Effect of interfacial intermixing on the Dzyaloshinskii-Moriya interaction in Pt/Co/Pt

We study the effect of sputter-deposition conditions, namely, substrate temperature and chamber base pressure, upon the interface quality of epitaxial Pt/Co/Pt thin films with perpendicular magnetic anisotropy. Here we define interface quality to be the inverse of the sum in quadrature of roughness and intermixing. We find that samples with the top Co/Pt layers grown at 250 C exhibit a local maximum in roughness intermixing and that the interface quality is better for lower or higher deposition temperatures, up to 400 C, above which the interface quality degrades. Imaging the expansion of magnetic domains in an in-plane field using wide-field Kerr microscopy, we determine the interfacial Dzyaloshinskii-Moriya interaction (DMI) in films in the deposition temperature range 100 C to 300 C. We find that the net DMI increases as the difference between top and bottom Co interface quality increases. Furthermore, for sufficiently low base pressures, the net DMI increases linearly with the deposition temperature, indicating that fine-tuning of the DMI may be achieved via the deposition conditions

Magnetic properties, domain-wall creep motion, and the Dzyaloshinskii-Moriya interaction in Pt/Co/Ir thin films

We study the magnetic properties of perpendicularly magnetized Pt/Co/Ir thin films and investigate the domain-wall creep method of determining the interfacial Dzyaloshinskii-Moriya (DM) interaction in ultrathin films. Measurements of the Co layer thickness dependence of saturation magnetization, perpendicular magnetic anisotropy, and symmetric and antisymmetric (i.e., DM) exchange energies in Pt/Co/Ir thin films have been made to determine the relationship between these properties. We discuss the measurement of the DM interaction by the expansion of a reverse domain in the domain-wall creep regime. We show how the creep parameters behave as a function of in-plane bias field and discuss the effects of domain-wall roughness on the measurement of the DM interaction by domain expansion. Whereas modifications to the creep law with DM field and in-plane bias fields have taken into account changes in the energy barrier scaling parameter α, we find that both α and the velocity scaling parameter v₀ change as a function of in-plane bias field

Exchange magnon induced resistance asymmetry in permalloy spin-Hall oscillators

We investigate magnetization dynamics in a spin-Hall oscillator using a direct current measurement as well as conventional microwave spectrum analysis. When the current applies an anti-damping spin-transfer torque, we observe a change in resistance which we ascribe mainly to the excitation of incoherent exchange magnons. A simple model is developed based on the reduction of the effective saturation magnetization, quantitatively explaining the data. The observed phenomena highlight the importance of exchange magnons on the operation of spin-Hall oscillators

Interactions of C+(2PJ) with rare gas atoms: incipient chemical interactions, potentials and transport coefficients

Accurate interatomic potentials were calculated for the interaction of a singly charged carbon cation, C+, with a single rare gas atom, RG (RG = Ne–Xe). The RCCSD(T) method and basis sets of quadruple-ζ and quintuple-ζ quality were employed; each interaction energy was counterpoise corrected and extrapolated to the basis set limit. The lowest C+(2P) electronic term of the carbon cation was considered, and the interatomic potentials calculated for the diatomic terms that arise from these: 2Π and 2Σ+. Additionally, the interatomic potentials for the respective spin-orbit levels were calculated, and the effect on the spectroscopic parameters was examined. In doing this, anomalously large spin-orbit splittings for RG = Ar–Xe were found, and this was investigated using multi-reference configuration interaction calculations. The latter indicated a small amount of RG → C+ electron transfer and this was used to rationalize the observations. This is taken as evidence of an incipient chemical interaction, which was also examined via contour plots, Birge–Sponer plots and various population analyses across the C+-RG series (RG = He–Xe), with the latter showing unexpected results. Trends in several spectroscopic parameters were examined as a function of the increasing atomic number of the RG atom. Finally, each set of RCCSD(T) potentials was employed, including spin-orbit coupling to calculate the transport coefficients for C+ in RG, and the results were compared with the limited available data

Measuring hearing in wild beluga whales

Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in "The Effects of Noise on Aquatic Life II," edited by Arthur N. Popper, Anthony Hawkins, 729-735. New York, NY: Springer, 2016. doi: 10.1007/978-1-4939-2981-8_88.We measured the hearing abilities of seven wild beluga whales (Delphinapterus leucas) during a collection-and-release experiment in Bristol Bay, AK, USA. Here we summarize the methods and initial data from one animal, discussing the implications of this experiment. Audiograms were collected from 4-150 kHz. The animal with the lowest threshold heard best at 80 kHz and demonstrated overall good hearing from 22-110 kHz. The robustness of the methodology and data suggest AEP audiograms can be incorporated into future collection-and-release health assessments. Such methods may provide high-quality results for multiple animals facilitating population-level audiograms and hearing measures in new species.Project funding and field support provided by Georgia Aquarium and the National Marine Mammal Laboratory of the Alaska Fisheries Science Center (NMML/AFSC). Field work also supported by National Marine Fisheries Service Alaska Regional Office (NMFS AKR), WHOI Arctic Research Initiative, WHOI Ocean Life Institute, U.S. Fish and Wildlife Service, Bristol Bay Native Association, Alaska SeaLife Center, Shedd Aquarium and Mystic Aquarium. Audiogram analyses were funded by the Office of Naval Research award number N000141210203 (from Michael Weise)

