Creation of skyrmions in van der Waals ferromagnet Fe3GeTe2 on (Co/Pd) n superlattice.

Magnetic skyrmions are topological spin textures, which usually exist in noncentrosymmetric materials where the crystal inversion symmetry breaking generates the so-called Dzyaloshinskii-Moriya interaction. This requirement unfortunately excludes many important magnetic material classes, including the recently found two-dimensional van der Waals (vdW) magnetic materials, which offer unprecedented opportunities for spintronic technology. Using photoemission electron microscopy and Lorentz transmission electron microscopy, we investigated and stabilized Néel-type magnetic skyrmion in vdW ferromagnetic Fe3GeTe2 on top of (Co/Pd) n in which the Fe3GeTe2 has a centrosymmetric crystal structure. We demonstrate that the magnetic coupling between the Fe3GeTe2 and the (Co/Pd) n could create skyrmions in Fe3GeTe2 without the need of an external magnetic field. Our results open exciting opportunities in spintronic research and the engineering of topologically protected nanoscale features by expanding the group of skyrmion host materials to include these previously unknown vdW magnets.

Tunable Magnetoelastic Effects in Voltage-Controlled Exchange-Coupled Composite Multiferroic Microstructures.

The magnetoelectric properties of exchange-coupled Ni/CoFeB-based composite multiferroic microstructures are investigated. The strength and sign of the magnetoelastic effect are found to be strongly correlated with the ratio between the thicknesses of two magnetostrictive materials. In cases where the thickness ratio deviates significantly from one, the magnetoelastic behavior of the multiferroic microstructures is dominated by the thicker layer, which contributes more strongly to the observed magnetoelastic effect. More symmetric structures with a thickness ratio equal to one show an emergent interfacial behavior which cannot be accounted for simply by summing up the magnetoelastic effects occurring in the two constituent layers. This aspect is clearly visible in the case of ultrathin bilayers, where the exchange coupling drastically affects the magnetic behavior of the Ni layer, making the Ni/CoFeB bilayer a promising next-generation synthetic magnetic system entirely. This study demonstrates the richness and high tunability of composite multiferroic systems based on coupled magnetic bilayers compared to their single magnetic layer counterparts. Furthermore, because of the compatibility of CoFeB with present magnetic tunnel junction-based spintronic technologies, the reported findings are expected to be of great interest for the development of ultralow-power magnetoelectric memory devices.

Coherent ac spin current transmission across an antiferromagnetic CoO insulator.

The recent discovery of spin current transmission through antiferromagnetic insulating materials opens up vast opportunities for fundamental physics and spintronics applications. The question currently surrounding this topic is: whether and how could THz antiferromagnetic magnons mediate a GHz spin current? This mismatch of frequencies becomes particularly critical for the case of coherent ac spin current, raising the fundamental question of whether a GHz ac spin current can ever keep its coherence inside an antiferromagnetic insulator and so drive the spin precession of another ferromagnet layer coherently? Utilizing element- and time-resolved x-ray pump-probe measurements on Py/Ag/CoO/Ag/Fe75Co25/MgO(001) heterostructures, here we demonstrate that a coherent GHz ac spin current pumped by the Py ferromagnetic resonance can transmit coherently across an antiferromagnetic CoO insulating layer to drive a coherent spin precession of the Fe75Co25 layer. Further measurement results favor thermal magnons rather than evanescent spin waves as the mediator of the coherent ac spin current in CoO.

Anomalous orbital structure in two-dimensional titanium dichalcogenides.

Generally, lattice distortions play a key role in determining the electronic ground states of materials. Although it is well known that trigonal distortions are generic to most two dimensional transition metal dichalcogenides, the impact of this structural distortion on the electronic structure and topological properties has not been understood conclusively. Here, by using a combination of polarization dependent X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS) and atomic multiplet cluster calculations, we have investigated the electronic structure of titanium dichalcogenides TiX2 (X = S, Se, Te), where the magnitude of the trigonal distortion increase monotonically from S to Se and Te. Our results reveal the presence of an anomalously large crystal field splitting. This unusual kind of crystal field splitting is likely responsible for the unconventional electronic structure of TiX2 compounds and ultimately controls the degree of the electronic phase protection. Our findings also indicate the drawback of the distorted crystal field picture in explaining the observed electronic ground state and emphasize the key importance of trigonal symmetry, metal-ligand hybridization and electron-electron correlations in defining the electronic structures at the Fermi energy.

