The attention filter for tones in noise has the same shape and effective bandwidth in the elderly as it has in young listeners

Listeners asked to detect tones masked by noise hear frequent signals but miss infrequent probes, suggesting that they attend to spectral regions where they expect the signals to occur. The narrow detection pattern centered on the frequent target approximates that obtained in notched noise, indicating that attention is focused on the auditory filter. We measured attention bands in young and elderly listeners (n=5, 4; 20-25 and 62-82 years of age) for targets (800 or 1200 Hz) and infrequent probe signals (target +/-25-100 Hz) masked in wideband noise. We anticipated that their width would increase with age, as has been reported for auditory filters. A yes-no single-interval procedure provided detection probabilities and detection response speeds. Both measures showed near-linear declines with decreasing signal level, and graded decay functions as probe frequency deviated from the target frequency. Probes deviating from the target by 25 to 50 Hz were equivalent to a 2-dB reduction in signal level for both measures. The equivalent rectangular bandwidth (ERB) for detection approximated 11% of the signal frequency for each age group. Confidence intervals (95%) showed that the elderly ERB could be at most only about 20% larger than that of younger listeners.     

Trace element speciation in largemouth bass ( Micropterus salmoides) from a fly ash settling basin by liquid chromatography-ICP-MS

Analytical techniques used to examine the chemical speciation of multiple trace elements are important for the investigation of biological systems. Size exclusion chromatography (SEC) coupled to ICP-MS was used to investigate the speciation of Se, As, Cu, Cd and Zn in tissue extracts from a largemouth bass (Micropterus salmoides) collected from a coal fly ash basin and results were compared to a largemouth bass collected at a reference site. Using a Biosil SEC column, with an effective separation range of 100-7 KDa, Cu, Zn and Cd were shown to be bound to metallothionein (MT) in the liver, gill and, to a lesser extent, gonad tissue extract. In liver, muscle and gill of the ash basin bass, Se was predominantly present as low molecular weight species. Only in the gonad extract was the major fraction of Se associated with high molecular weight species. For the liver and gill extracts, further SEC-ICP-MS on a column with an effective separation range of 7000-500 Da was performed, but Se species still eluted near the total volume of the column suggesting a low molecular weight organic or inorganic species. Ion chromatography (IC)-ICP-MS using an AS7 column and HNO(3) gradient elution indicated that the Se and As species in the liver and gill extracts had similar retention times but these retention times did not correspond to retention times for As(III), As(V), dimethylarsenate, arsenobetaine, Se(IV), Se(VI), seleno-methionine, or seleno-cystine.     

Confinement of nonneutral plasmas on magnetic surfaces

The confinement of a nonneutral plasma in a magnetic-surface, or stellarator, configuration is explored. The fluid equilibrium equations are derived and are found to be fundamentally different from previous results. Diocotron modes are predicted to be stable. The collisional confinement time can be very long. Possible applications include positron trapping and confinement of positron-electron plasmas. The basic physics can be addressed experimentally in the simple tabletop stellarator planned for construction at Columbia University.     

Dynamical precursor of nematic order in a dense fluid of hard ellipsoids of revolution

We investigate hard ellipsoids of revolution in a parameter regime where no long range nematic order is present but already finite-size domains are formed which show orientational order. Domain formation leads to a substantial slowing down of a collective rotational mode which separates well from the usual microscopic frequency regime. A dynamic coupling of this particular mode into all other modes provides a general mechanism which explains an excess peak in spectra of molecular fluids. Using molecular dynamics simulation on up to 4096 particles and on solving the molecular mode coupling equation we investigate dynamic properties of the peak and prove its orientational origin. Received 19 September 2001 and Received in final form 19 March 2002     

An Initial-Value Problem for Fully Three-Dimensional Inflectional Boundary Layer flows

In a recent paper the present authors considered the effects of small cross-flow upon the nonlinear evolution of two oblique waves of unequal amplitude. The present analysis extends this work in two ways: (i) the cross-flow is increased to O(1) making it of comparable magnitude to the streamwise component and (ii) by taking the long-wavelength limit of Rayleigh's equation a whole spectrum of wave numbers can now be catered for. Thus (ii) allows a fairly general initial disturbance to be accommodated. Another significant effect due to the presence of a whole spectrum of wave numbers is that the critical layer jump is now forced by a quadratic, as opposed to the usual cubic, nonlinearity. Numerical solutions of the new nonlinear amplitude evolution equation are presented for a special class of initial disturbance. Received 7 January 1998 and accepted 15 September 1998     

Amidrazones V. thermolysis of N1-benzyl-substituted amidrazone ylides

Thermolysis of 1,1-dimethyl-1-benzyl-2-(iminophenylmethyl)hydrazinium hydroxide inner salt gave dimethylamine, 2,4,6-triphenyl-s-triazine and 2,4,6-triphenyl-1,2-dihydro-s-triazine.     

Auger electron spectroscopy study of 18/8 stainless steel oxidation

Auger electron spectra have been recorded for Cr, Mn and Fe from both clean and oxidised surfaces. Changes in the low energy MVV transitions of these elements were observed on oxidation and these effects have been used to characterise the surface oxidation product on an 18/8 stainless steel.