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Investigating the effects of inter-annual weather variation (1968- 2016) on the functional response of cereal grain yield to applied nitrogen, using data from the Rothamsted Long-Term experiments
The effect of weather on inter-annual variation in the crop yield response to nitrogen (N) fertilizer for winter wheat (Triticum aestivvum L.) and spring barley (Hordeum vulgare L.) was investigated using yield data from the Broadbalk Wheat and Hoosfield Spring Barley long-term experiments at Rothamsted Research. Grain yields of crops from 1968 to 2016 were modelled as a function of N rates using a linear-plus-exponential (LEXP) function. The extent to which inter-annual variation in the parameters of these responses was explained by variations in weather (monthly summarized temperatures and rainfall), and by changes in the cultivar grown, was assessed. The inter-annual variability in rainfall and underlying temperature influenced the crop N response and hence grain yields in both crops. Asymptotic yields in wheat were particularly sensitive to mean temperature in November, April and May, and to total rainfall in October, February and June. In spring barley asymptotic yields were sensitive to mean temperature in February and June, and to total rainfall in April to July inclusive and September.
The method presented here explores the separation of agronomic and environmental (weather) influences on crop yield over time. Fitting N response curves across multiple treatments can support an informative analysis of the influence of weather variation on the yield variability. Whilst there are issues of the confounding and collinearity of explanatory variables within such models, and that other factors also influence yields over time, our study confirms the considerable impact of weather variables at certain times of the year. This emphasizes the importance of including weather temporal variation when evaluating the impacts of climate change on crops
Overlap properties of geometric expanders
The {\em overlap number} of a finite -uniform hypergraph is
defined as the largest constant such that no matter how we map
the vertices of into , there is a point covered by at least a
-fraction of the simplices induced by the images of its hyperedges.
In~\cite{Gro2}, motivated by the search for an analogue of the notion of graph
expansion for higher dimensional simplicial complexes, it was asked whether or
not there exists a sequence of arbitrarily large
-uniform hypergraphs with bounded degree, for which . Using both random methods and explicit constructions, we answer this
question positively by constructing infinite families of -uniform
hypergraphs with bounded degree such that their overlap numbers are bounded
from below by a positive constant . We also show that, for every ,
the best value of the constant that can be achieved by such a
construction is asymptotically equal to the limit of the overlap numbers of the
complete -uniform hypergraphs with vertices, as
. For the proof of the latter statement, we establish the
following geometric partitioning result of independent interest. For any
and any , there exists satisfying the
following condition. For any , for any point and
for any finite Borel measure on with respect to which
every hyperplane has measure , there is a partition into measurable parts of equal measure such that all but
at most an -fraction of the -tuples
have the property that either all simplices with
one vertex in each contain or none of these simplices contain
Precompact noncompact reflexive abelian groups
We present a series of examples of precompact, noncompact, reflexive
topological Abelian groups. Some of them are pseudocompact or even countably
compact, but we show that there exist precompact non-pseudocompact reflexive
groups as well. It is also proved that every pseudocompact Abelian group is a
quotient of a reflexive pseudocompact group with respect to a closed reflexive
pseudocompact subgroup
Ultrasound Imaging of Gene Expression in Mammalian Cells
The study of cellular processes occurring inside intact organisms requires methods to visualize cellular functions such as gene expression in deep tissues. Ultrasound is a widely used biomedical technology enabling noninvasive imaging with high spatial and temporal resolution. However, no genetically encoded molecular reporters are available to connect ultrasound contrast to gene expression in mammalian cells. To address this limitation, we introduce mammalian acoustic reporter genes. Starting with a gene cluster derived from bacteria, we engineered a eukaryotic genetic program whose introduction into mammalian cells results in the expression of intracellular air-filled protein nanostructures called gas vesicles, which produce ultrasound contrast. Mammalian acoustic reporter genes allow cells to be visualized at volumetric densities below 0.5% and permit high-resolution imaging of gene expression in living animals
Late Reheating, Hadronic Jets and Baryogenesis
If inflaton couples very weakly to ordinary matter the reheating temperature
of the universe can be lower than the electroweak scale. In this letter we show
that the late reheating occurs in a highly non-uniform way, within narrow areas
along the jets produced by ordinary particles originated from inflaton decays.
