Displaying publications 141 - 160 of 495 in total

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  1. Wah, Yap Bee, Nurain Ibrahim, Hamzah Abdul Hamid, Shuzlina Abdul-Rahman, Fong, Simon
    MyJurnal
    Feature selection has been widely applied in many areas such as classification of spam emails, cancer cells, fraudulent claims, credit risk, text categorisation and DNA microarray analysis. Classification involves building predictive models to predict the target variable based on several input variables (features). This study compares filter and wrapper feature selection methods to maximise the classifier accuracy. The logistic regression was used as a classifier while the performance of the feature selection methods was based on the classification accuracy, Akaike information criteria (AIC), Bayesian information criteria (BIC), Area Under Receiver operator curve (AUC), as well as sensitivity and specificity of the classifier. The simulation study involves generating data for continuous features and one binary dependent variable for different sample sizes. The filter methods used are correlation based feature selection and information gain, while the wrapper methods are sequential forward and sequential backward elimination. The simulation was carried out using R, an open-source programming language. Simulation results showed that the wrapper method (sequential forward selection and sequential backward elimination) methods were better than the filter method in selecting the correct features.
  2. Koohi, Sina Zangbari, Nor Asilah Wati Abdul Hamid, Mohamed Othman, Ibragimov, Gafurjan
    MyJurnal
    Heterogeneous parallel architecture (HPA) are inherently more complicated than their homogeneous counterpart. HPAs allow composition of conventional processors, with specialised processors that target particular types of task. However, this makes mapping and scheduling even more complicated and difficult in parallel applications. Therefore, it is crucial to use a robust modelling approach that can capture all the critical characteristics of the application and facilitate the achieving of optimal mapping. In this study, we perform a concise theoretical analysis as well as a comparison of the existing modelling approaches of parallel applications. The theoretical perspective includes both formal concepts and mathematical definitions based on existing scholarly literature. The important characteristics, success factors and challenges of these modelling approaches have been compared and categorised. The results of the theoretical analysis and comparisons show that the existing modelling approaches still need improvement in parallel application modelling in many aspects such as covered metrics and heterogeneity of processors and networks. Moreover, the results assist us to introduce a new approach, which improves the quality of mapping by taking heterogeneity in action and covering more metrics that help to justify the results in a more accurate way.
  3. Abdur Rahman Muhammad Abdul Majid, Nor Asilah Wati Abdul Hamid, Amir Rizaan Rahiman, Basim Zafar
    MyJurnal
    Tawaf ritual performed during Hajj and Umrah is one of the most unique, large-scale multi-cultural events in this modern day and age. Pilgrims from all over the world circumambulate around a stone cube structure called Ka’aba. Disasters at these types of events are inevitable due to erratic behaviours of pilgrims. This has prompted researchers to present several solutions to avoid such incidents. Agentbased simulations of a large number of pilgrims performing different the ritual can provide the solution to obviate such disasters that are either caused by mismanagement or because of irregular event plans. However, the problem arises due to limited parallelisation capabilities in existing models for concurrent execution of the agent-based simulation. This limitation decreases the efficiency by producing insufficient frames for simulating a large number of autonomous agents during Tawaf ritual. Therefore, it has become very necessary to provide a parallel simulation model that will improve the performance of pilgrims performing the crucial ritual of Tawaf in large numbers. To fill in this gap between large-scale agentbased simulation and navigational behaviours for pilgrim movement, an optimised parallel simulation software of agent-based crowd movement during the ritual of Tawaf is proposed here. The software comprises parallel behaviours for autonomous agents that utilise the inherent parallelism of Graphics Processing Units (GPU). In order to implement the simulation software, an optimized parallel model is proposed. This model is based on the agent-based architecture which comprises agents having a reactive design that responds to a fixed set of stimuli. An advantage of using agents is to provide artificial anomaly to generate heterogeneous movement of the crowd as opposed to a singular movement which is unrealistic. The purpose is to decrease the execution time of complex behaviour computation for each agent while simulating a large crowd of pilgrims at increased frames per second (fps). The implementation utilises CUDA (Compute Unified Device Architecture) platform for general purpose computing over GPU. It exploits the underlying data parallel capability of an existing library for steering behaviours, called OpenSteer. It has simpler behaviours that when combined together, produces more complex realistic behaviours. The data-independent nature of these agent-based behaviours makes it a very suitable candidate to be parallelised. After an in-depth review of previous studies on the simulation of Tawaf ritual, two key behaviours associated with pilgrim movement are considered for the new model. The parallel simulation is executed on three different high-performance configurations to determine the variation in different performance metrics. The parallel implementation achieved a considerable speedup in comparison to its sequential counterpart running on a single-threaded CPU. With the use of parallel behaviours, 100,000 pilgrims at 10 fps were simulated.
