Domain wall propagation and pinning induced by current pulses in cylindrical modulated nanowires.

The future developments in 3D magnetic nanotechnology require the control of domain wall dynamics by means of current pulses. While this has been extensively studied in 2D magnetic strips (planar nanowires), few reports on this exist in cylindrical geometry, where Bloch point domain walls are expected to have intriguing properties. Here, we report an investigation on cylindrical magnetic Ni nanowires with geometrical notches. An experimental work based on synchrotron X-ray magnetic circular dichroism (XMCD) combined with photoemission electron microscopy (PEEM) indicates that large current densities induce domain wall nucleation, while smaller currents move domain walls preferably antiparallel to the current direction. In the region where no pinning centers are present, we found a domain wall velocity of about 1 km s-1. Thermal modelling indicates that large current densities temporarily raise the temperature in the nanowire above the Curie temperature, leading to nucleation of domain walls during the system cooling. Micromagnetic modelling with a spin-torque effect shows that for intermediate current densities, Bloch point domain walls with chirality parallel to the Oersted field propagate antiparallel to the current direction. In other cases, domain walls can be bounced from the notches and/or get pinned outside their positions. We thus found that current is not only responsible for domain wall propagation, but also is a source of pinning due to the Oersted field action.

Tailoring the physical properties of thin nanohole arrays grown on flat anodic aluminum oxide templates.

The introduction of voids in a magnetic thin-film alters the stray field distribution and enables the tailoring of the corresponding physical properties. Here we present a detailed study on thin magnetic nanohole arrays (NhAs) grown on top of hexagonally-ordered anodic aluminum oxide (AAO) substrates. We address the effect of AAO topography on the corresponding electrical and magneto-transport properties. Optimization of the AAO topography led to NhAs with improved resistance and magnetoresistance responses, while retaining their most important feature of enhanced coercivity. This opens new pathways for the growth of more complex structures on AAO substrates, a crucial aspect for their technological viability.

CoCrPt/Ti perpendicular media onto nanostructured polymer templates.

The fabrication and the study of the magnetic properties of CoCrPt/Ti nanostructures produced by sputtering onto ordered polymer templates are reported here. Samples exhibit a significant out-of-plane component of the magnetization higher than for planar films, and it is stronger for the thicker CoCrPt films, and for nanostructured films with the shorter period ordering. The shape of the polymeric templates plays an important role for the determination of magnetic easy-axis. Magnetic Force Microscopy images of the samples show a single magnetic domain structure with high out-of-plane anisotropy for the samples with longer ordering (480 nm period).

Nanomagnets with high shape anisotropy and strong crystalline anisotropy: perspectives on magnetic force microscopy.

We report on a new approach for magnetic imaging, highly sensitive even in the presence of external, strong magnetic fields. Based on FIB-assisted fabricated high-aspect-ratio rare-earth nanomagnets, we produce groundbreaking magnetic force tips with hard magnetic character where we combine a high aspect ratio (shape anisotropy) together with strong crystalline anisotropy (rare-earth-based alloys). Rare-earth hard nanomagnets are then FIB-integrated to silicon microcantilevers as highly sharpened tips for high-field magnetic imaging applications. Force resolution and domain reversing and recovery capabilities are at least one order of magnitude better than for conventional magnetic tips. This work opens new, pioneering research fields on the surface magnetization process of nanostructures based either on relatively hard magnetic materials-used in magnetic storage media-or on materials like superparamagnetic particles, ferro/antiferromagnetic structures or paramagnetic materials.

Evidence of Skyrmion-Tube Mediated Magnetization Reversal in Modulated Nanowires.

Magnetic nanowires, conceived as individual building blocks for spintronic devices, constitute a well-suited model to design and study magnetization reversal processes, or to tackle fundamental questions, such as the presence of topologically protected magnetization textures under particular conditions. Recently, a skyrmion-tube mediated magnetization reversal process was theoretically reported in diameter modulated cylindrical nanowires. In these nanowires, a vortex nucleates at the end of the segments with larger diameter and propagates, resulting in a first switching of the nanowire core magnetization at small fields. In this work, we show experimental evidence of the so-called Bloch skyrmion-tubes, using advanced Magnetic Force Microscopy modes to image the magnetization reversal process of FeCoCu diameter modulated nanowires. By monitoring the magnetic state of the nanowire during applied field sweeping, a detected drop of magnetic signal at a given critical field unveils the presence of a skyrmion-tube, due to mutually compensating stray field components. That evidences the presence of a skyrmion-tube as an intermediate stage during the magnetization reversal, whose presence is related to the geometrical dimensions of the cylindrical segments.

