Search

The multiphoton excitation pathways of plasmonic nanorod assemblies are described. By using dolmen structures formed from the directed assembly of three gold nanorods, plasmon-mediated three-photon excitation is resolved. These high-order multiphoton excitation channels were accessed by resonantly exciting a hybrid mode of the dolmen structure that was resonant with the 800-nm carrier wavelength of an ultrafast laser system. Rotation of the exciting field polarization to a non-resonant configuration did not generate third-order responses. Hence, the multiphoton excitation and resultant non-equilibrium electron distributions were generated by structure- and mode-selective excitation. Correlation between high-order and resonant plasmon excitation was achieved through sub-cycle time-resolved interferometric detection of incoherent nonlinear emission signals. The results illustrate the advantages of nonlinear optical interferometry and Fourier analysis for distinguishing plasmon-mediated processes from those that do not require plasmon excitation. [ABSTRACT FROM AUTHOR]

We explore piezooptic and photoelastic properties of Ca3Ga2Ge4O14 (CGG) crystals. A Mach–Zehnder interferometry technique is utilized to determine a complete set of the piezooptic tensor constants πim, with particular attention to the measurement accuracy, reliability, and uncertainty resolution in the piezooptic measurements. For these reasons, independent piezooptic constants or their combinations were determined by performing interferometric measurements for different geometries of piezooptic coupling using samples of both principal (direct) and non-principal (X/45°) crystallographic cuts. Basing on the results of piezooptic measurements, a complete set of photoelastic tensor constants pim and the acousto-optic performance (figure of merit M2) of CGG crystals were evaluated. The obtained piezooptic, photoelastic, and acousto-optic characteristics of CGG crystals are compared with those of other crystals of the langasite group, langasite and CTGS (Ca3TaGa3Si2O14). A comparative analysis reveals a correlation between the values of the piezooptic or photoelastic constants and the lattice parameters for this group of crystals. High optical quality and optical transparency in the UV region of the spectrum up to 260 nm together with extremely high mechanical resistance to uniaxial compression (≤2000 kg/cm2) opens up the possibility for specific application of CGG crystal as an optical material for piezooptic sensors of high uniaxial compression. The presented piezooptic interference technique along with methodological and metrological approaches paves the way for accurate and unambiguous characterization of photoelastic crystal materials of trigonal symmetry. [ABSTRACT FROM AUTHOR]

Warm water from the Southern Ocean has a dominant impact on the evolution of Antarctic glaciers and in turn on their contribution to sea level rise. Using a continuous time series of daily-repeat satellite synthetic-aperture radar interferometry data from the ICEYE constellation collected in March-June 2023, we document an ice grounding zone, or region of tidally controlled migration of the transition boundary between grounded ice and ice afloat in the ocean, at the main trunk of Thwaites Glacier, West Antarctica, a strong contributor to sea level rise with an ice volume equivalent to a 0.6-m global sea level rise. The ice grounding zone is 6 km wide in the central part of Thwaites with shallow bed slopes, and 2 km wide along its flanks with steep basal slopes. We additionally detect irregular seawater intrusions, 5 to 10 cm in thickness, extending another 6 km upstream, at high tide, in a bed depression located beyond a bedrock ridge that impedes the glacier retreat. Seawater intrusions align well with regions predicted by the GlaDS subglacial water model to host a high-pressure distributed subglacial hydrology system in between lower-pressure subglacial channels. Pressurized seawater intrusions will induce vigorous melt of grounded ice over kilometers, making the glacier more vulnerable to ocean warming, and increasing the projections of ice mass loss. Kilometer-wide, widespread seawater intrusion beneath grounded ice may be the missing link between the rapid, past, and present changes in ice sheet mass and the slower changes replicated by ice sheet models.

Over 700 bright millisecond-duration radio transients, known as fast radio bursts (FRBs), have been identified to date. Nevertheless, the origin of FRBs remains unknown. Two repeating FRBs (FRB 20121102A and FRB 20190520B) have been verified to be associated with persistent radio sources (PRSs), making them the best candidates to study the nature of FRBs. Monitoring the variability in PRSs is essential for understanding their physical nature. We conducted 22 observations of the PRSs linked to FRB 20121102A and FRB 20190520B using the Karl G. Jansky Very Large Array, to study their variability. We have observed significant flux variability for the PRSs of FRB 20121102A and FRB 20190520B, with a confidence level exceeding 99.99%, based on the observations covering the longest timescale recorded to date. The observed variability of the two PRSs exhibits no significant difference in amplitude across both short and long timescales. We found that the radio-derived star formation rates of the two FRB hosts are significantly higher than those measured by the optical H α emissions, indicating that their host galaxies are highly obscured or most radio emissions are not from star formation processes. The observed timescale of PRS flux evolution constrained the magnetic field of FRB 20121102A with B ∥ ≳ 1 mG and FRB 20190520B with B ∥ ≳ 0.1 mG. [ABSTRACT FROM AUTHOR]

• A PolInSAR decomposition integrates generalized scattering models. • All model parameters are simultaneously solved using the cross-correlation matrix. • Performance is evaluated with simulated and real PolInSAR data. In this study, a general three-component polarimetric SAR interferometry (PolInSAR) target decomposition framework is proposed by modifying the existing generalized surface, double-bounce, and volume models. The resulting general models are then compared to the original Freeman-Durden modeling strategy. Three types of generalized volume scattering models (generalized volume scattering model (GVSM), simplified Neumann volume scattering model (SNVSM) and simplified adaptive volume scattering model (SAVSM)) were employed. Simulated L-band PolInSAR data over deciduous and pine forest stands generated by PolSARpro and DLR P-band airborne PolInSAR data over a tropical forest area from the AfriSAR 2016 campaign were used for performance analysis. A qualitative comparison of the decomposition results shows that the three generalized volume scattering models generally deviate from the Freeman-Durden model, showing that the GVSM and SNVSM models have very similar results. In the case of airborne data over tropical forests, a tomographic synthetic aperture radar (TomoSAR) profile was also computed and used as a benchmark for comparison with the phase-center profiles of all four volume-scattering components. Not only do the GVSM and SNVSM models exhibit similar results between them (as with simulated data), but also a better match with the HV TomoSAR profile. [ABSTRACT FROM AUTHOR]

