Magnetic fields at the periphery of UCHII regions from carbon recombination line observations

Several indirect evidences indicate a magnetic origin for the non-thermal width of spectral lines observed toward molecular clouds. In this letter, I suggest that the origin of the non-thermal width of carbon recombination lines (CRLs) observed from photo-dissociation regions (PDRs) near ultra-compact \HII\ regions is magnetic and that the magnitude of the line width is an estimate of the \alfven speed. The magnetic field strengths estimated based on this suggestion compare well with those measured toward molecular clouds with densities similar to PDR densities. I conclude that multi-frequency CRL observations have the potential to form a new tool to determine the field strength near star forming regions.Comment: To appear in ApJ Letter

LIS1 RNA interference blocks neural stem cell division, morphogenesis, and motility at multiple stages

Mutations in the human LIS1 gene cause the smooth brain disease classical lissencephaly. To understand the underlying mechanisms, we conducted in situ live cell imaging analysis of LIS1 function throughout the entire radial migration pathway. In utero electroporation of LIS1 small interference RNA and short hairpin dominant negative LIS1 and dynactin cDNAs caused a dramatic accumulation of multipolar progenitor cells within the subventricular zone of embryonic rat brains. This effect resulted from a complete failure in progression from the multipolar to the migratory bipolar state, as revealed by time-lapse analysis of brain slices. Surprisingly, interkinetic nuclear oscillations in the radial glial progenitors were also abolished, as were cell divisions at the ventricular surface. Those few bipolar cells that reached the intermediate zone also exhibited a complete block in somal translocation, although, remarkably, process extension persisted. Finally, axonal growth also ceased. These results identify multiple distinct and novel roles for LIS1 in nucleokinesis and process dynamics and suggest that nuclear position controls neural progenitor cell division

Gravito-magnetic amplification in cosmology

Magnetic fields interact with gravitational waves in various ways. We consider the coupling between the Weyl and the Maxwell fields in cosmology and study the effects of the former on the latter. The approach is fully analytical and the results are gauge-invariant. We show that the nature and the outcome of the gravito-magnetic interaction depends on the electric properties of the cosmic medium. When the conductivity is high, gravitational waves reduce the standard (adiabatic) decay rate of the B-field, leading to its superadiabatic amplification. In poorly conductive environments, on the other hand, Weyl-curvature distortions can result into the resonant amplification of large-scale cosmological magnetic fields. Driven by the gravitational waves, these B-fields oscillate with an amplitude that is found to diverge when the wavelengths of the two sources coincide. We present technical and physical aspects of the gravito-magnetic interaction and discuss its potential implications.Comment: Typos corrected, clarifications added, published in PR

Acid-Labile Traceless Click Linker for Protein Transduction

Intracellular delivery of active proteins presents an interesting approach in research and therapy. We created a protein transduction shuttle based on a new traceless click linker that combines the advantages of click reactions with implementation of reversible pH-sensitive bonds. The azidomethyl-methylmaleic anhydride (AzMMMan) linker was found compatible with different click chemistries, demonstrated in bioreversible protein modification with dyes, polyethylene glycol, or a transduction carrier. Linkages were stable at physiological pH but reversible at the mild acidic pH of endosomes or lysosomes. We show that pH-reversible attachment of a defined endosome-destabilizing three-arm oligo(ethane amino)amide carrier generates an effective shuttle for protein delivery. The cargo protein nlsEGFP, when coupled via the traceless AzMMMan linker, experiences efficient cellular uptake and endosomal escape into the cytosol, followed by import into the nucleus. In contrast, irreversible linkage to the same shuttle hampers nuclear delivery of nlsEGFP which after uptake remains trapped in the cytosol. Successful intracellular delivery of bioactive ß-galactosidase as a model enzyme was also demonstrated using the pH-controlled shuttle system

Neutralinos and the Origin of Radio Halos in Clusters of Galaxies

We assume that the supersymmetric lightest neutralino is a good candidate for the CDM and explore the possibility to produce diffuse radio emission from high-energy electrons arising from the neutralino annihilation in galaxy clusters whose intracluster medium is filled with a large-scale magnetic field. We show that these electrons fit the population of seed relativistic electrons postulated in many models for the origin of cluster radio halos. For magnetic fields with central values $3 \div 30$ $\mu$G (depending on the DM profile), the population of seed relativistic electrons from neutralino annihilation can fit the radio halo spectra of Coma and 1E0657-56. The shape and the frequency extension of the radio halo spectra are connected with the mass and physical composition of the neutralino. A pure-gaugino neutralino with mass $M_{\chi} \geq 80$ GeV can reasonably fit the spectra of both Coma and 1E0657-56. This model provides a number of extra predictions that make it definitely testable. On the one hand, it agrees with the observations that {\it (i)} the radio halo is centered on the cluster dynamical center, usually coincident with the X-ray center, {\it (ii)} the radio halo surface brightness is similar to the X-ray one, and {\it (iii)} the monochromatic radio luminosity at 1.4 GHz correlates strongly with the IC gas temperature. On the other hand, the model predicts that radio halos should be present in every cluster, which is not actually observed, although the predicted radio halo luminosities can change by a large amount ($\sim 10^2 \div 10^6$), depending on the amplitude and the structure of the IC magnetic field. Also, neutral pions arising from neutralino annihilation should give rise to substantial gamma-ray emission that could be tested by the next generation gamma-ray experiments.Comment: 49 pages, 11 Figures, Latex (using epsfig), submitted to The Astrophysical Journal. submitted to The Astrophysical Journa