  4. Muhammad Qadri Effendy Mubarak, Abdul Rahman Hassan, Aidil Abdul Hamid, Sahaid Khalil, Mohd Hafez Mohd Isa
    Sains Malaysiana, 2015;44:115-120.
    The aim of this study was to establish a simple, accurate and reproducible method for the identification and quantification of surfactin using high-performance liquid chromatography (HPLC). Previously reported method of identification and quantification of surfactin were time consuming and requires a large quantity of mobile phase. The new method was achieved by application of Chromolith® high performance RP-18 (100 × 4.6 mm, 5 μm) as the stationary phase and optimization of mobile phase ratio and flow rate. Mobile phase consisted of acetonitrile (ACN) and 3.8 mM trifluroacetic acid (TFA) solution of 80:20 ratio at flow rate of 2.2 mL/min was obtained as the optimal conditions. Total elution time of the obtained surfactin peaks was four times quicker than various methods previously reported in the literature. The method described here allowed for fine separation of surfactin in standard sample (98% purity) and surfactin in fermentation broth.
  5. Ainon Hamzah, Mazni Abu Zarin, Aidil Abdul Hamid, Othman Omar, Sahidan Senafi
    Sains Malaysiana, 2012;41:71-79.
    This study was carried out to determine the optimal parameters for the production of biomass of Trichoderma virens UKMP-1M, a fungus isolated from oil-polluted wastewater. The isolate showed maximum growth at day six after incubation in Mineral Salt Medium (MSM) in the presence of 3% (v/v) heavy Khefji Sour crude oil. Although it grew at pH between 5.0 and 7.0, it grew best at pH 5.5. T. virens UKMP-1M grew at temperatures between 25°C and 35°C, with its highest growth at 30°C. Aeration by agitation at 200 rpm was shown to yield the greatest biomass. Peptone at concentration of 1.5% (w/v) was determined to be a better nitrogen source than urea, potassium nitrate (KNO3), yeast extract, ammonium sulphate ((NH4)2SO4) and ammonium chloride (NH4Cl). Addition of 1% (v/v) crude oil to the MSM medium led to higher biomass production than the addition of 3%, 5%, 7% and 10% (v/v) crude oil. The result also revealed that 40% of total petroleum hydrocarbon (TPH), 100% of pristane and 74% of phytane compounds were degraded after 9 days of incubation at optimal physical and nutrient parameters.
  6. Roslinda Shamsudin, Abdul Razak Daud, Muhammad Azmi Abdul Hamid, Saiful Rizam Shamsudin
    Sains Malaysiana, 2007;36:195-200.
    Nitridation behaviour of Al-Mg-Si alloys was studied as a function of temperature by means of thermogravimetry method. A reactive gas, N2-4%H2 at a rate of 10 ml/min was purged into the thermogravimetry analyser chamber. The Al alloys were heated from 25oC to 625oC at the heating rate of 15oC/min and then reduced to 3oC/min until it reached 1500oC. It was found that by varying the amount of Mg and Si in Al-Mg-Si alloys significantly influenced the growth of the composites. A differential thermogravimetric curve shows the Mg containing alloys experienced many steps of chemical reactions. This indicates that besides AlN presence as a major phase, other compounds also exist in the final product. The X-ray diffraction results confirmed the existence of oxide phases such as a-Al2O3, MgAl2O4 and MgO in addition to residual Si and Al metal. The presence of oxide compounds is believed to be due to the reaction between the alloying elements and residual oxygen gas left in the reaction atmosphere. It was also found that Si could play a role in promoting the weight gain of the composite produced. The heating rate has also a profound effect on the weight gain, whereby higher heating rate resulted in low yielded of AlN during the nitridation reaction of the Al-Mg-Si alloys.
  7. Nur Nadiah Abdul Hamid, Ahmad Abd Majid, Ahmad Izani MD Ismail
    Sains Malaysiana, 2011;40:1285-1290.
