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Fulltext Fabrication of size-tunable nanocrystalline cobalt particles in propylene glycol

Balela, M.D.L., Lockman, Z., Azizan, A., Matsubara, E., Amorsolo , A.V. Jr.

Journal of Nuclear and Related Technologies, 2009;2009(1):190-198.
MyJurnal

Monodispersed and size-tunable nanocrystalline cobalt (Co) particles in the range of 100 to 400 nm are prepared by the reduction of Co(II) species in propylene glycol. Control of the particle size is achieved by varying the initial Co(II) species concentration and by the addition of nucleating agents. Smaller Co particles are produced with increasing amounts of Co(II) species and in the presence of nucleating agents. X-ray diffraction analysis (XRD) shows that the Co particles are predominantly face-centered cubic crystals of about 8-14 nm. The Co particles are also ferromagnetic at room temperature.
Effects of a Behavioral and Exercise Program on Depression and Quality of Life in Community-Dwelling Older Adults: A Controlled, Quasi-Experimental Study

Azizan A, Justine M

J Gerontol Nurs, 2016 Feb;42(2):45-54.
PMID: 26651863 DOI: 10.3928/00989134-20151124-01

Sedentary behavior and low participation in exercise among older adults can lead to depression and low quality of life (QOL). The current study investigated the effects of behavioral and exercise programs on depression severity and QOL among Malaysian community-dwelling older adults. A controlled, quasi-experimental, pre-posttest design was used. A total of 63 participants were divided into three groups: (a) exercise and behavior group (EBG), (b) exercise only group (EG), and (c) control group (CG). Results showed a significant difference in depression among groups (F(2,58) = 33.49, p < 0.01, η(2) = 0.54; mean, EBG < EG < CG) and in physical (F(2,58) = 5.33, p < 0.01, η(2)= 0.16; mean, EBG > EG > CG) and mental (F(2,58) = 4.08, p < 0.01, η(2) = 0.12; mean, EBG > CG > EG) scores of QOL. A combination of behavioral and exercise programs has superior effects on depression and QOL of older adults. [Journal of Gerontological Nursing, 42(2), 45-54.].
Fulltext Three-dimensional (3D) evaluation of liquid distribution in shake flask using an optical fluorescence technique

Azizan A, Büchs J

J Biol Eng, 2017;11:28.
PMID: 28785308 DOI: 10.1186/s13036-017-0070-7

BACKGROUND: Biotechnological development in shake flask necessitates vital engineering parameters e.g. volumetric power input, mixing time, gas liquid mass transfer coefficient, hydromechanical stress and effective shear rate. Determination and optimization of these parameters through experiments are labor-intensive and time-consuming. Computational Fluid Dynamics (CFD) provides the ability to predict and validate these parameters in bioprocess engineering. This work provides ample experimental data which are easily accessible for future validations to represent the hydrodynamics of the fluid flow in the shake flask.
RESULTS: A non-invasive measuring technique using an optical fluorescence method was developed for shake flasks containing a fluorescent solution with a waterlike viscosity at varying filling volume (VL = 15 to 40 mL) and shaking frequency (n = 150 to 450 rpm) at a constant shaking diameter (do = 25 mm). The method detected the leading edge (LB) and tail of the rotating bulk liquid (TB) relative to the direction of the centrifugal acceleration at varying circumferential heights from the base of the shake flask. The determined LB and TB points were translated into three-dimensional (3D) circumferential liquid distribution plots. The maximum liquid height (Hmax) of the bulk liquid increased with increasing filling volume and shaking frequency of the shaking flask, as expected. The toroidal shapes of LB and TB are clearly asymmetrical and the measured TB differed by the elongation of the liquid particularly towards the torus part of the shake flask.
CONCLUSION: The 3D liquid distribution data collected at varying filling volume and shaking frequency, comprising of LB and TB values relative to the direction of the centrifugal acceleration are essential for validating future numerical solutions using CFD to predict vital engineering parameters in shake flask.
What stops us and what motivates us? A scoping review and bibliometric analysis of barriers and facilitators to physical activity

