Topological magnon band structure of emergent Landau levels in a skyrmion lattice.

The motion of a spin excitation across topologically nontrivial magnetic order exhibits a deflection that is analogous to the effect of the Lorentz force on an electrically charged particle in an orbital magnetic field. We used polarized inelastic neutron scattering to investigate the propagation of magnons (i.e., bosonic collective spin excitations) in a lattice of skyrmion tubes in manganese silicide. For wave vectors perpendicular to the skyrmion tubes, the magnon spectra are consistent with the formation of finely spaced emergent Landau levels that are characteristic of the fictitious magnetic field used to account for the nontrivial topological winding of the skyrmion lattice. This provides evidence of a topological magnon band structure in reciprocal space, which is borne out of the nontrivial real-space topology of a magnetic order.

Detection of environmental contamination with feline and canine parvoviruses: new perspectives and challenges.

AIMS: To develop a protocol for environmental sampling to detect parvoviruses of dogs and cats in the environment. METHODS AND RESULTS: Environmental contamination was carried out using different dilutions of parvovirus-contaminated materials; further field samplings were performed in areas in which clinical cases of parvovirus infections were present. Sterile cotton swabs and sponges for microbial surface sampling were used. Viruses were detected in these samples with different methods: conventional PCR, nested PCR and real-time PCR, detecting viral DNA; virus isolation, detecting infectious virus; and a commercial rapid enzyme immunoassay, detecting viral antigen. No substantial differences were observed in the two sampling methods, although the sponge was more convenient for sampling rough surfaces. Molecular assays were the most sensitive methods, identifying even very low amounts of viral DNA (up to 10 copies of viral DNA/10 µl of sample). Virus isolation and the rapid test detected the viruses only at the highest viral concentrations, both in the experimental setting and field conditions. CONCLUSIONS: Environmental sampling and molecular protocols were effective in detecting environmental contamination with parvoviruses. SIGNIFICANCE AND IMPACT OF THE STUDY: The protocol will be useful to identify possible sources of infection and to assess the efficacy of disinfection protocols in the environment.

Communication: Chemisorption of muonium on gold nanoparticles: A sensitive new probe of surface magnetism and reactivity.

Chemisorption of muonium onto the surface of gold nanoparticles has been observed. Muonium (µ+e-), a light hydrogen-like atom, reacts chemically with uncapped 7 nm gold nanoparticles embedded in mesoporous silica (SBA-15) with a strong temperature-dependent rate. The addition rate is fast enough to allow coherent spin transfer into a diamagnetic muon state on the nanoparticle surface. The muon is well established as a sensitive probe of static or slowly fluctuating magnetic fields in bulk matter. These results represent the first muon spin rotation signal on a nanoparticle surface or any metallic surface. Only weak magnetic effects are seen on the surface of these Au nanoparticles consistent with Pauli paramagnetism.

Visualizing the morphology of vortex lattice domains in a bulk type-II superconductor.

Alike materials in the solid state, the phase diagram of type-II superconductors exhibit crystalline, amorphous, liquid and spatially inhomogeneous phases. The multitude of different phases of vortex matter has thence proven to act as almost ideal model system for the study of both the underlying properties of superconductivity but also of general phenomena such as domain nucleation and morphology. Here we show how neutron grating interferometry yields detailed information on the vortex lattice and its domain structure in the intermediate mixed state of a type-II niobium superconductor. In particular, we identify the nucleation regions, how the intermediate mixed state expands, and where it finally evolves into the Shubnikov phase. Moreover, we complement the results obtained from neutron grating interferometry by small-angle neutron scattering that confirm the spatially resolved morphology found in the intermediate mixed state, and very small-angle neutron scattering that confirm the domain structure of the vortex lattice.

Band Structure of Helimagnons in MnSi Resolved by Inelastic Neutron Scattering.

A magnetic helix realizes a one-dimensional magnetic crystal with a period given by the pitch length λh. Its spin-wave excitations-the helimagnons-experience Bragg scattering off this periodicity, leading to gaps in the spectrum that inhibit their propagation along the pitch direction. Using high-resolution inelastic neutron scattering, the resulting band structure of helimagnons was resolved by preparing a single crystal of MnSi in a single magnetic-helix domain. At least five helimagnon bands could be identified that cover the crossover from flat bands at low energies with helimagnons basically localized along the pitch direction to dispersing bands at higher energies. In the low-energy limit, we find the helimagnon spectrum to be determined by a universal, parameter-free theory. Taking into account corrections to this low-energy theory, quantitative agreement is obtained in the entire energy range studied with the help of a single fitting parameter.

