Seasonal changes in lipid and fatty acid composition of the freshwater mollusk,Diplodom patagonicus

Diplodom patagonicus is a freshwater bivalve mollusk living in lakes of the patagonian Andes mountains in Argentina. Lipid composition and seasonal changes in the mollusk were studied in the natural habitat. In addition to common nonpolar and polar lipids, small amounts of alk-1-enyldiacylglycerol ethers and significant quantities of ceramide aminoethyl phosphonate were present. Total lipid content changed during the year, primarily because of decreased triacylglycerols in winter. The fatty acid composition of the lipids, remarkably different from that of marine bivalves, and even from other fresh water animals, was especially rich in the ω6 fatty acids, linoleic and arachidonic (ca. 25%), and poor in the ω3 acids, 20∶5 and 22∶6. The ω6/ω3 acid ratio was ca. 2, which is very high compared to marine bivalves. The fatty acid composition and the ω6/ω3 acid ratio were constant during the whole year, suggesting a very stable diet, rich in vegetal detritus and poor in diatoms. The influence of environmental temperature fluctuation with season on fatty acid composition also was negible. Modest proportions of 22∶2 nonmethylene-interrupted (NMI) acids were detected and confirmed by mass spectrometry. It was shown that 20∶2 NMI acids were absent.     

Echtzeit-Suchprozessor-Architekturen

This paper deals with design and implementation of a random access dual ported memory with a sustained bandwidth of 100 MByte/s. Data blocks can be stored and retained in arbitrary order. This goal is achieved by a specialized scarch-processor based on Field Programmable Gate Arrays (FPGAs). The main advantage is the hardware-implemented search in alphabetical search trees which garantees the real-time behaviour. The concept is extendable to other applications affording data-buffering with extremly high bandwidth.     

Investigation of the atomic-scale friction and energy dissipation in diamond using molecular dynamics

We have used molecular dynamics simulations to examine friction when two diamond (111) surfaces are placed in sliding contact. The essence of atomic-scale friction was shown to be the mechanical excitation (in the form of vibrational and rotational energy) of the interface lattice layers upon sliding. This excitation was propagated to the rest of the lattice, and eventually dissipated as heat. In general, this excitation increases with increasing applied load; therefore, the atomic-scale friction also increases with load. Flexible hydrocarbon species, chemically bound to the diamond surface, can lead to a significant reduction of mechanical excitation upon sliding at high loads, leading to lower friction. In addition to clarifying the effects of chemically-bound hydrocarbon groups on atomic-scale friction at diamond interfaces, these simulations might also yield insight into more complicated systems, e.g. Langmuir-Blodgett films, and aid in the design of low-friction coatings.     

DIAGENETIC HISTORY OF LATE PALAEOCENE POTENTIAL CARBONATE RESERVOIR ROCKS, KOPET-DAGH BASIN, NE IRAN

The Upper Palaeocene (Thanetian) Chehel-Kaman Formation in the Kopet-Dagh Basin of NE Iran is principally composed of carbonates with minor siliciclastics and evaporites. Six stratigraphic sections were measured and more than 1,000 samples were collected for petrographic analysis, together with analyses of carbon and oxygen isotopes and trace element content. Four major carbonate lithofacies (and 13 subfacies) have been identified in previous studies and are interpretd in terms of deposition in a shallow-marine environment.
The petrographic analyses indicate that the Chehel-Kaman Formation carbonates have undergone a complex diagenetic history which includes compaction, cementation, micritization, dissolution, silicification, dolomitization, neomorphism and fracturing. δ¹⁸O and δ¹³C values in Chehel-Kaman Formation limestones range between +0.8 and -15.1%₀ PDB, and -2.82 and +3.5%₀ PDB, respectively. These variations are interpreted to reflect meteoric and burial diagenetic processes. Variations in trace-element concentrations (Fe and Mn increased while Na decreased) also indicated the effects of meteoric flushing. The limestones appear to have been formed at about 28°C.
Chehel-Kaman Formation dolomites were divided into d1 (finely-crystalline) and d2 (coarsely-crystalline) types. Petrographic and geochemical results indicated that the d1 dolomites formed under sabkha conditions from a parental solution at around 26°C, while d2 dolomites formed during burial diagenesis with much hotter pore fluids (around 72°C). The paragenetic sequence indicates that primary porosity decreased during early stages of diagenesis, although secondary porosity was subsequently created improving the reservoir quality of the carbonates.