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Convective Assembly of a Particle Monolayer.
Recently, the steady-state process of convective assembly has emerged as a viable production route for colloidal monolayers. The present study models the regions of particle assembly: Region I comprises convective concentration of a particle suspension in a liquid below a meniscus, Region II comprises permeation of fluid through the dense particle monolayer, and Region III comprises capillary densification. For each region, the dominant physics and nondimensional groups are identified, and quantitative models are derived to describe the evolution of microstructure in terms of the main process parameters. The concentration profile within the assembly zone of Region I is predicted, including the role of a concentration-dependent diffusion constant and the shape of the meniscus. The fluid flow through the assembled monolayer is treated in Region II, along with a stability calculation to reveal that isolated particle clusters do not survive on top of the monolayer. The physics of capillary crystallization is addressed in Region III, with an emphasis on the density of cracks that emerge. The Peclet number and Capillary number both play important roles but in different regions of the assembly process.Part of this work was performed during Norman Fleck’s stay at INM that was supported by the Alexander von Humboldt Foundation. The authors acknowledge Eduard Arzt’s continuing support of this project.This is the author accepted manuscript. The final version is available from ACS via http://dx.doi.org/10.1021/acs.langmuir.5b0363
Boundary Conditions and Unitarity: the Maxwell-Chern-Simons System in AdS_3/CFT_2
We consider the holography of the Abelian Maxwell-Chern-Simons (MCS) system
in Lorentzian three-dimensional asymptotically-AdS spacetimes, and discuss a
broad class of boundary conditions consistent with conservation of the
symplectic structure. As is well-known, the MCS theory contains a massive
sector dual to a vector operator in the boundary theory, and a topological
sector consisting of flat connections dual to U(1) chiral currents; the
boundary conditions we examine include double-trace deformations in these two
sectors, as well as a class of boundary conditions that mix the vector
operators with the chiral currents. We carefully study the symplectic product
of bulk modes and show that almost all such boundary conditions induce
instabilities and/or ghost excitations, consistent with violations of unitarity
bounds in the dual theory.Comment: 50+1 pages, 6 figures, PDFLaTeX; v2: added references, corrected
typo
Gravitational Chern-Simons Lagrangians and black hole entropy
We analyze the problem of defining the black hole entropy when Chern-Simons
terms are present in the action. Extending previous works, we define a general
procedure, valid in any odd dimensions both for purely gravitational CS terms
and for mixed gauge-gravitational ones. The final formula is very similar to
Wald's original formula valid for covariant actions, with a significant
modification. Notwithstanding an apparent violation of covariance we argue that
the entropy formula is indeed covariant.Comment: 39 page
On the new massive gravity and AdS/CFT
Demanding the existence of a simple holographic -theorem, it is shown that
a general (parity preserving) theory of gravity in 2+1 dimensions involving
upto four derivative curvature invariants reduces to the new massive gravity
theory. We consider extending the theory including upto six derivative
curvature invariants. Black hole solutions are presented and consistency with
1+1 CFTs is checked. We present evidence that bulk unitarity is still in
conflict with a positive CFT central charge for generic choice of parameters.
However, for a special choice of parameters appearing in the four and six
derivative terms reduces the linearized equations to be two derivative, thereby
ameliorating the unitarity problem.Comment: 16 pages, 2 figures. v4: typo correcte
Charged Magnetic Brane Solutions in AdS_5 and the fate of the third law of thermodynamics
We construct asymptotically AdS_5 solutions to 5-dimensional Einstein-Maxwell
theory with Chern-Simons term which are dual to 4-dimensional gauge theories,
including N=4 SYM theory, in the presence of a constant background magnetic
field B and a uniform electric charge density \rho. For the solutions
corresponding to supersymmetric gauge theories, we find numerically that a
small magnetic field causes a drastic decrease in the entropy at low
temperatures. The near-horizon AdS_2 \times R^3 geometry of the purely
electrically charged brane thus appears to be unstable under the addition of a
small magnetic field. Based on this observation, we propose a formulation of
the third law of thermodynamics (or Nernst theorem) that can be applied to
black holes in the AdS/CFT context.
