Abstract
Micro-pyramid shaped subwavelength structures (SWSs) were integrated on
both sides of a terahertz (THz) filter by means of stamping methods. Two
silicon-based stamping molds fabricated via crystallographic wet etching
were utilized to replicate SWSs onto cyclo-olefin copolymer (COC) films
coated onto both sides of a THz filter at the same time. The SWSs act
as an broadband antireflection coating to reduce the surfacereflection loss
in a frequency range of 0.2 THz to 1.4 THz. Compared to a THz filter
without SWSs, the filter integrated with double-sided SWSs exhibits a
low standing wave ratio inside the substrate and THz signal transmission
enhancement of up to 10.8%.
Full article available here
Wednesday, 6 January 2016
Tuesday, 5 January 2016
High-Temperature H2O Vapor Measurement Using Terahertz Spectroscopy for Industrial Furnace Applications
Abstract
We verified that high-temperature (773 K) H2O vapor can be measured quantitatively with terahertz (THz) spectroscopy in the frequency range of 0.5–0.8 THz. The linear relationships between the absorbance peak area and the H2O vapor volume mixing ratio (VMR) at three absorption peaks (0.557 THz, 0.658 THz, and 0.752 THz) match HITRAN-based simulations closely, which indicates that the HITRAN database can be used for practical applications. Particularly, since the peak at 0.658 THz only appears at high temperatures, it can be used to measure high-temperature H2O vapor directly in the presence of room-temperature ambient H2O vapor.
Full article here
We verified that high-temperature (773 K) H2O vapor can be measured quantitatively with terahertz (THz) spectroscopy in the frequency range of 0.5–0.8 THz. The linear relationships between the absorbance peak area and the H2O vapor volume mixing ratio (VMR) at three absorption peaks (0.557 THz, 0.658 THz, and 0.752 THz) match HITRAN-based simulations closely, which indicates that the HITRAN database can be used for practical applications. Particularly, since the peak at 0.658 THz only appears at high temperatures, it can be used to measure high-temperature H2O vapor directly in the presence of room-temperature ambient H2O vapor.
Full article here
Terahertz Detection of Wavelength-Size Metal Particles in Pressboard Samples
Abstract
Results of a theoretical and experimental investigation of THz detection of randomly-oriented metal particles smaller than 1 mm embedded in pressboard are reported and critically compared with X-ray scanner results. A theoretical description based on Gaussian beam theory and a transfer function approach enabled simulation of signals transmitted around and reflected from real particles and was able to predict signal detectability. Simulated signals and detection limits were compared with experimental transmission and reflection time domain spectroscopy (TDS) raster scanning data. Simulated and measured pulse amplitude and shape were in agreement. Reflection mode was superior to transmission mode in terms of both particle visibility and hit ratio. Imaging of particles was also possible in “reflection in transmission” mode, which can be used to complement classical transmission mode. X-ray images did not detect the smallest particles sufficiently and, therefore, could not be used as reference data for comparison with THz data. The results demonstrate that TDS reflection scanning is able to determine the position of small metal particles and the technique could be possibly used for quality control of pressboard insulation.
Read full article here
Results of a theoretical and experimental investigation of THz detection of randomly-oriented metal particles smaller than 1 mm embedded in pressboard are reported and critically compared with X-ray scanner results. A theoretical description based on Gaussian beam theory and a transfer function approach enabled simulation of signals transmitted around and reflected from real particles and was able to predict signal detectability. Simulated signals and detection limits were compared with experimental transmission and reflection time domain spectroscopy (TDS) raster scanning data. Simulated and measured pulse amplitude and shape were in agreement. Reflection mode was superior to transmission mode in terms of both particle visibility and hit ratio. Imaging of particles was also possible in “reflection in transmission” mode, which can be used to complement classical transmission mode. X-ray images did not detect the smallest particles sufficiently and, therefore, could not be used as reference data for comparison with THz data. The results demonstrate that TDS reflection scanning is able to determine the position of small metal particles and the technique could be possibly used for quality control of pressboard insulation.
