Displaying publications 1 - 20 of 31 in total

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  1. Fulltext An Improved Fabrication Technique for the 3-D Frequency Selective Surface based on Water Transfer Printing Technology
    Harnois M, Himdi M, Yong WY, Rahim SKA, Tekkouk K, Cheval N
    Sci Rep, 2020 Feb 03;10(1):1714.
    PMID: 32015444 DOI: 10.1038/s41598-020-58657-5
    Manufacturing an array of high-quality metallic pattern layers on a dielectric substrate remains a major challenge in the development of flexible and 3-D frequency selective surfaces (FSS). This paper proposes an improved fabrication solution for the 3-D FSS based on water transfer printing (WTP) technology. The main advantages of the proposed solution are its ability to transform complicated 2-D planar FSS patterns into 3-D structures while improving both manufacturing quality and production costs. WTP technology makes use of water surface tension to keep the thin metallic patterns of the proposed FSS floating flat with the absence of a solid planar substrate. This feature enables these metallic FSS patterns to be transferred onto 3-D structures through a dipping process. To test the effectiveness of the proposed technique, the FSS was designed using computer simulation software Microwave Studio to obtain the numerical performance of the FSS structure. The WTP technology was then used to fabricate the proposed FSS prototype before its performance was tested experimentally. The measurement results agreed well with the numerical results, indicating the proposed manufacturing solution would support the development of complicated 3-D electronics devices, such as conformal antenna arrays and metamaterials.
    Matched MeSH terms: Surface Tension
  2. Fulltext Antimycobacterial susceptibility evaluation of rifampicin and isoniazid benz-hydrazone in biodegradable polymeric nanoparticles against Mycobacterium tuberculosis H37Rv strain
    Hakkimane SS, Shenoy VP, Gaonkar SL, Bairy I, Guru BR
    Int J Nanomedicine, 2018;13:4303-4318.
    PMID: 30087562 DOI: 10.2147/IJN.S163925
    INTRODUCTION: Tuberculosis (TB) is the single largest infectious disease which requires a prolonged treatment regime with multiple drugs. The present treatment for TB includes frequent administration of a combination of four drugs for a duration of 6 months. This leads to patient's noncompliance, in addition to developing drug-resistant strains which makes treatment more difficult. The formulation of drugs with biodegradable polymeric nanoparticles (NPs) promises to overcome this problem.

    MATERIALS AND METHODS: In this study, we focus on two important drugs used for TB treatment - rifampicin (RIF) and isoniazid (INH) - and report a detailed study of RIF-loaded poly lactic-co-glycolic acid (PLGA) NPs and INH modified as INH benz-hydrazone (IH2) which gives the same therapeutic effect as INH but is more stable and enhances the drug loading in PLGA NPs by 15-fold compared to INH. The optimized formulation was characterized using particle size analyzer, scanning electron microscopy and transmission electron microscopy. The drug release from NPs and stability of drug were tested in different pH conditions.

    RESULTS: It was found that RIF and IH2 loaded in NPs release in a slow and sustained manner over a period of 1 month and they are more stable in NPs formulation compared to the free form. RIF- and IH2-loaded NPs were tested for antimicrobial susceptibility against Mycobacterium tuberculosis H37Rv strain. RIF loaded in PLGA NPs consistently inhibited the growth at 70% of the minimum inhibitory concentration (MIC) of pure RIF (MIC level 1 µg/mL), and pure IH2 and IH2-loaded NPs showed inhibition at MIC equivalent to the MIC of INH (0.1 µg/mL).

    CONCLUSION: These results show that NP formulations will improve the efficacy of drug delivery for TB treatment.

    Matched MeSH terms: Surface Tension
  3. Biosurfactants from Marine Cyanobacteria Collected in Sabah, Malaysia
    Mehjabin JJ, Wei L, Petitbois JG, Umezawa T, Matsuda F, Vairappan CS, et al.
    J Nat Prod, 2020 06 26;83(6):1925-1930.