Background: Sebaceous adenitis (SA) is an immune‐mediated disease targeting the sebaceous glands. Meibomian gland dysfunction is a disease affecting meibomian glands with inflammatory features. Sebaceous and meibomian glands share anatomical, physiological and embryological similarities. The involvement of meibomian glands in dogs with SA is currently unknown. Objectives: To evaluate meibomian glands in dogs affected by SA and compare them with healthy dogs. Animals: Eighteen dogs were enrolled. Nine dogs with SA were retrospectively identified from clinical records and represented the case group. Nine healthy, breed‐ and age‐matched dogs were prospectively enrolled in the control group. Materials and Methods: Both groups underwent dermatological examination, Schirmer tear test‐1 (STT‐1), tear meniscus height (TMH), slit‐lamp biomicroscopy, interferometry (INT) and noncontact infrared meibography (NIM). Results: One third of SA dogs presented subepithelial crystalline opacities. No significant difference between groups was observed in TMH (p = 0.944) and STT‐1 values (p = 0.066). INT (p = 0.016) and NIM grades (p = 0.010) were significantly higher and lower in the SA group compared to the control group, respectively. INT values decreased with age (η = 0.930), while NIM scores (η = 0.935) increased. Conclusions: Clinical Relevance: Subepithelial crystalline opacities in SA dogs might reflect a reduced tear film quality. In the absence of standardised methods, INT and NIM proved to be noninvasive and useful methods to examine meibomian glands. Dogs with SA showed a thinner lacrimal lipid layer and more severe meibomian gland abnormalities than control dogs, which seemed to progress with age. [ABSTRACT FROM AUTHOR]

Dynamical association of Efimov trimers in thermal gases by means of modulated magnetic fields has proven very fruitful in determining the binding energy of trimers. The latter was extracted from the number of remaining atoms, which featured oscillatory fringes stemming from the superposition of trimers with atom-dimers. Subsequent theoretical investigations utilizing the time-dependent three-body problem revealed additional association mechanisms, manifested as superpositions of the Efimov state with the trap states and the latter with atom-dimers. The three atoms were initialized in a way to emulate a thermal gas with uniform density. Here, this analysis is extended by taking into account the effects of the density profile of a semi-classical thermal gas. The supersposition of the Efimov trimer with the first atom-dimer remains the same, while the frequencies of highly oscillatory fringes shift to lower values. The latter refer to the frequencies of trimers and atom-dimers in free space since the density profile smears out the contribution of trap states. [ABSTRACT FROM AUTHOR]

Hypothesis Foaming in diesel fuels is not well understood and leads to operational challenges. To combat deleterious effects of foaming, diesel formulations can include additives called antifoams. Existing antifoams, unfortunately, are inherently ash-generating when combusted, with unknown environmental impacts. They are prohibited in certain countries, so identifying effective alternative ash-free antifoam chemistries is needed. Experiments We conduct systematic characterization of foam stabilization and antifoaming mechanisms in diesel for two different antifoams (silicone-containing & ashless chemistries). Employing a custom technique combining single-bubble/single-antifoam-droplet manipulation with white light interferometry, we also obtain mechanistic insights into foam stability and antifoam dynamics. Results Coalescence times from both bulk foam and single bubble experiments confirm ashless antifoams are effective at reducing foaming, demonstrating the potential of ashless antifoams. Further, we perform single-antifoam-droplet experiments and obtain direct experimental evidence revealing the elusive antifoaming mechanisms. Interestingly, the silicone-containing and ashless antifoams seemingly function via two different mechanisms: spreading and dewetting respectively. This surprising finding refutes conventional wisdom that spreading is likely the only antifoam mechanism in diesels. These results and the reported experimental framework significantly enhance the scientific understanding of non-aqueous foams and will accelerate the engineering of alternative antifoam chemistries for non-aqueous systems. • Single bubble/drop experiments facilitate mechanistic insight driven research into antifoams across non-aqueous systems. • This ashless antifoam is successfully incorporated as microdroplets and is effective at reducing foam. • Direct evidence of underlying antifoam mechanisms from modified antifoam droplet experiments. • Mechanism of action of tested ashless and silicone-containing antifoams are different. [ABSTRACT FROM AUTHOR]

Horizons and bound photon orbits are defining features of black holes that translate into key features of black hole images. We review a purely geometric proof that spherically symmetric, isolated objects with horizons in gravity theories with null-geodesic propagation of light must display bound photon orbits forming a photon sphere. Identifying the key elements of the proof, we articulate a simpler argument that carries over to more general situations with modified light propagation and implies the existence of equatorial spherical photon orbits in axisymmetric spacetimes with reflection symmetry. We conclude that the non-observation of photon rings with very-large-baseline interferometry would be a very strong indication against a horizon, irrespective of whether or not the image shows a central brightness depression. [ABSTRACT FROM AUTHOR]

We present super-resolved coherent anti-Stokes Raman scattering (CARS) microscopy by implementing phase-resolved image scanning microscopy, achieving up to two-fold resolution increase as compared with a conventional CARS microscope. Phase-sensitivity is required for the standard pixel-reassignment procedure since the scattered field is coherent, thus the point-spread function is well-defined only for the field amplitude. We resolve the complex field by a simple add-on to the CARS setup enabling inline interferometry. Phase-sensitivity offers additional contrast which informs the spatial distribution of both resonant and nonresonant scatterers. As compared with alternative super-resolution schemes in coherent nonlinear microscopy, the proposed method is simple, requires only low-intensity excitation, and is compatible with any conventional forward-detected CARS imaging setup. The authors present super-resolved CARS microscopy using phase-sensitive image scanning, achieving nearly twice the resolution of conventional CARS. This method requires low excitation laser power and integrates easily into existing systems. [ABSTRACT FROM AUTHOR]

The process of engineering construction typically impacts the nearby existing buildings, causing either localized or widespread deformation of these structures. The application of deformation monitoring technology enables the timely identification of damage or uneven deformation, thereby facilitating the implementation of appropriate maintenance and repair actions. This paper explores the application of ground-based synthetic aperture radar (GB-SAR) in building facade deformation monitoring. GB-SAR acquires two-dimensional (2D) images and measures deformation along the line of sight (LOS) direction through interference calculation. In order to accurately determine the location of deformation and retrieve the elevation information of image pixels, it is usually required to utilize external three-dimensional (3D) data to reconstruct the 3D coordinate of these pixels, which is known as geocoding, or georeferencing. In the case of the GB-SAR system, it is necessary for the observer to measure the angles between the antenna orientation, the radar movement direction and the reference plane of the local surveying coordinate system. Nevertheless, the measurement of these attitude angles may be overlooked in practice, and the impact of small attitude angles or their measurement errors on GB-SAR geocoding may be disregarded, which directly affects the slant range projection (SRP) calculation of the external 3D data, thereby leading to biased 3D coordinate reconstruction of GB-SAR pixels. This paper proposes a method to calculate the SRP coordinates of point cloud data considering the attitude inclination angles of radar sensor, and perform matching calculations on the high-quality pixels (HQPs) with the point cloud after SRP to extract building facade deformation. The results demonstrate that the method is capable of effectively mitigating the influence of the radar attitude inclination angles, resulting in a reduction of the average deviation of 3D coordinates to approximately one-third of the value without consideration of the sensor's attitude in a real-world building monitoring experiment. [ABSTRACT FROM AUTHOR]

