Search PubMed⌕ Search

Biomedical subjects

D Byrne

Publications and source records attributed to D Byrne.

At least 55 records · Page 3Linked to original sources
PubMed1996

Relationship of aided speech recognition to hearing thresholds and aided speech-peak sensation levels in severely and profoundly hearing-impaired adults.

The relationship of speech recognition to hearing threshold levels and to aided speech-peak sensation levels was examined in a group of severely and profoundly hearing-impaired adults. Closed-set vowel and consonant recognition tests were administered at the subjects' most comfortable levels. Both vowel and consonant recognition scores were relatively predictable from hearing threshold level at 2000 Hz, the correlations being -.84 and -.76, respectively. Recognition of most speech-feature contrasts was also predictable from hearing threshold levels, at one or two frequencies, always including 2000 Hz. The predictability of speech recognition was similar, but no better, from aided speech-peak sensation levels than from hearing threshold levels. Vowel and consonant scores were similar to or better than those reported in previous studies, possibly reflecting subject selection factors and/or extensive testing that was used to optimize hearing aid fittings. For the majority of subjects, altering the low-frequency response of the hearing aid did not significantly affect vowel or consonant recognition scores.

Adult↗
PubMed1996

Hearing aid selection for the 1990s: where to?

This paper discusses trends and issues in selecting amplification for new, mainly nonlinear, types of hearing aids. Some-concerns are that nonvalidated prescription formulae may proliferate; that, through concentration on loudness normalization, alternative rationales are not being evaluated; and that most new fitting procedures for nonlinear hearing aids ignore the findings of research with linear amplification. A possible philosophical concern is that the hearing aid fitter may lose control of the fitting process. The achieving of any particular loudness relationship, among different frequency components of amplified speech, may be unimportant in itself but may be critical for achieving other objectives such as maximizing audibility over a wide frequency range when speech is at a comfortable level. Amplification selection should seek to achieve objectives by the simplest means (linear frequency shaping, automatic volume control) and should proceed to more complex, but potentially detrimental, processing (syllabic compression) only to the extent necessary. New prescriptive procedures should build on established procedures because, for typical speech levels, amplification requirements should be similar, regardless of whether linear or nonlinear amplification is used.

Hearing Aids↗
PubMed1996

Guidelines for fitting multiple memory hearing aids.

Fitting guidelines to determine candidacy for multiple memory hearing aids and the choice of amplification for each memory are devised by reviewing studies on the selection of amplification for different listening conditions. The guideline for determining candidacy comprises three factors: (1) difficulty hearing in acoustically diverse conditions, (2) an average high-frequency hearing loss greater than about 55 dB HL, and (3) ability to vary the low-frequency gain by at least 5 dB. People who meet all three criteria are highly likely to benefit from multiple memories. People who meet criteria 1 and 2 or 1 and 3 are possible candidates. The guideline for determining the amplification characteristics needed for each memory also enables the fitter to determine the number of memories needed. The following recommendations for amplification characteristic for various listening conditions are based on the literature review: linear amplification with the prescribed National Acoustic Laboratories' (NAL) frequency response is recommended for listening to speech in quiet; substantial high-frequency compression is recommended for ease of understanding two voices that differed by 10 dB in overall level; a linear response steeper than the NAL response is recommended for ease of understanding speech in a low-frequency background noise; low-frequency compression is recommended to reduce annoyance of low-frequency background noise; and a linear response flatter than the NAL response is recommended for listening in high-frequency background noise, and possibly for listening to music.

Equipment Design↗
PubMed1995

Comparison of serum CA 72-4 and CA 19-9 levels in gastric cancer patients and correlation with recurrence.

BACKGROUND: This longitudinal prospective study evaluates the serum levels of the tumor markers CA 72-4 and CA 19-9, alone or in combination, in gastric cancer patients. PATIENTS AND METHODS: Serum tumor markers CA 72-4 and CA 19-9 were measured in 52 patients who had gastric adenocarcinomas and 32 with benign gastric disorders. Serial measurements of these markers were carried out in 30 cancer patients at a median follow-up time of 38 months. RESULTS: CA 72-4 and CA 19-9 had sensitivities of 42% and 46% for the preoperative detection of gastric cancer. Sensitivity for the two combined was 63%. CA 72-4 provided 100% specificity, compared to 72% for CA 19-9. Postoperatively, 17 cancer patients remained disease-free. Sixteen of these maintained normal levels of CA 72-4, and 10 of CA 19-9. Thirteen patients developed recurrent disease. In 9, serum CA 72-4 levels rose from near-normal after surgery and reached diagnostic values approximately 6 months before clinical diagnosis of recurrence. Only 3 patients exhibited such a pattern with CA 19-9. CONCLUSIONS: CA 72-4 is a reliable marker in gastric cancer. Postoperative serial sampling of CA 72-4 may facilitate early identification of recurrences.