    PMID: 32432877 DOI: 10.1021/acs.jnatprod.0c00164
    Chemical investigation of the organic extract from Moorea bouillonii, collected in Sabah, Malaysia, led to the isolation of three new chlorinated fatty acid amides, columbamides F (1), G (2), and H (3). The planar structures of 1-3 were established by a combination of mass spectrometric and NMR spectroscopic analyses. The absolute configuration of 1 was determined by Marfey's analysis of its hydrolysate and chiral-phase HPLC analysis after conversion and esterification with Ohrui's acid, (1S,2S)-2-(anthracene-2,3-dicarboximido)cyclohexanecarboxylic acid. Compound 1 showed biosurfactant activity by an oil displacement assay. Related known fatty acid amides columbamide D and serinolamide C exhibited biosurfactant activity with critical micelle concentrations of about 0.34 and 0.78 mM, respectively.
    Matched MeSH terms: Surface Tension
  4. Characterization of fatty acid liposome coated with low-molecular-weight chitosan
    Tan HW, Misran M
    J Liposome Res, 2012 Dec;22(4):329-35.
    PMID: 22881198 DOI: 10.3109/08982104.2012.700459
    Preparation of chitosan-coated fatty acid liposomes is often restricted by the solubility of chitosan under basic conditions. In this experiment, the preparation of chitosan-coated oleic acid (OA) liposomes using low molecular weight (LMW) chitosan (10 and 25 kDA) was demonstrated. These selected LMW chitosans are water soluble. The coating of the chitosan layer on OA liposomes was confirmed by its microscope images and physicochemical properties, such as zeta potential and the size of the liposomes. The "peeling off" effect on the surface of chitosan-coated OA liposomes was observed in the atomic force microscope images and showed the occurrence of the chitosan layer on the surface of OA liposomes. The size of the chitosan-coated liposomes was at least 20 nm smaller than the OA liposomes, and the increase of zeta potential with the increasing amount of LMW chitosan further confirmed the presence of the surface modification of OA liposomes.
    Matched MeSH terms: Surface Tension
  5. Cleaning potential of surfactin on fouled ultrafiltration (UF) membranes
    Mohd Hafez Mohd Isa, Frazier AR, Jauregi P
    Sains Malaysiana, 2012;41:1117-1124.
    Biosurfactants are microbially produced surface active agents that offer better biodegradability and lower toxicity than chemically synthesized surfactants because of their biogenetic origin. One of the most surface-active biosurfactants known is surfactin, a cyclic lipopeptide produced by various strains of Bacillus subtilis. In this study, the cleaning potential of surfactin on ultrafiltration (UF) membranes fouled with BSA was studied using centrifugal UF devices of 50 kDa and 100 kDa MWCO polyethersulfone (PES) membranes. Mechanisms of bovine serum albumin (BSA) displacement by surfactin on fouled UF membranes were studied using dynamic light scattering (DLS) technique and surface tension measurements. Hydrodynamic diameter and surface tension measurements of BSA-surfactin mixtures showed that the surfactin was efficient in displacing BSA fouled on UF membranes due to strong electrostatic repulsive interactions involved at pH8.5. This study demonstrated that surfactin can be used to effectively clean fouled UF membranes.
    Matched MeSH terms: Surface Tension
  6. Fulltext Determination of Temperature-Dependent Coefficients of Viscosity and Surface Tension of Tamarind Seeds (Tamarindus indica L.) Polymer
    Malviya R, Jha S, Fuloria NK, Subramaniyan V, Chakravarthi S, Sathasivam K, et al.
    Polymers (Basel), 2021 Feb 18;13(4).
    PMID: 33670569 DOI: 10.3390/polym13040610
    The rheological properties of tamarind seed polymer are characterized for its possible commercialization in the food and pharmaceutical industry. Seed polymer was extracted using water as a solvent and ethyl alcohol as a precipitating agent. The temperature's effect on the rheological behavior of the polymeric solution was studied. In addition to this, the temperature coefficient, viscosity, surface tension, activation energy, Gibbs free energy, Reynolds number, and entropy of fusion were calculated by using the Arrhenius, Gibbs-Helmholtz, Frenkel-Eyring, and Eotvos equations, respectively. The activation energy of the gum was found to be 20.46 ± 1.06 kJ/mol. Changes in entropy and enthalpy were found to be 23.66 ± 0.97 and -0.10 ± 0.01 kJ/mol, respectively. The calculated amount of entropy of fusion was found to be 0.88 kJ/mol. A considerable decrease in apparent viscosity and surface tension was produced when the temperature was raised. The present study concludes that the tamarind seed polymer solution is less sensitive to temperature change in comparison to Albzia lebbac gum, Ficus glumosa gum and A. marcocarpa gum. This study also concludes that the attainment of the transition state of viscous flow for tamarind seed gum is accompanied by bond breaking. The excellent physicochemical properties of tamarind seed polymers make them promising excipients for future drug formulation and make their application in the food and cosmetics industry possible.
