bluuebunny/crossref_metadata_2025 huggingface dataset:
Invariants of 3-manifolds derived from universal invariants of framed links
Authors: Ohtsuki Tomotada
Published: November 2008

Reshetikhin and Turaev [10] gave a method to construct a topological invariant of compact oriented 3-manifolds from a ribbon Hopf algebra (e.g. a quantum group Uq(sl2)) using finite-dimensional representations of it. In this paper we give another independent method to construct a topological invariant of compact oriented 3-manifolds from a ribbon Hopf algebra via universal invariants of framed links without using representations of the algebra. For Uq(sl2) these two methods give different invariants of 3-manifolds.
On quantumSU(2) invariants and generalized bridge numbers of knots
Authors: Yokota Yoshiyuki
Published: November 2008

Consider a knotKin a closed, oriented 3-manifoldM. A genusgHeegaard decomposition ofMis said to be agenus g bridge decompositionofKif it also decomposesKinto trivial arcs in each handlebody. Thegenus g bridge numberofK, denoted bybg(K), is defined as the minimal number of trivial arcs in a handlebody among all the genusgbridge decompositions ofK[2, 13].
A toral configuration space and regular semisimple conjugacy classes
Authors: Lehrer G. I.
Published: November 2008

For any topological space X and integer n ≥ 1, denote by Cn(X) the configuration space

The symmetric group Sn acts by permuting coordinates on Cn(X) and we are concerned in this note with the induced graded representation of Sn on the cohomology space H*(Cn(X)) = ⊕iHi (Cn(X), ℂ), where Hi denotes (singular or de Rham) cohomology. When X = ℂ, Cn(X) is a K(π, 1) space, where π is the n-string pure braid group (cf. [3]). The corresponding representation of Sn in this case was determined in [5], using the fact that Cn(C) is a hyperplane complement and a presentation of its cohomology ring appears in [1] and in a more general setting, in [8] (see also [2]).
Periodic orbits of transversal maps
Authors: Casasayas J. , Llibre J. , Nunes A.
Published: November 2008

One of the most useful theorems for proving the existence of fixed points, or more generally, periodic points of a continuous self-map f of a compact manifold, is the Lefschetz fixed point theorem. When studying the periodic points of f it is convenient to use the Lefschetz zeta function Zf(t) of f, which is a generating function for the Lefschetz numbers of all iterates of f. The function Zf(t) is rational in t and can be computed from the homological invariants of f. See Section 2 for a precise definition. Thus there exists a relation, based on the Lefschetz fixed point theorem, between the periodic points of a self-map of a manifold f:M → M and the properties of the induced homomorphism f*i on the homology groups of M. This relation has been used in several papers, namely [F1], [F2], [F3] and [M]. In these papers, sufficient conditions are given for the existence of infinitely many periodic points in the case when all the zeros and poles of the associated Lefschetz zeta function are roots of unit. Here we restrict ourselves to maps defined on manifolds with a certain homology type. For transversal maps f defined on this class of manifolds, it is possible to extend the techniques introduced in [F1], [F3] and [M] in order to obtain information on the set of periods of f. We recover the above mentioned results of J. Franks and T. Matsuoka, and derive new results on the set of periods of f when the associated Lefschetz zeta function has zeros or poles outside the unit circle.
The finite inner automorphism groups of division rings
Authors: Shirvani M.
Published: November 2008

Let G be a finite group of automorphisms of an associative ring R. Then the inner automorphisms (x↦ u−1xu = xu, for some unit u of R) contained in G form a normal subgroup G0 of G. In general, the Galois theory associated with the outer automorphism group G/G0 is quit well behaved (e.g. [7], 2·3–2·7, 2·10), while little group-theoretic restriction on the structure of G/G0 may be expected (even when R is a commutative field). The structure of the inner automorphism groups G0 does not seem to have received much attention so far. Here we classify the finite groups of inner automorphisms of division rings, i.e. the finite subgroups of PGL (1, D), where D is a division ring. Such groups also arise in the study of finite collineation groups of projective spaces (via the fundamental theorem of projective geometry, cf. [1], 2·26), and provide examples of finite groups having faithful irreducible projective representations over fields.
Covering properties of open continuous mappings having two valences between Riemann surfaces
Authors: Lyzzaik Abdallah
Published: November 2008

Let be an open Riemann surface with finite genus and finite number of boundary components, and let be a closed Riemann surface. An open continuous function from to is termed a (p, q)-map, 0 < q < p, if it has a finite number of branch points and assumes every point in either p or q times, counting multiplicity, with possibly a finite number of exceptions. These comprise the most general class of all non-trivial functions having two valences between and .

