Peltophryne fluviatica

Number of Pages: 2Integrative BiologyGeological Science

Crystal structure of [mu-1kappa^2C^1,C^4:2(1,2,3,4-eta)-1,2,3,4-tetraphenylbuta-1,3-diene-1,4-diyl]bis(tricarbonylosmium)(Os---Os)

In the title complex C34H20O6Os2 or (mu-eta^4-C4Ph4}$)Os2(CO)6, one Os atom is part of a metallacyclopentadiene ring, while the second Os atom is pi-bonded to the organic portion of this ring. The distance of 2.7494(2)A between the two Os atoms is typical of an Os---Os single bond. Three carbonyl ligands are attached to each Os atom and these six carbonyls adopt an eclipsed conformation. There are no bridging or semibridging CO groups. Two carbonyl ligands and all four phenyl groups are disordered over two slightly different positions for which each atom in the minor components is displaced less than 1A from the corresponding atom in the major components. The refined occupancies of the major components of the carbonyl ligands are 0.568(16) and 0.625(13), while those for the phenyl rings are 0.50(3), 0.510(12), 0.519(18), and 0.568(12)

Scattering of electromagnetic waves in metamaterial superlattices

The authors study experimentally both transmission and reflection of microwave radiation from metamaterialsuperlattices created by layers of periodically arranged wires and split-ring resonators. The authors measure the dependence of the metamaterial resonance on the spatial period of the superlattice and demonstrate resonance broadening and splitting for the binary metamaterial structures.The authors acknowledge support from the Australian Research Council and thank Ekmel Ozbay for providing additional details of the experimental results published earlier by his group

Adaptive unstructured triangular mesh generation and flow solvers for the Navier-Stokes equations at high Reynolds number

A method for generating high quality unstructured triangular grids for high Reynolds number Navier-Stokes calculations about complex geometries is described. Careful attention is paid in the mesh generation process to resolving efficiently the disparate length scales which arise in these flows. First the surface mesh is constructed in a way which ensures that the geometry is faithfully represented. The volume mesh generation then proceeds in two phases thus allowing the viscous and inviscid regions of the flow to be meshed optimally. A solution-adaptive remeshing procedure which allows the mesh to adapt itself to flow features is also described. The procedure for tracking wakes and refinement criteria appropriate for shock detection are described. Although at present it has only been implemented in two dimensions, the grid generation process has been designed with the extension to three dimensions in mind. An implicit, higher-order, upwind method is also presented for computing compressible turbulent flows on these meshes. Two recently developed one-equation turbulence models have been implemented to simulate the effects of the fluid turbulence. Results for flow about a RAE 2822 airfoil and a Douglas three-element airfoil are presented which clearly show the improved resolution obtainable

Phobos/Deimos Sample Return via Solar Sail

Abstract A sample-return mission to the martian satellites using a contemporary solar sail for all post-Earth-escape propulsion is proposed. The 0.015 kg/sq m areal mass-thickness sail unfurls after launch and injection onto a Mars-bound Hohmann-transfer ellipse. Structure and pay!oad increase spacecraft areal mass thickness to 0.028 kg/sq m. During Mars-encounter, the sail functions parachute-like in Mars s outer atmosphere to accomplish aerocapture. On-board thrusters or the sail maneuver the spacecraft into an orbit with periapsis near Mars and apoapsis near Phobos. The orbit is circularized for Phobos-rendezvous; surface samples are collected. The sail then raises the orbit for Deimos-rendezvous and sample collection. The sail next places the spacecraft on an Earth-bound Hohmann-transfer ellipse. During Earth-encounter, the sail accomplishes Earth-aerocapture or partially decelerates the sample container for entry into Earth s atmosphere. Mission mass budget is about 218 grams and; mission duration is <5 years

