Displaying publications 1 - 20 of 2561 in total

  1. Yahya M.D., Lung C, Pinnas YL
    Sains Malaysiana, 1996;25(1):77-86.
    The levels of malondialdehyde (MDA)-specific antibodies in lupus-prone MRL/ lpr mice of different ages were compared to those against DNA. These mice elicited anti-MDA antibodies earlier and in higher levels that anti-DNA antibodies. The levels of immune complexes containing MDA adducts were also higher in these mice when compared to 3 other non-lupus strains. MDA binding to a 100 kDa serum protein was observed in 3 and 5 month old mice. Immune complexes involving anti-MDA antibodies and MDA adducts may represent an additional mechanism that contributes to disease pathogenesis in these mice.
  2. Nor Azlin M, Lyn SK
    Sains Malaysiana, 2011;40(12):1461-1465.
    A controlled, single blinded experimental study was conducted to determine the effects of passive joint mobilization on pain and stairs ascending-descending time in subjects with knee osteoarthritis (OA knee). A total of 22 subjects aged 40 and above with mild and moderate OA knee were assigned to either passive knee mobilization plus conventional physiotherapy (experimental group) or conventional physiotherapy alone (control group). Both groups received 2 therapy sessions per week, for 4 weeks. A blinded assessor measured pain with Visual analogue scale and stairs ascending-descending time with Aggregated Locomotor Function test, at baseline and at week 4. There was a significant reduction in pain among subjects in the experimental group (18.07 mm, t = 3.48, p = 0.01) compared to the control group (6.66 mm, t = 0.44, p = 0.67). Non-significant clinical difference was found in stairs ascending-descending time between the two groups (i.e. 6.25s in the experimental group versus 6.78 s in the control group, F(1,10) = 0.70, p = 0.42). No significant correlation was found between pain score and stairs ascending-descending time, r = 0.34, p = 0.16. The addition of passive joint mobilization to conventional physiotherapy reduced pain but not stairs ascending-descending time among subjects with knee osteoarthritis.
  3. Ashkan Shafiee, Muhamad Mat Salleh, Muhammad Yahaya
    HOMO and LUMO of organic compounds are basic parameters for the design and fabrication of an organic solar cell. This paper presents a technique to obtain HOMO and LUMO of an n-type polymer of [6,6]-phenyl C61-butyric acid 3-ethylthiophene ester (PCBE) and a p-type polymer of poly (3-octyl-thiophene-2, 5-diyl) (P3OT). The energy of band gap for each material has been calculated using optical absorption spectrum. Cyclic Voltammetry was used to estimate the oxidation potential and energy band diagram consequently. The experiments were carried out in a three-electrode cell consisting of a platinum working electrode, a platinum counter electrode and a SCE reference electrode. P3OT showed energy band gap equal to 1.83 eV with HOMO and LUMO equal to 5.59 eV and 3.76 eV, respectively. PCBE showed energy band gap equal to 1.96 eV with HOMO and LUMO equal to 5.87 eV and 3.91 eV, respectively. Based on energy band diagram that was constructed from this experimental result, the couple materials may be successfully used to fabricate the feasible organic solar cells.
  4. Noriza Ahmad Zabidi, Hasan Abu Kassim, Shrivastava KN
    Magnetic induction in the superconductor (B=H +4πM) in the zero field cooled samples (ZFC) is not equal to zero. Depending upon the chemical environment it has negative value in some and positive values in some others. In the field cooled samples, the magnetization becomes paramagnetic. We have calculated the band structure of one layer of FeAs lattice with spin polarized as well as unpolarized orbitals as a function of doping by Li atoms. For n number of Li atoms (n=0, 1,…, 4), we calculated the band gap at all of the k-points as well as the Fermi energy. The reduced normal state gap was found to lead to superconductivity.
