A bottom-up approach for synthesizing silver nanoparticles (AgNPs-GA) phytomediated by Garcinia atroviridis leaf extract is described. Under optimized conditions, the AgNPs-GA were synthesized at a concentration of 0.1 M silver salt and 10% (w/v) leaf extract, 1:4 mixing ratio of reactants, pH 3, temperature 32 °C and 72 h reaction time. The AgNPs-GA were characterized by various analytical techniques and their size was determined to be 5–30 nm. FTIR spectroscopy indicates the role of phenolic functional groups in the reduction of silver ions into AgNPs-GA and in supporting their subsequent stability. The UV-Visible spectrum showed an absorption peak at 450 nm which reflects the surface plasmon resonance (SPR) of AgNPs-GA and further supports the stability of these biosynthesized nanoparticles. SEM, TEM and XRD diffractogram analyses indicate that AgNPs-GA were spherical and face-centered-cubic in shape. This study also describes the efficacy of biosynthesized AgNPs-GA as anti-proliferative agent against human breast cancer cell lines, MCF-7 and MCF-7/TAMR-1. Our findings indicate that AgNPs-GA possess significant anti-proliferative effects against both the MCF-7 and MCF-7/TAMR-1 cell lines, with inhibitory concentration at 50% (IC50 values) of 2.0 and 34.0 µg/mL, respectively, after 72 h of treatment. An induction of apoptosis was evidenced by flow cytometry using Annexin V-FITC and propidium iodide staining. Therefore, AgNPs-GA exhibited its anti-proliferative activity via apoptosis on MCF-7 and MCF-7/TAMR-1 breast cancer cells in vitro. Taken together, the leaf extract from Garcinia atroviridis was found to be highly capable of producing AgNPs-GA with favourable physicochemical and biological properties.
Reciprocal Peer tutoring (RPT) can support students in enhancing their critical thinking during learning process. The evolution of internet technology has shifted face-to-face peer tutoring to an online environment such as use of a social networking site, Facebook. In addition, Facebook Group provides a space for students and instructor to discuss academic related matters. However, depending solely on the Facebook medium without proper design learning activities do not guarantee active learning among students. In addition, educators might face multiple challenges by using social networking site such as Facebook for teaching and learning purpose. Thus, this study integrated online reciprocal peer tutoring arrangements in Facebook to stimulate students' critical thinking. A total of 29 students involved in the online discussions through Facebook with 14 Facebook Group pages were created. During discussion, tutor will used guided peer questioning strategy initiate tutee to think to the higher levels. This study employed lag sequential analysis to empirically explore patterns of critical thinking processing in Facebook discussions among High and Low critical thinking groups. The results showed that, apparently, High critical thinking group emerged thinking pattern which progressing from lower to higher order thinking processes which are very crucial in shaping their thinking to the higher levels. Additionally, by asking students' prior knowledge and understanding frequently can help students to gain greater understanding of the topic and further initiate their higher level of critical thinking. INDEX TERMS Facebook, critical thinking, online reciprocal peer tutoring, sequential analysis, type of question.
Garcinia celebica L., locally known as "manggis hutan" in Malaysia is widely used in folkloric medicine to treat various diseases. The present study was aimed to examine the chemical composition of the essential oil from the leaves of G. celebica L. (EO-GC) and its cytotoxic and antimicrobial potential. EO-GC obtained by hydrodistillation was analysed using capillary GC and GC-MS. Twenty-two compounds were identified, dominated by αcopaene (61.25%), germacrene D (6.72%) and β-caryophyllene (5.85%). In the in vitro MTT assay, EO-GC exhibited significant anti-proliferative effects towards MCF-7 human breast cancer cells with IC 50 value of 45.2 μg/mL. Regarding the antimicrobial activity, it showed better inhibitory effects on Gram-positive bacteria than Gram-negative bacteria and none on the fungi and yeasts tested.
Lipases are hydrolytic enzymes that have been widely used in industries. In order to meet the industrial demands, thermostable lipases which can withstand high temperatures are required. We sought to optimize the lipase production and to characterize the crude lipase from a locally isolated yeast. Yeast from rotten tomato (from Selangor, Malaysia) which has been identified Pichia sp. strain RT and was found to have thermostable lipase. The morphological features of the isolate were analyzed using SEM and TEM. The microscopy examination confirmed that strain RT was a yeast species. Amplification of lipase gene from cDNA library of the Pichia sp. strain RT showed the gene possessed 100% similarity to the hypothetical protein of Meyerozyma guilliermondii ATCC6260. In addition, the yeast achieved the maximum lipase activity at 30°C with 200 rpm after 72 hours of cultivation. The lipase has the optimum temperature at 75°C and retained nearly 50% of residual activity after 30 minutes of pre-incubation at 75°C. The optimal pH for RT lipase was at pH 9 and it highly stable within pH range 7–10. Physical parameters and the characteristics of crude lipase in strain RT have been successfully investigated. This finding has given an insight for the use of newly isolated thermostable lipase for industrial applications.
In spite of all the efforts in different industries to reduce the number of undesirable accidents, a lot of events always threat industrial societies. These events often cause huge damages to the environment, facilities and even in some cases, fatalities and disabilities for people. Therefore, it is important to predict these probable accidents and plan to prevent them. Hence, this research proposed to analysis hazards in one of the most important components of natural gas distribution network which is city gate station (C.G.S). In this analysis firstly, critical hazards are identified and classified based on HSE standards. Then for decreasing risk of selected hazards, a survey is done on a specific c.G.S according to previous accidents. Finally, some suggestions are offered to improve existing preventive activities.gas
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