We investigated the effects of activity, group size and sex composition on the cohesion of merino sheep (Ovis aries) groups. Mixed-sex (50% of each sex) and single-sex groups of 2, 4, 6 and 8 sheep were placed within 491-m arenas located in natural pastures and were video recorded during 6 daily hours. The behaviour, orientation and location of each sheep were then extracted from the films at 1...

Men who have sex with men (MSM) in China face a rapidly expanding HIV epidemic. Anal sex role plays a significant role in HIV infection. Research has already begun in China investigating the potential for circumcision-based interventions to slow the rise of HIV among Chinese MSM. Using peer referral recruitment, we sampled 491 men who reported anal sex role preference. We analyzed preferred ana...

Abstract The year 2021 marks the 150th anniversary of publication Charles Darwin’s extraordinary book Descent Man and Selection in Relation to Sex. Here, we review history impact a single profound insight from Man: that, some few species, females rather than males compete for access mates. In other words, these species are ‘sex-role reversed’ with respect mating competition sexual selection com...

See examples in Fig. 1(b). Many graph algorithms use an st-orientation. For instance, graph drawing algorithms [3], [4], [17], [19], [22], routing algorithms [1], [13] and partitioning algorithms [14]. Given a biconnected graph G and its two vertices s and t, one can find an st-orientation of G in O(m + n) time [5], [6], [22]. Note that if G is not biconnected then G may have no st-orientation....

Given a graph, does there exist an orientation of the edges such that the resulting directed graph is strongly connected? Robbins’ theorem [Robbins, Am. Math. Monthly, 1939] states that such an orientation exists if and only if the graph is 2-edge connected. A natural extension of this problem is the following: Suppose that the edges of the graph is partitioned into trails. Can we orient the tr...

In the last decades, orientation estimation has often been investigated for instance in the domain of still image analysis for feature extraction [5] or in the context of video stream processing for motion analysis [10] [20] [27]. Applications of orientation estimation vary, for example, from the enhancement of ancient engravings to the analysis of fingerprint images or seismic data [8]. Orient...

The cyclic and dihedral groups can be made to act on the set Acyc(Y ) of acyclic orientations of an undirected graph Y , and this gives rise to the equivalence relations ∼κ and ∼δ, respectively. These two actions and their corresponding equivalence classes are closely related to combinatorial problems arising in the context of Coxeter groups, sequential dynamical systems, the chip-firing game, ...

Given an undirected graph, one can assign directions to each of the edges of the graph, thus orienting the graph. To be as egalitarian as possible, one may wish to find an orientation such that no vertex is unfairly hit with too many arcs directed into it. We discuss how this objective arises in problems resulting from telecommunications. We give optimal, polynomial-time algorithms for: finding...

A tree-composition is a tree-like family that serves to describe the obstacles to k-edge-connected orientability of mixed graphs. Here we derive a structural result on tree-compositions that gives rise to a simple algorithm for computing an obstacle when the orientation does not exist. As another application, we show a min–max theorem on the minimal in-degree of a given node set in a k-edge-con...