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Trace element signatures of trapped KREEP in Olivine-rich clasts within lunar meteorite NWA773
Limitations on the extent of off-center displacements in TbMnO3 from EXAFS measurements
We present EXAFS data at the Mn K and Tb L3 edges that provide upper limits
on the possible displacements of any atoms in TbMnO3. The displacements must be
less than 0.005-0.01A for all atoms which eliminates the possibility of
moderate distortions (0.02A) with a small c-axis component, but for which the
displacements in the ab plane average to zero. Assuming the polarization arises
from a displacement of the O2 atoms along the c-axis, the measured polarization
then leads to an O2 displacement that is at least 6X10^{-4}A, well below our
experimental limit. Thus a combination of the EXAFS and the measured electrical
polarization indicate that the atomic displacements likely lie in the range
6X10^{-4} - 5X10^{-3}A.Comment: submitted to PRB; 11 pages (preprint form) 7 figure
Governing Shades of Grey: The Emergence of Market Governance in the Absence of a Formal Institutional Environment
How do governance structures emerge in the new institutional structure of the financial system? Since the 1980s, a market-based institutional structure has been developing in parallel with the traditional bank-based structure and has supplanted the traditional system as the dominant source of credit and liquidity for the US economy. The growth of this new parallel system, however, has not been accompanied by a corresponding expansion of the formal laws and regulations that govern economic action. As a result, large sectors of the US economy operate beyond traditional law and regulation and pose systemic risks to the broader economy and society. This article identifies and explicates the governance mechanisms that have emerged in one of the four major markets in the new parallel system—the U.S. hedge fund market—and the failures thereof. The empirical data for this study come from three years of fieldwork, 40 semi-structured interviews with expert informants, and eVestment|HFN database. This article advances the multilevel causal model developed by new institutionalism in economic sociology, with research findings that suggest that (1) the emergence of a governing social order is the result of interactions between the formal institutional environment regulating the traditional financial system and the social relations, informal norms, and institutionalized practices of interest-driven parallel financial organizations, and (2) governance failures emerge at specific locations where the formal institutional environment and the informal set of institutional and social structural governance mechanisms break down
Wave-Coupled W-Band LiNbO_3 Mach-Zehnder Modulator
Summary form only given. Mach-Zehnder amplitude modulators have been designed for W-band operation (94 GHz), at a 1.3-μm optical wavelength. These modulators use bow-tie antennas, which are relatively insensitive to DC bias connections made to the ends of the antenna elements. The bow-ties should also give a greater bandwidth than the dipole antennas
SCUBA Observations of NGC 1275
Deep SCUBA observations of NGC 1275 at 450 micron and 850 micron along with
the application of deconvolution algorithms have permitted us to separate the
strong core emission in this galaxy from the fainter extended emission around
it. The core has a steep spectral index and is likely due primarily to the AGN.
The faint emission has a positive spectral index and is clearly due to extended
dust in a patchy distribution out to a radius of 20 kpc from the
nucleus. These observations have now revealed that a large quantity of dust,
6 10 , 2 orders of magnitude larger than that
inferred from previous optical absorption measurements, exists in this galaxy.
We estimate the temperature of this dust to be 20 K (using an emissivity
index of = 1.3) and the gas/dust ratio to be 360. These values are
typical of spiral galaxies. The dust emission correlates spatially with the hot
X-ray emitting gas which may be due to collisional heating of broadly
distributed dust by electrons. Since the destruction timescale is short, the
dust cannot be replenished by stellar mass loss and must be externally
supplied, either via the infalling galaxy or the cooling flow itself.Comment: 13 pages, 4 figures. Figure 4 is colou
Antenna-coupled millimeter-wave LiNbO_3 electro-optic modulator
The phase-velocity mismatch due to material dispersion in traveling-wave LiNbO_3 optical
waveguide modulators may be greatly reduced by breaking the modulation transmission line into short
segments and connecting each segment to its own surface antenna. The array of antennas is then
illuminated by the modulation signal at an angle which produces a delay from antenna to antenna to
match the optical waveguide's delay
60 GHz and 94 GHz antenna-coupled LiNbO_3 electrooptic modulators
Antenna-coupled LiBbO_3 electrooptic modulators can overcome the material dispersion which would otherwise prevent sensitive high-frequency operation. The authors previously demonstrated the concept with a phase modulator at X-band. They have extended this demonstration to a narrowband 60-GHz phase modulator and broadband amplitude modulator designs at 60 and 94 GHz, respectively
Wave-coupled LiNbO_3 electrooptic modulator for microwave and millimeter-wave modulation
A new technique of phase velocity matching in electrooptic modulators was demonstrated. The results show that the phase velocity mismatch due to material dispersion in traveling-wave LiNbO_3 optical waveguide modulators can be greatly reduced by breaking the modulation transmission line into short segments and connecting each segment to its own surface dipole antenna. The array of antennas is then illuminated by the modulation signal from below at the proper angle to produce a delay from antenna to antenna that matches the optical waveguide's delay. A phase modulator 25 mm in length with five antennas and five transmission line segments was operated from 4.6 to 13 GHz with a maximum phase modulation sensitivity of over 100°/W^(1/2)
Novel Millimeter-Wave Electro-optic Modulator
A waveguide LiNbO_3 electro-optic modulator has been demonstrated with a novel wave-coupling technique which greatly reduces phase-velocity mismatch. An 8-12 GHz version produces 48° phase modulation with 126 mW of drive power. A 60 GHz version is being built
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