Parametric optimization for terabit perpendicular recording

The design of media for ultrahigh-density perpendicular recording is discussed in depth. Analytical and semianalytical models are developed to determine the constraints upon the media to fulfill requirements of writability and thermal stability, and the effect of intergranular exchange coupling is examined. The role of vector fields during the write process is examined, and it is shown that one-dimensional models of perpendicular recording have significant deficiencies. A micromagnetic model is described and the results of simulations of recording undertaken with the model are presented. The paper demonstrates that there is no physical reason why perpendicular recording should not be possible at or above 1 Tb/in(2)

Evaluation of an on-site sewage disposal system at the Lake of the Ozarks

An aeration device - conventional soil disposal field system was monitored for one year in the Lake of the Ozarks area to assess its treatment efficiency and effect on the water quality of the immediate area. The aeration unit consistently produced a well oxidized effluent (soluble COD=44 mg/L; N03-N=22 mg/L; P04=6. 3 mg /L; SS=l 4 mg /L). Soi1-water samples taken from the tile line and 2 and 5 m down slope indicate that considerable denitrification was occurring but may be decreasing. Little coliform movement was detected. The practice of excavating tile lines into the bedrock was discouraged due to a lack of treatment occurring.Project # G-1235-06 Agreement # 14-08-0001-G-1235-0

Position clamping of optically trapped microscopic non-spherical probes

We investigate the degree of control that can be exercised over an optically trapped microscopic non-spherical force probe. By position clamping translational and rotational modes in different ways, we are able to dramatically improve the position resolution of our probe with no reduction in sensitivity. We also demonstrate control over rotational-translational coupling, and exhibit a mechanism whereby the average centre of rotation of the probe can be displaced away from its centre

A compact holographic optical tweezers instrument

Holographic optical tweezers have found many applications including the construction of complex micron-scale 3D structures and the control of tools and probes for position, force, and viscosity measurement. We have developed a compact, stable, holographic optical tweezers instrument which can be easily transported and is compatible with a wide range of microscopy techniques, making it a valuable tool for collaborative research. The instrument measures approximately 30×30×35 cm and is designed around a custom inverted microscope, incorporating a fibre laser operating at 1070 nm. We designed the control software to be easily accessible for the non-specialist, and have further improved its ease of use with a multi-touch iPad interface. A high-speed camera allows multiple trapped objects to be tracked simultaneously. We demonstrate that the compact instrument is stable to 0.5 nm for a 10 s measurement time by plotting the Allan variance of the measured position of a trapped 2 μm silica bead. We also present a range of objects that have been successfully manipulated

Constructing 3D crystal templates for photonic band gap materials using holographic optical tweezers

A simple and robust method is presented for the construction of 3-dimensional crystals from silica and polystyrene microspheres. The crystals are suitable for use as templates in the production of three-dimensional photonic band gap (PBG) materials. Manipulation of the microspheres was achieved using a dynamic holographic assembler (DHA) consisting of computer controlled holographic optical tweezers. Attachment of the microspheres was achieved by adjusting their colloidal interactions during assembly. The method is demonstrated by constructing a variety of 3-dimensional crystals using spheres ranging in size from 3 µm down to 800 nm. A major advantage of the technique is that it may be used to build structures that cannot be made using self-assembly. This is illustrated through the construction of crystals in which line defects have been deliberately included, and by building simple cubic structures

Radiotherapy trial set-up in the UK: identifying inefficiencies and potential solutions

Aims: Radiotherapy clinical trials are integral to the development of new treatments to improve the outcomes of patients with cancer. A collaborative study by the National Cancer Research Institute Clinical and Translational Radiotherapy Research Working Group and the National Institute for Health Research was carried out to understand better if and why inefficiencies occur in the set-up of radiotherapy trials in the UK. Materials and methods: Two online surveys collected information on the time taken for UK radiotherapy trials to reach key milestones during set-up and the research support currently being provided to radiotherapy centres to enable efficient clinical trial set-up. Semi-structured interviews with project managers and chief investigators identified better ways of working to improve trial set-up in the future. Results: The timelines for the set-up of 39 UK radiotherapy trials were captured in an online survey showing that the median time from grant approval to trial opening was 600 days (range 169–1172). There were 38 responses from radiotherapy centres to a survey asking about the current support provided for radiotherapy research. Most of these centres have more than one type of staff member dedicated to supporting radiotherapy research. The most frequent barrier to radiotherapy trial set-up identified was lack of physicists' time and lack of time for clinical oncologists to carry out research activities. Four main themes around trial set-up were identified from semi-structured interviews: the importance of communication and building relationships, the previous experience of the chief investigator and clinical trials units, a lack of resources and having the time and personnel required to produce trial documentation and to process trial approval requests. Conclusions: This unique, collaborative project has provided up to date information about the current landscape of trial set-up and research support in the UK and identified several avenues on which to focus future efforts in order to support the excellent radiotherapy trial work carried out across the UK

