19672 research outputs found
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Influence of habitat complexity on fish density and species richness in structurally simple forereef seagrass meadows
No full textSeagrass meadows are highly productive habitats that support commercially and ecologically important fishes and invertebrates. However, evidence of fish-habitat relationships are seldom drawn from forereef seagrass meadows that are structurally simple in terms of species richness and relative size and, consequently, their role as habitats is unclear. In this study, fish-habitat relationships were examined in such meadows in the forereef seagrasses of Tinggi Island and Babi Besar Island, Malaysia, by documenting habitat complexity attributes (canopy height, shoot density and percent cover), distance to adjacent coral reefs, and water depth within 2×2 m quadrats. Fish assemblages were recorded using the Remote Underwater Video Station method. A total of 1166 individuals from 86 taxa were found and enumerated. This study showed that (1) fish density and species richness were significantly associated with seagrass percent cover alone; (2) commercially important carnivores formed the majority of the fish populations in the meadows, and (3) fish density and species richness were positively correlated with distance to the nearest adjacent coral reef, indicating the need to account for the effects of neighboring habitats in studies of this nature. Thus, structurally simple seagrass meadows are still important fish habitats, especially as feeding grounds for commercially significant carnivores
Motion control of a two-axis linear motor-driven stage in the micro-milling process
No full textThe application of linear motor-driven stages as the feed drivers of CNC micro milling machine tools is growing. In addition to employ high speed and high precision equipment such as linear motor-driven stages, the precision of the machined contours is highly dependent on the capabilities of the servo controllers. In this paper, the design of a precise controller for a two-axis LMDS has been investigated for micro-milling applications. In such feed drives, disturbances such as friction, force ripples, and machining forces have adverse effects on the workpiece positioning precision due to the direct drive concept behind them. Therefore, in order to have an acceptable transient response and disturbance rejection properties, a two-degree-of-freedom proportional–integral–derivative controller was employed for each axis. To design this controller, the zero-placement method was used. To compensate disturbances and machining contour errors, the utilization of Kalman filter observers, neural networks, cross-coupled controllers, and different integration of them were studied. The controllers were experimentally examined for circular motions. An integrated controller consisted of a Kalman filter disturbance observer, a cross-coupled controller, and a well-designed two-degree-of-freedom proportional–integral–derivative controller resulted in a high contouring and tracking precision. The controller could also reduce the spikes caused by the friction at the motion reversal points such as the quadrants in circle trajectories
The use of ionic liquids as additive to stabilize surfactant foam for mobility control application
No full textFoam application has been introduced in enhanced oil recovery processes for mobility control to overcome some issues occurred during gas injection. The stability of foam has become the main concern as it dictates the effectiveness of foam mobility control. Many attempts at enhancing foam stability under reservoir conditions involve the application of chemical additives which can produce synergistic effect in combination with surfactant. Ionic liquids (ILs), salts melting below 100 °C, are considered to be able to alter surface behavior of surfactant molecules, hence supporting the surfactant performance at the interface. Their alteration is expected to be favorable in improving surface properties of foam. This research has introduced ionic liquid based additives for the first time to improve surfactant foam stability. Identification of the effect of ILs was performed by conducting bulk foam experiments at ambient conditions and also at high temperature using Foamscan. The foaming properties of in-house surfactant (MFOMAX) were evaluated in the absence and presence of ILs at different mixture ratios. The results show that imidazolium- and eutectic-based ILs were able to improve surfactant foam stability to different extent at high temperature and their effect on foam stabilization was more pronounced at surfactant/IL mixture ratio of 60:40. The highest foam stability increment exhibited by the best formulation reached 136% of that achieved by the formulation without IL. This study has indicated that ionic liquid has a promising potential for improving surfactant-stabilized foam mobility control during EOR processes
Adsorption study of methyl orange by chitosan/polyvinyl alcohol/zeolite electrospun composite nanofibrous membrane
