Remote Surfaces Research Articles

Compositional Characterization of Glassy Volcanic Material From VSWIR and MIR Spectra Using Partial Least Squares Regression Models

AbstractThe glass phase in volcanic rocks presents a challenge to obtaining compositional data from visible and short‐wave‐infrared (VSWIR) and mid‐infrared (MIR) spectral data of remote surfaces due to its amorphous structure and variable composition. Nonetheless, glass is a common phase in volcanic materials because it forms via the rapid quench of magma and can constitute up to the entirety of a volcanic deposit. Use of partial least squares regression (PLS) to predict glass contents creates models that are insensitive to viewing geometry and sample conditions such as grain size and spectrally inactive compositional variables, enhancing the ability to detect glasses with remote sensing. PLS models are used here to predict crystallinity and oxide composition of samples from VSWIR and MIR spectral data using training spectra from natural volcanic rocks and geologically relevant synthetic samples. Three spectral resolutions of VSWIR and MIR spectra (1, 10, and 100 nm/band, and 1.9, 19, and 190 cm−1/band, respectively) were tested to assess the effects of collection configuration on different spectrometers. PLS models trained on 1 nm and 1.9 cm−1 data sets have the lowest uncertainties of glass modal abundance for VSWIR and MIR, respectively. MIR models predicting sample wt. % SiO2 and FeO, and VSWIR models of wt. % FeO provide accurate estimates (e.g., RMSE‐P of 3.4 wt. % FeO) at all spectral resolutions. Results are based on training data sets skewed to mafic compositions, which affects model accuracies.

Studies of erosion-deposition of plasma-facing materials due to plasma-wall interactions in EAST tokamak

Material erosion, migration, mixing, dust formation, and co-deposition were investigated on plasma-facing materials in the experimental advanced superconducting tokamak (EAST). The test samples (TSs) of molybdenum (Mo), tungsten (W), and carbon (C) were irradiated during EAST operations. All exposed TS surfaces are modified by erosion and deposition processes resulting in the formation of thin layers containing a mixture of PFCs (Mo, W, Cu, Cr, Fe) and light elements (Li, C, Ca, N, O). The majority of chemical species are in a layer of thickness <650–900 nm. The particle size and structure of co-deposition were observed on each TS. Depth profiling by laser-induced breakdown spectroscopy (LIBS) suggests the presence of local and global impurities on the TSs resulting from the plasma-wall interaction (PWI). The processes involved in the PWI that caused erosion of EAST materials are heat flux and high energy excited impurity particles. The material is sputtered from the first wall plasma-facing components. Erosion and deposition processes occur simultaneously in the EAST. The migrated impurities get deposited globally on remote surfaces. A crack was observed in one of the W TSs due to a high heat load. The spectral intensity of co-deposition and substrate continuously changed during successive laser shots.

Experimental investigation of a new photoelectrochemical cell design featuring a unique photocathode configuration for solar hydrogen production

The electrodeposition process and the subsequent assessment of a novel cuprous oxide photocathode are conducted for solar light-based hydrogen production. The mesh dome photocathode helps facilitate the optimal light harvesting, enabling the efficient collection of the maximum accessible light from the solar simulator. This particular design also ensures that light reaches the remote surfaces of the photocathode through penetrating the mesh structure. The electrodeposition method is then employed to coat cuprous oxide onto the stainless-steel electrode. The subsequent examination of this photocathode occurs within an alkaline solution of potassium dioxide to assess its performance in hydrogen production. The study investigates the impact of the new design of the mesh photocathode on hydrogen generation rates, as well as related efficiencies of energy and exergy, under varying light angles during daylight hours. The present experimental findings reveal that the maximum rates of hydrogen production, achieved at a 45° tilt light and 0.25 M KOH, are 15.38 μg/s and it is 15.83 μg/s for vertical light positions. Furthermore, the highest recorded system exergy and energy efficiencies under vertical light conditions are 2.19% and 3.20%, respectively, compared to 2.14% and 3.12% at applying tilted light. The new photocathode design contributes to a notable 80.3% improvement in hydrogen generation rate at tilted light angles in comparison to vertical light conditions.

Defensible Collections: Designing a Safe Exhibit Space

A startling number of conservators tell stories about mistreatment of collection material by the public. We used to hear a familiar type of problem: vitrines marred by strollers, glass broken by resting parents, or a pencil falling out of a pocket onto a background. Now, the story is more dramatic: French fries deposited on remote surfaces of large dinosaur specimens. Is an exhibit successful if attendance contributes to the damage of delicate material? This paper provides a broad overview of the risk to exhibited collection material imposed by visitors. Patterns of damage to collections correspond to specific characteristics of the exhibit spaces themselves. This investigation looks at problems encountered at one large paleontology exhibit and overlays successful concepts drawn from sources outside the museum world.

