Displaying publications 1 - 20 of 747 in total

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  1. AHMAD SHAHIR BIN JAMALUDIN, ABDULLAH BIN YASSIN
    Sains Malaysiana, 2013;42:1727-1733.
    Invention of milling combined laser sintering system (MLSS) is able to reduce the mould manufacturing time and improve the mould accuracy. Thus, more study is needed to increase the understanding for the laser sintered material machining characteristic to gain benefit from the invention of MLSS. This paper clarified the analysis of laser sintered material machinability with the application of Finite Element Method (FEM). Mild steel AISI1055 was applied in developing the Finite Element model in this study due to its popularity in machinability test and adequate level of data availability. 2D orthogonal cutting was employed on edge design tools with updated Lagrangian coupled thermo mechanical plane strain model. Adaptive meshing, tool edge radius and various types of friction models were assigned to obtain efficient simulations and precise cutting results. Cutting force and cutting-edge temperature estimated by Finite Element Method are validated against corresponding experimental values by previous researchers. In the study, cutting force increases when radial depth increases and lowest error acquired when the shear friction factor of 0.8 was applied. Machining simulation for laser sintered materials estimated lower cutting force compared with mild steel AISI1055 due to lower Young modulus. Higher cutting temperature estimated for machining simulation laser sintered material compared with machining simulation mild steel AISI1055 due to its low thermal conductivity.
    Matched MeSH terms: Hot Temperature
  2. Raoov M, Mohamad S, Abas MR
    J Hazard Mater, 2013 Dec 15;263 Pt 2:501-16.
    PMID: 24231314 DOI: 10.1016/j.jhazmat.2013.10.003
    Cyclodextrin-ionic liquid polymer (βCD-BIMOTs-TDI) was firstly synthesized using functionalized β-Cyclodextrin (CD) with 1-benzylimidazole (BIM) to form monofunctionalized CD (βCD-BIMOTs) and was further polymerized using toluene diisocyanate (TDI) linker to form insoluble βCD-BIMOTs-TDI. SEM characterization result shows that βCD-BIMOTs-TDI exhibits macropore size while the BET result shows low surface area (1.254 m(2)g(-1)). The unique properties of the ILs allow us to produce materials with different morphologies. The adsorption isotherm and kinetics of 2,4-dichlorophenol (2,4-DCP) onto βCD-BIMOTs-TDI is studied. Freundlich isotherm and pseudo-second order kinetics are found to be the best to represent the data for 2,4-DCP adsorption on the βCD-BIMOTs-TDI. The presence of macropores decreases the mass transfer resistance and increases the adsorption process by reducing the diffusion distance. The change in entropy (ΔS°) and heat of adsorption (ΔH°) for 2,4-DCP on βCD-BIMOTs-TDI were estimated as -55.99 J/Kmol and -18.10 J/mol, respectively. The negative value of Gibbs free energy (ΔG°) indicates that the adsorption process is thermodynamically feasible, spontaneous and chemically controlled. Finally, the interactions between the cavity of βCD-BIMOTs and 2,4-DCP are investigated and the results shows that the inclusion of the complex formation and π-π interaction are the main processes involved in the adsorption process.
    Matched MeSH terms: Hot Temperature
  3. Lasekan O, Salva JT, Abbas K
    J Sci Food Agric, 2010 Apr 15;90(5):850-60.
    PMID: 20355122 DOI: 10.1002/jsfa.3895
    Considering the importance of malting and roasting on the quality of 'acha' beverages, a study was conducted to find optimum conditions for malting and the production of a high-quality roasted extract that could be used for an 'acha' beverage.
    Matched MeSH terms: Hot Temperature
  4. Aziz R, Hashim I, Abbasbandy S
    Sains Malaysiana, 2018;47:1599-1605.
    This study analyzes the heat transfer of a thin film flow on an unsteady stretching sheet in nanofluids. Three different types of nanoparticles are considered; copper Cu, alumina Al2O3 and titania TiO2 with water as the base fluid. The governing equations are simplified using similarity transformations. The resulting coupled nonlinear differential equations are solved by the Homotopy Analysis Method (HAM). The analytical series solutions are presented and the numerical results obtained are tabulated. In particular, it shows that the heat transfer rate decreases when nanoparticles volume fraction increases.
