Showing papers by "National University of Malaysia published in 2002"

Modeling the Spatial Dynamics of Regional Land Use: The CLUE-S Model

Abstract: Land-use change models are important tools for integrated environmental management. Through scenario analysis they can help to identify near-future critical locations in the face of environmental change. A dynamic, spatially explicit, land-use change model is presented for the regional scale: CLUE-S. The model is specifically developed for the analysis of land use in small regions (e.g., a watershed or province) at a fine spatial resolution. The model structure is based on systems theory to allow the integrated analysis of land-use change in relation to socio-economic and biophysical driving factors. The model explicitly addresses the hierarchical organization of land use systems, spatial connectivity between locations and stability. Stability is incorporated by a set of variables that define the relative elasticity of the actual land-use type to conversion. The user can specify these settings based on expert knowledge or survey data. Two applications of the model in the Philippines and Malaysia are used to illustrate the functioning of the model and its validation.

Electromagnetic and absorption properties of some microwave absorbers

Abstract: Electromagnetic properties of a thermoplastic natural rubber (TPNR), a lithium–nickel–zinc (Li–Ni–Zn) ferrite and a TPNR–ferrite composite subjected to transverse electromagnetic (TEM) wave propagation were investigated. The incorporation of the ferrite into the matrix of the TPNR was found to reduce the dielectric loss but the magnetic loss increased. The absorption characteristics of all the samples subjected to a normal incidence of TEM wave were investigated based on a model of a single-layered plane wave absorber backed by a perfect conductor. It is evident from a computer simulation that the ferrite is a narrowband absorber, whereas the polymeric samples show broadband absorption characteristics. Minimal reflection of the microwave power or matching condition occurs when the thickness of the absorbers approximates an odd number multiple of a quarter of the propagating wavelength. This is discussed as due to cancellation of the incident and reflected waves at the surface of the absorbers. The Li–Ni–Z...

Self-similar Gaussian processes for modeling anomalous diffusion

Abstract: We study some Gaussian models for anomalous diffusion, which include the time-rescaled Brownian motion, two types of fractional Brownian motion, and models associated with fractional Brownian motion based on the generalized Langevin equation. Gaussian processes associated with these models satisfy the anomalous diffusion relation which requires the mean-square displacement to vary with ${t}^{\ensuremath{\alpha}},$ $0l\ensuremath{\alpha}l2.$ However, these processes have different properties, thus indicating that the anomalous diffusion relation with a single parameter is insufficient to characterize the underlying mechanism. Although the two versions of fractional Brownian motion and time-rescaled Brownian motion all have the same probability distribution function, the Slepian theorem can be used to compare their first passage time distributions, which are different. Finally, in order to model anomalous diffusion with a variable exponent $\ensuremath{\alpha}(t)$ it is necessary to consider the multifractional extensions of these Gaussian processes.

Science Trainee Teachers' Pedagogical Content Knowledge and its Influence on Physics Teaching

Abstract: This study examined Malaysian science teachers' pedagogical content knowledge (PCK) of selected physics concepts. The two components of PCK investigated were (i) knowledge of students' understanding, conceptions and misconceptions of topics, and (ii) knowledge of strategies and representations for teaching particular topics. The participants were 12 trainee teachers from various academic science backgrounds attending a one-year postgraduate teacher-training course. They were interviewed on selected basic concepts in physics that are found in the Malaysian Integrated Science curriculum for lower secondary level. The findings showed that trainee teachers' PCK for promoting conceptual understanding is limited. They lacked the ability to transform their understanding of basic concepts in physics required to teach lower secondary school science pupils. The trainees' level of content knowledge affected their awareness of pupils' likely misconceptions. Consequently, the trainees were unable to employ the appropr...

Obesity in Malaysia.

