A fast solver for systems of reaction-diffusion equations

In this paper we present a fast algorithm for the numerical solution of systems of reaction-diffusion equations, $\partial_t u + a \cdot \nabla u = \Delta u + F (x, t, u)$, $x \in \Omega \subset \mathbf{R}^3$, $t > 0$. Here, $u$ is a vector-valued function, $u \equiv u(x, t) \in \mathbf{R}^m$, $m$ is large, and the corresponding system of ODEs, $\partial_t u = F(x, t, u)$, is stiff. Typical examples arise in air pollution studies, where $a$ is the given wind field and the nonlinear function $F$ models the atmospheric chemistry.Comment: 8 pages, 3 figures, to appear in Proc. 13th Domain Decomposition Conference, Lyon, October 200

Asymptotic-induced numerical methods for conservation laws

Asymptotic-induced methods are presented for the numerical solution of hyperbolic conservation laws with or without viscosity. The methods consist of multiple stages. The first stage is to obtain a first approximation by using a first-order method, such as the Godunov scheme. Subsequent stages of the method involve solving internal-layer problems identified by using techniques derived via asymptotics. Finally, a residual correction increases the accuracy of the scheme. The method is derived and justified with singular perturbation techniques

Iron and bismuth bound human serum transferrin reveals a partially-opened conformation in the N-lobe

Human serum transferrin (hTF) binds Fe(III) tightly but reversibly, and delivers it to cells via a receptor-mediated endocytosis process. The metal-binding and release result in significant conformational changes of the protein. Here, we report the crystal structures of diferric-hTF (Fe N Fe C-hTF) and bismuth-bound hTF (Bi N Fe C-hTF) at 2.8 and 2.4 Å resolutions respectively. Notably, the N-lobes of both structures exhibit unique 'partially-opened' conformations between those of the apo-hTF and holo-hTF. Fe(III) and Bi(III) in the N-lobe coordinate to, besides anions, only two (Tyr95 and Tyr188) and one (Tyr188) tyrosine residues, respectively, in contrast to four residues in the holo-hTF. The C-lobe of both structures are fully closed with iron coordinating to four residues and a carbonate. The structures of hTF observed here represent key conformers captured in the dynamic nature of the transferrin family proteins and provide a structural basis for understanding the mechanism of metal uptake and release in transferrin families. © 2012 Macmillan Publishers Limited. All rights reserved.published_or_final_versio

Tracking team mental workload by multimodal measurements in the operating room

Mental workload and its effects on surgical performance are underexplored topics, despite their importance for operating room (OR) efficiency and patient safety. We developed a multimodal platform that can simultaneously collect data from EEG, heart rate and breathing rate, tool handle pressure, and eye tracker from mobile subjects. We performed experiments using the Fundamentals of Laparoscopic Surgery model, with 22 subjects of varying skill levels ranging from nonsurgeon to expert. The results indicated significant modulations of the measurements depending on pupil size, heart rate variability, P300 response, tool pressure, task difficulty, time-on-task, and skill level. These provide evidence that physiology based metrics can be used in automated classification of fine gradations of skill, the assessment and certification of surgery trainees, developing real-time flags and warnings for the OR, and validating new OR technology

Structural blueprint and ontogeny determine the adaptive value of the plastic response to competition in clonal plants: a modelling approach

International audienceLocal competitive interactions strongly influence plant community dynamics. To maintain their performance under competition, clonal plants may plastically modify their network architecture to grow in the direction of least interference. The adaptive value of this plastic avoidance response may depend, however, on traits linked with the plant's structural blueprint and ontogeny. We tested this hypothesis using virtual populations. We used an Individual Based Model to simulate competitive interactions among clones within a plant population. Clonal growth was studied under three competition intensities in plastic and non-plastic individuals. Plasticity buffered the negative impacts of competition at intermediate densities of competitors by promoting clone clumping. Success despite competition was promoted by traits linked with (1) the plant's structural blueprint (weak apical dominance and sympodial growth) and (2) ontogenetic processes, with an increasing or a decreasing dependence of the elongation process on the branch generation level or length along the competition intensity gradient respectively. The adaptive value of the plastic avoidance response depended on the same traits. This response only modulated their importance for clone success. Our results show that structural blueprint and ontogeny can be primary filters of plasticity and can have strong implications for evolutionary ecology, as they may explain why clonal plants have developed many species-specific plastic avoidance behaviours