  5. Shahriari E, Mahmood Mat Yunus W, Zainal Abidin Talib, Elias Saion
    The non-linear refractive index of Ag nano-fluids prepared by γ-radiation method was investigated using a single beam z-scan technique. Under CW 532 nm laser excitation with power output of 40 mW, the Ag nano-fluids showed a large thermal-induced non-linear refractive index. In the present work it was determined that the non-linear refractive index for Ag nano-fluids is -4.80×10-8 cm2/W. The value of Δn0 was calculated to be -2.05×10-4. Our measurements also confirmed that the non-linear phenomenon was caused by the self-defocusing process making them good candidates for non linear optical devices.
  6. Fahmi Fariq Muhammad, Khaulah Sulaiman
    Dihexyl-sexithiophene (DH6T) was doped with tris (8-hydroxyquinolinate) aluminum (Alq3) to prepare blends of DH6T/ Alq3 by dissolving the mixture in the chloroform/hexane co-solvent. Solid films with different thickness deposited on quartz substrates were obtained from the blends via casting process. Optical absorption spectroscopy has been performed to measure the optical band gap of pure and doped DH6T as well as variations in the band gap with dopant concentration (weight %). This variation in optical band gap with dopant concentration was determined quantitatively with fitted and extrapolated techniques and observed qualitatively from the red shift appeared along the optical absorption spectra. The results showed that within a specific dopant content, the optical energy gap, Eg of DH6T decreases from 2.69 eV to 1.8 eV with increasing dopant concentration to 23.1%.
  7. Woon C, Gopir G, Othman A
    We determined theoretically the confined electron states in a colloidal core-shell CdTe-CdS quantum dot system with CdTe as the core material with electron effective mass 0.095 me, CdS as barrier material of electron effective mass 0.25 me and having conduction band offset of 0.265 eV. Based on the one band effective mass approximation, the Schrödinger equation of this system with BenDaniel-Duke Hamiltonian is numerically solved using the finite difference method to obtain the energy level and wave function of the electron confined states. These electronic parameters are obtained by diagonalising the resultant N×N Hamiltonian matrix for principal quantum number n=l – 3, orbital quantum number l=0 – 3 and dot size r=10 – 100 Å. For comparison, we also analytically solve the Schrödinger equation with classical Hamiltonian and similar input parameters to determine the electronic properties. There is good agreement in the results of these two computational methods, where specifically their energy levels differ by less than 15%.
  8. Goh BT, Muhamad Rasat Muhamad, Saadah Abdul Rahman
    Optical constants derived from optical transmission (T) and reflectance (R) spectra in the wavelength range of 220 to 2200 nm are presented in this paper for hydrogenated silicon (Si:H) thin films deposited by plasma enhanced chemical vapor deposition (PECVD) using the layer-by-layer (LBL) deposition technique. The films were deposited on quartz substrate by decomposition of SiH4 and H2 gases at flow-rate of 5 sccm and 20 sccm, respectively. The substrate temperature, deposition pressure and deposition rate are 100°C, 0.8 mbar and 2.8 nm/s, respectively. The as-prepared films were annealed in nitrogen for one hour at annealing temperatures of 400°C, 600°C, 800°C and 1000°C. The as-prepared film thickness of 301 nm decreased to 260 nm when samples were annealed at 1000°C. The refractive indices (~ 3.0 to 3.4) of annealed films were determined from the interference fringes of transmission spectrum following Manifacier and Davies methods. The electronic transition from valence band to conduction band in these films are characterized from the optical energy gap; EG (~1.64 to 2.41 eV), the dispersion energy; Ed (~26.4 to 34.0 eV) and the oscillator strength; Eo (~2.8 to 3.2 eV). It is interesting to note that EG is lowest for the films annealed at temperature of 600°C which has the lowest hydrogen content, CH in the film. Evidence of the presence of nanocrystallites formed in amorphous matrix is also observed for the films annealed at temperatures above 600°C.
  9. Okhunov A, Hasan Abu Kassim, Usmanov P
    In this paper, a method of defining the even-even deformed nuclei inertial parameters is suggested. Calculations for isotopes 162-168Hf and 164-176Yb are listed. The parameters of inertia of rotational nuclei are also defined. Dependence of the parameters of inertia on the nucleons number is shown.
