• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.1-8
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• 2023

Research, such as developing alternative energy in the transportation field, including aviation, is being actively conducted to solve the issue of current climate change. Interest in ammonia fuel as a carbon free energy (CFE) source is increasing due to the ease of liquefaction and transportation and similarity in energy density to that of methanol. However, explosiveness and toxicity of ammonia make it difficult to handle. Therefore, in this study, stable ammonia production was attempted using relatively easy-to-handle urea water solution (UWS). High temperature steam was used to promote the hydrolysis of ammonia. In order to determine the causes for ammonia production below the theoretical equivalent ratio, it was suggested that there were not enough collisions to promote the hydrolysis based on the kinetic theory of gases. The hydrolysis of unreacted isocyanic acid (HNCO) was tested according to the change in water supply. As a result, an increased amount of ammonia produced was confirmed. The increased amount of ammonia produced in a certain section was dependent on the steam temperature and the flow rate of water supplied.

• Korean Journal of Soil Science and Fertilizer
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• v.27 no.1
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• pp.40-47
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• 1994

The objective of this research was to examine the effect of ammonium thiosulfate(ATS) on urease activity and on biological and chemical properties of flooded paddy soil especially having high organic matter content by comparing with the effect of sodium thiosulfate(STS). The results obtained are summarized as follows. 1. The hydrolysis of urea was inhibited at 3 and 5 days after treatment of thiosulfate(ATS and STS) +glucose and thiosulfate only, respectively. The inhibitory effect of ATS on urea hydrolysis was slightly lower than that of STS in glusoce-added soils, but when the glucose was not added, the effects of ATS and STS were not different significantly. 2. The soil pH and Eh was lowered by 0.3~0.5 units and 30~120 mV, respectively, when incubated flooded soil with ATS and glucose at $25^{\circ}C$. 3. Soil respiration rate in/flooded soil was increased by 10~70% with the treatment of ATS during the 20 day experimental period. 4. The contents of acetic and butyric acid in thiosulfate treatment soil was below $10{\mu}g/g$, which was lower than that($220.3{\mu}g/g$) of critical growth inhibition of rice.

• Korean Journal of Food Science and Technology
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• v.22 no.2
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• pp.129-133
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• 1990

The strain of Nuruk yeat No. 15 (NY-15) which ferments lactose in milk was Isolated from Nuruk and identified as Saccharomyces marxianus according to the API 20C profile index. The lactose hydrolysing ability of NY-15 was similar to that Saccharomyces fragilis ATCC 8583 which has ${\beta}-galactosidase$ activity. Its optimum growth temperature, pH and time for the production of maximum enzyme activity showed $28^{\circ}C$, 4.5 and 28hr, respectively. Galactose as well as sucrose as carbon sources, and urea as nitrogen source Increased the production of enzyme. In order to test the production of alcohol, NY-15 was inoculated in whey medium and whey medium added with sugar. In the former, NY-15 produced 2% alcohol and in the latter, it showed 12% alcohol production. The optimal medium pH for lactose hydrolysis of NY-15 is 4.5, whereas that of Saccharomyces fragilis ATCC 8583 is 3.5

• Journal of Microbiology and Biotechnology
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• v.13 no.5
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• pp.673-679
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• 2003

Glutamine and urea, abundant in body fluids or plasma, yield net ammonium ions upon hydrolysis by ${\gamma}-glutamyl$ transpeptidase (${\gamma}-GTP$) and urease, respectively, and these two enzymes are largely produced from Helicobacter pylori. To investigate bacterial potential of ammonium production, we first quantified those in whole-cell systems and found that the relative ratio of their amounts varied greatly, especially with pH values and the cell's aging. During the H. pylori cultivation, the ratio appeared to be inversely proportional to each other, showing a progressive increase of the ${\gamma}-GTP$ with decreasing of the urease. Under the urease-defective conditions due to low pH or coccoids, the bacterial cells still possessed a considerable amount of ${\gamma}-GTP$, which was found exclusively in the external compartment, therefore, the cell's ammonium production was found to be solely dependent upon glutamine, and the external ammonium concentration was constant without any contribution of urea concentration. Such ammonium constancy would definitely have an adverse effect on the host, because of its absolute requirement for vacuolar degeneration by H. pylori VacA, maximized at approximately 10 mM $NH_4Cl$. It was also found that, by using the metal-saturated membrane vesicles, ammonium ions were likely to be involved in the pH-dependent cation-flux across the H. pylori membrane, where the role of ${\gamma}-GTP$ in ammonium homeostasis around cells was suggested, especially under the hostile conditions against H. pylori.

