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Piezoelectric materials directly convert strain energy into electric energy and vice versa and are commonly used in sensing and actuating applications. They have been employed in mediums frequently undergoing vibrations, allowing harnessing of power at a small scale. Ideas of using the piezoelectric effect as a power take-off mechanism for ocean energy emerged in the 1970s and are still at a developing stage. This article overviews recent development on the application of the piezoelectric processes to the ocean field and provides a building block for future research work of ocean engineers who are interested in such possibilities. A brief discussion on the selection of the piezoelectric materials for different ocean-engineering applications is presented. Significant research projects on ocean-energy extraction through the use of these materials are then described and discussed with special scrutiny on the viability of proposed designs and their experimental or numerical validation. Various harvesting techniques in an ocean environment are categorized and compared. The challenges ahead and the outlook for success in this area are outlined.

ObjectivesHIV and tuberculosis (TB) are major global health threats and can result in household financial hardships. Here, we aim to estimate the household economic burden and the incidence of catastrophic health expenditures (CHE) incurred by HIV and TB care across income quintiles in Ethiopia.DesignA cross-sectional survey.Setting27 health facilities in Afar and Oromia regions for TB, and nationwide household survey for HIV.ParticipantsA total of 1006 and 787 individuals seeking HIV and TB care were enrolled, respectively.Outcome measuresThe economic burden (ie, direct and indirect cost) of HIV and TB care was estimated. In addition, the CHE incidence and intensity were determined using direct costs exceeding 10% of the household income threshold.ResultsThe mean (SD) age of HIV and TB patient was 40 (10), and 30 (14) years, respectively. The mean (SD) patient cost of HIV was $78 ($170) per year and $115 ($118) per TB episode. Out of the total cost, the direct cost of HIV and TB constituted 69% and 46%, respectively. The mean (SD) indirect cost was $24 ($66) per year for HIV and $63 ($83) per TB episode. The incidence of CHE for HIV was 20%; ranges from 43% in the poorest to 4% in the richest income quintile (p<0.001). Similarly, for TB, the CHE incidence was 40% and ranged between 58% and 20% among the poorest and richest income quintiles, respectively (p<0.001). This figure was higher for drug-resistant TB (62%).ConclusionsHIV and TB are causes of substantial economic burden and CHE, inequitably, affecting those in the poorest income quintile. Broadening the health policies to encompass interventions that reduce the high cost of HIV and TB care, particularly for the poor, is urgently needed.