Plant Community Patterns on Upland Prairie in the Eastern Nebraska Sandhills

Topography is an important factor in determining vegetation patterns in grasslands. We collected frequency of occurrence data from transects on dune tops, south-facing slopes, north-facing slopes, and interdunal valleys in the eastern Sandhills of Nebraska to determine the effect of topographical position on plant species composition. We used canonical discriminant analysis to separate the four topographical positions based on frequency of occurrence of the 18 principal planttaxa. Topographic position played an important role in plant distribution on upland prairie with interdunal transects strongly separated from transects on other topographical positions. Bluegrasses (Poa L. spp.), switchgrass (Panicum virgatum L.), and white sage (Artemisia ludoviciana Nutt.) were highly associated with interdunal valleys. Little bluestem [Schizachyrium scoparium (Michx.)] and cool-season grasses, such as needlegrasses (Stipa L. spp.) and Junegrass [Koeleria pyramidata (Lam.) Beauv.], tended to be associated with north-facing slopes and warm-season grasses, such as prairie sandreed [Calamovilfa longifolia (Hook) Scrihn.] and sand bluestem (Andropogon hallii Hack.), tended to be associated with south-facing slopes. Sedges (Carex L. spp.), western ragweed (Ambrosia psilostachya DC.), and Scribner dichanthelium [Dichanthelium oligosanthes (Schult.) Gould var. scribnerianum (Nash)] were the most common taxa occurring over all topographic positions. Aspect proved to be an important factor in influencing vegetation distribution in the eastern Sandhills of Nebraska

Persistence Wins: Long-Term Agricultural Conservation Outreach Pays Off

This article discusses the lesson learned from an Extension, state, and federal agency coordinated water quality project that was formally started in 1995. In the project, educational programing was provided, high risk areas were identified, and BMPs were implemented on these areas. The net result of BMP implementation was a 38% improvement in South Dakota Bad River water quality. This improvement was attributed to Extension and others providing leadership on: 1) the development of local learning communities and 2) identification and implementing BMP\u27s in high risk areas. This work demonstrates that Extension can make a difference

Reduced Lentivirus Susceptibility in Sheep with TMEM154 Mutations

Visna/Maedi, or ovine progressive pneumonia (OPP) as it is known in the United States, is an incurable slow-acting disease of sheep caused by persistent lentivirus infection. This disease affects multiple tissues, including those of the respiratory and central nervous systems. Our aim was to identify ovine genetic risk factors for lentivirus infection. Sixty-nine matched pairs of infected cases and uninfected controls were identified among 736 naturally exposed sheep older than five years of age. These pairs were used in a genome-wide association study with 50,614 markers. A single SNP was identified in the ovine transmembrane protein (TMEM154) that exceeded genome-wide significance (unadjusted p-value 3×10−9). Sanger sequencing of the ovine TMEM154 coding region identified six missense and two frameshift deletion mutations in the predicted signal peptide and extracellular domain. Two TMEM154 haplotypes encoding glutamate (E) at position 35 were associated with infection while a third haplotype with lysine (K) at position 35 was not. Haplotypes encoding full-length E35 isoforms were analyzed together as genetic risk factors in a multi-breed, matched case-control design, with 61 pairs of 4-year-old ewes. The odds of infection for ewes with one copy of a full-length TMEM154 E35 allele were 28 times greater than the odds for those without (p-value<0.0001, 95% CI 5–1,100). In a combined analysis of nine cohorts with 2,705 sheep from Nebraska, Idaho, and Iowa, the relative risk of infection was 2.85 times greater for sheep with a full-length TMEM154 E35 allele (p-value<0.0001, 95% CI 2.36–3.43). Although rare, some sheep were homozygous for TMEM154 deletion mutations and remained uninfected despite a lifetime of significant exposure. Together, these findings indicate that TMEM154 may play a central role in ovine lentivirus infection and removing sheep with the most susceptible genotypes may help eradicate OPP and protect flocks from reinfection

Are Political Orientations Genetically Transmitted?

We test the possibility that political attitudes and behaviors are the result of both environmental and genetic factors. Employing standard methodological approaches in behavioral genetics—–specifically, comparisons of the differential correlations of the attitudes of monozygotic twins and dizygotic twins—–we analyze data drawn from a large sample of twins in the United States, supplemented with findings from twins in Australia. The results indicate that genetics plays an important role in shaping political attitudes and ideologies but a more modest role in forming party identification; as such, they call for finer distinctions in theorizing about the sources of political attitudes. We conclude by urging political scientists to incorporate genetic influences, specifically interactions between genetic heritability and social environment, into models of political attitude formation

Formation of nanometer sized Cu Sn Se particles in Cu2ZnSnSe4 thin films and their effect on solar cell efficiency

Atom probe tomography and transmission electron microscopy are used to study the formation of nano sized Cu-Sn-Se particles in Cu2ZnSnSe4 thin -films. For a Cu -rich precursor, which was deposited at 320 degrees C under Cu- and Zn-rich growth conditions, Cu2-xSe grains at the surface are detected. During annealing the precursor at 500 degrees C in a SnSe + Se atmosphere most of the Cu2-xSe is transformed to Cu2ZnSnSe4 via the consumption of excessive ZnSe and incorporation of Sn. However, atom probe tomography studies also reveal the formation of various nanometer-sized Cu-Sn-Se particles close to the CdS/Cu(2)ZnSnSe4 interface. One of those particles has a composition close to the Cu2SnSe3 compound. This phase has a smaller band gap than Cu2ZnSnSe4 and is proposed to lead to a significant drop in the open -circuit voltage and could be the main cause for a detrimental p-n junction and the zero efficiency of the final device. Possible effects of the other phases on solar cell performance and formation mechanisms are discussed as well. (C)2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Atom probe tomography study of internal interfaces in Cu2ZnSnSe4 thin-films

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