117 research outputs found

    Redox Flow Batteries: Fundamentals and Applications

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    A redox flow battery is an electrochemical energy storage device that converts chemical energy into electrical energy through reversible oxidation and reduction of working fluids. The concept was initially conceived in 1970s. Clean and sustainable energy supplied from renewable sources in future requires efficient, reliable and cost‐effective energy storage systems. Due to the flexibility in system design and competence in scaling cost, redox flow batteries are promising in stationary storage of energy from intermittent sources such as solar and wind. This chapter covers basic principles of electrochemistry in redox flow batteries and provides an overview of status and future challenges. Recent progress in redox couples, membranes and electrode materials will be discussed. New demonstration and commercial development will be addressed

    Visualization of metabolic interaction networks in microbial communities using VisANT 5.0

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    The complexity of metabolic networks in microbial communities poses an unresolved visualization and interpretation challenge. We address this challenge in the newly expanded version of a software tool for the analysis of biological networks, VisANT 5.0. We focus in particular on facilitating the visual exploration of metabolic interaction between microbes in a community, e.g. as predicted by COMETS (Computation of Microbial Ecosystems in Time and Space), a dynamic stoichiometric modeling framework. Using VisANT's unique metagraph implementation, we show how one can use VisANT 5.0 to explore different time-dependent ecosystem-level metabolic networks. In particular, we analyze the metabolic interaction network between two bacteria previously shown to display an obligate cross-feeding interdependency. In addition, we illustrate how a putative minimal gut microbiome community could be represented in our framework, making it possible to highlight interactions across multiple coexisting species. We envisage that the "symbiotic layout" of VisANT can be employed as a general tool for the analysis of metabolism in complex microbial communities as well as heterogeneous human tissues.This work was supported by the National Institutes of Health, R01GM103502-05 to CD, ZH and DS. Partial support was also provided by grants from the Office of Science (BER), U.S. Department of Energy (DE-SC0004962), the Joslin Diabetes Center (Pilot & Feasibility grant P30 DK036836), the Army Research Office under MURI award W911NF-12-1-0390, National Institutes of Health (1RC2GM092602-01, R01GM089978 and 5R01DE024468), NSF (1457695), and Defense Advanced Research Projects Agency Biological Technologies Office (BTO), Program: Biological Robustness In Complex Settings (BRICS), Purchase Request No. HR0011515303, Program Code: TRS-0 Issued by DARPA/CMO under Contract No. HR0011-15-C-0091. Funding for open access charge: National Institutes of Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. (R01GM103502-05 - National Institutes of Health; 1RC2GM092602-01 - National Institutes of Health; R01GM089978 - National Institutes of Health; 5R01DE024468 - National Institutes of Health; DE-SC0004962 - Office of Science (BER), U.S. Department of Energy; P30 DK036836 - Joslin Diabetes Center; W911NF-12-1-0390 - Army Research Office under MURI; 1457695 - NSF; HR0011515303 - Defense Advanced Research Projects Agency Biological Technologies Office (BTO), Program: Biological Robustness In Complex Settings (BRICS); HR0011-15-C-0091 - DARPA/CMO; National Institutes of Health)Published versio

    A micromachined flow shear-stress sensor based on thermal transfer principles

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    Microhot-film shear-stress sensors have been developed by using surface micromachining techniques. The sensor consists of a suspended silicon-nitride diaphragm located on top of a vacuum-sealed cavity. A heating and heat-sensing element, made of polycrystalline silicon material, resides on top of the diaphragm. The underlying vacuum cavity greatly reduces conductive heat loss to the substrate and therefore increases the sensitivity of the sensor. Testing of the sensor has been conducted in a wind tunnel under three operation modes-constant current, constant voltage, and constant temperature. Under the constant-temperature mode, a typical shear-stress sensor exhibits a time constant of 72 ÎŒs

    Branching Ratio and CP Asymmetry of B→ρη(â€Č)B \to \rho \eta^{(\prime)} Decays in the Perturbative QCD Approach

