Schottky barrier heights at polar metal/semiconductor interfaces

Using a first-principle pseudopotential approach, we have investigated the Schottky barrier heights of abrupt Al/Ge, Al/GaAs, Al/AlAs, and Al/ZnSe (100) junctions, and their dependence on the semiconductor chemical composition and surface termination. A model based on linear-response theory is developed, which provides a simple, yet accurate description of the barrier-height variations with the chemical composition of the semiconductor. The larger barrier values found for the anion- than for the cation-terminated surfaces are explained in terms of the screened charge of the polar semiconductor surface and its image charge at the metal surface. Atomic scale computations show how the classical image charge concept, valid for charges placed at large distances from the metal, extends to distances shorter than the decay length of the metal-induced-gap states.Comment: REVTeX 4, 11 pages, 6 EPS figure

Perceptions and experiences of using a nipple shield among parents and staff - an ethnographic study in neonatal units

Background: Preterm infants have an immature sucking behavior and the capacity to be exclusively breastfed may be reduced for a period of weeks or months, depending on gestational age. Nipple shields have been used, not only as a device to help mothers with sore nipples, but also to facilitate the infant’s latch on to the breast. However, the benefits of using nipple shields have been debated. The aim of this study was to explore perceptions and experiences of using a nipple shield among parents and staff in neonatal units in Sweden and England. Methods: An ethnographic study was undertaken where observations and interviews were conducted in four neonatal units in Sweden and England. The data were analyzed using a thematic networks analysis. Result: The global theme was developed and named, ‘Nipple shield in a liminal time’. This comprised of two organizing themes: ‘Relational breastfeeding’ and ‘Progression’. ‘Relational breastfeeding’ was underpinned by the basic themes, ‘good enough breast’, ‘something in between’ and ‘tranquil moment’. ‘Progression’ was underpinned by the basic themes, ‘learning quicker’, ‘short-term solution’ and ‘rescue remedy’. Although breastfeeding was seen primarily as a nutritive transaction, the relational aspects of breastfeeding were of crucial importance. These two organizing themes show the tension between acknowledging the relational aspects of breastfeeding and yet facilitating or supporting the progression of breastfeeding in the period from tube feeding or cup feeding to breastfeeding. It is a liminal time as mothers and their infants are “in between” phases and the outcome, in terms of breastfeeding, is yet to be realized. Conclusion: This study demonstrates parents’ and staffs’ perceptions of the nipple shield as a short term solution to help initiation of breastfeeding but also as a barrier between the mother and infant. It is important that the mother and baby’s own particular needs are taken into account, in a person-centred way and on an ongoing basis. Furthermore, we need to emphasise the importance of the ‘relational’ whilst understanding the need for ‘progression’. Holding these in balance may be the key to appropriate use of the nipple shield

The role of micro-organisms (Staphylococcus aureus and Candida albicans) in the pathogenesis of breast pain and infection in lactating women: study protocol

Background: The CASTLE (Candida and Staphylococcus Transmission: Longitudinal Evaluation) study will investigate the micro-organisms involved in the development of mastitis and &ldquo;breast thrush&rdquo; among breastfeeding women. To date, the organism(s) associated with the development of breast thrush have not been identified. The CASTLE study will also investigate the impact of physical health problems and breastfeeding problems on maternal psychological health in the early postpartum period.Methods/Design: The CASTLE study is a longitudinal descriptive study designed to investigate the role of Staphylococcus spp (species) and Candida spp in breast pain and infection among lactating women, and to describe the transmission dynamics of S. aureus and Candida spp between mother and infant. The relationship between breastfeeding and postpartum health problems as well as maternal psychological well-being is also being investigated. A prospective cohort of four hundred nulliparous women who are at least thirty six weeks gestation pregnant are being recruited from two hospitals in Melbourne, Australia (November 2009 to June 2011). At recruitment, nasal, nipple (both breasts) and vaginal swabs are taken and participants complete a questionnaire asking about previous known staphylococcal and candidal infections. Following the birth, participants are followed-up six times: in hospital and then at home weekly until four weeks postpartum. Participants complete a questionnaire at each time points to collect information about breastfeeding problems and postpartum health problems. Nasal and nipple swabs and breast milk samples are collected from the mother. Oral and nasal swabs are collected from the baby. A telephone interview is conducted at eight weeks postpartum to collect information about postpartum health problems and breastfeeding problems, such as mastitis and nipple and breast pain.Discussion: This study is the first longitudinal study of the role of both staphylococcal and candidal colonisation in breast infections and will help to resolve the current controversy about which is the primary organism in the condition known as breast thrush. This study will also document transmission dynamics of S. aureus and Candida spp between mother and infant. In addition, CASTLE will investigate the impact of common maternal physical health symptoms and the effect of breastfeeding problems on maternal psychological well-being.<br /

Etnomatemáticas en artesanías de trenzado: un modelo metodológico para investigación

El área temática del Proyecto de Investigación, parte del cual exponemos en este artículo, es Etnomatemáticas. El propósito de investigación es la caracterización y valoración del conocimiento socio-cultural, implícito en la práctica diaria. En el contexto geográfico de Argentina, investigamos la matemática implícita en artesanías de trenzados, elaborando para esto un método propio de análisis etnomatemático. El instrumento metodológico MOMET que se crea para este estudio interpretativo formal de artesanías de trenzado tiene en cuenta dos aspectos: el producto final de la labor artesanal analizado en su complejidad global y el proceso que se lleva a cabo para realizarlo. La herramienta metodológica elaborada está constituida por dos componentes: un Método de análisis etnográfico (MET) y un Modelo de análisis matemático (MOM). El conjunto de los dos nos proporciona el instrumento metodológico MOMET, que permite la Modelización Etnomatemática de las artesanías de trenzado

Designed to 'Effectively Frustrate': Copyright, Technology, and the Agency of Users

Recently, the major U.S. music and movie companies have pursued a dramatic renovation in their approach to copyright enforcement. This shift, from the ?code? of law to the ?code? of software, looks to technologies themselves to regulate or make unavailable those uses of content traditionally handled through law. Critics worry about the ?compliance? rules built into such systems: design mandates for manufacturers indicating what users can and cannot do under particular conditions. But these are accompanied by a second set of limitations: ?robustness? rules. Robustness rules obligate manufacturers to build devices such that they prevent tinkering -- not only must the technology regulate its users, it must be inscrutable to them. I examine this aspect of technical copyright regulation, looking particularly at the CSS encryption system for DVDs and the recent ?broadcast flag? proposed for digital television. In the name of preventing piracy, these arrangements threaten to undermine users? sense of agency with their own technologies.This research was assisted by a grant from the Digital Cultural Institutions Project of the Social Science Research Council, with funds provided by the Rockefeller Foundation