Local interaction scale controls the existence of a non-trivial optimal critical mass in opinion spreading

We study a model of opinion formation where the collective decision of group is said to happen if the fraction of agents having the most common opinion exceeds a threshold value, a \textit{critical mass}. We find that there exists a unique, non-trivial critical mass giving the most efficient convergence to consensus. In addition, we observe that for small critical masses, the characteristic time scale for the relaxation to consensus splits into two. The shorter time scale corresponds to a direct relaxation and the longer can be explained by the existence of intermediate, metastable states similar to those found in [P.\ Chen and S.\ Redner, Phys.\ Rev.\ E \textbf{71}, 036101 (2005)]. This longer time-scale is dependent on the precise condition for consensus---with a modification of the condition it can go away.Comment: 4 pages, 6 figure

Network reachability of real-world contact sequences

We use real-world contact sequences, time-ordered lists of contacts from one person to another, to study how fast information or disease can spread across network of contacts. Specifically we measure the reachability time -- the average shortest time for a series of contacts to spread information between a reachable pair of vertices (a pair where a chain of contacts exists leading from one person to the other) -- and the reachability ratio -- the fraction of reachable vertex pairs. These measures are studied using conditional uniform graph tests. We conclude, among other things, that the network reachability depends much on a core where the path lengths are short and communication frequent, that clustering of the contacts of an edge in time tend to decrease the reachability, and that the order of the contacts really do make sense for dynamical spreading processes.Comment: (v2: fig. 1 fixed

Using intraspecific molecular and phenotypic variation to promote multi-functionality of reforestation during climate change – A review of tropical forest case studies in South-east Asia

The study of intraspecific genetic variation in plant traits for use in tropical forest restoration has broad potential for increasing our ability to achieve multi-functional objectives during this era of climate change. Developing seed-sourcing guidelines that optimize phenotypic characteristics best suited to a particular planting site as well as to future conditions imposed by environmental change could be useful for effective reforestation. Because evolution operates differently across tree species, this is an especially cumbersome task in tropical forests that contain thousands of species. Partially due to this high plant diversity, research and application of intraspecific variation in genetics, plant traits, and plant function in tropical forests wane far behind less diverse forest biomes. To examine the potential for improving reforestation efforts in tropical forests by considering intraspecific variation in plant traits and functions, we review the state of knowledge on intraspecific variation in South-east Asia as a case study. We focus on the dipterocarp family (Dipterocarpaceae), a highly diverse family of 16 genera with approximately 695 known species that often dominate lowland tropical rainforests of South-east Asia with many of these forests in a degraded state and in need of restoration. We found that there is research accumulating to understand genetic variation in approximately 10% of these 695 species. Intraspecific molecular variation exists at different spatial scales among species with 74% of species having moderate to high population differentiation (Fst > 0.10) and 92% of species with evidence of fine-scale genetic structure. Although this suggests a high potential for trait variation, few studies associated molecular with phenotypic variation. Seventeen tree species across 11 studies revealed intraspecific variation in traits or functions. Research indicates that intraspecific variation in growth may vary two-fold and drought tolerance four-fold among genotypes highlighting the possibility to pre-adapt trees to climate change during reforestation and to use intraspecific variation to promote the use of native species in commercial forestry. Our review presents opportunities and ideas for developing seed-sourcing guidelines to take advantage of intraspecific variation in traits and function by identifying how to locate this variation, which species would benefit, and how to test for trait variation. We also highlight an emerging area of research on local adaptation, common garden studies, and adaptive drought conditioning to improve reforestation during climate change

Symphony for the native wood(s): Global reforestation as an opportunity to develop a culture of conservation