    Matched MeSH terms: Hot Temperature
  5. Ramli MR, Siew WL, Ibrahim NA, Kuntom A, Abd Razak RA
    PMID: 25798697 DOI: 10.1080/19440049.2015.1032368
    This paper examines the processing steps of extracting palm oil from fresh fruit bunches in a way that may impact on the formation of chloropropandiol fatty esters (3-MCPD esters), particularly during refining. Diacylglycerols (DAGs) do not appear to be a critical factor when crude palm oils are extracted from various qualities of fruit bunches. Highly hydrolysed oils, in spite of the high free fatty acid (FFA) contents, did not show exceptionally high DAGs, and the oils did not display a higher formation of 3-MCPD esters upon heat treatment. However, acidity measured in terms of pH appears to have a strong impact on 3-MCPD ester formation in the crude oil when heated at high temperatures. The differences in the extraction process of crude palm oil from current commercial processes and that from a modified experimental process showed clearly the effect of acidity of the oil on the formation of 3-MCPD esters. This paper concludes that the washing or dilution step in palm oil mills removes the acidity of the vegetative materials and that a well-optimised dilution/washing step in the extraction process will play an important role in reducing formation of 3-MCPD esters in crude palm oil upon further heat processing.
    Matched MeSH terms: Hot Temperature
  6. Aleng NA, Sung YY, MacRae TH, Abd Wahid ME
    PLoS One, 2015;10(8):e0135603.
    PMID: 26288319 DOI: 10.1371/journal.pone.0135603
    Mild heat stress promotes thermotolerance and protection against several different stresses in aquatic animals, consequences correlated with the accumulation of heat shock protein 70 (Hsp70). The purpose of this study was to determine if non-lethal heat shock (NLHS) of the Asian green mussel, Perna viridis, an aquatic species of commercial value, promoted the production of Hsp70 and enhanced its resistance to stresses. Initially, the LT50 and LHT for P. viridis were determined to be 42°C and 44°C, respectively, with no heat shock induced death of mussels at 40°C or less. Immunoprobing of western blots revealed augmentation of constitutive (PvHsp70-1) and inducible (PvHsp70-2) Hsp70 in tissue from adductor muscle, foot, gill and mantel of P. viridis exposed to 38°C for 30 min followed by 6 h recovery, NLHS conditions for this organism. Characterization by liquid chromatography-tandem mass spectrometry (LC-MS/MS) revealed that PvHsp70-1 and PvHsp70-2 respectively corresponded most closely to Hsp70 from P. viridis and Mytilus galloprovincialis. Priming of adult mussels with NLHS promoted thermotolerance and increased resistance to V. alginolyticus. The induction of Hsp70 in parallel with enhanced thermotolerance and improved protection against V. alginolyticus, suggests Hsp70 functions in P. viridis as a molecular chaperone and as a stimulator of the immune system.
    Matched MeSH terms: Hot Temperature
  7. Abdul Hannan Damahuri, Hassan Mohamed, Abdul Aziz Mohamed
    MyJurnal
    Thorium is a fertile material that can undergo transmutation for it to become a fissile material,
    uranium-233. The fissile material can go through a fission process in order to generate heat energy
    and eventually electricity. Most nuclear reactors use uranium as their fission source. The use of
    thorium as nuclear fuel has been only investigated for few types of reactors such as a high, temperature
    gas reactor (HTGR), fast breeder reactor, light water reactor (LWR) and heavy water reactor
    (HWR). For research reactors specifically, there are limited academic publications related to the
    la,test u.se of thorium. Hence, the main, interest, of this work is to compile and review the latest
    academic publications related to the active use of thorium, for research reactors in particular. The
    reviewed studies have been, divided into two categories which are experimented and simulation projects.
