A theoretical classification of the types of representations possible for variable in connectionist networks has been developed [l]. This paper discusses the properties of some classes of connectionist representations. In particular, the representation of variables in value-unit, variable-unit and intermediate unit representations are analyzed, and a course-fine concept of representation developed.In addition, the relation between the measurement of a feature and it's representation is discussed.

Purpose of review

Hematopoietic cell transplantation (HCT) is a curative therapy for sickle cell disease (SCD) that is utilized very rarely because of limited allogeneic donor availability, limited healthcare resources needed to expand the treatment to regions in the world where most affected individuals reside, and by a view among SCD experts that HCT lacks the evidential rigor with short and long-term toxicity profiles that together might support its broader application.

Recent findings

In this update, recent advances focused on donor selection, reduced toxicity preparation for HCT, and treatment of young adults will be presented. The current status of conventional bone marrow transplantation with a human leukocyte antigen-identical sibling donor is summarized.

Summary

HCT for SCD is curative in almost all children who have a human leukocyte antigen-matched sibling donor. The future of this therapy will hinge on expanding the number of individuals who might be treated.

This paper empirically evaluates the cost-effectiveness of Head Start, the largest early- childhood education program in the United States. Using data from the randomized Head Start Impact Study (HSIS), we show that Head Start draws a substantial share of its participants from competing preschool programs that receive public funds. This both attenuates measured experimental impacts on test scores and reduces the program's net social costs. A cost-benefit analysis demonstrates that accounting for the public savings associated with reduced enrollment in other subsidized preschools can reverse negative assessments of the program's social rate of return. Estimates from a semi-parametric selection model indicate that Head Start is about as effective at raising test scores as competing preschools and that its impacts are greater on children from families unlikely to participate in the program. Efforts to expand Head Start to new populations are therefore likely to boost the program's social rate of return, provided that the proposed technology for increasing enrollment is not too costly.

Handheld technology devices allow users to be mobile and access the Internet, personal data, and third-party content applications in many different environments at the users' convenience. The explosion of these mobile learning devices around the globe has led adults to value them for communication, productivity, and learning. Outside of the school setting, many adolescents and children have access to, or own mobile devices. The use of these individual devices by children on a daily basis in schools is a relatively new phenomenon, with just four percent of elementary students doing so in classrooms in 2010(Gray, Thomas & Lewis, 2010). This mixed methods study researched a one-to-one implementation of percent devices in fourth- and fifth-grade elementary classrooms. The focus was to explore the mobile learning device's relationship to English language learners' reading achievement, to English language learners' self-efficacy in reading, and to explore the benefits and limitations of the device's daily use, as perceived by the students. The hypothesis was that the practice of reading and related literacy activities with mobile learning devices would augment English learners' vicarious learning experiences, and thereby effect student cognitive engagement, reading self-efficacy, and reading academic achievement. This study used validated surveys and assessments to measure students' beliefs about reading and their knowledge of reading. Additionally, English language learner interview data were also collected and analyzed to uncover perceived benefits and limitations of utilizing 1:1 mobile learning devices daily for literacy activities. Analysis of the data revealed significantly elevated levels of self-efficacy in reading for the experimental group with 1:1 handheld technology, while academic gains in reading for the experimental and control groups were statistically similar. Students in the experimental group described a virtually-enhanced socio-cultural context for communicating and learning with the handheld technology. Implications for practice, policy, and future research are discussed