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.
This project deals with the development of a computer interfacing technique for the study of Hall effect. A stepper motor with resolution of 0.1 mm was used to move a pair of permanent magnet backward and forward against the sample. The General Purpose Interface Bus (GPIB) card together with a digital nanovoltmeter and teslameter using serial port siri RS232, interface were used to measure the potential difference and magnetic field strength, respectively. Hall effect for YBa2Cu3-xTixO7-δ system (x=0.00, 0.01, 0.03 and 0.05) showed positive sign Hall coefficient showing that the material is
a hole type carrier at room temperature. Parameters such as Hall coefficient and charge carrier concentration were also display on the front panel of Lab View programming.
This study proposes a simple methodology to estimate the power-law tail index of the Malaysian stock exchange by using the maximum likelihood Hill’s estimator. Recursive procedures base on empirical distribution tests are use to determine the threshold number of observations in the tail estimation. The threshold extreme values can be selected bases on the desired level of p-value in the goodness-of-fit tests. Finally, these procedures are apply to three indices in the Malaysian stock exchange.
In this article, the general form of Runge-Kutta method for directly solving a special fourth- order ordinary differential
equations denoted as RKFD method is given. The order conditions up to order seven are derived, based on the order
conditions, we construct a new explicit four-stage sixth-order RKFD method denoted as RKFD6 method. Zero-stability of
the method is proven. Comparisons are made using the existing Runge–Kutta methods after the problems are reduced
to a system of first order ordinary differential equations. Numerical results are presented to illustrate the efficiency and
competency of the new method.
In this paper, a new reliable method called the step variational iteration method (SVIM) based on an adaptation of the variational iteration method (VIM) is presented to solve non–chaotic and chaotic systems. The SVIM uses the general Lagrange multipliers for constructing the correction functional for the problems. The SVIM yields a step analytical solution of the form of a rapidly convergent infinite power series with easily computable terms and obtain a good approximate solution for larger intervals. The accuracy of the presented solution obtained is in an excellent agreement with the previously published solutions.
The central theme of nanotechnology to miniaturize devices has stimulated interest in diluted magnetic semiconductors (DMS). DMS that simultaneously exhibit magnetic and semiconducting behavior are capable of parting properties of two different function devices into one. In this research we present our first principles investigations related to the structural and electronic properties of, Cr doped zinc-blende (zB) ZnO, DMS. These calculations are carried out using full potential linearized augmented plane wave plus local orbital (FP-L(APW+lo)) with generalized gradient approximations approach as implemented in WIEN2k code. In this study, the effect of Cr doping on lattice parameters, spin polarized electronic band structure, density of states (Dos) of ZnO is presented and analyzed in detail.
A fracture, which mostly results from a fall, is fatal for the elderly. A fall occurred when a person cannot maintain the
body position. Most falls occurred when a person walks on a slippery surface or trips over an object on the ground during
a gait. Most people try to avoid falls instinctively and fall when their attempt fails. As such, this study investigated the
difference between two movements- a movement to avoid falls and a forward-falling movement without a fall-avoiding
movement- by analyzing the body movements of the subjects. A fast-moving fall-guiding device with a pneumatic actuator
was used to guide falls. The movement of the device could simulate a foot slip that may happen during daily activities.
A three-axis acceleration sensor and a Bluetooth module were used to avoid disturbing the body movement during a fall
as a wire sensor or a movement analysis system does.
Cervical cancer afflicts women worldwide. The patients’ mortality with cancer has been increased by changing to
westernized dietary habit and lifestyle. In order to detect early cervical cancer, a liquid-based cytology (LBC) was used
to examine the exfoliated cells collected from the cervix. This procedure helps to decrease the mortality rate. However,
this test mostly involves manual examination by the pathologists. This procedure needs to develop more efficient tool
in detecting cervical cancer which rate kept increasing. As such, this study was designed to develop some methods to
increase the effectiveness of LBC. The diagnosis algorithm was also established to diagnose the processed cell images
via an imaging process algorithm based on the diagnosis criteria. A cell diagnosis program based on GUI, combined
with the imaging process and the diagnosis algorithms were developed to automate the test process. The results of this
studies showed that this new program can be used for effective diagnosis of cervical cancer. Moreover, it was deemed
to increase the precision and accuracy of diagnosis and save patient time.
Lignocellulose from oil palm empty fruit bunch fiber (EFB) has been identified as another source for conversion into renewable energy or value added products. Cellulose, hemicellulose and lignin were extracted from EFB via a new treatment method using aqueous glycerol as a potential delignification agent. The aim of this study was to investigate the effect of treatment time and EFB to solvent ratio on the analytical compositions of EFB with or without further treatment with aqueous glycerol. The cooking time was varied at 3, 5 and 7 h with temperature fixed at 85°C. Three types of EFB were used; untreated fiber (UT-EFB), pretreated fiber with 5% (w/v) sodium hydroxide solution (N-EFB) and pretreated fiber with 5% (w/v) acetic acid solution (A-EFB). The analyses carried out were determination of extractives content, Klason Lignin, α-cellulose, hemicelluloses, holocellulose and ash content based on dry weight of the EFB. An increase in the glycerolysis time resulted in reduced content of Klason lignin and extractives but high percentages of holocellulose and α-cellulose for all EFB samples. Treatment of EFB with alkaline solution prior to glycerolysis resulted in reduction in cellulose content compared with holocellulose.
