Easily manufactured TiO2 hollow fibers for quantum dot sensitized solar cells

TiO(2) hollow fibers with high surface area were manufactured by a simple synthesis method, using natural cellulose fibers as template. The effective light scattering properties of the hollow fibers, originating from their micron size, were observed by diffuse reflectance spectroscopy. In spite of the micrometric length of the TiO(2) hollow fibers, the walls were highly porous and high surface area (78.2 m(2) g(-1)) was obtained by the BET method. TiO(2) hollow fibers alone and mixed with other TiO(2) pastes were sensitized with CdSe quantum dots (QDs) by Successive Ionic Layer Adsorption and Reaction (SILAR) and integrated as a photoanode in quantum dot sensitized solar cells (QDSCs). High power conversion efficiency was obtained, 3.24% (V(oc) = 503 mV, J(sc) = 11.92 mA cm(-2), FF = 0.54), and a clear correspondence of the cell performance with the photoanode structure was observed. The unique properties of these fibers: high surface area, effective light scattering, hollow structure to facile electrolyte diffusion and the rather high efficiencies obtained here suggest that hollow fibers can be introduced as promising nanostructures to make highly efficient quantum dot sensitized solar cells.     

Synthesis and Characterization of Polyesters Based on Diethylketone Moiety

A new class of unsaturated polyesters based on diethylketone have been prepared by interfacial polymerization of 2,4-bis（4-hydroxybenzylidene）-3-pentanone（I） and 2,4-bis（4-hydroxy-3-methoxybenzylidene）-3-pentanone（II） with 4,4’-azodibenzoyl chloride and 3,3’-azodibenzoyl chloride at ambient temperature. The model compounds were synthesized by reaction of（I） and（II） with benzoyl chloride. The new monomers, model compounds and polyesters have been characterized by different spectral analyses. The polyesters have inherent viscosity of 0.55-0.80 d L/g and moderate number average molecular weight（Mn） in the range of 6150-7400 g/mol. Most of the compounds exhibited their solubility in aprotic solvents while partial solubility in various halogenated organic solvents was observed. The temperatures of 10% weight loss were high（225-330 °C） in nitrogen, indicating that these polyesters have excellent thermal stability. Doping with iodine dramatically raised the conductivity and produced brown colored semiconductive polymers with a maximum conductivity of 2.7 × 10-6 --1cm-1. Moreover, the morphological properties of selected example of polyesters were detected by SEM.     

Diastereoselective synthesis of novel <Emphasis Type="Italic">N</Emphasis>-substituted pyrrolidine-2-one containing piperazine derivatives

Synthesis of novel hybrid derivatives of two known scaffolds, pyrrolidine-2-one and piperazine, is described. Initially, the Ugi reaction of phenylglyoxal, aromatic amines, coumarin-3-carboxylic acid and isocyanides in methanol resulted in the formation of dihydrochromeno[3,4-c]pyrrole-3,4-diones. The obtained products were then treated with N-alkylpiperazines in dichloromethane to afford the novel N-substituted pyrrolidine-2-one containing piperazine derivatives in satisfactory yields. The proof of the structures was carried out by means of spectroscopic information and X-ray crystallography.     

Applications of Inorganic Polymeric Materials, III: Polyphosphazenes

Polyphosphazenes form one of the most important and interesting classes of inorganic polymers having a backbone of alternating phosphorus and nitrogen atoms with phosphorus atom bearing two organic side groups. The most important feature of these polymers is the synthesis route which allows the side groups to be changed over a wide range to obtain a broad variety of products with different properties from elastomers to glasses, water soluble to hydrophobic polymers, bioinert to bioactive materials, and electrical insulators to conductors. In this paper, some novel applications of these polymers in biomedical materials and advanced devices are reviewed.     

Some fixed point theorems in convex metric spaces

The concept of a convex metric space was introduced by Takahashi [10]. He observed that it is possible to generalize fixed point theorems in Banach spaces. Subsequently, Machado [8], Itoh [5], Naimpally, Singh and Whitfield [9] and Beg and Azam [2], among others have studied fixed point theorems in convex metric spaces. This paper is a continuation of these investigations.     

A presentation for reduced extended affine weyl groups

In 1985 K. Saito [Sal] introduced the concept of an extended affine Weyl group (EAWG), the Weyl group of an extended affine root system (EARS). In [A2, Section 5J, we gave a presentation called “a presentation by conjugation” for the class of EAWGs of index zero, a subclass of EAWGs. In this paper we will give a presentation wh.ich we call a “generalized present.ation by conjugation” for the class of reduced EAWGs. If the extended affine Weyl group is of index zero this presentation reduces to “a presentation by conjugation”. Our main result states that when the nullity of the EARS is 2, these two presentations coincide that is, EAWGs of nullity 2 have “a presentation by conjugation”. In [ST] another presentation for EAWGs of nullity 2 is given.     

A survey of parameter and state estimation in queues

Queueing Systems - We present a broad literature survey of parameter and state estimation for queueing systems. Our approach is based on various inference activities, queueing models, observations...