Ceramic-Polymer Additive Manufacturing System for Ultrasound Transducers

A modified multi-layer lithography process is used to additively manufacture highresolution netshape ceramic structures by photopolymerizing a ceramic-polymer slurry using structured light patterns. This paper will discuss the development of a low-cost, high speed manufacturing process method for the fabrication of piezoelectric ceramic transducer elements in the 1-25 MHz frequency range. The key considerations in the development of the process including the selection and optimization of slurry materials for the deposition of PZT 5H materials, optical exposure parameters, debinding/sintering profiles, process monitoring, and post manufacturing processing. Ongoing work includes improvements to the materials properties, improved throughput and geometric fidelity.Mechanical Engineerin

A mixed-methods study on toilet hygiene practices among Chinese in Hong Kong.

BACKGROUND: Public toilets are a common transmission vector of infectious diseases due to environmental contamination. Research on Chinese people's hygiene practices in public lavatories are lacking. This study examined Chinese people's hygiene practices in public lavatories in Hong Kong. METHODS: We conducted qualitative interviews and a self-administered questionnaire survey with local residents from June 2016 to April 2018. Four focus group discussions and three individual interviews informed the design of the questionnaire. We recruited interviewees and survey respondents via social service centers. The interviews and questionnaire focused on the public's daily practices and hygiene behaviors in public toilets. Content analysis of qualitative data was conducted. Multivariable logistic regressions were used to examine the association between age and toilet hygiene behaviors. RESULTS: Our qualitative component revealed a range of handwashing practices, from not washing at all, washing without soap, to washing for a longer time than instructions. Other toilet use practices were identified, such as not covering toilet lid before flushing and stepping on toilet seats due to dirtiness, and spitting into toilet bowls or hand basin. Totally, 300 respondents completed the questionnaire. Among them, 212 (70.9%) were female and 246 (86.1%) were aged 65 or below. More than two thirds always washed hands with soap (68.7%) and dried hands with paper towels (68.4%). Up to 16.2% reported stepping on toilet seats and 43.9% never covered the toilet lid before flushing. Over one fourth (26.4%) spit into squat toilets/ toilet bowl. Regression analyses showed that the elderly group were less likely to report stepping on toilet seats (adjusted odds ratio, AOR = 0.17, 95%CI 0.03-0.88), flushing with the toilet lid closed (AOR = 0.40, 0.16-0.96), but more likely to spit into squat toilets/ toilet bowl (AOR = 4.20, 1.50-11.74). CONCLUSIONS: Hong Kong Chinese's compliance to hygiene practices in public toilets is suboptimal. Stepping on toilet seat is a unique Chinese practice due to the dirtiness of toilet seats. Spitting practices may increase the risk of airborne infectious diseases and need improvement. Measures are needed to improve toilet hygiene behaviors, including public education campaigns and keeping toilet environment clean

Cyclic Aryl Ethers: New Intermediates for High Performance Polymers

Note:A high yield synthesis of cyclic(aryl ether ketone) oligomers containing a 1, 2- dibenzoylbenzene moiety via the nucleophilic aromatic substitution route has been developed. Chemical transformation of the 1,2-dibenzoylbenzene moiety of these cyclic(aryl ether ketone)s leads to the preparation of novel cyclic(aryl ether phthalazine)s and cyclic(aryl ether isoquinoline)s. Matrix assisted laser desorption ionization- time of flight- mass spectrometry, which enables the detection of oligomers with mass up to 5000 Da, was shown to be a very powerful tool for the analysis and proof of the cyclic nature of the oligomers. A preliminary rheology study on selected cyclic(aryl ether ketone)s shows that the viscosity of the cyclic oligomers is orders of magnitude lower than the high molecular weight polymers. […]Des oligomères cycliques contenant les groupements aryl, éther et cétone, écrit généralement cyclique(aryl éther cétone)s, et contenant spécifiquement le groupement dibenzoyl-1,2-benzène ont été synthétisés en haut rendement par une substitution aromatique nucléophile. La transformation chimique du groupement dibenzoyl-1,2-benzène par la réaction de ces cycliques avec l'hydrazine et lebenzylamine donne les cyclique(aryl éther phtalazine)s et cyclique( aryl éther isoquinoline)s. La nouvelle technique de spectrométrie de masse, MALDI-TOF (Matrix Assisted Laser Desorption Ionization-Time Of Flight) nous a aidé à détecter les oligomères cycliques avec une masse jusqu'à 5000 Da. Cette technique a démontré d'être un outil puissant pour l'analyse et la confirmation de la structure cyclique. Des études préliminaires de rhéologie sur certains cyclique(aryl éther cétone)s ont démontres qu'ils ont une viscosité plus basse d'ordres de magnitude de celle correspondante aux polymères de haut poids moléculaire et de même composition