Azizan A, Fadzil NHM

Ageing Res Rev, 2024 Aug;99:102384.
PMID: 38914263 DOI: 10.1016/j.arr.2024.102384

INTRODUCTION: Physical inactivity is a major global health concern, contributing to the rising non-communicable disease burden. Elucidating barriers and facilitators influencing participation is critical to promoting activity. This study aimed to synthesize the literature and analyze the extent of research on determinants of physical activity engagement.
METHODS: Scoping review methodology guided the synthesis of 272 publications on factors influencing physical activity. Bibliometric analysis examined publication trends, productivity, influential studies, content themes, and collaboration networks.
RESULTS: Since 2010, the United States has led a significant increase in research output. Highly cited articles identified physiological limitations and psychosocial determinants as key barriers and facilitators. Extensive focus was seen in clinical medicine and exercise science journals. Analysis revealed predominant attention to psychosocial factors, physiological responses, and applications in respiratory disease. Gaps remain regarding policy and environmental factors.
CONCLUSION: This review showed major advances in elucidating determinants while revealing the remaining needs to curb the pandemic of inactivity globally. Expanding international collaboration, contemporary theoretical models, and tailored mixed-methods approaches could promote progress through greater global participation. Addressing knowledge gaps across populations and disciplines should be a priority.
Fulltext Effects of a behavioral program on exercise adherence and exercise self-efficacy in community-dwelling older persons

Azizan A, Justine M, Kuan CS

Curr Gerontol Geriatr Res, 2013;2013:282315.
PMID: 24489539 DOI: 10.1155/2013/282315

Background. This study determines the effects of a behavioral program on exercise adherence (step counts) and level of exercise self-efficacy (ESE) in community-dwelling older persons. Methods. Sixty-three participants (age = 63.8 ± 4.5 years) were enrolled in this controlled quasi-experimental study. They were divided into 3 groups: (1) EBG performed a 6-week exercise intervention followed by a 5-week behavioral program, (2) EG performed exercise intervention similar to EBG, and (3) control group (CG) did not receive any interventions. Step counts were measured based on the scores recorded by a pedometer while ESE was measured by a self-reported ESE scale. Results. Data analysis showed significant differences due to time effect (F(1,2) = 39.884, P < 0.01, and η = .399); time and group interactions (F(2,60) = 112.683, P < 0.01, and η = .790); and between-group effect (F(2,60) = 12.524, P < 0.01, and η = .295) for step counts. As for ESE, significant differences were also found for time effect (F(2,4) = 66.628, P < 0.05, and η = .526); time and group interactions (F(2,60) = 4.562, P = 0.014, and η = .132); and between-group effect (F(2,60) = 13.632, P < 0.05, and η = .312). EBG presented with significantly higher mean changes for both step counts and ESE compared to other groups (all P < 0.05). Conclusion. This study suggests that the addition of a behavioral program is superior as compared to exercising alone on increasing exercise adherence and level of self-efficacy in older persons.
Reassessing the out-of-phase phenomenon in shake flasks by evaluating the angle-dependent liquid distribution relative to the direction of the centrifugal acceleration

Azizan A, Sieben M, Wandrey G, Büchs J

Biotechnol Bioeng, 2019 11;116(11):2983-2995.
PMID: 31350917 DOI: 10.1002/bit.27132

Shake flasks are still the most relevant experimental tool in the development of viscous fermentation processes. The phase number, which defines the onset of the unfavorable out-of-phase (OP) phenomenon in shake flasks, was previously defined via specific power input measurements. In the OP state, the bulk liquid no longer follows the orbital movement of the imposed centrifugal force, which is for example, detrimental to oxygen transfer. In this study, an optical fluorescence technique was used to measure the three-dimensional liquid distribution in shake flasks. Four new optically derived evaluation criteria for the phase transition between the in-phase and OP condition were established: (a) thickness of the liquid film left on the glass wall by the rotating bulk liquid, (b) relative slope of the leading edge of bulk liquid (LB) lines, (c) trend of the angular position of LB, and (d) very high angular position of the leading edge. In contrast to the previously applied power input measurements, the new optical evaluation criteria describe the phase transition in greater detailed. Instead of Ph = 1.26, a less conservative value of Ph = 0.91 is now suggested for the phase transfer, which implies a broader operating window for shake flask cultivations with higher viscosities.
Fulltext Dengue Virus NS1 Protein as a Diagnostic Marker: Commercially Available ELISA and Comparison to qRT-PCR and Serological Diagnostic Assays Currently Used by the State of Florida

