An early (and influential) scaling relation in the multifractal theory of diffusion limited aggregation (DLA) is the Turkevich-Scher conjecture that relates the exponent alpha(min) that characterizes the "hottest" region of the harmonic measure and the fractal dimension D of the cluster, i.e., D=1+alpha(min). Due to lack of accurate direct measurements of both D and alpha(min), this conjecture ...

We suggest the parallel computational complexity of simulating a system as a measure of its physical complexity. As an example, we present a parallel algorithm for simulating diiusion-limited aggregation (DLA) and calculate the algorithm's dynamic exponent z, which gives the scaling of the average running time with cluster radius. It is plausible that the algorithm attains the minimum possible ...

Diffusion limited aggregation (DLA) is a model of fractal growth that had attained a paradigmatic status due to its simplicity and its underlying role for a variety of pattern forming processes. We present a convergent calculation of the fractal dimension D of DLA based on a renormalization scheme for the first Laurent coefficient of the conformal map from the unit circle to the expanding bound...

Abstract. Recent measurements of nitrogen and alpha elements in over 20 damped Ly-α systems (DLA) are compared with similar measurements for numerous emission line objects and stars. It is found that the DLA distribution in the N/α-α/H plane is bimodal, where most sample DLAs fall along the N/α plateau defined at low Z by dwarf irregulars, while a small group possesses N/α values roughly 0.7 de...

We present the results of a numerical study of a galactic wind model and its implications on the properties of damped Lyman-α absorbers (DLAs) using cosmological hydrodynamic simulations. We vary both the wind strength and the internal parameters of the the wind model in a series of cosmological smoothed particle hydrodynamics (SPH) simulations that include radiative cooling and heating by a UV...

Using stacked Sloan Digital Sky Survey spectra, we present the detection of [O II]λλ3727,3730 nebular emission from the galaxies hosting Ca II absorption line systems and galaxies hosting Mg II-selected damped Lyman-α (DLA) absorbers. Both samples of absorbers, 345 Ca II systems and 3461 Mg II-selected DLA systems, span the redshift interval 0.4 6 zabs < 1.3; all of the former and half the latt...

background cancer is one of the leading causes of human death. the discovery of new generations of low-cost anticancer drugs with high efficacy and low toxicity is necessary, and is only possible by screening medicinal plants with prior knowledge. objectives in this study, the bioactivities of three medicinal plants from india, including alstonia scholaris, alstonia venenata, and moringa oleife...

In this first paper of a series, we report on the use of quasar spectra obtained with the UVES high resolution spectrograph and available through the ESO VLT archive to build the first homogeneous and unbiased sample of sub-DLA systems, absorbers with H i column densities > 10 cm −2 but lower than the classical definition of damped Lyα systems (DLAs) 2 × 10 cm. A systematic investigation of the...

Assuming that damped Lyman-α (DLA) systems are galactic discs, we calculate the corresponding evolution of metal abundances. We use detailed multi-zone models of galactic chemical evolution (reproducing successfully the observed properties of disc galaxies) and appropriate statistics (including geometrical propability factors) to calculate the average metallicity as a function of redshift. The ...