Wednesday, 24 May 2017

Structural changes of Bombyx mori fibroin from silk gland to fiber as evidenced by Terahertz spectroscopy and other methods

Wu, Xu, Xiaodong Wu, Min Shao, and Bin Yang. "Structural changes of Bombyx mori fibroin from silk gland to fiber as evidenced by Terahertz spectroscopy and other methods." International Journal of Biological Macromolecules (2017).

Abstract
Here we investigated the structural changes of silk fibroin during Bombyx mori silkworm spinning and reconstitution process. X-ray diffraction, Fourier transform infrared spectroscopy, polarized optical microscopy, and terahertz (THz) spectroscopy were applied to monitor the structural features of silk fibroin from posterior, middle silk glands, to cocoons, and then to reconstituted silk. Results show that from silk gland to cocoon, fibroin experiences a significant transformation in crystal structure from a typical silk I, to a silk I-rich mixed structure, and finally to a typical silk II state, accompanied with a change in secondary structure from α-helix and random coil structures to preferential orientation β-sheets. Compared with natural silk fibroins, the reconstituted silk fibroin lacks β-sheet conformation and orientation crystallization. Terahertz spectroscopy readily follows these silk fibroin structural changes. Two characteristic peaks for silk fibroin is observed in 2–10 THz. Their strength ratio is strongly correlated with the β-sheet conformation. The absorbance properties in 0.2–2.0 THz also significantly change as a function of changing their crystal structures caused by diverse sources. All of these observations will help in the study of overall structure in silk fibroin to understand more completely the fibroin assembly process in natural spinning and reconstitution process.

for full paper see http://www.sciencedirect.com/science/article/pii/S0141813017311303


... THz spectra in the frequency range of 0.2-2.5 THz were recorded on a TPS spectra 3000 (TeraView Ltd., UK) equipped with an Erbium-doped fiber laser  ...


for more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411

Tuesday, 23 May 2017

Tuning the plasmon resonance and work function of laser-scribed chemically doped graphene

Anis, Badawi, A. Abouelsayed, Amany M. Sawy, and Ahmed SG Khalil. "Tuning the plasmon resonance and work function of laser-scribed chemically doped graphene." Carbon 120 (2017): 44-53

Abstract
Here, we present terahertz spectroscopy study on laser scribed graphene (LSG) doped with monovalent Na+ cations (LSG/MNCs), silver nanoparticles (LSG/SNPs), and silver nanowires (LSG/SNWs), in the frequency range from 0.06 to 3 THz. The terahertz absorption peaks observed at ≈ 1.98, 2.06, 2.73, and 3.06 THz are attributed to the collective oscillations of free carriers in LSG, LSG/MNCs, LSG/SNPs, and LSG/SNWs, respectively. The plasmon peak position and Fermi energy Ef of LSG doped samples are shifted to higher energy compared to undoped LSG indicating the n-doping of graphene. The σdc and the charges concentration n show higher values in case of LSG/SNWs compared to other doped samples. This is mainly because silver nanowires create conducting paths between the neighboring graphene sheets. The charge density n   of the LSG and LSG doped samples versus Ef, scales as n1/4, illustrates power-law behavior which is the signature of the two-dimensional massless Dirac electrons.

for full paper see http://www.sciencedirect.com/science/article/pii/S0008622317304554

... NA objective). All terahertz measurements were carried out using TPS spectra 3000 system (Teraview Ltd. England) model by using the ATR unit (35) with silicon crystal and under Nitrogen gas N 2 N 2 purging. The measuring ...

for more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411

Monday, 22 May 2017

Terahertz spectroscopy and solid-state density functional theory calculations of structural isomers: Nicotinic acid, isonicotinic acid and 2-picolinic acid.

Ding, L., Fan, W. H., Chen, X., Chen, Z. Y., & Song, C. (2017). Terahertz spectroscopy and solid-state density functional theory calculations of structural isomers: Nicotinic acid, isonicotinic acid and 2-picolinic acid. Modern Physics Letters B, 1750149.

