Everything is Infinite: Children's Beliefs About Endless Space, Time, and Number.

How do children form beliefs about the infinity of space, time, and number? We asked whether children held similar beliefs about infinity across domains, and whether beliefs in infinity for domains like space and time might be scaffolded upon numerical knowledge (e.g., knowledge successors within the count list). To test these questions, 112 U.S. children (aged 4;0-7;11) completed an interview regarding their beliefs about infinite space, time, and number. We also measured their knowledge of counting, and other factors that might impact performance on linguistic assessments of infinity belief (e.g., working memory, ability to respond to hypothetical questions). We found that beliefs about infinity were very high across all three domains, suggesting that infinity beliefs may arise early in development for space, time, and number. Second, we found that-across all three domains-children were more likely to believe that it is always possible to add a unit than to believe that the domain is endless. Finally, we found that understanding the rules underlying counting predicted children's belief that it is always possible to add 1 to any number, but did not predict any of the other elements of infinity belief.

Preschoolers' relevance inferences in linguistic and non-linguistic contexts.

Understanding symbols requires going beyond what they literally are, and figuring out what they're intended to communicate. For example, a drawing of a bird (or the word bird) could refer to a particular bird, a species, etc… The interpreter must decide between these intended meanings. We ask how children go beyond the literal meanings of communicative acts (i.e., compute pragmatic inferences), and whether these inferences are domain-general. We tested 443 US 2- to 6-year-olds' inferences about the referential interpretation of ambiguous symbols. We manipulated the domain (e.g., word or a drawing) and task (interpret vs. create the communicative act). Children robustly identified the referents of ambiguous symbols and chose from among alternatives during linguistic and non-linguistic communication tasks. There were no effects of age or domain on performance. These data provide some of the earliest evidence of children's computations of pragmatic inferences, and provide exciting evidence that pragmatic inferences may extend beyond the domain of language.

Lack of alkaloids and tetrodotoxin in the neotropical frogs Allobates spp. (Aromobatidae) and Silverstoneia flotator (Dendrobatidae).

Frogs of the family Dendrobatidae are known to contain toxic alkaloids in their skin secretion, but Allobates species of the closely related Aromobatidae family are considered to lack toxic secretions. However, contradictory results have been reported. Analyses of alcohol extracts from three different Allobates species from South-America (Guiana Shield), Central America (Costa Rica), and from the dendrobatid frog Silverstoneia flotator confirm the absence of alkaloids and tetrodotoxin in aromobatids and in a dendrobatid of the subfamily Colostethinae.

From Arabia to Iberia: A Y chromosome perspective.

At different times during recent human evolution, northern Africa has served as a conduit for migrations from the Arabian Peninsula. Although previous researchers have investigated the possibility of the Strait of Gibraltar as a pathway of migration from North Africa to Iberia, we now revisit this issue and theorize that although the Strait of Gibraltar, at the west end of this corridor, has acted as a barrier for human dispersal into Southwest Europe, it has not provided an absolute seal to gene flow. To test this hypothesis, here we use the spatial frequency distributions, STR diversity and expansion time estimates of Y chromosome haplogroups J1-P58 and E-M81 to investigate the genetic imprints left by the Arabian and Berber expansions into the Iberian Peninsula, respectively. The data generated indicate that Arabian and Berber genetic markers are detected in Iberia. We present evidence that suggest that Iberia has received gene flow from Northwest Africa during and prior to the Islamic colonization of 711A.D. It is interesting that the highest frequencies of Arabia and Berber markers are not found in southern Spain, where Islam remained the longest and was culturally most influential, but in Northwest Iberia, specifically Galicia. We propose that Moriscos' relocations to the north during the Reconquista, the migration of cryptic Muslims seeking refuge in a more lenient society and/or more geographic extensive pre-Islamic incursions may explain the higher frequencies and older time estimates of mutations in the north of the Peninsula. These scenarios are congruent with the higher diversities of some diagnostic makers observed in Northwest Iberia.

Poor alkaloid sequestration by arrow poison frogs of the genus Phyllobates from Costa Rica.

Frogs of the genus Phyllobates from Colombia are known to contain the highly toxic alkaloid batrachotoxin, but species from Central America exhibit only very low levels or are entirely free of this toxin. In the present study alcohol extracts from 101 specimens of Phyllobates lugubris and Phyllobates vittatus and 21 of three sympatric species (Dendrobates pumilio, Dendrobates auratus, Dendrobates granuliferus) from Costa Rica were analyzed by gas chromatography-mass spectrometry. Whereas the extracts of the Dendrobates species exhibited typical profiles of toxic alkaloids, those of the two Phyllobates species contained low levels of few alkaloids only, batrachotoxin was not detected. Although the feeding pattern of the Dendrobates and Phyllobates species are similar as revealed by examination of their stomach content (mainly ants and mites), the Phyllobates species are poorly sequestering alkaloids from their food source in contrast to the Dendrobates frogs.

