PERFORMANCE OF A HEAT SINK WITH INTERRUPTED AND STAGGERED ELIIPITIC FINS

ABSTRACT: The power density of electronic devices has been increasing along with the rapid technology development. Cooling of electronic systems is therefore essential in controlling the component temperature and avoiding any hot spot. Heat sinks are commonly adopted in electronics cooling together with different technologies to enhance heat transfer process. Fin-based heat sinks are commonly designed so that coolants (gas or liquid) are forced to pass through the narrow straight channel. A driving fan is then needed to overcome the viscous pressure loss and maintain the coolant flow. As part of effort to improve the heat sink performance, this study simulated the details of the flow and temperature fields of heat sinks with interrupted and staggered elliptic fins cooled by forced convection. The focus of this study lies on three scenarios: Heat transfer before the flow reaches the periodic condition in the flow direction; effect of the heat sink base surface on flow and heat transfer; and conjugate heat transfer between convection and heat conduction inside the fins. In addition, studies were also conducted on the effect of the Reynolds number. The results of this paper can help design heat sinks for electronics cooling by employing the new concept of interrupted and staggered fins

Oral clinical status and oral health-related quality of life: is socioeconomic position a mediator or a moderator?

AIM: To evaluate whether socioeconomic position exerts a mediating and/or moderating effect on the association between oral clinical measures and oral health-related quality of life (OHRQoL) in adolescents. MATERIALS AND METHODS: The study analysed data on 5,445 adolescents aged 15-19 years from the Brazilian Oral Health Survey (SBBrasil Project). The numbers of decayed and missing teeth, number of sextants with gingivitis and malocclusion were assessed through oral clinical examinations. Participant's age, sex, OHRQoL and socioeconomic position were also collected. Monthly family income was used to indicate the participant's socioeconomic position, and OHRQoL was assessed using the Oral Impacts on Daily Performance. Moderation was tested using Poisson regression models. Structural equation modelling and Sobel's test assessed the mediation effects. RESULTS: Oral clinical measures, OHRQoL and socioeconomic position were significantly correlated (P < 0.001). The moderator effect of socioeconomic position on the association between all oral clinical measures and OHRQoL was observed. The impact of all oral clinical conditions on adolescents' OHRQoL was lower in the low-family-income groups compared with those with a better income. Socioeconomic position partially mediated the relationship between the four oral clinical measures and OHRQoL. Sobel's test confirmed these findings (P < 0.001). CONCLUSIONS: The findings suggest the importance of socioeconomic position as a moderator and mediator factor between oral clinical measures and OHRQoL. Disadvantaged adolescents are likely to experience poor OHRQoL due to oral conditions. The reduction of the impact of oral conditions on quality of life in adolescents may be enhanced by addressing social inequalities related to oral health

Does oral health influence school performance and school attendance? A systematic review and meta-analysis.

AIM: To examine the evidence on the influence of oral health status on school performance and school attendance in children and adolescents. DESIGN: A systematic review was performed in accordance with PRISMA included epidemiological studies that assessed concomitantly oral health measures, participants' school performance and/or school attendance. Electronic search was conducted on MEDLINE, SCOPUS, Web of Science, ScienceDirect, and LILACS. Studies published up to May 2018 in any language were eligible. The risk of bias was assessed using the Newcastle-Ottawa Scale. Meta-analysis was used to obtain pooled estimates between oral health measures and school performance and school attendance. RESULTS: Eighteen studies were included. Of them, fifteen studies were used for the meta-analyses. Most studies were assessed as moderate quality. Children with one or more decayed teeth had higher probability of poor school performance (OR = 1.44 95%CI: 1.24-1.64) and poor school attendance (OR = 1.57 95%CI: 1.08-2.05) than caries-free children. Poor parent's perception of child's oral health increased the odds of worse school performance (OR = 1.51 95%CI: 1.10-1.92) and poor school attendance (OR = 1.35 95%CI: 1.14-1.57). CONCLUSIONS: Children and adolescents with dental caries and those reporting worse oral health experience poor school performance and poor school attendance

Protective psychosocial factors and dental caries in children and adolescents: a systematic review and meta-analysis

