Scattered Light Images Research Articles

Rapid detection of microbial antibiotic susceptibility via deep learning supported analysis of angle-resolved scattered-light images of picoliter droplet cultivations

The progressive increase in microbial resistance to antibiotics is a global health threat that requires solutions for rapid and reliable determination of antibiotic susceptibility in order to select appropriate antibiotics and dosages prior to treatment. We have established a screening platform that enables the detection of cell growth after just a few cell divisions. Our methodological approach for a robust phenotypic antibiotic susceptibility testing is based on the innovative combination of three cutting-edge technologies: (i) a high-throughput microfluidic platform where individual bacterial cells are encapsulated in picoliter-sized droplets, (ii) a 2D angle-resolved light scattering sensor to perform label-free hourly screening of the droplets, and (iii) a computational image analysis approach based on convolutional neural networks to evaluate the dynamics of microbial growth in droplets. For the gram-positive Staphylococcus aureus and gram-negative Escherichia coli, we demonstrate that microbial growth in droplets can be successfully detected within one to two hours. Furthermore, the potential of this platform for rapid phenotypic antibiotic susceptibility testing is demonstrated as a proof-of-concept with the clinically relevant bacterium S. aureus under various concentrations of the antibiotic tetracycline. Notably, we reach a robust phenotypic decision regarding the sensitivity to this antibiotic within two hours.

The debris disc of HD 131488: bringing together thermal emission and scattered light

ABSTRACT We show the first SPHERE/IRDIS and IFS data of the CO-rich debris disc around HD 131488. We use N-body simulations to model both the scattered light images and the spectral energy distribution of the disc in a self-consistent way. We apply the Henyey–Greenstein approximation, Mie theory, and the Discrete Dipole Approximation to model the emission of individual dust grains. Our study shows that only when gas drag is taken into account can we find a model that is consistent with scattered light as well as thermal emission data of the disc. The models suggest a gas surface density of 2 × 10−5 M⊕ au−2 which is in agreement with estimates from ALMA observations. Thus, our modelling procedure allows us to roughly constrain the expected amount of gas in a debris disc without actual gas measurements. We also show that the shallow size distribution of the dust leads to a significant contribution of large particles to the overall amount of scattered light. The scattering phase function indicates a dust porosity of ∼0.2…0.6 which is in agreement with a pebble pile scenario for planetesimal growth.

Radio-continuum decrements associated to shadowing from the central warp in transition disc DoAr 44

ABSTRACT Warps have often been used to explain disc properties, but well-characterized examples are important due to their role in disc evolution. Scattered light images of discs with central gaps have revealed sharp warps, such that the outer rings are shadowed by tilted inner discs. The near-infrared intensity drops along the ring around T-Tauri star DoAr 44 have been interpreted in terms of a central warp. We report new ALMA observations of DoAr 44 in the continuum at 230 and 350 GHz (at ∼10 au), along with a new epoch of Spectro Polarimetric High-contrast Exoplanet REsearch (SPHERE)/Infrared Dual-band Imager and Spectrograph differential polarized imaging taken during excellent weather conditions. The ALMA observations resolve the ring and confirm the decrements proposed from deconvolution of coarse 336 GHz data. The scattered light image constrains the dips, which correspond to a misaligned inner disc with a relative inclination ξ = 21.4 $^{+6.7}_{-8.3}$ deg. The SPHERE intensity profile shows a morphological change compared to a previous epoch that may be interpreted as a variable orientation of the inner disc, from ξ ∼ 30 deg to ξ ∼ 20 deg. The intensity dips probably correspond to temperature decrements, as their mm-spectral index, $\alpha ^{230 \textrm {GHz}}_{350 \textrm {GHz}} \sim$ 2.0 ± 0.1, is indicative of optically thick emission. The azimuth of the two temperature decrements are leading clockwise relative to the infrared-dips, by η = 14.95 deg and η = 7.92 deg. For a retrograde disc, such shifts are expected from a thermal lag and imply gas surface densities of Σg = 117 ± 10 g cm−2 and Σg = 48 ± 10 g cm−2. A lopsided disc, with contrast ratio fr = 2.4 ± 0.5, is also consistent with the large continuum crescent.

