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PubMed2006

The application of cathodic reductions and anodic oxidations in the synthesis of complex molecules.

This tutorial review surveys the recent advances in electrochemical transformations as they pertain to the synthesis of complex organic molecules. Electrochemistry has emerged as a powerful tool to synthetic chemists, yet many have never considered electrochemical methodology as a means for synthesis. Here, an introduction to electrochemistry and voltammetry will be provided with descriptions of the four types of electrochemical cells. In addition, recent examples of both anodic oxidations and cathodic reductions will be discussed, along with the experimental setups for carrying out each reaction.

Electrochemistry↗
PubMed1997

Circulating anodic and cathodic antigen in serum and urine of mixed Schistosoma haematobium and S. mansoni infections in Office du Niger, Mali.

In Office du Niger, an area endemic for both Schistosoma haematobium and S. mansoni in Mali, circulating anodic (CAA) and cathodic (CCA) antigen detection assays were performed on pretreatment serum and urine samples from two villages, Rigandé and Siguivoucé, and compared with egg counting methods. The highest prevalence was obtained with the urine-CCA assay which also had the highest sensitivity to S. haematobium, S. mansoni or mixed infection. A single urine-CCA assay was as sensitive as repeated egg counts (one stool+two urine examinations per individual). When the different assays were tested in parallel, several combinations including assays on serum were found to be highly sensitive. As urine sampling is widely accepted, urine assays will be used for further monitoring these villages one and two years after chemotherapy.

Animals↗
PubMed2001

A study of the effect of color photostimulation from a cathode-ray tube (CRT) display on photosensitive patients: the effect of alternating red-cyan flicker stimulation.

PURPOSE: In an attempt to establish evidence for developing better guidelines for the production of animation programs that would not induce photosensitive seizures in Japan, we evaluated the effects of red flicker, alternating red/cyan (complementary color to red) flicker stimuli, and of contrast between the red and cyan frames from a cathode-ray tube (CRT) display in photosensitive patients. METHODS: We studied 35 photosensitive patients. They were exposed to seven types of flicker. The first three types were alternating red/cyan flicker (R/C) with the luminance of cyan set at three different levels, high, equal, and low luminance (65, 20, and 16 cd/m2, respectively) relative to the red (20 cd/m2). The following four types were red, cyan, yellow, and magenta flicker stimuli. EEGs were recorded while the patients watched these stimuli on a CRT display. RESULTS: Rates of photoparoxysmal response (PPR) provocation were 11.4, 13.7, and 14.0% with high-, no- and low-contrast R/C flicker, respectively, and 3.7% with red flicker. The differences between red and each of the other R/C flicker stimuli were all statistically significant (p<0.05, 0.01, 0.01). No significant differences were found between the effects by each of the three levels of contrast in alternating R/C flicker (p > 0.05). CONCLUSIONS: These findings suggest that alternating R/C flicker is more provocative than simple red flicker, and that contrast between frames of different colors may play some role in the effects of alternating flicker stimuli from a CRT display in photosensitive patients. Therefore, caution against the use of the combination of red and cyan, in addition to the red flicker stimulus, should be included in any guidelines drawn up to prevent photosensitive seizures.

Adolescent↗
PubMed1976

Peroxidase complex with concomitant anodal and cathodal variation in red-fruited tomato species.

Four groups of bands (a-d) are controlled by 19 alleles of the Peroxidase-4 (Prx-4) complex in the red-fruited tomato species, Lycopersicon esculentum and L. pimpinellifolium. Heterozygotes can be detected by virtue of codominance in all combinations except a few in which bands of single groups are absent ("semi-null" alleles). No recombinations were detected in 7419 F(2) segregants of 53 different combinations of alleles. A maximum fiducial limit (P = 0.01) of 0.08% crossing-over between any Prx-4 band groups is estimated. Variation of the anodal b bands is absolutely associated with that of the cathodal d band in respect to presence versus absence and direction of migration. In respect to the origin of these variants, the probability of 18 instances of simultaneous mutation of genes at two loci, always in such complete agreement, is so remote that no more than one locus could conceivably govern b and d. The disposition of a is not similarly associated with that of the other bands, while that of the faint-staining c could not always be reliably resolved. The negation of all save extremely low recombination rates and the observed concomitant variation of b and d strongly support the concept of single locus control of all Prx-4 banding, this hypothesis being espoused until rejection should be required be required by future research. Models of single locus control of several isozymes are discussed.

