Displaying publications 61 - 80 of 513 in total

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  1. Biodiesel synthesis from Prunus bokhariensis non-edible seed oil by using green silver oxide nanocatalyst
    Dawood S, Ahmad M, Zafar M, Asif S, Klemeš JJ, Bokhari A, et al.
    Chemosphere, 2022 Mar;291(Pt 2):132780.
    PMID: 34767846 DOI: 10.1016/j.chemosphere.2021.132780
    The present work investigates the proficiency of green silver oxide nanocatalyst synthesised from Monotheca buxifolia (Falc.) Dcne. leaves extract, and their application for biodiesel synthesis from novel Prunus bokhariensis seed oil (non-edible). The seed oil content of 55% and FFA content of 0.80 mg KOH/g were reported. Several analytical tools (EDX, FT-IR, SEM and XRD) were used to characterise the Ag2O nanocatalyst. Maximum (89%) FAME yield of the PBSOB (Prunus bokhariensis seed oil biodiesel) was achieved at ambient transesterification conditions i.e. 3.5 wt% nanocatalyst loading, 2.5 h reaction time, 130 °C of reaction temperature and 12:1 alcohol to oil ratio. The synthesised PBSOB was additionally characterised by analytical methods like, GC-MS and FT-IR. The different aspects of fuel were identified i.e. flash point (84 °C), kinematic viscosity (4.01 cSt @ 40 °C), sulphur content (0.0003 wt %), density (0.853 kg/L) and acid number (0.167 mg KOH/g). All the above properties were verified and agreed well with biodiesel international standards (European Union (14214), China GB/T (20828) and ASTM (6751, 951). In general, Prunus bokhariensis seed oil and Ag2O nanocatalyst seem to be remarkably active, cheap and stable candidates for the biodiesel industry in future.
  2. Fulltext Better outcome of COVID-19 positive kidney transplant recipients during the unremitting stage with optimized anticoagulation and immunosuppression
    AlOtaibi TM, Gheith OA, Abuelmagd MM, Adel M, Alqallaf AK, Elserwy NA, et al.
    Clin Transplant, 2021 Jun;35(6):e14297.
    PMID: 33768630 DOI: 10.1111/ctr.14297
    INTRODUCTION: COVID-19 is an ongoing pandemic with high morbidity and mortality and with a reported high risk of severe disease in kidney transplant recipients (KTR).

    AIM: We aimed to report the largest number of COVID-19-positive cases in KTR in a single center and to discuss their demographics, management, and evolution.

    METHODS: We enrolled all the two thousand KTR followed up in our center in Kuwait and collected the data of all COVID-19-positive KTR (104) from the start of the outbreak till the end of July 2020 and have reported the clinical features, management details, and both patient and graft outcomes.

    RESULTS: Out of the one hundred and four cases reported, most of them were males aged 49.3 ± 14.7 years. Eighty-two of them needed hospitalization, of which thirty-one were managed in the intensive care unit (ICU). Main comorbidities among these patients were hypertension in 64.4%, diabetes in 51%, and ischemic heart disease in 20.2%. Management strategies included anticoagulation in 56.7%, withdrawal of antimetabolites in 54.8%, calcineurin inhibitor (CNI) withdrawal in 33.7%, the addition of antibiotics in 57.7%, Tocilizumab in 8.7%, and antivirals in 16.3%. During a follow-up of 30 days, the reported number of acute kidney injury (AKI) was 28.7%, respiratory failure requiring oxygen therapy 46.2%, and overall mortality rate was 10.6% with hospital mortality of 13.4% including an ICU mortality rate of 35.5%.

    CONCLUSION: Better outcome of COVID-19-positive KTR in our cohort during this unremitting stage could be due to the younger age of patients and early optimized management of anticoagulation, modification of immunosuppression, and prompt treatment of secondary bacterial infections. Mild cases can successfully be managed at home without any change in immunosuppression.

