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Biomedical subjects

B Munson

Publications and source records attributed to B Munson.

13 recordsLinked to original sources
PubMed2001

Phonological pattern frequency and speech production in adults and children.

Recent studies have suggested that both adults and children are sensitive to information about phonological pattern frequency; however, the influence of phonological pattern frequency on speech production has not been studied extensively. The current study examined the effect of phonological pattern frequency on the fluency and flexibility of speech production. Normal- and fast- rate nonsense-word repetitions of three groups of participants (preschool children, school-aged children, and adults) were analyzed. Subjective ratings of the wordlikeness of nonsense words, percentage phonemes correctly repeated, mean duration, and durational variability were measured. In the first experiment, ratings of the wordlikeness of nonsense words were found to correlate with the pattern frequency of sequences embedded in them. In the second analysis, it was found that children, but not adults, repeated infrequent sequences of phonemes less accurately than frequent sequences. In the third experiment, infrequent sequences were produced with longer durations than frequent ones, with children demonstrating a larger difference between frequent and infrequent sequences than adults. Phonological pattern frequency also influenced variability in duration: infrequent sequences of sounds were more variable than frequent ones. Thus, there appears to be an influence of phonological pattern frequency on speech, and, for some measures, a larger effect size is noted for children.

Adult↗
PubMed2001

Is processing speed related to severity of language impairment?

Children with specific language impairment (SLI) typically respond more slowly on many tasks than do their typically developing peers. This paper addresses the question of whether speed of response is linearly related to severity of language impairment as measured by standardized test score. To address this question, we performed post hoc analyses of data from a study on lexical processing involving 66 children with SLI (mean age 6 years 9 months) and 66 typically developing children matched for age and nonverbal IQ. Response times derived from a series of tasks were correlated with language test scores. None of the Pearson correlations reached significance when corrected for number of correlations run, nor did a canonical correlation analysis reach significance. If these results are replicated in other studies, then they suggest that there is no direct linear relation between speed of processing and severity of language impairment as it is estimated from scores on standardized tests of language.

Child↗
PubMed2000

The use of deuterium oxide as a mobile phase for structural elucidation by HPLC/UV/ESI/MS

The use of deuterium oxide as a mobile phase in the routine analysis of pharmaceutical compounds was investigated. The deuterium exchange of labile hydrogen atoms aids in structural confirmation and elucidation of unknown impurities and degradation products. Although deuterium oxide as a mobile phase does in some cases change the retention times, the changes in retention times do not interfere with the analysis. A study of the high-performance liquid chromatography system shows that equilibration times for the deuterium-containing mobile phases are similar to equilibration times with changes of other mobile phases. The use of this technique in the analysis of pharmaceutical compounds and other small molecules is presented.

Journal Article↗
PubMed2000

Proton affinities of saturated aliphatic methyl esters

The kinetic method was used to determine the proton affinities of methyl esters of several saturated fatty acids. Decompositions of the proton-bound dimers of the methyl esters, AHB+, were observed under different conditions with two instruments. The proton affinities (PAs) of the methyl esters increase continually with increasing carbon number in the acid. Equilibrium and initial rate experiments were performed with a Fourier transform ion cyclotron resonance mass spectrometer on the methyl ester of the C22 saturated acid (methyl behenate). These experiments give values for PA (methyl behenate) that are perhaps slightly lower than those obtained with the kinetic method. The PAs of the methyl esters of the fatty acids could be correlated with the equation: PA (ester) = (40.0 +/- 2.5)*log(n) + (784.7 +/- 3.9) kJ/mol or PA (ester) = (864 +/- 2) - (479 +/- 41)/n, where n = number of atoms in the molecule. Proton affinities of smaller sets of 1-alkylamines and 1-alkanols can be fit to similar equations.

Journal Article↗
PubMed1999

Effects of mobile-phase additives, solution pH, ionization constant, and analyte concentration on the sensitivities and electrospray ionization mass spectra of nucleoside antiviral agents.

