bluuebunny/crossref_metadata_2025 huggingface dataset:
Respiratory syncytial virus prophylaxis in children with cardiac disease: a retrospective single-centre study
Authors: Butt Michelle , Symington Amanda , Janes Marianne , Steele Susan , Elliott LouAnn , Chant-Gambacort Catherine , Mondal Tapas , Paes Bosco
Published: April 2013

Objectives

To examine the characteristics of congenital heart disease patients hospitalised with respiratory syncytial virus infection after prophylaxis and determine the associated comorbidities and the incidence of breakthrough respiratory syncytial virus infections.

Study design

This is a retrospective, single-centre study that was conducted over a period of 7 years. Respiratory syncytial virus infection was identified by classification codes and confirmed by virological tests. Data on baseline demographics, cardiac anomalies, other underlying disease, criteria for hospitalisation, type of respiratory illness and management, complications, and palivizumab prophylaxis were analysed by standard descriptive methods and comparative statistics.

Results

A total of 30 patients were enrolled. The majority were ≤2 years (n = 24). The mean admission age was 15.1 months (standard deviation = 18.3). In all, 90% were acyanotic, 40% had haemodynamically significant disease, and 60% had ≥1 underlying medical illness. Patients were admitted with: respiratory distress (86.7%), hypoxaemia (66.7%), fever (60%), inability to maintain oral intake (36.7%), and apnoea (16.7%). More than 50% required mechanical ventilation and intensive care with a median stay of 11 days (range: 1–43); the length of hospital stay for all children was 10 days (range: 1–65). Complications included: concurrent bacterial sepsis (20%), electrolyte abnormalities (16.7%), and worsening pulmonary hypertension (13.3%). Of 10 infants ≤2 years with haemodynamically significant heart disease, four had received prophylaxis. There was one death, which was attributed to respiratory syncytial virus infection.

Conclusions

Overall, 185 infants ≤2 years with haemodynamically significant cardiac disease received prophylaxis. In all, six qualifying infants missed immunisation and were hospitalised. Breakthrough respiratory syncytial virus infections occurred in 2.2%, demonstrating good efficacy of palivizumab in this population compared with the original, multi-centre, randomised trial.
Adaptation can help mitigation: an integrated approach to post-2012 climate policy
Authors: Bosello Francesco , Carraro Carlo , De Cian Enrica
Published: April 2013

This paper analyzes the optimal mix of adaptation and mitigation expenditures in a cost-effective setting, in which countries cooperate to achieve a long-term stabilization target (550 CO2-eq). It uses an Integrated Assessment Model (AD-WITCH) that describes the relationships between different adaptation modes (reactive and anticipatory), mitigation and capacity building to analyze the optimal portfolio of adaptation measures. Results show that the optimal intertemporal distribution of climate policy measures is characterized by early investments in mitigation followed by large adaptation expenditures a few decades later. Hence, the possibility of adapting does not justify postponing mitigation. Moreover, a climate change policy combining mitigation and adaptation is less costly than mitigation alone. In this sense mitigation and adaptation are shown to be strategic complements rather than mutually exclusive.
In Situ Thickness Assessment During Ion Milling of a Free-Standing Membrane Using Transmission Helium Ion Microscopy
Authors: Hall Adam R.
Published: April 2013

We describe a novel method for in situ measurement of the local thickness of a freely suspended solid-state membrane after thinning with a focused helium ion beam. The technique utilizes a custom stage for the helium ion microscope that allows the secondary electron detector used for normal imaging to collect information from ions transmitted through the sample. We find that relative brightness in the transmission image scales directly with the membrane thickness as determined by atomic force microscopy measurements.
Effects of Ghrelin on the Structural Complexity of Exocrine Pancreas Tissue Architecture
Authors: Pantic Igor , Nesic Dejan , Stevanovic Darko , Starcevic Vesna , Pantic Senka , Trajkovic Vladimir
Published: April 2013

Recent studies have shown that ghrelin increases pancreatic exocrine secretion. However, the potential effects of ghrelin on the morphology of exocrine pancreas (EP) remain unknown. In this work, using fractal analysis, we demonstrate that centrally administered ghrelin increases structural complexity and tissue disorder in rat EP. The study was carried out on a total of 40 male Wistar rats divided into four groups (n = 10): ghrelin-treated animals (average age, 1.5 months), ghrelin-treated animals (8.5 months), and controls (1.5 and 8.5 months). The pancreas tissue sections were stained with hematoxylin/eosin and visualized by light microscopy. For each animal, the average values of tissue fractal dimension, lacunarity, as well as parameters of co-occurrence matrix texture, were determined using tissue digital micrographs. The results indicate that ghrelin administration increases EP fractal dimension and textural entropy, and decreases lacunarity, regardless of the age. To our knowledge, this is the first study to investigate the effects of ghrelin on the morphological properties of pancreatic tissue, and also the first to apply fractal and textural analysis methods in quantification of EP tissue architecture.
THINGS FALL APART: J. G. A. POCOCK, HANNAH ARENDT, AND THE POLITICS OF TIME
Authors: SIEGELBERG MIRA L.
Published: April 2013

