Postoperative complications of penetrating keratoplasty in herpes infected eyes. Differential diagnosis, therapy and prognostic significance

BACKGROUND: We evaluated in this retrospective study the impact of our diagnostic and therapeutic regimens--as illustrated by typical clinical pictures--on the frequency and prognostic values of postkeratoplasty complications in herpes eyes. PATIENTS AND METHODS: Between November 1986 and June 1994, 112 penetrating keratoplasties (KPS) in herpes eyes were performed, 76 as planned and 36 as emergency procedures. The results were compared with 646 KPS with normal risk. For statistical analysis we used the Kaplan-Meier estimation, and statistical significance was tested by the log rank test. RESULTS: After 6 years, 75% of the grafts in the planned herpes group, 86% of the à chaud KPS and 76% of the grafts of the normal-risk group were still clear without significant differences between these three groups. Fifty-four percent of the planned KPS in herpes eyes, 73% of the à chaud KPS in herpes eyes and 80% of the normal-risk KPS experienced no immune reaction, with both herpes groups showing significantly more reactions than the normal-risk KPS. There was, however, no significant difference in immune reactions between the two herpes groups. The percentage of grafts with recurrence of herpes simplex virus infection after 6 years was significantly higher in the à chaud group. CONCLUSIONS: With proper postoperative care and optimal management of immunologic and virologic complications--but only with this!--the prognosis of penetrating keratoplasties in herpes eyes equals that of normal risk eyes. An particular, the prognosis is not dependent on whether surgery was performed as a planned or as an emergency procedure.     

Spline‐Interpolation and Calculation of Machine Parameters for the Three‐Roll‐Pushbending of Spline‐Contours

Today, bending tasks become more and more complex. Not even constant bending radii are required in the industrial practice. There is a growing demand for bending spline‐contours, too. Such geometries are often produced with Freeform‐Bending procedures like Three‐Roll‐Pushbending. This paper presents a method to interpolate a given spline bending‐contour (by CAD data), in order to calculate its radii distribution, which is needed to determine the machine parameters in certain points for the Three‐Roll‐Pushbending. For the determination of the machine parameters one has to consider the different influences on the bending process. The material springback and the deflection of the bending machine per radius need to be compensated to reach a near net shape bending result. Nevertheless deviations cannot be avoided. To improve the results, a possibility to adjust the pre‐calculated machine parameters is shown. For the investigations tube profiles with constant wall thicknesses were considered. The corresponding plasticity calculations refer to tube cross‐sections. The results were validated by bending a representative spline contour on the bending machine of the Chair of Forming Technology at the University of Siegen.     

Optimizing main-memory join on modern hardware

In the past decade, the exponential growth in commodity CPU's speed has far outpaced advances in memory latency. A second trend is that CPU performance advances are not only brought by increased clock rates, but also by increasing parallelism inside the CPU. Current database systems have not yet adapted to these trends and show poor utilization of both CPU and memory resources on current hardware. In this paper, we show how these resources can be optimized for large joins and translate these insights into guidelines for future database architectures, encompassing data structures, algorithms, cost modeling and implementation. In particular, we discuss how vertically fragmented data structures optimize cache performance on sequential data access. On the algorithmic side, we refine the partitioned hash-join with a new partitioning algorithm called "radix-cluster", which is specifically designed to optimize memory access. The performance of this algorithm is quantified using a detailed analytical model that incorporates memory access costs in terms of a limited number of parameters, such as cache sizes and miss penalties. We also present a calibration tool that extracts such parameters automatically from any computer hardware. The accuracy of our models is proven by exhaustive experiments conducted with the Monet database system on three different hardware platforms. Finally, we investigate the effect of implementation techniques that optimize CPU resource usage. Our experiments show that large joins can be accelerated almost an order of magnitude on modern RISC hardware when both memory and CPU resources are optimized     

Correlation of esophageal conductance measurements with aortic and left ventricular diameters and stroke volume

Esophageal conductance measurements were correlated with hemodynamic events in 9 dogs chronically instrumented for measurement of left ventricular (LV) and aortic pressures, LV short axis and descending aortic diameters, and aortic blood flow. A four-electrode conductance catheter was positioned in the esophagus. Both an internal and an internal/external configuration were examined during anesthesia with hemodilution, pulmonary lavage and dobutamine infusion. LV stroke volume was altered by caval occlusion at each intervention. Stroke conductance was highly correlated to aortic or LV diameters and stroke volume over a range of diameters depending on the electrode configuration. Esophageal conductance measurements are directly influenced by local hemodynamic events adjacent to the site of measurement.     