A synthetic approach to Yuehchukene analogues via alpha beta-unsaturated-2-acylindoles

published_or_final_versionChemistryMasterMaster of Philosoph

Five-year outcomes of western mental health training for Traditional Chinese Medicine practitioners

Abstract Background There are increasing expectations for primary care practitioners to deal with mental health problems. In Hong Kong, 15 % of the general public consult Traditional Chinese Medicine (TCM) practitioners regularly for their primary health care needs. This study investigated the 5-year outcomes of a western mental health training course for TCM practitioners in Hong Kong. Method Structured questionnaire surveys were conducted to compare the TCM practitioners’ confidence and engagement in mental health care before and after the Course. The data collected during 2011–2015 were analyzed. Results A total of 151 TCM practitioners returned both pre- and post-Course questionnaires, with a response rate of 95.6 %. After the course, there were significant increases in the proportions of participants being confident of recognizing patients with psychological problems (62.9 % before the course vs 89.4 % after), diagnosing common mental health problems (47.7 % vs 77.5 %), and managing them (31.2 % vs 64.3 %). Overall, 66.9 % of the participants reported some increase in their confidence in recognizing patients with psychological problems, diagnosing or/and managing patients with common mental health problems. Qualitative responses illustrated the major improvements were increased awareness of mental symptoms, better understanding of classification of mental disorders and management approaches. On the other hand, barriers included difficulties in understanding medical terms in English, consultation time constraints, and a lack of formal referral system to psychiatrists. Conclusions The Course has positive impact on TCM practitioners in handling mental health patients. The findings are useful for designing similar trainings on complementary and alternative medicine practitioners in other countries

Photostability enhancement of an azobenzene photonic polymer

International audienceWe have found that the presence of a methacrylate group on an azobenzene electro-optic chromophore can provide an enhancement in photostability of up to one or two orders of magnitude. Systematic studies involving the change in chromophore structure and atmospheric environmentindicate that the photostabilization is due to antioxidant action by the unsaturated functional grou

Comparison of Atrial Fibrillation Recurrence Rates After Successful Electrical Cardioversion in Patients With Hyperthyroidism-Induced Versus Non-Hyperthyroidism-Induced Persistent Atrial Fibrillation

Hyperthyroidism-induced atrial fibrillation (AF) often spontaneously reverts to sinus rhythm after the return of euthyroid state, but a significant number of patients remain in persistent AF, which requires electrical cardioversion. The long-term outcome of hyperthyroidism-induced persistent AF after successful cardioversion remains unclear. The study group consisted of 58 patients with hyperthyroidism-induced persistent AF (mean age 57 ± 2 years, 72% men) who had undergone successful electrical cardioversion. The AF recurrence rate was prospectively studied and compared with age- and gender-matched controls with persistent AF of nonthyroid origins. After a 24-month follow-up period, 34 patients (59%) had developed AF recurrence, significantly fewer than among controls (83%) (hazard ratio 0.64, 95% confidence interval 0.39 to 0.97, p = 0.04). Cox regression analysis showed that long AF duration was the only predictor of AF recurrence in patients with hyperthyroidism-induced persistent AF. In conclusion, hyperthyroidism-induced persistent AF carries a lower recurrence rate after conversion to sinus rhythm than non-hyperthyroidism-induced persistent AF, and early electrical cardioversion should be considered. © 2009 Elsevier Inc. All rights reserved.link_to_subscribed_fulltex

Relative electrical resistivities and poling of nonlinear optical polymeric waveguides

A method based on Maker fringe measurements of nonlinear optical coefficients has been used to determine the relative dc electrical resistivities of a series of linear and nonlinear optical polymers. The method can be used to identify low resistivity linear cladding materials for optimized electric field poling of nonlinear optical polymeric waveguides. As an example of the application of the technique we have studied the resistivity of poly(methyl methacrylate)-polystyrene (PMMA-PS) copolymers with varying content of the two components. The resistivity of PMMA was found to be one order of magnitude lower than that of PS