Displaying publications 1 - 20 of 181 in total

  1. Agung, E.H., Sapuan, S.M., Hamdan, M.M., Zaman, H.M.D.K., Mustofa, U.
    The properties of fibre-reinforced composites are dependent not only on the strength of the reinforcementfibre but also on the distribution of fibre strength and the composition of the chemicals or additivesaddition within the composites. In this study, the tensile properties of abaca fibre reinforced high impactpolystyrene (HIPS) composites, which had been produced with the parameters of fibre loading (30,40,50wt.%), coupling agent maleic anhydride (MAH) (1,2,3 wt%) and impact modifier (4,5,6 wt.%) weremeasured. The optimum amount of MAH is 3% and the impact modifier is 6% and these give the besttensile properties. Meanwhile, Differential Scanning Calorimetry (DSC) was used to study the thermalbehaviour within the optimum conditions of the composites. In this research, glass transitions temperature(Tg) of neat HIPS occurred below the Tg of the optimum condition of composites as the temperature ofan amorphous state. The endothermic peak of the composites was in the range of 430-4350C, includingneat HIPS. It was observed that enthalpy of the abaca fibre reinforced HIPS composites yielded belowthe neat HIPS of 748.79 J/g.
    Matched MeSH terms: Calorimetry, Differential Scanning
  2. Daud NH, Leow TC, Oslan SN, Salleh AB
    Mol Biotechnol, 2019 Mar 27.
    PMID: 30919327 DOI: 10.1007/s12033-019-00169-3
    The application of native enzymes may not be economical owing to the stability factor. A smaller protein molecule may be less susceptible to external stresses. Haloalkane dehalogenases (HLDs) that act on toxic haloalkanes may be incorporated as bioreceptors to detect haloalkane contaminants. Therefore, this study aims to develop mini proteins of HLD as an alternative bioreceptor which was able to withstand extreme conditions. Initially, the mini proteins were designed through computer modeling. Based on the results, five designed mini proteins were deemed to be viable stable mini proteins. They were then validated through experimental study. The smallest mini protein (model 5) was chosen for subsequent analysis as it was expressed in soluble form. No dehalogenase activity was detected, thus the specific binding interaction of between 1,3-dibromopropane with mini protein was investigated using isothermal titration calorimetry. Higher binding affinity between 1,3-dibromopropane and mini protein was obtained than the native. Thermal stability study with circular dichroism had proven that the mini protein possessed two times higher Tm value at 83.73 °C than the native at 43.97 °C. In conclusion, a stable mini protein was successfully designed and may be used as bioreceptors in the haloalkane sensor that is suitable for industrial application.
    Matched MeSH terms: Calorimetry
  3. Lim AW, Löbmann K, Grohganz H, Rades T, Chieng N
    J Pharm Pharmacol, 2016 Jan;68(1):36-45.
    PMID: 26663364 DOI: 10.1111/jphp.12494
    The objective was to characterize the structural behaviour of indomethacin-cimetidine and naproxen-cimetidine co-amorphous systems (1 : 1 molar ratio) prepared by quench cooling, co-evaporation and ball milling.
    Matched MeSH terms: Calorimetry, Differential Scanning
  4. Dahimi O, Rahim AA, Abdulkarim SM, Hassan MS, Hashari SB, Mashitoh AS, et al.
    Food Chem, 2014 Sep 1;158:132-8.
    PMID: 24731324 DOI: 10.1016/j.foodchem.2014.02.087
    The adulteration of edible fats is a kind of fraud that impairs the physical and chemical features of the original lipid materials. It has been detected in various food, pharmaceutical and cosmeceutical products. Differential scanning calorimetry (DSC) is the robust thermo-analytical machine that permits to fingerprint the primary crystallisation of triacylglycerols (TAGs) molecules and their transition behaviours. The aims of this study was to assess the cross-contamination caused by lard concentration of 0.5-5% in the mixture systems containing beef tallow (BT) and chicken fat (CF) separately. TAGs species of pure and adulterated lipids in relation to their crystallisation and melting parameters were studied using principal components analysis (PCA). The results showed that by using the heating profiles the discrimination of LD from BT and CF was very clear even at low dose of less than 1%. Same observation was depicted from the crystallisation profiles of BT adulterated by LD doses ranging from 0.1% to 1% and from 2% to 5%, respectively. Furthermore, CF adulterated with LD did not exhibit clear changes on its crystallisation profiles. Consequently, DSC coupled with PCA is one of the techniques that might use to monitor and differentiate the minimum adulteration levels caused by LD in different animal fats.
