Combined liquid chromatography-mass spectrometry using electrospray or atmospheric-pressure chemical ionization has become an important tool in the quantitative analysis of pesticide residues in various matrices in relation to environmental analysis, food safety, and biological exposure monitoring. One of the major problems in the quantitative analysis using LC-MS is that compound and matrix-de...

A new chaotic system is presented using a single parameter for a two-scroll attractor with high complexity, high chaoticity and widely chaotic range. The system employs two quadratic nonlinearities and two piecewiselinear nonlinearities. The high chaoticity is measured by the the maximum Lyapunov Exponent of 0.429 and the high complexity is measured by the Kaplan-Yorke dimension of 2.3004. Dyna...

Metabolite profiling has been established as a modern technology platform for the description of complex chemical matrices and compound identification in biological samples. Gas chromatography coupled with mass spectrometry (GC-MS) in particular is a fast and accurate method widely applied in diagnostics, functional genomics and for screening purposes. Following solvent extraction and derivatiz...

This review focused on seven psychoactive drugs being six benzodiazepines (alprazolam, bromazepam, clonazepam, diazepam, lorazepam, and oxazepam) and one antidepressant (citalopram) widely consumed by modern society and detected in different aqueous matrices (drinking water, surface water, groundwater, seawater, estuary water, influent and effluent of wastewater treatment plants). The review in...

In this paper, an ordinary differential equation model of HIV infection of CD4 T-cells with saturated reverse function is studied. We prove that if the basic reproduction number R0 < 1, the virus-free equilibrium is locally asymptotically stable. And there will exhibit backward bifurcation when R0 < 1. If R0 > 1, some feasibly sufficient conditions are obtained for the global asymptotic stabili...

A wide class of structural models on multivariate normal covariance matrices can be expressed using symmetries. For example, a multivariate normal vector has the intraclass correlation structure (where all variances are equal, and all covariances are equal) if the covariance matrix is invariant under permutation of the components, and the components are independent if the covariance matrix in i...

The paper deals with the best unbiased estimators of the blocked compound symmetric covariance structure for m−variate observations over u sites under the assumption of multivariate normality. The free-coordinate approach is used to prove that the quadratic estimation of covariance parameters is equivalent to linear estimation with a properly defined inner product in the space of symmetric matr...

This paper studies monotone tridiagonal systems with negative feedback. These systems possess the Poincaré-Bendixson property, which implies that, if orbits are bounded, if there is a unique steady state and this unique steady state is asymptotically stable, and if one can rule out periodic orbits, then the steady state is globally asymptotically stable. Two different approaches are discussed t...

In a previous Method Article, we have presented the 'Structure-Activity Relationship (SAR) Matrix' (SARM) approach. The SARM methodology is designed to systematically extract structurally related compound series from screening or chemical optimization data and organize these series and associated SAR information in matrices reminiscent of R-group tables. SARM calculations also yield many virtua...

For the multivariate COGARCH(1,1) volatility process we show sufficient conditions for the existence of a unique stationary distribution, for the geometric ergodicity and for the finiteness of moments of the stationary distribution. One of the conditions demands a sufficiently fast exponential decay of the MUCOGARCH(1,1) volatility process. Furthermore, we show easily applicable sufficient cond...