1,685 research outputs found
Oyster reef restoration fails to recoup global historic ecosystem losses despite substantial biodiversity gain
Human activities have led to degradation of ecosystems globally. The lost ecosystem functions and services accumulate from the time of disturbance to the full recovery of the ecosystem and can be quantified as a “recovery debt,” providing a valuable tool to develop better restoration practices that accelerate recovery and limit losses. Here, we quantified the recovery of faunal biodiversity and abundance toward a predisturbed state following structural restoration of oyster habitats globally. We found that while restoration initiates a rapid increase in biodiversity and abundance of reef-associated species within 2 years, recovery rate then decreases substantially, leaving a global shortfall in recovery of 35% below a predisturbed state. While efficient restoration methods boost recovery and minimize recovery shortfalls, the time to full recovery is yet to be quantified. Therefore, potential future coastal development should weigh up not only the instantaneous damage to ecosystem functions but also the potential for generational loss of services
Vasodilatory and vascular mitochondrial respiratory function with advancing age: evidence of a free radically mediated link in the human vasculature
Recognizing the age-related decline in skeletal muscle feed artery (SMFA) vasodilatory function, this study examined the link between vasodilatory and mitochondrial respiratory function in the human vasculature. Twenty-four SMFAs were harvested from young (35 ± 6 yr, n = 9) and old (71 ± 9 yr, n = 15) subjects. Vasodilation in SMFAs was assessed, by pressure myography, in response to flow-induced shear stress, acetylcholine (ACh), and sodium nitroprusside (SNP) while mitochondrial respiration was measured, by respirometry, in permeabilized SMFAs. Endothelium-dependent vasodilation was significantly attenuated in the old, induced by both flow (young: 92 ± 3, old: 45 ± 4%) and ACh (young: 92 ± 3, old: 54 ± 5%), with no significant difference in endothelium-independent vasodilation. Complex I and I + II state 3 respiration was significantly lower in the old (CI young: 10.1 ± 0.8, old: 7.0 ± 0.4 pmol·s−1·mg−1; CI + II young: 12.3 ± 0.6, old: 7.6 ± 0.4 pmol·s−1·mg−1). The respiratory control ratio (RCR) was also significantly attenuated in the old (young: 2.2 ± 0.1, old: 1.1 ± 0.1). Furthermore, state 3 (CI + II) and 4 respiration, as well as RCR, were significantly correlated (r = 0.49–0.86) with endothelium-dependent, but not endothelium-independent, function. Finally, the direct intervention with mitochondrial-targeted antioxidant (MitoQ) significantly improved endothelium-dependent vasodilation in the old but not in the young. Thus, the age-related decline in vasodilatory function is linked to attenuated vascular mitochondrial respiratory function, likely by augmented free radicals
Geographic smoothing of solar photovoltaic electric power production in the Western USA
We examined the geographic smoothing of solar photovoltaic generation from 15 utility-scale plants in California, Nevada, and Arizona and from 19 commercial building installations in California. This is the first comparison of geographic smoothing from utility-scale and building-mounted PV and the first examination of solar PV smoothing in this region. Our research questions were (1) how does geographic smoothing of commercial building rooftop PV compare to that of utility scale PV?, (2) is the geographic smoothing found for utility-scale plants the same for the western US as in India?, and (3) how does the geographic smoothing for PV compare to that of wind? By examining the power output of these generators in the frequency domain, we quantified the smoothing obtained by combining the output of geographically separated plants. We found that utility-scale and commercial rooftop plants exhibited similar geographic smoothing, with 10 combined plants reducing the amplitude of fluctuations at 1 h to 18%–28% of those seen for a single plant. We find that combining a few PV sites together reduces fluctuations, but that the point of quickly diminishing returns is reached after ∼5 sites, and that for all the locations and plant sizes considered, PV does not exhibit as much geographic smoothing as is seen for combining wind plants. We present preliminary theoretical arguments for why geographic smoothing of PV plants is less effective than that for wind plants. The slope of the high-frequency part of the PV power spectrum can at best be geographically smoothed (steepen) to an asymptotic spectrum of f−2. This limit for PV has considerably less smoothing than that for wind\u27s geographic smoothing, shown theoretically and from observed data to be f−2.33
Hubble Space Telescope Imaging of Lyman Alpha Emission at z=4.4
We present the highest redshift detections of resolved Lyman alpha emission,
using Hubble Space Telescope/ACS F658N narrowband-imaging data taken in
parallel with the Wide Field Camera 3 Early Release Science program in the
GOODS CDF-S. We detect Lyman alpha emission from three spectroscopically
confirmed z = 4.4 Lyman alpha emitting galaxies (LAEs), more than doubling the
sample of LAEs with resolved Lyman alpha emission. Comparing the light
distribution between the rest-frame ultraviolet continuum and narrowband
images, we investigate the escape of Lyman alpha photons at high redshift.
