5,776 research outputs found
Sign switch of Gaussian bending modulus for microemulsions; a self-consistent field analysis exploring scale invariant curvature energies
Bending rigidities of tensionless balanced liquid-liquid interfaces as
occurring in microemulsions are predicted using self-consistent field theory
for molecularly inhomogeneous systems. Considering geometries with scale
invariant curvature energies gives unambiguous bending rigidities for systems
with fixed chemical potentials: The minimal surface Im3m cubic phase is used to
find the Gaussian bending rigidity, , and a torus with Willmore
energy allows for direct evaluation of the mean bending modulus,
. Consistent with this, the spherical droplet gives access to . We observe that tends to be negative for strong
segregation and positive for weak segregation; a finding which is instrumental
for understanding phase transitions from a lamellar to a sponge-like
microemulsion. Invariably, remains positive and increases with
increasing strength of segregation.Comment: 7 pages, 5 figure
Universal Dephasing Control During Quantum Computation
Dephasing is a ubiquitous phenomenon that leads to the loss of coherence in
quantum systems and the corruption of quantum information. We present a
universal dynamical control approach to combat dephasing during all stages of
quantum computation, namely, storage, single- and two-qubit operators. We show
that (a) tailoring multi-frequency gate pulses to the dephasing dynamics can
increase fidelity; (b) cross-dephasing, introduced by entanglement, can be
eliminated by appropriate control fields; (c) counter-intuitively and contrary
to previous schemes, one can increase the gate duration, while simultaneously
increasing the total gate fidelity.Comment: 4 pages,3 figure
Chain motion and viscoelasticity in highly entangled solutions of semiflexible rods
Brownian dynamics simulations are used to study highly entangled solutions of
semiflexible polymers. Bending fluctuations of semiflexible rods are
signficantly affected by entanglement only above a concentration ,
where for chains of similar length and
persistence length. For , the tube radius approaches a
dependence , and the linear viscoelastic response
develops an elastic contribution that is absent for . Experiments
on isotropic solutions of -actin span concentrations near for which
the predicted asymptotic scaling of the plateau modulus is
not yet valid.Comment: 4 pages, 5 figures, submitted to PR
Emergent modular neural control drives coordinated motor actions.
A remarkable feature of motor control is the ability to coordinate movements across distinct body parts into a consistent, skilled action. To reach and grasp an object, 'gross' arm and 'fine' dexterous movements must be coordinated as a single action. How the nervous system achieves this coordination is currently unknown. One possibility is that, with training, gross and fine movements are co-optimized to produce a coordinated action; alternatively, gross and fine movements may be modularly refined to function together. To address this question, we recorded neural activity in the primary motor cortex and dorsolateral striatum during reach-to-grasp skill learning in rats. During learning, the refinement of fine and gross movements was behaviorally and neurally dissociable. Furthermore, inactivation of the primary motor cortex and dorsolateral striatum had distinct effects on skilled fine and gross movements. Our results indicate that skilled movement coordination is achieved through emergent modular neural control
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Experimental evidence on promotion of electric and improved biomass cookstoves.
Improved cookstoves (ICS) can deliver "triple wins" by improving household health, local environments, and global climate. Yet their potential is in doubt because of low and slow diffusion, likely because of constraints imposed by differences in culture, geography, institutions, and missing markets. We offer insights about this challenge based on a multiyear, multiphase study with nearly 1,000 households in the Indian Himalayas. In phase I, we combined desk reviews, simulations, and focus groups to diagnose barriers to ICS adoption. In phase II, we implemented a set of pilots to simulate a mature market and designed an intervention that upgraded the supply chain (combining marketing and home delivery), provided rebates and financing to lower income and liquidity constraints, and allowed households a choice among ICS. In phase III, we used findings from these pilots to implement a field experiment to rigorously test whether this combination of upgraded supply and demand promotion stimulates adoption. The experiment showed that, compared with zero purchase in control villages, over half of intervention households bought an ICS, although demand was highly price-sensitive. Demand was at least twice as high for electric stoves relative to biomass ICS. Even among households that received a negligible price discount, the upgraded supply chain alone induced a 28 percentage-point increase in ICS ownership. Although the bundled intervention is resource-intensive, the full costs are lower than the social benefits of ICS promotion. Our findings suggest that market analysis, robust supply chains, and price discounts are critical for ICS diffusion
Influence of analysis and design models on minimum weight design
The results of numerical experiments designed to illustrate how the minimum weight design, accuracy, and cost can be influenced by: (1) refinement of the finite element analysis model and associated load path problems, and (2) refinement of the design variable linking model are examined. The numerical experiments range from simple structures where the modelling decisions are relatively obvious and less costly to the more complex structures where such decisions are less obvious and more costly. All numerical experiments used employ the dual formulation in ACCESS-3 computer program. Guidelines are suggested for creating analysis and design models that predict a minimum weight structure with greater accuracy and less cost. These guidelines can be useful in an interactive optimization environment and in the design of heuristic rules for the development of knowledge-based expert optimization systems
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