This article reconstructs J. G. A. Pocock's debt to Hannah Arendt's political philosophy inThe Machiavellian Momentand argues that her presentation of classical politics inThe Human Conditionand her account of the secular nature of American foundation inOn Revolutionwere important sources for Pocock's analysis of American liberal insecurity. However, a contextualization ofThe Machiavellian Momentwithin Pocock's immediate intellectual and professional milieu indicates that he placed himself in critical relation to Arendt's civic republican theory and located her philosophy of history in the same spectrum as the American political tradition he sought to historicize. While they did share a similar perspective on the ethical and political value of locating oneself within a long historicaldurée, their different conceptions of the problem of continuity for secular political structures provides a crucial context for their disparate responses to the discourse of political crisis in the United States in the late 1960s and the 1970s.
THE EDGE OF ENLIGHTENMENT: IRELAND AND SCOTLAND IN THE EIGHTEENTH CENTURY
Authors: MCBRIDE IAN
Published: April 2013

Was there an Enlightenment in Ireland? Was there even a distinctivelyIrish Enlightenment? Few scholars have bothered even to pose this question. Historians of Ireland during the era of Protestant Ascendancy have tended to be all-rounders rather than specialists; their traditional preoccupations are constitutional clashes between London and Dublin, religious conflict, agrarian unrest and popular politicization. With few exceptions there has been no tradition of intellectual history, and little interest in the methodological debates associated with the rise of the “Cambridge school”. Most advances in our understanding of Irish philosophical writing have consequently originated outside Ireland's history departments. One by-product of recent work on the Scottish Enlightenment has been the rediscovery of the “Molesworth Circle” by two scholars engaged in a painstaking reconstruction of Francis Hutcheson's early career in Dublin. At the other end of the century, meanwhile, some of the most exciting and ambitious attempts to conceptualize the republicanism of the United Irishmen have come from a leading historian of revolutionary France, James Livesey. His previous research on the “commercial republicanism” of Montesquieu, Adam Ferguson and Brissot has suggested a new framework for understanding Irish radicals such as Wolfe Tone, Thomas Addis Emmet and, in particular, Arthur O'Connor.
“IT'S NOT WHAT YOU KNOW . . .”: ENCOUNTERS, GO-BETWEENS AND THE GEOGRAPHY OF KNOWLEDGE
Authors: OGBORN MILES
Published: April 2013

Sometime in the 1760s, a Constantinople-born, French-educated Muslim arrived at the port of Balassor in north-east India. Known variously as Mustapha or Monsieur Raymond, he had, he later wrote, “with a mediocre dictionary and a bad grammar”, and by conversing with the ship's captain en route from Bombay, “learned enough of English . . . as I might delight in Bolingbroke's Philosophical works”. This student of contemporary intellectual history soon put his knowledge to work, securing a position translating for Robert Clive, the conquering hero of the English East India Company's new imperial administration in India. Subsequently falling from favour, Mustapha crossed over to seek employment with the English company's French rivals, earning himself a spell in prison as a spy. He also travelled to Mecca, where he gained the honorific “Haji” but lost his fortune, his cabinet of curiosities and his collection of books and manuscripts. He then became the keeper of a zenana (to the Europeans, a harem or seraglio), and he entered the world of publishing. In 1789, in Calcutta, Mustapha had printed for himself a pamphlet-length diatribe on the iniquitous administration of the law in British Bengal entitled Some Idea of the Civil and Criminal Courts of Justice at Moorshoodabad. In the same year he was also involved, as the pseudonymous editor “Nota Manus”, in the publication of a three-volume English translation of a Persian work of Indian history—Ghulam Hussain Khan Tabatabai's Seir Mutaqherin, or View of Modern Times (written in 1781–2)—which dealt with the British conquest and administration of Bengal, and offered a stern critique of the new rulers who seemed to have “an aversion to the Society of Indians, and a disdain against conversing with them”. Finally, Mustapha (who called himself a “Semi-Englishman” who had the interests of his “adopted countrymen” at heart) claimed to have published in London a work of futurology entitled State of Europe in 1800. In his encounters with Europeans, his travels within and beyond India (although he never made it to England as he had planned), and his involvement in the production of historical and geographical knowledge, Mustapha was deeply interested in that which shaped his own fortunes: the relationships of knowledge and power between Europe and other parts of the world.
MODERNISMS ENDLESS: IRONIES OF THE AMERICAN MID-CENTURY
Authors: WICKBERG DANIEL
Published: April 2013

Mid-twentieth century American intellectual history is in the midst of a boom; a younger generation of historians, now half a century distant from the era, and less inclined than their immediate forerunners to be committed to a vision of the 1960s as a critical turning point in modern culture, is reshaping what has been an underdeveloped field. Recent studies of thinkers such as C. Wright Mills, Ayn Rand, Lionel Trilling, and Whitaker Chambers, and subjects such as postcapitalist social thought and pollsters in mass society, to name a few, have regenerated interest in an arena that had once been dominated by studies of the New York Intellectuals and Richard Pells's useful summaries and evaluations of prominent intellectuals of the 1930s, 1940s and 1950s. The newer intellectual history of this period appears to be premised on several ideas: that the so-called “liberal consensus” of the era was an ideological product of liberalism itself, rather than an adequate description of the contours of thought; that thinking in terms of clear and sharp distinctions between right and left doesn't help us understand the ways in which ideas, sensibilities, and intellectual commitments were configured at mid-century; that there is a great deal more continuity in social, political, and cultural thought than an image of the 1960s as cultural watershed would allow; and that the mid-century decades are, in the most profound sense, the first years of our own time, with all the characteristic epistemic, moral, and critical problems that have characterized thought and culture in the world in which contemporary Americans live. What the Progressive Era was for mid-century historians and intellectuals such as Richard Hofstadter and Henry May, the mid-century, and particularly the early Cold War era of the late 1940s and 1950s, is, for the historian of today, the root of the destabilizing conundrums of modernity, particularly the puzzle of the role of critical intellect in a mass-mediated environment of socialized knowledge, feeling, and being.
The proteasome cap RPT5/Rpt5p subunit prevents aggregation of unfolded ricin A chain
Authors: Pietroni Paola , Vasisht Nishi , Cook Jonathan P. , Roberts David M. , Lord J. Michael , Hartmann-Petersen Rasmus , Roberts Lynne M. , Spooner Robert A.
Published: April 2013

