TERAHERTZ-FREQUENCY SPECTROSCOPY AS A TECHNIQUE FOR THE REMOTE DETECTION OF BIOLOGICAL WARFARE AGENTS
This paper discusses the potential use of terahertzfrequency spectroscopy as a technique for the remote detection of biological warfare agents. Here, design studies are presented for a differential-absorption-radar (DAR) approach that utilizes the spectral signatures of Bacillus (B.) subtillus spores within the terahertz (THz) regime as the detection mechanism. The signature data used in these studies is taken from laboratory measurements performed on uniform thin films of B. subtillus spores and the system performance is assessed for both incoherent and coherent detector modalities. These studies consider DAR remote sensing of biological (bio) clouds at significant ranges (i.e., 1 km) and include the effects of realistic atmospheric conditions. Specifically, THz spectral signatures were used in a highlevel remote-sensor design to estimate the probabilities of detection (Pd) and false-alarm (Pfa) associated with this general technique. The system design studies suggest useful remote-detection performance can be achieved (i.e., Pd > 0.9 & Pfa << 10 for bio-cloud densities < 10 cm) at 1 km ranges if the THz signature information remains predictably stable under varying atmospheric conditions (e.g., changes in humidity, spore activity state, etc). Hence, this paper will also present recent results from scientific studies on bio-molecules that are exploring the underlying mechanisms responsible for the spectral signatures. DAR system performance is also assessed in a more practical bio-warfare military or civilian defense scenario. Here, the Pd and Pfa statistics for the DAR system are mapped onto the time-dependent evolution of an aerosol bio-cloud release to give a real-time indication of the effectiveness of the detection methodology. All together, these results demonstrate that standoff detection of bio-agents is feasible for threat-level concentrations in practical battlefield environments at sufficient ranges to provide for early warning.
Submillimeter-wave phonon modes in DNA macromolecules.
A detailed investigation of phonon modes in DNA macromolecules is presented. This work presents experimental evidence to confirm the presence of multiple dielectric resonances in the submillimeter-wave spectra (i.e., approximately 0.01-10 THz) obtained from DNA samples. These long-wave (i.e., approximately 1-30 cm(-1)) absorption features are shown to be intrinsic properties of the particular DNA sequence under study. Most importantly, a direct comparison of spectra between different DNA samples reveals a large number of modes and a reasonable level of sequence-specific uniqueness. This work establishes the initial foundation for the future use of submillimeter-wave spectroscopy in the identification and characterization of DNA macromolecules.
Assessment of Ground Regeneration around Borehole Heat Exchangers between Heating Seasons in Cold Climates: A Case Study in Bialystok (NE, Poland)
Based on the experimental studies, the process of ground regeneration around the borehole loaded with brine-water heat pumps working exclusively for heating purposes in the period of four consecutive heating seasons in a cold climate was presented. The research was conducted in north-eastern Poland. The aim of the work is to verify the phenomenon of thermal ground regeneration in the period between heating seasons on the basis of the recorded data and to check whether the ground is able to regenerate itself and at what rate. It was noticed that the ground does not fully regenerate, especially during heating seasons with lower temperatures. In the analyzed period, from 22 September 2016 to 12 October 2020, the ground probably cooled irreversibly by 1.5 °C. In order to illustrate and evaluate the speed of changes in the ground, the one’s profile with an undisturbed temperature field was presented for each month of the year. The presented results can be a very important source of information for the analysis of geothermal conditions occurring in the ground. They can be used to verify mathematical models and conduct long-term simulations that allow us to see the complexity of the processes taking place in the ground.