Matrix continued fractions are directly related to the maximal (A, B)-invariant subspace in KerC

The maximal(A, B)-invariant subspace in KerCis characterized in terms of polynomial models, by its properties pertaining to the Hankel map. This characterization is directly related to the first stage in a continued fraction representation of the transfer function. The atoms of the continued fraction are given explicitly in terms of Tocplitz operators. We also obtain a complete characterization and parametrization of eligible first-atoms, based on Weiner-Hopf indexes. We show how to construct a first atom which is column proper and determines a feedback equivalent, feedback irreducible transfer function.     

On-the-fly Curve-skeleton Computation for 3D Shapes

The curve-skeleton of a 3D object is an abstract geometrical and topological representation of its 3D shape. It maps the spatial relation of geometrically meaningful parts to a graph structure. Each arc of this graph represents a part of the object with roughly constant diameter or thickness, and approximates its centerline. This makes the curve-skeleton suitable to describe and handle articulated objects such as characters for animation. We present an algorithm to extract such a skeleton on-the-fly, both from point clouds and polygonal meshes. The algorithm is based on a deformable model evolution that captures the object's volumetric shape. The deformable model involves multiple competing fronts which evolve inside the object in a coarse-to-fine manner. We first track these fronts' centers, and then merge and filter the resulting arcs to obtain a curve-skeleton of the object. The process inherits the robustness of the reconstruction technique, being able to cope with noisy input, intricate geometry and complex topology. It creates a natural segmentation of the object and computes a center curve for each segment while maintaining a full correspondence between the skeleton and the boundary of the object.     

Tunable, oblique incidence resonant grating filter for telecommunications

We have designed a tunable, oblique-incidence resonant grating filter that covers the C band as an add-drop device for incident TE-polarized light. We tune the filter by tilting a microelectromechanical systems platform onto which the filter is attached. The fabrication tolerances as well as the role of finite incident-beam size and limited device size were addressed. The maximum achievable efficiency of a finite-area device as well as a scaling law that relates the resonance peak width and the minimum device size is derived. In good agreement with simulations, measurements indicate a negligible change in shape of the resonance peak from 1526 nm at a 45 degrees angle of incidence to 1573 nm at a 53 degrees angle with a full width at half-maximum of 0.4 nm. In this range the shift of the peak wavelength is linear with respect to changes in the angle of incidence.     

Microstructural evolution of gold–aluminum wire-bonds

The purpose of this study is to understand the morphological changes that occur during annealing of Al–Au wire-bonds, by analyzing the interface region of annealed model wire-bonded samples between 5N (99.999%) Au wires and Al pads. Due to the small length scale of the intermetallic region at the interface of the bond, the analysis was done using scanning/transmission electron microscopy combined with energy dispersive spectroscopy. Samples were prepared using a dual-beam focused ion beam system. Microstructural characterization showed that during annealing, a Au-rich intermetallic region was formed under the bond and at the periphery of the bond. Two types of failures occurred during annealing: crack formation at the bond periphery due to an increase in volume during intermetallic growth and the formation of stresses; and oxidation of the AlAu₄ phase adjacent to the Au ball, which resulted in the formation of continuous cracks between the Au ball and the intermetallic region. The characteristic void-line found inside the intermetallic region played no part in failure that occurred during exposure to elevated temperatures.     

Does the transition to parenthood influence driving?

Most parents remember the first time they drove with a newborn child in the car. Feeling the need to protect the infant, they avoided sharp turns and drove more slowly and carefully than normal. But how long do these behaviors persist? Do parents ultimately revert to their previous driving patterns, or does some of the early protectiveness and caution continue to characterize their driving as their infant grows into a toddler and preschooler? In an attempt to answer these questions, two studies were conducted on parents of young children: a qualitative study consisting of personal interviews (16 parents); and a quantitative study in the form of a national telephone survey (165 parents). The results show that the most dominant reported effect of the transition to parenthood on driving is increased apprehension of traffic crashes and a stronger sense of responsibility. However, these changes were found to influence the reported actual driving behavior of only a portion of the parents. Possible explanations of the findings are discussed.     

Engineering nanostructured porous SiO2 surfaces for bacteria detection via "direct cell capture"

An optical label-free biosensing platform for bacteria detection ( Escherichia coli K12 as a model system) based on nanostructured oxidized porous silicon (PSiO(2)) is introduced. The biosensor is designed to directly capture the target bacteria cells on its surface with no prior sample processing (such as cell lysis). The optical reflectivity spectrum of the PSiO(2) nanostructure displays Fabry-Pe?rot fringes characteristic of thin-film interference, enabling direct, real-time observation of bacteria attachment within minutes. The PSiO(2) optical nanostructure is synthesized and used as the optical transducer element. The porous surface is conjugated with specific monoclonal antibodies (immunoglobulin G's) to provide the active component of the biosensor. The immobilization of the antibodies onto the biosensor system is confirmed by attenuated total reflectance Fourier transform infrared spectroscopy, fluorescent labeling experiments, and refractive interferometric Fourier transform spectroscopy. We show that the immobilized antibodies maintain their immunoactivity and specificity when attached to the sensor surface. Exposure of these nanostructures to the target bacteria results in "direct cell capture" onto the biosensor surface. These specific binding events induce predictable changes in the thin-film optical interference spectrum of the biosensor. Our preliminary studies demonstrate the applicability of these biosensors for the detection of low bacterial concentrations. The current detection limit of E. coli K12 bacteria is 10(4) cells/mL within several minutes.     

Selection of dark modes in resonators with conical reflectors

Selection of modes containing different dark regions was studied in resonators with conical reflectors. The possibility of selecting whole subgroups of such modes was shown in circularly symmetric resonators. To handle single-mode selection employing extra intracavity spatial filters, modified integral equations and a numerical method of their analysis are proposed. Usage of the filter symmetry reduces the size of the four-dimensional matrices corresponding to the equation kernels, and they are analyzed by algorithms for two-dimensional matrices with the best convergence. The optimum resonator parameters for effective selection of different dark modes are found.