Design and control of compliant tensegrity robots through simulation and hardware validation

To better understand the role of tensegrity structures in biological systems and their application to robotics, the Dynamic Tensegrity Robotics Lab at NASA Ames Research Center, Moffett Field, CA, USA, has developed and validated two software environments for the analysis, simulation and design of tensegrity robots. These tools, along with new control methodologies and the modular hardware components developed to validate them, are presented as a system for the design of actuated tensegrity structures. As evidenced from their appearance in many biological systems, tensegrity (‘tensile–integrity’) structures have unique physical properties that make them ideal for interaction with uncertain environments. Yet, these characteristics make design and control of bioinspired tensegrity robots extremely challenging. This work presents the progress our tools have made in tackling the design and control challenges of spherical tensegrity structures. We focus on this shape since it lends itself to rolling locomotion. The results of our analyses include multiple novel control approaches for mobility and terrain interaction of spherical tensegrity structures that have been tested in simulation. A hardware prototype of a spherical six-bar tensegrity, the Reservoir Compliant Tensegrity Robot, is used to empirically validate the accuracy of simulation.     

Floral Odor Bouquet Loses its Ant Repellent Properties After Inhibition of Terpene Biosynthesis

In their natural environment, plants are synchronously confronted with mutualists and antagonists, and thus benefit from signals that contain messages for both functional groups of interaction partners. Floral scents are complex blends of volatiles of different chemical classes, including benzenoids and terpenoids. It has been hypothesized that benzenoids have evolved as pollinator attracting signals, while monoterpenoids serve as defensive compounds against antagonists. In order to test this hypothesis, we reduced terpene emission in flowers of Phlox paniculata with specific biosynthetic inhibitors and compared the responses of Lasius niger ants to natural and inhibited floral scent bouquets. While the natural odors were strongly repellent to ants, the bouquets with a reduced emission rate of terpenoids were not. The loss of the flowers’ ability to repel ants could be attributed predominantly to reduced amounts of linalool, a monoterpene alcohol. Flying flower visitors, mainly hoverflies, did not discriminate between the two types of flowers in an outdoor experiment. Since individual compounds appear to be capable of either attracting pollinators or defending the flower from enemies, the complexity of floral scent bouquets may have evolved to allow flowers to respond to both mutualists and antagonists simultaneously.     

Increased response/recovery lifetimes and reinforcement of polyaniline nanofiber films using carbon nanotubes

We have prepared high surface area, conductive, mechanically robust, responsive polyaniline–carbon nanotube composite films. These were produced by filtration from dilute dispersions of polyaniline nanofibers and single-walled carbon nanotubes. Unlike polyaniline alone, these composites are mechanically stable, maintain large intractable surfaces and exhibit greatly enhanced response/recovery behavior to changes in their local environment. This is illustrated by exposing the films to ammonia.     

Use of laser scanning confocal microscopy for characterizing changes in film thickness and local surface morphology of UV-exposed polymer coatings

Laser scanning confocal microscopy (LSCM) has been used to characterize the changes in film thickness and local surface morphology of polymer coatings during the UV degradation process. With the noninvasive feature of LSCM, one can obtain thickness information directly and nondestructively at various exposure times without destroying the specimens or deriving the thickness values from IR measurement by assuming uniform film ablation. Two acrylic polymer coatings were chosen for the study, and the physical and chemical changes of the two systems at various exposure times were measured and analyzed. Those measurable physical changes caused by UV exposure include film ablation, formation of pits and other surface defects, and increases in surface roughness. It was found in both coatings that changes in measured film thickness by LSCM were not correlated linearly to the predicted thickness loss using the changes in the CH band obtained by the Fourier Transform Infrared (FTIR) spectroscopy measurements in the later degradation stages. This result suggested it was not a uniform film ablation process during the UV degradation. At later stages, where surface deformation became severe, surface roughness and profile information using LSCM were also proven to be useful for analyzing the surface degradation process Presented at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 13–14, 2004 in Philadelphia, PA.     

