The oral microbial community (microbiota) plays a critical role in human health and disease. Alterations in the oral microbiota may be associated with disorders such as gingivitis, periodontitis, ...childhood caries, alveolar osteitis, oral candidiasis and endodontic infections. In the immunosuppressed population, the spectrum of potential oral disease is even broader, encompassing candidiasis, necrotizing gingivitis, parotid gland enlargement, Kaposi's sarcoma, oral warts and other diseases. Here, we used 454 pyrosequencing of bacterial 16S rRNA genes to examine the oral microbiome of saliva, mucosal and tooth samples from HIV-positive and negative children. Patient demographics and clinical characteristics were collected from a cross-section of patients undergoing routine dental care. Multiple specimens from different sampling sites in the mouth were collected for each patient. The goal of the study was to observe the potential diversity of the oral microbiota among individual patients, sample locations, HIV status and various dental characteristics. We found that there were significant differences in the microbiome among the enrolled patients, and between sampling locations. The analysis was complicated by uneven enrollment in the patient cohorts, with only five HIV-negative patients enrolled in the study and by the rapid improvement in the health of HIV-infected children between the time the study was conceived and completed. The generally good oral health of the HIV-negative patients limited the number of dental plaque samples that could be collected. We did not identify significant differences between well-controlled HIV-positive patients and HIV-negative controls, suggesting that well-controlled HIV-positive patients essentially harbor similar oral flora compared to patients without HIV. Nor were significant differences in the oral microbiota identified between different teeth or with different dental characteristics. Additional studies are needed to better characterize the oral microbiome in children and those with poorly-controlled HIV infections.
The oral microbial community (microbiota) plays a critical role in human health and disease. Alterations in the oral microbiota may be associated with disorders such as gingivitis, periodontitis, ...childhood caries, alveolar osteitis, oral candidiasis and endodontic infections. In the immunosuppressed population, the spectrum of potential oral disease is even broader, encompassing candidiasis, necrotizing gingivitis, parotid gland enlargement, Kaposi's sarcoma, oral warts and other diseases. Here, we used 454 pyrosequencing of bacterial 16S rRNA genes to examine the oral microbiome of saliva, mucosal and tooth samples from HIV-positive and negative children. Patient demographics and clinical characteristics were collected from a cross-section of patients undergoing routine dental care. Multiple specimens from different sampling sites in the mouth were collected for each patient. The goal of the study was to observe the potential diversity of the oral microbiota among individual patients, sample locations, HIV status and various dental characteristics. We found that there were significant differences in the microbiome among the enrolled patients, and between sampling locations. The analysis was complicated by uneven enrollment in the patient cohorts, with only five HIV-negative patients enrolled in the study and by the rapid improvement in the health of HIV-infected children between the time the study was conceived and completed. The generally good oral health of the HIV-negative patients limited the number of dental plaque samples that could be collected. We did not identify significant differences between well-controlled HIV-positive patients and HIV-negative controls, suggesting that well-controlled HIV-positive patients essentially harbor similar oral flora compared to patients without HIV. Nor were significant differences in the oral microbiota identified between different teeth or with different dental characteristics. Additional studies are needed to better characterize the oral microbiome in children and those with poorly-controlled HIV infections.
We report a monolithic microwave integrated-circuit (MMIC) comb generator capable of producing a repetitive narrow pulse (7.1 ps pulse duration) with sharp edges (4.2 ps falling time). The circuit ...was designed in a 250 nm indium phosphide (InP) heterojunction bipolar transistor (HBT) technology using differential pairs. We characterized the output signal with a 110 GHz sampling oscilloscope and de-embedded the band-limited frequency spectrum of the pulse in the circuit reference plane. We measured a pulse duration of 7.1 ps and a peak amplitude of −0.333 V. In the frequency domain, the comb generator provided −48.7 dBm of output power at 110 GHz when the circuit is fed with a 1 GHz input signal.
In this paper, we investigate the effect of two calibration errors, probe placement and capacitance per unit length, on transistor characterization, from 220 GHz to 325 GHz, on both a microstrip and ...an inverted coplanar waveguide with a via-stitched ground plane (CPW-G) calibration kit. We find that the calibration errors tend to be greater for the microstrip calibration than for the CPW-G calibration. These findings have critical ramifications for transistor characterization and modelling, and active circuit design.
We report a novel design approach of on-wafer multiline thru-reflect-line (mTRL) calibration kit fabricated on a commercial semiconductor-based transistor process that we validate from 0.1 GHz to 1.1 ...THz. The on-wafer calibration standards are designed with an innovative inverted grounded-coplanar waveguide (G-CPW) transmission line, where the calibration reference planes, buried under multiple layers of interconnects, provide direct access to the heterojunction-bipolar-transistor (HBT). We connect the different levels of ground-plane metallization with vias to avoid coupling with adjacent structures and limit the propagation of higher-order modes. We validate this approach with measurements of the complex characteristic impedance of the inverted G-CPW lines, the S-parameters of a 775 μm line, and a 600 GHz common-base amplifier.
High-Gain 500-GHz InP HBT Power Amplifiers Cheron, Jerome; Jones, Rob D.; Chamberlin, Richard A. ...
2021 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS),
2021-Dec.-5
Conference Proceeding
We report two terahertz monolithic integrated circuit (TMIC) amplifiers operating at 500 GHz. The 6-stage single-ended power amplifiers use Teledyne's 130 nm indium-phosphide double heterojunction ...bipolar transistors in a common-base configuration. The impedance matching networks of the first amplifier are designed with shunt lines while the second amplifier uses shunt metal-insulator-metal capacitors. We measured and compared the small-signal and large-signal performance of the two amplifiers around 500 GHz. Although the two TMICs exhibit a similar transducer gain (24 dB) and output power (up to −0.7 dBm), we obtained better yield with the amplifiers designed with shunt lines.
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