Friday, 25 May 2018

Concentration analysis of breast tissue phantoms with terahertz spectroscopy

Image result for vince wallace terahertzTruong, Bao CQ, Anthony J. Fitzgerald, Shuting Fan, and Vincent P. Wallace. "Concentration analysis of breast tissue phantoms with terahertz spectroscopy." Biomedical optics express 9, no. 3 (2018): 1334-1349.


Terahertz imaging has been previously shown to be capable of distinguishing normal breast tissue from its cancerous form, indicating its applicability to breast conserving surgery. The heterogeneous composition of breast tissue is among the main challenges to progressing this potential research towards a practical application. In this paper, two concentration analysis methods are proposed for analyzing phantoms mimicking breast tissue. The dielectric properties and the double Debye parameters were used to determine the phantom composition. The first method is wholly based on the conventional effective medium theory while the second one combines this theoretical model with empirical polynomial models. Through assessing the accuracy of these methods, their potential for application to quantifying breast tissue pathology was confirmed.

The group used "All terahertz time-domain spectroscopy measurements were conducted in reflection mode using a TeraPulse4000 system (TeraView Ltd, Cambridge, UK). The system produces THz pulses with a spectral range from 0.06 to 4 THz."

Tuesday, 22 May 2018

Low dielectric constant composites based on B2O3 and SiO2 rich glasses, cordierite and mullite

Szwagierczak, D., B. Synkiewicz, and J. Kulawik. "Low dielectric constant composites based on B 2 O 3 and SiO 2 rich glasses, cordierite and mullite." Ceramics International(2018).

The paper reports on sintering and dielectric properties of several glass-ceramic composites based on B2O3 and SiO2 rich glasses, cordierite and mullite. The dielectric constant values for the developed composites are low, in the range of 4.8–6.7 at 1 MHz. Some of the investigated materials exhibit low sintering temperature, suitable for LTCC (low temperature cofired ceramics) technology. A selected composite characterized by a low sintering temperature of 920 °C, low dielectric constant of 4.7 at 1 THz, thermal expansion coefficient well fitted to silicon and compatibility with commercial thick film conductive pastes was used for preparation of green tapes destined for LTCC microwave substrates.

Dielectric constant of this material was additionally determined in the range 0.15–3 THz using time domain spectroscopy (Teraview). 3. Results and discussion. Fig … 

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Thursday, 22 March 2018

An assessment of multimodal imaging of subsurface text in mummy cartonnage using surrogate papyrus phantoms

Gibson, Adam, Kathryn E. Piquette, Uwe Bergmann, William Christens-Barry, Graham Davis, Marco Endrizzi, Shuting Fan et al. "An assessment of multimodal imaging of subsurface text in mummy cartonnage using surrogate papyrus phantoms." Heritage Science 6, no. 1 (2018): 7.

Ancient Egyptian mummies were often covered with an outer casing, panels and masks made from cartonnage: a lightweight material made from linen, plaster, and recycled papyrus held together with adhesive. Egyptologists, papyrologists, and historians aim to recover and read extant text on the papyrus contained within cartonnage layers, but some methods, such as dissolving mummy casings, are destructive. The use of an advanced range of different imaging modalities was investigated to test the feasibility of non-destructive approaches applied to multi-layered papyrus found in ancient Egyptian mummy cartonnage. Eight different techniques were compared by imaging four synthetic phantoms designed to provide robust, well-understood, yet relevant sample standards using modern papyrus and replica inks. The techniques include optical (multispectral imaging with reflection and transillumination, and optical coherence tomography), X-ray (X-ray fluorescence imaging, X-ray fluorescence spectroscopy, X-ray micro computed tomography and phase contrast X-ray) and terahertz-based approaches. Optical imaging techniques were able to detect inks on all four phantoms, but were unable to significantly penetrate papyrus. X-ray-based techniques were sensitive to iron-based inks with excellent penetration but were not able to detect carbon-based inks. However, using terahertz imaging, it was possible to detect carbon-based inks with good penetration but with less sensitivity to iron-based inks. The phantoms allowed reliable and repeatable tests to be made at multiple sites on three continents. The tests demonstrated that each imaging modality needs to be optimised for this particular application: it is, in general, not sufficient to repurpose an existing device without modification. Furthermore, it is likely that no single imaging technique will to be able to robustly detect and enable the reading of text within ancient Egyptian mummy cartonnage. However, by carefully selecting, optimising and combining techniques, text contained within these fragile and rare artefacts may eventually be open to non-destructive imaging, identification, and interpretation.
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THz Tomography and image processing: a new tool for polymer and ceramic additive manufacturing quality control

Perraud, J. B., A. F. Obaton, B. Recur, H. Balacey, F. Darracq, J. P. Guillet, and P. Mounaix. "THz Tomography and image processing: a new tool for polymer and ceramic additive manufacturing quality control."


Additive manufacturing (AM) is an essential tool to make 3D objects having very complex shapes and geometries, unachievable with standard manufacturing approaches. Meanwhile, quality controls of such objects become challenging for both industrials and applications in laboratories due to both their complexity and the materials they are made of. Consequently, we demonstrate that terahertz (THz) imaging and THz tomography can be considered as efficient methods for such object inspection in routine applications. Thus, this paper proposes an experimental study of 3D polymer objects obtained by AM techniques. This approach allows us to characterize defects and to control dimensions by volumetric measurements on 3D data reconstructed by tomography. 

Molecular Characterization and Theoretical Calculation of Plant Growth Regulators Based on Terahertz Time-Domain Spectroscopy

Qu, Fangfang, Lei Lin, Chengyong Cai, Tao Dong, Yong He, and Pengcheng Nie. "Molecular Characterization and Theoretical Calculation of Plant Growth Regulators Based on Terahertz Time-Domain Spectroscopy." Applied Sciences 8, no. 3 (2018): 420.


Terahertz (THz), as an advanced spectral technology, has unique absorption characteristics for most biological macromolecules. In this work, the theoretical fundamentals for the application of THz time-domain spectroscopy (THz-TDS) to molecular characterization and fingerprint peak detection of three plant growth regulators (PGRs), including 2,4-Dichlorophenoxyacetic acid (2,4-D), forchlorfenuron (CPPU) and indole-3-acetic acid (IAA) were researched. Meanwhile, the effects of eight types of window functions on THz spectra were studied when converting time-domain spectra into frequency-domain spectra by Fourier transform. Based on the optimal window function, the THz absorption coefficient and refractive index of PGRs in frequencies of 0.2–3 THz were extracted. The molecule structure and vibration mode of three PGR samples were simulated by using density functional theory (DFT). The results showed that the three PGRs had different fingerprint peaks. Characteristic absorption and anomalous dispersion of 2,4-D were found at 1.35, 1.57 and 2.67 THz, those of CPPU were found at 1.77 and 2.44 THz, and the absorption peak of IAA was located at 2.5 THz. The absorption peaks obtained from THz spectra were identified according to the theoretical calculation results of DFT. These fingerprint peaks in THz spectra were generated by the interior stretching vibration and external deformation vibration of molecular groups. The experimental results revealed the feasibility of identifying PGRs species and detecting residues using THz-TDS.

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