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Corundum is the crystalline alpha form of aluminium oxide, $\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$. Its strong bonded structure gives high hardness and chemical durability.

Salts or small amounts of impurity ions can alter its optical properties without changing the basic host lattice. Ruby and sapphire are gem varieties of corundum, demonstrating how composition at the impurity level affects color.

Manganese(II) oxide is $\mathrm{MnO}$, containing manganese predominantly in oxidation state $+2$. Its ideal structure is related to the rock-salt lattice.

It differs from manganese dioxide, $\mathrm{Mn}{\mathrm{O}}_2$, where manganese is formally $+4$. Comparing the two illustrates why the oxidation-state label determines both stoichiometry and redox chemistry.

Aluminium gallium nitride is the semiconductor alloy $\mathrm{A}{\mathrm{l}}_{\mathrm{x}}\mathrm{G}{\mathrm{a}}_{1-\mathrm{x}}\mathrm{N}$. Adjusting the aluminium fraction changes the band gap and lattice parameters.

Interfaces with related nitrides can confine electronic carriers and support ultraviolet optical devices. Composition, crystal orientation, and polarization at interfaces must be considered together when interpreting its behavior.

Aluminium nitride is $\mathrm{AlN}$, a wide-band-gap solid with useful thermal and piezoelectric properties. A common crystal structure is wurtzite.

Its combination of electrical insulation and heat transport supports electronic packaging, while its coupling between strain and electric polarization supports acoustic devices. These properties arise from the bonded lattice rather than from separate aluminium and nitrogen components.

Indium gallium nitride is the semiconductor alloy $\mathrm{I}{\mathrm{n}}_{\mathrm{x}}\mathrm{G}{\mathrm{a}}_{1-\mathrm{x}}\mathrm{N}$. Changing the indium fraction changes its electronic band structure and optical transition energies.

This compositional tuning supports light emission over different wavelength ranges. Strain and phase uniformity also matter, so wavelength is not set by composition independently of the material's structure.

Gallium nitride is $\mathrm{GaN}$, a wide-band-gap semiconductor. Its bonded crystal lattice supports electronic and optical behavior unlike that of either elemental gallium or molecular nitrogen.

It is important in light-emitting devices and power electronics. Crystal quality, defects, and doping influence performance, so elemental composition alone does not determine a device's properties.

Samarium hexaboride is a Kondo insulator whose narrow samarium $4f$-derived states mix with more dispersive conduction states. It motivates effective models of band hybridization between a nearly flat band and a light dispersive band.

Mutarotation is a change in optical rotation as anomers interconvert in a chemical solution. The glucose mutarotation experiment detects redistribution between cyclic forms through monosaccharide ring-chain interconversion.

Alkylation introduces an alkyl group into a molecule. The new group may attach to carbon, nitrogen, oxygen, sulfur, or another suitable atom; the name alone does not specify the mechanism.

For example, an alkoxide can react with a suitable alkyl halide to form an ether by nucleophilic substitution, while Friedel-Crafts alkylation attaches an alkyl group to an aromatic ring through an electrophilic pathway. Competing elimination, multiple substitution, or rearrangement depends on the particular reacting partners.

Chemical reactivity is the tendency of a species to undergo a specified chemical reaction under specified conditions. A meaningful comparison identifies the reacting partner, solvent or phase, temperature, and measured outcome.

Thermodynamic favorability and reaction speed are different: a transformation may lower Gibbs free energy yet proceed slowly because its activation energy is high. A catalyst can change that barrier without changing the equilibrium constant. Reactivity therefore connects molecular electronic structure and geometry with both chemical thermodynamics and chemical kinetics.

A separation process divides a mixture into streams with different compositions by exploiting a difference in physical or chemical behaviour. Distillation uses volatility, filtration uses particle or pore-scale exclusion, and solvent extraction uses partitioning between phases. Separation need not create chemically pure products, and recovery of one component can trade against its purity. A mass balance relates feed and product streams; thermodynamics and transport determine which separations are feasible and how rapidly they proceed.

The study of physical properties and processes in the oceans, including fluid flow, waves and transport of heat.

Soft matter studies materials whose large-scale structures respond strongly to modest mechanical or thermal disturbances, including polymers, liquid crystals and colloids. Polymer physics connects chain conformations to material response; the coil-stretch transition is one example.

Condensed matter physics studies the collective behavior of matter with many interacting constituents, especially solids and liquids. Crystal structure, electron interactions and thermal motion produce properties that are not apparent from one isolated atom.

A phonon describes a collective lattice vibration, while superconductivity involves a coherent many-electron state. The same microscopic ingredients can produce different phases as temperature, pressure or composition changes. Experiments connect structural, transport, magnetic and spectroscopic measurements with models of those phases.

A biologist specializing in botany.

A molecular motor couples an energy supply to directed mechanical motion. ATP synthase provides a rotary example.

Autoradiography localizes a radioactive label through its effect on a recording medium. In electron microscopy, developed photographic grains are compared with specimen structures; their positions have finite localization precision.

Pulse-chase analysis marks a cohort during a short pulse, then follows it while unlabeled precursor reduces subsequent labeling during the chase. Label specificity and effective suppression of new incorporation constrain interpretation.

Nature Communications 13, 2232 (2022), by Hui Guo and John L. Rubinstein.

Cited passages: abstract; Introduction; Figure 1. Yeast hydrolysis conditions; synthesis-related interpretation is distinguished.

Journal of Biological Chemistry 284, 22401–22410 (2009).

Cited passages: Experimental Procedures; Results, Figure 1. Isolated F1 rotation assay.