The object of this paper is to study the geometry of (p, q)-maps and establish a generalized embedding theorem which asserts that the image surfaces of (p, q)-maps embed in p-fold closed coverings possibly having branch points off the image surfaces.
Differential fields and differentiable functions of algebraic numbers
Authors: Müller Eric F.
Published: November 2008

We prove that each countable differential field of characteristic 0 can be embedded into the differential ring of infinitely differentiable functions from the algebraic numbers to the complex numbers. This statement remains valid when we replace the set of algebraic numbers by an arbitrary non-empty countable set of complex numbers without any isolated points.
A systematic approach to symmetric presentations. I. Involutory generators
Authors: Curtis R. T. , Hammas A. M. A. , Bray J. N.
Published: November 2008

In this paper we conduct a systematic, computerized search for groups generated by small, but highly symmetric, sets of involutions. Many classical groups are readily obtained in this way, as are a number of sporadic simple groups. The techniques of symmetric generation developed elsewhere are described afresh, and the results are presented in a convenient tabular form.
Note on the spectral sequence converging to cohomology of an extra special p-group for odd prime p
Authors: Yagita Nobuaki
Published: November 2008

Extra special p-groups are groups which are central extensions of ℤ/p by elementary abelian p-groups. The cohomology ring of these groups occupies an important place in equivariant cohomology theories and in representation theories. Quillen[6] decided the cohomology for p = 2 and Tezuka-Yagita [7] studied the varieties defined by its mod p cohomology for odd prime p. However, for applications we need more information about the behaviour of the Hochschild-Serre spectral sequence (see [3] p. 295, [1] p. 6).
The minimal extension of P-localization on groups
Authors: Berrick A. J. , Tan G. C.
Published: November 2008

Let P be a fixed set of primes, the category of all groups and group-homomorphisms, and the full subcategory of nilpotent groups. In [9], an idempotent functor called P-localization, was defined so as to extend the ℤ-module-theoretic localization of abelian groups. There are two well-known extensions of e to , namely, Bousfield's P-localization [2], [4], denoted by EZP, and Ribenboim's P-localization [13], usually denoted by ( )P. Ribenboim's P-localization is the maximal extension among localizations extending e to in that it maximizes the number of groups in its image [7]. The localized groups obtained after applying Ribenboim's P-localization are precisely the P-local groups, that is, the groups having unique nth-root for every n whichis co-prime to P, [13]. Being maximal is equivalent to this class of P-localized groups being the saturated class of groups generated by e–equivalences, that is, group homomorphisms between nilpotent groups which become isomorphisms after applying e.
On the zeros and Fourier transforms of entire functions in the Paley–Wiener space
Authors: Dyakonov Konstantin M.
Published: November 2008

Let f be an entire function of the form

where ø is a function in L2(ℝ) with compact support. If f|ℝ is real-valued then, for obvious reasons,
(a) the supporting interval for ø is symmetric with respect to the origin, and

Assuming that f has no zeros in {Im z > 0}, we prove that the converse is also true: (a) and (b) together imply that f|ℝ takes values in αℝ, where α is a fixed complex number.

The proof relies on a certain formula involving the Dirichlet integral, which may be interesting on its own.
Sublinear discrete-time order-preserving dynamical systems
Authors: Jiang J. F.
Published: November 2008

Suppose that the continuous mapping is order-preserving and sublinear. If every positive semi-orbit has compact closure, then every positive semi-orbit converges to a fixed point. This result does not require that the order be strongly preserved.
Betweenness relations and cycle-free partial orders
Authors: Truss J. K.
Published: November 2008

The intuition behind the notion of a cycle-free partial order (CFPO) is that it should be a partial ordering (X, ≤ ) in which for any sequence of points (x0, x1;…, xn–1) with n ≤ 4 such that xi is comparable with xi+1 for each i (indices taken modulo n) there are i and j with j ╪ i, i + 1 such that xj lies between xi and xi+1. As its turn out however this fails to capture the intended class, and a more involved definition, in terms of the ‘Dedekind–MacNeille completion’ of X was given by Warren[5]. An alternative definition involving the idea of a betweenness relation was proposed by P. M. Neumann [1]. It is the purpose of this paper to clarify the connections between these definitions, and indeed between the ideas of semi-linear order (or ‘tree’), CFPO, and the betweenness relations described in [1]. In addition I shall tackle the issue of the axiomatizability of the class of CFPOs.
Horizontal partitions and Kleshchev's algorithm
Authors: Walker Grant
Published: November 2008

We shall work with rational Mn(K)-modules, where K is an infinite field of prime characteristic p > 0, and Mn(K) is the full matrix semigroup of n × n matrices over K. Recall that equivalence classes of simple rational Mn(K)-modules are parametrized by the set of all partitions λ = (λ1, λ2, …, λl) of length l = l(λ) ≤ n, and that the socle L(λ) of the Schur module (or dual Weyl module) H0(λ) is a simple Mn(K)-module whose highest weight corresponds to the partition λ.
Symmetric amenability and the nonexistence of Lie and Jordan derivations
Authors: Johnson B. E.
Published: November 2008

A. M. Sinclair has proved that if is a semisimple Banach algebra then every continuous Jordan derivation from into is a derivation ([12, theorem 3·3]; ‘Jordan derivation’ is denned in Section 6 below). If is a Banach -bimodule one can consider Jordan derivations from into and ask whether Sinclair's theorem is still true. More recent work in this area appears in [1]. Simple examples show that it cannot hold for all modules and all semisimple algebras. However, for more restricted classes of algebras, including C*-algebras one does get a positive result and we develop two approaches. The first depends on symmetric amenability, a development of the theory of amenable Banach algebras which we present here for the first time in Sections 2, 3 and 4. A Banach algebra is symmetrically amenable if it has an approximate diagonal consisting of symmetric tensors. Most, but not all, amenable Banach algebras are symmetrically amenable and one can prove results for symmetric amenability similar to those in [8] for amenability. However, unlike amenability, symmetric amenability does not seem to have a concise homological characterisation. One of our results [Theorem 6·2] is that if is symmetrically amenable then every continuous Jordan derivation into an -bimodule is a derivation. Special techniques enable this result to be extended to other algebras, for example all C*-algebras. This approach to Jordan derivations appears in Section 6.
Packing dimension, Hausdorff dimension and Cartesian product sets
Authors: Xiao Yimin
Published: November 2008

