Inhomogeneous Spatial Distribution Research Articles

Mapping heavy elements in the supernova remnant G290.1-0.8

We present the imaging and spectroscopic study results of G290.1-0.8 Supernova Remnant (SNR) using the Suzaku X-ray archival data. The SNR belongs to the mixed-morphology class with its centrally peaked asymmetric X-ray core and distorted radio shell-like plasma. The X-ray spectra is well defined with isothermal plasma of kTe ∼ 0:5 keV. The radial profile shows enhanced elemental abundances. The EW maps reveal inhomogeneous asymmetric spatial distribution of elemental abundances. The northeast of the SNR is bright in Ne, Mg, and Si. The EW maps are enhanced in the direction of the X-ray elongation, suggesting that the distorted X-ray structure is dominated by a core-collapse 20∼25 M⊙ progenitor star ejecta.

Switching Purcell effect with nonlinear epsilon-near-zero media

An optical topological transition is defined as the change in the photonic iso-frequency surface around epsilon-near-zero (ENZ) frequencies which can considerably change the spontaneous emission of a quantum emitter placed near a metamaterial slab. Here, we show that due to the strong Kerr nonlinearity at ENZ frequencies, a high-power pulse can induce a sudden transition in the topology of the iso-frequency dispersion curve, leading to a significant change in the transmission of propagating as well as evanescent waves through the metamaterial slab. This evanescent wave switch effect allows for the control of spontaneous emission through modulation of the Purcell effect. We develop a theory of the enhanced nonlinear response of ENZ media to s and p polarized inputs and show that this nonlinear effect is stronger for p polarization and is almost independent of the incident angle. We perform finite-difference time-domain simulations to demonstrate the transient response of the metamaterial slab to an ultrafast pulse and fast switching of the Purcell effect at the sub-picosecond scale. The Purcell factor changes at ENZ by almost a factor of three which is an order of magnitude stronger than that away from ENZ. We also show that due to the inhomogeneous spatial field distribution inside the multilayer metal-dielectric super-lattice, a unique spatial topological transition metamaterial can be achieved by the control pulse induced nonlinearity. Our work can lead to ultra-fast control of quantum phenomena in ENZ metamaterials.

Holographic formation of phase diffractive elements for light beams conversion with photo-induced absorption coefficient changing in PDLCs

A theoretical model of the holographic formation of diffractive optical elements for the Gaussian light beams conversion into Bessel-like ones in polymer-dispersed liquid crystals (PDLCs) is developed. The model is based on the solution of the kinetic equations of photopolymerization-diffusion processes of holograms recording in PDLCs by light beams with inhomogeneous amplitude and phase spatial distributions. The model additionally takes into account the photo-induced changings in the absorption coefficient of the PDLC. It is shown that the absorption changings decreases the rate of the refractive index’s spatial profile decline over the thickness of the material. In this case, when the characteristic time of the absorption changing is much less than the characteristic polymerization time (the absorption changes more rapidly than the photopolymerization takes place), the diffractive element can be characterized by a homogeneous distribution of the refractive index over the thickness.

Macromolecular Crowding Induces Spatial Correlations That Control Gene Expression Bursting Patterns.

Recent superresolution microscopy studies in E.coli demonstrate that the cytoplasm has highly variable local concentrations where macromolecular crowding plays a central role in establishing membrane-less compartmentalization. This spatial inhomogeneity significantly influences molecular transport and association processes central to gene expression. Yet, little is known about how macromolecular crowding influences gene expression bursting-the episodic process where mRNA and proteins are produced in bursts. Here, we simultaneously measured mRNA and protein reporters in cell-free systems, showing that macromolecular crowding decoupled the well-known relationship between fluctuations in the protein population (noise) and mRNA population statistics. Crowded environments led to a 10-fold increase in protein noise even though there were only modest changes in the mRNA population and fluctuations. Instead, cell-like macromolecular crowding created an inhomogeneous spatial distribution of mRNA ("spatial noise") that led to large variability in the protein production burst size. As a result, the mRNA spatial noise created large temporal fluctuations in the protein population. These results highlight the interplay between macromolecular crowding, spatial inhomogeneities, and the resulting dynamics of gene expression, and provide insights into using these organizational principles in both cell-based and cell-free synthetic biology.