High-speed scattered-light imaging for sizing respiratory droplets

The COVID-19 pandemic has illuminated the lack of knowledge regarding the airborne transmission pathway of disease. The pathway consists of pathogens contained in small particles ejected when speaking and coughing. A crucial characteristic of these particles is their size that is connected to the their suspension longevity in the air as well as the location of generation and deposition within a subject’s respiratory system. Sizing of particles launched from the respiratory system is a challenge for a number of reasons: (1) the size of ejected particles varies over a wide range, between sub- to several hundreds of microns, (2) particles are ejected at various speeds in different directions, (3) each single event is unique where for example the number of particles can vary greatly between two occurrences of the same event and subject, (4) the size of the particles vary significantly as they evaporate over time. To overcome these challenges and categorize full coughing and speaking events, new measuring methods are needed. In this work, we present, in detail, high-speed scattered light imaging to size liquid particles (droplets) in unique respiratory events. A high-speed camera records scattered laser light at 16 000 frames per second in a semi-forward scattering direction. The illumination is close to the ejection source which means that the particles are sized before evaporation. The measurement can size stationary droplets from 3.4 to 44 μm and moving droplets from 4 to 80 μm resolved in both time and space. To get a reliable estimation, careful calibration of scattering angles and calibration uncertainty has been performed showing a general uncertainty of 8%. Thus, the approach proposed in this article can provide valuable and accurate data to improve the understanding of the airborne transmission pathway.

The edge-on protoplanetary disk HH 48 NE

Context. Observations of edge-on disks are an important tool for constraining general protoplanetary disk properties that cannot be determined in any other way. However, most radiative transfer models cannot simultaneously reproduce the spectral energy distributions (SEDs) and resolved scattered light and submillimeter observations of these systems because the geometry and dust properties are different at different wavelengths.Aims. We simultaneously constrain the geometry of the edge-on protoplanetary disk HH 48 NE and the characteristics of the host star. HH 48 NE is part of the JWST early-release science program Ice Age. This work serves as a stepping stone toward a better understanding of the physical structure of the disk and of the icy chemistry in this particular source. This type of modeling lays the groundwork for studying other edge-on sources that are to be observed with the JWST.Methods. We fit a parameterized dust model to HH 48 NE by coupling the radiative transfer codeRADMC-3Dand a Markov chain Monte Carlo framework. The dust structure was fit independently to a compiled SED, a scattered light image at 0.8 µm, and an ALMA dust continuum observation at 890 µm.Results. We find that 90% of the dust mass in HH 48 NE is settled to the disk midplane. This is less than in average disks. The atmospheric layers of the disk also exclusively contain large grains (0.3–10 µm). The exclusion of small grains in the upper atmosphere likely has important consequences for the chemistry because high-energy photons can penetrate very deeply. The addition of a relatively large cavity (~50 au in radius) is necessary to explain the strong mid-infrared emission and to fit the scattered light and continuum observations simultaneously.

A reinvestigation of debris disc halos

Context. Scattered-light images reveal that a significant fraction of debris discs consist of a bright ring beyond which extends a wide halo. This halo is expected and should be made of small grains collisionally produced in the ring of parent bodies (PBs) and pushed on high-eccentricity orbits by radiation pressure. It has been shown that, under several simplifying assumptions, the surface brightness (SB) of this halo should radially decrease as r−3.5 in scattered light Aims. We aim to revisit the halo phenomenon and focus on two unexplored issues: (1) how the unavoidable presence of small unbound grains, non-isotropic scattering phase functions (SPFs), and finite instrument resolution affect scattered-light SB profiles, and (2) how the halo phenomenon manifests itself at longer wavelengths in thermal emission, both on resolved images and on system-integrated spectral energy distributions (SEDs). Methods. We use a collisional evolution code to estimate the size-dependent spatial distribution of grains in a belt+halo system at steady state. We use the GRaTeR radiative-transfer code to derive synthetic images in scattered light and thermal emission, as well as SEDs. Results. We find that unbound grains account for a significant fraction of the halo’s luminosity in scattered light, and can significantly flatten the SB radial profile for the densest and brightest discs. Because halos are strongly size-segregated with radial distance, realistic size-dependent SPFs also have an effect, resulting here again in shallower SB profiles. For edge-on discs, non-resolving the vertical profile can also significantly flatten the projected SB profile. We show that roughly half of the observationally derived halo profiles found in the literature are compatible with our new results, and that roughly half of the remaining systems are probably shaped by additional processes (planets, stellar companions, etc.). We also propose that, in future observational studies, the characteristics of the PB belts and the halos should be fitted separately. In thermal emission, we find that wide halos should remain detectable up to the far-infrared (far-IR) and that, with the exception of the ~8–15 µm domain, the halo accounts for more than half of the system’s total flux up to λ ~ 80–90 µm. The contribution from the halo strongly decreases in the submm to mm but still represents a few percent of the system’s luminosity at λ ~ 1 mm. For unresolved systems, the presence of a halo can also affect the determination of the radius of the disc from its SED.

