Backscattering Of Light Research Articles

The interfacial behaviors of ball-milled gorgon euryale starch - quinoa protein complex and its stabilizing effect on Pickering emulsions

This study investigated the effects of ball-milling treatment on the characteristics of gorgon euryale starch (GES) and quinoa protein (QP), and developed a new strategy by compounding ball-milled GES with QP to study the mechanism of its action on the stability of Pickering emulsions. Through SEM and FTIR analyses, it was found that ball-milling treatment damaged the compound granular structure of GES, reduced the particle size of QP, and caused aggregation. However, the chemical structures of both substances did not change significantly. The Pickering emulsions prepared with the ball-milled GES/QP complex exhibited more significant thickening properties. Ball milling reduced the droplet size of the emulsions (D50 decreased from 6.73 ± 0.12 to 2.85 ± 0.91 μm) and made the distribution more uniform, though an excessive protein ratio led to droplet aggregation and a decrease in the emulsification index. Using the emerging observation method of DIC, it was confirmed that the emulsions prepared with GES/QP (8/2, g/g) and GES/QP (7/3, g/g) showed almost no change in backscattering light intensity and still had good storage stability after 20 days. This study provides a theoretical basis for the development of more stable and clean emulsifiers.

Sensitivity of backscattering to spherical particle physical properties: Size, refractive index, and shape deviations

The purpose of this paper is to study the dependency of light backscattering on particle physical properties: size, refractive index, and shape; and to demonstrate the extreme sensitivity of backscattering on these properties. We demonstrate how the nondescript backscattering pattern evolves seemingly chaotic, in contrast to the orderly forward scattering, with the particle's physical properties. The demonstration was carried out by light scattering from water droplets and with spherical particle Mie theory. Our results show systematic, descriptive evolution of the forward scattering pattern, which is clearly shown in logarithmic Q–space, whereas non-descriptive, chaotic evolution within the backscattering regime is displayed in linear θ–space. Additionally, our study shows that within the last 1°, the backscattering intensity remains constant and featureless for the ∼ 2.5 μm diameter water droplets investigated here.

Validation of an Optical Technology for the Determination of pH in Milk during Yogurt Manufacture.

Current systems that allow inline pH control in the fermented dairy industry have drawbacks, such as protein adhesion on the non-glass pH probes, measurement distortion, frequent recalibration needs, and sensitivity to extreme pH conditions encountered during clean-in-place operations. Therefore, the objective of this study was to validate the feasibility of estimating the pH of milk during the yogurt making process by using a NIR light backscatter sensor measuring under different fermentation temperatures and milk protein concentrations using a mathematical model that correlates the light scatter signal with pH. Three replications of the experiment with two protein concentrations (3.5 and 4.0%) and two fermentation temperatures (43 and 46 °C) were used to validate this inline pH prediction model. Continuous and discontinuous measurements of pH were collected as a reference during fermentation, simultaneously with the light backscatter data acquisition. Also, the effect of adjusting the initial voltage gain of the light scatter device on the accuracy of the pH prediction model was evaluated. Temperature and initial voltage were the main factors affecting the fitting accuracy of the model. The adjustment of the initial voltage gain improved the pH prediction model fit. The model has been successfully validated for both continuous and discontinuous measurements of pH, with SEP values < 0.09 pH units and CV < 1.78%. The proposed optical inline and non-destructive method was feasible for inline pH monitoring of milk fermentation, avoiding traditional manual pH measurement.

Transformer-based improved U-net for high-performance underwater polarization imaging

Polarization imaging plays an important role in underwater imaging technology, as it allows for the suppression of backscattering light and thus enhances the quality of underwater images. Furthermore, with advancements in computer hardware technology, deep learning (DL) has experienced rapid development in recent years. However, existing methods based on convolutional neural networks (CNN) have the limitations of local feature extraction and fail to full use of the salient target’s polarization features. In this paper, we propose a transformer-based improved U-Net (TIU-Net) to further improve the performance of underwater polarization imaging. The proposed TIU-Net leverages CNN and transformer module to extract short-range and long-range features respectively for underwater target reconstruction. Meanwhile, by entering multi-dimensional information, each of which has a different emphasis on the expression of target features, to enhance the performance and stability of the reconstruction model. Experimental results on our established polarization underwater dataset show the superiority of our proposed method for underwater imaging, achieving the efficient imaging and high-quality generalization imaging in highly turbid underwater environments.

