Imaging mesoscopic antiferromagnetic spin textures in the dilute limit from single-geometry resonant coherent x-ray diffraction

The detection and manipulation of antiferromagnetic domains and topological antiferromagnetic textures are of central interest to solid-state physics. A fundamental step is identifying tools to probe the mesoscopic texture of an antiferromagnetic order parameter. In this work, we demonstrate that Bragg coherent diffractive imaging can be extended to study the mesoscopic texture of an antiferromagnetic order parameter using resonant magnetic x-ray scattering. We study the onset of the antiferromagnet transition in PrNiO₃, focusing on a temperature regime in which the antiferromagnetic domains are dilute in the beam spot and the coherent diffraction pattern modulating the antiferromagnetic peak is greatly simplified. We demonstrate that it is possible to extract the arrangements and sizes of these domains from single diffraction patterns and show that the approach could be extended to a time-structured light source to study the motion of dilute domains or the motion of topological defects in an antiferromagnetic spin texture.

Real-space observation of fluctuating antiferromagnetic domains

Magnetic domains play a fundamental role in physics of magnetism and its technological applications. Dynamics of antiferromagnetic domains is poorly understood, although antiferromagnets are expected to be extensively used in future electronic devices wherein it determines the stability and operational speed. Dynamics of antiferromagnets also features prominently in the studies of topological quantum matter. Real-space imaging of fluctuating antiferromagnetic domains is therefore highly desired but has never been demonstrated. We use coherent x-ray diffraction to obtain videos of fluctuating micrometer-scale antiferromagnetic domains in Ni₂MnTeO₆ on time scales from 10^-1 to 10³ s. In the collinear phase, thermally activated domain wall motion is observed in the vicinity of the Néel temperature. Unexpectedly, the fluctuations persist through the full range of the higher-temperature helical phase. These observations illustrate the high potential significance of the dynamic domain imaging in phase transition studies and in magnetic device research.

Tuning spin excitations in magnetic films by confinement

Spin excitations of magnetic thin films are the founding element for magnetic devices in general. While spin dynamics have been extensively studied in bulk materials, the behaviour in mesoscopic films is less known due to experimental limitations. Here, we employ resonant inelastic X-ray scattering to investigate the spectrum of spin excitations in mesoscopic Fe films, from bulk-like films down to three unit cells. In bulk samples, we find isotropic, dispersive ferromagnons consistent with previous neutron scattering results for bulk single crystals. As the thickness is reduced, these ferromagnetic spin excitations renormalize to lower energies along the out-of-plane direction while retaining their dispersion in the in-plane direction. This thickness dependence is captured by simple Heisenberg model calculations accounting for the confinement in the out-of-plane direction through the loss of Fe bonds. Our findings highlight the effects of mesoscopic scaling on spin dynamics and identify thickness as a knob for fine tuning and controlling magnetic properties.

Periodontal Inflammation Primes the Systemic Innate Immune Response

The presence of periodontal diseases (PDs) often strongly correlates with other severe chronic inflammatory conditions, including cardiovascular disease, diabetes, and arthritis. However, the mechanisms through which these diseases interact are unclear. In PD, tissue and bone destruction in the mouth is driven by elevated recruitment of polymorphonuclear neutrophils (PMNs), which are primed and recruited from the circulation to sites of inflammation. We predicted that systemic effects on PMN mobilization or priming could account for the interaction between PD and other inflammatory conditions. We tested this using a mouse model of ligature-induced PD and found elevated PMN counts specifically in bone marrow, supporting a systemic effect of periodontal tissue inflammation on PMN production. In contrast, mice with induced peritonitis had elevated PMN counts in the blood, peritoneum, and colon. These elevated counts were further significantly increased when acute peritonitis was induced after ligature-induced PD in mice, revealing a synergistic effect of multiple inflammatory events on PMN levels. Flow cytometric analysis of CD marker expression revealed enhanced priming of PMNs from mice with both PD and peritonitis compared to mice with peritonitis alone. Thus, systemic factors associated with PD produce hyperinflammatory PMN responses during a secondary infection. To analyze this systemic effect in humans, we induced gingival inflammation in volunteers and also found significantly increased activation of blood PMNs in response to ex vivo stimulation, which reverted to normal following resolution of gingivitis. Together, these results demonstrate that periodontal tissue inflammation has systemic effects that predispose toward an exacerbated innate immune response. This indicates that peripheral PMNs can respond synergistically to simultaneous and remote inflammatory triggers and therefore contribute to the interaction between PD and other inflammatory conditions. This suggests larger implications of PD beyond oral health and reveals potential new approaches for treating systemic inflammatory diseases that interact with PD.

