Mass Density Parameter Research Articles

Galaxy And Mass Assembly (GAMA): the galaxy stellar mass function to z = 0.1 from the r-band selected equatorial regions

We derive the low redshift galaxy stellar mass function (GSMF), inclusive of dust corrections, for the equatorial Galaxy And Mass Assembly (GAMA) dataset covering 180 deg$^2$. We construct the mass function using a density-corrected maximum volume method, using masses corrected for the impact of optically thick and thin dust. We explore the galactic bivariate brightness plane ($M_\star-\mu$), demonstrating that surface brightness effects do not systematically bias our mass function measurement above 10$^{7.5}$ M$_{\odot}$. The galaxy distribution in the $M-\mu$-plane appears well bounded, indicating that no substantial population of massive but diffuse or highly compact galaxies are systematically missed due to the GAMA selection criteria. The GSMF is {fit with} a double Schechter function, with $\mathcal M^\star=10^{10.78\pm0.01\pm0.20}M_\odot$, $\phi^\star_1=(2.93\pm0.40)\times10^{-3}h_{70}^3$Mpc$^{-3}$, $\alpha_1=-0.62\pm0.03\pm0.15$, $\phi^\star_2=(0.63\pm0.10)\times10^{-3}h_{70}^3$Mpc$^{-3}$, and $\alpha_2=-1.50\pm0.01\pm0.15$. We find the equivalent faint end slope as previously estimated using the GAMA-I sample, although we find a higher value of $\mathcal M^\star$. Using the full GAMA-II sample, we are able to fit the mass function to masses as low as $10^{7.5}$ $M_\odot$, and assess limits to $10^{6.5}$ $M_\odot$. Combining GAMA-II with data from G10-COSMOS we are able to comment qualitatively on the shape of the GSMF down to masses as low as $10^{6}$ $M_\odot$. Beyond the well known upturn seen in the GSMF at $10^{9.5}$ the distribution appears to maintain a single power-law slope from $10^9$ to $10^{6.5}$. We calculate the stellar mass density parameter given our best-estimate GSMF, finding $\Omega_\star= 1.66^{+0.24}_{-0.23}\pm0.97 h^{-1}_{70} \times 10^{-3}$, inclusive of random and systematic uncertainties.

Approximate energies and thermal properties of a position-dependent mass charged particle under external magnetic fields

We solve the Schrödinger equation with a position-dependent mass (PDM) charged particle interacted via the superposition of the Morse-plus-Coulomb potentials and is under the influence of external magnetic and Aharonov–Bohm (AB) flux fields. The nonrelativistic bound state energies together with their wave functions are calculated for two spatially-dependent mass distribution functions. We also study the thermal quantities of such a system. Further, the canonical formalism is used to compute various thermodynamic variables for second choosing mass by using the Gibbs formalism. We give plots for energy states as a function of various physical parameters. The behavior of the internal energy, specific heat, and entropy as functions of temperature and mass density parameter in the inverse-square mass case for different values of magnetic field are shown.

Nonideal Behavior of Glass and Crystal.

We report deviations from an ideal behavior of binary chalcogenide glass composition Ge20Te80 with respect to its quenching rate on mass density and thermal parameters, including glass transition temperature. In an ideal glass, the increase in quenching rate will decrease the characteristic relaxation time and correspondingly shift in the glass transition temperature (Tg) to higher temperature and result in lower density. This, however, holds only when the liquid structure remains the same as in equilibrium glass structure independent of their quenching rate. We find Ge20Te80 glass composition with higher quenching rate is found to possess larger density and lower Tg than the lower rate quenched or well annealed glass specimen. In contrast to conventional glass forming liquids, the anomalous behavior of Ge20Te80 glass with respect to quenching rate is closely related to the change in the local atomic structure with thermal history. Additionally, we found that crystal derived from the Ge20Te80 glass with different thermal history but with identical annealing conditions leads to different mass density, specific heat capacity, and local atomic structure. Thus, the observed unusual variations in the mass density and various thermal properties of Ge20Te80 glass and crystal are mainly determined by the resulting local atomic structure and concentration of defect states associated with each state.

