Reconciling a Small Density Parameter to Inflation

Hemoglobin is the specific protein of red blood cells. Those cells in which hemoglobin synthesis is initiated are the earliest cells that can presently be considered to be committed to erythropoiesis. In order to identify such early cells electron microscopically, we have made use of the peroxidatic activity of hemoglobin by reacting the marrow of erythropoietically stimulated guinea pigs with diaminobenzidine (DAB). The reaction product appeared as a diffuse and amorphous electron opacity throughout the cytoplasm of reactive cells. The detection of small density increases of such a diffuse nature required an analytical method more sensitive and reliable than the visual examination of micrographs. A procedure was therefore devised for the evaluation of micrographs (negatives) with a densitometer (Weston Photographic Analyzer).

Download Full-text

Estimation of Vegetation-Induced Flow Resistance for Hydraulic Computations Using Airborne Laser Scanning Data

Water ◽

10.3390/w13131864 ◽

2021 ◽

Vol 13 (13) ◽

pp. 1864

Author(s):

Peter Mewis

Keyword(s):

Laser Scanning ◽

Flow Resistance ◽

Laser Scanner ◽

Airborne Laser Scanning ◽

Density Parameter ◽

Vegetation Density ◽

Airborne Laser Scanner ◽

Airborne Laser ◽

Bed Roughness ◽

Available Information

The effect of vegetation in hydraulic computations can be significant. This effect is important for flood computations. Today, the necessary terrain information for flood computations is obtained by airborne laser scanning techniques. The quality and density of the airborne laser scanning information allows for more extensive use of these data in flow computations. In this paper, known methods are improved and combined into a new simple and objective procedure to estimate the hydraulic resistance of vegetation on the flow in the field. State-of-the-art airborne laser scanner information is explored to estimate the vegetation density. The laser scanning information provides the base for the calculation of the vegetation density parameter ωp using the Beer–Lambert law. In a second step, the vegetation density is employed in a flow model to appropriately account for vegetation resistance. The use of this vegetation parameter is superior to the common method of accounting for the vegetation resistance in the bed resistance parameter for bed roughness. The proposed procedure utilizes newly available information and is demonstrated in an example. The obtained values fit very well with the values obtained in the literature. Moreover, the obtained information is very detailed. In the results, the effect of vegetation is estimated objectively without the assignment of typical values. Moreover, a more structured flow field is computed with the flood around denser vegetation, such as groups of bushes. A further thorough study based on observed flow resistance is needed.

Download Full-text

The effects of peculiar velocities in SN Ia environments on the local H0 measurement

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3456 ◽

2020 ◽

Vol 500 (3) ◽

pp. 3728-3742

Author(s):

Thomas M Sedgwick ◽

Chris A Collins ◽

Ivan K Baldry ◽

Philip A James

Keyword(s):

Hubble Constant ◽

Density Parameter ◽

Host Galaxies ◽

Peculiar Velocities ◽

Standard Candle ◽

Modern Cosmology ◽

Type Ia ◽

The Difference ◽

Ia Supernovae ◽

Distance Indicators

ABSTRACT The discrepancy between estimates of the Hubble constant (H0) measured from local (z ≲ 0.1) scales and from scales of the sound horizon is a crucial problem in modern cosmology. Peculiar velocities (vpec) of standard candle distance indicators can systematically affect local H0 measurements. We here use 2MRS galaxies to measure the local galaxy density field, finding a notable z < 0.05 underdensity in the SGC-6dFGS region of 27 ± 2 per cent. However, no strong evidence for a ‘Local Void’ pertaining to the full 2MRS sky coverage is found. Galaxy densities are used to measure a density parameter, Δϕ+−, which we introduce as a proxy for vpec that quantifies density gradients along a supernova (SN) line of sight. Δϕ+− is found to correlate with local H0 estimates from 88 Pantheon Type Ia supernovae (SNe Ia; 0.02 < z < 0.05). Density structures on scales of ∼50 Mpc are found to correlate strongest with H0 estimates in both the observational data and in mock data from the MDPL2-Galacticus simulation. Using trends of H0 with Δϕ+−, we can correct for the effects of density structure on local H0 estimates, even in the presence of biased vpec. However, the difference in the inferred H0 estimate with and without the peculiar velocity correction is limited to < 0.1 per cent. We conclude that accounting for environmentally induced peculiar velocities of SN Ia host galaxies does not resolve the tension between local and CMB-derived H0 estimates.

