Replica placement in peer-to-peer systems

In today’s distributed applications, replica placement is essential since moving the data in the vicinity of an application will provide many benefits. The increasing requirements of data for scientific applications and collaborative access to these data make data placement even more important. Until now, replication is one of the main mechanisms used in distributed data whereby identical copies of data are generated and stored at various distributed sites to improve data access performance and data availability. Most work considers file’s popularity as one of the important parameters taken into consideration when designing replica placement strategies. However, this thesis argues that a combination of popularity and affinity files are the most important parameters which can be used in decision making whilst improving data access performance and data availability in distributed environments. A replica placement mechanism called Affinity Replica Placement Mechanism (ARPM) is proposed focusing on popular files and affinity files. The idea of ARPM is to improve data availability and accessibility in peer-to-peer (P2P) replica placement strategy. A P2P simulator, PeerSim, was used to evaluate the performance of this dynamic replica placement strategy. The simulation results demonstrated the effectiveness of ARPM hence provided a proof that ARPM has contributed towards a new dimension of replica placement strategy that incorporates the affinity and popularity of files replicas in P2P systems

A comparison of student's errors in simple tenses.

This study aims to analyze and compare errors made by students when using simple tenses in essay writing. The comparison was made after 6 months. The respondents of the study consisted of secondary school students from the Alpha and Beta classes and UiTM Kelantan groups which consisted of first and third diploma students from three different programmes. All respondents were asked to write an essay twice, with 6-month gap based on the same writing stimulus. In total, there were 107 essays written by respondents in each writing session, giving a grand total of 214 essays being analyzed. The results indicated an increase in errors amounting to 4.47% among students in the Alpha group but there is a reduction of 13.76% among the Beta group which was the weaker group. As for UiTM students, Diploma in Banking students showed an increase in the amount of errors by 8.2%. On contrary, Diploma in Business and Diploma in Information Management students showed a decrease in the amount by 23.79% and 3.4 %, respectively. The results of the study also indicated that there were some similarities in the types of errors made by the students

Different media formulation on biocellulose production by Acetobacter xylinum (0416)

Biocellulose (BC), produced by Acetobacter xylinum (0416), was carried out using three types of medium composition under static surface culture. The media used in this experiment included CWHSM (Coconut water in Hestrin-Schramm medium), CM (Complex medium) and HSM (Hestrin-Schramm medium). CWHSM and CM used coconut water from agro-waste as the main source of sugar. The fermentation was conducted for 12 days and the results of BC dry weight, cell entrapped, pH medium and productivity were evaluated and compared. The results show that CWHSM is the most suitable medium for BC production with a productivity of up to 0.044 g l-1 day-1

Comparison of lipid quality of Nannochloropsis sp. flocculated via autoflocculation, AFlok-BP1 and alum

Nannocholoropsis sp. contains high lipid and polyunsaturated fatty acid that can further be used as a source of pharmaceutical and nutraceutical products. Removing the culture medium from algae cells is a prerequisite process before the products can be extracted and one common technique is called flocculation. Current commercial flocculants used for microalgae are either toxic or very costly. AFlok-BP1 is a biobased flocculant derived from plant offers non-toxic and cheap; thus has the potential to be applied in dewatering of microalgae cells. However, the flocculant has high tannin content. This study examines the effect of different flocculants on Nannocholoropsis sp. lipid yield following dewatering and extraction process. As the high tannin content presence in the spent medium and waste biomass after extraction is a concern; therefore, it was also evaluated. Cultures dewatered via autoflocculation at 10.5, 11 and 12, addition of AFlok-BP1 at 180 ppm and Alum at 300 ppm was selected for extraction of lipid. Bligh & Dryer method was used to extract the lipid and gas chromatography technique was used to analyse the fatty acid contents. The tannin content was evaluated via Folin-Ciocalteu method. AFlok-BP1 and Alum addition yielded lipid of only 18.2 and 17.2 mg/g dried biomass, respectively as compared to 34.4 mg/g when no flocculant was added. Autoflocculation using NaOH for pH 10.5, 11 and 12 resulted in even lower yield. Total fatty acid methyl ester was lowest in autoflocc treatment between 5.13 and 7.32 mg FAME/g biomass. Flocculation using AFlok-BP1 and Alum yielded slightly higher than 12 mg/g, but still lower than control (17.2 mg/g). However, the highest polyunsaturated fatty acid was found at 65.8% of the lipid extracted when added with AFlok-BP1 compared to only 11.1% in the control. Tannin was found highest in medium flocculated using AFlok-BP1 as expected at 1.428 mg/g. However, a measurable amount of tannin was also found in unflocculated medium (0.364 mg/g) and methanol-water layer during the lipid extraction. Low amount was found around 0.044 mg/g in the residual algae biomass after the extraction of lipid. The tannin amount is still low comparatively to concentrations that can be tolerated by marine animals as well as human. Based on some positive results, AFlok-BP1 is a potential to be used as green and cheap flocculants for microalgae dewatering process