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Tijing, Leonard D.,Jung, Min Young,Kim, Dong-Won,Kim, Cheol Sang American Scientific Publishers 2011 Journal of Nanoscience and Nanotechnology Vol.11 No.2
<P>This paper presents an investigation on the deposition behavior of self-assembled monolayers (SAMs) and bacteria on titanium and gold surfaces using an electrochemical quartz crystal nanobalance (EQCN). The tests included alkanethiol and alkanesilane and three bacteria, namely: E. coli, P. fluorescens and K. aerogenes. The mass change with respect to immersion time was measured by EQCN. The results showed SAM formation on both titanium and gold surfaces, but SAM formation on gold was generally higher by 26-74% as compared to that of titanium. On the other hand, bacteria also adhered well on the two metal surfaces. E. coli and P. fluorescens had high affinity on gold and titanium surfaces, respectively, while K. aerogenes was more adherent to titanium. The results showed that titanium and gold are good metals for biomaterials yet at the same time, their bioinert property provide excellent condition for bacterial adhesion. Therefore, there is a need for proper surface preparation to optimize the use of titanium and gold as biomaterials.</P>
Titong Sugihartono,Amal Arifi Hidayat,Michael Austin Pradipta Lusida,Kuntaman,Hafeza Aftab,Muhammad Miftahussurur 대한소화기학회 2023 대한소화기학회지 Vol.82 No.2
Background/Aims: The management decisions regarding gastroesophageal reflux disease (GERD) may differ according to the presence of erosive esophagitis. On the other hand, the availability of upper endoscopy in Indonesia is relatively limited. This study compared the Reflux Disease Questionnaire (RDQ) and the GERD questionnaire (GERDQ) performance in predicting the presence of clinically significant erosive esophagitis and determined the validity and reliability of the Indonesian-translated version of RDQ. Methods: Ninety-two adults with GERD suspicion were recruited. All patients completed RDQ and GERDQ. Receiver operating curve analysis was conducted on RDQ and GERDQ to evaluate their performance in discriminating LA GERD B or higher esophagitis from others. The translated RDQ preserved its main structure and was culturally adapted. Results: The patients were 66.3% female and 73.9% Javanese. Only 22 (23.9%) patients presented with LA grade B or higher erosive esophagitis. The RDQ showed a higher AUC than the GERDQ (0.602 vs. 0.589). A cutoff point of 20 was selected for the RDQ with sensitivity and specificity of 73% and 50%, respectively, whereas the optimal cutoff point of GERDQ was 8, with a sensitivity and specificity of 77% and 43%, respectively. The r-value greater than the critical value table (r>0.205, p<0.01) confirmed the construct validity of our translated RDQ. The questionnaire also demonstrated excellent reliability (α=0.900) and moderate similarity with the Indonesian version of GERDQ (κ=0.459, p<0.01). Conclusions: The RDQ is slightly superior to GERDQ in predicting the presence of clinically significant erosive esophagitis (LA grade B or higher). The Indonesian-translated RDQ is valid and reliable.
Titong Sugihartono,Amal Arifi Hidayat,Michael Austin Pradipta Lusida,Kuntaman,Hafeza Aftab,Muhammad Miftahussurur 대한소화기학회 2023 대한소화기학회지 Vol.82 No.1
Background/Aims: The Reflux Symptom Index (RSI) is a questionnaire that evaluates the severity of extra-esophageal symptoms and is one of the most widely used measures to evaluate LPR. This study assessed the validity and reliability of the RSI questionnaire in Bahasa Indonesia and investigated the association between each extra-esophageal symptom reported in the questionnaire and the severity of erosive esophagitis as determined by endoscopic findings. Methods: 85 adult patients with GERD symptoms had an upper endoscopy examination and were asked to complete the translated RSI. The validity and reliability of the questionnaire were assessed. Results: The construct validity of the RSI translated into Bahasa Indonesia was verified with the r value of each question being higher than the crucial table value (r>0.213, p<0.05). Our questionnaire had a Cronbach alpha value of 0.81, which indicates an acceptable level of internal consistency. At least one extra-esophageal symptom was seen in 91.7% of patients with Los Angeles (LA) grade B or higher-grade esophagitis. In addition, the presence of extra-esophageal symptoms was associated with significant mucosal erosion (p=0.20). The symptoms of cough after eating or lying down and chronic cough were associated with the severity of esophageal mucosal erosion (p<0.05). Conclusions: The version of RSI translated into Bahasa Indonesia is a valid and reliable tool for assessing extra-esophageal GERD symptoms. The occurrence of extra-esophageal symptoms in patients with typical GERD symptoms is associated with endoscopic findings of LA grade B or erosive esophagitis of higher severity.
