• Korean Journal of Animal Reproduction
• /
• v.15 no.3
• /
• pp.195-199
• /
• 1991

This study was carried out ot investigate effect of pH stimulation on acrosome reaction of bovine spermatozoa. The results obtained were as follows : 1. When sperm was sequentially washed with SHP solution of pH 7.4, 7.7 and 7.4 and incubated in mTALP solution of pH 7.4 for 120min, 15, 30, 60 and 120min incubations showed significantly(p<0.05) higher sperm acrosome reaction rate than 0 min. 2. When sperm was sequentially washed with SHP solution of pH 7.4, 8.0 and 7.4 and incubated in mTALP solution of pH 7.4 for 15 minutes, sperm acrosome reaction rate was significantly(p<0.01) increased until 9 min. Incubation, but not increased thereafter. 3. When sperm were separately washed with SHP solutions of pH 7.0, 7.4 and 8.0 and incubated in mTALP solution of pH 7.4 for 9min, sperm acrosome reaction rate was 74.8, 71.8 and 93.4%. pH 8.0 showed signifciantly(p<0.01) higher sperm acrosome reaction rate than pH 7.0 and 7.4. The results suggest that stimulation of sperm with high pH induces sperm crosome reaction.

• Journal of Plant Biology
• /
• v.19 no.4
• /
• pp.95-99
• /
• 1976

This work deals with different extraction media and reaction mixtures on photosystem II activity of Spinach chloroplasts. The photoreduction rate of ferricyanide and DPIP by intact chloroplasts which extracted with four kinds of extraction media; S-Tris-N pH 7.2, 8.0, S-Tricine-N pH 7.2, 8.0, was measured in five kinds of reaction mixtures; S-Tris-N pH 7.2, 8.0, S-Tricine-N pH 7.2, 8.0, 0.05 M-Tris pH 7.2. The extraction medium which shows the highest photoreduction rate was S-Tris-N at pH 7.2 and S-Tricine-N at pH 8.0. As to the reaciton mixture, S-Tricine-N pH 8.0 showed the highest rate. On the complex effects of extraction media and reaction mixtures, the highest photordeuction rate of Hill oxidant by intact chloroplasts was obtained by S-Tris-N pH 7.2 extraction medium and S-Tricine-N pH 8.0 reaction mixture. The second highest activity was obtained by S-Tricine-N pH 8.0 extraction medium and reaction mixture.

• Korean Chemical Engineering Research
• /
• v.43 no.1
• /
• pp.153-160
• /
• 2005

There have been large areas of soil contaminated with high levels of explosives. For this experimental work, 2,4,6-trinitrotoluene (TNT) was tested as a representative explosive contaminant of concern in both aqueous and soil samples and its removal was evaluated using three different chemical treatment methods: 1) the classical Fenton reaction which utilizes hydrogen peroxide ($H_2O_2$) and soluble iron at pH less than 3; 2) a modified Fenton reaction which utilizes chelating agents, $H_2O_2$, and soluble iron at pH 7; and 3) a Fenton-like process which utilizes iron minerals instead of soluble iron and $H_2O_2$, generating a hydroxyl radical. Using classic Fenton reaction, 93% of TNT was removed in 20 h at pH 3 (soil spiked with 300 mg/L of TNT, 3% $H_2O_2$ and 1mM Fe(III)), whereas 21% removed at pH 7. The modified Fenton reaction, using nitrilotriacetic acid (NTA), oxalate, ethylenediaminetetraacetic acid (EDTA), acetate and citrate as representative chelating agents, was tested with 3% $H_2O_2$ at pH 7 for 24 h. Results showed the TNT removal in the order of NTA, EDTA, oxalate, citrate and acetate, with the removal efficiency of 87%, 71%, 64%, 46%, and 37%, respectively, suggesting NTA as the most effective chelating agent. The Fenton-like reaction was performed with water contaminated with 100 mg/L TNT and soil contaminated with 300 mg/L TNT, respectively, using 3% $H_2O_2$ and such iron minerals as goethite, magnetite, and hematite. In the goethite-water system, 33% of TNT was removed at pH 3 whereas 28% removed at pH 7. In the magnetite-water system, 40% of TNT was removed at pH 3 whereas 36% removed at pH 7. In the hematite-water system, 40% of TNT was removed at pH 3 whereas 34% removed at pH 7. For further experiments combining the modified Fenton reaction with the Fenton-like reaction, NTA, EDTA, and oxalate were selected with the natural iron minerals, magnetite and hematite at pH 7, based on the results from the modified Fenton reaction. As results, in case magnetite was used, 79%, 59%, and 14% of TNT was removed when NTA, oxalate, and EDTA used, respectively, whereas 73%, 25%, and 19% removed in case of hematite, when NTA, oxalate, and EDTA used, respectively.

