Liquid chromatographic determination of ethambutol in serum samples based on intramolecular excimer-forming fluorescence derivatization.

A selective liquid chromatographic method has been developed for the assay of ethambutol in serum samples. The assay involves intramolecular excimer-forming derivatization with 4-(1-pyrene)butanoyl chloride (PBC) and isocratic reversed-phase chromatography with fluorescence detection. After acetonitrile-deproteinization of the serum sample, the derivatization reaction of ethambutol with PBC was completed within 30 min at 50 degrees C. N,N'-Diethylethylenediamine was used as an internal standard. The detection limit of ethambutol was 23 ng/ml serum, corresponding to 180 fmol on column at a signal-to-noise ratio of 3. The present method was selective enough to analyze ethambutol in rabbit serum without any tedious sample clean-up procedure because biogenic monoamines gave no peak in the chromatogram. The method was applicable to drug monitoring in rabbit serum.     

Semidefinite Programming Relaxation for Nonconvex Quadratic Programs

This paper applies the SDP (semidefinite programming)relaxation originally developed for a 0-1 integer program to ageneral nonconvex QP (quadratic program) having a linear objective functionand quadratic inequality constraints, and presents some fundamental characterizations of the SDP relaxation including its equivalence to arelaxation using convex-quadratic valid inequalities for the feasible regionof the QP.     

STM-induced molecular fluorescence from porphyrin molecules on metal substrates

Molecular fluorescence from ultrathin layers of H₂TBP porphyrin on Au(100) and ZnTBP porphyrin on Cu(100) has been generated by the electrical excitation using an ultrahigh-vacuum scanning tunneling microscope. The molecular origin of luminescence is justified by the good agreement of STM-induced emission spectra with conventional photoluminescence data excited from bulk molecules. The electronic states of top-layer molecules are effectively decoupled from the metal surface by controlling the thickness of molecular layers in a nanoscale regime. The porphyrin molecules are excited by the injection of hot electrons and then decay radioactively in a similar way to the photoluminescence process. These results provide a feasibility for the development of nanoscale molecular light source and spectroscopy. PACS  73.21.Ac; 68.37.Ef; 33.50.-j; 73.20.Mf     

The Stability of Self-inclusion Complexes of Cyclodextrin Derivatives Bearing a p-Dimethylaminobenze Moiety

An appending moiety of modified cyclodextrins acts as an intramolecular guest and forms a self-inclusion complex in aqueous solution. In this study, the stability of self-inclusion complexes of modified cyclodextrins which have a p-dimethylaminobenzene moiety was analyzed by fluorescent decay analyses, and the factor that determines the stability of the self-inclusion complex was determined by a computational approach. The self-inclusion form is stabilized mainly due to van der Waals interaction between the appending moiety and the cyclodextrin ring.     

Control of diameter,morphology, and structure of PVDF nanofiber fabricated by electrospray deposition

Poly(vinylidene fluoride) (PVDF) nanofibers were prepared by electrospray deposition (ESD). To control the diameter, morphology, and structure of PVDF nanofibers, some parameters were investigated, such as polymer concentration, nozzle‐to‐ground collector distance, feeding rate of the polymer solution, and applied voltage. The fabricated fiber was 80–700 nm in diameter. The increase in the polymer concentration caused an increase in the polymer viscosity and fiber diameter. At low polymer concentration (5 wt %), polymer nanoparticles were formed. An increase in applied voltage will increase the fiber diameter. Variation in the nozzle‐to‐ground collector distance did not result in significant changes in the fiber diameter. Increase in the feeding rate of the polymer solution decreased the fiber diameter. Differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) measurements showed that the melting point and total crystallinity were decreased. Fourier transform infrared spectroscopy (FTIR) measurement revealed that ESD process induced the formation of the oriented β‐phase PVDF structures. It was also demonstrated that the addition of hydrofluorocarbon solvent to polymer solution remarkably enhanced the formation of β‐phase crystalline structure of PVDF nanofiber. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 779–786, 2006     

Trace level determination of polycyclic aromatic hydrocarbons in river water with automated pretreatment HPLC

A novel on‐line pretreatment pump‐injection HPLC system for polycyclic aromatic hydrocarbons is proposed. We report novel pump‐injection HPLC‐based on‐line SPE with a specially designed pretreatment column for the determination of trace amounts of chemical substances in surface water. Polycyclic aromatic hydrocarbons are well known for strong carcinogenicity and thus a severe concentration control is required for drinking water and/or river water, which is the main resource of tap water. We found it possible to detect ng/L levels of polycyclic aromatic hydrocarbons by using pump‐injection column switching HPLC with fluorescence detection. To avoid the phenomenon, in which polycyclic aromatic hydrocarbons can be often adsorbed on the surface of flow lines of HPLC by their highly hydrophobicity especially resin‐made parts in sample delivery pump, we employed “autodilution” device that provides reliable recovery and repeatability. Additionally, real water samples were collected and then the spiked polycyclic aromatic hydrocarbons were determined at ng/L levels.     

Technology of electrochemical impedance spectroscopy for an energy-sustainable society

Electrochemical impedance spectroscopy has been widely used to understand the chemistry and physics of battery systems. This review covers electrochemical impedance spectroscopy used for the interpretation of impedance data of lithium-ion batteries (LIBs) from advanced equivalent circuit models to the mathematical model, which is developed by John Newman. In addition, as a method to realize an energy-sustainable society using diagnostics based on the combination of LIBs and electrochemical impedance spectroscopy, on-board diagnostics of battery packs are achieved based on an input signal generated by a power controller in a battery management system instead of the conventionally used frequency response analyzer. The diagnostic system is applicable to energy management systems which are installed in homes, buildings, and communities, accumulating the impedance data on state of health of LIBs. Finally, a future possibility regarding the diagnostics of battery packs coupled with the machine learning of impedance data is introduced.     

New ferroelectric liquid crystals with a trifluoromethyl group

Abstract

New chiral dopants, possessing a trifluoromethyl group, have been synthesized. These dopants have different polar groups, located between the chiral centre and the diphenylacetylene core. The polar part is chosen from ester, methylene ether and ether linkages. Each new chiral dopant was mixed with a non-chiral liquid crystal mixture or a ferroelectric liquid crystal mixture, and their transition temperatures and electrooptic properties measured. The largest spontaneous polarization, 4·1 nC cm^?2, was obtained at 25°C for the ferroelectric liquid crystal mixture in which the dopant, with a methylene ether linkage, was incorporated. Molecular orbital calculations (MNDO method) for the dopants show that the calculated dipole moments are correlated with the measured spontaneous polarization, and the calculated results explain the experimental results quite well. In addition, it has been found that the conformation of the chiral part is an important factor which affects the magnitude of spontaneous polarization.