Universiti Teknologi Malaysia

About: Universiti Teknologi Malaysia is a education organization based out in Johor Bahru, Malaysia. It is known for research contribution in the topics: Membrane & Control theory. The organization has 21644 authors who have published 39500 publications receiving 520635 citations.

Antioxidant Activity of Three Honey Samples in relation with Their Biochemical Components.

Abstract: The antioxidant activities based on the free radical scavenging, reducing power, and bleaching inhibition were investigated for the three commonly used honeys in Malaysia, namely, tualang, gelam, and acacia honey. The antioxidant capacity of the honey samples was correlated with their biochemical constituents such as total phenol, total flavonoid content, and total water-soluble vitamins (vitamin B1, B2, B3, B9, B12, and vitamin C). The total flavonoid content of honey samples was strongly correlated with the three antioxidative processes (r = 0.9276-0.9910). In contrast, the total water-soluble vitamins was found to be well correlated with the free radical scavenging activity (r = 0.8226). Vitamin B3 was likely to be in the highest concentration, which covered for 69-80% of the total vitamin content. A number of five phenolic acids, three flavonoids, and two organic acids had also been detected from the honey samples using UPLC-MS/MS, without sugar-removal procedure.

Photocatalytic reduction of carbon dioxide with water vapors over montmorillonite modified TiO2 nanocomposites

Abstract: Montmorillonite (MMT) modified TiO2 nanocomposites were synthesized by single step sol–gel method. The samples were characterized by XRD, FE-SEM, HR-TEM, FT-IR, N2-adsorption–desorption, UV–vis and photoluminescence (PL) spectroscopy. Modification of TiO2 with MMT controlled the crystal growth and produced anatase phase of delaminated TiO2 pillared montmorillonite. The size of TiO2 nanoparticles reduced from 18.73 to 13.87 nm after adding MMT, while the surface area and pore volume increased. The UV–vis results identified blue shift in TiO2 band gap for the MMT modified samples. In addition, PL spectroscopy revealed significant inhibition in recombination of photogenerated electron–hole pairs. The performance of MMT modified TiO2 samples for reducing CO2 with H2O to hydrocarbon fuels was investigated. The effects of parameters such as MMT loading on TiO2, H2O/CO2 feed ratios, and reaction temperature on TiO2 photocatalytic activity was studied. Loading MMT on TiO2 enhanced the performance of TiO2 and markedly increased CO2 reduction to C1–C3 hydrocarbon fuels. The highest yield rates produced were 441.5 and 103 μmol g cat−1 h−1 for CH4 and CO, respectively under UV light irradiations at 20 wt.% MMT loading, reactor pressure of 0.20 bars and 393 K reaction temperature. These results revealed silicate layers of MMT dispersed in the given TiO2 sol system and vacant d-orbits of the MMT transition metal ions have obvious effect on the photocatalytic activity of TiO2. The possible pathways and reaction mechanisms of CH4 and CO productions were also suggested. Thus, MMT is a potentially attractive material to improve TiO2 as a photocatalyst for application in photocatalytic CO2 reduction.

Empirical ocean-color algorithms to retrieve chlorophyll- a , total suspended matter, and colored dissolved organic matter absorption coefficient in the Yellow and East China Seas

Abstract: A bio-optical dataset collected during the 1998–2007 period in the Yellow and East China Seas (YECS) was used to provide alternative empirical ocean-color algorithms in the retrieval of chlorophyll-a (Chl-a), total suspended matter (TSM), and colored dissolved organic matter (CDOM) absorption coefficients at 440 nm (ag440). Assuming that remote-sensing reflectance (Rrs) could be retrieved accurately, empirical algorithms for TChl (regionally tuned Tassan’s Chl-a algorithm) in case-1 waters (TChl2i in case-2 waters), TTSM (regionally tuned Tassan’s TSM algorithm), and Tag440 or Cag440 (regionally tuned Tassan’s or Carder’s ag440 algorithm) were able to retrieve Chl-a, TSM, and ag440 with uncertainties as high as 35, 46, and 35%, respectively. Applying the standard SeaWiFS Rrs, TChl was not viable in the eastern part of the YECS, which was associated with an inaccurate SeaWiFS Rrs retrieval because of improper atmospheric correction. TChl behaved better than other algorithms in the turbid case-2 waters, although overestimation was still observed. To retrieve more reliable Chl-a estimates with standard SeaWiFS Rrs in turbid water (a proxy for case-2 waters), we modified TChl for data with SeaWiFS normalized water-leaving radiance at 555 nm (nLw555) > 2 mW cm−2 μm−1 sr−1 (TChl2s). Finally, with standard SeaWiFS Rrs, we recommend switching algorithms from TChl2s (for case-2 waters) to MOCChl (SeaWiFS-modified NASA OC4v4 standard algorithm for case-1 waters) for retrieving Chl-a, which resulted in uncertainties as high as 49%. To retrieve TSM and ag440 using SeaWiFS Rrs, we recommend empirical algorithms for TTSM (pre-SeaWiFS-modified form) and MTag440 or MCag440 (SeaWiFS Rrs-modified forms of Tag440 or Cag440). These could retrieve with uncertainties as high as 82 and 52%, respectively.