Enhanced Electron-Phonon Coupling for Charge-Density-Wave Formation in La_{1.8-x}Eu_{0.2}Sr_{x}CuO_{4+δ}

Charge density wave (CDW) correlations are prevalent in all copper-oxide superconductors. While CDWs in conventional metals are driven by coupling between lattice vibrations and electrons, the role of the electron-phonon coupling (EPC) in cuprate CDWs is strongly debated. Using Cu L_{3} edge resonant inelastic x-ray scattering, we study the CDW and Cu-O bond-stretching phonons in the stripe-ordered cuprate La_{1.8-x}Eu_{0.2}Sr_{x}CuO_{4+δ}. We investigate the interplay between charge order and EPC as a function of doping and temperature and find that the EPC is enhanced in a narrow momentum region around the CDW ordering vector. By detuning the incident photon energy from the absorption resonance, we extract an EPC matrix element at the CDW ordering vector of M≃0.36  eV, which decreases to M≃0.30  eV at high temperature in the absence of the CDW. Our results suggest a feedback mechanism in which the CDW enhances the EPC which, in turn, further stabilizes the CDW.

Strongly Correlated Charge Density Wave in La_{2-x}Sr_{x}CuO_{4} Evidenced by Doping-Dependent Phonon Anomaly

The discovery of charge-density-wave-related effects in the resonant inelastic x-ray scattering spectra of cuprates holds the tantalizing promise of clarifying the interactions that stabilize the electronic order. Here, we report a comprehensive resonant inelastic x-ray scattering study of La_{2-x}Sr_{x}CuO_{4} finding that charge-density wave effects persist up to a remarkably high doping level of x=0.21 before disappearing at x=0.25. The inelastic excitation spectra remain essentially unchanged with doping despite crossing a topological transition in the Fermi surface. This indicates that the spectra contain little or no direct coupling to electronic excitations near the Fermi surface, rather they are dominated by the resonant cross section for phonons and charge-density-wave-induced phonon softening. We interpret our results in terms of a charge-density wave that is generated by strong correlations and a phonon response that is driven by the charge-density-wave-induced modification of the lattice.

Genital tract infections in HIV-infected pregnant women in South West London

There are minimal UK data on the prevalence of genital tract infections in HIV‐infected pregnant women. British HIV Association guidelines suggest sexually transmitted infection (STI) screening as early as possible in pregnancy with consideration given to repeat at 28 weeks’ gestation. A retrospective case notes review of HIV-infected pregnant women at four South London HIV Centres (1 January 2004–1 January 2014) was carried out. Five hundred and ninety-eight pregnancies in 384 patients were identified. Median age 32 years (interquartile range [IQR] 27–36) and 96% (n = 346) were heterosexually infected. HIV was diagnosed antenatally in 21% of pregnancies (n = 107). Seventy-seven per cent of women (n = 384) were of Black African ethnicity and 75% were born in sub-Saharan Africa with 14% UK-born. The majority of pregnancies (279/507) were reported to be unplanned with 42 women proceeding to termination of pregnancy. A regular male partner was reported in 95% of pregnancies (n = 539) with median relationship duration (n = 347) of four years (IQR 1.5–7.0); 11/324 (3.4%) women reported additional sexual partners during the pregnancy. 76.6% (n = 427) of women had an initial STI screen which was done in the first trimester in 52.1%; 32.1% of women had a repeat STI screen in pregnancy, 96% of which was done in the third trimester. Overall, 61 (14.3%) women were diagnosed with at least one STI during their pregnancy. Vaginal candidiasis and bacterial vaginosis were diagnosed in 27.6% (n = 100) and 21.7% (n = 73) of pregnancies, respectively. STI prevalence was low and obstetric outcomes favourable in this cohort of women. Further information about STI prevalence in this population may impact future screening guidelines.