Artificial two-dimensional polar metal at room temperature.

Polar metals, commonly defined by the coexistence of polar crystal structure and metallicity, are thought to be scarce because the long-range electrostatic fields favoring the polar structure are expected to be fully screened by the conduction electrons of a metal. Moreover, reducing from three to two dimensions, it remains an open question whether a polar metal can exist. Here we report on the realization of a room temperature two-dimensional polar metal of the B-site type in tri-color (tri-layer) superlattices BaTiO3/SrTiO3/LaTiO3. A combination of atomic resolution scanning transmission electron microscopy with electron energy-loss spectroscopy, optical second harmonic generation, electrical transport, and first-principles calculations have revealed the microscopic mechanisms of periodic electric polarization, charge distribution, and orbital symmetry. Our results provide a route to creating all-oxide artificial non-centrosymmetric quasi-two-dimensional metals with exotic quantum states including coexisting ferroelectric, ferromagnetic, and superconducting phases.

Electron Accumulation and Emergent Magnetism in LaMnO_{3}/SrTiO_{3} Heterostructures.

Emergent phenomena at polar-nonpolar oxide interfaces have been studied intensely in pursuit of next-generation oxide electronics and spintronics. Here we report the disentanglement of critical thicknesses for electron reconstruction and the emergence of ferromagnetism in polar-mismatched LaMnO_{3}/SrTiO_{3} (001) heterostructures. Using a combination of element-specific x-ray absorption spectroscopy and dichroism, and first-principles calculations, interfacial electron accumulation, and ferromagnetism have been observed within the polar, antiferromagnetic insulator LaMnO_{3}. Our results show that the critical thickness for the onset of electron accumulation is as thin as 2 unit cells (UC), significantly thinner than the observed critical thickness for ferromagnetism of 5 UC. The absence of ferromagnetism below 5 UC is likely induced by electron overaccumulation. In turn, by controlling the doping of the LaMnO_{3}, we are able to neutralize the excessive electrons from the polar mismatch in ultrathin LaMnO_{3} films and thus enable ferromagnetism in films as thin as 3 UC, extending the limits of our ability to synthesize and tailor emergent phenomena at interfaces and demonstrating manipulation of the electronic and magnetic structures of materials at the shortest length scales.

Unconventional magnetisation texture in graphene/cobalt hybrids.

Magnetic domain structure and spin-dependent reflectivity measurements on cobalt thin films intercalated at the graphene/Ir(111) interface are investigated using spin-polarised low-energy electron microscopy. We find that graphene-covered cobalt films have surprising magnetic properties. Vectorial imaging of magnetic domains reveals an unusually gradual thickness-dependent spin reorientation transition, in which magnetisation rotates from out-of-the-film plane to the in-plane direction by less than 10° per cobalt monolayer. During this transition, cobalt films have a meandering spin texture, characterised by a complex, three-dimensional, wavy magnetisation pattern. In addition, spectroscopy measurements suggest that the electronic band structure of the unoccupied states is essentially spin-independent already a few electron-Volts above the vacuum level. These properties strikingly differ from those of pristine cobalt films and could open new prospects in surface magnetism.

Quantitative Trait Loci Associated with Phenological Development, Low-Temperature Tolerance, Grain Quality, and Agronomic Characters in Wheat (Triticum aestivum L.).