Inhomogeneous Spatial Distribution of Electrons in a Compressed Gas Bubble of Submicron Size

The inhomogeneous spatial distribution of the macroscopic amount of electrons (N <109) in a spherical potential well is considered. It is shown that the electron distribution has two spatial scales. The first scale is the Fermi length. By effect, we mean the existence of the second scale, which is related with the radius of the potential well and much larger than the first scale. Two systems are considered: a system of free electrons in a spherical well and electrons in a compressed gas bubble. Based on the analysis of the distribution function of a system of free semiclassical electrons, we demonstrate the cause of the appearance of the spatial heterogeneity. This result is confirmed by a numerical summation of exact solutions of the wave functions of electrons in an infinite potential well. It is shown that there is an analogous effect for the spatial distribution of electrons in compressed hydrogen gas bubble of submicron size (<0.1 μm). This system can be realized in the thermonuclear experiments. Numerical simulation of the electron distribution was carried out by the DFT method. The limiting factors of the effect are considered. The aim of problem considered in the article deals with the analysis of possible physical processes occurring in the thermonuclear experiments.

Enrichment of Zinc in Galactic Chemodynamical Evolution Models

Abstract The heaviest iron-peak element Zinc (Zn) has been used as an important tracer of cosmic chemical evolution. Spectroscopic observations of the metal-poor stars in Local Group galaxies show an increasing trend of [Zn/Fe] ratios toward lower metallicity. However, the enrichment of Zn in galaxies is not well understood due to poor knowledge of astrophysical sites of Zn, as well as metal mixing in galaxies. Here we show possible explanations for the observed trend by taking into account electron-capture supernovae (ECSNe) as one of the sources of Zn in our chemodynamical simulations of dwarf galaxies. We find that the ejecta from ECSNe contribute to stars with [Zn/Fe] ≳ 0.5. We also find that scatters of [Zn/Fe] in higher metallicities originate from the ejecta of type Ia supernovae. On the other hand, it appears difficult to explain the observed trends if we do not consider ECSNe as a source of Zn. These results come from an inhomogeneous spatial metallicity distribution due to the inefficiency of the metal mixing. We find that the optimal value of the scaling factor for the metal diffusion coefficient is ∼0.01 in the shear-based metal mixing model in smoothed particle hydrodynamics simulations. These results suggest that ECSNe could be one of the contributors of the enrichment of Zn in galaxies.

Effects of geometrical structure on spatial distribution of thermal energy in two-dimensional triangular lattices

Employing the correlation matrix technique, the spatial distribution of thermal energy in two-dimensional triangular lattices in equilibrium, interacting with linear springs, is studied. It is found that the spatial distribution of thermal energy varies with the included angle of the springs. In addition, the average thermal energy of the longer springs is lower. Springs with different included angle and length will lead to an inhomogeneous spatial distribution of thermal energy. This suggests that the spatial distribution of thermal energy is affected by the geometrical structure of the system: the more asymmetric the geometrical structure of the system is, the more inhomogeneous is the spatial distribution of thermal energy.

MULTIFRACTAL ANALYSIS OF SEISMICALLY INDUCED SOFT-SEDIMENT DEFORMATION STRUCTURES IMAGED BY X-RAY COMPUTED TOMOGRAPHY

Unconsolidated soft sediments deform and mix complexly by seismically induced fluidization. Such geological soft-sediment deformation structures (SSDSs) recorded in boring cores were imaged by X-ray computed tomography (CT), which enables visualization of the inhomogeneous spatial distribution of iron-bearing mineral grains as strong X-ray absorbers in the deformed strata. Multifractal analysis was applied to the two-dimensional (2D) CT images with various degrees of deformation and mixing. The results show that the distribution of the iron-bearing mineral grains is multifractal for less deformed/mixed strata and almost monofractal for fully mixed (i.e. almost homogenized) strata. Computer simulations of deformation of real and synthetic digital images were performed using the egg-beater flow model. The simulations successfully reproduced the transformation from the multifractal spectra into almost monofractal spectra (i.e. almost convergence on a single point) with an increase in deformation/mixing intensity. The present study demonstrates that multifractal analysis coupled with X-ray CT and the mixing flow model is useful to quantify the complexity of seismically induced SSDSs, standing as a novel method for the evaluation of cores for seismic risk assessment.