BACKGROUND: Psychosocial protective factors include dispositional and family attributes that may reduce the occurrence of dental caries. AIM: This review analysed the evidence on the relationship between protective psychosocial factors and dental caries in children and adolescents. DESIGN: Primary studies involving children and adolescents were searched in the following electronic databases: Medline, SCOPUS, LILACS, SciELO, and Web of Science. The reference lists were also screened. Protective psychosocial factor descriptors were in accordance with the salutogenic theory. The outcome was clinical measure of dental caries. Quality assessments were performed using the Newcastle-Ottawa scale. RESULTS: The final search resulted in 35 studies, including 7 cohort, one case-control, and 27 cross-sectional studies. Most studies were of moderate quality. Meta-analyses revealed that low parental internal locus of control (cohort studies: OR = 1.42, 95% CI: 1.20-1.64; cross-sectional studies: OR = 1.30, 95% CI: 1.19-1.41), high parental external chance (OR = 1.20, 95% CI: 1.10-1.29), and high maternal sense of coherence (OR = 0.77, 95% CI: 0.62-0.93) were associated with dental caries in children. High social support (OR = 0.81, 95% CI: 0.68-0.93) and greater self-efficacy (OR = 1.50, 95% CI: 1.12-1.22) were also associated with dental caries in adolescents. CONCLUSIONS: The current evidence suggests that some salutogenic factors are important protective factors of dental caries during childhood and adolescence

Development and evaluation of CARIES-QC: a caries-specific measure of quality of life for children.

BACKGROUND: Existing paediatric oral health-related quality of life (OHRQoL) measures are generic instruments designed to evaluate a range of oral conditions. It has been found that disease-specific measures may be more adept at detecting subtle changes which occur following treatment of the condition in question. Furthermore, existing self-report OHRQoL measures have not involved children at all stages of development of the measure. The aim of this study was to develop a caries-specific measure of quality of life for children. METHODS: The first stage of the study involved a qualitative enquiry with children, aged 5-16 years, to inform the development of the measure. Children generated the potential items, contributed to item reduction and questionnaire design and participated in the testing of face and content validity. The resulting measure was evaluated in a cross-sectional validation study. Ethical approval was granted for the study. RESULTS: The qualitative study found that children discussed a number of caries-related impacts which affected their daily lives. These were incorporated into a draft measure which was further refined following testing of face and content validity. This resulted in the production of the Caries Impacts and Experiences Questionnaire for Children (CARIES-QC), comprising 16 items and one global question. Two hundred participants with a mean (range) age of 8.1 (5-16) years took part in the further evaluation of CARIES-QC. Four items, which did not fit the Rasch model, were removed from further analysis. The remaining 12 items demonstrated good internal consistency (alpha = 0.9) and the total score showed significant correlations with the number of decayed teeth, presence of pain, pulpal involvement, the Child Perceptions Questionnaire (16-item short form) and the global score (p < 0.01, Spearman's rho). CONCLUSION: In conclusion, children's input allowed the development of a valid and reliable child-centred caries-specific quality of life measure. CARIES-QC can now be used to evaluate which interventions for dental caries are most effective in reducing impacts from the child's perspective

Assessment of the quality of measures of child oral health-related quality of life

Background Several measures of oral health-related quality of life have been developed for children. The most frequently used are the Child Perceptions Questionnaire (CPQ), the Child Oral Impacts on Daily Performances (C-OIDP) and the Child Oral Health Impact Profile (COHIP). The aim of this study was to assess the methodological quality of the development and testing of these three measures. Methods A systematic search strategy was used to identify eligible studies published up to December 2012, using both MEDLINE and Web of Science. Titles and abstracts were read independently by two investigators and full papers retrieved where the inclusion criteria were met. Data were extracted by two teams of two investigators using a piloted protocol. The data were used to describe the development of the measures and their use against existing criteria. The methodological quality and measurement properties of the measures were assessed using standards proposed by the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) group. Results The search strategy yielded 653 papers, of which 417 were duplicates. Following analysis of the abstracts, 119 papers met the inclusion criteria. The majority of papers reported cross-sectional studies (n = 117) with three of longitudinal design. Fifteen studies which had used the original version of the measures in their original language were included in the COSMIN analysis. The most frequently used measure was the CPQ. Reliability and construct validity appear to be adequate for all three measures. Children were not fully involved in item generation which may compromise their content validity. Internal consistency was measured using classic test theory with no evidence of modern psychometric techniques being used to test unidimensionality of the measures included in the COSMIN analysis. Conclusion The three measures evaluated appear to be able to discriminate between groups. CPQ has been most widely tested and several versions are available. COHIP employed a rigorous development strategy but has been tested in fewer populations. C-OIDP is shorter and has been used successfully in epidemiological studies. Further testing using modern psychometric techniques such as item response theory is recommended. Future developments should also focus on the development of measures which can evaluate longitudinal change