Displaying publications 1 - 20 of 23 in total

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  1. Zakaria SM, Sharif Zein SH, Othman MR, Jansen JA
    J Biomed Mater Res A, 2013 Jul;101(7):1977-85.
    PMID: 23225849 DOI: 10.1002/jbm.a.34506
    Electrospinning of hydroxyapatite (HA)/polyvinyl butyral solution resulted in the formation of fibers with average diameter of 937-1440 nm. These fibers were converted into HA nanoparticles with size <100 nm after undergoing calcination treatment at 600°C. The diameter of the fiber was found to be influenced by applied voltage and spinning distance. The injection flowrate did not affect the diameter significantly. The electrospinning method successfully reduced the commercial HA particle size in the range of 400-1100 nm into <100 nm. The dispersion of the finally calcined HA nanoparticles was improved significantly after anionic sodium dodecyl sulfate surfactant was introduced. The experimental data of HA growth kinetics were subjected to the integral method of analysis, and the rate law of the reaction was found to follow the first order reaction.
    Matched MeSH terms: Scattering, Radiation
  2. Yang HZ, Lim KS, Qiao XG, Chong WY, Cheong YK, Lim WH, et al.
    Opt Express, 2013 Jun 17;21(12):14808-15.
    PMID: 23787668 DOI: 10.1364/OE.21.014808
    We present a new theoretical model for the broadband reflection spectra of etched FBGs which includes the effects of axial contraction and stress-induced index change. The reflection spectra of the etched FBGs with several different taper profiles are simulated based on the proposed model. In our observation, decaying exponential profile produces a broadband reflection spectrum with good uniformity over the range of 1540-1560 nm. An etched FBG with similar taper profile is fabricated and the experimental result shows good agreement with the theoretical model.
    Matched MeSH terms: Scattering, Radiation
  3. Tan JS, Abbasiliasi S, Kadkhodaei S, Tam YJ, Tang TK, Lee YY, et al.
    BMC Microbiol, 2018 01 04;18(1):3.
    PMID: 29439680 DOI: 10.1186/s12866-017-1145-9
    BACKGROUND: Demand for high-throughput bioprocessing has dramatically increased especially in the biopharmaceutical industry because the technologies are of vital importance to process optimization and media development. This can be efficiently boosted by using microtiter plate (MTP) cultivation setup embedded into an automated liquid-handling system. The objective of this study was to establish an automated microscale method for upstream and downstream bioprocessing of α-IFN2b production by recombinant Escherichia coli. The extraction performance of α-IFN2b by osmotic shock using two different systems, automated microscale platform and manual extraction in MTP was compared.

    RESULTS: The amount of α-IFN2b extracted using automated microscale platform (49.2 μg/L) was comparable to manual osmotic shock method (48.8 μg/L), but the standard deviation was 2 times lower as compared to manual osmotic shock method. Fermentation parameters in MTP involving inoculum size, agitation speed, working volume and induction profiling revealed that the fermentation conditions for the highest production of α-IFN2b (85.5 μg/L) was attained at inoculum size of 8%, working volume of 40% and agitation speed of 1000 rpm with induction at 4 h after the inoculation.

    CONCLUSION: Although the findings at MTP scale did not show perfect scalable results as compared to shake flask culture, but microscale technique development would serve as a convenient and low-cost solution in process optimization for recombinant protein.

