71 research outputs found
Photon-noise limited sensitivity in titanium nitride kinetic inductance detectors
We demonstrate photon-noise limited performance at sub-millimeter wavelengths
in feedhorn-coupled, microwave kinetic inductance detectors (MKIDs) made of a
TiN/Ti/TiN trilayer superconducting film, tuned to have a transition
temperature of 1.4~K. Micro-machining of the silicon-on-insulator wafer
backside creates a quarter-wavelength backshort optimized for efficient
coupling at 250~\micron. Using frequency read out and when viewing a variable
temperature blackbody source, we measure device noise consistent with photon
noise when the incident optical power is ~0.5~pW, corresponding to noise
equivalent powers ~3 W/. This
sensitivity makes these devices suitable for broadband photometric applications
at these wavelengths
A fibril-specific, conformation-dependent antibody recognizes a subset of Aβ plaques in Alzheimer disease, Down syndrome and Tg2576 transgenic mouse brain
Beta-amyloid (Aβ) is thought to be a key contributor to the pathogenesis of Alzheimer disease (AD) in the general population and in adults with Down syndrome (DS). Different assembly states of Aβ have been identified that may be neurotoxic. Aβ oligomers can assemble into soluble prefibrillar oligomers, soluble fibrillar oligomers and insoluble fibrils. Using a novel antibody, OC, recognizing fibrils and soluble fibrillar oligomers, we characterized fibrillar Aβ deposits in AD and DS cases. We further compared human specimens to those obtained from the Tg2576 mouse model of AD. Our results show that accumulation of fibrillar immunoreactivity is significantly increased in AD relative to nondemented aged subjects and those with select cognitive impairments (p < 0.0001). Further, there was a significant correlation between the extent of frontal cortex fibrillar deposit accumulation and dementia severity (MMSE r = −0.72). In DS, we observe an early age of onset and age-dependent accumulation of fibrillar OC immunoreactivity with little pathology in similarly aged non-DS individuals. Tg2576 mice show fibrillar accumulation that can be detected as young as 6 months. Interestingly, fibril-specific immunoreactivity was observed in diffuse, thioflavine S-negative Aβ deposits in addition to more mature neuritic plaques. These results suggest that fibrillar deposits are associated with disease in both AD and in adults with DS and their distribution within early Aβ pathology associated with diffuse plaques and correlation with MMSE suggest that these deposits may not be as benign as previously thought
A fast DFT planar array synthesis tool for generating contoured beams
An efficient procedure based on a discrete Fourier
transform (DFT) expansion of planar array distributions is described
for synthesizing contoured beams in satellite antenna
applications. The DFT provides a global basis set that spans
over the entire array, and thus produces highly directional beam
patterns to serve as corresponding local basis functions for representing
the desired far zone radiation field of the array. The
unknown coefficients of the DFT expansion are then found via a
minimum least square error (MLSE) technique. While the total
number of DFT coefficients exactly equals the number of array
elements, it is found that only a small fraction of the total unknown
DFT coefficients generally remain dominant, and only these need
to be solved, thus making the present approach very fast
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