    Matched MeSH terms: Calorimetry, Differential Scanning/methods*
  5. Razalee S, Poh BK, Ismail MN
    Singapore Med J, 2010 Aug;51(8):635-40.
    PMID: 20848060
    INTRODUCTION: The basal metabolic rate (BMR) is essential in deriving estimates of energy requirements for a population. The aim of this study was to measure the BMR in order to derive a predictive equation for the Malaysian Armed Forces (MAF) naval trainees.
    METHODS: A total of 79 naval trainees aged 18 to 25 years from a training centre (Group A) and on board a ship (Group B) participated in the study. Anthropometric measurements included height and weight. Body fat and free fat mass were measured using the bioelectrical impedance analysis method. BMR was measured by indirect calorimetry with a canopy system.
    RESULTS: The mean height, weight and body fat for Group A was 1.67 +/- 0.04 m, 61.0 +/- 3.9 kg and 12.7 percent +/- 2.5 percent, respectively, and 1.67 +/- 0.05 m, 62.3 +/- 6.2 kg and 14.0 percent +/- 3.5 percent, respectively, for Group B. The mean BMR for Group A (6.28 +/- 0.40 MJ/ day) did not differ significantly (p is more than 0.05) from that of Group B (6.16 +/- 0.67 MJ / day). The Food and Agriculture Organization/World Health Organization/United Nations University and the Henry and Rees equations overestimated the measured BMR by 9 percent (p is less than 0.001) and 0.5 percent (p is more than 0.05), respectively, while the Ismail et al equation underestimated the measured BMR by 5.6 percent (p is less than 0.001). A predictive equation, BMR = 3.316 + 0.047 (weight in kg) expressed in MJ /day with weight as the only independent variable, was derived using regression analysis.
    CONCLUSION: We recommend that this predictive equation be used to estimate the energy requirements of MAF naval trainees.
    Matched MeSH terms: Calorimetry, Indirect/methods
  6. Zaliha O, Elina H, Sivaruby K, Norizzah AR, Marangoni AG
    J Oleo Sci, 2018 Jun 01;67(6):737-744.
    PMID: 29760328 DOI: 10.5650/jos.ess17168
    The in situ polymorphic forms and thermal transitions of refined, bleached and deodorized palm oil (RBDPO), palm stearin (RBDPS) and palm kernel oil (RBDPKO) were investigated using coupled X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Results indicated that the DSC onset crystallisation temperature of RBDPO was at 22.6°C, with a single reflection at 4.2Å started to appear from 23.4 to 17.1°C, and were followed by two prominent exothermic peaks at 20.1°C and 8.5°C respectively. Further cooling to -40°C leads to the further formation of a β'polymorph. Upon heating, a of β'→βtransformation was observed between 32.1 to 40.8°C, before the sample was completely melted at 43.0°C. The crystallization onset temperature of RBDPS was 44.1°C, with the appearance of the α polymorph at the same temperature as the appearance of the first sharp DSC exothermic peak. This quickly changed from α→β´ in the range 25 to 21.7°C, along with the formation of a small β peak at -40°C. Upon heating, a small XRD peak for the β polymorph was observed between 32.2 to 36.0°C, becoming a mixture of (β´+ β) between 44.0 to 52.5°C. Only the β polymorph survived further heating to 59.8°C. For RBDPKO, the crystallization onset temperature was 11.6°C, with the formation of a single sharp exothermic peak at 6.5°C corresponding to the β' polymorphic form until the temperature reached -40°C. No transformation of the polymorphic form was observed during the melting process of RBDPKO, before being completely melted at 33.2°C. This work has demonstrated the detailed dynamics of polymorphic transformations of PKO and PS, two commercially important hardstocks used widely by industry and will contribute to a greater understanding of their crystallization and melting dynamics.
