MyMedR

Displaying all 10 publications

Abstract:

Sort:

Fulltext Analysis on the Effects of the Human Body on the Performance of Electro-Textile Antennas for Wearable Monitoring and Tracking Application

Abd Rahman NH, Yamada Y, Amin Nordin MS

Materials (Basel), 2019 May 19;12(10).
PMID: 31109128 DOI: 10.3390/ma12101636

Previous works have shown that wearable antennas can operate ideally in free space; however, degradation in performance, specifically in terms of frequency shifts and efficiency was observed when an antenna structure was in close proximity to the human body. These issues have been highlighted many times yet, systematic and numerical analysis on how the dielectric characteristics may affect the technical behavior of the antenna has not been discussed in detail. In this paper, a wearable antenna, developed from a new electro-textile material has been designed, and the step-by-step manufacturing process is presented. Through analysis of the frequency detuning effect, the on-body behavior of the antenna is evaluated by focusing on quantifying the changes of its input impedance and near-field distribution caused by the presence of lossy dielectric material. When the antenna is attached to the top of the body fat phantom, there is an increase of 17% in impedance, followed by 19% for the muscle phantom and 20% for the blood phantom. These phenomena correlate with the electric field intensities (V/m) observed closely at the antenna through various layers of mediums (z-axis) and along antenna edges (y-axis), which have shown significant increments of 29.7% in fat, 35.3% in muscle and 36.1% in blood as compared to free space. This scenario has consequently shown that a significant amount of energy is absorbed in the phantoms instead of radiated to the air which has caused a substantial drop in efficiency and gain. Performance verification is also demonstrated by using a fabricated human muscle phantom, with a dielectric constant of 48, loss tangent of 0.29 and conductivity of 1.22 S/m.
Fulltext Critical Device Reliability Assessment in Healthcare Services

Abd Rahman NH, Ibrahim AK, Hasikin K, Abd Razak NA

J Healthc Eng, 2023;2023:3136511.
PMID: 36860328 DOI: 10.1155/2023/3136511

Medical device reliability is the ability of medical devices to endure functioning and is indispensable to ensure service delivery to patients. Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) technique was employed in May 2021 to evaluate existing reporting guidelines on medical device reliability. The systematic searching is conducted in eight different databases, including Web of Science, Science Direct, Scopus, IEEE Explorer, Emerald, MEDLINE Complete, Dimensions, and Springer Link, with 36 articles shortlisted from the year 2010 to May 2021. This study aims to epitomize existing literature on medical device reliability, scrutinize existing literature outcomes, investigate parameters affecting medical device reliability, and determine the scientific research gaps. The result of the systematic review listed three main topics on medical device reliability: risk management, performance prediction using Artificial Intelligence or machine learning, and management system. The medical device reliability assessment challenges are inadequate maintenance cost data, determining significant input parameter selection, difficulties accessing healthcare facilities, and limited age in service. Medical device systems are interconnected and interoperating, which increases complexity in assessing their reliability. To the best of our knowledge, although machine learning has become popular in predicting medical device performance, the existing models are only applicable to selected devices such as infant incubators, syringe pumps, and defibrillators. Despite the importance of medical device reliability assessment, there is no explicit protocol and predictive model to anticipate the situation. The problem worsens with the unavailability of a comprehensive assessment strategy for critical medical devices. Therefore, this study reviews the current state of critical device reliability in healthcare facilities. The present knowledge can be improved by adding new scientific data emphasis on critical medical devices used in healthcare services.
Fulltext Non-Mixture Cure Model Estimation in Bladder Cancer Patients: A Novel Approach with Exponentiated Weibull Exponential Distribution

Omer ME, Mustafa M, Ali N, Abd Rahman NH

Asian Pac J Cancer Prev, 2023 Dec 01;24(12):4167-4177.
PMID: 38156852 DOI: 10.31557/APJCP.2023.24.12.4167