Hyperspectral measurements of light backscattering by particles in water with a fixed angle setup: proof of concept and instrument calibration.

The light backscatter signal is the fraction of light scattered at angles greater than 90 degrees with respect to the direction of the incident light. Optical remote sensing platforms collect this signal, which, when measured from the ocean, holds crucial information about its constituents. Interpretation of this signal demands a rigorous understanding of scattering by water and by particles in water. Previous backscatter measurements have mainly focused on resolving the angular distribution of scattering with much less attention given to resolving the wavelength component of backscatter. Most heritage sensors have looked at most 9 wavelengths of light at one scattering angle. Just recently an in situ sensor was presented that can measure backscattering with a 10 nm resolution. Here, we present a laboratory hyperspectral backscatter setup capable of measuring from the ultraviolet to near-infrared wavelengths (320 - 850 nm) at 2 nm resolution.

Enhanced perturbation measurement range chirped pulse ϕ-OTDR for distributed static measurements using feedback frequency-shift compensation technology

Chirped-pulse phase-sensitive optical time-domain reflectometry (CP-ϕOTDR) is a newly developed distributed optical fiber sensing (DOFS) technology that can measure physical quantities across the length of optical fiber. The measurement of perturbations as strain or temperature changes is performed by comparing the time domain trace of Rayleigh backscattered (RBS) light with a reference trace. However, large strain or temperature fluctuations or laser frequency noises necessitate frequent updates of the reference, and short-term change measurements must be integrated to obtain absolute strain or temperature, which introduces a 1/f noise component due to the combination of noise with each cumulative change. In this study, we propose a novel CP-ϕOTDR system based on frequency-shift compensation (FSC) technology. This system utilizes real-time feedback control of the central frequency of the incident laser to compensate for time domain trace distortion caused by large perturbations. It overcomes the limitations associated with the total chirp bandwidth and eliminates the 1/f noise component by obviating the need for frequent updates of the reference trace. The measuring range for perturbations is only limited to the wavelength range supported by the integrated optical devices, typically on the order of nanometers, corresponding to at least tens of Kelvin in temperature fluctuations or hundreds of micro-strains. To validate the effectiveness, we conducted a temperature measurement experiment involving a 1 K variation, which is about 90 times the maximum measurable perturbation that the original CP-ϕOTDR system can demodulate with the reference unchanged. The results demonstrate that the FSC method significantly expands the perturbation measurement range of the CP-ϕOTDR system.

Frequency multiplexed dual-pulse fiber-optic Φ-OTDR for a fading-free distributed fiber sound sensor

Distributed fiber-optic sensor utilizing optical interference signal detection of the Rayleigh backscattering (RBS) light along the fiber under test (FUT) has greatly progressed over the past 20 years. It can now realize real-time sound signal recovery along the FUT with a good fidelity and high sensitivity. However, the performance of the practical distributed fiber-optic sound sensor is still limited by the fading problem, as invalid spatial channels at unknown positions arise due to the low signal intensity at these positions and the resulting near-zero signal-to-noise ratio (SNR). In this paper, we propose a novel, to the best of our knowledge, fading-free fiber sensor structure by incorporating an acousto-optic frequency shift (AOFS) loop into the light source in a dual-pulse phase optical time domain reflectometry (Φ-OTDR). As a result of stable frequency shifting and feedback within the loop, the loop source can output a high-repetition-rate narrow pulse train consisting of multiple separated frequencies. This pulse train is further shaped into two pulse bursts by an acousto-optic modulator (AOM) and an in-balanced fiber-optic Mach–Zehnder interferometer (MZI). The pulse bursts are then sent into the sensing fiber, while the RBS light is detected using an Avalanche photodiode after an erbium-doped fiber amplifier. The experimental results show that the proposed structure is capable of vibration signal recovery with a good SNR all along the FUT. The fading-free performance is evaluated under different AOFS loop gains, showing significant potential in practical fiber sensor network applications.

