Continuous fixed bed biosorption of reactive dyes by dried Rhizopus arrhizus: determination of column capacity

A continuous fixed bed study was carried out by using dried Rhizopus arrhizus as a biosorbent for the removal of three reactive dyes; Gemacion (Procion) Red H-E7B (GR), a monoclorotriazine mono-azo type reactive dye; Gemazol Turquise Blue-G (GTB), a vinyl sulfone mono-azo type reactive dye and Gemactive (Reactive) Black HFGR (GB), a vinyl sulfone di-azo type reactive dye from aqueous solution. The effect of operating parameters such as flow rate and inlet dye concentration on the sorption characteristics of R. arrhizus was investigated at pH 2.0 and at 25 degrees C for each dye. Data confirmed that the total amount of sorbed dye decreased with increasing flow rate and increased with increasing inlet dye concentration for each dye. The column biosorption capacity of dried R. arrhizus was 1007.8 mg g(-1) for GR dye, 823.8 mg g(-1) for GTB dye and 635.7 mg g(-1) for GB dye at the highest inlet dye concentration of approximately 750 mg l(-1) and at the minimum flow rate of 0.8 ml min(-1). Thomas and Yoon-Nelson models were applied to experimental data to predict the breakthrough curves and to determine the biosorption capacity of the column for each dye useful for process design. Both models were found suitable for describing the whole dynamic behavior of the column with respect to flow rate and inlet dye concentration.     

Construction of symmetric supercapacitors using anhydrous electrolytes containing heterocyclic oligomeric structures

The anhydrous electrolytes have become an important part of supercapacitors, which provide temperature-tolerant applications in various electronic devices. This work reports on the fabrication of a wide-temperature-range supercapacitor using 3-amino-1H-1,2,4-triazole (Atri)/1,4-butanediol diglycidyl ether (BG) and imidazole (Imi)/BG–based electrolytes in active carbon-based electrodes. The triazole-terminated BG (BG(Atri)₂) and Imi-terminated BG (BG(Imi)₂) were initially synthesized, and then anhydrous electrolytes were produced by doping BG(Atri)₂ and BG(Imi)₂ with phosphoric acid (H₃PO₄) and ionic liquid (IL) at different molar fractions. The supercapacitors constructed with the anhydrous BG(Atri)₂/H₃PO₄/0.1IL and BG(Imi)₂/H₃PO₄/0.1IL electrolytes provided maximum specific capacitances (Cs) of 114 and 191 F g⁻¹ at 1 A g⁻¹, respectively. The corresponding electrolytes yielded the highest energy densities of 15.8 and 26.7 Wh kg⁻¹ at the power densities of 1150 and 1225 W kg⁻¹, respectively. The Imi-terminated electrolyte-based supercapacitor indicated superior performance and efficiency even after 2300 charge-discharge cycles by holding 20% of its original capacitance. The temperature dependence of the supercapacitors' capacitances was studied, and they increased from 191 to 266 F g⁻¹ for BG(Imi)₂/H₃PO₄/0.1IL and from 114 to 148 F g⁻¹ for BG(Tri)₂/H₃PO₄/0.1IL as the temperature increased from 25°C to 75°C.     

Transparent, highly flexible, all nanowire network germanium photodetectors

We report on the fabrication and characterization of all nanowire (NW) network photodetectors. For this purpose, germanium (Ge) NW networks are used as active semiconducting elements, whereas single walled carbon nanotube (SWNT) and silver (Ag) NW networks are used as the contacts. Following their synthesis, all NW networks are deposited through simple solution based methods. Photoresponse characteristics and transparency of the photodetectors for different Ge NW densities are measured. The fabricated devices show a large response with short relaxation times (<10 ms), are flexible and transparent within the visible spectrum.     

The effect of the strength and direction of magnetic field on the assembly of magnetic nanoparticles into higher structures

The self-assembly of magnetic nanoparticles into higher-order organizations upon external magnetic stimulation has critical importance for the fabrication of discrete microstructures. In this study, the tuning of self-assembly behavior of magnetic Fe3O4 nanoparticles (MNPs), with an average size of 6 nm, under the enhanced magnetic force upon changing the applied field strength and direction is explored. Upon evaporation of the solvent where the MNPs are suspended, formation of particular micrometer sized structures is achieved with a surface constructed from sub-micrometer size magnetic beads in between the applied magnetic field and MNPs. In this study, three different surfaces fabricated using sub-micrometer size magnetic beads in between the applied magnetic field and MNPs are used and the effect of the template pattern, applied field strength and direction are explored.     

