Chirped pulse Fourier-transform microwave spectroscopy of alcohol and water tetramers.

In an effort to build towards quantitative models of alcohol:water microaggregation in liquid mixtures, the present works characterizes the energy landscape and structures of pure ethanol and mixed ethanol:water tetramers using Chirped Pulse Fourier-transform Microwave spectroscopy. Many conformers of each type of tetramer are available, and those with sufficiently strong dipole moments are experimentally examined. This analysis considers, but does not explicitly fit, the splitting of rotational states due to internal rotation of the methyl groups present, as well as utilizes isotopic substitution experiments to verify the conformer variations observed. Implications of the listed results include a suggestion of the stability of micro-aggregated structures as opposed to homogeneously mixed clusters, informing future work on characterization of larger clusters and any potential modeling of the hydrogen bond network at play.

Supersonic jet chirped pulse microwave spectroscopy of ring-like methanol : water pentamers.

The potential energy surfaces of pure methanol and mixed methanol-water pentamers have been explored using chirped pulse Fourier-transform microwave spectroscopy aided by ab initio calculations. Rotational constants, anharmonic corrections, dipole moments, and relative energies were calculated for different conformers. Predicted rotational transitions were then fit to experimental spectra from 10-18 GHz and the assignments were confirmed using double resonance experiments where feasible. The results show all 23 of the lowest energy conformers are bound in a planar ring of hydrogen bonding that display a steady decrease in the RO-O distance along this ring as methanol content is increased. Interspersed methanol and water conformers have comparable relative abundances to those with micro-aggregation, but structures with micro-aggregated methanol and water have a higher rigid rotor fitting error. The computational methods' high degree of accuracy when compared to our experimental results suggests the strong donor-acceptor hydrogen bonding in these clusters leads to well-defined minima on the intermolecular potential energy surface.

High throughput chirped pulse Fourier-transform microwave spectroscopy of ethanol and water clusters.

Here we discuss the design and performance of a novel high-throughput instrument for Chirped Pulse Fourier-transform Microwave (CP-FTMW) spectroscopy, and demonstrate its efficacy through the identification of the lowest energy conformers of the ethanol trimer and mixed water : ethanol trimers. Rotational constants for these trimers were calculated from observed lines in the spectra from 10 to 14 GHz, and compared to the results of anharmonic ab initio computations. As predicted, all trimers share a cyclic donor-acceptor hydrogen bonding structure, with the ethanol monomer favoring the gauche conformation in the lowest energy structures. The increased speed of data collection and resulting sensitivity opens a new avenue into rotational studies of higher order clusters.

Protocol for the Weight-bearing in Ankle Fractures (WAX) trial: a multicentre prospective non-inferiority trial of early versus delayed weight-bearing after operatively managed ankle fracture.

BACKGROUND: Unstable ankle fractures represent a substantial burden of disease, accounting for a mean hospital stay of nine days, a mean cost of £4,491 per patient and 20,000 operations per year. There is variation in UK practice around weight-bearing instructions after operatively managed ankle fracture. Early weight-bearing may reduce reliance on health services, time off work, and improve functional outcomes. However, concerns remain about the potential for complications such as implant failure. This is the protocol of a multicentre randomised non-inferiority clinical trial of weight-bearing following operatively treated ankle fracture. METHODS: Adults aged 18 years and over who have been managed operatively for ankle fracture will be assessed for eligibility. Baseline function (Olerud and Molander Ankle Score [OMAS]), health-related quality of life (EQ-5D-5L), and complications will be collected after informed consent has been obtained. A randomisation sequence has been prepared by a trial statistician to allow for 1:1 allocation to receive either instruction to weight-bear as pain allows from the point of randomisation, two weeks after the time of surgery ('early weight-bearing' group) or to not weight-bear for a further four weeks ('delayed weight -bearing' group). All other treatment will be as per the guidance of the treating clinician. Participants will be asked about their weight-bearing status weekly until four weeks post-randomisation. At four weeks post-randomisation complications will be collected. At six weeks, four months, and 12 months post-randomisation, the OMAS, EQ-5D-5L, complications, physiotherapy input, and resource use will be collected. The primary outcome measure is ankle function (OMAS) at four months post-randomisation. A minimum of 436 participants will be recruited to obtain 80% power to detect a non-inferiority margin of -6 points on the OMAS 4 months post-randomisation. A within-trial health economic evaluation will be conducted to estimate the cost-effectiveness of the treatment options. DISCUSSION: The results of this study will inform national guidance with regards to the most clinically and cost-effective strategy for weight-bearing after surgery for unstable ankle fractures. TRIAL REGISTRATION: ISRCTN12883981 , Registered 02 December 2019.