Patterning of rutile TiO2 surface by ion beam lithography through full-solid masks.

In this work we present and discuss the nanopatterning of rutile TiO(2) single crystal surfaces following their irradiation with energetic heavy ions through a stencil mask of Ni filled self-ordered porous anodic alumina. After etching in HF a corrugated surface morphology is obtained composed of parallel alternate furrows and ridges (or nanobars) 50 nm in diameter and with 100 nm pitch. In addition, isolated, but collapsed, TiO(2) nanorods are seen lying on the patterned surface. The stability of the nanopatterned surface under high temperatures treatments and crystalline properties are analyzed.

Nanostructured Co film on ordered polymer nanohills: a base for novel magnetic nanostructures.

The preparation of a nanostructured polymer (poly(methyl methacrylate)--PMMA) replicating the order of an anodized aluminium (Al) template is first described. Nanohills at the PMMA surface are structured following the ordering of the template with tailored lattice parameter and hexagonal symmetry. A nanostructured Co magnetic film is then deposited by sputtering onto the polymer surface so keeping the high ordering induced by the precursor template. The magnetic properties depend on the polymer periodicity as well as on the sputtering conditions. In particular, single-domain or multidomain structures have been identified inside every Co/polymer hill depending on the lattice parameter. Moreover, an intrinsic distribution of the magnetic anisotropy can be deduced from the hysteresis loops.

Variable-field magnetic force microscopy.

A new variable external field magnetic force microscope is introduced here. The most outstanding feature of the system is its capability to perform stable images under a variable external magnetic field that can be applied both in in-plane and out-of-plane directions. The performances of the microscope are illustrated for four different suitable selected samples: highly oriented pyrolytic graphite, longitudinal magnetic storage media, FePt thin films with in-plane anisotropy and Ni nanowires with axial easy axis embedded on a ceramic matrix. The use of this variable-field magnetic force microscope as a magnetic writing-reading technique is also shown in this contribution.

Is it possible to extrapolate the rates of resistance of Escherichia coli from asymptomatic bacteriuria in pregnant women to those of E. coli in uncomplicated community-acquired UTI?

OBJECTIVE: Treatment of uncomplicated urinary tract infections in primary care is generally empirical without requesting urine culture and based on biased resistance data collected from selected patients, most of them having risk factors for the isolation of resistant microorganisms. In order to overcome the lack of information on the real resistance rates in uncomplicated UTI, we compared antimicrobial phenotype and genotype of Escherichia coli isolated from pregnant women with asymptomatic bacteriuria (culture always performed) with those from women with uncomplicated acute cystitis (culture rarely performed) of different age groups. METHODS: Between September 2017 and March 2018, 103 urines were randomly collected from pregnant women aged between 16 and 47 with asymptomatic bacteriuria (AB) (n=42), not hospitalized women in the same age range with uncomplicated acute cystitis (UAC) (n=31) and women older than 47 not hospitalized with UAC (n=30). Bacteria identification was performed using mass spectrometry and the antibiogram by broth microdilution. Genetic typification was carried out by pulsed-field gel electrophoresis. RESULTS: There are no significant differences between the groups of patients in the antibiotic susceptibility. Likewise, as expected, a wide genetic diversity is observed among the strains of E. coli studied without significant differences between the three groups. CONCLUSIONS: We propose a simple model that could provide better guidance for selection of empirical antimicrobial therapy for non-pregnant women with UAC than do generic hospital antibiogram data based on reliably extrapolating the susceptibility data of strains isolated from pregnant women with AB as representation of women with community-acquired UAC.

Molecular determinants of human red/green color discrimination.

The human red and green color vision pigments are identical at all but 15 of their 364 amino acids, and yet their absorption maxima differ by 31 nm. In an extensive mutagenesis study, including a set of 28 chimeric proteins modeled after pigments in the color-deficient human population and an additional 30 single and multiple point mutants, the spectral difference between these 2 pigments is shown to be determined by 7 and only 7 amino acid residues. In going from the red pigment to the green pigment, the 7 residues are Ser116-->Tyr, Ser180-->Ala, Ile230-->Thr, Ala233-->Ser, Tyr277-->Phe, Thr285-->Ala, and Tyr309-->Phe.

Self-organized magnetic nanowire arrays based on alumina and titania templates.

