Terrestrially Derived n-Alkane δD Evidence of Shifting Holocene Paleohydrology in Highland Costa Rica

A previous study of carbon isotopes in the sediments of a glacial lake in Costa Rica led to the hypothesis that changes in the migration of the intertropical convergence zone (ITCZ) over the course of the Holocene significantly affected the hydrology of the surrounding high-elevation páramo ecosystem. This hypothesis was based on millennial-scale changes in terrestrial n-alkane carbon isotope (δ13C) values in a sediment core from Lago de las Morrenas 1, a tarn on the Chirripó massif of the Cordillera de Talamanca. Here we present terrestrial n-alkane hydrogen isotope (δD) data, a more direct proxy of ecosystem drought stress, from the same core. These new data support the previous hypothesis and confirm that the effects of millennial-scale ITCZ dynamics in the circum-Caribbean region were not restricted to tropical lowlands. In southern Central America, these dynamics may have played a fundamental role in millennial-scale fire dynamics in high-elevation páramo ecosystems

Methods for the Study of Soil Charcoal as an Indicator of Fire and Forest History in the Appalachian Region, U.S.A.

Charcoal particles in soils and sediments of the Appalachian region provide evidence of long-term fire history relevant to resource management and to studies of paleoclimate, vegetation history, and the effects of prehistoric and historic humans on the environment. Charcoal records of fire history are of low resolution in comparison to dendrochronological records, but reach well beyond the oldest trees in most areas, providing evidence of fires thousands or tens of thousands of years ago. We focus here on fire history reconstruction from soil charcoal, which provides site-specific evidence of past fires and potentially forest composition. Charcoal \u3e 2 mm may be large enough for taxonomic identification, and of sufficient mass to enable AMS radiocarbon dating of individual particles. Soil mixing due to physical and biological factors creates soil profiles in the southern Appalachians in which charcoal age is not predictable from charcoal depth; soil charcoal records thus require many radiocarbon dates

Hypericum irazuense Kuntze ex N. Robson in the Buenavista and Chirripó páramos of Costa Rica: Photographs of Stem Cross Sections, Plants, and Study Sites

Hypericum irazuense Kuntze ex N. Robson is a common shrub in the high-elevation páramos that occur above treeline on the high peaks of the Cordillera de Talamanca in Costa Rica and westernmost Panama. In this report and accompanying high-resolution images we make available photographs of stem cross sections, plants, and habitats of H. irazuense in support of a recent study of the dendrochronological potential of the species (Kerr et al., forthcoming paper in Physical Geography) and other research on this plant and the páramo vegetation in which it occurs. We also include images from the Google EarthTM map server and portions of topographic maps showing locations of study sites

Fire History of the Appalachian Region: A Review and Synthesis

The importance of fire in shaping Appalachian vegetation has become increasingly apparent over the last 25 years. This period has seen declines in oak (Quercus) and pine (Pinus) forests and other fire-dependent ecosystems, which in the near-exclusion of fire are being replaced by fire-sensitive mesophytic vegetation. These vegetation changes imply that Appalachian vegetation had developed under a history of burning before the fire-exclusion era, a possibility that has motivated investigations of Appalachian fire history using proxy evidence. Here we synthesize those investigations to obtain an up-to-date portrayal of Appalachian fire history. We organize the report by data type, beginning with studies of high-resolution data on recent fires to provide a context for interpreting the lower-resolution proxy data. Each proxy is addressed in a subsequent chapter, beginning with witness trees and continuing to fire-scarred trees, stand age structure, and soil and sediment charcoal. Taken together, these proxies portray frequent burning in the past. Fires had occurred at short intervals (a few years) for centuries before the fire-exclusion era. Indeed, burning has played an important ecological role for millennia. Fires were especially common and spatially extensive on landscapes with large expanses of oak and pine forest, notably in the Ridge and Valley province and the Blue Ridge Mountains. Burning favored oak and pine at the expense of mesophytic competitors, but fire exclusion has enabled mesophytic plants to expand from fire-sheltered sites onto dry slopes that formerly supported pyrogenic vegetation. These changes underscore the need to restore fire-dependent ecosystems

Limnología inicial de Laguna Pozo Verde, Costa Rica: Batimetría, agua, sedimentos y diatomeas

