69 research outputs found
POLLEN NUTRITION, PESTICIDES, AND PATHOGENS: INTERACTIVE EFFECTS ON HONEY BEE HEALTH
While a variety of stressors influence honey bee (Apis mellifera) health, it is the additive and interactive effects of these factors on bee health that have been driving modern research. We devised a set of two experiments to test the effects of multiple stressors on honey bee health. First, we grew sunflowers to test the effects of drought stress and seed treatment on sunflower pollen. We fed the pollen collected from these sunflowers to cohorts of bees that were either infected or uninfected with the microsporidian pathogen Nosema ceranae to find that drought stressed pollen leads to increased mortality in infected bees. Next, we fed 37 experimental pollen diets of different floral varieties and pesticide loads to honey bees infected with N. ceranae, but we were unable to find a connection between diet variety and pesticide exposure on bee health
Cognitive Effort Avoidance in Veterans with Suicide Attempt Histories
Suicide attempts (SA) are increasing in the United States, especially in veterans. Discovering individual cognitive features of the subset of suicide ideators who attempt suicide is critical. Cognitive theories attribute SA to facile schema-based negative interpretations of environmental events. Over-general autobiographical memory and facile solutions in problem solving tasks in SA survivors suggest that aversion to expending cognitive effort may be a neurobehavioral marker of SA risk. In veterans receiving care for mood disorder, we compared cognitive effort discounting and evidence-gathering in a beads task between veterans with (SAHx+; n = 26) versus without (SAHx-; n = 22) a history of SA. Groups did not differ in depressed mood or in a proxy metric of premorbid intelligence. Compared to SAHx- participants, SAHx+ participants self-reported significantly more severe cognitive problems in most domains, and also eschewed choice to earn higher monetary reward if earning it required a slightly increased working memory (WM) demand relative to an easy WM task. There was no group difference, however, in extent of evidence-gathering before declaring a conclusion in a beads task. These preliminary data suggest that aversion to expenditure of cognitive effort, potentially as a component of cognitive difficulties, may be a marker for SA risk
On the stability of tidal streams in action space
In the Gaia era it is increasingly apparent that traditional static,
parameterized models are insufficient to describe the mass distribution of our
complex, dynamically evolving Milky Way (MW). In this work, we compare
different time-evolving and time-independent representations of the
gravitational potentials of simulated MW-mass galaxies from the FIRE-2 suite of
cosmological baryonic simulations. Using these potentials, we calculate actions
for star particles in tidal streams around three galaxies with varying merger
histories at each snapshot from 7 Gyr ago to the present day. We determine the
action-space coherence preserved by each model using the Kullback-Leibler
Divergence to gauge the degree of clustering in actions and the relative
stability of the clusters over time. We find that all models produce a
clustered action space for simulations with no significant mergers. However, a
massive (mass ratio prior to infall more similar than 1:8) interacting galaxy
not present in the model will result in mischaracterized orbits for stars most
affected by the interaction. The locations of the action space clusters (i.e.
the orbits of the stream stars) are only preserved by the time-evolving model,
while the time-independent models can lose significant amounts of information
as soon as 0.5--1 Gyr ago, even if the system does not undergo a significant
merger. Our results imply that reverse-integration of stream orbits in the MW
using a fixed potential is likely to give incorrect results if integrated
longer than 0.5 Gyr into the past
LMC-driven anisotropic boosts in stream--subhalo interactions
Dark Matter (DM) subhalos are predicted to perturb stellar streams; stream
morphologies and dynamics can constrain the mass distribution of subhalos.
Using FIRE-2 simulations of Milky Way-mass galaxies, we show that presence of a
Large Magellanic Cloud (LMC)--analog significantly changes stream-subhalo
encounter rates. Three key factors drive these changes. First, the LMC--analog
brings in many subhalos, increasing encounter rates for streams near the
massive satellite by up to 20--40%. Second, the LMC--analog displaces the host
from its center-of-mass (inducing reflex motion), causing a north-south
asymmetry in the density and radial velocity distribution of subhalos. This
asymmetry results in encounter rates varying by 50--70% across the sky at the
same distance. Finally, the LMC--mass satellite induces a density wake in the
host's DM halo, further boosting the encounter rates near the LMC--analog. We
also explore the influence of stream orbital properties, finding a 50% increase
in encounters for streams moving retrograde to the LMC--analog's orbit in the
opposite hemisphere. The dependence of encounter rates on stream location and
orbit has important implications for where to search for new streams with spurs
and gaps in the Milky Way.Comment: 26 pages, 15 figures, submitted to AP
On the co-rotation of Milky Way satellites: LMC-mass satellites induce apparent motions in outer halo tracers
Understanding the physical mechanism behind the formation of a co-rotating
thin plane of satellite galaxies, like the one observed around the Milky Way
(MW), has been challenging. The perturbations induced by a massive satellite
galaxy, like the Large Magellanic Cloud (LMC) provide valuable insight into
this problem. The LMC induces an apparent co-rotating motion in the outer halo
by displacing the inner regions of the halo with respect to the outer halo.