    Matched MeSH terms: Scattering, Radiation
  4. Tan C, Seet G, Sluzek A, Wang X, Yuen CT, Fam CY, et al.
    Opt Express, 2010 Sep 27;18(20):21147-54.
    PMID: 20941011 DOI: 10.1364/OE.18.021147
    The range-gated imaging systems are reliable underwater imaging system with the capability to minimize backscattering effect from turbid media. The tail-gating technique has been developed to fine tune the signal to backscattering ratio and hence improve the gated image quality. However, the tail-gating technique has limited image quality enhancement in high turbidity levels. In this paper, we developed a numerical model of range-gated underwater imaging system for near target in turbid medium. The simulation results matched the experimental work favorably. Further investigation using this numerical model shows that the multiple scattering components of the backscattering noise dominate for propagation length larger than 4.2 Attenuation Length (AL). This has limited the enhancement of tail-gating technique in high turbidity conditions.
    Matched MeSH terms: Scattering, Radiation
  5. Shakhreet BZ, Bauk S, Tajuddin AA, Shukri A
    Radiat Prot Dosimetry, 2009 Jul;135(1):47-53.
    PMID: 19482883 DOI: 10.1093/rpd/ncp096
    The mass attenuation coefficients (mu/rho) of Rhizophora spp. were determined for photons in the energy range of 15.77-25.27 keV. This was carried out by studying the attenuation of X-ray fluorescent photons from zirconium, molybdenum, palladium, silver, indium and tin targets. The results were compared with theoretical values for average breast tissues in young-age, middle-age and old-age groups calculated using photon cross section database (XCOM), the well-known code for calculating attenuation coefficients and interaction cross-sections. The measured mass attenuation coefficients were found to be very close to the calculated XCOM values in breasts of young-age group.
    Matched MeSH terms: Scattering, Radiation
  6. Sayed, I. S., Yusri, N. H.
    MyJurnal
    In radiography, radiation workers are responsible to protect patients and their caregivers from adverse effects of X-rays during diagnostic procedures. The X-ray examination rooms are designated as controlled areas where only authorised persons are allowed to enter. However, sometimes radiographers allow next in-line patients’ and caregivers in X-ray examination room and ask them to stand behind the mobile lead shielding when exposure is on. The objectives of this study were to determine the amount of scatter radiation dose at different heights with respect to the floor in the X-ray examination room and to educate and increase the awareness of radiation workers about the scattered radiation in minimizing the unnecessary radiation dose to patient’s caregivers. Siemens Multix Top X-ray system was used. Kyoto Kagaku PBU-50 whole body phantom was scanned. The phantom (torso) was positioned for anteroposterior (AP) lumbar projection on the examination table. The nanoDot OSLDs were fixed behind the lead shielding at different heights (120, 130, 140, 150, 160 and 170 cm) with respect to the floor 2.5 meters away from the central ray of X-ray beam. The phantom was exposed using different tube voltages 68 kVp, 79 kVp and 90 kVp at a constant tube current of 32 mAs fixing a 100 cm source to image distance (SID). Scatter radiation doses measured at different heights were different for each exposure. The highest scattered radiation dose measured was 6.4 mGy at 130 cm height for 79 kVp exposure. In conclusion the measured scattered radiation doses were within the acceptable annual dose limits as recommended by NCRP 116 and ICRP 103 for patient caregiver. However, a smallest amount of radiation dose may increase the risk of cancer. Thus, the negligence must not be overlooked because it exposes the caregiver to unnecessary radiation.
    Matched MeSH terms: Scattering, Radiation
  7. Putra A, Saari NF, Bakri H, Ramlan R, Dan RM
    ScientificWorldJournal, 2013;2013:742853.
    PMID: 24324380 DOI: 10.1155/2013/742853
    A laboratory-based experiment procedure of reception plate method for structure-borne sound source characterisation is reported in this paper. The method uses the assumption that the input power from the source installed on the plate is equal to the power dissipated by the plate. In this experiment, rectangular plates having high and low mobility relative to that of the source were used as the reception plates and a small electric fan motor was acting as the structure-borne source. The data representing the source characteristics, namely, the free velocity and the source mobility, were obtained and compared with those from direct measurement. Assumptions and constraints employing this method are discussed.
    Matched MeSH terms: Scattering, Radiation
  8. Onwude DI, Hashim N, Abdan K, Janius R, Chen G
    J Sci Food Agric, 2018 Mar;98(4):1310-1324.
    PMID: 28758207 DOI: 10.1002/jsfa.8595
    BACKGROUND: Drying is a method used to preserve agricultural crops. During the drying of products with high moisture content, structural changes in shape, volume, area, density and porosity occur. These changes could affect the final quality of dried product and also the effective design of drying equipment. Therefore, this study investigated a novel approach in monitoring and predicting the shrinkage of sweet potato during drying. Drying experiments were conducted at temperatures of 50-70 °C and samples thicknesses of 2-6 mm. The volume and surface area obtained from camera vision, and the perimeter and illuminated area from backscattered optical images were analysed and used to evaluate the shrinkage of sweet potato during drying.

