Displaying publications 1 - 20 of 88 in total

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  1. Khan A, Zarin R, Hussain G, Ahmad NA, Mohd MH, Yusuf A
    Results Phys, 2021 Jan;20:103703.
    PMID: 33520623 DOI: 10.1016/j.rinp.2020.103703
    The dynamic of covid-19 epidemic model with a convex incidence rate is studied in this article. First, we formulate the model without control and study all the basic properties and results including local and global stability. We show the global stability of disease free equilibrium using the method of Lyapunov function theory while for disease endemic, we use the method of geometrical approach. Furthermore, we develop a model with suitable optimal control strategies. Our aim is to minimize the infection in the host population. In order to do this, we use two control variables. Moreover, sensitivity analysis complemented by simulations are performed to determine how changes in parameters affect the dynamical behavior of the system. Taking into account the central manifold theory the bifurcation analysis is also incorporated. The numerical simulations are performed in order to show the feasibility of the control strategy and effectiveness of the theoretical results.
  2. Hooi LS, Ong LM, Ahmad G, Bavanandan S, Ahmad NA, Naidu BM, et al.
    Kidney Int, 2013 Nov;84(5):1034-40.
    PMID: 23760287 DOI: 10.1038/ki.2013.220
    In this population-based study, we determine the prevalence of chronic kidney disease in West Malaysia in order to have accurate information for health-care planning. A sample of 876 individuals, representative of 15,147 respondents from the National Health and Morbidity Survey 2011, of the noninstitutionalized adult population (over 18 years old) in West Malaysia was studied. We measured the estimated glomerular filtration rate (eGFR) (CKD-EPI equation); albuminuria and stages of chronic kidney disease were derived from calibrated serum creatinine, age, gender and early morning urine albumin creatinine ratio. The prevalence of chronic kidney disease in this group was 9.07%. An estimated 4.16% had stage 1 chronic kidney disease (eGFR >90 ml/min per 1.73 m(2) and persistent albuminuria), 2.05% had stage 2 (eGFR 60-89 ml/min per 1.73 m(2) and persistent albuminuria), 2.26% had stage 3 (eGFR 30-59 ml/min per 1.73 m(2)), 0.24% had stage 4 (eGFR 15-29 ml/min per 1.73 m(2)), and 0.36% had stage 5 chronic kidney disease (eGFR <15 ml/min per 1.73 m(2)). Only 4% of respondents with chronic kidney disease were aware of their diagnosis. Risk factors included increased age, diabetes, and hypertension. Thus, chronic kidney disease in West Malaysia is common and, therefore, warrants early detection and treatment in order to potentially improve outcome.
    Study name: National Health and Morbidity Survey (NHMS-2011)
  3. Chee Cheong K, Yoon Ling C, Kuang Hock L, Mohd Ghazali S, Chien Huey T, Che Ibrahim MK, et al.
    PMID: 30781699 DOI: 10.3390/ijerph16040593
    A growing number of fast-food outlets in close proximity to residential areas raises a question as to its impact on childhood overweight and obesity. This study aimed at determining the relationship between the availability of fast-food outlets that were in close proximity to residential areas and overweight among Malaysian children aged 5 to 18 years. Measurement data on the weight and height of 5544 children (2797 boys, 2747 girls) were obtained from the National Health and Morbidity Survey 2011. Overweight (including obesity) is defined as BMI-for-age z-score > +1 SD based on the WHO growth reference. Geographic information system geospatial analysis was performed to determine the number of fast-food outlets within 1000 m radius from the children's residential address. Multiple logistic regression was conducted to examine the association between the availability of fast-food outlets (none or more than one outlet) and overweight with adjustment for age, sex, ethnicity, monthly household income, parental educational level, residential area and supermarket density. Our results showed that the prevalence of overweight was 25.0% and there was a statistically significant association between the density of fast-food outlets and overweight (odds ratio: 1.23, 95% confidence interval: 1.03, 1.47). Our study suggested that the availability of fast-food outlets with close proximity in residential areas was significantly associated with being overweight among children. Limiting the number of fast-food outlets in residential areas could have a significant effect in reducing the prevalence of overweight among Malaysian children.
  4. Shoaib LA, Safii SH, Naimie Z, Ahmad NA, Sukumaran P, Yunus RM
    Eur J Dent Educ, 2018 Feb;22(1):e26-e34.
    PMID: 27995730 DOI: 10.1111/eje.12252
    OBJECTIVES: This study was conducted in University of Malaya to evaluate student perceptions on the contribution and role of an effective clinical teacher based on the cognitive apprenticeship model in clinical practice.

