474 research outputs found
A magnetically induced quantum phase transition in holography
We investigate quantum phase transitions in a 2+1 dimensional gauge theory at
finite chemical potential and magnetic field . The gravity dual is
based on 4D Fayet-Iliopoulos gauged supergravity and the
solutions we consider---that are constructed analytically---are extremal,
dyonic, asymptotically black-branes with a nontrivial radial profile
for the scalar field. We discover a line of second order fixed points at
between the dyonic black brane and an extremal "thermal gas"
solution with a singularity of good-type, according to the acceptability
criteria of Gubser [1]. The dual field theory is the ABJM theory [2] deformed
by a triple trace operator and placed at finite charge and magnetic
field. This line of fixed points might be useful in studying the various
strongly interacting quantum critical phenomena such as the ones proposed to
underlie the cuprate superconductors. We also find curious similarities between
the behaviour of the VeV under B and that of the quark
condensate in 2+1 dimensional NJL models.Comment: 33 pages, 7 figure
Constraints on Conformal Windows from Holographic Duals
We analyze a beta function with the analytic form of
Novikov-Shifman-Vainshtein-Zakharov result in the five dimensional
gravity-dilaton environment. We show how dilaton inherits poles and fixed
points of such beta function through the zeros and points of extremum in its
potential. Super Yang-Mills and supersymmetric QCD are studied in detail and
Seiberg's electric-magnetic duality in the dilaton potential is explicitly
demonstrated. Non-supersymmetric proposals of similar functional form are
tested and new insights into the conformal window as well as determinations of
scheme-independent value of the anomalous dimension at the fixed point are
presented.Comment: Fig. 5b is corrected to match the discussion in the tex
Construction and characterization of a multilayered gingival keratinocyte culture model : the TURK-U model
In construction of epithelial cells as multilayers, the cells are grown submerged to confluence on fibroblast-embedded collagen gels and, then, lifted to air to promote their stratification. We recently demonstrated that gingival epithelial cells form uniform monolayers on semi-permeable nitrocellulose membranes, supported with a semi-solid growth medium, which allows the cells to grow at an air-liquid-solid interface from the beginning of the culturing protocol. In this study, the aim was to further develop our previous model to form a multilayered gingival epithelial culture model. Two different epithelial cell lines (HaCaT from skin and HMK from gingiva) were used in all experiments. Both cell lines were grown first as monolayers for 3 days. After that, keratinocytes were trypsinized, counted and seeded on a sterile semi-permeable nitrocellulose membrane placed on the top of a semi-solid growth medium, forming an air-liquid-solid interface for the cells to grow. At days 1, 4, and 7, epithelial cells were fixed, embedded in paraffin, and sectioned for routine Hematoxylin-Eosin staining and immunohistochemistry for cytokeratin (Ck). At day 1, HMK cells grew as monolayers, while HaCaT cells stratified forming an epithelium with two to three layers. At day 4, a stratified epithelium in the HMK model had four to five layers and its proliferation continued up to day 7. HaCaT cells formed a dense and weakly proliferating epithelium with three to four layers of stratification at day 4 but the proliferation disappeared at day 7. At all days, both models were strongly positive for Ck5, Ck7, and Ck 19, and weakly positive for Ck10. Gingival epithelial cells stratify successfully on semi-permeable nitrocellulose membranes, supported with a semi-solid growth medium. This technique allows researchers to construct uniform gingival epithelial cell multilayers at an air-liquid-solid interface, without using collagen gels, resulting in a more reproducible method.Peer reviewe
Improved Holographic QCD
We provide a review to holographic models based on Einstein-dilaton gravity
with a potential in 5 dimensions. Such theories, for a judicious choice of
potential are very close to the physics of large-N YM theory both at zero and
finite temperature. The zero temperature glueball spectra as well as their
finite temperature thermodynamic functions compare well with lattice data. The
model can be used to calculate transport coefficients, like bulk viscosity, the
drag force and jet quenching parameters, relevant for the physics of the
Quark-Gluon Plasma.Comment: LatEX, 65 pages, 28 figures, 9 Tables. Based on lectures given at
several Schools. To appear in the proceedinds of the 5th Aegean School
(Milos, Greece
Marginal Deformations of Field Theories with AdS_4 Duals
We generate new AdS_4 solutions of D=11 supergravity starting from AdS_4 x
X_7 solutions where X_7 has U(1)^3 isometry. We consider examples where X_7 is
weak G_2, Sasaki-Einstein or tri-Sasakian, corresponding to d=3 SCFTs with
N=1,2 or 3 supersymmetry, respectively, and where the deformed solutions
preserve N=1,2 or 1 supersymmetry, respectively. For the special cases when X_7
is M(3,2), Q(1,1,1) or N(1,1)_I we identify the exactly marginal deformation in
the dual field theory. We also show that the volume of supersymmetric 5-cycles
of N(1,1)_I agrees with the conformal dimension predicted by the baryons of the
dual field theory.Comment: 28 pages, 2 figures; v2. typos correcte
Supersymmetric defects in the Maldacena-Nunez background
We find supersymmmetric configurations of a D5-brane probe in the
Maldacena-Nunez background which are extended along one or two of the spatial
directions of the gauge theory. These embeddings are worldvolume solitons which
behave as codimension two or one defects in the gauge theory and preserve two
of the four supersymmetries of the background.Comment: 37 pages, 2 figures, LaTeX; v2: references adde
Marginal deformation of N=4 SYM and Penrose limits with continuum spectrum
We study the Penrose limit about a null geodesic with 3 equal angular momenta
in the recently obtained type IIB solution dual to an exactly marginal
-deformation of N=4 SYM. The resulting background has non-trivial NS
3-form flux as well as RR 5- and 3-form fluxes. We quantise the light-cone
Green-Schwarz action and show that it exhibits a continuum spectrum. We show
that this is related to the dynamics of a charged particle moving in a Landau
plane with an extra interaction induced by the deformation. We interpret the
results in the dual N=1 SCFT.Comment: 26 pages, 2 figures; v2: typos corrected, field theory interpretation
extende
HotPoint: hot spot prediction server for protein interfaces
The energy distribution along the proteinâprotein interface is not homogenous; certain residues contribute more to the binding free energy, called âhot spotsâ. Here, we present a web server, HotPoint, which predicts hot spots in protein interfaces using an empirical model. The empirical model incorporates a few simple rules consisting of occlusion from solvent and total knowledge-based pair potentials of residues. The prediction model is computationally efficient and achieves high accuracy of 70%. The input to the HotPoint server is a protein complex and two chain identifiers that form an interface. The server provides the hot spot prediction results, a table of residue properties and an interactive 3D visualization of the complex with hot spots highlighted. Results are also downloadable as text files. This web server can be used for analysis of any proteinâprotein interface which can be utilized by researchers working on binding sites characterization and rational design of small molecules for protein interactions. HotPoint is accessible at http://prism.ccbb.ku.edu.tr/hotpoint
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