The effect of an active transcutaneous bone conduction device on spatial release from masking

Objective: The aim was to quantify the effect of the experimental active transcutaneous Bone Conduction Implant (BCI) on spatial release from masking (SRM) in subjects with bilateral or unilateral conductive and mixed hearing loss. Design: Measurements were performed in a sound booth with five loudspeakers at 0\ub0, +/−30\ub0 and +/−150\ub0 azimuth. Target speech was presented frontally, and interfering speech from either the front (co-located) or surrounding (separated) loudspeakers. SRM was calculated as the difference between the separated and the co-located speech recognition threshold (SRT). Study Sample: Twelve patients (aged 22–76 years) unilaterally implanted with the BCI were included. Results: A positive SRM, reflecting a benefit of spatially separating interferers from target speech, existed for all subjects in unaided condition, and for nine subjects (75%) in aided condition. Aided SRM was lower compared to unaided in nine of the subjects. There was no difference in SRM between patients with bilateral and unilateral hearing loss. In aided situation, SRT improved only for patients with bilateral hearing loss. Conclusions: The BCI fitted unilaterally in patients with bilateral or unilateral conductive/mixed hearing loss seems to reduce SRM. However, data indicates that SRT is improved or maintained for patients with bilateral and unilateral hearing loss, respectively

Un modello stocastico di dinamica di una popolazione

I modelli stocastici sono modelli matematici utili per descrivere processi in cui compaiono elementi di imprevedibilità, o per sistemi composti da un elevato numero di elementi (ad esempio sistemi cellulari). Un esempio in cui tali modelli trovano un'utile applicazione è quello dello studio delle dinamiche all'interno di una popolazione, per la descrizione della sua evoluzione a partire da una determinata situazione iniziale. Un modello classico per descrivere la dinamica di una popolazione è quello di McKendrick-VonFoerster, un'equazione alle derivate parziali che permette di stimare la numerosità degli individui conoscendone i tassi di natalità e mortalità. Tale modello può essere applicato alla popolazione di cellule beta del pancreas, per studiarne l'età media in soggetti sani e affetti da disfunzioni metaboliche al fine di individuare un'efficace azione terapeuticaope

On Direct Drive Bone Conduction Devices - Hearing Rehabilitation and Objective Assessment of Stimulation Methods

Bone conduction devices (BCDs) rely on the transmission of sound in form of vibrations generated by a transducer to the inner ear via the skull and surrounding soft tissues. Direct drive BCDs stimulate the skull bone directly, either via a skin-penetrating abutment (BAHAs, Bone Anchored Hearing Aids), or with a transducer implanted under intact skin (active transcutaneous devices).In this thesis, several aspects related to direct drive stimulation were addressed with objective and subjective measurements. Vibrational measurements were performed to assess how the transducer to bone attachment affects the vibrations transmission to the cochleae. Three different attachments for active transcutaneous stimulation were compared to each other and to the BAHA screw. A comparative study was done also between the BAHA system and the novel active transcutaneous Bone Conduction Implant (BCI), where the transducer is attached to the skull bone via a flat surface contact. The BCI is currently on a clinical trial, and a comprehensive assessment of the rehabilitation after three years of device usage is included in this thesis, reporting on a number of audiometric tests, self-reported questionnaires, and objective measurements. Among the objective measures, a new method for intra and post operative verification of the implant functionality was evaluated, consisting in the measurement of the induced sound pressure in the nostril under bone conduction stimulation. In addition to the test battery from the clinical trial protocol, an exploratory study was conducted to investigate the effect of the BCI in a complex multi-talker listening environment.The results from the vibrational measurements were highly frequency-dependent, with a general trend of improved transmission when the contact area between transducer and bone was limited, especially for frequencies above 5 kHz. Sound field tone and speech tests, and user reported questionnaires show that the BCI provides considerable improvement from the unaided condition and contributes to a general increase of patients\u27 life quality, with consistent outcomes over time. The implant verification method seems promising and showed stable properties of the implant to bone transmission. When compared to BAHAs, the BCI was found to be a viable alternative for indicated patients. In noisy and complex listening environments, the BCI users showed a lower ability to make use of the spatial cues when aided with their device, but an overall greater tolerance to interfering talkers

Effect of transducer attachment on vibration transmission and transcranial attenuation for direct drive bone conduction stimulation

