Controlling dissociation processes in the D-2(+) molecular ion using high-intensity, ultrashort laser pulses

A novel technique is proposed to control the dissociation mechanism of small diatomic molecules. This technique, relying upon the creation of a coherent nuclear wavepacket, uses intense (> 10(14) W cm(-2)), ultrashort (similar to 10 fs) infrared laser pulses in a pump and probe scheme. In applying this technique to D-2(+) good agreement has been observed between a quantum simulation and experiment. This represents a major step towards quantum state control in molecules, using optical fields.

Time-resolved studies of ultrafast wavepacket dynamics in hydrogen molecules

Recent advances in the study of quantum vibrations and rotations in the fundamental hydrogen molecules are reported. Using the deuterium molecules (D-2(+) and D-2) as exemplars, the application of ultrafast femtosecond pump-probe experiments to study the creation and time-resolved imaging of coherent nuclear wavepackets is discussed. The ability to study the motion of these fundamental molecules in the time-domain is a notable milestone, made possible through the advent of ultrashort intense laser pulses with durations on sub-vibrational (and sub-rotational) timescales. Quantum wavepacket revivals are characterised for both vibrational and rotational degrees of freedom and quantum models are used to provide a detailed discussion of the underlying ultrafast physical dynamics for the specialist and non-specialist alike. (C) 2009 Elsevier B.V. All rights reserved.

Purification of entangled coherent states

We suggest an entanglement purification scheme for mixed entangled coherent states using 50-50 beam splitters and photodetectors. This scheme is directly applicable for mixed entangled coherent states of the Werner type, and can be useful for general mixed states using additional nonlinear interactions. We apply our scheme to entangled coherent states decohered in a vacuum environment and find the decay time until which they can be purified.

Differences in mitochondrial and nuclear DNA status of high-density and low-density sperm fractions after density centrifugation preparation

Background: In order to isolate the â??bestâ?? sperm for assisted conception a discontinuous two-step density gradient centrifugation is usually employed. This technique is known to isolate a subpopulation with good motility, morphology and nuclear DNA (nDNA) integrity. As yet its ability to isolate sperm with unfragmented mitochondrial DNA (mtDNA) is unknown. Methods: Semen was obtained from men (n=28) attending our Regional Fertility Centre for infertility investigations. We employed a modified long polymerase chain reaction to study mtDNA and a modified alkaline Comet assay to determine nDNA fragmentation. Results: The high- density fraction displayed significantly more wild type mtDNA (75% of samples) than that of the low- density fraction (25% of samples). In the high-density fraction, there was a higher incidence of single, rather than double or multiple deletions and the deletions were predominantly small scale (0.1-4.0kb). There was a strong correlation between nDNA fragmentation, the number of mtDNA deletions (r=0.7, p

A comparison of mitochondrial and nuclear DNA status in testicular sperm from fertile men and those with obstructive azoospermia

Background: Mitochondria are vital to sperm as their motility powerhouses. They are also the only animal organelles with their own unique genome; encoding subunits for the complexes required for the electron transfer chain. Methods: A modified long PCR technique was used to study mitochondrial DNA (mtDNA) in ejaculated and testicular sperm samples from fertile men (n=11) and testicular sperm from men with obstructive azoospermia (n=25). Nuclear DNA fragmentation was measured by an alkaline single cell gel electrophoresis (COMET) assay. Results: Wild-type mtDNA was detected in only 60% of fertile mens�??�?�¢?? testicular sperm, 50% of their ejaculated sperm and 46% of testicular sperm from men with obstructive azoospermia. The incidence of mitochondrial deletions in testicular sperm of fertile and infertile men was not significantly different but the mean size of the deletions was significantly less in testicular sperm from fertile men compared with men with obstructive azoospermia (p<0.02). Nuclear DNA fragmentation in testicular sperm from fertile men and men with obstructive azoospermia was not significantly different. Conclusion: Multiple mtDNA deletions are common in testicular and ejaculated sperm from both fertile and infertile men. However, in males with obstructive azoospermia the mtDNA deletions in testicular sperm are of a larger scale.