• Journal of Biosystems Engineering
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• 제40권3호
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• pp.271-276
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• 2015

Purpose: Quick freezing is widely used in commercial food storage. Well-known freezing techniques such as individual quick freezing require a low-temperature coolant and small cuts for the heat-transfer efficiency. However, the freezing method for bulk food resembles techniques used in the 1970s. In this study, electromagnetic (EM) heating was applied to improve the quick freezing of bulk food. Methods: During freezing, the surface of food can be rapidly cooled by an outside coolant, but the inner parts of the food cool slowly owing to the latent heat from the phase change. EM waves can directly heat the inner parts of food to prevent it from freezing until the outer parts finish their phase change and are cooled rapidly. The center temperature of garlic cloves was probed with optical thermo sensors while liquid nitrogen (LN) was sprayed. Results: When EM heating was applied, the center cooling time of the garlic cloves from freezing until $-10^{\circ}C$ was 48 s, which was approximately half the value of 85 s obtained without EM heating. For the white radish cubes, the center cooling time was also improved, from 288 to 132 s. The samples frozen by LN spray with EM heating had a closer hardness to the unfrozen samples than the samples frozen by LN only. Conclusions: The EM heating during quick freezing functions to maintain the hardness of fresh food by reducing the freezing time from 0 to $-10^{\circ}C$.

• Journal of Pharmaceutical Investigation
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• 제28권2호
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• pp.121-126
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• 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.

• Journal of Pharmaceutical Investigation
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• 제25권3호
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• pp.177-184
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• 1995

In order to formulate an aqueous topical preparation of epidermal growth factor(EGF) for the treatment of open wound and bum, the stability of EGF in aqueous vehicles containing various stabilizers was evaluated and the pharmacological activity of gel preparations formulated with poloxamer 407 was determined with wound model. Various additives, which are known as potent stabilizers for proteins and polypeptides so far, were used to increase the stability of EGF in aqueous vehicles. The contents of EGF in the vehicles containing stabilizers were determined with an HPLC method after the storage at $37^{\circ}C$. EGF was more stable in ultrapure water than RO water or saline. All the additives studied resulted in deleterious effects on EGF stability. Therefore, it was speculated that any additives or impurities in the vehicle made EGF unstable. However, nitrogen purge of solution increased the stability of EGF in aqueous vehicles. The aqueous topical preparations of EGF were formulated with poloxamer 407 as a gel base in saline. Gelatin or amastatin was employed as a protease inhibitor. The pharmacological effect of EGF gel was studied with open wound model in mice. EGF preparations, made of oleaginous base or poloxamer gel base, showed significant healing effect compared to the control group(p<0.05). The addition of protease inhibitor in poloxamer 407 gel resulted in significant healing effect compared to the gel without it(p<0.05). Body weights of mice treated with EGF preparation were increased at the first day after the formation of open wound, while those of the control group were decreased. The EGF gel made of poloxamer 407 containing a pretense inhibitor would be a promising aqueous topical preparation for EGF.

• Journal of Pharmaceutical Investigation
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• 제39권4호
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• pp.309-314
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• 2009

An enzyme immunoassay (EIA) was validated for quantitation of cacitriol in human plasma. Calcitriol was immunoextracted with immunocapsules, which contain monoclonal antibodies to calcitriol linked to solid phase particles in suspension with a vitamin D binding protein inhibitor. Calcitrol was eluated and the eluates were evaporated under a gentle stream of nitrogen gas. The absorbance of analytes was determined using a microplate reader (reference wavelength 650 nm; measurement wavelength 450 nm). The method was specific and sensitive enough to detect as low as 6.5 pmol/L of calcitriol. Linear calibration range was 6.5-491 pmol/L with correlation coefficient greater than 0.99. The overall accuracy was in the range of 83.8 to 111.2% and precision C.V. (%) 0.99 to 8.47%. The recovery was approximately 100% and stability was confirmed during storage and sample preparation. The pharmacokinetic parameters were calculated by baseline subtraction because calcitriol is an endogenous material. Following oral dose of calcitriol, the mean AUC$_{24h}$ was 1038${\pm}$539 pmol/Lhr and C$_{max}$ of 128${\pm}$63.1 pmol/L was reached at 3.50${\pm}$1.07 hr. The mean t$_{1/2}$ of calcitriol was 5.13${\pm}$2.10 hr. The present EIA method was successfully applied to study bioavailability after oral administration of 2 ${\mu}$g of calcitriol in healthy Korean subjects.

