5,416 research outputs found
Comment on "Interface state recombination in organic solar cells"
In a recent paper, Street et al. [Phys. Rev. B 81, 205307 (2010)] propose
first order recombination due to interface states to be the dominant loss
mechanism in organic bulk heterojunction solar cells, based on steady-state
current--voltage characteristics. By applying macroscopic simulations, we found
that under typical solar cell conditions, monomolecular or bimolecular
recombination cannot be inferred from the slope of the light intensity
dependent photocurrent. In addition, we discuss the validity of calculating a
mobility--lifetime product from steady-state measurements. We conclude that the
experimental technique applied by Street et al. is not sufficient to
unambiguously determine the loss mechanism.Comment: 4 pages, 2 figures. Corrected Eqns. (2) and (4): 1/... was missin
Forfeiture of Attorney\u27s Fees Under RICO and CCE
We present the matching relations of the variable flavor number scheme at next-to-leading order, which are of importance to define heavy quark partonic distributions for the use at high energy colliders such as Tevatron and the LHC. The consideration of the two-mass effects due to both charm and bottom quarks, having rather similar masses, are important. These effects have not been considered in previous investigations. Numerical results are presented for a wide range of scales. We also present the corresponding contributions to the structure function
Tunneling through magnetic molecules with arbitrary angle between easy axis and magnetic field
Inelastic tunneling through magnetically anisotropic molecules is studied
theoretically in the presence of a strong magnetic field. Since the molecular
orientation is not well controlled in tunneling experiments, we consider
arbitrary angles between easy axis and field. This destroys all conservation
laws except that of charge, leading to a rich fine structure in the
differential conductance. Besides single molecules we also study monolayers of
molecules with either aligned or random easy axes. We show that detailed
information on the molecular transitions and orientations can be obtained from
the differential conductance for varying magnetic field. For random easy axes,
averaging over orientations leads to van Hove singularities in the differential
conductance. Rate equations in the sequential-tunneling approximation are
employed. An efficient approximation for their solution for complex molecules
is presented. The results are applied to Mn12-based magnetic molecules.Comment: 10 pages, 10 figures include
Unexpected transformation of dissolved phenols to toxic dicarbonyls by hydroxyl radicals and UV light.
Water treatment systems frequently use strong oxidants or UV light to degrade chemicals that pose human health risks. Unfortunately, these treatments can result in the unintended transformation of organic contaminants into toxic products. We report an unexpected reaction through which exposure of phenolic compounds to hydroxyl radicals (•OH) or UV light results in the formation of toxic α,β-unsaturated enedials and oxoenals. We show that these transformation products damage proteins by reacting with lysine and cysteine moieties. We demonstrate that phenolic compounds react with •OH produced by the increasingly popular UV/hydrogen peroxide (H2O2) water treatment process or UV light to form toxic enedials and oxoenals. In addition to raising concerns about potential health risks of oxidative water treatment, our findings suggest the potential for formation of these toxic compounds in sunlit surface waters, atmospheric water, and living cells. For the latter, our findings may be particularly relevant to efforts to understand cellular damage caused by in vivo production of reactive oxygen species. In particular, we demonstrate that exposure of the amino acid tyrosine to •OH yields an electrophilic enedial product that undergoes cross-linking reaction with both lysine and cysteine residues
The magnetoresistance of homogeneous and heterogeneous silver-rich silver selenide
The magnetoresistance (MR) effect of the low-temperature phase of silver selenide (-Ag2 + Se) is measured as a function of composition. Very small composition variations in the order of = 10–6 are achieved by coulometric titration and can be performed simultaneously during the MR measurement. A homogeneous Ag2 + Se shows an ordinary magnetoresistance (OMR) effect, which can be well described by the two-band model. For silver selenide with a heterogenous silver excess, we found quite a different MR behavior. Up to a minor silver excess of 1×10–4 10–2) shows again an OMR effect
Cotunneling and non-equilibrium magnetization in magnetic molecular monolayers
Transport and non-equilibrium magnetization in monolayers of magnetic
molecules subject to a bias voltage are considered. We apply a master-equation
approach going beyond the sequential-tunneling approximation to study the
Coulomb-blockade regime. While the current is very small in this case, the
magnetization shows changes of the order of the saturation magnetization for
small variations of the bias voltage. Inelastic cotunneling processes manifest
themselves as differential-conductance steps, which are accompanied by much
larger changes in the magnetization. In addition, the magnetization in the
Coulomb-blockade regime exhibits strong signatures of sequential tunneling
processes de-exciting molecular states populated by inelastic cotunneling. We
also consider the case of a single molecule, finding that cotunneling processes
lead to the occurrence of magnetic sidebands below the Coulomb-blockade
threshold. In the context of molecular electronics, we study how additional
spin relaxation suppresses the fine structure in transport and magnetization.Comment: 8 pages, 8 figures, version as publishe
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