Abstract
Recently, complete in vitro generation of male gametes starting from pluripotent stem cells was obtained in a mouse model with live offspring as a result. This breakthrough was probably due ...to the use of a stepwise differentiation protocol taking the tightly regulated in vivo situation into account. As shown previously, factors of the TGFβ superfamily, metabolites of vitamin A, growth hormones, sex steroids and, most importantly, somatic cell support are major regulators of the development, survival, proliferation and differentiation of male gametes. However, up till now, all differentiation protocols starting from human pluripotent stem cells only focused on one or two of these substantive factors, not taking any timeframe into account, leading to promising but unsatisfying results with low efficiency. Therefore, progress might be achieved by including a stepwise differentiation protocol, including all proven contributing regulators, and therefore mimicking more closely human in vivo spermatogenesis and its temporo-spatial organization. In this review, the indispensable regulators of in vivo spermatogenesis and the outcomes of related human in vitro studies are discussed with the aim of unravelling the most successful combinations of medium factors to be used in future differentiation protocols.
This article proposes a new coulometric approach to calculate the state of charge of a lead-acid battery in electric vehicles. The main existing state of charge algorithms have two major defects: a ...state of charge definition not adapted to electric vehicle applications and the nonoptimal use of static performance of the accumulator to estimate its state under dynamic stresses. In order to improve these two weaknesses, we propose a new coulometric algorithm linked to the performance of the electric vehicle and where the ampere-hours virtually discharged are obtained by applying statistical equivalence coefficients to the real current profile. The evaluation of this new algorithm on real discharges reveals a significant improvement with less than 5% errors in all cases studied.
Le portage des nouveau-nés de faible poids de naissance en peau à peau a pris une place croissante dans les unités de néonatologie. Cette méthode privilégie les interactions parents–enfants mais ...présente de nombreux autres avantages, souvent moins bien connus par les équipes soignantes. Elle favorise notamment la stabilité cardiorespiratoire, l'équilibre thermique et le sommeil du nouveau-né. Son intérêt a également été démontré dans la réussite de l'allaitement maternel et dans la diminution des manifestations liées à la douleur au cours de prélèvements sanguins. Enfin, le devenir à moyen terme des nouveau-nés chez qui ce type de portage a été privilégié est meilleur en termes de développement psychomoteur et d'interactions avec leurs parents. Ceux-ci sont par ailleurs plus compétents dans les situations de stress de la période néonatale mais aussi dans l'environnement qu'ils procurent à domicile. Sa pratique nécessite cependant une formation des équipes afin d'en tirer tous les bénéfices, en respectant au mieux la stabilité neurocomportementale du nouveau-né.
Skin-to-skin contact has spread out in many neonatal units. This method enhanced parent–infant interactions, but has many other advantages, which are less well known by the neonatal teams. It promotes infant's cardio-respiratory stability, temperature regulation and sleep. It has also shown interest in improving breast-feeding of low birth weight infants, and in diminishing the response of preterm neonates to blood punctures. Finally, the outcome of babies cared skin-to-skin, is better in terms of psychomotor development and interactions with the parents. Those parents are also more competent to face stressful situations during the neonatal period and to improve the environment of the baby at home. However a better qualification of the neonatal staff is necessary to take benefit of all the advantages of skin-to-skin care, respecting the neurobehavioral stability of the newborn.
Objective: To evaluate the expectant management of asymptomatic small, anechoic, simple ovarian cysts diagnosed by echography in postmenopausal women. To gain insight in the natural history of these ...cysts.
Method: Thirty six postmenopausal women with asymptomatic ovarian cysts (from 1.5 to 5.0 cm) diagnosed by ultrasonography and with a CA 125 serum level within the normal range and a non-suspicious color Doppler were followed conservatively. Visits were scheduled at 8–10 weeks of the diagnosis, at 6-month intervals twice and annually thereafter.
Results: The follow-up period extended from 4 to 70 months with an average of 31.5 months. There were no cases of cyst enlargement. The cysts remained unchanged in 29 cases (80.5%), decreased in size in four cases (11.1%) and disappeared in three cases (8.3%).
Conclusion: We think that the possibility of malignant transformation of one of these cysts is remote and the benefits of conservative management greatly outweighs its risks.
This paper describes the modeling of the electrical and thermal behavior of semiconductor switching devices using bond graphs. An effective way to identify the parameters of the thermal system is ...presented. The model shows good consistency with measurements of the junction temperature response in steady state as well as in transient state.
Converters which have floating voltages in their topologies, made with capacitors. One aim of the capacitors is to divide voltages among switches. Then, each capacitor state of charge is crucial for ...the good running and the survival of the converter. Therefore, the understanding of voltage variation rules presents a primordial interest. A particular structure of multilevel converter appeared in the early nineties: the imbricated cell topology. The work proposed in the paper deals with the study of dynamic behaviour about capacitors making this kind of converter. The proposed analysis is dealt with in an original approach, based on physical and mathematical laws. Variation rules can then be established, allowing the modelling of capacitor charge according to the converter control parameters. This modelling will lead to some particular phenomena concerning the charge of capacitors, inducing a malfunction of running in the converter. The results obtained by modelling and simulation is proved with an experiment.
Power electronics converter modelling leads usually to define a multimodel representation due to the different states (ON and OFF) of the switching devices. The purpose of the paper is to show, ...through physical considerations and mathematical manipulations, how a unique model can be built, by using bond graph technique, causality properties and singular perturbation method. The study is made on the elementary commutation cell, and the proposed method is applied on a system corresponding to the association power converter-electrical load.< >
A methodology for modeling and simulating the electrothermal behavior of power semiconductor switching devices is illustrated and validated. The electrothermal model is constructed using the bond ...graph formalism. This bond graph model is centered around the idea of having a single model regardless of the switch state. The electrothermal model describes the dynamic temperature distribution of the device from the chip surface through the package and heat sink, and the influence of the chip temperature variation on the electrical characteristics of the device.
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