No full textThe chitosan/polyvinyl Alcohol/zeolite electrospun composite nanofibrous membrane was fabricated for adsorption of methyl orange. The EDX, TGA and tensile test were carried out for the characterization of the membrane. The Young's Modulus of the nanofibrous membranes increased by more than 100% with the addition of zeolite to chitosan/PVA. The batch adsorption tests were conducted by varying the initial concentration of methyl orange, contact time and pH of the dye solution. UV–vis results showed that most of the dye was adsorbed within 6 min. An adsorption kinetic study was carried out using the pseudo-second-order kinetic model, Lagergren-first-order model and intra particle diffusion model. The adsorption kinetics obeyed the Pseudo second order model. The adsorption mechanism was analyzed using the Langmuir and Freundlich isotherm model. The experimental data fits well with the Freundlich model. The adsorption capacity of the membrane was 153 mg/g. Adsorption capacity was decreased with increasing pH value. The resulting nanofiber became less active over methyl orange after several runs
Evaluation of conventional and response surface level optimisation of n-dodecane (n-C12) mineralisation by psychrotolerant strains isolated from pristine soil at Southern Victoria Island, Antarctica
No full textBackground: Biodegradation of hydrocarbons in Antarctic soil has been reported to be achieved through the utilisation of indigenous cold-adapted microorganisms. Although numerous bacteria isolated from hydrocarbon-contaminated sites in Antarctica were able to demonstrate promising outcomes in utilising hydrocarbon components as their energy source, reports on the utilisation of hydrocarbons by strains isolated from pristine Antarctic soil are scarce. In the present work, two psychrotolerant strains isolated from Antarctic pristine soil with the competency to utilise diesel fuel as the sole carbon source were identified and optimised through conventional and response surface method. Results: Two potent hydrocarbon-degraders (ADL15 and ADL36) were identified via partial 16S rRNA gene sequence analysis, and revealed to be closely related to the genus Pseudomonas and Rhodococcus sp., respectively. Factors affecting diesel degradation such as temperature, hydrocarbon concentration, pH and salt tolerance were studied. Although strain ADL36 was able to withstand a higher concentration of diesel than strain ADL15, both strains showed similar optimal condition for the cell's growth at pH 7.0 and 1.0% (w/v) NaCl at the conventional 'one-factor-at-a-time' level. Both strains were observed to be psychrotrophs with optimal temperatures of 20 °C. Qualitative and quantitative analysis were performed with a gas chromatograph equipped with a flame ionisation detector to measure the reduction of n-alkane components in diesel. In the pre-screening medium, strain ADL36 showed 83.75% of n-dodecane mineralisation while the reduction of n-dodecane by strain ADL15 was merely at 22.39%. The optimised condition for n-dodecane mineralisation predicted through response surface methodology enhanced the reduction of n-dodecane to 99.89 and 38.32% for strain ADL36 and strain ADL15, respectively. Conclusions: Strain ADL36 proves to be a better candidate for bioaugmentation operations on sites contaminated with aliphatic hydrocarbons especially in the Antarctic and other cold regions. The results obtained throughout strongly supports the use of RSM for medium optimisation
Nexus between economic sanctions and inflation: a case study in Iran
No full textConventional studies have applied dummy variables to analyse the relationship between economic sanctions and inflation while we construct an index which is called Trade-Financial Sanctions (TF index). TF Index is a liner combination of indices which includes trade openness and foreign investment by applying the principal component model. Through the TF index and market exchange rate the impact of economic sanctions on inflation is analysed in the three phases of sanctions; free sanctions, heavy sanctions, and light sanctions. The results illustrate that the TF index decreases inflation when the Iran’s economy experiences free sanctions or light sanctions relative to when the economy is in heavy sanctions. Heavy sanctions create instability in the market exchange rates and widening the gap between the market and the official exchange rates. Furthermore, economic sanctions increase expected inflation among the people and drive higher inflation. Therefore, these results suggest that the government should work more seriously to solve the main obstacles of trade and investment inflows imposed by the economic sanctions
Development of nanoparticle-assisted PCR assay in the rapid detection of brain-eating amoebae
No full textBrain-eating amoebae (Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri) have gained increasing attention owing to their capacity to produce severe human and animal infections involving the brain. Early detection is a pre-requisite in successful prognosis. Here, we developed a nanoPCR assay for the rapid detection of brain-eating amoebae using various nanoparticles. Graphene oxide, copper and alumina nanoparticles used in this study were characterized using Raman spectroscopy measurements through excitation with a He–Ne laser, while powder X-ray diffraction patterns were taken on a PANanalytical, X’Pert HighScore diffractometer and the morphology of the materials was confirmed using high-resolution transmission electron microscopy (HRTEM). Using nanoparticle-assisted PCR, the results revealed that graphene oxide, copper oxide and alumina nanoparticles significantly enhanced PCR efficiency in the detection of pathogenic free-living amoebae using genus-specific probes. The optimal concentration of graphene oxide, copper oxide and alumina nanoparticles for Acanthamoeba spp. was determined at 0.4, 0.04 and 0.4 μg per mL respectively. For B. mandrillaris, the optimal concentration was determined at 0.4 μg per mL for graphene oxide, copper oxide and alumina nanoparticles, and for Naegleria, the optimal concentration was 0.04, 4.0 and 0.04 μg per mL respectively. Moreover, combinations of these nanoparticles proved to further enhance PCR efficiency. The addition of metal oxide nanoparticles leads to excellent surface effect, while thermal conductivity property of the nanoparticles enhances PCR productivity. These findings suggest that nanoPCR assay has tremendous potential in the clinical diagnosis of parasitic infections as well as for studying epidemiology and pathology and environmental monitoring of other microbes
