Types Of Density Profiles Research Articles

The possible equation of state of dark matter in low surface brightness galaxies * *Supported by the National Natural Science Foundation (NSF) of China (11973081, 11573062, 11403092, 11390374, 11521303), the YIPACAS Foundation (2012048), the Chinese Academy of Sciences (CAS, KJZD-EW-M06-01), the NSF of Yunnan Province (2019FB006) and the Youth Project of Western Light of CAS

The observed rotation curves of low surface brightness (LSB) galaxies play an essential role in studying dark matter, and indicate the existence of a central constant density dark matter core. However, the cosmological N-body simulations of cold dark matter predict an inner cusped halo with a power-law mass density distribution, and cannot reproduce a central constant-density core. This phenomenon is called cusp-core problem. When dark matter is quiescent and satisfies the condition for hydrostatic equilibrium, the equation of state can be adopted to obtain the density profile in the static and spherically symmetric space-time. To address the cusp-core problem, we assume that the equation of state is independent of the scaling transformation. Its lower order approximation for this type of equation of state can naturally lead to a special case, i.e., , where p and represent the pressure and density, respectively, depicts the rotation velocity of galaxy, and and are positive constants. It can obtain a density profile that is similar to the pseudo-isothermal halo model when is approximately 0.15. To obtain a more universally used model, let the equation of state include the polytropic model, i.e. , from which we can obtain other types of density profiles, such as the profile that is nearly same as the Burkert profile, where s and are positive constants.

Differential Diffusivity Effects in Reactive Convective Dissolution

When a solute A dissolves into a host fluid containing a reactant B, an A + B → C reaction can influence the convection developing because of unstable density gradients in the gravity field. When A increases density and all three chemical species A, B and C diffuse at the same rate, the reactive case can lead to two different types of density profiles, i.e., a monotonically decreasing one from the interface to the bulk and a non-monotonic profile with a minimum. We study numerically here the nonlinear reactive convective dissolution dynamics in the more general case where the three solutes can diffuse at different rates. We show that differential diffusion can add new dynamic effects like the simultaneous presence of two different convection zones in the host phase when a non-monotonic profile with both a minimum and a maximum develops. Double diffusive instabilities can moreover affect the morphology of the convective fingers. Analysis of the mixing zone, the reaction rate, the total amount of stored A and the dissolution flux further shows that varying the diffusion coefficients of the various species has a quantitative effect on convection.

Nuclear longitudinal form factors for axially deformed charge distributions expanded by nonorthogonal basis functions**Supported by National Natural Science Foundation of China (11505292, 11175085, 11575082, 11235001, 11275138, and 11447226), by Shandong Provincial Natural Science Foundation, China (BS2014SF007), Fundamental Research Funds for Central Universities (15CX02072A).

In this paper, the nuclear longitudinal form factors are systematically studied from the intrinsic charge multipoles. For axially deformed nuclei, two different types of density profiles are used to describe their charge distributions. For the same charge distributions expanded with different basis functions, the corresponding longitudinal form factors are derived and compared with each other. Results show the multipoles Cλ of longitudinal form factors are independent of the basis functions of charge distributions. Further numerical calculations of longitudinal form factors of 12C indicates that the C0 multipole reflects the contributions of spherical components of all nonorthogonal basis functions. For deformed nuclei, their charge RMS radii can also be determined accurately by the C0 measurement. The studies in this paper examine the model-independent properties of electron scattering, which are useful for interpreting electron scattering experiments on exotic deformed nuclei.

Experimental and numerical analysis of buoyancy-induced instability during CO2 absorption in NaHCO3–Na2CO3 aqueous solutions

This work deals with the experimental analysis and the mathematical modelling of the CO2 absorption in an initially quiescent aqueous solution of NaHCO3 and Na2CO3 inside a Hele-Shaw cell. This absorption, initially driven by the coupling between diffusion and chemical reactions, eventually leads to the apparition of a peculiar gravitational instability with non-monotonic dynamics, and liquid plumes generated at some distance from the gas-liquid interface (Wylock et al., 2014). Considering that this instability is triggered by a Rayleigh–Taylor like mechanism, a two-dimensional model, coupling diffusion, chemical reaction and convection, is proposed to simulate the onset and the dynamics of such an instability. It is observed that the simulated instability dynamics agree qualitatively with the experimental observations and that the order of magnitude of the onset time is well estimated. Thanks to the simulation, the interaction between the various phenomena after the instability onset is further investigated and a mechanism is proposed to explain the unusual dynamics of the studied system. It is notably shown that this dynamics is due to the particular non-monotonic liquid density variations with the depth, induced by the absorption. A criterion to obtain such type of density profile is presented. In addition, the simulation enables to assess the influence of the instability on the CO2 absorption rate and it is observed that the generated flow pattern does not lead to a significant enhancement of the gas–liquid absorption rate. This result is of significant importance for optimizing chemisorption (e.g. for CO2 capture or sequestration) processes.