Abstract: This study was undertaken to assess the recent data on Malaysian adult body weights and associations of ethnic differences in overweight and obesity with comorbid risk factors, and to examine measures of energy intake, energy expenditure, basal metabolic rate (BMR) and physical activity changes in urban and rural populations of normal weight. Three studies were included (1) a summary of a national health morbidity survey conducted in 1996 on nearly 29 000 adults > or =20 years of age; (2) a study comparing energy intake, BMR and physical activity levels (PALs) in 409 ethnically diverse, healthy adults drawn from a population of 1165 rural and urban subjects 18-60 years of age; and (3) an examination of the prevalence of obesity and comorbid risk factors that predict coronary heart disease and type 2 diabetes in 609 rural Malaysians aged 30-65 years. Overweight and obesity were calculated using body mass index (BMI) measures and World Health Organization (WHO) criteria. Energy intake was assessed using 3-d food records, BMR and PALs were assessed with Douglas bags and activity diaries, while hypertension, hyperlipidaemia and glucose intolerance were specified using standard criteria. The National Health Morbidity Survey data revealed that in adults, 20.7% were overweight and 5.8% obese (0.3% of whom had BMI values of >40.0 kg m(-2)); the prevalence of obesity was clearly greater in women than in men. In women, obesity rates were higher in Indian and Malay women than in Chinese women, while in men the Chinese recorded the highest obesity prevalences followed by the Malay and Indians. Studies on normal healthy subjects indicated that the energy intake of Indians was significantly lower than that of other ethnic groups. In women, Malays recorded a significantly higher energy intake than the other groups. Urban male subjects consumed significantly more energy than their rural counterparts, but this was not the case in women. In both men and women, fat intakes (%) were significantly higher in Chinese and urban subjects. Men were moderately active with the exception of the Dayaks. Chinese women were considerably less active than Chinese men. Chinese and Dayak women were less active than Malay and Indian women. In both men and women, Indians recorded the highest PALs. Hence, current nutrition and health surveys reveal that Malaysians are already affected by western health problems. The escalation of obesity, once thought to be an urban phenomenon, has now spread to the rural population at an alarming rate. As Malaysia proceeds rapidly towards a developed economy status, the health of its population will probably continue to deteriorate. Therefore, a national strategy needs to be developed to tackle both dietary and activity contributors to the excess weight gain of the Malaysian population.

Prevalence of blindness and low vision in Malaysian population: results from the National Eye Survey 1996

Abstract: Background: A national eye survey was conducted in 1996 to determine the prevalence of blindness and low vision and their major causes among the Malaysian population of all ages. Methods: A stratified two stage cluster sampling design was used to randomly select primary and secondary sampling units. Interviews, visual acuity tests, and eye examinations on all individuals in the sampled households were performed. Estimates were weighted by factors adjusting for selection probability, non-response, and sampling coverage. Results: The overall response rate was 69% (that is, living quarters response rate was 72.8% and household response rate was 95.1%). The age adjusted prevalence of bilateral blindness and low vision was 0.29% (95% CI 0.19 to 0.39%), and 2.44% (95% CI 2.18 to 2.69%) respectively. Females had a higher age adjusted prevalence of low vision compared to males. There was no significant difference in the prevalence of bilateral low vision and blindness among the four ethnic groups, and urban and rural residents. Cataract was the leading cause of blindness (39%) followed by retinal diseases (24%). Uncorrected refractive errors (48%) and cataract (36%) were the major causes of low vision. Conclusion: Malaysia has blindness and visual impairment rates that are comparable with other countries in the South East Asia region. However, cataract and uncorrected refractive errors, though readily treatable, are still the leading causes of blindness, suggesting the need for an evaluation on accessibility and availability of eye care services and barriers to eye care utilisation in the country.

TAG composition and solid fat content of palm oil, sunflower oil, and palm kernel olein belends before and after chemical interesterification

Abstract: Modification of the characteristics of palm oil (PO), sunflower oil, and plam kernel olein (PKOo) according to conventional three-component mixture designs was undertaken by a combination of blending and chemical interesterification (CIE) techniques. TAG composition and solid fat content (SFC) profile of the starting blends were analyzed and compared with those of the interesterified blends. Upon CIE, extensive rearrangement of FA among TAG was evident. Concentrations of several TAG were increased, some were decreased, and several new TAG were formed. The resulting changes in TAG profile were reflected in the SFC of the blends. The SFC values of the chemically interesterified blends, except binary blends of PO/PKOo, revealed that they were softer than their respective starting blends. SFC data also indicated that eutectic interaction occurred between PO and PKOo in the starting blends and that this interaction was diminished after CIE.

The nutrition and health transition in Malaysia.