    The experimental projects are a,bold the ongoing thorium fuel tests that have been carried out. in an
    actual, research reactor. On the hand, the simulation work: is related to the computational analysis
    performed in predicting the neutronic behaviour of thorium based fuel in research reactors. The
    experimented study of thorium is currently active for the KAMINI research reactor. Additionally, most,
    simulation works focus on finding criticality and neutron spectra.
    Matched MeSH terms: Hot Temperature
  8. Usman MG, Rafii MY, Ismail MR, Malek MA, Abdul Latif M
    ScientificWorldJournal, 2014;2014:308042.
    PMID: 25478590 DOI: 10.1155/2014/308042
    High temperature tolerance is an important component of adaptation to arid and semiarid cropping environment in chili pepper. Two experiments were carried out to study the genetic variability among chili pepper for heat tolerance and morphophysiological traits and to estimate heritability and genetic advance expected from selection. There was a highly significant variation among the genotypes in response to high temperature (CMT), photosynthesis rate, plant height, disease incidence, fruit length, fruit weight, number of fruits, and yield per plant. At 5% selection intensity, high genetic advance as percent of the mean (>20%) was observed for CMT, photosynthesis rate, fruit length, fruit weight, number of fruits, and yield per plant. Similarly, high heritability (>60%) was also observed indicating the substantial effect of additive gene more than the environmental effect. Yield per plant showed strong to moderately positive correlations (r = 0.23-0.56) at phenotypic level while at genotypic level correlation coefficient ranged from 0.16 to 0.72 for CMT, plant height, fruit length, and number of fruits. Cluster analysis revealed eight groups and Group VIII recorded the highest CMT and yield. Group IV recorded 13 genotypes while Groups II, VII, and VIII recorded one each. The results showed that the availability of genetic variance could be useful for exploitation through selection for further breeding purposes.
    Matched MeSH terms: Hot Temperature
  9. Rosli Abu Bakar, Ahmad Rasdan Ismail, Norfadzilah Jusoh, Abdul Mutalib Leman
    MyJurnal
    This paper discuss thermal comfort studies of an under air conditioning in hot and humid climate which at one of the higher institution in East Coast of Malaysia. Indoor thermal environment is important as it affects the health and productivity of building occupants. The paper reports on an experimental investigation of indoor thermal comfort characteristics under the control of air conditioning. Firstly, the well known Fanger’s thermal comfort model was simplified for the current experimental investigation. This is followed by reporting the experimental results of indoor thermal comfort characteristics under the control of temperature, with eight different of temperatures which are 22oC to 29oC. Finally, indoor thermal comfort was merely affected by the increment ventilation and outdoor climate. PMV value was higher when near from the window because of the effects of the wall radiations and the metabolic heat.
    Matched MeSH terms: Hot Temperature
  10. Abedi Karjiban R, Lim WZ, Basri M, Abdul Rahman MB
    Protein J, 2014 Aug;33(4):369-76.
    PMID: 24871480 DOI: 10.1007/s10930-014-9568-8
    Lipases are known for their versatility in addition to their ability to digest fat. They can be used for the formulation of detergents, as food ingredients and as biocatalysts in many industrial processes. Because conventional enzymes are frangible at high temperatures, the replacement of conventional chemical routes with biochemical processes that utilize thermostable lipases is vital in the industrial setting. Recent theoretical studies on enzymes have provided numerous fundamental insights into the structures, folding mechanisms and stabilities of these proteins. The studies corroborate the experimental results and provide additional information regarding the structures that were determined experimentally. In this paper, we review the computational studies that have described how temperature affects the structure and dynamics of thermoenzymes, including the thermoalkalophilic L1 lipase derived from Bacillus stearothermophilus. We will also discuss the potential of using pressure for the analysis of the stability of thermoenzymes because high pressure is also important for the processing and preservation of foods.
    Matched MeSH terms: Hot Temperature*
  11. Rahimah Mahat, Noraihan Afiqah Rawi, Sharidan Shafie, Abdul Rahman Mohd Kasim
    Sains Malaysiana, 2018;47:1617-1623.
