Radiocarbon bomb-peak signal in tree-rings from the tropical Andes register low latitude atmospheric dynamics in the Southern Hemisphere.

South American tropical climate is strongly related to the tropical low-pressure belt associated with the South American monsoon system. Despite its central societal role as a modulating agent of rainfall in tropical South America, its long-term dynamical variability is still poorly understood. Here we combine a new (and world's highest) tree-ring 14C record from the Altiplano plateau in the central Andes with other 14C records from the Southern Hemisphere during the second half of the 20th century in order to elucidate the latitudinal gradients associated with the dissemination of the bomb 14C signal. Our tree-ring 14C record faithfully captured the bomb signal of the 1960's with an excellent match to atmospheric 14C measured in New Zealand but with significant differences with a recent record from Southeast Brazil located at almost equal latitude. These results imply that the spreading of the bomb signal throughout the Southern Hemisphere was a complex process that depended on atmospheric dynamics and surface topography generating reversals on the expected north-south gradient in certain years. We applied air-parcel modeling based on climate data to disentangle their different geographical provenances and their preformed (reservoir affected) radiocarbon content. We found that air parcel trajectories arriving at the Altiplano during the bomb period were sourced i) from the boundary layer in contact with the Pacific Ocean (41%), ii) from the upper troposphere (air above the boundary layer, with no contact with oceanic or continental carbon reservoirs) (38%) and iii) from the Amazon basin (21%). Based on these results we estimated the ∆14C endmember values for the different carbon reservoirs affecting our record which suggest that the Amazon basin biospheric 14C isoflux could have been reversed from negative to positive as early as the beginning of the 1970's. This would imply a much faster carbon turnover rate in the Amazon than previously modelled.

Six hundred years of South American tree rings reveal an increase in severe hydroclimatic events since mid-20th century.

South American (SA) societies are highly vulnerable to droughts and pluvials, but lack of long-term climate observations severely limits our understanding of the global processes driving climatic variability in the region. The number and quality of SA climate-sensitive tree ring chronologies have significantly increased in recent decades, now providing a robust network of 286 records for characterizing hydroclimate variability since 1400 CE. We combine this network with a self-calibrated Palmer Drought Severity Index (scPDSI) dataset to derive the South American Drought Atlas (SADA) over the continent south of 12°S. The gridded annual reconstruction of austral summer scPDSI is the most spatially complete estimate of SA hydroclimate to date, and well matches past historical dry/wet events. Relating the SADA to the Australia-New Zealand Drought Atlas, sea surface temperatures and atmospheric pressure fields, we determine that the El Niño-Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) are strongly associated with spatially extended droughts and pluvials over the SADA domain during the past several centuries. SADA also exhibits more extended severe droughts and extreme pluvials since the mid-20th century. Extensive droughts are consistent with the observed 20th-century trend toward positive SAM anomalies concomitant with the weakening of midlatitude Westerlies, while low-level moisture transport intensified by global warming has favored extreme rainfall across the subtropics. The SADA thus provides a long-term context for observed hydroclimatic changes and for 21st-century Intergovernmental Panel on Climate Change (IPCC) projections that suggest SA will experience more frequent/severe droughts and rainfall events as a consequence of increasing greenhouse gas emissions.

Multidecadal environmental pollution in a mega-industrial area in central Chile registered by tree rings.

One of the most polluted areas in Chile is the Ventanas Industrial Area (VIA; 32.74°S / 71.48°W), which started in 1958 and today comprises around 16 industries in an area of ca. 4 km2. A lack of consistent long-term instrumental records precludes assessing the history of contamination in the area and also limits the evaluation of mitigation actions taken since the late 1980s. Here, we use dendrochemistry as an environmental proxy to analyze environmental changes over several decades at the VIA. We present chemical measurements of tree rings from planted, exotic Cupressus macrocarpa growing near the VIA with 4-year resolution over a period of 52 years (1960-2011). These data provide unprecedented information on regional anthropogenic pollution and are compared with a tree-ring elemental record of 48 years (1964-2011) from the Isla Negra (INE) control site not exposed to VIA emissions. For the 48 years of overlap between both sites, higher concentrations of Zn, V, Co, Cd, Ag, Fe, Cr, and Al were especially registered after the year 2000 at VIA compared to INE for the periods under study. Concentrations of Pb, Cu, As, Fe, Mo, Cr, and Zn increased through time, particularly over the period 1980-1990. Decontamination plans activated in 1992 appear to have had a positive effect on the amount of some elements, but the chemical concentration in the tree rings suggest continued accumulation of pollutants in the environment. Only after several years of implementation of the mitigation measures have some elements tended to decrease in concentration, especially at the end of the evaluated period. Dendrochemistry is a useful tool to provide a long-term perspective of the dynamics of trace metal pollution and represents a powerful approach to monitor air quality variability to extend the instrumental records back in time.