The plant cytotoxin ricin enters mammalian cells by receptor-mediated endocytosis, undergoing retrograde transport to the ER (endoplasmic reticulum) where its catalytic A chain (RTA) is reductively separated from the holotoxin to enter the cytosol and inactivate ribosomes. The currently accepted model is that the bulk of ER-dislocated RTA is degraded by proteasomes. We show in the present study that the proteasome has a more complex role in ricin intoxication than previously recognized, that the previously reported increase in sensitivity of mammalian cells to ricin in the presence of proteasome inhibitors simply reflects toxicity of the inhibitors themselves, and that RTA is a very poor substrate for proteasomal degradation. Denatured RTA and casein compete for a binding site on the regulatory particle of the 26S proteasome, but their fates differ. Casein is degraded, but the mammalian 26S proteasome AAA (ATPase associated with various cellular activities)-ATPase subunit RPT5 acts as a chaperone that prevents aggregation of denatured RTA and stimulates recovery of catalytic RTA activity in vitro. Furthermore, in vivo, the ATPase activity of Rpt5p is required for maximal toxicity of RTA dislocated from the Saccharomyces cerevisiae ER. The results of the present study implicate RPT5/Rpt5p in the triage of substrates in which either activation (folding) or inactivation (degradation) pathways may be initiated.
A Systems Approach to Training Potential Communication Partners of People With Aphasia
Authors: Simmons-Mackie Nina
Published: April 2013

Experts have recommended communication partner training as an effective method of improving skills of communication partners and supporting communication of people with aphasia (Simmons-Mackie, Raymer, Armstrong, Holland & Cherney, 2010). Such training involves learning about aphasia, types of communication supports (e.g., low-tech, high-tech), and strategies for facilitating communication. Although much of this literature addresses the training of regular, familiar partners, there is evidence that “potential” communication partners can be trained to support communication with unfamiliar people with aphasia (e.g., training health care providers to communicate with patients with aphasia). However, direct training sessions with potential partners does not ensure that partners will implement these support practices in day-to-day activities in organizations such as those associated with health care, government, or business. Rather, experts must take a systems approach if communication support is to be supported by and included in organizational policy and practice. In this article, I describe a systems approach to implementing evidence-based practices in organizations.
Enhanced Milieu Teaching: Incorporating AAC Into Naturalistic Teaching With Young Children and Their Partners
Authors: Kaiser Ann , Wright Courtney
Published: April 2013

Enhanced Milieu Teaching (EMT) is an evidence-based naturalistic intervention strategy that teaches functional communication and language skills in everyday interactions with partners. In this manuscript, we describe the key communication support strategies used in EMT and how individuals can use these strategies with augmentative and alternative communication systems. We also present strategies for teaching partners to use EMT with AAC in interactions with young children.
Derzeitige Versorgungssituation der Bursitis olecrani und
praepatellaris in Österreich
Authors: Baumbach S. , Michel M. , Wyen H. , Buschmann C. , Kdolsky R. , Kanz K.-G.
Published: April 2013

Hintergrund: In der Literatur existiert kein international
einheitliches Behandlungskonzept für die Diagnose und Therapie der
septischen (SB) und nicht septischen Bursitis (NSB) olecrani und
praepatellaris. Das Ziel dieser Arbeit war daher die systematische Erhebung
des in Österreich vorherrschenden Behandlungsregimes. Material und
Methoden: Die derzeitige Behandlungssituation der SB und NSB in
Österreich wurde mittels einer Online-Umfrage unter den Mitgliedern der
Österreichischen Gesellschaft für Orthopädie und orthopädische Chirurgie
(ÖGO) und der Österreichischen Gesellschaft für Unfallchirurgie (ÖGU)
erhoben. Der Fragebogen umfasste Fragen zur Demografie, Standarddiagnostik,
Differenzierung und Therapie der SB und NSB. Ergebnisse: Die
Rücklaufrate betrug 46 % (ÖGU)/12 % (ÖGO). Die primäre Differenzierung
zwischen SB und NSB basierte vorrangig auf der Anamnese, Klinik (ÖGU:
100 %/ÖGO: 84 %) sowie laborchemischen Ergebnissen (ÖGU: 82 %/ÖGO: 77 %).
64/36 % der befragten ÖGO/ÖGU-Mitglieder gaben an, eine Bursapunktion
durchzuführen. Bei der SB/NSB präferierten die Unfallchirurgen einen primär
chirurgischen Behandlungsansatz (95/55 %), während Orthopäden eher einen
konservativen Therapieansatz (28/27 %) favorisierten.
Schlussfolgerungen: Es bestanden signifikante Unterschiede in der
Behandlung der SB und NSB zwischen den Mitgliedern der ÖGO und ÖGU, wobei
Letztere eine chirurgische Therapie bevorzugten. Im Gegensatz dazu tendiert
die englischsprachige Literatur zu einem primär konservativen Vorgehen für
beide Entitäten. Weitere qualitativ hochwertige Studien werden benötigt, um
einen evidenzbasierten Therapieansatz zu entwickeln.
Verkürzte Schockraumzeiten bei Traumapatienten durch vor Ort
integrierte Computertomografie
Authors: Riepl C. , Junghanns A. , Gebhard F. , Kraus M.
Published: April 2013

