Geometry of Vaidya spacetimes Coudray, Armand; Nicolas, Jean-Philippe
General relativity and gravitation,
08/2021, Letnik:
53, Številka:
8
Journal Article
Recenzirano
Odprti dostop
We investigate the geometrical structure of Vaidya’s spacetime in the case of a white hole with decreasing mass, stabilising to a black hole in finite or infinite time or evaporating completely. Our ...approach relies on a detailed analysis of the ordinary differential equation describing the incoming principal null geodesics, among which are the generators of the past horizon. We devote special attention to the case of a complete evaporation in infinite time and establish the existence of an asymptotic light-like singularity of the conformal curvature, touching both the past space-like singularity and future time-like infinity. This singularity is present independently of the decay rate of the mass. We derive an explicit formula that relates directly the strength of this null singularity to the asymptotic behaviour of the mass function.
We study the peeling on Kerr spacetime for fields satisfying conformally invariant linear and semi-linear scalar wave equations. We follow the approach initiated by Mason and Nicolas (J Inst Math ...Jussieu 8(1):179–208,
2009
; J Geom Phys 62(4):867–889,
2012
.
arXiv:1101.4333
) for the Schwarzschild metric, based on a Penrose compactification and energy estimates. This approach provides a definition of the peeling at all orders in terms of Sobolev regularity near
I
instead of
C
k
regularity at
I
, allowing to characterise completely and without loss the classes of initial data ensuring a certain order of peeling at
I
. This paper extends the construction to the Kerr metric, confirms the validity and optimality of the flat spacetime model (in the sense that the same regularity and fall-off assumptions on the data guarantee the peeling behaviour in flat spacetime and on the Kerr metric) and does so for the first time for a nonlinear equation. Our results are local near spacelike infinity and are valid for all values of the angular momentum of the spacetime, including for fast Kerr metrics.
We introduce a k-mer-based computational protocol, DE-kupl, for capturing local RNA variation in a set of RNA-seq libraries, independently of a reference genome or transcriptome. DE-kupl extracts all ...k-mers with differential abundance directly from the raw data files. This enables the retrieval of virtually all variation present in an RNA-seq data set. This variation is subsequently assigned to biological events or entities such as differential long non-coding RNAs, splice and polyadenylation variants, introns, repeats, editing or mutation events, and exogenous RNA. Applying DE-kupl to human RNA-seq data sets identified multiple types of novel events, reproducibly across independent RNA-seq experiments.
Carter and Lichnerowicz have established that barotropic fluid flows are conformally geodesic and obey Hamilton’s principle. This variational approach can accommodate neutral, or charged and poorly ...conducting, fluids. We show that, unlike what has been previously thought, this approach can also accommodate perfectly conducting magnetofluids, via the Bekenstein-Oron description of ideal magnetohydrodynamics. When Noether symmetries associated with Killing vectors or tensors are present in geodesic flows, they lead to constants of motion polynomial in the momenta. We generalize these concepts to hydrodynamic flows. Moreover, the Hamiltonian descriptions of ideal magnetohydrodynamics allow one to cast the evolution equations into a hyperbolic form useful for evolving rotating or binary compact objects with magnetic fields in numerical general relativity. In this framework, Ertel’s potential vorticity theorem for baroclinic fluids arises as a special case of a conservation law valid for any Hamiltonian system. Moreover, conserved circulation laws, such as those of Kelvin, Alfvén and Bekenstein-Oron, emerge simply as special cases of the Poincaré-Cartan integral invariant of Hamiltonian systems. We use this approach to obtain an extension of Kelvin’s theorem to baroclinic (nonisentropic) fluids, based on a temperature-dependent time parameter. We further extend this result to perfectly or poorly conducting baroclinic magnetoflows. Finally, in the barotropic case, such magnetoflows are shown to also be geodesic, albeit in a Finsler (rather than Riemann) space.
Purpose
The primary aim of this study was to determine cabazitaxel’s affinity for the
ABCB1
/P-glycoprotein (P-gp) transporter compared to first-generation taxanes.