Abstract

We report, for the first time to our knowledge, the terahertz (THz) spectra of isonicotinic acid and 2-picolinic acid. The distinct THz spectral differences among these two isomers and nicotinic acid have also been observed, indicating that the THz vibrational modes are highly sensitive to the structural differences even in similar molecular crystals. Besides, solid-state density functional theory calculations reveal better qualitative agreement with the measured absorption features, which are related to the molecular vibrations of nicotinic acid and isonicotinic acid. As for 2-picolinic acid, the calculation based on the primitive cell reproduces the absorption features at 1.46, 1.82 and 2.46 THz originating from intermolecular vibrations. These results suggest that THz spectra can identify the complex intermolecular interactions even in similar molecular crystals, which shows potential applications in identifying isomers in food and pharmaceutical production.


... 2. Experimental and Theoretical Methods The THz absorption spectra of three isomers, nicotinic acid, isonicotinic acid and 2-picolinic acid, were measured by using a spectrometer TPS-3000 (Teraview Ltd., UK) in the range of 0.1–4.0 THz with resolution of 0.03 THz. ...



Read More: http://www.worldscientific.com/doi/abs/10.1142/S0217984917501494


for more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411

Sunday, 21 May 2017

Non-destructive determination of disintegration time and dissolution in immediate release tablets by terahertz transmission measurements

Markl, D., Sauerwein, J., Goodwin, D. J., van den Ban, S., & Zeitler, J. A. (2017). Non-destructive determination of disintegration time and dissolution in immediate release tablets by terahertz transmission measurements. Pharmaceutical Research34(5), 1012-1022.


ABSTRACT
Purpose

The aim of this study was to establish the suitability of terahertz (THz) transmission measurements to accurately measure and predict the critical quality attributes of disintegration time and the amount of active pharmaceutical ingredient (API) dissolved after 15, 20 and 25 min for commercial tablets processed at production scale.
Methods
Samples of 18 batches of biconvex tablets from a production-scale design of experiments study into exploring the design space of a commercial tablet manufacturing process were used. The tablet production involved the process steps of high-shear wet granulation, fluid-bed drying and subsequent compaction. The 18 batches were produced using a 4 factor split plot design to study the effects of process changes on the disintegration time. Non-destructive and contactless terahertz transmission measurements of the whole tablets without prior sample preparation were performed to measure the effective refractive index and absorption coefficient of 6 tablets per batch.
Results
The disintegration time (R2 = 0.86) and API dissolved after 15 min (R2 = 0.96) linearly correlates with the effective refractive index, neff, measured at terahertz frequencies. In contrast, no such correlation could be established from conventional hardness measurements. The magnitude of neff represents the optical density of the sample and thus it reflects both changes in tablet porosity as well as granule density. For the absorption coefficient, αeff, we observed a better correlation with dissolution after 20 min (R2 = 0.96) and a weaker correlation with disintegration (R2 = 0.83) compared to neff.
Conclusion
The measurements of neff and αeff provide promising predictors for the disintegration and dissolution time of tablets. The high penetration power of terahertz radiation makes it possible to sample a significant volume proportion of a tablet without any prior sample preparation. Together with the short measurement time (seconds), the potential to measure content uniformity and the fact that the method requires no chemometric models this technology shows clear promise to be established as a process analyser to non-destructively predict critical quality attributes of tablets.
... Terahertz time-domain measurements of 6 tablets per batch (108 tablets in total) were acquired using a TeraPulse 4000 (TeraView Ltd., Cambridge, UK) in combination with a transmission module at an instrument resolution of 0.01 ps over a total range of 150 ps for each time ...

