Topological solitons in highly anisotropic two dimensional ferromagnets

e study the solitons, stabilized by spin precession in a classical two--dimensional lattice model of Heisenberg ferromagnets with non-small easy--axis anisotropy. The properties of such solitons are treated both analytically using the continuous model including higher then second powers of magnetization gradients, and numerically for a discrete set of the spins on a square lattice. The dependence of the soliton energy $E$ on the number of spin deviations (bound magnons) $N$ is calculated. We have shown that the topological solitons are stable if the number $N$ exceeds some critical value $N_{\rm{cr}}$. For $N < N_{\rm{cr}}$ and the intermediate values of anisotropy constant $K_{\mathrm{eff}} <0.35J$ ($J$ is an exchange constant), the soliton properties are similar to those for continuous model; for example, soliton energy is increasing and the precession frequency $\omega (N)$ is decreasing monotonously with $N$ growth. For high enough anisotropy $K_{\mathrm{eff}} > 0.6 J$ we found some fundamentally new soliton features absent for continuous models incorporating even the higher powers of magnetization gradients. For high anisotropy, the dependence of soliton energy E(N) on the number of bound magnons become non-monotonic, with the minima at some "magic" numbers of bound magnons. Soliton frequency $\omega (N)$ have quite irregular behavior with step-like jumps and negative values of $\omega$ for some regions of $N$. Near these regions, stable static soliton states, stabilized by the lattice effects, exist.Comment: 17 page

Optimizing SNR for multi-metabolite hyperpolarized carbon-13 MRI using a hybrid flip-angle scheme

Purpose: To improve the SNR of hyperpolarized carbon-13 MRI of [1-13C]pyruvate using a multispectral variable flip angle (msVFA) scheme in which the spectral profile and flip angle vary dynamically with time. Methods: Each image acquisition in a time-resolved imaging experiment used a unique spectrally varying RF pulse shape for msVFA. Therefore, the flip angle for every acquisition was optimized for pyruvate and each of its metabolites to yield the highest SNR across the acquisition. Multispectral VFA was compared with a spectrally varying constant flip-angle excitation model through simulations and in vivo. A modified broadband chemical shift-encoded gradient-echo sequence was used for in vivo experiments on six pregnant guinea pigs. Regions of interest placed in the placentae, maternal liver, and maternal kidneys were used as areas for SNR measurement. Results: In vivo experiments showed significant increases in SNR for msVFA relative to constant flip angle of up to 250% for multiple metabolites. Conclusion: Hyperpolarized carbon-13 imaging with msVFA excitation produces improved SNR for all metabolites in organs of interest

Enzymfreisetzung und Aktivierung der Kallikrein-Kinin-Systeme bei experimenteller Pankreatitis

Das klinische Bild der akuten Pankreatitis wird entscheidend durch die sekundäre Schädigung von Herz-Kreislauf-System, Lunge und Niere bestimmt. Ziel der vorliegenden Untersuchung war es, durch Messungen in venösem Pankreasblut, Pankreaslymphe und Peritonealexsudat die Kompartimente zu bestimmen, über die die systemischen Schädigungen vermittelt werden. An anästhesierten Schweinen wurden die systemischen, hämodynamischen Parameter durch gesteuerte Volumentherapie konstant gehalten. Die Schweine wurden randomisiert der Kontrollgruppe (n = 9) oder einer der Pankreatitisgruppen zugeteilt (jeweils n = 10). Die Pankreatitis wurde durch Infusion von freier Fettsäure in die Pankreasarterien (FFS) oder durch Infusion einer 5%igen Natrium-Taurocholat-Lösung retrograd in den Pankreasgang (NaT) ausgelöst. Nach Isolation des Pankreas wurde venöses Pankreasblut, Pankreaslymphe und Peritonealexsudat gewonnen und die Aktivität von Lipase, Phospholipase A und Plasmaprokallikrein sowie die Konzentration von Organkallikrein und Kininogen bestimmt. In beiden Pankreatitismodellen fand sich ein Anstieg der Enzymaktivitäten. Die höchsten Aktivitäten fanden sich im Peritonealexsudat (Phospholipase A nach 40 min: Kontrolle 10,0 U/1, NaT 72,2 U/1). In beiden Pankreatitismodellen fanden sich außerdem Hinweise für eine Aktivierung des Organkallikrein-Kinin-Systems durch den Anstieg der Organkallikreinkonzentration und den Abfall der Gesamtkininogenkonzentration. Die stärksten Veränderungen fanden sich wieder im Peritonealexsudat (Organkallikrein nach 40 min: Kontrolle 14,7 ng/ml, NaT 452 ng/ml).The clinical course of acute pancreatitis is strongly influenced by secondary cardiac, pulmonary and renal damage. The aim of the present study was to gather information about the compartment promoting the systemic damage. Therefore the activity of lipase, phospholipase A and plasmaprokallikrein and the concentration of tissue kallikrein and kininogen were measured in portal venous blood, pancreatic lymph and peritoneal exudate. Anaesthetized pigs were subjected to fluid resuscitation to keep systemic haemodynamic parameters constant. The pancreas was isolated in situ. The pigs were randomly assigned to a control group (n = 9) or one of the two pancreatitis groups (n = 10 each). Pancreatitis was induced by i.a. infusion of free fatty acid (FFS) or retrograde infusion of 5 % sodium taurocholate intraductally (NaT). In both pancreatitis groups the activity of lipase and phospholipase A increased. The most pronounced changes were seen in the peritoneal exsudate (phospholipase A activity 40 min after induction: control 10.0 U/1, NaT 72.2 U/1). In both pancreatitis groups there was evidence for activation of the tissue kallikreinkinin system in the form of an increase in the kallikrein concentration and a decrease in the kininogen concentration. Again the changes were most pronounced in the peritoneal exsudate (tissue kallikrein 40 min after induction: control 14.7 ng/ml, NaT 452 ng/ml)

