1,360 research outputs found

    Hybrid turbidite-drift channel complexes: An integrated multiscale model

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    The interaction of deep-marine bottom currents with episodic, unsteady sediment gravity flows affects global sediment transport, forms climate archives, and controls the evolution of continental slopes. Despite their importance, contradictory hypotheses for reconstructing past flow regimes have arisen from a paucity of studies and the lack of direct monitoring of such hybrid systems. Here, we address this controversy by analyzing deposits, high-resolution seafloor data, and near-bed current measurements from two sites where eastward-flowing gravity flows interact(ed) with northward-flowing bottom currents. Extensive seismic and core data from offshore Tanzania reveal a 1650-m-thick asymmetric hybrid channel levee-drift system, deposited over a period of ∼20 m.y. (Upper Cretaceous to Paleocene). High-resolution modern seafloor data from offshore Mozambique reveal similar asymmetric channel geometries, which are related to northward-flowing near-bed currents with measured velocities of up to 1.4 m/s. Higher sediment accumulation occurs on the downstream flank of channel margins (with respect to bottom currents), with inhibited deposition or scouring on the upstream flank (where velocities are highest). Toes of the drift deposits, consisting of thick laminated muddy siltstone, which progressively step back into the channel axis over time, result in an interfingering relationship with the sandstone-dominated channel fill. Bottom-current flow directions contrast with those of previous models, which lacked direct current measurements or paleoflow indicators. We finally show how large-scale depositional architecture is built through the temporally variable coupling of these two globally important sediment transport processes. Our findings enable more-robust reconstructions of past oceanic circulation and diagnosis of ancient hybrid turbidite-drift systems

    Simple Reciprocal Fairness Message to Enhance Non-Donor’s Willingness to Donate Blood

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    Background: Against a background of declining blood donor numbers, recruiting new donors is critical for the effective operations of healthcare providers. Thus, interventions are needed to recruit new blood donors. Purpose: We provide initial evidence for Voluntary Reciprocal Altruism (VRA) to enhance non-donors’ willingness to become blood donors. VRA interventions involve asking two questions: one on accepting a blood transfusion if needed and one on willingness to donate. As early trials often use self-reports of willingness to perform blood donation behavior, we derive a correction factor to better estimate actual behavior. Finally, we explore the effect of VRA interventions on two prosocial emotions: gratitude and guilt.Methods: Across three experiments (two in the UK and one in Australia: Total N = 1,214 non-donors) we manipulate VRA messages and explore how they affect both reported willingness to make a one-off or repeat blood donation and influence click through to blood donation, organ donation and volunteering registration sites (behavioral proxies). We report data from a longitudinal cohort that enables us to derive a correction for self-reported behavioral willingness.Results: Across the three experiments we show that exposure to a question that askes about accepting a transfusion if needed increased willingness to donate blood with some spillover to organ donor registration. We also show that gratitude has an independent effect on donation and report a behavioral correction factor of .10.Conclusions: Asking non-donors about accepting a transfusion if needed is likely to be an effective strategy to increase new donor numbers

    Australian Perspectives on Opt-In and Opt-Out Consent Systems for Deceased Organ Donation

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    Introduction: As many countries change to opt-out systems to address organ shortages, calls for similar reform in Australia persist. Community perspectives on consent systems for donation remain under-researched, therefore Australian perspectives on consent systems and their effectiveness in increasing donation rates were explored. Design: In this descriptive cross-sectional study, participants completed a survey presenting opt-in, soft opt-out, and hard opt-out systems, with corresponding descriptions. Participants chose the system they perceived as most effective and described their reasoning. Results: Participants (N = 509) designated soft opt-out as the most effective system (52.3%; hard opt-out 33.7%; opt-in 13.7%). Those who identified with an ethnic/cultural group or were not registered had greater odds of choosing opt-out. Six themes identified in thematic analysis reflected their reasoning: 1) who decides (individual, shared decision with family); 2) right to choose; 3) acceptability (ethics, fairness); and utility in overcoming barriers for 4) individuals (apathy, awareness, ease of donating, fear/avoidance of death); 5) family (easier family experience, family veto); 6) society (normalising donation, donation as default, expanding donor pool). Choice and overcoming individual barriers were more frequently endorsed themes for opt-in and opt-out, respectively. Discussion: Results suggested the following insights regarding system effectiveness: uphold/prioritise individual’s recorded donation decision above family wishes; involve family in decision-making if no donation preference is recorded; retain a register enabling opt-in and opt-out for unequivocal decisions and promoting individual control; and maximise ease of registering. Future research should establish whether systems considered effective are also acceptable to the community to address organ shortages

    Three dimensional tracking for volumetric spectral-domain optical coherence tomography

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    We present a three-dimensional (3D) tracker for a clinical ophthalmic spectral domain optical coherence tomography (SD-OCT) system that combines depth-tracking with lateral tracking, providing a stabilized reference frame for 3D data recording and post acquisition analysis. The depth-tracking system is implemented through a real-time dynamic feedback mechanism to compensate for motion artifact in the axial direction. Active monitoring of the retina and adapting the reference arm of the interferometer allowed the whole thickness of the retina to be stabilized to within +/- 100 mu m. We achieve a relatively constant SNR from image to image by stabilizing the image of the retina with respect to the depth dependent sensitivity of SD-OCT. The depth tracking range of our system is 5.2 mm in air and the depth is adjusted every frame. Enhancement in the stability of the images with the depth-tracking algorithm is demonstrated on a healthy volunteer.X1119sciescopu

