17,047 research outputs found
The uniting of Europe and the foundation of EU studies: revisiting the neofunctionalism of Ernst B. Haas
This article suggests that the neofunctionalist theoretical legacy left by Ernst B. Haas is somewhat richer and more prescient than many contemporary discussants allow. The article develops an argument for routine and detailed re-reading of the corpus of neofunctionalist work (and that of Haas in particular), not only to disabuse contemporary students and scholars of the normally static and stylized reading that discussion of the theory provokes, but also to suggest that the conceptual repertoire of neofunctionalism is able to speak directly to current EU studies and comparative regionalism. Neofunctionalism is situated in its social scientific context before the theory's supposed erroneous reliance on the concept of 'spillover' is discussed critically. A case is then made for viewing Haas's neofunctionalism as a dynamic theory that not only corresponded to established social scientific norms, but did so in ways that were consistent with disciplinary openness and pluralism
Relativistic Klein-Gordon-Maxwell multistream model for quantum plasmas
A multistream model for spinless electrons in a relativistic quantum plasma
is introduced by means of a suitable fluid-like version of the
Klein-Gordon-Maxwell system. The one and two-stream cases are treated in
detail. A new linear instability condition for two-stream quantum plasmas is
obtained, generalizing the previously known non-relativistic results. In both
the one and two-stream cases, steady-state solutions reduce the model to a set
of coupled nonlinear ordinary differential equations, which can be numerically
solved, yielding a manifold of nonlinear periodic and soliton structures. The
validity conditions for the applicability of the model are addressed
New World of Gossamer Superconductivity
Since the discovery of the high-T cuprate superconductor
LaBaCuO in 1986 by Bednorz and M\"{u}ller, controversy regarding
the nature or origin of this remarkable superconductivity has continued.
However, d-wave superconductivity in the hole-doped cuprates, arising due to
the anti-paramagnon exchange, was established around 1994. More recently we
have shown that the mean field theory, like the BCS theory of superconductivity
and Landau's Fermi liquid theory are adequate to describe the cuprates. The
keys for this development are the facts that a)the pseudogap phase is d-wave
density wave (dDW) and that the high-T cuprate superconductivity is
gossamer (i.e. it exists in the presence of dDW).Comment: 6 pages, 4 figure
Field-induced charge transport at the surface of pentacene single crystals: a method to study charge dynamics of 2D electron systems in organic crystals
A method has been developed to inject mobile charges at the surface of
organic molecular crystals, and the DC transport of field-induced holes has
been measured at the surface of pentacene single crystals. To minimize damage
to the soft and fragile surface, the crystals are attached to a pre-fabricated
substrate which incorporates a gate dielectric (SiO_2) and four probe pads. The
surface mobility of the pentacene crystals ranges from 0.1 to 0.5 cm^2/Vs and
is nearly temperature-independent above ~150 K, while it becomes thermally
activated at lower temperatures when the induced charges become localized.
Ruling out the influence of electric contacts and crystal grain boundaries, the
results contribute to the microscopic understanding of trapping and detrapping
mechanisms in organic molecular crystals.Comment: 14 pages, 4 figures. Submitted to J. Appl. Phy
Density of bulk trap states in organic semiconductor crystals: discrete levels induced by oxygen in rubrene
The density of trap states in the bandgap of semiconducting organic single
crystals has been measured quantitatively and with high energy resolution by
means of the experimental method of temperature-dependent
space-charge-limited-current spectroscopy (TD-SCLC). This spectroscopy has been
applied to study bulk rubrene single crystals, which are shown by this
technique to be of high chemical and structural quality. A density of deep trap
states as low as ~ 10^{15} cm^{-3} is measured in the purest crystals, and the
exponentially varying shallow trap density near the band edge could be
identified (1 decade in the density of states per ~25 meV). Furthermore, we
have induced and spectroscopically identified an oxygen related sharp hole bulk
trap state at 0.27 eV above the valence band.Comment: published in Phys. Rev. B, high quality figures:
http://www.cpfs.mpg.de/~krellner
Hole mobility in organic single crystals measured by a "flip-crystal" field-effect technique
We report on single crystal high mobility organic field-effect transistors
(OFETs) prepared on prefabricated substrates using a "flip-crystal" approach.