Enhanced propagation and focusing of an intense laser beam in high density magnetized plasma

In the present communication, the steady state propagation of an intense, circularly polarized Gaussian electromagnetic beam in high-density magnetized plasma is studied analytically and numerically. The relativistic oscillation of the mass of the electrons in the field of the pump and longitudinal magnetic field are shown to have a major effect on the dynamics of the propagation of intense electromagnetic wave. The wave equation has been solved under WKB and paraxial approximation by expanding the dielectric tensor for arbitrary large intensity. The propagation of electromagnetic waves in magnetized plasma, in the so-called extraordinary mode has been explicitly considered in the analysis. The variation of beamwidth parameter with distance of propagation has been obtained for chosen values of critical parameters in different regimes. These regimes are steady divergence, oscillatory divergence and self-focusing. Numerical computations are performed for a wide range of dimensionless parameters. It is seen that the laser beamwidth tends to attain a constant value depending upon plasma electron density, axial inhomogeneity and laser irradiance for different strength of magnetic field. Further, enhanced propagation, focusing and penetration of an intense laser beam is evident through plots from slightly underdense to overdense plasma with different types of density profiles.

Comparisons between Isothermal and NFW Mass Profiles for Strong‐Lensing Galaxy Clusters

While both isothermal and NFW-based mass models for galaxy clusters are widely adopted in strong-lensing studies, they cannot easily be distinguished based solely on observed positions of arcs and arclets. We compare the magnifications predicted for giant arcs obtained from isothermal and NFW profiles, taking axially symmetric and asymmetric mass distributions into account. We find that arc magnifications can differ strongly between the two types of density profile even if the image morphology is well reproduced. Magnifications by lenses with NFW density profiles are usually larger than those for lenses with singular or nearly singular isothermal density profiles, unless the latter have large cores. Asymmetries play an important role. We illustrate our results with the two well-studied clusters, MS 2137 and A370. We confirm earlier results showing that both isothermal and NFW mass models can very well reproduce the observed arcs, radial arcs, and other arclets. While the mass model for MS 2137 is not very well constrained, the two types of mass models produce strongly differing critical curves and caustics for A370. We find that the NFW mass profile is preferred for A370. We identify new arclet candidates in the field of A370. Redshift estimates allowed by the lens model are consistent with results in the literature, where available. Three newly found counterimages are suggested to arise from an active, dust-enshrouded star-forming galaxy at z approximate to 1.1.

Gravitational lensing of extended high redshift sources by dark matter haloes

ABSTRA C T High-redshift galaxies and quasi-stellar objects (QSOs) are most likely to be strongly lensed by intervening haloes between the source and the observer. In addition, a large fraction of lensed sources is expected to be seen in the submillimetre region, as a result of the enhanced magnification bias on the steep intrinsic number counts. We extend in three directions Blain’s earlier study of this effect. First, we use a modification of the Press ‐ Schechter mass function and detailed lens models to compute the magnification probability distribution. We compare the magnification crosssections of populations of singular isothermal spheres and Navarro, Frenk & White (NFW) haloes and find that they are very similar, in contrast to the image-splitting statistics which were recently investigated in other studies. The distinction between the two types of density profile is therefore irrelevant for our purposes. Secondly, we discuss quantitatively the maximum magnification, mmax, that can be achieved for extended sources (galaxies) with realistic luminosity profiles, taking into account the possible ellipticity of the lensing potential. We find that mmax plausibly falls into the range 10‐30 for sources of 1‐10 h 21 kpc effective radius at redshifts within 1‐4. Thirdly, we apply our model for the lensing magnification to a class of sources following the luminosity evolution typical for a unified scheme of QSO formation. As a result of the peculiar steepness of their intrinsic number counts, we find that the lensed source counts at a fiducial wave length of 850mm can exceed the unlensed counts by several orders of magnitude at flux densities *100 mJy, even with a conservative choice of the maximum magnification.

About the types of density profiles of fish aggregations and phytoplankton patches

This paper discusses the structure of fish and phytoplankton aggregations, using the transect characteristics method and the data collected during cruise 11 of the R/VArtemida in the South-West Atlantic Ocean. A method of phytoplankton field classification by the type of aggregation is suggested. On the basis of experimentally compiled data, a new way of determining the minimum living distances between hydrobionts has been developed.

