WorldWideScience

Sample records for aperture restriction localisation

  1. Aperture Restriction Localisation in the LHC Arcs using an RF Mole and the LHC Beam Position Measurement System

    CERN Document Server

    Albertone, J; Boccard, C; Bogey, T; Borowiec, P; Calvo, E; Caspers, Friedhelm; Gasior, M; González, J L; Jenninger, B; Jensen, L K; Jones, O R; Kroyer, T; Weisz, S

    2008-01-01

    Ensuring that the two 27km beam pipes of the LHC do not contain aperture restrictions is of utmost importance. Most of the ring is composed of continuous cryostats, so any intervention to remove aperture restrictions when the machine is at its operating temperature of 1.9K will require a substantial amount of time. On warming-up the first cooled sector, several of the sliding contacts which provide electrical continuity for the beam image current between successive sections of the vacuum chamber were found to have buckled into the beam pipe. This led to a search for a technique to verify the integrity of a complete LHC arc (~3km) before any subsequent cool-down. In this paper the successful results from using a polycarbonate ball fitted with a 40MHz RF transmitter are presented. Propulsion of the ball is achieved by sucking filtered air through the entire arc, while its progress is traced every 54m via the LHC beam position measurement system which is auto-triggered by the RF transmitter on passage of the bal...

  2. Apertures

    CERN Document Server

    Hansen, R C

    2014-01-01

    Microwave Scanning Antennas, Volume I: Apertures is a comprehensive account of phased arrays, multiple beam arrays, time domain and synthetic apertures, and adaptive antennas. Advances in continuous apertures and near field theory are discussed. Low noise and monopulse apertures, optical scanners, and large radomes are also covered, along with radio astronomy instruments and associated theory.Comprised of five chapters, this volume begins with an overview of aperture theory as well as aperture distributions and near field theory. The second and third chapters deal with mechanically steered and

  3. Localisation of silicon nanowires grown by UHV-CVD in (111)-oriented apertures opened in Si (001)

    International Nuclear Information System (INIS)

    In this paper, we have investigated an alternative method to obtain well-organized silicon nanowires grown by vapor-liquid-solid process. We have studied the influence of the droplet size on the growth direction of nanowires on plain wafers. By using self-organized Au droplets grown by molecular beam epitaxy on vicinal Si(111) surface with a 20 miscut towards the [11-2] crystallographic direction, we have obtained well organized gold droplets along the steps with small size dispersion. The growth of Si nanowires from these droplets allows defining a critical diameter for changing the Si nanowires growth direction. When the gold droplet diameter is larger than 100 nm, Si nanowires exhibit a orientation and remain free of structural defects. The localisation of Si nanowires was performed in nanoscale silicon seeds formed by modified local oxidation of silicon process. This approach, based on a simple and reliable method, enable the organisation of Si nanowires with orientation on Si(001) substrates.

  4. Energy localisation and transfer

    CERN Document Server

    Dauxois, Thierry; MacKay, Robert; Spanoudaki, Anna

    2004-01-01

    This book provides an introduction to localised excitations in spatially discrete systems, from the experimental, numerical and mathematical points of view. Also known as discrete breathers, nonlinear lattice excitations and intrinsic localised modes, these are spatially localised time periodic motions in networks of dynamical units. Examples of such networks are molecular crystals, biomolecules, and arrays of Josephson superconducting junctions. The book also addresses the formation of discrete breathers and their potential role in energy transfer in such systems. Contents: Computational Stud

  5. Localised Microwave Bursts During ELMs on MAST

    Directory of Open Access Journals (Sweden)

    Freethy Simon

    2015-01-01

    Full Text Available Bursts of microwave emission are observed during ELM events on the Mega Ampère Spherical Tokamak. In agreement with observations on other machines, these bursts are up to 3 orders of magnitude more intense than the thermal background, but are electron cyclotron in nature. The peak in microwave emission is ~20μ before the peak in midplane Dα emission. Using the Synthetic Aperture Microwave Imaging radiometer, we are able to demonstrate that these bursts are often highly spatially localised and preferentially occur at the tokamak midplane. It is hypothesised that the localisation is a result of Doppler resonance broadening for electron Bernstein waves and the high perpendicular electron energies could be the result of pitch angle scattering in high collisionality regions of the plasma.

  6. Sequential Beamforming Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

    Kortbek, Jacob; Jensen, Jørgen Arendt; Gammelmark, Kim Løkke

    2013-01-01

    Synthetic aperture sequential beamforming (SASB) is a novel technique which allows to implement synthetic aperture beamforming on a system with a restricted complexity, and without storing RF-data. The objective is to improve lateral resolution and obtain a more depth independent resolution...

  7. Localisation in Quantum Field Theory

    CERN Document Server

    Balachandran, A P

    2016-01-01

    In nonrelativistic quantum mechanics , Born's principle of localisation is as follows: For a single particle, if a wave function $\\psi_K$ vanishes outside a spatial region $K$, it is said to be localised in $K$. In particular if a spatial region $K'$ is disjoint from $K$, a wave function $\\psi_{K'}$ localised in $K'$ is orthogonal to $\\psi_K$. Such a principle of localisation does not exist compatibly with relativity and causality in quantum field theory (Newton and Wigner) or interacting point particles (Currie,Jordan and Sudarshan).It is replaced by symplectic localisation of observables as shown by Brunetti, Guido and Longo, Schroer and others. This localisation gives a simple derivation of the spin-statistics theorem and the Unruh effect, and shows how to construct quantum fields for anyons and for massless particles with `continuous' spin. This review outlines the basic principles underlying symplectic localisation and shows or mentions its deep implications. In particular, it has the potential to affect...

  8. Localisation of corneal foreign bodies.

    OpenAIRE

    Kay-Wilson, L. G.

    1992-01-01

    Of 50 patients attending the eye casualty department with a corneal foreign body (FB), 41 were able to say where they felt the FB and 78% of these were localised correctly for side or level of cornea. Patient handedness did not influence FB location. Indicating the upper lid was a particularly poor guide to localisation, whereas FB sensations within the palpebral fissure, in the lower lid or medially or laterally were good guides to actual FB location. A simple method of recording FB location...

  9. AUTOMATIC LICENSE PLATE LOCALISATION AND IDENTIFICATION VIA SIGNATURE ANALYSIS

    Directory of Open Access Journals (Sweden)

    Lorita Angeline

    2014-02-01

    Full Text Available A new algorithm for license plate localisation and identification is proposed on the basis of Signature analysis. Signature analysis has been used to locate license plate candidate and its properties can be further utilised in supporting and affirming the license plate character recognition. This paper presents Signature Analysis and the improved conventional Connected Component Analysis (CCA to design an automatic license plate localisation and identification. A procedure called Euclidean Distance Transform is added to the conventional CCA in order to tackle the multiple bounding boxes that occurred. The developed algorithm, SAICCA achieved 92% successful rate, with 8% failed localisation rate due to the restrictions such as insufficient light level, clarity and license plate perceptual information. The processing time for a license plate localisation and recognition is a crucial criterion that needs to be concerned. Therefore, this paper has utilised several approaches to decrease the processing time to an optimal value. The results obtained show that the proposed system is capable to be implemented in both ideal and non-ideal environments.

  10. Braneworld localisation in hyperbolic spacetime

    CERN Document Server

    Crampton, B; Stelle, K S

    2014-01-01

    We present a construction employing a type IIA supergravity and 3-form flux background together with an NS5-brane that localises massless gravity near the 5-brane worldvolume. The nonsingular underlying type IIA solution is a lift to 10D of the vacuum solution of the 6D Salam-Sezgin model and has a hyperbolic ${\\cal H}^{(2,2)}\\times S^1$ structure in the lifting dimensions. A fully back-reacted solution including the NS5-brane is constructed by recognising the 10D Salam-Sezgin vacuum solution as a "brane resolved through transgression." The background hyperbolic structure plays a key r\\^ole in generating a mass gap in the spectrum of the transverse-space wave operator, which gives rise to the localisation of gravity on the 6D NS5-brane worldvolume, or, equally, in a further compactification to 4D. Also key to the successful localisation of gravity is the specific form of the corresponding transverse wavefunction Schr\\"odinger problem, which asymptotically involves a $V=-1/(4\\rho^2)$ potential, where $\\rho$ is...

  11. Towards a theory of optimal localisation

    Directory of Open Access Journals (Sweden)

    Jonathan Flowerdew

    2015-02-01

    Full Text Available All practical ensemble-based atmospheric data assimilation (DA systems use localisation to reduce the damaging impact of spurious long-range correlations arising from the finite ensemble size. However, the form of the localisation function is generally ad-hoc, and requires expensive tuning to optimise the system. For the case of a single observation and known true background error correlation, we derive an expression for the localisation factor that minimises the expected root-mean-square (RMS analysis error. Idealised tests show this formulation performs well for multiple observations provided their density is not too high. The width of the optimal localisation function scales with the width of the underlying correlation, but does not have the same shape. The optimal observation-space localisation for a single spatially integrating observation depends on the observation-to-gridpoint background error correlation, making it broader than the optimal localisation for point observations and potentially competitive with model-space localisation. A new form of hybrid DA is proposed in which localisation damps the sample correlations towards their climatological mean rather than zero, reducing the RMS error and potentially improving the dynamic balance of the analysis. The presence of variance errors causes the optimal localisation factor to depend on the ratio of observation to background error variance, and raises the possibility that a small amount of variance damping may be beneficial. For dense observations, a more elaborate theory is required, which will almost certainly depend on the observation network. We present some preliminary analysis of the features of the multi-observation problem, which for instance suggests that the optimal solution may involve different localisation factors in the numerator and denominator of the Kalman filter equation. We note that even optimal localisation gives an expected RMS error which exceeds that of perfect DA

  12. Multimodal localisation : analysis, algorithms and experimental evaluation

    NARCIS (Netherlands)

    Muthukrishnan, Kavitha

    2009-01-01

    The term localisation is derived from the word locale, which traditionally means a small area or vicinity. In ancient days, localisation meant navigation -- an art of finding the way from one place to another. Tremendous advancement in the science of navigation dates back to the sixteenth century, w

  13. Stochastic metastability by spontaneous localisation

    International Nuclear Information System (INIS)

    Nonequilibrium, quasi-stationary states of a one-dimensional “hard” ϕ4 deterministic lattice, initially thermalised to a particular temperature, are investigated when brought into contact with a stochastic thermal bath at lower temperature. For lattice initial temperatures sufficiently higher than those of the bath, energy localisation through the formation of nonlinear excitations of the breather type during the cooling process occurs. These breathers keep the nonlinear lattice away from thermal equilibrium for relatively long times. In the course of time some breathers are destroyed by fluctuations, allowing thus the lattice to reach another nonequilibrium state of lower energy. The number of breathers thus reduces in time; the last remaining breather, however, exhibits amazingly long life-time demonstrated by extensive numerical simulations using a quasi-symplectic integration algorithm. For the single-breather states we have calculated the lattice velocity distribution unveiling non-Gaussian features describable in a closed functional form. Moreover, the influence of the coupling constant on the life-time of a single breather has been explored. The latter exhibits power-law behaviour as the coupling constant approaches the anticontinuous limit

  14. C.T. - guided percutaneous biopsy localisation

    International Nuclear Information System (INIS)

    CT guided percutaneous biopsy procedures are being performed with increasing frequency to provide specimens for cytologic analysis when small deeply positioned or inaccessible lesions within the body are suspected of malignancy. The localisation techniques employed are discussed

  15. Multimodal localisation : analysis, algorithms and experimental evaluation

    OpenAIRE

    Muthukrishnan, Kavitha

    2009-01-01

    The term localisation is derived from the word locale, which traditionally means a small area or vicinity. In ancient days, localisation meant navigation -- an art of finding the way from one place to another. Tremendous advancement in the science of navigation dates back to the sixteenth century, when instruments like compasses, sextants and the first ever clock to keep the time exactly were devised. Advancement in navigation brought ways and means to explore the world, be it for expansion o...

  16. Variable-aperture screen

    Science.gov (United States)

    Savage, George M.

    1991-01-01

    Apparatus for separating material into first and second portions according to size including a plurality of shafts, a plurality of spaced disks radiating outwardly from each of the shafts to define apertures and linkage interconnecting the shafts for moving the shafts toward or away from one another to vary the size of the apertures while the apparatus is performing the separating function.

  17. Mastering Apple Aperture

    CERN Document Server

    Fitzgerald, Thomas

    2013-01-01

    Written in a conversational style, the author will share his knowledge on advanced Aperture topics with detailed discussions of advanced topics, the theory behind some of those topics and lots of hints and tips for ways to improve your workflow.Photographer's who have a basic understanding of Aperture

  18. Synthetic Aperture Sequential Beamforming

    DEFF Research Database (Denmark)

    Kortbek, Jacob; Jensen, Jørgen Arendt; Gammelmark, Kim Løkke

    2008-01-01

    A synthetic aperture focusing (SAF) technique denoted Synthetic Aperture Sequential Beamforming (SASB) suitable for 2D and 3D imaging is presented. The technique differ from prior art of SAF in the sense that SAF is performed on pre-beamformed data contrary to channel data. The objective is to...

  19. Rotating Aperture System

    Science.gov (United States)

    Rusnak, Brian; Hall, James M.; Shen, Stewart; Wood, Richard L.

    2005-01-18

    A rotating aperture system includes a low-pressure vacuum pumping stage with apertures for passage of a deuterium beam. A stator assembly includes holes for passage of the beam. The rotor assembly includes a shaft connected to a deuterium gas cell or a crossflow venturi that has a single aperture on each side that together align with holes every rotation. The rotating apertures are synchronized with the firing of the deuterium beam such that the beam fires through a clear aperture and passes into the Xe gas beam stop. Portions of the rotor are lapped into the stator to improve the sealing surfaces, to prevent rapid escape of the deuterium gas from the gas cell.

  20. Sub-Aperture Interferometers

    Science.gov (United States)

    Zhao, Feng

    2010-01-01

    Sub-aperture interferometers -- also called wavefront-split interferometers -- have been developed for simultaneously measuring displacements of multiple targets. The terms "sub-aperture" and "wavefront-split" signify that the original measurement light beam in an interferometer is split into multiple sub-beams derived from non-overlapping portions of the original measurement-beam aperture. Each measurement sub-beam is aimed at a retroreflector mounted on one of the targets. The splitting of the measurement beam is accomplished by use of truncated mirrors and masks, as shown in the example below

  1. Geographical localisation of the geomagnetic secular variation

    DEFF Research Database (Denmark)

    Aubert, Julien; Finlay, Chris; Olsen, Nils

    2013-01-01

    Directly observed changes in Earth’s magnetic field occur most prominently at low latitudes beneath the Atlantic hemisphere, while the Pacific is comparatively quiet. This striking hemispheric asymmetry in geomagnetic secular variation is a consequence of the geographical localisation of intense...... control from either, or both, the inner-core boundary and the core-mantle boundary. In addition to presenting an Earth-like magnetic field morphology, these new numerical models also reproduce the morphology and localization of geomagnetic secular variation. In our models, the conservation of the angular...... thermochemical boundary control distorts this gyre (the strongest distortion being obtained with inner core heterogeneous control) and localises the field changes in a hemispherical longitudinal sector. The two effects combine to recreate the observed localisation of geomagnetic secular variation in both...

  2. Globally reasoning about localised security policies in distributed systems

    DEFF Research Database (Denmark)

    Hernandez, Alejandro Mario

    control decisions of the system, and the Semantics also takes care of this. Using the Semantics, a Labelled Transition System (LTS) can be induced for every particular system, and over this LTS some model checking tasks could be done. We identify how this LTS is indeed obtained, and propose an alternative......In this report, we aim at establishing proper ways for model checking the global security of distributed systems, which are designed consisting of set of localised security policies that enforce specific issues about the security expected. The systems are formally specified following a syntax...... way of model checking the not-yet-induced LTS, by using the system design directly. This may lead to over-approximation thereby producing imprecise, though safe, results. We restrict ourselves to finite systems, in the sake of being certain about the decidability of the proposed method. To illustrate...

  3. Primary localised cutaneous amyloidosis - a systematic review

    DEFF Research Database (Denmark)

    Kaltoft, Britta; Schmidt, Grethe; Lauritzen, Anne Falensteen;

    2013-01-01

    Amyloidosis is defined as extracellular deposits of heterogenic, misfolded proteins, amyloid fibrils, in various tissues. The aim of our study was to review the literature and to evaluate the risk of developing systemic amyloidosis (SA) and the risk of local recurrence of primary localised...

  4. A Localised Corrosion Cell for Industrial Applications

    DEFF Research Database (Denmark)

    Andersen, A.; Hilbert, Lisbeth Rischel; Jansen, P.;

    2003-01-01

    The LOCORR-CELL™ developed by FORCE TECHNOLOGY is an electrochemical cell for industrial applications estimating localised corrosion. The cell is constructed in a carbon steel casing for direct mounting into the system. It is based on an oxygen concentration element reflecting the interaction...

  5. An incremental approach to automated protein localisation

    Directory of Open Access Journals (Sweden)

    Kummert Franz

    2008-10-01

    Full Text Available Abstract Background The subcellular localisation of proteins in intact living cells is an important means for gaining information about protein functions. Even dynamic processes can be captured, which can barely be predicted based on amino acid sequences. Besides increasing our knowledge about intracellular processes, this information facilitates the development of innovative therapies and new diagnostic methods. In order to perform such a localisation, the proteins under analysis are usually fused with a fluorescent protein. So, they can be observed by means of a fluorescence microscope and analysed. In recent years, several automated methods have been proposed for performing such analyses. Here, two different types of approaches can be distinguished: techniques which enable the recognition of a fixed set of protein locations and methods that identify new ones. To our knowledge, a combination of both approaches – i.e. a technique, which enables supervised learning using a known set of protein locations and is able to identify and incorporate new protein locations afterwards – has not been presented yet. Furthermore, associated problems, e.g. the recognition of cells to be analysed, have usually been neglected. Results We introduce a novel approach to automated protein localisation in living cells. In contrast to well-known techniques, the protein localisation technique presented in this article aims at combining the two types of approaches described above: After an automatic identification of unknown protein locations, a potential user is enabled to incorporate them into the pre-trained system. An incremental neural network allows the classification of a fixed set of protein location as well as the detection, clustering and incorporation of additional patterns that occur during an experiment. Here, the proposed technique achieves promising results with respect to both tasks. In addition, the protein localisation procedure has been adapted

  6. Aperture distribution of rock fractures

    International Nuclear Information System (INIS)

    This thesis concerns the properties of the fracture void geometry of single rock fractures. It is suggested that the parameter aperture be used to describe the fracture void geometry and a definition of the aperture is proposed. The relation between void geometry and other fracture properties such as roughness, stiffness, conductivity and channelling are discussed. Different experimental techniques for aperture measurement have been developed in this work. The methods are applicable to fractures of different nature and size. A compilation of measurement results indicates that the spatial correlation (range) of fracture apertures increases with increasing mean aperture and that the range is correlated with the coefficient of variation. The existing data from aperture measurements and fracture flow experiments are still very scarce, in particular for fractures with large apertures. For future research, additional aperture measurements from fractures of different types is recommended. A further development of aperture measurement techniques suitable for field investigation is also suggested. 31 refs, 18 figs

  7. Apodizer aperture for lasers

    Science.gov (United States)

    Jorna, Siebe; Siebert, Larry D.; Brueckner, Keith A.

    1976-11-09

    An aperture attenuator for use with high power lasers which includes glass windows shaped and assembled to form an annulus chamber which is filled with a dye solution. The annulus chamber is shaped such that the section in alignment with the axis of the incident beam follows a curve which is represented by the equation y = (r - r.sub.o).sup.n.

  8. The LHC dynamic aperture

    CERN Document Server

    Koutchouk, Jean-Pierre

    1999-01-01

    In 1996, the expected field errors in the dipoles and quadrupoles yielded a long-term dynamic aperture of some 8sigma at injection. The target was set to 12sigma to account for the limitations of our model (imperfections and dynamics). From scaling laws and tracking, a specification for the field imperfections yielding the target dynamic aperture was deduced. The gap between specification and expected errors is being bridged by i) an improvement of the dipole field quality, ii) a balance between geometric and persistent current errors, iii) additional correction circuits (a3 ,b4 ). With the goal in view, the emphasis has now turned to the sensitivity of the dynamic aperture to the optical parameters.The distortion of the dynamics at the lower amplitudes effectively reached by the particles is minimized by optimizing the distribution of the betatron phase advance. At collision energy, the dynamic aperture is limited by the field imperfections of the low-beta triplets, enhanced by the crossing angle. With corre...

  9. Apertured paraxial Bessel beams.

    Science.gov (United States)

    Umul, Yusuf Z

    2010-03-01

    The paraxial Bessel beam is obtained by applying an approximation in the wavenumbers. The scattering of the beams by a circular aperture in an absorbing screen is investigated. The scattered fields are expressed in terms of the Fresnel integrals by evaluating the Kirchhoff diffraction integral in the paraxial approximation. The results are examined numerically. PMID:20208927

  10. Synthetic Aperture Radar Interferometry

    Science.gov (United States)

    Rosen, P. A.; Hensley, S.; Joughin, I. R.; Li, F.; Madsen, S. N.; Rodriguez, E.; Goldstein, R. M.

    1998-01-01

    Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristics of the surface. This paper reviews the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.

  11. Recovery of infrastructure networks after localised attacks

    Science.gov (United States)

    Hu, Fuyu; Yeung, Chi Ho; Yang, Saini; Wang, Weiping; Zeng, An

    2016-04-01

    The stability of infrastructure network is always a critical issue studied by researchers in different fields. A lot of works have been devoted to reveal the robustness of the infrastructure networks against random and malicious attacks. However, real attack scenarios such as earthquakes and typhoons are instead localised attacks which are investigated only recently. Unlike previous studies, we examine in this paper the resilience of infrastructure networks by focusing on the recovery process from localised attacks. We introduce various preferential repair strategies and found that they facilitate and improve network recovery compared to that of random repairs, especially when population size is uneven at different locations. Moreover, our strategic repair methods show similar effectiveness as the greedy repair. The validations are conducted on simulated networks, and on real networks with real disasters. Our method is meaningful in practice as it can largely enhance network resilience and contribute to network risk reduction.

  12. Comparing mobile robot localisation algorithms using Kalmtool

    DEFF Research Database (Denmark)

    Mogensen, Lars Valdemar; Hansen, Søren; Ravn, Ole;

    2009-01-01

    In this paper we present an estimation platform with simulation capabilities to evaluate methods for localisation of a mobile robot using a feature map. The platform is based on the Kalmtool 4 toolbox which is a set of MATLAB tools for state estimation of nonlinear systems. The toolbox contains f...... functions for extended Kalman filtering as well as for the DD1 filter and the DD2 filter. It also contains functions for Unscented Kalman filters as well as three versions of particle filters. The toolbox requires MATLAB version 7, but no additional toolboxes are required.......In this paper we present an estimation platform with simulation capabilities to evaluate methods for localisation of a mobile robot using a feature map. The platform is based on the Kalmtool 4 toolbox which is a set of MATLAB tools for state estimation of nonlinear systems. The toolbox contains...

  13. The Role of Localisation in Advertising Translation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ying

    2016-01-01

    Today, a growing number of international corporations have been seeking to boost their sales on the global scale. To achieve this, adverting, one of the most common way to stimulate consumption, is widely used in which translation is involved because of diverse languages. Thus, how to translate a source advertising in a target culture has a decisive influence on a compa-ny’s marketing. The aim of the target advertising is to sell products to the locals. In this sense, localisation plays a significant role in the translation of advertising. This essay will discuss the importance of localisation in the translation of advertising and analyse cases of English-Chinese advertising translation based on the purpose of advertising and advertising translation.

  14. SCANNING KELVIN PROBE APPLIED TO LOCALISED CORROSION

    OpenAIRE

    Hussain, A.; Sk M. Haque

    2015-01-01

    This paper focuses on specific applications of the SKP system. The instrument is calibrated, using different thickness of a model polymer Poly Vinyl Butyral (PVB) on mild steel and on galvanised steel. Artificial defects are used to show how the instrument is capable of detecting a localised corrosion cell and its ability to picture the delamination of the coating from the steel substrate. An industrial application is undertaken with the instrument, where epoxy coated galvanised steel; with a...

  15. Engineering Design of Localised Synergistic Production Systems

    OpenAIRE

    Leung Pah Hang, M; Martinez-Hernandez, E.; M. Leach; Yang, A.

    2015-01-01

    Centralised production of essential products and services based on fossil fuels and large scale distribution infrastructures have contributed to a plethora of issues such as deterioration of ecosystems, social-economic injustice and depletion of resources. The establishment of localised production systems can potentially reduce unsustainable resource consumption and bring socioeconomic and environmental benefits. The main objective of this work is to develop engineering tools for the rational...

  16. Survey of coded aperture imaging

    International Nuclear Information System (INIS)

    The basic principle and limitations of coded aperture imaging for x-ray and gamma cameras are discussed. Current trends include (1) use of time varying apertures, (2) use of ''dilute'' apertures with transmission much less than 50%, and (3) attempts to derive transverse tomographic sections, unblurred by other planes, from coded images

  17. Congenital pyriform aperture stenosis

    Energy Technology Data Exchange (ETDEWEB)

    Osovsky, Micky [Schneider Pediatric Hospital, Department of Neonatology, Petach Tikvah (Israel); Rabin Medical Center, Department of Neonatology, Schneider Children' s Medical Center of Israel, Beilinson Campus, Petah Tikvah (Israel); Aizer-Danon, Anat; Horev, Gadi [Schneider Pediatric Hospital, Department of Pediatric Radiology, Petach Tikvah (Israel); Sirota, Lea [Schneider Pediatric Hospital, Department of Neonatology, Petach Tikvah (Israel)

    2007-01-15

    Nasal airway obstruction is a potentially life-threatening condition in the newborn. Neonates are obligatory nasal breathers. The pyriform aperture is the narrowest, most anterior bony portion of the nasal airway, and a decrease in its cross-sectional area will significantly increase nasal airway resistance. Congenital nasal pyriform aperture stenosis (CNPAS) is a rare, unusual form of nasal obstruction. It should be considered in the differential diagnosis of any neonate or infant with signs and symptoms of upper airway compromise. It is important to differentiate this level of obstruction from the more common posterior choanal stenosis or atresia. CNPAS presents with symptoms of nasal airway obstruction, which are often characterized by episodic apnea and cyclical cyanosis. (orig.)

  18. Complex Aperture Networks

    CERN Document Server

    Owladeghaffari, Hamed

    2009-01-01

    A complex network approach on a rough fracture is developed. In this manner, some hidden metric spaces (similarity measurements) between apertures profiles are set up and a general evolutionary network in two directions (in parallel and perpendicular to the shear direction) is constructed. Evaluation of the emerged network shows the connectivity degree (distribution) of network, after a transition step; fall in to the stable states which are coincided with the Gaussian distribution. Based on this event and real observations of the complex network changes, an algorithm (COmplex Networks on Apertures: CONA) is proposed in which evolving of a network is accomplished using preferential detachments and attachments of edges (based on a competition and game manner) while the number of nodes is fixed. Also, evolving of clustering coefficients and number of edges display similar patterns as well as are appeared in shear stress, hydraulic conductivity and dilation changes, which can be engaged to estimate shear strengt...