Magnetic Excitations of the Classical Spin Liquid MgCr_{2}O_{4}.

We report a comprehensive inelastic neutron-scattering study of the frustrated pyrochlore antiferromagnet MgCr_{2}O_{4} in its cooperative paramagnetic regime. Theoretical modeling yields a microscopic Heisenberg model with exchange interactions up to third-nearest neighbors, which quantitatively explains all of the details of the dynamic magnetic response. Our work demonstrates that the magnetic excitations in paramagnetic MgCr_{2}O_{4} are faithfully represented in the entire Brillouin zone by a theory of magnons propagating in a highly correlated paramagnetic background. Our results also suggest that MgCr_{2}O_{4} is proximate to a spiral spin-liquid phase distinct from the Coulomb phase, which has implications for the magnetostructural phase transition in MgCr_{2}O_{4}.

Emergent magnetic order and correlated disorder in formate metal-organic frameworks.

Magnetic materials with strong local interactions but lacking long-range order have long been a curiosity of physicists. Probing their magnetic interactions is crucial for understanding the unique properties they can exhibit. Metal-organic frameworks have recently gathered more attention as they can produce more exotic structures, allowing for controlled design of magnetic properties not found in conventional metal-oxide materials. Historically, magnetic diffuse scattering in such materials has been overlooked but has attracted greater attention recently, with advances in techniques. In this study, we investigate the magnetic structure of metal-organic formate frameworks, using heat capacity, magnetic susceptibility and neutron diffraction. In Tb(DCO2)3, we observe emergent magnetic order at temperatures below 1.2 K, consisting of two k-vectors. Ho(DCO2)3 shows diffuse scattering above 1.6 K, consistent with ferromagnetic chains packed in a frustrated antiferromagnetic triangular lattice, also observed in Tb(DCO2)3 above 1.2 K. The other lanthanides show no short- or long-range order down to 1.6 K. The results suggest an Ising-like one-dimensional magnetic order associated with frustration is responsible for the magnetocaloric properties, of some members in this family, improving at higher temperatures. This article is part of the theme issue 'Mineralomimesis: natural and synthetic frameworks in science and technology'.

Problems persist in reporting of methods and results for the WOMAC measure in hip and knee osteoarthritis trials.

PURPOSE: The Western Ontario and McMaster Universities Arthritis Index (WOMAC) is a commonly used outcome measure for osteoarthritis. There are different versions of the WOMAC (Likert, visual analogue or numeric scales). A previous review of trials published before 2010 found poor reporting and inconsistency in how the WOMAC was used. This review explores whether these problems persist. METHODS: This systematic review included randomised trials of hip and/or knee osteoarthritis published in 2016 that used the WOMAC. Data were extracted on the version used, score range, analysis and results of the WOMAC, and whether these details were clearly reported. RESULTS: This review included 62 trials and 41 reported the WOMAC total score. The version used and item range for the WOMAC total score were unclear in 44% (n = 18/41) and 24% (n = 10/41) of trials, respectively. The smallest total score range was 0-10 (calculated by averaging 24 items scored 0-10); the largest was 0-2400 (calculated by summing 24 items scored 0-100). All trials reported the statistical analysis methods but only 29% reported the between-group mean difference and 95% confidence interval. CONCLUSION: Details on the use and scoring of the WOMAC were often not reported. We recommend that trials report the version of the WOMAC and the score range used. The between-group treatment effect and corresponding confidence interval should be reported. If all the items of the WOMAC are collected, the total score and individual subscale scores should be presented. Better reporting would facilitate the interpretation, comparison and synthesis of the WOMAC score in trials.

