Absorption and unbounded superradiance in a static regular black hole spacetime

Regular black holes (RBHs)—geometries free from curvature singularities—arise naturally in theories of nonlinear electrodynamics. Here we study the absorption and superradiant amplification of a monochromatic planar wave in a charged, massive scalar field impinging on the electrically charged Ayón-Beato-García (ABG) RBH. Comparisons are drawn with absorption and superradiance for the Reissner-Nordström (RN) black hole in linear electrodynamics. We find that, in a certain parameter regime, the ABG absorption cross section is negative, due to superradiance, and moreover it is unbounded from below as the momentum of the wave approaches zero; this phenomenon of “unbounded superradiance” is absent in the RN case. We show how the parameter space can be divided into regions, using the bounded/unbounded and absorption/amplification boundaries. After introducing a high-frequency approximation based on particle trajectories, we calculate the absorption cross section numerically, via the partial-wave expansion, as a function of wave frequency, and we present a gallery of results. The cross section of the ABG RBH is found to be larger (smaller) than in the RN case when the field charge has the same (opposite) sign as the black hole charge. We show that it is possible to find “mimics”: situations in which the cross sections of both black holes are very similar. We conclude with a discussion of unbounded superradiance and superradiant instabilities

Differential Expression Of Hdac3, Hdac7 And Hdac9 Is Associated With Prognosis And Survival In Childhood Acute Lymphoblastic Leukaemia: Research Paper

Altered expression of histone deacetylases (HDACs) is a common feature in several human malignancies and may represent an interesting target for cancer treatment, including haematological malignancies. We evaluated the mRNA gene expression profile of 12 HDAC genes by quantitative real-time polymerase chain reaction in 94 consecutive childhood acute lymphoblastic leukaemia (ALL) samples and its association with clinical/biological features and survival. ALL samples showed higher expression levels of HDAC2, HDAC3, HDAC8, HDAC6 and HDAC7 when compared to normal bone marrow samples. HDAC1 and HDAC4 showed high expression in T-ALL and HDAC5 was highly expressed in B-lineage ALL. Higher than median expression levels of HDAC3 were associated with a significantly lower 5-year event-free survival (EFS) in the overall group of patients (P = 0·03) and in T-ALL patients (P = 0·01). HDAC7 and HADC9 expression levels higher than median were associated with a lower 5-year EFS in the overall group (P = 0·04 and P = 0·003, respectively) and in B-lineage CD10-positive patients (P = 0·009 and P = 0·005, respectively). 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Crescimento relativo em Uca leptodactyla Rathbun (Crustacea Decapoda Ocypodidae) Relative growth in the fiddler crab Uca leptodactyla Rathbun (Crustacea Decapoda Ocypodidae)

<abstract language="eng">Relative growth of the male major chela and female abdome was studied in a population of the fiddler crab Uca leptodactyla Rathbun, 1898 from Itapoá, Santa Catarina coast, southern Brazil. Major chela length (CMQ) was measured from 191 males, and abdomen width (LAB) from 128 females. Carapace width (LC) was the reference dimension for both sexes, which ranged from 3.9 to 11.5 mm for males, and from 3.15 to 10.65 mm for females. Males grew bigger than females. Relationship between CMQ and LC showed a transition point at 8.35 mm LC in males, and between LA and LC at 7.10 mm LC in females. Growth was allometrically positive in the early ontogenesis and isometric after the puberal molting for both sexes. Regressions between LC and CMQ in males read as: logCMQ = -0,854536 + 2,19. logLC for empirical points at left of critical point and logCMQ = 0,063047 + 1,24. logLC for those at right. In females, this relation was logLAB = -0,603590 + 1,30. logLC and logLAB = -0,361464 + 1,07. logLC, respectively. These body dimensions were connected with reproductive activity of this species