Journal Article↗
PubMed2000

Temporal variation in the luminance level of stimuli displayed on a cathode-ray tube monitor: effects on performance on a visual vigilance task.

This paper assesses the extent to which the sensitivity decrement frequently observed in vigilance tasks is affected by temporal variations in the luminance level of the stimuli displayed on the screen of a cathode-ray tube (CRT) monitor. First, it was confirmed that the luminance of the stimuli displayed on the screen of the CRT monitor decreases substantially during the first hour after turning the monitor on, and then it remains quite stable. Second, an experiment was carried out in which participants performed a visual vigilance task at three different time periods within which the luminance of the stimuli displayed on the screen of a CRT monitor either decreased or remained stable. The results indicate that the vigilance decrement is modulated by temporal fluctuations of the luminance of the monitor screen, which is used to display the stimuli. However, the relationship between both variables is not simple: the largest sensitivity decrement was not associated with the largest luminance decrement, but to a medium luminance decrement.

Adult↗
PubMed2002

Determination of brilliant blue FCF in the presence and absence of erythrosine and quinoline yellow food colours by cathodic stripping voltammetry.

A study of the voltammetric behaviour of the food colours brilliant blue FCF (C.I. 42090), erythrosine (C.I. 45430) and quinoline yellow (C.I. 47005) in the pH range 2-10 have been carried out by cathodic#10; stripping voltammetry. At pH 4.5 (acetate buffer) with an accumulation potential of 0 V and accumulation time of 30s, the voltammograms presented well-defined reduction peaks at potential - 0.76 V for brilliant blue FCF, - 0.85 V for quinoline yellow and - 0.54 V for erythrosine. Linear calibration graphs were obtained from 8 to 80 microg l(-1) brilliant blue, from 4 to 43 microg l(-1) quinoline yellow and from 10 to 70 microg l(-1) erythrosine. The method has been successfully applied to identify and quantify binary mixtures of these dyes and applied for determining brilliant blue FCF in commercial food products.

Benzenesulfonates↗
PubMedDate not supplied

A new cathodal Gc variant in Australia.

A new cathodal Gc variant and a known rare variant were found in a study of 307 Australian caucasian blood donors, each with a gene frequency of 0.28%. The frequencies of the other alleles were 0.161 (Gc1F), 0.557 (Gc1S) and 0.279 (Gc2), and were comparable with those of two earlier surveys.

Australia↗
PubMed2005

Evaluation of biopolymer-modified concrete systems for disposal of cathode ray tube glass.

Cathode ray tubes (CRTs) from computer monitors and television sets, which contain significantly high percentage of lead (Pb) by weight, represent an enormous and growing hazardous waste problem in the United States and worldwide. As a result, new technologies are needed to cope with current CRT waste stream and increased hazard and build new markets for its recycled components, developing commercially viable concrete composites, as well as minimizing CRT disposal problems. In this study, commercially available biopolymers, such as xanthan gum, guar gum, and chitosan, were used to encapsulate CRT glass waste, reducing the Pb leachability. The biopolymers utilized contain a number of useful functional groups, such as carboxyl (xanthan), hydroxyl (guar), and amino groups (chitosan), which play important roles in binding and stabilizing Pb onto concrete structures. The use of biopolymers in concrete systems can create a stable interpenetrating cross-linking composite that will last for many years. Results from these new composites show 30% higher compressive strength than standard concrete and a sharp decrease in lead leachability from several thousand milligrams per liter initially to an amount of three-tenths milligrams per liter or lower values (much lower than the U.S. Environment Protection Agency standard for hazardous waste of 5 mg/L by the toxicity characteristic leaching procedure test), and for some of the composites leachability is below even the standard for drinking water. This efficient and cost-effective CRT-biopolymer-concrete composite is a new class of biopolymer-modified material that can potentially perform a significant role in relieving the current CRT issue.

Biopolymers↗
PubMed1985

Dosimetry comparison and characterisation of an Al K ultrasoft x-ray beam from an MRC cold-cathode source.

