Metamaterial microwave holographic imaging system.

We demonstrate a microwave imaging system that combines advances in metamaterial aperture design with emerging computational imaging techniques. The flexibility inherent to guided-wave, complementary metamaterials enables the design of a planar antenna that illuminates a scene with dramatically varying radiation patterns as a function of frequency. As frequency is swept over the K-band (17.5-26.5 GHz), a sequence of pseudorandom radiation patterns interrogates a scene. Measurements of the return signal versus frequency are then acquired and the scene is reconstructed using computational imaging methods. The low-cost, frequency-diverse static aperture allows three-dimensional images to be formed without mechanical scanning or dynamic beam-forming elements. The metamaterial aperture is complementary to a variety of computational imaging schemes, and can be used in conjunction with other sensors to form a multifunctional imaging platform. We illustrate the potential of multisensor fusion by integrating an infrared structured-light and optical image sensor to accelerate the microwave scene reconstruction and to provide a simultaneous visualization of the scene.

Metamaterial apertures for coherent computational imaging on the physical layer.

We introduce the concept of a metamaterial aperture, in which an underlying reference mode interacts with a designed metamaterial surface to produce a series of complex field patterns. The resonant frequencies of the metamaterial elements are randomly distributed over a large bandwidth (18-26 GHz), such that the aperture produces a rapidly varying sequence of field patterns as a function of the input frequency. As the frequency of operation is scanned, different subsets of metamaterial elements become active, in turn varying the field patterns at the scene. Scene information can thus be indexed by frequency, with the overall effectiveness of the imaging scheme tied to the diversity of the generated field patterns. As the quality (Q-) factor of the metamaterial resonators increases, the number of distinct field patterns that can be generated increases-improving scene estimation. In this work we provide the foundation for computational imaging with metamaterial apertures based on frequency diversity, and establish that for resonators with physically relevant Q-factors, there are potentially enough distinct measurements of a typical scene within a reasonable bandwidth to achieve diffraction-limited reconstructions of physical scenes.

Thin low-loss dielectric coatings for free-space cloaking.

We report stereolithographic polymer-based fabrication and experimental operation of a microwave X-band cloaking device. The device is a relatively thin (about one wavelength thick) shell of an air-dielectric composite, in which the dielectric component has negligible loss and dispersion. In a finite band (9.7-10.1 GHz), the shell eliminates the shadow and strongly suppresses scattering from a conducting cylinder of six-wavelength diameter for TE-polarized free-space plane waves. The device does not require an immersion liquid or conducting ground planes for its operation. The dielectric constant of the polymer is low enough (ε=2.45) to suggest that this cloaking technique would be suitable for higher frequency radiation, including visible light.

Metamaterial apertures for computational imaging.

By leveraging metamaterials and compressive imaging, a low-profile aperture capable of microwave imaging without lenses, moving parts, or phase shifters is demonstrated. This designer aperture allows image compression to be performed on the physical hardware layer rather than in the postprocessing stage, thus averting the detector, storage, and transmission costs associated with full diffraction-limited sampling of a scene. A guided-wave metamaterial aperture is used to perform compressive image reconstruction at 10 frames per second of two-dimensional (range and angle) sparse still and video scenes at K-band (18 to 26 gigahertz) frequencies, using frequency diversity to avoid mechanical scanning. Image acquisition is accomplished with a 40:1 compression ratio.

Performance of a three dimensional transformation-optical-flattened Lüneburg lens.

We demonstrate both the beam-forming and imaging capabilities of an X-band (8-12 GHz) operational Lüneburg lens, one side of which has been flattened via a coordinate transformation optimized using quasi-conformal transformation optics (QCTO) procedures. Our experimental investigation includes benchmark performance comparisons between the QCTO Lüneburg lens and a commensurate conventional Lüneburg lens. The QCTO Lüneburg lens is made from a metamaterial comprised of inexpensive plastic and fiberglass, and manufactured using fast and versatile numerically controlled water-jet machining. Looking forward towards the future and advanced TO designs, we discuss inevitable design trade-offs between affordable scalable manufacturing and rigorous adherence to the full TO solution, as well as possible paths to mitigate performance degradation in realizable designs.

TPMG Northern California appointments and advice call center.

Kaiser Permanente (KP) has been developing its use of call centers as a way to provide an expansive set of healthcare services to KP members efficiently and cost effectively. Since 1995, when The Permanente Medical Group (TPMG) began to consolidate primary care phone services into three physical call centers, the TPMG Appointments and Advice Call Center (AACC) has become the "front office" for primary care services across approximately 89% of Northern California. The AACC provides primary care phone service for approximately 3 million Kaiser Foundation Health Plan members in Northern California and responds to approximately 1 million calls per month across the three AACC sites. A database records each caller's identity as well as the day, time, and duration of each call; reason for calling; services provided to callers as a result of calls; and clinical outcomes of calls. We here summarize this information for the period 2000 through 2003.

The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).

The National Institutes of Health's Mammalian Gene Collection (MGC) project was designed to generate and sequence a publicly accessible cDNA resource containing a complete open reading frame (ORF) for every human and mouse gene. The project initially used a random strategy to select clones from a large number of cDNA libraries from diverse tissues. Candidate clones were chosen based on 5'-EST sequences, and then fully sequenced to high accuracy and analyzed by algorithms developed for this project. Currently, more than 11,000 human and 10,000 mouse genes are represented in MGC by at least one clone with a full ORF. The random selection approach is now reaching a saturation point, and a transition to protocols targeted at the missing transcripts is now required to complete the mouse and human collections. Comparison of the sequence of the MGC clones to reference genome sequences reveals that most cDNA clones are of very high sequence quality, although it is likely that some cDNAs may carry missense variants as a consequence of experimental artifact, such as PCR, cloning, or reverse transcriptase errors. Recently, a rat cDNA component was added to the project, and ongoing frog (Xenopus) and zebrafish (Danio) cDNA projects were expanded to take advantage of the high-throughput MGC pipeline.