The effect of specific alpha[ or alpha2 adrenoceptor agents on the response of rat superior mesenteric-portal vein to field stimulation was investigated. In. a dose related manner, phenylephrine (alpha[ agonist) and yohimbine (alpha2 antagonists) increased while prazosin (alpha[ antagonist) and clonidine (alpha2 agonist) decreased the response of the vein to field stimulation. These effects are the same as those seen with these agents on rat and mouse vas deferens. It is suggested that, as in vas deferens, alpha1 postsynaptic and alpha2 presynaptic receptors exist in rat superior mesenteric-portal vein and that these receptors may be sufficiently sensitive in vein for their existence to be of significance in the action of these agents at clinical doses.
Suspended solids, colour and chemical oxygen demand (COD) are among the main pollutants in landfill leachate. Application of physical or biological processes alone is normally not sufficient to remove these constituents, especially for leachate with a lower biochemical oxygen demand (BOD)/ COD ratio. The main objective of this research was to investigate the efficiency of coagulation and flocculation processes for removing suspended solids, colour and COD from leachate produced in a semi-aerobic landfill in Penang, Malaysia. A 12-month characterization study of the leachate indicated that it had a mean annual BOD/COD ratio of 0.15 and was partially stabilized, with little further biological degradation likely to occur. Particle size analysis of the raw leachate indicated that its 50th percentile (d50) was 11.68 microm. Three types of coagulants were examined in bench scale jar test studies: aluminium sulphate (alum), ferric chloride (FeCl3) and ferrous sulphate (FeSO4). The effects of agitation speed, settling time, pH, coagulant dosages and temperature were examined. At 300 rpm of rapid mixing, 50 rpm of slow mixing, and 60 min settling time, higher removals of suspended solids (over 95%), colour (90%) and COD (43%) were achieved at pH 4 and 12. FeCl3 was found to be superior to other coagulants tested. At pH 4 and 12, fair removal of suspended solids was observed at a reasonably low coagulant dose, i.e., 600 mg L(-1); hHowever, about 2500 mg L(-1) of coagulant was required to achieve good removals at pH 6. Better removals were achieved at higher temperature. The d50 of sludge after coagulation at pH 4 with a 2500 mg L(-1) FeCl3 dose was 60.16 microm, which indicated that the particles had been removed effectively from the leachate. The results indicate that coagulation and flocculation processes can be used effectively in integrated semi-aerobic leachate treatment systems, especially for removing suspended solids, colour and COD.
The presence of ammoniacal nitrogen (N-NH3) in leachate is one of the problems normally faced by landfill operators. Slow leaching of wastes producing nitrogen and no significant mechanism for transformation of N-NH3 in the landfills causes a high concentration of ammoniacal nitrogen in leachate over a long period of time. A literature review showed that the removal of ammoniacal nitrogen from leachate was not well documented and to date, there were limited studies in Malaysia on this aspect, especially in adsorption treatment. The main objective of the present study was to investigate the suitability of activated carbon, limestone and a mixture of both materials as a filtering medium, in combination with other treatments capable of attenuating ammoniacal nitrogen which is present in significant quantity (between 429 and 1909 mg L(-1)) in one of the landfill sites in Malaysia. The results of the study show that about 40% of ammoniacal nitrogen with concentration of more than 1000 mg L(-1) could be removed either by activated carbon or a mixture of carbon with limestone at mixture ratio of 5:35. This result shows that limestone is potentially useful as a cost-effective medium to replace activated carbon for ammoniacal nitrogen removal at a considerably lower cost.
A total of 719 wild rats were captured from four localities representing the west (Kuala Lumpur), east (Kuantan), north (Georgetown) and south (Malacca) to determine the diversity of blood protozoan from the urban wild rat population in peninsular Malaysia. Five rat species were recovered with Rattus rattus diardii being the most dominant species, followed by Rattus norvegicus, Rattus exulans, Rattus annandalei and Rattus argentiventer. Two blood protozoan species were found infecting the rodent population namely, Plasmodium sp. (42.1%) and Trypanosoma lewisi (25.0%). This study reports the presence of Plasmodium sp. for the first time in the rodent population in Malaysia. Two main intrinsic factors were identified affecting the parasitic infections. Trypanosoma lewisi infections were influenced by host age and sex with infections observed higher in male and juvenile rats meanwhile Plasmodium sp. infections were observed almost similar in both sexes. However, infections were higher in sub-adult rats.
The quantitative buffy coat (QBC) technique and conventional Giemsa thin blood smear was compared to determine the sensitivity and specificity of the technique in detecting blood parasitic infection of the rodent populations from four urban cities in Peninsular Malaysia. A total of 432 blood samples from four rat species (Rattus norvegicus, Rattus rattus diardii, Rattus exulans and Rattus argentiventer) were screened using both techniques and successfully detected two blood protozoan species (Trypanosoma lewisi and Plasmodium sp.) with Trypanosoma lewisi predominantly infecting the population. Results showed that Giemsa-stained thin film (GTF) was the better detection method on blood parasitemia (46.7%) compared to Quantitative Buffy Coat method (38.9%) with overall detection technique sensitivity and specificity at 83.2% and 74.8% respectively. The sensitivity in detection of Trypanosoma lewisi was 84.4% with value slightly lower for Plasmodium sp. infections at 76.6%. Statistical analysis proved that GTF technique was significantly more sensitive in the detection of blood protozoan infections in the rodent population compared to QBC (p<0.05).