    Matched MeSH terms: Calorimetry, Differential Scanning*
  7. Gorajana A, Rajendran A, Yew LM, Dua K
    Int J Pharm Investig, 2015 Jul-Sep;5(3):171-8.
    PMID: 26258059 DOI: 10.4103/2230-973X.160857
    The objective of the current study is to increase the dissolution rate of cefuroxime axetil (CA) by formation of binary CA solid dispersion using water soluble carriers such as polyvinylpyrrolidone (PVP K30) and polyethylene glycol (PEG 4000).
    Matched MeSH terms: Calorimetry, Differential Scanning
  8. Tan CP, Man YC
    Phytochem Anal, 2002 May-Jun;13(3):129-41.
    PMID: 12099103
    The melting curves of 11 vegetable oils have been characterised. Vegetable oil samples that were cooled at a constant rate (5 degrees C/min) from the melt showed between one and seven melting endotherms upon heating at four different heating rates (1, 5, 10 and 20 degrees C/min) in a differential scanning calorimeter (DSC). Triacylglycerol (TAG) profiles and iodine value analyses were used to complement the DSC data. Generally, the melting transition temperature shifted to higher values with increased rates of heating. The breadth of the melting endotherm and the area under the melting peak also increased with increasing heating rate. Although the number of endothermic peaks was dependent on heating rate, the melting curves of the oil samples were not straightforward in that there was no correlation between the number of endothermic peaks and heating rates. Multiple melting behaviour in DSC experiments with different heating rates could be explained by: (1) the melting of TAG populations with different melting points; and (2) TAG crystal reorganisation effects. On the basis of the corollary results obtained, vegetable oils and fats may be distinguished from their offset-temperature (Toff) values in the DSC melting curves. The results showed that Toff values of all oil samples were significantly (p < 0.01) different in the melting curves scanned at four different scanning rates. These calorimetric results indicate that DSC is a valuable technique for studying vegetable oils.
    Matched MeSH terms: Calorimetry, Differential Scanning
  9. Nur Fadzilah Basri, Fauziah Abdul Aziz, Mohd Omar, A.K., Nik Norulaini, A.R.
    The main purpose of this study was to analyzed and examined the cocoa butter samples from Sabah. This work presence the crystal phases present in cocoa butter sample thus proved the existence of polymorphs obtained from differential scanning calorimeter (DSC) analysis and confirmed by X-ray diffraction (XRD). The cocoa butter samples were extracted using a conventional method by Soxhlet Extraction method. Crystals were formed under controlled static and tempered conditions. Cocoa butter polymorphism demonstrates that it is the actual crystallization temperature, not the cooling rate that determines the polymorph that crystallizes.
    Matched MeSH terms: Calorimetry, Differential Scanning
  10. Siti Rohana Ahmad, Salmah Husseinsyah, Kamarudin Hussin
    In this study, dynamic vulcanization process was used to improve the thermal properties of calcium carbonate filled composites. The composites were prepared using a Z-blade mixer at 180oC and rotor speed 50rpm. Thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC) techniques were used to analyze the thermal properties of the composites. The vulcanized and unvulcanized PP/EPDM composites were filled by CaCO3 at 0, 10, 20, 30, and 40 %wt. Meanwhile, thermogravimetric analysis indicates that the total weight loss of PP/EPDM/CaCO3 composites decreased with increasing filler loading. Dynamic vulcanized composites have higher thermal stability, while the crystallinity of PP/EPDM/CaCO3 composites were increased as compared to unvulcanized composites. Therefore, the thermal properties were improved by the presence of
    dynamic vulcanization process.
    Matched MeSH terms: Calorimetry, Differential Scanning
  11. Nurul, A.I., Azura, A.
    Knowledge about the thermal and storage behavior of produced protein is important for the purpose of storage, transport and shelve life during industrial application. Recombinant bromelain thermal and storage stability were measured and compared to the commercial bromelain using Differential Scanning Calorimetry (DSC). Recombinant bromelain is more stable than commercial bromelain at higher temperature but the stability was reduced after 7 days of storage at 4oC. Higher energy is needed to break the bond between amino acid chains in recombinant bromelain as shown by the enthalpy obtained, suggesting that recombinant bromelain has good protein structure and conformation compared to commercial.
