bluuebunny/crossref_metadata_2025 huggingface dataset:
Ramsey Size Linear Graphs
Authors: Erdős Paul , Faudree R. J. , Rousseau C. C. , Schelp R. H.
Published: September 2008

A graph G is Ramsey size linear if there is a constant C such that for any graph H with n edges and no isolated vertices, the Ramsey number r(G, H) ≤ Cn. It will be shown that any graph G with p vertices and q ≥ 2p − 2 edges is not Ramsey size linear, and this bound is sharp. Also, if G is connected and q ≤ p + 1, then G is Ramsey size linear, and this bound is sharp also. Special classes of graphs will be shown to be Ramsey size linear, and bounds on the Ramsey numbers will be determined.
Minimization Problems for Infiniten-Connected Graphs
Authors: Halin R.
Published: September 2008

A graphGis calledn-minimizable if it can be reduced, by deleting a set of its edges, to a minimallyn-connected graph. It is shown that, ifn-connected graphsGandHdiffer only by finitely many vertices and edges, thenGisn-minimizable if and only ifHisn-minimizable (Theorem 4.12). In the main result, conditions are given that a tree decomposition of ann-connected graphGmust satisfy in order to guarantee that then-minimizability of each of the members of this decomposition implies then-minimizability of the graphG(Theorem 6.5).
Triangle-Free Graphs with High Minimal Degrees
Authors: Jin Guoping
Published: September 2008

The main result of this paper gives a structure of a triangle-free graph of order n with minimal degree greater than 10n/29. This extends results given by Andrásfai et al. [1] and Häggkvist [6].
Local-Global Phenomena in Graphs
Authors: Linial Nathan
Published: September 2008

This is a survey of a number of recent papers dealing with graphs from a geometric perspective. The main theme of these studies is the relationship between graph properties that are local in nature, and global graph parameters. Connections with the theory of distributed computing are pointed out and many open problems are presented.
Reciprocity and Polynomial Properties for Even Flows and Potentials on Directed Graphs
Authors: Arrowsmith D. K. , Essam J. W.
Published: September 2008

We consider special types of mod-λ flows, called odd and even mod-λ flows, for directed graphs, and prove that the numbers of such flows can be interpolated by polynomials in λ with the degree given by the cycle rank of the graph. The proofs involve computation of the number of integer solutions in a polyhedral region of Euclidean space using theorems due to Ehrhart. The resulting reciprocity properties of the interpolating polynomials for even flows are considered. The analogous properties of odd and even mod-λ potential differences and their associated potentials are also developed.
Deterministic Graph Games and a Probabilistic Intuition
Authors: Beck József
Published: September 2008

There is a close relationship between biased graph games and random graph processes. In this paper, we develop the analogy and give further interesting instances.
On Oriented Embedding of the Binary Tree into the Hypercube
Authors: Bezrukov Sergej L.
Published: September 2008

We consider the oriented binary tree and the oriented hypercube. The tree edges are oriented from the root to the leaves, while the orientation of the cube edges is induced by the direction from 0 to 1 in the coordinatewise form. The problem is to embed such a tree withllevels into the orientedn-cube as an oriented subgraph, for minimal possiblen. A new approach to such problems is presented, which improves the known upper boundn/l≤ 3/2 given by Havel [1] ton/l≤ 4/3 +o(1) asl→ ∞.
On Intersecting Chains in Boolean Algebras
Authors: Erdős Peter L. , Seress Ákos , Székely László A.
Published: September 2008

Analogues of the Erdős-Ko-Rado theorem are proved for the Boolean algebra of all subsets of {1,…n} and in this algebra truncated by the removal of the empty set and the whole set.
Randomised Approximation in the Tutte Plane
Authors: Welsh D. J. A.
Published: September 2008

It is shown that unless NP collapses to random polynomial time RP, there can be no fully polynomial randomised approximation scheme for the antiferromagnetic version of the Q-state Potts model.
Menger's Theorem for a Countable Source Set
Authors: Aharoni Ron , Diestel Reinhard
Published: September 2008

Paul Erdős has conjectured that Menger's theorem extends to infinite graphs in the following way: whenever A, B are two sets of vertices in an infinite graph, there exist a set of disjoint A−B paths and an A−B separator in this graph such that the separator consists of a choice of precisely one vertex from each of the paths. We prove this conjecture for graphs that contain a set of disjoint paths to B from all but countably many vertices of A. In particular, the conjecture is true when A is countable.
Matchings in Lattice Graphs and Hamming Graphs
Authors: Aigner Martin , Klimmek Regina
Published: September 2008

In this paper we solve the following problem on the lattice graph L(m1,…,mn) and the Hamming graph H(m1,…,mn), generalizing a result of Felzenbaum-Holzman-Kleitman on the n-dimensional cube (all mi = 2): Characterize the vectors (s1.…,sn) such that there exists a maximum matching in L, respectively, H with exactly si edges in the ith direction.
On Canonical Concurrent Flows, Crossing Number and Graph Expansion
Authors: Shahrokhi Farhad , Székely László A.
Published: September 2008

