Fe3O4(001) films on Fe(001): Termination and reconstruction of iron-rich surfaces

High-quality and impurity-free magnetite surfaces with (sqrt2xsqrt2)R45o reconstruction have been obtained for the Fe3O4(001) epitaxial films deposited on Fe(001). Based on atomically resolved STM images for both negative and positive sample polarity and Density Functional Theory calculations, a model of the magnetite (001) surface terminated with Fe ions forming dimers on the reconstructed (sqrt2xsqrt2)R45o octahedral iron layer is proposed.Comment: 17 pages 4 figure

Chemistry-dependent magnetic properties at the FeNi oxide–metal interface

Fe and Ni compounds and their oxides offer stoichiometry dependent magnetic properties, exploitable for the design of magnetic heterojunctions

Growth and electronic and magnetic structure of iron oxide films on Pt(111)

Ultrathin (111)-oriented polar iron oxide films were grown on a Pt(111) single crystal either by the reactive deposition of iron or oxidation of metallic iron monolayers. These films were characterized using low energy electron diffraction, scanning tunneling microscopy and conversion electron Mossbauer spectroscopy. The reactive deposition of Fe led to the island growth of Fe3O4, in which the electronic and magnetic properties of the bulk material were modulated by superparamagnetic size effects for thicknesses below 2 nm, revealing specific surface and interface features. In contrast, the oxide films with FeO stoichiometry, which could be stabilized as thick as 4 nm under special preparation conditions, had electronic and magnetic properties that were very different from their bulk counterpart, w\"ustite. Unusual long range magnetic order appeared at room temperature for thicknesses between three and ten monolayers, the appearance of which requires severe structural modification from the rock-salt structure.Comment: 17 pages, 6 figures, 50 reference

The dynamics of the non-heme iron in bacterial reaction centers from Rhodobacter sphaeroides

AbstractWe investigate the dynamical properties of the non-heme iron (NHFe) in His-tagged photosynthetic bacterial reaction centers (RCs) isolated from Rhodobacter (Rb.) sphaeroides. Mössbauer spectroscopy and nuclear inelastic scattering of synchrotron radiation (NIS) were applied to monitor the arrangement and flexibility of the NHFe binding site. In His-tagged RCs, NHFe was stabilized only in a high spin ferrous state. Its hyperfine parameters (IS=1.06±0.01mm/s and QS=2.12±0.01mm/s), and Debye temperature (θD0~167K) are comparable to those detected for the high spin state of NHFe in non-His-tagged RCs. For the first time, pure vibrational modes characteristic of NHFe in a high spin ferrous state are revealed. The vibrational density of states (DOS) shows some maxima between 22 and 33meV, 33 and 42meV, and 53 and 60meV and a very sharp one at 44.5meV. In addition, we observe a large contribution of vibrational modes at low energies. This iron atom is directly connected to the protein matrix via all its ligands, and it is therefore extremely sensitive to the collective motions of the RC protein core. A comparison of the DOS spectra of His-tagged and non-His-tagged RCs from Rb. sphaeroides shows that in the latter case the spectrum was overlapped by the vibrations of the heme iron of residual cytochrome c2, and a low spin state of NHFe in addition to its high spin one. This enabled us to pin-point vibrations characteristic for the low spin state of NHFe

Differential Photoelectron Holography: A New Approach for Three-Dimensional Atomic Imaging

We propose differential holography as a method to overcome the long-standing forward-scattering problem in photoelectron holography and related techniques for the three-dimensional imaging of atoms. Atomic images reconstructed from experimental and theoretical Cu 3p holograms from Cu(001) demonstrate that this method suppresses strong forward-scattering effects so as to yield more accurate three-dimensional images of side- and back-scattering atoms.Comment: revtex, 4 pages, 2 figure

Czy obecność zmian w tętnicach wieńcowych predysponuje do migotania przedsionków?