    Second order linear two-point boundary value problems were solved using extended cubic B-spline interpolation method. Extended cubic B-spline is an extension of cubic B-spline consisting of one shape parameter, called λ. The resulting approximated analytical solution for the problems would be a function of λ. Optimization of λ was carried out to find the best value of λ that generates the closest fit to the differential equations in the problems. This method approximated the solutions for the problems much more accurately compared to finite difference, finite element, finite volume and cubic B-spline interpolation methods.
  8. Abdul Hamid Othman, Ibrahim Baba, Yang Farina Abdul Aziz, Norman Awang
    Several triphenylphosphinosilver (I) complexes, viz. bis [acetatotriphenylphosphineargentum (I)], I, lactatotris (triphenylphosphine) argentum (I), II, N, N-diethanoldithiocarbamatobis (triphenylphosphine) silver (I), III, and N­ethanol, N-methyldithiocarbamatobis (triphenylphosphine) silver (I), IV, have been prepared. Apart from characterization by spectroscopic methods, the structures of I-III, have been characterised by single-crystal x-ray diffraction methods. I crystallized as a dimer with a 4-coordinate geometry around the silver atom, while the lactate complex is a monomer with a five-coordinate silver atom. In the four-coordinate complex III, the Ag - S bond distances are 2.6822 (13) and 2.5991 (12) Å indicating different modes of bonding to the dithiocarbamate ligands.
    Beberapa kompleks trifenilfosfinoargentum telah disintesis, iaitu bis [asetatotrifenilfosfinargentum (I)], I, laktatotris (trifenilfosfin) argentum (I), II dietanolditiokarbamatobis (trifenilfosfin) argentum (I), III dan metiletanolditiokarbamatobis (trifenilfosfin) argentum (I), IV. Selain daripada pencirian dengan kaedqh spektroskopi, struktur kompleks I-III telah ditentukan dengan kaedah pembelauan sinar-X hablur tunggal. Kompleks asetat terhablur sebagai dimer dengan argentum menunjukkan geomertri 4-koordinat, sementara kompleks laktat adalah monomer dengan argentum berkoordinatan lima. Dalam kompleks dietanolditiokarbamat argentum berkoordinatan empat dengan panjang ikatan Ag - S, 2.6822 (13) dan 2.5991 (12) Ã… menunjukkan dua mod pengikatan yang berbeza dengan ditiokarbamat.
  9. Siti Fazlili Abdullah, Shahidan Radiman, Muhammad Azmi Abdul Hamid, Noor Baa’yah Ibrahim
    Sains Malaysiana, 2008;37:233-237.
    Oleic acid (OA) capped wolfram (VI) oxide, WO3 nanoparticles were chemically synthesized and characterized by means of Fourier Transform-Infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The tribological properties of the capped WO3 nanoparticles as an additive in base oils were investigated using a four-ball machine. Results show that OA-capped WO3 nanoparticles are able to prevent water adsorption and capable of being dispersed stable in organic solvents which is base oils. The as-prepared capped WO3 nanoparticles have an average size of 15 nm. In addition, OA-capped WO3 nanoparticles as an additive in base oils perform good anti-wear (AW) and anti-friction (AF) properties owing to the formation of a boundary film.
  10. FARHILA MUHID, ABDUL JALIL ABDUL KADER, WAN MOHTAR WAN YUSOFF, OTHMAN OMAR, AIDIL ABDUL HAMID
    Sains Malaysiana, 2012;41:431-437.
    Ciri inokulum bagi pengkulturan kulat oleaginus pencilan tempatan, Cunninghamella bainieri 2A1 dibangunkan dengan mengenal pasti kesan jenis, umur dan saiz inokulum terhadap pertumbuhan, penghasilan lipid dan GLA. Pengkulturan dijalankan pada suhu 30ºC dengan kadar goncangan 250 rpm dalam kelalang goncangan 500 mL yang mengandungi 200 mL medium terhad nitrogen. Inokulum spora didapati lebih sesuai berdasarkan produktiviti penghasilan lipid yang tinggi iaitu 0.71 (g/L/hari) berbanding penggunaan inokulum sel vegetatif vegetatif 24 jam dan 48 jam yang masingmasing memberikan produktiviti hanya 0.51 dan 0.45 (g/L/hari). Selain itu, penghasilan GLA (5.3 × 10-2 g/g biojisim tanpa lipid) dalam kultur yang dimulakan dengan inokulum spora (1 × 105 spora/mL) didapati lebih tinggi sebanyak 23% berbanding inokulum sel vegetatif. Kepekatan spora sebanyak 1 × 103 spora/mL menghasilkan morfologi pellet bersaiz 1.04 mm dan berkadaran dengan kandungan lipid dan GLA masing-masing sebanyak 40% (g/g biojisim) dan 8.34 × 10-2 (g/g biojisim tanpa lipid).
