Feasibility and primary energy savings of absorption chillers for data centers, both direct fired and in trigeneration

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.Depending on the operating conditions, combined heat, cooling and power systems (CHCP) can sometimes compete energetically and economically with classical vapour compression chillers. Conclusions are often different if either the economic or energetic feasibility is investigated. The application of free chilling can highly affect the results. In this paper, simulations in TRNSYS are performed of a cooling installation of a datacenter of 1500 kW. The use of absorption chillers with gas engines is compared with the application of superchillers (air cooled vapour compression chillers that can run in free chilling). Both single effect and double effect, direct and hot water fired absorption chillers have been studied. The impact of the variation of some crucial parameters on the economic and energetic feasibility of trigeneration is studied. Concerning energetic feasibility, the efficiency of the gas engines and the temperature regimes are some crucial parameters. Varying energy prices highly affect the economic feasibility of trigeneration.mp201

Modelling heat and moisture transport in porous materials with CFD for building applications

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.Heat and moisture transport in buildings have a large impact on the building envelope durability, the energy consumption in buildings and the indoor climate. Nowadays HAM (Heat, Air and Moisture) models are widely used to simulate and predict the effect of these transport phenomena in detail. Recently these HAM models are being coupled to CFD (Computational Fluid Dynamics) to study the moisture exchange between air and porous materials on a local scale (microclimates). A direct coupling approach between CFD and HAM is applied. The transport equations for heat and moisture in a porous material are directly implemented into an existing CFD package and the transport equations in the air and in the porous material are solved in one iteration by only one solver. In this paper a model for moisture transport in the hygroscopic range and over-hygroscopic range is developed. This way a broad range of problems can be tackled such as drying phenomena and interstitial condensation in building components. The model is verified and validated with data from literature.mp201

Divergence of chemosensing during the early stages of speciation.

Chemosensory communication is essential to insect biology, playing indispensable roles during mate-finding, foraging, and oviposition behaviors. These traits are particularly important during speciation, where chemical perception may serve to establish species barriers. However, identifying genes associated with such complex behavioral traits remains a significant challenge. Through a combination of transcriptomic and genomic approaches, we characterize the genetic architecture of chemoperception and the role of chemosensing during speciation for a young species pair of Heliconius butterflies, Heliconius melpomene and Heliconius cydno We provide a detailed description of chemosensory gene-expression profiles as they relate to sensory tissue (antennae, legs, and mouthparts), sex (male and female), and life stage (unmated and mated female butterflies). Our results untangle the potential role of chemical communication in establishing barriers during speciation and identify strong candidate genes for mate and host plant choice behaviors. Of the 252 chemosensory genes, HmOBP20 (involved in volatile detection) and HmGr56 (a putative synephrine-related receptor) emerge as strong candidates for divergence in pheromone detection and host plant discrimination, respectively. These two genes are not physically linked to wing-color pattern loci or other genomic regions associated with visual mate preference. Altogether, our results provide evidence for chemosensory divergence between H. melpomene and H. cydno, two rarely hybridizing butterflies with distinct mate and host plant preferences, a finding that supports a polygenic architecture of species boundaries

Patternize: An R Package For Quantifying Color Pattern Variation

The use of image data to quantify, study and compare variation in the colors and patterns of organisms requires the alignment of images to establish homology, followed by color-based segmentation of images. Here we describe an R package for image alignment and segmentation that has applications to quantify color patterns in a wide range of organisms. patternize is an R package that quantifies variation in color patterns obtained from image data. patternize first defines homology between pattern positions across specimens either through manually placed homologous landmarks or automated image registration. Pattern identification is performed by categorizing the distribution of colors using an RGB threshold, k-means clustering or watershed transformation. We demonstrate that patternize can be used for quantification of the color patterns in a variety of organisms by analyzing image data for butterflies, guppies, spiders and salamanders. Image data can be compared between sets of specimens, visualized as heatmaps and analyzed using principal component analysis (PCA). patternize has potential applications for fine scale quantification of color pattern phenotypes in population comparisons, genetic association studies and investigating the basis of color pattern variation across a wide range of organisms.NSF grant DEB-1257839 NIH grant 5P20GM103475-1

Deep convergence, shared ancestry and evolutionary novelty in the genetic architecture of heliconius mimicry

