Scientists have predicted that carbon's immediate neighbors on the periodic chart, boron and nitrogen, may also form perfect nanotubes, since the advent of carbon nanotubes (CNTs) in 1991. First proposed then synthesized by researchers at UC Berkeley in the mid 1990's, the boron nitride nanotube (BNNT) has proven very difficult to make until now. Herein we provide an update on a catalyst-free method for synthesizing highly crystalline, small diameter BNNTs with a high aspect ratio using a high power laser under a high pressure and high temperature environment first discovered jointly by NASA/NIA/JSA. Progress in purification methods, dispersion studies, BNNT mat and composite formation, and modeling and diagnostics will also be presented. The white BNNTs offer extraordinary properties including neutron radiation shielding, piezoelectricity, thermal oxidative stability (> 800˚C in air), mechanical strength, and toughness. The characteristics of the novel BNNTs and BNNT polymer composites and their potential applications are discussed.

Bone marrow aspirate containing adult stem cells when mixed with bioengineered graft materials provide a scaffold to support the proliferation, differentiation, and maturation of the stem cells, as well as facilitating angiogenesis. This article presents histological evidence that stem cells aspirated from bone marrow and transplanted onto biocompatible scaffolds can successfully regenerate bone. This new standard for bone grafting may emerge as an alternative to autogenous bone grafts.

Doppler global velocimetry uses the absorption characteristics of iodine vapour to provide instantaneous three-component measurements of flow velocity within a plane defined by a laser light sheet. Although the technology is straightforward, its utilization as a flow diagnostics tool requires hardening of the optical system and careful attention to detail during data acquisition and processing if routine use in wind tunnel applications is to be achieved. A development programme that reaches these goals is presented. Theoretical and experimental investigations were conducted on each technology element to determine methods that increase measurement accuracy and repeatability. Enhancements resulting from these investigations included methods to ensure iodine vapour calibration stability, single frequency operation of the laser and image alignment to sub-pixel accuracies. Methods were also developed to improve system calibration, and eliminate spatial variations of optical frequency in the laser output, spatial variations in optical transmissivity and perspective and optical distortions in the data images. Each of these enhancements is described and experimental examples given to illustrate the improved measurement performance obtained by the enhancement. The culmination of this investigation was the measured velocity profile of a rotating wheel resulting in a 1.75% error in the mean with a standard deviation of 0.5 m s −1 . Comparing measurements of a jet flow with corresponding Pitot measurements validated the use of these methods for flow field applications.

SummaryRayleigh scattering has previously been used for multi-component velocity measurements 1 . However, past work has generally been limited to excitation with continuous wave lasers resulting in a longer time response. We are developing a diagnostic system for time-resolved simultaneous measurement of multiple components of velocity in gas flow using a l0-ns pulsed YAG laser. This system will be combined with Coherent anti-Stokes Raman spectroscopy (CARS) thermometry 2 to allow simultaneous temperature and velocity measurements in supersonic combustion flows. Since we will use the same green laser beam for CARS and Rayleigh we will ensure that the temperature and velocity are measured at the same time and place. Dedicated optics collect the Rayleigh scattered light from different angles. This light is mixed together with the unshifted laser light before it is passed through a Fabry-Perot interferometer 3 . At the output of the interferometer, a high-sensitivity CCD camera images the interference fringe pattern. This pattern contains both the Rayleigh scattered signal from multiple collecting angles and the reference frequency information. Image processing software is used to analyze interferograms for Doppler shift to solve for velocity. Figure 1 shows three examples of interferograms containing frequency information to solve for one velocity component. Experiments were performed in stagnant air and a 3-mm diameter underexpanded jet flow. The jet had a total temperature of 300 K and a total pressure of about 4 atm and issued into ambient air at atmospheric pressure. We used a pulsed Nd:YAG laser at 10 Hz and 9 nsec, at 90 mJ/pulse. Measurements to date have included up to 2 velocity components simultaneously and a third component can be measured using the same method.To improve light collection efficiency each part of the optical system was analyzed and optimized, including light collecting optics, light transmission through optical fibers, interferometer mirrors, and CCD camera. The use of lenses for collecting Rayleigh scattered light combined with an optical fiber for transmission, introduced photon loses about 15%. More importantly, the number of photons transmitted by the interferometer input mirror was found to be low: 60 to one (98% of the photons are rejected by the etalon). Pulse stretching of the investigation laser beam of up to 20 nsec allowed an increase in the number of photons collected of up to 1.85 times.The image processing methodology makes use of linearization of the concentric interference patterns from a planar Fabry-Perot interferometer and subsequent analysis 3 . The important variables are the center of the interferogram and the maximum fringe shift of the Doppler shifted signal. There are four steps of interferogram processing: 1. The image center is found. 2. The image is mapped by reading it in r-θ plane, where r is the radius from the center and θ is the angle, using the original (θ, r) coordinate as the new (x, y) coordinate. 3. The coordinates of the obtained data are rescaled...