  3. Is the Bahasa Malaysia version of the Montreal Cognitive Assessment (MoCA-BM) a better instrument than the Malay version of the Mini Mental State Examination (M-MMSE) in screening for mild cognitive impairment (MCI) in the elderly?
    Razali R, Jean-Li L, Jaffar A, Ahmad M, Shah SA, Ibrahim N, et al.
    Compr Psychiatry, 2014 Jan;55 Suppl 1:S70-5.
    PMID: 24314103 DOI: 10.1016/j.comppsych.2013.04.010
    Mild Cognitive Impairment (MCI) is a known precursor to Alzheimer disease, yet there is a lack of validated screening instruments for its detection among the Malaysian elderly.
  4. Edge AI-Based Automated Detection and Classification of Road Anomalies in VANET Using Deep Learning
    Bibi R, Saeed Y, Zeb A, Ghazal TM, Rahman T, Said RA, et al.
    Comput Intell Neurosci, 2021;2021:6262194.
    PMID: 34630550 DOI: 10.1155/2021/6262194
    Road surface defects are crucial problems for safe and smooth traffic flow. Due to climate changes, low quality of construction material, large flow of traffic, and heavy vehicles, road surface anomalies are increasing rapidly. Detection and repairing of these defects are necessary for the safety of drivers, passengers, and vehicles from mechanical faults. In this modern era, autonomous vehicles are an active research area that controls itself with the help of in-vehicle sensors without human commands, especially after the emergence of deep learning (DNN) techniques. A combination of sensors and DNN techniques can be useful for unmanned vehicles for the perception of their surroundings for the detection of tracks and obstacles for smooth traveling based on the deployment of artificial intelligence in vehicles. One of the biggest challenges for autonomous vehicles is to avoid the critical road defects that may lead to dangerous situations. To solve the accident issues and share emergency information, the Intelligent Transportation System (ITS) introduced the concept of vehicular network termed as vehicular ad hoc network (VANET) for achieving security and safety in a traffic flow. A novel mechanism is proposed for the automatic detection of road anomalies by autonomous vehicles and providing road information to upcoming vehicles based on Edge AI and VANET. Road images captured via camera and deployment of the trained model for road anomaly detection in a vehicle could help to reduce the accident rate and risk of hazards on poor road conditions. The techniques Residual Convolutional Neural Network (ResNet-18) and Visual Geometry Group (VGG-11) are applied for the automatic detection and classification of the road with anomalies such as a pothole, bump, crack, and plain roads without anomalies using the dataset from different online sources. The results show that the applied models performed well than other techniques used for road anomalies identification.
  5. Fulltext An IoMT-Enabled Smart Healthcare Model to Monitor Elderly People Using Machine Learning Technique
    Khan MF, Ghazal TM, Said RA, Fatima A, Abbas S, Khan MA, et al.
    Comput Intell Neurosci, 2021;2021:2487759.
    PMID: 34868288 DOI: 10.1155/2021/2487759
    The Internet of Medical Things (IoMT) enables digital devices to gather, infer, and broadcast health data via the cloud platform. The phenomenal growth of the IoMT is fueled by many factors, including the widespread and growing availability of wearables and the ever-decreasing cost of sensor-based technology. The cost of related healthcare will rise as the global population of elderly people grows in parallel with an overall life expectancy that demands affordable healthcare services, solutions, and developments. IoMT may bring revolution in the medical sciences in terms of the quality of healthcare of elderly people while entangled with machine learning (ML) algorithms. The effectiveness of the smart healthcare (SHC) model to monitor elderly people was observed by performing tests on IoMT datasets. For evaluation, the precision, recall, fscore, accuracy, and ROC values are computed. The authors also compare the results of the SHC model with different conventional popular ML techniques, e.g., support vector machine (SVM), K-nearest neighbor (KNN), and decision tree (DT), to analyze the effectiveness of the result.
  6. Fulltext An Intelligent Proposed Model for Task Offloading in Fog-Cloud Collaboration Using Logistics Regression
    Bukhari MM, Ghazal TM, Abbas S, Khan MA, Farooq U, Wahbah H, et al.
    Comput Intell Neurosci, 2022;2022:3606068.
    PMID: 35126487 DOI: 10.1155/2022/3606068
    Smart applications and intelligent systems are being developed that are self-reliant, adaptive, and knowledge-based in nature. Emergency and disaster management, aerospace, healthcare, IoT, and mobile applications, among them, revolutionize the world of computing. Applications with a large number of growing devices have transformed the current design of centralized cloud impractical. Despite the use of 5G technology, delay-sensitive applications and cloud cannot go parallel due to exceeding threshold values of certain parameters like latency, bandwidth, response time, etc. Middleware proves to be a better solution to cope up with these issues while satisfying the high requirements task offloading standards. Fog computing is recommended middleware in this research article in view of the fact that it provides the services to the edge of the network; delay-sensitive applications can be entertained effectively. On the contrary, fog nodes contain a limited set of resources that may not process all tasks, especially of computation-intensive applications. Additionally, fog is not the replacement of the cloud, rather supplement to the cloud, both behave like counterparts and offer their services correspondingly to compliance the task needs but fog computing has relatively closer proximity to the devices comparatively cloud. The problem arises when a decision needs to take what is to be offloaded: data, computation, or application, and more specifically where to offload: either fog or cloud and how much to offload. Fog-cloud collaboration is stochastic in terms of task-related attributes like task size, duration, arrival rate, and required resources. Dynamic task offloading becomes crucial in order to utilize the resources at fog and cloud to improve QoS. Since this formation of task offloading policy is a bit complex in nature, this problem is addressed in the research article and proposes an intelligent task offloading model. Simulation results demonstrate the authenticity of the proposed logistic regression model acquiring 86% accuracy compared to other algorithms and confidence in the predictive task offloading policy by making sure process consistency and reliability.
  7. A biological inspired fuzzy adaptive window median filter (FAWMF) for enhancing DNA signal processing
    Ahmad M, Jung LT, Bhuiyan AA
    Comput Methods Programs Biomed, 2017 Oct;149:11-17.
    PMID: 28802326 DOI: 10.1016/j.cmpb.2017.06.021
    BACKGROUND AND OBJECTIVE: Digital signal processing techniques commonly employ fixed length window filters to process the signal contents. DNA signals differ in characteristics from common digital signals since they carry nucleotides as contents. The nucleotides own genetic code context and fuzzy behaviors due to their special structure and order in DNA strand. Employing conventional fixed length window filters for DNA signal processing produce spectral leakage and hence results in signal noise. A biological context aware adaptive window filter is required to process the DNA signals.

