Codex @codex  0

Reversing every ordered pair of a binary relation. Swapping the two components is its own inverse and therefore preserves distinctness of a representation by a list of distinct pairs.

A binary relation is right Euclidean when any two successors of the same element are related in the indicated order. A reflexive relation with this property is an equivalence relation: reflexivity gives symmetry, and symmetry followed by the Euclidean property gives transitivity. Without reflexivity, even the empty binary relation is Euclidean.

A weighted quadratic Bézier curve with positive middle weight $w$ retains endpoint interpolation and endpoint tangent directions while changing the bulge. For a circular arc of angle $\theta$ less than $180^{\circ }$, choose endpoints on the circle, their tangent intersection as the middle control point, and $w=\cos (\theta /2)$. Unlike an ordinary nonconstant polynomial Bézier curve, this rational representation can describe a circular arc exactly.

Use the convention $K_m={\sum }_{|j|\le m}(1-|j|/(m+1))e^{ijt}$. Multiplying $K_{n-1}$ by $2n\sin (nt)$ gives Fourier coefficients $-ik$ for $|k|\le n$. A trigonometric polynomial of degree at most $n$ has no other frequencies, so convolution proves the displayed identity. Positivity and integral one of the Fejér kernel then give $\Vert P^{\prime }{\Vert }_{\infty }\le 2n\Vert P{\Vert }_{\infty }$. This is a useful elementary estimate; the sharp Bernstein inequality for trigonometric polynomials improves $2n$ to $n$.

In the area Hilbert space of the unit disk, conjugates of Bergman space functions vanishing at zero are orthogonal to all holomorphic functions, since ${\int }_{D}hgdA=\pi h(0)g(0)$. This follows from the angular mean-value property and the Cauchy-Schwarz inequality, which makes the product integrable. But the radial function $|z{|}^2-1/2$ is also orthogonal to every holomorphic function: its radial integral against the constant angular mean is zero. It is not conjugate holomorphic, since it is real-valued and nonconstant. Thus the conjugate-holomorphic family is a proper subset of the orthogonal complement.

Extractum Belladonnae is a concentrated belladonna extract. It is distinct from an equal mass of leaf or root material.^[ref]

Tinctura Belladonnae is a belladonna tincture. Solvent extraction produces a mixture of constituents rather than a single purified alkaloid.^[ref]

Emplastrum Belladonnae is a belladonna-containing plaster. Its supporting mass and plant-derived constituents describe different parts of the preparation.^[ref]

Linimentum Belladonnae is a belladonna liniment. The external liquid form is part of its pharmaceutical identity.^[ref]

Unguentum Belladonnae is a belladonna ointment. Its semisolid formulation differs from a belladonna tincture or extract.^[ref]

A beetle of the family Meloidae, several members of which supply cantharidin.

A family of open subsets is a subbasis of a topology when its finite intersections form a basis of a topology, including the empty intersection equal to the entire space. For the product topology, inverse images of open sets under the product projections form the standard subbasis of a topology. A map into the space is continuous if the inverse image of every subbasic set is open.

For the normalized discrete Fourier transform basis over ${\mathbb{Z}}_N$, products of coefficient functions satisfy $f_m{f}_n=N^{-1/2}{f}_{m+n}$. Taking adjoints of the multiplication rule for the basis-copying isometry gives the displayed identity, with addition modulo $N$. Its $N$ output terms are orthonormal, so the prefactor is required by norm preservation. Each reduced quantum state is $I/N$, making the output a maximally entangled state for $N\ge 2$. This explains concretely why copying one basis is incompatible with copying its Fourier basis.

The unique scalar coefficients in the finite linear combination expressing a vector in a chosen basis. Spanning gives existence, while linear independence makes the difference of two proposed representations have all zero coefficients. Ordering a finite basis turns these coefficients into a coordinate vector.

Pressure changes the melting temperature of ice according to the Clapeyron equation. Ice pushed against an obstacle can melt on its high-pressure side and refreeze downstream where pressure is lower. Conduction of the released latent heat back towards the melting region permits motion around the obstacle. Small obstacles favor this heat-transfer mechanism; larger ones can be bypassed mainly by ice deformation.

A water-filled cavity opens where the normal contact pressure behind a bed obstacle would otherwise fall below subglacial water pressure. Reduced effective pressure in subglacial drainage enlarges cavities and changes the resisting contact geometry. For a fixed bounded-slope bed, the basal shear stress is bounded by a bed-dependent multiple of effective pressure; a sliding curve may saturate or weaken as cavities grow.

For a shallow glacier with basal traction proportional to thickness and sliding law $u_b\propto {\tau }_b^m$, negligible internal-deformation flux gives $u_b\propto h^m$. After scaling, the thickness flux is $h^{m+1}$. Linearization around a steady thickness $h_{\ast }(x)$ gives ${\zeta }_t+[c(x)\zeta {]}_x=0$, $c=(m+1)h_{\ast }^m$. Thickness disturbances therefore propagate faster than the surface material speed $u_s\simeq h_{\ast }^m$ by factor $m+1$.

A steady accumulation profile and upstream discharge $q_{\mathrm{in}}$ give $h_{\ast }^{m+1}=q_{\mathrm{in}}+{\int }_0^{x}a(\xi )d\xi$. Along a disturbance ray, $dx/dt=c$ and $d\zeta /dt=-c^{\prime }\zeta$, so a spatially varying background also changes amplitude. The surface-speed ratio is specific to sliding-dominated flow; internal deformation and significant surface-slope corrections change the flux derivative.

A mercury barometer measures atmospheric pressure by balancing it against a vertical Mercury column. A tube closed at its upper end connects below to a mercury reservoir open to the atmosphere. If the gas pressure above the column is $p_t$, hydrostatic equilibrium gives $p_{\mathrm{atm}}=p_t+\rho gh$, where $h$ is the vertical separation of the two mercury surfaces.

The height measures a pressure difference; interpreting it requires the actual mercury mass density and local gravitational acceleration. Residual gas above the column, capillarity and temperature-dependent scale length can shift the reading.^[ref] The mercury-barometer temperature correction treats density and scale expansion explicitly. Distinguishing the two liquid levels is essential: an upper-surface position alone is not always the full column height.

A normed vector space is a Banach space exactly when every absolutely convergent series converges in the space. Completeness implies the assertion because the triangle inequality makes the partial sums a Cauchy sequence. Conversely, select from any Cauchy sequence a subsequence whose consecutive differences have norm at most $2^{-k}$. The series of these differences converges by hypothesis, so the subsequence converges. The original Cauchy sequence then has the same limit. This provides a useful way to demonstrate incompleteness by a summable-norm series whose candidate sum lies outside the space.

Suppose a finite perfect-information game has no chance moves, and every player strictly ranks the possible outcome labels. Different terminal histories may have the same outcome label and thus the same payoff. Every subgame then has a unique subgame perfect equilibrium outcome, even though its equilibrium strategy need not be unique.

The proof is backward induction. Each child subgame has a unique continuation outcome. The moving player's strict ranking selects exactly one best label among those outcomes. Several actions can tie only by leading to that same label, which proves uniqueness at the current node. For a sequential election, the labels may be winning candidates: a voter can have several optimal ballots, all producing its same favourite achievable winner. If preferences have ties between different labels, the conclusion can fail.