Proton polarization transfer in natural abundance 15N NMR studies of E- and Z-isomers of N-alkylformamides

Proton polarization transfer has been used for the convenient observation of proton coupled natural abundance ¹⁵N NMR spectra of the E- and Z-isomers of N-methylformamide at 10.14 MHz. Second-order spectral analysis is required to determine the ¹⁵N? H coupling constants, at least for the E-isomer of secondary formamides. An useful stereospecificity is observed for both the one- and two-bond ¹⁵N? H coupling constants.     

Cancellation of Simulated Environmental Noise as a Tool for Measuring Vocal Performance During Noise Exposure

It can be difficult for the voice clinician to observe or measure how a patient uses his voice in a noisy environment. We consider here a novel method for obtaining this information in the laboratory. Worksite noise and filtered white noise were reproduced over high-fidelity loudspeakers. In this noise, 11 subjects read an instructional text of 1.5 to 2 minutes duration, as if addressing a group of people. Using channel estimation techniques, the site noise was suppressed from the recording, and the voice signal alone was recovered. The attainable noise rejection is limited only by the precision of the experimental setup, which includes the need for the subject to remain still so as not to perturb the estimated acoustic channel. This feasibility study, with 7 female and 4 male subjects, showed that small displacements of the speaker's body, even breathing, impose a practical limit on the attainable noise rejection. The noise rejection was typically 30 dB and maximally 40 dB down over the entire voice spectrum. Recordings thus processed were clean enough to permit voice analysis with the long-time average spectrum and the computerized phonetogram. The effects of site noise on voice sound pressure level, fundamental frequency, long-term average spectrum centroid, phonetogram area, and phonation time were much as expected, but with some interesting differences between females and males.     

Rearrangement reactions of 2-nitrothiobenzamides upon electron impact

The decomposing molecular cations derived from (substituted) 2-nitrothiobenzamides fragment by complex rearrangement reactions. When the alkyl substituents (R) attached to N are methyl, the major fragmentations are [M]⁺˙ → [M? SO]^+˙ and [M? SO]^+˙ → [(M? SO)^+˙–R˙]⁺. This remains a basic pathway when R ? Et, but other rearrangements are also observed. For example, when R=Et, additional competitive processes are [M]^+˙ → [M? HO˙]⁺ and [M]^+˙ → [M? C₂H₄O]⁺˙.     

Enzyme catalysed hydrolysis of dialkylated propanedioic acid diesters,chain length dependent reversal of enantioselectivity

Enzyme catalysed hydrolyses of dialkylated propanedioic acid diesters have been studied. A novel change of enantioselectivity from pro-$\text{S}$ to pro-$\text{R}$ in the hydrolysis of ester groups was observed, depending on the chain length of the alkyl substituents of the substrate. Optically pure ($\text{S}$)-(-)-α-methylphenylalanine was prepared by α-chymotrypsin catalysed hydrolysis of benzylmethylpropanedioic acid dimethyl ester.     

Loud Speech in Realistic Environmental Noise: Phonetogram Data, Perceptual Voice Quality, Subjective Ratings, and Gender Differences in Healthy Speakers

A new method for cancelling background noise from running speech was used to study voice production during realistic environmental noise exposure. Normal subjects, 12 women and 11 men, read a text in five conditions: quiet, soft continuous noise (75 dBA to 70 dBA), day-care babble (74 dBA), disco (87 dBA), and loud continuous noise (78 dBA to 85 dBA). The noise was presented over loudspeakers and then removed from the recordings in an off-line processing operation. The voice signals were analyzed acoustically with an automatic phonetograph and perceptually by four expert listeners. Subjective data were collected after each vocal loading task. The perceptual parameters press, instability, and roughness increased significantly as an effect of speaking loudly over noise, whereas vocal fry decreased. Having to make oneself heard over noise resulted in higher SPL and F0, as expected, and in higher phonation time. The total reading time was slightly longer in continuous noise than in intermittent noise. The women had 4 dB lower voice SPL overall and increased their phonation time more in noise than did the men. Subjectively, women reported less success making themselves heard and higher effort. The results support the contention that female voices are more vulnerable to vocal loading in background noise.     

On tensor products of Banach lattices

Using techniques from harmonic analysis (more specifically Varopoulos' theory of tensor algebras) we study some tensor products of Banach lattices. Our main result is that if the Banach latticeB satisfies a certain additional property, the Gillespie factorization property, then a natural quotient of the spaceB^B is anL ^l-space, and we identify the kernel of this quotient map.