Displaying publications 1 - 20 of 43 in total

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  1. Fulltext A mobile ferromagnetic shape detection sensor using a Hall sensor array and magnetic imaging
    Misron N, Shin NW, Shafie S, Marhaban MH, Mailah NF
    Sensors (Basel), 2011;11(11):10474-89.
    PMID: 22346653 DOI: 10.3390/s111110474
    This paper presents a mobile Hall sensor array system for the shape detection of ferromagnetic materials that are embedded in walls or floors. The operation of the mobile Hall sensor array system is based on the principle of magnetic flux leakage to describe the shape of the ferromagnetic material. Two permanent magnets are used to generate the magnetic flux flow. The distribution of magnetic flux is perturbed as the ferromagnetic material is brought near the permanent magnets and the changes in magnetic flux distribution are detected by the 1-D array of the Hall sensor array setup. The process for magnetic imaging of the magnetic flux distribution is done by a signal processing unit before it displays the real time images using a netbook. A signal processing application software is developed for the 1-D Hall sensor array signal acquisition and processing to construct a 2-D array matrix. The processed 1-D Hall sensor array signals are later used to construct the magnetic image of ferromagnetic material based on the voltage signal and the magnetic flux distribution. The experimental results illustrate how the shape of specimens such as square, round and triangle shapes is determined through magnetic images based on the voltage signal and magnetic flux distribution of the specimen. In addition, the magnetic images of actual ferromagnetic objects are also illustrated to prove the functionality of mobile Hall sensor array system for actual shape detection. The results prove that the mobile Hall sensor array system is able to perform magnetic imaging in identifying various ferromagnetic materials.
    Matched MeSH terms: Magnets
  2. A thermostabilized magnetogenosensing assay for DNA sequence-specific detection and quantification of Vibrio cholerae
    Low KF, Karimah A, Yean CY
    Biosens Bioelectron, 2013 Sep 15;47:38-44.
    PMID: 23545172 DOI: 10.1016/j.bios.2013.03.004
    Vibrio cholerae is a human pathogen that causes mild to severe diarrheal illnesses and has major public health significance. Herein, we present a thermostabilized electrochemical genosensing assay combining the use of magnetic beads as a biorecognition platform and gold nanoparticles as a hybridization tag for the detection and quantification of V. cholerae lolB gene single-stranded asymmetric PCR amplicons as an alternative to the time-consuming classical isolation method. This thermostabilized, pre-mixed, pre-aliquoted and ready-to-use magnetogenosensing assay simplified the procedures and permitted the reaction to be conducted at room temperature. The asymmetric PCR amplicons were hybridized to a magnetic bead-functionalized capture probe and a fluorescein-labeled detection probe followed by tagging with gold nanoparticles. Electrochemical detection of the chemically dissolved gold nanoparticles was performed using the differential pulse anodic stripping voltammetry method. The real-time stability evaluation of thermostabilized assay was found to be stable for at least 180 days at room temperature (25-30°C). The analytical specificity of the assay was 100%, while its analytical sensitivity was linearly related to different concentrations of 200-mer synthetic target, purified genomic DNA, and bacterial culture with a limit of detection (LoD) of 3.9nM, 5pg/µl, and 10(3)CFU/ml, respectively. The clinical applicability of the assay was successfully validated using spiked stool samples with an average current signal-to-cut-off ratio of 10.8. Overall, the precision of the assay via relative standard deviation was <10%, demonstrating its reliability and accuracy.
    Matched MeSH terms: Magnets
  3. Fulltext An Eddy Current Testing Platform System for Pipe Defect Inspection Based on an Optimized Eddy Current Technique Probe Design
    Rifai D, Abdalla AN, Razali R, Ali K, Faraj MA
    Sensors (Basel), 2017 Mar 13;17(3).
