bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-dimensional planar plumes and fountains
Authors: van den Bremer T. S. , Hunt G. R.
Published: June 2014

Closed-form solutions describing the behaviour of two-dimensional planar turbulent rising plumes and fountains from horizontal planar area and line sources in unconfined quiescent environments of uniform density are proposed. Extending the analysis on axisymmetric releases by van den Bremer & Hunt (J. Fluid Mech., vol. 644, 2010, pp. 165–192) to planar releases, the local flux balance parameter$\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\varGamma =\varGamma (z)$is instrumental in describing the bulk behaviour of steady Boussinesq and non-Boussinesq planar plumes and the initial rise behaviour of Boussinesq planar fountains as a function of height$z$. Expressions for the asymptotic virtual source correction are developed and the results elucidated by ‘scale diagrams’ (cf. Morton & Middleton,J. Fluid Mech., vol. 58, 1973, pp. 165–176) showing certain characteristic heights for different source conditions. These diagrams capture all the different manifestations of plume behaviour, encompassing fountains, jets, source-momentum-dominated or ‘forced’ plumes, pure plumes and source-buoyancy-dominated or ‘lazy’ plumes, and their associated key features. Other flow features identified include a gravity-driven deceleration regime and a mixing-driven regime for forced fountains. Deceleration in lazy fountains is purely gravity-driven. The results can be shown to be valid for both Boussinesq and non-Boussinesq plumes (but not for non-Boussinesq fountains) thus resulting in universal solutions valid for both cases provided the entrainment velocity is unaffected by non-Boussinesq effects. This paper presents and explores these universal solutions. An accompanying paper (van den Bremer & Hunt,J. Fluid Mech., vol. 750, 2014, pp. 245–258) examines the implications for non-Boussinesq plumes. The existing solutions of Lee & Emmons (J. Fluid Mech., vol. 11, 1961, pp. 353–368) generalized herein are valid for a constant entrainment coefficient$\alpha $. New results for an entrainment coefficient that varies linearly with$\varGamma (z)$and thus captures experimental values far more realistically are presented for forced plumes.
TEXT, BOOK, AND TEXTBOOK: MARTIAL'S EXPERIMENTS IN THE CODEX
Authors: Blake Sarah
Published: June 2014

Of all the Roman poets, Martial is perhaps the most concerned with his material medium; the physical book itself is a major character in theEpigrams. In the context of epigram-writing, this is not so unusual; as a genre, epigram is traditionally self-conscious of its development from ‘stone to book’. As recent scholarly work has shown, however, Martial's concern with the materiality of his poetry goes to the heart of his poetic project, as he reworks images inherited from Greek epigram as well as from Catullus, Horace and Ovid to fashion a new poetics of Flavian epigram and a correspondingly unique concept of the poetry book.
Resolution of three cryptic agricultural pests (Ceratitis fasciventris, C. anonae, C. rosa, Diptera: Tephritidae) using cuticular hydrocarbon profiling
Authors: Vaníčková L. , Virgilio M. , Tomčala A. , Břízová R. , Ekesi S. , Hoskovec M. , Kalinová B. , Do Nascimento R. R. , De Meyer M.
Published: June 2014

Discrimination of particular species within the species complexes of tephritid fruit flies is a very challenging task. In this fruit-fly family, several complexes of cryptic species have been reported, including the African cryptic species complex (FAR complex). Cuticular hydrocarbons (CHCs) appear to be an excellent tool for chemotaxonomical discrimination of these cryptic species. In the present study, CHC profiles have been used to discriminate among three important agricultural pests from the FAR complex,Ceratitis fasciventris, Ceratitis anonaeandCeratitis rosa. Hexane body surface extracts of mature males and females were analyzed by two-dimensional gas chromatography with mass spectrometric detection and differences in CHC profiles between species and sexes tested through multivariate statistics and compared with species identification by means of microsatellite markers. Quantitative as well as qualitative CHC profile differences between sexes and species are reported. The CHC profiles consisted of a mixture of linear, internally methyl-branched and mono-, di- and tri-unsaturated alkanes. Twelve compounds were pinpointed as potential chemotaxonomical markers. The present study shows that presence or absence of particular CHCs might be used in the chemical diagnosis of the FAR complex. Moreover, our results represent an important first step in the development of a useful chemotaxonomic tool for cryptic species identification of these important agricultural pests.
Leaders, Followers, and Risk Dynamics in Industry Equilibrium
Authors: Carlson Murray , Dockner Engelbert J. , Fisher Adlai , Giammarino Ron
Published: June 2014

We study the distinct impacts of own and rival actions on risk and return when firms strategically compete in the product market. Contrary to simple intuition, a competitor’s options to adjust capacity reduce own-firm risk. For example, if a rival possesses a growth option, an increase in industry demand directly enhances profits but also encourages value-reducing competitor expansion. The rival option thus acts as a natural hedge. Within the industry, we obtain endogenous differences in expected returns. In a leader-follower equilibrium, own-firm and competitor risks and required returns move together through contractions and oppositely during expansions, providing testable new predictions.
Nervus intermedius meningioma
Authors: Rodgers B , Chamoun R , Newell K , Lin J
Published: June 2014

Objective:

To report a case of meningioma arising from the nervus intermedius.

Methods:

This paper comprises a case report, literature review, and discussion regarding the presentation of a nervus intermedius meningioma, comparing and contrasting this to other relevant neoplasms of the internal auditory canal and cerebellopontine angle.

