Analytical solution of two-layer beam taking into account interlayer slip and shear deformation

A mathematical model is proposed and its analytical solution derived for the analysis of the geometrically and materially linear two-layer beams with different material and geometric characteristics of an individual layer. The model takes into account the effect of the transverse shear deformation on displacements in each layer. The analytical study is carried out to evaluate the influence of the transverse shear deformation on the static and kinematic quantities. We study a simply supported two-layer planar beam subjected to the uniformly distributed load. Parametric studies have been performed to investigate the influence of shear by varying material and geometric parameters, such as interlayer slip modulus (K), flexural-to-shear moduli ratios (E/G) and span-to-depth ratios (L/h). The comparison of the results for vertical deflections shows that shear deformations are more important for high slip modulus, for ``short'' beams with small L/h ratios, and beams with high E/G ratios. In these cases, the effect of the shear deformations becomes significant and has to be addressed in design. It also becomes apparent that models, which consider the partial interaction between the layers, should be employed if beams have very flexible connections

Minimal cubic cones via Clifford algebras

We construct two infinite families of algebraic minimal cones in $R^{n}$. The first family consists of minimal cubics given explicitly in terms of the Clifford systems. We show that the classes of congruent minimal cubics are in one to one correspondence with those of geometrically equivalent Clifford systems. As a byproduct, we prove that for any $n\ge4$, $n\ne 16k+1$, there is at least one minimal cone in $R^{n}$ given by an irreducible homogeneous cubic polynomial. The second family consists of minimal cones in $R^{m^2}$, $m\ge2$, defined by an irreducible homogeneous polynomial of degree $m$. These examples provide particular answers to the questions on algebraic minimal cones posed by Wu-Yi Hsiang in the 1960's.Comment: Final version, corrects typos in Table

Isolation of Arabidopsis extracellular ATP‐binding proteins by affinity proteomics and identification of PHOSPHOLIPASE C‐LIKE 1 as an extracellular protein essential for fumonisin B1 toxicity

ATP is secreted to the extracellular matrix where it activates plasma membrane receptors for controlling plant growth and stress‐adaptive processes. DOES NOT RESPOND TO NUCLEOTIDES 1 (DORN1), the first plant ATP receptor was identified, but key downstream proteins are sought after. Here, we identified 120 proteins secreted by Arabidopsis cell cultures and screened them for putative stress‐responsive proteins using ATP‐affinity purification. We report three Arabidopsis proteins isolated by ATP‐affinity: PEROXIDASE 52, SUBTILASE‐LIKE SERINE PROTEASE 1.7, and PHOSPHOLIPASE C‐LIKE 1. In wildtype Arabidopsis, expression of genes encoding all three proteins responded to fumonisin B1, a cell death‐activating mycotoxin. Expression of PEROXIDASE 52 and PHOSPHOLIPASE C‐LIKE 1 genes was altered in fumonisin B1‐resistant salicylic acid induction‐deficient (sid2) mutants. Exposure to fumonisin B1 suppressed PHOSPHOLIPASE C‐LIKE 1 expression in sid2 mutants, suggesting that inactivation of this gene might provide mycotoxin tolerance. Accordingly, gene knockout mutants of PHOSPHOLIPASE C‐LIKE 1 were resistant to fumonisin B1‐induced death. Activation of PHOSPHOLIPASE C‐LIKE 1 gene expression by exogenous ATP was not blocked in dorn1 loss‐of‐function mutants, indicating that DORN1 is not required. Furthermore, exogenous ATP rescued both wildtype and dorn1 mutants from fumonisin B1 toxicity, suggesting that different ATP receptor(s) are operational in this process. Our results point to the existence of additional plant ATP receptor(s) and provide crucial downstream targets for use in designing screens to identify these receptors. Finally, PHOSPHOLIPASE C‐LIKE 1 serves as a convergence point for fumonisin B1 and extracellular ATP signalling, and functions in Arabidopsis stress response to fumonisin B1

