Chemistry

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    The Groundwater Geochemistry and the Human Health Risk Assessment of Drinking Water in anArea with aHighPrevalence of Chronic Kidney Disease of Unknown Etiology (CKDu), Sri Lanka
    (Journal of Chemistry, 2021, 2021) Botheju, W. S. M; Liyanage, J. A; Kannangara, S. D. P; Corchado, J.
    Chronic kidney disease of unknown etiology (CKDu) has become an alarming health issue in Sri Lanka. ,e disease is more notable among farming communities and people who consume groundwater as their main source of drinking ...
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    Hypoglycemic and Anti‑lipidemic Properties of Cinnamomum zeylanicum (“Sri Wijaya” Accession) Water‑soluble Nutraceutical in Streptozotocin‑induced Diabetic and Healthy Wistar Rats
    (Pharmacognosy Magazine, 2021) Jayawardena, B.; Madushika Wariyapperuma, W.N.; Thammitiyagodage, M.; Karunakaran, R.; Sisira Kumara, W.S.
    Background: Hyperglycemia is a serious health crisis worldwide, and more than 90% of the Sri Lankan patients effected with the condition have diabetes mellitus type 2. Natural therapeutic agents can manage the progression of the disease. Objectives: To investigate the hypoglycemic and antilipidemic effects of Cinnamomum zeylanicum (“Sri Wijaya” accession) water‑soluble nutraceuticals in diabetic‑induced and healthy Wistar rats. Materials and Methods: The diabetic and nondiabetic Wistar rats were treated with Cinnamon pressured water, Cinnamon decoction, pretreated pressured water Cinnamon extract for 1 month. The results were compared with the group treated with the positive control, Acarbose untreated normal group. Blood glucose and other biochemical parameters were estimated using commercial test kits. Results: There was a significant difference in the fasting serum glucose, food consumption, and water consumption in rats with induced diabetes. The total cholesterol level was significantly decreased in the normal groups treated with Cinnamon extracts, compared with the untreated groups. There was a significant increase in high‑density lipoprotein cholesterol levels in the normal group treated with pressured water Cinnamon extract and decoction when compared with the Acarbose‑treated diabetic group. Alanine aminotransferase (ALT) levels were significantly higher in the diabetic group treated with Acarbose than in all Cinnamon‑treated groups. However, no significant difference was shown in normal rat groups for aspartate aminotransferase and ALT. Conclusion: Cinnamon nutraceuticals have the potential to reduce hyperglycemia in diabetic rats. Cinnamon extracts may inhibit α‑amylase and α‑glucosidase enzymes in rat pancreatic tissues.
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    Antioxidant activity and chemical constituents of methanolic extract of Durio zibethinus Murr. (durian) peels
    (MEDICINAL PLANTS - INTERNATIONAL JOURNAL OF PHYTOMEDICINES AND RELATED INDUSTRIES, 2021) Perera, P.J.; Binuwangi, A.K.D.M.; Silva, A.A.G.; Attanayake, R.N.; Wickramarachchi, S.R.; Rajapakse, C.S.K.
    This study aimed to determine the DPPH free radical scavenging activity, total phenolic content (TPC) and total flavonoid content (TFC) of methanolic extract of Durio zibethinus Murr. (durian) peels and its fractions. The chemical constituents of durian peels extracted into methanol by soxhlet extraction were sequentially extracted into hexane, dichloromethane and aqueous methanol. Among the fractions, the dichloromethane fraction showed the highest DPPH free radical scavenging activity (IC50 179.9 ± 6.6 μg/ml) with high TPC and TFC (85.82 ± 12.11 mg gallic acid equivalent/g of dried weight of extract and 12.66 ± 1.94 mg of quercetin equivalent/g of dried weight of extract, respectively). A very strong positive correlation (r = 0.9677) was observed between the DPPH free radical scavenging activity and the TPC of fractions and a strong positive correlation (r = 0.7858) was noticed between the DPPH free radical scavenging activity and TFC of the fractions indicating that phenolic compounds in durian peels may contribute to their strong antioxidant activity. As the dichloromethane fraction had constituents with the highest antioxidant activity, it was analyzed by Gas chromatography-Mass spectrophotometry to identify its volatile constituents. The results revealed that the dichloromethane fraction was rich in [1,2-Benzenedicarboxylic acid, bis (2-ethylhexyl) ester], [2,3-diphenylquinoxaline], [2-coumaranone], [4-((1E)-3-hydroxy-1-propenyl)-2-methoxyphenol], [7,9-di-tert-butyl-1-oxaspiro (4,5) deca-6,9-diene-2,8-dione] and [phenol, 2,4-bis(1,1-dimethylethyl)], which are known to exhibit antioxidant activity.
