Active Formers Research Articles

Validation of a novel diagnostic test for assessing the risk of urinary uric acid crystallization

Background and aimsUric acid (UA) kidney stones account for 10 to 11% of all kidney stones, and this percentage has increased over time. An accurate, rapid, simple, and low-cost test is needed to distinguish urine that is susceptible and resistant to the formation of UA crystals. The aim of this paper is to develop a test to assess the risk for UA crystallization (RUAC) and to validate its utility in routine clinical practice by analysis of urine samples of UA stone formers and healthy volunteers. Patients and MethodsUrine samples of 20 healthy adult volunteers and 54 active formers of UA stones were collected. Three samples were collected from each participant, with at least 7 days between each collection. The main lithogenic parameters for UA stones were determined, and an RUAC test was performed in all urine samples. ResultsOur RUAC test reliably discriminated urine that was resistant and susceptible to the formation of UA crystals. This test had high specificity (94%) and a low percentage of false negatives. ConclusionThe RUAC test described here had high diagnostic accuracy, low-cost, and a rapid assay time, that make this test an attractive screening tool for UA stone fomers follow-up.

Formers of High-voltage Subnanosecond Pulses Based on Compression Energy Schemes with Capacitor Storage and Spark Dischargers

Two active formers of high-voltage subnanosecond unidirectional and monocycle pulses based on an energy compression scheme of a nanosecond pulse and two compact designs of passive stubs with oil insulation are presented. The pulse of the RADAN-303 (driver) initial generator with an amplitude of -145 kV and a duration of a 4 ns in one case was converted by the active former to a monocycle pulse (one period of sinusoid) with an amplitude drop of 350 kV and a period of 1.25 ns. The unidirectional pulse former allowed a maximum amplitude of 290 kV to be reached in 0.3 ns (FWHM), and with additional compression energy, the average amplitude amounted to 310 kV. The electrical strength of the compact passive stubs was sucient to convert an unidirectional pulse with an amplitude of 180 kV and a pulse width of 0.5 ns (FWHM) to a monocycle pulse with a drop of peak-to-peak amplitude of 150 kV and a drop duration of 0.5 ns for repetition rates up to 3 kHz.