RESIDUAL STRESS ANALYSIS OF CERAMIC COATINGS ON BIOCOMPATIBLE MAGNESIUM ALLOYS

poster abstractMagnesium and its alloys have gained special interest in medical applica-tions in recent years, as promising biodegradable metallic implant materials, due to their excellent mechanical properties and biocompatibilities. However, magnesium alloys rapidly corrode in human body. Therefore, a dense ceram-ic coating has been produced on the surface of the magnesium alloy through the method of microarc oxidation (MAO), which improves the corrosion re-sistance of the magnesium alloy. The objective of this study is to evaluate the residual stress of the ceramic coating on biocompatible AZ31 magnesium alloy. The corresponding residual stresses with different applied voltages have been examined in this study. An integrated experimental and modeling approach has been employed. Residual stresses attributed to the MgO constituent of the coatings at oxida-tion voltages between 250 V to 350 V have been evaluated by X-ray diffrac-tion (XRD) using sin2ψ method. An analytic model is also used to compute the stress distributions in the coatings. The residual stresses decreased with the increase of the applied voltage. The predicated stresses from the analytic model are in good agreement with the experimental measurements. At 350V, the coating has a uniform surface morphology and the lowest residual stress. This is the optimal voltage in the MAO process to produce the high-quality corrosion resistant coating. The measured stresses using sin2 ψ XRD method in the MgO constituent of the MAO coatings are tensile in nature. The voltage-dependent residual stress has been released during the microarc discharge process, which is attributed to the micro-pores and cracks formed in the coating

Distribution and flux of dissolved iron in the peatland-draining rivers and estuaries of Sarawak, Malaysian Borneo

Dissolved iron (dFe) is essential for multiple biogeochemical reactions in oceans, such as photosynthesis, respiration and nitrogen fixation. Currently, large uncertainties remain regarding the input of riverine dFe into coastal oceans, especially in tropical rivers in southeastern Asia. In the present study, the concentrations of dFe and distribution patterns of dFe were determined along the salinity gradient in the Rajang River and three blackwater rivers that drain from peatlands, including the Maludam River, the Sebuyau River and the Simunjan River. In the Rajang River, the dFe concentration in freshwater samples (salinity < 1 PSU – practical salinity units) in the wet season (March 2017) was higher than that in the dry season (August 2016), which might be related to the resuspension of sediment particles and soil erosion from cropland. In the Rajang estuary, an intense removal of dFe in low-salinity waters (salinity < 15 PSU) was observed, which was likely due to salt-induced flocculation and absorption of dFe onto suspended particulate matter (SPM). However, increases in the dFe concentration in the wet season were also found, which may be related to dFe desorption from SPM and the influences of agricultural activities. In the blackwater rivers, the dFe concentration reached 44.2 µmol L−1 , indicating a strong contribution to the dFe budget from peatland leaching. The dFe flux derived from the Rajang estuary to the South China Sea was estimated to be 6.4±2.3×105 kg yr−1 . For blackwater rivers, the dFe flux was approximately 1.1 ± 0.5 × 105 kg yr−1 in the Maludam River. Anthropogenic activities may play an important role in the dFe yield, such as in the Serendeng tributary of the Rajang River and Simunjan River, where intensive oil palm plantations were observed

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals &lt;1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Elucidating the role of <i>Rhodiola rosea</i> L. in sepsis-induced acute lung injury via network pharmacology: emphasis on inflammatory response, oxidative stress, and the PI3K-AKT pathway

Sepsis-induced acute lung injury (ALI) is associated with high morbidity and mortality. Rhodiola rosea L. (Crassulaceae) (RR) and its extracts have shown anti-inflammatory, antioxidant, immunomodulatory, and lung-protective effects. This study elucidates the molecular mechanisms of RR against sepsis-induced ALI. The pivotal targets of RR against sepsis-induced ALI and underlying mechanisms were revealed by network pharmacology and molecular docking. Human umbilical vein endothelial cells (HUVECs) were stimulated by 1 μg/mL lipopolysaccharide for 0.5 h and treated with 6.3, 12.5, 25, 50, 100, and 200 μg/mL RR for 24 h. Then, the lipopolysaccharide-stimulated HUVECs were subjected to cell counting kit-8 (CCK-8), enzyme-linked immunosorbent, apoptosis, and Western blot analyses. C57BL/6 mice were divided into sham, model, low-dose (40 mg/kg), mid-dose (80 mg/kg), and high-dose (160 mg/kg) RR groups. The mouse model was constructed through caecal ligation and puncture, and histological, apoptosis, and Western blot analyses were performed for further validation. We identified six hub targets (MPO, HRAS, PPARG, FGF2, JUN, and IL6), and the PI3K-AKT pathway was the core pathway. CCK-8 assays showed that RR promoted the viability of the lipopolysaccharide-stimulated HUVECs [median effective dose (ED50) = 18.98 μg/mL]. Furthermore, RR inhibited inflammation, oxidative stress, cell apoptosis, and PI3K-AKT activation in lipopolysaccharide-stimulated HUVECs and ALI mice, which was consistent with the network pharmacology results. This study provides foundational knowledge of the effective components, potential targets, and molecular mechanisms of RR against ALI, which could be critical for developing targeted therapeutic strategies for sepsis-induced ALI.</p

Biogeographical distribution of microbial communities along the Rajang River-South China Sea continuum

The Rajang River is the main drainage system for central Sarawak in Malaysian Borneo and passes through peat domes through which peat-rich material is being fed into the system and eventually into the southern South China Sea. Microbial communities found within peat-rich systems are important biogeochemical cyclers in terms of methane and carbon dioxide sequestration. To address the critical lack of knowledge about microbial communities in tropical (peat-draining) rivers, this study represents the first seasonal assessment targeted at establishing a foundational understanding of the microbial communities of the Rajang River–South China Sea continuum. This was carried out utilising 16S rRNA gene amplicon sequencing via Illumina MiSeq in size-fractionated samples (0.2 and 3.0 µm GF/C filter membranes) covering different biogeographical features and sources from headwaters to coastal waters. The microbial communities found along the Rajang River exhibited taxa common to rivers (i.e. predominance of β-Proteobacteria) while estuarine and marine regions exhibited taxa that were common to the aforementioned regions as well (i.e. predominance of α− and γ-Proteobacteria). This is in agreement with studies from other rivers which observed similar changes along salinity gradients. In terms of particulate versus free-living bacteria, nonmetric multi-dimensional scaling (NMDS) results showed similarly distributed microbial communities with varying separation between seasons. Distinct patterns were observed based on linear models as a result of the changes in salinity along with variation of other biogeochemical parameters. Alpha diversity indices indicated that microbial communities were higher in diversity upstream compared to the marine and estuarine regions, whereas anthropogenic perturbations led to increased richness but less diversity. Despite the observed changes in bacterial community composition and diversity that occur along the continuum of the Rajang River to the sea, the PICRUSt predictions showed minor variations. The results provide essential context for future studies such as further analyses on the ecosystem response to anthropogenic land-use practices and probable development of biomarkers to improve the monitoring of water quality in this region

International Workshop on Globalization, Education and Social Futures cum postgraduate student sharing session

With particular reference to the changing expectations of education and the growing concerns of mismatch of skills being found in the labour market, the International Workshop critically examines how the growing influence of globalization has affected educational development and governance, as well as reflecting upon social futures in Europe and East Asia. Specific attention is given to examine skill formation, changing labour needs and how educational institutions have responded to prepare students and graduates to become more adaptive and competitive in the intensified global market place. A special session is organized for postgraduate students to share their research with special focus on reflections on research methodology with leading speakers at the workshop