Observed trends in extreme temperature over the Klan

This study investigates the recent extreme temperature trends across 19 stations in the Klang Valley, Malaysia, over the period 2006−16. Fourteen extreme index trends were analyzed using the Mann−Kendall non-parametric test, with Sen’s slope as a magnitude estimator. Generally, the annual daily mean temperature, daily mean maximum temperature, and daily mean minimum temperature in the Klang Valley increased significantly, by 0.07°C yr−1, 0.07°C yr−1 and 0.08°C yr−1 , respectively. For the warm temperature indices, the results indicated a significant upward trend for the annual maximum of maximum temperature, by 0.09°C yr−1, and the annual maximum of minimum temperature, by 0.11°C yr−1. The results for the total number of warm days and warm nights showed significant increasing trends of 5.02 d yr−1 and 6.92 d yr−1 , respectively. For the cold temperature indices, there were upward trends for the annual minimum of maximum temperature, by 0.09°C yr−1, and the annual minimum of minimum temperature, by 0.03°C yr−1, concurrent with the decreases in the total number cold days (TX10P), with −3.80 d yr−1, and cold nights (TN10P), with −4.33 d yr−1. The 34°C and 37°C summer days results showed significant upward trends of 4.10 d yr−1 and 0.25 d yr−1, respectively. Overall, these findings showed upward warming trends in the Klang Valley, with the minimum temperature rate increasing more than that of the maximum temperature, especially in urban areas

Seasonal and long term variations of surface ozone concentrations in Malaysian Borneo

Malaysian Borneo has a lower population density and is an area known for its lush rainforests. However, changes in pollutant profiles are expected due to increasing urbanisation and commercial-industrial activities. This study aims to determine the variation of surface {O3} concentration recorded at seven selected stations in Malaysian Borneo. Hourly surface {O3} data covering the period 2002 to 2013, obtained from the Malaysian Department of Environment (DOE), were analysed using statistical methods. The results show that the concentrations of {O3} recorded in Malaysian Borneo during the study period were below the maximum Malaysian Air Quality Standard of 100 ppbv. The hourly average and maximum {O3} concentrations of 31 and 92 ppbv reported at Bintulu (S3) respectively were the highest among the {O3} concentrations recorded at the sampling stations. Further investigation on {O3} precursors show that sampling sites located near to local petrochemical industrial activities, such as Bintulu (S3) and Miri (S4), have higher NO2/NO ratios (between 3.21 and 5.67) compared to other stations. The normalised {O3} values recorded at all stations were higher during the weekend compared to weekdays (unlike its precursors) which suggests the influence of {O3} titration by {NO} during weekdays. The results also show that there are distinct seasonal variations in {O3} across Borneo. High surface {O3} concentrations were usually observed between August and September at all stations with the exception of station {S7} on the east coast. Majority of the stations (except {S1} and S6) have recorded increasing averaged maximum concentrations of surface {O3} over the analysed years. Increasing trends of {NO2} and decreasing trends of {NO} influence the yearly averaged maximum of {O3} especially at S3. This study also shows that variations of meteorological factors such as wind speed and direction, humidity and temperature influence the concentration of surface O3

The association between temperature and cause-specific mortality in the Klang Valley, Malaysia

This study aims to examine the relationship between daily temperature and mortality in the Klang Valley, Malaysia, over the period 2006–2015. A quasi-Poisson generalized linear model combined with a distributed lag non-linear model (DLNM) was used to estimate the association between the mean temperature and mortality categories (natural n=69,542, cardiovascular n= 15,581, and respiratory disease n=10,119). Particulate matter with an aerodynamic diameter below 10 μm (PM₁₀) and surface ozone (O₃) was adjusted as a potential confounding factor. The relative risk (RR) of natural mortality associated with extreme cold temperature (1st percentile of temperature, 25.2 °C) over lags 0–28 days was 1.26 (95% confidence interval (CI): 1.00, 1.60), compared with the minimum mortality temperature (28.2 °C). The relative risk associated with extremely hot temperature (99th percentile of temperature, 30.2 °C) over lags 0–3 days was 1.09 (95% CI: 1.02, 1.17). Heat effects were immediate whereas cold effects were delayed and lasted longer. People with respiratory diseases, the elderly, and women were the most vulnerable groups when it came to the effects of extremely high temperatures. Extreme temperatures did not dramatically change the temperature mortality risk estimates made before and after adjustments for air pollutant (PM₁₀ and O₃) levels

Technique for Determining the Viability of Acanthamoeba Cysts Treated with a Cysticidal Agent Based on Membrane Integrity