X-ray grating interferometry allows for the simultaneous acquisition of attenuation, differential-phase contrast, and dark-field images, resulting from X-ray attenuation, refraction, and small-angle scattering, respectively. The modulated phase grating (MPG) interferometer is a recently developed grating interferometry system capable of generating a directly resolvable interference pattern using a relatively large period grating envelope function that is sampled at a pitch that is small enough that X-ray spatial coherence can be achieved by using a microfocus X-ray source or G0 grating. We present the theory of the MPG interferometry system for a 2-dimensional staggered grating, derived using Fourier optics, and we compare the theoretical predictions with experiments we have performed with a microfocus X-ray system at Pennington Biomedical Research Center, LSU. The theoretical and experimental fringe visibility is evaluated as a function of grating-to-detector distance. Additionally, quantitative experiments are performed with porous carbon and alumina compounds, and the mean normalized dark-field signal is compared with independent porosimetry measurements. Qualitative analysis of attenuation and dark-field images of a dried anchovy are shown. [ABSTRACT FROM AUTHOR]

In recent years, drone-based Synthetic Aperture Radar (SAR) systems have emerged as flexible and cost-efficient solutions for detecting changes in the Earth's surface, retrieving topographic data, or detecting ground displacement processes in localized areas, among other applications. These systems offer a unique combination of short and versatile revisit times and flexible acquisition geometries that are not achievable with space-borne, airborne, or ground-based SAR sensors. However, due to platform limitations and flight stability issues, they also present significant challenges regarding instrument design and data processing, particularly when generating interferometric repeat-pass datasets. This paper demonstrates the feasibility of repeat-pass interferometry using a Ku-band drone-based SAR system. The system integrates a dual-channel Ku-band Frequency Modulated Continuous Wave (FMCW) radar with cross-track single-pass interferometric capabilities, mounted on a drone platform. The proposed repeat-pass interferometric processing chain leverages an accurate Digital Elevation Model (DEM), generated from the single-pass interferograms, to precisely coregister the entire stack of acquisitions, thereby producing repeat-pass interferograms free from residual motion errors. The results underscore the potential of this system and the processing chain proposed for generating multi-temporal repeat-pass stacks suitable for repeat-pass applications. [ABSTRACT FROM AUTHOR]

In recent years, phase linking (PL) methods in radar time-series interferometry (TSI) have proven to be powerful tools in geodesy and remote sensing, enabling the precise monitoring of surface displacement and deformation. While these methods are typically designed to operate on a complete network of interferograms, generating such networks is often challenging in practice. For instance, in non-urban or vegetated regions, decorrelation effects lead to significant noise in long-term interferograms, which can degrade the time-series results if included. Additionally, practical issues such as gaps in satellite data, poor acquisitions, or systematic errors during interferogram generation can result in incomplete networks. Furthermore, pre-existing interferogram networks, such as those provided by systems like COMET-LiCSAR, often prioritize short temporal baselines due to the vast volume of data generated by satellites like Sentinel-1. As a result, complete interferogram networks may not always be available. Given these challenges, it is critical to understand the applicability of PL methods on these incomplete networks. This study evaluated the performance of two PL methods, eigenvalue decomposition (EVD) and eigendecomposition-based maximum-likelihood estimator of interferometric phase (EMI), under various network configurations including short temporal baselines, randomly sparsified networks, and networks where low-coherence interferograms have been removed. Using two sets of simulated data, the impact of different network structures on the accuracy and quality of the results was assessed. These patterns were then applied to real data for further comparison and analysis. The findings demonstrate that while both methods can be effectively used on short temporal baselines, their performance is highly sensitive to network sparsity and the noise introduced by low-coherence interferograms, requiring careful parameter tuning to achieve optimal results across different study areas. [ABSTRACT FROM AUTHOR]

We propose Terahertz Intensity Interferometry (TII) to realize high angular resolution observations above 1 THz. TII uses fast detectors and readout circuits to measure intensity correlation and determine the delay time for synthesis imaging. The development of a fast photon detector at 1.5 THz is discussed for Antarctic TII experiments. The 1.5 THz photon detector is designed to detect terahertz photons with antenna-coupled SIS junctions by pair-breaking process. The detector uses small size and low leakage Nb/Al-AlOx/Al/Nb junctions for high sensitivity at high frequency. The first fabricated detectors show reasonable I-V characteristics at 4 K, and further tuning of fabrication parameters is ongoing. For evaluation of the detectors at 0.8 K using fast cryogenic readout electronics, a new cryostat for the TII experiment will be used. As an initial step, a GaAs-JFET first-stage source-follower is installed at 0.8 K to measure the I-V characteristics of a submillimeter-wave SIS photon detector. The performance shows the new cryostat and the first-stage source-follower at 0.8 K can be used to evaluate 1.5 THz photon detectors, which will be combined with fast readout electronics for TII experiments. [ABSTRACT FROM AUTHOR]

Optical aspheres are demanded with extremely high precision to meet functional requirements in space telescopes, extreme ultraviolet lithography, and other modern large optical systems. The nano-precision fabrication of optical aspheres requires high-precision measurements to guide deterministic optical processing. Null test is the preferred method for high-precision measurements. Null optics are required to compensate for the incident wavefront in the null test of optical aspheres. However, wavefront aberrations caused by the transmission flat or transmission sphere of interferometer and null optics can limit measurement accuracy and need to be separated. A nano-precision measurement method is proposed for the even optical aspheres of high order in this paper. A computer-generated hologram is used as a null optic to realize a null test on optical aspheres. Mapping distortion correction is performed on the measurement results to ensure that the transverse coordinates of the measurement results correspond correctly to those of the test surface. Absolute testing is applied to separate the wavefront aberrations caused by the computer-generated hologram and interferometer optics. Finally, the results obtained by this method were used to guide deterministic optical processing, enabling the nano-precision fabrication of optical aspheres. [ABSTRACT FROM AUTHOR]

