Size Of Inhomogeneities Research Articles

Magnifying endoscopy with crystal violet staining for immune checkpoint inhibitor-associated colitis.

There exists no evidence on the relationship between endoscopic and histologic findings. Furthermore, even after multiple biopsy specimens were obtained, histologic examination usually fails to show the characteristic features of immune checkpoint inhibitor-associated colitis. In this study, we explored the endoscopic and histologic findings of immune checkpoint inhibitor-associated colitis. Patients diagnosed with immune checkpoint inhibitor-associated colitis at our hospital between March 2018 and December 2018 were retrospectively assessed. The degree of mucosal inflammation was evaluated using endoscopic inflammation grade (inactive, mild, moderate, or severe disease) and further observed using magnifying endoscopy with crystal violet staining. Pit structures were classified into three types: regularly arranged pits with circular or elliptical shape (R type), irregularly arranged pits with inhomogeneous size and morphology (IR type), and pits with reduced density or pits that partially disappeared (AD type). Eleven patients (median age, 71years; range, 44-83years) were diagnosed with immune checkpoint inhibitor-associated colitis. All characteristic histologic findings, including crypt distortion, crypt abscesses, and apoptotic bodies, were observed at sites with moderate-to-severe endoscopic inflammation but not at sites with inactive-to-mild endoscopic inflammation. Characteristic histologic features were observed in 0%, 50%, and 100% of R-type, IR-type, and AD-type mucosa, respectively. We revealed the possible utility of endoscopic images for selecting suitable target sites for biopsy and showed that endoscopic findings could reduce the time lag associated with tissue diagnosis and sampling errors due to biopsy.

Comparative study on crystallographic orientation, precipitation, phase transformation and mechanical response of Ni-rich NiTi alloy fabricated by WAAM at elevated substrate heating temperatures

In this investigation, a Ni-rich NiTi alloy was in-situ deposited with different substrate heating temperatures and the evolution of crystallographic orientation, precipitation, phase transformation, and mechanical responses were evaluated. The experimental results indicated that with the increment of substrate heating temperature from 150 °C to 350 °C, the average B2 grain size and the high angle grain boundaries (HAGBs) gradually increased from 53.44 μm to 85.38 μm and 53.6%–62.4%, respectively. The crystallographic texture exhibited a dominant, strong (001) orientation with comparatively weak (111) and (101) orientations in all conditions and the intensity of {100}<001> increased slightly as the substrate heating temperature increased. Moreover, Ni4Ti3 precipitates with an inhomogeneous size distribution were identified within the B2 NiTi matrix. Increasing the substrate heating temperature coarsened the Ni4Ti3 precipitates. All the phase transformation temperatures increased when the substrate heating temperature increased, indicating that the martensitic transformation is more likely to occur. As the substrate heating temperature increased from 150 °C to 350 °C, the yield stress and ultimate tensile stress decreased from 683.9 to 513.1 MPa and 855.2 to 743.8 MPa, respectively, and the ductility decreased from 6.90% to 6.13%. In addition, a remarkable εir, poor recovery ratio and a broad stress hysteresis were obtained during the initial deformation of the cyclic loading-unloading tension. The highest recoverable strain (εre), recovery ratio and elastic energy storage efficiency (ƞ) were obtained in samples processed with the lowest substrate heating temperature. These findings provide useful references concerning process optimization in fabricating Ni-rich NiTi components by WAAM with acceptable microstructure and mechanical properties.

Reconstruction algorithms of an inverse conductive scattering problem for the Helmholtz equation

ABSTRACT In this paper, we consider an inverse conductive scattering problem for the Helmholtz equation from measurements on the outer boundary. We want to seek reconstruction algorithms to detect the number, location, size and shape of inhomogeneities within a body. This problem is nonlinear and ill-posed, thus we should consider regularization techniques in order to improve the corresponding approximation. We examine the viability of our proposed reconstruction algorithms through the use of numerical experiments.

