Discrimination and identification of vowels by young, hearing-impaired adults

This study examined the effects of mild-to-moderate sensorineural hearing loss on vowel perception abilities of young, hearing-impaired (YHI) adults. Stimuli were presented at a low conversational level with a flat frequency response (approximately 60 dB SPL), and in two gain conditions: (a) high level gain with a flat frequency response (95 dB SPL), and (b) frequency-specific gain shaped according to each listener's hearing loss (designed to simulate the frequency response provided by a linear hearing aid to an input signal of 60 dB SPL). Listeners discriminated changes in the vowels /I e E inverted-v ae/ when F1 or F2 varied, and later categorized the vowels. YHI listeners performed better in the two gain conditions than in the conversational level condition. Performances in the two gain conditions were similar, suggesting that upward spread of masking was not seen at these signal levels for these tasks. Results were compared with those from a group of elderly, hearing-impaired (EHI) listeners, reported in Coughlin, Kewley-Port, and Humes [J. Acoust. Soc. Am. 104, 3597-3607 (1998)]. Comparisons revealed no significant differences between the EHI and YHI groups, suggesting that hearing impairment, not age, is the primary contributor to decreased vowel perception in these listeners.     

Infrared and Mössbauer studies of some diamine complexes with trimethyltin halides and dimethyltin dihalides

To obtain more structural information on complexes formed between alkyltin halides and bidentate ligands, the solid-state IR and Mössbauer spectra of the 1,2-ethanediamine and 1,4-butanediamine complexes of trimethyltin halides and dimethyltin dihalides were examined. The structures of the trimethyltin halide complexes were found to be trigonal bipyramidal with coplnar methyl groups. The dimethyltin dihalide complexes were octahedral with the methyl groups in the cis-positions and the halides trans to each other. However, there were no differences in the structures of the chloro and bromo complexes of either type.     

An overview of reference materials prepared for standardization of DNA typing procedures

Although DNA typing is an accurate, precise, and robust procedure, quality assurance is enhanced by availability of a suitable reference material. The National Institute of Standards and Technology (NIST) recently released a Standard Reference Material (SRM) that meets the calibration and quality assurance needs of laboratories that perform DNA typing. Each step of the analytical process of DNA typing may be verified by one or more of twenty different components of the SRM. As newer, more sensitive methods for DNA typing have been introduced into the human identification laboratory repertoire, new SRMs will be required for quality assurance. A second SRM for PCR-based tests is under development and soon to be available, is also described.     

A review of the DNA standard reference materials developed by the National Institute of Standards and Technology

The Standard Reference Materials Program at the US National Institute of Standards and Technology (NIST) has three human DNA standard reference materials (SRM 2390, SRM 2391a, and SRM 2392) currently available [1, 2]. Both the DNA profiling SRM 2390 and the polymerase chain reaction (PCR)-based DNA profiling SRM 2391a are intended for use in forensic and paternity identifications, for instructional law enforcement, or for non-clinical research purposes and are not intended for clinical diagnostics. The mitochondrial DNA (mtDNA) SRM 2392 is to provide standardization and quality control when performing PCR and sequencing any segment or the entire 16,569 base pairs that comprise human mitochondrial DNA. SRM 2392 is designed for use by the forensic, medical, and toxicological communities for human identification, disease diagnosis or mutation detection.     

A review of the DNA standard reference materials developed by the National Institute of Standards and Technology

The Standard Reference Materials Program at the US National Institute of Standards and Technology (NIST) has three human DNA standard reference materials (SRM 2390, SRM 2391a, and SRM 2392) currently available¹ (Orders and requests for information concerning these SRMs should be directed to the Standard Reference Materials Program, National Institute of Standards and Technology, 100 Bureau Drive, Stop 2321, Gaithersburg, MD 20899-2321, Telephone (301) 975-6776, FAX: (301) 948-3730.) [1, 2]. Both the DNA profiling SRM 2390 and the polymerase chain reaction (PCR)-based DNA profiling SRM 2391a are intended for use in forensic and paternity identifications, for instructional law enforcement, or for non-clinical research purposes and are not intended for clinical diagnostics. The mitochondrial DNA (mtDNA) SRM 2392 is to provide standardization and quality control when performing PCR and sequencing any segment or the entire 16,569 base pairs that comprise human mitochondrial DNA. SRM 2392 is designed for use by the forensic, medical, and toxicological communities for human identification, disease diagnosis or mutation detection.