Neutron resonance spin flippers: static coils manufactured by electrical discharge machining.

Radiofrequency spin flippers (RFSF) are key elements of Neutron Resonance Spin Echo (NRSE) spectrometers, which allow performing controlled manipulations of the beam polarization. We report on the design and test of a new type of RFSF which originality lies in the new manufacturing technique for the static coil. The largely automated procedure ensures reproducible construction as well as an excellent homogeneity of the neutron magnetic resonance condition over the coil volume. Two salient features of this concept are the large neutron window and the closure of the coil by a µ-metal yoke which prevents field leakage outside of the coil volume. These properties are essential for working with large beams and enable new applications with coils tilted with respect to the beam axis such as neutron Larmor diffraction or the study of dispersive excitations by inelastic NRSE.

New diluted ferromagnetic semiconductor with Curie temperature up to 180 K and isostructural to the '122' iron-based superconductors.

Diluted magnetic semiconductors have received much attention due to their potential applications for spintronics devices. A prototypical system (Ga,Mn)As has been widely studied since the 1990s. The simultaneous spin and charge doping via hetero-valent (Ga(3+),Mn(2+)) substitution, however, resulted in severely limited solubility without availability of bulk specimens. Here we report the synthesis of a new diluted magnetic semiconductor (Ba(1-x)K(x))(Zn(1-y)Mn(y))(2)As(2), which is isostructural to the 122 iron-based superconductors with the tetragonal ThCr(2)Si(2) (122) structure. Holes are doped via (Ba(2+), K(1+)) replacements, while spins via isovalent (Zn(2+),Mn(2+)) substitutions. Bulk samples with x=0.1-0.3 and y=0.05-0.15 exhibit ferromagnetic order with T(C) up to 180 K, which is comparable to the highest T(C) for (Ga,Mn)As and significantly enhanced from T(C) up to 50 K of the '111'-based Li(Zn,Mn)As. Moreover, ferromagnetic (Ba,K)(Zn,Mn)(2)As(2) shares the same 122 crystal structure with semiconducting BaZn(2)As(2), antiferromagnetic BaMn(2)As(2) and superconducting (Ba,K)Fe(2)As(2), which makes them promising for the development of multilayer functional devices.

Improving medical records filing in a municipal hospital in Ghana.

BACKGROUND: Medical records are kept in the interest of both the patient and clinician. Proper filing of patient's medical records ensures easy retrieval and contributes to decreased patient waiting time at the hospital and continuity of care. This paper reports on an intervention study to address the issue of misfiling and multiple patient folders in a health facility. DESIGN: Intervention study. SETTING: Municipal Hospital, Goaso, Asunafo North District, Brong Ahafo Region, Ghana. METHODS: Methods employed for data collection were records review, direct observation and tracking of folders. Interventions instituted were staff durbars, advocacy and communication, consultations, in-service trainings, procurement and monitoring. Factors contributing to issuance of multiple folders and misfiling were determined. Proportion of multiple folders was estimated. RESULTS: Results revealed direct and indirect factors contributing to issuance of multiple patient folders and misfiling. Interventions and monitoring reduce acquisition of numerous medical folders per patient and misfiling. After the intervention, there was significant reduction in the use of multiple folders (i.e., overall 97% reduction) and a high usage of single patient medical folders (i.e., 99%). CONCLUSION: In conclusion, a defined medical records filing system with adequate training, logistics and regular monitoring and supervision minimises issuance of multiple folders and misfiling.

Long-range crystalline nature of the Skyrmion lattice in MnSi.

We report small angle neutron scattering of the Skyrmion lattice in MnSi using an experimental setup that minimizes the effects of demagnetizing fields and double scattering. Under these conditions, the Skyrmion lattice displays resolution-limited Gaussian rocking peaks that correspond to a magnetic correlation length in excess of several hundred micrometers. This is consistent with exceptionally well-defined long-range order. We further establish the existence of higher-order scattering, discriminating parasitic double scattering with Renninger scans. The field and temperature dependence of the higher-order scattering arises from an interference effect. It is characteristic for the long-range crystalline nature of the Skyrmion lattice as shown by simple mean-field calculations.

Behaviour of Listeria monocytogenes in packaged water buffalo mozzarella cheese.

