Dental health status of Hong Kong preschool children

Objectives. To describe the dental health status of preschool children in Hong Kong, and to investigate the e!ects of selected socio-demographic factors and oral health–related behaviors on the dental health of the children. Methods. The study population was Chinese preschool children. The sampling frame was kindergartens with an enrolment of 70 children or more, located on Hong Kong Island. Through strati'ed random sampling, 12 kindergartens were selected. All children attending grades 1 and 2 in the kindergartens were invited. Children with parental consent were clinically examined in the kindergartens in March 2007 by one of two calibrated examiners using a disposable mouth-mirror attached to an intraoral LED light and a ball-ended probe. Diagnostic criteria for dental caries followed those recommended by the World Health Organization. A questionnaire on the child’s socio-demographic background and oral health–related behaviors was completed by the parents. Results. A total of 1513 children were invited and 1343 (89%) were examined. Their mean (standard deviation) age was 3.9 (0.7) years and 51% were boys. Around one third (35%) of the children had experienced dental caries. The mean decayed, missing or 'lled teeth (dmft) score was 1.5, increasing from 1.2 at age 3 to 2.0 at age 5 (analysis of variance, P=0.016). Active decay (dt) accounted for 90% of the dmft score. Higher dmft scores were found in children who were born in Mainland China or came from lower socio-economic classes. Children who had poorer dietary or toothbrushing habits also had more dental caries. Conclusion. Prevalence of dental caries among the Hong Kong preschool children was not high but the severity of caries varied with the children’s socio-demographic background, and their dietary and toothbrushing habits.published_or_final_versio

On the color stability of phosphor-converted white LEDs under DC, PWM, and bilevel drive

Most commercial white LEDs are made from nitride-based blue LEDs coated with yttrium aluminium garnet phosphor, which produce spectra that shift in opposite directions under the influences of drive current and junction temperature changes. This property gives rise to different emitted spectra, hence chromaticity properties, when the LED is driven/dimmed by different current waveforms. By using a commercial white LED sample, LUXEON K2, the effects of drive current and junction temperature on the changes of chromaticity coordinates are studied experimentally. The impact of dc, pulse width modulation (PWM), and bilevel current waveform is discussed through a graphical analysis, followed by experimental verification. It is proven that dc offers the best color stability over dimming due to the counteracting influences of drive current and junction temperature variations, whereas an LED constantly suffers from noneliminable chromaticity changes when driven by the PWM. Theoretical explanations are given to justify these cases, and it is found that, for the case of dc drive, an ideal heat sinks thermal resistance can be selected based on a simple equation to minimize the overall chromaticity change over dimming. This paper provides an in-depth discussion on the relations between the chromaticity properties of phosphor-converted (pc) white LEDs and the driving/dimming methods used. © 2011 IEEE.published_or_final_versio

Stationary and adaptive color-shift reduction methods based on the bilevel driving technique for phosphor-converted white LEDs

The bilevel driving technique has realized a 2-D control of the luminosity and emitted color of white LEDs with duty cycle and forward current levels. Unfortunately, various combinations of these dimming control parameters can lead to significant changes in junction temperature, which further modify the luminosity and emitted color of LEDs. In this paper, the theoretical aspects of these complex interactions and the impact of bilevel drive on the color-shift properties of white LEDs are discussed in detail by using a mathematical color-shift model. Two color-shift reduction methods are proposed based on the insights obtained from this model. This study shows that a heat sinks thermal resistance that minimizes the overall color shift over dimming can be uniquely determined from the knowledge of some measurable LED parameters, and gives rise to a global minimum color shift. If such a thermal resistance cannot be realized due to practical limitations, the second method that utilizes an adaptive change of forward current levels over dimming can be adopted. Based on their nature, these methods are classified as stationary and adaptive methods, respectively. Their validity is supported by experimental measurements on a commercial white LED. © 2011 IEEE.published_or_final_versio

Transcranial Direct Current Stimulation Modulates Working Memory Maintenance Processes in Healthy Individuals

