Magnetic excitations of rare Earth atoms and clusters on metallic surfaces

Magnetic anisotropy and magnetization dynamics of rare earth Gd atoms and dimers on Pt(111) and Cu(111) were investigated with inelastic tunneling spectroscopy. The spin excitation spectra reveal that giant magnetic anisotropies and lifetimes of the excited states of Gd are nearly independent of the supporting surfaces and the cluster size. In combination with theoretical calculations, we argue that the observed features are caused by strongly localized character of 4f electrons in Gd atoms and clusters.     

Demonstration of liquid nitrogen wicking using a multi-layer metallic wire cloth laminate

Cryogenic heat transport devices are the most basic and critical component for the thermal integration between the cryogenic component and its cooling source. In space environments, containment of heat transfer fluid inside a capillary structure is critical due to the absence of gravity. Cryogenic heat pipes using the capillary force for circulation may provide a solution for heat transfer in space applications due to its independence of gravity and transport distance. To achieve a high effective capillary performance, several options of wicking structures have been investigated. An efficient wicking flow of liquid nitrogen is demonstrated with a sintered, multi-layer, porous lamination of metal wire (pore size as low as 5 μm) in an open cryogenic chamber. The test data are presented in this paper. This technology has potential for use in development of improved cryogenic heat transfer devices and containment of cryogenic propellants under micro-gravity environment.     

Visualization of a slow, ATP-induced structural transition in the bacterial molecular chaperone DnaK

Recent reports have shown that the binding of ATP to a 70-kDa molecular chaperone induces a rapid global conformational transition from a "high affinity" state to a "low affinity" state, where these states are defined by tight and weak binding to (poly)peptides, respectively. To complete the activity cycle, a chaperone molecule must ultimately return to the high affinity state. In this report, this return to the high affinity state was studied using a chemical cross-linking assay in conjunction with SDS-polyacrylamide gel electrophoresis. The basis for this assay is that in the absence of nucleotide or in the presence of ADP, conditions that stabilize the high affinity state, cross-linking of the Escherichia coli molecular chaperone DnaK yielded two monomeric forms, with apparent molecular masses of 70 kDa (77%) and 90 kDa (23%), whereas cross-linking yielded only the 70-kDa monomeric form in the presence of ATP. This ATP-dependent difference in cross-linking was used to follow the kinetics of the low affinity to high affinity transition under single turnover conditions. The rate of this transition (kobs = 3.4 (+/-0.6) x 10(-4) s-1 at 25 degrees C) is almost identical to the reported rate of ATP hydrolysis (khy = 2.7 (+/-0.7) x 10(-4) s-1 at 22 degrees C). These results are consistent with a two-step sequential reaction where rate-limiting ATP hydrolysis precedes the conformational change. Models for the formation of two cross-linked DnaK monomers in the absence of ATP are discussed.     

S1 nuclease hybrid analysis of mitochondrial DNA amplified by long-distance PCR: rapid screening for small-scale rearrangements

We report on a method suitable for screening large regions (>3 kb) of mtDNA for structural changes of <500 bp and their localization. Heteroduplexes consisting of a wild-type and a mutant strand are cleaved by S1nuclease when single-stranded loops are present due to deletions or duplications/insertions. This strategy was successfully applied to screen the muscle mtDNA of 20 patients with mitochondrial encephalomyopathies. In three of them, an altered cleavage pattern was observed caused by a homoplasmic 9 bp deletion as shown by subsequent mapping and sequencing studies.     

Parallelizing OODBMS traversals: a performance evaluation

In this paper we describe the design and implementation of ParSets, a means of exploiting parallelism in the SHORE OODBMS. We used ParSets to parallelize the graph traversal portion of the OO7 OODBMS benchmark, and present speedup and scaleup results from parallel SHORE running these traversals on a cluster of commodity workstations connected by a standard ethernet. For some OO7 traversals, SHORE achieved excellent speedup and scaleup; for other OO7 traversals, only marginal speedup and scaleup occurred. The characteristics of these traversals shed light on when the ParSet approach to parallelism can and cannot be applied to speed up an application. Edited by Henry F. Korth and Amith Sheth. Received November 1994 / Accepted March 20, 1995     

Structure‐Property Relationships of Extruded Starch, 2 Extrusion Products from Native Starch

The supermolecular structure and morphology of extruded flat films from several native starch materials of A‐ and B‐crystal type were investigated by wide‐angle X‐ray scattering and scanning electron microscopy. The degree of crystallinity and crystallite dimensions of both the different starting materials and the extruded films were determined and a scheme of the lattice transformations resulting from extrusion was established. The conditions of structure formation of the extruded starch films were varied in relation to plasticizer composition and extruder zone temperatures. The mechanical properties and biodegradability of the films were also measured. The extruded starches crystallized in the V_H polymorph with crystallinities between 33 and 41% and crystallite sizes of up to 35 nm. An increase in crystallite size was found for all starches (sometimes a doubling) with increasing extruder middle zone temperatures from 120 up to 210°C. For extruded potato and maize starches a steep rise in strength and modulus and a drop in elongation was observed above 190°C. Purified amylopectin from maize showed after extrusion the crystalline A‐type and small amounts of B polymorph with small crystallites (up to 3 nm) and the best mechanical performance with strengths and moduli of about 20 MPa and 1 500 MPa, respectively, for the present extrusion conditions. Native starch films that include 20 to 30% plasticizer biodegrade rapidly in 25 d consuming 90% of the oxygen needed for complete degradation, as analyzed by the Sapromat test.     

Numerical Simulation of Carbon Redistribution during Steel Composite Production

During heat treatment of cladded steel composites, element redistribution may occur between the various plating materials. Depending on alloy composition and the particular time–temperature profile, Carbon (C) diffusion between the plating materials is observed. Herein, C diffusion between different layers of roll-cladded steel composites during typical production routes is numerically simulated with the thermokinetic software package MatCalc. Two material combinations, 340LA–22MnB5 and 340LA–34MnB5, are compared with experimental results of large-scale manufactured steel composite material at different production steps, from hot strip to hardened cold strip material. The simulation agrees qualitatively and quantitatively well with the experimental results. It is demonstrated that even short heat treatment intervals can have significant influence on the C redistribution within the steel composite.