We show that the dimension adim introduced by R. Kaufman (1987) coincides with the packing dimension Dim, but the dimension aDim introduced by Hu and Taylor [7] is different from the Hausdorff dimension. These results answer questions raised by Hu and Taylor.
Pro-p groups of finite coclass
Authors: Shalev A. , Zelmanov E. I.
Published: November 2008

In 1980 Leedham-Green and Newman made a series of conjectures on the structure of pro-p groups and finite p-groups of a given coclass [10]. These insightful conjectures have gradually been proved, in a series of papers (some of which are still unpublished) by Leedham-Green, Donkin, McKay and Plesken (see, e.g. [11, 2, 8, 9, 13, 14]). Some simplifications (as well as additional information) have recently been given in [12, 15].
On the length formula of Hoskin and Deligne and associated graded rings of two-dimensional regular local rings
Authors: Johnston Bernard L. , Verma Jugal
Published: November 2008

Let (R, m) be a 2-dimensional regular local ring and I an m-primary ideal. The aim of this paper is to find conditions on I so that the associated graded ring of I,

and the Rees ring of I,

where t is an indeterminate, are Cohen–Macaulay (resp. Gorenstein). To this end, we use the results and techniques from Zariski's theory of complete ideals ([14], appendix 5) and its later generalizations and refinements due to Huneke [7] and Lipman[8]. The main result is an application of three deep theorems: (i) a generalization of Macaulay's classical theorem on Hilbert series of Gorenstein graded rings [13], (ii) a generalization of the Briançon–Skoda theorem due to Lipman and Sathaye [9], and (iii) a formula for the length of R/I, where I is a complete m-primary ideal, due to Hoskin[4] and Deligne[1].
Matrix generators for Fischer's group Fi24
Authors: Wilson Robert A.
Published: November 2008

In this paper we show how to construct 781 × 781 matrices over GF(3), generating the largest of the three Fischer groups. For some purposes these are more useful than the permutations on 306936 points, as they require only one-sixth of the storage space. We also construct generators for its triple cover, as 1566 × 1566 matrices over GF(2), and for the derived group thereof, as 783 × 783 matrices over GF(4).
Operators in finite distributive subspace lattices, I
Authors: Spanoudakis N. K.
Published: November 2008

The purpose of this paper is to settle in the negative an open problem in operator theory, which asks whether in a finite distributive subspace lattice ℒ on a Hilbert space, every finite rank operator of Alg ℒ can be written as a finite sum of rank one operators from Alg ℒ. The counter-example constructed is on a specific Hilbert space realization of the free distributive lattice on three generators and the operator which fails the above property has rank two.
Strongly spin-preserving solutions of the Yang-Baxter equation and their link invariants
Authors: Hennings M. A.
Published: November 2008

Recently Kauffman[2, 3] has classified the (strongly) spin-preserving solutions of the Yang—Baxter equation, and in particular discussed two solutions. One of these can be used to obtain the Jones polynomial, while the other (with care) leads to the Alexander polynomial. In this paper we shall complete this analysis, and shall describe all strongly spin-preserving invertible solutions of the Yang-Baxter equation which lead to link invariants. Having done this, we investigate what sort of link invariants can be obtained from these solutions. It turns out that these invariants are precisely those which have been described in Hennings [l].
A rational invariant for certain infinite discrete groups
Authors: Johnson F. E. A.
Published: November 2008

We introduce a rational-valued invariant which is capable of distinguishing between the commensurability classes of certain discrete groups, namely, the fundamental groups of smooth closed orientable aspherical manifolds of dimensional 4k(k ≥ 1) whose Euler characteristic χ(Λ) is non-zero. The invariant in question is the quotient

where Sign (Λ) is the absolute value of the signature of the intersection form

and [Λ] is a generator of H4k(Λ; ℝ).
Generators on the arc component of compact connected groups
Authors: Hofmann Karl H. , Morris Sidney A.
Published: November 2008

It is well-known that a compact connected abelian group G has weight w(G) less than or equal to the cardinality c of the continuum if and only if it is monothetic; that is, if and only if it can be topologically generated by one element. Hofmann and Morris [2] extended this by showing that a compact connected (not necessarily abelian) group can be topologically generated by two elements if and only if w(G) ≤ c.
On H-balls and canonical regions of loxodromic elements in complex hyperbolic space
Authors: Kamiya Shigeyasu
Published: November 2008

Let U(1, n; ℂ) be the automorphism group of the Hermitian form

for . We can regard an element of U(1, n; ℂ) as a transformation acting on , where is the closure of the complex unit ball

The non-trivial elements of U(1, n; ℂ) fall into three conjugacy types, depending on the number and the location of their fixed points. Let g be a non-trivial element of U(1, n; ℂ). We call g elliptic if it has a fixed point in Bn and g parabolic if it has exactly one fixed point and this lies on the boundary ∂Bn. An element g will be called loxodromic if it has exactly two fixed points and they lie on ∂Bn.
The relativistic clock problem
Authors: Mikhail F. I.
Published: November 2008

