Study of a carbon dioxide ring laser gyroscope

We have experimentally investigated a basic ring laser gyroscope (RLG) with carbon dioxide gain, and studied the prospects of developing a practical CO₂ RLG. Rotation sensing was demonstrated on a number of transitions in the 9.4 m and 10.4 m vibration-rotation bands. Gyro response is discussed with regard to lock-in, bias, homogeneous broadening effects, and high power operation. We show that such a system may offer important advantages over standard helium-neon RLGs, including reduced quantum limit and backscattering. The prospects and possible approaches for developing a practical high power CO₂ RLG are discussed, and a method of eliminating cross-saturation at high pressure is proposed and analyzed.     

Heritability of Stroop and flanker performance in 12-year old children

Background  

There is great interest in appropriate phenotypes that serve as indicator of genetically transmitted frontal (dys)function, such as ADHD. Here we investigate the ability to deal with response conflict, and we ask to what extent performance variation on response interference tasks is caused by genetic variation. We tested a large sample of 12-year old monozygotic and dizygotic twins on two well-known and closely related response interference tasks; the color Stroop task and the Eriksen flanker task. Using structural equation modelling we assessed the heritability of several performance indices derived from those tasks.     

Time-resolved measurements of self-focusing pulses in air

The spatial, spectral, and temporal properties of self-focusing 798-nm 100-fs pulses in air are experimentally measured with high-resolution, single-shot techniques at a set propagation distance of 10.91 m. The data, obtained with an initially collimated Gaussian beam, show significant evolution of spatial narrowing as well as temporal and spectral changes at intensities lower than those required for significant ionization of air.     

Bidirectional, synchronously pumped, ring optical parametric oscillator

We report the operation of a bidirectional femtosecond pulsed ring optical parametric oscillator based on periodically poled lithium niobate, pumped alternately with nonsimultaneous pulses from a Ti:sapphire mode-locked laser. A beat note between the two counterpropagating beams attests to a gyro response without dead band. The sensitivity of the device to differential phase changes is demonstrated by measurement of the nonlinear index of lithium niobate.     

The contribution of high frequencies to human brain activity underlying horizontal localization of natural spatial sounds

Background  

In the field of auditory neuroscience, much research has focused on the neural processes underlying human sound localization. A recent magnetoencephalography (MEG) study investigated localization-related brain activity by measuring the N1m event-related response originating in the auditory cortex. It was found that the dynamic range of the right-hemispheric N1m response, defined as the mean difference in response magnitude between contralateral and ipsilateral stimulation, reflects cortical activity related to the discrimination of horizontal sound direction. Interestingly, the results also suggested that the presence of realistic spectral information within horizontally located spatial sounds resulted in a larger right-hemispheric N1m dynamic range. Spectral cues being predominant at high frequencies, the present study further investigated the issue by removing frequencies from the spatial stimuli with low-pass filtering. This resulted in a stepwise elimination of direction-specific spectral information. Interaural time and level differences were kept constant. The original, unfiltered stimuli were broadband noise signals presented from five frontal horizontal directions and binaurally recorded for eight human subjects with miniature microphones placed in each subject's ear canals. Stimuli were presented to the subjects during MEG registration and in a behavioral listening experiment.     

Improving the catabolic functions of desiccation-tolerant soil bacteria

Bacterial strains were selected from a desiccated polluted soil for their drought tolerance and their ability to grow on diesel oil in view of incorporating them in a bioaugmentation product. These products are useful in case of recal citrant xenobiotic pollution, where there is no intrinsic biodegradation activity in the soil. These strains grow on the easily degradable components of diesel oil. In troduction of new catabolic genes into these desiccation-tolerant bacteria in order to improve their catabolic functions was considered. Plasmid-borne catabolic genes coding for enzymes in volved in the degradation of more recalcitrant compounds (Isopropylbenzene, trichloroethene, 3-chloroben zoate, 4-chlorobiphenyl, biphenyl) were successfully introduced in some of the desiccation-tolerant strains by means of natural conjugation. Strains exhibiting good tolerance to desiccation and able to grow on the new carbon sources were obtained. The frequencies of integration of the plasmids ranged from 2×10⁻⁸ to 9.2 10⁻² transconjugants/acceptor. Drought-tolerance is indeed important for bioaugmentation because of its in trinsic ecological significance and because a bioaugmentation starter has to be conditioned in a desic cated form to ensure good shelf-life. The conservation of the properties during storage was evaluated by accelerated storage tests.