• Journal of Pharmaceutical Investigation
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• 제37권4호
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• pp.211-216
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• 2007

The bark of Alnus japonica has been used for the treatment of fever, hemorrhage and diarrehea in oriental traditional medicine. Recently, it was revealed that the diarylheptanoids from the bark of Alnus japonica possess anti-inflammatory activity and are expected to be applicable for atopic dermatitis. In this study, oregonin, one of major active components in the bark of Alnus japonica, was developed in the form of semisolid formulations for topical delivery. Oregonin was incorporated into four ointment bases: O/W cream, W/O cream, hydrophilic ointment and lipophilic ointment. Oregonin release from all formulation prepared was evaluated. Franz cell method and immersion method were employed to characterize the release patterns of drug from each formulation based on solvent availability. O/W cream showed a better release profile than the other formulations when evaluated with Franz cell method with an order of O/W cream, hydrophilic ointment, W/O cream and lipophilic ointment. In the immersion method, hydrophilic ointment showed the greatest release rate at times 1 hour exceeding compared to other bases with an order of hydrophilic ointment, O/W cream, W/O cream and lipophilic ointment. Hydrophilicity and solvent availability of formulation seems to significantly influence the release rate of oregonin from ointment bases. In this study, we successfully characterized the oregon in ointment and found that o/w cream is a promising formulation for the topical delivery of oregonin.

• The Korean Journal of Physiology and Pharmacology
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• 제11권1호
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• pp.21-30
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• 2007

The present study was designed to establish comparatively the inhibitory effects of cilnidipine(CNP), nifedipine(NIF), and $\omega$-conotoxin GVIA(CTX) on the release of CA evoked by cholinergic stimulation and membrane depolarization from the isolated perfused model of the rat adrenal medulla. CNP(3 ${\mu}M$), NIF(3 ${\mu}M$), and CTX(3 ${\mu}M$) perfused into an adrenal vein for 60 min produced greatly inhibition in CA secretory responses evoked by ACh($5.32{\times}10^{-3}M$), DMPP($10^{-4}M$ for 2 min), McN-A-343($10^{-4}M$ for 2 min), high $K^+(5.6{\times}10^{-2}M)$, Bay-K-8644($10^{-5}M$), and cyclopiazonic acid($10^{-5}M$), respectively. For the CA release evoked by ACh and Bay-K-8644, the following rank order of potency was obtained: CNP>NIF>CTX. The rank order for the CA release evoked by McN-A-343 and cyclopiazonic acid was CNP>NIF>CTX. Also, the rank orders for high $K^+$ and for DMPP were NIF>CTX>CNP and NIF>CNP>CTX, respectively. Taken together, these results demonstrate that all voltage-dependent $Ca^{2+}$ channels(VDCCs) blockers of cilnidipine, nifedipine, and $\omega$-conotoxin GVIA inhibit greatly the CA release evoked by stimulation of cholinergic(both nicotinic and muscarinic) receptors and the membrane depolarization without affecting the basal release from the isolated perfused rat adrenal gland. It seems likely that the inhibitory effects of cilnidipine, nifedipine, and $\omega$-conotoxin GVIA are mediated by the blockade of both L- and N-type, L-type only, and N-type only VDCCs located on the rat adrenomedullary chromaffin cells, respectively, which are relevant to $Ca^{2+}$ mobilization. It is also suggested that N-type VDCCs play an important role in the rat adrenomedullary CA secretion, in addition to L-type VDCCs.

• Journal of Pharmaceutical Investigation
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• 제36권1호
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• pp.39-44
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• 2006

Tamsulosin or a salt thereof such as its hydrochloride salt has been known to have an adrenaline ${\alpha}$ receptor blocking action for urethra and prostate areas. It has been widely used as a drug which lowers the prostate pressure and improves urinary disturbance accompanied by prostate-grand enlargement, thus for the treatment of prostatic hyperplasia. To avoid dose-dependent side effects of tamsulosin upon oral administration, the development of sustained-release delivery system is essentially required, that can maintain therapeutic drug levels for a longer period of time. The aim of this study was therefore to formulate sustained-release tamsulosin granules and assess their formulation variables. We designed entric coated sustained-release tamsulosin granules for this purpose. Nano-pores in the outer controlled release membrane were needed in order to obtain initial tamsulosin release even in an acidic environment such as gastric region. In our sustained release osmotic granule system, hydroxypropylmethylcellulose in a drug-containing layer was used as a rate controller. The drug-containing granules were coated with hydroxypropylmethylcellulose phthalate (HPMCP) and Eudragit, along with glycerol triacetate as an aqueous nano-pore former. The release of tamsulosin depended heavily on the type of Eudragit such as RS, RL, NE 30D, used in the formulation of controlled release layer. These results obtained clearly suggest that the sustained-release oral delivery system for tamsulosin could be designed with satisfying drug release profile approved by the Korean Food and Drug Administration.

• 한국자동차공학회논문집
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• 제3권1호
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• pp.97-107
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• 1995

Global postbuckling analysis is accomplished for one-dimensional and two-dimensional delaminations. A new finite element model, which can be used to model the global postbuckling analysis of one-dimensional and two-dimensional delaminations, is presented. In order to calculate the strain energy release rate, geometrically nonlinear analysis is accomplished, and the incremental crack closure technique is introduced. To check the effectiveness of the finite element models and the incremental crack closure technique, the simplified closed-form sloution for a through-the-width delamination with plane strain condition is derived and compared with the finite element result. The finite element results show good agreement with the closed-foul1 solutions. The present method was extended to calculate the strain energy release rate for two-dimensional delamination. For a symmetric circular delamination, the strain energy release rate shows great variation along the delamination front. and the delamination growth appears to occur perpendicular to the loading direction.

