Evaluation of Esophageal Electrodes for Recording His?Purkinje Activity Based Upon Signal Variance

Signal averaging the ECG to observe low level signals generated by His?Purkinje system (HPS) has many disadvantages and has not been widely used. This is partly due to the inability to distinguish between atrial and HPS potentials within the PR segment. To more clearly observe the onset of the HPS activity, several leads with an esophageal electrode were studied and compared to a bipolar surface lead. Signal variance was calculated to estimate the noise levels present in all lead systems. The bipolar surface lead consistently provided reproducible HPS waveforms with accurate estimates of noise levels. The leads with an esophageal electrode (bipolar or esophago?thoracic) failed to show reproducible HPS waveforms and had higher noise levels than the bipolar surface lead as measured by signal variance. The cause of these problems is the motion of the electrode within the esophagus, as visualized fluoroscopically. While the novel lead systems were not adequate for recording HPS waveforms, the analytic methods for evaluating signal averaged recordings from various lead systems provided a basis for optimizing this approach for quantifying low level cardiac signals.     

The audibility of low-frequency sounds

Contours of equal loudness and threshold of hearing under binaural free-field conditions for the frequency range 20–15 000 Hz were standardized internationally in 1961. This paper describes an extension of the data in the low-frequency range down to 3·15 Hz, at l levels from threshold to 70 phon. The latter corresponds to nearly 140 dB sound pressure level at the lowest frequency. Direct loudness comparisons were made between tones at intervals of an octave, and the resulting contours were checked by numerical loudness estimation.     

Equation of state data for iron at pressures beyond 10 Mbar

We present equation of state points for iron, in the pressure range 10-45 Mbar, the first obtained with laser-driven shock waves. The experiment has been performed with the high energy laser Phebus, optically smoothed with Kinoform phase plates. Our results double the set of existing experimental data at very high pressures showing good agreement with the predictions of the quotidian equation of state model and with previous results.     

Spontaneous template-free assembly of ordered macroporous titania

Spontaneous formation of ordered macroporous titania is achieved by dropwise addition of titanium alkoxides to aqueous ammonia in the absence of auxiliary organic templates.     

A novel method for the generation of nitrile oxides on solid phase: application to the synthesis of substituted benzopyranoisoxazoles

A solid-phase synthesis of substituted benzopyranoisoxazoles is described. The six-step synthesis features a novel method of generating nitrile oxides on a polymer support followed by an intramolecular 1,3-dipolar cycloaddition with a tethered alkyne for assembly of the benzopyranoisoxazole scaffold. Furthermore, the utilization of single-bead attenuated total reflectance Fourier transform infrared (ATR-IR) microspectroscopy as an essential analytical tool for reaction optimization is highlighted.     

Electrospray ionization gas-phase electrophoresis under ambient conditions and it's potential or high-speed separations

A moderately high resolution nanoelectrospray ionization gas-phase electrophoresis instrument was constructed and evaluated for simple high-speed separations of several groups of compounds. The insertion of a plate containing a 1.6 cm diameter exit orifice, 2.5 cm from the location of electrospray, allowed ions to be created and desolvated under ambient conditions with minimal solvent contamination to the drift tube. Ion separation selectivity is discussed and shown to be slightly altered by changing the drift gas flow rate. Issues of using gas-phase electrophoresis as a high-speed separation technique are discussed. Gas-phase electrophoresis-spectra of selected benzodiazepines, triazine herbicides, and simple combinatorial chemistry libraries are demonstrated.     

Mechanism of coating by electropolymerization on metal cathodes from zinc chloride solutions of acrylamide

Electrocoating by polymerization of aqueous zinc chloride solutions of acrylamide and methylenebisacrylamide has been reexamined. The original investigators of this system proposed a mechanism in which the initiation was formed by electrochemical reduction of a zinc complex of molecular oxygen. That mechanism is not compatible with the present findings that polymerization occurs when oxygen is excluded by nitrogen bubbling. Evidence is presented for the intervention of a zinc complex with monomer. The pH dependence of electrocoating indicates that the species involved is ZnOH⁺. Failure to achieve coating in acidic solutions of monomers in the absence of zinc points to a multisite attchment of the metal species to monomer in a ring structure. The interpretation is consistent with the observed electropolymerization of N,N-dimethylacrylamide and with the correlation of electropolymerizability with shifts detected in laser Raman spectra of selected acrylic monomers.     

Validity of the Fowler-Nordheim parameters measured for silicon adsorption on single crystal faces of tungsten

The adsorption of silicon on the (112), (111), (100), (110), (113) and (116) planes of tungsten field emitters has been studied. As with Ge and CdS adsorption, anomalous behaviour of the Fowler-Nordheim parameters A and φ was observed together with non-linearity in the Fowler-Nordheim plots. This non-linearity is not explicable in terms of the theories proposed for bulk semiconductors. The present results support the suggestion that field-induced Si migration from the W substrate is responsible for anomalies in the F-N parameters.