Erratum: Fast Domain Wall Motion Governed by Topology and Œrsted Fields in Cylindrical Magnetic Nanowires [Phys. Rev. Lett. 123, 217201 (2019)].

This corrects the article DOI: 10.1103/PhysRevLett.123.217201.

Fast Domain Wall Motion Governed by Topology and Œrsted Fields in Cylindrical Magnetic Nanowires.

While the usual approach to tailor the behavior of condensed matter and nanosized systems is the choice of material or finite-size or interfacial effects, topology alone may be the key. In the context of the motion of magnetic domain walls (DWs), known to suffer from dynamic instabilities with low mobilities, we report unprecedented velocities >600 m/s for DWs driven by spin-transfer torques in cylindrical nanowires made of a standard ferromagnetic material. The reason is the robust stabilization of a DW type with a specific topology by the Œrsted field associated with the current. This opens the route to the realization of predicted new physics, such as the strong coupling of DWs with spin waves above >600 m/s.

Modeling magnetic-field-induced domain wall propagation in modulated-diameter cylindrical nanowires.

Domain wall propagation in modulated-diameter cylindrical nanowires is a key phenomenon to be studied with a view to designing three-dimensional magnetic memory devices. This paper presents a theoretical study of transverse domain wall behavior under the influence of a magnetic field within a cylindrical nanowire with diameter modulations. In particular, domain wall pinning close to the diameter modulation was quantified, both numerically, using finite element micromagnetic simulations, and analytically. Qualitative analytical model for gently sloping modulations resulted in a simple scaling law which may be useful to guide nanowire design when analyzing experiments. It shows that the domain wall depinning field value is proportional to the modulation slope.

Transmission XMCD-PEEM imaging of an engineered vertical FEBID cobalt nanowire with a domain wall.

Using focused electron-beam-induced deposition, we fabricate a vertical, platinum-coated cobalt nanowire with a controlled three-dimensional structure. The latter is engineered to feature bends along the height: these are used as pinning sites for domain walls, which are obtained at remanence after saturation of the nanostructure in a horizontally applied magnetic field. The presence of domain walls is investigated using x-ray magnetic circular dichroism (XMCD) coupled to photoemission electron microscopy (PEEM). The vertical geometry of our sample combined with the low incidence of the x-ray beam produce an extended wire shadow which we use to recover the wire's magnetic configuration. In this transmission configuration, the whole sample volume is probed, thus circumventing the limitation of PEEM to surfaces. This article reports on the first study of magnetic nanostructures standing perpendicular to the substrate with XMCD-PEEM. The use of this technique in shadow mode enabled us to confirm the presence of a domain wall without direct imaging of the nanowire.

[Which is the place of the human being inside the recommendations, multidisciplinary oncological meetings, and treatment plan?]. / Quelle est la place de l'humain au sein des recommandations, des concertations oncologiques multidisciplinaires et du projet thérapeutique?

Nowadays, the cancer patient has access to a highly technical, more and more targeted and increasingly individualized medicine. And the human being in that matter ? Numerous tools have been developed to help physicians and caregivers to reconcile contemporary medicine and the rights of the patient. Among these are multidisciplinary oncology meetings and treatment guidelines published by national and international scientific societies. The patients care must be cross-disciplinary and evidence-based. This shared decision-making process should at the end be in accordance with the wishes of the patient. This approach should allow him/her to maintain autonomy and be the main actor in the decision-making process.

Phase dependence of microwave-assisted switching of a single magnetic nanoparticle.

Microwave-assisted switching of the magnetization is an efficient way to reduce the magnetic field required to reverse the magnetization of nanostructures. Here, the phase sensitivity of microwave-assisted switching of an individual cobalt nanoparticle is studied using a pump-probe technique. The pump microwave pulse prepares an initial state of the magnetization, and the probe pulse tests its stability against switching. Precession states are established, which are stable against switching. Their basin of attraction is measured and is in qualitative agreement with numerical macrospin calculations. The damping parameter is evaluated using the variable delay pump-probe technique.

Spin-torque oscillator using a perpendicular polarizer and a planar free layer.

