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We present the first in situ observations of a small-scale flux rope locally formed at the separatrix region of magnetic reconnection without large guide field. Bidirectional electron beams (cold and hot beams) and density cavity accompanied by intense wave activity substantiate the crossing of the separatrix region. Density compression and one parallel electron beam are detected inside the flux rope. We suggest that this flux rope is locally generated at the separatrix region due to the tearing instability within the separatrix current layer. This observation sheds new light on the 3-D picture of magnetic reconnection in space plasma., QC 20190625

We report on measurements of the dielectric permittivity of NiO-based ceramics doped with Zr (ZNO). Samples were prepared by the traditional solid-state reaction method. The concentration of Zr has an effect on the dielectric properties of ZNO ceramics. High permittivity values (similar to 10(4)) were observed which remain almost constant from 200 K to 350 K at low frequencies. The high-dielectric-constant response of the ZNO ceramics is attributed mainly to a grain boundary (internal) barrier layer capacitance. (c) 2007 American Institute of Physics.

To clarify the electrical property of grain boundaries, the fine-grained ceramics CaCu3Ti4O12 have been treated with the hydrofluoric acid to remove the parts of grain boundaries. The dielectric response difference between the etched samples and the pristine ones indicates that the ceramic CaCu3Ti4O12 consists of insulating or semiconducting grains with conducting grain boundaries. Therefore, the giant dielectric phenomenon is supposed not to derive from the grain boundary barrier layer capacitance effect. The possible mechanism is discussed. (c) 2007 American Institute of Physics.

The objective of this program was to advance the performance of the semiconductor waveguide modulator in externally modulated RF fiber-optic links for space-based and airborne platforms such as true time delay beam formation and beam steering subsystem in phased array antennas. Device and material approaches were investigated to improve the modulator based on semiconductor structures for achieving high spur free dynamic range (SFDR) and high frequency operation. In these approaches, the semiconductor optical modulators were specifically designed to achieve high slope efficiency and high center frequency, while at the same time maintaining minimal generation of spurious signals. The fiber-optic links using these modulators are expected to satisfy the low noise figure, high center frequencies, low power requirements. A high performance electroabsorption modulator with more than 40 GHz bandwidth has been fabricated and evaluated. A new design was investigated for a quantum well modulator that includes an intra-barrier to enhance the power handling and slope efficiency. Both theory and experiment has beer carried out to demonstrate this concept., The original document contains color images.

The boundary element method (BEM) based cortical imaging technique (CIT) has been applied to an experimental study on human somatorsensory evoked potentials (SEPs) recorded from a patient. The accuracy of the analysis was determined by comparing SEPs recorded from the scalp with those recorded directly from the patient's cortex. The results indicate that the CIT improved the spatial resolution of the scalp potentials, and the reconstructed cortical potential maps are consistent with the direct cortical recordings., Papers from 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society, October 25-28, 2001, held in Istanbul, Turkey. See also ADM001351 for entire conference on cd-rom. The original document contains color images.

The objective of this program was to advance the performance of a semiconductor waveguide modulator in external modulated RF fiber-optic links for space-based and airborne platforms such as true time delay beam formation and beam steering subsystems in phased array antennas. Device and material approaches were investigated to improve the modulator based on semiconductor structures for achieving high spur free dynamic range (SFDR) and high frequency operation. In these approaches, the semiconductor optical modulators were specifically designed to achieve high slope efficiency and high center frequency, while with minimal generation of spurious signals. The fiber-optic links using these modulators are expected to satisfy the low noise figure, high center frequencies, low drive power requirements. The following were the main goals in this program: (1) to design and test electroabsorption waveguide modulator for high multi-octave SFDR and high slope efficiency and high saturation optical power operation, and (2) to collaborate with technical personnel at Air Force Research Laboratory at Rome on the overall link design and provide prototype electroabsorption waveguide modulator for link evaluation.

Optical transmission of analog RF signals is potentially useful in a number of applications including RF distribution systems. Such systems can be used in commercial CATV and wireless communications and in military communication and radar systems. With compatible components used at transmitters and receivers, analog fiber optic links suffer much less performance degradation than conventional coaxial cable links as the system bandwidth increases. In the first year program we studied large Optical Cavity waveguide modulator design and demonstrated a low optical insertion loss waveguide modulator at 1.34 microns wavelength (as low as 8 dB w/o AR coating). This design is based Upon the matching of the mode profile of the fiber and the modulator waveguides. The design is extended to 1.55 microns wavelength. We also demonstrated a novel scheme of bias-tracking of the electroabsorption waveguide modulator. The scheme is based upon the photocurrent generated at the modulator. Effective tracking is obtained as the polarization, wavelength (or ambient temperature), and power of the input light are varied. Experimental evidence was obtained for a combined Franz-Keldysh effect and Quantum Confined Stark Effect modulator for a large multi-octave spurious free dynamic range. Low loss planar photoelastic waveguide on both InP and GaAs substrates was achieved.

GATA-3 is expressed in a temporally dynamic manner and fulfills vital functions during vertebrate fetal development. Homozygous mGATA-3 mutant embryos die at midgestation, thus complicating the analysis of its contribution to the development of specific cell fates in the many tissues where it is expressed during embryogenesis. We show here that the elements controlling GATA-3 regulation can be precisely refined, using transgenic mice, to discrete cis-acting domains: within 6 kb surrounding the transcriptional initiation site, separate sequences were found to control the expression of mGATA-3 in early muscle masses, in a subset of PNS neurons, in the genital tubercle, and in the branchial arches. The branchial arch regulatory element is particularly robust and was refined to a discrete enhancer sequence lying between nt -2832 and -2462 from the transcription initiation site. The enhancer contains potential binding sites for many well-characterized transcription factors, suggesting that mGATA-3 transcriptional activity may be regulated by these proteins (or