• Archives of Pharmacal Research
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• v.26 no.4
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• pp.330-337
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• 2003

The effect of sixteen excipients on the transport of recombinant human epidermal growth factor (rhEGF) across Caco-2 cell monolayers was examined at $37^{\circ}C$. The apparent apical to basolateral (A-B) permeability ($P_{app}$) of 30 $\mu$ M rhEGF was $8.15\times 10^{-7}$ cm/sec, indicative of a poor level of absorption in the GI tract. The Papp was 1.7- and 6.3-fold greater than the $P_{app}$ in the basolateral to apical (B-A) direction and the A-B permeability of mannitol, respectively, and decreased dramatically to a negligible level at $4^{\circ}C$, consistent with a receptor mediated transcytosis of rhEGF. The stability of rhEGF was very poor, undergoing more than 85% degradation in 2 h in the transport medium at $37^{\circ}C$. A significant increase in the $P_{app}$ could be achieved by the addition of certain excipients, as exemplified by 23, 21, 20 and 16-fold increases, in the presence of sodium taurochenodeoxycholate (NaTCDC), sodium taurodeoxycholate (NaTDC), sodium glycodeoxycholate (NaGDC) and sodium laurylsulfate (SLS) (all at a concentration of 1 % w/v), respectively. A significant increase in stability could also be achieved by the addition of some of the excipients, as represented by 1 % SLS, which nearly completely stabilized the rhEGF. Unfortunately, however, an increase in the $P_{app}$ of rhEGF could not be achieved without a simultaneous and extensive decrease in the integrity of the cell membranes. Thus, more efficient excipients, that specifically enhance the permeation of rhEGF and do not alter the membrane integrity, should be pursued in order to safely enhance the permeation of rhEGF.

• Journal of the Korean Institute of Gas
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• v.26 no.3
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• pp.45-53
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• 2022

In order to improve the emission of diesel engines, natural gas-diesel dual fuel combustion compression ignition engines are in the spotlight. In particular, a reactivity controlled compression ignition (RCCI) combustion strategy is investigated comprehensively due to its possibility to improve both efficiency and emissions. With advanced diesel direct injection timing earlier than TDC, it achieves spontaneous reaction with overall lean mixture from a homogeneous mixture in the entire cylinder area, reducing nitrogen oxides (NOx) and particulate matter (PM) and improving braking heat efficiency at the same time. However, there is a disadvantage in that the amount of incomplete combustion increases in a low load region with a relatively small amount of fuel-air. To solve this, sensitive control according to the diesel injection timing and fuel ratio is required. In this study, experiments were conducted to improve efficiency and exhaust emissions of the natural gas-diesel dual fuel engine at low load, and evaluate combustion stability according to the diesel injection timing at the operation point for power generation. A 6 L-class commercial diesel engine was used for the experiment which was conducted under a 50% load range (~50 kW) at 1,800 rpm. Two injectors with different spray patterns were applied to the experiment, and the fraction of natural gas and diesel injection timing were selected as main parameters. Based on the experimental results, it was confirmed that the brake thermal efficiency increased by up to 1.3%p in the modified injector with the narrow-angle injection added. In addition, the spray pattern of the modified injector was suitable for premixed combustion, increasing operable range in consideration of combustion instability, torque reduction, and emissions level under Tier-V level (0.4 g/kWh for NOx).