Analysis and elimination of artifacts in indirect covariance NMR spectra via unsymmetrical processing

Indirect covariance NMR offers an alternative method of extracting spin-spin connectivity information via the conversion of an indirect-detection heteronuclear shift-correlation data matrix to a homonuclear data matrix. Using an IDR (inverted direct response)-HSQC-TOCSY spectrum as a starting point for the indirect covariance processing, a spectrum that can be described as a carbon-carbon COSY experiment is obtained. These data are analogous to the autocorrelated 13C-13C double quantum INADEQUATE experiment except that the indirect covariance NMR spectrum establishes carbon-carbon connectivities only between contiguous protonated carbons. Cyclopentafuranone and the complex polynuclear heteroaromatic naphtho[2',1':5,6]-naphtho[2',1':4,5]thieno[2,3-c]quinoline are used as model compounds. The former is a straightforward example because of its well-resolved proton spectrum, while the latter, which has considerable resonance overlap in its congested proton spectrum, gives rise to two types of artifact responses that must be considered when using the indirect covariance NMR method.     

Connection between the observable and centroid structural properties of a quantum fluid: application to liquid para-hydrogen

It is shown that the discrepancy between path integral Monte Carlo [M. Zoppi et al., Phys. Rev. B 65, 092204 (2002)] and path integral centroid molecular dynamics [F. J. Bermejo et al., Phys. Rev. Lett. 84, 5359 (2000)] calculations of the static structure factor of liquid para-hydrogen can be explained based on a deconvolution equation connecting centroid and physical radial distribution functions. An explicit expression for the kernel of the deconvolution equation has been obtained using functional derivative techniques. In the superposition approximation, this kernel is given by the functional derivative of the effective potential with respect to the pairwise classical potential. Results of path integral Monte Carlo calculations for the radial distribution function and the static structure factor of liquid para-hydrogen are presented.     

Measurement of the branching ratio for Υ(1S) state intoπ + π − andsearch for decaysΥ(1S)→π + π −,K + K −,p \bar p

In the experiment withe ⁺ e ^?-beams performed at the VEPP-4 storage ring with the MD-1 detector we have measuredB _μμ, the branching ratio for the decay of Υ(1S) state intoμ ⁺ μ ^?. We obtainedB _μμ=(2.12+0.20+0.10)%. It is shown that the continuum and resonance interference should be taken into account. For the first time the upper limits on the branching ratio for the decaysΥ→π ⁺ π ^?,K ⁺ K ^?,p \(\bar p\) have been measured: Br(Υ→π ⁺ π ^?)<5·10^?4, Br(Υ→K ⁺ K ^?)<5·10^?4, Br(Υ→p \(\bar p\) <9·10^?4 (90% CL).     

Total cross section of two-photon production of hadrons

The total cross section for hadrons was measured as a function of the invariant massW of the system (1.25 to 4.25 GeV) at thee ⁺ e ^–-collider VEPP-4 with the detector MD-1. For the first time the data were obtained by detecting both scattered leptons with almost zero emission angles. The mean squared four momentum transfer q ² is –0.005 GeV², the rmsW resolution is 100–250 MeV. The data on the mean charged multiplicity n _C are well described by the function n _C =(1.62 ±0.37)+(1.83±0.45)·ln(W(GeV)). TheW dependence of the total cross section is consistent with the theoretical prediction (nb)=240+270/W(GeV).     

The application of empirical methods of 13C NMR chemical shift prediction as a filter for determining possible relative stereochemistry

The reliable determination of stereocenters contained within chemical structures usually requires utilization of NMR data, chemical derivatization, molecular modeling, quantum‐mechanical (QM) calculations and, if available, X‐ray analysis. In this article, we show that the number of stereoisomers which need to be thoroughly verified, can be significantly reduced by the application of NMR chemical shift calculation to the full stereoisomer set of possibilities using a fragmental approach based on HOSE codes. The applicability of this suggested method is illustrated using experimental data published for a series of complex chemical structures. Copyright © 2009 John Wiley & Sons, Ltd.     

A systematic approach for the generation and verification of structural hypotheses

During the process of molecular structure elucidation the selection of the most probable structural hypothesis may be based on chemical shift prediction. The prediction is carried out using either empirical or quantum‐mechanical (QM) methods. When QM methods are used, NMR prediction commonly utilizes the GIAO option of the DFT approximation. In this approach the structural hypotheses are expected to be investigated by scientist. In this article we hope to show that the most rational manner by which to create structural hypotheses is actually by the application of an expert system capable of deducing all potential structures consistent with the experimental spectral data and specifically using 2D NMR data. When an expert system is used the best structure(s) can be distinguished using chemical shift prediction, which is best performed either by an incremental or neural net algorithm. The time‐consuming QM calculations can then be applied, if necessary, to one or more of the ‘best’ structures to confirm the suggested solution. Copyright © 2009 John Wiley & Sons, Ltd.     

Stability,estimation of state,and control in one nonlinear system

A controlled system of nonlinear ordinary differential equations is considered. In this system, we distinguish the time-varying linear part, the part that linearly depends on the control, and the nonlinearity, which vanishes on the steady-state solution and satisfies the Lipschitz condition. In addition, there are some constraints imposed on the control.     

Influence of high-power ion beam treatment on the resistance to oxidation in metals and alloys

The influence of high-power ion beam (HPIB) irradiation of metal (copper) and alloys (iron-St20 and titanium-VT6) on the resistance to oxidation has been investigated. The HPIB irradiation with the subsequent oxidation in air has been found to result in the formation of complex oxides on the surface of an alloy. The formation of discontinuous oxide films related to the crater formation under irradiation is the feature of oxidation processes of the irradiated materials. Oxidation resistance has been found to rise in the alloys containing nonmetals as the dopant.     

Motion of an electrolyte-gas interface in an electrical field

The article discusses the phenomenon of the motion of an electrolyte-gas interface, first observed on electrical levels. It gives a comparative characterization of the phenomena, for purposes of practical use, with a solution of problems of control by the position of a liquid-liquid interface.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 25–28, November–December, 1975.