For full paper see https://link.springer.com/article/10.1007/s11095-017-2108-4
for more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411


Saturday, 20 May 2017

On the role of API in determining porosity, pore structure and bulk modulus of the skeletal material in pharmaceutical tablets formed with MCC excipient

Ridgway, Cathy, Prince Bawuah, Daniel Markl, J. Axel Zeitler, Jarkko Ketolainen, Kai-Erik Peiponen, and Patrick Gane. "On the role of API in determining porosity, pore structure and bulk modulus of the skeletal material in pharmaceutical tablets formed with MCC excipient." International Journal of Pharmaceutics (2017).
Abstract
The physical properties and mechanical integrity of pharmaceutical tablets are of major importance when loading with active pharmaceutical ingredient(s) (API) in order to ensure ease of processing, control of dosage and stability during transportation and handling prior to patient consumption. The interaction between API and excipient, acting as functional extender and binder, however, is little understood in this context. The API indomethacin is combined in this study with microcrystalline cellulose (MCC) at increasing loading levels. Tablets from the defined API/MCC ratios are made under conditions of controlled porosity and tablet thickness, resulting from different compression conditions, and thus compaction levels. Mercury intrusion porosimetry is used to establish the accessible pore volume, pore size distribution and, adopting the observed region of elastic intrusion-extrusion at high pressure, an elastic bulk modulus of the skeletal material is recorded. Porosity values are compared to previously published values derived from terahertz (THz) refractive index data obtained from exactly the same tablet sample sets. It is shown that the elastic bulk modulus is dependent on API wt% loading under constant tablet preparation conditions delivering equal dimensions and porosity. The findings are considered of novel value in respect to establishing consistency of tablet production and optimisation of physical properties.

for full paper see http://www.sciencedirect.com/science/article/pii/S0378517317303393

or more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411

Friday, 19 May 2017

Use of a handheld terahertz pulsed imaging device to differentiate benign and malignant breast tissue

M. Grootendorst, A. Fitzgerald, S. Brouwer de Koning, A. Santaolalla, A. Portieri, M. Van Hemelrijck, M. Young, J. Owen, M. Cariati, M. Pepper, V. Wallace, S. Pinder, and A. Purushotham, "Use of a handheld terahertz pulsed imaging device to differentiate benign and malignant breast tissue," Biomed. Opt. Express  8, 2932-2945 (2017).


Abstract

Article CoverSince nearly 20% of breast-conserving surgeries (BCS) require re-operation, there is a clear need for developing new techniques to more accurately assess tumor resection margins intraoperatively. This study evaluates the diagnostic accuracy of a handheld terahertz pulsed imaging (TPI) system to discriminate benign from malignant breast tissue ex vivo. Forty six freshly excised breast cancer samples were scanned with a TPI handheld probe system, and histology was obtained for comparison. The image pixels on TPI were classified using (1) parameters in combination with support vector machine (SVM) and (2) Gaussian wavelet deconvolution in combination with Bayesian classification. The results were an accuracy, sensitivity, specificity of 75%, 86%, 66% for method 1, and 69%, 87%, 54% for method 2 respectively. This demonstrates the probe can discriminate invasive breast cancer from benign breast tissue with an encouraging degree of accuracy, warranting further study.

for information about TeraView's products see http://www.azom.com/equipment-details.aspx?EquipID=4411

Thursday, 18 May 2017

Diffraction Effects in Terahertz Band - Measurements and Analysis

Kokkoniemi, J., Rintanen, P., Lehtomaki, J., & Juntti, M. (2016, December). Diffraction Effects in Terahertz Band-Measurements and Analysis. In Global Communications Conference (GLOBECOM), 2016 IEEE (pp. 1-6). IEEE.

Abstract:
Measurement results and related analysis on the diffraction properties in the THz frequency band are reported. The results are given on the bands from approximately 100 GHz to 2 THz. Measurements were made for knife-edge diffraction, and diffraction through single and double slits. The diffraction effects are of interest in modeling the non-line-of-sight (NLOS) paths in the THz band. Therefore, the measurement results have significant practical value for designing the real communication systems. The theoretical models from the literature show a very good match to the measurement results. The key finding is that wireless communication links in the THz band can be established even in the shadows of the objects through diffraction with reasonable path loss. This also indicates another path in the THz multipath environment, as the previous studies have shown the THz radiation is capable on penetration, reflections, and scattering.