Plants must respond to environmental cues and schedule their development in order to react to periods of abiotic stress and commit fully to growth and reproduction under favorable conditions. This study was initiated to identify SNP markers for characters expressed from the seedling stage to plant maturity in spring and winter wheat (Triticum aestivum L.) genotypes adapted to western Canada. Three doubled haploid populations with the winter cultivar 'Norstar' as a common parent were developed and genotyped with a 90K Illumina iSelect SNP assay and a 2,998.9 cM consensus map with 17,541 markers constructed. High heritability's reflected large differences among the parents and relatively low genotype by environment interactions for all characters considered. Significant QTL were detected for the 15 traits examined. However, different QTL for days to heading in controlled environments and the field provided a strong reminder that growth and development are being orchestrated by environmental cues and caution should be exercised when extrapolating conclusions from different experiments. A QTL on chromosome 6A for minimum final leaf number, which determines the rate of phenological development in the seedling stage, was closely linked to QTL for low-temperature tolerance, grain quality, and agronomic characters expressed up to the time of maturity. This suggests phenological development plays a critical role in programming subsequent outcomes for many traits. Transgressive segregation was observed for the lines in each population and QTL with additive effects were identified suggesting that genes for desirable traits could be stacked using Marker Assisted Selection. QTL were identified for characters that could be transferred between the largely isolated western Canadian spring and winter wheat gene pools demonstrating the opportunities offered by Marker Assisted Selection to act as bridges in the identification and transfer of useful genes among related genetic islands while minimizing the drag created by less desirable genes.

Imaging magnetic and ferroelectric domains and interfacial spins in magnetoelectric La0.7Sr0.3MnO3/PbZr0.2Ti0.8O3 heterostructures.

Strong magnetoelectric coupling can occur at the interface between ferromagnetic and ferroelectric films. Similar to work on interfacial exchange bias, photoemission electron microscopy was utilized to image both magnetic and ferroelectric domains and the resulting interfacial Ti spin in the same locations of La0.7Sr0.3MnO3/PbZr0.2Ti0.8O3 heterostructures. Multiple image analysis techniques, which could be applicable for a variety of fields needing quantitative data on image switching, confirm both improved magnetic switching and an increased population of interfacial spins with increased thickness of the ultrathin La0.7Sr0.3MnO3 layer. The perpendicular orientation of the interfacial spins is also discussed. This work suggests a magnetoelectric dead layer, with reduced interfacial magnetoelectricity when thin magnetic films are present.

A novel low energy electron microscope for DNA sequencing and surface analysis.

Monochromatic, aberration-corrected, dual-beam low energy electron microscopy (MAD-LEEM) is a novel technique that is directed towards imaging nanostructures and surfaces with sub-nanometer resolution. The technique combines a monochromator, a mirror aberration corrector, an energy filter, and dual beam illumination in a single instrument. The monochromator reduces the energy spread of the illuminating electron beam, which significantly improves spectroscopic and spatial resolution. Simulation results predict that the novel aberration corrector design will eliminate the second rank chromatic and third and fifth order spherical aberrations, thereby improving the resolution into the sub-nanometer regime at landing energies as low as one hundred electron-Volts. The energy filter produces a beam that can extract detailed information about the chemical composition and local electronic states of non-periodic objects such as nanoparticles, interfaces, defects, and macromolecules. The dual flood illumination eliminates charging effects that are generated when a conventional LEEM is used to image insulating specimens. A potential application for MAD-LEEM is in DNA sequencing, which requires high resolution to distinguish the individual bases and high speed to reduce the cost. The MAD-LEEM approach images the DNA with low electron impact energies, which provides nucleobase contrast mechanisms without organometallic labels. Furthermore, the micron-size field of view when combined with imaging on the fly provides long read lengths, thereby reducing the demand on assembling the sequence. Experimental results from bulk specimens with immobilized single-base oligonucleotides demonstrate that base specific contrast is available with reflected, photo-emitted, and Auger electrons. Image contrast simulations of model rectangular features mimicking the individual nucleotides in a DNA strand have been developed to translate measurements of contrast on bulk DNA to the detectability of individual DNA bases in a sequence.

Novel chiral magnetic domain wall structure in Fe/Ni/Cu(001) films.