    Matched MeSH terms: Surface Tension
  7. Fulltext Effect of Biodegradable Binder Properties and Operating Conditions on Growth of Urea Particles in a Fluidized Bed Granulator
    Zhalehrajabi E, Lau KK, Ku Shaari KZ, Zahraee SM, Seyedin SH, Azeem B, et al.
    Materials (Basel), 2019 Jul 20;12(14).
    PMID: 31330846 DOI: 10.3390/ma12142320
    Granulation is an important step during the production of urea granules. Most of the commercial binders used for granulation are toxic and non-biodegradable. In this study, a fully biodegradable and cost-effective starch-based binder is used for urea granulation in a fluidized bed granulator. The effect of binder properties such as viscosity, surface tension, contact angle, penetration time, and liquid bridge bonding force on granulation performance is studied. In addition, the effect of fluidized bed process parameters such as fluidizing air inlet velocity, air temperature, weight of primary urea particles, binder spray rate, and binder concentration is also evaluated using response surface methodology. Based on the results, binder with higher concentration demonstrates higher viscosity and higher penetration time that potentially enhance the granulation performance. The viscous Stokes number for binder with higher concentration is lower than critical Stokes number that increases coalescence rate. Higher viscosity and lower restitution coefficient of urea particles result in elastic losses and subsequent successful coalescence. Statistical analysis indicate that air velocity, air temperature, and weight of primary urea particles have major effects on granulation performance. Higher air velocity increases probability of collision, whereby lower temperature prevents binder to be dried up prior to collision. Findings of this study can be useful for process scale-up and industrial application.
    Matched MeSH terms: Surface Tension
  8. Fulltext Effect of nanoparticles concentration on electromagnetic-assisted oil recovery using ZnO nanofluids
    Adil M, Lee K, Mohd Zaid H, A Shukur MF, Manaka T
    PLoS One, 2020;15(12):e0244738.
    PMID: 33382855 DOI: 10.1371/journal.pone.0244738
    Utilization of metal-oxide nanoparticles (NPs) in enhanced oil recovery (EOR) has generated substantial recent research interest in this area. Among these NPs, zinc oxide nanoparticles (ZnO-NPs) have demonstrated promising results in improving oil recovery due to their prominent thermal properties. These nanoparticles can also be polarized by electromagnetic (EM) field, which offers a unique Nano-EOR approach called EM-assisted Nano-EOR. However, the impact of NPs concentrations on oil recovery mechanism under EM field has not been well established. For this purpose, ZnO nanofluids (ZnO-NFs) of two different particle sizes (55.7 and 117.1 nm) were formed by dispersing NPs between 0.01 wt.% to 0.1 wt.% in a basefluid of sodium dodecylbenzenesulfonate (SDBS) and NaCl to study their effect on oil recovery mechanism under the electromagnetic field. This mechanism involved parameters, including mobility ratio, interfacial tension (IFT) and wettability. The displacement tests were conducted in water-wet sandpacks at 95˚C, by employing crude oil from Tapis. Three tertiary recovery scenarios have been performed, including (i) SDBS surfactant flooding as a reference, (ii) ZnO-NFs flooding, and (iii) EM-assisted ZnO-NFs flooding. Compare with incremental oil recovery from surfactant flooding (2.1% original oil in place/OOIP), nanofluid flooding reaches up to 10.2% of OOIP at optimal 0.1 wt.% ZnO (55.7 nm). Meanwhile, EM-assisted nanofluid flooding at 0.1 wt.% ZnO provides a maximum oil recovery of 10.39% and 13.08% of OOIP under EM frequency of 18.8 and 167 MHz, respectively. By assessing the IFT/contact angle and mobility ratio, the optimal NPs concentration to achieve a favorable ER effect and interfacial disturbance is determined, correlated to smaller hydrodynamic-sized nanoparticles that cause strong electrostatic repulsion between particles.
