11,247 research outputs found
Dna2p Helicase/Nuclease Is a Tracking Protein, Like FEN1, for Flap Cleavage during Okazaki Fragment Maturation
During cellular DNA replication the lagging strand is generated as discontinuous segments called Okazaki fragments. Each contains an initiator RNA primer that is removed prior to joining of the strands. Primer removal in eukaryotes requires displacement of the primer into a flap that is cleaved off by flap endonuclease 1 (FEN1). FEN1 employs a unique tracking mechanism that requires the recognition of the free 5' terminus and then movement to the base of the flap for cleavage. Abnormally long flaps are coated by replication protein A (RPA), inhibiting FEN1 cleavage. A second nuclease, Dna2p, is needed to cleave an RPA-coated flap producing a short RPA-free flap, favored by FEN1. Here we show that Dna2p is also a tracking protein. Annealed primers or conjugated biotin-streptavidin complex block Dna2p entry and movement. Single-stranded binding protein-coated flaps inhibit Dna2p cleavage. Like FEN1, Dna2p can track over substrates with a non-Watson Crick base, such as a biotin, or a missing base within a chain. Unlike FEN1, Dna2p shows evidence of a "threading-like" mechanism that does not support tracking over a branched substrate. We propose that the two nucleases both track, Dna2p first and then FEN1, to remove initiator RNA via long flap intermediates
Impurity-induced frustration in correlated oxides
Using the example of Zn-doped La2CuO4, we demonstrate that a spinless
impurity doped into a non-frustrated antiferromagnet can induce substantial
frustrating interactions among the spins surrounding it. This counterintuitive
result is the key to resolving discrepancies between experimental data and
earlier theories. Analytic and quantum Monte Carlo studies of the
impurity-induced frustration are in a close accord with each other and
experiments. The mechanism proposed here should be common to other correlated
oxides as well.Comment: 4 pages, updated figures, accepted versio
Mass Spectra of N=2 Supersymmetric SU(n) Chern-Simons-Higgs Theories
An algebraic method is used to work out the mass spectra and symmetry
breaking patterns of general vacuum states in N=2 supersymmetric SU(n)
Chern-Simons-Higgs systems with the matter fields being in the adjoint
representation. The approach provides with us a natural basis for fields, which
will be useful for further studies in the self-dual solutions and quantum
corrections. As the vacuum states satisfy the SU(2) algebra, it is not
surprising to find that their spectra are closely related to that of angular
momentum addition in quantum mechanics. The analysis can be easily generalized
to other classical Lie groups.Comment: 17 pages, use revte
Accountability and Relationship-Definition Among Food Banks Partnerships
Food pantries typically operate in a partnership structure where they are primarily supported by a larger food bank. However, the ability to execute that mission through cooperative arrangements greatly depends upon accountability, a key dynamic that ensures partners are fulfilling expectations and key roles. This exploratory study utilizes qualitative interview data (n = 61) from a large food bank network to understand the extent to which a lead agency (i.e., a large food bank) meets expectations of accountability among partners. The interview results demonstrate that the extent to which expectations are met relate to different types of relationships between the lead agency and partner members. Furthermore, the ways in which partners assess the strengths or weaknesses of the food bank’s accountability reveal different types of relationships within the network, namely that of supplier–customer, supporter–customer, and supporter–collaborator
The Chern-Simons Coefficient in Supersymmetric Non-abelian Chern-Simons Higgs Theories
By taking into account the effect of the would be Chern-Simons term, we
calculate the quantum correction to the Chern-Simons coefficient in
supersymmetric Chern-Simons Higgs theories with matter fields in the
fundamental representation of SU(n). Because of supersymmetry, the corrections
in the symmetric and Higgs phases are identical. In particular, the correction
is vanishing for N=3 supersymmetric Chern-Simons Higgs theories. The result
should be quite general, and have important implication for the more
interesting case when the Higgs is in the adjoint representation.Comment: more references and explanation about rgularization dpendence are
included, 13 pages, 1 figure, latex with revte
Janus Configurations, Chern-Simons Couplings, And The Theta-Angle in N=4 Super Yang-Mills Theory
We generalize the half-BPS Janus configuration of four-dimensional N=4 super
Yang-Mills theory to allow the theta-angle, as well as the gauge coupling, to
vary with position. We show that the existence of this generalization is
closely related to the existence of novel three-dimensional Chern-Simons
theories with N=4 supersymmetry. Another closely related problem, which we also
elucidate, is the D3-NS5 system in the presence of a four-dimensional
theta-angle.Comment: 66 p
Inflationary Universe in Higher Derivative Induced Gravity
In an induced-gravity model, the stability condition of an inflationary
slow-rollover solution is shown to be . The presence of higher derivative terms
will, however, act against the stability of this expanding solution unless
further constraints on the field parameters are imposed. We find that these
models will acquire a non-vanishing cosmological constant at the end of
inflation. Some models are analyzed for their implication to the early
universe.Comment: 6 pages, two typos correcte
Dynamic stability of a flexible booster subjected to a gimbled, periodically-varying end thrust Technical memorandum no. 104
Dynamic structural behavior of large rocket booster synthesized by two thin-walled cylinders and subjected to periodically varying end thrus
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