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PubMed2006

Ion energy distribution and gas heating in the cathode fall of a direct-current microdischarge.

This paper reports on measurements of the ion energy distribution (IED) at the cathode of an argon dc microdischarge using energy-resolved molecular beam mass spectrometry. The measurements are conducted at a fixed pressure-electrode separation product (pd) of 1 cm Torr with a maximum discharge pressure of 20 Torr. The measured IED is compared to the theory of Davis and Vanderslice [W. D. Davis and T. A. Vanderslice, Phys. Rev. 131, 219 (1963)]. A higher pressure in a case of almost constant normalized current densities by pressure (Jp(-2) = 0.080+/-0.006 mA/cm(-2) Torr(-2)) yields a lower ratio of the ion mean free path to the sheath thickness. The results in almost constant Jp(-2) case then indicate that a scaling law of Jp(-2) is no longer applicable for IED of microdischarge. Expected background gaseous temperatures from IEDs with the collisional Child law have reasonable increasing with increased current density (J) in both cases of almost constant Jp(-2) and a constant pressure of 10 Torr. Supported by temperature measurement by laser absorption spectroscopy, it is demonstrated that the expanded theory might be applicable also to microdischarges (Ar approximately 20 Torr) with temperature adjusting.

Journal Article↗
PubMed2000

New mechanism for electron emission from planar cold cathodes: the solid-state field-controlled electron emitter

A new mechanism for electron emission from planar cathodes is described. The theoretical analysis shows that, with an ultrathin wide band-gap semiconductor layer (UTSC) on a metal, the surface barrier is lowered to approximately 0.1 eV due to the creation of a space charge induced by the electrons injected from the metal. The barrier height depends mostly on the UTSC thickness and not on the state of the surface, as in thermionic and field emissions. This mechanism explains the measured stable emission at 300 K and 10(-7) Torr, with a threshold field of only approximately 50 V/&mgr;m, from these solid-state field-controlled emitters.

Journal Article↗
PubMed1978

Studies on the turnover of endogenous cathodal trypsinogen in man.

The concentration in serum of cathodal trypsinogen has been studied in certain clinical and experimental situations. The concentration correlated with pancreatic amylase activity. Low levels were found in patients with malabsorption due to exocrine pancreatic insufficiency. The concentration rose after endoscopic retrograde cholangiopancreatographic examinations (ERCP). After ERCP, however, no trypsin was detected complexed with protease inhibitors, as is generally found in acute pancreatitis. The trypsinogen concentration in serum also rose in renal failure indicating a renal elimination route for the endogenous trypsinogen.

Amylases↗
PubMed1978

Reliability of cutaneous oxygen measurement by skin sensors with large-size cathodes.

The oxygen partial pressure may be measured cutaneously by directly heated PO2 sensors attached to the surface of the skin. The use of a large-size cathods (diameter 4 mm) allows one to obtain an average PO2 value over a sufficiently large skin area. The permeability of the membrane for oxygen has to be kept low to prevent a disturbance of the oxygen profile in the cutaneous tissue as a result of the oxygen consumption of the sensor. When using of 6 micrometer Mylar membrane, the current can be limited by the diffusion of oxygen through the membrane and is a measure of the arterialized cutaneous PO2. One effect of using membrane of low permeability is that the response time of the sensor is long (tau 90% = ca 45 sec). The reliability of correctly reproducing cPO2 variations by sensors having different response times may be evaluated by determining the transfer function of the membrane which allows the calculation of the frequency characteristics for various membranes. The cutaneous tissue layer also acts as a filter for rapid PO2 fluctuations. The characteristic of this filter is essentially similar to that of a "slow" membrane such as Myler 6 micrometer. The information gained by using a "rapid" membrane such as Telfon 13 micrometer is negligible. In 490 comparative measurements in newborns performed with sensors heated to 44 degree C, the correlation between arterial PO2 and cutaneously measured PO2 is significant (correlation coefficient = 0.934) and the regression line does not deviate significantly from the identity line.

Blood Gas Analysis↗
PubMed1994

The immunologically reactive O-linked polysaccharide chains derived from circulating cathodic antigen isolated from the human blood fluke Schistosoma mansoni have Lewis x as repeating unit.