• 한국추진공학회지
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• 제11권2호
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• pp.54-61
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• 2007

액체로켓추진시스템에서 추진제 가압시스템은 추진제가 저장되어 있는 탱크의 얼리지 공간에 가압제인 가스를 제어된 압력으로 공급하는 것이다. 이러한 추진제 가압시스템의 가장 중요한 설계변수는 가압제를 저장하고 있는 탱크에서 토출되는 가압제의 온도이며, 기체상태인 가압제의 밀도는 토출되는 가압제의 온도에 따라 민감하게 변한다. 일반적으로 고추력을 요구하는 극저온 추진제가 적용되는 추진기관에서는 가압제를 고밀도 고압으로 저장하여 가압제 탱크의 무게를 줄이기 위하여 가압제 저장탱크를 극저온 추진제 탱크 내부에 설치하는 극저온 저장 가압시스템을 사용한다. 본 연구에서는 가압제가 가압제 저장탱크에서 토출 될 때 강하되는 온도 변화를 실험 및 해석을 통하여 고찰하였다. 본 연구에 적용된 유체는 외부유체로 공기와 액체산소 그리고 가압제로 $GN_2$와 GHe를 각각 사용하였다.

• 폴리머
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• 제37권2호
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• pp.156-161
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• 2013

페놀계 산화방지제는 가공 및 사용 시 열분해를 방지함으로써 뛰어난 열 안정성을 제공하는 대표적인 1차 산화방지제이다. 그러나 NOx 가스를 포함한 특정 환경에 의해 황변이 일어나기 쉽기 때문에 2차 산화방지제를 추가로 도입하여 시너지효과를 기대하는 경우가 많다. 열에 취약한 비결정성 폴리알파올레핀 수지(APAO)에 여러 가지 페놀계 1차 및 2차 산화방지제를 도입하여 황변 여부를 조사한 결과 2차 산화방지제의 함량이 증가할수록 황변이 줄어들었으며 BHT와 같은 단순 구조의 폐놀계 산화방지제보다 긴 알킬 사슬을 도입시켜 입체장애효과를 증대시킨 산화방지제가 2차 산화방지제와의 시너지 효과가 더 큰 것으로 확인되었다.

• 한국식품과학회지
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• 제33권1호
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• pp.72-77
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• 2001

고추장의 보존성 향상을 목적으로 고추장에 5, 10, 20 kGy의 선량으로 감마선을 조사하고 $25^{\circ}C$에 12주간 보존하면서 고추장의 미생물 및 일반품질 변화를 조사하였다. 고추장의 Bacillus는 감마선 조사에 대하여 3.94 kGy의 $D_{10}$값을 보여 감마선에 대한 저항성이 높았으며 효모와 젖산균은 10 kGy의 선량에서 완전 사멸에 가까운 살균효과를 보였다. 고추장 보존 중의 일반품질 평가 요소인 아미노산성질소, 총환원당, protease 및 amylase 활성, pH, 갈변도의 변화는 감마선 조사에 의하여 영향을 받지 않았다. 따라서 감마선 조사는 고추장의 품질에 영향을 주지 않고 미생물만을 선택적으로 사멸시켜 제품의 보존 유통 및 가공에서 미생물 관점의 품질을 유지하는데 유용한 방법이 될 것으로 평가되었다.