AIMS: The aim of the study was to evaluate the behaviour of Listeria monocytogenes in the conditioning liquid of packaged water buffalo mozzarella cheese (WBMC). METHODS AND RESULTS: The conditioning liquid was contaminated with L. monocytogenes, and the contaminated samples were stored at four different storage temperatures: 5 and 10 °C for 22 days; 20 °C for 9 days; 20 °C for 3 days and then at 5 °C for 6 days. The results showed that L. monocytogenes concentration decreased when contaminated samples were stored at 5 °C. When WBMC was stored at 20 °C and at 10 °C, L. monocytogenes started to grow after a lag phase of 3 and 10 days, respectively. When samples were stored at variable temperature conditions, L. monocytogenes numbers showed a lag phase of 5 days. CONCLUSIONS: Use of a conditioning liquid characterized by acidity and a correct storage temperature is able to counteract pathogen replication during shelf life. A high concentration of lactic acid bacteria was associated with effective control of L. monocytogenes but the role of lactic acid bacteria in WBMC conditioning liquid requires further investigation. SIGNIFICANCE AND IMPACT OF THE STUDY: According to European regulations, food producers should be able to justify decision-making on the shelf life assigned to their products, taking into account reasonable storage conditions and use by consumers. The results of the trial yielded information for producers of WBMC and similar cheeses for decision-making on product shelf life.

Detection of high frequency intensity oscillations at RESEDA using the CASCADE detector.

We have explored the technological potential of combining neutron resonance spin echo (NRSE) with the time-of-flight method in quasielastic neutron scattering (QENS) experiments. For these test measurements at the new NRSE instrument RESEDA (FRM II, Munich), we have employed CASCADE, one of the fastest neutron detectors in the world, developed at the University of Heidelberg. Conventionally, scintillation detectors are used, in order to detect neutron intensities with high time resolution. In contrast, we used the new CASCADE detector converting neutrons in thin (10)B layers being capable of resolving neutron intensity modulations up to the megahertz regime. This fast detector allows us to abandon the last resonance flip coil of a standard NRSE setup. The classical spin echo signal is replaced by a time-modulated signal. In this setup, fast intensity modulations are present at the detector position. In order to demonstrate, that NRSE-CASCADE operates well up to detector frequencies of 10 MHz, we performed elastic polarization test measurements on a standard sample. The CASCADE detector is a multidetector accumulating counts in 128 × 128 pixels on a surface of 200 mm × 200 mm. We have analyzed the signal in 600 pixels, providing information about the spin phase reaching the detector and about the resolution function of this new variant tested at RESEDA.

Spin transfer torques in MnSi at ultralow current densities.

Spin manipulation using electric currents is one of the most promising directions in the field of spintronics. We used neutron scattering to observe the influence of an electric current on the magnetic structure in a bulk material. In the skyrmion lattice of manganese silicon, where the spins form a lattice of magnetic vortices similar to the vortex lattice in type II superconductors, we observe the rotation of the diffraction pattern in response to currents that are over five orders of magnitude smaller than those typically applied in experimental studies on current-driven magnetization dynamics in nanostructures. We attribute our observations to an extremely efficient coupling of inhomogeneous spin currents to topologically stable knots in spin structures.

Is there an intrinsic limit to the charge-carrier-induced increase of the Curie temperature of EuO?

Rare earth doping is the key strategy to increase the Curie temperature (T(C)) of the ferromagnetic semiconductor EuO. The interplay between doping and charge carrier density (n), and the limit of the T(C) increase, however, are yet to be understood. We report measurements of n and T(C) of Gd-doped EuO over a wide range of doping levels. The results show a direct correlation between n and T(C), with both exhibiting a maximum at high doping. On average, less than 35% of the dopants act as donors, raising the question about the limit to increasing T(C).

Skyrmion lattices in metallic and semiconducting B20 transition metal compounds.

High pressure studies in MnSi suggest the existence of a non-Fermi liquid state without quantum criticality. The observation of partial magnetic order in a small pocket of the pressure versus temperature phase diagram of MnSi has additionally inspired several proposals of complex spin textures in chiral magnets. We used neutron scattering to observe the formation of a two-dimensional lattice of skyrmion lines, a type of magnetic vortices, under applied magnetic fields in metallic and semiconducting B20 compounds. In strongly disordered systems the skyrmion lattice is hysteretic and extends over a large temperature range. Our study experimentally establishes magnetic materials lacking inversion symmetry as an arena for new forms of spin order composed of topologically stable spin textures.

Elastic torsion effects in magnetic nanoparticle diblock-copolymer structures.