    Matched MeSH terms: Calorimetry, Differential Scanning
  12. Siti Rohana Ahmad, Salmah Husseinsyah, Kamarudin Hussin
    A chemical modifier (acrylic acid) was used to improve the thermal properties of polypropylene/ ethylene propylene diene terpolymer/calcium carbonate (PP/EPDM/CaCO3) composites. Treated
    and untreated PP/EPDM composites were filled by CaCO3 at 0, 20 and 40% wt. The composites
    were prepared using Z-blade mixer machine at 180oC and 50 rpm of rotor speed. Thermogravimetric
    analysis (TGA) and differential scanning calorimetry (DSC) methods were used to analyze the thermal properties of the composites. Thermogravimetric analysis indicated that the total weight loss of PP/EPDM/CaCO3 composites decreased with the increasing filler loading for the treated and untreated composites. Meanwhile, the presence of acrylic acid was found to have increased the thermal stability and crystallinity of PP/EPDM/CaCO3
    Matched MeSH terms: Calorimetry, Differential Scanning
  13. Rosdi, N.H., Mohd Kanafi, N., Abdul Rahman, N.
    Cellulose acetate (CA) is an interesting material due to its wide spectrum of utilities across different domains ranging from absorbent to membrane filters. In this study, polystyrene (PS) nanofibres, and cellulose acetate/polystyrene (CA/PS) blend nanofibres with various ratios of CA: PS from 20: 80 to 80: 20 were fabricated by using electrospinning technique. The SEM images show that the nanofibres exhibited non-uniform and random orientation with the average fibre diameter in the range of 100 to 800 nm. It was found that the incorporation of PS had a great effect on the morphology of nanofibre. At high proportion of PS, no or less beaded CA/PS nanofibres were formed. Thermal properties of the composite nanofibres were investigated by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. The TGA results showed thermal stability of CA/PS nanofibres were higher than pristine CA.
    Matched MeSH terms: Calorimetry, Differential Scanning
  14. Sim, S.Y., Noor Aziah, A.A., Teng, T.T., Cheng, L.H.
    The effects of food gums addition on wheat dough freeze-thaw and frozen storage stability were studied. Thermal and dynamic mechanical properties of frozen wheat dough without yeast addition were
    determined by means of Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA).
    DSC results revealed that food gums showed the ability to increase freeze-thaw stability in frozen-stored
    samples wherein lower difference in melting enthalpy between first and second freeze-thaw cycle was shown. Based on DMA results, in general, difference between Tg’ and storage temperature (- 18°C) of dough became smaller upon addition of food gums. This may have a practical implication whereby the unfrozen phase could be better protected against physical degradation.
    Matched MeSH terms: Calorimetry, Differential Scanning
  15. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Bergauer T, Brandstetter J, et al.
    Eur Phys J C Part Fields, 2020;80(8):718.
    PMID: 32834020 DOI: 10.1140/epjc/s10052-020-8166-5
    Central exclusive and semiexclusive production of pairs is measured with the CMS detector in proton-proton collisions at the LHC at center-of-mass energies of 5.02 and 13TeV. The theoretical description of these nonperturbative processes, which have not yet been measured in detail at the LHC, poses a significant challenge to models. The two pions are measured and identified in the CMS silicon tracker based on specific energy loss, whereas the absence of other particles is ensured by calorimeter information. The total and differential cross sections of exclusive and semiexclusive central production are measured as functions of invariant mass, transverse momentum, and rapidity of the system in the fiducial region defined as transverse momentum and pseudorapidity . The production cross sections for the four resonant channels , , , and are extracted using a simple model. These results represent the first measurement of this process at the LHC collision energies of 5.02 and 13TeV.
    Matched MeSH terms: Calorimetry
  16. Tah PC, Lee ZY, Poh BK, Abdul Majid H, Hakumat-Rai VR, Mat Nor MB, et al.
    Crit Care Med, 2020 05;48(5):e380-e390.
    PMID: 32168031 DOI: 10.1097/CCM.0000000000004282
    OBJECTIVES: Several predictive equations have been developed for estimation of resting energy expenditure, but no study has been done to compare predictive equations against indirect calorimetry among critically ill patients at different phases of critical illness. This study aimed to determine the degree of agreement and accuracy of predictive equations among ICU patients during acute phase (≤ 5 d), late phase (6-10 d), and chronic phase (≥ 11 d).