  10. Abd Rahim A, Hashim M, Ali N
    In this work we prepared germanium nanostructures by means of filling the material inside porous silicon (PS) using conventional and cost effective technique, thermal evaporator. The PS acts as patterned substrate. It was prepared by anodization of silicon wafer in ethanoic hydrofluoric acid (HF). A Ge layer was then deposited onto the PS by thermal evaporation. This was followed by deposition of Si layer by thermal evaporation and anneal at 650οC for 30 min. The process was completed by Ni metal deposition using thermal evaporator followed by metal annealing of 400οC for 10 min to form metal semiconductor metal (MSM) photodetector. Structural analysis of the samples was performed using energy dispersive x-ray analysis (EDX), scanning electron microscope (SEM), X-ray diffraction (XRD) and Raman spectroscopy (RS). EDX spectrum suggests the presence of Ge inside the pores structure. Raman spectrum showed that good crystalline structure of Ge can be produced inside silicon pores with a phase with the diamond structure by (111), (220) and (400) reflections. Finally current-voltage (I-V) measurement of the MSM photodetector was carried out and showed lower dark currents compared to that of Si control device. Interestingly the device showed enhanced current gain compared to Si device which can be associated with the presence of Ge nanostructures in the porous silicon.
  11. Ayub Mohd Yatim, Norazmir Md Nor
    Kajian ini dijalankan untuk menentukan kesan suplemen puri jambu batu merah (Psidium guajava) ke atas aktiviti enzim antioksidan, fungsi ginjal dan fungsi hati pada tikus teraruh obesiti. Sebanyak 30 ekor tikus Sprague-Dawley jantan dibahagi 5 kumpulan (kawalan negatif dan positif, CN dan CP (air suling); dos rendah, LDG (500 mg/kg bb); dos sederhana, MDG (1000 mg/kg bb); dos tinggi, HDG (2000 mg/kg bb). Suplemen puri jambu merah diberi bersama diet tinggi lemak selama 6 minggu. Pada akhir kajian, tikus dipuasa semalaman dan dibedah untuk kajian biokimia darah. Pengurangan signifikan dalam berat badan diperhatikan dalam kumpulan rawatan berbanding CN dan CP. Aktiviti spesifik seperti glutation peroksidase (GPx), glutatione redutase (GR) dan superoksida dismutase (SOD) pada tikus teraruh obesiti meningkat berbanding CN. Ujian fungsi ginjal bagi kepekatan urea menurun secara signifikan pada LDG (4.28±0.69 mmol/L), MDG (4.35±0.87 mmol/L) dan HDG (3.85±0.71 mmol/L) berbanding CN (7.02±1.81 mmol/L) masing-masing. Ujian fungsi hati bagi protein total, globulin, nisbah AG dan alanin aminotransferase (ALT) menunjukkan perbezaan signifikan LDG, MDG dan HDG berbanding CN. Nilai jumlah protein bagi MDG (72.67±3.65 g/L) dan HDG (76.00±2.49 g/L) lebih rendah berbanding CN (80.11±1.98 g/L). Nilai globulin bagi LDG (34.17±3.43 g/L), MDG (32.17±1.83 g/L) dan HDG (35.00±3.41 g/L) juga lebih rendah berbanding CN (39.67±0.82 g/L). Nilai nisbah AG bagi LDG (1.22±0.16), MDG (1.28±0.07) dan HDG (1.19±0.14) berbeza secara signifikan dengan CN (1.03±0.08). Nilai ALT bagi LDG (55.83±15.12 U/L), MDG (50.67±22.65 U/L) dan HDG (57.50±8.48 U/L) lebih rendah berbanding CN (77.00±16.26 U/L), masing-masing. Kesimpulannya, suplemen puri jambu merah bermanfaat dalam meningkatkan aktiviti enzim antioksidan dan mencegah komplikasi obesiti yang berhubungkait dengan fungsi ginjal dan hati.
  12. Sharifabad ME, Mastura Shafinaz Zainal Abidin, Shaharin Fadzli Abd Rahman, Abdul Manaf Hashim, Abdul Rahim Abdul Rahman, Nurul Afzan Omar, et al.
