Probing non-standard gravity with the growth index: a background independent analysis

Measurements of the growth index $\gamma(z)$ provide a clue as to whether Einstein's field equations encompass gravity also on large cosmic scales, those where the expansion of the universe accelerates. We show that the information encoded in this function can be satisfactorily parameterized using a small set of coefficients $\gamma_i$ in such a way that the true scaling of the growth index is recovered to better than $1\%$ in most dark energy and dark gravity models. We find that the likelihood of current data is maximal for $\gamma_0=0.74\pm 0.44$ and $\gamma_1=0.01\pm0.46$, a measurement compatible with the $\Lambda$CDM predictions. Moreover data favor models predicting slightly less growth of structures than the Planck LambdaCDM scenario. The main aim of the paper is to provide a prescription for routinely calculating, in an analytic way, the amplitude of the growth indices $\gamma_i$ in relevant cosmological scenarios, and to show that these parameters naturally define a space where predictions of alternative theories of gravity can be compared against growth data in a manner which is independent from the expansion history of the cosmological background. As the standard $\Omega$-plane provides a tool to identify different expansion histories $H(t)$ and their relation to various cosmological models, the $\gamma$-plane can thus be used to locate different growth rate histories $f(t)$ and their relation to alternatives model of gravity. As a result, we find that the Dvali-Gabadadze-Porrati gravity model is rejected with a $95\%$ confidence level. By simulating future data sets, such as those that a Euclid-like mission will provide, we also show how to tell apart LambdaCDM predictions from those of more extreme possibilities, such as smooth dark energy models, clustering quintessence or parameterized post-Friedmann cosmological models.Comment: 29 pages, 21 figure

Simulating Brain Tumor Heterogeneity with a Multiscale Agent-Based Model: Linking Molecular Signatures, Phenotypes and Expansion Rate

We have extended our previously developed 3D multi-scale agent-based brain tumor model to simulate cancer heterogeneity and to analyze its impact across the scales of interest. While our algorithm continues to employ an epidermal growth factor receptor (EGFR) gene-protein interaction network to determine the cells' phenotype, it now adds an explicit treatment of tumor cell adhesion related to the model's biochemical microenvironment. We simulate a simplified tumor progression pathway that leads to the emergence of five distinct glioma cell clones with different EGFR density and cell 'search precisions'. The in silico results show that microscopic tumor heterogeneity can impact the tumor system's multicellular growth patterns. Our findings further confirm that EGFR density results in the more aggressive clonal populations switching earlier from proliferation-dominated to a more migratory phenotype. Moreover, analyzing the dynamic molecular profile that triggers the phenotypic switch between proliferation and migration, our in silico oncogenomics data display spatial and temporal diversity in documenting the regional impact of tumorigenesis, and thus support the added value of multi-site and repeated assessments in vitro and in vivo. Potential implications from this in silico work for experimental and computational studies are discussed.Comment: 37 pages, 10 figure

Coupling DSSAT and HYDRUS-1D for simulations of soil water dynamics in the soil-plant-atmosphere system

Abstract Accurate estimation of the soil water balance of the soil-plant-atmosphere system is key to determining the availability of water resources and their optimal management. Evapotranspiration and leaching are the main sinks of water from the system affecting soil water status and hence crop yield. The accuracy of soil water content and evapotranspiration simulations affects crop yield simulations as well. DSSAT is a suite of field-scale, process-based crop models to simulate crop growth and development. A “tipping bucket” water balance approach is currently used in DSSAT for soil hydrologic and water redistribution processes. By comparison, HYDRUS-1D is a hydrological model to simulate water flow in soils using numerical solutions of the Richards equation, but its approach to crop-related process modeling is rather limited. Both DSSAT and HYDRUS-1D have been widely used and tested in their separate areas of use. The objectives of our study were: (1) to couple HYDRUS-1D with DSSAT to simulate soil water dynamics, crop growth and yield, (2) to evaluate the coupled model using field experimental datasets distributed with DSSAT for different environments, and (3) to compare HYDRUS-1D simulations with those of the tipping bucket approach using the same datasets. Modularity in the software design of both DSSAT and HYDRUS-1D made it easy to couple the two models. The pairing provided the DSSAT interface an ability to use both the tipping bucket and HYDRUS-1D simulation approaches. The two approaches were evaluated in terms of their ability to estimate the soil water balance, especially soil water contents and evapotranspiration rates. Values of the d index for volumetric water contents were 0.9 and 0.8 for the original and coupled models, respectively. Comparisons of simulations for the pod mass for four soybean and four peanut treatments showed relatively high d index values for both models (0.94–0.99)

On anisotropy function in crystal growth simulations using Lattice Boltzmann equation

In this paper, we present the ability of the Lattice Boltzmann (LB) equation, usually applied to simulate fluid flows, to simulate various shapes of crystals. Crystal growth is modeled with a phase-field model for a pure substance, numerically solved with a LB method in 2D and 3D. This study focuses on the anisotropy function that is responsible for the anisotropic surface tension between the solid phase and the liquid phase. The anisotropy function involves the unit normal vectors of the interface, defined by gradients of phase-field. Those gradients have to be consistent with the underlying lattice of the LB method in order to avoid unwanted effects of numerical anisotropy. Isotropy of the solution is obtained when the directional derivatives method, specific for each lattice, is applied for computing the gradient terms. With the central finite differences method, the phase-field does not match with its rotation and the solution is not any more isotropic. Next, the method is applied to simulate simultaneous growth of several crystals, each of them being defined by its own anisotropy function. Finally, various shapes of 3D crystals are simulated with standard and non standard anisotropy functions which favor growth in -, - and -directions

