Recent work suggests that hair cells are not the most vulnerable elements in the inner ear; rather, it is the synapses between hair cells and cochlear nerve terminals that degenerate first in the aging or noise-exposed ear. This primary neural degeneration does not affect hearing thresholds, but likely contributes to problems understanding speech in difficult listening environments, and may be important in the generation of tinnitus and/or hyperacusis. To look for signs of cochlear synaptopathy in humans, we recruited college students and divided them into low-risk and high-risk groups based on self-report of noise exposure and use of hearing protection. Cochlear function was assessed by otoacoustic emissions and click-evoked electrocochleography; hearing was assessed by behavioral audiometry and word recognition with or without noise or time compression and reverberation. Both groups had normal thresholds at standard audiometric frequencies, however, the high-risk group showed significant threshold elevation at high frequencies (10–16 kHz), consistent with early stages of noise damage. Electrocochleography showed a significant difference in the ratio between the waveform peaks generated by hair cells (Summating Potential; SP) vs. cochlear neurons (Action Potential; AP), i.e. the SP/AP ratio, consistent with selective neural loss. The high-risk group also showed significantly poorer performance on word recognition in noise or with time compression and reverberation, and reported heightened reactions to sound consistent with hyperacusis. These results suggest that the SP/AP ratio may be useful in the diagnosis of “hidden hearing loss” and that, as suggested by animal models, the noise-induced loss of cochlear nerve synapses leads to deficits in hearing abilities in difficult listening situations, despite the presence of normal thresholds at standard audiometric frequencies.

Self-healing materials are of fundamental interest and practical importance. Herein we report the synthesis of a new class of self-healing materials, formed by the copolymerization of ethylene and anisyl-substituted propylenes using a sterically demanding half-sandwich scandium catalyst. The copolymerization proceeded in a controlled fashion, affording unique multi-block copolymers composed of relatively long alternating ethylene-alt-anisylpropylene sequences and short ethylene–ethylene units. By controlling the molecular weight and varying the anisyl substituents, a series of copolymers that show a wide range of glass-transition temperatures (T g) and mechanical properties have been obtained. The copolymers with T g below room temperature showed high elastic modulus, high toughness, and remarkable self-healability, being able to autonomously self-heal upon mechanical damage not only in a dry environment but also in water and aqueous acid and alkaline solutions, while those with T g around or above room temperature exhibited excellent shape-memory property. The unique mechanical properties may be ascribed to the phase separation of the crystalline ethylene–ethylene nanodomains from the ethylene-alt-anisylpropylene matrix.

The preparation and characterization of several zinc and magnesium complexes bearing chiral aminophenolate ligands, [(S)-or (R)-L]ZnN(SiMe 3 ) 2 (1, 2), [(S)-or (R)-L]ZnO t Bu (3, 4) and [(S)-or (R)-L]MgN(SiMe 3 ) 2 (5, 6) ((S)-or (R)-L = (S)-or (R)-2-{N-benzyl-N-[(1-n butyl-2-pyrrolidinyl)methyl]}aminomethyl-4-methyl-6-tritylphenolate), have been reported. While the X-ray diffraction studies as well as the NMR spectroscopic data revealed that zinc and magnesium silylamido complexes possess similar structures both in the solid state and in solution, their catalytic performance toward rac-LA polymerization exhibited significant difference. The replacement of zinc center by magnesium realized an interesting stereoselectivity switch from isoselective (P m = 0.80) to heteroselective (P r = 0.81). The reactions of enantiopure zinc complexes 1 and 2 with (S)-methyl lactate or (R)-tert-butyl lactate resulted in the target lactate complexes 7−9 as a mixture of two diastereomers, but in different ratios. Two typical zinc lactate isomers 8α and 9β/9β′ were isolated and further characterized by the X-ray diffraction method to have pentacoordinated geometry where the coordination of lactate carbonyl group displays some hemilabile nature. The molecular structures of 8α and 9β/9β′ indicated that the specific configuration of lactate moiety in combination with the aminophenolate ligand of given chirality would favor the formation of one of the two diastereomers in each case. Based on the structures of zinc lactate model complexes and the active propagating species, as well as the preferential enchainment of one specific lactide monomer in the polymerization, a cooperation of enantiomorphic-site control and chain-end control mechanisms involving three types of active species was proposed for the formation of stereoblock PLAs from rac-LA by zinc initiators. Results of apparent rate constants for rac-, D-, and L-LA polymerizations by magnesium initiators are consistent with a chain-end control mechanism. The 13 C NMR spectra of magnesium lactate complexes proved that the bonding of carbonyl group to magnesium center is stronger than that in zinc active species. The coordination number of magnesium species can expand easily to six in the presence of coordinative molecules, suggesting that the heteroselective magnesium active species have a hexacoordinated core structure. The difference of coordination geometry between zinc and magnesium active species should be responsible for the stereoselectivity switch in the polymerization of rac-LA.

An enantiopure zinc complex supported by an aminophenolate ligand with multiple stereogenic centers has been diastereoselectively synthesized via the variation of the ortho-substituent of a phenoxy moiety and the N-alkyl group of a chiral pyrrolidinyl ring in the ligand framework, which displays high isoselectivity in the polymerization of rac-lactide.

Hypothesis-The goal of this study was to create a three-dimensional model of the anatomy of the hook region to identify the optimal site for cochleostomy in cochlear implant surgery.Background-The anatomy of the hook region is complex, and spatial relationships can be difficult to evaluate using two-dimensional histological slides or cadaveric temporal bones.