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This article reveals the dependence of crystalline phases in titania on the intrinsic activity during in situ polymerization of ethylene/1-hexene using the zirconocene/ dMMAO catalyst to produce LLDPE/TiO2 nanocomposites. First, the TiO2 nanoparticles having different crystalline phases were employed as the nanofillers by impregnation with dMMAO to obtain dMMAO/TiO2 Then, copolymerization of ethylene/1-hexene using zirconocene catalyst was performed in the presence of dMMAO/TiO2. It was found that the catalytic activity derived from the anatase TiO2 (A) was about four times higher than that obtained from the rutile TiO 2. (R). This was likely due to higher intrinsic activity of the active species present on the TiO2(A). In addition, increased [Al]dMMAO/[Zr]cat ratios apparently resulted in enhanced activities for both TiO2 (A) and Tio (R). However, the TiO2 (R) showed less deactivation upon increased [Al]dMMAO/[Zr]cat ratios. This can be attributed to strong interaction between dMMAO and TiO2.(R) as proven by the TGA measurement. The microstructure of the LLDPE/TiO2 obtained was found to be random copolymer for both TiO2 (A) and TiO2 (R). © Springer-Verlag 2010.


Chaichana E.,Nakhon Pathom Rajabhat University | Mekasuwandumrong O.,Silapakorn University
Iranian Polymer Journal (English Edition) | Year: 2012

ZnO nanoparticle was used for preparing supported catalyst, which was applied in copolymerization of ethylene and 1-octene to obtain LLDPE/ZnO nanocomposite. There were two different impregnation methods (in situ and ex situ) in preparing the nano-ZnO supported catalyst. The investigation to compare both methods was conducted by employing various 1-octene initial concentrations in copolymerization. It was found that a heterogeneous catalytic system comprised a supported catalyst, prepared by in situ impregnation, provided higher catalytic activities and 1-octene incorporations compared to those of ex situ impregnation under similar condition perhaps due to closer similarity to a homogeneous system. For the ex situ impregnation, it was found that when zirconocene was directly impregnated onto the support, the catalytic activity decreased. This was due to zirconocene close vicinity to the supports and even deep into the support structure proved by XPS and TGA measurements. Therefore, it was more inaccessible to monomer attack and reducing the catalytic activity. The separate study on each catalytic system relating to the comonomer effect was also conducted by applying initial comonomer concentrations varied between 0 and 18 mmol. The increase in catalytic activity with increasing comonomer concentration can be considered as a positive comonomer effect, and the opposite was true for a negative comonomer effect. It was found that both positive and negative comonomer effects occurred in in situ impregnation and ex situ impregnation systems with Zn/(Al ? Zr) support, whereas only positive comonomer effect was found in an ex situ impregnation system with Zn/Al support. This suggested that the comonomer effect was varied according to the nature of each system. The polymer properties, such as relative crystallinity and thermal properties were also investigated and found to alter with 1-octene concentration. © Iran Polymer and Petrochemical Institute 2011.


Khaodee W.,Chulalongkorn University | Wongsakulphasatch S.,Silapakorn University | Kiatkittipong W.,Silapakorn University | Arpornwichanop A.,Chulalongkorn University | And 2 more authors.
International Journal of Hydrogen Energy | Year: 2011

In order to select a proper hydrogen production system being compatible with fuel cell, a variety of interesting primary fuels such as light hydrocarbons and alcohols were tested in the decomposition (D) and the steam reforming (SR) processes by thermodynamic approach. The reaction performances of the systems particularly under thermally self-sustained condition were focused on. To obtain self-sustained condition, two approaches, splitting feed and splitting gas product streams to the burner for heat supply to endothermic hydrogen processor, are investigated. Our results revealed that splitting gas product gave higher carbon capture than splitting feed but lower in hydrogen yield. As expected, steam reforming provides higher hydrogen production, however, lower in hydrogen purity and carbon capture comparing to decomposition process. By considering primary fuels, D-alcohols could be applied to MCFC and SOFC, among these, D-C 2H 5OH was preferable because it gives the highest ratio of H 2/CO. For D-light hydrocarbon systems, which is operated at 1100 K providing 97% hydrogen purity, is suitable to be connected to MCFC, SOFC and also PEMFC. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.