A dynamic foundation model for the analysis of plates on foundation to a moving oscillator

This paper proposes a new foundation model called "Dynamic foundation model" for the dynamic analysis of plates on foundation subjected to a moving oscillator. This model includes a linear elastic spring, shear layer, viscous damping and the special effects of mass density parameters of foundation during vibration. By using finite element method and the principle of dynamic balance, the governing equation of motion of the plate travelled by the oscillator is derived and solved by the Newmark's time integration procedure. The accuracy of the algorithm is verified by comparing the numerical results with the other numerical results in the literature. Also, the effects of mass and damping ratio of system components, stiffness of suspension system, velocity of moving oscillator, and dynamic foundation parameters on dynamic responses are investigated. A very important role of these factors will be shown in the dynamic behavior of the plate.

Next generation cosmology: constraints from theEuclidgalaxy cluster survey

We study the characteristics of the galaxy cluster samples expected from the European Space Agency's Euclid satellite and forecast constraints on cosmological parameters describing a variety of cosmological models. The method used in this paper, based on the Fisher Matrix approach, is the same one used to provide the constraints presented in the Euclid Red Book (Laureijs et al.2011). We describe the analytical approach to compute the selection function of the photometric and spectroscopic cluster surveys. Based on the photometric selection function, we forecast the constraints on a number of cosmological parameter sets corresponding to different extensions of the standard LambdaCDM model. The dynamical evolution of dark energy will be constrained to Delta w_0=0.03 and Delta w_a=0.2 with free curvature Omega_k, resulting in a (w_0,w_a) Figure of Merit (FoM) of 291. Including the Planck CMB covariance matrix improves the constraints to Delta w_0=0.02, Delta w_a=0.07 and a FoM=802. The amplitude of primordial non-Gaussianity, parametrised by f_NL, will be constrained to \Delta f_NL ~ 6.6 for the local shape scenario, from Euclid clusters alone. Using only Euclid clusters, the growth factor parameter \gamma, which signals deviations from GR, will be constrained to Delta \gamma=0.02, and the neutrino density parameter to Delta Omega_\nu=0.0013 (or Delta \sum m_\nu=0.01). We emphasise that knowledge of the observable--mass scaling relation will be crucial to constrain cosmological parameters from a cluster catalogue. The Euclid mission will have a clear advantage in this respect, thanks to its imaging and spectroscopic capabilities that will enable internal mass calibration from weak lensing and the dynamics of cluster galaxies. This information will be further complemented by wide-area multi-wavelength external cluster surveys that will already be available when Euclid flies. [Abridged]

Comparison of the bone response to xenogenic bone screws and metallic screws in canine femur

The study compared the bone response to xenogenic screws and metallic screws of a similar design in a canine femur. The xenogenic bone screws and metallic bone screws were inserted into the femur diaphyses of dogs. Radiological and histological responses to the xenogenic bone screws were determined in canine bone and micro-computed tomography evaluation of bone mass and bone density parameter was performed 36 weeks after fixation of the xenogenic and metallic bone screws. There was no osteolysis and foreign body reaction associated with either bone screw. The radiological and histological results showed that the xenogenic bone screws formed a bony rim around the screws and facilitated incorporation of host bone. By micro-computed tomography, the bone volume was observed to be significantly (P < 0.01) increased at the screw-bone interface surface of xenogenic screws, compared to metallic screws. The bone mineral density of the metallic screw-bone interface was significantly (P < 0.01) higher than that of the xenogenic bone screw. The advantages of the clinical application of the xenogenic bone screw are the possibility of its resorption and incorporation. Therefore, additional surgery to remove the screw is not required.