While our data do not support a positional offset between the Lyman alpha and
rest-frame ultraviolet (UV) continuum emission, the half-light radii in two out
of the three galaxies are significantly larger in Lyman alpha than in the
rest-frame UV continuum. This result is confirmed when comparing object sizes
in a stack of all objects in both bands. Additionally, the narrowband flux
detected with HST is significantly less than observed in similar filters from
the ground. These results together imply that the Lyman alpha emission is not
strictly confined to its indigenous star-forming regions. Rather, the Lyman
alpha emission is more extended, with the missing HST flux likely existing in a
diffuse outer halo. This suggests that the radiative transfer of Lyman alpha
photons in high-redshift LAEs is complicated, with the interstellar-medium
geometry and/or outflows playing a significant role in galaxies at these
redshifts.Comment: Submitted to the Astrophysical Journal. 11 pages, 10 figure
Associations between police harassment and distrust in and reduced access to healthcare among Black sexual minority men: A longitudinal analysis of HPTN 061
Objective: Evaluate associations between racialized and homophobia-based police harassment (RHBPH) and healthcare distrust and utilization among Black Sexual Minority Men (BSMM). Methods: We utilized data from a longitudinal cohort study from HIV Prevention Trials Network (HPTN) 061 with baseline, six and 12 month follow-up assessments. Using multivariable analysis, we evaluated associations between RHBPH and healthcare distrust and utilization reported at the 6 and 12 month visits. Results: Of 1553 BSMM present at baseline, 1160 were available at six-month follow-up. In multivariable analysis, increasing frequency of RHBPH was associated with increasing levels of distrust in healthcare providers (aOR 1.31, 95% CI: 1.00, 1.74) and missing 50% or more of healthcare visits at six-month follow-up (aOR 1.93, 95% CI: 1.09, 3.43). Conclusions: Recent experiences of RHBPH are associated with reduced trust in and access to healthcare among BSMM, with more frequent RHBPH associated with greater vulnerability.</p
Shedding light on the elusive role of endothelial cells in cytomegalovirus dissemination.
Cytomegalovirus (CMV) is frequently transmitted by solid organ transplantation and is associated with graft failure. By forming the boundary between circulation and organ parenchyma, endothelial cells (EC) are suited for bidirectional virus spread from and to the transplant. We applied Cre/loxP-mediated green-fluorescence-tagging of EC-derived murine CMV (MCMV) to quantify the role of infected EC in transplantation-associated CMV dissemination in the mouse model. Both EC- and non-EC-derived virus originating from infected Tie2-cre(+) heart and kidney transplants were readily transmitted to MCMV-naïve recipients by primary viremia. In contrast, when a Tie2-cre(+) transplant was infected by primary viremia in an infected recipient, the recombined EC-derived virus poorly spread to recipient tissues. Similarly, in reverse direction, EC-derived virus from infected Tie2-cre(+) recipient tissues poorly spread to the transplant. These data contradict any privileged role of EC in CMV dissemination and challenge an indiscriminate applicability of the primary and secondary viremia concept of virus dissemination
Screen for Localized Proteins in Caulobacter crescentus
Precise localization of individual proteins is required for processes such as motility, chemotaxis, cell-cycle progression, and cell division in bacteria, but the number of proteins that are localized in bacterial species is not known. A screen based on transposon mutagenesis and fluorescence activated cell sorting was devised to identify large numbers of localized proteins, and employed in Caulobacter crescentus. From a sample of the clones isolated in the screen, eleven proteins with no previously characterized localization in C. crescentus were identified, including six hypothetical proteins. The localized hypothetical proteins included one protein that was localized in a helix-like structure, and two proteins for which the localization changed as a function of the cell cycle, suggesting that complex three-dimensional patterns and cell cycle-dependent localization are likely to be common in bacteria. Other mutants produced localized fusion proteins even though the transposon has inserted near the 5′ end of a gene, demonstrating that short peptides can contain sufficient information to localize bacterial proteins. The screen described here could be used in most bacterial species
The Cosmology of Composite Inelastic Dark Matter
Composite dark matter is a natural setting for implementing inelastic dark
matter - the O(100 keV) mass splitting arises from spin-spin interactions of
constituent fermions. In models where the constituents are charged under an
axial U(1) gauge symmetry that also couples to the Standard Model quarks, dark
matter scatters inelastically off Standard Model nuclei and can explain the
DAMA/LIBRA annual modulation signal. This article describes the early Universe
cosmology of a minimal implementation of a composite inelastic dark matter
model where the dark matter is a meson composed of a light and a heavy quark.
The synthesis of the constituent quarks into dark mesons and baryons results in
several qualitatively different configurations of the resulting dark matter
hadrons depending on the relative mass scales in the system.Comment: 31 pages, 4 figures; references added, typos correcte
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