Optical Functions of Methanol and Ethanol in Wide Spectral Range

Lesňák, Michal, Kamil Postava, František Staněk, and Jaromír Pištora. "Optical Functions of Methanol and Ethanol in Wide Spectral Range." In Advances in Signal Processing and Communication, pp. 479-489. Springer, Singapore, 2019.

Abstract

The motivation of this paper is to determinate the precise complex refractive indices dispersion of ethanol, methanol, and their solutions in the wide spectral range from 8 to 40 000 cm−1(wavelength range from 250 nm to 1.25 mm) in coupling to biosensors applications (body liquids analyses, tissue ethanol solutions testing, etc.) because a specification of the complex optical functions consistent with Kramers–Kronig dispersion relations in the whole mentioned spectral range was still missing. A general method combining UV/visible/near-infrared spectroscopy and Mueller matrix ellipsometry, Fourier transform infrared spectroscopy (FTIR), infrared attenuated total reflection (ATR) spectroscopy, and terahertz time-domain spectroscopy (THz-TDS) is proposed. The experimental data are modeled using a dielectric function parametrization based on the Brendel–Bormann oscillators.

for full paper see https://link.springer.com/chapter/10.1007/978-981-13-2553-3_46

… Optical properties in the terahertz spectral range were obtained using the terahertz time-domain spectroscopy (THz-TDS) TPS Spectra 3000 from TeraView. We have combined both ATR and transmission measurements … IEEE, pp 

Predicting capsule fill weight from in-situ powder density measurements using terahertz reflection technology

Stranzinger, Sandra, Eva Faulhammer, Jingyi Li, Runqiao Dong, J. Axel Zeitler, Stefano Biserni, Vittorio Calzolari, Johannes G. Khinast, and Daniel Markl. "Predicting capsule fill weight from in-situ powder density measurements using terahertz reflection technology." International Journal of Pharmaceutics: X 1 (2019): 100004.

Abstract

The manufacturing of the majority of solid oral dosage forms is based on the densification of powder. A good understanding of the powder behavior is therefore essential to assure high quality drug products. This is particularly relevant for the capsule filling process, where the powder bulk density plays an important role in controlling the fill weight and weight variability of the final product. In this study we present a novel approach to quantitatively measure bulk density variations in a rotating container by means of terahertz reflection technology. The terahertz reflection probe was used to measure the powder density using an experimental setup that mimics a lab-scale capsule filling machine including a static sampling tool. Three different grades of α-lactose monohydrate excipients specially designed for inhalation application were systematically investigated at five compression stages. Relative densities predicted from terahertz reflection measurements were correlated to off-line weight measurements of the collected filled capsules. The predictions and the measured weights of the powder in the capsules were in excellent agreement, where the relative density measurements of Lactohale 200 showed the strongest correlation with the respective fill weight (R2=0.995). We also studied how the density uniformity of the powder bed was impacted by the dosing process and the subsequent filling of the holes (with excipient powder), which were introduced in the powder bed after the dosing step. Even though the holes seemed to be filled with new powder (by visual inspection), the relative density in these specific segments were found to clearly differ from the undisturbed powder bed state prior to dosing. The results demonstrate that it is feasible to analyze powder density variations in a rotating container by means of terahertz reflection measurements and to predict the fill weight of collected capsules.

Graphical abstract

For full paper see https://www.sciencedirect.com/science/article/pii/S2590156718300045

… A commercial time-domain terahertz system (TeraPulse 4000, TeraView Ltd, Cambridge, UK) coupled with a fiber-based flexible reflection probe was used in this study. The system was configured to operate at an optical …

LIPOPOLYSACCHARIDES ASSOCIATION ON THE SURFACE OF A SILICON CRYSTAL ADDRESSED BY THz SPECTROSCOPY AND MOLECULAR MODELLING

JABERI, AKH, J. A. H. AL SAEDI, MARIA MERNEA, L. PETRESCU, O. CĂLBOREAN, I. VASILE, and DF MIHĂILESCU. "LIPOPOLYSACCHARIDES ASSOCIATION ON THE SURFACE OF A SILICON CRYSTAL ADDRESSED BY THz SPECTROSCOPY AND MOLECULAR MODELLING." Romanian Journal of Biophysics 29, no. 1 (2019).

Astract. 

