557 research outputs found
The Splitting of Branes on Orientifold Planes
Continuing the study in hep-th/0004092 and hep-th/0004092, we investigate a
non-trivial string dynamical process related to orientifold planes, i.e., the
splitting of physical NS-branes and D(p+2)-branes on orientifold Op-planes.
Creation or annihilation of physical Dp-branes usually accompanies the
splitting process. In the particular case p=4, we use Seiberg-Witten curves as
an independent method to check the results.Comment: 34 pages, 9 figure
On two-dimensional quantum gravity and quasiclassical integrable hierarchies
The main results for the two-dimensional quantum gravity, conjectured from
the matrix model or integrable approach, are presented in the form to be
compared with the world-sheet or Liouville approach. In spherical limit the
integrable side for minimal string theories is completely formulated using
simple manipulations with two polynomials, based on residue formulas from
quasiclassical hierarchies. Explicit computations for particular models are
performed and certain delicate issues of nontrivial relations among them are
discussed. They concern the connections between different theories, obtained as
expansions of basically the same stringy solution to dispersionless KP
hierarchy in different backgrounds, characterized by nonvanishing background
values of different times, being the simplest known example of change of the
quantum numbers of physical observables, when moving to a different point in
the moduli space of the theory.Comment: 20 pages, based on talk presented at the conference "Liouville field
theory and statistical models", dedicated to the memory of Alexei
Zamolodchikov, Moscow, June 200
Prolyl Isomerase Pin1 Regulates Mouse Embryonic Fibroblast Differentiation into Adipose Cells
isomerase, Pin1, regulates insulin signal transduction. Pin1 reduces responses to insulin stimulation by binding CRTC2 (CREB-regulated transcriptional co-activator 2) and PPARÎł (peroxisome prolifereator- activated receptor Îł), but conversely enhances insulin signaling by binding IRS-1 (insulin receptor substrate-1), Akt kinase, and Smad3. Therefore, it is still unclear whether Pin1 inhibits or enhances adipose cell differentiation. mice was restored by increasing expression of Pin1. We found that Pin1 binds to phosphoThr172- and phosphoSer271-Pro sites in CREB suppress the activity in COS-7 cells.Pin1 enhanced the uptake of triglycerides and the differentiation of MEF cells into adipose cells in response to insulin stimulation. Results of this study suggest that Pin1 down-regulation could be a potential approach in obesity-related dysfunctions, such as high blood pressure, diabetes, non-alcoholic steatohepatitis
Toda Lattice Hierarchy and Generalized String Equations
String equations of the -th generalized Kontsevich model and the
compactified string theory are re-examined in the language of the Toda
lattice hierarchy. As opposed to a hypothesis postulated in the literature, the
generalized Kontsevich model at does not coincide with the
string theory at self-dual radius. A broader family of solutions of the Toda
lattice hierarchy including these models are constructed, and shown to satisfy
generalized string equations. The status of a variety of string
models is discussed in this new framework.Comment: 35pages, LaTeX Errors are corrected in Eqs. (2.21), (2.36), (2.33),
(3.3), (5.10), (6.1), sentences after (3.19) and theorem 5. A few references
are update
No N=4 Strings on Wolf Spaces
We generalize the standard supersymmetric Kazama-Suzuki coset
construction to the case by requiring the {\it non-linear}
(Goddard-Schwimmer) quasi-superconformal algebra to be realized on
cosets. The constraints that we find allow very simple geometrical
interpretation and have the Wolf spaces as their natural solutions. Our results
obtained by using components-level superconformal field theory methods are
fully consistent with standard results about supersymmetric
two-dimensional non-linear sigma-models and WZNW models on Wolf spaces.
We construct the actions for the latter and express the quaternionic structure,
appearing in the coset solution, in terms of the symplectic structure
associated with the underlying Freudenthal triple system. Next, we gauge the
QSCA and build a quantum BRST charge for the string propagating on
a Wolf space. Surprisingly, the BRST charge nilpotency conditions rule out the
non-trivial Wolf spaces as consistent string backgrounds.Comment: 31 pages, LaTeX, special macros are include
Wnt/â€-Catenin Signaling Regulates Proliferation of Human Cornea Epithelial Stem/Progenitor Cells
PURPOSE. To investigate the expression and role of the Wnt signaling pathway in human limbal stem cells (LSCs). METHODS. Total RNA was isolated from the human limbus and central cornea. Limbal or cornea-specific transcripts were identified through quantitative real-time PCR. Protein expression of Wnt molecules was confirmed by immunohistochemistry on human ocular tissue. Activation of Wnt signaling using lithium chloride was achieved in vitro and its effects on LSC differentiation and proliferation were evaluated. RESULTS. Expression of Wnt2, Wnt6, Wnt11, Wnt16b, and four Wnt inhibitors were specific to the limbal region, whereas Wnt3, Wnt7a, Wnt7b, and Wnt10a were upregulated in the central cornea. Nuclear localization of â€-catenin was observed in a very small subset of basal epithelial cells only at the limbus. Activation of Wnt/â€-catenin signaling increased the proliferation and colony-forming efficiency of primary human LSCs. The stem cell phenotype was maintained, as shown by higher expression levels of putative corneal epithelial stem cell markers, ATP-binding cassette family G2 and âŹNp63âŁ, and low expression levels of mature cornea epithelial cell marker, cytokeratin 12. CONCLUSIONS. These findings demonstrate for the first time that Wnt signaling is present in the ocular surface epithelium and plays an important role in the regulation of LSC proliferation. Modulation of Wnt signaling could be of clinical application to increase the efficiency of ex vivo expansion of corneal epithelial stem/progenitor cells for transplantation. (Invest Ophthalmol Vis Sci. 2011;52:4734 -4741
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