Distinction between pristine and disorder-perturbed charge density waves in ZrTe3

Charge density waves (CDWs) in the cuprate high-temperature superconductors have evoked much interest, yet their typical short-range nature has raised questions regarding the role of disorder. Here we report a resonant X-ray diffraction study of ZrTe[Formula: see text], a model CDW system, with focus on the influence of disorder. Near the CDW transition temperature, we observe two independent signals that arise concomitantly, only to become clearly separated in momentum while developing very different correlation lengths in the well-ordered state that is reached at a distinctly lower temperature. Anomalously slow dynamics of mesoscopic charge domains are further found near the transition temperature, in spite of the expected strong thermal fluctuations. Our observations signify the presence of distinct experimental fingerprints of pristine and disorder-perturbed CDWs. We discuss the latter also in the context of Friedel oscillations, which we argue might promote CDW formation via a self-amplifying process.

Imaging antiferromagnetic antiphase domain boundaries using magnetic Bragg diffraction phase contrast

Manipulating magnetic domains is essential for many technological applications. Recent breakthroughs in Antiferromagnetic Spintronics brought up novel concepts for electronic device development. Imaging antiferromagnetic domains is of key importance to this field. Unfortunately, some of the basic domain types, such as antiphase domains, cannot be imaged by conventional techniques. Herein, we present a new domain projection imaging technique based on the localization of domain boundaries by resonant magnetic diffraction of coherent X rays. Contrast arises from reduction of the scattered intensity at the domain boundaries due to destructive interference effects. We demonstrate this approach by imaging antiphase domains in a collinear antiferromagnet Fe₂Mo₃O₈, and observe evidence of domain wall interaction with a structural defect. This technique does not involve any numerical algorithms. It is fast, sensitive, produces large-scale images in a single-exposure measurement, and is applicable to a variety of magnetic domain types.

Imaging the antiferromagnetic (AFM) domains facilitates the understanding and design of AFM spintronics but is still challenging. Here the authors show an imaging approach for antiphase domains in AFM Fe₂Mo₃O₈ by resonantly scattered coherent soft X-rays, which is also applicable to collinear antiferromagnets.

Orbital Domain Dynamics in Magnetite below the Verwey Transition

The metal-insulator phase transition in magnetite, known as the Verwey transition, is characterized by a charge-orbital ordering and a lattice transformation from a cubic to monoclinic structure. We use x-ray photon correlation spectroscopy to investigate the dynamics of this charge-orbitally ordered insulating phase undergoing the insulator-to-metal transition. By tuning to the Fe L_{3} edge at the (001/2) superlattice peak, we probe the evolution of the Fe t_{2g} orbitally ordered domains present in the low temperature insulating phase and forbidden in the high temperature metallic phase. We observe two distinct regimes below the Verwey transition. In the first regime, magnetite follows an Arrhenius behavior and the characteristic timescale for orbital fluctuations decreases as the temperature increases. In the second regime, magnetite phase separates into metallic and insulating domains, and the kinetics of the phase transition is dictated by metallic-insulating interfacial boundary conditions.

