Search

Healthcare professionals (HCPs) are exposed to highly infectious viruses, such as norovirus, through multiple exposure routes. Understanding exposure mechanisms will inform exposure mitigation interventions. The study objective was to evaluate the influences of hospital patient room layout on differences in HCPs' predicted hand contamination from deposited norovirus particles. Computational fluid dynamic (CFD) simulations of a hospital patient room were investigated to find differences in spatial deposition patterns of bioaerosols for right-facing and left-facing bed layouts under different ventilation conditions. A microbial transfer model underpinned by observed mock care for three care types (intravenous therapy (IV) care, observational care, and doctors' rounds) was applied to estimate HCP hand contamination. Viral accruement was contrasted between room orientation, care type, and by assumptions about whether bioaerosol deposition was the same or variable by room orientation. Differences in sequences of surface contacts were observed for care type and room orientation. Simulated viral accruement differences between room types were influenced by mostly by differences in bioaerosol deposition and by behavior sequences when deposition patterns for the room orientations were similar. Differences between care types were likely driven by differences in hand-to-patient contact frequency, with doctors' rounds resulting in the greatest predicted viral accruement on hands.

[EN] The accelerated urban expansion produced in large metropolitan areas such as Valencia Metropolitan Area in recent decades has important environmental impacts including “soil sealing” and the loss of valuable natural areas. The aim of this paper is to analyze the evolution of artificial soil in the Metropolitan Area of Valencia (AMV) between 1984-2011 using Landsat TM and ETM+ images, that have been validated from SIOSE data with larger spatial resolution. Results point out, with an accuracy of 71%, that artificial surface raised in 8000 ha which represents an increase of 10% for sealing soil and 34% of the whole land covers of the AMV., [ES] La expansión urbana acelerada producida en décadas recientes en las grandes áreas metropolitanas como Valencia conlleva importantes impactos ambientales, entre ellos la impermeabilización o “sellado antropogénico” del suelo y la pérdida de espacios naturales de gran valor paisajístico. Este trabajo analiza la evolución de la cobertura artificial en el Área Metropolitana de Valencia (AMV) en el periodo 1984-2011 a partir de imágenes Landsat TM y ETM+, validadas a partir de datos SIOSE de mayor resolución espacial. Los resultados muestran, con una precisión del 71%, un aumento de la superficie artificial en el AMV de 8000 ha en dicho periodo, lo que supone un incremento del 10% del suelo sellado que representa globalmente el 34% del AMV

In this paper, our interest is in the perturbation analysis of level‐dependent quasi‐birth‐and‐death (LD‐QBD) processes, which constitute a wide class of structured Markov chains. An LD‐QBD process has the special feature that its space of states can be structured by levels (groups of states), so that a tridiagonal‐by‐blocks structure is obtained for its infinitesimal generator. For these processes, a number of algorithmic procedures exist in the literature in order to compute several performance measures while exploiting the underlying matrix structure; among others, these measures are related to first‐passage times to a certain level L(0) and hitting probabilities at this level, the maximum level visited by the process before reaching states of level L(0), and the stationary distribution. For the case of a finite number of states, our aim here is to develop analogous algorithms to the ones analyzing these measures, for their perturbation analysis. This approach uses matrix calculus and exploits the specific structure of the infinitesimal generator, which allows us to obtain additional information during the perturbation analysis of the LD‐QBD process by dealing with specific matrices carrying probabilistic insights of the dynamics of the process. We illustrate the approach by means of applying multitype versions of the susceptible‐infective (SI) and susceptible‐infective‐susceptible (SIS) epidemic models to the spread of antibiotic‐sensitive and antibiotic‐resistant bacterial strains in a hospital ward.

Genetic differences contribute to variations in the immune response mounted by different individuals to a pathogen. Such differential response can influence the spread of infectious disease, indicating why such diseases impact some populations more than others. Here, we study the impact of population-level genetic heterogeneity on the epidemic spread of different strains of H1N1 influenza. For a population with known HLA class-I allele frequency and for a given H1N1 viral strain, we classify individuals into sub-populations according to their level of susceptibility to infection. Our core hypothesis is that the susceptibility of a given individual to a disease such as H1N1 influenza is inversely proportional to the number of high affinity viral epitopes the individual can present. This number can be extracted from the HLA genetic profile of the individual. We use ethnicity-specific HLA class-I allele frequency data, together with genome sequences of various H1N1 viral strains, to obtain susceptibility sub-populations for 61 ethnicities and 81 viral strains isolated in 2009, as well as 85 strains isolated in other years. We incorporate these data into a multi-compartment SIR model to analyse the epidemic dynamics for these (ethnicity, viral strain) epidemic pairs. Our results show that HLA allele profiles which lead to a large spread in individual susceptibility values can act as a protective barrier against the spread of influenza. We predict that populations skewed such that a small number of highly susceptible individuals coexist with a large number of less susceptible ones, should exhibit smaller outbreaks than populations with the same average susceptibility but distributed more uniformly across individuals. Our model tracks some well-known qualitative trends of influenza spread worldwide, suggesting that HLA genetic diversity plays a crucial role in determining the spreading potential of different influenza viral strains across populations., Author summary Levels of immunity to strains of H1N1 influenza can vary, depending on the individual. This strongly influences how the disease spreads in a population. Accounting for such variations is a major challenge for the epidemiology of infectious diseases. We study the effect of population-level genetic heterogeneity on the epidemic spread of different strains of H1N1 influenza. We model the immune response of specific ethnicities to a number of H1N1 viral strains, using this information to study disease spread for these (ethnicity, viral strain) epidemic pairs. Our results show that larger genetic diversity at the level of immune response, leading to the presence of susceptibility sub-populations with a broad distribution of susceptibilities, protects against the spread of influenza in a population. We also show that populations with a small number of highly susceptible individuals, but with a large number of less susceptible ones, should exhibit smaller outbreaks than populations with the same average susceptibility but where it is more uniformly distributed. Our work captures some qualitative trends of influenza spread worldwide, providing a first attempt at understanding how susceptibility heterogeneities arising from variations in immune response determine disease spread in populations.

