Reflection spectroscopy of optically active materials

Theoretical and experimental results are presented to determine under what conditions it is possible to obtain the optical constants of an optically active material by reflection techniques. Experimental results axe given for absorbing and non-absorbing materials. Typical examples include liquids, thin-films, and isotropic crystals. It is concluded that it is necessary to separate the back and front surface reflections. The front surface reflection contains information that is generally within the sensitivity of available spectropolarimeters. The back surface reflection contains recoverable data and is similar to the data found by transmission methods. Experimental verification of the front surface effect is presented for one highly absorbing amino acid, tryptophane.     

Nanocompatible chemistry toward fabrication of target-specific gold nanoparticles

Nanocompatible chemistry which utilizes a novel nontoxic phosphino amino acid as a reducing agent has resulted in the development of therapeutically useful gold nanoparticles under biologically benign media. Stabilization of gold nanoparticles by the edible gum arabic matrix has provided an effective pathway toward in vivo stable target-specific gold nanoparticles.     

A decentralized control mechanism for stream processing networks

Data streaming applications are becoming more and more common due to the rapid development in emerging areas such as sensor networks, multimedia streaming, and on-line data mining, etc. These applications are often running in a decentralized, distributed environment. The requirements for processing large volumes of streaming data at real time have posed many great design challenges. One of the critical issues is to optimize the ongoing resource consumption of multiple, distributed, cooperating processing units. In this paper, we consider a generic model for the general stream data processing systems. We address the resource allocation problem for a collection of processing units so as to maximize the weighted sum of the throughput of different streams. Each processing unit may require multiple input data streams simultaneously and produce one or many valuable output streams. We develop decentralized control mechanisms that maximize the overall system throughput in such data stream processing networks. Performance analysis on the optimality and complexity of these mechanisms are also provided.     

A multivariate study of the performance of an ultrasound-assisted madder dyes extraction and characterization by liquid chromatography-photodiode array detection

An extraction method of madder (Rubia tinctorum) roots dyes is established and optimized to obtain the original chemical composition. A central composite design (CCD) was developed to specify the importance of the three major factors studied (time, temperature and solvent composition) affecting the ultrasound-assisted extraction of this matrix. A preliminary granulometric study of madder roots is realized in the aim to determine the optimal particles size corresponding to the best ultrasound effects. A comparison with the classical extraction method of madder dyes by reflux is described. The identification of the constituents of R. tinctorum is carried out by liquid chromatography coupled with a photodiode array detector (LC-PDA). Anthraquinonic aglycone and heterosidic dyes compounds are characterized by retention time and UV spectrum: alizarin (1,2-dihydroxyanthraquinone), purpurin (1,2,4-trihydroxyanthraquinone), lucidin (1,3-dihydroxy-2-hydroxymethylanthraquinone), rubiadin (1,3-dihydroxy-2-methylanthraquinone), xanthopurpurin (1,3-dihydroxyanthraquinone), pseudopurpurin (1,2,4-trihydroxy-3-carboxyanthraquinone), lucidin primeveroside, ruberythric acid (alizarin primeveroside), galiosin (pseudopurpurin primeveroside) and rubiadin primeveroside. The optimal experimental conditions are 18min, 36 degrees C and 37/63 MeOH/H(2)O (v/v).     

A New Disubstituted Polyacetylene for the Detection of α‐Amino Acids

New imidazole‐functionalized disubstituted polyacetylene was synthesized by utilizing the postfunctional strategy. In addition, its ability to sense copper ions and α‐amino acids by fluorescence quenching has been studied. The quenching of the fluorescence of the imidazole‐functionalized disubstituted polyacetylene was observed at a very low level of Cu²⁺ (7.0 × 10⁻⁷ mol · L⁻¹). The fluorescent intensity decreased rapidly upon the increase of the concentration of the added solution of Cu²⁺. It was expected that the addition of α‐amino acids to the solution of the polyacetylene/Cu²⁺ complex could turn on the fluorescence of the polyacetylene, if α‐amino acids could remove the copper ions from the complex. Glycine, was used for testing: upon the addition of glycine the quenched fluorescence of P1 turned on immediately. The detection limit was as low as 6.0 × 10⁻⁵ mol · L⁻¹.

     

Preparation of Functional Poly(aroyltriazole)s by Metal-Free Click Polymerization

Functional poly(aroyltriazoles) (PATAs) were synthesized by heating mixtures of bis(aroylacetylene)s and diazides in polar solvents such as DMF/toluene at a moderate temperature of 100 °C with high molecular weights (M_w up to 17 200) and regioregularities (1,4-regioisomeric ratio up to ∼95%) in high yields (up to ∼95%). The obtained polymers are soluble in common organic solvents and are thermally stable. The PATAs containing triphenylamine units emit visible light and show unique solvatochromism, exhibiting large two-photon absorption cross sections due to the intramolecular charge transfer between their electron-donating triphenylamine and electron-accepting aroyltriazole units. The tetraphenylethene (TPE)-functionalized polymer shows intriguing aggregation-induced emission phenomenon, that is, the polymer is weakly emissive in its solution state but emit strongly in its aggregate/solid state with quantum yield of ∼7.1%.