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Infrared hyperspectral instrument is a complex optical instrument. The requirement for the application of the infrared hyperspectral interferometer is fine calibration accuracy. The accuracy of the spectral frequency of the infrared hyperspectral interferometer is a key influencing factor of the radiometric calibration accuracy. In order to meet the quantitative application, the spectral calibration accuracy is generally within 10ppm. For infrared hyperspectral instruments in geostationary orbit, the focal plane has the characteristics of large array and small detector size. When the detector size of an infrared hyperspectral interferometer is in the geostationary orbit whether the detector as a point detector will affect the spectral calibration accuracy. In this paper, we simulate and analyze the influence of the shape of the detector (square and point detector) on the spectral calibration accuracy. This paper first builds an infrared hyperspectral observation and calibration simulation model. The brightness temperature deviation between the calibration spectrum and the input spectrum is close to 0 K, which shows the rationality of building the simulation model. Then, in the process of spectral calibration, two methods, square detectors and point detectors, are adopted, respectively. The spectral calibration of the square detector needs to calculate the line shape function of the instrument according to the detector position. Regarding point detector spectral calibration, this paper proposes a spectral calibration parameter optimization algorithm based on the optimization algorithm, which does not depend on the physical parameters of the instrument, but only uses the observed simulated spectrum and the reference spectrum. The results show that the spectral calibration accuracy of the point detector based on the optimization method can be close to 0ppm, which is consistent with the spectral calibration accuracy of the square detector. [ABSTRACT FROM AUTHOR]

An experimental campaign is conducted on a 100g centrifuged monopile model, impact driven, into saturated dense sand, down to three embedding depths, corresponding to three slenderness ratios of 5, 4 and 3. These models are instrumented with optical fibres to measure the bending moment profile along the monopile. A new method is developed to determine the experimental soil reaction curves by considering the distributed moment part from the measured bending moment. This distributed moment is assessed by the one-dimensional finite-element (1D FE) model of the PISA (pile soil analysis) method. The key features of this study are: (a) the monopile behaves from pure rotation to combined rotation–flexure as the slenderness ratio is enhanced from 3 to 5, inducing a less pronounced linear rotation–deflection response at ground level; (b) although the distributed moment assessed in the PISA project is very low, the developed method is useful to explore the experimental local behaviour of laterally loaded monopiles; (c) the 1D FE PISA model captures reasonably well the overall behaviour of laterally loaded centrifuged driven monopiles, even if it is less accurate for the local behaviour. [ABSTRACT FROM AUTHOR]

The recent discovery of nanoplastics in most ecosystems is a major, yet poorly known health issue. Here, we review nanoplastics with focus on their presence in the environment, their methods of detection, and their impact on the nitrogen cycle. Nanoplastics are widely distributed in ecosystems; however, their real concentrations are not known due to the limitation of actual detection methods. Detection methods include techniques based on mass spectrometry, optical instruments, and total organic carbon. Total organic carbon-based methods involve first membrane filtration and oxidation as pretreatment, then the measurement of total organic carbon as the total concentration of nanoplastics. Total organic carbon-based methods are easy and cost-effective, compared with other methods. Nanoplastics negatively impact ecosystems and nitrogen removal. Nanoplastics can adsorb on microbial cell membranes then disrupt the membrane integrity. Nanoplastics can also induce oxidative stress. Nitrogen cycling is substantially inhibited by nanoplastics during laboratory tests. [ABSTRACT FROM AUTHOR]

Ammonia gas is a colorless gas that is known for its pungent odor. It is commonly used in various industries, such as agriculture, refrigeration, and chemical manufacturing. This paper provides a comprehensive overview of various technologies employed in ammonia gas sensors. The objective is to compare and identify the optimum method to detect ammonia gas. The review encompasses catalytic gas sensors, metal oxide gas sensors, polymer conductivity gas sensors, optical gas sensors, and indirect gas sensors, detailing their respective operational principles. Additionally, the advantages and disadvantages of each technology for ammonia gas detection are outlined. All these technologies have been used for many applications and some of them have been commercialized. Some sensor characteristics suggestions are also stated in order to develop an improved optical ammonia sensor for industrial applications. [ABSTRACT FROM AUTHOR]

The scattered-light time-history diagnostic (SLTD) suite measures time-resolved scattered light in three wavelength bands: stimulated Brillouin scattering (350–352 nm), stimulated Raman scattering (430–760 nm), and plasma emission at half the laser frequency (695–735 nm), at 15 locations around the National Ignition Facility (NIF) target chamber. The SLTD, along with the full-aperture backscatter station (FABS), collects scattered light from direct- and indirect-drive inertial confinement fusion experiments. The SLTD calibration was revisited after a discrepancy between FABS and SLTD measurements was observed on NIF polar direct-drive [Skupsky et al., Phys. Plasmas 11, 2763 (2004)] experiments. An integrated calibration of the SLTD was performed for the first time, and individual components were also calibrated for the wavelengths of 351, 527, and 532 nm. The optical transmission of the instrument was measured to be (1.12 ± 0.04) × 10−7 and (1.96 ± 0.11) × 10−7 for the wavelengths of 351 and 532 nm, respectively. The revised calibration at 351 nm brings the SLTD measured scattered energy in agreement with the FABS measured scattered energy after additionally accounting for the degradation of an optical element in FABS. This decreased the inferred absorption by 7% for a representative experiment. However, discrepancies remain between FABS and SLTD measurements in the SRS band (532 nm). [ABSTRACT FROM AUTHOR]

