I. Jones

T-Ray Sensing and Imaging

T-ray wavelengths are long enough to pass through dry, nonpolar objects opaque at visible wavelengths, but short enough to be manipulated by optical components to form an image. Sensing in this band potentially provides advantages in a number of areas of interest to security and defense such as screening of personnel for hidden objects and the retection of chemical and biological agents. Several private companies are developing smaller, reliable cheaper systems allowing for commercialization and this motivates us to review a number of promising applications within this paper. While there are a number of challenges to be overcome there is little doubt that T-ray technology will play a significant role in the near future for advancement of security, public health, and defense.

Wireless RF communication in biomedical applications

This paper focuses on wireless transcutaneous RF communication in biomedical applications. It discusses current technology, restrictions and applications and also illustrates possible future developments. It focuses on the application in biotelemetry where the system consists of a transmitter and a receiver with a transmission link in between. The transmitted information can either be a biopotential or a nonelectric value like arterial pressure, respiration, body temperature or pH value. In this paper the use of radio-frequency (RF) communication and identification for those applications is described. Basically, radio-frequency identification or RFID is a technology that is analogous to the working principle of magnetic barcode systems. Unlike magnetic barcodes, passive RFID can be used in extreme climatic conditions—also the tags do not need to be within close proximity of the reader. Our proposed solution is to exploit an exciting new development in making circuits on polymers without the need for battery power. This solution exploits the principle of a surface acoustic wave (SAW) device on a polymer substrate. The SAW device is a set of interdigitated conducting fingers on the polymer substrate. If an appropriate RF signal is sent to the device, the fingers act as microantennas that pick up the signal, and this energy is then converted into acoustic waves that travel across the surface of the polymer substrate. Being a flexible polymer, the acoustic waves cause stresses that can either contract or stretch the material. In our case we mainly focus on an RF controllable microvalve that could ultimately be used for fertility control.

Low-Frequency Spectroscopic Analysis of Monomeric and Fibrillar Lysozyme

Terahertz time-domain spectroscopy (THz-TDS) and Fourier transform infrared (FT-IR) spectroscopy were used to generate far-infrared and low-frequency spectral measurements of monomeric lysozyme and lysozyme fibrils. The formation of lysozyme fibrils was verified by the Thioflavin T assay and transmission electron microscopy (TEM). It was evident in the FT-IR spectra that between 150 and 350 cm−1 the two spectra diverge, with the lysozyme fibrils showing higher absorbance intensity than the monomeric form. The broad absorption phenomenon is likely due to light scattered from the fibrillar architecture of lysozyme fibrils as supported by simulation of Rayleigh light scattering. The lack of discrete phonon-like peaks suggest that far-infrared spectroscopy cannot detect vibrational modes between the highly ordered hydrogen-bonded beta-pleated sheets of the lysozyme subunit.

Ab initio molecular orbital theory: a tool for THz spectroscopic investigation

Terahertz spectroscopy, which investigates the electromagnetic spectrum of samples between 0.1 and 10 THz, allows not only for exploration of molecular structures but also of molecular dynamics. One difficulty in performing THz spectroscopy is that the data can be noisy and difficult to interpret. Ab initio molecular modelling has recently become more and more useful in the prediction of, for example, molecular structures, dynamic states and isomeric forms. Since the structure of biomolecules is closely related to their functionality there are broad ranging applications in biomedicine, for example in DNA sensing. An a priori knowledge of the expected THz spectra allows for improved experimentation. There is a growing and recognised need for THz spectroscopic databases to be created and made available along with classifiers that are able to effectively detect a specific substance. We show, for a specific example, the 9-cis and all-trans retinal isomers, how ab initio molecular orbital calculations and quantum chemical modelling programs, such as Gamess, can aid in this endeavour.

THz spectroscopy of protein complexses

We present our preliminary results on the detection of antigen-antibody complexes using terahertz spectroscopy. Our study indicates that a difference between the absorption spectra of pure antibody/antigen and the antibody-antigen complex may be useful for biomedical applications. Furthermore, we introduce a new carrier material, which has several advantages over previously used materials, such as high binding capacity along with high THz transparency.

Ab Initio Molecular Modelling of THz Spectra

Molecular modelling can be used to predict and confirm THz spectra, and to gain information that may be difficult or impossible to obtain experimentally. There are a variety of approaches, and consideration must be given to the likely sources of error in the molecular modelling of THz modes.

THz Fingerprinting of Biomolecules Supported by Ab Initio Molecular Modelling

In this paper we explore various ab initio molecular approaches and their usefulness for the prediction of vibrational spectra of biomolecules.

Calculation of low-frequency vibrational modes of biologically important isomers

In this paper we compare the value of different molecular modeling techniques for the prediction of vibrational modes, especially in the mid- and far-infrared region. There is a wide range of different levels of theory available for molecular modelling - the choice depending on the kind of system to be investigated. For our calculations we use different theoretical approaches such as Hartree-Fock and Density functional theory. We also compare the performances of two available electronic structure programs-Gamess-US and Gaussian03. As examples, we use two different retinoids - all-trans retinal and all-trans retinoic acid - derivatives of Vitamin A.