  11. Azita Ahmad Zawawi, Shiba M, Hazandy Abdul Hamid, Mohd Zaki Hamzah, Pakhriazah Hassan Zaki
    Sains Malaysiana, 2012;41:1079-1086.
    Kajian mengenai corak susunan sel salur dijalankan terhadap struktur kayu Baeckea frutescens bagi menilai perbezaan ciri anatomi spesies tersebut akibat impak daripada aktiviti rekreasi di Gunung Tahan, Malaysia. Plot kajian bersaiz 20 m × 20 m dibina di tiga kawasan perkhemahan utama dan penilaian dijalankan di sub-plot yang mewakili kawasan
    terganggu dan kawasan kawalan. Kajian menunjukkan terdapat perbezaan pada susunan dan struktur sel salur B. frutescens antara kawasan kajian. Keputusan menunjukkan spesies yang tumbuh di kawasan terganggu mempunyai saiz sel salur yang lebih tinggi dengan nilai 177.06 µm2 berbanding 106.40 µm2 di kawasan kawalan. Bagi parameter tumbesaran pokok, nilai purata diameter di keseluruhan kawasan terganggu adalah 2.10 berbanding 1.55 cm di kawasan kawalan manakala nilai purata bacaan tinggi pokok adalah 0.95± 0.04 dan 0.82 ± 0.06 m bagi kedua-dua kawasan. Kebanyakan kajian lepas menunjukkan ciri anatomi kayu adalah tertakluk kepada faktor genetik sesuatu spesies namun kajian ini menghasilkan pemerhatian yang menarik dan ia menunjukkan bahawa faktor genetik anatomi sesuatu spesies kayu itu boleh berubah sebagai tindak balas terhadap sebarang gangguan dan respons kepada perubahan ciri ekologi sesebuah kawasan.
  12. Manikan V, Mohd Sahaid Kalil, Othman Omar, Abdul Jalil Abdul Kader, Aidil Abdul Hamid
    Sains Malaysiana, 2014;43:443-449.
    Cunninghamella bainieri 2A1 is an oleaginous fungus whose lipid accumulation profile is significantly influenced by metal ion concentrations in growth medium. Mg2+, Fe3+, Mn2+ and Cu2+ were found to be the important elements affecting lipid accumulation in this fungus. This study employs a statistical method (Response Surface Methodology – RSM) to study the combined effects of Mg2+, Fe3+, Mn2+ and Cu2+ on lipid accumulation of C. baineri 2A1. Cultivation was carried out in 250 mL Erlenmeyer flasks containing 100 mL nitrogen limited medium at 30oC and 250 rpm agitation for 120 h. A thirty-run central composite design experiment was employed to identify and optimize the significant factors. In addition to Mg2+ and Fe3+ which were shown to have significant effects on lipid accumulation, the interactions between Mg2+ and Cu2+, as well as the effect of Cu2+ in quadratic terms were also found to have significant effect on the process (p<0.05). The highest amount of lipid obtained in this study was 39% g/g biomass with optimal levels of Mg2+, Fe3+ and Cu2+ at 5.00, 0.017 and 0.0005 g/L, respectively, while Mn2+ was omitted. A 32% increment in lipid yield was recorded, where the lipid content increased to 38%, compared to initial yield of 29% g/g biomass prior to optimization. In conclusion, Mg2+ and Fe3+ have significant positive effect on the lipid accumulation of this fungus, whereas Mn2+ and Cu2+ exert negative effects in combination.
