Further investigation on the alkaloidal composition on the bark of the Malaysian Popowia perakensis King collected from Mersing, Johore afforded four isoquinoline alkaloids, i.e atherospermidine 1, (-)-anonaine 2, (-)-norstephalagine 3 and (-)-asimilobine 4. These compounds were elucidated and identified via spectroscopic methods mainly 1H-NMR, 13C-NMR, IR, UV, GCMS and by comparison with literature data. The crude alkaloid extract was screened for antimalarial activity towards Plasmodium falciparum in vitro using the lactate dehyrogenase (LDH) assay to give IC50 value of 6.85 _g/ml. Keywords: Isoquinoline, Popowia perakensis, alkaloid, antimalarial activity, Plasmodium falciparum...

110 hits

Polarized beam is very vital for operating light switches. High polarization purity is pertinent in high power Q-Switched Nd:YAG laser system. The aim of this project is to diagnose two high-energy polarizers which are commonly used in QSwitched Nd:YAG laser system namely Glenn-Laser calcite and thin film. The polarization purity was determined by using low power He-Ne laser in place of high power Nd:YAG. The power of He-Ne laser was set at 10 mW with wavelength of 632.8 nm. The beam was aligned to produce parallel plane polarizer. A polaroid polarizer was used as analyzer. The transmission power was measured using a power meter at variable angular rotations from 00 to 360o. The result obtained shows that, both polarizers have produced linear polarization. However, the thin film polarizer had produced a closer result more similar to He- Ne beam polarization. Hence, the thin film polarizer is a better choice to polarize high power Nd:YAG beam since it has higher polarization purity and .....

126 hits

Phase-controlled technique through thyristors (SCR) is used instead of diodes in order to form a power converter. Output voltage of this power converter can be varied by controlling the firing angle of SCR and is used to charge the capacitor banks. Each firing angles are referred to zero-crossing point of each half of the 50 Hz AC voltage. Adjustable voltage is then used to charge the capacitor bank inside Capacitor Charging Power Supply (CCPS) for Xenon flashlamp driver. Flashlamp produced source of pulsed light that pumped the Nd:YAG laser crystal. The Nd:YAG laser usually operates at various input energies, thus requiring variable values of voltage to charge the capacitor bank. Developed phase-controlled converter can steadily controll the output voltage of CCPS from 500 V to 1000 V. Keywords: Phase-controlled technique, thyristors (SCR), Nd:YAG laser, Xenon flashlamp driver..

100 hits

Pengetahuan pedagogi isi kandungan (PCK) digambarkan sebagai pengetahuan yang khusus bagi guru di mana ia dapat mengenal pasti pengetahuan subjek bagi guru berbeza daripada yang difahami oleh pakar kandungan subjek. Kertas ini membincangkan bagaimana pengintergrasian komponen-komponen PCK yang melibatkan pengetahuan isi kandungan, pengetahuan pedagogi am, pengetahuan pedagogi khusus dan pengetahuan konteks semasa membuat transformasi pengajaran pembelajaran dengan menggunakan _Model of Pedagogical Reasoning and Action_. Metodologi kajian menggunakan pendekatan kajian kes untuk menyiasat dan meneroka PCK guru matematik semasa mengajar tajuk Trigonometri. Kajian ini melibatkan lima orang guru matematik baru (< 5 tahun) dan lima orang guru matematik berpengalaman (> 5 tahun) tingkatan 4 di daerah Batang Padang, Perak. Data kualitatif dikumpul melalui temu bual, pencerapan (pemerhatian) pengajaran pembelajaran, dan dokumen-dokumen yang berkaitan seperti silibus, buku rekod mengajar, dan la.....

73 hits

Sentiment Analysis (SA) field relies on lexicons to analyze people's perceptions. Therefore, evaluating and benchmarking lexicons is crucial for SA development, falling under Multi-Criteria Decision-Making (MCDM). The Fuzzy-Decision-by-Opinion-Score Method (FDOSM) and Fuzzy-Weighted-Zero-Inconsistency (FWZIC) techniques are novel MCDM extensions in a fuzzy-environment that address complexity-problems. Hence, this study aims to use these techniques to evaluate and benchmark dialectal lexicons. The methodology for this research is presented in four phases. The first phase includes developing four main criteria, along with its 28 sub-criteria for lexicon evaluation; the second phase proposes a multidimensional decision-matrix based on evaluation criteria and available lexicons; in the third phase, the multidimensional evaluation and benchmarking results of MCDM are obtained by FDOSM and are achieved by FWZIC; in the fourth phase, the validation was conducted based on the fusion of Systema.....