Methods
We determined the kinetics ...of drug accumulation and retention using
14
C-labeled taxanes in multidrug-resistant (MDR) cells. In addition, membrane-enriched fractions isolated from doxorubicin-selected MES-SA/Dx5 cells were used to determine sodium orthovanadate-sensitive ATPase stimulation after exposure to taxanes. Custom
3
H-azido-taxane analogues were synthesized for the photoaffinity labeling of P-gp.
Results
The maximum intracellular drug concentration was achieved faster with
14
C-cabazitaxel (5 min) than
14
C-docetaxel (15–30 min). MDR cells accumulated twice as much cabazitaxel than docetaxel, and these levels could be restored to parental levels in the presence of the P-gp inhibitor PSC-833 (valspodar). Efflux in drug-free medium confirmed that MDR cells retained twice as much cabazitaxel than docetaxel. There was a strong association (
r
2
= 0.91) between the degree of taxane resistance conferred by P-gp expression and the accumulation differences observed with the two taxanes. One cell model expressing low levels of P-gp was not cross-resistant to cabazitaxel while demonstrating modest resistance to docetaxel. Furthermore, there was a 1.9 × reduction in sodium orthovanadate-sensitive ATPase stimulation resulting from treatment with cabazitaxel compared to docetaxel. We calculated a dissociation constant (Kd) value of 1.7 µM for
3
H-azido-docetaxel and ~ 7.5 µM for
3
H-azido-cabazitaxel resulting in a 4.4 × difference in P-gp labeling, and cold docetaxel was a more effective competitor than cabazitaxel.
Conclusion
Our studies confirm that cabazitaxel is more active in
ABCB1
(+) cell models due to its reduced affinity for P-gp compared to docetaxel.
A new type of charged black hole bomb Di Menza, Laurent; Nicolas, Jean-Philippe; Pellen, Mathieu
General relativity and gravitation,
2020/1, Letnik:
52, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Black hole bombs are usually constructed by surrounding an ergoregion by a mirror. The fields propagating between the event horizon and the mirror are prevented from escaping to infinity and ...reflected back to the ergoregion, thus undergoing repeated superradiant scattering which leads to a linear instability. We introduce a new construction in which the field is outside the mirror and is therefore prevented from falling into the black hole but is free to escape to infinity. Provided the mirror is inside the ergoregion, it turns out that this still causes linear instabilities. This behaviour is observed on Reissner–Nordström and de Sitter–Reissner–Nordström backgrounds using numerical simulations, based on a semi-implicit discretisation on a first-order system formulation of the partial differential equations governing the evolution of the scalar field. We also perform simulations for a standard black hole bomb and for another type of contraption: a sandwich black hole bomb.
In grape (Vitis vinifera), abscisic acid (ABA) accumulates during fruit ripening and is thought to play a pivotal role in this process, but the molecular basis of this control is poorly understood. ...This work characterizes ABSCISIC ACTO RESPONSE ELEMENT-BINDING FACTOR2 (VvABF2), a grape basic leucine zipper transcription factor belonging to a phylogenetic subgroup previously shown to be involved in ABA and abiotic stress signaling in other plant species. VvABF2 transcripts mainly accumulated in the berry, from the onset of ripening to the harvesting stage, and were up-regulated by ABA. Microarray analysis of transgenic grape cells overexpressing VvABF2 snowed that this transcription factor up-regulates and/or modifies existing networks related to ABA responses. In addition, grape cells overexpressing VvABF2 exhibited enhanced responses to ABA treatment compared with control cells. Among the VvABF2-mediated responses highlighted in this study, the synthesis of phenolic compounds and cell wall softening were the most strongly affected. WABF2 overexpression strongly increased the accumulation of stilbenes that play a role in plant defense and human health (resveratrol and piceid). In addition, the firmness of fruits from tomato (Solarium lycopersicum) plants overexpressing VvABF2 strongly reduced. These data indicate that VvABF2 is an important transcriptional regulator of ABA-dependent grape berry ripening.
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