Remotely Detected Research Articles

Possible influence of Martian surface mineralogy on the detectability of atmospheric trace gases - mid-infrared simulation results

The paper focuses on the influence of the optical properties of Martian surface minerals on remotely detected gaseous components of the Martian atmosphere, when the spectrometer receives a combined signal from the Martian soil and atmosphere. Our considerations are primarily concerned with the detectability of methane, but the problem may also apply to other trace gases. Detections of methane in the Martian atmosphere have been reported from Mars Express (orbiting Mars), the Curiosity rover on the Martian surface, and from Earth. Its presence in the Martian atmosphere is being questioned today. The reason for these doubts is that both spectrometers onboard ExoMars Trace Gas Orbiter have not yet detected any methane in the Martian atmosphere using the very sensitive solar occultation method. The solar occultation method is unable to probe the lowest layers of the atmosphere at mid-latitudes, and so, its presence in this part of the atmosphere is assumed to be due to its possible source in the ground, as suggested by some works.This paper considers whether the spectral characteristics of the soil may hinder the remote detection of methane. One of the examples discussed in the article relates to the possible observation of methane over mineralogical surfaces that may be the source of this gas. The examples of other surface mineralogical compositions are also discussed. The series of numerical simulations carried out in the region of the strong methane absorption band and the examples where the optical properties of the surface change the shape and contrast of this absorption band are shown. The codes used provide estimates of the spectral reflectance/emittance and total radiance of the Martian surface and atmosphere in the mid-infrared spectral region. The surface covered by dust was described by the reflectance and emittance calculated from n,k using Mie and Hapke theories or known from laboratory measurements. The different concentrations of atmospheric trace gases were taken into account.

Energetic Neutral Atom Imaging of the Earth’s Ring Current and Some Results from the Chinese Double Star Program

The ring current region in the Earth’s magnetosphere contains energetic charged particles, which are injected from the magnetotail, get trapped in the inner magnetosphere, and finally drift around the Earth. The current, essentially carried by ions, is caused by the differences between the drift of the positively charged ions and that of negatively charged electrons. The charge exchange that occurs between ring current ions and geocoronal atoms determines the distribution and evolution of the ring current and lays the basis for remote detection techniques. By measuring the energetic neutral atoms produced by the charge-exchange process, the ring current can be remotely detected via energetic neutral atom imaging. The Chinese Double Star Program operated the NeUtral Atom Detector Unit (NUADU) onboard one of its two satellites for more than four years. A variety of studies were conducted using multiple methods applied to observations, such as intuitive image inspection, forward modeling, and inversion. Energetic neutral atom imaging was established as a promising technique for future imaging projects.

Remote detection of Cannabis-related impairments in performance?

Researchers have traditionally studied the effects of psychoactive drugs such as Cannabis in controlled laboratory settings or relied on retrospective self-reports to measure impairment. However, advances in technology afford opportunities to conduct assessments remotely. We considered whether objective click-stream data (time and number of clicks spent on a webpage) during an online survey could supplement self-reports of substance use problems. The clickstream data of participants (n = 236) were examined as they completed an online study which included validated psychometric tests (Cannabis Use Disorders Identification Test-Revised, Grit-O, Kessler Psychological Distress Scale, and Brief Self Control Scale). Clickstream data were compared to self-reported Cannabis use. People reporting Cannabis use within the last 4weeks required more time and more clicks to complete the online survey, and this was specifically associated with reported frequency of use, duration of impairment, and problems with memory and concentration. Longer amounts of time and more clicks on the online questionnaire were associated with more recent Cannabis use rather than demographic factors or stimulant use. These results imply clickstream data remotely detected indecision or other deficits associated with previous Cannabis use.

Realizing the Principles for Remote and Selective Detection of Cancer Cells Using Magnetic Nanowires.

The unmet demand for selective and remote detection of biological entities has urged nanobiotechnology to prioritize the innovation of biolabels that can be remotely detected. Magnetic nanowires (MNWs) have been deemed promising for remote detection as the magnetic fields can deeply and safely penetrate into tissue. However, the overlapping nature of the magnetic signatures has been a long-standing challenge for selective detection, which we resolve here. To do so, 13 types of MNWs with unique irreversible switching field (ISF) signatures were synthesized for labeling canine osteosarcoma (OSCA-8) cancer cells (one set) and polycarbonate biopolymers (12 sets). After characterizing the ISF signature of each MNW type, the MNW-labeled cancer cells were transferred onto MNW-labeled biopolymers to determine the most distinguishable ISF signatures and to discern the principles for reliable selective detection of biological entities. We show that tailoring the ISF of MNWs by tuning their coercivity is a highly effective approach for generating distinct magnetic biolabels for selective detection of cells. These findings smooth the path for the progression of nanobiotechnology by enabling the remote and selective detection of biological entities using MNWs.