We define and efficiently compute the canonical flow on a graph, which is a certain feasible solution for the concurrent flow problem and exhibits invariance under the action of the automorphism group of the graph. Using estimates for the congestion of our canonical flow, we derive lower bounds on the crossing number, bisection width, and the edge and vertex expansion of a graph in terms of sizes of the edge and vertex orbits and the average distance in the graph. We further exhibit classes of graphs for which our lower bounds are tight within a multiplicative constant. Also, in cartesian product graphs a concurrent flow is constructed in terms of the concurrent flows in the factors, and in this way lower bounds for the edge and vertex expansion of the power graphs are derived in terms of that of the original graph.
An Introduction to Random Topological Graph Theory
Authors: White Arthur T.
Published: September 2008

We introduce five probability models for random topological graph theory. For two of these models (I and II), the sample space consists of all labeled orientable 2-cell imbeddings of a fixed connected graph, and the interest centers upon the genus random variable. Exact results are presented for the expected value of this random variable for small-order complete graphs, for closed-end ladders, and for cobblestone paths. The expected genus of the complete graph is asymptotic to the maximum genus. For Model III, the sample space consists of all labeled 2-cell imbeddings (possibly nonorientable) of a fixed connected graph, and for Model IV the sample space consists of all such imbeddings with a rotation scheme also fixed. The event of interest is that the ambient surface is orientable. In both these models the complete graph is almost never orientably imbedded. The probability distribution in Models I and III is uniform; in Models II and IV it depends on a parameterpand is uniform precisely whenp= 1/2. Model V combines the features of Models II and IV.
Automorphisms of Dowling Lattices and Related Geometries
Authors: Bonin Joseph E.
Published: September 2008

Dowling lattices are a class of geometric lattices, based on groups, which have been shown to share many properties with projective geometries. In this paper we show that the automorphisms of Dowling lattices are analogs of the automorphisms of projective geometries. We also treat similar results for several related geometric lattices.
Some Small Circuit-Cocircuit Ramsey Numbers for Matroids
Authors: Hurst Fair Barbour , Reid Talmage James
Published: September 2008

Ramsey numbers for matroids, which mimic properties of Ramsey numbers for graphs, have been denned as follows. Let k and l be positive integers. Then n(k, l) is the least positive integer n such that every connected matroid with n elements contains either a circuit with at least k elements or a cocircuit with at least l elements. We determine the largest known value of these numbers in the sense of maximizing both k and l. We also find extremal matroids with small circuits and cocircuits. Results on matroid connectivity, geometry, and extremal matroid theory are used here.
Recurrence and Transience for a Card Shuffling Model
Authors: Lawler Gregory F.
Published: September 2008

A rule for shuffling an infinite deck of cards is considered where at each time step the first and jth card are interchanged with probability pj. Conditions are given under which this shuffling scheme, considered as a Markov chain on the space of permutations of integers, is recurrent or transient.
The Self-Avoiding-Walk and Percolation Critical Points in High Dimensions
Authors: Hara Takashi , Slade Gordon
Published: September 2008

We prove the existence of an asymptotic expansion in the inverse dimension, to all orders, for the connective constant for self-avoiding walks on ℤd. For the critical point, defined as the reciprocal of the connective constant, the coefficients of the expansion are computed through orderd−6, with a rigorous error bound of orderd−7Our method for computing terms in the expansion also applies to percolation, and for nearest-neighbour independent Bernoulli bond percolation on ℤdgives the 1/d-expansion for the critical point through orderd−3, with a rigorous error bound of orderd−4The method uses the lace expansion.
Almost Every Graph can be Covered by Linear Forests
Authors: McDiarmid Colin , Reed Bruce
Published: September 2008

A linear forest is the union of a set of vertex disjoint paths. Akiyama, Exoo and Harary, and independently Hilton, have conjectured that the edges of every graph of maximum degree Δ can be covered by linear forests. We show that almost every graph can be covered with this number of linear forests.
Conditional Independences among Four Random Variables I
Authors: Matúš F. , Studený M.
Published: September 2008

The conditional independences within a system of four discrete random variables are studied simultaneously. The problem of where independences can occur at the same time, called the problem of probabilistic representability, is attacked by an analysis of cones of polymatroids. New results on the cone of all polymatroids satisfying Ingleton inequalities imply a substantial reduction of the problem and an explicit description of the remaining open cases.†
Perfect Matchings in Random r-regular, s-uniform Hypergraphs
Authors: Cooper Colin , Frieze Alan , Molloy Michael , Reed Bruce
Published: September 2008

We show that r-regular, s-uniform hypergraphs contain a perfect matching with high probability (whp), provided The Proof is based on the application of a technique of Robinson and Wormald [7, 8]. The space of hypergraphs is partitioned into subsets according to the number of small cycles in the hypergraph. The difference in the expected number of perfect matchings between these subsets explains most of the variance of the number of perfect matchings in the space of hypergraphs, and is sufficient to prove existence (whp), using the Chebychev Inequality.
The Harmonious Chromatic Number of Bounded Degree Trees
Authors: Edwards Keith
Published: September 2008

A harmonious colouring of a simple graph G is a proper vertex colouring such that each pair of colours appears together on at most one edge. The harmonious chromatic number h(G) is the least number of colours in such a colouring. Let d be a fixed positive integer. We show that there is a natural number N(d) such that if T is any tree with m ≥ N(d) edges and maximum degree at most d, then the harmonious chromatic number h(T) is k or k + 1, where k is the least positive integer such that . We also give a polynomial time algorithm for determining the harmonious chromatic number of a tree with maximum degree at most d.
Precoloring Extension III: Classes of Perfect Graphs
Authors: Hujter M. , Tuza Zs.
Published: September 2008