We also find interesting behavior for smaller, non-supersymmetric, values of
the Chern-Simons coupling k. For k=1 we exhibit exact solutions corresponding
to warped AdS_3 black holes, and show that these can be connected to
asymptotically AdS_5 spacetime. For k\leq 1 the entropy appears to go to a
finite value at extremality, but the solutions still exhibit a mild singularity
at strictly zero temperature. In addition to our numerics, we carry out a
complete perturbative analysis valid to order B^2, and find that this
corroborates our numerical results insofar as they overlap.Comment: 45 pages v2: added note about subsequent results found in
arXiv:1003.130
No chiral truncation of quantum log gravity?
At the classical level, chiral gravity may be constructed as a consistent
truncation of a larger theory called log gravity by requiring that left-moving
charges vanish. In turn, log gravity is the limit of topologically massive
gravity (TMG) at a special value of the coupling (the chiral point). We study
the situation at the level of linearized quantum fields, focussing on a unitary
quantization. While the TMG Hilbert space is continuous at the chiral point,
the left-moving Virasoro generators become ill-defined and cannot be used to
define a chiral truncation. In a sense, the left-moving asymptotic symmetries
are spontaneously broken at the chiral point. In contrast, in a non-unitary
quantization of TMG, both the Hilbert space and charges are continuous at the
chiral point and define a unitary theory of chiral gravity at the linearized
level.Comment: 20 pages, no figures, references adde
PARP inhibitors and the treatment of breast cancer: beyond BRCA1/2?
Poly(ADP-ribose) polymerase (PARP) inhibitors have been explored as therapeutic agents for the treatment of hereditary breast and ovarian cancers harboring mutations in BRCA1 or BRCA2. In a new study, Inbar-Rozensal and colleagues show that phenanthridine-derived PARP inhibitors promote cell cycle arrest and cell death in breast cancer cells lacking BRCA1 and BRCA2 mutations and prevent the growth of tumors from xenografts of these cells in immunocompromised mice. These results suggest a potential broader utility of PARP-1 inhibitors in the treatment of breast cancer, although further mechanistic studies are needed
Warped black holes in 3D general massive gravity
We study regular spacelike warped black holes in the three dimensional
general massive gravity model, which contains both the gravitational
Chern-Simons term and the linear combination of curvature squared terms
characterizing the new massive gravity besides the Einstein-Hilbert term. The
parameters of the metric are found by solving a quartic equation constrained by
an inequality that imposes the absence of closed timelike curves. Explicit
expressions for the central charges are suggested by exploiting the fact that
these black holes are discrete quotients of spacelike warped AdS(3) and a known
formula for the entropy. Previous results obtained separately in topological
massive gravity and in new massive gravity are recovered as special cases.Comment: 38 pages, 7 figures. v2: minor changes, added refs and an appendix on
self-dual and null z-warped black hole
Low-background gamma spectroscopy at the Boulby Underground Laboratory
The Boulby Underground Germanium Suite (BUGS) comprises three low-background, high-purity germanium detectors operating in the Boulby Underground Laboratory, located 1.1 km underground in the north-east of England, UK. BUGS utilises three types of detector to facilitate a high-sensitivity, high-throughput radio-assay programme to support the development of rare-event search experiments. A Broad Energy Germanium (BEGe) detector delivers sensitivity to low-energy gamma-rays such as those emitted by 210 Pb and 234 Th. A Small Anode Germanium (SAGe) well-type detector is employed for efficient screening of small samples. Finally, a standard p-type coaxial detector provides fast screening of standard samples. This paper presents the steps used to characterise the performance of these detectors for a variety of sample geometries, including the corrections applied to account for cascade summing effects. For low-density materials, BUGS is able to radio-assay to specific activities down