A stochastic model for the spread of an SIS epidemic among a population consisting of N individuals, each having heterogeneous infectiousness and/or susceptibility, is considered and its behavior is analyzed under the practically relevant situation when N is small. The model is formulated as a finite time-homogeneous continuous-time Markov chain X. Based on an appropriate labeling of states, we first construct its infinitesimal rate matrix by using an iterative argument, and we then present an algorithmic procedure for computing steady-state measures, such as the number of infected individuals, the length of an outbreak, the maximum number of infectives, and the number of infections suffered by a marked individual during an outbreak. The time till the epidemic extinction is characterized as a phase-type random variable when there is no external source of infection, and its Laplace-Stieltjes transform and moments are derived in terms of a forward elimination backward substitution solution. The inverse iteration method is applied to the quasi-stationary distribution of X, which provides a good approximation of the process X at a certain time, conditional on non-extinction, after a suitable waiting time. The basic reproduction number R0 is defined here as a random variable, rather than an expected value. © 2014 Published by Elsevier B.V.

The chemical data of major elements is used to study the precise lithological composition and the sedimentology of Miocene diatomaceous sediments from 24 sections of the Guadalquivir Basin. Three main episodes (Lower, Middle and Upper), defined on the basis of diatom zones have been studied. They record a highly productive coastal upwelling regime in the area during the Miocene. The wide range of variation of SiO2 (12.1878.00), CaO (1.60-43.73) and Al2O3 (2.76-10.32) contents reflects the important variations of the main components: Opal A, calcite (mainly biogenic) and clay minerals-terrigenous components. Biogenic silica has been estimated by using normative calculations after determination of the mineralogical compositions of the samples by means of X-ray diffraction. Maximum and minimum contents in biogenic silica are related to the dominant diatom taxa, the structure of the rock and the geographicallocation in the basin. The ternary diagrams SiO2 biogenic- Al2O3-CaO reveal that the Upper Episode has the highest amounts of clay minerals-terrigenous components. Plots of SiO2 biogenic/CaO versus Al2O3show a relation between the biogenic calcite and the clay-minerals-terrigenous components. The plots of Fe2O3/TiO2 versus Al2O3/ Al2O3+ Fe2O3 show that most of the samples may be interpreted as deposited in a continental margin enviranment. The data obtained fram the slope of linear regressions Fe (y) - Al (x) are indicative of areas with varying influence of a terrigenous source. The MnO/ Al2O3 ratio is used to estimate rates of sedimentation of the diatomaceous sediments. The range is between 1.7 and 180 mm/103 years, which is consistent with the sedimentation rate values fram sediments formed in coastal upwelling regimes. The rate of sedimentation varies in relation to the structure of the rack, the dominant diatom taxa and the age of the episodes.La composición química de elementos mayores es utilizada para analizar las características composicionales y sedimentológicas en 24 afloramientos de sedimentos miocenos con diatomeas de la Cuenca del Guadalquivir. En función de las biozonas de diatomeas, se consideran tres episodios de sedimentación diatomítica (Inferior, Medio y Superior) que reflejan un medio de sedimentación de alta productividad biogénica ocasionada por corrientes ascensionales costeras («coastal upwelling»). Los grandes márgenes de variación de los tres óxidos más importantes SiO2 (12,1878,00), CaO (1,60-43,73) y Al2O3 (2,76-10,32) definen la gran variación que presentan los tres componentes mayoritarios de estos sedimentos: Opalo A, calcita y minerales de la arcilla-terrígenos. A través de cálculos normativos en función de la composición mineralógica de las muestras y de los análisis de difracción de RX, se ha definido el porcentaje de sílice biogénica. El estudio de los máximos y mínimos de sílice biogénica ha puesto de manifiesto su relación con tipos dominantes de diatomeas, la estructura de la roca y la posición geográfica dentro de la Cuenca. La proyección de las muestras en los diagramas triangulares SiO2 biogénica- Al2O3-CaO ha revelado que el Episodio Superior es el que manifiesta mayor proporción relativa de Al2O3 (arcillas-componentes terrígenos). Los diagramas SiO2 biogénicalCaO versus Al2O3 han demostrado que existe frecuentemente una asociación preferente entre el plancton calcáreo y los minerales de arcilla-terrígenos. La proyección de las muestras en el diagrama Fe2O3/TiO2 versus Al2O3/ Al2O3+FeO, junto con la pendiente de la recta de regresión Fe (y) - Al (x) indican que todas las series se pueden considerar de plataforma continental existiendo zonas con mayor o menor influencia del continente. La relación MnO/ Al2O3, se ha utilizado para medir la tasa sedimentación; los valores obtenidos (entre 1,7 y 180 mm/103 años) concuerdan con los hallados en otras zonas de corrientes ascensionales costeras, encontrándose diferencias en función de las estructura de la roca, las diatomeas dominantes y los episodios considerados.