Remote detection of marine debris using satellite observations in the visible and near infrared spectral range: Challenges and potentials

Despite the importance of remote detection of marine debris, nearly all published studies are focused on either controlled experiments, or Sentinel-2 data with mixed band resolutions that are subject to large uncertainties. To date, key questions such as the following have not been addressed adequately: To what extent can the various forms of marine debris be remotely detected and differentiated through satellite observations in the visible and near infrared (NIR) spectral range, and how? Here, using published reflectance spectra of various types of floating matters, I address these questions through sensitivity analyses, simulations, and spectral analyses of satellite images. While the study is by no means comprehensive, several observations can still be made. First, it appears impossible to remotely detect marine microplastics from all existing and planned optical sensors. This is simply because the contribution of these particles to the sensor signal, even when they are aggregated on the water surface at the reported maximum particle density, is at least 60 times lower than the required signal (~0.2% subpixel coverage) and 20 times lower than the sensor noise for a sensor with a signal-to-noise ratio (SNR) of 200. In contrast, detecting macroplastics and other debris is possible when they form large patches along ocean fronts or windrows. Second, assuming a SNR of 200, discriminating large patches of marine debris from floating algae is only possible with a subpixel coverage of >0.3%. These threshold values are based on the sensor SNRs only, and they represent the lower bounds of detection and discrimination, respectively. The real threshold values above which a detection or discrimination is possible also depend on the observing conditions, and therefore higher. Third, currently, Sentinel-2 MSI (Multi Spectral Instrument) sensors provide an optimal trade between resolution and coverage, yet MSI sensors have SNRs <200, and interpretation of the MSI spectra requires extra caution due to variable spatial resolutions in different bands, among other factors. From the perspective of pure spectroscopy, it is possible to discriminate floating algae from non-algae floating matters but difficult to differentiate the type of the latter (either plastic or non-plastic debris, foam, etc) because different non-algae floating matters all show relatively flat reflectance spectral shapes in the vis-NIR spectral range. Finally, based on these results, recommendations are made on algorithm designs and sensor designs, for example spectral analysis should be performed over the difference spectra to minimize the impact of variable subpixel coverage, and certain spectral bands are more important than others for the remote detection of marine debris.

Remote thermal detection of exfoliation sheet deformation

A growing body of research indicates that rock slope failures, particularly from exfoliating cliffs, are promoted by rock deformations induced by daily temperature cycles. Although previous research has described how these deformations occur, full three-dimensional monitoring of both the deformations and the associated temperature changes has not yet been performed. Here we use integrated terrestrial laser scanning (TLS) and infrared thermography (IRT) techniques to monitor daily deformations of two granitic exfoliating cliffs in Yosemite National Park (CA, USA). At one cliff, we employed TLS and IRT in conjunction with in situ instrumentation to confirm previously documented behavior of an exfoliated rock sheet, which experiences daily closing and opening of the exfoliation fracture during rock cooling and heating, respectively, with a few hours delay from the minimum and maximum temperatures. The most deformed portion of the sheet coincides with the area where both the fracture aperture and the temperature variations are greatest. With the general deformation and temperature relations established, we then employed IRT at a second cliff, where we remotely detected and identified 11 exfoliation sheets that displayed those general thermal relations. TLS measurements then subsequently confirmed the deformation patterns of these sheets showing that sheets with larger apertures are more likely to display larger thermal-related deformations. Our high-frequency monitoring shows how coupled TLS and IRT allows for remote detection of thermally induced deformations and, importantly, how IRT could potentially be used on its own to identify partially detached exfoliation sheets capable of large-scale deformation. These results offer a new and efficient approach for investigating potential rockfall sources on exfoliating cliffs.

