Displaying publications 1 - 20 of 25 in total

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  1. Balavandy SK, Shameli K, Biak DR, Abidin ZZ
    Chem Cent J, 2014;8(1):11.
    PMID: 24524329 DOI: 10.1186/1752-153X-8-11
    This study aims to investigate the influence of different stirring time for synthesis of silver nanoparticles in glutathione (GSH) aqueous solution. The silver nanoparticles (Ag-NPs) were prepared by green synthesis method using GSH as reducing agent and stabilizer, under moderate temperature at different stirring times. Silver nitrate (AgNO3) was taken as the metal precursor while Ag-NPs were prepared in the over reaction time.
  2. Abidin ZZ, Ismail N, Yunus R, Ahamad IS, Idris A
    Environ Technol, 2011 Jul;32(9-10):971-7.
    PMID: 21882550
    Many coagulants, mainly inorganic, are widely used in conventional water and wastewater treatment. Recent studies reported the occurrence of some chronic diseases associated with residual coagulant in treated wastewater. The use of alternative coagulants which are biodegradable and environmentally friendly could alleviate the problem associated with these diseases. This work investigates the capability of Jatropha curcas seed and presscake (the residue left after oil extraction) to reduce the turbidity of wastewater through coagulation. The coagulant was prepared by dissolving Jatropha curcas seed and presscake powder into solution. Then jar tests were conducted on kaolin solution as the model wastewater. The Jatropha seed was found to be an effective coagulant with more than 96% of turbidity removal at pH 1-3 and pH 11-12. The highest turbidity removal was recorded at pH 3 using a dosage of 120 mg/L. The flocs formed using Jatropha were observed to be bigger and to sediment faster when compared with flocs formed using alum. The turbidity removal was high (>98%) at all turbidities (100 NTU to 8000 NTU), suggesting its suitability for a wide range of industrial wastewater. The performance of Jatropha presscake after extraction of oil was also comparable to the fresh seed and alum at highly acidic and highly alkaline conditions. The addition of Jatropha did not significantly affect the pH of the kaolin samples after treatment and the sludge volume produced was less in comparison to alum. These results strongly support the use of Jatropha curcas seed and presscake as a potential coagulant agent.
  3. Azeez JH, Hwang CY, Abidin ZZ, Ibrahim ZA
    Sci Rep, 2016 06 01;6:26896.
    PMID: 27247251 DOI: 10.1038/srep26896
    We present the Atacama Large Millimeter/Sub-millimeter Array (ALMA) cycle-0 science verification data of the CO(1-0) line emission in the central region of NGC 4321 (also known as M100) at the distance of 17.1 Mpc and VLA, L-band data of HI of the same galaxy. We have drawn the center area of M100 in the (12)CO(J = 1-0) line with the resolution of (3.87″ × 2.53″) as viewed by ALMA, along with HI and Spitzer 8 and 3.6 μm data. The relationship between the surface density of molecular gas mass ∑H2 and that of star formation rate ∑SFR has been investigated, in addition to the relationship between the surface density of the neutral atomic hydrogen mass and that of ∑SFR (Kennicutt-Schmidt law) in this galaxy with a high spatial resolution. The results indicate that a significant correlation exists between the SFR surface density and the molecular gas mass density in the ~2 kpc region. The power-law index has been determined for three regions: center, upper and lower arms. The value of this index in the center region is 1.13, which follows the traditional (K-S) law and indicates that the molecular gas is affected by star formation.
  4. Ramli N, Kala S, Samsudin A, Rahmat K, Abidin ZZ
    Orbit, 2015;34(5):257-62.
    PMID: 26186249 DOI: 10.3109/01676830.2015.1057291
    To determine the correlation and agreement between Hertel exophthalmometry and computed tomography (CT) of the orbits in measuring proptosis.
  5. Razali SM, Abidin ZZ, Othman Z, Yassin MA
    Asian J Psychiatr, 2015 Aug;16:26-31.
    PMID: 26182843 DOI: 10.1016/j.ajp.2015.06.011
    The aim of the study is to screen and evaluate the efficacy of the screening tools in detecting subjects with sub-threshold psychosis among asymptomatic individuals at genetic risk, as compared with persons in the general public.
  6. Lyu S, Abidin ZZ, Yaw TCS, Resul MFMG
    Environ Sci Pollut Res Int, 2024 Mar;31(11):16940-16957.
    PMID: 38326685 DOI: 10.1007/s11356-024-32323-z
