Previous Analytical Method Research Articles

Simultaneous quantification of seven active metabolites of roxifiban in human plasma by LC/MS/MS in the presence of an interfering displacer at millimolar concentrations

Roxifiban (DMP 754) is a glycoprotein (GP) IIb/IIIa antagonist. Following oral administration to humans, roxifiban is metabolized to its primary active zwitterionic form, XV459, and several minor, active, hydrolyzed and hydroxylated metabolites, namely, M1a (DPC-AD3508), M1b (DPC-AD6128), M2 (SW156), M3 (DPC-AG2185), M8a (DPC-AF5814), and M8b (DPC-AF5818). Quantification of these metabolites in humans was not workable with a previous analytical method due to ion suppression of at least four of the analytes by a competitive displacer, DMP 728. This compound, which is another GP IIb/IIIa antagonist with very high affinity for the platelet receptor, was added to harvested blood samples in millimolar quantity to liberate XV459 from the GP IIb/IIIa receptor. An automated ion exchange solid phase extraction (IX-SPE) procedure was developed to selectively extract the seven metabolites of roxifiban and its deuterated internal standard while specifically excluding DMP 728. Among the six hydroxylation metabolites, there were two pairs of epimeric diastereomers (M1a/M1b and M8a/M8b) and one pair of geometric isomers (M2/M3), corresponding to three critical chromatographic pairs that needed to be base-line resolved because of the lack of specificity of MS/MS detection for these isomers. A new LC/MS/MS assay was developed to simultaneously quantify the seven metabolites in human plasma. The assay method was validated under GLP conditions over the concentration range of 0.5 to 80 nM for each of the analytes and successfully applied to assaying approximately 500 plasma samples from clinical trials.

Efficient Multiscale Methods for Optimal In Situ Bioremediation Design

This paper presents a multiscale derivative method for solving a successive approximation linear quadratic regulator model for optimal in situ bioremediation design. An efficient one-sided forward divided difference numerical derivatives calculation was implemented as the first stage of the method, which only required assembling the right-hand-side vector of the linear systems of equations of the simulation model and performing backward substitution. The derivative calculation was reduced from O( N 3 ) to nearly O(N 2 ), where N is the number of non-Dirichlet state variables. A V-cycle multiscale derivatives approximation was implemented as the second stage, which used coarser mesh derivatives to interpolate finer mesh derivatives. Implementing the numerical derivatives method in a case study with over 1,600 state variables caused a reduction of more than two-thirds in computing time over the previous analytical derivatives method without loss of accuracy. Using the V-cycle multiscale derivatives approximation further reduced computing time by 29%, resulting in an overall 77% reduction compared to the previous analytical derivatives method. The reduction will be even greater for applications with more state variables, enabling the solution of much larger-scale problems than was previously possible.

AUTOREGRESSIVE ANALYSIS FOR THE DETECTION OF EARTHQUAKES WITH A RING LASER GYROSCOPE

The second-order autoregressive AR(2) model is used to analyze rotational data for seismic events captured by a large ring laser gyroscope. Both the Sagnac frequency and linewidth estimates obtained from this model sense the rotational components of seismic waves. An event of magnitude ML= 6.5 at a distance of D = 5.4° from a large ring laser gyroscope operating at its quantum limit is used to compare the AR(2) model with the previous analytical phase angle method of analysis. The frequency, linewidth and analytic phase angle data each satisfactorily estimate the rotation magnitude. The direct detection of rotational motion in the P wave coda is observed, demonstrating the conversion to transverse S wave polarizations by the local geology.

すべり摩擦型免震構造の振動応答解析に関する研究 : 摩擦係数の分布とディンプルすべり支承上の地震応答解析

In this paper, the authors considered the analytical method and the distribution of friction of sliding seismic isolation system with friction for the lightweight houses. Now, previous analytical method as one direction was extended to new method that vibrates two directions at the same time. And, the authors verified the analytical method by directly comparing experimental values with analytical values. An optimum coefficient of friction and effects of sliding seismic isolation for much kind of seismic waves was predicted by simulating the distribution of various coefficients of friction.

An Analytical Study of Cavitation in Rubber-Toughened Polymers

An analysis is presented to study the cavitation of rubber particles, and its influence on the mechanical properties of rubber-toughened polymers. This analysis is developed from our previous analytical method using a quasi-sphere model to determine the mechanical properties of rubber-toughened polymers without a cavity. The behaviour of the rubber particle is described by Ogden's formulation and large deformation theory is used to explain the behaviour. Both initiation and elastic deformation of the cavity are considered. The method is simple and the formulas (including the cavitation criterion) are explained so that they can be used easily. It has been found that even a small defect in a rubber sphere has a significant influence on the bulk modulus of the rubber sphere and the properties of the composite material.

