Deterioration Of Signals Research Articles

Intraoperative neuromonitoring.

Intraoperative neuromonitoring (IONM) has been a valuable part of surgical procedures for over 25 years. Insight into the nervous system during surgery provides critical information to the surgeon allowing reversal or avoidance of neural insults. Electrophysiological tests including electroencephalography, electromyography, and multiple types of evoked potentials (somatosensory, auditory, and motor) are monitored during surgeries that involve risk to the nervous system. Deterioration of signals suggests a surgical insult and is associated with an increased risk of postoperative deficit. Intraoperative identification of this risk allows corrective action. In addition, IONM teams make use of their armamentarium of tests to evaluate anatomy or function of the nervous system in response to specific questions posed by the surgical team. Intraoperative recordings are now a routine part of many surgical procedures. Their correct application leads to improved surgical outcome.

Deterioration of photo-stimulated luminescence signals from materials by radiation

A photo-stimulated luminescent (PSL) material, BaFBr0.85I0.15:Eu2+, was irradiated by 1 and 2 MeV He+ ions. The deterioration of PSL signals caused by heavy irradiation was found quite stable for a long time. In situ measurements of scintillation were also made during He+ ion irradiation. A broad 400 nm peak and a decreasing continuum tail were observed for spectra of the scintillation. An afterglow effect was also observed as a function of time up to 10 s after stopping the He+ ion beam. Results are discussed relating with the incomplete erasing and the self generation of PSL signals which were reported in our previous study.

Ослабление радиосигналов и искажение радиолокационных характеристик космических аппаратов плазменными струями электрореактивных двигателей

Ослабление радиосигналов и искажение радиолокационных характеристик космических аппаратов плазменными струями электрореактивных двигателей

Radiation effects of helium ions, neutrons, and gamma-rays on photo-stimulated luminescence

A photo-stimulated luminescent (PSL) material, BaFBr 0.85I 0.15 : Eu 2+, was irradiated by 1 and 2 MeV He + ions. The radiation effects were compared with that of fission neutrons, 137Cs and 60Co gamma-rays. Deterioration of PSL signals was measured as a function of total fluence for ions and neutrons or dose for gamma-rays. Relative deteriorations for neutrons and gamma-rays were compared with that of 1 MeV He + ion irradiation. A self-generation of PSL signals depending on fluence and storage time was observed.

Visually induced motion perception and visual control of postural sway in congenital nystagmus

In congenital nystagmus (CN) the threshold for detecting motion of visual objects is increased. To determine whether this increase is due to a deterioration of visual motion signals or whether visual-vestibular interactions (which are necessary to judge object-motion in space) are also involved we examined how CN patients use visual motion signals to evaluate self-motion in perceptual and behavioral tasks. Using an optokinetic drum we measured the minimum optokinetic acceleration necessary to induced motion perception of the visual environment in CN patients. This threshold was significantly elevated in the CN patients compared with normals (20.1 deg/s 2 to 3.25 deg/s 2). We further addressed the question whether the elevation of this threshold is due to a deficiency in evaluating visual motion in general or to a specific modification affecting the percept of visual object-motion with respect to the inertial reference only. We thus measured the latency of visually induced self-motion perception, which was found to be very similar or even slightly smaller (1.7±0.7 s) compared with normals (2.2±1.7 s). Moreover, subjects with CN were found to use vision quite efficiently for the visual stabilization of posture (Romberg quotient 2.0±1.16), even if they did not reach the level of normals (Romberg quotient 3.7±1.1). The results indicate that CN affects the estimate of object-motion in a specific and much more severe way than the estimate of self-motion. The minimal effect of CN on self-motion perception can be explained by the low pass characteristics of the optokinetic input to self-motion perception. The specific deficiency in detecting object-motion indicates that adaptation to CN occurs on the level of visual–vestibular interactions for the perception of visual object-motion and not on the level of visual motion signals.

Multiple scattering of seismic waves, variable gas saturation and ZODs: theoretical considerations and an observational methodology

Summary. Deterioration of seismic signals in the subsurface is often ascribed to variable gas saturation, micro-fracturing of sedimentary strata, density and elastic constant variations as a result of cementation/dissolution and/or facies changes, as well as to irregularities in the bedding plane surfaces. In order to glean some information from deteriorated seismic signals, use of the correlated wave behaviour between pairs of receivers has recently been suggested as a possible method for extracting information. In this paper we use variable gas saturation in the subsurface as a vehicle to illustrate the behaviour of a solution to the equation which describes the correlated behaviour of two wave amplitudes at two different spatial locations at two different wavenumbers. The solution is valid for waves from a common source passing through a medium containing spatially variable amounts of gas, being multiply scattered by the variable gas saturation, and with the spatial fluctuations in gas concentration around a mean value described by a Gaussian correlation spectrum. The solution also allows for finite bandwidth effects in the receivers. It is shown that (a) the spatial scale of the correlated behaviour of two waves, as well as the shape of the correlation function, and (b) the shape of the bandwidth-smeared autocorrelation function at zero separation, provide a means of determining both the depth range and the level of fluctuations in gas saturation. An observational prescription is provided to show how to extract, from seismic data, the relevant quantities for comparison with the theoretical results. We also present a simple physical picture of the basic process, as well as some rough order of magnitudes, to show that the parameters quantifying the size of the scattering effect fall squarely in the middle of the seismic band.

Improvements in Color Television Studio Video System Performance

Signal sources such as Plumbicon live cameras, 4-channel vidicon film cameras and high-band video-tape machines provide very high quality inputs to today's color television broadcasting studios. To satisfy the needs of TV program procedures, the studio facilities have been made extremely complex. For example, studios in the CBS Broadcast Center in New York contain three cascaded video-fader and/or special effects generator units to satisfy unusual production situations. Depending on the particular path through the studio, a video signal will normally pass through at least seven or as many as fifteen different amplifiers. Also the studio must present the same electrical length to the color subcarrier regardless of the path taken by the signal. The above factors made it difficult to achieve the high quality color studio performance which is necessary to avoid deterioration of the input signals. One of the most serious problems has been a dip or saddle in the amplitude-frequency response between 1 and 4.2 MHz; another has been a midfrequency (15.7 kHz) smear. After discussion of the solutions to these problems, there are described special techniques developed to make amplitude-frequency response measurements to better than 0.05 dB and to detect midfrequency smears in the order of 1 mV peak-to-peak amplitude.

Coincident Current Magnetic Film Memories Using Locked Hard-Direction Films Having Microshape Anisotropy

Specially prepared NiFe films allow information storage in two hard-direction stable states. Most promising are films with very narrow strips of alternating thickness (e.g. D0=200 Å, D1=400 Å, strip widths b≈10 μ). The Néel wall forces, and the microshape anisotropy introduced by the strips of alternating thickness provide extremely stable locked magnetization states in the hard direction. A bias field forces the Néel walls to align along the thickness slopes, thus completely eliminating creeping. These unique magnetic properties can be utilized for coincident current selection and a nondestructive readout in memories of high storage capacity. A readout method is employed using two orthogonal high-frequency fields of different frequencies fx and fy, providing an output signal at the difference frequency fm=fx−fy. The readout amplitude differs by two orders of magnitude, depending on the information stored. Pulse measurements with a number of these films showed the feasibility of the method. No deterioration of the output signals was observed even after 108 read, write, or half-select cycles. An evaluation of possible speed and storage capacity is made, taking into account various sources of noise and disturb signals.