  19. Configurable Aperture Space Telescope

    Science.gov (United States)

    Ennico, Kimberly; Bendek, Eduardo

    2015-01-01

    In December 2014, we were awarded Center Innovation Fund to evaluate an optical and mechanical concept for a novel implementation of a segmented telescope based on modular, interconnected small sats (satlets). The concept is called CAST, a Configurable Aperture Space Telescope. With a current TRL is 2 we will aim to reach TLR 3 in Sept 2015 by demonstrating a 2x2 mirror system to validate our optical model and error budget, provide straw man mechanical architecture and structural damping analyses, and derive future satlet-based observatory performance requirements. CAST provides an alternative access to visible and/or UV wavelength space telescope with 1-meter or larger aperture for NASA SMD Astrophysics and Planetary Science community after the retirement of HST

  20. Synthetic Aperture Radiometer Systems

    Science.gov (United States)

    LeVine, David M.

    1999-01-01

    Aperture synthesis is a new technology for passive microwave remote sensing from space which has the potential to overcome the limitations set in the past by antenna size. This is an interferometric technique in which pairs of small antennas and signal processing are used to obtain the resolution of a single large antenna. The technique has been demonstrated successfully at L-band with the aircraft prototype instrument, ESTAR. Proposals have been submitted to demonstrate this technology in space (HYDROSTAR and MIRAS).

  1. Restrictive cardiomyopathy

    Science.gov (United States)

    Cardiomyopathy - restrictive; Infiltrative cardiomyopathy ... In a case of restrictive cardiomyopathy, the heart muscle is normal size or slightly enlarged. Most of the time, it also pumps normally. However, it does not ...

  2. SCANNING KELVIN PROBE APPLIED TO LOCALISED CORROSION

    Directory of Open Access Journals (Sweden)

    A. Hussain

    2015-01-01

    Full Text Available This paper focuses on specific applications of the SKP system. The instrument is calibrated, using different thickness of a model polymer Poly Vinyl Butyral (PVB on mild steel and on galvanised steel. Artificial defects are used to show how the instrument is capable of detecting a localised corrosion cell and its ability to picture the delamination of the coating from the steel substrate. An industrial application is undertaken with the instrument, where epoxy coated galvanised steel; with an introduced defect in the coating and various added inhibitors. Chromates and chromate replacements have been studied.

  3. SCANNING KELVIN PROBE APPLIED TO LOCALISED CORROSION

    Directory of Open Access Journals (Sweden)

    S. K. M. Haque

    2015-03-01

    Full Text Available This paper focuses on specific applications of the SKP system. The instrument is calibrated, using different thickness of a model polymer Poly Vinyl Butyral (PVB on mild steel and on galvanised steel. Artificial defects are used to show how the instrument is capable of detecting a localised corrosion cell and its ability to picture the delamination of the coating from the steel substrate. An industrial application is undertaken with the instrument, where epoxy coated galvanised steel; with an introduced defect in the coating and various added inhibitors. Chromates and chromate replacements have been studied.

  4. Coherent coupling between localised and propagating phonon polaritons

    OpenAIRE

    Gubbin, Christopher R.; De Martini, Francesco; Politi, Alberto; Maier, Stefan A.; De Liberato, Simone

    2015-01-01

    Following the recent observation of localised phonon polaritons in user-defined silicon carbide nano-resonators, here we demonstrate coherent coupling between those localised modes and propagating phonon polaritons bound to the surface of the nano-resonator's substrate. In order to obtain phase-matching, the nano-resonators have been fabricated to serve the double function of hosting the localised modes, while also acting as grating for the propagating ones. The coherent coupling between long...

  5. To localise or to be localised with Wifi in the Hubei museum?

    NARCIS (Netherlands)

    Verbree, E.; Zlatanova, S.; Van Winden, K.; Van der Laan, E.B.; Makri, A.; Taizhou, L.; Haojun, A.

    2013-01-01

    Indoor localisation is in demand for a variety of applications within the built environment. An overall solution based on a single technology has not yet been determined. The aim of this paper is to gain insight on Signal Strength monitoring by a special kind of WiFi Monitors in comparison to the co

  6. Synthetic Aperture Compound Imaging

    DEFF Research Database (Denmark)

    Hansen, Jens Munk

    Medical ultrasound imaging is used for many purposes, e.g. for localizing and classifying cysts, lesions, and other processes. Almost any mass is first observed using B-mode imaging and later classified using e.g. color flow, strain, or attenuation imaging. It is therefore important that the B...... and the limiting factor is the amount of memory IO resources available. An equally high demand for memory throughput is found in the computer gaming industry, where a large part of the processing takes place on the graphics processing unit (GPU). Using the GPU, a framework for synthetic aperture imaging...

  7. Localising deformation along the elevation of linear structures : an experiment with space-borne InSAR and RTK GPS on the Roman Aqueducts in Rome, Italy.

    OpenAIRE

    Tapete D.; Morelli S.; Fanti R.; Casagli N.

    2015-01-01

    We map and monitor the condition of linear structures using Measurement Points (MPs) from satellite Interferometric Synthetic Aperture Radar (InSAR), and deal with the uncertainty of localising the detected deformation along the building elevation. We combine spatial information of the MPs with elevation measurements collected by Real Time Kinematic (RTK) GPS surveying to understand where structural motions occurred. The MPs are geolocated along the z-direction by exploiting their height info...

  8. Backreaction of Localised Sources in String Compactifications

    CERN Document Server

    Junghans, Daniel

    2013-01-01

    Localised sources such as D-branes or orientifold planes play an important role in many string compactifications that are relevant for phenomenology. The presence of these objects typically induces complicated dynamics in the compact dimensions such that a full solution to the 10d equations of motion is often out of reach. In order to still be able to make statements about the 4d effective theory arising in the low-energy limit, the equations of motion are usually only solved in an integrated sense, while the backreaction of the localised sources on the internal fields is neglected. This simplification is often referred to as smearing. In this work, we investigate to what extent smearing may affect observables in the effective low-energy theory and whether it may lead to fake solutions that would cease to exist once the backreaction is properly taken into account. We analyse explicit examples for which smeared solutions exist and find that the reliability of the smeared approximation appears to depend on whet...

  9. Localised manifold learning for cardiac image analysis

    Science.gov (United States)

    Bhatia, Kanwal K.; Price, Anthony N.; Hajnal, Jo V.; Rueckert, Daniel

    2012-02-01

    Manifold learning is increasingly being used to discover the underlying structure of medical image data. Traditional approaches operate on whole images with a single measure of similarity used to compare entire images. In this way, information on the locality of differences is lost and smaller trends may be masked by dominant global differences. In this paper, we propose the use of multiple local manifolds to analyse regions of images without any prior knowledge of which regions are important. Localised manifolds are created by partitioning images into regular subsections with a manifold constructed for each patch. We propose a framework for incorporating information from the neighbours of each patch to calculate a coherent embedding. This generates a simultaneous dimensionality reduction of all patches and results in the creation of embeddings which are spatially-varying. Additionally, a hierarchical method is presented to enable a multi-scale embedding solution. We use this to extract spatially-varying respiratory and cardiac motions from cardiac MRI. Although there is a complex interplay between these motions, we show how they can be separated on a regional basis. We demonstrate the utility of the localised joint embedding over a global embedding of whole images and over embedding individual patches independently.

  10. Periostitis and localised myositis in polyarteritis nodosa

    International Nuclear Information System (INIS)

    Full text: A 20-year-old man with previously diagnosed polyarteritis nodosa was referred for a bone scan to investigate longstanding knee and lower leg pain. The patient's symptoms worsened with any reduction of steroid dose and his physician was concerned about avascular necrosis of the hips. Plain x-rays of the lower limbs were normal. The blood pool images showed bilaterally increased activity in the anterior muscle compartments of the lower legs, suggestive of localised myositis. Three-hour delayed images showed widespread, increased subperiosteal activity with no evidence of avascular necrosis. Subsequent MRI scanning showed patchy muscle enhancement in both lower legs, also typical of myositis. A muscle biopsy was performed which demonstrated features of both myositis and vasculitis. The patient remains dependent on high-dose steroids for symptom relief. Localised myositis has previously been reported in polyarteritis nodosa and is a recognised, albeit rare, complication of the disorder, the basis of which is not well understood. Diagnostic muscle biopsy should be directed at involved muscle groups, which are best detected with MRI. Lower limb periostitis is well described in polyarteritis nodosa and may result in gross deformity. Several cases have previously been reported in the literature based on radiographic abnormalities, which were not present in our patient. Bone scanning demonstrated the sub-periosteal activity well in our subject and is suggested as a useful investigation in patients with polyarteritis nodosa who complain of lower limb pain. Copyright (2003) The Australian and New Zealand Society of Nuclear Medicine Inc

  11. Tissue Harmonic Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

    Rasmussen, Joachim

    The main purpose of this PhD project is to develop an ultrasonic method for tissue harmonic synthetic aperture imaging. The motivation is to advance the field of synthetic aperture imaging in ultrasound, which has shown great potentials in the clinic. Suggestions for synthetic aperture tissue...... harmonic techniques have been made, but none of these methods have so far been applicable for in-vivo imaging. The basis of this project is a synthetic aperture technique known as synthetic aperture sequential beamforming (SASB). The technique utilizes a two step beamforming approach to drastically reduce...... system complexity compared to conventional synthetic aperture techniques. In this project, SASB is sought combined with a pulse inversion technique for 2nd harmonic tissue harmonic imaging. The advantages in tissue harmonic imaging (THI) are expected to further improve the image quality of SASB. The...

  12. Class of near-perfect coded apertures

    International Nuclear Information System (INIS)

    Coded aperture imaging of gamma ray sources has long promised an improvement in the sensitivity of various detector systems. The promise has remained largely unfulfilled, however, for either one of two reasons. First, the encoding/decoding method produces artifacts, which even in the absence of quantum noise, restrict the quality of the reconstructed image. This is true of most correlation-type methods. Second, if the decoding procedure is of the deconvolution variety, small terms in the transfer function of the aperture can lead to excessive noise in the reconstructed image. It is proposed to circumvent both of these problems by use of a uniformly redundant array (URA) as the coded aperture in conjunction with a special correlation decoding method. It is shown that the reconstructed image in the URA system contains virtually uniform noise regardless of the structure in the original source. Therefore, the improvement over a single pinhole camera will be relatively larger for the brighter points in the source than for the low intensity points. In the case of a large detector background noise the URA will always do much better than the single pinhole regardless of the structure of the object. In the case of a low detector background noise, the improvement of the URA over the single pinhole will have a lower limit of approximately (1/2f)/sup 1/2 / where f is the fraction of the field of view which is uniformly filled by the object

  13. Monitoring corrosion rates and localised corrosion in low conductivity water

    DEFF Research Database (Denmark)

    Hilbert, Lisbeth Rischel

    2006-01-01

    Monitoring of low corrosion rates and localised corrosion in a media with low conductivity is a challenge. In municipal district heating, quality control may be improved by implementing on-line corrosion monitoring if a suitable technique can be identified to measure both uniform and localised...

  14. Compounding in synthetic aperture imaging.

    Science.gov (United States)

    Hansen, Jens Munk; Jensen, Jørgen Arendt

    2012-09-01

    A method for obtaining compound images using synthetic aperture data is investigated using a convex array transducer. The new approach allows spatial compounding to be performed for any number of angles without reducing the frame rate or temporal resolution. This important feature is an intrinsic property of how the compound images are constructed using synthetic aperture data and an improvement compared with how spatial compounding is obtained using conventional methods. The synthetic aperture compound images are created by exploiting the linearity of delay-and-sum beamformation for data collected from multiple spherical emissions to synthesize multiple transmit and receive apertures, corresponding to imaging the tissue from multiple directions. The many images are added incoherently, to produce a single compound image. Using a 192-element, 3.5-MHz, λ-pitch transducer, it is demonstrated from tissue-phantom measurements that the speckle is reduced and the contrast resolution improved when applying synthetic aperture compound imaging. At a depth of 4 cm, the size of the synthesized apertures is optimized for lesion detection based on the speckle information density. This is a performance measure for tissue contrast resolution which quantifies the tradeoff between resolution loss and speckle reduction. The speckle information density is improved by 25% when comparing synthetic aperture compounding to a similar setup for compounding using dynamic receive focusing. The cystic resolution and clutter levels are measured using a wire phantom setup and compared with conventional application of the array, as well as to synthetic aperture imaging without compounding. If the full aperture is used for synthetic aperture compounding, the cystic resolution is improved by 41% compared with conventional imaging, and is at least as good as what can be obtained using synthetic aperture imaging without compounding. PMID:23007781

  15. Synthetic Aperture Ultrasound Imaging

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Nikolov, Svetoslav; Gammelmark, Kim Løkke;

    2006-01-01

    The paper describes the use of synthetic aperture (SA) imaging in medical ultrasound. SA imaging is a radical break with today's commercial systems, where the image is acquired sequentially one image line at a time. This puts a strict limit on the frame rate and the possibility of acquiring a...... SA imaging. Due to the complete data set, it is possible to have both dynamic transmit and receive focusing to improve contrast and resolution. It is also possible to improve penetration depth by employing codes during ultrasound transmission. Data sets for vector flow imaging can be acquired using...... short imaging sequences, whereby both the correct velocity magnitude and angle can be estimated. A number of examples of both phantom and in-vivo SA images will be presented measured by the experimental ultrasound scanner RASMUS to demonstrate the many benefits of SA imaging....

  16. Multiple Differential Aperture Microscopy

    International Nuclear Information System (INIS)

    Differential-aperture X-ray microscopy (DAXM) is a powerful approach to 3D tomography with particular relevance to X-ray microdiffraction. With DAXM, scattering from submicron volumes can be resolved. However, the method is intrinsically a scanning technique where every resolved volume element (voxel) requires at least one area-detector readout. Previous applications of DAXM have used a single wire for knife-edge step profiling. Here, we demonstrate a way to accelerate DAXM measurements using multiple wires. A proof-of-principle experiment with a three-wire prototype showed that the speed of measurements can be tripled, but careful calibrations of wires will be required to maintain the spatial accuracy. In addition, related possibilities for accelerating measurements are briefly discussed

  17. Localisation and World Modelling: an Architectural Perspective

    Directory of Open Access Journals (Sweden)

    Domenico G. Sorrenti

    2008-11-01

    Full Text Available Autonomous robot world modelling is a "chicken-and-egg" problem: position estimation needs a model of the world, whereas world modelling needs the robot position. Most of the works dealing with this issue propose holistic solutions under an algorithmic perspective by neglecting software architecture issues. This results in huge and monolithic pieces of software where implementation details reify strategic decisions. An architectural approach founded on separation of concerns may help to break the loop. Localisation and modelling, acting on different time scales, are mostly independent of each other. Sometimes synchronisation is required. Whenever needed, an external strategy tunes the relative rates of the two activities. The paper introduces rationale, design, and implementation of such a system which relies on Real-Time Performers, a software architecture providing suitable architectural abstractions to observe and control the system's temporal behaviour.

  18. Reaction-Diffusion Automata Phenomenology, Localisations, Computation

    CERN Document Server

    Adamatzky, Andrew

    2013-01-01

    Reaction-diffusion and excitable media are amongst most intriguing substrates. Despite apparent simplicity of the physical processes involved the media exhibit a wide range of amazing patterns: from target and spiral waves to travelling localisations and stationary breathing patterns. These media are at the heart of most natural processes, including morphogenesis of living beings, geological formations, nervous and muscular activity, and socio-economic developments.   This book explores a minimalist paradigm of studying reaction-diffusion and excitable media using locally-connected networks of finite-state machines: cellular automata and automata on proximity graphs. Cellular automata are marvellous objects per se because they show us how to generate and manage complexity using very simple rules of dynamical transitions. When combined with the reaction-diffusion paradigm the cellular automata become an essential user-friendly tool for modelling natural systems and designing future and emergent computing arch...

  19. Sparse synthetic aperture radar imaging with optimized azimuthal aperture

    Institute of Scientific and Technical Information of China (English)

    ZENG Cao; WANG MinHang; LIAO GuiSheng; ZHU ShengQi

    2012-01-01

    To counter the problem of acquiring and processing huge amounts of data for synthetic aperture radar (SAR) using traditional sampling techniques,a method for sparse SAR imaging with an optimized azimuthal aperture is presented.The equivalence of an azimuthal match filter and synthetic array beamforming is shown so that optimization of the azimuthal sparse aperture can be converted to optimization of synthetic array beamforming.The azimuthal sparse aperture,which is composed of a middle aperture and symmetrical bilateral apertures,can be obtained by optimization algorithms (density weighting and simulated annealing algorithms,respectively).Furthermore,sparse imaging of spectrum analysis SAR based on the optimized sparse aperture is achieved by padding zeros at null samplings and using a non-uniform Taylor window. Compared with traditional sampling,this method has the advantages of reducing the amount of sampling and alleviating the computational burden with acceptable image quality.Unlike periodic sparse sampling,the proposed method exhibits no image ghosts.The results obtained from airborne measurements demonstrate the effectiveness and superiority of the proposed method.

  20. To localise or to be localised with WiFi in the Hubei museum?

    Science.gov (United States)

    Verbree, E.; Zlatanova, S.; van Winden, K. B. A.; van der Laan, E. B.; Makri, A.; Taizhou, L.; Haojun, A.

    2013-11-01

    Indoor localisation is in demand for a variety of applications within the built environment. An overall solution based on a single technology has not yet been determined. The aim of this paper is to gain insight on Signal Strength monitoring by a special kind of WiFi Monitors in comparison to the commonly known fingerprinting method for the purpose of a 3D indoor navigation system. Ttwo different WiFi based localisation techniques are tested during the MSc Geomatics DaRen Syntheses Project in the Hubei Provincial Museum, China. The first method detects the beacon frames send by smartphones, laptops and other WiFi enabled devices in range using Libelium Meshlium Xtreme monitors. Their MAC addresses and the signal strength is measured by the Meshlium Xtreme and stored on an external database. We call this method WiFi monitoring. The second method a Wifi enabled device, like a smartphone, measures the signal strength of multiple Wifi Access Points in range to localise itself based on a previously created radio map. This method is known as WiFi fingerprinting. Both methods have some advantages and disadvantages. Advantages of the common way of WiFi fingerprinting are that the implementation costs are relatively low, because it is usually possible to use (a part of) the existing WiFi AP infrastructure. WiFi fingerprinting can reach a relatively high accuracy in the order of magnitude of meters. Finally, the location granularity can be adjusted to what is necessary for the purpose of the indoor localisation. This makes it employable for a wide range of purposes. The question remains how suitable these methods are for a 3D indoor navigation system for the Hubei provincial museum. One important aspect is the localisation-granularity necessary for the application. In a museum it is not necessary to know the exact X,Y position of a user (such high accuracy is unnecessary), more important is to know in which room the user is located so the information on exhibitions can be

  1. Restricted Airspace

    Data.gov (United States)

    Federal Laboratory Consortium — Redstone Technical Test Center has restricted airspace up to 30,000 feet ASL. Airspace encompasses R-2104 (Redstone). Airspace is used extensively for airborne/UAV...

  2. Interferometric synthetic aperture microscopy

    Science.gov (United States)

    Ralston, Tyler S.; Marks, Daniel L.; Scott Carney, P.; Boppart, Stephen A.

    2007-02-01

    State-of-the-art methods in high-resolution three-dimensional optical microscopy require that the focus be scanned through the entire region of interest. However, an analysis of the physics of the light-sample interaction reveals that the Fourier-space coverage is independent of depth. Here we show that, by solving the inverse scattering problem for interference microscopy, computed reconstruction yields volumes with a resolution in all planes that is equivalent to the resolution achieved only at the focal plane for conventional high-resolution microscopy. In short, the entire illuminated volume has spatially invariant resolution, thus eliminating the compromise between resolution and depth of field. We describe and demonstrate a novel computational image-formation technique called interferometric synthetic aperture microscopy (ISAM). ISAM has the potential to broadly impact real-time three-dimensional microscopy and analysis in the fields of cell and tumour biology, as well as in clinical diagnosis where in vivo imaging is preferable to biopsy.

  3. Localisation et cartographie simultannées avec vision monoculaire

    OpenAIRE

    Lemaire, Thomas

    2006-01-01

    Cette thèse aborde le problème de localisation et cartographie simultanée pour un robot mobile. Lorsque le robot évolue dans un environnement inconnu, il doit construire une carte au fur et à mesure qu'il explore le monde, tout en se localisant dans celle-ci. De l'anglais Simultaneous Localisation And Mapping, le SLAM est une brique essentielle de l'architecture d'un robot autonome. Plusieurs éléments sont nécessaires à la résolution du SLAM, en particulier la perception de l'environnement pe...

  4. Localisation of atomic populations in the optical radiation field

    International Nuclear Information System (INIS)

    The possibility of two-dimensional spatial localisation of atomic populations under the influence of the travelling wave fields in the tripod-configuration of quantum states is studied for the first time. Three travelling waves propagating in the same plane at an angle of 120° to each other form a system of standing waves under the influence of which atomic populations are localised. The size of the region of spatial localisation of the populations, in principle, can be hundredths of a wavelength of optical radiation. (quantum optics)

  5. Lucky imaging and aperture synthesis with low-redundancy apertures.

    Science.gov (United States)

    Ward, Jennifer E; Rhodes, William T; Sheridan, John T

    2009-01-01

    Lucky imaging, used with some success in astronomical and even horizontal-path imaging, relies on fleeting conditions of the atmosphere that allow momentary improvements in image quality, at least in portions of an image. Aperture synthesis allows a larger aperture and, thus, a higher-resolution imaging system to be synthesized through the superposition of image spatial-frequency components gathered by cooperative combinations of smaller subapertures. A combination of lucky imaging and aperture synthesis strengthens both methods for obtaining improved images through the turbulent atmosphere. We realize the lucky imaging condition appropriate for aperture synthesis imaging for a pair of rectangular subapertures and demonstrate that this condition occurs when the signal energy associated with bandpass spatial-frequency components achieves its maximum value. PMID:19107157

  6. Lucky imaging and aperture synthesis with low-redundancy apertures

    OpenAIRE

    Ward, Jennifer E.; Rhodes, William T.; Sheridan, John T.

    2009-01-01

    Lucky imaging, used with some success in astronomical and even horizontal-path imaging, relies on fleeting conditions of the atmosphere that allow momentary improvements in image quality, at least in portions of an image. Aperture synthesis allows a larger aperture and, thus, a higher-resolution imaging system to be synthesized through the superposition of image spatial-frequency components gathered by cooperative combinations of smaller subapertures. Acombination of lucky imaging and aper...

  7. Drosophila Syncrip binds the gurken mRNA localisation signal and regulates localised transcripts during axis specification

    Directory of Open Access Journals (Sweden)

    Suzanne M. McDermott

    2012-04-01

    In the Drosophila oocyte, mRNA transport and localised translation play a fundamental role in axis determination and germline formation of the future embryo. gurken mRNA encodes a secreted TGF-α signal that specifies dorsal structures, and is localised to the dorso-anterior corner of the oocyte via a cis-acting 64 nucleotide gurken localisation signal. Using GRNA chromatography, we characterised the biochemical composition of the ribonucleoprotein complexes that form around the gurken mRNA localisation signal in the oocyte. We identified a number of the factors already known to be involved in gurken localisation and translational regulation, such as Squid and Imp, in addition to a number of factors with known links to mRNA localisation, such as Me31B and Exu. We also identified previously uncharacterised Drosophila proteins, including the fly homologue of mammalian SYNCRIP/hnRNPQ, a component of RNA transport granules in the dendrites of mammalian hippocampal neurons. We show that Drosophila Syncrip binds specifically to gurken and oskar, but not bicoid transcripts. The loss-of-function and overexpression phenotypes of syncrip in Drosophila egg chambers show that the protein is required for correct grk and osk mRNA localisation and translational regulation. We conclude that Drosophila Syncrip is a new factor required for localisation and translational regulation of oskar and gurken mRNA in the oocyte. We propose that Syncrip/SYNCRIP is part of a conserved complex associated with localised transcripts and required for their correct translational regulation in flies and mammals.

  8. Overlapping Zone Partitioning Localisation Technique for RFID

    Directory of Open Access Journals (Sweden)

    Kavi K. Khedo

    2010-04-01

    Full Text Available Basically used for contactless identification, Radio Frequency Identification (RFID technology was originallythought as a complement for the drawbacks of the Barcode. Due to its capabilities and on-going drop in cost,researchers have started to look into other areas where RFID can be employed. One such area of research isReal-Time Location Tracking (RTLT, especially for indoor environments. While technologies such as Ultra-Sound, Infrared, WiFi, Bluetooth and GSM have been considered for indoor localisation, their requirements forline of sight and/or prohibitive cost have hindered their successful adoption. We are therefore presenting a lowcostsolution using RFID technology which we refer to as the ‘Overlapping Zone Partitioning’ (OZP techniquethat can be implemented using basic off-the-shelf RFID Readers and which has been derived from the zonebasedlocalisation technique. We have successfully implemented OZP and evaluated its performance. It hasbeen found that its accuracy is enhanced by nearly 40% in comparison to a normal zone-based localisationsystem. Its performance in terms of correct zone classification is within the range of 80-90%.

  9. UAVSAR Phased Array Aperture

    Science.gov (United States)

    Chamberlain, Neil; Zawadzki, Mark; Sadowy, Greg; Oakes, Eric; Brown, Kyle; Hodges, Richard

    2009-01-01

    This paper describes the development of a patch antenna array for an L-band repeat-pass interferometric synthetic aperture radar (InSAR) instrument that is to be flown on an unmanned aerial vehicle (UAV). The antenna operates at a center frequency of 1.2575 GHz and with a bandwidth of 80 MHz, consistent with a number of radar instruments that JPL has previously flown. The antenna is designed to radiate orthogonal linear polarizations in order to facilitate fully-polarimetric measurements. Beam-pointing requirements for repeat-pass SAR interferometry necessitate electronic scanning in azimuth over a range of -20degrees in order to compensate for aircraft yaw. Beam-steering is accomplished by transmit/receive (T/R) modules and a beamforming network implemented in a stripline circuit board. This paper, while providing an overview of phased array architecture, focuses on the electromagnetic design of the antenna tiles and associated interconnects. An important aspect of the design of this antenna is that it has an amplitude taper of 10dB in the elevation direction. This is to reduce multipath reflections from the wing that would otherwise be detrimental to interferometric radar measurements. This taper is provided by coupling networks in the interconnect circuits as opposed to attenuating the output of the T/R modules. Details are given of material choices and fabrication techniques that meet the demanding environmental conditions that the antenna must operate in. Predicted array performance is reported in terms of co-polarized and crosspolarized far-field antenna patterns, and also in terms of active reflection coefficient.

  10. Compounding in synthetic aperture imaging

    DEFF Research Database (Denmark)

    Hansen, J. M.; Jensen, J. A.

