Effects of internal fluctuations on the spreading of Hantavirus

We study the spread of Hantavirus over a host population of deer mice using a population dynamics model. We show that taking into account the internal fluctuations in the mouse population due to its discrete character strongly alters the behaviour of the system. In addition to the familiar transition present in the deterministic model, the inclusion of internal fluctuations leads to the emergence of an additional deterministically hidden transition. We determine parameter values that lead to maximal propagation of the disease, and discuss some implications for disease prevention policies

Disorder-specific functional abnormalities during sustained attention in youth with Attention Deficit Hyperactivity Disorder (ADHD) and with Autism

Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) are often comorbid and share behavioural-cognitive abnormalities in sustained attention. A key question is whether this shared cognitive phenotype is based on common or different underlying pathophysiologies. To elucidate this question, we compared 20 boys with ADHD to 20 age and IQ matched ASD and 20 healthy boys using functional magnetic resonance imaging (fMRI) during a parametrically modulated vigilance task with a progressively increasing load of sustained attention. ADHD and ASD boys had significantly reduced activation relative to controls in bilateral striato–thalamic regions, left dorsolateral prefrontal cortex (DLPFC) and superior parietal cortex. Both groups also displayed significantly increased precuneus activation relative to controls. Precuneus was negatively correlated with the DLPFC activation, and progressively more deactivated with increasing attention load in controls, but not patients, suggesting problems with deactivation of a task-related default mode network in both disorders. However, left DLPFC underactivation was significantly more pronounced in ADHD relative to ASD boys, which furthermore was associated with sustained performance measures that were only impaired in ADHD patients. ASD boys, on the other hand, had disorder-specific enhanced cerebellar activation relative to both ADHD and control boys, presumably reflecting compensation. The findings show that ADHD and ASD boys have both shared and disorder-specific abnormalities in brain function during sustained attention. Shared deficits were in fronto–striato–parietal activation and default mode suppression. Differences were a more severe DLPFC dysfunction in ADHD and a disorder-specific fronto–striato–cerebellar dysregulation in ASD

Estudio de la agregación de colorantes en películas mixtas ultrafinas

Uno de los objetivos de la química supramolecular ha sido y sigue siendo el desarrollo de métodos o estrategias para construir películas orgánicas ordenadas en estructuras bien definidas y de gran extensión. A escala nanoscópica, las propiedades físicas de estos sistemas moleculares se determinan mediante las relaciones entre su composición química, estructura y la organización de los materiales utilizados. En particular, cuando las moléculas que forman esos sistemas tienden a la agregación, también se ven afectadas sus características moleculares. De hecho, las consecuencias más importantes de la agregación molecular de colorantes orgánicos no son sólo los cambios químicos que se producen, sino principalmente los cambios detectados en las propiedades ópticas de las unidades cromóforas que interactúan entre sí. Ante este hecho es necesario buscar nuevas estrategias para la construcción de estructuras bi-dimensionales bien definidas en superficies (interfases) donde se facilite el control de la organización de los componentes de esos bloques moleculares. En este marco, la interfase aire-agua se constituye como interfase modelo donde la organización lateral es controlada mediante la preparación de películas delgadas. En estas películas ultrafinas mixtas, se seleccionan los componentes sobre la base de la formación de interacciones atractivas entre ellos, estableciendo la conexión lateral entre los mismos a través de la auto-agregación de los colorantes. Una estrategia para lograr esta conexión lateral es establecer un balance adecuado entre el tamaño de los grupos hidrofóbicos y los grupos polares. En este contexto mediante ciertos métodos experimentales se pueden formar películas con propiedades estructurales y ópticas bien definidas compuestas por mezclas de colorantes y lípidos. De esta forma, se preparan películas delgadas mixtas mediante el método de Langmuir en la interfase aire-agua y los métodos Langmuir-Blodgett (LB) y Langmuir-Schaeffer (LS) sobre soportes sólidos. Dichas películas mixtas están formadas por lípidos, tales como ácido 1,2-dimiristoil-sn-glicero-3-fosfato DMPA, ácido esteárico SA, y colorantes de carga opuesta como acridinas, cianinas y derivados de las cianinas, cuya estructura molecular les confiere un comportamiento anfifílico (cadenas alquílicas hidrófobas, grupo polar hidrofílico). Para poder estudiar y caracterizar estas películas delgadas mixtas es necesario disponer de técnicas que nos aporten información tanto de la organización de la parte polar, como de las cadenas alquílicas. No obstante, la mayoría de las técnicas de caracterización de monocapas Langmuir están centradas en el estudio y organización de las cadenas alquílicas que conforman el sistema, como la Espectroscopía infrarroja de absorción-reflexión con modulación de polarización (PM-IRRAS) , la técnica de Difracción de rayos X de incidencia rasante (GIXS) y la técnica de Reflectividad especular de rayos X (XRR), siendo más escasas aquellas que proporcionan información directa de la organización del grupo polar. Por todo ello es necesario desarrollar técnicas ópticas como la Microscopía de ángulo Brewster (BAM) y espectroscópicas como la Espectroscopía de Reflexión UV-visible bajo ángulo variable y luz polarizada (RAV) con el objetivo de obtener información útil acerca de la organización de las unidades moleculares que conforman la región polar y el uso de otras técnicas complementarias (fluorescencia, dicroismo circular), que aumenten el abanico de potenciales aplicaciones de estas películas. Por otra parte, es importante resaltar la utilización de técnicas de simulación en ordenador, así como el desarrollo de modelos teóricos y matemáticos en el sentido de validar y complementar los datos obtenidos experimentalmente

