The effect of brain hematoma location on volumetric inductive phase shift spectroscopy of the brain with circular and magnetron sensor coils: a numerical simulation study.

This numerical simulation study addressed the effects of the location of a discrete brain hematoma on the volumetric inductive phase shift of the brain measured with an induction circular sensor coil and an induction magnetron sensor coil. The theoretical study simulates the brain cavity as a circular sphere transversely centered with respect to the circular and magnetron sensor coils. As a case study for the effects of hematoma location, we employed similar size simulated spherical hematomas placed at three different positions from the center of the brain outward. A three-dimensional finite element analysis of the field equations in the frequency range from 100 kHz to 100 MHz revealed a substantial effect of hematoma location on the ability of both the circular and magnetron sensors to detect the hematomas. In particular it was found that there are frequencies, which may be related to resonance, at which the occurrence of the hematomas has no effect on the volumetric inductive phase shift of the brain. Furthermore it was found that the relative sensitivity of circular and magnetron sensor coils with respect to the occurrence of hematoma varies with the location of the hematoma.

Effects of Zernike wavefront aberrations on visual acuity measured using electromagnetic adaptive optics technology.

PURPOSE: This study measured the changes in visual acuity induced by individual Zernike ocular aberrations of various root-mean-square (RMS) magnitudes. METHODS: A crx1 Adaptive Optics Visual Simulator (Imagine Eyes) was used to modify the wavefront aberrations in nine eyes. After measuring ocular aberrations, the device was programmed to compensate for the eye's wavefront error up to the 4th order and successively apply different individual Zernike aberrations using a 5-mm pupil. The generated aberrations included defocus, astigmatism, coma, trefoil, and spherical aberration at a level of 0.1, 0.3, and 0.9 microm. Monocular visual acuity was assessed using computer-generated Landolt-C optotypes. RESULTS: Correction of the patients' aberrations improved visual acuity by a mean of 1 line (-0.1 logMAR) compared to best sphero-cylinder correction. Aberrations of 0.1 microm RMS resulted in a limited decrease in visual acuity (mean +0.05 logMAR), whereas aberrations of 0.3 microm RMS induced significant visual acuity losses with a mean reduction of 1.5 lines (+0.15 logMAR). Larger aberrations of 0.9 microm RMS resulted in greater visual acuity losses that were more pronounced with spherical aberration (+0.64 logMAR) and defocus (+0.62 logMAR), whereas trefoil (+0.22 logMAR) was found to be better tolerated. CONCLUSIONS: The electromagnetic adaptive optics visual simulator effectively corrected and generated wavefront aberrations up to the 4th order. Custom wavefront correction significantly improved visual acuity compared to best-spectacle correction. Symmetric aberrations (eg, defocus and spherical aberration) were more detrimental to visual performance.

Bioreactor coupled with electromagnetic field generator: effects of extremely low frequency electromagnetic fields on ethanol production by Saccharomyces cerevisiae.

The effect of extremely low frequency (ELF) magnetic fields on ethanol production by Saccharomyces cerevisiae using sugar cane molasses was studied during batch fermentation. The cellular suspension from the fermentor was externally recycled through a stainless steel tube inserted in two magnetic field generators, and consequently, the ethanol production was intensified. Two magnetic field generators were coupled to the bioreactor, which were operated conveniently in simple or combined ways. Therefore, the recycle velocity and intensity of the magnetic field varied in a range of 0.6-1.4 m s(-1) and 5-20 mT, respectively. However, under the best conditions with the magnetic field treatment (0.9-1.2 m s(-1) and 20 mT plus solenoid), the overall volumetric ethanol productivity was approximately 17% higher than in the control experiment. These results made it possible to verify the effectiveness of the dynamic magnetic treatment since the fermentations with magnetic treatment reached their final stage in less time, i.e., approximately 2 h earlier, when compared with the control experiment.

Reversible, high-voltage square-wave pulse generator for triggering spark gaps.