The effects of transcranial direct current stimulation (tDCS) at the pFC are often investigated using cognitive paradigms, particularly working memory tasks. However, the neural basis for the neuromodulatory cognitive effects of tDCS, including whi ch subprocesses are af f ected by sti mul ati on, i s not completely understood. We investigated the effects of tDCS on working memory task-related spectral activity during and after tDCS to gain better insights into the neurophysiological changes associated with stimulation. We reanalyzed data from 100 healthy participants grouped by allocation to receive either sham (0 mA, 0.016 mA, and 0.034 mA) or active (1 mA or 2 mA) stimulation during a 3-back task. EEG data were used to analyze event-related spectral power in frequency bands associated with working memory performance. Frontal theta event-related synchronization (ERS) was significantly reduced post-tDCS in the active group. Participants receiving active tDCS had slower RTs following tDCS compared with sham, suggesting interference with practice effects associated with task repetition. Theta ERS was not significantly correlated with RTs or accuracy. tDCS reduced frontal theta ERS poststimulation, suggesting a selective disruption to working memory cognitive control and maintenance processes. These findings suggest that tDCS selectively affects specific subprocesses during working memory, which may explain heterogenous behavioral effects

Association between neighbourhood walkability and metabolic risk factors influenced by physical activity: a cross-sectional study of adults in Toronto, Canada.

OBJECTIVE: To determine whether neighbourhood walkability is associated with clinical measures of obesity, hypertension, diabetes and dyslipidaemia in an urban adult population. DESIGN: Observational cross-sectional study. SETTING: Urban primary care patients. PARTICIPANTS: 78 023 Toronto residents, aged 18 years and over, who were formally rostered or had at least 2 visits between 2012 and 2014 with a primary care physician participating in the University of Toronto Practice Based Research Network (UTOPIAN), within the Canadian Primary Care Sentinel Surveillance Network (CPCSSN). MAIN OUTCOME MEASURES: Differences in average body mass index (BMI), systolic and diastolic blood pressure, fasting blood glucose, haemoglobin A1c (HbA1C), total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein and triglyceride between residents in the highest versus the lowest quartile of neighbourhood walkability, as estimated using multivariable linear regression models and stratified by age. Outcomes were objectively measured and were retrieved from primary care electronic medical records. Models adjusted for age, sex, smoking, medications, medical comorbidities and indices of neighbourhood safety and marginalisation. RESULTS: Compared with those in the lowest walkability quartile, individuals in the highest quartile had lower mean BMI (-2.64 kg/m2, 95% CI -2.98 to -2.30; p<0.001), systolic blood pressure (-1.35 mm Hg, 95% CI -2.01 to -0.70; p<0.001), diastolic blood pressure (-0.60 mm Hg, 95% CI 1.06 to -0.14; p=0.010) and HbA1c (-0.063%, 95% CI -0.11 to -0.021; p=0.003) and higher mean HDL (0.052 mmol/L, 95% CI 0.029 to 0.075; p<0.001). In age-stratified analyses, differences in the mean BMI were consistently observed for adults aged 18 to under 40 (-4.44 kg/m2, 95% CI -5.09 to -3.79; p<0.001), adults aged 40-65 (-2.74 kg/m2, 95% CI -3.24 to -2.23; p<0.001) and adults aged over 65 (-0.87 kg/m2, 95% CI -1.48 to -0.26; p=0.005). CONCLUSIONS: There was a clinically meaningful association between living in the most walkable neighbourhoods and having lower BMI in adults of all ages

The left anterior right temporal (LART) placement for electroconvulsive therapy: A computational modelling study

Electrode placement in electroconvulsive therapy (ECT) has a major impact on treatment efficacy and cognitive side effects. Left Anterior Right Temporal (LART) is a lesser utilised bilateral montage which may produce more optimal clinical outcomes relative to standard bitemporal ECT. In this study we used computational modelling to explore how stimulation effects from LART and two novel variants (LART – F3 and LART – Frontal) compared to the more common bilateral placements of bitemporal and bifrontal ECT. High resolution finite element human head models were generated from MRI scans of three subjects with Major Depressive Disorder. Differences in regional stimulation were examined through parametric tests for regions of interest and subtraction maps. Compared to bitemporal ECT, LART – Original resulted in significantly greater stimulation of the left cingulate gyrus (hypothesised to be associated with treatment efficacy), and relatively reduced stimulation of the bilateral hippocampi (potentially associated with cognitive side effects). No additional clinical benefit was suggested with the novel LART placements compared to the original LART. The original LART placement is a promising montage for further clinical investigation

Safety of repeated sessions of transcranial direct current stimulation: A systematic review