Chusri S.,Prince of Songkla University | McNeil E.B.,Prince of Songkla University | Hortiwakul T.,Prince of Songkla University | Charernmak B.,Prince of Songkla University | And 6 more authors.
Journal of Infection and Chemotherapy | Year: 2014

This study was conducted to investigate the protective efficacy of a single dosage of 200 mg doxycycline against leptospiral infection and leptospirosis and associated risk factors among residents exposed to flooding in southern Thailand. Of 641 participants, 600 received doxycycline while 41 did not. Twenty two participants were infected with Leptospira and six developed leptospirosis. Having a laceration wound was significantly associated with leptospiral infection (odds ratio [OR] = 37.20; P < 0.001) and leptospirosis (OR = 18.24; P = 0.003) whereas exposure to flood more than 3 h per day was associated with only leptospiral infection (OR = 3.70; P = 0.038). Seventeen participants who received doxycycline and five who did not, were infected with Leptospira, resulting a protective efficacy of 76.8% (95% confidence interval [CI] = 34.3%-92.0%). Four who received doxycycline and two who did not, developed leptospirosis, resulting a protective efficacy of 86.3% (CI = -9.8%-98.2%). Among the participants with laceration wound, the protective efficacy for leptospiral infection was 92.0% (CI = 81.2%-96.6%) and for leptospirosis was 95.6% (CI = 78.2%-99.3%). Among the participants exposed to flood water less than or equal to 3 h per day, the protective efficacy for leptospiral infection was 89.2% (95% CI 63.6%-96.67%). A single dosage of 200 mg doxycycline for prophylaxis might be effective for preventing leptospirosis among flood victims with laceration wound after recent flood exposure. © 2014, Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.


Suntimaleeworakul W.,Silapakorn University | Patharachayakul S.,Prince of Songkla University | Chusri S.,Prince of Songkla University
Journal of the Medical Association of Thailand | Year: 2012

Valproic acid and meropenam is commonly co-administrated in neurosurgical patients. Meropenem potentially decreases the valproic acid level, which may cause perioperative seizure. There has been no previous report of drug interaction between valproic acid and meropenem in Thailand. The authors report a patient who faced uncontrolled seizure after co-administrated valproic acid and meropenem. The level of valproic acid was assessed in different times after the administration of meropenem. Rapid decrease of valproic level was detected. However, due to the administration of other antiepileptic agents, seizure did not develop. It is important for the physicians to recognize drug interaction between valproic acid and meropenem. Avoiding co-administration of both agents, valproic acid level monitoring and additive of other antiepileptic agents seem to be the appropriate solution.


Santimaleeworagun W.,Prince of Songkla University | Pharm S.P.,Prince of Songkla University | Chusri S.,Silapakorn University | Chayagul P.,Prince of Songkla University
Journal of the Medical Association of Thailand | Year: 2013

Atazanavir is one highly active antiretroviral therapy for naïve patients or patients with previous regimen failure. However, it seems that the protease inhibitor induces hyperlipidemia. Hyperbillirubinemia is the most common clinical adverse events but reports of cardiotoxicity due to atazanavir are scarce. The authors report a patient who had QT prolongation, first-degree atrioventricularblock, and ventricular tachycardia. After atazanavir/ritonavir discontinuation, this patient got better and had normal electrocardiography. Lopinavir/ritonavir was carefully reintroduced during hospitalization without any adverse drug reaction. Atazanavir induced cardiotoxicity has to be monitored when using protease inhibitors.


