Enantio- and Diastereoselective 1,2-Additions to α-Ketoesters with Diborylmethane and Substituted 1,1-Diborylalkanes

The catalytic enantioselective synthesis of boronate-substituted tertiary alcohols through additions of diborylmethane and substituted 1,1-diborylalkanes to α-ketoesters is reported. The reactions are catalyzed by readily available chiral phosphine/copper(I) complexes and produce β-hydroxyboronates containing up to two contiguous stereogenic centers in up to 99:1 e.r. and greater than 20:1 d.r. The utility of the organoboron products is demonstrated through several chemoselective functionalizations. Evidence indicates the reactions occur via an enantioenriched α-boryl-copper-alkyl intermediate

Trait-based diet selection: Prey behaviour and morphology predict vulnerability to predation in reef fish communities

SUMMARY: 1. Understanding how predators select their prey can provide important insights into community structure and dynamics. However, the suite of prey species available to a predator is often spatially and temporally variable. As a result, species-specific selectivity data are of limited use for predicting novel predator–prey interactions because they are assemblage specific. 2. We present a method for predicting diet selection that is applicable across prey assemblages, based on identifying general morphological and behavioural traits of prey that confer vulnerability to predation independent of species identity. We apply this trait-based approach to examining prey selection by Indo-Pacific lionfish (Pterois volitans), an invasive predator that preys upon species-rich reef fish communities and is rapidly spreading across the Western Atlantic. 3. We first generate hypotheses about morphological and behavioural traits recurring across fish species that could facilitate or deter predation by lionfish. Constructing generalized linear mixed-models that account for relatedness among prey taxa, we test whether these traits predict patterns of diet selection by lionfish within two independent data sets collected at different spatial scales: (1) in situ visual observations of prey consumption and availability for individual lionfish and (2) comparisons of prey abundance in lionfish stomach contents to availability on invaded reefs at large. 4. Both analyses reveal that a number of traits predicted to affect vulnerability to predation, including body size, body shape, position in the water column and aggregation behaviour, are important determinants of diet selection by lionfish. Small, shallow-bodied, solitary fishes found resting on or just above reefs are the most vulnerable. Fishes that exhibit parasite cleaning behaviour experience a significantly lower risk of predation than non-cleaning fishes, and fishes that are nocturnally active are at significantly greater risk. Together, vulnerable traits heighten the risk of predation by a factor of nearly 200. 5. Our study reveals that a trait-based approach to studying diet selection yields insights into predator–prey interactions that are robust across prey assemblages. Importantly, in situ observations of selection yield similar results to broad-scale comparisons of prey use and availability, which are more typically gathered for predator species. A trait-based approach could therefore be of use across predator species and ecosystems to predict the outcomes of changing predator–prey interactions on community dynamics.Keywords: In situ observations, Pterois volitans/miles, Resource use and availability, Stomach contents analysis, Predator-prey interactions, Foraging behaviour, Prey characteristics, Selective predatio

Now You See It, Now You Don't: The Disappearing Central Engine of the Quasar J1011+5442

We report the discovery of a new "changing-look" quasar, SDSS J101152.98+544206.4, through repeat spectroscopy from the Time Domain Spectroscopic Survey. This is an addition to a small but growing set of quasars whose blue continua and broad optical emission lines have been observed to decline by a large factor on a time scale of approximately a decade. The 5100 Angstrom monochromatic continuum luminosity of this quasar drops by a factor of > 9.8 in a rest-frame time interval of < 9.7 years, while the broad H-alpha luminosity drops by a factor of 55 in the same amount of time. The width of the broad H-alpha line increases in the dim state such that the black hole mass derived from the appropriate single-epoch scaling relation agrees between the two epochs within a factor of 3. The fluxes of the narrow emission lines do not appear to change between epochs. The light curve obtained by the Catalina Sky Survey suggests that the transition occurs within a rest-frame time interval of approximately 500 days. We examine three possible mechanisms for this transition suggested in the recent literature. An abrupt change in the reddening towards the central engine is disfavored by the substantial difference between the timescale to obscure the central engine and the observed timescale of the transition. A decaying tidal disruption flare is consistent with the decay rate of the light curve but not with the prolonged bright state preceding the decay, nor can this scenario provide the power required by the luminosities of the emission lines. An abrupt drop in the accretion rate onto the supermassive black hole appears to be the most plausible explanation for the rapid dimming.Comment: Submitted to MNRA