Ultrasoft x-rays of 0.3-5 keV have provided a unique tool for the investigation of intracellular mechanisms of radiation action in biological organisms, including mammalian cells. However, their use presents unique practical problems in dosimetry and experimental design. Detailed interpretation of the biological results requires reliable dosimetry and well characterised monoenergetic beams. This paper presents a comparison between two fundamentally different dosimetric techniques, namely the ionisation current in an extrapolation chamber and photon counts in a proportional counter. Agreement within 7% was obtained when these two methods were applied to an Al K x-ray beam (1.5 keV) from an MRC cold-cathode transmission target discharge tube as previously used in many biological experiments. Photographic film was calibrated as a relative dosimetric technique and used for investigation of the intensity uniformity of the radiation field. These techniques provide a comprehensive characterisation of the beam in the position of the biological cells, including photon flux (or absorbed dose rate), spectral purity (showing much less than 1% bremsstrahlung relative to characteristic Al x-rays) and uniformity over the irradiation area (within about 5% for mammalian cell irradiations).

Cell Survival↗
PubMed1994

Circulating anodic and cathodic antigen in serum and urine from Schistosoma haematobium-infected Cameroonian children receiving praziquantel: a longitudinal study.

A cohort of 148 Cameroonian children infected with Schistosoma haematobium was followed before praziquantel therapy and 1, 2, 3, 5, and 12 months thereafter. Egg output, the reagent strip index (RSI, a pathological marker), and circulating anodic antigen (CAA) and circulating cathodic antigen (CCA) in serum and urine were quantified. At enrollment, the median level of egg output was 365/10 mL of urine; 97% of children had a positive RSI; CAA was detected in serum from 76% of children and in urine from 64%; and CCA was detected in serum from 55% of children and in urine from 87%. Two months after chemotherapy, egg output and RSI had decreased significantly; reinfection later developed in parallel with increases in the serum and urine concentrations of CAA and the urine concentrations of CCA. The measurement of CAA and CCA is useful for diagnosis, evaluation of disease severity, and follow-up of chemotherapy in individuals infected with S. haematobium.

Adolescent↗
PubMed1991

Diagnosis of human schistosomiasis by detection of circulating cathodic antigen with a monoclonal antibody.

Monoclonal antibody (MAb) 5H11 reacted with repeating epitopes on Schistosoma mansoni circulating cathodic antigen (CCA) and detected CCA in sera of Egyptian S. mansoni-infected patients. MAb 5H11 was both capture and biotinylated detection antibody in a sandwich ELISA of trichloroacetic acid-pretreated serum samples. Sera of patients with 7-500 eggs/g of stool were positive by MAb 5H11-CCA sandwich ELISA. Stool egg counts and CCA serum levels correlated (r = .52), and CCA levels decreased by 4 weeks after praziquantel treatment in patients with pretreatment egg counts of greater than or equal to 50/g of stool (P less than .05). Sera of Schistosoma haematobium-infected patients, uninfected individuals, and most patients with other helminths were negative in this assay. The MAb 5H11-CCA sandwich ELISA appears sensitive and specific for immunodetection of active schistosomiasis mansoni and useful for monitoring its chemotherapy.

Adolescent↗
PubMed1995

Analysis of worm burden variation in human Schistosoma mansoni infections by determination of serum levels of circulating anodic antigen and circulating cathodic antigen.

Serum circulating anodic antigen (CAA) and circulating cathodic antigen (CCA) concentrations, as a possible direct measure of worm burden, were compared with fecal egg counts in a heavily Schistosoma mansoni-infected population from Zaire to allow differentiation between worm loads and worm fecundity in relation to age and intensity of infection. Of the 517 subjects, 95% excreted eggs and 97% demonstrated circulating antigens. Fecal egg counts showed an age-related pattern characteristic for an area in which schistosomiasis is endemic with intense transmission levels. Regression analysis showed that antigen concentrations were strongly associated with egg counts. For CAA, but not for CCA, this relation was found to be nonlinear, which would be consistent with density-dependent fecundity or crowding. The trend was uniform for all age groups, which for this particular population indicated a genuine reduction of worm loads rather than reduced worm fecundity with age of the host.

Adolescent↗
PubMed2002

The effect of pixel nonlinearity on cathode-ray tube-based visual acuity tests.