Ambrose JH, Sekaran SD, Azizan A

J Trop Med, 2017;2017:8072491.
PMID: 28740517 DOI: 10.1155/2017/8072491

BACKGROUND: The proper management of patients infected with dengue virus requires early detection. Here, real-time molecular assays have proven useful but have limitations, whereas ELISAs that detect antibodies are still favored but results are obtained too late to be of clinical value. The production of DENV NS1 peaks early during infection and its detection can combine the advantages of both diagnostic approaches.
METHODS: This study compared assays currently used for detecting DENV infection at the Florida Department of Health including anti-DENV IgM and IgG ELISAs as well as qRT-PCR, against a commercially available DENV NS1 ELISA. These comparisons were made among a group of 21 human sera.
RESULTS: Nine of 14 (64.3%) DENV qRT-PCR+ samples were also DENV NS1+. Interestingly, the 5 NS1- samples that were qRT-PCR+ were additionally IgM- and IgG+ suggesting a nonprimary infection. Compared to qRT-PCR, the NS1 assay had a sensitivity of 64.3%, specificity 100%, PPV of 100%, and NPV of 58.3%.
CONCLUSIONS: The NS1 ELISA performed as expected in known DENV qRT-PCR+ samples; however negative NS1 results for qRT-PCR+ and IgG+ sera seemingly reduced the usefulness of the NS1 ELISA for nonprimary cases. We therefore conclude that diagnosis obtained via DENV NS1 ELISA deserves further investigation.
Fulltext Lumbar Spinal Stenosis: The Reliability, Sensitivity and Specificity of the Nerve Root Sedimentation Sign

Yusof MI, Azizan AF, Abdullah MS

Malays Orthop J, 2018 Jul;12(2):1-6.
PMID: 30112121 MyJurnal DOI: 10.5704/MOJ.1807.001

Introduction: This study is to evaluate the reliability, sensitivity and specificity of nerve root sedimentation sign (NRS) in our populations. The NRS is a radiological sign to diagnose lumbar spinal stenosis (LSS). It is claimed to be reliable with high sensitivity and specificity. Materials and Methods: A total of 82 MRI images from 43 patients in Group A (LSS) and 39 patients in Group B (non LSS) were analysed and compared for the presence of the NRS sign. Two assessors were used to evaluate intra and inter-assessor reliability of this sign based on 56 (33 patients, Group A and 23 patients, Group B). The findings were statistically analysed using SPSS software. Results: There was a significant association between spinal claudication and leg numbness with LSS (p<0.001 and Kappa=0.857, p<0.001). The inter-assessor reliability was also good (Kappa of 0.786, p<0.001). Conclusion: The NRS sign has high sensitivity and specificity for diagnosing LSS. The sign also has good intra and inter-assessor reliability.
Fulltext Corrigendum to "Dengue Virus NS1 Protein as a Diagnostic Marker: Commercially Available ELISA and Comparison to qRT-PCR and Serological Diagnostic Assays Currently Used by the State of Florida"

Ambrose JH, Sekaran SD, Azizan A

J Trop Med, 2017;2017:2046864.
PMID: 29209371 DOI: 10.1155/2017/2046864

[This corrects the article DOI: 10.1155/2017/8072491.].
Effects of vibration on occupant driving performance under simulated driving conditions

Azizan A, Fard M, Azari MF, Jazar R

Appl Ergon, 2017 Apr;60:348-355.
PMID: 28166895 DOI: 10.1016/j.apergo.2016.12.020

