• Archives of Pharmacal Research
• /
• 제12권2호
• /
• pp.143-147
• /
• 1989

The urea effect on skin permeation of clonidine was investigated to reduce a log time and to increase a permeability. ICR mouse skin and human skin were used and were assumed to be a two-layer membrane consisted of stratum corneum and viable epidermis. The urea acted as a skin denaturant and humectant in the whole epidermis. Also it enhanced the skin permeability of clonidine about 3.5 times. On the other hand, it enhanced the skin permeability by acting as a humectant in the viable epidermis. But the urea effect on the whole epidermis was shown to be greater than that on the viable epidermis. Therefore, it was found that the effect of urea was greater on the stratum corneum than the viable epidermis. Variation of enhancing effect according to the concentration of urea was not found in the range of 1% to 20%.

• 식물조직배양학회지
• /
• 제21권1호
• /
• pp.23-28
• /
• 1994

Nicotiana tabaccum 'Xanti', Petunia hybrida 'Blue Star' 그리고 Chrysanthemum morifolium 'Baeckwang'을 공시하여 엽조직 유래의 mesophyII protoplast(MP)와 paraveinal mesophyII protoplast (PVMP) 간의 세포 활성을 조사하기 위하여 urea 투과성을 측정하였다. 아울러 엽육 조직에서 원형질체 나출을 위한 각종 효소제를 처리하고 경과 시간별로 관찰했으며, 나출 원형질체로부터 식물체 재생을 위한 NAA와 thidiazuron의 효과를 조사하였다. Vibratome을 이용한 엽육조직 절단방법은 엽조직의 상해를 최소화하고 조직절편도 최소 50 $\mu\textrm{m}$까지 절단할 수 있기 때문에 urea 투과성 검정과 원형질체 나출을 위한 필수적인 기술이다. 세포활성에 대한 urea투과성 측정은 공시한 3종 식물의 PVMP에서 모두 Ks=2.Ox$10^{-5}$cm/sec 정도가 MP보다 높았다. 효소혼합 용액(1.5% Cellulase R-10, l% Driselase, 0.5% Macerozyme R-10, 0.05% Pectolyase)을 4-8 시간 처리하는 것이 PVMP 나출에 유효하였다. 나출 원형체로부터의 캘러스 유기와 식물체 재생에는 2 mg/L NAA + 0.01 mg/L thidiazuron 처리구에서 가장 양호하였으며 조직별로는 PVMP에서 월등한 결과를 나타내었다. 따라서 엽조직을 대상으로한 원형질체 배양에 있어서 엽록소의 함량이 많은 MP보다는 재생력이나 세포 활성이 강한 paraveinal 엽육조직 유래의 세포를 집약적으로 나출시켜 실험재료로 이용한다면 더 높은 식물체 재생률을 얻을 수 있을 것으로 사료된다.

• Macromolecular Research
• /
• 제15권1호
• /
• pp.22-30
• /
• 2007

High water vapor permeable coating materials were prepared by blending aqueous poly(vinyl alcohol) (PVA) solution with waterborne polyurethane-urea (WBPU) dispersions synthesized by prepolymer mixing process. Stable WBPU/PVA dispersions were achieved at PVA content below 30 wt%. As the water soluble polymer PVA content increased, the number and density of total micro-pores (tunnel-like/isolated micro-pores) formed after the dissolution of PVA in water increased, and the water vapor permeability of coated Nylon fabric also increased significantly. Using WBPU/water soluble polymer PVA blends as a coating material and then dissolving PVA in water was confirmed to be an effective method to obtain prominent breathable fabrics.

• 한국지반공학회논문집
• /
• 제32권5호
• /
• pp.5-13
• /
• 2016

요소 분해 미생물을 이용하여 흙 입자 사이에 칼사이트를 석출시킬 때 칼슘원이 필요하며, 일반적으로 염화칼슘을 칼슘원으로 사용하고 있다. 염화칼슘은 도로, 지반 및 주변 식물에 부작용을 일으키므로 본 연구에서는 버려지는 달걀껍질을 사용한 칼슘원을 개발하고자 하였다. 미생물에 기존 칼슘원인 염화칼슘 또는 식초로 달걀껍질을 분해하여 얻은 새로운 칼슘원을 혼합하여 모래 입자 사이에 칼사이트를 생성시킨 다음, 고결모래의 칼사이트 생성량, 투수계수 및 일축압축강도를 비교 분석하였다. 공시체 제작은 느슨한 상태의 Ottawa모래로 직경 5cm, 높이 10cm 공시체를 만든 다음 Sporosarcina pasteurii 미생물을 포함한 요소와 두 종류의 칼슘원을 1일 1회씩 30일 동안 주입하여 제작하였다. 칼슘원으로 달걀껍질을 사용한 경우 칼사이트 생성량은 평균 7.2%로 염화칼슘을 사용한 경우보다 1.2배 높았다. 또한 달걀껍질을 사용하여 고결시킨 공시체의 투수계수는 평균 3.82E-5cm/s로 7.7배 정도 감소하였으며, 일축압축강도는 평균 387kPa로 염화칼슘을 사용한 경우보다 1.2배 높았다. 한편, 칼슘원에 관계없이 칼사이트 생성량이 증가할수록 강도는 증가하고 투수계수는 감소하는 경향을 보였다.