The health monitoring of infrastructure is vital for ensuring the safety and structural integrity of bridges. Recently, ground-based real aperture radar (GB-RAR) systems have been successfully utilized in the dynamic and static monitoring of bridges. In this study, a comprehensive and innovative approach is presented to monitor the vertical deformation of a long-span metallic railway bridge and a reinforced concrete Shinkansen bridge in Japan using a polarimetric GB-RAR system. Distinct from conventional signal processing procedures, the proposed method omits the coherent scatterer selection step. Instead, polarization analysis is employed to evaluate the properties of scatterers and identify those corresponding to bridge sections requiring monitoring, while considering the structural characteristics of the bridge. Simultaneously, the signal-to-noise ratio for monitoring is enhanced by combining co-polarization responses from scatterers. Furthermore, the radar look angle is determined by accounting for the spatial configuration of the survey and the polarization orientation angle. Lastly, vertical deformation is assessed by projecting line of sight deformation in the vertical direction. The findings reveal the dynamic responses of the two bridges under diverse loading conditions, which include the transit of a low-speed train and a high-speed Shinkansen bullet train. The results demonstrate that the polarimetric GB-RAR interferometry technique, coupled with the developed algorithms, can be effectively applied to monitor any type of bridge with unparalleled spatial and temporal resolutions. [ABSTRACT FROM AUTHOR]

There is a long history of using VHF radar systems to detect ionospheric irregularities based on the theory of coherent scattering. According to previous work, there is a high occurrence of field-aligned irregularities (FAIs) in the ionospheric E-region over Kunming, China. In this paper, the VHF coherent scattering radar at Kunming is used to study the FAIs in the ionospheric E-region. Different arrangement of VHF radar antenna arrays, interferometry, and FAI echo parameter inversion methods are designed and tested. The measurement results show that the temporal and spatial characteristics of the irregularities can be obtained using these methods, as well as more refined spatial three-dimensional structure information. It is indicated that the new arrangement of the VHF radar antenna array is feasible to operate interferometry detection of E-region FAIs with the Kunming VHF radar. [ABSTRACT FROM AUTHOR]

Background: To analyze the difference and agreement between measurements obtained by a new fully automatic optical biometer, the SW-9000 μm Plus, based on optical low-coherence reflectometry (OLCR) and a commonly used optical biometer (Pentacam AXL) based on Scheimpflug imaging with partial coherence interferometry (PCI). Methods: The central corneal thickness (CCT), anterior chamber depth (ACD, from epithelium to anterior lens surface), lens thickness (LT), mean keratometry (Km), corneal astigmatism, corneal diameter (CD), pupil diameter (PD), and axial length (AL) of 74 eyes (from 74 healthy subjects) were measured using the SW-9000 μm Plus and the Pentacam AXL to determine the agreement. Double angle plots were used for astigmatism vector analysis. Bland–Altman and 95% limits of agreement (LoA) were calculated. Results: Statistically significant differences were detected for all parameters but J0 vector. The Bland–Altman analysis of AL, CCT, ACD, Km, CD, J0 and J45 indicated a high level of agreement between the two devices. Among AL, CCT, ACD, Km, J0, J45, CD, and PD, the 95% LoA ranged from -0.07 to 0.05 mm, -9.67 to 7.34 mm, -0.11 to 0.04 mm, -0.25 to 0.50 D, -0.22 to 0.20 D, -0.15 to 0.20 D, -0.23 to 0.35 mm and 1.55 to 3.77 mm, respectively. Conclusions: The measurements of AL, CCT, ACD, Km, corneal astigmatism, and CD showed a narrow LoA and may be used interchangeably in healthy subjects between the new OLCR optical biometer and the Scheimpflug/PCI biometer; however, a poor agreement was noted for PD values. [ABSTRACT FROM AUTHOR]

Rockfall phenomena are considered highly dangerous due to their rapid evolution and difficult prediction without applying preventive monitoring and mitigation actions. This research investigates a hazardous site in the Municipality of Vecchiano (Province of Pisa, Italy), characterized by vertical rock walls prone to instability due to heavy fracturing and karst phenomena. The presence of anthropical structures and a public road at the bottom of the slopes increases the vulnerability of the site and the site's risk. To create a comprehensive geological model of the area, Unmanned Aircraft System (UAS) photogrammetric surveys were conducted to create a 3D model useful in photointerpretation. In accessible and safe areas for personnel, engineering–geological surveys were carried out to characterize the rock mass and to define the portion of rock walls to be monitored. Results from nine multitemporal Robotic Total Station (RTS) measurement campaigns show that no monitoring prisms recorded significant displacement trends, both on the horizontal and vertical plane and in differential slope distance. Additionally, satellite Persistent Scatterer Interferometry (PSI) analysis indicates that the slopes were stable over the two years of study. The integration of these analysis techniques has proven to be an efficient solution for assessing slope stability in this specific rockfall-prone area. [ABSTRACT FROM AUTHOR]

The Cerro Prieto basin, a tectonically active pull-apart basin, hosts significant geothermal resources currently being exploited in the Cerro Prieto Geothermal Field (CPGF). Consequently, natural tectonic processes and anthropogenic activities contribute to three-dimensional surface displacements in this pull-apart basin. Here, we obtained the Cerro Prieto Step-Over 3D surface velocity field (3DSVF) by accomplishing a weighted least square algorithm inversion from geometrically quasi-orthogonal airborne UAVSAR and RADARSAT-2, Sentinel 1A satellite Synthetic Aperture-Radar (SAR) imagery collected from 2012 to 2016. The 3DSVF results show a vertical rate of 150 mm/yr and 40 mm/yr for the horizontal rate, where for the first time, the north component displacement is achieved by using only the Interferometric SAR time series in the CPGF. Data integration and validation between the 3DSVF and ground-based measurements such as continuous GPS time series and precise leveling data were achieved. Correlating the findings with recent geothermal energy production revealed a subsidence rate slowdown that aligns with the CPGF's annual vapor production. [ABSTRACT FROM AUTHOR]

