Effects of 3-d and 4-d-transition metal substitutional impurities on the electronic properties of CrO2

We present first-principles based density functional theory calculations of the electronic and magnetic structure of CrO2 with 3d (Ti through Cu) and 4d (Zr through Ag) substitutional impurities. We find that the half-metallicity of CrO2 remains intact for all of the calculated substitutions. We also observe two periodic trends as a function of the number of valence electrons: if the substituted atom has six or fewer valence electrons (Ti-Cr or Zr-Mo), the number of down spin electrons associated with the impurity ion is zero, resulting in ferromagnetic (FM) alignment of the impurity magnetic moment with the magnetization of the CrO2 host. For substituent atoms with eight to ten (Fe-Ni or Ru-Pd with the exception of Ni), the number of down spin electrons contributed by the impurity ion remains fixed at three as the number contributed to the majority increases from one to three resulting in antiferromagnetic (AFM) alignment between impurity moment and host magnetization. The origin of this variation is the grouping of the impurity states into 3 states with approximate "t2g" symmetry and 2 states with approximate "eg" symmetry. Ni is an exception to the rule because a Jahn-Teller-like distortion causes a splitting of the Ni eg states. For Mn and Tc, which have 8 valence electrons, the zero down spin and 3 down spin configurations are very close in energy. For Cu and Ag atoms, which have 11 valence electrons, the energy is minimized when the substituent ion contributes 5 Abstract down-spin electrons. We find that the interatomic exchange interactions are reduced for all substitutions except for the case of Fe for which a modest enhancement is calculated for interactions along certain crystallographic directions.Comment: 26 pages, 10 figures, 2 table

Contamination in complex healthcare trials:the falls in care homes (FinCH) study experience

BACKGROUND: Trials are at risk of contamination bias which can occur when participants in the control group are inadvertently exposed to the intervention. This is a particular risk in rehabilitation studies where it is easy for trial interventions to be either intentionally or inadvertently adopted in control settings. The Falls in Care Homes (FinCH) trial is used in this paper as an example of a large randomised controlled trial of a complex intervention to explore the potential risks of contamination bias. We outline the FinCH trial design, present the potential risks from contamination bias, and the strategies used in the design of the trial to minimise or mitigate against this. The FinCH trial was a multi-centre randomised controlled trial, with embedded process evaluation, which evaluated whether systematic training in the use of the Guide to Action Tool for Care Homes reduced falls in care home residents. Data were collected from a number of sources to explore contamination in the FinCH trial. Where specific procedures were adopted to reduce risk of, or mitigate against, contamination, this was recorded. Data were collected from study e-mails, meetings with clinicians, research assistant and clinician network communications, and an embedded process evaluation in six intervention care homes. During the FinCH trial, there were six new falls prevention initiatives implemented outside the study which could have contaminated our intervention and findings. Methods used to minimise contamination were: cluster randomisation at the level of care home; engagement with the clinical community to highlight the risks of early adoption; establishing local collaborators in each site familiar with the local context; signing agreements with NHS falls specialists that they would maintain confidentiality regarding details of the intervention; opening additional research sites; and by raising awareness about the importance of contamination in research among participants. CONCLUSION: Complex rehabilitation trials are at risk of contamination bias. The potential for contamination bias in studies can be minimized by strengthening collaboration and dialogue with the clinical community. Researchers should recognise that clinicians may contaminate a study through lack of research expertise

Revised target co-ordinates for the Beagle 2 lander

The revised, IAU 2000 target co-ordinates of the Mars Beagle 2 lander are 11.6oN, 90.75oE

A measurement system for vertical seawater profiles close to the air–sea interface