Results:

Tumours of the cerebellopontine angle include vestibular schwannomas, facial schwannomas and, more rarely, nervus intermedius schwannomas. The nervus intermedius is a division of the facial nerve at the cerebellopontine angle, with parasympathetic and afferent somatic components. Our patient presented with progressive hearing loss. An ipsilateral internal auditory canal mass at the fundus, as indicated by magnetic resonance imaging and electroneuronography, was suggestive of vestibular schwannoma. Intra-operative dissection revealed a nervus intermedius tumour. Histological evaluation indicated a meningioma rather than a schwannoma.

Conclusion:

This is the first reported case of meningioma involving the nervus intermedius. The implications this pathology may have on surgical approach, facial nerve outcomes, and the need for improved pre-operative imaging and intra-operative monitoring are discussed. A review of the current literature on nervus intermedius tumour is provided.
Air travellers' awareness of the preventability of otic barotrauma
Authors: Mitchell-Innes A , Young E , Vasiljevic A , Rashid M
Published: June 2014

Objective:

Otic barotrauma is common among air travellers and can cause severe otalgia, perforation of the tympanic membrane and hearing loss. Many prevention measures exist, with varying evidence to support their use. There are no data to establish if air travellers are aware of them or indeed use them. We aimed to establish air travellers' knowledge of such prevention measures.

Methods:

We surveyed air travellers at two UK airports by means of a questionnaire. Answers to the questionnaire were collected over a two-week period.

Results:

Overall, 179 air travellers with a mean age of 28 years (range: 15–72 years) completed the questionnaire. There were 66 female and 113 male air travellers. The majority (84 per cent) complained of symptoms while flying and 30 per cent were not aware of any prevention measures. Barotrauma-related symptoms were reported in 25 per cent of air travellers who were unaware of any prevention measures. Nearly all air travellers (86 per cent) indicated that more information regarding prevention measures would be useful.

Conclusion:

Air travellers are often not aware of prevention measures to avoid otic barotrauma, and the majority suffer as a result. Increasing public awareness of simple prevention measures would have a significant impact on air travellers.
Fabriciidae (Annelida, Sabellida) from a naturally acidified coastal system (Italy) with description of two new species
Authors: Giangrande A. , Gambi M.C. , Micheli F. , Kroeker K.J.
Published: June 2014

Polychaete worms are known to thrive in extreme environmental conditions, however little is known about how polychaete species will respond to major climatic stressors, such as ocean acidification. Here, we examined the distribution of Fabriciidae (Annelida, Sabellida) species along a gradient of ocean acidification, caused by carbon dioxide (CO2) vent emissions in a shallow, coastal system off the island of Ischia (Tyrrhenian Sea, Italy). A total of 265 specimens of Fabriciidae, representing six species from five genera, were collected along the gradient. Most of the species were found across the entire CO2 gradient, suggesting polychaetes may have a high tolerance for ocean acidification in the future. Two of the species were new to science, and two of the genera were previously unrecorded in the Mediterranean. A full description of the new species Brifacia aragonensis sp. nov. and Parafabricia mazzellae sp. nov. is given, both of which were most abundant in the most acidified areas (pH 6.6–7.2). The geographical distribution and ecology of the new taxa, as well as of the other fabriciid species collected, is discussed. Taxonomic keys to identify the Fabriciidae species currently recorded in the Mediterranean Sea are also provided.
Genitive variation: the niche role of the oblique genitive
Authors: PAYNE JOHN , BERLAGE EVA
Published: June 2014

This article discusses the niche role that the oblique genitive of the type the friend of John’s occupies in the context of genitive variation. The article shows that the oblique genitive should be considered an independent construction which competes marginally in two syntactic contexts with the s-genitive (as in John's friend) and the of-genitive (as in the friend of John). The first context is one in which all three constructions function as the predicative complement of the clause (e.g. He is a friend of John's / John's friend / a friend of John). Note that in this context the definiteness effect of the s-genitive is downplayed, so that competition is possible with indefiniteness of the other two constructions. The second context is one where the oblique genitive and the of-genitive are introduced by the determiner the. Contrary to the claim that oblique genitive constructions introduced by the definite article must receive restrictive modification of the head (see e.g. Barker 1998; Lyons 1986), the quantitative data presented in this article reveal that oblique genitives introduced by the determiner the are not confined to pre- or postmodification of the head but can occur, albeit rarely, without any modification as in the example the executor of Sir Ralph’s.

The article further compares the oblique genitive, s-genitive and of-genitive with respect to the following five features: noun-headed vs pronoun dependent; animacy of the dependent; length of the noun-headed dependent; determiner of the head; and the semantic relations that can hold between head (e.g. friend) and dependent (e.g. John). The most intriguing theoretical conclusion is that the semantic relations available to head and dependent in the oblique genitive are a subset of those found in the s-genitive, which, again constitute a subset of those that exist in the of-genitive. This means that variation between all three constructions is not only restricted to the two syntactic contexts outlined above but also to a shared set of semantic relations.
Point-of-Care Lung Ultrasound
Authors: Volpicelli Giovanni
Published: June 2014

