Wednesday, 31 May 2017

A Review of Disintegration Mechanisms and Measurement Techniques

Markl, Daniel, and J. Axel Zeitler. "A Review of Disintegration Mechanisms and Measurement Techniques." Pharmaceutical Research 34, no. 5 (2017): 890-917.


Pharmaceutical solid dosage forms (tablets or capsules) are the predominant form to administer active pharmaceutical ingredients (APIs) to the patient. Tablets are typically powder compacts consisting of several different excipients in addition to the API. Excipients are added to a formulation in order to achieve the desired fill weight of a dosage form, to improve the processability or to affect the drug release behaviour in the body. These complex porous systems undergo different mechanisms when they come in contact with physiological fluids. The performance of a drug is primarily influenced by the disintegration and dissolution behaviour of the powder compact. The disintegration process is specifically critical for immediate-release dosage forms. Its mechanisms and the factors impacting disintegration are discussed and methods used to study the disintegration in-situ are presented. This review further summarises mathematical models used to simulate disintegration phenomena and to predict drug release kinetics.

For full paper see

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Tuesday, 30 May 2017

Recent pharmaceutical papers using TeraView’s instruments

Sibik, Juraj, and J. Axel Zeitler. "Direct measurement of molecular mobility and crystallisation of amorphous pharmaceuticals using terahertz spectroscopy." Advanced drug delivery reviews 100 (2016): 147-157.

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.

Markl, Daniel, J. Axel Zeitler, Cecilie Rasch, Maria Høtoft Michaelsen, Anette Müllertz, Jukka Rantanen, Thomas Rades, and Johan Bøtker. "Analysis of 3D Prints by X-ray Computed Microtomography and Terahertz Pulsed Imaging." Pharmaceutical Research (2016): 1-16.

Zeitler, J. Axel. "Pharmaceutical terahertz spectroscopy and imaging." In Analytical Techniques in the Pharmaceutical Sciences, pp. 171-222. Springer New York, 2016.
Sibik, Juraj, and J. Axel Zeitler. "Study of disordered materials by terahertz spectroscopy." Disordered Pharmaceutical Materials (2016).

Bawuah, Prince, Tuomas Ervasti, Nicholas Tan, J. Axel Zeitler, Jarkko Ketolainen, and Kai-Erik Peiponen. "Noninvasive porosity measurement of biconvex tablets using terahertz pulses." International journal of pharmaceutics 509, no. 1 (2016): 439-443.

Ruggiero, Michael T., Juraj Sibik, Roberto Orlando, J. Axel Zeitler, and Timothy M. Korter. "Inside Cover: Measuring the Elasticity of PolylProline Helices with Terahertz Spectroscopy (Angew. Chem. Int. Ed. 24/2016)." Angewandte Chemie International Edition 55, no. 24 (2016): 6796-6796.

Sibik, J., and J. Axel Zeitler. "Terahertz response of organic amorphous systems: experimental concerns and perspectives." Philosophical Magazine 96, no. 7-9 (2016): 842-853.

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.

Ruggiero, Michael T., and J. Axel Zeitler. "Resolving the Origins of Crystalline Anharmonicity Using Terahertz Time-Domain Spectroscopy and ab Initio Simulations." The Journal of Physical Chemistry B 120, no. 45 (2016): 11733-11739.

Bawuah, Prince, Nicholas Tan, Samuel Nana A. Tweneboah, Tuomas Ervasti, J. Axel Zeitler, Jarkko Ketolainen, and Kai-Erik Peiponen. "Terahertz study on porosity and mass fraction of active pharmaceutical ingredient of pharmaceutical tablets." European Journal of Pharmaceutics and Biopharmaceutics 105 (2016): 122-133.

Ruggiero, Michael T., Juraj Sibik, J. Axel Zeitler, and Timothy M. Korter. "Examination of L-Glutamic Acid Polymorphs by Solid-State Density Functional Theory and Terahertz Spectroscopy." The Journal of Physical Chemistry A 120, no. 38 (2016): 7490-7495.

Bawuah, Prince, Mousumi Chakraborty, Tuomas Ervasti, J. Axel Zeitler, Jarkko Ketolainen, Patrick AC Gane, and Kai-Erik Peiponen. "A structure parameter for porous pharmaceutical tablets obtained with the aid of Wiener bounds for effective permittivity and terahertz time-delay measurement." International journal of pharmaceutics 506, no. 1 (2016): 87-92.