Using light and X-ray scattering to untangle complex neuronal orientations and validate diffusion MRI.

Disentangling human brain connectivity requires an accurate description of nerve fiber trajectories, unveiled via detailed mapping of axonal orientations. However, this is challenging because axons can cross one another on a micrometer scale. Diffusion magnetic resonance imaging (dMRI) can be used to infer axonal connectivity because it is sensitive to axonal alignment, but it has limited spatial resolution and specificity. Scattered light imaging (SLI) and small-angle X-ray scattering (SAXS) reveal axonal orientations with microscopic resolution and high specificity, respectively. Here, we apply both scattering techniques on the same samples and cross-validate them, laying the groundwork for ground-truth axonal orientation imaging and validating dMRI. We evaluate brain regions that include unidirectional and crossing fibers in human and vervet monkey brain sections. SLI and SAXS quantitatively agree regarding in-plane fiber orientations including crossings, while dMRI agrees in the majority of voxels with small discrepancies. We further use SAXS and dMRI to confirm theoretical predictions regarding SLI determination of through-plane fiber orientations. Scattered light and X-ray imaging can provide quantitative micrometer 3D fiber orientations with high resolution and specificity, facilitating detailed investigations of complex fiber architecture in the animal and human brain.

Capabilities and limits of surface roughness measurements with monochromatic speckles.

For coherent light illumination, surface roughness leads to speckles in the scattered light image. By evaluating the speckle contrast or image auto-correlation, a measurement of the roughness parameter S q is possible. While these measurement principles have been well known for decades, a fundamental understanding of the minimal achievable measurement uncertainty is missing. Therefore, the measurement uncertainty limits for four unavoidable sources of uncertainty are derived by means of theoretical and numerical approaches. The study is focused on the case of monochromatic speckles, which provide the highest sensitivity, as well as on the case of planar surface and isotropic surface roughness with a Gaussian height distribution and Gaussian correlation function. The considered uncertainty sources are the natural randomness of surface roughness itself, speckle noise, quantum shot noise, and camera noise. As a result, for the studied experimental configuration, speckle noise is determined as the largest contribution to measurement uncertainty, which leads to a minimal achievable relative uncertainty of 1%-2% for S q =(0.03-0.15)λ. According to theoretical studies, the speckle noise limit of the relative uncertainty is inversely proportional to four times the square root of the independent number of evaluated speckles. In addition, an absolute uncertainty limit is reached for ever-smoother surfaces, which amounts to λ divided by 64 times the square root of the independent number of evaluated speckles. Furthermore, systematic errors due to cross-sensitivity with respect to other parameters of surface roughness (height distribution, correlation length) as well as the surface position and shape (axial offset, tilt, curvature) are quantified and discussed. For the considered small deviations of different influencing quantities, the quantified errors are one order of magnitude smaller than the speckle noise limit.

Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): Characterization of the young star T CrA and its circumstellar environment

Context. In recent years, a new hot topic has emerged in the star and planet formation field, namely, the interaction between the circumstellar disk and its birth cloud. The birth environments of young stars leave strong imprints on the star itself and their surroundings. In this context, we present a detailed analysis of the rich circumstellar environment around the young Herbig Ae/Be star T CrA. Aims. Our aim is to understand the nature of the stellar system and the extended circumstellar structures, as seen in scattered light images. Methods. We conducted our analysis on the basis of a set of combined archival data and new adaptive optics images at a high contrast and high resolution. Results. The scattered light images reveal the presence of a complex environment around T CrA, composed of a bright, forward-scattering rim of the disk's surface that is seen at very high inclinations, along with a dark lane of the disk midplane, bipolar outflows, and streamer features that are likely tracing infalling material from the surrounding birth cloud onto the disk. The analysis of the light curve suggests that the star is a binary with a period of 29.6 yr, confirming previous assertions based on spectro-astrometry. The comparison of the scattered light images with the ALMA continuum and 12CO (2–1) line emission shows that the disk is in Keplerian rotation and the northern side of the outflowing material is receding, while the southern side is approaching the observer. The overall system lies on different geometrical planes. The orbit of the binary star is perpendicular to the outflows and is seen edge on. The disk is itself seen edge-on, with a position angle of ~7°. The direction of the outflows seen in scattered light is in agreement with the direction of the more distant molecular hydrogen emission-line objects (MHOs) associated with the star. Modeling of the spectral energy distribution using a radiative transfer scheme is in good agreement with the proposed configuration, as well as the hydrodynamical simulation performed using a smoothed particle hydrodynamics code. Conclusions. We find evidence of streamers of accreting material around T CrA. These streamers connect the filament, along which T CrA is forming along with the outer parts of the disk, suggesting that the strong misalignment between the inner and outer disk is due to a change in the direction of the angular momentum of the material accreting on the disk during the late phase of star formation. This impacts the accretion taking place in the components of the binary, favoring the growth of the primary with respect the secondary, in contrast to the case of aligned disks.

ALMA Observations of the HD 110058 Debris Disk

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the young, gas-rich debris disk around HD 110058 at 0.″3–0.″6 resolution. The disk is detected in the 0.85 and 1.3 mm continuum, as well as the J = 2–1 and J = 3–2 transitions of 12CO and 13CO. The observations resolve the dust and gas distributions and reveal that this is the smallest debris disk around stars of similar luminosity observed by ALMA. The new ALMA data confirm the disk is very close to edge-on, as shown previously in scattered-light images. We use radiative transfer modeling to constrain the physical properties of dust and gas disks. The dust density peaks at around 31 au and has a smooth outer edge that extends out to ∼70 au. Interestingly, the dust emission is marginally resolved along the minor axis, which indicates that it is vertically thick if truly close to edge-on with an aspect ratio between 0.13 and 0.28. We also find that the CO gas distribution is more compact than the dust (similar to the disk around 49 Ceti), which could be due to a low viscosity and a higher gas release rate at small radii. Using simulations of the gas evolution taking into account the CO photodissociation, shielding, and viscous evolution, we find that HD 110058's CO gas mass and distribution are consistent with a secondary origin scenario. Finally, we find that the gas densities may be high enough to cause the outward drift of small dust grains in the disk.

Stellar Flyby Analysis for Spiral Arm Hosts with Gaia DR3

Scattered-light imaging studies have detected nearly two dozen spiral arm systems in circumstellar disks, yet the formation mechanisms for most of them are still under debate. Although existing studies can use motion measurements to distinguish leading mechanisms such as planet–disk interaction and disk self-gravity, close-in stellar flybys can induce short-lived spirals and even excite arm-driving planets into highly eccentric orbits. With unprecedented stellar location and proper-motion measurements from Gaia Data Release 3 (DR3), here we study for known spiral arm systems their flyby history with their stellar neighbors by formulating an analytical on-sky flyby framework. For stellar neighbors currently located within 10 pc of the spiral hosts, we restrict the flyby time to within the past 104 yr and the flyby distance to within 10 times the disk extent in scattered light. Among a total of 12,570 neighbors that are identified in Gaia DR3 for 20 spiral systems, we do not identify credible flyby candidates for isolated systems. Our analysis suggests that a close-in recent flyby is not the dominant formation mechanism for isolated spiral systems in scattered light.

