3,762 research outputs found
Optical conductivity of wet DNA
Motivated by recent experiments we have studied the optical conductivity of
DNA in its natural environment containing water molecules and counter ions. Our
density functional theory calculations (using SIESTA) for four base pair B-DNA
with order 250 surrounding water molecules suggest a thermally activated doping
of the DNA by water states which generically leads to an electronic
contribution to low-frequency absorption. The main contributions to the doping
result from water near DNA ends, breaks, or nicks and are thus potentially
associated with temporal or structural defects in the DNA.Comment: 4 pages, 4 figures included, final version, accepted for publication
in Phys. Rev. Let
High-Field Electrical Transport in Single-Wall Carbon Nanotubes
Using low-resistance electrical contacts, we have measured the intrinsic
high-field transport properties of metallic single-wall carbon nanotubes.
Individual nanotubes appear to be able to carry currents with a density
exceeding 10^9 A/cm^2. As the bias voltage is increased, the conductance drops
dramatically due to scattering of electrons. We show that the current-voltage
characteristics can be explained by considering optical or zone-boundary phonon
emission as the dominant scattering mechanism at high field.Comment: 4 pages, 3 eps figure
Bulk and boundary zero-bias anomaly in multi-wall carbon nanotubes
We compute the tunneling density of states of doped multi-wall nanotubes
including disorder and electron-electron interactions. A non-conventional
Coulomb blockade reflecting nonperturbative Altshuler-Aronov-Lee power-law
zero-bias anomalies is found, in accordance with recent experimental results.
The presence of a boundary implies a universal doubling of the boundary
exponent in the diffusive limit.Comment: 4 pages, to appear in PRL (revised version
Current facilitation by plasmon resonances between parallel wires of finite length
The current voltage (IV) characteristics for perpendicular transport through
two sequentially coupled wires of finite length is calculated analytically. The
transport within a Coulomb blockade step is assisted by plasmon resonances that
appear as steps in the IV characteristics with positions and heights depending
on inter- and intrawire interactions. In particular, due to the interwire
interactions, the peak positions shift to lower voltages in comparison to the
noninteracting wires which reflects the facilitation of current by
interactions. The interwire interactions are also found to enhance the
thermally activated current.Comment: 5 pages, 1figur
The Tone from Above:The Effect of Communicating a Supportive Regulatory Strategy on Reporting Quality
In collaboration with the Authority for the Financial Markets in the Netherlands, we manipulate the content of official letters that instruct financial intermediaries to submit a mandatory self-assessment. As part of the Registered Report Process, we submitted our hypotheses, experimental procedure, and planned statistical analyses before data collection. We predicted that a request indicating a supportive regulatory attitude has a positive effect on reporting quality on average. We also predicted this effect to be stronger for small firms and for firms with a long-term orientation, and to become negative for firms with a short-term orientation. Planned analyses show that a supportive letter reduced reporting quality unless firms had a long-term orientation, supporting the moderating influence of time horizon, but providing no support for the expected average effect or for moderation by firm size
Spin-orbit coupling and ESR theory for carbon nanotubes
A theoretical description of ESR in 1D interacting metals is given, with
primary emphasis on carbon nanotubes. The spin-orbit coupling is derived, and
the resulting ESR spectrum is analyzed by field theory and exact
diagonalization. Drastic differences in the ESR spectra of single-wall and
multi-wall nanotubes are found. For single-wall tubes, the predicted double
peak spectrum could reveal spin-charge separation.Comment: 4 pages, 1 figure, final version to appear in PR
Professionals' perceptions of factors affecting implementation and continuation of a physical activity promotion programme in rehabilitation: A qualitative study
Objective: To describe professionals’ perceptions of factors that facilitate or hamper the implementation and continuation of a physical activity promotion programme in rehabilitation.
Design: This study used a qualitative design.
