77 research outputs found
Increasing the performance of the superconducting spin valve using a Heusler alloy
We have studied superconducting properties of the spin-valve thin layer
heterostructures CoO/F1/Cu/F2/Cu/Pb where the ferromagnetic F1 layer was
standardly made of Permalloy whereas for the F2 layer we have taken a specially
prepared film of the Heusler alloy CoCrFeAl with a small degree
of spin polarization of the conduction band. The heterostructures demonstrate a
significant superconducting spin-valve effect, i.e. a complete switching on and
off of the superconducting current flowing through the system by manipulating
the mutual orientations of the magnetization of the F1 and F2 layers. The
magnitude of the effect is doubled in comparison with the previously studied
analogous multilayers with the F2 layer made of the strong ferromagnet Fe.
Theoretical analysis shows that a drastic enhancement of the switching effect
is due to a smaller exchange field in the heterostructure coming from the
Heusler film as compared to Fe. This enables to approach almost ideal
theoretical magnitude of the switching in the Heusler-based multilayer with the
F2 layer thickness of \,nm
Anisotropic Exchange in LiCuVO probed by ESR
We investigated the paramagnetic resonance in single crystals of LiCuVO
with special attention to the angular variation of the absorption spectrum. To
explain the large resonance linewidth of the order of 1 kOe, we analyzed the
anisotropic exchange interaction in the chains of edge-sharing CuO
octahedra, taking into account the ring-exchange geometry of the
nearest-neighbor coupling via two symmetric rectangular Cu-O bonds. The
exchange parameters, which can be estimated from theoretical considerations,
nicely agree with the parameters obtained from the angular dependence of the
linewidth. The anisotropy of this magnetic ring exchange is found to be much
larger than it is usually expected from conventional estimations which neglect
the bonding geometry. Hence, the data yield the evidence that in copper oxides
with edge-sharing structures the role of the orbital degrees of freedom is
strongly enhanced. These findings establish LiCuVO as one-dimensional
compound at high temperatures.
PACS: 76.30.-v, 76.30.Fc, 75.30.EtComment: 18 pages, 6 figure
Strong enhancement of spin fluctuations in the low-temperature-tetragonal phase of antiferromagnetically ordered La_{2-x-y}Eu_ySr_xCuO_4
Measurements of the static magnetization, susceptibility and ESR of Gd spin
probes have been performed to study the properties of antiferromagnetically
ordered La_{2-x-y}Eu_ySr_xCuO_4 (x less or equal 0.02) with the low temperature
tetragonal structure. According to the static magnetic measurements the CuO_2
planes are magnetically decoupled in this structural phase. The ESR study
reveals strong magnetic fluctuations at the ESR frequency which are not present
in the orthorhombic phase. It is argued that this drastic enhancement of the
spin fluctuations is due to a considerable weakening of the interlayer exchange
and a pronounced influence of hole motion on the antiferromagnetic properties
of lightly hole doped La_2CuO_4. No evidence for the stripe phase formation at
small hole doping is obtained in the present study.Comment: 10 pages, LaTeX, 3 EPS figures; to be published in Journal of
Physics: Condensed Matte
Modeling of lactic acid fermentation of leguminous plant juices
Lactic acid fermentation of leguminous plant juices was modeled to provide a comparative efficiency assessment of the previously selected strains of lactic acid bacteria as potential components of starter cultures. Juices of the legumes fodder galega, red clover, and alfalfa were subjected to lactic acid fermentation in 27 variants of the experiment. Local strains (Lactobacillus sp. RS 2, Lactobacillus sp. RS 3, and Lactobacillus sp. RS 4) and the collection strain Lactobacillus plantarum BS 933 appeared the most efficient (with reference to the rate and degree of acidogenesis, ratio of lactic and acetic acids, and dynamics of microflora) in fermenting fodder galega juice; Lactobacillus sp. RS 1, Lactobacillus sp. RS 2, Lactobacillus sp. RS 3, Lactobacillus sp. RS 4, and L. plantarum BS 933 were the most efficient for red clover juice. Correction of alfalfa juice fermentation using the tested lactic acid bacterial strains appeared inefficient, which is explainable by its increased protein content and a low level of acids produced during fermentation. © MAIK "Nauka/Interperiodica", 2006
Fermentation of high-protein plant biomass by introduction of lactic acid bacteria
Lactic acid bacteria displaying increased ability to produce lactic acid, medium proteolytic activity, and tolerance to osmotic stress were isolated under selective conditions from phyllosphere and rhizosphere of registered and raised cultivars of legumes. Lactic fermentation of poorly ensilable leguminous plants (red clover and Caucasian goat's rue) was performed by introduction of rifampin-resistant homofermenting representatives of the genus Lactobacillus (selected according to a set of technologically important characteristics). The results demonstrate that introduction of active local strains of lactobacteria, as well as the collection strain Lactobacillus plantarum BS933, enhances activation of ensiling and increases the quality of fodder, as assessed according to the standard criteria (a decrease in pH of the medium, the ratio of lactic acid to fatty acid homologues, and the composition of silage microflora). © 2005 MAIK "Nauka/Interperiodica"
Backbone and side chain NMR assignments for the ribosome Elongation Factor P (EF-P) from Staphylococcus aureus
© 2018, Springer Nature B.V. Elongation Factor P (EF-P) is a 20.5 kDa protein that provides specialized translation of special stalling amino acid motifs. Proteins with stalling motifs are often involved in various processes, including stress resistance and virulence. Thus it has been shown that the virulent properties of microorganisms can be significantly reduced if the work of EF-P is disrupted. In order to elucidate the structure, dynamics and function of EF-P from Staphylococcus aureus (S. aureus), here we report backbone and side chains 1H, 13C and 15N chemical shift assignments of EF-P. Analysis of the backbone chemical shifts by TALOS+ suggests that EF-P contains 1 α-helix and 13 β-strands (β1-β2-β3-β4-β5-β6-β7-α1-β8-β9-β10-β11-β12-β13). The solution of the structure of this protein by NMR and X-ray diffraction analysis, as well as the structure of the ribosome complex by cryo-electron microscopy, will allow further screening of highly selective inhibitors of the translation of the pathogenic bacterium S. aureus. Here we report the almost complete 1H, 13C, 15N backbone and side chain NMR assignment of a 20.5 kDa EF-P
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