Santa Fe Institute

About: Santa Fe Institute is a nonprofit organization based out in Santa Fe, New Mexico, United States. It is known for research contribution in the topics: Population & Complex network. The organization has 558 authors who have published 4558 publications receiving 396015 citations. The organization is also known as: SFI.

A model for the emergence of pillars, walls and royal chambers in termite nests

Abstract: A simple model of the emergence of pillars in termite nests by Deneubourg is modified to include several additional features that break the homogeneity of the original model: (i) a convection air stream that drives molecules of pheromone along a given direction; (ii) a net flux of individuals in a specific direction; (iii) a well-defined self-maintained pheromone trail; and (iv) a pheromonal template representing the effect of the presence of a queen that continuously emits pheromone. It is shown that, under certain conditions, pillars are transformed into walls or galleries or chambers, and that this transformation may not be driven by any change in the termites' behaviour. Because the same type of response at the individual level can generate different patterns under different conditions, and because previous construction modifies current building conditions, we hypothesize that nest complexity can result from the unfolding of a morphogenetic process that progressively generates a diversity of history-dependent structures.

T-Cell Vaccine Strategies for Human Immunodeficiency Virus, the Virus with a Thousand Faces

Abstract: HIV's rapid global spread and the human suffering it has left in its wake have made AIDS a global heath priority for the 25 years since its discovery. Yet its capacity to rapidly evolve has made combating this virus a tremendous challenge. The obstacles to creating an effective HIV vaccine are formidable, but there are advances in the field on many fronts, in terms of novel vectors, adjuvants, and antigen design strategies. SIV live attenuated vaccine models are able to confer protection against heterologous challenge, and this continues to provide opportunities to explore the biological underpinnings of a protective effect (9). More indirect, but equally important, is new understanding regarding the biology of acute infection (43), the role of immune response in long-term non-progression (6,62, 81), and defining characteristics of broadly neutralizing antibodies (4). In this review we will focus on summarizing strategies directed towards a single issue, that of contending with HIV variation in terms of designing aT-cell vaccine. The strategies that prove most effective in this area can ultimately be combined with the best strategies under development in other areas, with the hope of ultimately converging on a viable vaccine candidate. Only two large HIV vaccine efficacy trials have been completed and both have failed to prevent infection or confer a benefit to infected individual (23,34), but there is ample reason to continue our efforts. A historic breakthrough came in 1996, when it was realized that although the virus could escape from a single antiretroviral (ARV) therapy, it could be thwarted by a combination of medications that simultaneously targeted different parts of the virus (HAART) (38). This revelation came after 15 years of research, thought, and clinical testing; to enable that vital progress the research and clinical communities had to first define and understand, then develop a strategy to counter, the remarkable evolutionary potential of the virus. HAART, for the first time, provided an effective treatment to help those with living with HIV stay healthy. Nonetheless, the treatment has limitations. People with HIV face a lifetime of expensive daily multi-drug regimens, often with side effects; drug resistance at the individual and population level are issues (56); and universal access, despite substantial progress, is a dream not yet realized for many of the millions of the world's poor who are living with HIV (68). These issues, combined with the growing numbers of people infected globally and impact of HIV on society, make the development of an HIV vaccine or a prophylactic prevention strategy a crucial if elusive goal. In some ways, the history of HIV vaccine deVelopment has paralleled the early stages of designing effective therapy. We had to test the simple strategies first, but meanwhile the story of the impact of diversity from an immunological perspective is still unfolding, and novel ideas countermeasures are being explored.

On the abundance of polyploids in flowering plants

Abstract: The wide distribution of polyploidy among plants has led to a variety of theories for the evolutionary advantages of polyploidy. Here we claim that the abundance of polyploidy may be the result of a simple ratcheting process that does not require evolutionary advantages due to the biological properties of organisms. The evolution of polyploidy is a one-way process in which chromosome number can increase but not decrease. Using a simple mathematical model, we show that average ploidal level within a plant lineage can continually increase to the levels observed today, even if there are ecological or physiological disadvantages to higher ploidy. The model allowed us to estimate the average net speciation and polyploidy rates for ten angiosperm genera. Based on these estimates, the model predicts distributions of ploidal levels statistically similar to those observed in nine of the 10 genera.