Fast Low-Rank Empirical Cross Gramians

The cross Gramian matrix encodes the input-output coherence of linear control systems and is used in projection-based model reduction. The empirical cross Gramian is a data-driven variant of the cross Gramian which also extends to nonlinear systems. A drawback of the empirical cross Gramian for large-scale systems is its full order and dense structure; yet, it may be computed column-wise. Using the hierarchical approximate proper orthogonal decomposition (HAPOD), this partial computability can be exploited to obtain a truncated projection for model order reduction without assembling a full cross Gramian. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,Photophysics and PDT Evaluation of Mono‐, Di‐, Tri‐ and Hexa‐PEG Chlorins for Pointsource Photodynamic Therapy

Pointsource photodynamic therapy (PSPDT) is a newly developed fiber optic method aimed at the delivery of photosensitizer, light and oxygen to a diseased site. Because of a need for developing photosensitizers with desirable properties for PSPDT, we have carried out a synthetic, photophysical and phototoxicity study on a series of PEGylated sensitizers. Chlorin and pheophorbide sensitizers were readily amenable to our synthetic PEGylation strategy to reach triPEG and hexaPEG galloyl pheophorbides and mono‐, di‐, triPEG chlorins. On screening these PEG sensitizers, we found that increasing the number of PEG groups, except for hexaPEGylation, increases phototoxicity. We found that three PEG groups but not less or more were optimal. Of the series tested, a triPEG gallyol pheophorbide and a triPEG chlorin were the most efficient at generating singlet oxygen, and produced the highest phototoxicity and lowest dark toxicity to Jurkat cells. A detailed kinetic analysis of the PEGylated sensitizers in solution and cell culture and media is also presented. The data provide us with steps in the development of PSPDT to add to the PDT tools we have in general.     

Surface Oxidation of Supported,Size-Selected Silver Clusters

We use surface second harmonic generation spectroscopy to study the oxidation of supported, size-selected silver clusters under ultra-high vacuum conditions. The oxidation reaction of small silver clusters between \(Ag_{9}\) and \(Ag_{55}\) is monitored by means of their localized surface plasmon resonance. We observe a rapid decline of the SH-intensity, as soon as cluster samples are exposed to an oxygen partial pressure of \(5 \cdot 10^{-6}\) mbar, which is attributed to the formation of silver–oxygen-bonds. The evolution of the SH-intensity under exposure to oxygen shows a double-exponential character for all investigated cluster sizes. Since the oxidation of single crystalline silver surfaces follow single-exponential Langmuir-kinetics, the two independent pathways of SH-intensity loss are attributed to a surface- and an interface-oxidation of supported clusters, respectiveley. For small cluster sizes, a complete loss of the SH intensity is obtained, which suggests the complete oxidation of the clusters. For larger clusters a plasmonic resonance is still observed after oxidation, indicating a residual free-electron density.     

Redox-Flow Batteries: From Metals to Organic Redox-Active Materials

Research on redox-flow batteries (RFBs) is currently experiencing a significant upturn, stimulated by the growing need to store increasing quantities of sustainably generated electrical energy. RFBs are promising candidates for the creation of smart grids, particularly when combined with photovoltaics and wind farms. To achieve the goal of “green”, safe, and cost-efficient energy storage, research has shifted from metal-based materials to organic active materials in recent years. This Review presents an overview of various flow-battery systems. Relevant studies concerning their history are discussed as well as their development over the last few years from the classical inorganic, to organic/inorganic, to RFBs with organic redox-active cathode and anode materials. Available technologies are analyzed in terms of their technical, economic, and environmental aspects; the advantages and limitations of these systems are also discussed. Further technological challenges and prospective research possibilities are highlighted.     

Carbon–Fluorine Reductive Elimination from Nickel(III) Complexes

We report a C−F reductive elimination from a characterized first-row aryl metal fluoride complex. Reductive elimination from the presented nickel(III) complexes is faster than C−F bond formation from any other characterized aryl metal fluoride complex.     

Configuration spaces,transfer, and 2-nodal solutions of a semiclassical nonlinear Schrödinger equation

We establish new lower bounds for the number of nodal bound states for the semiclassical nonlinear Schrödinger equation \(-\varepsilon^2 \Delta u+ a(x)u=|u|^{p-2}u\) with bounded and uniformly continuous potential a. The solutions we obtain have precisely two nodal domains, and their positive and negative parts concentrate near the set of minimum points of a. Our approach is independent of penalization techniques and yields, in some cases, the existence of infinitely many nodal solutions for fixed \(\varepsilon\). Via a dynamical systems approach, we exhibit positively invariant sets of sign changing functions for the negative gradient flow of the associated energy functional. We analyze these sets on the cohomology level with the help of Dold’s fixed point transfer. In particular, we estimate their cuplength in terms of the cuplength of equivariant configuration spaces of subsets of \(\mathbb{R}^N\). We also provide new estimates of the cuplength of configuration spaces.     

Measurement of the charge asymmetry in semileptonic Bs0 decays

We have performed the first direct measurement of the time-integrated flavor untagged charge asymmetry in semileptonic Bs0 decays ASLs,unt by comparing the decay rate of Bs0-->micro+Ds-nuX, where Ds- -->phipi- and phi-->K+K-, with the charge-conjugate Bs0 decay rate. This sample was selected from 1.3 fb-1 of data collected by the D0 experiment in run II of the Fermilab Tevatron collider. We obtain ASLs,unt=[1.23+/-0.97(stat)+/-0.17(syst)]x10(-2). Assuming that Deltam(s)/Gamma(s)>1, this result can be translated into a measurement of the CP-violating phase in Bs0 mixing: DeltaGamma(s)/Deltam(s)tanphi(s)=[2.45+/-1.93(stat)+/-0.35(syst)]x10(-2).     

Evidence for production of single top quarks and first direct measurement of |Vtb|

The D0 Collaboration presents first evidence for the production of single top quarks at the Fermilab Tevatron pp[over ] collider. Using a 0.9 fb(-1) dataset, we apply a multivariate analysis to separate signal from background and measure sigma(pp[over ]-->tb+X,tqb+X)=4.9+/-1.4 pb. The probability to measure a cross section at this value or higher in the absence of a signal is 0.035%, corresponding to a 3.4 standard deviation significance. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa matrix element that describes the Wtb coupling and find 0.68<|V(tb)|相似文献   

Resonance fluorescence in transport through quantum dots: noise properties

We study a two-level quantum dot embedded in a phonon bath and irradiated by a time-dependent ac field, and develop a method that allows us to extract simultaneously the full counting statistics of the electronic tunneling and relaxation (by phononic emission) events as well as their correlation. We find that the quantum noise of both the transmitted electrons and the emitted phonons can be controlled by the manipulation of external parameters such as the driving field intensity or the bias voltage.     

Lateral modulation boosts image quality in single plane illumination fluorescence microscopy

A new microscope combines optical sectioning by fluorophore excitation using a single light sheet with structured illumination. Several images with laterally intensity-modulated light sheets are recorded from scattering fluorescent specimens. By applying a simple data processing scheme, the nonmodulated volumes are identified. The blurred features become dark, and the resultant images are improved in terms of contrast and resolution. Hence, the instrument is capable of discriminating against contributions to the image that are induced by the optical properties of the specimen. The new microscope's capabilities are demonstrated by imaging the internals of the head of an adult Drosophila melanogaster (fruit fly) expressing green fluorescent protein-labeled polycomb proteins.