Read full article here
Sunday, 3 January 2016
Norfloxacin-loaded collagen/chitosan scaffold for skin reconstruction: Preparation, evaluation and in-vivo wound healing assessment
Abstract
Biomaterial scaffolds are versatile tools as drug carrier for treatment of wounds. A series of norfloxacin-loaded scaffolds were synthesized for treatment of wounds by combining collagen with two different types of chitosan using freeze-drying technique. Subsequently, scaffolds were screened in terms of morphology, water absorption and retention capacity, biodegradation, ex-vivo bioadhesive strength, in-vitro drug release biological compatibility, x-ray diffractometry, differential scanning calorimetry as well as in-vivo evaluation. The results indicate that the scaffold mechanical strength is dependent on the type of used chitosan. The prepared scaffolds contained interconnected porous architecture. The scaffolds had high water uptake and retention capacity with extended biodegradation rate. Scaffolds prepared with chitosan HCl showed superior bioadhesive strength compared to those prepared with low molecular weight chitosan. All scaffolds showed almost 100% drug release within 24 hours. As identified by the terahertz pulsed imaging measurements, there is single scaffold area with the same concentration. After 28 days of wound dressing with selected norfoloxacin-loaded or unloaded collagen/chitosan scaffolds in Albino rats, it was found that the tissue regeneration time was fast compared to non-treated wounds. Furthermore, the drug-loaded scaffolds showed normal structure of an intact epidermal layer as well as the underlying dermis as revealed by histopathological studies. The obtained results suggest that the investigated norfloxacin-loaded collagen/chitosan scaffold is a potential candidate for skin regeneration application.
Full article available here
Biomaterial scaffolds are versatile tools as drug carrier for treatment of wounds. A series of norfloxacin-loaded scaffolds were synthesized for treatment of wounds by combining collagen with two different types of chitosan using freeze-drying technique. Subsequently, scaffolds were screened in terms of morphology, water absorption and retention capacity, biodegradation, ex-vivo bioadhesive strength, in-vitro drug release biological compatibility, x-ray diffractometry, differential scanning calorimetry as well as in-vivo evaluation. The results indicate that the scaffold mechanical strength is dependent on the type of used chitosan. The prepared scaffolds contained interconnected porous architecture. The scaffolds had high water uptake and retention capacity with extended biodegradation rate. Scaffolds prepared with chitosan HCl showed superior bioadhesive strength compared to those prepared with low molecular weight chitosan. All scaffolds showed almost 100% drug release within 24 hours. As identified by the terahertz pulsed imaging measurements, there is single scaffold area with the same concentration. After 28 days of wound dressing with selected norfoloxacin-loaded or unloaded collagen/chitosan scaffolds in Albino rats, it was found that the tissue regeneration time was fast compared to non-treated wounds. Furthermore, the drug-loaded scaffolds showed normal structure of an intact epidermal layer as well as the underlying dermis as revealed by histopathological studies. The obtained results suggest that the investigated norfloxacin-loaded collagen/chitosan scaffold is a potential candidate for skin regeneration application.
Full article available here
Equivalent circuit for VO2 phase change material film in reconfigurable frequency selective surfaces
Abstract
We developed equivalent circuits of phase change materials based on vanadium dioxide (VO2) thin films. These circuits are used to model VO2thin films for reconfigurable frequency selective surfaces (FSSs). This is important as it provides a way for designing complex structures. A reconfigurable FSS filter using VO2 ON/OFF switches is designed demonstrating −60 dB isolation between the states. This filter is used to provide the transmission and reflection responses of the FSS in the frequency range of 0.1–0.6 THz. The comparison between equivalent circuit and full-wave simulation shows excellent agreement.
Read full article here
We developed equivalent circuits of phase change materials based on vanadium dioxide (VO2) thin films. These circuits are used to model VO2thin films for reconfigurable frequency selective surfaces (FSSs). This is important as it provides a way for designing complex structures. A reconfigurable FSS filter using VO2 ON/OFF switches is designed demonstrating −60 dB isolation between the states. This filter is used to provide the transmission and reflection responses of the FSS in the frequency range of 0.1–0.6 THz. The comparison between equivalent circuit and full-wave simulation shows excellent agreement.
Read full article here
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