Although much research has been devoted to the characterization of the effects of whole-body vibration on seated occupants' comfort, drowsiness induced by vibration has received less attention to date. There are also little validated measurement methods available to quantify whole body vibration-induced drowsiness. Here, the effects of vibration on drowsiness were investigated. Twenty male volunteers were recruited for this experiment. Drowsiness was measured in a driving simulator, before and after 30-min exposure to vibration. Gaussian random vibration, with 1-15 Hz frequency bandwidth was used for excitation. During the driving session, volunteers were required to obey the speed limit of 100 kph and maintain a steady position on the left-hand lane. A deviation in lane position, steering angle variability, and speed deviation were recorded and analysed. Alternatively, volunteers rated their subjective drowsiness by Karolinska Sleepiness Scale (KSS) scores every 5-min. Following 30-min of exposure to vibration, a significant increase of lane deviation, steering angle variability, and KSS scores were observed in all volunteers suggesting the adverse effects of vibration on human alertness level.
Coastal meteorology on the dispersion of air particles at the Bachok GAW Station

Rahim HA, Khan MF, Ibrahim ZF, Shoaib A, Suradi H, Mohyeddin N, et al.

Sci Total Environ, 2021 Aug 15;782:146783.
PMID: 33838363 DOI: 10.1016/j.scitotenv.2021.146783

Meteorology over coastal region is a driving factor to the concentration of air particles and reactive gases. This study aims to conduct a research to determine the level of year-round air particles and the interaction of the meteorological driving factors with the particle number and mass in 2018, which is moderately influenced by Southeast Asian haze. We obtained the measurement data for particle number count (PNC), mass, reactive gases, and meteorological factors from a Global Atmospheric Watch (GAW) station located at Bachok Marine Research Center, Bachok, Kelantan, Malaysia. For various timeseries and correlation analyses, a 60-second resolution of the data has been averaged hourly and daily and visualized further. Our results showed the slight difference in particle behavior that is either measured by unit mass or number count at the study area. Diurnal variations showed that particles were generally high during morning and night periods. Spike was observed in August for PM2.5/PNC2.5 and PM10/PNC10 and in November for PMCoarse/PNCCoarse. From a polar plot, the particles came from two distinct sources (e.g., seaside and roadside) at the local scale. Regional wind vector shows two distinct wind-blown directions from northeast and southwest. The air mases were transported from northeast (e.g., Philippines, mainland China, and Taiwan) or southwest (e.g., Sumatra) region. Correlation analysis shows that relative humidity, wind direction, and pressure influence the increase in particles, whereas negative correlation with temperature is observed, and wind speed may have a potential role on the decline of particle concentration. The particles at the study area was highly influenced by the changes in regional wind direction and speed.
Fulltext Barriers to participation in physical activity and exercise among middle-aged and elderly individuals

Justine M, Azizan A, Hassan V, Salleh Z, Manaf H

Singapore Med J, 2013 Oct;54(10):581-6.
PMID: 24154584

INTRODUCTION Although the benefits of physical activity and exercise are widely acknowledged, many middle-aged and elderly individuals remain sedentary. This cross-sectional study aimed to identify the external and internal barriers to physical activity and exercise participation among middle-aged and elderly individuals, as well as identify any differences in these barriers between the two groups. METHODS Recruited individuals were categorised into either the middle-aged (age 45-59 years, n = 60) or elderly (age ≥ 60 years, n = 60) group. Data on demographics, anthropometry, as well as external and internal barriers to participation in physical activity and exercise were collected. RESULTS Analysis showed no significant differences in the total scores of all internal barriers between the two groups (p > 0.05). The total scores for most external barriers between the two groups also showed no significant differences (p > 0.05); only 'cost' (p = 0.045) and 'exercise interferes with social/family activities' (p = 0.011) showed significant differences. The most common external barriers among the middle-aged and elderly respondents were 'not enough time' (46.7% vs. 48.4%), 'no one to exercise with' (40.0% vs. 28.3%) and 'lack of facilities' (33.4% vs. 35.0%). The most common internal barriers for middle-aged respondents were 'too tired' (48.3%), 'already active enough' (38.3%), 'do not know how to do it' (36.7%) and 'too lazy' (36.7%), while those for elderly respondents were 'too tired' (51.7%), 'lack of motivation' (38.4%) and 'already active enough' (38.4%). CONCLUSION Middle-aged and elderly respondents presented with similar external and internal barriers to physical activity and exercise participation. These factors should be taken into account when healthcare policies are being designed and when interventions such as the provision of facilities to promote physical activity and exercise among older people are being considered.
Fulltext Chemi- vs physisorption in the radical functionalization of single-walled carbon nanotubes under microwaves

