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The lead article for this issue of EJAM is Prof. Bernard J. Matkowsky's personalized survey-style article on the theory and application of singular perturbation methods to noisy dynamical systems in the limit of small noise. This article is based on his John von Neumann Prize lecture presented at the Society of Industrial and Applied Mathematics (SIAM) Annual Meeting in July 2017. The John von Neumann Lecture is awarded by SIAM for outstanding and distinguished contributions to the field of applied mathematical sciences and for the effective communication of these ideas to the community. From 1990–1996, Matkowsky was an inaugural editorial board member for EJAM.
This paper explores phrase-length-related alternations in the association of tones to positions in metrical structure in two melodic constructions of Spanish. An imitation-and-completion task eliciting (a) the low–falling–rising contour and (b) the circumflex contour on intonation phrases (IPs) of one, two, and three prosodic words revealed that, although the focus structure and pragmatic context is constant across conditions, phrases containing one prosodic word differ in their nuclear (i.e. final) pitch accents and edge tones from phrases containing more than one prosodic word. For contour (a), short intonation phrases (e.g. [Manolo]IP) were produced with a low accent followed by a high edge tone (L* H% in ToBI notation), whereas longer phrases (e.g. [El hermano de la amiga de Manolo]IP ‘Manolo's friend's brother’) had a low accent on the first stressed syllable, a rising accent on the last stressed syllable, and a low edge tone (L* L+H* L%). For contour (b), short phrases were produced with a high–rise (L+H* ¡H%), whereas longer phrases were produced with an initial accentual rise followed by an upstepped rise–fall (L+H* ¡H* L%). These findings imply that the common practice of describing the structure of intonation contours as consisting of a constant nuclear pitch accent and following edge tone is not adequate for modeling Spanish intonation. To capture the observed melodic alternations, we argue for clearer separation between tones and metrical structure, whereby intonational tones do not necessarily have an intrinsic culminative or delimitative function (i.e. as pitch accents or as edge tones). Instead, this function results from melody-specific principles of tonal–metrical association.
The special lead article in this issue of EJAM, by Profs. John Ockendon and Brian Sleeman, is dedicated to Prof. Joseph B. Keller (referred to as Joe by his friends), Emeritus professor of Stanford University, who was one of the greatest applied mathematicians of our time. Joe died in September 2016. A workshop in honour of Joe was held at the Isaac Newton Institute for Mathematical Sciences, Cambridge, UK, in March 2017, focussing on some of the astonishingly wide range of topics in the mathematical sciences and continuum mechanics that Joe made substantial contributions to over his long career. This article discusses some of these pioneering contributions, describes some modern developments as discussed by the workshop speakers, and provides a more personal tribute to Joe, his history, and to his large influence on the international applied mathematics community. May the spirit of Joe, and his flavour of applied mathematics, continue to be reflected in EJAM.
Modern water-supply systems — hidden beneath the ground, constructed, expanded, adapted and repaired intermittently by multiple groups of people — are often messy and difficult to comprehend. The ancient water-supply system we consider here is no different — and perhaps even more complex as it was developed over 1200 years and then had a modern city built on top. Despite this, we are beginning to understand how one of the Roman world's most important cities provided its population with water.
The remains of water infrastructure in Constantinople attest to a complex system of water-management and distribution, one that developed from the colony of Byzantium, through the growth and eventual decline of the new capital of the Roman empire, until conquest by the Ottomans. Aqueducts — the system of channels, bridges and tunnels designed to carry water through the landscape — were the focus of infrastructure investment in earlier periods, but cisterns for the storage and distribution of water were constructed throughout the time of Byzantine Constantinople.
A hoard of objects found at the early Roman colony at Colchester in a small hole scraped into the floor of a house destroyed during the Boudican revolt includes a group of high-quality gold jewellery, three silver military awards, a bag of coins, an unusual silver-clad wooden box and other items. Buried in haste as the British approached, they provide a remarkably clear image of one couple's background, achievements, taste and social standing. A bulla shows that the man was a Roman citizen, the awards that he was a veteran soldier of some distinction, while parallels for the woman's jewellery suggest that it was acquired in Italy.
