81 research outputs found
Comparison of Thermal and Microwave Paleointensity Estimates in Specimens Displaying NonâIdeal Behavior in ThellierâStyle Paleointensity Experiments
Determining the strength of the ancient geomagnetic field is vital to our understanding of the core and geodynamo but obtaining reliable measurements of the paleointensity is fraught with difficulties. Over a quarter of magnetic field strength estimates within the global paleointensity database from 0â5 Ma come from HawaiÊ»i. Two previous studies on the SOH1 drill core gave inconsistent, apparently methodâdependent paleointensity estimates, with an average difference of 30%. The paleointensity methods employed in the two studies differed both in demagnetization mechanism (thermal or microwave radiation) and Thellierâstyle protocol (perpendicular and Original Thellier protocols) â both variables that could cause the strong differences in the estimates obtained. Paleointensity experiments have therefore been conducted on 79 specimens using the previously untested combinations of ThermalâPerpendicular and MicrowaveâOriginal Thellier methods to analyze the effects of demagnetization mechanism and protocol in isolation. We find that, individually, neither demagnetization mechanism nor protocol entirely explains the differences in paleointensity estimates. Specifically, we found that nonâideal multiâdomainâlike effects are enhanced using the Original Thellier protocol (independent of demagnetization mechanism), often resulting in paleointensity overestimation. However, we also find evidence, supporting recent findings from the 1960 Kilauea lava flow, that MicrowaveâPerpendicular experiments performed without pTRM checks can produce underestimates of the paleointensity due to unaccountedâfor sample alteration at higher microwave powers. Together, these findings support that the true paleointensities fall between the estimates previously published and emphasize the need for future studies (thermal or microwave) to use protocols with both pTRM checks and a means of detecting nonâideal grain effects
Reproducibility of archaeointensity determinations with a multimethod approach on archaeological material reproductions
Archaeointensity determinations on burnt archaeological material are complex and reliable data scarce, although this kind of material can be of great interest in archaeological investigations. With the goal of analysing the reliability of archaeointensity determinations, an interlaboratory comparison study has been performed combining different experimental protocols on present-day reproductions of Pre-Columbian Mesoamerican archaeological artefacts and two brick samples. Samples were baked in an original kiln from an artisan workshop in western Mexico. The ambient magnetic field at the site during the experiment was measured and continuous temperature data were recorded at four different positions in the kiln during the heatingâcooling procedure.
Archaeointensity determinations were carried out with four different methods at four different palaeomagnetic laboratories: ThellierâCoe (Burgos, Spain), microwave (Liverpool, UK), multispecimen (Morelia, Mexico) and multispecimen with the extended protocols for fraction and domain-state correction (Montpellier, France). 26 conventional resistive heating determinations with the ThellierâCoe protocol yielded a 100 per cent success rate, while 7 out of 8 microwave-heating determinations with the ThellierâCoe protocol also provided successful results. Also, two multispecimen determinations performed with both multispecimen methods provided statistically reliable results. In all cases, a good agreement between the determined archaeointensities and the ambient field at the production site could be observed.
Highly reversible magnetization-versus-temperature curves yielded slightly Al, Mg or Ti-substituted magnetite as the main ferromagnetic (s.l.) phase. In addition, in several samples, a thermally stable low Curie-temperature phase displaying a high coercivity behaviour could be observed in thermomagnetic curves and by thermal demagnetization of saturation isothermal remanent magnetization. This phase is interpreted as Δ-Fe2O3. To our knowledge, its occurrence has never been reported through the experimental recreation of burnt archaeological materials. No correlation could be observed between the proxies of domain-state behaviour and deviation of palaeointensity determinations from the expected result.
Results obtained on clay samples heated in this type of ancient kiln can be considered a good source for determining the geomagnetic field strength variation in the past. Matching palaeointensity results obtained with different methods based on different principles can be taken as a quality criterion for result reliability and consistency.Projects BU0066U16 and BU235P18 (Junta de Castilla y LeĂłn, Spain) and the European Regional Development Fund (ERDF). AG is grateful for financial support of CONACyT 252149 and UNAM-PAPIIT project 101717. The GeÌosciences Montpellier survey was supported by a grant from the CNRS-PNP. The FUReMAG rapid furnace construction was supported by the French National Agency for Research (ANR-12-BS06â0015)
The Spectrally Resolved Lyman-alpha Emission of Three Lyman-alpha Selected Field Galaxies at z~2.4 from the HETDEX Pilot Survey
We present new results on the spectrally resolved Lyman-alpha (LyA) emission
of three LyA emitting field galaxies at z~2.4 with high LyA equivalent width
(>100 Angstroms) and LyA luminosity (~10^43 erg/s). At 120 km/s (FWHM) spectral
resolution, the prominent double-peaked LyA profile straddles the systemic
velocity, where the velocity zero-point is determined from spectroscopy of the
galaxies' rest-frame optical nebular emission lines. The average velocity
offset from systemic of the stronger redshifted emission component for our
sample is 176 km/s while the average total separation between the redshifted
and main blueshifted emission components is 380 km/s. These measurements are a
factor of ~2 smaller than for UV continuum-selected galaxies that show LyA in
emission with lower LyA equivalent width. We compare our LyA spectra to the
predicted line profiles of a spherical "expanding shell" LyA radiative transfer
grid that models large-scale galaxy outflows. Specifically blueward of the
systemic velocity where two galaxies show a weak, highly blueshifted (by ~1000
km/s) tertiary emission peak, the model line profiles are a relatively poor
representation of the observed spectra. Since the neutral gas column density
has a dominant influence over the shape of the LyA line profile, we caution
against equating the observed LyA velocity offset with a physical outflow
velocity, especially at lower spectral resolution where the unresolved LyA
velocity offset is a convoluted function of several degenerate parameters.