Separation-dependent near-field effects in Mie scattering spectra of two optically trapped aerosol droplets

The backscattering of ultraviolet and visible light by a model organic (squalane) aerosol droplet (1.0&lt;r&lt;1.4 μm) is investigated upon approach of a second isolated droplet at varying separations. Illumination and collection of light is along the interparticle axis. The conditions replicate typical broadband light spectroscopy studies of atmospheric aerosol. T-Matrix near-field modelling, which includes near-field effects, predicts separation-dependent changes in the intensity of the backscattered light on close approach of neighbouring spheres. However, the experimental results show no evidence of separation-dependent near-field effects on the scattering. The results are best replicated by modelling the droplets as individual Mie scatterers.

Futuristic opportunities for pretreatment processes in biofuel production from microalgae

AbstractMicroalgal biofuel is a promising solution to replace fossil fuel as a renewable and environmental‐friendly energy source, thereby contributing to the United Nations (UN) Sustainable Development Goals (SDGs), in particular SDG‐7, or Affordable and Clean Energy. Unlike energy crops (like oil palm and sugar cane), microalgae benefit from faster growth rate, higher lipid content, smaller land area required, ability to flourish using waste or brackish water, and posing zero competition with food crops. Microalgae‐derived biofuels (like biodiesel, bioethanol, biomethane, and biohydrogen) are sustainable energy sources that can be produced using well‐developed techniques (e.g., transesterification, fermentation, anaerobic digestion, and Fisher–Tropsch process). To prevent dire climate conditions resulting from the global temperature rise of 1.5°C and resolve worldwide energy security issue, our generation will need to establish and implement renewables on a global scale. To improve the industrial production of microalgal biofuel, the efficiencies of biomass and metabolite production to post‐cultivation biofuel synthesis processes must be enhanced. For the cultivation step, there exist three key techniques that can directly change the traits, structure, and behavior of microalgal cells, and induce them to accumulate targeted metabolites rapidly and in large amounts. These techniques are genetic engineering, chemical modulation, and nanomaterial approach. Genetic engineering commonly alters the chloroplast DNA of microalgae to overexpress or down‐regulate key genes in various metabolic pathways so that the cells accumulate more lipids. Chemicals can also be used to modulate microalgal growth and lipid accumulation by inducing oxidative stress or prevent conversion of lipid molecules. Nanomaterials and nanoparticles can also enhance microalgal lipid production by microenvironmental stress induction, vitamin supplementation, and light backscattering. Therefore, in this review, the recent progress as well as the pros and cons of genetic engineering, chemical modulation, and nanomaterial approach in achieving greater biofuel production from microalgae are comprehensively examined.

Rigorous Accounting for Dependent Scattering in Thick and Concentrated Nanoemulsions.

Concentrated and thick oil-in-water nanoemulsions have been observed to become more transparent with increasing oil volume fraction. This study demonstrates rigorously experimentally and numerically that such unusual behavior is due to dependent scattering including not only far-field but also near-field effects. Indeed, when the droplet concentration is sufficiently large, their interparticle distance becomes small compared to the wavelength of light and scattering by a given droplet may be affected by the proximity of others. This situation is referred to as dependent scattering. Light transfer through nanoemulsions and other colloids has previously been modeled by solving the radiative transfer equation accounting for dependent scattering using the static structure factor based on far-field approximations. Here, oil-in-water nanoemulsions were prepared with oil volume fraction ranging between 1 and 20% and a peak droplet radius of 16 nm. The spectral normal-hemispherical transmittance of the different nanoemulsions in 10 mm thick cuvettes was measured experimentally between 400 and 900 nm. Numerical predictions for nonoverlapping randomly distributed nanoscale oil droplets in water and accounting for dependent scattering including near-field effects-using the recently developed radiative transfer with reciprocal transactions (R2T2) method-were in excellent agreement with experimental measurements. Simulations revealed that assuming independent scattering underestimated the normal-hemispherical transmittance even for a relatively small oil volume fraction. Additionally, simulations using the dense medium radiative transfer (DMRT) and static structure factor predicted that dependent scattering prevailed for oil volume fractions slightly greater than those predicted by the R2T2 method. Interestingly, the DMRT method predicted large increases in transmittance when the oil droplet size and volume fraction were larger than 10 nm and 10%, respectively. Finally, simulations also revealed that dependent scattering enables the design of oil-in-water nanoemulsions to backscatter or absorb light by tuning the oil droplet size and volume fraction. The results validate that the R2T2 method could be used to characterize nanoemulsions or to investigate their formation, composition, and stability for drug delivery, food, and cosmetics applications. Future studies could extend the use of the R2T2 method to colloidal suspensions with particles of arbitrary shapes and to radiation transfer of polarized light in turbid media.