Evolution of domain structure and formation of charged domain walls during polarization reversal in lithium niobate single crystals modified by vacuum annealing

The evolution of the domain structure during polarization reversal has been investigated in plates of lithium niobate with spatially inhomogeneous electrical conductivity produced by vacuum annealing. The formation of charged domain walls in the crystal bulk has been studied. Revealed features of the domain growth in the bulk have been attributed to the formation of nanodomains under the pyroelectric field and inhomogeneous spatial distribution of the electric field. Creation of the charged domain walls with controlled parameters is of great interest for domain walls engineering.

Эволюция доменной структуры и формирование заряженных доменных стенок при переключении поляризации в монокристаллах ниобата лития, модифицированных отжигом в вакууме

AbstractThe evolution of the domain structure during polarization reversal has been investigated in plates of lithium niobate with spatially inhomogeneous electrical conductivity produced by vacuum annealing. The formation of charged domain walls in the crystal bulk has been studied. Revealed features of the domain growth in the bulk have been attributed to the formation of nanodomains under the pyroelectric field and inhomogeneous spatial distribution of the electric field. Creation of the charged domain walls with controlled parameters is of great interest for domain walls engineering.

Sample variance in the local measurements of the Hubble constant

The current $>3\sigma$ tension between the Hubble constant $H_0$ measured from local distance indicators and from cosmic microwave background is one of the most highly debated issues in cosmology, as it possibly indicates new physics or unknown systematics. In this work, we explore whether this tension can be alleviated by the sample variance in the local measurements, which use a small fraction of the Hubble volume. We use a large-volume cosmological $N$-body simulation to model the local measurements and to quantify the variance due to local density fluctuations and sample selection. We explicitly take into account the inhomogeneous spatial distribution of type Ia supernovae. Despite the faithful modelling of the observations, our results confirm previous findings that sample variance in the local Hubble constant $(H_0^{\rm loc})$ measurements is small; we find $\sigma(H_0^{\rm loc})=0.31\,{\rm km\ s^{-1}Mpc^{-1}}$, a nearly negligible fraction of the $\sim6\,{\rm km\ s^{-1}Mpc^{-1}}$ necessary to explain the difference between the local and the global $H_0$ measurements. While the $H_0$ tension could in principle be explained by our local neighbourhood being a underdense region of radius $\sim 150 \,\rm Mpc$ , the extreme required underdensity of such a void $(\delta\simeq -0.8)$ makes it very unlikely in a $\Lambda$CDM universe, and it also violates existing observational constraints. Therefore, sample variance in a $\Lambda$CDM universe cannot appreciably alleviate the tension in $H_0$ measurements even after taking into account the inhomogeneous selection of type Ia supernovae.

Spatial Inhomogeneity in Solar Faculae

AbstractIn this paper, we investigate the inhomogeneous spatial distribution of solar faculae. The focus is on the latitudinal and longitudinal distributions of these highly localised features covering ubiquitously the solar surface. The statistical analysis is based on white light observations of the Solar and Heliospheric Observatory (SOHO) and Solar Dynamics Observatory (SDO) between 1996 and 2014. We found that the fine structure of the latitudinal distribution of faculae displays a quasi-biennial oscillatory pattern. Furthermore, the longitudinal distribution of photospheric solar faculae does not show homogeneous behaviour either. In particular, the non-axisymmetric behaviour of these events show similar properties as that of the active longitude (AL) found in the distribution of sunspots. Our results, preliminary though, may provide a valuable observational constrain for developing the next-generation solar dynamo model.

Inhomogeneous spatial distribution of the magnetic transition in an iron-rhodium thin film

Monitoring a magnetic state using thermal or electrical activation is mandatory for the development of new magnetic devices, for instance in heat or electrically assisted magnetic recording or room-temperature memory resistor. Compounds such as FeRh, which undergoes a magnetic transition from an antiferromagnetic state to a ferromagnetic state around 100 °C, are thus highly desirable. However, the mechanisms involved in the transition are still under debate. Here we use in situ heating and cooling electron holography to quantitatively map at the nanometre scale the magnetization of a cross-sectional FeRh thin film through the antiferromagnetic–ferromagnetic transition. Our results provide a direct observation of an inhomogeneous spatial distribution of the transition temperature along the growth direction. Most interestingly, a regular spacing of the ferromagnetic domains nucleated upon monitoring of the transition is also observed. Beyond these findings on the fundamental transition mechanisms, our work also brings insights for in operando analysis of magnetic devices.

