Search results for "MELT"
showing 10 items of 435 documents
Halogen...halogen interactions in pressure-frozen ortho- and meta-dichlorobenzene isomers.
2007
Isomers 1,2-dichlorobenzene (o-DCB) and 1,3-dichlorobenzene (m-DCB) were high-pressure frozen in-situ in a Merrill–Bassett diamond–anvil cell and their structures determined at room temperature and at 0.18 (5) GPa for o-DCB, and 0.17 (5) GPa for m-DCB by single-crystal X-ray diffraction. The patterns of halogen...halogen intermolecular interactions in these structures can be considered to be the main cohesive forces responsible for the molecular arrangements in these crystals. The molecular packing of dichlorobenzene isomers, including three polymorphs of 1,4-dichlorobenzene (p-DCB), have been compared and relations between their molecular symmetry, packing arrangements, intermolecular inte…
Density and biomass of smelt (Osmerus eperlanus) in five Finnish lakes
2005
Abstract Hydro-acoustic stock assessment and exploratory sampling with small mesh-sized trawls and seines have sometimes suggested that the importance of smelt (Osmerus eperlanus) in pelagic fish communities might be greater than sampling from commercial fishery and gillnetting indicate. We studied the proportion of smelt in the total fish density (fish ha−1) and biomass (kg ha−1) of pelagic fish with echo sounding and trawling in five southern boreal lakes. Fish density varied between 460 and 2000 fish ha−1 in the study lakes. Smelt and vendace (Coregonus albula) accounted for more than 95% of the exploratory trawl-catches. The total fish biomass in the study areas varied between 3 and 13 …
Characteristics of lower crustal granulite xenoliths from the east Qinling orogenic belt and their tectonic significance
1994
The Tongbai granulites are present mainly as xenoliths in granodioritic gneisses. The xenoliths with a zircon age of 470Ma are older than the host rocks of granodioritic gneisses which yield a zircon age of 435Ma. It is suggested that the granulites were transported from the lower crust to the upper level along with granodioritic magma. Geothermometrical and geobarometrical studies based on the coexisting minerals (Opx-Cpx and Opx-Gar) show that the granulites were crystallized at 818 –840 °C and 9.5−9.8 × 108 Pa corresponding to the lower crust. Tectonically, the Shangdan suture zone constitutes the boundary between the North China and Yangtze plates. The zone is char acterized by the occu…
Porewater pressure control on subglacial soft sediment remobilization and tunnel valley formation: A case study from the Alnif tunnel valley (Morocco)
2014
25 pages; International audience; In the eastern part of the Moroccan Anti-Atlas Mountains, the Alnif area exposes a buried Ordovician glacial tunnel valley (5 km wide, 180 m deep) cut into preglacial marine sediments. The preglacial sedimentary sequence, deposited in a marine environment, is characterized by a typical "layer-cake" configuration of permeable (sand) and impermeable (clays and early-cemented sandstones) layers. At the base of the tunnel valley, a discontinuous and fan-shaped glacial conglomeratic unit 10 to 15 m thick occurs, erosively deposited over preglacial marine sediments. The conglomeratic unit is composed of preglacial intraclasts embedded within a sandy matrix. Both …
Melting behaviour of d-sucrose, d-glucose and d-fructose
2004
The melting behaviour of d-sucrose, d-glucose and d-fructose was studied. The melting peaks were determined with DSC and the start of decomposition was studied with TG at different rates of heating. In addition, melting points were determined with a melting point apparatus. The samples were identified as d-sucrose, alpha-d-glucopyranose and beta-d-fructopyranose by powder diffraction measurements. There were differences in melting between the different samples of the same sugar and the rate of heating had a remarkable effect on the melting behaviour. For example, T(o), DeltaH(f) and T(i) (initial temperature of decomposition) at a 1 degrees Cmin(-1) rate of heating were 184.5 degrees C, 126…
A contribution to the preparation of phenolic polynuclear compounds with sulfonyl bridges
1964
For the preparation of phenolic di- and tricyclic compounds with sulfonyl bridges the Fries rearrangement is suitable, and for the corresponding products with three and four benzene rings the Friedel-Crafts reaction may be used. The exchange of sulfonyl bridges for methylene bridges produces a marked increase in the melting point.
Computer simulation of disordering and premelting of low-index faces of copper.
1992
Molecular dynamics and the effective-medium theory have been applied to investigate the structure and dynamics of (110), (100), and (111) faces of copper in the whole temperature range from 0 K up to the bulk melting point, which has been determined to be 1240\ifmmode\pm\else\textpm\fi{}25 K. The observed order in the surface stability follows the order in the packing density. (110) disorders first via anharmonic effects (up to 700 K), then by vacancy-adatom formation and finally by premelting of the surface at about 1200 K. The (110) solid-melt interface is anisotropic and broadened, having a tendency to form small fluctuating (111) facets in equilibrium, which is suggested to be the atomi…
Molecular Dynamics Study of Disordering and Premelting of the Pb(110) Surface
1994
Molecular dynamics simulations incorporating a many-body (glue) potential have been used to investigate the atomic structure and dynamics of the Pb(110) surface in the range from room temperature up to the bulk melting point. The Pb (110) surface starts to disorder approximately at 360 K via the generation of vacancies and the formation of an adlayer. At about 520 K we observe the onset of a quasiliquid region at the surface, which exhibits liquid-like energetic, structural and surface properties. The disordering is enhanced in the direction parallel to the close-packed rows. While losing long range order, the two outermost quasiliquid layers retain a considerable degree of short range orde…
Enhanced Thermal Stability of Gold and Silver Nanorods by Thin Surface Layers
2007
Using in situ transmission electron microscopy, we find that a carbon shell governs the morphological transitions of gold and silver nanorods upon heating. Encapsulated Ag nanorods show a surprising nonuniform sublimation behavior starting from one side and leaving behind the shell. Uncovered gold nanorods transform their shape to spheres well below the bulk melting temperature through surface diffusion, which is prevented by a thin carbon shell.