Solitary and compact-like shear waves in the bulk of solids

We show that a model proposed by Rubin, Rosenau, and Gottlieb [J. Appl. Phys. 77 (1995) 4054], for dispersion caused by an inherent material characteristic length, belongs to the class of simple materials. Therefore, it is possible to generalize the idea of Rubin, Rosenau, and Gottlieb to include a wide range of material models, from nonlinear elasticity to turbulence. Using this insight, we are able to fine-tune nonlinear and dispersive effects in the theory of nonlinear elasticity in order to generate pulse solitary waves and also bulk travelling waves with compact support

Landscape impacts on pollinator communities in temperate systems: evidence and knowledge gaps

Summary 1. This review assesses current knowledge about the interplay between landscape and pollinator communities. Our primary aim is to provide an evidence base, identify key gaps in knowledge and highlight initiatives that will help develop and improve strategies for pollinator conservation. 2. Human-dominated landscapes (such as arable land and urban environments) can have detrimental impacts on pollinator communities but these negative effects can be ameliorated by proximity to semi-natural habitat and habitat corridors. There is also evidence to suggest that increased landscape heterogeneity and landscape configuration can play an important role in the maintenance of diverse pollinator communities. 3. Landscape characteristics have direct impacts on pollinator communities but can also influence abundance and richness through interaction with other drivers such as changing climate or increased chemical inputs in land management. 4. The majority of existing literature focuses on specific hymenopteran groups but there is a lack of information on the impact of landscape changes on non-bee taxa. Research is also needed on the effectiveness of management interventions for pollinators and multiple year observations are required for both urban and rural initiatives. 5. Current policies and monitoring schemes could contribute data that will plug gaps in knowledge, thus enabling greater understanding of relationships between landscapes and pollinator populations. This would in turn help design mitigation and adaptation strategies for pollinator conservation

The Dislocation Stress Functions From the Double Curl T(3)-Gauge Equation: Linearity and a Look Beyond

T(3)-gauge model of defects based on the gauge Lagrangian quadratic in the gauge field strength is considered. The equilibrium equation of the medium is fulfilled by the double curl Kroner's ansatz for stresses. The problem of replication of the static edge dislocation along third axis is analysed under a special, though conventional, choice of this ansatz. The translational gauge equation is shown to constraint the functions parametrizing the ansatz (the stress functions) so that the resulting stress component $\sigma_{3 3}$ is not that of the edge defect. Another translational gauge equation with the double curl differential operator is shown to reproduce both the stress functions, as well as the stress tensors, of the standard edge and screw dislocations. Non-linear extension of the newly proposed translational gauge equation is given to correct the linear defect solutions in next orders. New gauge Lagrangian is suggested in the Hilbert-Einstein form.Comment: 21 pages, LaTeX, no figure

The Cauchy problem for a class of two-dimensional nonlocal nonlinear wave equations governing anti-plane shear motions in elastic materials

This paper is concerned with the analysis of the Cauchy problem of a general class of two-dimensional nonlinear nonlocal wave equations governing anti-plane shear motions in nonlocal elasticity. The nonlocal nature of the problem is reflected by a convolution integral in the space variables. The Fourier transform of the convolution kernel is nonnegative and satisfies a certain growth condition at infinity. For initial data in $L^{2}$ Sobolev spaces, conditions for global existence or finite time blow-up of the solutions of the Cauchy problem are established.Comment: 15 pages. "Section 6 The Anisotropic Case" added and minor changes. Accepted for publication in Nonlinearit

A probabilistic model for gene content evolution with duplication, loss, and horizontal transfer

We introduce a Markov model for the evolution of a gene family along a phylogeny. The model includes parameters for the rates of horizontal gene transfer, gene duplication, and gene loss, in addition to branch lengths in the phylogeny. The likelihood for the changes in the size of a gene family across different organisms can be calculated in O(N+hM^2) time and O(N+M^2) space, where N is the number of organisms, $h$ is the height of the phylogeny, and M is the sum of family sizes. We apply the model to the evolution of gene content in Preoteobacteria using the gene families in the COG (Clusters of Orthologous Groups) database

Close Packing of Atoms, Geometric Frustration and the Formation of Heterogeneous States in Crystals

To describe structural peculiarities in inhomogeneous media caused by the tendency to the close packing of atoms a formalism based on the using of the Riemann geometry methods (which were successfully applied lately to the description of structures of quasicrystals and glasses) is developed. Basing on this formalism we find in particular the criterion of stability of precipitates of the Frank-Kasper phases in metallic systems. The nature of the ''rhenium effect'' in W-Re alloys is discussed.Comment: 14 pages, RevTex, 2 PostScript figure

Developing European conservation and mitigation tools for pollination services: approaches of the STEP (Status and Trends of European Pollinators) project

