94 research outputs found
On superembedding approach to type IIB 7-branes
In search for a dynamical description of Q7-branes, which were known as
solutions of supergravity equations and then conjectured to be dynamical
objects of type IIB string theory, we study the superembedding description of
7-branes in curved type IIB supergravity superspace. With quite minimal and
natural assumptions we have found that there is no place for Q7-branes as
dynamical branes in superembedding approach. Our study might give implications
for the old-standing problem of the covariant and supersymmetric description of
multiple Dp-brane systems.Comment: LaTeX, 40 pages, no figures. V2: 44 pages, misprints corrected, minor
cosmetic changes, improvements and extensions of discussion, in particular in
the parts devoted to derivation of D7-brane equations of motion (Sec. 3) and
in Secs. 4.2; appendices E,F added, footnote on page 30 extended, conclusions
remain the same. V3. More misprints correcte
Chemopreventive targeted treatment of head and neck precancer by Wee1 inhibition
HPV-negative head and neck squamous cell carcinomas (HNSCCs) develop in precancerous changes in the mucosal lining of the upper-aerodigestive tract. These precancerous cells contain cancer-associated genomic changes and cause primary tumors and local relapses. Therapeutic strategies to eradicate these precancerous cells are very limited. Using functional genomic screens, we identified the therapeutic vulnerabilities of premalignant mucosal cells, which are shared with fully malignant HNSCC cells. We screened 319 previously identified tumor-lethal siRNAs on a panel of cancer and precancerous cell lines as well as primary fibroblasts. In total we identified 147 tumor-essential genes including 34 druggable candidates. Of these 34, 13 were also essential in premalignant cells. We investigated the variable molecular basis of the vulnerabilities in tumor and premalignant cell lines and found indications of collateral lethality. Wee1-like kinase (WEE1) was amongst the most promising targets for both tumor and precancerous cells. All four precancerous cell lines were highly sensitive to Wee1 inhibition by Adavosertib (AZD1775), while primary keratinocytes tolerated this inhibitor. Wee1 inhibition caused induction of DNA damage during S-phase followed by mitotic failure in (pre)cancer cells. In conclusion, we uncovered Wee1 inhibition as a promising chemopreventive strategy for precancerous cells, with comparable responses as fully transformed HNSCC cells
Logarithmic Corrections to N=2 Black Hole Entropy: An Infrared Window into the Microstates
Logarithmic corrections to the extremal black hole entropy can be computed
purely in terms of the low energy data -- the spectrum of massless fields and
their interaction. The demand of reproducing these corrections provides a
strong constraint on any microscopic theory of quantum gravity that attempts to
explain the black hole entropy. Using quantum entropy function formalism we
compute logarithmic corrections to the entropy of half BPS black holes in N=2
supersymmetric string theories. Our results allow us to test various proposals
for the measure in the OSV formula, and we find agreement with the measure
proposed by Denef and Moore if we assume their result to be valid at weak
topological string coupling. Our analysis also gives the logarithmic
corrections to the entropy of extremal Reissner-Nordstrom black holes in
ordinary Einstein-Maxwell theory.Comment: LaTeX file, 66 page
Targeting PLK1 as a novel chemopreventive approach to eradicate preneoplastic mucosal changes in the head and neck
Toward a Systematic Holographic QCD: A Braneless Approach
Recently a holographic model of hadrons motivated by AdS/CFT has been
proposed to fit the low energy data of mesons. We point out that the infrared
physics can be developed in a more systematic manner by exploiting backreaction
of the nonperturbative condensates. We show that these condensates can
naturally provide the IR cutoff corresponding to confinement, thus removing
some of the ambiguities from the original formulation of the model. We also
show how asymptotic freedom can be incorporated into the theory, and the
substantial effect it has on the glueball spectrum and gluon condensate of the
theory. A simple reinterpretation of the holographic scale results in a
non-perturbative running for alpha_s which remains finite for all energies. We
also find the leading effects of adding the higher condensate into the theory.
The difficulties for such models to reproduce the proper Regge physics lead us
to speculate about extensions of our model incorporating tachyon condensation.Comment: 27 pages, LaTe
Curvature effects on the surface thickness and tension at the free interface of He systems
The thickness and the surface energy at the free interface of
superfluid He are studied. Results of calculations carried out by using
density functionals for cylindrical and spherical systems are presented in a
unified way, including a comparison with the behavior of planar slabs. It is
found that for large species is independent of the geometry. The obtained
values of are compared with prior theoretical results and experimental
data. Experimental data favor results evaluated by adopting finite range
approaches. The behavior of and exhibit overshoots
similar to that found previously for the central density, the trend of these
observables towards their asymptotic values is examined.Comment: 35 pages, TeX, 5 figures, definitive versio
The top-quark mass in SU(5)xU(1) supergravity
We show that the currently experimentally preferred values of the top-quark
mass (\ie, 130\lsim m_t\lsim180\GeV) are naturally understood in the context
of string models, where the top-quark Yukawa coupling at the string scale is
generically given by , with the unified gauge
coupling. A detailed study of the Yukawa sector of
supergravity shows that the ratio of the bottom-quark to tau-lepton Yukawa
couplings at the string scale is required to be in the range
0.7\lsim\lambda_b/\lambda_\tau\lsim1, depending on the values of and
. This result is consistent with symmetry, which does
{\em not} require the equality of these Yukawa couplings in the unbroken
symmetry phase of the theory. As a means of possibly predicting the value of
, we propose a procedure whereby the size of the allowed parameter space
is determined as a function of , since all sparticle and Higgs-boson
masses and couplings depend non-trivially on . At present, no significant
preference for particular values of in supergravity is
observed, except that high-precision LEP data requires m_t\lsim180\GeV.Comment: latex, 10 pages, 4 figures (included), CERN-TH.7138/94,
CTP-TAMU-05/9
Supersymmetry, Supergravity and R_b revisited in the light of LEP 2
A previous study of supersymmetric models has indicated that they are
unlikely to make a large contribution to R_b. We revisit this analysis, taking
into account the improved lower limits on sparticle masses provided recently by
LEP 2 and the Tevatron, finding that a generic supersymmetric model cannot
contribute more than about one-and-a-half current experimental standard
deviations to R_b. We then specialize this analysis to minimal supergravity
models with universal high-energy boundary conditions, and find a much more
stringent upper bound R^{susy}_b < 0.0003. We discuss in detail why such models
can only attain values of R^{susy}_b that are considerably smaller even than
those obtainable in more general supersymmetric models.Comment: 11 pages, LaTeX, 4 figures (included
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