Depending on inflaton mass and decay constant, the initial temperature inside
the lumps of the overheated plasma may be large enough to trigger the
unsuppressed sphaleron processes with baryon number non-conservation, allowing
for efficient local electroweak baryogenesis.Comment: 4 pages, 2 figures, revtex
Structured matrices, continued fractions, and root localization of polynomials
We give a detailed account of various connections between several classes of
objects: Hankel, Hurwitz, Toeplitz, Vandermonde and other structured matrices,
Stietjes and Jacobi-type continued fractions, Cauchy indices, moment problems,
total positivity, and root localization of univariate polynomials. Along with a
survey of many classical facts, we provide a number of new results.Comment: 79 pages; new material added to the Introductio
Singularities in Isotropic Non-Minimal Scalar Field Models
Non-minimally coupling a scalar field to gravity introduces an additional
curvature term into the action which can change the general behavior in strong
curvature regimes, in particular close to classical singularities. While one
can conformally transform any non-minimal model to a minimally coupled one,
that transformation can itself become singular. It is thus not guaranteed that
all qualitative properties are shared by minimal and non-minimal models. This
paper addresses the classical singularity issue in isotropic models and extends
singularity removal in quantum gravity to non-minimal models.Comment: 12 page
Neuronal synchrony: peculiarity and generality
Synchronization in neuronal systems is a new and intriguing application of dynamical systems theory. Why are neuronal systems different as a subject for synchronization? (1) Neurons in themselves are multidimensional nonlinear systems that are able to exhibit a wide variety of different activity patterns. Their âdynamical repertoireâ includes regular or chaotic spiking, regular or chaotic bursting, multistability, and complex transient regimes. (2) Usually, neuronal oscillations are the result of the cooperative activity of many synaptically connected neurons (a neuronal circuit). Thus, it is necessary to consider synchronization between different neuronal circuits as well. (3) The synapses that implement the coupling between neurons are also dynamical elements and their intrinsic dynamics influences the process of synchronization or entrainment significantly. In this review we will focus on four new problems: (i) the synchronization in minimal neuronal networks with plastic synapses (synchronization with activity dependent coupling), (ii) synchronization of bursts that are generated by a group of nonsymmetrically coupled inhibitory neurons (heteroclinic synchronization), (iii) the coordination of activities of two coupled neuronal networks (partial synchronization of small composite structures), and (iv) coarse grained synchronization in larger systems (synchronization on a mesoscopic scale
Investigations of Pairing in Anyon Systems
We investigate pairing instabilities in the Fermi-liquid-like state of a
single species of anyons. We describe the anyons as Fermions interacting with a
Chern-Simons gauge field and consider the weak coupling limit where their
statistics approaches that of Fermions. We show that, within the conventional
BCS approach, due to induced repulsive Coulomb and current-current
interactions, the attractive Aharonov-Bohm interaction is not sufficient to
generate a gap in the Fermion spectrum.Comment: (11 pages, 2 Figures not included
Effect of Covalence and Degree of Cation Order on the Luminous Efficacy of Mn4+ Luminescence in the Double Perovskites, Ba2BTaO6 (B = Y, Lu, Sc)
The spectroscopic properties of the Mn4+ ion are investigated in the series of isostructural double perovskite compounds, Ba2BTaO6 (B = Y, Lu, Sc). A comparison of these properties highlights the influence of covalent bonding within the perovskite framework and the degree of order between the B3+âTa cations on the energy and intensity of the Mn4+2E â 4A2 emission transition (R-line). These two parameters of the emission spectrum are of importance for practical application since they determine the phosphor luminous efficacy. The influence of covalent bonding within the corner shared BO6/2 and TaO6/2 perovskite framework on the energy of the R-line energy is investigated. From the spectroscopic data, we have derived information on the influence of the degree of order between the B3+ and Ta5+ cations on the intensity of the R-line. The lowest energy and the highest intensity of the R-line are found in the double perovskite, Ba2ScTaO6. The purpose of this work is to propose for first time an explanation of these effects in the considered double perovskites. The obtained results are useful guidelines for practical improvement and tuning of key parameters of phosphors to the desired values
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