On the origins, rapid expansion and genetic diversity of Native Americans from hunting-gatherers to agriculturalists.

Given the importance of Y-chromosome haplogroup Q to better understand the source populations of contemporary Native Americans, we studied 8 biallelic and 17 microsatellite polymorphisms on the background of 128 Q Y-chromosomes from geographically targeted populations. The populations examined in this study include three from the Tuva Republic in Central Asia (Bai-Tai, Kungurtug, and Toora-Hem, n = 146), two from the northeastern tip of Siberia (New Chaplino and Chukchi, n = 32), and two from Mesoamerica (Mayans from Yucatan, Mexico n = 72, and Mayans from the Guatemalan Highlands, n = 43). We also see evidence of a dramatic Mesoamerican post-migration population growth in the ubiquitous and diverse Y-STR profiles of the Mayan and other Mesoamerican populations. In the case of the Mayans, this demographic growth was most likely fueled by the agricultural- and trade-based subsistence adopted during the Pre-Classic, Classic and Post-Classic periods of their empire. The limited diversity levels observed in the Altaian and Tuvinian regions of Central Asia, the lowest of all populations examined, may be the consequence of bottleneck events fostered by the spatial isolation and low effective population size characteristic of a nomadic lifestyle. Furthermore, our data illustrate how a sociocultural characteristic such as mode of subsistence may be of impact on the genetic structure of populations. We analyzed our genetic data using Multidimensional Scaling Analysis of populations, Principal Component Analysis of individuals, Median-joining networks of M242, M346, L54, and M3 individuals, age estimations based on microsatellite variation utilizing genealogical and evolutionary mutation rates/generation times and estimation of Y- STR average gene diversity indices.

Poisson-based detection limit and signal confidence intervals for few total counts.

An alternative to the accepted method for calculating detection limits is presented that avoids difficulties often encountered with few total counts. In particular, excessive false positives and large relative uncertainty in the signal determination are prevented. The usually accepted method did not fully incorporate Poisson statistics in the derivation of detection limits. The alternate method defines detection at the same relative uncertainty for all magnitudes of total counts and includes the uncertainty of the signal counts. A method of determining confidence intervals for the signal in the presence of background is also proposed. Use of the confidence interval method to determine the mode or most probable value is particularly useful at few total counts because negative signal results are avoided.

Estudio descriptivo de los brotes de hepatitis A investigados en Cataluña (1999-2003) / Descriptive study of hepatitis outbreaks occurring in Catalonia (1999-2003)

Antecedentes y objetivo. Actualmente España presenta un patrón de baja endemicidad de hepatitis A que favorece que la enfermedad se manifieste en forma de brotes en colectivos susceptibles. El objetivo de este estudio es analizar los brotes de hepatitis A investigados en Cataluña durante el período 1999-2003. Métodos. Se definieron criterios para la inclusión de los brotes y posteriormente se clasificaron según el mecanismo de transmisión. Se analizaron variables de espacio, tiempo, sociodemográficas, ámbito, factores de riesgo y medidas preventivas. Se calcularon las tasas de incidencia y la razón de tasas según edad y sexo. Resultados. De 74 brotes, 73 cumplieron los criterios de inclusión: la mayoría con transmisión persona-persona (83,8%) y el resto con fuente de infección común (14,9%). En total, se incluyeron 334 casos (incidencia acumulada 1999-2003:5,27 por 100.000 habitantes), con una mediana de edad de 24,5 años. Los ámbitos con más casos fueron el familiar (143), el comunitario (97) y el escolar/guardería (87). El número de casos por brote osciló entre 2 y 11, excepto un brote que afectó a 83 varones con prácticas homosexuales de riesgo. Pertenecer a los grupos de edad de baja inmunidad (niños y adultos jóvenes) y viajar o proceder de zonas endémicas fueron las características más importantes relacionadas con el caso índice y/o con los casos coprimarios. Conclusión. Los brotes de hepatitis A en Cataluña todavía son frecuentes. La mayoría se producen en el ámbito familiar, por transmisión persona-persona, y en los subgrupos de población más susceptibles a la infección (trabajadores de guarderías o escuelas, viajeros y varones con prácticas homosexuales de riesgo) (AU)

