On the Perturbations of Viscous Rotating Newtonian Fluids

The perturbations of weakly-viscous, barotropic, non-self-gravitating, Newtonian rotating fluids are analyzed via a single partial differential equation. The results are then used to find an expression for the viscosity-induced normal-mode complex eigenfrequency shift, with respect to the case of adiabatic perturbations. However, the effects of viscosity are assumed to have been incorporated in the unperturbed (equilibrium) model. This paper is an extension of the normal-mode formalism developed by Ipser & Lindblom for adiabatic pulsations of purely-rotating perfect fluids. The formulas derived are readily applicable to the perturbations of thin and thick accretion disks. We provide explicit expressions for thin disks, employing results from previous relativistic analyses of adiabatic normal modes of oscillation. In this case, we find that viscosity causes the fundamental p- and g- modes to grow while the fundamental c-mode could have either sign of the damping rate.Comment: Accepted for publication by The Astrophysical Journal. 11 pages, no figure

Control de Posición e Inercial de Plataforma de Dos Grados de Libertad

ResumenEste artículo presenta una aplicación de control para la estabilización inercial de una plataforma de dos grados de libertad (2-GDL). El objetivo de la aplicación es, en primer lugar, controlar las posiciones angulares de la plataforma en ausencia de perturbaciones inerciales y en segundo lugar, controlar las velocidades de la plataforma medidas respecto a ejes inerciales independientemente de las perturbaciones a las que se ve sometida. Con respecto al primer objetivo, se propone una estrategia de control de conmutación con el fin de reducir los efectos del rozamiento que es la principal causa del comportamiento no deseado. Respecto al segundo objetivo, se propone un control con estructura en cascada para conseguir las especificaciones deseadas. Se presentan resultados de simulación y experimentales sobre una plataforma que ponen de manifiesto la bondad de los controladores

MINLP-based hybrid strategy for operating mode selection of TES-backed-up refrigeration systems

Es la versión aceptada del artículo. Se puede consultar la versión final en https://onlinelibrary.wiley.com/doi/10.1002/rnc.4674This brief deals with the satisfaction of the daily cooling demand by a hybrid system that consists of a vapor-compression refrigeration cycle and a thermal energy storage (TES) unit, based on phase change materials. The addition of the TES tank to the original refrigeration plant allows to schedule the cooling production regardless of the instantaneous demand, given that the TES tank can store cold energy and release it whenever deemed appropriate. The scheduling problem is posed as an optimization problem based on mixed-integer nonlinear programming (MINLP) since it includes both discrete and continuous variables. The latter corresponds to the references on the main cooling powers involved in the problem (cooling production at the evaporator and TES charging/discharging), whereas the discrete variables define the operating mode scheduling. Therefore, in addition to the hybrid features of the physical plant, a hybrid optimal control strategy is also proposed. A receding horizon approach is applied, similar to model predictive control (MPC) strategies, while economic criteria are imposed in the objective function, as well as feasibility issues. The TES state estimation is also addressed since its instantaneous charge ratio is not measurable. The proposed strategy is applied in simulation to a challenging cooling demand profile, and the main advantages of the MINLP-based strategy over a nonlinear MPC-based scheduling strategy previously developed are highlighted, regarding operating cost, ease of tuning, and ability to adapt to cooling demand variations.Ministerio de Ciencia e InnovaciónFCT (Portugal)POR Lisbo

Variabilidade e tendencias interanuais no fitoplancto mariño das costas de Galicia