A study was conducted to investigate the efficiency of coagulation and flocculation processes for removing colour from a semi-aerobic landfill leachate from one of the landfill sites in Malaysia. Four types of coagulant namely aluminium (III) sulphate (alum), ferric (III) chloride, ferrous (II) sulphate and ferric (III) sulphate were studied using standard jar test apparatus. Results indicated that ferric chloride was superior to the other coagulants and removed 94% of colour at an optimum dose of 800 mg/l at pH 4. The effect of coagulant dosages on colour removal showed similar trend as for COD, turbidity and suspended solids. This suggested that colour in landfill leachate was mainly contributed by organic matters with some insoluble forms that exhibited turbidity and suspended solids readings. The results from this study suggested that ferric chloride could be a viable coagulant in managing colour problems associated with landfill leachate.
Limestone has been proven effective in removing metals from water and wastewater. A literature review indicated that limestone is capable of removing heavy metals such as Cu, Zn, Cd, Pb, Ni, Cr, Fe and Mn are through a batch process or by filtration technique. The removal capability is reported at up to 90%. However, to date most of the studies have been focused on synthetic wastewater. The present study attempts to investigate the suitability of limestone to attenuate total iron (Fe) from semi aerobic leachate at Pulau Burung Landfill Site in Penang, Malaysia. Iron was found in significant quantities at the landfill site. The study also aims to establish the Fe isotherm and breakthrough time of the proposed limestone filter for post-treatment to the migrating landfill leachate before its release to the environment. The Fe isotherms were established using a batch equilibrium test, while the breakthrough characteristics were determined using continuous flow permeating through a limestone column. The latter was used in order to simulate the continuous flow of leachate that would occur in the proposed limestone filter. The limestone media used in the experiment contain more than 90% CaCO3 with particle sizes ranging from 2 to 4 mm. Four filter columns (each 150 mm in diameter and 1000 mm depth) were installed at the landfill site. Metal loadings were kept below 0.5 kg /m3 day and the experiment was run continuously for 30 days. Initial results indicated that 90% of Fe can be removed from the leachate based on retention time of 57.8 min and surface loading of 12.2 m3/m2 day. For the batch study on the Fe isotherm, the results indicated that limestone is potentially useful as an alternative leachate treatment system at a relatively low cost.
Palm oil fuel ash (POFA) has limited use as a fertilizer, while contribute effectively to the environmental contamination and health risks. Petroleum sludge poses a serious effect on the ecological environment and human health. The present work aimed to present a novel encapsulation process with POFA binder for treating petroleum sludge. Among 16 polycyclic aromatic hydrocarbons, four compounds were selected for the optimization of encapsulation process due to their high risk as carcinogenic substrates. Percentage PS (10-50%) and curing days (7-28 days) factors were used in the optimization process. The leaching test of PAHs was assessed using a GC-MS. The best operating parameters to minimize PAHs leaching from solidified cubes with OPC and10% POFA were recorded with 10% PS and after 28 days, at which PAH leaching was 4.255 and 0.388 ppm with R2 is 0.90%. Sensitivity analysis of the actual and predicted results for both the control and the test (OPC and 10% POFA) revealed that the actual results of the 10% POFA experiments have a high consistency with the predicted data (R2 0.9881) while R2 in the cement experiments was 0.8009. These differences were explained based on the responses of PAH leaching toward percentage of PS and days of cure. In the OPC encapsulation process, the main role was belonged to PS% (94.22%), while with 10% POFA, PS% contributed by 32.36 and cure day contributed by 66.91%.
This study aims to justify the mediating effect of organizational commitment in the association between training and development, career development, and work performance. Data was collected from 362 frontline hotel employees through a survey by random sampling technique. The analysis methodology comprises descriptive statistics, measurement, and structure models through SPSS 23 and Smarts PLS 3.0. This study significantly examined the correlation between training and development and work performance, career development, and work performance. Moreover, organizational commitment in the hotel sector is significantly associated with work performance. Furthermore, the significant correlation between training and development and work performance career development among hotel personnel is mediated by organizational commitment. Owners and managers should know the necessary policies to enhance employees' work performance and organizational commitment and consider appropriate behaviour. Besides, all required facilities for enhancing career development and training and development should be implemented to strengthen hotels' present and future demands. It is furthered by the study's explanations of the results and their limitations, which also included suggestions for future research possibilities. This research filled the gap in the hotel industry in Bangladesh, where study works into wide-ranging training and development, career development practices, organizational commitment, and work performance were rare.