Polarization fluctuations in vertical cavity surface emitting lasers: a key to the mechanism behind polarization stability

We investigate the effects of the electron-hole spin dynamics on the polarization fluctuations in the light emitted from a vertical cavity surface emitting laser (VCSEL). The Langevin equations are derived based on a rate equation model including birefringence, dichroism, and two carrier density pools seperately coupled to right and left circular polarization. The results show that the carrier dynamics phase lock the polarization fluctuations to the laser mode. This is clearly seen in the difference between fluctuations in ellipticity and fluctuations in polarization direction. Seperate measurements of the polarization fluctuations in ellipticity and in polarization direction can therefore provide quantitative information on the non-linear contribution of the carrier dynamics to polarization stability in VCSELs.Comment: 6 pages RevTex and 3 figures, to be published in Quantum and Semiclassical Optics, minor changes to the discussion of timescale

Results of Skylab medical experiment M171: Metabolic activity

The experiment was conducted to establish whether man's ability to perform mechanical work would be progressively altered as a result of exposure to the weightless environment of space flight. The Skylab crewmen exercised on a bicycle ergometer at workloads approximating 25, 50, and 75 percent of their maximum aerobic capacity. The physiological parameters monitored were respiratory gas exchange, blood pressure, and vectorcardiogram/heart rate. The results of these tests indicate that the crewmen had no significant decrement in their responses to exercise during their exposure to zero gravity. The results of the third manned Skylab mission (Skylab 4) are presented and a comparison is made of the overall results obtained from the three successively longer Skylab manned missions. The Skylab 4 crewmembers' 84-day in-flight responses to exercise were no worse and were probably better than the responses of the crewmen on the first two Skylab missions. Indications that exercise was an important contributing factor in maintaining this response are discussed

Radical pair recombination stereoselectivity as a probe of magnetic isotope and magnetic field effects

Photolysis of meso- or dl-2,4-diphenylpentan-3-one within NaY zeolites, coadsorbed with a chiral inductor, lead to enantioselective radical pair recombinations which are sensitive to 13C isotope effects, but insensitive towards external magnetic field effects

First photosensitized enantiodifferentiating isomerization by optically active sensitizer immobilized in zeolite supercages

Enantiodifferentiating photoisomerization of (Z)-cyclooctene sensitized by (R)- or (S)-1-methylheptyl benzoate immobilized in zeolite supercages afforded the respective enantiomer pair, (—)- and (+)-(E)-isomer (1E) in 5% enantiomeric excess, whilst racemic 1E was obtained upon homogeneous-phase photosensitization with the same antipodal sensitizer pair, thus demonstrating for the first time that chirally modified zeolites not only serve as supramolecular photosensitizing media but also enhance the original enantiodifferentiating ability of chiral photosensitizer

The Multiple Process Model of Goal-Directed Reaching Revisited

Recently our group forwarded a model of speed-accuracy relations in goal-directed reaching. A fundamental feature of our multiple process model was the distinction between two types of online regulation: impulse control and limb-target control. Impulse control begins during the initial stages of the movement trajectory and involves a comparison of actual limb velocity and direction to an internal representation of expectations about the limb trajectory. Limb-target control involves discrete error-reduction based on the relative positions of the limb and the target late in the movement. Our model also considers the role of eye movements, practice, energy optimization and strategic behavior in limb control. Here, we review recent work conducted to test specific aspects of our model. As well, we consider research not fully incorporated into our earlier contribution. We conclude that a slightly modified and expanded version of our model, that includes crosstalk between the two forms of online regulation, does an excellent job of explaining speed, accuracy, and energy optimization in goal-directed reaching

The origin of human chromosome 2 analyzed by comparative chromosome mapping with a DNA microlibrary

Fluorescencein situ hybridization (FISH) of microlibraries established from distinct chromosome subregions can test the evolutionary conservation of chromosome bands as well as chromosomal rearrangements that occurred during primate evolution and will help to clarify phylogenetic relationships. We used a DNA library established by microdissection and microcloning from the entire long arm of human chromosome 2 for fluorescencein situ hybridization and comparative mapping of the chromosomes of human, great apes (Pan troglodytes, Pan paniscus, Gorilla gorilla, Pongo pygmaeus) and Old World monkeys (Macaca fuscata andCercopithecus aethiops). Inversions were found in the pericentric region of the primate chromosome 2p homologs in great apes, and the hybridization pattern demonstrates the known phylogenetically derived telomere fusion in the line that leads to human chromosome 2. The hybridization of the 2q microlibrary to chromosomes of Old World monkeys gave a different pattern from that in the gorilla and the orang-utan, but a pattern similar to that of chimpanzees. This suggests convergence of chromosomal rearrangements in different phylogenetic lines