    RESULTS: The relationship between dimensionless moisture content and shrinkage of sweet potato in terms of volume, surface area, perimeter and illuminated area was found to be linearly correlated. The results also demonstrated that the shrinkage of sweet potato based on computer vision and backscattered optical parameters is affected by the product thickness, drying temperature and drying time. A multilayer perceptron (MLP) artificial neural network with input layer containing three cells, two hidden layers (18 neurons), and five cells for output layer, was used to develop a model that can monitor, control and predict the shrinkage parameters and moisture content of sweet potato slices under different drying conditions. The developed ANN model satisfactorily predicted the shrinkage and dimensionless moisture content of sweet potato with correlation coefficient greater than 0.95.

    CONCLUSION: Combined computer vision, laser light backscattering imaging and artificial neural network can be used as a non-destructive, rapid and easily adaptable technique for in-line monitoring, predicting and controlling the shrinkage and moisture changes of food and agricultural crops during drying. © 2017 Society of Chemical Industry.

    Matched MeSH terms: Scattering, Radiation
  9. Ng MY, Tan WS, Tey BT
    PMID: 22819608 DOI: 10.1016/j.jchromb.2012.06.043
    Fusion M13 phage with disulfide constrained heptapeptide, C-WSFFSNI-C, inserted into the minor coat protein (gpIII), has been selected in the current study as ligand in direct purification of hepatitis B core antigen (HBcAg) from unclarified Escherichia coli (E. coli) feedstock. The selected fusion phage showed strong association with the surface of the core particle. In the present study, this fusion M13 phage was immobilized onto Streamline base matrix via epoxy activation and used as adsorbent to capture HBcAg from crude E. coli homogenate. The maximum binding capacity for the adsorbent was 3.76 mg/mL with equilibrium coefficient of 1.83 mg/mL. Due to the slow uptake rate of HBcAg by M13 phage-immobilized adsorbents, a modified EBAC operation with recirculation of feedstock into the expanded bed has been investigated in this study. The introduction of feedstock recirculation has led to an 18% increase in yield; however, the purity of the eluted product was reduced by 15% compared with typical EBAC operation. The level of antigenicity exhibited by the core particles purified by both EBAC operations employed in the present study was comparable to that purified using sucrose ultracentrifugation.
    Matched MeSH terms: Scattering, Radiation
  10. Muzaffar TST, Imran Y, Iskandar MA, Zakaria A
    Med J Malaysia, 2005 Jul;60 Suppl C:26-9.
    PMID: 16381279
    Femoral interlocking nailing requires fluoroscopic assistance for insertion of the nail and distal screws. In this study, scattered radiation to the eye and hand of the operating surgeon was measured during the procedure. Thermo-luminescent dosimeter (TLD) was used to quantify the dose received by the surgeon. The mean radiation exposure time during the procedure was 3.89 minutes. The mean scattered radiation doses to the hand and eye were 0.27 mSv and 0.09 mSv per procedure respectively. These very low doses have made a surgeon very unlikely to receive more than the recommended annual dose limit set by the National Council on Radiological Protection.
    Matched MeSH terms: Scattering, Radiation
  11. Moradi F, Khandaker MU, Alrefae T, Ramazanian H, Bradley DA
    Appl Radiat Isot, 2019 Apr;146:120-126.
    PMID: 30769172 DOI: 10.1016/j.apradiso.2019.01.031