Chakraborty, Mousumi, Prince Bawuah, Nicholas Tan, Tuomas Ervasti, Pertti Pääkkönen, J. Axel Zeitler, Jarkko Ketolainen, and Kai-Erik Peiponen. "On the correlation of effective terahertz refractive index and average surface roughness of pharmaceutical tablets." Journal of Infrared, Millimeter, and Terahertz Waves 37, no. 8 (2016): 776-785.

Ruggiero, Michael T., Juraj Sibik, and J. Axel Zeitler. "The influence of intermolecular forces on the terahertz response of amorphous materials." In Infrared, Millimeter, and Terahertz waves (IRMMW-THz), 2016 41st International Conference on, pp. 1-2. IEEE, 2016.

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).

Markl, Daniel, and J. Axel Zeitler. "A Review of Disintegration Mechanisms and Measurement Techniques." Pharmaceutical Research 34, no. 5 (2017): 890-917.

Monday, 29 May 2017

Characterization of prospective explosive materials using terahertz time-domain spectroscopy

Palka, Norbert, Mateusz Szala, and Elzbieta Czerwinska. "Characterization of prospective explosive materials using terahertz time-domain spectroscopy." Applied optics 55, no. 17 (2016): 4575-4583.

We investigated six prospective explosive materials in the terahertz range using time-domain spectroscopy. A family of energetic azotetrazolate salts and two caged nitramines were studied. A number of distinct spectral features were observed in the 0.8–3.2 THz frequency range. In transmission configuration in ambient temperature, we determined the absorption coefficient and the refractive index of the materials, which were compressed as pellets. Because the visibility of some absorption peaks was not clear, additionally we performed characterization of these materials in a temperature range from -175 C to 0 C which resulted in highlighting peaks with low amplitude. Because the considered explosives are insensitive to compression, we also measured them using an attenuated total reflection (ATR) technique, in which sample preparation is easier than with pressed pellets. The absorption peaks measured by ATR agree well with those determined in transmission. This suggests that ATR also can be used for identification of these classes of materials. 

... This pulse has a broad spectrum, which is used for spectroscopic measurements. The commercially available TDS-based TPS 3000 (TeraView) spectrometer in basic configuration worked in the transmission mode in ambient temperature. ...

for full paper see

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Sunday, 28 May 2017

Terahertz transmission vs reflection imaging and model-based characterization for excised breast carcinomas

Bowman, Tyler, Magda El-Shenawee, and Lucas K. Campbell. "Terahertz transmission vs reflection imaging and model-based characterization for excised breast carcinomas."  Biomedical Optics Express 7, no. 9 (2016): 3756-3783.
This work presents experimental and analytical comparison of terahertz transmission and reflection imaging modes for assessing breast carcinoma in excised paraffin-embedded human breast tissue. Modeling for both transmission and reflection imaging is developed. The refractive index and absorption coefficient of the tissue samples are obtained. The reflection measurements taken at the system’s fixed oblique angle of 30° are shown to be a hybridization of TE and TM modes. The models are validated with transmission spectroscopy at fixed points on fresh bovine muscle and fat tissues. Images based on the calculated absorption coefficient and index of refraction of bovine tissue are successfully compared with the terahertz magnitude and phase measured in the reflection mode. The validated techniques are extended to 20 and 30 μm slices of fixed human lobular carcinoma and infiltrating ductal carcinoma mounted on polystyrene microscope slides in order to investigate the terahertz differentiation of the carcinoma with non-cancerous tissue. Both transmission and reflection imaging show clear differentiation in carcinoma versus healthy tissue. However, when using the reflection mode, in the calculation of the thin tissue properties, the absorption is shown to be sensitive to small phase variations that arise due to deviations in slide and tissue thickness and non-ideal tissue adhesion. On the other hand, the results show that the transmission mode is much less sensitive to these phase variations. The results also demonstrate that reflection imaging provides higher resolution and more clear margins between cancerous and fibroglandular regions, cancerous and fatty regions, and fibroglandular and fatty tissue regions. In addition, more features consistent with high power pathology images are exhibited in the reflection mode images.

... work. 2. Methodology. 2.1 Pulsed terahertz system. The measurements in this work make use of the TPS 3000 pulsed terahertz imaging and spectroscopy system from TeraVIEW, Ltd. The system diagram can be seen in Fig. 1 ...

for full paper see
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Saturday, 27 May 2017

Frequency domain penetration loss in the terahertz band

Kokkoniemi, Joonas, Janne Lehtomäki, Vitaly Petrov, Dmitri Moltchanov, and Markku Juntti. "Frequency domain penetration loss in the terahertz band." In Millimeter Waves (GSMM) & ESA Workshop on Millimetre-Wave Technology and Applications, 2016 Global Symposium on, pp. 1-4. IEEE, 2016.