Fragestellung: Zur Zertifizierung als überregionales Traumazentrum im
TraumaNetzwerkD (DGU) wurde ein neuer Schockraum (SR) mit integriertem CT
eingerichtet. Der alte SR befand sich räumlich vom CT getrennt. Ziel dieser
Arbeit war es, zu eruieren, ob sich die integrierte CT-Einheit auf die
Zeitintervalle der SR-Versorgung im Sinne einer Reduzierung auswirkt.
Methodik: Es wurde eine Analyse durchgeführt, bei der Daten des
alten SR (2005–2007) mit denen des neuen (2009) verglichen wurden.
Eingeschlossen wurden alle Traumapatienten, die an das Traumaregister der
DGU gemeldet wurden. Als statistisches Verfahren wurde der
Mann-Whitney-U-Test angewendet. Ergebnisse: Insgesamt wurden 457
Patienten erfasst. Das Intervall zwischen Aufnahme und CT-Scan betrug im
alten SR durchschnittlich 35 ± 27 min (4–240 min), im neuen 13 ± 10 min
(1–67 min) (p < 0,001). Ebenso reduzierte sich die SR-Gesamtzeit von
86 ± 42 min (10–240) im alten auf 61 ± 33 min (5–190; p < 0,001) im neuen
SR. Schlussfolgerung: Es zeigten sich signifikant kürzere
Versorgungszeiten im neuen SR. Diese scheinen insbesondere durch die vor Ort
integrierte CT-Einheit ermöglicht zu werden. So besteht die Möglichkeit,
Zeitabläufe im Rahmen der Frühphase nach Trauma zu reduzieren und Patienten
früher der weiteren Versorgung zuzuführen.
Klinische Erfahrungen mit dem Sourire Cage bei 113 Patienten mit
ventraler Spondylodese der Halswirbelsäule
Authors: Ottenhausen M. , Danne M. , Meier U.
Published: April 2013

Die ventrale Spondylodese ist ein Standardeingriff zur operativen Behandlung
von degenerativen Erkrankungen der Halswirbelsäule. Um die operative Fusion
zweier Wirbelkörper zu erreichen, werden auf dem Markt verschiedene
intervertebrodiskale Spacer zur Implantation angeboten. Das Ziel dieser
Studie ist es, den klinischen und implantatspezifischen Krankheitsverlauf
bei Patienten zu ermitteln, denen ein Sourire Cage implantiert wurde. Im
Zeitraum vom 01. 01. 2008 bis zum 26. 08. 2012 operierten wir 113 Patienten
aufgrund einer degenerativen Erkrankung der Halswirbelsäule mittels
ventraler Spondylodese und Sourire-Cage-Implantation in der
Neurochirurgischen Klinik im Unfallkrankenhaus Berlin. Bei allen Patienten
fanden Nachuntersuchungen im Rahmen der Qualitätskontrolle nach SGB V nach 6
Wochen, 6 Monaten und 1 Jahr statt. Zur Bewertung der klinischen Symptomatik
fand der von der Japanese Orthopedic Association eingeführte JOA-Score
Anwendung. Des Weiteren erfolgten Röntgenuntersuchungen. Im Rahmen einer
retrospektiven Studie untersuchten wir das Operationsergebnis sowie die
Sinterungs- und Dislokationsrate. Die Symptomatik der Patienten verbesserte
sich postoperativ zu 89 %. Die Verbesserung zeigte sich in den
Nachuntersuchungen konstant. Sinterung des Implantats zeigte sich bei 10 %
der Patienten. Eine Dislokation des Spacers ist bei keinem Patienten
aufgetreten. Die Studie zeigt, dass die ventrale Fusion mittels
Sourire-Cage-Implantation zu exzellenten und guten klinischen Ergebnissen
bei niedrigen Komplikationsraten führt.
Influence of the dissipation mechanism on collisionless magnetic reconnection in symmetric and asymmetric current layers
Authors: Aunai Nicolas , Hesse Michael , Black Carrie , Evans Rebekah , Kuznetsova Maria
Published: April 2013

