Hydration of soda-lime glass

The hydration of soda-lime glass is studied using resonant nuclear reactions to measure the hydrogen and sodium profiles of hydrated glasses. The rate of growth of the surface layer of hydrated glass is initially proportional to the square root of time as is characteristic of diffusion controlled processes. After longer exposure a steady-state hydration profile is observed, which indicates that in addition to the diffusion controlled reaction there is a slow etching of the glass surface. The measured hydration profiles are discussed in relationship to the Doremus model of interdiffusing ions, which is found to be in good agreement with the data. This model is also discussed in relationship to measured hydration profiles of vacuum heated samples of hydrated glass.     

Random replicators with high-order interactions

We use tools of the equilibrium statistical mechanics of disordered systems to study analytically the statistical properties of an ecosystem composed of N species interacting via random mutual interactions, as well as via deterministic self-interactions of order p>/=2. We show that the main effect of increasing the order of the interactions among the species is to make the system less competitive, in the sense that the fraction of extinct species is greatly reduced. In addition, we find that for p>2 there is a threshold value which gives a lower bound to the concentration of the surviving species, preventing then the existence of rare species and, consequently, increasing the robustness of the ecosystem to external perturbations.     

Effects of crystallographic ordering on the magnetic behaviour of (AgIn)1-zMn2zTe2 and (CuIn)1-zMn2zTe2 alloys

Measurements of magnetic susceptibility in the temperature range 4.2–300 K were made on polycrystalline samples of the (AgIn)_{1 - z}Mn_2zTe₂ and (CuIn)_{1 - z}Mn_2zTe₂ alloys, and the data used to give values of spin-glass transition te mperature T_g and Curie-Weiss paramagnetic temperature θ. For any sample for which the X-ray powder photograph indicated an apparently single phase condition, either zinc-blende or chalcopyrite, the susceptibility data could show up to three separate T_g values. These different magnetic conditions are attributed to crystallographic ordering of the Mn ions on the chalcopyrite and zinc-blende lattices, the three observed T_g values corresponding to disordered zinc-blende, ordered zinc-blende and ordered chalcopyrite. The value of θ obtained from the 1/χ vs. T plot is shown to be a weighted mean of the separate values of θ for the phases present. The relative sizes of the T_g peaks and the values of θ for any given sample gives an indication of the amount of each phase present. These amounts were varied by using different methods of heat treatment and it was shown that the magnetic behaviour was consistent with the T(z) phase diagram for the two alloy systems.     

Adaptive environment classification system for hearing aids

An adaptive sound classification framework is proposed for hearing aid applications. The long-term goal is to develop fully trainable instruments in which both the acoustical environments encountered in daily life and the hearing aid settings preferred by the user in each environmental class could be learned. Two adaptive classifiers are described, one based on minimum distance clustering and one on Bayesian classification. Through unsupervised learning, the adaptive systems allow classes to split or merge based on changes in the ongoing acoustical environments. Performance was evaluated using real-world sounds from a wide range of acoustical environments. The systems were first initialized using two classes, speech and noise, followed by a testing period when a third class, music, was introduced. Both systems were successful in detecting the presence of an additional class and estimating its underlying parameters, reaching a testing accuracy close to the target rates obtained from best-case scenarios derived from non-adaptive supervised versions of the classifiers (about 3% lower performance). The adaptive Bayesian classifier resulted in a 4% higher overall accuracy upon splitting adaptation than the minimum distance classifier. Merging accuracy was found to be the same in the two systems and within 1%-2% of the best-case supervised versions.     

Magnetic susceptibility,transport and Mössbauer measurements in CuFeSe2

The study of the magnetic, transport and Mössbauer properties of eskebornite, CuFeSe₂, shows significant differences from that of its homologous sulfide, chalcopyrite (CuFeS₂). From room temperature down to 77 K, CuFeSe₂ is paramagnetic and metallic with a non-magnetic Mössbauer spectrum showing two equally populated sites for iron with very small quadrupole splitting. It seems clear that the electronic state of iron has evolved in going from chalcopyrite to eskebornite, in which it has a very weak magnetism.     