Palladium-Catalyzed Remote ortho-C-H Alkenylation of Alkyl Aryl Sulfones: Access to Densely Functionalized Indane Derivatives

This is the peer-reviewed version of the following article: Advanced Synthesis and Catalysis 358.7 (2016): 1065-1072, which has been published in final form at http://dx.doi.org/10.1002/adsc.201501129. This article may be used for non-commercial purposes in accordance with Wiley-VCH Terms and Conditions for Self-ArchivingA practical method for the palladium-cat-alyzed ortho-olefination of benzyl and phenethyl 2-pyridyl sulfones with electron-deficient alkenes using N-fluoro-2,4,6-trimethylpyridinium triflate ([F+]) as the terminal oxidant is described. The che-lating auxiliary (2-pyridyl)sulfonyl unit was demon-strated to be the key to the success of this reaction, which occurs efficiently with excellent regioselectiv-ity and monosubstitution selectivity. A variety of steric and electronic changes to both coupling part-ners is tolerated, including substitution at the ben-zylic position of the sulfone compound. Further-more, no appreciable loss of enantiopurity is ob-served when using non-racemic substrates. This method provides access to indane derivatives hold-ing three contiguous stereogenic centers with high diastereocontrol. The indane framework was con-structed by intramolecular Michael addition of the a-sulfonyl carbanion to the electrophilic alkeneWe thank the Spanish Government (MINECO, CTQ2012- 35790) for financial support. P.D. L. thanks the Spanish Government (MINECO) for an FPU predoctoral fellowshi

Context Regulation of Mind Wandering in ADHD

OBJECTIVE: We aimed to understand the association between MW frequency and clinical measures, context regulation of MW and group differences in task performance. METHOD: 27 adults with ADHD and 29 controls performed tasks manipulating demand on working memory and sustained attention, and recorded their MW frequency using probes. RESULTS: A significant association between MW frequency and the clinical measures was demonstrated. Along with increased MW frequency, individuals with ADHD reported decreasing MW frequency during increasing demands on working memory (context regulation), but not on sustained attention (deficient context regulation). Controls, however, maintained continuous task focus across all conditions. Group differences in task performance were no longer significant after adding MW frequency as a covariate. CONCLUSION: Deficient context regulation during increasing demands on sustained attention suggests that sustained attention deficits may play a more important role in regulation of MW in ADHD. MW frequency might also underpin performance deficits in ADHD

2D chiral structures in quinoline mixed Langmuir monolayers.

