Diagnosing observation error correlations for Doppler radar radial winds in the Met Office UKV model using observation-minus-background and observation-minus-analysis statistics

With the development of convection-permitting numerical weather prediction the efficient use of high resolution observations in data assimilation is becoming increasingly important. The operational assimilation of these observations, such as Dopplerradar radial winds, is now common, though to avoid violating the assumption of un- correlated observation errors the observation density is severely reduced. To improve the quantity of observations used and the impact that they have on the forecast will require the introduction of the full, potentially correlated, error statistics. In this work, observation error statistics are calculated for the Doppler radar radial winds that are assimilated into the Met Office high resolution UK model using a diagnostic that makes use of statistical averages of observation-minus-background and observation-minus-analysis residuals. This is the first in-depth study using the diagnostic to estimate both horizontal and along-beam correlated observation errors. By considering the new results obtained it is found that the Doppler radar radial wind error standard deviations are similar to those used operationally and increase as the observation height increases. Surprisingly the estimated observation error correlation length scales are longer than the operational thinning distance. They are dependent on both the height of the observation and on the distance of the observation away from the radar. Further tests show that the long correlations cannot be attributed to the use of superobservations or the background error covariance matrix used in the assimilation. The large horizontal correlation length scales are, however, in part, a result of using a simplified observation operator.

A generalised background correction algorithm for a Halo Doppler lidar and its application to data from Finland

Current commercially available Doppler lidars provide an economical and robust solution for measuring vertical and horizontal wind velocities, together with the ability to provide co- and cross-polarised backscatter profiles. The high temporal resolution of these instruments allows turbulent properties to be obtained from studying the variation in radial velocities. However, the instrument specifications mean that certain characteristics, especially the background noise behaviour, become a limiting factor for the instrument sensitivity in regions where the aerosol load is low. Turbulent calculations require an accurate estimate of the contribution from velocity uncertainty estimates, which are directly related to the signal-to-noise ratio. Any bias in the signal-to-noise ratio will propagate through as a bias in turbulent properties. In this paper we present a method to correct for artefacts in the background noise behaviour of commercially available Doppler lidars and reduce the signal-to-noise ratio threshold used to discriminate between noise, and cloud or aerosol signals. We show that, for Doppler lidars operating continuously at a number of locations in Finland, the data availability can be increased by as much as 50 % after performing this background correction and subsequent reduction in the threshold. The reduction in bias also greatly improves subsequent calculations of turbulent properties in weak signal regimes.

Diagnostic tool to analyse colour-magnitude diagrams of poorly populated stellar concentrations

The dynamical processes that lead to open cluster disruption cause its mass to decrease. To investigate such processes from the observational point of view, it is important to identify open cluster remnants (OCRs), which are intrinsically poorly populated. Due to their nature, distinguishing them from field star fluctuations is still an unresolved issue. In this work, we developed a statistical diagnostic tool to distinguish poorly populated star concentrations from background field fluctuations. We use 2MASS photometry to explore one of the conditions required for a stellar group to be a physical group: to produce distinct sequences in a colour-magnitude diagram (CMD). We use automated tools to (i) derive the limiting radius; (ii) decontaminate the field and assign membership probabilities; (iii) fit isochrones; and (iv) compare object and field CMDs, considering the isochrone solution, in order to verify the similarity. If the object cannot be statistically considered as a field fluctuation, we derive its probable age, distance modulus, reddening and uncertainties in a self-consistent way. As a test, we apply the tool to open clusters and comparison fields. Finally, we study the OCR candidates DoDz 6, NGC 272, ESO 435 SC48 and ESO 325 SC15. The tool is optimized to treat these low-statistic objects and to separate the best OCR candidates for studies on kinematics and chemical composition. The study of the possible OCRs will certainly provide a deep understanding of OCR properties and constraints for theoretical models, including insights into the evolution of open clusters and dissolution rates.

Statistical analysis of the Doppler broadening coincidence spectrum of electron-positron annihilation radiation in silicon

We report a statistical analysis of Doppler broadening coincidence data of electron-positron annihilation radiation in silicon using a (22)Na source. The Doppler broadening coincidence spectrum was fit using a model function that included positron annihilation at rest with 1s, 2s, 2p, and valence band electrons. In-flight positron annihilation was also fit. The response functions of the detectors accounted for backscattering, combinations of Compton effects, pileup, ballistic deficit, and pulse-shaping problems. The procedure allows the quantitative determination of positron annihilation with core and valence electron intensities as well as their standard deviations directly from the experimental spectrum. The results obtained for the core and valence band electron annihilation intensities were 2.56(9)% and 97.44(9)%, respectively. These intensities are consistent with published experimental data treated by conventional analysis methods. This new procedure has the advantage of allowing one to distinguish additional effects from those associated with the detection system response function. (C) 2009 Elsevier B.V. All rights reserved.

Refraction corrected transmission ultrasound computed tomography for application in breast imaging

Purpose: We present an iterative framework for CT reconstruction from transmission ultrasound data which accurately and efficiently models the strong refraction effects that occur in our target application: Imaging the female breast. Methods: Our refractive ray tracing framework has its foundation in the fast marching method (FNMM) and it allows an accurate as well as efficient modeling of curved rays. We also describe a novel regularization scheme that yields further significant reconstruction quality improvements. A final contribution is the development of a realistic anthropomorphic digital breast phantom based on the NIH Visible Female data set. Results: Our system is able to resolve very fine details even in the presence of significant noise, and it reconstructs both sound speed and attenuation data. Excellent correspondence with a traditional, but significantly more computationally expensive wave equation solver is achieved. Conclusions: Apart from the accurate modeling of curved rays, decisive factors have also been our regularization scheme and the high-quality interpolation filter we have used. An added benefit of our framework is that it accelerates well on GPUs where we have shown that clinical 3D reconstruction speeds on the order of minutes are possible.