... Those studies also showed good agreement of the measurement data to the theories. We measure with a much larger band by utilizing the time domain spectroscopy for the channel sounding  (0.1–2.0 THz) with TeraView TeraPulse 4000 measurement device. ...
for full paper see http://ieeexplore.ieee.org/abstract/document/7841734/
or more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411

Wednesday, 17 May 2017

Terahertz time-domain spectroscopy and imaging of archival documents

Bardon, TB(2016) Terahertz time-domain spectroscopy and imaging of archival documents. Doctoral thesis, UCL (University College London). 
Abstract
Image result for Bardon ucl Terahertz time-domain spectroscopyThis project explores the scope of the cutting-edge terahertz time-domain (THz-TD) spectroscopy and imaging as a potentially non-invasive diagnostic and imaging tool for the study of archival documents. While some previous research successfully uncovered drawings or texts from inaccessible layers in heritage artefacts using THz-TD imaging, inscriptions in some historical documents investigated in this project could not be revealed with this technology. This work therefore explores the parameters influencing contrast in terahertz images of historical documents, in order to objectively inform curators when terahertz technologies are likely to give well-contrasted images of inscriptions in a complex archival document and are a useful non-invasive alternative to current digitization processes. These parameters include the dispersive refractive indices and absorption coefficients of various archival materials, the physical structure of documents, as well as the choice of signal parameters and terahertz imaging systems or configurations used to produce the terahertz image. This investigation was conducted systematically using historically informed models and historical documents, with different THz-TD set-ups and accessories, and complementary analytical and imaging tools. THz-TD imaging was found to be a useful non-invasive digitization technology for documents containing lamp black, carbon black or graphite but not for documents containing bistre, sepia, verdigris or Prussian blue. While deconvolution of the terahertz signal helps in distinguishing between layers in a complex document, it can also decrease the image contrast of inscriptions. The results further reveal the potential and limitations of the use of THz-TD spectroscopy for material identification in archival collections. Minium, vermilion and corrosive iron gall inks with excess iron(II) sulfate have a characteristic spectral signature below 3 THz, which can be extracted from the surface of an inked paper or parchment sheet. The project was developed in collaboration with TeraView Ltd, Cambridge, and Nationaal Archief (Netherlands).
for full Ph.D. Thesis is http://discovery.ucl.ac.uk/1502085/
or more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411

Tuesday, 16 May 2017

Measurements on penetration loss in terahertz band

Kokkoniemi, Joonas, Janne Lehtomäki, and Markku Juntti. "Measurements on penetration loss in terahertz band." In Antennas and Propagation (EuCAP), 2016 10th European Conference on, pp. 1-5. IEEE, 2016


Abstract:
Results on penetration measurements through different materials at the terahertz band (0.1 - 10 THz) are reported. These materials include common materials found at any home or office, i.e., plastic, glass, paper, and hardboard. The measurements were conducted with terahertz time domain spectroscopy (THz-TDS) method and with the TeraView TeraPulse measurement device. The results show that the THz radiation penetrates through these materials and the losses through the materials are small enough to theoretically allow communication through them. However, the propagation through the materials does not only introduce loss, but delay as well. It may cause problems in delay sensitive detection, e.g., the symbol to be detected may slide off the detection window if the signal is shadowed by an object. Also, it can cause inter-symbol interference if the symbol separation is small. Furthermore, we show frequency domain results for the penetration which show that the higher frequencies are more prone to the penetration loss than the lower end of the THz band.
for full paper see http://ieeexplore.ieee.org/abstract/document/7481176/


for more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411

Monday, 15 May 2017

Manufacturing and terahertz wave modulation properties of graphene/Y3Fe5O12/Si hybrid nanostructures

Zhang, Dainan, Lichuan Jin, Tianlong Wen, Yulong Liao, Qiye Wen, Huaiwu Zhang, and Qinghui Yang. "Manufacturing and terahertz wave modulation properties of graphene/Y 3 Fe 5 O 12/Si hybrid nanostructures." Composites Part B: Engineering 111 (2017): 10-16.