    The applications of polysulfides derived from natural plant oil and sulfur via the inverse vulcanization in the removal of heavy metals from aqueous solutions suffered from their low porosity and scarce surface functionality because of their hydrophobic surfaces and bulk characteristics. In this study, polysulfides from sulfur and palm oil (PSPs) with significantly enhanced porosity (13.7-24.1 m2/g) and surface oxygen-containing functional groups (6.9-8.6 wt.%) were synthesized with the optimization of process conditions including reaction time, temperature, and mass ratios of sulfur/palm oil/NaCl/sodium citrate. PSPs were applied as sorbents to remove heavy metals present in aqueous solutions. The integration of porosity and oxygen modification allowed a fast kinetic (4.0 h) and enhanced maximum sorption capacities for Pb(II) (218.5 mg/g), Cu(II) (74.8 mg/g), and Cr(III) (68.4 mg/g) at pH 5.0 and T 298 K comparing with polysulfides made without NaCl/sodium citrate. The sorption behaviors of Pb(II), Cu(II), and Cr(III) on PSPs were highly dependent on the solution pH values and ionic strength. The sorption presented excellent anti-interference capability for the coexisting cations and anions. The sorption processes were endothermic and spontaneous. This work would guide the preparation of porous polysulfides with surface modification as efficient sorbents to remediate heavy metals from aqueous solutions.
  7. Lyu S, Abidin ZZ, Yaw TCS, Resul MFMG
    Environ Sci Pollut Res Int, 2024 Apr;31(20):29264-29279.
    PMID: 38573576 DOI: 10.1007/s11356-024-33152-w
    Guided by efficient utilization of natural plant oil and sulfur as low-cost sorbents, it is desired to tailor the porosity and composition of polysulfides to achieve their optimal applications in the management of aquatic heavy metal pollution. In this study, polysulfides derived from soybean oil and sulfur (PSSs) with improved porosity (10.2-22.9 m2/g) and surface oxygen content (3.1-7.0 wt.%) were prepared with respect to reaction time of 60 min, reaction temperature of 170 °C, and mass ratios of sulfur/soybean oil/NaCl/sodium citrate of 1:1:3:2. The sorption behaviors of PSSs under various hydrochemical conditions such as contact time, pH, ionic strength, coexisting cations and anions, temperature were systematically investigated. PSSs presented a fast sorption kinetic (5.0 h) and obviously improved maximum sorption capacities for Pb(II) (180.5 mg/g), Cu(II) (49.4 mg/g), and Cr(III) (37.0 mg/g) at pH 5.0 and T 298 K, in comparison with polymers made without NaCl/sodium citrate. This study provided a valuable reference for the facile preparation of functional polysulfides as well as a meaningful option for the removal of aquatic heavy metals.
  8. Fakhru'l-Razi A, Peyda M, Ab Karim Ghani WA, Abidin ZZ, Zakaria MP, Moeini H
    Biotechnol Prog, 2014 Jul-Aug;30(4):797-805.
    PMID: 24692323 DOI: 10.1002/btpr.1911
    In this work, crude oil biodegradation has been optimized in a solid-liquid two phase partitioning bioreactor (TPPB) by applying a response surface methodology based d-optimal design. Three key factors including phase ratio, substrate concentration in solid organic phase, and sodium chloride concentration in aqueous phase were taken as independent variables, while the efficiency of the biodegradation of absorbed crude oil on polymer beads was considered to be the dependent variable. Commercial thermoplastic polyurethane (Desmopan®) was used as the solid phase in the TPPB. The designed experiments were carried out batch wise using a mixed acclimatized bacterial consortium. Optimum combinations of key factors with a statistically significant cubic model were used to maximize biodegradation in the TPPB. The validity of the model was successfully verified by the good agreement between the model-predicted and experimental results. When applying the optimum parameters, gas chromatography-mass spectrometry showed a significant reduction in n-alkanes and low molecular weight polycyclic aromatic hydrocarbons. This consequently highlights the practical applicability of TPPB in crude oil biodegradation.
  9. Pendashteh AR, Fakhru'l-Razi A, Chaibakhsh N, Abdullah LC, Madaeni SS, Abidin ZZ
    J Hazard Mater, 2011 Aug 30;192(2):568-75.
    PMID: 21676540 DOI: 10.1016/j.jhazmat.2011.05.052
    A membrane sequencing batch reactor (MSBR) treating hypersaline oily wastewater was modeled by artificial neural network (ANN). The MSBR operated at different total dissolved solids (TDSs) (35,000; 50,000; 100,000; 150,000; 200,000; 250,000mg/L), various organic loading rates (OLRs) (0.281, 0.563, 1.124, 2.248, and 3.372kg COD/(m(3)day)) and cyclic time (12, 24, and 48h). A feed-forward neural network trained by batch back propagation algorithm was employed to model the MSBR. A set of 193 operational data from the wastewater treatment with the MSBR was used to train the network. The training, validating and testing procedures for the effluent COD, total organic carbon (TOC) and oil and grease (O&G) concentrations were successful and a good correlation was observed between the measured and predicted values. The results showed that at OLR of 2.44kg COD/(m(3)day), TDS of 78,000mg/L and reaction time (RT) of 40h, the average removal rate of COD was 98%. In these conditions, the average effluent COD concentration was less than 100mg/L and met the discharge limits.
