19672 research outputs found
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Structural failure analysis of polycarbonate enclosures of electronic devices subjected to multiple ball impacts
No full textThe present study predicts the structural damage on polycarbonate enclosures of electronic devices in multiple ball impact tests, achieved through numerical simulation and experiments. A novel methodology in modelling repeated ball impacts was established and proven. It was found that the finite element model must be allowed to achieve static equilibrium at the end of each impact before the next impact. The ball impact was performed on the polycarbonate enclosures at different heights ranging from 20 to 70 cm. The results suggested that the maximum penetration depth from both finite element analysis (FEA) and experiment were in good agreement. The failure sites were also predicted with reasonable consistency
A numerical airflow pattern study of a floor swirl diffuser for UFAD system
No full textFloor swirl diffuser is one of the commonly used diffusers in underfloor air distribution (UFAD) system. Geometrical design of the floor swirl diffuser will affect the airflow pattern of the indoor environment. Thus, the purpose of this study is to examine the effect of geometrical design of a floor swirl diffuser on the aspects of airflow rate, number of diffuser blades, angle of attack of diffuser blades, and the grille thickness. Laboratory experiment was carried out to validate CFD simulation results. The results of this study have shown that diffuser blades have an important role in the airflow pattern. The grille thickness, which is required to withstand the impact and the load of human and furniture, needs to be minimized as the thickness is detrimental to the function of diffuser blades. Besides, airflow rate per diffuser is studied in UFAD system in order to achieve thermal stratification. The air throw is lower compared to a high angle of attack at the low angles of attack of 30° and 45°. The optimum number of diffuser blades to create the swirl effect is 18 blades with a free area of 18.86%
Evaluation of a group-based hypertension self-management education programme among hypertensive community dwellers
No full textIntroduction: Low self-efficacy level among patients with hypertension could be the underlying reason for poor daily disease self-management, leading to suboptimal blood pressure (BP) control. A structured, group-based hypertension self-management education (HSME) programme could be a potential solution to improve BP control; however, impact of HSME programme in the Malaysian setting remain unknown. This study aimed to evaluate the impact of a structured, group-based HSME programme on hypertensive patients’ clinical and psychosocial outcomes. Methods: A pretest-posttest quasi-experimental study design was employed. Participants attended a total of 4-weekly of the HSME programme at a community hall. Participants’ clinical and psychosocial outcomes were assessed at three time-points. Data were analysed using IBM SPSS version 23.0. Results: Forty-five participants consented to join the programme, with 36 (80.0%) attended two or more sessions. At post 1-week of intervention, participants were found to have significant improvement in high-density lipoprotein (HDL) cholesterol (p = 0.001), number of days spent on vigorous physical activity (p = 0.007), motivation (p = 0.005) and self-efficacy (p = 0.005). At 2-month, participants have sustained increased in HDL cholesterol, motivation and self-efficacy, in addition to a significant improvement in self-care behaviour (p = 0.002). Conclusions: The short-term HSME programme elicited certain positive clinical and psychosocial outcomes, a larger scale randomised controlled trial should be carried out to determine the effective elements of the HSME programme that lead to the self-care behavioural changes and to evaluate the long-term impacts of sustained self-care practices among community dwellers with hypertension
MWCNTs coated silica microfiber sensor for detecting Mg2+ in de-ionized water
No full textA multi-walled carbon nanotubes (MWCNTs) coated silica microfiber sensor for the detection of magnesium ions (Mg2+) in de-ionized water is reported. The change refractive index in the MWCNTs when sensor is being immersed in the magnesium solution is used as the working principle. The silica microfiber probe is fabricated by flame brushing technique and has a waist diameter of 6 μm with tapering length of 3 cm. The performance of the sensor is suitable for the low concentration ranging from 0.1% to 0.5% and as the sensitivity (Mg2+) solution increased, the transmitted power decreased. The results demonstrate that MWCNTs coated silica microfiber has many advantages such as low cost, enhanced sensitivity of the sensor and capability of a real time monitoring detection of (Mg2+)