Numerical studies implementing different versions of the collisionless Ohm's law have shown a reconnection rate insensitive to the nature of the non-ideal mechanism occurring at the X line, as soon as the Hall effect is operating. Consequently, the dissipation mechanism occurring in the vicinity of the reconnection site in collisionless systems is usually thought not to have a dynamical role beyond the violation of the frozen-in condition. The interpretation of recent studies has, however, led to the opposite conclusion that the electron scale dissipative processes play an important dynamical role in preventing an elongation of the electron layer from throttling the reconnection rate. This work re-visits this topic with a new approach. Instead of focusing on the extensively studied symmetric configuration, we aim to investigate whether the macroscopic properties of collisionless reconnection are affected by the dissipation physics in asymmetric configurations, for which the effect of the Hall physics is substantially modified. Because it includes all the physical scales a priori important for collisionless reconnection (Hall and ion kinetic physics) and also because it allows one to change the nature of the non-ideal electron scale physics, we use a (two dimensional) hybrid model. The effects of numerical, resistive, and hyper-resistive dissipation are studied. In a first part, we perform simulations of symmetric reconnection with different non-ideal electron physics. We show that the model captures the already known properties of collisionless reconnection. In a second part, we focus on an asymmetric configuration where the magnetic field strength and the density are both asymmetric. Our results show that contrary to symmetric reconnection, the asymmetric model evolution strongly depends on the nature of the mechanism which breaks the field line connectivity. The dissipation occurring at the X line plays an important role in preventing the electron current layer from elongating and forming plasmoids.
Reduced-order model based feedback control of the modified Hasegawa-Wakatani model
Authors: Goumiri I. R. , Rowley C. W. , Ma Z. , Gates D. A. , Krommes J. A. , Parker J. B.
Published: April 2013

In this work, the development of model-based feedback control that stabilizes an unstable equilibrium is obtained for the Modified Hasegawa-Wakatani (MHW) equations, a classic model in plasma turbulence. First, a balanced truncation (a model reduction technique that has proven successful in flow control design problems) is applied to obtain a low dimensional model of the linearized MHW equation. Then, a model-based feedback controller is designed for the reduced order model using linear quadratic regulators. Finally, a linear quadratic Gaussian controller which is more resistant to disturbances is deduced. The controller is applied on the non-reduced, nonlinear MHW equations to stabilize the equilibrium and suppress the transition to drift-wave induced turbulence.
Three dimensional complex plasma structures in a combined radio frequency and direct current discharge
Authors: Mitic S. , Klumov B. A. , Khrapak S. A. , Morfill G. E.
Published: April 2013

We report on the first detailed analysis of large three dimensional (3D) complex plasma structures in experiments performed in pure rf and combined rf+dc discharge modes. Inductively coupled plasma is generated by an rf coil wrapped around the vertically positioned cylindrical glass tube at a pressure of 0.3 mbar. In addition, dc plasma can be generated by applying voltage to the electrodes at the ends of the tube far from the rf coil. The injected monodisperse particles are levitated in the plasma below the coil. A scanning laser sheet and a high resolution camera are used to determine the 3D positions of about 105 particles. The observed bowl-shaped particle clouds reveal coexistence of various structures, including well-distinguished solid-like, less ordered liquid-like, and pronounced string-like phases. New criteria to identify string-like structures are proposed.
Non-modal analysis of the diocotron instability: Cylindrical geometry
Authors: Mikhailenko V. V. , June Lee Hae , Mikhailenko V. S. , Azarenkov N. A.
Published: April 2013

The temporal evolution of the linear diocotron instability of the cylindrical annular plasma column is investigated by employing the extension of the shearing modes methodology to the cylindrical geometry. It was obtained that the spatial time-dependent distortion of the electron density initial perturbations by shear flows leads to the non-modal evolution of the potential, which was referred to as the manifestation of the continuous spectrum. The evolution process leads toward the convergence to the phase-locking configuration of the mutually growing normal modes.
A new viewpoint on the ambipolar diffusion Schottky theory
Authors: Kurbatov P. F.
Published: April 2013

A modern modification of the Schottky theory is proposed. It enables overcoming some of the difficulties and contradictions of the old theory and extends its capabilities in the analysis of radial distributions of ionized species. This allows us to consider the distributions of positive column plasma in noble gas d.c. discharges within a proper universal framework. The radial distributions of plasma species are basically similar in their nature and are independent of the character and features of plasma reactions.
Ion-acoustic solitons in warm magnetoplasmas with super-thermal electrons
Authors: Choudhury B. , Goswami R. , Das G. C. , Bora M. P.
Published: April 2013

In this work, the phenomenon of formation of localised electrostatic waves (ESWs) or soliton is considered in a warm magnetoplasma with the possibility of non-thermal electron distribution. The parameter regime considered here is relevant in case of magnetospheric plasmas. We show that deviation from a usual relaxed Maxwellian distribution of the electron population has a significant bearing in the allowed parameter regime, where these ESWs can be found. We further consider the presence of more than one electron temperature, which is inspired by several space-based observations.
The effect of a dust size distribution on electrostatic sheaths in unmagnetized dusty plasmas
Authors: Benlemdjaldi D. , Tahraoui A. , Hugon R. , Bougdira J.
Published: April 2013

In this work, the structure of plasma sheaths in presence of dust particles with different sizes is investigated numerically in a multifluid framework, where the dust size distribution is modeled by Gauss' law. For this, we have established a 1D, stationary, unmagnetized, and weakly collisional electronegative dusty plasma sheath model. The electrons and negative ions are considered in a local thermodynamic equilibrium, therefore, described by a Boltzmann distribution. On the other hand, positive ions and dust grains are described by fluid equations. The charging process is described by the orbit motion limited model. It is shown that taking into account dust grains with different sizes reduces considerably the sheath thickness. The behavior of dust surface potential is not affected, but the dust charge number is reduced, as well as the electrostatic force. It results in a decrease of layered structure. The presence of negative ions makes the structure of the electrostatic potential more oscillatory. The other physical parameters are also analyzed and discussed.
Dynamic interaction potential and the scattering cross sections of the semiclassical plasma particles
Authors: Dzhumagulova K. N. , Shalenov E. O. , Gabdullina G. L.
Published: April 2013