This article identifies the recurring expression 'scope and method/s' in three published lectures by Henry Sidgwick, Halford Mackinder and James George Frazer between 1885 and 1921. It tracks transdisciplinary connections between the thought and practice of late nineteenth-century philosophy, economic science and geography, and early twentieth-century anthropology, thereby illuminating shifting perceptions, and applications, of historical geographical knowledge and imaginations in a broader speculative evolutionary epistemological scheme. At a time when science and humanities subjects were thought to be diverging, it shows that metaphorical uses of optical instruments helped draw synoptic spatio-temporal frames of reference which shaped transdisciplinary and trans -institutional practices. • Speculates about the metaphorical uses of optical instruments in satiotemoral frames of reference. • Presents a projected line of sight between Henry Sidgwick, Halford Mackinder and James George Frazer. • Suggests historical geographical conceptual frameworks were important to philosophy and political economy and anthropology. [ABSTRACT FROM AUTHOR]

Methods that supplement optical instruments with bait, such as baited remote underwater video (BRUV), are used worldwide to detect and quantify marine life. Optical instruments only detect targets within visible range, such that BRUVs may underestimate fishes in light‐limited habitats, especially fishes that respond to the bait at ranges beyond visibility. Alternatively, light‐independent instruments (e.g., imaging sonars) can detect and quantify fishes regardless of visibility. This study presents the first application of a baited imaging sonar (BISON), deployed to survey fishes around a small, shallow artificial habitat in a turbid embayment in southern Florida. To establish the influence of bait on fish detection, BISON trials were alternately conducted alongside deployments of an unbaited control, with a high‐definition camera integrated to ascertain visibility and inform species composition. For fishes of two size classes, larger (> 30 cm) and smaller (10–30 cm), maximum density (MaxD) and range of detection were quantified. Although the densities of larger and smaller fishes quantified by the BISON and unbaited control did not differ, over 55% of larger fishes were detected at ranges beyond maximum visibility, with asymptotes in fish density on the BISON identified at 15–20 min and 5–10 min for larger and smaller fishes, respectively. Overall, this study demonstrates the potential of BISONs as both a complementary and alternative method to BRUVs for quantifying fishes, especially in habitats of limited visibility. Future applications of BISONs in other habitats will further demonstrate its value as a tool to detect and enumerate aquatic assemblages. [ABSTRACT FROM AUTHOR]

Femtosecond laser machining offers high precision and minimal thermal impact, making it a promising technique for processing hard and brittle materials like single-crystal diamonds (SCDs). In this study, the femtosecond laser machining process for SCD material was systematically optimized to improve both machining efficiency and quality. Initial single-factor experiments were conducted to explore the effects of key process parameters—laser power, scanning speed, and number of scans—on machining performance. Subsequently, response surface methodology (RSM)-based experiments designed using the Box–Behnken method were employed to comprehensively refine the process. A regression model was developed to analyze the data, and the interaction effects of the parameters were thoroughly evaluated. The validated model identified an optimal set of parameters, resulting in a significant improvement in machining performance. This research provides a comprehensive framework for optimizing femtosecond laser machining processes, offering valuable insights critical for the production of advanced lightweight components in industries such as aerospace, optical instruments, and high-performance electronics. [ABSTRACT FROM AUTHOR]

This study assesses the reliability and limitations of the Geostationary Lightning Mapper (GLM) in detecting continuing currents by comparing observations from ground‐based high‐speed cameras with GLM‐16 data. Our findings show that the GLM's one‐group detection efficiency (DE_1) is 53%, while the more stringent five‐consecutive‐group detection efficiency (DE_5) is 10%. Optical signals detected by the GLM predominantly occur during the early stages of continuing currents. Additionally, there is a notable disparity in detection efficiencies between positive and negative continuing currents, with positive continuing currents being detected more frequently. The application of the logistic regression model developed by Fairman and Bitzer (2022) further illustrates the limitations in continuing current identification. The study underscores the challenges of relying solely on satellite data to monitor and analyze continuing currents, emphasizing the need for advancements in detection technologies and methodologies to reliably detect continuing current at a large spatial scale. Plain Language Summary: This study investigates continuing current in cloud‐to‐ground lightning—a prolonged electrical discharge known for causing significant damage, such as igniting large‐scale wildfires. For the first time, we used recordings from ground‐based high‐speed cameras to assess how effectively the Geostationary Lightning Mapper (GLM), an optical instrument on the GOES satellite, detects these currents. Our findings reveal that the GLM often captures only the early stages of continuing currents and struggles to detect them consistently, particularly those in weaker, negative types of lightning. These results underscore the limitations of current satellite‐based optical instruments in fully monitoring continuing currents, emphasizing the need for improved methods to better detect and understand these electrical discharges and mitigate their impacts. Key Points: The Geostationary Lightning Mapper is limited in detecting continuing current, with a one‐group DE of 53% and a five‐group DE of just 10%Optical signals captured by the Geostationary Lightning Mapper are predominantly during the early stage of continuing currentsA significant disparity is observed in GLM detection efficiencies between positive and negative continuing currents [ABSTRACT FROM AUTHOR]