The academic, economic and societal impacts of Open Access: an evidence-based review

Ongoing debates surrounding Open Access to the scholarly literature are multifaceted and complicated by disparate and often polarised viewpoints from engaged stakeholders. At the current stage, Open Access has become such a global issue that it is critical for all involved in scholarly publishing, including policymakers, publishers, research funders, governments, learned societies, librarians, and academic communities, to be well-informed on the history, benefits, and pitfalls of Open Access. In spite of this, there is a general lack of consensus regarding the potential pros and cons of Open Access at multiple levels. This review aims to be a resource for current knowledge on the impacts of Open Access by synthesizing important research in three major areas: academic, economic and societal. While there is clearly much scope for additional research, several key trends are identified, including a broad citation advantage for researchers who publish openly, as well as additional benefits to the non-academic dissemination of their work. The economic impact of Open Access is less well-understood, although it is clear that access to the research literature is key for innovative enterprises, and a range of governmental and non-governmental services. Furthermore, Open Access has the potential to save both publishers and research funders considerable amounts of financial resources, and can provide some economic benefits to traditionally subscription-based journals. The societal impact of Open Access is strong, in particular for advancing citizen science initiatives, and leveling the playing field for researchers in developing countries. Open Access supersedes all potential alternative modes of access to the scholarly literature through enabling unrestricted re-use, and long-term stability independent of financial constraints of traditional publishers that impede knowledge sharing. However, Open Access has the potential to become unsustainable for research communities if high-cost options are allowed to continue to prevail in a widely unregulated scholarly publishing market. Open Access remains only one of the multiple challenges that the scholarly publishing system is currently facing. Yet, it provides one foundation for increasing engagement with researchers regarding ethical standards of publishing and the broader implications of 'Open Research'

Inhomogeneity of the intrinsic magnetic field in superconducting YBa2Cu3OX compounds as revealed by rare-earth EPR-probe

X-band electron paramagnetic resonance on doped Er3+ and Yb3+ ions in Y0.99(Yb,Er)0.01Ba2Cu3OX compounds with different oxygen contents in the wide temperature range (4-120)K have been made. In the superconducting species, the strong dependencies of the linewidth and resonance line position from the sweep direction of the applied magnetic field are revealed at the temperatures significantly below TC. The possible origins of the observed hysteresis are analyzed. Applicability of the presented EPR approach to extract information about the dynamics of the flux-line lattice and critical state parameters (critical current density, magnetic penetration depth, and characteristic spatial scale of the inhomogeneity) is discussedComment: 17 pages, 5 Figures. Renewed versio

Soliton-Magnon Scattering in Two-Dimensional Isotropic Ferromagnets

It is studied the scattering of magnons by the 2d topological Belavin-Polyakov soliton in isotropic ferromagnet. Analytical solutions of the scattering problem are constructed: (i) exactly for any magnon wave vectors for the partial wave with the azimuthal number m=1 (translational mode), and (ii) in the long- and short-wave limits for the rest modes. The magnon mode frequencies are found for the finite size magnets. An effective equation of the soliton motion is constructed. The magnon density of states, connected with the soliton-magnon interaction, is found in a long-wave approximation.Comment: 4 pages, REVTe

