Implantable Organic Electronic Ion Pump Enables ABA Hormone Delivery for Control of Stomata in an Intact Tobacco Plant

Electronic control of biological processes with bioelectronic devices holds promise for sophisticated regulation of physiology, for gaining fundamental understanding of biological systems, providing new therapeutic solutions, and digitally mediating adaptations of organisms to external factors. The organic electronic ion pump (OEIP) provides a unique means for electronically‐controlled, flow‐free delivery of ions, and biomolecules at cellular scale. Here, a miniaturized OEIP device based on glass capillary fibers (c‐OEIP) is implanted in a biological organism. The capillary form factor at the sub‐100 µm scale of the device enables it to be implanted in soft tissue, while its hyperbranched polyelectrolyte channel and addressing protocol allows efficient delivery of a large aromatic molecule. In the first example of an implantable bioelectronic device in plants, the c‐OEIP readily penetrates the leaf of an intact tobacco plant with no significant wound response (evaluated up to 24 h) and effectively delivers the hormone abscisic acid (ABA) into the leaf apoplast. OEIP‐mediated delivery of ABA, the phytohormone that regulates plant's tolerance to stress, induces closure of stomata, the microscopic pores in leaf's epidermis that play a vital role in photosynthesis and transpiration. Efficient and localized ABA delivery reveals previously unreported kinetics of ABA‐induced signal propagation.     

A hybrid control approach to action coordination for mobile robots

In this paper, the problem concerning how to coordinate the contributions from concurrent controllers, when controlling mobile robots, is investigated. It is shown how a behavior based control system for autonomous robots can be modeled as a hybrid automaton, where each node corresponds to a distinct robot behavior. This type of construction gives rise to chattering executions, but it is shown how regularized automata can be used to solve this problem. As an illustration, the obstacle-negotiation problem is solved by using a combination of a robust path-following behavior and a reactive obstacle-avoidance behavior that move the robot around a given obstacle at a predefined safety distance.     

Hierarchical and Heterogeneous Bioinspired Composites—Merging Molecular Self‐Assembly with Additive Manufacturing

Biological composites display exceptional mechanical properties owing to a highly organized, heterogeneous architecture spanning several length scales. It is challenging to translate this ordered and multiscale structural organization in synthetic, bulk composites. Herein, a combination of top‐down and bottom‐up approach is demonstrated, to form a polymer‐ceramic composite by macroscopically aligning the self‐assembled nanostructure of polymerizable lyotropic liquid crystals via 3D printing. The polymer matrix is then uniformly reinforced with bone‐like apatite via in situ biomimetic mineralization. The combinatorial method enables the formation of macrosized, heterogeneous composites where the nanostructure and chemical composition is locally tuned over microscopic distances. This enables precise control over the mechanics in specific directions and regions, with a unique intrinsic–extrinsic toughening mechanism. As a proof‐of‐concept, the method is used to form large‐scale composites mimicking the local nanostructure, compositional gradients and directional mechanical properties of heterogeneous tissues like the bone‐cartilage interface, for mechanically stable osteochondral plugs. This work demonstrates the possibility to create hierarchical and complex structured composites using weak starting components, thus opening new routes for efficient synthesis of high‐performance materials ranging from biomaterials to structural nanocomposites.     

The core group revisited: the effect of partner mixing and migration on the spread of gonorrhea, Chlamydia, and HIV

A set of differential equations are used to model the spread of sexually transmitted diseases (STDs) in a one-sex population that includes a core group of highly sexually active subjects. The effects of partner mixing between groups and migration to and from the core on the equilibrium number of infected are shown for gonorrhea, chlamydia, and HIV. The STDs are described by the transmission probability per sexual contact and the duration of infectiousness. Partner change and intercourse frequencies are estimated from sexual survey data on heterosexual behavior. The core group is small (3% of the total population) with a partner change frequency 15 times and an intercourse frequency 2 times that of the remaining population. The degree of partner mixing and migration between the two groups can be varied. The number of sexual contacts in the three types of partnerships (core-core, "mixed," remaining population-remaining population) is also modeled. The mixed partnerships are assumed to be casual and to have a low frequency of intercourse. The model is fairly simple, and the emphasis is on qualitative rather that predictive results. The effects of partner mixing are found to be strikingly different for gonorrhea, chlamydia, and HIV. With increasing partner mixing between groups, gonorrhea shows a small increase and then a decrease in the total number of infected, whereas chlamydial infection shows a strong increase. For HIV infection the effect depends on the transmission probability; when it is 0.001 per sexual contact, the number of infected with HIV is almost unaffected by the partner mixing, and when the transmission probability is 0.002 per sexual contact, there is a strong increase in the number of HIV infected with increasing partner mixing. The effects of migration are also different for each disease. With increasing migration between groups, gonorrhea is almost unaffected in the total number of infected, whereas chlamydial infection shows a strong increase. For HIV the effect again depends on the transmission probability; when it is 0.001 per sexual contact, the number of infected with HIV shows a strong decrease, and when the transmission probability is 0.002 per sexual contact the number of HIV infected reaches its maximum for medium strong migration. A sensitivity analysis shows that for all three diseases the basic reproductive ratios (R0) and the total number of infected are sensitive to duration of infectiousness. In addition, for gonorrhea and chlamydia, RO is sensitive to the partner change rates in the core, whereas for HIV, RO is sensitive to the frequency of intercourse in the core.(ABSTRACT TRUNCATED AT 400 WORDS)     