The so-called ‘clock paradox’ is concerned with the difference in the time-intervals reckoned by two observers in relative motion for the lapse of time between two encounters. In this paper the problem is treated purely by general relativity by considering a particular example in which the two observers are attached to two test-particles moving freely in the field of a gravitating mass; one of these makes complete revolutions in a circular orbit while the other moves radially outwards and inwards. The time-interval between two successive encounters is shorter in the reckoning of the former than in that of the latter. The difference is found to agree qualitatively with a naïve application of special relativity.
Some results on the product of distributions
Authors: Fisher B.
Published: November 2008

The product of two distributions f and g on the open interval (a, b), where −∞ ≤ a < b ≤ ∞, was defined(1) as the limit of the sequence {fngn}, provided this sequence is regular on (a, b), where

for n = 1, 2, … and ρ is a fixed infinitely differentiable function having the following properties:

(1) ρ(x) = 0 for |x| ≥ 1,

(2) ρ(x) ≥ 0,

(3) ρ(x) = ρ(−x),
An extension of Cramér's estimate for the absorption probability of a random walk
Authors: Arjas E. , Speed T. P.
Published: November 2008

Consider a real-valued random walk

which is defined on a Markov chain {Xn: n ≥ 0} with countable state space I. We assume that a matrix Q(.) = (qij(.)) is given such that
On the congruence y2 ≡ x5 − a (mod p)
Authors: Rajwade A. R.
Published: November 2008

The object of this paper is to complete the half proved theorem 2 of (1).

Let be a primitive fifth root of unity. Any element of Z[ζ] is a polynomial f(ζ) in ζ of degree ≤ 3 since 1 + ζ + ζ2 + ζ3 + ζ4 = 0. The units of Z[ζ] are ± ζi(1 + ζ)i or better still , with 0 ≤ i ≤ 4, j ε Z, where is the fundamental unit of the maximal real subfield of Q(ζ).
On the historical development of the theory of finite inhomogeneous Markov chains
Authors: Seneta E.
Published: November 2008

The main purpose of the note is to compare necessary and sufficient conditions for weak ergodicity of finite inhomogeneous Markov chains given by Doeblin (3) and Hajnal (4), the former paper being little known; and more generally to expand on the nature and consequences of Doeblin's approach as compared to Hajnal's in some detail. A consequence is some insight into the relation between various ‘coefficients of ergodicity’.
Intersections of Loci on an Algebraic V4
Authors: Todd J. A.
Published: November 2008

The problem of residual intersections is one of considerable importance in algebraic geometry. In its most general form the problem may be stated as follows. On a given variety V of d dimensions two varieties A and B, of respective dimensions k and k′, pass through a variety C whose dimension r is not less than r′ = k + k′ – d. It is required to determine the variety D of dimension r′ which forms the residual intersection of A and B. The classical paper on this subject is that of Severi*. He considers the case in which V is a linear space, and obtains a large variety of enumerative results connecting the characters of the residual intersection with those of the given loci.
The Elastic Stability of a Corrugated Plate Under a Shearing Force
Authors: Green A. E.
Published: November 2008

1. The elastic stability of a long flat plate when acted on by a shearing force along its edges has been discussed by Southwell and Skan*, and Leggett† has solved the shearing problem when the plate has a small constant curvature. The present paper deals with the elastic stability of a long corrugated plate which is acted on by a shearing force along its generators, the work being applicable to plates with any given number of bays forming the corrugations. It is supposed that the plate is thin and that the depthdof a bay is a small multiple of the semithicknessh;little progress has been made without some such assumption as the second, which enables us to reduce the fundamental equations to a soluble form.
Functional Pearls: The Minout problem
Authors: Bird Richard S.
Published: November 2008

The problem of computing the smallest natural number not contained in a given set of natural numbers has a number of practical applications. Typically, the given set represents the indices of a class of objects ‘in use’ and it is required to find a ‘free’ object with smallest index. Our purpose in this article is to derive a linear-time functional program for the problem. There is an easy solution if arrays capable of being accessed and updated in constant time are available, but we aim for an algorithm that employs only standard lists. Noteworthy is the fact that, although an algorithm using lists is the result, the derivation is carried out almost entirely in the world of sets.
Type inference with simple subtypes
Authors: Mitchell John C.
Published: November 2008

Subtyping appears in a variety of programming languages, in the form of the ‘automatic coercion’ of integers to reals, Pascal subranges, and subtypes arising from class hierarchies in languages with inheritance. A general framework based on untyped lambda calculus provides a simple semantic model of subtyping and is used to demonstrate that an extension of Curry's type inference rules are semantically complete. An algorithm G for computing the most general typing associated with any given expression, and a restricted, optimized algorithm GA using only atomic subtyping hypotheses are developed. Both algorithms may be extended to insert type conversion functions at compile time or allow polymorphic function declarations as in ML.
Metamorph – a formal methods toolkit with application to the design of digital hardware
Authors: Brumfitt P.J.
Published: November 2008

MetaMorph is a software tool that supports transformation and proof for an equational non-strict functional language. It was developed as a vehicle for research into the synthesis of digital logic, but is equally suitable for reasoning about functional programs. The theorem prover may be used for verifying new reusable transforms and to assist the search for transformation sequences having a constrained goal. The paper provides an overview of all aspects of the project, and a brief discussion of its application to hardware.
The use of functional languages in teaching computer science
Authors: Harrison Rachel
Published: November 2008

