Resonance in Magnetostatically Coupled Transverse Domain Walls

We have observed the eigenmodes of coupled transverse domain walls in a pair of ferromagnetic nanowires. Although the pair is coupled magnetostatically, its spectrum is determined by a combination of pinning by edge roughness and dipolar coupling of the two walls. Because the corresponding energy scales are comparable, the coupling can be observed only at the smallest wire separations. A model of the coupled wall dynamics reproduces the experiment quantitatively, allowing for comparisons with the estimated pinning and domain wall coupling energies. The results have significant implications for the dynamics of devices based on coupled domain walls.Comment: 11 pages, 4 figure

FUNDING AND OVERFUNDING PHENOMENA IN CROWDFUNDING: RELEVANCE OF PLATFORM CHOICE AND VARYING INDUSTRY DYNAMICS

This study provides new evidence on factors relevant for the success of crowdfunding campaigns run in Europe between 2015 and 2017 on the most popular crowdfunding platforms in Germany/Austria – Kickstarter.com and Startnext.com. In particular, for this study, a sample of 10,514 campaigns from Germany and Austria for the first time serves as a basis for identifying the determinants of the level of projects’ (over-)funding. For crowdfunding projects, an increase in a project’s funding goal results in higher funding on both platforms, but this does not guarantee success, i.e. reaching the relevant funding goal. Projects with a higher success probability show lower funding goals, especially if launched on Startnext.com. In contrast, a longer duration negligibly increases the amount raised on Startnext and slightly decreases on Kickstarter. On Startnext, projects from the Art cluster have a higher chance to succeed, while these from the Technology cluster show smaller success probabilities as they regularly get less funding. On Kickstarter, projects from the Art, Technology, or Lifestyle field reach higher financing as compared to the Sustainability area. We show that the uncertainty about market size and project/founder quality leads to diverging over- and underfunding levels across platforms and industry clusters, which is of core importance to interested stakeholder groups. Key words: crowdfunding, crowd, reward, Kickstarter, Startnex

Resonance in Magnetostatically Coupled Transverse Domain Walls

This is the author accepted manuscript. The final version is available from American Physical Society via the DOI in this record.We have observed the eigenmodes of coupled transverse domain walls in a pair of ferromagnetic nanowires. Although the pair is coupled magnetostatically, its spectrum is determined by a combination of pinning by edge roughness and dipolar coupling of the two walls. Because the corresponding energy scales are comparable, the coupling can be observed only at the smallest wire separations. A model of the coupled wall dynamics reproduces the experiment quantitatively, allowing for comparisons with the estimated pinning and domain wall coupling energies. The results have significant implications for the dynamics of devices based on coupled domain walls.This work was supported in part by the NSF MRSEC program under Grant No. DMR-0804244 and the NSF/NRI NEB program under Grant No. ECCS-1124831, as well as the EU Marie Curie IOF Project No. 299376 and the European Community Seventh Framework Programme Contract No. 247368: 3SPIN. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program

Loss Potential and Disclosures Related to Credit Derivatives - A Cross-Country Comparison of Corporate Bond Funds under U.S. and German Regulation

This study analyzes the loss potential arising from investments into CDS for a sample of large U.S. and German mutual funds. Further, it investigates whether the comments funds make on CDS use in periodic fund reports are consistent with the disclosed CDS holdings. For several funds in the U.S., the potential losses arising from selling CDS protection are almost as high as net assets, while in Germany, this potential can be even higher. Regarding the information funds provide to investors about their use of CDS, the results of the study suggest that comments on CDS contained in periodic reports are often unspecific and sometimes misleading. Thus, investors might have to analyze portfolio holdings in order to learn about the true investment behavior of funds. For instance, in Germany, funds that use more short than long CDS often state that they only use long CDS for hedging purposes. Based on the results, it seems advisable that regulators in both countries tighten rules restricting the speculative use of derivatives by funds to a reasonable level, as well as implement more standardized disclosure policies

Loss Potential and Disclosures Related to Credit Derivatives - A Cross-Country Comparison of Corporate Bond Funds under U.S. and German Regulation

