814 research outputs found
A Precision Model Independent Determination of |Vub| from B -> pi e nu
A precision method for determining |Vub| using the full range in q^2 of B->
pi \ell nu data is presented. At large q^2 the form factor is taken from
unquenched lattice QCD, at q^2=0 we impose a model independent constraint
obtained from B-> pi pi using the soft-collinear effective theory, and the
shape is constrained using QCD dispersion relations. We find |Vub| =(3.54\pm
0.17\pm 0.44) x 10^{-3}. With 5% experimental error and 12% theory error, this
is competitive with inclusive methods. Theory error is dominated by the input
points, with negligible uncertainty from the dispersion relations.Comment: 4 pages, 3 figure
Constraint equations for heavy-to-light currents in SCET
A complete basis for the next-to-next-to leading order heavy-to-light
currents in the soft-collinear effective theory is constructed.
Reparameterization invariance is imposed by deriving constraint equations.
Their solutions give the set of allowed Dirac structures as well as relations
between the Wilson coefficients of operators that appear at different orders in
the power expansion. The completeness of reparameterization invariance
constraints derived on a projected surface is investigated. We also discuss the
universality of the ultrasoft Wilson line with boundary conditions.Comment: 35 page
Thermal entanglement of spins in a nonuniform magnetic field
We study the effect of inhomogeneities in the magnetic field on the thermal
entanglement of a two spin system. We show that in the ferromagnetic case a
very small inhomogeneity is capable to produce large values of thermal
entanglement. This shows that the absence of entanglement in the ferromagnetic
Heisenberg system is highly unstable against inhomogeneoity of magnetic fields
which is inevitably present in any solid state realization of qubits.Comment: 14 pages, 7 figures, latex, Accepted for publication in Physical
Review
A role for human N-alpha acetyltransferase 30 (Naa30) in maintaining mitochondrial integrity
N-terminal acetylation (Nt-acetylation) by N-terminal acetyltransferases (NATs) is one of the most common protein modifications in eukaryotes. The NatC complex represents one of three major NATs of which the substrate profile remains largely unexplored. Here, we defined the in vivo human NatC Nt-acetylome on a proteome-wide scale by combining knockdown of its catalytic subunit Naa30 with positional proteomics. We identified 46 human NatC substrates, expanding our current knowledge on the substrate repertoire of NatC which now includes proteins harboring Met-Leu, Met-Ile, Met-Phe, Met-Trp, Met-Val, Met-Met, Met-His and Met-Lys N termini. Upon Naa30 depletion the expression levels of several organellar proteins were found reduced, in particular mitochondrial proteins, some of which were found to be NatC substrates. Interestingly, knockdown of Naa30 induced the loss of mitochondrial membrane potential and fragmentation of mitochondria. In conclusion, NatC N-tacetylates a large variety of proteins and is essential for mitochondrial integrity and function
Power Corrections in Charmless Nonleptonic B-Decays: Annihilation is Factorizable and Real
We classify LambdaQCD/mb power corrections to nonleptonic B-> M1 M2 decays, where M1 and M2 are charmless non-isosinglet mesons. Using recent developments in soft-collinear effective theory, we prove that the leading contributions to annihilation amplitudes of O[alphas(mb) LambdaQCD/mb] are real and are determined by nonperturbative functions that already occur in the lowest order B-> M1 M2 factorization theorem. A complex nonperturbative parameter from annihilation first appears at O[alphas^2(sqrt{Lambda mb}) LambdaQCD/mb]. ``Chirally enhanced'' contributions are also factorizable and real at lowest order. Thus, incalculable strong phases are suppressed in annihilation amplitudes, unless the alphas(sqrt{Lambda mb}) expansion breaks down. Modeling the distribution functions, we find that (11 +- 9)% and (15 +- 11)% of the absolute value of the measured B-> K- pi+ and B-> K- K0 penguin amplitudes come from annihilation. This is consistent with the expected size of power corrections
Teleportation via thermally entangled state of a two-qubit Heisenberg XX chain
We find that quantum teleportation, using the thermally entangled state of
two-qubit Heisenberg XX chain as a resource, with fidelity better than any
classical communication protocol is possible. However, a thermal state with a
greater amount of thermal entanglement does not necessarily yield better
fidelity. It depends on the amount of mixing between the separable state and
maximally entangled state in the spectra of the two-qubit Heisenberg XX model.Comment: 5 pages, 1 tabl
Optimized bisubstrate inhibitors for the actin N-terminal acetyltransferase NAA80
Acetylation of protein N-termini is one of the most common protein modifications in the eukaryotic cell and is catalyzed by the N-terminal acetyltransferase family of enzymes. The N-terminal acetyltransferase NAA80 is expressed in the animal kingdom and was recently found to specifically N-terminally acetylate actin, which is the main component of the microfilament system. This unique animal cell actin processing is essential for the maintenance of cell integrity and motility. Actin is the only known substrate of NAA80, thus potent inhibitors of NAA80 could prove as important tool compounds to study the crucial roles of actin and how NAA80 regulates this by N-terminal acetylation. Herein we describe a systematic study toward optimizing the peptide part of a bisubstrate-based NAA80 inhibitor comprising of coenzyme A conjugated onto the N-terminus of a tetrapeptide amide via an acetyl linker. By testing various combinations of Asp and Glu which are found at the N-termini of ÎČ- and Îł-actin, respectively, CoA-Ac-EDDI-NH2 was identified as the best inhibitor with an IC50 value of 120Â nM
Werner states and the two-spinors Heisenberg anti-ferromagnet
We ascertain, following ideas of Arnesen, Bose, and Vedral concerning thermal
entanglement [Phys. Rev. Lett. {\bf 87} (2001) 017901] and using the
statistical tool called {\it entropic non-triviality} [Lamberti, Martin,
Plastino, and Rosso, Physica A {\bf 334} (2004) 119], that there is a one to
one correspondence between (i) the mixing coefficient of a Werner state, on
the one hand, and (ii) the temperature of the one-dimensional Heisenberg
two-spin chain with a magnetic field along the axis, on the other one.
This is true for each value of below a certain critical value . The
pertinent mapping depends on the particular value one selects within such a
range
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