Mamane V, Mercier G, Abdul Shukor J, Gleize J, Azizan A, Fort Y, et al.

Beilstein J Nanotechnol, 2014;5:537-45.
PMID: 24991489 DOI: 10.3762/bjnano.5.63

The effect of microwaves on the functionalization of single-walled carbon nanotubes (SWNTs) by the diazonium method was studied. The usage of a new approach led to the identification of the strength of the interaction (physical or chemical) between the functional groups and the carbon nanotube surface. Moreover, the nature (chemical formula) of the adsorbed/grafted functional groups was determined. According to thermogravimetric analysis coupled with mass spectrometry and Raman spectroscopy, the optimal functionalization level was reached after 5 min of reaction. Prolonged reaction times can lead to undesired reactions such as defunctionalization, solvent addition and polymerization of the grafted functions. The strength (chemi- vs physisorption) of the bonds between the grafted functional groups and the SWNTs is discussed showing the occurrence of physical adsorption as a consequence of defunctionalization after 15 min of reaction under microwaves. Several chemical mechanisms of grafting could be identified, and it was possible to distinguish conditions leading to the desired chemical grafting from those leading to undesired reactions such as physisorption and polymerization.
Fulltext Spatial pattern of 2009 dengue distribution in Kuala Lumpur using GIS application

Aziz S, Ngui R, Lim YA, Sholehah I, Nur Farhana J, Azizan AS, et al.

Trop Biomed, 2012 Mar;29(1):113-20.
PMID: 22543611 MyJurnal

In the last few years in Malaysia, dengue fever has increased dramatically and has caused huge public health concerns. The present study aimed to establish a spatial distribution of dengue cases in the city of Kuala Lumpur using a combination of Geographic Information System (GIS) and spatial statistical tools. Collation of data from 1,618 dengue cases in 2009 was obtained from Kuala Lumpur City Hall (DBKL). These data were processed and then converted into GIS format. Information on the average monthly rainfall was also used to correlate with the distribution pattern of dengue cases. To asses the spatial distribution of dengue cases, Average Nearest Neighbor (ANN) Analysis was applied together with spatial analysis with the ESRI ArcGIS V9.3 programme. Results indicated that the distribution of dengue cases in Kuala Lumpur for the year 2009 was spatially clustered with R value less than 1 (R = 0.42; z-scores = - 4.47; p < 0.001). Nevertheless, when this pattern was further analyzed according to month by each zone within Kuala Lumpur, two distinct patterns were observed which include a clustered pattern (R value < 1) between April to June and a dispersed pattern (R value > 1) between August and November. In addition, the mean monthly rainfall has not influenced the distribution pattern of the dengue cases. Implementation of control measures is more difficult for dispersed pattern compared to clustered pattern. From this study, it was found that distribution pattern of dengue cases in Kuala Lumpur in 2009 was spatially distributed (dispersed or clustered) rather than cases occurring randomly. It was proven that by using GIS and spatial statistic tools, we can determine the spatial distribution between dengue and population. Utilization of GIS tools is vital in assisting health agencies, epidemiologist, public health officer, town planner and relevant authorities in developing efficient control measures and contingency programmes to effectively combat dengue fever.
Fulltext Metabolite Profiling of the Microalgal Diatom Chaetoceros Calcitrans and Correlation with Antioxidant and Nitric Oxide Inhibitory Activities via ¹H NMR-Based Metabolomics

Azizan A, Ahamad Bustamam MS, Maulidiani M, Shaari K, Ismail IS, Nagao N, et al.

