5,582 research outputs found
Combined molecular/continuum modeling reveals the role of friction during fast unfolding of coiled-coil proteins
Coiled-coils are filamentous proteins that form the basic building block of important force-bearing cellular elements, such as intermediate filaments and myosin motors. In addition to their biological importance, coiled-coil proteins are increasingly used in new biomaterials including fibers, nanotubes, or hydrogels. Coiled-coils undergo a structural transition from an a-helical coil to an unfolded state upon extension, which allows them to sustain large strains and is critical for their biological function. By performing equilibrium and out-of-equilibrium all-atom molecular dynamics (MD) simulations of coiledcoils in explicit solvent, we show that two-state models based on Kramers’ or Bell’s theories fail to predict the rate of unfolding at high pulling rates. We further show that an atomistically informed continuum rod model accounting for phase transformations and for the hydrodynamic interactions with the solvent can reconcile two-state models with our MD results. Our results show that frictional forces, usually neglected in theories of fibrous protein unfolding, reduce the thermodynamic force acting on the interface, and thus control the dynamics of unfolding at different pulling rates. Our results may help interpret MD simulations at high pulling rates, and could be pertinent to cytoskeletal networks or protein-based artificial materials subjected to shocks or blasts
Experimental evidences of a large extrinsic spin Hall effect in AuW alloy
We report an experimental study of a gold-tungsten alloy (7% at. W
concentration in Au host) displaying remarkable properties for spintronics
applications using both magneto-transport in lateral spin valve devices and
spin-pumping with inverse spin Hall effect experiments. A very large spin Hall
angle of about 10% is consistently found using both techniques with the
reliable spin diffusion length of 2 nm estimated by the spin sink experiments
in the lateral spin valves. With its chemical stability, high resistivity and
small induced damping, this AuW alloy may find applications in the nearest
future
Appearance of room temperature ferromagnetism in Cu-doped TiO films
In recent years there has been an intense search for room temperature
ferromagnetism in doped dilute semiconductors, which have many potentially
applications in spintronics and optoelectronics. We report here the unexpected
observation of significant room temperature ferromagnetism in a semiconductor
doped with nonmagnetic impurities, Cu-doped TiO thin films grown by Pulsed
Laser Deposition. The magnetic moment, calculated from the magnetization
curves, resulted surprisingly large, about 1.5 per Cu atom. A large
magnetic moment was also obtained from ab initio calculations using the
supercell method for TiO with Cu impurities, but only if an oxygen vacancy
in the nearest-neighbour shell of Cu was present. This result suggests that the
role of oxygen vacancies is crucial for the appearance of ferromagnetism. The
calculations also predict that Cu doping favours the formation of oxygen
vacancies.Comment: 4 pages, 3 figures, published in Phys. Rev. B (Rapid Comm.
Sistemas caóticos y su aplicación a la encriptación de señales
La sincronización y control de señales caóticas es una activa área de investigación por sus posibles aplicaciones en telecomunicaciones y transmisión de señales [1, 2, 3, 4]. En el presente trabajo se estudia un sistema de comunicación basado
en la sincronización de dos sistemas no lineales caóticos, cada uno modelado a partir de las ecuaciones de movimiento de un péndulo forzado amortiguado y que se encuentran en el mismo punto de operación del espacio de parámetros.
Synchronization and control of chaotic signals is an active research area because of its applications
in telecommunications and secure signal transmission [1,2,3,4]. In this work a communication system
based in the synchronization of two chaotic nonlinear systems, each one being modeled by the motion
equations of a driven damped pendulum and operated in the same parameter space region is shown. Two
communication channels were used: the first one for the synchronizing signal and the second one for the
sent message. By using two channels the initial conditions sensibility problem is solved. In the receiver
system a feedback loop as a proportional controller is used in order to drive quickly the error between the
decoder and encoder states to zero. The last two facts make the system to be robust to external pertubative
signals such as noise in the communication channels
LiLO: Lightweight and low-bias LiDAR Odometry method based on spherical range image filtering
In unstructured outdoor environments, robotics requires accurate and
efficient odometry with low computational time. Existing low-bias LiDAR
odometry methods are often computationally expensive. To address this problem,
we present a lightweight LiDAR odometry method that converts unorganized point
cloud data into a spherical range image (SRI) and filters out surface, edge,
and ground features in the image plane. This substantially reduces computation
time and the required features for odometry estimation in LOAM-based
algorithms. Our odometry estimation method does not rely on global maps or loop
closure algorithms, which further reduces computational costs. Experimental
results generate a translation and rotation error of 0.86\% and 0.0036{\deg}/m
on the KITTI dataset with an average runtime of 78ms. In addition, we tested
the method with our data, obtaining an average closed-loop error of 0.8m and a
runtime of 27ms over eight loops covering 3.5Km.Comment: This paper is under review at the journal "Autonomous Robots"
(Springer
Influence of the Water Vapour Permeability of Airtight Sheets on the Behaviour of Facade
The air-tightness of the thermal envelope of buildings is one of the measures to reduce their
energy demands in order to achieve global warming reduction targets. To this end, airtight sheets
with different water vapour permeability characteristics are used. The different products studied are
highly dispersed in terms of equivalent air thickness values, leading to confusion. After the analysis
carried out, it is concluded that all airtight sheets are vapour barriers. To clarify whether or not
these sheets are necessary as vapour barriers, a condensation analysis was carried out on 13 different
facades for 3 climate zones with severe winters as defined in Spanish regulations. The results reveal
that interstitial condensation occurs in only 7 of the 39 case studies, with the traditional facades
of brickwork with render causing the greatest problems if the appropriate products are not used.
In these cases, airtight sheets with water vapour barrier characteristics must be applied on the interior
face of the insulating material. In all other cases (32), the airtight sheets must be permeable to water
vapour if it is looked for a more breathable wall to water vapour and a better control of the interior
humidity conditions
Reflection and transmission of waves in surface-disordered waveguides
The reflection and transmission amplitudes of waves in disordered multimode
waveguides are studied by means of numerical simulations based on the invariant
embedding equations. In particular, we analyze the influence of surface-type
disorder on the behavior of the ensemble average and fluctuations of the
reflection and transmission coefficients, reflectance, transmittance, and
conductance. Our results show anomalous effects stemming from the combination
of mode dispersion and rough surface scattering: For a given waveguide length,
the larger the mode transverse momentum is, the more strongly is the mode
scattered. These effects manifest themselves in the mode selectivity of the
transmission coefficients, anomalous backscattering enhancement, and speckle
pattern both in reflection and transmission, reflectance and transmittance, and
also in the conductance and its universal fluctuations. It is shown that, in
contrast to volume impurities, surface scattering in quasi-one-dimensional
structures (waveguides) gives rise to the coexistence of the ballistic,
diffusive, and localized regimes within the same sample.Comment: LaTeX (REVTeX), 12 pages with 14 EPS figures (epsf macro), minor
change
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