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  • 1
    Electronic Resource
    Electronic Resource
    Taylor relaxation and λ decay of unbounded, freely expanding spheromaks (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 3625-3640 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A magnetized coaxial gun is discharged into a much larger vacuum chamber and the subsequent evolution of the plasma is observed using high speed cameras and a magnetic probe array. Photographic results indicate four distinct regimes of operation, labeled I–IV, each possessing qualitatively different dynamics, with the parameter λgun=μ0Igun/Φbias determining the operative regime. Plasmas produced in Regime II are identified as detached spheromak configurations. Images depict a donut-like shape, while magnetic data demonstrate that a closed toroidal flux-surface topology is present. Poloidal flux amplification shows that Taylor relaxation mechanisms are at work. The spatial and temporal variation of plasma λ=μ0Jφ/Bφ indicate that the spheromak is decaying and expanding in a manner analogous to a self-similar expansion model proposed for interplanetary magnetic clouds. In Regime III, the plasma is unable to detach from the gun due to excess bias flux. Analysis of toroidal and poloidal flux as well as the λ profile shows that magnetic flux and helicity are confined within the gun for this regime. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1287137
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of body weight on dalteparin pharmacokinetics A preliminary study (2000)
    Springer
    European journal of clinical pharmacology 56 (2000), S. 293-297 
    Details
    ISSN: 1432-1041
    Keywords: Key words Dalteparin ; Low-molecular-weight heparins ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Aim: To investigate whether there were significant differences in the volume of distribution (V) and clearance (CL) of dalteparin in obese versus normal-weight patients, and thereby determine whether dosing of dalteparin should be based on total body weight, lean body weight or an adjusted body weight in obese patients. Methods: Patients (ten obese and ten normal weight) treated with dalteparin were matched for age, gender, lean body weight and creatinine CL. Two steady-state plasma dalteparin concentrations were taken from each patient and assayed in duplicate. The pharmacokinetic values of V and CL were estimated, for each patient, using the Bayesian maximum a posteriori method with the program ABBOTTBASE. Results: The mean V in obese patients was approximately 60% larger than in normal-weight patients, but this was not statistically significant (P=0.11; two-tailed). The mean value of V (8.4 l) in the normal-weight patients was similar to that reported in the literature. The mean difference in values of CL (18% larger in obese patients) was not clinically or statistically significant. A poor correlation was seen between V and lean body weight (r 2=0.05). There was a moderate correlation between V and total body weight (r 2=0.52) and between V and adjusted body weight (r 2=0.55); adjusted body weight=[lean body weight + 0.4(total body weight – lean body weight)]. Total body weight and adjusted body weight provided a better correlation with CL (r 2=0.39, 0.32, respectively) than did lean body weight (r 2=0.01). Conclusion: These results suggest that doses of dalteparin in obese patients should be based on total body weight or an adjusted body weight, but not lean body weight. This study highlights some potential differences in the pharmacokinetics of dalteparin in individuals who are obese, and further work is necessary to quantify these differences in more detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280000141
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  • 3
    Electronic Resource
    Electronic Resource
    Macroscopic strings as heavy quarks: Large-N gauge theory and anti-de Sitter supergravity (2001)
    Springer
    The European physical journal 22 (2001), S. 379-394 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We study some aspects of Maldacena's large-N correspondence between ${\cal N}=4$ superconformal gauge theory on the D3-brane and maximal supergravity on AdS $_5 \times S_5$ by introducing macroscopic strings as heavy (anti-) quark probes. The macroscopic strings are semi-infinite Type IIB strings ending on a D3-brane world-volume. We first study deformation and fluctuation of D3-branes when a macroscopic BPS string is attached. We find that both dynamics and boundary conditions agree with those for the macroscopic string in anti-de Sitter supergravity. As a by-product we clarify how Polchinski's Dirichlet and Neumann open string boundary conditions arise dynamically. We then study the non-BPS macroscopic string–anti-string pair configuration as a physical realization of a heavy quark Wilson loop. We obtain the $Q \bar Q$ static potential from the supergravity side and find that the potential exhibits non-analyticity of the square-root branch cut in the 't Hooft coupling parameter. We put forward non-analyticity as a prediction for large-N gauge theory in the strong 't Hooft coupling limit. By turning on the Ramond–Ramond zero-form potential, we also study the $\theta$ vacuum angle dependence of the static potential. We finally discuss the possible dynamical realization of the heavy N-prong string junction and of the large-N loop equation via a local electric field and string recoil thereof. Throughout comparisons of the AdS–CFT correspondence, we find that a crucial role is played by “geometric duality” between the UV and IR scales in directions perpendicular to the D3-brane and parallel ones, explaining how the AdS $_5$ spacetime geometry emerges out of four-dimensional gauge theory at strong coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100520100799
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  • 4
    Electronic Resource
    Electronic Resource
    Open Wilson lines as closed strings in non-commutative field theories (2002)
    Springer
    The European physical journal 22 (2002), S. 781-788 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Open Wilson line operators and the generalized star product have been studied extensively in non-commutative gauge theories. We show that they also show up in non-commutative scalar field theories as universal structures. We first point out that the dipole picture of non-commutative geometry provides an intuitive argument for robustness of the open Wilson lines and generalized star products therein. We calculate the one-loop effective action of the non-commutative scalar field theory with cubic self-interaction and show explicitly that the generalized star products arise in the non-planar part. It is shown that, in the low-energy, large non-commutativity limit, the non-planar part is expressible solely in terms of the scalar open Wilson line operator and descendants, the latter being interpreted as composite operators representing a closed string.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100520100848
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  • 5
    Electronic Resource
    Electronic Resource
    Anatomy of one-loop effective action in non-commutative scalar field theories (2002)
    Springer
    The European physical journal 22 (2002), S. 757-770 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The one-loop effective action of non-commutative scalar field theory with cubic self-interaction is studied. Utilizing the worldline formulation, both the planar and non-planar parts of the effective action are computed explicitly. We find complete agreement of the result with the Seiberg–Witten limit of a string worldsheet computation and with the standard Feynman diagrammatics. We prove that, in the low-energy and large non-commutativity limit, the non-planar part of the effective action is simplified enormously and is resummable into a quadratic action of scalar open Wilson line operators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100520100829
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