BACKGROUND: Pixel nonlinearity of a cathode-ray tube (CRT) display can cause differences between the actual image and the nominal image. One of the discrepancies, the anisotropy of interactions between neighboring pixels on the same raster line and between neighboring raster lines, may have an impact on the CRT-based visual acuity test where small horizontal and vertical gaps are used. We evaluated this impact. METHOD: Two high-quality color CRT monitors were tested. The stimulus target was a black square ring on a white background. White gaps of one stroke width were opened in the middle of the straight sides of the square ring. In a gap width comparison study, the up and down gaps were flanked with a one-pixel band on the left and right side. The pixel value of the bands was varied to determine the luminance that made up and down gaps appear to have the same width as left and right gaps. The comparison was made at 1 and 2 m. In a visual acuity study, horizontal gap (left/right) acuity and vertical gap (up/down) acuity were measured separately at several distances between 8 and 11 m. Similar measurements were made when the monitor was rotated 90 degrees. RESULTS: Gaps with edges that were parallel to raster lines (raster-parallel gaps) appeared wider than gaps with edges that were perpendicular to raster lines (raster-perpendicular gaps). To match the apparent width of the left and right gaps, the two one-pixel bands flanking the up and down gaps required a pixel value that corresponded approximately to a luminance of mid gray, indicating that the apparent width of a four-pixel left or right gap was similar to that of a five-pixel up or down gap. Raster-parallel gaps produced a higher percentage of correct responses than raster-perpendicular gaps in a visual acuity test. When nominal gap widths were equal, left and right gaps produced 10% or more correct responses than up and down gaps at some target sizes, which translated to a two-letter acuity difference. This acuity difference could not be accounted for by uncorrected astigmatism because the anisotropy persisted when the monitor was turned 90 degrees. CONCLUSIONS: Pixel nonlinearity of a CRT-display results in an anisotropy of gap width that can be observed at and above visual acuity size. This anisotropy may introduce uncertainties in the results of CRT-based visual acuity tests where gaps of different orientations are used.

Anisotropy↗
PubMed2001

Transitions of macroscopic structures and self-induced chaos observed in plasmas by a dc hollow cathode discharge having features of nonlinear open systems.

A novel experimental investigation is presented on the connection between discontinuous transitions of macroscopic structures of plasma and self-induced chaotic oscillations characterized by the positive Lyapunov exponents lambda(L) through the period-doubling route in a dc hollow cathode discharge, which has features of nonlinear open systems. We have clarified experimentally that there appear different discharge modes accompanying the discontinuous transitions, and detailed qualitative explanations are presented about the mechanism of those transitions. It is shown that fundamental frequencies of the self-induced periodic oscillations with nonpositive lambda(L) change with the changes of discharge current, and the amplitude of chaotic oscillations with the positive lambda(L) jumps up almost one order higher than that of nonchaotic ones with the nonpositive lambda(L). The self-induced chaotic oscillations with the positive lambda(L) have been observed near two edges of discontinuous transitions of plasma structures, suggesting that the chaotic mode is associated with the discontinuous transition of macroscopic structures in some nonlinear open systems.

Journal Article↗
PubMed2003

Time-resolved pinhole camera imaging and extreme ultraviolet spectrometry on a hollow cathode discharge in xenon.

A pinhole camera, an extreme ultraviolet (EUV) spectrometer, a fast gatable multichannel plate EUV detector, and a digital camera have been installed on the ASML EUV laboratory setup to perform time-resolved pinhole imaging and EUV spectroscopy on a copy of the Philips EUV hollow cathode discharge plasma source. The main properties of the setup have been characterized. Time-resolved measurements within the plasma pulse in the EUV have been performed on this source. Specific features of the plasma, such as a ring shape in the initiation phase and a propagating sphere during the pinch phase, have either been discovered or confirmed experimentally. Relative populations of various ionization stages in the pinch plasma have been estimated on the basis of line intensities and calculated transition probabilities. The changes in relative line intensities of a single ionization stage can be explained by a combination of temperature and excitation/deexcitation balance effects. Experiments with argon dilution on a newer version of the source show considerable effect on the shape of the xenon EUV spectrum.

Journal Article↗