Arctic river temperature dynamics in a changing climate

Climate change in the Arctic is expected to have a major impact on stream ecosystems, affecting hydrological and thermal regimes. Although temperature is important to a range of in‐stream processes, previous Arctic stream temperature research is limited—focused on glacierised headwaters in summer—with limited attention to snowmelt streams and winter. This is the first high‐resolution study on stream temperature in north‐east Greenland (Zackenberg). Data were collected from five streams from September 2013 to September 2015 (24 months). During the winter, streams were largely frozen solid and water temperature variability low. Spring ice‐off date occurred simultaneously across all streams, but 11 days earlier in 2014 compared with 2015 due to thicker snow insulation. During summer, water temperature was highly variable and exhibited a strong relationship with meteorological variables, particularly incoming shortwave radiation and air temperature. Mean summer water temperature in these snowmelt streams was high compared with streams studied previously in Svalbard, yet was lower in Swedish Lapland, as was expected given latitude. With global warning, Arctic stream thermal variability may be less in summer and increased during the winter due to higher summer air temperature and elevated winter precipitation, and the spring and autumn ice‐on and ice‐off dates may extend the flowing water season—in turn affecting stream productivity and diversity.     

Sorption enhanced hydrogen production by steam methane reforming using Li2ZrO3 as sorbent: Sorption kinetics and reactor simulation

The kinetics of CO₂ sorption on a solid adsorbent, namely lithium zirconate, have been studied in an oscillating microbalance. The solid sorbent has been prepared by a novel route resulting in a high capacity, good stability and much improved sorption rates, making it suitable for its application in sorption enhanced hydrogen production by steam methane reforming. A kinetic equation for the sorption kinetics as a function of CO₂ partial pressure and temperature has been developed. The hydrogen production by sorption enhanced reaction process has been simulated by a dynamic one-dimensional pseudo-homogenous model of a fixed-bed reactor, where a hydrotalcite-derived Ni catalyst has been used as steam reforming catalysts. Simulation results show that hydrogen purer than 95% with a concentration of carbon monoxide lower than 0.2 mol% can be produced in a single step.     

Optimal activation of regulating bids to handle bottlenecks in power system operation

In this article we investigate how to optimally activate regulating bids to handle bottlenecks in power system operation. This will lead to an optimal stopping problem, and activation of a regulating bid is to be performed when the transfer through a specific system bottleneck reaches a certain value. Compared to previous research in the area the work presented in this article includes a more detailed model of the structure of the regulating market, and reaction times of actors on the regulating market is taken into consideration. The emphasis of the presentation will be application to a two area test system. The method is compared to Monte Carlo simulation in a numerical example. The example shows a promising result for the suggested method.     

Au–TiO2 catalysts stabilised by carbon nanofibres

The catalytic activity and stability in the water–gas shift reaction have been tested for Au-based catalysts prepared by deposition of Au from colloid solutions. The supports that have been used are TiO₂, TiO₂ supported on carbon nanofibres (CNF) and CNF. Thermal treatments of the samples show that the Au particle size depends on the support material and hence the interaction between the Au particles and the support. In situ X-ray absorption spectroscopic (XAS) measurements during the water–gas shift reaction show no changes in the first Au–Au coordination number for the catalysts containing CNF. Furthermore, improved short-time stability is obtained compared to the AuTiO₂ catalysts. The improved stability is achieved by the CNF stabilising small TiO₂ particles and hence prevent subsequent sintering of the Au particles.     

Optimization of an acoustic horn with respect to efficiency and directivity

We consider the problem of designing an acoustic horn in order to efficiently transmit the incoming wave energy and favorably distribute the energy in the far field. A finite element solution of the Helmholtz equation, in planar or cylindrical symmetry, models the wave propagation. The transmission efficiency is monitored by measuring the back reflections into the feeding waveguide, and the far‐field directivity pattern is computed using an integral expression known from scattering theory. The design problem is formulated as a non‐linear least‐squares problem, which is solved using a gradient‐based algorithm, where the gradients are provided by solutions of the associated adjoint equations. The results demonstrate that this approach can generate horns with almost perfect transmission in a wide frequency band. Due to the improved transmission properties at the lower‐frequency region, the optimization with respect to efficiency also generates improved far‐field directivity patterns, that is, patterns that vary less with frequency. It is possible to obtain even more uniform directivity patterns by explicitly including directivity requirements in the optimization. However, those improvements in directivity seem to be associated with a substantial loss of efficiency. Copyright © 2007 John Wiley & Sons, Ltd.     

Design and configuration of neuro mechanical networks

Neuro mechanical network (NMN) is a new concept of adaptronic character. The governing idea is to include geometry, topology, load carrying, energy transfer, actuating, sensing and control of a machine in one single mathematical state model and, thereby, enable a formulation of the design and configuration problem as an optimization problem. We have focused our attention on a type of NMN consisting of what we call active trusses. For these, we have established a state model and given a design optimization problem from which we have obtained numerical solutions. These solutions show that the approach has the possibility to suggest new families of designs that are superior to those of classical passive trusses. We also indicate how activation may result in singularities, the treatment of which is, so far, essentially an open problem.