Detonation properties of solution of hydrazine nitrate/water

In our work, the study of detonation wave structure was performed by VISAR laser interferometer for a hydrazine nitrate/H2O (HN/water) solution and pressed HN with maximum density of 1.68 g/cm3. The range of water concentration in which the HN/water solution detonated at a room temperature was found to be 25 - 36 wt.%. For the HN/water solution, the detonation velocity decreases linearly with increasing water concentration whereas for pressed HN, the dependence of detonation velocity on initial density is not monotonic, but has a characteristic “s”-shape. It was shown that the particle velocity profiles in pressed HN are smoother than in the HN/water solution. This means that detonation waves in the liquid HN are unstable, and the characteristic amplitude size of inhomogeneities is about 400 µm. Optical registration of the detonation wave propagation in the HN/water solution was done by two different high speed optical recording techniques. A very poor glow of the detonation front in the visible part of the spectrum and its instability were observed. This may be due to the low temperature in the detonation waves in the water solution of HN.

Fluorination of Diamond Nanoparticles in Slow Neutron Reflectors Does Not Destroy Their Crystalline Cores and Clustering While Decreasing Neutron Losses.

If the wavelength of radiation and the size of inhomogeneities in the medium are approximately equal, the radiation might be intensively scattered in the medium and reflected from its surface. Such efficient nanomaterial reflectors are of great scientific and technological interest. In previous works, we demonstrated a significant improvement in the efficiency of reflection of slow neutrons from a powder of diamond nanoparticles by replacing hydrogen located on the surface of nanoparticles with fluorine and removing the residual sp2 amorphous shells of nanoparticles via the fluorination process. In this paper, we study the mechanism of this improvement using a set of complementary experimental techniques. To analyze the data on a small-angle scattering of neutrons and X-rays in powders of diamond nanoparticles, we have developed a model of discrete-size diamond nanospheres. Our results show that fluorination does not destroy either the crystalline cores of nanoparticles or their clustering in the scale range of 0.6–200 nm. This observation implies that it does not significantly affect the neutron scattering properties of the powder. We conclude that the overall increase in reflectivity from the fluorinated nanodiamond powder is primarily due to the large reduction of neutron losses in the powder caused by the removal of hydrogen contaminations.

Application of X-Ray Methods for Determining the Dimensions of Nanoparticles in the Nanosized Anatase–Poly(N-vinylcaprolactam) System

Nanocomposites prepared by mechanical mixing with grinding and mechanical activation of a mixture of Hombifine N with nanosized anatase (NA) and poly(N-vinylcaprolactam) (PVCL) polymer (PVCL25 and PVCL40 polymers were obtained by drying a PVC aqueous solution at 25 and 40°C, respectively) in different weight ratios have been studied by wide-angle X-ray scattering (WAXS) and (for the first time) small-angle X-ray scattering (SAXS). Amorphization of anatase (decrease in the average size of the coherent-scattering region), selection of X-ray amorphous hydrated titanium dioxide from the amorphous shell of anatase nanoparticles, destruction of PVCL, and disordering of its heterocycles in NA/PVCL (NA : PVCL = 1 : 1) nanocomposites upon mechanical activation have been revealed. The interaction (with water molecule exchange) between anatase, anatase, and PVCL nanoparticles during formation of NA/PVCL25 (NA : PVCL = 1 : 2) upon mechanical mixing with grinding is found to lead to segregation of anatase nanoparticles into two groups: particles with reduced and enhanced (formation of texture) degree of crystallinity (average sizes of coherent-scattering regions) in comparison with the initial anatase. SAXS made it possible to reveal structural inhomogeneities of different sizes in PVCL25 and PVCL40, which change differently upon mechanical activation, retaining the tendency to smaller sizes in PVCL25 (a coil) in comparison with PVCL40 (a globule). It is shown that the effects of mechanical activation and mechanical mixing with grinding on the components of NA–PVCL system differ, and that anatase nanoparticles play a decisive role in NA/PVCL nanocomposites, facilitating averaging of the inhomogeneity sizes upon mechanical activation. The results of studying the photocatalytic activity in the reaction of methyl orange decomposition (UV irradiation) in the presence of NA–PVCL samples indicate that it depends on the average sizes of coherent-scattering regions and is independent of the inhomogeneity sizes.