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    In this paper,we calculate the branching ratios and CP-violating asymmetries for B0→ρ0η(â€Č)B^0 \to \rho^0 \eta^{(\prime)} and B^+\to \rho^+ \etap decays in the perturbative QCD factorization approach. In this approach, we not only calculate the usual factorizable contributions, but also evaluate the non-factorizable and annihilation type contributions. Besides the current-current operators, the contributions from the QCD and electroweak penguin operators are also taken into account. The theoretical predictions for the branching ratios are Br(B+→ρ+η(â€Č))≈9×10−6Br(B^+ \to \rho^+ \eta^{(\prime)}) \approx 9 \times 10^{-6} and Br(B0→ρ0η(â€Č))≈5×10−8Br(B^0 \to \rho^0 \eta^{(\prime)}) \approx 5 \times 10^{-8}, which agree well with the measured values and currently available experimental upper limits. We also predict large CP-violating asymmetries in these decays: ACPdir(ρ±η)≈−13A_{CP}^{dir}(\rho^\pm \eta)\approx -13 %, ACPdir(ρ±ηâ€Č)≈−18A_{CP}^{dir}(\rho^\pm \eta^\prime)\approx -18 %, ACPdir(ρ0η)≈−41A_{CP}^{dir}(\rho^0 \eta)\approx -41%, ACPdir(ρ0ηâ€Č)≈−27A_{CP}^{dir}(\rho^0 \eta^\prime)\approx -27%, ACPmix(ρ0η)≈+25A_{CP}^{mix}(\rho^0 \eta)\approx +25%, and ACPmix(ρ0ηâ€Č)≈+11A_{CP}^{mix}(\rho^0 \eta^\prime) \approx +11%, which can be tested by the current or future B factory experiments.Comment: 29 pages, 9 ps figures, more phenomenological discussions added, scale dependence of computed observables are considered, typos corrected, the figures and conclusions remain unchange

    VisANT 3.5: multi-scale network visualization, analysis and inference based on the gene ontology

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    Despite its wide usage in biological databases and applications, the role of the gene ontology (GO) in network analysis is usually limited to functional annotation of genes or gene sets with auxiliary information on correlations ignored. Here, we report on new capabilities of VisANT—an integrative software platform for the visualization, mining, analysis and modeling of the biological networks—which extend the application of GO in network visualization, analysis and inference. The new VisANT functions can be classified into three categories. (i) Visualization: a new tree-based browser allows visualization of GO hierarchies. GO terms can be easily dropped into the network to group genes annotated under the term, thereby integrating the hierarchical ontology with the network. This facilitates multi-scale visualization and analysis. (ii) Flexible annotation schema: in addition to conventional methods for annotating network nodes with the most specific functional descriptions available, VisANT also provides functions to annotate genes at any customized level of abstraction. (iii) Finding over-represented GO terms and expression-enriched GO modules: two new algorithms have been implemented as VisANT plugins. One detects over-represented GO annotations in any given sub-network and the other finds the GO categories that are enriched in a specified phenotype or perturbed dataset. Both algorithms take account of network topology (i.e. correlations between genes based on various sources of evidence). VisANT is freely available at http://visant.bu.edu

    VisANT 3.5: multi-scale network visualization, analysis and inference based on the gene ontology

    Get PDF
    Despite its wide usage in biological databases and applications, the role of the gene ontology (GO) in network analysis is usually limited to functional annotation of genes or gene sets with auxiliary information on correlations ignored. Here, we report on new capabilities of VisANT—an integrative software platform for the visualization, mining, analysis and modeling of the biological networks—which extend the application of GO in network visualization, analysis and inference. The new VisANT functions can be classified into three categories. (i) Visualization: a new tree-based browser allows visualization of GO hierarchies. GO terms can be easily dropped into the network to group genes annotated under the term, thereby integrating the hierarchical ontology with the network. This facilitates multi-scale visualization and analysis. (ii) Flexible annotation schema: in addition to conventional methods for annotating network nodes with the most specific functional descriptions available, VisANT also provides functions to annotate genes at any customized level of abstraction. (iii) Finding over-represented GO terms and expression-enriched GO modules: two new algorithms have been implemented as VisANT plugins. One detects over-represented GO annotations in any given sub-network and the other finds the GO categories that are enriched in a specified phenotype or perturbed dataset. Both algorithms take account of network topology (i.e. correlations between genes based on various sources of evidence). VisANT is freely available at http://visant.bu.edu