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    Electrodeposition and characterization of as-deposited and annealed CdTe thin films.
    (Ceylon Journal of Science, 45(2), 53–59. DOI: http://doi.org/10.4038/cjs.v45i2.7388, 2016) Kumarasinghe, K. D. M. S. P. K.; De Silva, D. S. M.; Pathiratne, K. A. S.; Salim, H. I.; Abdul-Manaf, N. A.; Dharmadasa, I. M.
    Thin films of CdTe semiconductor materials were grown on fluorine doped tin oxide (FTO) conducting glass substrates using the technique of electrodeposition. CdSO4 at high concentrations and CdCl2, TeO2 at low concentrations were used as precursor salts for electrodeposition. The range of deposition potentials was estimated using cyclic voltammetric measurements. The electrical, optical, structural and morphological characteristics of as-deposited and annealed CdTe thin films were characterized using photo-electrochemical (PEC) cell studies, UV-Vis spectrophotometry, X-ray diffraction (XRD) and scanning electron microscopy (SEM). These particular samples were converted from n-type into p-type after heat treatment. UV-Vis spectrometric measurements for CdTe layers indicated that, the energy band gaps of 1.45±0.02 eV for both as-deposited and annealed samples which exhibited the required optical property for fabricating CdS/CdTe solar cells. Little increase in (220) and (311) peaks of XRD spectra were observed for annealed layers compared to the as-deposited material. However, annealing exhibited a small reduction of cubic phase preferential orientation (111). The optical transmission for both as-deposited and annealed CdTe samples were about 60% for wavelengths longer than about 850 nm.
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    Selenium content in meals consumed for lunch by Sri Lankans and the effect of cooking on selenium content.
    (Ceylon Journal of Science, 46(4), 21–25. DOI: http://doi.org/10.4038/cjs.v46i4.7465, 2017) Kiridena, K. M. S. D.; De Silva, D. S. M.; Wimalasena, S.
    The selenium (Se) content in meals consumed by Sri Lankans for lunch, composed of fixed and random menus, was determined using Hydride Generation Atomic Absorption Spectrometer. The samples were obtained from five districts in Sri Lanka. The Se content (μg/kg) in meals of fixed and random menus was in the range of 48-70 and 53-60 respectively. These values are comparable to the daily requirement of Se (55 μg/kg) prescribed by the World Health Organization and Food and Agriculture Organization of the United Nations. There is no significant difference in Se content in meals consumed by people in the districts of Kandy, Gampaha, Kurunegala, Rathnapura, and Colombo, as well as among individual households in each district. The effects of different cooking methods on the Se content indicate that the level of Se (μg/kg) in fried chicken (30.45 - 52.49) is less than that in a chicken curry (61.38 - 84.25). The percentage loss of Se during cooking for chicken, dahl (Lens culinaris) and Gotukola (Centella asiatica) were 89.6%, 84.1%, and 79.9% respectively. The present study revealed that Se content in Sri Lankan menus provides the required Se for people. However, the different methods of cooking indicate that there is a loss of Se during cooking.
