Model of light collimation by photonic crystal surface modes

We propose a quantitative model explaining the mechanism of light collimation by leaky surface modes that propagate on a corrugated surface around the output of a photonic crystal waveguide. The dispersion relation of these modes is determined for a number of surface terminations. Analytical results obtained on the basis of the model are compared to those of rigorous numerical simulations. Maximum collimation is shown to occur at frequency values corresponding to excitation of surface modes whose wave number retains a nonzero real part.Comment: 6 pages, 7 figures. Version 2: corrected sign of k_x' (sections 4-6, fig. 2), minor clarifications in section 2. Version 3: significant changes, including reformulation of the model using the theory of aperture antennas, as well as extended discussion of the accuracy of the mode

Numerical optimization of grating-enhanced second-harmonic generation in optical waveguides

Rigorous electromagnetic theory is combined with a phenomenological approach to permit optimization of grating-enhanced second-harmonic generation (SHG) in optical waveguides. Provided that the absorption losses in the optically nonlinear layer are not high, maximum SHG is observed when phase matching occurs between the incident wave at the pump frequency and guided waves at both the pump and the signal frequencies. Different coupling mechanisms are considered, and a procedure for determining the optimal groove depth and period of the grating is discussed. The phenomenological approach permits deeper physical insight into the problem and a considerable saving of computation time. Direct phase matching is shown to result in stronger SHG than indirect phase matching ( performed through the grating vector), even if the former includes coupling between waveguide modes of different orders

Thaliporphine Preserves Cardiac Function of Endotoxemic Rabbits by Both Directly and Indirectly Attenuating NFκB Signaling Pathway

Cardiac depression in sepsis is associated with the increased morbidity and mortality. Although myofilaments damage, autonomic dysfunction, and apoptosis play roles in sepsis-induced myocardial dysfunction, the underlying mechanism is not clear. All of these possible factors are related to NFκB signaling, which plays the main role in sepsis signaling. Thaliporphine was determined to possess anti-inflammatory and cardioprotective activity by suppressing NFκB signaling in rodents. The purpose of this study is to further prove this protective effect in larger septic animals, and try to find the underlying mechanisms. The systolic and diastolic functions were evaluated in vivo by pressure-volume analysis at different preloads. Both preload-dependent and -independent hemodynamic parameters were performed. Inflammatory factors of whole blood and serum samples were analyzed. Several sepsis-related signaling pathways were also determined at protein level. Changes detected by conductance catheter showed Thaliporphine could recover impaired left ventricular systolic function after 4 hours LPS injection. It could also reverse the LPS induced steeper EDPVR and gentler ESPVR, thus improve Ees, Ea, and PRSW. Thaliporphine may exert this protective effect by decreasing TNFα and caspase3 dependent cell apoptosis, which was consistent with the decreased serum cTnI and LDH concentration. Thaliporphine could protect sepsis-associated myocardial dysfunction in both preload-dependent and -independent ways. It may exert these protective effects by both increase of “good”-PI3K/Akt/mTOR and decrease of “bad”-p38/NFκB pathways, which followed by diminishing TNFα and caspase3 dependent cell apoptosis

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

CORRUGATED WAVEGUIDES USED AS BISTABLE COMPONENTS

On développe une théorie électromagnétique des réseaux gravés sur des diélectriques présentant un effet Kerr. Pour des puissances incidentes adéquates, ces réseaux peuvent avoir deux valeurs très différentes de leurs efficacités, dépendant de leur état antérieur. Ceci permet d'envisager leur utilisation comme composants optiques bistables. L'utilisation de résonances électromagnétiques (plasmons, ondes guidées, ...) permet une réduction intéressante des seuils de basculement. Une étude numérique pour les deux polarisations fondamentales (TE et TM) permet d'optimiser le dispositif. Une interprétation phénoménologique du comportement bistable est donnée, dans le cas d'un coupleur à prisme, en recherchant la trajectoire, dans le plan complexe, de pôles et de zéros du facteur de réflexion quand la puissance incidente varie.An electromagnetic theory of gratings ruled on a Kerr dielectric medium is presented in this paper. For convenient incident powers, gratings may exhibit two distinct values of their efficiencies, depending on their previous state. It is thus possible to use them as bistable optical components. The use of electromagnetic resonances (plasmons, guided waves, ...) allow reducing the bistability thresholds to interesting values. A numerical study for the TE and TM fondamental polarizations is done to optimize the device. A phenomenological explanation of the bistable behavior is done for a prism coupler by studying the reflectivity poles and zeros loci in the complex plane, when the incident power is varied