Interconfigurational and intraconfigurational transitions of Yb2+ and Yb3+ ions in hydroxyapatite: A cathodoluminescence study

We present a cathodoluminescence (CL) study of the interconfigurational transitions of Yb2+ and intraconfigurational transitions of Yb3+ dopant ions in hydroxyapatite (HAp) powders. Our results demonstrate that strong electric fields present in the HAp lattice induce manifold levels in the electronic configuration of the ytterbium ions, due to splitting of the 4f135d1 orbitals. CL spectra of Yb2+ display a series of sharp peaks centered at 3.27, 2.98, 2.85, 2.53, 2.27, 2.09 and 1.63 eV, corresponding to transitions between multiple levels produced by a trigonal distortion of the regular octahedral crystal field of the Yb2+ 4f135d1 configuration. CL spectra of Yb3+ display four emissions centered at 1.17, 1.21, 1.24 and 1.27 eV, generated by intraconfigurational transitions between the 2F5/2 and 2F7/2 states of Yb3+ ions. Two types of samples were synthesized at different pH values, resulting in variations of the valence of the ytterbium ions, such that the ratios of Yb2+/Yb3+ were 0.31 and 0.55 in calcined powders synthesized at pH values of 6 and 4, respectively, as determined from X-ray photoelectron spectroscopy. Infrared CL images of the two samples show an inhomogeneous spatial distribution of the Yb3+ dopant in the powders. Thermal treatment of the samples, at 873 K in an oxygen atmosphere, result in quenching of the Yb2+ luminescence due to oxidation of the Yb2+ into Yb3+.

A simulation study of capillary transport, preferential retention and distribution of salts in historic sandstone buildings

Salt crystallisation is a major problem of deterioration in historic stone buildings, monuments and sculptures. The capillary rise of soil water is one of the primary sources of salts in stone structures, which evaporates leaving the salts behind. It has been noted that the spatial distribution profile of different species of salts crystallised in historic stone buildings is not homogeneous, i.e. different salts crystallise at different locations. The capillary transport and inhomogeneous spatial distribution of different salts in the porous building materials has been considered to be a result of solubility-dependent crystallisation; however, the factors responsible for this phenomenon are not clearly known. This paper aims to investigate the factors influencing the differential distribution of salts during capillary rise of soil water. In this study, the capillary transport of salts was simulated on two different sandstones—Locharbriggs, a Permo–Triassic, red sandstone and Stoke Hall, a Carboniferous, buff sandstone. The experiments were carried out under controlled environmental conditions to eliminate the possibility of evaporation-driven crystallisation of salts depending on their solubilities. The results indicate that fractionation or differential distribution of salts takes place even in the absence of evaporation and crystallisation. The sandstones exhibit properties like an ion exchange column, and ionic species present in the salt solution show differential distribution within the porous network of sandstone.

Gauge invariant theory for super high resolution Raman images.

The use of a highly localized plasmonic field has enabled us to achieve sub-nanometer resolution of Raman images for single molecules. The inhomogeneous spatial distribution of plasmonic field has become an important factor that controls the interaction between the light and the molecule. We present here a gauge invariant interaction Hamiltonian (GIIH) to take into account the non-uniformity of the electromagnetic field distribution in the non-relativistic regime. The theory has been implemented for both resonant and nonresonant Raman processes within the sum-over-state framework. It removes the gauge origin dependence in the phenomenologically modified interaction Hamiltonian (PMIH) employed in previous studies. Our calculations show that, in most resonant cases, the Raman images from GIIH are similar to those from PMIH when the origin is set to the nuclear charge center of the molecule. In the case of nonresonant Raman images, distinct differences can be found from two different approaches, while GIIH calculations provide more details and phase information of the images. Furthermore, the results from GIIH calculations are more stable with respect to the computational parameters. Our results not only help to correctly simulate the resonant and nonresonant Raman images of single molecules but also lay the foundation for developing gauge invariant theory for other linear and nonlinear optical processes under the excitation of non-uniform electromagnetic field.