Abstract

In this paper, graphene/Bi:YIG(50 nm)/p-Si hybrid nanostructured graphene field effect transistors (GFETs) were fabricated at the first time. A 50 nm Bi-doped Y3Fe5O12 (Bi: YIG) garnet film was deposited using a vacuum RF sputtering technique, forming a nanometer thick high-K gate layer. With reduced Coulomb impurity scattering and cavity effect, a significantly improved modulation depth of 15% and modulation speed of 200 kHz have been successfully achieved with the YIG based GFETs. Moreover, since YIG is a magnetic insulator, we characterized and discussed the possibility of magnetic control of these graphene/Bi:YIG/p-Si hybrid structured THz modulators. A 7% enhancement of THz transmittance with applying an in-plane 22 Oe magnetic field has been revealed in the hybrid nanostructure, which provides a new route to realize electrical/magnetic functional modulators. The results show that graphene/Y3Fe5O12/Si hybrid nanostructures with good THz modulation performances have great potential for THz nondestructive evaluation as well as imaging applications.

For full paper see http://www.sciencedirect.com/science/article/pii/S1359836816319539

for more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411

Sunday, 14 May 2017

A terahertz in-line polarization converter based on through-via connected double layer slot structures

Woo, Jeong Min, Sajid Hussain, and Jae-Hyung Jang. "A terahertz in-line polarization converter based on through-via connected double layer slot structures." Scientific Reports 7 (2017).

Abstract

A terahertz (THz) in-line polarization converter that yields a polarization conversion ratio as high as 99.9% is demonstrated at 1 THz. It has double-layer slot structures oriented in orthogonal directions that are electrically connected by 1/8-wavelngth-long through-via holes beside the slot structures. The slots on the front metal-plane respond to the incident THz wave with polarization orthogonal to the slots and generates a circulating surface current around the slots. The surface current propagates along a pair of through-via holes that function as a two-wire transmission line. The propagating current generates a surface current around the backside slot structures oriented orthogonal to the slot structures on the front metal layer. The circulating current generates a terahertz wave polarized orthogonal to the backside slot structures and the 90° polarization conversion is completed. The re-radiating THz wave with 90° converted polarization propagates in the same direction as the incident THz wave.

for full paper see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5314401/

for more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411

Saturday, 13 May 2017

Methods for Assessment of Composite Aerospace Structures

Wandowski, T., P. Malinowski, M. Radzienski, S. Opoka, and W. Ostachowicz. "Methods for Assessment of Composite Aerospace Structures." In Smart Structures and Materials, pp. 227-244. Springer International Publishing, 2017

Abstract
In this paper results of detection and localization of artificially initiated delaminations in small carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymers (GFRP) samples were presented. The first method was electromechanical impedance method (EMI). In the research real part of electrical impedance (resistance) was measured. Delamination in CFRP sample caused frequency shift of certain resonance frequencies visible in resistance characteristic. The second method was based on scanning laser vibrometry. It is a noncontact technique that allows to measure vibration of structure excited by piezoelectric transducer. During research standing waves (vibration–based method) and propagating waves (guided waves–based method) were registered for CFRP sample. In the vibration–based method, the frequency shifts of certain resonance frequencies were analyzed. In guided waves-based technique, the interaction of elastic waves with delamination can be seen in the RMS energy map. The third method is based on terahertz spectroscopy. Equipment utilizes an electromagnetic radiation in the terahertz range (0.1–3 THz). During research time signals as well as sets of time signals creating B–scans and C–scans were analysed. The obtained results showed that the THz spectroscopy technique can detect and visualize delamination between the GFRP layers.

for full paper see https://link.springer.com/chapter/10.1007/978-3-319-44507-6_12

for more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411

Friday, 12 May 2017

Mechanical and laser impact effects on woven composites with hemp or glass fibres

Touchard, Fabienne, Michel Boustie, Laurence Chocinski-Arnault, Pedro Pascual González, Laurent Berthe, Davi de Vasconcellos, Luigi Sorrentino, Pawel Malinowski, and Wieslav Ostachowicz. "Mechanical and laser impact effects on woven composites with hemp or glass fibres." International Journal of Structural Integrity 8, no. 3 (2017).

