At Wuhan, in December 2019, the SRAS-CoV-2 outbreak was detected and it has been the pandemic worldwide. This study aims to investigate the mutations in sequence of the SARS-CoV-2 genome and characterize the mutation patterns in Egyptian COVID-19 patients during different waves of infection. The samples were collected from 250 COVID-19 patients and the whole genome sequencing was conducted using Next Generation Sequencing. The viral sequence analysis showed 1115 different genome from all Egyptian samples in the second wave mutations including 613 missense mutations, 431 synonymous mutations, 25 upstream gene mutations, 24 downstream gene mutations, 10 frame-shift deletions, and 6 stop gained mutation. The Egyptian genomic strains sequenced in second wave of infection are different to that of the first wave. We observe a shift of lineage prevalence from the strain B.1 to B.1.1.1. Only one case was of the new English B.1.1.7. Few samples have one or two mutations of interest from the Brazil and South Africa isolates. New clade 20B appear by March 2020 and 20D appear by May 2020 till January 2021.

Frequency-doubled light at 532 nm from the microchip Nd:YVO4 lasers is a promising candidate to replace the widely used He-Ne lasers in length metrology due to their superior characteristics, low-cost and rugged structure. In this paper, the spectral characteristics of a commercial microchip Nd:YVO4 laser are investigated. The laser temperature is initially controlled to facilitate the study of longitudinal mode structure of the laser at different pumping current and temperatures. Additionally, a simple method is suggested to obtain a single-mode operation at a relatively wide temperature range, namely from 20 to 25.8 °C, and pumping currents from 300 to 385 mA. The frequency stability is evaluated after controlling the laser temperature to be 1.9 × 10–8 at 1 s. Additionally, parameters that are important for locking the frequency of the laser to a molecular reference transition are investigated such as laser linewidth and the relation between current/temperature and wavelength.

Solid-state lasers are used in length metrology because it has narrow linewidth, single mode and wavelength stability. A simple method uses Nd:YVO4 laser to obtain single mode with stability 1.9 × 10-8 at 1 second.