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1

Pharmacokinetic studies of phloretin in beagle dogs plasma using LC–MS/MS

Libin W., Le M., Tian F., Xueying L., Shengyong Z.

Acta Chromatographica

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2017

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Vol. 29, no. 4

443--447

EN

A simple, sensitive, and rapid liquid chromatography–tandem mass spectrometry (LC–MS/MS) method has been developed and validated for determination of phloretin in dog plasma using darunavir as internal standard. The phloretin was separated by the Inertsil® ODS3 C18 column (150 mm × 4.6 mm, 5 μm) and determined by LC–MS/MS. The electrospray ionization (ESI) source was operated in negative ionization mode for phloretin and positive ionization mode for darunavir (internal standard, IS). The multiple reaction monitoring (MRM) transitions were chosen to be m/z 273.0 → m/z 148.9 for phloretin, m/z 443.2 → m/z 401.0 for 2′,4′,6′,4-tetra-acetylphloretin and m/z 548.1 → m/z 69.1 for IS. The method was validated for accuracy, precision, linearity, range, selectivity, lower limit of quantification (LLOQ), recovery, and matrix effect. All validation parameters met the acceptance criteria according to regulatory guidelines. 2′,4′,6′,4-Tetra-acetylphloretin, as a prodrug of phloretin, is more stable than phloretin (PH) in vitro, protecting phenolic hydroxy from being oxygenated. The method had been successfully applied to a pharmacokinetic study of administration of phloretin and 2′,4′,6′,4-tetra-acetylphloretin in beagle dogs. Significant differences of tmax, Cmax, and area under the plasma concentration curve (AUC) were observed between phloretin and 2′,4′,6′,4-tetra-acetylphloretin.

2

Frames and factorization of graph Laplacians

Jorgensen P., Tian F.

Opuscula Mathematica

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2015

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Vol. 35, no. 3

293--332

EN

Using functions from electrical networks (graphs with resistors assigned to edges), we prove existence (with explicit formulas) of a canonical Parseval frame in the energy Hilbert space [formula] of a prescribed infinite (or finite) network. Outside degenerate cases, our Parseval frame is not an orthonormal basis. We apply our frame to prove a number of explicit results: With our Parseval frame and related closable operators in [formula] we characterize the Priedrichs extension of the [formula]-graph Laplacian. We consider infinite connected network-graphs G = (V, E), V for vertices, and E for edges. To every conductance function c on the edges E of G, there is an associated pair [formula] where [formula] in an energy Hilbert space, and Δ (=Δc) is the c-graph Laplacian; both depending on the choice of conductance function c. When a conductance function is given, there is a current-induced orientation on the set of edges and an associated natural Parseval frame in [formula] consisting of dipoles. Now Δ is a well-defined semibounded Hermitian operator in both of the Hilbert [formula] and [formula]. It is known to automatically be essentially selfadjoint as an [formula]-operator, but generally not as an [formula] operator. Hence as an [formula] operator it has a Friedrichs extension. In this paper we offer two results for the Priedrichs extension: a characterization and a factorization. The latter is via [formula].

3

Fiber Orientation and Rheology Behavior of the Laminar Suspension Flow through a 2-D Curved Expansion Duct

Zhang Q., Tian F., Shi W., Gao X, Zhang D.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 9b

70-74

EN

By coupling the fiber extra stress into the laminar Newtonian flow equations, the fiber orientation and the fiber suspension rheology in a 2D curved expansion duct is numerically investigated. The orientation distribution probability function is numerically solved to obtain the bulk orientation distributions and the extra stress distributions. The results show that the overall distribution of the flow field parameters, such as velocity, pressure have not been significantly affected in the most regions of the duct. But for the shear stress and normal stress difference, the non-equilibrium is significant. In the inlet region, the fibers rotate frequently due to the nonuniform flow shear effects, the orientation becomes more random and are less aligned with the local streamlines. But in the downstream region, with flow shear becomes uniform, the non-equilibrium is less obvious. In addition, with the fiber extra viscosity increasing, the shear stress and normal stress difference increase correspondingly.

PL

Przeanalizowano numerycznie orientację włókna i naprężenia zawieszenia w zastosowaniach do reologii. Stwierdzono, że takie parametry jak ciśnienie i szybkość przepływu nie decydują o parametrach kanału. Natomiast istotny wpływ mają naprężenia.

4

Seed mass increase along altitude within four Saussurea (Asteraceae) species in Tibetian Plateau

Wu G., Tian F., Ren G., Liu Z.

Polish Journal of Ecology

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2011

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Vol. 59, nr 3

617-622

EN

Seed mass is a critical life-history character in seed evolutionary ecology. Plant species can present responses in seed mass to environment stresses. We tested the hypotheses that seed mass was positively correlated with altitude within species. We selected four congeneric Saussurea species as study objects, and collected their seeds along altitudinal gradients (2100.4200 m a.s.l.) in the alpine area of the Qinghai-Tibetan Plateau, China. Results showed that mean seed mass of the four species were significantly affected by altitude (P <0.001). There was a general trend of an increase in seed weight with altitude among the populations of the four species. In addition, mean seed mass of four species were not significantly different, but all presented a bigger coefficients of variation within species along altitude gradients. Our results indicate selection pressure within species, with larger seeds occurring at higher altitudes.