Small Scattering Research Articles

Dimensional Accuracy and Surface Quality of AZ91D Magnesium Alloy Components after Precision Milling.

This study investigates a precision milling process conducted with the use of conventional end mills and a standard CNC (Computer Numerical Control) machine tool. Milling tests were performed on samples of AZ91D magnesium alloy using TiB2- and TiAlN-coated three-edge end mills measuring 16 mm in diameter. The following technological parameters were made variable: cutting speed, feed per tooth and axial depth of cut. The effects of precision milling were evaluated by analysing the scatter of dimension values obtained in successive tool passes. In addition to that, deviations from the assumed nominal depth as well as obtained ranges of dimension varation were analysed. The study also examined surface quality obtained in the precision milling process, based on the basic surface roughness parameters: Ra, Rz and RSm. Results have confirmed that the use of conventional cutting tools and a standard CNC machine tool makes it possible to manufacture components characterized by relatively small scatter of dimension values and high accuracy classes. Additionally, the results have shown that the type of tool coating and variations of individual technological parameters exert impact on the dimensional accuracy and surface quality obtained.

Experimental investigation of single bubbles rising in stagnant liquid: Statistical analysis and image processing

Despite the large effort devoted to the study of single bubbles rising in a stagnant liquid, the complex phenomena involved have resulted in a large scatter in the terminal velocity. Providing new experimental data where the statistical uncertainty is thoroughly evaluated is therefore necessary. Single bubble experiments were conducted in a tall vertical column containing stagnant liquid at ambient conditions. To track the bubbles over the spatial range, high-speed cameras were mounted on a linear unit drive. The tall column allowed us to study the effect of hydrostatic pressure and late developed bubble dynamics on the bubble motion. The bubble properties, i.e., the bubble velocity, size, shape, and trajectory, were evaluated using an image analysis processing method. The analysis includes a quantitative evaluation of important parameters involved in the handling of the raw data. Several of the existing correlations for the terminal velocity were validated against the experimental data. The data are well predicted by the correlation proposed by Tomiyama et al. [“Terminal velocity of single bubbles in surface tension force dominant regime,” Int. J. Multiphase Flow 28, 1497–1519 (2002)]. The uncertainty in the experimental data has been emphasized, providing a quantitative evaluation based on several statistical methods. The number of experimental events necessary to obtain statistical significance was evaluated using a 95% confidence interval. Satisfying precision is found to be fulfilled for 10–15 bubble rise events. For bubbles of comparable size, the statistically significant terminal velocity data were found to exhibit a small scatter.

NGC 1261: An r-process enhanced globular cluster from the Gaia-Enceladus event

Our Milky Way (MW) has witnessed a series of major accretion events in the past. One of the later additions, the Gaia-Enceladus merger, has contributed a considerable mass to the inner Galaxy, but also generously donated to the outer halo. So far, associations with present-day MW globular clusters (GCs) have been chiefly based on their kinematics and ages. In this work, we present a chemical abundance study of the outer halo (RGC ∼ 18 kpc) GC NGC 1261, which has been suggested to be an accreted object based on its younger age. We measured 31 species of 29 elements in two stars from high-resolution Magellan/MIKE spectra and find that the cluster is moderately metal poor, at [Fe/H] = −1.26, with a low scatter of 0.02 dex. NGC 1261 is moderately α-enhanced to the 0.3 dex level. While from the small sample alone it is difficult to assert any abundance correlations, the light elements Na, O, Mg, and Al differ significantly between the two stars in contrast to the majority of other elements with smaller scatter; this argues in favor of multiple generations of stars coexisting in this GC. Intriguingly for its metallicity, NGC 1261 shows heavy element abundances that are consistent with r-process nucleosynthesis and we discuss their origin in various sites. In particular the Eu overabundance quantitatively suggests that one single r-process event, such as a neutron-star neutron-star merger or a rare kind of supernova, can be responsible for the stellar enhancement or even the enrichment of the cluster with the excess r material. Its heavy element pattern makes NGC 1261 resemble the moderately enhanced r-I stars that are commonly found in the halo and have been detected in Gaia-Enceladus as well. Therefore, combining all kinematical, age, and chemical evidence we conclude that NGC 1261 is a chemically intriguing GC that was born in the Gaia-Enceladus galaxy and has been subsequently accreted into the MW halo.