Using the Latte suite of FIRE-2 cosmological simulations of MW-mass galaxies,
we confirm that the apparent motion of the outer halo induced by the infall of
a massive satellite changes the observed distribution of orbital poles of
outer-halo tracers, including satellites. We quantify the changes in the
distribution of orbital poles using the two-point angular correlation function
and find that all satellites induce changes. However, the most massive
satellites with pericentric passages between 30-100kpc induce the largest
changes. The best LMC-like satellite analog shows the largest change in orbital
pole distribution. The dispersion of orbital poles decreases by 20{\deg} during
the first two pericentric passages. Even when excluding the satellites brought
in with the LMC-like satellite, there is clustering of orbital poles. These
results suggest that in the MW, the recent pericentric passage of the LMC
should have changed the observed distribution of orbital poles of all other
satellites. Therefore, studies of kinematically-coherent planes of satellites
that seek to place the MW in a cosmological context should account for the
existence of a massive satellite like the LMC.Comment: 20 pages, 10 figures. ApJ submitted, Comments are welcom
Social cartography and satellite-derived building coverage for post-census population estimates in difficult-to-access regions of Colombia
Democratizing Resource Governance Through Prior Consultations? Lessons from Bolivia’s Hydrocarbon Sector
Global estimates of pregnancies at risk of Plasmodium falciparum and Plasmodium vivax infection in 2020 and changes in risk patterns since 2000.
BACKGROUND: Women are at risk of severe adverse pregnancy outcomes attributable to Plasmodium spp. infection in malaria-endemic areas. Malaria control efforts since 2000 have aimed to reduce this burden of disease. METHODS: We used data from the Malaria Atlas Project and WorldPop to calculate global pregnancies at-risk of Plasmodium spp. infection. We categorised pregnancies as occurring in areas of stable and unstable P. falciparum and P. vivax transmission. We further stratified stable endemicity as hypo-endemic, meso-endemic, hyper-endemic, or holo-endemic, and estimated pregnancies at risk in 2000, 2005, 2010, 2015, 2017, and 2020. FINDINGS: In 2020, globally 120.4M pregnancies were at risk of P. falciparum, two-thirds (81.0M, 67.3%) were in areas of stable transmission; 85 2M pregnancies were at risk of P. vivax, 93.9% (80.0M) were in areas of stable transmission. An estimated 64.6M pregnancies were in areas with both P. falciparum and P. vivax transmission. The number of pregnancies at risk of each of P. falciparum and P. vivax worldwide decreased between 2000 and 2020, with the exception of sub-Saharan Africa, where the total number of pregnancies at risk of P. falciparum increased from 37 3M in 2000 to 52 4M in 2020. INTERPRETATION: Historic investments in malaria control have reduced the number of women at risk of malaria in pregnancy in all endemic regions except sub-Saharan Africa. Population growth in Africa has outpaced reductions in malaria prevalence. Interventions that reduce the risk of malaria in pregnancy are needed as much today as ever
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Spatiotemporal incidence of Zika and associated environmental drivers for the 2015-2016 epidemic in Colombia
Despite a long history of mosquito-borne virus epidemics in the Americas, the impact of the Zika virus (ZIKV) epidemic of 2015–2016 was unexpected. The need for scientifically informed decision-making is driving research to understand the emergence and spread of ZIKV. To support that research, we assembled a data set of key covariates for modeling ZIKV transmission dynamics in Colombia, where ZIKV transmission was widespread and the government made incidence data publically available. On a weekly basis between January 1, 2014 and October 1, 2016 at three administrative levels, we collated spatiotemporal Zika incidence data, nine environmental variables, and demographic data into a single downloadable database. These new datasets and those we identified, processed, and assembled at comparable spatial and temporal resolutions will save future researchers considerable time and effort in performing these data processing steps, enabling them to focus instead on extracting epidemiological insights from this important data set. Similar approaches could prove useful for filling data gaps to enable epidemiological analyses of future disease emergence events
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