Comparisons of ground-based tropospheric NO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; MAX-DOAS measurements to satellite observations with the aid of an air quality model over the Thessaloniki area, Greece

Abstract. One of the main issues arising from the comparison of ground-based and satellite measurements is the difference in spatial representativeness, which for locations with inhomogeneous spatial distribution of pollutants may lead to significant differences between the two data sets. In order to investigate the spatial variability of tropospheric NO2 within a sub-satellite pixel, a campaign which lasted for about 6 months was held in the greater area of Thessaloniki, Greece. Three multi-axial differential optical absorption spectroscopy (MAX-DOAS) systems performed measurements of tropospheric NO2 columns at different sites representative of urban, suburban and rural conditions. The direct comparison of these ground-based measurements with corresponding products from the Ozone Monitoring Instrument onboard NASA's Aura satellite (OMI/Aura) showed good agreement over the rural and suburban areas, while the comparison with the Global Ozone Monitoring Experiment-2 (GOME-2) onboard EUMETSAT's Meteorological Operational satellites' (MetOp-A and MetOp-B) observations is good only over the rural area. GOME-2A and GOME-2B sensors show an average underestimation of tropospheric NO2 over the urban area of about 10.51 ± 8.32 × 1015 and 10.21 ± 8.87 × 1015 molecules cm−2, respectively. The mean difference between ground-based and OMI observations is significantly lower (6.60 ± 5.71 × 1015 molecules cm−2). The differences found in the comparisons of MAX-DOAS data with the different satellite sensors can be attributed to the higher spatial resolution of OMI, as well as the different overpass times and NO2 retrieval algorithms of the satellites. OMI data were adjusted using factors calculated by an air quality modeling tool, consisting of the Weather Research and Forecasting (WRF) mesoscale meteorological model and the Comprehensive Air Quality Model with Extensions (CAMx) multiscale photochemical transport model. This approach resulted in significant improvement of the comparisons over the urban monitoring site. The average difference of OMI observations from MAX-DOAS measurements was reduced to −1.68 ± 5.01 × 1015 molecules cm−2.

In Depth Spatially Inhomogeneous Phase Transition in Epitaxial MnAs Film on GaAs(001).

Most studies on MnAs material in its bulk form have been focused on its temperature-dependent structural phase transition accompanied by a magnetic one. Magnetostructural phase transition parameters in thin MnAs films grown on substrates present however some differences from the bulk behavior, and local studies become mandatory for a deeper understanding of the mechanisms involved within the transition. Up to now, only surface techniques have been carried out, while the transition is a three-dimensional phenomenon. We therefore developed an original nanometer scale methodology using electron holography to investigate the phase transition in an epitaxial MnAs thin film on GaAs(001) from the cross-section view. Using quantitative magnetic maps recorded at the nanometer scale as a function of the temperature, our work provides a direct in situ observation of the inhomogeneous spatial distribution of the transition in the layer depth and brings new insights on the fundamental transition mechanisms.

A Study on Inhomogeneous Neutron Intensity Distribution Origin from Neutron Guide Transportation

The uniformity of the neutron intensity spatial distribution at the sample position will directly affect the neutron imaging quality. But the unexpected inhomogeneous spatial distribution phenomenon always appears in the neutron radiography facilities installed at the end of neutron guide. In this paper, the source of this phenomenon has been analyzed through geometrical optics and confirmed by Monte Carlo simulations, and several optimization solutions are also proposed.

Spatially resolved organic coating on clay minerals in bitumen froth revealed by atomic force microscopy adhesion mapping

Mineral solids in oil sands are often coated with organic matter. These organically-modified mineral solids hinder bitumen aeration and stabilize water-in-oil emulsions, leading to low bitumen recovery and poor bitumen product quality. The study of these organic coating on the fine solids has been elusive due to the nanometer length scale and the unsuitability of sampling in high vacuum sample chambers. In the present work, we report the first attempt of using PeakForce Quantitative Nanomechanical Mapping (QNM) Atomic Force Microscopy (AFM) to study the organic matter adsorption on fine mineral solids extracted from bitumen froth. Taking advantage of the simultaneous nano-scale resolution topographic imaging and adhesion force mapping enabled by PeakForce QNM-AFM, the mineral and organic components in the bitumen froth fine solids were clearly distinguished due to their variations in shapes and mechanical properties. The inhomogeneous spatial distribution of adhesion force on surfaces of platy particles indicated the existence of organic patches on clay minerals. The area percentage of surface organic matter coverage on the clay basal faces was calculated to be 17±6%, and the average thickness of the organic coating was estimated to be 1.4nm based on the adhesion force maps. The organic matter associated with the mineral solids, which cannot be washed off by toluene, was different from asphaltenes in terms of mechanical properties. More specifically, the irreversibly-adsorbed organic matter on clay minerals was found to be softer than the asphaltene fraction of oil sands bitumen.