Abstract-Preliminary study on discrimination of transgenic cotton seeds using terahertz time‐domain spectroscopy

Bin Li,  Xiaochen Shen

https://onlinelibrary.wiley.com/doi/full/10.1002/fsn3.1846

Presence of genetically modified (GM) organisms is considered to be controversial by legislation and public. It is very important to develop detection methods for early discriminations. Conventional gene detection methods, including protein detection (PCR, ELISA, and so on) and DNA detection (Southern blot, GC/MS, and so on), have the disadvantages of high costs, time‐consuming, complex operations, and destructive of the samples. Terahertz spectroscopy (THz) is a brand‐new radiation with many unique advantages. Most biological macromolecules have fingerprint characteristics in THz band from the current recognition. In this study, feasibility of identifying the transgenic cotton seeds from nontransgenic counterparts using THz spectroscopy method was investigated. The transgenic cotton seeds‐Lumianyan No.28 and nontransgenic cotton seeds‐Xinluzao No.51 were selected and the sample‐making methods were studied; then the refractive and absorption curves of samples were got and given a detailed discussion; finally, absorption index of transgenic and nontransgenic DNA was observed and discussed. The results showed there were small fluctuations in THz band, and refractive index of transgenic seeds was lower than nontransgenic ones and had obvious turning point at 1.4–2.0 THz region. There were significant peaks in 1.0–1.2 and 1.3–1.5 THz regions for the transgenic cotton seeds. Transgenic DNA had higher absorption index than nontransgenic DNA, and there were 3–4 peaks corresponding to the cotton seed samples in 1.0–1.6 THz region. These results showed cotton seeds samples can provide important bio‐information in THz band, and this study provided a basis for developing potential THz‐based gene detection technologies.

Abstract-Study on Terahertz Spectrum Analysis and Recognition Modeling of Common Agricultural Diseases

Author links open overlay panelBin Li, Dianpeng Zhang, Yin Shen,

https://www.sciencedirect.com/science/article/abs/pii/S138614252030799X

Diseases are critical factors that affect the yield and quality of crops. Therefore, it is of great research value to develop rapid and quantitative methods for identification of common agricultural diseases. This exploratory study involved data analysis of common fungal pathogens using identification modeling based on terahertz spectrum technology. The selected pathogens were Physalospora piricola, Erysiphe cichoracearum, and Botrytis cinerea, which are common fungal pathogens that cause apple ring rot, cucumber powdery mildew, and grape gray mold blight, respectively. Taking polyethylene as the control, the terahertz time-domain spectra, and frequency-domain spectra of samples of the three pathogens were both measured. The absorption and refraction characteristics of these samples in the range of 0.1-2.0 THz were calculated and analyzed, and samples were then divided using the KS algorithm. Terahertz spectrum-image data blocks of the pathogen samples were preprocessed, and the dimensions of data were reduced using non-local mean filtering and the SPA algorithm, respectively. K-nearest neighbors (KNN), support vector machine (SVM), and BP neural network (BPNN), and other algorithms were used for analysis of terahertz images at characteristic frequencies, and for investigating the identification model. The model was quantitatively evaluated, and its imaging visualization was studied. The results suggest that there are significant differences among P. piricola, E. cichoracearum, and B. cinerea in absorption and refraction in the terahertz band. SVM modeling identification results of the three pathogens at the frequency of 1.376 THz were satisfactory, with an Rp of 0.9649, RMSEP of 0.0273, and a high (93.8212%) comprehensive evaluation index F1-score, and a clearly identifiable visualization effect. This study demonstrated the potential of terahertz spectroscopy to be used for identification of common crop pathogens and has provided technical references for the rapid diagnosis and early warning of agricultural diseases.

Abstract-A Scientometric Analysis of Global Terahertz Research by Web of Science Data

Bin Li, Kai Hu, Yin Shen,

https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9042326

Terahertz is a high-tech technology that has been developed rapidly in recent years. Relevant research has been extensively carried out in physics, chemistry, communication, biology, agricultural food safety testing, industrial non-destructive testing, biochemical, medical, and biological imaging. To provide a summary of the research trend in the field, there is a need to analyze the literature by scientometrics. In this work, we have an overview of the literature in the terahertz field, and then analyze the literature from the aspects of terahertz source, terahertz detector, terahertz spectroscopy and imaging, and terahertz applications respectively. The focus of this work is to automatically extract the trend by co-words and cocitation network analysis, and the comparative point of view is used to understand two closely related but different fields of terahertz basic research and terahertz application research. Through the scientific basis measurement, the research characteristics of these two fields, including annual outputs, active journals, key authors, key research directions and hotspots, important research projects and the countries behind them are immediately obtained.