This method minimizes crystal handling and avoids direct processing of the
crystal that may degrade the FET electrical characteristics. A chemical
treatment process for the substrate ensures a reproducible device quality. With
limited purification of the starting materials, hole mobilities of 10.7, 1.3,
and 1.4 cm^2/Vs have been measured on rubrene, tetracene, and pentacene single
crystals, respectively. Four-terminal measurements allow for the extraction of
the "intrinsic" transistor channel resistance and the parasitic series contact
resistances. The technique employed in this study shows potential as a general
method for studying charge transport in field-accumulated carrier channels near
the surface of organic single crystals.Comment: 26 pages, 7 figure
Chemical propulsion research at MSFC
Chemical propulsion research reviews at Marshall Space Flight Cente
Ablation of Left Atrial Tachycardia following Catheter Ablation of Atrial Fibrillation: 12-Month Success Rates
The treatment of atrial tachycardia following catheter ablation of atrial fibrillation is often challenging. Electrophysiological studies using high-resolution 3D mapping systems have contributed significantly to their understanding, and new ablation approaches have shown high rates of acute terminations with low recurrences for the clinical AT. However, patient populations are very heterogeneous, and long-term data of the freedom from any atrial tachycardia or any arrhythmia are still sparse. To evaluate long-term success, a unified patient population and predefined ablation strategies are preferred. In this study, we present 12-month success and mean 30 month follow-up data of catheter ablation of left atrial tachycardia. All 35 patients had a history of pulmonary vein isolation (PVI), 71% of which had a previous substrate modification. A total of 54 ATs, with a mean cycle length 297 ± 86 ms, 31 macro-reentries, and 4 localized reentries, were targeted. The ablation strategy to be used was given by the study protocol, depending on the type of reentry and the number of critical isthmuses. All available ablation strategies were included: standard (anatomical) lines, individual lines, critical isthmuses, and focal ablation. All ATs were terminated by ablation. A total of 91% terminated upon the first ablation strategy. Freedom from any AT after 12 months was 82%, and from any arrhythmia, it was 77%. The multi-procedure success after 30 months was 65% for any AT and 55% for any arrhythmia. In conclusion, individual ablation strategies based on the reentry mechanism and the number of critical isthmuses seems promising and demonstrates a high long-term clinical success. Tachycardia comprising a single critical isthmus can be ablated by critical isthmus ablation only. These patients present with the highest 12-month and long-term success rates
Symmetries of the near horizon of a Black Hole by Group Theoretic methods
We use group theoretic methods to obtain the extended Lie point symmetries of
the quantum dynamics of a scalar particle probing the near horizon structure of
a black hole. Symmetries of the classical equations of motion for a charged
particle in the field of an inverse square potential and a monopole, in the
presence of certain model magnetic fields and potentials are also studied. Our
analysis gives the generators and Lie algebras generating the inherent
symmetries.Comment: To appear in Int. J. Mod. Phys.
Solitary vortex couples in viscoelastic Couette flow
We report experimental observation of a localized structure, which is of a
new type for dissipative systems. It appears as a solitary vortex couple
("diwhirl") in Couette flow with highly elastic polymer solutions. A unique
property of the diwhirls is that they are stationary, in contrast to the usual
localized wave structures in both Hamiltonian and dissipative systems which are
stabilized by wave dispersion. It is also a new object in fluid dynamics - a
couple of vortices that build a single entity somewhat similar to a magnetic
dipole. The diwhirls arise as a result of a purely elastic instability through
a hysteretic transition at negligible Reynolds numbers. It is suggested that
the vortex flow is driven by the same forces that cause the Weissenberg effect.
The diwhirls have a striking asymmetry between the inflow and outflow, which is
also an essential feature of the suggested elastic instability mechanism.Comment: 9 pages (LaTeX), 5 Postscript figures, submitte
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