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Simulating intertwined design processes that have similar structures: A case study of a small company that creates made-to-order fashion products
The authors use simulation to analyse the resource-driven dependencies between concurrent processes used to create customised products in a company. Such processes are uncertain and unique according to the design changes required. However, they have similar structures. For simulation, a level of abstraction is chosen such that all possible processes are represented by the same activity network. Differences between processes are determined by the customisations that they implement. The approach is illustrated through application to a small business that creates customised fashion products. We suggest that similar techniques could be applied to study intertwined design processes in more complex domains.The case study was carried out as part of Considerate Design for Personalised
Fashion funded by the EPSRC/AHRC Design in the 21st century programme. The
context of a multi-project environment was analysed as part of the EU Framework 7
CONVERGE project CP-FP 228746-2.Post-prin
Single-layer -MoS under electron irradiation from molecular dynamics
Irradiation with high-energy particles has recently emerged as an effective
tool for tailoring the properties of two-dimensional transition metal
dichalcogenides. In order to carry out an atomically-precise manipulation of
the lattice, a detailed understanding of the beam-induced events occurring at
the atomic scale is necessary. Here, we investigate the response of
-MoS to the electron irradiation by molecular dynamics
means. Our simulations suggest that an electron beam with energy smaller than
75 keV does not result in any knock-on damage. The displacement threshold
energies are different for the two nonequivalent sulfur atoms in -MoS
and strongly depend on whether the top or bottom chalcogen layer is considered.
As a result, a careful tuning of the beam energy can promote the formation of
ordered defects in the sample. We further discuss the effect of the electron
irradiation in the neighborhood of a defective site, the mobility of the sulfur
vacancies created and their tendency to aggregate. Overall, our work provides
useful guidelines for the imaging and the defect engineering of -MoS
using electron microscopy.Comment: 8 pages, 5 figure
Systems approaches to modelling pathways and networks.
Peer reviewedPreprin
Early stages of radiation damage in graphite and carbon nanostructures: A first-principles molecular dynamics study
Understanding radiation-induced defect formation in carbon materials is
crucial for nuclear technology and for the manufacturing of nanostructures with
desired properties. Using first principles molecular dynamics, we perform a
systematic study of the non-equilibrium processes of radiation damage in
graphite. Our study reveals a rich variety of defect structures (vacancies,
interstitials, intimate interstitial-vacancy pairs, and in-plane topological
defects) with formation energies of 5--15 eV. We clarify the mechanisms
underlying their creation and find unexpected preferences for particular
structures. Possibilities of controlled defect-assisted engineering of
nanostructures are analyzed. In particular, we conclude that the selective
creation of two distinct low-energy intimate Frenkel pair defects can be
achieved by using a 90--110 keV electron beam irradiation.Comment: 5 pages, 4 figure
On the enhancement of nuclear reaction rates in high-temperature plasma
We argue that the Maxwellian approximation can essentially underestimate the
rates of some nuclear reactions in hot plasma under conditions very close to
thermal equilibrium. This phenomenon is demonstrated explicitly on the example
of reactions in self-sustained DT fusion plasma with admixture of light
elements X = Li, Be, C. A kinetic analysis shows that the reactivity
enhancement results from non-Maxwellian knock-on perturbations of ion
distributions caused by close collisions with energetic fusion products. It is
found that although the fraction of the knock-on ions is small, these particles
appreciably affect the D+X and T+X reaction rates. The phenomenon discussed is
likely to have general nature and can play role in other laboratory and
probably astrophysical plasma processes.Comment: 12 pages, 4 figures, to be published in Phys. Lett.
Metabolic characterisation of E. coli citrate synthase and phosphoenolpyruvate carboxylase mutants in aerobic cultures
E. coli is still one of the most commonly used hosts for protein production. However, when it is grown with excess glucose, acetate accumulation occurs. Elevated acetate concentrations have an inhibitory effect on growth rate and recombinant protein yield, and thus elimination of acetate formation is an important aim towards industrial production of recombinant proteins. Here we examine if over-expression of citrate synthase (gltA) or phosphoenolpyruvate carboxylase (ppc) can eliminate acetate production. Knock-out as well as over-expression mutants were constructed and characterized. Knocking out ppc or gltA decreased the maximum cell density by 14% and increased the acetate excretion by 7%, respectively decreased it by 10%. Over-expression of ppc or gltA increased the maximum cell dry weight by 91% and 23%, respectively. No acetate excretion was detected at these increased cell densities (35 and 23 g/l, respectively)
Minimizing acetate formation in E. coli fermentations
Escherichia coli remains the best established production organisms in industrial biotechnology. However, during aerobic fermentation runs at high growth rates, considerable amounts of acetate are accumulated as by-product. This by-product has negative effects on growth and protein production. Over the last 20 years, substantial research efforts have been spent to reduce acetate accumulation during aerobic growth of E. coli on glucose. From the onset it was clear that this quest should not be a simple nor uncomplicated one. Simple deletion of the acetate pathway, reduced the acetate accumulation, but instead other by-products were formed. This minireview gives a clear outline of these research efforts and the outcome of them, including bioprocess level approaches and genetic approaches. Recently, the latter seems to have some promising results
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