This paper describes a near-surface ocean profiler, which has been designed to precisely measure vertical gradients in the top 10 m of the ocean. Variations in the depth of seawater collection are minimized when using the profiler compared to conventional CTD/rosette deployments. The profiler consists of a remotely operated winch mounted on a tethered yet free-floating buoy, which is used to raise and lower a small frame housing sensors and inlet tubing. Seawater at the inlet depth is pumped back to the ship for analysis. The profiler can be used to make continuous vertical profiles or to target a series of discrete depths. The profiler has been successfully deployed during wind speeds up to 10 m s−1 and significant wave heights up to 2 m. We demonstrate the potential of the profiler by presenting measured vertical profiles of the trace gases carbon dioxide and dimethylsulfide. Trace gas measurements use an efficient microporous membrane equilibrator to minimize the system response time. The example profiles show vertical gradients in the upper 5 m for temperature, carbon dioxide and dimethylsulfide of 0.15 °C, 4 µatm and 0.4 nM respectively

Knuth-Bendix algorithm and the conjugacy problems in monoids

We present an algorithmic approach to the conjugacy problems in monoids, using rewriting systems. We extend the classical theory of rewriting developed by Knuth and Bendix to a rewriting that takes into account the cyclic conjugates.Comment: This is a new version of the paper 'The conjugacy problems in monoids and semigroups'. This version will appear in the journal 'Semigroup forum

Identification of the Beagle 2 lander on Mars

The 2003 Beagle 2 Mars lander has been identified in Isidis Planitia at 90.43° E, 11.53° N, close to the predicted target of 90.50° E, 11.53° N. Beagle 2 was an exobiology lander designed to look for isotopic and compositional signs of life on Mars, as part of the European Space Agency Mars Express (MEX) mission. The 2004 recalculation of the original landing ellipse from a 3-sigma major axis from 174 km to 57 km, and the acquisition of Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment (HiRISE) imagery at 30 cm per pixel across the target region, led to the initial identification of the lander in 2014. Following this, more HiRISE images, giving a total of 15, including red and blue-green colours, were obtained over the area of interest and searched, which allowed sub-pixel imaging using super high-resolution techniques. The size (approx. 1.5 m), distinctive multilobed shape, high reflectivity relative to the local terrain, specular reflections, and location close to the centre of the planned landing ellipse led to the identification of the Beagle 2 lander. The shape of the imaged lander, although to some extent masked by the specular reflections in the various images, is consistent with deployment of the lander lid and then some or all solar panels. Failure to fully deploy the panels-which may have been caused by damage during landing-would have prohibited communication between the lander and MEX and commencement of science operations. This implies that the main part of the entry, descent and landing sequence, the ejection from MEX, atmospheric entry and parachute deployment, and landing worked as planned with perhaps only the final full panel deployment failing

Characterisation and Integration of Piezoelectric Trimorph Actuators for Blade Active Surface Control on a Scaled Wind Turbine

The paper investigates the integration of piezoelectric bending actuators on trailing edge flaps (TEF). The characterisation of piezoelectric actuators is of great importance due to differences in performance resulting from sample variability, actuator construction, circuit type and equipment. For the application of trailing edge flaps in scaled turbines, the total deflection these actuators can produce determines the possible flap angles and, consequently, the potential effects on wake evolution downwind of the wind turbine. In this paper, we fully characterise the performance of the piezoelectric bending actuator under a variety of operating conditions. The bridged bi-polar circuit is used to drive the piezoelectric actuators with both a static and a dynamic signal. Deflection results demonstrate that the piezoelectric actuator is capable of achieving flap angles of β ± 3° with a static signal, and β = 2.3° and β = −3.2° angles with a dynamic signal. Experimental force measurements using a dynamic signal result in a force reduction of up to 33% when compared to a static signal. Force values at increasing frequencies do not show a depreciation in force. Additionally, initial aerodynamic loads exerted on TEF are presented based on XFoil simulations to ensure that the piezoelectric actuating force can overcome aerodynamic loads for future experiments. Experimental force measurements from the piezoelectric actuator demonstrate that aerodynamic forces can be overcome. This work serves as the first step towards implementing the TEF technology in lab-scaled wind turbine models