881 research outputs found
Unifying model of driven polymer translocation
We present a Brownian dynamics model of driven polymer translocation, in
which non-equilibrium memory effects arising from tension propagation (TP)
along the cis side subchain are incorporated as a time-dependent friction. To
solve the effective friction, we develop a finite chain length TP formalism,
expanding on the work of Sakaue [Sakaue, PRE 76, 021803 (2007)]. The model,
solved numerically, yields results in excellent agreement with molecular
dynamics simulations in a wide range of parameters. Our results show that
non-equilibrium TP along the cis side subchain dominates the dynamics of driven
translocation. In addition, the model explains the different scaling of
translocation time w.r.t chain length observed both in experiments and
simulations as a combined effect of finite chain length and pore-polymer
interactions.Comment: 7 pages, 3 figure
Moving out but keeping in touch : contacts between endoplasmic reticulum and lipid droplets
The formation of neutral lipid filled and phospholipid monolayer engulfed lipid droplets (LDs) from the bilayer of the endoplasmic reticulum (ER) is an active area of investigation. This process harnesses the biophysical properties of the lipids involved and necessitates cooperation of protein machineries in both organelle membranes. Increasing evidence suggests that once formed, LDs keep close contact to the mother organelle and that this may be achieved via several, morphologically distinct and potentially functionally specialized connections. These may help LDs to dynamically respond to changes in lipid metabolic status sensed by the ER. In this review, we will discuss recent progress in understanding how LDs interact with the ER.Peer reviewe
On Impedance Bandwidth of Resonant Patch Antennas Implemented Using Structures with Engineered Dispersion
We consider resonant patch antennas, implemented using loaded
transmission-line networks and other exotic structures having engineered
dispersion. An analytical expression is derived for the ratio of radiation
quality factors of such antennas and conventional patch antennas loaded with
(reference) dielectrics. In the ideal case this ratio depends only on the
propagation constant and wave impedance of the structure under test, and it can
be conveniently used to study what kind of dispersion leads to improved
impedance bandwidth. We illustrate the effect of dispersion by implementing a
resonant patch antenna using a periodic network of LC elements. The analytical
results predicting enhanced impedance bandwidth compared to the reference
results are validated using a commercial circuit simulator. Discussion is
conducted on the practical limitations for the use of the proposed expression.Comment: 4 pages, 7 figure
Quantum Interference of Tunably Indistinguishable Photons from Remote Organic Molecules
We demonstrate two-photon interference using two remote single molecules as
bright solid-state sources of indistinguishable photons. By varying the
transition frequency and spectral width of one molecule, we tune and explore
the effect of photon distinguishability. We discuss future improvements on the
brightness of single-photon beams, their integration by large numbers on chips,
and the extension of our experimental scheme to coupling and entanglement of
distant molecules
On the Definition of Effective Permittivity and Permeability For Thin Composite Layers
The problem of definition of effective material parameters (permittivity and
permeability) for composite layers containing only one-two parallel arrays of
complex-shaped inclusions is discussed. Such structures are of high importance
for the design of novel metamaterials, where the realizable layers quite often
have only one or two layers of particles across the sample thickness. Effective
parameters which describe the averaged induced polarizations are introduced. As
an explicit example, we develop an analytical model suitable for calculation of
the effective material parameters and
for double arrays of electrically small electrically polarizable scatterers.
Electric and magnetic dipole moments induced in the structure and the
corresponding reflection and transmission coefficients are calculated using the
local field approach for the normal plane-wave incidence, and effective
parameters are introduced through the averaged fields and polarizations. In the
absence of losses both material parameters are purely real and satisfy the
Kramers-Kronig relations and the second law of thermodynamics. We compare the
analytical results to the simulated and experimental results available in the
literature. The physical meaning of the introduced parameters is discussed in
detail.Comment: 6 pages, 5 figure
An efficient auxin-inducible degron system with low basal degradation in human cells
Auxin-inducible degron technology allows rapid and controlled protein depletion. However, basal degradation without auxin and inefficient auxin-inducible depletion have limited its utility. We have identified a potent auxin-inducible degron system composed of auxin receptor F-box protein AtAFB2 and short degron minilAA7. The system showed minimal basal degradation and enabled rapid auxin-inducible depletion of endogenous human transmembrane, cytoplasmic and nuclear proteins in 1 h with robust functional phenotypes.Peer reviewe
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