We continue the study of the following general problem on the vertex colourings of graphs. Suppose that some vertices of a graphGare assigned to some colours. Can this ‘precolouring’ be extended to a proper colouring ofGwith at mostkcolours (for some givenk)? Here we investigate the complexity status of precolouring extendibility on some classes of perfect graphs, giving good characterizations (necessary and sufficient conditions) that lead to algorithms with linear or polynomial running time. It is also shown how a larger subclass of perfect graphs can be derived from graphs containing no induced path on four vertices.
Excluding Minors in Cubic Graphs
Authors: Kilakos K. , Shepherd B.
Published: September 2008

Let P10\e be the graph obtained by deleting an edge from the Petersen graph. We give a decomposition theorem for cubic graphs with no minor isomorphic to P10\e. The decomposition is used to show that graphs in this class are 3-edge-colourable. We also consider an application to a conjecture due to Grötzsch which states that a planar graph is 3-edge-colourable if and only if it is fractionally 3-edge-colourable.
An Improvement of Hind's Upper Bound on the Total Chromatic Number
Authors: Chetwynd Amanda , Häggkvist Roland
Published: September 2008

We show that the total chromatic number of a simple k-chromatic graph exceeds the chromatic index by at most 18k ⅓ log ½ 3k.
Computing Norms of Group-Invariant Transition Operators
Authors: Saloff-Coste Laurent , Woess Wolfgang
Published: September 2008

We consider transition operators P on a countable set, which are reversible, irreducible and invariant under a group G of permutations of X with compact point stabilizers. We relate the computation of the spectral radius (norm) of P with the spectral radii of certain matrices defined over the factor set G\X. In various cases, this allows easy computation of the norm of P.
A Characterization of Almost-Planar Graphs
Authors: Gubser Bradley S.
Published: September 2008

Kuratowski's Theorem, perhaps the most famous result in graph theory, states that K5 and K3,3 are the only non-planar graphs for which both G\e, the deletion of the edge e, and G/e, the contraction of the edge e, are planar for all edges e of G. We characterize the almost-planar graphs, those non-planar graphs for which G\e or G/e is planar for all edges e of G. This paper gives two characterizations of the almost-planar graphs: an explicit description of the structure of almost-planar graphs; and an excluded minor criterion. We also give a best possible bound on the number of edges of an almost-planar graph.
Small Submatroids in Random Matroids
Authors: Kordecki Wojciech
Published: September 2008

LetMbe a matroid and letXrcount copies ofMin a random matroid of rankr. The Poisson and normal convergence ofXrare investigated under some restriction.
Finding a Longest Alternating Cycle in a 2-edge-coloured Complete Graph is in RP
Authors: Saad Rachid
Published: September 2008

Jackson [10] gave a polynomial sufficient condition for a bipartite tournament to contain a cycle of a given length. The question arises as to whether deciding on the maximum length of a cycle in a bipartite tournament is polynomial. The problem was considered by Manoussakis [12] in the slightly more general setting of 2-edge coloured complete graphs: is it polynomial to find a longest alternating cycle in such coloured graphs? In this paper, strong evidence is given that such an algorithm exists. In fact, using a reduction to the well known exact matching problem, we prove that the problem is random polynomial.
On Recognition of Shift Registers
Authors: Szuster Janusz , Wlaź Pawel , Żurawiecki Jerzy
Published: September 2008

This paper deals with infinite binary sequences. Each sequence is treated as generated by a nondeterministic shift register. A measure-theoretic criterion helpful in finding a deterministic generator of the set of sequences is proposed.
Multiway Trees of Maximum and Minimum Probability under the Random Permutation Model
Authors: Dobrow Robert P. , Fill James Allen
Published: September 2008

Multiway trees, also known as m–ary search trees, are data structures generalising binary search trees. A common probability model for analysing the behaviour of these structures is the random permutation model. The probability mass function Q on the set of m–ary search trees under the random permutation model is the distribution induced by sequentially inserting the records of a uniformly random permutation into an initially empty m–ary search tree. We study some basic properties of the functional Q, which serves as a measure of the ‘shape’ of the tree. In particular, we determine exact and asymptotic expressions for the maximum and minimum values of Q and identify and count the trees achieving those values.
Subset sums in ℕ2
Authors: Hegyvári Norbert
Published: September 2008

Let A be a subset of the lattice Ñ x N. We answer a question of Sárközy, proving if A is well distributed then the set of subset sums of A contains an infinite arithmetic progression.
Fast String Matching in Stationary Ergodic Sources
Authors: Shawe-Taylor John
Published: September 2008

A connection is made between the theory of ergodicity and the expected complexity of string searching. In particular, a substring search algorithm is introduced which, when applied to searching in text that has been produced by an appropriate stationary ergodic source, has an expected running time of O((N/m + m)logm), for a text string of length N and search string of length m. Similar expected complexity results have been obtained before, but the analysis is performed in a significantly more general framework, which models with greater accuracy the statistics of many types of strings, including natural language. The analysis also sheds light on the performance of the Boyer-Moore algorithm and the Sunday algorithm when applied to natural language.
Technical terminology: some linguistic properties and an algorithm for identification in text
Authors: Justeson John S. , Katz Slava M.
Published: September 2008

This paper identifies some linguistic properties of technical terminology, and uses them to formulate an algorithm for identifying technical terms in running text. The grammatical properties discussed are preferred phrase structures: technical terms consist mostly of noun phrases containing adjectives, nouns, and occasionally prepositions; rerely do terms contain verbs, adverbs, or conjunctions. The discourse properties are patterns of repetition that distinguish noun phrases that are technical terms, especially those multi-word phrases that constitute a substantial majority of all technical vocabulary, from other types of noun phrase.