Active wavelength‐scale optoelectronic components are widely used in photonic integrated circuitry, however coherent sources of light – namely optical lasers – remain the most challenging component to integrate. Semiconductor nanowire lasers (NWLs) represent a flexible class of light source where each nanowire (NW) is both gain material and cavity; however, strong coupling between these properties and the performance leads to inhomogeneity across the population. While this has been studied and optimized for individual material systems, no architecture‐wide insight is available. Here, nine NWL material systems are studied and compared using 55,516 NWLs to provide statistically robust insight into performance. These results demonstrate that, while it may be important to optimize internal quantum efficiency for certain materials, cavity effects are always critical. The study provides a roadmap to optimize the performance of NWLs made from any material: this can be achieved by ensuring a narrow spread of lengths and end‐facet reflectivities. [ABSTRACT FROM AUTHOR]

This work discusses label-free biosensing application of a double-layer optical fiber interferometer where the second layer tailors the reflection conditions at the external plain and supports changes in reflected optical spectrum when a bio-layer binds to it. The double-layer nanostructure consists of precisely tailored thin films, i.e., titanium (TiO2) and hafnium oxides (HfO2) deposited on single-mode fiber end-face by magnetron sputtering. It has been shown numerically and experimentally that the approach besides well spectrally defined interference pattern distinguishes refractive index (RI) changes taking place in a volume and on the sensor surface. These are of interest when label-free biosensing applications are considered. The case of myeloperoxidase (MPO) detection—a protein, which concentration rises during inflammation—is reported as an example of application. The response of the sensor to MPO in a concentration range of 1 × 10−11–5 × 10−6 g/mL was tested. An increase in the MPO concentration was followed by a redshift of the interference pattern and a decrease in reflected power. The negative control performed using ferritin proved specificity of the sensor. The results reported in this work indicate capability of the approach for diagnostic label-free biosensing, possibly also at in vivo conditions. [ABSTRACT FROM AUTHOR]

We present an optical filter that is appropriate for use with Raman beams in atomic interferometry. This is a filter that lets the light of the two frequencies of the Raman pair go through and rejects spurious frequencies that may be close to the atomic resonance and cause decoherence. We characterized the filter's performance optically and also by shining the light into atoms in a Ramsey sequence, to look for decoherence effects from photon scattering. We found that it is safe to use tapered amplifiers in single and double pass for light amplification in the Raman beams since the pedestal of emission has a negligible effect, which can be further reduced by the use of the filter we present. [ABSTRACT FROM AUTHOR]

The technique of performing interferometry with two optical frequency combs is used by an increasing number of research groups and even for field deployed commercial applications. Real-time interferogram acquisition, correction, and averaging are, however, still not broadly accessible. This limits the deployment and wider adoption of this high resolution, high sensitivity technique. We herein introduce and describe a freely available correction software performing real-time processing on a graphics processing unit. [ABSTRACT FROM AUTHOR]

In the past few years, the remarkable progress of commercially operated spacecrafts, the success with reusable rocket engines, as well as the international competition to explore space, has led to a substantial acceleration of activities in the design and preparation of ambitious future lunar missions. In the search for ice and/or cavities imaging the shallow subsurface structure is of vital importance. Hereby, previous studies have shown that seismic interferometry is a promising method to investigate the subsurface properties from passive lunar data. In this study, we want to evaluate the potential of this method further by examining the required duration of seismic measurements and the influence of scattering on the Green's function retrieval. Therefore, we applied seismic interferometry to both measured Apollo 17 data and synthetic data. Our findings indicate that, under optimal conditions, a few hours of data are sufficient when using the method of time‐scaled phase‐weighted stack (ts‐PWS). However, this strongly depends on the inter‐station distance, the orientation toward the principal noise sources, and the timing of the measurement during the lunar cycle. Additionally, we were able to reproduce the measured data using numerical simulations in 2D. The synthetic results show that scattering effects clearly influence the Green's function extraction, especially for larger station distances. Key Points: Green's functions are retrieved from passive Apollo 17 data and synthetic data using seismic interferometryThe convergences time of the Green's function depends on inter‐station distance, noise source distribution and timing during the lunar cycleStrong scattering in the lunar regolith influences the Green's function retrieval, especially for larger station distances [ABSTRACT FROM AUTHOR]

Objectives: Lutan-1(LT-1) is the first formation-flying mission of China, enabling interferometry synthetic aperture radar (InSAR) in the L-band. High-precision inter-satellite baseline is crucial for InSAR processing and application. Methods: We investigate the dynamic precise baseline solution method and the inter-satellite double-difference ambiguity fixing method of low-orbit formation satellite, and analyze the contribution of BDS-3 (B1C, B2a) and GPS (L1, L2) observation of LT-1 A/B in precise baseline determination. Results: The results show that compared with GPS, the residuals of B1C and B2a observations of BDS-3 are significantly smaller, suggesting a higher signal accuracy. The baseline overlap accuracies of GPS-based, BDS-based, and GPS/BDS combined solutions are 0. 8 mm, 0. 6 mm, and 0. 5 mm, respectively. The BDS-based baseline accuracy is 25% higher than that of GPS, and the GPS/BDS combined solution can further improve the baseline accuracy by 37. 5% and 16. 7% relative to the GPS- and BDS-baselines. The baseline difference between the GPS-based and BDS-based baseline solutions is 1 mm in 3 dimensional directions. Conclusions: The analysis suggests that the single BDS-3 system can achieve precise baseline determination for low-orbit formation satellites at the 1 mm level and combined GPS/BDS solution will further improve the accuracy than single-system solution. [ABSTRACT FROM AUTHOR]

Elevation static correction is an important step in seismic data processing used to eliminate distortions in events caused by surface fluctuations. There is a well-established processing sequence for active-source seismic data, with static correction applied first, followed by subsequent processing. For passive-source data, static correction can be carried out using two methods. The first method is similar to the static correction of active-source seismic data and involves performing static correction on virtual shot gathers. The second method involves directly applying static correction to ambient noise and then using the corrected ambient noise to retrieve the virtual shot gathers. In this study, we derived and compared these two methods to perform static correction on passive-source data. We compared the above two methods through the forward modeling of passive-source data and field data from the Daqiao Gold Mine. The results showed that applying static correction to ambient noise and virtual shot gathers can correct passive-source data from an undulating surface to a flat surface. The equivalence of static correction on virtual shot gathers, and ambient noise offers more choices for conducting static correction of passive-source seismic reflection exploration on undulating surfaces. [ABSTRACT FROM AUTHOR]

