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Strain localization is a significant issue that poses interesting research challenges in viscoelastic materials because it is difficult to accurately predict the damage evolution behavior. Over time, the damage mechanism in the amorphous structure of viscoelastic materials leads to subsequent localization into a shear band, gradually jeopardizing the materials’ elastic sustainability. The primary goal of this study is to further understand the morphological effects and the role of shear bands in viscoelastic materials precipitated by strain localization. The current study aims to consolidate the various failure mechanisms of a sample and its geometry (surface-to-volume ratio) used in torsional testing, as well as to understand their effects on stress relaxation durability performance. A torsional shear load stress relaxation durability test was performed within the elastic region on an isotropic viscoelastic sample made of silicon rubber and a 70% weight fraction of micron-sized carbonyl iron particles. Degradation was caused by a shear band of localized plasticity that developed microscopically due to stress relaxation durability. The failure pattern deteriorated as the surface-to-volume ratio decreased. A field-emission scanning electron microscope (FESEM) and a tapping-mode atomic force microscope (AFM) were used for further observation and investigation of the sample. After at least 7500 cycles of continuous shearing, the elastic sustainability of the viscoelastic materials microstructurally degraded, as indicated by a decline in stress performance over time. Factors influencing the formation of shear bands were observed in postmortem, which was affected by simple micromanipulation of the sample geometry, making it applicable for practical implementation to accommodate any desired performance and micromechanical design applications.

The Naphthenic Acid (NA) found in the acidic crude oil is one of the main challenges that can lead to corrosion problem in oil refinery equipment and reduces the quality of the oil. In this study, catalytic neutralization reaction was investigated in order to lowering Total Acid Number (TAN) in crude oil to less than one mg KOH/g utilizing 2-Methylimidazole in Polyethylene Glycol (PEG) with aid of Ca/Al2O3 catalyst. The catalyst were supported on the alumina beads through Incipient Wetness Impregnation (IWI) methods and heated in an oven for 24 hours at 80-90°C then calcined at calcination temperatures of 800, 900 and 1000°C. The result showed that Ca/Al2O3 catalyst successfully reduced to 0.52 mg KOH/g from original TAN value 4.22 mg KOH/g by using a catalyst at calcination temperature 1000°C, 0.39 wt % (7 beads) of catalyst loading and 1000 ppm of 2-Methylimidazole in PEG. It can be concluded that catalytic deacidification method was effective method in reducing NAs from the crude oil and can lowered the TAN value to less than 1 mg KOH/g.

Previous studies on Calophyllum species have shown the existence of a wide variety of bioactive xanthones and coumarins. Phytochemical investigations carried out on the plant, Calophyllum hosei led...

Solvation free energy of six choline based ILs were computed under molecular dynamics (MD) simulation using Bennet Acceptance Ratio (BAR) method. H2S removal from the natural gas can be accomplished by absorption process using a solvent. Degree elimination of gases in liquid can be estimated by excess chemical potential (μex), Henry’s law constant (kH), enthalpy (hex), and entropy (sex). The Optimised Potential Liquids Simulation (OPLS) force fields used for ILs were validated against experimental density in order to get valid results of solvation free energy. The percentage error of the predicted density of six choline based ILs were below than 2.0% which is a good agreement with the previous study. The highest value of kH was 109.23 atm gained by choline thiocyanate [Chl][tcy] and the lowest value of kH was 23.25 atm obtained by choline acetate [Chl][act]. There are many features that influence the solubility of H2S for example length of alkyl chain, free volume effect, molar density, type of anions and hydrogen bonding interaction. In order to understand the behaviour of H2S molecules in ILs system, the radial distribution function (RDF) of H2S-ILs and RDF for specific atom were analysed. Basically, the shorter the alkyl chain, increase in molar density of ILs, reduce the free volume thus provide less space for H2S to occupy and decrease insolubility.

A compatibility and stability of Isoreticular Metal Organic Framework (IRMOF-1) impregnated with choline based ionic liquids (ILs) are studied by molecular dynamic simulation. Among three proposed IL/IRMOF-1 hybrid composites, cholinium formate, ([Chl][Fm]) is nominated as the best IL to be incorporated with IRMOF-1 since it shows the lowest RMSD value (0.502 nm, 0.637 nm, 0.923 nm) at three IL/IRMOF-1 w/w ratio (0.4%, 0.8% and 1.2%) respectively and become representative to all three ILs. Oxygen atom in the bridging carboxyl group shows the most flexible atom through RMSF analysis since it shows the highest fluctuation (1.001 nm) at WIL/IRMOF-1 = 0.4%. The RDF shows that the interaction between [Chl]+ and [Fm]− is higher in composite phase compare to bulky phase due to confinement effect of IRMOF-1. Both [Chl]+ and [Fm]− seem to be preferred to locate around carboxylate group inside the IRMOF-1 whereby [Fm]− shows the dominant interaction and strongly interacts with IRMOF-1 compared to [Chl]+. In terms of mobility, the cation shows high mobility with SDF value of 0.0419 nm2 in which mobility is expected to be increased with increasing of ILs ratio (0.4%, 0.8% and 1.2%) respectively. Intensity of the ions population around IRMOF-1 is interpreted by density map which is in agreement with the RDF analysis. Finally, the stability of the IRMOF-1 is confirmed by the radius of gyration (Rg) analysis in which 0.4% ILs shows the most stable conformation with the lowest Rg value = 1.667 nm that is in consistent with the RMSD analysis. Overall, the structural stability of IRMOF-1 is well interpreted and impregnation of ILs literally increase the stability of framework at lower IL/IRMOF-1 w/w ratio.