A Hybrid Volume-Surface Integral Equation Method for Rapid Electromagnetic Simulations in MRI.

We developed a hybrid volume surface integral equation (VSIE) method based on domain decomposition to perform fast and accurate magnetic resonance imaging (MRI) simulations that include both remote and local conductive elements. We separated the conductive surfaces present in MRI setups into two domains and optimized electromagnetic (EM) modeling for each case. Specifically, interactions between the body and EM waves originating from local radiofrequency (RF) coils were modeled with the precorrected fast Fourier transform, whereas the interactions with remote conductive surfaces (RF shield, scanner bore) were modeled with a novel cross tensor train-based algorithm. We compared the hybrid-VSIE with other VSIE methods for realistic MRI simulation setups. The hybrid-VSIE was the only practical method for simulation using 1 mm voxel isotropic resolution (VIR). For 2 mm VIR, our method could be solved at least 23 times faster and required 760 times lower memory than traditional VSIE methods. The hybrid-VSIE demonstrated a marked improvement in terms of convergence times of the numerical EM simulation compared to traditional approaches in multiple realistic MRI scenarios. The efficiency of the novel hybrid-VSIE method could enable rapid simulations of complex and comprehensive MRI setups.

Fringe Detection and Displacement Sensing for Variable Optical Feedback-Based Self-Mixing Interferometry by Using Deep Neural Networks

Laser feedback-based self-mixing interferometry (SMI) is a promising technique for displacement sensing. However, commercial deployment of such sensors is being held back due to reduced performance in case of variable optical feedback which invariably happens due to optical speckle encountered when sensing the motion of non-cooperative remote target surfaces. In this work, deep neural networks have been trained under variable optical feedback conditions so that interferometric fringe detection and corresponding displacement measurement can be achieved. We have also proposed a method for automatic labelling of SMI fringes under variable optical feedback to facilitate the generation of a large training dataset. Specifically, we have trained two deep neural network models, namely Yolov5 and EfficientDet, and analysed the performance of these networks on various experimental SMI signals acquired by using different laser-diode-based sensors operating under different noise and speckle conditions. The performance has been quantified in terms of fringe detection accuracy, signal to noise ratio, depth of modulation, and execution time parameters. The impact of network architecture on real-time sensing is also discussed.

SIMULATION TECHNIQUES IN THE DEVELOPMENT OF THE QUIESCENT PERIOD PREDICTION (QPP) FLIGHT DECK MOTION FORECASTING TOOL

Quiescent Period Prediction (QPP) purpose is to provide ship motion conditions and motion predictions with sufficient forecasted time to launch, recover, and complete other motion sensitive tasks regardless of the seaway. QPP operates within a federated architecture system containing measurement instruments such as a Wave Radar system used to map remote sea surfaces several hundred meters in advance of the ship. This enables the computation of future wave forces acting on the virtual vessel. Quiescent Period Prediction (QPP) system achieves this from the measured sea surface, a short-term deterministic wave model can be constructed allowing the wave system to be propagated to the ship's location. The ability to fully define a ship’s motion as a function of a recovery device, greatly enhances the overall system operational capability whilst fundamentally reducing the inherent risks associated with platform manipulation in high sea conditions. This article describes launch and recovery simulation model and the corresponding verification and validation of the QPP data program testing the accuracy of the simulation modeling. Verification information is discussed regarding the sensor operation and interfaces collected during this trial; a QPP simulation design specification is being produced based on High Level Architecture (HLA) technics. From initial simulation and trial results, QPP has been shown to offer the ability for operators to identify the most favourable deck motion periods to recover an approaching vehicle. The next challenge being studied from the data results is a notional navigational guidance system tool and visual landing aid to be trialled by simulation.