Purpose: We recently developed an optical instrument to non-invasively detect fluorescently labeled circulating tumor cells (CTCs) in mice called 'Diffuse in vivo Flow Cytometry' (DiFC). OTL38 is a folate receptor (FR) targeted near-infrared (NIR) contrast agent that is FDA approved for use in fluorescence guided surgery of ovarian and lung cancer. In this work, we investigated the use OTL38 for in vivo labeling and detection of FR + CTCs with DiFC. Procedures: We tested OTL38 labeling of FR + cancer cell lines (IGROV-1 and L1210A) as well as FR- MM.1S cells in suspensions of Human Peripheral Blood Mononuclear cells (PBMCs) in vitro. We also tested OTL38 labeling and NIR-DIFC detection of FR + L1210A cells in blood circulation in nude mice in vivo. Results: 62% of IGROV-1 and 83% of L1210A were labeled above non-specific background levels in suspensions of PBMCs in vitro compared to only 2% of FR- MM.1S cells. L1210A cells could be labeled with OTL38 directly in circulation in vivo and externally detected using NIR-DiFC in mice with low false positive detection rates. Conclusions: This work shows the feasibility of labeling CTCs in vivo with OTL38 and detection with DiFC. Although further refinement of the DiFC instrument and signal processing algorithms and testing with other animal models is needed, this work may eventually pave the way for human use of DiFC. [ABSTRACT FROM AUTHOR]

An inspection in tablet appearance integrity before bottling is regarded as a routine task in a pharmaceutical factory. Although some methods such as automated optical instrument, video or artificial intelligence (AI) are currently available in industry, it usually pays for a complex computational process as well as high cost. Based on the symmetry of tablet appearance in reality, this study develops a biaxial scanning slope symmetry algorithm to realize a dynamic real-time tablet defect detection with a simple arithmetic operation. First, the tablet is discretely scanned using image sensor in two axes, i.e. X and Y directions, simultaneously. Second, the analogy output signals generated from the sensor during the scanning process is discretely digitized and stored in an array. Third, the coordinate of center point in the series data array is identified from every line scanning. Fourth, every section slope between two nearby center points from the first to last lines is formulated and calculated sequentially. Finally, the square mean error (SME) is used to evaluate the shape defect situation according to all accumulated errors from every slope variation. The experimental results verify that the proposed algorithm can achieve both fast and accurate detection performance. [ABSTRACT FROM AUTHOR]

Simple Summary: Over the last decade, optical sensors have demonstrated great potential to provide complementary data to monitor insect abundance. This article introduces a field-deployable and non-destructive optical instrument to monitor the abundance of flying insects, called an Entomological Bistatic Optical Sensor System, or eBoss. The study focuses on comparing abundance measurements made by the eBoss and physical traps over an 8-month field campaign. The eBoss made over 302,000 insect observations and evaluated the aerial density (#/m3) of all flying insects as well as specifically male and female mosquitoes with a 1 min resolution, allowing us to monitor both the abundance over the season and daily peak of activity. The study's objectives were to validate the optical sensor's data against physical trap collections, which confirmed the correlation between the two methods. However, the eBoss demonstrated superior temporal resolution (1 min versus approximately 3 days) and statistical power due to its larger sample size. These findings suggest that an eBoss can significantly enhance flying insect monitoring efforts, such as mosquitoes or pollinators, providing valuable insights for vector control strategies, agriculture and public health planning. Optical sensors have shown significant promise in offering additional data to track insect populations. This article presents a comparative study between abundance measurements obtained from a novel near-infrared optical sensor and physical traps. The optical instrument, named an Entomological Bistatic Optical Sensor System, or eBoss, is a non-destructive sensor operating in the near-infrared spectral range and designed to continuously monitor the population of flying insects. The research compares the mosquito aerial density (#/m3) obtained through the eBoss with trap counts from eight physical traps during an eight-month field study. The eBoss recorded over 302,000 insect sightings and assessed the aerial density of all airborne insects as well as male and female mosquitoes specifically with a resolution of one minute. This capability allows for monitoring population trends throughout the season as well as daily activity peaks. The results affirmed the correlation between the two methods. While optical instruments do not match traps in terms of taxonomic accuracy, the eBoss offered greater temporal resolution (one minute versus roughly three days) and statistical significance owing to its much larger sample size. These outcomes further indicate that entomological optical sensors can provide valuable complementary data to more common methods to monitor flying insect populations, such as mosquitoes or pollinators. [ABSTRACT FROM AUTHOR]

The paper presents new detailed radar maps and polarimetric data covering the southern polar region of the near side of the Moon measuring 400 × 800 km with a spatial resolution of about 75 m. The data were obtained using the 64-meter antenna (TNA-1500) of the Satellite Communications Center Bear Lakes of the Special Design Bureau of the Moscow Power Engineering Institute and the 13.2-meter radio telescope (RT-13) of the Svetloe Observatory of the Institute of Applied Astronomy, Russian Academy of Sciences, at a wavelength of 4.2 cm. At this wavelength, radar signals penetrate the lunar regolith to depths of up to 1 m and are sensitive to surface and suspended rocks larger than 1 cm. The maps show 39% of the area of permanently shadowed regions not observable by optical Earth-based instruments, which may hide water ice deposits. Analysis of radar maps did not reveal any relationship between the polarization properties of the surface in these regions and the presence of solar illumination. The data obtained as a result of this work can be used to study the surface and subsurface regolith features of the lunar south polar region, including searching for ice deposits in permanently shadowed regions, as well as for planning future lunar missions. [ABSTRACT FROM AUTHOR]

