993 research outputs found

    Estimation of a Monotone Mean Residual Life

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    In survival analysis and in the analysis of life tables an important biometric function of interest is the life expectancy at age x,M(x), defined by M(x)=E[X?x|X\u3ex], where X is a lifetime. M is called the mean residual life function. In many applications it is reasonable to assume that M is decreasing (DMRL) or increasing (IMRL); we write decreasing (increasing) for nonincreasing (non-decreasing). There is some literature on empirical estimators of M and their properties. Although tests for a monotone M are discussed in the literature, we are not aware of any estimators of M under these order restrictions. In this paper we initiate a study of such estimation. Our projection type estimators are shown to be strongly uniformly consistent on compact intervals, and they are shown to be asymptotically root-n equivalent in probability to the (unrestricted) empirical estimator when M is strictly monotone. Thus the monotonicity is obtained free of charge , at least in the aymptotic sense. We also consider the nonparametric maximum likelihood estimators. They do not exist for the IMRL case. They do exist for the DMRL case, but we have found the solutions to be too complex to be evaluated efficiently

    Multi-scale accretion in dense cloud cores and the delayed formation of massive stars

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    The formation mechanism of massive stars remains one of the main open problems in astrophysics, in particular the relationship between the mass of the most massive stars, and that of the cores in which they form. Numerical simulations of the formation and evolution of large molecular clouds, within which dense cores and stars form self-consistently, show in general that the cores' masses increase in time, and also that the most massive stars tend to appear later (by a few to several Myr) than lower-mass stars. Here we present an idealized model that incorporates accretion onto the cores as well as onto the stars, in which the core's mass growth is regulated by a ``gravitational choking'' mechanism that does not involve any form of support. This process is of purely gravitational origin, and causes some of the mass accreted onto the core to stagnate there, rather than being transferred to the central stars. Thus, the simultaneous mass growth of the core and of the stellar mass can be computed. In addition, we estimate the mass of the most massive allowed star before its photoionizing radiation is capable of overcoming the accretion flow onto the core. This model constitutes a proof-of-concept for the simultaneous growth of the gas reservoir and the stellar mass, the delay in the formation of massive stars observed in cloud-scale numerical simulations, the need for massive, dense cores in order to form massive stars, and the observed correlation between the mass of the most massive star and the mass of the cluster it resides in. Also, our model implies that by the time massive stars begin to form in a core, a number of low-mass stars are expected to have already formed.Comment: Submitted to MNRAS. Originally submitted to Nature Astronomy, but withdrawn from that journal after not having received a reviewer's report for over four months. Comments welcom

    SIDM on FIRE: Hydrodynamical Self-Interacting Dark Matter simulations of low-mass dwarf galaxies

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    We compare a suite of four simulated dwarf galaxies formed in 1010M^{10} M_{\odot} haloes of collisionless Cold Dark Matter (CDM) with galaxies simulated in the same haloes with an identical galaxy formation model but a non-zero cross-section for dark matter self-interactions. These cosmological zoom-in simulations are part of the Feedback In Realistic Environments (FIRE) project and utilize the FIRE-2 model for hydrodynamics and galaxy formation physics. We find the stellar masses of the galaxies formed in Self-Interacting Dark Matter (SIDM) with σ/m=1cm2/g\sigma/m= 1\, cm^2/g are very similar to those in CDM (spanning M105.77.0MM_{\star} \approx 10^{5.7 - 7.0} M_{\odot}) and all runs lie on a similar stellar mass -- size relation. The logarithmic dark matter density slope (α=dlogρ/dlogr\alpha=d\log \rho / d\log r) in the central 250500250-500 pc remains steeper than α=0.8\alpha= -0.8 for the CDM-Hydro simulations with stellar mass M106.6MM_{\star} \sim 10^{6.6} M_{\odot} and core-like in the most massive galaxy. In contrast, every SIDM hydrodynamic simulation yields a flatter profile, with α>0.4\alpha >-0.4. Moreover, the central density profiles predicted in SIDM runs without baryons are similar to the SIDM runs that include FIRE-2 baryonic physics. Thus, SIDM appears to be much more robust to the inclusion of (potentially uncertain) baryonic physics than CDM on this mass scale, suggesting SIDM will be easier to falsify than CDM using low-mass galaxies. Our FIRE simulations predict that galaxies less massive than M<3×106MM_{\star} < 3 \times 10^6 M_{\odot} provide potentially ideal targets for discriminating models, with SIDM producing substantial cores in such tiny galaxies and CDM producing cusps.Comment: 10 Pages, 7 figures, submitted to MNRA

    Insecticide Resistance Mechanisms in the Green Peach Aphid Myzus persicae (Hemiptera: Aphididae) I: A Transcriptomic Survey

