High-frequency analysis of the Ellipticus antenna

Efficient numerical solution techniques have been developed and used to examine the electromagnetic fields that can be developed in the working volume of the CW Ellipticus antenna operated at frequencies from 100 kHz to 1 GHz. An exponentially tapered transition section is designed to obtain the desired illumination pattern in the working volume. The input transition section is needed for impedance matching and to drive efficiently the Ellipticus antenna. A parametric study is performed to ascertain the performance of the Ellipticus antenna for frequencies up to 1 GHz     

Langmuir-Blodgett deposited cadmium gate inverted InP-GaInAs modulation-doped field-effect transistors

We report on the Langmuir-Blodgett film deposition and plasma etching of cadmium distearate on n-Gao.47Ino.53As to form a high-barrier-height Schottky barrier. Using this technique to form the gate electrode, we fabricated a 1?m-gate-length inverted InP-GalnAs modulation-doped field-effect transistor (MODFET) with an extrinsic transconductance of 170mS/mm and a cutoff frequencyfT of 19 GHz.     

Infections in patients with cystic fibrosis following lung transplantation

BACKGROUND: There is controversy over whether colonization with drug-resistant organisms is a contraindication to lung transplantation. METHODS: We undertook a retrospective review of the results of lung transplantation for patients with cystic fibrosis (CF) at Duke University Medical Center. RESULTS: As of May 1996, 21 patients with CF underwent bilateral lung transplantation. The first patient died within 24 h of transplantation from sepsis due to Stenotrophomonas maltophilia. Of the remaining 20 patients, 17 (85%) are alive and in stable condition. The three deaths were related primarily to bronchiolitis obliterans at 4 and 18 months in two patients and to cytomegalovirus pneumonitis at 5 months in the other patient. The 17 surviving patients have been followed up for a mean of 13 months (range, 0.5 to 34 months). Most of them were colonized and infected with multidrug-resistant organisms before transplantation. Following transplantation, 11 patients had complications from infections. One patient had bacteremia due to a panresistant Burkholderia cepacia and was treated successfully. Two patients had bacteremia and wound infection due to Burkholderia gladioli, previously thought to be pathogenic only in plants. Both patients were treated successfully. Of the six patients with Aspergillus fumigatus isolated from cultures before transplantation, only one had invasive disease following transplantation and responded to treatment. CONCLUSION: The organisms present before transplantation were not the primary cause of mortality in our patient population. Our findings suggest that lung transplantation should be considered in CF patients infected with multidrug-resistant organisms.     

The effects of lead exposure on learning in a multiple repeated acquisition and performance schedule

This study sought to determine the selectivity of Pb-induced changes in learning, as distinct from non-specific or performance effects, and to explore the nature of the underlying error patterns contributing to any learning deficits. To accomplish this, rats were chronically exposed to 0, 50, or 250 ppm Pb acetate in drinking water from weaning and trained on a multiple repeated acquisition (RA) and performance (P) schedule beginning at 55 days of age. The RA component required the rat to learn a new 3-member sequence of responses during each experimental session (Center Right Left, RLC, CLR, RCL, and LRC), while the correct sequence of responses for the P component was constant across sessions (LCR). Significant decrements in accuracy on the RA component but not on the P component were found in Pb-exposed groups compared to control, effects that could not be attributed to differential rates of responding. Analyses of error patterns revealed that the effects of Pb exposure on RA accuracy levels derived from two sources. The first consisted of a perseveration of P-like sequence responding (LCR) even during the RA component. Secondly, Pb exposure increased perseverative responding on a single lever, even though the schedule itself never directly reinforced such repetitive responding. The increase in frequency of these two types of perseverative behavior was incompatible with acquisition of non P-like sequences during the RA component. Adding a 5 sec tone to the light stimuli signalling the transition between RA and P components of the multiple schedule failed to attenuate these effects of Pb, suggesting that deficits in stimulus control were not the sole behavioral mechanism of these impairments. Examination of individual data revealed the presence of both 'learners' and 'non-learners' in each group, with the prevalence of the latter being suggestively higher in Pb-exposed groups than in controls. These findings may be relevant to the classroom setting, where periods requiring learning may frequently be interspersed with periods of performance of learned skills.     

