Displaying publications 1 - 20 of 522 in total

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  1. Das K, Anis M, Azemi BM, Ismail N
    Biotechnol Bioeng, 1995 Dec 5;48(5):551-5.
    PMID: 18623521
    Glutamic acid produced from palm waste hydrolysate by fermentation with Brevibacterium lactofermentum ATCC 13869 is produced with a remarkably high yield compared with that produced from pure glucose as a carbon source. The produce yield is 70 g/L with glucose, wherease, when palm waste hydrolysate is the fermentation medium in the same bioreactor under same conditions, it is 88 g/L. The higher yield may be attributed to the fact that this organism has the ability to convert sugars other than only glucose present in the hydrolysate. Bioreactor conditions most conducive for maximum production are pH 7.5, temperature of 30 degrees rmentation period of 48 h, inoculum size 6%, substrate concentration of 10 g per 100 mL, yeast extract 0.5 g per 100 mL as a suitable N source, and biotin at a concentration of 10 pg/L. Palm waste hydrolysate used in this study was prepared by enzymic saccharification of treated palm press fiber under conditions that yielded a maximum of 30 g/L total reducing sugars. Glutamic acid from fermentation broth was recovered by using a chromatographic column (5cm x 60 cm) packed with a strong ion-exchange resin. The filtered broth containing glutamic acid and other inorganic ions was fed to the fully charged column. The broth was continuously recycled at a flow rate of 50 mL/min (retention time of 55 min) until glutamic acid was fully adsorbed on the column leaving other ions in the effluent. Recovery was done by eluting with urea and sodium hydroxide for total displacement of glutamic acid from the resin. The eluent containing 88 g/L of glutamic acid was concentrated by evaporation to obtain solid crystals of the product. (c) 1995 John Wiley & Sons, Inc.
    Matched MeSH terms: Physical Phenomena
  2. Khalid Md. Nor, Ithnin Abdul Jalil, Hassan Abu Kasim
    The relativistic Schrodinger equation is reinterpreted as describing a classical particle that mutually-interacts with other objects via electromagnetic-like gravity waves. The accompanying derivation equates the usual quantum mechanical energy and momentum operators to the effects of negative or attractive energy. Lorentz-like transformation equations are obtained that yield the uncertainty principle such that quantum uncertainty is ascribed to the disregard of a magnetic-like component of a gravity wave. Finally, quantum-level Maxwell-like equations that involve the above gravity waves are derived.
    Persamaan Schrodinger kerelatifan ditafsirkan sebagai memperihalkan suatu zarah klasik yang berinteraksi dengan jasad-jasad lain melalui gelombang graviti yang berciri keelektromagnetan. Terbitan sampingan menyamakan pengoperasi-pengeoperasi tenaga dan momentum mekanik kuantum dengan kesan-kesan tenaga negatif atau tarikan. Persamaan-persamaan bermirip transformasi Lorentz diperolehi yang menerbitkan prinsip ketakpastian dan memberi ketakpastian kuantum sebagai kesan pengabaian bahagian gelombang graviti yang bermirip kemagnetan. Akhir sekali, persamaan-persamaan diparas kuntum yang bermirip persamaan-persamaan Maxwell diterbitkan dan melibatkan gelombang graviti yang tersebut di atas.
    Matched MeSH terms: Physical Phenomena
  3. Abu Bakar Mohamad, Wan Ramli Wan Daud, Amir Kadhum, Fathi Messaud, Mohd. Ambar Yarmo
    Chemical structure of treated and untreated Aciplex membrane has been studied by X-ray Photoelectron Spectroscopy (XPS). Survey spectra showed that both membrane surfaces consist of Fluorine, Carbon, Oxygen, Sulphur and trace of Titanium. Binding energies for the elements are (C1s at 290.6 eV, F1s at 687.5 eV, O1s at 531.3 eV, S2P at 168.1 eV and Ti2P at 454.4 eV). Analysis of narrow scan XPS-spectra of each element demonstrate the presence of (-CF, -CF2, CF3, C-O-C and SO-3) groups, which are in agreement with the structural formula as disclosed by the manufacturer. There is no significant change in chemical states of untreated and treated membrane, which reflect its stability to treatment conditions.
