scholarly journals Constancy of the cluster gas mass fraction in the R h = ct Universe

2016 ◽  
Vol 472 (2186) ◽  
pp. 20150765 ◽  
Author(s):  
F. Melia
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Accurate Determination ◽  
Information Criterion ◽  
Angular Distance ◽  
Link Type ◽  
Mass Fractions ◽  
Parameter Values ◽  
Baryonic Mass

The ratio of baryonic to dark matter densities is assumed to have remained constant throughout the formation of structure. With this, simulations show that the fraction f gas ( z ) of baryonic mass to total mass in galaxy clusters should be nearly constant with redshift z . However, the measurement of these quantities depends on the angular distance to the source, which evolves with z according to the assumed background cosmology. An accurate determination of f gas ( z ) for a large sample of hot ( kT e >5 keV), dynamically relaxed clusters could therefore be used as a probe of the cosmological expansion up to z <2. The fraction f gas ( z ) would remain constant only when the correct cosmology is used to fit the data. In this paper, we compare the predicted gas mass fractions for both Λ cold dark matter ( Λ CDM) and the R h = ct Universe and test them against the three largest cluster samples (LaRoque et al. 2006 Astrophys. J. 652, 917–936 ( doi:10.1086/508139 ); Allen et al. 2008 Mon. Not. R. Astron. Soc. 383, 879–896 ( doi:10.1111/j.1365-2966.2007.12610.x ); Ettori et al. 2009 Astron. Astrophys. 501, 61–73 ( doi:10.1051/0004-6361/200810878 )). We show that R h = ct is consistent with a constant f gas in the redshift range z ≲ 2 , as was previously shown for the reference Λ CDM model (with parameter values H 0 =70 km s −1  Mpc −1 , Ω m =0.3 and w Λ =−1). Unlike Λ CDM, however, the R h = ct Universe has no free parameters to optimize in fitting the data. Model selection tools, such as the Akaike information criterion and the Bayes information criterion (BIC), therefore tend to favour R h = ct over Λ CDM. For example, the BIC favours R h = ct with a likelihood of approximately 95% versus approximately 5% for Λ CDM.

Development and Characterization of a Multimycotoxin Reference Material

2019 ◽  
Vol 102 (6) ◽  
pp. 1642-1650 ◽  
Author(s):  
Melissa M. Phillips ◽  
Tomás M. López Seal ◽  
Jennifer M. Ness ◽  
Kai Zhang
Keyword(s):  
Interlaboratory Comparison ◽  
Accurate Determination ◽  
Data Sets ◽  
Mass Fractions ◽  
Adequate Quality ◽  
Multiple Sample ◽  
Lc Tandem Ms ◽  
The U.S

Background: Matrix-matched reference materials (RMs) are critical for adequate quality assurance of extraction, digestion, separation, and/or detection processes for analytes of interest in foods and dietary supplements. The accurate determination of mycotoxins in foods is an international concern. While RMs for mycotoxins are available from a variety of RM producers, these mainly address a single mycotoxin or group of mycotoxins and therefore require the use of multiple RMs for multitarget methods. Objective: To address the increasing needs of laboratories moving toward LC-MS-based multimycotoxin analysis, the U.S. National Institute of Standards and Technology (NIST) collaborated with the U.S. Food and Drug Administration (FDA) to produce a naturally incurred RM for multiple mycotoxins in corn. Methods: Homogeneity of the RM has been assessed using a stratified random sampling of the final product based on mycotoxin mass fractions measured by the FDA and NIST. Multiple sample sizes were evaluated to maximize homogeneity in the obtained results. The mycotoxin levels in the final materials have been evaluated via interlaboratory comparison and isotope dilution LC–tandem MS measurements made at the FDA and NIST. The final value assignment combined results from these data sets. Conclusions: The study successfully developed a certified RM, SRM 1565 Mycotoxins in Corn, and a workflow for the future development of multimycotoxin RMs in different matrices.

scholarly journals How dark are filaments in the cosmic web?