Unter «Point-of-Care»-Lungen-Ultraschall versteht man eine neue Technik zur Beurteilung von Lungenerkrankungen. In den letzten Jahren war die Thoraxsonographie auf die Untersuchung von Pleuraerguss und oberflächlichen Thoraxveränderungen begrenzt, weil Alveolarluft und Knochen des Brustkorbs die Ausbreitung der Ultraschallwellen begrenzen. Erst kürzlich wurde erkannt, dass der Lungen-Ultraschall wie ein echtes Densitometer funktioniert, das sehr empfindlich auf Veränderungen des Lungeninhalts sowie das Gleichgewicht zwischen Luft und Flüssigkeit reagiert. Die dynamische und statische Analyse der Kombination aus Ultraschallartefakten und «realen» Bildern ermöglicht eine genaue Diagnose von vielen Lungenerkrankungen, insbesondere beim Einsatz im Notfall- oder Intensivmedizinbereich. Die Sonographie erweist sich v. a. bei der Diagnostik von Lungenerkrankungen mit reduzierter Alveolarluft und vermehrter interstitieller Flüssigkeit hilfreich, aber auch zur Beurteilung von Luft- oder Flüssigkeitsansammlungen im Pleuraraum. Der Artikel erklärt die grundlegenden Prinzipien des «Point-of-Care»-Lungen-Ultraschalls und verweist auf diagnostischen Nutzen und Limitationen dieser Technik. Es werden weiter die drei Hauptanwendungsgebiete des Lungen-Ultraschalls, nämlich die interstitiellen-, alveolären- sowie Pleuraveränderungen besprochen.
Vocational Designing and Career Counseling in Europe
Authors: Nota Laura , Soresi Salvatore , Ferrari Lea , Ginevra Maria Cristina
Published: June 2014

This article aims to illuminate new challenges in the field of vocational designing and career counseling in assisting persons planning for an uncertain and difficult future in the current economic climate in European and other Western nations. The first part of the paper starts with an analysis of the European socioeconomic context and provides a description of populations with significant career and life design needs: young people, older workers, migrants, temporary workers, women, people with disabilities, parents and children, employers. The second part of the paper focuses on an analysis of these challenges and suggests a revision of well-established vocational designing and career counseling assumptions in favor of a new form of awareness and new concepts. Social cognitive career theory (SCCT) and life design approaches are discussed as promising models to cope with the social, economic, and cultural challenges facing career counseling. Suggestions for interventions that could be implemented on a large scale, especially for at-risk populations and with preventive aims, are provided.
Telling What They Want to Know
Authors: Kemmelmeier Markus
Published: May 2014

According to a conversational approach, survey respondents provide answers they believe to be relevant to an interaction. Norenzayan and Schwarz (1999) demonstrated that participants provide dispositional accounts for an action to a personality researcher, but contextual accounts to a social scientist. Two studies sought to replicate this finding and test if the effects were due to social desirability. Using original materials, Study 1 manipulated researcher identity and varied whether participants had reasons to explain the action (replication) or reasons that could not explain the action (non-reasons). Study 2 varied researcher identity and asked participants what they want to be like in the future or what they do not want to be like in the future. Individual differences in socially desirable responding were also assessed. Results replicated original findings without social desirability qualifying critical effects. This confirms that participants provide the kinds of answers that they believe to be relevant to the researchers.
Commentary and Rejoinder on
Authors: Schnall Simone , Johnson David J. , Cheung Felix , Brent Donnellan M.
Published: May 2014

Johnson, Cheung, and Donnellan (2014a) reported a failure to replicate Schnall, Benton, and Harvey (2008) ’s effect of cleanliness on moral judgment. However, inspection of the replication data shows that participants provided high numbers of severe moral judgments – a ceiling effect. In the original data percentage of extreme responses per moral dilemma correlated negatively with the effect of the manipulation. In contrast, this correlation was absent in the replications, due to almost all items showing a high percentage of extreme responses. Therefore the parametric statistics reported by Johnson et al. (2014a) are inconclusive regarding the reproducibility of the original effect. Direct replications are prone to error when reviewers only judge similarity of methods, but not resulting data and conclusions. It is my conclusion that preventable problems can arise if publication decisions are made without independent post-data peer evaluation.
Exposure–Response Modeling of Clinical End Points Using Latent Variable Indirect Response Models
Authors: Hu C
Published: June 2014

Exposure–response modeling facilitates effective dosing regimen selection in clinical drug development, where the end points are often disease scores and not physiological variables. Appropriate models need to be consistent with pharmacology and identifiable from the time courses of available data. This article describes a general framework of applying mechanism‐based models to various types of clinical end points. Placebo and drug model parameterization, interpretation, and assessment are discussed with a focus on the indirect response models.

CPT Pharmacometrics Syst. Pharmacol. (2014) 3, e117; doi:10.1038/psp.2014.15; published online 4 June 2014
Surfactant-free CO2-based microemulsion-like systems
Authors: Hankel Robert F. , Rojas Paula E. , Cano-Sarabia Mary , Sala Santi , Veciana Jaume , Braeuer Andreas , Ventosa Nora
Published: June 2014

Water-rich and water-lean nanodomains in a transparent, pressurized surfactant-free “water–acetone–CO2” mixture.
Site-specific fluorescence labelling of RNA using bio-orthogonal reaction of trans-cyclooctene and tetrazine
Authors: Asare-Okai P. N. , Agustin E. , Fabris D. , Royzen M.
Published: June 2014

A cytidine triphosphate analogue modified with a trans-cyclooctene group was incorporated into the sequence of miR-122 by in vitro transcription.
Covalent assembly of a two-dimensional molecular “sponge” on a Cu(111) surface: confined electronic surface states in open and closed pores
Authors: Shchyrba Aneliia , Martens Susanne C. , Wäckerlin Christian , Matena Manfred , Ivas Toni , Wadepohl Hubert , Stöhr Meike , Jung Thomas A. , Gade Lutz H.
Published: June 2014