    Struktur kimia Aciplex membran yang sudah dibersihkan dan yang belum dibersihkan telah dikaji menggunakan Spektroskopi Fotoelektron Sinaran-X (XPS). Spektra yang telah ditinjau menunjukkan bahawa kedua-dua permukaan membran mengandungi Florin, Karbon, Oksigen, Sulfur dan sedikit Titanium. Tenaga ikatan bagi unsur-unsur tersebut adalah (C1s pada 290.6 eV, F1s pada 687.5 eV. O1s pada 531.3 eV, S2P pada 168.2 eV dan Ti2P pada 454.4 eV). Analisis imbasan kecil spektra-xps bagi setiap unsur menunjukkan kehadiran kilmpulan (-CF, - CF2, CF3, C-O-C dan SO-3) yang bertepatan dengan formula struktur dari pihak pembekal. Tiada terdapat perubahan nyata berhubung dengan keadaan kimia membran yang sudah dibersihkan dan yang belum dibersihkan yang menggambarkan kestabilannya terhadap keadaan pembersihan.
    Matched MeSH terms: Physical Phenomena
  4. Dolah MT, Samat SB, Kadni T
    Malays J Med Sci, 2000 Jan;7(1):47-53.
    PMID: 22844215
    Absorbed dose to water was measured with ionisation chambers NE 2561 (#267), NE 2581 (#334), NE 2571 (#1028), using the IAEA standard water phantom. The ionisation chamber was inserted in the water phantom at a reference depth dependent on the type of the radiation quality used. Three radiation qualities were used namely 1.25 MeV gamma ray, 6 MV x-rays and 10 MV x-rays. The values of the absorbed dose to water were determined by the N(K)- and N(X)- based methods, i.e with the use of IAEA, HPA, NACP, AAPM, NCRP and ICRU protocols. The aim of this study was to make an intercomparison of the results, by taking the IAEA protocol as a standard. The largest deviation contributed by any of these protocols was recorded for each quality. It was found that AAPM, NCRP and ICRU protocols contributed 0.94% for 1.25 MeV gamma ray, NACP contributed 2.12% for the 6 MV x-rays, and NACP contributed 2.35% for 10 MV x-rays. Since the acceptable limit of deviation set by the IAEA for this absorbed dose work is ± 3%, it is clear that the overall deviations obtained were all satisfactory.
    Matched MeSH terms: Physical Phenomena
  5. Ng SW, Yang Farina AA, Othman AH, Baba I, Sivakumar K, Fun HK
    Acta Crystallogr C, 2000 Mar 15;56(Pt 3):E84-5.
    PMID: 15263206
    The title compound, [Sn(CH(3))(2)(C(5)H(10)NO(2)S(2))(2)], has crystallographic mirror symmetry (C-Sn-C on mirror plane) and the coordination polyhedron around the Sn atom is a tetrahedron [C-Sn-C 139.3 (2) degrees and S-Sn-S 82.3 (1) degrees ] distorted towards a skew-trapezoidal bipyramid owing to an intramolecular Sn.S contact [3.0427 (6) A]. The molecules are linked into a linear chain by intermolecular O-H.O hydrogen bonds [O.O 2.646 (3) A].
    Matched MeSH terms: Physical Phenomena
  6. Bradley DA, Dahlan KZ, Roy SC
    Appl Radiat Isot, 2000 Oct;53(4-5):921-8.
    PMID: 11003542
    High-energy electron (2.0 MV) and gamma irradiation (60Co) has been used to modify polymeric silicone fluids of initial viscosities in the range, 90-700 cSt. Doses of electron and gamma radiation were delivered at rates of 0.246 kGy s(-1) and 15 kGy h(-1), respectively, exposure times being adjusted to ensure energy deposition in the range 30-360 kGy. Measurements were made using a differential viscometer based on a Bose Institute design. In line with expectation, samples of greater initial molecular weight (and hence greater viscosity), were observed to be more susceptible to radiation induced cross-linking than those of lower molecular weight. The role of dose rate and oxygen diffusion in determining the extent of change is discussed.
    Matched MeSH terms: Physical Phenomena
  7. Yusof NA, Ahmad M
    Talanta, 2002 Sep 12;58(3):459-66.
    PMID: 18968772
    Gallocynin immobilized in chitosan membrane has been studied as a sensor element of an optical sensor for lead using a flowing system. By using this set up, lead in solution has been determined in the concentration range from 1.0x10(-1) to 1.0x10(3) ppm with a detection limit of 0.075 ppm. The standard deviation of the method for the repeatability of lead detection at a concentration of 100 ppm was found to be 2.10%. The response of the sensor was reproducible and can be regenerated by using acidified saturated KNO(3) solution. Interference from foreign ions was also studied at 1:1 mole ratio of Pb(II):foreign ions.