• Korean Journal of Radiology
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• v.1 no.3
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• pp.121-126
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• 2000

Objective: To evaluate the therapeutic efficacy of a new liquid embolic material, Embol, in embolization of the renal artery. Materials and Methods: Embol is a new embolic material obtained by partial hydrolysis of polyvinyl acetate mixed in absolute ethanol and Iopromide 370 and manufactured by Schering Korea, Kyonggido, Korea. Six patients who underwent embolization of the renal artery using Embol were evaluated. Four were male and two were female and their ages ranged from 11 to 70 (mean, 53) years. Clinical and radiologic diagnoses referred for renal artery embolization were renal cell carcinoma (n = 3), renal angiomyolipoma (n = 2) and pseudoaneurysm of the renal artery (n = 1). After selective renal angiography, Embol was injected through various catheters, either with or without a balloon occlusion catheter. Changes in symptoms and blood chemistry which may have been related to renal artery embolization with Embol were analyzed. Results: The six patients showed immediate total occlusion of their renal vascular lesions. One of the three in whom renal cell carcinoma was embolized with Embol underwent radical nephrectomy, and the specimen thus obtained revealed 40% tumor necrosis. In the two patients with angiomyolipomas, the tumors decreased in size and abdominal pain subsided. Bleeding from pseudoaneurysm of the renal artery was successfully controlled. Four patients showed symptoms of post-embolization syndrome, and one of these also showed increased levels of blood urea nitrogen and creatinine. One patient experienced transient hypertension. Conclusion: Embol is easy to use, its radiopacity is adequate and it is a safe and effective embolic material which provides immediate and total occlusion of renal vascular lesions.

• Journal of Microbiology and Biotechnology
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• v.8 no.6
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• pp.700-704
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• 1998

Each of the recombinant structural genes of Helicobacter pylori urease, ureA and ureB, was cloned and overexpressed as inclusion bodies. Solubilization and renaturation of the inclusion bodies were carried out, to accelerate the pairing of sulfhydryl groups and the incorporation of nickel ions, which would lead to the native structure with high enzyme activity. Rates of urea hydrolysis were monitored as an indication of in vitro activation of renatured ureases. The activation of the apoprotein using 1 mM nickel ion, 100 mM sodium bicarbonate and a 10:1 ratio of reducing power resulted in a weak urease activity (about 11% of the native urease activity encoded by pTZ 19R/ure-l). When a sparse matrix screen method originally discovered for the crystallization of proteins was used, the activity increased higher than that obtained using glutathione. The effect of polyethylene glycol (PEG) on the activity was noticeable, giving two-fold increase in the specific activity (about 11 U/mg of protein corresponding to 22% of the native urease activity encoded by pTZ19R/ure-1).

• Journal of the Korean Ceramic Society
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• v.28 no.4
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• pp.338-346
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• 1991

The alumina-titania composite powders coated with Al2O3 were prepared by the method of hydrolysis-deposition of mixed aluminium salt solution of Al2(SO)4-Al(NO3)3-Urea. The effects of coating-process parameters on the characteristics of coated composite powders were also investigated. As the content of TiO2 dispersed in deionized water increased, the coated composite powders were found to be more uniform in size and unagglomerated. When TiO2 powders were coated for 30 min, the optimum TiO2 content in the coating process was 400 mg/ι. The size of TiO2 particle was increased approximately from 0.7${\mu}{\textrm}{m}$ to 1.0${\mu}{\textrm}{m}$ through coating of Al2O3. The IEP of coated composite powders was pH=8.3 identical to the value of aluminium hydroxides and the zeta-potential showed nearly similar values each other. When heat treating coated composite powders at 130$0^{\circ}C$, only two phases of TiO2(rutile) and Al2TiO5 were observed. These results showed that the suface of TiO2 could be uniformly coated with the aluminium hydroxide.

