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.

For an independent axiom set, semantic entailment of any one axiom from the remaining axioms fails. By the completeness theorem, this is equivalent to no member being formally derivable from the others in a complete calculus. To establish independence it suffices to give, for each axiom, a first-order structure satisfying all the other axioms and failing that one.

A stethoscope couples sounds at the body surface to a listener or recording system for auscultation. In an acoustic instrument, the chestpiece and air-filled tubing transmit sound waves toward the ears; electronic designs instead use a sensor and amplification. The instrument changes access to an acoustic signal, but interpreting the source still requires timing, anatomical context and comparison with other findings. ^[ref]

An equivalence-relation first-order structure with exactly two infinite classes, one countable and one uncountable, is atomic but lacks finite-tuple homogeneity. Its first-order theory has quantifier elimination: a new point is either assigned a previously used class or an available unused class, and can avoid finitely many forbidden points in that infinite class. Finite equality-and-equivalence patterns therefore isolate all tuple partial types. All elements have the same complete one-type, but no automorphism exchanges the two differently sized classes.

Coronary atherosclerosis is atherosclerotic disease of the arteries supplying cardiac muscle. Its consequences can involve altered perfusion and plaque-associated events. The amount of narrowing and the tissue’s current oxygen demand are different determinants of whether supply is adequate.

The prosoma is the anterior major body region in the chelicerate body plan. It carries the feeding appendages and walking legs in familiar Arachnida. Its relation to the opisthosoma helps describe how an arthropod body is divided into functional regions.

The opisthosoma is the posterior major body region in the chelicerate body plan, behind the prosoma. Its segmentation and appendages are modified differently among groups. The boundary is therefore a statement about body organization rather than identical external shape in every species.

A chelicera is one of the anterior feeding appendages of Arachnida and their relatives. Depending on the group, it can grasp, cut or pierce. It should be distinguished from a pedipalp, which belongs to a different appendage pair.

A pedipalp is one of the paired appendages behind the chelicerae in Arachnida. Its function varies among groups, including sensing, handling food and reproduction. Correspondence in position can persist despite large differences in size and form.

A book lung is a respiratory structure in some Arachnida, with many thin tissue sheets bordering air spaces. The repeated layers increase the interface available for gas exchange, much as pages provide a large surface within a compact volume.

A mite is a small member of Arachnida; the broad grouping includes forms with diverse feeding and host associations. Demodex and Sarcoptes scabiei are host-associated examples. Small size alone does not distinguish a mite from an immature insect.

A tick is a blood-feeding member of Arachnida closely related to other mites. Feeding on vertebrate hosts can connect its own life cycle to transmission of other organisms. Hard ticks such as Ixodes and soft ticks such as Argas differ in external structure and feeding patterns.

A sequence of continuous periodic functions satisfying the displayed conditions, with normalized Haar measure $m$ and every $\delta >0$, is a summability kernel. For $f$ in a homogeneous Banach space on the circle, subtract $f\int k_{n}dm$ from its convolution with $k_n$. Translation continuity controls the resulting integral near zero, while boundedness by $2\Vert f{\Vert }_B$ and the vanishing tails control its complement. Thus $\Vert f\ast k_n-f{\Vert }_B\to 0$. The nonnegative Fejér kernel is an example with $L^1$ norm one.

The aortic arch is the curved aortic region linking ascending and descending portions. Major branches supply the head, neck and upper limbs, with normal patterns subject to variation. Its shape and neighboring structures connect thoracic vascular anatomy with the thoracic inlet.

On an antiplane shear $F=I+e_3\otimes (p,q,0)$, the first strain invariant satisfy $I_1=I_2=3+p^2+q^2$, $I_3=1$. Restricting an isotropic objective strain energy density to this family determines only derivatives tangent to the family. It fixes $S_{31}=2w^{\prime }(p^2+q^2)p$ and $S_{32}=2w^{\prime }(p^2+q^2)q$, but does not specify the whole Cauchy stress tensor. For example the neo-Hookean solid energy $W=\mu (|F{|}^2-3)/2-\mu \log \det F$ gives $S=\mu (B-I)$ on this family. Even though the reference state is stress free, this is not generally a scalar multiple of $B$.

For a vector subspace $U$ of a finite-dimensional vector space $V$, its annihilator of a vector subspace $U^0\subseteq V^{\ast }$ determines $U$ exactly: $U={\bigcap }_{f\in U^0}\ker f$. Indeed, a basis of $U$ can be extended to one of $V$. If $v\notin U$, include $v$ among the added basis vectors and define a linear functional taking value one at $v$ and zero on all the other basis vectors. This functional vanishes on $U$ but not at $v$, excluding every outside vector from the intersection.

It suffices to intersect the kernels of any basis $g_1,\dots ,g_k$ of $U^0$: every other annihilating functional is their linear combination. The dual basis for a basis of $V$ extending a basis of $U$ shows $k=\dim V-\dim U$. If $U=V$, the empty intersection is $V$. This translates a subspace description by spanning vectors into an exact description by independent linear equations.