The utility of coal molecular models

There are a large number (> 125) of molecular representations for coals that span the rank range over seven decades. However, their utility has mostly been in representing chemical structural features, rather than in probing physical structure or exploring the structure-behavior relationship. This paper examines the utility of coal models and reviews the existing and emerging opportunities for coal models to contribute to coals effective utilization via demystification of the structure-behavior relationship. Coal models have been used to explore the coalification pathway, including contraction with water removal. Physical evaluations have probed the density of models as a check on their accuracy. Pore size distribution and sorption have been explored in simple pores and more recent work with carbon dioxide, water and methane sorption within the porous structure of large-scale (< 20,000 atoms) model. Pair distribution frequency and small angle X-ray scattering simulations have also been compared with experimental observations and offer an additional check on the constitution of the model structure. Simulated HRTEM and simulated (calculated) NMR spectra also exist. Models have been disassembled in efforts to represent the pyrolysis process, char formation, and char reactivity (including the role of ion-exchangable ions). Similar to the pyrolysis models, direct liquefaction has been explored with a pyrolysis style approach. Coal-solvent swelling, and coal-solvent solubility have also been explored. While considerable progress has accompanied improvements in computational power and software advances, it is the generation of the model that is the most significant barrier to the meaningful utility of these models. The ability to generate large-scale models (incorporation of molecular weight diversity and structural diversity) with new automation approaches, coupled with new dynamic force-fields that can simulate reactive events in complicated materials like coals, offers a new hope for the utility of coal or char molecular models to probe our understanding and aid in the scientific method rather than our current informed trial and error approach.     

Identification and Optimization of 4‐Anilinoquinolines as Inhibitors of Cyclin G Associated Kinase

4‐Anilinoquinolines were identified as potent and narrow‐spectrum inhibitors of the cyclin G associated kinase (GAK), an important regulator of viral and bacterial entry into host cells. Optimization of the 4‐anilino group and the 6,7‐quinoline substituents produced GAK inhibitors with nanomolar activity, over 50 000‐fold selectivity relative to other members of the numb‐associated kinase (NAK) subfamily, and a compound (6,7‐dimethoxy‐N‐(3,4,5‐trimethoxyphenyl)quinolin‐4‐amine; 49 ) with a narrow‐spectrum kinome profile. These compounds may be useful tools to explore the therapeutic potential of GAK in prevention of a broad range of infectious and systemic diseases.     

NMR microscopy of single neurons at 500 MHZ

Previous NMR microimaging studies at 360 MHz have demonstrated a clear differentiation between the nucleus and cytoplasm in isolated single neurons. In particular, theT ₂ of the cell nucleus is 2.5 times larger than that of the cytoplasm. In order to determine the magnitude of possibleT ₂ ^* influences on these observations, images of single cells have been obtained at 500 MHz using spin-echo and line-narrowing sequences. Comparison of the images acquired by the two sequences, and of the spin-echo images at 360 and 500 MHz, imply that anyT ₂ ^* contributions are relatively small. Consequently, the measuredT ₂ differences in spin-echo imaging represent a true difference in theT ₂ relaxation in the two cellular compartments.     

3D打印混凝土技术在澳大利亚的最近研究进展

3D打印,又被称为增材制造,是通过逐层累积叠加制造三维物体的一种技术手段。过去几年中,这种技术吸引了越来越多来自建筑业的关注。与传统混凝土浇筑技术相比,3D打印混凝土的应用可以实现更加高效的自由建筑制造,同时减小对人工劳动力的依赖。在全球范围内,由于相关高校和科研单位的积极参与,关于3D打印混凝土的研究工作取得了巨大的进展,其中包括澳大利亚的相关研究。本文主要对澳大利亚在3D打印混凝土研究方面有代表性的两所高校的最新进展进行介绍,两所学校分别是皇家墨尔本理工大学(RMIT大学)和斯威本科技大学。本文首先介绍了两所高校的打印设备及其特点,随后讨论了具体研究领域和近期发表的相关文章。RMIT大学主要侧重于研究纤维增强对3D打印混凝土力学性能方面的影响,而斯威本科技大学则着重研究3D打印地聚物混凝土的性能。本文旨在促进相关领域研究人员对澳大利亚3D打印混凝土研究团队和研究进展的理解。