Characterization and comparison of the bacterial community on environmental surfaces through a fresh-cut vegetables processing line in China

Zoning is typically adopted by food manufacturers and classified into three different zones including Zone 1 (food contact surface), Zone 2 (proximity to food and food contact surfaces) and Zone 3 (remote surfaces from processing). In this study, environmental surfaces belonging to these three zones were sampled during food processing in a fresh-cut vegetables (FVs) processing facility located in Beijing, China. Bacterial loads in terms of aerobic plate count and coliform count were evaluated by culture-dependent techniques. The profile and diversity of bacterial community in these three zones were investigated by high-throughput sequencing. Zone 1 showed similar microbiota and predominated by Pseudomonas and Acinetobacter, while the predominant genera on Zone 2 or 3 were quite varied among different processing steps. The SourceTracker analysis showed that most of the bacteria (above 80%) on surfaces were from unknown sources, while sorting and disinfection & cleaning steps contributed equally to the bacterial community of cutting areas. Microbial association network analysis revealed strong positive interactions of Comamonas and Janthinobacterium with Myroides and Serratia, respectively, whereas Pseudomonas showed no significant correlation with other genera. The function of microbial communities was predicted based on BugBase 16S rRNA database, and the results indicated that the proportions of potential biofilm-forming bacteria were above 70% in all samples, and species of Pseudomonas, Comamonas, Chryseobacterium and Janthinobacterium were opportunistic pathogens or spoilage bacteria. This study evaluated the bacteria risks including bacterial load, composition, as well as potential bacterial interaction, function and microbial transfer on food processing surfaces, which will facilitate our better understanding on the cross-contaminations and preventions of harmful microorganism in FVs processing industry.

Optimized algorithm for evapotranspiration retrieval via remote sensing

Many algorithms for surface energy balance (SEB) based on remote sensing (RS) have been advanced to determine evapotranspiration (ET). These algorithms were developed for specific conditions (e.g., sensors, land use, and crop management) in which functions and empirical parameters within its algorithms concur with those conditions. Therefore, this study aims to develop a SEB-RS algorithm for retrieving ET adjusted to in situ observations. The study was conducted in two experimental fields in Brazil with the crops Jatropha curcas, maize, soybean, and sugarcane. We used multispectral images from the orbital sensors, Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) coupled in Landsat 8 satellite and from the terrestrial sensor, Altum, on board of an unmanned aerial vehicle. The proposed algorithm termed as Ground-truthed Surface Energy Balance (GT-SEB) is based on physical formulation of SEB-RS algorithms, where two extra computational processes using in situ ET observations were proposed for originating the new algorithm. The first additional process for optimizing the automatic “anchor” pixels selection and another for algorithm parameters optimization. Thus, both processes aim to reduce the difference between the observed ET and estimated by GT-SEB. Being assessed for both orbital (OLI/TIRS) and suborbital (Altum) sensors, the GT-SEB yielded excellent results (root-mean-square-error, RMSE, ≤ 0.48 mm and modified Kling-Gupta efficiency, KGE, ≥ 0.92). In addition to GT-SEB being an optimized algorithm, it uses a classic parameterization of SEB-RS algorithms, providing efficiency and scalability for other remote sensors, climates, and surfaces.

Towards airborne laser Doppler vibrometry for structural health monitoring of large and curved structures

Laser Doppler vibrometry is an important sensing technology for many structural health monitoring (SHM) methods, such as modal analysis. However, when it comes to large civil structures, for example historic structures and bridges, the applicability of laser Doppler vibrometry is significantly constrained by inaccessible remote surfaces. Some of these surfaces are fully inaccessible to a ground-mounted laser Doppler vibrometer (LDV), while others are partially inaccessible, and measurements are only possible for low incident angles. Consequently, LDV measurements are either impossible or have a weak signal strength. In this study, the concept of constructing an airborne LDV for SHM is explored, including the examination of a recently developed mechanism, the partially airborne LDV, comprising a reflective mirror attached to a drone. Preliminary proof of concept laboratory tests have been successfully conducted using two different set-ups and drone models.

Transparent bilateral teleoperation interacting with unknown remote surfaces with a force/velocity observer design

ABSTRACTA master–slave teleoperation system is considered, in which the slave manipulator is interacting with a rigid surface with unknown geometry. It is assumed that neither force nor velocity measurements at the slave side are available. To deal with this problem, an extended-state high-gain observer is proposed to estimate in an arbitrary close manner the velocity and force signals. At the same time, the gradient vector for the remote surface is online estimated and employed into an hybrid position/force controller based on the orthogonal decomposition of the task space. A formal proof is presented, which guarantees ultimate boundedness of the state of the system, with arbitrarily small ultimate bound. Furthermore, it is established the transparency of the teleoperation system that, roughly speaking, gives the human operator the sensation of being interacting directly with the remote surface. The proposed scheme is validated through numerical simulations and experiments.

