Electronic structure of periodic curved surfaces -- topological band structure

Electronic band structure for electrons bound on periodic minimal surfaces is differential-geometrically formulated and numerically calculated. We focus on minimal surfaces because they are not only mathematically elegant (with the surface characterized completely in terms of "navels") but represent the topology of real systems such as zeolites and negative-curvature fullerene. The band structure turns out to be primarily determined by the topology of the surface, i.e., how the wavefunction interferes on a multiply-connected surface, so that the bands are little affected by the way in which we confine the electrons on the surface (thin-slab limit or zero thickness from the outset). Another curiosity is that different minimal surfaces connected by the Bonnet transformation (such as Schwarz's P- and D-surfaces) possess one-to-one correspondence in their band energies at Brillouin zone boundaries.Comment: 6 pages, 8 figures, eps files will be sent on request to [email protected]

Alcoholysis of palm oil mid-fraction by lipase from Rhizopus rhizopodiformis

A mycelial lipase from Rhizopus rhizopodiformis was prepared in fragment form. The lipase was examined to catalyze the alcoholysis of palm oil mid-fraction (PMF) in organic solvents. High percentage conversions of PMF to alkyl esters were achieved when methanol or propanol was used as acyl acceptor. Of the two most prevalent fatty acids in PMF, palmitic acid seemed to be preferred over oleic acid in the formation of methyl and propyl esters. The optimal ratio of oil to methanol in the alcoholysis reaction is 1 to 2 moles. The lipase exhibited high alcoholysis activities in nonpolar solvents (log P>2), such as hexane, benzene, toluene, and heptane. The enzyme showed exceptionally high thermostability

Cardiovascular magnetic resonance tagging imaging correlates with myocardial dysfunction and T2 mapping in idiopathic dilated cardiomyopathy

To evaluate the details of myocardial dysfunction in dilated cardiomyopathy (DCM) patients using tagging images and the correlation of tagging imaging with tissue characteristics. C

Local Ferromagnetism in Microporous Carbon with the Structural Regularity of Zeolite Y

Magnetization M(H,T) measurements have been performed on microporous carbon (MC) with a three-dimensional nano-array structure corresponding to that of a zeolite Y supercage. The obtained results unambiguously demonstrate the occurrence of high-temperature ferromagnetism in MC, probably originating from a topological disorder associated with curved graphene sheets. The results provide evidence that the ferromagnetic behavior of MC is governed by isolated clusters in a broad temperature range, and suggest the occurrence of percolative-type transition with the temperature lowering. A comparative analysis of the results obtained on MC and related materials is given.Comment: To be published in Physical Review B (2003

Easy fabrication of superporous zeolite templated carbon electrodes by electrospraying on rigid and flexible substrates

Electrospraying of colloidal suspensions of superporous zeolite templated carbon (ZTC) nanoparticles in ethanol is herein proposed for the controlled deposition of continuous carbon coatings over different substrates, both rigid and flexible. By simple tuning of the concentration, feed rate, voltage and treatment time, different electrode thicknesses can be obtained avoiding the difficult manipulation of ZTC nanopowder formed by around 200 nm size particles. The addition of sulfonated tetrafluoropolyethylene (Nafion) in low amounts into the ZTC suspension improves the adhesion, increases the allowable surface loading and enhances the electrochemical performance of ZTC electrodes. ZTC/Nafion coatings from 0.1 to 1.5 mg cm−2 have been successfully arranged over graphite sheet and conductive carbon paper substrates. The obtained electrodes have been electrochemically characterized in 1 M H2SO4 electrolyte, demonstrating the unique and well-known pseudocapacitive features of ZTC, while showing capacitances as high as 700 mF cm−2 and outstanding rate performance thanks to the improved arrangement and connectivity of the ZTC nanoparticles. A supercapacitor using electrosprayed ZTC electrodes is constructed, showing specific capacitance higher than 60 F g−1, capacitance retention of 63% when the current density is raised from 2.5 to 80 A g−1, energy density of 6.6 W h kg−1 and maximum deliverable power greater than 240 kW kg−1. These are promising results that make feasible the use of electrospraying for processing nanostructured carbon materials into electrodes of tunable thickness and deposited on substrates of different compositions and morphologies.The authors thank the Spanish Government (MINECO) and FEDER (projects CTQ2012-36408, CTQ2012-31762, MAT2013-42007-P, IJCI-2014-20012 and JCI-2012-12664) for financial support. This work is also supported by the Nano–Macro Materials, Devices and System Research Alliance and by the Network Joint Research Center for Materials and Devices

Preparation and characterization of superhydrophobic surfaces based on hexamethyldisilazane-modified nanoporous alumina

Superhydrophobic nanoporous anodic aluminum oxide (alumina) surfaces were prepared using treatment with vapor-phase hexamethyldisilazane (HMDS). Nanoporous alumina substrates were first made using a two-step anodization process. Subsequently, a repeated modification procedure was employed for efficient incorporation of the terminal methyl groups of HMDS to the alumina surface. Morphology of the surfaces was characterized by scanning electron microscopy, showing hexagonally ordered circular nanopores with approximately 250 nm in diameter and 300 nm of interpore distances. Fourier transform infrared spectroscopy-attenuated total reflectance analysis showed the presence of chemically bound methyl groups on the HMDS-modified nanoporous alumina surfaces. Wetting properties of these surfaces were characterized by measurements of the water contact angle which was found to reach 153.2 ± 2°. The contact angle values on HMDS-modified nanoporous alumina surfaces were found to be significantly larger than the average water contact angle of 82.9 ± 3° on smooth thin film alumina surfaces that underwent the same HMDS modification steps. The difference between the two cases was explained by the Cassie-Baxter theory of rough surface wetting

Capacitive energy storage from -50 to 100 °C using an ionic liquid electrolyte

Relying on redox reactions, most batteries are limited in their ability to operate at very low or very high temperatures. While performance of electrochemical capacitors is less dependent on the temperature, present-day devices still cannot cover the entire range needed for automotive and electronics applications under a variety of environmental conditions. We show that the right combination of the exohedral nanostructured carbon (nanotubes and onions) electrode and a eutectic mixture of ionic liquids can dramatically extend the temperature range of electrical energy storage, thus defying the conventional wisdom that ionic liquids can only be used as electrolytes above room temperature. We demonstrate electrical double layer capacitors able to operate from -50 to 100 °C over a wide voltage window (up to 3.7 V) and at very high charge/discharge rates of up to 20 V/s

Acidolysis of several vegetable oils by mycelium-bound lipase of Aspergillus flavus link

The ability of mycelium-bound lipase of a locally isolated Aspergillus flavus to modify the triglyceride structure of vegetables oils was studied. The catalysis involved the acidolysis of vegetable oils, such as palm olein, coconut oil, cotton-seed oil, rapeseed oil, corn oil and soybean oil, with selected fatty acids (FA). The reactions were followed against time, and the percentages of FA incorporated were determined by gas chromatography. Percentage of FA incorporated after 20-h reaction was in the range of 13 to 18%. Reaction between cottonseed oil with lauric acid gave the highest percentage of incorporation (18%), followed by soybean oil with lauric acid (16%) and coconut oil with oleic acid (16%). The results indicated that the hydrolytic affinity of A. flavus lipase demonstrates an acyl group specificity toward short-chain FA (C8–C10). Changes in triglyceride profiles of each oil were also monitored by reverse-phase high-pressure liquid chromatography. In all products, there were increases in the concentrations of several existing triglycerides and formation of new triglycerides. The melting points of all acidolyzed vegetable oils were determined by differential scanning calorimetry, and significant changes in melting profiles were noted