Comparison between Two Adaptive Optics Methods for Imaging of Individual Retinal Pigmented Epithelial Cells.

The Retinal Pigment Epithelium (RPE) plays a prominent role in diseases such as age-related macular degeneration, but imaging individual RPE cells is challenging due to their high absorption and low autofluorescence emission. The RPE lies beneath the highly reflective photoreceptor layer (PR) and contains absorptive pigments, preventing direct backscattered light detection when the PR layer is intact. Here, we used near-infrared autofluorescence adaptive optics scanning laser ophthalmoscopy (NIRAF AOSLO) and transscleral flood imaging (TFI) in the same healthy eyes to cross-validate these approaches. Both methods revealed a consistent RPE mosaic pattern and appeared to reflect a distribution of fluorophores consistent with findings from histological studies. Interestingly, even in apparently healthy RPE, we observed dynamic changes over months, suggesting ongoing cellular activity or alterations in fluorophore distribution. These findings emphasize the value of NIRAF AOSLO and TFI in understanding RPE morphology and dynamics.

Properties of Light Backscattering on Hollow Hexagonal Ice Columns for Optical Models of Cirrus Clouds

Properties of Light Backscattering on Hollow Hexagonal Ice Columns for Optical Models of Cirrus Clouds

Utility of ganglion cells for the evaluation of anterior visual pathway pathology: a review.

The management of optic neuropathy is fundamental to neuro-ophthalmic practice. Following the invention of the ophthalmoscope, clinicians, for a century or more, relied upon fundus examination in the evaluation of optic neuropathy. However, the advent of optical coherence tomography, based on the principle of backscattering of light and interferometry, has revolutionized the analysis of optic nerve and retinal disorders. Optical coherence tomography has proven of particular value in the measurement, at the micron level, of the peripapillary retinal nerve fibre layer and the ganglion cell layer. These measurements have proven critical in the differential diagnosis and monitoring of optic neuropathy. Specifically, thinning of the peripapillary nerve fibre layer provides evidence of axonal loss affecting any sector of the optic nerve. Thinning of the macular ganglion cell layer, on the other hand, shows a more precise correlation with visual deficits due to retrograde degeneration following optic nerve damage, although limited to central retina. In daily practise, optical coherence tomography is of great value in assessing the diagnosis, prognosis and response to treatment in optic neuropathy. Particular advances have been made, for example, in the assessment of optic neuritis, papilloedema and chiasmal compression which have translated to everyday practice. As with any other imaging technology the clinician must have a clear understanding of acquisition artefacts. A further issue is the relatively limited normative database in sub-populations such as the young and individuals with a refractive error > + 5 or < -5 dioptres.

A laser field synchronous scanning imaging system for underwater long-range detection

A novel underwater optical imaging system is proposed to improve underwater image degradation, which is severely deteriorated due to absorption and scattering under artificial illumination. The light source employs a line laser with 520 nm wavelength and a mirror galvanometer that controls the one-dimension scanning of the laser beam to form a planar illumination light field. The camera adopts an sCMOS image sensor with an electronic rolling shutter exposure pattern, compressing the camera’s instantaneous field of view(IFOV) into a narrow strip by reducing the exposure time. Meanwhile, the system controls the light source to irradiate the IFOV of the camera only synchronously, which significantly compressed the overlapping volume of the light path between the camera and the light source so that the backscattered light captured by the camera was dramatically reduced. Experimental results at different turbidity and distances in pool environments show that the laser field synchronous scanning imaging system obtains excellent performance in contrast ratio (CR) and contrast signal-to-noise ratio (CSNR). In the turbidity experiment, the peak CR of the target image improved by a factor of 3.88, and the peak CSNR improved by a factor of 2.33 in 19.6 FTU. In the distance experiment, the peak CR of the target image improved by a factor of 5.57, and the peak CSNR improved by a factor of 1.67 at a distance of 13 m, achieving a clear imaging range of 15 m. This system substantially diminishes the impact of light backscattering on imaging quality, which effectively facilitates further development of the underwater task and renders the system highly applicable in underwater imaging.