    DESIGN: This was a single-center prospective observational study that compared resting energy expenditure estimated by 15 commonly used predictive equations against resting energy expenditure measured by indirect calorimetry at different phases. Degree of agreement between resting energy expenditure calculated by predictive equations and resting energy expenditure measured by indirect calorimetry was analyzed using intraclass correlation coefficient and Bland-Altman analyses. Resting energy expenditure values calculated from predictive equations differing by ± 10% from resting energy expenditure measured by indirect calorimetry was used to assess accuracy. A score ranking method was developed to determine the best predictive equations.

    SETTING: General Intensive Care Unit, University of Malaya Medical Centre.

    PATIENTS: Mechanically ventilated critically ill patients.


    MEASUREMENTS AND MAIN RESULTS: Indirect calorimetry was measured thrice during acute, late, and chronic phases among 305, 180, and 91 ICU patients, respectively. There were significant differences (F= 3.447; p = 0.034) in mean resting energy expenditure measured by indirect calorimetry among the three phases. Pairwise comparison showed mean resting energy expenditure measured by indirect calorimetry in late phase (1,878 ± 517 kcal) was significantly higher than during acute phase (1,765 ± 456 kcal) (p = 0.037). The predictive equations with the best agreement and accuracy for acute phase was Swinamer (1990), for late phase was Brandi (1999) and Swinamer (1990), and for chronic phase was Swinamer (1990). None of the resting energy expenditure calculated from predictive equations showed very good agreement or accuracy.

    CONCLUSIONS: Predictive equations tend to either over- or underestimate resting energy expenditure at different phases. Predictive equations with "dynamic" variables and respiratory data had better agreement with resting energy expenditure measured by indirect calorimetry compared with predictive equations developed for healthy adults or predictive equations based on "static" variables. Although none of the resting energy expenditure calculated from predictive equations had very good agreement, Swinamer (1990) appears to provide relatively good agreement across three phases and could be used to predict resting energy expenditure when indirect calorimetry is not available.

    Matched MeSH terms: Calorimetry, Indirect/methods*; Calorimetry, Indirect/standards
  17. Dua K, Pabreja K, Ramana MV, Lather V
    J Pharm Bioallied Sci, 2011 Jul;3(3):417-25.
    PMID: 21966164 DOI: 10.4103/0975-7406.84457
    The objective of the present investigation was to study the effect of β-cyclodextrin (β-CD) on the in vitro dissolution of aceclofenac (AF) from molecular inclusion complexes. Aceclofenac molecular inclusion complexes in 1:1 and 1:2 M ratio were prepared using a kneading method. The in vitro dissolution of pure drug, physical mixtures, and cyclodextrin inclusion complexes was carried out. Molecular inclusion complexes of AF with β-CD showed a considerable increase in the dissolution rate in comparison with the physical mixture and pure drug in 0.1 N HCl, pH 1.2, and phosphate buffer, pH 7.4. Inclusion complexes with a 1:2 M ratio showed the maximum dissolution rate in comparison to other ratios. Fourier transform infrared spectroscopy and differential scanning calorimetry studies indicated no interaction between AF and β-CD in complexes in solid state. Molecular modeling results indicated the relative energetic stability of the β-CD dimer-AF complex as compared to β-CD monomer-AF. Dissolution enhancement was attributed to the formation of water soluble inclusion complexes with β-CD. The in vitro release from all the formulations was best described by first-order kinetics (R(2) = 0.9826 and 0.9938 in 0.1 N HCl and phosphate buffer, respectively) followed by the Higuchi release model (R(2) = 0.9542 and 0.9686 in 0.1 N HCl and phosphate buffer, respectively). In conclusion, the dissolution of AF can be enhanced by the use of a hydrophilic carrier like β-CD.
