• Journal of Pharmaceutical Investigation
• /
• v.27 no.2
• /
• pp.99-108
• /
• 1997

To evaluate the feasibility of mucosal delivery of thyrotropin releasing hormone (TRH) through various mucosae, enzymatic degradation and stabilization of TRH in the nasal, rectal and duodenal extracts of rabbits were studied. TRH in the extracts was assayed by HPLC and its degradation was found to follow apparent first-order kinetics. The residual concentrations of TRH in the mucosal extracts of nasal, rectal and duodenal segments after 24 hr of incubation were found to be $65.1({\pm}1.1),\;19.7({\pm}2.7)$ and 0%, and in the serosal extracts, $65.6({\pm}5.5),\;75.2({\pm}1.1)$ and $68.7({\pm}1.4)%$, respectively. This result suggests that there is a significant difference in the activity of TRH-degrading enzymes among the sites of administration. The inhibition of TRH degradation in the mucosa extracts was kinetically investigated using various additives such as thimerosal, benzalkonium chloride, disodium edetate, ${\sigma}-phenanthroline$, dithiothreitol and dithioerythritol, and $IC_{50}$ values of inhibitors were calculated. The results obtained showed that thimerosal (0.5 mM) and benzalkonium chloride (0.141 mM) protected TRH from the enzymatic degradation in all the mucosa extracts more than 95% after 24 hr of incubation.

• Journal of Pharmaceutical Investigation
• /
• v.22 no.3
• /
• pp.173-183
• /
• 1992

To study the feasibility of transmucosal delivery of $[D-ala^2]-methionine$ enkephalinamide (YAGFM), its enzymatic degradation and stabilization in various rabbit mucosal extracts were investigated by HPLC method. The degradation of YAGFM was observed to follow the first-order kinetics and the half-lives of YAGFM in the nasal, rectal and vaginal mucosal extracts were found to be 25.7, 3.0 and 7.8 hr, respectively. However, there was no significant difference in degradation rates of YAGFM between the mucosal and serosal extracts obtained from the same mucosal membrane. This finding suggests that even a synthetic enkephalin analog, which is designed to be resistent to aminopeptidases, needs to be fully protected from the enzymatic degradation in mucosal sites for the delivery of the analog through mucosal routes. To inhibit the degradation of YAGFM in various mucosal extracts, effects of enzyme inhibitors such as bestatin (BS), amastatin (AM), thiorphan (TP), thimerosal (TM) and EDTA, alone or in combination, and modified cyclodextrins were observed by assaying YAGFM staying intact during 24 hr-incubation at $37^{\circ}C$. It was found from the results that mixed inhibitors such as TM (0.5 mM)/EDTA (5 mM) or AM $(50{\mu}M)/TM$ (0.5 mM)/EDTA (5 mM) provided very useful means for the stabilization in various mucosal extracts. The latter was found to protect YAGFM from the degradation in the nasal, rectal, and vaginal mucosal extracts by 90.9, 90.4 and 91.3%, respectively, after 24 hr-incubation, suggesting almost complete inhibition of YAGFM-degrading enzymes present in the incubation mixture. However, BS $(50{\mu}M)$, AM 50 $(50{\mu}M)$ or TP$(50{\mu}M)$ alone did not reveal sufficient inhibition except TM (0.5 mM) or EDTA (5 mM). The adddition of $2-hydroxylpropyl-{\beta}-cyclodextrin$(10%) to the nasal mucosal extract, and $dimethyl-{\beta}-cyclodextrin$(10%) to the rectal and vaginal mucosal extracts reduced the first-order rate constants for the degradation of YAGFM by 5.8, 17.3 and 8.9 times, respectively, compared to those with no additive.

• Journal of Pharmaceutical Investigation
• /
• v.24 no.1
• /
• pp.1-9
• /
• 1994

In order to study systemic peptide delivery through the ocular route, the stabilities of methionine enkephalin (Met-Enk) and $[D-ala^2]-methionine$ enkephalinamide (YAGFM) in the corneal extracts of rabbits were investigated using reversed phase HPLC. Met-Enk was found to be hydrolyzed most rapidly in the corneal epithelium, but YAGFM was relatively stable. Aminopeptidases appeared to contribute over 60% to the degradation of Met-Enk and the degradation rate of Met-Enk followed the first order kinetics. The half-lives of Met-Enk in the extracts of the corneal epithelium and endothelium were 36 and 673 min, respectively. From the effects of enzyme inhibitors, it was found that the application of the mixture of amastatin, thimerosal and EDTA was very useful for the inhibition of peptide degradation.