Integrated analysis of genetic variation and gene expression reveals novel variant for increased warfarin dose requirement in African Americans

Essentials Genetic variants controlling gene regulation have not been explored in pharmacogenomics. We tested liver expression quantitative trait loci for association with warfarin dose response. A novel predictor for increased warfarin dose response in African Americans was identified. Precision medicine must take into account population-specific variation in gene regulation.

SUMMARY

Background Warfarin is commonly used to control and prevent thromboembolic disorders. However, because of warfarin's complex dose-requirement relationship, safe and effective use is challenging. Pharmacogenomics-guided warfarin dosing algorithms that include the well-established VKORC1 and CYP2C9 polymorphisms explain only a small proportion of inter-individual variability in African Americans (AAs). Objectives We aimed to assess whether transcriptomic analyses could be used to identify regulatory variants associated with warfarin dose response in AAs. Patients/Methods We identified a total of 56 expression quantitative trait loci (eQTLs) for CYP2C9, VKORC1 and CALU derived from human livers and evaluated their association with warfarin dose response in two independent AA warfarin patient cohorts. Results We found that rs4889606, a strong cis-eQTL for VKORC1 (log10 Bayes Factor = 12.02), is significantly associated with increased warfarin daily dose requirement (β = 1.1; 95% confidence interval [CI] 0.46 to 1.8) in the discovery cohort (n = 305) and in the replication cohort (β = 1.04; 95% CI 0.33 -1.7; n = 141) after conditioning on relevant covariates and the VKORC1 -1639G>A (rs9923231) variant. Inclusion of rs4889606 genotypes, along with CYP2C9 alleles, rs9923231 genotypes and clinical variables, explained 31% of the inter-patient variability in warfarin dose requirement. We demonstrate different linkage disequilibrium patterns in the region encompassing rs4889606 and rs9923231 between AAs and European Americans, which may explain the increased dose requirement found in AAs. Conclusion Our approach of interrogating eQTLs identified in liver has revealed a novel predictor of warfarin dose response in AAs. Our work highlights the utility of leveraging information from regulatory variants mapped in the liver to uncover novel variants associated with drug response and the importance of population-specific research.

Lopinavir and atazanavir in pregnancy: comparable infant outcomes, virological efficacies and preterm delivery rates

OBJECTIVES

The aim of the study was to identify differences in infant outcomes, virological efficacy, and preterm delivery (PTD) outcome between women exposed to lopinavir/ritonavir (LPV/r) and those exposed to atazanavir/ritonavir (ATV/r).

METHODS

A retrospective case note review was carried out. The case notes of 493 women who conceived while on LPV/r or ATV/r or initiated LPV/r or ATV/r during pregnancy and who delivered between 1 September 2007 and 30 August 2012 were reviewed. Data collected included demographics, antiretroviral use, HIV markers, and pregnancy and infant outcomes. Infant outcomes, virological efficacies and PTD rates for LPV/r and ATV/r were compared.

RESULTS

A total of 306 women received LPV/r (82 conceiving while on the drug and 224 commencing it post-conception) and 187 received ATV/r (96 conceiving while on the drug and 91 commencing it post-conception). Comparing the two protease inhibitors (PIs), viral suppression rates were similar and, in women starting antiretroviral therapy (ART) post-conception, the median times to first undetectable HIV viral load were not significantly different (P = 0.64). PTD rates did not differ by therapy overall (ATV/r, 13%; LPV/r, 14%) or when considering the timing of first exposure (conceiving on ART, P = 0.81; commencing ART in pregnancy, P = 0.08). Poor fetal outcomes were very uncommon. There were two transmissions, giving a mother-to-child transmission (MTCT) rate of 0.4% (95% confidence interval 0.05-1.5%).

CONCLUSIONS

Both ART regimens were well tolerated and successful in preventing MTCT. No significant differences in tolerability or in pregnancy or infant outcomes were observed, which supports the provision of a choice of PI in pregnancy.