  10. Fakhru'l-Razi A, Pendashteh A, Abidin ZZ, Abdullah LC, Biak DR, Madaeni SS
    Bioresour Technol, 2010 Sep;101(18):6942-9.
    PMID: 20434905 DOI: 10.1016/j.biortech.2010.04.005
    Oil and gas field wastewater or produced water is a significant waste stream in the oil and gas industries. In this study, the performance of a membrane sequencing batch reactor (MSBR) and membrane sequencing batch reactor/reverse osmosis (MSBR/RO) process treating produced wastewater were investigated and compared. The MSBR was operated in different hydraulic residence time (HRT) of 8, 20 and 44 h. Operation results showed that for a HRT of 20 h, the combined process effluent chemical oxygen demand (COD), total organic carbon (TOC) and oil and grease (O&G) removal efficiencies were 90.9%, 92% and 91.5%, respectively. The MSBR effluent concentration levels met the required standard for oil well re-injection. The RO treatment reduced the salt and organic contents to acceptable levels for irrigation and different industrial re-use. Foulant biopsy demonstrated that the fouling on the membrane surface was mainly due to inorganic (salts) and organic (microorganisms and their products, hydrocarbon constituents) matters.
  11. Fakhru'l-Razi A, Pendashteh A, Abdullah LC, Biak DR, Madaeni SS, Abidin ZZ
    J Hazard Mater, 2009 Oct 30;170(2-3):530-51.
    PMID: 19505758 DOI: 10.1016/j.jhazmat.2009.05.044
    Produced water is the largest waste stream generated in oil and gas industries. It is a mixture of different organic and inorganic compounds. Due to the increasing volume of waste all over the world in the current decade, the outcome and effect of discharging produced water on the environment has lately become a significant issue of environmental concern. Produced water is conventionally treated through different physical, chemical, and biological methods. In offshore platforms because of space constraints, compact physical and chemical systems are used. However, current technologies cannot remove small-suspended oil particles and dissolved elements. Besides, many chemical treatments, whose initial and/or running cost are high and produce hazardous sludge. In onshore facilities, biological pretreatment of oily wastewater can be a cost-effective and environmental friendly method. As high salt concentration and variations of influent characteristics have direct influence on the turbidity of the effluent, it is appropriate to incorporate a physical treatment, e.g., membrane to refine the final effluent. For these reasons, major research efforts in the future could focus on the optimization of current technologies and use of combined physico-chemical and/or biological treatment of produced water in order to comply with reuse and discharge limits.
  12. Abdulsalam M, Man HC, Abidin ZZ, Yunos KF, Idris AI
    Front Microbiol, 2020;11:675.
    PMID: 32477278 DOI: 10.3389/fmicb.2020.00675
    Colorants contained in palm oil mill effluent (POME) are recalcitrant and carcinogenic in nature. The commonly applied ponding treatment methods have been reported inefficient for remediating the concentration of the colorants before discharge. The need for sustainable and efficient treatment technique is crucial in order to preserve the environment. In this view, this study reported the first attempt to decolorize POME using a proliferate Klebsiella Pneumonia ABZ11 at varied inoculum sizes of 5-25% (v/v), initial color concentration (650-2,600 ADMI) and treatment time of 5-40 h. The treatment conditions were optimized using Response Surface Methodology. At optimal conditions of 20% (v/v) inoculum size, initial-color concentration of 2,600 ADMI, initial pH of 7 and 35 h treatment retention time, over 80.40% color removal was achieved with insignificant disparity compared with the model predicted value of 81.538%. Also, the Monod model excellently described the decolorization kinetic process with 0.9214 coefficient of correlation (R2), and the calculated maximum growth μ
    max
    ) and half-saturation constant (K
    s
    ) were 7.023 d-1 and 340.569 ADMI d-1, respectively. This study revealed that the Klebsiella Pneumonia ABZ11 was highly prolific and such feature may favor a synergistic biodegradation process.
  13. Fahrni ML, Misran NFL, Abidin ZZ, Chidambaram SK, Lazzarino AI
    J Infect Public Health, 2023 Jan;16(1):96-103.
    PMID: 36508946 DOI: 10.1016/j.jiph.2022.12.001
    BACKGROUND: While efavirenz-associated adverse drug events (ADEs) were widely established, the clinical relevance is uncertain.

