High conversion efficiency Hg0.77Cd0.23Te spin-flip Raman laser

Peak external conversion efficiencies of several percent have been measured in the 10 μm region when a CO₂ laser is used to pump a Hg_0.77Cd_0.23Te spin-flip Raman laser. Strong pump depletion is observed in the experiments. Quantum oscillations from the n = 0, 1 and 2 Landau levels are observed in the tuning characteristics. At 710 G the spontaneous linewidth is measured to be 8 G. Large effects due to conduction band nonparabolicity are observed.     

A study of the phase transition and relaxation of a Pt(100) surface by MeV ion backscattering and channeling

MeV He⁺ ion backscattering has been used to show that the phase transition on a Pt(100) surface involves the lateral displacement of an entire plane of atoms. It is further shown that the outward relaxation of the unreconstructed surface plane is negligible, i.e. 0.5 ± 0.5% of thebulk interplanar spacing.     

Interactions in metal clusters : III. Racemization barriers and reversible hydrogen addition of a series of chiral clusters

The barriers to racemization in C₂D₄Cl₂ of [Ir{Fe(P(p-tolyl)₂)(CO)₂(η⁵-C₅H₅)}₂]⁺ BF₄^? and [Ir{Ru(P(p-tolyl)₂)(CO)₂(η⁵-C₅H₅)}₂]⁺ BF₄^? are 17.5 and 17.8 kcal/mol respectively. Both clusters add H₂ reversibly at 1 atmosphere and room temperature. The former also forms an adduct with H₂ and CO when exposed to both gases simultaneously.     

Measurement of surface relaxation by MeV ion backscattering and channeling

The ion channeling technique has been used to investigate surface relaxation effects in Pt. Preliminary results for a (111) surface indicate an outward relaxation of 0.31 ± 0.06 Å.     

Very short OH?hydrogen bond in l-histidinium difluoride

The crystal structure of C₆H₁₁N₃O₂²⁺·2F²⁻ is reported. The structure contains a fluoride ion strongly H-bonded to a carboxylic O atom, a rare, very strong, hydrogen bond. The donor-acceptor distance is 2.3818(10) Å, the shortest value reported to date, considerably less than the sum of the van der Waals radii of the atoms implicated, as expected from a very strong hydrogen bond. The di-cation has an open conformation. There is an extensive H-bonding network between anions and cations assembling rings on the ac plane and chains in several directions. Two extra intermolecular interactions of the type CH?π are found, exhausting the aromatic π electron system ability to act as a proton acceptor.     

Synthesis of 6-phenanthridinones and their heterocyclic analogues through palladium-catalyzed sequential aryl-aryl and N-aryl coupling

[reaction: see text] 6-Phenanthridinones and their heterocyclic analogues were synthesized through a one-pot procedure based on consecutive Pd-catalyzed aryl-aryl and N-aryl coupling from iodoarenes ortho-substituted by electron-releasing substituents and amides of o-bromoarene- and heteroarenecarboxylic acids.     

Sample injection in capillary electrochromatography by heart-cut technique

The splitter working in heart-cut regime was used for sample injection in capillary electrochromatography. The principle was implemented in an automated microgradient system allowing to inject from microlitre down to nanolitre volumes with high repeatability and minimal extra-column band broadening. The apparatus is able to deliver discrete volumes of liquids at a preset volumetric flow rate and to stop and restore the flow at any moment. This brings a high degree of liquid manipulation flexibility. An extremely low split ratio is sufficient during the analysis, which saves mobile phase consumption substantially. The key parameters influencing the function of the heart-cut splitter were characterised. The function of the apparatus was demonstrated under isocratic, preconcentration and gradient capillary electrochromatography separation conditions. In all cases the statistic evaluation of the main parameters was performed, showing that high repeatability of retention times, peak heights and areas was achieved.     

Hybrid Genetic Algorithm for DNA Sequencing with Errors

In the paper, a new hybrid genetic algorithm solving the DNA sequencing problem with negative and positive errors is presented. The algorithm has as its input a set of oligonucleotides coming from a hybridization experiment. The aim is to reconstruct an original DNA sequence of a known length on the basis of this set. No additional information about the oligonucleotides nor about the errors is assumed. Despite that, the algorithm returns for computationally hard instances surprisingly good results, of a very high similarity to original sequences.