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PubMed2002

Determination of trace amounts of thallium by adsorptive cathodic stripping voltammetry with xylenol orange.

Trace amounts of thallium(I) can be determined using adsorptive cathodic stripping voltammetry in the presence of Xylenol Orange (XO). The reduction current of the thallium(I)-XO complex ion was measured by square-wave cathodic stripping voltammetry. The peak potential was at -0.44 V vs. Ag/AgCl. The effect of various parameters (pH, ligand concentration, accumulation potential and collection time) on the response are discussed. The response was linearly related to the thallium concentration in the range 0.5-110 ng ml(-1) and 110-2000 ng ml(-1). The limit of detection was 0.2 ng ml(-1). The relative standard deviation for the determination of 80 ng ml(-1) thallium was 2.8%. Many common anions and cations did not interfere with the determination of thallium. The interference of lead was reduced by the addition of 0.003 M sodium carbonate. The voltammetric procedure was then successfully applied to the determination of thallium in various complex samples.

Journal Article↗
PubMed1993

Dot immunoassay with biotinylated antigen for determination of antibodies against the circulating cathodic antigen (CCA) in schistosomiasis japonica.

Based on the fact that schistosomiasis patients in both the acute and chronic phase of the infection show a strong humoral immune response against the gut-associated circulating cathodic antigen, a simple and sensitive dot immunobinding assay for schistosomiasis japonica was developed. Circulating cathodic antigen that had been purified by immunoadsorption using monoclonal antibody was biotinylated with biotin aminocaproylhydrazide via the carbohydrate moiety of the antigen. Serum samples dotted onto nitrocellulose strips were then tested in an assay involving a combined incubation step of biotinylated antigen and streptavidin peroxidase, and a subsequent staining; the total assay time was 1.5 hr. Assaying the sera of 105 uninfected controls and 104 Schistosoma japonicum-infected individuals showed a specificity of 99.0%, and sensitivities of 96.2% (acute infections) and 94.1% (chronic infections). The described assay is economic, rapid, and reproducible and lends itself to use under field conditions.

Animals↗
PubMed2003

New sol-gel synthetic route to phospho-olivines as environmentally friendly cathodes for Li-ion cells.

A new sol-gel synthetic route was developed to prepare single-phase phospho-olivines LiMPO4 (M = Fe or Mn), potential cathode materials for the next generation of Li-ion secondary batteries. Triethyl phosphite was used as phosphate organic precursor, with absolute ethanol as solvent. The sol-gel synthesis ensures homogeneity of the precursors at the nanometric scale and improved reactivity, allowing to obtain very small agglomerates and crystal grain size. Several carbon sources were used in order to improve the electrochemical performances of the samples. Galvanostatic cycling tests of the cathodic materials were made on coin cells with Li metal as anode in order to study the influence of the synthesis and the structural-morphological characteristics on the electrochemical performance of the phosphate/C composite.

Conservation of Energy Resources↗
PubMed1999

[Study on magnesium ionization in cathodic sputtering glow discharge plasma].

A method, based on the Doppler broadening-dependent absorption width and the ionization degree measured by the ratio of relative atomic and ionic absorbance in cathodic sputtering glow discharge (CSGD) plasma with aluminum-magnesium alloys as cathodes, is proposed. The experimental reveals that the plentiful magnesium ions in the plasma under the conventional discharge conditions of the atomizer do influence the analytic working curves. Corrected method is derived and factors which result in magnesium ionization degree are disscused.

English Abstract↗
PubMed1992

Cathodic voltammetry of riboflavin at platinum and gold rotating disc electrodes.

The electroreduction of riboflavin (FMN) has been examined by cathodic rotating disc voltammetry in acidic and basic media at platinum and gold electrodes. It has proved to be diversely reducible best at gold electrode in the alkaline media. Rapid voltametric determination of the substance at gold electrode was effective and gave a mean standard deviation of 1%. Riboflavin at platinum electrode is cathodically active but the voltammograms do not obey the Levich relationship and adsorption destroys the electrode activity. The technique can be conveniently applied to the rapid determination of riboflavin in pure solution and in formulated products.

Journal Article↗
PubMed1978

Oxygen cathode measurements and radiation response in tumour-bearing mice treated with misonidazole.