• Environmental Engineering Research
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• 제10권4호
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• pp.199-204
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• 2005

Experiments were performed to estimate the organic release from the aquifer soil in riverbank and/or riverbed filtration via a kinetic approach. Organic release was assumed as a reaction of first order regarding concentrations in both soil and water phases. The reaction rate constants were obtained by comparing the model predictions with the experimental data of organic release reaction and the equilibrium distribution of organic matter between water and soil phases. Results show that the organic release from the aquifer soil was not negligible under normal conditions in Korea reaching 4.7mg-COD/L-day. This indicates that manganese and iron start to be released from aquifer soil in the riverbank filtration in the middle reach of the Nakdong river if the travel time of the filtrate exceeds about 5 days. It was also seen that the COD of the soil organic matter was 0.89mg-COD/mg-OM and that 65% of the COD was BOD5.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.405-410
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• 1996

New methodology for mass and energy release assessment in LBLOCA post blowdown is needed and, first of all, the phenomenologically improved and quantitative assessments through experiment are essential. For tile experiment of a hot leg break LBLOCA in post blowdown, the test facility was set and its feature is that tile broken hot leg has two broken sections in the tore side and in the SG side respectively and a separation valve between the two in order to measure the release rate dividedly. Specially it was focused on whether the mass release through the SG side broken section happened or not. The mass release through the core side broken section is dependent on tile safety injection flow and that through the SG side broken section varies depending on several factors. The principal factor is the primary system pressure and the subfactors such as SI flow rate, SI temperature and initial primary pressure, may contribute, too.

• Coupled systems mechanics
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• 제12권1호
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• pp.69-81
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• 2023

This paper considers a delamination analysis of a statically undetermined inhomogeneous beam structure of rectangular section with viscoelastic behavior under torsion. The beam is built in at its two ends. The beam has two longitudinal inhomogeneous layers with a delamination crack between them. A notch is made in the upper crack arm. The external torsion moment applied on the beam is a function of time. Under these conditions, the beam has one degree of indeterminacy. In order to derive the strain energy release rate, first, the static indeterminacy is resolved. Then the strain energy release rate is obtained by analyzing the balance of the energy with considering the viscoelastic behavior. The strain energy release rate is found also by analyzing the compliance of the beam for checkup. Solution of the strain energy release rate in a beam without a notch in the upper crack arm is derived too. In this case, the beam has two degrees of static indeterminacy (the torsion moment in the upper crack arm is treated as an additional internal redundant unknown). A parametric investigation of the strain energy release rate is carried-out.

• 한국재료학회지
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• 제33권11호
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• pp.458-464
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• 2023

In order to develop catechin patches for skin regeneration at wound sites, patches with varying concentrations of catechin and chitosan were manufactured. An optimal composition ratio was determined by adjusting the drug release rate and amount, to maximize efficiency. The catechin used in this study was extracted from green tea leaves using a solvent/ultrasonication method, and its characteristics were confirmed through Fourier transform-infrared spectroscopy (FT-IR) and high-performance liquid chromatography (HPLC) analyses. Patches were prepared with different concentrations of catechin and chitosan, and various properties were analyzed using techniques such as FT-IR, water contact angle analysis, and UV-Vis spectroscopy. It was observed that as the chitosan concentration increased, the release of catechin slowed down or almost ceased. A patch manufactured with 1.5 mg/cm² of catechin at a 1 % chitosan concentration exhibited a high initial release rate over 24 h and demonstrated cellular biocompatibility. Consequently, these patches, with tailored release characteristics based on the concentrations of chitosan and catechin, hold promise for use as drug delivery systems in wound healing applications.

• Journal of Pharmaceutical Investigation
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• 제37권2호
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• pp.95-99
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• 2007

To develop topical nitroglycerin (NTG) preparation far chronic anal fissure treatment, the release rate of NTG should be controlled carefully. For this, microemulsion was prepared from the phase diagram construction with Cremophor ELP, ethanol and Labrafil $M1944CS^{(R)}$ and the topical gel was prepared by dispersing NTG containing microemulsion into hydrophilic polymers. in viかo release characteristics were evaluated with Franz diffusion cell using cellulose membrane and compared with control hydrogels. The release rate of NTG was followed $1^{st}$ order kinetics and, when comparing the NTG release from control hydrogel with that from the microemulsion-based hydrogel, the NTG release rate was controlled by the content of polymers within continuous phase and the concentration of dispersed phase.

• 대한기계학회논문집A
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• 제20권9호
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• pp.2792-2799
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• 1996

It was shown in the previous study that the numerically derived elastic work factor for CLS specimen was independent of fiber direction for a unidirectional case. Also, it was proposed the elastic work factor could be used to determine energy release rate from a single test record. In the present study, elastic work factor was derived from a simple beam theory to investigate its dependence on material property and geometric condition. Also, the elastic work factor of CLS specimen was applied experimentally to determine critical energy release rate in order to prove its validity determining critical energy release rate from a single specimen. For this purpose, critical energy release rate determined using the elastic work factor was compared with that determined by the compliance method. The results showed that while elastic work factor is affected by $t_2/t_1$ and $L_2/L_1$ it is independent of fiber angle for a unidirectional case. It was also found that critical energy release rates determined by both methods are comparable each other, thus elastic work factor approach can be used to determine energy release rate from a single test specimen.