• 대한토목학회논문집
• /
• 제30권2A호
• /
• pp.169-176
• /
• 2010

일반적으로 폴리우레아는 부착성능, 신장률, 투수 저항성이 매우 높아서 구조물의 방수 코팅재료로 많이 사용되고 있다. 또한, 스프레이건을 이용하여 쉽고 빠르게 작업이 가능하며, 약 30초 이내에 경화가 되기 때문에 시공성도 매우 뛰어나 우수한 기능성 재료로 각광받고 있다. 그러나, 건설산업에서 폴리우레아는 대부분이 방수코팅재료로 사용되고 있으며, 구조물의 성능을 향상시키는 보강재로 사용하기 위한 연구는 전무하다. 따라서, 본 연구는 폴리우레아를 일반 구조물의 보강재로 사용하기 위한 기초적인 연구로 폴리우레아의 구성성분의 변화에 따른 영향을 파악하고자 한다. 또한, 개발된 폴리우레아의 구조 보강성능을 확인하기 위하여, RC 보와 슬래브를 제작하여 휨 성능 실험을 수행하였다. 실험 결과, 폴리우레아는 콘크리트 시험체와 일체거동을 보이며, 연성과 강성이 상승하는 것으로 나타났다. 그러나, 섬유시트와 폴리우레아로 2중 보강한 시편은 오히려 섬유시트만으로 보강한 시편보다 낮은 성능을 보이는 것으로 나타났다.

• Bulletin of the Korean Chemical Society
• /
• 제6권3호
• /
• pp.128-131
• /
• 1985

A series of copolymer membranes of 2-hydroxyethylmethacrylate (HEMA) with selected hydrophobic monomers were prepared without crosslinking agents. The equilibrium water content, the partition coefficient, and the permeability of the solutes such as urea, methylurea, 1,3-di-methylurea, and acetamide via these membranes were measured. The partition coefficient data show that as the hydrophobicity of solutes increased, the partition of solutes were dictated by hydrophobic interaction between solute and polymer matrix. Diffusion coefficients obtained in these experiments decrease as the water content of polymer membrane decreases. This decrease is blunt as the excess heat capacities, ${\phi}C^0_p$ (excess) in aqueous solution at infinite dilution of solute increases. To investigate the relationship between water content and diffusion coefficient, the results of the diffusion experiments were examined in light of a free-volume model of diffusive transport. The remarkable increase of urea mobility in the polymer network containing relatively larger bulk water can be considered as water structure breaking effect.

• 대한약학회:학술대회논문집
• /
• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
• /
• pp.145.1-145.1
• /
• 2003

Oxidative stress has been implicated in a range of disease states, including end-stage renal failure treated with hemodialysis [Westhuyzen J. et al, 2003]. Free radicals react with biological molecules and destroy the structure of cells, which eventually causes free-radical induced disease such as cancer, renal failure, aging, etc. Exogenous or endogenously produced nitric oxide (NO) inhibits superoxide-stimulated urea permeability. In the inner medulla, superoxide generation by local oxidases may stimulate urea transport, and the role of endogenous No may be to dampen this effect by decreasing superoxide levels ［Zimpelmann J. et al, 2003 (Epub ahead of print)］. (omitted)

• Geomechanics and Engineering
• /
• 제12권5호
• /
• pp.803-813
• /
• 2017

This study discussed the possible optimization of enzyme-mediated calcite precipitation (EMCP) as a soil-improvement technique. Magnesium chloride was added to the injection solution to delay the reaction rate and to improve the homogenous distribution of precipitated minerals within soil sample. Soil specimens were prepared in 1-m PVC cylinders and treated with the obtained solutions composed of urease, urea, calcium, and magnesium chloride, and the mineral distribution within the sand specimens was examined. The effects of the precipitated minerals on the mechanical and hydraulic properties were evaluated by unconfined compressive strength (UCS) and permeability tests, respectively. The addition of magnesium was found to be effective in delaying the reaction rate by more than one hour. The uniform distribution of the precipitated minerals within a 1-m sand column was obtained when 0.1 mol/L and 0.4 mol/L of magnesium and calcium, respectively, were injected. The strength increased gradually as the mineral content was further increased. The permeability test results showed that the hydraulic conductivity was approximately constant in the presence of a 6% mineral mass. Thus, it was revealed that it is possible to control the strength of treated sand by adjusting the amount of precipitated minerals.