The disk of FU Orionis viewed with MATISSE/VLTI

Aims. We studied the accretion disk of the archetypal eruptive young star FU Orionis with the use of mid-infrared interferometry, which enabled us to resolve the innermost regions of the disk down to a spatial resolution of 3 milliarcseconds (mas) in the L band, that is, within 1 au of the protostar. Methods. We used the interferometric instrument MATISSE/VLTI to obtain observations of FU Ori’s disk in the L, M, and N bands with multiple baseline configurations. We also obtained contemporaneous photometry in the optical (UBVRIr′i′; SAAO and Konkoly Observatory) and near-infrared (JHKs; NOT). Our results were compared with radiative transfer simulations modeled by RADMC-3D. Results. The disk of FU Orionis is marginally resolved with MATISSE, suggesting that the region emitting in the thermal infrared is rather compact. An upper limit of ~1.3 ± 0.1 mas (in L) can be given for the diameter of the disk region probed in the L band, corresponding to 0.5 au at the adopted Gaia EDR3 distance. This represents the hot, gaseous region of the accretion disk. The N-band data indicate that the dusty passive disk is silicate-rich. Only the innermost region of said dusty disk is found to emit strongly in the N band, and it is resolved at an angular size of ~5 mas, which translates to a diameter of about 2 au. The observations therefore place stringent constraints for the outer radius of the inner accretion disk. Dust radiative transfer simulations with RADMC-3D provide adequate fits to the spectral energy distribution from the optical to the submillimeter and to the interferometric observables when opting for an accretion rate M ~ 2 × 10−5 M⊙ yr−1 and assuming M* = 0.6 M⊙, Most importantly, the hot inner accretion disk’s outer radius can be fixed at 0.3 au. The outer radius of the dusty disk is placed at 100 au, based on constraints from scattered-light images in the literature. The dust mass contained in the disk is 2.4 × 10−4 M⊙, and for a typical gas-to-dust ratio of 100, the total mass in the disk is approximately 0.02 M⊙. We did not find any evidence for a nearby companion in the current interferometric data, and we tentatively explored the case of disk misalignment. For the latter, our modeling results suggest that the disk orientation is similar to that found in previous imaging studies by ALMA. Should there be an asymmetry in the very compact, inner accretion disk, this might be resolved at even smaller spatial scales (≤1 mas).

Kinematic Evidence for an Embedded Planet in the IM Lupi Disk

We test the hypothesis that an embedded giant planet in the IM Lupi protostellar disk can produce velocity kinks seen in CO line observations as well as the spiral arms seen in scattered light and continuum emission. We inject planets into 3D hydrodynamics simulations of IM Lupi, generating synthetic observations using Monte Carlo radiative transfer. We find that an embedded planet of 2–3 M Jup can reproduce non-Keplerian velocity perturbations, or “kinks”, in the 12CO J = 2–1 channel maps. Such a planet can also explain the spiral arms seen in 1.25 mm dust continuum emission and 1.6 μm scattered-light images. We show that the wake of the planet can be traced in the observed peak velocity map, which appears to closely follow the morphology expected from our simulations and from analytic models of planet–disk interaction.

Observation and analysis of nonlinear scattering using the scattered-light imaging method

Optical phenomena like nonlinear absorption and nonlinear refraction are often determined through light transmittance techniques. However, in turbid or resonant media, scattering may also significantly attenuate the laser beam, such that absorptive losses may be overestimated. Thus, while transmittance techniques are suitable to determine the power extinction, it is often difficult to characterize the contribution of nonlinear scattering in a sample. In this work we applied the scattered-light imaging method to discriminate the nonlinear extinction due to nonlinear absorption and nonlinear scattering contributions in a turbid medium constituted of ${\mathrm{TiO}}_{2}$ nanoparticles suspended in acetone. The single-shot method collects an image of the beam transverse profile evolution along the propagation axis inside the sample. It was observed that while the results obtained by the transmittance technique indicate the extinction coefficient (including scattering and absorption contributions), the results obtained with the scattered-light imaging method discriminate the contribution of each phenomenon. Therefore, the results of both approaches are complementary and allow a more complete characterization of turbid media.