The paper presents a terminology indentification algorithm that is motivated by these linguistic properties. An implementation of the algorithm is described; it recovers a high proportion of the technical terms in a text, and a high proportaion of the recovered strings are vaild technical terms. The algorithm proves to be effective regardless of the domain of the text to which it is applied.
Natural language interfaces to databases – an introduction
Authors: Androutsopoulos I. , Ritchie G.D. , Thanisch P.
Published: September 2008

This paper is an introduction to natural language interfaces to databases (NLIDBS). A brief overview of the history of NLIDBS is first given. Some advantages and disadvantages of NLIDBS are then discussed, comparing NLIDBS to formal query languages, form-based interfaces, and graphical interfaces. An introduction to some of the linguistic problems NLIDBS have to confront follows, for the benefit of readers less familiar with computational linguistics. The discussion then moves on to NLIDB architectures, portability issues, restricted natural language input systems (including menu-based NLIDBS), and NLIDBS with reasoning capabilities. Some less explored areas of NLIDB research are then presented, namely database updates, meta-knowledge questions, temporal questions, and multi-modal NLIDBS. The paper ends with reflections on the current state of the art.
Several knowledge models and a blackboard memory for human-machine robust dialogues
Authors: Prince Violaine , Pernel Didier
Published: September 2008

This contribution focuses on a dialogue model using an intelligent working memory that aims at facilitating a robust human-machine dialogue in written natural language. The model has been designed as the core of an information seeking dialogue application. The particularity of this project is to rely on the potent interpretation and behaviour capabilities of pragmatic knowledge. Within this framework, the designed dialogue model appears as a kind of ‘forum’ for various facets, impersonated by different models extracted from both intentional and structural approaches of conversation. The approach is based on assuming that multiple expertise is the key to flexibility and robustness. Also, an intelligent memory that keeps track of all events and links them together from as many angles as necessary is crucial for multiple expertise management. This idea is developed by presenting an intelligent dialogue history which is able to complement the wide coverage of the co-operating models. It is no longer a simple chronological record, but a communication area, common to all processes. We illustrate our topic through examples brought out from collected corpora.
Anaphora and ellipsis in artificial languages
Authors: Pulman Stephen G.
Published: September 2008

Artificial languages for person-machine communication seldom display the most characteristic properties of natural languages, such as the use of anaphoric or other referring expressions, or ellipsis. This paper argues that useful use could be made of such devices in artificial languages, and proposes a mechanism for the resolution of ellipsis and anaphora in them using finite state transduction techniques. This yields an interpretation system displaying many desirable properties: easily implementable, efficient, incremental and reversible.

Linguists in general, and computational linguists in particular, do well to employ finite state devices wherever possible. They are theoretically appealing because they are computationally weak and best understood from a mathematical point of view. They are computationally appealing because they make for simple, elegant, and highly efficient implementations. In this paper, I hope I have shown how they can be applied to a problem… which seems initially to require heavier machinery.
Syntactic Analysis of Hebrew Sentences
Authors: Wintner Shuly , Ornan Uzzi
Published: September 2008

Due to recent developments in the area of computational formalisms for linguistic representation, the task of designing a parser for a specified natural language is now shifted to the problem of designing its grammar in certain formal ways. This paper describes the results of a project whose aim was to design a formal grammar for modern Hebrew. Such a formal grammar has never been developed before. Since most of the work on grammatical formalisms was done without regarding Hebrew (and other Semitic languages as well), we had to choose a formalism that would best fit the specific needs of the language. This part of the project has been described elsewhere. In this paper we describe the details of the grammar we developed. The grammar deals with simple, subordinate and coordinate sentences as well as interrogative sentences. Some structures were thoroughly dealt with, among which are noun phrases, verb phrases, adjectival phrases, relative clauses, object and adjunct clauses; many types of adjuncts; subcategorization of verbs; coordination; numerals, etc. For each phrase the parser produces a description of the structure tree of the phrase as well as a representation of the syntactic relations in it. Many examples of Hebrew phrases are demonstrated, together with the structure the parser assigns them. In cases where more than one parse is produced, the reasons of the ambiguity are discussed.
Shouldandought:the rise of individually oriented modality in American English
Authors: Myhill John
Published: September 2008