Motion of a solid sphere in a general flow near a plane boundary at zero Reynolds number

It is demonstrated how the hydrodynamic force and moment of force acting on a solid sphere may be calculated when it is placed at rest at an arbitrary position in a two dimensional flow at zero Reynolds number in which the region of flow is bounded by either an undeformable planar free surface or by a plane solid wall. The results so obtained are used to calculate the motion of a freely moving solid sphere in an asymmetric vortex in the presence of an underformable free surface. It is seen that the sphere, depending on the direction of the undisturbed flow, will either spiral into or out of the vortex. This implies that when a dilute suspension of such spherical particles undergoes such a vortex motion in the presence of the free surface, the vortex will either fill up with particles from the surrounding flow or become devoid of particles.Deceased, July 31, 1995     

The domain composition method applied to Poisson's equation in two dimensions

Domain composition, a recently described method for formulating continuum field problems, removes certain restrictions on the construction of finite element models such that it is possible to solve a finite element problem without using a global compatible mesh. The domain composition method couples or otherwise constrains meshes in local regions to obtain a solution equivalent to that produced by conventional finite element methods. In particular, the domain composition method enables finite element models to be formulated with overlapping elements. Several advantages come from this, including an ability to automatically generate a finite element model from a solid geometric model, an ability to use a variety of element types in a single finite element model and an ability to exactly match element boundaries to the local geometry. This paper shows in detail a finite element formulation of Poisson's equation using domain composition and presents certain key algorithms that incorporate the domain composition method into well-established finite element procedures.     

Ovarian mucinous cystadenocarcinoma with mural nodules of anaplastic carcinoma: report of a case and review of the literature

A decline of cytosol protein kinase C activity was observed in rat myocardial cells at 4 and 8 h after endotoxin administration, and membrane-associated protein kinase C activity rose at the same time. The activity of membrane protein kinase C in aortic smooth muscle cells at 0.5 and 4 h after endotoxin injection was higher than that in control, while cytosol protein kinase C activity was lower. The results indicate that protein kinase C was activated in myocardial cells and aortic smooth muscle cells during various phases of endotoxemia.     

Remote sensing of species mixtures in conifer plantations using LiDAR height and intensity data

In even-aged, single species conifer plantations LiDAR height data can be modelled to provide accurate estimates of tree height and volume. However, it is apparent that growth models developed for single species stands are not directly transferable to a more general situation of mixed species plantations. This paper evaluates the ability of small footprint, dual-return, pulsed airborne LiDAR data to estimate the proportion of the productive species when mixed with a nurse crop in closed canopy plantations. A study area located in Galloway Forest District in Scotland is used as an example of Lodgepole pine and Sitka spruce mixed plantation; this area contains good examples of a wide range of pure and mixed species plantation types. Three species groups are studied: areas of pure Sitka spruce, areas of pure Lodgepole pine and areas where the two species have been planted together. Two approaches are assessed for detection of plantation mixtures: the first uses LiDAR intensity data to separate spruce and pine species and the second uses LiDAR-derived canopy density measures, coefficient of variation, skewness, percent of ground returns (which provides a measure of canopy openness) and the mean canopy height, which enables areas with height variations to be identified. From analysis of LiDAR data extracted from 54 study plots using logistic regression, the coefficient of variation and LiDAR intensity data provide the most useful predictors of the proportion of spruce in a pine/spruce mixture with coefficients of determination (R²) of 0.914 and 0.930 respectively. The method could be developed as a mapping tool, which in combination with existing inventory data should help to improve timber volume forecasting for mixed species even-aged plantations.