Introducción : Costa Rica tiene cientos de lagos, muchos de los cuales nunca han sido estudiados científicamente.  Objetivo: Conocer limnológia  de la Laguna Pozo Verde en el Parque Nacional Juan Castro Blanco, Costa Rica (~1935 m de elevación), para proporcionar datos de referencia para estudiar cambios futuros. Métodos: Medimos la profundidad y temperatura del agua y la profundidad de Secchi; sedimentos superficiales analizados; y examinó mapas e imágenes de satélite. Resultados: Aunque algunos la describen como formada por procesos volcánicos, la Laguna Pozo Verde probablemente se formó en un deslizamiento de tierra, que ocurre con frecuencia en esta zona lluviosa en la empinada ladera sur del inactivo volcán Porvenir. Nuestros sondeos mostraron una profundidad máxima de 9,25 m cerca del centro del lago. El agua era moderadamente transparente (profundidad de Secchi 2,6 m), con pH circunneutro y temperaturas de 15,9 a 18,1 °C, con estratificación débil a 0,5 m. Los sedimentos superficiales contenían 27% de materia orgánica y tenían relaciones C/N y valores de isótopos de carbono estables consistentes con algas lacustres y plantas C 3 ; Surirella angusta compuso más del 90% de las diatomeas. Conclusión: La laguna es significativamente más omera de lo informado y los sedimentos superficiales albergar una combinación de diatomeas única entre los 88 lagos examinados en Costa Rica.Introducción: Costa Rica tiene cientos de lagos, muchos nunca estudiados científicamente. Objetivo: Conocer la limnología de Laguna Pozo Verde en el Parque Nacional Juan Castro Blanco, Costa Rica (~1935m de elevación), como referencia para estudiar futuros cambios. Métodos: Medimos la profundidad y temperatura del agua y la profundidad de Secchi; analizamos sedimentos superficiales; y examinamos mapas e imágenes satelitales. Resultados: Aunque algunos la describen como formada por procesos volcánicos, es probable que Laguna Pozo Verde se haya formado en un deslizamiento de tierra, algo común en esta zona lluviosa de la empinada ladera sur del Volcán Porvenir (inactivo). Hallamos una profundidad máxima de 9,25m cerca del centro. El agua era moderadamente transparente (profundidad de Secchi 2,6m), con un pH cercano a neutro y temperaturas de 15,9-18,1°C, y una débil estratificación a 0,5m. Los sedimentos superficiales contenían un 27% de materia orgánica y tenían cocientes C/N y valores de isótopos de carbono estables, coherentes con algas lacustres y plantas C 3 ; más del 90% de las diatomeas eran Surirella angusta . Conclusión: La laguna es significativamente más somera de lo informado y los sedimentos superficiales albergan una combinación de diatomeas única entre los 88 lagos examinados en Costa Rica

Recent changes in breast cancer incidence and risk factor prevalence in San Francisco Bay area and California women: 1988 to 2004

IntroductionHistorically, the incidence rate of breast cancer among non-Hispanic white women living in the San Francisco Bay area (SFBA) of California has been among the highest in the world. Substantial declines in breast cancer incidence rates have been documented in the United States and elsewhere during recent years. In light of these reports, we examined recent changes in breast cancer incidence and risk factor prevalence among non-Hispanic white women in the SFBA and other regions of California.MethodsAnnual age-adjusted breast cancer incidence and mortality rates (1988 to 2004) were obtained from the California Cancer Registry and analyzed using Joinpoint regression. Population-based risk factor prevalences were calculated using two data sources: control subjects from four case-control studies (1989 to 1999) and the 2001 and 2003 California Health Interview Surveys.ResultsIn the SFBA, incidence rates of invasive breast cancer increased 1.3% per year (95% confidence interval [CI], 0.7% to 2.0%) in 1988-1999 and decreased 3.6% per year (95% CI, 1.6% to 5.6%) in 1999-2004. In other regions of California, incidence rates of invasive breast cancer increased 0.8% per year (95% CI, 0.4% to 1.1%) in 1988-2001 and decreased 4.4% per year (95% CI, 1.4% to 7.3%) in 2001-2004. In both regions, recent (2000-2001 to 2003-2004) decreases in invasive breast cancer occurred only in women 40 years old or older and in women with all histologic subtypes and tumor sizes, hormone receptor-defined types, and all stages except distant disease. Mortality rates declined 2.2% per year (95% CI, 1.8% to 2.6%) from 1988 to 2004 in the SFBA and the rest of California. Use of estrogen-progestin hormone therapy decreased significantly from 2001 to 2003 in both regions. In 2003-2004, invasive breast cancer incidence remained higher (4.2%) in the SFBA than in the rest of California, consistent with the higher distributions of many established risk factors, including advanced education, nulliparity, late age at first birth, and alcohol consumption.ConclusionOngoing surveillance of breast cancer occurrence patterns in this high-risk population informs breast cancer etiology through comparison of trends with lower-risk populations and by highlighting the importance of examining how broad migration patterns influence the geographic distribution of risk factors