Statistical and Fourier analysis of the vortex dynamics of fluids in an external magnetic field

For the first time, we perform comprehensive statistical and Fourier analysis (both spatial and temporal) of the vortex dynamics of fluids near a magnetized ferromagnetic surface under electrochemical etching and effect of an external magnetic field resulting in autocatalytic formation of spatiotemporal vortex structures. The used experimental technique allows avoiding any distortions in the nature of the reaction. By using the proposed methods of analysis, we obtain integral and time dependences of the frequency distributions of the motion of fluids over the volume of the medium under investigation. As a result of the statistical analysis, the areas with the most intense motion of reaction products are detected. We perform the analysis of the dynamics of these areas during the electrochemical reaction. By means of 1D and 2D Fourier transforms, we determine the characteristic time, spatial frequencies and the characteristic sizes of the optical inhomogeneities that occur during the electrochemical reaction. • Statistical and Fourier analysis of fluids vortex dynamics near a magnetized surface • Integral dependences and time frequencies distributions of the fluids motion • The areas with the most intense motion of reaction products are detected. • Analysis of the dynamics of the selected areas during the electrochemical reaction • Characteristic time, spatial frequencies and characteristic sizes of inhomogeneities

Elastic fields and effective stiffness of ellipsoidal particle composite using the representative unit cell model and multipole expansion method

The representative unit cell (RUC) model of elastic heterogeneous solid with imperfectly bonded ellipsoidal inhomogeneities is developed. The periodic displacement solution has been obtained by combining the superposition principle, Papkovich-Neuber representation of displacement in terms of scalar harmonic potentials and expansion of these potentials in terms of periodic ellipsoidal harmonics. By accurate fulfilling the interface conditions, the RUC model boundary value problem is reduced to an infinite system of linear algebraic equations for the series expansion coefficients. The modified Rayleigh homogenization scheme has been extended to the elastic composite with ellipsoidal inhomogeneities and imperfect interface. The scheme takes into account volume content and elastic moduli of constituents, shape, size and arrangement of inhomogeneities, interaction between them and elastic stiffness of interface. Numerical algorithm of the method provides an accurate analysis of the RUC model for a whole range of the structure parameters. The reported numerical data illustrate convergence rate of the series solution and discover an effect of the volume content, elastic properties and arrangement of particles and interface stiffness on the stress field and macroscopic elastic moduli of the ellipsoidal particle composite.

Size dependent of the effective conductivity of composite with imperfect interfaces

Based on the circle assemblage model, the effective properties of the inclusion with imperfect interface are derived. The equivalent inclusion is incorporated in the Fourier Transform algorithm to determine the effective conductivity of the composite with lowly conducting or highly conducting interface. The size effect is considered for both cases. Numerical results are provided to illustrate the dependence of the effective conductivity on the size of inhomogeneities.

Effect of annealing on the photoluminescence and thermoluminescence properties of Eu2+ doped BaSO4 microgravels

