Abstract In zebrafish, the formation of primordial germ cells depends on the inheritance of a compartmentalized membrane-less subcellular structure containing a pool of maternally expressed germ plasm ribonucleoparticles (gpRNPs) and proteins. Interactions between cytoskeletal components and gpRNPs are crucial for the movement and collection of gpRNPs into the furrows during the first few cellular division of the early embryo. Previous work has identified motley/ birc5b , a maternally-expressed homolog of a known Chromosomal Passenger Complex (CPC) component, Survivin, as a linker between gpRNPs and microtubules during gpRNP aggregation. However, Survivin can also function independent of the CPC in other cellular contexts. Here we investigated whether a maternally inherited CPC is necessary for gpRNP aggregation. We identified cdca9 as a maternally-expressed duplicated homolog of Borealin, another member of the CPC. Similar to motley , embryos from homozygous cdca9 mutant females exhibit defects in chromosome segregation and cytokinesis during meiosis and mitosis, phenotypes associated with mutations in CPC members. Additionally, embryos lacking Cdca9 displayed decreased gpRNP aggregation prior to furrow formation in the early embryo, a phenotype indistinguishable from that observed in motley mutants. As previously shown for Birc5b, Cdca9 and other CPC components INCENP and Aurora B kinase colocalize at the tips of astral microtubules as gpRNPs are transported to the forming furrow. Unexpectedly, Birc5b, but not other CPC components, accumulates within the growing gpRNP aggregate prior to and during furrow formation. The association of Birc5b with germ plasm masses continues during their asymmetric segregation in the cleavage stages, ceasing only when gpRNPs undergo cytoplasmic dispersal during gastrulation. Our studies reveal a role for a non-conventional, maternally-inherited CPC for spindle and furrow formation, and, unexpectedly, gpRNP aggregation during early development. Additionally, we find that Birc5b, but not other CPC proteins, remains a component of zebrafish germ plasm during and after its aggregation. Author Summary Maternal products are necessary for early development across species, and the removal of these products from the embryo can cause developmental defects or death. The zebrafish has been widely used to discover the role of maternal products during early development. Using zebrafish, we discovered that a mutation in a maternal-specific duplicated borealin gene not only affects early development but also the aggregation of germ cell determinants. We also find that this duplicated Borealin interacts within a specialized Chromosomal Passenger Complex, a complex that traditionally regulates multiple steps of cellular division. This specialized Chromosomal Passenger Complex acts as a linker between germ cell determinants and the cytoskeleton during early development. These results highlight a unique role for the Chromosomal Passenger Complex outside of cellular division during early development. Further, these findings underscore the intricate mechanisms by which gene duplications contribute to the regulation of early developmental processes, providing valuable insight into the molecular events of embryogenesis.
In this work, the behavior of magnetohydrodynamic waves in optically thin plasmas considering dissipative processes, thermal and magnetic diffusion, a given ionization, and the heating and cooling functions are investigated for several particular cases. A numerical eigenvalues analysis of the dimensionless secular equations according to various cases is performed for the entire set of MHD equations.
The proof of the Jacobi property of the guiding-center Vlasov-Maxwell bracket underlying the Hamiltonian structure of the guiding-center Vlasov-Maxwell equations is presented.
Daniel Faraco, Sauli Lindberg, David MacTaggart
et al.
In this Letter we extend the proof, by Faraco and Lindberg, of Taylor's conjecture in multiply connected domains to cover arbitrary vector potentials and remove the need to impose conditions on the magnetic field due to gauge invariance. This extension allows us to treat general magnetic fields in closed domains that are important in laboratory plasmas and brings closure to a problem that has been open for almost 50 years.
A recent paper by A.~Z.~Janda [J.~Math.~Phys.~{\bf 59}, 061509 (2018)] presented a partial solution of the equations of dissipationless Hall magnetohydrodynamics (MHD) in terms of the Weierstrass elliptic function. Unfortunately, an error crept up in the analysis, where the kinetic and potential energies of the initial Hall MHD state were misidentified. The present comment presents the correct energy analysis and offers a complete solution of dissipationless Hall magnetohydrodynamics in terms of the Jacobi elliptic functions.
Telegraph equation describing the compression of electromagnetic waves in a waveguide (resonator) with moving boundary are derived. It is shown that the character of oscillations of the compressed electromagnetic field depends on the parameters of the resonator, and under certain conditions, the oscillations of voltage (current) yield the exponential growth, leading to a noticeable change in the radiation losses.
A microscopic model in the framework of fractional kinetics to describe spatial dispersion of power-law type is suggested. The Liouville equation with the Caputo fractional derivatives is used to obtain the power-law dependence of the absolute permittivity on the wave vector. The fractional differential equations for electrostatic potential in the media with power-law spatial dispersion are derived. The particular solutions of these equations for the electric potential of point charge in this media are considered.
A 2+1-dimensional anisentropic magnetogasdynamic system with a polytropic gas law is shown to admit an integrable elliptic vortex reduction when $γ=2$ to a nonlinear dynamical subsystem with underlying integrable Hamiltonian-Ermakov structure. Exact solutions of the magnetogasdynamic system are thereby obtained which describe a rotating elliptic plasma cylinder. The semi-axes of the elliptical cross-section, remarkably, satisfy a Ermakov-Ray-Reid system.