Using spin-polarized low energy electron microscopy, we discovered a new type of domain wall structure in perpendicularly magnetized Fe/Ni bilayers grown epitaxially on Cu(100). Specifically, we observed unexpected Néel-type walls with fixed chirality in the magnetic stripe phase. Furthermore, we find that the chirality of the domain walls is determined by the film growth order with the chirality being right handed in Fe/Ni bilayers and left handed in Ni/Fe bilayers, suggesting that the underlying mechanism is the Dzyaloshinskii-Moriya interaction at the film interfaces. Our observations may open a new route to control chiral spin structures using interfacial engineering in transition metal heterostructures.

[Mitral valve repair for rheumatic valve disease in children in Senegal: a review of 100 cases]. / La plastie mitrale sur valve rhumatismale chez l'enfant au Sénégal: 100 observations.

Mitral valve repair is a better therapeutic alternative than valve replacement for rheumatic valve disease in children. Repair procedures are especially well suited to developing countries where heart prostheses and life-long anti-coagulation therapy are largely unaffordable. The purpose of this study was to evaluate medium-term outcome of mitral valve repair in children in Senegal. A retrospective review was conducted in a cohort of 100 patients who underwent mitral valve repair for rheumatic mitral lesions over the 8-year period from 1999 to 2007. Mean age was 12 +/- 5 years (range, 7 to 17 years). The most common symptom of valve disease was dysypnea (stage IV in 26 cases and stage III in 74). Valve lesions were complex with anterior leaflet prolapse in 62 cases, posterior leaflet restriction in 35, commissural fusion in 30, and fusion of chordaes in 54. Repair procedures consisted of transfer and shortening of chordaes in 73 cases in association with commissurotomy in 22 cases and cleft closure in 17. Ring annuloplasty was performed in 84 patients. Hospital mortality was 2%. Postoperative morbidity was characterized by residual mitral regurgitation in four cases. Mean follow-up was 5 years. No late deaths were observed. Outcome was satisfactory in 84 patients with low-grade mitral regurgitation (grade I-II). Reduction of left ventricle diameter was statistically significant during systole and diastole, i.e., from 29.5 +/- 6.2 mm to 33.1 +/- 5.3 mm (p<0.05) and from 47.1 +/- 8.6 mm to 50.5 +/- 9.4 mm (p<0.05) respectively. Improvement in cardiac function was not significant, i.e., from 63.3 +/- 4.8% to 62 +/- 6.4% (p = 0.99). Mitral valve repair was successful in stabilizing myocardial function and remodeling the left ventricle. Outcome is dependent on careful patient selection and evaluation of lesions. Middle-term outcome is encouraging.

[Klippel-Trenaunay syndrome: a case report]. / Le syndrome de Klippel-Trenaunay: a propos d'un cas.

OBJECTIVES: The purpose of this study is to illustrate a rare vascular malformation and to make a literature review. PATIENT: Klippel-Trenaunay's syndrome is a congenital disorder which characterized by capillary malformation, varicosities and bony or soft tissue hypertrophy. This disease is subject to significant morbidity like bleeding, deep vein thrombosis, embolic complications and in some cases enlargement of limb that may require amputation. Our case study was a young woman of twenty years suffering since birth, from a painful, heaviness and enlarged left lower limb that reached 2.5 cm. The distal hypertrophy at the big toe which the site of a botriomycoma (telengectasic granuloma). The inner side of the thigh was also the site of small port-wine stains and varicose of the great saphenous vein. Vascular Doppler ultrasound, skeletal computed tomography and angio-MRI of the limb indicated a klippel-Trenaunay disease. A surgical abstention was decided. The patient underwent only to resection of the toe's botriomycoma followed by an elastic contention associated with "a heel pad compensation" and an anti platelet therapy to prevent deep vein thrombosis and embolic complications. CONCLUSION: The syndrome of Klippel-Trenaunay is a rare vascular malformation. The basic pathology can not be corrected. The treatment's aims are to control varicose veins, to prevent complications and to preserve aesthetic and functional prognosis of the leg.