Adenocarcinoma↗
PubMed1995

Effects of groove placement on retention/resistance of maxillary anterior resin-bonded retainers.

Debonding of resin-bonded fixed partial dentures has been partly resolved with modification of tooth preparations. Tooth preparations for resin-bonded retainers were completed on a maxillary central incisor, a lateral incisor, and a canine. Fifteen metal replicas were constructed (five of each tooth morphotype). The three tooth morphotypes were then modified with proximal grooves prepared parallel to the long axes, and another 15 metal replicas were prepared. Cast metal retainers were constructed and cemented to the replicas with a resin cement. Tensile shearing dislodging loads were applied at 20 degrees to the long axes of the teeth with a testing machine. The addition of proximal grooves made statistically significant differences in resistance to debonding forces for all three tooth morphotypes (p < 0.01). An increase of 76.7% was seen in dislodging forces for lateral incisors with proximal grooves compared with incisors without grooves.

Cuspid↗
PubMed1995

Candidates for multiple frequency response characteristics.

This study examined what types of subjects may benefit from the use of multiple memory hearing aids that offer variation in their frequency response characteristics. Thirty subjects with varied degrees and configurations of hearing loss compared an individually prescribed frequency response (NAL) and two variations in which the real-ear response slope was either increased (more high-frequency emphasis) or decreased by about 3 dB/octave over the range from 500 Hz to 4000 Hz. The evaluations consisted of paired comparison judgments of pleasantness and of ease of understanding speech, in quiet and in three background noises with substantially different acoustic spectra (traffic noise, speech babble, and high-frequency noise). Twelve of the 30 subjects selected different frequency responses for different background noises and/or for different response criteria. These subjects were characterized as having the more severe high-frequency hearing losses (averaged across 2000, 3000, and 4000 Hz). They also tended to be those for whom the three frequency responses provided the greatest variation in real-ear low-frequency gain. (Despite substantial electronic variations, some subjects received only small variations in real-ear gain at the low frequencies). When subjects chose a different response for different conditions, they tended to prefer responses for which the slope was negatively related to the spectrum of the stimulus. This was true for both response criteria. The conclusion is that hearing aid users with substantial high-frequency losses, and who can be fitted with sufficient variation in the low-frequency real-ear gain, have the potential to benefit from having a choice of frequency response characteristics.

Adolescent↗
PubMed1995

Consonant perception with linear and compression amplification.

The consonant perception of 15 subjects with mild to moderate sensorineural hearing loss was evaluated using linear amplification and two different types of compression amplification. A specially modified hearing aid was used which allowed for variation of the amplifier input/output function in three steps, such that the compression ratio could be set to 1 (linear), 1.3 or 1.8. The Nonsense Syllable Test (NST) was recorded through the aid in quiet and in two different noise conditions (four-talker babble and a background noise with sharp intermittent sounds), and replayed to the listeners through headphones. No differences in consonant perception were found between the different types of amplification in the quiet condition. In the babble condition, consonant perception was significantly better with linear amplification than with either form of compression. In the sharp noise condition, there was no difference in performance between linear amplification and compression amplification with the ratio of 1.8. Consonant perception was adversely affected, however, by the compression and amplification with the ratio of 1.3 in this condition. Overall NST results and results for particular classes of consonants are discussed.

Adult↗
PubMed1995

Disabilities and handicaps associated with impaired auditory localization.

A questionnaire on (1) difficulties in everyday sound localization (localization disabilities), (2) limitations and disadvantages related to such disabilities (localization handicaps), and (3) everyday speech hearing disabilities was completed by 104 people with symmetrical hearing losses. Respondents considered situations when listening with and without their usual hearing aid fittings. The hearing-impaired group rated their unaided localization ability as significantly poorer than a sample with no reported hearing loss, particularly discrimination of distance. Only slight limitations on everyday activity due to localization disability were found, but disadvantage was reported in the form of experiences of confusion of sounds, of resultant loss of concentration, and of a wish to escape settings where this occurred. There was a moderate correlation between localization and speech hearing, even when hearing level was controlled for. Aided listening, whether with one or with two hearing aids, was reported as enabling significant improvements in both functions.

Adult↗
PubMed1994

Novel algorithms for searching conformational space.