Chirality at interfaces is a relevant topic in nanoscience, as well as a key point for prebiotic chemistry. Mixed Langmuir monolayers, composed of the anionic phospholipid dimyristoyl phosphatidic acid (DMPA) and the cationic amphiphilic quinoline derivative 2-methyl-1-octadecylquinoline (MQ) have been built at the air-water interface. Both DMPA and MQ molecules are miscible, thus the equimolar mixture yields homogeneous monolayers completely. Chiral domains have been formed by this monolayer and observed in situ by Brewster angle microscopy (BAM). These chiral domains display a large array of shapes and sizes. The chirality of the monolayers has been confirmed by circular dichroism spectroscopy. The ordered aggregation of the quinoline group into large chiral supramolecular structures is proposed as the molecular origin of the observed chirality. Theoretical simulations using molecular mechanics confirm the strong trend of the quinoline group to form chiral aggregates. The great diversity in the size and shape of the chiral domains has been found to be strongly influenced by the competition between two nuclei growth mechanisms. An experimental procedure allowing a minimized growth through one of these mechanism is proposed, achieving a homogeneous distribution of ring-shaped domains. An overshoot in the pi-A isotherms of this mixed monolayer appears at an intermediate surface pressure. This overshoot is interpreted as being due to the large difference between the surface pressure which starts the nuclei formation, pi(crit) and the superficial pressure in which the nuclei can grow, pi(e). The rather small pi(e) value compared to pi(crit) observed for this system must be attributed to the molecular interactions involved in the mixed monolayer, which facilitate the incorporation of molecules in preformed nuclei

First-principles calculation of intrinsic defect formation volumes in silicon

We present an extensive first-principles study of the pressure dependence of the formation enthalpies of all the know vacancy and self-interstitial configurations in silicon, in each charge state from -2 through +2. The neutral vacancy is found to have a formation volume that varies markedly with pressure, leading to a remarkably large negative value (-0.68 atomic volumes) for the zero-pressure formation volume of a Frenkel pair (V + I). The interaction of volume and charge was examined, leading to pressure--Fermi level stability diagrams of the defects. Finally, we quantify the anisotropic nature of the lattice relaxation around the neutral defects.Comment: 9 pages, 9 figure

Cu-Catalyzed Silylation of Alkynes: A Traceless 2-Pyridylsulfonyl Controller Allows Access to either Regioisomer on Demand

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/jacs.5b02667The Cu-catalyzed silylation of terminal and internal alkynes bearing a 2-pyridyl sulfonyl group (SO2Py) at the propar-gylic position affords a breadth of vinyl silanes in good yields and excellent regio- and stereocontrol under mild conditions. The directing SO2Py group is essential in terms of reaction efficiency and chemoselectivity. Importantly, this group also provides the ability to reverse the regiochemical outcome of the reaction, opening the access to either regioisomer without modification of the starting substrate by virtue of an in situ base-promoted alkyne to allene equilibration which takes place prior to the silylcupration process. Furthermore, removal of the directing SO2Py allows for further elaboration of the silylation products. In particular, a one-pot tandem alkyne silylation/allylic substitution sequence, in which both steps are catalyzed by the same Cu species, opens up a new approach for the access to either formal hydrosilylation regioisomer of unsymmetrical aliphatic-substituted internal alkynes from propargyl sulfonesThis work was supported by the Ministerio de Economía y Com-petitividad (MINECO, CTQ2012-35790) and the European Union for a Marie Curie Career Integration Grant (to P.M). J. R. and P.M. thank MINECO for a FPI predoctoral fellowship and a Ramón y Cajal contract, respectivel

Dynamical properties of the Landau-Ginzburg model with long-range correlated quenched impurities

We investigate the critical dynamics of the time-dependent Landau-Ginzburg model with non conserved n-component order parameter (Model A) in the presence of long-range correlated quenched impurities. We use a special kind of long-range correlations, previously introduced by Weinrib and Halperin. Using a double expansion in \epsilon and \delta we calculate the critical exponent z up to second order on the small parameters. We show that the quenched impurities of this kind affect the critical dynamics already in first order of \epsilon and \delta, leading to a relevant correction for the mean field value of the exponent zComment: 7 pages, REVTEX, to be published in Phys. Rev.