The dynamic model of the charged particles interaction in non-ideal semiclassical plasma is presented. This model takes into account the quantum mechanical diffraction effect and the dynamic screening effect. On the basis of the dynamic interaction potential, the electron scattering cross sections are investigated. Comparison with the results obtained on the basis of other models and conclusions were made.
Spatiotemporal study of the local thermodynamic equilibrium deviations in high-intensity discharge lamps
Authors: Helali H. , Bchir T. , Araoud Z. , Charrada K.
Published: April 2013

The aim of this work is to study the local thermodynamic equilibrium (LTE) deviations in arc discharges plasma generated in high-intensity discharge lamps operating under an ac (50 Hz) power supply. To achieve this goal, we elaborate a two-temperature, two-dimensional, and time-depending model. We have found numerical results almost reproducing the experimental data, which allows us to validate this model. After validation, we have discussed different energy term effects on the LTE deviations.
Three-dimensional particle-in-cell modeling of terahertz gyrotrons with cylindrical and planar configurations of the interaction space
Authors: Zaslavsky V. Yu. , Ginzburg N. S. , Glyavin M. Yu. , Zheleznov I. V. , Zotova I. V.
Published: April 2013

We perform 3D particle-in-cell simulations of terahertz gyrotrons with two different configurations of the interaction space. For a gyrotron with conventional cylindrical configuration of the interaction cavity, we demonstrate reasonable agreement between simulations and experimental results, including output frequency, structure of the higher-order operating mode (TE17,4), output power, and ohmic losses. For a novel planar gyrotron scheme with transverse energy extraction, a possibility of further increasing the oversized factor with the single-mode operation regime retained is shown. Frequency detuning by mechanical variation of the gap between waveguide plates is also demonstrated.
Enhanced momentum delivery by electric force to ions due to collisions of ions with neutrals
Authors: Makrinich G. , Fruchtman A.
Published: April 2013

Ions in partially ionized argon, nitrogen, and helium gas discharges are accelerated across a magnetic field by an applied electric field, colliding with neutrals during the acceleration. The momentum delivered by the electric force to the ions, which is equal to the momentum carried by the mixed ion-neutral flow, is found by measuring the force exerted on a balance force meter by that flow exiting the discharge. The power deposited in the ions is calculated by measuring the ion flux and the accelerating voltage. The ratio of force over power is found for the three gases, while the gas flow rates and magnetic field intensities are varied over a wide range of values, resulting in a wide range of gas pressures and applied voltages. The measurements for the three different gases confirm our previous suggestion [G. Makrinich and A. Fruchtman, Appl. Phys. Lett. 95, 181504 (2009)] that the momentum delivered to the ions for a given power is enhanced by ion-neutral collisions during the acceleration and that this enhancement is proportional to the square root of the number of ion-neutral collisions.
On the toroidal current density flowing across a poloidal-magnetic-field null in an axisymmetric plasma
Authors: Rodrigues Paulo , Bizarro João P. S.
Published: April 2013

The axisymmetry condition and two of Maxwell's equations are used to show that, in general, there are no nested magnetic surfaces around a poloidal-magnetic-field null for a sufficiently small value of the toroidal current density flowing there. Hence, the toroidal current density at the axis of a magnetic configuration with extreme shear reversal cannot continuously approach zero unless nested surfaces are first broken or particular values are assigned to boundary conditions and other plasma parameters. The threshold of the toroidal current-density at which the topology changes is shown to be set by such parameters, and some examples of the predicted topology transition are presented using analytical solutions of the Grad-Shafranov equation.
The properties of photonic band gaps for three-dimensional plasma photonic crystals in a diamond structure
Authors: Zhang Hai-Feng , Liu Shao-Bin , Kong Xiang-Kun , Chen-Chen  , Bian Bo-Rui
Published: April 2013

In this paper, the properties of photonic band gaps (PBGs) for two types of three-dimensional plasma photonic crystals (PPCs) composed of isotropic dielectric and unmagnetized plasma with diamond lattices are theoretically investigated for electromagnetic waves based on a modified plane wave expansion method. The equations for type-1 structure are theoretically deduced, which depend on the diamond lattices realization (dielectric spheres immersed in plasma background). The influences of dielectric constant of dielectric, plasma collision frequency, filling factor, and plasma frequency on PBGs are investigated, respectively, and some corresponding physical explanations and the possible methods to realize the three-dimensional PPCs in experiments are also given. From the numerical results, it has been shown that not only the locations but also the gap/midgap ratios of the PBGs for two types of PPCs can be tuned by plasma frequency, filling factor, and the relative dielectric constant, respectively. However, the plasma collision frequency has no effect on the frequency ranges and gap/midgap ratios of the PBGs for two types of PPCs.
Relationship between the ion drag and electric forces in dense dust clouds
Authors: Yaroshenko V. V. , Khrapak S. A. , Morfill G. E.
Published: April 2013

