We describe the construction of a ultrasonic device suitable for micro patterning particles and cells for tissue engineering applications. The device is formed by seven transducers shaped into a heptagon cavity. By exciting two and three transducers simultaneously, lines or hexagonal shapes can be formed with beads and cells. Furthermore, phase control of the transducers allows shifting the standing waves and thus patterning at different positions on a surface in a controlled manner. The paper discusses direct patterning of mammalian cells by ultrasound "stencil".
We describe the construction of an ultrasonic device capable of micro-patterning a range of microscopic particles for bioengineering applications such as targeted drug delivery. The device is formed from seven ultrasonic transducers positioned around a heptagonal cavity. By exciting two or three transducers simultaneously, lines or hexagonal shapes can be formed with microspheres, emulsions and microbubbles. Furthermore, phase control of the transducers allows patterning at any desired position in a controlled manner. The paper discusses in detail direct positioning of functionalised microspheres, emulsions and microbubbles. With the advantages of miniaturization, rapid and simple fabrication, ultrasonic tweezers is a potentially useful tool in many biomedical applications.
An acoustic particle manipulation system is presented, using a flexible printed circuit board formed into a regular heptagon. It is operated at 4 MHz and has a side dimension of 10 mm. The heptagonal geometry was selected for its asymmetry, which tends to reduce standing wave behavior. This leads to the possibility of having fine control over the acoustic field by varying the output phases of the transducer elements. Configurations with two and three active transducers are demonstrated experimentally. It is shown that with two transducers, the particles align along straight lines, the position of which can be moved by varying the relative excitation phases of the two transducers. With three active transducers, hexagonal-shaped patterns are obtained that can also be moved, again according to the phase of the excitation signals. Huygens' principle-based simulations were used to investigate the resultant pressure distributions. Good agreement was achieved between these simulations and both Schlieren imaging and particle manipulation observations.
Background Identification of symptomatic patients followed by prompt on-site investigation form the foundation of facility-based tuberculosis (TB) screening and diagnosis. However, underdiagnosis is common, contributing to ongoing transmission and adverse health outcomes. We conducted this systematic review with the hypothesis that underdiagnosis is largely secondary to patient drop out from presentation, through the diagnostic and care pathway, to treatment initiation. Methods We searched (to 22 January 2019) MEDLINE, Embase, and Cinahl for studies investigating the pathway of care for patients (and standardised patients) presenting to health facilities or pharmacies with TB symptoms. We used QUADAS-2 to assess risk of bias. We reported the proportions of symptomatic patients at each stage of the diagnostic and care pathway from symptom screening to treatment initiation. Results After screening 3,184 titles and abstracts, we identified 14 eligible studies. None provided data addressing the full cascade of care from clinical presentation to treatment initiation in the same patient population. Symptom-screening, the critical entry point for diagnosis of TB, was not done for 40%, 50%, and 96% of symptomatic participants in the three studies that reported this outcome. The proportion of symptomatic attendees offered a diagnostic investigation (data available for 13 studies), was very low with a study level median of 38% (IQR: 22% to 45%, range 5% to 84%).Conclusions Inefficiencies of the TB symptom screen-based patient pathway are a major contributor to underdiagnosis of TB in health facilities, and reflect inconsistent implementation of longstanding guidelines to ask all patients attending health facilities about respiratory symptoms and to offer diagnostic tests to all patients promptly once TB symptoms are identified. Better screening tools and interventions to improve the efficiency of TB screening and diagnosis pathways in health facilities are urgently needed.
Background Fishing exposes fishermen to schistosomiasis-infested fresh water and concurrently through precarious livelihoods to risky sexual behaviour, rendering these two infections occupational hazards for fishermen. This study aimed to characterize the knowledge of the two conditions to obtain necessary data for a subsequent cluster randomized trial designed to investigate demand creation strategies for joint HIV-schistosomiasis service provision in fishing villages on the shores of southern Lake Malawi. Methods Enumeration of all resident fishermen in 45 clusters (fishing communities) was carried out between November 2019 and February 2020. In a baseline survey, fishermen reported their knowledge, attitudes and practices in the uptake of HIV and schistosomiasis services. Knowledge of HIV status and previous receipt of praziquantel were modelled using random effects binomial regression, accounting for clustering. Prevalence of willingness to attend a beach clinic was computed. Results A total of 6,297 fishermen were surveyed from the 45 clusters with harmonic mean number of fishermen per cluster of 112 (95% CI: 97; 134). The mean age was 31.7y (SD: 11.9) and nearly 40% (2,474/6,297) could not read or write. Overall, 1,334/6,293 (21.2%) had never tested for HIV, with 64.4% (3,191/4,956) having tested in the last 12 months, and 5.9% (373/6290) taking antiretroviral therapy (ART). In adjusted analyses, being able to read and write (adjusted risk ratio [aRR: 1.91, 95% CI: 1.59–2.29, p<0.001); previous use of praziquantel (aRR: 2.00,95% CI: 1.73–2.30, p<0.001); knowing a relative or friend who died of HIV (aRR: 1.54,95% CI: 1.33–1.79, p<0.001); and being on ART (aRR: 12.93, 95% CI: 6.25–32.93, p<0.001) were associated with increased likelihood of ever testing for HIV. Only 40% (1,733/4,465) had received praziquantel in the last 12 months. Every additional year of age was associated with 1% decreased likelihood of having taken praziquantel in the last 12 months (aRR: 0.99, 95% CI: 0.98–0.99, p<0.001). However, recent HIV testing increased the likelihood of taking praziquantel by over 2-fold (aRR 2.24, 95% CI: 1.93–2.62, p<0.001). Willingness to attend a mobile beach clinic offering integrated HIV and schistosomiasis services was extremely high at 99.0% (6,224/6,284). Conclusion In a setting with an underlying high prevalence of both HIV and schistosomiasis, we found low knowledge of HIV status and low utilization of free schistosomiasis treatment. Among fishermen who accessed HIV services, there was a very high likelihood of taking praziquantel suggesting that integrated service delivery may lead to good coverage. Trial registration This trial is registered in the ISRCTN registry: ISRCTN14354324; date of registration: 05 October 2020.
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