    METHODS: Self-administered questionnaires were distributed to 233 undergraduate dental students involved with clinical teaching. This modified and validated questionnaire focusing on students' learning environment was used in order to gain relevant information related to dental clinical teaching. Six domains with different criteria applicable to clinical teaching in dentistry were selected consisting of modelling (four criteria), coaching (four criteria), scaffolding (four criteria), articulation (four criteria), reflection (two criteria) and general learning environment (six criteria). Data analyses were performed using IBM SPSS Statistics 20.

    RESULTS: Majority of the students expressed positive perceptions on their clinical learning experience towards the clinical teachers in the Faculty of Dentistry, University of Malaya, in all criteria of the domains. Few negative feedbacks concerning the general learning environment were reported.

    CONCLUSION: Further improvement in the delivery of clinical teaching preferably by using wide variety of teaching-learning activities can be taken into account through students' feedback on their learning experience.

  5. Aziz FAA, Ahmad NA, Razak MAA, Omar M, Kasim NM, Yusof M, et al.
    BMC Public Health, 2018 Dec 11;18(1):1363.
    PMID: 30537956 DOI: 10.1186/s12889-018-6266-z
    BACKGROUND: Globally, diarrhoea is one of the major causes of morbidity and mortality among children under than 5 years of age. There is a scarcity of published data on acute gastroenteritis (AGE) prevalence in Malaysia among children. This study aims to determine factors associated with diarrhoea in children aged less than 5 years in Malaysia.

    METHOD: Data from the National Health and Morbidity Survey 2016 conducted by Ministry of Health was analysed. This nationwide survey involved 15,188 children below five years old. The survey was carried out using a two-stage stratified sampling design to ensure national representativeness. The Questionnaire from UNICEF's Multiple Indicator Cluster Survey (MCIS) was adapted to suit local requirements. Analysis was done using SPSS Version 23. Descriptive followed by multiple logistic regression were done to identify relevant factors.

    RESULT: The prevalence of diarrhoea among children under five in Malaysia was 4.4% (95% CI: 3.8,5.2). Analysis using logistic regression indicated that only ethnicity and usage of untreated water were significantly associated with diarrhoea among children after controlling for relevant factors. By ethnicity, children in the 'Other Bumiputera' group had 2.5 times the odds of having diarrhoea compared to children of Malay ethnicity. Children of Indian ethnicity were also at higher risk, at almost double the odds, as well as other ethnic groups (1.5 times). Children who used untreated water supply were two times more likely to develop diarrhoea.

    CONCLUSION: There is a higher risk of diarrhoea among children of 'Other Bumiputera' ethnicity, Indian ethnicities, and other ethnic groups and those who consume untreated water. Strategies to reduce diarrhoea among children should be targeted towards these at-risk populations. In addition, the Government must strive to ensure universal access to treated clean water in Malaysia and the Ministry of Health must focus on raising awareness on how to prevent diarrhoea.