Referring to rest-frame ultraviolet and optical Hubble Space Telescope imaging,
we find that galaxy-galaxy interactions may play an important role in inducing
a starburst that results in copious LyA emission, as well as perturbing the gas
distribution and velocity field which have strong influence over the LyA
emission line profile.Comment: 20 pages, 8 figures, 3 tables; Accepted for publication in The
Astrophysical Journal; Updated v2 fixes incorrectly processed LaTeX symbol
Spectral Energy Distribution Fitting of Hetdex Pilot Survey Ly-alpha Emitters in Cosmos and Goods-N
We use broadband photometry extending from the rest-frame UV to the near-IR to fit the individual spectral energy distributions of 63 bright (L(Ly-alpha) greater than 10(exp 43) erg s(exp 1) Ly-alpha emitting galaxies (LAEs) in the redshift range 1.9 less than z less than 3.6. We find that these LAEs are quite heterogeneous, with stellar masses that span over three orders of magnitude, from 7.5 greater than logM/solar mass less than 10.5. Moreover, although most LAEs have small amounts of extinction, some high-mass objects have stellar reddenings as large as E(B V ) is approximately 0.4. Interestingly, in dusty objects the optical depths for Ly-alpha and the UV continuum are always similar, indicating that Ly photons are not undergoing many scatters before escaping their galaxy. In contrast, the ratio of optical depths in low-reddening systems can vary widely, illustrating the diverse nature of the systems. Finally, we show that in the star-formation-rate-log-mass diagram, our LAEs fall above the "main-sequence" defined by z is approximately 3 continuum selected star-forming galaxies. In this respect, they are similar to submillimeter-selected galaxies, although most LAEs have much lower mass
Male-Mediated Gene Flow in Patrilocal Primates
BACKGROUND: Many group-living species display strong sex biases in dispersal tendencies. However, gene flow mediated by apparently philopatric sex may still occur and potentially alters population structure. In our closest living evolutionary relatives, dispersal of adult males seems to be precluded by high levels of territoriality between males of different groups in chimpanzees, and has only been observed once in bonobos. Still, male-mediated gene flow might occur through rare events such as extra-group matings leading to extra-group paternity (EGP) and female secondary dispersal with offspring, but the extent of this gene flow has not yet been assessed. METHODOLOGY/PRINCIPAL FINDINGS: Using autosomal microsatellite genotyping of samples from multiple groups of wild western chimpanzees (Pan troglodytes verus) and bonobos (Pan paniscus), we found low genetic differentiation among groups for both males and females. Characterization of Y-chromosome microsatellites revealed levels of genetic differentiation between groups in bonobos almost as high as those reported previously in eastern chimpanzees, but lower levels of differentiation in western chimpanzees. By using simulations to evaluate the patterns of Y-chromosomal variation expected under realistic assumptions of group size, mutation rate and reproductive skew, we demonstrate that the observed presence of multiple and highly divergent Y-haplotypes within western chimpanzee and bonobo groups is best explained by successful male-mediated gene flow. CONCLUSIONS/SIGNIFICANCE: The similarity of inferred rates of male-mediated gene flow and published rates of EGP in western chimpanzees suggests this is the most likely mechanism of male-mediated gene flow in this subspecies. In bonobos more data are needed to refine the estimated rate of gene flow. Our findings suggest that dispersal patterns in these closely related species, and particularly for the chimpanzee subspecies, are more variable than previously appreciated. This is consistent with growing recognition of extensive behavioral variation in chimpanzees and bonobos
Introduction: Toward an Engaged Feminist Heritage Praxis
We advocate a feminist approach to archaeological heritage work in order to transform heritage practice and the production of archaeological knowledge. We use an engaged feminist standpoint and situate intersubjectivity and intersectionality as critical components of this practice. An engaged feminist approach to heritage work allows the discipline to consider womenâs, menâs, and gender non-conforming personsâ positions in the field, to reveal their contributions, to develop critical pedagogical approaches, and to rethink forms of representation. Throughout, we emphasize the intellectual labor of women of color, queer and gender non-conforming persons, and early white feminists in archaeology
Proceedings of the 3rd Biennial Conference of the Society for Implementation Research Collaboration (SIRC) 2015: advancing efficient methodologies through community partnerships and team science