    Matched MeSH terms: Physical Phenomena
  8. Khan N
    Appl Opt, 2004 Jan 20;43(3):678-81.
    PMID: 14765930
    The theoretical basis for simultaneous oscillation of 2N - 3 laser lines is due to interference of N (for all even N > or = 2) pump beams in a distributed-feedback dye laser is described. Multiple gratings are produced in a dye solution by interference patterns of N/2 pairs of a frequency-doubled Nd:YAG laser. N/2 pairs of mutually time-delayed pulses induce multiple gratings of different periodicities, of which 2N - 3 gratings support oscillation of 2N - 3 lines and the remaining gratings, because of their larger periods, cannot support Bragg scattering. The maximum number of laser lines depends on the mutual delay between adjacent pairs of beams, coherence, states of polarization, pulse lengths, and of course the number of pulses. For three pairs of excitation beams derived from the same source through wave-front or amplitude phase division techniques, the output lasing lines varied from a minimum of three to a maximum of nine. This research was carried out by pumping of a dye solution with two, four, and six pulses, but the principle may be extended to multiple output lines, depending on the number of pump pulses and on the gain of the dye solution.
    Matched MeSH terms: Physical Phenomena
  9. Roslinda Nazar, Pop I
    The unsteady mixed convection boundary layer flow near the forward stagnation point of a two-dimensional symmetric body prescribed by a uniform heat flux rate is studied in this paper. The main aim of the investigation is to identify situations in which dual solutions for the steady-state flow can be determined when the flow is opposing. It is also shown that there is a smooth transition from the unsteady initial flow (short time) to the final steady state flow (large time).
    Matched MeSH terms: Physical Phenomena
  10. Supian Samat, Siaw S
    IAEA in its publication year 2000 has recommended a worksheet for the determination of absorbed dose to water in an electron beam. We evaluated the worksheet via an absorbed dose to water determination work at a local radiotherapy center using a 12 MeV electron beam. We found that if several modifications are made, this IAEA worksheet will become more user-friendly and could facilitate and fasten the process of quality assurance audit. The modifications are given and discussed.
    [IAEA dalam penerbitannya tahun 2000 telah mengesyorkan satu helaian kerja untuk menentukan dos terserap kepada air dalam alur electron. Helaian kerja ini dinilai melalui satu kerja penentuan dos terserap kepada air di satu Pusat radioterapi tempatan menggunakan satu alur electron 12 MeV. Sekiranya beberapa pengubahsuai dibuat, helaian kerja IAEA ini akan menjadi lebih mesra pengguna dan dapat mempermudahkan dan mempercepatkan lagi proses audit jaminan kualiti. Pengubahsuaian ini diberikan dan dibincangkan].
    Matched MeSH terms: Physical Phenomena
  11. Razidah Ismail
    Scientific Research Journal, 2006;3(1):37-52.
    MyJurnal
    The state space modeling approach was developed to cope with the demand
    and performance due to the increase in system complexity, which may have
    multiple inputs and multiple outputs (MIMO). This approach is based on timedomain
    analysis and synthesis using state variables. This paper describes the
    development of a state space representation of a furnace system of a combined
    cycle power plant. Power plants will need to operate optimally so as to stay
    competitive, as even a small improvement in energy efficiency would involve
    substantial cost savings. Both the quantitative and qualitative analyses of the
    state space representation of the furnace system are discussed. These include
    the responses of systems excited by certain inputs and the structural properties
    of the system. The analysis on the furnace system showed that the system is
    bounded input and bounded output stable, controllable and observable. In
    practice, the state space formulation is very important for numerical computation
    and controller design, and can be extended for time-varying systems.
    Matched MeSH terms: Physical Phenomena; Biophysical Phenomena
  12. Supian Samat, Lee YK
    Sains Malaysiana, 2006;35:57-60.
    This note describes a method for the determination of the peak-to-total ratio, P/T versus gamma-ray energy of range 59.54-1836.03 keV of a HPGe detector. Results show that this ratio decreases with energy. To check the validity of these results, two approaches of results comparison, namely with the ratio reported by Cesana and Terrani in year 1989 and with the shape of total efficiency reported by Debertin and Helmer in year 1988 were taken. lt is shown that this method gives satisfactory results since the obtained values of P/T and the shape of the total efficiency curve were in good agreement with the reported works. The precautional step that need to be taken when dealing with energy 59.54 keV 241Am source and the reason for taking the total efficiency as the evaluation tool are given.