Spintronics materials have recently been considered for radio-frequency devices such as oscillators by exploiting the transfer of spin angular momentum between a spin-polarized electrical current and the magnetic nanostructure it passes through. While previous spin-transfer oscillators (STOs) were based on in-plane magnetized structures, here we present the realization of an STO that contains a perpendicular spin current polarizer combined with an in-plane magnetized free layer. This device is characterized by high-frequency oscillations of the free-layer magnetization, consistent with out-of-plane steady-state precessions induced at the threshold current by a spin-transfer torque from perpendicularly polarized electrons. The results are summarized in static and dynamic current-field state diagrams and will be of importance for the design of STOs with enhanced output signals.

Spin-torque influence on the high-frequency magnetization fluctuations in magnetic tunnel junctions.

Voltage noise measurements were performed in the 3-7 GHz frequency range on magnetic tunnel junctions biased with a dc current. Magnetic noise associated with ferromagnetic resonance excitations is either amplified or reduced depending on the direction of the bias current. This effect is interpreted as the influence of spin transfer torque on the magnetization fluctuations and described using Gilbert dynamics equation including spin transfer torque and effective field terms.

Comparative evaluation of five different methods for the measurement of plasma factor II levels in carriers of the 20210A prothrombin variant.

The common genetic G to A variation of the prothrombin gene is associated with elevated levels of prothrombin [factor II (FII)] and is recognized as a risk factor for thrombosis. To determine whether one type of assay for plasma FII measurement was more efficient than other assays in displaying high FII levels in 20210A carriers, we compared five methods of measuring FII levels [i.e. an enzyme-linked immunosorbent assay (ELISA), a standard clotting assay, and three chromogenic methods using three different activators: Ecarin, Oxyuranus, and Textarin] in 30 G20210A patients and 30 G20210G controls. Plasma concentrations of factor X and factor VII + factor X were also determined by a clotting procedure. Functional assays were found to be equally efficient in demonstrating significantly higher FII levels in 20210A carriers than in non-carriers (P < 0.0001). With ELISA, the difference observed was less significant (P < 0.005). The specificity of every assay increased with FII cut-off levels; when a cut-off of 115% was applied, sensitivities of functional assays were between 73 and 93%, while sensitivities of ELISA declined dramatically to 33%. FII/factor X and FII/factor VII + factor X ratios were significantly higher in 20210A carriers (P < 0.0001). In conclusion, functional assays are preferentially required for measurements of FII levels in carriers of the 20210A variant.

Cytochrome c oxidase deficiency due to mutations in SCO2, encoding a mitochondrial copper-binding protein, is rescued by copper in human myoblasts.

Mutations in SCO2, a cytochrome c oxidase (COX) assembly gene, have been reported in nine infants with early onset fatal cardioencephalomyopathy and a severe COX deficiency in striated muscle. Studies on a yeast homolog have suggested that human Sco2 acts as a copper chaperone, transporting copper to the Cu(A) site on the Cox II subunit, but the mechanism of action remains unclear. To investigate the molecular basis of pathogenesis of Sco2 defects in humans we performed genetic and biochemical studies on tissues, myoblasts and fibroblasts from affected patients, as well as on a recombinant human C-terminal Sco2 segment (22 kDa), bearing the putative CxxxC metal-binding motif. Recombinant Sco2 was shown to bind copper with a 1:1 stoichiometry and to form homomeric complexes in vitro, independent of the metal-binding motif. Immunohistochemistry using antibodies directed against different COX subunits showed a marked tissue-specific decrease in the Cox II/III subunits that form part of the catalytic core, consistent with the differential tissue involvement, but a more uniform distribution of Cox Vab, a nuclear-encoded subunit. Sco2 was severely reduced in patient fibroblasts and myoblasts by immunoblot analysis. Patient fibroblasts showed increased (64)Cu uptake but normal retention values and, consistent with this, the copper concentration was four times higher in Sco2-deficient myoblasts than in controls. COX activity in patient myoblasts was completely rescued by transduction with a retroviral vector expressing the human SCO2 coding sequence, and more interestingly by addition of copper-histidine (300 microM) to the culture medium. Whether the latter is accomplished by the very low residual levels of Sco2 in the patient cells, direct addition of copper to the Cu(A) site, or by another copper-binding protein remains unknown. Whatever the mechanism, this result suggests a possible therapy for the early treatment of this fatal infantile disease.

Characterization of human muscle type cofilin (CFL2) in normal and regenerating muscle.