    PMID: 28335399 DOI: 10.3390/s17030579
    The use of the eddy current technique (ECT) for the non-destructive testing of conducting materials has become increasingly important in the past few years. The use of the non-destructive ECT plays a key role in the ensuring the safety and integrity of the large industrial structures such as oil and gas pipelines. This paper introduce a novel ECT probe design integrated with the distributed ECT inspection system (DSECT) use for crack inspection on inner ferromagnetic pipes. The system consists of an array of giant magneto-resistive (GMR) sensors, a pneumatic system, a rotating magnetic field excitation source and a host PC acting as the data analysis center. Probe design parameters, namely probe diameter, an excitation coil and the number of GMR sensors in the array sensor is optimized using numerical optimization based on the desirability approach. The main benefits of DSECT can be seen in terms of its modularity and flexibility for the use of different types of magnetic transducers/sensors, and signals of a different nature with either digital or analog outputs, making it suited for the ECT probe design using an array of GMR magnetic sensors. A real-time application of the DSECT distributed system for ECT inspection can be exploited for the inspection of 70 mm carbon steel pipe. In order to predict the axial and circumference defect detection, a mathematical model is developed based on the technique known as response surface methodology (RSM). The inspection results of a carbon steel pipe sample with artificial defects indicate that the system design is highly efficient.
    Matched MeSH terms: Magnets
  4. Fulltext Analisis data pengimejan resonans magnet kefungsian: pra pemprosesan ruang menggunakan kaedah pemetaan statistik berparameter
    Ahmad Nazlim Yusoff, Mohd Harith Hashim, Mohd Mahadir Ayob, Iskandar Kassim
    Jurnal Sains Kesihatan Malaysia, 2006;4(1):21-36.
    MyJurnal
    Kajian garis pangkal pengimejan resonans magnet kefungsian (fMRI) telah dijalankan ke atas 2 orang subjek lelaki sihat (kidal dan tidak kidal) masing-masing berumur 22 dan 25 tahun. Imbasan fMRI dijalankan menggunakan sistem pengimejan resonans magnet (MRI) 1.5 T di Jabatan Radiologi, Hospital Universiti Kebangsaan Malaysia. Kajian ini menggunakan gerakanjari tangan kanan dan kiri untuk merangsang aktiviti neuron di dalam korteks serebrum. Paradigma 5 kitar aktifIrehat digunakan dengan setiap kitar mengandungi satu blok aktif dan satu blok rehat yang masing-masing mengandungi 10 siri pengukuran. Imej fMRI dianalisis menggunakan pekej perisian MatLab dan pemetaan statistik berparameter 2 (sPM2). Proses pendaftaran jasad tegar menggunakan penjelmaan afin 6 parameter dilakukan ke atas kesemua imej kefungsian berwajaran T2*. Keputusan menunjukkan bahawa pergerakan subjek adalah minimum sama ada dalam arah translasi (< 1 mm) atau putaran (< 1 ). Kesemua imej dinormalkan melalui proses peledingan tak linear menggunakan penjelmaan afin 12 parameter dan didapati sepadan dengan pencontoh yang telahpun mematuhi ruang anatomi piawai. Walau bagaimanapun, bentuk, resolusi dan kontras imej kefungsian telah berubah sedikit berbanding dengan imej asal. Pelicinan imej menggunakan kernel Gaussian isotropik 6 mm menyebabkan data imej lebih bersifat parametrik dengan kehilangan yang ketara dalam resolusi dan kontras. Pengasingan struktur yang dilakukan ke atas imej berwajaran T1 mengklaskan tisu otak kepadajirim kelabu, jirim putih dan bendalir serebrospina. Pasca pemprosesan ruang bagi imej kefungsian dan struktur menjadikan data imej bersifat parametrik dengan taburan jenis Gaussian dan sedia untuk dianalisis menggunakan model linear am dan teori medan rawak Gaussian.
    Matched MeSH terms: Magnets
  5. Anomalous Temperature Dependence of Electrical Resistivity in Mg0.6Zn0.4Fe2O4 Ferrite
    Mustafa Hj. Abdullah, Ahmad Nazlim Yusoff
    Sains Malaysiana, 1996;25.
    The electrical resistivity of Mg0.6Zn0.4Fe2O4 ferrite was measured as a function of temperature in the range 300-630 K. Two anomalies are observed in the resistivity curves for measurements during heating up. These anomalies are identified as a magnetic anomaly at the Neel temperature, TN = 598 K, while the other one at TOt = 445 K is discussed as due to the contribution of conduction from the tetrahedral sites. The anomaly at Tot was reduced in the measurements during recooling, while the anomaly at TN was disappeared completely during recooling and second cycle. These effects are discussed as due to the increase of Fe2+ ions at the octahedral sites as a result of cation redistribution at higher temperatures. A relatively small anomaly at Tot still can be observed during the second run. This is possible if the Fe2+ ions have a preference to be relocated at the tetrahedral sites at lower temperatures.