OBJECTIVE: Cure models are frequently used in survival analysis to account for a cured fraction in the data. When there is a cure rate present, researchers often prefer cure models over parametric models to analyse the survival data. These models enable the ability to define the probability distribution of survival durations for patients who are at risk. Various distributions can be considered for the survival times, such as Exponentiated Weibull Exponential (EWE), Exponential Exponential (EE), Weibull and lognormal distribution. The objective of this research is to choose the most appropriate distribution that accurately represents the survival times of patients who have not been cured. This will be accomplished by comparing various non-mixture cure models that are based on the EWE distribution with its sub-distributions, and distributions distinct from those belonging to the EWE distribution family.
MATERIAL AND METHODS: A sample of 85 patients diagnosed with superficial bladder tumours was selected to be used in fitting the non-mixture cure model. In order to estimate the parameters of the suggested model, which takes into account the presence of a cure rate, censored data, and covariates, we utilized the maximum likelihood estimation technique using R software version 3.5.7.
RESULT: Upon conducting a comparison of various parametric models fitted to the data, both with and without considering the cure fraction and without incorporating any predictors, the EE distribution yields the lowest AIC, BIC, and HQIC values among all the distributions considered in this study, (1191.921/1198.502, 1201.692/1203.387, 1195.851/1200.467). Furthermore, when considering a non-mixture cure model utilizing the EE distribution along with covariates, an estimated ratio was obtained between the probabilities of being cured for placebo and thiotepa groups (and its 95% confidence intervals) were 0.76130 (0.13914, 6.81863).
CONCLUSION: The findings of this study indicate that EE distribution is the optimal selection for determining the duration of survival in individuals diagnosed with bladder cancer.
Immobilization of recombinant Escherichia coli on multi-walled carbon nanotubes for xylitol production

Abd Rahman NH, Md Jahim J, Abdul Munaim MS, A Rahman R, Fuzi SFZ, Md Illias R

Enzyme Microb Technol, 2020 Apr;135:109495.
PMID: 32146929 DOI: 10.1016/j.enzmictec.2019.109495

E. coli has been engineered to produce xylitol, but the production faces bottlenecks in terms of production yield and cell viability. In this study, recombinant E. coli (rE. coli) was immobilized on untreated and treated multiwalled carbon nanotubes (MWCNTs) for xylitol production. The immobilized rE. coli on untreated MWCNTs gave the highest xylitol production (5.47 g L-1) and a productivity of 0.22 g L-1 h-1. The doubling time for the immobilized cells increased up to 20.40 h and was higher than that of free cells (3.67 h). Cell lysis of the immobilized cells was reduced by up to 73 %, and plasmid stability improved by up to 17 % compared to those of free cells. Xylitol production using the optimum parameters (pH 7.4, 0.005 mM and 29 °C) achieved a xylitol production and productivity of 6.33 g L-1 and 0.26 g L-1 h-1, respectively. A seven-cycle repeated batch fermentation was carried out for up to 168 h, which showed maximum xylitol production of 7.36 g L-1 during the third cycle. Hence, this new adsorption immobilization system using MWCNTs is an alternative to improve the production of xylitol.
Innovative biocatalyst synthesis of pectinolytic enzymes by cross-linking strategy: Potentially immobilised pectinases for the production of pectic-oligosaccharides from pectin

Abd Rahman NH, Rahman RA, Rahmat Z, Jaafar NR, Puspaningsih NNT, Illias RM

Int J Biol Macromol, 2024 Jan;256(Pt 1):128260.
PMID: 38000618 DOI: 10.1016/j.ijbiomac.2023.128260

Pectinases are outstanding multienzymes, which have the potential to produce new emerging pectic-oligosaccharides (POS) via enzymatic hydrolysis of pectin. However, free pectinase is unable to undergo repeated reaction for the production of POS. This study proposed a sustainable biocatalyst of pectinases known as cross-linked pectinase aggregates (CLPA). Pectinase from Aspergillus aculeatus was successfully precipitated using 2 mg/mL pectinase and 60 % acetone for 20 min at 20 °C, which remained 36.3 % of its initial activity. The prepared CLPA showed the highest activity recovery (85.0 %), under the optimised conditions (0.3 % (v/v) starch and glutaraldehyde mixture (St/Ga), 1.5: 1 of St/Ga, 25 °C, 1.5 h). Furthermore, pectin-degrading enzymes from various sources were used to produce different CLPA. The alteration of pectinase secondary structure gave high stability in acidic condition (pH 4), thermostability, deactivation energy and half-life, and improved storage stability at 4 °C for 30 days. Similarly to their free counterpart, the CLPA exhibited comparable enzymatic reaction kinetics and could be reused eight times with approximately 20 % of its initial activity. The developed CLPA does not only efficaciously produced POS from pectin as their free form, but also exhibited better operational stability and reusability, making it more suitable for POS production.
Novel cross-linked enzyme aggregates of levanase from Bacillus lehensis G1 for short-chain fructooligosaccharides synthesis: Developmental, physicochemical, kinetic and thermodynamic properties