This study presents a straightforward and reliable method for determining the viability of Acanthamoeba cysts. A standard method for determining Acanthamoeba cyst viability in an in vitro cytotoxicity analysis is required to ensure that the double-walled and sturdy cysts are affected by the substance tested. In this study, a new approach was used to determine the cysticidal potential of redox Cleland’s reagent, dithiothreitol (DTT), against Acanthamoeba cysts. This approach constitutes a significant breakthrough, as the cyst form of Acanthamoeba is known for its high resistance to various chemicals and drugs used to treat infections of the central nervous system and eyes caused by Acanthamoeba. Cyst viability was evaluated based on the intensity of the cyst population under fluorescence produced by propidium iodide (PI) dye and measured using an enzyme-linked immunosorbent assay (ELISA) reader at an absorbance of 636 nm. The results were validated using high-content screening (HCS). For analysis, an individual cell was imaged and examined for phenotypic changes in the Acanthamoeba cyst at the cyst population level. Fluorescence intensity of the cysts in each well in a 96-well plate was measured using Image J software. HCS is an automated technique that uses fluorescence microscopy to produce quantitative data

Calibration model of a low-cost air quality sensor using an adaptive neuro-fuzzy inference system

Conventional air quality monitoring systems, such as gas analysers, are commonly used in many developed and developing countries to monitor air quality. However, these techniques have high costs associated with both installation and maintenance. One possible solution to complement these techniques is the application of low-cost air quality sensors (LAQSs), which have the potential to give higher spatial and temporal data of gas pollutants with high precision and accuracy. In this paper, we present DiracSense, a custom-made LAQS that monitors the gas pollutants ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO). The aim of this study is to investigate its performance based on laboratory calibration and field experiments. Several model calibrations were developed to improve the accuracy and performance of the LAQS. Laboratory calibrations were carried out to determine the zero offset and sensitivities of each sensor. The results showed that the sensor performed with a highly linear correlation with the reference instrument with a response-time range from 0.5 to 1.7 min. The performance of several calibration models including a calibrated simple equation and supervised learning algorithms (adaptive neuro-fuzzy inference system or ANFIS and the multilayer feed-forward perceptron or MLP) were compared. The field calibration focused on O3 measurements due to the lack of a reference instrument for CO and NO2. Combinations of inputs were evaluated during the development of the supervised learning algorithm. The validation results demonstrated that the ANFIS model with four inputs (WE OX, AE OX, T, and NO2) had the lowest error in terms of statistical performance and the highest correlation coefficients with respect to the reference instrument (0.8 < r < 0.95). These results suggest that the ANFIS model is promising as a calibration tool since it has the capability to improve the accuracy and performance of the low-cost electrochemical sensor

Ozone Trends from Two Decades of Ground Level Observation in Malaysia

We examine the change in surface ozone and its precursor behavior over 20 years at four locations in western Peninsular Malaysia which have undergone urban-commercial development. Trend and correlation analyses were carried out on ozone and oxides of nitrogen observation data over the periods of 1997&ndash;2016 as well as the decadal intervals of 1997&ndash;2006 and 2007&ndash;2016. Diurnal variation composites for decadal intervals were also plotted. Significant increasing ozone concentrations were observed at all locations for the 20-year period, with a range between 0.09 and 0.21 ppb yr&minus;1. The most urbanized location (S3) showed the highest ozone trend. Decadal intervals show that not all stations record significant increasing trends of ozone, with S1 recording decreasing ozone at a rate of &minus;0.44 ppb yr&minus;1 during the latter decade. Correlation analysis showed that only oxides of nitrogen ratios (NO/NO2) had significant inverse relationships with ozone at all stations corresponding to control of ozone by photostationary state reactions. The diurnal composites show that decadal difference in NO/NO2 is mostly influenced by change in nitric oxide concentrations

