Postlingual deaf speech and the role of audition in speech production: comments on Waldstein's paper [R.S. Waldstein, J. Acoust. Soc. Am. 88, 2099-2114 (1990)

Using acoustic analysis techniques, Waldstein [J. Acoust. Soc. Am. 88, 2099-2114 (1990] reported abnormal speech findings in postlingual deaf speakers. She interpreted her findings to suggest that auditory feedback is important in motor speech control. However, it is argued here that Waldstein's interpretation may be unwarranted without addressing the possibility of neurologic deficits (e.g., dysarthria) as confounding (or even primary) causes of the abnormal speech in her subjects.     

Radiation-induced dehalogenation of 1,1,1,2 tetrachloroethane and 1,1,2 trichloro-1 bromoethane reactions of 1,1,2 trichloroethyl radicals

The kinetics of the radiation-induced free radical chain reactions in solutions of CCl₃CClH₂ and CCl₂BrCH₂Cl in cyclohexane (RH) were studied in the temperature range of 90–225°C. 1,1,2 trichloroethyl and 1,1,1,2 tetrachloroethyl radicals were produced by the reaction of radiolytically generated cyclohexyl (R) radicals with solutes. The reactions studied were The following rate expressins were obtained: where θ = 2.303RT in kcal/mole. From the activation parameters of the k₄/k₅ rate constant ratio and the assumption that E₄ = E, E₅ was calculated to be 20.2 ± 0.2 kcal/mole. The Arrhenius parameters for the Cl atom elimination reaction from chloroethyl radicals derived from liquid and gas-phase studies are compared.     

Polymeric Carbon Nitride with Chirality Inherited from Supramolecular Assemblies

The facile synthesis of chiral materials is of paramount importance for various applications. Supramolecular preorganization of monomers for thermal polymerization has been proven as an effective tool to synthesize carbon and carbon nitride-based (CN) materials with ordered morphology and controlled properties. However, the transfer of an intrinsic chemical property, such as chirality from supramolecular assemblies to the final material after thermal condensation, was not shown. Here, we report the large-scale synthesis of chiral CN materials capable of enantioselective recognition. To achieve this, we designed supramolecular assemblies with a chiral center that remains intact at elevated temperatures. The optimized chiral CN demonstrates an enantiomeric preference of ca. 14 %; CN electrodes were also prepared and show stereoselective interactions with enantiomeric probes in electrochemical measurements. By adding chirality to the properties transferrable from monomers to the final product of a thermal polymerization, this study confirms the potential of using supramolecular precursors to produce carbon and CN materials and electrodes with designed chemical properties.     

Irrepresentability of short semilattices by euclidean subspaces

A semilatticeS isrepresentable by subspaces of R ^k if, to eachx S we can assign a subspace so thatx y=z inS if and only if . Every height-2 semilattice is representable inR ². We show that for everyk there is a height-3 semilattice which is not representable by subspaces ofR ^k.Presented by J. Berman.Research supported in part by the National Science Foundation.Research supported in part by the Office of Naval Research.