Trichloroacetic acid is a chlorinated carboxylic acid, used for protein precipitation in the Nirenberg and Matthaei experiment.

Lactic acid is 2-hydroxypropanoic acid, $\mathrm{C}{\mathrm{H}}_3\mathrm{CH}(\mathrm{OH})\mathrm{COOH}$. Its central carbon is a stereogenic centre, and its conjugate base is lactate.

In lactic acid fermentation, reduction of pyruvate to lactate regenerates NAD+ from NADH. That regeneration allows glycolysis to continue when the pathway cannot rely on sufficiently rapid respiratory oxidation of NADH.

Phosphoenolpyruvic acid is the acid form of phosphoenolpyruvate, a phosphorylated enol derivative of pyruvic acid. Its phosphate group is attached through oxygen to the enol system.

In glycolysis, transfer of that phosphate group to ADP forms ATP and pyruvate. Conversion of the initial enol product into the more stable keto form helps favour the overall reaction, connecting molecular rearrangement with energy transfer.

Oxalic acid is the simplest dicarboxylic acid, with structure $\mathrm{HOOC}-\mathrm{COOH}$. Stepwise loss of two protons gives hydrogen oxalate and then oxalate.

Oxalic acid combines acid-base chemistry with metal-ion binding. Some oxalate salts have low solubility, so the behaviour of an oxalate-containing system depends on both pH and the available metal ions.

Graphene is a single layer of carbon chemical atoms arranged in a honeycomb lattice. A nearby gate can select predominantly electron or electron hole conduction, as demonstrated by the graphene exfoliation and field-effect experiments.^[ref]

A useful question is how geometry changes motion. The nearest-neighbour model of graphene starts with three equivalent bonds from each site and two sites per primitive cell. Interference between those three hopping paths makes two energy bands meet; near their meeting, energy grows linearly with distance in wave vector. The resulting Dirac cones explain why an atomic sheet can imitate one aspect of a relativistic particle while remaining an ordinary material with contacts, defects and boundaries.

Diamond is an allotrope of carbon with a three-dimensional tetrahedral covalent network. The connected structure gives high hardness and distinguishes it from layered graphite.

Diamond can transport heat well while remaining an electrical insulator in a sufficiently pure form, because heat transport and charge transport have different microscopic carriers. Defects and impurities can introduce optical or electronic features without changing the host material's basic identity.

Carbon-14 has six protons and eight neutrons. Atmospheric production is dominated by ${}^{14}\mathrm{N}(n,p){}^{14}\mathrm{C}$ using secondary cosmic ray neutrons. It undergoes beta-minus decay to nitrogen-14, with a physical half-life of approximately $5730$ years.

A gate, insulating oxide and semiconductor form a capacitor. Applied electric potential difference changes the near-surface distribution of charge carriers.

The electronic contribution to differential capacitance arising from a change of chemical potential as particles are added. For noninteracting electrons at zero temperature, it is $e^2$ times the density of states of the whole sample at the Fermi energy. The quantum capacitance of a graphene cone gives a worked example.

For a collection of fixed electrical conductors in linear electrostatics, the capacitance matrix relates conductor charges to potentials relative to a specified reference: $Q_i={\sum }_j{C}_{ij}{V}_j$. It includes mutual electrostatic effects omitted when each conductor is treated as an isolated capacitor. Its electrostatic energy is $U=\frac{1}{2}{\mathbf{V}}^{\mathsf{T}}\mathbf{CV}=\frac{1}{2}{\sum }_i{Q}_i{V}_i$. Geometry and separation are needed to determine its entries.

For a parallel-plate capacitor of area $A$ and separation $d$, filled by a spatially varying positive scalar permittivity, neglect edge fields. At fixed terminal voltage, the physical electric potential minimizes $\int \epsilon |\nabla V{|}^{2}d\mathcal{V}/2$. A linear trial potential gives the arithmetic upper bound. At fixed plate charge, minimizing $\int |\mathbf{D}{|}^2/(2\epsilon )d\mathcal{V}$ over divergence-free electric displacement fields gives the harmonic lower bound by using a uniform trial displacement. The averages are volume averages. Layers parallel to the field attain the arithmetic bound; layers perpendicular to the field attain the harmonic bound. Equal volumes of vacuum and relative permittivity $ϵ$ therefore give $2ϵC_0/(1+ϵ)\le C\le (1+ϵ)C_0/2$, where $C_0={\epsilon }_{0}A/d$.

Two independently available parts of a thermodynamic system are noninteracting in the canonical description when their state space is a Cartesian product and their energy is additive, $E(a,b)=E_A(a)+E_B(b)$. Both conditions are needed for the canonical partition function to factor:An additive expression on a constrained set of allowed state pairs need not give this factorization. Relabeling the states to make their allowed labels independent can instead introduce an interaction into the energy. For two two-state labels, an additive energy necessarily satisfies the rectangular identity $E_{11}+E_{22}=E_{12}+E_{21}$.

A quantum Gibbs state is the density operator of a canonical ensemble with inverse temperature $\beta =1/(k_{B}T)$. It exists when the canonical partition function $Z=\mathrm{Tr}(e^{-\beta H})$ is finite. The spectral theorem assigns probabilities $e^{-\beta E_j}/Z$ to an orthonormal eigenbasis of the Quantum Hamiltonian. An additive constant in the Quantum Hamiltonian cancels between numerator and denominator. For $H=-\mu B{\sigma }_z$, the exponential of a Pauli vector, continued to an imaginary argument, gives ${\rho }_{\beta }=[I+\tanh (\beta \mu B){\sigma }_z]/2$.

A particle calorimeter designed to measure electron and photon energies through particle showers. Track reconstruction helps distinguish charged electrons from neutral photons.

The record for one active invocation in a call stack, containing information such as local variables and the place to resume its caller. Returning removes that invocation's stack frame, allowing the caller's computation to continue.

A californium isotope used as a neutron calibration source for the Sudbury Neutrino Observatory.

Calcium hydroxide supplies calcium cations and hydroxide anions on dissolution in water. The ideal one-to-two stoichiometry relates molar solubility to the dissolved concentrations; solubility product measurement by titration explains how the hydroxide inventory is measured.

Calcium-40 is an even-even nucleus with the closed-shell values $Z=N=20$. Its extra stability illustrates nuclear shell corrections beyond a smooth semi-empirical mass formula.