Probing temperature- and solvent-dependent protein dynamics using terahertz time-domain spectroscopy

The effect of temperature on the terahertz-frequency-range material properties of lyophilized and single-crystal hen egg-white lysozyme has been measured using terahertz time-domain spectroscopy, with the results presented and discussed in the context of protein and solvent dynamical and glass transitions. Lyophilized hen egg-white lysozyme was measured over a temperature range from 4 to 290 K, and a change in the dynamical behaviour of the sample at around 100 K was observed through a change in the terahertz absorption spectrum. Additionally, the effect of cryoprotectants on the temperature-dependent absorption coefficient is studied, and it is demonstrated that terahertz time-domain spectroscopy is capable of resolving the true glass transition temperature of single-crystal hen egg-white lysozyme at 150 K, which is in agreement with literature values measured using differential scanning calorimetry

Accurate Parameter Extraction From Liquids Measured Using On-chip Terahertz Spectroscopy

We introduce a method for estimating the permittivity of liquid samples measured using integrated microfluidic/planar Goubau line terahertz waveguides, in which simulation results are incorporated with measurement data to enable accurate frequency-dependent analysis

On-chip Terahertz Spectroscopy of Liquid Mixtures

We demonstrate 'through-substrate' sensing of fluids for application in the terahertz spectroscopy of biological materials. This technique employs planar Goubau lines with integrated photoconductive material, formed on a flexible, thin polyimide substrate, and bonded to a microfluidic channel. Few-picosecond pulses are used to probe liquid samples confined within the channel, over a total interaction length of 4 mm, overcoming water-absorption limitations of free-space terahertz transmission measurements

THz-TDS of liquids in a temperature-controlled transmission flowcell

Precise temperature-control is necessary for many spectroscopic measurements. We present the temperature-dependent complex THz refractive index of liquid samples measured in a flowcell, analysed by a numerical method that allows simultaneous extraction of the sample's thickness to verify the temperature-stability of the cell

Investigation into free-space terahertz radiation from a LT-GaAs-on-quartz photoconductive emitter

We report on large-area photoconductive THz emitters and detectors with an LT-GaAs active region fabricated on quartz substrates using a lift-off transfer process. These devices are compared to the same LT-GaAs emitters when fabricated on the growth substrate. We find that the transferred devices show higher optical-to-THz conversion efficiencies and significantly larger breakdown fields

Free-space terahertz radiation from a LT-GaAs-on-quartz large-area photoconductive emitter

We report on large-area photoconductive terahertz (THz) emitters with a low-temperature-grown GaAs (LT-GaAs) active layer fabricated on quartz substrates using a lift-off transfer process. These devices are compared to the same LT-GaAs emitters when fabricated on the growth substrate. We find that the transferred devices show higher optical-to-THz conversion efficiencies and significantly larger breakdown fields, which we attribute to reduced parasitic current in the substrate. Through these improvements, we demonstrate a factor of ~8 increase in emitted THz field strength at the maximum operating voltage. In addition we find improved performance when these devices are used for photoconductive detection, which we explain through a combination of reduced parasitic substrate currents and reduced space-charge build-up in the device

Does BCR/ABL1 positive Acute Myeloid Leukaemia Exist?

The BCR/ABL1 fusion gene, usually carried by the Philadelphia chromosome (Ph) resulting from t(9;22)(q34;q11) or variants, is pathognomonic for chronic myeloid leukaemia (CML). It is also occasionally found in acute lymphoblastic leukaemia (ALL) mostly in adults and rarely in de novo acute myeloid leukaemia (AML). Array Comparative Genomic Hybridization (aCGH) was used to study six Ph(+)AML, three bi-lineage and four Ph(+)ALL searching for specific genomic profiles. Surprisingly, loss of the IKZF1 and/or CDKN2A genes, the hallmark of Ph(+)ALL, were recurrent findings in Ph(+)AML and accompanied cryptic deletions within the immunoglobulin and T cell receptor genes. The latter two losses have been shown to be part of 'hot spot' genome imbalances associated with BCR/ABL1 positive pre-B lymphoid phenotype in CML and Ph(+)ALL. We applied Significance Analysis of Microarrays (SAM) to data from the 'hot spot' regions to the Ph(+)AML and a further 40 BCR/ABL1(+) samples looking for differentiating features. After exclusion of the most dominant markers, SAM identified aberrations unique to de novo Ph(+)AML that involved relevant genes. While the biological and clinical significance of this specific genome signature remains to be uncovered, the unique loss within the immunoglobulin genes provides a simple test to enable the differentiation of clinically similar de novo Ph(+) AML and myeloid blast crisis of CML. © 2013 John Wiley & Sons Ltd and Crown

Spectroscopy of polycrystalline materials using thinned-substrate planar Goubau line at cryogenic temperatures.

We investigate the effect of substrate thickness on the transmission bandwidth of on-chip terahertz-frequency-range planar Goubau lines both experimentally and theoretically. The bandwidth and frequency resolution are improved through substrate thinning and geometry modifications (reducing reflections arising from the THz photoconductive generators and detectors). We demonstrate that the enhanced bandwidth (2 THz) and resolution (3.75 GHz) allows this type of on-chip waveguide to be used for spectroscopic measurements of polycrystalline materials from cryogenic (4 K) to room temperature (292 K) by recording vibrational absorption spectra from overlaid samples of lactose monohydrate

Increasing the sensitivity of terahertz split ring resonator metamaterials for dielectric sensing by localized substrate etching

We demonstrate a significant enhancement in the sensitivity of split ring resonator terahertz metamaterial dielectric sensors by the introduction of etched trenches into their inductive-capacitive gap area, both through finite element simulations and in experiments performed using terahertz time-domain spectroscopy. The enhanced sensitivity is demonstrated by observation of an increased frequency shift in response to overlaid dielectric material of thicknesses up to 18 μm deposited on to the sensor surface. We show that sensitivity to the dielectric is enhanced by a factor of up to ~2.7 times by the incorporation of locally etched trenches with a depth of ~3.4 μm, for example, and discuss the effect of the etching on the electrical properties of the sensors. Our experimental findings are in good agreement with simulations of the sensors obtained using finite element methods

Accurate Material Parameter Extraction from Broadband Terahertz Spectroscopy

We demonstrate how a transfer function model based parameter extraction method, combined with total variance analysis, allows the extraction of both the complex refractive index and the thickness of a sample over a bandwidth of > 6 THz from THz time-domain spectroscopy measurements. We discuss how the techniques developed have been applied to absorbent powders measured at variable low temperatures