    Gallium nitride with wurtzite crystal structure is a chemically stable semiconductor with high internal spontaneous and piezoelectric polarization, which make it highly suitable materials to create very sensitive and robust sensors for the detection of ions, gases and liquids. Sensing characteristics of an open-gate liquid-phase sensor fabricated on undoped-AlGaN/GaN high-electron-mobility-transistor (HEMT) structure in aqueous solution was investigated. In ambient atmosphere, the open-gate undoped AlGaN/GaN HEMT clearly showed only the presence of linear region of currents while Si-doped AlGaN/GaN showed the linear and saturation regions of currents, very similar to those of gated devices. This seems to show that very low Fermi level pinning by surface states exists in undoped AlGaN/GaN sample. In aqueous solution, the typical current-voltage (I-V) characteristics of HEMTs with good gate controllability were observed. The potential of the AlGaN surface at the open-gate area is effectively controlled via aqueous solution by Ag/AgCl reference gate electrode. The open-gate undoped AlGaN/GaN HEMT structure is capable of stable operation in aqueous electrolytes and exhibit linear sensitivity, and high sensitivity of 1.9 mA/pH or 3.88 mA/mm/pH at drain-source voltage, VDS = 5 V was obtained. Due to large leakage current where it increases with the negative reference gate voltage, the Nernstian’s like sensitivity cannot be determined. Suppression of current leakage is likely to improve the device performance. The open-gate undoped-AlGaN/GaN structure is expected to be suitable for pH sensing application.
  13. Lim V, Nowshad Amin, Foong C, Ibrahim Ahmad, Azami Zaharim, Rozaidi Rasid, et al.
    Kertas ini membentangkan kesan dua teknik pengaktifan bermangkin yang berbeza terhadap prestasi terma bagi penyebar haba cip balikan. Penyaduran nikel tanpa elektrik digunakan sebagai salah satu teknik saduran kerana ia boleh membentuk satu lapisan nikel yang ketebalannya seragam ke atas substrat kuprum. Proses pengaktifan bermangkin perlu dilakukan dahulu untuk mengenapkan sesetengah atom nikel ke atas substrat kuprum, supaya enapan nikel mampu untuk memangkinkan proses penurunan yang seterusnya. Dua jenis teknik pengakitfan telah dikaji, iaitu pemulaan galvani dan penyaduran nipis nikel-kuprum. Ujian simpanan suhu tinggi telah dijalankan untuk mengkaji takat resapan antara logam bagi lapisan nikel and kuprum. Kemeresapan terma bagi penyebar haba telah dikaji dengan menggunakan peralatan Nano-flash. Keputusan yang diperolehi menunjukkan bahawa penyebar haba yang diproses dengan penyaduran nipis nikel-kuprum mempunyai nilai kemeresapan terma (35-65 mm2 s-1) yang lebih rendah berbanding dengan penyebar haba yang diproses dengan teknik pemulaan galvani (60-85 mm2 s-1). Selain daripada itu, kajian ini juga menemui ketebalan lapisan antara logam nikel-kuprum dalam penyebar haba ini bertambah daripada 0.2 μm pada keadaan asal kepada 0.55 μm selepas 168 jam simpanan suhu tinggi. Lapisan antara logam nikel-kuprum mempunyai kekonduksian terma yang lebih rendah berbanding dengan kuprum tulen, ini telah merendahkan kemeresapan terma bagi penyebar haba. Kesimpulannya, teknik pemulaan galvani meyediakan prestasi terma yang lebih baik untuk penyebar haba yang digunakan dalam pembungkusan semikonduktor.
