Students’ performance cannot be based solely on their ability to answer questions. The accuracy of the examination questions must also be considered when measuring the outcome of the course. The objective of this paper was to study the reliability of a question and its impact on students’ performance. A well-constructed question should be commensurate with the level of the intended knowledge. In this study, results from a linear algebra examination were analysed using the Rasch Model. The Rasch Model was used to analyse the reliability, non-redundancy and suitability of examination questions. The results showed that, in this particular case, the linear algebra questions were correctly constructed without any redundancy and suitable for the intended students.
The main aim of this paper was to validate the relative price monetary model (RPMM) of exchange rate determination for the Malaysian exchange rate (RM/USD) using monthly data set from 1986-2010. The Johansen multivariate cointegration test and vector error correction model were employed. Because the time period under consideration includes the South
East Asian financial crisis, the analysis is done using two time periods; the full time period as well as the period after the crisis. Two interesting results were observed from this empirical exercise. First, there is a long-run relationship between exchange rate and the selected macro variables only for the period after the crisis. Second, the forecasting performance of monetary approach based on the error correction model outperformed the Random Walk model.
This article investigates the performance of two-sample pseudo-median based procedure in testing differences between groups. The procedure is a modification of the one-sample Wilcoxon procedure using the pseudo-median of differences between group values as the central measure of location. The test was conducted on two groups with moderate sample
sizes of symmetric and asymmetric distributions. The performance of the procedure was measured in terms of Type I error and power rates computed via Monte Carlo methods. The performance of the procedure was compared against the t-test and Mann-Whitney-Wilcoxon test. The findings from this study revealed that the pseudo-median procedure performed very
well in controlling Type I error rates close to the nominal value. The pseudo-median procedure outperformed the MannWhitney-Wilcoxon test and is comparable to the t-test in controlling Type I error and maintaining adequate power.
MeSH terms: Maintenance; Monte Carlo Method; Models, Statistical; Meridians
Evaporation of vaporize organic liquid has ecological consequences when the compounds are introduced into both freshwater and marine environments through industrial effluents, or introduced directly into the air from industrial unit processes such as bioreactors and cooling towers. In such cases, a rapid and simple method are needed to measure physicochemical properties of the organic liquids. The Reversed-Flow Gas Chromatography (RF-GC) sampling technique is an easy, fast and accurate procedure. It was used to measure the diffusion coefficients of vapors from liquid into a carrier gas and at the same time to determine the rate coefficients for the evaporation of the respective liquid. The mathematical expression describing the elution curves of the samples peaks was derived and used to calculate the respective parameters for the selected liquid pollutants selected such as methanol, ethanol, 1-propanol, 1-butanol, n-pentane, n-hexane, n-heptane and n-hexadecane, evaporating into the carrier gas of nitrogen. The values of diffusion coefficients found were compared
with those calculated theoretically or reported in the literature. The values of evaporation rate were used to determine the activation energy of respective samples using Arrhenius equation. An interesting finding of this work is by using an alternative mathematical analysis based on equilibrium at the liquid-gas interphase, the comparison leads to profound
agreement between theoretical values of diffusion coefficients and experimental evidence.
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.
The optimization of protein content in earthworm-based fish feed formulation was investigated in the study. Full factorial design (FFD) and central composite design (CCD) were used as a statistical tool to screen the range of the selected parameters and to optimize the process, respectively. Three components were combined in the fish feed formulation
namely earthworm powder, chicken guts and soybean waste as the protein source. The optimum nutritional values were obtained at 25%, 25% and 5.95% for earthworm powder, soybean waste and chicken guts, respectively, to give an optimum protein content of 35.97%. Formulation of fish feed from earthworm powder can be an alternative in aquaculture industry in the near future.