Abstract: The accelerated phase of industrialisation and urbanisation in recent decades has inevitably brought about changes in the lifestyle of Malaysians. Changes in dietary habits and sedentary lifestyles are known to be associated with changes in health and increased prevalence of chronic diseases in the population. The objective of this paper is to provide a better understanding of the link between demographic variables and food consumption patterns related to the nutrition transition in Malaysia. This review uses various reports and publications from several ministries and selected local studies. The statistics compiled over the last two decades have shown that as the population achieves affluence, intakes of calories, fats and sugars increase, which may account for the substantial increase in food importation bills over the same period. Similarly, the rapid growth of the fast food industry during the last decade has added another dimension to the change in food consumption patterns of Malaysians. With the exception of a study on adolescents, the prevalences of overweight and obesity in children and adults are not strictly comparable due to the difference in body mass index (BMI) cut-off points in children and the study protocol in adults, and hence should not be misinterpreted as trends. The recent recommendation to lower the BMI cut-off points for Asians would only increase the magnitude of the existing prevalence among adults. The need to promote healthy nutrition for the population must be pursued vigorously, as the escalation of nutrition-related chronic degenerative diseases ‐ once an urban phenomenon ‐ has now spread to the rural population at an alarming rate. This paper indicates that the problem is real and needs urgent attention because it may be just the tip of the iceberg.

Effect of vitamin E on plasma malondialdehyde, antioxidant enzyme levels and the rates of wound closures during wound healing in normal and diabetic rats.

Abstract: Vitamin E is composed of various subfamilies that include tocopherols and tocotrienols. These compounds have antioxidant properties but differ in structure, dietary source and potency. In this study we evaluated the efficacy of alpha-tocopherol as an antioxidant and its role in wound closure in normal and streptozotocin-induced diabetic rats. The healing of 6 cm linear incisions created on the back of each male Sprague-Dawley rat (250-300 g) was monitored by measuring the length of the wounds daily. The rats were divided into two categories; normal and streptozotocin-induced diabetic rats. For each category, the animals were further divided into two groups; those untreated and those receiving 200 mg/kg bodyweight alpha-tocopherols daily by oral gavage. All rats were fed standard food and water ad libitum. Blood samples were taken at 0, 5 and 10 days after the wounds were created for the determination of malondialdehyde levels and red cell superoxide dismutase, catalase and glutathione peroxidase activities. The results showed that alpha-tocopherol reduced plasma malondialdehyde levels, increased glutathione peroxidase activity and accelerated the rate of wound closure in treated rats.

Dietary calcium intake in postmenopausal Malaysian women: comparison between the food frequency questionnaire and three-day food records.

Abstract: The objective of this study was to compare the dietary calcium intakes assessed by a quantitative food frequency questionnaire (FFQ) and the three-day food record method in 230 Chinese postmenopausal women aged 50–65 years in Kuala Lumpur. The results showed that the mean calcium intake from the dietary records was 447 ± 168 mg/day and 499 ± 211 mg/day from the FFQ. The mean difference in intake by the two methods was 51.3 mg (95% CI = – 30.8 – 77.9; SD = 181.2, P > 0.05), which did not differ significantly from zero. Pearson’s correlation coefficient of 0.56 was obtained between the two methods. Ninety-five percent of the individuals classified by food records fell into the same or within-one-quartile category when classified by FFQ. Forty-eight percent were classified into the same quartile by both methods. No subjects were grossly misclassified by the FFQ. The FFQ correctly identified subjects with calcium intakes below the Malaysian recommended daily allowance (450 mg/day) with 60% specificity and with 92% specificity for women consuming less than 800 mg calcium/day. In conclusion, the FFQ developed was a useful, rapid clinical tool for assessing calcium intake and identifying postmenopausal Chinese women with low calcium intakes in Malaysia.