Direct measurements using 200 micron oxygen cathode electordes have been made in tumour and subcutaneous tissues of anaesthetized C3H mice treated with misonidazole. In air-breathing animals a six-fold increase in tumour oxygen cathode readings was observed by 23 min after i.p. injection of misonidazole at 0.5 mg/g body weight. A similar rise, but of 2.5 times, was observed for the subcutaneous tissues. Comparison of tumour oxygen readings for drug-treated and control mice breathing 100% O2 at different pressures showed markedly increased levels for the drug-treated animals. Tumour response to radiation was measured for 250 kV X-rays and 15 MeV electrons. In each case, when a dose of radiation was combined with pre-treatement with misonidazole an increased radiation response was observed when compared with the same dose of radiation given alone. At the highest dose (40 Gy) there was a suggestion of an increased normal tissue reaction. The significance of the measurements is discussed.

Adenocarcinoma↗
PubMedDate not supplied

[Derivation of the working equations of a CO2-CO-H2O-H2-N2 gas mixture for the cathode space of an electrolyzer with solid electrolyte taking into account its oxygen extraction].

Equations of thermodynamic equilibrium of the gas mixture CO2-CO--H2O-H2--N2 for the cathode space of the electrolyzer containing a solid electrolyte with extracted oxygen taken into consideration were derived. Equilibrium partial gas pressures, thermal effect of reactions, theoretical voltage of dissociation (the system of equations included 11 unknown parameters) were determined. These parameters are functions of temperature, total pressure of the gas mixture, initial gas composition, and the coefficient characterizing the degree of oxygen transfer from the cathode cell to the anode cell of the electrolyzer.

Carbon Dioxide↗
PubMed1977

Design of the pulsed oxygen cathode.

This paper presents a theoretical design of the pulsed oxygen cathode. The analysis concerns two major areas: First, a description of the oxygen diffusion currents during the initial 5 msec. after the application of the polarization potential. Second, a determination of the limiting sample rate imposed by a protective coating of given characteristics. It is shown that at 5 msec. after application of the polarization potential the 99% isoconcentration line is 11.8 micron from the cathode surface. The currents during this time can be modeled as linear diffusion. Also, for a minimum step response of 100 msec. the protective coating should have a thickness less than or equal to 13.6 micron.

Cold Temperature↗
PubMed1989

Comparison of conventional fluorescein angiography film images with a cathode ray tube display.

We evaluated the effectiveness of cathode ray tube (CRT) displays in the transfer of diagnostic information to the ophthalmologist. Retinal fluorescein angiography images were used and data were taken using the receiver operating characteristic experimental paradigm. Three ophthalmologists with experience ranging from two to 12 years participated in the study. Sixty-eight images were selected from proof sheets of 800 original images. Next, these images were digitized, then each set was shown on its respective display (slide projection for the proof sheet images and CRT for the digital images). These 68 images were from a variety of patients and represented a broad range of normal and abnormal retinas (including diabetic retinopathy, hypertension independent of diabetes, and sickle-cell disease). Results show (1) that there is no difference between the systems in terms of diagnostic accuracy; (2) that certainty of diagnosis was not a function of the system; and (3) that although there was an effect due to experience of the ophthalmologist, it did not affect diagnosis accuracy. We conclude that CRT displays at conventional video resolutions can deliver the needed diagnostic information as well as film. We also hypothesize that digital enhancement techniques can increase the available diagnostic information beyond that of film.

Computer Systems↗
PubMed2007

Cathodic electrografting of versatile ligands on Si(100) as a low-impact approach for establishing a Si--C bond: a surface-coordination study of substituted 2,2'-bipyridines with CuI ions.

