123 research outputs found
Untersuchung von photoinduziertem Elektronentransfer in modifizierter DNA und bioorthogonaler Diels-Alder-Konjugation
Das artifizielle HQ-HQ-Basenpaar konnte als Strangbruchsonde und als intermediärer Ladungsüberträger für den photoinduzierten Elektronentransfer in DNA mit einem neuen ED-, EA-System eingesetzt und analysiert werden. Ein neues Tetrazinnukleosid konnte hergestellt werden, welches über die automatisierte Festphasensynthese in DNA eingebracht und onbead mit einem cyclooktinmodifizierten Fluoreszeinbaustein mittels Diels-Alder Reaktion mit inversem Elektronenbedarf zur Reaktion gebracht werden
Double polarization experiments at intermediate energy
At modern electron accelerators with highly polarized, intense, high duty
factor beams double polarization coincidence experiments became feasible with
good statistical accuracy. The strong potential towards the precise
determination of small nucleon structure quantities is illustrated by two
recent examples from MAMI. The measurement of in the quasifree reaction
lead to a new parametrization of which is
significantly above the previously preferred one from elastic scattering.
A experiment at the energy of the resonance
yields preliminary results for the longitudinal quadrupole mixing. Both
experimental errors and model uncertainties are complementary to unpolarized
measurements.Comment: 8 pages, 6 figures, plenary talk given at PANIC'9
Proton irradiation of CdTe thin film photovoltaics deposited on cerium-doped space glass
Space photovoltaics is dominated by multi-junction (III-V) technology. However, emerging applications will require solar arrays with high specific power (kW/kg), flexibility in stowage and deployment, and a significantly lower cost than the current III-V technology offers. This research demonstrates direct deposition of thin film CdTe onto the radiation-hard cover glass that is normally laminated to any solar cell deployed in space. Four CdTe samples, with 9 defined contact device areas of 0.25 cm2, were irradiated with protons of 0.5-MeV energy and varying fluences. At the lowest fluence, 1 × 1012 cm−2, the relative efficiency of the solar cells was 95%. Increasing the proton fluence to 1 × 1013 cm−2 and then 1 × 1014 cm−2 decreased the solar cell efficiency to 82% and 4%, respectively. At the fluence of 1 × 1013 cm−2, carrier concentration was reduced by an order of magnitude. Solar Cell Capacitance Simulator (SCAPS) modelling obtained a good fit from a reduction in shallow acceptor concentration with no change in the deep trap defect concentration. The more highly irradiated devices resulted in a buried junction characteristic of the external quantum efficiency, indicating further deterioration of the acceptor doping. This is explained by compensation from interstitial H+ formed by the proton absorption. An anneal of the 1 × 1014 cm−2 fluence devices gave an efficiency increase from 4% to 73% of the pre-irradiated levels, indicating that the compensation was reversible. CdTe with its rapid recovery through annealing demonstrates a radiation hardness to protons that is far superior to conventional multi-junction III-V solar cells
Quasifree Pion Electroproduction from Nuclei in the Region
We present calculations of the reaction in the
distorted wave impulse approximation. The reaction allows for the study of the
production process in the nuclear medium without being obscured by the details
of nuclear transition densities. First, a pion electroproduction operator
suitable for nuclear calculations is obtained by extending the Blomqvist-Laget
photoproduction operator to the virtual photon case. The operator is gauge
invariant, unitary, reference frame independent, and describes the existing
data reasonably well. Then it is applied in nuclei to predict nuclear cross
sections under a variety of kinematic arrangements. Issues such as the effects
of gauge-fixing, the interference of the resonance with the
background, sensitivities to the quadrupole component of the
excitation and to the electromagnetic form factors, the role of final-state
interactions, are studied in detail. Methods on how to experimentally separate
the various pieces in the coincidence cross section are suggested. Finally, the
model is compared to a recent SLAC experiment.Comment: 27 pages in REVTEX, plus 22 PS figures embedded using psfig.sty
(included), uuencode
The annual energy yield of mono- and bifacial silicon heterojunction solar modules with high-index dielectric nanodisk arrays as anti-reflective and light trapping structures
While various nanophotonic structures applicable to relatively thin
crystalline silicon-based solar cells were proposed to ensure effective light
in-coupling and light trapping in the absorber, it is of great importance to
evaluate their performance on the solar module level under realistic
irradiation conditions. Here, we analyze the annual energy yield of relatively
thin heterojunction (HJT) solar module architectures when optimized
anti-reflective and light trapping titanium dioxide (TiO) nanodisk square
arrays are applied on the front and rear cell interfaces. Our numerical study
shows that upon reducing crystalline silicon (c-Si) wafer thickness, the
relative increase of the annual energy yield can go up to 11.0 %
and 43.0 % for mono- and bifacial solar modules, respectively,
when compared to the reference modules with flat optimized anti-reflective
coatings of HJT solar cells.Comment: 24 pages, 7 figure
- …