Two broad aims drive weed science research: improved management and improved
understanding of weed biology and ecology. In recent years, agricultural
weed research addressing these two aims has effectively split into separate
subdisciplines despite repeated calls for greater integration. Although some
excellent work is being done, agricultural weed research has developed a
very high level of repetitiveness, a preponderance of purely descriptive
studies, and has failed to clearly articulate novel hypotheses linked to
established bodies of ecological and evolutionary theory. In contrast,
invasive plant research attracts a diverse cadre of nonweed scientists using
invasions to explore broader and more integrated biological questions
grounded in theory. We propose that although studies focused on weed
management remain vitally important, agricultural weed research would
benefit from deeper theoretical justification, a broader vision, and
increased collaboration across diverse disciplines. To initiate change in
this direction, we call for more emphasis on interdisciplinary training for
weed scientists, and for focused workshops and working groups to develop
specific areas of research and promote interactions among weed scientists
and with the wider scientific community.
Compound Poisson population models are particular conditional branching process models. A formula for the transition probabilities of the backward process for general compound Poisson models is verified. Symmetric compound Poisson models are defined in terms of a parameter θ ∈ (0, ∞) and a power series φ with positive radius r of convergence. It is shown that the asymptotic behaviour of symmetric compound Poisson models is mainly determined by the characteristic value θrφ′(r−). If θrφ′(r−)≥1, then the model is in the domain of attraction of the Kingman coalescent. If θrφ′(r−) < 1, then under mild regularity conditions a condensation phenomenon occurs which forces the model to be in the domain of attraction of a discrete-time Dirac coalescent. The proofs are partly based on the analytic saddle point method. They draw heavily from local limit theorems and from results of S. Janson on simply generated trees, conditioned Galton-Watson trees, random allocations and condensation. Several examples of compound Poisson models are provided and analysed.
Let H be a graph, and let CH(G) be the number of (subgraph isomorphic) copies of H contained in a graph G. We investigate the fundamental problem of estimating CH(G). Previous results cover only a few specific instances of this general problem, for example the case when H has degree at most one (the monomer-dimer problem). In this paper we present the first general subcase of the subgraph isomorphism counting problem, which is almost always efficiently approximable. The results rely on a new graph decomposition technique. Informally, the decomposition is a labelling of the vertices such that every edge is between vertices with different labels, and for every vertex all neighbours with a higher label have identical labels. The labelling implicitly generates a sequence of bipartite graphs, which permits us to break the problem of counting embeddings of large subgraphs into that of counting embeddings of small subgraphs. Using this method, we present a simple randomized algorithm for the counting problem. For all decomposable graphs H and all graphs G, the algorithm is an unbiased estimator. Furthermore, for all graphs H having a decomposition where each of the bipartite graphs generated is small and almost all graphs G, the algorithm is a fully polynomial randomized approximation scheme.
We show that the graph classes of H for which we obtain a fully polynomial randomized approximation scheme for almost all G includes graphs of degree at most two, bounded-degree forests, bounded-width grid graphs, subdivision of bounded-degree graphs, and major subclasses of outerplanar graphs, series-parallel graphs and planar graphs of large girth, whereas unbounded-width grid graphs are excluded. Moreover, our general technique can easily be applied to proving many more similar results.
We have investigated the electrical properties of a ZnO microwire grown by carbo-thermal evaporation, a ZnO thin film grown by pulsed-laser deposition on an a-plane sapphire, and a hydrothermally grown Zn-face ZnO single crystal (Tokyo Denpa Co. Ltd.). The samples were investigated by means of current-voltage measurements, capacitance-voltage measurements, and deep-level transient spectroscopy.
The defects T2 [1,2] and E3 [1,3,4] were identified in all three sample types. Additionally, in the single crystal and thin film samples E64  and E4  were detected. These findings support the common opinion that T2 is an intrinsic defect since it is found in all the samples investigated and thus its occurrence is not related to any growth technique.
The population-based Northern Survey of Twin and Multiple Pregnancy (NorSTAMP, formerly the Multiple Pregnancy Register) has collected data since 1998 on all multiple pregnancies in North of England (UK) from the earliest point of ascertainment in pregnancy. This paper updates recent developments to the NorSTAMP and presents some early mortality data from the first 10 years of data collection (1998–2007). Since 2005, mothers have been asked to give explicit consent for their identifiable data to be held by the survey, in line with changing guidance and legal frameworks for identifiable data. In 2009, regional standards of care for multiple pregnancies were developed, agreed, and disseminated. During 1998–2007, 4,865 twin maternities (pregnancies with at least one live birth or stillbirth) were registered, with an average twinning rate of 14.9 per 1,000 maternities. The overall stillbirth and neonatal mortality rates in twins were 18.0/1,000 births and 23.0/1,000 live births respectively. Stillbirth and neonatal mortality rates were significantly higher in monochorionic than dichorionic twins: 44.4 versus 12.2 per 1,000 births (relative risk [RR] 3.6, 95% Confidence Intervals [CI] 2.6–5.1), and 32.4 versus 21.4 per 1,000 live births (RR 1.5, 95% CI 1.04–2.2) respectively. There was no significant improvement during this period in either stillbirth or neonatal mortality rates in either chorionicity group. This population-based survey is an important source of data on multiple pregnancies, which allows monitoring of trends in multiple birth rates and pregnancy losses, providing essential information to support improvements in clinical care and for epidemiological research.
