Resolving the 150 year debate over the ecological history of the common periwinkle snail, Littorina littorea, in northeast North America

Littorina littorea (common periwinkle snail) is highly abundant in both Europe and North America. A known native of Europe, its presence in North America has been the subject of a one-hundred year debate. Prior published work attempting to resolve its cryptogenic (=uncertain origin) status with historical, archaeological, ecological and/or genetic data were not successful. I therefore included novel parasite and molecular evidence to definitively resolve L. littorea\u27s North American cryptogenic status. First, I explored trematode species richness patterns in European versus North American L. littorea and two co-occurring native congeners, L. saxatilis and L. obtusata. Through extensive field and literature surveys, I found only L. littorea to possess significantly fewer trematode species in North America, while all Littorina sp. North American trematodes were a nested subset of Europe. Overall, these results suggest a recent invasion to North America for L. littorea and an older, natural expansion to North America for L. saxatilis and L. obtusata.. Second, I explored genetic founder effect signatures in North American L. littorea. I sequenced a ∼1200 base-pair region of mitochondrial DNA in nearly 400 Europe and North American snails. My results demonstrate a significant reduction in overall genetic diversity in North America versus Europe, nested and common haplotype frequencies in North America, and a divergence estimate of no greater than 450 years ago. Third, I explored genetic founder effect signatures in L. littorea\u27s most common trematode parasite, Cryptocotyle lingua. I sequenced a 1043 base-pair region of mitochondrial DNA and found Cr. lingua to show several signatures of a recent introduction to North America, including a significant reduction in haplotype diversity in North America, nested and common haplotype frequencies in North America, and a range of divergence estimates between 240-480 years ago. Altogether, these three corroborative pieces of evidence suggest a recent, likely human-mediated introduction of North American L. littorea from Europe. This work represents the first time ecological studies of parasites and genetics have been used in concert to resolve the cryptogenic status of an important marine species. The successful application of these techniques can therefore be useful in cryptogenic investigations worldwide

Optimization of solar cells for air mass zero operation and a study of solar cells at high temperatures, phase 3

The etch-back epitaxy process is described for producing thin, graded composition GaAlAs layers. The palladium-aluminum contact system is discussed along with its associated problems. Recent solar cell results under simulated air mass zero light and at elevated temperatures are reported and the growth of thin polycrystalline GaAs films on foreign substrates is developed

Powder metallurgy in aerospace research: A survey

The various techniques by which powders can be produced, as pure metals or as alloys, are discussed; the methods by which these powders can be formed into the final parts are explained as well as further processing that may be necessary to meet specific requirements. The NASA developments are detailed, and references are provided for those who wish to obtain further information characteristic of any methodology

Intervention Development to Improve Foster Youth Mental Health by Targeting Coping Self-Efficacy and Help-seeking

This study articulates the iterative development of an intervention called Strengthening Youth Networks and Coping (SYNC), which is designed to target coping self-efficacy and help-seeking intentions and behaviors among youth in foster care. The overarching goal is to design an intervention that will be a feasible and acceptable enhancement to existing child welfare services, and that will address modifiable determinants among adolescents involved in child welfare system that are related to elevated risk for mental health challenges, limited support network capacity, and service disengagement after exiting foster care. In this paper, we describe our initial needs assessment, explain how we selected proximal intervention mechanisms (i.e., intermediate outcomes) to target, and outline the preliminary intervention development process, including ongoing insights we received from a research advisory group including members with lived experience. Next, we report and discuss the initial acceptability pre-testing data collected from youth (N=30) as well as feasibility data collected from providers (N=82), results from which were used to refine the SYNC intervention framework prior to robust efficacy testing. Findings highlight the need and importance of targeting youth coping and help-seeking, integrating programming within existing transition services, delivering this content in a group-based format that includes near-peer mentors and facilitators with lived experience, and developing options that work for the heterogeneous population of young people in foster care. The results also highlight the key objective of capturing youth’s interests prior to enrolling in the program (e.g., language used in recruitment materials), holding their interest throughout the program (e.g., creating opportunities for youth to engage with other youth with similar experiences), and suggestions to encourage youth’s engagement and participation. This paper articulates the value of this intervention development approach, and the sequential phases of this intervention development process as well as the results, which may be useful to applied researchers and practitioners working with youth in foster care and other priority populations

Principal Component Analysis of the Time- and Position-Dependent Point Spread Function of the Advanced Camera for Surveys

We describe the time- and position-dependent point spread function (PSF) variation of the Wide Field Channel (WFC) of the Advanced Camera for Surveys (ACS) with the principal component analysis (PCA) technique. The time-dependent change is caused by the temporal variation of the $HST$ focus whereas the position-dependent PSF variation in ACS/WFC at a given focus is mainly the result of changes in aberrations and charge diffusion across the detector, which appear as position-dependent changes in elongation of the astigmatic core and blurring of the PSF, respectively. Using >400 archival images of star cluster fields, we construct a ACS PSF library covering diverse environments of the $HST$ observations (e.g., focus values). We find that interpolation of a small number ($\sim20$) of principal components or ``eigen-PSFs'' per exposure can robustly reproduce the observed variation of the ellipticity and size of the PSF. Our primary interest in this investigation is the application of this PSF library to precision weak-lensing analyses, where accurate knowledge of the instrument's PSF is crucial. However, the high-fidelity of the model judged from the nice agreement with observed PSFs suggests that the model is potentially also useful in other applications such as crowded field stellar photometry, galaxy profile fitting, AGN studies, etc., which similarly demand a fair knowledge of the PSFs at objects' locations. Our PSF models, applicable to any WFC image rectified with the Lanczos3 kernel, are publicly available.Comment: Accepted to PASP. To appear in December issue. Figures are degraded to meet the size limit. High-resolution version can be downloaded at http://acs.pha.jhu.edu/~mkjee/acs_psf/acspsf.pd