Abstract-Investigation of terahertz radiation based on forward and backward wave feedback circuit

Physics of Plasmas

Luanfeng Gao, Yulu Hu, Xiaofang Zhu, Quan Hu, Jianqing Li, Bin Li,

https://aip.scitation.org/doi/10.1063/1.5124493

A forward and backward wave feedback circuit for a vacuum terahertz radiation source is proposed and demonstrated. In the feedback circuit, two bunched electron beams with different velocities interact with two spatial harmonics, respectively. The simulation reveals that the forward wave and the backward wave form a feedback circuit and affect each other through beam-wave interaction. Furthermore, the maximum gain of the forward wave of the feedback circuit is about 12.4 dB higher than the single beam traveling wave tube. When observing the excitation of the backward wave, it is found that the starting current is 44.4% lower than the traditional backward wave oscillator. The forward and backward wave feedback circuit is a promising choice for the watt-level tunable compact terahertz source that can be potentially used in a transmitter for Terahertz radar detection.

Abstract-Continuous-wave Terahertz Computed Tomography for Analysing Biological Bone

Bin Li, Dayong Wang, Lu Rong, Jie Zhao, Yunxin Wang, and Xiaoyu Shi

https://www.osapublishing.org/abstract.cfm?URI=dh-2019-Th4B.5

We reported an application of terahertz computed tomography for bone density analysis. Two-dimensional cross-sectional images of the chicken ulna were obtained through the continuous-wave terahertz imaging system.

© 2019 The Author(s)

Abstract-Terahertz Devices with EMXT Structure Fabricated by MEMS

Shengjie Yang, Hongda Lu, Zhipeng Liu, Yong Liu,  Bin Li , Xin Lv

https://ieeexplore.ieee.org/document/8563681

Due to the micro-dimension of terahertz devices and antennas, it requires more stringent processing technology. Micro-Electro-Mechanical Systems (MEMS) used to fabricate terahertz functional devices and antennas is a good choice for the high accuracy, good consistence and low cost. In this paper, one approach to obtain antennas and passive devices in terahertz band is proposed, which based on electromagnetic crystal structure and MEMS technology. The band-pass filter, 90° bend waveguide and H-plane horn antenna operating at terahertz band are presented as examples. All of them have good agreement between simulation and measurement.

Abstract-Numerical and experimental analysis of Bessel beam properties based on continuous-wave terahertz radiation

Zhihao Xu, Lu Rong, Dayong Wang, Bin Li, Yanlin Zhao, Jie Zhao, Yunxin Wang

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10826/108261C/Numerical-and-experimental-analysis-of-Bessel-beam-properties-based-on/10.1117/12.2501241.short

Terahertz imaging technology has been widely used in various fields. In continuous-wave terahertz imaging system, when the large size object is located at the unfocused position, Bessel beam with non-diffractive properties show its large depth of focus advantage over Gaussian beam. Bessel beam can be generated by the axicon, which has high conversion efficiency. The non-diffraction distance and the main lobe size of the Bessel beam depend on the parameters of the axicon and incident light wavelength. We analyzed that the influence on the axial two-dimensional intensity distribution of a zero-order Bessel beam by changing the axicon parameters and the incident Gaussian beam size. Experimentally, the axicon with different parameters were fabricated using different materials. Then the two-dimensional intensity distribution of the Bessel beam in the axial and transverse direction were recorded and analyzed. The experimental results is basically consistent with the theoretical ones.

© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Abstract-Application of continuous-wave terahertz computed tomography for the analysis of chicken bone structure

Bin Li,  Dayong Wang,  Lu Rong; Changchao Zhai, Yunxin Wang,  Jie Zhao

https://www.spiedigitallibrary.org/journals/Optical-Engineering/volume-57/issue-2/023105/Application-of-continuous-wave-terahertz-computed-tomography-for-the-analysis/10.1117/1.OE.57.2.023105.short

Terahertz (THz) radiation is able to penetrate many different types of nonpolar and nonmetallic materials without the damaging effects of x-rays. THz technology can be combined with computed tomography (CT) to form THz CT, which is an effective imaging method that is used to visualize the internal structure of a three-dimensional sample as cross-sectional images. Here, we reported an application of THz as the radiation source in CT imaging by replacing the x-rays. In this method, the sample cross section is scanned in all translation and rotation directions. Then, the projection data are reconstructed using a tomographic reconstruction algorithm. Two-dimensional (2-D) cross-sectional images of the chicken ulna were obtained through the continuous-wave (CW) THz CT system. Given by the difference of the THz absorption of different substances, the compact bone and spongy bone inside the chicken ulna are structurally distinguishable in the 2-D cross-sectional images. Using the filtered back projection algorithm, we reconstructed the projection data of the chicken ulna at different projection angle intervals and found that the artifacts and noise in the images are strikingly increased when the projection angle intervals become larger, reflected by the blurred boundary of the compact bone. The quality and fidelity of the 2-D cross-sectional images could be substantially improved by reducing the projection angle intervals. Our experimental data demonstrated a feasible application of the CW THz CT system in biological imaging.

