2,403 research outputs found
The Global Networked Value Circle: A new model for best-in-class manufacturing
As companies face deflation, slowing production and declining prices, they will need to assess their entire value chain as they look for ways to keep costs low and improve efficiencies while continuing to innovate. To help address this challenge, this report reflects fresh research undertaken by Capgemini in collaboration with the University of Edinburgh into the ?Best-in-Class Global Manufacturing Value Chain?
Confined compression of collagen hydrogels
Reconstituted collagen hydrogels are often used for in vitro studies of cell-matrix interaction and as scaffolds for tissue engineering. Understanding the mechanical and transport behaviours of collagen hydrogels is therefore extremely important, albeit difficult due to their very high water content (typically > 99.5%). In the present study the mechanical behaviour of collagen hydrogels in confined compression was investigated using biphasic theory (J. Biomech. Eng. 102 (1980) 73), to ascertain whether the technique is sufficiently sensitive to determine differences in the characteristics of hydrogels of between 0.2% and 0.4% collagen. Peak stress, equilibrium stress, aggregate modulus and hydraulic permeability of the hydrogels exhibited sensitivity to collagen content, demonstrating that the technique is clearly able to discriminate between hydrogels with small differences in collagen content and may also be sensitive to factors that affect matrix remodelling. The results also offer additional insight into the deformation-dependent permeability of collagen hydrogels. This study suggests that confined compression, together with biphasic theory, is a suitable technique for assessing the mechanical properties of collagen hydrogels
Kolab: appropriation & improvisation in mobile tangible collaborative interaction
Current design guidelines for conventional tangible systems suggest that the representational significance of tangible tokens is an important consideration in the design of tangible interaction, especially in collaborative contexts. Such advice might be assumed to imply that nomadic tangible systems that employ improvised tokens are liable to have highly impaired usability. In this paper we describe a proof of concept experiment for Kolab, a nomadic tangible interaction system that permits any surface to be appropriated as a collaborative tabletop, and which affords the use of a wide range of appropriated artifacts as improvised tangibles. We demonstrate an approach for realizing the necessary interaction techniques combining tangibles and hand gestures using a fusion of image and depth sensing. We present the results of a user study showing that while users' choices of artifacts were seen to follow an unexpected pattern, various artifacts were appropriated and improvised as tangibles, and the system was found to be both usable and well able to support user collaboration
On columnar thin films as platforms for surface-plasmonic-polaritonic optical sensing: higher-order considerations
The ability to tailor the porosity and optical properties of columnar thin
films (CTFs) renders them promising platforms for optical sensing. In
particular, surface-plasmon-polariton (SPP) waves, guided by the planar
interface of an infiltrated CTF and a thin layer of metal, may be harnessed to
detect substances that penetrate the void regions in between the columns of a
CTF. This scenario was investigated theoretically using a higher-order
homogenization technique, based on an extended version of the second-order
strong-permittivity-fluctuation theory, which takes into account the size of
the component particles which make up the infiltrated CTF and the statistical
distribution of these particles. Our numerical studies revealed that as the
size of the component particles increases and as the correlation length that
characterizes their distribution increases: (i) the phase speed of the SPP wave
decreases and the SPP wave's attenuation increases; (ii) the SPP wave's
penetration into the CTF decreases; (iii) the angle of incidence required to
excite the SPP wave in a modified Kretschmann configuration increases; (iv) the
sharpness of the SPP trough in the graph of reflectance versus angle of
incidence increases; and (v) the sensitivity to changes in refractive index of
the infiltrating fluid decreases
``Critical'' phonons of the supercritical Frenkel-Kontorova model: renormalization bifurcation diagrams
The phonon modes of the Frenkel-Kontorova model are studied both at the
pinning transition as well as in the pinned (cantorus) phase. We focus on the
minimal frequency of the phonon spectrum and the corresponding generalized
eigenfunction. Using an exact decimation scheme, the eigenfunctions are shown
to have nontrivial scaling properties not only at the pinning transition point
but also in the cantorus regime. Therefore the phonons defy localization and
remain critical even where the associated area-preserving map has a positive
Lyapunov exponent. In this region, the critical scaling properties vary
continuously and are described by a line of renormalization limit cycles.