Using data drawn from twenty American plays written since 1889, this paper analyzes the usage of the weak obligation modalsshouldandought, which previous researchers (e.g. Coates, 1983; Leech, 1987; Palmer, 1987) have regarded as essentially synonymous. It is shown that there is a clear distinction between these words, withshouldexpressing individual opinions andoughtemphasizing a common opinion regarding the obligation in question. This use of obligationshoulddoes not occur in five plays written between 1889 and 1911, appearing for the first time in this database in a play written in 1926. The development of obligationshouldparallels other changes in the modal system which have taken place at the same time – asshouldhas increased in frequency, so have the other individually-oriented modalsgot toandgonna, and asoughthas declined in frequency, so have the other group-oriented modalsmustandwill.
The phonology of ‘/ɔː/’ and ‘/ɑː/’ in RP English: Henry Sweet and after
Authors: Giegerich Heinz J.
Published: September 2008

This paper attempts to account for the synchronic representations and surface distributions of the long low vowels (particularly of [ɔː] and [ɔə]) in present-day RP and Cockney, as well as to map in detail the twentieth-century developments that have given rise to them. It is argued that the long low vowels must still be underlyingly centring diphthongs in modern RP (as they were at Henry Sweet's time), now synchronically monophthongized by a spread-and-delink rule, while the corresponding underliers in Cockney must since have been restructured into monophthongs. The theoretical framework for this analysis is a version of Lexical Phonology that assumes an English lexicon comprising two levels, where the first level is characterized by cyclic rule application and the presence of the Strict Cycle and Structure Preservation Conditions (Giegerich, 1988; Kiparsky, 1982), and the second level by noncyclic rule application as well as the presence of neither condition (Borowsky, 1989).
The past perfect with future time reference
Authors: Declerck Renaat
Published: September 2008

The standard analysis of the past perfect is that it represents the time of a situation as anterior to a time of orientation which is itself past with respect to the time of speech. However, there are a couple of uses in which the situation referred to actually lies in the future. This article concentrates on one of these uses, illustrated by sentences likeSoon you will again be able to do all the things that youhad donebefore. In this use, the past perfect refers to the future and there does not seem to be a past time of orientation at all. The article not only attempts to account for this use of the past perfect but also offers an explanation for the fact that the same tense cannot be used in other, seemingly similar, sentences, such as the following: [If you peep through this hole in the curtain]you will see the audience that {have/*had} come to see the play.
Constraint ranking in Middle English stress-shifting
Authors: Minkova Donka
Published: September 2008

Developing an idea first articulated by Luick in 1896, Halle & Keyser (1971) posit the introduction of a new accentuation rule in Middle English (ME), the weight-sensitive Romance Stress Rule (RSR). All post-1971 accounts of English stress take the syllable weight principle of the RSR as their starting point. For twenty-five years there has been no scrutiny of the assumption that syllable weight became relevant for stress assignment in ME. It has been claimed, and the claims have not been addressed, that the RSR is part of the phonology of late OE (O'Neil, 1973), that by late ME the RSR had completely replaced the Germanic accentuation patterns (Nakao, 1977), and that the existence of the RSR in ME justifies the reconstruction of analogical pronunciations such ashardi, holi, riding(e), a real shift from the Germanic to the Romance category (Halle & Keyser, 1971; Luick, 1896). The paper refutes these claims on the basis of new evidence and analysis in terms of generalized prosodic constraints.
English Flapping and the feature [vibrant]
Authors: Picard Marc
Published: September 2008

In certain varieties of English, and most notably in the majority of North American dialects, alveolar oral and nasal stops undergo a process known as Flapping or Tapping in certain well-defined environments. At the present time, the resulting segments [ɾ] and [ɾ̃] cannot be satisfactorily captured by any known phonetic feature mainly because there is no way to distinguish a nasal stop from a nasal tap or flap. In this paper, I will argue that since vibration is the primary articulatory characteristic of taps, flaps and trills, the phonological rule of Flapping or Tapping constitutes evidence that [vibrant] should be added to the current inventory of features.
Scope and the development of epistemic modality: evidence fromought to
Authors: Nordlinger Rachel , Traugott Elizabeth Closs
Published: September 2008

Discussions of modality (e.g. Bybee, Perkins & Pagliuca, 1994; Coates, 1983; Lyons, 1977; Palmer, 1986; Traugott, 1989) typically center around two issues: deonticity vs. epistemicity, and degree of subjectivity. Using diachronic evidence from the quasi-modalought to, this paper argues for the need to recognize a third, crosscutting these two: narrow vs. wide scope. We argue that the epistemic use ofought todeveloped out of a wide-scope deontic construction, in which the modal was used with deontic meaning, but with propositional scope (contraBybee, 1988). Rather than attributing an obligation to the subject (i.e. having narrow scope), the modal in this construction makes an assertion about the proposition as a whole, like an epistemic. However, suchought toconstructions are found some four hundred years before the first epistemic examples, and thus can be shown to be distinct from epistemic uses (contraGamon, 1994).
Time reference in reported speech
Authors: Salkie Raphael , Reed Susan
Published: September 2008

English tenses in indirect reported speech appear to behave in unusual ways. InJohn said that he was happy, the most likely interpretation is that John's being happy was simultaneous with the time of John's speaking. This has led many analysts to invoke a ‘Sequence of Tenses’ rule, while others have proposed that English has two formally identical but semantically distinct past tenses, treatingwasin the preferred interpretation as a ‘relative past’. Under either treatment, a simple semantics for English tenses cannot be maintained.

