1,002 research outputs found
The role of videourodynamic studies in diagnosis and treatment of vesicoureteral reflux
Abstract
From January 1986 to January 1988, 63 children with 95 refluxing ureters have been studied in a prospective study with videourodynamic examination. All children with reflux grades I, II, and III received antibacterial treatment. Surgical treatment was adopted for reflux grades IV and V, provided detrusor instability had been excluded. However, if there was detrusor instability, anticholinergic drugs and antibacterial treatment were given in all grades of reflux and videourodynamic examination was repeated after 3 to 6 months and after 12 months of therapy. Bilateral reflux was found in 22 of 38 patients with a stable bladder, and reimplantation was performed in 11 patients with 18 refluxing ureters. In 25 children with 35 refluxing ureters of various grades of reflux, detrusor instability was found and unilateral reflux was noted more frequently than bilateral reflux. Surgery was necessary for only five children, because in the majority of the patients detrusor instability and reflux could be treated by anticholinergic drugs and antibacterial treatment. For the decision as to which treatment should be given in vesicoureteral reflux, a videourodynamic study is mandatory
Efficient storage of urodynamic signals by computer: application of FAN adaptive sampling
Digital storage of urodynamic signals such as detrusor pressure and flowrate at a sufficiently high sampling rate (10 samples per second) to allow subsequent analysis requires considerable computer memory. A procedure for compressing these data by deleting redundant samples (the fan method of adaptive sampling) was tested. The method allows a flexible adaptation to specific hardware and a compromise between storage requirements and accuracy. In this study the number of samples required for adequate reconstruction of the detrusor pressure signal could be varied from 80% to 4% of the original number of samples by varying the average difference between reconstructed and original signal from 0.01 to 2 cm H2O. Fast components of the measurements (for example cough peaks) which were lost if a lower sampling rate or averaging was used to obtain equally low storage requirements were unaffected by this compression technique
An Evaluation of Contractility Parameters Determined from Isometric Contractions and Micturition Studies
In a group of 110 patients of mixed pathology 218 micturitions were investigated. Using an on-line computer, two contractility parameters were calculated: the parameter U/l, which is derived from the isometric pressure rise in the detrusor before micturition actually started, and the parameter wmax, which is derived from flow and pressure during micturition. It was found that neither of the parameters conforms to the definition of an ideal contractility parameter. Both parameters are subject to the influence of the urethral resistance or the degree of neurogenic stimulation of the bladder, and both measure to some degree the actual performance of the detrusor during a given micturition instead of its myogenic properties. Nevertheless, by dividing patients into groups according to these two measured values, it was shown that clinically relevant types of detrusor behaviour can be distinguished
Clinical comparison of bladder contractility parameters calculated from isometric contractions and pressure-flow studies
Parameters describing the contractility of the urinary bladder can be calculated from both isometric contractions and pressure-flow studies. The first method has the advantage of making very little demand either on the patient or on the urodynamicist, and the disadvantage of yielding a parameter that is not clearly related to muscle physiology. The second method demands more from both patient and experimenter but yields straightforward parameters. For a group of 86 patients with mixed pathologic findings, a correlation between the two types of parameters was demonstrated, showing that both methods test, at least partly, the same mechanism
The current of fermions scattered off a bubble wall
Proceeding from WKB quantization conditions, we derive a semiclassical
expression for the current of fermions scattered off a propagating bubble wall
in the presence of longitudinal gauge field. It agrees with the expression used
by Nasser and Turok in semiclassical analysis of instability of electroweak
bubble walls with respect to longitudinal condensation. We discuss the
resulting dispersion relation for longitudinal field and show that light
species are important for the analysis of stability, because of their large
contribution to plasma frequency.Comment: 7 pages, latex, no figures; misprint in eq.(12) correcte
Universal Self Force from an Extended-Object Approach
We present a consistent extended-object approach for determining the self
force acting on an accelerating charged particle. In this approach one
considers an extended charged object of finite size , and calculates
the overall contribution of the mutual electromagnetic forces. Previous
implementations of this approach yielded divergent terms
that could not be cured by mass-renormalization. Here we explain the origin of
this problem and fix it. We obtain a consistent, universal, expression for the
extended-object self force, which conforms with Dirac's well known formula.Comment: Latex, one postscript figure, 4 page
Nitrogen sources, transport and processing in peri-urban floodplains
Peri-urban floodplains are an important interface between developed land and the aquatic environment and may act as a source or sink for contaminants moving from urban areas towards surface water courses. With increasing pressure from urban development the functioning of floodplains is coming under greater scrutiny. A number of peri-urban sites have been found to be populated with legacy landfills which could potentially cause pollution of adjacent river bodies. Here, a peri-urban floodplain adjoining the city of Oxford, UK, with the River Thames has been investigated over a period of three years through repeated sampling of groundwaters from existing and specially constructed piezometers. A nearby landfill has been found to have imprinted a strong signal on the groundwater with particularly high concentrations of ammonium and generally low concentrations of nitrate and dissolved oxygen. An intensive study of nitrogen dynamics through the use of N-species chemistry, nitrogen isotopes and dissolved nitrous oxide reveals that there is little or no denitrification in the majority of the main landfill plume, and neither is the ammonium significantly retarded by sorption to the aquifer sediments. A simple model has determined the flux of total nitrogen and ammonium from the landfill, through the floodplain and into the river. Over an 8 km reach of the river, which has a number of other legacy landfills, it is estimated that 27.5 tonnes of ammonium may be delivered to the river annually. Although this is a relatively small contribution to the total river nitrogen, it may represent up to 15% of the ammonium loading at the study site and over the length of the reach could increase in-stream concentrations by nearly 40%. Catchment management plans that encompass floodplains in the peri-urban environment need to take into account the likely risk to groundwater and surface water quality that these environments pose
Scattering and delay time for 1D asymmetric potentials: the step-linear and the step-exponential cases
We analyze the quantum-mechanical behavior of a system described by a
one-dimensional asymmetric potential constituted by a step plus (i) a linear
barrier or (ii) an exponential barrier. We solve the energy eigenvalue equation
by means of the integral representation method, classifying the independent
solutions as equivalence classes of homotopic paths in the complex plane.
We discuss the structure of the bound states as function of the height U_0 of
the step and we study the propagation of a sharp-peaked wave packet reflected
by the barrier. For both the linear and the exponential barrier we provide an
explicit formula for the delay time \tau(E) as a function of the peak energy E.
We display the resonant behavior of \tau(E) at energies close to U_0. By
analyzing the asymptotic behavior for large energies of the eigenfunctions of
the continuous spectrum we also show that, as expected, \tau(E) approaches the
classical value for E -> \infty, thus diverging for the step-linear case and
vanishing for the step-exponential one.Comment: 14 pages, 10 figure
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