APPLICATION OF 2D-NMR TECHNIQUES IN THE STRUCTURE DETERMINATION OF HYPODEMATINE

An alkaloid with a novel structure,named Hypodematine,was isolated from Hypodematium sinense Iwatsuki(belonging to Thelypterdaceae).Its structure was elucidated by means of the ~1H-~1H COSY' ~1H-^(13)C COSY and long-range ~1H-^(13)C COSY spectroscopy to have the skeleton of benzo-aza-cyclooctatetraene with a phenyl substituent.Such basic structure has not been found in the na- tural product before.

A Comparative Study of Dispersion Characteristics Determination of a Trapezoidally Corrugated Slow Wave Structure Using Different Techniques

The linear dispersion relation of a trapezoidally corrugated slow wave structure （TCSWS） is analyzed and presented. The size parameters of the TCSWS are chosen in such a way that they operate in the x-band frequency range. The dispersion relation is solved by utilizing the Rayleigh-Fourier method by expressing the radial function in terms of the Fourier series. A highly accurate synthetic technique is also applied to determine the complete dispersion characteristics from experimentally measured resonances （cold test）. Periodic structures resonate at specific frequencies when the terminals are shorted numerical calculation, synthetic technique and cold appropriately. The dispersion characteristics obtained from test are compared, and an excellent agreement is achieved.

STEREOSTRUCTURAL DETERMINATION OF ADDITION PRODUCTS FROM ISOFURANOGERMACRENE AND MALEIMIDE BY NMR TECHNIQUES

The stereostructures of the title compounds were shown to be represented by (A) and (B).

Operational method for determining bottom hole pressure in mechanized oil producing wells,based on the application of multivariate regression analysis

One of the major tasks of monitoring production well operations is to determine bottom-hole flowing pressure.The overwhelming majority of wells in the Perm Krai are serviced using borehole pumps,which makes it difficult to take direct bottom-hole flowing pressure measurements.The bottomhole filtration pressure(BHFP)in these wells is very often determined by recalculating the parameters measured at the well mouth(annulus pressure,dynamic fluid level depth).The recalculation is done by procedures based on analytically determining the characteristics of the gas-liquid mixture in the wellbore,which is very inconsistent to perform due to the mixture's complex behavior.This article proposes an essentially different approach to BHFP measurements that relies on the mathematical processing of the findings of more than 4000 parallel mouth and deep investigations of the oil production wells of a large oil-production region.As a result,multivariate mathematical models are elaborated that allow reliably determining the BHFP of oil-production wells in operation.

Fabrication and Determination of Refractive Index Profile of the Planar Waveguides by Wedge Technique

Several planar waveguides have been fabricated. The waveguides have been polished for determination of their refractive index profiles (RIP) by wedge method. The RIP determined by inserting the sample in a Mach-Zehnder interferometer and applying fringe analysis methods.

Nonisospectral Lotka–Volterra Systems as a Candidate Model for Food Chain

In this paper,we derive a generalized nonisospectral semi-infinite Lotka-Volterra equation,which possesses a determinant solution.We also give its a Lax pair expressed in terms of symmetric orthogonal polynomials.In addition,if the simplified case of the moment evolution relation is considered,that is,without the convolution term,we also give a generalized nonisospectral finite Lotka-Volterra equation with an explicit determinant solution.Finally,an application of the generalized nonisospectral continuous-time Lotka-Volterra equation in the food chain is investigated by numerical simulation.Our approach is mainly based on Hirota’s bilinear method and determinant techniques.

Explicit Multisoliton Solution to the Coupled Nonlinear Schrodinger Equations

Based on the inverse scattering transform for the coupled nonlinear Schrodinger （NLS） equations with vanishing boundary condition （VBC）, the multisoliton solution has been derived by some determinant techniques of some special matrices and determinants, especially the Cauchy-Binet formula. The oneand two-soliton solutions have been given as the illustration of the general formula of the multisoliton solution. Moreover, new nonsymmetric solutions corresponding to different number of zeros of the scattering data on the upper and lower half plane are discussed.