• Journal of Pharmaceutical Investigation
• /
• v.26 no.3
• /
• pp.175-185
• /
• 1996

To inhibit the enzymatic degradation of leucine enkephalin (Leu-Enk) and its synthetic analog. $[D-ala^2]$-leucine enkephalinamide (YAGFL), in the nasal, rectal and vaginal mucosal and serosal extracts of rabbits, effects of enzyme inhibitors such as amastatin (AM), puromycin (PM), thiorphan (TP), thimerosal (TM), EDTA, N-carboxymethyl-Phe-Leu (CPL), phenylethyl alcohol (PEA), phenylmercuric acetate (PMA), benzalkonium chloride (BC) and modified cyclodextrins, alone or in combination, were observed by assaying the pentapeptides staying intact during incubation. Mucosa extracts were prepared by exposing freshly-excised mucosal specimens mounted on Valia-Chien cells to isotonic phosphate buffer while stirring. The degradation of Leu-Enk and YAGFL followed the apparent first-order kinetics. The half-lives (mean) in the nasal, rectal and vaginal mucosal extracts were found to be 1.07, 0.33 and 1.14 hr for Leu-Enk, and 16.9, 6.2 and 6.8 hr for YAGFL, respectively. AM or PM, which is an aminopeptidase inhibitor, did not show a sufficient inhibition of Leu-Enk $(50\;{\mu}g/ml)$ degradation in all kinds of extracts. $Dimethyl-{\beta}-cyclodextrin\;(DM-{\beta}-CyD)$ decreased the degradation rate constants of Leu-Enk about 2 or 3 times, comparing with no additive. However, the use of mixed inhibitors of AM $(50\;{\mu}M)$/TM (0.25 mM)/EDTA (5 mM) resulted in a full stabilization of Leu-Enk by decreasing the degradation rate constants 67.3, 161.3 and 113.8 times far the nasal, rectal and vaginal mucosal extracts, respectively, comparing with no inhibitor. With mixed inhibitors, Leu-Enk remained intact more than 90% after 6 hr-incubation. In the stabilization of YAGFL, hM, TP or CPL alone showed little efffct, and some additives demonstrated a considerable inhibition of YAGFL degradation in the rank order of TM > BC > EDTA. However, the addition of mixed inhibitors such as TM (0.5 mM) and EDTA (5 mM) into the extracts protected YAGFL from the degradation by more than 85% even after 24 hr-incubation, suggesting almost complete inhibition of YAGFL degradation in the extract. On the other hand, $DM-{\beta}-CyD\;or\;hydroxypropyl-{\beta}-cyclodextrin$ (10%) were also found to retard enzymatic degradation rates of YAGFL markedly, and resulted in staying intact more than 80% of YAGFL in the nasal and vaginal mucosal extracts, and more than 60% in the rectal mucosal extract after 16 hr-incubation.

• Current Applied Physics
• /
• v.18 no.12
• /
• pp.1600-1604
• /
• 2018

This paper reports on a systematic and quantitative assessment of light induced degradation (LID) and regeneration in full Al-BSF and passivated emitter rear contact cells (PERC) along with the fundamental understanding of the difference between the two. After LID, PERC cells showed a much greater loss in cell efficiency than full Al-BSF cells (~0.9% vs ~0.6%) because the degradation in bulk lifetime also erodes the benefit of superior BSRV in PERC cells. Three main regeneration conditions involving the combination of heat and light ($75^{\circ}C/1\;Sun/48h$, $130^{\circ}C/2\;Suns/1.5h$ and $200^{\circ}C/3\;Suns/30s$) were implemented to eliminate LID loss due to BO defects. Low temperature/long time ($75^{\circ}C/48h$) and high temperature/short time ($200^{\circ}C/30s$) regeneration process was unable to reach 100% stabilization. The intermediate temperature/time ($130^{\circ}C/1.5h$) generation achieved nearly full recovery and stabilization (over 99%) for both full Al-BSF and PERC cells. We discussed the effect of temperature, time and suns in regeneration mechanism for two cells.

• Journal of Institute of Control, Robotics and Systems
• /
• v.16 no.5
• /
• pp.411-414
• /
• 2010

As high quality image is required for digital cameras in recent use, the image stabilization technique has drawn much attention to prevent image degradation from shaky disturbance by users. In this paper, the optical image stabilization (OIS) system for DSLR (Digital Single Lens Reflex) camera is considered. First, the analytic model of an OIS system is presented to demonstrate the mechanism of image destabilization due to unknown disturbance that causes blurry images on CCD sensor. Then, to enhance the stabilization performance, a sliding mode control based on the min-max nonlinear control is introduced. Through the experiments and simulations, the effectiveness of the proposed method will be verified.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.10
• /
• pp.1034-1038
• /
• 2008