Photon Sail History, Engineering, and Mission Analysis

This Appendix summarizes the results of a Teledyne Brown Engineering, Inc. report to the In-Space propulsion research group of the NASA Marshall Space Flight Center (MSFC) that was authored by Taylor et al. in 2003. The subject of this report is the technological maturity, readiness, and capability of the photon solar sail to support space-exploration missions. Technological maturity for solar photon sail concepts is extremely high high for rectangular (or square) solar sail configurations due to the historical development of the rectangular design by the NASA Jet Propulsion Laboratory (JPL). L'Garde Inc., ILC Dover Inc., DLR, and many other corporations and agencies. However, future missions and mission analysis may prove that the rectangular sail design is not the best architecture for achieving mission goals. Due to the historical focus on rectangular solar sail spacecraft designs, the maturity of other architectures such as hoop-supported disks, multiple small disk arrays, parachute sails, heliogyro sails, perforated sails, multiple vane sails (such as the Planetary Society's Cosmos 1), inflated pillow sails, etc., have not reached a high level of technological readiness. (Some sail architectures are shown in Fig. A.1.) The possibilities of different sail architectures and some possible mission concepts are discussed in this Appendix

Green means green, not asphalt gray: State parks and development of the Raleigh metropolitan area, 1936-2016

State parks are a ubiquitous presence on the American landscape with thousands of units in all fifty states that attract far more visitors than the U.S. National Park System. While the sheer diversity and number of state parks can be daunting, their pervasiveness also positions state parks as valuable sources of gauging economic, social, cultural, environmental, and historic development of given locales. This study examines the establishment and development of four units of the North Carolina state parks system located near the state capital of Raleigh and a large, forest tract owned by Duke University often mistaken for a state park by area resident to examine cultural changes that occurred in the region accompanied by rapid urbanization from the 1960s to the present. This urbanization was characterized by the arrival of large numbers of individuals from outside the region who represented the shift from a rural, agricultural region to a densely populated area with large numbers of highly educated, white collar workers in technology industries associated with area research universities.In this context, the development of recreational opportunities in the form of state parks, which dates to the 1930s, illustrated this rapid expansion of the Raleigh metropolitan area in terms of motivations for their establishment and influences upon their development that involved local, state, regional, and national trends and politics. This included processes such as New Deal-era efforts to utilize denuded farm land for recreation, centrality of recreation to post-World War Two urbanization and suburbanization, 1950s- and 1960s-era desegregation efforts, efforts to procure drinking water and implement flood control measures, and the emergence of the "modern" environmental movement. These processes and events, and the interactions of individual residents, politicians, grassroots organizations, university officials, and municipal bodies illustrate the role of politics and ideology upon environmental perspectives, which may be observed in the presence and development of the region's state parks

Simulation of Hazards and Poses for a Rocker-Bogie Rover

Provisions for specification of hazards faced by a robotic vehicle (rover) equipped with a rocker-bogie suspension, for prediction of collisions between the vehicle and the hazards, and for simulation of poses of the vehicle at selected positions on the terrain have been incorporated into software that simulates the movements of the vehicle on planned paths across the terrain. The software in question is that of the Web Interface for Telescience (WITS), selected aspects of which have been described in a number of prior NASA Tech Briefs articles. To recapitulate: The WITS is a system of computer software that enables scientists, located at geographically dispersed computer terminals connected to the World Wide Web, to command instrumented robotic vehicles (rovers) during exploration of Mars and perhaps eventually of other planets. The WITS also has potential for adaptation to terrestrial use in telerobotics and other applications that involve computer-based remote monitoring, supervision, control, and planning

Strategies for Peripheral Nerve Repair

PURPPOSE AND REVIEW: This review focuses on biomechanical and cellular considerations required for development of biomaterials and engineered tissues suitable for implantation following PNI, as well as translational requirements relating to outcome measurements for testing success in patients. RECENT FINDINGS: Therapies that incorporate multiple aspects of the regenerative environment are likely to be key to improving therapies for nerve regeneration. This represents a complex challenge when considering the diversity of biological, chemical and mechanical factors involved. In addition, clinical outcome measures following peripheral nerve repair which are sensitive and responsive to changes in the tissue microenvironment following neural injury and regeneration are required. SUMMARY: Effective new therapies for the treatment of PNI are likely to include engineered tissues and biomaterials able to evoke a tissue microenvironment that incorporates both biochemical and mechanical features supportive to regeneration. Translational development of these technologies towards clinical use in humans drives a concomitant need for improved clinical measures to quantify nerve regeneration