Trends in illegal wildlife trade: Analyzing personal baggage seizure data in the Pacific Northwest.

This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.The illegal import of wildlife and wildlife products is a growing concern, and the U.S. is one of the world’s leading countries in the consumption and transit of illegal wildlife and their derivatives. Yet, few U.S. studies have analyzed the illegal wildlife trade (IWT) on a national or local scale. Moreover, to our knowledge, no studies have specifically examined the trends associated with IWT moving through personal baggage. This work aimed to better understand the magnitude of illegal wildlife importation into U.S. ports of entry by determining trends associated with illegal wildlife products from personal baggage seizures, using the Pacific Northwest (PNW) as a specific case study. To identify the most influential factors determining the numbers and types of personal baggage seizures into PNW, we analyzed 1,731 records between 1999 and 2016 from the Fish and Wildlife Service’s (FWS) Law Enforcement Management Information System (LEMIS) database. We found five significant contributors: taxonomic classification of wildlife, categorical import date, wildlife product, source region, and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) status. While wildlife seizures across taxonomic categories have generally decreased in the PNW since 2008, other findings provide a reason for concern. More specifically, mammals were identified as the largest animal group of seized wildlife, and temporal trends indicate increases in seizures for this and several other taxonomic groups. Many of the seizures originated from overseas, with East Asia serving as the largest source. Our PNW case study can be a model for how large-scale geographical seizure data can be used to inform about the major factors that have historically and presently contribute to IWT, with conservation implications globally.ECU Open Access Publishing Support Fun

A Lensed Arc in the Low Redshift Cluster Abell 2124

We report the discovery of an arc-like object 27" from the center of the cD galaxy in the redshift $z=0.066$ cluster A2124. Observations with the Keck II telescope reveal that the object is a background galaxy at $z=0.573$, apparently lensed into an arc of length \sim 8 \farcs5 and total R magnitude $m_R = 20.86\pm0.07$. The width of the arc is resolved; we estimate it to be $\sim$0\farcs6 after correcting for seeing. A lens model of the A2124 core mass distribution consistent with the cluster galaxy velocity dispersion reproduces the observed arc geometry and indicates a magnification factor \gta 9. With this magnification, the strength of the [OII] \lambda 3727 line implies a star-formation rate of SFR \sim 0.4 h^{-2}\msun yr^{-1}$. A2124 thus appears to be the lowest redshift cluster known to exhibit strong lensing of a distant background galaxy.Comment: 6 pages using emulateapj.sty; 4 Postscript figures; Figure 4 uses color. Accepted for publication, but ApJ Letters' new policy of counting data images makes the manuscript too long; will appear in main journal. This final version has minor correction

The ACS Fornax Cluster Survey. III. Globular Cluster Specific Frequencies of Early-Type Galaxies

The globular cluster (GC) specific frequency ($S_N$), defined as the number of GCs per unit galactic luminosity, represents the efficiency of GC formation (and survival) compared to field stars. Despite the naive expectation that star cluster formation should scale directly with star formation, this efficiency varies widely across galaxies. To explore this variation we measure the z-band GC specific frequency ($S_{N,z}$) for 43 early-type galaxies (ETGs) from the Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) Fornax Cluster Survey. Combined with the homogenous measurements of $S_{N,z}$ in 100 ETGs from the HST/ACS Virgo Cluster Survey from Peng et al. (2008), we investigate the dependence of $S_{N,z}$ on mass and environment over a range of galaxy properties. We find that $S_{N,z}$ behaves similarly in the two galaxy clusters, despite the clusters' order-of-magnitude difference in mass density. The $S_{N,z}$ is low in intermediate-mass ETGs ($-20<M_z<-23$), and increases with galaxy luminosity. It is elevated at low masses, on average, but with a large scatter driven by galaxies in dense environments. The densest environments with the strongest tidal forces appear to strip the GC systems of low-mass galaxies. However, in low-mass galaxies that are not in strong tidal fields, denser environments correlate with enhanced GC formation efficiencies. Normalizing by inferred halo masses, the GC mass fraction, $\eta=(3.36\pm0.2)\times10^{-5}$, is constant for ETGs with stellar masses $\mathcal{M}_\star \lesssim 3\times10^{10}M_\odot$, in agreement with previous studies. The lack of correlation between the fraction of GCs and the nuclear light implies only a weak link between the infall of GCs and the formation of nuclei.Comment: 16 pages, 7 figures, 6 tables; accepted by Ap