• Childhood Kidney Diseases
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• v.25 no.2
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• pp.112-116
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• 2021

Hyperammonemia is mainly caused by diseases related to liver failure. However, there are also non-hepatic causes of hyperammonemia, such as urinary tract infection (UTI) due to urease-producing organisms. Urease production by these bacteria induces a hydrolysis of urinary urea into ammonia that can cross the urothelial cell membrane and diffuse into blood vessels, leading to hyperammonemia. Delayed diagnosis and treatment of hyperammonemia can lead to lethal encephalopathy that can cause brain damage and life-threatening conditions. In the presence of obstructive uropathy, UTI by urease-producing bacteria can lead to more severe hyperammonemia due to enhanced resorption of ammonia into the systemic circulation. In this report, we present a case of acute severe hyperammonemic encephalopathy leading to brain death due to accumulation of ammonia in blood caused by Morganella morganii UTI in a 10-year-old girl with cloacal anomaly, causing obstructive uropathy even after multiple corrections.

• Korean Journal of Soil Science and Fertilizer
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• v.24 no.2
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• pp.102-108
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• 1991

A field experiment with microplots(D.20cm, L. 85cm) was conducted to obtain quantitative information on the downward movement of nutrients applied to the soils by different amount of irrigation water. The microplots were installed by embedding PVC column(D. 20cm, L. 90cm) filled with sieved soils in the field. Urea, fused and superphosphate, and KCl were broadcasted over the soil in the microplots and surface layer was covered with lime-amended soils. Microplots were removed 1 week after water application and analysed for Cl, $NH_4$ and $NO_3-N$, Bray 1-P and exchangeable cations of Ca, Mg, and K in each segment. Effect of irrigation rate on the movement of these ions were evaluated with the mean downward movement(MDM) determined with nutrient concentration of each segment and the distance to the segment from the site fertilized. For the nutrient studied, MDM was linearly related to the amount of water applied. When one pore volume of water needed for 0.1 bar soil moisture tension was applied, MDM(cm), computed as the piston front of applied water advanced 10cm, was found to be in the order; Cl, 7.52>Inorganic N, 6.03> K, 3.50> Mg, 2.69>Ca, 1.19>P, 0.29. After the downward movement of applied nutrients soil pH seemed to decrease with irrigation in the surface layer(0-15cm) and increase in the subsurface layer. It was also found that ammonium-nitrogen evolved from urea hydrolysis was more effective in raising the subsoil pH rather than the exchangeable Ca and Mg.

• Microbiology and Biotechnology Letters
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• v.26 no.6
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• pp.515-522
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• 1998

Plant root rotting fungi, Fusarium solani are suppressed their growth by the chitinase which is produced from the antagonistic soil bacteria. The chitinase producable antagonistic bacterium Pseudomonas sp. 3098 was selected as a powerful biocontrol agent of F. solani from ginseng rhizosphere. The antagonistic Pseudomonas sp. 3098 was able to produce a large amount of extracellular chitinase which is key enzyme in the decomposition of fusarial hypal walls. The chitinase was purified from cultural filtrate of Pseudomonas sp. 3098 by the procedure of ammonium sulfate precipitation, anion exchange chromatography, gel filtration on Bio-Gel P-100, and 1st and 2nd hydroxyapatite chromatography. The molecular mass of the purified enzyme was ca. 45 kDa on SDS-FAGE. The optimal pH and temperature for the activity of purified chitinase were 5.0 and 45$^{\circ}C$, respectively. The enzyme was stable in pH range of 5.0 to 9.0 up to 5$0^{\circ}C$ The enzyme was significantly inhibited by metal compounds such as FeCl$_2$, AgNO$_3$ and HgCl$_2$, and was slightly inhibited by p-CMB, iodoacetic acid, urea, 2,4-DNP and EDTA. The enzyme had ability of digestion on colloidal chitin and chitin from shrimp shell, but could not digest chitosan and chitin from crab shell. Km value of the enzyme was 0.11% on colloidal chitin, and the maximum hydrolysis rate of the enzyme was 34% on colloidal chitin.