Recognition of filtered words in noise at higher-than-normal levels: decreases in scores with and without increases in masking

To examine spectral effects on declines in speech recognition in noise at high levels, word recognition for 18 young adults with normal hearing was assessed for low-pass-filtered speech and speech-shaped maskers or high-pass-filtered speech and speech-shaped maskers at three speech levels (70, 77, and 84 dB SPL) for each of three signal-to-noise ratios (+8, +3, and -2 dB). An additional low-level noise produced equivalent masked thresholds for all subjects. Pure-tone thresholds were measured in quiet and in all maskers. If word recognition was determined entirely by signal-to-noise ratio, and was independent of signal levels and the spectral content of speech and maskers, scores should remain constant with increasing level for both low- and high-frequency speech and maskers. Recognition of low-frequency speech in low-frequency maskers and high-frequency speech in high-frequency maskers decreased significantly with increasing speech level when signal-to-noise ratio was held constant. For low-frequency speech and speech-shaped maskers, the decline was attributed to nonlinear growth of masking which reduced the "effective" signal-to-noise ratio at high levels, similar to previous results for broadband speech and speech-shaped maskers. Masking growth and reduced "effective" signal-to-noise ratio accounted for some but not all the decline in recognition of high-frequency speech in high-frequency maskers.     

Acetylation of aromatic ethers using acetic anhydride over solid acid catalysts in a solvent-free system. Scope of the reaction for substituted ethers

The acetylation of aryl ethers using acetic anhydride in the presence of zeolites under modest conditions in a solvent-free system gave the corresponding para-acetylated products in high yields. The zeolite can be recovered, regenerated and reused to give almost the same yield as that given when fresh zeolite is used.     

On the hydration of the phosphocholine headgroup in aqueous solution

The hydration of the phosphocholine headgroup in 1,2-dipropionyl-sn-glycero-3-phosphocholine (C(3)-PC) in solution has been determined by using neutron diffraction enhanced with isotopic substitution in combination with computer simulation techniques. The atomic scale hydration structure around this head group shows that both the -N(CH(3))(3) and -CH(2) portions of the choline headgroup are strongly associated with water, through a unique hydrogen bonding regime, where specifically a hydrogen bond from the C-H group to water and a strong association between the water oxygen and N(+) atom in solution have both been observed. In addition, both PO(4) oxygens (P=O) and C=O oxygens are oversaturated when compared to bulk water in that the average number of hydrogen bonds from water to both X=O oxygens is about 2.5 for each group. That water binds strongly to the glycerol groups and is suggestive that water may bind to these groups when phosophotidylcholine is embedded in a membrane bilayer.     

A new multidimensional integral relationship between heat flux and temperature for direct internal assessment of heat flux

This paper derives a new integral relationship between heat flux and temperature in a transient, two-dimensional heat conducting half space. A unified mathematical treatment is proposed that is extendable to higher-dimensional and finite-region geometries. The analytic expression provides the local heat flux perpendicular to the front surface solely based on an embedded line of temperature sensors parallel to the surface. The relationship does not require apriori knowledge of the surface boundary condition. A new sensor strategy is analytically conceived based on the integral relationship for estimating the local, in-depth heat flux without surface instrumentation. It should further be clarified that the integral relationship requires only knowledge of the local, in-depth temperature and heating/cooling rate (time rate of change of temperature). The resulting formulation is mildly ill-posed and either requires digital filtering of the temperature signal to remove high frequency components of noise or the development of direct heating/cooling rate sensors. This paper (a) develops the new mathematical relationship; (b) demonstrates that the proposed relationship reduces to well-known (i) one-dimensional results under the appropriate assumptions; and, (ii) two-dimensional surface results; and, (c) provides a simple numerical example validating the concept.     