Dirac cones and minigaps for graphene on Ir(111).

Epitaxial graphene on Ir(111) prepared in excellent structural quality is investigated by angle-resolved photoelectron spectroscopy. It clearly displays a Dirac cone with the Dirac point shifted only slightly above the Fermi level. The moiré resulting from the overlaid graphene and Ir(111) surface lattices imposes a superperiodic potential giving rise to Dirac cone replicas and the opening of minigaps in the band structure.

La plastie mitrale sur valve rhumatismale chez l'enfant au Senegal : 100 observations

La chirurgie mitrale reconstructrice est une alternative de choix au remplacement valvulaire chez l'enfant. Cette chirurgie est adaptee aux pays en voie de developpement ou le cout des protheses cardiaques associees ou non a l'anti coagulation a vie est exorbitant. Le but de cette etude est d'evaluer les resultats a court et amoyen terme de la plastiemitrale chez l'enfant au Senegal. Il s'agit d'une etude retrospective sur 8 ans (1999-2007); concernant 100 patients porteurs d'atteintes valvulaires rhumatismales. L'age moyen etait de 12 +/- 5 ans (7-17 ans). La symptomatologie etait dominee par la dyspnee. Les lesions valvulaires etaient complexes; la fonction myocardique des patients etait conservee et le ventricule gauche dilate. Des gestes (transfert et raccourcissement) etaient effectues sur les cordages (73) completes par des commissurotomies (22) et des fermetures de fentes (17).Une annuloplastie etait realisee chez 84 malades. La mortalite hospitaliere etait de 2. La morbidite post operatoire etait caracterisee par 4 plasties fuyantes. Pour un suivi moyen de 5 ans; il n'y avait pas de mortalite tardive. Les resultats etaient satisfaisants avec 84 patients presentant des fuitesminimes oumoderees. La reduction du diametre du ventricule gauche etait statistiquement significative en systole (29;5+/-6;2 mm vs 33;1+/- 5;3 mm; p 0;05) et en diastole (47;1+/-8;6 mm vs 50;5+/-9;4 mm; p 0;05).Ainsi; la plastie mitrale permet une stabilisation de la fonction myocardique et un remodelage significatif du ventricule gauche; au prix d'une faible morbi mortalite post operatoire. Une analyse lesionnelle precise est determinante. Les resultats a moyen terme sont encourageants

[Using PubMed subject headings to enhance reference searches]. / Utiliser les descripteurs dans PubMed pour améliorer une recherche bibliographique.

The PubMed search engine is an essential tool to stay abreast of the latest medical literature on specific topics. While the basic search techniques are common knowledge, the ability to use medical subject headings properly is an essential in obtaining valuable references. The purpose of this article is to explain what medical subject headings are and how they can be used to improve the results of reference searches in PubMed.

[Setting up a data collection and assessment system of the Permanent Healthcare Access Activities (PASS)]. / Mise en place d'un système de recueil et d'évaluation de l'activité médicosociale des permanences d'accès aux soins de santé (PASS).

INTRODUCTION: Five years after introducing the Permanent Access to Healthcare activity (PASS), it became necessary to analyse how it works. MATERIAL AND METHODS: A computerized data collection and assessment system intended to evaluate the PASS health activities has been set up in 11 University Hospitals and ten General Hospitals. From January 1st to June, 30th 2003 data was captured in a computer. RESULTS: The patients requiring medical advice are young (with an average age of 35 years) and present several signs of poverty in terms of accommodation, social relationships and financial means. Besides, almost all of them are uninsured. The PASS public corresponds completely to the created system. Poverty risk factors vary according to the geographic origin. Indeed, French people often suffer from isolation, whereas foreign patients present financial problems. The major part of patients are foreigners and more than a third of them do not speak French, which is an additional obstacle to care. Most of the time, the PASS patients present digestive disorders, nevertheless there are some differences between French and foreign patients. Indeed, foreigners very frequently have digestive and osteoarticluar problems, whereas French patients suffer from psychic disorders and present addictive behaviours. Some patients are sent to physicians downtown (9%) and to external medicosocial assistance centres (39.5%). DISCUSSION: This study (first one in France) provides us with homogenous data regarding the activities of PASS centres nationwide. The usefulness of computers and its acceptability facilitate data diffusion, with possibilities of adapting to each centre while preserving a common basis.

