Sequential Metric Dimension

International audienceSeager introduced the following game in 2013. An invisible and immobile target is hidden at some vertex of a graph $G$. Every step, one vertex $v$ of $G$ can be probed which results in the knowledge of the distance between $v$ and the target. The objective of the game is to minimize the number of steps needed to locate the target, wherever it is. We address the generalization of this game where $k ≥ 1$ vertices can be probed at every step. Our game also generalizes the notion of the metric dimension of a graph. Precisely, given a graph $G$ and two integers $k, ≥ 1$, the Localization Problem asks whether there exists a strategy to locate a target hidden in $G$ in at most steps by probing at most $k$ vertices per step. We show this problem is NP-complete when $k$ (resp.,) is a fixed parameter. Our main results are for the class of trees where we prove this problem is NP-complete when $k$ and are part of the input but, despite this, we design a polynomial-time (+1)-approximation algorithm in trees which gives a solution using at most one more step than the optimal one. It follows that the Localization Problem is polynomial-time solvable in trees if $k$ is fixed

Use of personal digital assistants for data collection in a multi-site AIDS stigma study in rural south Nyanza, Kenya

Objectives: To describe the development, cost effectiveness and implementation of a PDA based electronic system to collect, verify and manage data from a multi-site study on HIV/AIDS stigma and pregnancy in a rural, resource-poor area. Methods: We worked within a large prevention of mother-to-child- transmission (PMTCT) program in nine rural health facilities to implement a PDA-based data collection system and to study the feasibility of its use in a multisite HIV research study in rural Kenya. The PDAs were programmed for collecting screening and eligibility data, and responses to structured interviews on HIV/AIDS stigma and violence in three local languages. Results: Between November 2007 and December 2008, nine PDAs were used by Clinic and Community Health Assistants to enrol 1,270 participants on to the PMTCT program. Successes included: capacity-building of interviewers, low cost of implementation, quick turnaround time of data entry with good data quality, and convenience. Conclusion: Our study demonstrated the feasibility of utilizing PDAs for data collection in a multi-site observational study on HIV/AIDS stigma conducted in remote rural health facilities in Kenya. However, appropriate and frequent data backup protocols need to be established and paper forms are still needed as backup tools in resource-poor settings.Keywords: Personal Digital Assistants, Developing countries, multisite studies, feasibility, cost effectivenessAfrican Health Sciences 2011; 11(3): 464 - 47

Protocolo para Observação do Desenvolvimento Cognitivo e de Linguagem Expressiva (PODCLE) Protocol for Expressive Language and Cognition Development Observation (PELCDO)

OBJETIVO: O objetivo do presente estudo foi a proposição de protocolo para observação do desenvolvimento cognitivo e de linguagem expressiva, referente ao período sensório-motor e início do pré-operatório, que pudesse ser utilizado como instrumento de análise objetiva das realizações observadas em crianças, possibilitando assim, a localização e acompanhamento das mesmas nesse processo de construção. MÉTODOS: O Protocolo para Observação do Desenvolvimento Cognitivo e de Linguagem Expressiva (PODCLE) foi elaborado com base na literatura a respeito dos indicadores que caracterizam os estágios iniciais do desenvolvimento cognitivo e de linguagem expressiva, considerando-se o modelo proposto pela Epistemologia Genética. O Protocolo foi aplicado em crianças com desenvolvimento típico para verificação de sua viabilidade e levantamento de possíveis dúvidas ou dificuldades durante sua aplicação ou análise dos dados. Juízes foram utilizados para a seleção dos componentes deste Protocolo. RESULTADOS: O Protocolo é constituído por quatro quadros contendo os indicadores do desenvolvimento cognitivo e de linguagem expressiva em seus estágios iniciais, bem como a pontuação correspondente às realizações apresentadas pela criança. CONCLUSÃO: O Protocolo para Observação do Desenvolvimento Cognitivo e de Linguagem Expressiva apresentado neste estudo é uma proposta de sistematização da observação de dados longitudinais referentes ao desenvolvimento cognitivo e de linguagem expressiva, durante o período sensório-motor e início do pré-operatório. Tal Protocolo permite, não apenas a localização, como também o acompanhamento da criança em seu processo de construção do conhecimento e da linguagem expressiva nos estágios iniciais do desenvolvimento.<br>PURPOSE: The aim of the present study was to propose a protocol for the observation of expressive language and cognition development during sensorimotor and the beginning of pre-operatory periods that could be used as a tool for the objective analysis of children's productions, allowing the localization and follow-up of these children during this construction process. METHODS: The Protocol for Expressive Language and Cognition Development Observation (PELCDO) was based on literature concerning the indicators of early expressive language and cognition development. The PELCDO was applied in typically developing children, with the aim to verify its viability and to identify possible doubts or difficulties during its management or data analysis. Judges were used for the selection of the indicators of cognitive and expressive language development. RESULTS: The Protocol has four tables that comprise the indicators of early expressive language and cognition development, as well as its related score, according to the child's performance. CONCLUSION: The Protocol presented in this study is an attempt to systematize the observation of longitudinal data regarding language and cognition development, during the sensorimotor and beginning of pre-operatory periods. Such Protocol not only allows the child's localization, but also makes possible to follow the individual along the knowledge and language construction process on these early developmental stages