  6. Kpokiri EE, Wu D, Srinivas ML, Anderson J, Say L, Kontula O, et al.
    Sex Transm Infect, 2022 02;98(1):38-43.
    PMID: 33846277 DOI: 10.1136/sextrans-2020-054822
    Population health surveys are rarely comprehensive in addressing sexual health, and population-representative surveys often lack standardised measures for collecting comparable data across countries. We present a sexual health survey instrument and implementation considerations for population-level sexual health research. The brief, comprehensive sexual health survey and consensus statement was developed via a multi-step process (an open call, a hackathon, and a modified Delphi process). The survey items, domains, entire instruments, and implementation considerations to develop a sexual health survey were solicited via a global crowdsourcing open call. The open call received 175 contributions from 49 countries. Following review of submissions from the open call, 18 finalists and eight facilitators with expertise in sexual health research, especially in low- and middle-income countries (LMICs), were invited to a 3-day hackathon to harmonise a survey instrument. Consensus was achieved through an iterative, modified Delphi process that included three rounds of online surveys. The entire process resulted in a 19-item consensus statement and a brief sexual health survey instrument. This is the first global consensus on a sexual and reproductive health survey instrument that can be used to generate cross-national comparative data in both high-income and LMICs. The inclusive process identified priority domains for improvement and can inform the design of sexual and reproductive health programs and contextually relevant data for comparable research across countries.
  7. Ahmad NA, Praveena SM, Tee KS
    Front Psychol, 2022;13:895816.
    PMID: 36300062 DOI: 10.3389/fpsyg.2022.895816
    The study examines the psychometric properties of the adapted Schutte Emotional Intelligence Scale (A-SEIS) with 200 undergraduate students at the Universiti Putra Malaysia (UPM). Upon the permission, the researchers adapted the original instrument, SEIS by incorporating a new construct which is understanding of emotions and some ability-based items into the perceived emotions construct. The A-SEIS is a mixed (trait and ability) measure EI instrument that aims at assessing four important dimensions of EI, including perception of emotions, utilization of emotions, understanding of emotions, and management of emotions. The study investigated the content validity of the A-SEIS by using the content validity indexing (CVI). Three expert panels translated and back-translated the A-SEIS and rated the degree of relevance of every item based on the four-point scale provided in the content validation form. The exploratory factor analysis (EFA) methods were used to explore the underlying structure of the A-SEIS. The general validity testing of the adapted instrument was carried out in the framework of the structural equation modeling (SEM) approach by applying two iterations of confirmatory factor analysis (CFA), the first approach is the covariance-based SEM (CB-SEM) approach, followed by the partial least squares based SEM (PLS-SEM) using two different software: AMOS and smartPLS. Research findings concluded that the instrument is reliable and valid to be applied in tertiary education settings and future research.
  8. Alareqe NA, Roslan S, Nordin MS, Ahmad NA, Taresh SM
    Front Psychol, 2021;12:562619.
    PMID: 34566736 DOI: 10.3389/fpsyg.2021.562619
