Using sources of opportunity to compensate for receiver mismatch in HF arrays

© 2001 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.The spatial processing performance of adaptive sensor arrays is often limited by the nonidentical frequency responses of the receivers in the array over the passband of interest. Addressed here is the problem of estimating digital compensation for mismatches between receiver passbands in high frequency (HF) antenna arrays using interference sources of opportunity. A mathematical model of ionospherically-propagated multipath HF interference is used to develop an adaptive algorithm which estimates the receiver frequency response corrections for each receiver. The effectiveness of the proposed algorithm is experimentally demonstrated and compared against (1) a commonly used least squares technique, and (2) a highly accurate calibration system using data collected by the receiving antenna array of the Jindalee over-the-horizon radar near Alice Springs in central AustraliaFabrizio, G.A.; Gray, D.A.; Turley, M.D

The Effects of Oxidation on the Refractive Index of Uranium Thin Films in the Extreme Ultraviolet

We measured the transmittance and reflectance of two samples in the extreme ultraviolet (XUV) at the Advanced Light Source at Lawrence Berkeley National Laboratory. The samples were prepared with approximately 20 nm of UOx with one reactively sputtered onto a diode, and one allowed to oxidize naturally on an identical diode. Fitting the reflectance data to the Parratt model yielded a more precise thickness of the UOx film. This thickness combined with a simple analysis of the transmission measurements provides estimates for the imaginary part of the index of refraction for UOx at approximately every tenth of a nanometer from about 3 nm to 30 nm with emphasis in the 12- to 13-nm range. Using these values, a first approximation for the real part of the refractive index has also been calculated. These values provide researchers with information for modeling, design, and fabrication of optical systems in the extreme ultraviolet

High-pressure melt curve of shock-compressed tin measured using pyrometry and reflectance techniques

We have developed a new technique to measure the melt curve of a shocked metal sample and have used it to measure the high-pressure solid-liquid phase boundary of tin from 10 to 30 GPa and 1000 to 1800 K. Tin was shock compressed by plate impact using a single-stage powder gun, and we made accurate, time-resolved radiance, reflectance, and velocimetry measurements at the interface of the tin sample and a lithium fluoride window. From these measurements, we determined temperature and pressure at the interface vs time. We then converted these data to temperature vs pressure curves and plotted them on the tin phase diagram. The tin sample was initially shocked into the high-pressure solid γ phase, and a subsequent release wave originating from the back of the impactor lowered the pressure at the interface along a constant entropy path (release isentrope). When the release isentrope reaches the solid-liquid phase boundary, melt begins and the isentrope follows the phase boundary to low pressure. The onset of melt is identified by a significant change in the slope of the temperature-pressure release isentrope. Following the onset of melt, we obtain a continuous and highly accurate melt curve measurement. The technique allows a measurement along the melt curve with a single radiance and reflectance experiment. The measured temperature data are compared to the published equation of state calculations. Our data agree well with some but not all of the published melt curve calculations, demonstrating that this technique has sufficient accuracy to assess the validity of a given equation of state model

From laboratory manipulations to Earth system models: scaling calcification impacts of ocean acidification

The observed variation in the calcification responses of coccolithophores to changes in carbonate chemistry paints a highly incoherent picture, particularly for the most commonly cultured "species", <i>Emiliania huxleyi</i>. The disparity between magnitude and potentially even sign of the calcification change under simulated end-of-century ocean surface chemical changes (higher <i>p</i>CO<sub>2</sub>, lower pH and carbonate saturation), raises challenges to quantifying future carbon cycle impacts and feedbacks because it introduces significant uncertainty in parameterizations used for global models. Here we compile the results of coccolithophore carbonate chemistry manipulation experiments and review how ocean carbon cycle models have attempted to bridge the gap from experiments to global impacts. Although we can rule out methodological differences in how carbonate chemistry is altered as introducing an experimental bias, the absence of a consistent calcification response implies that model parameterizations based on small and differing subsets of experimental observations will lead to varying estimates for the global carbon cycle impacts of ocean acidification. We highlight two pertinent observations that might help: (1) the degree of coccolith calcification varies substantially, both between species and within species across different genotypes, and (2) the calcification response across mesocosm and shipboard incubations has so-far been found to be relatively consistent. By analogy to descriptions of plankton growth rate vs. temperature, such as the "Eppley curve", which seek to encapsulate the net community response via progressive assemblage change rather than the response of any single species, we posit that progressive future ocean acidification may drive a transition in dominance from more to less heavily calcified coccolithophores. Assemblage shift may be more important to integrated community calcification response than species-specific response, highlighting the importance of whole community manipulation experiments to models in the absence of a complete physiological understanding of the underlying calcification process. However, on a century time-scale, regardless of the parameterization adopted, the atmospheric <i>p</i>CO<sub>2</sub> impact of ocean acidification is minor compared to other global carbon cycle feedbacks

