Turbulence Modulation by Slender Fibers

In this paper, we numerically investigate the turbulence modulation produced by long flexible fibres in channel flow. The simulations are based on an Euler–Lagrangian approach, where fibres are modelled as chains of constrained, sub-Kolmogorov rods. A novel algorithm is deployed to make the resolution of dispersed systems of constraint equations, which represent the fibres, compatible with a state-of-the-art, Graphics Processing Units-accelerated flow-solver for direct numerical simulations in the two-way coupling regime on High Performance Computing architectures. Two-way coupling is accounted for using the Exact Regularized Point Particle method, which allows to calculate the disturbance generated by the fibers on the flow considering progressively refined grids, down to a quasi-viscous length-scale. The bending stiffness of the fibers is also modelled, while collisions are neglected. Results of fluid velocity statistics for friction Reynolds number of the flow (Formula presented.) and fibers with Stokes number (Formula presented.) = 0.01 (nearly tracers) and 10 (inertial) are presented, with special regard to turbulence modulation and its dependence on fiber inertia and volume fraction (equal to (Formula presented.) · (Formula presented.) and (Formula presented.) · (Formula presented.)). The non-Newtonian stresses determined by the carried phase are also displayed, determined by long and slender fibers with fixed aspect ratio (Formula presented.), which extend up to the inertial range of the turbulent flow

Proximity extension of circular DNA aptamers with real-time protein detection

Multivalent circular aptamers or ‘captamers’ have recently been introduced through the merger of aptameric recognition functions with the basic principles of DNA nanotechnology. Aptamers have strong utility as protein-binding motifs for diagnostic applications, where their ease of discovery, thermal stability and low cost make them ideal components for incorporation into targeted protein assays. Here we report upon a property specific to circular DNA aptamers: their intrinsic compatibility with a highly sensitive protein detection method termed the ‘proximity extension’ assay. The circular DNA architecture facilitates the integration of multiple functional elements into a single molecule: aptameric target recognition, nucleic acid hybridization specificity and rolling circle amplification. Successful exploitation of these properties is demonstrated for the molecular analysis of thrombin, with the assay delivering a detection limit nearly three orders of magnitude below the dissociation constants of the two contributing aptamer–thrombin interactions. Real-time signal amplification and detection under isothermal conditions points towards potential clinical applications, with both fluorescent and bioelectronic methods of detection achieved. This application elaborates the pleiotropic properties of circular DNA aptamers beyond the stability, potency and multitargeting characteristics described earlier

All-polymer methylammonium lead iodide perovskite microcavities

open8Thanks to a high photoluminescence quantum yield, large charge carrier diffusion, and ease of processing from solution, perovskite materials are becoming increasingly interesting for flexible optoelectronic devices. However, their deposition requires wide range solvents that are incompatible with many other flexible and solution-processable materials, including polymers. Here, we show that methylammonium lead iodide (MAPbI3) films can be directly synthesized on all-polymer microcavities via simple addition of a perfluorinated layer which protects the polymer photonic structure from the perovskite processing solvents. The new processing provides microcavities with a quality factor Q = 155, that is in agreement with calculations and the largest value reported so far for fully solution processed perovskite microcavities. Furthermore, the obtained microcavity shows strong spectral and angular redistribution of the the MAPbI3 photoluminescence spectrum, which shows a 3.5 fold enhanced intensity with respect to the detuned reference. The opportunity to control and modify the emission of a MAPbI3 film via a simple spun-cast polymer structure is of great interest in advanced optoelectronic applications requiring high colour purity or emission directionality.openLova, Paola; Giusto, Paolo; Di Stasio, Francesco; Manfredi, Giovanni; Paternò, Giuseppe M; Cortecchia, Daniele; Soci, Cesare; Comoretto, DavideLova, Paola; Giusto, Paolo; DI STASIO, Francesco; Manfredi, Giovanni; Paternò, Giuseppe M; Cortecchia, Daniele; Soci, Cesare; Comoretto, David

D1D5 microstate geometries from string amplitudes

We reproduce the asymptotic expansion of the D1D5 microstate geometries by computing the emission amplitudes of closed string states from disks with mixed D1D5 boundary conditions. Thus we provide a direct link between the supergravity and D-brane descriptions of the D1D5 microstates at non-zero string coupling. Microscopically, the profile functions characterizing the microstate solutions are encoded in the choice of a condensate for the twisted open string states connecting D1 and D5 branes.Comment: 21 pages; added reference

Coordination of Dynamic Software Components with JavaBIP

JavaBIP allows the coordination of software components by clearly separating the functional and coordination aspects of the system behavior. JavaBIP implements the principles of the BIP component framework rooted in rigorous operational semantics. Recent work both on BIP and JavaBIP allows the coordination of static components defined prior to system deployment, i.e., the architecture of the coordinated system is fixed in terms of its component instances. Nevertheless, modern systems, often make use of components that can register and deregister dynamically during system execution. In this paper, we present an extension of JavaBIP that can handle this type of dynamicity. We use first-order interaction logic to define synchronization constraints based on component types. Additionally, we use directed graphs with edge coloring to model dependencies among components that determine the validity of an online system. We present the software architecture of our implementation, provide and discuss performance evaluation results.Comment: Technical report that accompanies the paper accepted at the 14th International Conference on Formal Aspects of Component Softwar

New D1-D5-P geometries from string amplitudes

We derive the long range supergravity fields sourced by a D1-D5-P bound state from disk amplitudes for massless closed string emission. We suggest that since the parameter controlling the string perturbation expansion for this calculation decreases with distance from the bound state, the resulting asymptotic fields are valid even in the regime of parameters in which there is a classical black hole solution with the same charges. The supergravity fields differ from the black hole solution by multipole moments and are more general than those contained within known classes of solutions in the literature, whilst still preserving four supersymmetries. Our results support the conjecture that the black hole solution should be interpreted as a coarse-grained description rather than an exact description of the gravitational field sourced by D1-D5-P bound states in this regime of parameters.Comment: 48 pages, 2 figures, v2: typos correcte