Results on penetration loss measurements in the THz frequencies between 0.1-2 THz are reported. The measurements were conducted with time domain spectroscopy using the TeraView TeraPulse 4000 measurement equipment. We concentrate on the frequency-dependent penetration characteristics of various materials typical for indoor environments, providing both qualitative and quantitative assessment. The results show that the lower end of the THz band (<; 0.5 THz) suffers only modest loss in comparison to the higher frequencies. For the materials considered in this paper, plastic, glass and hard-board, the exact penetration properties are both frequency- and material-dependent. The incident angle to the material increases the penetration loss through increased path length inside the material. The exact values of these losses are provided.

... The measurements were conducted with time domain spectroscopy using the TeraView TeraPulse 4000 measurement equipment. ... II. MEASUREMENT SETUP The measurements were made with the TeraView TeraPulse 4000 device. ...

for full paper see

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Friday, 26 May 2017

Terahertz Time-Domain Spectroscopy for In Situ Monitoring of Ceramic Nuclear Waste Forms

Clark, Braeden M., and S. K. Sundaram. "Terahertz Time-Domain Spectroscopy for In Situ Monitoring of Ceramic Nuclear Waste Forms." Journal of Infrared, Millimeter, and Terahertz Waves 37, no. 10 (2016): 993-1000.

The use of terahertz time-domain spectroscopy (THz-TDS) is presented as a non-contact method for in situ monitoring of ceramic waste forms. Single-phase materials of zirconolite (CaZrTi2O7), pyrochlore (Nd2Ti2O7), and hollandite (BaCs0.3Cr2.3Ti5.7O16 and BaCs0.3CrFeAl0.3Ti5.7O16) were characterized. The refractive index and dielectric properties in THz frequencies demonstrate the ability to distinguish between these materials. Differences in processing methods show distinct changes in both the THz-TDS spectra and optical and dielectric properties of these ceramic phases. The temperature dependence of the refractive index and relative permittivity of pyrochlore and zirconolite materials in the range of 25–200 °C is found to follow an exponential increasing trend. This can also be used to monitor the temperature of the ceramic waste forms on storage over extended geological time scales.
... A Teraview TPS 3000 (Teraview, UK) was used to measure the spectra of the samplesfrom 0.1 to 1.2 THz at room temperature in transmission mode. A reference measurementwas made in pure nitrogen prior to the sample measurements. ...
for full paper see
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Thursday, 25 May 2017

Call for papers Photonics West 2018

Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XI
This conference has an open call for papers:


Abstract Due:
17 July 2017

Author Notification:
25 September 2017

Manuscript Due Date:
3 January 2018


Conference Chairs

Program Committee
  • René Beigang, Technische Univ. Kaiserslautern (Germany)
  • Jianji Dong, Huazhong Univ. of Science and Technology (China)
  • Frank Ellrich, Univ. of Applied Sciences Bingen (Germany)
  • Fabian Friederich, Fraunhofer-Institut für Physikalische Messtechnik (Germany)
  • Robert H. Giles, Univ. of Massachusetts Lowell (United States)
  • R. Jennifer Hwu, InnoSys, Inc. (United States)
Program Committee continued...
Call for
This conference brings together researchers and engineers from academia, industry, and government laboratories to explore and present work in the frequency range covering approximately less than 1 GHz (300 mm) to greater than 3 THz (100 μm). Papers on RF and millimeter technology including advances in wireless communications, radar, lidar, microwave and mm-wave photonics, metamaterials, antennas, phased array radar, modulation, security, monitoring, detection, imaging are encouraged. Papers in photonic-related fields including, but not limited to, radio over fiber (RoF) RF photonics including photonic generation of microwave signals, photonic processing of microwave signals, and photonic distribution of microwave signals and semiconductor (including Si, SiC, SOI, GaAs, GaN, InP, SiGe, diamond, graphene and other materials) RF, mm-wave and terahertz devices and related applications are also encouraged, as well as the hybrid photonic systems and applications. Terahertz (THz) technology deals with the generation and utilization of electromagnetic energy covering what is also known as the sub-millimeter wave region of the spectrum. In this region, which lies between the millimeter wave and far infrared spectral regions, materials exhibit properties that can be exploited to advantage for use over a broad range of important technologies and applications. Papers on terahertz photonics including photonic generation and detection of terahertz waves, THz lasers are also encouraged. 

