The APOE e4 allele, which confers an increased risk of developing dementia in older adulthood, has been associated with enhanced cognitive performance in younger adults. An objective of the current ...study was to compare task-related behavioural and neural signatures for e4 carriers (e4+) and non-e4 carriers (e4−) to help elucidate potential mechanisms behind such cognitive differences. On two measures of attention, we recorded clear behavioural advantages in young adult e4+ relative to e4−, suggesting that e4+ performed these tasks with a wider field of attention. Behavioural advantages were associated with increased task-related brain activations detected by fMRI (BOLD). In addition, behavioural measures correlated with structural measures derived from a former DTI analysis of white matter integrity in our cohort. These data provide clear support for an antagonistic pleiotropy hypothesis — that the e4 allele confers some cognitive advantage in early life despite adverse consequences in old age. The data implicate differences in both structural and functional signatures as complementary mediators of the behavioural advantage.
► We explore behavioural and neural profiles of APOE e4-positive young adults. ► We found that young adult e4+ show sustained and covert attention advantages. ► Functional imaging results indicate greater task-related activation in e4s. ► Behavioural performance also correlated with indices of white matter coherence. ► These data provide clear support for an antagonistic pleiotropy hypothesis.
Dam removal: Listening in Foley, M. M.; Bellmore, J. R.; O'Connor, J. E. ...
Water resources research,
July 2017, 2017-07-00, 20170701, Letnik:
53, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Dam removal is widely used as an approach for river restoration in the United States. The increase in dam removals—particularly large dams—and associated dam‐removal studies over the last few decades ...motivated a working group at the USGS John Wesley Powell Center for Analysis and Synthesis to review and synthesize available studies of dam removals and their findings. Based on dam removals thus far, some general conclusions have emerged: (1) physical responses are typically fast, with the rate of sediment erosion largely dependent on sediment characteristics and dam‐removal strategy; (2) ecological responses to dam removal differ among the affected upstream, downstream, and reservoir reaches; (3) dam removal tends to quickly reestablish connectivity, restoring the movement of material and organisms between upstream and downstream river reaches; (4) geographic context, river history, and land use significantly influence river restoration trajectories and recovery potential because they control broader physical and ecological processes and conditions; and (5) quantitative modeling capability is improving, particularly for physical and broad‐scale ecological effects, and gives managers information needed to understand and predict long‐term effects of dam removal on riverine ecosystems. Although these studies collectively enhance our understanding of how riverine ecosystems respond to dam removal, knowledge gaps remain because most studies have been short (< 5 years) and do not adequately represent the diversity of dam types, watershed conditions, and dam‐removal methods in the U.S.
Key Points
Dam removal is an increasingly common approach to river restoration in the United States
Dam‐removal studies provide insights on key controls influencing the physical and ecological responses to dam removal
Although many aspects of physical and ecological systems react quickly to dam removal, overall response trajectories depend on how and where dams are removed and overall watershed conditions
Individuals often avoid or delay seeking professional help for mental health problems. Stigma may be a key deterrent to help-seeking but this has not been reviewed systematically. Our systematic ...review addressed the overarching question: What is the impact of mental health-related stigma on help-seeking for mental health problems? Subquestions were: (a) What is the size and direction of any association between stigma and help-seeking? (b) To what extent is stigma identified as a barrier to help-seeking? (c) What processes underlie the relationship between stigma and help-seeking? (d) Are there population groups for which stigma disproportionately deters help-seeking?
Five electronic databases were searched from 1980 to 2011 and references of reviews checked. A meta-synthesis of quantitative and qualitative studies, comprising three parallel narrative syntheses and subgroup analyses, was conducted.
The review identified 144 studies with 90,189 participants meeting inclusion criteria. The median association between stigma and help-seeking was d = - 0.27, with internalized and treatment stigma being most often associated with reduced help-seeking. Stigma was the fourth highest ranked barrier to help-seeking, with disclosure concerns the most commonly reported stigma barrier. A detailed conceptual model was derived that describes the processes contributing to, and counteracting, the deterrent effect of stigma on help-seeking. Ethnic minorities, youth, men and those in military and health professions were disproportionately deterred by stigma.
Stigma has a small- to moderate-sized negative effect on help-seeking. Review findings can be used to help inform the design of interventions to increase help-seeking.