  14. Wan Zurina Samad, Mohd Ambar Yarmo, Muhamad Mat Salleh, Ashkan Shafiee
    This paper reports on structural, optical transmittance and electrical properties of fluorine-doped tin oxide (FTO) thin films deposited using an inkjet printer. The FTO ink was synthesized from a mixture of tin chloride pentahydrate (SnCl4.5H2O) and ammonium fluoride (NH4F) solutions. The thin films were deposited on glass substrates at ambient temperature or heated at 40oC and 60oC. The surface electronic state and the elemental composition of the thin films were analyzed using XPS spectroscopy. The spectra of the FTO thin films revealed that tin, oxygen, fluoride and carbon were present in the samples. The signals corresponding to Sn 3d5/2, O1s, and F1s were found at 486.6 eV, 530.5 eV and 684.5 eV, respectively. XRD analysis showed that the FTO films were in the form of crystalline with cassiterite shape. The optical and electrical properties of the films were affected by the deposition temperatures. It was observed the film deposited at 40oC has the optimum optical transmittance and sheet resistivity which were 91%T and 16 Ω/, respectively.
  15. Theyirakumar J, Gopir G, Yatim B, Megat Mahmud P, Hoe T, Sanusi H
    An ultraviolet A (UVA) radiation intensity sensor with responsivity in the wavelength range of 320-360 nm was developed based on a gallium nitride (GaN) photodiode. In this sensor system, a GaN photodiode in reverse-biased mode converts the radiation intensity into current, which was then converted and amplified into an output voltage by a transimpedance amplifier (TIA), or current-voltage converter, consisting of an operational amplifier and a feedback resistor. For a narrowband UV source, the radiation intensity could be calculated from the values of the output voltage, feedback
    resistor, photodiode responsivity and photodiode effective area. The sensor was tested by performing measurements over different values of UV source wavelength, source distance, ambient temperature and sampling time. For calibration with a broadband UV source, the GaN-UVA sensor was used simultaneously with a standard Si-UVA sensor to measure solar radiation. The observed linear relationship between the sensors’ outputs enables us to convert the output voltage of the GaN-UVA sensor to UVA intensity. Thus, we have successfully developed, tested and calibrated an ultraviolet A radiation sensor based on the GaN photodiode.
  16. Muhamad Ramdzan Buyong, Norazreen Abd Aziz, Burhanuddin Yeop Majlis
    The CMOS standard process with advantage of simplicity in term of design and fabrication process compatibility has triggered the invention of MEMS very low capacitive pressure sensor, (MEMS-VLCPS). In this paper the development of the whole structure of MEMS-VLCPS that involves the design simulation, fabrication and testing is described. The novelty of this work lies in the design and fabrication process itself. A new technique in fabricating thin sensor membrane of VLCPS using seal-off techniques is also presented. The physical structure of the membrane consists of parallel plate. The top plate acts as the flexible electrode membrane and the bottom plate acts as the counter electrode membrane. Both plates are separated by absolute air gap with fixed end at both sides. As a result, it was found that the etch-opening holes of 0.8 μm and seal-off thickness of 4000 Å gave the optimum sealing surface. The percentage of relative capacitance change is extracted from the reference capacitance measurement. Air gap thickness of 0.3 μm gives the highest percentage of PRCC showing that smaller air gap thickness provides a larger change in capacitance value.
  17. Yuzine Esa, Khairul Adha A. Rahim, Siti Shapor Siraj, Muhammad Fadhil Syukri, Siti Khalijah Daud, Ho GC, et al.
    Sains Malaysiana, 2011;40:1087-1095.
    This study examined the genetic characteristics of twenty-six microsatellite primers developed from three cyprinid fishes (Cyprinus carpio Linnaeus, Barbus barbus Linnaeus and Barbonymus gonionotus Bleeker) in two indigenous mahseer. The Tor douronensis Valenciennes were randomly collected from two locations in Sarawak (N=52), while Tor tambroides Bleeker were obtained from Peninsular Malaysia (N=56). A total of ten and twelve primers were successfully amplified producing four and five polymorphic loci in T. douronensis and T. tambroides, respectively. The number of alleles per locus ranging from 2 to 5 in T. douronensis and 2 to 7 in T. tambroides. A significant deviation from Hardy-Weinberg equilibrium (HWE) was observed at three loci (Barb37, Barb59 and Barb62) in one or more populations in T. tambroides while two loci (Barb37 and Barb62) were deviated in T. douronensis population of Batang Ai. Population structure analysis showed low level of inter-population genetic differentiation in both mahseer. Overall, the identified microsatellite loci should be useful in analysing T. douronensis and T. tambroides natural populations.
