7,083 research outputs found
Protein transduction: A novel tool for tissue regeneration
Tissue regeneration in humans is limited and excludes vitals organs like heart and brain. Transformation experiments with oncogenes like T antigen have shown that retrodifferentiation of the respective cells is possible but hard to control. To bypass the risk of cancer formation a protein therapy approach has been developed. The transient delivery of proteins rather than genes could still induce terminallydifferentiated cells to reenter the cell cycle. This approach takes advantage of proteintransducing domains that mediate the transfer of cargo proteins into cells. The goal of this brief review is to outline the basics of protein transduction and to discuss potential applications for tissue regeneration
Nearly Massless Electrons in the Silicon Interface with a Metal Film
We demonstrate the realization of nearly massless electrons in the most
widely used device material, silicon, at the interface with a metal film. Using
angle-resolved photoemission, we found that the surface band of a monolayer
lead film drives a hole band of the Si inversion layer formed at the interface
with the film to have nearly linear dispersion with an effective mass about 20
times lighter than bulk Si and comparable to graphene. The reduction of mass
can be accounted for by repulsive interaction between neighboring bands of the
metal film and Si substrate. Our result suggests a promising way to take
advantage of massless carriers in silicon-based thin-film devices, which can
also be applied for various other semiconductor devices.Comment: 4 pages, 4 figures, accepted for publication in Physical Review
Letter
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Irreversibility at macromolecular scales in the flake graphite of the lithium-ion battery anode.
Charging a commercial lithium-ion battery intercalates lithium into the graphite-based anode, creating various lithium carbide structures. Despite their economic importance, these structures and the dynamics of their charging-discharging transitions are not well-understood. We have videoed single microcrystals of high-quality, natural graphite undergoing multiple lithiation-delithiation cycles. Because the equilibrium lithium-carbide compounds corresponding to full, half, and one-third charge are gold, red, and blue respectively, video observations give direct insight into both the macromolecular structures and the kinematics of charging and discharging. We find that the transport during the first lithiation is slow and orderly, and follows the core-shell or shrinking annuli model with phase boundaries moving at constant velocities (i.e. non-diffusively). Subsequent lithiations are markedly different, showing transport that is both faster and disorderly, which indicates that the initially pristine graphite is irreversibly and considerably altered during the first cycle. In all cases deintercalation is not the time-reverse of intercalation. These findings both illustrate how lithium enters nearly defect-free host material, and highlight the differences between the idealized case and an actual, cycling graphite anode
On black hole masses, radio-loudness and bulge luminosities of Seyfert galaxies
We estimated black hole masses for 9 Seyfert 1 and 13 Seyfert 2 galaxies in
the Palomar and CfA bright Seyfert samples using the tight correlation between
black hole mass and bulge velocity dispersion. Combining other 13 Seyfert 1s
and 2 Seyfert 2s in these samples but with black hole masses measured recently
by reverberation mapping and stellar/gas dynamics, we studied the correlations
of black hole masses with radio loudness and bulge luminosities for a sample of
37 Seyfert galaxies. We found that if radio-loudness is measured using the
optical and radio luminosities of the nuclear components, the black hole masses
of radio-loud Seyfert 1s tend to increase with the radio-loudness. The black
hole masses of all Seyfert galaxies increase with the radio power, but Seyfert
galaxies have larger radio powers than nearby galaxies with the same black hole
masses. In addition, the correlation between black hole masses and bulge V-band
luminosities for Seyfert galaxies is consistent with that found for quasars and
normal galaxies. The combined sample of 37 Seyfert galaxies, 15 quasars and 30
normal galaxies suggests a possible universal nonlinear relation between black
hole and bulge masses, , which is
slightly steeper than that found recently by Laor (2001) for a smaller sample.
This nonlinear relation is supported by a larger sample including 65 Seyfert
galaxies. The different M(BH)/M(bulge) ratio for galaxies with different bulge
luminosities or different black hole masses may be explained by this relation.
These results are consistent with some theoretical implications and are
important for understanding the nature of radio emissions and the formation and
evolution of supermassive black holes and galaxies.Comment: 10 pages, A&A accepte
Far-Ultraviolet Cooling Features of the Antlia Supernova Remnant
We present far-ultraviolet observations of the Antlia supernova remnant
obtained with Far-ultraviolet IMaging Spectrograph (FIMS, also called SPEAR).
The strongest lines observed are C IV 1548,1551 and C III 977. The C IV
emission of this mixed-morphology supernova remnant shows a clumpy
distribution, and the line intensity is nearly constant with radius. The C III
977 line, though too weak to be mapped over the whole remnant, is shown to vary
radially. The line intensity peaks at about half the radius, and drops at the
edge of the remnant. Both the clumpy distribution of C IV and the rise in the C
IV to C III ratio towards the edge suggest that central emission is from
evaporating cloudlets rather than thermal conduction in a more uniform, dense
medium.Comment: 9 pages, 4 figures, will be published in ApJ December 1, 2007, v670n2
issue. see http://astro.snu.ac.kr/~jhshinn/ms.pd
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