Magnetic properties of thin composite films, consisting of non-interacting polystyrene-coated γ-Fe(2)O(3) (maghemite) nanoparticles embedded into polystyrene-block-polyisoprene P(S-b-I) diblock-copolymer films are investigated. Different particle concentrations, ranging from 0.7 to 43 wt%, have been used. The magnetization measured as a function of external field and temperature shows typical features of anisotropic superparamagnets including a hysteresis at low temperatures and blocking phenomena. However, the data cannot be reconciled with the unmodified Stoner-Wohlfarth-Néel theory. Applying an appropriate generalization we find evidence for either an elastic torque being exerted on the nanoparticles by the field or a broad distribution of anisotropy constants.

An outbreak of viral gastroenteritis linked to municipal water supply, Lombardy, Italy, June 2009.

We report an outbreak of viral gastroenteritis linked to municipal drinking water in a town in northern Italy in June 2009. Over one month we identified 299 probable cases of whom 30 were confirmed for at least one of the following viruses: norovirus, rotavirus, enterovirus or astrovirus. Water samples and filters from the water system also tested positive for norovirus and enterovirus. Control measures included treating the water system with chlorine dioxide and filters with peracetic acid, while providing temporary alternative sources of drinking water to the population.

Topological Hall effect in the A phase of MnSi.

Recent small angle neutron scattering suggests that the spin structure in the A phase of MnSi is a so-called triple-Q state, i.e., a superposition of three helices under 120 degrees. Model calculations indicate that this structure in fact is a lattice of so-called Skyrmions, i.e., a lattice of topologically stable knots in the spin structure. We report a distinct additional contribution to the Hall effect in the temperature and magnetic field range of the proposed Skyrmion lattice, where such a contribution is neither seen nor expected for a normal helical state. Our Hall effect measurements constitute a direct observation of a topologically quantized Berry phase that identifies the spin structure seen in neutron scattering as the proposed Skyrmion lattice.

Morphology of the superconducting vortex lattice in ultrapure niobium.

The morphology of the superconducting flux line lattice (FLL) of Nb comprises gradual variations with various lock-in transitions and symmetry breaking rotations. We report a comprehensive small-angle neutron scattering study of the FLL in an ultrapure single crystal of Nb as a function of the orientation of the applied magnetic field. We attribute the general morphology of the FLL and its orientation to three dominant mechanisms; first, nonlocal contributions, second, the transition between open and closed Fermi surface sheets and, third, the intermediate mixed state between the Meissner and the Shubnikov phase.

Skyrmion lattice in a chiral magnet.

Skyrmions represent topologically stable field configurations with particle-like properties. We used neutron scattering to observe the spontaneous formation of a two-dimensional lattice of skyrmion lines, a type of magnetic vortex, in the chiral itinerant-electron magnet MnSi. The skyrmion lattice stabilizes at the border between paramagnetism and long-range helimagnetic order perpendicular to a small applied magnetic field regardless of the direction of the magnetic field relative to the atomic lattice. Our study experimentally establishes magnetic materials lacking inversion symmetry as an arena for new forms of crystalline order composed of topologically stable spin states.

Assessment of liver fibrosis in transplant recipients with recurrent HCV infection: usefulness of transient elastography.

BACKGROUND: Progression of recurrent hepatitis C is accelerated in liver transplant recipients, leading to special need of non-invasive validated methods to estimate liver fibrosis. AIM: To assess the efficacy of liver stiffness measurement by transient elastography (Fibroscan) and serum parameters in predicting fibrosis stage in HCV-infected transplant recipients. METHODS: The correlation between liver fibrosis, assessed at liver histology on bioptic specimens obtained for clinical indications, and stiffness or clinico-serological indexes (Benlloch, APRI, Forns, Fibrotest and Doppler resistance index), was investigated in transplant recipients with recurrence of HCV chronic hepatitis. A total of 56 patients (of which 36 with all clinico-serological indexes), presenting with the following METAVIR fibrosis stage F1=38, F2=9, F3=8, F4=1, were enrolled in the study population. Differences between fibrosis stages were calculated by non-parametric analysis. The best cut-off for identifying significant fibrosis (F2-F4) was assessed by ROC curve analysis. RESULTS: Stiffness (median and range) was 7.7 KPa (range 4.2-13.9) in F1 and 17.0KPa (range 6.8-36.3) in >or=F2 (p<0.001). A stiffness cut-off of 10.1 KPa revealed 94% Sensitivity, 89% Specificity, 81% PPV and 94% NPV in differentiating F1 from F2-F4. The area under the receiver operator curve in the assessment of fibrosis was significantly higher for Liver stiffness (AUROC 0.943) than for any of the other non-invasive indexes (AUROCs ranging 0.591-0.815). CONCLUSIONS: Transient elastography of the liver provides good accuracy in identifying patients with significant fibrosis and performs better than non-invasive indexes based on clinico-serological parameters in transplant recipients.