Combined conjugate and pupil adaptive optics in widefield microscopy

Traditionally, adaptive optics (AO) systems for microscopy have focused on AO at the pupil plane, however this produces poor performance in samples with both spatially-variant aberrations, such as non-flat sample interfaces, and spatially-invariant aberrations, such as spherical aberration due to a difference between the sample index of refraction and the sample for which the objective was designed. Here, we demonstrate well-corrected, wide field-of-view (FOV) microscopy by simultaneously correcting the two types of aberrations using two AO loops. Such an approach is necessary in wide-field applications where both types of aberration may be present, as each AO loop can only fully correct one type of aberration. Wide FOV corrections are demonstrated in a trans-illumination microscope equipped with two deformable mirrors (DMs), using a partitioned aperture wavefront (PAW) sensor to directly control the DM conjugated to the sample interface and a sensor-less genetic algorithm to control the DM conjugated to the objective’s pupil

Computation of the modes and polar moment of inertial of the blades of an HAWT

The coupled differential equations of motion of the blades of a horizontal axis wind turbine are solved numerically, permitting the optimization of the design at relatively low cost. The equation of motion is transformed into a set of first order equations and solved with fourth order Runge-Kutta integrators. This technique is applied to a twisted, tapered blade of variable cross section and stiffness including discontinuities. The first six natural frequencies and mode shapes are obtained. The polar moment of inertia of the blades is obtained as a function of frequency and rotational speed

Microlensing planet detection via geosynchronous and low Earth orbit satellites

Planet detection through microlensing is usually limited by a well-known degeneracy in the Einstein timescale $t_E$, which prevents mass and distance of the lens to be univocally determined. It has been shown that a satellite in geosynchronous orbit could provide masses and distances for most standard planetary events ($t_E \approx 20$ days) via a microlens parallax measurement. This paper extends the analysis to shorter Einstein timescales, $t_E \approx 1$ day, when dealing with the case of Jupiter-mass lenses. We then study the capabilities of a low Earth orbit satellite on even shorter timescales, $t_E \approx 0.1$ days. A Fisher matrix analysis is employed to predict how the 1-$\sigma$ error on parallax depends on $t_E$ and the peak magnification of the microlensing event. It is shown that a geosynchronous satellite could detect parallaxes for Jupiter-mass free floaters and discover planetary systems around very low-mass brown dwarfs. Moreover, a low Earth orbit satellite could lead to the discovery of Earth-mass free-floating planets. Limitations to these results can be the strong requirements on the photometry, the effects of blending, and in the case of the low orbit, the Earth's umbra.Comment: 5 pages, 3 figures. Minor language edits. Accepted for publication in Astronomy & Astrophysic

Financial Characteristics of Acquired Firms in the Canadian Food Industry

Mergers and acquisitions represent an important reallocation of resources. In 1998, the value of these transactions jumped to almost $160 billion in Canada. The motives for firms to merge or acquire other firms change for different periods and industries. This study provides a financial profile of Canadian corporations in the food industry that were acquired during the 1996-98 period. Overall, acquired firms did not represent a significant share of the total sales of incorporated Canadian food firms. Firms with balanced (or matched) growth-resources, less liquidity and leverage were more likely to be acquired in 1997 and 1998. Large firms with matched growth resources were also more likely to be taken over.Agribusiness,

Intensive Livestock Farming: Does Farm Size Matter?

Farm Management, Livestock Production/Industries,