Mar Drugs, 2018 May 07;16(5).
PMID: 29735927 DOI: 10.3390/md16050154

Microalgae are promising candidate resources from marine ecology for health-improving effects. Metabolite profiling of the microalgal diatom, Chaetoceros calcitrans was conducted by using robust metabolomics tools, namely ¹H nuclear magnetic resonance (NMR) spectroscopy coupled with multivariate data analysis (MVDA). The unsupervised data analysis, using principal component analysis (PCA), resolved the five types of extracts made by solvents ranging from polar to non-polar into five different clusters. Collectively, with various extraction solvents, 11 amino acids, cholesterol, 6 fatty acids, 2 sugars, 1 osmolyte, 6 carotenoids and 2 chlorophyll pigments were identified. The fatty acids and both carotenoid pigments as well as chlorophyll, were observed in the extracts made from medium polar (acetone, chloroform) and non-polar (hexane) solvents. It is suggested that the compounds were the characteristic markers that influenced the separation between the clusters. Based on partial least square (PLS) analysis, fucoxanthin, astaxanthin, violaxanthin, zeaxanthin, canthaxanthin, and lutein displayed strong correlation to 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and nitric oxide (NO) inhibitory activity. This metabolomics study showed that solvent extractions are one of the main bottlenecks for the maximum recovery of bioactive microalgal compounds and could be a better source of natural antioxidants due to a high value of metabolites.
Fulltext Antioxidant and α-glucosidase inhibitory activities of eight neglected fruit extracts and UHPLC-MS/MS profile of the active extracts

Mohamed Yunus SN, Abas F, Jaafar AH, Azizan A, Zolkeflee NKZ, Abd Ghafar SZ

Food Sci Biotechnol, 2021 Feb;30(2):195-208.
PMID: 33732510 DOI: 10.1007/s10068-020-00856-x

The 70% ethanolic extracts from eight neglected fruits; Muntingia calabura, Leucaena leucocephala, Spondias dulcis, Syzygium jambos, Mangifera caesia, Ardisia elliptica, Cynometra cauliflora and Ficus auriculata were evaluated for their 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, α-glucosidase inhibitory activities as well as total phenolic content. The results of this study revealed that M. caesia fruit extract demonstrated the most potent radical scavenging activity. Among the fruits examined for α-glucosidase inhibitory activity, M. calabura and F. auriculata exhibited strong activity with no significant difference. The Pearson correlation indicated that the activities of M. caesia and F. auriculata contributed by phenolic compounds. A total of 65 metabolites were tentatively identified by using ultra-high-performance liquid chromatography tandem mass spectrometry (UHLPC-MS/MS). These findings suggested that the possible application of M. caesia and F. auriculata as a functional food with antioxidant and α-glucosidase inhibitory properties.
Validation of computational fluid dynamics of shake flask experiments at moderate viscosity by liquid distributions and volumetric power inputs

Dinter C, Gumprecht A, Menze MA, Azizan A, Niehoff PJ, Hansen S, et al.

Sci Rep, 2024 Feb 13;14(1):3658.
PMID: 38351095 DOI: 10.1038/s41598-024-53980-7

Computational fluid dynamics (CFD) has recently become a pivotal tool in the design and scale-up of bioprocesses. While CFD has been extensively utilized for stirred tank reactors (STRs), there exists a relatively limited body of literature focusing on CFD applications for shake flasks, almost exclusively concentrated on fluids at waterlike viscosity. The importance of CFD model validation cannot be overstated. While techniques to elucidate the internal flow field are necessary for model validation in STRs, the liquid distribution, caused by the orbital shaking motion of shake flasks, can be exploited for model validation. An OpenFOAM CFD model for shake flasks has been established. Calculated liquid distributions were compared to suitable, previously published experimental data. Across a broad range of shaking conditions, at waterlike and moderate viscosity (16.7 mPa∙s), the CFD model's liquid distributions align excellently with the experimental data, in terms of overall shape and position of the liquid relative to the direction of the centrifugal force. Additionally, the CFD model was used to calculate the volumetric power input, based on the energy dissipation. Depending on the shaking conditions, the computed volumetric power inputs range from 0.1 to 7 kW/m3 and differed on average by 0.01 kW/m3 from measured literature data.
Fulltext Clinical and immunological markers of dengue progression in a study cohort from a hyperendemic area in Malaysia

Rathakrishnan A, Klekamp B, Wang SM, Komarasamy TV, Natkunam SK, Sathar J, et al.