• Journal of Technologic Dentistry
• /
• v.26 no.1
• /
• pp.89-96
• /
• 2004

Hydroxyapatite powder were synthesized by precipitation method, varying pH, and reaction temperature. The powders were heated at 1,200$^{\circ}{\cdots}$ and 1,300$^{\circ}{\cdots}$ for fabrication of dental prosthesis. The results are as follows: Synthesized powder showed the smallest particle in size, under the conditions of pH 11 and reaction temperature 37$^{\circ}{\cdots}$. The hydroxyapatite was partially converted to $\alpha,\;\beta$-TCP at 1,200$^{\circ}{\cdots}$ and 1,300$^{\circ}{\cdots}$. Mechanical strength of sample was affected by such powder preparation conditions as pH and reaction temperature and sintering temperature. The mechanical strength of sample prepared under the same conditions was increased with increasing pH, reaction temperature and sintering temperature.

• Journal of the Korean Chemical Society
• /
• v.16 no.4
• /
• pp.232-240
• /
• 1972

The rate constants for the addition reaction of n-butylmercaptan to ethylacrylate have been measured by iodometry and for the proposed reaction mechanism a rate equation which can be applied over wide pH range was derived. From this rate equation, one may conclude that the reaction is started by addition of n-butylmercaptan molecule below pH 4. However, above pH 7, this addition reaction is proceeded by the n-butylmercaptide ions. At pH 4-7, the complex addition reaction mechanism can also be revealed by this rate equation.

• Journal of the Korean Chemical Society
• /
• v.13 no.4
• /
• pp.289-296
• /
• 1969

The rate constants for the addition reaction of ethylmercaptan to ethylcinnamate has been measured by iodometry and for the proposed reaction mechanism a rate equation which can be applied over wide pH range was derived. From this rate equation, one may conclude that the reaction is started by addition of ethylmercaptan molecule below pH 3. However, above pH 7, this addition reaction is proceeded by the ethylmercaptide ion. At pH 3-7, the complex addition reaction mechanism can also be revealed by this rate equation.

• Journal of the Korean Ceramic Society
• /
• v.28 no.11
• /
• pp.885-891
• /
• 1991

Calcium hydroxyapatite have been synthesized by a direct precipitation reaction between 0.05 M calcium hydroxide suspension and 0.3 M orthophosphoric acid solution. 0.01 M calcium hydroxide solution was added during the reaction in order to increase the total Ca/P mol ration and reaction pH of the solution. The stoichiometric hydroxyapatite was synthesized over 1.75 as total Ca/P mol ratio, but the calcium-deficient hydroxyapatite was prepared under 1.725 as total Ca/P mol ratio. The nonstoichiometry of the precipitates were interpreted in terms of the pH change during the reaction.

• YAKHAK HOEJI
• /
• v.6 no.1
• /
• pp.5-7
• /
• 1962

Like the condensation reaction of general aldehyde, that of benzaldehyde with semicarbazide also depends upon the concentration of carbonium ion that is produced by hydrogen ion. The lower pH value is the facility of the formation of carbonium ion in the condensation reaction, while the reactivity of semicarbazide as a reactant is reduced. In this paper, therefore we want to find out the optimum pH value in the condensation reaction of benzaldehyde with semicarbazide. This optimum pH value was determined by using the simple paper-chromatographic method. According to the result of this experiment, the condensation reaction between benzaldehyde and semicarbazide reacts with its highest point at 3.5pH value. It seems clear that at this point the benzaldehyde acquires the most suitable amount of carbonium ion for the condensation reaction with semicarbazide, and the semicarbazide also has the optimum reactivity.

• Bulletin of the Korean Chemical Society
• /
• v.6 no.5
• /
• pp.280-284
• /
• 1985

Kinetic measurements of the 5-nitrofurfural-hydrazine reaction in various pH ranges of aquous solution were carried out by ultraviolet spectrophotometry at $25^{\circ},\;35^{\circ}\;and\;45^{\circ}C$. The observed rate of the reaction varies with the change in pH, which gives characteristic "bell-type" rate acidity profile. The maximum rate is shown in the vicinity of pH 4. This reaction procceds with rate-determining attack of hydrazine on the 5-nitrofurfural at low pH and undergoes a change in rate-determining step to dehydration of the addition intermediate as pH increases. The reaction has a "reactant-like transition state" which precedes intermediate in low pH and "product-like transition state" which follows it in neutral pH. The geometry of 5-nitrofurfural-hydrazine intermediate was estimated with PCILO method associated with CNDO/2 scheme.

• Proceedings of the Membrane Society of Korea Conference
• /
• 2004.05a
• /
• pp.191-194
• /
• 2004

A novel type of intelligent microcapsule reactor system was prepared. The reactor can recognize pH change in the medea and control reaction rate by itself. For the reactor system, acrylic acid (AA), N-isopropylacrylamide (NIPAM), and glucose oxidase (GOD) were selected as a pH-responsive device, a gating device according and a reaction device, respectively. Poly(NIPAM-co-AA) (P-NIPAM-co-AA) are known to change its hydrophilicity-hydrophobicity due to pH change. They were integrated in a core-shell microcapsule space. GOD was loaded inside the core space and the pores in the outside shell layer were filled with P-NIPAM-co-AA linear grafted chains as pH-responsive gates by plasma graft filling polymerization method. When P-NIPAM-co-AA gates are hydrophilic at high pH value, this microcapsule permits glucose penetration into the core space and GOD reaction proceeds. However, when P-NIPAM-co-AA gates are hydrophobic at low pH value, this microcapsule forbids glucose penetration and GOD reaction will not occur. The accuracy of this concept was examined.