Displaying publications 1 - 20 of 73 in total

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  1. Shah SN, Tan TH, Tey OW, Leong GW, Chin YS, Yuen CW, et al.
    Sci Prog, 2022;105(2):368504221091186.
    PMID: 35379044 DOI: 10.1177/00368504221091186
    Lightweight cementitious composite (LCC) produced by incorporating lightweight silica aerogel was explored in this study. Silica aerogel was incorporated as 60% replacement of fine aggregate (sand/crushed glass) in producing the LCC. The effect of aerogel on the drying shrinkage and alkali-silica expansion of LCC was evaluated and compared with those of lightweight expanded perlite aggregate. At the density of 1600  ±  100 kg/m3, the aerogel/ expanded perlite LCC had attained compressive strength of about 17/24 MPa and 22/26 MPa in mixtures with sand and crushed glass as a fine aggregate, respectively. The inclusion of aerogel and expanded perlite increased the drying shrinkage. The drying shrinkage of aerogel LCC was up to about 3 times of the control mixtures. Although the presence of aerogel and expanded perlite could reduce the alkali-silica expansion when partially replacing crushed glass, the aerogel-glass LCC still recorded expansion exceeding the maximum limit of 0.10% at 14 days. However, when 15% cement was replaced with fly ash and granulated blast furnace slag, the alkali-silica expansion was reduced to 0.03% and 0.10%, respectively. Microstructural observations also revealed that the aerogel with fly ash can help in reducing the alkali-silica expansion in mixes containing the reactive crushed glass aggregate.
    Matched MeSH terms: Alkalies*
  2. Khan MN, Sim YL, Ariffin A
    ScientificWorldJournal, 2014;2014:592691.
    PMID: 24574900 DOI: 10.1155/2014/592691
    The values of pseudo-first-order rate constants (k(obs)) for alkaline hydrolysis of 1, obtained at 1.0 mM NaOH and within [C(m)E(n)]T (total concentration of C(m)E(n)) range of 3.0-5.0 mM for C(12)E(23) and 10-20 mM for C(18)E(20), fail to obey pseudophase micellar (PM) model. The values of the fraction of near irreversible C m E n micellar trapped 1 molecules (F(IT1)) vary in the range ~0-0.75 for C(12)E(23) and ~0-0.83 for C(18)E(20) under such conditions. The values of F(IT1) become 1.0 at ≥ 10 mM C(12)E(23) and 50 mM C(18)E(20). Kinetic analysis of the observed data at ≥ 10 mM C(12)E(23) shows near irreversible micellar entrapment of 1 molecules under such conditions.
    Matched MeSH terms: Alkalies/chemistry
  3. COLLINS CP
    Med J Malaya, 1957 Dec;12(2):448-55.
    PMID: 13515877
    Matched MeSH terms: Alkalies*
  4. Sim YL, Ariffin A, Khan MN
    J Org Chem, 2007 Mar 30;72(7):2392-401.
    PMID: 17341117
    The rates of the hydrolyses of N-(o-hydroxyphenyl)phthalimide (1) and N-(o-methoxyphenyl)phthalimide (2), studied at different pH, show that the hydrolysis of 1 involves intramolecular general base (IGB) assistance where the o-O- group of ionized 1 acts as IGB and H2O as the reactant. The rate enhancement due to the IGB-assisted reaction of H2O with ionized 1 is>8x10(4)-fold. Pseudo-first-order rate constant for the reaction of water with 2 is approximately 2x10(3)-fold smaller than the first-order rate constant (0.10 s-1) for pH-independent hydrolysis of 1 within the pH range of 9.60-10.10. Second-order rate constants (kOH) for hydroxide ion-assisted hydrolysis of ionized 1 and 2 are 3.0 and 29.1 M-1 s-1, respectively. The solvent deuterium kinetic isotope effect (dKIE) on the rate of alkaline hydrolysis of 1 and 2 reveals that the respective values of kOH/kOD are 0.84 and 0.78, where kOD represents the second-order rate constant for DO--assisted cleavage of these imides (1 and 2). The value of kwH2O/kdD2O is 2.04, with kwH2O and kdD2O representing pseudo-first-order rate constants for the reactions of ionized 1 with H2O and D2O, respectively.