Direct drive bone conduction devices (BCDs) are used to rehabilitate patients with conductive or mixed hearing loss by stimulating the skull bone directly, either with an implanted transducer (active transcutaneous BCDs), or through a skin penetrating abutment rigidly coupled to an external vibrating transducer (percutaneous BCDs). Active transcutaneous BCDs have been under development to overcome limitations of the percutaneous bone anchored hearing aid (BAHA), mainly related to the skin penetration. The attachment of a direct drive BCD to the skull bone can differ significantly between devices, and possibly influence the vibrations\u27 transmission to the cochleae. In this study, four different attachments are considered: (A) small-sized flat surface, (B) extended flat surface, (C) bar with a screw at both ends, and (D) standard bone anchored hearing aid screw. A, B, and C represent three active transcutaneous options, while D is for percutaneous applications. The primary aim of this study was to investigate how the different transcutaneous attachments (A, B, and C) affect the transmission of vibrations to the cochleae to the ipsilateral and the contralateral side. A secondary aim was to evaluate and compare transcranial attenuation (TA, ipsilateral minus contralateral signal level) between transcutaneous (A, B, and C) and percutaneous attachments (D). Measurements were performed on four human heads, measuring cochlear promontory velocity with a LDV (laser Doppler vibrometer) and sound pressure in the ear canal (ECSP) with an inserted microphone. The stimulation signal was a swept sine between 0.1 and 10 kHz. The comparison of ipsilateral transmission between transcutaneous adaptors A, B, and C was in agreement with previous findings, confirming that: (1) Adaptor C seems to give the most effective transmission for frequencies around 6 kHz but somewhat lower in the mid frequency range, and (2) keeping a smaller contact area seems to provide advantages compared to a more extended one. The same trends were seen ipsilaterally and contralaterally. The observed TA was similar for adaptors A, B, and C at the mastoid position, ranging -10-0 dB below 500 Hz, and 10-20 dB above. A lower TA was seen above 500 Hz when using adaptor D at the parietal position

Avaliações subjetivas e relacionais: o equívoco do sistema avaliativo docente para a qualidade dos cursos de pós-graduação MBA

The purpose of this paper was to analyze, from the point of view of the coordination of the programs, how and why the professors evaluations carried out by the students at the end of the courses taught can influence the quality of the lato sensu postgraduate courses in business administration called MBAs. In a qualitative approach, a case study was conducted where individual in-depth interviews were conducted with program coordinators involving more than 6,000 students and 500 teachers within the city of São Paulo. The content analysis of the interviews with the coordinators showed that the evaluation system, currently practiced by the teaching institution of the case studied, is much more associated to an attempt to measure relational and behavioral aspects between student-teacher than to aspects of improvement of quality of the programs or their learning objectives. It was not evident the relation of the accomplishment of the teacher evaluations with a logic of permanent improvement of quality. As an additional output of the research, the main components that could be included in an evaluation system that really focused on a continuous quality improvement program were identified.Key- words: MBA; executive education; teacher evaluation; quality.Este trabalho teve por objetivo analisar, sob a ótica da coordenação de curso, como e porque as avaliações docentes realizadas pelos alunos ao final das disciplinas ministradas podem auxiliar o gestor a melhorar a qualidade dos cursos de pós-graduação lato sensu em Administração de Empresas denominados MBAs. Numa abordagem qualitativa, foi conduzido um estudo de caso em que foram realizadas entrevistas individuais em profundidade com os coordenadores dos programas que envolvem mais de 6.000 alunos e 500 professores da cidade de São Paulo. A análise de conteúdo das entrevistas com os coordenadores mostrou que o sistema avaliativo, atualmente praticado pela instituição de ensino do caso estudado, está mais associado a uma tentativa de mensuração de aspectos relacionais e comportamentais entre aluno-professor do que a aspectos de melhoria de qualidade dos programas ou aos seus objetivos de aprendizagem. Não ficou evidente a relação da realização das avaliações docentes com uma lógica de melhoria permanente de qualidade. Como saída adicional da pesquisa foram identificados os principais componentes que poderiam constar num sistema de avaliação que tivesse foco num programa contínuo de melhoria de qualidade.Palavras-chave: MBA; educação executiva; avaliação docente; qualidade

Three-Year Follow-Up with the Bone Conduction Implant

Background: The bone conduction implant (BCI) is an active transcutaneous bone conduction device where the transducer has direct contact to the bone, and the skin is intact. Sixteen patients have been implanted with the BCI with a planned follow-up of 5 years. This study reports on hearing, quality of life, and objective measures up to 36 months of follow-up in 10 patients. Method: Repeated measures were performed at fitting and after 1, 3, 6, 12, and 36 months including sound field warble tone thresholds, speech recognition thresholds in quiet, speech recognition score in noise, and speech-to-noise thresholds for 50% correct words with adaptive noise. Three quality of life questionnaires were used to capture the benefit from the intervention, appreciation from different listening situations, and the ability to interact with other people when using the BCI. The results were compared to the unaided situation and a Ponto Pro Power on a soft band. The implant functionality was measured by nasal sound pressure, and the retention force from the audio processor against the skin was measured using a specially designed audio processor and a force gauge. Results: Audiometry and quality of life questionnaires using the BCI or the Ponto Pro Power on a soft band were significantly improved compared to the unaided situation and the results were statistically supported. There was generally no significant difference between the two devices. The nasal sound pressure remained stable over the study period and the force on the skin from the audio processor was 0.71 \ub1 0.22 N (mean \ub1 1 SD). Conclusion: The BCI improves the hearing ability for tones and speech perception in quiet and in noise for the indicated patients. The results are stable over a 3-year period, and the patients subjectively report a beneficial experience from using the BCI. The transducer performance and contact to the bone is unchanged over time, and the skin area under the audio processor remains without complications during the 3-year follow-up

