330 research outputs found
Single-cell analysis of circulating tumor cells
No full textPlease refer to our publication:Su Bin Lim, Trifanny Yeo, Wen Di Lee, Ali Asgar Bhagat, Swee Jin Tan, Daniel Shao Weng Tan, Wan-Teck Lim, and Chwee Teck Lim. Addressing cellular heterogeneity in tumor and circulation for refined prognostication. PNAS, 2019 (in press)</div
Enhanced bio-production from CO<sub>2 </sub>by microbial electrosynthesis (MES) with continuous operational mode
No full textTechnologies able to convert CO2 to various feedstocks for fuels and chemicals are emerging due to the urge of reducing greenhouse gas emissions and de-fossilizing chemical production. Microbial electrosynthesis (MES) has been shown a promising technique to synthesize organic products particularly acetate using microorganisms and electrons. However, the efficiency of the system is low. In this study, we demonstrated the simple yet efficient strategy in enhancing the efficiency of MES by applying continuous feeding regime. Compared to the fed-batch system, continuous operational mode provided better control of pH and constant medium refreshment, resulting in higher acetate production rate and more diverse bio-products, when the cathodic potential of -1.0 V Ag/AgCl and dissolved CO2 were provided. It was observed that hydraulic retention time (HRT) had a direct effect on the pattern of production, acetate production rate and coulombic efficiency. At HRT of 3 days, pH was around 5.2 and acetate was the dominant product with the highest production rate of 651.8 ± 214.2 ppm per day and a significant coulombic efficiency of 90%. However at the HRT of 7 days, pH was lower at around 4.5, and lower but stable acetate production rate of 280 ppm per day and a maximum coulombic efficiency of 80% was obtained. In addition, more diverse and longer chain products, such as butyrate, isovalerate and caproate, were detected with low concentrations only at the HRT of 7 days. Although microbial community analysis showed the change in the planktonic cells communities after switching the fed-batch mode to continuous feeding regime, Acetobacterium still remained as the responsible bacteria for CO2 reduction to acetate, dominating the cathodic biofilm
Chinese literary works translated into Baba Malay: a bibliographical study
No full textAnalyses 68 unique titles of Baba translated works published between 1889 and 1950. The titles are held in the libraries of the University of Malaya (UM), Science University Malaysia (USM), National University of Malaysia (UKM), the Dewan Bahasa dan Pustaka (DBP), National University of Singapore (NUS), National Library of Singapore (NLS) and the British Library (BL). The results reveal three periods of active publication of Baba translated works. A total of 18 works were translated before World War I, followed by 10 just after the war, 39 titles were published before the break of the World War II and 1 was identified in 1950. There were 103 persons involved in the 68 translated works, some of whom are responsible for more than one title. The most prominent translators were Chan Kim Boon, Wan Boon Seng, Seow Chin San and Lee Seng Poh. Some of the translators were also be editors, illustrators or editors. There were 31 publishers and 21 printing presses involved, all were located in Singapore. The most active publishers were Wan Boon Seng, Kim Seck Chy Press and Nanyang Romanised Malay Book Co. The translated works mainly cover historical classical Chinese stories, chivalrous stories, romances, folklore and legends. The titles were priced between 10 cents to 2 dollars in Straits currency. The University of Malaya Library held the largest number of unique title (62) out of which 15 were unique titles
The Self, National Identity, and Sisterhood in Shirley Geok-lin Lim\ue2s Writings
No full textThis thesis aims to explore the shifting of identities in Shirley Geok-lin Lim\ue2s writings in terms of self, gender, and nation. In chapter one, I will focus on how the subject of Among the White Moon Faces, also called Shirley Geok-lin Lim, forms her ideal self. I will use Jane Gallop\ue2s idea of \ue2retroaction and anticipation\ue2 to examine the formation of the ideal self in the constant interactions between the narrated \ue2I\ue2 and the narrating \ue2I.