    Kerintangan elektrik Mg0.6Zn0.4Fe2O4 ferit telah diukur sebagai fungsi suhu dalam julat 300 - 630 K. Dua anomali dapat dicerap pada lengkung kerintangan bagi pengukuran semasa pemanasan. Dua anomali tersebut dikenalpasti sebagai anomali magnet pada suhu Neel, TN = 598 K, manakala yang satu lagi pada Tot = 445 K dibincangkan sebagai berpunca daripada sumbangan kekonduksian pada tapak tetrahedron. Anomali pada Tot mengurang dalam pengukuran semasa penyejukan semula pada julat suhu yang sarna, manakala anomali pada TN terus lenyap dalam pengukuran semasa penyejukan semula dan juga semasa kitar kedua. Kesan ini dibincangkan sebagai disebabkan oleh peningkatan ion Fe2+ pada tapak oktahedron daripada proses taburan semula kation pada suhu tinggi. Anomali yang berkurang pada Tot masih boleh dicerap semasa pengukuran kitar kedua. Keadaan seperti ini adalah mungkin jika ion Fe2+ mempunyai kecenderongan untuk bertempat semula pada tapak tetrahedron apabila suhu menurun.
    Matched MeSH terms: Magnets
  6. Fulltext Artifacts reduction in strain maps of tagged magnetic resonance imaging using harmonic phase
    Wang D, Fu Y, Ashraf MA
    Open Med (Wars), 2015;10(1):425-433.
    PMID: 28352731 DOI: 10.1515/med-2015-0074
    Tagged Magnetic Resonance Imaging (MRI) is a noninvasive technique for examining myocardial function and deformation. Tagged MRI can also be used in quasi-static MR elastography to acquire strain maps of other biological soft tissues. Harmonic phase (HARP) provides automatic and rapid analysis of tagged MR images for the quantification and visualization of myocardial strain. We propose a new artifact reduction method in strain maps. Image intensity of the DC component is estimated and subtracted from spatial modulation of magnetization (SPAMM) tagged MR images. DC peak interference in harmonic phase extraction is greatly reduced after DC component subtraction. The proposed method is validated using both simulated and MR acquired tagged images. Strain maps are obtained with better accuracy and smoothness after DC component subtraction.
    Matched MeSH terms: Magnets
  7. Coarsening Dynamics of an Isotropic Ferromagnetic Superfluid
    Williamson LA, Blakie PB
    Phys Rev Lett, 2017 Dec 22;119(25):255301.
    PMID: 29303307 DOI: 10.1103/PhysRevLett.119.255301
    In zero magnetic field the ground-state manifold of a ferromagnetic spin-1 condensate is SO(3) and exhibits Z_{2} vortices as topological defects. We investigate the phase-ordering dynamics of this system after being quenched into this ferromagnetic phase from a zero-temperature unmagnetized phase. Following the quench, we observe the ordering of both magnetic and gauge domains. We find that these domains grow diffusively, i.e., with domain size L(t)∼t^{1/2}, and exhibit dynamic scale invariance. The coarsening dynamics progresses as Z_{2} vortices annihilate; however, we find that at finite energy a number of these vortices persist in small clumps without influencing magnetic or gauge order. We consider the influence of a small nonzero magnetic field, which reduces the ground-state symmetry, and show that this sets a critical length scale such that when the domains reach this size the system dynamically transitions in order parameter and scaling behavior from an isotropic to an anisotropic ferromagnetic superfluid.
    Matched MeSH terms: Magnets
  8. Current and conductance modulation at elevated temperature in siliconand InAs-based spin field-effect transistors
    Osintsev D, Sverdlov V, Makarov A, Selberherr S
    Sains Malaysiana, 2013;42:205-211.
