Fugitive Diffusion Barrier for Integration of Sol-Gel-Derived Lead Titanate with Oxidized Silicon Substrates

The crystalline phase development and microstructural changes with heating of sol-gel-derived lead titanate (PT) particles and films on silica with and without a fugitive (or removable) diffusion barrier layer were investigated. Amorphous gel-derived PT particles were deposited on SiO₂-coated TEM grids with and without polyimide (PI) or carbon barrier layers between SiO₂ and PT. TEM analysis showed that PI or carbon barriers prevented reaction between the gel-derived PT particles and SiO₂. PT particles crystallize and then the PI or carbon film decomposes. Sol-gel-derived PT films were deposited on oxidized Si substrates (Si/SiO₂) with and without a PI barrier layer. Perovskite PT films were prepared on Si/SiO₂ substrates with a PI barrier; however, some porosity remained in the films. Identically prepared films without the PI barrier formed a mixture of pyrochlore and perovskite. X-ray photoelectron spectroscopy results indicate that the PI film pre- vents the diffusion of Si into the PT film.     

Bending and torsional fatigue of nylon 66 monofilaments

Using newly developed test equipment, the fatigue behavior of nylon 66 monofilaments was studied under two loading conditions, pure bending or simple torsion. For each mode, results are expressed in terms of the measured decay in stiffness with numbers of cycles over a range of maximum applied strain levels. Fatigue lifetimes are presented in S–N format where the log number of cycles of fatigue for a 40% decay in stiffness (N) is plotted as a function of applied strain (S). The failure mechanism for these fibers in each fatigue mode reflects the morphology of semicrystalline-oriented synthetic fibers. In torsion, many longitudinal cracks form around the perimeter of a fiber as the result of cleavage of the relatively weak interfibrillar bonds in nylon 66. In bending, cracks form within kink band boundaries and grow at an oblique angle to the fiber axis. © 1992 John Wiley & Sons, Inc.     

Opposite phenotypes of hypomorphic and Y766 phosphorylation site mutations reveal a function for Fgfr1 in anteroposterior patterning of mouse embryos

Intercellular communication is needed for both the generation of the mesodermal germ layer and its division into distinct subpopulations. To dissect the functions of fibroblast growth factor receptor-1 (FGFR1) during mouse gastrulation as well as to gain insights into its possible roles during later embryonic development, we have introduced specific mutations into the Fgfr1 locus by gene targeting. Our results show functional dominance of one of the receptor isoforms and suggest a function for the autophosphorylation of site Y766 in the negative regulation of FGFR1 activity. Y766F and hypomorphic mutations in Fgfr1 generate opposite phenotypes in terms of homeotic vertebral transformations, suggesting a role for FGFR1 in patterning the embryonic anteriorposterior axis by way of regulation of Hox gene activity.     

Metastatic carcinoma of the prostate mimicking primary carcinoid tumor of the lung and mediastinum

AIMS: To investigate the current use of thrombolytic therapy in the management of patients with acute myocardial infarction and to determine the potential for an increased use of thrombolysis or percutaneous transluminal coronary angioplasty (PTCA). METHODS AND RESULTS: All hospitalised cases of acute myocardial infarction were identified in three health districts in the UK (population of 960,000) in patients under the age of 76 years during a 2-year period; 2439 patients had acute myocardial infarction, of whom 1264 (52%) received thrombolytic therapy. Failure to administer thrombolytic therapy was a result of the absence of diagnostic electrocardiograms in 712 (29.2%) patients, late presentation in 127 (5.2%), therapeutic error in 112 (4.6%), presence of a bleeding risk in 139 (5.7%) and other miscellaneous reasons in 80 (3.3%) patients. Thirty-eight of the 139 patients in whom bleeding risk was reported as a contra-indication could, in retrospect, have received thrombolytic therapy and a further 76 would have been suitable for primary PTCA. CONCLUSIONS: The potential for increasing the use of thrombolytic therapy seems to be limited and is unlikely to make a major impact on the in-hospital mortality from acute myocardial infarction. However, primary PTCA should be considered in those who are ineligible for thrombolysis because of bleeding risk as a contra-indication.     

Keratoacanthoma

The keratoacanthoma is a common cutaneous neoplasm that most often occurs on sun-exposed sites in light-skinned persons of middle age or older. It is considered the prototype of cutaneous pseudo-malignancies because it is a rapidly growing tumor with a histologic pattern resembling squamous cell carcinoma. It may be best viewed as an aborted malignancy that only rarely progresses into an invasive squamous cell carcinoma. It is most likely derived from hair follicle cells. The common type of keratoacanthoma and its many variants are discussed with emphasis on clinical and histologic features, biologic behavior, and response to therapy.     

The Mona Lisa identification: Evidence from a computer analysis

A recent computer-aided study identified the model immortalized in Leonardo da Vinci's celebratedMona Lisa to be none other than the artist himself. A follow-up investigation empolying similar techniques identifies the subject of asecond HiddenMona Lisa by the same artist. Analysis of photographic and x-ray images indicates that Leonardo first created a sketch of Isabella, Duchess of Aragon, which he later painted over with theMona Lisa, using himself as the model.     

A method for quantitative display of three-dimensional regional myocardial function

The DSR (dynamic spatial reconstructor), a multiple X-ray source scanner that generates stop action three-dimensional (3-D) images of a cylindrical volume, was used for quantitative imaging of left ventricular 3-D wall geometry and function in experimentally induced canine left ventricular myocardial infarction. Impaired regional myocardial function was induced by myocardial ischemia or infarction in four mongrel dogs by closed-chest occlusion of the proximal left anterior descending (LAD) coronary artery. At intervals of 6-14 weeks post occlusion, the dogs were scanned with the DSR during biatrial contrast injection. The 3-D shape, extent, and function of hypokinetic myocardium was measured from the DSR images utilizing measurement of the rate of local systolic wall thickening to detect regions of normal, ischemic, or scarred myocardium. The results were compared to scar size and anatomic distribution measured at postmortem examination. The anatomic extent and relationship of hypocontractile to normally contracting muscle was visualized by computer generated, pseudo 3-D shaded surface displays of the left ventricular chamber and by topographic projections of regional wall thickening rates onto a map of the left ventricular endocardial surface. The location of myocardial infarction and the surrounding zone of impaired function is clearly defined by this 3-D CT scanning procedure. The display method presented here provides both localization and quantification of the volume of ischemic and infarcted myocardium.     

Electrodeposition of Fe−Ni−Co alloys part I: Direct current deposition

Effects of hydrodynamic conditions, current density and solution temperature on the d.c. electrodeposition of Fe–Ni–Co alloys have been investigated with stationary planar and rotating cylindrical electrodes. The deposition rate of Fe showed mass transfer effects at cathodic potentials –1.35 V/sce. Deposition of Ni appeared to be kinetically controlled; deposition of Co appeared to be under kinetic control at potentials –1.35 V/sce but under mixed control at –1.65 V. Current efficiency of the codeposition process increased with increasing current density and decreased with increasing rotation rate. Higher solution temperatures and rotation rates extended the applied current density range where smooth, adherent, and metallic-looking deposits could be obtained. An increase in solution temperatures also decreased anomalous codeposition of Fe–Ni–Co. Calculations based on the Hessami-Tobias model provide qualitative agreement with dependence of experimental electrodeposition on applied current density, hydrodynamics and temperature.