A Candidate Sub-Parsec Supermassive Binary Black Hole System

We identify SDSS J153636.22+044127.0, a QSO discovered in the Sloan Digital Sky Survey, as a promising candidate for a binary black hole system. This QSO has two broad-line emission systems separated by 3500 km/sec. The redder system at z=0.3889 also has a typical set of narrow forbidden lines. The bluer system (z=0.3727) shows only broad Balmer lines and UV Fe II emission, making it highly unusual in its lack of narrow lines. A third system, which includes only unresolved absorption lines, is seen at a redshift, z=0.3878, intermediate between the two emission-line systems. While the observational signatures of binary nuclear black holes remain unclear, J1536+0441 is unique among all QSOs known in having two broad-line regions, indicative of two separate black holes presently accreting gas. The interpretation of this as a bound binary system of two black holes having masses of 10^8.9 and 10^7.3 solar masses, yields a separation of ~ 0.1 parsec and an orbital period of ~100 years. The separation implies that the two black holes are orbiting within a single narrow-line region, consistent with the characteristics of the spectrum. This object was identified as an extreme outlier of a Karhunen-Loeve Transform of 17,500 z < 0.7 QSO spectra from the SDSS. The probability of the spectrum resulting from a chance superposition of two QSOs with similar redshifts is estimated at 2X10^-7, leading to the expectation of 0.003 such objects in the sample studied; however, even in this case, the spectrum of the lower redshift QSO remains highly unusual.Comment: 8 pages, 2 figures, Nature in pres

Beyond the Refugee Crisis how the UK news media represent asylum seekers across national boundaries

Migration is one of the most pressing, divisive issues in global politics today, and media play a crucial role in how communities understand and respond. This study examines how UK newspapers (n = 974) and popular news websites (n = 1044) reported on asylum seekers throughout 2017. It contributes to previous literature in two important ways. First, by examining the ‘new normal’ of daily news coverage in the wake of the 2015 ‘refugee crisis’ in Europe. Second, by looking at how asylum seekers from different regions are represented. The content analysis finds significant variations in how asylum seekers are reported, including terminology use and topics they are associated with. The paper also identifies important commonalities in how all asylum seekers are represented - most notably, the dominance of political elites as sources across all media content. It argues that Entman’s ‘cascade network model’ can help to explain this, with elites in one country able to influence transnational reports

A recent whole-genome duplication divides populations of a globally-distributed microsporidian

This is the final version of the article. Available from Oxford University Press via the DOI in this record.The Microsporidia are a major group of intracellular fungi and important parasites of animals including insects, fish, and immunocompromised humans. Microsporidian genomes have undergone extreme reductive evolution but there are major differences in genome size and structure within the group: some are prokaryote-like in size and organisation (<3 Mb of gene-dense sequence) whilst others have more typically eukaryotic genome architectures. To gain fine-scale, population-level insight into the evolutionary dynamics of these tiny eukaryotic genomes, we performed the broadest microsporidian population genomic study to date, sequencing geographically isolated strains of Spraguea, a marine microsporidian infecting goosefish worldwide. Our analysis revealed that population structure across the Atlantic Ocean is associated with a conserved difference in ploidy, with American and Canadian isolates sharing an ancestral whole genome duplication that was followed by widespread pseudogenisation and sorting-out of paralogue pairs. Whilst past analyses have suggested de novo gene formation of microsporidian-specific genes, we found evidence for the origin of new genes from noncoding sequence since the divergence of these populations. Some of these genes experience selective constraint, suggesting the evolution of new functions and local host adaptation. Combining our data with published microsporidian genomes, we show that nucleotide composition across the phylum is shaped by a mutational bias favouring A and T nucleotides, which is opposed by an evolutionary force favouring an increase in genomic GC content. This work reveals ongoing dramatic reorganisation of genome structure and the evolution of new gene functions in modern microsporidians despite extensive genomic streamlining in their common ancestor.The authors would like to thank John Brookfield and David Studholme for helpful discussions. This work was supported by a Marie Curie Intra-European postdoctoral fellowship (T.A.W.) and the European Research Council Advanced Investigator Programme and the Wellcome Trust (grant numbers ERC- 2010- AdG-268701 045404 to T.M.E.) It is also supported by a Royal Society University Research Fellowship (B.A.P.W.)

Appetite suppressants and valvular heart disease - a systematic review

Background Although appetite suppressants have been implicated in the development of valvular heart disease, the exact level of risk is still uncertain. Initial studies suggested that as many as 1 in 3 exposed patients were affected, but subsequent research has yielded substantially different figures. Our objective was to systematically assess the risk of valvular heart disease with appetite suppressants. Methods We accepted studies involving obese patients treated with any of the following appetite suppressants: fenfluramine, dexfenfluramine, and phentermine. Three types of studies were reviewed: controlled and uncontrolled observational studies, and randomized controlled trials. Outcomes of interest were echocardiographically detectable aortic regurgitation of mild or greater severity, or mitral regurgitation of moderate or greater severity. Results Of the 1279 patients evaluated in seven uncontrolled cohort studies, 236 (18%) and 60 (5%) were found to have aortic and mitral regurgitation, respectively. Pooled data from six controlled cohort studies yielded, for aortic regurgitation, a relative risk ratio of 2.32 (95% confidence intervals 1.79 to 3.01, p < 0.00001) and an attributable rate of 4.9%, and for mitral regurgitation, a relative risk ratio of 1.55 (95% confidence intervals 1.06 to 2.25, p = 0.02) with an attributable rate of 1.0%. Only one case of valvular heart disease was detected in 57 randomized controlled trials, but this was judged unrelated to drug therapy. Conclusions The risk of valvular heart disease is significantly increased by the appetite suppressants reviewed here. Nevertheless, when considering all the evidence, valvulopathy is much less common than suggested by the initial, less methodologically rigorous studies