Application of activated barrier hopping theory to viscoplastic modeling of glassy polymers.

An established statistical mechanical theory of amorphous polymer deformation has been incorporated as a plastic mechanism into a constitutive model and applied to a range of polymer mechanical deformations. The temperature and rate dependence of the tensile yield of PVC, as reported in early studies, has been modeled to high levels of accuracy. Tensile experiments on PET reported here are analyzed similarly and good accuracy is also achieved. The frequently observed increase in the gradient of the plot of yield stress against logarithm of strain rate is an inherent feature of the constitutive model. The form of temperature dependence of the yield that is predicted by the model is found to give an accurate representation. The constitutive model is developed in two-dimensional form and implemented as a user-defined subroutine in the finite element package ABAQUS. This analysis is applied to the tensile experiments on PET, in some of which strain is localized in the form of shear bands and necks. These deformations are modeled with partial success, though adiabatic heating of the instability causes inaccuracies for this isothermal implementation of the model. The plastic mechanism has advantages over the Eyring process, is equally tractable, and presents no particular difficulties in implementation with finite elements.

Word-learning skills of deaf preschoolers: the development of novel mapping and rapid word-learning strategies.

Word-learning skills of 19 deaf/hard-of-hearing preschoolers were assessed by observing their ability to learn new words in two contexts. The first context required the use of a novel mapping strategy (i.e., making the inference that a novel word refers to a novel object) to learn the new words. The second context assessed the ability to learn new words after minimal exposure when reference was explicitly established. The children displayed three levels of word-learning skills. Eleven children learned words in both contexts. Five were able to learn new words rapidly only when reference was explicitly established. Two children did not learn new words rapidly in either context. The latter seven children were followed longitudinally. All children eventually acquired the ability to learn new words in both contexts. The deaf children's word-learning abilities were related to the size of their vocabularies. The present study suggests that word-learning strategies are acquired even when children are severely delayed in their language development and they learn language in an atypical environment.

Looking without listening: is audition a prerequisite for normal development of visual attention during infancy?

Potential effects of auditory and other communicative experience on development of visual attention were investigated for four groups of infants at 9, 12, and 18 months of age. Participants included 20 deaf infants with deaf mothers, 19 deaf infants with hearing mothers, 21 hearing infants with hearing mothers, and 20 hearing infants with deaf mothers. Infants' hearing status alone did not associate with patterns of visual attention. Deaf infants with deaf mothers showed significantly longer times in the most advanced attention state (coordinated joint) than did deaf infants with hearing mothers. However, other aspects of experience were associated with group differences. Both deaf and hearing children with deaf mothers who signed spent more time onlooking (or watching) their mothers than did children (deaf or hearing) with hearing mothers. Hearing children with hearing mothers spent more time looking at objects than did children with deaf mothers. Despite these differences in time in various attention states, the general trajectory of development of each of the attention states was similar across groups. Results indicate that early visual attention is associated with and potentially influenced by a complex interaction of maturation, communicative experiences, and other developing skills.

Play, language, and maternal responsiveness: a longitudinal study of deaf and hearing infants.

Language, maternal responsiveness, and developmental play levels were investigated in 43 middle-class dyads at 9, 12, and 18 months: hearing child/hearing mother (hH), deaf child/deaf mother (dD), deaf child/hearing mother (dH). Group dH provides information about play when language is delayed and maternal responsiveness decreased. Group dD provides information on developmental effects of diminished audition. There were no 9-month group play differences. At 12 months, hH infants displayed more representational play than infants in either deaf group (p < .001). At 18 months, hH and dD children displayed more preplanned play than dH children (p = .01). At 12 and 18 months, language was associated only marginally with play levels. Maternal responsiveness was significantly associated with 18-month-olds' preplanned play (p = .01).

The association between language and symbolic play at two years: evidence from deaf toddlers.

