A set of hydrogenated nanocrystalline silicon (nc-Si:H) films prepared in a home-built plasma enhanced chemical vapour deposition (PECVD) system using the layer-by-layer (LBL) deposition technique have been studied. The 13.56 MHz rf power was varied from 20 W to 100 W to study the influence of rf power on the structural properties of the nc-Si:H films. The structure of the films was studied by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. Appearance of XRD peaks at 2q angles of 28o and 56o which correspond to silicon orientation of (111) and (311) respectively were observed in all films deposited on c-Si substrate indicating evidence of crystallinity in the films. The crystallite sizes were in the range of 8 to 100 nm as determined using the Scherrer technique. The integrated intensities of absorption bands at 630 cm-1, 780 - 880 cm-1 and 2000 – 2090 cm-1 from FTIR spectrum which corresponds to various Si-H bonding configurations in the films were studied and were related to the presence of small clusters of nanocrystallites embedded in an amorphous matrix. Based on the dependence of amplitudes of Si-H vibrational modes on crystallite size and rf power, the properties and the role of hydrogen in nc-Si:H films prepared using the LBL technique were discussed.
This paper reports on the effect of oxide particle Dy2O3 additions on the superconducting properties of MgB2. The polycrystalline samples were prepared by well mixing magnesium and boron elemental powders, followed by heat treatment for in situ reaction in inert gas environment. All the samples showed MgB2 as the main phase with MgO and DyB4 as impurities. Magnetization measurements showed that the superconducting transition temperature, Tc remained largely unchanged (37.5 – 38K) even for Dy2O3 additions up to 15.0 wt.%. However, the transition curve was broadened in samples with larger amount of additions. The best sample with only 0.5 wt.% Dy2O3 additions had a Jc of around a factor of 4 higher compared to the pure sample at 6K(1T). Tem imaging showed the distribution of nano precipitates of DyB4 and MgO within the grain which may improve the pinning leading to enhancement in critical current density, Jc.
The effects of Fe buffer layer on the microstructures and GMR property of magnetron sputtered Co/Cu multilayers were studied. The main focus was to systematically identify the types of microstructural features present in the multilayers and to determine their characteristic length scales via qualitative and quantitative microstructural characterisation techniques. Both diffraction and imaging techniques were used to extract useful information on layering and crystallographic structures of the materials. This has provided an insight into the structure-property relationship of the materials system. Co/Cu multilayered samples grown with iron buffer layers were found to display better structural coherency and layering quality as compared to those grown without the iron buffer layers. The high GMR effect as demonstrated by these multilayers was associated with highly correlated interface profiles, sharp columnar grain boundaries and high degree of lateral coherency in columnar grain growth.
MeSH terms: Biological Phenomena; Buffers; Edible Grain; Crystallography; Iron
Corrosion caused by sulphate-reducing bacteria (SRB) isolated from seawater nearby to Pasir Gudang has been studied. The test coupon was a AISI 304 stainless steel. Potential and corrosion rate measurements were carried out in various types of culturing solutions, with SRB1, SRB2, combination of SRB1 & SRB2 and without SRBs inoculated (sterilized). From Tafel plots a higher corrosion rate has been found in medium inoculated with SRBs than that of the sterilized medium (control). When SRBs were present in the medium, the Tafel plot shifted towards more negative values (Ecorr was shifted to much less anodic values) and increase in current density compared to that of the sterilized medium (control). Localized corrosion was observed on the metal surface, and it was associated to the SRB activity. X-ray analysis (EDAX) showed that the corrosion product has higher content of sulphur for medium containing SRBs than that of the sterilized medium. X-Ray Diffraction analysis carried out on corrosion products which showed the presence of iron sulphide. This indicates the influence of the presence of SRB in corrosion process.