We present a new class of on-surface covalent reactions, formed between diborylene-3,4,9,10-tetraaminoperylene and trimesic acid on Cu(111), which gives rise to a porous 2D-‘sponge’.
Synthesis and photovoltaic performances in solution-processed BHJs of oligothiophene-substituted organocobalt complexes [(η4-C4(nT)4)Co(η5-C5H5)]
Authors: Bertrand Guillaume H. V. , Tortech Ludovic , Gandon Vincent , Aubert Corinne , Fichou Denis
Published: May 2014

New cobalt complexes substituted by four oligothiophene arms have been synthesized. Solution processed solar cells based on CpCoCb(3T)4 exhibit conversion efficiencies of up to 2.1%.
Robust Pt–Sn alloy decorated graphene nanohybrid cocatalyst for photocatalytic hydrogen evolution
Authors: Kong Chao , Min Shixiong , Lu Gongxuan
Published: June 2014

A novel platinum–tin alloy decorated graphene nanohybrid (Pt–Sn/G) as a robust photocatalyst exhibited higher hydrogen evolution activity than Pt/G under visible light irradiation.
The anion-binding polyanion: a molecular cobalt vanadium oxide with anion-sensitive visual response
Authors: Seliverstov Andrey , Forster Johannes , Heiland Magdalena , Unfried Johannes , Streb Carsten
Published: June 2014

A polyanionic cobalt vanadate cluster is reported which acts as a reversible anion binding site for carboxylates and halides with visual binding signaling in solution.
Preparation, crystal structures and conformations of six complexes based on 1,4-bis(benzimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene
Authors: Liu Qing-Xiang , Zhao Zhi-Xiang , Zhao Xiao-Jun , Bi Yue , Yu Jie , Wang Xiu-Guang
Published: June 2014

Six manganese(ii), cobalt(ii), copper(ii) and cadmium(ii) complexes based on dibenzimidazolyl ligands with the 1,2,4,5-tetramethylbenzene linker have been prepared and characterized.
Highly efficient (In2Te3)x(GeTe)3−3x thermoelectric materials: a substitute for TAGS
Authors: Sun Hui , Lu Xu , Chi Hang , Morelli Donald T. , Uher Ctirad
Published: June 2014

GeTe is a versatile base compound to produce highly efficient p-type thermoelectric materials such as the TAGS materials (AgSbTe2)1−x(GeTe)x and GeTe–PbTe nanocomposites.
Mechanistic analysis of water oxidation catalyzed by mononuclear copper in aqueous bicarbonate solutions
Authors: Winikoff Stuart G. , Cramer Christopher J.
Published: May 2014

We characterize a mechanism for a monomeric copper catalyst reported to oxidize water in bicarbonate solution when subject to sufficiently high external potentials at near neutral pH values.
Thermodynamics for complex formation between palladium(ii) and oxalate
Authors: Pilný Radomír , Lubal Přemysl , Elding Lars I.
Published: June 2014

Overall stability constants and thermodynamic parameters for formation of palladium(ii) oxalato complexes have been determined. The chelate effect is discussed.
Synthesis, complex stability and small animal PET imaging of a novel 64Cu-labelled cryptand molecule
Authors: Foerster Christian , Knight James C. , Wuest Melinda , Rowan Brendan , Lapi Suzanne E. , Amoroso Angelo J. , Edwards Peter G. , Wuest Frank
Published: May 2014

The radiosynthesis and radiopharmacological evaluation including small animal PET imaging of a novel 64Cu-labelled cryptand molecule ([64Cu]CryptTM) possessing a tris-pyridyl/tris-amido set of donor atoms is described.
Hydriding characteristics of NaMgH2F with preliminary technical and cost evaluation of magnesium-based metal hydride materials for concentrating solar power thermal storage
Authors: Sheppard D. A. , Corgnale C. , Hardy B. , Motyka T. , Zidan R. , Paskevicius M. , Buckley C. E.
Published: June 2014

An economic assessment is performed on NaMgH2F and magnesium-based metal hydrides as heat storage materials for concentrating solar thermal power.
A “clicked” porphyrin cage with high binding affinity towards fullerenes
Authors: Zhang Jianhong , Zheng Xiaoyan , Jiang Runsheng , Yu Yanwen , Li Yongjun , Liu Huibiao , Li Qikai , Shuai Zhigang , Li Yuliang
Published: June 2014

A cage-structured receptor synthesized via a facile “click” approach is easy to synthesize and modify and shows high affinity for fullerenes.
Monte-Carlo simulations of PAMAM dendrimer–DNA interactions
Authors: Yu Shi , Larson Ronald G.
Published: May 2014

DNA–PAMAM dendrimer complexes with structures similar to those in a nucleosome can form at low salt concentration, but have two different handedness when most dendrimer surface amine groups are nonacetylated.
A facile, single-step synthesis of flowery shaped, pure/lithium-doped 3D iron oxides
Authors: Barik Rasmita , Pandey Brajesh , Anand Shashi , Mohapatra Mamata
Published: June 2014

