Flow regime map of a liquid-solid micro-circulating fluidized bed

Solid-liquid micro-fluidised beds (FBs), which are essentially fluidisation of micro-particles in sub-centimetre beds, hold promise of applications in the microfluidics and micro-process technology context. This is mainly due to fluidised particles providing enhancement of mixing, mass and heat transfer under the low Reynolds number flows that dominate in micro-devices. Sometimes particle circulations is required or desirable (e.g. continuous regeneration of a catalyst) for which circulating fluidised beds are ideal, not to mention advantages of better interfacial contacting and reduced backmixing compared to a classical fluidised bed (1). Albeit there are quite a few studies of solid-liquid micro-fluidised beds, we are presenting the first study of micro-circulating fluidised bed. A transparent micro-circulating fluidised bed was made by micro-machining channels of 1 mm2 square cross section in Perspex as shown in Fig. 1. We used soda-lime glass microparticles and tap water as fluidising medium to study flow regime transition for this micro-circulating fluidised bed. The flow regime map as proposed by Liang et al. (2) was produced for a micro-circulating fluidised bed and is given in Fig. 2. Essentially results are almost the same as for the macroscopic counterparts with the transition to the circulating fluidised regime occurring at velocities, Ucr, slightly above the particle terminal velocities, Ut (1,2). The reported critical transition velocity is for high enough solid inventories (above 10% of the system volume) where this transition velocity is constant, while for lower solid inventories it is bigger as in previous experiments (1,2). While the minimum fluidization velocity, Umf, is influenced by adhesion forces and wall effects (3), there is a weak increase in the normalized critical transition velocity for circulating regime, Ucr/Ut, with an increase of particle diameter (not shown here). This may be due to the wall effects but more studies are needed to elucidate this further. Please click Additional Files below to see the full abstract

The Niemann-Pick C1 and caveolin-1 proteins interact to modulate efflux of low density lipoprotein-derived cholesterol from late endocytic compartments

The Niemann-Pick C1 (NPC1) protein has a central role in regulating the efflux of lipoprotein-derived cholesterol from late endosomes/lysosomes and transport to other cellular compartments. Since the NPC1 protein has been shown to regulate the transport of cholesterol to cellular compartments enriched with the ubiquitous cholesterol-binding and transport protein caveolin-1, the present study was performed to determine whether the NPC1 and caveolin-1 proteins interact and function to modulate efflux of low density lipoprotein (LDL)-derived cholesterol from endocytic compartments. To perform these studies, normal human fibroblasts were grown in media with lipoprotein-deficient serum (LPDS) or media with LPDS supplemented with purified human LDL. The results indicated reciprocal co-immunoprecipitation and partial co-localization of the NPC1 and caveolin-1 proteins that was decreased when fibroblasts were grown in media with LDL. Consistent with interaction of the NPC1 and caveolin-1 proteins, a highly conserved caveolin-binding motif was identified within a cytoplasmic loop located adjacent to the sterol-sensing domain (SSD) of the NPC1 protein. To examine the functional relevance of this interaction, fibroblasts were transfected with caveolin-1 siRNA and found to accumulate increased amounts of LDL-derived cholesterol within late endosomes/lysosomes. Together, this report presents novel results demonstrating that the NPC1 and caveolin-1 proteins interact to modulate efflux of LDL-derived cholesterol from late endocytic compartments

Detailed diagnostics of an X-ray flare in the single giant HR 9024

We analyze a 96 ks Chandra/HETGS observation of the single G-type giant HR 9024. The high flux allows us to examine spectral line and continuum diagnostics at high temporal resolution, to derive plasma parameters. A time-dependent 1D hydrodynamic model of a loop with half-length $L = 5 \times 10^{11}$ cm ($\sim R_{\star}/2$), cross-section radius $r = 4.3 \times 10^{10}$ cm, with a heat pulse of 15 ks and $2 \times 10^{11}$~erg cm$^{-2}$ s$^{-1}$ deposited at the loop footpoints, satisfactorily reproduces the observed evolution of temperature and emission measure, derived from the analysis of the strong continuum emission. For the first time we can compare predictions from the hydrodynamic model with single spectral features, other than with global spectral properties. We find that the model closely matches the observed line emission, especially for the hot ($\sim 10^8$ K) plasma emission of the FeXXV complex at $\sim 1.85$\AA. The model loop has $L/R_{\star} \sim 1/2$ and aspect ratio $r/L \sim 0.1$ as typically derived for flares observed in active stellar coronae, suggesting that the underlying physics is the same for these very dynamic and extreme phenomena in stellar coronae independently on stellar parameters and evolutionary stage.Comment: 26 pages. Accepted for publication on the Astrophysical Journa

Reconstructing Spatiotemporal Gene Expression Data from Partial Observations

Developmental transcriptional networks in plants and animals operate in both space and time. To understand these transcriptional networks it is essential to obtain whole-genome expression data at high spatiotemporal resolution. Substantial amounts of spatial and temporal microarray expression data previously have been obtained for the Arabidopsis root; however, these two dimensions of data have not been integrated thoroughly. Complicating this integration is the fact that these data are heterogeneous and incomplete, with observed expression levels representing complex spatial or temporal mixtures. Given these partial observations, we present a novel method for reconstructing integrated high resolution spatiotemporal data. Our method is based on a new iterative algorithm for finding approximate roots to systems of bilinear equations.Comment: 19 pages, 4 figure

Schr\"odinger Deformations of AdS_3 x S^3

We study Schr\"odinger invariant deformations of the AdS_3 x S^3 x T^4 (or K3) solution of IIB supergravity and find a large class of solutions with integer and half-integer dynamical exponents. We analyze the supersymmetries preserved by our solutions and find an infinite number of solutions with four supersymmetries. We study the solutions holographically and find that the dual D1-D5 (or F1-NS5) CFT is deformed by irrelevant operators of spin one and two.Comment: 23 page

Detecting separate time scales in genetic expression data.

