Molecular Dynamics Study on Configuration Energy and Radial Distribution Functions of Ammonium Dihydrogen Phosphates Solution

Molecular dynamics simulations were carried out to study the configuration energy and radial distribution functions of mmonium dihydrogen phosphate solution at different temperatures. The dihydrogen phosphate ion was treated as a seven-site model and the ammonium ion was regarded as a five-site model, while a simple-point-charge model for water molecule. An unusually local particle number density fluctuation was observed in the system at saturation temperature. It can be found that the potential energy increases slowly with the temperature from 373 K to 404 K, which indicates that the ammonium dihydrogen phosphate has partly decomposed. The radial distribution function between the hydrogen atom of ammonium cation and the oxygen atom of dihydrogen phosphate ion at three different temperatures shows obvious difference, which indicates that the average H-bond number changes obviously with the temperature. The temperature has an influence on the combination between hydrogen atoms and phosphorus atoms of dihydrogen phosphate ion and there are much more growth units at saturated solutions.

Molecular Dynamics Study on Microstructure of Potassium Dihydrogen Phosphates Solution

Molecular dynamics simulations were carried out to study the internal energy and microstructure of potassium dihydrogen phosphates （KDP） solution at different temperatures. The water molecule was treated as a simple-point-charge model, while a seven-site model for the dihydrogen phosphate ion was adopted. The internal energy functions and the radial distribution functions of the solution were studied in detail. An unusually large local particle number density fluctuation was observed in the system at saturation temperature. It has been found that the specific heat of oversaturated solution is higher than that of unsaturated solution, which indicates the solution experiences a crystallization process below saturation temperature. The radial distribution function between the oxygen atom of water and the hydrogen atom of the dihydrogen phosphate ion shows a very strong hydrogen bond structure. There are strong interactions between potassium cation and oxygen atom of dihydrogen phosphate ion in KDP solution, and much more ion pairs were formed in saturated solution.

Comparative study of two bowel preparaton regimens for colonoscopy: Senna tablets vs sodium phosphate solution

AIM: To compare the efficacy and acceptance of senna tablet and sodium phosphate solution for bowel preparation before colonoscopy.METHODS: One hundred and thirty four patients, who needed elective colonoscopy, were randomly allocated to take 180 mg senna tablet or 95 mL sodium phosphate solution on the day before colonoscopy. The effi cacies of both laxatives were compared using the mean difference of colon-cleanliness score of the rectum, sigmoid segments, descending colon, transverse colon and cecum. The scores were rated by two observers who were blinded to the laxatives administered. The higher score means that the colon is cleaner. The efficacy of both laxatives were equivalent if the 95% confidence interval of the mean difference of the score of colon lie within -1 to +1. RESULTS: On intention-to-treat analysis, the mean cleanliness scores in the four segments of colon except the cecum were higher in the sodium phosphate group than those in senna group (7.9 ± 1.7 vs 8.3 ± 1.5, 8.0 ± 1.8 vs 8.5 ± 1.4, 7.9 ± 2.0 vs 8.5 ± 1.3, 7.9 ± 2.0 vs 8.2 ± 1.4 and 7.2 ± 1.7 vs 6.9 ± 1.4, respectively). The 95% conf idence intervals (95% CI) of mean difference in each segment of colon were not found to lie within 1 point which indicated that their effi cacies were not equivalent. The taste of senna was better than sodium phosphate solution. Also, senna had fewer side effects. CONCLUSION: The effi cacy of senna is not equivalentto sodium phosphate solution in bowel preparation for colonoscopy, but senna may be considered an alternative laxative.

