Organic composition of C/1999 S4 (LINEAR): a comet formed near Jupiter?

In the current paradigm, Oort cloud comets formed in the giant planets' region of the solar nebula, where temperatures and other conditions varied greatly. The measured compositions of four such comets (Halley, Hyakutake, Hale-Bopp, and Lee) are consistent with formation from interstellar ices in the cold nebular region beyond Uranus. The composition of comet C/1999 S4 (LINEAR) differs greatly, which suggests that its ices condensed from processed nebular gas, probably in the Jupiter-Saturn region. Its unusual organic composition may require reevaluation of the prebiotic organic material delivered to the young Earth by comets.

Strong water isotopic anomalies in the martian atmosphere: probing current and ancient reservoirs.

We measured maps of atmospheric water (H2O) and its deuterated form (HDO) across the martian globe, showing strong isotopic anomalies and a significant high deuterium/hydrogen (D/H) enrichment indicative of great water loss. The maps sample the evolution of sublimation from the north polar cap, revealing that the released water has a representative D/H value enriched by a factor of about 7 relative to Earth's ocean [Vienna standard mean ocean water (VSMOW)]. Certain basins and orographic depressions show even higher enrichment, whereas high-altitude regions show much lower values (1 to 3 VSMOW). Our atmospheric maps indicate that water ice in the polar reservoirs is enriched in deuterium to at least 8 VSMOW, which would mean that early Mars (4.5 billion years ago) had a global equivalent water layer at least 137 meters deep.

Audible pedestrian traffic signals: Part 1. Prevalence and impact.

A collaborative project between the San Diego Association of Governments and San Diego State University (5) evaluated the effectiveness of audible pedestrian traffic signals in aiding visually disabled and elderly persons to walk in their community with greater safety. Three aspects of audible pedestrian traffic signals were investigated: 1) the patterns of use and the impact of these signals on pedestrian traffic safety; 2) the physical characteristics of the sound emitted by the devices; and, 3) the detection of the emitted sounds in the presence of various traffic noise levels. This paper reports on the prevalence and impact of audible traffic signals were ascertained through seeking information from traffic engineers in 71 North American cities; soliciting opinions about these signals from various school officials, social agencies, and volunteer organizations that serve persons with vision impairments; and analyzing pedestrian accident rates at intersections before and after the installation of such signals. The other two aspects of the project are reported in accompanying articles (6,7) that appear in this issue of the Journal of Rehabilitation Research and Development.

Audible pedestrian traffic signals: Part 2. Analysis of sounds emitted.

This project evaluated audible pedestrian traffic signals from three perspectives: 1) the patterns of use and the impact of these signals on pedestrian travel; 2) the physical characteristics of the sound emitted by these devices; and, 3) the detection of their emitted sounds in the presence of various traffic noise levels. This paper, the second of three companion articles (2, 3), examines the sounds emitted by the Nagoya/Traconex audible traffic signal, the unit most commonly found in the western United States and almost exclusively in California. The sounds emitted by the north-south and east-west Traconex audible signals were analyzed for their loudness, directionality, frequency spectrum, and temporal characteristics using standard engineering tools including an anechoic chamber, sound level meters, spectrum analyzers, and signal analyzers.

Audible pedestrian traffic signals: Part 3. Detectability.

This project (10) evaluated audible pedestrian traffic signals (APTS) from three perspectives: 1) the patterns of use and the impact of these signals on pedestrian travel; 2) the physical characteristics of the sound emitted by the Nagoya/Traconex APTS; and, 3) the detectability of the sounds emitted by this brand of APTS. This paper, the last of three companion articles (13,14), describes the detectability of the sounds emitted by the Nagoya/Traconex audible traffic signal, the unit most commonly found in the western United States and almost exclusively in California. To determine detectability, three groups of subjects with normal hearing--young sighted adults (controls), elderly sighted adults, and elderly blind adults--participated in an audiological study. Auditory stimuli, which consisted of APTS sounds embedded in various levels of interfering traffic noise, were presented to subjects seated inside a double-walled sound-treated chamber. The subjects were instructed to press down on a response button as soon as they heard the audible pedestrian traffic signal. The percentage of correct detections determined the absolute detectability of APTS under various S/N ratios. The subjects' speed of response indicated how quickly a pedestrian might begin to cross the intersection upon hearing the APTS.

Equipotentiality of function in dichotic listening.

Listeners who had demonstrated right-ear dichotic listening preference in the first of four listening sessions were randomly assigned to an experimental and control group. Both groups participated in three more dichotic listening sessions. For sessions 2 and 3, left-ear responses were reinforced for the experimental group listeners. There was a significant interaction between groups and sessions. After a drop to equal numbers of right- and left-ear responses in session 2, the control group demonstrated significant right-ear preference in sessions 3 and 4. The responses of the experimental group showed strong left-ear preferences in sessions 2 and 3. Their left-ear gains were preserved in session 4, while their right-ear responses returned to the level demonstrated in session 1. It was concluded that the experimental group had learned to attend to and report left-ear stimuli without loss of right-ear report competence. Within the experimental paradigm, equipotentiality of function has been demonstrated.

Hearing conservation and occupational exposure to noise.