Optimization of the ultrasound-assisted synthesis of allyl 1-naphthyl ether using response surface methodology

Allyl 1-naphthyl ethers are useful compounds for different purposes, but reported methods to synthesize them require long reaction times. In this work, we have obtained allyl 1-naphthyl ether in good yield using ultrasonic-assisted methodology in a 1-h reaction. A central composite design was used to obtain a statistical model and a response surface (p < 0.05; R(2) = 0.970; R(adj)(2) = 0.949; R(pred)(2) = 0.818) that can predict the optimal conditions to maximize the yield, validated experimentally. (C) 2010 Elsevier B.V. All rights reserved.

Ultrasound promoted greener synthesis of 2-(3,5-diaryl-4,5-dihydro-1H-pyrazol-1-yl)-4-phenylthiazoles

A rapid and cleaner procedure for the synthesis of a series of 2-(3,5-diaryl-45-dihydro-1H-pyrazol-1-yl)-4-phenylthiazoles under ultrasonic irradiation in ethanol is described. (C) 2010 Elsevier B.V. All rights reserved.

Evaluation of Red Colour Segmentation Algorithms in Traffic Signs Detection

Colour segmentation is the most commonly used method in road signs detection. Road sign contains several basic colours such as red, yellow, blue and white which depends on countries.The objective of this thesis is to do an evaluation of the four colour segmentation algorithms. Dynamic Threshold Algorithm, A Modification of de la Escalera’s Algorithm, the Fuzzy Colour Segmentation Algorithm and Shadow and Highlight Invariant Algorithm. The processing time and segmentation success rate as criteria are used to compare the performance of the four algorithms. And red colour is selected as the target colour to complete the comparison. All the testing images are selected from the Traffic Signs Database of Dalarna University [1] randomly according to the category. These road sign images are taken from a digital camera mounted in a moving car in Sweden.Experiments show that the Fuzzy Colour Segmentation Algorithm and Shadow and Highlight Invariant Algorithm are more accurate and stable to detect red colour of road signs. And the method could also be used in other colours analysis research. The yellow colour which is chosen to evaluate the performance of the four algorithms can reference Master Thesis of Yumei Liu.

Printing colour hard proofs using EFI Colorproof XF v. 3.1 and Photoshop CS3, and production substrates.

EFI Colorproof XF was found to be more convenient from a user’s aspect, and had features which are covered in the ISO 12647-7 standard (e.g. the ability to simulate screening and print margin information), which Photoshop CS3 lacked. None of the proofing systems distinguished itself in a clear way from the other; sometimes, on certain substrates, Photoshop CS3 produced most accurate colours, sometimes EFI Colorproof XF did. Further investigations need to be carried out to tell more exactly which system produce most accurate colours. Only 6 out of 34 simulation-combinations had colours within the tolerances in the standard. The result also shows that the production substrates should not be used as proofing substrates. Instead the proofing papers especially made for ink jet should be used to obtain more colour-accurate prints.

'Ultrasound is an invaluable third eye, but it can't see everything' : a qualitative study with obstetricians in Australia

Background: Obstetric ultrasound has come to play a significant role in obstetrics since its introduction in clinical care. Today, most pregnant women in the developed world are exposed to obstetric ultrasound examinations, and there is no doubt that the advantages of obstetric ultrasound technique have led to improvements in pregnancy outcomes. However, at the same time, the increasing use has also raised many ethical challenges. This study aimed to explore obstetricians' experiences of the significance of obstetric ultrasound for clinical management of complicated pregnancy and their perceptions of expectant parents' experiences. Methods: A qualitative study was undertaken in November 2012 as part of the CROss-Country Ultrasound Study (CROCUS). Semi-structured individual interviews were held with 14 obstetricians working at two large hospitals in Victoria, Australia. Transcribed data underwent qualitative content analysis. Results: An overall theme emerged during the analyses, 'Obstetric ultrasound - a third eye', reflecting the significance and meaning of ultrasound in pregnancy, and the importance of the additional information that ultrasound offers clinicians managing the surveillance of a pregnant woman and her fetus. This theme was built on four categories: I:'Everyday-tool' for pregnancy surveillance, II: Significance for managing complicated pregnancy, III: Differing perspectives on obstetric ultrasound, and IV: Counselling as a balancing act. In summary, the obstetricians viewed obstetric ultrasound as an invaluable tool in their everyday practice. More importantly however, the findings emphasise some of the clinical dilemmas that occur due to its use: the obstetricians' and expectant parents' differing perspectives and expectations of obstetric ultrasound examinations, the challenges of uncertain ultrasound findings, and how this information was conveyed and balanced by obstetricians in counselling expectant parents. Conclusions: This study highlights a range of previously rarely acknowledged clinical dilemmas that obstetricians face in relation to the use of obstetric ultrasound. Despite being a tool of considerable significance in the surveillance of pregnancy, there are limitations and uncertainties that arise with its use that make counselling expectant parents challenging. Research is needed which further investigates the effects and experiences of the continuing worldwide rapid technical advances in surveillance of pregnancies.

Rastreamento da insuficiência placentária através do Doppler das artérias uterinas por via transvaginal entre 22 e 24 semanas de gestação

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