Evidence for the existence of two electronic states in the chalcopyrite-type alloys CuFe(S1−zSez)2

Results of Mössbauer spectroscopy for the chalcopyrite-type of alloys CuFe(S_1–z Se _z )₂ in the range of composition 0z0.45 are presented. Room temperature spectra show two contributions: one is a magnetic spectrum (six lines) with a value of the hyperfine field near to that of chalcopyrite (z=0, in which an antiferromagnetic order occurs belowT=823 K), the other having only one line. The relative area of the single-line contribution increases asz increases. Forz=0.2, we also made Mössbauer measurements as a function of temperature. The ratio of the two contributions evolves according to a Boltzmann law, in which the single line corresponds to the excited state at 81 K above the antiferromagnetic ground state.     

Theoretical prediction of the hydrogen-bond basicity pK(HB)

Ab initio and DFT calculations on around 65 hydrogen bond or Lewis bases and their complexes with hydrogen fluoride have been performed, and a range of calculated properties from both free bases and complexes correlated with pK(HB), an experimental scale of hydrogen-bond basicity. For the entire range of bases, we found that the hydrogen-bond binding Gibbs free energy computed at the B3LYP/6-31+G(d,p) level of theory linearly correlated with pK(HB). Further improvements in the correlation and prediction of pK(HB) were possible with a non-linear fit by considering the hydrogen bonding Gibbs free energy of another possible stereoisomeric 1:1 complex and/or that of a linear 2:1 complex, which included a second hydrogen fluoride.     

Maturation of auditory temporal integration and inhibition assessed with event-related potentials (ERPs)

Background

We examined development of auditory temporal integration and inhibition by assessing electrophysiological responses to tone pairs separated by interstimulus intervals (ISIs) of 25, 50, 100, 200, 400, and 800 ms in 28 children aged 7 to 9 years, and 15 adults.

Results

In adults a distinct neural response was elicited to tones presented at ISIs of 25 ms or longer, whereas in children this was only seen in response to tones presented at ISIs above 100 ms. In adults, late N1 amplitude was larger for the second tone of the tone pair when separated by ISIs as short as 100 ms, consistent with the perceptual integration of successive stimuli within the temporal window of integration. In contrast, children showed enhanced negativity only when tone pairs were separated by ISIs of 200 ms. In children, the amplitude of the P1 component was attenuated at ISIs below 200 ms, consistent with a refractory process.

Conclusions

These results indicate that adults integrate sequential auditory information into smaller temporal segments than children. These results suggest that there are marked maturational changes from childhood to adulthood in the perceptual processes underpinning the grouping of incoming auditory sensory information, and that electrophysiological measures provide a sensitive, non-invasive method allowing further examination of these changes.     

An Exploration of Skin Acceleration Level as a Measure of Phonatory Function in Singing

Two kinds of fluctuations are observed in phonetogram recordings of singing. Sound pressure level (SPL) can vary due to vibrato and also due to the effect of open and closed vowels. Since vowel variation is mostly a consequence of vocal tract modification and is not directly related to phonatory function, it could be helpful to suppress such variation when studying phonation. Skin acceleration level (SAL), measured at the jugular notch and on the sternum, might be less influenced by effects of the vocal tract. It is explored in this study as an alternative measure to SPL. Five female singers sang vowel series on selected pitches and in different tasks. Recorded data were used to investigate two null hypotheses: (1) SPL and SAL are equally influenced by vowel variation and (2) SPL and SAL are equally correlated to subglottal pressure (P(S)). Interestingly, the vowel variation effect was small in both SPL and SAL. Furthermore, in comparison to SPL, SAL correlated weakly to P(S). SAL exhibited practically no dependence on fundamental frequency, rather, its major determinant was the musical dynamic. This results in a non-sloping, square-like phonetogram contour. These outcomes show that SAL potentially can facilitate phonetographic analysis of the singing voice.