25,952 research outputs found
Calculating Biological Behaviors of Epigenetic States in Phage lambda Life Cycle
Gene regulatory network of lambda phage is one the best studied model systems
in molecular biology. More 50 years of experimental study has provided a
tremendous amount of data at all levels: physics, chemistry, DNA, protein, and
function. However, its stability and robustness for both wild type and mutants
has been a notorious theoretical/mathematical problem. In this paper we report
our successful calculation on the properties of this gene regulatory network.
We believe it is of its first kind. Our success is of course built upon
numerous previous theoretical attempts, but following 3 features make our
modeling uniqu:
1) A new modeling method particular suitable for stability and robustness
study;
2) Paying a close attention to the well-known difference of in vivo and in
vitro;
3) Allowing more important role for noise and stochastic effect to play.
The last two points have been discussed by two of us (Ao and Yin,
cond-mat/0307747), which we believe would be enough to make some of previous
theoretical attempts successful, too. We hope the present work would stimulate
a further interest in the emerging field of gene regulatory network.Comment: 16 pages, 3 figures, 1 tabl
Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFeCoAs
We present an atomic resolution scanning tunneling spectroscopy study of
superconducting BaFeCoAs single crystals in magnetic fields
up to . At zero field, a single gap with coherence peaks at
is observed in the density of states. At and , we image a disordered vortex lattice, consistent
with isotropic, single flux quantum vortices. Vortex locations are uncorrelated
with strong scattering surface impurities, demonstrating bulk pinning. The
vortex-induced sub-gap density of states fits an exponential decay from the
vortex center, from which we extract a coherence length , corresponding to an upper critical field .Comment: 4 pages, 4 figure
Proximity and anomalous field-effect characteristics in double-wall carbon nanotubes
Proximity effect on field-effect characteristic (FEC) in double-wall carbon
nanotubes (DWCNTs) is investigated. In a semiconductor-metal (S-M) DWCNT, the
penetration of electron wavefunctions in the metallic shell to the
semiconducting shell turns the original semiconducting tube into a metal with a
non-zero local density of states at the Fermi level. By using a two-band
tight-binding model on a ladder of two legs, it is demonstrated that anomalous
FEC observed in so-called S-M type DWCNTs can be fully understood by the
proximity effect of metallic phases.Comment: 4 pages, 4 figure
Dinitrosyl formation as an intermediate stage of the reduction of NO in the presence of MoO_3
We present first-principles calculations in the framework of
density-functional theory and the pseudopotential approach, aiming to model the
intermediate stages of the reduction of NO in the presence of MoO(010). In
particular, we study the formation of dinitrosyl, which proves to be an
important intermediate stage in the catalytic reduction. We find that the
replacement of an oxygen of MoO by NO is energetically favorable, and that
the system lowers further its energy by the formation of (NO). Moreover,
the geometry and charge distribution for the adsorbed dinitrosyl indicates a
metal-oxide mediated coupling between the two nitrogen and the two oxygen
atoms. We discuss the mechanisms for the dinitrosyl formation and the role of
the oxide in the reaction.Comment: 6 pages, 4 figs, RevTeX. To be published in J. Chem. Phy
The correlations between the twin kHz QPO frequencies of LMXBs
We analyzed the recently published kHz QPO data in the neutron star low-mass
X-ray binaries (LMXBs), in order to investigate the different correlations of
the twin peak kilohertz quasi-eriodic oscillations (kHz QPOs) in bright Z
sources and in the less luminous Atoll sources. We find that a power-law
relation \no\sim\nt^{b} between the upper and the lower kHz QPOs with
different indices: 1.5 for the Atoll source 4U 1728-34 and
1.9 for the Z source Sco X-1. The implications of our results for
the theoretical models for kHz QPOs are discussed.Comment: 6 pages, accepted by MNRA
- …