A two dimensional grating has been fabricated from hybrid polymer incorporated with organic dye-laser. The precursor hybrid polymers were synthesized from TMSPMA by sol-gel method. The precursor was mixed with photo-initiator to make sensitive with UV light. The photosensitive film was irradiated by laser interference of THG Nd-YAG laser (λ = 355 nm) yield 2D grating with hexagonal structure. The characteristic of lasing was investigated using strip-line excitation light of SHG Nd-YAG laser (λ = 532 nm). The lasing wavelengths are observed at 606 and 621 nm for grating period of 400 and 410 nm, respectively. The spectral width (FWHM) of lasing is about 3 nm at pumping power 14.88 mJ/pulse cm2.
In this paper, we report the effect of BaAl2O4 addition (0-30 wt. %) on power consumption and oxygen sensing response of hot-spots developed on short Er123 ceramic rods of around 12 mm length synthesized using standard solid-state reaction. All the sensor rods showed increase in output current with increasing voltage followed by sudden reduction in output current and appearance of hot spot. After appearance of hot spot, for each rod, output current was observed to decrease gradually with increasing voltage with the slope of the I-V curve gradually approaching zero. Output current after the hot spot formation showed sensitivity to oxygen partial pressure, pO2 between 1 to 100 kPa. Addition of 30 wt. % BaAl2O4 reduced the fluctuation of current and increased the sensitivity for pO2 below 10 kPa. In addition, overshoot current was also reduced and resulted in improvement of response time from around 10 s to 5 s. Our result also showed that minimum power consumption was significantly reduced in the Er123 rods with 30 wt. % BaAl2O4.
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.
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%.
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.
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.
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.
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.
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.
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.
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.
The aim of this study is to identify the predominating lactic acid bacteria (LAB) in a spontaneous fermented wheat sourdough. At the same time, an investigation towards volatile compounds that were produced was also carried out. Lactobacillus plantarum has been identified as the dominant species of lactobacilli with characters of a facultative heterofermentative strain. The generated volatile compounds that were produced during spontaneous fermentation were isolated by solvent extraction method, analysed by gas chromatography (GC), and identified by mass spectrophotometer (MS). Butyric acid has been found to be the main volatile compound with relative abundance of 6.75% and acetic acid at relative abundance of 3.60%. Esters that were formed at relatively low amount were butyl formate (1.23%) and cis 3 hexenyl propionate (0.05%). Butanol was also found at low amount with relative abundance of 0.60%. The carbohydrate metabolism of Lactobacillus plantarum may contributed to the production of acetic acid in this study via further catabolism activity on lactic acid that was produced. However, butyric acid was not the major product via fermentation by LAB but mostly carried out by the genus Clostridium via carbohydrate metabolism which needs further investigation
Holothuria (Mertensiothuria) leucospilota (Brandt 1835), white threads fish or locally known as bat puntil is currently considered as the most abundant sea cucumber species in Malaysia. This study aimed to generate the genetic profile of H. leucospilota from Malaysia and then to determine the phylogenetic relationship between H. leucospilota and other members of genus Holothuria using partial sequences of cytochrome c oxidase I (COI) mitochondrial DNA (mtDNA) gene. In this study, specimens of H. leucospilota were collected from Intan Besar Island, Langkawi, Kedah Darul Aman in the west coast of Peninsular Malaysia. Three main methods namely neighbour joining, maximum parsimony and maximum likelihood were used for the phylogenetic tree reconstruction. Tree topologies showed that H. leucospilota has its own monophyletic clade clearly distinct from the other species. The pairwise genetic distance calculated further supported these findings. In addition, the results also should that the COI mtDNA gene is capable to unravel the phylogenetic relationship of H. leucospilota.
MeSH terms: Amantadine; Animals; Chiroptera; Electron Transport Complex IV; DNA, Mitochondrial; Fishes; Malaysia; Mitochondria; Phylogeny; Probability; Sea Cucumbers; Holothuria; Islands
The tolerance of Cu by Trichoderma atroviride, a tolerant fungus isolated from the drainage surface sediment of the Serdang Industrial Area was investigated under in vitro conditions. Only this fungus species can tolerate up to 600 mg/L of Cu on solid medium Potato Dextrose Agar based on the isolation of the most tolerant fungus from the polluted sediment. Toxicity test performed on T. atroviride, showed a maximum tolerance at 300 mg/L of Cu concentration when grown in liquid medium Potato Dextrose Broth (PDB). The EC50 value of the isolate was 287.73 mg/L of Cu concentration in PDB. The Cu concentration in the drainage surface sediment, where the T. atroviride was isolated from, was 347.64 μg/g while the geochemical distributions of the non-resistant and resistant fractions of Cu were 99.6 and 0.4%, respectively. The sediment data indicated that the drainage had greatly received anthropogenic Cu from the nearby industries which are involved in the manufacturing of plastics and electronic products. The present findings indicate that the high Cu tolerance showed by T. atroviride could be due to the well adaptation of the fungus to the Cu polluted sediment. Therefore, T. atroviride could be a potential bioremediator of Cu pollution in the freshwater ecosystem.
