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The individual compounds and sources of polycyclic aromatic hydrocarbon (PAHs) were studied in the surface sediments at 32 locations in the tourism area of Langkawi Island. A total of 15 PAHs were determined and quantified by gas chromatography coupled with mass spectrometry (GC-MS). The total PAH concentrations of surface sediments from Langkawi Island ranged from 228.13 to 990.25 ng/g and they were classified as being in the low to moderate pollution range. All sampling stations were dominated by high molecular weight PAHs with 4 rings (31.59%) and 5-6 rings (42.73%). The diagnostic ratio results showed that in most cases, the sampling stations have pyrogenic input. Further analysis using principal component analysis (PCA) combined with absolute principal component score (APCS) and multiple linear regression (MLR) showed that the natural gas emissions contributed to 57% of the total PAH concentration, 22% from the incomplete combustion and pyrolysis of fuel, 15% from pyrogenic and petrogenic sources and 6% from an undefined source.

A kinetic model of bacterial growth and metabolite production can adequately explain the trends and interaction of important parameters in a fermentation process. Production of surfactin by two bacterial strains, namely, Bacillus subtilis MSH1 and Bacillus subtilis ATCC 21322, in a 5 L bioreactor was investigated using Cooper’s media with 4% (v/v) glucose. The present kinetic study was carried out in order to determine the correlation between microbial cell growth, surfactin production and glucose consumption. Batch fermentation was performed by cultivation of each selected strain in a bioreactor at 30°C for 55 h. The experimental results showed production of surfactin in the culture medium after 5 and 10 h of incubation for B. subtilis ATCC 21332 and B. subtilis MSH1, respectively, at which the bacterial cells were at an early stage of the log phase. The maximum concentration of surfactin (Pmax) achieved by B. subtilis MSH1 and B. subtilis ATCC 21332 was 226.17 and 447.26 mg/L, respectively. The kinetic study of bacterial cell growth of both strains indicated that B. subtilis MSH1 had a specific growth rate (μmax) of 0.224 h-1 and attained a maximum biomass concentration (Xmax) as high as 2.90 g/L after 28 h of fermentation, while B. subtilis ATCC 21332, with μmax of 0.087 h-1, attained an Xmax of 2.62 g/L after 45 h of incubation. B. subtilis MSH1 showed higher growth kinetics, thus exhibited higher values of μmax and Xmax compared with B. subtilis ATCC 21332 under identical fermentation conditions. The Pmax achieved by B. subtilis ATCC 21332 was 447.26 mg/L, two times higher than that achieved by B. subtilis MSH1 (226.17 mg/L). The results obtained provide kinetics information including values of Pmax, μmax and Xmax for better understanding of interactions of bacterial cell growth and glucose consumption towards surfactin production by a commercial strain of B. subtilis ATCC 21332 and a local isolate of B. subtilis MSH1.

The uniaxial compressive strength test is a destructive and time consuming test. A number of non-destructive methods using portable testing equipment are more applicable and easier to conduct. This paper presents the results of a systematic approach to determine the uniaxial compressive strength of rock material using the Schmidt hammer rebound test. A total of five distinct locations (Graham Coast, Davis Coast, Nanson Island, Danco Coast and Trinity Island) were tested using the Schmidt rebound hammer test. Peninsula Antarctic located at northwest of Antarctic region comprising of igneous and metamorphic rocks. Statistical analysis of the results at 95% confidence level showed the Schmidt rebound value of the Graham Coast ranges from 40±1.7 to 41±1.3 with standard deviation of 8.2 to 6.4. The rebound value for Davis Coast was 39±1.6 with standard deviation of 7.7. Rocks from Nanson Island and Danco Coast have the Schmidt rebound value of 54±1.7 with standard deviation of 8.0 and 36±1.3 with standard deviation of 6.2, respectively. The Schmidt rebound value of rocks at Trinity Island ranges from 29±1.4 to 32±1.7 with standard deviation of 6.8 to 8.1. Thus, the respective uniaxial compressive strengths of rock materials from Graham Coast, Davis Coast, Danco Coast, Nanson Island and Trinity Island were 73-108, 50, 59, 164 and 45-59 MPa. The respective ISRM strength classification of rock materials of Graham Coast, Davis Coast, Danco Coast, Nanson Island and Trinity Island were strong (R4) to very strong rock (R5), medium strong rock (R3), strong rock (R4), very strong rock (R5) and medium strong (R3) to strong rock (R4). The results showed a mean of quantification of rock material strength based on the Schmidt Hammer rebound test in Antarctic Peninsula.