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Abstract Direct imaging of supermassive black holes (SMBHs) at event horizon-scale resolutions, as recently done by the Event Horizon Telescope, allows for testing alternative models to SMBHs such as Kerr naked singularities (KNSs). We demonstrate that the KNS shadow can be closed, open, or vanishing, depending on the spins and observational inclination angles. We study the critical parameters where the KNS shadow opens a gap, a distinctive phenomenon that does not happen with the black hole shadow. We show that the KNS shadow can only be closed for dimensionless spina≲ 1.18 and vanishing fora≳ 1.18 for certain ranges of inclination angles. We further analyze the effective angular momentum of photon orbits to demonstrate the fundamental connections between light geodesics and the KNS shadow geometry. We also perform numerical general relativistic ray-tracing calculations, which reproduce the analytical topological change in the KNS shadow, and illustrate other observational features within the shadow due to the lack of an event horizon. By comparing the geometric features of the KNS shadow with black hole shadow observations, the topological change in the shadow of KNSs can be used to test the cosmic censorship hypothesis and KNSs as alternative models to SMBHs. 

Chromatin is an essential component of nuclear mechanical response and shape that maintains nuclear compartmentalization and function. However, major genomic functions, such as transcription activity, might also impact cell nuclear shape via blebbing and rupture through their effects on chromatin structure and dynamics. To test this idea, we inhibited transcription with several RNA polymerase II inhibitors in wild type cells and perturbed cells that present increased nuclear blebbing. Transcription inhibition suppresses nuclear blebbing for several cell types, nuclear perturbations, and transcription inhibitors. Furthermore, transcription inhibition suppresses nuclear bleb formation, bleb stabilization, and bleb-based nuclear ruptures. Interestingly, transcription inhibition does not alter either H3K9 histone modification state, nuclear rigidity, or actin compression and contraction, which typically control nuclear blebbing. Polymer simulations suggest that RNA pol II motor activity within chromatin could drive chromatin motions that deform the nuclear periphery. Our data provide evidence that transcription inhibition suppresses nuclear blebbing and rupture, separate and distinct from chromatin rigidity. 

Abstract With the well‐documented chemical and biological applications, piperidine and pyridine are among the most important N‐heterocycles, and a new synthetic strategy, especially one with an alternative bond‐forming design, is of general interest. Using the gold‐catalyzed intermolecular condensation of amine and diyne‐ene, we report herein the first example of enantioselective 1,2‐dihydropyridine synthesis through a formal [3+2+1] fashion (up to 95 % yield, up to 99 % e.e.).