Background and objective. The currently low endemic level of hepatitis A in Spain favors manifestation of the disease as outbreaks among specific risk groups. The aim of this study is to analyze the hepatitis A outbreaks investigated in Catalonia (Spain) during the period of 1999 to 2003. Methods. The criteria for including an outbreak were defined and outbreaks were classified according to the type of transmission. The variables analyzed were space, time, socio-demographic parameters, setting, risk factors, and preventive measures adopted. The incidence rate and rate ratio were calculated according to age and sex. Results. Among 74 outbreaks, 73 fulfilled the inclusion criteria. Most outbreaks involved person-to-person transmission (83.8%) and the rest had a common source of infection (14.9%). In total, 334 cases were included (cumulative incidence 1999-2003: 5.27 per 100,000 inhabitants), with an average age of 24.5 years. The settings yielding the most cases were family (143), community (97) and schools/preschools (87). The number of cases per outbreak ranged from 2 to 11, except one outbreak that occurred in 83 young homosexual men with high-risk sexual practices. The main factors related to the case index or to coprimary cases included belonging to age groups with low immunity (children and young adults) and travelling to or from endemic areas. Conclusion. Hepatitis A outbreaks in Catalonia are still frequent. They mainly occur in the family environment, by person-to-person transmission and in the most vulnerable groups (preschool or school employees, travelers, and men who perform high-risk sexual practices with other men) (AU)

Declaración de los nuevos diagnósticos de infección por el VIH en Cataluña. Implementación y resultados / Reporting of newly diagnosed HIV infections in Catalonia. Barcelona. Spain. Implementation and results

Objetivos: Describir los resultados de la notificación de nuevos diagnósticos de infección por el virus de la inmunodeficiencia humana (NDIVIH) en Cataluña (2001-2003), y comparar las características de la epidemia como resultado de la utilización de este nuevo sistema de información junto con el Registro de casos de sida de Cataluña, con las halladas únicamente en el Registro de casos de sida. Métodos: Datos de las notificaciones de NDIVIH y de casos de sida entre 2001 y 2003 en Cataluña. Resultados: Entre los NDIVIH (n = 1.765), la vía de transmisión más frecuente fue las relaciones heterosexuales (46,8%), seguida de las relaciones homosexuales entre varones (26,7%) y el uso de drogas por vía parenteral (19,9%). Entre los 1.210 casos de sida, la forma de transmisión más frecuente fue el uso de drogas por vía parenteral (42,2%), seguida de relaciones heterosexuales (34,5%) y de las relaciones homosexuales entre varones (18,0%). La diferencia de utilizar una o 2 fuentes de información respecto a la variable vía de transmisión de la infección fue estadísticamente significativa. Conclusiones: El sistema de información basado en los datos sobre NDIVIH es viable, ha sido útil para conseguir los objetivos previstos en el sistema de vigilancia epidemiológica del VIH y proporciona información más precisa que el Registro de sida para describir los actuales patrones de transmisión del virus. La exhaustividad del nuevo sistema de información podría mejorar mediante la incorporación del diagnóstico de infección al sistema de enfermedades de declaración obligatoria

Objectives: To describe newly diagnosed HIV infections from the HIV Reporting System in Catalonia (2001-2003), and to compare the characteristics of the epidemic based on the use of the HIV Reporting System and the Catalonian AIDS Registry versus those based on the Catalonian AIDS Registry alone. Methods: Data were collected from newly diagnosed HIV infections and AIDS cases between 2001 and 2003 in Catalonia. Results: Among the newly diagnosed HIV infections (1,765) the most frequent route of HIV infection was heterosexual transmission (46.8%), followed by men who had sex with men (26.7%), and injecting drug use (19.9%). Out of the 1,210 AIDS cases, the most common route of HIV transmission was injecting drug used (42.2%), followed by (heterosexual transmission 34.5%) and MSM (18.0%). Comparison of routes of HIV transmission in the two reporting systems (HIV/AIDS versus AIDS) revealed statistically significant differences. Conclusions: The HIV/AIDS Reporting System based on reporting of newly diagnosed HIV infections is feasible, since it has been useful in achieving the objectives of epidemiological HIV infection surveillance. It also provides more accurate information than does the AIDS Registry, which can be used to describe recent patterns of HIV transmission. The completeness of the new reporting system may be enhanced by including the diagnosis of HIV infection among the diseases of mandatory notification