Harmonics and size reduced microstrip branch‐line baluns using shunt open‐stubs

This article presents the design of harmonic suppressed compact microstrip balun, using shunt open‐stubs. Two approaches using Π‐shaped and T‐shaped open‐stub configurations are investigated. Because of the stopband effect of the open‐stubs, the harmonic passband responses are suppressed effectively. A compact‐size balun is realized because both kinds of structures have slow wave characteristics. To validate theoretical predictions, two prototype baluns operating at f₀ = 1 GHz, showing size reduction up to 75% and no spurious passband up to 4f₀ compared with the conventional design are fabricated in microstrip form. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Selective Protection of Carbonyl Compounds over Nano-sized Nickel Catalysts

Abstract An efficient method for the preparation of 1,3-dithiolanes of aliphatic and both activated and deactivated aromatic carbonyl compounds with 1,2-ethanedithiol in the presence of a catalytic amount of inexpensive, easily recyclable, monodispersed, chemoselective Ni-nanoparticles having high TON and TOF is reported. An efficient method for the chemoselective thioacetalization of ketones in the presence of aldehydes using Ni-nanoparticles is also reported in this article. Our reaction is kinetically controlled and the method is relatively expedient, avoids the use of cost-prohibitive reagents, high temperatures and leads to excellent yield. Graphical Abstract Selective Protection of Carbonyl Compounds Over Nano-sized Nickel Catalysts Ajeet Kumar,^a Santosh Kumar,^a Amit Saxena,^a Arnab De,^b Subho Mozumdar^a* ^aDepartment of Chemistry, University of Delhi, Delhi, 110007, India; ^b Department of Chemistry, Indiana University, Bloomington, USA; subhoscom@yahoo.co.in An efficient method for the preparation of 1,3-dithiolanes of aliphatic and both activated and deactivated aromatic carbonyl compounds with 1,2-ethanedithiol in the presence of a catalytic amount of inexpensive, easily recyclable, monodispersed, chemoselective Ni-nanoparticles having high TON and TOF is reported. We report an efficient method for the chemoselective thioacetalization of ketones in the presence of aldehydes using Ni-nanoparticles. Our reaction is kinetically controlled and the method is relatively expedient, avoids the use of cost-prohibitive reagents, high temperatures and leads to excellent yield.      

Factors governing the electrochemical synthesis of α-nickel (ii) hydroxide

The electrodeposition of -nickel hydroxide is promoted by the simultaneous chemical corrosion of the electrode by an acidic nitrate bath. Chemical corrosion results in the formation of a poorly ordered layered phase which is structurally similar to -nickel hydroxide and provides nucleation sites for the deposition of the latter. Therefore under conditions which enhance corrosion rates such as low current density (<1.3 mA cm–2), high temperature (60 C), high nickel nitrate concentration ( 1M) and the resultant low pH (1.7), -nickel hydroxide electrodeposition is observed, while -nickel hydroxide forms under other conditions. Further, -nickel hydroxide deposition is more facile on an iron electrode compared to nickel or platinum.     

Structure–property relationship studies in amine functionalized multiwall carbon nanotubes filled polypropylene composite fiber

Amine functionalized multiwalled carbon nanotubes (a‐MWNT) based polypropylene (PP) composite fibers were prepared in the presence of polypropylene‐g‐maleic anhydride (PP‐g‐MA) by melt‐mixing followed by melt‐spinning with subsequent post‐drawing of the as‐spun fibers of varying draw ratio (DR). In order to enhance the interfacial interaction, a‐MWNT were utilized in combination with PP‐g‐MA during melt‐mixing. Fourier transform infrared spectroscopic analysis revealed the formation of imide bonds between MA functionality of PP‐g‐MA and amine functional group of a‐MWNT. Higher tensile properties of PP/a‐MWNT/PP‐g‐MA composite fibers were registered with varying DR of the as‐spun fiber. Orientation factors of a‐MWNT and PP chains along the fiber axis were correlated with the higher tensile modulus and tensile strength of PP/a‐MWNT/PP‐g‐MA composite fiber of varying DR. Crystallization studies indicated the role of hetero‐nucleating action of a‐MWNT in PP/a‐MWNT/PP‐g‐MA composite fiber. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Nickel oxyhydroxide/manganese dioxide composite as a candidate electrode material for alkaline secondary cells