Synthesis and summary of patient-reported outcome measures to inform the development of a core outcome set in colorectal cancer surgery.

AIM: Patient-reported outcome (PRO) measures (PROMs) are standard measures in the assessment of colorectal cancer (CRC) treatment, but the range and complexity of available PROMs may be hindering the synthesis of evidence. This systematic review aimed to: (i) summarize PROMs in studies of CRC surgery and (ii) categorize PRO content to inform the future development of an agreed minimum 'core' outcome set to be measured in all trials. METHOD: All PROMs were identified from a systematic review of prospective CRC surgical studies. The type and frequency of PROMs in each study were summarized, and the number of items documented. All items were extracted and independently categorized by content by two researchers into 'health domains', and discrepancies were discussed with a patient and expert. Domain popularity and the distribution of items were summarized. RESULTS: Fifty-eight different PROMs were identified from the 104 included studies. There were 23 generic, four cancer-specific, 11 disease-specific and 16 symptom-specific questionnaires, and three ad hoc measures. The most frequently used PROM was the EORTC QLQ-C30 (50 studies), and most PROMs (n = 40, 69%) were used in only one study. Detailed examination of the 50 available measures identified 917 items, which were categorized into 51 domains. The domains comprising the most items were 'anxiety' (n = 85, 9.2%), 'fatigue' (n = 67, 7.3%) and 'physical function' (n = 63, 6.9%). No domains were included in all PROMs. CONCLUSION: There is major heterogeneity of PRO measurement and a wide variation in content assessed in the PROMs available for CRC. A core outcome set will improve PRO outcome measurement and reporting in CRC trials.

Evaluation of the indoor air quality minimum ventilation rate procedure for use in California retail buildings.

This research assesses benefits of adding to California Title-24 ventilation rate (VR) standards a performance-based option, similar to the American Society of Heating, Refrigerating, and Air Conditioning Engineers 'Indoor Air Quality Procedure' (IAQP) for retail spaces. Ventilation rates and concentrations of contaminants of concern (CoC) were measured in 13 stores. Mass balance models were used to estimate 'IAQP-based' VRs that would maintain concentrations of all CoCs below health- or odor-based reference concentration limits. An intervention study in a 'big box' store assessed how the current VR, the Title 24-prescribed VR, and the IAQP-based VR (0.24, 0.69, and 1.51 air changes per hour) influenced measured IAQ and perceived of IAQ. Neither current VRs nor Title 24-prescribed VRs would maintain all CoCs below reference limits in 12 of 13 stores. In the big box store, the IAQP-based VR kept all CoCs below limits. More than 80% of subjects reported acceptable air quality at all three VRs. In 11 of 13 buildings, saving energy through lower VRs while maintaining acceptable IAQ would require source reduction or gas-phase air cleaning for CoCs. In only one of the 13 retail stores surveyed, application of the IAQP would have allowed reduced VRs without additional contaminant-reduction strategies.

Studies of the Room-Temperature Multiferroic Pb(Fe0.5Ta0.5)0.4(Zr0.53Ti0.47)0.6O3: Resonant Ultrasound Spectroscopy, Dielectric, and Magnetic Phenomena.

