The spectrum of Ih ice using terahertz time-domain spectroscopy.

Here, we report the frequency-dependent spectrum of ice Ih in the range of 0.2-2 THz. We confirm the presence of a feature that blue-shifts from around 1.55-1.65 THz with a decreasing temperature from 260 to 160 K. There is also a change in the trend of the refractive index of ice corresponding to a dispersion, which is also around 1.6 THz. The features are reproduced in data acquired with three commercial terahertz time-domain spectrometers. Computer-simulated spectra assign the feature to lattice translations perpendicular to the 110 and 1̄10 planes of the ice Ih crystal. The feature's existence should be recognized in the terahertz measurements of frozen aqueous solution samples to avoid false interpretations.

Hydration water drives the self-assembly of guanosine monophosphate.

Guanosine monophosphate (GMP) is a nucleotide that can self-assemble in aqueous solution under certain conditions. An understanding of the process at the molecular level is an essential step to comprehend the involvement of DNA substructures in transcription and replication, as well as their relationship to genetic diseases such as cancer. We present the temperature-dependent terahertz (1.5-12 THz, 50-400 cm-1) absorptivity spectra of aqueous Na2 GMP solution in comparison with the aqueous solutions of other RNA nucleotides. Distinct absorption features were observed in the spectrum of GMP, which we attribute to the intramolecular modes of the self-assemblies (i.e., G-complexes) that, at 1 M, start to form at 313 K and below. Changes in broad-band features of the terahertz spectrum were also observed, which we associate with the release of hydration water in the temperature-dependent formation of guanine quadruplexes. Using a state-of-the-art THz calorimetry approach correlating spectroscopic to thermodynamic changes, we propose a molecular mechanism of hydrophilic hydration driving GMP self-assembly as a function of temperature. The free energy contribution of hydrophilic hydration is shown as a decisive factor in guanine-quadruplex formation. Our findings spotlight the role of hydration in the formation of macromolecular structures and suggest the potential of hydration tuning for regulating DNA transcription and replication.

Non-Contact, Non-Destructive Testing in Various Industrial Sectors with Terahertz Technology.

In this article, we survey various non-contact, non-destructive testing methods by way of terahertz (THz) spectroscopy and imaging designed for use in various industrial sectors. A brief overview of the working principles of THz spectroscopy and imaging is provided, followed by a survey of selected applications from three industries-the building and construction industry, the energy and power industry, and the manufacturing industry. Material characterization, thickness measurement, and defect/corrosion assessment are demonstrated through the examples presented. The article concludes with a discussion of novel spectroscopy and imaging devices and techniques that are expected to accelerate industry adoption of THz systems.