Structure And Dynamics Of Modulated Traveling Waves In Cellular Flames

We describe spatial and temporal patterns in cylindrical premixed flames in the cellular regime, $Le < 1$, where the Lewis number $Le$ is the ratio of thermal to mass diffusivity of a deficient component of the combustible mixture. A transition from stationary, axisymmetric flames to stationary cellular flames is predicted analytically if $Le$ is decreased below a critical value. We present the results of numerical computations to show that as $Le$ is further decreased traveling waves (TWs) along the flame front arise via an infinite-period bifurcation which breaks the reflection symmetry of the cellular array. Upon further decreasing $Le$ different kinds of periodically modulated traveling waves (MTWs) as well as a branch of quasiperiodically modulated traveling waves (QPMTWs) arise. These transitions are accompanied by the development of different spatial and temporal symmetries including period doublings and period halvings. We also observe the apparently chaotic temporal behavior of a disordered cellular pattern involving creation and annihilation of cells. We analytically describe the stability of the TW solution near its onset+ using suitable phase-amplitude equations. Within this framework one of the MTW's can be identified as a localized wave traveling through an underlying stationary, spatially periodic structure. We study the Eckhaus instability of the TW and find that in general they are unstable at onset in infinite systems. They can, however, become stable for larger amplitudes.Comment: to appear in Physica D 28 pages (LaTeX), 11 figures (2MB postscript file

Impact of habitat environment on Potamogeton perfoliatus L. morphology and its within-plant variability in Lake Balaton

Plastic effect of environmental factors acting on an aquatic submerged plant, Potamogeton perfoliatus L. at the plant-level (nutrient availability) and the leaf-level (light intensity) at different sites in Lake Balaton was studied. Light-dependent morphological traits (foliar morphology and internode length) of P. perfoliatus were measured and analysed across the environmental gradients of the lake. The size of leaves was influenced by both trophic state and light environment: nutrient surplus increased the size of leaves by y29%, whereas a more heterogeneous light environment resulted in 15% larger leaves. The light environment influenced shoot morphology (internode length) to a greater extent than nutrient surplus (38% vs. 19%). Contrary to this, within-plant morphological variability was significantly higher (41%) at the nutrient limiting sites as a result of diversification effect of the leaf-level environmental factor, light. Foliar parameters and within-plant variability showed correlation only with the total N content of the sediment. Appearance of P. perfoliatus is shaped by counteracting effects: within-plant differentiation, promoted by leaf-level environmental sensitivity and within-plant homogenization triggered by perception of the surroundings at plant-level. Both light attenuation, stimulating an increase of morphological variability, and nutrient surplus, initiating the stabilization of morphological parameters, could have adaptive advantages. The variability of leaf size leads to diversification of foliar parameters, thus increasing the efficiency of light harvest at low-nutrient sites and making responses to changes in the light environment more dynamic. These results suggest that leaf-level-induced diversification is counteracted by the standardization effect triggered by plantlevel environmental factors

Producción científica sobre aneurisma de la aorta abdominal en Scielo en el período 2021-2023