Methods: Semi-structured interviews (n = 22) were conducted with rehabilitation professionals (n = 28) involved in the implementation of a physical activity promotion programme. Two additional interviews were conducted with the programme coordinators (n = 2). The study involved 18 rehabilitation organizations implementing the programme that targets people with disabilities or chronic diseases. Organizations were supported in the implementation process by the programme coordinators.
Results: Commonly perceived facilitating factors were: involvement of committed and enthusiastic professionals; agreement with their organizations’ vision/wishes; the perceived additional value of the programme; and opportunities to share knowledge and experience with professionals from other organizations. Commonly perceived hampering factors were: uncertainty about continuing the programme; limited flexibility; and lack of support from physicians and therapists to implement the programme.
Conclusion: Professionals perceived a heterogeneous set of factors that facilitate and/or hamper the implementation and continuation of a physical activity promotion programme in rehabilitation. Based on these findings, recommendations were formulated to enhance embedding of physical activity promotion during and after rehabilitation
Effects of rocker radii with two longitudinal bending stiffnesses on plantar pressure distribution in the forefoot
INTRODUCTION: Outsole parameters of the shoe can be adapted to offload regions of pain or region of high pressures. Previous studies already showed reduced plantar pressures in the forefoot due to a proximally placed apex position and higher longitudinal bending stiffness (LBS). The aim of this study was to determine the effect of changes in rocker radii and high LBS on the plantar pressure profile during gait. METHOD: 10 participants walked in seven shoe conditions of which one control shoe and six rocker shoes with small, medium and large rocker radii and low and high longitudinal bending stiffness. Pedar in-shoe plantar pressure measuring system was used to quantify plantar pressures while walking on a treadmill at self-selected walking speed. Peak plantar pressure, maximum mean pressure and force-time integral were analyzed with Generalized Estimated Equation (GEE) and Tukey post hoc correction (α = .05). RESULTS: Significantly lower plantar pressures were found in the first toe, toes 2-5, distal and proximal forefoot in all rocker shoe conditions as compared to the control shoe. Plantar pressures in the first toe and toes 2-5 were significantly lower in the small radius compared to medium and large radii. For the distal forefoot both small and medium radii significantly reduced plantar pressure compared to large radii. Low LBS reduced plantar pressure at the first toe significantly compared to high LBS independent of the rocker radius. Plantar pressures in the distal forefoot and toes 2-5 were lower in high LBS compared to low LBS. CONCLUSION: Manipulation of the rocker radius and LBS can effectively reduce peak plantar pressures in the forefoot region during gait. In line with previous studies, we showed that depending on the exact target location for offloading, different combinations of rocker radius and LBS need to be adopted to maximize treatment effects
Coulomb drag shot noise in coupled Luttinger liquids
Coulomb drag shot noise has been studied theoretically for 1D interacting
electron systems, which are realized e.g. in single-wall nanotubes. We show
that under adiabatic coupling to external leads, the Coulomb drag shot noise of
two coupled or crossed nanotubes contains surprising effects, in particular a
complete locking of the shot noise in the tubes. In contrast to Coulomb drag of
the average current, the noise locking is based on a symmetry of the underlying
Hamiltonian and is not limited to asymptotically small energy scales.Comment: 4 pages Revtex, accepted for publication in PR
Multiwalled carbon nanotube: Luttinger liquid or not?
We have measured IV-curves of multiwalled carbon nanotubes using end
contacts. At low voltages, the tunneling conductance obeys non-Ohmic power law,
which is predicted both by the Luttinger liquid and the
environment-quantum-fluctuation theories. However, at higher voltages we
observe a crossover to Ohm's law with a Coulomb-blockade offset, which agrees
with the environment-quantum-fluctuation theory, but cannot be explained by the
Luttinger-liquid theory. From the high-voltage tunneling conductance we
determine the transmission line parameters of the nanotubes.Comment: RevTeX, 4 pages, 2 EPS-figures, submitted to Phys. Rev. Let
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