1. The stewardship of forests across multiple human generations has potential to lead to cultural innovations fostering sustainable uses. Nevertheless, positive culture-nature interactions are often disrupted due to colonial exploitation and a lack of intrinsic value ascribed to nature in capitalist economies. There is global recognition that restoring degraded ecosystems is critical to promote the welfare of people and nature by reducing the negative impacts of global climate change and diminishing biodiversity. However, with a focus on technical remedies, restoration and reforestation efforts generally fail to address the root causes of ecosystem degradation.2. In this perspective paper, we call for explicit incorporation of cultural values into global reforestation efforts. We focus on music as a cultural ecosystem service as music has been a prominent part of human history with clear sociological and psychological attributes that may invite mass interest and participation. We illustrate the value of musical linkages via three case studies from Europe, Africa and Hawaii focusing on native tree species, their wood, musical ecology and their interaction with culture.3. We show that multi-generational stewardship of native ecosystems in Europe has allowed the refinement of the violin to its current form, one that is culturally significant for millions of people and has created a multi-million dollar industry. This development stems from a 500-year tradition of craftsmanship handed down across generations and illustrates that ecocultural interactions can be a strong dynamo for development of unique commodities.4. In contrast, in regions where extirpation of native plant species was used as a deliberate colonization strategy, many ecocultural linkages face risk of extinction. Our case studies from Africa and Hawaii illustrate how native tree species of particular value for musical expression were nearly lost and along with loss of music, important cultural connections to nature.5. In the context of restoration, there is also evidence that music-based linkages can revitalize nature-culture interactions and promote restoration of native ecosystems. Incorporating native trees in global reforestation efforts is critical for ensuring that reforestation efforts capture the synergies needed for developing new ideologies that promote the well-being of co-dependent humans and all life

A Vicious Cycle: A Cross-Sectional Study of Canine Tail-Chasing and Human Responses to It, Using a Free Video-Sharing Website

Tail-chasing is widely celebrated as normal canine behaviour in cultural references. However, all previous scientific studies of tail-chasing or ‘spinning’ have comprised small clinical populations of dogs with neurological, compulsive or other pathological conditions; most were ultimately euthanased. Thus, there is great disparity between scientific and public information on tail-chasing. I gathered data on the first large (n = 400), non-clinical tail-chasing population, made possible through a vast, free, online video repository, YouTube™. The demographics of this online population are described and discussed. Approximately one third of tail-chasing dogs showed clinical signs, including habitual (daily or ‘all the time’) or perseverative (difficult to distract) performance of the behaviour. These signs were observed across diverse breeds. Clinical signs appeared virtually unrecognised by the video owners and commenting viewers; laughter was recorded in 55% of videos, encouragement in 43%, and the commonest viewer descriptors were that the behaviour was ‘funny’ (46%) or ‘cute’ (42%). Habitual tail-chasers had 6.5+/−2.3 times the odds of being described as ‘Stupid’ than other dogs, and perseverative dogs were 6.8+/−2.1 times more frequently described as ‘Funny’ than distractible ones were. Compared with breed- and age-matched control videos, tail-chasing videos were significantly more often indoors and with a computer/television screen switched on. These findings highlight that tail-chasing is sometimes pathological, but can remain untreated, or even be encouraged, because of an assumption that it is ‘normal’ dog behaviour. The enormous viewing figures that YouTube™ attracts (mean+/−s.e. = 863+/−197 viewings per tail-chasing video) suggest that this perception will be further reinforced, without effective intervention

Daydream Believing: Visionary Formalism and the Constitution

The failure of traditional strands of legal formalism to provide a satisfactory account of law\u27s relation to material conditions, and its distinction from political practice, has given rise to a new variant of formalist theory: visionary formalism. In this essay, the authors examine visionary formalism through the work of one of its leading exponents, William E. Conklin. They contend that, far from rescuing legal formalism, the visionary account of constitutional adjudication put forward in Conklin\u27s recent treatise, Images of the Constitution, exposes formalism for what it is: an effort to romanticize and legitimize a peculiarly regressive mode of political practice. In the final sections of the essay, the authors provide their own account of the connections among law, politics and material conditions. They conclude that only a constitutive legal theory , embracing a critical understanding of the political nature and historical contingency of legal structures, offers any real hope of harnessing law as a progressive social instrument