The shape-dependent surface properties of iron oxides are being paid increasing attention for their many advanced and synergistic applications.
Acetylene oligomerization on the surface of TiO2: a step forward in the in situ synthesis of nanostructured carbonaceous structures on the surface of photoactive oxides
Authors: Jain Sagar Motilal , Biedrzycki Jakub Jan , Maurino Valter , Zecchina Adriano , Mino Lorenzo , Spoto Giuseppe
Published: June 2014

In situ acetylene oligomerization allows synthesis of polycyclic condensed hydrocarbons in close contact with the TiO2 surface. These products represent intermediate steps in the production of photoactive graphene-like layers on TiO2.
Highly activated K-doped iron carbide nanocatalysts designed by computational simulation for Fischer–Tropsch synthesis
Authors: Park Ji Chan , Yeo Sang Chul , Chun Dong Hyun , Lim Jung Tae , Yang Jung-Il , Lee Ho-Tae , Hong Sungjun , Lee Hyuck Mo , Kim Chul Sung , Jung Heon
Published: June 2014

Highly activated K-doped Hägg-carbide/charcoal nanocatalyst at K/Fe = 0.075 showed the highest FTY value, the best hydrocarbon yield, and a good gasoline selectivity for the high-temperature Fischer–Tropsch reaction.
Identification and Multiplicity of Double Vowels in Cochlear Implant Users
Authors: Kwon Bomjun J. , Perry Trevor T.
Published: May 2014

Purpose

The present study examined cochlear implant (CI) users' perception of vowels presented concurrently (i.e.,
double vowels
) to further our understanding of auditory grouping in electric hearing.

Method

Identification of double vowels and single vowels was measured with 10 CI subjects. Fundamental frequencies (F0s) of vowels were either 100 + 100 Hz or 100 + 300 Hz. Vowels were presented either synchronously or with a time delay. In “Double” sessions, subjects were given only double vowels. In “Double + Single” sessions, while double and single vowels were presented, subjects reported the number and identity of the vowel(s). In addition to clinical settings, stimuli were delivered via an experimental method that interleaved pulse streams of two vowels.

Results

Although the time delay between vowels had a large effect on identification, the effect of change in fundamental frequency (ΔF0) was modest. Enumeration was poor in general, and identification of synchronous vowels was above chance in only the Double sessions with a priori knowledge about presentation. Interleaved presentation of vowel streams provided no benefit for identification and a marginal benefit for enumeration.

Conclusions

The results demonstrate the importance of episodic context for CI users. Unreliable perception of multiplicity observed in the present results suggests that auditory grouping in CIs may be driven by a schema-based process.
Impact of buffer sizing on energy efficiency and performance
Authors: Ai Tingting , Wijeratne Vindya , Wahid Amna Abdul
Published: June 2014

Internet router buffers are commonly made very large with the aim of minimising losses and maximising link utilisation, supported by the ever‐decreasing cost of memory. However, large packet queues not only increase the energy consumption, but can also adversely affect network performance which has recently been attracting attention under ‘bufferbloat’. This study compares the buffer‐related energy consumption of two models, that is, ‘large‐buffer with on–off server’ and ‘small‐buffer with always‐on server’ in the presence of multiplexed on–off traffic and FTP traffic; and demonstrates that the latter model is more energy efficient. Further analysis is then carried out on the ‘small‐buffer model with always‐on server’ for the evaluation of its performance against different levels of energy consumption. Relationships among energy, delay, throughput and loss are studied in a range of scenarios, quantifying the variations in performance metrics in relation to energy consumption. In general, lower buffer sizes which reduce the energy consumption were found to improve delay, but sacrifice throughput by 5–8% at high load. Based on a broad set of results, this study provides guidelines for sizing router buffers in realistic networks which would lead to optimal trade‐offs between energy consumption and quality of service.
High‐voltage boost quasi‐Z‐source isolated DC/DC converter
Authors: Siwakoti Yam P. , Blaabjerg Frede , Loh Poh Chiang , Town Graham E.
Published: June 2014

A high‐voltage gain two‐switch quasi‐Z‐source isolated DC/DC converter has been presented in this study. It consists of a quasi‐Z‐source network at its input, a push–pull square‐wave inverter at its middle, and a voltage‐doubler rectifier at its output. When coordinated appropriately, the new converter uses less switches, a smaller common duty cycle and less turns for the transformer when compared with existing topologies. Its size and weight are therefore smaller, whereas its efficiency is higher. It is therefore well‐suited for applications, where a wide range of voltage gain is required like renewable energy systems, DC power supplies found in telecom, aerospace and electric vehicles. To demonstrate the performance of the proposed converter, a 400 V, 500 W prototype has been implemented in the laboratory. Efficiency of the prototype measured is found to vary from 89.0 to 97.4% when its input voltage changes from 44 to 82 V at full load.
Canonical transformations for hyperkahler structures and hyperhamiltonian dynamics
Authors: Gaeta G. , Rodríguez M. A.
Published: May 2014

We discuss generalizations of the well known concept of canonical transformations for symplectic structures to the case of hyperkahler structures. Different characterizations, which are equivalent in the symplectic case, give rise to non-equivalent notions in the hyperkahler framework; we will thus distinguish between hyperkahler and canonical transformations. We also discuss the properties of hyperhamiltonian dynamics in this respect.
Negative differential resistance and resistance switching behaviors in BaTiO3 thin films
Authors: Yang G. , Jia C. H. , Chen Y. H. , Chen X. , Zhang W. F.
Published: May 2014