Calcium molybdate (CaMoO 4) and Dy3+ doped CaMoO 4 (Dy3+ = 0.5, 1, 1.5, 2 and 2.5 at.%) nanoparticles were successfully obtained by mechanochemical approach. The influence of Dy3+ ion concentration on the structure, morphology, and photoluminescent properties were investigated. The CaMoO 4 and Dy3+ doped CaMoO 4 phases with tetragonal structure were completely prepared after 30 min milling time with applied milling speed of 850 rpm. TEM analysis shows that the synthesized samples consist of mainly spherical particles with narrow particle size distribution. According to both XRD and TEM analysis, the average particles size is below 40 nm. The UV–vis absorption spectra show one peak at 240–245 nm. The calculated optical band gap of pure CaMoO 4 is 3.96 eV and it decreases to 3.65 eV with increasing the concentration of Dy3+ ion up to 2.5 at %. The excitation spectra of the Dy3+-doped CaMoO 4 samples contain absorption peaks corresponding to the MoO 4 group and to the Dy3+ ion. The green and blue light emissions were observed for pure CaMoO 4 and Dy3+ doped CaMoO 4 samples under different wavelengths excitation (250 and 350 nm) typical for absorption of the host matrix. Emission spectra of all doped powders consist of the characteristic peaks of Dy3+ in the blue (∼480 nm) and yellow (∼575 nm) regions which are assigned to the 4F 9/2 → 6H 15/2 and 4F 9/2 → 6H 13/2 transitions, respectively. The weak peak at 660 nm also is observed due to 4F 9/2 → 6H 11/2 transition of Dy3+ ion. The highest photoluminescence emission intensity was detected when the sample is doped with 1.5 at.% Dy3+ concentration. It was found that the color coordinates (x and y) of 1.5 at.% and 2 at.% Dy3+-doped CaMoO 4 fall close to the white light region in the CIE diagram. The results indicate that the mechanochemically obtained Dy3+ doped CaMoO 4 nanoparticles can find application in different optical instruments. [ABSTRACT FROM AUTHOR]

Nanofilms (NFs) have been widely used in many emerging applications, such as microelectronic devices, spintronics, and optical instruments. Characterizing the thermal conductivity (k) of NFs, kNFs, is nontrivial for both fundamental science and industrial applications. Time-domain thermoreflectance (TDTR) is a powerful technique for thermal characterizations under nano-to-micro-scales. However, both the kNFs and the interface thermal resistance between layers are generally unknown parameters when analyzing TDTR signals. So that an effective thermal resistance model (ETRM) is often utilized, where the impact of heat capacity of NFs, cNFs, has been always ignored. Previous studies have proposed viewpoints on how to validate this assumption, however, which still needs to be verified further by considering the parameters' sensitivities for TDTR signals. In this work, we have highlighted the significance of sensitivity analysis for the investigation of the impact of cNFs with the example experiments on Ni NFs. The error of ETRM has been quantitatively and systematically studied. We found that the application requirements of ETRM in TDTR data analysis rely on the sensitivity relations between kNFs and interface thermal resistance. Finally, suggestions for future characterization of the kNFs have been discussed for reference. Our results and conclusions deepen the understanding of both the transient thermal transport process of multilayer NFs and the ability of TDTR on characterizing kNFs. [ABSTRACT FROM AUTHOR]

The recent development of optical measuring instruments has increased the use of surface topographic data for monitoring the quality of the engineered surface. Due to the complexities of modern industrial processes, however, surfaces of final products under the normal manufacturing process may have multiple modes, such that the surface consists of different topographic features from one in-control mode to another. In this case, existing monitoring approaches based on the single mode surface cannot characterise normal surfaces with multiple modes, and result in poor detection performance. In this article, a new approach for monitoring variations in multimode surface topography is presented. We propose a multimode surface prediction model, which characterises the generic behaviour of normal surfaces with multiple in-control modes. Moreover, we present a mode-specific surface monitoring approach that identifies topographic variations on the surfaces based on the similarity between probability density function (PDF) of residuals from observed and normal surfaces obtained through the prediction model. A novel probabilistic distance measure is introduced to effectively measure the similarity between a single residual PDF and a set of residual PDFs under the same mode. The effectiveness of the proposed approach is demonstrated through numerical simulation and real-life application of paper surface monitoring. [ABSTRACT FROM AUTHOR]

Byline: K. Ahmad, H. M. Ahmed and A. Shah Keywords: NIR spectroscopy, support vector machine, SIMCA, standard normal variate, Savitzky-Golay, classification INTRODUCTION Rapeseed is considered to be the second-highest yielding [...]