This study analyzes the loss potential arising from investments into CDS for a sample of large U.S. and German mutual funds. Further, it investigates whether the comments funds make on CDS use in periodic fund reports are consistent with the disclosed CDS holdings. For several funds in the U.S., the potential losses arising from selling CDS protection are almost as high as net assets, while in Germany, this potential can be even higher. Regarding the information funds provide to investors about their use of CDS, the results of the study suggest that comments on CDS contained in periodic reports are often unspecific and sometimes misleading. Thus, investors might have to analyze portfolio holdings in order to learn about the true investment behavior of funds. For instance, in Germany, funds that use more short than long CDS often state that they only use long CDS for hedging purposes. Based on the results, it seems advisable that regulators in both countries tighten rules restricting the speculative use of derivatives by funds to a reasonable level, as well as implement more standardized disclosure policies

Manager Characteristics and Credit Derivative Use by U.S. Corporate Bond Funds

This study provides a comprehensive overview of the use of credit default swaps by U.S. corporate bond funds and analyzes in detail whether certain characteristics of managers, in addition to the fundamentals of a fund, determine how their use these credit derivatives. Results suggest that a manager’s education, age, experience, and skill are positively correlated with a fund’s CDS holdings. In particular, managers holding a master’s degree or educated at prestigious universities prefer using CDS. However, funds with older, more experienced managers or these keeping higher assets under their management are more likely to take on credit risk via selling CDS protection. Younger managers or managers that were educated at prestigious universities rather tend to buy CDS protection possibly due to differing concerns about their careers. If considering the Heckman correction for self-selection of funds into CDS use, the aforementioned findings remain stable

Magnetic domain wall dynamics in patterned nanowires

University of Minnesota Ph.D. dissertation. August 2015. Major: Physics. Advisor: Paul Crowell. 1 computer file (PDF); ix, 118 pages.This thesis describes the dynamics of magnetic domain walls in two very different ferromagnetic systems. In one system, the magnetization prefers to lie in the plane of the film, which leads to relatively large and complex domain wall structures. In the other system, in which the magnetization is oriented out of the film plane, the domain walls are much smaller and simpler but are more susceptible to the influence of interface effects. In both cases, the dynamics of the domain walls are strongly influenced by the presence of defects, e.g. the inevitable edge and surface roughness of a patterned nanowire. In this dissertation, I explore the resonance dynamics of isolated and coupled transverse domain walls. I show that an intrinsic domain wall mode arises as a result of the pinning effects of the wire edge roughness, by comparing experimental results with micromagnetic simulations. Because of the strong pinning effects, the dynamics of coupled transverse domain walls are also influenced by the edge roughness, leading to the presence of two distinct modes. Using a simple onedimensional model, the domain wall separation dependence of the two resonant frequencies is explained. As edge roughness is unavoidable, I argue that stochastic pinning effects will be present in other DW resonance experiments. I also explore the propagation of a domain wall through a wire, driven under the influence of magnetic fields and electrical currents. The velocity of the domain wall is shown to follow a model where the domain wall moves via a succession of thermally-activated jumps between pinning sites in the wire. A current-to-field equivalence is established, and the nature of this equivalence is explored through the application of static magnetic fields in the plane of the film. These fields influence the internal structure of the domain wall and thus the torques generated by the current. From the symmetry of these torques, it is revealed that the application of a current leads to a spin-Hall effect in an adjacent non-magnetic layer in the film structure, which influences the domain wall dynamics. A nontrivial suppression of the current-to-field efficiency is observed under large in-plane fields, which is potentially linked to how the domain wall moves through a defect landscape

