328 research outputs found
Gyrokinetic studies of the effect of beta on drift-wave stability in NCSX
The gyrokinetic turbulence code GS2 was used to investigate the effects of
plasma beta on linear, collisionless ion temperature gradient (ITG) modes and
trapped electron modes (TEM) in National Compact Stellarator Experiment (NCSX)
geometry. Plasma beta affects stability in two ways: through the equilibrium
and through magnetic fluctuations. The first was studied here by comparing ITG
and TEM stability in two NCSX equilibria of differing beta values, revealing
that the high beta equilibrium was marginally more stable than the low beta
equilibrium in the adiabatic-electron ITG mode case. However, the high beta
case had a lower kinetic-electron ITG mode critical gradient. Electrostatic and
electromagnetic ITG and TEM mode growth rate dependencies on temperature
gradient and density gradient were qualitatively similar. The second beta
effect is demonstrated via electromagnetic ITG growth rates' dependency on
GS2's beta input parameter. A linear benchmark with gyrokinetic codes GENE and
GKV-X is also presented.Comment: Submitted to Physics of Plasmas. 9 pages, 27 figure
Response of Mouse Breast Cancer Cells to Anastrozole, Tamoxifen, and the Combination
The murine breast cancer cells (4T1) grown both in female BALB/c mice and in culture were treated with anastrozole (50 μg/mL), tamoxifen citrate (5 μg/mL), and the combination of the two drugs in order to determine treatment efficacies, toxic potential, and the mechanism of cell death. The in vivo treatments were evaluated by monitoring tumor growth, development, and life span. The in vitro effects were measured through cell growth kinetics, cell proliferation, mitochondrial membrane potential disruption assay, and light and scanning electron microscopy. All drug treatments extended the mean life span of the 4T1-inoculated tumor-bearing mice; however, only tamoxifen and combination treatments statistically increased the life span when compared to untreated mice. Although the most drug inhibitory effect on cell multiplication was observed in the combination treatment, both anastrozole and tamoxifen individually inhibited cell proliferation significantly at most time periods in this mouse breast cancer cell line. The mitochondrial membrane potential disruption assay demonstrated significant increase in the percent of cells undergoing apoptosis in all treatment groups. However, the combination treatment was the most effective in inducing cell death via apoptosis. Light and scanning electron microscopy of the treated cells revealed characteristics such as rounding, clumping, and shrinkage of the cells as well as formation of cell surface blebbing and apoptotic bodies suggestive of cell death via apoptotic pathway
Conformally dressed black hole in 2+1 dimensions
A three dimensional black hole solution of Einstein equations with negative
cosmological constant coupled to a conformal scalar field is given. The
solution is static, circularly symmetric, asymptotically anti-de Sitter and
nonperturbative in the conformal field. The curvature tensor is singular at the
origin while the scalar field is regular everywhere. The condition that the
Euclidean geometry be regular at the horizon fixes the temperature to be
. Using the Hamiltonian formulation including
boundary terms of the Euclidean action, the entropy is found to be
of the standard value (), and in agreement with
the first law of thermodynamics.Comment: LaTeX ,RevTeX, 13pages, no figure
Simulating Gyrokinetic Microinstabilities in Stellarator Geometry with GS2
The nonlinear gyrokinetic code GS2 has been extended to treat
non-axisymmetric stellarator geometry. Electromagnetic perturbations and
multiple trapped particle regions are allowed. Here, linear, collisionless,
electrostatic simulations of the quasi-axisymmetric, three-field period
National Compact Stellarator Experiment (NCSX) design QAS3-C82 have been
successfully benchmarked against the eigenvalue code FULL. Quantitatively, the
linear stability calculations of GS2 and FULL agree to within ~10%.Comment: Submitted to Physics of Plasmas. 9 pages, 14 figure
Conformal Black Hole Solutions of Axi-Dilaton Gravity in D-dimensions
Static, spherically symmetric solutions of axi-dilaton gravity in
dimensions is given in the Brans-Dicke frame for arbitrary values of the
Brans-Dicke constant and an axion-dilaton coupling parameter . The
mass and the dilaton and axion charges are determined and a BPS bound is
derived. There exists a one parameter family of black hole solutions in the