Download Full-text

An Overall Approach for Microcrack and Inhomogeneity Toughening in Brittle Solids

Journal of Mechanics ◽

10.1017/s1727719100000332 ◽

1999 ◽

Vol 15 (2) ◽

pp. 57-68

Author(s):

Huang Hsing Pan

Keyword(s):

Poisson Ratio ◽

Crack Density ◽

Mean Field ◽

Analytic Form ◽

Density Parameter ◽

Brittle Solids ◽

The Matrix ◽

Microcrack Toughening ◽

Average Quantity ◽

The Mean

ABSTRACTBased on the weight function theory and Hutchinson's technique, the analytic form of the toughness change near a crack-tip is derived. The inhomogeneity toughening is treated as an average quantity calculated from the mean-field approach. The solutions are suitable for the composite materials with moderate concentration as compared with Hutchinson's lowest order formula. The composite has the more toughened property if the matrix owns the higher value of the Poisson ratio. The composite with thin-disc inclusions obtains the highest toughening and that with spheres always provides the least effective one. For the microcrack toughening, the variations of the crack shape do not significantly affect the toughness change if the Budiansky and O'Connell crack density parameter is used. The explicit forms for three types of the void toughening and two types of the microcrack toughening are also shown.

Download Full-text

On Population III Star Formation

Symposium - International Astronomical Union ◽

10.1017/s0074180900038778 ◽

1983 ◽

Vol 104 ◽

pp. 119-120

Author(s):

A. Kashlinsky ◽

M. J. Rees

Keyword(s):

Background Radiation ◽

Free Fall ◽

Compact Objects ◽

Centrifugal Forces ◽

Tidal Interactions ◽

Geometrical Cross Section ◽

Spin Parameter ◽

Small Density ◽

Major Factors ◽

Population Iii

If primordial fluctuations were isothermal their amplitude at recombination would be non-linear on scales Mo ≃ 106÷9 M⊙. Since the Jeans mass after recombination is MJo ≃ 8 × 105 Ω−1/2 M⊙ the clouds of mass Mo would be able to form the first generation of compact objects, the so-called Population III. These clouds would acquire angular momentum via tidal interactions with their neighbours. The importance of rotation can be conveniently characterised by the spin parameter λ = Vrotation/Vfree-fall and tidal interactions lead to a spin λo = 0.07 ± 0.03. As the cloud collapses λ increases as r−1/2. Any fragment forming in a rotating cloud would have the same spin λ as the whole cloud. It could therefore collapse only by ≃ λo2 in radius before centrifugal forces intervened, thus leaving a large geometrical cross-section for coalescence to be important. At radii r ≲ λo8/5 (Mo/MJo)2/15 ro the coalescence time is shorter than the free-fall time and no fragmentation is possible below this radius. In the primordial clouds two major factors prevent fragmentation at larger radii. First, the background radiation is still ‘hot’ and the trapping of it would prevent fragmentation until the whole cloud has collapsed to a radius 10−2 x−2/3 ro. Here x = 10−2(M/107 M⊙)1/3 is the ionization fraction given by the balance between gravitational contraction and recombination cooling. Furthermore, any small density fluctuation would lead to fragmentation only after the paternal cloud had collapsed by a factor (δ/5)2/3 in radius. For these reasons fragmentation is unlikely until centrifugal forces halt the collapse and a disk forms. The disk will be initially at T ≃ 104K but after a small fraction of H2 forms it will cool to T3 ≃ T/103K ≃ 1 and the final fragments mass could be as low as ≃ 0.2(λo/0.07)4 T32(MJo/Mo)1/3 M⊙.