Cosmological General Relativity with Scale Factor and Dark Energy

In this paper the four-dimensional space-velocity Cosmological General Relativity of Carmeli is developed by a general solution to the Einstein field equations. The metric is given in the Tolman form and the vacuum mass density is included in the energy-momentum tensor. The scale factor redshift equation is obtained, forming the basis for deriving the various redshift-distance relations of cosmological analysis. A linear equation of state dependent on the scale factor is assumed to account for the effects of an evolving dark energy in the expansion of the universe. Modeling simulations are provided for a few combinations of mass density, vacuum density and state parameter values over a sample of high redshift SNe Ia data. Also, the Carmeli cosmological model is derived as a special case of the general solution.

On Robe's Circular Restricted Problem of Three Variable Mass Bodies

This paper investigates the motion of a test particle around the equilibrium points under the setup of the Robe’s circular restricted three-body problem in which the masses of the three bodies vary arbitrarily with time at the same rate. The first primary is assumed to be a fluid in the shape of a sphere whose density also varies with time. The nonautonomous equations are derived and transformed to the autonomized form. Two collinear equilibrium points exist, with one positioned at the center of the fluid while the other exists for the mass ratio and density parameter provided the density parameter assumes value greater than one. Further, circular equilibrium points exist and pairs of out-of-plane equilibrium points forming triangles with the centers of the primaries are found. The out-of-plane points depend on the arbitrary constant , of the motion of the primaries, density ratio, and mass parameter. The linear stability of the equilibrium points is studied and it is seen that the circular and out-of-plane equilibrium points are unstable while the collinear equilibrium points are stable under some conditions. A numerical example regarding out-of-plane points is given in the case of the Earth, Moon, and submarine system. This study may be useful in the investigations of dynamic problem of the “ocean planets” Kepler-62e and Kepler-62f orbiting the star Kepler-62.

Technical Note: Contrast solution density and cross section errors in inhomogeneity-corrected dose calculation for breast balloon brachytherapy

Recent recommendations by the American Association of Physicists in Medicine Task Group 186 emphasize the importance of understanding material properties and their effect on inhomogeneity-corrected dose calculation for brachytherapy. Radiographic contrast is normally injected into breast brachytherapy balloons. In this study, the authors independently estimate properties of contrast solution that were expected to be incorrectly specified in a commercial brachytherapy dose calculation algorithm. The mass density and atomic weight fractions of a clinical formulation of radiographic contrast solution were determined using manufacturers' data. The mass density was verified through measurement and compared with the density obtained by the treatment planning system's CT calibration. The atomic weight fractions were used to determine the photon interaction cross section of the contrast solution for a commercial high-dose-rate (HDR) brachytherapy source and compared with that of muscle. The density of contrast solution was 10% less than that obtained from the CT calibration. The cross section of the contrast solution for the HDR source was 1.2% greater than that of muscle. Both errors could be addressed by overriding the density of the contrast solution in the treatment planning system. The authors estimate the error in mass density and cross section parameters used by a commercial brachytherapy dose calculation algorithm for radiographic contrast used in a clinical breast brachytherapy practice. This approach is adaptable to other clinics seeking to evaluate dose calculation errors and determine appropriate density override values if desired.

Nature of the transmission eigenvalue spectrum for elastic bodies

This study develops a spectral theory of the interior transmission problem (ITP) for heterogeneous and anisotropic elastic solids. The subject is central to the so-called qualitative methods for inverse scattering involving penetrable obstacles. Although simply stated as a coupled pair of elastodynamic wave equations, the ITP for elastic bodies is neither self-adjoint nor elliptic. To help deal with such impediments, earlier studies have established the well-posedness of an elastodynamic ITP under notably restrictive assumptions on the contrast in elastic and mass density parameters between the scatterer and the background solid. Due to lack of self-adjointness of the problem, these analyses were further successful in substantiating the discreteness of the relevant eigenvalue spectrum but not its existence. The aim of this work is to provide a systematic treatment of the ITP for elastic bodies that transcends the limitations of earlier analyses. Considering a broad range of material-contrast configurations, this paper investigates the questions of the solvability of the ITP, the discreteness of its eigenvalues and, for the first time, of the existence of such eigenvalue spectrum. Necessitated by the breadth of material configurations studied, the relevant claims are established via a suite of variational formulations, each customized to meet the needs of a particular subclass of eigenvalue problems.