This study compared some allometric parameters (shell length, shell width, shell height, total dry weight of soft tissues, condition index and heavy metals (Cd, Cu, Pb and Zn) in the different soft tissues of Perna viridis collected from Sebatu and Muar estuary. It was found that the total dry weight of soft tissues and condition index of mussels collected from Sebatu were significantly (p<0.05) higher than those in Muar. The significantly (p<0.05) higher concentrations of Cu in most soft tissues and some of Cd indicated a higher bioavailability of Cu and Cd at Muar than Sebatu. In addition, the significantly (p<0.05) higher levels of Cu, Cd, Zn and Pb in surface sediments collected from Muar supported the observable anthropogenic impacts at Muar than Sebatu and hence, higher metal contamination at Muar than Sebatu. The higher condition index value in mussels recorded in Sebatu than in Muar was believed to be a result of higher metal contamination at Muar estuary.
A study on the importance of Xylocopa varipuncta (Hymenoptera: Apidae) as pollination agent was conducted at the Setiu Mangrove Forest, Terengganu from September to December 2010. The objective of this study was to identify the pollens collected by carpenter bees (X. varipuncta) in the mangrove community of Setiu Wetlands. A total of 35 types of pollens were collected from the body of X. varipuncta and only 10 types of the pollens were successfully identified. The identified pollens were of Avicennia alba, Lumnitzera racemosa, Sonneratia caseolaris, S. ovata and Rhizophora apiculata from exclusive mangroves, while Suregada multiflora, Melaleuca cajuputi, Derris trifoliata, Acacia auriculiformis and Hibiscus tiliaceus were from non-exclusive mangroves. Melaleuca cajuputi was the highest number of pollen carried by X. varipuncta. This study showed that X. varipuncta is an important pollen carrier in the mangrove community of Setiu Wetlands, Terengganu.
A good adhesive is an important factor to consider in orthodontic bonding. Frequent bracket failure prolongs treatment duration and causes inconvenience to patient and operator. This study aimed to compare the effectiveness of two bonding agents, i.e. the self etching primer (SEP) and the conventional etch and bond (CEB) by monitoring the incidence, time and
sites of bracket failure. Eighty orthodontic patients were recruited after informed consent were obtained. A randomized split mouth technique was used where one side was bonded with CEB agent, while the other side was bonded using SEP agent. All bonded brackets were examined every 4 weeks for 20 months. Incidence of bracket failure was noted and
comparison between the two groups was done using paired t-test. Time and frequent site of failure were also assessed. Out of 1314 brackets, only 33 brackets were debonded with 16 from SEP group and 17 from CEB group which statistically insignificant (p>0.05). Almost 55% of bracket failure occurred during the first 3 months after bonding for both adhesives
with lower premolars was most the frequent site to fail in both adhesives (39.4%). Bracket bonded on the left side failed significantly compared to the right side. In conclusion, both self-etching primer and conventional acid-etch bonding agents are equally effective in retaining brackets clinically. Bracket failure mostly occurres during the first 3 months after bonding. The premolar brackets and the left side are mostly debonded when compared to other sites.
This paper presents facile and rapid synthesis route of Ni nanoparticles at approximately 180°C in the mixture composed of ethylene glycol (EG) with hydrazine (N2H4) as a reducing agent. X-ray diffraction (XRD) analysis revealed that Ni2+ can be reduced completely to Ni metal in 15 min. XRD analysis also indicated that the as-synthesized nanoparticles were pure Ni with face-centered cubic (fcc) crystal structure. Transmission electron microscopy (TEM) results showed that the sample with heating duration of 15 min has the most narrow size distribution and the size increased as the reaction time increased.
In this study TiO2 films have been prepared using two different techniques i.e. sol-gel and electron gun evaporation (e-gun) techniques. The films were annealed at 300, 350 and 400oC in air. The microstructure study using field emission scanning electron microscope and x-ray diffractometer showed nanometer grains size and only the film prepared by sol-gel and annealed at 400oC has anatase phase while others are amorphous. To study the effect of the films (as buffer layer) onto the dielectric bolometer Ba0.6Sr 0.4TiO3 as distance sensor, sensors with the configuration of Al/BST/TiO2/RuO2/SiO2/Si were built. Two different measurements i.e. with and without infrared source were carried out to measure the sensitivity and repeatability of the sensors. The sensors which contained sol-gel TiO2 films gave reading for both type of measurements, indicating that the sensor can act as active and passive sensors. However, the sensors which contained e-gun TiO2 films only gave responses when the IR source was used, indicating that they can only act as passive sensors. The most sensitive sensor was TiO2 film prepared by sol gel and annealed at 350oC. In general sensors which contained TiO2 films prepared by sol gel showed good repeatability.
