Effect of Soil Buffer Capacity on Soil Reaction (pH) Modification and Subsequent Effects on Growth and Nutrient Uptake of Plantanus occidentalis L. Seedlings

The buffer capacity of a soil is a significant factor in determining the longevity of soil reaction (pH) adjustments by aluminum sulfate, Al2(SO4)3, or calcium carbonate, CaCO₂. After 12 weeks the modified pH values of the highly buffered Emory silt loam had changed substantially toward the original pH value of 7.6. Modified pH values for the Groseclose silt loam soil remained essentially unchanged under the same conditions. These differences in soil response to modified soil pH are related to the differences in the percentage of vermiculite chlorite and chlorite in the clay fractions of the two soils. The longevity of soil pH modification is related to total sycamore seedling dry weight and nutrient uptake. Though these components were significantly affected for plants grown in a Groseclose soil, the lack of significant response differences, except at the extremely low pH adjustment (5.21), in the Emory soil suggests a rapid change in modified soil pH toward the original soil pH value. The condition of the seedlings coupled with total dry weight accumulation and foliar nutrient content elimiates acid toxicity as a factor affecting growth and nutrient uptake. Plants grown in the Groseclose soil at pH 4.31 could be the exception

Effect of Soil Buffer Capacity on Soil Reaction (pH) Modification and Subsequent Effects on Growth and Nutrient Uptake of Plantanus occidentalis L. Seedlings

The buffer capacity of a soil is a significant factor in determining the longevity of soil reaction (pH) adjustments by aluminum sulfate, Al2(SO4)3, or calcium carbonate, CaCO₂. After 12 weeks the modified pH values of the highly buffered Emory silt loam had changed substantially toward the original pH value of 7.6. Modified pH values for the Groseclose silt loam soil remained essentially unchanged under the same conditions. These differences in soil response to modified soil pH are related to the differences in the percentage of vermiculite chlorite and chlorite in the clay fractions of the two soils. The longevity of soil pH modification is related to total sycamore seedling dry weight and nutrient uptake. Though these components were significantly affected for plants grown in a Groseclose soil, the lack of significant response differences, except at the extremely low pH adjustment (5.21), in the Emory soil suggests a rapid change in modified soil pH toward the original soil pH value. The condition of the seedlings coupled with total dry weight accumulation and foliar nutrient content elimiates acid toxicity as a factor affecting growth and nutrient uptake. Plants grown in the Groseclose soil at pH 4.31 could be the exception

An exact relation between Eulerian and Lagrangian velocity increment statistics

We present a formal connection between Lagrangian and Eulerian velocity increment distributions which is applicable to a wide range of turbulent systems ranging from turbulence in incompressible fluids to magnetohydrodynamic turbulence. For the case of the inverse cascade regime of two-dimensional turbulence we numerically estimate the transition probabilities involved in this connection. In this context we are able to directly identify the processes leading to strongly non-Gaussian statistics for the Lagrangian velocity increments.Comment: 5 pages, 3 figure

A Minimalist Turbulent Boundary Layer Model

We introduce an elementary model of a turbulent boundary layer over a flat surface, given as a vertical random distribution of spanwise Lamb-Oseen vortex configurations placed over a non-slip boundary condition line. We are able to reproduce several important features of realistic flows, such as the viscous and logarithmic boundary sublayers, and the general behavior of the first statistical moments (turbulent intensity, skewness and flatness) of the streamwise velocity fluctuations. As an application, we advance some heuristic considerations on the boundary layer underlying kinematics that could be associated with the phenomenon of drag reduction by polymers, finding a suggestive support from its experimental signatures.Comment: 5 pages, 10 figure

Sub-Kolmogorov-Scale Fluctuations in Fluid Turbulence

We relate the intermittent fluctuations of velocity gradients in turbulence to a whole range of local dissipation scales generalizing the picture of a single mean dissipation length. The statistical distribution of these local dissipation scales as a function of Reynolds number is determined in numerical simulations of forced homogeneous isotropic turbulence with a spectral resolution never applied before which exceeds the standard one by at least a factor of eight. The core of the scale distribution agrees well with a theoretical prediction. Increasing Reynolds number causes the generation of ever finer local dissipation scales. This is in line with a less steep decay of the large-wavenumber energy spectra in the dissipation range. The energy spectrum for the highest accessible Taylor microscale Reynolds number R_lambda=107 does not show a bottleneck.Comment: 8 pages, 5 figures (Figs. 1 and 3 in reduced quality

Large-eddy simulations of stratified plane Couette flow using the anisotropic minimum-dissipation model

