2,674 research outputs found
Entropy driven key-lock assembly
The effective interaction between a sphere with an open cavity (lock) and a
spherical macroparticle (key), both immersed in a hard sphere fluid, is studied
by means of Monte Carlo simulations. As a result, a 2d map of the key-lock
effective interaction potential is constructed, which leads to the proposal of
a self-assembling mechanism: there exists trajectories through which the
key-lock pair could assemble avoiding trespassing potential barriers. Hence,
solely the entropic contribution can induce their self-assembling even in the
absence of attractive forces. This study points out the solvent contribution
within the underlying mechanisms of substrate-protein assembly/disassembly
processes, which are important steps of the enzyme catalysis and protein
mediated transport
Electrostatic control of quantum dot entanglement induced by coupling to external reservoirs
We propose a quantum transport experiment to prepare and measure
charge-entanglement between two electrostatically defined quantum dots.
Coherent population trapping, as realized in cavity quantum electrodynamics,
can be carried out by using a third quantum dot to play the role of the optical
cavity. In our proposal, a pumping which is quantum mechanically
indistinguishable for the quantum dots drives the system into a state with a
high degree of entanglement. The whole effect can be switched on and off by
means of a gate potential allowing both state preparation and entanglement
detection by simply measuring the total current.Comment: 5 pages, 4 figures, Latex2e with EPL macros, to appear in Europhysics
Letter
Crop Yields: Stripper Header Technology vs. Conventional Header Technology
The purpose of this paper is to compare crop yields on acres where stripper header technology was used to those where conventional header technology was used in a dryland cropping system. The results are based on experimental data collected at the USDA-ARS Central Great Plains Research Station, and include information on Northeastern Colorado wheat, millet, and sorghum yields. This analysis is important to demonstrate the benefits of using stripper header technology in a dryland cropping system. In the next section, the approaches and major findings of the previous literature are reviewed
Quasiparticle Chirality in Epitaxial Graphene Probed at the Nanometer Scale
Graphene exhibits unconventional two-dimensional electronic properties
resulting from the symmetry of its quasiparticles, which leads to the concepts
of pseudospin and electronic chirality. Here we report that scanning tunneling
microscopy can be used to probe these unique symmetry properties at the
nanometer scale. They are reflected in the quantum interference pattern
resulting from elastic scattering off impurities, and they can be directly read
from its fast Fourier transform. Our data, complemented by theoretical
calculations, demonstrate that the pseudospin and the electronic chirality in
epitaxial graphene on SiC(0001) correspond to the ones predicted for ideal
graphene.Comment: 4 pages, 3 figures, minor change
High-precission neutron capture gamma-ray spectroscopy using germanium detectors in compton-suppression technique
Stub model for dephasing in a quantum dot
As an alternative to Buttiker's dephasing lead model, we examine a dephasing
stub. Both models are phenomenological ways to introduce decoherence in chaotic
scattering by a quantum dot. The difference is that the dephasing lead opens up
the quantum dot by connecting it to an electron reservoir, while the dephasing
stub is closed at one end. Voltage fluctuations in the stub take over the
dephasing role from the reservoir. Because the quantum dot with dephasing lead
is an open system, only expectation values of the current can be forced to
vanish at low frequencies, while the outcome of an individual measurement is
not so constrained. The quantum dot with dephasing stub, in contrast, remains a
closed system with a vanishing low-frequency current at each and every
measurement. This difference is a crucial one in the context of quantum
algorithms, which are based on the outcome of individual measurements rather
than on expectation values. We demonstrate that the dephasing stub model has a
parameter range in which the voltage fluctuations are sufficiently strong to
suppress quantum interference effects, while still being sufficiently weak that
classical current fluctuations can be neglected relative to the nonequilibrium
shot noise.Comment: 8 pages with 1 figure; contribution for the special issue of J.Phys.A
on "Trends in Quantum Chaotic Scattering
Geometric Universality of Currents
We discuss a non-equilibrium statistical system on a graph or network.
Identical particles are injected, interact with each other, traverse, and leave
the graph in a stochastic manner described in terms of Poisson rates, possibly
dependent on time and instantaneous occupation numbers at the nodes of the
graph. We show that under the assumption of constancy of the relative rates,
the system demonstrates a profound statistical symmetry, resulting in geometric
universality of the statistics of the particle currents. This phenomenon
applies broadly to many man-made and natural open stochastic systems, such as
queuing of packages over the internet, transport of electrons and
quasi-particles in mesoscopic systems, and chains of reactions in bio-chemical
networks. We illustrate the utility of our general approach using two enabling
examples from the two latter disciplines.Comment: 15 pages, 5 figure
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