Recently, lead iron tantalate/lead zirconium titanate (PZTFT) was demonstrated to possess large, but unreliable, magnetoelectric coupling at room temperature. Such large coupling would be desirable for device applications but reproducibility would also be critical. To better understand the coupling, the properties of all 3 ferroic order parameters, elastic, electric, and magnetic, believed to be present in the material across a range of temperatures, are investigated. In high temperature elastic data, an anomaly is observed at the orthorhombic mm2 to tetragonal 4mm transition, Tot = 475 K, and a softening trend is observed as the temperature is increased toward 1300 K, where the material is known to become cubic. Thermal degradation makes it impossible to measure elastic behavior up to this temperature, however. In the low temperature region, there are elastic anomalies near ≈40 K and in the range 160-245 K. The former is interpreted as being due to a magnetic ordering transition and the latter is interpreted as a hysteretic regime of mixed rhombohedral and orthorhombic structures. Electrical and magnetic data collected below room temperature show anomalies at remarkably similar temperature ranges to the elastic data. These observations are used to suggest that the three order parameters in PZTFT are strongly coupled.

The proportion of tumor-stroma as a strong prognosticator for stage II and III colon cancer patients: validation in the VICTOR trial.

BACKGROUND: The intra-tumor stroma percentage in colon cancer (CC) patients has previously been reported by our group as a strong independent prognostic parameter. Patients with a high stroma percentage within the primary tumor have a poor prognosis. PATIENTS AND METHODS: Tissue samples from the most invasive part of the primary tumor of 710 patients (52% Stage II, 48% Stage III) participating in the VICTOR trial were analyzed for their tumor-stroma percentage. Stroma-high (>50%) and stroma-low (≤50%) groups were evaluated with respect to survival times. RESULTS: Overall and disease-free survival times (OS and DFS) were significantly lower in the stroma-high group (OS P<0.0001, hazard ratio (HR)=1.96; DFS P<0.0001, HR=2.15). The 5-year OS was 69.0% versus 83.4% and DFS 58.6% versus 77.3% for stroma-high versus stroma-low patients. CONCLUSION: This study confirms the intra-tumor stroma ratio as a prognostic factor. This parameter could be a valuable and low cost addition to the TNM status and next to current high-risk parameters such as microsatellite instability status used in routine pathology reporting. When adding the stroma-parameter to the ASCO criteria, the rate of 'undertreated' patients dropped from 5.9% to 4.3%, the 'overtreated' increased with 6.8% but the correctly classified increased with an additional 14%.

A systematic review of outcome reporting in colorectal cancer surgery.

AIM: Evaluation of surgery for colorectal cancer (CRC) is necessary to inform clinical decision-making and healthcare policy. The standards of outcome reporting after CRC surgery have not previously been considered. METHOD: Systematic literature searches identified randomized and nonrandomized prospective studies reporting clinical outcomes of CRC surgery. Outcomes were listed verbatim, categorized into broad groups (outcome domains) and examined for a definition (an appropriate textual explanation or a supporting citation). Outcome reporting was considered inconsistent if results of the outcome specified in the methods were not reported. Outcome reporting was compared between randomized and nonrandomized studies. RESULTS: Of 5644 abstracts, 194 articles (34 randomized and 160 nonrandomized studies) were included reporting 766 different clinical outcomes, categorized into seven domains. A mean of 14 ± 8 individual outcomes were reported per study. 'Anastomotic leak', 'overall survival' and 'wound infection' were the three most frequently reported outcomes in 72, 60 and 44 (37.1%, 30.9% and 22.7%) studies, respectively, and no single outcome was reported in every publication. Outcome definitions were significantly more often provided in randomized studies than in nonrandomized studies (19.0% vs 14.9%, P = 0.015). One-hundred and twenty-seven (65.5%) papers reported results of all outcomes specified in the methods (randomized studies, n = 21, 61.5%; nonrandomized studies, n = 106, 66.2%; P = 0.617). CONCLUSION: Outcome reporting in CRC surgery lacks consistency and method. Improved standards of outcome measurement are recommended to permit data synthesis and transparent cross-study comparisons.

Quantum spin liquid in frustrated one-dimensional LiCuSbO4.