Charge-induced equilibrium dynamics and structure at the Ag(001)–electrolyte interface

The applied potential dependent rate of atomic step motion of the Ag(001) surface in weak NaF electrolyte has been measured using a new extension of the technique of X-ray Photon Correlation Spectroscopy (XPCS).

Growth of arrays of oriented epitaxial platinum nanoparticles with controlled size and shape by natural colloidal lithography

We developed a method for production of arrays of platinum nanocrystals of controlled size and shape using templates from ordered silica bead monolayers. Silica beads with nominal sizes of 150 and 450 nm were self-assembled into monolayers over strontium titanate single crystal substrates. The monolayers were used as shadow masks for platinum metal deposition on the substrate using the three-step evaporation technique. Produced arrays of epitaxial platinum islands were transformed into nanocrystals by annealing in a quartz tube in nitrogen flow. The shape of particles is determined by the substrate crystallography, while the size of the particles and their spacing are controlled by the size of the silica beads in the monolayer mask. As a proof of concept, arrays of platinum nanocrystals of cubooctahedral shape were prepared on (100) strontium titanate substrates. The nanocrystal arrays were characterized by atomic force microscopy, scanning electron microscopy, and synchrotron X-ray diffraction techniques.

Ethnicity-specific pharmacogenetics: the case of warfarin in African Americans

Using a derivation cohort (N=349), we developed the first warfarin dosing algorithm that includes recently discovered polymorphisms in VKORC1 and CYP2C9 associated with warfarin dose requirement in African Americans (AAs). We tested our novel algorithm in an independent cohort of 129 AAs and compared the dose prediction to the International Warfarin Pharmacogenetics Consortium (IWPC) dosing algorithms. Our algorithm explains more of the phenotypic variation (R(2)=0.27) than the IWPC pharmacogenomics (R(2)=0.15) or clinical (R(2)=0.16) algorithms. Among high-dose patients, our algorithm predicted a higher proportion of patients within 20% of stable warfarin dose (45% vs 29% and 2% in the IWPC pharmacogenomics and clinical algorithms, respectively). In contrast to our novel algorithm, a significant inverse correlation between predicted dose and percent West African ancestry was observed for the IWPC pharmacogenomics algorithm among patients requiring ⩾60 mg per week (β=-2.04, P=0.02).

Neutron investigations of rotational motions in monolayer and multilayer films at the interface of MgO and graphite surfaces

Recent experimental investigations of the rotational motion of methane and molecular hydrogen using inelastic neutron scattering (INS) measurements in combination with thermodynamic techniques have provided a unique view of the evolution of the interaction of these two molecules with the MgO (100) surface and graphite basal plane. Despite significant differences in the chemical and physical properties and surface symmetry of these two adsorbents, the dynamical behavior of the adsorbed films is remarkably similar. The interaction of a CH4 monolayer solid with MgO and graphite, as monitored by the behavior of the J = 0 --> J = 1 free rotor transition, is so strong that there is no evidence for unhindered rotation of the molecule below 20 K. Using this same transition as a probe, H2 monolayer solids exhibit nearly free or significantly hindered motion on graphite and MgO (100) surfaces, respectively. Investigations of CH4 and H2 multilayer films on MgO find that once the film thickness exceeds approximately 3 layers, the molecule-molecule interactions predominantly determine the dynamical properties of the molecular film furthest from the surface. INS signals indicate that the dynamical motion in thicker films is closely related to that observed in the bulk system. The results of these studies serve as a valuable pathway for developing a qualitatively accurate description of the potential energy surfaces that govern the microscopic properties of these systems.

Current concepts of tumour metastasis

BACKGROUND

Tumour metastasis remains the principal cause of treatment failure and poor prognosis in patients with cancer. Recent advances in our understanding of the biology of metastasis are providing novel potential targets for anti-cancer therapies.

AIM

This paper reviews the current concepts in tumour metastasis.

METHODS

A review of Medline publications relating to the molecular biology and therapy of human tumour metastasis was conducted.

