Exponential Replication of Patterns in the Signal Tile Assembly Model

Chemical self-replicators are of considerable interest in the field of nanomanufacturing and as a model for evolution. We introduce the problem of self-replication of rectangular two-dimensional patterns in the practically motivated Signal Tile Assembly Model (STAM) [9]. The STAM is based on the Tile Assembly Model (TAM) which is a mathematical model of self-assembly in which DNA tile monomers may attach to other DNA tile monomers in a programmable way. More abstractly, four-sided tiles are assigned glue types to each edge, and self-assembly occurs when singleton tiles bind to a growing assembly, if the glue types match and the glue binding strength exceeds some threshold. The signal tile extension of the TAM allows signals to be propagated across assemblies to activate glues or break apart assemblies. Here, we construct a pattern replicator that replicates a two-dimensional input pattern over some fixed alphabet of size φ with O(φ) tile types, O(φ) unique glues, and a signal complexity of O(1). Furthermore, we show that this replication system displays exponential growth in n, the number of replicates of the initial patterned assembly

The evolution of cooperation and altruism--a general framework and a classification of models.

One of the enduring puzzles in biology and the social sciences is the origin and persistence of intraspecific cooperation and altruism in humans and other species. Hundreds of theoretical models have been proposed and there is much confusion about the relationship between these models. To clarify the situation, we developed a synthetic conceptual framework that delineates the conditions necessary for the evolution of altruism and cooperation. We show that at least one of the four following conditions needs to be fulfilled: direct benefits to the focal individual performing a cooperative act; direct or indirect information allowing a better than random guess about whether a given individual will behave cooperatively in repeated reciprocal interactions; preferential interactions between related individuals; and genetic correlation between genes coding for altruism and phenotypic traits that can be identified. When one or more of these conditions are met, altruism or cooperation can evolve if the cost-to-benefit ratio of altruistic and cooperative acts is greater than a threshold value. The cost-to-benefit ratio can be altered by coercion, punishment and policing which therefore act as mechanisms facilitating the evolution of altruism and cooperation. All the models proposed so far are explicitly or implicitly built on these general principles, allowing us to classify them into four general categories

Hyperglycemia in Dogrib Indians of the Northwest Territories, Canada: Association with Age and a Centripetal Distribution of Body Fat

Glucose tolerance tests on 157 adult Athapaskan-speaking Dogrib Indians residing in three villages in the Canadian Northwest Territories were carried out in April and October, 1979. The proportions of hyperglycemia in males and females, respectively, were: fasting (5= 140 mg/dl) 2% and 1%; hour-2 (\u3e 160 mg/dl) 27% and 20%; hour-2 (2= 200 mg/dl) 13% and 7%. The regression of log (hour-2 glucose) on age was significant within each sex (males: y = 1.887 + .0044X; females: y = 1.993 + .0023X). Skinfold measurements were also obtained at seven body sites (4 on the trunk, 3 on the appendages) and compared between low glucose (hour-2: 160 mg/ dl) and high glucose (\u3e 160 mg/dl) categories within each sex. Significant differences were observed at 2 sites in males only. Principal components analysis was also done on the skinfold measurements. Three components, which collectively account for 90 + % of the general variance, were identified. Hierarchical analysis of variance was used to test age-adjusted principal components for effects of sex, glucose level and localities sampled in different seasons. A significant effect was observed only on the second principal component, indicating that a trunkal deposition of body fat is significantly associated with elevated glucose level (F = 3.968, P \u3c .05) and locality/season (F = 6.777, p .01). Examination of the same data in more rigorously defined glucose groups (low: \u3c 200 mg/dl; high: 3= 200 mg/dl) increased the significance of these associations. Persons at risk for developing diabetes may be those who begin to deposit fat centripetally relative to age/sex appropriate members of their own population

Geographical distribution of diabetes among the native population of Canada: A national survey

The prevalence of diagnosed diabetes was determined for 76% of the registered Indian and Inuit (Eskimo) population of Canada from case registers maintained by the federal agency responsible for Indian health services. A total of 5324 cases were ascertained. The age-sex adjusted rate varied among the Indians from a low of 0.8% in the Northwest Territories to a high of 8.7% in the Atlantic region. Among Inuit, the prevalence was 0.4%. Most cases occur in middle-aged or older individuals, with a higher prevalence among Indian (but not Inuit) females. An ecologic analysis was performed with the crude prevalence of individual communities regressed upon independent variables that included longitude, latitude, geographic isolation, culture area, and language family. Stepwise regressions were also carried out within the Algonkian, Athapaskan, and Eskimoan language families. For the national sample, composite language phylum--culture area predictors were used. The results in the national sample confirmed most findings in the individual language family analysis. Six predictors: latitude, Northeast-Algonkian, Northeast-Iroquoian, Subarctic-Algonkian, Plains-Siouan, and Plains-Algonkian, ranked here in decreasing order of importance, explained 48.4% of the variation in diabetes prevalence. All the named groups had rates significantly greater than found in the reference group of Arctic-Eskimoans. We conclude that the distribution of diabetes among Canadian natives is determined by both genetic and environmental factors.non-insulin dependent diabetes mellitus Canadian Indians and Eskimos national survey

The Northern and Southeastern Ojibwa: Blood Group Systems and the Causes of Genetic Divergence

The ABO, MNSs, Diego, Duffy, Kell, Kidd, Lutheran and P blood groups of 105 Ojibwa Indians from Wikwemikong and 96 Ojibwa Indians from Pikangikum are described. Both samples were obtained from reservation populations, the former located on Manitoulin Island in Lake Huron, the latter located in northwestern Ontario. Both populations lack r and R° which have been identified in the cognate Chippewa Indians of Minnesota.The Pikangikum Ojibwa have the highest incidence of Rz in North America, and the highest incidence of Dia north of Mexico. The Wikwemikong Ojibwa lack Dia, but are distinguished by the presence of B, r, Lua and K, which are not found in Pikangikum. Genic chi-square indicates considerable genetic divergence between the two Ontario Ojibwa populations. Given the small effective population size of the Pikangikum Ojibwa during the past 100 years, genetic drift is probably responsible for the unusual frequencies of Dia, Rz, Ms, and NS on that reservation. Caucasian gene flow is responsible for the occurrence of B, r, Lua and K in Wikwemikong. Estimates of the “aboriginal” frequencies of several blood group, serum protein and red cell enzyme genes in the Wikwemikong Ojibwa are also presented. A highly significant amount of genetic heterogeneity remains between the Ontario Ojibwa after adjustment of the frequencies for gene flow. Genetic drift is considered principally responsible for this divergence