    OBJECTIVES: We aimed to assess the extent of treatment interruption caused by efavirenz-associated ADEs.

    METHODS: A case-control study of efavirenz recipients who did, versus did not (control) develop adverse drug events (ADE), and who were matched for baseline CD4 + at a ratio of 1:1.3 was conducted. Antiretroviral -naïve patients who were started on efavirenz were followed up retrospectively, and their records scrutinized every month for 2 years. Demographic and clinical predictors of treatment interruption were computed using Cox proportional hazard models. Kaplan- Meier curves were plotted to assess time to treatment interruption for the two groups. Clinical endpoints were: i) efficacy -improved CD4 + counts and/or viral load (VL) suppression, ii) safety -absence of treatment-limiting toxicities, and iii) durability - no interruption until follow-up ended.

    RESULTS: Both groups had comparable CD4 + counts at baseline (p = 0.15). At t = 24-months, VL in both groups were suppressed to undetectable levels (<20 copies/mL) while median CD4 + was 353 cells/µL (IQR: 249-460). The mean time on treatment was 23 months (95% CI, 22.3 -23.4) in the control group without ADE and 20 months (95% CI, 18.9 - 21.6) in the ADE group (p = 0.001). Kaplan-Meier plots demonstrated that 59.5% of patients who experienced ≥ 1 ADE versus 81% of those who did not experience any ADE were estimated to continue treatment for up to 24 months with no interruption (p = 0.001). Most interruptions to EFV treatment occurred in the presence of opportunistic infections and these were detected within the first 5 months of treatment initiation. Independent predictors which negatively impacted the dependent variable i.e., treatment durability, were intravenous drug use (adjusted hazard ratio, aHR 2.17, 95% CI, 1.03-4.61, p = 0.043), presence of ≥ 1 opportunistic infection(s) (aHR 2.2, 95% CI, 1.13-4.21, p = 0.021), and presence of ≥ 1 serious ADE(s) (aHR 4.18, 95% CI, 1.98-8.85, p = 0.00).

