Economic phases of erosion control in southern Iowa and northern Missouri

The Soil Erosion Service of the United States Department of Agriculture has 32 Erosion Control Projects under way in 31 states. More projects will be initiated in the near future. One of these demonstrational and experimental projects embraces about 152,000 acres of the Big Creek watershed area in Ringgold and Decatur counties, Iowa, and Harrison County, Missouri. The headquarters for this project of the Soil Erosion Service are at Bethany, Mo. The government invites the farmers of this area to enter a cooperative agreement, under which the Soil Erosion Service agrees to assist the farmer in controlling erosion, and the farmer agrees to follow an erosion control program for 5 years. This program is worked out individually, for each cooperating farmer, by the farmer himself and the soil erosion experts. The government furnishes special equipment for terracing and gully control, as well as a portion of the seed, fertilizer and limestone necessary for an erosion control program

Weed Control Methods Handbook: Tools & Techniques for Use in Natural Areas

Invasive non-native plants are a serious threat to native species, communities, and ecosystems in many areas around the world. They can compete with and displace native plants, animals, and other organisms that depend on them, alter ecosystem functions and cycles significantly, hybridize with native species, and promote other invaders. The good news is that many plant invasions can be reversed, halted or slowed, and in certain situations, even badly infested areas can be restored to healthy systems dominated by native species. In most instances this requires taking action to control and manage those invasive plants. This handbook provides you with detailed information about the tools and techniques available for controlling invasive plants, or weeds, in natural areas. Whenever possible, language familiar to natural area managers is used, and unfamiliar terms and jargon borrowed from other fields are defined. Before embarking on a weed management program, it is important to develop a straightforward rationale for the actions you plan to take. We believe this is best accomplished using an adaptive management approach as follows (see Figure 1): (1) establish management goals and objectives for the site; (2) determine which plant species or populations, if any, block or have potential to block attainment of the management goals and objectives; (3) determine which methods are available to control the weed(s); (4) develop and implement a management plan designed to move conditions toward management goals and objectives; (5) monitor and assess the impacts of management actions in terms of their effectiveness in moving conditions toward these goals and objectives; and (6) reevaluate, modify, and start the cycle again. Note that control activities are not begun until the first three steps have been taken. A weed control program is best viewed as part of an overall restoration program, so focus on what you want in place of the weed, rather than simply eliminating the weed. When selecting control methods, keep in mind that the ultimate purpose of the work is to preserve native species, communities, and/or functioning ecosystems

Actual and Predicted Behavior of Large Metal Culverts

The stability of large metal culverts depends on the performance of the backfill around the pipe, which must be considered as a part of the structure when evaluating its safety. A simplified method to evaluate the current stability of such a structure on the basis of the structure\u27s shape is derived. Useful when limited amount of information is available, this method provides an economical procedure for: (1) evaluating the condition of the existing backfill and its capability to provide a safe support for the structure; (2) predicting final movements and determining if additional investigations are necessary to establish the safety of the structure; and (3) determining if measured deflections are in agreement with those predicted and, if not, determining if the safety of the structure is endangered by phenomena other than the expected behavior of surrounding soil (e.g. voids near pipe, soil erosion, non-symmetric loadings)

Spin susceptibilities, spin densities and their connection to spin-currents

We calculate the frequency dependent spin susceptibilities for a two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit interaction. The resonances of the susceptibilities depends on the relative values of the Rashba and Dresselhaus spin-orbit constants, which could be manipulated by gate voltages. We derive exact continuity equations, with source terms, for the spin density and use those to connect the spin current to the spin density. In the free electron model the susceptibilities play a central role in the spin dynamics since both the spin density and the spin current are proportional to them.Comment: 6 pages, revtex4 styl

Matching concepts across HOL libraries

Many proof assistant libraries contain formalizations of the same mathematical concepts. The concepts are often introduced (defined) in different ways, but the properties that they have, and are in turn formalized, are the same. For the basic concepts, like natural numbers, matching them between libraries is often straightforward, because of mathematical naming conventions. However, for more advanced concepts, finding similar formalizations in different libraries is a non-trivial task even for an expert. In this paper we investigate automatic discovery of similar concepts across libraries of proof assistants. We propose an approach for normalizing properties of concepts in formal libraries and a number of similarity measures. We evaluate the approach on HOL based proof assistants HOL4, HOL Light and Isabelle/HOL, discovering 398 pairs of isomorphic constants and types

