Versatile mass excited impact oscillator

Nonlinear Dynamics - This paper presents the design and the initial experimental results of a novel impact oscillator rig developed by the Centre of Applied Dynamic Research at the University of...     

Virial-bias Monte Carlo methods

A new sampling technique is proposed for the isothermal-isobaric (T, P, N) ensemble Monte Carlo computer simulation. The new method selects the volume perturbations by using the partial derivative of the volume with respect to the internal energy. Test calculations on the Lennard-Jones fluid show significant improvements over the conventionally used method.     

Untersuchungen über die Aufnahme von Nitratstickstoff durch Hafer mit Hilfe von 15N

Die Aufnahme von Nitratstickstoff durch Hafer wurde in Gegenwart von Ammoniumstickstoffüberschuß sowie verschiedener Stickstoffdügermichungen untersucht. Ebenfalls wurde der Einfluß phosphor-, kalium-, und spurenelementhaliger Düngemittel auf den Ausmutzungskoeffizienten des Nitratstickstoffs durch Hafer geprüft. Der Nitratstickstoff des angewandten Ammonium- nitrats wurde mit dent stabilen Stickstoffisotop ¹⁵N markiert. Die Masse der trockenen Planzen, der Gesamtstickstoffgehalt und der Ausnutzungskoeffizient des Nitratstickstoffs durch die Planzen wurden bestimut. Die Versuche haben gezeigt, daß der Ausmutzungskoeffizient des Nitratstickstoffs durch die Pfanzen in Geganwart con Ammoniumstickstoffüberschuß nicht wesentlich beeinflußt wird.     

Production and NMR characterization of hyperpolarized (107,109)Ag complexes

Both isotopes of silver, (107)Ag and (109)Ag, were simultaneously polarized by dynamic nuclear polarization (DNP), thus allowing large signal enhancements and the NMR characterization of Ag complexes in the millimolar concentration range. Since both isotopes have long relaxation times T(1), the hyperpolarized NMR signal of one isotope could still be observed even after the magnetization of the other isotope had been destroyed by radio-frequency pulses.     

Sensitivity enhancement of multidimensional NMR experiments by paramagnetic relaxation effects

One of the main goals of NMR method development is to increase the sensitivity of multidimensional NMR experiments or reduce the required acquisition time. In these experiments, more than 80% of the NMR instrument time is spent on the recycle delay, where the instrument idles to wait for the recovery of proton magnetization. In this study, we report a method of using paramagnetic relaxation effects to shorten the recycle delays required in multidimensional NMR experiments of biological macromolecules. This approach significantly reduces the NMR instrument time required. Ni(2+) ion, complexed with the chelating molecule DO2A, is used to decrease the proton T(1) relaxation time of biological macromolecules without the significant line-broadening effects that are associated with most paramagnetic ions. The Ni(DO2A) also significantly decreases the T(1) relaxation time of water, thus providing additional sensitivity gain by eliminating the saturation of labile amide resonances.     

W3 theory: robust computational thermochemistry in the kJ/mol accuracy range

We are proposing a new computational thermochemistry protocol denoted W3 theory, as a successor to W1 and W2 theory proposed earlier [Martin and De Oliveira, J. Chem. Phys. 111, 1843 (1999)]. The new method is both more accurate overall (error statistics for total atomization energies approximately cut in half) and more robust (particularly towards systems exhibiting significant nondynamical correlation) than W2 theory. The cardinal improvement rests in an approximate account for post-CCSD(T) correlation effects. Iterative T3 (connected triple excitations) effects exhibit a basis set convergence behavior similar to the T3 contribution overall. They almost universally decrease molecular binding energies. Their inclusion in isolation yields less accurate results than CCSD(T) nearly across the board: It is only when T4 (connected quadruple excitations) effects are included that superior performance is achieved. T4 effects systematically increase molecular binding energies. Their basis set convergence is quite rapid, and even CCSDTQ/cc-pVDZ scaled by an empirical factor of 1.2532 will yield a quite passable quadruples contribution. The effect of still higher-order excitations was gauged for a subset of molecules (notably the eight-valence electron systems): T5 (connected quintuple excitations) contributions reach 0.3 kcal/mol for the pathologically multireference X 1Sigmag+ state of C2 but are quite small for other systems. A variety of avenues for achieving accuracy beyond that of W3 theory were explored, to no significant avail. W3 thus appears to represent a good compromise between accuracy and computational cost for those seeking a robust method for computational thermochemistry in the kJ/mol accuracy range on small systems.