Analysis of symmetries in models of multi-strain infections

In mathematical studies of the dynamics of multi-strain diseases caused by antigenically diverse pathogens, there is a substantial interest in analytical insights. Using the example of a generic model of multi-strain diseases with cross-immunity between strains, we show that a significant understanding of the stability of steady states and possible dynamical behaviours can be achieved when the symmetry of interactions between strains is taken into account. Techniques of equivariant bifurcation theory allow one to identify the type of possible symmetry-breaking Hopf bifurcation, as well as to classify different periodic solutions in terms of their spatial and temporal symmetries. The approach is also illustrated on other models of multi-strain diseases, where the same methodology provides a systematic understanding of bifurcation scenarios and periodic behaviours. The results of the analysis are quite generic, and have wider implications for understanding the dynamics of a large class of models of multi-strain diseases

An enigmatic hypoplastic defect of the maxillary lateral incisor in recent and fossil orangutans from Sumatra (Pongo abelii) and Borneo (Pongo pygmaeus)

Developmental dental pathologies provide insight into health of primates during ontogeny, and are particularly useful for elucidating the environment in which extant and extinct primates matured. Our aim is to evaluate whether the prevalence of an unusual dental defect on the mesiolabial enamel of the upper lateral incisor, thought to reflect dental crowding during maturation, is lesser in female orangutans, with their smaller teeth, than in males; and in Sumatran orangutans, from more optimal developmental habitats, than in those from Borneo. Our sample includes 49 Pongo pygmaeus (87 teeth), 21 P. abelii (38 teeth), Late Pleistocene paleo-orangutans from Sumatra and Vietnam (67 teeth), Late Miocene catarrhines Lufengpithecus lufengensis (2 teeth), and Anapithecus hernyaki (7 teeth). Methods include micro-CT scans, radiography, and dental metrics of anterior teeth. We observed fenestration between incisor crypts and marked crowding of unerupted crowns, which could allow tooth-to-tooth contact. Tooth size does not differ significantly in animals with or without the defect, implicating undergrowth of the jaw as the proximate cause of dental crowding and defect presence. Male orangutans from both islands show more defects than do females. The defect is significantly more common in Bornean orangutans (71 %) compared to Sumatran (29 %). Prevalence among fossil forms falls between these extremes, except that all five individual Anapithecus show one or both incisors with the defect. We conclude that maxillary lateral incisor defect is a common developmental pathology of apes that is minimized in optimal habitats and that such evidence can be used to infer habitat quality in extant and fossil apes

The Churches' Bans on Consanguineous Marriages, Kin-Networks and Democracy

This paper highlights the role of kin-networks for the functioning of modern societies: countries with strong extended families as characterized by a high level of cousin marriages exhibit a weak rule of law and are more likely autocratic. To assess causality, I exploit a quasi-natural experiment. In the early medieval ages the Church started to prohibit kin-marriages. Using the variation in the duration and extent of the Eastern and Western Churches' bans on consanguineous marriages as instrumental variables, reveals highly significant point estimates of the percentage of cousin marriage on an index of democracy. An additional novel instrument, cousin-terms, strengthens this point: the estimates are very similar and do not rest on the European experience alone. Exploiting within country variation of cousin marriages in Italy, as well as within variation of a 'societal marriage pressure' indicator for a larger set of countries support these results. These findings point to a causal effect of marriage patterns on the proper functioning of formal institutions and democracy. The study further suggests that the Churches' marriage rules - by destroying extended kin-groups - led Europe on its special path of institutional and democratic development

Use of Surnames in the Study of Population Structure

An analysis of surname frequencies was used for the study of population structure. The surnames in the register of the parish of Los Teques, Venezuela, from 1790 to 1869 were classified in three classes, frequent, intermediate, and rare. Using the surnames of the male spouses it was found that a relationship exists among the surname class and consanguinity, place of birth and marriage with a woman belong­ing to an equal surname class. The individuals with frequent surnames have a higher probability to belong to a consanguineous marriage, of being born in Los Teques and of having married a woman of the same surname class than the indi­viduals with rare surnames.There is evidence that “endogamic clusters” exist within the frequent surnames, since eight surnames composed a fifth of the total sample. It is believed the surname frequencies could be used as indicators of inbreeding, endogamy and migration

Torus palatinus: a segregation analysis

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Inbreeding as Measured by Isonymy in Two Venezuelan Populations and Its Relationship to Other Variables

Isonymy is a useful approach to the study of population structure and thus can be utilized to detect deviations from random mating. In this study we give the results of an analysis of inbreeding levels and relate such variables as mean marital distance, surnames repeated in isonymous couples, and percentage of people using only maternal surnames to inbreeding and endogamy in two Venezuelan populations of black ancestry, Birongo and La Sabana. These populations differ in their sociocultural development and degree of isolation. We estimated inbreeding through isonymy and directly from genealogy. The most important findings are that the Ft values are higher than the α’s, that the Fn component of Ft is higher than the Fr component, and that there is higher endogamy, inbreeding, and isolation in Birongo than in La Sabana. These results are in agreement with the sociocultural and historical background and development of each population. Nevertheless, both populations show similar temporal trends in almost all the variables analyzed. The use of isonymy as a complementary tool to study population structure is proposed, especially for Ibero-American populations

Comparison of Two Venezuelan Populations Using the Coefficient of Relationship by Isonymy

The coefficient of relationship by isonymy Ri is a good indicator of similarities between and within populations by means of identity of surnames. In this study we present the results of an analysis of Ri obtained using two surnames for each person in two small Venezuelan populations of African origin: Birongo and La Sabana. The analyses of six Ri values within each population in two periods and of sixteen Ri values within each population between two periods and within each period between populations show that the higher values of Ri are those that include combinations of maternal surnames compared with any other combination and that in one period the relationship between Birongo and La Sabana was equal to 0, as measured with combinations of paternal surnames. These facts are indicators of a tendency toward matrifocal behavior and show that the use of four surnames for estimating Ri permits detailed comparisons of the relationship between and within groups

Surnames in Ferrara: distribution, isonimy and levels of inbreeding

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