‘Skinny Milky Way please’, says Sagittarius Gibbons, S. L. J; Belokurov, V; Evans, N. W
Monthly notices of the Royal Astronomical Society,
12/2014, Letnik:
445, Številka:
4
Journal Article
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Motivated by recent observations of the Sagittarius stream, we devise a rapid algorithm to generate faithful representations of the centroids of stellar tidal streams formed in a disruption of a ...progenitor of an arbitrary mass in an arbitrary potential. Our method works by releasing swarms of test particles at the Lagrange points around the satellite and subsequently evolving them in a combined potential of the host and the progenitor. We stress that the action of the progenitor's gravity is crucial to making streams that look almost indistinguishable from the N-body realizations, as indeed ours do. The method is tested on mock stream data in three different Milky Way potentials with increasing complexity, and is shown to deliver unbiased inference on the Galactic mass distribution out to large radii. When applied to the observations of the Sagittarius stream, our model gives a natural explanation of the stream's apocentric distances and the differential orbital precession. We, therefore, provide a new independent measurement of the Galactic mass distribution beyond 50 kpc. The Sagittarius stream model favours a light Milky Way with the mass 4.1 ± 0.4 × 1011 M⊙ at 100 kpc, which can be extrapolated to 5.6 ± 1.2 × 1011 M⊙ at 200 kpc. Such a low mass for the Milky Way Galaxy is in good agreement with estimates from the kinematics of halo stars and from the satellite galaxies (once Leo I is removed from the sample). It entirely removes the ‘Too Big To Fail Problem’.
We use the Sloan Digital Sky Survey/SEGUE spectroscopic sample of stars in the leading and trailing streams of the Sagittarius (Sgr) to demonstrate the existence of two sub-populations with distinct ...chemistry and kinematics. The metallicity distribution function (MDF) of the trailing stream is decomposed into two Gaussians describing a metal-rich sub-population with means and dispersions (-0.74, 0.18) dex and a metal-poor with (-1.33, 0.27) dex. The metal-rich sub-population has a velocity dispersion ~8 km s super( -1), whilst the metal-poor is nearly twice as hot ~13 km s super( -1). For the leading stream, the MDF is again well described by a superposition of two Gaussians, though somewhat shifted as compared to the trailing stream. The metal-rich has mean and dispersion (-1.00, 0.34) dex, the metal-poor (-1.39, 0.22) dex. The velocity dispersions are inflated by projection effects to give 15-30 kms super( -1) for the metal-poor, and 6-20 kms super( -1) for the metal-rich, depending on longitude. We infer that, like many dwarf spheroidals, the Sgr progenitor possessed a more extended, metal-poor stellar component and less extended, metal-rich one. We study the implications of this result for the progenitor mass by simulating the disruption of the Sgr, represented as King light profiles in dark haloes of masses between 10 super( 10) and 10 super( 11) M..., in a three-component Milky Way whose halo is a live Truncated Flat potential in the first phase of accretion and a triaxial Law & Majewski model in the second phase. We show that that the dark halo of the Sgr must have been ... 6 x 10 super( 10) M... to reproduce the run of velocity dispersion with longitude for the metal-rich and metal-poor sub-populations in the tails. (ProQuest: ... denotes formulae/symbols omitted.)
Initial Observations by the GOLD Mission Eastes, R. W.; McClintock, W. E.; Burns, A. G. ...
Journal of geophysical research. Space physics,
July 2020, Letnik:
125, Številka:
7
Journal Article
Recenzirano
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The NASA Global‐scale Observations of the Limb and Disk (GOLD) mission has flown an ultraviolet‐imaging spectrograph on SES‐14, a communications satellite in geostationary orbit at 47.5°W longitude. ...That instrument observes the Earth's far ultraviolet (FUV) airglow at ~134–162 nm using two identical channels. The observations performed include limb scans, stellar occultations, and images of the sunlit and nightside disk from 6:10 to 00:40 universal time each day. Initial analyses reveal interesting and unexpected results as well as the potential for further studies of the Earth's thermosphere‐ionosphere system and its responses to solar‐geomagnetic forcing and atmospheric dynamics. Thermospheric composition ratios for major constituents, O and N2, temperatures near 160 km, and exospheric temperatures are retrieved from the daytime observations. Molecular oxygen (O2) densities are measured using stellar occultations. At night, emission from radiative recombination in the ionospheric F region is used to quantify ionospheric density variations in the equatorial ionization anomaly (EIA). Regions of depleted F region electron density are frequently evident, even during the current solar minimum. These depletions are caused by the “plasma fountain effect” and are associated with the instabilities, scintillations, or “spread F” seen in other types of observations, and GOLD makes unique observations for their study.
