Phase transformation behaviour of porous NiTi alloys fabricated by capsule-free hot isostatic pressing

Differential scanning calorimetry (DSC) was used to characterize the phase transformation behaviour of porous Ni50Ti50 alloys fabricated by capsule-free hot isostatic pressing (CF-HIP) with different cold compaction pressures. Experimental results reveal that a multi-stage martensitic transformation (MST) exists in the sintered porous NiTi alloys on cooling while the reverse transformation upon heating is either a single or two-stage phase transformation. The DSC thermal analysis indicates that the cold compaction pressure has great effect on the subsequent transformation temperatures. Generally, the phase transformation temperatures of porous NiTi alloys with lower cold compaction pressure are higher than those compacted with higher pressure. With increase in the annealing time, the transformation temperatures increase quickly when the cold compaction pressure was 150MPa. On the other hand, the transformation temperatures change only slightly when the cold compaction pressure was varied from 300MPa to 400MPa. These phenomena can be attributed to the combined effect of larger plastic deformation with higher dislocations density produced by cold compaction and the precipitation of the second phase in the porous NiTi alloys.published_or_final_versio

Unified analysis of switched-capacitor resonant converters

Author name used in this publication: Y. P. Benny YeungAuthor name used in this publication: K. W. E. ChengAuthor name used in this publication: S. L. HoAuthor name used in this publication: K. K. Law2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

香港結核病患者的特徵與治療結果

OBJECTIVES: To identify the general characteristics of patients with tuberculosis, and to evaluate their treatment outcomes. DESIGN: Retrospective study. SETTING: Tuberculosis and Chest Service, Department of Health, Hong Kong. SUBJECTS AND METHODS: All patients with tuberculosis registered for treatment from 1 January 1996 to 31 December 1996 were included in the study. Information was extracted from their medical records at treatment commencement and at 12 and 24 months after treatment was instigated. Data gathered included demographic data, past treatment, site of disease, case category, treatment regimen, bacteriological status, and treatment outcome. RESULTS: There were 5757 patients for analysis. Approximately one third of patients were aged 60 years or older, and 69.1% were male. Pulmonary disease alone occurred in 77.7% of patients, while both pulmonary and extrapulmonary diseases occurred in 8.6%. New patients comprised 84.6% of cases, and 16.3% had concomitant illnesses. There was excess risk of disease among patients who were male, elderly, or who had silicosis. Only 0.1% of patients were co-infected with human immunodeficiency virus infection. Among the 5757 cases evaluated, 1324 (23.0%) were new patients with a positive sputum smear, 299 (5.2%) were patients who were retreated with a positive sputum smear, and 4134 (71.8%) were new or retreatment patients with a negative sputum smear. The overall treatment completion rates at 12 and 24 months were 80.4% and 84.8%, respectively. Males and patients aged 60 years or older had lower treatment completion rates. Non-adherence, transfer to other services, and mortality among the elderly were key factors influencing treatment outcomes. Co-morbidity was associated with better case-holding, and this more than compensated for its effect on prolongation of treatment and mortality. CONCLUSIONS: There was an excess risk of tuberculosis among male and elderly patients, who also had a less favourable outcome. Active screening of clearly identified risk groups may be appropriate but requires the completion of more in-depth studies and careful cost-effectiveness analyses. Further efforts with respect to case-holding are indicated to address treatment defaulting and transfer rates.published_or_final_versio

Prevalence and predictors of default from tuberculosis treatment in Hong Kong

OBJECTIVE: To determine the prevalence and risk factors of default from tuberculosis treatment in Hong Kong. DESIGN: Retrospective study. SETTING: Data were obtained from programme forms completed by physicians in the Hong Kong Government Tuberculosis and Chest Service and from medical records from Hong Kong chest clinics. PATIENTS: In all, 5917 patients registered for antituberculous drug therapy in 1996; medical records of 5757 patients were reviewed. MAIN OUTCOME MEASURES: Patients who defaulted treatment were defined as those who had failed to collect medication for more than 2 consecutive months after the date of the last attendance during the course of treatment. Demographic and clinical characteristics, including history, treatment, and outcome, were compared between defaulters and non-defaulters, both among the whole group and among those with pulmonary disease. RESULTS: There were 442 (8%) patients who defaulted from treatment. Forty-five percent of those who defaulted did so in the first 2 months of treatment. Key risk factors associated with non-compliance were a history of default, male sex, and a history of concomitant liver disease or lung cancer. Among patients with pulmonary tuberculosis (381 defaulters and 1537 non-defaulters), multiple drug resistance was also associated with default from treatment. Among defaulters with pulmonary disease, 39% were still bacteriologically positive at the time of default. CONCLUSION: Default from treatment may be partially responsible for the persistent high rates of tuberculosis in Hong Kong in the past decade. Health professionals should ensure that all barriers to treatment be removed and that incentives be used to encourage treatment compliance.published_or_final_versio

Biomimetic deposition of apatite on surface chemically modified porous NiTi shapememory alloy