Abstract

The aim of this paper is to study the damage induced in ‘green’ and synthetic composites under impact loading.
The study was focused on epoxy based composites reinforced with woven hemp or glass fibres. Six assessment techniques were employed in order to analyse and compare impact damages: eye observation, back face relief, terahertz spectroscopy, laser vibrometry, X-ray micro-tomography and microscopic observations.
Different damage detection thresholds for each material and technique were obtained. 
Damage induced by mechanical and laser impacts showed relevant differences but the damage mechanisms are similar in both types of impact: matrix cracks, fibre failure, debonding at the fibres/matrix interface and delamination. Damage shape on back surfaces is similar after mechanical or laser impacts but differences were detected inside samples.
The combination of these six diagnoses provides complementary information on the damage induced by mechanical or laser impacts in the studied green and synthetic composites.

for full paper see http://www.emeraldinsight.com/doi/abs/10.1108/IJSI-06-2016-0022

for information about TeraView's products see http://www.azom.com/equipment-details.aspx?EquipID=4411

Thursday, 11 May 2017

Enabling simultaneous cooling and data transmission in the terahertz band for board-to-board communications

Petrov, Vitaly, Joonas Kokkoniemi, Dmitri Moltchanov, Janne Lehtomäki, and Yevgeni Koucheryavy. "Enabling simultaneous cooling and data transmission in the terahertz band for board-to-board communications." Physical Communication 22 (2017): 9-18.


Abstract

A system enabling simultaneous cooling and board-to-board communications is proposed and analyzed. It is shown that hollow pipes used in computer cooling systems can be applied for communications with extreme data rates at distances up to tens of centimeters. This is done by using wireless communications in the terahertz frequency band, 0.1–10 THz. The experiments were performed in order to observe how straight and curved pipes of different diameters and lengths affect THz signals propagating inside the pipes. The measured pulses were recorded and used in numerical evaluation of bit error rate and throughput taking into account the effect of all possible combinations of Nprevious symbols. The numerical results show the dependency of the intersymbol interference on the delay profile of the channel and on the symbol period. The results demonstrate that even with simple on–off keying modulation the throughput reaches few terabits per second with qualitatively low bit error rates. This enables communications between rate-hungry electronics inside computers such as central and graphical processing units while simultaneously providing the cooling functionality.

for full paper see http://www.sciencedirect.com/science/article/pii/S1874490716301999

see more information see http://www.azom.com/equipment-details.aspx?EquipID=4411

Wednesday, 10 May 2017

Ultrathin Film Broadband Terahertz Antireflection Coating Based on Impedance Matching Method

Ding, L., Wang, X., Ang, N. S. S., Lu, C., Suresh, V., Chua, S. J., & Teng, J. (2017). Ultrathin Film Broadband Terahertz Antireflection Coating Based on Impedance Matching Method. IEEE Journal of Selected Topics in Quantum Electronics23(4), 1-8.

Abstract:

Broadband antireflection coatings for terahertz (THz) components are extremely important in the application of THz technology. We present an in-depth materials study on the broadband antireflection design based on the concept of impedance matching. Several selected conductive materials are tested and compared. They can all be used as THz broadband antireflection coatings regardless of their nature of conductivity. We provide a facile method to approximately predict the impedance matching condition for various conductive materials based on their dc real conductivity. The theoretical predications are in good agreement with experimental results and published data. Doped metal oxides or polymers are recommended as good candidates for fabricating antireflection coating in THz range. The thickness-independent dc real conductivity enables better control on individual tuning parameter-film thickness. Given a substrate, THz transmission in antireflection coating has a theoretical upper limit which is further reduced with non-negligible imaginary conductivity.
for full paper see http://ieeexplore.ieee.org/abstract/document/7745979/
for more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411

Tuesday, 9 May 2017

THz spatial filter employing bimaterial switching for temperature sensing

Sanphuang, V., Nahar, N. K., & Volakis, J. L. (2017). THz spatial filter employing bimaterial switching for temperature sensing. Microwave and Optical Technology Letters59(1), 168-171

ABSTRACT

We propose a THz spatial filter using frequency selective surfaces (FSS) integrated with bimaterial actuator for temperature sensing. The actuator consists of two materials that have different thermal expansion rates and controlled based on temperature tuning. In this paper, we develop reconfigurable filters operating in the THz band that subjected to the temperature gradient of the surrounding medium. The filter was fabricated using gold to create the filter pattern printed on silicon substrate. SiO2 and Al were used as bimaterial actuators. The equivalent circuit was extracted and demonstrated. Measurement and simulation results show good agreement with excellent transmittance (>80%). According to different gap of the actuator (up and down), the peak frequency is varied from 0.36 to 0.34 THz.