Cofilins are actin binding proteins and regulate actin assembly in vivo. Numerous cofilin homologues have been characterized in various organisms including mammals. In mice, a ubiquitously expressed cofilin (CFL1) and a skeletal muscle specific cofilin (CFL2) have been described. In the present study, we identified and characterized a human CFL2 gene localized on chromosome 14, with high homology to murine CFL2. Furthermore, we provide evidence for differentially spliced CFL2 transcripts (CFL2a and CFL2b). CFL2b is expressed predominantly in human skeletal muscle and heart, while CFL2a is expressed in various tissues. Genetic defects of CFL2 were excluded for one human muscle disorder, the chromosome 14 linked distal myopathy MPD1, and shown to be only possible to be a rare cause of another, nemaline myopathy. In a mouse model of mechanically induced muscle damage the changes of cofilin expression were monitored during the first 10 days of regeneration, with dephosphorylated CFL2 being the major isoform at later stages of muscle regeneration. A similar predominance of dephosphorylated CFL2 was observed in chronically regenerating dystrophin-deficient muscles of Duchenne muscular dystrophy patients. Therefore, the CFL2 isoform may play an important role in normal muscle function and muscle regeneration.

Magnetic anisotropy of a single cobalt nanocluster.

Using a new micro-SQUID setup, we investigate magnetic anisotropy in a single 1000-atom cobalt cluster. This system opens new fields in the characterization and understanding of the origin of magnetic anisotropy in such nanoparticles. For this purpose, we report three-dimensional switching field measurements performed on a 3 nm cobalt cluster embedded in a niobium matrix. We are able to separate the different magnetic anisotropy contributions and evidence the dominating role of the cluster surface.

Toxoplasma gondii-structure variations of the antigen P30.

The major surface immunodominant antigen (P30) of Toxoplasma gondii was purified by two methods (i) SDS-PAGE and (ii) immunoaffinity chromatography. The secondary elements within this protein were assessed by circular dichroism and spectra obtained were compared to those proposed by Manavalan & Johnson (1983). The results allowed us to determine an all beta protein status for this antigen. This experimental result was in agreement with the predicted secondary structures deduced from the P30 primary sequence. Modifications in conformation according to pH and temperature were recorded without any change in immunoactivity. The epitope, which was always recognized by a monoclonal antibody against P30, could be a linear epitope.

Protective effect of sucrose on spray drying of oxyhemoglobin.

As far as we know, spray drying has previously not been applied to oxyhemoglobin, undoubtedly because of the sensitivity of oxyhemoglobin to temperature and oxidation. Our experience with freeze drying encouraged us to perform spray-drying trials in order to compare the results of the two methods, in the absence and the presence of protective compounds. Spray drying of hemoglobin without a protective compound led, as in freeze drying, to formation of a percentage of methemoglobin (50%) that makes it unsuitable for transporting oxygen. In the presence of 0.25 M sucrose (optimum) and at 80-100 degrees C, the functional properties of the hemoglobin were well preserved (methemoglobin approximately 4%), and the residual humidity was limited to approximately 3%. Structural investigation by optical circular dichroism confirmed the results obtained by freeze drying: in the presence of an effective protector, the spectra were similar to those of control hemoglobin and the immediate environment of the heme did not undergo any major change. Electron spin resonance absorption bands in all samples were similar for each value of the spectral decomposition factor, g. This suggests that the structure of the heme is not altered by desiccation and that the protector does not penetrate into the heme pocket since it would have disturbed the symmetry of the crystalline field. Fundamentally, these results are equivalent or similar to those observed with freeze drying; since spray drying is a different process of dehydration, the results indicate a lack of specificity in the phenomena of oxidation or of protection affecting hemoglobin.

Conformational studies of NADPH cytochrome P-450 reductase by circular dichroism: interaction with phospholipids.

Ultraviolet circular dichroism spectrum of purified NADPH cytochrome P-450 reductase was characterized by two negative bands centered at 208 and 222 nm. The approximation of the alpha-helical content from the value of the mean residue ellipticity at 222 nm indicated 28% of alpha-helical structures. Heat inactivation of the enzyme was associated to a drastic change in the secondary structure of the protein. Membrane reconstitution experiments by inclusion of the enzyme into liposomes revealed that the conformation of NADPH cytochrome P-450 reductase was sensitive to its phospholipid environment. Egg lecithin as well as synthetic phosphatidylcholines, at the optimal phospholipid-enzyme molar ratio 200, was able to increase up to 37% the mean residue ellipticity at 222 nm. Addition of phosphatidylserine or phosphatidylethanolamine produced no effect. Non-ionic detergent such as Emulgen 913 weakly enhanced the mean residue ellipticity.