92 hits

Model Persamaan Berstruktur (MPB) secara khususnya sesuai digunakan bagi memodelkan hubungkait antara konstruk bersandar dan tak bersandar berbilang secara serentak. MPB mampu menjawab set persoalan kajian yang berhubungkait secara komprehensif dan sistematik kebiasaannya dengan menggunakan dua pendekatan, iaitu, MPB berdasarkan anggaran kebolehjadian maksimum (MPBAKM) dan kuasa dua terkecil separa (MPB-KTS). Bagi membangunkan MPB yang melibatkan konstruk pendam psikologi. Konstruk pendam psikologi perlu dianggarkan. Diketahui daripada beberapa kajian, data psikologi tidak bertaburan secara normal, dan wujud multikolinearan antara pembolehubah penunjuk yang membentuk pembolehubah konstruk tersebut. Dalam kajian ini, didapati bahawa wujud multikolinearan antara pembolehubah penunjuk dalam konstruk psikologi. Pendekatan MPB-AKM mengandaikan data bertaburan secara multivariat normal. Walau bagaimanapun pendekatan MPB-KTS adalah bebas-taburan, di samping tidak memerlukan andaian yang ketat.....

69 hits

Banyak kajian menunjukkan ramai dalam kalangan pelajar menghadapi masalah untuk memahami, seterusnya mengaplikasikan konsep yang dipelajari di dalam bilik darjah ke dalam kehidupan harian. Sehubungan dengan ini satu kajian telah dijalankan untuk mengenal pasti tahap kefahaman pelajar terhadap konsep asid-bes dan aplikasinya dalam kehidupan harian. Seramai 280 orang pelajar tingkatan empat aliran sains di tujuh buah sekolah daerah Johor Bahru, telah dilibatkan dalam kajian. Data kajian diperolehi dengan menggunakan satu set soal selidik _Aplikasi Konsep Asid-Bes Dalam Kehidupan Harian_. Data-data dianalisis dengan mengira frekuensi skor, peratusan, min dan sisihan piawai serta korelasi Pearson. Hasil kajian menunjukkan tahap kefahaman pelajar terhadap kosep asid-bes adalah sederhana; manakala, kemampuan mereka untuk mengaplikasikan konsep tersebut dalam kehidupan harian adalah lemah. Walau bagaimanapun, tidak terdapat perkaitan yang jelas antara tahap kefahaman pelajar terhadap konsep a.....

100 hits

This study reported on glutamate sensors based on chitosan as a heterogeneous membrane. The linearity was found to vary from 1.0 _ 10-5 M to 1.0 _ 10-1 M. The limit of detection was 5.0 _ 10-6 M and the pH values were in the range from 4 to 6. The presence of ionic species normally found in foodstuffs did not interfere the electrode. The material for proposed electrodes were cheap and environmental friendly and therefore are suggested as alternative tools for the analysis of glutamate. Keywords: Chitosan, heterogeneous membrane, glutamate..

110 hits

This study aimed to molecularly barcode fish diversity found in Tasik Raban, Lenggong Perak, using cytochrome c oxidase subunit I (COI) markers and to develop an educational manual for public reference, consisting of BOLD online data. Freshwater fish were sampled from Tasik Raban and a fin clip from each specimen was collected for molecular amplification utilizing the COI gene. Prior to creating the manual through the implementation of the ADDIE instructional learning methodology, various tasks such as morphological identification, COI divergence assessment, species delimitation, and phylogenetic analysis were undertaken. A total of 142 samples were collected encompasses eight families, 15 genera, and 16 species. Sequencing of extracted DNA revealed 77 DNA barcode with pairwise distance ranging from 0.00% to 2.00%. The application of Neighbour-Joining, Maximum Parsimony, and Maximum Likelihood in phylogenetic analysis showed consistent tree structures without any overlapping clusters. .....

156 hits

The benzaldehyde_(1R)_(-)_fenchone azine (1) and derivatives (3), (4), (5), (6) and (7) were prepared by heating the desired benzaldehyde derivatives and fenchone hydrazone in boiling ethanol solution in the presence of acetic acid as catalyst for 3 h. Treatment of the ligands (L) with Na2PdCl4H2O or [PdCl2(NCPh)2] in the ratio of 1 : 1 or 2 : 1 gave the complexes of the type PdL2Cl2 (2), (8), (9), (10), (11) and (12) of which the palladium was bonded to the nitrogen near to fenchone residue. Keywords: Fenchone azine, chiral terpene, palladium complexes..

121 hits