Disk Evolution Study through Imaging of Nearby Young Stars (DESTINYS): A Panchromatic View of DO Tau’s Complex Kilo-astronomical-unit Environment

While protoplanetary disks are often treated as isolated systems in planet formation models, observations increasingly suggest that vigorous interactions between Class II disks and their environments are not rare. DO Tau is a T Tauri star that has previously been hypothesized to have undergone a close encounter with the HV Tau system. As part of the DESTINYS ESO Large Programme, we present new Very Large Telescope (VLT)/SPHERE polarimetric observations of DO Tau and combine them with archival Hubble Space Telescope (HST) scattered-light images and Atacama Large Millimeter/submillimeter Array (ALMA) observations of CO isotopologues and CS to map a network of complex structures. The SPHERE and ALMA observations show that the circumstellar disk is connected to arms extending out to several hundred astronomical units. HST and ALMA also reveal stream-like structures northeast of DO Tau, some of which are at least several thousand astronomical units long. These streams appear not to be gravitationally bound to DO Tau, and comparisons with previous Herschel far-IR observations suggest that the streams are part of a bridge-like structure connecting DO Tau and HV Tau. We also detect a fainter redshifted counterpart to a previously known blueshifted CO outflow. While some of DO Tau’s complex structures could be attributed to a recent disk–disk encounter, they might be explained alternatively by interactions with remnant material from the star formation process. These panchromatic observations of DO Tau highlight the need to contextualize the evolution of Class II disks by examining processes occurring over a wide range of size scales.

Silver Nanoparticles Induce Apoptosis in HepG2 Cells through Particle-Specific Effects on Mitochondria.

Silver nanoparticles (AgNPs) have been widely used in biomedical and consumer products. It remains challenging to distinguish the toxicity of AgNPs derived from the particle form or the released silver ions (Ag+). In this study, the toxic effects of two citrate-coated AgNPs (20 and 100 nm) and Ag+ were investigated in hepatoblastoma cells (HepG2 cells). The suppression tests showed that AgNPs and Ag+ induced cell apoptosis via different pathways, which led us to speculate on the AgNP-induced mitochondrial damage. Then, the mitochondrial damages induced by AgNPs and Ag+ were compared under the same intracellular Ag+ concentration, showing that the mitochondrial damage might be mainly attributed to Ag nanoparticles but not to Ag+. The interaction between AgNPs and mitochondria was analyzed using a scattered light imaging method combined with light intensity profiles and transmission electron microscopy. The colocalization of AgNPs and mitochondria was observed in both NP20- and NP100-treated HepG2 cells, indicating a potential direct interaction between AgNPs and mitochondria. These results together showed that AgNPs induced apoptosis in HepG2 cells through the particle-specific effects on mitochondria.

Probing inner and outer disk misalignments in transition disks

Context. Transition disks are protoplanetary disks with dust-depleted cavities, possibly indicating substantial clearing of their dust content by a massive companion. For several known transition disks, dark regions interpreted as shadows have been observed in scattered light imaging and are hypothesized to originate from misalignments between distinct regions of the disk. Aims. We aim to investigate the presence of misalignments in transition disks. We study the inner disk (<1 au) geometries of a sample of 20 well-known transition disks with Very Large Telescope Interferometer (VLTI) GRAVITY observations and use complementary 12CO and 13CO molecular line archival data from the Atacama Large Millimeter/submillimeter Array (ALMA) to derive the orientation of the outer disk regions (>10 au). Methods. We fit simple parametric models to the visibilities and closure phases of the GRAVITY data to derive the inclination and position angle of the inner disks. The outer disk geometries were derived from Keplerian fits to the ALMA velocity maps and compared to the inner disk constraints. We also predicted the locations of expected shadows for significantly misaligned systems. Results. Our analysis reveals six disks to exhibit significant misalignments between their inner and outer disk structures. The predicted shadow positions agree well with the scattered light images of HD 100453 and HD 142527, and we find supporting evidence for a shadow in the south of the disk around CQ Tau. In the other three targets for which we infer significantly misaligned disks, V1247 Ori, V1366 Ori, and RY Lup, we do not see any evident sign of shadows in the scattered light images. The scattered light shadows observed in DoAr 44, HD 135344 B, and HD 139614 are consistent with our observations, yet the underlying morphology is likely too complex to be described properly by our models and the accuracy achieved by our observations. Conclusions. The combination of near infrared and submillimeter interferometric observations allows us to assess the geometries of the innermost disk regions and those of the outer disk. Whereas we can derive precise constraints on the potential shadow positions for well-resolved inner disks around Herbig Ae/Be stars, the large statistical uncertainties for the marginally resolved inner disks around the T Tauri stars of our sample make it difficult to extract conclusive constraints for the presence of shadows in these systems.