    2012-01-01

    A method for obtaining compound images using synthetic aperture data is investigated using a convex array transducer. The new approach allows spatial compounding to be performed for any number of angles without reducing the frame rate or temporal resolution. This important feature is an intrinsic...... from multiple spherical emissions to synthesize multiple transmit and receive apertures, corresponding to imaging the tissue from multiple directions. The many images are added incoherently, to produce a single compound image. Using a 192-element, 3.5-MHz, λ-pitch transducer, it is demonstrated from...... tissue-phantom measurements that the speckle is reduced and the contrast resolution improved when applying synthetic aperture compound imaging. At a depth of 4 cm, the size of the synthesized apertures is optimized for lesion detection based on the speckle information density. This is a performance...

  11. Optimizing Synthetic Aperture Compound Imaging

    DEFF Research Database (Denmark)

    Hansen, Jens Munk; Jensen, Jørgen Arendt

    2012-01-01

    Spatial compound images are constructed from synthetic aperture data acquired using a linear phased-array transducer. Compound images of wires, tissue, and cysts are created using a method, which allows both transmit and receive compounding without any loss in temporal resolution. Similarly to...... optimal for lesion detection. Synthetic aperture data are acquired from unfocused emissions and 154 compound images are constructed by synthesizing different aperture configurations with more or less compounding, all maintaining a constant resolution across depth corresponding to an f-number of 2.0 for...... transmit and receive. The same configurations are used for scanning a phantom with cysts, and it is demonstrated how an improved cysts contrast follows from an aperture configuration, which gives a higher value for the performance measure extracted from the phantom without cysts. A correlation value R = 0...

  12. Synthetic Aperture Radar - Hardware Development

    OpenAIRE

    Rosner, V.; Seller, R.; L. Dudas; Kazi, K.; Miko, G.

    2009-01-01

    Experimental real and synthetic aperture radar are developed from the base-band digital unit to the analogue RF parts, based on solid state units, using pulse compression for radar imaging. Proper QPSK code is found for matched filter.

  13. Localised fibrous mesothelioma arising in an intralobar pulmonary sequestration.

    OpenAIRE

    Paksoy, N.; Demircan, A.; Altiner, M; Artvinli, M

    1992-01-01

    A localised fibrous mesothelioma arising from an intralobar lung sequestration occurred in a 64 year old Turkish woman. This appears to be the first report of a mesothelioma occurring within a pulmonary sequestration.

  14. Computerised tomography localisation of intrarenal calculi prior to nephrolithotomy

    International Nuclear Information System (INIS)

    The use of the EMI CT 5005 scanner in patients with renal calculus disease is described. This investigation was found to be a useful aid in the accurate localisation of calculi within the renal collecting system prior to surgery. (author)

  15. Méthodes ensemblistes pour la localisation en robotique mobile

    OpenAIRE

    Guyonneau, Rémy

    2013-01-01

    Cette thèse s'intéresse aux problèmes de localisation en robotique mobile, et plus particulièrement à l'intérêt d'une approche ensembliste pour ces problèmes. Actuellement les méthodes probabilistes sont les plus utilisées pour localiser un robot dans son environnement, cette thèse propose des approches alternatives basées sur l'analyse par intervalles. Dans un premier temps, une méthode ensembliste s'intéressant au problème de localisation globale est proposée. Le problème de localisation gl...

  16. Synthetic aperture controlled source electromagnetics

    OpenAIRE

    Fan, Y.; Snieder, R.; Slob, E.; Hunziker, J.W.; Singer, J.; Sheiman, J.; Rosenquist, M.

    2010-01-01

    Controlled‐source electromagnetics (CSEM) has been used as a de‐risking tool in the hydrocarbon exploration industry. Although there have been successful applications of CSEM, this technique is still not widely used in the industry because the limited types of hydrocarbon reservoirs CSEM can detect. In this paper, we apply the concept of synthetic aperture to CSEM data. Synthetic aperture allows us to design sources with specific radiation patterns for different purposes. The ability to detec...

  17. Localisation et Cartographie Simultanées avec Vision Monoculaire

    OpenAIRE

    Lemaire, Thomas

    2006-01-01

    This thesis tackles the Simultaneous Localisation And Mapping problem (SLAM for short). When the robot moves in an unknown environment, it has to incrementally build a map of the environment while using this map to localise itself. A SLAM algorithm is a fundamental part of the architecture of a fully autonomous robot. Several elements are required to solve SLAM, among which perception is of main importance since it produces observations of the objects of the environment (referred as landmarks...

  18. Two-Dimensional Synthetic-Aperture Radiometer

    Science.gov (United States)

    LeVine, David M.

    2010-01-01

    A two-dimensional synthetic-aperture radiometer, now undergoing development, serves as a test bed for demonstrating the potential of aperture synthesis for remote sensing of the Earth, particularly for measuring spatial distributions of soil moisture and ocean-surface salinity. The goal is to use the technology for remote sensing aboard a spacecraft in orbit, but the basic principles of design and operation are applicable to remote sensing from aboard an aircraft, and the prototype of the system under development is designed for operation aboard an aircraft. In aperture synthesis, one utilizes several small antennas in combination with a signal processing in order to obtain resolution that otherwise would require the use of an antenna with a larger aperture (and, hence, potentially more difficult to deploy in space). The principle upon which this system is based is similar to that of Earth-rotation aperture synthesis employed in radio astronomy. In this technology the coherent products (correlations) of signals from pairs of antennas are obtained at different antenna-pair spacings (baselines). The correlation for each baseline yields a sample point in a Fourier transform of the brightness-temperature map of the scene. An image of the scene itself is then reconstructed by inverting the sampled transform. The predecessor of the present two-dimensional synthetic-aperture radiometer is a one-dimensional one, named the Electrically Scanned Thinned Array Radiometer (ESTAR). Operating in the L band, the ESTAR employs aperture synthesis in the cross-track dimension only, while using a conventional antenna for resolution in the along-track dimension. The two-dimensional instrument also operates in the L band to be precise, at a frequency of 1.413 GHz in the frequency band restricted for passive use (no transmission) only. The L band was chosen because (1) the L band represents the long-wavelength end of the remote- sensing spectrum, where the problem of achieving adequate

  19. Indoor Localisation Based on GSM Signals: Multistorey Building Study

    Directory of Open Access Journals (Sweden)

    Rafał Górak

    2016-01-01

    Full Text Available Among the accurate indoor localisation systems that are using WiFi, Bluetooth, or infrared technologies, the ones that are based on the GSM rely on a stable external infrastructure that can be used even in an emergency. This paper presents an accurate GSM indoor localisation system that achieves a median error of 4.39 metres in horizontal coordinates and up to 64 percent accuracy in floor prediction (for 84 percent of cases the floor prediction is mistaken by not more than a single floor. The test and reference measurements were made inside a six-floor academic building, with an irregular shape, whose dimensions are around 50 metres by 70 metres. The localisation algorithm uses GSM signal readings from the 7 strongest cells available in the GSM standard (or fewer, if fewer than 7 are available. We estimate the location by a three-step method. Firstly, we propose a point localisation solution (i.e., localisation based on only one measurement. Then, by applying the central tendency filters and the Multilayer Perceptron, we build a localisation system that uses a sequence of estimations of current and past locations. We also discuss major accuracy factors such as the number of observed signals or the types of spaces in the building.

  20. Localised hydrogen peroxide sensing for reproductive health

    Science.gov (United States)

    Purdey, Malcolm S.; Schartner, Erik P.; Sutton-McDowall, Melanie L.; Ritter, Lesley J.; Thompson, Jeremy G.; Monro, Tanya M.; Abell, Andrew D.

    2015-05-01

    The production of reactive oxygen species (ROS) is known to affect the developmental competence of embryos. Hydrogen peroxide (H2O2) an important reactive oxygen species, is also known to causes DNA damage and defective sperm function. Current techniques require incubating a developing embryo with an organic fluorophore which is potentially hazardous for the embryo. What we need is a localised ROS sensor which does not require fluorophores in solution and hence will allow continuous monitoring of H2O2 production without adversely affect the development of the embryo. Here we report studies on such a fibre-based sensor for the detection of H2O2 that uses a surface-bound aryl boronate fluorophore carboxyperoxyfluor-1(CPF1). Optical fibres present a unique platform due to desirable characteristics as dip sensors in biological solutions. Attempts to functionalise the fibre tips using polyelectrolyte layers and (3-aminopropyl)triethoxysilane (APTES) coatings resulted in a limited signal and poor fluorescent response to H2O2 due to a low tip surface density of the fluorophore. To increase the surface density, CPF1 was integrated into a polymer matrix formed on the fibre tip by a UV-catalysed polymerisation process of acrylamide onto a methacrylate silane layer. The polyacrylamide containing CPF1 gave a much higher surface density than previous surface attachment methods and the sensor was found to effectively detect H2O2. Using this method, biologically relevant concentrations of H2O2 were detected, enabling remote sensing studies into ROS releases from embryos throughout early development.

  1. Localisation strategy for the South African nuclear power programme / Alden Willem Johan van Wyk

    OpenAIRE

    Van Wyk, Alden Willem Johan

    2012-01-01

    Through this study, a strategy for the localisation and development of the South African nuclear industry was developed. As background, the Korean localisation experience was investigated, along with international recommendations regarding nuclear localisation, and South African governmental policies. This research was used as foundation for the formulation of a localisation strategy. The possibility of using localisation and nuclear industry development as a means to address governmental soc...

  2. Localisation and quantification of elements within seeds of Cd/Zn hyperaccumulator Thlaspi praecox by micro-PIXE.

    Science.gov (United States)

    Vogel-Mikus, Katarina; Pongrac, Paula; Kump, Peter; Necemer, Marijan; Simcic, Jure; Pelicon, Primoz; Budnar, Milos; Povh, Bogdan; Regvar, Marjana

    2007-05-01

    Cd, Zn and Pb accumulation, spatial distribution within seeds and germinating seedlings, and seeds fitness of metal hyperaccumulating Thlaspi praecox were investigated in order to gain more knowledge on plant reproductive success at metal polluted sites. The seeds contained up to 1351 microg g-1 (dry weight) of Cd, 121 microg g-1 of Zn and 17 microg g-1 of Pb. Seed fitness was negatively influenced by seed Cd hyperaccumulation. Nevertheless, the viability of seeds was decreased by maximally 20%, indicating very efficient tolerance of the plant embryos to Cd. Localisation by micro-PIXE revealed preferential storage of most elements in the embryonic axis. Cd and Zn were preferentially localised in the epidermis of cotyledons. The restriction of seed Pb and Zn uptake and hyperaccumulation of Cd, accompanied by partitioning of Cd in the epidermal tissues of cotyledons, may enable the survival of T. praecox embryos and seedlings in Cd polluted environments. PMID:17070633

  3. NPS high resolution synthetic aperture sonar

    OpenAIRE

    Welter, Joseph Donald

    1995-01-01

    This thesis investigated the use of synthetic aperture techniques to achieve a long effective aperture, high resolution, imaging sonar. The approach included a full simulation of the system using the MATLAB programming environment that provided a model for developing six data processing algorithms and a working 25KHz, 1 m baseline, air medium synthetic aperture sonar. The six azimuthal processing techniques included: (1) a normal, real aperture, (2) an unfocussed synthetic aperture, (3) a hyb...

  4. A flat laser array aperture

    Science.gov (United States)

    Papadakis, Stergios J.; Ricciardi, Gerald F.; Gross, Michael C.; Krill, Jerry A.

    2010-04-01

    We describe a design concept for a flat (or conformal) thin-plate laser phased-array aperture. The aperture consists of a substrate supporting a grid of single-mode optical waveguides fabricated from a linear electro-optic material. The waveguides are coupled to a single laser source or detector. An arrangement of electrodes provides for two-dimensional beam steering by controlling the phase of the light entering the grid. The electrodes can also be modulated to simultaneously provide atmospheric turbulence modulation for long-range free-space optical communication. An approach for fabrication is also outlined.

  5. Bayesian Joint Modelling for Object Localisation in Weakly Labelled Images.

    Science.gov (United States)

    Shi, Zhiyuan; Hospedales, Timothy M; Xiang, Tao

    2015-10-01

    We address the problem of localisation of objects as bounding boxes in images and videos with weak labels. This weakly supervised object localisation problem has been tackled in the past using discriminative models where each object class is localised independently from other classes. In this paper, a novel framework based on Bayesian joint topic modelling is proposed, which differs significantly from the existing ones in that: (1) All foreground object classes are modelled jointly in a single generative model that encodes multiple object co-existence so that "explaining away" inference can resolve ambiguity and lead to better learning and localisation. (2) Image backgrounds are shared across classes to better learn varying surroundings and "push out" objects of interest. (3) Our model can be learned with a mixture of weakly labelled and unlabelled data, allowing the large volume of unlabelled images on the Internet to be exploited for learning. Moreover, the Bayesian formulation enables the exploitation of various types of prior knowledge to compensate for the limited supervision offered by weakly labelled data, as well as Bayesian domain adaptation for transfer learning. Extensive experiments on the PASCAL VOC, ImageNet and YouTube-Object videos datasets demonstrate the effectiveness of our Bayesian joint model for weakly supervised object localisation. PMID:26340253

  6. High resolution non-iterative aperture synthesis.

    Science.gov (United States)

    Kraczek, Jeffrey R; McManamon, Paul F; Watson, Edward A

    2016-03-21

    The maximum resolution of a multiple-input multiple-output (MIMO) imaging system is determined by the size of the synthetic aperture. The synthetic aperture is determined by a coordinate shift using the relative positions of the illuminators and receive apertures. Previous methods have shown non-iterative phasing for multiple illuminators with a single receive aperture for intra-aperture synthesis. This work shows non-iterative phasing with both multiple illuminators and multiple receive apertures for inter-aperture synthesis. Simulated results show that piston, tip, and tilt can be calculated using inter-aperture phasing after intra-aperture phasing has been performed. Use of a fourth illuminator for increased resolution is shown. The modulation transfer function (MTF) is used to quantitatively judge increased resolution. PMID:27136816

  7. Caloric restriction.

    Science.gov (United States)

    Speakman, John R; Mitchell, Sharon E

    2011-06-01

    Restricting the intake of calories has been practiced as a method for increasing both the length and quality of life for over 500 years. Experimental work confirming the success of this approach in animals has accumulated over the last 100 years. Lifelong caloric restriction (CR) may extend life by up to 50% in rodents, with progressively less impact the later in life it is started. This effect is matched by profound impacts on age related diseases including reduced risk of cancer, neurodegenerative disorders, autoimmune disease, cardiovascular disease and type II diabetes mellitus. The disposable soma theory of ageing suggests that CR evolved as a somatic protection response to enable animals to survive periods of food shortage. The shutdown of reproductive function during CR is consistent with this suggestion, but other features of the phenomenon are less consistent with this theory, and some have suggested that in rodents it may be mostly an artifact of domestication. CR induces profound effects on animals at all levels from the transcriptome to whole animal physiology and behavior. Animals under CR lose weight which is disproportionately contributed to by white adipose tissue. Generally animals on CR change their activity patterns so that they are more active prior to food delivery each day but total activity may be unchanged or reduced. Considerable debate has occurred over the effects of CR on resting metabolic rate (RMR). Total RMR declines, but as body mass and body composition also change it is unclear whether metabolism at the tissue level also declines, is unchanged or even increases. Body temperature universally decreases. Hunger is increased and does not seem to abate even with very long term restriction. Circulating adipokines are reduced reflecting the reduction in white adipose tissue (WAT) mass under restriction and there is a large reduction in circulating insulin and glucose levels. There are profound tissue level changes in metabolism with a

  8. Localisation of beam offset jitter sources at ATF2

    CERN Document Server

    Pfingstner, J; Patecki, M; Schulte, D; Tomás, R

    2014-01-01

    For the commissioning and operation of modern particle accelerators, automated error detection and diagnostics methods are becoming increasingly important. In this paper, we present two such methods, which are capable of localising sources of beam offset jitter with a combination of correlation studies and so called degree of freedom plots. The methods were applied to the ATF2 beam line at KEK, where one of the major goals is the reduction of the beam offset jitter. Results of this localisation are shown in this paper. A big advantage of the presented method is its high robustness especially to varying optics parameters. Therefore, we believe that the developed beam offset jitter localisation methods can be easily applied to other accelerators.

  9. Anderson localisation of visible light on a nanophotonic chip

    CERN Document Server

    Crane, Tom; Sapienza, Luca

    2016-01-01

    Controlling the propagation of visible light on a chip is of tremendous interest in research areas such as energy harvesting, imaging, sensing and biology. Technological advances allow us to control light at the nanoscale and to strongly enhance the light-matter interaction in highly engineered devices. However, compared to state-of-the-art two-dimensional optical cavities operating at longer wavelengths, the quality factor of on-chip visible light confinement is several orders of magnitude lower. Our approach makes use of fabrication imperfections to trap light: we demonstrate, for the first time, Anderson localisation of visible light on a chip. Remarkably, compared to quality factors of engineered cavities, disorder-induced localisation proves to be more efficient in trapping light than highly engineered devices, thus reversing the trend observed so far. We measure light-confinement quality factors as high as 7600 and, by implementing a sensitive imaging technique, we directly visualise the localised modes...

  10. An ultrastructural and irradiation study of diffuse and localised kinetochore

    International Nuclear Information System (INIS)

    An electron microscope study of plant types Luzula nivea and Cyperus eragrostis with diffuse kinetochores and Crepis neglecta with localised kinetochore showed that Luzula has a rather different kinetochore organisation from Cyperus, with features approaching the localised type of Crepis. These studies included an examination of the ultrastructure of the kinetochore at metaphase at low magnification in control and irradiated material of Luzula; the chromosomal ultrastructure at high magnification at interphase and all stages of mitosis in Luzula, Cyperus and Crepis; and the ultrastructure of the nucleolus in Luzula, Cyperus and Crepis. Light microscopic studies were also performed showing the effects of irradiation on first mitotic division in Cyperus, Luzula and Crepis, mitotic aberrations in Cyperus and Crepis and meiosis in Cyperus. Finally, the survival with the diffuse as opposed to the localised kinetochore in M1 and M2 generations following seed irradiation was studied. (U.K.)

  11. Ultrasound fields from triangular apertures

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    1996-01-01

    The pulsed field from a triangular aperture mounted in an infinite, rigidbaffle is calculated. The approach of spatial impulse responses,as developed by Tupholme and Stepanishen, is used. By this both the emitted and received pulsed ultrasound field can be found for any transducerexcitation and...

  12. Synthetic Aperture Radar - Hardware Development

    Directory of Open Access Journals (Sweden)

    V. Rosner

    2009-06-01

    Full Text Available Experimental real and synthetic aperture radar are developed from the base-band digital unit to the analogue RF parts, based on solid state units, using pulse compression for radar imaging. Proper QPSK code is found for matched filter.

  13. Experimental investigation of edge localised modes in JET

    International Nuclear Information System (INIS)

    Edge Localised Modes (ELMs) in the JET tokamak have been studied experimentally, using density profile and fluctuation data from a multichannel reflectometer and temperature profile data from an ECE heterodyne radiometer. The following topics have been investigated: The radial extent and localisation of the density and temperature profile perturbations caused by the ELMs. Fluctuations in the density and magnetic field in connection with the ELMs. The correlation between the repetition frequency of the L-H transition ELMs, and the plasma edge temperature and density. Trajectories in n-T space prior to ELMs later in the H-mode. (au) (39 refs.)

  14. Control and mixing for 2D Navier-Stokes equations with space-time localised noise

    CERN Document Server

    Shirikyan, Armen

    2011-01-01

    We consider randomly forced 2D Navier-Stokes equations in a bounded domain with smooth boundary. It is assumed that the random perturba- tion is non-degenerate, and its law is periodic in time and has a support localised with respect to space and time. Concerning the unperturbed problem, we assume that it is approximately controllable in infinite time by an external force whose support is included in that of the random force. Under these hypotheses, we prove that the Markov process generated by the restriction of solutions to the instants of time proportional to the period possesses a unique stationary distribution, which is exponentially mixing. The proof is based on a coupling argument, a local controllability property of the Navier-Stokes system, an estimate for the total variation distance between a measure and its image under a smooth mapping, and some classical results from the theory of optimal transport.

  15. Restricted Mobilities

    DEFF Research Database (Denmark)

    Nielsen, Mette; Lassen, Claus

    2012-01-01

    exclusion and stratification mechanisms. In conclusion the article therefore suggests that future urban research and planning also needs a mobile understanding of spaces in the cities and how different mobility systems play an important role to sustain the exclusiveness that often characterises the private......Privatisation of public spaces in the contemporary city has increased during the last decades but only few studies have approached this field from a mobility perspective. Therefore the article seeks to rectify this by exploring two Australian examples of private spaces in the city; gated...... communities and shopping centres through mobility lenses. The article shows how different mobility systems enable and restrict the public access to private-public spaces, and it points out that proprietary communities create an unequal potential for human movement and access in the city. The main argument in...

  16. Three-dimensional localisation of NANOG, OCT4, and E-CADHERIN in porcine pre- and peri-implantation embryos

    DEFF Research Database (Denmark)

    Wolf, Xenia Asbæk; Serup, Palle; Hyttel, Poul

    2011-01-01

    The expression patterns of NANOG and OCT4 have previously been reported to differ markedly between mammalian species indicating distinct species-specific roles during development. We investigate the three-dimensional expression pattern of NANOG and OCT4 in porcine pre- and peri-implantation embryos......-gastrulating, filamentous embryos NANOG was localised to nuclei in a minor portion of the epiblast cells in which E-CADHERIN seemed to be up-regulated and OCT4 down-regulated. Later NANOG was restricted to the potential PGCs. OCT4 was detected in inner cell mass, epiblast, and mesoderm, and we found that OCT4 expression...

  17. Time Localisation of Surface Defects on Optical Discs

    DEFF Research Database (Denmark)

    Odgaard, Peter Fogh; Wickerhauser, M.V.

    Many have experienced problems with their Compact Disc player when a disc with a scratch or a finger print is tried played. One way to improve the playability of discs with such a defect, is to locate the defect in time and then handle it in a special way. As a consequence this time localisation is...

  18. Lung resection in cystic fibrosis patients with localised pulmonary disease.

    OpenAIRE

    Lucas, J; Connett, G J; Lea, R.; Rolles, C J; Warner, J. O.

    1996-01-01

    The results of lobar resection to treat severe localised bronchiectasis in six children with cystic fibrosis are described. Sustained clinical improvements occurred in children undergoing this surgical approach to treatment. Detailed assessment and intensive preoperative and postoperative medical treatment are essential to a favourable outcome in carefully selected patients.

  19. Chinese Localisation of Evergreen: An Open Source Integrated Library System

    Science.gov (United States)

    Zou, Qing; Liu, Guoying

    2009-01-01

    Purpose: The purpose of this paper is to investigate various issues related to Chinese language localisation in Evergreen, an open source integrated library system (ILS). Design/methodology/approach: A Simplified Chinese version of Evergreen was implemented and tested and various issues such as encoding, indexing, searching, and sorting…

  20. Scintiscanning with a coded aperture

    International Nuclear Information System (INIS)

    In scintigraphy the quality of the recorded image is a function of the quantum statistics of the photons, because only a small number of photons are available for an image. If the apertured or parallel-hole collimator is replaced by a coded aperture, e.g., a Fresnel-type zone plate of the proper size, a much larger fraction of the gamma quanta emitted by the object under investigation are captured, and there is no loss in resolution. A technique is described which allows the sequential reconstruction of various planes of the object while, at the same time, eliminating the spurious constant light fraction. For recording of the incoherent gamma hologram an on-axis zone plate can be used. In the coherent-optical reconstruction the gamma hologram is correlated with the zone plate used for the recording process. The experimental results shown are optical reconstructions of phantoms filled with 57Co. (orig./ORU)

  1. Airborne synthetic aperture acoustic imaging.

    Science.gov (United States)

    Soumekh, M

    1997-01-01

    This paper presents a system model and inversion for airborne synthetic aperture acoustic (SAA) imaging. The system model accurately represents the intercation of the acoustic source and the target region at near range values. Moreover, the model incorporates the fact that the relative speed of the vehicle's (transmitter/receiver) with respect to the target region is comparable to the acoustic wave propagation speed. The inversion utilizes the principle of spectral decomposition of spherical phase functions to develop a wavefront reconstruction method from SAA data. Processing issues and selection of appropriate acoustic FM-CW sources are discussed. Results are provided that exhibit the superior accuracy of the proposed SAA system model and inversion over their synthetic aperture radar (SAR) counterpart in which the vehicle's speed is assumed to be much smaller than the wave propagation speed. PMID:18282912

  2. The study on aperture configuration of optical synthetic aperture imaging system

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A model based on Fourier domain consideration on aperture configuration of optical synthetic aperture imaging system is introduced in this paper. The derivation of the model is directly linked to the restoration error of the original object from the recorded image. The aperture configuration is a function of the maximum frequency of interest, and takes into account the diameter of the aperture. The simulative results of genetic algorithms illustrate the usefulness of this model for designing a synthetic aperture optical imaging system, and the aperture configuration of a good synthetic aperture optical imaging system should be non-redundant.

  3. Multifocal interferometric synthetic aperture microscopy

    OpenAIRE

    Xu, Yang; Chng, Xiong Kai Benjamin; Adie, Steven G.; Boppart, Stephen A.; Scott Carney, P.

    2014-01-01

    There is an inherent trade-off between transverse resolution and depth of field (DOF) in optical coherence tomography (OCT) which becomes a limiting factor for certain applications. Multifocal OCT and interferometric synthetic aperture microscopy (ISAM) each provide a distinct solution to the trade-off through modification to the experiment or via post-processing, respectively. In this paper, we have solved the inverse problem of multifocal OCT and present a general algorithm for combining mu...

  4. Short term dynamic aperture with AC dipoles

    CERN Document Server

    Mönig, Saskia; Persson, Tobias Hakan Bjorn; Coello De Portugal, Jaime; Langner, Andy; Tomas, Rogelio; CERN. Geneva. ATS Department

    2015-01-01

    The dynamic aperture of an accelerator is determined by its non-linear components and errors. Control of the dynamic aperture is important for a good understanding and operation of the accelerator. The AC dipole, installed in the LHC for the diagnostic of linear and non-linear optics, could serve as a tool for the determination of the dynamic aperture. However, since the AC dipole itself modifies the non-linear dynamics, the dynamic aperture with and without AC dipole are expected to differ. The effect of the AC dipole on the dynamic aperture is studied within this note.

  5. Self-Referencing Hartmann Test for Large-Aperture Telescopes

    Science.gov (United States)

    Korechoff, Robert P.; Oseas, Jeffrey M.