Previous studies on

The compatibility and performance of an Isoreticular Metal-Organic Frameworks (IRMOF-1) impregnated with choline-based ionic liquids (ILs) for selective adsorption of H

In this paper, we investigate the potency of Leea indica locally known as Memali plant from Tasik Chini, Pahang as a potent antioxidant and antimicrobial agent. Antibacterial activity of root, stem and leaf extracts of L. indica was evaluated against skin disease caused-microb Staphylococcus aureus and Staphylococcus epidermidis. Antioxidant activity was assessed by 2,2 diphenyl-1-picrylhydrazyl ( DPPH) thin layer chromatography (TLC) and dot blot assay method. The dichloromethane (DCM) extracts of all three parts displayed obvious antibacterial effect compared to other extracts and DCM extracts from leaves was the most effective in inhibiting the growth of S. epidermis with inhibition zone (IZ) of 18 mm. The methanol extracts from stem scavenged DPPH radicals more effective than root and leaf extracts at a concentration as low as 0.19 mg/ml. The antibacterial and antioxidant properties of leaves and stem might be attributed to the high content of terpenoid and phenolic. Thus, Memali appears to be a promising source of bioactive ingredients with antioxidant and antimicrobial activity.

A detailed phytochemical study on the stem bark of Garcinia benthamiana has afforded a new benzophenone, benthamianone (1), together with congestiflorone (2), a mixture of stigmasterol (3) and γ-sitosterol (4) as well as a mixture of phloroglucinol (5) and methyl palmitate (6). The structural elucidation of these compounds was performed through analysis of their spectroscopic data (NMR spectra and MS). This is the first report on the phytochemistry of Garcinia benthamiana.

The compatibility and performance of an Isoreticular Metal-Organic Frameworks (IRMOF-1) impregnated with choline-based ionic liquids (ILs) for selective adsorption of H2S/CO2, were studied by molecular dynamics (MD) simulation. Cholinium alanate ([Chl][Ala]) was nominated as the suitable IL for impregnation into IRMOF-1, consistent with the low RMSD values (0.546 nm, 0.670 nm, 0.776 nm) at three IL/IRMOF-1 w/w ratios (WIL/IRMOF-1 = 0.4, 0.8, and 1.2). The [Chl]+ and [Ala]- ion pair was located preferentially around the carboxylate group within the IRMOF-1 framework, with the latter interacting strongly with the host than the [Chl]+. Results of radius of gyration (Rg) and root mean square displacement (RMSD) revealed that a ratio of 0.4 w/w of IL/IRMOF-1 (Rg = 1.405 nm; RMSD = 0.546 nm) gave the best conformation to afford an exceptionally stable IL/IRMOF-1 composite. It was discovered that the IL/IRMOF-1 composite was more effective in capturing H2S and CO2 compared to pristine IRMOF-1. The gases adsorbed in higher quantities in the IL/IRMOF-1 composite phase compared to the bulk phase, with a preferential adsorption for H2S, as shown by the uppermost values of adsorption ( [Formula: see text] = 17.954 mol L-1 bar-1) and an adsorption selectivity ( [Formula: see text] = 43.159) at 35 IL loading.

A new pyranoxanthone, venuloxanthone (1), was isolated from the stem bark of Calophyllum venulosum, together with three other xanthones, tovopyrifolin C (2), ananixanthone (3) and caloxanthone I (4), along with two common triterpenes, friedelin (5) and lupeol (6). The structures of these compounds were identified using several spectroscopic analyses which are NMR, GCMS and FTIR experiments.

A new pyranoxanthone, buxixanthone (1), was isolated from the stem bark of Calophyllum buxifolium along with three other chemical constituents, ananixanthone (2), pyranojacareubin (3), and macluraxanthone (4). The structures of these compounds were confirmed through spectroscopic analysis, which included 1D and 2D NMR, GC/MS, and IR experiments.

A new coumarin, hoseimarin (1), together with four other xanthones, trapezifolizanthone (2), osajaxanthone (3), β-mangostin (4) and caloxanthone A (5), were isolated from the stem bark of Calophyllum hosei. The structures of these compounds were established by using spectroscopic analysis which included 1H NMR, 13C NMR, COSY, DEPT, HMQC and HMBC experiments.