Interesting renormalization bifurcation diagrams are obtained by monitoring the
cycles as the parameters of the system are varied from an integrable case to
the anti-integrable limit. Both of these limits are described by a trivial
decimation fixed point. Very surprisingly we find additional special parameter
values in the cantorus regime where the renormalization limit cycle degenerates
into the above trivial fixed point. At these ``degeneracy points'' the phonon
hull is represented by an infinite series of step functions. This novel
behavior persists in the extended version of the model containing two
harmonics. Additional richnesses of this extended model are the one to two-hole
transition line, characterized by a divergence in the renormalization cycles,
nonexponentially localized phonons, and the preservation of critical behavior
all the way upto the anti-integrable limit.Comment: 10 pages, RevTeX, 9 Postscript figure
A detailed binding free energy study of 2 : 1 ligand–DNA complex formation by experiment and simulation
In 2004, we used NMR to solve the structure of the minor groove binder thiazotropsin A bound in a 2 : 1 complex to the DNA duplex, d(CGACTAGTCG)2. In this current work, we have combined theory and experiment to confirm the binding thermodynamics of this system. Molecular dynamics simulations that use polarizable or non-polarizable force fields with single and separate trajectory approaches have been used to explore complexation at the molecular level. We have shown that the binding process invokes large conformational changes in both the receptor and ligand, which is reflected by large adaptation energies. This is compensated for by the net binding free energy, which is enthalpy driven and entropically opposed. Such a conformational change upon binding directly impacts on how the process must be simulated in order to yield accurate results. Our MM-PBSA binding calculations from snapshots obtained from MD simulations of the polarizable force field using separate trajectories yield an absolute binding free energy (-15.4 kcal mol-1) very close to that determined by isothermal titration calorimetry (-10.2 kcal mol-1). Analysis of the major energy components reveals that favorable non-bonded van der Waals and electrostatic interactions contribute predominantly to the enthalpy term, whilst the unfavorable entropy appears to be driven by stabilization of the complex and the associated loss of conformational freedom. Our results have led to a deeper understanding of the nature of side-by-side minor groove ligand binding, which has significant implications for structure-based ligand development
The realities of storing carbon dioxide - A response to CO2 storage capacity issues raised by Ehlig-Economides & Economides
In a recent publication, Ehlig-Economides & Economides (2010) have sought to demonstrate that carbon dioxide capture and storage (CCS) is not technically or economically feasible, based on a supposed lack of underground storage capacity. We consider this to be a serious misrepresentation of the scientific, engineering and operational facts surrounding CCS. Ehlig-Economides & Economides raise a number of storage related issues: reservoir boundaries, capacity, pressure management, storage integrity, dissolution and storage in depleted reservoirs. We take each one in turn, highlighting specific errors in the paper but also drawing attention to more general background issues. Finally, we discuss in more detail some inconsistencies in the paper surrounding the reservoir engineering calculations
Classical and Quantum Transport Through Entropic Barriers Modelled by Hardwall Hyperboloidal Constrictions
We study the quantum transport through entropic barriers induced by hardwall
constrictions of hyperboloidal shape in two and three spatial dimensions. Using
the separability of the Schrodinger equation and the classical equations of
motion for these geometries we study in detail the quantum transmission
probabilities and the associated quantum resonances, and relate them to the
classical phase structures which govern the transport through the
constrictions. These classical phase structures are compared to the analogous
structures which, as has been shown only recently, govern reaction type
dynamics in smooth systems. Although the systems studied in this paper are
special due their separability they can be taken as a guide to study entropic
barriers resulting from constriction geometries that lead to non-separable
dynamics.Comment: 59 pages, 22 EPS figures
Solar Magnetic Carpet I: Simulation of Synthetic Magnetograms
This paper describes a new 2D model for the photospheric evolution of the
magnetic carpet. It is the first in a series of papers working towards
constructing a realistic 3D non-potential model for the interaction of
small-scale solar magnetic fields. In the model, the basic evolution of the
magnetic elements is governed by a supergranular flow profile. In addition,
magnetic elements may evolve through the processes of emergence, cancellation,
coalescence and fragmentation. Model parameters for the emergence of bipoles
are based upon the results of observational studies. Using this model, several
simulations are considered, where the range of flux with which bipoles may
emerge is varied. In all cases the model quickly reaches a steady state where
the rates of emergence and cancellation balance. Analysis of the resulting
magnetic field shows that we reproduce observed quantities such as the flux
distribution, mean field, cancellation rates, photospheric recycle time and a
magnetic network. As expected, the simulation matches observations more closely
when a larger, and consequently more realistic, range of emerging flux values
is allowed (4e16 - 1e19 Mx). The model best reproduces the current observed
properties of the magnetic carpet when we take the minimum absolute flux for
emerging bipoles to be 4e16 Mx. In future, this 2D model will be used as an
evolving photospheric boundary condition for 3D non-potential modeling.Comment: 33 pages, 16 figures, 5 gif movies included: movies may be viewed at
http://www-solar.mcs.st-and.ac.uk/~karen/movies_paper1
Genetic resistance to yellow rust infection of the wheat ear is controlled by genes controlling foliar resistance and flowering time
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