The aim of this research was to investigate the ability of organometallic titanium-PANi hybrid materials as gas sensor at room temperature. To form the hybrid materials, commercially available polyaniline (PANi) powder were directly added into organometallic titanium sols which was synthesized using the sol gel method. The composite films were prepared via spin coating technique followed by electrode deposition for sensors fabrication. Five different organometallic titanium:PANi ratios namely 1 wt% to 5 wt% of PANi were prepared for this experiment. For gas sensing test, all samples were exposed to ethanol vapour. The sensing mode is based on the variation in the electrical conductivity due to the
interaction between the gas molecules and the film. It was observed that the composite sensors required appropriate ratio to exhibit optimum sensing properties. This finding proved that the hybridization process is successful and offered much cheaper and easier method for fabrication of room temperature gas sensor.
During the last quarter of the twentieth century there have been intensive research activities looking for green sources of energy. The main aim of the green generators or converters of energy is to replace the conventional (fossil) energy sources, hence reducing further accumulation of the green house gasses GHGs. Conventional silicon and III-V semiconductor solar cell based on crystalline bulk, quantum well and quantum dots structure or amorphous and thin film structures provided a feasible solution. However, natural dye sensitized solar cells NDSSC are a promising class of photovoltaic cells with the capability of generating green energy at low production cost since no vacuum systems or expensive equipment are required in their fabrication. Also, natural dyes are abundant, easily extracted and safe materials. In NDSSC, once dye molecules exposed to light they become oxidized and transfer electrons to a nanostructured layer of wide bandgap semiconductors such as TiO2. The generated electrons are drawn outside the cell through ohmic contact to a load. In this paper we review the structure and operation principles of the dye sensitized solar cell DSSC. We discuss preparation procedures, optical and electrical characterization of the NDSSC using local dyes extracted from Henna (lawsonia inermis L.), pomegranate, cherries and Bahraini raspberries (rubus spp.). These natural organic dyes are potential candidates to replace some of the man-made dyes used as sensitizer in many commercialized photoelectrochemical cells. Factors limiting the operation of the DSSC are discussed. NDSSCs are expected to be a favored choice in the building-integrated
photovoltaics (BIPV) due to their robustness, therefore, requiring no special shielding from natural events such as tree strikes or hails.
Si3N4-TiN composites were prepared by conventional powder processing (SPS1) and in-situ reaction sintering (SPS2). Rapid densification of SPS was achieved for sample SPS1 and SPS2 within a few minutes at low temperature. Sample SPS1 sintered at 1550ºC showed rapid transformation of α to β Si3N4 while for sample SPS2 sintered at 1350ºC, a significant
degree of α to β Si3N4 transformation was achieved. Homogeneous distribution of equiaxed TiN grains in matrix Si3N4 resulting in high hardness (21.7 GPa) and bending strength (621 MPa) for sample SPS1 sintered at 1550ºC. Elongated TiN grains as the reinforcement of Si
3N4 matrix composites was found to increase the toughness (8.39 MPa m1/2) of sample
SPS2 sintered at 1350ºC. The composites prepared by SPS2 sintered at 1250-1350ºC had low electrical resistivity and could be machined by electrical discharge machining (EDM).
The aim of this project was to investigate the effect of ZnO addition on the structural properties of ZnO-PANi/carbon black thin films. The sol gel method was employed for the preparation of ZnO sol. The sol was dried for 24 h at 100°C and then annealed at 600°C for 5 h. XRD characterization of the ZnO powder showed the formation of wurtzite type ZnO
crystals. The ZnO powder were mixed into PANi/carbon black solution which was dissolved into M-Pyrol, N-Methyl-2-Pyrrolidinone (NMP) to produce a composite solution of ZnO-PANi/carbon black. The weight ratio of ZnO were 4 wt%, 6 wt% and 8 wt%. The composite solutions were deposited onto glass substrates using a spin-coating technique to fabricate
ZnO-PANi/carbon black thin films. AFM characterization showed the decreasing of average roughness from 7.98 nm to 2.23 nm with the increment of ZnO addition in PANi/carbon black films. The thickness of the films also decreased from 59.5 nm to 28.3 nm. FESEM image revealed that ZnO-PANi/carbon black thin films have changed into agglomerated
surface morphology resulting in the increment of porosity of the films.