    Spin field-effect transistors (SpinFETs) are promising candidates for future integrated microelectronic circuits. A SpinFET is composed of two ferromagnetic contacts (source and drain), which sandwich a semiconductor channel. Current modulation is achieved by electrically tuning the gate voltage dependent strength of the spin-orbit interaction in the semiconductor region. We investigated the properties of SpinFETs for various parameters - the band mismatch, the barrier height between the contacts and the channel and the strength of the spin-orbit coupling, for various temperatures. We demonstrated that the creation of Schottky barriers between the channel and the contacts guarantees a pronounced modulation of the magnetoresistance sufficient to open a possibility to operate SpinFETs at room temperature. We also demonstrated that silicon fins with [100] orientation exhibit a stronger dependence on the value of the spin-orbit interaction and are thus preferable for practical realization of silicon-based SpinFETs.
    Matched MeSH terms: Magnets
  9. Design and simulation of a PWM based phase synchronous inverter for utility grid systems with 20km feeder line
    Tawfikur Rahman, Motakabber, S.M.A., Ibrahimy, M.I.
    Scientific Research Journal, 2017;14(2):17-34.
    MyJurnal
    In recent years, the utility grid system is more essential for the power
    transmission and distribution system because it cannot produce harmful
    gases or no discharge waste in the environment. PWM based phase
    synchronous invert systems are generally utilised in the high efficiency
    energy supply, long distance and higher power quality. The inverter output
    voltage depends on the coupling transformer, input sources and invert
    controllers. An inverter using a three leg IGBT has been designed for utility
    grid and simulated by using MATLAB2014a. In this paper, both sides of
    the LCL filters are used for removing the DC ripple current, reducing the
    noise and synchronous the output phase between inverter and the utility
    grid. The PWM controller has created pulse signal to control the inverter,
    electronic switches and precisely synchronise with grid line frequency. In
    this system, the input DC voltage 500V, switching frequency 1.65 kHz, grid
    frequency 50Hz, 20 km feeder (resistance, inductance and capacitance per
    unit length, which are 0.1153, 1.05e-3 and 11.33e-09 ohms/km) with 30MW
    three phase load (active and inductive reactive power which are 30e6 W
    and 2e6 var) and also a balanced utility grid load of star configuration (00,
    1200, and 2400 degree) are considered in the design. On the other hand,
    three phase transformer consists of three signal phase transformers, normal
    power 100e3, magnetization resistance and inductance which are 500 pu and
    416.67pu are considered in this design. The system conversion efficiency
    is 99.94% and 99.96%, while the total THD are 0.06% on inverter side
    and 0.04% on grid side.
    Matched MeSH terms: Magnets
  10. Fulltext Development of internet-based instrumentation for the study of hall effect
    Ariffin Abas, Abdul Halim Shaari, Zainal Abidin Talib, Zaidan Abdul Wahab
    Pertanika Journal of Science & Technology, 2014;22(1):105-112.
    MyJurnal
    The computer, together with Lab View software, can be used as an automatic data acquisition system. This project deals with the development of a computer interfacing technique for the study of Hall Effect and converting the existing automation system into a Web-based automation system. The drive board RS 217-3611 with PCI 6025E card and stepper motor RS191-8340 with a resolution of 0.1mm, was used to move a pair of permanent magnets backward and forward against the sample. The General Interface Bus (GPIB) card interfaces, together with digital nano voltmeter and Tesla meter using serial port RS232 interface, are used for measuring the potential difference and magnetic field strength respectively. Hall Effect measurement on copper (Cu) and tantalum (Ta) showed negative and positive sign Hall coefficient. Therefore, the system has electron and hole charge carriers respectively at room temperature. The parameters such as drift velocity, conductivity, mobility, Hall Coefficient and charge carrier concentration were also automatically displayed on the front panel of Lab View programming and compared with standard value. The Web-based automation system can be remotely controlled and monitored by users in remote locations using only their web browsers. In addition, video conferencing through Net Meeting has been used to provide audio and video feedback to the client.
    Matched MeSH terms: Magnets
  11. Development of magnetic porous coordination polymer adsorbent for the removal and preconcentration of Pb(II) from environmental water samples
    Al'Abri AM, Mohamad S, Abdul Halim SN, Abu Bakar NK
    Environ Sci Pollut Res Int, 2019 Apr;26(11):11410-11426.