Neuromorphic sensors have inherently‐fast speeds and low data rates, which potentially make them ideal for the observation of transient sources, such as lightning and sprites. Particularly, for remote observations. In this article, we report the first observations of sprites from the ground with a neuromorphic sensor. These observations are accompanied by measurements with established instruments such as low‐light level and high‐frame rate cameras. We determine that neuromorphic sensors can capture sprites and determine their duration to an accuracy of roughly 6 ms. Average sprite durations were found to be 55 ms within our data set. We have also ascertained that sprites may be too dim for the neuromorphic sensors to resolve the internal spatiotemporal dynamics, at least without the aid of intensifiers. Plain Language Summary: Neuromorphic sensors are a relatively new tool with great potential for imaging transient sources. Neuromorphic sensors track light changes in individual pixels and only store information when the light intensity surpasses a pre‐set threshold, a design choice made with the intent of mimicking how the human eye works. Sprites and lightning are fast, transient light sources and, thus, are an ideal target to test this new technology. In this work, we report the first observations of sprites from the ground with a neuromorphic sensor, and compare these observations with recordings made with an established and well‐understood instrument: an intensified high‐speed camera. Our results show that there is a lot of promise in using this new technology for observation of sprites and lightning, particularly for autonomous, long‐duration observations. We conclude by speculating that the use of neuromorphic sensors in atmospheric sciences will grow substantially in the coming years. They will find many uses in autonomous optical instruments, such as employed for monitoring the aurora, atmospheric gravity waves, and bolide/fireball detection. Key Points: Fast speeds and low data rates potentially make neuromorphic cameras ideal for observation of sprites and lightningNeuromorphic sensors can measure sprite durations in good agreement with high frame rate camerasSprites are very dim making it challenging for the neuromorphic sensor to resolve their internal spatiotemporal dynamics [ABSTRACT FROM AUTHOR]

The cylindrical surface with Bragg-enhanced Fresnel reflectivity constructed from non-close-packed photonic crystals (NPCs) was designed for spectral selectivity and optical gain, which broke through the limitations of traditional Fresnel curved mirror with lowest central reflectivity and inability to perform spectral selectivity, and was conducive to expending the application of Fresnel mirror in the fields of signal transmission, optical measurement and instrument design. [Display omitted] According to the Fresnel theory, the reflectivity intensity of spherical and cylindrical convex surfaces decreases from their edge to center, and it is noteworthy and interesting for optical gain to study the enhancement of center reflectance. In this paper, a polydimethylsiloxane (PDMS) − encapsulated cylindrical non-closed-packed photonic crystals (NPCs) composite with Bragg-enhanced Fresnel reflectance was designed for spectral selectivity and optical gain. Theoretically and experimentally, the periodically ordered structure of NPCs achieved high-reflection of light in photonic bandgap and high-transmission in other bands, which enhanced Fresnel reflectivity of the convex center to specific bands. Furtherly, the cylindrical NPCs hydrogel with stretchability was applied for the dynamic tuning of optical signals. The reflection peak of the PDMS-encapsulated cylindrical NPCs composite blue-shifted from 608 nm to 413 nm with 50 % tensile strain and achieved a rapid transition of structural color from orange to blue-violet in 60 cycles. The new kind of photonic crystals composite for optical gain and spectral selection broke through the limitations of traditional Fresnel curved mirrors with the lowest central reflectivity and inability to perform spectral selectivity, and have great significance and application prospects in fields of signal transmission, optical measurement, and instrument design. [ABSTRACT FROM AUTHOR]

This article examines the evolution of zooming and its impact on human perception, blending historical analysis with concepts from enaction and ecological psychology. The paper traces the advancement of magnifying tools from ancient lenses to modern optical instruments, highlighting their transformative role in extending human capabilities to perceive beyond natural limits. Central to this exploration are Zoomable User Interfaces (ZUIs), which exemplify the integration of perceptual theories into technological innovation. ZUIs are presented not just as tools but as interactive platforms that embody enactive and ecological principles, enabling users to engage dynamically with multi-scale digital environments. This approach challenges traditional views of perception, emphasizing an active, embodied experience that aligns with our cognitive abilities, opening up new perceptual agencies. The paper concludes by exploring future possibilities in virtual reality and multimodality, suggesting new directions for zoom technologies to enrich human perceptual experiences. This work offers a narrative that underscores the continuous human quest to enhance our understanding and interaction with the world, marking the expansion of human perception and interaction with our environment. [ABSTRACT FROM AUTHOR]

The spaceborne turntable is a piece of precision optical equipment utilized for monitoring space information and facilitating laser communication. The measurement accuracy of optical instruments is correlated to some extent with the mechanical properties of the structure. Addressing the design challenge posed by the U-frame in the spaceborne optoelectronic tracking and pointing turntable, this paper proposes a multi-constraint topology optimization method utilizing Abaqus/CAE and TOSCA. This method offers insights for U-frame design and has undergone scientific validation. Initially, the empirical design structure is established, optimization design areas are defined, and the initial model undergoes pre-processing in Abaqus/CAE. Subsequently, conceptual and mathematical models for topology optimization are developed, with the objective of minimizing structural compliance (thereby maximizing stiffness), and including constraints related to volume fraction, first-order natural frequency, and stress. Utilizing TOSCA, the U-frame topology optimization design is finalized, resulting in an optimized conceptual model. A comparative analysis of the optimized design against the empirical design structure demonstrates a significant 27.53% reduction in maximum stress, enhanced static stiffness, an increase of 11.48% in the first natural frequency, and a 4.3% reduction in mass. Moreover, the turntable that utilizes the optimized design structure not only meets reliability requirements in spacecraft structural design but also provides a stable platform for precise optical load alignment. The static and dynamic performance of the optimized U-frame has been enhanced, effectively mitigating the impact of external excitation on optical instrument measurement accuracy and meeting the lightweight design requirements for the U-frame, thus demonstrating the efficacy of the topology optimization method. This research offers valuable insights into U-frame design for spaceborne optoelectronic tracking and pointing turntables and carries significant guiding implications. [ABSTRACT FROM AUTHOR]