Human Activity Mediates a Trophic Cascade Caused by Wolves

Experimental evidence of trophic cascades initiated by large vertebrate predators is rare in terrestrial ecosystems. A serendipitous natural experiment provided an opportunity to test the trophic cascade hypothesis for wolves (Canis lupus) in Banff National Park, Canada. The first wolf pack recolonized the Bow Valley of Banff National Park in 1986. High human activity partially excluded wolves from one area of the Bow Valley (low-wolf area), whereas wolves made full use of an adjacent area (high-wolf area). We investigated the effects of differential wolf predation between these two areas on elk (Cervus elaphus) population density, adult female survival, and calf recruitment; aspen (Populus tremuloides) recruitment and browse intensity; willow (Salix spp.) production, browsing intensity, and net growth; beaver (Castor canadensis) density; and riparian songbird diversity, evenness, and abundance. We compared effects of recolonizing wolves on these response variables using the log response ratio between the low-wolf and high-wolf treatments. Elk population density diverged over time in the two treatments, such that elk were an order of magnitude more numerous in the low-wolf area compared to the high-wolf area at the end of the study. Annual survival of adult female elk was 62% in the high-wolf area vs. 89% in the low-wolf area. Annual recruitment of calves was 15% in the high-wolf area vs. 27% without wolves. Wolf exclusion decreased aspen recruitment, willow production, and increased willow and aspen browsing intensity. Beaver lodge density was negatively correlated to elk density, and elk herbivory had an indirect negative effect on riparian songbird diversity and abundance. These alternating patterns across trophic levels support the wolf-caused trophic cascade hypothesis. Human activity strongly mediated these cascade effects, through a depressing effect on habitat use by wolves. Thus, conservation strategies based on the trophic importance of large carnivores have increased support in terrestrial ecosystems. Read More: http://www.esajournals.org/doi/full/10.1890/04-126

Mastering the Hard Stuff: The History of College Concrete-Canoe Races and the Growth of Engineering Competition Culture

This article details the history of college engineering competitions, originating with student concrete-canoe racing in the 1970s, through today’s multi-million-dollar international multiplicity of challenges. Despite initial differences between engineering educators and industry supporters over the ultimate purpose of undergraduate competitions, these events thrived because they evolved to suit many needs of students, professors, schools, corporations, professional associations, and the engineering profession itself. The twenty-first-century proliferation of university-level competitions in turn encouraged a trickling-down of technical contests to elementary-age children and high schools, fostering the institutionalization of what might be called a competition culture in engineering

Ciliary entry of the kinesin-2 motor KIF17 is regulated by importin-beta2 and RanGTP

The biogenesis, maintenance, and function of primary cilia are controlled through intraflagellar transport (IFT) driven by two kinesin-2 family members, the heterotrimeric KIF3A/KIF3B/KAP complex and the homodimeric KIF17 motor1,2. How these motors and their cargoes gain access to the ciliary compartment is poorly understood. We identify a ciliary localization signal (CLS) in the KIF17 tail domain that is necessary and sufficient for ciliary targeting. Similarities between the CLS and classic nuclear localization signals (NLS) suggests that similar mechanisms regulate nuclear and ciliary import. We hypothesize that ciliary targeting of KIF17 is regulated by a Ran-GTP gradient across the ciliary base. Consistent with this, cytoplasmic expression of GTP-locked Ran(G19V) disrupts the gradient and abolishes ciliary entry of KIF17. Furthermore, KIF17 interacts with importin-β2 in a manner dependent on the CLS and inhibited by Ran-GTP. We propose that Ran plays a global role in regulating cellular compartmentalization by controlling the shuttling of cytoplasmic proteins into nuclear and ciliary compartments

Dnmt3a regulates emotional behavior and spine plasticity in the nucleus accumbens.

Despite abundant expression of DNA methyltransferases (Dnmts) in brain, the regulation and behavioral role of DNA methylation remain poorly understood. We found that Dnmt3a expression was regulated in mouse nucleus accumbens (NAc) by chronic cocaine use and chronic social defeat stress. Moreover, NAc-specific manipulations that block DNA methylation potentiated cocaine reward and exerted antidepressant-like effects, whereas NAc-specific Dnmt3a overexpression attenuated cocaine reward and was pro-depressant. On a cellular level, we found that chronic cocaine use selectively increased thin dendritic spines on NAc neurons and that DNA methylation was both necessary and sufficient to mediate these effects. These data establish the importance of Dnmt3a in the NAc in regulating cellular and behavioral plasticity to emotional stimuli