BACKGROUND: Biological processes occur on a vast range of time scales, and many of them occur concurrently. As a result, system-wide measurements of gene expression have the potential to capture many of these processes simultaneously. The challenge however, is to separate these processes and time scales in the data. In many cases the number of processes and their time scales is unknown. This issue is particularly relevant to developmental biologists, who are interested in processes such as growth, segmentation and differentiation, which can all take place simultaneously, but on different time scales. RESULTS: We introduce a flexible and statistically rigorous method for detecting different time scales in time-series gene expression data, by identifying expression patterns that are temporally shifted between replicate datasets. We apply our approach to a Saccharomyces cerevisiae cell-cycle dataset and an Arabidopsis thaliana root developmental dataset. In both datasets our method successfully detects processes operating on several different time scales. Furthermore we show that many of these time scales can be associated with particular biological functions. CONCLUSIONS: The spatiotemporal modules identified by our method suggest the presence of multiple biological processes, acting at distinct time scales in both the Arabidopsis root and yeast. Using similar large-scale expression datasets, the identification of biological processes acting at multiple time scales in many organisms is now possible.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Energy dependence of {\rm K}S0^0_{\rm S} and hyperon production at CERN SPS

Recent results on K$^0_{\rm S}$ and hyperon production in Pb-Pb collisions at 40 and 158 $A$ GeV/$c$ beam momentum from the NA57 experiment at CERN SPS are presented. Yields and ratios are compared with those measured by the NA49 experiment, where available. The centrality dependence of the yields and a comparison with the higher collision energy data from RHIC are discussed.Comment: 4 pages, 3 figures, proceedings of QM2004 conferenc

Response of different types of wood treatment regarding the different products application to the management of drywood termites Cryptotermes brevis populations in the Azores

A térmita de madeira seca das Índias Ocidentais, a Cryptotermes brevis (Walker, 1953) (Isoptera: Kalotermitidae) está perfeitamente estabelecida nos Açores, sendo considerada uma praga urbana com grande impacto económico e social pelos graves prejuízos que causa, através da destruição estrutural, principalmente das madeiras de suporte dos telhados. Espera-se com esta contribuição: i) determinar qual o produto com a maior taxa de absorção em todas as madeiras usadas na estrutura dos telhados açorianos; ii) contribuir de uma forma decisiva para que as empresas dos Açores possam adoptar esta prática no tratamento de todas as madeiras a usar nas estruturas; iii) contribuir, indirectamente, para a redução do ataque das térmitas nas madeiras, através do seu tratamento com estes produtos, tendo em vista o controlo desta praga nas zonas urbanas afectadas. De todos os seis produtos utilizados, o XT-2000 (d-limonene), líquido com propriedades insecticidas extraído da casca de citrinos, foi o que melhor foi absorvido e se difundiu no interior da madeira tratada em todas as modalidades ensaiadas. Analisando esta capacidade de difusão no interior da madeira por cada tipo de produto e atendendo ao facto de se tratar de madeira do cerne ou do borne (superfície), o XT-2000 (d-limonene) e o TERMINATE (cialotrina) foram os que registaram a maior percentagem de absorção. Na madeira do cerne, o WOCOSEN (permetrina) foi o que melhor foi absorvido por todas as madeiras. É de referir que a acácia, o sapé e o eucalipto foram as madeiras que registaram a menor taxa de absorção após a aplicação dos produtos ensaiados.ABSTRACT: The West Indian drywood termite, Cryptotermes brevis (Walker, 1953) (Isoptera: Kalotermitidae), is a well-established and serious pest of structural wood in the Azores. It is therefore important to study different ways to fight against this insect, and among the several research studies in progress, in these contribution we discuss the rate of diffusion of six products inside five different kinds of wood that are normally used for construction of Azorean building roofs. Our aims are: i) to test which product is best absorbed in each type of wood tested and used in the building of Azorean roofs; ii) to contribute with methods that can be adopted by Azorean commercial enterprises to develop a domestic termite control industry; iii) to contribute indirectly in understanding the best woods and products we expect to enhance control of these pest in the affected urban areas. Of the six products tested, XT-2000 (d-limonene), a liquid extracted from citrus peels, gave the best results in terms of diffusion on all the wood types tested. When we compared the performance of each kind of product tested in both heartwood and sapwood, XT-2000 and TERMINATE were the products with the greatest amount absorbed in the woods tested. In the heartwood alone, WOCOSEN (permethrin) was the one that gave the best results for all woods. It is also important to note that acácia, sapé and Eucalyptus sp. were the woods that absorbed the least with all the products tested