Nickel hydroxide and manganese dioxide are used in alkaline cells as positive electrode materials. Positive electrodes comprising a nickel oxyhydroxide/manganese dioxide composite, with modification by Bi₂O₃, deliver a combined reversible discharge capacity of 2.25e per metal atom (650 mAh g⁻¹ metal content), which is higher than that realized from electrodes of either component taken singly. The composite discharges with two potential plateaux, the first appearing at 325 mV corresponds to the discharge of the nickel component, whereas the second at −600 mV is due to the manganese component. Composites of NiO(OH)/MnO₂ can be used as a new electrode material with higher discharge capacity than conventional electrodes.     

Experience on mixed carbide fuels with high ‘Pu’ content for Indian fast breeder reactor - An overview

Hyperstoichiometric Plutonium rich (70%) mixed Uranium Plutonium carbide fuel was proposed as the driver fuel for Indian Fast Breeder Test Reactor (FBTR) after some deliberations. The issues of mixed carbide fuel and of plutonium rich (70%) carbide fuel, in particular, are: presence of ‘O’ impurity, clad carburization, lower solidus temperature, lower thermal conductivity and pyrophorocity. The paper highlights the extensive research and development carried out to address the above issues. The modification incorporated in the different process steps of fabrication flow sheet is also presented. The performance of the fuel has been assessed by periodic Post Irradiation Examination (PIE) of the fuel sub-assemblies for extension of life. Till date the fuel has seen a burn up of 155 Gwd/t without any pin failure.     

Immobilization of cholesterol oxidase onto electrochemically polymerized film of biocompatible polyaniline-Triton X-100

Cholesterol oxidase (ChOx) has been successfully immobilized on electrochemically-polymerized polyaniline (PANI) with Triton X-100 (TX-100) thin film through covalent bonding. The change in the surface morphology of PANI-TX-100 thin film due to immobilization of ChOx was investigated using Atomic Forced Microscopy. The absorption band at 660 nm in the UV–vis absorption spectra and the presence of the infrared markers corresponds to the amide group in ChOx/PANI-TX-100 film confirm the immobilization of ChOx in PANI-TX-100 matrix. The broad hump in cyclic voltammogram and an increase in charge transfer resistance in electrochemical impedance measurement of ChOx/PANI-TX-100/ITO revealing covalently immobilization of ChOx on PANI-TX-100 networks.     

Optimal electrical stimulation modality for cortical esophageal evoked potentials: transmural or intraesophageal?

Esophageal electrical stimulation using short and a relatively small number of (200 micros, 0.2 Hz, n = 25) electrical pulses generates a characteristic and well defined cortical evoked potential response (EP). There are two methods of stimulation: either through intraesophageal electrodes or with transmural electrodes. The objective of this paper is to compare EP response, sensations and heart rate variability power spectra elicited by both stimulation modalities in healthy volunteers. Our results suggest that transmural stimulation is more accurately perceived and at lower intensities, produces more reproducible peaks of higher amplitude than during intraesophageal stimulation. During either mode of esophageal stimulation, power within the high-frequency component of the heart rate variability power spectrum is enhanced.     

Electrocatalysis of oxygen evolution at stainless steel anodes by electrosynthesized cobalt hydroxide coatings

Controlled growth of cobalt hydroxide coatings (1–2 m thick) on stainless steel electrodes was achieved by electrogeneration of base by cathodic reduction of aqueous cobalt nitrate solutions. These coatings catalyse the oxygen evolution reaction in alkaline medium (1 M KOH) by as much as 100 mV, making cobalt hydroxide a candidate catalyst for these applications.