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Detecting pathogen exposure during the non-symptomatic incubation period using physiological data

Summary

Early pathogen exposure detection allows better patient care and faster implementation of public health measures (patient isolation, contact tracing). Existing exposure detection most frequently relies on overt clinical symptoms, namely fever, during the infectious prodromal period. We have developed a robust machine learning based method to better detect asymptomatic states during the incubation period using subtle, sub-clinical physiological markers. Starting with highresolution physiological waveform data from non-human primate studies of viral (Ebola, Marburg, Lassa, and Nipah viruses) and bacterial (Y. pestis) exposure, we processed the data to reduce short-term variability and normalize diurnal variations, then provided these to a supervised random forest classification algorithm and post-classifier declaration logic step to reduce false alarms. In most subjects detection is achieved well before the onset of fever; subject cross-validation across exposure studies (varying viruses, exposure routes, animal species, and target dose) lead to 51h mean early detection (at 0.93 area under the receiver-operating characteristic curve [AUCROC]). Evaluating the algorithm against entirely independent datasets for Lassa, Nipah, and Y. pestis exposures un-used in algorithm training and development yields a mean 51h early warning time (at AUCROC=0.95). We discuss which physiological indicators are most informative for early detection and options for extending this capability to limited datasets such as those available from wearable, non-invasive, ECG-based sensors.
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Summary

Early pathogen exposure detection allows better patient care and faster implementation of public health measures (patient isolation, contact tracing). Existing exposure detection most frequently relies on overt clinical symptoms, namely fever, during the infectious prodromal period. We have developed a robust machine learning based method to better detect asymptomatic states...

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Detecting virus exposure during the pre-symptomatic incubation period using physiological data

Summary

Early pathogen exposure detection allows better patient care and faster implementation of public health measures (patient isolation, contact tracing). Existing exposure detection most frequently relies on overt clinical symptoms, namely fever, during the infectious prodromal period. We have developed a robust machine learning method to better detect asymptomatic states during the incubation period using subtle, sub-clinical physiological markers. Using high-resolution physiological data from non-human primate studies of Ebola and Marburg viruses, we pre-processed the data to reduce short-term variability and normalize diurnal variations, then provided these to a supervised random forest classification algorithm. In most subjects detection is achieved well before the onset of fever; subject cross-validation lead to 52±14h mean early detection (at >0.90 area under the receiver-operating characteristic curve). Cross-cohort tests across pathogens and exposure routes also lead to successful early detection (28±16h and 43±22h, respectively). We discuss which physiological indicators are most informative for early detection and options for extending this capability to lower data resolution and wearable, non-invasive sensors.
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Summary

Early pathogen exposure detection allows better patient care and faster implementation of public health measures (patient isolation, contact tracing). Existing exposure detection most frequently relies on overt clinical symptoms, namely fever, during the infectious prodromal period. We have developed a robust machine learning method to better detect asymptomatic states during...

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Distributed multi-modal sensor system for searching a foliage-covered region

Summary

We designed and constructed a system that includes aircraft, ground vehicles, and throwable sensors to search a semiforested region that was partially covered by foliage. The system contained 4 radio-controlled (RC) trucks, 2 aircraft, and 30 SensorMotes (throwable sensors). We also investigated communications links, search strategies, and system architecture. Our system is designed to be low-cost, contain a variety of sensors, and distributed so that the system is robust even if individual components are lost.
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Summary

We designed and constructed a system that includes aircraft, ground vehicles, and throwable sensors to search a semiforested region that was partially covered by foliage. The system contained 4 radio-controlled (RC) trucks, 2 aircraft, and 30 SensorMotes (throwable sensors). We also investigated communications links, search strategies, and system architecture. Our...

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Circuit-fed tile-approach configuration for millimeter-wave spatial power combining

Published in:
IEEE Trans. Microw. Theory Tech., Vol. 50, No. 1, Part 1, January 2002, pp. 17-21.

Summary

In this paper, a circuit-fed spatially combined transmitter array is described for operation at 44 GHz. The array contains 256 elements where each element consists of a monolithic-microwave integrated-circuit amplifier and a circularly polarized microchip patch antenna. The array is constructed using 16-element tile-approach subarrays. Each subarray is a two RF-level (three-dimensional) multichip module containing integrated microstrip patch antennas. The basic construction of the transmitter array resembles tile-approach phased arrays; however, the implementation has been tailored for the power-combining application. The peak performance at 43.5 GHz is equivalent isotropic radiated power of 40.6 dBW (11570 W), effective transmitted power (Peff) of 5.9 W, dc-to-RF efficiency of 7.3%, and system gain of 35 dB.
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Summary

In this paper, a circuit-fed spatially combined transmitter array is described for operation at 44 GHz. The array contains 256 elements where each element consists of a monolithic-microwave integrated-circuit amplifier and a circularly polarized microchip patch antenna. The array is constructed using 16-element tile-approach subarrays. Each subarray is a two...

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Comparison of two flat reflector-type designs for dual-polarization, dual-band operation

Published in:
IEEE Antennas and Propagation Society Int. Synp. 2001 Digest, Vol. 2, 8-13 July 2001, pp. 288-291.