Densely packed arrays of magnetic nanowires have been synthesized by electrodeposition filling of nanopores in alumina and titania membranes formed by self-assembling during anodization process. Emphasis is made on the control of the production parameters leading to ordering degree and lattice parameter of the array as well as nanowires diameter and length. Structural, morphological and magnetic properties exhibited by nanowire arrays have been studied for several nanowire compositions, different ordering degree and for different nanowire aspect ratios. The magnetic behaviour of nanowires array is governed by the balance between different energy contributions: shape anisotropy of individual nanowires, the magnetostatic interaction of dipolar origin among nanowires, and magnetocrystalline and magnetoelastic anisotropies induced by the pattern templates. These novel nanocomposites, based on ferromagnetic nanowires embedded in anodic nanoporous templates, are becoming promising candidates for technological applications such as functionalised arrays for magnetic sensing, ultrahigh density magnetic storage media or spin-based electronic devices.

A discrete mathematical model applied to genetic regulation and metabolic networks.

This paper describes the use of a discrete mathematical model to represent the basic mechanisms of regulation of the bacteria E. coli in batch fermentation. The specific phenomena studied were the changes in metabolism and genetic regulation when the bacteria use three different carbon substrates (glucose, glycerol, and acetate). The model correctly predicts the behavior of E. coli vis-à-vis substrate mixtures. In a mixture of glucose, glycerol, and acetate, it prefers glucose, then glycerol, and finally acetate. The model included 67 nodes; 28 were genes, 20 enzymes, and 19 regulators/biochemical compounds. The model represents both the genetic regulation and metabolic networks in an inrtegrated form, which is how they function biologically. This is one of the first attempts to include both of these networks in one model. Previously, discrete mathematical models were used only to describe genetic regulation networks. The study of the network dynamics generated 8 (2(3)) fixed points, one for each nutrient configuration (substrate mixture) in the medium. The fixed points of the discrete model reflect the phenotypes described. Gene expression and the patterns of the metabolic fluxes generated are described accurately. The activation of the gene regulation network depends basically on the presence of glucose and glycerol. The model predicts the behavior when mixed carbon sources are utilized as well as when there is no carbon source present. Fictitious jokers (Joker1, Joker2, and Repressor SdhC) had to be created to control 12 genes whose regulation mechanism is unknown, since glycerol and glucose do not act directly on the genes. The approach presented in this paper is particularly useful to investigate potential unknown gene regulation mechanisms; such a novel approach can also be used to describe other gene regulation situations such as the comparison between non-recombinant and recombinant yeast strain, producing recombinant proteins, presently under investigation in our group.

Multisegmented Nanowires: a Step towards the Control of the Domain Wall Configuration.

Cylindrical nanowires synthesized by controlled electrodeposition constitute excellent strategic candidates to engineer magnetic domain configurations. In this work, multisegmented CoNi/Ni nanowires are synthesized for tailoring a periodic magnetic structure determined by the balance between magnetocrystalline and magnetostatic energies. High-resolution Transmission Electron Microscopy confirms the segmented growth and the sharp transition between layers. Although both CoNi and Ni segments have similar fcc cubic crystal symmetry, their magnetic configuration is quite different as experimentally revealed by Magnetic Force Microscopy (MFM) imaging. While the Ni segments are single domain with axial magnetization direction, the CoNi segments present two main configurations: a single vortex state or a complex multivortex magnetic configuration, which is further interpreted with the help of micromagnetic simulations. This original outcome is ascribed to the tight competition between anisotropies. The almost monocrystalline fcc structure of the CoNi segments, as revealed by the electron diffraction patterns, which is atypical for its composition, contributes to balance the magnetocrystalline and shape anisotropies. The results of MFM measurements performed under in-plane magnetic field demonstrate that it is possible to switch from the multivortex configuration to a single vortex configuration with low magnetic fields.

Magnetization reversal in circular vortex dots of small radius.

We present a detailed study of the magnetic behavior of Permalloy (Ni80Fe20 alloy) circular nanodots with small radii (30 nm and 70 nm) and different thicknesses (30 nm or 50 nm). Despite the small size of the dots, the measured hysteresis loops manifestly display the features of classical vortex behavior with zero remanence and lobes at high magnetic fields. This is remarkable because the size of the magnetic vortex core is comparable to the dot diameter, as revealed by magnetic force microscopy and micromagnetic simulations. The dot ground states are close to the border of the vortex stability and, depending on the dot size, the magnetization distribution combines attributes of the typical vortex, single domain states or even presents features resembling magnetic skyrmions. An analytical model of the dot magnetization reversal, accounting for the large vortex core size, is developed to explain the observed behavior, providing a rather good agreement with the experimental results. The study extends the understanding of magnetic nanodots beyond the classical vortex concept (where the vortex core spins have a negligible influence on the magnetic behavior) and can therefore be useful for improving emerging spintronic applications, such as spin-torque nano-oscillators. It also delimits the feasibility of producing a well-defined vortex configuration in sub-100 nm dots, enabling the intracellular magneto-mechanical actuation for biomedical applications.