Determination of zones with different chemical composition on remote surfaces

Determination of zones with different chemical composition on remote surfaces

Mechanism of catalysis, E2 recognition, and autoinhibition for the IpaH family of bacterial E3 ubiquitin ligases

IpaH enzymes are secreted bacterial effectors that function within host cells as E3 ubiquitin (Ub) ligases. Catalytic activity is imparted by a conserved novel E3 ligase (NEL) domain that is unique to Gram-negative pathogens and whose activity is repressed by a flanking substrate-binding leucine-rich repeat (LRR) domain when substrate is absent. How the NEL domain catalyzes the conjugation of Ub onto substrates, recognizes host E2s, and maintains its autoinhibited state remain poorly understood. Here we used mutagenesis and enzyme kinetic analyses to address these gaps in knowledge. Mutagenesis of conserved residues on two remote surfaces of the NEL domain identified functional clusters proximal to and distal to the active site cysteine. By analyzing the kinetics of Ub charging and discharging, we identified proximal active site residues that function as either the catalytic acid or catalytic base for aminolysis. Further analysis revealed that distal site residues mediate the direct binding of E2. In studying the full-length protein, we also have uncovered that IpaH family autoinhibition is achieved by a short-circuiting mechanism wherein the LRR domain selectively blocks productive aminolysis, but not the nonproductive discharge of Ub from the E3 to solvent. This mode of autoinhibition, which is not shared by the HECT domain ligase Smurf2, leads to the unanticipated depletion of E2∼Ub and thus a concomitant dominant-negative effect on other E3s in vitro, raising the possibility that short circuiting also may serve to restrict the function of host E3s in cells.

Effects of viewing geometry, aggregation state, and particle size on reflectance spectra of the Murchison CM2 chondrite deconvolved to Dawn FC band passes

Several current and soon-to-launch missions will investigate ‘dark’ asteroids, whose spectra have few weak or no distinct spectral features. Some carbonaceous chondrites, particularly the CI and CM groups, are reasonable material analogues for many dark asteroid surfaces. In addition to compositional variations, many non-compositional effects, including viewing geometry, surface particle size and particle sorting, can influence reflectance spectra, potentially complicating mineralogical interpretation of such data from remote surfaces. We have carried out an investigation of the effects of phase angle, particle size, aggregation state, and intra-sample heterogeneity on the reflectance spectra (0.4–1.0μm) of the Murchison CM2 carbonaceous chondrite, deconvolved to Dawn Framing Camera (FC) band passes. This study was motivated by the desire to derive information about the surface of Ceres from Dawn FC data. Key spectral parameters derived from the FC multispectral data include various two-band reflectance ratios as well as three-band ratios that have been derived for mineralogical analysis.Phase angle effects include increased visible slope with increasing phase angle, a trend that may reverse at very high phase angles. Fine-grained particles exert a strong influence on spectral properties relative to their volumetric proportion. Grain size variation effects include a decrease in spectral contrast and increased visible spectral slope with decreasing grain size. Intra-sample heterogeneity, while spectrally detectable, is of relatively limited magnitude.

A Lipopolysaccharide from Pantoea Agglomerans Is a Promising Adjuvant for Sublingual Vaccines to Induce Systemic and Mucosal Immune Responses in Mice via TLR4 Pathway.

A lipopolysaccharide from Pantoea agglomerans (LPSpa) has been applied to various fields for human use as a Toll-like receptor 4 ligand and its safety has been confirmed. Here, we showed for the first time the application of LPSpa as an effective mucosal adjuvant for activating vaccine-induced antigen specific immune responses. Mice sublingually immunized with influenza vaccine (HA split vaccine) with LPSpa induced both HA-specific IgG (systemic) and IgA (mucosal) antibody responses, which led to a significant increase in survival rate against lethal influenza virus challenge compared with subcutaneous vaccination. After sublingual administration of ovalbumin with LPSpa, ovalbumin-specific mucosal IgA responses were induced at both mucosal surfaces close to the immunized site and at remote mucosal surfaces. Sublingual administration of LPSpa evoked local antigen-uptake by dendritic cells in cervical lymph nodes. LPSpa induced cytokine production and the maturation and proliferation of innate immune cells via Toll-like receptor 4 in dendritic cells. Collectively, these results suggest that LPSpa can be used as an effective mucosal adjuvant to stimulate and activate local innate immune cells to improve and enhance mucosal vaccine potency against various pathogens.

Fibre‐tree network for water‐surface ranging using an optical time‐domain reflectometry technique

To monitor water level at long distance, a fibre-based time-domain reflectometry network is proposed. A collimator at each fibre end of a tree-type network retrieves 1.55 μm wavelength pulses that are reflected back from remote surfaces. Since this enables a power-supply-free sensor network with non-metal media, this system is expected to be less susceptible to lightning strikes and power cuts than conventional systems that use electrically powered sensors and metal cables. In the present Letter, a successful simultaneous monitoring experiment of two water levels in the laboratory, as well as a trial for detecting a disturbed surface by beam-expanding is reported.