2020 ◽  
Vol 498 (3) ◽  
pp. 3158-3170
Author(s):  
Tianyi Yang ◽  
Michael J Hudson ◽  
Niayesh Afshordi
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Weak Lensing ◽  
Sky Survey ◽  
Mass Fractions ◽  
The Masses ◽  
Red Galaxies

ABSTRACT The cold dark matter model predicts that dark matter haloes are connected by filaments. Direct measurements of the masses and structure of these filaments are difficult, but recently several studies have detected these dark-matter-dominated filaments using weak lensing. Here we study the efficiency of galaxy formation within the filaments by measuring their total mass-to-light ratios and stellar mass fractions. Specifically, we stack pairs of luminous red galaxies (LRGs) with a typical separation on the sky of 8 h−1 Mpc. We stack background galaxy shapes around pairs to obtain mass maps through weak lensing, and we stack galaxies from the Sloan Digital Sky Survey to obtain maps of light and stellar mass. To isolate the signal from the filament, we construct two matched catalogues of physical and non-physical (projected) LRG pairs, with the same distributions of redshift and separation. We then subtract the two stacked maps. Using LRG pair samples from the Baryon Oscillation Spectroscopic Survey at two different redshifts, we find that the evolution of the mass in filament is consistent with the predictions from perturbation theory. The filaments are not entirely dark: Their mass-to-light ratios (M/L = 351 ± 137 in solar units in the rband) and stellar mass fractions (Mstellar/M = 0.0073 ± 0.0030) are consistent with the cosmic values (and with their redshift evolutions).

scholarly journals Developing an internally consistent methodology for K-feldspar MAAD TL thermochronology

2021 ◽  
Author(s):  
Nathan Brown ◽  
Edward Rhodes
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Dose Response ◽  
Accurate Determination ◽  
Rock Surface ◽  
Exhumation Rates ◽  
Parameter Values ◽  
Center Density ◽  
Best Fit

Luminescence thermochronology and thermometry can quantify recent changes in rock exhumation rates and rock surface temperatures, but these methods require accurate determination of several kinetic parameters. For K-feldspar thermoluminescence (TL) glow curves, which comprise overlapping signals of different thermal stability, it is challenging to develop measurements that capture these parameter values. Here, we present multiple-aliquot additive-dose (MAAD) TL dose response and fading measurements from bedrock-extracted K-feldspars. These measurements are compared with Monte Carlo simulations to identify best-fit values for recombination center density ($\rho$) and activation energy ($\Delta E$). This is done for each dataset separately, and then by combining dose-response and fading misfits to yield more precise $\rho$ and $\Delta E$ values consistent with both experiments. Finally, these values are used to estimate the characteristic dose ($D_0$) of samples. This approach produces kinetic parameter values consistent with comparable studies and results in expected fractional saturation differences between samples.

scholarly journals Stellar profile independent determination of the dark matter distribution of the Fornax Local Group dwarf spheroidal galaxy

2020 ◽  
Vol 501 (2) ◽  
pp. 2332-2351
Author(s):  
Sasha R Brownsberger ◽  
Lisa Randall
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Local Group ◽  
Axial Ratio ◽  
Dwarf Spheroidal Galaxies ◽  
Stellar Velocity ◽  
Best Fitting ◽  
Kinematic Models ◽  
Velocity Dispersions

ABSTRACT We detail a method to measure the correspondence between dark matter (DM) models and observations of stellar populations within Local Group dwarf spheroidal galaxies (LG dSphs) that assumes no parametric stellar distribution. Solving the spherical or cylindrical Jeans equations, we calculate the consistency of DM and stellar kinematic models with stellar positions and line-of-sight velocities. Our method can be used to search for signals of standard and exotic DM distributions. Applying our methodology to the Fornax LG dSph and using statistical bootstrapping, we find: (i) that oblate or prolate cored DM haloes match the stellar data, respectively, ≃60 or ≃370 times better than oblate or prolate cusped DM haloes for isotropic and isothermal stellar velocity dispersions, (ii) that cusped spherical DM haloes and cored spherical DM haloes match the Fornax data similarly well for isotropic stellar velocity dispersions, (iii) that the semiminor to semimajor axial ratio of spheroidal DM haloes are more extreme than 80 per cent of those predicted by Lambda cold dark matter with baryon simulations, (iv) that oblate cored or cusped DM haloes are, respectively, ≃5 or ≃30 times better matches to Fornax than prolate cored or cusped DM haloes, and (v) that Fornax shows no evidence of a disc-like structure with more than two per cent of the total DM mass. We further note that the best-fitting cusped haloes universally favour the largest mass and size fit parameters. If these extreme limits are decreased, the cusped halo likelihoods decrease relative to those of cored haloes.