    PMID: 30805837 DOI: 10.1007/s11356-019-04467-w
    A novel porous coordination polymer adsorbent (BTCA-P-Cu-CP) based on a piperazine(P) as a ligand and 1,2,4,5-benzenetetracarboxylic acid (BTCA) as a linker was synthesized and magnetized to form magnetic porous coordination polymer (BTCA-P-Cu-MCP). Fourier transform infrared (FTIR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), field emission scanning electron microscope(FESEM), energy-dispersive X-ray spectroscopy(EDS), CHN, and Brunauer-Emmett-Teller(BET) analysis were used to characterize the synthesized adsorbent. BTCA-P-Cu-MCP was used for removal and preconcentration of Pb(II) ions from environmental water samples prior to flame atomic absorption spectrometry(FAAS) analysis. The maximum adsorption capacity of BTCA-P-Cu-MCP was 582 mg g-1. Adsorption isotherm, kinetic, and thermodynamic parameters were investigated for Pb(II) ions adsorption. Magnetic solid phase extraction (MSPE) method was used for preconcentration of Pb(II) ions and the parameters influencing the preconcentration process have been examined. The linearity range of proposed method was 0.1-100 μg L-1 with a preconcentration factor of 100. The limits of detection and limits of quantification for lead were 0.03 μg L-1 and 0.11 μg L-1, respectively. The intra-day (n = 7) and inter-day (n = 3) relative standard deviations (RSDs) were 1.54 and 3.43% respectively. The recoveries from 94.75 ± 4 to 100.93 ± 1.9% were obtained for rapid extraction of trace levels of Pb(II) ions in different water samples. The results showed that the BTCA-P-Cu-MCP was steady and effective adsorbent for the decontamination and preconcentration of lead ions from the aqueous environment.
    Matched MeSH terms: Magnets/chemistry*
  12. Effects of Yttria Doping on Some Properties of YBa2Cu3O7-δ Superconductor
    Mustaffa Hj. Abdullah, Tan TK
    Sains Malaysiana, 1997;26.
    Samples of Y-Ba-Cu-O superconductor with nominal compositions of YBa2Cu3O7-d + x (weight %) Y2O3 (x = 0 - 15) were prepared by solid state reaction method using the Y2Cu2O5 and BaCuO2 precursors as the starting reagents. The X-ray diffraction (XRD) diffractograms for the doped samples (x> 0) show an additional non-superconducting Y2BaCuO5 (211) phase. The scanning electron microscope (SEM) micrographs show that the smaller Y2BaCuO5 grains are precipitated on the surface of the larger YBa2Cu3O7-d (YBCO) crystals. The grain size of the YBCO decreases with increasing yttria. The superconducting zero resistivity critical temperature (Tco) of the doped samples is very close to the Tco of the YBCO for x < 5, but it seems to be significantly decreasing for larger x. The transport critical current density (J) for x < 5 is enhanced due to magnetic flux pinning process by the 211 phase. However, Jc decreased for larger x due to the increase of weak links at the grain boundaries of the YBCO phase.
    Sampel superkonduktor Y-Ba-Cu-O dengan komposisi nominal YBa2Cu3O7-d + x (% berat) Y2O3 (x = 0 -15) disediakan dengan kaedah tindakbalas keadaan pepejal menggunakan bahan pelopor Y2Cu2O5 dan BaCuO2 Difraktogram pembelauan sinar-X (XRD) bagi sampel yang didop (x > 0) menunjukkan wujudnya fasa tak mensuperkonduksi Y2BaCuO5 (211). Mikrograf mikroskop imbasan elektron (SEM) menunjukkan bahawa butiran Y2BaCuO5 yang lebih kecil itu termendap di atas permukaan hablur YBa2Cu3O7-d yang lebih besar. Saiz hablur YBCO mengecil dengan peningkatan yittria. Suhu genting kerintangan sifar (Tc) bagi sampel yang didop adalah hampir dengan Tco bagi YBCO untuk x<5, tetapi menurun dengan agak cepat untuk x yang lebih besar. Ketumpatan arus genting angkutan (J) untuk x < 5 meningkat jika dibandingkan dengan YBCO disebabkan oleh proses kepinan fluks magnet oleh fasa 211. Walau bagaimanapun, Jc menurun untuk x yang lebih tinggi kerana meningkatnya hubungan lemah pada sempadan butiran fasa YBCO.
    Matched MeSH terms: Magnets
  13. Effects of aging on effective brain connectivity during speech perception processing from dynamic causal modeling perspective: an fMRI study
    Hanani Abdul Manan, Ahmad Nazlim Yusoff, Siti Zamratol-Mai Sarah Mukari
    Sains Malaysiana, 2018;47:1843-1852.
