2,082 research outputs found
Different critical points of chiral and deconfinement phase transitions in (2+1)-dimensional fermion-gauge interacting model
Based on the truncated Dyson-Schwinger equations for fermion and massive
boson propagators in QED, the fermion chiral condensate and the mass
singularities of the fermion propagator via the Schwinger function are
investigated. It is shown that the critical point of chiral phase transition is
apparently different from that of deconfinement phase transition and in Nambu
phase the fermion is confined only for small gauge boson mass.Comment: 5 Pages and 3 figure
New Method for Numerically Solving the Chemical Potential Dependence of the Dressed Quark Propagator
Based on the rainbow approximation of Dyson-Schwinger equation and the
assumption that the inverse dressed quark propagator at finite chemical
potential is analytic in the neighborhood of , a new method for
obtaining the dressed quark propagator at finite chemical potential from
the one at zero chemical potential is developed. Using this method the dressed
quark propagator at finite chemical potential can be obtained directly from the
one at zero chemical potential without the necessity of numerically solving the
corresponding coupled integral equations by iteration methods. A comparison
with previous results is given.Comment: Revtex, 14 pages, 5 figure
General formula for the four-quark condensate and vacuum factorization assumption
By differentiating the dressed quark propagator with respect to a variable
background field, the linear response of the dressed quark propagator in the
presence of the background field can be obtained. From this general method,
using the vector background field as an illustration, we derive a general
formula for the four-quark condensate . This formula contains the
corresponding fully dressed vector vertex and it is shown that factorization
for holds only when the dressed vertex is taken to be the bare one.
This property also holds for all other type of four-quark condensate.Comment: Revtex4, 11 pages, no figure
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Expanding the Toolkit for Metabolic Engineering
The essence of metabolic engineering is the modification of microbes for the overproduction of useful compounds. These cellular factories are increasingly recognized as an environmentally-friendly and cost-effective way to convert inexpensive and renewable feedstocks into products, compared to traditional chemical synthesis from petrochemicals. The products span the spectrum of specialty, fine or bulk chemicals, with uses such as pharmaceuticals, nutraceuticals, flavors and fragrances, agrochemicals, biofuels and building blocks for other compounds. However, the process of metabolic engineering can be long and expensive, primarily due to technological hurdles, our incomplete understanding of biology, as well as redundancies and limitations built into the natural program of living cells. Combinatorial or directed evolution approaches can enable us to make progress even without a full understanding of the cell, and can also lead to the discovery of new knowledge. This thesis is focused on addressing the technological bottlenecks in the directed evolution cycle, specifically de novo DNA assembly to generate strain libraries and small molecule product screens and selections
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