Two general equations for deriving SIF expressions of some axisymmetric finite domain problems

Using the previous analytical method (Wang QZ, The crack-line (plane) stress field method for estimating SIFs—a review. Engineering Fracture Mechanics 1996; 55(4): 593–603.) and Green's function approach, two general equations are formulated for deriving approximate stress intensity factor (SIF) expressions for two categories of finite domain problems: (1) a finite-width strip with a center crack; (2) a circular cylinder with a concentric penny-shaped crack, both under various axisymmetric tensile loading at the crack faces. Examples with concentrated and distributed (up to quadratic variation) loading conditions are given to show the efficiency of these two general equations. As compared with the previous method, now the necessity of finding out the exact crack-line (plane) stress solution for the counterpart infinite problem is eventually waived. Another merit is that some SIF results for concentrated loading cases derived by using the general equations may have better accuracy than those given by the previous method. These two general equations are almost identical in form except for a small difference. Examples also show that the dimensionless SIF expressions for some problems in category (1) are identical with those in category (2), and there exists a regular correspondence between their loading conditions. Such identities in the dimensionless SIF expressions are useful in applications. Several example solutions given in this paper fill in the vacancy of missing solutions in present SIF handbooks, while other solutions are much simpler than the corresponding solutions in SIF handbooks.

CDMA cellular systems performance with fading, shadowing, and imperfect power control

This paper addresses capacity estimation for cellular code-division multiple-access (CDMA) systems, assuming the IS-95 standard as a reference. Extending a previous analytical method (Viterbi et al., 1994), we obtain a sequence of bounds on capacity, and then we introduce an accurate approximation to reduce computation complexity. The analysis accounts for interference internal and external to the reference cell, fading, shadowing, and imperfect power control. Outage probability is expressed in terms of the characteristic functions (cf's) of the interference and imperfect power control random variables (RV's). The interference contributions are computed on the basis of a Poisson distribution for the number of users in a lognormally shadowed channel. Results are provided for different channel conditions and are validated against Monte Carlo simulations. A comparison against previously published CDMA capacity estimates is carried out, aimed at clarifying some controversial issues. It is also confirmed that large system capacity is achievable under tight power control.

Measurement of methyl tert-butyl ether and tert-butyl alcohol in human blood by purge-and-trap gas chromatography-mass spectrometry using an isotope-dilution method.

We developed an isotope-dilution method for measuring methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) in whole human blood using a purge-and-trap gas chromatographic-mass spectrometric method. The labeled analogues for MTBE and TBA were [2H12]methyl tert-butyl ether and [2H9]-tert-butyl alcohol, respectively. Volatiles were removed from the blood by direct helium purging of the liquid; were trapped on a Tenax trap; and were desorbed, cryofocused, and chromatographed on a DB-624 capillary column that was connected directly to the ion source of a mass spectrometer. Detection was by mass analysis using a double-focusing magnetic-sector mass spectrometer operating in the full-scan mode at the medium mass resolution of 3000. For the isotope-dilution method, the minimum detection limits in blood (5-10 mL) are 0.01 microgram/L for MTBE and 0.06 microgram/L for TBA. The isotope-dilution method proved to be a big improvement in recovery, reproducibility, and sensitivity over our previous analytical method, which used the labeled ketone, [4-2H3]-2-butanone, as the internal standard for both MTBE and TBA. The isotope-dilution method has sufficient sensitivity for monitoring blood levels of MTBE and TBA in populations exposed to oxygenated fuels containing MTBE.

Determination of lead in blood using electrothermal atomisation atomic absorption spectrometry with a L'vov platform and matrix modifier.

Accuracy in the determination of blood lead is of primary importance in such diverse activities as screening for childhood lead poisoning, occupational exposure monitoring and population surveys. To meet the stringent requirements of the third National Health and Nutrition Examination Survey (NHANES III), a large normative population study to be held from 1988–1994, we needed a method for the determination of lead in blood that was simple, accurate, rugged and of defined accuracy for both calibration and control materials. The recent availability of the National Bureau of Standards Standard Reference Materials 2121–2 and 955, a lead standard solution (10 000 mg l–1) and a certified lead in blood reference material has made it possible to evaluate a method against definitive values and NBS reference materials.In the proposed method, sample preparation consists of a simple dilution (1 + 9) with a matrix modifier which contains 0.5%V/V Triton X-100, 0.2%V/V 16 M nitric acid and 0.2%m/V dibasic ammonium phosphate. This matrix modifier stabilises lead so that the majority of the blood matrix may be removed during the char step. Maximum accuracy in dilution is achieved with the use of autopipettes which have been shown to deliver viscous materials such as blood and serum with high accuracy. The method described in this study has a detection limit of about 0.07 µmol l–1(3 SD) and a precision and accuracy of ±2–5% at the 0.24–2.4 µmol l–1 concentration level. Linearity has been demonstrated up to about 4 µmol l–1. Comparability has been established with the previous blood lead analytical method used in other surveys via the analysis of 435 specimens by both the previous (modified Delves cup) and proposed methods. The equation of the resulting line is [ETA-AAS]= 1.0007[Delves]– 0.051, r= 0.924.

Calculation of the resistance of induction motor end rings

The paper describes a simple 2-dimensional finite-element model for calculating the resistance of rotor cage end rings. The method is capable of modelling the end rings in a realistic manner, and experimental measurements show that it gives results which are more accurate than the previous analytical method.