Income convergence in the ASEAN-5 countries
No full textMainstream economic arguments posit that liberalization is the route latecomer economies should pursue to achieve income convergence between countries. The Association of Southeast Asian Nations (ASEAN) offers a useful platform to test if trade liberalization has been accompanied by income convergence since the grouping have been among the most aggressive in promoting the removal of trade restrictions in the world. Owing to data limitations involving Brunei and the transition economies of Cambodia, Laos, Myanmar and Vietnam, the assessment is confined to the founding members, namely, Indonesia, Malaysia, the Philippines, Singapore, and Thailand. The current paper tested the income convergence hypothesis by deploying some innovative and powerful unit root tests, such as the Fourier augmented Dickey–Fuller (FADF) and the Fourier ADF with structural breaks (FADF–SB) methods. However, the results show a positive causal relationship with 10% of the two-country pairings. Sixty percent of the two-country pairings showed no causal relationship at all, while the remaining 30% produced inconclusive results. These findings suggest that other variables, such as government focus on the science, technology and innovation infrastructure to promote structural transformation may be more important than trade liberalization efforts to reduce inter-country income gaps
Improving awareness, knowledge and attitude of epilepsy using an interactive animated epilepsy education programme (IAEEP) among Malaysian teachers and students
No full textBackground: Improving awareness, knowledge and attittude (AKA) of teachers and students about epilepsy is an important step to reduce the stigma experienced by children with epilepsy. To date there are no studies evaluating effectiveness of an information technology based epilepsy education programme in improving AKA among teachers and students. Method: Cross-sectional study was to assess the baseline AKA of epilepsy among Malaysian teachers and secondary school students, and to examine effectiveness improving their AKA using the Interactive Animated Epilepsy Education Programme (IAEEP). AKA of teachers and students were assessed pre-and post-implementation of IAEEP. Results: Total of 54 teachers and 67 secondary students participated in this study. The baseline AKA on epilepsy among Malaysian teachers was low in the awareness domain, moderate in the knowledge domain, and positive in the attitude domain. The baseline AKA on epilepsy among students was very low in the awareness domain, low in the knowledge domain, and indifferent in the attitude domain. The AKA scores in all domains of teachers and students improved significantly after introduction of IAEEP (P<0.001). Post-IAEEP the AKA of teachers was moderate in the awareness domain, high in the knowledge domain, and very positive in the attitude domain; the AKA of students was low in the awareness domain, very high in the knowledge domain, and very positive in the attitude domain Conclusion: Our findings highlight a need for epilepsy educational programmes to be implemented in Malaysian schools. The IAEEP is an effective educational programme to improve the AKA particularly in the knowledge domain among teachers and students
Enhancement of Thermoelectric Properties in Cold Pressed Nickel Doped Bismuth Sulfide Compounds
No full textAbstract: Nanostructured Ni doped Bi2S3 (Bi2−xNixS3, 0 ≤ x ≤ 0.07) is explored as a candidate for telluride free thermoelectric material, through a combination process of mechanical alloying with subsequent consolidation by cold pressing followed with a sintering process. The cold pressing method was found to impact the thermoelectric properties in two ways: (1) introduction of the dopant atom in the interstitial sites of the crystal lattice which results in an increase in carrier concentration, and (2) introduction of a porous structure which reduces the thermal conductivity. The electrical resistivity of Bi2S3 was decreased by adding Ni atoms, which shows a minimum value of 2.35 × 10−3 Ω m at 300 °C for Bi1.99Ni0.01S3 sample. The presence of porous structures gives a significant effect on reduction of thermal conductivity, by a reduction of ~ 59.6% compared to a high density Bi2S3. The thermal conductivity of Bi2−xNixS3 ranges from 0.31 to 0.52 W/m K in the temperature range of 27 °C (RT) to 300 °C with the lowest κ values of Bi2S3 compared to the previous works. A maximum ZT value of 0.13 at 300 °C was achieved for Bi1.99Ni0.01S3 sample, which is about 2.6 times higher than (0.05) of Bi2S3 sample. This work show an optimization pathway to improve thermoelectric performance of Bi2S3 through Ni doping and introduction of porosity. Graphical Abstract: [Figure not available: see fulltext.]