\ue2 Chapter Two will focus on the oppositional relationship between national identity and nationalism in Lim\ue2s Joss and Gold. My discussion is to unveil the fact that the national identity of Li An, a Malaysian Chinese woman, faces challenges under the influence of patriotic ideologies and Confucian values. I will interpret Li An\ue2s Eurasian daughter, Suyin Yeh as an embodiment of national identity beyond race and culture by applying Homi Bhabha\ue2s notion of cultural hybridity. The third chapter will discuss sisterhood in Lim\ue2s second novel, Sister Swing. I argue that the relationships between women depicted in the novel remain confined to sexual and racial ideologies. The sisterhood between Wing Su Swee and her two sisters represents the shackle of female physical body in the patriarchal structure of Southeast Asia. After travelling to America, Swee\ue2s conflicts with the Afro-American professor, Mrs. Butler, the Puerto Rican businesswoman, Carmen Lopez, and her college classmate, Hong Nga, demonstrate the difference between the third world women and the first world women. I will use Gallop\ue2s notion of active participation to examine the two forms of sisterhood. The instance is Swee\ue2s efforts to know about America again through her eyes to build connections with the first world women
Bioanode as a limiting factor to biocathode performance in microbial electrolysis cells
No full textThe bioanode is important for a microbial electrolysis cell (MEC) and its robustness to maintain its catalytic activity affects the performance of the whole system. Bioanodes enriched at a potential of +0.2 V (vs. standard hydrogen electrode) were able to sustain their oxidation activity when the anode potential was varied from −0.3 up to +1.0 V. Chronoamperometric test revealed that the bioanode produced peak current density of 0.36 A/m2 and 0.37 A/m2 at applied potential 0 and +0.6 V, respectively. Meanwhile hydrogen production at the biocathode was proportional to the applied potential, in the range from −0.5 to −1.0 V. The highest production rate was 7.4 L H2/(m2 cathode area)/day at −1.0 V cathode potential. A limited current output at the bioanode could halt the biocathode capability to generate hydrogen. Therefore maximum applied potential that can be applied to the biocathode was calculated as −0.84 V without overloading the bioanode.</p
Effects of Applied Potential and Reactants to Hydrogen-Producing Biocathode in a Microbial Electrolysis Cell
No full textUnderstanding the mechanism of electron transfer between the cathode and microorganisms in cathode biofilms in microbial electrolysis cells (MECs) for hydrogen production is important. In this study, biocathodes of MECs were successfully re-enriched and subjected to different operating parameters: applied potential, sulfate use and inorganic carbon consumption. It was hypothesized that biocathode catalytic activity would be affected by the applied potentials that initiate electron transfer. While inorganic carbon, in the form of bicarbonate, could be a main carbon source for biocathode growth, sulfate could be a terminal electron acceptor and thus reduced to elemental sulfurs. It was found that potentials more negative than −0.8 V (vs. standard hydrogen electrode) were required for hydrogen production by the biocathode. In additional, a maximum hydrogen production was observed at sulfate and bicarbonate concentrations of 288 and 610 mg/L respectively. Organic carbons were found in the cathode effluents, suggesting that microbial interactions probably happen between acetogens and sulfate reducing bacteria (SRB). The hydrogen-producing biocathode was sulfate-dependent and hydrogen production could be inhibited by excessive sulfate because more energy was directed to reduce sulfate (E° SO42-/H2S = −0.35 V) than proton (E° H+/H2 = −0.41 V). This resulted in a restriction to the hydrogen production when sulfate concentration was high. Domestic wastewaters contain low amounts of organic compounds and sulfate would be a better medium to enrich and maintain a hydrogen-producing biocathode dominated by SRB. Besides the risks of limited mass transport and precipitation caused by low potential, methane contamination in the hydrogen-rich environment was inevitable in the biocathode after long term operation due to methanogenic activities
Impact of applied cell voltage on the performance of a microbial electrolysis cell fully catalysed by microorganisms
