Dissecting and reducing the heterogeneity of excited-state energy transport in DNA-based photonic wires

Molecular photonic wires are one-dimensional representatives of a family of nanoscale molecular devices that transport excited-state energy over considerable distances in analogy to optical waveguides in the far-field. In particular, the design and synthesis of such complex supramolecular devices is challenging concerning the desired homogeneity of energy transport. On the other hand, novel optical techniques are available that permit direct investigation of heterogeneity by studying one device at a time. In this article, we describe our efforts to synthesize and study DNA-based molecular photonic wires that carry several chromophores arranged in an energetic downhill cascade and exploit fluorescence resonance energy transfer to convey excited-state energy. The focus of this work is to understand and control the heterogeneity of such complex systems, applying single-molecule fluorescence spectroscopy (SMFS) to dissect the different sources of heterogeneity, i.e., chemical heterogeneity and inhomogeneous broadening induced by the nanoenvironment. We demonstrate that the homogeneity of excited-state energy transport in DNA-based photonic wires is dramatically improved by immobilizing photonic wires in aqueous solution without perturbation by the surface. In addition, our study shows that the in situ construction of wire molecules, i.e., the stepwise hybridization of differently labeled oligonucleotides on glass cover slides, further decreases the observed heterogeneity in overall energy-transfer efficiency. The developed strategy enables efficient energy transfer between up to five chromophores in the majority of molecules investigated along a distance of approximately 14 nm. Finally, we used multiparameter SMFS to analyze the energy flow in photonic wires in more detail and to assign residual heterogeneity under optimized conditions in solution to different leakages and competing energy-transfer processes.     

Kovariante Superpotentiale in der Allgemeinen Relativitätstheorie

We consider the connection between EINSTEIN 's, v. FREUD 's, and MØLLER 's views concerning the energy-momentum problem. First we generalize MØLLER 's expressions in such a way that the tetrad need not be orthonormalized. Then we mark out a covering of space-time with holonomic tetrads in the sense given by SCHOUTEN . In case that the covering of space-time with natural bases used to give the components of all quantities, is identical with the marked out covering of space-time with holonomic tetrads, we obtain from the generalized MØLLER 's expressions the well known ones given by EINSTEIN and v. FREUD .     

Holographic dynamics of unstable branes in AdS

The gauge theory dual to the decay of an unstable D-particle in AdS is analysed in terms of coherent states. We discuss in detail how to count the number of particles in the decay product. We find, in agreement with the analysis in flat space, that the emission amplitude is suppressed as the mass of the radiated particles increases. To cite this article: M. Zamaklar, K. Peeters, C. R. Physique 5 (2004).

Résumé

La théorie de jauge duale à la désintégration de D-particules instables dans AdS est analysée en termes d'état cohérents. Nous discutons en détails le comptage du nombre de particule dans le produit de désintégration. Nous trouvons, en accord avec l'analyse en espace plat, que le taux d'émission est supprimé quand la masse de la particule augmente. Pour citer cet article : M. Zamaklar, K. Peeters, C. R. Physique 5 (2004).     

MRI as a key tool for understanding and modeling the filtration kinetics of fibrous media

Applying MRI techniques to low-density fibrous filter media provides us with unique information about the initial structure and deposited mass within the same filter sample. This now enables us to obtain the necessary link between structure and deposition for validation and further enhancement of modeling filtration kinetics. However, additional work is needed before achieving a realistic understanding of filtration kinetics.     

Study of the D(+)(s)-->pi(-)pi(+)pi(+) decay and measurement of f(0) masses and widths

From a sample of 848+/-44 D(+)(s)-->pi(-)pi(+)pi(+) decays, we find gamma(D(+)(s)-->pi(-)pi(+)pi(+))/gamma(D(+)(s)-->straight phipi(+)) = 0.245+/-0.028(+0.019)(-0.012). Using a Dalitz plot analysis of this three body decay, we find significant contributions from the channels rho(0)(770)pi(+), rho(0)(1450)pi(+), f(0)(980)pi(+), f(2)(1270)pi(+), and f(0)(1370)pi(+). We also present the values obtained for masses and widths of the resonances f(0)(980) and f(0)(1370).     

CW IMPATTs made from silicon molecular beam epitaxy material

CW-IMPATT diodes for W-band operation are fabricated from Silicon Molecular Beam Epitaxy material. Using different preparation techniques, the active layer of single drift structures is grown at 750 °C and 550 °C. Doping is performed by molecular beams from Sb (n-type) or Ga (p-type) effusion cells. The influence of the p⁺-doping level on the series resistance of the diode is investigated. Measurements of efficiency as a function of the active region data deliver fine design rules. The output power is 450 mW at 87 GHz from diodes mounted in a hermetically sealed package on a diamond heat sink.     

On the variation of the effective cosmological term

In the framework of classical field theory, we try to explain why the effective cosmological constant is so small. The basis of the attempt is a Higgs field that shall determine the global structure of the universe. Einstein's theory of gravitation does not allow one to realize the idea. But we are successful if we start from some variant of the scalar-tensor theory of gravitation, choosing for the parameters that enter the Lagrangean of the Higgs field the Compton length of a proton and Eddington's number as self-coupling constant.     

Search for rare and forbidden Charm Meson decays D0 --> Vl+l- and hhll

We report results of a search for flavor-changing neutral current (FCNC), lepton flavor, and lepton-number violating decays of the D0 (and its antiparticle) into three and four bodies. Using data from Fermilab charm hadroproduction experiment E791, we examine modes with two leptons (muons or electrons) and a rho(0), K( *0), or straight phi vector meson or a nonresonant pi(pi), Kpi, or KK pair of pseudoscalar mesons. No evidence for any of these decays is found. Therefore, we present branching-fraction upper limits at 90% confidence level for the 27 decay modes examined (18 new).     

Structures of three halo(tetramethylethylenediamine)copper(I) complexes

The X-ray crystal structures of three halo(tetramethylethylenediamine)copper(I) complexes have been determined. (TMED)₂Cu⁺CuCl ₂ ^– (I) crystallizes in monoclinic space groupP2₁/n with lattice constantsa=9.332(9),b=15.126(7),c=14.49(1) Å,=96.95(7)°. (TMEDCuBr)₂ (II) crystallizes in monoclinic space groupP2₁/c with lattice constantsa=12.064(5),b=11.888(6),c=15.841(6) Å,=113.97(3)°. (TMED CuI)₂ (III) crystallizes in monoclinic space groupP2₁/c with lattice constantsa=12.401(6),b=12.159(6),c=15.412(9) Å,=109.12(4)°. Compound (I) is a molecule exhibiting two discrete environments for copper(I). The cation is a pseudotetrahedral monomer and the anion a linear monomer. Both (II) and (III) are dimers with asymmetrically bridging bromine and iodine atoms, respectively. Distortions from tetrahedral geometry are observed about the copper atoms in (II) and (III).