This study explores the role of sterols as lipid biomarkers to indicate their input which originates from various sources in the marine environment. Sterols and their ratios were investigated in sediments taken from sixteen sampling stations at Pulau Tinggi, Johor in order to assess the sources of organic matter. The compounds extracted from the sediments were quantified using a gas chromatography-mass spectrometry (GC-MS). The distributions of sterols indicated that organic matter at all sampling stations originated from a mixture of marine source and terrestrial origins at different proportions. A total of eleven sterols were quantified, with the major compounds being phytosterols (44% of total sterols), cholesterol (11%), brassicasterol (11%) and fecal sterols (12%).
The microbial composition in coastal water of the Port Dickson beach in Negeri Sembilan, Malaysia was analyzed using several microbial indicators for the purpose of selecting the best indicator for marine water pollution. The indicators studied were total coliform (TC), fecal coliform (FC), fecal streptococci (FS) and coliphage. Five locations were selected along the Port Dickson beaches and samplings were carried out in 1998 and 2001. The results showed an increase in the number of total coliform (TC), fecal coliform (FC) and fecal streptococci (FS) between these two sampling by 98.12%, 86.12% and 99%, respectively. The numbers of TC, FC and FS exceeded the recommended limit for recreational seawater based on U.S. EPA 1986 standard. There was a positive correlation between TC, FC and FS and negative to coliphages.
MeSH terms: Coliphages; Malaysia; Recreation; Seawater; Water Pollution
Surface sediment samples from 2 transects (20 sampling points) of Tanjung Lumpur mangrove forest were analyzed for the concentrations of Pb, Cu, Co and Mn. In this study, the average concentrations of Pb, Cu, Co and Mn were 44.41 μg/g dry weight, 32.79 μg/g dry weight, 5.79 μg/g dry weight and 117.73 μg/g dry weight, respectively. The calculated enrichment factors (EF) obtained for Co and Mn can be considered to have the terigeneous in sources while Pb and Cu are considered to have anthropogenic input.
The Sungai Pulai Mangrove Forest Reserve (SPMFR) is the largest riverine mangrove system in Johore. In 2003 about 9,126 ha of the Sungai Pulai mangrove was designated as a RAMSAR site. RAMSAR sites are wetland areas that are deemed to have international importance and are included in the List of Wetlands of International Importance. The SPMFR plays a significant socio-economic role to the adjacent 38 villages. Satellite remote sensing is a useful source of information where it provides timely and complete coverage for vegetation mapping especially in mangroves where the accessibility is difficult. This study was carried out to identify and map land cover types using SPOT-4 imagery at the Sungai Pulai-RAMSAR site and its surrounding areas. Through unsupervised classification technique a total of seven classes of land cover type were mapped, where about 90% mapping accuracy was gained from the accuracy assessment. Later, vegetation densities were classified into five levels namely very high, high, medium, low and very low based on crown density scale using vegetation indices model such as NDVI, AVI and OSAVI. Results from NDVI and OSAVI model were almost similar but AVI model detected more on medium vegetation which did not show the real ground condition. The study concludes that SPOT-4 imagery was able to discriminate mangrove area clearly from other land covers type. Vegetation indices model can be used as a tool for mapping vegetation density level in the SPMFR and its surrounding area. Therefore VI’s models from remote sensing are useful to monitor and manage the mangrove forest for sustainable management and preserve the SPMFR as a RAMSAR site in Peninsular Malaysia.
A novel dual-pulse actuation voltage that reduces dielectric charging in micro-electromechanical system (MEMS) switch and thus leading to a longer switch lifetime, are shown to simultaneously mitigate MEMS switch contact bouncing. A simple mass-spring-damper mathematical model is used to simulate movement of the switch contact as the excitation voltage is applied. The model shows that the novel dual-pulse voltages damped the acceleration of the switch membrane as it approaches the contact point, eventually slowing it down and minimizes the impact force. This has the effect of minimizing the occurrence of contact bouncing. Practical experiment on the commercial TeraVicta TT712-68CSP MEMS switch corroborates that the novel excitation voltages reduced bouncing.
A Piezoelectric Actuated Valveless Micropump (PAVM) has been designed and successfully fabricated using MEMS fabrication processes. The micropump uses a PZT: Pb(ZrTi)Ox ceramic plate to actuate a silicon membrane which bends when a voltage is applied to the piezoelectric actuator. The resultant reciprocating movement of the pump membrane is then converted into pumping effect. By integrating dynamic passive valves into the device, the pump would then operate continuously with volumetric pumping rate determined by the frequency of the driving voltage. Simulation work to determine the micropump fluidic characteristics was performed using CoventorWare MemFSI™ module. The pump was fabricated on a double side polished silicon wafer via simple two-mask micromachining process. The fabricated micropump, having an outer dimension of 14 mm × 14 mm × 2 mm, was then tested with DI (deionized) water as the test liquid. A driving voltage of 16 Vpp was applied to the PZT actuator. Pump rate of 4.98 nL per min was obtained at 0.673 kHz. The fabricated micropump envisages a promising pumping method to be implemented into drug delivery systems.