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    BACKGROUND: Insecticide resistance is one of the best examples of rapid micro-evolution found in nature. Since the development of the first synthetic insecticide in 1939, humans have invested considerable effort to stay ahead of resistance phenotypes that repeatedly develop in insects. Aphids are a group of insects that have become global pests in agriculture and frequently exhibit insecticide resistance. The green peach aphid, Myzus persicae, has developed resistance to at least seventy different synthetic compounds, and different insecticide resistance mechanisms have been reported worldwide. METHODOLOGY/PRINCIPAL FINDINGS: To further characterize this resistance, we analyzed genome-wide transcriptional responses in three genotypes of M. persicae, each exhibiting different resistance mechanisms, in response to an anti-cholinesterase insecticide. The sensitive genotype (exhibiting no resistance mechanism) responded to the insecticide by up-regulating 183 genes primarily ones related to energy metabolism, detoxifying enzymes, proteins of extracellular transport, peptidases and cuticular proteins. The second genotype (resistant through a kdr sodium channel mutation), up-regulated 17 genes coding for detoxifying enzymes, peptidase and cuticular proteins. Finally, a multiply resistant genotype (carrying kdr and a modified acetylcholinesterase), up-regulated only 7 genes, appears not to require induced insecticide detoxification, and instead down-regulated many genes. CONCLUSIONS/SIGNIFICANCE: This study suggests strongly that insecticide resistance in M. persicae is more complex that has been described, with the participation of a broad array of resistance mechanisms. The sensitive genotype exhibited the highest transcriptional plasticity, accounting for the wide range of potential adaptations to insecticides that this species can evolve. In contrast, the multiply resistant genotype exhibited a low transcriptional plasticity, even for the expression of genes encoding enzymes involved in insecticide detoxification. Our results emphasize the value of microarray studies to search for regulated genes in insects, but also highlights the many ways those different genotypes can assemble resistant phenotypes depending on the environmental pressure

    Combining satellite data and appropriate objective functions for improved spatial pattern performance of a distributed hydrologic model

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    Abstract. Satellite-based earth observations offer great opportunities to improve spatial model predictions by means of spatial-pattern-oriented model evaluations. In this study, observed spatial patterns of actual evapotranspiration (AET) are utilised for spatial model calibration tailored to target the pattern performance of the model. The proposed calibration framework combines temporally aggregated observed spatial patterns with a new spatial performance metric and a flexible spatial parameterisation scheme. The mesoscale hydrologic model (mHM) is used to simulate streamflow and AET and has been selected due to its soil parameter distribution approach based on pedo-transfer functions and the build in multi-scale parameter regionalisation. In addition two new spatial parameter distribution options have been incorporated in the model in order to increase the flexibility of root fraction coefficient and potential evapotranspiration correction parameterisations, based on soil type and vegetation density. These parameterisations are utilised as they are most relevant for simulated AET patterns from the hydrologic model. Due to the fundamental challenges encountered when evaluating spatial pattern performance using standard metrics, we developed a simple but highly discriminative spatial metric, i.e. one comprised of three easily interpretable components measuring co-location, variation and distribution of the spatial data. The study shows that with flexible spatial model parameterisation used in combination with the appropriate objective functions, the simulated spatial patterns of actual evapotranspiration become substantially more similar to the satellite-based estimates. Overall 26 parameters are identified for calibration through a sequential screening approach based on a combination of streamflow and spatial pattern metrics. The robustness of the calibrations is tested using an ensemble of nine calibrations based on different seed numbers using the shuffled complex evolution optimiser. The calibration results reveal a limited trade-off between streamflow dynamics and spatial patterns illustrating the benefit of combining separate observation types and objective functions. At the same time, the simulated spatial patterns of AET significantly improved when an objective function based on observed AET patterns and a novel spatial performance metric compared to traditional streamflow-only calibration were included. Since the overall water balance is usually a crucial goal in hydrologic modelling, spatial-pattern-oriented optimisation should always be accompanied by traditional discharge measurements. In such a multi-objective framework, the current study promotes the use of a novel bias-insensitive spatial pattern metric, which exploits the key information contained in the observed patterns while allowing the water balance to be informed by discharge observations.</jats:p

    Metabolic syndrome in rural Peruvian adults living at high altitudes using different cookstoves

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    This study determined the prevalence of metabolic syndrome (MetS) in open fire stoves and improved cookstoves users (ICS) in the rural Peruvian Andes. Participants answered a socioeconomic questionnaire, one 24-hour food recall and underwent a physical examination. We analysed data from 385 participants, 190 (112 women and 78 men) were ICS users and 195 (123 women and 72 men) were open fire stove users. The prevalence of MetS was 21.3, 26.4% in women and 13.3% in men. We found no statistically significant association between the type of cookstove and MetS. Body mass index and altitude were important determinants of MetS. Research on cardiometabolic diseases and open fire stove use contributes to understanding the effect of household air pollution on health in high altitude populations