A hearing impairment can have profound psychologic consequences. A major cause of hearing loss is exposure to excessive noise in the workplace. Stricter regulations to protect the hearing of workers became effective this year. A constructive role for the family physician is to educate the patient about the importance of hearing conservation, to reinforce compliance with personal hearing protection measures, and to support appropriate rehabilitative intervention.

Differentiation of types of presbycusis using the masking-level difference.

Masking-level differences in quiet at 500 Hz were used to demonstrate evidence of elevated noise levels within the auditory systems of subjects with assumed neural presbycusis. The following five groups of subjects were evaluated: normal-hearing young and old adults; and older adults with metabolic, sensory, or neural presbycusis. The group with assumed neural presbycusis--that is, bilateral high-frequency sensorineural hearing loss and poor word-recognition performance--had masking-level differences (a) in quiet that were significantly larger than those for the other groups and (b) in noise that were significantly smaller than those for the other groups. The data suggest that elevated internal noise levels accompany neural presbycusis.

Detection and recognition masking-level differences for the individual CID W-1 spondaic words.

The detection and recognition masking-level differences for the 36 individual CID W-1 spondaic words (Technisonic Studios) were established on 36 listeners with normal hearing. The masking for two conditions, SoNo and S pi No, was accomplished with 70-dB-SPL speech-spectrum noise. The word lists were administered in 2-dB decrements with the 36 words presented at each signal-to-noise ratio, which ranged from 9 dB to -19 dB for SoNo and from 3 dB to -25 dB for S pi No. The detection and recognition thresholds determined for each spondaic word under both masking conditions are presented. Additionally, the slopes of the psychometric functions for each word under both conditions are given. The mean masking-level difference (SoNo-S pi No) for the detection-response task was 9.4 dB (SD = .7 dB). The mean masking-level difference for the recognition task was 7.2 dB (SD = 1.4 dB). The recognition masking-level differences for the individual spondaic words ranged from 4.4 dB (stairway) to 10.0 dB (oatmeal). A list of 10 words that had the largest masking-level differences for recognition is suggested to enhance the clinical utility of the masking-level difference for speech.

Sensorineural hearing loss and Kawasaki disease: a prospective study.

PURPOSE: Kawasaki disease (KD) is an acute, self-limited vasculitis of infants and children that is now the most common cause of acquired heart disease in the pediatric age group in the United States and Japan. Reports have documented the association of acute KD with sensorineural hearing loss. To assess the prevalence of hearing loss following acute KD in a geographically and ethnically diverse population, a prospective, multicenter study of hearing loss in patients with KD was conducted. MATERIALS AND METHODS: Patients with acute KD were enrolled in 7 clinical centers and underwent a primary audiologic evaluation within 30 days of the onset of fever. Patients were subsequently reevaluated after resolution of the acute phase of the disease. A questionnaire assessing risk factors for hearing loss was also administered. RESULTS: A total of 62 patients were evaluated during the 29-month study period. At the first audiologic evaluation, 19 patients (30.6%) had sensorineural hearing loss, 6 patients (9.7%) had conductive hearing loss, 17 patients (27.4%) had normal hearing, and 20 patients (32.3%) had inconclusive studies. Overall, 2 of 36 patients (5.5%) had sensorineural hearing loss documented on their second audiologic evaluation. No risk factors for hearing loss were identified by the questionnaire. CONCLUSIONS: Transient sensorineural hearing loss (20 to 35 dB) is a frequent complication of acute KD and may be related to salicylate toxicity in some patients. Persistent sensorineural hearing loss is uncommon. Parents and primary care providers should be made aware of the potential for persistent sensorineural hearing loss following resolution of KD, but routine audiologic screening of this patient population does not appear to be warranted.

Audiologic profiles of children with Kawasaki disease.

Kawasaki disease (KD) is an idiopathic vasculitis associated with systemic inflammation and profound immunoregulatory changes. Recent reports from Japan and the United States have documented the association of sensorineural hearing loss (SNHL) with acute KD. To further characterize the nature and prevalence of this complication, we prospectively evaluated the hearing of 40 consecutive patients with acute KD at a single institution. Standard audiometric procedures were used, including visual reinforcement audiometry and play audiometry. Auditory brainstem response (ABR) testing using clicks and tone pips (1000-4000 Hz) was performed in patients with abnormal or unreliable results on behavioral audiometry. Acoustic immittance measurements were obtained on all patients. Of the 23 males and 17 females (mean age 3.2 +/- 2.3 years, range 0.6-11.1 years), all but three were evaluated and treated with aspirin and intravenous gama globulin within 1 month of onset of fever. Seven children had test results suggesting sensorineural threshold shifts, 16 had normal hearing, and 14 had inconclusive hearing evaluations. Laboratory data in patients with hearing threshold shifts revealed significantly longer duration of fever (4.1 +/- 1.0 versus 1.9 +/- 0.5 days), and a tendency for higher temperatures and white blood cell counts at diagnosis compared to those with normal hearing. Results suggest that transient as well as persistent SNHL may be associated with the acute vasculitis of KD, and may be associated with laboratory markers indicating more severe systemic inflammation. Audiologic screening should be considered for all patients following KD.