A device for a noninvasive evaluation of coronary bypass grafts

A new device is presented for evaluating the patency of coronary bypass grafts. Bypass grafts are located within the chest cavity using a Compton backscatter imaging (CBI) technique that creates frontal plane tomographic images. The tomographic image pixels are mapped into computer memory and displayed. A display pointer is used to mark the position of the bypass graft. The computer uses that information to subsequently position a radiation detector, such that it "looks" at the location of the bypass graft within the closed chest. The patency of the graft is then evaluated by monitoring an X-ray induced iodine fluorescence transient in the graft, subsequent to a peripheral intravenous contrast injection. This imaging and graft evaluation device is relatively inexpensive and its application does not require cutdowns or catheterization. The associated radiation dose is 1/10 to 1/50 of that associated with alternative X-ray graft patency evaluation techniques. Preliminary testing has been performed on mechanical and animal models.     

A second-order analytic solution for oscillatory wind-induced flow in an idealized shallow lake

We present a second-order analytic solution to the nonlinear depth-integrated shallow water equations for free-surface oscillatory wind-driven flow in an idealized lake. Expressing the solution as an asymptotic expansion in the dimensionless wave amplitude (ζ/h), which is considered to be a small parameter, enables simplification of the governing equations and permits the use of a perturbation approach to solve them.This analytic solution provides a benchmark for testing numerical models. In particular, the main merit of this solution is that it accounts for advective effects, which are typically omitted from analytic solutions of two-dimensional free surface flow. In order to retain these effects in an analytic solution, we restrict our attention to forcing from a monochromatic wind stress, consider a constant depth rectangular lake, and simplify the governing equations by omitting the Coriolis and eddy viscosity terms and using a linearised friction factor. As such, the analytic solution is of limited use for considering real world problems. Due to the complexity of the analytic solution computer code for this solution is available online.Our solution is valid for cases where changes in the water surface level are small compared with the depth of the lake, and the advective terms in the momentum equations are small compared with acceleration terms. We examine the validity of these assumptions for three test cases, and compare the second-order analytic solution to numerical results to verify an existing hydrodynamic model.     

Laser Doppler velocimetry with polarization-bistable VCSELs

We present a rate equation model of a single mode vertical-cavity surface-emitting laser (VCSEL) with two states of linear polarization, subject to Doppler-shifted optical feedback. Recent experimental work has shown that the polarization bistability often observed in VCSELs can be exploited to enhance the responsivity of these semiconductor lasers in speed-sensing applications. We review these experimental results briefly and use the rate equation model to explain the increased signal-to-noise ratio.     

Topology adaptive deformable surfaces for medical image volume segmentation

Deformable models, which include deformable contours (the popular snakes) and deformable surfaces, are a powerful model-based medical image analysis technique. We develop a new class of deformable models by formulating deformable surfaces in terms of an affine cell image decomposition (ACID). Our approach significantly extends standard deformable surfaces, while retaining their interactivity and other desirable properties. In particular, the ACID induces an efficient reparameterization mechanism that enables parametric deformable surfaces to evolve into complex geometries, even modifying their topology as necessary. We demonstrate that our new ACID-based deformable surfaces, dubbed T-surfaces, can effectively segment complex anatomic structures from medical volume images.     

Magnetic nanoparticles and nanoparticle assemblies from metallorganic precursors

Magnetic nanoparticles of -Fe₂O₃, Fe₂O₃SiO₂ composite and magnetite Fe₃O₄ have been prepared using novel metallorganic precursors Fe[NC(C₆H₄)C(NSiMe₃)₂]₂Cl, Fe₂[O₂Si(C₆H₅)₂]₃ and [Fe(OBu^t)₃Na(THF)]₂) by hydrolysis, sol-gel condensation and further ultrasound and thermal treatment of the samples. The nanoparticles have been investigated by X-ray powder diffraction, TEM, SEM and AFM.     

Cross-cultural validation of the Inventory of School Motivation (ISM): Motivation Orientations of Navajo and Anglo students

The Motivation Orientation scales of the Inventory of School Motivation (ISM) were validated across Navajo (n = 760) and Anglo (n = 1012) students in the U.S. Confirmatory factor analysis (CFA) supported the 8-factor structure of motivation orientations for the total sample and the Navajo and Anglo subsamples, although Navajo students did not distinguish well between the Effort and Task constructs. However, of 39 survey items, only 30 items were invariant across groups in factor loadings on respective a priori constructs. The findings show that even though the ISM Motivation Orientation scales are applicable to students of different cultural backgrounds, meaningful cross-cultural comparisons should use the 30 items that mean the same to both cultural groups; whereas studies that do not involve cross-cultural comparisons may use the complete version of the scales.     

Multiple feedback effects in asymmetric external cavitysemiconductor lasers

Multiple feedback effects on the output power and spectral characteristics of an external cavity semiconductor laser with asymmetric feedback induced by misalignment of an external mirror are discussed. The external mirror tilt modifies the round-trip phase condition as well as the coupling efficiency. Undulation in power as a function of external mirror tilt have been observed. At particular tilt angles where strong interaction between odd-order round-trip beams and even-order round-trip beams occurs, unique optical spectra featuring double peaks within a compound-cavity mode spectrum or uneven compound-cavity mode spacings have been observed. A quasi-static model for asymmetric external cavity systems explains qualitatively the power undulations and complex spectral characteristics. The model also predicts the existence of two nearby phase-matched mode groups, which may result in complex and chaotic instabilities     

Internal temperature distribution measurements in high powersemiconductor lasers

A novel technique to measure internal temperature distributions within high power semiconductor lasers with substrates transparent to the laser radiation is presented. The temperature resolution is better than 1°C with a spatial resolution of 1-2 μm. The results show highly non-uniform transverse temperature distributions and significant heating close to the facet at high output powers     

Bilateral elastofibroma: a case report and review of the literature

Elastofibroma, or elastofibroma dorsi as it was first described, is an uncommon tumor-like process that characteristically appears as an ill-defined mass in the infrascapular region of elderly patients. This lesion can occur bilaterally and may appear asynchronously. The occurrence of elastofibroma in other anatomic sites has been reported, although with much less frequency. Elastofibromas display typical diagnostic histologic, cytologic, and electron microscopic features. The use of magnetic resonance imaging can lead to a presumptive diagnosis in elderly individuals with suprascapular lesions. It is important to differentiate this lesion from other soft-tissue lesions, such as sarcomas and desmoid tumors. This study presents a case of bilateral elastofibromas in a 72-year-old man and a review of the literature.     

Flared semiconductor laser with integrated resistive heaters for beam control

A split contact high power laser design scheme, incorporating a singlemode and a flared section, is presented. The design can be operated either as a single or a split contact flared resonator. The devices include integrated resistive heaters (IRHs) which allow mode selection and beam control. The use of IRHs, with the laser under CW operation in both configurations, results in improved performance.