    2010-01-01

    A method is proposed for end-to-end, full aperture testing of large-aperture telescopes using an innovative variation of a Hartmann mask. This technique is practical for telescopes with primary mirrors tens of meters in diameter and of any design. Furthermore, it is applicable to the entire optical band (near IR, visible, ultraviolet), relatively insensitive to environmental perturbations, and is suitable for ambient laboratory as well as thermal-vacuum environments. The only restriction is that the telescope optical axis must be parallel to the local gravity vector during testing. The standard Hartmann test utilizes an array of pencil beams that are cut out of a well-corrected wavefront using a mask. The pencil beam array is expanded to fill the full aperture of the telescope. The detector plane of the telescope is translated back and forth along the optical axis in the vicinity of the nominal focal plane, and the centroid of each pencil beam image is recorded. Standard analytical techniques are then used to reconstruct the telescope wavefront from the centroid data. The expansion of the array of pencil beams is usually accomplished by double passing the beams through the telescope under test. However, this requires a well-corrected, autocollimation flat, the diameter or which is approximately equal to that of the telescope aperture. Thus, the standard Hartmann method does not scale well because of the difficulty and expense of building and mounting a well-corrected, large aperture flat. The innovation in the testing method proposed here is to replace the large aperture, well-corrected, monolithic autocollimation flat with an array of small-aperture mirrors. In addition to eliminating the need for a large optic, the surface figure requirement for the small mirrors is relaxed compared to that required of the large autocollimation flat. The key point that allows this method to work is that the small mirrors need to operate as a monolithic flat only with regard to

  6. Neuroglobin in the rat brain (II): co-localisation with neurotransmitters

    DEFF Research Database (Denmark)

    Hundahl, Christian Ansgar; Kelsen, Jesper; Dewilde, Sylvia;

    2008-01-01

    In an accompanying article, we found that neuroglobin (Ngb) was expressed in a few well-defined nuclei in the rat brain. Here, we show by use of immunohistochemistry and in situ hybridisation (ISH) that Ngb co-localise with several specific neurotransmitters. Ngb co-localise consistently with......-localised melanin concentration hormone (MCH). A few Ngb-ir perikarya in the paraventricular hypothalamic nucleus (PVN) co-localised arginine vasopressin (aVP). Ngb were not observed to co-localise with serotonin, vasointestinal peptide (VIP), or cocaine amphetamine-regulated transcript (CART) at any places. In the...

  7. Directional synthetic aperture flow imaging

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Nikolov, Svetoslav

    2004-01-01

    A method for flow estimation using synthetic aperture imaging and focusing along the flow direction is presented. The method can find the correct velocity magnitude for any flow angle and full color flow images can be measured using only 32 to 128 pulse emissions. The approach uses spherical wave...... emissions using a number of defocused elements and a linear frequency modulated pulse (chirp) to improve the signal-to-noise ratio. The received signals are dynamically focused along the flow direction and these signals are used in a cross-correlation estimator for finding the velocity magnitude. The flow...

  8. The Large Aperture GRB Observatory

    CERN Document Server

    Allard, D; Asorey, H; Barros, H; Bertou, X; Castillo, M; Chirinos, J M; De Castro, A; Flores, S; González, J; Berisso, M Gomez; Grajales, J; Guada, C; Day, W R Guevara; Ishitsuka, J; López, J A; Martínez, O; Melfo, A; Meza, E; Loza, P Miranda; Barbosa, E Moreno; Murrugarra, C; Núñez, L A; Ormachea, L J Otiniano; Pérez, G; Perez, Y; Ponce, E; Quispe, J; Quintero, C; Rivera, H; Rosales, M; Rovero, A C; Saavedra, O; Salazar, H; Tello, J C; Peralda, R Ticona; Varela, E; Velarde, A; Villaseñor, L; Wahl, D; Zamalloa, M A

    2009-01-01

    The Large Aperture GRB Observatory (LAGO) is aiming at the detection of the high energy (around 100 GeV) component of Gamma Ray Bursts, using the single particle technique in arrays of Water Cherenkov Detectors (WCD) in high mountain sites (Chacaltaya, Bolivia, 5300 m a.s.l., Pico Espejo, Venezuela, 4750 m a.s.l., Sierra Negra, Mexico, 4650 m a.s.l). WCD at high altitude offer a unique possibility of detecting low gamma fluxes in the 10 GeV - 1 TeV range. The status of the Observatory and data collected from 2007 to date will be presented.

  9. Ultrasonic large aperture imaging system

    International Nuclear Information System (INIS)

    A new ultrasonic large aperture imaging technique is described. This device combines a focussed transducer as a transmitter, producing a small ultrasonic beam, with N transducers as receivers. We show that is possible to considerably reduce the number of receivers if, on the one hand, we limit the reconstitution process to the emitter beam area and, on the other hand, we ensure that the artefacts, caused by the spatial sampling of the reception, are outside this area. Under these conditions, the result is a high resolution image which does not require large reconstitution processing times. Theoretical and experimental results are given

  10. Localisation of directional scale-discretised wavelets on the sphere

    CERN Document Server

    McEwen, Jason D; Wiaux, Yves

    2015-01-01

    Scale-discretised wavelets yield a directional wavelet framework on the sphere where a signal can be probed not only in scale and position but also in orientation. Furthermore, a signal can be synthesised from its wavelet coefficients exactly, in theory and practice (to machine precision). Scale-discretised wavelets are closely related to spherical needlets (both were developed independently at about the same time) but relax the axisymmetric property of needlets so that directional signal content can be probed. Needlets have been shown to satisfy important quasi-exponential localisation and asymptotic uncorrelation properties. We show that these properties also hold for directional scale-discretised wavelets on the sphere and derive similar localisation and uncorrelation bounds in both the scalar and spin settings. Scale-discretised wavelets can thus be considered as directional needlets.

  11. [Frequency and most common localisation of root canal curvature].

    Science.gov (United States)

    Blasković-Subat, V

    1991-01-01

    The root canal therapy of the curved canals is a complex operative procedure. Therefore 260 root canals were analysed radiologically to determine the frequency and the most common localisation of the root canal curvature. The frequency of the curved canals averaged at 59%, being greater in the sample of posterior than in the anterior teeth (p less than 0.05). The root canal curvature was most frequently localised at the apical third part (53.9%), followed by the cervical (33.3%) and the middle (12.8%) third part. The apical curvature was predominant in the sample of the anterior, while the cervical predominant (45.2%) in the sample of the posterior teeth. This study pointed out that the frequency of the curved canals is rather high. Consequently, the necessity for practising the modern root canal preparation techniques, bearing in mind their potential danger, is emphasized. PMID:1819932

  12. Localised plasma density enhancements around comet CG/67P

    Science.gov (United States)

    Henri, Pierre; Broiles, Tom; Eriksson, Anders; Béghin, Christian; Lebreton, Jean-Pierre; Vallieres, Xavier; More, Jerome; Wattieaux, Gaetan; Engelhardt, Ilka A. D.; Edberg, Niklas; Odelstad, Elias; Vigren, Erik; Glassmeier, Karl-Heinz; Goetz, Charlotte; Koenders, Christoph; Richter, Ingo; Volwerk, Martin; Burch, James L.; Goldstein, Ray; Mandt, Kathleen

    2016-04-01

    Comet 67P/Churyumov-Gerasimenko, target of the ESA's Rosetta mission, reached its perihelion at 1.3 AU from the Sun in August 2015. Its plasma environment will go on being monitored by the Rosetta Plasma Consortium (RPC) as the distance to the sun increases, until end of mission in September 2016. Combining observations from the different RPC sensors, we investigate localised, strong enhancements of the cometary plasma density over short timescales (~ minutes to seconds) observed during the period April 2015 - January 2016. These strong plasma density variations (RPC-MIP and RPC-LAP) are likely associated to cold electrons (RPC-IES) and generally observed during magnetic field rotations (RPC-MAG). The location of such events, both in the rotating comet frame and with regard to the magnetic field direction, is discussed to better constrain the mechanism at the origin of these localised plasma density enhancements.

  13. Bremstrahlung Detection and Chamber Obstruction Localisation Using Scanning Radiation Detectors

    CERN Document Server

    Naylor, G A; Robinson, D

    2005-01-01

    Radiation monitors consisting of scintillating plastic coupled to photomultipliers are used for diagnostic purposes. By scanning such a detector or a radiation scatterer, two applications are demonstrated: i) Monitoring of vacuum chamber conditioning by monitoring gas Bremstrahlung from residual gas. ii) Localisation of beam interception (beam losses) by longitudinal scanning of a radiation detector. The measurement of gas pressure inside long, small cross section, vacuum vessels is difficult due to the distance between the centre of the vacuum vessel and vacuum gauges (leading to a low vacuum conductance). The narrow beam of gamma Bremstrahlung radiation is intercepted by scanning tungsten blades in the beam line front-end allowing a radiation shower to be detected outside the vacuum vessel proportional to the gas pressure in the corresponding storage ring straight section. A second detector mounted on rails can be moved over a length of 6.5m parallel to the ESRF storage ring so as to localise regions of bea...

  14. Limitations in localising and killing tumours using radiolabelled antibodies

    International Nuclear Information System (INIS)

    Radiolabelled antibodies against tumours are being studied intensely for their use in tumour detection and tumour destruction. Although a host of different tumour types can be localised, results at present are no better than other scanning techniques. In addition no tumour has been eradicated using labelled antibodies. Dramatic improvements will depend upon a fuller understanding of tumour cell biology and optimising all the parameters involved. (orig.)

  15. Simultaneous Mapping and Localisation for Small Military Unmanned Underwater Vehicle

    OpenAIRE

    Arom Hwang; Woojae Seong

    2012-01-01

    Paper proposes a simultaneous localisation and mapping (SLAM) scheme which is applicable to small military unmanned underwater vehicles (UUVs). The SLAM is a process which enables concurrent estimation of the position of UUV and landmarks in the environment through which the vehicle is passing. An unscented Kalman filter (UKF) is utilised to develop a SLAM suitable to nonlinear motion of UUV. A range sonar is used as a sensor to collect the relative position information of the landmark in the...

  16. APPLYING INNOVATIVE METHODOLOGICAL MODELS IN THE LITERARY TEXT LOCALISATION

    OpenAIRE

    Franciskovic, Dragana

    2012-01-01

    The paper deals with the research aimed at evaluating the possibilities and the level of influence of modern teaching methods on the quality of literary text analysis. Modern teaching methods certainly have a certain influence on student's literary experience and ability to analyse literary works. We have researched the aforementioned level of influence within the specific educational sphere using literary excerpts in the phase of text localisation. The research presents the results of parall...

  17. Automated quantum conductance calculations using maximally-localised Wannier functions

    OpenAIRE

    Shelley, Matthew; Poilvert, Nicolas; Mostofi, Arash A.; Marzari, Nicola

    2011-01-01

    A robust, user-friendly, and automated method to determine quantum conductance in disordered quasi-one-dimensional systems is presented. The scheme relies upon an initial density- functional theory calculation in a specific geometry after which the ground-state eigenfunctions are transformed to a maximally-localised Wannier function (MLWF) basis. In this basis, our novel algorithms manipulate and partition the Hamiltonian for the calculation of coherent electronic transport properties within ...

  18. The case for localised energy management to support resilient cities

    OpenAIRE

    Rodrigues, Lucélia Taranto; Marsh, Julian; Kiamba, Lorna; Gillott, Mark C.; O'Doherty, Travis

    2016-01-01

    Localised energy generation, ownership and management provide a mechanism to address issues of affordability, energy security, infrastructure resilience and the need to reduce greenhouse gases emissions. There is potential for the growth of community energy schemes in the UK. However, small to medium-sized schemes find it hard to compete with large energy providers. Energy Service Companies (ESCOs) are created to manage the local production and distribution of energy. In Nottingham, the Meado...

  19. A Framework for Designing Usable Localised Business Websites

    OpenAIRE

    Ali H. Al-Badi; Pam J. Mayhew

    2010-01-01

    Website localisation is the process of adapting the linguistic and cultural content of an internationalised web design for a specific target audience in a specific locale. With the advent of globalisation, website l ocalisation is becoming a powerful way to attract online customers in a global market. Hence, the main driving force behind such moves is financial, but with a strong motivation towards cross-cultural sensitivity. The primary aim of this research therefore is to explore the desig...

  20. Experimental determination of critical exponents in Anderson localisation of light

    OpenAIRE

    Aegerter, Christof M.; Störzer, Martin; Maret, Georg

    2006-01-01

    Anderson localisation predicts a phase transition in transport, where the diffuse spread of particles comes to a halt with the introduction of a critical amount of disorder. This is due to constructive interference on closed multiple scattering loops which leads to a renormalisation of the diffusion coefficient. This can be described by a slowing-down of diffusion, where the diffusion coefficient decreases with time according to a power law with an exponent a. In the case of strong localisati...

  1. Diagnostic approach to localised organising pneumonia: A case report

    OpenAIRE

    Đurić Mirna; Považan Đorđe; Đurić Dejan; Eri Živka; Trudić Anika

    2015-01-01

    Introduction. Localised organising pneumonia, radiologically presented with oval or round shadows mimicing lung cancer or metastases, is a major issue in differential diagnosis. Case report. A female patient was hospitalized to clarified the etiology of multiple nodular lung lesions. The chest X-ray and the chest computed tomography (CT) revealed bilateral patchy and nodular shadows, and round lung lesions, respectively. Neither sputum analyses, nor histolo...

  2. Strain localisation in mechanically Layered Rocks, insights from numerical modelling

    Directory of Open Access Journals (Sweden)

    L. Le Pourhiet

    2012-09-01

    Full Text Available Small scale deformation in stratified rocks displays a large diversity of micro-structures, from the microscopic scale to the scale of orogens. We have designed a series of fully dynamic numerical simulations aimed at assessing which parameters control this structural diversity and which underlying mechanisms lead to strain localisation. The influence of stratification orientation on the occurrence and mode of strain localisation is tested by varying the initial dip of inherited layering versus the large scale imposed simple shear. The detailed study of the models indicates that (1 the results are length-scale independent, (2 the new shear zones are always compatible with the kinematics imposed at the boundary (3 micro-structures formed encompass the full diversity of micro-structures observed in the field and chiefly depend on the direction of the initial anisotropy versus shear direction, (4 depending on the orientation of the anisotropy, the layers may deform along subtractive or additive shear bands, (5 the deformation in anisotropic media results in non-lithostatic pressure values that are on the order of the deviatoric stress in the strong layers and (6 the introduction of brittle rheology is necessary to form localised shear bands in the ductile regime.

  3. Weak localisation in high quality two dimensional systems

    International Nuclear Information System (INIS)

    Full text: The quantum properties of two dimensional (2D) electronic devices are of great interest both scientifically and, increasingly, technologically. The time scale over which quantum effects operate in these systems is limited by the phase breaking time τφ. Study of the weak localisation effect (the increase in electrical resistance due to phase coherent backscattering) can enable τφ to be quantified. We investigate phase coherent weak localisation effects in high quality 2D electron and hole systems, and show how the values of phase coherence time extracted from the raw data depend critically on which of the methods selected from the literature is used to fit the weak localisation correction to the magneto-conductivity. We compare four different methods available in the literature and discuss the differences and relative merits of each. All four methods are then used to fit magneto-conductivity data from high quality 2D GaAs hole systems over a range of carrier densities and temperatures. We compare the extracted phase coherence time, τφ, to the phase breaking rate expected from Fermi liquid theory and show that the method of Dimitriev et al. - the most sophisticated method, used for the first time here - is in good quantitative agreement with Fermi liquid theory despite the presence of strong hole-hole interactions, rs ∼ 20

  4. Diagnostic approach to localised organising pneumonia: A case report

    Directory of Open Access Journals (Sweden)

    Đurić Mirna

    2015-01-01

    Full Text Available Introduction. Localised organising pneumonia, radiologically presented with oval or round shadows mimicing lung cancer or metastases, is a major issue in differential diagnosis. Case report. A female patient was hospitalized to clarified the etiology of multiple nodular lung lesions. The chest X-ray and the chest computed tomography (CT revealed bilateral patchy and nodular shadows, and round lung lesions, respectively. Neither sputum analyses, nor histology of bronchoscopy samples clarified the etiology of these lung lesions. As secondary deposits in the lungs were suspected, video-assisted thoracoscopy and anterolateral right minithoracotomy with atypical upper and lower lobe resection were performed. The frozen-section analysis suggested the benign nature of the lesion, and the definite histopathological finding of localised organising pneumonia was established. Due to bilateral lung lesions, corticosteroids were applied. Seven weeks later, the chest CT finding revealed a total regression of the lesions. Conclusion. A surgical resection was necessary to diagnose the localised organising pneumonia which mimiced secondary malignant lesions, thus establishing the definite etiology of lung lesions. Bronchoscopic cryobiopsy, recently introduced in order to obtain peripheral lung biopsy samples, has provided new possibilities in the diagnosis and treatment of neoplastic and non-neoplastic lung diseases.

  5. Resonant Effects in Nanoscale Bowtie Apertures

    Science.gov (United States)

    Ding, Li; Qin, Jin; Guo, Songpo; Liu, Tao; Kinzel, Edward; Wang, Liang

    2016-06-01

    Nanoscale bowtie aperture antennas can be used to focus light well below the diffraction limit with extremely high transmission efficiencies. This paper studies the spectral dependence of the transmission through nanoscale bowtie apertures defined in a silver film. A realistic bowtie aperture is numerically modeled using the Finite Difference Time Domain (FDTD) method. Results show that the transmission spectrum is dominated by Fabry-Pérot (F-P) waveguide modes and plasmonic modes. The F-P resonance is sensitive to the thickness of the film and the plasmonic resonant mode is closely related to the gap distance of the bowtie aperture. Both characteristics significantly affect the transmission spectrum. To verify these numerical results, bowtie apertures are FIB milled in a silver film. Experimental transmission measurements agree with simulation data. Based on this result, nanoscale bowtie apertures can be optimized to realize deep sub-wavelength confinement with high transmission efficiency with applications to nanolithography, data storage, and bio-chemical sensing.

  6. Practical Applications of Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav Ivanov; Kortbek, Jacob; Jensen, Jørgen Arendt

    2010-01-01

    Synthetic aperture imaging has been a focus of research for almost 3 decades. The research carried out at the Center for Fast Ultrasound Imaging has demonstrated that synthetic aperture focusing not only can be used in-vivo, but that it also yields superior B-mode and blood flow images. In the last...... years synthetic aperture focusing has moved from the lab to commercial products. The implementations vary in their scope and purpose. Some scanners use synthetic aperture imaging to improve the detail and contrast resolution of the system. Others to increase the image uniformity. Yet others use...... synthetic aperture acquisition to achieve high frame rates and superior flow estimations. On the other end of the scale are the systems that utilize synthetic aperture techniques to reduce the data rate and take advantage of modern computer hardware. Retrospecitve transmit beamformation, zone sonography...

  7. Doppler synthetic aperture hitchhiker imaging

    International Nuclear Information System (INIS)

    In this paper we consider passive airborne receivers that use backscattered signals from sources of opportunity transmitting single-frequency or ultra-narrowband waveforms. Because of its combined passive synthetic aperture and the single-frequency nature of the transmitted waveforms, we refer to the system under consideration as Doppler synthetic aperture hitchhiker (DSAH). We present a novel image formation method for DSAH. Our method first correlates the windowed signal obtained from one receiver with the windowed, filtered, scaled and translated version of the received signal from another receiver. This processing removes the transmitter-related variables from the phase of the Fourier integral operator that maps the radiance of the scene to the correlated signal. Next, we use microlocal analysis to reconstruct the scene radiance by the weighted backprojection of the correlated signal. The image reconstruction method is applicable to both cooperative and non-cooperative sources of opportunity using one or more airborne receivers. It has the desirable property of preserving the visible edges of the scene radiance. Additionally, it is an analytic reconstruction technique that can be made computationally efficient. We present numerical simulations to demonstrate the performance of the image reconstruction method and to verify the theoretical results

  8. Colored coded-apertures for spectral image unmixing

    Science.gov (United States)

    Vargas, Hector M.; Arguello Fuentes, Henry

    2015-10-01

    Hyperspectral remote sensing technology provides detailed spectral information from every pixel in an image. Due to the low spatial resolution of hyperspectral image sensors, and the presence of multiple materials in a scene, each pixel can contain more than one spectral signature. Therefore, endmember extraction is used to determine the pure spectral signature of the mixed materials and its corresponding abundance map in a remotely sensed hyperspectral scene. Advanced endmember extraction algorithms have been proposed to solve this linear problem called spectral unmixing. However, such techniques require the acquisition of the complete hyperspectral data cube to perform the unmixing procedure. Researchers show that using colored coded-apertures improve the quality of reconstruction in compressive spectral imaging (CSI) systems under compressive sensing theory (CS). This work aims at developing a compressive supervised spectral unmixing scheme to estimate the endmembers and the abundance map from compressive measurements. The compressive measurements are acquired by using colored coded-apertures in a compressive spectral imaging system. Then a numerical procedure estimates the sparse vector representation in a 3D dictionary by solving a constrained sparse optimization problem. The 3D dictionary is formed by a 2-D wavelet basis and a known endmembers spectral library, where the Wavelet basis is used to exploit the spatial information. The colored coded-apertures are designed such that the sensing matrix satisfies the restricted isometry property with high probability. Simulations show that the proposed scheme attains comparable results to the full data cube unmixing technique, but using fewer measurements.

  9. Advanced Optics Experiments Using Nonuniform Aperture Functions

    CERN Document Server

    Wood, Lowell T

    2012-01-01

    A method to create instructive, nonuniform aperture functions using spatial frequency filtering is described. The diffraction from a single slit in the Fresnel limit and the interference from a double slit in the Fraunhofer limit are spatially filtered to create electric field distributions across an aperture to produce apodization, inverse apodization or super-resolution, and apertures with phase shifts across their widths. The diffraction effects from these aperture functions are measured and calculated. The excellent agreement between the experimental results and the calculated results makes the experiment ideal for use in an advanced undergraduate or graduate optics laboratory to illustrate experimentally several effects in Fourier optics.

  10. Ion mobility spectrometer with virtual aperture grid

    Science.gov (United States)

    Pfeifer, Kent B.; Rumpf, Arthur N.

    2010-11-23

    An ion mobility spectrometer does not require a physical aperture grid to prevent premature ion detector response. The last electrodes adjacent to the ion collector (typically the last four or five) have an electrode pitch that is less than the width of the ion swarm and each of the adjacent electrodes is connected to a source of free charge, thereby providing a virtual aperture grid at the end of the drift region that shields the ion collector from the mirror current of the approaching ion swarm. The virtual aperture grid is less complex in assembly and function and is less sensitive to vibrations than the physical aperture grid.

  11. Practical Applications of Synthetic Aperture Imaging

    OpenAIRE

    Nikolov, Svetoslav Ivanov; Kortbek, Jacob; Jensen, Jørgen Arendt

    2010-01-01

    Synthetic aperture imaging has been a focus of research for almost 3 decades. The research carried out at the Center for Fast Ultrasound Imaging has demonstrated that synthetic aperture focusing not only can be used in-vivo, but that it also yields superior B-mode and blood flow images. In the last years synthetic aperture focusing has moved from the lab to commercial products. The implementations vary in their scope and purpose. Some scanners use synthetic aperture imaging to improve the det...

  12. Strain weakening and localisation: material properties or boundary effects?

    Science.gov (United States)

    Ritter, Malte C.; Leever, Karen; Rosenau, Matthias; Oncken, Onno

    2015-04-01

    Strain weakening is commonly seen as one of the major causes of localisation of deformation into shear zones in brittle media. Several studies, both numerical and physical experiments, investigate its influence. Typically, these studies choose a certain model configuration and test various material properties and their influence on localisation in that particular configuration. This approach, however, does not take into account the fundamental importance of boundary conditions on the processes of localisation, weakening and overall shear zone evolution. To address this issue, we perform physical experiments in granular materials. We create shear fractures within a sample of granular material (sand) using different experimental apparatuses that apply different boundary conditions. Among them are standard machines such as a Ring-Shear Tester and the classical Riedel set up, as well as a newly designed set up. Boundary conditions can be varied from purely kinematic to more dynamically controlled and from laterally confined to unconfined. Nevertheless, the final result of deformation is an approximately straight strike-slip shear zone in all cases. We monitor boundary force (i. e. material strength) and, where experimentally accessible, strain, at high temporal resolution during deformation. With our different set ups we are able to produce very different patterns of deformation and weakening in the same material under the same constant rate of shearing and with the same final result. Observed patterns span from nearly instantaneous formation of one single through-going shear zone to slow, step-wise growth of a complex network of interacting cracks. Weakening in all cases matches well the structural evolution. Variations of weakening for a given material in different set ups are larger than for different materials in a given set up. Our results show that for a given material the style and rate of localisation can change drastically, depending on only slight changes of

  13. Multifocal interferometric synthetic aperture microscopy.

    Science.gov (United States)

    Xu, Yang; Chng, Xiong Kai Benjamin; Adie, Steven G; Boppart, Stephen A; Carney, P Scott

    2014-06-30

    There is an inherent trade-off between transverse resolution and depth of field (DOF) in optical coherence tomography (OCT) which becomes a limiting factor for certain applications. Multifocal OCT and interferometric synthetic aperture microscopy (ISAM) each provide a distinct solution to the trade-off through modification to the experiment or via post-processing, respectively. In this paper, we have solved the inverse problem of multifocal OCT and present a general algorithm for combining multiple ISAM datasets. Multifocal ISAM (MISAM) uses a regularized combination of the resampled datasets to bring advantages of both multifocal OCT and ISAM to achieve optimal transverse resolution, extended effective DOF and improved signal-to-noise ratio. We present theory, simulation and experimental results. PMID:24977909

  14. Synthetic aperture interferometry: error analysis

    International Nuclear Information System (INIS)

    Synthetic aperture interferometry (SAI) is a novel way of testing aspherics and has a potential for in-process measurement of aspherics [Appl. Opt.42, 701 (2003)].APOPAI0003-693510.1364/AO.42.000701 A method to measure steep aspherics using the SAI technique has been previously reported [Appl. Opt.47, 1705 (2008)].APOPAI0003-693510.1364/AO.47.001705 Here we investigate the computation of surface form using the SAI technique in different configurations and discuss the computational errors. A two-pass measurement strategy is proposed to reduce the computational errors, and a detailed investigation is carried out to determine the effect of alignment errors on the measurement process.

  15. Deliverable navigation for multicriteria IMRT treatment planning by combining shared and individual apertures

    International Nuclear Information System (INIS)

    We consider the problem of deliverable Pareto surface navigation for step-and-shoot intensity-modulated radiation therapy. This problem amounts to calculation of a collection of treatment plans with the property that convex combinations of plans are directly deliverable. Previous methods for deliverable navigation impose restrictions on the number of apertures of the individual plans, or require that all treatment plans have identical apertures. We introduce simultaneous direct step-and-shoot optimization of multiple plans subject to constraints that some of the apertures must be identical across all plans. This method generalizes previous methods for deliverable navigation to allow for treatment plans with some apertures from a collective pool and some apertures that are individual. The method can also be used as a post-processing step to previous methods for deliverable navigation in order to improve upon their plans. By applying the method to subsets of plans in the collection representing the Pareto set, we show how it can enable convergence toward the unrestricted (non-navigable) Pareto set where all apertures are individual. (paper)

  16. Deliverable navigation for multicriteria IMRT treatment planning by combining shared and individual apertures

    Science.gov (United States)

    Fredriksson, Albin; Bokrantz, Rasmus

    2013-11-01

    We consider the problem of deliverable Pareto surface navigation for step-and-shoot intensity-modulated radiation therapy. This problem amounts to calculation of a collection of treatment plans with the property that convex combinations of plans are directly deliverable. Previous methods for deliverable navigation impose restrictions on the number of apertures of the individual plans, or require that all treatment plans have identical apertures. We introduce simultaneous direct step-and-shoot optimization of multiple plans subject to constraints that some of the apertures must be identical across all plans. This method generalizes previous methods for deliverable navigation to allow for treatment plans with some apertures from a collective pool and some apertures that are individual. The method can also be used as a post-processing step to previous methods for deliverable navigation in order to improve upon their plans. By applying the method to subsets of plans in the collection representing the Pareto set, we show how it can enable convergence toward the unrestricted (non-navigable) Pareto set where all apertures are individual.

