Synthesis of fluorescent and coloured pyrylium and pyridinium salts

The synthesis is described of fluorescent and coloured pyrylium and pyridinium salts, including water-soluble derivatives, designed to serve as marker reagents for primary amines.     

Influence of the preparation method on the physicochemical properties of econazole-β-cyclodextrin complexes

Econazole (C₁₈H₁₅Cl₃N₂O) is one of the common antifungal agents whose poor aqueous solubility restricts its use for the treatment of oropharyngeal candidiasis, which is the first symptom of HIV infection. Therefore, the aim of the current study was to investigate the effect of different preparation methods (i.e. kneading, coevaporation, sealed-heating, and supercritical carbon dioxide (SC CO₂)) for obtaining solid inclusion complexes between β-cyclodextrin and econazole. The physico-chemical properties of the different products were characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffractometry (PXRD). For the complexes prepared by the SC CO₂ method, the effects of temperature and pressure have also been investigated and related to the solubility of econazole in SC CO₂. Results suggested the validity of the SC CO₂ method for preparing solid complexes between cyclodextrins and econazole, avoiding the use of organic solvents and problems of their complete removal. Moreover, temperature played a major role in promoting drug-carrier interactions, whereas pressure had limited effects.     

Mössbauer study of glasses in meteorites: the D'Orbigny angrite and Cachari eucrite

Mössbauer spectroscopy measurements at room temperature (RT) and at liquid helium temperature (4.2 K) were carried out on bulk and glass samples from the D'Orbigny (angrite) and Cachari (eucrite) meteorites. The RT Mössbauer spectrum of the bulk sample of D'Orbigny shows the presence of Fe²⁺ in olivine and pyroxene and that of bulk Cachari contains only pyroxene. Very small amounts of Fe³⁺ are also present in the bulk samples, but are attributed to surface contamination. The RT spectra of the D'Orbigny and Cachari glasses are fitted with three doublets, which are assigned to Fe²⁺ at three different octahedral positions. No Fe³⁺ was detected in the glass samples. The spectra of the glasses measured at 4.2 K show the presence of relaxation effects. The results suggest a certain degree of structural ordering in these glasses.     

Fluorosis Caused Cellular Apoptosis and Oxidative Stress of Rat Kidneys

As the strongest electronegative element, fluorine can stimulate the production of superoxide radicals in cells. In view of the important roles of kidneys in bone metabolism, the authors analyzed the quantitative pathomorphological characteristics of renal damage and the potential cellular apoptosis and oxidative stress mechanisms in rats treated with excessive fluoride. Wistar rats were exposed to 50 mg F^-(110.5 mg NaF)/L, 100 mg F^-(221.0 mg NaF)/L and 150 mg F^-(331.5 mg NaF)/L in drinking water for 70 and 140 d, respectively. Microscope with image analysis was used to quantitate pathomorphological changes in renal tissues of the rats. Reactive oxygen species(ROS), the cell cycle and apoptosis of renal cells were measured by flow cytometry and TUNEL technique(terminal deoxynucleotidyl transferase dUTP nick end labeling), respectively. The ion concentrations in serum and renal functional parameters were detected by automatic biochemical analyzer. Quantitative analysis results demonstrate the expanded Bowman’s space of glomerulus and obvious dilatation of renal tubule. TUNEL technique revealed that NBT/BCIP (nitro blue tetrazolium/5-bromo-4-chloro-3′-indolylphosphate, p-toluidine salt)-staining positive apoptotic cells selectively located in medullocortical junction areas. The data suggest that renal damage in chronic fluorostic rats is associated with the cellular apoptosis and oxidative stress.     

Twisted Orbifold K-Theory

 We use equivariant methods to define and study the orbifold K-theory of an orbifold X. Adapting techniques from equivariant K-theory, we construct a Chern character and exhibit a multiplicative decomposition for K ^* _orb (X)⊗ℚ, in particular showing that it is additively isomorphic to the orbifold cohomology of X. A number of examples are provided. We then use the theory of projective representations to define the notion of twisted orbifold K–theory in the presence of discrete torsion. An explicit expression for this is obtained in the case of a global quotient. Received: 21 August 2001 / Accepted: 27 January 2003 Published online: 13 May 2003 RID="*" ID="*" Both authors were partially supported by the NSF RID="*" ID="*" Both authors were partially supported by the NSF Communicated by R.H. Dijkgraaf     

Hexa-BODIPY Linked-Triazole Based on a Cyclotriphosphazene Core as a Highly Selective and Sensitive Fluorescent Sensor for Fe<Superscript>2+</Superscript> Ions

A new type of fluorescent chemosensor based on tethered hexa-borondipyrromethene cyclotriphosphazene platform (HBTC) linked via triazole groups was designed and synthesized. Its sensing behavior toward metal ions was investigated by ultraviolet-visible and fluorescence spectroscopies. Addition of a Fe²⁺ ion to a tetrahydrofuran solution of HBTC gave a visual color change as well as a significantly quenched fluorescence emission, while other tested 19 metal ions induced no color or spectral changes. This compound was found to be highly selective and sensitive for Fe²⁺ with a low limit of detection (2.03 μM) which is, to the best of our knowledge, the superior than the previously studied chemosensors for Fe²⁺.

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Fabrication of magnetic gold nanorod particles for immunomagnetic separation and SERS application

The preparation and application of rod-shaped core–shell structured Fe₃O₄–Au nanoparticles for immunomagnetic separation and sensing were described for the first time with this study. To synthesize magnetic gold nanorod particles, the seed-mediated synthetic method was carried out and the resulting nanoparticles were characterized with transmission electron microscopy (TEM), ultraviolet visible spectroscopy (UV–Vis), energy-dispersive X-ray (EDX), and X-ray diffraction (XRD). Magnetic properties of the nanoparticles were also examined. Characterization of the magnetic gold nanorod particles has proven that the resulting nanoparticles were composed of Fe₃O₄ core and the gold shell. The rod-shaped gold-coated iron nanoparticles have an average diameter of 16 ± 2 nm and an average length of about 50 ± 5 nm (corresponding aspect ratio of 3). The saturation magnetization value for the magnetic gold nanorod particles was found to be 37 emu/g at 300 K. Rapid and room temperature reaction synthesis of magnetic gold nanorod particles and subsequent surface modification with E. coli antibodies provide immunomagnetic separation and SERS application. The analytical performance of the SERS-based homogenous sandwich immunoassay system with respect to linear range, detection limit, and response time is also presented.     

Comparative study of electrical properties of Au/n-Si (MS) and Au/Si3N4/n-Si (MIS) Schottky diodes

In this paper, the electrical parameters of Au/n-Si (MS) and Au/Si₃N₄/n-Si (MIS) Schottky diodes are obtained from the forward bias current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. Experimental results show that the rectifying ratios of MS and MIS diode at ± 5 V are found to be 1.25×10³ and 1.27×10⁴, respectively. The main electrical parameters of MS and MIS diode, such as the zero-bias barrier height (Φ _Bo) and ideality factor (n) are calculated to be 0.51 eV (I-V), 0.53 eV (C-V), and 4.43, and 0.65 eV (I-V), 0.70 eV (C-V), and 3.44, respectively. Also, the energy density distribution profile of the interface states (N_ss) is obtained from the forward bias I-V. In addition, the values of series resistance (R_s) for the two diodes are calculated from Cheung's method and Ohm's law.