    Matched MeSH terms: Alkalies/chemistry
  5. Tablit S, Krache R, Amroune S, Jawaid M, Hachaichi A, Ismail AS, et al.
    J Mech Behav Biomed Mater, 2024 Apr;152:106438.
    PMID: 38359736 DOI: 10.1016/j.jmbbm.2024.106438
    Arundo donax L. is investigated in this study as a suitable reinforcing agent for PLA/PP waste blend 3D printing filament. To improve the compatibility of the fibre and polymer, the Arundo fibre was chemically modified using alkali and silane treatment. Untreated and treated fibres were extruded with Polymer blends before being 3D printed. Effect of chemical treatment on thermal, mechanical, and morphological properties of the composites was investigated. The tensile, Izod impact, and water absorption of the 3D printed specimens were also tested. The Alkali treated (ALK) and combination of alkali and silane treatment (SLN) composites displayed good results. Tensile strength and modulus of the materials increased, as well as their maintained stability in the Izod impact test, demonstrating that the incorporation of ArF did not result in a loss in performance. SEM examination supported these findings by confirming the creation of beneficial interfacial contacts between the matrix and fibre components, as demonstrated by the lack of void between the matrix and the fibre surface. Furthermore, the alkali treatment of the ArF resulted in a considerable reduction in water absorption inside the biocomposite, with a 64% reduction seen in ALK composite comparison to the untreated composite (Un). After the 43-day assessment period.
    Matched MeSH terms: Alkalies*
  6. Siti Aisyah Shamsudin, Jenniver Junas
    Sains Malaysiana, 2018;47:2841-2849.
    Pengimejan tradisi mempunyai banyak kekurangan seperti mempunyai jangka hayat yang pendek serta bersaiz besar
    kerana sifat pendafluornya tidak tahan lama atau berlakunya pelunturanfoto. Melalui kajian ini, nanohablur kadmium
    sulfida dihasilkan dan berfungsi sebagai pengimejan titik kuantum yang sesuai dengan sifat optiknya yang pelbagai
    mengikut saiz zarahnya. Sifat optik titik kuantum kadmium sulfida (TK CdS) boleh dipengaruhi oleh saiz dan juga
    komposisi kimia TK seperti perubahan pH. Dalam kajian ini, sifat optik TK CdS dikaji terhadap perubahan nilai pH
    dengan menghasilkan TK CdS melalui kaedah koloidal. Kadmium asetat dihidrat (C4
    H6
    CdO4
    .2H2
    O) dan natrium sulfida
    (Na2
    S) digunakan sebagai sebagai bahan pemula bagi menghasilkan TK CdS. Nilai pH diubah suai dengan menitiskan
    natrium hidroksida (NaOH) ke dalam larutan TK CdS. Lima jenis larutan disediakan iaitu pada nilai pH5, pH7, pH8,
    pH9 dan pH10. Masalah penggumpalan sering berlaku semasa proses sintesis CdS. Oleh itu, kajian ini menggunakan
    asid tioglikolik (HSCH2
    CO2
    H) sebagai agen penstabil kepada TK CdS. Spektra keserapan UV memberi anjakan biru
    apabila TK CdS pada pH alkali kerana saiz nanohablur mengecil. Hasil daripada spektroskopi pendarfluor mendapati
    larutan yang mempunyai nilai pH8 memberi puncak yang tertinggi. Hal ini adalah kerana pada pH ini nanohablur
    mampu berubah pada posisi yang tepat dan membentuk TK CdS pada kehabluran yang tinggi. Oleh itu, mekanisme ini
    dapat membentuk perangkap lubang dan seterusnya eksiton terbentuk.
    Matched MeSH terms: Alkalies
  7. Barling, Peter Michael
    MyJurnal
    This paper presents the solution to a calculation of the pH of a very dilute solution of a strong acid or base, taking into account the effect of the hydronium or hydroxyl ions generated from the ionisation of the strong acid or base on the ionisation of water, as a second very weak acid. To be solved successfully, this calculation involves the concepts of conservation of charge, pH and the application of the general solution to a quadratic equation. Such an exercise involves the application of skills in basic numeracy, and can provide a core of understanding that can prepare students for
    many different sorts of calculations that represent reallife problems in the medical and biological sciences.A programme is presented in C++ which enables the work of students to be individualised so that each student in a class can work through a slightly different pH calculation, in such a way that a class supervisor can quickly check each student’s result for accuracy. This exercise is presented as a potential means of enabling students to undertake and master similar types of calculations involving simple or more complex equilibria.
