Spectral beam combining of 2 μm Tm fiber laser systems

Output beams from three independently frequency-stabilized thulium master-oscillator power-amplifier fiber laser systems were spectrally combined using a plane-ruled metal diffraction grating. Two laser channels were frequency-stabilized with guided mode resonance filters and the third was stabilized using a plane-ruled metal diffraction grating. The systems had output wavelengths between 1984 and 2015 nm, each with a spectral width of 100-450 pm and output powers between 40-120 W. The combined beam had powers up to 49 W and was 32% efficient with respect to the launched pump power.     

Qualitative Identification of an Unknown Pesticide Using GC-MS and Online Resources

A senior-level instrumental analysis experiment is described in which students examine fruit for pesticide residues. This experiment involves fundamental instruction in sample preparation, the use of gas chromatography (GC) to resolve and deduce important components of a commercial pesticide preparation by matching against a certified standard, and unambiguous identification of the active pesticide by using mass spectrometry in conjunction with public data available on the Internet.     

Amorphous BeN as a new solid host for rare‐earth‐related luminescent materials

Beryllium‐nitride (BeN) thin films were prepared by sputtering a Be target in an atmosphere of pure nitrogen. The films were doped with samarium simply by placing a piece of Sm metal on the surface of the Be target. Under these deposition conditions the films present an amorphous structure and an optical bandgap of approx. 4 eV. They also exhibit visible light emission due to Sm³⁺ ions as a result of either photon or electron excitation. The present experimental results show that amorphous BeN films are suitable, and efficient, III‐nitride hosts for rare‐earth doping purposes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Speaking rate of adventitiously deaf male cochlear implant candidates

No objective group data on speaking rate or speaking duration have been reported on the speech of adventitiously profoundly hearing-impaired adults. Results of the present study showed that speaking rate, i.e., number of syllables per second, was significantly slower and speaking duration was significantly longer for 25 adventitiously profoundly hearing-impaired adult male cochlear implant candidates than for 10 normal-hearing control subjects. The factors of length of time since onset of profound hearing loss and hearing aid use did not significantly affect speaking rate. Based on these objective data, a rationale and method are presented for aural rehabilitation of the profoundly hearing-impaired who exhibit speaking rate abnormalities.     

Effects of bleaching on the sensitivity to dose of the infrared-stimulated luminescence of potassium-rich feldspars from Ynyslas, Wales

Reduction of the luminescence signal to a residual level before irradiation is an inherent part of the regeneration method of equivalent dose (ED) determination, but is likely to lead to changes in the sensitivity of the dosimeter. Sensitivity changes caused by different methods of reduction of the infrared- stimulated luminescence (IRSL) signal have been investigated by subjecting potassium-rich feldspars extracted from modern dune sand from Ynyslas, on the Dyfi Estuary in Wales, to repeated cycles of removal of the luminescence signal and beta irradiation. The methods used to remove the signal were exposure to natural sunlight, a solar simulator and infrared-emitting diodes with a wavelength of 880Δ 80 nm and heating to 450°C.     

Comparative extreme ultraviolet emission measurements for lithium and tin laser plasmas

Detailed spectroscopic studies on extreme UV emission from laser plasmas using tin and lithium planar solid targets were completed. At 13.5 nm, the best conversion efficiency (CE) for lithium was found to be 2.2% at intensities near 7 x 10(10) W/cm(2). The highest CE measured for tin was near 5.0% at an intensity close to 1 x 10(11) W/cm(2).     

Freezing-off in disc cavities

A semi-quantitative analysis is presented of freezing-off in a disc cavity during the injection moulding of thermoplastics. A criterion is obtained which enables the occurrence of freezing-off to be predicted, at least crudely. The form of the criterion is found to depend on the direction of flow (radially outward or inward) in the disc.