Natural Fat Nanoemulsions for Enhanced Optical Coherence Tomography Neuroimaging and Tumor Imaging in the Second Near-Infrared Window.

Optical coherence tomography (OCT) imaging mainly uses backscattered light to visualize the structural and functional information on biological tissues. In particular, OCT angiography can not only map the capillary networks but also capture the blood flow in the tissue microenvironment, making it a good candidate for neuroimaging and tumor imaging in vivo and in real time. To further improve the detection accuracy of cancer or brain disorders, it is essential to develop a natural and nontoxic contrast agent for enhanced OCT imaging in the second near-infrared (NIR-II) window. In this study, a superior biocompatible and highly scattering NIR-II fat nanoemulsion was constructed to improve OCT imaging contrast and depth for monitoring the vascular network changes of the cerebral cortex or tumor. In vivo experimental results demonstrated that a natural fat nanoemulsion can serve as an excellent probe for enhanced OCT neuroimaging and tumor imaging.

Squalene production under oxygen limitation by Schizochytrium sp. S31 in different cultivation systems

The triterpene squalene is widely used in the food, cosmetics and pharmaceutical industries due to its antioxidant, antistatic and anti-carcinogenic properties. It is usually obtained from the liver of deep sea sharks, which are facing extinction. Alternative production organisms are marine protists from the family Thraustochytriaceae, which produce and store large quantities of various lipids. Squalene accumulation in thraustochytrids is complex, as it is an intermediate in sterol biosynthesis. Its conversion to squalene 2,3-epoxide is the first step in sterol synthesis and is heavily oxygen dependent. Hence, the oxygen supply during cultivation was investigated in our study. In shake flask cultivations, a reduced oxygen supply led to increased squalene and decreased sterol contents and yields. Oxygen-limited conditions were applied to bioreactor scale, where squalene accumulation and growth of Schizochytrium sp. S31 was determined in batch, fed-batch and continuous cultivation. The highest dry matter (32.03 g/L) was obtained during fed-batch cultivation, whereas batch cultivation yielded the highest biomass productivity (0.2 g/L*h−1). Squalene accumulation benefited from keeping the microorganisms in the growth phase. Therefore, the highest squalene content of 39.67 ± 1.34 mg/g was achieved by continuous cultivation (D = 0.025 h−1) and the highest squalene yield of 1131 mg/L during fed-batch cultivation. Volumetric and specific squalene productivity both reached maxima in the continuous cultivation at D = 0.025 h−1 (6.94 ± 0.27 mg/L*h−1 and 1.00 ± 0.03 mg/g*h−1, respectively). Thus, the choice of a suitable cultivation method under oxygen-limiting conditions depends heavily on the process requirements.Key points• Measurements of respiratory activity and backscatter light of thraustochytrids• Oxygen limitation increased squalene accumulation in Schizochytrium sp. S31• Comparison of different cultivation methods under oxygen-limiting conditions

The comparison of corneal densitometry in cases with glaucoma following childhood cataract surgery and juvenile glaucoma

PurposeTo compare the corneal densitometry (CD) in pediatric cases with glaucoma following childhood cataract surgery and juvenile open-angle glaucoma (JOAG).MethodsThis prospective comparative study involved 13 eyes with JOAG, 12 eyes with pseudophakic glaucoma, 13 eyes with aphakic glaucoma, and 15 control subjects. Pentacam HR Scheimpflug corneal topography was employed to evaluate corneal thickness (CCT) and CD values.ResultsThe mean intraocular pressure (IOP) and CCT were significantly higher in aphakic glaucoma cases than the other groups (p = 0.001). In aphakic eyes, the mean CD values were higher in most of the anterior, center, and posterior layers of 0–2 mm, 2–6 mm, 6–10 mm, and total zones (p < 0.001 for all). In pseudophakic eyes, the mean CD values were statistically similar with that of aphakic eyes and higher than that of JOAG and control eyes in all layers of 0–2 mm zone and in anterior layer of 10–12 mm and anterior and total layers of 2–6 mm zones (p < 0.05 for all). The CD values demonstrated significant correlations with CCT values in both aphakic and pseudophakic eyes. However, a significant correlation of CD values with IOP was only demonstrated in aphakic eyes (p = 0.01 for all).ConclusionThe probable effects of childhood cataract surgery especially aphakia might cause corneal backscatter of light and increased CD in all layers in all zones of the cornea. Increased CD values and its correlation with CCT and IOP in aphakic glaucoma eyes may be of importance in clinical management.