Forensic medical evaluation of hemorrhages into the brain of traumatic and non-traumatic genesis by the Mueller matrix microscopy of circular dichroism

The aim of the work is to develop forensic criteria for differentiation of hemorrhages of traumatic and non-traumatic genesis by digital Mueller matrix (MM) polarization microscopy of histological sections of human brain substance (HBS).Material and methods. Native histological preparations of HBS from 32 corpses with ischemic stroke (1 group), 35 corpses with hemorrhages of traumatic origin (2 groups), 33 corpses with hemorrhages in HBS of non-traumatic genesis (3 group) and 30 corpses caused by acute coronary insufficiency (4 control group). The method of research is azimuthal-invariant MM microscopy of circular dichroism (CD) of histological sections of the brain.Results. The results of studies of the coordinate and statistical structure of maps of the size of values at the points of digital microscopic images of histological sections of HBS of the dead of all groups revealed a coordinate-inhomogeneous structure of all distributions of the size of the CD of microscopic images of histological sections of the dead of all groups. Probable distributions that characterize MM invariants CD maps of histological sections of brain samples from all groups have a small scatter of values of the statistical moment of the 2nd order, as well as significant values of statistical moments of the 3rd and 4th orders.Conclusion. The efficiency of using the Mueller-matrix mapping method in diagnosing of hemorrhage genesis in the brain substance in the differentiation of the set of samples of control and experimental groups reaches a satisfactory level - 77% - 78%.

Recovering Density Fields inside Quasar Proximity Zones at z ∼ 6

Abstract The matter density field at z ∼ 6 is very challenging to probe. One of the traditional probes of the low density intergalactic medium that works successfully at lower redshifts is the Lyα forest in quasar spectra. However, at the end of reionization, the residual neutral hydrogen usually creates saturated absorption, thus much of the information about the gas density is lost. Luckily, in a quasar proximity zone, the ionizing radiation is exceptionally intense, thus creating a large region with nonzero transmitted flux. In this study we use the synthetic spectra from simulations to investigate how to recover the density fluctuations inside the quasar proximity zones. We show that, under ideal conditions, the density can be recovered accurately with a small scatter. We also discuss how systematics such as the quasar continuum fitting and reionization models affect the results. This study shows that by analyzing the absorption features inside quasar proximity zones we can potentially constrain quasar properties and the environments they reside in.

Vector coherence imaging for enhancement of small omni-directional scatterers and suppression of geometric reflections

Ultrasonic imaging with full-matrix capture (FMC) datasets using the total focusing method (TFM) has been demonstrated to improve the detection, sizing and characterization of small defects in the area of Nondestructive Evaluation (NDE). Despite the general improvements in resolution and signal to noise ratio (SNR) offered by FMC/TFM, detection of small flaws remains challenging - particularly when flaws are in immediate proximity to the bounding surfaces of a test piece. In this paper, it is shown that by retaining only phase information during the application of the TFM algorithm, it is possible increase the image intensity of small omni-directional reflectors with respect to large specular reflectors (i.e. backwall/frontwall). The proposed algorithm, called Vector Coherence Imaging, is derived from the Vector Coherence Factor phase coherence metric and represents the amount of statistical (Shannon) information in favour of the presence of a coherent scatterer everywhere in the imaging domain. The VCI algorithm is shown to aid in detection of small defects located close to the boundaries of the specimen. Notably, VCI is seen to facilitate detection tip diffraction/scattering originating from surface connected fatigue cracks (less than 2 ultrasonic wavelengths in height) and early stage high temperature hydrogen attack (HTHA) damage (void nucleation and micro-fissuring).