It is shown that the relation between the ion drag and electric forces is strongly dependent on the dust number density in complex plasmas. The effect of the particle size and discharge parameters on the force balance is investigated. Examples are given for realistic complex plasma parameters and comparison with microgravity experiments is presented.
Higher order nonlinear equations for the dust-acoustic waves in a dusty plasma with two temperature-ions and nonextensive electrons
Authors: Emamuddin M. , Yasmin S. , Mamun A. A.
Published: April 2013

The nonlinear propagation of dust-acoustic waves in a dusty plasma whose constituents are negatively charged dust, Maxwellian ions with two distinct temperatures, and electrons following q-nonextensive distribution, is investigated by deriving a number of nonlinear equations, namely, the Korteweg-de-Vries (K-dV), the modified Korteweg-de-Vries (mK-dV), and the Gardner equations. The basic characteristics of the hump (positive potential) and dip (negative potential) shaped dust-acoustic (DA) Gardner solitons are found to exist beyond the K-dV limit. The effects of two temperature ions and electron nonextensivity on the basic features of DA K-dV, mK-dV, and Gardner solitons are also examined. It has been observed that the DA Gardner solitons exhibit negative (positive) solitons for qqc) (where qc is the critical value of the nonextensive parameter q). The implications of our results in understanding the localized nonlinear electrostatic perturbations existing in stellar polytropes, quark-gluon plasma, protoneutron stars, etc. (where ions with different temperatures and nonextensive electrons exist) are also briefly addressed.
Non-linear modulation of short wavelength compressional Alfvén eigenmodes
Authors: Fredrickson E. D. , Gorelenkov N. N. , Podesta M. , Bortolon A. , Crocker N. A. , Gerhardt S. P. , Bell R. E. , Diallo A. , LeBlanc B. , Levinton F. M. , Yuh H.
Published: April 2013

Most Alfvénic activity in the frequency range between toroidal Alfvén eigenmodes and roughly one half of the ion cyclotron frequency on National Spherical Torus eXperiment [Ono et al., Nucl. Fusion 40, 557 (2000)], that is, approximately 0.3 MHz up to ≈1.2 MHz, are modes propagating counter to the neutral beam ions. These have been modeled as Compressional and Global Alfvén Eigenmodes (CAE and GAE) and are excited through a Doppler-shifted cyclotron resonance with the beam ions. There is also a class of co-propagating modes at higher frequency than the counter-propagating CAE and GAE. These modes have been identified as CAE, and are seen mostly in the company of a low frequency, n = 1 kink-like mode. In this paper, we present measurements of the spectrum of these high frequency CAE (hfCAE) and their mode structure. We compare those measurements to a simple model of CAE and present a predator-prey type model of the curious non-linear coupling of the hfCAE and the low frequency kink-like mode.
Role of ion temperature on scrape-off layer plasma turbulence
Authors: Bisai N. , Kaw P. K.
Published: April 2013

Turbulence in Scrape-off layer (SOL) of tokamak plasma has been studied numerically using interchange modes with the help of electron continuity, quasineutrality, and ion energy equations. Electron temperature is assumed uniform. We have studied dynamics of seeded plasma blob and plasma turbulence to identify the role of ion temperature and its gradient. The ion temperature elongates the blob poloidally and reduces its radial velocity. Initial dipole nature of the plasma blob potential breaks and generates few more dipoles during its propagation in the SOL. Plasma turbulence simulation shows poloidally elongated density and ion temperature structures that are similar to the seeded blob simulation studies. Fluctuations of the density and ion temperature have been presented as function of scale lengths of the density and ion temperature. Reduction of the SOL width and increase of radial electric field have been measured in the presence of the ion temperature. Particle and energy transports have been also presented as the function of the density and ion temperature scale lengths.
The isotropic-to-nematic phase transition in hard helices: Theory and simulation
Authors: Frezza Elisa , Ferrarini Alberta , Kolli Hima Bindu , Giacometti Achille , Cinacchi Giorgio
Published: April 2013

We investigate the isotropic-to-nematic phase transition in systems of hard helical particles, using Onsager theory and Monte Carlo computer simulations. Motivation of this work resides in the ubiquity of the helical shape motif in many natural and synthetic polymers, as well as in the well known importance that the details of size and shape have in determining the phase behaviour and properties of (soft) condensed matter systems. We discuss the differences with the corresponding spherocylinder phase diagram and find that the helix parameters affect the phase behaviour and the existence of the nematic phase. We find that for high helicity Onsager theory significantly departs from numerical simulations even when a modified form of the Parsons-Lee rescaling is included to account for the non-convexity of particles.
Electromagnetic envelope solitary waves with transverse perturbation in a plasma
Authors: Borhanian J.
Published: April 2013

The system of fluid-Maxwell equations governing the two-dimensional dynamics of electromagnetic waves in a plasma is analyzed by means of multiple scale perturbation method. It is shown that the evolution of the amplitude of wave field is governed by a two-dimensional nonlinear Schrödinger equation. The stability of bright envelope solitons is studied using the variational method. It is found that the development of transverse periodic perturbations on bright solitons is faster for a plasma with near critical density. Dynamics of electromagnetic bright solitons is investigated in the long-wave approximation. Our model predicts the appearance of collapse of electromagnetic waves in plasmas and describes the collapse dynamics at initial stages.
Crystallization and collapse in relativistically degenerate matter
Authors: Akbari-Moghanjoughi M.
Published: April 2013

