405 research outputs found
Three dimensional Casimir piston for massive scalar fields
We consider Casimir force acting on a three dimensional rectangular piston
due to a massive scalar field subject to periodic, Dirichlet and Neumann
boundary conditions. Exponential cut-off method is used to derive the Casimir
energy in the interior region and the exterior region separated by the piston.
It is shown that the divergent term of the Casimir force acting on the piston
due to the interior region cancels with that due to the exterior region, thus
render a finite well-defined Casimir force acting on the piston. Explicit
expressions for the total Casimir force acting on the piston is derived, which
show that the Casimir force is always attractive for all the different boundary
conditions considered. As a function of a -- the distance from the piston to
the opposite wall, it is found that the magnitude of the Casimir force behaves
like when and decays exponentially when .
Moreover, the magnitude of the Casimir force is always a decreasing function of
a. On the other hand, passing from massless to massive, we find that the effect
of the mass is insignificant when a is small, but the magnitude of the force is
decreased for large a in the massive case.Comment: 22 pages, 8 figure
Condensate fluctuations in finite Bose-Einstein condensates at finite temperature
A Langevin equation for the complex amplitude of a single-mode Bose-Einstein
condensate is derived. The equation is first formulated phenomenologically,
defining three transport parameters. It is then also derived microscopically.
Expressions for the transport parameters in the form of Green-Kubo formulas are
thereby derived and evaluated for simple trap geometries, a cubic box with
cyclic boundary conditions and an isotropic parabolic trap. The number
fluctuations in the condensate, their correlation time, and the
temperature-dependent collapse-time of the order parameter as well as its
phase-diffusion coefficient are calculated.Comment: 29 pages, Revtex, to appear in Phys.Rev.
Finding Shuffle Words That Represent Optimal Scheduling of Shared Memory Access
In the present paper, we introduce and study the problem
of computing, for any given finite set of words, a shuffle word with a
minimum so-called scope coincidence degree. The scope coincidence degree is the maximum number of different symbols that parenthesise any
position in the shuffle word. This problem is motivated by an application of a new automaton model and can be regarded as the problem of
scheduling shared memory accesses of some parallel processes in a way
that minimises the number of memory cells required. We investigate the
complexity of this problem and show that it can be solved in polynomial
time
Granular Solid Hydrodynamics
Granular elasticity, an elasticity theory useful for calculating static
stress distribution in granular media, is generalized to the dynamic case by
including the plastic contribution of the strain. A complete hydrodynamic
theory is derived based on the hypothesis that granular medium turns
transiently elastic when deformed. This theory includes both the true and the
granular temperatures, and employs a free energy expression that encapsulates a
full jamming phase diagram, in the space spanned by pressure, shear stress,
density and granular temperature. For the special case of stationary granular
temperatures, the derived hydrodynamic theory reduces to {\em hypoplasticity},
a state-of-the-art engineering model.Comment: 42 pages 3 fi
Dupilumab reduces systemic corticosteroid use and sinonasal surgery rate in CRSwNP
BACKGROUND: Chronic rhinosinusitis with nasal polyps (CRSwNP) is a type 2 inflammatory disease with a high symptom burden and poor quality of life. Treatment options include recurrent surgeries and/or frequent systemic corticosteroids (SCS). Dupilumab, a fully human monoclonal antibody, blocks the shared receptor component for interleukin-4 and interleukin-13, key drivers of type 2-mediated inflammation. We report results of pooled analyses from 2 randomised, double-blind, placebo-controlled phase 3 studies (SINUS 24 [NCT02912468]; SINUS-52 [NCT02898454]) to evaluate dupilumab effect versus placebo in adults with CRSwNP with/without SCS use and sinonasal surgery.
METHODOLOGY: SINUS-24 patients were randomised 1:1 to subcutaneous dupilumab 300 mg (n=143) or placebo (n=133) every 2 weeks (q2w) for 24 weeks. SINUS-52 patients were randomised 1:1:1 to 52 weeks of subcutaneous dupilumab 300 mg q2w (n=150), 24 weeks q2w followed by 28 weeks of dupilumab 300 mg every 4 weeks (n=145) or 52 weeks of placebo q2w (n=153).
RESULTS: Dupilumab reduced the number of patients undergoing sinonasal surgery (82.6%), the need for in-study SCS use (73.9%), and SCS courses (75.3%). Significant improvements were observed with dupilumab vs placebo regardless of prior sinonasal surgery or SCS use in nasal polyp, nasal congestion, Lund-MacKay, and Sinonasal Outcome Test (22-items) scores, and the University of Pennsylvania Smell Identification Test.
CONCLUSIONS: Dupilumab demonstrated significant improvements in disease signs and symptoms and reduced the need for sino-nasal surgery and SCS use versus placebo in patients with severe CRSwNP, regardless of SCS use in the previous 2 years, or prior sinonasal surgery
Border crossings in the African travel narratives of Ibn Battuta, Richard Burton and Paul Theroux
This article compares the representation of African borders in the 14th-century
travelogue of Ibn Battuta, the 19th-century travel narrative of Richard Burton and the
21st-century travel writing of Paul Theroux. It examines the mutually constitutive
relationship between conceptions of literal territorial boundaries and the figurative
boundaries of the subject that ventures across borders in Africa. The border is seen as
a liminal zone which paradoxically separates and joins spaces. Accounts of border
crossings in travel writing from different periods suggest the historicity and cultural
specificity of conceptions of geographical borders, and the way they index the “boundaries”
of the subjects who cross them. Tracing the transformations in these conceptions
of literal and metaphorical borders allows one to chart the emergence of the dominant
contemporary idea of “Africa” as the inscrutable, savage continent
Climate change impacts on groundwater hydrology – where are the main uncertainties and can they be reduced?
From Coherent Modes to Turbulence and Granulation of Trapped Gases
The process of exciting the gas of trapped bosons from an equilibrium initial
state to strongly nonequilibrium states is described as a procedure of symmetry
restoration caused by external perturbations. Initially, the trapped gas is
cooled down to such low temperatures, when practically all atoms are in
Bose-Einstein condensed state, which implies the broken global gauge symmetry.
Excitations are realized either by imposing external alternating fields,
modulating the trapping potential and shaking the cloud of trapped atoms, or it
can be done by varying atomic interactions by means of Feshbach resonance
techniques. Gradually increasing the amount of energy pumped into the system,
which is realized either by strengthening the modulation amplitude or by
increasing the excitation time, produces a series of nonequilibrium states,
with the growing fraction of atoms for which the gauge symmetry is restored. In
this way, the initial equilibrium system, with the broken gauge symmetry and
all atoms condensed, can be excited to the state, where all atoms are in the
normal state, with completely restored gauge symmetry. In this process, the
system, starting from the regular superfluid state, passes through the states
of vortex superfluid, turbulent superfluid, heterophase granular fluid, to the
state of normal chaotic fluid in turbulent regime. Both theoretical and
experimental studies are presented.Comment: Latex file, 25 pages, 4 figure
Spinor condensates and light scattering from Bose-Einstein condensates
These notes discuss two aspects of the physics of atomic Bose-Einstein
condensates: optical properties and spinor condensates. The first topic
includes light scattering experiments which probe the excitations of a
condensate in both the free-particle and phonon regime. At higher light
intensity, a new form of superradiance and phase-coherent matter wave
amplification were observed. We also discuss properties of spinor condensates
and describe studies of ground--state spin domain structures and dynamical
studies which revealed metastable excited states and quantum tunneling.Comment: 58 pages, 33 figures, to appear in Proceedings of Les Houches 1999
Summer School, Session LXXI
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