The anisotropic minimum-dissipation (AMD) model for large-eddy simulation (LES) has been recently developed, and here the model performance is examined in strat- ified plane Couette flow. To our knowledge this is the first use of the AMD model for resolved LES of stratified wall-bounded flow. A comparison with previously pub- lished direct numerical simulations (DNS) provides insight into model and grid re- quirements. Prandtl numbers of P r = 0.7 − 70 and a range of Richardson numbers show that the AMD LES performs well even with a strong stabilising buoyancy flux. We identify three new requirements for accurate LES of stratified wall-bounded flow. First, the LES must resolve the turbulent structures at the edge of the viscous sublayer in order to satisfy the Obukov length scale condition, L+s > 200. Other- wise the LES solution may laminarise where the DNS solution remains turbulent. Second, the LES must have enough vertical grid resolution within the viscous and diffusive sublayers to resolve the wall fluxes. Third, the grid must be reasonably isotropic (vertical-to-horizontal grid aspect ratio > 0.25) at the edge of the sublayer and through the turbulent interior for the AMD LES to correctly simulate the scalar flux. When these model requirements are fulfilled the AMD LES performs very well, producing vertical mean profiles, friction Reynolds number and Nusselt number con- sistent with DNS solutions at significantly higher grid resolution

Saturation of Turbulent Drag Reduction in Dilute Polymer Solutions

Drag reduction by polymers in turbulent wall-bounded flows exhibits universal and non-universal aspects. The universal maximal mean velocity profile was explained in a recent theory. The saturation of this profile and the crossover back to the Newtonian plug are non-universal, depending on Reynolds number Re, concentration of polymer $c_p$ and the degree of polymerization $N_p$. We explain the mechanism of saturation stemming from the finiteness of extensibility of the polymers, predict its dependence on $c_p$ and $N$ in the limit of small $c_p$ and large Re, and present the excellent comparison of our predictions to experiments on drag reduction by DNA.Comment: 4 pages, 4 figs., included, PRL, submitte

A bioenergetic model for zebrafish \u3ci\u3eDanio rerio\u3c/i\u3e (Hamilton)

A bioenergetics model was developed from observed consumption, respiration and growth rates for zebrafish Danio rerio across a range (18–32° C) of water temperatures, and evaluated with a 50 day laboratory trial at 28° C. No significant bias in variable estimates was found during the validation trial; namely, predicted zebrafish mass generally agreed with observed mass

The Spectral Energy Distribution and Infrared Luminosities of z ≈ 2 Dust-obscured Galaxies from Herschel and Spitzer

Dust-obscured galaxies (DOGs) are a subset of high-redshift (z ≈ 2) optically-faint ultra-luminous infrared galaxies (ULIRGs, e.g., L_(IR) > 10^(12) L_☉). We present new far-infrared photometry, at 250, 350, and 500 μm (observed-frame), from the Herschel Space Telescope for a large sample of 113 DOGs with spectroscopically measured redshifts. Approximately 60% of the sample are detected in the far-IR. The Herschel photometry allows the first robust determinations of the total infrared luminosities of a large sample of DOGs, confirming their high IR luminosities, which range from 10^(11.6) L_☉ 10^(13) L_☉. The rest-frame near-IR (1-3 μm) spectral energy distributions (SEDs) of the Herschel-detected DOGs are predictors of their SEDs at longer wavelengths. DOGs with "power-law" SEDs in the rest-frame near-IR show observed-frame 250/24 μm flux density ratios similar to the QSO-like local ULIRG, Mrk 231. DOGs with a stellar "bump" in their rest-frame near-IR show observed-frame 250/24 μm flux density ratios similar to local star-bursting ULIRGs like NGC 6240. None show 250/24 μm flux density ratios similar to extreme local ULIRG, Arp 220; though three show 350/24 μm flux density ratios similar to Arp 220. For the Herschel-detected DOGs, accurate estimates (within ~25%) of total IR luminosity can be predicted from their rest-frame mid-IR data alone (e.g., from Spitzer observed-frame 24 μm luminosities). Herschel-detected DOGs tend to have a high ratio of infrared luminosity to rest-frame 8 μm luminosity (the IR8 = L_(IR)(8-1000 μm)/νL_ν(8 μm) parameter of Elbaz et al.). Instead of lying on the z = 1-2 "infrared main sequence" of star-forming galaxies (like typical LIRGs and ULIRGs at those epochs) the DOGs, especially large fractions of the bump sources, tend to lie in the starburst sequence. While, Herschel-detected DOGs are similar to scaled up versions of local ULIRGs in terms of 250/24 μm flux density ratio, and IR8, they tend to have cooler far-IR dust temperatures (20-40 K for DOGs versus 40-50 K for local ULIRGs) as measured by the rest-frame 80/115 μm flux density ratios (e.g., observed-frame 250/350 μm ratios at z = 2). DOGs that are not detected by Herschel appear to have lower observed-frame 250/24 μm ratios than the detected sample, either because of warmer dust temperatures, lower IR luminosities, or both