19672 research outputs found
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α-glucosidase inhibitors isolated from Mimosa pudica L.
No full textThe aim of the study was to isolate digestive enzymes inhibitors from Mimosa pudica through a bioassay-guided fractionation approach. Repeated silica gel and sephadex LH 20 column chromatographies of bioactive fractions afforded stigmasterol, quercetin and avicularin as digestive enzymes inhibitors whose IC50 values as compared to acarbose (351.02 ± 1.46 μg mL−1) were found to be as 91.08 ± 1.54, 75.16 ± 0.92 and 481.7 ± 0.703 μg mL−1, respectively. In conclusion, M. pudica could be a good and safe source of digestive enzymes inhibitors for the management of diabetes in future. © 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group
Comparative proteomes, immunoreactivities and neutralization of procoagulant activities of Calloselasma rhodostoma (Malayan pit viper) venoms from four regions in Southeast Asia
No full textThe intraspecific geographical venom variations of Calloselasma rhodostoma from Malaysia (CR-M), Indonesia (CR-I), Thailand (CR-T) and Vietnam (CR-V) were investigated through 1D SDS-PAGE and nano-ESI-LCMS/MS. The venom antigenicity, procoagulant activities and neutralization using Thai C. rhodostoma Monovalent Antivenom (CRMAV) were also investigated. SDS-PAGE patterns of the venoms were relatively similar with minor variations. Proteomic analysis revealed that snake venom metalloproteinases (SVMPs, particularly P–I class), serine proteases (SVSPs) and snaclecs dominated the venom protein composition (68.96–81.80%), followed by L-amino acid oxidase (LAAO) and phospholipase A2 (PLA2) (7.37–11.08% and 5.18–13.81%, respectively), corroborating C. rhodostoma envenoming effects (hemorrhage, consumptive coagulopathy, thrombocytopenia and local tissue necrosis). Other proteins of lower abundances (2.82–9.13%) identified include cysteine-rich secretory proteins (CRISP), phospholipase B, phosphodiesterase, nerve growth factor, 5′-nucleotidase, aminopeptidase and hyaluronidase. All four venoms exhibited strong procoagulant effects which were neutralized by CRMAV to different extents. CRMAV immunoreactivity was high toward venoms of CR-M, CR-I and CR-T but relatively low for CR-V venom. Among the venom samples from different locales, CR-V venom proteome has the smallest SVMP composition while SVSP, PLA2 and phosphodiesterase were more abundant in the venom. These variations in C. rhodostoma venom protein composition could partly explain the differences seen in immunoreactivity. (198 words). © 201
Self‐generating Brillouin fiber laser using highly nonlinear hafnium bismuth erbium‐doped fiber
No full textA compact Brillouin fiber laser (BFL) utilizing a newly developed hafnium bismuth erbium-doped fiber (HB-EDF), which functions as both the Brillouin and linear gain media, is realized in the absence of Brillouin pump. It is achieved by the self-Brillouin generation from a 0.2 m length of HB-EDF with high nonlinearity in a laser cavity. The self-generating BFL was obtained in both ring and linear laser cavities. Compared to the ring cavity, the BFL in the linear cavity produced more Brillouin stokes at a lower pump threshold. In the experiment, an eight-line comb with average spacing of 0.087 nm was generated at the HB-EDF pump power of 75.27 mW. This compact BFL has total cavity length of less than 0.5 m, and thus, this is the shortest gain medium reported for Brillouin erbium fiber laser generation without using any Brillouin pump. © 2019 Wiley Periodicals, Inc
85 nm wide-band tunable erbium doped fiber laser using a gallium selenide (GaSe)-based saturable absorber for passive optical modulation
No full textA wide-band and tunable passively optically modulated fiber laser using a gallium selenide (GaSe) based saturable absorber (SA) is proposed and demonstrated. The GaSe-based SA is prepared by mechanical exfoliation and is able to generate self-starting pulses that have a maximum repetition rate of 57.9 kHz and minimum pulse width of 3.6 s. The highest pulse energy generated by the pulse laser is 30 nJ. The laser has wide-band tunability covering a broad wavelength range of 1501 nm to 1586 nm, giving a total tuning range of over 85 nm. The proposed laser would have potential for use in various optical telecommunications and measurement applications. © 2019 Astro Ltd
Ultraviolet photoconduction in tungsten disulphide based Schottky heterostructure photodetector