  17. Synthetic aperture radar: principles and applications

    International Nuclear Information System (INIS)

    In this paper an introduction to synthetic aperture radar is presented. Synthetic aperture radar is a relatively new remote sensing platform and the technology has matured a lot in the last two decades. This paper introduces the concepts behind SAR principles as well as the major areas where this new technology has shown additional information. (author)

  18. Thermal emission by a subwavelength aperture

    Science.gov (United States)

    Joulain, Karl; Ezzahri, Younès; Carminati, Rémi

    2016-04-01

    We calculate, by means of fluctuational electrodynamics, the thermal emission of an aperture separating from the outside, vacuum or a material at temperature T. We show that thermal emission is very different whether the aperture size is large or small compared to the thermal wavelength. Subwavelength apertures separating vacuum from the outside have their thermal emission strongly decreased compared to classical blackbodies which have an aperture much larger than the wavelength. A simple expression of their emissivity can be calculated and their total emissive power scales as T8 instead of T4 for large apertures. Thermal emission of disk of materials with a size comparable to the wavelength is also discussed. It is shown in particular that emissivity of such a disk is increased when the material can support surface waves such as phonon polaritons.

  19. Orthogonal views improves localisation in bone scans of wrist

    Energy Technology Data Exchange (ETDEWEB)

    Roth, A.L.

    1997-09-01

    Full text: Of all nuclear medicine studies, bone scans are the most fundamental. However, straightforward these may seem, there are always mechanisms that can be implemented which assist in a more precise diagnosis, particularly in areas with an intricate bone structure. An 18-year-old right-handed student presented to her doctor with a one month history of pain over the right distal radio-ulna joint area. Clinically, she had prominence of the right ulna, which suggested that there may have been a previous injury to the wrist. Also, pronation/supination were painful where there was swelling of the extensor carpi ulnaris tendon, as well as some discomfort with clicking in ulna deviation/rotation. The X-rays demonstrated some premature radial epiphysial closure. A bone scan was requested to attempt to localise the main inflammatory focus. The dynamic study was performed in the planar projection with an immediate blood pool for 300k being taken. These demonstrated a vascular blush medially. A medial blood pool image was acquired and it localised the abnormal vascularity as being dorsal. A separate focal area of less intense blood pooling was also noted in the line of the distal ulna. Delayed images showed increased uptake localised to the ulna styloid. Anatomically, the superficial vascular blush correlated with tenosynovitis. Hence, the orthogonal initial and delayed images were definitive in the diagnoses of tenosynovitis of the extensor carpi ulnaris tendon. This clearly complements the information provided by the palmar view. However, it is important to remember that an increased radiation dose to the technologist is incurred as a result of the extra orthogonal view, hence attention to technique is imperative.

  20. Orthogonal views improves localisation in bone scans of wrist

    International Nuclear Information System (INIS)

    Full text: Of all nuclear medicine studies, bone scans are the most fundamental. However, straightforward these may seem, there are always mechanisms that can be implemented which assist in a more precise diagnosis, particularly in areas with an intricate bone structure. An 18-year-old right-handed student presented to her doctor with a one month history of pain over the right distal radio-ulna joint area. Clinically, she had prominence of the right ulna, which suggested that there may have been a previous injury to the wrist. Also, pronation/supination were painful where there was swelling of the extensor carpi ulnaris tendon, as well as some discomfort with clicking in ulna deviation/rotation. The X-rays demonstrated some premature radial epiphysial closure. A bone scan was requested to attempt to localise the main inflammatory focus. The dynamic study was performed in the planar projection with an immediate blood pool for 300k being taken. These demonstrated a vascular blush medially. A medial blood pool image was acquired and it localised the abnormal vascularity as being dorsal. A separate focal area of less intense blood pooling was also noted in the line of the distal ulna. Delayed images showed increased uptake localised to the ulna styloid. Anatomically, the superficial vascular blush correlated with tenosynovitis. Hence, the orthogonal initial and delayed images were definitive in the diagnoses of tenosynovitis of the extensor carpi ulnaris tendon. This clearly complements the information provided by the palmar view. However, it is important to remember that an increased radiation dose to the technologist is incurred as a result of the extra orthogonal view, hence attention to technique is imperative

  1. Nerve growth factor levels and localisation in human asthmatic bronchi.

    Science.gov (United States)

    Olgart Höglund, C; de Blay, F; Oster, J P; Duvernelle, C; Kassel, O; Pauli, G; Frossard, N

    2002-11-01

    Nerve growth factor (NGF) has recently been suggested to be an important mediator of inflammation. In support of this, serum levels of NGF have been shown to be enhanced in asthmatics. However, it has not yet been shown whether the levels of NGF are also altered locally in asthmatic airways, when compared with healthy subjects, and the localisation of potential sources of NGF in the human bronchus have not yet been described. The aim of the present study was to assess NGF levels in bronchoalveolar lavage fluid (BALF) from asthmatics and to compare them to those of control subjects. Furthermore, the authors wanted to localise potential sources of NGF in bronchial tissue, and to number NGF-immunopositive infiltrating cells in the bronchial submucosa. BALF and bronchial biopsies were obtained from seven control subjects and seven asthmatic patients by fibreoptic bronchoscopy. NGF protein levels were quantified by enzyme-linked immunosorbent assay in BALF. NGF localisation was examined by immunohistochemistry on bronchial biopsy sections. The asthmatics exhibited significantly enhanced NGF levels in BALF. Intense NGF-immunoreactivity was observed in bronchial epithelium, smooth muscle cells and infiltrating inflammatory cells in the submucosa, and to a lesser extent in the connective tissue. The asthmatics exhibited a higher number of NGF-immunoreactive infiltrating cells in the bronchial submucosa than control subjects. This study provides evidence that nerve growth factor is locally produced in the airways, and shows that this production is enhanced in asthmatics. These findings suggest that nerve growth factor is produced by both structural cells and infiltrating inflammatory cells in human bronchus in vivo, and the authors suggest that the increase in nerve growth factor protein in bronchoalveolar lavage fluid observed in asthmatic patients may originate both from structural cells, producing increased nerve growth factor levels in inflammatory conditons, and from

  2. Simultaneous Localisation and Mapping Using a Single Camera

    OpenAIRE

    Williams, Brian P.; Reid, Ian D.

    2009-01-01

    This thesis describes a system which is able to track the pose of a hand-held camera as it moves around a scene. The system builds a 3D map of point landmarks in the world while tracking the pose of the camera relative to this map using a process called simultaneous localisation and mapping (SLAM). To achieve real-time performance, the map must be kept sparse, but rather than observing only the mapped landmarks like previous systems, observations are made of features across the entire image. ...

  3. SLAM contraint pour la localisation dans des environnements partiellement connus

    OpenAIRE

    Naudet, Sylvie; Gay-Bellile, Vincent; Bourgeois, Steve; Tamaazousti, Mohamed; Larnaout, Dorra; Dhome, Michel

    2014-01-01

    National audience Cet article porte sur la localisation temps réel d'une caméra mobile dans un environnement partiellement connu. Ces travaux reposent sur une solution de type SLAM monoculaire et traitent la problématique de dérive inhérente à ce type de méthode en proposant un nouvel ajustement de faisceaux, dit ajustement de faisceaux contraint. Ce dernier permet d'intégrer des contraintes géométriques apportées par le modèle partiellement connu de la scène. Nous montrons l'apport de cet...

  4. The application of nuclear localisation technologies in environmental biology

    International Nuclear Information System (INIS)

    Nuclear and related localisation technologies at ANSTO have been applied to a range biological matrices, in relation to specific environmental questions. Several of these applications are summarised, including the localization of lead and other elements in crocodile osteoderms and validation of bivalve shell micro-laminations as archival monitors of pollution signals. The co-location of Ca and its metabolic analogue Ra-226 led to further development of a theoretical model of bioaccumulation of alkaline-earth and other elements in the tissue of Australian freshwater bivalves under natural conditions, which were not appreciably altered by uranium mining in the region

  5. Spatially Adaptive Density Estimation by Localised Haar Projections

    CERN Document Server

    Gach, Florian; Spokoiny, Vladimir

    2011-01-01

    Given a random sample from some unknown density $f_0: \\mathbb R \\to [0, \\infty)$ we devise Haar wavelet estimators for $f_0$ with variable resolution levels constructed from localised test procedures (as in Lepski, Mammen, and Spokoiny (1997, Ann. Statist.)). We show that these estimators adapt to spatially heterogeneous smoothness of $f_0$, simultaneously for every point $x$ in a fixed interval, in sup-norm loss. The thresholding constants involved in the test procedures can be chosen in practice under the idealised assumption that the true density is locally constant in a neighborhood of the point $x$ of estimation, and an information theoretic justification of this practice is given.

  6. Suppressing proton decay in theories with localised fermions

    International Nuclear Information System (INIS)

    We calculate the contribution to the proton decay amplitude from Kaluza-Klein lepto-quarks in theories with extra dimensions, localised fermions and gauge fields which propagate in the bulk. Such models naturally occur within the context of M theory. In SU(5) models we show that carefully including all such modes gives a distinctive pattern of decays through various channels including a strong suppression of decays into neutrinos or right handed positrons. By contrast there is no such suppression for SO(10). (author)

  7. Active surveillance strategy for patients with localised prostate cancer

    DEFF Research Database (Denmark)

    Thomsen, Frederik Birkebæk

    2014-01-01

    BACKGROUND: Active surveillance - an initial observational strategy - offers a tailored management of patients with localised prostate cancer. The aim of the strategy is to appoint patients with potentially lethal prostate cancer to curatively intended treatment, while patients with slowly evolving...... criteria in the management of prostate cancer patients on active surveillance is emphasised....... measurements, repeated biopsies, and regular digital rectal examinations. The programme recommended change of management from active surveillance to curatively intended treatment based on PSA doubling time, deteriorating histopathology in repeated prostatic biopsies, and increased clinical tumour category...

  8. Localised wedge shaped defects of the retinal nerve fibre layer in glaucoma.

    OpenAIRE

    Jonas, J. B.; Schiro, D

    1994-01-01

    Glaucoma can be associated with a diffuse or localised loss of the retinal nerve fibre layer (RNFL). This study evaluated the wedge shaped localised RNFL defects. Red free wide angle RNFL photographs of 421 patients with glaucoma and 193 normal subjects were examined. Localised RNFL defects were described for one eye of the normal group and for 20% of the patients with glaucoma. They were usually located in the inferior temporal and superior temporal fundus regions. Within the glaucoma group,...

  9. Making Sense of Localisation in China - Voices from A German multinational in Shanghai

    OpenAIRE

    Siegrist, Katharina Cornelia

    2010-01-01

    In a globalising world economy the issue of localisation among foreign invested enterprises in China has been a hot topic throughout the last years. Not only in terms of sourcing and procurement, or more and more relocations of manufacturing or R&D to China localisation was discussed and supported by the Chinese government (e.g. subsidies for foreign firms investing in research laboratories in China), but also in terms of HR work and localisation of management positions. With huge numbers of ...

  10. Localisation and quantification of elements within seeds of Cd/Zn hyperaccumulator Thlaspi praecox by micro-PIXE

    Energy Technology Data Exchange (ETDEWEB)

    Vogel-Mikus, Katarina [Department of Biology, Biotechnical Faculty, University of Ljubljana, Vecna pot 111, SI-1000 Ljubljana (Slovenia); Pongrac, Paula [Department of Biology, Biotechnical Faculty, University of Ljubljana, Vecna pot 111, SI-1000 Ljubljana (Slovenia); Kump, Peter [Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Necemer, Marijan [Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Simcic, Jure [Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Pelicon, Primoz [Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Budnar, Milos [Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Povh, Bogdan [Max-Planck-Institut fuer Kernphysik, P.O. Box 103980, 69029 Heidelberg (Germany); Regvar, Marjana [Department of Biology, Biotechnical Faculty, University of Ljubljana, Vecna pot 111, SI-1000 Ljubljana (Slovenia)]. E-mail: marjana.regvar@bf.uni-lj.si

    2007-05-15

    Cd, Zn and Pb accumulation, spatial distribution within seeds and germinating seedlings, and seeds fitness of metal hyperaccumulating Thlaspi praecox were investigated in order to gain more knowledge on plant reproductive success at metal polluted sites. The seeds contained up to 1351 {mu}g g{sup -1} (dry weight) of Cd, 121 {mu}g g{sup -1} of Zn and 17 {mu}g g{sup -1} of Pb. Seed fitness was negatively influenced by seed Cd hyperaccumulation. Nevertheless, the viability of seeds was decreased by maximally 20%, indicating very efficient tolerance of the plant embryos to Cd. Localisation by micro-PIXE revealed preferential storage of most elements in the embryonic axis. Cd and Zn were preferentially localised in the epidermis of cotyledons. The restriction of seed Pb and Zn uptake and hyperaccumulation of Cd, accompanied by partitioning of Cd in the epidermal tissues of cotyledons, may enable the survival of T. praecox embryos and seedlings in Cd polluted environments. - Hyperaccumulation of Cd with partitioning in the epidermis of cotyledons was observed in T. praecox embryos.

  11. Interferometric Synthetic Aperture Microscopy (ISAM)

    Science.gov (United States)

    Adie, Steven G.; Shemonski, Nathan D.; Ralston, Tyler S.; Carney, P. Scott; Boppart, Stephen A.

    The trade-off between transverse resolution and depth-of-field, and the mitigation of optical aberrations, are long-standing problems in optical imaging. The deleterious impact of these problems on three-dimensional tomography increases with numerical aperture (NA), and so they represent a significant impediment for real-time cellular resolution tomography over the typical imaging depths achieved with OCT. With optical coherence microscopy (OCM), which utilizes higher-NA optics than OCT, the depth-of-field is severely reduced, and it has been postulated that aberrations play a major role in reducing the useful imaging depth in OCM. Even at lower transverse resolution, both these phenomena produce artifacts that degrade the imaging of fine tissue structures. Early approaches to the limited depth-of-field problem in time-domain OCT utilized dynamic focusing. In spectral-domain OCT, this focus-shifting approach to data acquisition leads to long acquisition times and large datasets. Adaptive optics (AO) has been utilized to correct optical aberrations, in particular for retinal OCT, but in addition to requiring elaborate and expensive setups, the real-time optimization requirements at the time of imaging, and the correction of spatially varying effects of aberrations throughout an imaged volume, remain as significant challenges. This chapter presents computed imaging solutions for the reconstruction of sample structure when imaging with ideal and aberrated Gaussian beams.

  12. Pattern Formation on Networks: from Localised Activity to Turing Patterns.

    Science.gov (United States)

    McCullen, Nick; Wagenknecht, Thomas

    2016-01-01

    Networks of interactions between competing species are used to model many complex systems, such as in genetics, evolutionary biology or sociology and knowledge of the patterns of activity they can exhibit is important for understanding their behaviour. The emergence of patterns on complex networks with reaction-diffusion dynamics is studied here, where node dynamics interact via diffusion via the network edges. Through the application of a generalisation of dynamical systems analysis this work reveals a fundamental connection between small-scale modes of activity on networks and localised pattern formation seen throughout science, such as solitons, breathers and localised buckling. The connection between solutions with a single and small numbers of activated nodes and the fully developed system-scale patterns are investigated computationally using numerical continuation methods. These techniques are also used to help reveal a much larger portion of of the full number of solutions that exist in the system at different parameter values. The importance of network structure is also highlighted, with a key role being played by nodes with a certain so-called optimal degree, on which the interaction between the reaction kinetics and the network structure organise the behaviour of the system. PMID:27273339

  13. Localising fast radio bursts and other transients using interferometric arrays

    CERN Document Server

    Obrocka, Monika; Wilkinson, Peter

    2015-01-01

    A new population of sources emitting fast and bright transient radio bursts has recently been identified. The observed large dispersion measure values of FRBs suggests an extragalactic origin and an accurate determination of their positions and distances will provide an unique opportunity to study the magneto-ionic properties of the IGM. So far, FRBs have all been found using large dishes equipped with multi-pixel arrays. While large single dishes are well-suited for the discovery of transient sources they are poor at providing accurate localisations. A 2D snapshot image of the sky, made with a correlation interferometer array, can provide an accurate localisation of many compact radio sources simultaneously. However, the required time resolution to detect FRBs and a desire to detect them in real time, makes this currently impractical. In a beamforming approach, where many narrow tied-array beams are produced, the advantages of single dishes and interferometers can be combined. We present a proof-of-concept a...

  14. Pattern Formation on Networks: from Localised Activity to Turing Patterns

    Science.gov (United States)

    McCullen, Nick; Wagenknecht, Thomas

    2016-06-01

    Networks of interactions between competing species are used to model many complex systems, such as in genetics, evolutionary biology or sociology and knowledge of the patterns of activity they can exhibit is important for understanding their behaviour. The emergence of patterns on complex networks with reaction-diffusion dynamics is studied here, where node dynamics interact via diffusion via the network edges. Through the application of a generalisation of dynamical systems analysis this work reveals a fundamental connection between small-scale modes of activity on networks and localised pattern formation seen throughout science, such as solitons, breathers and localised buckling. The connection between solutions with a single and small numbers of activated nodes and the fully developed system-scale patterns are investigated computationally using numerical continuation methods. These techniques are also used to help reveal a much larger portion of of the full number of solutions that exist in the system at different parameter values. The importance of network structure is also highlighted, with a key role being played by nodes with a certain so-called optimal degree, on which the interaction between the reaction kinetics and the network structure organise the behaviour of the system.

  15. Mechanistic insight into Type I restriction endonucleases.

    Science.gov (United States)

    Youell, James; Firman, Keith

    2012-01-01

    Restriction and modification are two opposing activities that are used to protect bacteria from cellular invasion by DNA (e.g. bacteriophage infection). Restriction activity involves cleavage of the DNA; while modification activity is the mechanism used to "mark" host DNA and involves DNA methylation. The study of Type I restriction enzymes has often been seen as an esoteric exercise and this reflects some of their more unusual properties - non-stoichiometric (non-catalytic) cleavage of the DNA substrate, random cleavage of DNA, a massive ATPase activity, and the ability to both cleave DNA and methylate DNA. Yet these enzymes have been found in many bacteria and are very efficient as a means of protecting bacteria against bacteriophage infection, indicating they are successful enzymes. In this review, we summarise recent work on the mechanisms of action, describe switching of function and review their mechanism of action. We also discuss structural rearrangements and cellular localisation, which provide powerful mechanisms for controlling the enzyme activity. Finally, we speculate as to their involvement in recombination and discuss their relationship to helicase enzymes. PMID:22652768

  16. Fast Parametric Beamformer for Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt; Tomov, Borislav Gueorguiev

    2008-01-01

    This paper describes the design and implementation of a real-time delay-and-sum synthetic aperture beamformer. The beamforming delays and apodization coefficients are described parametrically. The image is viewed as a set of independent lines that are defined in 3-D by their origin, direction, and...... implementation of the beamformer is optimized with respect to the architecture of a novel synthetic aperture real-time ultrasound scanner (SARUS), in which 4 channels are processed by the same set of field-programmable gate arrays (FPGA). In synthetic transmit aperture imaging, low-resolution images are formed...

  17. On the localisation of four-dimensional brane-world black holes: II. The general case

    Science.gov (United States)

    Kanti, P.; Pappas, N.; Pappas, T.

    2016-01-01

    We perform a comprehensive analysis of a number of scalar field theories in an attempt to find analytically five-dimensional, localised-on-the-brane, black-hole solutions. Extending a previous analysis, we assume a generalised Vaidya ansatz for the five-dimensional metric tensor that allows for a time-dependent, non-trivial profile of the mass function in terms of the bulk coordinate and a deviation from the over-restricting Schwarzschild-type solution on the brane. In order to support such a solution, we study a variety of theories including single or multiple scalar fields, with canonical or non-canonical kinetic terms, minimally or non-minimally coupled to gravity. We demonstrate that for such a metric ansatz and for a carefully chosen energy-momentum tensor which is non-isotropic in five dimensions, solutions that have the form of a Schwarzschild-(anti)de Sitter or Reissner-Nordstrom type of solution do emerge. However, the resulting profile of the mass function along the bulk coordinate, when allowed, is not the correct one for eliminating bulk singularities.

  18. First study of pathogen load and localisation of ovine footrot using fluorescence in situ hybridisation (FISH).

    Science.gov (United States)

    Witcomb, Luci A; Green, Laura E; Calvo-Bado, Leo A; Russell, Claire L; Smith, Edward M; Grogono-Thomas, Rose; Wellington, Elizabeth M H

    2015-04-17

    Analysis of bacterial populations in situ provides insights into pathogen population dynamics and potential reservoirs for disease. Here we report a culture-independent study of ovine footrot (FR); a debilitating bacterial disease that has significant economic impact on sheep farming worldwide. Disease begins as an interdigital dermatitis (ID), which may then progress to separation of the hoof horn from the underlying epidermis causing severe footrot (SFR). Dichelobacter nodosus is the causative agent of ovine FR, however, the role of Fusobacterium necrophorum and other bacteria present in the environment and on the feet of sheep is less clear. The objective of this study was to use fluorescence in situ hybridisation (FISH) to detect, localise and quantify D. nodosus, F. necrophorum and the domain Bacteria from interdigital skin biopsies of healthy, ID- and SFR-affected feet. D. nodosus and F. necrophorum populations were restricted primarily to the epidermis, but both were detected more frequently in feet with ID or SFR than in healthy feet. D. nodosus cell counts were significantly higher in feet with ID and SFR (p25742734

  19. Thermal Emission by a Subwavelength Aperture

    CERN Document Server

    Joulain, Karl; Carminati, Rémi

    2015-01-01

    We calculate, by means of fluctuational electrodynamics, the thermal emission of an aperture filled by vacuum or a material at temperature T. We show that thermal emission is very different whether the aperture size is large or small compared to the thermal wavelength. Subwavelength apertures filled with vacuum (subwavelength blackbody) have their thermal emission strongly decreased compared to classical blackbodies. A simple expression of their emissivity can be calculated and their total emittance scales as T 8 instead of T 4 for large apertures. Thermal emission of disk of materials with a size comparable to the wavelength is also discussed. It is shown in particular that emissivity of such a disk is increased when the material can support surface waves such as phonon polaritons.

  20. Beam Combination for Sparse Aperture Telescopes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal is for funding to continue development of an alternative beam combiner for Stellar Imager (SI), a 30-aperture, interferometric telescope chosen as one...

  1. Beam Combination for Sparse Aperture Telescopes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Stellar Imager, an ultraviolet, sparse-aperture telescope, was one of the fifteen Vision Missions chosen for a study completed last year. Stellar Imager will...

  2. Synthetic Aperture Radar Missions Study Report

    Science.gov (United States)

    Bard, S.

    2000-01-01

    This report reviews the history of the LightSAR project and summarizes actions the agency can undertake to support industry-led efforts to develop an operational synthetic aperture radar (SAR) capability in the United States.

  3. Fresnel aperture pre-stack depth migration

    OpenAIRE

    2005-01-01

    In this thesis, I present the results of a new approach to pre-stack Kirchoff depth migration using the Kirchoff algorithm and the Fresnel aperture features in order to improve the signal-to-noise ratio of the seismic data in depth imaging. Another advantage of this method is that it requires no additionnal measurments compared to the traditionnal PSDM. Indeed, the Fresnel apertures are picked interactively, in a way that is similar to velocity picking, and thereafter used during the migratio...

  4. New multiple aperture arrangements for speckle photography

    OpenAIRE

    Angel-Toro, Luciano; Tebaldi, Myrian; Trivi, Marcelo; Bolognini, Néstor

    2000-01-01

    Abstract. We propose a multiple exposure specklegram by using an optical system whose multiple aperture pupil changes between exposures. In particular, we analyze experimentally two arrangements and we show that it is possible to store the required information by employing a minimum number of registers if an adequate selection of the pupil is done. We study the effect of the decorrelation (among the stored speckle pattern) introduced by changing the multiple aperture pupil arrangements betwee...

  5. Synthetic Aperture Techniques for Sonar Systems

    OpenAIRE

    Silva, S&#;rgio Rui; Cunha, S&#;rgio; Matos, An&#;bal; Cruz, Nuno

    2009-01-01

    As demonstrated, synthetic aperture sonar is a technique that enables attainment of high quality, high resolution underwater images. Autonomous surface vehicles provides several advantages for synthetic aperture imagery. Not only it is possible to control the boat motion in this way, it is also possible to obtain navigation measurements with precisions in the order of the wavelength used in high resolution sonar systems. Furthermore unsupervised surveillance applications that combine the high...

  6. An autonomous boat based Synthetic Aperture Sonar

    OpenAIRE

    Sergio Rui Silva; Sergio Cunha; Anibal Matos; Nuno Cruz

    2007-01-01

    This paper describes a Synthetic Aperture Sonar (SAS) system being developed at the University of Porto to be used in a small autonomous boat for the survey of shallow water environments, such as rivers, deltas, estuaries and dams. Its purpose is to obtain high resolution echo reflectivity maps through synthetic aperture techniques, taking advantage of the high precision navigation system of the boat. In the future the production of bottom tomography maps is also considered through the use of...

  7. The importance of strain localisation in shear zones

    Science.gov (United States)

    Bons, Paul D.; Finch, Melanie; Gomez-Rivas, Enrique; Griera, Albert; Llorens, Maria-Gema; Steinbach, Florian; Weikusat, Ilka

    2016-04-01

    The occurrence of various types of shear bands (C, C', C'') in shear zones indicate that heterogeneity of strain is common in strongly deformed rocks. However, the importance of strain localisation is difficult to ascertain if suitable strain markers are lacking, which is usually the case. Numerical modelling with the finite-element method has so far not given much insight in the development of shear bands. We suggest that this is not only because the modelled strains are often not high enough, but also because this technique (that usually assumes isotropic material properties within elements) does not properly incorporate mineral deformation behaviour. We simulated high-strain, simple-shear deformation in single- and polyphase materials with a full-field theory (FFT) model coupled to the Elle modelling platform (www.elle.ws; Lebensohn 2001; Bons et al. 2008). The FFT-approach simulates visco-plastic deformation by dislocation glide, taking into account the different available slip systems and their critical resolved shear stresses in relations to the applied stresses. Griera et al. (2011; 2013) have shown that this approach is particularly well suited for strongly anisotropic minerals, such as mica and ice Ih (Llorens 2015). We modelled single- and polyphase composites of minerals with different anisotropies and strengths, roughly equivalent to minerals such as ice Ih, mica, quartz and feldspar. Single-phase polycrystalline aggregates show distinct heterogeneity of strain rate, especially in case of ice Ih, which is mechanically close to mica (see also Griera et al. 2015). Finite strain distributions are heterogeneous as well, but the patterns may differ from that of the strain rate distribution. Dynamic recrystallisation, however, usually masks any strain and strain rate localisation (Llorens 2015). In case of polyphase aggregates, equivalent to e.g. a granite, we observe extensive localisation in both syn- and antithetic shear bands. The antithetic shear bands

  8. Source localisation and dose verification for a novel brachytherapy unit

    Science.gov (United States)

    Metaxas, Marinos G.

