Search

The graphene is a substance with carbon atoms arranged in a honeycomb lattice. The dynamics of the electrons in the structure is governed by the Hamilton equations of the system in the form of its associated spectral problem: H = ?, with the additional condition that the eigenfunction must satisfy the so-called Kirchhoff's conditions. In this paper, we study a class of solutions (?;) that, in addition to meeting these conditions, are periodic in one of the two main directions of the lattice, and satisfy a pseudo-periodicity type like condition in the other direction. Our main results lead to an adequate characterization of the dispersion relationships of the honeycomb lattice, providing a precise description of the regions of stability and instability of the eigenfunctions in terms of ?. As a consequence, a tool is thus obtained for a better understanding of the propagation properties and the behavior of the wave function of electrons in a hexagonal lattice, a key issue in graphene-based technologies. [ABSTRACT FROM AUTHOR]

We consider the Robin boundary value problem div (A ∇ u) = div f + F in Ω , a C 1 domain, with (A ∇ u - f) · n + α u = g on Γ , where the matrix A belongs to V M O (R 3) , and discover the uniform estimates on ‖ u ‖ W 1 , p (Ω) , with 1 < p < ∞ , independent of α . At the difference with the case p = 2 , which is simpler, we call here the weak reverse Hölder inequality. This estimates show that the solution of the Robin problem converges strongly to the solution of the Dirichlet (resp. Neumann) problem in corresponding spaces when the parameter α tends to ∞ (resp. 0). [ABSTRACT FROM AUTHOR]

We solve a second-order elliptic equation with quasi-periodic boundary conditions defined on a honeycomb lattice that represents the arrangement of carbon atoms in graphene. Our results generalize those found by Kuchment and Post (Commun Math Phys 275(3):805–826, 2007) to characterize not only the stability but also the instability intervals of the solutions. This characterization is obtained from the solutions of the energy eigenvalue problem given by the lattice Hamiltonian. We employ tools of the one-dimensional Floquet theory and specify under which conditions the one-dimensional theory is applicable to the structure of graphene. The systematic study of such stability and instability regions provides a tool to understand the propagation properties and behavior of the electrons wavefunction in a hexagonal lattice, a key problem in graphene-based technologies. [ABSTRACT FROM AUTHOR]

The paper presents a theoretical study of an identification problem by shape optimization methods. The question is to detect an object immersed in a fluid. Here, the problem is modeled by the Stokes equations and treated as a nonlinear least-squares problem. We consider both the Dirichlet and Neumann boundary conditions. Firstly, we prove an identifiability result. Secondly, we prove the existence of the first-order shape derivatives of the state, we characterize them and deduce the gradient of the least-squares functional. Moreover, we study the stability of this setting. We prove the existence of the second-order shape derivatives and we give the expression of the shape Hessian. Finally, the compactness of the Riesz operator corresponding to this shape Hessian is shown and the ill-posedness of the identification problem follows. This explains the need of regularization to numerically solve this problem. [ABSTRACT FROM AUTHOR]

Articulated solid bodies (ASB) is a basic model for the study of shape-changing underwater vehicles made of rigid parts linked together by pivoting joints. In this paper we study the locomotion of such swimming mechanisms in an ideal fluid. Our study ranges over a wide class of problems: several ASBs can be involved (without being hydrodynamically decoupled), the fluid-bodies system can be partially or totally confined and fluid circulation, buoyancy force and possible collisions between bodies are taken into account. We derive the Euler-Lagrange equation governing the dynamics of the system, study its well-posedness and describe a numerical scheme implemented in a Matlab toolbox (Biohydrodynamics Toolbox). [ABSTRACT FROM AUTHOR]