to 3.6mBqkg −1 for 234 Th and 6.6mBqkg −1 for 210 Pb both of which have uncovered some significant equilibrium breaks in the 238 U chain. In denser materials, where gamma-ray self-absorption increases, sensitivity is demonstrated to specific activities of 0.9mBqkg −1 for 226 Ra, 1.1mBqkg −1 for 228 Ra, 0.3mBqkg −1 for 224 Ra, and 8.6mBqkg −1 for 40 K with all upper limits at a 90% confidence level. These meet the requirements of most screening campaigns presently under way for rare-event search experiments, such as the LUX-ZEPLIN (LZ) dark matter experiment. We also highlight the ability of the BEGe detector to probe the X-ray fluorescence region which can be important to identify the presence of radioisotopes associated with neutron production; this is of particular relevance in experiments sensitive to nuclear recoils
Orbital Elements and Stellar Parameters of the Active Binary UX Arietis
This is the final version of the article. Available from American Astronomical Society via the DOI in this record.Stellar activity observed as large surface spots, radio flares, or emission lines is often found in binary systems. UX
Arietis exhibits these signs of activity, originating on the K0 subgiant primary component. Our aim is to resolve the
binary, measure the orbital motion, and provide accurate stellar parameters such as masses and luminosities to aid
in the interpretation of the observed phenomena. Using the CHARA six-telescope optical long-baseline array on
Mount Wilson, California, we obtained amplitudes and phases of the interferometric visibility on baselines up to
330 m in length, resolving the two components of the binary. We reanalyzed archival Center for Astrophysics
spectra to disentangle the binary component spectra and the spectrum of the third component, which was resolved
by speckle interferometry. We also obtained new spectra with the Nordic Optical Telescope, and we present new
photometric data that we use to model stellar surface spot locations. Both interferometric visibilities and
spectroscopic radial velocities are modeled with a spotted primary stellar surface using the Wilson–Devinney code.
We fit the orbital elements to the apparent orbit and radial velocity data to derive the distance (52.1 ± 0.8 pc) and
stellar masses (MP = 1.30 0.06 M, MS = 1.14 0.06 M). The radius of the primary can be determined to be
RP = 5.6 0.1 R and that of the secondary to be RS = 1.6 0.2 R. The equivalent spot coverage of the
primary component was found to be 62% with an effective temperature 20% below that of the unspotted surface.We thank Robert Wilson (University of Florida) for providing a custom version of his code to compute images of spotted stellar surfaces and for his help with using it. This work is based upon observations obtained with the Georgia State University (GSU) Center for High Angular Resolution Astronomy (CHARA) array at Mount Wilson Observatory. The CHARA array is supported by the National Science Foundation under grant numbers AST-1211929 and AST-1411654. Institutional support has been provided by the GSU College of Arts and Sciences and the GSU Office of the Vice President for Research and Economic Development. The MIRC instrument at the CHARA array was funded by the University of Michigan. F.B., R.R., and J.D.M. acknowledge support from NSF-AST 1210972 and 1108963. G.T. acknowledges partial support from NSF grant AST-1509375. S.K. acknowledges support from an STFC Rutherford Fellowship (ST/J004030/1) and ERC Starting Grant (grant agreement no. 639889). This work is also based on observations made with the Nordic Optical Telescope (NOT), operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. This research has made use of the SIMBAD database, operated at the CDS, Strasbourg, France. This research has made use of the Jean-Marie Mariotti Center SearchCal service13 codeveloped by FIZEAU and LAOG/IPAG and of the CDS astronomical databases SIMBAD and VIZIER.14 This research has made use of the Washington Double Star Catalog, maintained at the U.S. Naval Observatory. We thank Nicholas Elias II for discussions. We thank Dimitri Pourbaix for maintaining and providing access to the SB9 database of RV measurements of spectroscopic binaries
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