PubMed | Medial Research, Silapakorn University and Prince of Songkla University
Type: Controlled Clinical Trial | Journal: Journal of infection and chemotherapy : official journal of the Japan Society of Chemotherapy | Year: 2014

This study was conducted to investigate the protective efficacy of a single dosage of 200 mg doxycycline against leptospiral infection and leptospirosis and associated risk factors among residents exposed to flooding in southern Thailand. Of 641 participants, 600 received doxycycline while 41 did not. Twenty two participants were infected with Leptospira and six developed leptospirosis. Having a laceration wound was significantly associated with leptospiral infection (odds ratio [OR] = 37.20; P < 0.001) and leptospirosis (OR = 18.24; P = 0.003) whereas exposure to flood more than 3 h per day was associated with only leptospiral infection (OR = 3.70; P = 0.038). Seventeen participants who received doxycycline and five who did not, were infected with Leptospira, resulting a protective efficacy of 76.8% (95% confidence interval [CI] = 34.3%-92.0%). Four who received doxycycline and two who did not, developed leptospirosis, resulting a protective efficacy of 86.3% (CI = -9.8%-98.2%). Among the participants with laceration wound, the protective efficacy for leptospiral infection was 92.0% (CI = 81.2%-96.6%) and for leptospirosis was 95.6% (CI = 78.2%-99.3%). Among the participants exposed to flood water less than or equal to 3 h per day, the protective efficacy for leptospiral infection was 89.2% (95% CI 63.6%-96.67%). A single dosage of 200 mg doxycycline for prophylaxis might be effective for preventing leptospirosis among flood victims with laceration wound after recent flood exposure.


Polwiang S.,Silapakorn University | Coster A.,University of New South Wales
Experimental and Clinical Cardiology | Year: 2014

The objective of this study was to investigate the electrical characteristic and synchronization of coupled sinoatrial node (SAN) cells, using experimental validated mathematical models. Generally, the SAN can be divided into a central and a peripheral region. There is also a transition region between these. The mathematical models were employed to accurately reproduce a wide range of action potential waveforms of central and peripheral SAN cells, with a smooth transition of characteristics for those cells in between. The electrophysiological characteristics modeled included cycle length, maximum diastolic potential, action potential amplitude, diastolic depolarization rate and maximum upstroke velocity. The critical coupling conductance, the minimum coupling conductance required for 1:1 frequency entrainment, was found the linearly increase as the difference between the cycle lengths of coupled cells increased and the number is range between 0.05-0.7nS. Extending this to string networks, the critical coupling conductance was found to be higher than any individual pair within the networks, but still only a small number of active gap junction channels, indicating substantial redundancy in the biological system. © 2013 et al.


PubMed | Silapakorn University
Type: Case Reports | Journal: Journal of the Medical Association of Thailand = Chotmaihet thangphaet | Year: 2012

Valproic acid and meropenam is commonly co-administrated in neurosurgical patients. Meropenem potentially decreases the valproic acid level, which may cause perioperative seizure. There has been no previous report of drug interaction between valproic acid and meropenem in Thailand. The authors report a patient who faced uncontrolled seizure after co-administrated valproic acid and meropenem. The level of valproic acid was assessed in different times after the administration of meropenem. Rapid decrease of valproic level was detected. However due to the administration of other antiepileptic agents, seizure did not develop. It is important for the physicians to recognize drug interaction between valproic acid and meropenem. Avoiding co-administration of both agents, valproic acid level monitoring and additive of other antiepileptic agents seem to be the appropriate solution.


PubMed | Silapakorn University
Type: Journal Article | Journal: Journal of travel medicine | Year: 2015

Dengue fever is one of the important causes of illness among travelers returning from Thailand. The risk of infection depends on the length of stay, activities, and arrival time. Due to globalization, there is a concern that infected travelers may carry dengue virus (DENV) to their country of residence and cause an outbreak.To estimate the infective person-days of travelers returning from Thailand, we developed a model with the following parameters: the probability of travelers being infected, number of arrivals, length of stay of travelers, incubation period, and duration of the infective period. The data used in this study were the dengue incidences in Thailand during 2004-2013 and foreign traveler arrivals in 2013.We estimated the highest infective person-days for each country group. The highest value was from June to August during the rainy season in Thailand for all groups. Infective person-days ranged from 87 to 112 per 100,000 travelers each year.Our results provided a fundamental step toward estimation of the risk of the secondary transmission of DENV in non-epidemic countries via travelers, which can serve as an early warning of a dengue outbreak. The highest infective person-day is associated with the rainy season in Thailand. The increasing number of overseas travelers may increase the risk of global transmission of the DENV. Better understanding of the virus transmission dynamics will enable further quantitative predictions of epidemic risk.

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