For full paper see http://onlinelibrary.wiley.com/doi/10.1002/mop.30254/full

For more information about TeraView see http://www.azom.com/equipment-details.aspx?EquipID=4411

Monday, 8 May 2017

Terahertz Quantitative Nondestructive Evaluation of Failure Modes in Polymer-Coated Steel

Dong, J., Locquet, A., & Citrin, D. S. (2017). Terahertz Quantitative Nondestructive Evaluation of Failure Modes in Polymer-Coated Steel. IEEE Journal of Selected Topics in Quantum Electronics23(4), 1-7.


Abstract:
Terahertz reflective imaging is applied to characterize the failure modes in a polymer coating on a steel plate. The coating was initially scratched, then after accelerated aging, several types of failure have occurred. In order to resolve the thin coating (~50 μm), terahertz frequency-wavelet domain deconvolution is implemented. With the deconvolved signals, the temporally overlapping echoes of the incident, roughly single-cycle terahertz pulse are clearly resolved, and three important failure modes, viz. corrosion, delamination, and blistering, are characterized quantitatively. Terahertz images in three dimensions clearly exhibit the coating thickness distribution across the entire damaged coating, highlighting the terahertz features associated with different failure modes, thus demonstrating that terahertz imaging can be considered as an effective modality for characterizing damage mechanisms in polymer coatings on metals.


....................EXPERIMENT The THz time-domain reflection imaging system (Teraview TPS Spectra 3000), which is employed in this study, is shown Page 3. ...........................

For more information about TeraView  see http://www.azom.com/equipment-details.aspx?EquipID=4411

Sunday, 7 May 2017

Characterization of the Pore Structure of Functionalized Calcium Carbonate Tablets by Terahertz Time-Domain Spectroscopy and X-Ray Computed Microtomography

Markl, D., Wang, P., Ridgway, C., Karttunen, A. P., Chakraborty, M., Bawuah, P., ... & Zeitler, J. A. (2017). Characterization of the Pore Structure of Functionalized Calcium Carbonate Tablets by Terahertz Time-Domain Spectroscopy and X-Ray Computed Microtomography. Journal of Pharmaceutical Sciences.

Abstract

Performing Transmission and Reflection Measurements with the TeraPulse 4000Novel excipients are entering the market to enhance the bioavailability of drug particles by having a high porosity and, thus, providing a rapid liquid uptake and disintegration to accelerate subsequent drug dissolution. One example of such a novel excipient is functionalized calcium carbonate, which enables the manufacture of compacts with a bimodal pore size distribution consisting of larger interparticle and fine intraparticle pores. Five sets of functionalized calcium carbonate tablets with a target porosity of 45%-65% were prepared in 5% steps and characterized using terahertz time-domain spectroscopy and X-ray computed microtomography. Terahertz time-domain spectroscopy was used to derive the porosity using effective medium approximations, that is, the traditional and an anisotropic Bruggeman model. The anisotropic Bruggeman model yields the better correlation with the nominal porosity (R2 = 0.995) and it provided additional information about the shape and orientation of the pores within the powder compact. The spheroidal (ellipsoids of revolution) shaped pores have a preferred orientation perpendicular to the compaction direction causing an anisotropic behavior of the dielectric porous medium. The results from X-ray computed microtomography confirmed the nonspherical shape and the orientation of the pores, and it further revealed that the anisotropic behavior is mainly caused by the interparticle pores. The information from both techniques provides a detailed insight into the pore structure of pharmaceutical tablets. This is of great interest to study the impact of tablet microstructure on the disintegration and dissolution performance.