This paper argues that time reference in reported speech can only be analysed within a coherent theory of speech reporting. We propose a new way of distinguishing direct and indirect reported speech, based on the notion ofPragmatic Source. Within this framework we then argue that tense in indirect reported speech can be handled by pragmatic principles, without any enrichment of the semantics of tense.

Previous analyses of tense in reported speech by Comrie and Declerck are examined and rejected. Unlike other accounts of reported speech, our approach does not presuppose an ‘original utterance’.
A core morphology for Old English verbs
Authors: Anderson John
Published: September 2008

A characterization of the morphology of ‘regular’ Old English verbs is offered on the basis of a ‘word-and-paradigm’ approach to morphological structure. Thus rules of expression are formulated providing for the phonological realization(s) of (combinations of) morphosyntactic categories of tense, mood, person, number etc. However, it is argued that the organization of categories (in terms of compatibility and presupposition) differs with respect to the syntax–morphology interface and the morphology–phonology interface (the rules of expression). There is therefore proposed a set of rules of category realignment which relate the function-oriented system of categories to the expression-oriented system, which (among other things) minimize syncretism in the elements introduced by the rules of expression. Analysis of the preterite-present and weak-present verbs provides further support for this distinction in systems of category organization. The expression rules themselves do not introduce or realize ‘zeros’ and ‘mutations’ are interpreted as correspondences between base and derived/inflected form. An appendix offers a description of Present-day English verb inflexions for comparison.
GOD AND MORALITY
Authors: Swinburne Richard
Published: September 2008

The first six articles in this issue of THINK have the theme “Good without God”. Here, Richard Swinburne argues that the existence of God is not a precondition of there being moral truths, but his existence does impact on what moral truths there are.
A PLEA FOR DISTINCTIONS: DISENTANGLING ANTI-AMERICANISM AND ANTI-SEMITISM TODAY
Authors: Klug Brian
Published: September 2008

The first of three articles discussing the Israel/Palestine conflict and the charge of anti-semitism. The second article is a response by Tamar Meisels, and the third a reply to Meisels by Klug.
LOCKE: AN EMPIRICIST?
Authors: Moore Terence
Published: September 2008

Terence Moore explains why Locke is perhaps not quite the “empiricist” many suppose him to be.
Synthesis of various ionospheric convection patterns for IMF BY‐dominated periods: Split crescent cells, exchange cells, and theta aurora formation
Authors: Watanabe Masakazu , Sofko George J.
Published: September 2008

When the dawn‐to‐dusk component of the interplanetary magnetic field (IMF BY) is dominant, ionospheric convection exhibits a distorted two‐cell pattern with its dawn‐dusk and interhemispheric asymmetries regulated by the IMF BY polarity. For BY > 0, the convection in the Northern (Southern) Hemisphere usually consists of a relatively round cell on the duskside (dawnside) and a crescent‐shaped cell on the dawnside (duskside); for BY < 0, the dawn‐dusk relationship is reversed. However, deviations from the basic round/crescent cell pattern are sometimes seen. Such nonstandard convection patterns include the dayside‐enhanced crescent cell pattern, nightside‐enhanced crescent cell pattern, split crescent cell pattern, and exchange cell pattern. Although at times the nonstandard convection patterns appear to be quite different from the basic round/crescent cell pattern, the underlying physical processes (i.e., the types of reconnection) and field line topologies are basically the same. We show that these various convection patterns can be synthesized by considering the topologies of magnetic field lines involved in eight types of reconnection. We also discuss the formation mechanism of the theta aurora configuration in terms of magnetic topology and ionospheric convection. The theta aurora configuration results from transient reconnection‐driven convection when an IMF BY polarity switch reconfigures the exchange cell pattern. The bifurcation of the polar cap occurs as a consequence of accumulation of closed magnetic flux in the sunward return flow region of the round cell and intrusion of open magnetic flux into the “sub polar cap” that had been established by the primary exchange cell prior to the IMF change.
Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates
Authors: Facchini Maria Cristina , Rinaldi Matteo , Decesari Stefano , Carbone Claudio , Finessi Emanuela , Mircea Mihaela , Fuzzi Sandro , Ceburnis Darius , Flanagan Robert , Nilsson E. Douglas , de Leeuw Gerrit , Martino Manuela , Woeltjen Janina , O'Dowd Colin D.
Published: September 2008

The chemical properties of sea‐spray aerosol particles produced by artificially generated bubbles using oceanic waters were investigated during a phytoplankton bloom in the North Atlantic. Spray particles exhibited a progressive increase in the organic matter (OM) content from 3 ± 0.4% up to 77 ± 5% with decreasing particle diameter from 8 to 0.125 μm. Submicron OM was almost entirely water insoluble (WIOM) and consisted of colloids and aggregates exuded by phytoplankton. Our observations indicate that size dependent transfer of sea water organic material to primary marine particles is mainly controlled by the solubility and surface tension properties of marine OM. The pattern of WIOM and sea‐salt content in the different size intervals observed in bubble bursting experiments is similar to that measured in atmospheric marine aerosol samples collected during periods of high biological activity. The results point to a WIOM/sea‐salt fingerprint associated with submicron primary marine aerosol production in biologically rich waters.
Causes of decadal subsurface cooling in the tropical Indian Ocean during 1961–2000
Authors: Trenary Laurie L. , Han Weiqing
Published: September 2008