The gut-associated excretory antigen circulating cathodic antigen (CCA) was isolated by immunoaffinity chromatography from adult Schistosoma mansoni worms, which were collected from infected golden hamsters. This antigen is probably involved in protection of the schistosome gut and is increasingly used in highly sensitive and specific immunodiagnostic assays. Amino acid analysis before and after alkaline borohydride treatment of CCA and monosaccharide analysis indicated that CCA is O-glycosylated mostly via GalNAc-Thr. After reductive alkaline treatment, the O-linked carbohydrate chains were fractionated by gel-permeation chromatography, followed by normal-phase HPLC on LiChrosorb-NH2. Carbohydrate-positive fractions were investigated by one-dimensional and two-dimensional 1H-NMR spectroscopy, fast atom bombardment mass spectrometry and collision-induced-dissociation tandem mass spectrometry. The analyses showed that the low-molecular-mass O-linked oligosaccharide alditols (the minor fraction) consist of disaccharides to hexasaccharides having the Gal beta (1-3)GalNAc-OL core in common. The major carbohydrate fraction comprises a population of polysaccharides, containing Lewis x repeating units (-3)Gal beta (1-4)[Fuc alpha (1-3)]GlcNAc beta (1-). CCA-specific monoclonal antibodies and IgM antibodies in patient sera recognized the fucosylated O-linked carbohydrate antigenic structures. Since CCA evokes a strong IgM antibody response and carbohydrate structures containing repeating Lewis x units are found on circulating neutrophils, it is proposed that the antigenic poly-Lewis x polysaccharide of CCA is involved in the induction of auto-immunity against granulocytes, resulting in the mild to moderate neutropenia observed during schistosome infection.

Animals↗
PubMed1995

Prediction of cathodal iontophoretic transport of various anions across excised skin from different vehicles using conductivity measurements.

Solute concentration, buffer concentration, applied pH and buffer constituents affect the cathodal iontophoresis of salicylate, benzoate and butyrate across excised skin. Experiments were conducted in which the iontophoretic flux of salicylate was measured across excised human skin with variations in salicylate concentration, donor solution pH, buffer concentrations and buffer consitutents. The conductivity of these solutes and of solutions described in studies on the iontophoresis of benzoate and butyrate were then measured. The observed variations in salicylate, benzoate and butyrate fluxes across a range of conditions were found to be related to the ratio of specific conductance of the solutes in deionized distilled water to that in the buffer solution containing the solutes. The present results suggest that conductivity of solutes in vehicle solutions is one means of predicting the iontophoretic flux of solutes from different vehicle compositions.

Biological Transport↗
PubMed2005

Compact monochromatic flash x-ray generator utilizing a disk-cathode molybdenum tube.

The high-voltage condensers in a polarity-inversion two-stage Marx surge generator are charged from -50 to -70 kV by a power supply, and the electric charges in the condensers are discharged to an x-ray tube after closing gap switches in the surge generator with a trigger device. The x-ray tube is a demountable diode, and the turbo molecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Clean molybdenum Kalpha lines are produced using a 20 microm-thick zirconium filter, since the tube utilizes a disk cathode and a rod target, and bremsstrahlung rays are not emitted in the opposite direction to that of electron acceleration. At a charging voltage of -70 kV, the instantaneous tube voltage and current were 120 kV and 1.0 kA, respectively. The x-ray pulse widths were approximately 70 ns, and the generator produced instantaneous number of Kalpha photons was approximately 3 x 10(7) photons/cm2 per pulse at 0.5 m from the source of 3.0 mm in diameter.

Animals↗
PubMed1998

Comparison of a cathode-ray-tube and film for display of computed radiographic images.

The goal of the study was to compare a cathode-ray-tube (CRT) digital display with film by using task-dependent image quality assessment methods. Contrast-detail analysis was utilized. Human observers performed a simple detection task, specifically, detecting a pillbox target in a uniform Poisson field, using either film or a digital display that employed a CRT monitor. Observers performed equally well on both film and CRT when the window settings of the digital display were established subjectively by a radiologist. Changing the window settings of the digital display to match the average background luminance of a film-illuminator combination decreased the luminance contrast of the targets and observer performance was reduced, though these effects were probably not linked. The "gold standard" film had lower luminance contrast than the CRT displayed images, yet observer performance was never lower for film than for the CRT. Therefore we concluded that luminance contrast was not a limiting factor for observer performance in this study. The CRT monitor changed fairly rapidly after it was calibrated. During a period of six months the gamma of the display increased from 1.82 to 2.42 and the maximum luminance decreased from 319 to 228 cd/m2. Low luminance output demonstrated a larger percentage decrease (approximately equal to 85%) than high luminance output (approximately equal to 29%) over the same time period. These observations suggest that standard window settings should be reviewed from time to time to ensure that the display is used optimally. No special look-up table setup such as perceptual linearization was used.

Calibration↗
PubMed2004

Diagnosis of schistosomiasis by reagent strip test for detection of circulating cathodic antigen.