Three-dimensional trace element analysis by confocal X-ray microfluorescence imaging

A three-dimensional (3D) variant of scanning micro X-ray fluorescence (XRF) is described and evaluated at the ID18F instrument of the European Synchrotron Radiation Facility (ESRF). The method is based on confocal excitation/detection using a polycapillary half-lens in front of the energy-dispersive detector. The experimental arrangement represents a significant generalization of regular two-dimensional (2D) scanning micro-XRF and employs a detector half-lens whose focus coincides with that of the focused incoming beam. The detection volume defined by the intersection of the exciting beam and the energy-dependent acceptance of the polycapillary optics is 100-350 mum(3). Minimum detection limits are sub-ppm, and sensitivities are comparable with regular scanning XRF. Next to the reduction of in-sample single/multiple scattering, the setup provides the possibility of sample depth scans with an energy-dependent resolution of 10-35 mum in the energy range of 3-23 keV and the possibility of performing 3D-XRF analysis by simple XYZ linear scanning. This provides a suitable alternative to X-ray fluorescence tomography. The method is illustrated with results of the analysis of solid inclusions in diamond and fluid inclusions in quartz.     

A Bayesian framework for automated cardiovascular risk scoring on standard lumbar radiographs

We present a fully automated framework for scoring a patient's risk of cardiovascular disease (CVD) and mortality from a standard lateral radiograph of the lumbar aorta. The framework segments abdominal aortic calcifications for computing a CVD risk score and performs a survival analysis to validate the score. Since the aorta is invisible on X-ray images, its position is reasoned from 1) the shape and location of the lumbar vertebrae and 2) the location, shape, and orientation of potential calcifications. The proposed framework follows the principle of Bayesian inference, which has several advantages in the complex task of segmenting aortic calcifications. Bayesian modeling allows us to compute CVD risk scores conditioned on the seen calcifications by formulating distributions, dependencies, and constraints on the unknown parameters. We evaluate the framework on two datasets consisting of 351 and 462 standard lumbar radiographs, respectively. Promising results indicate that the framework has potential applications in diagnosis, treatment planning, and the study of drug effects related to CVD.     

Perfusion of ischemic myocardium during anesthesia with sevoflurane

BACKGROUND: Sevoflurane produces direct vasodilation of coronary arteries in vitro and decreases coronary vascular resistance in vivo, pharmacologic properties that may contribute to the development of "coronary steal." This investigation examined the effects of sevoflurane on the distribution of regional myocardial perfusion in chronically instrumented dogs with steal-prone coronary artery anatomy. METHODS: Dogs were chronically instrumented for measurement of aortic and left ventricular pressure, diastolic coronary blood flow velocity and subendocardial segment length. After recovery from surgery, dogs underwent repetitive, brief, left anterior descending coronary artery (LAD) occlusions via an implanted hydraulic vascular occluder to enhance collateral development. A progressive left circumflex coronary artery (LCCA) stenosis was also obtained using an ameroid constrictor. After development of LCCA stenosis, the LAD was totally occluded to produce a model of multivessel coronary artery disease. Systemic hemodynamics, regional contractile function and myocardial perfusion measured with radioactive microspheres were assessed in the conscious state and during sevoflurane anesthesia at 1.0 and 1.5 MAC with and without restoration of arterial blood pressure and heart rate to conscious levels. RESULTS: Total LAD occlusion with simultaneous LCCA stenosis increased heart rate, mean arterial pressure, left ventricular systolic and end-diastolic pressures, end-diastolic segment length, and rate-pressure product in conscious dogs. Subsequent administration of sevoflurane caused dose-related decreases in arterial pressure, left ventricular systolic pressure, double product, and peak rate of increase of left ventricular pressure at 50 mmHg. Perfusion of normal myocardium was unchanged during sevoflurane anesthesia. In contrast, sevoflurane caused dose-dependent decreases in blood flow to myocardium supplied by the stenotic LCCA, which returned to control levels after restoration of heart rate and arterial pressure. No reduction in collaterally derived blood flow to the occluded region was produced by 1.0 or 1.5 MAC sevoflurane. No redistribution of blood flow away from the occluded LAD region to normal or stenotic myocardium occurred during sevoflurane anesthesia. In fact, increases in the ratio of blood flow between occluded and normal zones or occluded and stenotic zones were observed in the subepicardium during 1.5 MAC sevoflurane with maintenance of the heart rate and arterial pressure at conscious levels. CONCLUSIONS: The results demonstrate that sevoflurane does not reduce or abnormally redistribute myocardial blood flow derived from coronary collateral vessels in a chronically instrumented canine model of multivessel coronary artery obstruction.