An Interdisciplinary Approach to Community-Engaged Research Surrounding Lead in Drinking Water in the Mississippi Delta

Childhood lead poisoning is a problem requiring interdisciplinary attention from toxicology, public health, social sciences, environmental law, and policy. In the U.S., Mississippi was ranked as one of the worst states for lead poisoning with limited childhood screening measures. We conducted community-engaged research by working with leaders in the largely rural Mississippi Delta region from 2016-2019 to collect household water samples and questionnaires and involve their communities in lead poisoning risk awareness and outreach. Drinking water from 213 homes was collected and analyzed for pH and lead concentrations. Highest lead concentrations were from households served by private wells, and detectable concentrations at or above 0.09 ppb were found in 66.2 percent of all samples. Nine samples exceeded 5 ppb, and these households received certified sink filters. Findings indicated that community-engaged research and outreach could be used to address data gaps relating to lead in drinking water in rural decentralized water systems

Towards an Understanding of Changing-Look Quasars: An Archival Spectroscopic Search in SDSS

The uncertain origin of the recently-discovered `changing-looking' quasar phenomenon -- in which a luminous quasar dims significantly to a quiescent state in repeat spectroscopy over ~10 year timescales -- may present unexpected challenges to our understanding of quasar accretion. To better understand this phenomenon, we take a first step to building a sample of changing-look quasars with a systematic but simple archival search for these objects in the Sloan Digital Sky Survey Data Release 12. By leveraging the >10 year baselines for objects with repeat spectroscopy, we uncover two new changing-look quasars, and a third discovered previously. Decomposition of the multi-epoch spectra and analysis of the broad emission lines suggest that the quasar accretion disk emission dims due to rapidly decreasing accretion rates (by factors of >2.5), while disfavoring changes in intrinsic dust extinction for the two objects where these analyses are possible. Broad emission line energetics also support intrinsic dimming of quasar emission as the origin for this phenomenon rather than transient tidal disruption events or supernovae. Although our search criteria included quasars at all redshifts and transitions from either quasar-like to galaxy-like states or the reverse, all of the clear cases of changing-look quasars discovered were at relatively low-redshift (z ~ 0.2 - 0.3) and only exhibit quasar-like to galaxy-like transitions.Comment: 15 pages, 8 figures. Updated to accepted versio

Widespread nitrogen fixation in sediments from diverse deep-sea sites of elevated carbon loading

Nitrogen fixation, the biological conversion of N_2 to NH_3, is critical to alleviating nitrogen limitation in many marine ecosystems. To date, few measurements exist of N_2 fixation in deep‐sea sediments. Here, we conducted > 400 bottle incubations with sediments from methane seeps, whale falls and background sites off the western coast of the United States from 600 to 2893 m water depth to investigate the potential rates, spatial distribution and biological mediators of benthic N_2 fixation. We found that N2 fixation was widespread, yet heterogeneously distributed with sediment depth at all sites. In some locations, rates exceeded previous measurements by > 10×, and provided up to 30% of the community anabolic growth requirement for nitrogen. Diazotrophic activity appeared to be inhibited by pore water ammonium: N_2 fixation was only observed if incubation ammonium concentrations were ≤ 25 μM, and experimental additions of ammonium reduced diazotrophy. In seep sediments, N_2 fixation was dependent on CH_4 and coincident with sulphate reduction, consistent with previous work showing diazotrophy by microorganisms mediating sulphate‐coupled methane oxidation. However, the pattern of diazotrophy was different in whale‐fall and associated reference sediments, where it was largely unaffected by CH_4, suggesting catabolically different diazotrophs at these sites