The effects of rf power on the structural properties of hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited using layer-by-layer (LbL) deposition technique in a home-built plasma enhanced chemical vapor deposition (PECVD) system were investigated. The properties of the films were characterized by X-ray diffraction (XRD), microRaman scattering spectroscopy, high resolution transmission electron microscope (HRTEM) and Fourier transform infrared (FTIR) spectroscopy. The results showed that the films consisted of different size of Si crystallites embedded within an amorphous matrix and the growth of these crystallites was suppressed at higher rf powers. The crystalline volume fraction of the films was optimum at the rf power of 60 W and contained both small and big crystallites
with diameters of 3.7 nm and 120 nm, respectively. The hydrogen content increased with increasing rf power and enhanced the structural disorder of the amorphous matrix thus decreasing the crystalline volume fraction of the films. Correlation of crystalline volume fraction, hydrogen content and structure disorder of the films under the effect of rf
power is discussed.
Proses pengeringan adalah proses akhir dalam penghasilan gelatin. Kaedah tradisi yang diaplikasi dalam industri adalah lebih rumit berbanding dengan kaedah pengering sembur. Serbuk gelatin dapat diperoleh dengan proses pengering sembur, tetapi jarang digunakan kerana dikhuatiri kualiti gelatin yang terhasil akan terjejas disebabkan proses degradasi
protein. Objektif kajian ini adalah mendapatkan keadaan optimum penghasilan serbuk gelatin dengan menggunakan kaedah sambutan permukaan (RSM). Gelatin komersial jenis B (berkekuatan gel dalam julat 151-160) diperbuat daripada tulang lembu dan pengering sembur skala pandu digunakan dalam kajian ini. Pemboleh ubah tak bersandar yang
diambil kira ialah kepekatan suapan larutan gelatin (6%(w/w) – 15%(w/w)) dan suhu pengoperasian (150oC-170oC). Pemboleh ubah bersandar yang diambil kira ialah peratus penghasilan, kandungan lembapan dan kekuatan gel serbuk gelatin. Keputusan uji kaji menunjukkan bahawa perbezaan kepekatan larutan suapan dan suhu masukan memberi
kesan kepada ketiga-tiga sambutan tersebut di atas dengan faktor kepekatan larutan suapan adalah faktor utama yang memberi kesan kepada peratus penghasilan serbuk gelatin. Semakin tinggi kepekatan suapan, semakin berkurang peratus penghasilan. Serbuk gelatin yang dihasilkan mempunyai kekuatan Bloom di antara 149 – 173 dan ia tidak jauh berbeza
dengan kekuatan Bloom gelatin komersial yang digunakan. Keadaan optimum yang diperoleh daripada analisis RSM ialah kepekatan suapan 9.23% (w/w) dan suhu masukan 170oC dengan penghasilan serbuk gelatin yang diperoleh ialah 22.15% dengan kandungan lembapan 3.81% dan kekuatan gel 168.5. Sisihan nilai daripada nilai ramalan ialah 0.09%
bagi peratus penghasilan, 3.05% bagi kandungan lembapan dan 0.78% bagi kekuatan gel.