    Matched MeSH terms: Surface Tension
  9. Fulltext Effect of nutritional factors on the growth and production of biosurfactant by Pseudomonas aeruginosa strain 181
    Al-Araji, L., Rahman, R.N.Z.A., Basri, M., Salleh, A.B.
    ASM Science Journal, 2008;2(1):45-56.
    MyJurnal
    The growth and production of biosurfactant by P. seudomonas aeruginosa (181) was dependant on nutritional factors. Among the eleven carbon sources tested, glucose supported the maximum growth (0.25 g/L) with the highest biosurfactant yield and this was followed by glycerol. Glucose reduced the surface tension to 35.3 dyne/cm and gave an E24 reading of 62.7%. Butanol gave the lowest growth and had no biosurfactant production. For the nitrogen sources tested, casamino acid supported a growth of 0.21 g/L which reduced the surface tension to 41.1 dyne/cm and gave an E24 reading of 56%. Soytone was assimilated similarly, with good growth and high biosurfactant production. Corn steep liquor gave the lowest growth and did not show any biosurfactant activity.
    Matched MeSH terms: Surface Tension
  10. Fulltext Experimental evaluation of oil recovery mechanism using a variety of surface-modified silica nanoparticles: Role of in-situ surface-modification in oil-wet system
    Adil M, Mohd Zaid H, Raza F, Agam MA
    PLoS One, 2020;15(7):e0236837.
    PMID: 32730369 DOI: 10.1371/journal.pone.0236837
    Recent developments propose renewed use of surface-modified nanoparticles (NPs) for enhanced oil recovery (EOR) due to improved stability and reduced porous media retention. The enhanced surface properties render the nanoparticles more suitable compared to bare nanoparticles, for increasing the displacement efficiency of waterflooding. However, the EOR mechanisms using NPs are still not well established. This work investigates the effect of in-situ surface-modified silica nanoparticles (SiO2 NPs) on interfacial tension (IFT) and wettability behavior as a prevailing oil recovery mechanism. For this purpose, the nanoparticles have been synthesized via a one-step sol-gel method using surface-modification agents, including Triton X-100 (non-ionic surfactant) and polyethylene glycol (polymer), and characterized using various techniques. These results exhibit the well-defined spherical particles, particularly in the presence of Triton X-100 (TX-100), with particle diameter between 13 to 27 nm. To this end, SiO2 nanofluids were formed by dispersing nanoparticles (0.05 wt.%, 0.075 wt.%, 0.1 wt.%, and 0.2 wt.%) in 3 wt.% NaCl to study the impact of surface functionalization on the stability of the nanoparticle suspension. The optimal stability conditions were obtained at 0.1 wt.% SiO2 NPs at a basic pH of 10 and 9.5 for TX-100/ SiO2 and PEG/SiO nanofluids, respectively. Finally, the surface-treated SiO2 nanoparticles were found to change the wettability of treated (oil-wet) surface into water-wet by altering the contact angle from 130° to 78° (in case of TX-100/SiO2) measured against glass surface representing carbonate reservoir rock. IFT results also reveal that the surfactant treatment greatly reduced the oil-water IFT by 30%, compared to other applied NPs. These experimental results suggest that the use of surface-modified SiO2 nanoparticles could facilitate the displacement efficiency by reducing IFT and altering the wettability of carbonate reservoir towards water-wet, which is attributed to more homogeneity and better dispersion of surface-treated silica NPs compared to bare-silica NPs.
    Matched MeSH terms: Surface Tension
  11. Fulltext Experimental study on electromagnetic-assisted ZnO nanofluid flooding for enhanced oil recovery (EOR)
    Adil M, Lee K, Mohd Zaid H, Ahmad Latiff NR, Alnarabiji MS
    PLoS One, 2018;13(2):e0193518.
