Consequences of cochlear damage for the detection of interaural phase differences

Thresholds for detecting interaural phase differences (IPDs) in sinusoidally amplitude-modulated pure tones were measured in seven normal-hearing listeners and nine listeners with bilaterally symmetric hearing losses of cochlear origin. The IPDs were imposed either on the carrier signal alone-not the amplitude modulation-or vice versa. The carrier frequency was 250, 500, or 1000 Hz, the modulation frequency 20 or 50 Hz, and the sound pressure level was fixed at 75 dB. A three-interval two-alternative forced choice paradigm was used. For each type of IPD (carrier or modulation), thresholds were on average higher for the hearing-impaired than for the normal listeners. However, the impaired listeners' detection deficit was markedly larger for carrier IPDs than for modulation IPDs. This was not predictable from the effect of hearing loss on the sensation level of the stimuli since, for normal listeners, large reductions of sensation level appeared to be more deleterious to the detection of modulation IPDs than to the detection of carrier IPDs. The results support the idea that one consequence of cochlear damage is a deterioration in the perceptual sensitivity to the temporal fine structure of sounds.     

Microviscoelastic moduli of biomimetic cell envelopes

Bioanalogue models of composite cell envelopes were designed by electrostatically driven self-assembly of actin shells inside giant vesicles. Viscoelastic relaxation moduli were measured between 0.03 and 20 s as a function of actin density by magnetic bead microrheometry. The shear relaxation spectra exhibited by the composite shells compare well with those of natural cell envelopes and bulk entangled actin networks. Absolute value of the shear modulus was measured for the first time by deformation field mapping. Shear and bending moduli agree well with values obtained by bead fluctuations analysis.     

Electrical control of hole spin relaxation in charge tunable InAs/GaAs quantum dots

We report on optical orientation of singly charged excitons (trions) in charge-tunable self-assembled InAs/GaAs quantum dots. When the charge varies from 0 to -2, the trion photoluminescence of a single quantum dot shows up and under quasiresonant excitation gets progressively polarized from zero to approximately 100%. This behavior is interpreted as the electric control of the trion thermalization process, which subsequently acts on the hole-spin relaxation driven in nanosecond time scale by the anisotropic electron-hole exchange. This is supported by the excitation spectroscopy and time-resolved measurements of a quantum dot ensemble.     

Experimental investigation of amplitude and phase quantum correlations in a type II optical parametric oscillator above threshold: from nondegenerate to degenerate operation

We describe a stable type II optical parametric oscillator operated above threshold that provides 9.7 +/- 0.5 dB (89%) of quantum noise reduction on the intensity difference of the signal and idler modes. We also report the first experimental study, to our knowledge, by homodyne detection of the generated bright two-mode state in the case of frequency-degenerate operation obtained by the introduction of a birefringent plate inside an optical cavity.     

Equilateral Dimension of the Rectilinear Space

Itis conjectured that there exist at most 2k equidistantpoints in the k-dimensional rectilinear space.This conjecture has been verified for k ≤ 3; we show here its validity in dimension k = 4. We alsodiscuss a number of related questions. For instance, what isthe maximum number of equidistant points lying in the hyperplane: $\sum\nolimits_{i = 1}^k {x_i } = 0?$ If this number would be equal to k, then the above conjecture would follow. Weshow, however, that this number is ≥ k + 1 for k ≥ 4.     

Selective alkylation of a 6,7-dihydroxyquinazoline

A convenient 3-step multi-parallel process for the preparation of 4-(3-chloro-2-fluoroanilino)-6,7-bisalkoxyquinazolines is highlighted.     

Structure of the bromination product of 2-ethyl-1,4-benzothiazin-3(4H)-one

2-Ethyl-1,4-benzothiazin-3(4H)-one and bromine react smoothly to give Z-2-(1-bromoethylidine)-2(H)-1,4-benzothiazin-3(4H)-one, which results from a complex bromination-oxidation sequence. The structure of this product was determined by an X-ray study.