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Register a new userSpider silks mechanics: predicting humidity and temperature effects
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We deduce a microstructure inspired model for humidity and temperature effects on the mechanical response of spider silks, modelled as a composite material with a hard crystalline and a soft amorphous region. Water molecules decrease the percentage of crosslinks in the softer region inducing a variation of natural configuration of the macromolecules. The resulting kinematic incompatibility between the regions crucially influences the final mechanical response. We demonstrate the predictivity of the model by quantitatively reproducing the experimentally observed behavior
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The dielectrophoresis method for trapping and attaching nanoscale double-stranded DNA between nanoelectrodes was developed. The method gives a high yield of trapping single or a few molecules only which enables transport measurements at the single molecule level. Electrical conductivity of individual 140-nm-long DNA molecules was measured, showing insulating behavior in dry conditions. In contrast, clear enhancement of conductivity was observed in moist conditions, relating to the interplay between the conformation of DNA molecules and their conductivity.
Spider is a balloon-borne instrument designed to map the polarization of the cosmic microwave background (CMB) with degree-scale resolution over a large fraction of the sky. Spiders main goal is to measure the amplitude of primordial gravitational waves through their imprint on the polarization of the CMB if the tensor-to-scalar ratio, r, is greater than 0.03. To achieve this goal, instrumental systematic errors must be controlled with unprecedented accuracy. Here, we build on previous work to use simulations of Spider observations to examine the impact of several systematic effects that have been characterized through testing and modeling of various instrument components. In particular, we investigate the impact of the non-ideal spectral response of the half-wave plates, coupling between focal plane components and the Earths magnetic field, and beam mismatches and asymmetries. We also present a model of diffuse polarized foreground emission based on a three-dimensional model of the Galactic magnetic field and dust, and study the interaction of this foreground emission with our observation strategy and instrumental effects. We find that the expected level of foreground and systematic contamination is sufficiently low for Spider to achieve its science goals.
We present the first systematic study of the stability of the structure and electrical properties of FeCl$_3$ intercalated few-layer graphene to high levels of humidity and high temperature. Complementary experimental techniques such as electrical transport, high resolution transmission electron microscopy and Raman spectroscopy conclusively demonstrate the unforeseen stability of this transparent conductor to a relative humidity up to $100 %$ at room temperature for 25 days, to a temperature up to $150,^circ$C in atmosphere and up to a temperature as high as $620,^circ$C in vacuum, that is more than twice higher than the temperature at which the intercalation is conducted. The stability of FeCl$_3$ intercalated few-layer graphene together with its unique values of low square resistance and high optical transparency, makes this material an attractive transparent conductor in future flexible electronic applications.
We review opportunities for stochastic geometric mechanics to incorporate observed data into variational principles, in order to derive data-driven nonlinear dynamical models of effects on the variability of computationally resolvable scales of fluid motion, due to unresolvable, small, rapid scales of fluid motion.
The recent discovery of electro-active polymers has shown great promises in the field of soft robotics, and was logically followed by experimental, numerical and theoretical developments. Most of these studies were concerned with systems entirely covered by electrodes. However, there is a growing interest for partially active polymers, in which the electrode covers only one part of the membrane. Indeed, such actuation can trigger buckling instabilities and so represents a route toward the control of 3D shapes. Here, we study theoretically the behaviour of such partially active electro-active polymer. We address two problems: (i) the electrostatic elastica including geometric non-linearities and partially electro-active strip using a variational approach. We propose a new interpretation of the equations of deformation, by drawing analogies with biological growth, in which the effect of the electric voltage is seen as a change in the reference stress-free state. (ii) we explain the nature of the distribution of electrostatic forces on this simple system, which is not trivial. In particular we find that edge effects are playing a major role in this problem.
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