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    Gestational diabetes mellitus and risk of type 2 diabetes 10 years after the index pregnancy in Sri Lankan women—A community based retrospective cohort study
    (PLOS ONE, 2017, DOI: 10.1371/journal.pone.0179647 /http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0179647&type=printable, 2017) Herath, H.; Herath, R.; Wickremasinghe, R.
    Background Women with a history of gestational diabetes mellitus (GDM) have an increased risk of type 2 diabetes mellitus (T2DM) later in life compared to women with no GDM. This study was aimed to determine the risk of developing T2DM 10 years after GDM in Sri Lankan women. Methods A retrospective cohort study was conducted in the Colombo district, Sri Lanka. 7205 women who delivered a child in 2005 were identified through Public Health Midwives in the field. Women with antenatal records were interviewed and relevant data were extracted from medical records to identify potential participants. One hundred and nineteen women who had GDM and 240 women who did not have GDM were recruited. Current diagnosis of diabetes was based on history, relevant medical records and blood reports within the past 1 year. Results The mean duration of follow up was 10.9 (SD = 0.35) years in the GDM group and 10.8 (SD = 0.31) years in the non-GDM group. The incidence density of diabetes in the GDM group was 56.3 per 1000 person years compared to 5.4 per 1000 person years in non GDM group giving a rate ratio of 10.42 (95% CI: 6.01–19.12). A woman having GDM in the index pregnancy was 10.6 times more likely to develop diabetes within 10 years compared to women with no GDM after controlling for other confounding variables. Delivering a child after 30 years, being treated with insulin during the pregnancy and delivering a baby weighing more than 3.5 Kg were significant predictors of development of T2DM after controlling for family history of diabetes mellitus (DM), GDM in previous pregnancies, parity and gestational age at delivery. Conclusions Women with GDM had a 10-fold higher risk of developing T2DM during a 10-year follow up period as compared to women with no GDM after controlling for other confounding variables.
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    Host gene expression analysis in Sri Lankan melioidosis patients.
    (PLoS Negl Trop Dis 11(6), 2017) Krishnananthasivam, S.; Jayathilaka, N.; Sathkumara, H.D.; Corea, E.; Natesan, M.; De Silva, A.D.
    Melioidosis is a life threatening infectious disease caused by the gram-negative bacillus Burkholderia pseudomallei predominantly found in southeast Asia and northern Australia. Studying the host transcription profiles in response to infection is crucial for understanding disease pathogenesis and correlates of disease severity, which may help improve therapeutic intervention and survival. The aim of this study was to analyze gene expression levels of human host factors in melioidosis patients and establish useful correlation with disease biomarkers, compared to healthy individuals and patients with sepsis caused by other pathogens.
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    Synthesis, Optimization, and Performance Demonstration of Electrospun Carbon Nanofiber–Carbon Nanotube Composite Sorbents for Point-of-Use Water Treatment
    (American Chemical Society., 2016) Peter, K.T.; Vargo, J.D.; Rupasinghe, T.P.; De Jesus, A.; Tivanski, A.V.; Sander, E.A.; Myung, N.V.; Cwiertny, D.M.
    We developed an electrospun carbon nanofiber–carbon nanotube (CNF–CNT) composite with optimal sorption capacity and material strength for point-of-use (POU) water treatment. Synthesis variables including integration of multiwalled carbon nanotubes (CNTs) and macroporosity (via sublimation of phthalic acid), relative humidity (20 and 40%), and stabilization temperature (250 and 280 °C) were used to control nanofiber diameter and surface area (from electron microscopy and BET isotherms, respectively), surface composition (from XPS), and strength (from AFM nanoindentation and tensile strength tests). Composites were then evaluated using kinetic, isotherm, and pH-edge sorption experiments with sulfamethoxazole (log Kow = 0.89) and atrazine (log Kow = 2.61), representative micropollutants chosen for their different polarities. Although CNFs alone were poor sorbents, integration of CNTs and macroporosity achieved uptake comparable to granular activated carbon. Through reactivity comparisons with CNT dispersions, we propose that increasing macroporosity exposes the embedded CNTs, thereby enabling their role as the primary sorbent in nanofiber composites. Because the highest capacity sorbents lacked sufficient strength, our optimal formulation (polyacrylonitrile 8 wt %, CNT 2 wt %, phthalic acid 2.4 wt %; 40% relative humidity; 280 °C stabilization) represents a compromise between strength and performance. This optimized sorbent was tested with a mixture of ten organic micropollutants at environmentally relevant concentrations in a gravity-fed, flow-through filtration system, where removal trends suggest that both hydrophobic and specific binding interactions contribute to micropollutant uptake. Collectively, this work highlights the promise of CNF–CNT filters (e.g., mechanical strength, ability to harness CNT sorption capacity), while also prioritizing areas for future research and development (e.g., improved removal of highly polar micropollutants, sensitivity to interfering cosolutes).
