Benzil bis(carbohydrazone)(BBC) is prepared and explored as new N N Schiff's base, which plays the role of an excellent ion carrier in the construction of a Cd(II) ion membrane sensor. The tris(2-ethylhexyl) phosp...Benzil bis(carbohydrazone)(BBC) is prepared and explored as new N N Schiff's base, which plays the role of an excellent ion carrier in the construction of a Cd(II) ion membrane sensor. The tris(2-ethylhexyl) phosphate best performance corresponds to a membrane composition of 30% poly(vinyl chloride), 65%(TEHP), 3.5% BBC and 1.5% tetradodecyl-ammoniumtetrakis(4-chlorophenyl) borate(ETH 500). This sensor shows very good selectivity and sensitivity towards cadmium ion over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The effect of membrane composition, selectivity, pH and influence of additive on the response properties of electrode were investigated. The response mechanism was discussed in the view of UV-spectroscopy. The electrode exhibits a Nernstian behavior(with slope of 29.7 mV per decade) over a very wide concentration range from 1.0×10?1 to 1.0×10?8 mol·L?1 with a detection limit of 3.2×10?8 mol·L?1. It shows rela-tively fast response time in whole concentration range(<8 s) and can be used for at least 10 weeks in the pH range of 2.0-9.0. The proposed sensor is successfully used for the determination of cadmium in different chocolate sam-ples and as indicator electrode in titration with ethylene diamine tetraacetate(EDTA).展开更多
This paper presents the results of the research conducted at the English language course of the students of Polytechnic of Medimurje in Cakovec, Croatia. The purpose of the research was to introduce the method of stud...This paper presents the results of the research conducted at the English language course of the students of Polytechnic of Medimurje in Cakovec, Croatia. The purpose of the research was to introduce the method of students＇ presentations in foreign language teaching, as well as the topics related to the culture and civilization of the English-speaking countries. After the introductory lectures on how the presentation on the given topic in the English language should be prepared, and after the presentations were delivered by the students during one semester, the results of the questionnaires which the students had to solve at the beginning and the end of the semester, were compared. The goal of the research was to examine the extent in which the students acquired the contents presented to them in such a way. The obtained results are satisfactory, although they have not fully met the expectations. However, if the problems and flaws are identified and addressed, the method can be further improved and better results achieved, both regarding the foreign language competencies, as well as multicultural awareness of young people.展开更多
文摘Benzil bis(carbohydrazone)(BBC) is prepared and explored as new N N Schiff's base, which plays the role of an excellent ion carrier in the construction of a Cd(II) ion membrane sensor. The tris(2-ethylhexyl) phosphate best performance corresponds to a membrane composition of 30% poly(vinyl chloride), 65%(TEHP), 3.5% BBC and 1.5% tetradodecyl-ammoniumtetrakis(4-chlorophenyl) borate(ETH 500). This sensor shows very good selectivity and sensitivity towards cadmium ion over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The effect of membrane composition, selectivity, pH and influence of additive on the response properties of electrode were investigated. The response mechanism was discussed in the view of UV-spectroscopy. The electrode exhibits a Nernstian behavior(with slope of 29.7 mV per decade) over a very wide concentration range from 1.0×10?1 to 1.0×10?8 mol·L?1 with a detection limit of 3.2×10?8 mol·L?1. It shows rela-tively fast response time in whole concentration range(<8 s) and can be used for at least 10 weeks in the pH range of 2.0-9.0. The proposed sensor is successfully used for the determination of cadmium in different chocolate sam-ples and as indicator electrode in titration with ethylene diamine tetraacetate(EDTA).
文摘This paper presents the results of the research conducted at the English language course of the students of Polytechnic of Medimurje in Cakovec, Croatia. The purpose of the research was to introduce the method of students＇ presentations in foreign language teaching, as well as the topics related to the culture and civilization of the English-speaking countries. After the introductory lectures on how the presentation on the given topic in the English language should be prepared, and after the presentations were delivered by the students during one semester, the results of the questionnaires which the students had to solve at the beginning and the end of the semester, were compared. The goal of the research was to examine the extent in which the students acquired the contents presented to them in such a way. The obtained results are satisfactory, although they have not fully met the expectations. However, if the problems and flaws are identified and addressed, the method can be further improved and better results achieved, both regarding the foreign language competencies, as well as multicultural awareness of young people.