Abd Rahman NH, Jaafar NR, Abdul Murad AM, Abu Bakar FD, Shamsul Annuar NA, Md Illias R

Int J Biol Macromol, 2020 Sep 15;159:577-589.
PMID: 32380107 DOI: 10.1016/j.ijbiomac.2020.04.262

Short-chain fructooligosaccharides (scFOSs) can be produced from the levan hydrolysis using levanase. Levanase from Bacillus lehensis G1 (rlevblg1) is an enzyme that specifically converts levan to scFOSs. However, the use of free levanase presents a lack of stability and reusability, thus hindering the synthesis of scFOSs for continuous reactions. Here, CLEAs for rlevblg1 were prepared and characterized. Cross-linked levanase aggregates using glutaraldehyde (CLLAs-ga) and bovine albumin serum (CLLAs-ga-bsa) showed the best activity recovery of 92.8% and 121.2%, respectively. The optimum temperature of CLLAs-ga and CLLAs-ga-bsa was increased to 35 °C and 40 °C, respectively, from its free rlevblg1 (30 °C). At high temperature (50 °C), the half-life of CLLAs-ga-bsa was higher than that of free rlevblg1 and CLLAs-ga. Both CLLAs exhibited higher stability at pH 9 and pH 10. Hyperactivation of CLLAs-ga-bsa was achieved with an effectiveness factor of more than 1 and with improved catalytic efficiency. After 3 h reaction, CLLAs-ga-bsa produced the highest total scFOSs yield of 35.4% and total sugar of 60.4% per gram levan. Finally, the reusability of CLLAs for 8 cycles with more than 50% activity retained makes them as a potential synthetic catalyst to be explored for scFOSs synthesis.
Efficient substrate accessibility of cross-linked levanase aggregates using dialdehyde starch as a macromolecular cross-linker

Abd Rahman NH, Jaafar NR, Shamsul Annuar NA, A Rahman R, Abdul Murad AM, El-Enshasy HA, et al.

Carbohydr Polym, 2021 Sep 01;267:118159.
PMID: 34119133 DOI: 10.1016/j.carbpol.2021.118159

Cross-linked enzyme aggregates (CLEAs) are influenced by mass diffusion limitations such as the degree of molecular cross-linking attained, which affects substrate accessibility. Thus, this study seeks to improve substrate accessibility using macromolecular cross-linkers in cross-linked levanase aggregates (CLLAs) formation for levan-type fructooligosaccharides (L-FOS) production. Dialdehyde starch-tapioca (DAST) was successfully developed and used to cross-link levanase to form CLLAs-D and with bovine serum albumin (BSA) to form CLLAs-DB which showed activity recoveries of 65.6% and 81.6%, respectively. After cross-linking, the pH (6-10) and thermal stability (30-40 °C) increased, and organic solvent tolerance resulted in the activation of CLLAs. Likewise, CLLAs-DB had higher substrate affinity and accessibility and a higher effectiveness factors than CLLAs-D. The total L-FOS yield of CLLAs-DB (78.9% (w/v)) was higher than that of CLLAs-D (62.4% (w/v)). Therefore, as a cross-linker, DAST may have application prospects as a promising and green biocatalyst for product formation.
Fulltext The impact of radiofrequency exposure on Aedes aegypti (Diptera: Culicidae) development

Nik Abdull Halim NMH, Mohd Jamili AF, Che Dom N, Abd Rahman NH, Jamal Kareem Z, Dapari R

