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Responder por exclusão em treinos de discriminação condicional com estímulos temporais por universitários
(Universidade Federal de São Carlos, 2012-03-27) Cippola, Nathália Sabaine; Domeniconi, Camila; https://lattes.cnpq.br/9684535663947328; https://lattes.cnpq.br/1911605025436199
Choose by exclusion has been extensively investigated and documented in different human populations. The pattern of conditional discrimination of an undefined stimulus obtained for an undefined model when possible experimentally defined choices exist has attracted the attention of researchers interested in symbolic processes such as vocabulary acquisition. Studies employing concrete stimuli have generated compelling data at the same time that they have also highlighted the need for refining knowledge about the properties of the stimuli controlling the response. The utilization of a onedimensional stimulus, like time, could add empirical data about the exact moment when the participant starts to see the undefined stimulus as being different from those used during training. Temporal stimuli have been applied in many investigations of temporal perception. In this context, this work aims to verify how university students respond to exclusion tasks and generalization tests using temporal stimuli as the stimulus mode,on the basis of double temporal bisection trainings. Forty-four university students aged between 18 and 26 years participated in this study, conducted under four different experimental conditions. For the first condition, training consisted in the formation of two conditionals between stimuli lasting 0.5 and 2 seconds for the colors red and green (first bisection), and the relation between stimuli lasting 2 and 8 seconds for the colors blue and yellow (second bisection).For the second condition, the model stimuli lasted 0.3 and 1.2 seconds for red and green, and 1.2 and 4.8for blue and yellow. Models with even shorter duration were utilized for the third and fourth conditions, 0.2 and 0.6,and 0.6 and 1.8 seconds for red and green, and blue and yellow, respectively. The other difference between the conditions lay on the stimulus mode; i.e., visual (time during which a black square remained on the screen) for the first three conditions, and auditory (time during which a beep could be heard) for the last condition. Once the baseline was established, we conducted five blocks of generalization tests with attempts consisting in the presentation of model stimuli lasting for a time period different from the trained periods and undefined and defined comparison stimuli (colors). The generalization test results revealed that the preference for red diminished with longer stimuli, and that the preference for yellow followed an inverse trend. Compared with blue, the choice of green was more frequent during shorter time intervals. As for the Exclusion Test, there was preference for defined stimuli compared with stimuli closer to the trained ones and for undefined stimuli compared with periods less close to the trained ones. These findings contribute to the investigation of responding by exclusion, since there is preference for the undefined stimulus compared with models never seen previously, especially if the models are distant from the trained ones. The generalization data differed from those achieved for non-humans, which opens a discussion about temporal discrimination learning and the role of verbalization and counting.
Efeitos de spin em diodos de tunelamento ressonante tipo-p
(Universidade Federal de São Carlos, 2012-03-27) Galeti, Helder Vinicius Avanço; Gobato, Yara Galvão; https://lattes.cnpq.br/7558531056409406; https://lattes.cnpq.br/3876752605313288
In this work, we have investigated the spin effects in p-i-p GaAs/AlAs resonant tunneling diodes under magnetic field parallel to the tunnel current. The spin-dependent tunneling of carriers was studied by analyzing the current-voltage characteristics (I(V)) and the right (+) and left (-) circular polarized PL from the contact layers and the QW as a function of the applied bias. We have observed that the polarization degree from QW and contact emission is highly bias voltage sensitive. For low voltages the QW polarization exhibits strong oscillations with values up to 50% at 15 T and sign inversions for the voltages corresponding to the resonant tunneling of carriers into the well. The GaAs contact emission shows several bands including the indirect recombination between free electrons and holes localized at the 2DHG formed at the accumulation layer (2DHG-e). We have evidence that the spin polarized hole gas can contribute to the circular polarization degree of carriers in the QW. However, our results show that the circular polarization of the carriers in the QW is a complex issue which depends on various points, including the g-factors of the different layers, the spin-polarization of carriers in the contact layers, the density of carriers along the structure and the Rashba effect. The temporal evolution of the spin-polarization carriers was also investigated. We have measured the time-resolved polarized PL emission from the GaAs quantum well (QW) of a p-i-p GaAs/AlAs Resonant Tunneling Device (RTD). We have used a linearly-polarized Ti:Saphire laser and tuned below the QW absorption edge. Therefore, the electrons are created solely at the top GaAs layer and with no defined spin polarization. Under applied bias, the tunneling holes from the p-doping contact attain a quasi-stationary distribution along the RTD structure, while electrons are only photocreated during the pulse excitation with a ps Ti:Sa laser. These photogenerated electrons are driven by the applied bias and tunnel into the QW, where they might recombine with holes or tunnel out of the well. Under illumination, the current-voltage characteristics of the device present two additional features attributed, respectively, to resonant and -X electron tunneling. Optical measurements for biases where these two alternative transport mechanisms have competitive probabilities revealed an unusual carrier dynamics. The quantum well emission is strongly delayed and we observe a remarkable nonlinear effect where the emission