The Integration of Nature-Inspired Algorithms with Least Square Support Vector Regression Models: Application to Modeling River Dissolved Oxygen Concentration
No full textThe current study investigates an improved version of Least Square Support Vector Machines integrated with a Bat Algorithm (LSSVM-BA) for modeling the dissolved oxygen (DO) concentration in rivers. The LSSVM-BA model results are compared with those obtained using M5 Tree and Multivariate Adaptive Regression Spline (MARS) models to show the efficacy of this novel integrated model. The river water quality data at three monitoring stations located in the USA are considered for the simulation of DO concentration. Eight input combinations of four water quality parameters, namely, water temperature, discharge, pH, and specific conductance, are used to simulate the DO concentration. The results revealed the superiority of the LSSVM-BA model over the M5 Tree and MARS models in the prediction of river DO. The accuracy of the LSSVM-BA model compared with those of the M5 Tree and MARS models is found to increase by 20% and 42%, respectively, in terms of the root-mean-square error. All the predictive models are found to perform best when all the four water quality variables are used as input, which indicates that it is possible to supply more information to the predictive model by way of incorporation of all the water quality variables
Application of the Hybrid Artificial Neural Network Coupled with Rolling Mechanism and Grey Model Algorithms for Streamflow Forecasting Over Multiple Time Horizons
No full textStreamflow forecasting is paramount process in water and flood management, determination of river water flow potentials, environmental flow analysis, agricultural practices and hydro-power generation. However, the dynamicity, stochasticity and inherent complexities present in the temporal evolution of streamflow could hinder the accurate and reliable forecasting of this important hydrological parameter. In this study, the uncertainty and nonstationary characteristics of streamflow data has been treated using a set of coupled data pre-processing methods before being considered as input for an artificial neural network algorithm namely; rolling mechanism (RM) and grey models (GM). The rolling mechanism method is applied to smooth out the dataset based on the antecedent values of the model inputs before being applied to the GM algorithm. The optimization of the input datasets selection was performed using auto-correlation (ACF) and partial auto-correlation (PACF) functions. The pre-processed data was then integrated with two artificial neural network models, the back propagation (RMGM-BP) and Elman Recurrent Neural Network (RMGM-ERNN). The development, training, testing and evaluation of the proposed hybrid models were undertaken using streamflow data for two tropical hydrological basins (Johor and Kelantan Rivers). The hybrid RMGM-ERNN was found to provide better results than the hybrid RMGM-BP model. Relatively good performance of the proposed hybrid models with a data pre-processing approach provides a successful alternative to achieve better accuracy in streamflow forecasting compared to the traditional artificial neural network approach without a data pre-processing scheme
Molecular attributes and apoptosis-inducing activities of a putative serine protease isolated from Tiger Milk mushroom (Lignosus rhinocerus) sclerotium against breast cancer cells in vitro
No full textBackground: The highly valued medicinal tiger milk mushroom (also known as Lignosus rhinocerus) has the ability to cure numerous ailments. Its anticancer activities are well explored, and recently a partially purified cytotoxic protein fraction termed F5 from the mushroom's sclerotial cold water extract consisting mainly of fungal serine proteases was found to exhibit potent selective cytotoxicity against a human breast adenocarcinoma cell line (MCF7) with IC50 value of 3.00 μg/ml. However, characterization of its cell death-inducing activity has yet to be established. Methods: The mechanism involved in the cytotoxic activities of F5 against MCF7 cells was elucidated by flow cytometry-based apoptosis detection, caspases activity measurement, and expression profiling of apoptosis markers by western blotting. Molecular attributes of F5 were further mined from L. rhinocerus's published genome and transcriptome for future exploration. Results and Discussion: Apoptosis induction in MCF7 cells by F5 may involve a cross-talk between the extrinsic and intrinsic apoptotic pathways with upregulation of caspase-8 and -9 activities and a marked decrease of Bcl-2. On the other hand, the levels of pro-apoptotic Bax, BID, and cleaved BID were increased accompanied by observable actin cleavage. At gene level, F5 composed of three predicted nonsynonymous single nucleotide polymorphisms (T > C) and an alternative 5' splice site. Conclusions: Findings from this study provide an advanced framework for further investigations on cancer therapeutics development from L. rhinocerus