The effects of various mobile-phase additives, solution pH, pKa, and analyte concentration on electrospray ionization mass spectra of a series of purine and pyrimidine nucleoside antiviral agents were studied in both positive and negative ion models. The use of 1% acetic acid resulted in good HPLC separation and the greatest sensitivity for [M + H]+ ions. In the negative ion mode, 50 mM ammonium hydroxide gave the greatest sensitivity for [M - H]- ions. The sensitivities as [M + H]+ ions were significantly larger than the sensitivities as [M - H]- ions for purine antiviral agents. Vidarabine monophosphate and pyrimidine antiviral agents, however, showed comparable or greater sensitivities as [M - H]- ions. The sensitivity as [M + H]+ showed no systematic variation with pH; however, the sensitivity as [M - H]- did increase with increasing pH. At constant pH, the ion intensity of the protonated species increased with increasing pKa. At higher analyte concentrations, dimer (M2H+) and trimer (M3H+) ions were observed. [M + Na]+ adducts were the dominant ions with 0.5 mM sodium salts for these compounds. The spectra of the more basic purine antiviral agents showed no [M + NH4]+ adduct ions, but [M + NH4]+ ions were the major peaks in the spectra of the less basic pyrimidine antiviral agents with ammonium salts. The ammonium adduct ion was formed preferentially when the proton affinity of the analyte was close to that of NH3. Abundant [M + OAc]- ions were observed for all of the antiviral agents except vidarabine monophosphate from solutions with added HOAc, NaOAc, and NH4OAc. The utility of mobile phases containing 1% HOAc or 50 mM NH4OH was demonstrated for chromatographic separations.

Antiviral Agents↗
PubMed1997

Are speech perception deficits associated with developmental dyslexia?

Phonological awareness and phoneme identification tasks were administered to dyslexic children and both chronological age (CA) and reading-level (RL) comparison groups. Dyslexic children showed less sharply defined categorical perception of a bath-path continuum varying voice onset time when compared to the CA but not the RL group. The dyslexic children were divided into two subgroups based on phoneme awareness. Dyslexics with low phonemic awareness made poorer /b/-/p/ distinctions than both CA and RL groups, but dyslexics with normal phonemic awareness did not. Examination of individual profiles revealed that the majority of subjects in each group exhibited normal categorical perception. However, 7 of 25 dyslexics had abnormal identification functions, compared to 1 subject in the CA group and 3 in the RL group. The results suggest that some dyslexic children have a perceptual deficit that may interfere with processing of phonological information. Speech perception difficulties may also be partially related to reading experience.

Child↗
PubMed1980

Inhibition of purified wheat germ DNA dependent RNA polymerase by pyran copolymer.

The inhibition of DNA and RNA polymerases in vitro by pyran copolymer has been shown to be related to its affinity for divalent cations. The present investigation was designed to explore further the nature of this inhibition using completely purified eukaryotic RNA polymerase II from wheat germ. Inhibition was determined as a function of divalent ion concentration and, as previously seen with less pure enzyme preparation, was greatest at low (Mn2+) and least at higher concentrations. No inhibition was observed at concentrations greater than 4.8 mM MgCl2 in the presence of 10 micrograms pyran/mL. The inhibition by pyran copolymer was exerted immediately unlike other polyanions, such as heparin and polynucleotides. This indicates that it stops RNA chain growth immediately as do known chelators of divalent cations. The size of pyran copolymer was shown to affect the extent of inhibition when different sized polymers were fractionated from a heterogenous single lot. However, when sized fractions were obtained from different lots we could not show a size-dependent inhibition. Although the mechanisms by which pyran copolymer exerts its biological effect is unknown, it may well be related to its association with cations. The inhibition of enzymes requiring these cations appears to be a sensitive method of observing such an association.

DNA-Directed RNA Polymerases↗