinte des capacités aérobies maximales, dans certains cas. Dans cette étude, nous avons voulu comparer les variations de certains paramètres ventilatoires (ventilation, volume courant, fréquence respiratoire) et systémiques (rendement mécanique externe brut [RMEC], consommation d’oxygène [VO2]) entre deux protocoles d’effort maximal, l’un à puissance constante (100 % PAM), l’autre à puissance décrémentée (> 95 % VO2max). En effet, comparativement à un protocole d’effort classique à puissance constante, un protocole décrémenté implique l’utilisation de VO2 et non de la puissance mécanique comme critère de sélection de l’intensité d’effort, et augmente la durée de l’épreuve. En conséquence, le maintien de la consommation d’oxygène maximale (VO2max), et non de la puissance aérobie maximale (PAM), nous a permis d’observer des réponses physiologiques différentes de celles généralement décrites lors d’efforts incrémentés ou à puissance constante. Ces différences se sont traduites par une fréquence respiratoire plus élevée et un volume courant plus bas, indiquant l’existence d’une réponse tachypnéique plus prononcée lors d’un protocole décrémenté par rapport à un protocole à puissance constante, et reflétant ainsi une respiration plus superficielle, probablement due à une fatigue plus accrue des muscles ventilatoires. Cette fatigue serait caractérisée par un rendement mécanique plus bas et un VO2 plus élevé, et ce, malgré la diminution progressive de la puissance de travail lors de l’atteinte d’une consommation d’oxygène proche de VO2max.Aerobic endurance is more commonly measured at submaximal rather than maximal work intensities, mainly through constant-power output trials, or time trials. However, real competition conditions are better represented through the ability to sustain the highest power output (PO) for the largest period of time. That implies the use of self-pacing strategies, which leads power output to vary throughout the exercise duration, and can also induce the attainment of maximal oxygen consumption (VO2max), in some cases. The aim of this study was thus to compare the variation of some ventilatory (tidal volume, breathing frequency) and systemic (gross mechanical efficiency, O2 cost) parameters, between two maximal endurance protocols, the first one consisting of a constant-load test (100% MAP) and the second one a decremental test at near-maximal aerobic capacity (> 95 % VO2max). Indeed, compared to a “classical” constant-power output test, a decremental test implies the use of VO2 rather than mechanical PO to control intensity throughout the task, and a higher effort duration. Consequently, we observed that the sustainment of maximal O2 consumption rather than maximal aerobic power (MAP) led to different physiological responses from those usually observed during constant-power output tests. These differences were caracterized by a higher breathing frequency as well as a lower tidal volume during the decremental test, which both reflect a more exagerated tachypneic response, and therefore indicate the existence of a shallower breathing pattern in this type of effort, probably due to a higher ventilatory muscle fatigue. This fatigue could also be expressed through a lower gross mechanical efficiency and a higher O2 cost, despite a progressive decrease of mechanical power as soon as oxygen consumption gets near VO2max

Novel Β-lactams and Thiazolidinone Derivatives from 1,4-dihydroquinoxaline Schiff’s Base: Synthesis, Antimicrobial Activity and Molecular Docking Studies

A series of novel isolated β-lactams 3a-c and thiazolidinone derivatives 4a-c were successfully synthesized from reactions of new Schiff's bases 2a-c with chloroacetyl chloride and thioglycolic acid. The chemical structures of the new compounds were confirmed through different spectroscopic techniques including IR, 1H NMR, 13C NMR, mass spectrometry and elemental analysis. The antimicrobial activity of the obtained compounds was assessed in-vitro against gram-positive Staphylococcus aureus and gram-negative Escherichia coli bacteria and Aspergillus flavus and Candida albicans fungi. Furthermore, a molecular docking study was carried out and the results indicated that compounds 3b and 4b displayed comparable binding affinity scores as that of glutamate. These two compounds are promising candidates as antibacterial and antifungal agents that would deserve further investigations

Botanical and Genetic Identification Followed by Investigation of Chemical Composition and Biological Activities on the Scabiosa atropurpurea L. Stem from Tunisian Flora

Scarce information about the phenolic composition of Scabiosa atropurpurea L. is available, and no carotenoid compounds have been reported thus far. In this study the phenolic and carotenoid composition of this plant was both investigated and associated bioactivities were evaluated. Aiming to obtain extracts and volatile fractions of known medicinal plants to valorize them in the pharmaceutical or food industries, two techniques of extraction and five solvents were used to determine the biologically active compounds. Gas chromatography coupled to flame ionization and mass spectrometry and liquid chromatography coupled to photodiode array and atmospheric pressure chemical ionization/electrospray ionization mass spectrometry highlighted the presence of 15 volatiles, 19 phenolic, and 24 natural pigments in Scabiosa atropurpurea L. stem samples; among them, the most abundant were 1,8-cineole, chlorogenic acid, cynaroside, and lutein. Bioactivity was assessed by a set of in vitro tests checking for antioxidant, antibacterial, antifungal, and allelopathic (against Brassica oleracea L. and Lens culinaris Medik) effects. Scabiosa atropurpurea L. stem extracts presented a considerable antioxidant, antibacterial, and allelopathic potential, with less antifungal effectiveness. These results indicate that the volatile fractions and extracts from S. atropurpurea L. stem could be considered as a good source of bioactive agents, with possible applications in food-related, agriculture, and pharmaceutical fields. Genetic investigations showed 97% of similarity with Scabiosa tschiliensis, also called Japanese Scabiosa

