Ru/Al Multilayers Integrate Maximum Energy Density and Ductility for Reactive Materials.

Established and already commercialized energetic materials, such as those based on Ni/Al for joining, lack the adequate combination of high energy density and ductile reaction products. To join components, this combination is required for mechanically reliable bonds. In addition to the improvement of existing technologies, expansion into new fields of application can also be anticipated which triggers the search for improved materials. Here, we present a comprehensive characterization of the key parameters that enables us to classify the Ru/Al system as new reactive material among other energetic systems. We finally found that Ru/Al exhibits the unusual integration of high energy density and ductility. For example, we measured reaction front velocities up to 10.9 (± 0.33) ms(-1) and peak reaction temperatures of about 2000 °C indicating the elevated energy density. To our knowledge, such high temperatures have never been reported in experiments for metallic multilayers. In situ experiments show the synthesis of a single-phase B2-RuAl microstructure ensuring improved ductility. Molecular dynamics simulations corroborate the transformation behavior to RuAl. This study fundamentally characterizes a Ru/Al system and demonstrates its enhanced properties fulfilling the identification requirements of a novel nanoscaled energetic material.

Effect of activity on supraventricular tachyarrhythmias after coronary artery bypass surgery.

The purpose of this study was to evaluate patient activities, professional staff activities, backrest position, and diurnal variations as factors that may contribute to the onset of supraventricular tachyarrhythmias (SVT) after coronary artery bypass surgery (CABG). The activities surrounding the recognition of first-onset SVT, as well as preoperative and postoperative data and patient characteristics were examined in 249 patients having CABG. One hundred seventy-three patients qualified for the study; 28% of these patients (n = 49) had SVT. No statistical difference was found between the subjects with SVT and those without SVT when sex, cross-clamp time, creatine kinase peak, hemoglobin and hematocrit levels, and number of bypasses were examined. Patients who had SVT were older than those who did not: 64.8 years for the SVT group versus 60.7 years for the non-SVT group (p less than 0.01). SVT was rare in the first 24 hours after surgery, whereas 60% of the cases occurred during the next 48 hours, without significant diurnal variation: mean time of onset was 11:50 AM. No particular activity of the patient or nurse influenced the onset of SVT during the postoperative period in this group.

ATP-sensitive potassium channels in adult mouse skeletal muscle: different modes of blockage by internal cations, ATP and tolbutamide.

Single ATP-sensitive K channels were studied in membrane patches excised from enzymatically dissociated mouse toe muscle. The channel conductance is 74 pS in symmetrical 160 mM KCl solutions. Replacement of K+ by Na+ in the internal solution or 2 mM internal Ca2+ or Mg2+ induced a rectification of the current-voltage curve at positive potentials. No change of the current-voltage curve was observed by adding small amounts of the channel blockers ATP (20-100 microM) or tolbutamide (0.5 mM) to internal 160 mM KCl solutions. The openings of the channel occurred in bursts. Open (tau o), closed (tau c) times within bursts and pauses (tau p) between bursts were determined over a wide range of positive and negative membrane potentials. At increasing potentials tau o increases, tau c reaches a minimum near 0 mV and tau p decreases. According to the voltage dependence and the time scale of channel blockage three types of blocking agents could be distinguished: (i) small internal cations (Na+, Ca2+, Mg2+) are "fast" blockers at positive voltages; at negative voltages they decrease tau o and increase tau c. (ii) Internal ATP anions produce a voltage-dependent decline of the open-state probability and strongly decrease tau o. (iii) Tolbutamide causes a voltage-independent decrease of the open-probability and its main effect is an increase of tau p. The results suggest that the ATP-sensitive K channel has an internal gate like those of other voltage-gated cation channels and that different blockers interfere with different transitions in channel gating.

A high-conductance anion channel in adult amphibian skeletal muscle.

Membrane patches were excised from enzymatically dissociated frog toe muscle. High-conductance anion channels could be induced in previously quiet patches by 20-120 s depolarizations beyond +20 mV and then studied in the potential range from -80 to +60 mV for a long time. From reversal potentials the estimated permeability ratios PCl/PNa and PCl/Pglucuronate were near 3.5 and 4, respectively. There were probably 5 or more conductance levels (substates) for a single channel, the most common in symmetrical 110 mM NaCl being 260 and 70 pS at 10 degrees C. Gating was complex, with rapid and slow events and several gating modes, including periods of rapid flickering. Channels closed reversibly at potentials more negative than -50 mV. The channel was blocked by application to the cytoplasmic face of tannic acid, gallic acid, and zinc but not of DIDS or 9-anthracene-carboxylic acid, and it was blocked by extracellular zinc.

Conductance properties and voltage dependence of an anion channel in amphibian skeletal muscle.

Single anion-selective channels were studied in excised membrane patches of adult frog toe muscle. The conductance gamma and the probability po of the main open state were determined for various ionic compositions of the extra- and intracellular solutions. gamma = 280 pS in symmetrical 110 mM NaCl, pH 7.4 solutions at 15 degrees C. Higher gamma values were found at elevated internal or external NaCl concentrations, in 70 mM external CaCl2 and at lower extracellular pH. The po(E) curve declined steeply with hyperpolarization and was shifted towards more negative potentials at increased internal ionic strength and at higher external pH. Positive shifts were induced by extracellular Ca. The results show that the anion channel saturates at Cl concentrations greater than 110 mM, that the potential profile of an open channel is almost symmetrical and that channel gating is affected by neighboring channels. It is suggested that the anion channel has a voltage sensor (effective gating charge 4.3) and a similar collection of local fixed charges on the extra- and intracellular sides as voltage-gated cation channels.

Effects of chemical modification of carboxyl groups on the voltage-clamped nerve fiber of the frog.

Voltage-clamped single nerve fibers of the frog Rana esculenta were treated with the carboxyl group activating reagent N-ethoxy-carbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) in the presence of different primary amines and without added amine. Carboxyl groups form stable amide bonds with primary amines in the presence of EEDQ. EEDQ treatment reduced the sodium current considerably and irreversibly, regardless of the presence of a primary amine in the Ringer's solution. The potassium current was also reduced. After modification the reduced sodium currents inactivated slowly and incompletely. The descending branch of the sodium current-voltage relation, INa(E), was shifted along the voltage axis in the depolarizing direction. The size of the shift was strongly dependent on the amine present during modification with EEDQ. The voltage-dependence of sodium inactivation, h infinity (E), was shifted to more positive values of membrane potential by EEDQ in the presence of ethylenediamine (11 mV) and glucosamine (3 mV). In contrast, a small shift to more negative potentials occurred in the presence of taurine (-3 mV) or without the addition of an amine (-2 mV). A tenfold increase of the calcium concentration still shifted the INa(E) and h infinity (E) curves of the chemically modified fibers. However, these shifts were smaller than those observed on untreated fibers. The currents remaining after the modification were completely blocked by tetrodotoxin; no change of the reversal potential occurred.

The effect of internal barium on the K current of the node of Ranvier.

Voltage clamp experiments were performed on single myelinated nerve fibres of the frog Rana esculenta to study the influence of internally applied Ba on the potassium outward current IK. Potassium currents of Ba-treated fibres decay rapidly during 30 ms depolarizations of more than 60 mV. The time constant tau of decay and the steady state potassium current IKss are strongly voltage dependent. The equilibrium dissociation constant K of the Ba-receptor complex decreases e-fold for a 39 mV change of potential. The analysis suggests that the binding site is located at 30% of the membrane field seen from the inside of the axon.