Three new compounds of dibutyltin(IV) with N-alkylcyclohexyldithiocarbamate were successfully synthesized using in situ methods. Elemental analysis data of these complexes were in agreement with the general formula of (C4H9)2Sn[S2CNR(C6H11)]2 (R = CH3, C2H5, i-C3H7). Infrared spectra showed that the thioureide bands, ν(C=N) appeared
in the region of 1475 - 1479 cm-1, ν(C=S) bands in the region of 978 - 998 cm-1 and ν(Sn-S) bands in the region of 375 – 389 cm-1. Crystal structure of dibutyltin(IV) ethylcyclohexyldithiocarbamate showed a triclinic system and space group P-1. The crystal structure of the dithiocarbamate ligands were bidentically chelated to the tin atom with Sn-S unsymmetrical: Sn(1)-S(1) = 2.9255(11) and Sn(1)-S(2) = 2.5419(10); Sn(1)-S(3) = 2.8922(9) and Sn(1)-S(4) = 2.5293(10)Å. These compounds were screened for antibacterial activity against four bacteria species using the disc diffusion method. The results showed that (C4H9)
2Sn[S2CN(i-C3H7)(C6H11)]2 was mildly active against those three bacteria. Whereas all of
these compounds exhibited in vitro cytotoxicity activity toward human leukemic promyelocites HL-60 cell line with CD50 values lower than 1.00 µg/mL.
Gynura procumbens, a medicinal plant locally known as Sambung nyawa, is widely used traditionally in South East Asia as a remedy to alleviate symptoms of various ailments including diabetes mellitus. Previous investigators reported that the ethanol plant extract was hypoglycemic in streptozotocin (STZ)-induced diabetic rats and suggested the blood glucose-reducing effect could be due to G. procumbens mimicking insulin effects. Our present study aimed to reevaluate the hypoglycemic effect(s) of G. procumbens and to ascertain the involvement of glycogen synthase kinase (GSK3), a key component of insulin biosignaling in the plant activity. A cell-based assay showed that the three G. procumbens fractions tested did not exhibit anti-GSK3 activities. Oral administrations of hexane, ethyl acetate, n-butanol fractions of G. procumbens (250 mg/kg b.w.) and Glibenclamide (5 mg/kg b.w.) for 14 days in STZ-induced diabetic rats reduced blood glucose levels by 29.7%, 60.1%, 33.5% and 61.7% (p<0.05), respectively compared to diabetic control. Liver glycogen contents were elevated (p<0.05), following administration of the three fractions of
G. procumbens in diabetic rats when analysed after 14 days of treatment. Western blot analysis also showed GSK3β in the liver of G. procumbens fractions-treated and Glibenclamide-treated animals were phosphorylated at Ser-9. The above findings indicated that the hypoglycemic action of G. procumbens fractions resulted in the inactivation of
GSK3β in liver of diabetic rats. Since G. procumbens fractions did not exhibit GSK3 inhibitory properties, it is possible that the hypoglycemic action of the fractions observed here could be due to direct or indirect effects on upstream components of the insulin biosignaling pathway.
Many challenges arise in candidaemia treatment which involves emergence of antifungal resistance. New species have been identified due to improved methods of detection and some are resistant to commonly prescribed antifungal agents such as fluconazole and amphotericin B. Therefore, the objective of the study was to observe any changes in the susceptibility patterns and distribution of Candida species. This cross sectional study was conducted at the Department of Medical Microbiology and Immunology in UKMMC, a tertiary teaching hospital. One hundred and fifty one data were collected from the department’s laboratory records from January 2008 to December 2010. The yeasts were identified using ID32C carbohydrate assimilation tests whilst the antifungal susceptibility test was performed using Sensititre® YeastOne® broth microdilution method. Antifungal agents tested included amphotericin B, fluconazole, itraconazole, voriconazole, 5-flucytosine and caspofungin. Out of 151 blood isolates, 47 (31.1%) were Candida albicans and 104 (68.9%) were non-albicans Candida species. Candida tropicalis has surpassed C. albicans as the most commonly isolated Candida species from blood. Overall susceptibility (as compared to 2005-2006 data in brackets) to caspofungin was 99.3% (n/a), 5-flucytosine 97.4% (98%), amphotericin B 94.7% (100%), voriconazole 92.7% (98%), fluconazole 86.8% (90%) and
itraconazole 39.1% (40%). In conclusion, although the isolates were generally still susceptible to amphotericin B and fluconazole, resistance to these drugs is increasing.