13 páginas, 2 tablas, 7 figuras[EN] The available information on phytoplankton biomass and species composition in Galician waters was studied to find out their spatial variability as well as the annual trends. The areas covered included the oceanic zone, the shelf and the inner part of the Rías. In general a significant drop in diatoms was observed. The series also indicated an increase in dinoflagellates, although it was not statistically significant. The diatom species related to blooms in the area declined, whereas those indicative of weak upwelling or stratificacion showed an increase. Even though not all trends were significant, the available data are consistent with the decrease in upwelling intensity over the last 40 years. The results also suggest that effects of climate changes on phytoplankton may be delayed for several years. In any case, the large oceanographic variability of the region, along with the lack of continuity of some o[GA] Co obxecto de coñecer a variabilidade espacial e as tendencias interanuais do fitoplancto galego, estudáronse as series de datos históricos dispoñibles para Galicia, abarcando desde a zona oceánica ata as zonas máis costeiras das rías e a plataforma continental. En xeral, observouse unha diminución significativa das diatomeas, especialmente na zona oceánica. Tamén hai indicios dun incremento, aínda que non significativo, dos dinoflaxelados. O descenso das diatomeas foi debido á caída das abundancias de especies propias de floracións, tanto primaverais como estivais asociadas ao afloramento. Así mesmo, aumentaron as especies de diatomeas propias de afloramentos febles ou estratificación. Malia que non todas as tendencias foron significativas, os resultados son coherentes cunha diminución da intensidade do afloramento nos últimos 40 anos e un cambio nas condicións climáticas desde a década de 1980. Os resultados indican que os efectos dos cambios climáticos sobre o fitoplancto se poden manifestar con varios anos de retardo. Con todo, a alta variabilidade oceanográfica da zona, especialmente de alta frecuencia, e mais a falta de continuidade de moitas series de datos dificultan o establecemento de relacións claras entre cambios ambientais e o fitoplanctoEsta análise das tendencias do fitoplancto en Galicia foi financiada parcialmente pola Consellería de Medio Ambiente e Desenvolvemento Sostible (Programa CLIGAL) e polo proxecto REFORZA (PGIDT06RMA60401PR) da Consellería de Innovación e Industria da Xunta de Galicia. O traballo de María Huete-Ortega estivo financiado polo Programa Predoutoral de Formación de Profesorado Universitario do Ministerio de Educación y Ciencia.Peer reviewe

Practical guide to single-protein AFM nanomechanical spectroscopy mapping: insights and pitfalls as unraveled by all-atom MD simulations on immunoglobulin G

Atomic force microscopy is an invaluable characterization tool in almost every biophysics laboratory. However, obtaining atomic/sub-nanometer resolution on single proteins has thus far remained elusive - a feat long achieved on hard substrates. In this regard, nanomechanical spectroscopy mapping may provide a viable approach to overcome this limitation. By complementing topography with mechanical properties measured locally, one may thus enhance spatial resolution at the single-protein level. In this work, we perform all-atom molecular dynamics simulations of the indentation process on a single immunoglobulin G (IgG) adsorbed on a graphene slab. Our simulations reveal three different stages as a function of strain: a noncontact regime - where the mechanical response is linked to the presence of the water environment - followed by an elastic response and a final plastic deformation regime. In the noncontact regime, we are able to identify hydrophobic/hydrophilic patches over the protein. This regime provides the most local mechanical information that allows one to discern different regions with similar height/topography and leads to the best spatial resolution. In the elastic regime, we conclude that the Young modulus is a well-defined property only within mechanically decoupled domains. This is caused by the fact that the elastic deformation is associated with a global reorganization of the domain. Differences in the mechanical response are large enough to clearly resolve domains within a single protein, such as the three subunits forming the IgG. Two events, unfolding or protein slipping, are observed in the plastic regime. Our simulations allow us to characterize these two processes and to provide a strategy to identify them in the force curves. Finally, we elaborate on possible challenges that could hamper the interpretation of such experiments/simulations and how to overcome them. All in all, our simulations provide a detailed picture of nanomechanical spectroscopy mapping on single proteins, showing its potential and the challenges that need to be overcome to unlock its full potentialJ.G.V. acknowledges funding from a Marie Sklodowska-Curie Fellowship within the Horizon 2020 framework (Grant No. DLV-795286) and the Swiss National Science Foundation (Grant No. CRSK-2 190731/1). R.P. acknowledges support from the Spanish MINECO (Grant No. MAT2017-83273-R) and from the Ministerio de Ciencia e Innovación (MICINN) through the “María de Maeztu” Programme for Units of Excellence in R&D (Grant No. CEX2018-000805-M). R.G. acknowledges funding from the MICINN (Grant No. PID2019-106801GB-I00) and Comunidad de Madrid Grant No. S2018/NMT-4443 (Tec4Bio-CM). We thankfully acknowledge the computer resources, technical expertise, and assistance provided by the Red Española de Supercomputación (RES) at the Minotauro and CTE-Power9 supercomputers (BSC, Barcelona). We thank Dr. Alejandro Martín-González for fruitful discussion

Automatic segmentation of the Foveal Avascular Zone in ophthalmological OCT-A images