Crude fat and fatty acids composition were examined in 16 different species of Malaysian freshwater fishes. Nine species of farmed and seven species of wild fishes lipids were extracted using chloroform: methanol sohxlet extraction. The results showed that the crude lipids in muscle of farmed fishes were higher than the wild fishes, ranging from 20 - 50 % (wt/wt) and 4 – 15 % (wt/wt) respectively. Asian red-tail catfish showed highest total lipid among other fishes which was of 51.64 % (wt/wt), followed by red pomfret and yellow-tail catfish which were of 46.2% and 43.2% respectively. Eicosapentaenoic acid, EPA and docosahexaenoic acid, DHA in wild fishes were found higher compared to captive fish. Among the fishes studied, grey feather back contain high in EPA (2.9%) and DHA (12.1%) as well as snakeskin gouramy (EPA; 3.0% and DHA; 12.8%) and tengalan (EPA; 1.1% and DHA; 7.2%). Other fishes, on the other hand contain less percentage in w-3 fatty acids. The diet and the environment where the fishes were found are the main reason for the differences in fish fatty acids content.
Bottom sediment samples from the Kuala Sepetang River, Taiping, Perak were analysed for the grain size in order to understand better the sedimentation processes in the estuary and along the river. The mean, standard deviation and skewness value of each sample were calculated by the moment’s method where each of every grain plot data was used to obtain the statistical information concerning the sedimentary population. In this study, there is no significant (p<0.05) relationship between sediment characteristic with the seasonal changes, but the mean particle size became a relatively smaller size during the monsoon season. Finer sediments (7.4 Ø) were dominated during monsoon season while coarser sediments (6.2 Ø) dominated during the dry season. The characteristics of deposited sediments at each station are much dependent upon the combination of physical forces such as freshwater runoff, tidal currents and waves.
The emergence of primate malaria known as Plasmodium knowlesi in humans, which is always misdiagnosed by microscopy as P. malariae, has contribute to the needs of nucleic acid based technology to be applied in detection and differentiation of malaria parasites. The target DNA sequence of the 18SrRNA gene was amplified by a nested PCR assay for detection and identification of Plasmodium species in 31 Giemsa-stained blood smears examined as P. malariae. The assay demonstrated three samples identified as positive to genus-specific primers but negative to all species-specific primers. Three cases of misdiagnosed species were detected. The samples were diagnosed as P. malariae microscopically, but detected as P. falciparum by PCR assay. Twenty five out of 31 samples were detected as P. knowlesi. None of the samples diagnosed microscopically as P. malariae were identified as P. malariae with the nested PCR assay. Over 80.6% of all malaria cases in this study showed naturally acquired P. knowlesi infections.
Malaysia mempunyai tanggungjawab mendepositkan koordinat-koordinat titik-titik pangkal yang digunakan untuk mengukur lebar batas laut wilayah dan sempadan zon-zon maritim yang lain kepada Setiausaha Agung, Pertubuhan Bangsa-Bangsa Bersatu (PBB). Titik-titik pangkal adalah asas kepada penetapan bagi zon-zon maritim, perundangan batas maritim dan perlaksanaan penguatkuasaan. Kertas ini menghuraikan bagaimana dua parameter penting iaitu kecerunan pesisir depan dan datum carta boleh menyebabkan ketidakpastian terhadap posisi titik-titik pangkal. Hubungkait trigonometri antara parameter membuktikan sisihan datum sebanyak 0.2 m dan kecerunan pesisir depan sebanyak 0.1º menyebabkan ketidakpastian posisi mendatar sebanyak 114.6 m. Ketidakpastian kedudukan titik pangkal menjadi signifikan apabila sisihan antara datum carta meningkat dan kecerunan pesisir depan semakin landai. Hasil prosesan kedudukan titik-titik pangkal melalui perisian “CARIS” mendapati perbezaan kedudukan titik-titik pangkal sebanyak 108 m, 169 m dan 107 m. Kesimpulannya, ketidakpastian ini boleh menyebabkan negara kerugian kawasan maritim.