    Matched MeSH terms: Alkalies
  8. Ng TF, Raj JK, Ghani AA
    Sains Malaysiana, 2013;42:773-781.
    The Bukit Lagong area is the most important aggregate supply centre in Selangor. Geological studies were carried out in four quarries in the Bukit Lagong area and samples were subjected to petrographic examination and accelerated expansion tests to assess the potential alkali-aggregate reactivity of granite aggregates. The granitic rocks comprise mainly of coarse grained megacrystic granite, minor medium grained megacrystic granite and microgranite. Petrographic examination showed that the primary minerals in these undeformed granitic rocks are not alkali reactive. Faulting and related alteration and mineralization have produced potentially alkali reactive minerals including microcrystalline and strained quartz and fine phyllosilicates. Marginally deleterious and deleterious expansion is shown by the accelerated mortar bar tests. Although alkali reactive rocks are present in some quarries in Bukit Lagong, their volume is small. When blended with the undeformed granitic rocks, the aggregates produced are not expected to cause alkali-aggregate reaction in concrete.
    Matched MeSH terms: Alkalies
  9. Riyanto, Jumat Salimon, Mohamed Rozali Othman
    Sains Malaysiana, 2007;36:175-181.
    Elektrod platinum-polivinilklorida (Pt-PVC) untuk pengoksidaan elektrokimia etanol dalam larutan alkali telah direkabentuk. Elektrod Pt-PVC dibina dengan mencampurkan serbuk-serbuk logam platinum dengan PVC (95:5 w/w), diaduk untuk mendapatkan campuran yang homogen, ditambahkan dengan tetrahidrofuran (THF) untuk melarutkan PVC, dikeringkan, dimasukkan ke dalam acuan berdiameter 1 cm dan ditekan pada tekanan kira-kira 10 tan/cm2. Kajian elektrokimia dilakukan menggunakan voltammetri kitaran (CV) dan kronokoulometri (CC). CV untuk etanol yang menggunakan elektrod-elektrod kepingan logam Pt dan Pt-PVC masing-masing memberikan ketumpatan arus 0.25 mA/cm2 dan 85 mA/cm2 untuk puncak penjerapan hidroksida. Ini menunjukkan bahawa elektrod Pt-PVC mempunyai nilai konduktiviti dan perilaku elektrokimia yang lebih baik untuk pengoksidaan etanol dalam KOH berbanding elektrod kepingan logam Pt. Hasil kajian mendapati bahawa terdapat peningkatan peratus hasil elektrolisis dari 3.64% kepada 23.64% asid asetik apabila elektrod Pt-PVC digunakan untuk pengoksidaan elektrokimia 0.25 M etanol dalam larutan elektrolit 1.0 M KOH menggantikan elektrod kepingan logam Pt.
    Matched MeSH terms: Alkalies
  10. Abdulkareem OA, Abdullah MMAB, Hussin K, Ismail KN, Binhussain M
    Materials (Basel), 2013 Oct 09;6(10):4450-4461.
    PMID: 28788339 DOI: 10.3390/ma6104450
    This paper presents the mechanical and microstructural characteristics of a lightweight aggregate geopolymer concrete (LWAGC) synthesized by the alkali-activation of a fly ash source (FA) before and after being exposed to elevated temperatures, ranging from 100 to 800 °C. The results show that the LWAGC unexposed to the elevated temperatures possesses a good strength-to-weight ratio compared with other LWAGCs available in the published literature. The unexposed LWAGC also shows an excellent strength development versus aging times, up to 365 days. For the exposed LWAGC to the elevated temperatures of 100 to 800 °C, the results illustrate that the concretes gain compressive strength after being exposed to elevated temperatures of 100, 200 and 300 °C. Afterward, the strength of the LWAGC started to deteriorate and decrease after being exposed to elevated temperatures of 400 °C, and up to 800 °C. Based on the mechanical strength results of the exposed LWAGCs to elevated temperatures of 100 °C to 800 °C, the relationship between the exposure temperature and the obtained residual compressive strength is statistically analyzed and achieved. In addition, the microstructure investigation of the unexposed LWAGC shows a good bonding between aggregate and mortar at the interface transition zone (ITZ). However, this bonding is subjected to deterioration as the LWAGC is exposed to elevated temperatures of 400, 600 and 800 °C by increasing the microcrack content and swelling of the unreacted silicates.
