An experimental and computational study of the hydrodynamics of high-velocity water microdrops for interproximal tooth cleaning.

The flow field and local hydrodynamics of high-velocity water microdrops impacting the interproximal (IP) space of typodont teeth were studied experimentally and computationally. Fourteen-day old Streptococcus mutans biofilms in the IP space were treated by a prototype AirFloss delivering 115 µL of water at a maximum exit-velocity of 60 ms(-1) in a 33-ms burst. Using high-speed imaging, footage was generated showing the details of the burst, and demonstrating the removal mechanism of the biofilms. Footage was also generated to characterize the viscoelastic behavior of the biofilms when impacted by an air-only burst, which was compared to the water burst. Image analysis demonstrated the importance of fluid forces on the removal pattern of interdental biofilms. X-ray micro-Computed Tomography (µ-CT) was used to obtain 3D images of the typodont and the IP spaces. Computational Fluid Dynamics (CFD) simulations were performed to study the effect of changing the nozzle position and design on the hydrodynamics within the IP space. Results confirmed our previous data regarding the wall shear stress generated by high-velocity water drops which dictated the efficacy of biofilm detachment. Finally, we showed how CFD models could be used to optimize water drop or burst design towards a more effective biofilm removal performance.

Fluorescence microscopy techniques for quantitative evaluation of organic biocide distribution in antifouling paint coatings: application to model antifouling coatings.

A test matrix of antifouling (AF) coatings including pMMA, an erodible binder and a novel trityl copolymer incorporating Cu2O and a furan derivative (FD) natural product, were subjected to pontoon immersion and accelerated rotor tests. Fluorescence and optical microscopy techniques were applied to these coatings for quantification of organic biocide and pigment distribution. Total leaching of the biocide from the novel copolymer binder was observed within 6 months of rotor immersion, compared to 35% from the pMMA coating. In pontoon immersions, 61% of the additive was lost from the pMMA coating, and 53% from the erodible binder. Profiles of FD content in the binders revealed an accelerated loss of additive from the surface of the CDP resulting from rosin degradation, compared to even depletion from pMMA. In all samples, release of the biocide was inhibited beyond the Cu2O front, corresponding to the leached layer in samples where Cu2O release occurred.

A review of experimental techniques to produce a nacre-like structure.

The performance of man-made materials can be improved by exploring new structures inspired by the architecture of biological materials. Natural materials, such as nacre (mother-of-pearl), can have outstanding mechanical properties due to their complicated architecture and hierarchical structure at the nano-, micro- and meso-levels which have evolved over millions of years. This review describes the numerous experimental methods explored to date to produce composites with structures and mechanical properties similar to those of natural nacre. The materials produced have sizes ranging from nanometres to centimetres, processing times varying from a few minutes to several months and a different range of mechanical properties that render them suitable for various applications. For the first time, these techniques have been divided into those producing bulk materials, coatings and free-standing films. This is due to the fact that the material's application strongly depends on its dimensions and different results have been reported by applying the same technique to produce materials with different sizes. The limitations and capabilities of these methodologies have been also described.

Unusual presentations of pleomorphic adenoma and adenoid cystic carcinoma of the lacrimal gland.

PURPOSE: To report two atypical cases of pleomorphic adenoma and adenoid cystic tumours of the lacrimal gland. METHODS: Two case reports are presented. The first is of a 65-year-old female with a long history of right hypoglobus with sudden recent worsening. Computed tomography (CT) showed a round, well-defined lesion in the fossa for the lacrimal gland with an anterior hypodense extension suggestive of possible malignancy in a pleomorphic adenoma. The tumour in the second case, a 35-year-old male, was diagnosed after presentation following a relatively minor periorbital injury. The smooth rounded mass on CT scan was suggestive of a benign lacrimal gland tumour. RESULTS: The lesion in case 1 was excised with a diagnosis of haemorrhage within a pleomorphic adenoma. The lesion in case 2 was excised with a diagnosis of adenoid cystic carcinoma of the lacrimal gland with pseudocapsule. CONCLUSIONS: Haemorrhagic cyst developing beneath the pseudocapsule of a pleomorphic adenoma should be considered in the differential diagnosis of secondary development of malignancy in a pleomorphic adenoma. Adenoid cystic tumours of the lacrimal gland can present with a pseudocapsule.

Self-focused and somatic attention in patients with tinnitus.

Self-focused and somatic attention were examined in a sample of 51 patients with tinnitus using the Self-Focus Sentence Completion Test, Private Self-Consciousness Subscale of the Self-Consciousness Scale, Modified Somatic Perception Questionnaire, and the Somatization Subscale of the Symptoms Checklist-90-Revised. Two subgroups of patients emerged following a cluster analysis of the attentional tasks. One group scored lower on both self-attention and somatic attention measures ("low self-attenders"), whereas a second group was more internally directed and scored higher on the attention measures ("high self-attenders"). Between-group comparisons showed that the high self-attenders were, on average, more depressed, had greater emotional distress due to tinnitus, and had greater perceived tinnitus handicap. In contrast, no differences were observed for pitch and loudness measures using either psychophysical or rating scale techniques. Results of this investigation support the belief that attentional mechanisms play an important role in patients' perception of tinnitus and should be considered when planning management strategies.

Electrophysiological indices of selective auditory attention in subjects with and without tinnitus.