    CONCLUSION: Efavirenz' role as the preferred first-line regimen for South-East Asia's resource-limited regions will need to be carefully tailored to suit the regional population. Findings have implications to policy-makers and clinicians, particularly for the treatment of patients who develop ADEs and opportunistic infections, and for intravenous drug user subgroups.

  14. Adnan O, Abidin ZZ, Idris A, Kamarudin S, Al-Qubaisi MS
    Environ Sci Pollut Res Int, 2017 Aug;24(24):20104-20112.
    PMID: 28702910 DOI: 10.1007/s11356-017-9560-x
    A new commercial cationic polyelectrolyte chitosan (CM), obtained from the waste of mushroom production, was examined using models of water and wastewater namely kaolin and palm oil mill effluent (pome). As it is biocompatible, widely available, and economically feasible, chitosan mushroom has high potential to be a suitable replacement for alum. Also, it can be a promising alternative to chitosan obtained traditionally from Crustaceans due to its higher zeta potential and homogeneity based on the raw material required for its production. A wide range of coagulant dose (5-60 mg l(-1)) and wastewater pH (2-12) were taken into account to find the optimal conditions of coagulation. The optimal doses are 10 and 20 mg l(-1) at best pH (11 and 3) when treated with kaolin and palm oil mill effluent, respectively, while 1200 mg l(-1) of alum was not enough to reach the efficiency of chitosan mushroom. On the other hand, the optimum dose of chitosan mushroom (20 mg l(-1)) at pH 3 of pome produced (75, 73, and 98%) removal of chemical oxygen demand (COD), biological oxygen demand (BOD), and total suspended solids (TSS), respectively. The significant potential of chitosan mushroom was proved by zeta potential measurement. Indeed, it possesses the highest zeta potential (+70 mV) as compared to the traditional chitosan produced from crustaceans. In short, chitosan mushroom as a biocoagulant is eco-friendly and it enhances water quality that meets the requirements of environmental conservatives.
  15. Pudza MY, Abidin ZZ, Abdul-Rashid S, Yasin FM, Noor ASM, Abdullah J
    Environ Sci Pollut Res Int, 2020 Apr;27(12):13315-13324.
    PMID: 32020456 DOI: 10.1007/s11356-020-07695-7
    The need for the sensing of environmental pollutants cannot be overemphasized in the twenty-first century. Herein, a sensor has been developed for the sensitive and selective detection of copper (Cu2+), lead (Pb2+) and cadmium (Cd2+) as major heavy metals polluting water environment. A screen-printed carbon electrode (SPCE) modified by fluorescent carbon dots (CDs) and gold nanoparticles (AuNPs) was successfully fabricated for sensing Cu2+, Pb2+ and Cd2+. Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were deployed for the analysis of ternary analytes. CV was set at a potential range of - 0.8 to + 0.2 V at a scan rate of 100 mV/s, and DPV at a potential range of - 0.8 to + 0.1 V, scan rate of 50 mV/s, pulse rate of 0.2 V and pulse width of 50 ms. DPV technique was applied through the modified electrode for sensitive and selective determination of Cu2+, Pb2+ and Cd2+ at a concentration range of 0.01 to 0.27 ppm for Cu2+, Pb2+ and Cd2+. Tolerance for the highest possible concentration of foreign substances such as Mg2+, K+, Na+, NO3-, and SO42- was observed with a relative error less than ± 3%. The sensitivity of the modified electrode was at 0.17, 0.42 and 0.18 ppm for Cd2+, Pb2+ and Cu2+, respectively, while the limits of detection (LOD) achieved for cadmium, lead and copper were 0.0028, 0.0042 and 0.014 ppm, respectively. The quality of the modified electrode for sensing Cu2+, Pb2+ and Cd2+ at trace levels is in accordance with the World Health Organization (WHO) and Environmental Protection Agency (EPA) water regulation standard. The modified SPCE provides a cost-effective, dependable and stable means of detecting heavy metal ions (Cu2+, Pb2+ and Cd2+) in an aqueous solution. Graphical abstract .
  16. Wong YS, Abidin ZZ, Musa AN, Kadir RFA, Johari B
    Respir Med Case Rep, 2023;43:101834.
    PMID: 36950023 DOI: 10.1016/j.rmcr.2023.101834
    INTRODUCTION: Unilateral pulmonary artery agenesis (UPAA) is a rare congenital malformation of the pulmonary artery due to agenesis of the sixth aortic arch during embryogenesis. Diagnosis can be challenging due to variable clinical presentations.