Removal of Chromium(Ⅲ) from Monoammonium Phosphate Solutions by a Porous Adsorbent of Fluor(calcium silicate) Composites

The products of monoammonium phosphate containing Cr^3+resulted in disqualification,and further posed a serious threat to ecological environment and human beings.Herein,the porous adsorbent of fluor(calcium silicate)composites(FCSc)was prepared by hydrothermal method using diatomaceous earth,hydrated lime and additive(NaF)as raw materials,which was characterized and used for the removal of Cr^3+from monoammonium phosphate solutions.The effects of different parameters,such as solution pH,initial Cr^3+concentration,temperature and contact time on the adsorption of Cr^3+onto FCSc were investigated in details.The results indicated that the adsorption process was in agreement with the pseudo-second-order kinetic model and Freundlich isotherm.The spontaneous and endothermic nature of the adsorption process was obtained by analyzing various thermodynamic parameters(△G0,△H0,and△S0).In addition,computational monte carlo simulations between Cr3+ions and FCSc were conducted to elucidate the adsorption mechanism.Such kind of porous adsorbent provided a potential application in the removal of impurities from monoammonium phosphate industry.

Leaching Phenomena of Antifouling Agents from Ships＇ Hull Paints

The effects ofpH, dissolved ion content and relative water velocity on the release rate of an antifouling agent, cuprous oxide, from ships＇ hull paint have been investigated by rotating cylinder tests. Additionally, test paint panels were attached to a vessel and recovered after a certain period of voyage for the validation of the laboratory tests. In the initial period, the release rates are influenced by pH, dissolved ion content and water velocity, but once after a certain period of test, those effects become less significant. These phenomena can be explained when the paint film is fresh, the rate is controlled by chemical reaction, the surface and/or diffusion layer in the water phase governs the rate. After the antifouling substance in the paint film leached out from the near-surface region, a diffused layer （leached layer）, that has little antifouling agent remained, is formed at the surface of the coating, and the diffusion in that layer can be a rate-determining process. The development of the leached layer is affected by a balance between the leaching rate of the antifouling ingredient and paint resin determined by the chemical properties and speed of the water. Thus, the leaching rates of antifouling agents are affected by the history of the paint in the water.

An Uncommon Potentially Fatal Complication in a Patient without Predisposing Factor Following Oral Bowel Preparation Commonly Used for Colonoscopy

We described the case report of a patient presented with no known predisposing factor, generalized malaise with vomiting, locked jaw, perioral paraesthesia, carpopedal spasm and a positive Chvostek’s sign which resulted from severe electrolyte disturbance at 5 hours after use of oral sodium phosphate solution (NaPO4) as bowel preparation for colonoscopy. On presentation, she developed hyperphosphatemia and symptomatic hypocalcaemia with serum phosphate of 1.84 mmol/L and adjusted calcium level 1.67 mmol/L respectively. Her symptoms subsided after immediate intravenous calcium gluconate followed by oral calcium supplement. The electrolyte disturbances were normalized with an uneventful clinical course. The potentially fatal complications of sodium phosphate solution which commonly prescribed as bowel preparation for conventional colonoscopy could develop though previously reported as uncommon in patients without predisposing factors, and should not be overlooked. Urgent assessment and immediate correction of electrolyte disturbances are needed. Recommendations on patient selection of use of sodium phosphate to minimize risk of developing adverse events are needed to incorporate in clinical protocols.

Integration of Chemical Methods and Biomarkers for Assessment of Chlorimuron-Ethyl Bioavailability in Soil

Bioavailability is a critical factor for assessing the environmental risk of organic pollutants in soil. In this study, extractions with 3 different solvents, including 2 aqueous solutions, calcium chloride(CaCl_2) and a phosphate buffer solution(PBS), and a mixture of aqueous solution and organic solvent, a PBS-methanol(8:2,volume/volume) mixture(PBS-M), were performed to assess the bioavailability of chlorimuron-ethyl in soil in comparison to a battery of toxicity tests in wheat seedlings. The results indicated that the peroxidase(POD) activity in wheat leaves after 7 d of exposure was one of the sensitive biomarkers of chlorimuron-ethyl in soil.The extractability of chlorimuron-ethyl by all the 3 solvents decreased with exposure time, and the rate of decrease of the PBS-M extraction between 1 and 7 d of exposure was substantially higher than those of the aqueous solution extractions. Chlorimuron-ethyl gradually changed from a water-soluble form into a soil organic matter(SOM)-bound form in the soil. The PBS extraction correlated best with the POD activity in the leaves after 7 d of exposure.