Tuesday, 18 June 2019

Measuring bulk density variations in a moving powder bed via terahertz in-line sensing

    Stranzinger, Sandra, Eva Faulhammer, Jingyi Li, Runqiao Dong, Johannes G. Khinast, J. Axel Zeitler, and Daniel Markl. "Measuring bulk density variations in a moving powder bed via terahertz in-line sensing." Powder Technology 344 (2019): 152-160.
    Monitoring the relative density of static or moving powder inside a process line is essential for manufacturing high-quality products. The aim of this study was to predict density variations in a moving powder bed using terahertz reflection technology. We systematically investigated three grades (varying true density and particle size) of two materials: lactose and silicified microcrystalline cellulose (SMCC). These six powders specifically differ in their compressibility, which can be applied to assess the sensitivity and applicability of our method. The powders were filled into a round container, and terahertz reflection measurements were acquired continuously during the container’s rotation. The setup allowed to adjust the relative density by compacting the powders into specific powder bed heights. Each powder was compacted to various relative densities (compression pressures up to 100 kPa). We calculated the surface refractive index based on the in-line terahertz measurements acquired during rotation, which has a linear dependence on the relative density of the powder. This was confirmed by correlating the refractive index values with the theoretical relative densities based on the bulk and true densities of the powder. The coefficient of determination (R2) was larger than 0.962 (Lactohale 100) for all six powders, with the highest coefficients for Lactohale 220 (R2 = 0.996) and SMCC 50 LD (R2 = 0.995). The results suggest that the proposed method can resolve relative densities averaged across the powder bed that are as small as 0.3% (Lactohale 100). The high acquisition rate of the terahertz system (15 Hz) made it possible to determine the powder density in 230 positions uniformly distributed throughout the container, facilitating the investigation of the relative density uniformity in the container as a function of the powder bed height. It was observed that SMCC powders undergo a smaller change in the relative density variations upon compaction than the lactose powders. Moreover, the relative density maps clearly indicate local density differences in the powder bed for all powders. The relative density variations that were introduced by packing of the container prevailed throughout the compaction process for all samples with the exception of Lactohale 220. The presented approach allows a precise resolution of the spatial distribution of relative density, which facilitates an in-depth analysis of powder behavior upon compaction.
    … In order to use THz-TDS to quantify the porosity and relative density of powders and porous media,
    pulses of terahertz radiation are propagated through the material of … A commercial time-domain
    terahertz spectrometer (TeraPulse 4000TeraView Ltd., Cambridge …

    Millimeter Wave Radiation Activates Leech Nociceptors via TRPV1-Like Receptor Sensitization

    Romanenko, Sergii, Alan R. Harvey, Livia Hool, Shuting Fan, and Vincent P. Wallace. "Millimeter Wave Radiation Activates Leech Nociceptors via TRPV1-Like Receptor Sensitization." Biophysical journal (2019).


    There is evidence that millimeter waves (MMWs) can have an impact on cellular function, including neurons. Earlier in vitro studies have shown that exposure levels well below the recommended safe limit of 1 mW/cm2 cause changes in the action potential (AP) firing rate, resting potential, and AP pulse shape of sensory neurons in leech preparations as well as alter neuronal properties in rat cortical brain slices; these effects differ from changes induced by direct heating. In this article, we compare the responses of thermosensitive primary nociceptors of the medicinal leech under thermal heating and MMW irradiation (80–170 mW/cm2 at 60 GHz). The results show that MMW exposure causes an almost twofold decrease in the threshold for activation of the AP compared with thermal heating (3.9 ± 0.4 vs. 8.3 ± 0.4 mV, respectively). Our analysis suggests that MMWs-mediated threshold alterations are not caused by the enhancement of voltage-gated sodium and potassium conductance. We propose that the reduction in AP threshold can be attributed to the sensitization of the transient receptor potential vanilloid 1-like receptor in the leech nociceptor. In silico modeling supported our experimental findings. Our results provide evidence that MMW exposure stimulates specific receptor responses that differ from direct thermal heating, fostering the need for additional studies.