PLoS One, 2024;19(2):e0298738.
PMID: 38412167 DOI: 10.1371/journal.pone.0298738

INTRODUCTION: Wireless communication connects billions of people worldwide, relying on radiofrequency electromagnetic fields (RF-EMF). Generally, fifth-generation (5G) networks shift RF carriers to higher frequencies. Although radio, cell phones, and television have benefitted humans for decades, higher carrier frequencies can present potential health risks. Insects closely associated with humans (such as mosquitoes) can undergo increased RF absorption and dielectric heating. This process inadvertently impacts the insects' behaviour, morphology, and physiology, which can influence their spread. Therefore, this study examined the impact of RF exposure on Ae. aegypti mosquitoes, which are prevalent in indoor environments with higher RF exposure risk. The morphologies of Ae. aegypti eggs and their developments into Ae. aegypti mosquitoes were investigated.
METHODS: A total of 30 eggs were exposed to RF radiation at three frequencies: baseline, 900 MHz, and 18 GHz. Each frequency was tested in triplicate. Several parameters were assessed through daily observations in an insectarium, including hatching responses, development times, larval numbers, and pupation periods until the emergence of adult insects.
RESULTS: This study revealed that the hatching rate for the 900 MHz group was the highest (79 ± 10.54%) compared to other exposures (p = 0.87). The adult emergence rate for the 900 MHz group was also the lowest at 33 ± 2.77%. A significant difference between the groups was demonstrated in the statistical analysis (p = 0.03).
CONCLUSION: This work highlighted the morphology sensitivity of Ae. aegypti eggs and their developments in the aquatic phase to RF radiation, potentially altering their life cycle.
Post-impact disaster surveillance - a medical reconnaissance team at tsunami-struck sri lanka

Mohamad N, Abu Bakar NH, Mohamed NA, Baharudin KA, Noh AY, Ahmad R, et al.

Malays J Med Sci, 2007 Jan;14(1):79-83.
PMID: 22593659 MyJurnal

Emergency Medicine and Disaster Medicine are two specialties which are similar in the multidisciplinary involvement during the acute phase of the disaster. Recently, there was an increase in the number of disasters in the world but not many physicians are familiar with the principles for dealing with such situations, the unique organizational demands, coordination and the urgent need for medical assistance and relief. This case report delineates our experiences at a tsunami disaster area and the approach to setting up a medical relief team in the affected area. A medical reconnaissance team comprising of an emergency doctor from Hospital Universiti Sains Malaysia (H.U.S.M) and two MERCY Malaysia members was assembled. The team flew to Colombo on day 5 after the tsunami with medical supplies and related materials. The mission started from December 31(st) 2004 until January 8(th) 2005. Our surveillance area covered the Southern and Eastern Province with a total distance of 1700 km along the coast. The strategies employed during this medical reconnaissance included risk analysis, devising a resources matrix, developing lines of communication and rapport with other relief teams, Sri Lankan government agencies, and local and international non-government organizations. As a result, our team was able to set up a medical relief camp and distribute the relief items to the tsunami victims. In conclusion, the Disaster Emergency Medical Assistant Team (DEMAT) from H.U.S.M and MERCY Malaysia were able to set up and provide medical relief with our limited resources to a large scale disaster situation.
Fulltext Mathematical epidemiologic and simulation modelling of first wave COVID-19 in Malaysia

Ariffin MRK, Gopal K, Krishnarajah I, Che Ilias IS, Adam MB, Arasan J, et al.

Sci Rep, 2021 Oct 20;11(1):20739.
PMID: 34671103 DOI: 10.1038/s41598-021-99541-0

Since the first coronavirus disease 2019 (COVID-19) outbreak appeared in Wuhan, mainland China on December 31, 2019, the geographical spread of the epidemic was swift. Malaysia is one of the countries that were hit substantially by the outbreak, particularly in the second wave. This study aims to simulate the infectious trend and trajectory of COVID-19 to understand the severity of the disease and determine the approximate number of days required for the trend to decline. The number of confirmed positive infectious cases [as reported by Ministry of Health, Malaysia (MOH)] were used from January 25, 2020 to March 31, 2020. This study simulated the infectious count for the same duration to assess the predictive capability of the Susceptible-Infectious-Recovered (SIR) model. The same model was used to project the simulation trajectory of confirmed positive infectious cases for 80 days from the beginning of the outbreak and extended the trajectory for another 30 days to obtain an overall picture of the severity of the disease in Malaysia. The transmission rate, β also been utilized to predict the cumulative number of infectious individuals. Using the SIR model, the simulated infectious cases count obtained was not far from the actual count. The simulated trend was able to mimic the actual count and capture the actual spikes approximately. The infectious trajectory simulation for 80 days and the extended trajectory for 110 days depicts that the inclining trend has peaked and ended and will decline towards late April 2020. Furthermore, the predicted cumulative number of infectious individuals tallies with the preparations undertaken by the MOH. The simulation indicates the severity of COVID-19 disease in Malaysia, suggesting a peak of infectiousness in mid-March 2020 and a probable decline in late April 2020. Overall, the study findings indicate that outbreak control measures such as the Movement Control Order (MCO), social distancing and increased hygienic awareness is needed to control the transmission of the outbreak in Malaysia.

Filters

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links