Three distinct wet chemistry recipes were applied to hydrogen-terminated n- and p-Si(100) surfaces in a comparative study of the covalent grafting of two differently substituted 2,2'-bipyridines. The applied reactions require the use of heat, or visible light under a controlled atmosphere, or a suitable potential in an electrochemical cell. In this last case, hydrogen-terminated silicon is the working electrode in a cathodic electrografting (CEG) reaction, in which it is kept under reduction conditions. The resulting Si--C bound hybrids were characterized by a combination of AFM, dynamic contact-angle, and XPS analysis, with the help of theoretical calculations. The three distinct approaches were found to be suitable for obtaining ligand-functionalized Si surfaces. CEG resulted in the most satisfactory anchoring procedure, because of its better correlation between high coverage and preservation of the Si surface from both oxidation and contamination. The corresponding Si-bipyridine hybrid was reacted in a solution of CH3CN containing CuI ions coordinatively bound to the anchored ligands, as evidenced from the XPS binding-energy shift of the N atom donor functions. The reaction gave a 1:2 Cu-bipyridine surface complex, in which two ligands couple to a single CuI ion. The surface complex was characterized by the Cu Auger parameter and Cu/N XPS atomic-ratio values coincident with those for pure, unsupported CuI complex with the same 2,2'-bipyridine. Further support for such a specific metal-ligand interaction at the functionalized Si surface came from the distinct values of Cu2p binding energy and the Cu Auger parameter, which were obtained for the species resulting from CuI ion uptake on hydrogen-terminated Si(100).

Journal Article↗
PubMed1993

Schistosoma mansoni circulating anodic antigen but not circulating cathodic antigen interacts with complement component C1q.

Adult schistosome parasites, living in the blood vessels of their mammalian hosts, protect themselves against immune damage in a variety of ways. In addition to the tegument, the intestinal epithelium of the blood-feeding worms is permanently exposed to both the innate and the acquired immune system. In this study, we investigated whether the Schistosoma gut-associated antigens CAA and CCA (circulating anodic antigen and circulating cathodic antigen, respectively), which are excreted in relatively large quantities into the host's circulation, might play a role in evading complement attack. Of several complement components tested, only purified C1q showed significant binding to CAA, a negatively charged highly glycosylated glycoprotein. CCA, also highly glycosylated, but neutral or slightly positively charged, did not bind to C1q. CAA bound only to the collagen-like stalks of C1q and not to the globular heads. No detectable interaction of CAA with precursor human C1 was found and CAA did not induce activation of C1 in whole human serum as assessed by consumption of hemolytic C4 activity. Also CAA could not induce activation of precursor C1 in vitro. These results suggest that CAA behaves like a receptor for C1q, and might be involved in protecting the vulnerable schistosome gut against complement-mediated attack.

Animals↗
PubMedDate not supplied

Ti/IrO2 as anode and Zr as cathode in multicompartment electrolyzers with Immobiline membranes.

Multicompartment electrolyzers with isoelectric Immobiline membranes are used for large-scale preparative protein purification. A series of isoelectric membranes, of defined pI values, is utilized for keeping any desired species isoelectric within each compartment of the electrolyzer. It is preferable to have electrode disks of the same surface area as the membranes for a proper performance of the instrument because electrolyte solutions of low conductivity are used. The use of Pt disks would be quite expensive; we therefore propose using Zr as a cathode and Ti/IrO2 as an anode in the electrodic compartments. This pairing of electrodes seems to give the same performance as Pt wires. Also, conventional isoelectric focusing, as well as isoelectric focusing in immobilized pH gradients, both requiring a good contact area between gel and electrodes, would benefit by using flat laminae of these metals as electrodes.

Acrylamides↗
PubMed2006

Hybrid silica monolithic column for capillary electrochromatography with enhanced cathodic electroosmotic flow.

A hybrid silica monolithic stationary phase for RP CEC was prepared by in situ co-condensation of (3-mercaptopropyl)-trimethoxysilane (MPTMS), phenyltriethoxysilane (PTES), and tetraethoxysilane (TEOS) via a sol-gel process. The thiol groups on the surface of the stationary phase were oxidized to sulfonic acids by peroxytrifluoroacetic acid. The introduced sulfonic acid moieties on the monoliths were characterized by a strong and relatively stable EOF in a broad pH range from 2.35 to 7.0 in CEC. Aromatic acids and neutral compounds can be simultaneously separated in this column under cathodic EOF. The CEC column exhibited a typical RP chromatographic mechanism for neutral compounds due to the introduced phenyl groups.

Amino Acids, Aromatic↗
PubMed1984

The electrical stimulation of bone using a filamentous carbon cathode.