Schistosomiasis co-infection in humans influences inflammatory markers in uncomplicated Plasmodium falciparum malaria.

Malaria and schistosomiasis are the two major parasite diseases present in developing countries. The epidemiological co-infection with schistosomiasis could influence the development of the physiological reaction associated with Plasmodium falciparum infection in human. Most studies have demonstrated the association of circulating levels of interferon-gamma (IFN-gamma), tumour necrosis factor-a (TNF-alpha), interleukin-10 (IL-10), transforming growth factor (TGF-beta) and soluble Tumour Necrosis Factor Receptors (sTNF-RI and sTNF-RII) with the morbidity of malaria. In the present study, we showed that Schistosoma haematobium co-infection influences, in an age-dependent manner, the unbalance between pro- and anti-inflammatory circulating cytokines that play a key role during malaria infection. Indeed, children co-infected by S. haematobium have higher levels of IFN-gamma and sTNF-RII than children infected only by P. falciparum. In contrast, co-infected adults presented a significant increase of IFN-gamma, IL-10, TGF-beta, sTNF-RI and sTNF-RII rates and IL-10/TNF-alpha ratio. Taken together, this study indicates that schistosomiasis co-infection can unbalance the regulation of inflammatory factors in uncomplicated P. falciparum malaria. The possible consequences of the schistosomiasis co-infection for age-dependent malaria morbidity are discussed.

Comparative study of the lubricant performance of Compritol 888 ATO either used by blending or by hot melt coating.

Compritol 888 ATO is used as a lubricant in oral solid dosage formulations. It can also be used as a hot melt coating agent sprayed onto a powder. In this study, we compare the lubricant performance of Compritol 888 ATO either used by classical blending or by hot melt coating onto Lactopress by compression tests. In physical mix, the Compritol concentration does not affect the compressibility. The same compressibility is obtained with lactose coated by 0.5 or 1% of Compritol, but a higher compressibility can be observed with 2 and 3%. Cohesiveness of lactose depends on the process: hot melt coating induces a decrease of tablet tensile strength. In terms of forces transmission during compression phase and axial ejection pressures, Compritol used by hot melt coating allows for a concentration of 0.5% to directly obtain the lubricant performance of 3% of Compritol used by blending. These results suggest that the hot melt coating process induces an homogeneous repartition of the lubricant on the lactose surface, contrary to classical blending procedure. Thus, lubrication by hot melt coating seems to be a very efficient procedure. It could be used specifically for large surface area particulate systems producing a lot of friction.

Comparative study of the lubricant performance of Compritol HD5 ATO and Compritol 888 ATO: effect of polyethylene glycol behenate on lubricant capacity.

The aim of this paper is to study the lubricant capacity of Compritol HD5 ATO, a glyceryl and polyethylene glycol dibehenate, obtained by atomization. This material is compared to Compritol 888 ATO, constituted only by glyceryl dibehenate. First, this study verifies that Compritol HD5 ATO and Compritol 888 ATO present the same granular characteristics and that their mixes with Lactopress present no structural differences. Secondly, in term of compressibility and cohesiveness, the use of Compritol 888 ATO or Compritol HD5 ATO with Lactopress does not involve any significant modification. Finally, the minor difference of lubricant capacity between Compritol HD5 ATO and Compritol 888 ATO has no consequence in compression practice. The presence of polyethylene glycol behenate does not decrease the glyceryl dibehenate compression functionality. This study concludes that Compritol HD5 ATO could be a very interesting excipient because it associates the glyceryl dibehenate lubricant capacity with the polyethylene glycol behenate-specific capacity in terms of dissolution enhancement.