Introduction: an abdominal aortic aneurysm is a multifactorial disease in which genetic and environmental factors intervene. Its incidence makes it one of the pathologies of the cardiovascular system with the most research on it. SciELO as a collaboration program for the dissemination of scientific material stands out in its production on this disease. Objective: to characterize the scientific production on abdominal aortic aneurysm in SciELO in the period 2021-2023. Methods: bibliometric and descriptive study of scientific production on abdominal aortic aneurysm in SciELO in the period 2021-2023. In the search, 69 articles were rescued, which were analyzed considering the following variables: type of publication, year of publication, country of origin, language and bibliographic references. Graphs and tables were prepared to represent the data and a quantitative analysis was concluded. Results: the most frequent type of article was the case report with 46.38% and the year 2021 was the year with the most publication (44 publications). The country of origin with the highest number of articles was Brazil (27.54%); Spanish was the language most used in the publications (55%). The Price index obtained had a maximum value of 0.28. Conclusions: the scientific production on abdominal aortic aneurysm in SciELO presents a predominance of case reports. Brazil is the country that makes the greatest contributions to the platform on the topic and the Spanish language was the most used.Introducción: un aneurisma de aorta abdominal es una enfermedad multifactorial en la que intervienen factores genéticos y ambientales. Su incidencia la convierte en una de las patologías del aparato cardiovascular con más investigaciones. SciELO, como programa de colaboración para la difusión de material científico, se destaca en su producción sobre esta enfermedad. Objetivo: caracterizar la producción científica sobre aneurisma de la aorta abdominal en SciELO, en el período 2021-2023. Métodos: estudio bibliométrico y descriptivo de producción científica sobre aneurisma de la aorta abdominal en SciELO en el período 2021-2023. En la búsqueda se rescataron 69 artículos, los cuales fueron analizados a partir de las siguientes variables: tipo de publicación, año de publicación, país de procedencia, idioma y referencias bibliográficas. Se elaboraron gráficos y tablas para representar los datos y se concluyó con un análisis cuantitativo. Resultados: el tipo de artículo más frecuente fue el reporte de caso con un 46,38%, y el año 2021 fue el de mayor publicación (44 publicaciones). El país de procedencia con mayor número de artículos fue Brasil (27,54 %); el idioma español fue el más empleado en las publicaciones (55%). El índice de Price obtenido tuvo un valor máximo de 0,28. Conclusiones: la producción científica sobre aneurisma de la aorta abdominal en SciELO presenta un predominio de los reportes de casos. Brasil es el país que mayores aportes realiza a la plataforma sobre el tema y el idioma español fue el más usado

Experimental Assessment of the Water Quality Influence on the Phosphorus Uptake of an Invasive Aquatic Plant: Biological Responses throughout Its Phenological Stage

International audienceUnderstanding how an invasive plant can colonize a large range of environments is still a great challenge in freshwater ecology. For the first time, we assessed the relative importance of four factors on the phosphorus uptake and growth of an invasive macrophyte Elodea nuttallii (Planch.) St. John. This study provided data on its phenotypic plasticity, which is frequently suggested as an important mechanism but remains poorly investigated. The phosphorus uptake of two Elodea nuttallii subpopulations was experimentally studied under contrasting environmental conditions. Plants were sampled in the Rhine floodplain and in the Northern Vosges mountains, and then maintained in aquaria in hard (Rhine) or soft (Vosges) water. Under these conditions, we tested the influence of two trophic states (eutrophic state, 100 mu g.l(-1) P-PO43- and hypertrophic state, 300 mu g.l(-1) P-PO43-) on the P metabolism of plant subpopulations collected at three seasons (winter, spring and summer). Elodea nuttallii was able to absorb high levels of phosphorus through its shoots and enhance its phosphorus uptake, continually, after an increase of the resource availability (hypertrophic > eutrophic). The lowest efficiency in nutrient use was observed in winter, whereas the highest was recorded in spring, what revealed thus a storage strategy which can be beneficial to new shoots. This experiment provided evidence that generally, the water trophic state is the main factor governing P uptake, and the mineral status (softwater > hardwater) of the stream water is the second main factor. The phenological stage appeared to be a confounding factor to P level in water. Nonetheless, phenology played a role in P turnover in the plant. Finally, phenotypic plasticity allows both subpopulations to adapt to a changing environment