The quest for developing phosphors emitting intense ultra violet (UV) rays and thermoluminescence (TL) occurring in the temperature range between 180 and 250 °C is on the progressive surge as the phosphors are highly desirable for phototherapy lamps and X-ray dosimetry. For this work, strong UV and TL emitting Eu2+ doped BaSO4 gravels of sub-micro size were synthesized by acid-assisted co-precipitation method. The as-prepared phosphors were annealed at different temperatures (300–700 °C) for 10 h to enhance the UV and TL emissions. The influence of annealing on the crystallite size, morphology, vibrational bands, PL and TL were studied by X-ray diffraction (XRD), Field emission gun scanning electron microscopy (FEGSM), Fourier transform infrared spectroscopy (FTIR), Photoluminescence (PL) and TL spectroscopies, respectively. From XRD, it is noticed that the crystallite size and crystal quality increase when the annealing temperature is raised from 300 to 500 °C, whereas they are found to be decreasing at 600 °C and the trend continues till 700 °C. FEGSEM images show that all the phosphors have similar gravel morphology with inhomogeneous sub-micro size distribution. Formation of clusters is also noticed for phosphors while annealing in the range 300–500 °C. The vibrational bands related to the phosphor have been identified from the FTIR spectra. From PL and TL studies, the prominent emission intensity is found to be the maximum for 500 °C annealed phosphor revealing optimization. PL spectra also exhibit a strong UV emission at ~ 374 nm. The TL glow curve of the phosphors shows the first deconvoluted peak in the temperature range 198–210 °C and the second peak in the range 240.3–259.1 °C. The activation energy for the first peak is in the range 1.02 to 1.30 eV, whereas the second peak is in the range 0.72 to 2.98 eV. Thus the optimized multi-utility phosphor could be beneficial for phototherapy lamps and X-ray dosimeters.

Temporal Dynamics of the Scattering Properties of Deionized Water

Changes occurring in deionized water with time, recorded by dynamic light scattering, have been investigated. It is demonstrated that the mean size of optical inhomogeneities in deionized water, formed under an external mechanical impact, depends on the storage time of water (from its preparation to mechanical impact). Presumably, these optical inhomogeneities can be considered as submicron air bubbles. The recorded changes in sizes occurring in the course of time may be related to the saturation of water with air and increase in its ionic strength. It is also shown that a mechanical impact on water is a complex physical process changing its physicochemical properties and that the consequences of mechanical impact on water are retained for at least a week. The data obtained may be useful for standardizing the deionized water used in experimental studies.

Robust phase-stepping interferometry for traceable length measurements in a Hilger–Watts gauge-block interferometer

We demonstrate a simple adaptation of the venerable Hilger–Watts gauge-block interferometer capable of performing automated, traceable calibrations of gauge block length by phase-stepping interferometry (PSI). We discuss the selection of robust PSI filtering algorithms to counteract in software the flaws of the hardware implementation, including markedly non-sinusoidal fringes and inhomogeneous phase step size. We find that the length measurement errors attributable to the phase measurement can be reduced to 0.6 nm, even with a simple retrofit to an instrument not originally designed for PSI.

Estimation of the Characteristics of the Domain of Multiple Filamentation of Femtosecond Laser Pulses in Air Based on the Single Filamentation Model

Characteristics of the domain of multiple filamentation in air are estimated based on the numerical solution of a nonlinear Schrodinger equation in the single filamentation statement. The method of diffraction-ray tubes was used to describe the single filamentation of laser pulses. The efficiency of this method for interpreting experimental results and predicting effects is shown, which is important when planning experiments. The characteristic size of small-scale intensity inhomogeneities in the laser centimeter-radius beam profile, which induce a multiple filamentation of femtosecond pulses, is shown to be several millimeters. An increase in the initial laser beam radius during telescoping increases the sizes of the initial small-scale intensity inhomogeneities, and reduces their power. This leads to an increase in the distance to the start of filamentation. An increase in the initial beam power promotes the elongation of the filaments and increases their number.