Selective Electrochemical Determination of Etoposide Using a Molecularly Imprinted Overoxidized Polypyrrole Coated Glassy Carbon Electrode

A simple and efficient new electrochemical sensor based on molecularly imprinted polymer has been developed for selective detection of an anticancer agent Etoposide (ETP). The sensor was prepared by electropolymerization via cyclic voltammetry (CV) of pyrrole onto a glassy carbon electrode (GCE) in the presence of ETP molecules. The extraction of ETP molecules embedded in the polymeric matrix was carried out by overoxidation in sodium hydroxide medium using CV. Various important parameters affecting the performance of the imprinted film (MIP) coated sensor were studied and optimized using differential pulse voltammetry (DPV). Under optimal conditions, the sensor response exhibited a linear dependence on ETP concentration (R2 = 0.999) over the range 5.0×10−7 M – 1.0×10−5 M with a LOD (3σ/m) of 2.8×10−9 M. The precision (% RSD, n=6) of the proposed sensor for intra- and interdays was found to be 0.84 and 2.46%, respectively. The selectivity of MIP/GCE sensor toward ETP was investigated in the presence of different interfering molecules including excipients and ETP metabolites. The developed sensor showed great recognition ability toward ETP and was successfully applied for its determination in injectable dosage forms and biological human fluids

Central odontogenic fibroma: retrospective study of 8 clinical cases

Introduction and Objectives: The central odontogenic fibroma (COF) is a benign odontogenic tumour derived from the dental mesenchymal tissues. It is a rare tumour and only 70 cases of it have been published. Bearing in mind the rareness of the tumour, 8 new cases of central odontogenic fibroma have been found by analyzing the clinical, radiological and histopathological characteristics of COF. Patients and Method: A retrospective study was carried out on 3011 biopsies in the Service of Oral and Maxillofacial Surgery of the Dental Clinic of Barcelona University between January 1995 and March 2008. 85 odontogenic tumours were diagnosed of which 8 were central odontogenic fibroma. The radiological study was based on orthopantomographs, periapical and occlusal radiographies and computerised tomographics. The variables collected were: sex, age, clinical characteristics of the lesion, treatment received and possible reappearances of the tumour. Results: The central odontogenic fibroma represents 9.4% of all odontogenic tumours. Of the 8 cases, 5 were diagnosed in men and 3 in women. The average age was 19.9 years with an age range of 11 to 38 years. The most common location of the tumour was in the mandible. All cases were associated with unerupted teeth. Of the 8 tumours, 3 provoked rhizolysis of the adjacent teeth and 4 cases caused cortical bone expansion. 50% of the patients complained of pain associated to the lesion. No case of recurrence was recorded up to 2 years after the treatment. Conclusions: Central odontogenic fibromas usually evolve asymptomatically although they can manifest very aggressively provoking dental displacement and rhizolysis. Radiologically, COF manifest as a uni or multilocular radiotransparent image although they can be indistinguishable from other radiotransparent lesions making diagnosis more difficult. COF treatment involves conservative surgery as well as follow-up patient checks

La fidélité envers la marque de « Deal » à travers une atmosphère inter@ctive : une étude qualitative exploratoire « Le cas d’achat groupé en ligne »

La présente étude qualitative s’inscrit dans le contexte du commerce électronique, elle se veut une tentative pour expliquer, à travers deux échantillons, la contribution des caractéristiques fonctionnelles et relationnelles d’un site web d’une marque de « Deal », via une atmosphère interactive, à la fidélité des clients dans le secteur d’achat groupé en ligne, et que les responsables des marques de « Deal » opèrent dans des stratégies de fidélisation à l’égard de leurs clients. Ceci se justifie par les outils technologiques utilisés par ces marques et l’originalité de la fidélité en groupe face à une rationalisation de choix de la part du consommateur tunisien

Using SoaML Models and Event-B Specifications for Modeling SOA Design Patterns

International audienceAlthough design patterns have become increasingly popular, most of them are presented in an informal way. Patterns, proposed by the SOA design pattern community, are described with a proprietary informal notation, which can raise ambiguity and may lead to their incorrect usage. Modeling SOA design patterns with a standard formal notation avoids misunderstanding by software architects and helps endow design methods. In this paper, we present an approach that aims, first, to model message-oriented SOA design patterns with the SoaML language, and second to transform them to Event-B specifications. These two steps are performed before undertaking the effective coding of a design pattern providing correct by construction pattern-based software architectures. Our approach is enhanced with a tool supporting it. Specification results are imported under the Rodin platform which we use to prove model consistency

New soluble anthracene-based polymer for opto-electronic applications

International audienc