30,907 research outputs found
Translational aspects of cardiac cell therapy.
Cell therapy has been intensely studied for over a decade as a potential treatment for ischaemic heart disease. While initial trials using skeletal myoblasts, bone marrow cells and peripheral blood stem cells showed promise in improving cardiac function, benefits were found to be short-lived likely related to limited survival and engraftment of the delivered cells. The discovery of putative cardiac 'progenitor' cells as well as the creation of induced pluripotent stem cells has led to the delivery of cells potentially capable of electromechanical integration into existing tissue. An alternative strategy involving either direct reprogramming of endogenous cardiac fibroblasts or stimulation of resident cardiomyocytes to regenerate new myocytes can potentially overcome the limitations of exogenous cell delivery. Complimentary approaches utilizing combination cell therapy and bioengineering techniques may be necessary to provide the proper milieu for clinically significant regeneration. Clinical trials employing bone marrow cells, mesenchymal stem cells and cardiac progenitor cells have demonstrated safety of catheter based cell delivery, with suggestion of limited improvement in ventricular function and reduction in infarct size. Ongoing trials are investigating potential benefits to outcome such as morbidity and mortality. These and future trials will clarify the optimal cell types and delivery conditions for therapeutic effect
Magic Doping Fractions in High-Temperature Superconductors
We report hole-doping dependence of the in-plane resistivity \rho_{ab} in a
cuprate superconductor La_{2-x}Sr_{x}CuO_{4}, carefully examined using a series
of high-quality single crystals. Our detailed measurements find a tendency
towards charge ordering at particular rational hole doping fractions of 1/16,
3/32, 1/8, and 3/16. This observation appears to suggest a specific form of
charge order and is most consistent with the recent theoretical prediction of
the checkerboard-type ordering of the Cooper pairs at rational doping fractions
x = (2m+1)/2^n, with integers m and n.Comment: 5 pages, 3 figure, resubmitted to Phys. Rev. Lett. The Tc vs. x
diagram has been added and the discussions have been modified to focus more
on the experimental result
Pair Density Wave in the Pseudogap State of High Temperature Superconductors
Recent scanning tunneling microscopy (STM) experiments of
BiSrCaCuO have shown evidence of real-space
organization of electronic states at low energies in the pseudogap state. We
argue based on symmetry considerations as well as model calculations that the
experimentally observed modulations are due to a density wave of d-wave
Cooper-pairs without global phase coherence. We show that STM measurements can
distinguish a pair-density-wave from more typical electronic modulations such
as those due to charge density wave ordering or scattering from an onsite
periodic potential.Comment: 4 pages, 4 figures. Final version. PRL 93, 187002 (2004
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