Porous NiTi shape memory alloy (SMA) with 48% porosity and an average pore size of 50800 μm was synthesized by capsule-free hot isostatic pressing (CF-HIP). To enhance the surface bioactivity, the porous NiTi SMA was subjected to H"2O"2 and subsequent NaOH treatment. Scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses revealed that a porous sodium titanate (Na"2TiO"3) film had formed on the surface of the porous NiTi SMA. An apatite layer was deposited on this film after immersion in simulated body fluid at 37°C, while no apatite could be found on the surface of the untreated porous NiTi SMA. The formation of the apatite layer infers that the bioactivity of the porous NiTi SMA may be enhanced by surface chemical treatment, which is favorable for its application as bone implants. © 2008 World Scientific Publishing Company.postprin

Evaluation of moderate alcohol use and cognitive function among men using a mendelian randomization design in the guangzhou biobank cohort study

Observational studies usually show that moderate alcohol use is associated with better cognitive function. Such studies are vulnerable to residual confounding arising from systematic differences between moderate alcohol users and others. A Mendelian randomization study carried out in a suitable population, such as southern Chinese men, in which alcohol use is low to moderate and is influenced by genotype, offers an alternative and superior approach for clarifying the causal effect of moderate alcohol use on cognitive function. The authors used aldehyde dehydrogenase 2 (ALDH2) genotype (AA, GA, or GG) as an instrumental variable in 2-stage least squares analysis to obtain unbiased estimates of the relation of alcohol consumption (measured in alcohol units (10 g ethanol) per day) with cognitive function, assessed from delayed 10-word recall score (n = 4,707) and Mini-Mental State Examination (MMSE) score (n = 2,284), among men from the Guangzhou Biobank Cohort Study (2003-2008). ALHD2 genotype was strongly associated with alcohol consumption, with an F statistic of 71.0 in 2-stage least squares analysis. Alcohol consumption was not associated with delayed 10-word recall score (-0.03 words per alcohol unit, 95% confidence interval:-0.18, 0.13) or MMSE score (0.06 points per alcohol unit, 95% confidence interval:-0.22, 0.34). Moderate alcohol use is unlikely to be cognitively protective. © The Author 2012. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved.postprin

Suppression of nickel out-diffusion from porous nickel-titanium shape memory alloy by plasma immersion ion implantation

Summary form only given. Porous nickel titanium is a promising material for medical application not only because of its super elasticity and shape memory effect but also the porous structure which may enhance bone growth due to the increased surface area. It is thus especially suitable for bone tissue in-growth and fixation of biomedical implants. However, like its dense counterpart, Ni leaching from the materials causes health concern. Thus, in order to suppress Ni diffusion from the materials to body fluids and tissues in humans, a diffusion barrier or similar structure must be introduced. In this work, we produced this diffusion barrier layer by oxygen or nitrogen plasma immersion ion implantation (PIII). In vitro tests were conducted by immersing the plasma-treated NiTi into simulated body fluid (SBF) at 37plusmn0.5degC for 5 weeks and the resulting SBF was analyzed for Ni and Ti using inductively-coupled plasma mass spectrometry (ICMPS). Our results show that Ni leaching is significantly mitigated by both nitrogen and oxygen PIII.published_or_final_versio

Estimated birth weight and adult cardiovascular risk factors in a developing southern Chinese population: a cross sectional study

Background. Birth weight is negatively associated with cardiovascular diseases and diabetes, but the associations are less well-established in developing populations where birth weight is often unavailable. We studied the association of birth weight and cardiovascular risk, using birth rank as an instrumental variable, in Southern China. Methods. We used published data on birth weight by birth rank from an appropriate population and baseline data from the Guangzhou Biobank Cohort Study phases 2 & 3 (2005-8) to examine the adjusted associations, using instrumental variable analysis, of birth weight with clinically measured cardiovascular risk factors and the metabolic syndrome in older (≥ 50 years) men (n = 5,051) and women (n = 13,907). Results. Estimated birth weight was associated with lower blood pressure (systolic -0.25 mm Hg 95% confidence interval (CI), -0.53 to 0.03 and diastolic -0.33 mm Hg 95% CI -0.48 to -0.18 per standard deviation higher birth weight), but had little association with glucose, lipids, waist-hip ratio, body mass index or the metabolic syndrome, adjusted for age, sex, early environment and number of offspring. Conclusion. Birth weight may impact blood pressure; however associations of birth weight with other cardiovascular risk factors may not be related to foetal exposures, but speculatively could be an historical co-incidence, with corresponding implications for prevention. © 2010 Schooling et al; licensee BioMed Central Ltd.published_or_final_versio

Clinical features, management, and prognostic factors of status epilepticus in Chinese

Poster PresentationINTRODUCTION: Status epilepticus (SE) is a neurological emergency with significant mortality and morbidity. There are currently limited data regarding the causes and outcomes of SE in our locality, and identification of prognostic factors, especially those available at presentation, could lower risk of under- or over-treatment in SE. METHODS: We retrospectively studied the clinical characteristics, management, and clinical outcome of adults diagnosed with incident SE, excluding episodes due to cerebral anoxia, at a regional hospi…published_or_final_versio