204 research outputs found
Comparison principle for stochastic heat equations driven by -stable white noises
For a class of non-linear stochastic heat equations driven by -stable
white noises for with Lipschitz coefficients, we first show
the existence and pathwise uniqueness of -valued c\`{a}dl\`{a}g solutions
to such a equation for by considering a sequence of
approximating stochastic heat equations driven by truncated
-stable white noises obtained by removing the big jumps from the
original -stable white noises.
If the -stable white noise is
spectrally one-sided, under additional monotonicity assumption on noise
coefficients, we prove a comparison theorem on the -valued c\`{a}dl\`{a}g
solutions of such a equation. As a consequence, the non-negativity of the
-valued c\`{a}dl\`{a}g solution is established for the above stochastic
heat equation with non-negative initial function
Existence of weak solutions to stochastic heat equations driven by truncated -stable white noises with non-Lipschitz coefficients
We consider a class of stochastic heat equations driven by truncated
-stable white noises for with noise coefficients that are
continuous but not necessarily Lipschitz and satisfy globally linear growth
conditions. We prove the existence of weak solution, taking values in two
different spaces, to such an equation using a weak convergence argument on
solutions to the approximating stochastic heat equations. For the
weak solution is a measure-valued c\`{a}dl\`{a}g process. However, for
the weak solution is a c\`{a}dl\`{a}g process taking function
values, and in this case we further show that for the uniform -th
moment for -norm of the weak solution is finite, and that the weak
solution is uniformly stochastic continuous in sense and satisfies a flow
property
Production of dihydroxyacetone from glycerol by engineered Escherichia coli cells co-expressing gldA and nox genes
Glycerol can be converted into more valuable compound dihydroxyacetone by the nicotinamide adenine dinucleotide (NAD+)-dependent glycerol dehydrogenase. However, it is economically prohibitive to produce dihydroxyacetone using purified glycerol dehydrogenase at the expense of a stoichiometric amount of the cofactor NAD+. In this study, Escherichia coli was engineered for dihydroxyacetone production by enhancing its glycerol dehydrogenase activity and introducing NADH oxidase activity. Under optimized conditions, dihydroxyacetone productivity reached 0.13 g/h/g wet cell mass by recombinant E. coli D4 (pET-24b-gldA+nox) cells co-expressing gldA gene from E. coli and nox gene from Enterococcus faecalis. It was interesting to note that exogenous NAD+ greatly improved dihydroxyacetone production for the whole-cell biotransformation process. These results should be useful for the development of advanced bioprocess in terms of glycerol utilization.Keywords: Dihydroxyacetone, Glycerol dehydrogenase, NAD+, whole-cell biotransformation, Escherichia coliAfrican Journal of Biotechnology Vol. 12(27), pp. 4387-439
Fatty Acid-Derived Biofuels and Chemicals Production in Saccharomyces cerevisiae
Volatile energy costs and environmental concerns have spurred interest in the development of alternative, renewable, sustainable and cost-effective energy resources. Advanced biofuels have potential to replace fossil fuels in supporting high-power demanding machinery such as aircrafts and trucks. Microbial biosynthesis is generally considered as an environmental friendly refinery process, and fatty acid biosynthesis is an attractive route to synthesize chemicals and especially drop-in biofuels due to the high degree of reduction of fatty acids. The robustness and excellent accessibility to molecular genetics make the yeast S. cerevisiae a suitable host for the production of biofuels, chemicals and pharmaceuticals, and recent advances in metabolic engineering as well as systems and synthetic biology allow us to engineer the yeast fatty acid metabolism and modification pathways for production of advanced biofuels and chemicals
Online Customer Service System Using Hybrid Model
In a traditional customer service support environment, service engineers typically provide a worldwide customer base support through the use of telephone calls. Such a mode of support is inefficient, ineffective and generally results in high costs, long service cycles, and poor quality of service. The rapid growth of the World Wide Web and Intelligent Agent technology, with its widespread acceptance and accessibility, have resulted in the emergence of Web-based and AI Agent-based systems. Depending on the functionality provided by such systems, most of the associated disadvantages of the traditional customer service support environment can be eliminated. This paper describes a framework for Web-based and AI Agent-based online customer service support system, and discusses the method to use Rough Set Theory and Neural Network Theory to support intelligent fault diagnosis by customers or service engineers
Functional screening of aldehyde decarbonylases for long-chain alkane production by Saccharomyces cerevisiae
Background: Low catalytic activities of pathway enzymes are often a limitation when using microbial based chemical production. Recent studies indicated that the enzyme activity of aldehyde decarbonylase (AD) is a critical bottleneck for alkane biosynthesis in Saccharomyces cerevisiae. We therefore performed functional screening to identify efficient ADs that can improve alkane production by S. cerevisiae
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