Ovine pedomics : the first study of the ovine foot 16S rRNA-based microbiome

We report the first study of the bacterial microbiome of ovine interdigital skin based on 16S rRNA by pyrosequencing and conventional cloning with Sanger-sequencing. Three flocks were selected, one a flock with no signs of footrot or interdigital dermatitis, a second flock with interdigital dermatitis alone and a third flock with both interdigital dermatitis and footrot. The sheep were classified as having either healthy interdigital skin (H), interdigital dermatitis (ID) or virulent footrot (VFR). The ovine interdigital skin bacterial community varied significantly by flock and clinical condition. The diversity and richness of operational taxonomic units was greater in tissue from sheep with ID than H or VFR affected sheep. Actinobacteria, Bacteriodetes, Firmicutes and Proteobacteria were the most abundant phyla comprising 25 genera. Peptostreptococcus, Corynebacterium and Staphylococcus were associated with H, ID and VFR respectively. Sequences of Dichelobacter nodosus, the causal agent of ovine footrot, were not amplified due to mismatches in the 16S rRNA universal forward primer (27F). A specific real time PCR assay was used to demonstrate the presence of D. nodosus which was detected in all samples including the flock with no signs of ID or VFR. Sheep with ID had significantly higher numbers of D. nodosus (104-109 cells/g tissue) than those with H or VFR feet

Characterisation of the bacterial and fungal communities associated with different lesion sizes of Dark Spot Syndrome occurring in the Coral Stephanocoenia intersepta

The number and prevalence of coral diseases/syndromes are increasing worldwide. Dark Spot Syndrome (DSS) afflicts numerous coral species and is widespread throughout the Caribbean, yet there are no known causal agents. In this study we aimed to characterise the microbial communities (bacteria and fungi) associated with DSS lesions affecting the coral Stephanocoenia intersepta using nonculture molecular techniques. Bacterial diversity of healthy tissues (H), those in advance of the lesion interface (apparently healthy AH), and three sizes of disease lesions (small, medium, and large) varied significantly (ANOSIM R = 0.052 p,0.001), apart from the medium and large lesions, which were similar in their community profile. Four bacteria fitted into the pattern expected from potential pathogens; namely absent from H, increasing in abundance within AH, and dominant in the lesions themselves. These included ribotypes related to Corynebacterium (KC190237), Acinetobacter (KC190251), Parvularculaceae (KC19027), and Oscillatoria (KC190271). Furthermore, two Vibrio species, a genus including many proposed coral pathogens, dominated the disease lesion and were absent from H and AH tissues, making them candidates as potential pathogens for DSS. In contrast, other members of bacteria from the same genus, such as V. harveyii were present throughout all sample types, supporting previous studies where potential coral pathogens exist in healthy tissues. Fungal diversity varied significantly as well, however the main difference between diseased and healthy tissues was the dominance of one ribotype, closely related to the plant pathogen, Rhytisma acerinum, a known causal agent of tar spot on tree leaves. As the corals’ symbiotic algae have been shown to turn to a darker pigmented state in DSS (giving rise to the syndromes name), the two most likely pathogens are R. acerinum and the bacterium Oscillatoria, which has been identified as the causal agent of the colouration in Black Band Disease, another widespread coral disease

Distinct bacterial microbiomes associate with the deep-sea coral Eguchipsammia fistula from the Red Sea and from aquaria settings.

Microbial communities associated with deep-sea corals are beginning to be studied in earnest and the contribution of the microbiome to host organismal function remains to be investigated. In this regard, the ability of the microbiome to adjust to prevailing environmental conditions might provide clues to its functional importance. In this study, we characterized bacterial community composition associated with the deep-sea coral Eguchipsammia fistula under natural (in situ) and aquaria (ex situ) settings using 16S rRNA gene amplicon sequencing. We compared freshly collected Red Sea coral specimens with those reared for >1 year at conditions that partially differed from the natural environment, in particular regarding increased oxygen and food availability under ex situ conditions. We found substantial differences between the microbiomes associated with corals under both environmental settings. The core microbiome comprised only six bacterial taxa consistently present in all corals, whereas the majority of bacteria were exclusively associated either with freshly collected corals or corals under long-term reared aquaria settings. Putative functional profiling of microbial communities showed that corals in their natural habitat were enriched for processes indicative of a carbon- and nitrogen-limited environment, which might be reflective of differences in diet under in situ and ex situ conditions. The ability of E. fistula to harbor distinct microbiomes under different environmental settings might contribute to the flexibility and phenotypic plasticity of this cosmopolitan coral. Future efforts should further assess the role of these different bacteria in holobiont function, in particular since E. fistula is naturally present in markedly different environments.This work was supported by baseline funds to CRV by King Abdullah University of Science and Technology (KAUST) and by the Center Competitive Funding (CCF) Program FCC/1/1973-18-01