    PrEP and HIV prevention decision-making among social network members of women who have experienced incarceration: a qualitative study

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    Incarceration and HIV are a syndemic for US women, yet very few women who have experienced incarceration use pre-exposure prophylaxis (PrEP) for HIV. We conducted semi-structured interviews with 32 participants recruited by women who have experienced incarceration from their social networks, informed by the modified social ecological model for PrEP. Emergent themes from the interviews included individual-level (low personal HIV risk assessment, personal responsibility for HIV prevention, and decisions in addiction versus recovery), network-level (influential sex partners and the importance of trust, supportive treatment peers, and high-risk but indifferent drug use networks), community-level (stigma, and mitigation of stigma in supportive substance use disorder treatment environments), and public policy-level (incarceration and PrEP cost and access) determinants. PrEP interventions for women who have experienced incarceration and their networks will need to incorporate contingency planning into HIV risk assessment, navigate complex network dynamics, and be situated in trusted contexts to address structural barriers

    The first long-read nuclear genome assembly of Oryza australiensis, a wild rice from northern Australia

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    Oryza australiensis is a wild rice native to monsoonal northern Australia. The International Oryza Map Alignment Project emphasises its significance as the sole representative of the EE genome clade. Assembly of the O. australiensis genome has previously been challenging due to its high Long Terminal Repeat (LTR) retrotransposon (RT) content. Oxford Nanopore long reads were combined with Illumina short reads to generate a high-quality ~ 858 Mbp genome assembly within 850 contigs with 46× long read coverage. Reference-guided scaffolding increased genome contiguity, placing 88.2% of contigs into 12 pseudomolecules. After alignment to the Oryza sativa cv. Nipponbare genome, we observed several structural variations. PacBio Iso-Seq data were generated for five distinct tissues to improve the functional annotation of 34,587 protein-coding genes and 42,329 transcripts. We also report SNV numbers for three additional O. australiensis genotypes based on Illumina re-sequencing. Although genetic similarity reflected geographical separation, the density of SNVs also correlated with our previous report on variations in salinity tolerance. This genome re-confirms the genetic remoteness of the O. australiensis lineage within the O. officinalis genome complex. Assembly of a high-quality genome for O. australiensis provides an important resource for the discovery of critical genes involved in development and stress tolerance.Aaron L. Phillips, Scott Ferguson, Nathan S. Watson, Haigh, Ashley W. Jones, Justin O. Borevitz, Rachel A. Burton, Brian J. Atwel

    The Morphology of Passively Evolving Galaxies at Z-2 from HST/WFC3 in the Hubble Ultra Deep Field

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    We discuss near-IR images of six passive galaxies (SSFR< 10(exp -2)/Gyr) at redshift 1.3 < z < 2.4 with stellar mass M approx 10(exp 11) solar mass, selected from the Great Observatories Origins Deep Survey (GOODS), obtained with WFC3/IR and the Hubble Space Telescope (HST). These WFC3 images provide the deepest and highest angular resolution view of the optical rest-frame morphology of such systems to date. We find that the light profile of these; galaxies is generally regular and well described by a Sersic model with index typical of today's spheroids. We confirm the existence of compact and massive early-type galaxies at z approx. 2: four out of six galaxies have T(sub e) approx. 1 kpc or less. The WFC3 images achieve limiting surface brightness mu approx. 26.5 mag/sq arcsec in the F160W bandpass; yet there is no evidence of a faint halo in the five compact galaxies of our sample, nor is a halo observed in their stacked image. We also find very weak "morphological k-correction" in the galaxies between the rest-frame UV (from the ACS z band), and the rest-frame optical (WFC3 H band): the visual classification, Sersic indices and physical sizes of these galaxies are independent or only mildly dependent on the wavelength, within the errors

    The UDF05 follow-up of the Hubble Ultra Deep Field. I. The faint-end slope of the Lyman Break Galaxy Population at z ~ 5

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    We present the UDF05 HST program, which consists of three disjoint fields—NICP12, NICP34, plus the HUDF—with deep ACS (F606W, F775W, and F850LP) and NICMOS (F110W and F160W) imaging. Here we use the ACS data for the NICP12 and HUDF fields to implement a (V − i) − (i − z) selection criterion that allows us to identify a sample of 101 (133) z ~ 5 Lyman break galaxies (LBGs) down to z850 = 28.5 (29.25) mag in NICP12 (HUDF). We construct the rest-frame 1400 Å LBG luminosity function (LF) over the range M1400 = [ − 21.4, − 17.1] , i.e. down to ~0.04L* at z ~ 5, and use Subaru Deep Field results (Yoshida et al. 2006) to constrain our LF at the bright end (M1400 ≥ − 22.2). We show that (1) different assumptions regarding the LBG SED distribution, dust properties, and intergalactic absorption result in a 25% variation in the number density of LBGs at z ~ 5; (2) under consistent assumptions for dust properties and intergalactic absorption, the HUDF is ~30% underdense in z ~ 5 LBGs relative to the NICP12 field, a variation which is well explained by cosmic variance; and (3) the faint-end slope of the LF does not depend on the input parameters, and has a value of α ~ − 1.6, similar to the faint-end slope of the LF of z ~ 3 and z ~ 6 LBGs. Our study therefore supports no variation in the faint end of the LBG LF over the whole redshift range z ~ 3 to z ~ 6. Based on a comparison with semianalytical models, we speculate that the z ~ 5 LBGs might have a top-heavy IMF
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