Sadao Isotani

Influence of ion energy and arrival rate on x-ray crystallographic properties of thin ZrOx films prepared on Si(111) substrate by ion-beam assisted deposition

Thin zirconium oxide films, formed on Si(111) substrate by ion-beam assisted deposition, have been investigated by x-ray diffractometry with respect to the microstructure of the films, such as preferred orientation, interplanar spacing, crystallite size. The results of the interplanar spacing and diffraction intensity analysis could be interpreted in terms of relative amount of Zr4+ ions estimated by analyses of Zr 3d x-ray photoelectron spectroscopy spectra for the films.

Effects of ion energy and arrival rate on the composition of zirconium oxide films prepared by ion‐beam assisted deposition

Thin zirconium oxide films were grown using the ion‐beam assisted deposition method. Zirconium metal was evaporated by an electron beam and condensed on a Si substrate, while oxygen ions were directed simultaneously onto the substrate, allowing the fundamental deposition parameters of ion energy and arrival rate ratio ARR(O/Zr) to be measured and controlled easily. X‐ray photoelectron spectroscopy (XPS) was used to study the oxidation and the composition of the films. XPS analyses indicated the presence of four oxidation states of zirconium (Zr4+−Zr1+) in Zr 3d spectra and two peaks in O 1s spectra; Zr4+ is a predominant ion in all the films and the two peaks in O 1s spectra are related to the oxide and to hydroxyl groups and/or carbonates, respectively. Composition analyses of the films suggested that these oxygen‐associated species may be bound to zirconium. The variation of composition as a function of ion energy (from 2 to 20 keV) and ARR(O/Zr) (at 0.54 and 1.09) could be explained with the preferenti...

A Semantic Web-based authoring tool to facilitate the planning of collaborative learning scenarios compliant with learning theories

When the goal of group activities is to support long-term learning, the task of designing well-thought-out collaborative learning (CL) scenarios is an important key to success. To help students adequately acquire and develop their knowledge and skills, a teacher can plan a scenario that increases the probability for learning to occur. Such a scenario defines pedagogically sound structures that prevent off-task behavior and engage students in more meaningful interactions. The main difficulty in designing effective CL scenarios is transforming the teachers intentions into elements that constitute the learning scenario. This problem is frequently observed when novice teachers attempt to improve the quality of learning and instruction by blending collaborative activities with individual activities without careful planning. With the goal of helping teachers in planning collaborative scenarios, we have developed an intelligent authoring tool referred to as CHOCOLATO using Semantic Web technologies (e.g. ontologies) in order to represent knowledge about different pedagogies and practices related to collaboration. Through the use of this knowledge, CHOCOLATO can provide intelligent guidance that helps teachers to create theory-based CL scenarios which has proven to be effective in a variety of situations. We evaluated it by conducting two experiments. We were interested in verifying whether the recommendations given by CHOCOLATO help novice teachers to design pedagogically sound CL activities, and if these activities help students to learn collaboratively in real classroom settings. The first experiment had the participation of 58 pre-service teachers that created CL scenarios with and without our authoring tool and the second experiment was carried out in a Brazilian public school together with 218 students. The results suggest that the guidance provided by CHOCOLATO do help novice teachers plan, understand and share CL scenarios more easily. They also suggest that the continuous utilization of well-designed theory-based CL activities create favorable conditions for students (particularly less knowledgeable ones) to improve their overall performance throughout the school year.

Optical absorption and electron spin resonance in blue and green natural beryl

A comparative study of blue and green beryl crystals (from the region of Governador Valadares, Minas Gerais, Brazil) using electron paramagnetic resonance (EPR) and optical absorption (OA) spectroscopy is reported. The EPR spectra show that Fe3+ in blue beryl occupies a substitutional Al3+ site and in green beryl is localized in the structural channels between two O6 planes. On the other hand the infrared spectra show that the alkali content in the blue beryl is mostly at substitutional and/or interstitial sites and in green beryl is mostly in the structural channels. The OA spectra show two types of Fe2+. Thermal treatments above 200° C in green beryl cause the reduction of Fe3+ into Fe2+ accompanied by a change of color to blue. The blue beryl color does not change on heating. The kinetics of the thermal conversion of Fe3+ into Fe2+ is composed of two first order processes; the first one has an activation energy ΔE 1=0.30 eV and the second one has an activation energy ΔE 2=0.46 eV.