Association of comorbidity and health service usage among patients with dementia in the UK: a population-based study.

BACKGROUND: The majority of people with dementia have other long-term diseases, the presence of which may affect the progression and management of dementia. This study aimed to identify subgroups with higher healthcare needs, by analysing how primary care consultations, number of prescriptions and hospital admissions by people with dementia varies with having additional long-term diseases (comorbidity). METHODS: A retrospective cohort study based on health data from the Clinical Practice Research Datalink (CPRD) was conducted. Incident cases of dementia diagnosed in the year starting 1/3/2008 were selected and followed for up to 5 years. The number of comorbidities was obtained from a set of 34 chronic health conditions. Service usage (primary care consultations, hospitalisations and prescriptions) and time-to-death were determined during follow-up. Multilevel negative binomial regression and Cox regression, adjusted for age and gender, were used to model differences in service usage and death between differing numbers of comorbidities. RESULTS: Data from 4999 people (14 866 person-years of follow-up) were analysed. Overall, 91.7% of people had 1 or more additional comorbidities. Compared with those with 2 or 3 comorbidities, people with ≥6 comorbidities had higher rates of primary care consultations (rate ratio (RR) 1.31, 95% CI 1.25 to 1.36), prescriptions (RR 1.68, 95% CI 1.57 to 1.81), and hospitalisation (RR 1.62, 95% CI 1.44 to 1.83), and higher risk of death (HR 1.56, 95% CI 1.37 to 1.78). DISCUSSION: In the UK, people with dementia with higher numbers of comorbidities die earlier and have considerably higher health service usage in terms of primary care consultations, hospital admissions and prescribing. This study provides strong evidence that comorbidity is a key factor that should be considered when allocating resources and planning care for people with dementia.

Coupled Socio-Environmental Changes Triggered Indigenous Aymara Depopulation of the Semiarid Andes of Tarapacá-Chile during the Late 19th-20th Centuries.

Socio-economic and environmental changes are well known causes of demographic collapse of agrarian cultures. The collapse of human societies is a complex phenomenon where historical and cultural dimensions play a key role, and they may interact with the environmental context. However, the importance of the interaction between socio-economic and climatic factors in explaining possible breakdowns in Native American societies has been poorly explored. The aim of this study is to test the role of socio-economic causes and rainfall variability in the collapse suffered by the Aymara people of the semiarid Andean region of Tarapacá during the period 1820-1970. Our motivation is to demonstrate that simple population dynamic models can be helpful in understanding the causes and relative importance of population changes in Andean agro-pastoral societies in responses to socio-environmental variability. Simple logistic models that combine the effects of external socio-economic causes and past rainfall variability (inferred from Gross Domestic Product [GDP] and tree-rings, respectively) were quite accurate in predicting the sustained population decline of the Aymara people. Our results suggest that the depopulation in the semiarid Tarapacá province was caused by the interaction among external socio-economic pressures given by the economic growth of the lowlands and demands for labor coupled with a persistent decline in rainfall. This study constitutes an example of how applied ecological knowledge, in particular the application of the logistic equation and theories pertaining to nonlinear population dynamics and exogenous perturbations, can be used to better understand major demographic changes in human societies.

Genetic structure, behaviour and invasion history of the Argentine ant supercolony in Australia.

