Thermodynamics of hypoelasticity

A thermodynamic framework for hypoelasticity is constructed based on a modified Gibbs Function which depends on the stress deviator and specific volume. In the hypoelastic equations considered here, the stress deviator is obtained from a rate equation involving the corotational derivative and coefficients which depend on the invariants of the stress deviator as well as specific volume. Non-negative entropy production is enforced, leading to a non-dissipative condition in the sense that entropy is produced only by heat transfer. The resulting conditions lead to relations among the coefficients in the rate equation. These relations underdetermine the coefficients, so that there is leeway in specifying these coefficients. An example of a set of rate equations which satisfy the thermodynamics is presented.     

Über ein geometrisches Theorem und seine Anwendung auf die partiellen Differentialgleichungen vom elliptischen Typus

Ohne ZusammenfassungDie vorliegende Note ist die Übersetzung des bereits im Jahre 1914 in den Mitteilungen der Mathematischen Gesellschaft in Charkow erschienenen Aufsatzes Sur un théorème de géométrie et son application aux equations aux dérivées partielles du type elliptique. Für die freundliche Übersetzung sind die Schriftleitung und der Verfasser Herrn Tibor Radó in Szeged zu Dank verpflichtet.     

Lateralization produced by envelope-based interaural temporal disparities of high-frequency, raised-sine stimuli: empirical data and modeling

An acoustic pointing task was used to measure extents of laterality produced by ongoing interaural temporal disparities (ITDs) conveyed by the envelopes of 4-kHz-centered raised-sine stimuli while varying, parametrically, their peakedness, depth of modulation, and frequency of modulation. One purpose of the study was to determine whether such manipulations would produce changes in laterality logically consistent with those found for ITD-discrimination thresholds reported by Bernstein and Trahiotis [J. Acoust. Soc. Am. 125, 3234-3242 (2009)]. The data obtained revealed that they did in that (1) increasing depth of modulation, peakedness, or frequency of modulation between 32 and 128 Hz produced smaller threshold ITDs and greater laterality and (2) increasing frequency of modulation to 256 Hz produced modest increases in threshold ITDs and modest decreases in laterality. The extents of laterality measured were successfully accounted for via an augmentation of the cross-correlation-based "position-variable" modeling approach developed by Stern and Shear [J. Acoust. Soc. Am. 100, 2278-2288 (1996)] to account for ITD-based extents of laterality obtained at low spectral frequencies.     

Ultrafast photodissociation dynamics of HMX and RDX from their excited electronic states via femtosecond laser pump–probe techniques

Femtosecond laser pump–probe techniques are employed to investigate the mechanisms and dynamics of the photodissociation of HMX and RDX from their excited electronic states at three wavelengths (230 nm, 228 nm, and 226 nm). The only observed product is the NO molecule. Parent HMX and RDX ions are not observed. The NO molecule has a resonant A²Σ ← X²Π (0, 0) transition at 226 nm and off-resonance two-photon absorption at 228 nm and 230 nm. Pump–probe transients of the NO product at both off-resonance and resonance absorption wavelengths indicate the decomposition dynamics of HMX and RDX falls into the timescale of our laser pulse duration (180 fs).     

Direct control of electron transfer to the surface-CO bond on a Pt/TiO2 catalytic diode

We study CO adsorption on a multilayer catalytic diode in which electron transfer at the metal-semiconductor (Pt/TiO(2)) junction is controlled by an applied external voltage. The multilayer diode structure enhances infrared absorption signals from CO molecules adsorbed on the small area Pt surface. We find that the diode behaves like a Schottky junction and that changes in electron transfer at the junction are directly correlated with reversible shifts in the vibrational frequency of adsorbed CO. Infrared polarization and incidence angle dependent studies show that the magnitude of vibrational frequency shift varies with orientation of the molecules being probed and increases with proximity to the Pt/TiO(2) interface. The results demonstrate the ability to control the metal-adsorbate bond through external electronic modifications of a metal-support junction. The catalytic diode can potentially provide control of the surface chemical bond by an external voltage, providing a new approach for investigations in heterogeneous catalysis, sensors, and plasmonic devices.     

Hydrogenation reactions of ethylene on neutral vanadium sulfide clusters: experimental and theoretical studies

The reactions of C(2)H(4) with H(2) on neutral vanadium sulfide clusters in a fast flow reactor are investigated by time-of-flight mass spectrometry employing 118 nm (10.5 eV) single photon ionization. The experimental products of these reactions are V(m)S(n)C(2)H(x) (m=1, n=1-3; m=2, n=1-5, and x=4-6). Observation of these products indicates that these V(m)S(n) clusters have high catalytic activity for hydrogenation reactions of C(2)H(4). Density functional theory calculations at the BPW91/TZVP level are carried out to explore the geometric and electronic structures of the V(m)S(n) clusters and to determine reaction intermediates and transition states, as well as reaction mechanisms. All reactions are estimated as overall barrierless or with only a small barrier (0.1 eV), and are thermodynamically favorable processes at room temperature. The ethylene molecule is predicted to connect with active V atoms through its π-orbital or form a σ-bond with active V atoms of catalytic V(m)S(n) clusters. The S atoms bonding with active V atoms play an important role in the dissociation of the H(2) molecule; H atoms transfer to the C(2)H(4) (one after another) following breaking of the H-H bond. A catalytic cycle for C(2)H(4) hydrogenation reactions on a vanadium sulfide catalyst surface is suggested based on our experimental and theoretical investigations.     

Sur l'ultraconvergence d'une classe de séries de Dirichlet

Sans résumé     

Eine Methode zur Phosphorbestimmung in Gu?eisen und Stahl mittels o-Oxychinolins

Ohne Zusammenfassung     

Demonstration du théorème de M. Hilbert sur la nature analytique des solutions des équations du type elliptique sans l'emploi des séries normales

Sans résumé