    Matched MeSH terms: Alkalies
  11. Mazlee MTF, Heidelberg T, Ariffin A, Zain SM
    Carbohydr Res, 2023 Oct;532:108923.
    PMID: 37598565 DOI: 10.1016/j.carres.2023.108923
    In the attempt to create a delivery system for an alkali-cation stimulated drug release, a computational study was conducted, aiming for the evaluation of synthetic access towards glycolipid crown ethers analogs and their potential for coordination-induced changes of packing constraints for molecular assemblies. The results disfavor amide-linkages for the creation of macrocycles around the inter-glycosidic bond of a disaccharide. Conformational changes upon cation coordination of the macrocycle decrease the intersection area for easily accessible macrocycles based on lactose. This leads to shrinking intersection areas upon alkali complexation. Maltose-based analogs, on the other hand, exhibited the targeted increase of the glycolipid intersection area and, hence, may be considered as a promising resource.
    Matched MeSH terms: Alkalies
  12. Vijay R, Lenin Singaravelu D, Vinod A, Sanjay MR, Siengchin S, Jawaid M, et al.
    Int J Biol Macromol, 2019 Mar 15;125:99-108.
    PMID: 30528990 DOI: 10.1016/j.ijbiomac.2018.12.056
    The aim of this study is to investigate natural cellulosic fibers extracted from Tridax procumbens plants. The obtained fibers were alkali treated for their effective usage as reinforcement in composites. The physical, chemical, crystallinity, thermal, wettability and surface characteristics were analyzed for raw, and alkali treated Tridax procumbens fibers (TPFs). The test results conclude that there was an increase in cellulose content with a reduction in hemicellulose, lignin, and wax upon alkali treatment. This enhanced the thermal stability, tensile strength, crystallinity, and surface roughness characteristics. The contact angle was also lesser for treated TPFs which prove its better wettability with the liquid phase. The Weibull distribution analysis was adopted for the analysis of the fiber diameter and tensile properties. Thus the considerable improvement in the properties of alkali treated TPFs would be worth for developing high-performance polymer composites.
    Matched MeSH terms: Alkalies/chemistry*
  13. Zhao P, Wang Y, Zhang Y, Guo T, Zhang Z, Zhang WJ, et al.
    Saudi J Biol Sci, 2016 May;23(3):353-7.
    PMID: 27081360 DOI: 10.1016/j.sjbs.2015.08.007
    In this study, the selenium enriched peanuts and the different solubility proteins extracted from them were investigated. The dried defatted selenium enriched peanuts (SeP) powder (0.3147 μg/g) had a 2.5-fold higher mean total selenium concentration than general peanuts (GP) power (0.1233 μg/g). The SeP had higher concentration of selenium, manganese and zinc than that of GP, but less calcium. The rate of extraction of protein was 23.39% for peanuts and alkali soluble protein was the main component of protein in SeP, which accounted for 92.82% of total soluble protein and combined selenium was 77.33% of total selenium protein. In different forms of proteins from SeP, the WSePr due to higher concentration of selenium had higher DPPH free-radical scavenging activity, higher reducing activity and longer induction time than other proteins.
    Matched MeSH terms: Alkalies
  14. Ikramullah, Rizal S, Nakai Y, Shiozawa D, Khalil HPSA, Huzni S, et al.
    Materials (Basel), 2019 Jul 10;12(14).