    PMID: 29489897 DOI: 10.1371/journal.pone.0193518
    Recently, nano-EOR has emerged as a new frontier for improved and enhanced oil recovery (IOR & EOR). Despite their benefits, the nanoparticles tend to agglomerate at reservoir conditions which cause their detachment from the oil/water interface, and are consequently retained rather than transported through a porous medium. Dielectric nanoparticles including ZnO have been proposed to be a good replacement for EOR due to their high melting point and thermal properties. But more importantly, these particles can be polarized under electromagnetic (EM) irradiation, which provides an innovative smart Nano-EOR process denoted as EM-Assisted Nano-EOR. In this study, parameters involved in the oil recovery mechanism under EM waves, such as reducing mobility ratio, lowering interfacial tensions (IFT) and altering wettability were investigated. Two-phase displacement experiments were performed in sandpacks under the water-wet condition at 95°C, with permeability in the range of 265-300 mD. A crude oil from Tapis oil field was employed; while ZnO nanofluids of two different particle sizes (55.7 and 117.1 nm) were prepared using 0.1 wt. % nanoparticles that dispersed into brine (3 wt. % NaCl) along with SDBS as a dispersant. In each flooding scheme, three injection sequential scenarios have been conducted: (i) brine flooding as a secondary process, (ii) surfactant/nano/EM-assisted nano flooding, and (iii) second brine flooding to flush nanoparticles. Compare with surfactant flooding (2% original oil in place/OOIP) as tertiary recovery, nano flooding almost reaches 8.5-10.2% of OOIP. On the other hand, EM-assisted nano flooding provides an incremental oil recovery of approximately 9-10.4% of OOIP. By evaluating the contact angle and interfacial tension, it was established that the degree of IFT reduction plays a governing role in the oil displacement mechanism via nano-EOR, compare to mobility ratio. These results reveal a promising way to employ water-based ZnO nanofluid for enhanced oil recovery purposes at a relatively high reservoir temperature.
    Matched MeSH terms: Surface Tension
  12. Fulltext Formulation of aerosol concentrates containing haruan (Channa striatus) for wound dressing
    Febriyenti, Azmin Mohd. Noor, Saringat Baei
    Malaysian Journal of Pharmaceutical Science, 2008;6(1):43-58.
    MyJurnal
    The objective of this research was to formulate an aerosol concentrate containing haruan (Channa
    striatus) water extract that would produce a thin film when sprayed onto a wound and could be used for wound dressing. The aerosol concentrates were formulated with various polymer and plasticiser mixtures and tested in dispersion systems. The polymers evaluated were hydroxypropyl methylcellulose (HPMC), carboxymethylcellulose sodium (CMC Sodium), acacia, tragacanth, chitosan, gelatine and gelatine (bloom 151–160), all at concentrations of 2%. The plasticisers evaluated were polyethylene glycol (PEG) 400 and 4000, glycerine, propylene glycol, and triacetin. Films were prepared from film-forming dispersions by casting techniques. Film-forming dispersions were characterised in terms of pH, density, surface tension, rheological properties, particle size distribution, and tackiness. Based on these evaluations, HPMC was chosen as the best polymer. It produced a film with the expected qualities and was easy to reproduce in the form of dispersions or as thin transparent films. Glycerine was judged as the most appropriate plasticiser because it produced the concentrate having the desired qualities and properties expected from an aerosol concentrate.
    Matched MeSH terms: Surface Tension
  13. Interaction of Aqueous Solutions of a Surface Active Copper(II) Complex with Several Common Surfactants
    Lim YY, Lim KH
    J Colloid Interface Sci, 1997 Dec 01;196(1):116-9.