The vertical structure of temperature change in the Indian Ocean (IO) during 1961–2000 indicates that a region of tropical thermocline cooling accompanies the upper level warming. Results from data analysis and ocean general circulation model experiments suggest that the cooling signals exceed the cross‐data and cross‐model differences. Spatial patterns of the temperature trend above 200 m resemble the negative IO dipole structure, with the strongest cooling occurring in the western‐central basin south of the equator. The upper thermocline cooling is mainly caused by enhanced Ekman pumping velocity, which shoals the thermocline. The enhanced upwelling is consistent with the strengthened Southern subtropical cell. Enhanced equatorial westerly winds contribute to the negative dipole pattern. Remote forcing from the Pacific may contribute to the cooling below 200 m and further south.
Understanding the global evolution of Saturn's ring current
Authors: Brandt P. C. , Paranicas C. P. , Carbary J. F. , Mitchell D. G. , Mauk B. H. , Krimigis S. M.
Published: September 2008

An explanation for the morphology and evolution of the ring current in Saturn's magnetosphere is provided. We use global Energetic Neutral Atom (ENA) images of the 20–140 keV proton distribution obtained by the Ion and Neutral Camera (INCA) on board the Cassini spacecraft. A case where the ring current displays an exceptionally clear spiral shape is analyzed and by using a simple model of rotational velocities and curvature‐gradient drifts we reproduce the observed spiral patterns and dispersions. The spiral evolve from an initial large‐scale injection around midnight consistent with INCA observations. The drift patterns of the inner magnetosphere have to be relatively undisturbed in order for a clear spiral to evolve. Clear spiral patterns like this do not always occur, which reminds us that the inner magnetosphere of Saturn is indeed very dynamic.
Angular beaming model of Jupiter's decametric radio emissions based on Cassini RPWS data analysis
Authors: Imai Masafumi , Imai Kazumasa , Higgins Charles A. , Thieman James R.
Published: September 2008

Observations of the low frequency part of Jupiter decameter wavelength (DAM) emissions were made using the Cassini radio and plasma wave science (RPWS) instrument. We have analyzed non‐Io‐DAM occurrence dependence from 4 MHz to 16 MHz based on the System III central meridian longitude (CML) of the Cassini spacecraft and calculated the occurrence probability for each frequency. As a result of this analysis, the two peaks of non‐Io‐B and non‐Io‐A occurrence probability showed a dramatic change in longitude between 9 MHz and 16 MHz. At 16 MHz two peaks of probability occurred at 160° and 240° CML. As the frequency decreases to 9 MHz, the two peaks converged to become one peak near 205° CML at 9 MHz. This peak gradually disappeared below 9 MHz. Based on Jupiter's magnetic VIP4 model, an angular beaming model was made to explain these observational results by taking into account the decreasing cone half‐angle of the emitting cone from 16 MHz down to 9 MHz. We found the active magnetic flux tubes of non‐Io‐B and non‐Io‐A sources are localized at about 180° ± 10° of System III longitude projected on Jupiter's surface.
Statistical analysis of the occurrence of medium‐scale traveling ionospheric disturbances over Brazilian low latitudes using OI 630.0 nm emission all‐sky images
Authors: Candido C. M. N. , Pimenta A. A. , Bittencourt J. A. , Becker‐Guedes F.
Published: September 2008

In this work we report a statistical analysis of the occurrence frequency of medium‐scale traveling ionospheric disturbances (MSTIDs) observed over Cachoeira Paulista (22.7°S, 45.0°W, −13.2° mag lat), Brazil. The optical signatures of the low‐latitude MSTIDs in the southern hemisphere observed in the OI 630.0 nm emission images can be a single dark band structure or alternating dark/light bands aligned in the northeast‐southwest direction and propagating towards northwest. Because this feature these events were also referred as thermospheric dark band structures. The statistical study is based on 28 events of MSTIDs observed during seven years of optical data, obtained during low, medium, and high solar activities, for geomagnetically quiet nights. We find that the occurrence frequency of the MSTIDs presents a maximum during low solar activity, decreasing during medium solar activity with no occurrences during high solar activity. Also, the occurrence rates are greater near the June‐solstice months.
Total ozone and tropopause zonal asymmetry during the Antarctic spring
Authors: Evtushevsky O. M. , Grytsai A. V. , Klekociuk A. R. , Milinevsky G. P.
Published: September 2008

Analysis of zonal anomalies in total ozone and thermal tropopause height shows that ozone depletion during austral spring has a strong influence on the height and sharpness of the tropopause over West Antarctica. The seasonal change of tropopause peak height occurs between 9 km (summer and autumn) and 13–14 km (winter and spring) over the Weddell Sea region, and in the range of 9–10 km at opposite longitudes in the Australian sector. Elevation of the tropopause is explained by low stratospheric temperature due to the seasonal temperature minimum in winter and ozone losses in spring. Accordingly, tropopause zonal asymmetry is determined by strong east‐west asymmetry of the surface temperatures in the winter and total ozone asymmetry in spring. Lowering of the elevated tropopause over the boundary of the Antarctic continent is explained by the influence of the cold continental troposphere both in winter and spring. Overall, this work reports some details of relative contribution of radiative (strong cooling of the lower stratosphere and continental troposphere) and dynamical (quasi‐stationary planetary wave 1 in total ozone) processes to the Antarctic tropopause formation. The sloping meridional profile of the tropopause and widening of the transition layer between the troposphere and stratosphere over West Antarctica suggest the possibility of enhanced air mixing not only vertically but also horizontally. This may contribute to the east‐west asymmetry in Antarctic climate change.
A joint satellite and global cloud‐resolving model analysis of a Madden‐Julian Oscillation event: Model diagnosis
Authors: Masunaga H. , Satoh M. , Miura H.
Published: September 2008