Dust entrainment in photoevaporative winds: Densities and imaging

Context. X-ray- and extreme-ultraviolet- (together: XEUV-) driven photoevaporative winds acting on protoplanetary disks around young T-Tauri stars may crucially impact disk evolution, affecting both gas and dust distributions. Aims. We constrain the dust densities in a typical XEUV-driven outflow, and determine whether these winds can be observed at μm-wavelengths. Methods. We used dust trajectories modelled atop a 2D hydrodynamical gas model of a protoplanetary disk irradiated by a central T-Tauri star. With these and two different prescriptions for the dust distribution in the underlying disk, we constructed wind density maps for individual grain sizes. We used the dust density distributions obtained to synthesise observations in scattered and polarised light. Results. For an XEUV-driven outflow around a M* = 0.7 M⊙ T-Tauri star with LX = 2 × 1030 erg s−1, we find a dust mass-loss rate Ṁdust ≲ 4.1 × 10−11 M⊙ yr−1 for an optimistic estimate of dust densities in the wind (compared to Ṁgas ≈ 3.7 × 10−8 M⊙ yr−1). The synthesised scattered-light images suggest a distinct chimney structure emerging at intensities I∕Imax < 10−4.5 (10−3.5) at λobs = 1.6 (0.4) μm, while the features in the polarised-light images are even fainter. Observations synthesised from our model do not exhibit clear features for SPHERE IRDIS, but show a faint wind signature for JWST NIRCam under optimal conditions. Conclusions. Unambiguous detections of photoevaporative XEUV winds launched from primordial disks are at least challenging with current instrumentation; this provides a possible explanation as to why disk winds are not routinely detected in scattered or polarised light. Our calculations show that disk scale heights retrieved from scattered-light observations should be only marginally affected by the presence of an XEUV wind.

Scatterometry Measurements With Scattered Light Imaging Enable New Insights Into the Nerve Fiber Architecture of the Brain

The correct reconstruction of individual (crossing) nerve fibers is a prerequisite when constructing a detailed network model of the brain. The recently developed technique Scattered Light Imaging (SLI) allows the reconstruction of crossing nerve fiber pathways in whole brain tissue samples with micrometer resolution: the individual fiber orientations are determined by illuminating unstained histological brain sections from different directions, measuring the transmitted scattered light under normal incidence, and studying the light intensity profiles of each pixel in the resulting image series. So far, SLI measurements were performed with a fixed polar angle of illumination and a small number of illumination directions, providing only an estimate of the nerve fiber directions and limited information about the underlying tissue structure. Here, we use a display with individually controllable light-emitting diodes to measure the full distribution of scattered light behind the sample (scattering pattern) for each image pixel at once, enabling scatterometry measurements of whole brain tissue samples. We compare our results to coherent Fourier scatterometry (raster-scanning the sample with a non-focused laser beam) and previous SLI measurements with fixed polar angle of illumination, using sections from a vervet monkey brain and human optic tracts. Finally, we present SLI scatterometry measurements of a human brain section with 3 μm in-plane resolution, demonstrating that the technique is a powerful approach to gain new insights into the nerve fiber architecture of the human brain.

Imaging-based particle sizing system combining scattered-light imaging and particle-shade imaging for submicron particles

Particle-processing industries, such as those for manufacturing pharmaceuticals, ceramics and polymers, require accurate and reliable monitoring and controlling techniques for particle-size distribution to stabilize product quality and maximize productivity. Imaging is a highly valuable monitoring technique because it can measure precise particle-size distributions by detecting particles individually and also can measure particle shape. However, detecting submicron particles or smaller is difficult due to the diffraction of light in the optics. We propose an imaging-based monitoring system that extends the detectable particle-size range towards the submicron level by combining particle-shade and scattered-light imaging. The system consists of newly developed optics and an analysis algorithm. We evaluated the accuracy of the proposed system using polystyrene standard spheres.