Did a Shifting Ecological Baseline Mask the Predatory Effect of Striped Bass on Delta Smelt?

Striped Bass, Morone saxatilis, has been an established member of the San Francisco Estuary’s (estuary’s) aquatic community for nearly a century and a half. As a predator, it has the potential to shape community composition through top-down control of lower trophic species, including the endangered Delta Smelt, Hypomesus transpacificus. Invasive predators can be particularly disruptive to native communities because they present novel dangers to naïve populations, but, as a long-established member of the aquatic community, Striped Bass has not previously been considered to limit the Delta Smelt population. Here, we develop an argument that Striped Bass are important to controlling Delta Smelt. We support this argument by reviewing historical data which suggests that declines in Delta Smelt before the current-day monitoring program were driven by the invasion of Striped Bass into the estuary. We describe this phenomenon as the ‘phantom predator’ hypothesis in the context of an analog to the shifting baseline syndrome previously described for marine fisheries. A deeper understanding of how well studied (and rapidly changing) bottom-up drivers of the estuary food web interact with poorly understood (but also rapidly changing) controls at the top of the food web could prove very important to the conservation of other declining native fishes and possible future attempts to re-introduce captive-reared Delta Smelt to the estuary

Intrinsic Differences in the Inner Jets of High- and Low-Optically Polarized Radio Quasars

A significant fraction of compact radio-loud quasars display most of the characteristics of relativistically beamed, high-optical polarization blazars, yet are weakly polarized in the optical regime. We have used the VLBA at 22 and 43 GHz to look for differences in the parsec-scale magnetic field structures of 18 high- and low-optically polarized, compact radio-loud quasars (HPQs and LPRQs, respectively). We find a strong correlation between the polarization level of the unresolved parsec-scale radio core at 43 GHz and overall optical polarization of the source, which suggests a common (possibly co-spatial) origin for the emission at these two wavelengths. The magnetic fields of the polarized 43 GHz radio cores are aligned roughly transverse to the jet axis. Similar orientations are seen in the optical, suggesting that the polarized flux at both wavelengths is due to one or more strong transverse shocks located very close to the base of the jet. In LPRQs, these shocks appear to be weak near the core, and gradually increase in strength down the jet. The LPRQs in our sample tend to have less luminous radio cores than the HPQs, and jet components with magnetic fields predominantly parallel to the flow. The components in HPQ jets, on the other hand, tend to have transverse alignments. These differences cannot be accounted for by a simple model in which HPQs and LPRQs are the same type of object, seen at different angles to the line of sight. A more likely scenario is that LPRQs represent a quiescent phase of blazar activity, in which the inner jet flow does not undergo strong shocks.Comment: 29 pages, includes 25 figures and 6 tables. Uses emulateapj5.sty. Accepted for publication in the Astrophysical Journal. A version with better quality figures (785Kb, gzipped) can be found at http://sgra.jpl.nasa.gov/html_lister/LPQ

Testable theory development for small-N studies: critical realism and middle-range theory

Theory testing within small-N research designs is generally considered problematic. Developments in the philosophy of social science have opened up new methodological possibilities through, among other things, a novel notion of contingent causality that allows for contextualized hypothesis generation, hypothesis testing and refinement, and generalization. This article looks to contribute to the literature by providing an example of critical realist (one such new development in the philosophy of social science) research on a small-N comparative case study that includes hypothesis testing. The article begins with the key ontological assumptions of critical realism and its relation to theory and explanation. Then, the paper presents an illustrative example of an e-government and trust comparative case study following these ontological assumptions. Given word length limitations, the focus of the example is on the nature and process of theory and hypothesis development, rather than the actually testing that occurred. Essential to developing testable hypotheses is the generation of tightly linked middle-range and case-specific theories that provide propositions that can be tested and refined. The link provides a pathway to feedback the concrete empirical data to the higher level (more abstract) and generalizable middle-range theories

Far-reaching dust distribution in galaxy discs

In most studies of dust in galaxies, dust is only detected from its emission to approximately the optical radius of the galaxy. By combining the signal of 110 spiral galaxies observed as part of the Herschel Reference Survey, we are able to improve our sensitivity by an order of magnitude over that for a single object. Here we report the direct detection of dust from its emission that extends out to at least twice the optical radius. We find that the distribution of dust is consistent with an exponential at all radii with a gradient of ∼−1.7 dex R^(−1)_(25). Our dust temperature declines linearly from ∼25 K in the centre to 15 K at R_(25) from where it remains constant out to ∼2.0 R_(25). The surface density of dust declines with radius at a similar rate to the surface density of stars but more slowly than the surface density of the star-formation rate. Studies based on dust extinction and reddening of high-redshift quasars have concluded that there are substantial amounts of dust in intergalactic space. By combining our results with the number counts and angular correlation function from the SDSS, we show that with Milky Way-type dust we can explain the reddening of the quasars by the dust within galactic discs alone. Given the uncertainties in the properties of any intergalactic dust, we cannot rule out its existence, but our results show that statistical investigations of the dust in galactic haloes that use the reddening of high-redshift objects must take account of the dust in galactic discs