The shift–rotation method is an absolute testing method that has attracted much attention in recent years, and detection accuracy at the subnanometer level has been achieved. However, for flat absolute calibration, the power aberration cannot be calibrated via the traditional shift–rotation absolute testing method. To solve this problem, we propose a shift–rotation absolute testing method based on autocollimation, which detects the tilt error of the tested mirror caused by the external environment and guides the adjustment of the stage to remove it. Simulations and experiments are conducted to prove this theory. A comparison with liquid experiments shows that the autocollimated shift–rotation method can achieve accurate absolute power aberration and can compensate for the shortcomings of the traditional shift–rotation method. [ABSTRACT FROM AUTHOR]

In 2023, the Chinese company PIESAT launched the multi-static X-band SAR constellation Hongtu-1 (HT1). HT1 consists of the active monostatic SAR sensor HT1-A and the three additional passive SAR receivers HT1-B, HT1-C and HT1-D. The passive sensors are arranged as a cartwheel in a circle around the active sensor. For our SAR interferometric investigation, we were able to use a multi-static HT1 recording. After a brief introduction of HT1, we describe the processing performed. Based on the phases of the six single-pass interferometric pairs, we calculated height differences relative to the Copernicus DEM. Larger deviations were observed mainly for mining areas and for forest areas. Thanks to the simultaneous acquisition of the interferometric pairs, the high spatial resolution and the good signal quality, the necessary processing was relatively easy to perform. Besides the interferometric phase, we also investigated possible applications of multi-static coherence. Forest can be recognized by its reduced single-pass coherence values. Based on our results, we expect that the multi-static HT1 coherence and its dependence on the interferometric baseline can be used to estimate parameters such as forest biomass. [ABSTRACT FROM AUTHOR]

We discuss the application of the three-laser optical digital interferometry method for the determination of transport properties such as the thermodiffusion, the molecular diffusion and the Soret coefficients by the thermogravitational column technique. The primary objective of this study is to illustrate the capabilities and limitations of the method for quantifying these properties in both binary and ternary liquid mixtures from an optical viewpoint. It is concluded that the system is highly robust for the analysis of binary mixtures, with the combination of the results obtained by the three wavelengths increasing the accuracy of the measurement. The study of ternary mixtures, on the contrary, is limited to certain types of conditions. While the accuracy of a three-laser interferometer can be improved, the method may be compromised if the optical contrast factor matrices are poorly conditioned. [ABSTRACT FROM AUTHOR]

Very-long-baseline interferometry (VLBI) networks have historically lacked enough antennas to densify the southern hemisphere adequately. This situation not only impacts directly the realization of the Celestial Reference System but also the determination of the Earth Orientation Parameters (EOP). In the last years, a significant step in the modernization of the VLBI infrastructure has been taken with the VLBI Global Observing System (VGOS). However, the distribution of VGOS antennas is still far from being homogeneous. In this work, we used the software VieSched++ for VLBI scheduling to simulate nine new VGOS arrays. These networks, which are more dense in the southern hemisphere and focus on South America, were planned considering existing geodetic sites where a VGOS antenna could be added and new sites where the installation is feasible. We compared the statistical performance of the proposed networks with that of a simulated standard VGOS network and the actual VGOS performance for the last 2 years. A more uniform station distribution does not seem to be associated with better repeatabilities for station coordinates, but the results for EOP and source coordinates improve as expected. [ABSTRACT FROM AUTHOR]

Spacecraft positioning plays a crucial role in scientific space mission design, as well as in the further scheduling of scientific observations for such a mission. We examine the application of global navigation satellite systems (GNSS) to solve the orbit determination problem in a pure space very long baseline interferometer (VLBI) project. A network of GPS, GLONASS, Galileo and BeiDou navigation satellites may be a more efficient solution to determining the position and velocity of space radio telescopes and space interferometer baselines. For such a project, it is necessary to take into account the special conditions of GNSS observations, as well as the high accuracy of determining not only position but also velocity. In this paper, we estimate visibility of navigation satellite systems for Low and Medium orbits of a pure space-VLBI system and simulate GNSS code and phase measurements. Orbit determination was performed on smoothed code measurements. Phase measurements simulated with a step of 1 s and combined in Doppler measurements yield average position and velocity errors of 1.01 m and 8.8 mm/s in Medium Earth orbit. The results showed that GNSS observations are sufficient to solve the problems of orbit determination of a space-VLBI interferometer both in Low-Earth and Medium Earth orbits. • Simulated GNSS observations for medium and low Earth orbits using special noise model. • Calculated the visibility of navigation satellites for low and medium Earth orbits. • Obtained navigation solution for space radio interferometers in low and medium orbits. • GNSS observations provide sufficient accuracy of orbit determination. [ABSTRACT FROM AUTHOR]

Recent advances in cold atom interferometry have cleared the path for space applications of quantum inertial sensors, whose level of stability is expected to increase dramatically with the longer interrogation times accessible in space. In this study, an in-orbit model is developed for a Mach–Zehnder-type cold-atom accelerometer. Performance tests are realized under different assumptions about the positioning and rotation compensation method, and the impact of various sources of errors on instrument stability is evaluated. Current and future advances for space-based atom interferometry are discussed, and their impact on the performance of quantum sensors on-board satellite gravity missions is investigated in three different scenarios: state-of-the-art scenario (expected to be ready to launch in 5 years), near-future (expected to be launched in the next 10 to 15 years) and far-future scenarios (expected for the next 20 to 25 years). Our results indicate that the highest sensitivity is achievable by positioning the electrostatic accelerometer at the center of mass of the satellite and the quantum accelerometer aside, on the cross-track axis of the satellite. We show that one can achieve a sensitivity level close to 5 × 10−10 m/s2/ Hz with the current state-of-the-art technology. We also estimate that in the near and far-future, atom interferometry in space is expected to achieve sensitivity levels of 1 × 10−11 m/s2/ Hz and 1 × 10−12 m/s2/ Hz , respectively. A roadmap for improvements in atom interferometry is provided that would maximize the performance of future quantum accelerometers, considering their technical capabilities. Finally, the possibility and challenges of having ultra-sensitive atom interferometry in space for future space missions are discussed. [ABSTRACT FROM AUTHOR]