Mapping Cropland Abandonment in the Aral Sea Basin with MODIS Time Series

Cropland abandonment is globally widespread and has strong repercussions for regional food security and the environment. Statistics suggest that one of the hotspots of abandoned cropland is located in the drylands of the Aral Sea Basin (ASB), which covers parts of post-Soviet Central Asia, Afghanistan and Iran. To date, the exact spatial and temporal extents of abandoned cropland remain unclear, which hampers land-use planning. Abandoned land is a potentially valuable resource for alternative land uses. Here, we mapped the abandoned cropland in the drylands of the ASB with a time series of the Normalized Difference Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) from 2003–2016. To overcome the restricted ability of a single classifier to accurately map land-use classes across large areas and agro-environmental gradients, “stratum-specific” classifiers were calibrated and classification results were fused based on a locally weighted decision fusion approach. Next, the agro-ecological suitability of abandoned cropland areas was evaluated. The stratum-specific classification approach yielded an overall accuracy of 0.879, which was significantly more accurate ( p &lt; 0.05) than a “global” classification without stratification, which had an accuracy of 0.811. In 2016, the classification results showed that 13% (1.15 Mha) of the observed irrigated cropland in the ASB was idle (abandoned). Cropland abandonment occurred mostly in the Amudarya and Syrdarya downstream regions and was associated with degraded land and areas prone to water stress. Despite the almost twofold population growth and increasing food demand in the ASB area from 1990 to 2016, abandoned cropland was also located in areas with high suitability for farming. The map of abandoned cropland areas provides a novel basis for assessing the causes leading to abandoned cropland in the ASB. This contributes to assessing the suitability of abandoned cropland for food or bioenergy production, carbon storage, or assessing the environmental trade-offs and social constraints of recultivation

Explanation and Elaboration Document for the STROBE-Vet Statement: Strengthening the Reporting of Observational Studies in Epidemiology—Veterinary Extension

The STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) statement was first published in 2007 and again in 2014. The purpose of the original STROBE was to provide guidance for authors, reviewers and editors to improve the comprehensiveness of reporting; however, STROBE has a unique focus on observational studies. Although much of the guidance provided by the original STROBE document is directly applicable, it was deemed useful to map those statements to veterinary concepts, provide veterinary examples and highlight unique aspects of reporting in veterinary observational studies. Here, we present the examples and explanations for the checklist items included in the STROBE-Vet Statement. Thus, this is a companion document to the STROBE-Vet Statement Methods and process document, which describes the checklist and how it was developed

Internal Modes and Magnon Scattering on Topological Solitons in 2d Easy-Axis Ferromagnets

We study the magnon modes in the presence of a topological soliton in a 2d Heisenberg easy-axis ferromagnet. The problem of magnon scattering on the soliton with arbitrary relation between the soliton radius R and the "magnetic length" Delta_0 is investigated for partial modes with different values of the azimuthal quantum numbers m. Truly local modes are shown to be present for all values of m, when the soliton radius is enough large. The eigenfrequencies of such internal modes are calculated analytically on limiting case of a large soliton radius and numerically for arbitrary soliton radius. It is demonstrated that the model of an isotropic magnet, which admits an exact analytical investigation, is not adequate even for the limit of small radius solitons, R<<Delta_0: there exists a local mode with nonzero frequency. We use the data about local modes to derive the effective equation of soliton motion; this equation has the usual Newtonian form in contrast to the case of the easy-plane ferromagnet. The effective mass of the soliton is found.Comment: 33 pages (REVTeX), 12 figures (EPS

Direct and indirect effects of interspecific competition in a highly partitioned guild of reef fishes

Competitive interactions and resource partitioning facilitate species coexistence in complex ecosystems. However, while pairwise interactions between ecologically similar species have been well studied, multi‐species competitive networks have received less attention. When interference competition between two species results in partitioning of resources, this may have indirect consequences for other species distributed along the same resource gradient. Here, we tested whether interference competition between two territorial damselfish influenced the fine‐scale species distributions of five other territorial damselfish in Kimbe Bay, Papua New Guinea. These species partition habitat across three reef zones—the flat, crest, and slope, with distinct patterns of distribution within these zones. We predicted the two species with similar distributions and microhabitat use, Pomacentrus adelus and Pomacentrus bankanensis, would display the greatest level of aggression toward one another. This was tested through an intruder experiment where stimulus fish were introduced into a resident's territory, which confirmed disproportionately high levels of interspecific aggression between these two species. We also predicted that the fine‐scale differences in the distribution of each species were maintained through multi‐species interference competition among neighboring species, with further indirect effects on species that did not directly interact. To test this, we conducted a large‐scale (22 × 10 m) experimental removal of the most abundant species, Po. adelus, and quantified the abundance and distribution of all territorial damselfish species for 6 months to a 25 cm resolution. The main direct competitor, Po. bankanensis, exhibited a marked increase in abundance and expanded its distribution (+1.33 m) to acquire the space previously occupied by Po. adelus. This competitive release triggered indirect effects on the distribution of other neighboring species further back on the reef flat, with Chrysiptera unimaculata moving into the zone formerly occupied by Po. bankanensis. This study indicates that the distinct distribution patterns among the reef crest species are linked to levels of interspecific agonistic behavior. We argue that the competitive release following the removal of a superior competitor resulted in both direct and indirect effects, with the immediate neighbor shifting into the newly available space, followed by successive shifts in species responding to the change in the distributions of their immediate neighbors