Influence of WC-Co hard metal microstructure on defect density, initiation and propagation kinetics of fatigue cracks starting at intrinsic and artificial defects under a negative stress ratio

The fracture behavior of WC-Co hard metals depends on the size of material inhomogeneities or defects from which cracks emanate. The size and frequency of these defects is of high significance to the quantitative understanding of the failure behavior of structural components and metalworking tools made of hard metal. Currently, the interdependence of a hard metal's microstructure, its defect density, its crack nucleation and growth kinetics and its observed fatigue behavior is not completely understood. The current work provides information on the defect density, fatigue limits, fatigue crack initiation thresholds and growth kinetics at a cyclic mean stress of zero for various hard metal grades as a function of their microstructure. The average WC grain size of the investigated materials varied from ultrafine to medium; the Co binder content ranged from 9 to 15 wt.%. The distribution of size and density of defects was determined by analytic relations based on Weibull theory applied to strength distributions determined in three-point bending experiments performed under monotonously increasing load. Fatigue limits were derived from stress amplitude-life curves determined in a six-point bending arrangement under a stress ratio R = σmin/ σmax = –1. Crack growth kinetics were determined for the same stress ratio for artificially cracks in eight-point bending, as well as for cracks emanating from intrinsic subsurface material defects in six-point bending. The observed differences in the fatigue behavior are discussed based on the determined defect densities and the influence of ambient air / vacuum conditions on crack initiation and growth.

Numerical simulation on thermal properties of closed-cell metal foams with different cell size distributions and cell shapes

In this study, the effect of cell structure on the thermal properties of closed-cell foam metals are studied numerically. To do this, a novel modeling procedure is proposed to generate the FEM foam models with different cell structures. The cell size distribution and cell shape in the established models can be controlled by the modeling parameters applied in the modeling process. Two structural parameters termed as characteristic diameter Dch and characteristic shape anisotropy αch are then introduced to describe the cell size inhomogeneity and cell shape irregularity in the established models. The steady-state heat transfer simulation is carried out to calculate the effective thermal conductivity of foam models. It can be concluded from the simulation results that relative density is not the only factor that influences the thermal properties of closed-cell metal foams. Both the increase of Dch and αch could also induce a reduction in the normalized thermal conductivity. It indicates that, at a given relative density, the foams with the inhomogeneous cell size distribution and irregular cell shape are inclined to have a degraded thermal conductivity. Finally, the underlying mechanism governing the heat transfer behavior is also discussed.

Effect of mesoscale inhomogeneity and fibers size distribution on the initial stage of deep-bed filtration process

Aerosol filtration in fibrous filters is one of the principal methods of accurate removal of particulate matter from gas stream. The classical theory of depth filtration in fibrous structures is based on the assumption of existence of single fiber efficiency, which may be used for calculation of overall efficiency of the filter. There are several reasons for inappropriate estimation of the single fiber efficiency including assumption of negligible effect of presence of neighbouring fibers and perpendicular orientation of the homogenous fibers in filter structure. The aim of this work is to investigate influence of mesoscale inhomogeneity on fibrous filters performance using Digital Fluid Dynamics in models of filters differed by internal structure and to compare obtained results with experimental data. The influence of both, irregularity of structure and fiber size distribution on macroscopic filter performance (initial fractional efficiency, initial pressure drop and their time evolutions) is presented. The neglection of fiber size distribution in theoretical models of filtration efficiency leads to the underestimation of both, filtration efficiency and pressure drop.

Microstructure and Mechanical Properties of Nb- and Nb + Ti-Stabilised 18Cr–2Mo Ferritic Stainless Steels

To explore the optimum use of stabilised elements and study the influences of stabilisation in 18Cr–2Mo grades, the Nb and Nb + Ti microalloying investigation focused on the relationships of the microstructure and mechanical properties of the microalloyed 18Cr–2Mo ferritic stainless steel thick plates. Thermo-Calc calculation was performed to predict the equilibrium phase diagrams. Afterwards, the microstructure, i.e. grain size and precipitation, of as-annealed specimens was analysed by means of optical microscopy, scanning electron microscopy and transmission electron microscopy, X-ray diffraction and energy-dispersive spectroscopy. Also, electron backscatter diffraction mapping was constructed to characterise grain boundary. The mechanical properties, including tensile strength and impact toughness, were tested to correlate with the microstructure. The results show that the grain sizes of Nb-stabilised steel are comparatively smaller, which is related to the fine precipitation at the grain boundaries and beneficial to the impact toughness. The increase in its strength is not apparent due to the inhomogeneous grain sizes. The grain boundary characters are similar, which is not the main factor related to their mechanical properties. When Ti is added, TiN forms above the liquidus, and large TiN particles evidently impair impact toughness.