    METHODS: This paper introduces a biological inspired fuzzy adaptive window median filter (FAWMF) which computes the fuzzy membership strength of nucleotides in each slide of window and filters nucleotides based on median filtering with a combination of s-shaped and z-shaped filters. Since coding regions cause 3-base periodicity by an unbalanced nucleotides' distribution producing a relatively high bias for nucleotides' usage, such fundamental characteristic of nucleotides has been exploited in FAWMF to suppress the signal noise.

    RESULTS: Along with adaptive response of FAWMF, a strong correlation between median nucleotides and the Π shaped filter was observed which produced enhanced discrimination between coding and non-coding regions contrary to fixed length conventional window filters. The proposed FAWMF attains a significant enhancement in coding regions identification i.e. 40% to 125% as compared to other conventional window filters tested over more than 250 benchmarked and randomly taken DNA datasets of different organisms.

    CONCLUSION: This study proves that conventional fixed length window filters applied to DNA signals do not achieve significant results since the nucleotides carry genetic code context. The proposed FAWMF algorithm is adaptive and outperforms significantly to process DNA signal contents. The algorithm applied to variety of DNA datasets produced noteworthy discrimination between coding and non-coding regions contrary to fixed window length conventional filters.

  8. On fuzzy semantic similarity measure for DNA coding
    Ahmad M, Jung LT, Bhuiyan MA
    Comput Biol Med, 2016 Feb 1;69:144-51.
    PMID: 26773936 DOI: 10.1016/j.compbiomed.2015.12.017
    A coding measure scheme numerically translates the DNA sequence to a time domain signal for protein coding regions identification. A number of coding measure schemes based on numerology, geometry, fixed mapping, statistical characteristics and chemical attributes of nucleotides have been proposed in recent decades. Such coding measure schemes lack the biologically meaningful aspects of nucleotide data and hence do not significantly discriminate coding regions from non-coding regions. This paper presents a novel fuzzy semantic similarity measure (FSSM) coding scheme centering on FSSM codons׳ clustering and genetic code context of nucleotides. Certain natural characteristics of nucleotides i.e. appearance as a unique combination of triplets, preserving special structure and occurrence, and ability to own and share density distributions in codons have been exploited in FSSM. The nucleotides׳ fuzzy behaviors, semantic similarities and defuzzification based on the center of gravity of nucleotides revealed a strong correlation between nucleotides in codons. The proposed FSSM coding scheme attains a significant enhancement in coding regions identification i.e. 36-133% as compared to other existing coding measure schemes tested over more than 250 benchmarked and randomly taken DNA datasets of different organisms.
  9. Fulltext A Deep Neural Network for Simultaneous Estimation of b Jet Energy and Resolution
    Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Bergauer T, Dragicevic M, et al.
    Comput Softw Big Sci, 2020;4(1):10.
    PMID: 33196702 DOI: 10.1007/s41781-020-00041-z
    We describe a method to obtain point and dispersion estimates for the energies of jets arising from b quarks produced in proton-proton collisions at an energy of s = 13 TeV at the CERN LHC. The algorithm is trained on a large sample of simulated b jets and validated on data recorded by the CMS detector in 2017 corresponding to an integrated luminosity of 41 fb - 1 . A multivariate regression algorithm based on a deep feed-forward neural network employs jet composition and shape information, and the properties of reconstructed secondary vertices associated with the jet. The results of the algorithm are used to improve the sensitivity of analyses that make use of b jets in the final state, such as the observation of Higgs boson decay to b b ¯ .
  10. Meta-analysis contrasting freshwater biodiversity in forests and oil palm plantations with and without riparian buffers