Gram-negative bacteria lipopolysaccharides (LPS) are lipids with a chemical structure comprising a lipidic region with several hydrocarbonate chains and a large saccharide region. Due to their structure, LPS can associate through hydrophobic forces, but also can dissolve in water. Here we investigated the association of LPS molecules on the surface of a silicon crystal by terahertz (THz) spectroscopy. We measured the THz absorption of LPS molecules directly deposited on the crystal or deposited on the crystal coated with a CaCl2 solution. Resulting spectra present a non-linear increase of THz absorption, with two absorption shoulders at 1.05 THz (~35 cm–1 ) and 1.37 THz (~45 cm–1 ). The presence of the CaCl2 solution does not influence the shoulders localization, suggesting a similar association of LPS molecules in both situations. Based on the comparison with previous THz studies on phospholipid bilayers, we suggested a layer ordering of LPS molecules in our samples that was validated through molecular modelling methods. We modelled LPS monolayers and simulated the THz spectra by normal modes analysis (NMA) and molecular dynamics (MD). The NMA spectrum of a LPS monolayer resulted in agreement with experiments, allowing us to validate the proposed LPS layer organization and the spectra simulation method.

For full paper see https://www.rjb.ro/wp-content/uploads/Mernea_4_F.pdf

… LPS molecules (2 mg/mL) were dissolved into a 7:3 chloroform-methanol mixture [16]. THz spectra were recorded using a TPS spectra 3000 spectrometer (TeraView Ltd., United Kingdom) in attenuated total reflection (ATR) setup under continuous nitrogen purge …

Flexible terahertz and FarIR polymer‐supported filter

Sanphuang, Varittha, and Niru K. Nahar. "Flexible terahertz and FarIR polymer‐supported filter." Microwave and Optical Technology Letters 60, no. 11 (2018): 2801-2805.

Abstract

We present the design, fabrication, and measurement of a terahertz (THz) polymer‐supported filter. A periodic structure, frequency selective surfaces (FSS) is employed to provide bandpass characteristic for this filter design with polyimide (PI) film as a substrate. This PI film (13 μm thick) is very thin and thus provides a flexible support to the filter. The average extracted dielectric constant ε r is 3.35 and the average refractive index n s is 1.84. The final filter structure was fabricated using standard microfabrication process. The measured transmission response shows high percentage of transmission (~80%) with the peak at 0.58 THz and sharp roll‐off that covers the broad range of frequency from 0.1 to 1 THz (wavelength of 300 μm‐3000 μm).

For full paper see https://onlinelibrary.wiley.com/doi/abs/10.1002/mop.31414

… The transmission responses of these PI films were measured using a time domain THz spectroscopy (TPS3000, TeraView Ltd.) as shown in Figure 2. The transmission responses show high percentage of transmission starting …

Pulsed terahertz reflection imaging of tumors in a spontaneous model of breast cancer

Vohra, Nagma, Tyler Bowman, Paola M. Diaz, Narasimhan Rajaram, Keith Bailey, and Magda El-Shenawee. "Pulsed terahertz reflection imaging of tumors in a spontaneous model of breast cancer." Biomedical Physics & Engineering Express 4, no. 6 (2018): 065025.

Abstract

We report the use of reflection-mode terahertz (THz) imaging in a transgenic mouse model of breast cancer. Unlike tumor xenografts that are grown from established cell lines, these tumors were spontaneously generated in the mammary fat pad of mice, and are a better representation of human breast cancer. THz imaging results from 7 tumors that recapitulate the compartmental complexity of breast cancer are presented here. Imaging was first performed on freshly excised tumors within an hour of excision and then repeated after fixation with formalin and paraffin. These THz images were then compared with histopathology to determine reflection-mode signals from specific regions within tumor. Our results demonstrate that the THz signal was consistently higher in cancerous tissue compared with fat, muscle, and fibrous tissue. Almost all tumors presented in this work demonstrated advanced stages where cancer infiltrated other tissues like fat and fibrous stroma. As the first known THz investigation in a transgenic model, these results hold promise for THz imaging at different stages of breast cancer.

for full paper see https://iopscience.iop.org/article/10.1088/2057-1976/aae699/meta

… Experimental Terahertz Imaging System. Terahertz imaging in this work is performed
using a commercial THz system from TeraView, Ltd shown in the diagram in Fig. 2a. An
800 nm pulse from a Ti:Sapphire laser is passed through a beam splitter …