Highly Efficient 68-W Green-Beam Generation by Use of an Intracavity Frequency-Doubled Diode Side-Pumped Q-Switched Nd:YAG Rod Laser

An intracavity frequency-doubled diode side-pumped Nd:YAG laser was developed by use of an advanced cavity configuration and a diffusive close-coupled side-pumping design. A maximum green power of 68 W was generated at a 20-kHz repetition rate with 18.4% optical-to-optical conversion efficiency and 7.1% electrical-to-optical conversion efficiency.     

Preparation of high-temperature filter by pressure-pulsed chemical vapour infiltration of SiC into carbonized paper-fibre preforms

SiC was partially infiltrated into three types of carbonized paper-fibre preforms using pressure-pulsed chemical vapour infiltration from SiCl4(4%)–CH4(4%)–H2 at 1100 °C (A-type preforms, source fibres of filter paper; BH- and BL-type preforms, source fibres of recycled paper). The porosity of the preforms decreased linearly with the number of pulses. After 10 000 pulses, the porosity of A-, BH- and BL-type samples was 77,78 and 85%, respectively. Average pore sizes of A-, BH- and BL-type samples after 10 000 pulses were about 5.0, 2.7 and 7.0 m, respectively. On an A-type sample of 10 mm and 5 mm long after 10 000 pulses, pressure drop along the direction of axial air flow was 10 kPa at a face velocity of 0.8 m s–1. The order of pressure drop was BH,>, A >, BL. Flexural strength of A-type sample reached 10 MPa after 15,000 pulses.     

Edge dispersion of supported MoS2 and WS2 catalysts as evaluated by using Co(CO)3NO as a probe molecule

SiO₂- and Al₂O₃-supported MoS₂ and WS₂ catalysts were prepared to exploit the evaluation technique of the edge dispersion of MoS₂ and WS₂ particles. A chemical vapor deposition (CVD) technique using Co(CO)₃NO as a probe molecule was used for the evaluation. Results were compared with those from conventional techniques such as NO adsorption and TEM. A proportional correlation was obtained between the amount of NO adsorption and the amount of Co atoms accommodated by the CVD technique on WS₂/SiO₂ and WS₂/Al₂O₃ catalysts, demonstrating a selective location of the Co atoms on the edges of WS₂ particles, as previously established for MoS₂ catalysts. A comparison of the amounts of NO adsorption and Co accommodation on MoS₂ and WS₂ catalysts suggested a 70% higher density of sulfur vacancy on MoS₂ particles than on WS₂ particles regardless of the support. The Co atoms on the edges of MoS₂ and WS₂ particles showed the identical NO adsorption property. We propose that Co(CO)₃NO can be used as a probe molecule to evaluate and directly compare the edge dispersions of MoS₂ and WS₂ catalysts. The dispersion of MoS₂ particles was about two times higher than that of WS₂ particles with the SiO₂-supported catalysts. With the Al₂O₃-supported catalysts, MoS₂ and WS₂ particles were dispersed to a similar extent but much more highly dispersed than the counterparts in the SiO₂-supported catalysts. The evaluation of the edge dispersion of MoS₂ and WS₂ particles by means of TEM may pose problems when SiO₂- and Al₂O₃-supported catalysts are compared. The edges of unpromoted MoS₂ particles exhibited a significantly higher intrinsic activity for the HDS of thiophene than those of WS₂ particles.     

Time reversal in polarized neutron decay: the emiT experiment

The standard electro-weak model predicts negligible violation of time-reversal invariance in light quark processes. We report on an experimental test of time-reversal invariance in the beta decay of polarized neutrons as a search for physics beyond the standard model. The emiT collaboration has measured the time-reversal-violating triple-correlation in neutron beta decay between the neutron spin, electron momentum, and neutrino momentum often referred to as the D coefficient. The first run of the experiment produced 14 million events which are currently being analyzed. However, a second run with improved detectors should provide greater statistical precision and reduced systematic uncertainties.     

Performance of the prototype LANL solid deuterium ultra-cold neutron source

A prototype of a solid deuterium (SD₂) source of Ultra-Cold Neutrons (UCN) is currently being tested at LANSCE. The source is contained within an assembly consisting of a 4 K polyethylene moderator surrounded by a 77 K beryllium flux trap in which is embedded a spallation target. Time-of-flight measurements have been made of the cold neutron spectrum emerging directly from the flux trap assembly. A comparison is presented of these measurements with results of Monte Carlo (LAHET/MCNP) calculations of the cold neutron fluxes produced in the prototype assembly by a beam of 800 MeV protons incident on the tungsten target. A UCN detector was coupled to the assembly through a guide system with a critical velocity of 8 m/s (⁵⁸Ni). The rates and time-of-flight data from this detector are compared with calculated values. Measurements of UCN production as a function of SD₂ volume (thickness) are compared with predicted values. The dependence of UCN production on SD₂ temperature and proton beam intensity are also presented.     