It is well documented that the majority of adults, children and families in need of evidence-based behavioral health interventionsi do not receive them [1, 2] and that few robust empirically supported methods for implementing evidence-based practices (EBPs) exist. The Society for Implementation Research Collaboration (SIRC) represents a burgeoning effort to advance the innovation and rigor of implementation research and is uniquely focused on bringing together researchers and stakeholders committed to evaluating the implementation of complex evidence-based behavioral health interventions. Through its diverse activities and membership, SIRC aims to foster the promise of implementation research to better serve the behavioral health needs of the population by identifying rigorous, relevant, and efficient strategies that successfully transfer scientific evidence to clinical knowledge for use in real world settings [3]. SIRC began as a National Institute of Mental Health (NIMH)-funded conference series in 2010 (previously titled the âSeattle Implementation Research Conferenceâ; $150,000 USD for 3 conferences in 2011, 2013, and 2015) with the recognition that there were multiple researchers and stakeholdersi working in parallel on innovative implementation science projects in behavioral health, but that formal channels for communicating and collaborating with one another were relatively unavailable. There was a significant need for a forum within which implementation researchers and stakeholders could learn from one another, refine approaches to science and practice, and develop an implementation research agenda using common measures, methods, and research principles to improve both the frequency and quality with which behavioral health treatment implementation is evaluated. SIRCâs membership growth is a testament to this identified need with more than 1000 members from 2011 to the present.ii SIRCâs primary objectives are to: (1) foster communication and collaboration across diverse groups, including implementation researchers, intermediariesi, as well as community stakeholders (SIRC uses the term âEBP championsâ for these groups) â and to do so across multiple career levels (e.g., students, early career faculty, established investigators); and (2) enhance and disseminate rigorous measures and methodologies for implementing EBPs and evaluating EBP implementation efforts. These objectives are well aligned with Glasgow and colleaguesâ [4] five core tenets deemed critical for advancing implementation science: collaboration, efficiency and speed, rigor and relevance, improved capacity, and cumulative knowledge. SIRC advances these objectives and tenets through in-person conferences, which bring together multidisciplinary implementation researchers and those implementing evidence-based behavioral health interventions in the community to share their work and create professional connections and collaborations
Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK.
BACKGROUND: A safe and efficacious vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), if deployed with high coverage, could contribute to the control of the COVID-19 pandemic. We evaluated the safety and efficacy of the ChAdOx1 nCoV-19 vaccine in a pooled interim analysis of four trials. METHODS: This analysis includes data from four ongoing blinded, randomised, controlled trials done across the UK, Brazil, and South Africa. Participants aged 18 years and older were randomly assigned (1:1) to ChAdOx1 nCoV-19 vaccine or control (meningococcal group A, C, W, and Y conjugate vaccine or saline). Participants in the ChAdOx1 nCoV-19 group received two doses containing 5âĂâ1010 viral particles (standard dose; SD/SD cohort); a subset in the UK trial received a half dose as their first dose (low dose) and a standard dose as their second dose (LD/SD cohort). The primary efficacy analysis included symptomatic COVID-19 in seronegative participants with a nucleic acid amplification test-positive swab more than 14 days after a second dose of vaccine. Participants were analysed according to treatment received, with data cutoff on Nov 4, 2020. Vaccine efficacy was calculated as 1â-ârelative risk derived from a robust Poisson regression model adjusted for age. Studies are registered at ISRCTN89951424 and ClinicalTrials.gov, NCT04324606, NCT04400838, and NCT04444674. FINDINGS: Between April 23 and Nov 4, 2020, 23â848 participants were enrolled and 11â636 participants (7548 in the UK, 4088 in Brazil) were included in the interim primary efficacy analysis. In participants who received two standard doses, vaccine efficacy was 62·1% (95% CI 41·0-75·7; 27 [0·6%] of 4440 in the ChAdOx1 nCoV-19 group vs71 [1·6%] of 4455 in the control group) and in participants who received a low dose followed by a standard dose, efficacy was 90·0% (67·4-97·0; three [0·2%] of 1367 vs 30 [2·2%] of 1374; pinteraction=0·010). Overall vaccine efficacy across both groups was 70·4% (95·8% CI 54·8-80·6; 30 [0·5%] of 5807 vs 101 [1·7%] of 5829). From 21 days after the first dose, there were ten cases hospitalised for COVID-19, all in the control arm; two were classified as severe COVID-19, including one death. There were 74â341 person-months of safety follow-up (median 3·4 months, IQR 1·3-4·8): 175 severe adverse events occurred in 168 participants, 84 events in the ChAdOx1 nCoV-19 group and 91 in the control group. Three events were classified as possibly related to a vaccine: one in the ChAdOx1 nCoV-19 group, one in the control group, and one in a participant who remains masked to group allocation. INTERPRETATION: ChAdOx1 nCoV-19 has an acceptable safety profile and has been found to be efficacious against symptomatic COVID-19 in this interim analysis of ongoing clinical trials. FUNDING: UK Research and Innovation, National Institutes for Health Research (NIHR), Coalition for Epidemic Preparedness Innovations, Bill & Melinda Gates Foundation, Lemann Foundation, Rede D'Or, Brava and Telles Foundation, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midland's NIHR Clinical Research Network, and AstraZeneca
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