Leonard D. Tijing,Bock Choon Pak(박복춘),Byung Joon Baek(백병준),Dong Hwan Lee(이동환) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
The present study investigated the mechanism of physical water treatment through particle count analysis of the water sample with and without physical water treatment (PWT) technology. The PWT methods utilized catalytic devices and low-voltage-high-frequency device wherein water continuously recirculated through them. Concentrated hard water at 2,300-2,700 μS/㎝ electrical conductivity was utilized in the study at two different flow rates (i.e., 500 l/h, and 800 l/h). After 66 hours of operation for each test, the results showed that the total number of particles in the PWT-treated cases increased from 165-539% as compared with the no-treatment cases depending on the flow rate used. The present results provided by particle counting support the bulk precipitation hypothesis as the mechanism of PWT and electro-flocculation mechanism with the use of catalytic materials and LVHF technique.
Leonard D. Tijing,Woorim Choi,Zhe Jiang,Altangerel Amarjargal,Chan-Hee Park,Hem Raj Pant,Ik-Tae Im,김철생 한국물리학회 2013 Current Applied Physics Vol.13 No.7
Composite nanofibrous mat composed of neat polyurethane (PU) and multiwalled carbon nanotubes/polyurethane (MWNT/PU) nanofibers have been fabricated by one-step angled two-nozzle electrospinning. The morphological, thermal, and mechanical properties of the electrospun nanofibers were evaluated. The diameters of electrospun neat PU and composite nanofibers ranged from 239 to 1058 nm. The two-nozzle electrospun (MWNT/PU)/PU composite nanofibers showed curly, and randomly-oriented fibers with interfiber bonding, and were generally bigger in size than single-nozzle electrospun nanofibers. The tensile strength of the neat PU composite nanofiber mat obtained from two-nozzle electrospinning was 25% higher than that obtained from neat PU single-nozzle electrospinning. The incorporation of MWNTs in the composite nanofiber increased the tensile strength by as much as 64%without reducing elongation, made the composite nanofiber more thermally stable, and improved the melting zone. The present results showed that side-by-side angled two-nozzle electrospinning can improve the quality of the electrospun nanofibers that could have potential application in different fields such as filtration, protective clothing and tissue engineering.
USING LOW-VOLTAGE-HIGH-FREQUENCY ELECTRIC FIELD TO MITIGATE MINERAL FOULING IN A HEAT EXCHANGER
Leonard D. Tijing,Bock Choon Pak,Byung Joon Baek,Dong Hwan Lee,Young I. Cho 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
This paper presents an investigative study on the efficacy of a new physical water treatment (PWT) technology using an oscillating electric field to mitigate mineral fouling in heat exchangers. Parallel graphite electrode plates immersed in water were used to generate the electric field directly in water. Artificial hard water at 500 ppm hardness was used in all fouling tests. The inlet temperatures were maintained at 23.5±0.5℃ and 85±0.5℃ for cold and hot water sides, respectively. The results at a cold water-side velocity of 0.3 ㎧ showed a 16-60% drop in fouling resistances from the baseline test depending on the frequency of the electric field for the PWT-treated cases.
A study on heat transfer enhancement using straight and twisted internal fin inserts
Leonard D. Tijing,Bock Choon Pak(박복춘),Byung Joon Baek(백병준),Young I. Cho(조영일) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The present study investigated the effect of internal aluminum fins with a star shape cross section on the heat transfer enhancement and pressure drop in a counterflow heat exchanger. A concentric tube heat exchanger was used with water as the working fluid. The heat transfer rate increased by 12-51% over the plain tube value, depending on the internal fin configuration used. However, the pressure drop also increased substantially by an average of 286-338%. The results showed that a straight fin configuration is good enough to produce a heat transfer increase in a counterflow heat exchanger. Twisted fin configurations did not further increase the heat transfer rate.