Solvation free energy of H2S in five cholinium-based amino acid ILs was computed using Bennet Acceptance Ratio (BAR) method under molecular dynamics (MD) simulation. From the predicted free energy, degree of removal of acid gases in liquids system can be measured and quantified by looking at excess chemical potential (μex) and Henry's law constant (kH). In order to obtain accurate value of predicted free energy, the optimised potential for liquid simulation (OPLS) force field used was validated against experimental density. The predicted density of five cholinium-based amino acid ILs showed a great agreement with the experimental results showing percentage error of

A new alkylated coumarin derivative, hexapetarin (1) along with three other xanthones, trapezifolixanthone (2), cudraxanthone G (3) and 1,3,7-trihydroxy-2,4-di (3-methyl-2-butenyl)xanthone (4), and four common triterpenoids, friedelin (5), stigmasterol (6), beta-sitosterol (7) and gamma-sitosterol (8) were isolated from the stem bark of Mesua hexapetala (Clusiaceae), a plant, native to Malaysia. The structures of these compounds were elucidated and determined using spectroscopic techniques such as NMR and MS. Anti-inflammatory activity assay indicated hexapetarin (1) to possess moderate anti-inflammatory activity, while 1,3,7-trihydroxy-2,4-di (3-methyl-2-butenyl)xanthone (4) gave very good activity. A new alkylated coumarin derivative, hexapetarin (1) along with three other xanthones, trapezifolixanthone (2), cudraxanthone G (3) and 1,3,7-trihydroxy-2,4-di (3-methyl-2-butenyl)xanthone (4) were isolated from the stem bark of Mesua hexapetala (Clusiaceae). The structures of these compounds were elucidated and determined using spectroscopic techniques such as NMR and MS.

Our phytochemical study on the stem bark of Garcinia mangostana has led to the discovery of a new furanoxanthone, mangaxanthone A (1), together with five known analogs. The five known analogs that were isolated are α-mangostin (2), β-mangostin (3), cowagarcinone B (4), and dulcisxanthone F (5). The structural elucidations of these compounds were carried out by interpreting their spectroscopic data, mainly 1D and 2D NMR spectra and MS.

Our current interest in searching for natural anti-cancer lead compounds from plants has led us to the discovery that the stem and roots of Garcinia mangostana can be a source of such compounds. The stem furnished 2,8-dihydroxy-6-methoxy-5-(3-methylbut-2-enyl)-xanthone (1), which is a new xanthone. Meanwhile, the root bark of the plant furnished six xanthones, namely alpha-mangostin (2), beta-mangostin (3), gamma-mangostin (4), garcinone D (5), mangostanol (6), and gartanin (7). The hexane and chloroform extracts of the root bark of G. mangostana as well as the hexane extract of the stem bark were found to be active against the CEM-SS cell line. gamma-Mangostin (4) showed good activity with a very low IC(50) value of 4.7 microg/ml, while alpha-mangostin (2), mangostanol (6), and garcinone D (5) showed significant activities with IC(50) values of 5.5, 9.6, and 3.2 microg/ml, respectively. This is the first report on the cytotoxicity of the extracts of the stem and root bark of G. mangostana and of alpha-mangostin, mangostanol, and garcinone D against the CEM-SS cell line.

Studies on the stem of Garcinia mangostana have led to the isolation of one new xanthone mangosharin (1) (2,6-dihydroxy-8-methoxy-5-(3-methylbut-2-enyl)-xanthone) and six other prenylated xanthones, alpha-mangostin (2), beta-mangostin (3), garcinone D (4), 1,6-dihydroxy-3,7-dimethoxy-2-(3-methylbut-2-enyl)-xanthone (5), mangostanol (6) and 5,9-dihydroxy-8- methoxy-2,2-dimethyl-7-(3-methylbut-2-enyl)-2H,6H-pyrano-[3,2-b]-xanthene-6-one (7). The structures of these compounds were determined by spectroscopic methods such as 1H NMR, 13C NMR, mass spectrometry (MS) and by comparison with previous studies. All the crude extracts when screened for their larvicidal activities indicated very good toxicity against the larvae of Aedes aegypti. This article reports the isolation and identification of the above compounds as well as bioassay data for the crude extracts. These bioassay data have not been reported before.

Calophyllum spp have been known for their biological activities. This genus belongs to the Guttifereae family where are rich with secondary metabolites such as xanthones, flavonoids and coumarins. Our recent phytochemical study on the bark of Calophyllum sclerophyllum and Calophyllum hoseii has led to the isolation of six xanthones, one coumarin and one flavanoid. These compounds are macluraxanthone (1), trapezifolixanthone (2), rubraxanthone (3), thwaitesixanthone (4), dombakinaxanthone (5), osajaxanthone (6), calopolyanolide A (7) and catechin (8). We report here the structural elucidations of these compounds based on the basis of detailed 1D-NMR (H, C and DEPT) and 2D-NMR (COSY, HMQC and HMBC) spectroscopic analysis.