    PMID: 31295885 DOI: 10.3390/ma12142225
    The aim of this paper is to evaluate the Mode II interfacial fracture toughness and interfacial shear strength of Typha spp. fiber/PLLA and Typha spp. fiber/epoxy composite by using a double shear stress method with 3 fibers model composite. The surface condition of the fiber and crack propagation at the interface between the fiber and the matrix are observed by scanning electron microscope (SEM). Alkali treatment on Typha spp. fiber can make the fiber surface coarser, thus increasing the value of interfacial fracture toughness and interfacial shear strength. Typha spp. fiber/epoxy has a higher interfacial fracture value than that of Typha spp. fiber/PLLA. Interfacial fracture toughness on Typha spp. fiber/PLLA and Typha spp. fiber/epoxy composite model specimens were influenced by the matrix length, fiber spacing, fiber diameter and bonding area. Furthermore, the interfacial fracture toughness and the interfacial fracture shear stress of the composite model increased with the increasing duration of the surface treatment.
    Matched MeSH terms: Alkalies
  15. Zhang, Q., Ismail, N., Cheng, L.H.
    MyJurnal
    Chicken breast muscle powder (CBMP) was treated as a function of heating temperature, heating time and amount of alkali added. The pre-treated CBMP was then blended with modified waxy corn starch (MWCS) and characterized by flow analysis and temperature sweep. Flow analysis revealed that the blend behaved as a shear thickening and time dependent fluid with a yield stress. Statistical analysis showed that only linear and quadratic effects of heating temperature and heating time caused significant effects on flow behaviour index, consistency index and yield stress (p
    Matched MeSH terms: Alkalies
  16. Suparta, W., Samah, A.A., Harper, A.R.
    ASM Science Journal, 2009;3(2):152-160.
    MyJurnal
    Katabatic winds dramatically affect the polar climate. Their activity depends on density of air and temperature in the source region. This paper presents for first time an analysis of the precipitable water vapour (PWV) variability and its relation to a katabatic event at Scott Base station, Antarctica. A significant effect in their characteristics toward calculation of a reliable user accuracy in GPS applications is addressed. Our investigations using the data between 21st and 30th of November 2002 showed that the PWV profile exhibited an irregular pattern with a maximum value of 7.38 mm (~ 6 mm on average), and was more strongly influenced by relative humidity than by wind speed activity. The dominant wind flow during this period was from the North-Northeast (blowing from the Ross Sea) with a median speed of 4.96 ms–1. The PWV was high when the temperature was between –15ºC and –11ºC. During the dates identified as a katabatic event between 21:30 UT of 28th November and 18:40 UT on 29th November, the wind blew from the Southeast-South direction (from the Ross Ice Shelf) with a maximum speed of 10.92 ms–1. The PWV increased ~1.4 mm (23%) from the mean value, indicating severe wind during this event which had pronounced effect on GPS observations.
    Matched MeSH terms: Alkalies
  17. Ahmad Zakuan Ahmad Azmi, Mohd. Saaid, Irawan, Sonny
    MyJurnal
    The present project investigated the potential of utilizing corncobs and sugar cane waste as viscosivier in drilling fluid. For this purpose, the synthetic-based drilling fluid, Sarapar 147, was used as the base fluid. Both the materials were subjected to pre-treatment of drying, dehumidifying, grinding and sieving process prior to rheological tests. The rheological tests were conducted in accordance with the API 13B specifications to measure mud density, plastic viscosity, yield point, 10-second and 10-minute gel strength. The study found that plastic viscosity and yield point had a direct relationship with the amount of materials added. To drill fluid additive with corn cobs, the density, plastic viscosity and yield point were increased when the amount of additives were increased. Based on these experiments, both additives were found to have the potential to be used as additive in drilling fluid. In particular, they were able to improve its rheological properties by increasing the density, plastic viscosity and yield point. The suitable concentration for the corn cobs and sugar cane is 6.45 lb/bbl and 9.43 lb/bbl, respectively.
    Matched MeSH terms: Alkalies
  18. Boopathi G, Ragavan R, Jaimohan SM, Sagadevan S, Kim I, Pandurangan A, et al.
    Chemosphere, 2024 Jan;348:140650.