    CASE: A 29-year-old female at third trimester of twin pregnancy presented with massive hemoptysis. Computed tomography angiogram (CTA) showed unilateral absence of the right pulmonary artery with multiple dilated tortuous bronchial arteries supplying the right lung. Selective embolization of the bronchial artery was performed post-partum.

    CONCLUSION: Clinicians should have a high clinical suspicion of collateral artery bleeding in patients who present with unexplained hemoptysis and typical UPAA radiographic findings.

  17. May LW, John J, Seong LG, Abidin ZZ, Ibrahim N, Danaee M, et al.
    J Indian Prosthodont Soc, 2021 5 4;21(2):198-203.
    PMID: 33938871 DOI: 10.4103/jips.jips_41_21
    Aim: To investigate the effect of different cooling methods on denture base adaptation of rapid heat-cured acrylic resin using 3D superimposition technique.

    Setting and Design: In vitro - Comparative study.

    Materials and Methods: Denture base adaptation of two different rapid heat-cured polymethyl methacrylate acrylic resins using five different cooling methods were compared. Forty maxillary edentulous stone cast were prepared to produce the denture bases with standardized thickness. The specimens were divided into five groups (n = 8) according to type of materials and cooling methods. The master stone cast and all forty denture bases were scanned with 3Shape E1 laboratory scanner. The scanned images of each of the denture bases were superimposed over the scanned image of the master cast using Materialize 3-matic software. Three dimensional differences between the two surfaces were calculated and color surface maps were generated for visual qualitative assessment.

    Statistical Analysis Used: Generalized Linear Model Test, Bonferroni Post Hoc Analysis.

    Results: All bench-cooled specimens showed wide green-colored area in the overall palatal surface, while the rapid cooled specimens presented with increased red color areas especially at the palate and post dam area. Generalized Linear Model test followed by Bonferroni post hoc analysis showed significant difference in the root mean square values among the specimen groups.

    Conclusion: Samples that were bench cooled, demonstrated better overall accuracy compared to the rapid cooling groups. Regardless of need for shorter denture processing time, bench cooling of rapid heat-cured PMMA is essential for acceptable denture base adaptation.

  18. Issa MA, Abidin ZZ, Sobri S, Rashid SA, Mahdi MA, Ibrahim NA
    Sci Rep, 2020 Jul 16;10(1):11710.
    PMID: 32678157 DOI: 10.1038/s41598-020-68390-8
    A versatile synthetic approach for development of highly fluorescent nitrogen-doped carbon dots (N-CDs) from carboxymethylcellulose in the presence of linear polyethyleneimine (LPEI) has been developed. According to single factor method, central composite design incorporated with response surface methodology matrix was applied to find and model optimal conditions for the temperature (220-260 °C), duration (1-3 h) and LPEI weight (0.5-1.5%). The statistical results show that duration was the most significant parameter for efficient carbonization conversion rate in comparison with temperature and LPEI weight. The reduced cubic model (R2 = 0.9993) shows a good correlation between the experimental data and predicted values. The optimal variables were temperature of 260 °C, duration of 2 h and LPEI weight of 1%. Under these conditions, quantum yield of up to 44% was obtained. The numerically optimized N-CDs have an average size of 3.4 nm with graphitic nature owing to the abundant amino species incorporated into the carbon core framework. The blue-green N-CDs possess emission dependent upon the solvent polarity, wide pH stability with enhanced emission in an acidic environment. Impressively, the N-CDs show long-shelf-life for up to 1 year with no noticeable precipitation. The N-CDs were able to recognize a high concentration of Fe3+ ions with a detection limit of 0.14 μM in acidic solution owing to the special coordination for Fe3+ to be captured by electron-donating oxygen/ amino groups around N-CDs. Moreover, the N-CDs can also be used as a new kind of fluorescent ink for imaging applications.
  19. Elhadery SS, Alhajj MN, Yunus N, Ibrahim N, Abidin ZZ, Ahmad SF, et al.
    J Prosthet Dent, 2024 Apr 15.
    PMID: 38627176 DOI: 10.1016/j.prosdent.2024.03.020
    STATEMENT OF PROBLEM: Three-dimensional (3D) printing of cobalt chromium (Co-Cr) removable partial dentures (RPDs)by selective laser melting (SLM) has been claimed to be less challenging than by conventional casting and provides significant improvements. However, the adaptation and fit of the SLM framework and the optimum build orientation are still unclear.

