1,312 research outputs found
Uncultured Gammaproteobacteria and Desulfobacteraceae Account for Major Acetate Assimilation in a Coastal Marine Sediment
Acetate is a key intermediate in anaerobic mineralization of organic matter in marine sediments. Its turnover is central to carbon cycling, however, the relative contribution of different microbial populations to acetate assimilation in marine sediments is unknown. To quantify acetate assimilation by in situ abundant bacterial populations, we incubated coastal marine sediments with C-14-labeled acetate and flow-sorted cells that had been labeled and identified by fluorescence in situ hybridization. Subsequently, scintillography determined the amount of C-14-acetate assimilated by distinct populations. This approach fostered a high-throughput quantification of acetate assimilation by phylogenetically identified populations. Acetate uptake was highest in the oxic-suboxic surface layer for all sorted bacterial populations, including deltaproteobacterial sulfate-reducing bacteria (SRB), which accounted for up to 32% of total bacterial acetate assimilation. We show that the family Desulfobulbaceae also assimilates acetate in marine sediments, while the more abundant Desulfobacteraceae dominated acetate assimilation despite lower uptake rates. Unexpectedly, members of Gammaproteobacteria accounted for the highest relative acetate assimilation in all sediment layers with up to 31-62% of total bacterial acetate uptake. We also show that acetate is used to build up storage compounds such as polyalkanoates. Together, our findings demonstrate that not only the usual suspects SRB but a diverse bacterial community may substantially contribute to acetate assimilation in marine sediments. This study highlights the importance of quantitative approaches to reveal the roles of distinct microbial populations in acetate turnover
Fabrication of epitaxial CoSiâ‚‚ nanowires
We have developed a method for fabricatingepitaxialCoSiâ‚‚nanowires using only conventional optical lithography and standard silicon processing steps. This method was successfully applied to ultrathin epitaxialCoSiâ‚‚ layers grown on Si(100) and silicon-on-insulator substrates. A nitride mask induces a stress field near its edges into the CoSiâ‚‚/Siheterostructure and leads to the separation of the CoSiâ‚‚ layer in this region during a rapid thermal oxidation step. A subsequent etching step and a second oxidation generate highly homogenous silicide wires with dimensions down to 50 nm
Teaching Faith with the Lantern: Audio-Visual Lantern Performances by the Clergy in France and Belgium Around 1900
This contribution first discusses the age-old practice of the multi-sensory address of churchgoers in the Catholic tradition. Visual representations played a particularly important but not uncontroversial role. The introduction of the projected image by the Catholic clergy in Belgium and France was advocated with explicit reference to this tradition. The optical lantern was used for religious lectures as well as for illustrated sermons. Several examples of audio-visual performances combining the projected image with music and chants are discussed as a particular practice that also allowed the active participation of the audience or congregation
Experimental and theoretical analysis of the upper critical field in FSF trilayers
The upper critical magnetic field H_{c2} in thin-film FSF trilayer spin-valve
cores is studied experimentally and theoretically in geometries perpendicular
and parallel to the heterostructure surface. The series of samples with
variable thicknesses of the bottom and of the top Cu_{41}Ni_{59} F-layers are
prepared in a single run, utilizing a wedge deposition technique. The critical
field H_{c2} is measured in the temperature range K and for magnetic
fields up to 9 Tesla. A transition from oscillatory to reentrant behavior of
the superconducting transition temperature versus F-layers thickness, induced
by an external magnetic field, has been observed for the first time. In order
to properly interpret the experimental data, we develop a quasiclassical
theory, enabling one to evaluate the temperature dependence of the critical
field and the superconducting transition temperature for an arbitrary set of
the system parameters. A fairly good agreement between our experimental data
and theoretical predictions is demonstrated for all samples, using a single set
of fit parameters. This confirms adequacy of the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) physics in determining the unusual
superconducting properties of the studied Cu_{41}Ni_{59}/Nb/Cu_{41}Ni_{59}
spin-valve core trilayers.Comment: 16 pages, 7 figures; published versio
Nanopatterning of epitaxial CoSiâ‚‚ using oxidation in a local stress field and fabrication of nanometer metal-oxide-semiconductor field-effect transistors
A patterning method for the generation of epitaxialCoSi₂nanostructures was developed based on anisotropic diffusion of Co∕Si atoms in a stress field during rapid thermal oxidation (RTO). The stress field is generated along the edge of a mask consisting of a thin SiO₂ layer and a Si₃N₄ layer. During RTO of the masked silicide structure, a well-defined separation of the silicide layer forms along the edge of the mask. The technique was used to make 50-nm channel-length metal-oxide-semiconductor field-effect transistors(MOSFETs). These highly uniform gaps define the channel region of the fabricated device. Two types of MOSFETs have been fabricated: symmetric transistor structures, using the separated silicide layers as Schottky source and drain, and asymmetric transistors, with n+ source and Schottky drain. The asymmetric transistors were fabricated by an ion implantation into the unprotected CoSi₂ layer and a subsequent out diffusion to form the n+ source. The detailed fabrication process as well as the I–V characteristics of both the symmetric and asymmetric transistor structures will be presented
Memory Effect and Triplet Pairing Generation in the Superconducting Exchange Biased Co/CoOx/Cu41Ni59/Nb/Cu41Ni59 Layered Heterostructure
We fabricated a nanolayered hybrid superconductor-ferromagnet spin-valve
structure, the resistive state of which depends on the preceding magnetic field
polarity. The effect is based on a strong exchange bias (about -2 kOe) on a
diluted ferromagnetic copper-nickel alloy and generation of a long range odd in
frequency triplet pairing component. The difference of high and low resistance
states at zero magnetic field is 90% of the normal state resistance for a
transport current of 250 {\mu}A and still around 42% for 10 {\mu}A. Both logic
states of the structure do not require biasing fields or currents in the idle
mode.Comment: 9 pages, 4 figures, Accepted to Applied Physics Letter
Reentrant Superconductivity and Superconducting Critical Temperature Oscillations in F/S/F trilayers of Cu41Ni59/Nb/Cu41Ni59 Grown on Cobalt Oxide
Ferromagnet/Superconductor/Ferromagnet (F/S/F) trilayers constitute the core
of a superconducting spin valve. The switching effect of the spin valve is
based on interference phenomena occurring due to the proximity effect at the
S/F interfaces. A remarkable effect is only expected if the core structure
exhibits strong critical temperature oscillations, or most favorable, reentrant
superconductivity, when the thickness of the ferromagnetic layer is increased.
The core structure has to be grown on an antiferromagnetic oxide layer (or such
layer to be placed on top) to pin by exchange bias the
magnetization-orientation of one of the ferromagnetic layers. In the present
paper we demonstrate that this is possible, keeping the superconducting
behavior of the core structure undisturbed.Comment: 22 pages, 12 figures, 1 tabl
- …