This survey presents information concerning the use of functional languages (both strict and non-strict) for teaching in higher education. It lists the languages used by over 70 different institutions, the years in which the courses are given, and the recommended textbooks.
An incremental, exploratory and transformational environment for lazy functional programming
Authors: Runciman Colin , Toyn Ian , Firth Mike
Published: November 2008

Most programming environments for functional languages offer a single tool used to evaluate programs – either a batch compiler or an interpreter with a read-eval-print loop. This paper presents a programming environment that supports not only evaluation, but also a range of other programming activities including transformation. The environment is designed to encourage working in an incremental and exploratory style, avoiding constraints on the order in which things must be done yet guarenteeing security. What has already been done towards the development of a program automatically persists, as does information about what has yet to be done. For instance, new laws can be introduced as conjectures and used in program transformation, but full details of proof obligations and dependencies are maintained.

The paper outlines the functional language supported by the environment, and uses an extended example to illustrate program construction, execution, tracing, modification and transformation.
Pattern matching with abstract data types
Authors: Burton F. Warren , Cameron Robert D
Published: November 2008

Pattern matching in modern functional programming languages is tied to the representation of data. Unfortunately, this is incompatible with the philosophy of abstract data types.

Two proposals have been made to generalize pattern matching to a broader class of types. The laws mechanism of Miranda allows pattern matching with non-free algebraic data types. More recently, Wadler proposed the concept of views as a more general solution, making it possible to define arbitrary mappings between a physical implementation and a view supporting pattern matching. Originally, it was intended to include views in the new standard lazy functional programming language Haskell.

Laws and views each offer important advantages, particularly with respect to data abstraction. However, if not used with great care, they also introduce serious problems in equational reasoning. As a result, laws have been removed from Miranda and views were not included in the final version of Haskell.

We propose a third approach which unifies the laws and views mechanisms while avoiding their problems. Philosophically, we view pattern matching as a bundling of case recognition and component selection functions instead of a method for inverting data construction. This can be achieved by removing the implied equivalence between data constructors and pattern constructors. In practice, we allow automatic mapping into a view but not out of the view. We show that equational reasoning can still be used with the resulting system. In fact, equational reasoning is easier, since there are fewer hidden traps.
Dynamics in ML
Authors: Leroy Xavier , Mauny Michel
Published: November 2008

Objects with dynamic types allow the integration of operations that essentially require runtime type-checking into statically-typed languages. This paper presents two extensions of the ML language with dynamics, based on our work on the CAML implementation of ML, and discusses their usefulness. The main novelty of this work is the combination of dynamics with polymorphism.
A paradigmatic object-oriented programming language: Design, static typing and semantics
Authors: Bruce Kim B.
Published: November 2008

To illuminate the fundamental concepts involved in object-oriented programming languages, we describe the design of TOOPL, a paradigmatic, statically-typed, functional, object-oriented programming language which supports classes, objects, methods, hidden instance variables, subtypes and inheritance.

It has proven to be quite difficult to design such a language which has a secure type system. A particular problem with statically type checking object-oriented languages is designing typechecking rules which ensure that methods provided in a superclass will continue to be type correct when inherited in a subclass. The type-checking rules for TOOPL have this feature, enabling library suppliers to provide only the interfaces of classes with actual executable code, while still allowing users to safely create subclasses. To achieve greater expressibility while retaining type-safety, we choose to separate the inheritance and subtyping hierarchy in the language.

The design of TOOPL has been guided by an analysis of the semantics of the language, which is given in terms of a model of the F-bounded second-order lambda calculus with fixed points at both the element and type level. This semantics supports the language design by providing a means to prove that the type-checking rules are sound, thus guaranteeing that the language is type-safe.

While the semantics of our language is rather complex, involving fixed points at both the element and type level, we believe that this reflects the inherent complexity of the basic features of object-oriented programming languages. Particularly complex features include the implicit recursion inherent in the use of the keyword, self, to refer to the current object, and its corresponding type, MyType. The notions of subclass and inheritance introduce the greatest semantic complexities, whereas the notion of subtype is more straightforward to deal with. Our semantic investigations lead us to recommend caution in the use of inheritance, since small changes to method definitions in subclasses can result in major changes to the meanings of the other methods of the class.
Principal signatures for higher-order program modules
Authors: Tofte Mads
Published: November 2008

In this paper we present a language for programming with higher-order modules. The language HML is based on Standard ML in that it provides structures, signatures and functors. In HML, functors can be declared inside structures and specified inside signatures; this is not possible in Standard ML. We present an operational semantics for the static semantics of HML signature expressions, with particular emphasis on the handling of sharing. As a justification for the semantics, we prove a theorem about the existence of principal signatures. This result is closely related to the existence of principal type schemes for functional programming languages with polymorphism.
A system of constructor classes: overloading and implicit higher-order polymorphism
Authors: Jones Mark P.
Published: November 2008

This paper describes a flexible type system that combines overloading and higher-order polymorphism in an implicitly typed language using a system of constructor classes—a natural generalization of type classes in Haskell. We present a range of examples to demonstrate the usefulness of such a system. In particular, we show how constructor classes can be used to support the use of monads in a functional language. The underlying type system permits higher-order polymorphism but retains many of the attractive features that have made Hindley/Milner type systems so popular. In particular, there is an effective algorithm that can be used to calculate principal types without the need for explicit type or kind annotations. A prototype implementation has been developed providing, amongst other things, the first concrete implementation of monad comprehensions known to us at the time of writing.
Combinators for parsing expressions
Authors: Hill Steve
Published: November 2008