A Large Old Landslide in Sichuan Province, China: Surface Displacement Monitoring and Potential Instability Assessment

Using advanced Differential Interferometric Synthetic Aperture Radar (InSAR) with small baseline subsets (SBAS) and Permanent Scatter Interferometry (PSI) techniques and C-band Sentinel-1A data, this research monitored the surface displacement of a large old landslide at Xuecheng town, Lixian County, Sichuan Province, China. Based on the MassMov2D model, the effect of the dynamic process and deposit thickness of the potentially unstable rock mass (deformation rate < −70 mm/year) on this landslide body were numerically simulated. Combined with terrain data and images generated by an Unmanned Aerial Vehicle (UAV), the driving factors of this old landslide were analyzed. The InSAR results show that the motion rate in the middle part of the landslide body is the largest, with a range of −55 to −80 mm/year on average, whereas those of the upper part and toe area were small, with a range of −5 to −20 mm/year. Our research suggests that there is a correlation between the LOS (line of sight) deformation rate and rainfall. In rainy seasons, particularly from May to July, the deformation rate is relatively high. In addition, the analysis suggests that SBAS can provide smoother displacement time series, even in areas with vegetation and the steepest sectors of the landslide. The simulation results show that the unstable rock mass may collapse and form a barrier dam with a maximum thickness of about 16 m at the Zagunao river in the future. This study demonstrates that combining temporal UAV measurements and InSAR techniques from Sentinel-1A SAR data allows early recognition and deformation monitoring of old landslide reactivation in complex mountainous areas. In addition, the information provided by InSAR can increase understanding of the deformation process of old landslides in this area, which would enhance urban safety and assist in disaster mitigation.

The Forensic Utility of Photogrammetry in Surface Scene Documentation

Outdoor crime scene documentation needs to be accurate and precise to preserve evidence. Photogrammetry is a potential option. Structure from Motion (SfM) processes photographs into 3D models. As commercial software does not disclose this process, this documentation technique could be legally inappropriate. A potential solution to this problem is open-source software. A series of mock outdoor crime scenes were documented using SfM and total station mapping. Ten large surface scatter scenes containing plastic human remains and personal objects were laid out in 10 × 10 m units in a New England forested environment. The small surface scatter scenes consisted of a pig (Sus scrofa) mandible placed in different environments. The resulting models were built using PhotoScan by AgiSoft and MicMac by IGN. Accuracy was measured by the amount of variance in fixed-datum measurements, whereas visual qualitywas determined by comparison.
 The average total variance in fixed-datum lengths for six of the ten scenes was below 0.635 cm. The maximum differences in measurement between the total station and software measurements were 0.0917 m (PhotoScan) and 0.178 m (MicMac). Comparative histograms had low standard deviations and mean distances between points. Conditions such as light, ground foliage and topography affect model quality. This research shows that SfM has the potential to be a rapid, accurate and low-cost resource, but there are limitations that must be considered.

Small Data Scattering of Hartree Type Fractional Schrödinger Equations in a Scaling Critical Space

In this paper we study the small-data scattering of Hartree type fractional Schrödinger equations in space dimension 2, 3. It has Lévy index α between 1 and 2, and Hartree type nonlinearity F(u) = μ(|x|-γ * |u|2)u with 2d/(2d-1) < γ < 2, γ ≥ α > 1. This equation is scaling-critical in Ḣsc with sc = (γ-α)/2. We show that the solution scatters in Ḣsc,1, where Ḣsc,1 is also a scaling critical space of Sobolev type taking in angular regularity with norm defined by ||ϕ||Ḣsc,1 = ||ϕ||Ḣsc + ||∇Sϕ||Ḣsc. For this purpose we use the recently developed Strichartz estimate which is Lθ2-averaged on the unit sphere Sd-1.

