16 research outputs found
Analytical studies of Hawking radiation and quasinormal modes in rotating linear dilatonic black hole
The rotating linear dilatonic black hole is an asymptotically non-flat
solution to Einstein-Maxwell-Dilaton-Axion gravity theory due to the existence
of non-trivial matter fields. We have analytically studied the wave equation of
scalar field in this background and shown that the radial wave equation can be
solved in terms of hypergeometric function. By determining the ingoing and the
outgoing fluxes at the asymptotic infinity, we have found the analytical
expressions for reflection coefficient and greybody factor for certain scalar
modes. In the high frequency regime, we obtain the Hawking temperature by
comparing the blackbody spectrum with the radiation spectrum resulting from
reflection coefficient. It is shown that the Hawking temperature, which depends
only on the linear dilatonic background parameter, does not agree with the
temperature calculated from surface gravity. At last, the quasinormal modes of
scalar field perturbation are presented, which shows that the rotating linear
dilationic black hole is unstable for certain modes apart from the superradiant
modes.Comment: 7 pages, 2 figures Comments are welcom
Condensation of an ideal gas with intermediate statistics on the horizon
We consider a boson gas on the stretched horizon of the Schwartzschild and
Kerr black holes. It is shown that the gas is in a Bose-Einstein condensed
state with the Hawking temperature if the particle number of the
system be equal to the number of quantum bits of space-time N \simeq
{A}/{{\l_{p}}^{2}}. Entropy of the gas is proportional to the area of the
horizon by construction. For a more realistic model of quantum degrees of
freedom on the horizon, we should presumably consider interacting bosons
(gravitons). An ideal gas with intermediate statistics could be considered as
an effective theory for interacting bosons. This analysis shows that we may
obtain a correct entropy just by a suitable choice of parameter in the
intermediate statistics.Comment: 12 pages, added new sections related to an ideal gas with
intermediate statistic
Constraining the electric charges of some astronomical bodies in Reissner-Nordstrom spacetimes and generic r^-2-type power-law potentials from orbital motions
We put model-independent, dynamical constraints on the net electric charge Q
of some astronomical and astrophysical objects by assuming that their exterior
spacetimes are described by the Reissner-Nordstroem metric, which induces an
additional potential U_RN \propto Q^2 r^-2. Our results extend to other
hypothetical power-law interactions inducing extra-potentials U_pert = r^-2 as
well (abridged).Comment: LaTex2e, 16 pages, 3 figures, no tables, 128 references. Version
matching the one at press in General Relativity and Gravitation (GRG). arXiv
admin note: substantial text overlap with arXiv:1112.351
GATA1 insufficiencies in primary myelofibrosis and other hematopoietic disorders: consequences for therapy
Introduction: GATA1, the founding member of a family of transcription factors, plays important roles in the development of hematopoietic cells of several lineages. Although loss of GATA1 has been known to impair hematopoiesis in animal models for nearly 25 years, the link between GATA1 defects and human blood diseases has only recently been realized. Areas covered: Here the current understanding of the functions of GATA1 in normal hematopoiesis and how it is altered in disease is reviewed. GATA1 is indispensable mainly for erythroid and megakaryocyte differentiation. In erythroid cells, GATA1 regulates early stages of differentiation, and its deficiency results in apoptosis. In megakaryocytes, GATA1 controls terminal maturation and its deficiency induces proliferation. GATA1 alterations are often found in diseases involving these two lineages, such as congenital erythroid and/or megakaryocyte deficiencies, including Diamond Blackfan Anemia (DBA), and acquired neoplasms, such as acute megakaryocytic leukemia (AMKL) and the myeloproliferative neoplasms (MPNs). Expert commentary: Since the first discovery of GATA1 mutations in AMKL, the number of diseases that are associated with impaired GATA1 function has increased to include DBA and MPNs. With respect to the latter, we are only just now appreciating the link between enhanced JAK/STAT signaling, GATA1 deficiency and disease pathogenesis
Constitutive Activation of RAS/MAPK Pathway Cooperates with Trisomy 21 and Is Therapeutically Exploitable in Down Syndrome B-cell Leukemia
©2020 American Association for Cancer Research. PURPOSE: Children with Down syndrome (constitutive trisomy 21) that develop acute lymphoblastic leukemia (DS-ALL) have a 3-fold increased likelihood of treatment-related mortality coupled with a higher cumulative incidence of relapse, compared with other children with B-cell acute lymphoblastic leukemia (B-ALL). This highlights the lack of suitable treatment for Down syndrome children with B-ALL. EXPERIMENTAL DESIGN: To facilitate the translation of new therapeutic agents into clinical trials, we built the first preclinical cohort of patient-derived xenograft (PDX) models of DS-ALL, comprehensively characterized at the genetic and transcriptomic levels, and have proven its suitability for preclinical studies by assessing the efficacy of drug combination between the MEK inhibitor trametinib and conventional chemotherapy agents. RESULTS: Whole-exome and RNA-sequencing experiments revealed a high incidence of somatic alterations leading to RAS/MAPK pathway activation in our cohort of DS-ALL, as well as in other pediatric B-ALL presenting somatic gain of the chromosome 21 (B-ALL+21). In murine and human B-cell precursors, activated KRASG12D functionally cooperates with trisomy 21 to deregulate transcriptional networks that promote increased proliferation and self renewal, as well as B-cell differentiation blockade. Moreover, we revealed that inhibition of RAS/MAPK pathway activation using the MEK1/2 inhibitor trametinib decreased leukemia burden in several PDX models of B-ALL+21, and enhanced survival of DS-ALL PDX in combination with conventional chemotherapy agents such as vincristine. CONCLUSIONS: Altogether, using novel and suitable PDX models, this study indicates that RAS/MAPK pathway inhibition represents a promising strategy to improve the outcome of Down syndrome children with B-cell precursor leukemia