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661.
Cyclic deformation has been performed at ambient temperature on ultrafine-grained copper processed by equal channel angular pressing. Observations by electron channelling contrast in a scanning electron microscope revealed that pronounced recrystallization occurred and several distinct dislocation configurations such as dislocation walls and labyrinth structures were found within the recrystallized regions. A model is proposed to account for the evolution of recrystallization, emphasizing that its development results from an interaction between the cyclic deformation and the growth of recrystallized regions. The formation of recrystallized regions of different sizes is discussed. 相似文献
662.
The microstructural evolution of epitaxial SrRuO3 thin films from ambient temperature (about 293K) to about 900K has been studied by in-situ transmission electron microscopy. Upon heating from the ambient temperature, the intensities of h, k, 2n+1 and h, -h+2n+1, 0 reflections in selected-area electron diffraction patterns decrease with increasing temperature. Two structural phase transitions were observed at about 673and about 783K, revealed by the vanishing of the h, k, 2n+1 and h,-h+2n+1, 0 reflections respectively. The examination of electron diffraction patterns along several different zone axes, taking into account the possible tilting configurations of RuO6 octahedra, indicates that, upon heating, the orthorhombic structure of SrRuO3 transforms into a tetragonal structure at about 673K, and further transforms into a cubic structure at about 783K. Possible structural models for the high-temperature phases are considered. 相似文献
663.
Virve Vuontela Ping Jiang Maksym Tokariev Petri Savolainen YuanYe Ma Eeva T. Aronen Tuija Fontell Tiina Liiri Matti Ahlström Oili Salonen Synnöve Carlson 《Brain and cognition》2013
Developmental studies have demonstrated that cognitive processes such as attention, suppression of interference and memory develop throughout childhood and adolescence. However, little is currently known about the development of top-down control mechanisms and their influence on cognitive performance. In the present study, we used functional magnetic resonance imaging to investigate modulation of activity in the ventral visual cortex in healthy 7–11-year-old children and young adults. The participants performed tasks that required attention to either face (Fs task) or scene (Sf task) images while trying to ignore distracting scene or face images, respectively. A face-selective area in the fusiform gyrus (fusiform face area, FFA) and an area responding preferentially to scene images in the parahippocampal gyrus (parahippocampal place area, PPA) were defined using functional localizers. Children responded slower and less accurately in the tasks than adults. In children, the right FFA was less selective to face images and regulation of activity between the Fs and Sf tasks was weaker compared to adults. In the PPA, selectivity to scenes and regulation of activity, there according to the task demands were comparable between children and adults. During the tasks, children activated prefrontal cortical areas including the middle (MFG) and superior (SFG) frontal gyrus more than adults. Functional connectivity between the right FFA and left MFG was stronger in adults than children in the Fs task. Children, on the other hand, had stronger functional connectivity than adults in the Sf task between the right FFA and right PPA and between right MFG and medial SFG. There were no group differences in the functional connectivity between the PPA and the prefrontal cortex (PFC). Together the results suggest that, in 7–11-year-old children, the FFA is still immature, whereas the selectivity to scenes and regulation of activity in the PPA is comparable to adults. The results also indicated functional immaturity of the PFC in children compared to adults and weaker connectivity between the PFC and the rFFA, explaining the weaker regulation of activity in the rFFA between the Fs and Sf tasks. 相似文献
664.
Xiuyan Guo Shan Jiang Hongyi Wang Lei Zhu Jinghua Tang Zoltan Dienes Zhiliang Yang 《Consciousness and cognition》2013,22(1):203-211
We demonstrated unconscious learning of task-irrelevant perceptual regularities in a Serial Reaction Time (SRT) task in both visual and auditory domains. Participants were required to respond to different letters (‘F’ or ‘J’, experiment 1) or syllables (‘can’ or ‘you’, experiment 2) which occurred in random order. Unbeknownst to participants, the color (red, green, blue or yellow) of the two letters or the tone (1–4) of the syllables varied according to certain rules. Reaction times indicated that people indeed learnt both the color and tonal regularities indicating that task-irrelevant sequence structure can be learned perceptually. In a subsequent prediction test of knowledge of the color or tonal cues using subjective measures, we showed that people could acquire task irrelevant knowledge unconsciously. 相似文献
665.
