High-Sensitivity High-Resolution Full-Wafer Imaging of the Properties of Large n-Type SiC Using the Relative Reflectance of Two Terahertz Waves

THz imaging was performed in 2 s intervals with 1 mm resolution on a 3 in., 0.42 mm thick, as-cut n-type Silicon Carbide wafer. Carrier density, relaxation time, mobility, and resistivity obtained from imaging results are 0.91 × 1018 cm-3, 4.36 × 10-14 s, 218 cm2V-1s-1, and 3.14 × 10-2 Ωcm, respectively. Compared with the standard values provided by the manufacturers, the results suggest that THz imaging has reliable precision and accuracy.

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High-Sensitivity RF Choke-Enhanced Dipole Antenna-Coupled Nb5N6 THz Detector

Frontiers in Physics ◽

10.3389/fphy.2021.768192 ◽

2021 ◽

Vol 9 ◽

Author(s):

Chengtao Jiang ◽

Xuecou Tu ◽

Chao Wan ◽

Lin Kang ◽

Xiaoqing Jia ◽

...

Keyword(s):

Electric Field ◽

Field Intensity ◽

Electric Field Intensity ◽

Imaging System ◽

High Sensitivity ◽

Dipole Antenna ◽

Thz Imaging ◽

Antenna Structure ◽

Imaging Results ◽

Thz Detector

In this study, we demonstrate an Nb5N6 terahertz (THz) detector with radio frequency (RF) choke-enhanced dipole antenna structure for 0.3 THz detection. The maximum electric field intensity of 218 V/m is obtained by optimizing the parameters of the dipole antenna with RF choke. Compared to a dipole antenna without RF choke, the electric field intensity of that with RF choke is improved by 2.6 times. The RF choke-enhanced dipole antenna-coupled Nb5N6 THz detector is fabricated and characterized. The measured maximum responsivity of the detector is 1100 V/W at 0.308 THz, and the corresponding noise equivalent power (NEP) is 6.4 × 10–12 W/Hz1/2. The measured response time of the Nb5N6 THz detector is as low as 8.46 μs. Furthermore, the Nb5N6 THz detector is applied to a homemade THz transmission imaging system for demonstrating its performance. The THz imaging results of a blade and access card show that the contrast of the blade image is sharp and the components hidden within the access card are clearly visible. This indicates that the Nb5N6 THz detector can be used in THz imaging, particularly in THz active imaging, which will have greater application prospects.

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A Single LC-MS/MS Analysis to Quantify CoA Biosynthetic Intermediates and Short-Chain Acyl CoAs

Metabolites ◽

10.3390/metabo11080468 ◽

2021 ◽

Vol 11 (8) ◽

pp. 468

Author(s):

Anthony E. Jones ◽

Nataly J. Arias ◽

Aracely Acevedo ◽

Srinivasa T. Reddy ◽

Ajit S. Divakaruni ◽

...

Keyword(s):

Mass Spectrometry ◽

Sample Preparation ◽

Biosynthetic Pathway ◽

Solid Phase ◽

High Sensitivity ◽

Short Chain ◽

Extraction Column ◽

Chain Acyl ◽

Precision And Accuracy ◽

Mass Spectrometry Mass Spectrometry

Coenzyme A (CoA) is an essential cofactor for dozens of reactions in intermediary metabolism. Dysregulation of CoA synthesis or acyl CoA metabolism can result in metabolic or neurodegenerative disease. Although several methods use liquid chromatography coupled with mass spectrometry/mass spectrometry (LC-MS/MS) to quantify acyl CoA levels in biological samples, few allow for simultaneous measurement of intermediates in the CoA biosynthetic pathway. Here we describe a simple sample preparation and LC-MS/MS method that can measure both short-chain acyl CoAs and biosynthetic precursors of CoA. The method does not require use of a solid phase extraction column during sample preparation and exhibits high sensitivity, precision, and accuracy. It reproduces expected changes from known effectors of cellular CoA homeostasis and helps clarify the mechanism by which excess concentrations of etomoxir reduce intracellular CoA levels.

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Fabrication of Graphene Nanomesh FET Terahertz Detector

Micromachines ◽

10.3390/mi12060641 ◽

2021 ◽

Vol 12 (6) ◽

pp. 641

Author(s):

Yuan Zhai ◽

Yi Xiang ◽

Weiqing Yuan ◽

Gang Chen ◽

Jinliang Shi ◽

...