RESULTS AND DISCUSSION

Early metastasis models were based upon the premise of uninterrupted tumour growth, with the inevitable formation of distant metastases and eventual death of the patient. However, current research suggests that metastasis is an inefficient process governed by several rate-limiting steps, and that failure to negotiate these steps can lead to tumour dormancy. Successful metastatic tumour growth depends upon appropriate tumour-host microenvironment interactions and, ultimately, the development of vascularised metastases post-extravasation in the target organ. An understanding of the molecular mechanisms involved in this dynamic process will aid in the identification of therapeutic targets that may allow earlier diagnosis and more specific therapies for patients with metastasis.

Comparison of the Growth and Survival of Larval Turbot in the Absence of Culturable Bacteria with Those in the Presence of Vibrio anguillarum, Vibrio alginolyticus, or a Marine Aeromonas sp

Larval turbot (Scophthalmus maximus) were reared on rotifers (Brachionus plicatilis) in the absence of culturable bacteria for up to 14 days and exhibited growth and high rates of survival (>55% in five experiments). Low numbers of known bacteria were introduced into similar cultures by exposure of the rotifers to a suspension of bacteria prior to addition of rotifers to the larval cultures; Vibrio anguillarum 91079 caused a highly significant decrease (P <0.01) in the proportion of survivors in two separate trials. With an Aeromonas sp. previously isolated from a healthy batch of copepod-fed larvae, there was no significant difference in survival compared with control larvae, even though the density of bacteria in the water of larval cultures reached 10(sup7) ml(sup-1). Bacteria colonized the gut of larvae exposed to Aeromonas-treated rotifers to levels similar to those in conventionally reared fish (>4 x 10(sup4) CFU per larva). Rearing of larvae in the presence of known bacteria provides a means of investigating the interaction of specific bacteria with turbot larvae and could provide a method for the selection of bacteria which may restrict the growth of opportunistic pathogens which would be harmful to turbot larvae.

Production of Eicosapentaenoic Acid (20:5 n-3) by Vibrio pelagius Isolated from Turbot ( Scophthalmus maximus (L.)) Larvae

Fourteen bacterial strains isolated from turbot, Scophthalmus maximus (L.), larvae were screened for eicosapentaenoic acid (20:5 n-3) (EPA) production. Gas chromatography analysis revealed that one bacterial species, Vibrio pelagius, contained a high proportion of EPA in cellular lipid. This finding was confirmed by gas chromatography-mass spectrometry analysis. A higher concentration of EPA was detected when the bacterium was cultured at 4�C.

Molecular mimicry and Lyme borreliosis: a shared antigenic determinant between Borrelia burgdorferi and human tissue

The pathogenesis of chronic manifestations in Lyme borreliosis, a disease induced by Borrelia burgdorferi, is at present unresolved. By testing monoclonal antibodies directed against various borrelia antigens, we found an antigenic determinant shared by the 41 kDa flagella protein and human tissue, especially prominent on myelinated fibers of human peripheral nerve, on nerve cells and axons of the central nervous system, as well as on certain epithelial cells (including joint synovia) and on heart muscle cells. Immune reactions against such a shared antigen could play a pathogenetic role in chronic organ manifestations of Lyme borreliosis.

Mother-child interaction in high-risk and contrast preschoolers of low socioeconomic status

Children's activities with their mothers and the techniques used by mothers while interacting with their child were examined in older (30--46 months) and younger (12--27 months) low SES preschool children from high-risk (in terms of cultural-familial retardation) and contrast homes. Older high-risk children interacted less often with their mothers and spent less time in "highly intellectual" activities than did the contrast children. The mothers of older high-risk children, in comparison with the contrast group, engaged less often in didactic teaching, showed less encouragement of their child's activities, and their attempts to control their child's activities more often resulted in failure. The differences between younger high-risk and contrast groups however were nonsignificant. Implications for future home intervention programs for high-risk low SES children are discussed.