Frequency combs are powerful tools for many applications and high performances are achieved by stabilizing these lasers. For operation in the mid‐infrared, quantum cascade lasers (QCL) are ideal candidates as they present numerous advantages. However, stabilized QCL‐combs lack a detailed characterization of their noise properties due to the sensitivity limits of current analyzing techniques. To overcome these challenges, what is believed to be the first tightly locked dual QCL‐comb system is developed. Its use is twofold. First, phase noise analysis of the dual‐comb signal shows residual phase noise below 600 mrad for all comb lines, and the comb coherence as well as the performances of the repetition frequency locking mechanism is characterized. Second, coherent averaging with a 7 × 105 Hz1/2 figure‐of‐merit system is demonstrated, which is compatible with high‐precision spectroscopy. [ABSTRACT FROM AUTHOR]

The machining of implants and parts for dental prostheses to eliminate biofilm in the implantoplasty process causes a loss of mechanical properties and also characteristics of the surfaces, making tissue regeneration difficult. In the present work, treatments consisting of elements that can reduce infection, such as citric acid and magnesium, together with elements that can improve cell adhesion and proliferation, such as collagen, are proposed for implant–crown assembly. Titanium, zirconia, composite (PMMA + feldspar) and cobalt–chromium discs were immersed in four different solutions: 25% citric acid, 25% citric acid with the addition of collagen 0.25 g/L, 25% citric acid with the addition of 0.50 g/L and the latter with the addition of 1% Mg (NO3)2. After immersion was applied for 2 and 10 min, the roughness was determined by interferometric microscopy and the contact angle (CA) was evaluated. Human fibroblastic and osteoblastic line cells (HFFs and SaOS-2) were used to determine cell viability and proliferation capacity. Cell binding and cytotoxicity were determined by resazurin sodium salt assay (Alamar Blue) and cell morphology by confocal assay (immunofluorescence F-actin (phalloidin)) after 3 days of incubation. For the evaluation of bacterial activity, the bacterial strains Sptreptococcus gordonii (Gram+) and Pseudomonas aeruginosa (Gram−) were used. The antibacterial properties of the proposed treatments were determined by means of the resazurin sodium salt (Alamar Blue) assay after 1 day of incubation. The treatments considerably decreased the contact angle of the treated samples with respect to the control samples. The treatments endowed the surfaces of the samples with a hydrophilic/super-hydrophilic character. The combination of elements proposed for this study provided cell viability greater than 70%; considering the absence of cytotoxicity, it therefore promotes the adhesion and proliferation of fibroblasts and osteoblasts. In addition, it also endows the surface with antibacterial characteristics against from Gram+ and Gram− bacteria without damaging the cells. These results show that this mouthwash can be useful in oral applications to produce a new passivation layer that favors the hydrophilicity of the surface and promotes cellular activity for the formation of fibroblasts and osteoblasts, as well as showing bactericidal activity. [ABSTRACT FROM AUTHOR]

Abstract This work discusses label-free biosensing application of a double-layer optical fiber interferometer where the second layer tailors the reflection conditions at the external plain and supports changes in reflected optical spectrum when a bio-layer binds to it. The double-layer nanostructure consists of precisely tailored thin films, i.e., titanium (TiO2) and hafnium oxides (HfO2) deposited on single-mode fiber end-face by magnetron sputtering. It has been shown numerically and experimentally that the approach besides well spectrally defined interference pattern distinguishes refractive index (RI) changes taking place in a volume and on the sensor surface. These are of interest when label-free biosensing applications are considered. The case of myeloperoxidase (MPO) detection—a protein, which concentration rises during inflammation—is reported as an example of application. The response of the sensor to MPO in a concentration range of 1 × 10−11–5 × 10−6 g/mL was tested. An increase in the MPO concentration was followed by a redshift of the interference pattern and a decrease in reflected power. The negative control performed using ferritin proved specificity of the sensor. The results reported in this work indicate capability of the approach for diagnostic label-free biosensing, possibly also at in vivo conditions.

Dynamic multiple light scattering (DMLS) has found numerous applications, including soft matter physics and biomedical optics. Yet biological tissues may have complex internal geometries, presenting a challenge for noninvasive measurements. Deciphering laminar dynamics is crucial to accurately interpret tissue or organ physiology. Seminal DMLS work noted that one can probe deeper layers indirectly by analyzing light fluctuations on shorter time scales. Recent technologies have enabled probing deeper layers directly by analyzing fluctuations at longer path lengths. The following question arises: are the indirect and direct approaches synergistic or redundant? Here, by adding an optical switch to path-length-filtered interferometric diffusing wave spectroscopy, we experimentally address this question in the context of a forearm occlusion study. We find that both approaches afford better distinction of light scattering dynamics in layered tissues than either approach alone. This motivates further development of methods that integrate both decorrelation time scale and light path length to probe layered tissues.

[Display omitted] Hypothesis: Despite its importance in colloid and interface science, contact line pinning remains poorly understood, especially in the presence of a precursor film. We hypothesized that this is due to a lack of an experimental method capable of directly observing their physics at the nanoscale. Using coherence scanning interferometry, we visualized the three-dimensional behavior of contact lines with a precursor film near a nanogroove structure composed of flat terrace surfaces and steps with an inclination angle of 30° while achieving nanoscale vertical resolution. We found that even when the contact line is pinned at the edge of the step, the precursor film is not and advances beyond the edge. Furthermore, we discovered that the precursor film has two distinct effects on contact line motion. Specifically, the precursor film facilitates depinning when the contact line descends the step — a contact angle change was 0.9°, only 3.0% of the value predicted by a classical theory of contact angle at a solid edge. This ultra-early depinning is attributed to the formation of a new liquid film past the edge, driven by the progression of the precursor film that overcomes the pinning effect. In contrast, when the contact line ascends the step, the precursor film acts as a resistance to movement due to steric interaction. [ABSTRACT FROM AUTHOR]

AIM: To invastigate intra- and interobserver reliability of interferometry, tear meniscus height (TMH) measurement and meibography (MBG) of an ocular surface analyzer, LacryDiag (Quantel Medical, France). METHODS: Five consecutive measurements and subsequent analysis of interferometry, TMH, and MBG were recorded by two examiners using the LacryDiag. To assess intra- and interobserver reliability, we used Cohen's kappa for categorical variables (interferometry), or intraclass correlation coefficient for continuous variables (TMH, MBG). RESULTS: Thirty eyes of 30 examinees were included. For both observers, there was excellent intraobserver reliability for MBG (0.955 and 0.970 for observer 1 and 2, respectively). Intraobserver reliability for observer 1 was substantial for interferometry (0.799), and excellent for TMH (0.863). Reliability for observer 2 was moderate for interferometry (0.535) and fair to good for TMH (0.431). Interobserver reliability was poor for interferometry (0.074) and fair to good for TMH (0.680) and MBG (0.414). CONCLUSION: LacryDiag ocular surface analyzer in our study proves to be a reliable noninvasive tool for the evaluation of TMH and MBG. As for interferometry, poor interobserver reliability, fair to good intraobserver reliability for observer 1, and moderate for observer 2, leave room for improvement.