In the past, simulating charge dynamics in solid state devices, such as current mobility, transient current drift velocities are done on mainframe systems or on high performance computing facilities. This is due to the fact that, such simulations are costly in terms of computational requirements when implemented on a single processor-based personal computers (PCs). When simulating charge dynamics, large ensembles of particles are usually preferred, such as exceeding 40000 particles, to ensure a numerically sound result. When implementing this type of simulation on a single processor PCs using the conventional ensemble or single particle Monte Carlo method, the computational time is very long even on the fast 2.0 MHz PCs. Lately, a more efficient, easily made available tools and cost effective solution to this problem is the application of an array of PCs employed in a parallel application. This is done using a computer cluster network in a master-slave model. In this paper we report the development of a LINUX cluster for the purpose of implementing parallel ensemble Monte Carlo modelling for solid states device. We have proposed the use of Parallel Virtual Machine (PVM) standards when running the parallel algorithm of the ensemble MC simulation. Some results of the development are also presented in this paper.
MeSH terms: Algorithms; Computers; Computing Methodologies; Microcomputers; Monte Carlo Method; Running; Slaves
Electron beam vulcanization of natural rubber latex has been developed as an alternative to the conventional sulphur vulcanization method. This study aimed at determining the effect of electron beam dose, beam current and centrifugation to the tensile properties of field natural rubber latex. Irradiation dose and beam current ranged from 50 to 300 kGy and 1 to 15 mA respectively. The determination of tensile properties were done on cast film prepared from irradiated field latex before and after centrifugation. It was found that tensile properties increased with radiation dose but decreased with beam current. Rubber films made from centrifuged irradiated field latex were softer and showed higher tensile strength.
This study was carried out to elucidate the effect of three types of cation (K+, Ca2+ and Na+) at various concentrations on the gelling properties of untreated Eucheuma cottoni, with the ultimate aim to explore the possibility of utilizing the seaweed in its natural form as gelling agent. Results obtained suggest that E. cottonii also exhibited the dramatic cation specificity of k-carrageenan, in which the dependence of gel strength follows the order: K+ > Ca2+ > Na+. As expected, cations addition exerts adverse effect on the syneresis, water holding capacity and freeze-thaw stability of the seaweed gel. Water holding capcity of the gel is however independent of the increased concentrations of K+(p>0.05). Storage duration and storage temperature significantly (p<0.05) affect the syneresis and water holding capacity of the gel. Among the cations, K+ appears to be better in improving the gel properties of the seaweed.
MeSH terms: Carrageenan; Cations; Freezing; Gels; Seaweed; Temperature; Water
Sifat pengelatinan salutan semasa peringkat awal penggorengan pada beberapa suhu yang berbeza telah dikaji. Nuget ayam, sebagai substrat, dicelup ke dalam cecair penyalut dan kemudiannya digoreng pada 150, 165 dan 180oC selama 0, 6, 18 dan 30s. Selepas penggorengan, bahagian salutan dan substrat dianalisis secara berasingan untuk kandungan lembapan. Bahagian salutan juga dianalisis untuk suhu permulaan (To), puncak (Tp) dan akhir (Te) serta entalpi pengelatinan. Keputusan menunjukkan tiada kesan ketara oleh suhu penggorengan terhadap kandungan lembapan kedua-dua bahagian salutan dan substrat. Tetapi, terdapat pola pengurangan kandungan lembapan dengan peningkatan masa penggorengan sehingga 30s untuk setiap suhu yang dikaji. Tiada kesan ketara oleh suhu penggorengan terhadap To, Tp dan Te. Tetapi, penggorengan pada 180 oC menghasilkan darjah pengelatinan yang lebih tinggi selepas 6s. Peningkatan kadar pengelatinan apabila digoreng pada suhu yang lebih tinggi boleh disebabkan oleh peningkatan kadar perpindahan haba semasa penggorengan.