The long-term assessment of air quality on an island in Malaysia

This study aims to evaluate the air quality on Langkawi Island, a famous tourist destination in Malaysia, using 13 years of data (1999-2011) recorded by the Malaysian Department of Environment. Variations of seven air pollutants (O3, CO, NO, NO2, NOx, SO2 and PM10) and three meteorological factors (temperature, humidity and wind speed) were analysed. Statistical methods used to analyse the data included principal component regression (PCR) and sensitivity analysis. The results showed PM10 was the dominant air pollutant in Langkawi and values ranged between 5.0 μg m−3 and 183.2 μg m−3. The patterns of monthly values showed that the concentrations of measured air pollutants on Langkawi were higher during the south-west monsoon (June-September) due to seasonal biomass burning activities. High CO/NOx ratio values (between 28.3 and 43.6), low SO2/NOx ratio values (between 0.04 and 0.12) and NO/NO2 ratio values exceeding 2.2 indicate the source of air pollutants in this area was motor vehicles. PCR analysis grouped the seven variables into two factor components: the F1 component consisted of SO2, NO and NOx and the F2 component consisted of PM10. The F1 component (R2 = 0.931) indicated a stronger standardized coefficient value for meteorological variables compared to the F2 component (R2 = 0.059). The meteorological variables were statistically significant (p \u3c 0.05) in influencing the distribution of the air pollutants. The status of air quality on the island could be improved through control on motor vehicle emissions as well as collaborative efforts to reduce regional air pollution, especially from biomass burning

The Characterization and Study of Antibacterial, Free Radical Scavenging, and Anticancer Potential of <i>Livistona chinensis</i>-Mediated Silver Nanoparticles

In the present research, Livistona chinensis leaf extracts were utilized as reductants to bio-fabricate silver nanoparticles (LC-AgNPs) and this was followed by the evaluation of their antioxidant, antibacterial, and anticancer potential. Multiple parameters were optimized for the formation and fidelity of LC-AgNPs. The color shift of the reaction mixture from yellow to dark brown confirmed the LC-AgNPs formation. UV/VIS spectroscopy exhibited a surface plasmon resonance (SPR) band at 436 nm. The Fourier transform infrared (FTIR) spectroscopy spectrum depicted phytochemicals in the plant extract acting as bio-reducers for LC-AgNPs synthesis. The XRD pattern confirmed the presence of LC-AgNPs by showing peaks corresponding to 2θ angle at 8.24° (111), 38.16° (200), 44.20° (220), and 64.72° (311). Zetasizer analysis exhibited size distribution by intensity of LC-AgNPs with a mean value of 255.7 d. nm. Moreover, the zeta potential indicated that the AgNPs synthesized were stable. The irregular shape of LC-AgNPs with a mean average of 38.46 ± 0.26 nm was found by scanning electron microscopy. Furthermore, the antioxidant potential of LC-AgNPs was examined using a DPPH assay and was calculated to be higher in LC-AgNPs than in leaf extracts. The calculated IC50 values of the LC-AgNPs and plant extract are 85.01 ± 0.17 and 209.44 ± 0.24, respectively. The antibacterial activity of LC-AgNPs was investigated against Escherichia coli, Pseudomonas aeruginosa, and Bacillus subtilis as well as Staphylococcus aureus, and maximum potential was observed after 24 h against P. aeruginosa. Moreover, LC-AgNPs exhibited maximum anticancer potential against TPC1 cell lines compared to the plant extract. The findings suggested that LC-AgNPs could be used as antioxidant, antibacterial, and anticancer agents for the cure of free-radical-oriented bacterial and oncogenic diseases

Observed Trends in Extreme Temperature over the Klang Valley, Malaysia

This study investigates the recent extreme temperature trends across 19 stations in the Klang Valley, Malaysia, over the period 2006–16. Fourteen extreme index trends were analyzed using the Mann-Kendall non-parametric test, with Sen’s slope as a magnitude estimator. Generally, the annual daily mean temperature, daily mean maximum temperature, and daily mean minimum temperature in the Klang Valley increased significantly, by 0.07°C yr−1, 0.07°C yr−1 and 0.08°C yr−1, respectively. For the warm temperature indices, the results indicated a significant upward trend for the annual maximum of maximum temperature, by 0.09°C yr−1, and the annual maximum of minimum temperature, by 0.11°C yr−1. The results for the total number of warm days and warm nights showed significant increasing trends of 5.02 d yr−1 and 6.92 d yr−1, respectively. For the cold temperature indices, there were upward trends for the annual minimum of maximum temperature, by 0.09°C yr−1, and the annual minimum of minimum temperature, by 0.03°C yr−1, concurrent with the decreases in the total number cold days (TX10P), with −3.80 d yr−1, and cold nights (TN10P), with −4.33 d yr−1. The 34°C and 37°C summer days results showed significant upward trends of 4.10 d yr−1 and 0.25 d yr−1, respectively. Overall, these findings showed upward warming trends in the Klang Valley, with the minimum temperature rate increasing more than that of the maximum temperature, especially in urban areas. © 2019, Institute of Atmospheric Physics/Chinese Academy of Sciences, and Science Press and Springer-Verlag GmbH Germany, part of Springer Nature