    PMID: 9441659
    Micellar properties of binary mixed surfactants of a surface active mixed copper(II) chelate, [Cu(C12-tmed)(acac)Cl] (where C12-tmed is N,N,N'-trimethyl-N'-dodecylethylenediamine) with three common surfactants, viz. sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and octaethylene glycol monododecyl ether (C12E8), were investigated by surface tensiometry, ESR, and UV-visible absorption techniques. The surface tension data were treated with Rubingh's method for mixed micelle formation and Rosen's method for mixed monolayer formation at the aqueous solution/air interface. It was found that in the mixed micelle there is strong attractive interaction between cationic copper surfactant and anonic dodecyl sulfate while there is almost ideal mixing between copper surfactant and CTAB and C12E8. From the ESR and UV-visible studies, a mixed block-type arrangement of head groups is proposed. Copyright 1997 Academic Press. Copyright 1997Academic Press
    Matched MeSH terms: Surface Tension
  14. Fulltext Optical Response Analysis at Various Pb2+ Concentration by Using Fiber Optic Displacement Sensor
    Nurul Syafiqah Hirman, Nur Athirah Mohd Taib
    Malaysian Journal of Science, Health & Technology, 2021;7(1):43-48.
    MyJurnal
    A simple and low-cost Fiber Optic Displacement Sensor (FODS) using reflective intensity modulation technique was developed to analyze various concentrations of Pb2+, a compound classified under heavy metal ions. Lead is harmful to the environment including to human but is used in the cosmetic field for beauty without realizing and considering the hazardousness of lead as it would cause a long-term effect. Therefore, a feasible way has been identified in this study to demonstrate the level of Pb2+ concentration in cosmetics field by employing the theory of modulation of intensity as a function of displacement sensor. The permissible limit according to Malaysian Cosmetics Guidelines and ASEAN Cosmetic Directive was 20 ppm. The concentration sensor’s system exhibits 0.0018 V/ppm sensitivity with a linearity of 96% and 94% respectively, for both peaks. Meanwhile, the sensitivity was 0.034 V/ppm for the first peak and 27.72 V/ppm for the second peak, with slope linearity of more than 96% for surface tension parameter. The credibility of these optical response curves data might be useful, especially in the cosmetic’s industrial application.

    Matched MeSH terms: Surface Tension
  15. Fulltext Optimization and Characterization of Palm Oil-based Nanoemulsion Loaded with Parthenium hysterophorus Crude Extract for Natural Herbicide Formulation
    Zainuddin NJ, Ashari SE, Salim N, Asib N, Omar D, Lian GEC
    J Oleo Sci, 2019 Aug 01;68(8):747-757.
    PMID: 31292338 DOI: 10.5650/jos.ess18209
    The present study revealed the optimization of nanoemulsion containing palm oil derivatives and Parthenium hysterophorus L. crude extract (PHCE) as pre-emergence herbicide formulation against Diodia ocimifolia. The nanoemulsion formulation was prepared by high energy emulsification method, and it was optimized by mixture experimental design (MED). From the optimization process, analysis of variance (ANOVA) showed a fit quadratic polynomial model with an optimal formulation composition containing 30.91% of palm kernel oil ester (PKOE), 28.48% of mixed surfactants (Tensiofix and Tween 80, 8:2), 28.32% of water and 12.29% of PHCE. The reading of both experimental and predicted particle size in the verification experiment were acceptable with a residual standard error (RSE) was less than 2%. Under the optimal condition, the smallest particle size obtained was 140.10 nm, and the particle was shown by morphology analysis to be spherical and demonstrated good stability (no phase separation) under centrifugation and different storage conditions (25 ± 5°C and 45°C). Nanoemulsion stored for 60 days exhibits monodisperse emulsion with a slight increase of particle size. The increase in particle size over time might have contributed by Ostwald ripening phenomenon which is shown by a linear graph from Ostwald ripening rate analysis. In the in vitro germination test, P. hysterophorus nanoemulsion (PHNE) was shown to cause total inhibition of D. ocimifolia seed at lower concentration (5 g L-1) as compared to PHCE (10 g L-1). The finding of the research could potentially serve as a platform for the development of palm oil based formulation containing plant crude extract for green weed management.
    Matched MeSH terms: Surface Tension
  16. Fulltext Phase behavior and fluid interactions of a CO2-Light oil system at high pressures and temperatures
    Rezk MG, Foroozesh J
    Heliyon, 2019 Jul;5(7):e02057.