    Studies of radiation interactions with tissue equivalent material find importance in efforts that seek to avoid unjustifiable dose to patients, also in ensuring quality control of for instance nuclear medicine imaging equipment. Use of the Monte Carlo (MC) simulation tool in such characterization processes allows for the avoidance of costly experiments involving transmitted X- and γ-ray spectrometry. Present work investigates MC simulations of γ-ray transmission through tissue equivalent solid phantoms. Use has been made of a range of radionuclide gamma ray sources, 99mTc, 131I, 137Cs, 60Co (offering photons in the energy range from a few keV up to low MeV), popularly applied in medicine and in some cases for gauging in industry, obtaining the transmission spectra following their interaction with various phantom materials and thicknesses. In validation of the model, the simulated values of mass attenuation coefficients (μ/ρ) for different phantom materials and thicknesses were found to be in good agreement with reference values (NIST, 2004) to within 1.1% for all material compositions. For all of the primary photon energies and medium thicknesses of interest herein, results show that multiple scattering peaks are generally located at energies lower than 100 keV, although for the larger phantom thicknesses it is more difficult to distinguish single, double and multiple scattering in the gamma spectra. Transmitted photon spectra investigated for water, soft tissue, breast, brain and lung tissue slab phantoms are demonstrated to be practically independent of the phantom material, while a significant difference is observed for the spectra transmitted through bone that was proved to be due to the density effect and not material composition.
    Matched MeSH terms: Scattering, Radiation
  12. Liu KF, Chai HK, Mehrabi N, Yoshikazu K, Shiotani T
    ScientificWorldJournal, 2014;2014:194295.
    PMID: 24737961 DOI: 10.1155/2014/194295
    Imaging techniques are high in demand for modern nondestructive evaluation of large-scale concrete structures. The travel-time tomography (TTT) technique, which is based on the principle of mapping the change of propagation velocity of transient elastic waves in a measured object, has found increasing application for assessing in situ concrete structures. The primary aim of this technique is to detect defects that exist in a structure. The TTT technique can offer an effective means for assessing tendon duct filling of prestressed concrete (PC) elements. This study is aimed at clarifying some of the issues pertaining to the reliability of the technique for this purpose, such as sensor arrangement, model, meshing, type of tendon sheath, thickness of sheath, and material type as well as the scale of inhomogeneity. The work involved 2D simulations of wave motions, signal processing to extract travel time of waves, and tomography reconstruction computation for velocity mapping of defect in tendon duct.
    Matched MeSH terms: Scattering, Radiation
  13. Lee KW, Tan WS
    J Virol Methods, 2008 Aug;151(2):172-180.
    PMID: 18584885 DOI: 10.1016/j.jviromet.2008.05.025
    The recombinant hepatitis B virus (HBV) core antigen (HBcAg) expressed in Escherichia coli self-assembles into icosahedral capsids of about 35 nm which can be exploited as gene or drug delivery vehicles. The association and dissociation properties of the C-terminally truncated HBcAg with urea and guanidine hydrochloride (GdnHCl) were studied. Transmission electron microscopy (TEM) revealed that the dissociated HBcAg was able to re-associate into particles when the applied denaturing agents were physically removed. In order to evaluate the potential of the particles in capturing molecules, purified green fluorescent protein (GFP) was applied to the dissociated HBcAg for encapsidation. The HBcAg particles harbouring the GFP molecules were purified using sucrose density gradient ultracentrifugation and analysed using native agarose gel electrophoresis and TEM. A method for the encapsidation of GFP in HBcAg particles which has the potential to capture drugs or nucleic acids was established.
    Matched MeSH terms: Scattering, Radiation
  14. Lambak Z, Abdul Rahman F, Mokhtar MR, Tengku IA
    Opt Express, 2009 Feb 16;17(4):2926-37.
    PMID: 19219196