Emergent Mesoscale Phenomena in Magnetized Accretion Disc Turbulence

We study how the structure and variability of magnetohydrodynamic (MHD) turbulence in accretion discs converge with domain size. Our results are based on a series of vertically stratified local simulations, computed using the Athena code, that have fixed spatial resolution, but varying radial and azimuthal extent (from \Delta R = 0.5H to 16H, where H is the vertical scale height). We show that elementary local diagnostics of the turbulence, including the Shakura-Sunyaev {\alpha} parameter, the ratio of Maxwell stress to magnetic energy, and the ratio of magnetic to fluid stresses, converge to within the precision of our measurements for spatial domains of radial size Lx \geq 2H. We obtain {\alpha} = 0.02-0.03, consistent with recent results. Very small domains (Lx = 0.5H) return anomalous results, independent of spatial resolution. The convergence with domain size is only valid for a limited set of diagnostics: larger spatial domains admit the emergence of dynamically important mesoscale structures. In our largest simulations, the Maxwell stress shows a significant large scale non-local component, while the density develops long-lived axisymmetric perturbations (zonal flows) at the 20% level. Most strikingly, the variability of the disc in fixed-sized patches decreases strongly as the simulation volume increases. We find generally good agreement between our largest local simulations and global simulations with comparable spatial resolution. There is no direct evidence that the presence of curvature terms or radial gradients in global calculations materially affect the turbulence, except to perhaps introduce an outer radial scale for mesoscale structures. The demonstrated importance of mean magnetic fields, seen in both large local and global simulations implies that the growth and saturation of these fields is likely of critical importance for the evolution of accretion discs. (abridged)Comment: 18 pages, 20 figures, accepted to MNRA

Multiparameter entangled state engineering using adaptive optics

We investigate how quantum coincidence interferometry is affected by a controllable manipulation of transverse wave-vectors in type-II parametric down conversion using adaptive optics techniques. In particular, we discuss the possibility of spatial walk-off compensation in quantum interferometry and a new effect of even-order spatial aberration cancellation.Comment: 11 pages, 7 figure

A systematic review of phenotypic responses to between-population outbreeding

This work was supported by the UK Population Biology Network, through funding from the Natural Environment Research Council and Natural England. We thank Jack Brodie, Helen Hipperson, Marie Chadburn and Sophie Allen for assistance with literature searching, article assessment and data extraction. We also thank our review group for constructive criticism on the scope, development and structure of this review, and two peer reviewers for useful feedback on the review protocol. Finally we thank three peer reviewers who each provided constructive comments on this systematic review report.Peer reviewedPublisher PD

Bounds on the heat kernel of the Schroedinger operator in a random electromagnetic field

We obtain lower and upper bounds on the heat kernel and Green functions of the Schroedinger operator in a random Gaussian magnetic field and a fixed scalar potential. We apply stochastic Feynman-Kac representation, diamagnetic upper bounds and the Jensen inequality for the lower bound. We show that if the covariance of the electromagnetic (vector) potential is increasing at large distances then the lower bound is decreasing exponentially fast for large distances and a large time.Comment: some technical improvements, new references, to appear in Journ.Phys.

High rates of infection by blood parasites during the nestling phase in UK Columbids with notes on ecological associations

Studies of blood parasite infection in nestling birds rarely find a high prevalence of infection. This is likely due to a combination of short nestling periods (limiting the age at which nestlings can be sampled) and long parasite prepatent periods before gametocytes can be detected in peripheral blood. Here we examine rates of blood parasite infection in nestlings from three Columbid species in the UK. We use this system to address two key hypotheses in the epidemiology of avian haemoparasites: first, that nestlings in open nests have a higher prevalence of infection; and second, that nestlings sampled at 14 days old have a higher apparent infection rate than those sampled at 7 days old. Open-nesting individuals had a 54% infection rate compared with 25% for box-nesters, probably due to an increased exposure of open-nesting species to dipteran vectors. Nestlings sampled at 14 days had a 68% infection rate compared with 32% in nestlings sampled at 7 days, suggesting that rates of infection in the nest are high. Further work should examine nestlings post-fledging to identify rates of successful parasite infection (as opposed to abortive development within a dead-end host) as well as impacts on host post-fledging survival and behaviour

Active blood parasite infection is not limited to the breeding season in a declining farmland bird

Avian blood parasites can have significant impacts on adult breeding birds but studies of parasitism outside the breeding season are rare, despite their potentially important implications for host–parasite dynamics. Here we investigate temporal dynamics of blood parasite infection in adult yellowhammers Emberiza citrinella. We screened blood samples collected between December and April of 2 consecutive winters using PCR. We found a high prevalence of both Haemoproteus and Leucocytozoon parasites, with a mean prevalence of 50% across 2 winters. Prevalence of both parasites was higher during the second, colder winter of the study. Temporal trends differed between the 2 genera, suggesting that chronic Haemoproteus infections gradually disappear throughout the winter but that Leucocytozoon infections exhibit a relapse during late winter, possibly coincident with reduced food availability. Our results highlight the difference in temporal dynamics between 2 blood parasite genera infecting the same host population and emphasize the need for accurate assessment of infection status at appropriate time periods when examining impacts of, and associations with, blood parasite infection. We suggest that further research should investigate the implications of over-winter infection for birds’ physiology, behavior, and survival