Mode of Action: Synergistic Interaction of Peppermint (Mentha x piperita L. Carl) Essential Oil and Meropenem Against Plasmid-Mediated Resistant E. coli
No full textThis study investigated the bactericidal mechanism of peppermint essential oil (PEO) when used singly and in combination with meropenem against multidrug resistant Escherichia coli. Chemical compositions of PEO were identified via GC-MS, followed by time-kill analysis which was performed to evaluate the antibacterial activities of PEO and meropenem. Furthermore, outer membrane permeability test, zeta potential measurement and scanning electron microscopy were performed to evaluate the ability of PEO in bacterial membrane disruption. Next, anti-quorum sensing assay was performed to assess the ability of PEO in quorum sensing inhibition. A complete killing activity was observed within five minutes of treatment with PEO and meropenem at sub-lethal concentrations. In addition, the outer membrane permeability test and zeta potential measurement performed indicated increase in the membrane permeability and membrane disruption which can be observed in the scanning electron micrograph. Furthermore, significant decrease in the light production of E. coli pSB1075 treated by PEO indicates the presence of quorum sensing inhibitors within PEO. The findings suggest that PEO has the ability to disrupt the bacterial outer membrane which increases membrane permeability, in addition to the possible inhibition of bacterial quorum sensing ability in multidrug resistant E. coli, aiding in the reversal of antibiotic resistance
Correlation between polar surface area and bioferroelectricity in DNA and RNA nucleobases
No full textAbstract.: We have performed computational molecular modelling to study the polarization switching and hysteresis loop behaviours of DNA and RNA nucleobases using the PM3 semi-empirical quantum mechanical approaches. All the nucleobases: adenine (A), thymine (T), guanine (G), cytosine (C), and uracil (U) were modelled. Our study indicates that all the nucleobases exhibit a zero-field polarization due to the presence of polar atoms or molecules such as amidogen and carbonyl. The shape of polarization Pversus an applied electric field E hysteresis loop is square, implying typical ferroelectrics behaviour. The total energy U as a function of an applied electric field E exhibits a butterfly-like loop. The presence of zero-field polarization and ferroelectrics hysteresis loop behaviours in nucleobases may support the hypothesis of the existence of bioferroelectricity in DNA and RNA. We also found an interesting relationship between the minimum electric field required for switching EC and the ratio of the topological polar surface area (TPSA) to the total surface area (TSA) of a nucleobase. In particular, the EC of a nucleobase is inversely proportional to the TPSA/TSA ratio. This work may provide useful information for understanding the possible existence of ferroelectricity in biomaterials
Antibiofilm activity and mode of action of DMSO alone and its combination with afatinib against Gram-negative pathogens
No full textBiofilms are complex microbial communities that tend to attach to either biotic or abiotic surface. Enclosed in a self-produced extracellular polymeric substance (EPS) matrix, the biofilms often cause persistent infections. The objective of this study was to investigate the antibiofilm activity of dimethyl sulfoxide (DMSO) and afatinib against Gram-negative pathogens. Test microorganisms used in this study were Escherichia coli ATCC 1299, Pseudomonas aeruginosa ATCC 10145, and Salmonella typhimurium ATCC 14028. Biofilms were developed in 96-well microplate at 37°C for 24 h. Following removal of non-adherent cells, analysis of biofilm viability, biofilm biomass, and extracellular polymeric substances (EPS) matrix were performed using resazurin assay, crystal violet assay, and attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy, respectively. Bradford protein assay was conducted to determine the total amount of EPS proteins. The results demonstrated that both 32% DMSO alone and its combination with 3.2 μg/mL afatinib were effective in killing biofilm cells and reducing biofilm biomass. IR spectral variations of EPS matrix of biofilms in the range between 1700 and 900 cm−1 were also observed. Reduction in EPS proteins verified the chemical modifications of EPS matrix. In conclusion, 32% DMSO alone and its combination with 3.2 μg/mL afatinib showed remarkable antibiofilm activities against Gram-negative pathogens. It was suggested that the biofilm inhibition was mediated by the chemical modification of EPS matrix