• 한국자원식물학회지
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• 제28권6호
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• pp.697-703
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• 2015

Twenty apple germplasm accessions from the Korean Genebank were successfully cryopreserved using two-step freezing to back up genetic resources maintained by field collections. This study examined the morphological and genetic stability of cryopreserved dormant apple buds that were stored in liquid nitrogen, and then rewarmed and regrown. Whole plants were regenerated directly from dormant buds through budding without an intermediary callus phase. The cryopreserved buds produced high levels of shoot formation (76.2-100%), similar to those of noncryopreserved buds (91.3-100%), with no observed differences between cryopreserved and noncryopreserved materials. Three of the twenty cryopreserved apple germplasm accessions were used to assess morphological and genetic stability. No differences in morphological characteristics including shoot length, leaf shape, leaf width/length ratio, and root length were observed between controls (fresh control and noncryopreserved) and cryopreserved plantlets. The genetic stability of regenerants (before and after cryopreservation) was investigated using inter simple sequence repeat (ISSR) markers. The ISSR markers produced 253 bands using four primers, ISSR 810, SSR 835, ISSR 864, and ISSR 899. These markers showed monomorphic banding patterns and revealed no polymorphism between the mother plant and regenerants before and after cryopreservation, suggesting that cryopreservation using two-step freezing does not affect the genetic stability of apple germplasm. These results show that two-step freezing cryopreservation is a practical method for long-term storage of apple germplasms.

• Environmental Engineering Research
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• 제19권3호
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• pp.261-268
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• 2014

Leachate quality and methane emission from pilot-scale lysimeters operated under semi-aerobic and anaerobic conditions were monitored for 650 days. Two semi-aerobic lysimeters were filled with un-compacted and compacted municipal solid wastes whereas two anaerobic lysimeters containing compacted wastes were operated with leachate storage at 50% and 100% of waste height, respectively. Despite having high moisture in wastes and operating under tropical rainfall events, leachate stabilization in semi-aerobic lysimeters took place much faster resulting in BOD reduction by 90% within 60 days, significantly shorter than 180-210 days observed in anaerobic lysimeters. Nitrogen concentration in leachate from semi-aerobic lysimeter could be reduced by 90%. In term of gas emission, semi-aerobic lysimeter with un-compacted wastes had much lower methane emission rate of $2.8g/m^2/day$ compare to anaerobic lysimeters ($62.6g/m^2/day$) through seasonal fluctuation was observed. Nevertheless, semi-aerobic lysimeter with waste compaction has similar performance to anaerobic lysimeter.

• Applied Biological Chemistry
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• 제16권1호
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• pp.31-40
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• 1973

Azotobacter vinelandi의 세포추출물(細胞抽出物)들이 Shethna flavoprotein의 free radical 형(型)으로의 전자전달기구(電子傳達機構)에 관하여 연구(硏究)하였다. 전자전달(電子傳達)에 관여도(關與度)가 높은 단백질(蛋白質)로 황색형광성단백질(黃色榮光性蛋白質)(protein I)과 갈색단백질(褐色蛋白質)(protein II)을 정제(精製)하였고 이들은 $N_2$ 기압하(氣壓下) 또는 aceton-dry ice 동결(凍結)저장하에서도 쉽게 실활(失活)되었고 반응속도(反應速度) 역시 너무 완만하여 생체내반응(生體內反應)이기에는 의문점을 보였다. 한편 세포추출물중(細胞抽出物中)의 FMN은 NADH에 의(依)하여 환원이 쉽게 이루어졌으며, 환원형 $FMNH_2$는 비효소적(非酵素的)으로 Shethna flavoprotein 의 free radical 을 형성(形成)시켰으며 , 효소적반응속도(酵素的反應速度)보다 15배(倍)의 높은 반응속도(反應速度)를 보였다. 비록 FMN이 생체내(生體內)에서 타(他)단백질과 비결합형(非結合型)으로 존재(存在)하지 않는다해도 FMN의 전자전달체(電子電達體)의 가능성(可能性)을 제시(提示)하였다.