Biological invasions have significant ecological, evolutionary and economic consequences. Ants are exemplary invaders and their invasion success is frequently attributed to a shift in social structure between native and introduced populations. Here, we use a multidisciplinary approach to determine the social structure, origin and expansion of the invasive Argentine ant, Linepithema humile, in Australia by linking behavioural and genetic studies with indicators of dispersal pathways and propagule pressure. Behavioural assays revealed a complete absence of aggression within and between three cities - Melbourne, Adelaide and Perth - spanning 2700 km across Australia. Microsatellite analyses showed intracity genetic homogeneity and limited but significant intercity genetic differentiation. Exceptions were two Perth nests that likely represent independent translocations from Adelaide. These patterns suggest efficient local gene flow with more limited jump dispersal via transport corridors between cities. Microsatellite analyses of L. humile from potential source regions, combined with data from port interceptions, trade pathways and the timeline of spread within Australia, implicate the main European supercolony as the source of L. humile in Melbourne. Such an introduction probably then redistributed across Australia and spread to New Zealand to form an expansive Australasian supercolony.

Functional disconnection of the substantia nigra pars compacta from the pedunculopontine nucleus impairs learning of a conditioned avoidance task.

The pedunculopontine tegmental nucleus (PPTg) targets nuclei in the basal ganglia, including the substantia nigra pars compacta (SNc), in which neuronal loss occurs in Parkinson's disease, a condition in which patients show cognitive as well as motor disturbances. Partial loss and functional abnormalities of neurons in the PPTg are also associated with Parkinson's disease. We hypothesized that the interaction of PPTg and SNc might be important for cognitive impairments and so investigated whether disrupting the connections between the PPTg and SNc impaired learning of a conditioned avoidance response (CAR) by male Wistar rats. The following groups were tested: PPTg unilateral; SNc unilateral; PPTg-SNc ipsilateral (ipsilateral lesions in PPTg and SNc); PPTg-SNc contralateral (contralateral lesions in PPTg and SNc); sham lesions (of each type). SNc lesions were made with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine HCl (MPTP, 0.6micromol); PPTg lesions with ibotenate (24nmol). After recovery, all rats underwent 50-trial sessions of 2-way active avoidance conditioning for 3 consecutive days. Rats with unilateral lesions in PPTg or SNc learnt this, however rats with contralateral (but not ipsilateral) combined lesions in both structures presented no sign of learning. This effect was not likely to be due to sensorimotor impairment because lesions did not affect reaction time to the tone or footshock during conditioning. However, an increased number of non-responses were observed in the rats with contralateral lesions. The results support the hypothesis that a functional interaction between PPTg and SNc is needed for CAR learning and performance.

Surveillance of HIV risk and prevention behaviors of men who have sex with men--a national application of venue-based, time-space sampling.

In collaboration with the Centers for Disease Control and Prevention, participating state and local health departments, universities, and community-based organizations applied venue-based, time-space sampling methods for the first wave of National HIV Behavioral Surveillance of men who have sex with men (NHBS-MSM). Conducted in 17 metropolitan areas in the United States and Puerto Rico from November 2003 through April 2005, NHBS-MSM methods included: (1) formative research to learn the venues, times, and methods to recruit MSM; (2) monthly sampling frames of eligible venues and day-time periods that met attendance, logistical, and safety criteria; and (3) recruitment of participants in accordance with randomly generated venue calendars. Participants were interviewed on HIV risk and prevention behaviors, referred to care when needed, and compensated for their time. By identifying the prevalence and trends of HIV risk and prevention behaviors, NHBS-MSM data may be used at local, state, and federal levels to help obtain, direct, and evaluate HIV prevention resources for MSM.

Are Brazil nuts attractive?

We present event-driven simulation results for single and multiple intruders in a vertically vibrated granular bed. Under our vibratory conditions, the mean vertical position of a single intruder is governed primarily by a buoyancylike effect. Multiple intruders also exhibit buoyancy governed behavior; however, multiple neutrally buoyant intruders cluster spontaneously and undergo horizontal segregation. These effects can be understood by considering the dynamics of two neutrally buoyant intruders. We have measured an attractive force between such intruders which has a range of five intruder diameters, and we provide a mechanistic explanation for the origins of this force.