This conference includes low- to high-power sources, detectors, systems, including both photonic and electronic modulated sources, detectors, and systems. At THz frequencies, the primary difficulty encountered by scientists and engineers working in this field is the lack of convenient and affordable sources and detectors of terahertz radiation, but this difficulty is gradually changing as new sources and improved detectors are being developed as the technology continues to mature and broaden. At RF and millimeter frequencies, more and more hybrid systems are being integrated with photonic devices that enhance the functions, specifications and stabilities tremendously compared to their traditional counterpart systems. The purpose of this conference is to gather scientists and engineers from a diverse set of disciplines, who are interested in either learning more about terahertz and sub-millimeter and millimeter wave and RF technology and related and coupled technologies, or who are contributing to the field through their own research, development, or manufacturing activities. 

Disciplines utilizing terahertz technology include physical chemistry (certain molecules or molecular segments exhibit strong resonances in the 10 cm-1 to 100 cm-1 spectral region), military, and homeland security (terahertz radiation can penetrate clothing and packing materials but is reflected by metals and other materials), biomedical technology (tissue exhibits reflection and absorption properties that change dramatically with tissue characteristics), medical and dental, secure short-distance wireless communications (atmospheric water content prevents terahertz radiation from traveling very far), astronomy (the cold background of the universe exhibits a peak in this spectral region), space communications (where the terahertz region is wide open for use) and other disciplines where new, yet-to-be-discovered applications will undoubtedly come forth. Since the low energy associated with terahertz radiation is expected to be no more harmful than infrared or microwave radiation, safety issues are not expected to limit the use of terahertz radiation at low-power levels. 

Papers on power supplies and electronic power conditioners and associated power protection systems including energy-efficient power supplies are also encouraged. 

Papers are solicited in the following and related areas: 