    A recent development in the field of radiotherapy has been the introduction of the PRS Intrabeam system (Carl Zeiss Surgical GmbH, Oberkochen, Germany). This is essentially a portable, miniaturised, electron-driven photon generator that allows high intensity, soft-energy x-rays (50 kVp) to be delivered directly to the tumour site in a single fraction. The system has been used for the interstitial radiation treatment of both brain and breast tumours. At present, a standardised in-vivo dose verification technique is not available for the PRS treatments. The isotropical distribution of photons about the tip of the PRS probe inserted in the tissue can effectively be viewed as a point source of radiation buried in the body. This work has looked into ways of localising the PRS source utilising its own radiation field. Moreover, the response of monoenergetic sources, mimicking realistic brachytherapy sources, has also been investigated. The purpose of this project was to attempt to localise the source as well as derive important dosimetric information from the resulting image. A detection system comprised of a well-collimated Germanium detector (HPGe) has been devised in a rotate-translate Emission Computed Tomography (ECT) modality. The superior energy resolving ability of the detection system allowed for energy selective reconstruction to be carried out in the case of the monoenergetic source (241Am). Results showed that the monoenergetic source can be localised to within 1 mm and the continuous PRS x-ray source to within 3mm. For the PRS dose map derivation, Monte Carlo studies have been employed in order to extract information on the dosimetric aspect of the resulting image. The final goal of this work was therefore to formulate a direct mathematical relation (Transform Map) between the image created by the escaping photons and the dose map as predicted by the theoretical model. The formation therefore of the in-vivo PRS image could allow for a real-time monitoring

  9. A size-dependent constitutive modelling framework for localised failure analysis

    Science.gov (United States)

    Nguyen, Giang D.; Nguyen, Chi T.; Nguyen, Vinh P.; Bui, Ha H.; Shen, Luming

    2016-08-01

    Localised deformation of materials usually takes place in thin bands during the nonlinear phase of the deformation process. The orientation and size of these localisation bands are important properties characterising the post-localisation behaviour of the materials, and hence should be taken into account in constitutive modelling. In this research, a new approach is proposed for the integration of both size and orientation of a localisation band in the constitutive description beyond the onset of localisation. Since a length scale related to the size of the localisation band appears in the model description, its post-localisation response then scales with both the band size and the size of the volume element containing it. Therefore, size effects are intrinsically included and post-localisation behaviour is correctly captured, which helps ensure convergence of numerical solutions upon discretisation refinement in numerical analysis of boundary value problems. The concept together with implementation features of the framework and its performances at constitutive level and in the analysis of boundary value problems are presented in this paper.

  10. Localised structures in 2D Kolmogorov flow in large domains: Kinks, Snakes and 'Kolmotons'

    CERN Document Server

    Lucas, Dan

    2013-01-01

    Kolmogorov flow in two dimensions - the 2D Navier-Stokes equations with a sinusoidal body force - is considered over extended periodic domains to reveal localised spatiotemporal complexity. The flow response mimicks the forcing at small forcing amplitudes but beyond a critical value, the vorticity of the flow localises into `kink' structures. These kinks act as building blocks for multiple localised attractors which emerge as the forcing further intensifies. Most notable of these is a temporally-periodic state which consists of two intertwined and wiggling kinks (resembling a snake) bordered by two steady chaperoning kinks. As the forcing is increased, this `snake' experiences a period doubling cascade to spatially-localised chaos before becoming a localised chaotic repeller through a boundary crisis. Further interesting dynamics arise when these kink and snake structures are confronted with each other. The most eye-catching example of this is the `particle-like' interaction of propagating kinks (christened `...

  11. Simultaneous Mapping and Localisation for Small Military Unmanned Underwater Vehicle

    Directory of Open Access Journals (Sweden)

    Arom Hwang

    2012-07-01

    Full Text Available Paper proposes a simultaneous localisation and mapping (SLAM scheme which is applicable to small military unmanned underwater vehicles (UUVs. The SLAM is a process which enables concurrent estimation of the position of UUV and landmarks in the environment through which the vehicle is passing. An unscented Kalman filter (UKF is utilised to develop a SLAM suitable to nonlinear motion of UUV. A range sonar is used as a sensor to collect the relative position information of the landmark in the environment in which the UUV is navigating. The proposed SLAM scheme was validated through towing tank experiments about two degrees of freedom motion with UUV motion simulator and real range sonar system for small UUV. The results of these experiments showed that proposed SLAM scheme is capable of estimating the position of the UUV and the surrounding objects under real underwater environment.

  12. Survival after radical prostatectomy for clinically localised prostate cancer

    DEFF Research Database (Denmark)

    Røder, Martin Andreas; Brasso, Klaus; Christensen, Ib Jarle; Johansen, Jørgen; Langkilde, Niels-Christian; Hvarness, Helle; Carlsson, Steen; Jakobsen, Henrik; Borre, Michael; Iversen, Peter

    2014-01-01

    OBJECTIVES: To describe survival and cause of death in a nationwide cohort of Danish patients with prostate cancer undergoing radical prostatectomy (RP). To describe risk factors associated with prostate cancer mortality. PATIENTS AND METHODS: Observational study of 6489 men with localised prostate...... cancer treated with RP at six different hospitals in Denmark between 1995 and 2011. Survival was described using Kaplan-Meier estimates. Causes of death were obtained from the national registry and cross-checked with patient files. Cumulative incidence of death, any cause and prostate cancer......-specific, was described using Nelson-Aalen estimates. Risk for prostate cancer death was analysed in a Cox multivariate regression model using the covariates: age, cT-category, PSA level and biopsy Gleason score. RESULTS: The median follow-up was 4 years. During follow-up, 328 patients died, 109 (33.2%) from...

  13. A search for moment localisation in UMn2

    International Nuclear Information System (INIS)

    μSR, high resolution neutron powder diffraction and heat capacity have been used to study the spin fluctuation compound UMn2. The μSR spectra are dominated by muon depolarisation due to static fields from the Mn nuclei, features in the temperature dependence of the associated relaxation rate, σ, correlating well with the structural transitions observed at 210K. While a weak exponential relaxation (λ ∼ 0.01μs-1) indicates the presence of atomic spin fluctuations between 50K and 325K, μSR provides little evidence of moment localisation or long range magnetic order, although an anomalous increase in σ below 40K is observed. (orig.)

  14. Dark matter and localised fermions from spherical orbifolds?

    CERN Document Server

    Cacciapaglia, Giacomo; Deutschmann, Nicolas

    2016-01-01

    We study a class of six-dimensional models based on positive curvature surfaces (spherical 2-orbifolds) as extra-spaces. Using the Newman-Penrose formalism, we discuss the particle spectrum in this class of models. The fermion spectrum problem, which has been addressed with flux compactifications in the past, can be avoided using localised fermions. In this framework, we find that there are four types of geometry compatible with the existence of a stable dark matter candidate and we study the simplest case in detail. Using the complementarity between collider resonance searches and relic density constraints, we show that this class of models is under tension, unless the model lies in a funnel region characterised by a resonant Higgs s-channel in the dark matter annihilation.

  15. Law of Localised Fine Structure with application in mass spectrometry

    CERN Document Server

    Łącki, Mateusz Krzysztof

    2014-01-01

    This paper presents a brand new methodology to deal with isotopic fine structure calculations. By using the Poisson approximation in an entirely novel way, we introduce mathematical elegance into the discussion on the trade-off between resolution and tractability. Our considerations unify the concepts of fine-structure, equatransneutronic configurations, and aggregate isotopic structure in a natural and simple way. We show how to boost the theoretical resolution in a seemingly costless way by several orders of magnitude with respect to the already very efficient algorithms operating on isotopic aggregates. We also develop an effective new way to obtain the important peaks in the most disaggregated isotopic structure localised in a precise region in the mass domain.

  16. Selectional Restrictions in HPSG

    OpenAIRE

    Androutsopoulos, Ion; Dale, Robert

    2000-01-01

    Selectional restrictions are semantic sortal constraints imposed on the participants of linguistic constructions to capture contextually-dependent constraints on interpretation. Despite their limitations, selectional restrictions have proven very useful in natural language applications, where they have been used frequently in word sense disambiguation, syntactic disambiguation, and anaphora resolution. Given their practical value, we explore two methods to incorporate selectional restrictions...

  17. Radio-Frequency Interference Detection and Mitigation Algorithms for Synthetic Aperture Radiometers

    OpenAIRE

    Antonio Gutierrez; Jose Barbosa; Rita Castro; Jose Miguel Tarongi; Mercedes Vall Llossera; Adriano Camps; Jerome Gourrion

    2011-01-01

    The European Space Agency (ESA) successfully launched the Soil Moisture and Ocean Salinity (SMOS) mission in November 2, 2009. SMOS uses a new type of instrument, a synthetic aperture radiometer named MIRAS that provides full-polarimetric multi-angular L-band brightness temperatures, from which regular and global maps of Sea Surface Salinity (SSS) and Soil Moisture (SM) are generated. Although SMOS operates in a restricted band (1400–1427 MHz), radio-frequency interference (RFI) appears in SM...

  18. Double exposure specklegrams obtained by using scaled aperture pupils

    OpenAIRE

    Angel-Toro, Luciano; Tebaldi, Myrian; Trivi, Marcelo; Bolognini, N??stor

    2001-01-01

    In speckle photography the pupil aperture is usually not modified between exposures. In our work, the change of the pupil aperture scale between exposures is analyzed on the basis of double-exposed image speckle, before and after a diffuse in-plane displacement is done. The apertures have the same shape but its scale is modified between exposures. Note that the relative position of the aperture is maintained. In particular, we analyze a simple case that uses a circular aperture whose diameter...

  19. Aperture effects in squid jet propulsion.

    Science.gov (United States)

    Staaf, Danna J; Gilly, William F; Denny, Mark W

    2014-05-01

    Squid are the largest jet propellers in nature as adults, but as paralarvae they are some of the smallest, faced with the inherent inefficiency of jet propulsion at a low Reynolds number. In this study we describe the behavior and kinematics of locomotion in 1 mm paralarvae of Dosidicus gigas, the smallest squid yet studied. They swim with hop-and-sink behavior and can engage in fast jets by reducing the size of the mantle aperture during the contraction phase of a jetting cycle. We go on to explore the general effects of a variable mantle and funnel aperture in a theoretical model of jet propulsion scaled from the smallest (1 mm mantle length) to the largest (3 m) squid. Aperture reduction during mantle contraction increases propulsive efficiency at all squid sizes, although 1 mm squid still suffer from low efficiency (20%) because of a limited speed of contraction. Efficiency increases to a peak of 40% for 1 cm squid, then slowly declines. Squid larger than 6 cm must either reduce contraction speed or increase aperture size to maintain stress within maximal muscle tolerance. Ecological pressure to maintain maximum velocity may lead them to increase aperture size, which reduces efficiency. This effect might be ameliorated by nonaxial flow during the refill phase of the cycle. Our model's predictions highlight areas for future empirical work, and emphasize the existence of complex behavioral options for maximizing efficiency at both very small and large sizes. PMID:24501132

  20. Large-aperture subwavelength grating couplers.

    Science.gov (United States)

    Qi, Fan; Ma, Qingyan; Wang, Yufei; Zheng, Wanhua

    2016-04-10

    Subwavelength nanostructure grating couplers fabricated on silicon-on-insulator substrates are used to simplify the fabrication process while maintaining high coupling efficiency. The main obstacle for their application in photonic integrated circuits is the small aperture size of the nanostructure when TE polarization is involved, since they are difficult to achieve with 193 nm deep-ultraviolet lithography and cause problems in inductively coupled plasma etching. A larger lateral period has been used to increase the aperture size. Here, we propose that decreasing the effective index of the nanostructure can also enlarge the aperture size. We analyze the two methods in detail with a rectangle-hole nanostructure and 220 nm thick waveguide layer, aiming at TE polarization centered at 1560 nm. We find performance degenerations for large lateral periods, and this can be simply compensated by adjusting the width of the rectangle hole. The minimum linewidth of the nanostructure can reach 240 nm, while the coupling efficiency is just slightly decreased. The backreflections of a large-aperture grating increase but stay in the same order with ordinary ones, and we also show that this can be overcome by apodizing the grating structure. Finally, we experimentally demonstrate the designed large-aperture grating couplers and the coupling efficiencies are higher than 35%, and reach a rectangle-hole width. PMID:27139860

  1. SSC [Superconducting Super Collider] aperture workshop summary

    International Nuclear Information System (INIS)

    The SSC Aperture Workshop was held November 5-9, 1984 at Lawrence Berkeley Laboratory. The workshop focused on issues related to the selection of an optimum aperture for the SSC. Aperture is a critical issue at this early stage of design, because it strongly affects both the construction cost and the satisfactory commissioning and operation of the collider. The workshop had a double purpose: To design a course of action for determining the needed physical and dynamic aperture and commensurate magnetic field specifications of a high luminosity proton collider with a beam energy of 20 TeV, and to prepare a proposal for carrying out the recommended R ampersand D program in two steps -- a four-month intensive phase to provide knowledge essential for conceptual design and magnet selection, and a longer term effort to supply details and ultimately to support the construction, commissioning, and operation of the new collider. To accomplish these objectives, the participants met in the following working groups, each led by a coordinator, which are discussed in this paper: test lattices; aperture requirements; magnet errors; formats, data bases, networks and lattice codes; tracking codes; analytical screening; and experiments on existing machines

  2. Colonoscopy and computerised tomography scan are not sufficient to localise right sided colonic lesions accurately.

    LENUS (Irish Health Repository)

    Solon, Jacqueline Gemma

    2009-11-23

    : Aim: accurate pre-operative localisation of colonic lesions is critical especially in laparoscopic colectomy where tactile localisation is absent particularly in screen-detected tumours. The study aimed to evaluate the accuracy of colonoscopy and double-contrast computerised tomography (CT) to localise lesions treated by right hemicolectomy. Method: a retrospective chart review was performed of patients treated by right hemicolectomy under the colorectal service between July 2003 and October 2006. Pre-operative tumour location determined by CT scan and colonoscopy were compared with the intra-operative and histopathologic findings. Results: of 101 patients, 73 (73%) were for adenoma or cancer, with a final diagnosis of adenocarcinoma in 59 (59%). Pre-operative localisation was inaccurate in 29% of lesions using both CT and colonoscopy. In the transverse colon colonoscopy alone was only 37.5% accurate, increasing to 62.5% when information from the CT scan was added. Conclusion: pre-operative localisation of right-sided colon cancers using colonoscopy and CT scanning is unreliable in at least 29% of cases. Inaccurate localisation of transverse colon tumours risks inadequate lymphadenectomy with an adverse cancer outcome. Pre-operative abdominal CT scan improves accuracy but endoscopic tattoo localisation should be employed routinely especially in patients undergoing laparoscopic resection.

  3. Radioguided localisation of impalpable breast lesions using 99m-Technetium macroaggregated albumin: Lessons learnt during introduction of a new technique to guide preoperative localisation

    Energy Technology Data Exchange (ETDEWEB)

    Landman, Joanne [Department of Nuclear Medicine, Royal Perth Hospital, Perth, Western Australia (Australia); Kulawansa, Sagarika [Department of Diagnostic and Interventional Radiology, Royal Perth Hospital, Perth, Western Australia (Australia); McCarthy, Michael; Troedson, Russell [Department of Nuclear Medicine, Royal Perth Hospital, Perth, Western Australia (Australia); Phillips, Michael [Western Australian Institute for Medical Research, University of Western Australia, Perth, Western Australia (Australia); Tinning, Jill [The Multidisciplinary Breast Service, Royal Perth Hospital, Perth, Western Australia (Australia); Taylor, Donna, E-mail: Donna.Taylor@health.wa.gov.au [Department of Diagnostic and Interventional Radiology, Royal Perth Hospital, Perth, Western Australia (Australia); School of Surgery, University of Western Australia, Perth, Western Australia (Australia); Department of Nuclear Medicine, Royal Perth Hospital, Perth, Western Australia (Australia)

    2015-03-15

    Preoperative wire-guided localisation (WGL) of impalpable breast lesions is widely used but can be technically difficult. Risks include wire migration, inaccurate placement, and inadequate surgical margins. Research shows that radioguided occult lesion localisation (ROLL) is quicker, easier, and can improve surgical and cosmetic outcomes. An audited introduction of ROLL was conducted to validate the technique as a feasible alternative to WGL. Fifty patients with single impalpable lesions and biopsy proven malignancy or indeterminate histology underwent WGL followed by intralesional radiopharmaceutical injection of 99m-Technetium macroaggregated albumin. Postprocedural mammography was performed to demonstrate wire position, and scintigraphy to evaluate radiopharmaceutical migration. Lymphoscintigraphy and intraoperative sentinel node biopsy were performed if indicated, followed by lesion localisation and excision using a gamma probe. Specimen imaging was performed, with immediate reexcision for visibly inadequate margins. Accurate localisation was achieved in 86% of patients with ROLL compared to 72% with WGL. All lesions were successfully removed, with clear margins in 71.8% of malignant lesions. Reexcision and intraoperative sentinel node localisation rates were equivalent to preaudit figures for WGL. ROLL was easy to perform and problems were infrequent. Inaccurate radiopharmaceutical placement necessitating WGL occurred in four patients. Minor radiopharmaceutical migration was common, but precluded using ROLL in only two cases. ROLL is effective, simple, inexpensive, and easily learnt; however, preoperative confirmation of correct radiopharmaceutical placement using mammography and the gamma probe is important to help ensure successful lesion removal. Insertion of a backup hookwire is recommended during the initial introduction of ROLL.

  4. Radioguided localisation of impalpable breast lesions using 99m-Technetium macroaggregated albumin: Lessons learnt during introduction of a new technique to guide preoperative localisation

    International Nuclear Information System (INIS)

    Preoperative wire-guided localisation (WGL) of impalpable breast lesions is widely used but can be technically difficult. Risks include wire migration, inaccurate placement, and inadequate surgical margins. Research shows that radioguided occult lesion localisation (ROLL) is quicker, easier, and can improve surgical and cosmetic outcomes. An audited introduction of ROLL was conducted to validate the technique as a feasible alternative to WGL. Fifty patients with single impalpable lesions and biopsy proven malignancy or indeterminate histology underwent WGL followed by intralesional radiopharmaceutical injection of 99m-Technetium macroaggregated albumin. Postprocedural mammography was performed to demonstrate wire position, and scintigraphy to evaluate radiopharmaceutical migration. Lymphoscintigraphy and intraoperative sentinel node biopsy were performed if indicated, followed by lesion localisation and excision using a gamma probe. Specimen imaging was performed, with immediate reexcision for visibly inadequate margins. Accurate localisation was achieved in 86% of patients with ROLL compared to 72% with WGL. All lesions were successfully removed, with clear margins in 71.8% of malignant lesions. Reexcision and intraoperative sentinel node localisation rates were equivalent to preaudit figures for WGL. ROLL was easy to perform and problems were infrequent. Inaccurate radiopharmaceutical placement necessitating WGL occurred in four patients. Minor radiopharmaceutical migration was common, but precluded using ROLL in only two cases. ROLL is effective, simple, inexpensive, and easily learnt; however, preoperative confirmation of correct radiopharmaceutical placement using mammography and the gamma probe is important to help ensure successful lesion removal. Insertion of a backup hookwire is recommended during the initial introduction of ROLL

  5. Solar energy apparatus with apertured shield

    Science.gov (United States)

    Collings, Roger J. (Inventor); Bannon, David G. (Inventor)

    1989-01-01

    A protective apertured shield for use about an inlet to a solar apparatus which includesd a cavity receiver for absorbing concentrated solar energy. A rigid support truss assembly is fixed to the periphery of the inlet and projects radially inwardly therefrom to define a generally central aperture area through which solar radiation can pass into the cavity receiver. A non-structural, laminated blanket is spread over the rigid support truss in such a manner as to define an outer surface area and an inner surface area diverging radially outwardly from the central aperture area toward the periphery of the inlet. The outer surface area faces away from the inlet and the inner surface area faces toward the cavity receiver. The laminated blanket includes at least one layer of material, such as ceramic fiber fabric, having high infra-red emittance and low solar absorption properties, and another layer, such as metallic foil, of low infra-red emittance properties.

  6. Optimization of Synthetic Aperture Image Quality

    DEFF Research Database (Denmark)

    Moshavegh, Ramin; Jensen, Jonas; Villagómez Hoyos, Carlos Armando;

    2016-01-01

    Synthetic Aperture (SA) imaging produces high-quality images and velocity estimates of both slow and fast flow at high frame rates. However, grating lobe artifacts can appear both in transmission and reception. These affect the image quality and the frame rate. Therefore optimization of parameters...... F-number, number of emissions and the aperture size. They are considered to be the most contributing acquisition factors in the quality of the high resolution images in SA. Therefore, the performance of image quality is quantified in terms of full-width at half maximum (FWHM) and the cystic...... resolution (CTR). The results of the study showed that SA imaging with only 32 emissions and maximum sweep angle of 22 degrees yields a very good image quality compared with using 256 emissions and the full aperture size. Therefore the number of emissions and the maximum sweep angle in the SA can be...

  7. A machine-hearing system exploiting head movements for binaural sound localisation in reverberant conditions

    DEFF Research Database (Denmark)

    May, Tobias; Ma, Ning; Wierstorf, Hagen;

    2015-01-01

    investigated the influence of different head movement strategies on binaural sound localisation. A machine-hearing system that exploits a multi-step head rotation strategy for sound localisation was found to produce the best performance in simulated reverberant acoustic space. This paper also reports the......This paper is concerned with machine localisation of multiple active speech sources in reverberant environments using two (binaural) microphones. Such conditions typically present a problem for ‘classical’ binaural models. Inspired by the human ability to utilise head movements, the current study...

  8. Optimal localisation of next generation Biofuel production in Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Wetterlund, Elisabeth [Linkoeping Univ., Linkoeping (Sweden); Pettersson, Karin [Chalmers Univ. of Technology, Goeteborg (Sweden); Mossberg, Johanna [SP Technical Research Inst. of Sweden, Boraas (Sweden)] [and others

    2013-09-01

    With a high availability of lignocellulosic biomass and various types of cellulosic by-products, as well as a large number of industries, Sweden is a country of great interest for future large scale production of sustainable, next generation biofuels. This is most likely also a necessity as Sweden has the ambition to be independent of fossil fuels in the transport sector by the year 2030 and completely fossil free by 2050. In order to reach competitive biofuel production costs, plants with large production capacities are likely to be required. Feedstock intake capacities in the range of about 1-2 million tonnes per year, corresponding to a biomass feed of 300-600 MW, can be expected, which may lead to major logistical challenges. To enable expansion of biofuel production in such large plants, as well as provide for associated distribution requirements, it is clear that substantial infrastructure planning will be needed. The geographical location of the production plant facilities is therefore of crucial importance and must be strategic to minimise the transports of raw material as well as of final product. Competition for the available feedstock, from for example forest industries and CHP plants (combined heat and power) further complicates the localisation problem. Since the potential for an increased biomass utilisation is limited, high overall resource efficiency is of great importance. Integration of biofuel production processes in existing industries or in district heating systems may be beneficial from several aspects, such as opportunities for efficient heat integration, feedstock and equipment integration, as well as access to existing experience and know-how. This report describes the development of Be Where Sweden, a geographically explicit optimisation model for localisation of next generation biofuel production plants in Sweden. The main objective of developing such a model is to be able to assess production plant locations that are robust to varying

  9. Large aperture calorimeter for fusion laser measurements

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, J.G.; Smith, P.A.

    The authors designed and constructed a large aperture calorimeter intended for laser fusion measurements on beams up to 20 cm diameter. The laser beam is absorbed in a glass disc backed by a disc carry a resistance wire. Although it performs essentially as expected with a noise equivalent energy of 20 mJ and a maximum energy of about 100 J, difficulties in construction give a 17% variation of sensitivity across the aperture. To overcome this problem it would probably be necessary to adopt an integral construction with the resistance bridge formed from an etched film on the back of the absorbing glass.

  10. Synthetic aperture radar capabilities in development

    Energy Technology Data Exchange (ETDEWEB)

    Miller, M. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    The Imaging and Detection Program (IDP) within the Laser Program is currently developing an X-band Synthetic Aperture Radar (SAR) to support the Joint US/UK Radar Ocean Imaging Program. The radar system will be mounted in the program`s Airborne Experimental Test-Bed (AETB), where the initial mission is to image ocean surfaces and better understand the physics of low grazing angle backscatter. The Synthetic Aperture Radar presentation will discuss its overall functionality and a brief discussion on the AETB`s capabilities. Vital subsystems including radar, computer, navigation, antenna stabilization, and SAR focusing algorithms will be examined in more detail.

  11. Multi-antenna synthetic aperture radar

    CERN Document Server

    Wang, Wen-Qin

    2013-01-01

    Synthetic aperture radar (SAR) is a well-known remote sensing technique, but conventional single-antenna SAR is inherently limited by the minimum antenna area constraint. Although there are still technical issues to overcome, multi-antenna SAR offers many benefits, from improved system gain to increased degrees-of-freedom and system flexibility. Multi-Antenna Synthetic Aperture Radar explores the potential and challenges of using multi-antenna SAR in microwave remote sensing applications. These applications include high-resolution imaging, wide-swath remote sensing, ground moving target indica

  12. A Method for Synthetic Aperture Compounding

    DEFF Research Database (Denmark)

    Hansen, Jens Munk; Jensen, Jørgen Arendt

    2010-01-01

    An approach to perform ultrasound spatial compounding using synthetic aperture data is proposed. The approach allows compounding to be performed for any number of directions without reducing the frame rate or temporal resolution. It is demonstrated how the contrast is improved by compounding and...... obtained when using 5 images. Using the same RF data, a synthetic aperture image without compounding reveals a CNR of -0.36, -0.93, -1.23, and -1.61 dB for the four cysts, respectively....

  13. IMPROVED SYNTHETIC APERTURE SONAR MOTION COMPENSATION COMBINED DPCA WITH SUB-APERTURE IMAGE CORRELATION

    Institute of Scientific and Technical Information of China (English)

    Liu Wei; Zhang Chunhua; Liu Jiyuan

    2009-01-01

    Estimation precision of Displaced Phase Center Algorithm (DPCA) is affected by the number of displaced phase center pairs, the bandwidth of transmitting signal and many other factors. Detailed analysis is made on DPCA's estimation precision. Analysis results show that the directional vector estimation precision of DPCA is low, which will produce accumulating errors when phase centers' track is estimated. Because of this reason, DPCA suffers from accumulating errors seriously. To overcome this problem, a method combining DPCA with Sub Aperture Image Correlation (SAIC) is presented. Large synthetic aperture is divided into sub-apertures. Micro errors in sub-aperture are estimated by DPCA and compensated to raw echo data. Bulk errors between sub-apertures are estimated by SAIC and compensated directly to sub-aperture images. After that, sub-aperture images are directly used to generate ultimate SAS image. The method is applied to the lake-trial dataset of a 20 kHz SAS prototype system. Results show the method can successfully remove the accumulating error and produce a better SAS image.

