The Effect of a Porous Layer on I-V Characterization of a Polysilicon p-n Junction

In this study, we investigate the effect of an etching process on the rectification property of a p-n junction. To achieve this goal, electrochemical etching (ECE) was employed, using a HF based solution. The morphological properties of the porous samples were characterized by Field Emission Scanning Electron Microscopy (FESEM). The images showed distributed pores in the range of several nanometers. Also, the distribution showed improvement in the size of meso- to macropores. The Current-Voltage measurement of porous and pristine poly silicon p-n junctions was done in dark and illumination conditions. I-V properties in illumination revealed intensive rectification in the proposed junction. Under dark condition, the ideality factor of the porous poly silicon p-n junction was approximately 3.9, which compared to 4.2 for the pristine sample demonstrates 7% improvement. Also, the light sensitivity was increased in the porous one. Furthermore, the light response (Δφ _BP) of the porous sample gave the value of 0.02. In conclusion, the rectification mode could be enhanced through relevant porosity.     

Preparation and characterization of poly(methyl methacrylate) grafted sago starch using potassium persulfate as redox initiator

In this article, the graft copolymerization of methyl methacrylate (MMA) onto sago starch (AGU) was carried out in aqueous medium using potassium persulfate (PPS) under nitrogen gas atmosphere. The maximum percentage of grafting achieved was 90% under optimized conditions of reaction temperature, monomer, PPS, AGU, and reaction period corresponding to 50°C, 47 mmol, 1.82 mmol, 6.17 × 10^?3 mol L^?1, and 1.5 h, respectively. The grafting of MMA onto sago starch was confirmed by the differences in infrared spectroscopy. The viscosity measurement and the average molecular weight determination were estimated using Huggin's and Mark Houwink's equations, respectively. This material may have application as a biodegradable plastic. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1891–1897, 2004     

Efficient Chemoenzymatic Synthesis of N-Glycans with a β1,4-Galactosylated Bisecting GlcNAc Motif

In human serum immunoglobulin G (IgG), a rare modification of biantennary complex N-glycans lead to a β1,4-galactosylated bisecting GlcNAc branch. We found that the bisecting GlcNAc on a biantennary core-fucosylated N-glycan was enzymatically galactosylated under stringent reaction conditions. Further optimizations led to an efficient enzymatic approach to this particular modification for biantennary substrates. Notably, tri- and tetra-antennary complex N-glycans were not converted by bovine galactosyltransferase. An N-glycan with a galactosylated bisecting GlcNAc was linked to a lanthanide binding tag. The pseudo-contact shifts (PCS) obtained from the corresponding Dy-complex were used to calculate the conformational preferences of the rare N-glycan. Besides two extended conformations only a single folded conformation was found.     

Stochastic game theoretical model for packet forwarding in relay networks

In this article, a new game theoretical method is proposed to model packet forwarding in relay networks. A simple case of relay network that consists of a source, a relay and a destination node communicating on a common channel is considered. A stationary Markovian game model is utilized to optimize the system performance in terms of throughput, delay and power consumption cost. Both cooperative and non-cooperative solutions are provided for this model. Best strategy set taken by players as well as system performance is studied for different system parameters. Also, the proposed method is extended to model a more general case of Ad-hoc networks considering different packet error rates in case of collision occurrence that improves the system performance further. Simulation results show that performance of the non-cooperative solution, in which players do not require to know each other’s selected strategy, asymptotically approaches the cooperative system performance. Hence, the proposed model with non-cooperative solution is an appropriate method to apply in practical Ad-hoc networks.     

Preparation and characterization of a new coagulant based on the sago starch biopolymer and its application in water turbidity removal

A new organic coagulant, sago starch (SS)‐graft‐polyacrylamide (PAm), was prepared by the ceric‐ion‐induced redox polymerization of acrylamide (Am) onto SS at room temperature. The effects of the variation of the concentration of Am and the initiator on the percentages of yield and total conversion were investigated. The chemical composition, viscosity, and side‐chain‐average molecular weight of the obtained graft copolymers were determined. The newly obtained coagulant was tested for the treatment of the turbidity of water. The SS‐g‐PAm coagulants were found to achieve water turbidity removal up to 96.6%. The results of this study suggest that SS‐g‐PAm copolymer is a potential coagulant for reducing turbidity during water treatment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008