The polycrystalline BaTiO3 (BTO) thin films were grown on F-doped SnO2 substrates by pulsed laser deposition. The devices show a rectification at a small voltage, while bipolar resistive switching (RS) and negative differential resistance (NDR) appear at a large voltage. Furthermore, RS remains and NDR disappears when no positive bias is applied, while both RS and NDR behaviors improve when increasing the positive bias. The electrons trapped/detrapped by interface states at Au/BTO interface are proposed to understand the above behaviors.
Nuclear and in-source laser spectroscopy with the ISAC yield station
Authors: Kunz Peter , Andreoiu Corina , Bricault Pierre , Dombsky Marik , Lassen Jens , Teigelhöfer Andrea , Heggen Henning , Wong Fiona
Published: May 2014

A new decay station has been built for the ISAC facility at TRIUMF for the rapid and reliable characterization of radioactive ion beam (RIB) compositions and intensities with the capability of simultaneously collecting α, β, and γ decay data from RIB with intensities between a few and ≈1011 ions per second. It features user-friendly control, data acquisition, and analysis software. The analysis of individual decay time structures allows the unambiguous assignment of α and γ lines even with substantial isobaric contamination present. The capability for accurate half-life measurements is demonstrated with the example of 46K. The coupling of the yield station to the laser ion source, TRILIS, allows the correlation of radiometric data with automated laser frequency scans. First results of in-source laser spectroscopy measurements on astatine are discussed.
Hydration dynamics in water clusters via quantum molecular dynamics simulations
Authors: Turi László
Published: May 2014

We have investigated the hydration dynamics in size selected water clusters with n = 66, 104, 200, 500, and 1000 water molecules using molecular dynamics simulations. To study the most fundamental aspects of relaxation phenomena in clusters, we choose one of the simplest, still realistic, quantum mechanically treated test solute, an excess electron. The project focuses on the time evolution of the clusters following two processes, electron attachment to neutral equilibrated water clusters and electron detachment from an equilibrated water cluster anion. The relaxation dynamics is significantly different in the two processes, most notably restoring the equilibrium final state is less effective after electron attachment. Nevertheless, in both scenarios only minor cluster size dependence is observed. Significantly different relaxation patterns characterize electron detachment for interior and surface state clusters, interior state clusters relaxing significantly faster. This observation may indicate a potential way to distinguish surface state and interior state water cluster anion isomers experimentally. A comparison of equilibrium and non-equilibrium trajectories suggests that linear response theory breaks down for electron attachment at 200 K, but the results converge to reasonable agreement at higher temperatures. Relaxation following electron detachment clearly belongs to the linear regime. Cluster relaxation was also investigated using two different computational models, one preferring cavity type interior states for the excess electron in bulk water, while the other simulating non-cavity structure. While the cavity model predicts appearance of several different hydrated electron isomers in agreement with experiment, the non-cavity model locates only cluster anions with interior excess electron distribution. The present simulations show that surface isomers computed with the cavity predicting potential show similar dynamical behavior to the interior clusters of the non-cavity type model. Relaxation associated with cavity collapse presents, however, unique dynamical signatures.
Differential and integral cross sections for the rotationally inelastic scattering of methyl radicals with H2 and D2
Authors: Tkáč Ondřej , Ma Qianli , Rusher Cassandra A. , Greaves Stuart J. , Orr-Ewing Andrew J. , Dagdigian Paul J.
Published: May 2014

Comparisons are presented of experimental and theoretical studies of the rotationally inelastic scattering of CD3 radicals with H2 and D2 collision partners at respective collision energies of 680 ± 75 and 640 ± 60 cm−1. Close-coupling quantum-mechanical calculations performed using a newly constructed ab initio potential energy surface (PES) provide initial-to-final CD3 rotational level (n, k → n′, k′) integral and differential cross sections (ICSs and DCSs). The DCSs are compared with crossed molecular beam and velocity map imaging measurements of angular scattering distributions, which serve as a critical test of the accuracy of the new PES. In general, there is very good agreement between the experimental measurements and the calculations. The DCSs for CD3 scattering from both H2 and D2 peak in the forward hemisphere for n′ = 2–4 and shift more to sideways and backward scattering for n′ = 5. For n′ = 6–8, the DCSs are dominated by backward scattering. DCSs for a particular CD3 n → n′ transition have a similar angular dependence with either D2 or H2 as collision partner. Any differences between DCSs or ICSs can be attributed to mass effects because the PES is unchanged for CD3−H2 and CD3–D2 collisions. Further comparisons are drawn between the CD3–D2 scattering and results for CD3–He presented in our recent paper [O. Tkáč, A. G. Sage, S. J. Greaves, A. J. Orr-Ewing, P. J. Dagdigian, Q. Ma, and M. H. Alexander, Chem. Sci. 4, 4199 (2013)]. These systems have the same reduced mass, but are governed by different PESs.
Hypervalence in monoxides and dioxides of superalkali clusters
Authors: Cochran Elizabeth , Meloni Giovanni
Published: May 2014

F2Li3, a superalkali cluster, is characterized as having a lower adiabatic ionization energy than its elemental alkali counterpart and, coupled with the presence of complex molecular orbitals, suggests promise for novel bonding possibilities. CBS-QB3 composite method was used to study three distinct cluster isomers, as well as their cationic (+1) and anionic (−1) species, to identify energetic trends and observe geometric changes. Oxides were then generated from these clusters, of which three distinct monoxides and nine dioxides were obtained upon structure optimization. Identical calculations were performed for the oxide species and their charged counterparts. Some of the most stable oxides produced appear to possess hypervalent lithium and oxygen atoms, forming unique structures with exceptional stability.
Plasma oscillations in a 6-kW magnetically shielded Hall thruster
Authors: Jorns Benjamin A. , Hofer Richard R.
Published: May 2014