Terahertz sources

  • solid-state sources, electron-beam sources, vacuum electronics sources, frequency mixers, frequency multipliers, parametric oscillators, hybrids, graphene, FET and HEMT sources, gas lasers, quantum cascade lasers and related sources, p-germanium sources, photoconductive switches, resonant tunneling diodes, backward wave oscillators
  • novel stabilized photonic THz sources
  • fabrication processes
  • systems and systems integration.
RF, sub-millimeter-wave and millimeter-wave sources
  • power sources of all types in the range of 1 GHz to 300 GHz and 300 GHz and higher (i.e. from S-band to the higher end of the millimeter-wave frequencies and all of the sub-millimeter-wave frequency region)
  • novel stabilized photonic RF, millimeter-wave, sub-millimeter-wave sources.
  • bolometers and other thermal detectors, Schottky and other mixers, thermopiles, quantum devices, antenna integrated detectors, heterodyne detection techniques, hybrid detection, direct detection techniques
  • transistor-based detectors including graphene, silicon, III-V, II-VI, nitride-based, etc.
  • theoretical modeling
  • novel detectors.
High-power sources, modules, and systems
  • THz, RF, millimeter-wave and sub-millimeter-wave high power sources
  • THz, RF, millimeter-wave and sub-millimeter-wave modules
  • THz, RF, millimeter-wave and sub-millimeter-wave systems
  • power supplies and support circuits, electronics, optoelectronics, systems.
Terahertz, RF, millimeter-wave, and sub-millimeter-wave passive components
  • optics, lenses, gratings, waveguides, photonic crystal structures and metamaterials, couplers, wire guides, other components.
Materials for THz and GHz devices
  • linear and nonlinear optical materials and devices
  • organic and inorganic source and modulator materials and devices
  • RF, millimeter-wave and sub-millimeter-wave materials, devices and fabrication processes
  • THz material systems
  • silicon (Si)-based
  • silicon carbide (SiC)-based
  • silicon-on-insulator (SOI)-based
  • gallium arsenide (GaAs)-based
  • gallium nitride (GaN)-based
  • indium phosphide (InP)-based
  • silicon germanium (SiGe)-based
  • quantum dot-(QD) based including for QDs for sensors, detectors and sources
  • diamond-based
  • graphene-based
  • other-based.
Enhancements, improvements and advances in RF, millimeter-wave and sub-millimeter wave generation, modulation and detection
  • RF, millimeter-wave and sub-millimeter-wave integrated photonic devices
  • RF, millimeter-wave and sub-millimeter-wave and photonic integration process development
  • RF, millimeter-wave and sub-millimeter-wave performance characterization
  • phased-array and single-element photonically-driven antennas
  • phased-array and single-element antennas, systems, concepts, approaches
  • low-Vp and wide-bandwidth modulators
  • direct-driven millimeter-wave lasers and amplifiers
  • millimeter-wave, sub-millimeter and THz photonic crystal devices and applications
  • RF, millimeter-wave, sub-millimeter-wave and THz photonic up- and down-converters
  • photonic phase locked loops
  • RF, millimeter-wave, sub-millimeter-wave, and THz MMICs
  • RF, millimeter-wave, sub-millimeter-wave, high power solid-state and electronic vacuum devices.
Simulations and modeling
  • simulations and/or modeling of RF devices, components, and/or systems
  • simulations and/or modeling of millimeter-wave devices, components, and/or systems
  • simulations and/or modeling of sub-millimeter-wave devices, components, and/or systems
  • simulations and/or modeling of THz devices, components, and/or systems
  • modeling of optical components, optical systems, imaging systems, wave propagation, modes, Gaussian beam characteristics, couplers, antennas, performance limitations, software designs.
  • terahertz and/or sub-millimeter spectroscopy, DNA segment identification, cell abnormalities, cancer identification and screening, imaging, medical and dental detection
  • identification of biological and chemical detection and fingerprinting
  • identification of hazardous, explosive, and/or dangerous materials
  • identification of chemical or biological threats
  • scalar and vector network analysis at sub-millimeter and terahertz frequencies
  • measurement techniques at sub-millimeter, millimeter, and terahertz frequencies
  • identification of organic and inorganic compounds using terahertz and/or sub-millimeter wave spectroscopy
  • high-speed and/or high-resolution spectroscopic techniques, methods, approaches
  • novel approaches, systems, designs, techniques, reflection, sensitivity, applications.
Biomedical applications
  • DNA identification, burn analysis, tissue abnormality identification, pharmaceutical, dentistry, medical, clinical, commercial applications
  • cancer, burn, and/or water content detection; high sensitivity, high contrast, etc.
  • biological and/or physiological aspects and/or related effects of RF, millimeter-wave, sub-millimeter-wave and/or THz
  • imaging techniques, methods, hardware design, strategies, technologies and techniques.
Communication and sensing systems
  • terahertz, RF, millimeter-wave and sub-millimeter-wave communications, media characteristics, wireless communications, inspection systems, detection systems, screening systems
  • RF, millimeter, sub-millimeter-wave and microwave links
  • RF, millimeter-wave, sub-millimeter-wave photonic communication and sensing systems
  • Internet of things (IOT) sensors, detectors and communication interfaces, protocols and implementations including but not limited to wireless sensors and wireless communications.
Imaging and security
  • RF imaging devices, components, and/or systems
  • millimeter-wave imaging devices, components, and/or systems
  • sub-millimeter-wave imaging devices, components, and/or systems
  • THz imaging devices, components, and/or systems
  • RF, millimeter-wave and sub-millimeter-wave active and passive imaging systems
  • x-ray imaging including components, systems, power supplies, applications, techniques, etc.
Astronomy and space and other areas of photonics, light, and matter
  • imaging techniques, ultra-sensitive detection, applications, programs
  • satellite communications
  • space based electronics and devices
  • satellite components and systems
  • space and satellite qualifications and testing
  • radiation hard electronics
  • high-energy physics and related topics
  • fusion and related topics
  • fission and related topics.
  • new or novel terahertz, RF, millimeter-wave and sub-millimeter, microwave concepts, systems, applications
  • new or novel developments in THz or sub-millimeter waves including teaching, instruction, course offerings, simulations, conceptional and/or experimental procedures, implementations, concepts, etc.
Power supplies and electronic power conditioners
  • high-power power supplies
  • low- and ultra-low-power power supplies
  • low-noise power supplies
  • high- and ultra-efficient power supplies
  • associated power protection systems
  • energy-efficient power supplies
  • novel designs and architectures
  • specialized power electronics
  • portable power supplies
  • power supplies tailored for photonics and/or RF, mm-wave and/or THz applications
  • power supplies for lighting applications including solid state lighting such as LEDs, OLEDs and quantum dots.
Organic electronics
  • DC and low frequency
  • high frequency
  • novel designs and architectures
  • passive and active addressable arrays
  • low power
  • modulated configurations
  • sensing, detection and/or emitting
  • organic light emitting diodes and associated electronics
  • lighting therapy using solid state lighting including OLEDs.

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).

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

... 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

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

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

... 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

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.


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. ...

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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.


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.
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.
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.
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
for more information about TeraView see

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).
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.

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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).


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.

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