The lithological composition and biostratigraphy of diatomaceous marls have been defined in 93 outcrops of the Guadalquivir Basin. The diatomaceous marls display a wide variety of lithological types, mainly comprised of opal A (10-85 %) (mainly diatoms and to a lesser extent silicoflagellates, spicules and radiolarians), calcite (5-80 %) (principally foraminifers, nannoplankton, sparite, micrite and microspar), c1ay minerals (5-40 %) (smectite in greater quantities than illite; and kaolinite in small quantities) and terrigenous quartz (< 15 %). The diatom assemblages in the marls reflect the occurrence of temperate to warm water conditions in this area during middle and late Miocene. The diatoms are dominated by the fol1owing upwelling species: Thalassiosira nitzshoides, Thalassiotrix longuissima and Thalassionema baci//aris. Benthic diatoms are scarce but they have great species diversity. However, in sorne outcrops the genus Delphineis is more frequent thus indicating environments c10ser to shore areas. Three episodes based on Barron's (1985) low latitude zonation have been defined. The Lower Episode includes Cestodiscus peplum and Coscinodiscus lewisianus Zone and is assigned to the upper Langhian- lower Serravalian. After a period of no diatom occurrence (e. gigas var. diorama Zone is missing), the Middle Episode is defined by Craspedodiscus coscinodiscus and Actinocyclus moronensis Zones and covers the latest Serravalian-early Tortonian. The Upper Episode corresponds to Thalassiosira yabei Zone and it is assigned to middle Tortonian. The fundamental types of dilutants in diatomic sedimentation (biogenic calcareous, terrigenous and c1ay minerals), do not vary throughout the three episodes but there are great variations in the proportions. The coastal upwelling regime produces tongue-like patterns of sedimentation and the sedimentary record displays different changes of facies. The Upper Episode, where the c1ay-terrigenous dilutants predominate over calcareous dilutants and Delphineis appear in greater quantities, is interpreted as having been formed in an environment closer to the shore than other episodes. El estudio de 93 puntos en el Mioceno de la cuenca del Guadalquivir ha permitido definir en esta cuenca la situación, bioestratigráfica y composición litológica de las margas con diatomeas o «moronitas». Dichas rocas incluyen gran variedad de términos litológicos estando constituidos principalmente por ópalo A (10-85 %) (mayoritariamente diatomeas; silicoflagelados, espículas de esponja y radiolarios en menor proporción), calcita (5-80 %) (microforaminíferos, nanoplancton calcáreo, micrita y esparita fundamentalmente), minerales de la arcilla (5-40 %) (esmectita predominando sobre illita y caolinita en menores proporciones) y cuarzo terrígeno « 15 %). Las asociaciones de diatomeas están constituidas fundamentalmente por diatomeas planctónicas de aguas templado-cálidas, con dominio de Thalassionema nitzschoides, Thalassionema bacillaris y Thalassiotrix longuissima, definiendo áreas de alta productividad (upwelling) en la zona durante el Mioceno Medio y Superior. El componente bentónico es escaso y diversificado, sin embargo localmente adquiere importancia el género Delphineis indicando zonas más litorales. Se determinan tres episodios de sedimentación diatomítica basados en la zonación de baja latitud de Barron (1985c). El Episodio Inferior definido por las biozonas Cestodiscus peplum y Coscinodiscus lewisianus, comprende desde el Langhiense superior al Serrava¡ iense inferior. Después de un período de tiempo sin deposición de diatomeas comienza el Episodio Medio definido por las biozonas Craspedodiscus coscinodiscus y Actinocyclus moronensis, y que incluye el techo del Serravaliense y el Tortoniense Inferior. El Episodio Superior que corresponde a la biozona Thalassiosira yabei comprende el Tortoniense Medio. Los tipos de diluyentes fundamentales de la sedimentación diatomítica (componentes biogénicos calcáreos, terrígenos y arcillas), se mantienen en los tres episodios pero presentan gran variación en sus proporciones debido a la morfología «en lenguas» y composición de los depósitos sedimentarios formados bajo zonas de «coastal upwelling». El Episodio Superior diferenciado por el predominio del diluyente arcilloso-terrígeno y por una mayor proporción de Delphineis en las asociaciones de diatomeas. se interpreta formado más cerca del continente.