Regional Economic Policy: Structured Approach and Tools (The Oretical Formulation

The subject matter of the article is the development of a doctrine of coordinated regional development and the study of the structural quality of development of regional systems based on the theoretical analysis of institutional factors (parameters) that determine the technological efficiency of the regional economy. The purpose is to show possibilities of technological changes and the shift of economic growth in a particular regional system, with strict limits for accelerated development, with emphasis on industrial regions. For this purpose, we generated a number of structural models, analyzed the impact of technological factors on parameters of growth of the regional economy and determined conditions for development of industrial regions. We applied correlative and regression analysis to establish a statistically significant correlation between relevant parameters, used econometric models to show the possibility to estimate parameters of growth through control parameters, including technological factor. The structural aspect of regional economic growth is measured by dividing investments into two classes: old and new technologies. It is possible to increase the technological efficiency of the regional economy by improving results with regard to used (old) technologies and applying new technologies. This approach fundamentally refines the priority queue algorithm for regional development, provides a choice of a strategy of regional technological development. When resources are directed only to the latest technologies, the disproportion in development of the regional economic system can dramatically increase, and parameters related to diversion of resources and creation of a new resource will determine the growth rate of the region. The behavior of investment in old technologies has a major impact on the rate of regional economic growth in Russia, while investments in new technologies are minor and did not have an equivalent impact on the economic growth rate compared with old technologies. Institutional corrections that define parameters of resource diversion from old technologies and creation of a new resource for development, will determine the quality of new economic growth

Pensioner poverty over the next decade: what role for tax and benefit reform?

Recent falls in poverty amongst those aged 65 and over are unlikely to continue after 2007-08, even after the implementation of the proposals outlined in the Government's Pensions White Paper. This report looks at the prospects for pensioner poverty in England over the next decade. The authors find that that the proportion of those aged 65 and over living in poverty is set to remain at its current level - around one-in-five - between 2007-08 and 2017-18. This is despite the overall increase in the generosity of state pensions arising from the Pensions White Paper, and the fact that younger cohorts are expected to have more private pension income and higher employment rates at older ages than those preceding them

Single dose pharmacodynamics of amphotericin B against Aspergillus species in an in vitro pharmacokinetic/pharmacodynamic model

Conventional MIC testing of amphotericin B results in narrow MIC ranges challenging the detection of resistant strains. In order to discern amphotericin B pharmacodynamics, the in vitro activity of amphotericin B was studied against Aspergillus isolates with the same MIC with a new in vitro pharmacokinetic/pharmacodynamic (PK/PD) model that simulates amphotericin B human plasma levels. Clinical isolates of A. fumigatus, A. terreus and A flavus with the same CLSI modal MICs of 1 mg/l were exposed to amphotericin B concentrations following the plasma concentration-time profile after single bolus administration with Cmax 0.6, 1.2, 2.4 and 4.8 mg/L. Fungal growth was monitored up to 72h based on galactomannan production. Complete growth inhibition was observed only against A. fumigatus with amphotericin B Cmax ≥2.4 mg/L. At lower Cmaxs 0.6 and 1.2 mg/L, a significant growth delay of 34h and 52h was observed, respectively (pA flavus>A. terreus in the in vitro PK/PD model possibly reflecting the different concentration- and time-dependent inhibitory/killing activities amphotericin B exerting against these species

Quantitative Genetics and Functional-Structural Plant Growth Models: Simulation of Quantitative Trait Loci Detection for Model Parameters and Application to Potential Yield Optimization

Background and Aims: Prediction of phenotypic traits from new genotypes under untested environmental conditions is crucial to build simulations of breeding strategies to improve target traits. Although the plant response to environmental stresses is characterized by both architectural and functional plasticity, recent attempts to integrate biological knowledge into genetics models have mainly concerned specific physiological processes or crop models without architecture, and thus may prove limited when studying genotype x environment interactions. Consequently, this paper presents a simulation study introducing genetics into a functional-structural growth model, which gives access to more fundamental traits for quantitative trait loci (QTL) detection and thus to promising tools for yield optimization. Methods: The GreenLab model was selected as a reasonable choice to link growth model parameters to QTL. Virtual genes and virtual chromosomes were defined to build a simple genetic model that drove the settings of the species-specific parameters of the model. The QTL Cartographer software was used to study QTL detection of simulated plant traits. A genetic algorithm was implemented to define the ideotype for yield maximization based on the model parameters and the associated allelic combination. Key Results and Conclusions: By keeping the environmental factors constant and using a virtual population with a large number of individuals generated by a Mendelian genetic model, results for an ideal case could be simulated. Virtual QTL detection was compared in the case of phenotypic traits - such as cob weight - and when traits were model parameters, and was found to be more accurate in the latter case. The practical interest of this approach is illustrated by calculating the parameters (and the corresponding genotype) associated with yield optimization of a GreenLab maize model. The paper discusses the potentials of GreenLab to represent environment x genotype interactions, in particular through its main state variable, the ratio of biomass supply over demand

Simulating spin-3/2 particles at colliders

Support for interactions of spin-3/2 particles is implemented in the FeynRules and ALOHA packages and tested with the MadGraph 5 and CalcHEP event generators in the context of three phenomenological applications. In the first, we implement a spin-3/2 Majorana gravitino field, as in local supersymmetric models, and study gravitino and gluino pair-production. In the second, a spin-3/2 Dirac top-quark excitation, inspired from compositness models, is implemented. We then investigate both top-quark excitation and top-quark pair-production. In the third, a general effective operator for a spin-3/2 Dirac quark excitation is implemented, followed by a calculation of the angular distribution of the s-channel production mechanism.Comment: 20 pages, 7 figure