  14. Simultaneous Mapping and Localisation for Small Military Unmanned Underwater Vehicle

    Directory of Open Access Journals (Sweden)

    Arom Hwang

    2012-07-01

    Full Text Available Paper proposes a simultaneous localisation and mapping (SLAM scheme which is applicable to small military unmanned underwater vehicles (UUVs. The SLAM is a process which enables concurrent estimation of the position of UUV and landmarks in the environment through which the vehicle is passing. An unscented Kalman filter (UKF is utilised to develop a SLAM suitable to nonlinear motion of UUV. A range sonar is used as a sensor to collect the relative position information of the landmark in the environment in which the UUV is navigating. The proposed SLAM scheme was validated through towing tank experiments about two degrees of freedom motion with UUV motion simulator and real range sonar system for small UUV. The results of these experiments showed that proposed SLAM scheme is capable of estimating the position of the UUV and the surrounding objects under real underwater environment.Defence Science Journal, 2012, 62(4, pp.223-227, DOI:http://dx.doi.org/10.14429/dsj.62.1002

  15. Preferred water flow and localised recharge in a variable regolith

    Science.gov (United States)

    Johnston, Colin D.

    1987-10-01

    The mechanisms of water flow and recharge to groundwater were investigated in a deep clayey regolith in southwest Western Australia. A 700 m 2 area was intensively studied for a period of two years. Vertical distributions of natural chloride in thirteen profiles up to 31 m deep were used to estimate the distribution of vertical soil-water flux density in the 16 m unsaturated zone and rates of recharge to groundwater. Groundwater dynamics were monitored using ten single and four multilevel piezometers. The regolith showed marked heterogeneity over horizontal and vertical distances of only a few metres. This resulted in complex patterns of water and solute movement through the profiles. Over most of the experimental area, vertical water flux density below 5 m in the unsaturated zone was from 2.2 to 7.2 mm yr -1. However, within a relatively small portion of the site, vertical soil-water flux density was 50-100 mm yr -1 throughout the unsaturated zone. This flux more closely matched the apparent rate of recharge to groundwater. The area of preferred flow is apparently due to a discontinuity within the regolith. A groundwater mound was seen to develop below the localised recharge area within 12-14 h of intense rainstorms, and then dissipated over a period of 2-4 days.

  16. Embedded discontinuous Galerkin transport schemes with localised limiters

    Science.gov (United States)

    Cotter, C. J.; Kuzmin, D.

    2016-04-01

    Motivated by finite element spaces used for representation of temperature in the compatible finite element approach for numerical weather prediction, we introduce locally bounded transport schemes for (partially-)continuous finite element spaces. The underlying high-order transport scheme is constructed by injecting the partially-continuous field into an embedding discontinuous finite element space, applying a stable upwind discontinuous Galerkin (DG) scheme, and projecting back into the partially-continuous space; we call this an embedded DG transport scheme. We prove that this scheme is stable in L2 provided that the underlying upwind DG scheme is. We then provide a framework for applying limiters for embedded DG transport schemes. Standard DG limiters are applied during the underlying DG scheme. We introduce a new localised form of element-based flux-correction which we apply to limiting the projection back into the partially-continuous space, so that the whole transport scheme is bounded. We provide details in the specific case of tensor-product finite element spaces on wedge elements that are discontinuous P1/Q1 in the horizontal and continuous P2 in the vertical. The framework is illustrated with numerical tests.

  17. Major lower intestinal haemorrhage: angiographic localisation and current management

    International Nuclear Information System (INIS)

    Thirty-four patients with major lower intestinal bleeding underwent emergency selective mesenteric angiography during a 6-year period. Angiography identified a bleeding site in 16 patients (47%). Diverticulosis, found in 22 patients (65%), and angiodysplasia, found in 4 (12%), were the most common causes of major colonic bleeding and originated more frequently from the right colon. Eight patients (24%) bled from less common sources. Radiological control of bleeding was unreliable with a significant complication rate. Fourteen of 16 patients with positive angiograms and 6 of 18 patients with negative angiograms required surgery for persistent major bleeding. Angiographic localisation of colonic bleeding allowed limited resection in 9 of 11 patients with control of haemorrhage in 8 (89%). Fourteen of 34 patients were managed non-operatively; of these 2 had minor recurrent bleeding. The overall mortality rate was 29%, the operative mortality rate 40% and the non-operative mortality rate 14%. A rational diagnostic approach is presented, emphasising the role of selective mesenteric angiography in the management and surgical strategy of major lower intestinal bleeding

  18. A method for accurate localisation of EBSD pattern centres

    Energy Technology Data Exchange (ETDEWEB)

    Maurice, Claire, E-mail: maurice@emse.fr [SMS Centre, UMR CNRS 5146, Ecole des Mines de Saint-Etienne, 158 cours Fauriel, 42023 Saint-Etienne, Cedex 2 (France); Dzieciol, Krzysztof, E-mail: dzieciol@emse.fr [SMS Centre, UMR CNRS 5146, Ecole des Mines de Saint-Etienne, 158 cours Fauriel, 42023 Saint-Etienne, Cedex 2 (France); Fortunier, Roland, E-mail: fortunier@emse.fr [SMS Centre, UMR CNRS 5146, Ecole des Mines de Saint-Etienne, 158 cours Fauriel, 42023 Saint-Etienne, Cedex 2 (France)

    2011-01-15

    The moving screen technique for pattern centre localisation is revisited. A cross-correlation based iterative procedure is developed to find both the zoom factor and the zoom centre (which is also the pattern centre) between two EBSD diffraction patterns acquired at two camera positions. The procedure involves two steps: first, a rough estimate of the pattern centre position and zoom factor (the ratio of the two detector distances) is obtained by cross-correlating the entire images. Then, based on this first estimate, cross-correlation of smaller regions of interest (ROIs) gives the displacement field which is interpreted as a zoom factor misfit coupled with a zoom centre position misfit. These misfits are iteratively decreased until the displacement field is reduced to the noise level. The procedure is first applied to simulated patterns and it is shown that the iterative procedure converges very rapidly to the exact solution with an accuracy better than 1/100th of pixel. The potential of this technique for experimental patterns is discussed and recommendations for new EBSD detectors are proposed. -- Research Highlights: {yields}Numerical and experimental study of measuring the pattern centre of EBSD patterns. {yields}Advanced moving screen technique coupled with sub-pixel cross-correlation. {yields}In theory, using simulated patterns, the precision is of the order of 1/100th pixel. {yields}In practice, the precision is drastically reduced due to camera imperfections. {yields}Methods of improving camera design for high resolution EBSD are outlined.

  19. Ignalina accident localisation system response to maximum design basis accident

    International Nuclear Information System (INIS)

    In this paper the study of the accident localisation system (ALS) of the Ignalina nuclear power plant (NPP) with RBMK-1500 reactors (large-power channel-type water-cooled graphite-moderated reactor) with regard to a maximum design basis accident (MDBA) is presented. The MDBA for Ignalina NPP constitutes a guillotine rupture of the maximum diameter pipe. The thermal-hydraulic and structural analyses were performed using the RELAP5, CONTAIN and ALGOR codes. The coolant mass and energy discharge source terms to the accident compartment were established using the RELAP5 code. This was then used as a source term for the long-term accident thermal-hydraulic analysis of ALS compartments employing the CONTAIN code. Results obtained by the CONTAIN calculations establish a basis for the structural analysis. A finite-element method has been used for ALS structural analysis using the ALGOR code, the results of which show that the structures of the ALS would not be breached by the pressure attained in the event of an MDBA. (author)

  20. Localised excitation of a single photon source by a nanowaveguide

    Science.gov (United States)

    Geng, Wei; Manceau, Mathieu; Rahbany, Nancy; Sallet, Vincent; de Vittorio, Massimo; Carbone, Luigi; Glorieux, Quentin; Bramati, Alberto; Couteau, Christophe

    2016-01-01

    Nowadays, integrated photonics is a key technology in quantum information processing (QIP) but achieving all-optical buses for quantum networks with efficient integration of single photon emitters remains a challenge. Photonic crystals and cavities are good candidates but do not tackle how to effectively address a nanoscale emitter. Using a nanowire nanowaveguide, we realise an hybrid nanodevice which locally excites a single photon source (SPS). The nanowire acts as a passive or active sub-wavelength waveguide to excite the quantum emitter. Our results show that localised excitation of a SPS is possible and is compared with free-space excitation. Our proof of principle experiment presents an absolute addressing efficiency ηa ~ 10-4 only ~50% lower than the one using free-space optics. This important step demonstrates that sufficient guided light in a nanowaveguide made of a semiconductor nanowire is achievable to excite a single photon source. We accomplish a hybrid system offering great potentials for electrically driven SPSs and efficient single photon collection and detection, opening the way for optimum absorption/emission of nanoscale emitters. We also discuss how to improve the addressing efficiency of a dipolar nanoscale emitter with our system.

  1. Parametric Beamformer for Synthetic Aperture Ultrasound Imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Tomov, Borislav Gueorguiev; Jensen, Jørgen Arendt

    2006-01-01

    In this paper a parametric beamformer, which can handle all imaging modalities including synthetic aperture imaging, is presented. The image lines and apodization coefficients are specified parametrically, and the lines can have arbitrary orientation and starting point in 3D coordinates. The beam...

  2. Vowel Aperture and Syllable Segmentation in French

    Science.gov (United States)

    Goslin, Jeremy; Frauenfelder, Ulrich H.

    2008-01-01

    The theories of Pulgram (1970) suggest that if the vowel of a French syllable is open then it will induce syllable segmentation responses that result in the syllable being closed, and vice versa. After the empirical verification that our target French-speaking population was capable of distinguishing between mid-vowel aperture, we examined the…

  3. Perceiving Affordances for Fitting through Apertures

    Science.gov (United States)

    Ishak, Shaziela; Adolph, Karen E.; Lin, Grace C.

    2008-01-01

    Affordances--possibilities for action--are constrained by the match between actors and their environments. For motor decisions to be adaptive, affordances must be detected accurately. Three experiments examined the correspondence between motor decisions and affordances as participants reached through apertures of varying size. A psychophysical…

  4. Synthetic Aperture Beamformation using the GPU

    DEFF Research Database (Denmark)

    Hansen, Jens Munk; Schaa, Dana; Jensen, Jørgen Arendt

    2011-01-01

    A synthetic aperture ultrasound beamformer is implemented for a GPU using the OpenCL framework. The implementation supports beamformation of either RF signals or complex baseband signals. Transmit and receive apodization can be either parametric or dynamic using a fixed F-number, a reference, and a...

  5. Diffraction contrast imaging using virtual apertures

    International Nuclear Information System (INIS)

    Two methods on how to obtain the full diffraction information from a sample region and the associated reconstruction of images or diffraction patterns using virtual apertures are demonstrated. In a STEM-based approach, diffraction patterns are recorded for each beam position using a small probe convergence angle. Similarly, a tilt series of TEM dark-field images is acquired. The resulting datasets allow the reconstruction of either electron diffraction patterns, or bright-, dark- or annular dark-field images using virtual apertures. The experimental procedures of both methods are presented in the paper and are applied to a precipitation strengthened and creep deformed ferritic alloy with a complex microstructure. The reconstructed virtual images are compared with conventional TEM images. The major advantage is that arbitrarily shaped virtual apertures generated with image processing software can be designed without facing any physical limitations. In addition, any virtual detector that is specifically designed according to the underlying crystal structure can be created to optimize image contrast. - Highlights: • A dataset containing all structural information of a given position is recorded. • The dataset allows reconstruction of virtual diffraction patterns or images. • Specific virtual apertures are designed to image precipitates in a complex alloy. • Virtual diffraction patterns from arbitrarily small regions can be established. • Using STEM diffraction to record the dataset is more efficient than TEM dark-field

  6. Dynamic metamaterial aperture for microwave imaging

    Science.gov (United States)

    Sleasman, Timothy; F. Imani, Mohammadreza; Gollub, Jonah N.; Smith, David R.

    2015-11-01

    We present a dynamic metamaterial aperture for use in computational imaging schemes at microwave frequencies. The aperture consists of an array of complementary, resonant metamaterial elements patterned into the upper conductor of a microstrip line. Each metamaterial element contains two diodes connected to an external control circuit such that the resonance of the metamaterial element can be damped by application of a bias voltage. Through applying different voltages to the control circuit, select subsets of the elements can be switched on to create unique radiation patterns that illuminate the scene. Spatial information of an imaging domain can thus be encoded onto this set of radiation patterns, or measurements, which can be processed to reconstruct the targets in the scene using compressive sensing algorithms. We discuss the design and operation of a metamaterial imaging system and demonstrate reconstructed images with a 10:1 compression ratio. Dynamic metamaterial apertures can potentially be of benefit in microwave or millimeter wave systems such as those used in security screening and through-wall imaging. In addition, feature-specific or adaptive imaging can be facilitated through the use of the dynamic aperture.

  7. Parametric Transverse Patterns in Broad Aperture Lasers

    DEFF Research Database (Denmark)

    Grigorieva, E.V.; Kashchenko, S.A.; Mosekilde, Erik

    1998-01-01

    Parametrically generated optical patterns are investigated for finite and large-scale transverse aperture lasers. Standing and rotating patterns as well as periodic and chaotic pattern alternations are described in the framework of the amplitude equation formalism. Sensitive dependence on the...... geometrical size of the system is demonstrated even in the case of large-scale systems....

  8. Dynamic metamaterial aperture for microwave imaging

    Energy Technology Data Exchange (ETDEWEB)

    Sleasman, Timothy; Imani, Mohammadreza F.; Gollub, Jonah N.; Smith, David R. [Center for Metamaterials and Integrated Plasmonics, Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina, 27708 (United States)

    2015-11-16

    We present a dynamic metamaterial aperture for use in computational imaging schemes at microwave frequencies. The aperture consists of an array of complementary, resonant metamaterial elements patterned into the upper conductor of a microstrip line. Each metamaterial element contains two diodes connected to an external control circuit such that the resonance of the metamaterial element can be damped by application of a bias voltage. Through applying different voltages to the control circuit, select subsets of the elements can be switched on to create unique radiation patterns that illuminate the scene. Spatial information of an imaging domain can thus be encoded onto this set of radiation patterns, or measurements, which can be processed to reconstruct the targets in the scene using compressive sensing algorithms. We discuss the design and operation of a metamaterial imaging system and demonstrate reconstructed images with a 10:1 compression ratio. Dynamic metamaterial apertures can potentially be of benefit in microwave or millimeter wave systems such as those used in security screening and through-wall imaging. In addition, feature-specific or adaptive imaging can be facilitated through the use of the dynamic aperture.

  9. Analytic inversion in synthetic aperture radar.

    OpenAIRE

    Rothaus, O. S.

    1994-01-01

    A method of processing synthetic aperture radar signals that avoids some of the approximations currently in use that appear to be responsible for severe phase distortions is described. As a practical matter, this method requires N3 numerical operations, as opposed to the N2 ln N currently the case, but N3 is now easily managed, for N in the range of interest.

  10. Experiences on synthetic aperture focussing technique (SAFT)

    International Nuclear Information System (INIS)

    Imaging based on the synthetic aperture focussing technique (SAFT) improves the reliability of sizing and characterisation of structural discontinuities found in non-destructive testing of nuclear components. One of the main advantages of this technique is an improvement of signal-to-noise-ratio. The advantages are discussed in terms of practical applications and theory. (orig.)

  11. Compound imaging using Synthetic Aperture Sequential Beamformation

    DEFF Research Database (Denmark)

    Jensen, Casper Bo; Jensen, Jonas; Hemmsen, Martin Christian;

    2011-01-01

    Synthetic Aperture Sequential Beamforming (SASB) is a technique with low complexity and the ability to yield a more uniform lateral resolution with range. However, the presence of speckle artifacts in ultrasound images degrades the contrast. In conventional imaging speckle is reduced by using...

  12. Interferometric Synthetic Aperture Microwave Radiometers : an Overview

    Science.gov (United States)

    Colliander, Andreas; McKague, Darren

    2011-01-01

    This paper describes 1) the progress of the work of the IEEE Geoscience and Remote Sensing Society (GRSS) Instrumentation and Future Technologies Technical Committee (IFT-TC) Microwave Radiometer Working Group and 2) an overview of the development of interferometric synthetic aperture microwave radiometers as an introduction to a dedicated session.

  13. Synthetic Aperture Imaging in Medical Ultrasound

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Gammelmark, Kim; Pedersen, Morten;

    2004-01-01

    Synthetic Aperture (SA) ultrasound imaging is a relatively new and unexploited imaging technique. The images are perfectly focused both in transmit and receive, and have a better resolution and higher dynamic range than conventional ultrasound images. The blood flow can be estimated from SA images...

  14. Localisation and Acquisition of Knowledge in Software Developing Organisations in the Light of Empirical Research

    OpenAIRE

    Chrabański, Karol

    2013-01-01

    The purpose of the paper is to present the organisation and results of the empirical research facilitating the localisation and acquisition of knowledge in software developing organisations which have designed, documented, implemented and maintain quality management systems.The author's interest is focused on presenting a project of empirical research aimed at the localisation and acquisition of knowledge in software developing organisations.The paper contains an assessment of the usability o...

  15. Computer modelling of response of the Modelo-2 gamma probe used in intraoperative localisation of tumors

    International Nuclear Information System (INIS)

    During the last decade hand-held gamma probes have been introduced into both tumor localisation and surgery. The technique, labelled RIGA (radioimmuno-guided endoscopy), proved to be of help in various stages of the patient treatment preoperational (localisation, as accurate, as possible of even small-size tumor targets), intraoperational (an on-line assessment of the efficiency of the radical surgery) and postoperational, identification of possible local recurrence and metastases

  16. In planta localisation patterns of MADS domain proteins during floral development in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Kaufmann Kerstin

    2009-01-01

    Full Text Available Abstract Background MADS domain transcription factors play important roles in various developmental processes in flowering plants. Members of this family play a prominent role in the transition to flowering and the specification of floral organ identity. Several studies reported mRNA expression patterns of the genes encoding these MADS domain proteins, however, these studies do not provide the necessary information on the temporal and spatial localisation of the proteins. We have made GREEN FLUORESCENT PROTEIN (GFP translational fusions with the four MADS domain proteins SEPALLATA3, AGAMOUS, FRUITFULL and APETALA1 from the model plant Arabidopsis thaliana and analysed the protein localisation patterns in living plant tissues by confocal laser scanning microscopy (CLSM. Results We unravelled the protein localisation patterns of the four MADS domain proteins at a cellular and subcellular level in inflorescence and floral meristems, during development of the early flower bud stages, and during further differentiation of the floral organs. The protein localisation patterns revealed a few deviations from known mRNA expression patterns, suggesting a non-cell autonomous action of these factors or alternative control mechanisms. In addition, we observed a change in the subcellular localisation of SEPALLATA3 from a predominantly nuclear localisation to a more cytoplasmic localisation, occurring specifically during petal and stamen development. Furthermore, we show that the down-regulation of the homeodomain transcription factor WUSCHEL in ovular tissues is preceded by the occurrence of both AGAMOUS and SEPALLATA3 proteins, supporting the hypothesis that both proteins together suppress WUSCHEL expression in the ovule. Conclusion This approach provides a highly detailed in situ map of MADS domain protein presence during early and later stages of floral development. The subcellular localisation of the transcription factors in the cytoplasm, as observed at

  17. Scalable Software-Defect Localisation by Hierarchical Mining of Dynamic Call Graphs

    OpenAIRE

    Eichinger, Frank; Oßner, Christopher; Böhm, Klemens

    2011-01-01

    The localisation of defects in computer programmes is essential in software engineering and is important in domain-specific data mining. Existing techniques which build on call-graph mining localise defects well, but do not scale for large software projects. This paper presents a hierarchical approach with good scalability characteristics. It makes use of novel call-graph representations, frequent subgraph mining and feature selection. It first analyses call graphs of a coarse granularity, be...

  18. Real-time Dense Simultaneous Localisation and Mapping over Large Scale Environments

    OpenAIRE

    Whelan, Thomas J.

    2014-01-01

    The ability for a robot to create a map of an unknown environment and localise within that map is of critical importance in intelligent autonomous operation. This problem is referred to as Simultaneous Localisation and Mapping (or SLAM) and has been one of the major focusses of robotics research over the past 25 years. Although the initial focus was on 2D laser scan SLAM, more recently full 3D SLAM has become the dominant paradigm. The recent expansion in popularity of fu...

  19. Non-Gaussian probabilistic MEG source localisation based on kernel density estimation ☆

    OpenAIRE

    Mohseni, Hamid R.; Kringelbach, Morten L.; Woolrich, Mark W; Baker, Adam; Aziz, Tipu Z; Probert-Smith, Penny

    2014-01-01

    There is strong evidence to suggest that data recorded from magnetoencephalography (MEG) follows a non-Gaussian distribution. However, existing standard methods for source localisation model the data using only second order statistics, and therefore use the inherent assumption of a Gaussian distribution. In this paper, we present a new general method for non-Gaussian source estimation of stationary signals for localising brain activity from MEG data. By providing a Bayesian formulation for ME...

  20. Dual-sensor fusion for seamless indoor user localisation and tracking

    OpenAIRE

    Redzic, Milan

    2013-01-01

    Indoor localisation based on ubiquitous WLAN has exhibited the capability of being a cheap and relatively precise technology and has been verified by many successful examples. Its performance is subject to change due to multipath propagation and changes in the environment (people, building layouts, antenna characteristics etc.) which cannot be easily eliminated. This thesis addresses the automatic localisation of indoor user and proposes solutions for both positioning and seamlessly tracking ...

  1. Intelligent UAV-Assisted Localisation to Conserve Battery Energy in Military Sensor Networks

    Directory of Open Access Journals (Sweden)

    P.Shunmuga Perumal

    2014-11-01

    Full Text Available Wireless sensor networks (WSNs are extensively used in military applications for border area monitoring, battle-field surveillance, tracking enemy troops, where the sensor nodes run on battery power. Localisation of sensor nodes is extremely important to identify the location of event in military applications for further actions. Existing localisation algorithms consume more energy by heavy computation and communication overheads. The objective of the proposed research is to increase the lifetime of the military sensor networks by reducing the power consumption in each sensor node during localisation. For the state-of-the-art, we propose a novel intelligent unmanned aerial vehicle anchor node (IUAN with an intelligent arc selection (IAS-based centralised localisation algorithm, which removes computation cost and reduces communication cost at every sensor node. The IUAN collects the signal strength, distance data from sensor nodes and the central control station (CCS computes the position of sensor nodes using IAS algorithm. Our approach significantly removes computation cost and reduces communication cost at each sensor node during localisation, thereby radically extends the lifetime and localisation coverage of the military sensor networks.Science Journal, Vol. 64, No. 6, November 2014, pp.557-563, DOI:http://dx.doi.org/10.14429/dsj.64.5295

  2. Indoor Localisation Using a Context-Aware Dynamic Position Tracking Model

    Directory of Open Access Journals (Sweden)

    Montserrat Ros

    2012-01-01

    Full Text Available Indoor wireless localisation is a widely sought feature for use in logistics, health, and social networking applications. Low-powered localisation will become important for the next generation of pervasive media applications that operate on mobile platforms. We present an inexpensive and robust context-aware tracking system that can track the position of users in an indoor environment, using a wireless smart meter network. Our context-aware tracking system combines wireless trilateration with a dynamic position tracking model and a probability density map to estimate indoor positions. The localisation network consisted of power meter nodes placed at known positions in a building. The power meter nodes are tracked by mobile nodes which are carried by users to localise their position. We conducted an extensive trial of the context-aware tracking system and performed a comparison analysis with existing localisation techniques. The context-aware tracking system was able to localise a person's indoor position with an average error of 1.21 m.

  3. localisation et dys-localisation dans le foncier contemporain Delocalization and dyslocalization in land today

    Directory of Open Access Journals (Sweden)

    Gérard Chouquer

    2011-10-01

    Full Text Available Dans cet article, l’auteur étudie un aspect des changements majeurs qui affectent le foncier et, notamment, les acquisitions massives de terre, tels l'effet de délocalisation du rapport à la terre et l'éviction de fait des habitants du territoire qu'ils occupent et travaillent. On voit se multiplier les projets dans lesquels la terre fait l'objet d'une contractualisation dont les habitants sont exclus. L'article analyse d'abord le projet de Varun International à Madagascar, abandonné depuis dans le sillage de l'affaire Daewoo et de la chute du gouvernement de M. Ravalomanana. Le contrat envisagé entre Varun International et le gouvernement malgache était un projet d’agriculture contractuelle (contract farming, qui concernait 465 000 hectares et la création de treize périmètres irrigués permettant de produire 2,8 millions de tonnes de riz paddy et 400 000 tonnes de maïs dès la 4e année. Or, ce projet est révélateur pour deux raisons. La première est qu'il organisait l'irresponsabilité sociale de l'entreprise par la multiplication de sociétés-écrans chargées de la libérer des relations avec la population. La seconde est qu'il comportait des clauses économiques iniques, qui conduisaient Varun à contrôler 91 % de la production, et qui aurait conduit les agriculteurs malgaches les plus pauvres à devoir acheter du riz pour leur propre nourriture. Ce projet montre comment on aurait pu aboutir à une délocalisation qui est, en réalité, une dys-localisation, c'est-à-dire un dysfonctionnement du rapport normal au lieu. Ce projet organisait les conditions d'une appropriation de la terre et d'un transfert de production dans un pays qui, par ailleurs, dépend du programme d'aide alimentaire mondial. Les conditions du contrat conduisaient à multiplier les schémas triangulaires, par la création d'intermédiaires censés libérer l'entreprise principale de ses devoirs vis-à-vis des hommes et du sol. Comparant ce

  4. Cavity-excited Huygens' metasurface antennas: near-unity aperture efficiency from arbitrarily-large apertures

    CERN Document Server

    Epstein, Ariel; Eleftheriades, George V

    2015-01-01

    One of the long-standing problems in antenna engineering is the realization of highly-directive beams using low-profile devices. In this paper we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source cavity excitation is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectrum typical to standard partially-reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern. As shown, a single semianalytical formalism can be followed to achieve control of a variety of radiation features, such as the d...

  5. Modeling AXAF Obstructions with the Generalized Aperture Program.

    Science.gov (United States)

    Nguyen, D.; Gaetz, T.; Jerius, D.; Stern, I.

    The generalized aperture program is designed to simulate the effects on the incident photon stream of physical obstructions, such as thermal baffles and pre- and post-collimators. It can handle a wide variety of aperture shapes, and has provisions to allow alterations of the photons by the apertures. The philosophy behind the aperture program is that a geometrically complicated aperture may be modeled by a combination of geometrically simpler apertures. This is done by incorporating a language, lua, to lay out the apertures. User provided call-back functions enable the modeling of the interactions of the incident photon with the apertures. This approach allows for maximum flexibility, since the geometry and interactions of obstructions can be specified by the user at run time.