Plain Language Summary
The NASA Global‐scale Observations of the Limb and Disk (GOLD) mission has flown a dual‐channel, ultraviolet‐imaging spectrograph on SES‐14, a communications satellite in geostationary orbit at 47.5°W longitude. That instrument observes the Earth's far ultraviolet (FUV) airglow at ~134–162 nm. The observations performed include images of the Earth's sunlit and nightside disk, limb scans, and stellar occultations, from 6:10 to 00:40 universal time each day. Initial analyses reveal interesting and unexpected results as well as the potential for further studies of the Earth's thermosphere‐ionosphere system and its responses to solar‐geomagnetic forcing and atmospheric dynamics. Thermospheric temperatures and composition ratios for major constituents, O and N2, near 160‐km altitude and exospheric temperatures are retrieved from the daytime observations. Molecular oxygen (O2) densities are measured using stellar occultations. At night, emission from radiative recombination in the ionospheric F region is used to quantify ionospheric density variations in the equatorial ionization anomaly (EIA). Regions of depleted F region electron density are frequently evident in the EIA, even during the current solar minimum.
Key Points
GOLD makes global‐scale, synoptic measurements of the temperature, composition, and densities in the thermosphere‐ionosphere system
Most measurements by the GOLD instrument are made in one of four modes
The observations are providing new and surprising insights into the characteristics and behavior of the thermosphere and ionosphere
In many species, sexual differentiation is a vital prelude to reproduction, and disruption of this process can have severe fitness effects, including sterility. It is thus interesting that genetic ...systems governing sexual differentiation vary among-and even within-species. To understand these systems more, we investigated a rare example of a frog with three sex chromosomes: the Western clawed frog, Xenopus tropicalis. We demonstrate that natural populations from the western and eastern edges of Ghana have a young Y chromosome, and that a male-determining factor on this Y chromosome is in a very similar genomic location as a previously known female-determining factor on the W chromosome. Nucleotide polymorphism of expressed transcripts suggests genetic degeneration on the W chromosome, emergence of a new Y chromosome from an ancestral Z chromosome, and natural co-mingling of the W, Z, and Y chromosomes in the same population. Compared to the rest of the genome, a small sex-associated portion of the sex chromosomes has a 50-fold enrichment of transcripts with male-biased expression during early gonadal differentiation. Additionally, X. tropicalis has sex-differences in the rates and genomic locations of recombination events during gametogenesis that are similar to at least two other Xenopus species, which suggests that sex differences in recombination are genus-wide. These findings are consistent with theoretical expectations associated with recombination suppression on sex chromosomes, demonstrate that several characteristics of old and established sex chromosomes (e.g., nucleotide divergence, sex biased expression) can arise well before sex chromosomes become cytogenetically distinguished, and show how these characteristics can have lingering consequences that are carried forward through sex chromosome turnovers.
The Earth’s thermosphere and ionosphere constitute a dynamic system that varies daily in response to energy inputs from above and from below. This system can exhibit a significant response within an ...hour to changes in those inputs, as plasma and fluid processes compete to control its temperature, composition, and structure. Within this system, short wavelength solar radiation and charged particles from the magnetosphere deposit energy, and waves propagating from the lower atmosphere dissipate.
Understanding the global-scale response of the thermosphere-ionosphere
(
T-I
)
system to these drivers is essential to advancing our physical understanding of coupling between the space environment and the Earth’s atmosphere
. Previous missions have successfully determined how the “climate” of the T-I system responds. The Global-scale Observations of the Limb and Disk (GOLD) mission will determine how the “weather” of the T-I responds, taking the next step in understanding the coupling between the space environment and the Earth’s atmosphere. Operating in geostationary orbit, the GOLD imaging spectrograph will measure the Earth’s emissions from 132 to 162 nm. These measurements will be used image two critical variables—thermospheric temperature and composition, near 160 km—on the dayside disk at half-hour time scales. At night they will be used to image the evolution of the low latitude ionosphere in the same regions that were observed earlier during the day. Due to the geostationary orbit being used the mission observes the same hemisphere repeatedly, allowing the unambiguous separation of spatial and temporal variability over the Americas.
Around the globe several observatories are seeking the first direct detection of gravitational waves (GWs). These waves are predicted by Einstein's general theory of relativity and are generated, for ...example, by black-hole binary systems. Present GW detectors are Michelson-type kilometre-scale laser interferometers measuring the distance changes between mirrors suspended in vacuum. The sensitivity of these detectors at frequencies above several hundred hertz is limited by the vacuum (zero-point) fluctuations of the electromagnetic field. A quantum technology--the injection of squeezed light--offers a solution to this problem. Here we demonstrate the squeezed-light enhancement of GEO 600, which will be the GW observatory operated by the LIGO Scientific Collaboration in its search for GWs for the next 3-4 years. GEO 600 now operates with its best ever sensitivity, which proves the usefulness of quantum entanglement and the qualification of squeezed light as a key technology for future GW astronomy.
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