Complete coupling of focused light to surface polaritons

Surface polaritons display short wavelengths compared to propagating light, thus enabling large spatial concentration and enhancement of electromagnetic energy. However, this wavelength mismatch is generally accompanied by poor light-to-polariton coupling that limits potential applications in areas such as optical sensing and optoelectronics. Here, we address this problem by demonstrating that a small scatterer placed at a suitable distance from a planar surface can produce complete coupling of a focused light beam to surface polaritons. We present rigorous theoretical results for light coupling to plasmons in silver films and graphene, as well as phonon polaritons in hexagonal boron nitride films. We further formulate detailed general prescriptions on the beam profile and particle response that are required to achieve maximum coupling, which we supplement by analytical calculations for dipolar scatterers and finite-size particles. Our results open a practical route to circumvent the long-standing photon-polariton wavelength mismatch problem in nanophotonics.

Fatigue assessment of welded joints at sub-zero temperatures by means of stress averaging approach

ABSTRACT The problem of typical stress-based fatigue assessment methods is that additional influencing factors like temperature effects do not directly influence the respective stress and can thus only be incorporated via modification factors. The stress averaging approach is expected to account for effects that influence the support around notches via the micro-structural support length ρ*. This study thus investigates the applicability of the stress averaging approach for welded joints in engineering structures exposed to sub-zero temperatures. For this purpose, fatigue test results of welded joints in the temperature range of 20°C down to −50°C are assessed. It is shown that it is possible to assess data for different temperature with the same reference fatigue curve while maintaining a small scatter without the need for modification factors.

Solving Two-Dimensional Scattering From Multiple Dielectric Cylinders by Artificial Neural Network Accelerated Numerical Green's Function

A number of real-life applications involve the determination of scattered field of an unchanged large object and several varying small scatterers in its vicinity. Integral equation methods based on free-space Green's function (FSGF) are usually applied to solve this problem. In this letter, we propose an artificial neural network (ANN) accelerated numerical Green's function (NGF) to reduce the computational cost of conventional methods. For explicit demonstration, 2-D scattering from infinite cylinders is considered. Since the unchanged large object is considered as part of the background, its scattering is included in NGF. In our approach, its scattering is extracted via an FSGF scheme in order to exploit the regression ability of ANN efficiently. Then a dataset in possession of the scattering feature is constructed. By feeding ANN with the dataset, ANN can be trained as a good representation of NGF, where only a small number of ANN parameters are computed and stored. Since the dataset only contains part of all the possible field-source pairs in the computation region, the calculation of NGF can be accelerated. Once the ANN accelerated NGF is obtained, the scattering analysis can be easily conducted with a small numerical system where the unknowns are only associated with small scatters. The combination of ANN and NGF assists us to construct a framework that can save the CPU time and memory usage in both online scattering solver and offline NGF solver.

Numerical Simulations of Light Scattering in Soft Anisotropic Fibrous Structures and Validation of a Novel Optical Setup from Fibrous Media Characterization

The insight of biological microstructures is at the basis of understanding the mechanical features and the potential pathologies of tissues, like the blood vessels. Different techniques are available for this purpose, like the Small Angle Light Scattering (SALS) approach. The SALS method has the advantage of being fast and non-destructive, however investigation of its physical principles is still required. Within this work, a numerical study for SALS irradiation of soft biological fibrous tissues was carried out through in-silico simulations based on a Monte Carlo approach to evaluate the effect of the thickness of the specimen. Additionally, the numerical results were validated with an optical setup based on SALS technique for the characterization of fibrous samples with dedicated tests on four 3D-printed specimens with different fibers architectures. The simulations revealed two main regions of interest according to the thickness (thk) of the analyzed media: a Fraunhofer region (thk &lt; 0.6 mm) and a Multiple Scattering region (thk &gt; 1 mm). Semi-quantitative information about the tissue anisotropy was successfully gathered by analyzing the scattered light spot. Moreover, the numerical results revealed a remarkable coherence with the experimental data, both in terms of mean orientation and dispersion of fibers.