A 2D electrical resistivity survey was conducted to investigate the subsurface contamination underneath a domestic waste disposal site at Ampar Tenang, Dengkil, Selangor. The resistivity imaging technique was used in this study to locate the vertical and horizontal extend of contamination plumes underneath the site. A total of six 2-D resistivity imaging lines were established with two of them located outside the landfill area while one of them located in inactive landfill site. Another three lines were situated in the active landfill site. The results of the survey show that the resistivity value of the decomposed waste material in the inactive site of landfill is relatively low and the contaminated leachate plumes has low resistivity value of less than 2 Ωm. Characterisation of subsurface resisitivity and its relation to lithology was interpreted based on the available borehole data.
A study was carried out to look at dynamics and above ground biomass of Lauraceae trees in the 50 ha plot at Pasoh Forest Reserve, Negeri Sembilan. Census data for the year 1985, 1990, 1995 and 2000 were obtained from the Forest Research Institute of Malaysia (FRIM), Kepong. The study was mainly focused on the year 2000 data; nevertheless, comparisons between each census year were carried out to look at variation between each census. Based on the year 2000 data, a total of 6,667 stems of Lauraceae were recorded, representing 11 genera and 49 species. The genera of Cryptocarya, Litsea and Beilschmiedia were abundantly present with 2,216 trees (33.24%), 1,769 trees (26.53%), and 673 trees (10.09%), respectively. Species-wise, Litsea magnifica showed the highest number of individuals of 916 trees (18 trees/ha). In general, distribution pattern analysis using Morisita’s Index of Dispersion (Id) showed a random distribution for this family with value Id = 1.02. Estimation of total above ground biomass of Lauraceae for the year 2000 was estimated at 39.71 t/ha. The genus of Litsea contributed the highest biomass with an estimation of 11.11 t/ha; species-wise, the Dehaasia cuneata indicated the highest biomass estimated at 5.16 t/ha. As a whole, the number of deaths of Lauraceae stems is greater than the number of new individuals recruited during the 15-year census whereby deaths mainly occurred among small individuals with diameter of 1.0-19.9 cm.
McIntyre was the first to suggest ranked set sampling (RSS) method for estimating the population mean. In this paper, we modify RSS to come up with new sampling method, namely, two stage ranked set sampling (TSRSS) for samples of size m=3k (k=1,2,..). The TSRSS is suggested for estimating the population median in order to increase the efficiency of the estimators. The TSRSS was compared to the simple random sampling (SRS), ranked set sampling (RSS), extreme ranked set sampling (ERSS), median ranked set sampling (MRSS) and balance groups ranked set sampling (BGRSS) methods. It is found that, TSRSS gives an unbiased estimator of the population median of symmetric distributions and it is more efficient than SRS. Also, it is more efficient than RSS, ERSS, MRSS and BGRSS based on the same number of measured units. For asymmetric distributions considered in this study, TSRSS has a small bias and smaller variance than SRS, RSS, ERSS, MRSS and BGRSS methods.
