287 research outputs found
Josephson super-current in graphene-superconductor junction
Within the tunneling Hamiltonian formulation for the eight-component
spinors,the Josephson critical super-current has been calculated in a planar
superconductor-normal graphene-superconductor junction. Coupling between
superconductor regions and graphene is taken into account by a tunneling
Hamiltonian which contains two types of tunneling, intra-valley and
inter-valley tunneling. Within the present tunneling approach, we find that the
contributions of two kinds of tunneling to the critical super-current, are
completely separable. Therefore, it is possible to consider the effect of the
inter-valley tunnelings in the critical super-current. The incorporation of
these type of processes into the tunneling Hamiltonian, exposes a special
feature of the graphene Josephson junctions. The effect of inter-valley
tunneling appears in the length dependence plot of critical current in the form
of oscillations. We also present the results for temperature dependence of
critical super-current and compare with experimental results and other
theoretical calculations
Shaping in Practice: Training Wheels to Learn Fast Hopping Directly in Hardware
Learning instead of designing robot controllers can greatly reduce
engineering effort required, while also emphasizing robustness. Despite
considerable progress in simulation, applying learning directly in hardware is
still challenging, in part due to the necessity to explore potentially unstable
parameters. We explore the concept of shaping the reward landscape with
training wheels: temporary modifications of the physical hardware that
facilitate learning. We demonstrate the concept with a robot leg mounted on a
boom learning to hop fast. This proof of concept embodies typical challenges
such as instability and contact, while being simple enough to empirically map
out and visualize the reward landscape. Based on our results we propose three
criteria for designing effective training wheels for learning in robotics. A
video synopsis can be found at https://youtu.be/6iH5E3LrYh8.Comment: Accepted to the IEEE International Conference on Robotics and
Automation (ICRA) 2018, 6 pages, 6 figure
Nonlinear Rheology of Unentangled Polymer Melts Reinforced with High Concentration of Rigid Nanoparticles
A scaling model is presented to analyze the nonlinear rheology of unentangled polymer melts filled with high concentration of small spherical particles. Assuming the majority of chains to be reversibly adsorbed to the surface of the particles, we show that the emergence of nonlinearity in the viscoelastic response of the composite system subjected to a 2D shear flow results from stretching of the adsorbed chains and increasing desorption rate of the adsorbed segments due to the imposed deformation. The steady-state shear viscosity of the mixture in nonlinear shear thinning regime follows the power lawwhereis the applied shear rate. At large strain amplitude Îł 0, the storage and loss moduli in strain sweep tests scale asandrespectively
Fire Scenarios Inside a Room-and-Pillar Underground Quarry Using Numerical Modeling to Define Emergency Plans
Underground fires are still one of the most significant risks in mines today. In order to manage this risk, it is necessary to know the potential evolution of a fire and the effects it can have on people and other objects. Ventilation plays an essential role in the development of a fire; it also influences the propagation of toxic fumes and the variation of temperatures in all other areas of a mine. Currently, it is possible to jointly analyze, through numerical modeling, the ventilation circuit and a fire for different possible scenarios in order to define, in detail, the emergency plans that need to be adopted. In this paper, a numerical study was conducted via the use of Ventsim Software (an integrated mine and tunnel ventilation numerical package that is able to analyze airflows, pressures, heat, gases, and fires along all of a defined circuit over time using an iterative procedure to solve Kirchhoff’s current law). Furthermore, in this study, it is illustrated how the joint numerical modeling of the ventilation circuit and fire, when applied to an underground gypsum mine in the northwest of Italy, provides all the elements necessary to define the safety procedures that should be adopted in standard conditions as well as during an emergency due to a fire. More specifically, it was possible to identify suitable escape routes depending on the location of the possible fire and the time available for the staff to be able to evacuate safely
The norovirus NS3 protein is a dynamic lipid- and microtubule-associated protein involved in viral RNA replication
Norovirus (NoV) infections are a significant health burden to society, yet the lack of reliable tissue culture systems has hampered the development of appropriate antiviral therapies. Here we show that the NoV NS3 protein, derived from murine NoV (MNV), is intimately associated with the MNV replication complex and the viral replication intermediate double-stranded RNA (dsRNA). We observed that when expressed individually, MNV NS3 and NS3 encoded by human Norwalk virus (NV) induced the formation of distinct vesicle-like structures that did not colocalize with any particular protein markers to cellular organelles but localized to cellular membranes, in particular those with a high cholesterol content. Both proteins also showed some degree of colocalization with the cytoskeleton marker β-tubulin. Although the distribution of MNV and NV NS3s were similar, NV NS3 displayed a higher level of colocalization with the Golgi apparatus and the endoplasmic reticulum (ER). However, we observed that although both proteins colocalized in membranes counterstained with filipin, an indicator of cholesterol content, MNV NS3 displayed a greater association with flotillin and stomatin, proteins known to associate with sphingolipid- and cholesterol-rich microdomains. Utilizing time-lapse epifluorescence microscopy, we observed that the membrane-derived vesicular structures induced by MNV NS3 were highly motile and dynamic in nature, and their movement was dependent on intact microtubules. These results begin to interrogate the functions of NoV proteins during virus replication and highlight the conserved properties of the NoV NS3 proteins among the seven Norovirus genogroups
Investigation of the performance of an optimised MicroCAT, a GEM and their combination by simulations and current measurements
A MicroCAT (Micro Compteur A Trous) structure which is used for avalanche
charge multiplication in gas filled radiation detectors has been optimised with
respect to maximum electron transparency and minimum ion feedback. We report on
the charge transfer behaviour and the achievable gas gain of this device. A
three-dimensional electron and ion transfer simulation is compared to results
derived from electric current measurements. Similarly, we present studies of
the charge transfer behaviour of a GEM (Gas Electron Multiplier) by current
measurements and simulations. Finally, we investigate the combination of the
MicroCAT and the GEM by measurements with respect to the performance at
different voltage settings, gas mixtures and gas pressures.Comment: 26 pages, 32 figure
Effect of light and water deficiency on growth and concentration of various primary and secondary metabolites of aloe vera l
Assessment of salinity indices to identify mint ecotypes using an intelligent and regression models
The Density of States of hole-doped Manganites: A Scanning Tunneling Microscopy/Spectroscopy study
Variable temperature scanning tunneling microscopy/spectroscopy studies on
single crystals and epitaxial thin films of hole-doped manganites, which show
colossal magnetoresistance, have been done. We have investigated the variation
of the density of states, at and near the Fermi energy (), as a function
of temperature. Simple calculations have been carried out, to find out the
effect of temperature on the tunneling spectra and extract the variation of
density of states with temperature, from the observed data. We also report
here, atomic resolution images, on the single crystals and larger range images
showing the growth patterns on thin films. Our investigation shows
unambiguously that there is a rapid variation in density of states for
temperatures near the Curie temperature (). While for temperatures below
, a finite DOS is observed at , for temperatures near a hard
gap opens up in the density of states near . For temperatures much higher
than , this gap most likely gives way to a soft gap. The observed hard gap
for temperatures near , is somewhat higher than the transport gap for all
the materials. For different materials, we find that the magnitude of the hard
gap decreases as the of the material increases and eventually, for
materials with a close to 400 K, the value of the gap approaches zero.Comment: 9 pages RevTeX, 12 postscript figures, 1 table included in text,
submitted to Physical Review
The potential of the synthetic strigolactone analogue GR24 for the maintenance of photosynthesis and yield in winter wheat under drought: Investigations on the mechanisms of action and delivery modes
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