Identification of self-discharge mechanisms of ionic liquid electrolyte based supercapacitor under high-temperature operation

Ionic liquids (ILs) are promising electrolytes for supercapacitors (SCs) aimed for high-temperature applications, where increased ionic conductivity results in superior capacitive performance compared to room temperature (RT) performance. However, an increased temperature also accelerates the self-discharge rate that adversely affects energy retention and restricts the usage of SCs in standalone applications. In this study, a detailed electrochemical investigation on the self-discharge behaviour of carbon-based SCs containing an IL, 1-Ethyl-3-methylimidazolium acetate (EMIM Ac), has been carried out in the temperature range RT - 60\ua0\ub0C, and the underlying self-discharge mechanisms are identified. The results reveal that at a high voltage of 1.5\ua0V, the self-discharge is characterized by a combination of charge redistribution and diffusion at both RT and 60\ua0\ub0C. At 60\ua0\ub0C, the diffusion-controlled mechanism dominates at lower voltages over the charge redistribution effect, while at RT both mechanisms contribute to a similar extent. The observed difference in the self-discharge mechanism between RT and 60\ua0\ub0C is explained in terms of a decreased RC time constant (τRC) at elevated temperature, and the same conclusions are potentially applicable to other IL-containing SCs as well

The bone conduction implant - a review and 1-year follow-up

Objective: The objective of this study is to evaluate its safety and effectiveness of the bone conduction implant (BCI) having an implanted transducer and to review similar bone conduction devices. Design: This is a consecutive prospective case series study where the patients were evaluated after 1, 3, 6 and 12 months. Outcome measures were focussed on intraoperative and postoperative safety, the effectiveness of the device in terms of audiological performance and patient\u27s experience. Study sample: Sixteen patients with average age of 40.2 (range 18-74) years have been included. Thirteen patients were operated in Gothenburg and three in Stockholm. Results: It was found that the procedure for installing the BCI is safe and the transmission condition was stable over the follow-up time. No serious adverse events or severe adverse device effects occurred. The hearing sensitivity, speech in noise and the self-assessment as compared with the unaided condition improved significantly with the BCI. These patients also performed similar or better than with a conventional bone conduction reference device on a softband. Conclusions: In summary, it was found that the BCI can provide a safe and effective hearing rehabilitation alternative for patients with mild-to-moderate conductive or mixed hearing impairments

Nasal sound pressure as objective verification of implant in active transcutaneous bone conduction devices

Objective: Active transcutaneous bone conduction devices consist of an external audio processor and an internal implant under intact skin. During the surgical procedure, it is important to verify the functionality of the implant before the surgical wound is closed. In a clinical study with the new bone conduction implant (BCI), the functionality of the implant was tested with an electric transmission test, where the output was the nasal sound pressure (NSP) recorded in the ipsilateral nostril. The same measurement was performed in all follow-up visits to monitor the implant\u27s functionality and transmission to bone over time. The objective of this study was to investigate the validity of the NSP method as a tool to objectively verify the implant\u27s performance intraoperatively, as well as to follow-up the implant\u27s performance over time. Design: Thirteen patients with the BCI were included, and the NSP measurement was part of the clinical study protocol. The implant was electrically stimulated with an amplitude-modulated signal generator using a swept sine 0.1-10 kHz. The NSP was measured with a probe tube microphone in the ipsilateral nostril. Results: The NSP during surgery was above the noise floor for most patients within the frequency interval 0.4-5 kHz, showing NSP values for expected normal transmission of a functioning implant. Inter-subject comparison showed large variability, but follow-up results showed only minor variability within each subject. Further investigation showed that the NSP was stable over time. Conclusion: The NSP method is considered applicable to verify the implant\u27s functionality during and after surgery. Such a method is important for implantable devices, but should be simplified and clinically adapted. Large variations between subjects were found, as well as smaller variability in intra-subject comparisons. As the NSP was found to not change significantly over time, stable transmission to bone, and implant functionality, were indicated

Robustness and lifetime of the bone conduction implant - a pilot study

Objectives: The objective of this study was to develop methods for evaluating the mechanical robustness and estimating the lifetime of the novel bone conduction implant (BCI) that is used in a clinical study. The methods are intended to be applicable to any similar device. Materials and methods: The robustness was evaluated using tests originally developed for cochlear implants comprising a random vibration test, a shock test, a pendulum test, and an impact test. Furthermore, magnetically induced torque and demagnetization during magnetic resonance imaging at 1.5 T were investigated using a dipole electromagnet. To estimate the lifetime of the implant, a long-term age-accelerated test was performed. Results: Out of all the tests, the pendulum and the impact tests had the largest effect on the electro-acoustic performance of the BCI implant, even if the change in performance was within acceptable limits (< 20%). In comparison with baseline data, the lower and higher resonance peaks shifted down in frequency by 13% and 18%, respectively, and with a loss in magnitude of 1.1 and 2.0 dB, respectively, in these tests. Conclusion: A complete series of tests were developed, and the BCI passed all the tests; its lifetime was estimated to be at least 26 years for patients who are using the implant for 12 hours on a daily basis