Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Modelling of mechanical behaviour of a coarse soil subjected to rock impact using a discrete element method

As rockfalls direct strong disasters, they stand as a major natural hazard. In order to manage this phenomenon, it is of great interest to predict as accurate as possible the trajectory of falling blocks. This allows the spatial extension of the risk to be assessed. But the modelling of the trajectory of a falling block requires to take into account the mechanical interaction that occurs between the boulder and natural obstacles, such as the ground or a forest stand. This paper deals with the analysis of the impact of a block onto a rocky ground; the purpose consists in expressing a reflecting law relating both incident and reflected velocities. Designing protective structures require to know the trajectory of the block, as well as the velocity of the block. Thus, the improving in the modelling of the contact between the block and the ground represents an actual challenge

Modélisation numérique de l’impact d’un bloc rocheux sur un éboulis. Analyse stochastique des coefficients de réflexion

De par les destructions et dégradations importantes qu’elles occasionnent, les chutes de blocs isolés dans les régions montagneuses constituent un risque naturel majeur. Sur le plan de la prévention, la simulation de la trajectoire de ces blocs en interaction avec les éventuels obstacles naturels du versant (terrain naturel, couverture forestière), à l’aide d’outils appropriés, constitue une étape essentielle permettant de présenter une cartographie d’intensité du phénomène redouté. Dans cette vaste problématique, l’article traite plus spécifiquement de l’étude de l’impact d’un bloc rocheux sur un sol composé d’éboulis, dans l’objectif d’établir une loi de réflexion qui sera intégrée à terme dans un code de trajectographie. Le caractère fortement stochastique de cette loi a été clairement établi. Dans le cas d’un impact normal à la surface du sol, une première analyse a permis de montrer qu’il existait une dépendance linéaire entre la vitesse incidente et les vitesses réfléchies normale, tangentielle, et de rotation ; de plus, il est apparu que le coefficient de réflexion normale suivait une distribution normale, alors que le coefficient de réflexion tangentielle était plutôt décrit par une loi Bêta. Une modélisation plus réaliste de la phase de contact entre le bloc et le sol contribue, en effet, à une évaluation plus judicieuse des vitesses du bloc ainsi que de ses hauteurs de passage. Ce sont ces paramètres qui permettent de définir les stratégies de protection les plus adaptées (localisation et dimensionnement)

Modélisation numérique de l`impact d`un bloc rocheux sur un éboulis. Analyse stochastique des coefficients de réflexion

National audienceAs rockfalls direct strong disasters, they stand as a major natural hazard. In order to manage this phenomenon, it is of great interest to predict as accurate as possible the trajectory of falling blocks. This allows the spatial extension of the risk to be assessed. But the modelling of the trajectory of a falling block requires to take into account the mechanical interaction that occurs between the boulder and natural obstacles, such as the ground or a forest stand. This paper deals with the analysis of the impact of a block onto a rocky ground; the purpose consists in expressing a reflecting law relating both incident and reflected velocities. Stochastic nature of the reflecting law was clearly established. In the case of an impact normal to the ground surface, simulations have shown that the relation between both incident and reflected velocities was quasi-linear; furthermore, it has appeared that the normal reflecting coefficient could be described by a Normal distribution, whereas a Beta distribution could be associated to the tangential reflecting coefficient. Designing protective structures requires to know the trajectory of the block, as well as the velocity of the block. Thus, the improving in the modelling of the contact between the block and the ground represents an actual challenge.De part les destructions et dégradations importantes qu`elles occasionnent, les chutes de blocs isolés dans les régions montagneuses constituent un risque naturel majeur. Sur le plan de la prévention, la simulation de la trajectoire de ces blocs en interaction avec les éventuels obstacles naturels du versant (terrain naturel, couverture forestière), à l`aide d`outils appropriés, constitue une étape essentielle permettant de présenter une cartographie d`intensité du phénomène redouté. Dans cette vaste problématique, l`article traite plus spécifiquement de l`étude de l`impact d`un bloc rocheux sur un sol composé d`éboulis, dans l`objectif d`établir une loi de réflexion qui sera intégrée à terme dans un code de trajectographie. Le caractère fortement stochastique de cette loi a été clairement établi. Dans le cas d`un impact normal à la surface du sol, une première analyse a permis de montrer qu`il existait une dépendance linéaire entre la vitesse incidente et les vitesses réfléchies normale, tangentielle, et de rotation ; de plus, il est apparu que le coefficient de réflexion normale suivait une distribution normale, alors que le coefficient de réflexion tangentielle était plutôt décrit par une loi Bêta. Une modélisation plus réaliste de la phase de contact entre le bloc et le sol contribue, en effet, à une évaluation plus judicieuse des vitesses du bloc ainsi que de ses hauteurs de passage. Ce sont ces paramètres qui permettent de définir les stratégies de protection les plus adaptées (localisation et dimensionnement)