Keyword(s):

Room Temperature ◽

Energy Gap ◽

Coupling Efficiency ◽

High Sensitivity ◽

Fabrication Process ◽

Monolayer Graphene ◽

Terahertz Waves ◽

Wet Process ◽

Graphene Nanomesh ◽

Thz Detector

High sensitivity detection of terahertz waves can be achieved with a graphene nanomesh as grating to improve the coupling efficiency of the incident terahertz waves and using a graphene nanostructure energy gap to enhance the excitation of plasmon. Herein, the fabrication process of the FET THz detector based on the rectangular GNM (r-GNM) is designed, and the THz detector is developed, including the CVD growth and the wet-process transfer of high quality monolayer graphene films, preparation of r-GNM by electron-beam lithography and oxygen plasma etching, and the fabrication of the gate electrodes on the Si3N4 dielectric layer. The problem that the conductive metal is easy to peel off during the fabrication process of the GNM THz device is mainly discussed. The photoelectric performance of the detector was tested at room temperature. The experimental results show that the sensitivity of the detector is 2.5 A/W (@ 3 THz) at room temperature.

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Three-Dimensional Imaging of Terahertz Circular SAR with Sparse Linear Array

Sensors ◽

10.3390/s18082477 ◽

2018 ◽

Vol 18 (8) ◽

pp. 2477 ◽

Cited By ~ 6

Author(s):

Jubo Hao ◽

Jin Li ◽

Yiming Pi

Keyword(s):

3D Imaging ◽

Linear Array ◽

Ground Plane ◽

Three Dimensional ◽

Terahertz Waves ◽

Recovery Method ◽

Imaging Algorithm ◽

Imaging Geometry ◽

Imaging Results ◽

Sparse Linear Array

Due to the non-contact detection ability of radar and the harmlessness of terahertz waves to the human body, three-dimensional (3D) imaging using terahertz synthetic aperture radar (SAR) is an efficient method of security detection in public areas. To achieve high-resolution and all aspect imaging, circular trajectory movement of radar and linear sensor array along the height direction were used in this study. However, the short wavelength of terahertz waves makes it practically impossible for the hardware to satisfy the half-wavelength spacing condition to avoid grating lobes. To solve this problem, a sparse linear array model based on the equivalent phase center principle was established. With the designed imaging geometry and corresponding echo signal model, a 3D imaging algorithm was derived. Firstly, the phase-preserving algorithm was adopted to obtain the 2D image of the ground plane for each sensor. Secondly, the sparse recovery method was applied to accomplish the scattering coefficient reconstruction along the height direction. After reconstruction of all the range-azimuth cells was accomplished, the final 3D image was obtained. Numerical simulations and experiments using terahertz radar were performed. The imaging results verify the effectiveness of the 3D imaging algorithm for the proposed model and validate the feasibility of terahertz radar applied in security detection.

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Absorptiometric Microdetermination of Total Sulfur in Rubber Products

Rubber Chemistry and Technology ◽

10.5254/1.3542565 ◽

1956 ◽

Vol 29 (2) ◽

pp. 620-634 ◽

Cited By ~ 3

Author(s):

K. E. Kress

Keyword(s):

Barium Sulfate ◽

Lead Nitrate ◽

Gravimetric Method ◽

High Sensitivity ◽

Lead Sulfate ◽

Chloride Complex ◽

Lead Chloride ◽

Excess Lead ◽

Precision And Accuracy ◽

Low Sulfur

Abstract The 1.0 to 2.5 per cent of sulfur normally present in rubber products is oxidized with concentrated nitric acid-bromine reagent, followed by perchloric acid in the presence of excess lead nitrate. Sulfur as lead sulfate is precipitated and washed with acetone. The lead sulfate is dissolved in 50 per cent hydrochloric acid, and absorbance of the lead chloride complex is recorded at 270 mµ. Sulfur is calculated on the basis of the measured lead content of the precipitate. The high sensitivity puts the method in the micro-range. An experienced analyst can analyze 40 to 50 samples a day. Precision and accuracy are comparable to those of the conventional barium sulfate gravimetric method at the low sulfur concentrations normally found in rubber products.

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Predictive value of D-dimer and analysis of risk factors in pregnant women with suspected pulmonary embolism after cesarean section

BMC Pulmonary Medicine ◽

10.1186/s12890-021-01757-3 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Limin Zhang ◽

Yunqiu Chen ◽

Wenjuan Liu ◽

Xinzhuo Wang ◽

Shuang Zhang ◽

...

