Indirect capillary electrophoresis with 8-anilino-1-naphthalenesulfonic acid as a fluorescence probe for determining the apparent stability constant of an inclusion complex formed between a cyclodextrin and a solute

An indirect capillary electrophoresis (CE) method was developed based on two competitive chemical equilibria for determining the stability constant of an inclusion complex formed between a cyclodextrin and a solute. 8-Anilino-1-naphthalenesulfonic acid was employed as a fluorescence probe. A linear relationship between mobility difference and concentration of uncomplexed ligand was theoretically established and experimentally verified. The principle of the method was explained using an example of determining stability constant of an inclusion complex formed between a ligand of hydroxypropyl-beta-cyclodextrin and a solute of amantadine. The stability constant was determined to be approximately 2 x 10(2) M(-1). It was calculated without knowledge of the mobility of the complex measured at saturating ligand concentrations. This indirect method can be applied to solutes and ligands lacking signal response on the selected detector in the CE. In addition, the indirect method is valid for both charged and neutral solutes and ligands.     

Determination of the bacterial pathogen Edwardsiella tarda in fish species by capillary electrophoresis with blue light-emitting diode-induced fluorescence

High-performance capillary electrophoresis (HPCE) has been applied to the identification, separation, and quantitation of intact bacteria. We demonstrate that a pathogen (Edwardsiella tarda) which causes systemic infection in commercially important fish species can be rapidly identified and determined (< 10 min) after direct injection into fish fluid by CE blue light-emitting diode (LED)-induced fluorescence. SYTO 13 (488 nm/509 nm), a cell-permeable green nucleic acid stain, was used to stain the cells. Remarkably high efficiency (> 1,200,000 theoretical plates/m) was achieved with this rapid and efficient CE method. It was found that proper sample vortexing (90 s) would be beneficial to disperse aggregated cells and facilitate the focusing of intact cells during electrophoresis. Ionization of the surface constituents of Edwardsiella tarda cells provided efficient surface charges for the intact cells to be separated from the EOF and damaged or lysed cells when the separation was performed in running buffer (3.94 mM Tris, 0.56 mM borate, 0.013 mM EDTA) at pH 10.5. The limit of detection (LOD) and recovery were found to be 4.2 x 10(4) cells/mL and 70.0%, respectively. This proposed CE method could become an effective tool for diagnosis and tracking of certain diseases caused by bacteria in fish species as well as in human beings.     

Determination of pharmaceuticals classified as emerging pollutants using capillary electrophoresis with capacitively coupled contactless conductivity detection

A study on the simultaneous separation of 13 pharmaceutical products by capillary electrophoresis with capacitively coupled contactless conductivity detection was presented. The parameters of the background electrolyte, such as pH, organic additives as well as types and concentrations of cyclodextrins (CD) were studied. The optimal separation conditions were achieved with a background electrolyte consisting of 9 mM Tris/5 mM lactic acid at pH 8.0, containing 5% n-propanol, 0.025% gamma-CD, 0.075% hydroxyl-beta-CD and 0.15% dimethyl-beta-CD. Limits of detections ranged from 61 to 1676 microg/L (S/N=3) and the relative standard deviations for migration time and peak area were below 2 and 6%, respectively. This demonstrated the potential of the capillary electrophoresis-capacitively coupled contactless conductivity detection method for biomedical and environmental analysis, as shown in the determination of pharmaceuticals identified as emerging pollutants in water samples.     

On formulas for Dedekind sums and the number of lattice points in tetrahedra

This paper explores a simple yet powerful relationship between the problem of counting lattice points and the computation of Dedekind sums. We begin by constructing and proving a sharp upper estimate for the number of lattice points in tetrahedra with some irrational coordinates for the vertices. Besides providing a sharper estimate, this upper bound (Theorem 1.1) becomes an equality (i.e. gives the exact number of lattice points) in a tetrahedron where the lengths of the edges divide each other. This equality condition can then be applied to the explicit computation of the classical Dedekind sums, a topic that is the central focus in the second half of our paper. In this half of the paper, we come up with a number of interesting results related to Dedekind sums, based on our upper estimate (Theorem 1.1). Among these findings, Theorem 1.9 and Theorem 1.10 deserve special attention, for they successfully generalize two of Apostol's formulas in [T.M. Apostol, Modular Functions and Dirichlet Series in Number Theory, Springer-Verlag, New York, 1997], and also directly imply the famous Reciprocity Law of Dedekind sums.     

Robust decentralized adaptive control for uncertain large-scale delayed systems with input nonlinearities

The paper is concerned with the problem of robust stabilization for uncertain large-scale time-varying delayed systems with input nonlinearities. Based on the sliding mode control, a memoryless decentralized adaptive sliding mode controller (DASMC) is developed. The proposed controller ensures the occurrence of the sliding manifold of the composite system even subjected to input nonlinearity. It shows that the uncertain nonlinear large-scale system also possesses the property of insensitivity to uncertainties and disturbances as a linear system does. A numerical example is given to verify the validity of the developed memoryless DASMC.     

Diffeomorphic types of complements of nice point arrangements in CP<Superscript><Emphasis Type="Italic">l</Emphasis></Superscript>

We use a new method to study arrangement in CP ^l , define a class of nice point arrangements and show that if two nice point arrangements have the same combinatorics, then their complements are diffeomorphic to each other. In particular, the moduli space of nice point arrangements with same combinatorics in CP ^l is connected. It generalizes the result on point arrangements in CP ³ to point arrangements in CP ^l for any l.     

Adaptive sliding mode control of a high-precision ball-screw-driven stage

High-precision position control has been widely used in scientific instruments and semiconductor fabrication equipment. Traditionally, controllable displacements with sub-micron and nano-level resolution are usually achieved by piezoelectric actuators because of their high bandwidth and ease of control. However, the travel range of piezoelectric actuator is usually small. In this paper, the ball-screw-driven system is studied to provide long-range and high-precision performance for positioning and tracking control. In such a system, the friction dynamics are divided into the static and the dynamic regimes to describe the dynamic behavior of a conventional ball-screw-driven x-y stage. The same form of adaptive sliding mode controllers are designed in the static and dynamic regimes to obtain the precision performance for controlled stage. A proportional-integral switching surface is proposed to make it easy to assign the performance of the systems in the sliding mode motion and the controller is robust without knowing the bound of disturbance in advance. An illustrative example is included to demonstrate that the system achieves high precision (10 nm) and long-range (10 cm) positioning performance with repeatability and robustness by the proposed control approach.