No full textA proposed Ag/WS2/SiO2/p-Si/Ag Schottky heterostructure photodetector is tested for its photoconduction behaviour under ultraviolet (UV) illumination using a light emitting diode (LED) at 380 nm. This is done at various illumination powers as well as different direct current (DC) bias voltages. A simple and feasible drop casting method and heating process allows good adhesion of tungsten disulphide (WS2) onto a silicon dioxide/p-silicon (SiO2/p-Si) substrate forming a Schottky contact. In order to enhance photoconduction, iron (Fe) powder is introduced to build contacts between WS2 and the substrate. Field emission scanning electron microscope (FESEM) analysis, energy dispersive x-ray (EDX) spectroscopy and x-ray diffraction (XRD) results confirm the formation of the WS2 thin film. Raman spectrum peaks at 357 cm−1 (E1 2g) and 417 cm−1 (A1g) confirm the presence of WS2 while peaks 214, 223, 274 and 292 cm−1 and a small broad shoulder at 694 cm−1 confirm the presence of iron (III) oxide (Fe2O3). Furthermore, profound D and G bands at 1370 and 1585 cm−1 respectively indicate defected carbon (C) structures in the WS2 thin film. Excellent photoconduction of UV LED 380 nm light source showed power and DC bias voltage dependent characteristics. Wide variations in rise and fall time justifies that the device can be operated at selected bias voltages and frequency modulations. © 201
Dispersion-engineered silicon nitride waveguides for mid-infrared supercontinuum generation covering the wavelength range 0.8–6.5 μm
No full textWe numerically demonstrate the generation of a mid-infrared supercontinuum (SC) through the design of an on-chip complementary metal oxide semiconductor compatible 10 mm-long air-clad rectangular waveguide made using stoichiometric silicon nitride (Si3N4) as the core and MgF2 glass as the lower cladding. The proposed waveguide is designed for pumping in both the anomalous and all-normal dispersion regimes. A number of waveguide geometries are tailored for pumping at 1.55 μm with ultrashort pulses of 50 fs duration and a peak power of 5 kW. By initially keeping the thickness constant at 0.8 μm, four different structures are engineered with varying widths between 3 μm and 6 μm. The largest SC spectral evolution covering a region of 0.8 μm to beyond 6.5 m could be realized by a waveguide geometry with a width of 3 μm. Numerical analysis shows that increasing width beyond 3 μm while keeping thickness constant at 0.8 μm results in a reduction of the SC extension in the long wavelength side. However, the SC spectrum can be enhanced beyond 6.5 μm by increasing the waveguide thickness beyond 0.9 μm with the same peak power and pump source. To the best of our knowledge, this is the first report of a broad SC spectral evolution through numerical demonstration in the mid-infrared region by the Si3N4 waveguide. In the case of all-normal dispersion pumping, a flatter SC spectra can be predicted with the same peak power and pump pulse but with a reduced bandwidth spanning 950-2100 nm. © 2019 Astro Ltd
A new angiotensin-converting enzyme inhibitor from Peperomia pellucida (L.) Kunth
No full textObjective: To isolate, identify, and evaluate a new angiotensin-converting enzyme inhibitor from Peperomia pellucida (L.) Kunth herbs. Methods: A dried sample of Peperomia pellucida herb was successively macerated with n-hexane and ethyl acetate. The ethyl acetate extract solution was evaporated to obtain the crude extract. Vacuum liquid column chromatography and thin layer chromatography were performed to obtain two pure compounds. Then, both compounds were elucidated and identified using the spectroscopic method. Angiotensin-converting enzyme inhibitory activity studies of both compounds were determined using angiotensin-converting enzyme kit WST-1 with spectrophotometer microplate reader 96-well at 450 nm wavelength. Results: Two bioactive compounds were successfully isolated from Peperomia pellucida herb, including a new compound of 2,3,5-trimethoxy-9-(12,14,15-trimethoxybenzyl)-1H-indene and pellucidin A. Both compounds demonstrated angiotensin-converting enzyme inhibitory activity, with IC50 values of 72 μM (27.95 μg/mL) and 11 μM (4.4 μg/mL), respectively. Conclusions: In the present study, two active angiotensin-converting enzyme inhibitors were successfully isolated and purified from Peperomia pellucida which is used as an antihypertensive in traditional medicine, and support its use as an angiotensin-converting enzyme-inhibiting drug. © 2019 Wolters Kluwer Medknow Publications. All rights reserved