    Matched MeSH terms: Physical Phenomena
  13. Zaili MA, Kuppuswamy R, Harun H
    Forensic Sci Int, 2007 Aug 24;171(1):27-32.
    PMID: 17088038
    It is known that restoration of erased engraved identification marks on the engine and the chassis of a car or on a firearm has low success rate. Unlike stamping, engraving on a metal surface leaves no pronounced, permanent subsurface deformation in the crystalline structure, also called dislocation that can be revealed by suitable methods. Hence, the current research work investigated whether metallographic reagents used in the restoration of stamp (compression) marks could be applied to recover engraved marks on steel surfaces and also to establish the sensitivity and effectiveness of some of these reagents for the restoration of the marks. Experiments were conducted by mechanically engraving alphanumeric characters on several steel plates using a computer controlled engraving machine called Gravograph. The markings were later erased from the above steel plates by removing the metal in stages of 0.01 mm through 0.04 mm below the bottom of the engraving. Several plates were thus prepared wherein each one had been abraded to a specific depth. Then eight metallographic reagents were tested on each one of the above erased plates using a swabbing technique. The results had shown that while most of the reagents were able to restore marks up to certain levels of erasure, the reagent 5 g copper sulphate, 60 ml water, 30 ml concentrated ammonium hydroxide and 60 ml concentrated hydrochloric acid restored marks erased to a depth of 0.04 mm below the engraving depth, thus presenting itself the most sensitive reagent. Quite significantly, the above reagent was also able to decipher successfully the original engraved marks that had been erased and engraved with a new number, or obliterated by centre punching. The results of this research work should benefit the forensic practitioners engaged in the serial number recovery on vehicles, firearms and other objects.
    Matched MeSH terms: Physical Phenomena
  14. Loo JL, Lai OM, Long K, Ghazali HM
    World J Microbiol Biotechnol, 2007 Dec;23(12):1771-8.
    PMID: 27517833 DOI: 10.1007/s11274-007-9427-2
    Mycelium-bound lipase (MBL) was prepared using a strain of Geotrichum candidum isolated from local soil. At the time of maximum lipase activity (54 h), the mycelia to which the lipase was bound were harvested by filtration and centrifugation. Dry MBL was prepared by lyophilizing the mycelia obtained. The yield of MBL was 3.66 g/l with a protein content of 44.11 mg/g. The lipase activity and specific lipase activity were 22.59 and 510 U/g protein, respectively. The moisture content of the MBL was 3.85%. The activity of free (extracellular) lipase in the culture supernatant (after removal of mycelia) was less than 0.2 U/ml. The MBL showed selectivity for oleic acid over palmitic acid during hydrolysis of palm olein, indicating that the lipase from G. candidum displayed high substrate selectivity for unsaturated fatty acid containing a cis-9 double bond, even in crude form. This unique specificity of MBL could be a direct, simple and inexpensive way in the fats and oil industry for the selective hydrolysis or transesterification of cis-9 fatty acid residues in natural triacylglycerols.
    Matched MeSH terms: Physical Phenomena
  15. Ismail Saad, Razali Ismail, Ima Sulaiman
    Sains Malaysiana, 2008;37:233-237.
    Conventional lateral and vertical n-channel MOS transistors with channel length in the range of 100nm to 50nm have been systematically investigated by means of device simulation. The comparison analysis includes critical parameters that govern device performance. Threshold voltage VT roll-off, leakage current Ioff, drain saturation current IDsat and sub-threshold swing S were analyze and compared between the device. Due to double gate (DG) structure over the side of silicon pillar a better electrostatics potential control of channel is obtained in vertical device shown by an analysis on VT roll-off. A two decade higher of Ioff in planar device is observed with Lg=50nm. A factor of three times larger IDsat is observed for vertical MOSFETs compared to planar device. The sub-threshold swing S remains almost the same when the Lg larger than 80 nm. It increased rapidly when the Lg is scaled down to 50 nm due to the short channel effect SCE. However, the vertical device has a steady increase whereas the planar device has suffered immediate enhance of SCE. The analysis results confirmed that vertical MOSFET with double-gate structure is a potential solution to overcome SCE when scaled the channel length to 50nm and beyond.
    Matched MeSH terms: Physical Phenomena
  16. Lee HW, Azid IH
    Sensors (Basel), 2009;9(9):7481-97.