Convergent evolution can occur through different genetic mechanisms in different species. It is now clear that convergence at the genetic level is also widespread, and can be caused by either (i) parallel genetic evolution, where independently evolved convergent mutations arise in different populations or species, or (ii) collateral evolution in which shared ancestry results from either ancestral polymorphism or introgression among taxa. The adaptive radiation of Heliconius butterflies shows color pattern variation within species, as well as mimetic convergence between species. Using comparisons from across multiple hybrid zones, we use signals of shared ancestry to identify and refine multiple putative regulatory elements in Heliconius melpomene and its comimics, Heliconius elevatus and Heliconius besckei, around three known major color patterning genes: optix, WntA, and cortex. While we find that convergence between H. melpomene and H. elevatus is caused by a complex history of collateral evolution via introgression in the Amazon, convergence between these species in the Guianas appears to have evolved independently. Thus, we find adaptive convergent genetic evolution to be a key driver of regulatory changes that lead to rapid phenotypic changes. Furthermore, we uncover evidence of parallel genetic evolution at some loci around optix and WntA in H. melpomene and its distant comimic Heliconius erato. Ultimately, we show that all three of convergence, conservation, and novelty underlie the modular architecture of Heliconius color pattern mimicry

Prediction of mold risk in cavity walls combining a coupled CFD/HAM-model and a 2D hygrothermal model: the influence of the outer cavity layer on the inner cavity layer

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.Preventing mould risk in buildings is important to ensure a healthy environment for the people and to avoid material damage. A reliable prediction is especially important for ventilated cavity walls made of a moisture sensitive material such as wood. In this paper the influence of the outer cavity layer on the inner cavity layer has been analyzed. The cavity wall consists of a timber frame on the inside and a brick veneer on the outside separated by an air layer. For this hygrothermal evaluation of air cavities, coupled CFD/HAM-software and a commercial hygrothermal software package WUFI-2D® are used. First the coupled CFD/HAM-software is used to examine the heat and mass transfer coefficients at the surfaces between the air and the material layer and the applicability of the heat/mass-analogy. Afterwards, the effect of long-wave radiation in the cavity will be simulated with the coupled CFD/HAM-model. Finally the model developed in WUFI to simulate a ventilated cavity wall and the influence of different materials for the outer layer will be examined combining the coupled CFD/HAM-model and WUFI-2D.dc201

The Combined Effect of Air Layers and Membrane Superhydrophobicity on Biofouling in Membrane Distillation

Previous studies of membrane distillation (MD) have shown that superhydrophobic membranes experience dramatically less inorganic and particulate fouling. However, little explanation for this improved performance has been given in the literature. Furthermore, studies comparing membrane superhydrophobicity and biofouling are lacking, though superhydrophobic surfaces are known to be more vulnerable to biofouling than other types. In non-membrane surfaces, visible air layers on superhydrophobic surfaces have been correlated with significant decreases in biofouling. Therefore, it was proposed here to use superhydrophobic MD membranes with periodic introduction of air to maintain an air layer on the membrane surface. Superhydrophobic membranes were created with initiated chemical vapor deposition (iCVD) of a fluorinated compound, perfluorodecyl acrylate (PFDA). The substrate membrane was PVDF. To test MD fouling, an MD membrane was placed on top of a fouling solution, with a heater and stirrer to caus e evaporation of water through the membrane. Results were analyzed with foulant mass measurements. Alginate gel fouling was examined, as this compound is a common proxy for biological fouling in ocean w ater. The introduction of air layers was found to dramatically decrease foulant adhesion to the membrane, by 95-97%. Membrane superhydrophobicity made a much smaller impact in reducing fouling. Keywords membrane distillation, superhydrophobic surfaces, alginate, air layers, anti-foulin

Solutions for global marine litter pollution

Since the 1950s the amount of plastics in the marine environment has increased dramatically. Worldwide there is a growing concern about the risks and possible adverse effects of (micro) plastics. This paper reflects on the sources and effects of marine litter and the effects of policies and other actions taken worldwide. Current knowledge offers a solid basis for effective action. Yet, so far the effects of policies and other initiatives are still largely insufficient. The search for appropriate responses could be based on possible interventions and profound understanding of the context specific factors for success. Moreover, the scope, timeframe and dynamics of all initiatives are distinctly different and orchestration at all levels, in close cooperation with one another is currently lacking

Selective sweeps on novel and introgressed variation shape mimicry loci in a butterfly adaptive radiation.

Natural selection leaves distinct signatures in the genome that can reveal the targets and history of adaptive evolution. By analysing high-coverage genome sequence data from 4 major colour pattern loci sampled from nearly 600 individuals in 53 populations, we show pervasive selection on wing patterns in the Heliconius adaptive radiation. The strongest signatures correspond to loci with the greatest phenotypic effects, consistent with visual selection by predators, and are found in colour patterns with geographically restricted distributions. These recent sweeps are similar between co-mimics and indicate colour pattern turn-over events despite strong stabilising selection. Using simulations, we compare sweep signatures expected under classic hard sweeps with those resulting from adaptive introgression, an important aspect of mimicry evolution in Heliconius butterflies. Simulated recipient populations show a distinct 'volcano' pattern with peaks of increased genetic diversity around the selected target, characteristic of sweeps of introgressed variation and consistent with diversity patterns found in some populations. Our genomic data reveal a surprisingly dynamic history of colour pattern selection and co-evolution in this adaptive radiation