A newly developed reagent strip assay for the diagnosis of schistosomiasis based on parasite antigen detection in urine of infected individuals was evaluated. The test uses the principle of lateral flow through a nitrocellulose strip of the sample mixed with a colloidal carbon conjugate of a monoclonal antibody specific for Schistosoma circulating cathodic antigen (CCA). The strip assay to diagnose a group of highly infected schoolchildren in Mwanza, Tanzania, demonstrated a high sensitivity and association with the intensity of infection as measured both by egg counts, and by circulating anodic antigen and CCA levels determined by enzyme-linked immunosorbent assay. A specificity of ca. 90% was shown in a group of schistosome-negative schoolchildren from Tarime, Tanzania, an area where schistosomiasis is not endemic. The test is easy to perform and requires no technical equipment or special training. The stability of the strips and the conjugate in the dry format lasts for at least 3 months at ambient temperature in sealed packages, making it suitable for transport and use in areas where schistosomiasis is endemic. This assay can easily be developed to an end-user format.

Adolescent↗
PubMed1989

Electrode catheter ablation for ventricular tachycardia: efficacy of a single cathodal shock.

Electrode catheter ablation was used to treat 11 distinct types of sustained ventricular tachycardias in eight patients. Rigid electrophysiological criteria were used to identify five left and five right ventricular arrhythmogenic sites; one of them gave rise to tachycardia with two distinct configurations. A single R-wave-synchronised 250 or 150 J cathodal shock was delivered at each site. One patient had mildly symptomatic episodes of sustained ventricular tachycardia during the first four days after the shock--there were no other complications. At discharge none of the patients was taking antiarrhythmic drugs. They were followed for 8-20 months (mean 14). Ablation abolished five of the 11 ventricular tachycardias. There was no recurrence in three of the eight patients. In two patients identical ventricular tachycardias recurred because the identification of the arrhythmogenic site was incorrect.

Adult↗
PubMedDate not supplied

Cathode ray tube quality control and acceptance testing program: initial results for clinical PACS displays.

The use of picture archiving and communication systems (PACS) and primary soft-copy interpretation in radiology is growing rapidly. The authors present a cathode ray tube (CRT) acceptance test and quality control (QC) program developed over a 5-year period on the basis of experience with multiple PACS and CRT vendors. The CRT QC procedures address monitor cleanliness and setup, qualitative image quality, and quantitative luminance and color measurements. Required materials include a photometer with luminance and color probes and 100%-video, flat-field window and test images from the Society of Motion Picture Test Engineers (SMPTE). Luminance was found to change over time for all gray-scale CRTs examined, which necessitated quarterly recalibration. The phosphor color of these monitors was also found to change, but changes were consistent and slow enough to warrant only annual measurements. Color measurements were found to be especially useful at initial setup and for CRT replacement. Use of this program allowed standardization of absolute luminance of individual CRTs, matching of phosphor color for multimonitor workstations, and systematic tracking of image artifacts. Implementation of a QC program is strongly recommended owing to the dynamic nature of CRT displays.

Color↗
PubMed2004

Detectability of catheters on bedside chest radiographs: comparison between liquid crystal display and high-resolution cathode-ray tube monitors.

PURPOSE: To compare observer performance with a flat-panel liquid crystal display (LCD) monitor and with a high-resolution gray-scale cathode-ray tube (CRT) monitor in the detection of simulated support catheters on bedside chest radiographs. MATERIALS AND METHODS: The ethics committee did not require approval or patient informed consent when this study began. Because of a change in regulations, before images were acquired the nature of the study and procedures were explained to patients or their relatives, and consent was then obtained. A total of 131 catheter fragments (12-14 per radiograph) were superimposed over 10 anteroposterior bedside chest radiographs obtained with storage phosphor technology. Images were displayed on an LCD monitor (1536 x 2048 matrix) and a CRT monitor (2048 x 2560 matrix). Five radiologists independently located the catheter fragments and rated their confidence in detection with bright and subdued ambient light. A two-way analysis of variance and the Friedman test were used for statistical analysis. RESULTS: There was no significant difference for either display type with respect to correctly detected catheter fragments (mean sensitivity, 56.6% and 56.0% for the CRT and the LCD monitors, respectively, with bright light and 61.2% for both monitors with subdued light). With both display types, detection rate with bright light decreased significantly (P < .05). False-positive rates and confidence ratings were not significantly affected by monitor type or ambient light. CONCLUSION: In a study with simulation of clinical conditions, performance of the LCD monitor and high-resolution CRT monitor for detection of support catheters on bedside chest radiographs was equivalent. With both displays, detection performance was equally reduced with bright ambient light.

Aged↗
PubMed1987

Improved fabrication of double-barreled recessed cathode O2 microelectrodes.

