Do envelope solitons radiate?

In dispersive wave systems, when leading-order nonlinear and dispersive effects, are taken into account the envelope of a small-amplitude narrow-band wave pulse is known to satisfy the nonlinear Schrödinger (NLS) equation which, under certain conditions, admits envelope-soliton solutions. These solitons describe locally confined wave groups with envelopes of permanent form and find applications in various physical contexts. Here, is addressed the question of whether NLS envelope solitons survive when higher-order effects are taken into account. Based on a kinematic argument first, it is suggested that oscillatory tails are inevitably emitted, and this claim is further supported by numerical computations by use of a fifth-order Korteweg-deVries equation as a simple example. The radiation of tails is caused by a resonance mechanism that lies beyond all orders of the usual multiple-scale expansion leading to the NLS equation, and a procedure for calculating these tails by use of exponential asymptotics is outlined. Despite having exponentially small amplitude in the asymptotic sense, the radiated tails can be significant when pulses of relatively short duration are considered.     

Do citations and readership identify seminal publications?

This work presents a new approach for analysing the ability of existing research metrics to identify research which has strongly influenced future developments. More specifically, we focus on the ability of citation counts and Mendeley reader counts to distinguish between publications regarded as seminal and publications regarded as literature reviews by field experts. The main motivation behind our research is to gain a better understanding of whether and how well the existing research metrics relate to research quality. For this experiment we have created a new dataset which we call TrueImpactDataset and which contains two types of publications, seminal papers and literature reviews. Using the dataset, we conduct a set of experiments to study how citation and reader counts perform in distinguishing these publication types, following the intuition that causing a change in a field signifies research quality. Our research shows that citation counts work better than a random baseline (by a margin of 10%) in distinguishing important seminal research papers from literature reviews while Mendeley reader counts do not work better than the baseline.     

Do ResearchGate Scores create ghost academic reputations?

Scientometrics - Technology is a complex system with technologies relating to each other in a space that can be mapped as a network. The technology network’s structure can reveal properties...     

Do today's projects need powerful network planning tools?

Since the 1960s, when network planning tools were ‘invented’, management has been pressed to use the methodologies embedded in the Critical Path Method (CPM) and in the Project Evaluation and Review Technique (PERT). Gradually benefits have been seen and these planning tools are now more widely used. Even so, there can be compelling reasons to use more comprehensive tools in order to model a greater degree of uncertainty than is possible with CPM or PERT. This situation may arise for instance when competition propels a firm into tight time, cost and performance contracts.

In this paper we will use a compressed network to illustrate how three planning tools—CPM, PERT and the newer Venture and Evaluation and Review Technique (VERT)—yield different results. So different in fact that we suggest the use of CPM and PERT can be very misleading. And used in too cavalier a fashion, these methods may present to management an over-confident prediction of the termination of the project. But the more difficult to use VERT could help unravel many probabilistic and stochastic choices that occur in real networks. Furthermore, this technique can offer a superior estimate of the final turn-around time and cost of the project.     

Do international management researchers need a code of ethics?

Abstract and Key Results

Do superconductors change as fast as possible when quenched?

If superconductors change as fast as possible as they pass through a phase transition, then the initial domain structure is constrained by causality. We shall see that Josephson junctions do indeed display such behaviour. However, we shall argue that causal bounds arise through the Gaussian nature of the order parameter, which can be thought of as a consequence of instabilities growing as fast as possible.     

Do properties of bioactive glasses exhibit mixed alkali behavior?

The effect of substituting K₂O for Na₂O on the physical and chemical properties of 15 glasses in the system Na₂O–K₂O–CaO–P₂O₅–SiO₂ was studied for three series: low (52 mol% SiO₂), medium (60 mol% SiO₂) and high (66 mol% SiO₂) silica. The SiO₂ content expressed as weight-% varied from 46 to 64 wt%, thus suggesting that the compositions were either bioactive or biocompatible. The crystallization tendency and sintering behavior were studied using differential thermal analysis and hot stage microscopy. Formation of silica- and hydroxy-apatite-rich layers were studied for glass plates immersed in static simulated body fluid. The release of inorganic ions into Tris buffer solution was analyzed using inductively coupled plasma optical emission spectrometer in dynamic and static conditions. Substitution of K₂O for Na₂O suggested mixed alkali effect (MAE) for the thermal properties with a minimum value around 25% substitution. With increased share of K₂O in total alkali oxides, the hot working window markedly expanded in each series. Silica and hydroxyapatite layers were seen only on the low silica glasses, while a thin silica-rich layer formed on the other glasses. In each series, greater dissolution of alkali and alkali earth ions was seen from K-rich glasses. Clear MAE and preferential ion dissolution were recorded for medium and high silica series, while for low silica glasses, the initial MAE dissolution trends become rapidly covered by other simultaneous surface reactions. MAE enables designing especially low silica bioactive glasses for improved hot working properties and medium and high silica glasses for controlled dissolution.     