The existing optimal design of the fixed sampling interval S2-EWMA control chart to monitor the sample variance of a process is based on the average run length (ARL) criterion. Since the shape of the run length distribution changes with the magnitude of the shift in the variance, the median run length (MRL) gives a more meaningful explanation about the in-control and out-of-control performances of a control chart. This paper proposes the optimal design of the S2-EWMA chart, based on the MRL. The Markov chain technique is employed to compute the MRLs. The performances of the S2-EWMA chart, double sampling (DS) S2 chart and S chart are evaluated and compared. The MRL results indicated that the S2-EWMA chart gives better performance for detecting small and moderate variance shifts, while maintaining almost the same sensitivity as the DS S2 and S charts toward large variance shifts, especially when the sample size increases.
Research on the development of lightweight concrete (LWC) utilizing wastes and natural resources as lightweight
aggregates (LWA) is increasingly gaining attention worldwide due to sustainable and environmental concerns. A new
alternative is using palm kernel oil polyol (PKO-p)-based polyurethane (PU) as filler. Rigid PU is a block copolymer
comprised of a monomeric PKO-p and 2, 4-methylene diphenyl diisocyanate (crude MDI). The property of PKO-p, its
ratio with crude MDI and reaction time were determined. The reaction time showed the average of 60 s for cream
time and 95 s for rise time with maximum hardening time of 8 min. The reaction between PKO-p to MDI at 1:1 ratio
resulted in a very short hardening time (within 2 min). The compressive strength of the rigid PU was at 7.0 MPa at a
density of 206 kg/m3
. Further increase in the amount of PKO-p increased the density and compressive strength of the
PU. PU aggregate in the concrete mixture was added at 1 to 5% (w/w) to obtain concrete with density of less than 1800
kg/m3
. The resulting concrete has excellent compressive strength (17.5 MPa) and thermal conductivity (0.24 W/m⋅K).
The results showed that physical properties of PU played the most significant effect on the physical and mechanical
properties of the lightweight concrete
A well-known planting medium in soilless culture is a coconut based material famously known in Malaysia as cocopeat.
It is a viable ecologically friendly peat soil substitute for containerized crop production. The multipurpose growing media
had received much interest particularly in commercial applications. This study focused on the physical and hydraulic
characteristics of cocopeat perlite mixture as a growing media in containerized plant production. Perlite was added to
cocopeat at a ratio of 3 cocopeat: 1 perlite. Bulk density, particle density, porosity, particle size distribution, water holding
capacity, wettability and hydraulic conductivity of the media were evaluated. About 82.93% of the total particles were
in the range between 0.425 and 4 mm in diameter at a bulk density of 0.09 g/cm3
. Total porosity (79%) and wettability
improved with the incorporation of perlite to cocopeat. This study showed that water holding capacity was very high at
912.54% whereas the saturated hydraulic conductivity was low at 0.1 cm/s. The results showed that adding perlite to
cocopeat had improved the physical and hydraulic characteristics of the media.
The periostracum is the outermost layer overlying the inner prismatic and nacreous layers of the shells of bivalves. In the present study, the distributions of Cd and Pb in the soft tissues (ST) and periostracum of the green-lipped mussel Perna viridis sampled from 15 sampling sites in the coastal waters of Peninsular Malaysia were determined. The concentrations of Cd (0.21-10.87 mg/g dry weight) and Pb (1.16-40.20 mg/g dry weight) in the periostracum were generally higher than those in the ST (Cd: 0.10-5.55 mg/g dry weight; Pb: 2.53-18.62 mg/g dry weight). Based on correlation analysis from nine geographical populations, the higher correlation coefficients (R values) between the periostracum-geochemical fractions of the sediments than between the ST-geochemical fractions of the sediments indicated that the periostracum could be a potential biomonitoring material for Pb. Hence, the present results supported the use of the periostracum of P. viridis as a potential biomonitoring material for Pb but not for Cd. However, more studies are warranted to verify its usefulness for the biomonitoring of heavy metal pollution in tropical coastal waters.
A synthetic route towards the synthesis of TAN1251B was developed utilizing an alkylidene carbene insertion reaction as a key step to construct the quartenary centre. The α-hydroxylation of the 5,6-spirocyclic enone with iodosobenzene was successful to give a mixture of diastereomer compounds 20 and 21 in 1:1.2 ratios.
