Broadband THz absorption spectrometer based on excitonic nonlinear optical effects.

A broadly tunable THz source is realized via difference frequency generation, in which an enhancement to χ(3) that is obtained via resonant excitation of III-V semiconductor quantum well excitons is utilized. The symmetry of the quantum wells (QWs) is broken by utilizing the built-in electric-field across a p-i-n junction to produce effective χ(2) processes, which are derived from the high χ(3). This χ(2) media exhibits an onset of nonlinear processes at ~4 W cm-2, thereby enabling area (and, hence, power) scaling of the THz emitter. Phase matching is realized laterally through normal incidence excitation. Using two collimated 130 mW continuous wave (CW) semiconductor lasers with ~1-mm beam diameters, we realize monochromatic THz emission that is tunable from 0.75 to 3 THz and demonstrate the possibility that this may span 0.2-6 THz with linewidths of ~20 GHz and efficiencies of ~1 × 10-5, thereby realizing ~800 nW of THz power. Then, transmission spectroscopy of atmospheric features is demonstrated, thereby opening the way for compact, low-cost, swept-wavelength THz spectroscopy.

Predictors of health-related quality of life in adult cochlear implant recipients in South Africa.

OBJECTIVE: To identify and describe predictors of health-related quality of life (HRQoL) outcomes for adult cochlear implant (CI) recipients in South Africa. DESIGN: A retrospective study of adult CI recipients was conducted and cross-sectional HRQoL outcome data were added at the time of data collection, using the Nijmegen Cochlear Implant Questionnaire (NCIQ). Twenty-two potential predictive factors were identified from the retrospective dataset, including demographic, hearing loss, CI and risk-related factors. Multiple regression analyses were performed to identify predictor variables that influence HRQoL outcomes. STUDY SAMPLE: The study sample included 100 adult CI recipients from four CI programs, implanted for at least 12 months. RESULTS: History of no tinnitus prior to CI, bilateral implantation and mainstream schooling were strongly predictive of better overall HRQoL outcomes. Factors such as age, age at implant, gender, onset of hearing loss, duration of CI use and presence of risk factors did not predict HRQoL scores. CONCLUSION: A range of significant prognostic indicators were identified for HRQoL outcomes in adult CI recipients. These predictors of HRQoL outcomes can guide intervention services' informational counselling.

Predictors of pediatric cochlear implantation outcomes in South Africa.

OBJECTIVE: To identify and describe predictors of pediatric cochlear implantation outcomes in a South African population. METHODS: A retrospective study of 301 pediatric cochlear implant (CI) recipients from five CI programs was conducted and cross-sectional outcome data were added at the time of data collection. Twenty potential prognostic factors were identified from the retrospective dataset, including demographical, CI, risk and family factors. Multiple regression analyses were performed to identify predictor variables that influence outcomes in terms of auditory performance (CAP scores), speech production (SIR scores), communication mode and educational placement. RESULTS: Although implanted children within this sample did not have equal opportunity to access a second implant, bilateral implantation was strongly predictive of better auditory performance and speech production scores, an oral mode of communication and mainstream education. NICU admittance/prematurity were associated with poorer auditory performance and speech production scores, together with a higher probability for non-oral communication and non-mainstream education. The presence of one or more additional developmental condition was predictive of poorer outcomes in terms of speech production and educational placement, while a delay between diagnosis and implantation of more than one year was also related to non-mainstream education. Ethnicities other than Caucasian were predictive of poorer auditory performance scores and a lower probability for mainstream education. CONCLUSION: An extensive range of prognostic indicators were identified for pediatric CI outcomes in South Africa. These predictive factors of better and poorer outcomes should guide pediatric CI services to promote optimal outcomes and assist professionals in providing evidence-based informational counseling.

Co-morbidities in children presenting with chronic suppurative otitis media--a South African study.

BACKGROUND: Chronic suppurative otitis media (CSOM) is common among children in southern Africa. Managing associated co-morbidities may result in earlier disease resolution. METHODS: Children <13 years of age with otorrhoea lasting >4 weeks were recruited to the study. Each child underwent a full clinical examination, a blood count, an HIV test and CD4 cell count, if found to be infected. RESULTS: The study included 86 children, and the median age was 4.6 years. HIV infection was present in 45 of 83 children (54.2%), of which 23 (51.1%) were receiving antiretroviral treatment at the time of presentation. Underweight was present in 22 of 85 (25.9%) children and in 17 of the 45 (37.8%) HIV-infected children. One or more clinical signs (not aural-related) were found in 46 of 86 (53.4%) children. Cholesteatoma was found in 23 of 113 (20.4%) ears, and 9 of 86 (10.5%) children had serious associated aural or intracranial complications. CONCLUSIONS: A high percentage of children with CSOM have associated pathology that needs to be diagnosed to optimally manage CSOM.