Hexagonal boron nitride is a wide-band-gap van der Waals material that has recently emerged as a promising platform for quantum photonics experiments. In this work, we study the formation and ...localization of narrowband quantum emitters in large flakes (up to tens of micrometers wide) of hexagonal boron nitride. The emitters can be activated in as-grown hexagonal boron nitride by electron irradiation or high-temperature annealing, and the emitter formation probability can be increased by ion implantation or focused laser irradiation of the as-grown material. Interestingly, we show that the emitters are always localized at the edges of the flakes, unlike most luminescent point defects in three-dimensional materials. Our results constitute an important step on the roadmap of deploying hexagonal boron nitride in nanophotonics applications.
Anosmia, the loss of smell, is a common and often the sole symptom of COVID-19. The onset of the sequence of pathobiological events leading to olfactory dysfunction remains obscure. Here, we have ...developed a postmortem bedside surgical procedure to harvest endoscopically samples of respiratory and olfactory mucosae and whole olfactory bulbs. Our cohort of 85 cases included COVID-19 patients who died a few days after infection with SARS-CoV-2, enabling us to catch the virus while it was still replicating. We found that sustentacular cells are the major target cell type in the olfactory mucosa. We failed to find evidence for infection of olfactory sensory neurons, and the parenchyma of the olfactory bulb is spared as well. Thus, SARS-CoV-2 does not appear to be a neurotropic virus. We postulate that transient insufficient support from sustentacular cells triggers transient olfactory dysfunction in COVID-19. Olfactory sensory neurons would become affected without getting infected.
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•A postmortem bedside surgical procedure was developed for COVID-19 and control patients•Ciliated cells are the main target cell type for SARS-CoV-2 in the respiratory mucosa•Sustentacular cells (non-neuronal) are the main target cell type in the olfactory mucosa•No evidence for infection of olfactory sensory neurons or olfactory bulb parenchyma
Postmortem samples of respiratory and olfactory mucosa and whole olfactory bulbs are harvested immediately after the death of COVID-19 patients revealing ciliated cells and sustentacular cells but not olfactory sensory neurons as the main target cell types for SARS-CoV-2 infection and replication.
Single photon sources are required for a wide range of applications in quantum information science, quantum cryptography, and quantum communications. However, the majority of room temperature ...emitters to date are only excited optically, which limits their proper integration into scalable devices. In this work, we overcome this limitation and present room temperature electrically driven light emission from localized defects in zinc oxide (ZnO) nanoparticles and thin films. The devices emit in the red spectral range and show excellent rectifying behavior. The emission is stable over an extensive period of time, providing an important prerequisite for practical devices. Our results open possibilities for building new ZnO-based quantum integrated devices that incorporate solid-state single photon sources for quantum information technologies.
In this paper, for the first time, we designed and analyzed channels between a graphic processing unit and memory in a silicon interposer for a 3-D stacked high bandwidth memory (HBM). We thoroughly ...analyzed and verified the electrical characteristics of the silicon interposer considering various design parameters, such as the channel width and space, redistribution layer via, and under bump metallurgy pads. In particular, we also considered the meshed ground planes used for the proposed transmission lines, which are microstrip and strip lines. Signal integrity (SI) of the proposed channels in the silicon interposer was successfully analyzed and verified using a full 3-D electromagnetic solver and circuit simulations. Based on the extracted lumped circuit resistance, inductance, conductance and capacitance parameters, we thoroughly analyzed the channel characteristics and identified the parameters that dominantly affect SI in relation to each frequency range. From the analyzed insertion loss and far end crosstalk, we verified SI of the silicon interposer by eye-diagram simulations in terms of eye-height voltage and timing jitter in the time domain. In the worst case, the eye-height voltage and timing jitter of the proposed microstrip lines are 0.911 V and 36.8 ps, respectively, with 72 mV of signal coupling. The eye-height voltage and timing jitter of the proposed strip line are 0.887 V and 42.1 ps with 34 mV of single couplings. We show that the proposed channels of the silicon interposer can successfully transfer data at a 2-Gb/s data rate. Finally, we propose concepts and solutions for the next-generation HBM interface with higher data rates up to 8 Gb/s.
