2,209 research outputs found
RESTING CYSTS FROM COASTAL MARINE PLANKTON
Coastal plankton show fluctuations in abundance and species composition. Resting stage (cyst) production is a common strategy adopted by hundreds of plankton species to ensure reproduction and to avoid adverse conditions. During the resting period, these species are normally absent from the water column, and cysts produced in the plankton accumulate in the sediment where they wait for the return of suitable conditions. A portion of the cyst bank does not hatch, instead undergoing a dormancy that may extend for decades. Confined coastal areas accumulate cysts in sediment due to one or more possibilities, including reduced water movement/hydrodynamics, high population density, abundance of cyst-producing species, and the absence or scarcity of possible cyst consumers in the benthos. The pelagic-benthic nexus, which affects both the sediment and the water column (and possibly sea ice) is still poorly understood. In fact, the presence of cysts in the life cycle of organisms is likely to have considerable consequences for the ecology of coastal plankton, as well as the evolution and biogeography of species. This review aims to depict the presence (and even abundance) of resting stages in marine environments and their impact on ecosystem functioning. The review starts with a description of encysted resting stages in all marine planktonic taxa, listing a total of 501 species with known cysts, and methods and tools for their collection and study. The physiology and timing of the rest period is then described for various taxa, followed by a discussion of the evolutionary implications of resting. The presence of encysted stages in different realms and phyla of plankton suggests an ancient origin and a successive diversification of morphologies that, today, roughly characterise each taxa. Ecological and biogeographical implications stem from this general framework and support the hypothesis of seasonal occurrences of planktonic life in ecosystems where productivity is suspended for a long time (e.g. in polar seas). The potential to suspend or resume life has implications for human activities, such as the risk of translocations through ship ballast water and contamination of water and seafood with toxins but also the benefit of cysts for the production of aquaculture feed. The review concludes with perspectives on present knowledge and outstanding questions to address in future studies
Implementation of a Modular Growing When Required Neural Gas Architecture for Recognition of Falls
In this paper we aim for the replication of a state of the art architecture for recognition of human actions using skeleton poses obtained from a depth sensor. We review the usefulness of accurate human action recognition in the field of robotic elderly care, focusing on fall detection. We attempt fall recognition using a chained Growing When Required neural gas classifier that is fed only skeleton joints data. We test this architecture against Recurrent SOMs (RSOMs) to classify the TST Fall detection database ver. 2, a specialised dataset for fall sequences. We also introduce a simplified mathematical model of falls for easier and faster bench-testing of classification algorithms for fall detection. The outcome of classifying falls from our mathematical model was successful with an accuracy of 97.12±1.65% and from the TST Fall detection database ver. 2 with an accuracy of 90.2±2.68% when a filter was added.CNP
Ab initio thermal expansion and thermoelastic properties of ringwoodite (\u3b3-Mg2SiO4) at mantle transition zone conditions
Thermal convection in the Earth\u2019s mantle is driven by lateral variations in temperature and density which are substantially controlled by the local volume thermal expansion of the constituent mineral phases. Ringwoodite is a major component of the lower mantle transition zone, but its thermal expansivity and thermoelastic properties are still affected by large uncertainties. Ambient thermal expansion coefficient (\u3b1_V0), for instance, can vary as much as 100% according to different experimental investigations available from the literature. In this work, we perform ab initio density functional theory calculations of vibrational properties of spinel-structured Mg2SiO4 ringwoodite in order to provide reliable thermophysical data up to mantle transition zone conditions. Temperature- and pressure-dependent thermal expansivity has been obtained by phonon dispersion calculations in the framework of quasi-harmonic approximation (QHA) up to 25 GPa and 2000 K. Theoretical analysis of vibrational spectra reveals that accurate prediction of IR and silent modes, along with their relative mode Gr\ufcneisen parameters, is crucial to define thermal expansivity. A six-parameter analytical function is able to reproduce ab initio values fairly well in the whole investigated P-T range, i.e. \u3b1_V (P,T) = (1.6033\ub710-5 + 8.839\ub710-9 T + 11.586\ub710-3 T-1 \u2013 6.055 T-2 + 804.31 T-3)\ub7exp-(\u20132.52\ub710-2 P), with temperature in Kelvin and pressure in Gigapascal. Ab initio static and isothermal bulk moduli have been derived for ringwoodite along with their P, T and cross derivatives, i.e. K_0 = 184.3 GPa, K_(T,300K) = 176.6 GPa; K_0^' = 4.13, K_(T,300K)^' = 4.16; (\u3016 02K\u3017_T/ 02T)_P = -0.0233 GPa/K and (\u3016 02^2 K\u3017_T/ 02P 02T)_0= 1.0\ub710-4 K-1. Computed thermal expansivity and thermoelastic properties supports the evidence that QHA performs remarkably well for Mg2SiO4 ringwoodite up to mantle transition zone temperatures. Since volume thermal expansion of ringwoodite is strongly pressure-dependent and its pressure dependence becomes more marked with the increasing temperature, internally-consistent assessments and empirical extrapolation of thermoelastic data to deep mantle conditions should be taken with care to avoid inaccurate or spurious predictions in phase equilibrium and mantle convection numerical modelling
Las inundaciones en España en los últimos veinte años. Una perspectiva geográfica
En España, las inundaciones constituyen el mayor riesgo natural. Durante los años 80 una sucesión de episodios catastróficos propició la implantación de un sistema moderno contra avenidas. Los geógrafos también se han implicado en el análisis de un fenómeno hidrológico con una fuerte componente territorial
El estado actual de los ambientes del agua
Los ambientes del agua –recursos singulares por sus funciones en la naturaleza y por sus prestaciones y connotaciones para los grupos humanos- son un valioso patrimonio. En concreto, los lagos, los ríos y las masas marinas y subterráneas constituyen bienes territoriales que aportan diversidad ecológica, estructuran paisajes y, a menudo, son utilizados por los humanos para el desarrollo de sus actividades (Martín Montalvo, 1996). A lo largo del tiempo, los ambientes del agua no son estables en términos cuantitativos y/o cualitativos, sino muy variables y sensibles a la dinámica de los sistemas naturales locales y regionales y a los crecientes impactos antrópicos sobre un recurso renovable.