• Journal of Microbiology and Biotechnology
• /
• 제23권9호
• /
• pp.1269-1278
• /
• 2013

Crack remediation on the surface of cement mortar using microbiological calcium carbonate ($CaCO_3$) precipitation (MICP) has been investigated as a microbial sealing agent on construction materials. However, MICP research has never acknowledged the antifungal properties of calcite-forming bacteria (CFB). Since fungal colonization on concrete surfaces can trigger biodeterioration processes, fungi on concrete buildings have to be prevented. Therefore, to develop a microbial sealing agent that has antifungal properties to remediate cement cracks without deteriorative fungal colonization, we introduced an antifungal CFB isolated from oceanic islands (Dokdo islands, territory of South Korea, located at the edge of the East Sea in Korea.). The isolation of CFB was done using B4 or urea-$CaCl_2$ media. Furthermore, antifungal assays were done using the pairing culture and disk diffusion methods. Five isolated CFB showed $CaCO_3$ precipitation and antifungal activities against deteriorative fungal strains. Subsequently, five candidate bacteria were identified using 16S rDNA sequence analysis. Crack remediation, fungi growth inhibition, and water permeability reduction of antifungal CFB-treated cement surfaces were tested. All antifungal CFB showed crack remediation abilities, but only three strains (KNUC2100, 2103, and 2106) reduced the water permeability. Furthermore, these three strains showed fungi growth inhibition. This paper is the first application research of CFB that have antifungal activity, for an eco-friendly improvement of construction materials.

• The Korean Journal of Physiology
• /
• 제2권2호
• /
• pp.33-43
• /
• 1968

Histamine, 0.5 mg as histamine base in 4 ml of normal saline solution, was injected into rabbits anesthetized with nembutal and the mean blood pressure was kept in the range of $52{\sim}80\;mmHg$ for over one hour by supplemental additions. Following the injection of the test substances, 300 mg of urea and 200 mg of antipyrine intravenously, serial blood samples were obtained from the femoral artery and the internal jugular vein at $0.5{\sim}3$ minutes interval. The decreasing patterns in the concentrations of arterial and venous blood plasma samples were compared with each other. The ratio of the concentration of brain tissue to that of the final arterial plasma was also studied. By these measures the degrees of penetration of the test substances in the brain in the control and in the histamine treated rabbits were observed. The concentrations of antipyrine and urea in the arterial blood plasma were decreasing exponentially with respect to the time elapsed. The venous concentrations were anticipated to increase initially and to cross the arterial concentration curve in the point of equlibrium between the plasma and the tissue. On the contrary to the expectation venous concentration also revealed the decreasing tendency similar to that of arterial plasma. The similarity between these two curves, arterial and venous, would be atributable to the fact that the cerebral blood flow rate was large enough and the rising phase in the venous concentration curve was instantly over before serial blood samples were taken. Inspite of some similarity in the decreasing tedency in both concentration curves there were appreciable discrepancies between the arterial and venous plasma which would reflect the situation far from the equlibria among several compartments in the brain. Changes in plasma potassium levels caused by the injection of histamine or bleeding were observed, too. Using 8 rabbits as the control and 12 rabbits for the histamine treated group following results were obtained: 1. Both of the concentration curves, arterial and venous, declined rapidly at_first and slowly later on and approached same equilibrium concentration with the passage of time after a single injection. The time at which attained the same concentration was $2.0{\pm}0.54\;min.$ in the control and $4.3{\pm}1.92\;min.$ in the histamine treated group with respect to antipyrine. On the other hand in the case of urea they were $2.4{\pm}0.59\;min.$ in the control and $4.4{\pm}1.31\;min.$ in the histamine group, respectively. In the histamine treated group enlarged spaces for distribution of test substances were postulated. 2. The concentration of antipyrine in the brain tissue water revealed no significant differences between the control and experimental groups, showing $212{\pm}40.2\;mg/l$ in the control and $206{\pm}64.1\;mg/l$ in the histamine treated group. On the other hand urea revealed higher value in the histamine treated group than in the control, showing an enhanced penetration of urea into the tissue after injection of histamine. Urea concentration in the brain water was $32.3{\pm}3.36\;mg%$ in the control and $39.2{\pm}4.25\;mg%$ in the histamine treated group. 3. The distribution ratio of antipyrine in the brain tissue was very close to unity in the histamine treated animals as well as in the control. 4. The average of the distribution ratio of urea in the control animals was 0.77 and it showed the presence of blood-brain barrier with regard to urea. However in the histamine treated animals the distribution ratios climbed up to 0.86 and they were closer to unity than in the control animals. Out of 12 cases 5 were greater than 0.9 and 8 exceeded 0.85. It appeared that histamine enhanced the penetration of urea through the barrier. 5. Histamine injection and or hemorrhage caused an elevation of the concentration of potassium in plasma. In the event that histamine and hemorrhage were applied together the elevation of potassium exceed the elevation seen at the histamine alone. There was no evidence that the leakage of potassium from the brain tissue was dominant in comparison with the general leakage from the whole body.