Acidosis slows electrical conduction through the atrio-ventricular node

Acidosis affects the mechanical and electrical activity of mammalian hearts but comparatively little is known about its effects on the function of the atrio-ventricular node (AVN). In this study, the electrical activity of the epicardial surface of the left ventricle of isolated Langendorff-perfused rabbit hearts was examined using optical methods. Perfusion with hypercapnic Tyrode's solution (20% CO2, pH 6.7) increased the time of earliest activation (Tact) from 100.5 ± 7.9 to 166.1 ± 7.2 ms (n = 8) at a pacing cycle length (PCL) of 300 ms (37°C). Tact increased at shorter PCL, and the hypercapnic solution prolonged Tact further: at 150 ms PCL, Tact was prolonged from 131.0 ± 5.2 to 174.9 ± 16.3 ms. 2:1 AVN block was common at shorter cycle lengths. Atrial and ventricular conduction times were not significantly affected by the hypercapnic solution suggesting that the increased delay originated in the AVN. Isolated right atrial preparations were superfused with Tyrode's solutions at pH 7.4 (control), 6.8 and 6.3. Low pH prolonged the atrial-Hisian (AH) interval, the AVN effective and functional refractory periods and Wenckebach cycle length significantly. Complete AVN block occurred in 6 out of 9 preparations. Optical imaging of conduction at the AV junction revealed increased conduction delay in the region of the AVN, with less marked effects in atrial and ventricular tissue. Thus acidosis can dramatically prolong the AVN delay, and in combination with short cycle lengths, this can cause partial or complete AVN block and is therefore implicated in the development of brady-arrhythmias in conditions of local or systemic acidosis

LABOR LAW-INJUNCTION-UNITED STATES v. UNITED MINE WORKERS OF AMERICA

This comment was originally prepared as a discussion of the decision of the District Court for the District of Columbia. Since it seemed probable that the Supreme Court\u27s decision would be rendered before or shortly after the comment could be published in normal course, the editors decided to delay the printing of this issue of the Review so that a discussion of the Supreme Court opinions could be included. References to the opinions of the Supreme Court Justices appear in brackets.Ed.] Following a breakdown in the collective bargaining process in the spring of 1946 between the majority of the nation\u27s bituminous coal mine operators on the one hand and the United Mine Workers of America on the other, the President of the United States, acting under authority of the War Labor Disputes Act, ordered the Secretary of the Interior to take possession of the mines where operation was interrupted or threatened with interruption. Pursuant to the order, on May 22, 1946 the United States, through the Secretary of the Interior, took possession of most of the bituminous coal mines of the nation. Subsequently, a contract, embodying changes in wages and other terms and conditions of employment, was executed by the Secretary of the Interior, Julius A. Krug, for the government and by the president of the United Mine Workers, John L. Lewis, for the union. After approximately five months of operation under this contract, Lewis demanded renegotiation, relying on a construction of the contract which Krug insisted was erroneous. After a series of conferences, which began on November 1, 1946, the union and the government had not agreed on the construction of the contract or on any change in the terms of employment. On November 15, 1946, Lewis issued a unilateral notice of termination of the contract, effective November 20, in accordance with the construction of the contract for which he contended

Dihydrolevoglucosenone (Cyrene™) as a bio-renewable solvent for Cu(0)wire-mediated reversible deactivation radical polymerization (RDRP) without external deoxygenation

Biorenewable dihydrolevoglucosenone (Cyrene™) is used as an effective dipolar aprotic solvent for Cu(0) wire-mediated RDRP of various monomers without external deoxygenation being applied

Optimization of a high work function solution processed vanadium oxide hole-extracting layer for small molecule and polymer organic photovoltaic cells

We report a method of fabricating a high work function, solution processable vanadium oxide (V2Ox(sol)) hole-extracting layer. The atmospheric processing conditions of film preparation have a critical influence on the electronic structure and stoichiometry of the V2Ox(sol), with a direct impact on organic photovoltaic (OPV) cell performance. Combined Kelvin probe (KP) and ultraviolet photoemission spectroscopy (UPS) measurements reveal a high work function, n-type character for the thin films, analogous to previously reported thermally evaporated transition metal oxides. Additional states within the band gap of V2Ox(sol) are observed in the UPS spectra and are demonstrated using X-ray photoelectron spectroscopy (XPS) to be due to the substoichiometric nature of V2Ox(sol). The optimized V2Ox(sol) layer performance is compared directly to bare indium–tin oxide (ITO), poly(ethyleneoxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and thermally evaporated molybdenum oxide (MoOx) interfaces in both small molecule/fullerene and polymer/fullerene structures. OPV cells incorporating V2Ox(sol) are reported to achieve favorable initial cell performance and cell stability attributes