    PMID: 31384679 DOI: 10.1016/j.heliyon.2019.e02057
    This paper investigates the phase behavior and mutual interactions between a light crude oil and CO2 at high pressures and high temperatures (HPHT). To do so, we have measured PVT properties of the CO2-oil system at HPHT using a PVT setup. We have also tried to present a detailed methodology for measuring PVT properties of CO2-oil systems and highlight the difficulties such as oil vaporization by CO2 during the experiments. A crude oil sample, collected from a Malaysian oil field, was used here. Our experiments indicated that, CO2 solubility in the oil increased at higher pressures when measured at a fixed temperature. Our experiments also showed that increasing the test temperature would reduce CO2 solubility in the oil, while its effect is more significant at higher pressures. The swelling factor (SF) measurements showed an increasing trend with pressure up to a certain value so-called extraction pressure, at which, the SF started to be reduced even became less than one. The measurements of oil viscosity indicated that CO2 dissolution in the oil sample could reduce the mixture viscosity up to 61%. The interfacial tensions between CO2 and the crude oil at different pressures were also measured while the results were used to estimate the minimum miscibility pressure (MMP) and the first contact miscibility (FCM) pressure. The IFT measurements at various pressures displayed a reduction trend as a result of more CO2 dissolution in the oil but with two different slopes. That is, at lower pressure values, the measured IFTs were sharply reduced with pressure, while the reduction rate of the IFT became less when pressures exceeded the extraction pressure. This study helps with determining the optimum pressure and temperature conditions of CO2-oil systems to have a minimum IFT, a maximum CO2 solubility and SF, and a minimum oil viscosity that are favorable for CO2-enhanced oil recovery projects. Additionally, the methodology presented here gives guidelines on how to design PVT experiments of CO2-oil systems for petroleum and chemical engineering applications.
    Matched MeSH terms: Surface Tension
  17. Polysaccharide-anchored fatty acid liposome
    Tan HW, Misran M
    Int J Pharm, 2013 Jan 30;441(1-2):414-23.
    PMID: 23174410 DOI: 10.1016/j.ijpharm.2012.11.013
    In this study, the preparation of N-pamitoyl chitosan (ChP) anchored oleic acid (OA) liposome was demonstrated. Two different types of water-soluble ChPs with different degrees of acylation (DA) were selected for this study. The presence of ChPs on the surface of OA liposome was confirmed with their micrographs and physicochemical properties. The "peeling off" effect on the surface of the ChP-anchored OA (OAChP) liposomes was observed on the atomic force microscope micrographs and confirmed the presence of the ChPs layer on the liposome surface. The surface tension of the OAChPs liposome solution was found to be higher than that of the OA liposome solution. This result indicated the removal of OA monomer by ChPs from the air-water interface. The increase in the minimum area per headgroup (A(min)) of the OA with the presence of ChPs has further proved the interaction between OA monomer and the hydrophobic moieties of the ChPs. The ChPs anchored onto the OA monolayer increased the curvature of the OAChP liposomes monolayer and reduced the liposome size. The size of the OAChP liposomes was reduced by 30 nm as compared with the unmodified OA liposome. Results revealed that the anchored ChPs can improve the integrity and rigidity of the OA liposome.
    Matched MeSH terms: Surface Tension
  18. Production and characterization of rhamnolipid using palm oil agricultural refinery waste
    Radzuan MN, Banat IM, Winterburn J
    Bioresour Technol, 2017 Feb;225:99-105.
    PMID: 27888734 DOI: 10.1016/j.biortech.2016.11.052
    In this research we assess the feasibility of using palm oil agricultural refinery waste as a carbon source for the production of rhamnolipid biosurfactant through fermentation. The production and characterization of rhamnolipid produced by Pseudomonas aeruginosa PAO1 grown on palm fatty acid distillate (PFAD) under batch fermentation were investigated. Results show that P. aeruginosa PAO1 can grow and produce 0.43gL(-1) of rhamnolipid using PFAD as the sole carbon source. Identification of the biosurfactant product using mass spectrometry confirmed the presence of monorhamnolipid and dirhamnolipid. The rhamnolipid produced from PFAD were able to reduce surface tension to 29mNm(-1) with a critical micelle concentration (CMC) 420mgL(-1) and emulsify kerosene and sunflower oil, with an emulsion index up to 30%. Results demonstrate that PFAD could be used as a low-cost substrate for rhamnolipid production, utilizing and transforming it into a value added biosurfactant product.