Degradative Solidification/Stabilization(DS/S) is a modification of conventional Solidification/Stabilization(S/S) that incorporates degradative processes for organic contaminant destruction with the low cost of conventional S/S. Inorganic contaminants are immobilized and chlorinated organic contaminants are destroyed by DS/S treatment. In this study, a DS/S using cement/slag/Fe(II) systems as binder was investigated to assess its effectiveness in degrading chloroform(CF) and methylene chloride(MC) contained in hazardous liquid wastes. The initial concentration of CF was 0.26 mM, 1.0 mM, 8.4 mM, 25 mM and 42 mM and Fe(II) was 200 mM. The result showed that degradation of CF in various concentration was in one kind reaction as pseudo-first-order and 95% of 0.26 mM initial concentration of CF was removed in five days. 50 mg/L of heavy metal was added in order to accelerate the rate of degradation of MC and initial concentration of MC was 3.50 mM however, degradation did not occur in system. Thus additional studies needed for degradation of MC and more studies on other reaction pathways products will help elucidate reaction mechanisms and pathways for chlorinated methanes in cement/slag/Fe(II) systems.

• Journal of Soil and Groundwater Environment
• /
• v.18 no.7
• /
• pp.25-31
• /
• 2013

Hydrogen peroxide takes much of the cost for Fenton reaction applied for treatment of organic contaminants. Therefore, the effective use of hydrogen peroxide makes the technology more cost effective. The effective use of hydrogen peroxide is especially needed in the soil and groundwater remediation where complete mixing is not possible and it takes a long time for reactive species to transport to the fixed target compounds. Stabilization ability for hydrogen peroxide of malonic acid was evaluated in Fenton and Fenton-like reactions in this study. Malonic acid contributes on the stabilization of hydrogen peroxide by weak interaction between iron and the stabilizer and inhibiting the catalytic role of iron. The stabilization effect increased as the solution pH decrease below the $pK_{a1}$. The stabilization effect increased as the concentration of malonic acid increased and the effect was maximized at the malonic acid concentration of about ten times higher than the iron concentration. The model organic contaminant was successfully oxidized in the presence of the stabilizer but the degradation rate was slower than the system without the stabilizer. The stabilization effect was also proved in a Fenton-like reaction where magnetite and hematite were used instead of soluble iron species.

• Journal of Pharmaceutical Investigation
• /
• v.28 no.2
• /
• pp.121-126
• /
• 1998

The solubility and physicochemical stability of caroverine hydrochloride (CRV), an antispasmodic, in buffered aqueous solutions were studied using a reverse phase high performance liquid chromatography. The solubilty of the drug at pH 2.76-5.40 was similar at the range 31.9-36.2 mg/ml $(34^{circ}C)$, but, at the pH higher than 6.0, markedly decreased. The use of polyethylene glycol 400 as a cosolvent did not increase the solubility at any compositions examined. Moreover. increasing molar concentration of aqueous phosphate buffer from 0 to 0.5 M remarkably decreased the solubility. The degradation of CRY followed the apparent first-order kinetics. The degradation was accelerated with decreasing pH and increasing storage temperature. The half-lives for the degradation of CRY (1.0 mg/ml) at pH 1.28. 4.01 and 5.93 $(45^{\circ}C)$ were 2.8, 31.4 and 124 hr. respectively. The pHs of incubated solutions were to some extent lowered perhaps due to the formation of acidic degradation products. The addition of disodium edetate (0.01%) to the CRY solution (pH 4.95) retarded 2.5 times the degradation rate at $45^{\circ}C$, but the use of sodium bisulfite (0.1%) accelerated 2.9 times the rate. The activation energy for the CRY solution (20 mg/ml. pH 5.4) containing 0.01% EDTA was calculated to be 5.98 kcal/mole. When the solution was stored under nitrogen displacement in ampoule, there was no significant degradation even after 3 months at $40^{\circ}C$, indicating that protection from oxidation by air (oxygen) is essential for the complete stabilization of CRY solution.

• Fibers and Polymers
• /
• v.4 no.4
• /
• pp.195-198
• /
• 2003

Epoxidized polybutadiene (EPB) was prepared by polybutadiene (PB) with m-chloroperbenzoic acid (MCPBA) in homogeneous solution. EPB was blended with poly(3-hydroxybutyrate) (PHB) up to 30 wt% by solution-precipitation procedure. The thermal decomposition of PHB/EPB blends was studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and differential thermal analysis (DTA). The thermograms of PHB/EPB blends contained a two-step degradation process, while that of pure PHB sample exhibited only one-step degradation process. This degradation behavior of PHB/EPB blends, which have a higher thermal stability as measured by maximum decomposition temperature and residual weight, is probably due to crosslinking reactions of the epoxide groups in the EPB component with the carboxyl chain ends of PHB fragments during the degradation process, and the occurrence of such reactions can be assigned to the exothermic peaks in their DTA thermograms.