Exploring the dynamics of remotely detected fluorescence transients from basil as a potential feedback for lighting control in greenhouses

Optimizing artificial lighting control in industrial scale greenhouses has a potential for increased crop yields, energy savings and production timing. One possible component in controlling greenhouse lighting is continuous and accurate measurement of plant photosynthetic performance. A widely used tool for measuring photosynthetic performance non-invasively is chlorophyll fluorescence. For the purpose of automatic control, remote sensing of fluorescence is favourable, since it provides an aggregated measure for a large canopy area. However, adaptation of traditional fluorescence methodologies to remote sensing is problematic since they are based on the analysis of fluorescence intensities and therefore sensitive to distance and morphology. Other problems with using traditional methods remotely in a greenhouse are a need for dark adaption and use of saturating light. This paper presents a novel concept for the detection of photosynthetic performance based on the dynamics of remotely sensed light induced fluorescence signals. The dynamics of the fluorescence signal is insensitive to distance and morphology and hence provide a good basis for remote detection of photosynthetic performance. Through experiments we have explored how the dynamics of the time-varying fluorescence signal from basil plants was affected by light intensity, light acclimation and light induced stress. This was done by first identifying a dynamic model by transient analysis and then applying frequency analysis on the model. We conclude that the capacity of basil plants to use a certain light intensity was reflected by how fast and how complex the dynamics are. These results show that an identified resonance peak frequency is a potential indicator of plants' ability to adapt to light, which could be a valuable feedback signal for lighting control in greenhouses.

Remote measurement of cognitive stress via heart rate variability.

Remote detection of cognitive load has many powerful applications, such as measuring stress in the workplace. Cognitive tasks have an impact on breathing and heart rate variability (HRV). We show that changes in physiological parameters during cognitive stress can be captured remotely (at a distance of 3m) using a digital camera. A study (n=10) was conducted with participants at rest and under cognitive stress. A novel five band digital camera was used to capture videos of the face of the participant. Significantly higher normalized low frequency HRV components and breathing rates were measured in the stress condition when compared to the rest condition. Heart rates were not significantly different between the two conditions. We built a person-independent classifier to predict cognitive stress based on the remotely detected physiological parameters (heart rate, breathing rate and heart rate variability). The accuracy of the model was 85% (35% greater than chance).

Remote sensing of subsurface fractures in the Otway Basin, South Australia

AbstractNaturally occurring fractures were remotely detected in a 3‐D seismic volume from the Penola Trough in South Australia's Otway Basin and validated through an integrated approach. Identified in image logs are 508 fractures and 523 stress indicators, showing maximum horizontal stress orientation in the Penola Trough is 127°N. Two fracture types were identified: (1) 268 electrically conductive (potentially open to fluid flow) fractures with mean NW‐SE strikes and (2) 239 electrically resistive (closed to fluid flow) fractures with mean E‐W strikes. Core from Jacaranda Ridge‐1 shows that open fractures are rarer than what image logs indicate, due to the presence of fracture‐filling siderite, an electrically conductive cement which may cause fractures to appear hydraulically conductive in image logs. The majority of fractures detected is favorably oriented for reactivation under in situ stresses, although it is demonstrated that fracture fills primarily control which fractures are open. Seismic attributes calculated from the 3‐D Balnaves/Haselgrove survey are mapped to the Pretty Hill Formation to enhance observations of structural fabrics, showing linear discontinuities likely representing faults and fractures. Discontinuity orientations are consistent with natural fracture orientations identified in image logs, striking E‐W and NW‐SE, limited to zones around larger faults. However, it is unlikely that a large proportion of these fractures are open given observations of core and image logs, limiting possible fracture connectivity and therefore significant secondary permeability in the Penola Trough. The integrated methodology presented herein provides an effective workflow for remote detection of subsurface fractures and determining if electrically conductive fractures are also hydraulically conductive.

Propagation of gamma rays and production of free electrons in air

This paper is devoted to the analysis of production of free electrons in air by gamma-rays leaking from radioactive materials. A model based on the Klein-Nishina scattering theory is used to calculate scattering cross sections and approximate the electron production rate. The model includes the effects of primary gamma-quanta radiated by the source as well as that scattered in air. Comparison of the model with the mcnpx kinetic code (http://mcnpx.lanl.gov/) in a sample problem shows excellent agreement. The motivation for this research comes from the recently proposed concept of remote detection of concealed radioactive materials [V. L. Granatstein and G. S. Nusinovich, J. Appl. Phys. 108, 063304 (2010)]. The concept is based on the breakdown in air at the focal point of a high-power beam of electromagnetic waves produced by a THz gyrotron with a 10-20 μs pulse. The presence of a radioactive material can greatly exceed the production rate of free electrons over the natural background rate. Additional electrons act as seeds to initiate the breakdown and create sufficiently dense plasma at the focal region. The dense plasma can then be remotely detected as an unambiguous effect of the concealed radioactive material.