    The method of lines (MoL) has been developed to study coupling efficiency on hemispherical lens. In this paper, the physical shape of the lens is approximated by cascading a number of straight waveguide segments. The perfectly matched layer (PML) is applied as an absorber for the MoL to reduce numerical reflection in the simulation region. Analysis is done by calculating coupling efficiency at the plane of integration where the coupling efficiency is an overlap integral between laser diode field and fiber field. The result of coupling efficiency in this analysis is compared to the experiment and ABCD matrix. It is found that MoL gives good result accuracy.
    Matched MeSH terms: Scattering, Radiation
  15. Keck CM
    Int J Pharm, 2010 May 5;390(1):3-12.
    PMID: 19733647 DOI: 10.1016/j.ijpharm.2009.08.042
    The influence of optical parameters, additional techniques (e.g. PIDS technology) and the importance of light microscopy were investigated by comparing laser diffraction data obtained via the conventional method and an optimized analysis method. Also the influence of a possible dissolution of nanocrystals during a measurement on the size result obtained was assessed in this study. The results reveal that dissolution occurs if unsaturated medium or microparticle saturated medium is used for the measurements. The dissolution is erratic and the results are not reproducible. Dissolution can be overcome by saturating the measuring medium prior to the measurement. If nanocrystals are analysed the dispersion medium should be saturated with the nanocrystals, because the solubility is higher than for coarse micro-sized drug material. The importance of using the optimized analysis method was proven by analysing 40 different nanosuspensions via the conventional versus the optimized sizing method. There was no large difference in the results obtained for the 40 nanosuspensions using the conventional method. This would have led to the conclusion, that all the 40 formulations investigated are physically stable. However, the analysis via the optimized method revealed that from 40 formulations investigated only four were physically stable. In conclusion an optimized analysis saves time and money and avoids misleading developments, because discrimination between "stable" and "unstable" can be done reliably at a very early stage of the development.
    Matched MeSH terms: Scattering, Radiation
  16. Hambali NA, Mahdi MA, Al-Mansoori MH, Abas AF, Saripan MI
    Opt Express, 2009 Jul 06;17(14):11768-75.
    PMID: 19582091
    We have investigated the characteristics of Brillouin-Erbium fiber laser (BEFL) with variation of Erbium-doped fiber amplifier (EDFA) locations in a ring cavity configuration. Three possible locations of the EDFA in the laser cavity have been studied. The experimental results show that the location of EDFA plays vital role in determining the output power and the tuning range. Besides the Erbium gain, Brillouin gain also contributes to the performance of the BEFL. By placing the EDFA next to the Brillouin gain medium (dispersion compensating fiber), the Brillouin pump signal is amplified thereby generating higher intensities of Brillouin Stokes line. This efficient process suppresses the free running self-lasing cavity modes from oscillating in cavity as a result of higher Stokes laser power and thus provide a wider tuning range. At the injected Brillouin pump power of 1.6 mW and the maximum 1480 nm pump power of 135 mW, the maximum Stokes laser power of 25.1 mW was measured and a tuning range of 50 nm without any self-lasing cavity modes was obtained.
    Matched MeSH terms: Scattering, Radiation
  17. Chew HP, Zakian CM, Pretty IA, Ellwood RP
    Caries Res, 2014;48(3):254-62.
    PMID: 24481141 DOI: 10.1159/000354411
    BACKGROUND: Measurement of initial enamel erosion is currently limited to in vitro methods. Optical coherence tomography (OCT) and quantitative light-induced fluorescence (QLF) have been used clinically to study advanced erosion. Little is known about their potential on initial enamel erosion.