    Millon Clinical Multiaxial Inventory MCMI-III is a multidimensional measure of psychopathology with excellent construct validity, test-retest reliability as well as internal consistency. Factor analysis of the MCMI-III has produced mixed results, extracting parsimonious three-factor solutions, or replicating the original four-factor solution in psychiatric samples from Western countries. However, little work has been done on the psychometric properties of the MCMI-III, using non-Western psychiatric samples. Outpatients (N = 212) completed the MCMI-III during a semi-structured interview. Eight exploratory factor analysis (EFA) methods were used to explore the underlying structure of MCMI-III. Skewness, kurtosis, and descriptive statistics confirmed that scales of MCMI-III were normally distributed. High-internal consistency was found. The eight EFA methods applied to the 24 clinical scales identified a consensual three-factor solution: factor I (internalizing psychopathology; 18 scales), factor II (externalizing psychopathology; 4 scales) and factor III (psychological disturbance; 2 scales), accounting for a total of 72% of the common variance. Regarding the cross-cultural equivalence of the MCMI-III structure, Tucker's congruence coefficient (Φ) was used and confirmed that internalizing (F1) and externalizing psychopathology (F2) factors obtained in this study are similar to high vs. low psychopathology and emotional constraint factors provided by American study of Haddy et al. (2005) (Φ was 0.86 and 0.97). These two factors are also similar to the general adjustment and antisocial acting out factors provided by the American study of Craig and Bivens (1998) (Φ was 0.82 and 0.96). The first two factors in this study also reflect high similarity with the factor solutions obtained with the Italian and Dutch versions of MCMI-III (Rossi et al., 2007; Pignolo et al., 2017). Despite using a psychiatric sample from a non-Western culture, the two factors identified for this MCMI-III Arabic version were similar to those reported on studies with MCMI-III, using primarily Western samples (Craig and Bivens, 1998; Rossi et al., 2007).
  9. Yusof M, Awaluddin SM, Omar M, Ahmad NA, Abdul Aziz FA, Jamaluddin R, et al.
    J Environ Public Health, 2018;2018:1803025.
    PMID: 29853924 DOI: 10.1155/2018/1803025
    Introduction: Anaemia is common among the elderly, yet it remains an underresearched clinical condition. This study investigates ethnic differences in prevalence of anaemia and identifies potential factors associated with anaemia in the elderly.
    Methods: Data from the National Health & Morbidity Survey (NHMS) 2015 conducted by Ministry of Health was analyzed. Haemoglobin levels were measured using point-of-care testing, HemoCue® Hb 201+ System©, from consenting individuals. Demographic information and other clinical information were obtained through a structured questionnaire. Descriptive and multivariate analyses were conducted and significant results were presented as adjusted odds ratio.
    Results: A total of 3794 participants aged 60 years and older responded to the anaemia module with a response rate of 93.7%. 64.0% of respondents were of Malay ethnicity, 21.6% were Chinese, 6.1% were Indians, and 8.3% were of other ethnicities. The overall prevalence of anaemia among older people was 35.3%. The highest prevalence of anaemia was found among respondents of Indian ethnicity (45.5%). The Indian (aOR: 1.72; 95% CI 1.26-2.34) and Malay (aOR: 1.25; 95% CI 1.04-1.49) ethnic groups were more likely to be anaemic in comparison to those of Chinese ethnicity. Anaemia in older people was also associated with increasing age, history of hospital admission, and the presence of diabetes mellitus.
    Conclusion: Anaemia in the elderly is associated with Indian and Malay ethnicities, increasing age, hospitalization, and diabetes. Our study has identified important information on a common condition which will guide and assist future studies in reducing the burden of anaemia.
    Study name: National Health and Morbidity Survey (NHMS-2015)
  10. Liew SH, Razak MAA, Kassim MSA, Ahmad NA, Tan L
    BMC Public Health, 2023 Nov 06;23(1):2165.
    PMID: 37932717 DOI: 10.1186/s12889-023-17019-2
    BACKGROUND: According to World Health Organization (WHO), the fourth leading cause of death among adolescents aged 15 -19 years is suicide. The National Health and Morbidity Survey (NHMS) 2017 reported that suicidal attempts among school adolescents increased from 6.8%-6.9% as compared to NHMS 2012. Suicide attempts can cause significant negative impacts on health, social and economic status. Bullying is one of the factors for adolescent suicide attempts, and its relationship to suicidality in adolescents has been shown in numerous research.