Effects of Growth Solutions Ageing Time to the Formation of Gold Nanorods via Two-Step Approach for Plasmonic Applications

We demonstrate the structural reorganization of gold nanorods (GNRs) that could fine-tune localized surface plasmon resonance (LSPR) by using modified wet chemical synthesis on the solid substrate. Controlling the growth solution ageing time using the modifiable GNRs is an approach to overcome the limitations of rods formation due to inhomogeneous and uncontrollable size and aspect ratio. In this study, the suitable ageing time of GNRs was determined to produce optimum GNRs in terms of surface density and aspect ratio. As the ageing time was increased from 30 min to 24 h, the colour of the growth solution was changed from light to dark purple. The change is associated with the density of the nanorods formation. The optical spectral peaks of GNRs occur in a range between 500 nm and 800 nm in the visible and near-infrared region spectrum for transverse surface resonance (t-SPR) and longitudinal surface resonance (l-SPR), respectively. From the morphological analysis, it was found that 20 h ageing time resulting in high density and homogeneous GNRs with 74.81% surface density with 4.23 ± 0.04 aspect ratio. Hence, the growth ageing time of GNRs can be manipulated to control their shape evolution and dimension in terms of size and aspect ratio. The controllable aspect ratio and size GNRs can be potentially used as sensing material in plasmonic applications.

The nanoeffeсt in epoxynanocomposites

It was shown that the distribution of silica nanoparticles (silicon dioxide) and the size of inhomogeneities (heterogeneity level) in the epoxy oligomers and epoxy nanocomposites effect on the structure and properties of epoxy composites.It was established that the maximum value of epoxy composites impact strength is achieved only when the particles of the optimal size (~ 150 nm) are formed in their structure from silica nanoparticles of different grades (BS-50, BS-100 and BS-120), sizes and specific surface.The nano effect in dispersed-filled epoxy composites caused by the formation of clusters of silica nanoparticles of size ~ 150-190 nm was discovered and proved for the first time. It is accompanied by an increase in impact strength by ~2 times and proves the high efficiency of nanoparticles for creating impact-resistant plastics.It was shown that monolithic ultrafine particles of powdered quartz (silicon dioxide) with a particle diameter of ~150 nm lead to an increase in the toughness of epoxy composites by only ~20% and are much less efficient than nanoparticles.

Описание колоссального магнитосопротивления La-=SUB=-1.2-=/SUB=-Sr-=SUB=-1.8-=/SUB=-Mn-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=- на основе "спин-поляронного" и "ориентационного" механизмов проводимости в парамагнитной области температур

Experimental and theoretical investigations of the resistance of the La1.2Sr1.8Mn2O7 single crystal in magnetic fields from 0 to 90 kOe and in the temperature range from 75 to 300 K has been studied. The magnetoresistance is determined by the “spin-polaron” and “orientation” conduction mechanisms. Using the method of separating contributions to the magnetoresistance from several conduction mechanisms, the observed magnetoresistance of La1.2Sr1.8Mn2O7 manganite in the temperature range of 75-300 K is described, good agreement between the calculated and experimental data is obtained. In a magnetic field of 0 and 90 kOe, the temperature dependences of the size of the spin polaron (in relative units) are calculated for the temperature range 75–300 K. It is shown, that the КМС value is determined by an increase in the linear size of the spin polaron (along the magnetic field), i.e. the main role in the magnitude of the colossal magnetoresistance is made by the change in the size of the magnetic inhomogeneities of the crystal.