A quantum magnet, LiCuSbO4, with chains of edge-sharing spin-1/2 CuO6 octahedra is reported. While short-range order is observed for T<10 K, no zero-field phase transition or spin freezing occurs down to 100 mK. Specific heat indicates a distinct high-field phase near the 12 T saturation field. Neutron scattering shows incommensurate spin correlations with q=(0.47±0.01)π/a and places an upper limit of 70 µeV on any spin gap. Exact diagonalization of 16-spin easy-plane spin-1/2 chains with competing ferro- and antiferromagnetic interactions (J1=-75 K, J2=34 K) accounts for the T>2 K data.

Delivery of Echinococcus granulosus antigen EG95 to mice and sheep using recombinant vaccinia virus.

The tapeworm Echinococcus granulosus is the causative agent of hydatid disease and affects sheep, cattle, dogs and humans worldwide. It has a two-stage life cycle existing as worms in the gut of infected dogs (definitive host) and as cysts in herbivores and humans (intermediate host). The disease is debilitating and can be life threatening where the cysts interfere with organ function. Interruption of the hydatid life cycle in the intermediate host by vaccination may be a way to control the disease, and a protective oncosphere antigen EG95 has been shown to protect animals against challenge with E. granulosus eggs. We explored the use of recombinant vaccinia virus as a delivery vehicle for EG95. Mice and sheep were immunized with the recombinant vector, and the result monitored at the circulating antibody level. In addition, sera from immunized mice were assayed for the ability to kill E. granulosus oncospheres in vitro. Mice immunized once intranasally developed effective oncosphere-killing antibody by day 42 post-infection. Antibody responses and oncosphere killing were correlated and were significantly enhanced by boosting mice with either EG95 protein or recombinant vector. Sheep antibody responses to the recombinant vector or to EG95 protein mirrored those in mice.

Referral proformas improve compliance to national colorectal 2-week wait targets: does this affect cancer detection rates?

AIM: To facilitate implementation of National Institute for Health and Clinical Excellence (NICE) guidelines for urgent colorectal cancer referral, local cancer networks have promoted the use of standardized proformas in primary care. This clinical audit assessed use of the proforma within the Thames Valley Cancer Network (TVCN) to see whether increased proforma use was associated with higher compliance to NICE guidelines and higher cancer detection rates. METHOD: All 2-week wait referrals for lower bowel cancer to the six Acute NHS Trusts in the TVCN received during the month of June 2010 were identified, anonymized and analysed in relation to colorectal cancer detection rates. RESULTS: Of the 586 referrals audited, proforma usage varied significantly across the six Acute NHS Trusts from 18% to 96%. Referral letters from primary care had NICE compliance ranging from 30 to 50%. In those which received a referral protocol, 50-90% were NICE compliant. Proforma use was associated with higher cancer detection rates (P = 0.03). CONCLUSION: These results have wide-ranging implications since they suggest that the adoption of a simple proforma in primary care can improve the effectiveness of referral for suspected cancer.

Magnetoelastic properties and behaviour of 4C pyrrhotite, Fe7S8, through the Besnus transition.

Pyrrhotite, Fe7S8, is a commonly occurring carrier of magnetic remanence and has a low temperature transition, the Besnus transition, involving a change in spin state. Variations of the thermodynamic, magnetic and elastic properties through this transition at ∼33 K in a natural sample of 4C pyrrhotite have been tested against a group theoretical model for coupling between order parameters relating to Fe/vacancy ordering (irrep U 1(1/2,0,1/4)) and magnetic ordering (irreps m[Formula: see text] and m[Formula: see text]). Magnetoelastic coupling is weak but the pre-existing microstructure of ferroelastic and magnetic domains, that develop as a consequence of Fe/vacancy and ferrimagnetic ordering during slow cooling in nature (P63/mmc → C2'/c'), causes subtle changes in the low temperature transition (C2'/c' → P [Formula: see text]). The Besnus transition involves a rotation of magnetic moments out of the a-c plane of the monoclinic structure, but it appears that the transition temperature might vary locally according to whether it is taking place within the pre-existing domain walls or in the domains that they separate. Evidence of metamagnetic transitions suggests that the magnetic field-temperature phase diagram will display some interesting diversity. Low temperature magnetic transitions in minerals of importance to the palaeomagnetism community have been used to identify the presence of magnetite and haematite in rocks and the Besnus transition is diagnostic of the existence of pyrrhotite, Fe7S8.