Variation in foliar water content and hyperspectral reflectance of Pinus patula trees infested by Sirex noctilio

The remote detection and quantification of symptoms associated with declining forest health is critical for the introduction of proper pest monitoring and control measures. Sirex noctilio, the Eurasian wood wasp, is one of the major pests responsible for declining forest health in pine forests located in KwaZulu-Natal, South Africa. Researchers have shown that stress induced by S. noctilio causes a rapid decrease in foliar water content, with the foliage of the tree changing from a dark green to a reddish brown hue. This study examined if the variation in foliar water content due to S. noctilio infestation can be remotely detected. Foliar water content and in situ hyperspectral measurements were obtained from Pinus patula trees experiencing varying levels of stress induced by S. noctilio. Subsequently, foliar water content was correlated to selected spectral variables consisting of known water absorption features, spectral indices and continuum-removed absorption features. Results showed that the variations in foliar water content across the varying levels of S. noctilio infestation were strongly linked to the variation in hyperspectral reflectance. Except for water absorption features located at 970 nm and 1200 nm, there was a strong correlation between the majority of the spectral variables and foliar water content. Of the spectral variables tested, the water index (WI) provided the strongest linear correlation (r = 0.84) with foliar water content. Ultimately, results obtained from this study provide the foundation for the detection and monitoring of S. noctilio infestations at a landscape level using airborne or spaceborne hyperspectral platforms.

Compressed sensing of remotely detected MRI velocimetry in microfluidics

NMR and MRI can yield detailed chemical and dynamic information about flow at microscopic resolutions, but suffer from low signal to noise relative to alternative techniques for flow measurements. In porous media and microfluidic devices, this sensitivity problem is further exacerbated by magnetic susceptibility broadening and low coil filling factor. Fortunately, remote detection can mitigate these issues by physically separating signal detection from the other steps of the experiment. The technique requires, however, that any measured interactions be encoded in indirectly sampled dimensions, leading to experiments of high dimensionality and correspondingly long acquisition times. We have applied compressed sensing, a reconstruction technique used in MRI, to dramatically reduce these experiment times by 8–64× through partial sampling (sub-sampling) of k-space, allowing for the collection of images with significantly higher resolutions in reasonable amounts of time. Here, we demonstrate this reconstruction technique to remotely detected flow measurements in a serpentine mixing chip and in a microfluidic channel harboring a constriction. We find that compressed sensing allows for significantly higher resolution images to be collected in a practical amount of time, thus significantly enhancing the applicability of remote detection to flow imaging.

Magnetic resonance imaging of oscillating electrical currents

Functional MRI has become an important tool of researchers and clinicians who seek to understand patterns of neuronal activation that accompany sensory and cognitive processes. However, the interpretation of fMRI images rests on assumptions about the relationship between neuronal firing and hemodynamic response that are not firmly grounded in rigorous theory or experimental evidence. Further, the blood-oxygen-level-dependent effect, which correlates an MRI observable to neuronal firing, evolves over a period that is 2 orders of magnitude longer than the underlying processes that are thought to cause it. Here, we instead demonstrate experiments to directly image oscillating currents by MRI. The approach rests on a resonant interaction between an applied rf field and an oscillating magnetic field in the sample and, as such, permits quantitative, frequency-selective measurements of current density without spatial or temporal cancellation. We apply this method in a current loop phantom, mapping its magnetic field and achieving a detection sensitivity near the threshold required for the detection of neuronal currents. Because the contrast mechanism is under spectroscopic control, we are able to demonstrate how ramped and phase-modulated spin-lock radiation can enhance the sensitivity and robustness of the experiment. We further demonstrate the combination of these methods with remote detection, a technique in which the encoding and detection of an MRI experiment are separated by sample flow or translation. We illustrate that remotely detected MRI permits the measurement of currents in small volumes of flowing water with high sensitivity and spatial resolution.

Remote NADH imaging through an ordered array of electrochemiluminescent nanoapertures

