Search

Purpose: Human hands are excellent in performing sensory and motor function. We have hypothesized that blood flow of the hand is dynamically regulated by sympathetic outflow during concentrated finger perception. To identify this hypothesis, we measured radial blood flow (RBF), radial vascular conductance (RVC), heart rate (HR), and arterial blood pressure (AP) during Braille reading performed under the blind condition in nine healthy subjects. The subjects were instructed to read a flat plate with raised letters (Braille reading) for 30 s by the forefinger, and to touch a blank plate as control for the Braille discrimination procedure. Results: HR and AP slightly increased during Braille reading but remained unchanged during the touching of the blank plate. RBF and RVC were reduced during the Braille character discrimination task (decreased by −46% and −49%, respectively). Furthermore, the changes in RBF and RVC were much greater during the Braille character discrimination task than during the touching of the blank plate (decreased by −20% and −20%, respectively). Conclusions: These results have suggested that the distribution of blood flow to the hand is modulated via sympathetic nerve activity during concentrated finger perception.

In chemical grouting, a method to evaluate the region improved by the grouting has not yet been established. This problem has been a major obstacle to the enhancement of reliability of chemical grouting. To solve this problem, the author noted that the electrical resistivity of chemical grout is much lower than the electrical resistivities of ground and groundwater. This study investigated the applicability of resistivity tomography to the evaluation of regions improved by chemical grouting through model tests in the laboratory. The resistivity tomography can measure the resistivity distributions of ground before and after grouting. As a result, it was clarified that a relatively high degree of accuracy can be obtained in the evaluation of the improved regions made by chemical grouting. The method proposed to evaluate the improved region in chemical grouting utilizes data on ground resistivities before and after grouting which can be determined by resistivity tomography, and it has been demonstrating a satisfactory applicability.En matière de stabilisation chimique, aucune méthode permettant d'évaluer la région améliorée par la stabilisation n'a pas encore été établie. Ce problème empêche d'améliorer la fiabilité de la stabilisation chimique. Pour le résoudre, l'auteur a noté que la résistivité électrique du scellage chimique est bien plus basse que la résistivité électrique du sol et des nappes d'eau souterraines. Cette étude, au moyen d'essais sur maquettes en laboratoire, se penche sur l'applicabilité de la tomographie de résistivité pour évaluer les régions améliorées par une stabilisation chimique. La tomographie de résistivité peut mesurer les répartitions de résistivité du sol avant et après la stabilisation. Ainsi, il est apparu qu'on peut obtenir un degré d'exactitude relativement élevé dans l'évaluation des régions améliorées par une stabilisation chimique. La méthode proposée pour évaluer la région améliorée par stabilisation chimique utilise des données de résistivité du sol avant et après la stabilisation, données qui peuvent être déterminées par la tomographie de résistivité. Cette méthode montre une applicabilité satisfaisante.In chemical grouting, a method to evaluate the region improved by the grouting has not yet been established. This problem has been a major obstacle to the enhancement of reliability of chemical grouting. To solve this problem, the author noted that the electrical resistivity of chemical grout is much lower than the electrical resistivities of ground and groundwater. This study investigated the applicability of resistivity tomography to the evaluation of regions improved by chemical grouting through model tests in the laboratory. The resistivity tomography can measure the resistivity distributions of ground before and after grouting. As a result, it was clarified that a relatively high degree of accuracy can be obtained in the evaluation of the improved regions made by chemical grouting. The method proposed to evaluate the improved region in chemical grouting utilizes data on ground resistivities before and after grouting which can be determined by resistivity tomography, and it has been demonstrating a satisfactory applicability.En matière de stabilisation chimique, aucune méthode permettant d'évaluer la région améliorée par la stabilisation n'a pas encore été établie. Ce problème empêche d'améliorer la fiabilité de la stabilisation chimique. Pour le résoudre, l'auteur a noté que la résistivité électrique du scellage chimique est bien plus basse que la résistivité électrique du sol et des nappes d'eau souterraines. Cette étude, au moyen d'essais sur maquettes en laboratoire, se penche sur l'applicabilité de la tomographie de résistivité pour évaluer les régions améliorées par une stabilisation chimique. La tomographie de résistivité peut mesurer les répartitions de résistivité du sol avant et après la stabilisation. Ainsi, il est apparu qu'on peut obtenir un degré d'exactitude relativement élevé dans l'évaluation des régions améliorées par une stabilisation chimique. La méthode proposée pour évaluer la région améliorée par stabilisation chimique utilise des données de résistivité du sol avant et après la stabilisation, données qui peuvent être déterminées par la tomographie de résistivité. Cette méthode montre une applicabilité satisfaisante.