    The purpose of this study was to examine the effect of viscous dissipation on mixed convection flow of viscoelastic
    nanofluid past a horizontal circular cylinder. Carboxymethyl cellulose solution (CMC) is chosen as the base fluid and
    copper as a nanoparticle with the Prandtl number Pr = 6.2. The transformed boundary layer equations for momentum
    and temperature subject to the appropriate boundary conditions are solved numerically by using Keller-box method. The
    influenced of the dimensionless parameters such as Eckert number, mixed convection parameter, nanoparticles volume
    fraction and viscoelastic parameter on the flow and heat transfer characteristics is analyzed in detail and presented
    graphically. The results come out with the velocity profiles are increased while the temperature profiles are decreased
    by increasing the values of nanoparticles volume fraction and viscoelastic parameter, respectively. The graph shows
    that, increasing Eckert number the skin friction is also increases. The values of skin friction are increased by increasing
    mixed convection parameter, but the values of Nusselt number produce an opposite behavior. The present study has many
    applications especially in heat exchangers technology and oceanography. Therefore, in future, it is hoping to study the
    viscoelastic nanofluid flow past a different geometric such as sphere and cylindrical cone.
    Matched MeSH terms: Hot Temperature
  12. Yacob N, Ahmad NA, Safii SH, Yunus N, Abdul Razak F
    J Prosthet Dent, 2023 Jul;130(1):131.e1-131.e7.
    PMID: 37210224 DOI: 10.1016/j.prosdent.2023.04.017
    STATEMENT OF PROBLEM: How the build orientation of a 3-dimensionally (3D) printed denture affects microbial adhesion is unclear.

    PURPOSE: The purpose of this in vitro study was to compare the adherence of Streptococcus spp. and Candida spp. on 3D-printed denture bases prepared at different build orientations with conventional heat-polymerized resin.

    MATERIAL AND METHODS: Resin specimens (n=5) with standardized 28.3 mm2 surface area were 3D printed at 0 and 60 degrees, and heat-polymerized (3DP-0, 3DP-60, and HP, respectively). The specimens were placed in a Nordini artificial mouth (NAM) model and exposed to 2 mL of clarified whole saliva to create a pellicle-coated substratum. Suspensions of Streptococcus mitis and Streptococcus sanguinis, Candida albicans and Candida glabrata, and a mixed species, each at 108 cfu/mL were pumped separately into the model for 24 hours to promote microbial adhesion. The resin specimens were then removed, placed in fresh media, and sonicated to dislodge attached microbes. Each suspension (100 μL) was aliquoted and spread on agar plates for colony counting. The resin specimens were also examined under a scanning electron microscope. The interaction between types of specimen and groups of microbes was examined with 2-way ANOVA and then further analysis with Tukey honest significant test and Kruskal-Wallis post hoc tests (α=.05).

    RESULTS: A significant interaction was observed between the 3DP-0, 3DP-60, and HP specimen types and the groups of microbes adhering to the corresponding denture resin specimens (P

    Matched MeSH terms: Hot Temperature
  13. Abedi Karjiban R, Abdul Rahman MB, Basri M, Salleh AB, Jacobs D, Abdul Wahab H
    Protein J, 2009 Jan;28(1):14-23.
    PMID: 19130194 DOI: 10.1007/s10930-008-9159-7
    Molecular Dynamics (MD) simulations have been used to understand how protein structure, dynamics, and flexibility are affected by adaptation to high temperature for several years. We report here the results of the high temperature MD simulations of Bacillus stearothermophilus L1 (L1 lipase). We found that the N-terminal moiety of the enzyme showed a high flexibility and dynamics during high temperature simulations which preceded and followed by clear structural changes in two specific regions; the small domain and the main catalytic domain or core domain of the enzyme. These two domains interact with each other through a Zn(2+)-binding coordination with Asp-61 and Asp-238 from the core domain and His-81 and His-87 from the small domain. Interestingly, the His-81 and His-87 were among the highly fluctuated and mobile residues at high temperatures. The results appear to suggest that tight interactions of Zn(2+)-binding coordination with specified residues became weak at high temperature which suggests the contribution of this region to the thermostability of the enzyme.