The present investigation was conducted in an attempt to determine whether selective auditory attention abilities differed between normal subjects and subjects with bothersome tinnitus. Subjects were 37 adults with tinnitus and high-frequency hearing loss (not affecting thresholds at 500 and 1000 Hz) and 15 subjects who were audiometrically and otologically normal. Results suggested that an electrophysiological index of early selective auditory attention (i.e., the negative difference wave, Nd) was of greater magnitude in tinnitus patients. Also, the cortical NI component occurred significantly later in the presence of selective attention in tinnitus subjects only. Results of this investigation may support the view that early selective auditory attention in subjects with bothersome tinnitus differs from that of normal subjects.

Retest stability of the tinnitus handicap questionnaire.

The test-retest stability of the Tinnitus Handicap Questionnaire was assessed for a sample of 32 tinnitus patients. The questionnaire is a self-report measure that quantifies the physical, emotional, and social consequences of tinnitus (factor 1), the interfering effects of tinnitus on the hearing ability of the patient (factor 2), and the patients' view of tinnitus (factor 3). Retest stability estimates were obtained in order to determine the applicability of using the questionnaire as an outcome measure following tinnitus management. High test-retest correlations emerged for factors 1 and 2, whereas factor 3 yielded inadequate retest reliability. Therefore, it is recommended that only factors 1 and 2 be used for documenting changes in self-perceived tinnitus handicap following medical, surgical, or rehabilitative intervention.

Relationships among psychoacoustic judgments, speech understanding ability and self-perceived handicap in tinnitus subjects.

Tinnitus is often a disturbing symptom which affects 6-20% of the population. Relationships among tinnitus pitch and loudness judgments, audiometric speech understanding measures and self-perceived handicap were evaluated in a sample of subjects with tinnitus and hearing loss (THL). Data obtained from the THL sample on the audiometric speech measures were compared to the performance of an age-matched hearing loss only (HL) group. Both groups had normal hearing through 1 kHz with a sloping configuration of < or = 20 dB/octave between 2-12 kHz. The THL subjects performed more poorly on the low predictability items of the Speech Perception in Noise Test, suggesting that tinnitus may interfere with the perception of speech signals having reduced linguistic redundancy. The THL subjects rated their tinnitus as annoying at relatively low sensation levels using the pitch-match frequency as the reference tone. Further, significant relationships were found between loudness judgment measures and self-rated annoyance. No predictable relationships were observed between the audiometric speech measures and perceived handicap using the Tinnitus Handicap Questionnaire. These findings support the use of self-report measures in tinnitus patients in that audiometric speech tests alone may be insufficient in describing an individual's reaction to his/her communication breakdowns.

False negative auditory brainstem response findings in vestibular schwannoma: case reports.

The false negative rate of the auditory brainstem response (ABR) for the detection of vestibular schwannoma (VS; acoustic neuroma) has been reported to range from 2 to 9 percent. The introduction of magnetic resonance with gadolinium contrast (Gd MRI) may be expected to raise the false negative rate, because smaller tumors can now be detected. We present two cases that illustrate some of the complex issues raised by the detection of small asymptomatic VS by Gd MRI that were missed by ABR. The role of ABR testing in the diagnosis and management of VS remains well established and will continue to evolve.

The influence of hearing aid cost on perceived benefit in older adults.

Self-report hearing handicap scales are gaining widespread acceptance among clinicians as a technique for quantifying hearing aid benefit. Both auditory and nonauditory (e.g., personality, health, motivation) factors contribute to an individual's response to hearing loss and ultimately to perceived hearing aid benefit. Among the recognized extra-audiological variables, financial concerns may influence a hearing aid user's expectations regarding hearing aid benefit. The present study compared self-perceived benefit in 26 insured and 26 uninsured new hearing aid wearers using the Hearing Handicap Inventory for the Elderly (HHIE). HHIE scores at 3 weeks and 6 mo postfitting were equivalent between groups. The findings suggest that the HHIE may be used as an index of hearing aid benefit without concern that the source of funds required to purchase amplification may act as an uncontrolled variable.

Infant hearing screening 1984 to 1989: the Henry Ford Hospital experience.

From 1984 to 1989 the Infant Hearing Screening (IHS) program at Henry Ford Hospital identified 1,300 infants as being "at risk" for hearing loss. The prevalence of significant sensorineural hearing loss in this sample was 1.4%. Additionally, 80 infants who passed the IHS program and reached 3 years of age were found to have normal hearing sensitivity by conventional audiometric techniques (ie, no false-negative predictions). There were three false-positive predictions. It was discovered that infants of low birthweight (ie, less than 1,500 g) were three times more likely to fail IHS than those whose weight exceeded 1,500 g. A higher return rate was found for infants failing an initial hearing screening conducted in the neonatal intensive care unit in comparison to those screened as outpatients one week postdischarge. The sensitivity and specificity of behavioral observation audiometry were 43% and 92%, respectively, when brainstem auditory-evoked potentials was used as the criterion validity measure.

Influence of menopause on the auditory brainstem response.

Auditory brainstem response (ABR) wave latency, interpeak interval and amplitude as a function of intensity were measured in 40 subjects divided into equal groups of postmenopausal females, age-matched males and young adults of both sexes. The results illustrate that age and gender play a significant role in ABR wave latency and amplitude. A larger age effect occurred for the female subjects. While this does not dispute an anatomical explanation for the gender effect in ABR, hormonal changes accompanying menopause may also account for some of the gender differences noted in ABR.