    Proses penuaan seringkali dikaitkan dengan kemerosotan pada sistem kognitif. Kemerosotan kognitif bermula seawal
    usia dua puluhan dan berterusan secara linear. Selain itu, kemerosotan kognitif juga menjadi lebih nyata dengan
    kehadiran hingar latar. Walau bagaimanapun, kesan penuaan ke atas mekanisme pemprosesan persepsi pertuturan
    menggunakan tugasan mengulang secara terus (FRT) dalam senyap dan hingar belum difahami dengan jelas. Dalam
    kajian ini, pengimejan resonans magnet kefungsian (fMRI) digunakan untuk membandingkan kesan penuaan ke atas
    kehubungan efektif otak yang terhasil daripada tugasan FRT ke atas subjek normal dengan empat kumpulan umur yang
    berlainan iaitu 20 - 29 tahun (n = 15), 30 - 39 tahun (n = 15), 40 - 49 tahun (n = 10) dan 50 - 65 tahun (n = 14). Satu siri
    lima perkataan yang diselang-seli dalam keadaan hingar dengan senyap diberikan secara auditori. Pemetaan statistik
    berparameter (SPM8) dan pemodelan dinamik penyebab (DCM10) digunakan untuk menentukan kehubungan efektif otak.
    Kawasan yang terlibat dalam pembinaan model kehubungan efektif otak adalah STG, HG dan PCG. Model optimum yang
    dipilih dalam kajian ini adalah model yang menunjukkan keseimbangan antara ketepatan dan kesukaran. Keputusan
    fMRI kehubungan efektif menunjukkan bahawa komunikasi antara intrahemisfera tidak berubah dengan menggunakan
    tugasan FRT ini apabila seseorang semakin berusia, tetapi komunikasi antara interhemisfera menjadi semakin kompleks.
    Matched MeSH terms: Magnets
  14. Electrical and magneto-transport properties of magneto-resistive La 0.7 Ca 0.28 Sr 0.2 MnO3 prepared at different sintering temperature
    Ewe L, Ramli R, Lim K, Abd-Shukor R
    Sains Malaysiana, 2012;41:761-768.
    The effects of strontium doping on the electrical and magneto-transport properties of magneto resistive La0.7Ca0.28Sr0.02MnO3 at different sintering temperatures have been studied. The samples were prepared by the co-precipitation technique (COP) and sintered at 1120, 1220 and 1320 oC. XRD patterns revealed that the samples have an orthorhombic structure and the diffraction patterns can be indexed with the Pbnm space group. The insulator metal transition, TIM increased linearly from 261 K to 272 K with the increase in sintering temperature. The magnetoresistance (MR) measurements were made in magnetic fields from 0.1 to 1 T at room temperature. The percentage of MR increased with increasing of magnetic field and sintering temperature for all samples. The electrical resistivity data were fitted with several equations in the metallic (ferromagnetic) and insulator (paramagnetic) regime. The density of states at the Fermi level N(EF) and the activation energy (Ea) of electron hopping were estimated by using variable range hopping and small polaron hopping model.
    Matched MeSH terms: Magnets
  15. Fulltext Electromagnetic Characterization of a Multiwalled Carbon Nanotubes-Silver Nanoparticles-Reinforced Polyvinyl Alcohol Hybrid Nanocomposite in X-Band Frequency
    Yusof Y, Moosavi S, Johan MR, Badruddin IA, Wahab YA, Hamizi NA, et al.
    ACS Omega, 2021 Feb 16;6(6):4184-4191.