A study of surface pressure - area (Π-A) isotherms, surface potential (ΔV) and effective dipole moment (μ⊥) of two calix[4]arenes, 5,11,17,23-tetra-tert-butyl-25,27-diethoxycarbonyl methyleneoxy-26,28,dihydroxycalix[4]arene (calixarene I) and 5,17-(3-nitrobenzylideneamino)-11,23-di-tert-butyl-25,27-diethoxycarbonyl methyleneoxy-26,28-dihydroxycalix[4]arene (calixarene II) LB films which have the same lower rim but different upper rim has been carried out. This work used a NIMA Surface Potential (S-POT) sensor attached to an LB trough. Space filling model or Corey, Pauling and Koltun (CPK) precision molecular models have been used to estimate the size and the flexibility of both calix[4]arenes, which has been confirmed by X-Ray analysis in one case. The Π-A-isotherms confirmed that both of the calix[4]arenes form a monolayer film and the orientations of the plane of the calix ring are parallel with the air-water interface. The value of limiting area, (Alim) increases as a result of adding Fe3+ salt in the water subphase. For I, the value increases from 1.28 nm2 to 1.44 nm2 while for II, it increases from 1.70 nm2 to 1.86 nm2. ΔV measurements were performed on a water subphase containing Fe3+ salt in the concentration range 0 – 1.25 × 10–1 mM. ΔV of the compressed monolayer films increased with increasing Fe3+ concentration indicating the presence of Fe3+ salt bound within the calix[4]arenes. Using the ΔV values, the effective dipole moment has been found using the Helmholtz equation.
The stability of the limestone cliff at Gunung Kandu, Gopeng, Perak, Malaysia was assessed based on the Slope Mass
Rating (SMR) system on 53 cross sections of the Gunung Kandu hill slopes. The slopes of Gunung Kandu were identified
as class I (very good) to IV (poor). The kinematic analysis showed that 12 out of 53 hill slopes of Gunung Kandu were
identified as having potential wedge, planar and toppling failures. The assessment showed that the stability of the western
flanks can be classified as stable to unstable with the probability of failure from 0.2 to 0.6. The stability of the eastern and
southern flanks range from very stable to partially stable with the probability of failure from 0.0 to 0.4. While the stability
of northern flanks are from very stable to stable with the probability of failure of 0.0 - 0.2. This systematic approach
offers a practical method especially for large area of rock slope stability assessment and the results from probability of
failure values will help engineers to design adequate mitigation measures.
Bio-pesticides are becoming increasingly important as pest management tools in various cropping systems in the tropics essentially to remedy problems associated with the indiscriminate use of ‘hard’ and non-environmental friendly inorganic pesticide. In these past few decades, many bio-pesticidal products, both microbial-based (bacteria, fungi, microsprodia, entomopathogenic nematodes and viruses) and plant-based botanicals (rotenone and azadiracthin) have been studied for their use against insect pests in the tropics. In this study, the effects of the concentration process with respect to the yield of rotenone (mg) and its concentration (mg/mL) are presented extensively. The raw plants were collected from Kota Johor Lama, Johor and sorted to obtain the roots and stems. Only the roots and stems were utilized as raw materials of the extraction process. The rotenone from roots and stems was extracted using the normal soaking extraction (NSE) at 28 to 30oC with 95% (v/v) of acetone as a solvent and the solvent-to-solid ratio of 10 mL/g. The extraction was carried out for 24 h. Next, the liquid crude extract was concentrated using the rotary evaporator at 50oC and 80 mbar of vacuum pressure to remove approximately 90% of solvent. The fractions of the liquid crude extract were collected (15 min/mL/fraction), diluted (1/100 with acetone) and cleaned up (to remove any fine debris) prior to determination of rotenone content (mg) and concentration (mg/mL) by using the reverse-phase high performance liquid chromatography (RP-HPLC). Finally, the results showed that there was a significant effect of thermal degradation or dissipation of rotenone content at higher operating temperature (greater than 40oC) with a rapid rotenone reduction for the first 15 min of exposure. The possibilities for better exploitation and identification of the effective operating parameters based on the above mentioned results will be perhaps discussed in the future.
A third order Nakashima type implicit Pseudo Runge-Kutta method is presented. The free parameter was determined by minimizing the error bound. The stability region of the method was presented. Some problems on delay differential equations are tested to compare the accuracy of the proposed method with third order RADAU I.
A unit root test based on the modified least squares (MLS) estimator for first-order autoregressive process is proposed and compared with unit root tests based on the ordinary least squares (OLS), the weighted symmetric (WS) and the modified weighted symmetric (MWS) estimators. The percentiles of the null distributions of the unit root test are also reported. The empirical probabilities of type I error and powers of the unit root tests were estimated via Monte Carlo simulation. The simulation results showed that all unit root tests can control the probability of type I error for all situations. The empirical power of the test is higher than the other unit root tests, and Apart from that, the and tests also provide the highest empirical power. As an illustration, the monthly series of U.S. nominal interest rates on three-month treasury bills is analyzed.
This study was concerned with shape preserving interpolation of 2D data. A piecewise C1 univariate rational quadratic trigonometric spline including three positive parameters was devised to produce a shaped interpolant for given shaped data. Positive and monotone curve interpolation schemes were presented to sustain the respective shape features of data. Each scheme was tested for plentiful shaped data sets to substantiate the assertion made in their construction. Moreover, these schemes were compared with conventional shape preserving rational quadratic splines to demonstrate the usefulness of their construction.