Diabetis mellitus merupakan sejenis penyakit metabolik yang disebabkan oleh peningkatan aras glukosa darah serta memberi kesan komplikasi terhadap kesihatan. Peningkatan aras glukosa dalam darah berpunca daripada kegagalan penghasilan insulin yang berperanan dalam mengawalatur aras glukosa darah. Lebih 90 % pesakit diabetis turut mengalami masalah gangguan fungsi seksual lelaki seperti penurunan libido, impoten dan infertiliti di mana kesemua masalah ini adalah disebabkan oleh kegagalan testis yang berkaitan dengan ciri hiperglisemia pesakit diabetis itu sendiri. Infertiliti merujuk kepada ketidaksuburan sperma atau ketidakupayaan individu untuk menghasilkan sperma yang normal. Kajian ini dijalankan untuk melihat potensi ekstrak akues Gynura procumbens (GP) untuk menurunkan aras glukosa darah serta meningkatkan kualiti sperma tikus jantan strain Sprague dawley teraruh diabetis. Tikus diaruh diabetik melalui suntikan intravena streptozotocin (STZ), 65 mg/kg. Kualiti sperma ditentukan berdasarkan parameter berbeza yang dikaji iaitu bilangan, motiliti dan peratus mortaliti sperma. Tikus-tikus ini dibahagi kepada dua kumpulan iaitu normal dan diabetik. Setiap kumpulan ini dibahagi kepada 2 sub kumpulan dengan perlakuan yang berbeza iaitu kawalan (n=5) dan dos 50 mg/kg (n=5) di mana tikus ini diberikan rawatan selama 10 hari berturut-turut menggunakan ekstrak akues GP melalui kaedah suap paksa. Hasil menunjukkan rawatan dengan ekstrak GP menurunkan aras glukosa darah tikus diabetik daripada 15.08 ± 1.878 mmol/L kepada 10.42 ± 2.71 mmol/L secara signifikan (p<0.05). Rawatan dengan ekstrak GP turut meningkatkan bilangan sperma normal dalam tikus diabetik secara signifikan (p<0.05). Bilangan sperma normal dalam tikus diabetik yang diberi rawatan ekstrak ialah (50.23 ± 3.12) x 107 berbanding tikus kawalan diabetik (39.93 ± 8.06) x 107. Sebanyak 38.5% tikus kawalan diabetik menghasilkan motiliti sperma gred d iaitu sperma tidak bergerak (immotil). Walau bagaimanapun, tikus diabetik yang diberi rawatan ekstrak GP menunjukkan penurunan sperma dalam gred d kepada 30.48% serta peningkatan sperma gred a iaitu sperma bergerak paling pantas daripada 31.25% kepada 34.86%. Tikus diabetik yang dirawat dengan ekstrak GP menunjukkan penurunan secara signifikan (p<0.05) dalam peratusan mortaliti sperma iaitu daripada 50.09 ± 14.34% kepada 30.57 ± 4.61%. Hasil ini menunjukkan ekstrak akues Gynura procumbens dapat menurunkan aras glukosa darah, merawat ketidaksuburan serta meningkatkan spermatogenesis pada tikus diabetik jantan.
Penghasilan CGTase daripada Bacillus sp. G1 berjaya ditingkatkan dengan menggunakan sistem kultur selanjar mengatasi penghasilan daripada kultur kelompok. Aktiviti CGTase tertinggi yang didapati dalam kultur kelompok ialah 28.1 U/ml. Kajian kultur selanjar difokuskan kepada masa kemasukan medium segar yang berbeza (12, 24 dan 48 jam ), kadar pencairan ditetapkan pada 0.03 per jam. Hasil menunjukkan masa memulakan pam medium segar tidak memberi perubahan yang signifikan terhadap aktiviti CGTase (25.7, 26.3 dan 26.1 U/ml masing-masing) dan produktiviti CGTase (0.77, 0.79 dan 0.78 U/ml/j masing-masing) pada keadaan mantap tetapi produktiviti CGTase (0.77 U/ml/j) akan lebih tinggi berbanding produktiviti kultur kelompok apabila masa di antara larian kultur kelompok diambil kira. Malah peningkatan berpotensi ditingkatkan lagi dengan memulakan pam medium segar lebih awal daripada 12 jam dan juga dengan meningkatkan kadar pencairan.
This study suggests the regression models of Lognormal, Normal and Gamma for the construction of an insurance scoring system. Comparison between Lognormal, Normal and Gamma regression models were also carried out, and the comparison were centered upon three main elements; fitting procedures, parameter estimates and structure of scores. The main advantage of utilizing a scoring system is that the system may be used by insurers to differentiate between good and bad insureds and thus allowing the profitability of insureds to be predicted.
