Multiphoton microscopes have become important tools for non-contact sub-wavelength three-dimensional nanoprocessing of living biological specimens based on multiphoton ionization and plasma formation. Ultrashort laser pulses are required, however, dispersive effects limit the shortest pulse duration achievable at the focal plane. We report on a compact nonlinear laser scanning microscope with sub-20 femtosecond 75 MHz near infrared laser pulses for nanosurgery of human stem cells and two-photon high-resolution imaging. Single point illumination of the cell membrane was performed to induce a transient nanopore for the delivery of extracellular green fluorescent protein plasmids. Mean powers of less than 7 mW (<93 pJ) and low millisecond exposure times were found to be sufficient to transfect human pancreatic and salivary gland stem cells in these preliminary studies. Ultracompact sub-20 femtosecond laser microscopes may become optical tools for nanobiotechnology and nanomedicine including optical stem cell manipulation.
Novel ultracompact multiphoton. sub-20 femtosecond near infrared 85MHz laser scanning microscopes and conventional 250 fs laser microscopes have been used to perform, high spatial resolution two-photon imaging of stem cell clusters as well, as selective-,int.l.lacellula,r nanoprocessing and knock out of living single stem cells within an 3D microenvironment without any collateral damage. Also lethal, cell exposure of large, parts of cell clusters was successfully probed while maintaining single cells of interest alive. The mew power could be kept in the milliwatt range for 3D nanoprocessing and even in the microwatt range for two-photon imabing. Ultracompact low power sub-20 fs laser systems may becone interesting tools for optical nanobiotechnology such as optical cleaning of stem clusters as well as optical transfection. [GRAPHICS] Optical knock out of a single human pancreatic stem cell without collateral damage
Efficient high-power operation of Cr:LiSAF, Cr:LiSGAF, and Cr:LiCAF lasers pumped by broad-area laser diodes is demonstrated. A maximum slope efficiency of 51 % and output power of 0.55 W was reached at 1.2 W of absorbed pump power, which is the highest output power to date with broad-area laser diode pumping. With the laser design used the onset of thermal quenching in Cr:LiSAF due to high temperatures was pushed to higher pump powers and good mode matching was achieved.
A 6-dimensional grand unified theory with the compact space having the topology of a real projective plane, i.e., a 2-sphere with opposite points identified, is considered. The space is locally flat except for two conical singularities where the curvature is concentrated. One supersymmetry is preserved in the effective 4d theory. The unified gauge symmetry, for example SU(5) , is broken only by the non-trivial global topology. In contrast to the Hosotani mechanism, no adjoint Wilson-line modulus associated with this breaking appears. Since, locally, SU(5) remains a good symmetry everywhere, no UV-sensitive threshold corrections arise and SU(5)-violating local operators are forbidden. Doublettriplet splitting can be addressed in the context of a 6d N = 2 super Yang-Mills theory with gauge group SU(6). If this symmetry is first broken to SU(5) at a fixed point and then further reduced to the standard model group in the above non-local way, the two light Higgs doublets of the MSSM are predicted by the group-theoretical and geometrical structure of the model.
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