X-ray photoemission spectroscopy using synchrotron radiation from 100 to 1486.6 eV was used to investigate polarity-dependent differences between the Zn-polar (0001) and the O-polar () faces of ultrahigh vacuum cleaved hydrothermally grown ZnO single crystals. The cleaved polar surfaces showed a characteristic polarity effect in that the intensity of emission from the lowest binding energy O 2p related valence band states was significantly stronger on the Zn-polar face, even when the cleaved surfaces were imperfect with irregular nonatomically flat features. A residual submonolayer hydroxyl termination of approximately 0.5 ML was observed on both the Zn-polar and O-polar surfaces immediately after cleaving. The near-surface downward band bending on the O-polar face was removed by the cleaving process leaving almost flat bands, while on the cleaved Zn-polar face, emission from states above the valence band edge was observed.
Accurate assessment of neonatal body composition is essential to studies investigating neonatal nutrition or developmental origins of obesity. Bioelectrical impedance analysis or bioimpedance analysis is inexpensive, non-invasive and portable, and is widely used in adults for the assessment of body composition. There are currently no prediction algorithms using bioimpedance analysis in neonates that have been directly validated against measurements of fat-free mass (FFM). The aim of the study was to evaluate the use of bioimpedance analysis for the estimation of FFM and percentage of body fat over the first 4 months of life in healthy infants born at term, and to compare these with estimations based on anthropometric measurements (weight and length) and with skinfolds. The present study was an observational study in seventy-seven infants. Body fat content of infants was assessed at birth, 6 weeks, 3 and 4·5 months of age by air displacement plethysmography, using the PEA POD body composition system. Bioimpedance analysis was performed at the same time and the data were used to develop and test prediction equations for FFM. The combination of weight+sex+length predicted FFM, with a bias of < 100 g and limits of agreement of 6–13 %. Before 3 months of age, bioimpedance analysis did not improve the prediction of FFM or body fat. At 3 and 4·5 months, the inclusion of impedance in prediction algorithms resulted in small improvements in prediction of FFM, reducing the bias to < 50 g and limits of agreement to < 9 %. Skinfold measurements performed poorly at all ages.
This paper describes a new method for recognizing whether a student's response to an automated tutor's question entails that they understand the concepts being taught. We demonstrate the need for a finer-grained analysis of answers than is supported by current tutoring systems or entailment databases and describe a new representation for reference answers that addresses these issues, breaking them into detailed facets and annotating their entailment relationships to the student's answer more precisely. Human annotation at this detailed level still results in substantial interannotator agreement (86.2%), with a kappa statistic of 0.728. We also present our current efforts to automatically assess student answers, which involves training machine learning classifiers on features extracted from dependency parses of the reference answer and student's response and features derived from domain-independent lexical statistics. Our system's performance, as high as 75.5% accuracy within domain and 68.8% out of domain, is very encouraging and confirms the approach is feasible. Another significant contribution of this work is that it represents a significant step in the direction of providing domain-independent semantic assessment of answers. No prior work in the area of tutoring or educational assessment has attempted to build such domain-independent systems. They have virtually all required hundreds of examples of learner answers for each new question in order to train aspects of their systems or to hand-craft information extraction templates.
Pt, Ir, Ni, Pd, and silver oxide Schottky contacts were fabricated on the Zn-polar surface of hydrothermally grown bulk ZnO. A relationship was observed between the barrier height of the contact and the free energy of formation of the “metal” oxide. This is consistent with the dominating influence of oxygen vacancies (VO) which tend to pin the ZnO Fermi level close to the VO (+2,0) defect level at approximately EC - 0.7 eV, where EC is the conduction band minimum. Valence band x-ray photoemission spectroscopy and the current - voltage characteristics of planar Schottky diodes, measured on similar Zn-polar surfaces, showed the existence of a vacuum activated surface accumulation layer. This is possibly a consequence of the observed OH termination of the Zn-polar surface. The surface accumulation layer is compensated in atmospheric conditions by the presence of acceptor-like adsorbates, such as O2 and H2O. The formation of high quality Schottky contacts to ZnO should therefore involve the reduction of near surface oxygen vacancies and the removal of H or OH from the surface.