University of Nebraska–Lincoln

About: University of Nebraska–Lincoln is a education organization based out in Lincoln, Nebraska, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 28059 authors who have published 61544 publications receiving 2139104 citations. The organization is also known as: Nebraska & UNL.

The microbiome of uncontacted Amerindians

Abstract: Most studies of the human microbiome have focused on westernized people with life-style practices that decrease microbial survival and transmission, or on traditional societies that are currently in transition to westernization We characterize the fecal, oral, and skin bacterial microbiome and resistome of members of an isolated Yanomami Amerindian village with no documented previous contact with Western people These Yanomami harbor a microbiome with the highest diversity of bacteria and genetic functions ever reported in a human group Despite their isolation, presumably for >11,000 years since their ancestors arrived in South America, and no known exposure to antibiotics, they harbor bacteria that carry functional antibiotic resistance (AR) genes, including those that confer resistance to synthetic antibiotics and are syntenic with mobilization elements These results suggest that westernization significantly affects human microbiome diversity and that functional AR genes appear to be a feature of the human microbiome even in the absence of exposure to commercial antibiotics AR genes are likely poised for mobilization and enrichment upon exposure to pharmacological levels of antibiotics Our findings emphasize the need for extensive characterization of the function of the microbiome and resistome in remote nonwesternized populations before globalization of modern practices affects potentially beneficial bacteria harbored in the human body

Two-Dimensional Boron Monolayer Sheets

Abstract: Boron, a nearest-neighbor of carbon, is possibly the second element that can possess free-standing flat monolayer structures, evidenced by recent successful synthesis of single-walled and multiwalled boron nanotubes (MWBNTs). From an extensive structural search using the first-principles particle-swarm optimization (PSO) global algorithm, two boron monolayers (α1- and β1-sheet) are predicted to be the most stable α- and β-types of boron sheets, respectively. Both boron sheets possess greater cohesive energies than the state-of-the-art two-dimensional boron structures (by more than 60 meV/atom based on density functional theory calculation using PBE0 hybrid functional), that is, the α-sheet previously predicted by Tang and Ismail-Beigi and the g1/8- and g2/15-sheets (both belonging to the β-type) recently reported by Yakobson and co-workers. Moreover, the PBE0 calculation predicts that the α-sheet is a semiconductor, while the α1-, β1-, g1/8-, and g2/15-sheets are all metals. When two α1 monolayers are sta...

Scaling behavior of moisture-induced grain degradation in polycrystalline hybrid perovskite thin films

Abstract: The stability of perovskite solar cells has shown a huge variation with respect to the film process and film morphology, while the underlining mechanism for the morphology-dependent degradation of the perovskite film has remained elusive. Herein, we report a scaling behavior of moisture-induced grain degradation in polycrystalline CH3NH3PbI3 films. The degradation rates of CH3NH3PbI3 films in moisture were shown to be sensitive to the grain sizes. The duration that was needed for different films to degrade by the same percent showed a linear relationship with the grain size, despite the fact that the films were formed by five different deposition methods. This scaling behavior can be explained by the degradation along the in-plane direction, which is initiated at the grain boundary (GB). The GBs of CH3NH3PbI3 films consist of an amorphous intergranular layer, which allows quick diffusion of moisture into the perovskite films. It was found that thermal annealing induced surface self-passivation plays a critical role in stabilizing the surfaces of thin films and single crystals by reducing the moisture-sensitive methylammonium ions at the surface. The determination of the scaling behavior of grain degradation highlights the importance of stabilizing the GBs to improve the stability of perovskite solar cells.

Statistical evaluation of image quality measures

Abstract: In this work we comprehensively categorize image qual- ity measures, extend measures defined for gray scale images to their multispectral case, and propose novel image quality measures. They are categorized into pixel difference-based, correlation-based, edge-based, spectral-based, context-based and human visual sys- tem (HVS)-based measures. Furthermore we compare these mea- sures statistically for still image compression applications. The sta- tistical behavior of the measures and their sensitivity to coding artifacts are investigated via analysis of variance techniques. Their similarities or differences are illustrated by plotting their Kohonen maps. Measures that give consistent scores across an image class and that are sensitive to coding artifacts are pointed out. It was found that measures based on the phase spectrum, the multireso- lution distance or the HVS filtered mean square error are computa- tionally simple and are more responsive to coding artifacts. We also demonstrate the utility of combining selected quality metrics in build- ing a steganalysis tool. © 2002 SPIE and IS&T.