Do Online Students Perform as Well as Lecture Students?

This paper reports research on whether online delivery performs as well as traditional lecture delivery for a computer science course at North Carolina State University. The comparisons made are for two large sections of the course for which almost the only difference was that one section attended on‐campus lectures and the other did not. Where significant differences in outcomes appear for students who completed the course, they favor the online students. However, online students who started the course were less likely to complete it.     

Do electromagnetic fields enhance the effects of environmental carcinogens?

Epidemiological studies have reported an increased risk of leukaemia in children who are exposed to extremely low-frequency (ELF) magnetic fields (MF), suggesting that ELF MFs may be carcinogenic to humans. No carcinogenic effects have been found in animal studies that have tested ELF MFs alone. Similarly, genotoxicity studies have generally not shown effects from MFs alone. However, ELF MFs have been reported to enhance the effects of known carcinogenic or mutagenic agents in a few animal studies and in several in vitro studies. This paper discusses the findings of studies on such combined effects. The majority of in vitro studies have reported positive findings, which supports the conclusion that MFs of 100 microT or higher interact with other chemical and physical agents. Further studies should address biophysical mechanisms and dose-response relationship below 100 microT. Animal studies designed according to the classical initiation-promotion concept may not be sufficient for studying the cocarcinogenic effects of MFs, and further studies using novel study designs would be useful. Epidemiological data on the interaction between MFs and other environmental agents are scant and inconclusive, and any further studies may be difficult because of the scarcity of subjects with suitable combined exposures.     

Do ‘Functional Barriers’ Function?

The direct recycling of plastics (food grade plastic to food grade plastic) obviously gives rise to possible health hazards. Contaminants, picked up by the material during first usage, may migrate into food during second use. ‘Functional barrier’ layers have been used for a long time (e.g. aluminium, silica and silicates), but there is now considerable research and development on ‘barrier’ layers of plastics for the purpose. For technological and regulatory reasons, use of the same plastic in virgin form as the recyclate is favoured. A theoretical study shows that such a layer, in general, must function more as a sponge than a barrier. Moreover, in general, migration into and through the barrier must start at manufacture of the package, and not at containment of the food (as assumed in all legislation). Although in some instances there may be adequate delay and reduction of migration to ensure safety, this is not so in general and certainly cannot be guaranteed. Hence the concept needs reconsideration in the interest of public safety.     

Do highly cited researchers successfully use the social web?

Academics can now use the web and the social websites to disseminate scholarly information in a variety of different ways. Although some scholars have taken advantage of these new online opportunities, it is not clear how widespread their uptake is or how much impact they can have. This study assesses the extent to which successful scientists have social web presences, focusing on one influential group: highly cited researchers working at European institutions. It also assesses the impact of these presences. We manually and systematically identified if the European highly cited researchers had profiles in Google Scholar, Microsoft Academic Search, Mendeley, Academia and LinkedIn or any content in SlideShare. We then used URL mentions and altmetric indicators to assess the impact of the web presences found. Although most of the scientists had an institutional website of some kind, few had created a profile in any social website investigated, and LinkedIn—the only non-academic site in the list—was the most popular. Scientists having one kind of social web profile were more likely to have another in many cases, especially in the life sciences and engineering. In most cases it was possible to estimate the relative impact of the profiles using a readily available statistic and there were disciplinary differences in the impact of the different kinds of profiles. Most social web profiles had some evidence of uptake, if not impact; nevertheless, the value of the indicators used is unclear.     

Do interdisciplinary research teams deliver higher gains to science?

The present paper takes its place in the stream of studies that analyze the effect of interdisciplinarity on the impact of research output. Unlike previous studies, in this study the interdisciplinarity of the publications is not inferred through their citing or cited references, but rather by identifying the authors’ designated fields of research. For this we draw on the scientific classification of Italian academics, and their publications as indexed in the WoS over a 5-year period (2004–2008). We divide the publications in three subsets on the basis the nature of co-authorship: those papers coauthored with academics from different fields, which show high intensity of inter-field collaboration (“specific” collaboration, occurring in 110 pairings of fields); those papers coauthored with academics who are simply from different “non-specific” fields; and finally co-authorships within a single field. We then compare the citations of the papers and the impact factor of the publishing journals between the three subsets. The results show significant differences, generally in favor of the interdisciplinary authorships, in only one third (or slightly more) of the cases. The analysis provides the value of the median differences for each pair of publication subsets.