Microelectrode-based probing of charge propagation and redox transitions in concentrated polyoxometallate electrolyte of potential utility for redox flow battery

Concentrated solutions of Keggin-type silicotungstic acid, as well as the system's single crystals (H4SiW12O40*31H2O) and their colloidal suspensions have been tested using the microelectrode methodology to determine mass-transport, electron self-exchange and apparent (effective) diffusion-type coefficients for charge propagation and homogeneous (electron self-exchange) rates of electron transfers. Silicotungstic acid facilitates proton conductivity, and undergoes fast, reversible, multi-electron transfers leading to the formation of highly conducting, mixed-valence (tungsten(VI,V) heteropoly blue) compounds. To develop useful electroanalytical diagnostic criteria, electroanalytical approaches utilizing microdisk electrodes have been adapted to characterize redox transitions of the system and to determine kinetic parameters. Combination of microelectrode-based experiments performed in two distinct diffusional regimes: radial (long-term experiment; e.g., slow scan rate voltammetry or long-pulse chronoamperometry) and linear (short-term experiment; e.g., fast scan rate voltammetry or short-pulse chronocoulometry) permits absolute determination of such parameters as effective concentration of redox centers (C0) and apparent transport (diffusion) coefficient (Dapp). The knowledge of these parameters, in particular of [Dapp1/2 C0] seems to be of importance to the evaluation of utility of redox electrolytes for charge storage. For the colloidal suspension of silicotungstic acid (H4SiW12O40) crystals in the saturated solution, the following values have been obtained: Dapp = 1.8*10-6 cm2 s−1 and C0 = 1.1 mol dm−3, as well as the [Dapp1/2 C0] diagnostic parameter has reached the value as high as 6*10-3 mol/dm−3 cm s−1/2, provided that four electrons are involved in the H4SiW12O40 redox transitions. In this respect, the fact that crystals (dispersed solids) are characterized by high electron self-exchange rate (kex = 1.1*108 dm3 mol−1 s−1) and low activation energy (EA = 18.7 kJ mol−1) facilitating electron transfers between immobilized WVI and WV redox sites is also advantageous

Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR

Simulation results for future measurements of electromagnetic proton form factors at \PANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision with which the proton form factors can be determined is estimated. The signal channel $\bar p p \to e^+ e^-$ is studied on the basis of two different but consistent procedures. The suppression of the main background channel, $\textit{i.e.}$ $\bar p p \to \pi^+ \pi^-$, is studied. Furthermore, the background versus signal efficiency, statistical and systematical uncertainties on the extracted proton form factors are evaluated using two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam conditions and detector performance

The functional cancer map: A systems-level synopsis of genetic deregulation in cancer

<p>Abstract</p> <p>Background</p> <p>Cancer cells are characterized by massive dysegulation of physiological cell functions with considerable disruption of transcriptional regulation. Genome-wide transcriptome profiling can be utilized for early detection and molecular classification of cancers. Accurate discrimination of functionally different tumor types may help to guide selection of targeted therapy in translational research. Concise grouping of tumor types in cancer maps according to their molecular profile may further be helpful for the development of new therapeutic modalities or open new avenues for already established therapies.</p> <p>Methods</p> <p>Complete available human tumor data of the Stanford Microarray Database was downloaded and filtered for relevance, adequacy and reliability. A total of 649 tumor samples from more than 1400 experiments and 58 different tissues were analyzed. Next, a method to score deregulation of KEGG pathway maps in different tumor entities was established, which was then used to convert hundreds of gene expression profiles into corresponding tumor-specific pathway activity profiles. Based on the latter, we defined a measure for functional similarity between tumor entities, which yielded to phylogeny of tumors.</p> <p>Results</p> <p>We provide a comprehensive, easy-to-interpret functional cancer map that characterizes tumor types with respect to their biological and functional behavior. Consistently, multiple pathways commonly associated with tumor progression were revealed as common features in the majority of the tumors. However, several pathways previously not linked to carcinogenesis were identified in multiple cancers suggesting an essential role of these pathways in cancer biology. Among these pathways were 'ECM-receptor interaction', 'Complement and Coagulation cascades', and 'PPAR signaling pathway'.</p> <p>Conclusion</p> <p>The functional cancer map provides a systematic view on molecular similarities across different cancers by comparing tumors on the level of pathway activity. This work resulted in identification of novel superimposed functional pathways potentially linked to cancer biology. Therefore, our work may serve as a starting point for rationalizing combination of tumor therapeutics as well as for expanding the application of well-established targeted tumor therapies.</p

Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR

This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented

Study of doubly strange systems using stored antiprotons

Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the P‾ANDA experiment at FAIR. For the first time, high resolution γ-spectroscopy of doubly strange ΛΛ-hypernuclei will be performed, thus complementing measurements of ground state decays of ΛΛ-hypernuclei at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange Ξ−-atoms will be feasible and even the production of Ω−-atoms will be within reach. The latter might open the door to the |S|=3 world in strangeness nuclear physics, by the study of the hadronic Ω−-nucleus interaction. For the first time it will be possible to study the behavior of Ξ‾+ in nuclear systems under well controlled conditions

Precision resonance energy scans with the PANDA experiment at FAIR: Sensitivity study for width and line shape measurements of the X(3872)

This paper summarises a comprehensive Monte Carlo simulation study for precision resonance energy scan measurements. Apart from the proof of principle for natural width and line shape measurements of very narrow resonances with PANDA, the achievable sensitivities are quantified for the concrete example of the charmonium-like X(3872) state discussed to be exotic, and for a larger parameter space of various assumed signal cross-sections, input widths and luminosity combinations. PANDA is the only experiment that will be able to perform precision resonance energy scans of such narrow states with quantum numbers of spin and parities that differ from J P C = 1 - -