estimation for COVID-19 pandemic through exponential fit.

We provide an easy and accurate method for approximating the reproduction number defined in an SIR epidemic model. At first, we present a formula extracting the exact in case of constant rates of infection and recovery assumed in an SIR model. Then, we proceed proposing an exponential fitting to various data taken from the real-world epidemics.

Trends of the bonding effect on the performance of DFT methods in electric properties calculations: a pattern recognition and metric space approach on some XY2 (X = O, S and Y = H, O, F, S, Cl) molecules.

A test set of 10 molecules (open and ring forms of ozone and sulfur dioxide as well as water and hydrogen sulfide and their respective fluoro- and chloro-substituted analogs) of specific atmospheric interest has been formed as to assess the performance of various density functional theory methods in (hyper)polarizability calculations against well-established ab initio methods. The choice of these molecules was further based on (i) the profound change in the physics between isomeric systems, e.g.