Evaluation of Coating Properties of Enteric-Coated Tablets Using Terahertz Pulsed Imaging

Masahiro Niwa, Yasuhiro Hiraishi, Katsuhide Terada

Abstract

Purpose

Enteric coatings are used to reduce gastrointestinal side effects and control the release properties of oral medications. Although widely used, the effect of formulation and process conditions on physicochemical and functional properties of enteric coatings remains unclear.

Methods

Terahertz pulsed imaging (TPI) was employed to evaluate the coat properties of enteric coated tablets (ECTs) with various acid resistance. Other analytic methods, such as loss on drying, scanning electron microscopy and X-ray computed tomography were then used to validate the relationships established among 4 TPI-derived parameters and the physicochemical properties of enteric coatings.

Results

Weight gain measurement did not provide any information to assess acid resistance of enteric coating, whereas four TPI-derived parameters non-destructively reflected the coating properties such as thickness, coat uniformity, density, and water distribution, allowing the identification of the causes of poor acid resistance in certain ECT batches using a single measurement. These parameters also revealed the effect of coating conditions; in particular, coating under dry conditions led to less dense and nonuniform coatings with poor acid resistance.

Conclusion

We demonstrated the utility of TPI to identify structural defects within ECTs with poor acid resistance. TPI-derived parameters can aid in formulation development and quality control of ECTs.

Full Article: http://link.springer.com/article/10.1007/s11095-014-1314-6

Foreign-body detection in dry food using continuous sub-terahertz wave imaging

Gyeongsik Oka, Hyun Jung Kima, Hyang Sook Chunb, Sung-Wook Choia


Abstract

Recently, significant attention has been paid to the food safety issue of foreign-body detection in the food industry. Commercialized X-ray imaging is extensively used for monitoring any foreign bodies that may be embedded in food products. However, foreign bodies such as low- density organic materials cannot be easily observed by conventional detection methods. The sub-terahertz and terahertz wave methods can provide not only the identification of a low-density foreign body but also a safe inspection due to the non-ionizing radiation. In this study, foreign bodies concealed in dry food were detected with a high-resolution raster scan imaging system at 210 GHz in the sub-terahertz wave range. Our raster-scan imaging system using Gaussian beam focusing demonstrated the diffraction-limited spatial resolution in the sub-terahertz wave range. Transmission images of foreign bodies showed better contrast than reflection images. Nondense materials, such as insects and plastics, were observed with the continuous sub-terahertz wave, in contrast to the difficulty in observing them in X-ray transmission imaging.

This study was performed using TeraView's TPS Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://www.sciencedirect.com/science/article/pii/S0956713514000905

Xi-Cheng Zhang Named As American Association for the Advancement of Science Fellow

TeraView would like congratulate Xi-Cheng Zhang on being named a fellow of the American Association for the Advancement of Science for his contributions to the generation and detection of broadband terahertz waves, after being elected by his peers in the association.










Click here for the full article:  http://www.photonics.com/Article.aspx?PID=6&VID=107&IID=723&AID=55400

Orbital-selective metal–insulator transition and gap formation above TC in superconducting Rb1−xFe2−ySe2

Zhe Wang, M. Schmidt, J. Fischer, V. Tsurkan, M. Greger, D. Vollhardt, A. Loidl & J. Deisenhofer

Abstract

Understanding the origin of high-temperature superconductivity in copper- and iron-based materials is one of the outstanding tasks of current research in condensed matter physics. Even the normal metallic state of these materials exhibits unusual properties. Here we report on a hierarchy of temperatures Tc<Tgap<Tmet in superconducting Rb1−xFe2−ySe2 observed by THz spectroscopy (Tc=critical temperature of the superconducting phase; Tgap=temperature below which an excitation gap opens; Tmet=temperature below which a metallic optical response occurs). Above Tmet=90 K the material reveals semiconducting characteristics. Below Tmet a coherent metallic THz response emerges. This metal-to-insulator-type, orbital-selective transition is indicated by an isosbestic point in the temperature dependence of the optical conductivity and dielectric constant at THz frequencies. At Tgap=61 K, a gap opens in the THz regime and then the superconducting transition occurs at Tc=32 K. This sequence of temperatures seems to reflect a corresponding hierarchy of the electronic correlations in different bands.

This study was performed using TeraView's TPS Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://www.nature.com/ncomms/2014/140128/ncomms4202/abs/ncomms4202.html

Terahertz dual-band pass filter using double-layer reformative complementary metamaterial structures

Feng Lan, Ziqiang Yang, Limei Qi, Xi Gao, and Zongjun Shi


Abstract

A dual-band frequency selective surface filter in the THz range that uses double-layer modified complementary metamaterial structures is proposed in this paper. The band-pass filter, with dual bands centered at 0.315 THz and 0.48 THz, uses a single crystal quartz substrate and is simulated, fabricated and measured. To minimize the manufacturing risks of working with fragile and thin quartz substrates, efforts have been made to improve the transmission frequency response features at realizable substrate thicknesses. Experimental results from 0.1 THz to 0.6 THz measured by THz time-domain spectroscopy show excellent agreement with the simulation results.


Full Article: http://www.opticsinfobase.org/ol/upcoming_pdf.cfm?id=202012