Detection of a local slow potential preceding the surface QRS complex during non-preexcited impulse propagation--a phenomenon reflecting anterograde concealed conduction through the accessory pathway?

A case of Wolff-Parkinson-White (WPW) syndrome with several interesting electrophysiologic findings is presented. Although manifest preexcitation had not been documented in clinical routine check-ups for the 2 years before the ablation session, an intermittent preexcitation emerged after an initial unsuccessful radiofrequency current delivery directed at the subvalvular mitral annulus 1 cm distal from the subsequent successful ablation site. During intermittent manifestation of preexcitation, the following observations were made: (1) during manifest preexcitation, a possible Kent potential was recorded at the successful ablation site; (2) during non-preexcited impulse propagation, a local slow potential preceding the QRS complex (pre-QRS potential) was clearly observed at the same site; (3) the pre-QRS potential disappeared during orthodromic atrioventricular reciprocating tachycardia, spontaneous atrial premature contraction and after the subsequent successful ablation; and (4) when the pre-QRS potential was obvious, a small change in QRS morphology of the body-surface ECG was appreciable, compared with that during beats of negative pre-QRS potential. A comparable preceding component was also detected in a signal-averaged ECG. It is considered that the pre-QRS potential might be related to the anterograde concealed conduction through the accessory pathway.     

Specific Heat Measurement of High Temperature Thermal Insulations by Drop Calorimeter Method

By applying the drop calorimeter method, a specific heat measuring apparatus that can be used in the temperature range from 100 to 1000°C has been developed. It is generally difficult to measure the specific heat of thermal insulation, because the insulation material is porous, and has low thermal conductivity and small heat capacity. In the present apparatus, the specific heat of thermal insulation is simply measured by dropping a heated specimen into water. The specific heat of the specimen obtained by the apparatus is the mean specific heat between the initial specimen temperature before dropping and the equilibrium water temperature after dropping. This apparatus was used to measure the mean specific heat of standard specimen SRM 720 Synthetic Sapphire (-Al₂O₃) whose reference values are certified by the National Institute of Standards and Technology (NIST). The measured values agreed well with the reference values within an error of ±10%. The specific heats of SiC refractory material, rock wool, alumina silica fiber, alumina silica board, calcium silicate, and SiO₂ glass measured with this apparatus are also presented.     

Investigation of precipitation behavior in a weld deposit of 11Cr-2W ferritic steel

This article is aimed at investigating the difference in precipitation behavior in the fine-grained heat-affected zone (FGHAZ), coarse-grained heat-affected zone (CGHAZ), and base metal for the welded joint of high Cr ferritic heat-resistant steel (11Cr-0.4Mo-2W-1Cu-V-Nb, normalized 1323 K×1 h and tempered 1033 K×1 h). Simulated HAZ (SHAZ) specimens were used, whose thermal cycles were controlled to be the same as those in the actual welded joint with peak temperatures of 1523 and 1173 K to represent CGHAZ and FGHAZ, respectively. Based on scanning electron microscopy (SEM) observation, it looks that the precipitates in FGHAZ specimens (1173 K) were fewer and larger than those in CGHAZ (1523 K) specimens and base metal specimens. This phenomenon implied that the growth and coarsening of precipitates in FGHAZ may play a role in the deterioration of creep properties and type IV cracking, which was observed in previous creep tests. X-ray diffraction analysis for the electrolytic extraction showed that the types of precipitates are the same for the 1173 K specimens and base metal specimens, including M₂₃C₆, MX, Laves phase, and μ phase. Further, the elemental analysis of the extraction showed that the mass percentages of Cr, W, and Mo in the precipitates to specimen mass were higher in the FGHAZ specimen than those in the base metal specimen, especially during the period between 600 and 2464 hours. Finally, a two-dimensional (2-D) model was proposed to simulate the precipitation behavior of the Laves phase.     