    PMID: 33644542 DOI: 10.1021/acsomega.0c04864
    This study presents the electromagnetic (EM) characterization of a multiwalled carbon nanotubes (MWCNT)-silver nanoparticles (AgNP)-reinforced poly(vinyl alcohol) (PVA) hybrid nanocomposite fabricated via the solution mixing technique. Primarily, the structure and morphological properties of the PVA/MWCNT-AgNP hybrid nanocomposite are confirmed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The complex permittivity (ε*) and permeability (μ*), as well as the electromagnetic scattering parameters are measured using a PNA network analyzer equipped with X-band waveguide. The results showed an enhanced permittivity (ε' ≈ 25) value of the hybrid nanocomposite in the frequency range of 8-12 GHz. However, the permeability decreased to almost zero (μ' ≈ 0.4) since the inclusion of AgNP with an average particle size of 40 nm is not susceptible to magnetization and causes higher magnetic losses (tan δμ) than dielectric losses (tan δε). Remarkably, the hybrid nanocomposite reduced transmission of electromagnetic (EM) wave by nearly 60% in comparison to PVA/MWCNT. This is attributed to the enhanced absorption and reflection at the nanotubes, and metal-dielectric interfaces have induced multiple internal reflections owing to the porous structure of the nanocomposite. The prospect of the PVA/MWCNT-AgNP hybrid nanocomposite is favorable as a thin absorbing material for EM shielding applications.
    Matched MeSH terms: Magnets
  16. Fulltext Enhanced Recyclable Magnetized Palm Shell Waste-Based Powdered Activated Carbon for the Removal of Ibuprofen: Insights for Kinetics and Mechanisms
    Wong KT, Yoon Y, Jang M
    PLoS One, 2015;10(10):e0141013.
    PMID: 26496196 DOI: 10.1371/journal.pone.0141013
    A novel preparation method of magnetized palm shell waste-based powdered activated carbon (MPPAC, avg. size 112 μm) was developed. The prepared MPPAC was assessed by several physicochemical analyses, and batch tests were performed for ibuprofen (IBP) removal. Field emission scanning electron microscopy (FESEM) and N2 gas isotherms revealed that magnetite and maghemite were homogeneous and deposited mostly on the surface of PPAC without a significant clogging effect on the micropores. Isotherm results showed that 3.8% Fe (w/w) impregnated PPAC [MPPAC-Fe(3.8%)] had about 2.2-fold higher maximum sorption capacity (157.3 mg g-1) and a 2.5-fold higher sorption density (0.23 mg m-2) than pristine PPAC. Both Fourier-transform infrared spectroscopy (FTIR) and isotherm data indicated that the high sorption capacity and density of IBP by MPPAC was primarily attributable to donor-acceptor complexes with the C = O group and dispersive π-π interactions with the carbon surface. Based on kinetic and repeated adsorption tests, pore diffusion was the rate-limiting step, and MPPAC-Fe(3.8%) had about 1.9~2.8- and 9.1~15.8-fold higher rate constants than MPPAC-Fe(8.6%) and palm shell-waste granular activated carbon (PGAC, avg. size 621 μm), respectively. MPPAC showed almost eight fold greater re-adsorption capacity than PPAC due to a thermal catalytic effect of magnetite/maghemite.
    Matched MeSH terms: Magnets
  17. Fulltext Fabrication of size-tunable nanocrystalline cobalt particles in propylene glycol
    Balela, M.D.L., Lockman, Z., Azizan, A., Matsubara, E., Amorsolo , A.V. Jr.
    Journal of Nuclear and Related Technologies, 2009;2009(1):190-198.
    MyJurnal
    Monodispersed and size-tunable nanocrystalline cobalt (Co) particles in the range of 100 to 400 nm are prepared by the reduction of Co(II) species in propylene glycol. Control of the particle size is achieved by varying the initial Co(II) species concentration and by the addition of nucleating agents. Smaller Co particles are produced with increasing amounts of Co(II) species and in the presence of nucleating agents. X-ray diffraction analysis (XRD) shows that the Co particles are predominantly face-centered cubic crystals of about 8-14 nm. The Co particles are also ferromagnetic at room temperature.
    Matched MeSH terms: Magnets
  18. Fulltext Facile aerobic construction of iron based ferromagnetic nanostructures by a novel microbial nanofactory isolated from tropical freshwater wetlands
    Jacob PJ, Masarudin MJ, Hussein MZ, Rahim RA
    Microb Cell Fact, 2017 Oct 11;16(1):175.
    PMID: 29020992 DOI: 10.1186/s12934-017-0789-3
    BACKGROUND: Iron based ferromagnetic nanoparticles (IONP) have found a wide range of application in microelectronics, chemotherapeutic cell targeting, and as contrast enhancers in MRI. As such, the design of well-defined monodisperse IONPs is crucial to ensure effectiveness in these applications. Although these nanostructures are currently manufactured using chemical and physical processes, these methods are not environmentally conducive and weigh heavily on energy and outlays. Certain microorganisms have the innate ability to reduce metallic ions in aqueous solution and generate nano-sized IONP's with narrow size distribution. Harnessing this potential is a way forward in constructing microbial nanofactories, capable of churning out high yields of well-defined IONP's with physico-chemical characteristics on par with the synthetically produced ones.