The Denver Aerosol Sources and Health (DASH) Study: Overview and Early Findings.

Improved understanding of the sources of air pollution that are most harmful could aid in developing more effective measures for protecting human health. The Denver Aerosol Sources and Health (DASH) study was designed to identify the sources of ambient fine particulate matter (PM(2.5)) that are most responsible for the adverse health effects of short-term exposure to PM (2.5). Daily 24-hour PM(2.5) sampling began in July 2002 at a residential monitoring site in Denver, Colorado, using both Teflon and quartz filter samplers. Sampling is planned to continue through 2008. Chemical speciation is being carried out for mass, inorganic ionic compounds (sulfate, nitrate and ammonium), and carbonaceous components, including elemental carbon, organic carbon, temperature-resolved organic carbon fractions and a large array of organic compounds. In addition, water soluble metals were measured daily for 12 months in 2003. A receptor-based source apportionment approach utilizing positive matrix factorization (PMF) will be used to identify PM (2.5) source contributions for each 24-hour period. Based on a preliminary assessment using synthetic data, the proposed source apportionment should be able to identify many important sources on a daily basis, including secondary ammonium nitrate and ammonium sulfate, diesel vehicle exhaust, road dust, wood combustion and vegetative debris. Meat cooking, gasoline vehicle exhaust and natural gas combustion were more challenging for PMF to accurately identify due to high detection limits for certain organic molecular marker compounds. Measurements of these compounds are being improved and supplemented with additional organic molecular marker compounds. The health study will investigate associations between daily source contributions and an array of health endpoints, including daily mortality and hospitalizations and measures of asthma control in asthmatic children. Findings from the DASH study, in addition to being of interest to policymakers, by identifying harmful PM(2.5) sources may provide insights into mechanisms of PM effect.

A systematic review of cardiovascular responses associated with ambient black carbon and fine particulate matter.

BACKGROUND: Exposure to fine particulate matter (PM2.5), an ambient air pollutant with mass-based standards promulgated under the Clean Air Act, and black carbon (BC), a common component of PM2.5, are both associated with cardiovascular health effects. OBJECTIVES: To elucidate whether BC is associated with distinct, or stronger, cardiovascular responses compared to PM2.5, we conducted a systematic review. We evaluated the associations of short- and long-term BC, or the related component elemental carbon (EC), with cardiovascular endpoints including heart rate variability, heart rhythm, blood pressure and vascular function, ST segment depression, repolarization abnormalities, atherosclerosis and heart function, in the context of what is already known about PM2.5. DATA SOURCES: We conducted a stepwise systematic literature search of the PubMed, Web of Science and TOXLINE databases and applied Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines for reporting our results. STUDY ELIGIBILITY CRITERIA: Studies reporting effect estimates for the association of quantitative measurements of ambient BC (or EC) and PM2.5, with relevant cardiovascular endpoints (i.e. meeting inclusion criteria) were included in the review. Included studies were evaluated for risk of bias in study design and results. STUDY APPRAISAL AND SYNTHESIS METHODS: Risk of bias evaluations assessed aspects of internal validity of study findings based on study design, conduct, and reporting to identify potential issues related to confounding or other biases. Study results are presented to facilitate comparison of the consistency of associations with PM2.5 and BC within and across studies. RESULTS: Our results demonstrate similar associations for BC (or EC) and PM2.5 with the cardiovascular endpoints examined. Across studies, associations for BC and PM2.5 varied in their magnitude and precision, and confidence intervals were generally overlapping within studies. Where differences in the magnitude of the association between BC or EC and PM2.5 within a study could be discerned, no consistent pattern across the studies examined was apparent. LIMITATIONS: We were unable to assess the independence of the effect of BC, relative the effect of PM2.5, on the cardiovascular system, nor was information available to understand the impact of differential exposure misclassification. CONCLUSIONS: Overall, the evidence indicates that both BC (or EC) and PM2.5 are associated with cardiovascular effects but the available evidence is not sufficient to distinguish the effect of BC (or EC) from that of PM2.5 mass.