Synthesis of valuable intermediate products from natural rubber under supercritical alcohol conditions
No full textIn this study, thermal liquefaction of natural rubber was performed using different alcohols to produce valuable intermediate product. The experiment was conducted in autoclave reactor at different temperatures (250–375 °C), different solvent-to-natural rubber mass ratios (0.5:1 to 4:1), and at different reaction times (15–75 min.). The results showed the maximum liquid yield of 89.53 wt.% was obtained by using propanol at optimum conditions. Around 51.23% and 10.65% of liquid comprised of D-limonene and Isoprene respectively, which are being used as potential feedstock in different industrial sectors. Besides these compounds, the liquid product also consisted other hydrocarbon such as aromatics, alkyls, and alkene with high HHV (46 MJ/kg), and low oxygen contents (1.02%). These properties make this liquid suitable to be used for substitution the conventional fossil fuels. In addition, alcohol solvents played an important role to facilitate the liquefaction process by providing milder process conditions and hydrogen donor. Among the solvents, propanol has significant improvement on the liquid yield, solvent recovery and energy density. © 2019 Elsevier B.V
Microwave-assisted conversion of agro-industrial copra residue oil to diesel engine compatible fatty acid methyl esters
Get PDFDue to the increasing concern towards fossil fuel reserve and its fluctuating price, many countries shifted towards producing biodiesel as an alternative green fuel. In this study, the main objective is to synthesis biodiesel from coconut copra, an agro-industrial residue, as potential feedstock using different transesterification techniques, namely stirring mechanical-assisted technique (SAT), ultrasonic-assisted technique (UAT), and microwave-assisted technique (MAT). The current study will show comparison between the biodiesel yields, fatty acid methyl ester (FAME) compositions and fuel properties of the transesterification techniques used. The result showed that the copra residue biodiesel (CRB) using SAT produced the highest yield of biodiesel compared to UAT and MAT, which are 96.85% (±0.69), 93.79% (±1.00), and 91.76% (±0.87), respectively. Furthermore, different volumes of solvent and catalyst amount were found to affect the biodiesel yields, relatively. On the other hand, for FAME compositions, insignificant results were observed. The fuel properties in CRB complied with the international standards, thus, showing high compatibility to be used in diesel engine
Environmental study of developing index on the health and well-being of occupants in affordable housing in Malaysia
No full textThe rise of affordable housing in Malaysia has inspired a study on the indoor environmental quality (IEQ) of affordable housing. This is because there are several studies that have proven that IEQ influences the health and wellbeing of the residents. The study was conducted in four different apartment developments in Klang Valley, Malaysia, by using a questionnaire survey. The Human Development Index (HDI) is developed based on the data collected from the study, using the formula provided by the Ministry of Youth and Sports Malaysia in their annual Malaysia Youth Index report (IBM). The HDI has indicated that the health and well-being of the occupants in Malaysian affordable housing developments are at the neutral category, scoring 72.16 over 100. Physical condition stands at an index score of 74.29 whilst no fatigue is at poor level with a score of 56.82, whereas for psychological condition, all the indicators are in the neutral category except for No annoyance item, which is in the good category. The index was developed for IEQ factors in affordable housing with data collected from the questionnaire survey. The index developed has shown that factors of IEQ are in both the Extremely disappointed range and the Extremely important range. The acoustic comfort factor gained the lowest score for level of satisfaction whilst indoor air quality gained the highest score for level of importance of IEQ. Noise level scored the lowest in the level of satisfaction and state of health scored the highest score for level of importance. This study aims to provide an overview on the health and wellbeing of occupants in Malaysian affordable housing and to assist the improvement of affordable housing for future development in order to improve the quality of life of residents in affordable housing developments. © Foundation Environmental Protection & Research-FEPR