Covid-19 y el uso de herramientas virtuales: el desafío de enseñar y aprender viviendo en pandemia

Debido a la emergencia sanitaria por COVID-19 la UBA suspendió las clases presenciales. Sin embargo, la UA1 del Departamento de Fisiología y Biofísica, Facultad de Medicina, garantizó, desde el comienzo de la pandemia hasta la actualidad, el dictado de clases virtuales. Transcurrido un año decidimos investigar cómo nos adaptamos al método de enseñanza virtual. El objetivo del trabajo consistió en relevar las experiencias de docentes y alumnos en torno a las herramientas virtuales utilizadas para el dictado de trabajos prácticos de Fisiología Renal y de la Sangre durante el primer cuatrimestre 2021. El relevamiento de datos se realizó mediante Google Forms. Se crearon dos encuestas anónimas, una dirigida al plantel docente (n=65) y otra dirigida a alumnos (n=1207). Del total de encuestados respondieron 40 docentes (62%) y 448 alumnos (37%). Las herramientas virtuales utilizadas en mayor porcentaje fueron: para los encuentros sincrónicos Google Meet (80%); para el seguimiento de la cursada Google Classroom (98%) y WhatsApp (50%); para la resolución de la guía de actividades Google Docs (88%), pizarras dinámicas (62%) y encuentros adicionales (60%). El 82% de alumnos informó que las herramientas utilizadas fueron útiles para la comprensión y el seguimiento de la materia. La percepción del efecto anímico frente a la modalidad virtual fue neutra (41%), negativa (37%) y positiva (22%). El 73% de docentes reportó que invirtió más tiempo en la enseñanza virtual que en la presencial. En conclusión, aunque la enseñanza virtual implicó un mayor esfuerzo docente, los alumnos resultaron conformes con la cursada; demostrando que el uso de estas herramientas resultó beneficioso en el contexto actual. Sin embargo, una posible opción mixta (seminarios virtuales y prácticos presenciales) predomina entre los encuestados, lo que nos motiva a continuar investigando el impacto a futuro del uso de herramientas virtuales en estas nuevas modalidades de enseñanza-aprendizaje.Fil: Rivera, María Florencia. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas. Cátedra de Fisiologia; ArgentinaFil: Majul Conte Grand, María Victoria. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas. Cátedra de Fisiologia; ArgentinaFil: García, C. G.. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas. Cátedra de Fisiologia; ArgentinaFil: Marzilli Cesar, Franco. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas. Cátedra de Fisiologia; ArgentinaFil: Di Giusto, Gisela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Fisiología y Biofísica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Fisiología y Biofísica Bernardo Houssay; ArgentinaVI Encuentro de Docentes de Fisiología y Física BiológicaArgentinaSociedad Argentina de Fisiologí

A viscoelastic deadly fluid in carnivorous pitcher plants

Background : The carnivorous plants of the genus Nepenthes, widely distributed in the Asian tropics, rely mostly on nutrients derived from arthropods trapped in their pitcher-shaped leaves and digested by their enzymatic fluid. The genus exhibits a great diversity of prey and pitcher forms and its mechanism of trapping has long intrigued scientists. The slippery inner surfaces of the pitchers, which can be waxy or highly wettable, have so far been considered as the key trapping devices. However, the occurrence of species lacking such epidermal specializations but still effective at trapping insects suggests the possible implication of other mechanisms. Methodology/Principal Findings : Using a combination of insect bioassays, high-speed video and rheological measurements, we show that the digestive fluid of Nepenthes rafflesiana is highly viscoelastic and that this physical property is crucial for the retention of insects in its traps. Trapping efficiency is shown to remain strong even when the fluid is highly diluted by water, as long as the elastic relaxation time of the fluid is higher than the typical time scale of insect movements. Conclusions/Significance : This finding challenges the common classification of Nepenthes pitchers as simple passive traps and is of great adaptive significance for these tropical plants, which are often submitted to high rainfalls and variations in fluid concentration. The viscoelastic trap constitutes a cryptic but potentially widespread adaptation of Nepenthes species and could be a homologous trait shared through common ancestry with the sundew (Drosera) flypaper plants. Such large production of a highly viscoelastic biopolymer fluid in permanent pools is nevertheless unique in the plant kingdom and suggests novel applications for pest control

Integrated evaluation of indoor particulate exposure. The viepi project

Despite the progress made in recent years, reliable modeling of indoor air quality is still far from being obtained. This requires better chemical characterization of the pollutants and airflow physics included in forecasting tools, for which field observations conducted simultaneously indoors and outdoors are essential. The project “Integrated Evaluation of Indoor Particulate Exposure” (VIEPI) aimed at evaluating indoor air quality and exposure to particulate matter (PM) of humans in workplaces. VIEPI ran from February 2016 to December 2019 and included both numerical simulations and field campaigns carried out in universities and research environments located in urban and non-urban sites in the metropolitan area of Rome (Italy). VIEPI focused on the role played by micrometeorology and indoor airflow characteristics in determining indoor PM concentration. Short-and long-term study periods captured diurnal, weekly, and seasonal variability of airflow and PM concentration. Chemical characterization of PM10, including the determination of elements, ions, elemental carbon, organic carbon, and bioaerosol, was also carried out. Large differences in the composition of PM10 were detected between inside and outside as well as between different periods of the day and year. Indoor PM composition was related to the presence of people, to the season, and to the ventilation regime