Keyword(s):

Risk Factors ◽

Pulmonary Embolism ◽

Cesarean Section ◽

Diagnostic Imaging ◽

Pregnant Women ◽

Cesarean Delivery ◽

High Sensitivity ◽

Imaging Results ◽

Acute Pe ◽

D Dimer

Abstract Background Acute pulmonary embolism (PE) is one of the leading causes of maternal mortality, and cesarean section is an established independent risk factor for PE. The diagnostic utility of D-dimer for PE in non-pregnant women has been well-established, but its role in women with suspected PE after cesarean section is unclear. Furthermore, the optimal threshold level in this patient population is unknown. Traditional D-dimer levels have low diagnostic specificity, resulting in many pregnant women being exposed to potentially harmful radiation despite negative diagnostic imaging results. This research aimed to optimize the clinical threshold for D-dimer to improve specificity while ensuring high sensitivity and to identify risk factors for PE after cesarean section. Methods This retrospective study of 289 women who underwent diagnostic imaging (ventilation/perfusion [V/Q] or computed tomographic pulmonary angiography [CTPA]) for suspected acute PE after cesarean delivery from 2010 to 2021 was conducted. Clinical data and laboratory indicators within 24 h postpartum including D-dimer levels were collected for analyses. Results The final analysis included 125 patients, among whom 33 were diagnosed with acute PE (incidence of 11.42%, 95% confidence interval 7.7–15.1). The receiver operating characteristic curve analysis suggested that a D-dimer cut-off value of 800 ng/mL had specificity of 25.26% and sensitivity of 100% for detecting PE. The cut-off value was adjusted to 1000 ng/mL with a specificity of 34.74% and a sensitivity of 96.67%. Using a D-dimer cut-off value of 800 ng/mL (instead of the conventional value of 500 ng/mL) increased the number of patients excluded from suspected PE from 9.6 to 18.4% without additional false-negative results. Of note, a history of known thrombophilia was significantly more common in patients with PE than in those without (P < 0.05). No other independent risk factors were noted in our study. Conclusions The D-dimer cut-off value of 800 ng/mL ensures high sensitivity and increases specificity compared to the conventional threshold of 500 ng/mL. Utilizing this higher threshold can reduce the number of unnecessary CT and subsequently unnecessary radiation exposure, in women after cesarean delivery. Prospective studies should also be conducted to verify these results.

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Enhanced Scanning Nonlinear Dielectric Microscopy with Stepwise dC/dV and dC/dz Imaging—Achieving Qualitative, Quantitative and Artifact-Free Carrier Density Profiling of Semiconductor Devices

10.31399/asm.cp.istfa2018p0538 ◽

2018 ◽

Author(s):

T. Yamaoka ◽

S. Hasumura ◽

R. Hirose ◽

T. Ueno ◽

K. Tamura ◽

...

Keyword(s):

Carrier Density ◽

Semiconductor Devices ◽

High Sensitivity ◽

Free Carrier ◽

Nonlinear Dielectric ◽

Microwave Microscopy ◽

Free Carrier Density ◽

Scanning Microwave Microscopy ◽

Device Miniaturization ◽

High Sensitivity Detection

Abstract High-resolution and high-sensitivity detection of free carriers in semiconductors is critical due to the trend of device miniaturization and diversification. To address this need, the AFM-based techniques of scanning spreading resistance microscopy, scanning capacitance microscopy, scanning nonlinear dielectric microscopy (SNDM), scanning microwave impedance microscopy, and scanning microwave microscopy are used. This paper demonstrates enhanced SNDM with stepwise dC/dV and dC/dz imaging, qualitative analysis, quantitative analysis, and artifact-free carrier-density profiling of semiconductor devices. The trace mode in enhanced SNDM is switched between contact (dC/dV measurement) state and non-contact (dC/dz measurement) state for every line scan whereby the sampling intelligent scan mode is switched these states every pixel. Using IMEC Si standards and Si power MOSFET as examples demonstrates that this SNDM methodology can provide qualitative, quantitative, and artifact-free carrier density profiling of semiconductor devices.