    Charmless hadronic decays B→PP,PV,VVB \to PP, PV, VV and new physics effects in the general two-Higgs doublet models

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    Based on the low-energy effective Hamiltonian with the generalized factorization, we calculate the new physics contributions to the branching ratios of the two-body charmless hadronic decays of BuB_u and BdB_d mesons induced by the new gluonic and electroweak charged-Higgs penguin diagrams in the general two-Higgs doublet models (models I, II and III). Within the considered parameter space, we find that: (a) the new physics effects from new gluonic penguin diagrams strongly dominate over those from the new Îł\gamma- and Z0Z^0- penguin diagrams; (b) in models I and II, new physics contributions to most studied B meson decay channels are rather small in size: from -15% to 20%; (c) in model III, however, the new physics enhancements to the penguin-dominated decay modes can be significant, ∌(30−200)\sim (30 -200)%, and therefore are measurable in forthcoming high precision B experiments; (d) the new physics enhancements to ratios {\cal B}(B \to K \etap) are significant in model III, ∌(35−70)\sim (35 -70)%, and hence provide a simple and plausible new physics interpretation for the observed unexpectedly large B \to K \etap decay rates; (e) the theoretical predictions for B(B→K+π){\cal B}(B \to K^+ \pi) and B(B→K0π+){\cal B}(B \to K^0 \pi^+) in model III are still consistent with the data within 2σ2\sigma errors; (f) the significant new physics enhancements to the branching ratios of B→K0π0,K∗η,K∗+π−,K+ϕ,K∗0ω,K∗+ϕB \to K^0 \pi^0, K^* \eta, K^{*+} \pi^-, K^+ \phi, K^{*0} \omega, K^{*+} \phi and K∗0ϕK^{*0} \phi decays are helpful to improve the agreement between the data and the theoretical predictions; (g) the theoretical predictions of B(B→PP,PV,VV){\cal B}(B \to PP, PV, VV) in the 2HDM's are generally consistent with experimental measurements and upper limits (9090% C.L.)Comment: 55 pages, Latex file, 17 PS and EPS figures. With minor corrections, final version to be published in Phys.Rev. D. Repot-no: PKU-TH-2000-4

    Branching ratios and CP-violating asymmetries of Bs→h1h2B_s \to h_1 h_2 decays in the general two-Higgs doublet models

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    Based on the low-energy effective Hamiltonian with the generalized factorization, we calculate the new physics contributions to branching ratios and CP-violating asymmetries of the charmless hadronic decays Bs→h1h2B_s \to h_1 h_2 in the standard model and the general two-Higgs doublet models (models I, II, and III). Within the considered paramter space, we find the following. (a) In models I and II, the new physics corrections are always small in size and will be masked by other larger known theoretical uncertainties. (b) In model III, the new physics corrections to the branching ratios of those QCD penguin-dominated decays \ov B_s \to K^0\etapp, K^+ K^{-*}, etc., are large in size and insensitive to the variations of \mhp and \nceff. For tree- or electroweak penguin-dominated decay modes, however, the new physics corrections are very small in size. (c) For \ov B_s \to K^+ K^{-*} and other seven decay modes, the branching ratios are at the level of (1−3)×10−5(1-3)\times 10^{-5} and will be measurable at the future hadron colliders with large bb production. (d) Among the studied thirty nine BsB_s meson decay modes, seven of them can have a CP-violating asymmetry ACP{\cal A}_{CP} larger than 20% in magnitude. The new physics corrections are small or moderate in magnitude. (e) Because of its large and \nceff stable branching ratio and CP violating asymmetry, the decay \ov B_s \to K^+ K^{-*} seems to be the "best" channel to find CP violation of BsB_s system through studies of two-body charmless decays of BsB_s meson.Comment: 39 pages, Revtex, 9 eps figures, final version accepted for publication in Phys.Rev.