This paper describes a scheme for constructing parsers based on the top-down combinator approach. In particular, it describes a set of combinators for parsing expressions described by ambiguous grammars with precedence and associativity rules. The new combinators embody the mechanical grammar manipulations typically employed to remove left-recursion and hence help to avoid the possibility of a non-terminating parser. A number of approaches to the problem are described—the most elegant and efficient method is based on continuation passing. As a practical demonstration, a parser for the expression part of the C programming language is presented. The expression combinators are general, and may be constructed from any suitable set of top-down combinators. A comparison with parser generators shows that the combinator approach is most applicable for rapid development.
λν, a calculus of explicit substitutions which preserves strong normalisation
Authors: Benaissa Zine-El-Abidine , Briaud Daniel , Lescanne Pierre , Rouyer-Degli Jocelyne
Published: November 2008

Explicit substitutions were proposed by Abadi, Cardelli, Curien, Hardin and Lévy to internalise substitutions into λ-calculus and to propose a mechanism for computing on substitutions. λν is another view of the same concept which aims to explain the process of substitution and to decompose it in small steps. It favours simplicity and preservation of strong normalisation. This way, another important property is missed, namely confluence on open terms. In spirit, λν is closely related to another calculus of explicit substitutions proposed by de Bruijn and called CλξΦ. In this paper, we introduce λν, we present CλξΦ in the same framework as λν and we compare both calculi. Moreover, we prove properties of λν; namely λν correctly implements β reduction, λν is confluent on closed terms, i.e. on terms of classical λ-calculus and on all terms that are derived from those terms, and finally λν preserves strong normalisation in the following sense: strongly β normalising terms are strongly λν normalising.
π-RED+ An interactive compiling graph reduction system for an applied λ-calculus
Authors: Gärtner Dietmar , Kluge Werner E.
Published: November 2008

This paper describes a compiling graph reduction system which realizes the reduction semantics of a fully-fledged applied λ-calculus. High-level functional programs are conceptually executed as sequences of program transformations governed by full β-reductions. They may be carried out step-by-step, and intermediate programs may be displayed in high-level notation, rendering the system suitable for interactive program design, high-level debugging, and also for teaching basic programming language concepts and language interpretation. Run-time efficiency for production runs is achieved by means of an abstract stack machine ASM which serves as an intermediate level of code generation. It employs multiple stacks for reasonably fast function calls, optimized tail-end recursions, and earliest possible releases of subgraphs that are no longer needed. The ASM involves an interpreter if and only if potential naming conflicts need to be resolved when reducing partial function applications.
Numerical methods for differential algebraic equations
Authors: März Roswitha
Published: November 2008

Differential algebraic equations (DAE) are special implicit ordinary differential equations (ODE)

where the partial Jacobian f′y(y, x, t) is singular for all values of its arguments.
Automatic grid generation
Authors: Henshaw William D.
Published: November 2008

Current methods for the automatic generation of grids are reviewed. The approaches to grid generation that are discussed include Cartesian, multi-block-structured, overlapping and unstructured. Emphasis is placed on those methods that can create high-quality grids appropriate for the solution of equations of a hyperbolic nature, such as those that arise in fluid dynamics. Numerous figures illustrate the different grid generation techniques.
Selbstregulationsförderung in einer Biologie-Unterrichtseinheit
Authors: Labuhn Andju Sara , Bögelholz Susanne , Hasselhorn Marcus
Published: November 2008

Zusammenfassung. Im vorliegenden Artikel werden langfristige und differentielle Effekte von unterrichtsintegrierter Selbstregulationsförderung in einer Biologie-Unterrichtseinheit im Fach Naturwissenschaften berichtet. Aufbauend auf einer Studie von Labuhn, Bögeholz und Hasselhorn (2008) mit 199 Schüler(inne)n der siebten Jahrgangsstufe wurde die langfristige Interventionswirkung auf die Selbstregulation und auf die fachbezogene Leistung untersucht. Es zeigte sich trotz eines generellen Absinkens der Selbstregulationswerte in den motivationalen Selbstregulationskomponenten ein stabiler Fördereffekt. Die im Follow-up gemessene fachbezogene Leistung der Trainingsgruppe lag deutlich über der Leistung der Vergleichsgruppe. Differentielle Analysen ergaben, dass Schüler(innen) mit unterschiedlichen Ausgangsvoraussetzungen im selbstregulierten Lernen gleichermaßen profitierten. Der deutliche langfristige Vorteil der Trainingsgruppe im fachbezogenen Test war jedoch nur für Schüler(innen) ohne Migrationshintergrund nachzuweisen.
Comparison of local energy conversion estimates from Cluster with global MHD simulations
Authors: Rosenqvist L. , Opgenoorth H. J. , Rastaetter L. , Vaivads A. , Dandouras I. , Buchert S.
Published: November 2008