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Adaptive 3D Imaging for Moving Targets Based on a SIMO InISAR Imaging System in 0.2 THz Band

Remote Sensing ◽

10.3390/rs13040782 ◽

2021 ◽

Vol 13 (4) ◽

pp. 782

Author(s):

Hongwei Li ◽

Chao Li ◽

Shiyou Wu ◽

Shen Zheng ◽

Guangyou Fang

Keyword(s):

Synthetic Aperture Radar ◽

3D Imaging ◽

Imaging System ◽

Synthetic Aperture ◽

Moving Targets ◽

Thz Imaging ◽

Inverse Synthetic Aperture Radar ◽

3D Images ◽

Imaging Results ◽

Aperture Radar

Terahertz (THz) imaging technology has received increased attention in recent years and has been widely applied, whereas the three-dimensional (3D) imaging for moving targets remains to be solved. In this paper, an adaptive 3D imaging scheme is proposed based on a single input and multi-output (SIMO) interferometric inverse synthetic aperture radar (InISAR) imaging system to achieve 3D images of moving targets in THz band. With a specially designed SIMO antenna array, the angular information of the targets can be determined using the phase response difference in different receiving channels, which then enables accurate tracking by adaptively adjusting the antenna beam direction. On the basis of stable tracking, the high-resolution imaging can be achieved. A combined motion compensation method is proposed to produce well-focused and coherent inverse synthetic aperture radar (ISAR) images from different channels, based on which the interferometric imaging is performed, thus forming the 3D imaging results. Lastly, proof-of-principle experiments were performed with a 0.2 THz SIMO imaging system, verifying the effectiveness of the proposed scheme. Non-cooperative moving targets were accurately tracked and the 3D images obtained clearly identify the targets. Moreover, the dynamic imaging results of the moving targets were achieved. The promising results demonstrate the superiority of the proposed scheme over the existing THz imaging systems in realizing 3D imaging for moving targets. The proposed scheme shows great potential in detecting and monitoring moving targets with non-cooperative movement, including unmanned military vehicles and space debris.

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THz imaging in the frame of the Archaeological Urban Park of Naples project

10.5194/egusphere-egu2020-18736 ◽

2020 ◽

Author(s):

Ilaria Catapano ◽

Carlo Noviello ◽

Giovanni Ludeno

Keyword(s):

Data Processing ◽

Cultural Heritage ◽

Time Domain ◽

Imaging Techniques ◽

Urban Park ◽

Thz Imaging ◽

Terahertz Waves ◽

Non Invasive ◽

Processing Chain ◽

Molecular Stability

The Archaeological Urban Park of Naples (PAUN) project aims at addressing the need of analytical information relating to cultural heritage with modalities that encourage innovation systems of protection and enhancement. In this frame, one of the specific goals is the testing of multiple non-invasive or only minimally invasive investigation techniques, aimed at identifying a permanent diagnostic system calibrated to the specific context of the Urban Archaeological Park of Piazza Municipio, Napoli, Italy.Among the electromagnetic sensing technologies, those exploiting Terahertz waves (1THz = 1012 Hz) are the newest among the imaging techniques, which offers the attractive chance of characterizing the inner features of manmade objects with a sub-millimeter spatial resolution in a non-invasive way while assuring negligible long-term risks to the molecular stability of the exposed objects.This possibility together with the recent development of compact, transportable and easily reconfigurable devices make THz imaging a more and more widespread considered investigation tool in the frame of cultural heritage. THz imaging allows, indeed, the gaining of information useful to improve knowledge about the design technique adopted by the artist and to detect possible damages affecting the conservation state of precious artworks [1].In the frame of PAUN project, THz imaging is considered as part of the sensor network, which is dedicated to the material characterization and supports the conservation and use of the assets of the Urban Archaeological Park of Piazza Municipio. Specifically, THz imaging is adopted to analyze ancient decorated mortar specimens and gather information on their stratigraphy. At this regard, it is worth pointing out that the effectiveness of THz imaging, i.e. the capability of obtaining high resolution images of the object under test, is dependent not only on the performances of the hardware technology but also on the data processing approaches. Herein, we consider the time domain Z-Omega Fiber-Coupled Terahertz Time Domain (FICO) system, which is available at IREA-CNR, and a data processing chain specifically designed to improve the discrimination of different material layers and to reconstruct the inner features characterizing the investigated artworks [2].&#160;[1] Fukunaga, THz Technology Applied to Cultural Heritage in Practice, Cultural Heritage Science, Springer.[2] Catapano, I., Soldovieri, F. A Data Processing Chain for Terahertz Imaging and Its Use in Artwork Diagnostics. J Infrared Milli Terahz Waves 38, 518&#8211;530 (2017).&#160;Acknowledge: Authors would like to thank the PAUN project &#8220;Archaeological Urban Park of Naples&#8221; by which the present work has been financed.&#160;

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