La presente aportación sobre Ambientes del agua en España analiza su evolución reciente (básicamente a lo largo del siglo XX) y de su estado hidrogeomorfológico actual. En general, han resultado, directa o indirectamente, alterados por la intensificación de la demanda social del recurso, por las profundas transformaciones territoriales y por la escasa valoración de un patrimonio natural y cultural. El diagnóstico del cambio hidroambiental y de su estado actual exige una referencia a la gestión y al desarrollo de las políticas públicas
Bases metodológicas para la evaluación, uso y gestión sostenible de los recursos agrarios. Aplicación a la cuenca de Santa Catalina (Argentina)
Los recursos agrarios que son utilizados por el hombre para obtener alimentos y generar bienes económicos son el
clima, los suelos, los genotipos vegetales y animales mejorados y las tecnologías. La intensificación en el uso del
recurso suelo ha conducido a un deterioro del mismo con disminución en los rendimientos afectando negativamente
la rentabilidad de las empresas. Esta situación ha generado serios interrogantes sobre el principio de sostenibilidad
de la producción agraria. El desarrollo económico - social del área Centro – Sur de la provincia de Córdoba
(Argentina) está directamente vinculado con la producción agraria regional, pues constituye la actividad económica
más importante. Actualmente, uno de los principales problemas para el desarrollo deriva de la rentabilidad negativa
de las empresas agrarias por bajos rendimientos físicos, situación que conduce a quebrantos económicos con el
consiguiente éxodo rural.
En este trabajo se propone una metodología para evaluar el potencial productivo de los recursos agrarios de la
cuenca Santa Catalina localizada en el Centro - Sur de la provincia de Córdoba, con el fin de optimizar el uso y
gestión de dichos recursos bajo principios de máxima eficiencia ecológica y sostenibilidad. Se delimitaron quince
unidades ecológicamente homogéneas, se estimó la producción potencial y la susceptibilidad a la degradación
ambiental. La producción potencial supera entre un 300% a un 400% a la producción real para la gran mayoría de
los productos agrarios y el área presenta un elevado deterioro por erosión hídrica. Se ha realizado un análisis de
alternativas productivas viables y, mediante la evaluación multicriterio discreta, se propone una nueva estructura
productiva de la cuenca, incrementando de tres a once las alternativas de producción. Se concluye que, mediante la
evaluación cuantitativa de la capacidad productiva y de la degradación de los recursos naturales, es posible
seleccionar alternativas productivas ecológicamente eficientes, sostenibles y tecnológicamente viables para
estabilizar el deterioro ambiental e incrementar la producción física en las actuales condiciones socio - económicas
del sector productivo regional
A model of maxilla resection to test new hybrid implants:macroporous titanium and tissue engineering elements
Maxillary bone loss in commonly found in humans, due to bone ageing, tooth loos, periodontal disease and, more severely, to trauma, radiotherapy and tumor resection. Masillofacial reconstructive surgery is a still unmet clinical demand, available therapies include grafting of autologous or heterologous bone tissue and/or the implantation of metallic plates, buy these treatments are still unable to resume form and function. The emrgence of 3D-printing technology applied to metal alloys now allows the manufacturing of customized, patient-tailored prosthetic implants. However, poor bone quiality at the implant site due to ageing or disease still hamper proper osseointegration. By combining Electron Beam Melting metal sintering and tissue engineering, we are developing hybrid maxillofacial implants, wher a metal framework of Ti6Al4V alloy confers both and appropiaate shape and mechanical stabilty, while stem cells and osteogenic molecules stimulate bone growth into the metal framework, thus pormoting osseointegration. We hereby present the in vitro work driving to the development of our hybrid maxillofacial prostheses, as well as the setting up of an in vivo model of complete maxilla full resection, created in order to test the prostheses in a preclinical studyUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
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