Search results for " Circular"
showing 10 items of 253 documents
Genetics for Pseudoalteromonas provides tools to manipulate marine bacterial virus PM2
2008
ABSTRACT The genetic manipulation of marine double-stranded DNA (dsDNA) bacteriophage PM2 ( Corticoviridae ) has been limited so far. The isolation of an autonomously replicating DNA element of Pseudoalteromonas haloplanktis TAC125 and construction of a shuttle vector replicating in both Escherichia coli and Pseudoalteromonas enabled us to design a set of conjugative shuttle plasmids encoding tRNA suppressors for amber mutations. Using a host strain carrying a suppressor plasmid allows the introduction and analysis of nonsense mutations in PM2. Here, we describe the isolation and characterization of a suppressor-sensitive PM2 sus2 mutant deficient in the structural protein P10. To infect an…
X-Ray Detected Magnetic Resonance: A Unique Probe of the Precession Dynamics of Orbital Magnetization Components
2011
X-ray Detected Magnetic Resonance (XDMR) is a novel spectroscopy in which X-ray Magnetic Circular Dichroism (XMCD) is used to probe the resonant precession of local magnetization components in a strong microwave pump field. We review the conceptual bases of XDMR and recast them in the general framework of the linear and nonlinear theories of ferromagnetic resonance (FMR). Emphasis is laid on the information content of XDMR spectra which offer a unique opportunity to disentangle the precession dynamics of spin and orbital magnetization components at given absorbing sites. For the sake of illustration, we focus on selected examples in which marked differences were found between FMR and XDMR s…
Giant magnetic anisotropy energy and coercivity in Fe island and atomic wire on W(110)
2012
We have directly investigated the giant magnetic anisotropy energy and coercivity of monolayer (ML) Fe islands and stripes on flat and stepped W(110) surfaces using x-ray magnetic circular dichroism. Both for islands and stripes, the magnetic anisotropy energy is $\ensuremath{\sim}$1.0 meV/atom, independent of the coverage below 0.5 ML. On the contrary, the coercive field of the islands rapidly drops from 4.3 T at 0.25 ML to 1.9 T at 0.50 ML, while that of the stripes moderately degrades from 3.5 T at 0.15 ML ($\ensuremath{\sim}$3 atom rows) to 3.0 T at 0.50 ML. We explain the contrastive behavior for the islands and stripes by different nucleation and remagnetization processes. Considering…
Magnetic circular and linear dichroism in VUV-photoemission from thin iron films on W(110)
1996
Abstract We report on two different photoemission techniques for ferromagnetic surfaces: the phenomena of magnetic circular and linear dichroism in the angular distribution of photoelectrons MCDAD and MLDAD. MCDAD had already been studied in detail for different systems. Now we are able to compare our MCDAD results from thin iron films on W(110) to new data from magnetic linear dichroism MLDAD. Both effects (MCDAD and MLDAD) have been studied in the identical photon energy region (up to hv = 36 eV). The results will be discussed with respect to a bandstructure calculation.
MAGNETIC COUPLING OF ALKALI AND RARE-GAS FILMS ADSORBED ON A FERROMAGNETIC SURFACE
2002
The observation of magnetic circular dichroism in the angular distribution of photoelectrons (MCDAD) from alkali and rare-gas films adsorbed on a thin remanently magnetized Co layer is reported. The observation of an antisymmetric MCDAD near normal emission for Co(0001)–Cs 5p semi core level is shown. The reversed magnetization leads to a mirror-image-like distribution. The second system under investigation, physisorbed Co(0001)–Xe 5p, does not give such an but shows significant differences in the MCDAD signal for both directions of magnetization, in particular in the |mj| substates of the p3/2 level. A magnetic coupling between Xe and Co is evident when we take results of spin-resolved ph…
Colour centres in LiBaF3
1997
Abstract The X-ray-induced optical absorption (OA) and the spectra of magnetic circular dichroism (MCD) followed by optically detected EPR (ODEPR) have been investigated in undoped LiBaF3 crystals. According to ODEPR, the absorption bands in the spectral region 470–770 nm correspond to the F-type centres, whereas the absorption band at 420 nm is assigned to the hole centres. The redistribution of electrons to the thermal more stable F-type centres indicates that all types of colour centres are annealed in the course of the thermal release of electrons from F-type centres, accompanied by a thermostimulated luminescence.
Optical magnetic circular dichroism in threshold photoemission from a magnetite thin film
2011
Threshold photoemission excited by polarization-modulated ultraviolet femtosecond laser light is exploited for phase-sensitive detection of magnetic circular dichroism (MCD) for a magnetite thin film. Magnetite (Fe(3)O(4)) shows a magnetic circular dichroism of ∼(4.5 ± 0.3) × 10(-3) for perpendicularly incident circularly polarized light and a magnetization vector switched parallel and antiparallel to the helicity vector by an external magnetic field. The asymmetry in threshold photoemission is discussed in comparison to the magneto-optical Kerr effect. The optical MCD contrast in threshold photoemission will provide a basis for future laboratory photoemission studies on magnetic surfaces.
Interface magnetization of ultrathin epitaxial Co2FeSi(110)/Al2O3films
2007
Element-specific magnetic properties of ultrathin epitaxial Co2FeSi(110) films were measured using x-ray magnetic circular dichroism (XMCD). The epitaxial Heusler films were grown by RF magnetron sputtering on substrates. The magnetization of thicker films as determined by XMCD is smaller than expected for a half-metallic material. In addition, the magnetization decreases considerably for films thinner than 10 nm. The thickness dependence of the magnetic moment can be described by introducing a certain number of dead layers representing a deficiency of magnetization at the interfaces. Quantitative evaluation results in a dead layer thickness of 0.8 nm at room temperature, consisting of a te…
Martensite transition and microscopic magnetism of epitaxial Ni2MnGa films
2007
AbstractA magnetically induced shape memory effect in Ni2MnGa results in huge magnetostrictive effects of several percent. Using x-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) we investigated element specific magnetic moments and electronic structure of single crystalline, (110) oriented Ni2MnGa films on a-plane Al2O3 substrates in the austenite and martensite state. The structural phase transition of the samples is evident from temperature dependent x-ray diffraction and magnetization measurements. The Ni XAS differ significantly for temperatures above and below the martensite transition in agreement with published ab-initio calculations. Using XAS in transmissi…
Hepatitis B virus maintains its pro-oncogenic properties in the case of occult HBV infection.
2003
Background & Aims: Occult hepatitis B virus (HBV) infection is characterized by persistence of HBV DNA into the tissue of hepatitis B surface antigen-negative individuals. The clinical relevance of this peculiar infection is still under debate. In particular, the impact of occult HBV infection in cases of hepatocellular carcinoma (HCC) is uncertain. We investigated the prevalence and molecular status of occult HBV in patients with HCC. Methods: We tested tumor tissues from 107 patients with HCC and the corresponding nontumor liver tissue from 72 of these patients for HBV DNA. We also examined liver specimens from 192 patients with chronic hepatitis. All cases were hepatitis B surface antige…