Evaluation of range of motion restriction within the hip joint

In Total Hip Arthroplasty, determining the impingement free range of motion requirement is a complex task. This is because in the native hip, motion is restricted by both impingement as well as soft tissue restraint. The aim of this study is to determine a range of motion benchmark which can identify motions which are at risk from impingement and those which are constrained due to soft tissue. Two experimental methodologies were used to determine motions which were limited by impingement and those motions which were limited by both impingement and soft tissue restraint. By comparing these two experimental results, motions which were limited by impingement were able to be separated from those motions which were limited by soft tissue restraint. The results show motions in extension as well as flexion combined with adduction are limited by soft tissue restraint. Motions in flexion, flexion combined with abduction and adduction are at risk from osseous impingement. Consequently, these motions represent where the maximum likely damage will occur in femoroacetabular impingement or at most risk of prosthetic impingement in Total Hip Arthroplasty

Doing it differently: Engaging interview participants with imaginative variation

Imaginative variation was identified by Husserl (1936/1970) as a phenomenological technique for the purpose of elucidating the manner in which phenomena appear to consciousness. Briefly, by engaging in the phenomenological reduction and using imaginative variation, phenomenologists are able to describe the experience of consciousness, having stepped outside of the natural attitude through the epochē. Imaginative variation is a stage aimed at explicating the structures of experience, and is best described as a mental experiment. Features of the experience are imaginatively altered in order to view the phenomenon under investigation from varying perspectives. Husserl argued that this process will reveal the essences of an experience, as only those aspects that are invariant to the experience of the phenomenon will not be able to change through the variation. Often in qualitative research interviews, participants struggle to articulate or verbalise their experiences. The purpose of this article is to detail a radical and novel way of using imaginative variation with interview participants, by asking the participants to engage with imaginative variation, in order to produce a rich and insightful experiential account of a phenomenon. We will discuss how the first author successfully used imaginative variation in this way in her study of the erotic experience of bondage, discipline, dominance & submission, and sadism & masochism (BDSM), before considering the usefulness of this technique when applied to areas of study beyond sexuality

Use of patient-held information about medication (PHIMed) to support medicines optimisation: protocol for a mixed-methods descriptive study

Introduction: Risks of poor information transfer across health settings are well documented, particularly for medication. There is also increasing awareness of the importance of greater patient activation. Patients may use various types of patient-held information about medication (PHIMed) to facilitate medication transfer, which may be paper or electronic. However, it is not known how PHIMed should best be used, whether it improves patient outcomes, nor is its key ‘active ingredients’ known. Discussion with patients and carers has highlighted this as a priority for research. We aim to identify how PHIMed is used in practice, barriers and facilitators to its use and key features of PHIMed that support medicines optimisation in practice. // Methods and analysis: This study will take place in Greater London, England. We will include patients with long-term conditions, carers and healthcare professionals. The study has four work packages (WPs). WP1 involves qualitative interviews with healthcare professionals (n=16) and focus groups with patients and carers (n=20), including users and non-users of PHIMed, to study perceptions around its role, key features, barriers and facilitators, and any unintended consequences. WP2 will involve documentary analysis of how PHIMed is used, what is documented and read, and by whom, in a stratified sample of 60 PHIMed users. In WP3, we will carry out a descriptive analysis of PHIMed tools used/available, both electronic and paper, and categorise their design and key features based on those identified in WP1/2. Finally, in WP4, findings from WPs 1–3 will be integrated and analysed using distributed cognition as a theoretical framework to explore how information is recorded, transformed and propagated among different people and artefacts. // Ethics and dissemination: The study has National Health Service ethics approval. It will provide initial recommendations around the present use of PHIMed to optimise patient care for patients, carers and healthcare professionals