    Matched MeSH terms: Calorimetry, Differential Scanning
  18. Woo HJ, Arof AK
    PMID: 26945998 DOI: 10.1016/j.saa.2016.02.034
    A flexible solid polymer electrolyte (SPE) system based on poly(ε-caprolactone) (PCL), a FDA approved non-toxic and biodegradable material in the effort to lower environmental impact was prepared. Ammonium thiocyanate (NH4SCN) and ethylene carbonate (EC) were incorporated as the source of charge carriers and plasticizing agent, respectively. When 50wt.% of ethylene carbonate (EC) was added to PCL-NH4SCN system, the conductivity increased by two orders from of 3.94×10(-7)Scm(-1) to 3.82×10(-5)Scm(-1). Molecular vibrational analysis via infrared spectroscopy had been carried out to study the interaction between EC, PCL and NH4SCN. The relative percentage of free ions, ion pairs and ion aggregates was calculated quantitatively by deconvoluting the SCN(-) stretching mode (2030-2090cm(-1)). This study provides fundamental insight on how EC influences the free ion dissociation rate and ion mobility. The findings are also in good agreement to conductivity, differential scanning calorimetry and X-ray diffraction results. High dielectric constant value (89.8) of EC had made it an effective ion dissociation agent to dissociate both ion pairs and ion aggregates, thus contributing to higher number density of free ions. The incorporation of EC had made the polymer chains more flexible in expanding amorphous domain. This will facilitate the coupling synergy between ionic motion and polymer segmental motion. Possible new pathway through EC-NH4(+) complex sites for ions to migrate with shorter distance has been anticipated. This implies an easier ion migration route from one complex site to another.
    Matched MeSH terms: Calorimetry, Differential Scanning
  19. Che Man YB, Tan CP
    Phytochem Anal, 2002 May-Jun;13(3):142-51.
    PMID: 12099104
    The effects of scanning rates (1, 5, 10 and 20 degrees C/min) on the DSC cooling profiles of 11 vegetable oils have been determined in order to monitor peak transition temperatures, onset temperatures and crystallisation enthalpies. Triacylglycerol (TAG) profiles and iodine value analyses were used to complement the DSC data. The melted samples exhibited complicated crystallising exotherms. As the cooling rate increased, the crystallisation temperature decreased and the breadth of the crystallisation exotherm on cooling from the melt increased. In addition, the intensity of the exothermic peak increased somewhat when the cooling rate was increased. At slow cooling rates, TAG had more time to interact. It is conceivable that, at a low cooling rate (1 degree C/min), a prominent exotherm would be observed on crystallisation of vegetable oils and fats. The occurrence of one exotherm upon cooling indicated the co-crystallisation of the TAG upon slow cooling. On the basis of the corollary results obtained, vegetable oils may be differentiated by their onset temperature (Ton) values in the DSC cooling curves. Generally, there was a shift of Ton toward lower values with increasing cooling rates.
    Matched MeSH terms: Calorimetry, Differential Scanning
  20. Arif, M.A.M., Omar, M.Z., Muhamad, N.
    The effect of solid solution treatment on semisolid microstructure of Zn-22Al with developed dendrites was investigated. Zn-22Al is a zinc-based alloy with aluminium as its main alloying element. Producing Zn-22Al product by semisolid metal processing (SSM) offers significant advantages, such as reduction of macrosegregations, porosity and low forming efforts. Meanwhile, thermal and microstructure analyses of Zn-22Al alloy were studied using differential scanning calorimeter (DSC) and Olympus optical microscope. Solidus and liquidus of the alloy can be determined by DSC analysis. In addition, changes to the microstructures in response to solid solution treatments were also analyzed. The major effort of all the semi-solid technologies is the generation of small and spherical morphologies. Prior to the generation of spherical morphologies, the fine grains should be first produced. The as-cast samples were isothermally held at 315°C, ranging from 0.5 to 5 hours before they were partially re-melted at semisolid temperature of 438°C to produce solid globular grains structure in liquid matrix. The results indicated that a non-dendritic semisolid microstructure could not be obtained if the traditionally cast Zn-22Al alloy with developed dendrites was directly subjected to partial remelting. After solid solution treatment at 315°C, the black interdendritic eutectics were dissolved and gradually transformed into ß structure when the treatment time was increased. The microstructure of the solid solution treated sample changed into a small globular structure with the best shape factor of 0.9 and this corresponded to 40±16µm when the sample was treated for 3 hours, followed by directly partial remelting into its semi solid zone.
    Matched MeSH terms: Calorimetry, Differential Scanning
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