SDSS-IV MaNGA: A Star Formation–Baryonic Mass Relation at Kiloparsec Scales

Abstract Star formation rate density, ΣSFR, has shown a remarkable correlation with both components of the baryonic mass kiloparsec scales (i.e., the stellar mass density and molecular gas mass density, Σ* and Σmol, respectively) for galaxies in the nearby universe. In this study, we propose an empirical relation between ΣSFR and the baryonic mass surface density (Σb = Σmol,Av + Σ*, where Σmol,Av is the molecular gas derived from the optical extinction, A V ) at kiloparsec scales using the spatially resolved properties of the MaNGA survey, the largest sample of galaxies observed via integral field spectroscopy (∼8400 objects). We find that ΣSFR tightly correlates with Σb. Furthermore, we derive an empirical relation between ΣSFR and a second-degree polynomial of Σb, yielding a one-to-one relation between these two observables. Both Σb and its polynomial form show a stronger correlation and smaller scatter with respect to ΣSFR than the relations derived using the individual components of Σb. Our results suggest that these three parameters are indeed physically correlated, suggesting a scenario in which the two components of the baryonic mass regulate the star formation activity at kiloparsec scales.

Application of the Pattern Equation Method to the Problem of Diffraction by a Group of Randomly Located Small Scatterers

A technique of calculating the averaged scattering pattern of a group of identical infinite perfectly reflecting cylinders is suggested on the basis of the pattern equation method and the method of small perturbations. The cylinders have random coordinates and random orientations. The problem is solved under the supposition that dimensions of the scatterers’ sections are small as compared with the wavelength and the average distance between the bodies. It is supposed also that the root-mean-square deviation of the scatterers’ coordinates is small as compared with the wavelength. The method is tested for a small number of bodies by comparing the calculation results obtained with the help of the method of small perturbations with the results obtained with the help of direct averaging of the scattering pattern.

The Similarity of Abundance Ratio Trends and Nucleosynthetic Patterns in the Milky Way Disk and Bulge

Abstract We compare abundance ratio trends in a sample of ∼11,000 Milky Way bulge stars (R GC &lt; 3 kpc) from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) to those of APOGEE stars in the Galactic disk (5 kpc &lt; R GC &lt; 11 kpc). We divide each sample into low-Ia (high-[Mg/Fe]) and high-Ia (low-[Mg/Fe]) populations, and in each population, we examine the median trends of [X/Mg] versus [Mg/H] for elements X = Fe, O, Na, Al, Si, P, S, K, Ca, V, Cr, Mn, Co, Ni, Cu, and Ce. To remove small systematic trends of APOGEE abundances with stellar , we resample the disk stars to match the distributions of the bulge data. After doing so, we find nearly identical median trends for low-Ia disk and bulge stars for all elements. High-Ia trends are similar for most elements, with noticeable (0.05–0.1 dex) differences for Mn, Na, and Co. The close agreement of abundance trends (with typical differences ≲0.03 dex) implies that similar nucleosynthetic processes enriched bulge and disk stars despite the different star formation histories and physical conditions of these regions. For example, we infer that differences in the high-mass slope of the stellar initial mass function between disk and bulge must have been ≲0.30. This agreement, and the generally small scatter about the median sequences, means that one can predict all of a bulge star's APOGEE abundances with good accuracy knowing only its measured [Mg/Fe] and [Mg/H] and the observed trends of disk stars.

Scattering methods for determining structure and dynamics of polymer gels

Polymer gels are unique materials, which consist of a polymer network swollen in a solvent. The modulus and the overall state of the gel depend on thermodynamic parameters, such as strand length, structure, and chemical compatibility of the solvent. Scattering techniques have been used to study the gel structure and osmotic pressure and are discussed in this Tutorial pedagogically. These techniques are not always straightforward because of trapped inhomogeneities and complicated interactions. Nevertheless, there has been considerable progress in developing analytical tools to determine the internal structure and dynamics of polymer gels. In addition to these tools, we showcase modern spatially resolved techniques, such as Diffusing Wave Spectroscopy, and offer a perspective on similar methods such as Dynamic Small Angle Light Scattering and Differential Dynamic Microscopy, which can be used to study local and interface effects in gel systems as well as any anisotropy. These new tools can fundamentally advance our understanding of local gel dynamics, which have so far been too challenging to observe.

