Measuring probe for fast transients monitoring in gas insulatedsubstation

This paper describes the construction of four probes adjusted for fast transient monitoring in 123 kV SF₆ insulated substations. The primary requirement was the ability to monitor without distortion very fast transients containing frequencies up to 200 MHz. The measuring system was tested and calibrated with the help of computer modeling techniques. The verified experimental apparatus was then used for testing and calibrating the measuring probes. During the test, various effects on the measuring system characteristics were analyzed with respect to materials used for the components of the system     

Electrooxidation of CO and CO/H2 mixtures on a Pt-Sn catalyst prepared by an implantation method

A new type of ion implantation technique is used to create a non-equilibrium Pt-Sn(IMP) near-surface alloy with ca. 8.6 at% Sn. The surface composition was determined by low-energy ion-scattering (LEIS). The kinetics of the electrooxidation of CO and 2% CO/H₂ mixtures on Pt-Sn(IMP) is essentially identical to that of Pt₃Sn(110). The fact that any non-equilibrium composition can be easily prepared by this implantation method opens an interesting practical opportunity to create a new Pt-Sn alloy fuel cell catalyst having an otherwise unobtainable surface composition of Sn. This method also appears to have general utility in alloy catalysis as a means of exploring compositions in thermodynamically unfavorable regions of the bulk phase diagram. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chemical correlates of α-tocopherol (Vitamin E) alteredMalacosoma disstria herbivory inFraxinus pennsylvanica var.Subintegerrinia,green ash

The antioxidant -tocopherol (vitamin E), applied in a basal trunk band to the green ash tree,Fraxinus pennsylvanica var.subintergerrinia, elicited an alteration of foliar feeding byMalacosoma disstria larvae (Lepidoptera: Lasiocampidae). The bioassayed effects were dependent on the dosage of elicitor, the time after elicitation, and the position in the tree. Leaves for chemical analysis were collected from trees receiving two dosages and at two intervals after elicitation. Compounds in the ethyl acetate extractables from the ash tree leaves were separated by TLC and HPLC. TLC separations showed differences in the nonhydrolyzed extractables attributable to elicitor dosage and time after elicitation. TLC-resolved differences were also evident among acid-hydrolyzed samples. HPLC-resolved profiles revealed eight peaks in the nonhydrolyzed extractables that were quantitatively negatively correlated with larval feeding preference between elicited versus control foliage on at least one of the two sampling dates. Results from this study and other investigations reported in the literature indicate that the antioxidant-tocopherol (vitamin E) can function as an environmental-stress elicitor of alterable defensive chemistry in green ash and other plants.     

Structural components in needle-cokes as studied by etching with chromic acid

Structures within commercial calcined needle-cokes are characterized by optical microscopy to reveal optical texture and by scanning electron microscopy before and after etching with chromic acid solution at 400 to 423 K. The needle-cokes exhibit an optical texture of medium and coarse-grained mosaics, acicular flow domains and flow domains. The etching studies indicate that the acicular flow domains are made up of rolled and convoluted lamellae which etch to form laths (needle-like) 3 m across. The mosaics appear when the rolled structures are viewed microscopically sectioned perpendicular to the lamellae. The acicular flow domains appear in longitudinal section. The etching of the flow domains shows that they have a sedimentary structure, 1 to 2 m layer thickness, suggesting that mesophase coalesces within a layer but not between layers. A model is proposed to explain the origin and separation of structures in needle-cokes as created in the delayed coker.     

An exact formula for "Tooth-to-Tooth" permeance

We present a new, completely original exact method to determine the permeance between two opposing iron teeth. This configuration is important because it is often encountered in electrical machines and apparatus. The method is based on conformal mapping. The given "tooth-to-tooth" configuration is mapped into a simpler one, in which the same permeance can be analytically determined. We derive an explicit formula for this permeance, and confirm our results using the finite-element method.     

Determination of tooth cogging force in a hard-disk brushless DC motor

The paper proposes a new method to determine the tooth cogging force in a brushless DC (BLDC) motor which is used in a hard-disk application. This force might be a source of tooth vibrations and motor noise. In the new method, the permanent-magnet (PM) poles are substituted with their equivalent currents. Then, the conformal mapping (CM) method is applied to determine the PM magnetic field. Finally, the cogging force is determined by integrating the magnetic field pressure over the tooth surface. The paper also analyzes the harmonic content of both radial and tangential force components.     

Thermal analysis and microscopic characterization of the piston alloy AlSi13Cu4Ni2Mg

In this research paper, the phases identified by thermal and microscopic analysis of the piston alloy AlSi13Cu4Ni2Mg, which was solidified under different conditions, are presented and compared with different piston alloys. Piston alloys are a group of casting Al–Si alloys, well-known as wear resistant materials, which are widely used as the piston materials for internal combustion engines because of their low thermal expansion coefficient and high wear resistance when alloyed with other elements such as copper, magnesium and nickel. Depending on the combination of alloying elements and other impacting factors, pistons alloys with different mechanical and physical properties are obtained.     

Electrochemical routes for environmentally friendly recycling of rare-earth-based (Sm–Co) permanent magnets

Journal of Applied Electrochemistry - The consumption of critical raw materials, especially those in permanent magnets of Nd–Fe–B and Sm–Co-type, has significantly grown in the...     

Phospholipid Cyclosporine Prodrugs Targeted at Inflammatory Bowel Disease (IBD) Treatment: Design,Synthesis, and in Vitro Validation

Novel phospholipid (PL)-cyclosporine conjugates were prepared and studied as potential prodrugs for inflammatory bowel disease (IBD). Our approach relies on phospholipase A₂ (PLA₂), which is overexpressed in the inflamed intestinal tissues, as the prodrug activator to potentially release cyclosporine at the site of inflammation. PL-cyclosporine prodrug conjugates with methylene linkers of various lengths between the sn-2 position of the PL and cyclosporine were synthesized and evaluated for in vitro activation. Surprisingly, despite previous work indicating that conjugates with six methylene linkers between the lipid and drug would suffer rapid enzymatic hydrolysis, with cyclosporine this was not observed. However, compounds with longer linkers (n=10, 12 methylene units) display complete release of the drug by PLA₂-catalyzed hydrolysis, thus demonstrating the importance and profound impact of structural fine-tuning. This study represents a proof-of-concept for our hypothesis and a first step towards a truly targeted IBD treatment with cyclosporine that could be administered throughout the GI tract.     

New Electrocatalysts for Fuel Cells from Model Surfaces to Commercial Catalysts

In the last decade of the 20th century, we have witnessed a resurgence of interest in fuel cell technology, a technology whose basic principles were demonstrated in the mid-19th century. One of the drivers of this resurgence is the use of hydrogen as a transportation fuel, and the certification by the California Air Resources Board (CARB) of a hydrogen - air fuel cell powered vehicle as a "zero emission vehicle" or ZEV. Another driver is the simplicity of construction and assembly of fuel cell stacks when a polymer membrane is used as the electrolyte versus the more conventional aqueous electrolyte. The polymer electrolyte membrane (PEM) fuel cell offers the promise of substantially lower cost for the cell hardware. Unfortunately, two of the fundamental catalytic limitations that have plagued fuel cells for more than a century still remain: 1.) it is difficult to use any fuel other than highly purified hydrogen; 2.) there has been no cost-effective replacement of Pt as the electrocatalyst. Fortunately, there are signs that help is on the way, particularly with respect to the development of new electrocatalysts for electrooxidation of impure hydrogen, e.g. CO-contaminated, or even syngas. In this article, we describe some of these developments, which have come from over two decades of basic research on electrocatalysis.