  13. Mohamad Azhar Mohd Noor, Zailina Hashim, Shamsul Bahari Shamsudin, Heryati Abdul Hamid, Dasrilsyah Syahrial
    This is a study of the incidence of dental fluorosis and the urine fluoride concentration among school children. About 84 Malay students with the age range of 16 to 17 years from a National Secondary School in the district of Kuala Lipis, Pahang was selected as respondents. The selection was based on the exposure to fluoride in drinking water supply systems. Fifty two respondents were selected from the fluoridated water supply area while 32 others were selected from the non-fluoridated area (comparative group). The objectives of this study were to determine the relationship between urine fluoride concentrations with the incidence of dental fluorosis and to compare the difference in these two variables between the 2 groups of respondents. The urine fluoride concentration was determined using a fluoride-ion specific electrode. Dental fluorosis was examined through a physical examination using the Tooth Surface Index of Fluorosis (TSIF). There was no significant difference in the mean urine fluoride concentration (mg/L) (t=0.186, p=0.853), mean urine fluoride concentration (mg/g creatinine) (t=0.069, p=0.945) and dental fluorisis (TSIF mean score) (t=0.288, p=0.774) between the two groups. There was a significant direct correlation between the urine fluoride concentrations (mg/L) (r= 0.425, p<0.00l) and the urine fluoride concentra­tions (mg/g creatinine) (r=0.252, p=0.021) with dental fluorisis (TSIF mean score). Multiple regression statistics, indicated that dental fluorosis was significantly related to urine fluoride concentrations (b=0.0.61, p=0.028) and the number of glass of their favourite drink consumed daily (b=0.071, p=0.003). In conclusion, the urine fluoride concentrations, which represent the degree of exposure to fluoride, were found to be related to dental fluorosis, which is the biological indicator for excessive exposure to fluoride. There is no difference on the degree and the effects of exposure to fluoride between the two groups of respondents although they consumed water from two different water supply systems. Thus, the exposure to fluoride is not only through the drinking water supply, but also by other sources such as the intake of carbonated drinks and fruit juice.
  14. Ng KW, Aidil Abdul Hamid, Mohd Sahaid Kalil, Wan Mohtar Wan Yusoff
    Pertumbuhan sel secara selanjar pada keadaan mantap telah diperolehi dalam pengkulturan dengan bioreaktor padat. Produktiviti (0.02 g/L/j) bioetanol yang paling tinggi diperolehi adalah pada pengudaraan 0.003 vvm. Produktiviti bioetanol didapati meningkat dengan peningkatan kadar pencairan. Produktiviti tertinggi sebanyak 0.037 g/L/j direkod semasa kadar pencairan (D) 0.05 per jam. Penghasilan bioetanol secara selanjar telah berjaya diselenggarakan pada keadaan tidak 100% anaerobik. Pengudaraan yang terbaik untuk produktiviti bioetanol dalam keadaan seimbang pertumbuhan sel dan penghasilan bioetanol ialah pada 0.003 vvm.
  15. Farhila Muhid, Wan Mokhtar Wan Yusof, Othman Omar, Aidil Abdul Hamid, Abdul Jalil Abdul Kader
    The effects of ammonium tartrate and glucose concentration on biomass, lipid and GLA accumulation in Cunninghamella sp. 2A1 were investigated using Response Surface Methodology (RSM). Cultivation was carried out in 250 mL shake flask containing 100 mL of nitrogen limiting medium (with various combinations of concentration of ammonium tartrate (1-3 g/L) and glucose (30-60 g/L) at 30°C and 250 rpm agitation for 120 h. The concentration of both compounds significantly affected the biomass, lipid and GLA yield (p<0.05), with the production of each of them being represented by quadratic models. Higher concentration of ammonium tartrate and glucose (2.99 and 59.33 g/L, respectively) was required for enhanced biomass production whereas low nitrogen content with excess glucose was otherwise favoured for lipid and GLA production. Ammonium tartrate and glucose concentration at 1 and 43 g/L, respectively were estimated by the model and proven to give the highest lipid production and GLA yield of 31.06 % (g/g biomass) and 4.15 ×10-2 (g/g lipid less biomass), respectively
  16. Wan Mohtar Wan Yusoff, Hutari A, Jaseem WS, Aidil Abdul Hamid
    Sains Malaysiana, 2011;40:1115-1122.