In this paper, it is shown that a mass density limit exists beyond which the relativistically degenerate matter would crystallize. The mass density limit, found here, is quite analogous to the mass limit predicted by Chandrasekhar for a type of compact stars called white dwarfs (MCh≃1.43 Solar Mass). In this study, the old problem of white dwarf core collapse, which has been previously investigated by Chandrasekhar using hydrostatic stability criteria, is revisited in the framework of the quantum hydrodynamics model by inspection of the charge screening at atomic scales in the relativistic degeneracy plasma regime taking into account the relativistic Fermi-Dirac statistics and electron interaction features such as the quantum statistical pressure, Coulomb attraction, electron exchange-correlation, and quantum recoil effects. It is revealed that the existence of ion correlation and crystallization of matter in the relativistically degenerate plasma puts a critical mass density limit on white dwarf core region. It is shown that a white dwarf star with a core mass density beyond this critical limit can undergo the spontaneous core collapse (SCC). The SCC phenomenon, which is dominantly caused by the electron quantum recoil effect (interference and localization of the electron wave function), leads to a new exotic state of matter. In such exotic state, the relativistic electron degeneracy can lead the white dwarf crystallized core to undergo the nuclear fusion and an ultimate supernova by means of the volume reduction (due to the enhanced compressibility) and huge energy release (due to the increase in cohesive energy), under the stars huge inward gravitational pressure. Moreover, it is found that the SCC phenomenon is significantly affected by the core composition (it is more probable for heavier plasmas). The critical mass density found here is consistent with the values calculated for core density of typical white dwarf stars.
Impurity modes in Frenkel exciton systems with dipolar interactions and cubic symmetry
Authors: Avgin I. , Huber D. L.
Published: April 2013

We introduce a continuum model for impurity modes of Frenkel excitons in fully occupied face-centered and body-centered cubic lattices with dipole-dipole interactions and parallel moments. In the absence of impurities, the model reproduces the small-k behavior found in numerical calculations of dipolar lattice sums. The exciton densities of states near the upper and lower band edges are calculated and compared with the corresponding results for a random array of dipoles. The Green function obtained with the continuum model, together with a spherical approximation to the Brillouin zone, is used to determine the conditions for the formation of a localized exciton mode associated with a shift in the transition energy of a single chromophore. The dependence of the local mode energy on the magnitude of the shift is ascertained. The formation of impurity bands at high concentrations of perturbed sites is investigated using the coherent potential approximation. The contribution of the impurity bands to the optical absorption is calculated in the coherent potential approximation. The locations of the optical absorption peaks of the dipolar system are shown to depend on the direction of propagation of the light relative to the dipolar axis, a property that is maintained in the presence of short-range interactions.
Comment on “Nonplanar dust-ion acoustic Gardner solitons in a dusty plasma with q-nonextensive electron velocity distribution” [Phys. Plasmas 19, 033703 (2012)]
Authors: Mannan A. , Tanjia F. , Yasmin S.
Published: April 2013

The basic characteristics of cylindrical and spherical dust-ion acoustic Gardner solitary waves in a dusty plasma with q-nonextensive electron velocity distribution have been represented by Ghosh et al. [Phys. Plasmas 19, 033703 (2012)]. In this manuscript, they use the double layer stationary solution of the standard Gardner equation but they explain the whole article in terms of Gardner solitons which is completely incorrect.
Electron random walk and collisional crossover in a gas in presence of electromagnetic waves and magnetostatic fields
Authors: Bhattacharjee Sudeep , Dey Indranuj , Paul Samit
Published: April 2013

This paper deals with random walk of electrons and collisional crossover in a gas evolving toward a plasma, in presence of electromagnetic (EM) waves and magnetostatic (B) fields, a fundamental subject of importance in areas requiring generation and confinement of wave assisted plasmas. In presence of EM waves and B fields, the number of collisions N suffered by an electron with neutral gas atoms while diffusing out of the volume during the walk is significantly modified when compared to the conventional field free square law diffusion; N=1.5(Λ/λ)2, where Λ is the characteristic diffusion length and λ is the mean free path. There is a distinct crossover and a time scale associated with the transition from the elastic to inelastic collisions dominated regime, which can accurately predict the breakdown time (τc) and the threshold electric field (EBD) for plasma initiation. The essential features of cyclotron resonance manifested as a sharp drop in τc, lowering of EBD and enhanced electron energy gain is well reproduced in the constrained random walk.
Electrokinetic microscopy: A technique for imaging three-dimensional surface topography and heterogeneity of surface material
Authors: Kwon G. H. , Kim T. Y. , Kim S. J.
Published: April 2013

In the present study, we introduce the concept of an electrokinetic microscope (EKM), a non-contact type probe microscope that can simultaneously provide a test specimen's three-dimensional surface topography and heterogeneity of surface material. In the EKM, the flow impedance and the streaming potential are measured during the scanning process to reproduce the topography and the heterogeneity, respectively. The working principle of the EKM is experimentally demonstrated by measuring specimens whose surfaces consist of thin layers of various materials and topographical differences. Experimental results also show that the EKM can be used regardless of the electrical conductivity of test specimens.