Development and Realization of an Experimental Bench Test for Synchronized Small Angle Light Scattering and Biaxial Traction Analysis of Tissues

Insights into the mechanical and microstructural status of biological soft tissues are fundamental in analyzing diseases. Biaxial traction is the gold standard approach for mechanical characterization. The state of the art methods for microstructural assessment have different advantages and drawbacks. Small angle light scattering (SALS) represents a valuable low energy technique for soft tissue assessment. The objective of the current work was to develop a bench test integrating mechanical and microstructural characterization capabilities for tissue specimens. The setup’s principle is based on the integration of biaxial traction and SALS analysis. A dedicated control application was developed with the objective of managing the test procedure. The different components of the setup are described and discussed, both in terms of hardware and software. The realization of the system and the corresponding performances are then presented.

From Haloes to Galaxies. II. The Fundamental Relations in Star Formation and Quenching

Abstract Star formation and quenching are two of the most important processes in galaxy formation and evolution. We explore in the local universe the interrelationships among key integrated galaxy properties, including stellar mass M *, star formation rate (SFR), specific SFR (sSFR), molecular gas mass M H 2 , star formation efficiency (SFE) of the molecular gas, and the molecular gas to stellar mass ratio μ. We aim to identify the most fundamental scaling relations among these key galaxy properties and their interrelationships. We show that the integrated M H 2 –SFR, SFR–M *, and M H 2 –M * relations can be simply transformed from the μ–sSFR, SFE–μ, and SFE–sSFR relations, respectively. The transformation, in principle, can increase or decrease the scatter of each relation. Interestingly, we find that the latter three relations all have significantly smaller scatter than the corresponding former three. We show that the probability to achieve the observed small scatter by accident is extremely close to zero. This suggests that the smaller scatters of the latter three relations are driven by a more universal physical connection among these quantities. We then show that the large scatters in the former relations are due to their systematic dependence on other galaxy properties, and on the star formation and quenching process. We propose the sSFR–μ–SFE relation as the fundamental formation relation (FFR), which governs the star formation and quenching process and provides a simple framework to study galaxy evolution. Other scaling relations, including the integrated Kennicutt–Schmidt law, star-forming main sequence, and molecular gas main sequence, can all be derived from the FFR.

Fabrication of fluorescent nanospheres by heating PEGylated tetratyrosine nanofibers

Aromatic polypeptides have recently drawn the interest of the research community for their capability to self-assemble into a variety of functional nanostructures. Due to their interesting mechanical, electrical and optical properties, these nanostructures have been proposed as innovative materials in different biomedical, biotechnological and industrial fields. Recently, several efforts have been employed in the development of these innovative materials as nanoscale fluorescence (FL) imaging probes. In this context, we describe the synthesis and the functional properties of a novel fluorescent tyrosine (Tyr, Y)-based nanospheres, obtained by heating at 200 °C a solution of the PEGylated tetra-peptide PEG6-Y4. At room temperature, this peptide self-assembles into not fluorescent low ordered water-soluble fibrillary aggregates. After heating, the aggregation of different polyphenolic species generates Y4-based nanospheres able to emit FL into blue, green and red spectral regions, both in solution and at the solid state. The aggregation features of PEG6-Y4 before and after heating were studied using a set of complementary techniques (Fluorescence, CD, FT-IR, Small and Wide-Angle X-ray Scattering and SEM). After a deep investigation of their optoelectronic properties, these nanospheres could be exploited as promising tools for precise biomedicine in advanced nanomedical technologies (local bioimaging, light diagnostics, therapy, optogenetics and health monitoring).