Nucleophagy contributes to genome stability though TOP2cc and nucleolar components degradation

ABSTRACTThe nuclear architecture of mammalian cells can be altered as a consequence of anomalous accumulation of nuclear proteins or genomic alterations. Most of the knowledge about nuclear dynamics comes from studies on cancerous cells. How normal, healthy cells maintain genome stability avoiding accumulation of nuclear damaged material is less understood. Here we describe that primary mouse embryonic fibroblasts develop a basal level of nuclear buds and micronuclei, which increase after Etoposide-induced DNA Double-Stranded Breaks. These nuclear buds and micronuclei co-localize with autophagic proteins BECN1 and LC3 and with acidic vesicles, suggesting their clearance by nucleophagy. Some of the nuclear alterations also contain autophagic proteins and Type II DNA Topoisomerases (TOP2A and TOP2B), or nucleolar protein Fibrillarin, implying they are also targets of nucleophagy. We propose that a basal nucleophagy contributes to genome and nuclear stability and also in response to DNA damage and nucleolar stress.

Radioactivity and Nuclear Reactions

Radioactivity and Nuclear Reactions gives an overview of nuclear chemistry with emphasis on radioactive decay, binding energy and nuclear stability. Modes of radioactive decay are discussed, along with writing and balancing nuclear equations. Decay modes covered include alpha emission, beta emission, gamma emission, positron emission, and electron capture, along with a summary of how each type of decay process affects the parent radioisotope and determines the daughter isotope formed. Nuclear transmutation induced by changes in the nuclei is discussed. The chapter covers the kinetics of radioactive decay including the relationship between the half-lives of radioisotopes and radioisotopic dating. The chapter concludes with a quantitative coverage of the energy of nuclear reactions including the interconversion of mass and energy via the mass defect.

Binary and Ternary Fragmentation Analysis of 252Cf Nucleus using Different Nuclear Radii

Pioneering study reveals that a radioactive nucleus may split into two or three fragments and the phenomena are known as binary fission and ternary fission respectively. In order to understand the nuclear stability and related structure aspects, it is of huge interest to explore the fragmentation behavior of a radioactive nucleus in binary and ternary decay modes. In view of this, Binary and ternary fission analysis of 252Cf nucleus is carried out using quantum mechanical fragmentation theory (QMFT). The nuclear potential and Coulomb potential are estimated using different versions of radius vector. The fragmentation structure is found to be independent to the choice of fragment radius for binary as wellas ternary decay paths. The deformation effect is included up to quadrupole (β2) with optimum cold orientations and their influence is explored within binary splitting mode. Moreover, the most probable fission channels explore the role of magic shell effects in binary and ternary fission modes.

No paradox here? Improving theory and testing of the nuclear stability–instability paradox with synthetic counterfactuals

This article contributes to both the theoretical elaboration and empirical testing of the ‘stability–instability paradox’, the proposition that while nuclear weapons deter nuclear war, they also increase conventional conflict among nuclear-armed states. Some recent research has found support for the paradox, but quantitative studies tend to pool all international dyads while qualitative and theoretical studies focus almost exclusively on the USA–USSR and India–Pakistan dyads. This article argues that existing empirical tests lack clearly relevant counterfactual cases, and are vulnerable to a number of inferential problems, including selection on the dependent variable, unintentionally biased inference, and extrapolation from irrelevant cases. The limited evidentiary base coincides with a lack of consideration of the theoretical conditions under which the paradox might apply. To address these issues this article theorizes some scope conditions for the paradox. It then applies synthetic control, a quantitative method for valid comparison when appropriate counterfactual cases are lacking, to model international conflict between India–Pakistan, China–India, and North Korea–USA, before and after nuclearization. The article finds only limited support for the paradox when considered as a general theory, or within the theorized scope conditions based on the balance of resolve and power within each dyad.

Nuclear Structure and Stability Arise from Alternating Quarks within Light Nuclei

<div> <div> <p>The atomic nucleus is made of protons and neutrons, each comprising a mix of 3 up or down quarks. No consensus exists for nuclear structure from among the 30+ proposed models of the atomic nucleus, although they generally agree that quarks play no role. The light nuclides of interest to nuclear fusion exist in a purgatory of uncertainty, wanting not only for structure but also for some insight into their erratic sizes. The deuterium nucleus is twice the mass of the proton but 2.5 times larger. In fact, deuterium is larger than either tritium or helium-4. The lithium-7 nucleus is larger than all of these, yet smaller than lithium-6. Here we show that an alternating quark model (AQM) predicts these erratic nuclear radii to within 99% of experimental (SD 2.5%). The distance between sequential quarks is constant and equal to the radius of the proton. Quark structures assume simple geometries. Alternating quarks predict nuclear stability, the height of the Coulomb barrier, near-range attraction, and far-range repulsion. Through the lens of nonlinear dynamics, quarks behave as linked harmonic oscillators traveling within a basin of attraction. This satisfies the uncertainty principle while allowing localization of an average quark position. The alternating quark model thus represents an intersection between chaos theory and quantum mechanical uncertainty.<br></p> </div> </div>

A possible shortcut for neutron–antineutron oscillation through mirror world

Existing bounds on the neutron-antineutron mass mixing, $$\epsilon _{n{\bar{n}}} < \mathrm{few} \times 10^{-24}$$ ϵ n n ¯ < few × 10 - 24 eV, impose a severe upper limit on $$n - {\bar{n}}$$ n - n ¯ transition probability, $$P_{n{\bar{n}}}(t) < (t/0.1 ~\mathrm{s})^2 \times 10^{-18}$$ P n n ¯ ( t ) < ( t / 0.1 s ) 2 × 10 - 18 or so, where t is the neutron flight time. Here we propose a new mechanism of $$n- {\bar{n}}$$ n - n ¯ transition which is not induced by direct mass mixing $$\epsilon _{n{\bar{n}}}$$ ϵ n n ¯ but is mediated instead by the neutron mass mixings with the hypothetical states of mirror neutron $$n'$$ n ′ and mirror antineutron $${{\overline{n}}} '$$ n ¯ ′ . The latter can be as large as $$\epsilon _{nn'}, \epsilon _{n\bar{n}'} \sim 10^{-15}$$ ϵ n n ′ , ϵ n n ¯ ′ ∼ 10 - 15 eV or so, without contradicting present experimental limits and nuclear stability bounds. The probabilities of $$n-n'$$ n - n ′ and $$n-\bar{n}'$$ n - n ¯ ′ transitions, $$P_{nn'}$$ P n n ′ and $$P_{n\bar{n}'}$$ P n n ¯ ′ , depend on environmental conditions in mirror sector, and they can be resonantly amplified by applying the magnetic field of the proper value. This opens up a possibility of $$n-{\bar{n}}$$ n - n ¯ transition with the probability $$P_{n{\bar{n}}} \simeq P_{nn'} P_{n\bar{n}'}$$ P n n ¯ ≃ P n n ′ P n n ¯ ′ which can reach the values $$\sim 10^{-8} $$ ∼ 10 - 8 or even larger. For finding this effect in real experiments, the magnetic field should not be suppressed but properly varied. These mixings can be induced by new physics at the scale of few TeV which may also originate a new low scale co-baryogenesis mechanism between ordinary and mirror sectors.