scale invariant limit.Comment: 6 PAGES, Rev-tex file, no figures, to appear in Phys-Rev
Stellarator microinstabilities and turbulence at low magnetic shear
[EN] Gyrokinetic simulations of drift waves in low-magnetic-shear stellarators reveal that simulation domains comprised of multiple turns can be required to properly resolve critical mode structures important in saturation dynamics. Marginally stable eigenmodes important in saturation of ion temperature gradient modes and trapped electron modes in the Helically Symmetric Experiment (HSX) stellarator are observed to have two scales, with the envelope scale determined by the properties of the local magnetic shear and an inner scale determined by the interplay between the local shear and magnetic field-line curvature. Properly resolving these modes removes spurious growth rates that arise for extended modes in zero-magnetic-shear approximations, enabling use of a zero-magnetic-shear technique with smaller simulation domains and attendant cost savings. Analysis of subdominant modes in trapped electron mode (TEM)-driven turbulence reveals that the extended marginally stable modes play an important role in the nonlinear dynamics, and suggests that the properties induced by low magnetic shear may be exploited to provide another route for turbulence saturation.The authors would like to thank F. Jenko for insightful questions that motivated this research and J. Smoniewski and J. H. E. Proll for engaging discussions. This work was supported by US DoE grant nos. DE-FG02-99ER54546, DE-FG02-93ER54222 and DE-FG02-89ER53291. J.E.R. was supported by Agencia Estatal de Investigacion (AEI) under grant TIN2016-75985-P, which includes European Commission ERDF funds. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a US Department of Energy Office of Science User Facility operated under contract no. DE-AC02-05CH11231. This research was performed using the compute resources and assistance of the UW-Madison Center For High Throughput Computing (CHTC) in the Department of Computer Sciences. The CHTC is supported by UW-Madison, the Advanced Computing Initiative, the Wisconsin Alumni Research Foundation, the Wisconsin Institutes for Discovery and the National Science Foundation, and is an active member of the Open Science Grid, which is supported by the National Science Foundation and the US Department of Energy's Office of Science.Faber, BJ.; Pueschel, MJ.; Terry, PW.; Hegna, CC.; Roman, JE. (2018). Stellarator microinstabilities and turbulence at low magnetic shear. Journal of Plasma Physics. 84(5). https://doi.org/10.1017/S0022377818001022S845Connor, J. W., & Hastie, R. J. (2004). Microstability in tokamaks with low magnetic shear. Plasma Physics and Controlled Fusion, 46(10), 1501-1535. doi:10.1088/0741-3335/46/10/001Terry, P. W., Faber, B. J., Hegna, C. C., Mirnov, V. V., Pueschel, M. 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No Scalar Hair Theorem for a Charged Spherical Black Hole
This paper consolidates noscalar hair theorem for a charged spherically
symmetric black hole in four dimension in general relativity as well as in all
scalar tensor theories, both minimally and nonminimally coupled, when the
effective Newtonian constant of gravity is positive. However, there is an
exception when the matter field itself is coupled to the scalar field, such as
in dilaton gravity.Comment: 13 pages, Latex format, some minor corrections are made, accepted for
publication in Physical Review
Chaos in black holes surrounded by gravitational waves
The occurrence of chaos for test particles moving around Schwarzschild black
holes perturbed by a special class of gravitational waves is studied in the
context of the Melnikov method. The explicit integration of the equations of
motion for the homoclinic orbit is used to reduce the application of this
method to the study of simple graphics.Comment: 15 pages, LaTex
Collisions of Einstein-Conformal Scalar Waves
A large class of solutions of the Einstein-conformal scalar equations in
D=2+1 and D=3+1 is identified. They describe the collisions of asymptotic
conformal scalar waves and are generated from Einstein-minimally coupled scalar
spacetimes via a (generalized) Bekenstein transformation. Particular emphasis
is given to the study of the global properties and the singularity structure of
the obtained solutions. It is shown, that in the case of the absence of pure
gravitational radiation in the initial data, the formation of the final
singularity is not only generic, but is even inevitable.Comment: 17 pages, LaTe
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