FOOD CONCENTRATION AND TEMPERATURE EFFECTS ON LIFE CYCLE CHARACTERISTICS OF TROPICAL CLADOCERA (Daphnia gessneri Herbst, Diaphanosoma sarsi Richard, Moina reticulata (Daday)): I. DEVELOPMENT TIME

The effects of food concentration and temperature on embryonic and postem-bryonic duration of three tropical species, Daphnia gessneri(1.5mm), Diaphanosoma sarsi(1.2mm) and Moina reticulata(0.8mm), were investigated as part of life cycle studies which included growth, body size and reproduction. These are the very first experimental studies undertaken on these species. The long-term growth experiments were performed under controlled laboratory conditions at all combinations of temperature (22"C, 27"C and 32"C) and constant food concentration (0.03, 0.05, 0.10, 0.25, 0.50 and 1.00 mgC/L) of the unicellular green alga Scenedesmus acutus.Animals were examined twice daily throughout their life cycle from the neonate to third adult instar. In all three species, temperature exerted the most powerful influence on embryonic duration but there was also a smaller food effect. In D. gessneri,postembry-onic durations remained more or less the same at food levels 0.25 mgC/L but were influenced by temperature. At food concentrations of 0.1 mgC/L or lower, postembryonic durations became increasingly prolonged, particularly at high temperatures. This threshold concentration is affected by temperature: in D. gessneri,it was 0.1 mgC/L at 22oC and 27oC but higher at 32oC (between 0.25 and 0.50 mgC/L). At the same temperature of 27oC, the food threshold level varied between species: it was higher (0.25 mgC/L) for D. sarsiand lower (0.05 mgC/L) for M. reticulatacompared with D. gessneri(0.1 mgC/L). In both embryonic and postembryonic durations there is a body size effect as the absolute durations were longest in the largest species and shortest in the smallest species In all three species, prolongation of postembryonic duration at combinations of high temperature and lowered food levels was accompanied by increased number of juvenile instars.

Os efeitos de temperatura e concentração de alimento na duração do desenvolvimento embrionário e postembrionário de três espécies tropicais, Daphnia gessneri(1.5mm), Diaphanosoma sarsi(1.2mm) and Moina reticulata(0.8mm), foram investigados como parte dos estudos de ciclo de vida incluindo crescimento, tamanho do corpo e reprodução. Estes são os primeiros estudos experimentais realizados com estas espécies. Os experimentos de crescimento de longa duração foram feitos em condições controladas de laboratório em todas as combinações de temperature (22°C, 27°C e 32°C) e concentração constante de alimento (0.03, 0.05,0.10,0.25, 0.50 and 1.00 mgC/L) de alga verde unicelular Scenedesmus acutus.Os animais foram analisados duas vezes por dia durante o ciclo de vida desde neonata ao terceiro estádio adulto. Nas três espécies, a temperatura exerceu um maior efeito no tempo do desenvolvimento embrionário mas ocorreu também um pequeno efeito de concentração de alimento. Em Daphnia gessneri, a duração postembriônica permaneceu mais ou menos a mesma na concentração de alimento de 0.25 mgC/L mas foi influenciada pela temperature. Na concentração de 0.1 mgC/L ou mais baixa, a duração postembrionária tornou-se mais prolongada, particularmente em alta temperatura. O valor absoluto do nivel crítico de concentração de alimento foi afetado pela temperatura: em D. gessneri, foi 0.1 mgC/L em 22°C e 27°C mas aumentou em 32°C (entre 0.25 e 0.50 mgC/L). Na mesma temperatura de 27°C, o nivel crítico de alimento variou entre as espécies: foi mais alta (0.25 mgC/L) para D. sarsi e mais baixa (0.05 mgC/L) para M. reticulata comparada com D. gessneri (0.1 mgC/L). Em ambos, no desenvolvimento embrionário e postembrionário ocorreu o efeito do tamanho do corpo visto que as durações absolutas foram mais longas nas espécies maiores e mais curtas.na espécie menor. Nas três espécies, o prolongamento do desenvolvimento postembrionário nas combinações de alta temperatura e menores concentrações de alimento foi acompanhado por aumento no número de estádios juvenis.

