6,816 research outputs found
High energy-charged cell factory for heterologous protein synthesis
Overexpression of gluconeogenic phosphoenolpyruvate carboxykinase (PCK) under glycolytic conditions enables Escherichia coli to maintain a greater intracellular ATP concentration and, consequently, to up-regulate genes for amino acid and nucleotide biosynthesis. To investigate the effect of a high intracellular ATP concentration on heterologous protein synthesis, we studied the expression of a foreign gene product, enhanced green fluorescence protein (eGFP), under control of the T7 promoter in E. coli BL21(DE3) strain overexpressing PCK. This strain was able to maintain twice as much intracellular ATP and to express two times more foreign protein than the control strain. These results indicate that a high energy-charged cell can be beneficial as a protein-synthesizing cell factory. The potential uses of such a cell factory are discussed
Fishbone-Associated Actinomycosis of the Anterior Cervical Space: A Diagnostic Dilemma
We report the imaging and pathologic findings of fishbone-associated actinomycosis of the anterior cervical space in a 57-year-old man, misdiagnosed preoperatively as a malignancy originating from thyroglossal duct cyst. CT revealed an enhancing mass containing a small abscess pocket and two sharp linear calcifications within it, which infiltrated into the strap muscle. Pathologic examination demonstrated two fishbones within the actinomycotic abscess. Fishbone-associated actinomycosis should be considered when a cervical mass contains sharp linear calcifications
Obstructions for Matroids of Path-Width at most k and Graphs of Linear Rank-Width at most k
International audienceEvery minor-closed class of matroids of bounded branch-width can be characterized by a minimal list of excluded minors, but unlike graphs, this list could be infinite in general. However, for each fixed finite field , the list contains only finitely many -representable matroids, due to the well-quasi-ordering of -representable matroids of bounded branch-width under taking matroid minors [J. F. Geelen, A. M. H. Gerards, and G. Whittle (2002)]. But this proof is non-constructive and does not provide any algorithm for computing these -representable excluded minors in general. We consider the class of matroids of path-width at most for fixed . We prove that for a finite field , every -representable excluded minor for the class of matroids of path-width at most~ has at most elements. We can therefore compute, for any integer and a fixed finite field , the set of -representable excluded minors for the class of matroids of path-width , and this gives as a corollary a polynomial-time algorithm for checking whether the path-width of an -represented matroid is at most . We also prove that every excluded pivot-minor for the class of graphs having linear rank-width at most has at most vertices, which also results in a similar algorithmic consequence for linear rank-width of graphs
Observation of Young's Double-Slit Interference with the Three-Photon N00N State
Spatial interference of quantum mechanical particles exhibits a fundamental
feature of quantum mechanics. A two-mode entangled state of N particles known
as N00N state can give rise to non-classical interference. We report the first
experimental observation of a three-photon N00N state exhibiting Young's
double-slit type spatial quantum interference. Compared to a single-photon
state, the three-photon entangled state generates interference fringes that are
three times denser. Moreover, its interference visibility of is
well above the limit of 0.1 for spatial super-resolution of classical origin.
The demonstration of spatial quantum interference by a N00N state composed of
more than two photons represents an important step towards applying quantum
entanglement to technologies such as lithography and imaging
Unavoidable induced subgraphs in large graphs with no homogeneous sets
A homogeneous set of an -vertex graph is a set of vertices () such that every vertex not in is either complete or
anticomplete to . A graph is called prime if it has no homogeneous set. A
chain of length is a sequence of vertices such that for every vertex
in the sequence except the first one, its immediate predecessor is its unique
neighbor or its unique non-neighbor among all of its predecessors. We prove
that for all , there exists such that every prime graph with at least
vertices contains one of the following graphs or their complements as an
induced subgraph: (1) the graph obtained from by subdividing every
edge once, (2) the line graph of , (3) the line graph of the graph in
(1), (4) the half-graph of height , (5) a prime graph induced by a chain of
length , (6) two particular graphs obtained from the half-graph of height
by making one side a clique and adding one vertex.Comment: 13 pages, 3 figure
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