Definition and validation of the ranges of normal values and agreement among echocardiographic measures of mechanical synchrony in healthy subjects are mostly lacking. The aims of this study were (1) to assess the ranges of normal values for 5 tissue Doppler imaging parameters, real-time 3-dimensional echocardiographic measures, and speckle-tracking measures of mechanical synchrony; (2) to evaluate interinstitutional variability; (3) to compare the ranges of normal values with those reported in previous research; and (4) to analyze the agreement among all parameters in the same healthy subject. Time to peak systolic velocity (Ts), the delay between Ts at the basal septal and lateral segments, peak velocity difference, strain derived by tissue Doppler imaging, Ts derived by tissue synchronization imaging, systolic synchrony index (SSI) derived by real-time 3-dimensional echocardiography, and longitudinal and radial strain derived by speckle tracking were prospectively collected and analyzed at 2 different institutions in 160 consecutive healthy subjects. The ranges of normal values, expressed as means +/- 2 SDs, were 30.32 +/- 29.36 ms for the SD of Ts, 15.51 +/- 99.88 ms for septal-lateral delay, 60.75 +/- 81.62 ms for peak velocity difference, 33.07 +/- 29.96 ms for tissue synchronization imaging, 34.16 +/- 23.26 ms for the SD of strain, 2.74 +/- 2.16% for SSI, 28.91 +/- 23.02 ms for the SD of longitudinal strain, and 10.4 +/- 6.31 ms for radial strain. There was large interinstitutional variability for all parameters. Three-dimensional SSI and radial strain were within the published upper range limit for healthy subjects. Ninety percent of healthy subjects were consistently classified to be synchronous by 1 parameter. With a composite index, more subjects than expected showed dyssynchrony (10% vs 2.5%). In conclusion, 3-dimensional SSI and radial strain were the most reproducible parameters and consistently discriminated normal healthy subjects from the cardiac resynchronization therapy volume responders. [ABSTRACT FROM AUTHOR]

In this work, we consider low contrast periodic media and we study the dependence of the effective or homogenized tensor and the dispersion tensor in terms of the microstructure. We treat both one-dimensional structures and some laminated structures in higher dimension. Interesting properties of the sign of these coefficients are found. Surprisingly, these depend on the microstructure only through the local proportion parameter, and in some cases, they do not depend on the microstructure at all. [ABSTRACT FROM AUTHOR]

The equations that govern elastostatic equilibrium between a prescribed force field and an unknown displacement field for materials with periodic skeletal micro-structures are studied. It is shown that as the size of the micro-structure tends to zero, the displacement field will converge to the solution of a constant coefficient partial differential equation. This equation is shown to be either a classical or a micro-polar continuum elasticity equation, depending on the micro-structural geometry and the nature of the external load field. Convergence is proved for representative model problems in Sobolev energy norms and in the maximum norm. In addition, it is shown that by considering pseudo-differential homogenized equations, any order of convergence can be achieved. [ABSTRACT FROM AUTHOR]

In this article we study the asymptotic behaviour of the eigenvalues of a family of nonlinear monotone elliptic operators of the form Aε = −div(aε (x, ∇u)), which are sub-differentials of even, positively homogeneous convex functionals, under the assumption that the operators G-converge to an operator Ahom = −div(ahom(x, ∇u)). We show that any limit point λ of a sequence of eigenvalues λε is an eigenvalue of the limit operator Ahom, where λε is an eigenvalue corresponding to the operator Aε. We also show the convergence of the sequence of first eigenvalues to the corresponding first eigenvalue of the homogenized operator. [ABSTRACT FROM PUBLISHER]

The classical problem of homogenization deals with elliptic operators in periodically oscillating media of small period ℇ>0 and the asymptotic behavior of solution uℇ of boundary value problems associated with such operators. In a previous work [Conca et al., SIAM J. Math. Anal. 33 (2002), 1166–1198], the authors introduced what is called Bloch approximation which provided energy norm approximation for the solution in $\mathbb{R}^{N}$. This paper continues with the above development and proposes a modified Bloch approximation. This function takes into account boundary effects. Its connection with the first order classical correctors is also established with the corresponding error estimate. All the proofs are worked out entirely in the Fourier–Bloch space. [ABSTRACT FROM AUTHOR]

In the book by Hornung, Chap. 6, the author proposes a homogenization strategy for the effective behavior of some chemical processes involving adsorption and reactions arising in porous media. Rigorous proofs of the convergence results are given in the case of linear adsorption rates and linear chemical reactions. The author leaves as an open question the case of a nonlinear adsorption rate. Our goal in this paper is to study two well-known examples of such nonlinear models, namely the so-called Freundlich and Langmuir kinetics. [ABSTRACT FROM AUTHOR]

Elliptic problems on unbounded domains with periodic coefficients and geometries are analyzed and two-scale regularity results for the solution are given. These are based on a detailed analysis in weighted Sobolev spaces of the so-called unit-cell problem in which the critical parameters (the period ∊ the wave number t, and the differentiation order) enter explicitly. [ABSTRACT FROM AUTHOR]

We introduce what are called regular materials for which, by definition, the corresponding solution of the classical periodic homogenization problem remains bounded in . We give examples of two types of such materials depending on whether the coefficients representing them belong to W1,∞ or not. A complete characterization is obtained in the former case. [ABSTRACT FROM PUBLISHER]

An abstract of the article "Registration of three-dimensional coronary sinus computed tomographic images with projection images obtained using fluoroscopy," by A. Sorgente and colleagues is presented.

