The damped self-interaction

A self-interaction with damped off-diagonal coefficients is used to illustrate techniques for dealing directly with Hamiltonians in strange representations of the CCR.     

Could temporal order differences underlie 2-month-olds' discrimination of English voicing contrasts?

Previous studies have shown that infants discriminate voice onset time (VOT) differences for certain speech contrasts categorically. In addition, investigations of nonspeech processing by infants also yield evidence of categorical discrimination of temporal-order differences. These findings have led some researchers to argue that common auditory mechanisms underlie the infant's discrimination of timing differences in speech and nonspeech contrasts [e.g., Jusczyk et al., J. Acoust. Soc. Am. 67, 262-270 (1980)]. Nevertheless, some discrepancies in the location of the infant's category boundaries for different kinds of contrasts have been noted [e.g., Eilers et al. (1980)]. Because different procedures were used to study the different kinds of contrasts, interpretation of the discrepancies between the studies has been difficult. In the present study, three different continua were examined: [ba]-[pa] stimuli, which differed in VOT; [du]-[tu] stimuli, which differed in VOT but which lacked format transitions; nonspeech formant onset time (FOT) stimuli that varied in the time that lower harmonics increased in amplitude. An experiment with adults indicated a close match between the perceptual boundaries for the three series. Similarly, tests with 2-month-old infants using high amplitude sucking procedure yielded estimates of perceptual category boundaries at between 20 and 40 ms for all three stimulus series.     

The synthesis of bis(benzo-15-crown-5) derivatives and their use in potassium-PVC membrane electrodes

Five new bis(benzo-15-crown-5) derivatives with different connecting groups were synthesized. Potassium ion-selective PVC membrane electrodes based on these bis(crown ether)s were prepared and their selective properties were measured. The results showed that most of these electrodes are stable over a wide pH range and their selectivity coefficients were better than those of an electrode based on natural valinomycin.     

Organometallic ligands : II. The coordination chemistry of 1-[(dimethylamino)-methyl]-2-(diphenylphosphino)ferrocene

Complexes of the organometallic ligand (h⁵-C₅H₅)Fe[(h⁵-C₅H₃)(1-CH₂NMe₂)(2-PPh₂)] (FcCNP) have been prepared with the carbonyls of chromium, molybdenum, tungsten, iron, and cobalt and with borane. With the Group VIB metals, the ligand forms complexes of the type (FcCNP)M(CO)₄ in which the FcCNP ligand is chelating. However, in the case of (FcCNP)Fe(CO)₄ and [(FcCNP)₂Co(CO)₃]BPh₄ the ligand is monodentate, the phosphorus acting as the donor atom. Infrared and NMR data were used to establish the mode of coordination in each case. The electrochemistry of the Group VIB metal carbonyl complexes has been investigated, the chromium complex being of particular interest. The cyclic voltammogram of (FcCNP)Cr(CO)₄ consists of two, reversible, one electron redox waves at E_{peak, anodic} + 0.54 V and + 0.96 V (vs. SCE in CH₂Cl₂), and a third, irreversible wave at E_{peak, anodic} + 1.47 V. At + 0.54 V the solution color changed from yellow to orange and the v(CO) bands shifted from 2011 w, 1891 s, and 1831 s (cm^?1) in the neutral complex to 2080 m, 2000 s, and 1970 s (cm^?1) in the singly oxidized species. At + 0.96 V, the color changed further to blue-green, but no additional shift in v(CO) was observed. On the basis of this information, it is concluded that the first redox wave represents the process Cr⁰ → Cr⁺ and the second wave Fe²⁺ → Fe³⁺. Other aspects of the electrochemistry of the Group VIB metal carbonyl complexes are discussed.