Some necessary and sufficient conditions for Hypercyclicity Criterion

We give necessary and sufficient conditions for an operator on a separable Hilbert space to satisfy the hypercyclicity criterion. This paper is a part of the second author’s Doctoral thesis, written at Shiraz University under the direction of the first author.     

Synthesis of New Dibenzosulfide and Dibenzosulfoxide Macrocyclic Compounds

Some new dibenzosulfo, dibenzosulfoxo macrocyclic diamides are synthesized.     

Highly selective thiocyanate poly(vinyl chloride) membrane electrode based on a cadmium-Schiff's base complex

A PVC membrane electrode based on a cadmium-salen (N,N'-bis-salicylidene-1,2-ethylenediamine) complex as an anion carrier is described. The electrode has an anti-Hofmeister selectivity sequence with a preference for thiocyanate at pH 1.5-11.0. It has a linear response to thiocyanate from 1.0 x 10(-6) to 1.0 x 10(-1) mol L(-1) with a slope of 59.1 +/- 0.2 mV per decade, and a detection limit of 7 x 10(-7) mol L(-1). This electrode has high selectivity for thiocyanate relative to many common organic and inorganic anions. The proposed sensor has a fast response time of approximately 15 s. It was applied to the determination of thiocyanate in a milk sample.     

Synthesis and properties of biodegradable elastomeric epoxy modified polyurethanes based on poly(ε-caprolactone) and poly(ethylene glycol)

Biodegradable polyurethane elastomers with potential for applications in medical implants with tunable degradation rate and physical properties were synthesized from reaction of epoxy terminated polyurethanes (EUP) with 1,6-hexamethylene diamine (HMDA) as curing agent. Poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG) as well as 1,6-hexamethylene diisocyanate (HDI) were used for preparation of isocyanate terminated polyurethanes which were subsequently blocked with glycidol to prepare EUPs. All materials were characterized by conventional methods, and their properties were studied fully. Results showed that elastomers based on PEG exhibit superior degradation rate and inferior mechanical properties in comparison to elastomers based on PCL. Optimum degradation rate and mechanical properties were obtained from elastomers made from mixture of PCL and PEG base EUPs.     

Chemical composition and antimicrobial activity of the essential oils of Ferula latisecta and Mozaffariania insignis from Iran

The hydrodistilled oils from the aerial parts of Ferula latisecta and Mozaffariania insignis, which is endemic to Iran, were analyzed by GC and GC/MS. (Z)-Ocimenone (32.4%), (E)-ocimenone (20.3%), and cis-pinocarvone (11.4%) were the main components among the 22 constituents characterized in the oil of F. latisecta, representing 87.7% of the total components detected. Twenty-five compounds were identified in the oil of M. insignis, representing 99.0% of the total oil, with octyl acetate (41.1%), β-pinene (30.3%), and α-pinene (23.9%) as the main constituents. The essential oils were examined for their potential antimicrobial activities. Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 561–563, November–December, 2006.     

Photocatalytic Activity of Supported Metal Nanoparticles and Single Atoms

Photocatalysis has been known as one of the promising technologies due to its eco-friendly nature. However, the potential application of many photocatalysts is limited owing to their large bandgaps and inefficient use of the solar spectrum. One strategy to overcome this problem is to combine the advantages of heteroatom-containing supports with active metal centers to accurately adjust the structural parameters. Metal nanoparticles (MNPs) and single atom catalysts (SACs) are excellent candidates due to their distinctive coordination environment which enhances photocatalytic activity. Metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and carbon nitride (g-C₃N₄) have shown great potential as catalyst support for SACs and MNPs. The numerous combinations of organic linkers with various heteroatoms and metal ions provide unique structural characteristics to achieve advanced materials. This review describes the recent advancement of the modified MOFs, COFs and g-C₃N₄ with SACs and NPs for enhanced photocatalytic applications with emphasis on environmental remediation.     

Mathematical modeling of a slurry reactor for DME direct synthesis from syngas

In this paper,an axial dispersion mathematical model is developed to simulate a three-phase slurry bubble column reactor for direct synthesis of dimethyl ether(DME) from syngas.This large-scale reactor is modeled using mass and energy balances,catalyst sedimentation andsingle-bubble as well as two-bubbles class flow hydrodynamics.A comparison between the two hydrodynamic models through pilot plantexperimental data from the literature shows that heterogeneous two-bubbles flow model is in better agreement with the experimental data thanhomogeneous single-bubble gas flow model.Also,by investigating the heterogeneous gas flow and axial dispersion model for small bubblesas well as the large bubbles and slurry(i.e.including paraffins and the catalyst) phase,the temperature profile along the reactor is obtained.Acomparison between isothermal and non-isothermal reactors reveals no obvious performance difference between them.The optimum values ofreactor diameter and height were obtained at 7 m and 50 m,respectively.The effects of operating variables on the axial catalyst distribution,DME productivity and CO conversion are also investigated in this research.     

Investigating the effect of operating parameters on the open circuit voltage of a passive DMFC

The variations of the open circuit voltages (OCVs) were studied in a passive air-breathing direct methanol fuel cell with an air-breathing cathode using Nafion 115 as the electrolyte membrane. The effects of some operating parameters such as cell temperature, cell orientation, and also methanol concentration on the OCV of fabricated fuel cell were investigated experimentally. The experimental results showed that the OCV values depend strongly on the cell orientation, cell temperature, and methanol concentration. The OCV values decrease with an increase in methanol concentration and cell temperature. Also, the OCV values in vertical orientation are lower than the OCV values in other orientations.     

A Facile Room Temperature Synthesis of Zinc Oxide Nanostructure and Its Influence on the Flame Retardancy of Poly Vinyl Alcohol

In this work, poly vinyl alcohol–ZnO nanocomposites were synthesized via two different in situ and ex-situ methods. In ex-situ, at first zinc oxide nanostructures were synthesized by one-step precipitation reaction between zinc acetate and sodium hydroxide. The effect of different surfactants such as poly vinyl pyrrolidone, poly vinyl alcohol and poly ethylene glycol on the morphology of ZnO nanostructures was investigated. Nanostructures were characterized by X-ray diffraction, scanning electron microscopy. The influence of ZnO nanostructures on the flame retardancy of the poly vinyl alcohol matrix was studied using underwriter laboratories UL-94 analysis.