Polarization Conversion for Specular Components of Surface Reflection

Certain characteristics of a material such as the surface reflectivities can be determined even without knowledge of its internal properties. In this letter, a direct relationship (Azzam relationship) and an analytical approximation (Azzam-Sohn-Hong (ASH) approximation) between the vertically and horizontally polarized reflectivities of specular surfaces are derived and validated using the refractive indices of water and metal in a variety of spectral regions. For the purpose of practical remote applications, land, sea water, sea ice, and oil surfaces are considered and compared using the Hong and ASH approximations. Consequently, ASH approximation has an advantage in a variety of spectral bands for materials with a small imaginary part of refractive index, while the Hong approximation does well in the microwave spectral region, or when the imaginary part of the reflective index is not neglected. Thus, a combination of the Hong and ASH approximations is suggested to improve upon previous studies that used only the Hong approximation in a variety of applications.

Modelling thermal radiation from one-meter diameter methane pool fires

The first objective of this article is to implement a comprehensive radiation model in order to predict the radiant fractions and radiative fluxes on remote surfaces in large-scale methane pool fires. The second aim is to quantify the importance of Turbulence-Radiation Interactions (TRIs) in such buoyant flames. The fire-induced flow is modelled by using a buoyancy-modified k-ε model and the Steady Laminar Flamelet (SLF) model coupled with a presumed probability density function (pdf) approach. Spectral radiation is modelled by using the Full-Spectrum Correlated-k (FSCK) method. TRIs are taken into account by considering the Optically-Thin Fluctuation Approximation (OTFA). The emission term and the mean absorption coefficient are closed by using a presumed pdf of the mixture fraction, scalar dissipation rate and enthalpy defect. Two 1m-diameter fires with Heat Release Rates (HRR) of 49 kW and 162 kW were simulated. Predicted radiant fractions and radiative heat fluxes are found in reasonable agreement with experimental data. The importance of TRIs is evidenced, computed radiant fractions and radiative heat fluxes being considerably higher than those obtained from calculations based on mean properties. Finally, model results show that the complete absorption coefficient-Planck function correlation should be considered in order to properly take into account the influence of TRIs on the emission term, whereas the absorption coefficient self-correlation in the absorption term reduces significantly the radiant fractions.

Exosites, Allostery, &amp; Active Site in MMP Engagement of Elastin, Collagen, and Heparin from the Matrix

MMP‐12 and MT1‐MMP digest protease‐resistant elastin and collagen in inflammatory diseases. ProMMP‐7 is activated by glycosaminoglycans (GAGs). How do these matrix components interact with these MMPs? We sought to locate using NMR the binding sites of elastin and collagen triple‐helical peptides upon MMP‐12, collagen upon MT1‐MMP, and heparin fragments upon proMMP‐7. Two remote loops enhance its degradation of elastin substrates. Mutations at both remote loops plus the active site knock down specifically the elastase activity to that of the negative control. A collagen triple‐helical peptide crosses the active site of MMP‐12 at an angle and may separate the peptide chains in the primed positions for one chain to fit into the narrow slot formed by the primed subsites. Solubilized collagen binds a patch across blades III and IV of the β‐propeller of the hemopexin domain of MT1‐MMP. Binding of 6 to 12‐mer pieces of heparin to proMMP‐7 achieves part of the GAG‐dependent activation. The binding site is on the back of the catalytic domain. Adjustments in the interface between catalytic and pro‐domains and activation can then follow, suggesting allosteric communication at long range. Overall, pericellular proteolysis can engage remote surfaces of MMPs. Supported by NIH grants GM57289 and CA98799 and AHA grant 0855714G.

In Situ Tritum Measurements and Control by Laser Techniques

In this paper, in situ tritium measurements and control by laser techniques are presented. It is proposed to use Laser-Induced Breakdown Spectroscopy (LIBS) as an efficient technique to measure the tritium concentration in ablated material. However, LIBS could be limited due to material melting observed during ablation possibly leading to hydrogen losses. Laser ablation is shown to be an efficient process to recover the in vessel tritium if the dust produced during ablation is collected. This could be forbidden if ITER cannot be operated at high pressure. To overcome this difficulty and detritiate remote surfaces, laser heating could be applied since it generates gaseous compounds. However, inward diffusion could be expected leading to burry tritium in bulk material which is a counterproductive action. Finally, all these techniques must be embarked on remote handling system in order to explore and treat large surfaces. Obviously, this carrier is needed for a reliable and an efficient operation of the ITER nuclear facility.