Optical instrumentation used in space normally employs optical coatings. Future interplanetary space missions will be characterized by ever longer stays in environmental conditions where low energy protons represent one of the main types of radiation impacting the coating longevity and performance. To ensure the reliability of coated optics, environmental resistance tests should be accurately planned to be representative for a mission. To this end, the existing standards for coating tests and the test results interpretation have been constantly improved. In this study, we analyze the relevant standards of the European Space Agency (ESA) and of the Chinese Space Agency (CSA) for testing coated optics for interplanetary missions, and in particular for the missions at the Lagrange points. We focus in particular on the applicability of these standards and hence on their possible refinement when specifically implemented to the optical thin films and coatings. We proceed with the development of a methodology for reliable interpretation of the proton irradiation tests for the optical coatings for interplanetary missions, first briefly overviewing the existing tools which allow for space environment simulation and hence deriving the test conditions for the Lagrange points. Furthermore, we apply the approach to testing of aluminum oxide optical coatings for applications in the visible spectral range, concluding on the representativeness of the proposed approach and on possible refinement of the existing standards for coating tests when they are specifically developed for optical applications. [ABSTRACT FROM AUTHOR]

Results from two independent clinical validation studies for measuring hemodynamics at the patient's bedside using a compact finger probe are reported. Technology comprises a barometric pressure sensor, and in one implementation, additionally, an optical sensor for photoplethysmography (PPG) is developed, which can be used to measure blood pressure and analyze rhythm, including the continuous detection of atrial fibrillation. The capabilities of the technology are shown in several form factors, including a miniaturized version resembling a common pulse oximeter to which the technology could be integrated in. Several main results are presented: i) the miniature finger probe meets the accuracy requirements of non‐invasive blood pressure instrument validation standard, ii) atrial fibrillation can be detected during the blood pressure measurement and in a continuous recording, iii) a unique comparison between optical and pressure sensing mechanisms is provided, which shows that the origin of both modalities can be explained using a pressure‐volume model and that recordings are close to identical between the sensors. The benefits and limitations of both modalities in hemodynamic monitoring are further discussed. [ABSTRACT FROM AUTHOR]

Airborne mineral dust significantly impacts air quality, human health, and the global climate. Due to sparse ground sensors, particularly in source regions, dust monitoring relies mainly on remote sensing through Aerosol Optical Depth (AOD) retrievals from polar-orbiting satellite optical instruments. These are valuable but lack the temporal resolution for precise plume tracking and source characterization. We introduce DustSCAN, a five-year, hourly dust plume dataset derived from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) images on geostationary-orbit Meteosat satellites. Using multi-channel infrared images, we detect atmospheric dust and track hourly dust-affected pixels. These are clustered into discrete plumes using the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm. DustSCAN includes 9950 discrete plumes over 2018-2022 across the Sahara, the Arabian Desert, and Western and Central Asia. It complements existing resources and provides a framework for detailed analysis of dust sources, trajectories, and impacts. Its distinctive event-based and spatio-temporal detail offers an advancement in unraveling the complexities of dust storm dynamics. [ABSTRACT FROM AUTHOR]

This article explores the electrochemical hydro- and deuterocarboxylation of allenes using carbon dioxide (CO2) and deuterium oxide (D2O) as starting materials. The authors discuss the challenges of activating CO2 and propose photochemical and electrochemical methods as potential solutions. They present their own findings on the electrochemical hydrocarboxylation and deuterocarboxylation of allenes, demonstrating good regioselectivity and high yields of carboxylic acids. The authors suggest possible mechanisms for these reactions and highlight their potential applications in reaction mechanism studies and drug development. The article also provides detailed experimental procedures and results, including information on the synthesis and characterization of various compounds. [Extracted from the article]

We present a goniometer designed for capturing spectral and angular-resolved data from scattering and absorbing media. The experimental apparatus is complemented by a comprehensive Monte Carlo simulation, meticulously replicating the radiative transport processes within the instrument's optical components and simulating scattering and absorption across arbitrary volumes. Consequently, we were able to construct a precise digital replica, or "twin", of the experimental setup. This digital counterpart enabled us to tackle the inverse problem of deducing optical parameters such as absorption and scattering coefficients, along with the scattering anisotropy factor from measurements. We achieved this by fitting Monte Carlo simulations to our goniometric measurements using a Levenberg–Marquardt algorithm. Validation of our approach was performed using polystyrene particles, characterized by Mie scattering, supplemented by a theoretical analysis of algorithmic convergence. Ultimately, we demonstrate strong agreement between optical parameters derived using our novel methodology and those obtained via established measurement protocols. [ABSTRACT FROM AUTHOR]

