10,610 research outputs found
Pomeron and Odderon Regge Trajectories from a Dynamical Holographic Model
In this work we use gauge/string dualities and a dynamical model that takes
into account dynamical corrections to the metric of the anti de Sitter space
due to a quadratic dilaton field and calculate the masses of even and odd spin
glueball states with , and , respectively. Then we construct
the corresponding Regge trajectories which are associated with the pomeron for
even states with , and with the odderon for odd states with .
We compare our results with those coming from experimental data as well as
other models.Comment: V3: 12 pages, 8 figures, 2 tables. Results slightly modified due to
the redefinition of the relation between the five dimensional mass, conformal
dimension and spin. Text improved. We also comment now that the twist two
operator does not work in this model. References added. This version matches
the published one in PL
Holographic Description of Chiral Symmetry Breaking in a Magnetic Field in 2+1 Dimensions with an Improved Dilaton
We consider a holographic description of the chiral symmetry breaking in an
external magnetic field in -dimensional gauge theories from the
softwall model using an improved dilaton field profile given by . We find inverse magnetic catalysis for
, where is the pseudocritical
magnetic field. The transition between these two regimes is a crossover and
occurs at , which depends on the fermion mass and temperature. We also
find spontaneous chiral symmetry breaking (the chiral condensate ) at in the chiral limit () and chiral symmetry
restoration for finite temperatures. We observe that changing the parameter
of the dilaton profile only affects the overall scales of the system such as
and . For instance, by increasing one sees an increase of
and . This suggests that increasing the parameters and
will decrease the values of and .Comment: V2: 13 pages, 10 figures. New figure added. Text improved. Typos
corrected. New references added. Results unchanged. This version matches the
published one in EP
Hydrostatic Pressure Effects on the Structural and Electronic Properties of Carbon Nanotubes
We study the structural and electronic properties of isolated single-wall
carbon nanotubes (SWNTs) under hydrostatic pressure using a combination of
theoretical techniques: Continuum elasticity models, classical molecular
dynamics simulations, tight-binding electronic structure methods, and
first-principles total energy calculations within the density-functional and
pseudopotential frameworks. For pressures below a certain critical pressure
, the SWNTs' structure remains cylindrical and the Kohn-Sham energy gaps
of semiconducting SWNTs have either positive or negative pressure coefficients
depending on the value of , with a distinct "family" (of the same )
behavior. The diameter and chirality dependence of the pressure coefficients
can be described by a simple analytical expression. At ,
molecular-dynamics simulations predict that isolated SWNTs undergo a
pressure-induced symmetry-breaking transformation from a cylindrical shape to a
collapsed geometry. This transition is described by a simple elastic model as
arising from the competition between the bond-bending and terms in the
enthalpy. The good agreement between calculated and experimental values of
provides a strong support to the ``collapse'' interpretation of the
experimental transitions in bundles.Comment: To appear in the Proceedings of the 11th International Conference on
High Pressure Semiconductor Physics (invited paper
Targeting human apurinic/apyrimidinic endonuclease 1 (APE1) in phosphatase and tensin homolog (PTEN) deficient melanoma cells for personalized therapy
Phosphatase and tensin homolog (PTEN) loss is associated with genomic instability. APE1 is a key player in DNA base excision repair (BER) and an emerging drug target in cancer. We have developed small molecule inhibitors against APE1 repair nuclease activity. In the current study we explored a synthetic lethal relationship between PTEN and APE1 in melanoma. Clinicopathological significance of PTEN mRNA and APE1 mRNA expression was investigated in 191 human melanomas. Preclinically, PTEN-deficient BRAF-mutated (UACC62, HT144, and SKMel28), PTEN-proficient BRAF-wildtype (MeWo), and doxycycline-inducible PTEN-knockout BRAF-wildtype MeWo melanoma cells were DNA repair expression profiled and investigated for synthetic lethality using a panel of four prototypical APE1 inhibitors. In human tumours, low PTEN mRNA and high APE1 mRNA was significantly associated with reduced relapse free and overall survival. Pre-clinically, compared to PTEN-proficient cells, PTEN-deficient cells displayed impaired expression of genes involved in DNA double strand break (DSB) repair. Synthetic lethality in PTEN-deficient cells was evidenced by increased sensitivity, accumulation of DSBs and induction of apoptosis following treatment with APE1 inhibitors. We conclude that PTEN deficiency is not only a promising biomarker in melanoma, but can also be targeted by a synthetic lethality strategy using inhibitors of BER, such as those targeting APE1
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