Dislocation core structures in GaN grown on Si(111) substrate

The Ga-N bond extension and compression at the cores of different types of dislocation in hexagonal GaN films grown on Si(111) substrates have been studied by high-resolution transmission electron microscopy. The relative bond extension and compression are about 6 4 and 7 4% respectively around the cores of mixed dislocations and about 9 6 and 12 7% respectively around the cores of pure edge dislocations. The core structure of a pure edge dislocation is an eightfold atom-column ring.     

Adolescent girls' perceived barriers to participation in physical activity

Research shows a decline in physical activity levels during adolescence, particularly among girls. This study explored perceived barriers to participation in moderate and vigorous physical activity among adolescent girls who live in a large ethnoracially and socioeconomically diverse city. A total of 73 adolescent girls in Toronto participated in 1 of 7 focus group sessions which were audiotaped and transcribed verbatim, and qualitative software was used to facilitate data analysis. A constant comparison approach was used to inductively develop themes. Participants' perceived barriers to participating in physical activity included: lack of time; involvement in technology-related activities; influence peers, parents and teachers; concern about safety; inaccessibility of facilities and cost of using them; competition; and body-centered issues. The results suggest that strategies to address specific intrapersonal, social-environmental, and physical-environmental barriers to physical activity participation should be used in physical activity promotion programs for adolescent girls.     

Male adolescents' reasons for participating in physical activity, barriers to participation, and suggestions for increasing participation

This study explored male adolescents' reasons for participating in moderate and vigorous physical activity, perceived barriers to moderate and vigorous physical activity, and suggestions as to what can be done to increase participation in physical activity. A total of 26 male 15- and 16-year-old adolescents participated in focus group sessions, which were audiotaped and transcribed verbatim; qualitative software facilitated data analysis. A constant comparison approach was used to inductively develop themes. It was found that participants engaged in physical activity for both intrinsic and extrinsic reasons. Their perceived barriers to physical activity included both internal factors (individual characteristics, lower priority for physical activity, and involvement in technology-related activities) and external factors (the influence of peers and family, lack of time, and inaccessibility and cost of facilities). Participants suggested that physical activity be promoted more in the community and that an environment more supportive of physical activity be developed. Results suggest that a variety of strategies should be used to help male adolescents maintain or increase participation in moderate and vigorous physical activity.     

Fourteen‐month‐old infants learn similar‐sounding words

Can infants, in the very first stages of word learning, use their perceptual sensitivity to the phonetics of speech while learning words? Research to date suggests that infants of 14 months cannot learn two similar‐sounding words unless there is substantial contextual support. The current experiment advances our understanding of this failure by testing whether the source of infants’ difficulty lies in the learning or testing phase. Infants were taught to associate two similar‐sounding words with two different objects, and tested using a visual choice method rather than the standard Switch task. The results reveal that 14‐month‐olds are capable of learning and mapping two similar‐sounding labels; they can apply phonetic detail in new words. The findings are discussed in relation to infants’ concurrent failure, and the developmental transition to success, in the Switch task.     

Measuring biting behavior induced by acute stress in the rat

Previous reports have indicated that biting behavior is enhanced in rats that are subject to acute stress. Several methods have been proposed for studying this phenomenon, one of which is the electromyography (EMG) of the jaw muscles. In this study, we compared total EMG activity with the EMG activity related to biting behavior, as determined by video monitoring, before and after restraint stress. Wistar albino rats (150 g) were subject to surgery for electrode placement 48 h before measurements. The EMG activity of the masseter muscle on one side was recorded for 10 min before and immediately after 30 min of restraint stress. Restraint stress increased jaw muscle EMG activity, although some of the activity was related to behaviors other than biting. Recording the EMG activity of jaw muscles is useful for measuring the stress response in rats, but careful video monitoring is needed if biting behavior is to be studied in particular.     

Smiling emphasizes perceived distinctiveness of faces

In this study, 114 Japanese observers (56 men and 58 women) rated the distinctiveness of 48 neutral faces and 48 smiling faces. Analysis showed smiling faces were rated as significantly more distinctive than neutral ones. Greater perceived distinctiveness provides an explanation for previous results that smiling faces are better remembered than faces with neutral expressions.     

Effects of Social Conditions on the Expression of Sex-role Stereotypes

In this study, 129 female and 83 male undergraduates were asked to make judgments about identical male and female law school applicants. Evaluations of the candidate employed two types of measures: (a) direct measures set up to assess judgments based upon objective criteria such as GPA and aptitude test scores, and (b) indirect measures designed to provide more opportunity for subjective factors and subtle ways for stereotyping to operate. It was hypothesized that increased social awareness of sex discrimination would reduce more blatant types of stereotyping expressed in the direct measures and force stereotyping into more subtle forms, measurable through the construction of the indirect indices. The results revealed no differences between male and female candidates on the direct measures. However, stereotyping appeared on indirect measures associated with personality characteristics and employment alternatives. The investigators concluded that prejudicial attitudes toward women continue to exist and are expressed in more subtle or „hidden” forms. Suggestions for developing means for measuring these attitudes as well as practical considerations for reducing discrimination in employment settings were presented.     

Visual Dominance in Amending the Directional Parameter of Feedforward Control

The authors examined visual dominance between trials in which the movement program was amended (i.e., off-line processing). Weighting between visual and proprioceptive feedback was examined in a trial-by-trial analysis of the directional parameter of feedforward control. Eight participants moved a cursor to a target displayed on a computer screen by manipulating a hand-held stylus on a digitizing tablet. In the first 30 trials, the cursor followed the stylus movement (practice condition). In the next 30 trials, the directional error of the stylus movement was presented in the opposite direction (reversal condition). Subjects knew the presence and the nature of the reversal. In the last 10 trials, the reversal was withdrawn (transfer condition). Directional error of feedforward control was relatively small in the practice condition, and it increased gradually in 1 of 2 directions as trials proceeded in the reversal condition. Positive aftereffect was observed in the transfer condition. A constant increment of the directional error indicated that both visual and proprioceptive feedback are registered, with higher weight on vision, and that weighting between those inputs is determined automatically or is fixed without any strategic control.     

Exclusion constraints facilitate statistical word learning

The roles of linguistic, cognitive, and social-pragmatic processes in word learning are well established. If statistical mechanisms also contribute to word learning, they must interact with these processes; however, there exists little evidence for such mechanistic synergy. Adults use co-occurrence statistics to encode speech-object pairings with detailed sensitivity in stochastic learning environments (Vouloumanos, 2008). Here, we replicate this statistical work with nonspeech sounds and compare the results with the previous speech studies to examine whether exclusion constraints contribute equally to the statistical learning of speech-object and nonspeech-object associations. In environments in which performance could benefit from exclusion, we find a learning advantage for speech over nonspeech, revealing an interaction between statistical and exclusion processes in associative word learning.