Terahertz on-chip antenna based on metasurface and SIW with stacked layers of resonators on GaAs substrate

This paper presents a 100μm GaAs-based 0.45-0.50 THz on-chip antenna based on metasurface and substrate integrated waveguide (SIW) technologies to realize a high-performance antenna. The antenna design consists of 2×4 array of circular slot resonators embedded in rectangular ground-plane segments in a horizontal arrangement. The ground-plane segments are separated from each other by a narrow channel to create a coplanar waveguide which is used to excite the structure. This antenna structure, which is constructed on GaAs substrate, reduces substrate loss and surface waves. In addition, the metasurface essentially enlarges the effective aperture area of the antenna to enhance the gain and radiation efficiency of the antenna. The dimensions of the metasurface on-chip antenna is 0.8×0.8×0.13 mm3. The antenna exhibits an average gain and efficiency of 6.9dBi and 61.82%, respectively, which makes it a promising candidate for packaging in terahertz components

Amalgamation of metamaterial and SIW technologies for realizing wide-bandwidth and high-radiation properties of on-chip antennas for application in packaging of terahertz components

This paper shows that by employing a combination of metamaterial (MTM) and substrate integrated waveguide (SIW) technologies, the drawbacks of narrow-bandwidth and low radiation properties encountered in terahertz on-chip antennas can be overcome. In addition, an effective feeding mechanism is introduced to excite the on-chip antenna. The proposed antenna is constructed on the three stacked layers comprising Silicon-metal-Silicon substrates. Dimensions of on-chip antenna are 1×1×0.265 mm3. The on-chip antenna is shown to have an average impedance match, gain, and efficiency parameters of -35dB, 8.5dBi, and 67.5%, respectively, over a wide frequency range of 0.20-0.22 THz

An Active Learning Approach for Rapid Characterization of Endothelial Cells in Human Tumors

Currently, no available pathological or molecular measures of tumor angiogenesis predict response to antiangiogenic therapies used in clinical practice. Recognizing that tumor endothelial cells (EC) and EC activation and survival signaling are the direct targets of these therapies, we sought to develop an automated platform for quantifying activity of critical signaling pathways and other biological events in EC of patient tumors by histopathology. Computer image analysis of EC in highly heterogeneous human tumors by a statistical classifier trained using examples selected by human experts performed poorly due to subjectivity and selection bias. We hypothesized that the analysis can be optimized by a more active process to aid experts in identifying informative training examples. To test this hypothesis, we incorporated a novel active learning (AL) algorithm into FARSIGHT image analysis software that aids the expert by seeking out informative examples for the operator to label. The resulting FARSIGHT-AL system identified EC with specificity and sensitivity consistently greater than 0.9 and outperformed traditional supervised classification algorithms. The system modeled individual operator preferences and generated reproducible results. Using the results of EC classification, we also quantified proliferation (Ki67) and activity in important signal transduction pathways (MAP kinase, STAT3) in immunostained human clear cell renal cell carcinoma and other tumors. FARSIGHT-AL enables characterization of EC in conventionally preserved human tumors in a more automated process suitable for testing and validating in clinical trials. The results of our study support a unique opportunity for quantifying angiogenesis in a manner that can now be tested for its ability to identify novel predictive and response biomarkers

High-Isolation Antenna Array Using SIW and Realized with a Graphene Layer for Sub-Terahertz Wireless Applications

This paper presents the results of a study on developing an effective technique to increase the performance characteristics of array antennas for sub-THz integrated circuit applications. This is an essential to compensate the limited power of sub-THz sources. Although conventional array structures can provide a solution to enhance the radiation-gain however in the case of small-sized array structures the radiation properties can be adversely affect due to mutual coupling between the radiating elements. It is demonstrated here the effectiveness of using SIW technology to suppress surface wave propagations and near field mutual coupling. Prototype 2×3 antenna array with dimensions 20×13.5×0.125 mm 3 were designed and constructed on a dielectric substrate with thickness of 125 m for operation across 0.19-0.20 THz. The metallization of the antenna was coated with 500 nm layer of Graphene. With the proposed technique the isolation between the radiating elements was improved on average by 22.5 dB compared to a reference array antenna with no SIW isolation. The performance of the array was enhanced by transforming the patch to exhibit metamaterial characteristics. This was achieved by embedding an array of periodic slots of sub-wavelength in the patch. Compared to the reference array the metamaterial inspired structure exhibits an isolation, radiation gain and efficiency improvement on average by 28.5dB, 6.7dBi, and 36%, respectively. These results show the viability of proposed approach in developing array antennas for application in sub-THz integrated circuits. Keywords: Sub-terahertz (THz) frequency, substrate integrated waveguide (SIW), metamaterial (MTM), high isolation, high gain, graphene-layer, antennas arrays

High‑isolation antenna array using SIW and realized with a graphene layer for sub‑terahertz wireless applications

This paper presents the results of a study on developing an effective technique to increase the performance characteristics of antenna arrays for sub-THz integrated circuit applications. This is essential to compensate the limited power available from sub-THz sources. Although conventional array structures can provide a solution to enhance the radiation-gain performance however in the case of small-sized array structures the radiation properties can be adversely affected by mutual coupling that exists between the radiating elements. It is demonstrated here the effectiveness of using SIW technology to suppress surface wave propagations and near field mutual coupling effects. Prototype of 2 × 3 antenna arrays were designed and constructed on a polyimide dielectric substrate with thickness of 125 μm for operation across 0.19–0.20 THz. The dimensions of the array were 20 × 13.5 × 0.125 mm3. Metallization of the antenna was coated with 500 nm layer of Graphene. With the proposed technique the isolation between the radiating elements was improved on average by 22.5 dB compared to a reference array antenna with no SIW isolation. The performance of the array was enhanced by transforming the patch to exhibit metamaterial characteristics. This was achieved by embedding the patch antennas in the array with sub-wavelength slots. Compared to the reference array the metamaterial inspired structure exhibits improvement in isolation, radiation gain and efficiency on average by 28 dB, 6.3 dBi, and 34%, respectively. These results show the viability of proposed approach in developing antenna arrays for application in sub-THz integrated circuits

Quantitative evidence for the effects of multiple drivers on continental-scale amphibian declines.

Since amphibian declines were first proposed as a global phenomenon over a quarter century ago, the conservation community has made little progress in halting or reversing these trends. The early search for a "smoking gun" was replaced with the expectation that declines are caused by multiple drivers. While field observations and experiments have identified factors leading to increased local extinction risk, evidence for effects of these drivers is lacking at large spatial scales. Here, we use observations of 389 time-series of 83 species and complexes from 61 study areas across North America to test the effects of 4 of the major hypothesized drivers of declines. While we find that local amphibian populations are being lost from metapopulations at an average rate of 3.79% per year, these declines are not related to any particular threat at the continental scale; likewise the effect of each stressor is variable at regional scales. This result - that exposure to threats varies spatially, and populations vary in their response - provides little generality in the development of conservation strategies. Greater emphasis on local solutions to this globally shared phenomenon is needed