The quantitative prediction and control of assembly stress are crucial for the accuracy of precision optical instruments during their manufacturing process. As a typical optical component, the multipoint bonded flat lens is widely used in precision optical instruments, in which the main assembly stress (i.e., radial adhesive stress) and its induced nonuniform stress field in the lens vary with environmental parameters and time. These factors ultimately determine the accuracy and stability of such precision instruments. Effective prediction of the radial adhesive stress is important for bonding parameter optimization and accuracy enhancement but remains difficult to obtain due to the lack of direct measurement devices and effective prediction methods. Here, a novel prediction method is presented to estimate the radial adhesive stress applied on a multipoint bonded flat lenses. First, a quantitative characterization method (QCM) is developed to concisely describe the nonuniform stress field in a lens using quantitative characterization parameters (QCPs). Then, based on the QCM and the theoretical model established in our previous work (Xiong et al., 2022), a prediction method is developed for the radial adhesive stress applied on a lens by analyzing the stress field in the lens. In this method, a backpropagation neural network is constructed to obtain the mapping relationship between the key QCPs of the stress field and the radial adhesive stress applied on the lens. Finally, an experimental verification of the prediction method is carried out. This paper proposes a novel method to predict the radial adhesive stress for multipoint bonded optical lenses, which can be adopted to monitor the variation characteristics of assembly stress in optical instruments during the entire life cycle and then further employed to optimize the bonding parameters during the lens manufacturing process. This paper attempts to construct a direct mapping relationship between assembly quality and assembly parameters for precision instruments, supporting the quantitative optimization of assembly parameters and quantitative control and prediction of assembly quality during the manufacturing and working process. [Display omitted] • A quantitative characterization method to describe the stress field in a lens is proposed. • Quantitative features of the stress field in multipoint bonded lenses are revealed. • The radial adhesive stress is predicted by analyzing the stress field in the lens. • A mapping relationship between assembly quality and assembly parameter is constructed. [ABSTRACT FROM AUTHOR]

We use in this work a gold grating structure, as a plasmonic refractive index sensor, for sensing chemical or biological entities in aqueous solutions. This device was operated in an infrared band by using the rigorous coupled-wave analysis. The performance parameters of the proposed sensor in terms of absorbance at resonance are refractive index sensitivity, figure of merit (FoM), and quality factor (QF), were examined by applying the optical interrogation technique. Based on some numerical results, we optimize the geometric structure and the direction of the incident light to improve the performance of our device as a perfect absorber sensor. The analysis of the results obtained shows us the effect of several geometric and also optical parameters on the function of the instrument proposed as an optical detector of the variation of the refractive index. Our detector shows excellent results compared to others published in the literature. With azimuthally incident direction and optimal geometric and optical parameters, we obtain an optimal absorbance peak ranging between 99.92 and 99.99%, a high refractive index sensitivity of 1400 nm/RIU, a FoM of 211.54 RIU−1, and a QF of 285.28. In addition, the performance of our sensor is demonstrated by high sensitivity values of 1555.55 nm/RIU and 1522.84 nm/RIU for polydimethylsiloxane and ethanol solutions. [ABSTRACT FROM AUTHOR]

The dimensional accuracy of a laser scanner has been extensively evaluated using various measurement methods and diverse reference standards. This study specifically focuses on two key considerations. Firstly, it assesses the dimensional accuracy of the laser scanner by employing another laser scanner, a handheld scanner, as the reference measurement method. Secondly, the study involves the use of three spheres fixed on each wall in both coplanar and non-coplanar positions within a laboratory room at SENAI ISI-SIM. The primary objective is to determine the dimensional accuracy between the centers of the coplanar and non-coplanar spheres up to 10 m. The comparison includes measurement uncertainties, as per ISO GUM standards, obtained using the laser scanner in a laboratory setting with controlled temperature and humidity. Analyzing non-coplanar dimensional accuracy enhances our understanding of the metrological performance of the laser scanner, particularly when assessing the dimensions of objects positioned randomly within a scanning scene. [ABSTRACT FROM AUTHOR]

There has been a recent uptake in the use of polyether-ether-ketone (PEEK), which is an organic thermoplastic polymer, in the manufacturing of various medical devices, implants, and equipment. Finding the best time and procedure for PEEK after sulfonation is the goal of this research. A total of 30 PEEK discs were sulfonated in this study by immersing them in concentrated (H2SO4) sulfuric acid for various durations and subsequently treated using various post-treatment techniques. Five experiments were carried out, aimed studying the effect of immersion time (5 s–2 min). The methods used as post-treatment were hydrothermal treatment, immersion in NaOH, and washing with acetone. The sulfonation time was measured, and the post-treatment techniques, surface characterizations, were conducted using scanning electron microscopy (SEM) (Electron Optics Instruments, LLC., West Orange, NJ, USA), atomic force microscopy (AFM) (AFM, Vía Burton, CA, USA), and hydrophilic properties. The results were confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The findings of this study demonstrate that sulfonating PEEK caused a structure with a porous network to form in every sample. As the sulfonation time increased, the porous structure became more noticeable and the concentration increased. As a consequence, the roughness of the surface increased notably, and the modified PEEK surface's wettability improved noticeably. Hydrothermal treatment was determined to be the most successful way for eliminating the leftover sulfuric acid, and sulfonation for 2 min was determined to be ideal. By understanding the best post-treatment procedures and ideal sulfonation duration, a theoretical foundation for the production of sulfonated PEEK for orthopedic uses may be laid. [ABSTRACT FROM AUTHOR]