Regulated but not constitutive human respiratory syncytial virus (HRSV) P protein phosphorylation is essential for oligomerization.

Purified human respiratory syncytial virus (HRSV) P phosphoprotein from transfected HEp-2 cells is able to oligomerize forming tetramers. The bulk of constitutive P protein phosphorylation (99. 8%) (serine residues 116, 117, 119, 232 and 237) can be removed without affecting protein oligomerization. However, dephosphorylated P protein, produced in bacteria, is unable to oligomerize. This difference can be explained by a transient P protein phosphorylation, detected in HEp-2 cells, that could be essential for P protein oligomerization.

Interactions between cellular actin and human respiratory syncytial virus (HRSV).

Actin the main component of the cellular microfilament network, is present in human respiratory syncytial virus (HRSV) purified virions, as an internal component. This fact and the results of immunoprecipitation studies indicate that during HRSV infection in HEp-2 cells there are interactions between cellular actin and viral components, that can promote a transitory increase in the polymerization of synthetized actin, mainly of the beta isotype. This increased actin polymerization can be related with the formation of cytoplasmic extensions, that contain beta actin and viral particles observed in the HRSV infected HEp-2 cells. The formation of these structures may indicate that HRSV has developed an actin-based motility system similar to that described for other viral and bacterial systems.

Worldwide survey of neurosurgical training requirements and certifying mechanisms: report of the Committee on Neurosurgical Education of the World Federation of Neurosurgical Societies.

This is the report of the Committee on Neurosurgical Education of the World Federation of Neurosurgical Societies, which report was presented at the Seventh International Congress of Neurological Surgery in Munich in July 1981. The Committee was charged to conduct a survey of neurosurgical training requirements and certifying mechanisms throughout the world. These data are summarized in the tables in this report.

[Profiles of the duration of temporary work incapacity in a health district and its comparison with some proposed standards]. / Perfiles de duración de incapacidad laboral transitoria en un distrito sanitario y su comparación con algunos estándares propuestos.

OBJECTIVE: To describe the Work Disability (WD) Profiles Lengths issued according to diagnostic in Usera's Sanitary District of Madrid, and compare them with recommended standards obtained with different methodology (consensual-practical experience) by several authors. METHOD: A descriptive study of 3555 WD informed by 31 general practitioners during 1992. Variables were achieved from P-14 registers, using by Medical Inspection. Diagnoses were processed according to CIPSAP-2-Def. The results were compared with recommended standards lengths proposed by INSALUD Experts Commission, (consensus) and with another obtained by practical experience by others. RESULTS: Grate variability in day's lengths of WD were observed (mean average = 45.1 +/- 79.7 days; medium = 16 days; mode = 4 days). Respiratory diseases score for the highest frequency (20.6%) while Muscle skeletics accounts for more days out of work (23.1% of working days lost). Applying to our study the intervals of lengths days proposed by the INSALUD (consensus), up to 75% of potential long-lasting and only 25% of short-lasting processes could be included. Nevertheless, a higher concordance is observed when they are compared with other authors with a similar methodology. CONCLUSIONS: The recommended lengths standards of work disability established by the INSALUD are difficult to be achieved in actual practice.

[Dental caries in 2 families with tuberous sclerosis]. / Puits dentaires dans deux familles avec sclérose tubéreuse.

Four cases of tuberous sclerosis in two families are presented. We studied the oral manifestations of the disease and we suggest that dental pits should be taken as clinical markers for diagnosis in oligosymptomatic cases. We found that feature in all patients affected by tuberous sclerosis.

Phosphorylation of the human respiratory syncytial virus N protein provokes a decrease in viral RNA synthesis.

When HEp-2 cells are infected by human respiratory syncytial virus (HRSV) its N protein becomes phosphorylated at tyrosine (Y) Y38, in a strictly regulated way. To determine how this phosphorylation affects nucleocapsid (NC) template activity during viral RNA synthesis, N protein variants were analysed in which Y38 and nearby Y residues were substituted by phenylalanine (F; Y23F, Y38F and Y69F) or aspartic acid (D; Y23D and Y38D). While the capacity of these proteins to form the NC and to interact with the P protein was maintained, their NC template activity was altered affecting distinctly viral transcription and replication of HRSV based minigenomes. Thus, Y38 phosphorylation of the HRSV N protein modulates NC template activity probably by altering the interactions of the monomeric components of the NC.