    … Values for the leech saline solution, the paraffin, and the polystyrene Petri dish were measured
    using a commercial THz time-domain spectroscopy system (TeraPulse 4000TeraViewCambridge, UK) over the temperature range used in the experiments (24–45°C). At ambient …

    Thursday, 25 April 2019

    Optimization of THz diffractive optical elements thickness

    Surma, Mateusz, Izabela Ducin, Maciej Sypek, Przemyslaw Zagrajek, and Agnieszka Siemion. "Optimization of THz diffractive optical elements thickness." Photonics Letters of Poland 10, no. 4 (2018): 115-117.


    Diffractive optical elements (DOEs) are strictly related to the design wavelength due to the fact that they must introduce particular phase delay of the wavefront propagating through the structure. Mostly the attenuation of the material is not taken into account. In this article we propose to optimize thickness of the DOE by reducing introduced phase retardation but also attenuation. The efficiency of DOEs is determined by the method of coding phase distribution and can be easily measured by using diffraction orders of corresponding diffraction grating. Here, we analyze binary phase diffraction gratings with assumed attenuation. 

    … The designed gratings were manufactured in a 3D printing technique in paper using an MCor Iris printer [15]. Prior to the design process was the determination of the material optical properties. Time Domain Spectroscopy (TDS ‒ TeraView) was used for this task … 

    Monday, 22 April 2019

    Utilizing multilayer structures to enhance terahertz characterization of thin films ranging from aqueous solutions to histology slides

    SUN, QIUSHUO, KAI LIU, XUEQUAN CHEN, XUDONG LIU, AI HERNANDEZSERRANO, and E. M. M. A. PICKWELL-MACPHERSON. "Utilizing multilayer structures to enhance terahertz characterization of thin films ranging from aqueous solutions to histology slides." Optics Letters


    We propose a multilayer geometry to characterize thin film samples in reflection terahertz time domain spectroscopy. Theory indicates that this geometry has higher sensitivity compared to ordinary transmission or reflection geometries when characterizing both low and high absorption samples. Pure water and water-ethanol mixtures are measured to verify the characterization accuracy of the proposed geometry and its capability to measure trace liquids. Paraffin-embedded oral cancer tissues are imaged to further show how the proposed geometry enhances the sensitivity for solid low-absorptive films.

    .......The Srefl lines are calculated by Eqn (3), light green and light blue lines are calculated by Eqn (2) and Eqn (1), respectively. The TF liquid measurements were conducted using the Terapulse 4000 from Teraview 

    Thursday, 18 April 2019

    Terahertz pulse time-domain holography method for phase imaging of breast tissue

    Balbekin, Nikolay S., Quentin Cassar, Olga A. Smolyanskaya, Maksim S. Kulya, Nikolay V. Petrov, Gaetan MacGrogan, Jean-Paul Guillet, Patrick Mounaix, and Valery V. Tuchin. "Terahertz pulse time-domain holography method for phase imaging of breast tissue." In Quantitative Phase Imaging V, vol. 10887, p. 108870G. International Society for Optics and Photonics, 2019.


    Pulse holographic imaging along with time-domain spectroscopy scan and tomographic techniques are of great interest. Since the advantages of holography are the lack of focusing optics and high spatial resolution, and, comparing with tomography, less computation cost for numerical reconstruction, this technique is preferable for the analysis of thin histological samples. In this work we have created the experimental scheme that involves measurement of diffraction pattern of the collimated THz pulse field spatial distribution at some distance behind the object in the time-domain mode, thus allowing reconstruction of amplitude and phase distribution at the object plane by numerical backpropagation of the wavefront in the spectral domain. In our experiment, we used a breast biopsy sample containing cancer tissues, we also performed numerical simulations accounting for experimental conditions to confirm the conceptual applicability of the reconstruction method.

    BREAST TISSUE PROBING 3.1 Material & Methods A commercially available TeraPulse4000 (TeraView Ltd, Cambridge, UK) configured in reflection geometry by the means of external added optics was used to probe freshly excised breast tissues …