An Anglo-Saxon execution cemetery at Walkington Wold, Yorkshire

This paper presents a re-evaluation of a cemetery excavated over 30 years ago at Walkington Wold in east Yorkshire. The cemetery is characterized by careless burial on diverse alignments, and by the fact that most of the skeletons did not have associated crania. The cemetery has been variously described as being the result of an early post-Roman massacre, as providing evidence for a ‘Celtic’ head cult or as an Anglo-Saxon execution cemetery. In order to resolve the matter, radiocarbon dates were acquired and a re-examination of the skeletal remains was undertaken. It was confirmed that the cemetery was an Anglo-Saxon execution cemetery, the only known example from northern England, and the site is set into its wider context in the paper

Earth-as-an-exoplanet: comparing earthshine observations to models of an exo-Earth

Traditional methods of exoplanet characterization that only make use of emitted or reflected flux lack the ability to fully distinguish between different physical features of the target, such as cloud layers, hazes, or surface features. Polarimetry, however, is a powerful, more sensitive technique that has this ability, as it measures light as a vector (by the orientation of the electric field) rather than a scalar intensity. It is therefore extremely sensitive to the composition and structure of the planetary atmosphere and surface, being affected by properties such as the mixing ratios of atmospheric absorbing gases, cloud optical thickness, cloud top pressure, cloud particle size, and surface albedo. Various groups have theoretically studied the optical linear polarimetric signals of Earth-like exoplanets as functions of both orbital phase and wavelength. With this project we assess the accuracy of these theoretical models against observations of the Earthshine, the only known observations of an Earth-like planet thus far. Using data of the atmosphere and surface taken by the MODIS instrument aboard the Terra and Aqua satellites, as well as surface reflectance spectra from the JPL EcoStress Spectral Library, we created a gridded model of the Earth. Then, using this model data as input for three separate radiative transfer algorithms, we generate the flux and linear polarization spectra for the model exoplanet-Earth across the optical to near-infrared wavelengths. We compare the results from all three codes to each other and to the observational linear spectropolarimetric data of the Earthshine obtained by a member of our group. We identify similarities and potential pitfalls between the codes, and make necessary adjustments to them, in an effort to improve our future characterizations of terrestrial exoplanets.Stars and planetary system

Comparing models of an exoplanet-earth to earthshine observations

Polarimetry is widely becoming recognized as a powerful technique for enhancing the contrast between a star and an exoplanet, and thus improving upon the direct detection of exoplanets. The real power of polarimetry, however, is in its ability to characterize the physical properties of these worlds. This is because the state of the polarization of the light from the planet is very sensitive to the composition and structure of the planetary atmosphere and surface, being affected by properties such as the mixing ratios of atmospheric absorbing gases, cloud optical thickness, cloud top pressure, cloud particle size, and surface albedo. Various groups have theoretically studied the optical linear polarimetric signals of Earth-like exoplanets as functions of both orbital phase and wavelength. This project aims to validate the accuracy of these theoretical models against the only known observations of an Earth-like planet thus far: Earthshine. Using atmospheric and surface data taken by the MODIS instrument aboard the Terra and Aqua satellites, as well as surface albedo spectra from the EcoStress Spectral Library, we created a detailed model of the Earth. Then, using this model data as input for three separate radiative transfer algorithms, we generate the flux and linear polarization spectra for the model exoplanet-Earth from the optical to near-infrared wavelengths. We compare the results from all three codes to each other and to observational linear spectropolarimetric data of the Earthshine obtained by a member of our group. We identify similarities and potential pitfalls between these codes in an effort to improve our future characterizations of Earth-like exoplanets.Stars and planetary system

The SPAIR method: Isolating incident and reflected directional wave spectra in multidirectional wave basins

Wave tank tests aiming to reproduce realistic or site specific conditions will commonly involve using directionally spread, short-crested sea states. The measurement of these directional characteristics is required for the purposes of calibrating and validating the modelled sea state. Commonly used methods of directional spectrumreconstruction, based on directional spreading functions, have an inherent level of uncertainty associated with them. In this paper we aim to reduce the uncertainty in directional spectrum validation by introducing the SPAIR (Single-summation PTPD Approach with In-line Reflections) method, in combination with a directional wave gauge array. A variety of wave conditions were generated in the FloWave Ocean Energy Research Facility, Edinburgh, UK, to obtain a range of sea state and reflection scenarios. The presented approach is found to provide improved estimates of directional spectra over standardmethods, reducing the mean apparent directional deviation down to below 6% over the range of sea states. Additionally, the method isolates incident and reflected spectra in both the frequency and time domain, and can separate these wave systems over 360°. The accuracy of themethod is shown to be only slightly sensitive to the level of in-line reflectionpresent,but at present cannot dealwithoblique reflections. The SPAIRmethod, as presented or with slightmodification, will allow complex directional sea states to be validated more effectively, enabling multidirectional wave basins to simulate realistic wave scenarios with increased confidence