Molecular engineering of chiral colloidal liquid crystals using DNA origami

Establishing precise control over the shape and the interactions of the microscopic building blocks is essential for design of macroscopic soft materials with novel structural, optical and mechanical properties. Here, we demonstrate robust assembly of DNA origami filaments into cholesteric liquid crystals, 1D supramolecular twisted ribbons and 2D colloidal membranes. The exquisite control afforded by the DNA origami technology establishes a quantitative relationship between the microscopic filament structure and the macroscopic cholesteric pitch. Furthermore, it also enables robust assembly of 1D twisted ribbons, which behave as effective supramolecular polymers whose structure and elastic properties can be precisely tuned by controlling the geometry of the elemental building blocks. Our results demonstrate the potential synergy between DNA origami technology and colloidal science, in which the former allows for rapid and robust synthesis of complex particles, and the latter can be used to assemble such particles into bulk materials

Satellite power system: Concept development and evaluation program. Volume 3: Power transmission and reception. Technical summary and assessment

Efforts in the DOE/NASA concept development and evaluation program are discussed for the solar power satellite power transmission and reception system. A technical summary is provided together with a summary of system assessment activities. System options and system definition drivers are described. Major system assessment activities were in support of the reference system definition, solid state system studies, critical technology supporting investigations, and various system and subsystem tradeoffs. These activities are described together with reference system updates and alternative concepts for each of the subsystem areas. Conclusions reached as a result of the numerous analytical and experimental evaluations are presented. Remaining issues for a possible follow-on program are identified

Data Center Site Redundancy

Commonly, disaster contingency calls for separation of location for redundant locations to maintain the needed redundancy. This document addresses issues for the data center redundancy, including limits to the distribution, distance and location that may impact on the efficiency or energy

Nonperiodic echoes from mushroom billiard hats

Mushroom billiards have the remarkable property to show one or more clear cut integrable islands in one or several chaotic seas, without any fractal boundaries. The islands correspond to orbits confined to the hats of the mushrooms, which they share with the chaotic orbits. It is thus interesting to ask how long a chaotic orbit will remain in the hat before returning to the stem. This question is equivalent to the inquiry about delay times for scattering from the hat of the mushroom into an opening where the stem should be. For fixed angular momentum we find that no more than three different delay times are possible. This induces striking nonperiodic structures in the delay times that may be of importance for mesoscopic devices and should be accessible to microwave experiments.Comment: Submitted to Phys. Rev. E without the appendi

First Experimental Observation of Superscars in a Pseudointegrable Barrier Billiard

With a perturbation body technique intensity distributions of the electric field strength in a flat microwave billiard with a barrier inside up to mode numbers as large as about 700 were measured. A method for the reconstruction of the amplitudes and phases of the electric field strength from those intensity distributions has been developed. Recently predicted superscars have been identified experimentally and - using the well known analogy between the electric field strength and the quantum mechanical wave function in a two-dimensional microwave billiard - their properties determined.Comment: 4 pages, 5 .eps figure

Standardized assessment of walking capacity after spinal cord injury: the European network approach

OBJECTIVES: After a spinal cord injury (SCI), walking function is an important outcome measure for rehabilitation and new treatment interventions. The current status of four walking capacity tests that are applied to SCI subjects is presented: the revised walking index for spinal cord injury (WISCI II), the 6 minute walk test (6MinWT), 10 meter walk test (10MWT) and the timed up and go (TUG) test. Then, we investigated which categories of the WISCI II apply to SCI subjects who participated in the European Multicenter Study of Human Spinal Cord Injury (EM-SCI), and the relationship between the 10MWT and the TUG. METHODS: In the EM-SCI, the walking tests were applied 2 weeks and 1, 3, 6 and 12 months after SCI. We identified the WISCI II categories that applied to the EM-SCI subjects at each time point and quantified the relationship between the 10MWT and the TUG using Spearman's correlation coefficients (rho) and linear regression. RESULTS: Five WISCI II categories applied to 71% of the EM-SCI subjects with walking ability, while 11 items applied to 11% of the subjects. The 10MWT correlated excellently with the TUG at each time point (rho>0.80). However, this relationship changed over time. One year after SCI, the time needed to accomplish the TUG was 1.25 times greater than the 10MWT time. DISCUSSION: Some categories of the WISCI II appear to be redundant, while some discriminate to an insufficient degree. In addition, there appear to be ceiling effects, which limit its usefulness. The relationship between the 10MWT and TUG is high, but changes over time. We suggest that, at present, the 10MWT appears to be the best tool to assess walking capacity in SCI subjects. Additional valuable information is provided by assessing the needs for walking aids or personal assistance. To ensure comparability of study results, proposals for standardized instructions are presented

Obstacle stepping in patients with Parkinson's disease: Complexity does influence performance

Patients with Parkinson's disease (PD) have difficulties in performing complex bimanual movements. Here we have examined acquisition and performance of a bilateral obstacle stepping task to see whether these difficulties are also present during bipedal movements. Subjects had to minimize foot clearance when repeatedly stepping on a treadmill over randomly approaching obstacles on either side. The subjects had full vision and received acoustic feedback information about task performance. Foot clearance improved in healthy and PD subjects during the acquisition of the task. However, PD subjects showed a slower improvement and achieved a poorer performance level. Thus, in contrast to unilateral obstacle stepping, where no deficits in performance after task repetition were found in PD subjects, bilateral obstacle stepping was poorer in these subjects compared to healthy subjects. The present results extend findings from upper to lower limb movements, namely that PD subjects have difficulties in the performance of bilateral motor task

Long-Term Community Service Projects in the Purdue Engineering Curriculum

Purdue University\u27s School of Electrical and Computer Engineering has initiated a new program called EPlCS:Engineering Projects in Community Service 2. Under the EPICS program, students earn academic credit for long-term, team projects that solve technology-based problems for local community service agencies. Each EPICS project team consists of seven to ten engineering students. The teams are vertically integrated - each is a mix of sophomores, juniors and seniors - and a student can participate in a project for up to three years. The continuity provided by this structure allows projects to last for many years. Projects of significant size and impact are thus possible. The goals of the EPICS program include: providing students with multi-year, team-based, design and development experience; teaching students, by direct experience, how to interact with each other and with customers to specify, design, develop and deploy systems that solve real problems; and showing engineering students how their expertise can benefit even the most disadvantaged members of their community

Experimental Test of a Two-dimensional Approximation for Dielectric Microcavities

Open dielectric resonators of different shapes are widely used for the manufacture of microlasers. A precise determination of their resonance frequencies and widths is crucial for their design. Most microlasers have a flat cylindrical geometry, and a two-dimensional approximation, the so-called method of the effective index of refraction, is commonly employed for numerical calculations. Our aim has been an experimental test of the precision and applicability of a model based on this approximation. We performed very thorough and accurate measurements of the resonance frequencies and widths of two passive circular dielectric microwave resonators and found significant deviations from the model predictions. From this we conclude that the model generally fails in the quantitative description of three-dimensional dielectric resonators.Comment: 10 pages, 13 figure

Chaotic Scattering in the Regime of Weakly Overlapping Resonances

We measure the transmission and reflection amplitudes of microwaves in a resonator coupled to two antennas at room temperature in the regime of weakly overlapping resonances and in a frequency range of 3 to 16 GHz. Below 10.1 GHz the resonator simulates a chaotic quantum system. The distribution of the elements of the scattering matrix S is not Gaussian. The Fourier coefficients of S are used for a best fit of the autocorrelation function if S to a theoretical expression based on random--matrix theory. We find very good agreement below but not above 10.1 GHz