    PMID: 37951405 DOI: 10.1016/j.chemosphere.2023.140650
    In recent years, intensive research efforts have focused on translating biomass waste into value-added carbon materials broadcasted for their significant role in energy and environmental applications. For the first time, high-performance carbonaceous materials for energy storage applications were developed from the multi-void structure of the boat-fruited shells of Sterculia Foetida (SF). In that view, synthesized mesoporous graphitic activated carbon (g-AC) via the combination of carbonization at various elevating temperatures of 700, 800, and 900 °C, respectively, and alkali activation by KOH, with a high specific surface area of 1040.5 m2 g-1 and a mesopore volume of 0.295 cm3 g-1. In a three-electrode configuration, the improved electrode (SF-K900) exhibited excellent electrochemical behavior, which was observed in an aqueous electrolyte (1 M H2SO4) with a high specific capacitance of 308.6 F/g at a current density of 1 A/g, owing to the interconnected mesopore structures and high surface area of SF-K900. The symmetric supercapacitor (SSC) delivered the specific capacitance of 138 F/g at 1 A/g with a high energy density (ED) of 13.4 Wh/kg at the power density (PD) of 24.12 kW/kg with remarkable cycle stability and supercapacitive retention of 93% over 5000 cycles. Based on the findings, it is possible to develop low-cost active electrode materials for high-rate performance SSC using mesoporous g-AC derived from SF boat-fruited shells.
    Matched MeSH terms: Alkalies
  19. Abdullah A, Hussin K, Abdullah MMAB, Yahya Z, Sochacki W, Razak RA, et al.
    Materials (Basel), 2021 Feb 27;14(5).
    PMID: 33673522 DOI: 10.3390/ma14051111
    Aggregates can be categorized into natural and artificial aggregates. Preserving natural resources is crucial to ensuring the constant supply of natural aggregates. In order to preserve these natural resources, the production of artificial aggregates is beginning to gain the attention of researchers worldwide. One of the methods involves using geopolymer technology. On this basis, this current research focuses on the inter-particle effect on the properties of fly ash geopolymer aggregates with different molarities of sodium hydroxide (NaOH). The effects of synthesis parameters (6, 8, 10, 12, and 14 M) on the mechanical and microstructural properties of the fly ash geopolymer aggregate were studied. The fly ash geopolymer aggregate was palletized manually by using a hand to form a sphere-shaped aggregate where the ratio of NaOH/Na2SiO3 used was constant at 2.5. The results indicated that the NaOH molarity has a significant effect on the impact strength of a fly ash geopolymer aggregate. The highest aggregate impact value (AIV) was obtained for samples with 6 M NaOH molarity (26.95%), indicating the lowest strength among other molarities studied and the lowest density of 2150 kg/m3. The low concentration of sodium hydroxide in the alkali activator solution resulted in the dissolution of fly ash being limited; thus, the inter-particle volume cannot be fully filled by the precipitated gels.
    Matched MeSH terms: Alkalies
  20. Ramjan S, Tangchirapat W, Jaturapitakkul C, Chee Ban C, Jitsangiam P, Suwan T
    Materials (Basel), 2021 Mar 20;14(6).
    PMID: 33804759 DOI: 10.3390/ma14061528
    The alkali-silica reaction (ASR) is an important consideration in ensuring the long-term durability of concrete materials, especially for those containing reactive aggregates. Although fly ash (FA) has proven to be useful in preventing ASR expansion, the filler effect and the effect of FA fineness on ASR expansion are not well defined in the present literature. Hence, this study aimed to examine the effects of the filler and fineness of FA on ASR mortar expansion. FAs with two different finenesses were used to substitute ordinary Portland cement (OPC) at 20% by weight of binder. River sand (RS) with the same fineness as the FA was also used to replace OPC at the same rate as FA. The replacement of OPC with RS (an inert material) was carried out to observe the filler effect of FA on ASR. The results showed that FA and RS provided lower ASR expansions compared with the control mortar. Fine and coarse fly ashes in this study had almost the same effectiveness in mitigating the ASR expansion of the mortars. For the filler effect, smaller particles of RS had more influence on the ASR reduction than RS with coarser particles. A significant mitigation of the ASR expansion was obtained by decreasing the OPC content in the mortar mixture through its partial substitution with FA and RS.
    Matched MeSH terms: Alkalies
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