The Ivughli salt dome, located in the West Azerbaijan province of Iran, is sourced in the Miocene Upper Red Formation, which includes salt and gypsum layers, red marl, and sandstone. The salt diapirs of West Azerbaijan are located along the North Tabriz Fault. Faults related to fractures around the Ivughli salt dome have displaced the folded layers and have caused subsidence in some parts of the salt dome. Based on the results of interferometry data, there are smaller and bigger elevation/subsidency rates with a total average of 4 mm for the whole body of the dome. The east of the dome shows high elevation and this may be due to the effect of a hidden fault that branches off the North Tabriz Fault. As well as the role of normal faults in the lower elevation of the western parts of the dome, there may have been subsidence related to surface washing and driven by erosion and agriculture in the region. Regarding the emplacement and shape of the Ivughli salt dome, it is young diapirism and currently acctive. In general, tectonic activity is still causing the rise of the Ivughli salt dome at a rate of movement that is not uniform across its structure.

Mining-induced subsidence poses a serious hazard to the surrounding environment and infrastructure, necessitating the detection of such subsidence for effective disaster mitigation and the safeguarding of local residents. Fucheng 1 is the first high-resolution mini-satellite interferometric Synthetic Aperture Radar (SAR) launched by China in June 2023. In this study, we used Fucheng 1 SAR images to analyze mining-induced subsidence in Karamay by InSAR Stacking and D-InSAR. The findings were compared with Sentinel-1A imagery to evaluate the effectiveness of Fucheng 1 in monitoring subsidence and its interferometric performance. Analysis revealed significant mining-induced subsidence in Karamay, and the results from Fucheng 1 closely corresponded with those from Sentinel-1A, particularly regarding the extent of the subsidence. It is indicated that the precision of Fucheng 1 SAR imagery has reached leading standards. In addition, due to its higher resolution, the maximum detectable deformation gradient (MDDG) of Fucheng 1 is 2.15 times higher than that of Sentinel images. This study provides data support for the monitoring of mining-induced subsidence in the Karamay and give a theoretical basis for the application of Fucheng 1 in the field of Geohazard monitoring. [ABSTRACT FROM AUTHOR]

Time series interferometric SAR (TSInSAR) techniques face challenges related to the availability of highly coherent point targets in non-urban, vegetated, and mountainous regions. In this study, we tested an improved TSInSAR approach with the help of distributed scatterers (DS) detected through the fast statistically homogeneous pixel selection (faSHP) approach and jointly processed with persistent scatterers (PS) within the interferometric point target analysis (IPTA) framework. The method is applied to a seismically active and highly gradient terrain to investigate the earthquake-induced active unstable slopes (AUS) in the Muzaffarabad-Balakot region of northern Pakistan, particularly using sixteen PALSAR-2 images acquired between October 2014 and May 2020. However, its effectiveness was also assessed by using Sentinel-1 data from the same time period. The quantitative assessment showed the effectiveness of the method in delineating the sliding surfaces of the unstable slopes and achieving approximately four times higher point density as compared to the standard PSI approach when applied to PALSAR-2 data and approximately nine times higher point targets when Sentinel-1 data is used. Exhibiting an average deformation rate varying between −40 mm yr−1 and 20 mm yr−1 along the line of sight (LOS) direction, the obtained results from PALSAR-2 data revealed the existence of 451 AUS in the region. The study also reports the discovery of a giant destabilized slope (~2.30 sq. km) located near Patika Village along the Neelam River. The majority of these unstable slopes are found at altitudes above 780 m, with slope angles ranging from 15 to 50 degrees. The study also found a significant correlation between deformation patterns and local precipitation. The rainwater gradually penetrates into the joints and cracks, accelerating the processes of deformation and slope failure. The research and its findings could help decision-making entities by providing first-hand information for managing the risks associated with slope failure. [ABSTRACT FROM AUTHOR]

Objective Methods Results Conclusion The aim of this pilot study was to establish a satisfactory, scientific approach to effectively compare quantitative measurements of various ocular surface parameters before and after surgical treatment in dogs suffering from distichiasis.An ophthalmic examination was conducted on 12 dogs (23 eyes) before and after surgical treatments for distichiasis, at four different time points, (t0 = before surgery, t1 = 1–2 h after surgery, t2 = 1 week after surgery, t3 = 1 month after surgery, and t4 = 6 months after surgery) between 2021 and 2022, and analyzed retrospectively. The examination included Schirmer tear test‐1 (STT‐1), interferometry, noninvasive tear film break‐up time (NIBUT), tear meniscus size (TMS), and meibography.No statistically significant changes were found in STT‐1 (t0: 22.2 ± 6.5 mm, t2: 22.5 ± 5.7 mm, t3: 20.8 ± 5.1 mm, and t4: 22.6 mm ± 4.8 mm) before and after surgery. Mean interferometry scores showed a slight, not statistically significant, decrease from t0 to t3 and t4 (t0: 2.1 ± 0.8, t1: 2.1 ± 0.7, t2: 2.1 ± 0.9, t3: 1.8 ± 0.6, and t4: 1.9 ± 1.1). Mean NIBUT did not change significantly between time points (t0: 3.9 ± 1.3 s, t1: 4.0 ± 1.3 s, t2: 4.0 ± 1.4 s, t3: 3.5 ± 0.7 s, and t4: 3.5 ± 0.9 s). TMS showed a slight, not statistically significant increase (t0: 0.5 ± 0.3 mm, t1: 0.5 ± 0.3, t2: 0.5 ± 0.3 mm, t3: 0.6 ± 0.2 mm, and t4: 0.7 ± 0.3 mm). There were no changes in the gross morphology of the meibomian glands (MG).This pilot study could not detect a negative effect of different forms of treatment of distichiasis on the precorneal tear film parameters in dogs. However, due to the study's retrospective nature and small sample size, no definitive conclusion can be drawn regarding the changes at the different time points. [ABSTRACT FROM AUTHOR]