Machine learning uncovers the most robust self-report predictors of relationship quality across 43 longitudinal couples studies

Given the powerful implications of relationship quality for health and well-being, a central mission of relationship science is explaining why some romantic relationships thrive more than others. This large-scale project used machine learning (i.e., Random Forests) to 1) quantify the extent to which relationship quality is predictable and 2) identify which constructs reliably predict relationship quality. Across 43 dyadic longitudinal datasets from 29 laboratories, the top relationship-specific predictors of relationship quality were perceived-partner commitment, appreciation, sexual satisfaction, perceived-partner satisfaction, and conflict. The top individual-difference predictors were life satisfaction, negative affect, depression, attachment avoidance, and attachment anxiety. Overall, relationship-specific variables predicted up to 45% of variance at baseline, and up to 18% of variance at the end of each study. Individual differences also performed well (21% and 12%, respectively). Actor-reported variables (i.e., own relationship-specific and individual-difference variables) predicted two to four times more variance than partner-reported variables (i.e., the partner’s ratings on those variables). Importantly, individual differences and partner reports had no predictive effects beyond actor-reported relationship-specific variables alone. These findings imply that the sum of all individual differences and partner experiences exert their influence on relationship quality via a person’s own relationship-specific experiences, and effects due to moderation by individual differences and moderation by partner-reports may be quite small. Finally, relationship-quality change (i.e., increases or decreases in relationship quality over the course of a study) was largely unpredictable from any combination of self-report variables. This collective effort should guide future models of relationships

Symbols of Power: The Firearm Paintings of Madjedbebe (Malakunanja II)

Depictions of firearms in Australian Aboriginal rock art provide a unique opportunity to archaeologically explore the roles that this type of material culture played in times of culture contact. From the earliest interactions with explorers to the buffalo shooting enterprises of the twentieth century—firearms played complex and shifting roles in western Arnhem Land Aboriginal societies. The site of Madjedbebe (sometimes referred to as Malakunanja II in earlier academic literature) in Jabiluka (Mirarr Country), offers the opportunity to explore these shifting roles over time with an unprecedented 16 paintings of firearms spanning the nineteenth and twentieth centuries. This rock art provides evidence for early firearms as objects of curiosity and threat to local groups, as well as evidence for later personal ownership and use of such weaponry. Moreover, we argue that the rock art suggests increasing incorporation of firearms into traditional cultural belief and artistic systems over time with Madjedbebe playing a key role in the communication of the cultural meanings behind this new subject matter.Arts, Education & Law Group, School of Humanities, Languages and Social SciencesFull Tex

Effects of cooling and internal wave motions on gas transfer coefficients in a boreal lake

Peer reviewe

Dissecting the Shared Genetic Architecture of Suicide Attempt, Psychiatric Disorders, and Known Risk Factors

Background Suicide is a leading cause of death worldwide, and nonfatal suicide attempts, which occur far more frequently, are a major source of disability and social and economic burden. Both have substantial genetic etiology, which is partially shared and partially distinct from that of related psychiatric disorders. Methods We conducted a genome-wide association study (GWAS) of 29,782 suicide attempt (SA) cases and 519,961 controls in the International Suicide Genetics Consortium (ISGC). The GWAS of SA was conditioned on psychiatric disorders using GWAS summary statistics via multitrait-based conditional and joint analysis, to remove genetic effects on SA mediated by psychiatric disorders. We investigated the shared and divergent genetic architectures of SA, psychiatric disorders, and other known risk factors. Results Two loci reached genome-wide significance for SA: the major histocompatibility complex and an intergenic locus on chromosome 7, the latter of which remained associated with SA after conditioning on psychiatric disorders and replicated in an independent cohort from the Million Veteran Program. This locus has been implicated in risk-taking behavior, smoking, and insomnia. SA showed strong genetic correlation with psychiatric disorders, particularly major depression, and also with smoking, pain, risk-taking behavior, sleep disturbances, lower educational attainment, reproductive traits, lower socioeconomic status, and poorer general health. After conditioning on psychiatric disorders, the genetic correlations between SA and psychiatric disorders decreased, whereas those with nonpsychiatric traits remained largely unchanged. Conclusions Our results identify a risk locus that contributes more strongly to SA than other phenotypes and suggest a shared underlying biology between SA and known risk factors that is not mediated by psychiatric disorders.Peer reviewe