Measuring fluorescence into a nanofiber by observing field quadrature noise

We perform balanced homodyne detection of the electromagnetic field in a single-mode tapered optical nanofiber surrounded by rubidium atoms in a magneto-optical trap. Resonant fluorescence of atoms into the nanofiber mode manifests itself as increased quantum noise of the field quadratures. The autocorrelation function of the homodyne detector's output photocurrent exhibits exponential fall-off with a decay time constant of $26.3\pm 0.6$ ns, which is consistent with the theoretical expectation under our experimental conditions. To our knowledge, this is the first experiment in which fluorescence has been observed and measured by balanced optical homodyne detection

Discrete Routh Reduction

This paper develops the theory of abelian Routh reduction for discrete mechanical systems and applies it to the variational integration of mechanical systems with abelian symmetry. The reduction of variational Runge-Kutta discretizations is considered, as well as the extent to which symmetry reduction and discretization commute. These reduced methods allow the direct simulation of dynamical features such as relative equilibria and relative periodic orbits that can be obscured or difficult to identify in the unreduced dynamics. The methods are demonstrated for the dynamics of an Earth orbiting satellite with a non-spherical $J_2$ correction, as well as the double spherical pendulum. The $J_2$ problem is interesting because in the unreduced picture, geometric phases inherent in the model and those due to numerical discretization can be hard to distinguish, but this issue does not appear in the reduced algorithm, where one can directly observe interesting dynamical structures in the reduced phase space (the cotangent bundle of shape space), in which the geometric phases have been removed. The main feature of the double spherical pendulum example is that it has a nontrivial magnetic term in its reduced symplectic form. Our method is still efficient as it can directly handle the essential non-canonical nature of the symplectic structure. In contrast, a traditional symplectic method for canonical systems could require repeated coordinate changes if one is evoking Darboux' theorem to transform the symplectic structure into canonical form, thereby incurring additional computational cost. Our method allows one to design reduced symplectic integrators in a natural way, despite the noncanonical nature of the symplectic structure.Comment: 24 pages, 7 figures, numerous minor improvements, references added, fixed typo

Effects of proteins on the permeability of monolayers of cultured bovine arterial endothelium.

1. Monolayers of arterial endothelium on porous membranes were exposed to a pressure of 15 cmH2O at 37 degrees C, or of 30 cmH2O at 0 degree C. At constant pressure, the rate of liquid flow per unit area (Jv/A) through each monolayer decreased with time, in the way previously described for cultured endothelium. This phenomenon has been called sealing. After Jv/A stabilized, the pressure was reduced and the hydraulic permeability (Lp) of the endothelium was calculated from the relationship between Jv/A and pressure. Endothelium was seen to be damaged after some experiments at 37 degrees C, but appeared undamaged after experiments at 0 degree C. 2. Bovine serum albumin (BSA) did not influence the Lp of cultured endothelium. At 37 degrees C, the mean (+/- S.E.M.) endothelial Lp was 47.2 +/- 7.3 x 10(-7) cm s-1 cmH2O-1 (n = 10) in the presence of BSA (5 g (100 ml)-1). This is not significantly different from the mean (+/- S.E.M.) Lp of 53.4 +/- 9.0 x 10(-7) cm s-1 cmH2O-1 (n = 9) in the absence of added protein (P greater than 0.10). At 0 degree C also, there was no significant difference between mean Lps in the presence of BSA (0.1 g (100 ml)-1) and in the absence of added protein. 3. Solutions of BSA (5 g (100 ml)-1 or of the neutral polymer Ficoll 70 (4 g (100 ml)-1) did not exert any effective osmotic pressure across endothelium at 37 or 0 degrees C, respectively. 4. BSA (0.1 g (100 ml)-1) did not enable solutions of Ficoll 70 (4 g (100 ml)-1) to exert an effective osmotic pressure across endothelium at 0 degree C. 5. The mean Lp of endothelium at 0 degree C was significantly lower in the presence of cationized ferritin (CF; 0.1 g (100 ml)-1) than in the absence of added protein (P less than 0.001). Native ferritin (NF; 0.1 g (100 ml)-1) had no effect on Lp. 6. In the presence of CF (0.1 g (100 ml)-1), solutions of Ficoll 70 (4 g (100 ml)-1) exerted a mean effective osmotic pressure of 27.7 cmH2O (n = 5) across endothelium at 0 degree C. The mean effective osmotic pressure exerted across endothelium by solutions of Ficoll 70 (4 g (100 ml)-1) plus NF (0.1 g (100 ml)-1) was 1.2 cmH2O (n = 4)