The association between expressive language and symbolic play was investigated in 3 groups of 2-year-olds: deaf children with hearing parents (dH), deaf children with deaf parents (dD), and hearing children with hearing parents (hH). (Each group included 6 girls and 4 boys.) 3 language-level groups were defined. The highest group was well into the vocabulary "explosion" and frequently produced multiword/sign utterances; a middle group was beginning the period of vocabulary expansion and occasionally produced utterances of more than 1 word/sign; a third group produced single word/sign utterances only, and had a limited vocabulary. Hearing status was associated with duration of symbolic play (deaf > hearing). Higher language levels were associated with more canonically sequenced and preplanned play, even when language delays were due to exogenous factors.

The expressive communication of hearing mothers and deaf infants.

This paper describes the expressive communication and language of seven hearing mothers and their deaf infants. Severe-profound or profound bilateral sensorineural hearing loss was identified in the infants by 7 months of age; intervention programs emphasizing use of signing systems plus speech were started before 9 months of age. Communication behaviors during free play were observed when the infants were 12 and 18 months old. The frequency of the mothers' signing at 12 and 18 months was significantly correlated: mothers' patterns of frequent or infrequent signing were evident within several months of their infants' entry into programming. Mothers who signed most frequently reported that other adults (father and other relatives, friends) were also learning and using signs. Frequency of sign production by the infants at 18 months correlated significantly with frequency of sign production by the mothers when the infants were 12 and 18 months. The mothers' reports of their typical frequency of signing and of the sign lexicon size of their infants failed to correlate significantly with observed performance.

Communication behaviors of infants with hearing loss and their hearing mothers.

This study documented communication behaviors of hearing mothers and infants with a hearing loss that had been identified before 9 months of age (Group HL). Their behaviors were compared with those of mothers and infants without hearing loss (Group H). Each group was composed of 18 dyads videotaped during mother-infant play with toys at 12- and 18-months. Group HL mothers produced more gestural and tactile communications (but similar numbers of vocal communications) compared to H mothers. In contrast with earlier reports, infants with and without hearing loss were similar in quantity of gestural and vocal expressive prelinguistic communication behaviors. Despite group similarities in quantity of prelinguistic communications, H infants as a group surpassed HL infants in expression of formal language by 18 months. There was considerable variation within each group in formal language expression, however, with performance of some HL infants matching that of H infants.

Social support, motivation, language, and interaction. A longitudinal study of mothers and deaf infants.

This project examined the effect of early cognitive, social, and communicative experiences on later social and language development in deaf infants with hearing mothers. Interactions between mothers and deaf infants were found to be positively influenced by social support provided to mothers in the early months of the infants' lives, mothers' visual and tactile responsiveness when their infants were 9 months of age, infants' ability to cope with interactive stress at 9 months of age, and fewer attempts by infants to engage with the social environment during the mastery motivation assessment at 9 months of age. Neither mother-infant affective matching nor maternal visual-tactile responsiveness correlated with the deaf infants' language level.

Education in pediatric basic and advanced life support.

Curricula in pediatric resuscitation must be based on adult learning principles. The Pediatric Basic and Advanced Life Support Courses (PBLS, PALS) should use educational strategies fostering positive interactions between the instructor and learners and should take into consideration the learner's motivation for taking the course. Materials should be developed for a specific target audience; course design should be flexible to meet individual needs. The PBLS and PALS courses have different audiences. PBLS is targeted toward caretakers of children. This course will continue to emphasize primary injury prevention as the major strategy but also will give learners the knowledge and skills to perform CPR. To optimize retention of knowledge and skills, the course content must be simplified, and the sequencing of steps in basic life support must be modified. Health care providers caring for pediatric patients in acute care settings are the primary audience for the PALS course. This course already incorporates adult learning principles; only minor revisions are anticipated. Discussion of the trauma patient is limited in the PALS course; additional trauma education could be facilitated by the addition of a trauma module or by other educational courses. All aspects of the PBLS and PALS educational programs must be evaluated continually to determine whether learning objectives have been met and whether the teaching format is appropriate. The answers to evaluation questions will help determine the degree to which the American Heart Association is meeting its educational objectives and how to allocate resources for development and training.