279 research outputs found
Pathobiology and management of hypergastrinemia and the Zollinger-Ellison syndrome.
Gastrin is both stimulatory and trophic to the cells of the gastric fundus--parietal and peptic cells, and enterochromaffin-like (ECL) cells which are major intermediaries of the gastrin effect. Gastrin (from the antrum) and acid (from the fundus) represent the interactive positive and negative limbs of a feedback loop. The nature and extent of sub-loops, perhaps involving the vagus, acetylcholine, histamine, and other peptides and cell products are at present unclear or unknown. Loss of either gastrin or acid has predictable consequences. Absent acid, as in pernicious anemia or as a result of omeprazole, leads to hypergastrinemia. In rats, such hypergastrinemia (gastrin > 1,000 pg/ml) causes fundic ECL hyperplasia and, eventually, carcinoids; in humans with pernicious anemia, hypergastrinemia causes ECL-cell hyperplasia, which may progress to carcinoids that are reversible upon withdrawal of gastrin, illustrated by three cases described here. Loss of gastrin by antrectomy for duodenal ulcer leads to fundic involution and marked reduction in basal acid output, maximal acid output, and fundic histamine. An uncontrolled excess of gastrin, as from a gastrinoma outside the negative feedback loop, causes acid and pepsin hypersecretion with upper GI mucosal damage, the Zollinger-Ellison syndrome. This paper summarizes the abnormal regulation of gastrin and the biology, natural history, diagnosis, and management of ZE syndrome by medical and surgical means
Compilation of extended recursion in call-by-value functional languages
This paper formalizes and proves correct a compilation scheme for
mutually-recursive definitions in call-by-value functional languages. This
scheme supports a wider range of recursive definitions than previous methods.
We formalize our technique as a translation scheme to a lambda-calculus
featuring in-place update of memory blocks, and prove the translation to be
correct.Comment: 62 pages, uses pi
Initial Semantics for Strengthened Signatures
We give a new general definition of arity, yielding the companion notions of
signature and associated syntax. This setting is modular in the sense requested
by Ghani and Uustalu: merging two extensions of syntax corresponds to building
an amalgamated sum. These signatures are too general in the sense that we are
not able to prove the existence of an associated syntax in this general
context. So we have to select arities and signatures for which there exists the
desired initial monad. For this, we follow a track opened by Matthes and
Uustalu: we introduce a notion of strengthened arity and prove that the
corresponding signatures have initial semantics (i.e. associated syntax). Our
strengthened arities admit colimits, which allows the treatment of the
\lambda-calculus with explicit substitution.Comment: In Proceedings FICS 2012, arXiv:1202.317
Initiality for Typed Syntax and Semantics
We give an algebraic characterization of the syntax and semantics of a class
of simply-typed languages, such as the language PCF: we characterize
simply-typed binding syntax equipped with reduction rules via a universal
property, namely as the initial object of some category. For this purpose, we
employ techniques developed in two previous works: in [2], we model syntactic
translations between languages over different sets of types as initial
morphisms in a category of models. In [1], we characterize untyped syntax with
reduction rules as initial object in a category of models. In the present work,
we show that those techniques are modular enough to be combined: we thus
characterize simply-typed syntax with reduction rules as initial object in a
category. The universal property yields an operator which allows to specify
translations - that are semantically faithful by construction - between
languages over possibly different sets of types.
We specify a language by a 2-signature, that is, a signature on two levels:
the syntactic level specifies the types and terms of the language, and
associates a type to each term. The semantic level specifies, through
inequations, reduction rules on the terms of the language. To any given
2-signature we associate a category of models. We prove that this category has
an initial object, which integrates the types and terms freely generated by the
2-signature, and the reduction relation on those terms generated by the given
inequations. We call this object the (programming) language generated by the
2-signature.
[1] Ahrens, B.: Modules over relative monads for syntax and semantics (2011),
arXiv:1107.5252, to be published in Math. Struct. in Comp. Science
[2] Ahrens, B.: Extended Initiality for Typed Abstract Syntax. Logical
Methods in Computer Science 8(2), 1-35 (2012)Comment: presented at WoLLIC 2012, 15 page
Pseudoconvex domains spread over complex homogeneous manifolds
Using the concept of inner integral curves defined by Hirschowitz we
generalize a recent result by Kim, Levenberg and Yamaguchi concerning the
obstruction of a pseudoconvex domain spread over a complex homogeneous manifold
to be Stein. This is then applied to study the holomorphic reduction of
pseudoconvex complex homogeneous manifolds X=G/H. Under the assumption that G
is solvable or reductive we prove that X is the total space of a G-equivariant
holomorphic fiber bundle over a Stein manifold such that all holomorphic
functions on the fiber are constant.Comment: 21 page
On the implementation of recursion in call-by-value functional languages
Functional languages encourage the extensive use of recursive fonctions and data structures. It is therefore important that they efficiently implement recursion. In this paper, we formalize and improve a known implementation technique for recursion. The original technique was introduced by Cousineau and Mauny as the «in-place updating trick». Consider a list of mutually recursive definitions. The technique consists in allocating a dummy, uninitialized heap block for each recursive definition. The size of these blocks is guessed from the shape of each definition. Then, the right-hand sides of the definitions are computed. Recursively-defined identifiers thus refer to the corresponding dummy blocks. This leads, for each definition, to a block of the expected size. Eventually, the contents of the obtained blocks are copied to the dummy blocks, updating them in place. The only change we propose to this scheme is to update the dummy blocks as soon as possible, immediately after each definition is computed, thus making it available for further use. At the source language level, the improvement allows to extend the class of expressions allowed as right-hand sides of recursive definitions, usually restricted to syntactic functions. We formalize our technique as a translation scheme to a lambda-calculus featuring in-place updating of memory blocks, and prove the translation to be faithful
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