Eko Magazine

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Crystal science fundamentals

The fundamentals of crystal science notably crystallography, crystal chemistry, crystal defects, crystal morphology and the surface chemistry of crystals are introduced with particular emphasis on organic crystals

Community Benefit Agreements: A Symptom, Not the Antidote, of Bilateral Land Use Regulation

Community Benefits Agreements (CBAs)—private agreements between land developers and community members exchanging benefits for support or tolerance of a project—have recently emerged as part of a larger movement in American land use regulation away from a unilateral, government-dominated model toward a more negotiated paradigm. Unfortunately, though they arose in part to address issues found in the predominantly bilateral negotiated model, CBAs have been accompanied by significant problems of their own. Most notably, concerns such as whether to engage in a CBA process, the appropriate framework for negotiation, and the relationship of CBAs to the public regulatory-approval process are typically left to the discretion of the developer. As a result, such agreements typically develop in parallel to the public process but largely independent of it—a redundancy that leads to additional costs for both developers and community members. More importantly, the negotiation process results in less-than-optimal agreements that disproportionately reflect the interests of the developer. These weaknesses, however, ultimately point to the continued inadequacy of the underlying public process in advancing legitimate land use decisions. This symposium essay briefly outlines the modern public land use decision-making process’s transition from a unilateral model to a bilateral-negotiation model; discusses the rise of CBAs as a response to shortcomings of the bilateral process; analyzes CBAs’ benefits and drawbacks; and suggests how elements of the CBA process can be integrated into a more effective negotiating model. In particular, rather than encouraging the creation of CBAs, local governments should seek to integrate the most successful elements of the CBA process into the existing bilateral negotiation framework, creating a more multilateral, community-oriented decision-making process

Intra-Annual Variability of Silver Carp Populations in the Des Moines River, USA

Since their introduction in the 1970s, Silver Carp Hypophthalmichthys molitrix have spread throughout the Mississippi River basin. Management of any species relies on an accurate understanding of population characteristics and dynamics. However, Silver Carp seasonal sampling variation is unknown. Sampling during periods of peak catch rates would facilitate Silver Carp assessment and management, improving monitoring and removal techniques. The objective of this study was to evaluate adult Silver Carp seasonal sampling variation with boat electroshocking and trammel nets. Silver Carp were collected monthly (April–October) during 2014 and 2015 from four locations in the Des Moines River, Iowa. Trammel nets rarely captured Silver Carp (mean ± SE = 4.9 ± 1.6 fish/net; 60% of fish were captured in 6.3% of net sets) and therefore were not included in analyses. Electroshocking catch rates (CPUEs) exhibited a bimodal distribution, with peak CPUEs generally occurring in May, June, and September and lower catch rates observed during July and August. Catch rates were positively related to river discharge at upstream sites but not at downstream sites. Silver Carp size structure was similar among months and sites except at Cliffland, where fish were smaller during August and October compared to earlier in the year. Finally, Silver Carp condition peaked during April and May and decreased throughout the year except at Keokuk, where peaks were observed during both May and August. Although spatiotemporal variability was substantial, these results suggest that sampling of Silver Carp via electroshocking in May–June and September–October generally produces higher catch rates compared to July–August sampling and generates a more representative size structure. Using site-specific knowledge, monitoring and surveillance programs could more effectively sample during these periods of high vulnerability and densities in order to manage the spread and impacts of Silver Carp at statewide and regionwide scales

Titanium K-Shell X-Ray Production from High Velocity Wire Arrays Implosions on the 20-MA Z Accelerator

The advent of the 20-MA Z accelerator [R.B. Spielman, C. Deeney, G.A. Chandler, et al., Phys. Plasmas 5, 2105, (1997)] has enabled implosions of large diameter, high-wire-number arrays of titanium to begin testing Z-pinch K-shell scaling theories. The 2-cm long titanium arrays, which were mounted on a 40-mm diameter, produced between 75{+-}15 to 125{+-}20 kJ of K-shell x-rays. Mass scans indicate that, as predicted, higher velocity implosions in the series produced higher x-ray yields. Spectroscopic analyses indicate that these high velocity implosions achieved peak electron temperatures from 2.7{+-}0.1 to 3.2{+-}0.2 keV and obtained a K-shell emission mass participation of up to 12%