PLoS One, 2014;9(3):e92021.
PMID: 24647042 DOI: 10.1371/journal.pone.0092021

With its elusive pathogenesis, dengue imposes serious healthcare, economic and social burden on endemic countries. This study describes the clinical and immunological parameters of a dengue cohort in a Malaysian city, the first according to the WHO 2009 dengue classification.
Fulltext Biological Activities of Selected Plants and Detection of Bioactive Compounds from Ardisia elliptica Using UHPLC-Q-Exactive Orbitrap Mass Spectrometry

Wong PL, Fauzi NA, Mohamed Yunus SN, Abdul Hamid NA, Abd Ghafar SZ, Azizan A, et al.

Molecules, 2020 Jul 06;25(13).
PMID: 32640504 DOI: 10.3390/molecules25133067

Plants and plant-based products have been used for a long time for medicinal purposes. This study aimed to determine the antioxidant and anti-α-glucosidase activities of eight selected underutilized plants in Malaysia: Leucaena leucocephala, Muntingia calabura, Spondias dulcis, Annona squamosa, Ardisia elliptica, Cynometra cauliflora, Ficus auriculata, and Averrhoa bilimbi. This study showed that the 70% ethanolic extract of all plants exhibited total phenolic content (TPC) ranging from 51 to 344 mg gallic acid equivalent (GAE)/g dry weight. A. elliptica showed strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) scavenging activities, with half maximal inhibitory concentration (IC50) values of 2.17 and 49.43 μg/mL, respectively. Most of the tested plant extracts showed higher inhibition of α-glucosidase enzyme activity than the standard, quercetin, particularly A. elliptica, F. auriculata, and M. calabura extracts with IC50 values of 0.29, 0.36, and 0.51 μg/mL, respectively. A total of 62 metabolites including flavonoids, triterpenoids, benzoquinones, and fatty acids were tentatively identified in the most active plant, i.e., A. elliptica leaf extract, by using ultra-high-performance liquid chromatography (UHPLC)-electrospray ionization (ESI) Orbitrap MS. This study suggests a potential natural source of antioxidant and α-glucosidase inhibitors from A. elliptica.
Fulltext An Extended Thickness-Dependent Moisture Absorption Model for Unidirectional Carbon/Epoxy Composites

Azizan A, Johar M, Karam Singh SS, Abdullah S, Koloor SSR, Petrů M, et al.

Polymers (Basel), 2021 Jan 30;13(3).
PMID: 33573112 DOI: 10.3390/polym13030440

Moisture absorption tests for materials that exhibit non-Fickian behavior generally require a relatively long period to reach saturation. Therefore, it would be beneficial to establish a relationship between the moisture content and the thickness to minimize the experimental time and cost. This research characterizes the moisture absorption behavior of AS4/8552 carbon/epoxy composites. Specimens were prepared at 4, 8, and 16 plies and immersed in distilled water at 60 °C. The relationship between the non-Fickian parameters (Fickian to non-Fickian maximum moisture content ratio ϕ, non-Fickian diffusivity per square thickness α, and non-Fickian initiation time to) and thickness was characterized using a thickness-dependent model. A comparison with other materials revealed that all three non-Fickian parameters are able to be fitted using a power law. Nevertheless, the upper boundary for the applicability of this model was not determined in this study. The Weibull distribution plots indicate that the probability of non-Fickian moisture absorption is influenced by ϕ and α at approximately 62% within a normalized thickness range of 2-3. In regards to to, it is 82% at a normalized thickness of 6. Therefore, the Weibull distribution is proposed for the assessment of non-Fickian moisture absorption based on the material's thickness.

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