A 980-nm band laser diode pump source with a detuned wavelength of1000 nm for praseodymium-doped fiber amplifiers

By using practical high-power 980-nm band laser diodes, efficient direct pumping for a praseodymium-doped fiber amplifier (PDFA) is achieved. The lasing wavelength is detuned from 980 to 1000 nm by selective optical feedback from a fiber grating     

Integration of Computer Assisted Learning in Teaching and Learning in Secondary Schools in Kenya

The purpose of this study was to establish factors that lead to poor integration of Information and communication technology （ICT） for teaching and learning in schools in Kenya, despite comprehensive policy, institutional, infrastructural frameworks and capacity building by the Ministry of Education. The subject of this study was administered by use of questionnaires in three categories of public schools： national school, provincial schools and district schools. The respondents were students from each level that is from one, two, three and four and teachers based on the most offered subjects in the secondary schools. The computer assisted learning facilities were classified into computers, internet and content in optical media. In national school Internet based research, optical media content provided by Kenya Institute of Curriculum Development and Cyber School program for science subjects was used in learning. In provincial school, it lacks adequate computers, reliable Internet and content in optical media. In district school, it lacks adequate computer, no internet connection and content in optical media. A learner management system which can be accessed by all learners by use of any internet access devices like mobile phone access will be an ideal tool with over 4,000,000 mobile phone subscribers currently in Kenya.     

Velocity vector profile measurement using multiple ultrasonic transducers

This paper proposes a new technique that enables the measurement of the velocity vector in multi-dimensions on a line of the flow field. A system to achieve this goal was developed based on the ultrasonic velocity profiling by using multiple transducers. A two-dimensional system was constructed and successfully applied to an actual flow field for two-dimensional velocity vector measurements. To estimate the influence of the existence of a wall, acoustic field under the developed system was calculated by solving two-dimensional wave equation and then the focal point of an ultrasonic beam was determined to optimize the system. The system was applied to measure the two-directional velocity components of a periodic velocity fluctuation in the wake of a cylinder as an example of unsteady flow. Temporal variation of velocity vector profiles well represent the velocity fluctuation, and vorticity distribution, which is obtained from the spatial distribution of velocity vector, well represents the vertical motion in the wake.     

Chemical and irradiation treatments for killing Escherichia coli O157:H7 on alfalfa,radish, and mung bean seeds

In this study, the effectiveness of dry-heat treatment in combination with chemical treatments (electrolyzed oxidizing [EO] water, califresh-S, 200 ppm of active chlorinated water) with and without sonication in eliminating Escherichia coli O157:H7 on laboratory-inoculated alfalfa, radish, and mung bean seeds was compared with that of dry-heat treatment in combination with irradiation treatment. The treatment of mung bean seeds with EO water in combination with sonication followed by a rinse with sterile distilled water resulted in reductions of approximately 4.0 log10 CFU of E. coli O157:H7 per g. whereas reductions of ca. 1.52 and 2.64 log10 CFU/g were obtained for radish and alfalfa seeds. The maximum reduction (3.70 log10 CFU/g) for mung bean seeds was achieved by treatment with califresh-S and chlorinated water (200 ppm) in combination with sonication and a rinse. The combination of dry heat, hot EO water treatment, and sonication was able to eliminate pathogen populations on mung bean seeds but was unable to eliminate the pathogen on radish and alfalfa seeds. Other chemical treatments used were effective in greatly reducing pathogen populations on radish and alfalfa seeds without compromising the quality of the sprouts, but these treatments did not result in the elimination of pathogens from radish and alfalfa seeds. Moreover, a combination of dry-heat and irradiation treatments was effective in eliminating E. coli O157:H7 on laboratory-inoculated alfalfa, radish, and mung bean seeds. An irradiation dose of 2.0 kGy in combination with dry heat eliminated E. coli O157:H7 completely from alfalfa and mung bean seeds, whereas a 2.5-kGy dose of irradiation was required to eliminate the pathogen completely from radish seeds. Dry heat in combination with irradiation doses of up to 2.0 kGy did not unacceptably decrease the germination percentage for alfalfa seeds or the length of alfalfa sprouts but did decrease the lengths of radish and mung bean sprouts.     

