Breath gas analysis is a promising tool for medical research and diagnosis. A particularly powerful technological approach is millimeter-wave/terahertz (mmW/THz) spectroscopy, because it is a very ...sensitive and highly selective technique. In addition, it offers the potential for compact and affordable sensing systems for wide use. In this work, we demonstrate the capability of a mmW/THz spectrometer for breath analysis. Samples from three volunteers and a sample from ambient air were analyzed with respect to 31 different molecular species. High-resolution absorption spectra were measured by scanning two absorption lines from each species. Out of the 31, a total of 21 species were detected. The results demonstrate the potential of mmW/THz spectroscopy for breath analysis.
Terahertz (THz) radiation meaning electromagnetic radiation in the range from 0.1 (3) to 10 (30) has the unique advantage of easily penetrating many obstructions while being non-hazardous to organic ...tissue since it is non-ionizing. A shortcoming of this domain is the limited availability of high-sensitivity detector arrays respective THz cameras with >1k pixels. To overcome the imaging limitations of the THz domain, compressive imaging in combination with an optically controllable THz spatial light modulator is a promising approach especially when used in a single-pixel imaging modality. The imaging fidelity, performance and speed of this approach depend crucially on the imaging patterns also called masks and their properties used in the imaging process. Therefore, in this paper, it is investigated how the image quality after reconstruction is specifically influenced by the different mask types and their properties in a compressive imaging modality. The evaluation uses an liquid-crystal display based projector as spatial light modulator to derive specific guidelines for the use of binary and true greyscale masks in THz single-pixel imaging setups respective THz single-pixel cameras when used in far-field applications e.g. stand-off security imaging.
Abstract
Atomic oxygen is a key species in the mesosphere and thermosphere of Venus. It peaks in the transition region between the two dominant atmospheric circulation patterns, the retrograde ...super-rotating zonal flow below 70 km and the subsolar to antisolar flow above 120 km altitude. However, past and current detection methods are indirect and based on measurements of other molecules in combination with photochemical models. Here, we show direct detection of atomic oxygen on the dayside as well as on the nightside of Venus by measuring its ground-state transition at 4.74 THz (63.2 µm). The atomic oxygen is concentrated at altitudes around 100 km with a maximum column density on the dayside where it is generated by photolysis of carbon dioxide and carbon monoxide. This method enables detailed investigations of the Venusian atmosphere in the region between the two atmospheric circulation patterns in support of future space missions to Venus.
Laser‐induced breakdown spectroscopy (LIBS) and Raman spectroscopy are powerful key techniques for the geoanalytical exploration of extraterrestrial bodies, especially when combined. Their data are ...complementary, which motivates the question of how it can be best combined to maximize the scientific output. For this study, LIBS and Raman data from pure sulfates and their mixtures as well as from other Mars‐relevant salts such as carbonates, chlorides, perchlorates, and sulfates in a basaltic matrix were measured and investigated. All measurements were performed with miniaturized setups, and LIBS experiments were done in simulated Martian atmospheric conditions. Multivariate data analysis (MVA) techniques such as principal component analysis (PCA) and partial least squares discriminant analysis (PLS‐DA) were employed to evaluate the potential for identifying the sulfates or the salts in the basalt with LIBS and Raman data alone and with their low‐level fused data. We found that low‐level data fusion, that is, combination of LIBS and Raman spectra at the data level, can improve the identification of sulfates and salts. Although the approach of low‐level data fusion aims to use all relevant information from both techniques, we observed that not all benefits from the single models are completely represented by the fused model. The computation and performance of appropriate MVA models are affected by the weighting of the single spectra in the combined one, by the dimensionality of the MVA models, and in case of PLS‐DA, by the given input data. From this study, we conclude that generally, data fusion of LIBS and Raman is an advantage for the identification of unknown samples but that more levels, especially, high‐level data fusion (decision level), should be further investigated.
With low‐level LIBS and Raman data fusion, a more comprehensive sample identification is possible. As the complexity of the data is increased, a careful analysis including balancing between the data of both techniques is necessary. Depending on the science goal, the particular approach should be chosen.
Schottky diodes are well-known nonlinear elements allowing for effective detection and mixing of electromagnetic radiation in the range through microwave to terahertz. Although less sensitive than ...their superconducting counterparts, they generally do not require cooling that makes them the devices of choice for applications where the ultimate sensitivity is not needed. In the emerging field of terahertz technology, there is a long-time quest for cheap and handy detectors for laboratory use, as well as for serial compact and midsize instruments. We describe the use of a quasi-optically coupled zero-bias planar Schottky-diode detector for monitoring picosecond pulses of synchrotron terahertz radiation and weak continuous-wave emission from an array of Josephson junctions.
The oxygen spectrometer for atmospheric science on a balloon (OSAS-B) is the first 4.7-THz heterodyne spectrometer on a stratospheric balloon. It has been developed for remote sensing of the 4.7-THz ...emission of neutral atomic oxygen in the mesosphere and lower thermosphere of the Earth. OSAS-B comprises a heterodyne receiver based on a hot-electron bolometer mixer and a quantum-cascade laser as local oscillator. The high sensitivity of the superconducting detector and the large resolving power of approximately <inline-formula><tex-math notation="LaTeX">1\times 10^{7}</tex-math></inline-formula> enable the detection of subtle signatures of radiation transport and high-altitude winds in the measured spectra. The first flight of the instrument took place on September 7th, 2022 from Esrange, Sweden.
•Simulation of space weathering effects by micrometeorite impacts induced by pulsed intense infrared laser.•Differences in the microstructure of minerals due to the weathering source in ...space.•Transparency feature increases due to impact gardening.
We studied space-weathering effects caused by micrometeorite bombardment simulated by pulsed intense infrared laser, generating ∼15 mJ per pulse in high vacuum. For our investigation, we selected a natural olivine (San Carlos olivine (Fo91)) and a natural pyroxene (Bamble orthopyroxene (En87)) as important rock forming minerals of the Earth upper mantle as well as key planetary minerals. Irradiated areas of powdered pressed samples were examined by optical reflection spectroscopy in a broad optical and infrared wavelength range (visible-, near-, and mid-infrared) and transmission electron microscopy to identify changes due to micrometeorite impacts. The present study aims to investigate especially the effects of micrometeorite bombardment on reflectance spectra in the mid-IR in preparation for future space missions, as well as for the MERTIS experiment onboard the BepiColombo mission.
For both irradiated samples, we found a reduction in albedo and in the reflectance of characteristic Reststrahlen bands and an increase of the transparency feature. VIS and NIR spectra of both minerals show the typical darkening and reddening as described for other space-weathered samples. TEM studies revealed that space-weathered layers in olivine and pyroxene differ in their respective thickness, ∼450 nm in olivine, 100-250 nm in pyroxene, as well as in developed “nanostratigraphy” of laser-ablated material, like nanophase iron (npFe).
In conclusion, our spectral and structural findings were compared to samples in which space weathering was caused by different processes. A comparison with these data demonstrates that there is no difference in optical reflectance spectroscopy, but a significant difference in the microstructure of minerals due to the weathering source in space, as there are solar wind and solar flares cause other structural and chemical changes as the bombardment with micrometeorites.
PDF