    Matched MeSH terms: Hot Temperature
  14. Yetti, M., Nazamid, B.S., Roselina, K., Abdulkarim, S.M.
    MyJurnal
    The native sago starch exists as a compact crystalline structure and is not efficiently hydrolyzed by Raw Starch Degrading Enzyme (RSDE). In order to enhance its hydrolysability, the starch was treated with acid and heated below its gelatinization temperature, thus increasing the accessibility of the sago starch granule to enzymatic attack. Results showed that treatment of sago starch with acid at pH 2.0 and temperature 65oC for 2 hours greatly enhanced its conversion rate to glucose from 53.3% to 71.9%. It is clearly shown that high yield of glucose is produced during hydrolysis of acid-treated sago starch using the Raw Starch Degrading Enzyme from Acremonium sp. The difference between the acid-treated and untreated sago starch in this study could be due to the differences on the surface of the sago starch granule which may influence the accessibility and diffusion of enzyme into the starch during hydrolysis.
    Matched MeSH terms: Hot Temperature
  15. Azlan CA, Mohd Nasir NF, Saifizul AA, Faizul MS, Ng KH, Abdullah BJ
    Australas Phys Eng Sci Med, 2007 Dec;30(4):288-91.
    PMID: 18274069
    Percutaneous image-guided needle biopsy is typically performed in highly vascular organs or in tumours with rich macroscopic and microscopic blood supply. The main risks related to this procedure are haemorrhage and implantation of tumour cells in the needle tract after the biopsy needle is withdrawn. From numerous conducted studies, it was found that heating the needle tract using alternating current in radiofrequency (RF) range has a potential to minimize these effects. However, this solution requires the use of specially designed needles, which would make the procedure relatively expensive and complicated. Thus, we propose a simple solution by using readily available coaxial core biopsy needles connected to a radiofrequency ablation (RFA) generator. In order to do so, we have designed and developed an adapter to interface between these two devices. For evaluation purpose, we used a bovine liver as a sample tissue. The experimental procedure was done to study the effect of different parameter settings on the size of coagulation necrosis caused by the RF current heating on the subject. The delivery of the RF energy was varied by changing the values for delivered power, power delivery duration, and insertion depth. The results showed that the size of the coagulation necrosis is affected by all of the parameters tested. In general, the size of the region is enlarged with higher delivery of RF power, longer duration of power delivery, and shallower needle insertion and become relatively constant after a certain value. We also found that the solution proposed provides a low cost and practical way to minimizes unwanted post-biopsy effects.
    Matched MeSH terms: Hot Temperature/therapeutic use
  16. Mehmood A, Mubarak NM, Khalid M, Jagadish P, Walvekar R, Abdullah EC
    Sci Rep, 2020 11 18;10(1):20106.
    PMID: 33208815 DOI: 10.1038/s41598-020-77139-2
    Strain sensors in the form of buckypaper (BP) infiltrated with various polymers are considered a viable option for strain sensor applications such as structural health monitoring and human motion detection. Graphene has outstanding properties in terms of strength, heat and current conduction, optics, and many more. However, graphene in the form of BP has not been considered earlier for strain sensing applications. In this work, graphene-based BP infiltrated with polyvinyl alcohol (PVA) was synthesized by vacuum filtration technique and polymer intercalation. First, Graphene oxide (GO) was prepared via treatment with sulphuric acid and nitric acid. Whereas, to obtain high-quality BP, GO was sonicated in ethanol for 20 min with sonication intensity of 60%. FTIR studies confirmed the oxygenated groups on the surface of GO while the dispersion characteristics were validated using zeta potential analysis. The nanocomposite was synthesized by varying BP and PVA concentrations. Mechanical and electrical properties were measured using a computerized tensile testing machine, two probe method, and hall effect, respectively. The electrical conducting properties of the nanocomposites decreased with increasing PVA content; likewise, electron mobility also decreased while electrical resistance increased. The optimization study reports the highest mechanical properties such as tensile strength, Young's Modulus, and elongation at break of 200.55 MPa, 6.59 GPa, and 6.79%, respectively. Finally, electrochemical testing in a strain range of ε ~ 4% also testifies superior strain sensing properties of 60 wt% graphene BP/PVA with a demonstration of repeatability, accuracy, and preciseness for five loading and unloading cycles with a gauge factor of 1.33. Thus, results prove the usefulness of the nanocomposite for commercial and industrial applications.