    Rojas-Castillo OA, Kepfer Rojas S, Juen L, Montag LFA, Carvalho FG, Mendes TP, et al.
    Conserv Biol, 2024 Feb;38(1):e14172.
    PMID: 37650444 DOI: 10.1111/cobi.14172
    The expansion of oil palm plantations has led to land-use change and deforestation in the tropics, which has affected biodiversity. Although the impacts of the crop on terrestrial biodiversity have been extensively reviewed, its effects on freshwater biodiversity remain relatively unexplored. We reviewed the research assessing the impacts of forest-to-oil palm conversion on freshwater biota and the mitigating effect of riparian buffers on these impacts. We searched for studies comparing taxa richness, species abundance, and community composition of macroinvertebrates, amphibians, and fish in streams in forests (primary and disturbed) and oil palm plantations with and without riparian buffers. Then, we conducted a meta-analysis to quantify the overall effect of the land-use change on the 3 taxonomic groups. Twenty-nine studies fulfilled the inclusion criteria. On average, plantations lacking buffers hosted 44% and 19% fewer stream taxa than primary and disturbed forests, respectively. Stream taxa on plantations with buffers were 24% lower than in primary forest and did not differ significantly from disturbed forest. In contrast, stream community composition differed between forests and plantations regardless of the presence of riparian buffers. These differences were attributed to agrochemical use and altered environmental conditions in the plantations, including temperature changes, worsened water conditions, microhabitat loss, and food and shelter depletion. On aggregate, abundance did not differ significantly among land uses because increases in generalist species offset the population decline of vulnerable forest specialists in the plantation. Our results reveal significant impacts of forest-to-oil palm conversion on freshwater biota, particularly taxa richness and composition (but not aggregate abundance). Although preserving riparian buffers in the plantations can mitigate the loss of various aquatic species, it cannot conserve primary forest communities. Therefore, safeguarding primary forests from the oil palm expansion is crucial, and further research is needed to address riparian buffers as a promising mitigation strategy in agricultural areas.
  11. Current Trends of Analytical Techniques for Total Alkalinity Measurement in Water Samples: A Review
    Ahmad M, Ahmad A, Omar TFT, Mohammad R
    Crit Rev Anal Chem, 2023 Apr 13.
    PMID: 37052389 DOI: 10.1080/10408347.2023.2199432
    Increasing acidity of seawater caused by increasing anthropogenic carbon dioxide absorbed into the seawater attracted the interest of researchers due to increased concern on the deterioration of marine systems and food supply to humans. Total alkalinity (TA) is one of the important parameters in determining carbonate chemistry and is described as the capacity of the sample to neutralize acids. Over the last two decades, many analytical techniques have been developed to determine TA. This article presents a review of different analytical techniques including titration, colorimetric, spectrophotometric, and potentiometric analyses in measuring TA. Among these analytical techniques, potentiometry analysis, which utilizes electrode systems such as glass electrode and ion-selective electrode used as indicator electrodes, is the most used technique. Important features such as principle, limitations, and challenges of the involved technique are discussed in detail.
  12. Fulltext COVID-19 Vaccine Hesitancy Among the Adult Population in Saudi Arabia
    Alrajeh AM, Daghash H, Buanz SF, Altharman HA, Belal S
    Cureus, 2021 Dec;13(12):e20197.
    PMID: 35004019 DOI: 10.7759/cureus.20197
    BACKGROUND: Vaccine hesitancy in Saudi Arabia continues even after reaching 17 million doses. This study was conducted to comprehensively assess coronavirus disease 2019 (COVID-19) vaccine hesitancy in adult people who ignore the COVID-19 vaccine in the Saudi Arabian population and explore community awareness of public health after 17 million doses of COVID-19 vaccination.