Background: Repeated sessions of transcranial direct current stimulation (tDCS) are increasingly used for therapeutic applications. However, adverse events (AEs) associated with repeated sessions have not been comprehensively evaluated. Objective: The aim of this study was therefore to evaluate the safety of repeated sessions of tDCS, examining AE risk relative to tDCS exposure. Further, to identify whether certain participant populations are particularly at risk from tDCS. Methods: A systematic review and meta-analysis included sham-controlled studies (up to June 2017) involving two or more tDCS sessions, spaced not more than a day apart. Data was extracted on AEs reported, total tDCS exposure (cumulative charge), and diagnostic groups (Healthy, Pain Disorder, Stroke, Neurocognitive Disorder, Neuropsychiatric Disorder, and Other). Univariate simple linear meta-regression analyses examined AE likelihood, comparing active and sham tDCS, with increasing exposure. Rates of AEs were compared for diagnostic groups. Results: 158 studies (total 4130 participants) met inclusion criteria and were included for quantitative analyses. The incidence of AEs (examined per session, by proportion of participants, and by the number of studies reporting AEs) did not increase with higher levels of tDCS exposure. Furthermore, AE rates were not found to be greater for any diagnostic group. Conclusions: Little evidence was found to suggest that repeated sessions of active tDCS pose increased risk to participants compared to sham tDCS within the limits of parameters used to date. Increased risks associated with greater levels of exposure to tDCS, or rare and under-reported AEs, however, cannot be ruled out

Population Pharmacokinetics and Pharmacodynamics of the Therapeutic and Adverse Effects of Ketamine in Patients With Treatment-Refractory Depression

We aimed to develop population pharmacokinetic/pharmacodynamic (PK/PD) models that can effectively describe ketamine and norketamine PK/PD relationships for Montgomery–Åsberg Depression Rating Scale (MADRS) scores, blood pressure (BP), and heart rate (HR) following i.v., s.c., and i.m. ketamine administration in patients with treatment-refractory depression. Ketamine PK/PD data were collected from 21 treatment-refractory depressed participants who received ketamine (dose titration 0.1–0.5 mg/kg as single doses) by i.v., s.c., or i.m. administration. Model development used nonlinear mixed effect modeling. Ketamine and norketamine PK were best described using two-compartment models with first-order absorption after s.c. and i.m. administration. Estimated ketamine bioavailability after i.m. and s.c. was ~ 64% with indistinguishable first-order absorption rate constants. Allometric scaling of body weight on all clearance and volumes of distribution improved the model fit. The delay in the concentration-response relationship for MADRS scores was best described using a turnover model (turnover time ~ 42 hours), whereas for the BP and HR rates this was an immediate effect model. For all PD effects, ketamine alone was superior to models with norketamine concentration linked to an effect. No covariates were identified for PD effects. The estimated half-maximal effective concentration from the MADRS score, BP, and HR were 0.44, 468, and 7,580 ng/mL, respectively. The integrated population models were able to effectively describe the PK/PD relationships for MADRS scores, BP, and HR after i.v., s.c., and i.m. ketamine administration. These findings allow for a deeper understanding of the complex relationships between route of ketamine administration and clinical response and safety

Dental caries situation of Hong Kong kindergarten children

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A new early cognitive screening measure to detect cognitive side-effects of electroconvulsive therapy?

Cognitive side-effects from electroconvulsive therapy (ECT) can be distressing for patients and early detection may have an important role in guiding treatment decisions over the ECT course. This prospective study examined the utility of an early cognitive screening battery for predicting cognitive side-effects which develop later in the ECT course. The screening battery, together with the Mini Mental Status Examination (MMSE), was administered to 123 patients at baseline and after 3 ECT treatments. A more detailed cognitive battery was administered at baseline, after six treatments (post ECT 6) and after the last ECT treatment (post treatment) to assess cognitive side-effects across several domains: global cognition, anterograde memory, executive function, speed and concentration, and retrograde memory. Multivariate analyses examined the predictive utility of change on items from the screening battery for later cognitive changes at post ECT 6 and post treatment. Results showed that changes on a combination of items from the screening battery were predictive of later cognitive changes at post treatment, particularly for anterograde memory ( p<0.01), after controlling for patient and treatment factors. Change on the MMSE predicted cognitive changes at post ECT 6 but not at post treatment. A scoring method for the new screening battery was tested for discriminative ability in a sub-sample of patients. This study provides preliminary evidence that a simple and easy-to-administer measure may potentially be used to help guide clinical treatment decisions to optimise efficacy and cognitive outcomes. Further development of this measure and validation in a more representative ECT clinical population is required. © 2013 Elsevier Ltd