Filamentous carbon fiber is an extremely compatible biomaterial. It does not corrode and elicits almost no foreign body response. In addition, this material is an efficient electrical conductor in vivo. These desirable characteristics suggest that carbon fiber may be of use as an electrode material for the stimulation of bone and/or soft tissue growth. This possibility has been investigated in a well established laboratory animal model. When used as a cathode material in conjunction with an implantable constant direct current device, carbon fiber was shown to be an effective electrode material for the stimulation of bone and fibrous tissue within the medullary canal of the tibia of the rabbit. Further, adjustment of current levels appear to allow some selectivity in terms of the amount and type of tissue produced. Currents in the 1 microA range produced a maximum amount of bone, whereas a 20 microA current produced a maximum amount of fibrous tissue. Intermediate current levels produced a proportional mix of bone and soft tissue.

Animals↗
PubMed1979

Neurites grow faster towards the cathode than the anode in a steady field.

We explanted fragments of embryonic chick dorsal root ganglia on to polylysine coated glass and cultured them in a medium containing one unit of nerve growth factor plus enough methylcellulose to give viscosities from 0.01-3,000 poise. We allowed them to grow out in the absence of a field, and then selected explants with halos of neurites which were relatively dense, relatively symmetrical, and practically free of glial cells. These selected explants were then exposed to electrical fields of up to 140 mV/mm for some hours. In media with viscosities of one poise or less, the field some times dragged the central cell mass of an explant towards the anode. However, in cases where the central cell mass did not move, fields of 70-140 mV/mm induced that sector of each neurite halo which faced the cathode to grow out several times faster than the one facing the anode.

Animals↗
PubMed2006

Minimal structural requirements for root effect: crystal structure of the cathodic hemoglobin isolated from the antarctic fish Trematomus newnesi.

The cathodic hemoglobin component of the Antarctic fish Trematomus newnesi (HbCTn) is a Root-effect protein. The interpretation of its functional properties in relation to its sequence is puzzling. Indeed, HbCTn sequence is characterized by an extremely low histidyl content, and in particular by the lack of His146beta and His69beta, which are believed to be important in Bohr and Root effects, respectively. Furthermore, previous analyses suggested that the local environment of Asp95alpha, Asp99beta, and Asp101beta should not be appropriate for the formation of Asp-Asp interactions, which are important for the Root effect. Here, we report the high-resolution crystal structure of the deoxy form of HbCTn. Our data provide a structural interpretation for the very low oxygen affinity of the protein and insights into the structural determinants of the Root effect protein. The structure demonstrates that the presence of Ile41alpha and Ser97alpha at the alpha1beta2 interface does not prevent the formation of the inter-Asp interactions in HbCTn, as previous studies had suggested. The present data indicate that the hydrogen bond formed between Asp95alpha and Asp101beta, which is stabilized by Asp99beta, is per se sufficient to generate the Root effect, and it is the minimal structural requirement needed for the design of Root-effect Hbs.

Animals↗
PubMedDate not supplied

Scanning electron microscopy of nonconductive specimens at critical energies in a cathode lens system.

A method for scanning electron microscopy imaging of nonconductive specimens, based on measurement and utilisation of a critical energy, is described in detail together with examples of its application. The critical energy, at which the total electron yield curve crosses the unit level, is estimated on the basis of measurement of the image signal development from the beginning of irradiation. This approach, concentrated onto the detected signal as the only quantity crucial for the given purpose of acquiring a noncharged micrograph, evades consequences of any changes in an irradiated specimen that influence the total electron yield curve and possibly also the critical energy value. Implementation of the automated method, realised using a cathode lens-equipped scanning electron microsope (SEM), enables one to establish a mean rate of charging over the field of view and its dependence on the electron landing energy. This dependence enables one to determine the energy of a minimum damage of the image of the given field of view. Factors influencing reliability and applicability of the method are discussed and examples of noncharged micrographs of specimens from both life and material science fields are presented.

Actinomycetales↗
PubMed1996

Simulation calculations of cardiac virtual cathode effects.

The anisotropic bidomain model has been used to perform computer simulations of cardiac tissue stimulated externally. Virtual cathode distances, Rvc, are found to be affected by type of stimulation and the degree of conductance between the extracellular domain and the ground provided by, for example, a saline bath. For no such conductance, hyperpolarizing blocking regions develop in the longitudinal direction of propagation. These regions are much reduced by even a small conductance to ground. They do not occur for transmembrane stimulation. They result in much reduced Rvc sizes in the longitudinal direction even in the presence of some ground conductance, and negative Rvc values for no such conductance.

Computer Simulation↗