175 research outputs found
Hydrogen-controlled interlayer exchange coupling in Fe/LaHx multilayers
No full textMagneto-optic Kerr magnetometry and neutron reflectometry reveal that Fe layers exhibit magnetic exchange coupling through LaHx spacer layers. Ferromagnetic and antiferromagnetic coupling is observed on multilayers of these materials depending on the thickness of the hydride layers, but without oscillatory behavior. Starting from metallic La dihydride spacer layers the effect of dissolving increasingly more hydrogen was examined. Sign and value of the coupling depend crucially on the hydrogen content x. The coupling can be inverted from antiferromagnetic to ferromagnetic and vice versa. These alterations are due to modifications of the electronic structure of the hydride. When the hydrogen absorption saturates the hydride layers become insulating and the exchange coupling is likely to disappear. In this final state the multilayers are always characterized by a very soft ferromagnetic rectangular hysteresis curve. Upon removal of the hydrogen to the initial concentration the original magnetic structure is restored. (C) 2001 Elsevier Science B.V. All rights reserved
The fragile magnetic structures of Fe/CeH2−δ multilayers
No full textFe/CeH2-delta multilayers exhibit at room temperature evidence of interlayer exchange coupling. Subsequent Fe layers are either parallel or antiparallel to each other, depending on the Fe and CeH2-delta layer thickness. However, when both layers have thickness larger than similar to 15 Angstrom, the antiferromagnetic structure becomes fragmented into domains laterally limited to a few microns, and the magnetic structures become very fragile. Small magnetic fields of a few Oersteds acting on the samples during growth induce helimagnetic configurations which coexist with antiferromagnetic coupling. The magnetic structures can be permanently destroyed by applying magnetic fields larger than 150 Oe. (C) 2000 Elsevier Science B.V. All rights reserved
Water response to ganglioside GM1 surface remodelling
No full textBackground Gangliosides are biological glycolipids participating in rafts, structural and functional domains of cell membranes. Their headgroups are able to assume different conformations when packed on the surface of an aggregate, more lying or standing. Switching between different conformations is possible, and is a collective event. Switching can be induced, in model systems, by concentration or temperature increase, then possibly involving ganglioside–water interaction. In the present paper, the effect of GM1 ganglioside headgroup conformation on the water structuring and interactions is addressed. Methods Depolarized Rayleigh Scattering, Raman Scattering, Quasielastic Neutron Scattering and NMR measurements were performed on GM1 ganglioside solutions, focusing on solvent properties. Results All used techniques agree in evidencing differences in the structure and dynamics of solvent water on different time-and-length scales in the presence of either GM1 headgroup conformations. Conclusions In general, all results indicate that both the structural properties of solvent water and its interactions with the sugar headgroups of GM1 respond to surface remodelling. The extent of this modification is much higher than expected and, interestingly, ganglioside headgroups seem to turn from cosmotropes to chaotropes upon collective rearrangement from the standing- to the lying-conformation. Significance In a biological perspective, water structure modulation could be one of the physico-chemical elements contributing to the raft strategy, both for rafts formation and persistence and for their functional aspects. In particular, the interaction with approaching bodies could be favoured or inhibited or triggered by complex-sugar-sequence conformational switch. This article is part of a Special Issue entitled “Science for Life” Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo
Magnesium imide: synthesis and structure determination of an unconventional alkaline earth imide from decomposition of magnesium amide
No full textMagnesium imide (MgNH) was produced by monitoring the decomposition process of magnesium amide with in situ neutron diffraction. Significant changes in the structure of magnesium amide are detected during heat treatment and eventually result in the formation of crystalline MgNH. A model for the crystal structure of magnesium imide (MgNH) is presented for the first time. Remarkably, magnesium imide offers unique structural features similar to the cyclosilicate class and can be described as a porous solid formed by a sequence of linked chains of face sharing Mg6N6 hexagonal prism clusters
Structure and Thermodynamic Properties of the NaMgH(3) Perovskite: A Comprehensive Study RID A-2096-2009
No full textOne of the bottlenecks in the implementation of a hydrogen economy is the development of storage materials that can uptake high content of H2 and release it within a suitable temperature and pressure range. Among the proposed hydride systems, the perovskite NaMgH3 is receiving increasing attention, not only as the Mg ternary based hydride with the highest hydrogen gravimetric (6 wt %) and volumetric density (88 g L-1) but also as a stable hydride likely to be formed in the transformation reactions of mixed hydrides. However, there is a large scatter in the literature for both the structure of the NaMgH3 compound and the thermodynamics of the hydrogenation/dehydrogenation processes. In this paper a critical review of the literature data, supported by a new set of experimental (in situ synchrotron X-ray diffraction, infrared spectroscopy, high-pressure differential scanning calorimetry, pressure composition isotherms) and theoretical data is presented. The influence of ball milling on the microstructure is studied in the NaMgH 3 in comparison to NaH and MgH2. The infrared spectrum of NaMgH3 compound, assigned by calculated and experimental results, is characterized by vibrational regions around 1100 and 600 cm-1. In situ synchrotron X-ray diffraction measurements show the desorption reaction of NaMgH3 into NaH and Mg at about 673 K under 0.2 MPa H2, and the successive reabsorption of NaH and Mg back to NaMgH3 at 623 K under 0.5 MPa H2. From high-pressure differential calorimetry, it was measured a formation enthalpy of 141 kJ/mol f.u for NaMgH3 compound. It was confirmed the possible reaction of NaH with Mg with observation of NaMgH3 formation in 1.0 MPa H2. Finally, this work provides a thermodynamic description of the NaMgH3 phase by a critical assessment of the available information using the CALPHAD approach and the equilibrium pressure-temperature phase diagram is presented
Lohstroh, Joseph (Birth, 1889-12-17)
No full textAddress: 136 W. Front St.6332/Pg 154/1889/M W/Ger./Am./Dr. T.M. Denman,Original record filed in drawer labeled 'LOC-LONGO'
Lohstroh, Robert (Birth, 1900-08-28)
No full textAddress: S. W. Cor Highlans & Donahue3387/Pg 16/1900/M W/Ky./Ohio/Dr. F. P. DorschugOriginal record filed in drawer labeled 'LOC-LONGO'
Lohstroh, Julian (Death, 1908-07-29)
No full textAddress: 2915 Highland Ave.Age at death: 9 days516/Pg. 90/1908/M W S/B. P.City/Dr. Charles Heissel/John Lietemeyer/Spring Grove Cem.Original record filed in drawer labeled 'LOC-LONGO'
Lohstroh, Maria (Death, 1899-04-07)
No full textAddress: S.W. Cor. Donahue & HighlandAge at death: 2 yrs 5 months134/Pg 42/1899/F W S/Cinti, Ohio/Dr. F. P. Dorschug/John E. G. Leitemeyer/Walnut Hills ProtestantOriginal record filed in drawer labeled 'LOC-LONGO'
Cyber-Physical Systems Education: Explorations and Dreams
No full textThe field of cyber-physical systems (CPS), as a well-defined intellectual discipline, is entering its second decade. The past decade has seen several explorations in CPS education, accompanied by related research projects and technologies. This article reviews some of these explorations that the author has been involved with, and tries to extrapolate these to “dreams” for what the future may bring
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