    OBJECTIVES: This study examined the relationship between suicide attempts and bullying among school adolescents in Malaysia.

    METHODS: Data from the Malaysia NHMS 2017, a nationwide study that adopted a two-stage cluster sampling design, were analysed. The survey used a self-administered questionnaire in bilingual language adapted from GSHS developed by WHO. Participants were secondary school students aged 13 -17 in all states. Descriptive and multiple logistic regression analyses were performed using IBM SPSS version 28.

    RESULTS: A total of 27,497 school adolescents participated in the study. Results showed that 6.9% of school adolescents had attempted suicide. There was 16.2% of adolescents being bullied. Multiple logistic regression revealed that students who were bullied were more likely to have suicide attempts (aOR 4.827, 95% CI: 4.143, 5.624) P 

  11. Abd Razak MA, Ahmad NA, Abd Aziz FA, Jamaluddin R, Sidik SM, Awaluddin SM, et al.
    Asia Pac J Public Health, 2019 11;31(8_suppl):30S-37S.
    PMID: 31402682 DOI: 10.1177/1010539519867796
    Limited evidence on the association of being bullied with depression among adolescents was found in Malaysia. This study aimed to determine the association of being bullied and depression among Malaysian school-going adolescents. Data from the National Health and Morbidity Survey 2017, a cross-sectional study conducted from March to May 2017, was analyzed using descriptive and multiple logistic regression analysis. A validated tool, the Depression, Anxiety, and Stress Scale-21 was used to categorize those with moderate or higher levels of depressive symptoms as having depression. A total of 27 399 school-going adolescents participated and 18.3% were found depressed. Adolescents of Indian ethnicity (adjusted odds ratio [aOR] = 2.02, P < .001), those with parents living apart (aOR = 1.41, P < .001), and those who were being bullied (aOR = 2.98, P < .001) were more likely to have depression. This study demonstrated the association between being bullied and having depression. Comprehensive preventive strategies should be implemented taking into consideration the findings from this study.
  12. Ahmad NA, Mancini MV, Ant TH, Martinez J, Kamarul GMR, Nazni WA, et al.
    Philos Trans R Soc Lond B Biol Sci, 2021 02 15;376(1818):20190809.
    PMID: 33357050 DOI: 10.1098/rstb.2019.0809
    Aedes aegypti mosquitoes carrying the wAlbB Wolbachia strain show a reduced capacity to transmit dengue virus. wAlbB has been introduced into wild Ae. aegypti populations in several field sites in Kuala Lumpur, Malaysia, where it has persisted at high frequency for more than 2 years and significantly reduced dengue incidence. Although these encouraging results indicate that wAlbB releases can be an effective dengue control strategy, the long-term success depends on wAlbB maintaining high population frequencies and virus transmission inhibition, and both could be compromised by Wolbachia-host coevolution in the field. Here, wAlbB-carrying Ae. aegypti collected from the field 20 months after the cessation of releases showed no reduction in Wolbachia density or tissue distribution changes compared to a wAlbB laboratory colony. The wAlbB strain continued to induce complete unidirectional cytoplasmic incompatibility, showed perfect maternal transmission under laboratory conditions, and retained its capacity to inhibit dengue. Additionally, a field-collected wAlbB line was challenged with Malaysian dengue patient blood, and showed significant blocking of virus dissemination to the salivary glands. These results indicate that wAlbB continues to inhibit currently circulating strains of dengue in field populations of Ae. aegypti, and provides additional support for the continued scale-up of Wolbachia wAlbB releases for dengue control. This article is part of the theme issue 'Novel control strategies for mosquito-borne diseases'.
  13. Hoffmann AA, Ahmad NW, Keong WM, Ling CY, Ahmad NA, Golding N, et al.
    iScience, 2024 Feb 16;27(2):108942.
    PMID: 38327789 DOI: 10.1016/j.isci.2024.108942
    Partial replacement of resident Aedes aegypti mosquitoes with introduced mosquitoes carrying certain strains of inherited Wolbachia symbionts can result in transmission blocking of dengue and other viruses of public health importance. Wolbachia strain wAlbB is an effective transmission blocker and stable at high temperatures, making it particularly suitable for hot tropical climates. Following trial field releases in Malaysia, releases using wAlbB Ae. aegypti have become operationalized by the Malaysian health authorities. We report here on an average reduction in dengue fever of 62.4% (confidence intervals 50-71%) in 20 releases sites when compared to 76 control sites in high-rise residential areas. Importantly the level of dengue reduction increased with Wolbachia frequency, with 75.8% reduction (61-87%) estimated at 100% Wolbachia frequency. These findings indicate large impacts of wAlbB Wolbachia invasions on dengue fever incidence in an operational setting, with incidence expected to further decrease as wider areas are invaded.
  14. Abdul Wahab RM, Zainal Ariffin SH, Yeen WW, Ahmad NA, Senafi S
    ScientificWorldJournal, 2012;2012:236427.
    PMID: 22629122 DOI: 10.1100/2012/236427
    Three specific orthodontic tooth movement genes, that is, FCRL1, HSPG2, and LAMB2 were detected at upper first premolar (with appliance) dental pulp tissue by using GeneFishing technique as compared to lower first premolar (without appliance). These three differentially expressed genes have the potential as molecular markers during orthodontic tooth movement by looking at molecular changes of pulp tissue.
  15. Harith AA, Ahmad NA, Sahril N, Wahab NA, Kassim NA, Othman S, et al.
    Geriatr Gerontol Int, 2020 Dec;20 Suppl 2:43-48.
    PMID: 33370862 DOI: 10.1111/ggi.14039
    AIM: An aging population is a potential burden for unprepared developing countries. Malaysia is foreseen to be an aging country by 2035. Thus, this study aimed to determine the prevalence and factors associated with hearing disability among older persons in Malaysia.