Download Full-text

Background Light from Population III Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900150636 ◽

1987 ◽

Vol 117 ◽

pp. 414-414

Author(s):

Jonathan C. McDowell

Keyword(s):

Dark Matter ◽

Background Radiation ◽

Large Fraction ◽

Rest Mass ◽

Critical Density ◽

Density Parameter ◽

Extragalactic Background Light ◽

Background Light ◽

Far Ultraviolet ◽

The Universe

It has been proposed (e.g. Carr, Bond and Arnett 1984) that the first generation of stars may have been Very Massive Objects (VMOs, of mass above 200 M⊙) which existed at large redshifts and left a large fraction of the mass of the universe in black hole remnants which now provide the dynamical ‘dark matter’. The radiation from these stars would be present today as extragalactic background light. For stars with density parameter Ω* which convert a fraction ϵ of their rest-mass to radiation at a redshift of z, the energy density of background radiation in units of the critical density is ΩR = εΩ* / (1+z). The VMOs would be far-ultraviolet sources with effective temperatures of 105 K. If the radiation is not absorbed, the constraints provided by measurements of background radiation imply (for H =50 km/s/Mpc) that the stars cannot close the universe unless they formed at a redshift of 40 or more. To provide the dark matter (of one-tenth closure density) the optical limits imply that they must have existed at redshifts above 25.

Download Full-text

An Improved Approach for Reduction of Defect Density Using Optimal Module Sizes

Advances in Software Engineering ◽

10.1155/2014/803530 ◽

2014 ◽

Vol 2014 ◽

pp. 1-7 ◽

Cited By ~ 4

Author(s):

Dinesh Verma ◽

Shishir Kumar

Keyword(s):

Goodness Of Fit ◽

Defect Density ◽

Optimal Size ◽

Data Sets ◽

Density Parameter ◽

Proposed Model ◽

Module Size ◽

Curve Fitting Method ◽

Improved Model ◽

Effective Distribution

Nowadays, software developers are facing challenges in minimizing the number of defects during the software development. Using defect density parameter, developers can identify the possibilities of improvements in the product. Since the total number of defects depends on module size, so there is need to calculate the optimal size of the module to minimize the defect density. In this paper, an improved model has been formulated that indicates the relationship between defect density and variable size of modules. This relationship could be used for optimization of overall defect density using an effective distribution of modules sizes. Three available data sets related to concern aspect have been examined with the proposed model by taking the distinct values of variables and parameter by putting some constraint on parameters. Curve fitting method has been used to obtain the size of module with minimum defect density. Goodness of fit measures has been performed to validate the proposed model for data sets. The defect density can be optimized by effective distribution of size of modules. The larger modules can be broken into smaller modules and smaller modules can be merged to minimize the overall defect density.

Download Full-text

Distribution of crack density parameter in Central Betic Cordillera (Southern Spain)

Geophysical Journal International ◽

10.1093/gji/ggt394 ◽

2013 ◽

Vol 196 (1) ◽

pp. 22-33 ◽

Cited By ~ 2

Author(s):

Inmaculada Serrano ◽

Federico Torcal ◽

José Morales

Keyword(s):

Crack Density ◽

Betic Cordillera ◽

Southern Spain ◽

Density Parameter

Download Full-text

Statistics of Cosmic Microwave Background Radiation with the Cosmic String Model

International Journal of Modern Physics D ◽

10.1142/s0218271897000327 ◽

1997 ◽

Vol 06 (05) ◽

pp. 535-544

Author(s):

Petri Mähönen ◽

Tetsuya Hara ◽

Toivo Voll ◽

Shigeru Miyoshi

Keyword(s):

Cosmic Microwave Background ◽

Cosmic String ◽

Large Scale ◽

Background Radiation ◽

Unit Length ◽

Angular Size ◽

Cosmic Microwave Background Radiation ◽

Density Parameter ◽

Microwave Background ◽

Microwave Background Radiation

We have studied the cosmic microwave background radiation by simulating the cosmic string network induced anisotropies on the sky. The large-angular size simulations are based on the Kaiser–Stebbins effect calculated from full cosmic-string network simulation. The small-angular size simulations are done by Monte-Carlo simulation of perturbations from a time-discretized toy model. We use these results to find the normalization of μ, the string mass per unit length, and compare this result with one needed for large-scale structure formation. We show that the cosmic string scenario is in good agreement with COBE, SK94, and MSAM94 microwave background radiation experiments with reasonable string network parameters. The predicted rms-temperature fluctuations for SK94 and MSAM94 experiments are Δ T/T=1.57×10-5 and Δ T/T=1.62×10-5, respectively, when the string mass density parameter is chosen to be Gμ=1.4×10-6. The possibility of detecting non-Gaussian signals using the present day experiments is also discussed.

Download Full-text