Shallow carrier traps in hydrothermal ZnO crystals

Native and hydrogen-plasma induced shallow traps in hydrothermally grown ZnO crystals have been investigated by charge-based deep level transient spectroscopy, photoluminescence and cathodoluminescence microanalysis. The as-grown ZnO exhibits a trap state at 23 meV, while H-doped ZnO produced by plasma doping shows two levels at 22 meV and 11 meV below the conduction band. As-grown ZnO displays the expected thermal decay of bound excitons with increasing temperature from 7 K, while we observed an anomalous behaviour of the excitonic emission in H-doped ZnO, in which its intensity increases with increasing temperature in the range 140-300 K. Based on a multitude of optical results, a qualitative model is developed which explains the Y line structural defects, which act as an electron trap with an activation energy of 11 meV, being responsible for the anomalous temperature-dependent cathodoluminescence of H-doped ZnO. © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft

Assignment of the Human and Mouse Prion Protein Genes to Homologous Chromosomes

Purified preparations of scrapie prions contain one major macromolecule, designated prion protein (PrP). Genes encoding PrP are found in normal animals and humans but not within the infectious particles. The PrP gene was assigned to human chromosome 20 and the corresponding mouse chromosome 2 using somatic cell hybrids. In situ hybridization studies mapped the human PrP gene to band 20p12→pter. Our results should lead to studies of genetic loci syntenic with the PrP gene, which may play a role in the pathogenesis of prion diseases or other degenerative neurologic disorders

Quantum Maxwell-Bloch equations for spatially inhomogeneous semiconductor lasers

We present quantum Maxwell-Bloch equations (QMBE) for spatially inhomogeneous semiconductor laser devices. The QMBE are derived from fully quantum mechanical operator dynamics describing the interaction of the light field with the quantum states of the electrons and the holes near the band gap. By taking into account field-field correlations and field-dipole correlations, the QMBE include quantum noise effects which cause spontaneous emission and amplified spontaneous emission. In particular, the source of spontaneous emission is obtained by factorizing the dipole-dipole correlations into a product of electron and hole densities. The QMBE are formulated for general devices, for edge emitting lasers and for vertical cavity surface emitting lasers, providing a starting point for the detailed analysis of spatial coherence in the near field and far field patterns of such laser diodes. Analytical expressions are given for the spectra of gain and spontaneous emission described by the QMBE. These results are applied to the case of a broad area laser, for which the frequency and carrier density dependent spontaneous emission factor beta and the evolution of the far field pattern near threshold are derived.Comment: 22 pages RevTex and 7 figures, submitted to Phys.Rev.A, revisions in abstract and in the discussion of temporal coherenc

The Effects of a Proprietary Fenugreek Extract on Strength & Body Composition

Fenugreek extract has been marketed in dozens of dietary products as having performance enhancing potential for resistance trained athletes. PURPOSE: The purpose of this study was to investigate the potential performance enhancing effects of a proprietary fenugreek extract in conjunction with a controlled resistance training program. METHODS: Thirty resistance trained male subjects were matched according to fat free mass and randomly assigned to ingest in a double-blind manner capsules containing 500mg of a placebo or fenugreek (Trigonella Foenun greacum) once per day for 8-weeks (Active: N = 17, 21 ± 2.8 yrs, 178 ± 5.8 cm, 85 ± 9.6 kg, 18.8 ± 4.8 BF%; Placebo: N = 13, 21 ± 3 yrs, 180 ± 6.4 cm, 84 ± 15 kg, 18.3 ± 6.8 BF%). Subjects were instructed to participate in a periodized 4-day per week resistance-training program split into two upper and two lower extremity workouts per week for a total of 8-weeks. Body composition was analyzed using hydrodensiometry and strength tests involved performing a one repetition max (1RM) on the isotonic bench press and leg press. Statistical analyses utilized a two-way ANOVA with repeated measures for all criterion variables (p \u3c 0.05). RESULTS: A significant (p \u3c 0.05) group x time interaction for body composition was observed indicating the Active (-1.8 ± 0.5 BF%) group decreased body fat percentage in comparison to Placebo (-0.05 ± 0.3 BF%) over the 8-week investigation period. In addition, there was a significant (p \u3c 0.05) main effect for time over the eight week period in lean muscle mass (Active: 2.4 ± 0.1 kg; Placebo: 1.0 ± 0.1 kg). No significant effects for group or time were observed for upper or lower body strength (p \u3e 0.05). CONCLUSION: In addition to a controlled resistance training program fenugreek had a significant impact on body composition in comparison to placebo. This study was funded by Indus Biotech