Sunday, 23 April 2017

Intermolecular anharmonicity in molecular crystals: interplay between experimental low-frequency dynamics and quantum quasi-harmonic simulations of solid purine

Ruggiero, Michael T., J. Axel Zeitler, and Alessandro Erba. "Intermolecular anharmonicity in molecular crystals: interplay between experimental low-frequency dynamics and quantum quasi-harmonic simulations of solid purine." Chemical Communications (2017).


Abstract

Image result for axel terahertzThe intermolecular anharmonic potential of crystalline purine is probed by means of temperature-dependent terahertz time-domain spectroscopy, low-frequency Raman scattering, X-ray diffraction, and ab initio quasi-harmonic quantum-chemical simulations. As temperature increases, anharmonicity in the intermolecular interactions results in strongly anisotropic thermal expansion – with a negative thermal expansion along the b crystallographic axis – yielding corresponding bulk structural modifications. The observed thermally-induced shifts of most vibrational bands in the terahertz region of the spectra are shown to arise from volume-dependent thermal changes of the hydrogen-bond pattern along the a and b crystallographic axes.

Dr Zeilter's group uses a TeraPulse 4000 for more information see http://www.azom.com/equipment-details.aspx?EquipID=4411

Friday, 21 April 2017

Non-contact paint thickness measurement system for industrial deployment




Abstract
We present a non-contact, multi-layer coating thickness sensor based on the use of pulsed terahertz light.
The coated surface is illuminated from a short distance with a terahertz light pulse. The reflected signal, containing reflections at the interface of adjacent coating layers, is analysed to determine the thickness of each layer.
The unit has been designed and tested for deployment in manufacturing environments and is available in both manual and automated (robotic) forms.
Being non-contact, it offers significant advantages over existing technologies: for example, line scans and measurement of curved surfaces, including windshield flanges.
The system has been tested by a number of automobile manufacturers. Summary results of trials are discussed.
For more information see http://dsctfocus.org/
Also, see http://www.azom.com/article.aspx?ArticleID=13544

Terahertz Imaging of Three-Dimensional Dehydrated Breast Cancer Tumors

T. Bowman, Y. Wu, J. Gauch, L. K. Campbell, and M. El-Shenawee

Bowman, T., Wu, Y., Gauch, J. et al. J Infrared Milli Terahz Waves (2017) 38: 766. doi:10.1007/s10762-017-0377-y

Abstract
Professor Magda El-Shenawee and graduate assistant, Tyler Bowman, use THz imaging technology to assess the margins of cancerous breast tumors.
This work presents the application of terahertz imaging to three-dimensional formalin-fixed, paraffin-embedded human breast cancer tumors. The results demonstrate the capability of terahertz for in-depth scanning to produce cross section images without the need to slice the tumor. Samples of tumors excised from women diagnosed with infiltrating ductal carcinoma and lobular carcinoma are investigated using a pulsed terahertz time domain imaging system. A time of flight estimation is used to obtain vertical and horizontal cross section images of tumor tissues embedded in paraffin block. Strong agreement is shown comparing the terahertz images obtained by electronically scanning the tumor in-depth in comparison with histopathology images. The detection of cancer tissue inside the block is found to be accurate to depths over 1 mm. Image processing techniques are applied to provide improved contrast and automation of the obtained terahertz images. In particular, unsharp masking and edge detection methods are found to be most effective for three-dimensional block imaging.

For more information about Professor El-Shenawee see http://terahertz.uark.edu/

For more information about TeraView visit www.teraview.com

Friday, 27 January 2017

TeraView to present results from pharmaceutical studies at this year’s Photonics West

TeraView's Dr Philip Taday will be presenting a talk entitled 'Using terahertz-pulsed imaging (TPI) to study osmotic tablets' at this years SPIE Photonics West conference. The event will take place at The Moscone Center, San Francisco, California, USA.

The conference runs from 28th January until 2nd February 2017. TeraView will be presenting their talk on Tuesday 31 January, 10:30 - 12:20 pm (Room 270).

More details on the conference can be found here.

Wednesday, 18 January 2017

Contrast in Terahertz Images of Archival Documents—Part I: Influence of the Optical Parameters from the Ink and Support

Tiphaine Bardon ; Robert K. May ; J. Bianca Jackson ; Gabriëlle Beentjes ; Gerrit de Bruin ; Philip F. Taday ; Matija Strlič


Abstract:

This study aims to objectively inform curators when terahertz time-domain (TD) imaging set in reflection mode is likely to give well-contrasted images of inscriptions in a complex archival document and is a useful non-invasive alternative to current digitisation processes. To this end, the dispersive refractive indices and absorption coefficients from various archival materials are assessed and their influence on contrast in terahertz images from historical documents is explored. Sepia ink and inks produced with bistre or verdigris mixed with a solution of Arabic gum or rabbit skin glue are unlikely to lead to well-contrasted images. However, dispersions of bone black, ivory black, iron gall ink, malachite, lapis lazuli, minium and vermilion are likely to lead to well-contrasted images. Inscriptions written with lamp black, carbon black and graphite give the best imaging results. The characteristic spectral signatures from iron gall ink, minium and vermilion pellets between 5 and 100 cm−1 relate to a ringing effect at late collection times in TD waveforms transmitted through these pellets. The same ringing effect can be probed in waveforms reflected from iron gall, minium and vermilion ink deposits at the surface of a document. Since TD waveforms collected for each scanning pixel can be Fourier-transformed into spectral information, terahertz TD imaging in reflection mode can serve as a hyperspectral imaging tool. However, chemical recognition and mapping of the ink is currently limited by the fact that the morphology of the document influences more the terahertz spectral response of the document than the resonant behaviour of the ink.

Full article here.