Pollinating insects form a key component of European biodiversity, and provide a vital ecosystem service to crops and wild plants. There is growing evidence of declines in both wild and domesticated pollinators, and parallel declines in plants relying upon them. The STEP project (Status and Trends of European Pollinators, 2010-2015, www.step-project.net) is documenting critical elements in the nature and extent of these declines, examining key functional traits associated with pollination deficits, and developing a Red List for some European pollinator groups. Together these activities are laying the groundwork for future pollinator monitoring programmes. STEP is also assessing the relative importance of potential drivers of pollinator declines, including climate change, habitat loss and fragmentation, agrochemicals, pathogens, alien species, light pollution, and their interactions. We are measuring the ecological and economic impacts of declining pollinator services and floral resources, including effects on wild plant populations, crop production and human nutrition. STEP is reviewing existing and potential mitigation options, and providing novel tests of their effectiveness across Europe. Our work is building upon existing and newly developed datasets and models, complemented by spatially-replicated campaigns of field research to fill gaps in current knowledge. Findings are being integrated into a policy-relevant framework to create evidence-based decision support tools. STEP is establishing communication links to a wide range of stakeholders across Europe and beyond, including policy makers, beekeepers, farmers, academics and the general public. Taken together, the STEP research programme aims to improve our understanding of the nature, causes, consequences and potential mitigation of declines in pollination services at local, national, continental and global scales.[ES] Los insectos polinizadores forman un componente clave de la biodiversidad europea, y proporcionan servicios vitales a los ecosistemas de plantas cultivadas y silvestres. Existe una creciente evidencia del declive de polinizadores silvestres y domesticados, y del declive paralelo de las plantas que dependen de ellos. El proyecto STEP (Estado y tendencias de los polinizadores europeos, 2010-2015, www.step-project.net) está documentando elementos críticos en la naturaleza y la extensión de estos declives, examinando características funcionales claves asociadas con el déficit de polinización, y desarrollando una Lista Roja de grupos de polinizadores europeos. Todas estas actividades juntas suponen el trabajo preliminar base para futuros programas de monitorización de polinizadores. STEP también investiga la importancia relativa de factores potenciales del declive de polinizadores, incluido el cambio climático, pérdida de hábitats y fragmentación, agroquímicos, patógenos, especies invasoras, contaminación lumínica, y otras interacciones. Se están midiendo los impactos ecológicos y económicos del declive de los servicios de polinizadores y de sus fuentes florales, incluyendo los efectos en las poblaciones de plantas silvestres, producción de cultivos y la alimentación humana. STEP está revisando las opciones de mitigación potenciales y las existentes, y proporcionando nuevos tests para su eficacia a lo largo de Europa. El trabajo se basa en modelos y conjuntos de datos desarrollados de novo y en otros ya existentes, complementados con campañas de trabajo de campo con replicación espacial para crear herramientas de soporte de decisiones basadas en la evidencia. STEP está estableciendo nexos de comunicación con un rango amplio de participantes a lo largo de Europa y fuera de ella, incluyendo a políticos, apicultores, granjeros, académicos y el público general. En conjunto, el programa de investigación STEP quiere mejorar nuestra comprensión de la naturaleza, las causas, consecuencias y mitigación potencial del declive de servicios de polinización a escala global, continental, nacional y localPeer reviewe

Intramural Duodenal Haematoma after Endoscopic Biopsy: Case Report and Review of the Literature

The development of intramural duodenal haematoma (IDH) after small bowel biopsy is an unusual lesion and has only been reported in 18 children. Coagulopathy, thrombocytopenia and some special features of duodenal anatomy, e.g. relatively fixed position in the retroperitoneum and numerous submucosal blood vessels, have been suggested as a cause for IDH. The typical clinical presentation of IDH is severe abdominal pain and vomiting due to duodenal obstruction. In addition, it is often associated with pancreatitis and cholestasis. Diagnosis is confirmed using imaging techniques such as ultrasound, magnetic resonance imaging or computed tomography and upper intestinal series. Once diagnosis is confirmed and intestinal perforation excluded, conservative treatment with nasogastric tube and parenteral nutrition is sufficient. We present a case of massive IDH following endoscopic grasp forceps biopsy in a 5-year-old girl without bleeding disorder or other risk for IDH, which caused duodenal obstruction and mild pancreatitis and resolved within 2 weeks of conservative management. Since duodenal biopsies have become the common way to evaluate children or adults for suspected enteropathy, the occurrence of this complication is likely to increase. In conclusion, the review of the literature points out the risk for IDH especially in children with a history of bone marrow transplantation or leukaemia

Beliefs about Appropriate Antibacterial Therapy, California

To our knowledge, previous population-based surveys have not assessed misconceptions about antibacterial drug use over time. We documented a 26.3% decline in a key misconception in California women in 2003 compared to 2000; declines varied significantly by education level. Educational campaigns specifically designed to influence important subpopulations are needed

Interpreting 16S metagenomic data without clustering to achieve sub-OTU resolution

The standard approach to analyzing 16S tag sequence data, which relies on clustering reads by sequence similarity into Operational Taxonomic Units (OTUs), underexploits the accuracy of modern sequencing technology. We present a clustering-free approach to multi-sample Illumina datasets that can identify independent bacterial subpopulations regardless of the similarity of their 16S tag sequences. Using published data from a longitudinal time-series study of human tongue microbiota, we are able to resolve within standard 97% similarity OTUs up to 20 distinct subpopulations, all ecologically distinct but with 16S tags differing by as little as 1 nucleotide (99.2% similarity). A comparative analysis of oral communities of two cohabiting individuals reveals that most such subpopulations are shared between the two communities at 100% sequence identity, and that dynamical similarity between subpopulations in one host is strongly predictive of dynamical similarity between the same subpopulations in the other host. Our method can also be applied to samples collected in cross-sectional studies and can be used with the 454 sequencing platform. We discuss how the sub-OTU resolution of our approach can provide new insight into factors shaping community assembly.Comment: Updated to match the published version. 12 pages, 5 figures + supplement. Significantly revised for clarity, references added, results not change