  18. Norazrina Azmi, Loh WT, Siti Suriani Omar, Juriyati Jalil, Aishah Adam
    Sains Malaysiana, 2011;40:1097-1103.
    The aqueous extract of Prismatomeris glabra root has been used traditionally in Malaysia by the aborigines and certain rural Malays for its ergogenic effects, to maintain wellness and to enhance physical stamina. It has also been used as an aphrodisiac for generations in the east coast of Peninsular Malaysia. Previous studies have shown that plants with ergogenic effects may also act as a stimulant and impair cognitive function. Therefore, we seek to investigate the effects of P. glabra on non-spatial memory in male Sprague Dawley rats using object recognition test. Trial rats were injected intraperitoneally with an aqueous extract of P. glabra roots at doses of 50 and 100 mg/kg for the acute (30 min) and subacute (7 days) studies. Scopolamine (0.3 mg/kg) was used as a positive control only in the acute study meanwhile control rats were injected with saline. The locomotor activity of rats was also determined in the same test. We demonstrated that groups treated with 50 and 100 mg/kg of the extract lost their ability to discriminate the novel from familiar object in choice phase and did not alter the locomotor activity in both studies. Our results also indicated that the deficits in non-spatial working memory occured at these doses were not due to impaired locomotor activity.
  19. Hossain M, Oh MJ
    Sains Malaysiana, 2011;40:1049-1052.
    Lymphocystis disease (LCD) in fishes is caused by the agent called lymphocystis disease virus (LCDV). LCDV is a chronic and benign virus. The disease affects 96 species of marine and fresh water fishes ranged among 34 families in the world. Affected fish with LCD has a typical external symptom with clusters consisted of enormously hypertrophied dermal cells on the skin and fins. The hypertrophied cells, generally named lymphocystis cells, have a thick hyaline capsule, an enlarged nucleus and prominent basophilic cytoplasmic inclusions. Among the four species of fishes, olive flounder Paralichthys olivaceus, and rockfish Sebastes schlegeli were marine cultured fish, and gourami Trichogaster leeri and painted glassfish Channa baculis were freshwater ornamental fish. Although LCD causes low mortality, the disfigurement of infected fish can make them unsellable. Thus LCD has resulted in an important economic loss in the aquaculture industry. This study of histopathology may be adequate for a presumptive diagnosis of lymphocystis diseases both in marine and freshwater fish species.
  20. Yap C, Chee M, Shamarina S, Edward F, Chew W, Tan S
    Sains Malaysiana, 2011;40:1053-1064.
    Coastal water samples were collected from 20 sampling sites in the southern part of Peninsular Malaysia. Seven physico-chemical parameters were measured directly in-situ while water samples were collected and analysed for 6 dissolved trace metal concentrations. The surface water (0-20 cm) physico-chemical parameters including temperature, salinity, dissolved oxygen (DO), pH, total dissolved solids (TDS), specific conductance (SpC) and turbidity while the dissolved trace metals were Cd, Cu, Fe, Ni, Pb and Zn. The ranges for the physico-chemical parameters were 28.07-35.6ºC for temperature, 0.18-32.42 ppt for salinity, 2.20-12.03 mg/L for DO, 5.50-8.53 for pH, 0.24-31.65 mg/L for TDS, 368-49452 μS/cm for SpC and 0-262 NTU for turbidity while the dissolved metals (mg/L) were 0.013-0.147 for Cd, 0.024-0.143 for Cu, 0.266- 2.873 for Fe, 0.027-0.651 for Ni, 0.018-0.377 for Pb and 0.032-0.099 for Zn. Based on multivariate analysis (including correlation, cluster and principal component analyses), the polluted sites were found at Kg. Pasir Puteh and Tg. Kupang while Ni and Pb were identified as two major dissolved metals of high variation in the coastal waters. Therefore, water quality monitoring and control of release of untreated anthropogenic wastes into rivers and coastal waters are strongly needed.
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