Electrochemical biosensor for detection of formaldehyde in rain water

BACKGROUD: This study describes the construction of an electrochemical formaldehyde biosensor based on poly(glycidyl methacrylate‐co‐3‐methylthienyl methacrylate)/formaldehyde dehydrogenase/polypyrrole [poly(GMA‐co‐MTM)/FDH/PPy] composite film electrode. Formaldehyde dehydrogenase (FDH) was chemically immobilized via the epoxy groups of the glycidyl methacrylate (GMA) side chain of the polymer. Formaldehyde measurements were conducted in 0.1 mol L^?1, pH 8 phosphate buffer solution (PBS) including 0.1 mol L^?1 KCl, 0.5 mmol L^?1 of NAD⁺ (cofactor of the enzyme) and 1 mmol L^?1 of 1,2‐napthoquinone‐4‐sulfonic acid sodium salt (NQS) as mediator with an applied potential of ? 0.23 V (vs. Ag/AgCl, 3 mol L^?1 NaCl). Analytical parameters of the biosensor were calculated and discussed. The biosensor was tested in rain water samples. RESULTS: Sensitivity was found to be 15 000 per mmol L^?1 (500 nA ppm^?1) in a linear range between 0.1 ppm and 3 ppm (3.3–100 µmol L^?1). A minimum detectable concentration of 4.5 ppb (0.15 µmol L^?1) (S/N = 3) with a relative standard deviation (RSD) of 0.73% (n = 5) was obtained from the biosensor. Response time of the biosensor was very short, reaching 99% of its maximum response in about 4 s. The biosensor was also tested for formaldehyde measurements in rain water samples. Formaldehyde concentrations in samples were calculated using the proposed biosensor with recovery values ranged between 92.2 and 97.7% in comparison with the colorimetric Nash method. CONCLUSION: The poly(GMA‐co‐MTM)/FDH/PPy) electrode showed excellent measurement sensitivity in comparison with other formaldehyde biosensor studies. Strong chemical bonding between the enzyme and the copolymer was created via the epoxy groups of the composite film. The proposed biosensor could be used successfully in rain waters without a pretreatment step. © 2012 Society of Chemical Industry     

A scheduling problem in blocking hybrid flow shop robotic cells with multiple robots

This paper addresses the robotic scheduling problem in blocking hybrid flow shop cells that consider multiple part types, unrelated parallel machines, multiple robots and machine eligibility constraints. Initially, a mixed integer linear programming (MILP) model is proposed to minimize the makespan for this problem. Due to the complexity of the model, a simulated annealing (SA) based solution approach is developed for its solution. To increase the efficiency of the SA algorithm, a new neighborhood structure based on block properties is applied. The performance of the proposed SA is assessed over a set of randomly generated instances. The computational results demonstrate that the SA algorithm is effective with the employed neighborhood structure. Additionally, this study shows that the appropriate number of robots depends on the sequence of processing operations to be performed at each stage.     

Vinylferrocene copolymers based biosensors for phenol derivatives

BACKGROUND: Newly synthesized composite films of P(glycidyl methacrylate₈₅‐co‐vinylferrocene₁₅)/Poly(glutaraldehyde)/ Polypyrrole [P(GMA₈₅‐co‐VFc₁₅)/PGA/PPy] and Poly(3‐methylthienyl methacrylate₈₅‐co‐vinylferrocene₁₅)/Polypyrrole [P (MTM₈₅‐co‐VFc₁₅)/PPy] were used as matrices for tyrosinase based working electrodes. Direct covalent attachment of enzyme was carried out via the pendant epoxy groups of P(GMA₈₅‐co‐VFc₁₅) film, and the entrapment of enzyme was achieved for electrode containing P(MTM₈₅‐co‐VFc₁₅) film via electropolymerization of pyrrole in the presence of enzyme. The aim of the study is amperometric determination of various phenolics and investigation of the effect of interfacial interactions between enzyme and matrices on biosensor response. RESULTS: The lowest detection limit and the highest sensitivity for a P(GMA₈₅‐co‐VFc₁₅) based working electrode was found to be 0.113 µmol L^?1 for 4‐methoxyphenol, 40 nA (µmol L^?1)^?1 for pyrocatechol, respectively. Results showed that sensitivities were at least 8500–55000 times higher than the results in previous P(GMA‐co‐VFc) related studies. CONCLUSION: Facilitated electron transfer was achieved by means of mediator incorporated in conductive composites of VFc based redox copolymers. The effect was greater when enzyme was covalently bonded via epoxy groups due to the proximity of enzyme, mediator and electrode surface. Results showed that a multifunctional surface was provided on electrodes since the suggested copolymers could mediate an electrochemical reaction, and the multifunctional surface was capable of coating with conductive PPy. Copyright © 2011 Society of Chemical Industry     

Detection of a homozygous four base pair deletion in the protein X gene in a case of pyruvate dehydrogenase complex deficiency

While the presence of a lipoyl-containing protein (protein X) separate from lipoyl transacetylase in the pyruvate dehydrogenase complex (PDC) has been known for some time, until recently only the cDNA for the yeast enzyme has been cloned. We have cloned, sequenced and characterized the cDNA encoding the human protein X and localized the protein X gene to chromosome 11p13. We also report here a new case of protein X deficiency identified immunologically, with decreased activity of PDC and without mutations in the E1alpha subunit or E1beta subunit. We report that the cDNA and gene of this patient for protein X has a homozygous 4 bp deletion, specifically in the putative mitochondrial targeting signal sequence which results in a premature stop codon. This is the first documented case of a molecular defect in pyruvate dehydrogenase protein X.