In this report, we present an ordered array comprising thousands of nanoapertures for the electrochemiluminescent (ECL) detection of NADH. It was fabricated on the distal face of a coherent optical fiber bundle. Such a high-density array of nanoapertures combines optical, imaging and electrochemical properties. Indeed, each nanoaperture is surrounded by a gold nanoring, which acts as an electrode material. The behavior of the array was characterized by cyclic voltammetry and it shows excellent electrochemical performances. NADH is the analyte, which is measured in presence of Ru(bpy) 3 2+. The ruthenium complex mediates the NADH oxidation and this coenzyme acts as a co-reactant in the ECL mechanism. ECL light is generated at the distal face of the array by each gold ring electrode. A fraction of this ECL light is collected by the corresponding nanoaperture, transmitted through the optical fiber bundle and finally imaged on the proximal face with a CCD camera. In this work, we show that NADH concentration is remotely detected by an oxidative-reductive ECL mechanism. We present also some preliminary results about the ECL process of NADH with Ru(bpy) 3 2+. The ECL behavior of NADH on gold surface is reported. The influence of the applied potential on the collected light intensity was investigated. The variation of the ECL intensity measured through the nanoaperture array with NADH concentration is linear. Remote ECL detection of NADH is spatially resolved over a large area with a micrometer resolution through the array. Therefore, such array integrates several complementary functions: ECL light generation, collection, transmission and remote imaging in an array format.

Remotely detected high-field MRI of porous samples

Remote detection of NMR is a novel technique in which an NMR-active sensor surveys an environment of interest and retains memory of that environment to be recovered at a later time in a different location. The NMR or MRI information about the sensor nucleus is encoded and stored as spin polarization at the first location and subsequently moved to a different physical location for optimized detection. A dedicated probe incorporating two separate radio frequency (RF)—circuits was built for this purpose. The encoding solenoid coil was large enough to fit around the bulky sample matrix, while the smaller detection solenoid coil had not only a higher quality factor, but also an enhanced filling factor since the coil volume comprised purely the sensor nuclei. We obtained two-dimensional (2D) void space images of two model porous samples with resolution less than 1.4 mm 2. The remotely reconstructed images demonstrate the ability to determine fine structure with image quality superior to their directly detected counterparts and show the great potential of NMR remote detection for imaging applications that suffer from low sensitivity due to low concentrations and filling factor.

Remote Query Resonant-Circuit Sensors for Monitoring of Bacteria Growth: Application to Food Quality Control

This paper presents a technique for in-situ remote query monitoring of bacteria growth utilizing a printed thin or thick-film sensor comprised of an inductor-capacitor (LC) resonant circuit. The sensor, which is placed within the biological medium of interest and remotely detected using a loop antenna, measures the complex permittivity of the medium. Since bacteria growth increases the complex permittivity of a biological medium the LC sensor can be used to determine bacteria concentration. This paper presents results on monitoring of three different bacteria strains, Bacillus subtilis, Escherichia coli JM109, and Pseudomonas putida, demonstrating application of the sensor for monitoring bacteria growth in milk, meat, and beer. Due to its low unit cost and remote query detection, the sensor is potentially useful for commercial scale monitoring of food quality.

Design Theory for a Laminar Flow-Type Clean Room and Image Processing on Remotely Detected Particulates

Clean room technology is growing and is being applied rapidly in various fields such as the electronic industry, semiconductor industry, pharmaceutical industry, etc. This paper initially presents an outline of activities and recent studies in Japan. Clean room research is independently conducted in universities, research laboratories, research institutions, etc. Subsequently, the paper presents a design concept for laminar flow-type clean rooms. In the design of clean rooms, since sufficient theoretical approaches and analyses were not available, U.S. Federal Standard 209B was generally applied. Particle concentration and diameter are the main components by which a clean room is evaluated. This paper reports the importance of a third component: the number of particles reaching an object. Finally, the paper describes the remote detection of particles in clean rooms. Particulate scattered light of a He-Ne laser is remotely detected by using an optical system, a video system, and an image processing system. This paper presents an outline of this system and gives examples of measuring behavior and adhesion.

クリーンルームにおける表面汚染測定のためのレーザー遠隔計測

As to the design of clean rooms, theoretical approaches and analyses were not sufficiently developed and the U. S. A. Federal Standard 209 B was generally applied. At present, the equation of homogeneous momentary diffusion is used for calculations. There is a problem, however not only in reducing particulate concentration in clean room but also in decreasing the number of particles reaching the objective as well as their adhesion ratio. Particulate behavior in clean rooms is considered at three scales, which are : (1) macro analysis of the whole clean room (2) analysis of particulate behavior near the objective (3) analysis of particulate adhesion mechanisms. From the viewpoint of above-mentioned items (2) and (3), it is very important to make direct micro-measurement of particulate bahavior near the objective and adhesion to it without field disturbance. In this paper, a remote detection system of particles in clean rooms is described, Particulate scattered light of a He-Ne laser is remotely detected by using an optical system, a video system and an image processing system. Furthermore, by using the system, particulate behavior near the objective and adhesion are evaluated. These results are considered to be useful for the development of design methods for unidirectional airflow type clean rooms.