The local energy conversion across the magnetopause has been estimated with Cluster for two magnetopause crossings. A load region, conversion from magnetic to particle energy, was identified on the dayside high‐latitude magnetopause during south/dawnward IMF. Another crossing of the dawn flank magnetotail during dominantly duskward IMF was identified as a generator region where the magnetosphere is loaded with magnetic energy. The observations have been compared to results of the BATS‐R‐US global MHD simulation based on observed IMF conditions. BATS‐R‐US reproduced the magnetopause regions crossed by Cluster as a load and a generator region, correspondingly. The magnitude of the estimated energy conversion from Cluster and the model are in quite good agreement. BATS‐R‐US cannot reproduce the observed sharp magnetopause and some topological differences between the observations and the model occur.
Atherosklerose - Früherkennung mit hochauflösendem Ultraschall am Beispiel von Typ II-Diabetikern
Authors: Enderle M. D. , Balletshofer B. M. , Schmülling R. M. , Häring H. U. , Pfohl M.
Published: November 2008

Studienziel: Die endothelial Dysfunktion (ED) gilt als frühfunktioneller, die Intima-Media-Dicke (IMT) als frühmorphologischer Marker der Atherogenese. Gibt es ein einfaches, nichtinvasives, routinemaßig einsetzbares Ver-fahren zur Darstellung des Atherosklerosestatus, welches die frühfunktionellen Veränderungen z.B. bei Typ II-Diabetikern mitberücksichtigt? Methode: Wir untersuchten mittels hochauflosendem Ultraschall bei 25 Typ II-Diabetikern und gematchten Kontrollpersonen die periphere Endothelfunktion (ausgedrückt durch die flußassoziierte Vasodilatation nach Ischämie = FAD %) und die endothelunabhangige Vasodilatation nach Gabe von 400 μg Glyceroltrinitrat (Postnitro %) an der A. brachialis sowie die IMT an der A. carotis communis. Ergebnisse (Mittelwerte ± SD): Die Typ II-Diabetiker zeigen eine deutliche Endothelschadigung (FAD %: 3,8 ±3,3 vs. 6,9 ± 4,4%, p = 0,01) sowie eine bereits verdickte IMT (0,72 ±0,14 vs. 0,62 ± 0,10 mm, p > 0,01). Die Vasodilatation nach Nitrogabe als Ausdruck eines prinzipiell noch dilatierfähigen Gefäßsystems unterscheidet sich nicht von der der Gesunden (Postnitro %: 14,3 ±9,4 vs. 14,9 ±8,5%, p = ns). Schlußfolgerung: Die hier verwendete diagnostische Trias ermöglicht die Darstellung des Atherosklerosestatus unter Berücksichtigung der frühfunktionellen Störungen bei Typ II-Diabetikern.
Altersabhängigkeit dopplersonographisch ermittelter Flußgeschwindigkeiten in den Hirnarterien von Neugeborenen und Säuglingen
Authors: Rupprecht Th. , Deeg K. H. , Zeilinger G.
Published: November 2008

Bei 121 gesunden Frühgeborenen, Neugeborenen und Säuglingen (Alter 1-30 Tage, Untersuchungsgewicht 1070-3750 g) wurden mit Hilfe der gepulsten DopplerSonographie die Strömungsgeschwindigkeiten in der Arteria cerebri anterior, der Arteria carotis interna und der Arteria basilaris gemessen.

Alle Untersuchungen wurden mit dem Computer-Sonographie-Gerät Acuson 128, mit einem 5-MHz-Schallkopf, durchgeführt.

Die maximale systolische, die endsystolische, die enddiastolische und die mittlere Flußgeschwindigkeit wurden aus dem Doppler-Frequenzspektrum ermittelt. Aus den Flußgeschwindigkeiten wurden ein Pulsatilitätsund ein Widerstands-Index errechnet. Es zeigte sich ein deutlicher linearer Anstieg aller Fluzßgeschwindigkeiten mit dem Lebensalter als Ausdruck der reifebedingt ansteigenden Hirnperfusion, während sich die berechneten Indices als altersunabhängig erwiesen. Für alle gemessenen Werte wurden Normalbereiche in Abhängigkeit vom Lebensalter angegeben.
Selektive sakrale Vorderwurzelstimulation der Blase mittels Anodenblocktechnik unter Verwendung einer modifizierten Brindley-Elektrode beim Hund
Authors: Wipfler G. , Scheepe J. R. , Seif Ch. , Gropp A. , Berle B. , Zendler S. , Jünemann K.-P. , Alken P.
Published: November 2008

Bei Patienten mit suprasakraler Querschnittläsion und spastischer Blase wird die sakrale Deafferentation in Kombination mit der Implantation eines Vorderwurzelstimulators nach Brindley seit mehreren Jahren erfolgreich zur funktionellen Wiedererlangung der Blasenfunktion eingesetzt. Ein Nachteil des verwendeten Stimulators ist jedoch seine fehlende Selektivität in bezug auf die Stimulation der Blase, da es zu einer simultanen Kontraktion des Harnröhrensphinkters kommt, was eine den physiologischen Verhältnissen nahekommende Miktion verhindert. In früheren tierexperimentellen Studien konnte mittels Anodenblocktechnik und unter Verwendung von tripolaren Manschettenelektroden eine weitgehend selektive Blasenstimulation ohne bzw. mit nur geringfügiger Miterregung des Harnröhrenschließmuskels erzielt werden. In der vorliegenden Studie ließ sich mit dieser Stimulationstechnik eine solche selektive Stimulation der Blase erstmals unter Verwendung einer modifizierten Brindley-Elektrode im Tierversuch erfolgreich durchführen. Sollen sich die von uns gewonnenen Ergebnisse beim Menschen reproduzieren lassen, so müßte eine klinische Einführung dieser neuartigen Stimulationstechnik relativ einfach zu realisieren sein, da eine bereits langjährig erprobte Elektrode verwendet werden könnte.
Temperature dependence of the E2h phonon mode of wurtzite GaN/AlN quantum dots
Authors: Budagosky J. A. , García-Cristóbal A. , Cros A.
Published: November 2008