Possibility of Postliquefaction Flow Failure due to Seepage

This study examines the postliquefaction flow failure mechanism, in which shear strain develops due to seepage upward during the redistribution of excess pore water pressure after an earthquake. The mechanism is addressed as both a soil element and a boundary value problem. Triaxial tests that reproduce the stress state of a gentle slope subjected to upward pore water inflow were performed, with the results showing that shear strain can increase significantly after the stress state reaches the failure line. In addition, when subject to equivalent volumetric strain, shear strain is considerably larger in loose sand conditions than in dense sand. Compared with consolidated and drained test results, the dilatancy coefficient β, which indicates the rate of dilation, is the same as that obtained from pore water inflow tests. Torsional hollow cylinder tests were also performed to ascertain the limit of dilation of sand specimens. It was found that the β values are nonlinear in behavior. In addition, a postliquefaction flow failure mechanism based on one-dimensional consolidation theory and shear deformation behavior as a result of pore water inflow is proposed.     

New star quad symmetrical cable

The letter proposes a new star quad structure for symmetrical cable which makes the quad diameter smaller with no loss change and the quad manufacturing processes simpler than conventional star quad structures. The characteristics are also shown of a new specially manufactured trial star quad symmetrical cable.     

Semi-quantitative approach to estimating GFR by magnetic resonance imaging

Objective: The purpose of this study was to compare a semi-quantitative approach to estimating glomerular filtration rate (GFR) by magnetic resonance imaging with radionuclide calculation of GFR, and to investigate whether spin echo or gradient echo is more suitable for estimating GFR.Methods and patients: Fourteen kidneys of seven patients (GFR ranging from 26 to 57 ml/min) were studied. Spin echo and gradient echo sequences interleaving each other at every excitation were used. After intravenous injection of gadopentetate dimeglumine, serial scans were performed. The signal intensities measured in the regions of interest were converted to time-transverse relaxation rate changes for both spin echo (ΔR2) and gradient echo (ΔR2^*). The areas under the time-ΔR2 and time-ΔR2^* curves were calculated as a semi-quantitative index of GFR for both spin echo and gradient echo images, and the results were compared by GFR measured by radionuclide imaging.Results: The semi-quantitative index of the GFR calculated from spin echo images showed a significant correlation with the GFR measured by radionuclide imaging (r=0.85,P<0.001). On the other hand, the semi-quantitative index of the GFR calculated from gradient echo images showed no such correlation (r=0.46,P=0.10).Conclusion: Spin echo sequences may be more suitable than gradient echo sequences for the evaluation of GFR.     

Phase equilibria and microstructural control of gamma TiAl based alloys

Phase equilibria among the β (bcc or B2), (hcp) and γ (L1₀) phases in Ti---Al---M ternary systems at elevated temperatures have been studied, where the M is β stabilizing element for pure titanium. The β(B2) + + γ three-phase coexisting region exists at temperatures above 1473 K, and it moves towards a direction of high aluminum and high M concentrations with increasing temperature. The change in the phase equilibria by the addition M is associated with the ↔ β allotropic transformation temperature of pure titanium and can be thermodynamically interpreted in terms of the lattice stability ratios of M to Ti. The change in the phase equilibria results in new reaction pathways peculiar to the ternary systems, thereby opening more possibility for microstructure control of the gamma based alloys. The vertical section drawn based on these studies demonstrates that the γ phase can be in equilibrium with the β(B2) phase at relatively low temperatures in the ternary systems and create a reaction pathway of → β(B2) + γ. Upon cooling along the same pathway of → γ as in the binary alloy, the addition of third element affects the transformation rate, and the massive γ structure is found to be formed even under slow cooling rate.     

Induction of cytokines in a human colon epithelial cell line by Shiga toxin 1 (Stx1) and Stx2 but not by non-toxic mutant Stx1 which lacks N-glycosidase activity

Stx1 and Stx2 produced by Shiga toxin-producing Escherichia coli are cytotoxic due to their N-glycosidase activity on 28S rRNA. In this study, we have shown that proinflammatory cytokine mRNAs, especially IL-8, were induced by Stx1 and Stx2 in Caco-2 cells. A non-toxic mutant of Stxl which lacks N-glycosidase activity did not induce cytokine mRNAs. IL-8 production at the protein level was enhanced by Stx1 and Stx2, but not by the mutant Stx1. These results demonstrate that Shiga toxins induce expression and synthesis of cytokines in Caco-2 cells and their N-glycosidase activity is essential for the induction.