788 research outputs found
Nanostructure determination from the pair distribution function: A parametric study of the INVERT approach
We present a detailed study of the mechanism by which the INVERT method
[Phys. Rev. Lett. 104, 125501] guides structure refinement of disordered
materials. We present a number of different possible implementations of the
central algorithm and explore the question of algorithm weighting. Our analysis
includes quantification of the relative contributions of variance and
fit-to-data terms during structure refinement, which leads us to study the
roles of density fluctuations and configurational jamming in the RMC fitting
process. We present a parametric study of the pair distribution function
solution space for C60, a-Si and a-SiO2, which serves to highlight the
difficulties faced in developing a transferable weighting scheme.Comment: 15 pages, 7 figures, formatted for JPCM (RMC issue
The Broiler-Corn Ratio: Is it an Indicator of Fattened Broiler Profits?
As consumers eat healthier and obesity concerns increase, the poultry industry continues growth in sales and revenues. Data reflect ten years of broiler prices, exports, egg and chick production, cold storage stocks, company earnings and stock price. Expected results suggest a broiler-corn ratio is an indicator of company profits.Livestock Production/Industries,
A Comparative Assessment of the Broiler:Corn Ratio and Its Impact on Broiler Processors' Profitability
Input prices for broiler production, particularly corn, are becoming increasingly volatile due to increasing competition for corn from ethanol and biofuels production suggesting volatility in poultry profits will follow indicator of profits relating feed input prices and broiler meat output prices, such as a Broiler:corn ratios. Total chicken exports, total chicken ready-to-cook production, number of eggs set, number of chicks placed, and cold storage chicken inventory are used to estimate. Utilizing a distributed lag model, seventeen years of data for three Broiler:corn ratios, broiler exports, egg set, chick placements, cold storage stocks, and ready-to-cook broiler production were utilized to estimate stock share price for four major broiler producers.Demand and Price Analysis, Livestock Production/Industries,
Structure determination of disordered materials from diffraction data
We show that the information gained in spectroscopic experiments regarding
the number and distribution of atomic environments can be used as a valuable
constraint in the refinement of the atomic-scale structures of nanostructured
or amorphous materials from pair distribution function (PDF) data. We
illustrate the effectiveness of this approach for three paradigmatic disordered
systems: molecular C60, a-Si, and a-SiO2 . Much improved atomistic models are
attained in each case without any a-priori assumptions regarding coordination
number or local geometry. We propose that this approach may form the basis for
a generalised methodology for structure "solution" from PDF data applicable to
network, nanostructured and molecular systems alike.Comment: 4 pages, 3 figures, set out as for PR
Design of crystal-like aperiodic solids with selective disorder--phonon coupling
Functional materials design normally focuses on structurally-ordered systems
because disorder is considered detrimental to many important physical
properties. Here we challenge this paradigm by showing that particular types of
strongly-correlated disorder can give rise to useful characteristics that are
inaccessible to ordered states. A judicious combination of low-symmetry
building unit and high-symmetry topological template leads to aperiodic
"procrystalline" solids that harbour this type of topological disorder. We
identify key classes of procrystalline states together with their
characteristic diffraction behaviour, and establish a variety of mappings onto
known and target materials. Crucially, the strongly-correlated disorder we
consider is associated with specific sets of modulation periodicities
distributed throughout the Brillouin zone. Lattice dynamical calculations
reveal selective disorder-phonon coupling to lattice vibrations characterised
by these same periodicities. The principal effect on the phonon spectrum is to
bring about dispersion in energy rather than wave-vector, as in the
poorly-understood "waterfall" effect observed in relaxor ferroelectrics. This
property of procrystalline solids suggests a mechanism by which
strongly-correlated topological disorder might allow new and useful
functionalities, including independently-optimised thermal and electronic
transport behaviour as required for high-performance thermoelectrics.Comment: 4 figure
Evidence against memorial facilitation and context-dependent memory effects through the chewing of gum
The experiment examined the prediction that chewing gum at learning and/or recall facilitated subsequent word recall. Chewing gum at learning significantly impaired recall, indicating that the chewing of gum has a detrimental impact upon initial word encoding. In addition, a context-dependent memory effect was reported for those participants who both learned and recalled in the absence of gum, however a context dependent effect was not found with chewing gum. The findings contradict previous research
Defect-dependent colossal negative thermal expansion in UiO-66(Hf) metal-organic framework
Thermally-densified hafnium terephthalate UiO-66(Hf) is shown to exhibit the
strongest isotropic negative thermal expansion (NTE) effect yet reported for a
metal-organic framework (MOF). Incorporation of correlated vacancy defects
within the framework affects both the extent of thermal densification and the
magnitude of NTE observed in the densified product. We thus demonstrate that
defect inclusion can be used to tune systematically the physical behaviour of a
MOF.Comment: 8 pages, 4 figures, revise
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