    METHODS: Data from a nationwide survey implemented using a stratified cluster sampling design were analyzed. This study was carried out through face-to-face interviews and guided questionnaires. The questions were based on the Washington Group of Disability (WG) questionnaires, which produce multiple disability identifiers. Hearing disability is defined as at least one domain or question out of four questions coded as "A lot of difficulty" or "Cannot hear at all".

    RESULTS: The prevalence of hearing disability among older persons aged ≥60 years was 6.4% (95% CI 5.0-8.3), whereas 1.5% (95% CI 0.90, 2.50) older persons were reported to be using a hearing aid. The determinants of hearing disability are being male (aOR 2.67, 95% CI 1.94-3.66), being unemployed (retired, homemaker, unemployed; aOR 1.86, 95% CI 1.86-4.14) and had no formal education (aOR 18.25, 95% CI 4.18-79.55).

    CONCLUSIONS: Promoting healthy aging is important and crucial for Malaysia, in preparation toward an aging nation, as it could reduce the country's financial burden in the long term. Health-related agencies should promote health awareness and treatment centers in relation to hearing disability among older persons, as they should be educated and informed about healthcare choices availability, which is aligned with the Global Disability Action Plan 2014-2021. Geriatr Gerontol Int 2020; 20: 43-48.

  16. Jeyaprakasam NK, Razak MF, Ahmad NA, Santhanam J
    Mycopathologia, 2016 Jun;181(5-6):397-403.
    PMID: 26847667 DOI: 10.1007/s11046-016-9984-8
    Although non-sporulating molds (NSM) are frequently isolated from patients and have been recognized as agents of pulmonary disease, their clinical significance in cutaneous specimens is relatively unknown. Therefore, this study aimed to identify NSM and to determine the keratinolytic activity of isolates from cutaneous sites. NSM isolates from clinical specimens such as skin, nail, and body fluids were identified based on their ribosomal DNA sequences. Of 17 NSM isolates (7 Ascomycota, 10 Basidiomycota), eleven were identified to species level while five were identified to the genus level. These include Schizophyllum commune, a known human pathogen, Phoma multirostrata, a plant pathogen, and Perenniporia tephropora, a saprophyte. To determine fungal pathogenicity, keratinolytic activity, a major virulence factor, was evaluated ex vivo using human nail samples by measuring dye release from keratin azure, for NSM along with pathogens (Trichophyton mentagrophytes, Trichophyton rubrum, Microsporum canis and Fusarium spp.) and nonpathogenic (endophyte) fungi for comparison. This study showed that pathogenic fungi had the highest keratinolytic activity (7.13 ± 0.552 keratinase units) while the nonpathogenic endophytes had the lowest activity (2.37 ± 0.262 keratinase units). Keratinolytic activity of two Ascomycota NSM (Guignardia mangiferae and Hypoxylon sp.) and one Basidiomycota NSM (Fomitopsis cf. meliae) was equivalent to that of pathogenic fungi, while Xylaria feejeensis showed significantly higher activity (p 
  17. Smran A, Abdullah M, Ahmad NA, Alrahlah A, Al-Maflehi N, Samran A
    BMC Oral Health, 2023 Sep 18;23(1):673.
    PMID: 37723511 DOI: 10.1186/s12903-023-03377-1
    BACKGROUND: The aim of this study was to evaluate the effect of thermal and mechanical cyclic aging using a mastication simulator on push-out bond strength of mandibular premolars obturated with AH Plus and BioRoot RCS root canal sealers.