    Charm multiplicity and the branching ratios of inclusive charmless b quark decays in the general two-Higgs-doublet models

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    In the framework of general two-Higgs-doublet models, we calculate the branching ratios of various inclusive charmless b decays by using the low energy effective Hamiltonian including next-to-leading order QCD corrections, and examine the current status and the new physics effects on the determination of the charm multiplicity ncn_c and semileptonic branching ratio BSLB_{SL}. Within the considered parameter space, the enhancement to the ratio BR(b→sg)BR(b \to s g) due to the charged-Higgs penguins can be as large as a factor of 8 (3) in the model III (II), while the ratio BR(b→nocharm)BR(b \to no charm) can be increased from the standard model prediction of 2.49% to 4.91% (2.99%) in the model III (II). Consequently, the value of BSLB_{SL} and ncn_c can be decreased simultaneously in the model III. The central value of BSLB_{SL} will be lowered slightly by about 0.003, but the ratio ncn_c can be reduced significantly from the theoretical prediction of nc=1.28±0.05n_c= 1.28 \pm 0.05 in the SM to nc=1.23±0.05n_c= 1.23 \pm 0.05, 1.18±0.051.18 \pm 0.05 for mH+=200,100m_{H^+}=200, 100 GeV, respectively. We find that the predicted ncn_c and the measured ncn_c now agree within roughly one standard deviation after taking into account the effects of gluonic charged Higgs penguins in the model III with a relatively light charged Higgs boson.Comment: 25 pages, Latex file, axodraw.sty, 6 figures. Final version to be published in Phys.Rev.

    Branching Ratio and CP Asymmetry of B→πη(â€Č)B \to \pi \eta^{(\prime)} Decays in the Perturbative QCD Approach

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    We calculate the branching ratios and CP-violating asymmetries for B0→π0η(â€Č)B^0 \to \pi^0 \eta^{(\prime)} and B+→π+η(â€Č)B^+\to \pi^+ \eta^{(\prime)} decays in the perturbative QCD (pQCD) factorization approach here. We not only calculate the usual factorizable contributions, but also evaluate the non-factorizable and annihilation type contributions. Besides the current-current operators, the contributions from the QCD and electroweak penguin operators are also taken into account. The pQCD results for the CP-averaged branching ratios are Br(B+→π+η)≈4.1×10−6Br(B^+ \to \pi^+ \eta) \approx 4.1 \times 10^{-6}, Br(B+→π+ηâ€Č)≈2.4×10−6Br(B^+ \to \pi^+ \eta^\prime) \approx 2.4 \times 10^{-6}, and Br(B0→π0η(â€Č))≈0.2×10−6Br(B^0 \to \pi^0 \eta^{(\prime)}) \approx 0.2 \times 10^{-6}, which agree very well with the measured values or currently available experimental upper limits. We also predict large CP-violating asymmetries in these decays: A_{CP}^{dir}(\pi^\pm \etap)\sim A_{CP}^{dir}(\pi^0 \etap)\sim -0.35 , and A_{CP}^{mix}(\pi^0 \etap)\sim 0.67, but with large errors. The pQCD prediction for ACPdir(π±η)A_{CP}^{dir}(\pi^\pm \eta) (ACPdir(π±ηâ€Č))A_{CP}^{dir}(\pi^\pm \eta^\prime)) has the same (opposite) sign with the primary measured values. Further improvements in both theory and experiments are needed to clarify this discrepancy.Comment: 28 pages, 8 figures, several typos correcte
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