Raman scattering has been used to study the temperature dependence of the frequency and linewidth of the E2h phonon mode of GaN/AlN quantum dot stacks grown on 6H-SiC. The evolution of the nonpolar phonon mode was analyzed in the temperature range from 80 to 655 K for both quantum dots and barrier materials. The experimental results are interpreted by comparison with a model that takes into account symmetric phonon decay and the different thermal expansions of the constituents of the heterostructure. We find a small increase in the anharmonic parameters of the phonon modes in the heterostructure with respect to bulk.
Cytosolic chaperones influence the fate of a toxin dislocated from the endoplasmic reticulum
Authors: Spooner Robert A. , Hart Philip J. , Cook Jonathan P. , Pietroni Paola , Rogon Christian , Höhfeld Jörg , Roberts Lynne M. , Lord J. Michael
Published: November 2008

The plant cytotoxin ricin enters target mammalian cells by receptor-mediated endocytosis and undergoes retrograde transport to the endoplasmic reticulum (ER). Here, its catalytic A chain (RTA) is reductively separated from the cell-binding B chain, and free RTA enters the cytosol where it inactivates ribosomes. Cytosolic entry requires unfolding of RTA and dislocation across the ER membrane such that it arrives in the cytosol in a vulnerable, nonnative conformation. Clearly, for such a dislocated toxin to become active, it must avoid degradation and fold to a catalytic conformation. Here, we show that,
in vitro
, Hsc70 prevents aggregation of heat-treated RTA, and that RTA catalytic activity is recovered after chaperone treatment. A combination of pharmacological inhibition and cochaperone expression reveals that,
in vivo
, cytosolic RTA is scrutinized sequentially by the Hsc70 and Hsp90 cytosolic chaperone machineries, and that its eventual fate is determined by the balance of activities of cochaperones that regulate Hsc70 and Hsp90 functions. Cytotoxic activity follows Hsc70-mediated escape of RTA from an otherwise destructive pathway facilitated by Hsp90. We demonstrate a role for cytosolic chaperones, proteins typically associated with folding nascent proteins, assembling multimolecular protein complexes and degrading cytosolic and stalled, cotranslocational clients, in a toxin triage, in which both toxin folding and degradation are initiated from chaperone-bound states.
Limnological characteristics of three aquatic systems of the pre-amazonian floodplain, Baixada Maranhense (Maranhão, Brazil)
Authors: Ibañez M.S.R. , Cavalcante P.R.S. , Costa Neto J.P. , Barbieri R. , Pontes J.P. , Santana S.C.C. , Serra C.L.M. , Nakamoto N. , Mitamura O.
Published: November 2008

Preliminary information is provided on physical and chemical characteristics of three aquatic systems in the pre-amazonian floodplain, Baixada Maranhense: Pindaré (Viana Lake) and the Pericumã and Turiaçu rivers. Emphasis is given to the nutrients analyzed spectrophotometrically from the bottom sediments of Viana Lake. The water bodies differ from each other with respect to conductivity, total suspended solids and nutrient contents in the water, with higher values (except for total nitrogen) in the dry season. The main factors responsible for such differences, besides the annual flood, are the presence of macrophytes on Pericumã, riparian vegetation on Turiaçu (both systems with lotic characteristics) and water buffalo at Viana Lake. Bottom sediments with low nutrient concentrations at Viana Lake may be due to the rapid mineralization of organic matter in this lentic environment.
Tidal effects on nutrients and phytoplankton distribution in Bertioga Channel, São Paulo, Brazil
Authors: Gianesella S.M.F. , Saldanha-Corrêa F.M.P. , Teixeira C.
Published: November 2008

Dissolved nutrients and phytoplankton distribution in the Bertioga Channel, São Paulo State, were studied over a neap and a spring tide during the austral winter of 1991. Tidal influence and freshwater flow were the main forcing agents on the water column structure, nutrient availability and phytoplankton distribution as pointed out by the principal component analysis. The channel was vertically stratified during neap tide, but almost fully homogeneous during spring tide, especially in the flood phase. The inner area of the channel had high nutrient concentrations (up to 25 μM ammonium) and low dissolved oxygen saturation (minimum 20%). Phytoplankton biomass, measured as chlorophyll-a concentration, was low (maximum, 4.5 mg m−3) considering the high nutrient availability. The highest chlorophyll-a levels were associated with waters of coastal origin and flood periods. The phytoplankton community was dominated by phytoflagellates but the contribution of diatoms became very significant during spring tide. The major microphytoplankton forms were Skeletonema costatum and Pseudonitzschia species. The noticeable presence of freshwater species (Pinnularia, Synedra and Scenedesmus species), indicated the important role of freshwater inflow in the composition of local phytoplankton community. Data suggest that the high flushing rates and hydrodynamic instability at Bertioga Channel accounted for the low phytoplankton biomass observed in the environment.