An intelligent procedure for updating deformation prediction of braced excavation in clay using gated recurrent unit neural networks

202307 bcchVersion of RecordRGCOthersPolyU; Zhongtian Construction Group Co. Ltd.Publishe

Transient model of early stages in compartment fires

Peer reviewed: YesNRC publication: Ye

Overview and modeling of mechanical and thermomechanical impact of underground coal gasification exploitation

International audienceFrom an economic point of view Underground Coal Gasification (UCG) is a promising technology that can be used to reach coal resources that are difficult or expensive to by conventional mining methods. Furthermore, the process addresses safety concerns, by avoiding the presence of workers underground. An optimal UCG process requires the integration of various scientific fields (chemistry, geochemistry, geomechanics) and the demonstration of limited of environmental impacts. This paper focuses on the mechanical component of the UCG operation and its impact on the surrounding environment in terms of stability and land subsidence. The mechanical components are also considered. Underground mining by coal combustion UCG challenges include the mechanical behavior of the site and of stability of the overburden rock layers. By studying the underground reactor, its inlet and outlet, we confirm the key role played by mechanical damage and thermo-mechanical phenomena are identified. Deformation or collapse above the cavity may cause a collapse in the overlying layers or subsidence at the surface level. These phenomena are highly dependent on the thermoporomechanical behavior of the rock surrounding the cavity (the host rocks). Unlike conventional methods, the UCG technology introduces an additional variable into the physical problem: the high temperatures, which evolve with time and space. In this framework, we performed numerical analyses of the coal site that could be exploited using this method. The numerical results presented in this paper are derived from models based on different assumptions describing a raw geological background. Several 3D (3 dimensional) and 2D (2 dimensional, plane) nonlinear finite element modelings are performed based on two methods. The first assumes a rock medium as a perfect thermo-elastoplastic continuum. In the second, in order to simulate large space scale crack propagation explicitly, we develop a method based upon finite element deactivation. This method is built on a finite element mesh refinement and uses Mohr-Coulomb failure criterion. Based on the analysis of the numerical results, we can highlight two main factors influencing the behavior and the mechanical stability of the overburden, and consequently the UCG process evolution. The first is the size of the cavity. This geometrical parameter, which is common to all types of coal exploitation, is best controlled using the classic exploitation method. We show that in the case of UCG, the shape of the cavity and its evolution over time can be modified considerably by the thermomechanical behavior of the host rocks. The second is the presence of a heat source whose location and intensity evolve over time. Even if thermal diffusivity of the rock is low and only a small distance from the coal reactor is thermally affected, we show that the induced mechanical changes extend significantly in the overburden, and that subsidence can therefore be estimated at the surface. We conclude the integration of the mechanical analysis into a risk analysis process mechanical analysis can be integrated in a thorough risk analysis

Hydro-mechanical modelling of landslides with a material instability criterion

International audienc