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121.
Particular analytical expressions based on a curve fitting on numerical results for primary dendritic growth have been proposed in the literature to encompass binary alloy systems whose redistribution coefficient (k 0) approaches zero. To date, these expressions have not been checked against experimental results of transient solidification. The present study developed a comparative analysis between the theoretical predictions furnished by such expressions and results from transient solidification experiments with low k 0 aluminum alloys. The analysis has shown that the proposed approach generally describes the primary dendritic spacing during solidification of Al–Sn alloys which are characterized by very low k 0 values as well as by very large solidification ranges. 相似文献
122.
Mariño TC Armiñán RR Cedeño HJ Mesa JM Zaldivar YG Rodríguez RA Santos MV Mederos LE Herrera MP Pérez LV 《Journal of genetic counseling》2011,20(3):241-248
Predictive testing protocols are intended to help patients affected with hereditary conditions understand their condition
and make informed reproductive choices. However, predictive protocols may expose clinicians and patients to ethical dilemmas
that interfere with genetic counseling and the decision making process. This paper describes ethical dilemmas in a series
of five cases involving predictive testing for hereditary ataxias in Cuba. The examples herein present evidence of the deeply
controversial situations faced by both individuals at risk and professionals in charge of these predictive studies, suggesting
a need for expanded guidelines to address such complexities. 相似文献
123.
In historical claims for nativism, mathematics is a paradigmatic example of innate knowledge. Claims by contemporary developmental psychologists of elementary mathematical skills in human infants are a legacy of this. However, the connection between these skills and more formal mathematical concepts and methods remains unclear. This paper assesses the current debates surrounding nativism and mathematical knowledge by teasing them apart into two distinct claims. First, in what way does the experimental evidence from infants, nonhuman animals and neuropsychology support the nativist hypothesis? Second, granting that infants have some elementary mathematical skills, does this mean that such skills play an important role in the development of mathematical knowledge? 相似文献
124.
Teachers regularly make judgements about their pupils’ intelligence while interacting with them in the classroom. The main aims of this paper are to analyse the structure of teachers’ judgements of their pupils’ intelligence, and to evaluate the influence that teachers have on pupils’ judgements of their own and their peers’ intelligence. Cross-cultural comparisons between English and Portuguese pupils are considered. In total 58 children 10- to 11-year-old and two teachers from London, UK and 47 children 5- to 6-year-old and two teachers from Lisbon, Portugal participated. The children completed aptitude tests and self-perception measures for general ability, reading and mathematical ability. The teachers ranked their pupils’ academic abilities from ‘best in the class’ to ‘weakest in the class’. Results show that teachers’ implicit conceptions of intelligence reflect a view of intelligence that is similar to what IQ tests measure. In addition the results support the notion that children’s verbal ability is more highly valued than mathematical ability. Moreover, the results also suggest that teachers have a considerable impact on their pupils’ self-perception as learners. Cultural differences are also discussed. 相似文献
125.
Thirty-eight middle- to lower-income Brazilian fathers in two-parent families provided estimates of different dimensions of their involvement with their school-aged children, assessed children’s social competence, and rated their beliefs on family roles. Analyses showed that fathers and mothers spent similar amounts of time in different activities with children, but did differ in didactic interactions, their responsibility for, and actually disciplining children. There were no significant differences in participation due to gender of child or income. Fathers’ ideological beliefs about gender roles were positively related to involvement in disciplining children and inversely related to engagement in social activities with children. Fathers’ involvement in disciplining children was negatively associated with childhood social competence after controlling for mothers’ contribution. 相似文献
126.
Protein synthesis underlies post-retrieval memory consolidation to a restricted degree only when updated information is obtained
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Rodriguez-Ortiz CJ De la Cruz V Gutiérrez R Bermudez-Rattoni F 《Learning & memory (Cold Spring Harbor, N.Y.)》2005,12(5):533-537
Consolidation theory proposes that through the synthesis of new proteins recently acquired memories are strengthened over time into a stable long-term memory trace. However, evidence has accumulated suggesting that retrieved memory is susceptible to disruption, seeming to consolidate again (reconsolidate) to be retained in long-term storage. Here we show that intracortical blockade of protein synthesis in the gustatory cortex after retrieval of taste-recognition memory disrupts previously consolidated memory to a restricted degree only if the experience is updated. Our results suggest that retrieved memory can be modified as part of a mechanism for incorporating updated information into previously consolidated memory. 相似文献
127.
Perirhinal cortex muscarinic receptor blockade impairs taste recognition memory formation 总被引:1,自引:0,他引:1
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Gutiérrez R De la Cruz V Rodriguez-Ortiz CJ Bermudez-Rattoni F 《Learning & memory (Cold Spring Harbor, N.Y.)》2004,11(1):95-101
The relevance of perirhinal cortical cholinergic and glutamatergic neurotransmission for taste recognition memory and learned taste aversion was assessed by microinfusions of muscarinic (scopolamine), NMDA (AP-5), and AMPA (NBQX) receptor antagonists. Infusions of scopolamine, but not AP5 or NBQX, prevented the consolidation of taste recognition memory using attenuation of neophobia as an index. In addition, learned taste aversion in both short- and long-term memory tests was exclusively impaired by scopolamine. These data provide neurochemical support for the theory that cholinergic activity of the perirhinal cortex participates in the formation of the taste memory trace and that it is independent of the NMDA and AMPA receptor activity. These results support the idea that cholinergic neurotransmission in the perirhinal cortex is also essential for acquisition and consolidation of taste recognition memory. 相似文献
128.
Colón-Cesario WI Martínez-Montemayor MM Morales S Félix J Cruz J Adorno M Pereira L Colón N Maldonado-Vlaar CS Peña de Ortiz S 《Learning & memory (Cold Spring Harbor, N.Y.)》2006,13(6):734-744
Nurr1 expression is up-regulated in the brain following associative learning experiences, but its relevance to cognitive processes remains unclear. In these studies, rats initially received bilateral hippocampal infusions of control or antisense oligodeoxynucleotides (ODNs) 1 h prior to training in a holeboard spatial discrimination task. Such pre-training infusions of nurr1 antisense ODNs caused a moderate effect in learning the task and also impaired LTM tested 7 d later. In a second experiment, ODN infusions were given immediately after the animals had received two sessions of training, during which all animals showed normal learning. Although antisense treated rats were significantly impaired during the post-infusion stages of acquisition of the task, no group differences were observed during the LTM test given 7 d later. These animals were subjected 3 d later to reversal training in the same maze in the absence of any additional treatments. Remarkably, rats previously treated with antisense ODNs displayed perseveration: The animals were fixated with the previously learned pattern of baited holes, causing them to be significantly impaired in the extinction of acquired spatial preferences and future learning. We postulate that Nurr1 function in the hippocampus is important for normal cognitive processes. 相似文献
129.
130.
Jeannette Cruz John M. Littrell 《Journal of multicultural counseling and development》1998,26(4):227-239
Sixteen Hispanic American college students met with a Puerto Rican counselor for 2 brief counseling sessions. Brief counseling was a viable and effective approach in helping the students reach their goals. Types of student concerns about and student perceptions of brief counseling were also examined. 相似文献