Autoradiographische Untersuchungen zur Vermisechung von Baustoffkomponenten

Die Feinverteilung des Kalkes im Kalk-Quarzsand-Gemisch ist eine notwendige Bedingung fur hohe erreichbare Festigkeit der Silikatbaustoffe. Vergleiehende Untersuchungen über die Kalkverteilung an neutronenaktivierten feinkörnigen Baustoffproben mit Hilfe von Szintillationsmessungen des ⁴⁷Ca-Gehaltes und mittels autoradiographischer Darstellung der Kalkverteilung in kleinen Prüfkörpern unter Ausnützung der relativ weichen β-Strahlung des ⁴⁵Ca ergaben, daβ die autoradiographischen Aussagen über die Homogenität der Proben am besten mit den Festigkeitsiwerten der Prüfkörper korrespondieren.     

High pressure fast-flow technique for gas phase kinetics studies

A fast-flow technique suitable for measuring elementary rate constants over a wide range of pressures has been developed. The method operates under turbulent flow conditions, in contrast to laminar flow which characterizes the conventional low pressure technique. Flow visualization, velocity profile measurements, and tracer pulse studies have been carried out in a flow tube reactor to investigate the dynamics of both laminar and turbulent flow for chemical kinetics purposes. Furthermore, the wall collision frequency for the reactants has been determined: at the higher pressures it is greatly reduced in comparison with the frequency characteristic of the conventional low pressure laminar flow technique. Also, to test and validate the technique the bimolecular rate constants for the reactions H+Cl₂ and H+O₃ have been measured at total pressures in the 3–300 torr range; at pressures below 5 torr, as well as above 50 torr in the turbulent flow regime the agreement with the recommended literature values is excellent. © 1993 John Wiley & Sons, Inc.     

Molecular dynamics simulations of the interfacial and structural properties of dimethyldodecylamine-N-oxide micelles

A series of large-scale atomistic molecular dynamics simulations were conducted to study the structural and interfacial properties of nonionic dimethyldodecylamine-N-oxide (DDAO) micelles with an aggregation number of 104 in pure water, which was determined using small-angle neutron scattering (SANS). From these simulations, the micelles were found to be generally ellipsoidal in shape with axial ratios of ～1.3-1.4, which agrees well with that found from small-angle neutron scattering measurements. The resulting micelles have an area per DDAO molecule of 94.8 ?(2) and an average number of hydration water molecules per DDAO molecule of ～8. The effect of the encapsulation of ethyl butyrate (CH(3)(CH(2))(2)COOCH(2)CH(3), C(4)) and ethyl caprylate (CH(3)(CH(2))(6)COOCH(2)CH(3), C(8)) on the structural and interfacial properties of the nonionic DDAO aggregates was also examined. In the presence of the C(4) oil molecules, the aggregates were found to be less ellipsoidal and more spherical than the pure DDAO micelles, while the aggregates in the presence of the C(8) oil molecules were almost perfect spheres. In addition, the C(4) oil molecules move into the core of the aggregates, while the C(8) oil molecules stay in the headgroup region of the aggregates. Finally, the structural properties of two micelles formed from different starting states (a "preassembled" sphere and individual DDAO molecules distributing in water) were found to be nearly identical.     

Novel and efficient copper-catalysed synthesis of nitrogen-linked medium-ring biaryls

Herein, a new copper-catalysed strategy for the synthesis of rare nitrogen-linked seven-, eight- and nine-membered biaryl ring systems is described. It is proposed that the reaction proceeds through a highly activated intramolecularly co-ordinated copper catalyst. The process is technically simple, proceeds under relatively mild conditions, displays a broad substrate scope and forms biologically valuable products that are difficult to synthesise by other methods. We envisage that this methodology will prove useful in a wide synthetic context, with possible applications in both target-oriented and diversity-oriented synthesis.     

On the stability of a domain-wall brane model

We establish stability and nonstability results for a domain-wall brane model arising in classical field theory. In particular, we show the nonexistence of nontrivial bounded solutions on the real line for a coupled pair of parameter dependent linear second order ordinary differential equations for an open set of those parameters. Moreover, we establish the existence of nontrivial solutions for a hypersurface of the parameters. We use Fredholm theory for compact linear operators combined with the Lyapunov-Schmidt method to prove our results. The model is stable, respectively unstable, for those parameters for which the coupled system does not, respectively does, have nontrivial solutions.