    Matched MeSH terms: Hot Temperature
  17. Shakeri M, Zulkifli I, Soleimani AF, O'Reilly EL, Eckersall PD, Anna AA, et al.
    Poult Sci, 2014 Nov;93(11):2700-8.
    PMID: 25143595 DOI: 10.3382/ps.2014-03910
    A study was conducted to determine whether supplementing AminoGut (a commercial dietary supplement containing a mixture of l-glutamine and l-glutamic acid) to broiler chickens stocked at 2 different densities affected performance, physiological stress responses, foot pad dermatitis incidence, and intestinal morphology and microflora. A randomized design in a factorial arrangement with 4 diets [basal diet, basal diet + 0.5% AminoGut from d 1 to 21, basal diet + 0.5% AminoGut from d 1 to 42, and basal diet + virginiamycin (0.02%) for d 1 to 42] and 2 stocking densities [0.100 m(2)/bird (23 birds/pen; LD) or 0.067 m(2)/bird (35 birds/pen; HD)]. Results showed that villi length and crypt depth were not changed by different dietary treatments. However, birds in the HD group had smaller villi (P = 0.03) compared with those of the LD group. Regardless of diet, HD consistently increased the serum concentrations of ceruloplasmin, α-1 acid glycoprotein, ovotransferin, and corticosterone (P = 0.0007), and elevated heterophil to lymphocyte ratio (0.0005). Neither AminoGut supplementation nor stocking density affected cecal microflora counts. In conclusion, under the conditions of this study, dietary supplementation of AminoGut, irrespective of stocking density, had no beneficial effect on growth performance, intestinal morphology, and physiological adaptive responses of broiler chickens raised under hot and humid tropical conditions. However, AminoGut supplementation from d 1 to 42 was beneficial in reducing mortality rate. Also, the increased serum concentrations of a wide range of acute phase proteins together with elevated corticosterone and heterophil to lymphocyte ratio suggested that high stocking density induced an acute phase response either indirectly as a result of increased incidence of inflammatory diseases such as foot pad dermatitis or possibly as a direct physiological response to the stress of high stocking density.
    Matched MeSH terms: Hot Temperature*
  18. Ravanfar SA, Aziz MA, Saud HM, Abdullah JO
    Curr Genet, 2015 Nov;61(4):653-63.
    PMID: 25986972 DOI: 10.1007/s00294-015-0494-x
    An efficient system for shoot regeneration and Agrobacterium tumefaciens-mediated transformation of Brassica oleracea cv. Green Marvel cultivar is described. This study focuses on developing shoot regeneration from hypocotyl explants of broccoli cv. Green Marvel using thidiazuron (TDZ), zeatin, and kinetin, the optimization of factors affecting Agrobacterium-mediated transformation of the hypocotyl explants with heat-resistant cDNA, followed by the confirmation of transgenicity of the regenerants. High shoot regeneration was observed in 0.05-0.1 mg dm(-3) TDZ. TDZ at 0.1 mg dm(-3) produced among the highest percentage of shoot regeneration (96.67 %) and mean number of shoot formation (6.17). The highest percentage (13.33 %) and mean number (0.17) of putative transformant production were on hypocotyl explants subjected to preculture on shoot regeneration medium (SRM) with 200 µM acetosyringone. On optimization of bacterial density and inoculation time, the highest percentage and mean number of putative transformant production were on hypocotyl explants inoculated with a bacterial dilution of 1:5 for 30 min. Polymerase chain reaction (PCR) assay indicated a transformation efficiency of 8.33 %. The luciferase assay showed stable integration of the Arabidopsis thaliana HSP101 (AtHSP101) cDNA in the transgenic broccoli regenerants. Three out of five transgenic lines confirmed through PCR showed positive hybridization bands of the AtHSP101 cDNA through Southern blot analysis. The presence of AtHSP101 transcripts in the three transgenic broccoli lines indicated by reverse transcription-PCR (RT-PCR) confirmed the expression of the gene. In conclusion, an improved regeneration system has been established from hypocotyl explants of broccoli followed by successful transformation with AtHSP101 for resistance to high temperature.