Kajian yang dijalankan adalah berkaitan dengan penentuan model yang sesuai serta analisis data penyerapan logam berat oleh sayuran berdaun yang terpilih iaitu kangkung (Ipomea aquatica), sawi bunga (Brassica chinensis var parachinensis), bayam (Amaranthus oleraceus L) dan sawi putih (Brassica chinensis L.). Kajian ini bertujuan untuk menentukan dan membandingkan kandungan serta corak pengambilan logam berat yang diserap oleh sayuran dan juga bahagian-bahagiannya yang meliputi daun, batang dan akar. Penentuan model yang dibuat bertujuan bagi melihat corak penyerapan logam berat oleh sayuran atau bahagian sayuran tertentu. Logam berat yang dikaji terdiri daripada kadmium , kromium, kuprum, ferum , mangan, plumbum dan zink. Plot serakan digunakan bagi menentukan corak pengambilan logam berat dalam sayuran dan bahagian-bahagiannya. Selain itu ujian Kruskal-Wallis digunakan bagi membuat perbandingan median di antara logam berat yang diserap oleh sayuran yang dikaji. Nilai khi-kuasa dua dan juga nilai-p digunakan bagi menentukan sama ada sesuatu logam berat yang diserap itu berkait rapat dengan jenis sayuran secara signifikan. Secara umum bolehlah dikatakan bahawa logam Fe, Mn dan Zn adalah dominan dalam semua bahagian sayuran yang dikaji. Selain itu, melalui ujian Kruskal-Wallis didapati penyerapan kesemua logam berat pada setiap bahagian sayuran adalah berbeza secara signifikan. Penyuaian model regresi linear, kuadratik, kubik atau eksponen telah dilakukan terhadap data ini dan didapati kebanyakan data dapat disuaikan dengan baik oleh model kuadratik dan kubik berdasarkan nilai pekali penentuan (R2).
MeSH terms: Brassica; Fenofibrate; Zinc; Linear Models; Amaranthus; Ipomoea; Tetrahydroisoquinolines
Sixteen topsoil samples from Bukit Jernih, Gua Kelam and Bukit Merah were analysed for their major elements and heavy metal composition, together with several physico-chemical parameters. Major elements determined were SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O, P2O5, whereas heavy metals determined were As, Co, Cu, Cr, Ni, Pb and Zn. Physico-chemical parameters determined were percentage of organic matter, clay, silt and sand composition, pH and electrical conductivity. The results showed that the average soil pH in limestone soil was between 6.38 to 6.93, whereas average soil pH in quartzite soil was 6.23. The average soil electrical conductivity for all sampling stations was below 1.7 mScm-1. High organic matter content average was shown in soil samples from Bukit Jernih (7.45%), followed by Gua Kelam (5.21%) and Bukit Merah (3.31%). Soil samples from Bukit Jernih and Gua Kelam showed a clayey texture with more than 35% clay content, whereas soil from Bukit Merah was sandy in texture with more than 67% sand content. In general, soil samples from limestone area of Bukit Jernih and Gua Kelam recorded higher content of heavy metals compared to quartzite soil from Bukit Merah. The average concentration of Cr and Co at Bukit Jernih at 413 µg/g and 88 µg/g, respectively, whereas the concentration at Gua Kelam was 152 µg/g dan 76 µg/g. These concentrations exceeded the potential toxic concentration in soil. The main major elements were SiO2 followed by Al2O3 and Fe2O3. SiO2 content in quartzite soil from Bukit Merah(89.45%) was higher compared to limestone soil from Bukit Jernih (59.74%) and Gua Kelam (53.16%). Nevertheless, Al2O3 and Fe2O3 content in limestone soil was higher compared to quartzite soil. The percentage of easily ignited content in limestone soil was two fold higher than quartzite soil. Other major elements were less than 2.5%. The study showed that enrichment of Cr, Zn, Pb, Ni and Cu in soil was influenced by the presence of SiO2, Al2O3 and Fe2O3.
Keywords: Enrichment; heavy metals; limestones hill; major elements; toxicity