Investigation of Microwave Absorption of Surface-State Electrons on Liquid 3He

We report on the experimental study of the resonance microwave absorption of surface-state electrons (SSE) on liquid ³He. The absorption is detected as a variation of the microwave power passing through the experimental cell, or as a resonance-induced change in the electron conductivity. In the latter method a decrease of the conductivity is observed, which points out on the possibility of substantial heating of the electrons by the absorbed microwave power. In a vapor-atom scattering regime the temperature dependence of the linewidth agrees well with the theoretical model, and the absolute value of the measured linewidth is about twice larger than the theoretical one. At very high microwave power the side band absorption peaks are observed.     

Inhibition of growth of Escherichia coli O157:H7 in fresh radish (Raphanus sativus L.) sprout production by calcinated calcium

The inhibitory effect of calcinated calcium on the growth of Escherichia coli O157:H7 during fresh radish (Raphanus sativus L.) sprout production was studied. It was revealed that the addition of 0.4% (wt/vol) calcinated calcium into radish sprouting medium which was artificially contaminated with E. coli O157:H7 (3.0 to 3.2 log CFU/ml) completely inhibited the growth or inactivated the microorganism. When radish seed extract was used instead of radish sprout production, the same extent of growth inhibition or inactivation was observed with much lower amounts (0.07%) of calcinated calcium under similar experimental conditions. The findings suggested that calcinated calcium may be useful to control E. coli O157:H7 contamination during the production of radish sprouts.     

Simultaneous particulate design of primary and agglomerated crystals of steroid by spherical agglomeration in liquid for dry powder inhalation

Spherical agglomerates of steroid KSR-592, consisting of fine primary drug crystals suitable for dry powder inhalation (DPI), were prepared by the spherical agglomeration method in liquid with a bridging liquid. It was found that the particle size of primary crystals increased until the dispersing medium was saturated with the bridging liquid, whereas the spherical agglomeration of primary crystals was continued even after the saturation of medium with the bridging liquid. The growth rates of primary crystals and agglomerates increased with an increase in the temperature and/or a reduction in the agitation speed of the system. The agglomerates were easily disintegrated into the primary crystals depositing ideally on carrier lactose particles for DPI by mixing. The in vitro efficiency of the mixed system of lactose and disintegrated primary crystals of drug was 2 to 3 times higher than that of crystals prepared conventionally. Furthermore, the soft agglomerates disintegrated easily into respirable particles in air stream when emitted from the inhalation device were prepared by reducing the agitation speed after the dispersing medium was saturated with the bridging liquid.     

Brief review of oxidation kinetics of copper at 350 °C to 1050 °C

Copper’s oxication mechanism and purity effects were elucidated by oxidizing 99.99 pct (4N), 99.9999 pct (6N), and floating zone refined (>99.9999 pct) specimens in 0.1 MPa oxygen at 350 °C to 1050 °C. Throughout the temperature range, the oxidation kinetics for all specimens obeys the parabolic oxidation rate law. The Cu₂O scale grows predominantly, and the rate-determining step is concluded to be outward diffusion of copper atoms in Cu₂O. The activation energy at high temperatures, where the lattice diffusion predominates, is 173 kJ/mol, but it becomes lower at intermediate temperatures and even lower at low temperatures because of the contribution of the grain boundary diffusion. At high temperatures, oxidation kinetics is almost uninfluenced by purity, but the lattice-diffusion temperature range is wider for higher-purity copper. At intermediate temperatures, copper oxidation is enhanced because trace impurities can impede growth of Cu₂O grains to facilitate grain boundary diffusion. At low temperatures, grain boundary diffusion is possibly hindered by impurities segregated at grain boundaries.     

Effect of iron purity on oxidation kinetics at 600 °C to 900 °C

The effect of iron purity on oxidation kinetics was examined at 600 °C to 900 °C under oxygen pressure of 0.1 MPa using a commercial electrolytically purified iron (ET-Fe, 99.9 wt pct) and a solvent extraction and anion-exchange refined iron (AE-Fe, >99.999 wt pct). ET-Fe oxidizes slower than AE-Fe. Oxidation of AE-Fe follows the parabolic oxidation rate law, but a downward deviation from the parabolic relationship was observed for ET-Fe. Analysis shows that the difference between AE-Fe and ET-Fe is attributable to a concentrated impurity layer at the FeO/Fe interface and to dissolution of copper, silicon, nitrogen, and carbon dissolved in FeO for ET-Fe.