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Spin-polarized transient EPR spectra measured at 9 GHz (X-band) and 24 GHz (K-band) are observed for the metalloporphyrin heterodimers formed by MTTAP (metal/free base meso-tetrakis[4-trimethylanilinium]porphyrin, M = Zn, Mg or H2) and CuTSPP (copper meso-tetrakis[p-sulfonatophenyl]porphyrin). In the temperature range 5−120 K, the EPR transients obtained following pulsed light excitation at 532 nm show a strong temperature dependence. The dimers exhibit two distinct types of EPR signals which may be separated on the basis of their different decay kinetics. The spectrum of one of the signals can be assigned to a triplet state of the dimers, whereas the other spin-polarized spectrum clearly shows involvement of the Cu(II) metal ion. This spectrum is tentatively assigned to the doublet ground state of the CuTSPP moiety in the dimers. It is proposed that the observed spin polarization is generated by a radical triplet pair mechanism (RTPM). In ZnTTAP−CuTSPP and H2TTAP−CuTSPP both spectra are observed, whereas only the latter spectrum is obtained in MgTTAP−CuTSPP. In ZnTTAP−CuTSPP, the triplet-state spectrum shows only small but significant differences from that of the isolated ZnTTAP monomer, indicating that the triplet state is localized on the ZnTTAP component of the dimer. The corresponding spectrum in the free-base dimer is considerably narrower than that of the monomer H2TTAP which suggests that, in this case, the triplet state is partly delocalized over both halves of the dimer.

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This paper presents a study focusing on differences in Israeli Jewish and Arab chemistry teachers' beliefs regarding teaching and learning of chemistry in the upper secondary schools. Israel is a country experiencing the problems of diverse cultural orientation of its inhabitants but applying the same educational system to its diverse cultural sectors. Education includes the same curriculum in chemistry for both the Israeli Jewish and Arab cultural sectors as well as final examinations (matriculation) set centrally by the Ministry of Education. Thus, this study can serve as a striking case for other countries facing similar cultural diversity. The study is based on two different instruments that are both qualitative and quantitative in nature. The qualitative data stem from chemistry teachers' drawings of themselves as teachers in a typical classroom situation accompanied by four open questions. The data analysis follows three qualitative scales: beliefs about classroom organization, beliefs about teaching objectives and epistemological beliefs. A quantitative study gives insights into teachers' beliefs about what characterizes good education. The main goal of the present paper is to determine whether both groups of chemistry teachers with different sociocultural background in Israel hold different views about education in general and chemistry education in particular. The findings provide evidence that in Israeli chemistry classrooms, the beliefs of Arabic teachers differ from those of the Jewish teachers, although both groups live in the same country and operate the same educational system.

In this study we explored whether the use of teachers' demonstrations significantly improves students' understanding of redox reactions compared with control group counterparts who were not exposed to the demonstrations. The sample consisted of 131 Israeli 8th graders in middle schools (junior high school). Students' attitudes and achievements as well as their understanding of redox and electrolysis were assessed by administering a questionnaire that investigated their attitudes (perceptions) towards a demonstration in chemistry. The findings showed that the experimental group's achievements and understanding of the subject were statistically significantly better than those of their control group counterparts.

Students' attitudes and motivations affect their learning process and their academic success. The purpose of the present study is to examine the influence of the use of Project-Based Learning (PBL) on Arab sector middle-school students' attitudes and motivation towards biology. The study was conducted using a mixed design, quantitative as well as qualitative. The quantitative part took the form of questionnaires and the qualitative part consisted of a semi-structured interview with students. In this quasi experimental study, the research population consisted of 178 7th grade students of the Arab sector in northern Israel. The study's findings indicate that an intervention program consisting mainly of combining the teaching of biology with PBL resulted in both increased motivation among students and more positive attitudes towards biology. Students reported greater pleasure, curiosity, interest and cooperation as a result of using PBL in learning about the cell in biology. Introduction of PBL into standard teaching can bring about improvements in both students' motivation and their attitudes. It may be argued that the intervention that was applied in this case contributed to the improvement. The results helps in the formulation of recommendations for applying the PBL in biology and perhaps in other subjects as well.

The photoexcited triplet state of a cofacial heterodimer, [Mg-Hz], comprised of Mg and HZ porphyrins, and photoinduced electron transfer (ET) between the heterodimer and duroquinone in 1 : 1 mixture of CH2Cl2/ ethanol were studied by selective laser excitation combined with time-resolved C W or with pulsed EPR spectroscopies. ET originates from the photoexcited triplet or triplet radical pair states. Upon photoexcitation of the Mgsubunit (580 nm), a noticeable delay time of -20 ns in ET is observed, whereas with photoexcitation of the H2 part (620 nm), no delay time in ET is noticed. The dependence of ET upon excitation wavelength is interpreted in terms of the formation and participation of a charge-transfer state that is operative at 205 K.The delay time is attributed to an intradimer ET that produces the triplet radical pair state 3[Mg+-Hf-].Photoexcitation at 620 nm results in ET via the lower-lying triplet of HZ without involvement of the chargetransfer state.