intensity decreases at the arrival of a laser pulse. We propose a simple model that adequately describes our results where we assume that the indirect transition rate depends on the density of electrons accumulated along the structure. Under magnetic field, the PL transients reveal two rather distinct time constants, a short time ( ~ 1 ns) and a long one, which is longer than the laser repetition time (> 12 ns). The bi-exponential behavior indicates additional electron-tunneling processes, which may be associated to indirect tunneling through X-AlAs levels and tunneling of hot vs quasiequilibrium carriers at the accumulation layer. Immediately after the laser pulse, while the faster tunneling process dominates, the QW emission shows a rather small polarization. As the faster tunneling process dies out, the polarization increases to a value that remains approximately constant along the whole transient. This result demonstrates that electrons tunneling through these two distinct processes should present different spin-polarization values. We have also observed that at low biases, around to the expected -X resonance , the QW polarization is very sensitive to the excitation intensity, showing a signal inversion as a function the laser intensity. We attribute this effect to a critical dependence of the electron polarization on the occupation of the various levels involved on the process. Furthermore, at large biases, the long decay component almost disappears for low-excitation conditions and show an unusual time-dependent polarization behavior under high-excitation regime. For the analysis of this complex dynamics, we have also considered the process of tunneling out of the QW, which should become more effective, competing with the radiactive recombination process under high bias voltages. Finally, our results reveal new insights on the mechanisms that determine the spin-polarization of carriers tunneling through a doublebarrier structure and can be explored to develop spin-filter devices based on a RTD structure.
A construção de significados sobre letramento e seus recentes estudos durante a formação inicial e contínua de professores de língua estrangeira
(Universidade Federal de São Carlos, 2012-03-27) Jesus, Deborah Nathalia Silva de; Paula, Sandra Regina Buttros Gattolin de; https://lattes.cnpq.br/9228036521343293; https://lattes.cnpq.br/7388658055234525
The contemporary period is marked by technological development and by economic, political, cultural and social changes influenced by globalization. Such changes had its impact on Brazilian education, encouraging researches and new proposals for education, in order to adapt it to new goals and needs of society. It is intended to leave behind teaching practices based on a banking model of education and to introduce new concepts and technologies, such as literacy and its more recent studies, such as multiliteracies, new literacies and critical literacy. The school has the responsibility of forming critical citizens, prepared for social and political interaction and for new demands of labor market. Meanwhile, teachers must be updated to understand, discuss and work in the classroom with the new guidelines for education, as well as to reflect about their practice. Foreign language teachers, especially of English, the language of globalization, have also the challenge of affirming the social and educational role of their discipline. This research is interested, therefore, in understanding how knowledge about educational theories is constructed by English teachers in initial or continuous formation. The concern with the theoretical knowledge construction by teachers is justified by its importance for the development of an informed and conscious practice, in which the teacher can explain the process of teaching, analyze it and, above all, transform it.
O dialogismo e a construção de sentido nas cartas encíclicas do papa Bento XVI
(Universidade Federal de São Carlos, 2012-03-27) Branco, Nanci Moreira; Miotello, Valdemir; https://lattes.cnpq.br/9131819326282708; https://lattes.cnpq.br/8778865168706085
This study aims to analyze how the dialogical relationships and construction of meaning are built in current Catholic religious discourse, here represented by the encyclical letters of Pope Benedict XVI. I understand that even a discourse as established as the religious it is influenced by several others with which they share and to which they oppose ideas or use them to establish the meaning of the discourse. Thus, the dialogism and construction of meaning will be observed in the clash that occurs between the texts of the pope and the present discourses in society in different contexts, explicity and implicity referred to by the author, or even the discourses that are formed in different contexts in which these themes are inserted. So, the developed analysis will seek to understand, from the observation of dialogism in the documents in question, how to organize such discursive genre, and then establish, from the undeniable formation of extraverbal on the verbal, which is the relationship they have with these texts that circulate in society. I therefore consider that dialogical relations enable convergence or divergence, acceptance or refusal. In that way, one must do the question: what kind of opposing discourses should they keep deleted to preserve the hegemony of the official discourse? Which discourses are confronted with it? A discourse that intends to be dominant it tends to exclude others, not belonging to their universe that are not accepted or are discredited. The fundamental question of this analysis is therefore to understand the discourses of which we must defend and discourses to which we must resort to form the intended meaning in the encyclical letters in Authier Revuz (1990): that another one needs to defend, the other is needed to resort to be formed (p.31). Hence, this analysis seeks to verify how it happens, in the language, the confrontation of ideas which constitutes the discourse of this letter, analyzing how the voice of the Other is part of such discourse. The thought that will guide this research will be based on studies of the Russian philosopher Milkhail Bakhtin on Dialogism and Ideology.