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

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

The general form of supersymmetric solutions of N=(1,0) U(1) and SU(2) gauged supergravities in six dimensions

We obtain necessary and sufficient conditions for a supersymmetric field configuration in the N=(1,0) U(1) or SU(2) gauged supergravities in six dimensions, and impose the field equations on this general ansatz. It is found that any supersymmetric solution is associated to an $SU(2)\ltimes \mathbb{R}^4$ structure. The structure is characterized by a null Killing vector which induces a natural 2+4 split of the six dimensional spacetime. A suitable combination of the field equations implies that the scalar curvature of the four dimensional Riemannian part, referred to as the base, obeys a second order differential equation. Bosonic fluxes introduce torsion terms that deform the $SU(2)\ltimes\mathbb{R}^4$ structure away from a covariantly constant one. The most general structure can be classified in terms of its intrinsic torsion. For a large class of solutions the gauge field strengths admit a simple geometrical interpretation: in the U(1) theory the base is K\"{a}hler, and the gauge field strength is the Ricci form; in the SU(2) theory, the gauge field strengths are identified with the curvatures of the left hand spin bundle of the base. We employ our general ansatz to construct new supersymmetric solutions; we show that the U(1) theory admits a symmetric Cahen-Wallach$_4\times S^2$ solution together with a compactifying pp-wave. The SU(2) theory admits a black string, whose near horizon limit is $AdS_3\times S_3$. We also obtain the Yang-Mills analogue of the Salam-Sezgin solution of the U(1) theory, namely $R^{1,2}\times S^3$, where the $S^3$ is supported by a sphaleron. Finally we obtain the additional constraints implied by enhanced supersymmetry, and discuss Penrose limits in the theories.Comment: 1+29 pages, late

Variant N=(1,1) Supergravity and (Minkowski)_4 x S^2 Vacua

We construct the fermionic sector and supersymmetry transformation rules of a variant N=(1,1) supergravity theory obtained by generalized Kaluza-Klein reduction from seven dimensions. We show that this model admits both (Minkowski)_4 x S^2 and (Minkowski)_3 x S^3 vacua. We perform a consistent Kaluza-Klein reduction on S^2 and obtain D=4, N=2 supergravity coupled to a vector multiplet, which can be consistently truncated to give rise to D=4, N=1 supergravity with a chiral multiplet.Comment: Latex, 17 pages. Version appearing in Classical and Quantum Gravit

British research in accounting and finance (2001–2007): the 2008 research assessment exercise

No abstract available

Lagrangian filtered density function for LES-based stochastic modelling of turbulent dispersed flows

The Eulerian-Lagrangian approach based on Large-Eddy Simulation (LES) is one of the most promising and viable numerical tools to study turbulent dispersed flows when the computational cost of Direct Numerical Simulation (DNS) becomes too expensive. The applicability of this approach is however limited if the effects of the Sub-Grid Scales (SGS) of the flow on particle dynamics are neglected. In this paper, we propose to take these effects into account by means of a Lagrangian stochastic SGS model for the equations of particle motion. The model extends to particle-laden flows the velocity-filtered density function method originally developed for reactive flows. The underlying filtered density function is simulated through a Lagrangian Monte Carlo procedure that solves for a set of Stochastic Differential Equations (SDEs) along individual particle trajectories. The resulting model is tested for the reference case of turbulent channel flow, using a hybrid algorithm in which the fluid velocity field is provided by LES and then used to advance the SDEs in time. The model consistency is assessed in the limit of particles with zero inertia, when "duplicate fields" are available from both the Eulerian LES and the Lagrangian tracking. Tests with inertial particles were performed to examine the capability of the model to capture particle preferential concentration and near-wall segregation. Upon comparison with DNS-based statistics, our results show improved accuracy and considerably reduced errors with respect to the case in which no SGS model is used in the equations of particle motion

Drag Reduction by Polymers in Wall Bounded Turbulence

We address the mechanism of drag reduction by polymers in turbulent wall bounded flows. On the basis of the equations of fluid mechanics we present a quantitative derivation of the "maximum drag reduction (MDR) asymptote" which is the maximum drag reduction attained by polymers. Based on Newtonian information only we prove the existence of drag reduction, and with one experimental parameter we reach a quantitative agreement with the experimental measurements.Comment: 4 pages, 1 fig., included, PRL, submitte

Bedrock Geologic Map of Iowa

https://ir.uiowa.edu/igs_ofm/1070/thumbnail.jp