© 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)

Abstract-Analysis of fluoroquinolones antibiotic residue in feed matrices using terahertz spectroscopy

Yuan Long, Bin Li, Huan Liu,

http://65.202.222.105/ao/abstract.cfm?uri=ao-57-3-544

As antibiotic residue becomes more and more serious all over the world, a rapid and effective detection method is needed to evaluate the antibiotic residue in feed matrices to ensure food safety for consumers. In this study, three different kinds of fluoroquinolones (norfloxacin, enrofloxacin, and ofloxacin) in feed matrices were analyzed using terahertz (THz) spectroscopy, respectively. Meanwhile, pure fluoroquinolones and pure feed matrices were also measured in the same way. Then, the absorption spectra of all of the samples were extracted in the transmission mode. Pure norfloxacin has two absorption peaks at 0.825 and 1.187 THz, and they could still be observed when mixing norfloxacin with feed matrices. Also, there was an obvious and strong absorption peak for ofloxacin at 1.044 THz. However, no obvious absorption peak for enrofloxacin was observed, and only a weak absorption peak was located at 0.8 THz. Then, the different models were established with different chemometrics to identify the fluoroquinolones in feed matrices and determined the fluoroquinolones content in the feed matrices. The least squares support vector machines, Naive Bayes, Mahalanobis distance, and back propagation neural network (BPNN) were used to build the identification model with a Savitzky–Golay filter and standardized normal variate pretreatments. The results show that the excellent classification model was acquired with the BPNN combined with no pretreatment. The optimal classification accuracy was 80.56% in the testing set. After that, multiple linear regression and stepwise regression were used to establish the quantitative detection model for different kinds of fluoroquinolones in feed matrices. The optimal correlation coefficients for norfloxacin, enrofloxacin, and ofloxacin in the prediction set were obtained with multiple linear regression that combined absorption peaks with wavelengths selected by stepwise regression, which were 0.867, 0.828, and 0.964, respectively. Overall, this research explored the potential of identifying the fluoroquinolones in feed matrices using THz spectroscopy without a complex pretreatment process and then quantitatively detecting the fluoroquinolones content in feed matrices. The results demonstrate that THz spectra could be used to identify fluoroquinolones in feed matrices and also detect their content quantitatively, which has great significance for the food safety industry.

© 2018 Optical Society of America

Abstract-Broadband tunable terahertz polarization converter based on graphene metamaterial

Shiwen Luo, Bin Li, Anlan Yu, Jun Gao, Xinbing Wang,  Duluo Zuo,

https://www.sciencedirect.com/science/article/pii/S0030401817311574

We design and numerically investigate a broadband tunable terahertz polarization converter based on graphene metamaterial. The converter presents a broad conversion band with high polarization conversion ratio (>0.95) in terahertz frequency over a bandwidth which is 25.8% of the central frequency. The converter can be dynamically tuned by varying the Fermi Energy of the graphene without changing the geometric structure. The converter shows high conversion ratio for a wide range of incident angles from 0 to 40°. By the scaling of the proposed structure, the broadband properties of the converter can be easily spread to other frequency. The proposed metamaterial offers an approach in the manipulation of the light polarization and has potential applications in imaging, sensing and communications.

Abstract-Synthetic aperture in terahertz in-line digital holography for resolution enhancement

Haochong Huang, Lu Rong, Dayong Wang, Weihua Li, Qinghua Deng, Bin Li, Yunxin Wang, Zhiqiang Zhan, Xuemin Wang, and Weidong Wu

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-55-3-A43&origin=search

Terahertz digital holography is a combination of terahertz technology and digital holography. In digital holography, the imaging resolution is the key parameter in determining the detailed quality of a reconstructed wavefront. In this paper, the synthetic aperture method is used in terahertz digital holography and the in-line arrangement is built to perform the detection. The resolved capability of previous terahertz digital holographic systems restricts this technique to meet the requirement of practical detection. In contrast, the experimental resolved power of the present method can reach 125 μm, which is the best resolution of terahertz digital holography to date. Furthermore, the basic detection of a biological specimen is conducted to show the practical application. In all, the results of the proposed method demonstrate the enhancement of experimental imaging resolution and that the amplitude and phase distributions of the fine structure of samples can be reconstructed by using terahertz digital holography.

© 2015 Optical Society of America

Abstract-Biological Imaging Application by Using Continuous-wave Terahertz In-line Digital Holography

Haochong Huang, Dayong Wang, Lu Rong, Bin Li, and Yunxin Wang

https://www.osapublishing.org/abstract.cfm?uri=OMP-2017-JTu4A.22

Continuous-wave terahertz in-line digital holography is a novel quantitative phase-contrast imaging approach. The exprimental verification confirms that the present method is an high resolution biological detection technique in terahertz wave.

© 2017 OSA

Abstract-Continuous-wave Terahertz Computed Tomography Based on Pyroelectric Array Detector

Bin Li, Dayong Wang, Lu Rong, Xun Zhou, and Min Wan
https://www.osapublishing.org/abstract.cfm?URI=dh-2016-DW2E.3

We report continuous-wave terahertz computed tomography based on pyroelectric array detector. The 2D cross-sectional images and 3D internal structure of a polyethylene straw are obtained by angular spectrum integral and filtered back projection algorithm.

© 2016 OSA

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