A design is presented for a reversible, square-pulse generator that employs coaxial cables for charge storage and pulse formation and a thyratron as the switch. The generator has a nominal output voltage of 5-30 kV and a pulse duration determined by the cable's physical length. Two variations are presented: (1) a single-stage one consisting of cable that is charged via its shield on one end and discharged with a thyratron on the opposite end and (2) a two-stage one having an inverting circuit that uses a coaxial cable to reverse the polarity of the pulse. The generator operates with "flying shields," i.e., high-voltage pulses also propagate on the outside of the cables; this calls for a dedicated insulation that avoids breakdown between sections of the cable's shield. The rise time obtained is mostly dictated by the switching time of the thyratron; with the one we used in the tests, rise times in the range of 30-40 ns were obtained. We present the results obtained in the implementation of the generators as well as its application to fire a large Marx generator.

Craniofacial measurements based on 3D-CT volume rendering: implications for clinical applications.

OBJECTIVES: This study was designed to determine the precision and accuracy of anthropometric measurements using three-dimensional computed tomography (3D-CT) volume rendering by computer systems for craniofacial clinical applications, and to compare the craniometric landmarks using bone and soft tissue protocols. METHODS: The study population consisted of 13 cadaver heads that were examined with spiral CT. The archived CT data were transferred to a workstation, and 3D-CT volume rendered images were generated using computer graphics tools. Linear measurements (n = 10), based upon conventional craniometric anatomical landmarks (n = 08), were identified in 2D-CT and in 3D-CT images by two radiologists twice each independently, and then performed by 3D-CT imaging using a computer graphics systems using bone and soft tissue protocols. In total, 520 imaging measurements were made. The soft tissues were subsequently removed from the cadaver heads and the measurements were repeated using an electromagnetic 3 Space trade mark digitizer. RESULTS: The results demonstrated no statistically significant difference between interobserver and intraobserver measurements or between imaging and physical measurements in both 3D-CT protocols. The standard error was found to be between 0.45% and 1.44% for all the measurements in both protocols, indicating a high level of precision. Furthermore, there was no statistically significant difference between imaging and physical measurements (P > 0.01). The error between the mean actual and mean 3D-based linear measurements was 0.83% for bone and 1.78% for soft tissue measurements, demonstrating high accuracy of both 3D-CT protocols. CONCLUSIONS: 3D-CT volume rendering images using craniometric measurements can be used for anthropological studies involving craniofacial applications.

Ultrasonic pulsed Doppler blood flowmeter for use in extracorporeal circulation.

In cardiac surgeries, it is frequently necessary to make the external blood circulation and oxygenation artificially. This procedure is called extracorporeal circulation (EC) or heart-lung bypass. During EC, one of the most important parameters, which demands continuous monitoring, is the blood flow. In many cases, the blood flow is estimated by the pump velocity (in roller pumps) or measured with transducers based on electromagnetic methods (in centrifugal pumps). This article presents an ultrasonic Doppler blood flowmeter to be used in the arterial line of an extracorporeal circulation system. The ultrasonic probe is coupled to a half-inch tube connector of the extracorporeal arterial line, is not disposable, and does not need sterilization. The developed flowmeter revealed itself to be efficient and reliable and can be inserted in a closed-loop pump controller system or be used as stand-alone equipment.

Comparative blood flow study of arteriovenous fistulae in canine femoral arteries: modified latero-lateral and end-lateral techniques.

The aim of this study was to evaluate the blood flow of an arteriovenous fistula comparing the modified latero-lateral (LLM) and end-lateral (TL) techniques in canine femoral arteries. Ten mongrel dogs were submitted to 2 arteriovenous fistulae each, with a LLM on one side and a TL procedure on the other side. Cranial and caudal average blood flow as well as average venous flow were measured by an electronic fluxometer 15, 20, and 25 min after surgery. Mann-Whitney, Friedman, and Wilcoxon nonparametric tests were used for data analysis (alpha

Successful use of a metal detector in locating coins ingested by children.

The purpose of this study was to examine the accuracy of a metal detector in locating coins ingested by children. The metal detector correctly identified the presence or absence of coins in 13 patients (93%), as confirmed by radiologic studies.