THE ENERGY ASPECT OF THE RECIPROCAL INTERACTIONS OF PAIRS OF TWO DIFFERENT VIBRATION MODES OF A CLAMPED ANNULAR PLATE

The standardized mutual active and reactive sound power of a clamped plate, representing the energy aspect of the reciprocal interactions of two different in vacuo modes, has been computed. It was assumed that the vibrations are axisymmetric, elastic and time harmonic, the plate's transverse deflection is small as compared with the plate's size, and that the vibration velocity is small as compared with the acoustic wavenumber generated. The Kirchhoff-Love theory of a perfectly elastic plate was used. The integral formulae for the mutual sound power were transformed into their Hankel representations which made possible their subsequent computation. A closed path integral was used to express the integral in its Hankel representation to compute the mutual active sound power. The asymptotic stationary phase method was used to compute the two magnitudes, i.e., the mutual active and reactive sound power. The results obtained are the asymptotic formulae valid for the acoustically fast waves. The oscillating as well as the non-oscillating terms have been identified in the formulae to make possible their further separate analysis. The availability of the asymptotic formulae makes possible some fast numerical computations of the mutual sound power. Moreover, the formulae presented herein, together with those for the individual modes known from the literature, make a complete basis for further computations of the total sound power of the plate's damped and forced vibrations in fluid.     

Coexistence of multiple conformations in cysteamine monolayers on Au(111)

The structural organization, catalytic function, and electronic properties of cysteamine monolayers on Au(111) have been addressed comprehensively by voltammetry, in situ scanning tunneling microscopy (STM) in anaerobic environment, and a priori molecular dynamics (MD) simulation and STM image simulation. Two sets of voltammetric signals are observed. One peak at -(0.65-0.70) V (SCE) is caused by reductive desorption of cysteamine. The other signal, at -(0.25-0.40) V consists of a peak doublet. The pH dependence of the latter suggests that the origin is catalytic dihydrogen evolution. The doublet feature is indicative of two distinct cysteamine configurations. Cysteamine monolayer formation from initial nucleation to a highly ordered phase has been successfully observed in real time using oxygen-free in situ STM. Random cellular patterns, disordered adlayer formation accompanied by high step edge mobility, and ultimately a highly ordered (square root 3 x 4) R30 degrees lattice are observed sequentially. Pits are formed due to enclosure of the mobile edges during the adsorption process. In the highly ordered cysteamine layer, each unit has two spots with apparent 0.6 A height difference in STM images. The coverage 5.7 +/- 0.1 x 10(-10) mol cm(-2) determined by voltammetry supports that the spots represent two individual cysteamine molecules. A priori MD and density functional simulations hold other clues to the image interpretation and indicate that the NH(3)(+) groups dominate the tunneling contrast. A wide range of interface structures, showing variations in the sulfur binding site and orientation, gauche and trans conformers, and especially hydrogen-bonding interactions, are examined, from which it is concluded that the adsorbate structure is controlled by interactions with the solvent rather than with the substrate.     

Physically based molecular device model in a transient circuit simulator

Two efficient, physically based models for the real-time simulation of molecular device characteristics of single molecules are developed. These models assume that through-molecule tunnelling creates a steady-state Lorentzian distribution of excess electron density on the molecule and provides for smooth transitions for the electronic degrees of freedom between the tunnelling, molecular-excitation, and charge-hopping transport regimes. They are implemented in the fREEDA™ transient circuit simulator to allow for the full integration of nanoscopic molecular devices in standard packages that simulate entire devices including CMOS circuitry. Methods are presented to estimate the parameters used in the models via either direct experimental measurement or density-functional calculations. The models require 6–8 orders of magnitude less computer time than do full a priori simulations of the properties of molecular components. Consequently, molecular components can be efficiently implemented in circuit simulators. The molecular-component models are tested by comparison with experimental results reported for 1,4-benzenedithiol.     

Analysis of the OH bend and stretch region in the vibrational spectrum of water

A method for calculating the infrared absorption spectrum of water in a range of different physical environments is described. Calculations are based on Monte Carlo simulations together with local-mode analyses of the H₂O vibrations. Results for liquid water and amorphous ice show clearly that the major features of the OH stretching motions are reproduced with good accuracy.     

Komplexometrische Bestimmung von Natrium, Kalium und von deren Summe durch Ionenaustausch

Zusammenfassung Es wird eine Methode zur komplexometrischen Bestimmung von Natrium, Kalium und deren Summe beschrieben. Mit Hilfe eines Ionenaustauschers in der Mg-Form werden die Alkalimetalle quantitativ und stöchiometrisch gegen Magnesium ausgetauscht, welches dann mit Eriochromschwarz T als Indicator komplexometrisch bestimmt werden kann. Das Verfahren ist im Makro-, Halbmikro- und bei Beachtung bestimmter Vorsichtsmaßregeln auch im Mikromaßstab anwendbar. Bei Vorliegen von Natrium und Kalium nebeneinander wird deren Summe bestimmt. Durch Hinzuziehen der Kaliumbestimmung mit Tetraphenyloborat ist eine Natrium-Kalium-Trennung möglich. Das Resultat liegt nach 30 min vor; die reine Arbeitszeit beträgt etwa 10 min. Dies läßt die Methode zur Schnellbestimmung geeigneter erscheinen, als die vor kurzem beschriebene Natriumbestimmung durch Ionenaustausch gegen Kalium³. Die Methode zeichnet sich durch hohe Genauigkeit aus.Wir sprechen der Firma Heyl & Co., Hildesheim, für die Überlassung von Natriumtetraphenyloborat (Handelsname Kalignost) und den Farbenfabriken Bayer, Leverkusen, für die Überlassung von Ionenaustauschern (Handelsname Lewatit) auf diesem Wege unseren herzlichsten Dank aus.