    A total of eight strains of Lactobacillus and two strains of Salmonella were isolated from free-range Malaysian chickens intestine. Evaluation based on in vitro studies included aggregation, co-aggregation, growth with bile salts, tolerance to acidic pH, and inhibitory activity were carried out. The isolated Lactobacillus were Lactobacillus fermentum IA, Lactobacillus fermentum IB, Lactobacillus fermentum IC, Lactobacillus fermentum ID, Lactobacillus salivarius subsp. salicinus IE, Lactobacillus salivarius subsp. salicinus IF, Lactobacillus salivarius subsp. salivarius IG, and Lactobacillus spp. IH. The corresponding isolated Salmonella were Salmonella spp. 3B21 and Salmonella spp. 1A12. The ability of aggregation and also tolerance to pH 2.5 are found in Lactobacillus fermentum ID, Lactobacillus salivarius subsp. salicinus IF, Lactobacillus salivarius subsp. salivarius IG, and Lactobacillus spp. IH. The isolate most resistance to 1% bile salts is Lactobacillus fermentum ID but observed to be weak in inhibitory activity against Salmonella spp. The best co-aggregation and strongest inhibitory activity against Salmonella spp. was observed in Lactobacillus salivarius subsp. salivarius IG. Despite being not so resistant in the presence of bile salts 0.5 and 1% (w/v), the lag time in the presence of bile salts 0.3% (w/v) of Lactobacillus salivarius subsp. salivarius IG and also for Lactobacillus spp. IH are the shortest. Based on good aggregation properties, the best co-aggregation, tolerance to acidic pH 2.5 and bile salts 0.3% (w/v) and strongest inhibitory activity against Salmonella spp., Lactobacillus salivarius subsp. salivarius IG comes out as the best candidate as probiotic for chicken.
  17. Ahmad Nazlim Yusoff, Khairiah Abdul Hamid, Saemah Rahman, Shahlan Surat, Syazarina Sharis Osman, Maziah Ahmad Marzuki
    Jurnal Sains Kesihatan Malaysia, 2018;16(2):101-111.
    MyJurnal
    Inferior parietal lobule (IPL) and inferior temporal gyrus (ITG) are two important brain regions for the default mode
    network (DMN). IPL has been known to be involved in the control of attention and responding to given information while
    ITG is involved in the processing and perception awakened by visual stimuli. These two key DMN regions are highly
    interconnected as determined from white matter and fiber tracking studies. However, little is known about their nature
    of connectivity while the brain is at rest, whether it is linear, bilinear or nonlinear and whether it is of mono- or bidirection. Resting state functional magnetic resonance imaging (rsfMRI) data were obtained from 7 healthy male and
    female participants (average age = 20.7 ± 4.5 years) and were concatenated. Data were analyzed using statistical
    parametric mapping (SPM12). Endogenous brain signals were modelled by Fourier series at 0.01 – 0.08 Hz. IPL-ITG
    connected linear, bilinear and non-linear causal models in both hemispheres were constructed and estimated by means of
    stochastic dynamic causal modelling (sDCM) and were compared using Bayesian Model Selection (BMS) for group studies.
    Group fixed-effects results indicated that bilateral IPL and ITG exhibited high neural activity at a corrected significant
    level (pFWE < 0.05). Neural activity was centered in ITG (-32/2/-38) in the left hemisphere but shifted to IPL (32/-38/50) in
    the right hemisphere indicating different control center for both hemispheres. BMS selected bilinear model as the optimal
    model for both hemispheres (model posterior probability ~ 1.0; log evidence > 1000) which has the best balance between
    model accuracy and difficulty. The minimum free energy (F) = -4.41 × 104
    and -4.09 × 104
    for left and right hemisphere
    bilinear models respectively. From BMS and DCM results, it was found that IPL and ITG do have a dynamic collaboration
    between each other, a connectivity that belongs to a greater network when the brain is at rest. The intrinsic connections
    between them are negative in both directions i.e. IPL and ITG mutually inhibited each other. The effective connectivity
    was modulated by the endogenous fluctuation of the brain signal.
  18. Abdul Hamid Abdul Aziz, Mohamed Kamel Abd Ghani, Ahmad Zorin Sahalan, Hing, Hiang Lian
    MyJurnal
    Suatu kajian pemencilan dan pengenalpastian mikroflora bakteria daripada kolam air panas telah dilakukan di kolam
    air panas Bentong, Pahang. Kebanyakan bakteria yang dipencil dari kolam air panas adalah dari Bacillus sp. kerana ia
    mempunyai ciri adaptasi yang membolehkannya hidup di kawasan ekstrem suhu tinggi dengan pembentukan endospora.