Conformational study of purified epoxide hydrolase from rat liver.

Hepatic epoxide hydrolase (EC 3.3.2.3) was purified from phenobarbital-treated rats by ion-exchange chromatography followed by hydrophobic chromatography. The enzyme had a specific activity of 300--400 nmol min-1 mg-1 protein with benzo[a]pyrene-4,5-oxide as the substrate. Circular dichroism (CD) spectra of the purified enzyme gave two negative bands, centered at 210 nm and 222 nm, respectively. The mean residue ellipticity at 222 nm was 12,9000 deg X cm(2) X dmol(-1), which indicated the presence of about 35% alpha-helical structures. Sodium dodecyl sulfate (SDS) greatly affected the shape of the CD spectra, which were gradually shifted to the blue. This suggested a decrease in the aggregation state of the protein. Electrostatic interactions were important in the organization of the enzyme structure since the conformation was stable between pH 7.4 and pH 10. At pH-values 5.0, 6.0 and 12.0, the CD bands underwent considerable changes in both amplitude and shape. Moreover there was a good correlation between the optimal pH range of the epoxide hydrolase activity and the organization state of the protein. After membrane reconstitution with liposomes, the conformation of the enzyme was not significantly modified by the presence of dimyristoyl L-alpha-phosphatidylcholine or other phospholipids. This constancy was obtained over a wide range of molar ratios of phospholipids to protein (0--500). However, phospholipids did increase the thermal stability of the enzyme. Fluorescence measurements of diphenylhexatriene (DPH) bound to dimyristoyl L-alpha-phosphatidylcholine indicated that addition of epoxide hydrolase modified the thermal transition of the lipid phase. On the other hand, electron paramagnetic resonance (EPR) signals of the nitroxide-labelled fatty acid, 2-(14-carboxy-tetradecyl)-2-ethyl-4,4-dimethyl-3,3,-oxazolidiny-oxyl, bound to the phospholipid, indicated that the presence of the protein decreased by about 53% the correlation time of the label, suggesting that its motion had increased. In conclusion, phospholipid-epoxide hydrolase interactions enhanced the fluidity of dimyristoyl L-alpha-phosphatidylcholine liposomes without changing the secondary structure of the enzyme. Electrostatic interactions also played an important role in the conformational stability of the protein.

Effects of membrane perturbants on UDP-glucuronosyltransferase activity in rat-liver microsomes. Circular dichroism studies.

Rat-liver microsomes were treated with two non-ionic detergents, Triton X-100 and Lubrol WX, with phospholipase A2, or with aqueous acetone solution. The activity of the membrane-bound UDP-glucoronosyltransferase (UDPGT, EC 2.4.1.17) was measured after the treatment with these perturbants. At the same time, modifications of the secondary structure of the microsomal proteins were followed and studied by circular dichroism (CD) spectroscopy. The detergents greatly activated UDPGT, maximally at a 1 mM concentration of either detergent. The maximally activating Triton X-100 treatment did not greatly change the ellipticity of the microsomes at 222 nm ((theta)222), whereas that with Lubrol WX affected the secondary structure of the membrane proteins more strongly. UDPGT activation also occurred in phospholipase A2-treated microsomes. Maximal activation was obtained after 1--5 min of incubation and was stable throughout the experiment. Phospholipase A2 at the ratio of microsomal protein to phospholipase 250 : 1 (w/w) slightly increased (theta)222 after 10 min of incubation and did not change it further even after 30 min of incubation. Treatment of liver microsomes with a 10 : 90 (v/v) aqueous acetone solution removed 90% of the total membrane phospholipids, particularly phosphatidylcholine and phosphatidylethanolamine. The UDPGT activity was decreased in lipid-depleted microsomes, and the enzyme was not reactivated when phosphatidylcholine-lysophosphatidylcholine liposomes were added at a low temperature. An even greater decrease was obtained when the lipid binding was carried out at 37 degree C. Lipid-depleted microsomes had a high (theta)222 associated with a red-shift of 2 nm, indicating partial aggregation of membrane proteins and an increase in the alpha-helical content of the protein after acetone extraction. However, this particular protein structure was partially reversible, since a binding of phospholipids to lipid-depleted microsomes gave a (theta)222 close to that found in control microsomes. The UDPGT activity was not dependent on the secondary structure of the membrane proteins.