117 research outputs found
Redox Flow Batteries: Fundamentals and Applications
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 costâeffective 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
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
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 Decays in the Perturbative QCD Approach
In this paper,we calculate the branching ratios and CP-violating asymmetries
for 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 and ,
which agree well with the measured values and currently available experimental
upper limits. We also predict large CP-violating asymmetries in these decays:
, , ,
, , and , 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
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 VisANTâan integrative software platform for the visualization, mining, analysis and modeling of the biological networksâwhich 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
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 VisANTâan integrative software platform for the visualization, mining, analysis and modeling of the biological networksâwhich 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 and new physics effects in the general two-Higgs doublet models
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 and 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 -
and - 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, , 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, , 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 and
in model III are still consistent with the data
within errors; (f) the significant new physics enhancements to the
branching ratios of and decays are helpful to improve the
agreement between the data and the theoretical predictions; (g) the theoretical
predictions of in the 2HDM's are generally
consistent with experimental measurements and upper limits ()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 decays in the general two-Higgs doublet models
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
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 and will
be measurable at the future hadron colliders with large production. (d)
Among the studied thirty nine meson decay modes, seven of them can have a
CP-violating asymmetry 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
system through studies of two-body charmless decays of 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
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 and semileptonic branching ratio .
Within the considered parameter space, the enhancement to the ratio due to the charged-Higgs penguins can be as large as a factor of 8 (3) in
the model III (II), while the ratio 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 and can be decreased simultaneously
in the model III. The central value of will be lowered slightly by
about 0.003, but the ratio can be reduced significantly from the
theoretical prediction of in the SM to , for GeV, respectively. We find that
the predicted and the measured 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 Decays in the Perturbative QCD Approach
We calculate the branching ratios and CP-violating asymmetries for and 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 , , and , 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 ( 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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