Endoscopic ultrasonography combines an endoscope with an acoustic transducer to obtain ultrasonography images from within the gastrointestinal tract. Positioning the source and receiver near a target shortens the intervening acoustic path and can reveal the wall and nearby structures. A probe integrated into the endoscope tip and a probe passed through its working channel are different apparatus arrangements.^[ref]

Pelvic ultrasonography uses ultrasonography to image structures in the pelvis, including the reproductive organs and urinary bladder. The probe's position determines the acoustic path and which structures lie in view: transabdominal and transvaginal ultrasound approaches observe the region from different geometries. Returning echoes provide information about interfaces and motion, with the usual limitations of acoustic access through gas and bone.^[ref]

By Marc Lackenby.

Author-hosted lecture notes: people.maths.ox.ac.uk/lackenby/tg050908.pdf

Definitions I.17–I.18, printed pp. 8–9, describe an abstract simplicial complex and its topological realization by gluing labelled faces of standard simplexes.

UC San Diego technical report, August 2010.

Author-hosted PDF: scicomp.ucsd.edu/~peg/papers/sqpReview.pdf

Expression notation specifies how operators and operands are arranged to encode a mathematical computation. Infix notation places an operator between operands, as in $a+b$; Polish notation places it first, and reverse Polish notation places it last.

The computation $(a+b)c$ can be written in prefix form as * + a b c or postfix form as a b + c *. Known operator arities make these forms parse without parentheses. Infix notation instead uses parentheses and precedence conventions to distinguish this expression from $a+bc$. All three can describe the same abstract syntax tree.

A numeral system represents numbers by finite strings of symbols with stated interpretation rules. A positional notation assigns place values according to powers of a base: in base $b$, the string $d_n{d}_{n-1}\cdots d_0$ means ${\sum }_{j=0}^n{d}_j{b}^j$, with $0\le d_j<b$.

Thus $1011_2=8+2+1=11_{10}$. The unary numeral system instead represents a count by repeated marks. A numeral is a representation of a number, not the number itself: different strings and bases can name the same abstract integer. Computational costs can depend strongly on the representation length.

A mathematical model parameter is a quantity held fixed while solving a particular instance of a model, but allowed to vary between instances. Changing a parameter can change equilibria, their stability and the qualitative behavior of trajectories. Parameter constancy does not mean probabilistic independence.

A parameter specifies a member of a family of mathematical models and is held fixed while a particular solution evolves. Varying it can change equilibrium existence, stability or long-term dynamics, producing a bifurcation. A model parameter differs from its evolving state variables and from an initial condition, even though all may be numerical inputs to a computation.

A function-free rule language based on definite first-order Horn clauses, normally with safety conditions on rule variables. Positive Datalog has a least Herbrand model obtained by forward chaining.

Goal-directed rule evaluation that replaces a goal by premises of a matching rule. Shared variables require consistent answer first-order substitutions across the premises.

Rule evaluation that repeatedly adds consequences of premises already known to hold. Positive Datalog evaluation computes its least Herbrand model in this way.

Negation as failure interprets failure of a specified proof search as a negative result. In the Prolog operation \+ Goal, the negative goal succeeds when trying Goal fails in finite time; it fails when Goal succeeds. A search that never finishes does not establish the negative result.^[ref]

For example, suppose a finite knowledge base records penguin(opus) and has no rule capable of deriving penguin(robin). A search for penguin(robin) finitely fails, so its negation succeeds under this operational rule. That result relies on the chosen knowledge base and search semantics. Adding the missing fact changes the result; an unrecorded fact in the outside world has not been independently disproved.

Stable model semantics gives a related model-based interpretation for negative rule premises through the stable model reduct. The rules $p\leftarrow \mathrm{not}q$ and $q\leftarrow \mathrm{not}p$ have two stable models, $\{p\}$ and $\{q\}$: in either candidate, the surviving rule forces exactly its one member. Neither atom follows by skeptical entailment. Operational finite failure and a chosen model semantics must therefore be distinguished when interpreting a negative rule.

A vessel of water used to heat another vessel indirectly and comparatively uniformly.

A chemical substance with the same molecular formula as another but a different connectivity of chemical atoms.

An instruction whose encoding contains no explicit operand addresses. A stack machine obtains operands implicitly from its operand stack, but absence of explicit addresses does not logically force that design: fixed implicit processor registers are another possibility. A zero-address indirect-load instruction can still obtain an arbitrary memory address from the stack; “zero-address” describes the instruction's encoding, not the absence of address-valued data.

The POWER processor architecture family, whose shared-memory ordering uses dependency rules and barriers such as sync, lwsync and isync. The relevant ordering examples are documented in Understanding POWER Multiprocessors (2011).

A device-independent interface expresses requests without exposing each peripheral's control registers or protocol to the client. A device driver translates these requests into device-specific operations. This lets an application retain its interface when the supported hardware changes.

A data storage device records encoded information in a physical medium so it can be read later. Semiconductor memory, magnetic disks and optical media use different physical states, access mechanisms and persistence properties. Important quantities include capacity, access latency, transfer bandwidth and endurance. A device's logical address space is an interface: internal controllers may remap blocks or cache writes. Successful submission of a write request is therefore distinct from a specified durability guarantee after power loss; the system's synchronization contract must establish that guarantee.

The elapsed delay between a request or event and the corresponding response. A latency model must specify whether setup, waiting, transfer and processing overhead are included.

Potassium bicarbonate is potassium hydrogen carbonate, $\mathrm{KHC}{\mathrm{O}}_3$. Its bicarbonate ion can accept or donate a proton, connecting carbonate and dissolved carbon-dioxide acid-base chemistry.

Adding acid can release carbon dioxide. Compared with potassium carbonate, it retains an additional hydrogen and therefore has a different acid-neutralizing capacity per mole.