    METHODS: With REVO-S files up to SU/0.06 taper, 48 single-rooted premolar teeth were instrumented. The teeth were randomly divided into two main groups (n = 24) based on the two root canal sealers used (AH Plus and BioRoot RCS). All teeth were obturated with h matched-taper single-cone. Each main group was then subdivided into three subgroups (A, B, and C) (n = 8). Group A served as the negative control group (no-thermocycling aging). While groups B and C were subjected to thermal changes in a thermocycler machine (15,000 and 30,000 thermal cycles, respectively), followed by two different dynamic loading periods, 3 × 105 and 6 × 105 in a masticatory simulator with a nominal load of 5 kg at 1.2 Hz which represent roughly 1½ and 3 years of clinical function respectively. 2 mm slice at 3 levels, apical, middle, and coronal, to obtain 3 sections were prepared and subjected to push-out test using a universal testing machine. Statistical analysis was performed using analysis of variance (ANOVA) followed by a Tukey post hoc comparisons test and an independent T-test. A significance level of 5% was used.

    RESULTS: After thermal-mechanical cyclic aging, the two root canal sealers showed a significantly decreased in push-out bond strength (p 

  18. Smran A, Abdullah M, Ahmad NA, Ben Yahia F, Fouda AM, Alturaiki SA, et al.
    PLoS One, 2024;19(3):e0299552.
    PMID: 38483853 DOI: 10.1371/journal.pone.0299552
    This research aimed to assess the stress distribution in lower premolars that were obturated with BioRoot RCS or AH Plus, with or without gutta percha (GP), and subjected to vertical and oblique forces. One 3D geometric model of a mandibular second premolar was created using SolidWorks software. Eight different scenarios representing different root canal filling techniques, single cone technique with GP and bulk technique with sealer only with occlusal load directions were simulated as follows: Model 1 (BioRoot RCS sealer and GP under vertical load [VL]), Model 2 (BioRoot RCS sealer and GP under oblique load [OL]), Model 3 (AH Plus sealer with GP under VL), Model 4 (AH Plus sealer with GP under OL), Model 5 (BioRoot RCS sealer in bulk under VL), Model 6 (BioRoot RCS in bulk under OL), Model 7 (AH Plus sealer in bulk under VL), and Model 8 (AH Plus sealer in bulk under OL). A static load of 200 N was applied at three occlusal contact points, with a 45° angle from lingual to buccal. The von Mises stresses in root dentin were higher in cases where AH Plus was used compared to BioRoot RCS. Furthermore, shifting the load to an oblique direction resulted in increased stress levels. Replacing GP with sealer material had no effect on the dentin maximum von Mises stress in BioRoot RCS cases. Presence of a core material resulted in lower stress in dentin for AH Plus cases, however, it did not affect the stress levels in dentin for cases filled with BioRoot RCS. Stress distribution in the dentin under oblique direction was higher regardless of sealer or technique used.
  19. Firdaus F, Ahmad NA, Sahibuddin S
    Sensors (Basel), 2019 Dec 15;19(24).
    PMID: 31847488 DOI: 10.3390/s19245546
    Wireless local area networks (WLAN)-fingerprinting has been highlighted as the preferred technology for indoor positioning due to its accurate positioning and minimal infrastructure cost. However, its accuracy is highly influenced by obstacles that cause fluctuation in the signal strength. Many researchers have modeled static obstacles such as walls and ceilings, but few studies have modeled the people's presence effect (PPE), although the human body has a great impact on signal strength. Therefore, PPE must be addressed to obtain accurate positioning results. Previous research has proposed a model to address this issue, but these studies only considered the direct path signal between the transmitter and the receiver whereas multipath effects such as reflection also have a significant influence on indoor signal propagation. This research proposes an accurate indoor-positioning model by considering people's presence and multipath using ray-tracing, we call it (AIRY). This study proposed two solutions to construct AIRY: an automatic radio map using ray tracing and a constant of people's effect for the received signal strength indicator (RSSI) adaptation. The proposed model was simulated using MATLAB software and tested at Level 3, Menara Razak, Universiti Teknologi Malaysia. A K-nearest-neighbor (KNN) algorithm was used to define a position. The initial accuracy was 2.04 m, which then reduced to 0.57 m after people's presence and multipath effects were considered.
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