In this study, a methodology to diagnose a global cloud‐resolving model (GCRM) is explored on the basis of a joint analysis with satellite measurements. The Madden‐Julian Oscillation experiment carried out with the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) is used as the test bed. The NICAM output is compared with Tropical Rainfall Measuring Mission (TRMM) and CloudSat measurements in terms of composite analysis, contoured frequency by altitude diagrams (CFADs), and the joint histogram of cloud top and precipitation top heights. It is found in the composite diagram that the GCRM reproduces a slow, eastward migration of a convective envelope well comparable to the satellite measurement. The GCRM CFAD qualitatively reproduces TRMM and CloudSat CFADs, except that the GCRM tends to overly produce snow in deep convection. The joint histograms reveal that, while the overproduction of snow is evident, NICAM‐simulated snow is incapable of producing 94‐GHz radar echoes higher than 5 dBZ. This deficiency can be mitigated by a modification to microphysical parameterization in the way that a proportion of small particles is enhanced in the snow mass spectrum.
Regulation of Wnt protein secretion and its role in gradient formation
Authors: Bartscherer Kerstin , Boutros Michael
Published: September 2008

In metazoans, many developmental and disease‐related processes are mediated by Wnt proteins, which are secreted by specific cells to regulate cellular programmes in the surrounding tissue. Although the Wnt‐induced signal‐transduction cascades are well studied, little is known about how Wnts are secreted. The discovery of Porcupine, an endoplasmic‐reticulum‐resident acyltransferase, led to closer inspection of the secretory routes of Wnts, and the analysis of Wnt secretion has become an exciting new area of research. Wnt post‐translational modifications, interaction partners and subcellular localizations now indicate that Wnt release is tightly regulated. In this review, we summarize recent advances in the field of Wnt secretion and discuss the possibility that separate pathways might regulate the release of lipid‐linked morphogens for short‐range and long‐range signalling.
Photochemistry
Authors: Horspool William M , Allen Norman S , Gilbert A
Published: September 2008

The breadth of scientific and technological interests in the general topic of photochemistry is truly enormous and includes for example, such diverse areas as microelectronics, atmospheric chemistry, organic synthesis, non-conventional photoimaging, photosynthesis, solar energy conversion, polymer technologies, and spectroscopy. This Specialist Periodical Report on Photochemistry aims to provide an annual review of photo-induced processes that have relevance to the above wide-ranging academic and commercial disciplines, and interests in chemistry, physics, biology and technology. In order to provide easy access to this vast and varied literature, each volume of Photochemistry comprises sections concerned with photophysical processes in condensed phases, organic aspects which are sub-divided by chromophore type, polymer photochemistry, and photochemical aspects of solar energy conversion. Volume 36 covers literature published from July 2003 to June 2004.
Glycosylphosphatidylinositol-specific phospholipase C regulates transferrin endocytosis in the African trypanosome
Authors: Subramanya Sandesh , Hardin C. Frank , Steverding Dietmar , Mensa-Wilmot Kojo
Published: September 2008

GPI-PLC (glycosylphosphatidylinositol-specific phospholipase C) is expressed in bloodstream-form Trypanosoma brucei, a protozoan that causes human African trypanosomiasis. Loss of genes encoding GPI-PLC reduces the virulence of a pleomorphic strain of the parasite, for reasons that are not clear. In the present paper, we report that GPI-PLC stimulates endocytosis of transferrin by 300–500%. Surprisingly, GPI-PLC is not detected at endosomes, suggesting that the enzyme does not interact directly with the endosomal machinery. We therefore hypothesized that a diffusible product of the GPI-PLC enzyme reaction [possibly DAG (diacylglycerol)] mediated the biological effects of the protein. Two sets of data support this assertion. First, a catalytically inactive Q81L mutant of GPI-PLC, expressed in a GPI-PLC-null background, had no effect on endocytosis, indicating that enzyme activity is essential for the protein to stimulate endocytosis. Secondly, the exogenous DAGs OAG (1-oleyl-2-acetyl-sn-glycerol) and DMG (dimyristoylglycerol) independently stimulated endocytosis of transferrin. Furthermore, the DAG mimic PMA, a phorbol ester, also activated endocytosis in T. brucei. DAG-stimulated endocytosis is a novel pathway in the trypanosome. We surmise that (i) GPI-PLC regulates transferrin endocytosis in T. brucei, (ii) GPI-PLC is a signalling enzyme, and (iii) DAG is a second messenger for GPI-PLC. We propose that regulation of endocytosis is a physiological function of GPI-PLC in bloodstream T. brucei.