Diagnosis and treatment of aortic valve stenosis

The present review has attempted to summarize the classic symptoms and signs of aortic valve stenosis, especially in an adult. It is emphasized that all the classic signs rarely are present and their absence may mislead an unwary clinician. The diagnostic help provided by noninvasive tests, including echocardiography and phonocardiography, has been emphasized. A need for cardiac catheterization and angiography in most patients prior to corrective surgery is stressed. The natural history of the disease without operative intervention is dim and a significant risk of sudden death exists. The current surgical approach with immediate and long-term results is summarized. Finally, attention has been drawn to the special clinical circumstances when the aortic valve stenosis provides a strinkingly different clinical picture. We cannot find a better way to end this review than by quoting a warning note given by Thomas Lewis in 1920: "It is the faint cry of an anguished and fast failing muscle, which, when it comes, all should strain to hear, for it is not long repeated. A few months, a few years at most, and the end comes."     

Wear of filled and unfilled dental restorative resins

The influence of double-pass sliding on the surface failure of filled and unfilled dental restorative resins was evaluated. Damage was more severe for double-pass than for single-pass sliding. Wear of restorative resins and composites was influenced by the resistance to penetration and by the mode of deformation during sliding.     

A microcomputer-based system for stereogrammetric analysis

A system for the quantitative analysis of stereo-pairs of photomicrographs has been devised using a Commodore ‘PET’ microcomputer coupled to a digitizing pad, plotter and printer. The system need not use any form of stereo-viewer and does not require any particular alignment of the photographs. Height differences, derived from parallax measurements, can be obtained quickly even by operators who might normally experience difficulties with stereoscope-based systems due to either poor stereo vision or inexperience. Three-dimensional coordinates, input from point-pairs, are stored inside the computer and may be sorted to draw line profiles along any operator-selected line. Such profiles may be referred to either the projection of the median plane of the two images or rotated (‘levelled’) to the 0° tilt plane. The operation of the system is described and illustrated using both specially-constructed left- and right-hand ‘images’ from test contours and also real SEM stereo pairs. Finally, both the potential and limitations of such a system for development and application are discussed.     

Life stress and treatment course of recurrent depression: II. Postrecovery associations with attrition, symptom course, and recurrence over 3 years.

Life stress was studied in relation to postrecovery attrition, symptom course, and recurrence of depression over 3 yrs. Participants were 67 individuals with recurrent depression who had responded to treatment. Life stress was assessed for the prior 12 wks at acute treatment entry (T1), initial recovery (T2), and after 17 wks of sustained recovery (T3). Severe life events at T1 predicted greater attrition, a more favorable postrecovery symptom course, and a lower likelihood of recurrence over 3 yrs. Life stress at T2 was not predictive of outcomes. Finally, undesirable life events at T3 tended to predict a worse symptom course and a higher likelihood of recurrence, particularly for individuals on medication. The findings are discussed in terms of (a) different processes influenced by life stress over time and (b) limitations of existing longitudinal research for studying the effects of life stress over prolonged intervals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of normal alcohols on the abrasive wear of glass

Normal alcohols were used as cutting fluids in a study of friction and wear of soda lime silicate glass against silicon carbide. Abrasion surfaces were 600 grit silicon carbide paper and a roughened plate of hot-pressed silicon carbide. As the alcohol chain length increased, the coefficient of friction decreased. This result was attributed in part to better lubrication of the abrading surfaces by the long chain length alcohols. The wear rate and the coefficient of friction were strongly dependent on pullout of carbide grains from the silicon carbide paper. Wear on fresh abrasive paper was independent of alcohol chain length. As the paper becomes used, long chain length alcohols were more effective cutting fluids. On the silicon carbide plate, the wear rate decreased in a non-linear fashion as the alcohol chain length increased. For all conditions, the highest wear rate and coefficient of friction were obtained in water. Data are explained in terms of classical theories of friction and wear.     

Model-updated image guidance: initial clinical experiences with gravity-induced brain deformation

Image-guided neurosurgery relies on accurate registration of the patient, the preoperative image series, and the surgical instruments in the same coordinate space. Recent clinical reports have documented the magnitude of gravity-induced brain deformation in the operating room and suggest these levels of tissue motion may compromise the integrity of such systems. We are investigating a model-based strategy which exploits the wealth of readily-available preoperative information in conjunction with intraoperatively acquired data to construct and drive a three dimensional (3-D) computational model which estimates volumetric displacements in order to update the neuronavigational image set. Using model calculations, the preoperative image database can be deformed to generate a more accurate representation of the surgical focus during an operation. In this paper, we present a preliminary study of four patients that experienced substantial brain deformation from gravity and correlate cortical shift measurements with model predictions. Additionally, we illustrate our image deforming algorithm and demonstrate that preoperative image resolution is maintained. Results over the four cases show that the brain shifted, on average, 5.7 mm in the direction of gravity and that model predictions could reduce this misregistration error to an average of 1.2 mm.     

Chromatic dispersion and bandshape improvement of SOI flatband AWG multi/demultiplexers by phase-error correction

By measuring the phase and amplitude distribution of the optical paths in a flatband arrayed waveguide grating, the array mask was redesigned to correct for the slow varying phase errors within the array waveguides, leading to a reduction in both the chromatic dispersion across the passband of the device and in the transmission band tilt.     

A generalization of intermediate transfer function analysis to arbitrary linear networks

This paper is concerned with the generalization of the intermediate transfer function analysis method, proposed in [1] for state-space filter circuits, to arbitrary continuous-time linear networks. This analysis technique involves the intermediate step of calculating a set of intermediate transfer functions (IFs) that can in turn be used to compute any desired transfer function, various sensitivity functions, output noise power spectral densities, harmonic and intermodulation distortion products (when the network contains quasilinear, or weakly nonlinear, elements), and various other linear network attributes. The salient feature of this approach is that all computations can be carried out in symbolic form, thus highlighting the interrelationship of the various network attributes.1. This work is not intended to compete with SPICE but rather help one better understand the behavior of circuits with the aid of a special set of transfer functions.2. No attempt to measure the input-referred noise current was made because its value is expected to be beyond our measuring capabilities.     

18-42 GHz experimental verification of microstrip coupler and openend capacitance models

A cavity resonance technique is used to experimentally verify microstrip coupler and open end capacitance models over the frequency range of 18-42 GHz. In addition, these results are confirmed using an alternate version of the technique which directly determines open end discontinuity capacitance. In the second case, knowledge of substrate dielectric constant is not required, and the method also yields the microstrip relative effective dielectric constant