    Comparative Analysis of the Physicochemical Properties and Antioxidant Capacity of a Morphotype Of Oregano (O. Vulgare L.) Cultivated in Two Locations of the Ecuadorian Sierra

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    Oregano (O.vulgare L.) is a species introduced in the Ecuadorian flora. Because of its properties it is highly appreciated and consumed, and it is important to determine the nature of its benefits. The chemical composition and the content of functional compounds responsible for the antioxidant activity of the plant identified by the INIAP Germplasm Bank as ECU-20229 were evaluated. It was cultivated in two areas of the provinces of Imbabura (Italquí) and Pichincha (Tumbaco). The whole plant and its parts (root, stem and leaves) were analyzed in order to determine where the highest content was found. Proximal analysis, minerals, polyphenols and total flavonoids were analyzed, as well as the antioxidant capacity. The analyses carried out on the plant parts showed significant differences, determining the influence of the environment where it was grown. It was possible to determine the presence of nutrients such as protein, fat and carbohydrates, which is higher in the leaves; macro elements are abundant in the stem and leaves and micro elements are found in greater quantity when it was cultivated in Italquí, as well as the content of polyphenols and total flavonoids; the antioxidant capacity is higher in the environmental conditions of Tumbaco. The properties described for this plant have been proven to benefit human and animal health, as well as adding value to its wasted parts.&nbsp

    Intervenciones de enfermería para la familia cuidadora de un paciente con cáncer

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    Introducción: La enfermedad del cáncer va a ir en aumento en los próximos años, debido al incremento de la población, del envejecimiento y de la exposición a comportamientos de riesgo. Es la principal causa de muerte en el mundo. Afecta tanto al paciente como a la familia, por ello es necesario llevar a cabo intervenciones de enfermería dirigidas a la familia para satisfacer sus necesidades. Objetivos: Realizar una revisión de la literatura acerca de las intervenciones de enfermería para la familia cuidadora con un paciente con cáncer. Metodología: Se realizó una revisión bibliográfica en las bases de datos PubMed y CINAHL durante los meses de octubre a diciembre del 2022. Resultados: Se identificaron cinco tipos de intervenciones: Intervención de conversación terapéutica, intervención psicoeducativa, mindfulness, musicoterapia e intervención educativa y apoyo. Todas ellas tuvieron un impacto positivo en distintas esferas de la persona. Conclusiones: Las intervenciones de enfermería ayudan a sobrellevar mejor el proceso de enfermedad oncológica y logran una reducción de la ansiedad y angustia. Por ello, es importante seguir investigando para poder utilizarlas en la práctica clínica.Introduction: Cancer disease is set to increase in the upcoming years, due to population growth, ageing and exposure to risk behaviours. It is the leading cause of death in the world. It affects both the patient and the family, so it is necessary to carry out nursing interventions aimed at the family to meet their needs. Objective: To conduct a literature review of nursing interventions for the family caregiver with a cancer patient. Methodology: A literature review was conducted in PubMed and CINAHL databases during October to December 2022. Results: Five types of interventions were identified: Therapeutic conversation intervention, psychoeducational intervention, mindfulness, music therapy and educational intervention and support. All of them had a positive impact on different spheres of the person. Conclusions: Nursing interventions help to cope better with the cancer disease process and obtain a reduction in anxiety and distress. Therefore, further research is important in order to be able to use them in clinical practice

    Near-complete genome sequencing of swine vesicular disease virus using the Roche GS FLX sequencing platform

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    Swine vesicular disease virus (SVDV) is an enterovirus that is both genetically and antigenically closely related to human coxsackievirus B5 within the Picornaviridae family. SVDV is the causative agent of a highly contagious (though rarely fatal) vesicular disease in pigs. We report a rapid method that is suitable for sequencing the complete protein-encoding sequences of SVDV isolates in which the RNA is relatively intact. The approach couples a single PCR amplification reaction, using only a single PCR primer set to amplify the near-complete SVDV genome, with deep-sequencing using a small fraction of the capacity of a Roche GS FLX sequencing platform. Sequences were initially verified through one of two criteria; either a match between a de novo assembly and a reference mapping, or a match between all of five different reference mappings performed against a fixed set of starting reference genomes with significant genetic distances within the same species of viruses. All reference mappings used an iterative method to avoid bias. Further verification was achieved through phylogenetic analysis against published SVDV genomes and additional Enterovirus B sequences. This approach allows high confidence in the obtained consensus sequences, as well as provides sufficiently high and evenly dispersed sequence coverage to allow future studies of intra-host variation
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