    Objektif kajian adalah untuk mengenal pasti spesies bakteria selain dari spesies Bacillus sp. yang mampu mandiri dalam
    kolam air panas ini. Tiga buah kolam air panas dikenal pasti sebagai A, B dan C. Julat suhu berada antara 36°C-52°C
    dan nilai pH antara 7.88-8.65. Kajian ini telah berjaya memencilkan dua isolat bakteria kokus Gram positif bersama
    tiga spesies Gram negatif. Spesies Gram positif tersebut adalah dari spesies Streptococcus sp. dan Staphylococcus sp,
    manakala Gram negatif pula dikenal pasti sebagai Pseudomonas sp., Klebsiella sp. dan Proteus sp.. Sebagai kesimpulan,
    bakteria tak berspora yang bukan Bacillus sp. mampu mandiri dalam kolam air panas.
  19. Nor Rahafza Abdul Manap, Roslinda Shamsudin, Mohd Norhafsam MaghpoR, Muhammad Azmi Abdul Hamid, Azman Jalar
    Sains Malaysiana, 2017;46:953-965.
    Sifat isoterma dan kinetik penjerapan formaldehid ke atas komposit serbuk serat kelapa sawit-TiO2 yang melibatkan sistem gas-pepejal adalah dikaji. Komposit serbuk serat kelapa sawit-TiO2 dihasilkan dengan mencampurkan serbuk kelapa sawit dan serbuk TiO2 dengan nisbah 8:2 menggunakan teknik pengisaran mekanik. Pengujian dijalankan di dalam kebuk ujian dengan komposit serbuk kelapa sawit-TiO2 dibiarkan untuk menjerap dan mengurangkan nilai kepekatan formaldehid secara pasif. Didapati nilai penjerapan maksima dan sifat kinetik penjerapan bergantung kepada kepekatan awal formaldehid. Kepekatan awal, Ci, 2.1 ppm dan 0.5 ppm masing-masing diwakili oleh pseudo-tertib pertama dan pseudo tertib kedua, manakala Ci = 0.75 dan 0.9 ppm diwakili oleh model Elovich. Isoterma penjerapan formaldehid diwakili oleh isoterma Freundlich dengan nilai korelasi tertinggi R2 = 0.9397 berbanding nilai korelasi isoterma Langmuir (R2 = 0.8692) dan isoterma Temkin (R2 = 0.8756). Parameter keseimbangan, 0
  20. Nurul Shazana Abdul Hamid, Viksuthorn Ai Wen, Nur Izzati Mohd Rosli, Akimasa Yoshikawa, Akimasa Yoshikawa
    Sains Malaysiana, 2018;47:1923-1929.
    Sistem arus di ionosfera khatulistiwa terdiri daripada elektrojet khatulistiwa (EEJ) dan suria senyap (Sq). Arus EEJ merupakan satu jalur arus yang mengalir ke arah timur sepanjang kawasan dip khatulistiwa. Arus Sq pula adalah gegelung arus yang mengalir di hemisfera utara dan selatan bumi pada arah yang bertentangan. Kajian ini bertujuan untuk menganalisis kesan aktiviti matahari terhadap profil latitud sistem arus, khususnya di kawasan Asia Tenggara. Data yang digunakan dalam kajian ini merangkumi data geomagnet daripada lima stesen magnetometer dalam rangkaian MAGDAS iaitu stesen Muntinlupa (MUT), Cebu (CEB), Davao (DAV), Manado (MND) dan Pare Pare (PRP). Keamatan arus EEJ yang paling tinggi adalah pada waktu tengah hari sekitar 1000 dan 1100 LT semasa solar minimum dan kajian ini telah menganalisis sistem arus daripada 1000 hingga 1400 LT. Analisis menunjukkan bahawa ribut geomagnet yang berlaku pada 23 April 2008 adalah disebabkan oleh letusan jirim korona (CME) yang memberikan peningkatan kepada nilai arus pada hari tersebut. Peningkatan yang ketara dapat dilihat pada arus di stesen hemisfera selatan, iaitu stesen MND dan PRP. Berdasarkan analisis yang dilakukan, ia turut mendapati bahawa ribut geomagnet memberikan peningkatan kepada nilai arus walaupun di luar waktu puncak. Selain itu, profil arus ini turut dibandingkan dengan profil arus pada hari senyap iaitu pada 21 April 2008.
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