Investigation of the Effects of the Short QT Syndrome D172N Kir2.1 Mutation on Ventricular Action Potential Profile Using Dynamic Clamp

The congenital short QT syndrome (SQTS) is a cardiac condition that leads to abbreviated ventricular repolarization and an increased susceptibility to arrhythmia and sudden death. The SQT3 form of the syndrome is due to mutations to the KCNJ2 gene that encodes Kir2.1, a critical component of channels underlying cardiac inwardly rectifying K(+) current, I(K1). The first reported SQT3 KCNJ2 mutation gives rise to the D172N Kir2.1 mutation, the consequences of which have been studied on recombinant channels in vitro and in ventricular cell and tissue simulations. The aim of this study was to establish the effects of the D172N mutation on ventricular repolarization through real-time replacement of I(K1) using the dynamic clamp technique. Whole-cell patch-clamp recordings were made from adult guinea-pig left ventricular myocytes at physiological temperature. Action potentials (APs) were elicited at 1 Hz. Intrinsic I(K1) was inhibited with a low concentration (50 µM) of Ba(2+) ions, which led to AP prolongation and triangulation, accompanied by a ∼6 mV depolarization of resting membrane potential. Application of synthetic I(K1) through dynamic clamp restored AP duration, shape and resting potential. Replacement of wild-type (WT) I(K1) with heterozygotic (WT-D172N) or homozygotic (D172N) mutant formulations under dynamic clamp significantly abbreviated AP duration (APD(90)) and accelerated maximal AP repolarization velocity, with no significant hyperpolarization of resting potential. Across stimulation frequencies from 0.5 to 3 Hz, the relationship between APD(90) and cycle length was downward shifted, reflecting AP abbreviation at all stimulation frequencies tested. In further AP measurements at 1 Hz from hiPSC cardiomyocytes, the D172N mutation produced similar effects on APD and repolarization velocity; however, resting potential was moderately hyperpolarized by application of mutant I(K1) to these cells. Overall, the results of this study support the major changes in ventricular cell AP repolarization with the D172N predicted from prior AP modelling and highlight the potential utility of using adult ventricular cardiomyocytes for dynamic clamp exploration of functional consequences of Kir2.1 mutations

An assessment for the viability of recovering heat from a smoke extract system

Over the course of industrial manufacturing, additional heat within the extract systems is usually released into the atmosphere and its intrinsic energy is wasted. This paper investigated a cold abatement smoke extract system for a fire testing wall furnace to determine the viability in recovering heat from the hot smoke. Three scenarios were investigated: 1) the extract system was closed and only 300°C smoke was present; 2) the system took in ambient air around the furnace and heat recovery occurred at 80°C in smoky air; 3) the smoke had been removed from the air and the temperature was 60°C. It was found that there was a significant build-up of soot on Scenarios 1 & 2 with a build-up rate of 0.25 μm/s which totalled 2.7 mm of soot after a three-hour test. The soot had a low heat transfer rate and therefore acted as an insulator on the heat exchanger which reduced the efficiency significantly of it over time. Due to this loss in efficiency, it was more viable to recover heat in Scenario 3 at 60°C in clean air than it was to recover heat at 300°C or 80°C in smoky air. The results show that having clean air was more important than a higher temperature when it came from recovering heat from a cold abatement system for a fire testing furnace. This paper contributes to reveal the possibilities of harnessing the “waste heat” for use in other applications in the vicinity of the manufacturing processes, such as heating water within a central heating plant, domestic hot water or electricity generation, or re-cycled within the industrial plant itself

Flux Creep and Flux Jumping

We consider the flux jump instability of the Bean's critical state arising in the flux creep regime in type-II superconductors. We find the flux jump field, $B_j$, that determines the superconducting state stability criterion. We calculate the dependence of $B_j$ on the external magnetic field ramp rate, $\dot B_e$. We demonstrate that under the conditions typical for most of the magnetization experiments the slope of the current-voltage curve in the flux creep regime determines the stability of the Bean's critical state, {\it i.e.}, the value of $B_j$. We show that a flux jump can be preceded by the magneto-thermal oscillations and find the frequency of these oscillations as a function of $\dot B_e$.Comment: 7 pages, ReVTeX, 2 figures attached as postscript file