The utilization of urban green areas has increased, but it is unclear whether urban green areas can decrease the concentration of particulate matter at an industrial complex city in Korea. We ...measured the extent of particulate matter (PM) reduction at a buffer green area in the Sihwa Industrial Complex. PM was measured at the industrial complex, the urban green area, and a nearby residential area from April to October 2019. PM reduction rates were highest at the urban green area in August and October, which is related to increased atmospheric mixing height and the active west wind blowing from the industrial complex to the residential area. Reduction rates of PM10 and PM2.5 at the urban green area showed the lowest values, namely 14.4% and 25.3%, respectively. The air temperature, wind speed, and humidity could affect the PM reduction rate by influencing the movement and dispersion of PM at the micro-spatiotemporal scale. These results indicated that PM concentration could be reduced by the structural change of a forest layer at a micro scale in urban green areas.
The emerging field of nanophotonics initiated a dedicated study of single photon
sources and optical resonators in new class of materials. One such material is
zinc oxide (ZnO) that has been long ...considered only for classical light-emitting
applications. However, it recently showed promise for quantum photonics
technologies. In this review, we highlight the recent advances in studying
single emitters in ZnO, engineering of optical cavities and practical
nanophotonics devices including nanolasers and electrically triggered devices.
We finalize with an outlook at this promising area, as well as provide
perspectives and open questions in solid state nanophotonics employing ZnO.
Oak species are the major dominant tree species of deciduous forests, but the little study was conducted to understand the change of particulate matter concentration after changing the forest ...structure. This study analyzed the effects of changing forest structure (CFS) on the changes in meteorological factors and air particulate matter (PM) concentration after leaf emergence in oak-dominated forests nearby highway pollutants' sources. In June 2019, 33% of the total trees were removed from the CFS of oak forests in the vicinity of the tollgate of Misiryeong in Goseong-gun, Gangwon-do, Korea. To understand the changes in leaf emergence between the treatment site (TRS is the site changing forest structure) and control site (CS), we investigated the foliage height profile (FHP, %) at each class of tree height in December 2019 and June 2020. The results showed that FHP (%) was lower in TRS than in CS in both months, and the FHP of the middle canopy class increased after TRS while that of the upper canopy class decreased. The correlation was significant with temperature in March (p < 0.01) and with wind speed in June (p < 0.01), indicating that CFS improved the airflow. There was no significant difference in the PM concentration between CS (PM
10
: 37.7 µg/m
3
, PM
2.5
: 21.1 µg/m
3
) and TRS (PM
10
: 37.5 µg/m
3
, PM
2.5
: 20.8 µg/m
3
) in March; however, the PM concentration in TRS (PM
10
: 65.0 µg/m
3
, PM
2.5
: 26.2 µg/m
3
) was lower than that in CS (PM
10
: 73.9 µg/m
3
, PM
2.5
: 29.1 µg/m
3
) in June. The rate of PM reduction (%) in TRS was higher in June (PM
10
: 11.3%, PM
2.5
: 10.0%) than in March (PM
10
: 2.3%, PM
2.5
: 4.0%). The low value of PM concentration in June could be related to the leaf emergence. Overall, the results indicated that meteorological factors and PM concentrations had changed in the inner part of the forest after leaf emergence and that the temperature and wind speed were strongly correlated with the PM concentration. These results suggest that CFS can change the forest structure and the airflow in oak-dominated forests, which PM can flow and settle down into the inner forest's nearby pollutants sources of a tollgate. The results provide basic information for understanding the reduction effect of PM by CFS in oak-dominated deciduous forests nearby highway pollutants source.
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