An abstract of the article "Diagnostic assessment of leaflet motion in prosthetic mitral and aortic valve by transthoracic and transesophageal echocardiography," by M. Muratori and colleagues is presented.

Harmful algal blooms (HABs) of toxin-producing microalgae are recurrent in Patagonian fjord systems. Like toxigenic HABs, high-biomass harmful algal blooms (HB-HABs) have important socio-economic repercussions, but most studies have focused on the former. Here we report the formation and development of an intense HB-HAB of Prorocentrum micans that occurred in Northwest Chilean Patagonia in the late summer (February-March) of 2022. Concentrated and extensive brown spots were visible on the water surface, accompanied at the end of February by a strong odour. Prorocentrum micans cells were detected at relatively low densities (up to 215 cells mL -1 ) in January but by February 11 cell densities exceeded 1000 cells mL -1 , reaching a maximum of 8.3 × 10 3 cell mL -1 in the surface layer. The high cell densities at Reloncaví Sound and the Gulf of Ancud were closely associated with narrow-ranging increases in the sea surface temperature (17-18.5 °C) and salinity (29-31 g kg -1 ). Sentinel-2 satellite images from February 22 showed a colour change corresponding to the presence of the brown patches at both locations, consistent with the increases in the normalized index of chlorophyll differences (NDCI) and chlorophyll a concentrations (~50 μg L -1 ). Satellite images from GHRSST indicated warmer waters in Reloncaví Sound and the Gulf of Ancud than in the Gulf of Corcovado, located 170-km to the south. An oceanographic 3-D model (MOSA) showed surface currents with a cyclonic eddy centred in the Gulf of Ancud. This circulation pattern suggested greater water retention in the study area during January and February, with the drifting and rotation of the coastal currents around the eddy maintaining the P. micans bloom. Thus, the elevated cell density of P. micans in the Gulf of Ancud, near the periphery of the eddy, confirm the presence of a material accumulation hotspot for HABs and HB-HABs., Competing Interests: Declaration of competing interest We have not financial interests/personal relationships which may be considered as potential competing interests., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Environmental monitoring is crucial for assessing the overall state of the ecosystems in terms of contaminant impact and chemical landscape. The use of honey bee (Apis mellifera) colonies considerably eases the sampling activities, as honey bees are exposed to a wide range of substances that are transported and accumulated within the beehives. In this work, combining low-resolution and high-resolution mass spectrometry, the APIStrip passive sampler has been employed to evaluate the presence of pesticide residues and the overall characterization of beehive environments. A total of 180 APIStrips have been deployed in 10 Danish apiaries, located in different landscapes, during a five-month sampling period. The targeted methodology for pesticide analysis was based on gas and liquid chromatography coupled with triple quadrupole mass spectrometry, covering 430 pesticide residues. A total of 29 pesticide residues were identified (fluopyram and azoxystrobin being the most frequently detected), with remarkable differences in the pesticide load between apiaries. For its part, the use of non-targeted approaches through liquid chromatography coupled with an Orbitrap mass spectrometer allowed the detection of unknown compounds that were specific of certain environments. Natural products such as eupatilin and gnaphaliin, which are derived from plant sources, were present exclusively in one of the apiaries. Additionally, the detection of drimane sesquiterpenoids, including compounds potentially originating from the Aspergillus genus, suggests the capability of APIStrips to early detect fungal contamination within beehives. This dual approach of low- and high-resolution mass spectrometry maximizes the analytical potential of APIStrips as a tool capable of detecting a wide range of substances with implications for both agricultural practices and ecological health., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Amadeo R. Fernndez-Alba reports financial support was provided by European Commission. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: One of the main lessons of the COVID-19 pandemic is that we must prepare to face another pandemic like it. Consequently, this article aims to develop a general framework consisting of epidemiological modeling and a practical identifiability approach to assess combined vaccination and non-pharmaceutical intervention (NPI) strategies for the dynamics of any transmissible disease., Materials and Methods: Epidemiological modeling of the present work relies on delay differential equations describing time variation and transitions between suitable compartments. The practical identifiability approach relies on parameter optimization, a parametric bootstrap technique, and data processing. We implemented a careful parameter optimization algorithm by searching for suitable initialization according to each processed dataset. In addition, we implemented a parametric bootstrap technique to accurately predict the ICU curve trend in the medium term and assess vaccination., Results: We show the framework's calibration capabilities for several processed COVID-19 datasets of different regions of Chile. We found a unique range of parameters that works well for every dataset and provides overall numerical stability and convergence for parameter optimization. Consequently, the framework produces outstanding results concerning quantitative tracking of COVID-19 dynamics. In addition, it allows us to accurately predict the ICU curve trend in the medium term and assess vaccination. Finally, it is reproducible since we provide open-source codes that consider parameter initialization standardized for every dataset., Conclusion: This work attempts to implement a holistic and general modeling framework for quantitative tracking of the dynamics of any transmissible disease, focusing on accurately predicting the ICU curve trend in the medium term and assessing vaccination. The scientific community could adapt it to evaluate the impact of combined vaccination and NPIs strategies for COVID-19 or any transmissible disease in any country and help visualize the potential effects of implemented plans by policymakers. In future work, we want to improve the computational cost of the parametric bootstrap technique or use another more efficient technique. The aim would be to reconstruct epidemiological curves to predict the combined NPIs and vaccination policies' impact on the ICU curve trend in real-time, providing scientific evidence to help anticipate policymakers' decisions., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Cumsille, Rojas-Díaz and Conca.)

