Search results for "Exchange"
showing 10 items of 2035 documents
Energetic coupling between plastids and mitochondria drives CO2 assimilation in diatoms.
2015
International audience; Diatoms are one of the most ecologically successful classes of photosynthetic marine eukaryotes in the contemporary oceans. Over the past 30 million years, they have helped to moderate Earth's climate by absorbing carbon dioxide from the atmosphere, sequestering it via the biological carbon pump and ultimately burying organic carbon in the lithosphere. The proportion of planetary primary production by diatoms in the modern oceans is roughly equivalent to that of terrestrial rainforests. In photosynthesis, the efficient conversion of carbon dioxide into organic matter requires a tight control of the ATP/NADPH ratio which, in other photosynthetic organisms, relies prin…
A quantum mechanics-molecular mechanics study of dissociative electron transfer : The methylchloride radical anion in aqueous solution
2002
The dissociative electron transfer reaction CH3Cl+e−→CH3•+Cl− in aqueous solution is studied by using a QM/MM method. In this work the quantum subsystem (a methylchloride molecule plus an electron) is described using density functional theory while the solvent (300 water molecules) is described using the TIP3P classical potential. By means of molecular dynamics simulations and the thermodynamic integration technique we obtained the potential of mean force (PMF) for the carbon–chlorine bond dissociation of the neutral and radical anion species. Combining these two free energy curves we found a quadratic dependence of the activation free energy on the reaction free energy in agreement with Ma…
Optimization of the sorption process of copper cations from aqueous solution by pine bark (Pinus sylvestris)
2020
This study examined the effect of the chemical modification of pine bark (Pinus sylvestris) on the sorption efficiency of copper cations. The results were interpreted using pseudo-first order and pseudo-second order reaction models as well as Langmuir and Freundlich isothermal models. The sorption experiments were carried out using the batch technique. The study indicated the effect of the competitive sorption of copper cations and hydrogen cations as well as the adverse effect on the sorption efficiency of copper hydroxides formed under alkaline conditions. The need to assess the measurement uncertainty in determining the basic parameters of the sorption process was indicated. It was also …
Solubility of Zn(II) in Association with Calcium Silicate Hydrates in Alkaline Solutions
1999
The binding of Zn(II) to the cement mineral calcium silicate hydrate (CSH) was investigated in a well-defined laboratory system. CSH (Ca:Si = 1:1) was synthesized by coprecipitation with varying contents of Zn(II). Zn(II) was added in the proportions 0, 0.1, 1.0, 5.0, and 10% in exchange for Ca. The resulting CSH was characterized by X-ray diffraction. The solid phases were then equilibrated in aqueous suspensions, and the solubilities of Ca, Si, and of Zn(II) were determined as a function of pH and Zn(II) content in the solid phase. The solubility of Ca and Si in equilibrium with the CSH phases was in agreement with that predicted by thermodynamic calculations. Dissolved Zn(II) concentrati…
Physical origin of Na+/Cl− selectivity of tight junctions between epithelial cells. Nonlocal electrostatic approach
2020
Abstract Tight junctions (TJs) of epithelial cells play a key role in regulation of the ion exchange between NaCl solutions separated by the layer of these cells. Their functioning is based on a strong difference in the permeabilities of these channels for Na+ and Cl− ion migrational fluxes owing to specific properties of the protein network inside TJs. It has been assumed in this study that this phenomenon originates from combination of two effects related to this specific TJ protein (claudin) which segments are partially located inside the TJ space. First, their ionogenic groups create a negative charge distributed inside TJs, thus inducing a difference between the Na+ and Cl− concentrati…
BIM Modelling of Ancient Buildings
2018
In the last years, new procedures on design and management of constructions, based on 3D standardised models of building elements, have been proposed. It’s the case of Building Information Modelling (BIM) applications, that, differently from CAD ones, allow to work with libraries of 3D parametrical objects (smart objects) describing geometric, structural and material properties of building elements. This methodology is based on the Industry Foundation Classes (IFC) model, that represents a global standard for the building data exchange. Initially used for the design of new architectures, BIM methodology has been even more considered also for the management and the conservation of historical…
Scenarios of Climatic Resilience, Economic Feasibility and Environmental Sustainability for the Refurbishment of the Early 20th Century Buildings
2019
This paper aims to examine the theme of energy retrofit within the circumscribed field of refurbishment interventions on load-bearing masonry buildings built in the early 20th century. These include a remarkable share of the fabric of many European cities and, in particular, they can be found in geographical areas characterized by a Mediterranean (mild) climate. The main objective is to increase the climate resilience of the buildings by verifying the economic feasibility and the environmental sustainability of the interventions at the same time observing the specific architectural features of the buildings. We put forward alternative retrofit solutions carrying out synoptic comparisons of …
Assessment of the Operating Temperature of Crystalline PV Modules Based on Real Use Conditions
2014
Determining the operating temperatureTcof photovoltaic panelsPVis important in evaluating the actual performance of these systems. In the literature, different correlations exist, in either explicit or implicit forms, which often do not account for the electrical behaviour of panels; in this way, estimatingTcis based only on the passive behaviour of thePV. In this paper, the authors propose a new implicit correlation that takes into account the standard weather variables and the electricity production regimes of aPVpanel in terms of the proximity to the maximum power points. To validate its reliability, the new correlation was tested on two different PV panels (Sanyo and Kyocera panels) and…
Artificial ventilation for basic life support leads to hyperventilation in first aid providers.
2003
The 'Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care - International Consensus on Science' recommend an artificial ventilation volume of 10 ml/kg bodyweight (equivalent to a tidal volume of 700-1000 ml) without the use of supplemental oxygen in adults with respiratory arrest. For first aid providers using the mouth-to-mouth or mouth-to-nose-ventilation technique, respectively, a ventilation volume of approximately 9.6 l/min results. Additionally, a deep breath is recommended before each ventilation to increase the end-expiratory oxygen concentration of the air exhaled by the first aid provider. To investigate the effects of these recommendations in health…
Successful treatment of a patient with ARDS after pneumonectomy using high-frequency oscillatory ventilation.
1999
High frequency oscillatory ventilation (HFOV) was used in a patient who developed the acute respiratory distress syndrome 5 days following a right pneumonectomy for bronchogenic carcinoma. When conventional pressure-controlled ventilation failed to maintain adequate oxygenation, HFOV dramatically improved oxygenation within the first few hours of therapy. Pulmonary function and gas exchange recovered during a 10-day period of HFOV. No negative side effects were observed. Early use of HFOV may be a beneficial ventilation strategy for adults with acute pulmonary failure, even in the postoperative period after lung resection.