A new generalization of the sullivan model for wetting transitions

A new generalization of the Sullivan model for the wetting transition is constructed. To the exponential wall potential of the Sullivan model is added a square well of arbitrary depth and range. Although explicit solutions cannot be given, the different possible types of density profiles are systematically classified. It is argued that for shallow wells of long range, the wetting transition is of first order. Shallow wells of short range give continuous transitions, and the shift from the Sullivan case is calculated explicitly. A simplified version of the model allows a more quantitative criterion for a first-order transition to be formulated. It also points to the possibility that a continuous wetting transition is preceded by a first-order transition between two distinct, partially wet, states.

The influence of stimulated Brillouin scattering on stimulated Raman scattering in inhomogeneous density plasma

A numerical investigation of the interplay of the two parametric scattering processes is reported. A 11/2 D particle-in-cell code has been used to simulate the laser irradiation of a plasma with a linear density profile. Fixed ion and mobile ion simulations have been carried out. In the latter, ion temperature allowed the onset of Brillouin scattering. Two types of density profile have been used: the first one centered on quart-critical density allows one to observe absolute Raman scattering; the second one with an uppermost density below quart-critical density has isolated convective Raman scattering. Absorption and scatter rates are presented for both profiles. Fast electron temperatures are also reported. Raman scattering is reduced by Brillouin scattering presence for both profiles, except in particular conditions below nc/4 where the Raman process appears to be enforced by Brillouin-driven ion-acoustic waves.

Computer automated lanes detection and profiles evaluation of one‐dimensional gel electrophoretic autoradiograms

AbstractA new fast, precise and reproducible method for lanes detection and profiles evaluation of one‐dimensional gel electrophoretic autoradiograms is presented. It is fully automated, and its principles are based on image and signal processing techniques. The operator usually has only to specify the number of lanes that are present in the preparation, but still may retain overall control. In the first phase, the program automatically locates the lateral position of the lanes, and approximates their left and right boundaries by polynomials (which allow curved as well as straight lanes). The operator can then intervene, if necessary, to adjust these positions. In the second phase, the background variations are corrected; two types of density profiles are computed, representing the average density as well as the total amount of material in the lanes. This calculation is carried out with correction for tilt or curvature for each lane. Finally, prinouts are produced that contain graphs of the profiles together with quantitative measurements. Use of this method is illustrated by analysis of electrophoretic gels containing proteins and lipopolysaccharides of varying mobilities. Experiments made on these gels as well as others yield accurate quantitation of the relative amount of each component.

Special case of the density distribution behind a nonstationary shock wave

The density distribution behind a nonstationary shock wave for a definite value of the Mach number M*, which depends on γ = cp/cv, is considered. Use is made of the previously established fact [1] that for M = M*(γ) there exists a connection between the first and second derivatives of the density along the normal behind the wave. An investigation is made into the density profile in dimensionless variables behind plane, cylindrical, and spherical shock waves in the neighborhood of the shock front. In the first case, if the gas in front of the wave is homogeneous, only two types of density profile are possible (up to small quantities of third order in the coordinate). In the second and third cases, the form of the density distribution also depends on a parameter, the ratio of the first derivative along the normal of the density behind the wave to the radius of curvature of the wave.

Observations from Ogo 5 of the thermal ion density and temperature within the magnetosphere

The Ogo 5 retarding potential analyzer experiment is operated in a voltage mode designed to yield the integral spectrum of particles in the energy interval from 0 to 500 ev. Detailed results obtained with the spacecraft inside 7 RE during the first 15 orbits (March–April 1968) are presented. We can identify and group the data into three types of density profile. First, a smooth decrease in ion density from approximately 104 ions/cm−3 at 1.5 RE down to the experiment threshold level of ∼20 ions/cm³ at approximately 5 to 6 RE. A second general type of observed density profile is typified by considerable structure within the plasmasphere, and the plasmapause is identified by a factor of 3 or more drop in ion density. The third type of profile shows a density drop of a factor of 20 or more inside the L = 7 RE radial distance to values below our minimal detectable level of 20 cm−3. The ion temperature observations show that within the plasmasphere the day to night temperature ratio is about a factor of 2, with the temperature ranging from a low of 5×10³°K at 1.5 RE on the night side to as high as 3×104°K at 3.6 RE on the day side. At the plasmapause a sudden increase in the ion temperature is observed. This increase is generally a factor of 5 or more within 0.8 RE, and it has been used to pinpoint the plasmapause location. Beyond the plasmapause we find a region of relatively high ion temperature, Ti>105°K.