Probabilistic Modeling of Bridge Deck Unseating during Hurricane Events

Although coastal bridges have exhibited significant susceptibility to damage during hurricane-induced wave and surge events, probabilistic models are lacking to quantify the vulnerability of bridges under a range of structural or hazard parameters and support hurricane risk assessment and mitigation activities. This paper introduces a computationally efficient methodology to assess the fragility, or conditional failure probability, of bridges, targeting the deck shifting or unseating failure mode, which is a predominant severe mode of failure for vast inventories of simply supported span bridges. The method propagates uncertainties in parameters affecting the structural capacity and demand, such as mass density, connection strength, material properties, workmanship, and wave parameters. Fragility surfaces are derived in which failure probability is presented over a range of relative surge elevation and wave heights. The application of this technique is shown through a regional fragility assessment of 136 bridges in the greater Houston area. The results reveal that a failure zone emerges in the fragility surfaces of the bridges studied, with a dramatic transition in probability of failure. Additionally, bridges with similar trends in fragility surfaces can be readily classified based on estimates of their mean mass per span length. Finally, application of the new vulnerability models in a case-study regional risk assessment for Hurricane Ike reveals consistency with observed damage and also offers an opportunity for future studies to investigate alternative scenarios for risk-mitigation planning or extensions of the methodology to consider other regions or failure modes.

New constraints on H 0 and Ω m from SZE/X-ray data and baryon acoustic oscillations

The Hubble constant, H 0, sets the scale of the size and age of the Universe and its determination from independent methods is still worthwhile to be investigated. In this article, by using the Sunyaev–Zeldovich effect and X-ray surface brightness data from 38 galaxy clusters observed by Bonamente et al. (Astrophys J 647:25, 2006), we obtain a new estimate of H 0 in the context of a flat Λ CDM model. There is a degeneracy on the mass density parameter (Ω m ) which is broken by applying a joint analysis involving the baryon acoustic oscillations (BAO) as given by Sloan Digital Sky Survey. This happens because the BAO signature does not depend on H 0. Our basic finding is that a joint analysis involving these tests yield $${H_0 = 76.5^{+3.35}_{-3.33}}$$ km/s/mpc and $${\Omega_{m} = 0.27^{+0.03}_{-0.02}}$$ . Since the hypothesis of spherical geometry assumed by Bonamente et al. is questionable, we have also compared the above results to a recent work where a sample of galaxy clusters described by an elliptical profile was used in analysis.

Cloud modeling of a network region in Hα

AbstractIn this paper, we analyze the physical properties of dark mottles in the chromospheric network using two‐dimensional spectroscopic observations in Hα obtained with the Göttingen Fabry‐Perot Spectrometer in the Vacuum Tower Telescope at the Observatory del Teide, Tenerife. Cloud modeling was applied to measure the mottles' optical thickness, source function, Doppler width, and line‐of‐sight velocity. Using these measurements, the number density of hydrogen atoms in levels 1 and 2, total particle density, electron density, temperature, gas pressure, and mass density parameters were determined with the method of Tsiropoula & Schmieder (1997). We also analyzed the temporal behaviour of a mottle using cloud parameters. Our result shows that it is dominated by 3 minute signals in source function, and 5 minutes or more in velocity (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Application of a Regular Solution-Based Model to Asphaltene Precipitation from Live Oils

