Nonlinear underwater propagation of picosecond ultraviolet laser beams.

Meter-scale nonlinear propagation of a picosecond ultraviolet laser beam in water, sufficiently intense to cause stimulated Raman scattering (SRS), nonlinear focusing, pump-Stokes nonlinear coupling, and photoexcitation, was characterized in experiments and simulations. Pump and SRS Stokes pulse energies were measured, and pump beam profiles were imaged at propagation distances up to 100 cm for a range of laser power below and above self-focusing critical power. Simulations with conduction band excitation energy UCB=9.5eV, effective electron mass meff=0.2me, Kerr nonlinear refractive index n2=5×10-16cm2/W, and index contribution due to SRS susceptibility n2r=1.7×10-16cm2/W produced the best agreement with experimental data.

Postnatal neuro-development of fetuses with absent end-diastolic flow in the umbilical artery and/or fetal descending aorta.

OBJECTIVE: To determine whether absence of end-diastolic flow in the umbilical artery and/or fetal aorta impacts postnatal neuro-development in preterm-born children. METHODS: The study group, consisting of 43 fetuses with absent end-diastolic flow in the umbilical artery and/or fetal aorta, was compared with a control group, consisting of 30 fetuses, matching for gestational age but with normal doppler-flow results. The children's neuro-developmental status was assessed using the 'Munich functional developmental diagnostics' (MFDD), between the 2nd and 3rd year of life. RESULTS: Gestational age at birth was 33 + 6 weeks in the study group and 34 + 4 weeks in the control group. A brain-sparing effect was observed in 37.3% of fetuses in the study group compared with 10.0% in the control group (p = 0.014). For all seven MFDD domains, the number of children with deficiencies was higher in the study group. For the domains perception, active speech and comprehension this effect was statistically significant (p < 0.05). Overall, 30.2% of children in the study group and 16.7% of the control group had pathologic test results (p < 0.013). CONCLUSION: Pathological doppler-flow in the umbilical artery and/or fetal descending aorta in preterm born children is associated with neuro-developmental deficiencies. Intensive pediatric care is recommended to mitigate these deficiencies during early childhood.

Local preconditioning by thermal stress accelerates microvascular thrombus formation.

Heme oxygenase 1 (HO-1) has been shown to suppress microvascular thrombus formation. Because stress conditioning induces HO-1 and, in addition, the anticoagulant thrombomodulin and thrombospondin 1, we studied the effect of hyperthermic and hypothermic local stress conditioning on microvascular thrombus formation. For local stress conditioning, the hindlimb of Sprague-Dawley rats was subjected to local heating (42.5 degrees C) or cooling (4 degrees C) for 30 min at 24 h before induction of thrombosis. Sham-exposed hindlimbs served as controls. Thrombosis was induced photochemically in arterioles and venules of the preconditioned tissue (muscle, subcutis, and periosteum) by continuous light exposure after injection of a fluorescent dye. Immunohistochemistry revealed that stress conditioning distinctly induced HO-1, thrombomodulin, and thrombospondin 1 but also von Willebrand factor in endothelial cells. Of interest, intravital fluorescence microscopic analysis of the kinetics of thrombus formation could not confirm an antithrombotic effect of stress conditioning but showed, in contrast, a significant acceleration of thrombosis (P < 0.05) in both arterioles and venules of either of the tissues studied. Although hypothermic and hyperthermic stress conditioning induces antithrombotic HO-1, thrombomodulin, and thrombospondin 1, it enhances endogenous thrombogenicity, most probably due to upregulation of the prothrombotic von Willebrand factor. Thus, preconditioning with local stress cannot be considered as a strategy to prevent thrombus formation.