FOOD CONCENTRATION AND TEMPERATURE EFFECTS ON LIFE CYCLE CHARACTERISTICS OF TROPICAL CLADOCERA (Daphnia gessneri Herbst, Diaphanosoma sarsi Richard, Moina reticulata (Daday)): I. DEVELOPMENT TIME

The effects of food concentration and temperature on embryonic and postem-bryonic duration of three tropical species, Daphnia gessneri(1.5mm), Diaphanosoma sarsi(1.2mm) and Moina reticulata(0.8mm), were investigated as part of life cycle studies which included growth, body size and reproduction. These are the very first experimental studies undertaken on these species. The long-term growth experiments were performed under controlled laboratory conditions at all combinations of temperature (22"C, 27"C and 32"C) and constant food concentration (0.03, 0.05, 0.10, 0.25, 0.50 and 1.00 mgC/L) of the unicellular green alga Scenedesmus acutus.Animals were examined twice daily throughout their life cycle from the neonate to third adult instar. In all three species, temperature exerted the most powerful influence on embryonic duration but there was also a smaller food effect. In D. gessneri,postembry-onic durations remained more or less the same at food levels 0.25 mgC/L but were influenced by temperature. At food concentrations of 0.1 mgC/L or lower, postembryonic durations became increasingly prolonged, particularly at high temperatures. This threshold concentration is affected by temperature: in D. gessneri,it was 0.1 mgC/L at 22oC and 27oC but higher at 32oC (between 0.25 and 0.50 mgC/L). At the same temperature of 27oC, the food threshold level varied between species: it was higher (0.25 mgC/L) for D. sarsiand lower (0.05 mgC/L) for M. reticulatacompared with D. gessneri(0.1 mgC/L). In both embryonic and postembryonic durations there is a body size effect as the absolute durations were longest in the largest species and shortest in the smallest species In all three species, prolongation of postembryonic duration at combinations of high temperature and lowered food levels was accompanied by increased number of juvenile instars.

Os efeitos de temperatura e concentração de alimento na duração do desenvolvimento embrionário e postembrionário de três espécies tropicais, Daphnia gessneri(1.5mm), Diaphanosoma sarsi(1.2mm) and Moina reticulata(0.8mm), foram investigados como parte dos estudos de ciclo de vida incluindo crescimento, tamanho do corpo e reprodução. Estes são os primeiros estudos experimentais realizados com estas espécies. Os experimentos de crescimento de longa duração foram feitos em condições controladas de laboratório em todas as combinações de temperature (22°C, 27°C e 32°C) e concentração constante de alimento (0.03, 0.05,0.10,0.25, 0.50 and 1.00 mgC/L) de alga verde unicelular Scenedesmus acutus.Os animais foram analisados duas vezes por dia durante o ciclo de vida desde neonata ao terceiro estádio adulto. Nas três espécies, a temperatura exerceu um maior efeito no tempo do desenvolvimento embrionário mas ocorreu também um pequeno efeito de concentração de alimento. Em Daphnia gessneri, a duração postembriônica permaneceu mais ou menos a mesma na concentração de alimento de 0.25 mgC/L mas foi influenciada pela temperature. Na concentração de 0.1 mgC/L ou mais baixa, a duração postembrionária tornou-se mais prolongada, particularmente em alta temperatura. O valor absoluto do nivel crítico de concentração de alimento foi afetado pela temperatura: em D. gessneri, foi 0.1 mgC/L em 22°C e 27°C mas aumentou em 32°C (entre 0.25 e 0.50 mgC/L). Na mesma temperatura de 27°C, o nivel crítico de alimento variou entre as espécies: foi mais alta (0.25 mgC/L) para D. sarsi e mais baixa (0.05 mgC/L) para M. reticulata comparada com D. gessneri (0.1 mgC/L). Em ambos, no desenvolvimento embrionário e postembrionário ocorreu o efeito do tamanho do corpo visto que as durações absolutas foram mais longas nas espécies maiores e mais curtas.na espécie menor. Nas três espécies, o prolongamento do desenvolvimento postembrionário nas combinações de alta temperatura e menores concentrações de alimento foi acompanhado por aumento no número de estádios juvenis.