Moving in temporal graphs with very sparse random availability of edges

In this work we consider temporal graphs, i.e. graphs, each edge of which is assigned a set of discrete time-labels drawn from a set of integers. The labels of an edge indicate the discrete moments in time at which the edge is available. We also consider temporal paths in a temporal graph, i.e. paths whose edges are assigned a strictly increasing sequence of labels. Furthermore, we assume the uniform case (UNI-CASE), in which every edge of a graph is assigned exactly one time label from a set of integers and the time labels assigned to the edges of the graph are chosen randomly and independently, with the selection following the uniform distribution. We call uniform random temporal graphs the graphs that satisfy the UNI-CASE. We begin by deriving the expected number of temporal paths of a given length in the uniform random temporal clique. We define the term temporal distance of two vertices, which is the arrival time, i.e. the time-label of the last edge, of the temporal path that connects those vertices, which has the smallest arrival time amongst all temporal paths that connect those vertices. We then propose and study two statistical properties of temporal graphs. One is the maximum expected temporal distance which is, as the term indicates, the maximum of all expected temporal distances in the graph. The other one is the temporal diameter which, loosely speaking, is the expectation of the maximum temporal distance in the graph. We derive the maximum expected temporal distance of a uniform random temporal star graph as well as an upper bound on both the maximum expected temporal distance and the temporal diameter of the normalized version of the uniform random temporal clique, in which the largest time-label available equals the number of vertices. Finally, we provide an algorithm that solves an optimization problem on a specific type of temporal (multi)graphs of two vertices.Comment: 30 page

The early evolution of land plants, from fossils to genomics: a commentary on Lang (1937) ‘On the plant-remains from the Downtonian of England and Wales'

© 2015 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited. The file attached is the published version of the article

Over-diagnosis of malaria is not a lost cause.

BACKGROUND: Recent studies have highlighted the over-diagnosis of malaria in clinical settings in Africa. This study assessed the impact of a training programme implemented as part of an intervention trial on diagnostic behaviour of clinicians in a rural district hospital in a low-moderate malaria transmission setting. METHODS: From the beginning of 2005, a randomized controlled trial (RCT) of intermittent preventive treatment for malaria in infants (IPTi) has been conducted at the study hospital. As part of the RCT, the study team offered laboratory quality assurance, and supervision and training of paediatric ward staff using information on malaria epidemiology in the community. Data on clinical and blood slide confirmed cases of malaria from 2001 to 2005 were extracted from the hospital records. RESULTS: The proportion of blood slides positive for malaria parasites had decreased from 21% in 2001 to 7% in 2005 (p < .01). The proportion of outpatient and inpatient cases diagnosed as malaria ranged between 34% and 28% from 2001 to 2004 and this decreased substantially to 17% after the introduction of the package of training and support in 2005 (p < .01). There was no clear trend in the ratio of blood slide examined versus total diagnosis of malaria. CONCLUSION: It may be possible to change the diagnostic behaviour of clinicians by rigorous training using local malaria epidemiology data and supportive supervision

Key feature-based approach for efficient exploration of structured environments

© 2015 IEEE. This paper presents an exploration approach for robots to determine sensing actions that facilitate the building of surface maps of structured partially-known environments. This approach uses prior knowledge about key environmental features to rapidly generate an estimate of the rest of the environment. Specifically, in order to quickly detect key features, partial surface patches are used in combination with pose optimisation to select a pose from a set of nearest neighbourhood candidates, from which to make an observation of the surroundings. This paper enables the robot to greedily search through a sequence of nearest neighbour poses in configuration space, then converge upon poses from which key features can best be observed. The approach is experimentally evaluated and found to result in significantly fewer exploration steps compared to alternative approaches

The Forgotten Tribe in ODL Systems: Challenges Faced by Visually Impaired Students in Institutions of Higher Learning

This study sought to evaluate the challenges faced by visually impaired students in Open and Distance Learning (ODL) Institutions of Higher Learning. This was a case study of the Zimbabwe Open University. Twenty purposefully selected lecturers in the Faculty of Applied Social Sciences and ten blind and visually impaired students participated in the research. Data was collected through student interviews and questionnaires for lecturers and thematically analysed. The results indicated that whilst ODL offers flexible learning opportunities to all, there remains a forgotten tribe in the form of blind and visually impaired students. Consequently, visually impaired students face numerous challenges in their effort to become successful college students. These include lack of qualified lectures to teach them, equipment and services to adequately serve their needs. Both lecturers and visually impaired students felt there was need to have qualified professionals designated to the various needs of these students, appropriate resources for their learning environment should be provided, encourage faculty, academic advisors, staff and other students to proactively respond to the needs of students with visual impairment. The greater awareness that exists regarding visual impairment, the more likely it is that ODL institutions will meet the students’ needs. Further studies need to be done on facilitating the smooth inclusion of visually impaired students in ODL institutions of higher learning.Key words: visually impaired students, Braille, special needs students, academic advisors, IT systems, ODL institutions of higher learnin

Proučavanje Landauovog prigušenja ionsko-zvučnih valova u punjenoj plazmi

Landau damping of ion-acoustic waves is theoretically studied in a dope plasma of a light inert gas like helium in the presence of plasma of a heavy inert gas like argon, considering both fluid model and kinetic model. Damping rates of the ion-acoustic waves in dope plasma are different for the two models which may be experimentally investigated by imposing some conditions. Other cases of Landau damping in Vlasov plasma are also considered. The study is intended to be in support of the experimental investigation of Landau damping free from the influence of other non-collisional as well as collisional damping.Proučavamo teorijski Landauovo prigušenje ionsko-zvučnih valova u plazmi teških inertnih iona, npr. argonskoj, punjenoj lakim inertnim ionima, npr. helijevim, razmatrajući fluidni i kinetički model. Prigušenje ionsko-zvučnih valova u punjenoj plazmi je različito za ta dva modela, što se u nekim uvjetima može eksperimentalno proučavati. Razmatraju se i drugi slučajevi Landauovog prigušenja u Vlasovoj plazmi. Ovim se radom želi potaknuti eksperimentalno istraživanje Landauovog prigušenja s isključenjem utjecaja drugih sudarnih prigušenja i sudarnih prigušenja