Modeling exposure-lag-response associations with distributed lag non-linear models.

In biomedical research, a health effect is frequently associated with protracted exposures of varying intensity sustained in the past. The main complexity of modeling and interpreting such phenomena lies in the additional temporal dimension needed to express the association, as the risk depends on both intensity and timing of past exposures. This type of dependency is defined here as exposure-lag-response association. In this contribution, I illustrate a general statistical framework for such associations, established through the extension of distributed lag non-linear models, originally developed in time series analysis. This modeling class is based on the definition of a cross-basis, obtained by the combination of two functions to flexibly model linear or nonlinear exposure-responses and the lag structure of the relationship, respectively. The methodology is illustrated with an example application to cohort data and validated through a simulation study. This modeling framework generalizes to various study designs and regression models, and can be applied to study the health effects of protracted exposures to environmental factors, drugs or carcinogenic agents, among others

Simulations of Solid-on-Solid Models of Spreading of Viscous Droplets

We have studied the dynamics of spreading of viscous non-volatile fluids on surfaces by MC simulations of SOS models. We have concentrated on the complete wetting regime, with surface diffusion barriers neglected for simplicity. First, we have performed simulations for the standard SOS model. Formation of a single precursor layer, and a density profile with a spherical cap shaped center surrounded by Gaussian tails can be reproduced with this model. Dynamical layering (DL), however, only occurs with a very strongly attractive van der Waals type of substrate potential. To more realistically describe the spreading of viscous liquid droplets, we introduce a modified SOS model. In the new model, tendency for DL and the effect of the surface potential are in part embedded into the dynamics of the model. This allows a relatively simple description of the spreading under different conditions, with a temperature like parameter which strongly influences the droplet morphologies. Both rounded droplet shapes and DL can easily be reproduced with the model. Furthermore, the precursor width increases proportional to the square root of time, in accordance with experimental observations. PACS: 68.10.Gw, 05.70.Ln, 61.20.Ja.Comment: to appear in Physica A (1994), standard LaTex, 20 page

Historical biogeography and ecological niche modelling of the Asimina-Disepalum clade (Annonaceae): role of ecological differentiation in Neotropical-Asian disjunctions and diversification in Asia

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Nine new species of Begonia (Begoniaceae) from South and West Sulawesi, Indonesia

Nine new species of Begonia (Begoniaceae), Begonia comestibilis D.C.Thomas & Ardi, B. insueta D.C.Thomas & Ardi, B. lasioura D.C.Thomas & Ardi, B. nobmanniae D.C.Thomas & Ardi, B. prionota D.C.Thomas & Ardi, B. rantemarioensis D.C.Thomas & Ardi, B. sanguineopilosa D.C.Thomas & Ardi, B. torajana D.C.Thomas & Ardi and B. vermeulenii D.C.Thomas, are described from South and West Sulawesi, Indonesia. All belong to Begonia section Petermannia. Proposed conservation categories for these species are Vulnerable (VU) for Begonia comestibilis, B. nobmanniae, B. prionota, B. sanguineopilosa and B. vermeulenii; Least Concern (LC) for B. lasioura, B. rantemarioensis and B. torajana; and Data Deficient (DD) for B. insueta. An identification key to Begonia in South and West Sulawesi (Sulawesi Selatan and Sulawesi Barat) is provided. © 2011 Trustees of the Royal Botanic Garden Edinburgh.published_or_final_versio

Phylogenetic Reconstruction, Morphological Diversification and Generic Delimitation of Disepalum (Annonaceae)

Taxonomic delimitation of Disepalum (Annonaceae) is contentious, with some researchers favoring a narrow circumscription following segregation of the genus Enicosanthellum. We reconstruct the phylogeny of Disepalum and related taxa based on four chloroplast and two nuclear DNA regions as a framework for clarifying taxonomic delimitation and assessing evolutionary transitions in key morphological characters. Maximum parsimony, maximum likelihood and Bayesian methods resulted in a consistent, well-resolved and strongly supported topology. Disepalum s.l. is monophyletic and strongly supported, with Disepalum s. str. and Enicosanthellum retrieved as sister groups. Although this topology is consistent with both taxonomic delimitations, the distribution of morphological synapomorphies provides greater support for the inclusion of Enicosanthellum within Disepalum s.l. We propose a novel infrageneric classification with two subgenera. Subgen. Disepalum (= Disepalum s. str.) is supported by numerous synapomorphies, including the reduction of the calyx to two sepals and connation of petals. Subgen. Enicosanthellum lacks obvious morphological synapomorphies, but possesses several diagnostic characters (symplesiomorphies), including a trimerous calyx and free petals in two whorls. We evaluate changes in petal morphology in relation to hypotheses of the genetic control of floral development and suggest that the compression of two petal whorls into one and the associated fusion of contiguous petals may be associated with the loss of the pollination chamber, which in turn may be associated with a shift in primary pollinator. We also suggest that the formation of pollen octads may be selectively advantageous when pollinator visits are infrequent, although this would only be applicable if multiple ovules could be fertilized by each octad; since the flowers are apocarpous, this would require an extragynoecial compitum to enable intercarpellary growth of pollen tubes. We furthermore infer that the monocarp fruit stalks are likely to have evolved independently from those in other Annonaceae genera and may facilitate effective dispersal by providing a color contrast within the fruit.published_or_final_versio

Historical biogeography of Asimina-Disepalum (Annonaceae): origins of tropical intercontinental disjunctions and diversifications in Southeast Asia

Oral Session: Secondary forestsStudies of tropical intercontinental disjunctions, common biogeographical patterns in flowering plants, enable insights into the origin of extant distributions and diversity patterns. We investigate the temporal origin of the Neotropical-Asian disjunction in the Asimina-Disepalum clade of the early-divergent angiosperm family Annonaceae, and temporal congruence with underlying palaeoclimatic and geological processes. Moreover, we aim to identify the geographical origin of Disepalum, and to infer dispersal and vicariance events as well as potentially correlated climate niche differentiation in the evolution of the genus in …postprin

A Study of Initialization in Linux and OpenBSD

The code that initializes a system can be notoriously difficult to understand. In secure systems, initialization is critical for establishing a starting state that is secure. This paper explores two architectures used for bringing an operating system to its initial state, once the operating system gains control from the boot loader. Specifically, the ways in which the OpenBSD and Linux operating systems handle initialization are dissected

Time-dependent trapping of pollinators driven by the alignment of floral phenology with insect circadian rhythms

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Cross-taxon biogeographic patterns at the Malesian floristic interchange: insights from phylogenetic analyses of species rich Malesian angiosperm genera

Session: BiogeographyMalesia is one of the geologically most dynamic tropical regions in the world. The archipelago’s geological past, characterized by the evolution of an ever-changing mosaic of terrestrial and marine areas throughout the Cenozoic, provides the geographical back...postprin