Sea Level-Driven Marsh Migration Results in Rapid Net Loss of Carbon

Sea level rise alters coastal carbon cycling by driving the rapid migration of coastal ecosystems, salinization of freshwater systems, and replacement of terrestrial forests with tidal wetlands. Wetland soils accumulate carbon (C) at faster rates than terrestrial soils, implying that sea level rise may lead to enhanced carbon accumulation. Here, we show that carbon stored in tree biomass greatly exceeds carbon stored in adjacent marsh soils so that marsh migration reduces total carbon stocks by 50% in less than 100years. Continued marsh soil carbon accumulation may eventually offset forest carbon loss, but we estimate that the time for replacement is similar to estimates of marsh survival (i.e., centuries), which suggests that forest C may never be replaced. These findings reveal a critical C source not included in coastal C budgets driven by migrating ecosystems and rapidly shifting allocations between carbon stored in soils and biomasS

Silk-fibronectin protein alloy fibres support cell adhesion and viability as a high strength, matrix fibre analogue

Silk is a natural polymer with broad utility in biomedical applications because it exhibits general biocompatibility and high tensile material properties. While mechanical integrity is important for most biomaterial applications, proper function and integration also requires biomaterial incorporation into complex surrounding tissues for many physiologically relevant processes such as wound healing. In this study, we spin silk fibroin into a protein alloy fibre with whole fibronectin using wet spinning approaches in order to synergize their respective strength and cell interaction capabilities. Results demonstrate that silk fibroin alone is a poor adhesive surface for fibroblasts, endothelial cells, and vascular smooth muscle cells in the absence of serum. However, significantly improved cell attachment is observed to silk-fibronectin alloy fibres without serum present while not compromising the fibres' mechanical integrity. Additionally, cell viability is improved up to six fold on alloy fibres when serum is present while migration and spreading generally increase as well. These findings demonstrate the utility of composite protein alloys as inexpensive and effective means to create durable, biologically active biomaterials.T32 EB006359 - NIBIB NIH HH

Developing Professional Identity and Networks at Conferences

Professional conferences play an important role in the development of health behavior researchers. These venues are essential for applying academic coursework and advancing or strengthening skills in professional settings. Attending meetings enables students and early career scholars to interact with researchers and practitioners in the field for the purposes of sharing research findings, discussing practice strategies, and exploring career options through networking opportunities. Conference experiences can be enhanced by proper planning and execution before, during, and after the event. This editorial provides recommendations to junior conference attendees related to a variety of topics including time management, presentation etiquette, networking, locating mentors, and post-meeting follow-up procedures

Immune Response Testing of Electrospun Polymers: An Important Consideration in the Evaluation of Biomaterials

Due primarily to cell sourcing issues, many in the field of tissue engineering have opted to create scaffolds that promote in situ regeneration, using the body as both the bioreactor and the cell source for the remodeling of scaffolds, resulting in the formation of native tissue. This practice raises many concerns, with the body’s immune response to such an implant often being neglected as a potential problem in preliminary design and biocompatibility testing. More importantly, what happens over time in terms of the immune responses as the biodegradable scaffold structures being utilized to promote in situ regeneration begin to degrade, forming structural fragments and degradation products? In summary, immune response evaluations are critical considerations that must be conducted when evaluating bioresorbable scaffolds. In addition, it is essential that these evaluations analyze materials for their potential dose-response and time-course effects on the various components of innate and acquired immunity

A Dust Twin of Cas A: Cool Dust and 21-micron Silicate Dust Feature in the Supernova Remnant G54.1+0.3

We present infrared (IR) and submillimeter observations of the Crab-like supernova remnant (SNR) G54.1+0.3 including 350 micron (SHARC-II), 870 micron (LABOCA), 70, 100, 160, 250, 350, 500 micron (Herschel) and 3-40 micron (Spitzer). We detect dust features at 9, 11 and 21 micron and a long wavelength continuum dust component. The 21 micron dust coincides with [Ar II] ejecta emission, and the feature is remarkably similar to that in Cas A. The IRAC 8 micron image including Ar ejecta is distributed in a shell-like morphology which is coincident with dust features, suggesting that dust has formed in the ejecta. We create a cold dust map that shows excess emission in the northwestern shell. We fit the spectral energy distribution of the SNR using the continuous distributions of ellipsoidal (CDE) grain model of pre-solar grain SiO2 that reproduces the 21 and 9 micron dust features and discuss grains of SiC and PAH that may be responsible for the 10-13 micron dust features. To reproduce the long-wavelength continuum, we explore models consisting of different grains including Mg2SiO4, MgSiO3, Al2O3, FeS, carbon, and Fe3O4. We tested a model with a temperature-dependent silicate absorption coefficient. We detect cold dust (27-44 K) in the remnant, making this the fourth such SNR with freshly-formed dust. The total dust mass in the SNR ranges from 0.08-0.9 Msun depending on the grain composition, which is comparable to predicted masses from theoretical models. Our estimated dust masses are consistent with the idea that SNe are a significant source of dust in the early Universe.Comment: MNRAS: accepted on June 28, 2018 and published on July 4, 201