The 220-GHz continuous wave (CW) folded waveguide (FWG) traveling wave tube (TWT) is presented as the high-power amplifier for the terahertz (THz) communication system in this article. This tube is designed and fabricated including FWG circuit, electron gun, periodical permanent magnet system, coupling window, and thermal management structure. The test results show that with the pencil beam of 20.5 kV and 52.4 mA, the output power is 16 W and the corresponding bandwidth is 7 GHz from 213 to 220 GHz, and the maximum power and the corresponding gain are 30 W and 31.2 dB at the frequency of 217 GHz.

Although neurophysiological and psychophysical proof of osseoperception is accumulating, histomorphometric evidence for the neural mechanisms of functional compensation following immediate and delayed implant loading is still lacking. For this randomized split-mouth study, six mongrel dogs randomly received one of four treatment protocols at 36 implant-recipient sites over 16 weeks (third maxillary incisor, third and fourth mandibular premolar): immediate implant placement and immediate loading (IIP+IL); delayed implant placement and delayed loading (DIP+DL); delayed implant placement and immediate loading (DIP+IL); and natural extraction socket healing (control). Histomorphometry was performed in the peri-implant bone and soft tissues within 300 µm around the implants. Immunocytochemistry and transmission electron microscopy were used to confirm the presence of neural structures and to reveal their ultrastructural characteristics, respectively. Myelinated nerve fibres densely populated the peri-implant crestal gingival and apical regions, although they were also identified in the woven bone and in the osteons near the implant threads. Compared with the control group in the mandible, the group that received IIP+IL showed a higher innervation (in N ⋅ mm⁻², 5.94±1.12 vs. 3.15±0.63, P<0.001) and smaller fibre diameter (in µm, 1.37±0.05 vs. 1.64±0.13, P=0.016), smaller axon diameter (in µm, 0.89±0.05 vs. 1.24±0.10, P=0.009) and g-ratio (0.64±0.04 vs. 0.76±0.05, P<0.001) in the middle region around the implants. Compared with DIP+IL in the mandible, IIP+IL had a higher nerve density (in N ⋅ mm⁻², 13.23±2.54 vs. 9.64±1.86, P=0.027), greater fibre diameter (in µm, 1.32±0.02 vs. 1.20±0.04, P=0.021), greater axon diameter (in µm, 0.92±0.01 vs. 0.89±0.03, P=0.035) and lower g-ratio (0.69±0.01 vs. 0.74±0.01, P=0.033) in the apical region around the implants. It may be assumed that the treatment protocol with IIP+IL is the preferred method to allow optimized peri-implant re-innervation, but further functional measurements are still required.

Oral squamous cell carcinoma (OSCC) is usually preceded by the oral premalignant lesions, mainly oral leukoplakia (OLK) after repeated insults of carcinogens, tobacco. B(a)P and DMBA are key carcinogens in tobacco smoke. In the present study, for the first time we established the cancerous cell line OSCC-BD induced by B(a)P/DMBA mixture and transformed from dysplastic oral leukoplakia cell line DOK. Cell morphology, proliferation ability, migration ability, colony formation and tumorigenicity were studied and confirmed the malignant characteristics of OSCC-BD cells. We further identified the differential proteins between DOK and OSCC-BD cells by stable isotope dimethyl labeling based quantitative proteomic method, which showed 18 proteins up-regulated and 16 proteins down-regulated with RSD < 8%. Differential proteins are mainly related to cell cycle, cell proliferation, DNA replication, RNA splicing and apoptosis. Abberant binding function, catalysis activity and transportor activity of differential proteins might contribute to the malignant transformation of OLK. Of the 34 identified differential proteins with RSD < 8%, 13 novel cancer-related proteins were reported in the present study. This study might provide a new insight into the mechanism of OLK malignant transformation and the potent biomarkers for early diagnosis, meanwhile further facilitate the application of the quantification proteomics to carcinogenesis research.

A slotted piecewise sine waveguide (SPWSWG) is suggested as the slow wave structure (SWS) to develop the terahertz traveling wave tube (TWT). This letter is the first to report the SPWSWG SWS with the advantages of flat dispersion and large coupling impedance from our calculation. Based on this novel SWS, a wideband 220-GHz TWT has been designed, fabricated and tested. The cold test results show that the reflection parameters at the input and output port of the TWT are less than -15.2 dB in the frequency range of 209-235 GHz. Moreover, the hot test results demonstrate that the maximum saturated output power reaches 28.6 W at 215 GHz and the 3-dB bandwidth exceeds 15.5 GHz, which are basically consistent with the simulation results.

In this article, we propose a low reflection folded waveguide (LRFWG) as the slow wave structure (SWS) for the development of a terahertz (THz) traveling-wave tube (TWT). Our simulation results show that the LRFWG SWS has lower reflection and larger coupling impedance compared to the conventional folded waveguide (FWG) SWS over a wide frequency range. Using this modified SWS, we have designed, simulated, and manufactured a wide-band high-power TWT operating in the G-band. The cold test results demonstrate that the reflection parameters at the input and output ports of the TWT are less than -13.8 dB from 200 to 240 GHz, confirming the effectiveness of our proposed structure. In addition, the hot test results show that the maximum output power of the 220 GHz LRFWG TWT amplifier reaches 31.2 W at 220 GHz, with a 3 dB bandwidth exceeding 23 GHz. The power-bandwidth product of the device is greater than 717.6 W $\cdot $ GHz, providing a demonstration of a wideband high power THz source.

High-quality axis-encircling electron beam is essential to drive a high-harmonic gyrotron. A magnetic cusp gun that can generate a low-spread axis-encircling electron beam at an extremely high magnetic-compression ratio was developed for a 1-THz fourth-harmonic gyrotron toward continuous-wave operation. The optimized gun could generate an axis-encircling electron beam with 80-kV voltage, 1-A current, and a nearly constant pitch factor of about 1.5 in a wide range of magnetic field strength. The transverse velocity spread was less than 2.1% and the guiding center radius was $26.6 ~\mu \text{m}$ . The design was verified by using MAGIC, EGUN, and CST simulations and good agreements were achieved.