Significance: Phase retardation of circularly polarized light (CPL), backscattered by biological tissue, is used extensively for quantitative evaluation of cervical intraepithelial neoplasia, presence of senile Alzheimer's plaques, and characterization of biotissues with optical anisotropy. The Stokes polarimetry and Mueller matrix approaches demonstrate high potential in definitive non-invasive cancer diagnosis and tissue characterization. The ultimate understanding of CPL interaction with tissues is essential for advancing medical diagnostics, optical imaging, therapeutic applications, and the development of optical instruments and devices. Aim: We investigate propagation of CPL within turbid tissue-like scattering medium utilizing a combination of Jones and Stokes--Mueller formalisms in a Monte Carlo (MC) modeling approach. We explore the fundamentals of CPL memory effect and depolarization formation. Approach: The generalized MC computational approach developed for polarization tracking within turbid tissue-like scattering medium is based on the iterative solution of the Bethe--Salpeter equation. The approach handles helicity response of CPL scattered in turbid medium and provides explicit expressions for assessment of its polarization state. Results: Evolution of CPL backscattered by tissue-like medium at different conditions of observation in terms of source--detector configuration is assessed quantitatively. The depolarization of light is presented in terms of the coherence matrix and Stokes--Mueller formalism. The obtained results reveal the origins of the helicity flip of CPL depending on the source--detector configuration and the properties of the medium and are in a good agreement with the experiment. Conclusions: By integrating Jones and Stokes--Mueller formalisms, the combined MC approach allows for a more complete representation of polarization effects in complex optical systems. The developed model is suitable to imitate propagation of the light beams of different shape and profile, including Gaussian, Bessel, Hermite--Gaussian, and Laguerre--Gaussian beams, within tissue-like medium. Diverse configuration of the experimental conditions, coherent properties of light, and peculiarities of polarization can be also taken into account. [ABSTRACT FROM AUTHOR]

Modern high-sensitivity spectrometers rely on photons reflecting thousands of times between extremely reflective mirrors to generate absorption pathlengths that are kilometers long. The absorption spectrum of trace gas species is enhanced when cooling the gas sample, however, should any atmospheric volatiles condense within the gas cell, the highly-reflective mirrors may become marred, drastically cutting down the effective optical path length. In the Martian atmosphere, the first volatile to condense is typically water vapor, thus understanding the variability of the water frost point is essential for determining the performance limit of any optical instrument. We will examine these performance limits and map the maximum temperatures at which water vapor will condense on the Martian surface with respect to a model instrument being prepared for flight. The variability of the frost point with time and solar longitude (L s) therefore reveals areas of the Martian surface at which the precision of a high-sensitivity spectrometer is optimized. We find that the optimal performance is achieved during northern fall and winter (L s = 180°–360°) at polar and mid-latitude locations in the northern hemisphere, and during northern spring (L s = 0°–90°) at equatorial and mid-latitude locations in the southern hemisphere when the frost point reaches the lowest maximums. • Instrument precision is higher with lower temperatures without risk of frost. • On Mars, water vapor can condense within instrumentation, decreasing the precision. • The water frost point (FP) varies based on the atmospheric water vapor abundance. • Northern mid-latitude and polar regions have lower FPs during fall and winter. • The FPs at Gale crater near the equator have little variation throughout the year. [ABSTRACT FROM AUTHOR]

With the ever-growing emphasis on global decarbonization and rapid increases in the power densities of electronics equipment in recent years, new methods and lightweight materials have been developed to manage heat load as well as interfacial stresses associated with coefficient of thermal expansion (CTE) mismatches between components. The Al–Si system provides an attractive combination of CTE performance and high thermal conductivity whilst being a very lightweight option. Such materials are of interest to industries where thermal management is a key design criterion, such as the aerospace, automotive, consumer electronics, defense, EV, and space sectors. This paper will describe the development and manufacture of a family of high-performance hypereutectic Al–Si alloys (AyontEX™) by a powder metallurgy method. These alloys are of particular interest for structural heat sink applications that require high reliability under thermal cycling (CTE of 17 μm/(m·°C)), as well as reflective optics and instrument assemblies that require good thermal and mechanical stability (CTE of 13 μm/(m·°C)). Critical performance relationships are presented, coupled with the microstructural, physical, and mechanical properties of these Al–Si alloys. [ABSTRACT FROM AUTHOR]

This article discusses Rayleigh's criterion, which is a measure of the minimum separation needed for two objects to produce distinct images when observed with diffraction-limited optical instruments. It presents an approximate method for finding the dark rings in the diffraction pattern using a two-point interference problem, which is accurate to 3.4%. The article also explains the diffraction of waves through a circular aperture and how dividing the aperture into quadrants and octants affects the diffraction pattern. It acknowledges the limitations of the approach and mentions advances in super-resolution microscopy techniques that have surpassed the diffraction limit. The author, Alexander R. Small, is a professor and researcher in the field of super-resolution technologies. [Extracted from the article]