A previously developed regular solution approach was adapted to model asphaltene precipitation caused by compositional changes and depressurization. The model inputs are the mass fraction, molecular weight, density, and solubility parameters for each component. A Gulf of Mexico crude oil was characterized into components, and mass fractions were assigned on the basis of gas chromatographic and saturates, aromatics, resins, and asphaltenes (SARA) analysis. Densities for pentane plus and SARA fractions were obtained from published data. For lighter components, effective densities were determined from extrapolated n-alkane data. The density of the live oil from 80 to 120 °C and pressures from 10 to 100 MPa was predicted to within the error of the data assuming ideal mixing. Solubility parameters of each component were determined as a function of the temperature and pressure. The only unknown was the average molar mass of the asphaltene nano-aggregates in the oil, which was used to fit the measured precipitation onset pressure data. The model successfully predicted asphaltene yield data below the onset pressure for the live oil as well as yields for the dead oil diluted with n-heptane. The results indicate that a common characterization can be used to model both solvent- and pressure-induced precipitation. However, the pressure-induced precipitation is very sensitive to the average aggregate molar mass. Thus, the predictive capability of this approach is limited.

On the Existence and Uniqueness of a Solution to the Interior Transmission Problem for Piecewise-Homogeneous Solids

The interior transmission problem (ITP), which plays a fundamental role in inverse scattering theories involving penetrable defects, is investigated within the framework of mechanical waves scattered by piecewise-homogeneous, elastic or viscoelastic obstacles in a likewise heterogeneous background solid. For generality, the obstacle is allowed to be multiply connected, having both penetrable components (inclusions) and impenetrable parts (cavities). A variational formulation is employed to establish sufficient conditions for the existence and uniqueness of a solution to the ITP, provided that the excitation frequency does not belong to (at most) countable spectrum of transmission eigenvalues. The featured sufficient conditions, expressed in terms of the mass density and elasticity parameters of the problem, represent an advancement over earlier works on the subject in that (i) they pose a precise, previously unavailable provision for the well-posedness of the ITP in situations when both the obstacle and the background solid are heterogeneous, and (ii) they are dimensionally consistent, i.e., invariant under the choice of physical units. For the case of a viscoelastic scatterer in an elastic solid it is further shown, consistent with earlier studies in acoustics, electromagnetism, and elasticity that the uniqueness of a solution to the ITP is maintained irrespective of the vibration frequency. When applied to the situation where both the scatterer and the background medium are viscoelastic, i.e., dissipative, on the other hand, the same type of analysis shows that the analogous claim of uniqueness does not hold. Physically, such anomalous behavior of the “viscoelastic-viscoelastic” case (that has eluded previous studies) has its origins in a lesser known fact that the homogeneous ITP is not mechanically insulated from its surroundings—a feature that is particularly cloaked in situations when either the background medium or the scatterer are dissipative. A set of numerical results, computed for ITP configurations that meet the sufficient conditions for the existence of a solution, is included to illustrate the problem. Consistent with the preceding analysis, the results indicate that the set of transmission values is indeed empty in the “elastic-viscoelastic” case, and countable for “elastic-elastic” and “viscoelastic-viscoelastic” configurations.

Dark matter halo growth - II. Diffuse accretion and its environmental dependence

Dark matter haloes in Lambda CDM simulations grow by mergers with other haloes as well as accretion of "diffuse" non-halo material. We quantify the mass growth rates via these two processes, dM_mer/dt and dM_dif/dt, and their dependence on halo environment using the ~500,000 haloes in the Millennium simulation. Adopting a local mass density parameter as a measure of halo environment, we find the two rates show strong but opposite environmental dependence, with mergers playing an increasingly important role for halo growths in overdense regions and diffuse accretion dominating growth in voids. This behaviour is independent of the mass cuts used to define haloes vs non-haloes. For galaxy-scale haloes, these two opposite correlations largely cancel out, but a weak environmental dependence remains that results in a slightly lower mean total growth rate, and hence an earlier mean formation redshift, for haloes in denser regions. The mean formation redshift of the ~5000 cluster-mass haloes, on the other hand, appears to have no correlation with halo environment. The origin of the positive correlation of dM_mer/dt with local density can be traced to the surrounding mass reservoir outside the haloes, where more progenitor haloes are available in denser regions. The negative correlation of dM_dif/dt with density, however, is not explained by the available diffuse mass in the reservoir, which is in fact larger in denser regions. The non-halo component may therefore be partially comprised of truly diffuse dark matter particles that are dynamically hotter and are accreted at a suppressed rate in denser regions. We also discuss the implications of these results for how to modify the Extended Press-Schechter model of halo growth, which in its original form does not predict environmental dependence.