Electrically-controlled suppression of Rayleigh backscattering in an integrated photonic circuit

Abstract Undesirable light scattering is a fundamental cause for photon loss in nanophotonics. Rayleigh backscattering can be particularly difficult to avoid in wave-guiding systems and arises from both material defects and geometric defects at the subwavelength scale. It has recently been shown that systems exhibiting chiral dispersion due to broken time-reversal symmetry (TRS) can naturally mitigate Rayleigh backscattering, yet this has never been explored in integrated photonics. Here we demonstrate the dynamic suppression of disorder-induced Rayleigh backscattering in integrated photonics even when defects are clearly present. Our experiments are performed using lithium niobate on insulator resonators in which TRS is broken through an electrically-driven acousto-optic interaction. We experimentally observe near-complete suppression of Rayleigh backscattering within the resonator by measuring the optical states and through direct measurements of the back-scattered light. We additionally provide a new and intuitive generalization argument that explains this suppression of backscattering as a form of topological protection in synthetic space.

A Multi-Stage Progressive Network with Feature Transmission and Fusion for Marine Snow Removal.

Improving underwater image quality is crucial for marine detection applications. However, in the marine environment, captured images are often affected by various degradation factors due to the complexity of underwater conditions. In addition to common color distortions, marine snow noise in underwater images is also a significant issue. The backscatter of artificial light on marine snow generates specks in images, thereby affecting image quality, scene perception, and subsequently impacting downstream tasks such as target detection and segmentation. Addressing the issues caused by marine snow noise, we have designed a new network structure. In this work, a novel skip-connection structure called a dual channel multi-scale feature transmitter (DCMFT) is implemented to reduce information loss during downsampling in the feature encoding and decoding section. Additionally, in the feature transfer process for each stage, iterative attentional feature fusion (iAFF) modules are inserted to fully utilize marine snow features extracted at different stages. Finally, to further optimize the network's performance, we incorporate the multi-scale structural similarity index (MS-SSIM) into the loss function to ensure more effective convergence during training. Through experiments conducted on the Marine Snow Removal Benchmark (MSRB) dataset with an augmented sample size, our method has achieved significant results. The experimental results demonstrate that our approach excels in removing marine snow noise, with a peak signal-to-noise ratio reaching 38.9251 dB, significantly outperforming existing methods.

Detection of internal tendon breaks by fiber-optical measurements – influence of the re-anchoring behavior

Unannounced tendon breaks belong to the most dreaded failure mechanisms in prestressed concrete bridges. Failure of single wires or tendons does not necessarily cause concrete cracking. Hence, such damage cannot always be detected by visual inspection. In the case of tendons bonded in concrete, re-anchoring after breaking induces characteristic local strain fields: tensile strains occur between the separated extremities, while compressive strains develop around the tendons, until the initial prestressing strain is reached again. On the more distant concrete surface, these strains are rather small and depend on multiple factors, e.g., the depth of the tendon, the transfer length or the concrete stiffness.Nevertheless, such strain fields can be detected by fiber-optical sensors attached to the surface in two-dimensional grids. By evaluating the backscatter of emitted light, minimal strain changes (uncertainty: ±1 µm/m) can be recorded in quasi-continuous resolution (0.65 mm pitch). An experimental investigation of artificial tendon failure in two prestressed concrete beams is presented. The tendons were mechanically cut to simulate failure, while strains were measured on the concrete faces. The failure can be localized within a few centimeters by monitoring.The bond to the tendon mainly depends on the concrete strength. To investigate its effect on the surface strain a normal strength concrete is compared to a high-performance concrete. Better bond conditions result in lower expansion of the strain field and smaller strains in general. The results show potential to detect the position and quantity of broken tendons, solely from the strain signal on the concrete surface.