Feifei Li Shan Jiang Xiuyan Guo Zhiliang Yang Zoltan Dienes 《Consciousness and cognition》2013,22(3):920-930
Previous research has established that people can implicitly learn chunks, which (in terms of formal language theory) do not require a memory buffer to process. The present study explores the implicit learning of nonlocal dependencies generated by higher than finite-state grammars, specifically, Chinese tonal retrogrades (i.e. centre embeddings generated from a context-free grammar) and inversions (i.e. cross-serial dependencies generated from a mildly context-sensitive grammar), which do require buffers (for example, last in-first out and first in-first out, respectively). People were asked to listen to and memorize artificial poetry instantiating one of the two grammars; after this training phase, people were informed of the existence of rules and asked to classify new poems, while providing attributions of the basis of their judgments. People acquired unconscious structural knowledge of both tonal retrogrades and inversions. Moreover, inversions were implicitly learnt more easily than retrogrades constraining the nature of the memory buffer in computational models of implicit learning. 相似文献
666.
How does visual long-term memory store representations of different entities (e.g., objects, actions, and scenes) that are present in the same visual event? Are the different entities stored as an integrated representation in memory, or are they stored separately? To address this question, we asked observers to view a large number of events; in each event, an action was performed within a scene. Afterward, the participants were shown pairs of action–scene sets and indicated which of the two they had seen. When the task required recognizing the individual actions and scenes, performance was high (80 %). Conversely, when the task required remembering which actions had occurred within which scenes, performance was significantly lower (59 %). We observed this dissociation between memory for individual entities and memory for entity bindings across multiple testing conditions and presentation durations. These experiments indicate that visual long-term memory stores information about actions and information about scenes separately from one another, even when an action and scene were observed together in the same visual event. These findings also highlight an important limitation of human memory: Situations that require remembering actions and scenes as integrated events (e.g., eyewitness testimony) may be particularly vulnerable to memory errors. 相似文献
667.
Song Xue Jingjing Cui Kangcheng Wang Songyan Zhang Jiang Qiu Yuejia Luo 《Scandinavian journal of psychology》2013,54(2):82-88
There is substantial evidence to indicate that negative emotion can modulate cognitive control processing. However, only a few studies have investigated this effect with positive emotion. Therefore, the present study explored the electrophysiological correlates of the impact of positive emotional stimuli on cognitive control, using event‐related potentials (ERPs). Sixteen healthy young adults completed a modified Simon task (Simon, 1969). Behavioral data indicated that reaction times were faster for positive emotional stimuli than for neutral emotional stimuli in the incongruent condition, but not in the congruent condition, which suggested that positive emotion expedited conflict resolution. The ERP data showed that two negative ERP components (N300–400 and N450–550) were associated with the positive emotional stimuli in the incongruent minus congruent condition. It is suggested that these components may respectively be related to the conflict monitoring (N300–400) and response selection (N450–550) stages of cognitive control processing. Overall, our results indicated that positive emotion could facilitate cognitive control processing. These results are in line with the neuropsychological theory, according to which, positive emotion could modulate cognitive control mediated by increased dopamine levels in frontal brain areas. 相似文献
668.
669.
该研究运用事件相关电位技术,采用肯定和否定的表达方式呈现自我参照任务,探讨不同表达方式对自我积极偏向效应的影响。实验一中,行为数据显示,自我积极偏向效应表现的并不完整;ERP数据显示,P200波幅的结果与行为数据结果相一致。实验二中,行为数据显示,自我积极偏向效应表现得完整;ERP数据显示,P200成分上并未产生任何实验效应。综合两个实验结果,证明了不同表达方式对自我积极偏向效应的表现存在影响。导致这种差异的根本原因可能在于两种表达方式造成的注意资源不同。 相似文献
670.
This study investigated gender differences in anxiety and coping styles under the stress of intense military training. We surveyed Chinese female (n = 470) and male (n = 379) military officers who were surveyed during the third month of a 10-month intensive training program. Results indicated that state and trait anxiety were highly correlated in both women and men. In general, female officers had higher levels of anxiety, greater negative coping tendencies, and less perceived self-efficacy than their male counterparts. When compared with the norm, both women and men had significantly more positive coping strategies. A hierarchical multiple regression analysis showed factors that influenced male and female state anxiety. Avoidance, which was chosen by women more often than men, in general was less useful for female officers. The most common positive coping style for female officers was problem solving, whereas for men it was help seeking. We suggested that even female officers with lower mental health levels than their male counterparts made active cognitive changes to their coping styles when undergoing intense military training. 相似文献