Plasma oscillations from 0–100 kHz in a 6-kW magnetically shielded Hall thruster are experimentally characterized with a high-speed, optical camera. Two modes are identified at 7–12 kHz and 70–90 kHz. The low frequency mode is found to be azimuthally uniform across the thruster face, while the high frequency oscillation is peaked close to the centerline-mounted cathode with an m = 1 azimuthal dependence. An analysis of these results in the context of wave-based theory suggests that the low frequency wave is the breathing mode oscillation, while the higher frequency mode is gradient-driven. The effect of these oscillations on thruster operation is examined through an analysis of thruster discharge current and a comparison with published observations from an unshielded variant of the thruster. Most notably, it is found that although the oscillation spectra of the two thrusters are different, they exhibit nearly identical steady-state behavior.
Ferroelectric phase transition effect of doping trifluoroethylene monomer in poly(vinylidene fluoride)
Authors: Li Dan , Xiong Jinwen , Guo Yuqi , Li Gao
Published: May 2014

We present the potential energy surfaces of molecular chains of poly(vinylidene-fluoride) (PVDF) and its copolymer with trifluoroethylene P(VDF-TrFE) determined by ab initio calculations. Based on the activation energy, we estimate a Curie temperature for pure PVDF of about 183 °C, which is slightly higher than its melt temperature of 170 °C. The Curie temperature decreases due to introduction of TrFE monomers to PVDF, and the origin of the ferroelectric-paraelectric phase transition of P(VDF-TrFE) is a conformational change between trans and gauche in the VDF segment. No conformational change in the position of TrFE monomers is observed during the phase transition of P(VDF-TrFE), and the gauche conformation is introduced in the all-trans molecule by the TrFE monomers.
Complementary study of molecular dynamics and domain sizes in heterogenous nanocomposites PBT/DA-C60 and PBT/TCNEO-C60
Authors: Woźniak-Braszak A. , Baranowski M. , Jurga K. , Jurga J. , Brycki B. , Mikuli E. , Hołderna-Natkaniec K.
Published: May 2014

A comprehensive study of molecular dynamics and structure in new heterogenous nanocomposites based on poly(butylene terephthalate) and nanoparticles C60 modified by n-decylamine or tetracyanoethylene oxide has been performed. The domain structure of new nanocomposites has been investigated by Fourier transform infrared spectroscopy, wide-angle X-ray scattering, and differential scanning calorimetry techniques. Solid-state 1H NMR techniques were used to study molecular dynamics and domain sizes in new nanocomposites. Information about the electronic properties of these nanocomposites was obtained by means of electron paramagnetic resonance method. It was shown that the structure and molecular dynamics of new nanocomposites were strongly dependent on the properties and concentration of fullerene derivates.
Analysis of high-temperature thermoelectric properties of p-type CoSb3 within a two-valence-band and two-conduction-band model
Authors: Kajikawa Y.
Published: May 2014

Experimental data on the thermoelectric properties of p-type CoSb3 reported by Caillat et al. [J. Appl. Phys. 80, 4442 (1996)] have been analyzed, assuming not only a pair of the first valence (v1) and the first conduction (c1) bands but also the second valence (v2) and the second conduction (c2) bands. By taking into account the excitation of carriers into the v2 and the c2 bands, the behavior of the Hall coefficient as well as that of the Seebeck coefficient at high temperatures is well explained. By taking into account the nonparabolicity of the v1 band, the temperature dependence of mobility is well explained with assuming scattering due to acoustic phonons, nonpolar and polar optical phonons, and ionized impurities. Furthermore, various material parameters of CoSb3, such as the band-gap energy, effective masses, and deformation potentials, have been deduced from fitting the calculation to the experimental data on the temperature dependences of the Hall coefficient, the mobility, and the Seebeck coefficient. Among them, the band-gap energy and the effective mass of the v1 band have been corrected from the original values estimated by Caillat et al. In addition, it is shown that the experimental data on the hole-concentration dependences of both the room-temperature Seebeck coefficient and the cyclotron mass are well reproduced by the theoretical calculation using the deduced values for the nonparabolic v1 band.
Dynamic damage nucleation and evolution in multiphase materials
Authors: Fensin S. J. , Escobedo J. P. , Gray G. T. , Patterson B. M. , Trujillo C. P. , Cerreta E. K.
Published: May 2014

For ductile metals, dynamic fracture occurs through void nucleation, growth, and coalescence. Previous experimental works in high purity metals have shown that microstructural features such as grain boundaries, inclusions, vacancies, and heterogeneities can act as initial void nucleation sites. However, for materials of engineering significance, those with, second phase particles it is less clear what the role of a soft second phase will be on damage nucleation and evolution. To approach this problem in a systematic manner, two materials have been investigated: high purity copper and copper with 1% lead. These materials have been shock loaded at ∼1.5 GPa and soft recovered. In-situ free surface velocity information and post mortem metallography reveals the presence of a high number of small voids in CuPb in comparison to a lower number of large voids in Cu. This suggests that damage evolution is nucleation dominated in the CuPb and growth dominated in the pure Cu.
Simulation-based design of a strained graphene field effect transistor incorporating the pseudo magnetic field effect
Authors: Souma Satofumi , Ueyama Masayuki , Ogawa Matsuto
Published: May 2014