Estimation of viable Salmonella cell numbers in meat and meat product using real-time PCR

Recently we developed a novel method for estimating viable Salmonella cell numbers by means of a 5'-nuclease real-time PCR [Fujikawa et al., J. Food Hyg. Japan, 47, 151-156 (2006)]. The method was based on the increase kinetics of the target DNA region (inv A) of the microorganism growing in a culture medium during incubation. The index for the PCR was the threshold cycle. In this study, we validated the method for application in food. Namely, Salmonella cells spiked into ground chicken, pork, and beef and raw hamburger patty at various cell concentrations were cleaned up using buoyant density centrifugation and the Salmonella cell numbers were estimated with our method. Linear decreases in the threshold cycle value were observed during incubation of the samples. The standard curves for the cell number in all food samples were almost identical. With a standard curve using the mean parameter values, we successfully estimated viable Salmonella cell concentrations of the foods. The results indicate that our method is applicable for viable cell number estimation of the target microorganism in foods. Further, we used this method to study Salmonella growth in ground chicken stored at a constant temperature.     

Diode-pumped Nd:YAG laser producing 122-W CW power at 1.319 μm

A high-power diode-pumped Nd:YAG laser oscillating at a wavelength of 1.319 μm is reported. A 122-W CW laser beam with an M2 factor of 35 has been achieved with an optical efficiency of 19.6%. The lasing characteristics, including thermal lensing, at 1.319 μm are compared with those at 1.06 μm. Under lasing conditions, the focal length of thermal lensing at 1.319 μm decreases by 25% and increases by 15% at 1.06 μm with respect to the nonlasing conditions. Based on the experimental results, the heat dissipation in an Nd:YAG rod is discussed with reference to nonradiative transitions from the upper laser level     

Enhancement of Faraday rotation in 3D/Bi:YIG/1D photonic heterostructures

We suggest a new design of magnetophotonic crystals. Microcavity-type magnetic photonic heterostructures exhibiting enhanced magneto-optical Faraday rotation have been fabricated. Such a heterostructure comprises an opal film (3D photonic crystals), a bismuth substituted iron garnet (Bi:YIG) spacer film acting as the defect layer, and a dielectric multilayer (1D photonic crystal). Localized mode was shown to exist in the photonic band gap as a result of resonant interference in heterostructures. The observed enhancement of Faraday rotation was more than three times as compared with that of the Bi:YIG constituent. We have also found that the heterostructures exhibit an unusual polarization-dependent response.     

Novel method for estimating viable Salmonella cell counts using real-time PCR

A novel method for estimating viable Salmonella Enteritidis cell counts with 5'-nuclease real-time PCR was developed in this study. Our method was based on the increase kinetics of the target DNA region (invA) of the microorganism growing in a food/clinical sample in a culture medium during incubation. The index of increase in the target DNA region studied here was threshold cycle, CT. A test Salmonella strain was grown in buffered peptone water at the optimal temperature (39 degrees C). As Salmonella cells were grown, the value of CT decreased with time, generating a downward sigmoidal curve. The slope of the curve was constant at various initial cell concentrations. With higher initial cell concentration, the CT value evaluated from the slope at a given time was lower. With this relationship, a novel method for estimating the initial viable cell concentration of a sample was developed. Dead Salmonella cells or bacteria other than the target cell caused deviation in the CT curve. Incubation in a selective media suppressed the deviation caused by other bacterial cells. We think that this method could be applied to many other microorganisms cultivable in a suitable medium.     

Flavor production from a non-stick oil by moulds

Natural flavor was accidentally produced from rice cake products in Japan. A non-stick oil had been sprayed on the products during the production process. It was found that a Penicillium corylophilum strain, a contaminant of the oil, produced the flavor from the oil. The ingredients of the flavor were four volatile substances, 2-heptanone, 2-nonanone, 2-heptanol, and 2-nonanol. Challenge tests with the mould strain in a rice cake system were performed under various conditions. The volatile substances were produced in the largest amounts at 25 degrees C, followed by 20 or 30 degrees C then 10 degrees C. 2-Heptanone was produced most remarkably at 25 degrees C, followed by 2-nonanone, 2-heptanol, and 2-nonanol. The growth patterns of the mould were similar between 20-30 degrees C, and the growth at 10 degrees C was delayed. The non-stick oil itself had neither flavor nor volatile substance. The flavor was also produced from coconut oil, which was one of the materials of the non-stick oil. No bacteria or yeasts tested produced any flavor from the non-stick oil, whereas most of the moulds tested produced flavor components.