Cel pracy: Rola niedokrwienia jako czynnika sprzyjającego migotaniu przedsionków (AF, atrial fibrillation) nie jest w pełni ustalona. Celem pracy było porównanie częstości występowania AF u pacjentów ze zmianami w naczyniach wieńcowych i bez nich. Szczególną uwagę zwrócono na duże naczynia zaopatrujące przedsionki serca, tzn. prawą tętnicę wieńcową i gałąź okalającą lewej tętnicy wieńcowej. Materiał i metody: Dokonano retrospektywnej analizy badania koronarograficznego, które przeprowadzono u 1314 pacjentów. Wydzielono 191 chorych ze zmianami miażdżycowymi w prawej tętnicy wieńcowej oraz gałęzi okalającej &#8212; grupa I, oraz 278 osób, u których nie stwierdzono zmian miażdżycowych w powyższych naczyniach &#8212; grupa II. W obu grupach określono częstość AF i uwzględniono jedynie tych chorych, u których niemiarowość całkowitą stwierdzono podczas hospitalizacji oraz osoby z napadowym AF w wywiadzie udokumentowanym elektrokardiograficznie. Prześledzono obecność innych czynników ryzyka wystąpienia AF, takich jak wady zastawki dwudzielnej, niewydolność serca, przebyty zawał serca. Analizy statystycznej dokonano przy użyciu testu c2 i testu t-Studenta. Wyniki: Migotanie przedsionków występowało u 11 pacjentów (5,2%) z grupy I oraz u 30 (10,8%) z grupy II (różnica nieistotna statystycznie). Jednocześnie niedomykalność mitralną stwierdzono u 61% chorych z AF oraz u 14,5% z rytmem zatokowym (p < 0,001). U 42,5% pacjentów z AF występowały objawy niewydolności serca. Wnioski: Badanie nie potwierdziło faktu, że niedokrwienie przedsionków predysponuje do migotania przedsionków. Uzyskane dane wskazują na związek AF z wadami zastawki dwudzielnej oraz niską frakcją wyrzutową

New miniPromoter Ple345 (NEFL) drives strong and specific expression in retinal ganglion cells of mouse and primate retina.

Retinal gene therapy is leading the neurological gene therapy field, with 32 ongoing clinical trials of recombinant adeno-associated virus (rAAV)-based therapies. Importantly, over 50% of those trials are using restricted promoters from human genes. Promoters that restrict expression have demonstrated increased efficacy and can limit the therapeutic to the target cells thereby reducing unwanted off-target effects. Retinal ganglion cells are a critical target in ocular gene therapy; they are involved in common diseases such as glaucoma, rare diseases such as Leber's hereditary optic neuropathy, and in revolutionary optogenetic treatments. Here, we used computational biology and mined the human genome for the best genes from which to develop a novel minimal promoter element(s) designed for expression in restricted cell types (MiniPromoter) to improve the safety and efficacy of retinal ganglion cell gene therapy. Gene selection included the use of the first available droplet-based single-cell RNA sequencing (Drop-seq) dataset, and promoter design was bioinformatically driven and informed by a wide range of genomics datasets. We tested seven promoter designs from four genes in rAAV for specificity and quantified expression strength in retinal ganglion cells in mouse, and then the single best in nonhuman primate retina. Thus, we developed a new human-DNA MiniPromoter, Ple345 (NEFL), which in combination with intravitreal delivery in rAAV9 showed specific and robust expression in the retinal ganglion cells of the nonhuman-primate rhesus macaque retina. In mouse, we also developed MiniPromoters expressing in retinal ganglion cells, the hippocampus of the brain, a pan neuronal pattern in the brain, and peripheral nerves. As single-cell transcriptomics such as Drop-seq become available for other cell types, many new opportunities for additional novel restricted MiniPromoters will present

Dynamics in sub-monolayer Fe-films

Abstract The properties of thin films are directly connected with the atomic structure. At elevated temperatures this structure is determined by atomic dynamics. Pronounced effects are expected for thin films of low coverage. We have investigated electronic and dynamical properties of a submonolayer Fe film on a W(1 1 0) substrate with nuclear resonance scattering (NRS) in grazing-incidence geometry. This atomistic technique is best suited for such investigations due to its element (isotopic) and submonolayer sensitivity as demonstrated in the model system of Fe/W(1 1 0). A simple relaxation model was used to explain the temperature dependence of the NRS spectra. The relaxation rates and diffusion coefficients have been calculated

Giant magneto-optical anisotropy in Fe/Au monoatomic multilayer

Abstract A giant magneto-optical anisotropy (MOA) in a magnetic monoatomic Fe/Au multilayer structure is reported. The dependence of the off-diagonal part of the optical conductivity tensor on the angle between the magnetization and crystallographic axes is evidenced by measurements of both the polar and longitudinal Kerr effects. The microscopic origin of the MOA is elucidated on the basis of the first principles&apos; band-structure calculations. A relationship of the MOA with the predicted strong anisotropy of Fe d orbital magnetic moment and the magnetocrystalline anisotropy is discussed.