    PURPOSE: The purpose of this in vitro and clinical study was to evaluate the effect of different build orientations on the adaptation of removable partial denture frameworks fabricated by SLM technology in vitro and to compare the adaptation of the SLM and conventional RPD frameworks clinically.

    MATERIAL AND METHODS: A master model simulating a maxillary arch of Kennedy class III modification 1 was scanned and duplicated to create a virtual 3D cast and reference cast. Four groups (n=40) of Co-Cr RPD frameworks were fabricated. For the SLM groups, the Co-Cr framework was virtually designed and exported for SLM printing. The SLM printing was done in 3 different build orientations: 0-degree (n=10), 45-degree (n=10), and 90-degree (n=10) groups. Other Co-Cr frameworks were conventionally cast (n=10). All Co-Cr frameworks were scanned and virtually superimposed with the master model using a surface-matching software program. The gap under 9 selected points in the palatal major connectors was analyzed and calculated. A smaller gap indicates more surface adaptation and close contact between the palatal major connector and the master model. The data were analyzed using the Kruskal-Wallis and Dunnett T3 tests (α=.05). Three patients with a partially dentate maxillary arch were enrolled in the clinical part based on inclusion criteria. Two RPD frameworks were provided for each patient (conventional casting and SLM printing). The adaptation of each framework was assessed by measuring the gap between the palatal major connector of the framework and the palate with light-body silicone. The differences in adaptation between the conventional and SLM frameworks were compared by using independent t tests (α=.05).

    RESULTS: The in vitro study identified significant differences in the adaptation of the palatal major connector among the 4 groups (P

  20. Abdul Habib NS, Yunus R, Rashid U, Taufiq-Yap YH, Abidin ZZ, Syam AM, et al.
    J Oleo Sci, 2014;63(5):497-506.
    PMID: 24717547
    The use of vegetable oil-based ester as a base fluid in synthetic drilling fluid has become a trend in drilling operations due to its environmental advantages. The transesterification reaction of palm oil methyl ester (POME) with 2-ethylhexanol (2EH) produced 98% of palm oil-based ethylhexyl ester in less than 30 minutes. Since the transesterification reaction of POME with 2EH is a reversible reaction, its kinetics was studied in the presence of excess EH and under vacuum. The POME-to-EH molar ratio and vacuum pressure were held constant at 1:2 and 1.5 mbar respectively and the effects of temperature (70 to 110°C) were investigated. Using excess of EH and continual withdrawal of methanol via vacuum promoted the reaction to complete in less than 10 minutes. The rate constant of the reaction (k) obtained from the kinetics study was in the range of 0.44 to 0.66 s⁻¹ and the activation energy was 15.6 kJ.mol⁻¹. The preliminary investigations on the lubrication properties of drilling mud formulated with palm oil-based 2EH ester indicated that the base oil has a great potential to substitute the synthetic ester-based oil for drilling fluid. Its high kinematic viscosity provides better lubrication to the drilling fluid compared to other ester-based oils. The pour point (-15°C) and flash point (204°C) values are superior for the drilling fluid formulation. The plastic viscosity, HPHT filtrate loss and emulsion stability of the drilling fluid had given acceptable values, while gel strength and yield point could be improved by blending it with proper additives.
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