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This is the first report of a distributed amplifier (DA) realized through monolithic integration of transistors with a substrate-integrated waveguide (SIW). The DA uses a steppedimpedance microstrip line as the input divider like in conventional DAs, but uses a low-loss, high-power-capacity SIW as the output combiner. The input signal is distributed to four GaN high-electron mobility transistors (HEMTs) evenly in magnitude but with the phase successively delayed by 90° at the fundamental frequency. The HEMTs are separated by a half wavelength at the second harmonic frequency in the SIW, so that their outputs are combined coherently at the SIW output. To overcome the limited speed of the GaN HEMTs, they are driven nonlinearly to generate second harmonics, and their fundamental outputs are suppressed with the SIW acting as a high-pass filter. The measured characteristics of the DA agree with that simulated at the small-signal level, but exceeds that simulated at the large-signal level. For example, under an input of 68 GHz and 10 dBm, the output at 136 GHz is 24-dB above the fundamental. Under an input of 68 GHz and 20 dBm, the output at 136 GHz is 14 dBm, with a conversion loss of 6 dB and a power consumption of 882 mW. This proof-of-principle demonstration opens the path to improving the gain, power and efficiency of DAs with higher-performance transistors and drive circuits. Although the demonstration is through monolithic integration, the approach is applicable to heterogeneous integration with the SIW and transistors fabricated on separate chips. 

F-band substrate-integrated waveguides (SIWs) are designed, fabricated, and characterized on a SiC wafer, along with SIW-based filters, impedance standards, and transitions to grounded coplanar waveguides (GCPW). The GCPW-SIW transitions not only facilitate wafer probing, but also double as resonators to form a 3-pole band-pass filter together with an SIW resonator. The resulted filter exhibits a 1.5-dB insertion loss at 115 GHz with a 34-dB return loss and a 19-GHz (16%) 3-dB bandwidth. The size of the filter is only 63% of previous filters comprising three SIW resonators. These results show the feasibility for monolithic integration of high-quality filters with high-efficiency antennas and amplifiers in a single-chip RF frontend above 110 GHz, which is particularly advantageous for 6G wireless communications and next-generation automobile radars. 

As 6G wireless communications push the operation frequency above 110 GHz, it is critical to have low-loss interconnects that can be accurately tested. To this end, D-band (110 GHz to 170 GHz) substrate-integrated waveguides (SIWs) are designed on a 100-μm-thick SiC substrate. The fabricated SIWs are probed on-wafer in a single sweep from 70 kHz to 220 GHz with their input/output transitioned to grounded coplanar waveguides (GCPWs). From CPW-probed scattering parameters, two-tier calibration is used to de-embed the SIW-GCPW transitions and to extract the intrinsic SIW characteristics. In general, the record low loss measured agrees with that obtained from finite-element full-wave electromagnetic simulation. For example, across the D band, the average insertion loss is approximately 0.2 dB/mm, which is several times better than that of coplanar or microstrip transmission lines fabricated on the same substrate. A 3-pole filter exhibits a 1-dB insertion loss at 135 GHz with 20-dB selectivity and 11% bandwidth, which is order-of-magnitude better than typical on-chip filters. These results underscore the potential of using SIWs to interconnect transistors, filters, antennas, and other circuit elements on the same monolithically integrated chip. 

Though many studies suggest the positive effects of gamification on participants’ learning and motivation, limited research has examined the basic psychological needs satisfaction in gamified learning. Based on self-determination theory (SDT), this study examined students’ actual competence, perceived competence, perceived autonomy, and perceived relatedness in a gamified math practice. The results showed that students had varied degree of needs satisfaction in perceived competence, perceived autonomy, and perceived relatedness. The implications and significance of the study provide practical teaching implementation suggestions and research insights for gamification research. 

Living systems can use a single periphery to perform a variety of tasks and adapt to a dynamic environment. This multifunctionality is achieved through the use of neural circuitry that adaptively controls the reconfigurable musculature. Current robotic systems struggle to flexibly adapt to unstructured environments. Through mimicry of the neuromechanical coupling seen in living organisms, robotic systems could potentially achieve greater autonomy. The tractable neuromechanics of the sea slug Aplysia californica’s feeding apparatus, or buccal mass, make it an ideal candidate for applying neuromechanical principles to the control of a soft robot. In this work, a robotic grasper was designed to mimic specific morphology of the Aplysia feeding apparatus. These include the use of soft actuators akin to biological muscle, a deformable grasping surface, and a similar muscular architecture. A previously developed Boolean neural controller was then adapted for the control of this soft robotic system. The robot was capable of qualitatively replicating swallowing behavior by cyclically ingesting a plastic tube. The robot’s normalized translational and rotational kinematics of the odontophore followed profiles observed in vivo despite morphological differences. This brings Aplysia-inspired control in roboto one step closer to multifunctional neural control schema in vivo and in silico. Future additions may improve SLUGBOT’s viability as a neuromechanical research platform. 

Quaternary ammonium compounds (QACs), a large class of chemicals that includes high production volume substances, have been used for decades as antimicrobials, preservatives, and antistatic agents, and for other functions in cleaning, disinfecting, personal care products, and durable consumer goods. QAC use has accelerated in response to the COVID-19 pandemic and the banning of 19 antimicrobials from several personal care products by the US Food and Drug Administration in 2016. Studies conducted before and after the onset of the pandemic indicate increased human exposure to QACs. Environmental releases of these chemicals have also increased. Emerging information on adverse environmental and human health impacts of QACs is motivating a reconsideration of the risks and benefits across the life cycle of their production, use, and disposal. This paper presents a critical review of the literature and scientific perspective developed by a multidisciplinary, multi-institutional team of authors from academia, governmental, and nonprofit organizations. The review evaluates currently available information on the ecological and human health profile of QACs and identifies multiple areas of potential concern. Adverse ecological effects include acute and chronic toxicity to susceptible aquatic organisms, with concentrations of some QACs approaching levels of concern. Suspected or known adverse health outcomes include dermal and respiratory effects, developmental and reproductive toxicity, disruption of metabolic function such as lipid homeostasis, and impairment of mitochondrial function. QACs’ role in antimicrobial resistance has also been demonstrated. In the US regulatory system, how a QAC is managed depends on how it is used, for example, in pesticides or personal care products. This can result in the same QACs receiving different degrees of scrutiny depending on the use and the agency regulating it. Further, the EPA’s current method of grouping QACs based on structure, first proposed in 1988, is insufficient to address the wide range of QAC chemistries, potential toxicities, and exposure scenarios. Consequently, exposures to common mixtures of QACs and from multiple sources remain largely unassessed. Some restrictions on the use of QACs have been implemented in the US and elsewhere, primarily focused on personal care products. Assessing the risks posed by QACs is hampered by their vast structural diversity and a lack of quantitative data on exposure and toxicity for the majority of these compounds. This review identifies important data gaps and provides research and policy recommendations for preserving the utility of QAC chemistries while also seeking to limit adverse environmental and human health effects.