The modelling of biological molecules by molecular dynamics is beset by a range of problems. The most important of these is the multiple-minima problem. The deep metastable minima can cause difficulties in proper equilibration of a molecular system and result in the simulated system being trapped in a long-lived metastable state. One way to overcome these problems is to re-engineer the 'Newtonian Rules' in order to more efficiently search conformational space. Re-engineering of the 'Newtonian Rules' implies a redesign of the physical laws arising from them. This is done in various ways by the RUSH, Hybrid Monte Carlo and PEACS algorithms. This paper explores applications of these algorithms, and compares them to a traditional molecular dynamics method.

Alanine↗
PubMed1994

Evaluation of ultrasound as a tool in the follow-up of patients with breast implants: a preliminary, prospective study.

We prospectively reviewed clinical findings in 93 patients with 154 silicone breast implants (SBIs), as well as ultrasound findings in 57 patients with 94 SBIs. Ultrasound findings of implant wall redundancy, combined with abnormal silicone echogenicity, correlated well with predicted and surgically confirmed SBI rupture. Age-related implant findings (i.e., length of time since implant placement) included capsular contracture, a variety of abnormal ultrasound findings, subjective reports of joint pain or fatigue, and a greater probability of rupture. Prospective screening of otherwise satisfied patients with SBIs raises concerns about the need for removal when satisfactory alternatives for maintaining breast size are limited. The ability to predict impending rupture will increase this dilemma.

Adult↗
PubMed1994

Effects on sound localization of configuration and type of hearing impairment.

Localization ability of 87 bilaterally hearing-impaired listeners was tested in the horizontal and vertical planes, frontally and laterally. In those with sensorineural hearing loss, it was found that deficits in localization accuracy in different regions of auditory space could be related to different configurations of hearing loss. For example, there were associations between vertical plane discrimination and high-frequency sensitivity; and front-rear discrimination and mid-to-high-frequency sensitivity. These results agree with theoretical expectations, while the outcome overall contrasts with previous reports that localization performance is unrelated to audiometric configuration. A comparison of 13 listeners with conductive/mixed types of impairment with a sensorineural-loss group, matched for degree of loss, showed that a conductive component adds significantly to localization disturbance, particularly in the horizontal plane. The probable reason is a disturbance of low-frequency interaural time cues, and this occurs because a higher proportion of low-frequency sound is likely to be transmitted via bone conduction relative to air conduction. Correlations between hearing loss and localization are only moderate, suggesting that aspects of hearing impairment, in addition to simple attenuation, may also reduce auditory localization performance.

Adult↗
PubMed1994

Sustained cellular immune responses to Borrelia burgdorferi: lack of correlation with clinical presentation and serology.

Fifty-one patients with erythema migrans were followed up prospectively with serial clinical evaluations, serologic determinations for antiborrelial antibodies, and lymphocyte stimulation responses to Borrelia burgdorferi antigens to determine (i) the factors associated with sustained cellular immune responses and (ii) whether lymphocyte stimulation is a good indicator of prior exposure to B. burgdorferi in patients treated early after erythema migrans. Positive lymphocyte stimulation responses ( > 2 standard deviations above normal control values) were found in 15 (29%) of 51 patients 3 months after treatment for erythema migrans and in 8 (18%) of 44 patients 1 year posttreatment. Heightened lymphocyte responses were not associated with the number or duration of erythema migrans lesions prior to treatment, the mean size of the largest erythema migrans lesion, or the number of symptoms at the time of presentation. The development of Jarisch-Herxheimer reaction, choice of antibiotic, and clinical outcome also were not associated with a positive lymphoproliferation assay result. Changes in the lymphocyte stimulation indices between the two time points assessed (3 months and 1 year posttreatment) also did not correlate with the above variables. When serologic results and lymphoproliferative responses were evaluated as categorical or continuous variables, there were no correlations between values. One year after treatment for early Lyme disease, lymphocyte reactivity is not a good indicator of prior infection with B. burgdorferi.

Adult↗
PubMed1992

Fetal nuchal translucency: ultrasound screening for chromosomal defects in first trimester of pregnancy.

OBJECTIVE: To examine the significance of fetal nuchal translucency at 10-14 weeks' gestation in the prediction of abnormal fetal karyotype. DESIGN: Prospective screening study. SETTING: The Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London. SUBJECTS: 827 fetuses undergoing first trimester karyotyping by amniocentesis or chorionic villus sampling. MAIN OUTCOME MEASURE: Incidence of chromosomal defects. RESULTS: The incidence of chromosomal defects was 3% (28 of 827 cases). In the 51 (6%) fetuses with nuchal translucency 3-8 mm thick the incidence of chromosomal defects was 35% (18 cases). In contrast, only 10 of the remaining 776 (1%) fetuses were chromosomally abnormal. CONCLUSION: Fetal nuchal translucency > or = 3 mm is a useful first trimester marker for fetal chromosomal abnormalities.

Adult↗