A chemical genetics approach reveals H,K-ATPase-mediated membrane voltage is required for planarian head regeneration

Biophysical signaling is required for both embryonic polarity and regenerative outgrowth. Exploiting endogenous ion transport for regenerative therapies will require direct regulation of membrane voltage. Here, we develop a pharmacological method to target ion transporters, uncovering a role for membrane voltage as a key regulator of anterior polarity in regenerating planaria. Utilizing the highly specific inhibitor, SCH-28080, our data reveal that H(+),K(+)-ATPase-mediated membrane depolarization is essential for anterior gene expression and brain induction. H(+),K(+)-ATPase-independent manipulation of membrane potential with ivermectin confirms that depolarization drives head formation, even at?posterior-facing wounds. Using this chemical genetics approach, we demonstrate that membrane voltage controls head-versus-tail identity during planarian regeneration. Our data suggest well-characterized drugs (already approved for human use) might be exploited to control adult stem cell-driven pattern formation during the regeneration of complex structures.     

PAT – a Reliable Path-Following Algorithm

This paper presents a new technique for the reliable computation of the -pseudospectrum defined by (A)={zC : _min(A–zI)} where _min is the smallest singular value. The proposed algorithm builds an orbit of adjacent equilateral triangles to capture the level curve (A)={zC : _min(A–zI)=} and uses a bisection procedure on specific triangle vertices to compute a numerical approximation to . The method is guaranteed to terminate, even in the presence of round-off errors.     

Thermal evolution and light curves of young bare strange stars

We study numerically the cooling of a young bare strange star and show that its thermal luminosity, mostly due to e(+)e(-) pair production from the quark surface, may be much higher than the Eddington limit. The mean energy of photons far from the strange star is approximately 10(2) keV or even more. This differs both qualitatively and quantitatively from the thermal emission from neutron stars and provides a definite observational signature for bare strange stars. It is shown that the energy gap of superconducting quark matter may be estimated from the light curves if it is in the range from approximately 0.5 MeV to a few MeV.     

Rotations of Periodic Strings and Short Superstrings

This paper presents two simple approximation algorithms for the shortest superstring problem with approximation ratios 2 ( ≈ 2.67) and( ≈ 2.596). The framework of our improved algorithms is similar to that of previous algorithms in the sense that they construct a superstring by computing some optimal cycle covers on the distance graph of the given strings and then break and merge the cycles to finally obtain a Hamiltonian path, but we make use of new bounds on the overlap between two strings. We prove that for each periodic semiinfinite string α = a₁a₂··· of periodq, there exists an integerk, such that forany(finite) stringsof periodpwhich isinequivalentto α, the overlap betweensand therotationα[k] = a_ka_{k + 1}··· is at mostp + q. Moreover, ifp ≤ q, then the overlap betweensand α[k] is not larger than (p + q). The bounds are tight. In the previous shortest superstring algorithmsp + qwas used as the standard (tight) bound on overlap between two strings with periodspandq.     

Dynamics of Synthetic Membraneless Organelles in Microfluidic Droplets

Cells can form membraneless organelles by liquid–liquid phase separation. As these organelles are highly dynamic, it is crucial to understand the kinetics of these phase transitions. Here, we use droplet‐based microfluidics to mix reagents by chaotic advection and observe nucleation, growth, and coarsening in volumes comparable to cells (pL) and on timescales of seconds. We apply this platform to analyze the dynamics of synthetic organelles formed by the DEAD‐box ATPase Dhh1 and RNA, which are associated with the formation of processing bodies in yeast. We show that the timescale of phase separation decreases linearly as the volume of the compartment increases. Moreover, the synthetic organelles coarsen into one single droplet via gravity‐induced coalescence, which can be arrested by introducing a hydrogel matrix that mimics the cytoskeleton. This approach is an attractive platform to investigate the dynamics of compartmentalization in artificial cells.     

Reply to the Letter-to-the-editor written by J. J. Bevelacqua and S. M. J. Mortazavi on: “Radon survey in the kindergartens of three Visegrad countries (Hungary,Poland and Slovakia)” (DOI 10.1007/s10967-018-6374-3)

Journal of Radioanalytical and Nuclear Chemistry - An IAEA coordinated research project that began in 2012 and ended in 2016 was primarily dedicated to the compilation, evaluation and...     

Structural study of the Li(0.5)Na(0.5)MnFe2(PO4)3 and Li(0.75)Na(0.25)MnFe2(PO4)3 alluaudite phases and their electrochemical properties as positive electrodes in lithium batteries

The alluaudite lithiated phases Li(0.5)Na(0.5)MnFe(2)(PO(4))(3) and Li(0.75)Na(0.25)MnFe(2)(PO(4))(3) were prepared via a sol-gel synthesis, leading to powders with spongy characteristics. The Rietveld refinement of the X-ray and neutron diffraction data coupled with ab initio calculations allowed us for the first time to accurately localize the lithium ions in the alluaudite structure. Actually, the lithium ions are localized in the A(1) and A(1)' sites of the tunnel. M?ssbauer measurements showed the presence of some Fe(2+) that decreased with increasing Li content. Neutron diffraction revealed the presence of a partial Mn/Fe exchange between the two transition metal sites that shows clearly that the oxidation state of the element is fixed by the type of occupied site. The electrochemical properties of the two phases were studied as positive electrodes in lithium batteries in the 4.5-1.5 V potential window, but they exhibit smaller electrochemical reversible capacity compared with the non-lithiated NaMnFe(2)(PO(4))(3). The possibility of Na(+)/Li(+) ion deintercalation from (Na,Li)MnFe(2)(PO(4))(3) was also investigated by DFT+U calculations.