Given an arbitrary spacetime (M, g), we prove a simple criterion to check when many of the good properties of the time-separation (Lorentzian distance) d valid in globally hyperbolic spacetimes hold for M . Concretely, when the product P = M × R, g̃ = g + dy is causally simple, then not only M is causally simple, but also d is continuous and AvezSeifert connectedness (each two causally related e...

The ubiquity of online programs in higher education requires continued focus on designing instructional environments that improve students’ learning. We examine students’ perceptions of sense of community and learning, as well as academic achievement, using grades obtained from a final project and participation in asynchronous discussion forums. Findings indicate a significant correlation betwe...

We propose several connectedness measures built from pieces of variance decompositions, and we argue that they provide natural and insightful measures of connectedness among financial asset returns and volatilities. We also show that variance decompositions define weighted, directed networks, so that our connectedness measures are intimately-related to key measures of connectedness used in the ...

Counselors, psychologists, and evaluators of intervention programs for youth increasingly view the promotion of connectedness as an important intervention outcome. When evaluating these programs, researchers frequently test whether the treatment effects differ across gender and ethnic or racial groups. Doing so necessitates the availability of culturally and gender-invariant measures. We used t...

We propose several connectedness measures built from pieces of variance decompositions, and we argue that they provide natural and insightful measures of connectedness among financial asset returns and volatilities. We also show that variance decompositions define weighted, directed networks, so that our connectedness measures are intimately-related to key measures of connectedness used in the ...

IMPLEMENTATION This reprint corresponds to the book-chapter " Algorithms for the detection of connectedness and their neural implementation " , Connectedness is one of the most important grouping criteria that allow the visual system to segregate objects from each other and from the background. We review algorithms for the detection of connectedness from a physiological point of view. Connected...

a r t i c l e i n f o This study compared perceptions of school connectedness to traditional community schools and residential treatment center (RTC) schools for youths between the ages of 12 and 18 receiving treatment within two RTCs. The influence of gender, report card grades, and engagement in treatment were also examined in relation to school connectedness in the RTC schools. Findings indi...

School connectedness is an important protective factor for adolescent risk-taking behaviour. This study examined a pilot version of the Skills for Preventing Injury in Youth (SPIY) programme, combining teacher professional development (PD) for increasing school connectedness (connectedness component) with a risk and injury prevention curriculum for early adolescents (curriculum component). A pr...

Ryser’s Conjecture states that any r-partite r-uniform hypergraph has a vertex cover of size at most r− 1 times the size of the largest matching. For r = 2, the conjecture is simply König’s Theorem. It has also been proven for r = 3 by Aharoni using a beautiful topological argument. This paper is the first part of the proof of a characterization of those 3-uniform hypergraphs for which Aharoni’...