    RESULTS: In this work, we report the molecular characterization of an actinomycetes, isolated from tropical freshwater wetlands sediments, that demonstrated rapid aerobic extracellular reduction of ferric ions to generate iron based nanoparticles. Characterization of these nanoparticles was carried out using Field Emission Scanning Electron Microscope with energy dispersive X-ray spectroscopy (FESEM-EDX), Field Emission Transmission Electron Microscope (FETEM), Ultraviolet-Visible (UV-Vis) Spectrophotometer, dynamic light scattering (DLS) and Fourier transform infrared spectroscopy (FTIR). This process was carried out at room temperature and humidity and under aerobic conditions and could be developed as an environmental friendly, cost effective bioprocess for the production of IONP's.

    CONCLUSION: While it is undeniable that iron reducing microorganisms confer a largely untapped resource as potent nanofactories, these bioprocesses are largely anaerobic and hampered by the low reaction rates, highly stringent microbial cultural conditions and polydispersed nanostructures. In this work, the novel isolate demonstrated rapid, aerobic reduction of ferric ions in its extracellular matrix, resulting in IONPs of relatively narrow size distribution which are easily extracted and purified without the need for convoluted procedures. It is therefore hoped that this isolate could be potentially developed as an effective nanofactory in the future.

    Matched MeSH terms: Magnets/chemistry*
  19. Fluoride adsorption by doped and un-doped magnetic ferrites CuCe(x)Fe(2-x)O4: Preparation, characterization, optimization and modeling for effectual remediation technologies
    Rehman MA, Yusoff I, Alias Y
    J Hazard Mater, 2015 Dec 15;299:316-24.
    PMID: 26143194 DOI: 10.1016/j.jhazmat.2015.06.030
    A series of doped and un-doped magnetic adsorbents CuCexFe2-xO4 (x=0.0-0.5) for fluoride were prepared with the micro-emulsion method. Fluoride adsorption was optimized for solution pH, temperature, contact time, and initial concentration and was monitored via normal phase ion chromatography (IC). The effect of concomitant anions was also explored to perform and simulate competitive fluoride adsorption in real water samples. Optimal adsorption was discovered by a simple quadratic model based on central composite design (CCD) and the response surface method (RSM). The adsorption, electrochemical and magnetic properties were compared between doped and un-doped ferrites. Doped ferrites (x=0.1-0.5) were found to be superior to un-doped ferrites (x=0) regarding the active sites, functional groups and fluoride adsorption. The characterization, optimization and application results of the doped ferrites indicated enhanced fluoride adsorption and easy separation with a simple magnet.
    Matched MeSH terms: Magnets
  20. Fulltext Giant Magnetoresistance Sensors: A Review on Structures and Non-Destructive Eddy Current Testing Applications
    Rifai D, Abdalla AN, Ali K, Razali R
    Sensors (Basel), 2016;16(3):298.
    PMID: 26927123 DOI: 10.3390/s16030298
    Non-destructive eddy current testing (ECT) is widely used to examine structural defects in ferromagnetic pipe in the oil and gas industry. Implementation of giant magnetoresistance (GMR) sensors as magnetic field sensors to detect the changes of magnetic field continuity have increased the sensitivity of eddy current techniques in detecting the material defect profile. However, not many researchers have described in detail the structure and issues of GMR sensors and their application in eddy current techniques for nondestructive testing. This paper will describe the implementation of GMR sensors in non-destructive testing eddy current testing. The first part of this paper will describe the structure and principles of GMR sensors. The second part outlines the principles and types of eddy current testing probe that have been studied and developed by previous researchers. The influence of various parameters on the GMR measurement and a factor affecting in eddy current testing will be described in detail in the third part of this paper. Finally, this paper will discuss the limitations of coil probe and compensation techniques that researchers have applied in eddy current testing probes. A comprehensive review of previous studies on the application of GMR sensors in non-destructive eddy current testing also be given at the end of this paper.
    Matched MeSH terms: Magnets
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