A growing body of evidence indicates that dietary polyphenols could be used as an early intervention to treat glucose-insulin (G-I) dysregulation. However, studies report heterogeneous information, and the targets of the intervention remain largely elusive. In this work, we provide a general methodology to quantify the effects of any given polyphenol-rich food or formulae over glycemic regulation in a patient-wise manner using an Oral Glucose Tolerance Test (OGTT). We use a mathematical model to represent individual OGTT curves as the coordinated action of subsystems, each one described by a parameter with physiological interpretation. Using the parameter values calculated for a cohort of 1198 individuals, we propose a statistical model to calculate the risk of dysglycemia and the coordination among subsystems for each subject, thus providing a continuous and individual health assessment. This method allows identifying individuals at high risk of dysglycemia-which would have been missed with traditional binary diagnostic methods-enabling early nutritional intervention with a polyphenol-supplemented diet where it is most effective and desirable. Besides, the proposed methodology assesses the effectiveness of interventions over time when applied to the OGTT curves of a treated individual. We illustrate the use of this method in a case study to assess the dose-dependent effects of Delphinol® on reducing dysglycemia risk and improving the coordination between subsystems. Finally, this strategy enables, on the one hand, the use of low-cost, non-invasive methods in population-scale nutritional studies. On the other hand, it will help practitioners assess the effectiveness of an intervention based on individual vulnerabilities and adapt the treatment to manage dysglycemia and avoid its progression into disease., Competing Interests: AL is currently employed by MNL-Group, company producing Delphinol®. However, he did not participate in conceptualisation of the study, data collection, investigation, processing, or analysis of the results. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Olivera-Nappa, Contreras, Tevy, Medina-Ortiz, Leschot, Vigil and Conca.)

Wolbachia are endosymbiont bacteria known to infect arthropods causing different effects, such as cytoplasmic incompatibility and pathogen blocking in Aedes aegypti. Although several Wolbachia strains have been studied, there is little knowledge regarding the relationship between this bacterium and their hosts, particularly on their obligate endosymbiont nature and its pathogen blocking ability. Motivated by the potential applications on disease control, we developed a genome-scale model of two Wolbachia strains: w Mel and the strongest Dengue blocking strain known to date: w MelPop. The obtained metabolic reconstructions exhibit an energy metabolism relying mainly on amino acids and lipid transport to support cell growth that is consistent with altered lipid and cholesterol metabolism in Wolbachia -infected mosquitoes. The obtained metabolic reconstruction was then coupled with a reconstructed mosquito model to retrieve a symbiotic genome-scale model accounting for 1,636 genes and 6,408 reactions of the Aedes aegypti- Wolbachia interaction system. Simulation of an arboviral infection in the obtained novel symbiotic model represents a metabolic scenario characterized by pathogen blocking in higher titer Wolbachia strains, showing that pathogen blocking by Wolbachia infection is consistent with competition for lipid and amino acid resources between arbovirus and this endosymbiotic bacteria. IMPORTANCE Arboviral diseases such as Zika and Dengue have been on the rise mainly due to climate change, and the development of new treatments and strategies to limit their spreading is needed. The use of Wolbachia as an approach for disease control has motivated new research related to the characterization of the mechanisms that underlie its pathogen-blocking properties. In this work, we propose a new approach for studying the metabolic interactions between Aedes aegypti and Wolbachia using genome-scale models, finding that pathogen blocking is mainly influenced by competition for the resources required for Wolbachia and viral replication.