    PMID: 22400004 DOI: 10.3390/s90907481
    In this study, a hybridized neuro-genetic optimization methodology realized by embedding numerical simulations trained artificial neural networks (ANN) into a genetic algorithm (GA) is used to optimize the flow rectification efficiency of the diffuser element for a valveless diaphragm micropump application. A higher efficiency ratio of the diffuser element consequently yields a higher flow rate for the micropump. For that purpose, optimization of the diffuser element is essential to determine the maximum pumping rate that the micropump is able to generate. Numerical simulations are initially carried out using CoventorWare® to analyze the effects of varying parameters such as diffuser angle, Reynolds number and aspect ratio on the volumetric flow rate of the micropump. A limited range of simulation results will then be used to train the neural network via back-propagation algorithm and optimization process commence subsequently by embedding the trained ANN results as a fitness function into GA. The objective of the optimization is to maximize the efficiency ratio of the diffuser element for the range of parameters investigated. The optimized efficiency ratio obtained from the neuro-genetic optimization is 1.38, which is higher than any of the maximum efficiency ratio attained from the overall parametric studies, establishing the superiority of the optimization method.
    Matched MeSH terms: Physical Phenomena
  17. Samat S, Too S, Kadni T, Dollah M
    The values of beam quality correction factor kQ that were experimentally determined from year 2002 to 2008 were analysed. As kQ is the function of ionization chamber and beam quality, the analysis were based on three cases namely (a) kQ(NE2571, 6 MV x-rays) that were determined from 17 measurements in the duration of 69 months at 6 radiotherapy centres, (b) kQ(NE2571, 10 MV x-rays) from 7 measurements in the duration of 12 months at one radiotherapy centre, and (c) kQ(NE2581, 6 MV x-rays) from 5 measurements in the duration of 5 months also at one radiotherapy centre. The purpose is to examine, in each case, the variation kQ for all the measurements. In other words, to see variation kQ with time. Results obtained are 0.993(NE2571, 6 MV), 0.986(NE2571, 10 MV) and 0.986(NE2581, 6 MV). This shows that in each case, despite the difference in the experimental data in getting kQ for all measurement, kQ remains constant with time. Reasons for this are explained.
    Matched MeSH terms: Physical Phenomena
  18. Noor Fadiya Mohd Noor, Ishak Hashim
    The magnetohydrodynamic (MHD) boundary-layer flow and heat transfer due to a shrinking sheet in a porous medium is considered for the first time. The Navier-Stokes equations and the heat equation are reduced to two nonlinear ordinary differential equations via similarity transformations. The transformed equations are solved by a semi-analytic method. The effects of the suction and porosity parameters, the Prandtl and Hartmann numbers on the skin friction, heat transfer rate, velocity and temperature profiles are discussed and presented, respectively.
    Matched MeSH terms: Physical Phenomena
  19. Ng SF, Rouse J, Sanderson D, Eccleston G
    Pharmaceutics, 2010 May 18;2(2):209-223.
    PMID: 27721352
    Synthetic membranes used in Franz diffusion cells for topical formulation quality assessment should provide least resistance to drug diffusion. In this study, the diffusion rates of ibuprofen across thirteen membranes were determined using Franz diffusion cells. Correlation of the membrane thickness, pore size and MWCO with drug fluxes was also made. The drug diffusion results showed that the porous membranes were categorized into high-flux (8-18 mg/cm²/h) and low-flux (0.1-3 mg/cm²/h) membranes. The drug fluxes did not show strong correlations (r² < 0.99) with membrane parameters. Synthetic membranes can give variable drug fluxes, thus investigators should be careful in choosing membrane for formulation quality assessment.
    Matched MeSH terms: Physical Phenomena
  20. Lau EV, Gan S, Ng HK
    Int J Anal Chem, 2010;2010:398381.
    PMID: 20396670 DOI: 10.1155/2010/398381
    This paper aims to provide a review of the analytical extraction techniques for polycyclic aromatic hydrocarbons (PAHs) in soils. The extraction technologies described here include Soxhlet extraction, ultrasonic and mechanical agitation, accelerated solvent extraction, supercritical and subcritical fluid extraction, microwave-assisted extraction, solid phase extraction and microextraction, thermal desorption and flash pyrolysis, as well as fluidised-bed extraction. The influencing factors in the extraction of PAHs from soil such as temperature, type of solvent, soil moisture, and other soil characteristics are also discussed. The paper concludes with a review of the models used to describe the kinetics of PAH desorption from soils during solvent extraction.
    Matched MeSH terms: Physical Phenomena
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