CAN OLD GALAXIES AT HIGH REDSHIFTS AND BARYON ACOUSTIC OSCILLATIONS CONSTRAIN H 0 ?

A new age--redshift test is proposed in order to constrain H 0 on the basis of the existence of old high-redshift galaxies (OHRGs). In the flat Λ cold dark matter model, the value of H 0 is heavily dependent on the mass density parameter Ω M = 1 – ΩΛ. Such a degeneracy can be broken through a joint analysis involving the OHRG and baryon acoustic oscillation signature. By assuming a galaxy incubation time, t inc = 0.8 ± 0.4 Gyr, our joint analysis yields a value of H 0 = 71 ± 4 km s–1 Mpc–1 (1σ) with the best-fit density parameter Ω M = 0.27 ± 0.03. Such results are in good agreement with independent studies from the Hubble Space Telescope key project and recent estimates of the Wilkinson Microwave Anisotropy Probe, thereby suggesting that the combination of these two independent phenomena provides an interesting method to constrain the Hubble constant.

DARK ENERGY IN GLOBAL BRANE UNIVERSE

We discuss the exact solutions of brane universes and the results indicate that the Friedmann equations on the branes are modified with a new density term. Then, we assume the new term as the density of dark energy. Using Wetterich's parametrization equation of state (EOS) of dark energy, we obtain that the new term varies with the redshift z. Finally, the evolutions of the mass density parameter Ω2, dark energy density parameter Ωx and deceleration parameter q2 are studied.

Constraining H0 from the Sunyaev–Zel'dovich effect, galaxy cluster X-ray data and baryon oscillations

Abstract Estimates of H0 from the Sunyaev–Zel'dovich effect (SZE) and X-ray surface brightness of galaxy clusters depends on the underlying cosmology. In the current Λ cold dark matter (ΛCDM) flat cosmology, a possible technique to broke the degeneracy on the mass density parameter (Ωm) is to apply a joint analysis involving the baryon acoustic oscillations (BAOs). By adopting this technique to the (H0, Ωm) parameter space, we obtain new constraints on the Hubble constant H0 from BAO signatures as given by the Sloan Digital Sky Survey (SDSS) catalogue. Our analysis based on the SZE/X-ray data for a sample of 25 clusters yields H0= 74+4−3.5 km s−1 Mpc−1 (1σ, neglecting systematic uncertainties). This result is in good agreement with independent studies from the Hubble Space Telescope key project and the recent estimates of the Wilkinson Microwave Anisotropy Probe, thereby suggesting that the combination of these three independent phenomena provides an interesting method to constrain the Hubble constant.

Dynamical and structural properties of charged and uncharged lidocaine in a lipid bilayer

Molecular dynamics computer simulations have been performed to investigate dynamical and structural properties of a lidocaine local anesthetic. Both charged and uncharged forms of the lidocaine molecule were investigated. Properties such as membrane area per lipid, diffusion, mass density, bilayer penetration and order parameters have been examined. An analysis of the lidocaine interaction with the lipid surrounding according to a simple mean field theory has also been performed. Almost all examined properties were found to depend on which of the two forms of lidocaine, charged or uncharged, is studied. The overall picture is a rather static behavior determined by the lipids for the charged molecules and more mobile situation of the uncharged form with higher diffusion and lower orientational and positional order.