Polarographic recessed cathode gold microelectrodes are the preferred type of O2 microelectrode for tissue measurements, but the method originally described for their construction is difficult. An improved method of constructing such electrodes consists of several steps: 1) insertion of a rod made of a special low-melting point alloy into a pulled glass micropipette, 2) heating of the electrode tip as the alloy is pushed toward the tip, 3) beveling, and 4) gold plating the alloy, leaving a recess of the desired length. This method can be used to make single- or double-barreled electrodes in which the O2 barrel is as small as 2-3 micron. The electrodes retain their characteristics for several weeks.

Equipment Design↗
PubMed2001

Luminance artifacts of cathode-ray tube displays for vision research.

Phosphor persistence, video bandwidth, DC restoration and high-voltage regulation affect the appearance of images presented on cathode-ray tubes (CRTs), potentially resulting in differences between nominal and actual stimuli. We illustrate these effects by measuring physical parameters of horizontal and vertical static and counter-phase flickering gratings, and we illustrate problems for vision research by measuring contrast sensitivity to these gratings. We also measured the extent to which calibration protocols actually result in the monitor being calibrated over its entire area regardless of image size. The results of our physical measurements indicate substantial differences between gratings that nominally differ only as to orientation. Consistent with these differences, our psychophysical measurements indicate different sensitivities when the bars of the gratings are parallel or orthogonal to raster lines, regardless of the retinal orientation of the gratings. The results of our calibration check show that only a small region around the target area of calibration can be regarded as effectively linearized, and only if the size of the test image used during the check is similar to the size of the calibration patch. Overall, our results indicate potentially severe problems with the use of CRTs in vision research, and we discuss some published results that are likely to have been affected by these problems.

Artifacts↗
PubMed1997

Raster-scan cathode-ray tubes for vision research--limits of resolution in space, time and intensity, and some solutions.

Raster-based cathode-ray tubes (CRTs) are increasingly used for stimulus presentation. While very flexible, their design based on consumer electronics can limit their value in vision research. Here their limitations of resolution in time, space, intensity and wavelength are systematically compiled. Often, ingenious ideas can circumvent such limitations for specific experiments. Some ad-hoc solutions, as well as the more general techniques of dithering and anti-aliasing, are presented.

Artifacts↗
PubMed1997

A note on luminance calibration of raster-scan cathode-ray tubes: temporal resolution, ripple, and accuracy.

Accurate luminance calibration is an important issue for stimuli in vision research. Raster-scan cathode-ray tubes present a rapidly scanning spot with a luminance of the order of 10,000 cd m-2 (the actual value depends on video timing and phosphor persistence). With little spatial integration this may result in overloading of the front stage of a photometer. More importantly, even if averaged over hundreds of milliseconds, the pulsed nature of the luminance signal will markedly reduce accuracy of the luminance measurement. A frame-synchronised photometer is described to increase measurement accuracy whilst still rapidly acquiring the result.

Computer Terminals↗
PubMed2006

Electrochemical behavior of alpha-MoO3 nanorods as cathode materials for rechargeable lithium batteries.

The electrochemical properties of alpha-MoO3 nanorods, which were synthesized via a solution-based method and following calcination, have been reported as a cathode material for rechargeable lithium batteries. Detailed lithium-insertion process of the material has been conducted by means of cyclic voltammetry, galvanostatic method, and impedance technique, and superior features associated with the nanostructures have been observed. The alpha-MoO3 nanorods exhibited an initial discharge capacity of 271.8 mAh/g under a current density of 0.1 mA/cm2 in the range 1.0 approximately 3.0 V, which nearly approached the theoretical capacity 280 mAh/g. Comparison of the structural and electrochemical characteristics with those of bulk alpha-MoO3 suggests the enhanced electrochemical performance might be related to the rodlike structure and increased edge and corner effects.

Crystallization↗
PubMed2005

Cathode ray tube glass recycling: an example of clean technology.

In this study the use of 'cleaned' end of life (EOL) cathode ray tube (CRT) glass as a raw material in ceramic glazes is described. At present, the recycling and industrial utilization of CRT, a glass material from TV and computer sets, is a subject of intense research with particular regard to the so-called open-loop recycling, namely cycles different from that of the origin. However, the use of CRT glass as a secondary raw material is strictly related to the demand of high-quality raw material. The good preliminary results reached by introducing clean TV and PC monitor panel and cone glass into ceramic glaze formulations pushed research toward the setting-up of a base glaze that is exploitable for the production of pigmented, silk-screened and flame-hardened glazes (products used industrially for coating floor tiles). The aesthetic and chemical characterization of the tiles glazed by this product showed an extremely similar behaviour to originals that did not contain CRT glass. The good technical results achieved have been supported by the life cycle assessment analysis, which has demonstrated a reduction of the environmental impact of the CRT glass-containing ceramic glaze with respect to the standard one.

Beta Particles↗