We present a numerical study on the performance of strained graphene-based field-effect transistors. A local strain less than 10% is applied over a central channel region of the graphene to induce the shift of the Dirac point in the channel region along the transverse momentum direction. The left and the right unstrained graphene regions are doped to be either n-type or p-type. By using the atomistic tight-binding model and a Green's function method, we predict that the gate voltage applied to the central strained graphene region can switch the drain current on and off with an on/off ratio of more than six orders of magnitude at room temperature. This is in spite of the absence of a bandgap in the strained channel region. Steeper subthreshold slopes below 60 mV/decade are also predicted at room temperature because of a mechanism similar to the band-to-band tunneling field-effect transistors.
Experimental evidence of the increased transport due to the wall bounded magnetic drift in low temperature plasma
Authors: Gaboriau F. , Baude R. , Hagelaar G. J. M.
Published: May 2014

This paper presents experimental results on plasma transport across the magnetic field (B) in magnetized low-temperature plasma sources. Due to the presence of chamber walls, this transport can be complex even in a non-turbulent regime. In particular, in configurations without cylindrical symmetry, the magnetic drifts tend to be bounded by the chamber walls, thereby inducing plasma asymmetry and reducing magnetic confinement. In this work, we measure electron and ion current densities at metal chamber walls bounding a rectangular magnetic filter and demonstrate that these current densities are asymmetrically nonuniform. We also provide an experimental confirmation of model predictions of increased cross-field electron transport in such filter configuration, scaling as 1/B rather than the classical 1/B2 scaling.
Observation of early shell-dopant mix in OMEGA direct-drive implosions and comparisons with radiation-hydrodynamic simulations
Authors: Baumgaertel J. A. , Bradley P. A. , Hsu S. C. , Cobble J. A. , Hakel P. , Tregillis I. L. , Krasheninnikova N. S. , Murphy T. J. , Schmitt M. J. , Shah R. C. , Obrey K. D. , Batha S. , Johns H. , Joshi T. , Mayes D. , Mancini R. C. , Nagayama T.
Published: May 2014

Temporally, spatially, and spectrally resolved x-ray image data from direct-drive implosions on OMEGA were interpreted with the aid of radiation-hydrodynamic simulations. Neither clean calculations nor those using a turbulent mix model can explain fully the observed migration of shell-dopant material (titanium) into the core. Shell-dopant migration was observed via time-dependent, spatially integrated spectra, and spatially and spectrally resolved x-ray images of capsule implosions and resultant dopant emissions. The titanium emission was centrally peaked in narrowband x-ray images. In post-processed clean simulations, the peak titanium emission forms in a ring in self-emission images as the capsule implodes. Post-processed simulations with mix reproduce trends in time-dependent, spatially integrated spectra, as well having centrally peaked Ti emission in synthetic multiple monochromatic imager. However, mix simulations still do not transport Ti to the core as is observed in the experiment. This suggests that phenomena in addition to the turbulent mix must be responsible for the transport of Ti. Simple diffusion estimates are unable to explain the early Ti mix into the core. Mechanisms suggested for further study are capsule surface roughness, illumination non-uniformity, and shock entrainment.
Thermal cycling breaks down asteroid boulders
Authors: Day Charles
Published: May 2014

A process that occurs in Earth’s deserts could also be at work on asteroids.
Pulsed-power machine studies weapons, simulates stars
Authors: Feder Toni
Published: May 2014

The research that weapons scientists are allowed to talk about is key to attracting and retaining them at the labs.
Synthesis and Structural Characterization of a Series of Group 11 2,2-Dialkyl-1,3-dicyclohexylguanidinate Complexes
Authors: Adas Sonya K. , Ocana Jesus A. , Bunge Scott D.
Published: June 2014

The addition of either lithium dimethylamide or lithium diethylamide to a tetrahydrofuran (THF) solution of 1,3-dicyclohexylcarbodiimide yielded THF adducts of lithium 2,2-dimethyl-1,3-dicyclohexylguandidinate (1) and lithium 2,2-diethyl-1,3-dicyclohexylguandidinate (2), respectively. One equivalent of either 1 or 2 was subsequently reacted with one equivalent of Group 11 halide (CuCl, AgBr, and AuCl) to generate oligonuclear complexes with the general formula {M[CyNC(NR2)NCy]}n where M, R, and n are respectively Cu, CH3, 2 (3); Cu, CH2CH3, 2 (4); Ag, CH3, 3 (5); Ag, CH2CH3, 3 (6); Au, CH3, 2 (7); and Au, CH2CH3, 2 (8). Compounds 1–8 were characterized by single-crystal X-ray diffraction. The bulk powders for all complexes were found to be in agreement with the crystal structures based on elemental analyses, Fourier transform infrared spectroscopy, and 1H, 13C, and 7Li NMR studies. The unique structural aspects of this family of Group 11 complexes are highlighted.
Computing the moment polynomials of the zeta function
Authors: Rubinstein Michael , Yamagishi Shuntaro
Published: June 2014

We describe a method to accelerate the numerical computation of the coefficients of the polynomials

P
k

(
x
)

P_k(x)

that appear in the conjectured asymptotics of the

2
k

2k

-th moment of the Riemann zeta function. We carried out our method to compute the moment polynomials for

k
≤
13

k \leq 13

, and used these to experimentally test conjectures for the moments up to height

10
8

10^8

.