University of Belgrade

About: University of Belgrade is a education organization based out in Belgrade, Serbia. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 20667 authors who have published 47148 publications receiving 896243 citations. The organization is also known as: Univerzitet u Beogradu & Belgrade University.

Recycled Concrete as Aggregate for Structural Concrete Production

Abstract: A comparative analysis of the experimental results of the properties of fresh and hardened concrete with different replacement ratios of natural with recycled coarse aggregate is presented in the paper. Recycled aggregate was made by crushing the waste concrete of laboratory test cubes and precast concrete columns. Three types of concrete mixtures were tested: concrete made entirely with natural aggregate (NAC) as a control concrete and two types of concrete made with natural fine and recycled coarse aggregate (50% and 100% replacement of coarse recycled aggregate). Ninety-nine specimens were made for the testing of the basic properties of hardened concrete. Load testing of reinforced concrete beams made of the investigated concrete types is also presented in the paper. Regardless of the replacement ratio, recycled aggregate concrete (RAC) had a satisfactory performance, which did not differ significantly from the performance of control concrete in this experimental research. However, for this to be fulfilled, it is necessary to use quality recycled concrete coarse aggregate and to follow the specific rules for design and production of this new concrete type.

DNA sequence determination by hybridization: A strategy for efficient large-scale sequencing

Abstract: The concept of sequencing by hybridization (SBH) makes use of an array of all possible n-nucleotide oligomers (n-mers) to identify n-mers present in an unknown DNA sequence. Computational approaches can then be used to assemble the complete sequence. As a validation of this concept, the sequences of three DNA fragments, 343 base pairs in length, were determined with octamer oligonucleotides. Possible applications of SBH include physical mapping (ordering) of overlapping DNA clones, sequence checking, DNA fingerprinting comparisons of normal and disease-causing genes, and the identification of DNA fragments with particular sequence motifs in complementary DNA and genomic libraries. The SBH techniques may accelerate the mapping and sequencing phases of the human genome project.

The Mechanism of the Dendritic Electrocrystallization of Zinc

Abstract: Measurements have been made of the growth rate of zinc dendrites in alkaline zincate solutions as a function of overpotential (η), concentration , and temperature The tip radii have been measured by electron microscopy At constant potential, an initiation time of between 5 and 100 min is observed, depending on η, c, and T The dendrite grows linearly with time, at a rate depending on η, c, and T The total current to base and dendrite was independent of time until a time , where (the time for initiation obtained from the growth rate vs time relation) Thereafter, A critical overpotential was determined, Below this , sponge was formed Dendrites were observed up to ; above this the deposition was heavy sponge At a given , the growth rate of a given dendrite increased with η according to an exponential law The growing tip is parabolic, where No twinning was observedThe basic model used depended on the increase in cd possible for an electrodic reaction when the diffusion current depends on a radius of curvature of the substrate, rather than the linear diffusion layer thickness, When the tip of a dendrite‐precursor attains this condition, its growth is released from the diffusion control characteristic of it in the predendrite situation, and it grows further under predominantly activation control at a rate far greater than that possible in any other direction, where the radii of curvature are much greater The Gibbs radius‐dependent overpotential term is also present, although it has a minimized influence The initiation of the dendrite is treated in terms of growing pyramids on the substrate surface At first the growth is linear‐diffusion controlled, but it is shown that the rotation of the spiral, within the linear diffusion boundary surrounding the sphere, gives rise to a decrease of the effective radius of curvature of the dendrite tip until the value is attained, which is effectively the condition for the dendrite initiation The theory of the propagation in terms of the activation, diffusion and Gibbs overpotential is consistent, in terms of , with experiment A derived growth‐time line is also numerically consistent with experiment The dendrite growth rate as a function of and η are numerically calculated with reasonable consistency The tip radius can also be approximately calculated in terms of the present model