No full textThe effect of the operating voltage on the performance of a microbial electrolysis cell (MEC) equipped with both a bioanode and a biocathode for hydrogen production is reported. Chronoamperometry tests ranged between 0.3 and 2.0 V were carried out after both bioelectrodes were developed. A maximum current density up to 1.6 A m−2 was recorded at 1.0 V with hydrogen production rate of nearly 6.0 ± 1.5 L m−2 cathode day−1. Trace amounts of methane, acetone and formate were detected in cathode's headspace and catholyte which followed the same trend as hydrogen production rate. Meanwhile substrate consumption in anolyte also followed the trend of hydrogen production and current density changes. The bioanode could utilise up to 95% of acetate in the tested voltage ranges, however, at a cell voltage of 2.0 V the bioanode's activity stopped due to oxygen evolution from water hydrolysis. Cyclic voltammograms revealed that the bioanode activity was vital to maintain the functionality of the whole system. The biocathode relied on the bioanode to maintain its potential during the hydrogen evolution. The overall energy efficiency recovered from both bioanode and external power in terms of hydrogen production at the cathode was determined as 29.4 ± 9.0%, within which substrate oxidation contributed up to nearly 1/3 of the total energy marking the importance of bioanode recovering energy from wastewater to reduce the external power supply
Gas diffusion electrodes modified with binary doped polyaniline for enhanced CO<sub>2</sub> conversion during microbial electrosynthesis
No full textMicrobial electrosynthesis (MES) is a promising technology to convert CO2 into value-added chemicals. Enhancing the interactions between biofilms and electrodes is the key of bioelectrochemical systems (BES). In this work, we studied the conversion of CO2 by MES in reactors equipped with novel gas diffusion electrodes (GDEs) modified with a polyaniline (PANI) polymer binary doped with H2SO4 and ammonium lauryl sulfate. The enhanced conductive and hydrophilic properties of the polymer increased the biocompatibility of the PANI-modified GDEs compared to the non-modified carbon GDEs. This increased biocompatibility resulted in faster start-up and higher bioproduction of volatile fatty acids (VFAs) such as acetate and butyrate. Up to 4400 ppm acetate was produced in PANI-modified reactors after 24 days of operation, compared to 408 ppm in reactors equipped with non-modified GDEs. A maximum acetate concentration of 7500 ppm (production rate of 554.8 ± 267.5 ppm day−1) was reached in reactors equipped with PANI-GDEs. After 60 days, apart from acetate, 245 ppm butyrate was produced in reactors equipped with the electrodes modified with PANI, while less than 60 ppm was produced with non-modified GDEs. SEM analysis revealed the development of biofilms on both modified and non-modified electrodes, but the images also suggest differences in compositions.</p
Pembangunan sel fuel mikrob untuk rawatan air sisa kilang sawit
No full textSel fuel mikrob (SFM) merupakan peranti yang menggunakan bakteria sebagai biomangkin untuk mengoksidakan bahan organik dan bukan organik bagi menjanakan arus elektrik. Tujuan utama kajian ini ialah menguji kebolehan SFM skala makmal dengan menggunakan enapcemar yang mengandungi kultur campuran yang hidup dalam air sisa buangan kilang pemprosesan sawit (POME). Kajian ini juga bertujuan membina reka bentuk SFM yang sesuai dan mengkaji keaktifan kultur campuran yang boleh menghasilkan kuasa elektrik. POME telah digunakan dalam bentuk yang dicairkan dengan kandungan COD bersamaan dengan 3750 mg-COD L-1. Prestasi penghasilan kuasa elektrik dan kecekapan rawatan yang dinilai daripada segi penyingkiran COD, nitrogen dan jumlah karbohidrat dalam SFM dwi-ruang telah dicatat dan dianalisis setiap hari selama 15 hari. Hasil padanan uji kaji dan model kekutuban adalah memuaskan dan telah menjelaskan ketumpatan kuasa elektrik yang dapat dihasilkan pada setiap hari. Ketumpatan kuasa didapati meningkat dari hari pertama 1.607 mW m-2 (3.816 mA m-2) ke nilai maksimum pada hari ketiga 1.979 mW m-2 (4.780 mA m-2) dan mula turun sehingga minimum pada hari ketujuh 1.311 mW m-2 (3.346 mA m-2). Peringkat rawatan air sisa kilang sawit oleh SFM boleh dibahagikan kepada tiga tahap yang berbeza. Kecekapan rawatan yang rendah walaupun ketumpatan kuasa meningkat pada tahap pertama, manakala pada tahap kedua kecekapan rawatan lebih tinggi dan akhirnya pada tahap ketiga penghasilan kuasa SFM mula turun. Kecekapan rawatan paling tinggi berlaku pada tahap ketiga semasa penghasilan kuasa elektrik yang terhasil agak malar. Kecekapan rawatan yang dinilaikan dalam bentuk penyingkiran COD, penggunaan nitrogen dan karbohidrat paling tinggi berlaku pada hari ke-15 dengan nilai masing-masing adalah 54.9, 100 dan 98.9%. Hubungan penghasilan kuasa elektrik dan kecekapan rawatan telah berjaya dimodelkan dalam persamaan linear matematik berdasarkan kepada tahap-tahap penghasilan kuasa elektrik ini
Facilitators and barriers of human papillomavirus vaccine uptake in young females 18–26 years old in Singapore: A qualitative study
No full text10.1016/j.vaccine.2019.08.053Vaccin
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