Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...

Efflorescence in masonry walls appears as a fluffy crystalline powder, often white, resulting from water-soluble salts within the masonry or mortar. When water penetrates the masonry, it dissolves these salts and brings them to the surface, where they are deposited upon evaporation of water.
While initial efflorescence is common post-construction and can be cleaned with water and a brush, in certain instances, efflorescence can reappear and gradually diminish over time as salts are leached out...

A Winogradsky column provides a powerful tool for studying microbial ecology and metabolic interactions in a stratified, self-contained environment. This artificial ecosystem, developed by Sergei Winogradsky in the late 19th century, replicates the complex biogeochemical gradients found in natural sediments, allowing researchers to observe microbial succession and interactions over time.The column is typically assembled in a transparent glass cylinder filled halfway with sediment mixed with...

Fluorescence in situ hybridization, or FISH, was developed in the early 1980s and has quickly become one of the most widely used techniques in cytogenetics. Labeled probes are used to bind complementary DNA or RNA sequences on a chromosome or in a region within a cell. Earlier, the probes could only be obtained by cloning or reverse transcription of a DNA template. Currently, the probe oligonucleotides can be synthesized synthetically. Additionally, with the advancement of optical techniques,...

The chair conformation is the most stable form of cyclohexane due to the absence of angle and torsional strain. The absence of angle strain is a result of cyclohexane’s bond angle being very close to the ideal tetrahedral bond angle of 109.5° in its chair conformer. Similarly, the torsional strain is also absent owing to the perfectly staggered arrangement of bonds.
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this...

In situ hybridization (ISH) is a technique used to detect and localize specific DNA or RNA molecules in cells, tissue, or tissue sections using a labeled probe. The technique was first used in 1969 for the investigation of nucleic acids. It is currently an essential tool in scientific research and clinical settings, especially for diagnostic purposes.
Types of probes and labels
A probe is a complementary strand of DNA or RNA that binds to corresponding nucleotide sequences in a cell. Many...