Angiography by Optical Coherence Tomography is a non-invasive retinal imaging modality of recent appearance that allows the visualization of the vascular structure at predefined depths based on the detection of the blood movement. OCT-A images constitute a suitable scenario to analyse the retinal vascular properties of regions of interest, measuring the characteristics of the foveal vascular and avascular zones. Extracted parameters of this region can be used as prognostic factors that determine if the patient suffers from certain pathologies, indicating the associated pathological degree. The manual extraction of these biomedical parameters is a long, tedious and subjective process, introducing a significant intra and inter-expert variability, which penalizes the utility of the measurements. In addition, the absence of tools that automatically facilitate these calculations encourages the creation of computer-aided diagnosis frameworks that ease the doctor's work, increasing their productivity and making viable the use of this type of vascular biomarkers. We propose a fully automatic system that identifies and precisely segments the region of the foveal avascular zone (FAZ) using a novel ophthalmological image modality as is OCT-A. The system combines different image processing techniques to firstly identify the region where the FAZ is contained and, secondly, proceed with the extraction of its precise contour. The system was validated using a representative set of 168 OCT-A images, providing accurate results with the best correlation with the manual measurements of two experts clinician of 0.93 as well as a Jaccard's index of 0.82 of the best experimental case. This tool provides an accurate FAZ measurement with the desired objectivity and reproducibility, being very useful for the analysis of relevant vascular diseases through the study of the retinal microcirculation

Identificación de parámetros de colectores solares planos mediante algoritmos genéticos

[Resumen] En este trabajo se identifican los parámetros de un modelo de parámetros distribuidos de colectores solares planos mediante un algoritmo genético de codificación real utilizando datos de una planta piloto experimental.Los autores quieren expresar su agradecimiento al Ministerio de Ciencia e Innovación por la financiación de este trabajo a través del proyecto DPI2013-44135-Rhttps://doi.org/10.17979/spudc.978849749808

Alimentación de los caprélidos (Crustacea: Amphipoda) de la costa oeste de Méjico. ¿Se alimentan de los sustratos en los que viven?

We studied the gut contents of the dominant species of the West coast of Mexico to explore if caprellids can use their host substrates (mainly hydroids and gorgonians) as food resource or just as a place to cling on. Two hundred and forty two specimens of four species of caprellids were examined: Aciconula acanthosoma Chess, 1989, Caprella equilibra Say, 1818, Caprella aff. penantis Leach, 1814 and Paracaprella sp. Detritus was the dominant component in all the species, although hydroids were also abundant in C. equilibra and Paracaprella sp. Crustaceans were present in the digestive tracts of the four species, being an important component in Aciconula acanthosoma and Paracaprella sp. Caprella aff. penantis and C. equilibra collected from gorgonians did not show any trace of gorgonian sclerites in their guts. Therefore, the present study reveals that caprellids from the Pacific coast of Mexico are able to feed on hydroids but not on gorgonians. Furthermore, Paracaprella sp. associated to hydroids also showed a significant amount of harpacticoid copepods in the digestive tract, supporting the idea of cleptocomensalism. Further experimental studies are needed to explore the complex relationships between hydroids and caprellids.Se estudió el contenido del digestivo de las especies dominantes de la costa oeste de Méjico para explorar si los caprélidos pueden usar los sustratos en los que viven (principalmente hidrozoos y gorgonias) como fuente de alimento o solamente como sustrato al que anclarse. Se examinaron doscientos cuarenta y dos ejemplares de cuatro especies de caprélidos: Aciconula acanthosoma Chess, 1989, Caprella equilibra Say, 1818, Caprella aff. penantis Leach, 1814 y Paracaprella sp. El componente dominante en todas las especies fue el detritus, aunque los hidrozoos también fueron abundantes en C. equilibra y Paracaprella sp. Se encontraron restos de crustáceos en los tractos digestivos de las cuatro especies, siendo un componente importante en Aciconula acanthosoma y Paracaprella sp. Caprella aff. penantis y C. equilibra recolectadas en gorgonias no mostraron ningún resto de escleritos en sus digestivos. Por tanto, el presente estudio revela que los caprélidos de la costa pacífica de Méjico son capaces de alimentarse de hidrozoos pero no de gorgonias. Además, Paracaprella sp. asociada a hidrozoos también mostró una cantidad importante de copépodos harpacticoides en el tracto digestivo, lo que apoya la idea de cleptocomensalismo. Para el futuro, sería interesante desarrollar estudios experimentales para explorar las complejas relaciones entre hidrozoos y caprélidos

[2-(sec-Butyl­imino­meth­yl)quinoline]­chlorido(η6-1-isopropyl-4-methyl­benzene)­ruthenium(II) hexa­fluorido­phosphate

In the title compound, [RuCl(C10H14)(C14H16N2)]PF6, the aromatic ring of the isopropyl­methyl­benzene fragment shows an η6-arene coordination to the ruthenium atom. Its coordination sphere is completed by a chloride ligand and 2-(sec-butyl­imino­meth­yl)quinoline. The dihedral angle between the η6-arene ring and the quinoline Schiff base is 45.64 (9)°. The sec-butyl substituent and the PF6 − anion are disordered over two positions with ratios of 0.595 (11):0.405 (11) and 0.752 (8):0.248 (8), respectively