Summary

The parabolic reflector remains an essential antenna for high-gain applications. This is a result of its desirable characteristics based on geometric optics. These include relative frequency independence for sufficiently large apertures and high aperture efficiency. However, the parabolic reflector occupies a large volume. This may be aesthetically unappealing on the sides of buildings and structures. Also, from a mobile user perspective, a desirable characteristic is having a large aperture during operation while having a small volume when packed away and not in use. The parabolic reflector is typically constructed of multiple petals for mobile uses, but it does not pack into as small a volume as a flat, thin antenna would due to the curvature of the paraboloid. Therefore, the primary goal of the antennas studied in this work is developing flat reflector antennas to utilize the advantages of large reflector apertures while remaining capable of packing into a small volume. In addition, system requiremenls dictated dual-band, dual-polarized operation. Two flat reflectors are compared: a reflectarray and a zoned reflector. While each design is inherently narrow-band, methods of achieving dual-band operation were employed.
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Summary

The parabolic reflector remains an essential antenna for high-gain applications. This is a result of its desirable characteristics based on geometric optics. These include relative frequency independence for sufficiently large apertures and high aperture efficiency. However, the parabolic reflector occupies a large volume. This may be aesthetically unappealing on the...

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Accurate modeling of dual dipole and slot elements used with photomixers for coherent terahertz output power

Summary

Accurate circuit models derived from electromagnetic simulations have been used to fabricate photomixer sources with optimized high-impedance antennas. Output powers on the order of 1 uW were measured for various designs spanning 0.6-2.7 THz. The improvement in output power ranged from 3 to 10 dB over more conventionally designed photomixers using broad-band log-spiral antennas. Measured data on single dipoles, twin dipoles, and twin slots are in good agreement with the characteristics predicted by the design simulations.
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Summary

Accurate circuit models derived from electromagnetic simulations have been used to fabricate photomixer sources with optimized high-impedance antennas. Output powers on the order of 1 uW were measured for various designs spanning 0.6-2.7 THz. The improvement in output power ranged from 3 to 10 dB over more conventionally designed photomixers...

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MEMS microswitches for reconfigurable microwave circuitry

Summary

The performance is reported for a new microelectromechanical structure (MEMS) cantilever microswitch. We report on both dc- and capacitively-contacted microswitches. The dc-contacted microswitches have contact resistance of less than 1 ohm, and the RF loss of the switch up to 40 GHz in the closed position is 0.1-0.2 dB. Capacitively-contacted switches have an impedance ratio of 141:1 from the open to closed state and in the closed position have a series capacitance of 1.2 pF. The capacitively-contacted switches have been measured up to 40 GHz with S(21) less than -0.7 dB across the 5-40 GHz band.
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Summary

The performance is reported for a new microelectromechanical structure (MEMS) cantilever microswitch. We report on both dc- and capacitively-contacted microswitches. The dc-contacted microswitches have contact resistance of less than 1 ohm, and the RF loss of the switch up to 40 GHz in the closed position is 0.1-0.2 dB. Capacitively-contacted...

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Combining-efficiency X-band spatial power-combined array using a multilayered packaging architecture

Author:
Published in:
IEEE Trans. Microw. Theory Tech., Vol. 48, No. 10, October 2000, pp. 1769-1771.

Summary

The design of a high combining-efficiency spatial power-combined array is described in this paper. A multilayered stacked stripline architecture enables a compact stable design. An array incorporating antenna active impedance and proper amplifier matching is measured with a combining efficiency of 87%, radiating 6.8 W of an available 7.8 W into the ideal uniformly illuminated array directivity at 10.1 GHz.
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Summary

The design of a high combining-efficiency spatial power-combined array is described in this paper. A multilayered stacked stripline architecture enables a compact stable design. An array incorporating antenna active impedance and proper amplifier matching is measured with a combining efficiency of 87%, radiating 6.8 W of an available 7.8 W...

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MEMs microswitch arrays for reconfigurable distributed microwave components

Summary

A revolutionary device technology and circuit concept is introduced for a new class of reconfigurable microwave circuits and antennas. The underlying mechanism is a compact MEMs cantilever microswitch that is arrayed in two-dimensions. The switches have the ability to be individually actuated. By constructing distributed circuit components from an array, the individual addressability of the microswitch provides the means to reconfigure the circuit trace and, thus, provides the ability to either fine-tune or completely reconfigure the circuit element's behavior. Device performance can be reconfigured over a decade in bandwidth in the nominal frequency range of 1 to 100 GHz. In addition, other circuit-element attributes can be reconfigured such as instantaneous bandwidth, impedance, and polarization (for antennas). This will enable the development of next-generation communication, radar and surveillance systems with agiIity to reconfigure operation for diverse operating bands, modes, power levels, and waveforms.
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Summary

A revolutionary device technology and circuit concept is introduced for a new class of reconfigurable microwave circuits and antennas. The underlying mechanism is a compact MEMs cantilever microswitch that is arrayed in two-dimensions. The switches have the ability to be individually actuated. By constructing distributed circuit components from an array...

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An enhanced bandwidth design technique for electromagnetically coupled microstrip antennas

Author:
Published in:
IEEE Trans. Antennas Propag., Vol. 48, No. 2, February 2000, pp. 161-164.

Summary

This paper describes a method of enhancing the bandwidth of two different electromagnetically coupled microstrip antennas by utilization of a tuning stub. An approximate theory and equations are developed to demonstrate the potential bandwidth improvement and required stub impedance characteristics. A novel dual-stub design is presented that achieves better characteristics than a conventional quarter wavelength open-end stub. As examples, the bandwidth (VSWR < 2) of a conventional proximity-coupled microstrip antenna is increased from 4.8 to 8.4% and the bandwidth of a stacked aperture-coupled microstrip antenna is increased from 27.5 to 34.5% using this technique.
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Summary

This paper describes a method of enhancing the bandwidth of two different electromagnetically coupled microstrip antennas by utilization of a tuning stub. An approximate theory and equations are developed to demonstrate the potential bandwidth improvement and required stub impedance characteristics. A novel dual-stub design is presented that achieves better characteristics...

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