The EPR Spectra of X-Ray Irradiated Gypsum

EPR spectroscopy in X-Ray irradiated natural crystals of gypsum (CaSO 4 2H 2 O) from Ceara, Brazil, showed the presence of four paramagnetic centers. The spectra of these centers were separated using temperature and power variations techniques. The g and A tensor parameters of two of these centers, identified as OH · and O 2 .H · were calculated.

EPR and IR spectra of Ni(ClO4)2)·6H2O between 98 and 298 K

Abstract EPR measurements between 98 and 298 K on single crystal of Ni(ClO 4 ) 2 ·6H 2 O have indicated the appearance of a rhombic component in the axial crystal field at Ni 2+ sites at T c = 224 K, confirming a phase transition first reported by Chaudhuri from magnetic susceptibility measurements. Temperature variations of g , D and E parameters were determined. IR spectra at room and liquid nitrogen temperatures are consistent with our EPR results.

An authoring tool to support the design and use of theory-based collaborative learning activities

Design of pedagogically sound collaborative learning (CL) activities is a complex task, but necessary if the goal is to support learning Through the design of CL scenarios, a designer can define structures that increase the chance for learning to occur It means that the effectiveness of the collaboration depends on the transformation of the designers intentions into elements that will constitute the learning scenario To support the creation of CL scenarios this paper presents an intelligent authoring tool that is equipped with the knowledge about different pedagogies and practices related to collaboration Through the use of this information, the tool can provide intelligent guidance that support designers to create more effective CL scenarios The results of an experiment suggest that our tool helps teachers to more easily introduce CL activities in classroom and creates favorable conditions for students to perform collaboration improving their overall learning performance throughout the year.

Heating effects on the optical absorption spectra of irradiated, natural spodumene

Abstract We have studied the lilac spodumene through optical absorption and electron paramagnetic resonance measurements. The effects of increasing doses of γ-rays from 60Co on the spectra were determined. The following absorption bands were analysed: 10500, 15600 and 21500cm−1 assigned to d-d transitions of Mn3+ (G); 11000, 12000, 18600 and 22000cm−1 assigned to d-d transitions of Mn3+ (L). The G and L refer to distinct octahedral sites, both tetragonally distorted with the axial Mn–O bonds extended (Jahn-Teller effect).

EPR Spectra of Ni (BF4)26H2O between 100 and 300 K

EPR spectra of Ni(BF 4 ) 2 6H 2 O single crystal were obtained between 100 K and 300 K. An analysis of the spectra indicated a slightly distorted crystal field from the cubic symmetry, with trigonal axis along the c -axis of the crystal. The spin Hamiltonian parameters g // , g ⊥ and D were determined in the above range of temperatures. D varies linearly as D =0.021(1+0.081 T ) cm -1 probably due to the phonon modulation of the octahedron of the 6H 2 O charges. The line-width of the spectra obeys a Δ H m s = a + b T 2 law. The quadratic term comes from the spin-lattice relaxation by a two-phonon Raman process and the constant term represents spin-spin interaction contribution. No phase transition was detected and it is likely that this salt is more stable than some other isomorphous compounds where structure transformation was observed.

A grid procedure applied to the determination of parameters of a kinetic process

Abstract A fitting procedure for one trap and one recombination centre kinetic model is described here. The procedure makes use of a grid in the parameters space obtained by changing each parameter back and forth and calculating robust cost functions on the surfaces of this grid. The lengths of the changes are determined empirically. The best set of parameters is calculated by the projection on the grid surface with smallest cost function. The fitting procedure applied to the fit of one, two and three parameters of the kinetic model is analyzed. In all cases the optimization procedure shows reliable fitting within a feasible interval of processing time.