The continuous emission bands of molecular mercury at 0.335 and 0.485 μm are excited in a pure mercury vapor by direct optical pumping of the weakly bound ground state molecules with a 5 nsec pulse of intense 0.266 μm radiation in order to study the radiative and collisional properties of the excited molecules at densities between 1014 and 1015 cm−3. Fluorescence time history of both bands are empirically analyzed in terms of dynamics governing the excited molecules. The analysis includes a density‐dependent nonexponential decay caused by bimolecular excimer quenching with a measured rate constant of k?2±1×10−10 cm3 sec−1 molecule−1. Because of interest in the mercury system as a potential laser medium, estimates of gain coefficients are derived from fluorescent power measurements. However, transmission measurements of the excited medium at 0.325 and 0.4416 μm show significant net loss due to excited state absorption with an estimated absorption cross section on the order of 10−17 cm2 at 0.325 μm. Energy storage limitations implied by the bimolecular excimer quenching are also examined.

We demonstrate a scalable architecture for a high-power, high-brightness, solid-state laser based on coherent combinations of master oscillator power amplifier chains. A common master oscillator injects a sequence of multikilowatt Nd:YAG zigzag slab amplifiers. Adaptive optics correct the wavefront of each amplified beamlet. The beamlets are tiled side by side and actively phase locked to form a single output beam. The laser produces 19 kW with beam quality <2× diffraction limited. To the best of our knowledge, this is the brightest cw solid-state laser demonstrated to date.

We have observed near-monochromatic gains in a Raman amplifier pumped by a laser with a bandwidth up to 30 times wider than the molecular linewidth. This gain enhancement is obtained when the corresponding temporal fine structure of the pump and Stokes waveforms are superimposed in the amplifier.

We fabricated a novel quasi-phase-matched frequency converter, using a zigzag optical beam path in a thin, polished parallel plate. Second-harmonic generation experiments demonstrated angle-tuned output at 4.6 to 5.3 µm in GaAs and 1.7 to 2.0 µm in ZnSe crystals when pulsed infrared laser sources were used.

We have shown theoretically and experimentally that very high conversion efficiencies can be obtained in high-peak-power wavelength converters utilizing small amounts of feedback, at fluences similar to the no-feedback case. Maximum efficiencies are obtained with radially varying reflectivity profiles. We have demonstrated the concept, using second-harmonic generation in a deuterated potassium dihydrogen phosphate crystal in which 70% energy conversion was obtained, in agreement with simulation results. Energy conversion efficiencies of 56% were also obtained in a beta-barium borate optical parametric oscillator.

We have obtained nearly 1 J of blue-green radiation in 60-nsec pulses by Raman shifting an injection-locked XeCl laser in Pb vapor. The measured 50% Raman energy conversion has been observed in both oscillator and oscillator–amplifier experiments. These results indicate that an XeCl/Pb blue-green laser efficiency of >1.4% should be possible.

Efficient conversion of ultraviolet-laser output to visible radiation has been demonstrated with multiple Stokes Raman amplification in hydrogen gas using an oscillator–amplifier combination. Initial experiments with the third harmonic of a Q-switched Nd:YAG laser at 355 nm yielded nearly complete pump depletion in a 2-m amplifier, whereas photon-conversion efficiencies of 49 and 51% have been observed for the first and second Stokes orders, respectively.

Efficient XeCl-laser Raman downconversion has been demonstrated with a novel oscillator–amplifier system based on higher-Stokes-order generation in H_2 gas. Simultaneous generation of the first (353-nm), second (414-nm), and third (499-nm) Stokes outputs has been observed in a Raman amplifier at energy-conversion efficiencies of 18, 22, and 14%, respectively, in good agreement with computer simulations.