    METHODS: A cross-sectional survey was used in this study. The questionnaire included three domains: demographic information, vaccine hesitancy by the health belief model related to the COVID-19 vaccine, and hesitancy by attitude and conspiracy towards the COVID-19 vaccine. A total of 401 adults participated in this study.

    RESULTS: The respondents' perceptions of COVID-19 susceptibility and severity showed that the participants did not feel at risk nor believe that COVID-19 was serious. Connivance beliefs were found to be associated with reliance on social media as a major source of information about COVID-19 vaccines, and lack of trust in vaccine manufacturers (pharmaceutical companies). The majority of the respondents were concerned about the efficacy and safety of the COVID-19 vaccine, which can be reported as a major barrier to vaccination.

    RECOMMENDATIONS: To increase vaccination rates, health authorities need to communicate both the benefits and risks of vaccination. In addition, we recommend using a qualitative study to understand and evaluate the participants' concepts in depth.

  13. Fulltext Mucosal-associated invariant T cell alterations during the development of human type 1 diabetes
    Gazali AM, Schroderus AM, Näntö-Salonen K, Rintamäki R, Pihlajamäki J, Knip M, et al.
    Diabetologia, 2020 11;63(11):2396-2409.
    PMID: 32880687 DOI: 10.1007/s00125-020-05257-7
    AIMS/HYPOTHESIS: Mucosal-associated invariant T (MAIT) cells are innate-like T cells that recognise derivatives of bacterial riboflavin metabolites presented by MHC-Ib-related protein 1 (MR1) molecules and are important effector cells for mucosal immunity. Their development can be influenced by the intestinal microbiome. Since the development of type 1 diabetes has been associated with changes in the gut microbiome, this can be hypothesised to lead to alterations in circulating MAIT cells. Accordingly, peripheral blood MAIT cell alterations have been reported previously in patients with type 1 diabetes. However, a comprehensive analysis of the frequency and phenotype of circulating MAIT cells at different stages of type 1 diabetes progression is currently lacking.

    METHODS: We analysed the frequency, phenotype and functionality of peripheral blood MAIT cells, as well as γδ T cells, invariant natural killer T (iNKT) cells and natural killer (NK) cells with flow cytometry in a cross-sectional paediatric cohort (aged 2-15) consisting of 51 children with newly diagnosed type 1 diabetes, 27 autoantibody-positive (AAb+) at-risk children, and 113 healthy control children of similar age and HLA class II background. The frequency of MAIT cells was also assessed in a separate cross-sectional adult cohort (aged 19-39) of 33 adults with established type 1 diabetes and 37 healthy individuals of similar age.

    RESULTS: Children with newly diagnosed type 1 diabetes displayed a proportional increase of CD8-CD27- MAIT cells compared with healthy control children (median 4.6% vs 3.1% of MAIT cells, respectively, p = 0.004), which was associated with reduced expression of C-C chemokine receptor (CCR)5 (median 90.0% vs 94.3% of MAIT cells, p = 0.02) and β7 integrin (median 73.5% vs 81.7% of MAIT cells, p = 0.004), as well as decreased production of IFN-γ (median 57.1% vs 69.3% of MAIT cells, p = 0.04) by the MAIT cells. The frequency of MAIT cells was also decreased in AAb+ children who later progressed to type 1 diabetes compared with healthy control children (median 0.44% vs 0.96% of CD3+ T cells, p = 0.04), as well as in adult patients with a short duration of type 1 diabetes (less than 6 years after diagnosis) compared with control individuals (median 0.87% vs 2.19% of CD3+ T cells, p = 0.007). No alterations in γδ T cell, iNKT cell or NK cell frequencies were observed in children with type 1 diabetes or in AAb+ children, with the exception of an increased frequency of IL-17A+ γδ T cells in children with newly diagnosed diabetes compared with healthy control children (median 1.58% vs 1.09% of γδ T cells, p = 0.002).