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    Dissolution and aggregation of zinc oxide nanoparticles at circumneutral pH; a study of size effects in the presence and absence of citric acid
    (The University of Iowa, ProQuest Dissertations., 2011) Rupasinghe, R.A.
    Understanding the size dependent dissolution of engineered nanoparticles is one important aspect in addressing the potential environmental and health impacts of these materials as well as their long-term stability. In this study, experimental measurements of size dependent dissolution of well-characterized zinc oxide (ZnO) nanoparticles with particle diameters in the range of 4 to 130 nm have been measured and compared at circumneutral pH (pH 7.5). Enhanced dissolution was found for the smaller particles with the largest enhancement observed in Zn2+(aq) concentrations for 4 nm diameter ZnO nanoparticles compared to larger-sized particles. Interestingly, size dependent dissolution was observed even though the nanoparticles aggregated with hydrodynamic diameters on the order of 1-3 µm in diameter. Although these results are found to be in qualitative agreement with theoretical predictions used to predict the dissolution of solids, a linearized form of the Kelvin equation to calculate a bulk dissolution value for ZnO and a surface free energy yielded quantities inconsistent with known literature values. It is therefore concluded that deviations from solubility behavior from classical thermodynamics are due to a lack of the detailed knowledge of the surface free energy as well as its dependence on the details of the surface structure, surface properties, including the presence of different surface crystal facets and adsorbed ligands, as well of aggregation state. The presence of citric acid significantly enhances the extent of ZnO dissolution for all sizes such that no significant differences were observed for total Zn2+(aq) concentrations for nanoparticles between 4 to 130 nm. This can be attributed to ligand enhanced dissolution of ZnO nanoparticles where there is no dependence on size. PREVIEW v Adsorption of citrates onto ZnO nanoparticles was observed using ATR-FTIR spectroscopy. A reversal of surface charge of ZnO nanoparticles was observed upon adsorption of citrates. Adsorption of negatively charged Cit3- onto ZnO nanoparticles make the surfaces negatively charged and this result in a repulsion between nanoparticles eventually leading to a lesser extent of aggregation. Formation of a stable suspension was also observed in the presence of citric acid. These trends observed in aggregation pattern are of great environmental and biological importance as citric acid is abandon in the environment as well as in human body.
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    Nanocrystals of a Metal–Organic Complex Exhibit Remarkably High Conductivity that Increases in a Single-Crystal-to-Single-Crystal Transformation
    (American Chemical Society., 2014) Hutchins, K.M.; Rupasinghe, T.P.; Ditzler, L.R.; Swenson, D.C.; Sander, J.R.G.; Baltrusaitis, J.; Tivanski, A.V.; MacGillivray, L.R.
    Ag(I) is used to form a π-stacked metal–organic solid that exhibits remarkably high electrical conductivity. The solid undergoes a single-crystal-to-single-crystal [2+2] photodimerization to generate a 1D coordination polymer with over 40% higher conductivity. The Ag(I) complex represents the first example of an increase in conductivity resulting from a [2+2] photodimerization. Density of states calculations show a higher contribution from Ag(I) ions to the valence band in the photodimerized solid, supporting the increase in conductivity.