    Matched MeSH terms: Hot Temperature
  19. Sadri R, Hosseini M, Kazi SN, Bagheri S, Abdelrazek AH, Ahmadi G, et al.
    J Colloid Interface Sci, 2018 Jan 01;509:140-152.
    PMID: 28898734 DOI: 10.1016/j.jcis.2017.07.052
    In this study, we synthesized covalently functionalized graphene nanoplatelet (GNP) aqueous suspensions that are highly stable and environmentally friendly for use as coolants in heat transfer systems. We evaluated the heat transfer and hydrodynamic properties of these nano-coolants flowing through a horizontal stainless steel tube subjected to a uniform heat flux at its outer surface. The GNPs functionalized with clove buds using the one-pot technique. We characterized the clove-treated GNPs (CGNPs) using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). We then dispersed the CGNPs in distilled water at three particle concentrations (0.025, 0.075 and 0.1wt%) in order to prepare the CGNP-water nanofluids (nano-coolants). We used ultraviolet-visible (UV-vis) spectroscopy to examine the stability and solubility of the CGNPs in the distilled water. There is significant enhancement in thermo-physical properties of CGNPs nanofluids relative those for distilled water. We validated our experimental set-up by comparing the friction factor and Nusselt number for distilled water obtained from experiments with those determined from empirical correlations, indeed, our experimental set-up is reliable and produces results with reasonable accuracy. We conducted heat transfer experiments for the CGNP-water nano-coolants flowing through the horizontal heated tube in fully developed turbulent condition. Our results are indeed promising since there is a significant enhancement in the Nusselt number and convective heat transfer coefficient for the CGNP-water nanofluids, with only a negligible increase in the friction factor and pumping power. More importantly, we found that there is a significant increase in the performance index, which is a positive indicator that our nanofluids have potential to substitute conventional coolants in heat transfer systems because of their overall thermal performance and energy savings benefits.
    Matched MeSH terms: Hot Temperature
  20. Jaafar NR, Mahadi NM, Mackeen MM, Illias RM, Murad AMA, Abu Bakar FD
    J Biotechnol, 2021 Mar 10;329:118-127.
    PMID: 33539893 DOI: 10.1016/j.jbiotec.2021.01.019
    Dehydroquinase or 3-dehydroquinate dehydratase (DHQD) reversibly cleaves 3-dehydroquinate to form 3-dehydroshikimate. Here, we describe the functional and structural features of a cold active type II 3-dehydroquinate dehydratase from the psychrophilic yeast, Glaciozyma antarctica PI12 (GaDHQD). Functional studies showed that the enzyme was active at low temperatures (10-30 °C), but displayed maximal activity at 40 °C. Yet the enzyme was stable over a wide range of temperatures (10-70 °C) and between pH 6.0-10.0 with an optimum pH of 8.0. Interestingly, the enzyme was highly thermo-tolerant, denaturing only at approximately 84 °C. Three-dimensional structure analyses showed that the G. antarctica dehydroquinase (GaDHQD) possesses psychrophilic features in comparison with its mesophilic and thermophilic counterparts such as higher numbers of non-polar residues on the surface, lower numbers of arginine and higher numbers of glycine-residues with lower numbers of hydrophobic interactions. On the other hand, GaDHQD shares some traits (i.e. total number of hydrogen bonds, number of proline residues and overall folding) with its mesophilic and thermophilic counterparts. Combined, these features contribute synergistically towards the enzyme's ability to function at both low and high temperatures.
    Matched MeSH terms: Hot Temperature*
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