    CONCLUSIONS/INTERPRETATION: Changes in the frequency and phenotype of circulating MAIT cells were detectable before, at the onset and after diagnosis of type 1 diabetes in cross-sectional cohorts. Our results suggest a possible temporal association between peripheral blood MAIT cell alterations and the clinical onset of type 1 diabetes. Graphical abstract.

  14. Occurrence of the vanA and vanC2/C3 genes in Enterococcus species isolated from poultry sources in Malaysia
    Radu S, Toosa H, Rahim RA, Reezal A, Ahmad M, Hamid AN, et al.
    Diagn Microbiol Infect Dis, 2001 Mar;39(3):145-53.
    PMID: 11337180
    Enterococcus species isolated from poultry sources were characterized for their resistance to antibiotics, plasmid content, presence of van genes and their diversity by randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). The results showed that all isolates were multi-resistance to the antibiotics tested. Ampicillin (15/70) followed by chloramphenicol (37/70) were the most active antibiotics tested against the Enterococcus spp. isolates, while the overall resistant rates against the other antibiotics were between 64.3% to 100%. All vancomycin-resistant E. faecalis, E. durans, E. hirae and E. faecium isolates tested by the disk diffusion assay were positive in PCR detection for presence of vanA gene. All E. casseliflavus isolates were positive for vanC2/C3 gene. However, none of the Enterococcus spp. isolates were positive for vanB and vanC1 genes. Plasmids ranging in sizes between 1.1 to ca. 35.8 MDa were detected in 38/70 of the Enterococcus isolates. When the genetic relationship among all isolates of the individual species were tested by RAPD-PCR, genetic differences detected suggested a high genetic polymorphisms of isolates in each individual species. Our results indicates that further epidemiological studies are necessary to elucidate the role of food animals as reservoir of VRE and the public health significance of infections caused by Enterococcus spp.
  15. Fulltext Acceptance of online distance learning (ODL) among students: Mediating role of utilitarian and hedonic value
    Alam SS, Masukujjaman M, Ahmad M, Jaffor R
    Educ Inf Technol (Dordr), 2022 Dec 23.
    PMID: 36589518 DOI: 10.1007/s10639-022-11533-3
    Nowadays, the teaching methods are changed from offline to online primarily for the advent of the internet facility. The Industrial Revolution 4.0 ("Education 4.0") stresses offering online courses at the university level. The study aims to find out the factors influencing students' intentions to admit to online distance learning courses. In addition, the study wanted to establish the utilitarian and hedonic value construct in mediating the association between attitude and intention. Based on an intensive literature survey, an extended Technology Acceptance Model was proposed including some cognitive and technology-specific factors to test empirically. This is a quantitative study with an exploratory and descriptive scope and cross-sectional design. The information was gathered by applying the convenience sampling method from 293 Malaysian students who participated in anonymous surveys. The obtained data were analyzed using structural equation modeling applying AMOS 21 version. The study reveals that hedonic value, utilitarian value, perceived ease of use, and attitude except for perceived usefulness, affect behavioral intention to accept online distance learning courses except for perceived usefulness construct. The antecedents of utilitarian value are perceived fees, attitude, perceived usefulness, and perceived ease of use, whereas the antecedents of hedonic value are perceived fees, attitude, and perceived usefulness, except for perceived ease of use. Finally, self-efficacy affects perceived ease of use, perceived usefulness, and attitude towards joining online distance learning courses. This study's conclusions will benefit all stakeholders in the education system who are considering or have already adopted e-learning.
  16. Some observations on the breakage of ultrasonic files driven piezoelectrically
    Ahmad M, Roy RA
    Endod Dent Traumatol, 1994 Apr;10(2):71-6.
    PMID: 8062810