Semiquantitative assessment of subchondral bone marrow edema-like lesions and subchondral cysts of the knee at 3T MRI: A comparison between intermediate-weighted fat-suppressed spin echo and Dual Echo Steady State sequences

Background\ud Choice of appropriate MR pulse sequence is important for any research studies using imaging-derived data. The aim of this study was to compare semiquantitative assessment of subchondral bone marrow edema-like lesions and subchondral cysts using intermediate-weighted (IW) fat-suppressed (fs) spin echo and Dual Echo Steady State (DESS) sequences on 3 T MRI.\ud \ud Methods\ud Included were 201 subjects aged 35-65 with frequent knee pain. 3T MRI was performed with the same sequence protocol as in the Osteoarthritis Initiative (OAI). In a primary reading subchondral bone marrow edema-like lesions were assessed according to the WORMS system. Two hundred subregions with such lesions were randomly chosen. The extent of subchondral bone marrow edema-like lesions was re-evaluated separately using sagittal IW fs and DESS sequences according to WORMS. Lesion size and confidence of the differentiation between subchondral bone marrow edema-like lesions and subchondral cysts located within or adjacent to them was rated from 0 to 3. Wilcoxon signed-rank tests and chi-square statistics were used to examine differences between the two sequences.\ud \ud Results\ud Of 200 subchondral bone marrow edema-like lesions detected by IW fs sequence, 93 lesions (46.5%) were not depicted by the DESS sequence. The IW fs sequence depicted subchondral bone marrow edema-like lesions to a larger extent than DESS (p < 0.0001), and the opposite was true for subchondral cysts. Confidence scores for differentiation of the two types of lesions were not significantly different between the two sequences.\ud \ud Conclusions\ud In direct comparison the IW fs sequence depicts more subchondral bone marrow edema-like lesions and better demonstrate the extent of their maximum size. The DESS sequence helps in the differentiation of subchondral bone marrow edema-like lesions and subchondral cysts. The IW fs sequence should be used for determination of lesion extent whenever the size of subchondral bone marrow edema-like lesions is the focus of attention

Return of individual research results from genomic research: A systematic review of stakeholder perspectives.

Funder: Franca FundFunder: Canada Research Chair in Law and MedicineFunder: Canada Institute of Health ResearchFunder: Genome QuebecFunder: Genome CanadaFunder: Can-SHARE ConnectFunder: CIHRDespite the plethora of empirical studies conducted to date, debate continues about whether and to what extent results should be returned to participants of genomic research. We aimed to systematically review the empirical literature exploring stakeholders' perspectives on return of individual research results (IRR) from genomic research. We examined preferences for receiving or willingness to return IRR, and experiences with either receiving or returning them. The systematic searches were conducted across five major databases in August 2018 and repeated in April 2020, and included studies reporting findings from primary research regardless of method (quantitative, qualitative, mixed). Articles that related to the clinical setting were excluded. Our search identified 221 articles that met our search criteria. This included 118 quantitative, 69 qualitative and 34 mixed methods studies. These articles included a total number of 118,874 stakeholders with research participants (85,270/72%) and members of the general public (40,967/35%) being the largest groups represented. The articles spanned at least 22 different countries with most (144/65%) being from the USA. Most (76%) discussed clinical research projects, rather than biobanks. More than half (58%) gauged views that were hypothetical. We found overwhelming evidence of high interest in return of IRR from potential and actual genomic research participants. There is also a general willingness to provide such results by researchers and health professionals, although they tend to adopt a more cautious stance. While all results are desired to some degree, those that have the potential to change clinical management are generally prioritized by all stakeholders. Professional stakeholders appear more willing to return results that are reliable and clinically relevant than those that are less reliable and lack clinical relevance. The lack of evidence for significant enduring psychological harm and the clear benefits to some research participants suggest that researchers should be returning actionable IRRs to participants