for full paper see http://www.sciencedirect.com/science/article/pii/S0022354917301430
For more information see http://www.azom.com/equipment-details.aspx?EquipID=4411

Saturday, 6 May 2017

Terahertz sensor used as non-contact paint thickness measurement at Focus2017



Padraig O'Kelly from talked about non-contact paint thickness measurement on 4th May at  on the uses of terahertz sensors in the car paint industry. See for more information about the application at http://www.azom.com/article.aspx?ArticleID=13544

Plasmonic behavior of III-V semiconductors in far-infrared and terahertz range

Chochol, Jan, Kamil Postava, Michael Čada, Mathias Vanwolleghem, Martin Mičica, Lukáš Halagačka, Jean-François Lampin, and Jaromír Pištora. "Plasmonic behavior of III-V semiconductors in far-infrared and terahertz range." Journal of the European Optical Society-Rapid Publications 13, no. 1 (2017): 13.

Abstact

Background

In this article, III-V semiconductors are proposed as materials for far-infrared and terahertz plasmonic applications. We suggest criteria to estimate appropriate spectral range for each material including tuning by fine doping and magnetic field.

Methods

Several single-crystal wafer samples (n,p-doped GaAs, n-doped InP, and n,p-doped and undoped InSb) are characterized using reflectivity measurement and their optical properties are described using the Drude-Lorentz model, including magneto-optical anisotropy.

Results

The optical parameters of III-V semiconductors are presented. Moreover, strong magnetic modulation of permittivity was demonstrated on the undoped InSb crystal wafer in the terahertz spectral range. Description of this effect is presented and the obtained parameters are compared with a Hall effect measurement.

Conclusion

Analyzing the phonon/free carrier contribution to the permittivity of the samples shows their possible use as plasmonic materials; the surface plasmon properties of semiconductors in the THz range resemble those of noble metals in the visible and near infrared range and their properties are tunable by either doping or magnetic field.


... The first one is the terahertz time-domain spectrometer TPS Spectra 3000 from TeraView Co.,  measuring in the THz range of 2-100 cm−1 .......


for full paper see https://link.springer.com/article/10.1186/s41476-017-0044-x

For more information about TeraView see http://www.azom.com/suppliers.aspx?SupplierID=12145

Friday, 5 May 2017

Preparation, characterization, Raman, and terahertz spectroscopy study on carbon nanotubes, graphene nano-sheets, and onion like carbon materials

Abouelsayed, A., Anis, B., Hassaballa, S., Khalil, A. S., Rashed, U. M., Eid, K. A., & Al-Ashkar, E. (2017). Preparation, characterization, Raman, and terahertz spectroscopy study on carbon nanotubes, graphene nano-sheets, and onion like carbon materials. Materials Chemistry and Physics.

Abstract

We present the optical properties of carbon nanotubes, graphene nanosheets, and onion like carbon (OLC) samples with different cages size in wide frequency range from 0.06 to 1650 THz. The samples were characterized by high resolution transmission electron microscope (HRTEM), Raman, and UV–Vis-IR-THz spectroscopy. The broad absorption bands centered at around 10, 3, 2.5, 1.5, and 1.8 THz for SWCNTs, MWCNTs, graphene nanosheets, large cages (OLC1), and small cages (OLC2) samples, respectively, are assigned to plasmon resonance due to the localization of free carriers in a finite length. For SWCNTs, both the plasmon band position and the Drude weight (D) are located at higher values as compared with MWCNTs, graphene nanosheets, and OLC sample, suggesting that the dimensionality of the system plays a major role regarding the carrier mobility of the graphene structure. The differences in the estimated values of D, the Fermi energy (Ef), and density of carriers (N) in case of OLC samples can be due to the variation in sizes of the cages and the variation of the defects in the structure of the outermost layers of cages, where each cages consist of multi-layers of graphene enclosed one into another.

All terahertz measurements were carried out using (TPS spectra 3000 system (Teraview Ltd. ...

For more information about TeraView see http://www.azom.com/suppliers.aspx?SupplierID=12145

For full paper see http://www.sciencedirect.com/science/article/pii/S0254058416309774