Ferroelasticity, anelasticity and magnetoelastic relaxation in Co-doped iron pnictide: Ba(Fe0.957Co0.043)2As2.

The hypothesis that strain has a permeating influence on ferroelastic, magnetic and superconducting transitions in 122 iron pnictides has been tested by investigating variations of the elastic and anelastic properties of a single crystal of Ba(Fe0.957Co0.043)2As2 by resonant ultrasound spectroscopy as a function of temperature and externally applied magnetic field. Non-linear softening and stiffening of C 66 in the stability fields of both the tetragonal and orthorhombic structures has been found to conform quantitatively to the Landau expansion for a pseudoproper ferroelastic transition which is second order in character. The only exception is that the transition occurs at a temperature (T S ≈ 69 K) ~10 K above the temperature at which C 66 would extrapolate to zero ([Formula: see text] ≈ 59 K). An absence of anomalies associated with antiferromagnetic ordering below T N ≈ 60 K implies that coupling of the magnetic order parameter with shear strain is weak. It is concluded that linear-quadratic coupling between the structural/electronic and antiferromagnetic order parameters is suppressed due to the effects of local heterogeneous strain fields arising from the substitution of Fe by Co. An acoustic loss peak at ~50-55 K is attributed to the influence of mobile ferroelastic twin walls that become pinned by a thermally activated process involving polaronic defects. Softening of C 66 by up to ~6% below the normal-superconducting transition at T c ≈ 13 K demonstrates an effective coupling of the shear strain with the order parameter for the superconducting transition which arises indirectly as a consequence of unfavourable coupling of the superconducting order parameter with the ferroelastic order parameter. Ba(Fe0.957Co0.043)2As2 is representative of 122 pnictides as forming a class of multiferroic superconductors in which elastic strain relaxations underpin almost all aspects of coupling between the structural, magnetic and superconducting order parameters and of dynamic properties of the transformation microstructures they contain.

Strain relaxation behaviour of vortices in a multiferroic superconductor.

The elastic and anelastic properties of a single crystal of Co-doped pnictide Ba(Fe0.957Co0.043)2As2 have been determined by resonant ultrasound spectroscopy in the frequency range 10-500 kHz, both as a function of temperature through the normal-superconducting transition (T c ≈ 12.5 K) and as a function of applied magnetic field up to 12.5 T. Correlation with thermal expansion, electrical resistivity, heat capacity, DC and AC magnetic data from crystals taken from the same synthetic batch has revealed the permeating influence of strain on coupling between order parameters for the ferroelastic (Q E) and superconducting (Q SC) transitions and on the freezing/relaxation behaviour of vortices. Elastic softening through T c in zero field can be understood in terms of classical coupling of the order parameter with the shear strain e 6, λe 6 [Formula: see text], which means that there must be a common strain mechanism for coupling of the form λ [Formula: see text] Q E. At fields of ~5 T and above, this softening is masked by Debye-like stiffening and acoustic loss processes due to vortex freezing. The first loss peak may be associated with the establishment of superconductivity on ferroelastic twin walls ahead of the matrix and the second is due to the vortex liquid-vortex glass transition. Strain contrast between vortex cores and the superconducting matrix will contribute significantly to interactions of vortices both with each other and with the underlying crystal structure. These interactions imply that iron-pnictides represent a class of multiferroic superconductors in which strain-mediated coupling occurs between the multiferroic properties (ferroelasticity, antiferromagnetism) and superconductivity.