    The incidence of breakage of Piezon-Master ultrasonic K files were evaluated. Three groups of unused files were subjected to three treatments, namely; free vibration in air without irrigation, free vibration in root canal while minimizing contact with the wall of canal in the presence of irrigation and light filing in root canal with free flow of irrigation. Cavitation produced by files in contact and free of contact with a glass surface was examined in order to observe the relationship between cavitation defects and breakage. In addition, the fractured and unfractured files were examined under a scanning electron microscope for the presence of cavitation pits. The results indicated that more files broke in air. In water, a higher incidence of breakage occurred when files were allowed to freely vibrate while no breakage occurred when the files were used in filing. All files generated cavitation which resulted in pitting of their surfaces. However, it was considered unlikely that the pits contributed to fracture. Fatigue cracks which could be the result of the manufacturing process were observed at some of the corners of the cross sections of the fractured files and could be the main contributory factor to fracture.
  17. Observations of acoustic streaming fields around an oscillating ultrasonic file
    Ahmad M, Roy RA, Kamarudin AG
    Endod Dent Traumatol, 1992 Oct;8(5):189-94.
    PMID: 1302678
    The steady acoustic streaming generated around straight and precurved oscillating ultrasonic files driven by the Piezon-Master 400 unit was examined in the free field and in small channels using a stereomicroscope. In addition, the effect of file-wall contact on streaming production was also investigated. The results indicated that the ultrasonic files can generate acoustic streaming both in the free field and in the small channel. Higher velocity streaming was observed when smaller size files were employed and when the file was precurved. Light file-wall contact did not totally inhibit streaming while severe file-wall contact inhibited movement of the file and, as a result, no streaming was observed. The positions and length scales of the streaming vortices appeared to be influenced by the presence of boundaries. In the free field, two rows of vortices were situated along the sides of the file while in the small channel, the vortices were positioned above the surface of the file. These results indicated that it is possible for acoustic streaming to occur in a confined space as in a root canal provided that severe file-wall contact is avoided. It is therefore recommended that light filing or allowing the file to freely vibrate during some stage of treatment should be carried out in order to generate streaming in the root canal.
  18. Comparison between two ultrasonic units in shaping curved canals in teeth using macroradiography
    Ahmad M
    Endod Dent Traumatol, 1991 Apr;7(2):55-8.
    PMID: 1782894
    The efficacy of two ultrasonic units in shaping curved canals in teeth were compared. Twenty teeth were instrumented using the Cavi-Endo unit at a power setting 1 using the technique recommended by the manufacturer. Another group of 20 teeth received similar treatment but were instrumented with the Enac unit. The time taken to instrument each canal was recorded. The pre- and post-instrumented radiographs of the teeth of x 10 magnification were taken using a microfocal technique. The radiographs were subjected to a subtraction technique to result in composite images of the pre- and post-instrumented shapes. The canal shape and the incidence of elbows were evaluated using various measurements taken from the radiographs. The manner the dentine was removed was similar in both groups. All canals exhibited unequal removal along the canal with more dentine being removed at the coronal end. The Enac group exhibited a higher incidence of elbows which occurred further apically than those in the Cavi-Endo group. There was no significant difference between groups in the following: time of instrumentation, amount of apical and coronal canal enlargement, apical deviation and change in width at the elbow. These findings were no different from those of another study using simulated canals.
  19. Some observations on the mechanics of oscillation of ultrasonic files
    Ahmad M
    Endod Dent Traumatol, 1990 Feb;6(1):12-5.
    PMID: 2202589
    The resonant characteristics of ultrasonic files driven by the Cavi-Endo unit were examined. The investigation was carried out by evaluating the pattern of oscillation and the power emitted by the ultrasonic files. It was observed that the files oscillated in a sinusoidal fashion, exhibiting a standing wave pattern along the file. The power emitted was found to be directly proportional to the flexibility of the file. Such behaviour is typical of a system that exhibits resonance.
  20. Shape of the root canal after ultrasonic instrumentation with K-Flex files
    Ahmad M
    Endod Dent Traumatol, 1990 Jun;6(3):104-8.
    PMID: 2079012
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