Accurate determination of meat mass fractions using DNA measurements for quantifying meat adulteration by digital PCR

2021 ◽  
Author(s):  
Sasithon Temisak ◽  
Pattanapong Thangsunan ◽  
Jiranun Boonnil ◽  
Watiporn Yenchum ◽  
Kanjana Hongthong ◽  
...  
Keyword(s):  
Accurate Determination ◽  
Digital Pcr ◽  
Mass Fractions ◽  
Dna Measurements

scholarly journals Galaxy Formation in a Universe Dominated by Cold Dark Matter

1987 ◽  
Vol 117 ◽  
pp. 360-360
Author(s):  
Edmund Bertschinger
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Globular Clusters ◽  
Cold Dark Matter ◽  
Mass Function ◽  
Spherical Approximation ◽  
De Sitter ◽  
Density Peaks ◽  
Lower Amplitude ◽  
Baryonic Mass

ABSTRACT The mass spectrum of bound baryonic systems (galaxies and globular clusters) is computed as a function of redshift in an Einstein-de Sitter (Ω=1) universe dominated by weakly interacting, cold dark matter. Baryons are assumed to fall into primordial density peaks in the cold particle distribution when the mass in the peaks exceeds the baryon Jeans mass. The distribution of peaks is computed using Gaussian statistics. As the universe expands the baryonic mass attached to a given peak increases because of infall (treated in a spherical approximation), and new peaks of lower amplitude become nonlinear. Globular clusters form first (by z∼40 if the galaxies represent a biased mass distribution). The remaining gas may be reheated to ∼10000 K if a few percent of globular cluster (or Pop. III) stars are very massive. Reheating increases the baryon Jeans mass and delays galaxy formation until z≲10. The present method reproduces the shape (but not the amplitude) of the Schechter galaxy mass function when merging of substructure is included in an approximate fashion.

Development and Characterization of a Multimycotoxin Reference Material

2019 ◽  
Vol 102 (6) ◽  
pp. 1642-1650 ◽  
Author(s):  
Melissa M Phillips ◽  
Tomás M López Seal ◽  
Jennifer M Ness ◽  
Kai Zhang
Keyword(s):  
Interlaboratory Comparison ◽  
Accurate Determination ◽  
Data Sets ◽  
Mass Fractions ◽  
Adequate Quality ◽  
Multiple Sample ◽  
Lc Tandem Ms ◽  
The U.S

Abstract Background: Matrix-matched reference materials (RMs) are critical for adequate quality assurance of extraction, digestion, separation, and/or detection processes for analytes of interest in foods and dietary supplements. The accurate determination of mycotoxins in foods is an international concern. While RMs for mycotoxins are available from a variety of RM producers, these mainly address a single mycotoxin or group of mycotoxins and therefore require the use of multiple RMs for multitarget methods. Objective: To address the increasing needs of laboratories moving toward LC-MS-based multimycotoxin analysis, the U.S. National Institute of Standards and Technology (NIST) collaborated with the U.S. Food and Drug Administration (FDA) to produce a naturally incurred RM for multiple mycotoxins in corn. Methods: Homogeneity of the RM has been assessed using a stratified random sampling of the final product based on mycotoxin mass fractions measured by the FDA and NIST. Multiple sample sizes were evaluated to maximize homogeneity in the obtained results. The mycotoxin levels in the final materials have been evaluated via interlaboratory comparison and isotope dilution LC–tandem MS measurements made at the FDA and NIST. The final value assignment combined results from these data sets. Conclusions: The study successfully developed a certified RM, SRM 1565 Mycotoxins in Corn, and a workflow for the future development of multimycotoxin RMs in different matrices.

scholarly journals Multivariate chemometrics as a key tool for prediction of K and Fe in a diverse German agricultural soil-set using EDXRF

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Dominique Büchele ◽  
Madlen Chao ◽  
Markus Ostermann ◽  
Matthias Leenen ◽  
Ilko Bald
Keyword(s):  
Precision Agriculture ◽  
Accurate Determination ◽  
Principal Component ◽  
Least Squares Regression ◽  
Calibration Sample ◽  
Mass Fractions ◽  
Study Sites ◽  
Sample Set

AbstractWithin the framework of precision agriculture, the determination of various soil properties is moving into focus, especially the demand for sensors suitable for in-situ measurements. Energy-dispersive X-ray fluorescence (EDXRF) can be a powerful tool for this purpose. In this study a huge diverse soil set (n = 598) from 12 different study sites in Germany was analysed with EDXRF. First, a principal component analysis (PCA) was performed to identify possible similarities among the sample set. Clustering was observed within the four texture classes clay, loam, silt and sand, as clay samples contain high and sandy soils low iron mass fractions. Furthermore, the potential of uni- and multivariate data evaluation with partial least squares regression (PLSR) was assessed for accurate determination of nutrients in German agricultural samples using two calibration sample sets. Potassium and iron were chosen for testing the performance of both models. Prediction of these nutrients in 598 German soil samples with EDXRF was more accurate using PLSR which is confirmed by a better overall averaged deviation and PLSR should therefore be preferred.

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