    Matched MeSH terms: Surface Tension
  19. Fulltext Production of Lipopeptide Biosurfactant by a Hydrocarbon-Degrading Antarctic Rhodococcus
    Habib S, Ahmad SA, Wan Johari WL, Abd Shukor MY, Alias SA, Smykla J, et al.
    Int J Mol Sci, 2020 Aug 26;21(17).
    PMID: 32858859 DOI: 10.3390/ijms21176138
    Rhodococci are renowned for their great metabolic repertoire partly because of their numerous putative pathways for large number of specialized metabolites such as biosurfactant. Screening and genome-based assessment for the capacity to produce surface-active molecules was conducted on Rhodococcus sp. ADL36, a diesel-degrading Antarctic bacterium. The strain showed a positive bacterial adhesion to hydrocarbon (BATH) assay, drop collapse test, oil displacement activity, microplate assay, maximal emulsification index at 45% and ability to reduce water surface tension to < 30 mN/m. The evaluation of the cell-free supernatant demonstrated its high stability across the temperature, pH and salinity gradient although no correlation was found between the surface and emulsification activity. Based on the positive relationship between the assessment of macromolecules content and infrared analysis, the extracted biosurfactant synthesized was classified as a lipopeptide. Prediction of the secondary metabolites in the non-ribosomal peptide synthetase (NRPS) clusters suggested the likelihood of the surface-active lipopeptide production in the strain's genomic data. This is the third report of surface-active lipopeptide producers from this phylotype and the first from the polar region. The lipopeptide synthesized by ADL36 has the prospect to be an Antarctic remediation tool while furnishing a distinctive natural product for biotechnological application and research.
    Matched MeSH terms: Surface Tension
  20. Fulltext Role of Phase-Dependent Dielectric Properties of Alumina Nanoparticles in Electromagnetic-Assisted Enhanced Oil Recovery
    Adil M, Lee KC, Zaid HM, Manaka T
    Nanomaterials (Basel), 2020 Oct 06;10(10).
    PMID: 33036153 DOI: 10.3390/nano10101975
    The utilization of metal-oxide nanoparticles in enhanced oil recovery (EOR) has generated considerable research interest to increase the oil recovery. Among these nanoparticles, alumina nanoparticles (Al2O3-NPs) have proved promising in improving the oil recovery mechanism due to their prominent thermal properties. However, more significantly, these nanoparticles, coupled with electromagnetic (EM) waves, can be polarized to reduce water/oil mobility ratio and create disturbances at the oil/nanofluid interface, so that oil can be released from the reservoir rock surfaces and travelled easily to the production well. Moreover, alumina exists in various transition phases (γ, δ, θ, κ, β, η, χ), providing not only different sizes and morphologies but phase-dependent dielectric behavior at the applied EM frequencies. In this research, the oil recovery mechanism under EM fields of varying frequencies was investigated, which involved parameters such as mobility ratio, interfacial tension (IFT) and wettability. The displacement tests were conducted in water-wet sandpacks at 95 °C, by employing crude oil from Tapis. Alumina nanofluids (Al2O3-NFs) of four different phases (α, κ, θ and γ) and particle sizes (25-94.3 nm) were prepared by dispersing 0.01 wt. % NPs in brine (3 wt. % NaCl) together with SDBS as a dispersant. Three sequential injection scenarios were performed in each flooding scheme: (i) preflushes brine as a secondary flooding, (ii) conventional nano/EM-assisted nanofluid flooding, and (iii) postflushes brine to flush NPs. Compared to conventional nanofluid flooding (3.03-11.46% original oil in place/OOIP) as incremental oil recovery, EM-assisted nanofluid flooding provided an increase in oil recovery by approximately 4.12-12.90% of OOIP for different phases of alumina. It was established from these results that the recovery from EM-assisted nanofluid flooding is itself dependent on frequency, which is associated with good dielectric behavior of NPs to formulate the oil recovery mechanism including (i) mobility ratio improvement due to an electrorheological (ER) effect, (ii) interfacial disturbances by the oil droplet deformation, and (iii) wettability alteration by increased surface-free energy.
    Matched MeSH terms: Surface Tension
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