Enriching the selectivity of metalloporphyrins chemical sensors by means of optical technique

Abstract: In the electronic nose, the sensing elements must demonstrate high selectivity feature toward various kinds of gases. This paper reports the use of the optical technique to enrich the selectivity of four metallo-octaethyl porphyrins (with the metal atoms of Mn, Fe, Co and Ru) Langmuir–Blodgett (LB) films toward four vapor samples; 2-propanol, ethanol, acetone and cyclohexane. The optical system was developed using these materials as sensing elements and four LED’s of different colors; red, yellow, green and blue, as light sources. The sensing sensitivity was based on the change on the light intensity at the peak wavelength of light sources after being reflected by the films. The sensitivity of the films was observed to depend on the wavelength of the light source used and the metal atom at the center of the metalloporphyrins molecules. Each thin film produced four response signals or 16 signals for the whole system for a particular vapor. These 16 signals constituted the pattern of the “signature” of a vapor. The signature of each vapor was found to be different from each other. This work indicated that the amount of the sensing elements used to create a high selectivity gas sensor system may be reduced.

Effects of aqueous extracts and decomposition of Mikania micrantha H.B.K. debris on selected agronomic crops

Abstract: Laboratory and greenhouse experiments were conducted to determine the effects of aqueous extract and the debris of Mile-a-Minute (Mikania micrantha H.B.K.) on the germination and growth of four test species, viz. tomato (Lycopersicon esculentum Mill.), Chinese cabbage (Brassica chinensis L.), corn (Zea mays L.) and long bean (Vigna sesquipedalis L.). Germination percentage, radicle length and fresh weight of two crops, Chinese cabbage and tomato, decreased progressively when plants were exposed to increasing concentrations (12.5, 25, 37.5 and 50 g L−1) of aqueous extract of Mikania, but did not affect those of corn and long bean seedlings. The emergence of tomato and Chinese cabbage was greatly reduced when Mikania debris was incorporated into the soil, irrespective of the amount of debris and the decomposition period. In contrast, the emergence of corn and long bean seedlings was not affected. The application of fertilizer (NPK 15 : 15 : 15) enhanced the fresh weight of all seedlings tested as compared with those not supplied with the fertilizer. Four compounds were identified in the leaf extract of Mikania, viz. caffeic acid, p-hydroxybenzaldehyde, resorcinol and vanillic acid.

Optical fibre Al(III) sensor based on solid surface fluorescence measurement

Abstract: An optical Al(III) sensor based on the use of purpurin immobilised on XAD 4 (styrene-divinylbenzene cross-linked copolymer) and solid surface fluorescence measurement has been developed. An optical fibre attachment for the spectrofluorometer and the probe have also been designed in this study. The plot of log[Al(III)] against the sensor response was linear for Al(III) concentration in the range of 5.0×10−5 to 3.2×10−3 M, with a limit of detection of 3.0×10−5 M. Fluoride solution was shown not to quench the complex during measurement and was used as regenerating agent to regenerate the probe. A good repeatability (1%) and reproducibility (4%) of measurement were obtained with this probe.

Germination and seedling emergence of glyphosate-resistant and susceptible biotypes of goosegrass (Eleusine indica [L.] Gaertn.)

Abstract: Effects of environmental factors on the germination and seedling emergence of glyphosate-resistant (R) and -susceptible (S) biotypes of Eleusine indica (L.) Gaertn. were examined under laboratory and greenhouse conditions. The R biotype exhibited a higher germination percentage compared with the S biotype at constant temperatures of 20 and 35°C under dark conditions, and alternating temperatures of 30/25°C, and 35/25°C during a 12 h photo period. For both biotypes, germination was optimal at alternating temperatures of 30/20°C and 35/20°C. However, there was no significant difference (P > 0.05) in the germination between the R and S biotypes at these temperature regimes. The germination of both biotypes was inhibited by osmotic stress imposed by a water potential of −0.80 MPa. When the moisture stress was released and the seeds were subsequently transferred to distilled water, the germination was enhanced to approximately 90% and 16% for the R and S biotype seeds, respectively. Higher emergence rates were obtained in shallow seed depths (0 or 2 cm) compared to deep depths. Emergence percentage of the R biotype was higher than that of the S biotype at 0 cm and 2 cm depths. The maximum emergence percentage of the R biotype was higher than that of S biotype when seeds were sown on the surface of either loamy or clay loam soil taken from three different sites.

Pathophysiology of Chronic Urticaria

Abstract: Chronic urticaria includes several different subsets with distinct pathophysiologies, and with important implications for investigation and treatment. Chronic ‘idiopathic’ urticaria represents a speci