Formulas for calculation of transversal dielectric function and transversal electric conductivity in quantum non-degenerate collisional plasmas under arbitrary degree of degeneracy of the electron gas are received. The Wigner-Vlasov-Boltzmann kinetic equation with collision integral in BGK (Bhatnagar, Gross and Krook) form in coordinate space is used. Various special cases are investigated
The linearized problem of plasma oscillations in layer (particularly, in thin films) in external longitudinal alternating electric field is solved analytically. Specular - accommodative boundary conditions of electron reflection from the plasma boundary are considered. Coefficients of continuous and discrete spectra of the problem are found, and electron distribution function on the plasma boundary and electric field are expressed in explicit form. Absorption of energy of electric field in layer is calculated.
In the present paper the linearized problem of half-space plasma oscillations in external longitudinal alternating electric field is solved analytically. Specular - accommodative boundary conditions of electron reflection from the plasma boundary are considered. Coefficients of continuous and discrete spectra of the problem are found, and electron distribution function on the plasma boundary and electric field are expressed in explicit form.
For the first time it is shown that for thin metallic films thickness of which not exceed thickness of skin -- layer, the problem of description of surface plasma oscillations allows analytical solution by arbitrary ratio between length of electrons free path and thickness of a film. The dependance of frequency surface plasma oscillations on wave number is carry out.
We discuss the fundamentals of the implicit moment method for Particle In Cell (PIC) simulation as presently implemented in the CELESTE3D code. We present the method in its fully electromagnetic and fully kinetic version. The application of the method is to problems with multiple temporal and spatial scales, common in all space, astrophysical and laboratory plasmas.
We investigate the structure of magnetic field amplified by turbulent velocity fluctuations, in the framework of the kinematic Kazantsev-Kraichnan model. We consider Kolmogorov distribution of velocity fluctuations, and assume that both Reynolds number and magnetic Reynolds number are very large. We present the full numerical solution of the model for the spectra and the growth rates of magnetic fluctuations. We consider astrophysically relevant limits of large and small magnetic Prandtl numbers, and address both helical and nonhelical cases.
In the precleavage zygote of Tubifex, pole plasm, which is yolk‐free cytoplasm, is located at the animal and vegetal poles. The present study describes the fate and localization pattern of the pole plasms in embryonic development of Tubifex. The process of pole plasm localization during cleavage stages is comprised of three steps. The first step is asymmetric segregation which results in bipolar localization of pole plasm masses in the D‐cell of the 4‐cell embryo. The spatial organization of pole plasm at this stage depends on F‐actin but not on microtubules. The second step is the redistribution of the vegetal pole plasm toward the animal pole and its unification with the animal pole plasm. These give rise to localization of unified pole plasm at the animal side (i.e. future dorsal side of the embryo) of the D‐quadrant. The polarized redistribution is sensitive to colchicine and topographically related to the mitotic apparatus located at the animal pole of the D‐cell. Electron microscopy shows the association with astral microtubules of constituents of pole plasm, suggesting the involvement of astral microtubules in cytoplasmic movement which gives rise to redistribution. In addition, centrifuge experiments suggest that the directional information for this polarized redistribution may be provided by some cytoplasmic organizations which are resistant to centrifugal force. The last step of the localization process is partitioning of unified pole plasm into two micromeres 2d and 4d. The spatial organization of pole plasm at this stage depends on microtubules but not on F‐actin.
AbstractGerm plasm is a cluster of fibrogranular bodies present in the cytoplasm of oocytes and incorporated into a few cells during early embryogenesis. These cells become the precursors to primordial germ cells, the founders of the germ cell lineage. Germ cell‐fate determinants associated with the germ plasm specify that the cells in which they reside shall become primordial germ cells.
It is shown that the turbulent dynamo $α$-effect converts magnetic helicity from the turbulent field to the mean field when the turbulence is electromagnetic while the magnetic helicity of the mean-field is transported across space when the turbulence is electrostatic or due to the electron diamagnetic effect. In all cases, however, the dynamo effect strictly conserves the total helicity except for resistive effects and a small battery effect. Implications for astrophysical situations, especially for the solar dynamo, are discussed.
We develop a series expansion of the plasma screening length away from the classical limit in powers of $\hbar^{2}$. It is shown that the leading order quantum correction increases the screening length in solar conditions by approximately 2% while it decreases the fusion rate by approximately $ 0.34%$. We also calculate the next higher order quantum correction which turns out to be approximately 0.05%.
We consider the parametric excitation of a Langmuir wave and an electromagnetic wave by gravitational radiation, in a thin plasma on a Minkowski background. We calculate the coupling coefficients starting from a kinetic description, and the growth rate of the instability is found. The Manley-Rowe relations are fulfilled only in the limit of a cold plasma. As a consequence, it is generally difficult to view the process quantum mechanically, i.e. as the decay of a graviton into a photon and a plasmon. Finally we discuss the relevance of our investigation to realistic physical situations.