    OBJECTIVES: To evaluate the sensitivity of QLF and OCT in detecting initial dental erosion in vitro.

    METHODS: 12 human incisors were embedded in resin except for a window on the buccal surface. Bonding agent was applied to half of the window, creating an exposed and non-exposed area. Baseline measurements were taken with QLF, OCT and surface microhardness. Samples were immersed in orange juice for 60 min and measurements taken stepwise every 10 min. QLF was used to compare the loss of fluorescence between the two areas. The OCT system, OCS1300SS (Thorlabs Ltd.), was used to record the intensity of backscattered light of both areas. Multiple linear regression and paired t test were used to compare the change of the outcome measures.

    RESULTS: All 3 instruments demonstrated significant dose responses with the erosive challenge interval (p < 0.05) and a detection threshold of 10 min from baseline. Thereafter, surface microhardness demonstrated significant changes after every 10 min of erosion, QLF at 4 erosive intervals (20, 40, 50 and 60 min) while OCT at only 2 (50 and 60 min).

    CONCLUSION: It can be concluded that OCT and QLF were able to detect demineralization after 10 min of erosive challenge and could be used to monitor the progression of demineralization of initial enamel erosion in vitro.

    Matched MeSH terms: Scattering, Radiation
  18. Che HX, Yeap SP, Osman MS, Ahmad AL, Lim J
    ACS Appl Mater Interfaces, 2014 Oct 8;6(19):16508-18.
    PMID: 25198872 DOI: 10.1021/am5050949
    The synthesis of nanocomposite with controlled surface morphology plays a key role for pollutant removal from aqueous environments. The influence of the molecular size of the polyelectrolyte in synthesizing silica-iron oxide core-shell nanocomposite with open shell structure was investigated by using dynamic light scattering, atomic force microscopy, and quartz crystal microbalance with dissipation (QCM-D). Here, poly(diallydimethylammonium chloride) (PDDA) was used to promote the attachment of iron oxide nanoparticles (IONPs) onto the silica surface to assemble a nanocomposite with magnetic and catalytic bifunctionality. High molecular weight PDDA tended to adsorb on silica colloid, forming a more extended conformation layer than low molecular weight PDDA. Subsequent attachment of IONPs onto this extended PDDA layer was more randomly distributed, forming isolated islands with open space between them. By taking amoxicillin, an antibiotic commonly found in pharmaceutical waste, as the model system, better removal was observed for silica-iron oxide nanocomposite with a more extended open shell structure.
    Matched MeSH terms: Scattering, Radiation
  19. Bohari A, Hashim S, Mohd Mustafa SN
    Radiat Prot Dosimetry, 2020 Jun 24;188(3):397-402.
    PMID: 31950168 DOI: 10.1093/rpd/ncz299
    Radiation scattered throughout the room during fluoroscopy-guided interventional (FGI) procedures was quantified at different locations using nanoDot optically stimulated luminescence dosemeters. All the tube angulation imaging shows that the radiation spectrum resembled a single peak distribution. The left anterior oblique 90° shows the highest single peak distribution (28.65 mSv/h). The single peak distribution for standard anteroposterior, left anterior oblique 45° and right anterior oblique 45° imaging was 13.32, 22.99 and 17.40 mSv/h, respectively. All tube angulation shows that the position of the interventional radiologist experienced a higher radiation level compared to other staffs. The doses of radiation varied widely around the perimeter of the patient's table and changed in accordance to imaging angles during procedures. Knowledge pertaining to radiation exposure levels is integral in order to avoid adverse risks, particularly among staff.
    Matched MeSH terms: Scattering, Radiation
  20. Banjade DP, Shrestha SL, Shukri A, Tajuddin AA, Bhat M
    Australas Phys Eng Sci Med, 2002 Sep;25(3):110-8.
    PMID: 12416587
    This is a study using LiF:Mg;Ti thermoluminescent dosimeter (TLD) rods in phantoms to investigate the effect of lack of backscatter on exit dose. Comparing the measured dose with anticipated dose calculated using tissue maximum ratio (TMR) or percentage depth dose (PDD) gives rise to a correction factor. This correction factor may be applied to in-vivo dosimetry results to derive true dose to a point within the patient. Measurements in a specially designed humanoid breast phantom as well as patients undergoing radiotherapy treatment were also been done. TLDs with reproducibility of within +/- 3% (1 SD) are irradiated in a series of measurements for 6 and 10 MV photon beams from a medical linear accelerator. The measured exit doses for the different phantom thickness for 6 MV beams are found to be lowered by 10.9 to 14.0% compared to the dose derived from theoretical estimation (normalized dose at dmax). The same measurements for 10 MV beams are lowered by 9.0 to 13.5%. The variations of measured exit dose for different field sizes are found to be within 2.5%. The exit doses with added backscatter material from 2 mm up to 15 cm, shows gradual increase and the saturated values agreed within 1.5% with the expected results for both beams. The measured exit doses in humanoid breast phantom as well as in the clinical trial on patients undergoing radiotherapy also agreed with the predicted results based on phantom measurements. The authors' viewpoint is that this technique provides sufficient information to design exit surface bolus to restore build down effect in cases where part of the exit surface is being considered as a target volume. It indicates that the technique could be translated for in vivo dose measurements, which may be a conspicuous step of quality assurance in clinical practice.
    Matched MeSH terms: Scattering, Radiation
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