Determination of the trap-assisted recombination strength in polymer light emitting diodes

The recombination processes in poly(p-phenylene vinylene) based polymer light-emitting diodes (PLEDs) are investigated. Photogenerated current measurements on PLED device structures reveal that next to the known Langevin recombination also trap-assisted recombination is an important recombination channel in PLEDs, which has not been considered until now. The dependence of the open-circuit voltage on light intensity enables us to determine the strength of this process. Numerical modeling of the current-voltage characteristics incorporating both Langevin and trap-assisted recombination yields a correct and consistent description of the PLED, without the traditional correction of the Langevin prefactor. At low bias voltage the trap-assisted recombination rate is found to be dominant over the free carrier recombination rate.

Nonmutagenic carcinogens induce intrachromosomal recombination in dividing yeast cells.

A large number of animal and human carcinogens without apparent genotoxic activity exist (nonmutagenic carcinogens) that are difficult or impossible to detect with the currently used short-term tests. Because of the association of carcinogenesis with genome rearrangement, a system selecting for intrachromosomal recombination (DEL recombination) that results in genome rearrangement has been constructed in the yeast Saccharomyces cerevisiae. Because DEL recombination is under different genetic control than interchromosomal recombination and meiotic recombination, it is probably due to a different mechanism. It has been found that DEL recombination is readily inducible by 10 mutagenic carcinogens and 17 nonmutagenic carcinogens that are not detectable (false negatives) with the Ames assay. In addition, three out of four mutagens that do not cause cancer (false positives in the Ames assay) do not induce DEL recombination. DEL recombination is inducible by UV only in dividing cells but not in cells synchronized in the G1 or G2 phase of the cell cycle. Interchromosomal recombination, on the other hand, is inducible in G1 but not in G2. The nonmutagenic carcinogens induce DEL recombination only in actively growing cells, which may give some indication as to their mechanism. Further characterization of the mechanism involved in induction of DEL recombination may contribute to the understanding of the biological activity of nonmutagenic carcinogens

Recombination Models

We review the current status of recombination and coalescence models that have been successfully applied to describe hadronization in heavy ion collisions at RHIC energies. Basic concepts as well as actual implementations of the idea are discussed. We try to evaluate where we stand in our understanding at the moment and what remains to be done in the future.Comment: Plenary Talk at Quark Matter 2004, submitted to J. Phys. G, 8 pages, 3 figure

Delayed Recombination

Under the standard model for recombination of the primeval plasma, and the cold dark matter model for structure formation, recent measurements of the first peak in the angular power spectrum of the cosmic microwave background temperature indicate the spatial geometry of the universe is nearly flat. If sources of Lya resonance radiation, such as stars or active galactic nuclei, were present at z ~ 1000 they would delay recombination, shifting the first peak to larger angular scales, and producing a positive bias in this measure of space curvature. It can be distinguished from space curvature by its suppression of the secondary peaks in the spectrum.Comment: submitted to ApJ

The Accelerated Recombination, and the ACBAR and WMAP data

We have investigated the deviation from the standard recombination process, using the ACBAR 2008 and the WMAP 3 year data. In this investigation, we have considered the possibility of the accelerated recombination as well as the delayed recombination. We find that the accelerated recombination is as likely as the delayed recombination, and there is some degeneracy between $\epsilon_{\alpha}$ and \{$n_s$, $\log[10^{10}A_s]$, $H_0$\}.Comment: v2: matched with the accepted version (minor change) v3: typo corrections v4: a duplicated pdf file fixe

Sex Differences in Recombination in Sticklebacks.

Recombination often differs markedly between males and females. Here we present the first analysis of sex-specific recombination in Gasterosteus sticklebacks. Using whole-genome sequencing of 15 crosses between G. aculeatus and G. nipponicus, we localized 698 crossovers with a median resolution of 2.3 kb. We also used a bioinformatic approach to infer historical sex-averaged recombination patterns for both species. Recombination is greater in females than males on all chromosomes, and overall map length is 1.64 times longer in females. The locations of crossovers differ strikingly between sexes. Crossovers cluster toward chromosome ends in males, but are distributed more evenly across chromosomes in females. Suppression of recombination near the centromeres in males causes crossovers to cluster at the ends of long arms in acrocentric chromosomes, and greatly reduces crossing over on short arms. The effect of centromeres on recombination is much weaker in females. Genomic differentiation between G. aculeatus and G. nipponicus is strongly correlated with recombination rate, and patterns of differentiation along chromosomes are strongly influenced by male-specific telomere and centromere effects. We found no evidence for fine-scale correlations between recombination and local gene content in either sex. We discuss hypotheses for the origin of sexual dimorphism in recombination and its consequences for sexually antagonistic selection and sex chromosome evolution

Electron-Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements VI. Ni II

We present the first detailed ab initio quantum mechanical calculations for total and state-specific recombination rate coefficients for e + Ni III --> Ni II. These rates are obtained using a unified treatment for total electron-ion recombination that treats the nonresonant radiative recombination and the resonant dielectronic recombination in a self-consistent unified manner in the close coupling approximation. Large-scale calculations are carried out using a 49-state wavefunction expansion from core configurations 3d^8, 3d^74s, and 3d^64p that permits the inclusion of prominent dipole allowed core transitions. These extensive calculations for the recombination rates of Ni II required hundreds of CPU hours on the Cray T90. The total recombination rate coefficients are provided for a wide range of temperature. The state-specific recombination rates for 532 bound states of doublet and quartet symmetries, and the corresponding photoionization cross sections for leaving the core in the ground state, are presented. Present total recombination rate coefficients differ considerably from the currently used data in astrophysical models.Comment: ApJ Suppl. (submitted), 4 figure

Could the Cosmological Recombination Spectrum Help Us Understand Annihilating Dark Matter?

In this paper we explore the potential effects of DM annihilations on the cosmological recombination spectrum. With this example we want to demonstrate that the cosmological recombination spectrum in principle is sensitive to details related to possible extra energy release during recombination. We restrict ourselves to DM models which produce a negligible primordial distortion of the CMB energy spectrum. However, since during the epoch of cosmological recombination a large fraction of the deposited energy can directly go into ionizations and excitations of neutral atoms, both the cosmological recombination spectrum and ionization history can still be affected significantly. We compute the modifications to the cosmological recombination spectrum using our multi-level HI and HeI recombination code, showing that additional photons are created due to uncompensated loops of transitions which are induced by DM annihilations. As we illustrate here, the results depend on the detailed branching of the deposited energy into heating, ionizations and excitations. This dependence in principle should allow us to shed light on the nature of the underlying annihilating DM model (or more generally speaking, the mechanism leading to energy injection) when measuring the cosmological recombination spectrum. However, for current upper limits on the potential DM annihilation rate during recombination the cosmological recombination spectrum is only affected at the level of a few percent. Nevertheless, we argue here that the cosmological recombination spectrum would provide another independent and very direct way of checking for the presence of sources of extra ionizing or exciting photons at high redshifts. This would open an new window to possible (non-standard) processes occurring (abridged)Comment: 14 pages, 11 figure, submitted to MNRA