  6. Localised uptake and extraction of calcium45 in dinoflagellate nuclei

    International Nuclear Information System (INIS)

    The uptake of Ca45 into cells of the dinoflagellate Glenodinium foliaceum was investigated using insoluble compound light microscope autoradiography. The distribution of silver grains showed marked localisation to the dinocaryotic nucleus, with a random scatter of grains over the surrounding protoplasm (cytoplasm and supernumerary nucleus). Correction of grain counts for lateral sensitisation from the dinocaryotic nucleus indicated an isotope concentration 16 32 times greater in this organelle compared to the rest of the cell. Cells labelled for varying periods of time showed differences in the pattern of Ca45 uptake throughout the sample populations, but no increase in the mean level of uptake per cell. This would suggest a rapid incorporation of isotope within 1-2 hours, with little subsequent uptake. The presence of high levels of label after processing with both additive (glutaraldehyde, paraformaldehyde) and coagulative (acetic alcohol) fixatives indicated that the retention of Ca45 in these preparations was not simply a fixation artefact. Although the isotope did not appear to be suitable for (high resolution) electron microscope autoradiography, the intranuclear site of incorporation was demonstrated indirectly using a buffer extraction technique. Prolonged treatment with phosphate buffer resulted in a large scale loss of label from both cytoplasm and dinocaryotic nucleus. The latter appeared to show specific correlation with the loss of (protein) matrix from the chromosomes - as observed under both light and electron microscopy, with no apparent change in either nucleolus or nucleoplasm. This would suggest that incorporated Ca45 in the nucleus was largely confined to the condensed chromatin, where it was combined with the acidic proteins which make up the bulk of the chromatin matrix. The results obtained in this investigation are related to previous studies involving X-ray microanalysis and uptake of Ni63. (Author)

  7. Coded-aperture imaging using photo-induced reconfigurable aperture arrays for mapping terahertz beams

    CERN Document Server

    Kannegulla, Akash; Rahman, Syed; Fay, Patrick; Xing, Huili Grace; Cheng, Li-Jing; Liu, Lei

    2013-01-01

    We report terahertz coded-aperture imaging using photo-induced reconfigurable aperture arrays on a silicon wafer. The coded aperture was implemented using programmable illumination from a commercially available digital light processing projector. At 590 GHz, each of the array element apertures can be optically turned on and off with a modulation depth of 20 dB and a modulation rate of ~1.3 KHz. Prototype demonstrations of 4 by 4 coded-aperture imaging using Hadamard coding have been performed and this technique has been successfully applied to mapping THz beams by using a 6 by 6 aperture array at 590 GHz. The imaging results agree closely with theoretical calculations based on Gaussian beam transformation, demonstrating that this technique is promising for realizing real-time and low-cost terahertz cameras for many applications. The reported approach provides a simple but powerful means to visualize THz beams, which is highly desired in quasi-optical system alignment, quantum-cascade laser design and characte...

  8. Multi-static synthetic aperture radar and inverse scattering

    OpenAIRE

    Gustafsson, Mats

    2004-01-01

    In this paper synthetic aperture radar is analyzed from an inverse scattering perspective. It is shown that the classical point scattering model can be generalized to a dipole scattering model. The dipole scattering model reduces to the point scattering model for small aperture angles. For large aperture angles or multiple illumination apertures the dipole model gives an anisotropic reflectivity such that orthogonal scattering processes are separated. Moreover, it is shown th...

  9. In-vivo examples of synthetic aperture vector flow imaging

    DEFF Research Database (Denmark)

    Oddershede, Niels; Hansen, Kristoffer Lindskov; Nielsen, Michael Bachmann;

    2007-01-01

    would be needed. Synthetic aperture vector flow imaging could potentially provide this. The purpose of this paper is to test the synthetic aperture vector flow imaging method on challenging in-vivo data. Two synthetic aperture in-vivo data sets are acquired using a commercial linear array transducer and...

  10. An optimization algorithm for volumetrically segmented aperture-based IMRT

    International Nuclear Information System (INIS)

    There are few algorithms to create aperture-based IMRT such as Iterative least-square algorithm, Simultaneous projection algorithm (Cimmino's algorithm), Mixed integer programming, etc. In this present work, a Volumetrically Segmented Aperture Optimization (VSAO) algorithm is introduced and its usefulness in generating aperture-based IMRT plans is investigated in different case studies

  11. High Gain, Very Low Areal Density, Scalable RF Apertures Enabled by Membrane Aperture Shell Technology (MAST) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose that the Membrane Aperture Shell Technology (MAST) approach be expanded with a specific focus on space exploration orbiting comm network RF aperture...

  12. Orbital angular momentum mode-demultiplexing scheme with partial angular receiving aperture.

    Science.gov (United States)

    Zheng, Shilie; Hui, Xiaonan; Zhu, Jiangbo; Chi, Hao; Jin, Xiaofeng; Yu, Siyuan; Zhang, Xianmin

    2015-05-01

    For long distance orbital angular momentum (OAM) based transmission, the conventional whole beam receiving scheme encounters the difficulty of large aperture due to the divergence of OAM beams. We propose a novel partial receiving scheme, using a restricted angular aperture to receive and demultiplex multi-OAM-mode beams. The scheme is theoretically analyzed to show that a regularly spaced OAM mode set remain orthogonal and therefore can be de-multiplexed. Experiments have been carried out to verify the feasibility. This partial receiving scheme can serve as an effective method with both space and cost savings for the OAM communications. It is applicable to both free space OAM optical communications and radio frequency (RF) OAM communications. PMID:25969311

  13. Restrictions of stable bundles

    CERN Document Server

    Balaji, V

    2011-01-01

    The Mehta-Ramanathan theorem ensures that the restriction of a stable vector bundle to a sufficiently high degree complete intersection curve is again stable. We improve the bounds for the "sufficiently high degree" and propose a possibly optimal conjecture.

  14. Performance limits for Synthetic Aperture Radar.

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2006-02-01

    The performance of a Synthetic Aperture Radar (SAR) system depends on a variety of factors, many which are interdependent in some manner. It is often difficult to ''get your arms around'' the problem of ascertaining achievable performance limits, and yet those limits exist and are dictated by physics, no matter how bright the engineer tasked to generate a system design. This report identifies and explores those limits, and how they depend on hardware system parameters and environmental conditions. Ultimately, this leads to a characterization of parameters that offer optimum performance for the overall SAR system. For example, there are definite optimum frequency bands that depend on weather conditions and range, and minimum radar PRF for a fixed real antenna aperture dimension is independent of frequency. While the information herein is not new to the literature, its collection into a single report hopes to offer some value in reducing the ''seek time''.

  15. IR aperture measurement at β*=40 cm

    CERN Document Server

    Bruce, Roderik; Hermes, Pascal Dominik; Kwee-Hinzmann, Regina; Mereghetti, Alessio; Mirarchi, Daniele; Redaelli, Stefano; Salvachua Ferrando, Belen Maria; Skowronski, Piotr Krzysztof; Valentino, Gianluca; Valloni, Alessandra; CERN. Geneva. ATS Department

    2015-01-01

    This note summarizes MD 307, performed on August 27 2015, during which we measured with beam the global apertures at 6.5 TeV with IR1 and IR5 squeezed to β* =40 cm and a half crossing angle of 205 rad. The measurement technique involved opening collimators in steps, while inducing beam losses at each step, until the main loss location moved from the collimators to the global bottleneck in one of the triplets. Measurements were performed in both beams and planes, and each measurement gave the minimum triplet aperture over IR1 and IR5. The results are in very good agreement with theoretical predictions. At the end of the MD, an asynchronous beam dump test was performed with all collimators moved in to so-called 2-σ retraction settings. This MD is one in a series meant to address various open points for the reach in β* in Run II.

  16. Polarization-sensitive interferometric synthetic aperture microscopy

    Science.gov (United States)

    South, Fredrick A.; Liu, Yuan-Zhi; Xu, Yang; Shemonski, Nathan D.; Carney, P. Scott; Boppart, Stephen A.

    2015-11-01

    Three-dimensional optical microscopy suffers from the well-known compromise between transverse resolution and depth-of-field. This is true for both structural imaging methods and their functional extensions. Interferometric synthetic aperture microscopy (ISAM) is a solution to the 3D coherent microscopy inverse problem that provides depth-independent transverse resolution. We demonstrate the extension of ISAM to polarization sensitive imaging, termed polarization-sensitive interferometric synthetic aperture microscopy (PS-ISAM). This technique is the first functionalization of the ISAM method and provides improved depth-of-field for polarization-sensitive imaging. The basic assumptions of polarization-sensitive imaging are explored, and refocusing of birefringent structures is experimentally demonstrated. PS-ISAM enables high-resolution volumetric imaging of birefringent materials and tissue.

  17. Flame Reconstruction Using Synthetic Aperture Imaging

    CERN Document Server

    Murray, Preston; Tree, Dale; Truscott, Tadd

    2011-01-01

    Flames can be formed by burning methane (CH4). When oxygen is scarce, carbon particles nucleate into solid particles called soot. These particles emit photons, making the flame yellow. Later, methane is pre-mixed with air forming a blue flame; burning more efficiently, providing less soot and light. Imaging flames and knowing their temperature are vital to maximizing efficiency and validating numerical models. Most temperature probes disrupt the flame and create differences leading to an inaccurate measurement of the flame temperature. We seek to image the flame in three dimensions using synthetic aperture imaging. This technique has already successfully measured velocity fields of a vortex ring [1]. Synthetic aperture imaging is a technique that views one scene from multiple cameras set at different angles, allowing some cameras to view objects that are obscured by others. As the resulting images are overlapped different depths of the scene come into and out of focus, known as focal planes, similar to tomogr...

  18. High frame rate synthetic aperture duplex imaging

    DEFF Research Database (Denmark)

    Stuart, Matthias Bo; Tomov, Borislav Gueorguiev; Pihl, Michael Johannes;

    2013-01-01

    Conventional color flow images are limited in velocity range and can either show the high velocities in systole or be optimized for the lower diastolic velocities. The full dynamics of the flow is, thus, hard to visualize. The dynamic range can be significantly increased by employing synthetic...... aperture flow imaging as demonstrated in this paper. Synthetic aperture, directional beamforming, and cross-correlation are used to produce B-mode and vector velocity images at high frame rates. The frame rate equals the effective pulse repetition frequency of each imaging mode. Emissions for making the B...... estimation is −1.8% and the relative standard deviation 5.4%. The approach can thus estimate both high and low velocities with equal accuracy and thereby makes it possible to present vector flow images with a high dynamic range. Measurements are made using the SARUS research scanner, a linear array...

  19. Intermediation under Trade Restrictions.

    OpenAIRE

    Winkler, G Michael

    1989-01-01

    Intermediation is the activity of buying and selling simultaneously in one market. In this paper, intermediation in the market for an arbitrary good is derived from trade restrictions in a general equilibrium exchange model. The trade restrictions are given by a trade feasibility relation defined on the set of households, and they necessitate dropping the one price assumption of standard general equilibrium theory. It is shown that, in this setting, equilibria need not exist in spite of well-...

  20. Variable-Aperture Reciprocating Reed Valve

    Science.gov (United States)

    Lindner, Jeffrey L. (Inventor); Myers, W. Neill (Inventor); Kelley, Anthony R. (Inventor); Yang, Hong Q. (Inventor)

    2015-01-01

    A variable-aperture reciprocating reed valve includes a valve body defining a through hole region having a contoured-profile portion. A semi-rigid plate is affixed on one side thereof to the valve body to define a cantilever extending across the through hole region. At least one free edge of the cantilever opposes the contoured-profile portion of the through hole region in a non-contact relationship.

  1. A Tutorial on Synthetic Aperture Radar

    OpenAIRE

    Moreira, Alberto; Prats-Iraola, Pau; Younis, Marwan; Krieger, Gerhard; Hajnsek, Irena; Papathanassiou, Konstantinos

    2013-01-01

    Synthetic Aperture Radar (SAR) has been widely used for Earth remote sensing for more than 30 years. It provides high-resolution, day-and-night and weather-independent images for a multitude of applications ranging from geoscience and climate change research, environmental and Earth system monitoring, 2-D and 3-D mapping, change detection, 4-D mapping (space and time), security-related applications up to planetary exploration. With the advances in radar technology and geo/bio-physical paramet...

  2. Real-time interferometric synthetic aperture microscopy

    OpenAIRE

    Ralston, Tyler S.; Marks, Daniel L.; Carney, P. Scott; Boppart, Stephen A.

    2008-01-01

    An interferometric synthetic aperture microscopy (ISAM) system design with real-time 2D cross-sectional processing is described in detail. The system can acquire, process, and display the ISAM reconstructed images at frame rates of 2.25 frames per second for 512 × 1024 pixel images. This system provides quantitatively meaningful structural information from previously indistinguishable scattering intensities and provides proof of feasibility for future real-time ISAM systems.

  3. Real-time interferometric synthetic aperture microscopy.

    Science.gov (United States)

    Ralston, Tyler S; Marks, Daniel L; Carney, P Scott; Boppart, Stephen A

    2008-02-18

    An interferometric synthetic aperture microscopy (ISAM) system design with real-time 2D cross-sectional processing is described in detail. The system can acquire, process, and display the ISAM reconstructed images at frame rates of 2.25 frames per second for 512 X 1024 pixel images. This system provides quantitatively meaningful structural information from previously indistinguishable scattering intensities and provides proof of feasibility for future real-time ISAM systems. PMID:18542337

  4. Motion compensation of Synthetic Aperture Radar

    OpenAIRE

    Duncan, David; Long, David

    2003-01-01

    Synthetic aperture radar (SAR) is a digital signal processing technique which enhances the azimuth resolution of a radar image using the target doppler history created by the motion of the radar platform. If the platform deviates from a constant velocity, straight-line path then image quality is lost and image details become unfocused. Motion compensation (MOCO) is a technique in which the position and attitude of the platform is recorded or estimated and then used to correct the scene's dopp...

  5. Simultaneous Navigation and Synthetic Aperture Radar Focusing

    OpenAIRE

    Sjanic, Zoran; Gustafsson, Fredrik

    2015-01-01

    Synthetic aperture radar (SAR) equipment is a radar imaging system that can be used to create high-resolution images of a scene by utilizing the movement of a flying platform. Knowledge of the platforms trajectory is essential to get good and focused images. An emerging application field is real-time SAR imaging using small and cheap platforms where estimation errors in navigation systems imply unfocused images. This contribution investigates a joint estimation of the trajectory and SAR image...

  6. Feasibility of Swept Synthetic Aperture Ultrasound Imaging.

    Science.gov (United States)

    Bottenus, Nick; Long, Will; Zhang, Haichong K; Jakovljevic, Marko; Bradway, David P; Boctor, Emad M; Trahey, Gregg E

    2016-07-01

    Ultrasound image quality is often inherently limited by the physical dimensions of the imaging transducer. We hypothesize that, by collecting synthetic aperture data sets over a range of aperture positions while precisely tracking the position and orientation of the transducer, we can synthesize large effective apertures to produce images with improved resolution and target detectability. We analyze the two largest limiting factors for coherent signal summation: aberration and mechanical uncertainty. Using an excised canine abdominal wall as a model phase screen, we experimentally observed an effective arrival time error ranging from 18.3 ns to 58 ns (root-mean-square error) across the swept positions. Through this clutter-generating tissue, we observed a 72.9% improvement in resolution with only a 3.75 dB increase in side lobe amplitude compared to the control case. We present a simulation model to study the effect of calibration and mechanical jitter errors on the synthesized point spread function. The relative effects of these errors in each imaging dimension are explored, showing the importance of orientation relative to the point spread function. We present a prototype device for performing swept synthetic aperture imaging using a conventional 1-D array transducer and ultrasound research scanner. Point target reconstruction error for a 44.2 degree sweep shows a reconstruction precision of 82.8 μm and 17.8 μm in the lateral and axial dimensions respectively, within the acceptable performance bounds of the simulation model. Improvements in resolution, contrast and contrast-to-noise ratio are demonstrated in vivo and in a fetal phantom. PMID:26863653

  7. Optimization of Synthetic Aperture Image Quality

    OpenAIRE

    Moshavegh, Ramin; Jensen, Jonas; Villagómez Hoyos, Carlos Armando; Stuart, Matthias Bo; Hemmsen, Martin Christian; Jensen, Jørgen Arendt

    2016-01-01

    Synthetic Aperture (SA) imaging produces high-quality images and velocity estimates of both slow and fast flow at high frame rates. However, grating lobe artifacts can appear both in transmission and reception. These affect the image quality and the frame rate. Therefore optimization of parameters effecting the image quality of SA is of great importance, and this paper proposes an advanced procedure for optimizing the parameters essential for acquiring an optimal image quality, while generati...

  8. The Effects of Localisation Decisions on New Product Superiority and Performance: Empirical Research on Consumer-Goods Subsidiaries

    Directory of Open Access Journals (Sweden)

    Firmanzah

    2009-06-01

    Full Text Available New products, while essential, are risky and expensive for subsidiaries. The main objective of this research is to determine success factors for new product launch (NPL by subsidiaries operating in developing countries. It is argued that localisation of NPL decisions contributes positively to new product superiority and commercial performance, with partial least squares used to test the hypothesis. The results show that localisation of innovation decisions increases localisation of branding and commercialisation decisions in the local market. However, localisation of commercialisation decisions positively influences new product superiority, while localisation of innovation decisions reduces this superiority. Finally, hypothesis testing reveals that localisation of commercial decisions and new product superiority both increase the commercial performance of new products in the local market.

  9. Restoring Aperture Profile At Sample Plane

    International Nuclear Information System (INIS)

    Off-line conditioning of full-size optics for the National Ignition Facility required a beam delivery system to allow conditioning lasers to rapidly raster scan samples while achieving several technical goals. The main purpose of the optical system designed was to reconstruct at the sample plane the flat beam profile found at the laser aperture with significant reductions in beam wander to improve scan times. Another design goal was the ability to vary the beam size at the sample to scan at different fluences while utilizing all of the laser power and minimizing processing time. An optical solution was developed using commercial off-the-shelf lenses. The system incorporates a six meter relay telescope and two sets of focusing optics. The spacing of the focusing optics is changed to allow the fluence on the sample to vary from 2 to 14 Joules per square centimeter in discrete steps. More importantly, these optics use the special properties of image relaying to image the aperture plane onto the sample to form a pupil relay with a beam profile corresponding almost exactly to the flat profile found at the aperture. A flat beam profile speeds scanning by providing a uniform intensity across a larger area on the sample. The relayed pupil plane is more stable with regards to jitter and beam wander. Image relaying also reduces other perturbations from diffraction, scatter, and focus conditions. Image relaying, laser conditioning, and the optical system designed to accomplish the stated goals are discussed

  10. Coded-aperture imaging in nuclear medicine

    Science.gov (United States)

    Smith, Warren E.; Barrett, Harrison H.; Aarsvold, John N.

    1989-01-01

    Coded-aperture imaging is a technique for imaging sources that emit high-energy radiation. This type of imaging involves shadow casting and not reflection or refraction. High-energy sources exist in x ray and gamma-ray astronomy, nuclear reactor fuel-rod imaging, and nuclear medicine. Of these three areas nuclear medicine is perhaps the most challenging because of the limited amount of radiation available and because a three-dimensional source distribution is to be determined. In nuclear medicine a radioactive pharmaceutical is administered to a patient. The pharmaceutical is designed to be taken up by a particular organ of interest, and its distribution provides clinical information about the function of the organ, or the presence of lesions within the organ. This distribution is determined from spatial measurements of the radiation emitted by the radiopharmaceutical. The principles of imaging radiopharmaceutical distributions with coded apertures are reviewed. Included is a discussion of linear shift-variant projection operators and the associated inverse problem. A system developed at the University of Arizona in Tucson consisting of small modular gamma-ray cameras fitted with coded apertures is described.

  11. Large-aperture hybrid photo-detector

    International Nuclear Information System (INIS)

    We have developed the first complete large-aperture (13-inch diameter) hybrid photo-detector (HPD). The withstanding voltage problem has been overcome and we were able to attain an HPD operating voltage of +20 kV. Adoption of our newly developed backside illumination avalanche diode (AD) was also critical in successfully countering the additional problem of an increase in AD leakage after the activation process. We observed single photon signal timing jitter of under 450 ps in FWHM, electron transit time of ∼12 ns, and clear pulse height separation up to several photoelectron peaks, all greatly superior to the performance of any conventional large-aperture photomultiplier tubes (PMTs). In addition, our HPD has a much simpler structure than conventional large-aperture PMTs, which simplifies mass production and lowers manufacturing cost. We believe that these attributes position our HPD as the most suitable photo-detector for the next generation mega-ton class water-Cherenkov detector, which is expected to be more than 20x larger than the Super-Kamiokande (SK) detector

  12. Outdoor synthetic aperture acoustic ground target measurements

    Science.gov (United States)

    Bishop, Steven; Ngaya, Therese-Ann; Vignola, Joe; Judge, John; Marble, Jay; Gugino, Peter; Soumekh, Mehrdad; Rosen, Erik

    2010-04-01

    A novel outdoor synthetic aperture acoustic (SAA) system consists of a microphone and loudspeaker traveling along a 6.3-meter rail system. This is an extension from a prior indoor laboratory measurement system in which selected targets were insonified while suspended in air. Here, the loudspeaker and microphone are aimed perpendicular to their direction of travel along the rail. The area next to the rail is insonified and the microphone records the reflected acoustic signal, while the travel of the transceiver along the rail creates a synthetic aperture allowing imaging of the scene. Ground surfaces consisted of weathered asphalt and short grass. Several surface-laid objects were arranged on the ground for SAA imaging. These included rocks, concrete masonry blocks, grout covered foam blocks; foliage obscured objects and several spherical canonical targets such as a bowling ball, and plastic and metal spheres. The measured data are processed and ground targets are further analyzed for characteristics and features amenable for discrimination. This paper includes a description of the measurement system, target descriptions, synthetic aperture processing approach and preliminary findings with respect to ground surface and target characteristics.

  13. Coded-aperture imaging of the heart

    International Nuclear Information System (INIS)

    Coded-aperture imaging of the heart combines the advantages of tomography with good sensitivity, high resolution, and accurate size scaling. Since the images are multiplexed, the method may be adapted to small, portable cameras for bedside use without sacrificing image resolution. A new coded aperture designed especially for cardiac imaging has been constructed and tested. This aperture incorporates significant improvements over previous designs. Longitudinal tomograms are calculated at 1-cm intervals using a modified ART algorithm. Experimental lateral resolution at 140 keV with a portable scintillation camera is 3.8 mm FWHM at 4 cm, and 7.8 mm FWHM at 12 cm. Depth resolution determined from a sloping line source is 1.1 cm FWHM at 4 cm, and 2.9 cm at 12 cm. The calculated point-source sensitivities in air at 4 cm and 12 cm, respectively, are 20 and 8 cps/μCi. Images of good diagnostic quality have been obtained in phantoms and in a dog model of acute myocardial infarction, using thallium-201, technetium-99m pyrophosphate, and gated ventricular blood-pool imaging with Tc-labeled red blood cells. Preliminary studies in humans confirm the good results in animals

  14. Jacobi-Bessel Analysis Of Antennas With Elliptical Apertures.

    Science.gov (United States)

    Rahmat-Samii, Y.

    1989-01-01

    Coordinate transformation improves convergence pattern analysis of elliptical-aperture antennas. Modified version of Jacobi-Bessel expansion for vector diffraction analysis of reflector antennas uses coordinate transformation to improve convergence with elliptical apertures. Expansion converges rapidly for antennas with circular apertures, but less rapidly for elliptical apertures. Difference in convergence behavior between circular and elliptical Jacobi-Bessel algorithms indicated by highest values of indices m, n, and p required to achieve same accuracy in computed radiation pattern of offset paraboloidal antenna with elliptical aperture.

  15. Cluster speckle structures through multiple apertures forming a closed curve

    Science.gov (United States)

    Mosso, E.; Tebaldi, M.; Lencina, A.; Bolognini, N.

    2010-04-01

    In this work, cluster-like speckle patterns are analyzed. These patterns are generated when a diffuser illuminated by coherent light is imaged by a lens having a pupil mask with multiple apertures forming a closed curve. We show that the cluster structure results from the complex modulation produced inside each speckle which is generated by multiple interferences of light through the apertures. In particular, when the apertures are uniformly distributed along a closed curve, the resulting image speckle cluster replicates the pupil aperture distribution. Experimental results and theoretical simulations show that cluster features depend on the apertures distribution and the size of the closed curves.

  16. Calibration of the TUD Ku-band Synthetic Aperture Radiometer

    DEFF Research Database (Denmark)

    Laursen, Brian; Skou, Niels

    1995-01-01

    The TUD Synthetic Aperture Radiometer is a 2-channel demonstration model that can simulate a thinned aperture radiometer having an unfilled aperture consisting of several small antenna elements. Aperture synthesis obtained by interferometric measurements using the antenna elements in pairs......, followed by an image reconstruction based on an inverse Fourier transform, results in an imaging instrument without the need of mechanical scan. The thinned aperture and the non-scanning feature make the technique attractive for low frequency spaceborne radiometer systems, e.g. at L-band. Initial...

  17. Crossed aperture lenses for the correction of chromatic and aperture aberrations

    International Nuclear Information System (INIS)

    The chromatic and aperture aberrations of crossed five-aperture lenses are analyzed by direct ray tracing. The apertures are rectangular and the voltages are applied in such a way that the first-order properties of the crossed lens are similar to those of a quadrupole doublet. It is shown that in astigmatic modes the chromatic and aperture aberrations of one of the linear images can be simultaneously eliminated or made negative. It is also shown that stigmatic modes exist in which the magnification is different in two perpendicular planes and in which the image blurring caused by the chromatic and aperture aberrations in the direction of smaller magnification is ten times smaller than that given by a round lens of the same focal length and the blurring in the other direction is at least two times smaller. The stigmatic crossed lens also gives a larger working distance than the equivalent round lens. The crossed lens will therefore be preferable for many probe forming systems. copyright 1996 American Institute of Physics

  18. Parameters for HL-LHC aperture calculations and comparison with aperture measurements

    CERN Document Server

    Bruce, R; Fartoukh, S; Giovannozzi, M; Redaelli, S; Tomas, R; Wenninger, J

    2014-01-01

    When β∗ is squeezed to smaller values in the LHC, the beam size in the inner triplet increases so that the aperture risks to be exposed to unwanted beam losses. A 2D calculation model was used during the design stage to study the aperture margins, both there and at other potential bottlenecks. Based on assumptions on orbit and optics errors, as well as mechanical tolerances, it gives the available aperture in units of the RMS beam size, which can be compared with what can be protected by the collimation system. During the LHC Run I in 2010-2013, several of the error tolerances have been found smaller than the design assumptions. Furthermore, the aperture has been measured with beam several times and the results are compatible with a very well aligned machine, with results close to the design values. In this report, we therefore review the assumptions in the model and propose an updated set of input parameters to be used for aperture calculations at top energy in HL-LHC. The new parameter set is based on th...

  19. Aperture Size Effect on Extracted Negative Ion Current Density

    Science.gov (United States)

    de Esch, H. P. L.; Svensson, L.; Riz, D.

    2009-03-01

    This paper discusses experimental results obtained at the 1 MV testbed at CEA Cadarache that appear to show a higher extracted D- current density from small apertures. Plasma grids with different shapes have been installed and tested. All grids had one single aperture. The tests were done in volume operation and in caesium operation. We tested four grids, two with O/14 mm, one with O/11 mm and one with O/8 mm apertures. No aperture size effect was observed in volume operation. In caesiated operation the extracted current density for the O/8 mm aperture appears to be significantly higher (˜50%) than for the O/14 mm aperture. Simulations with a 3D Monte Carlo Trajectory Following Code have shown an aperture size effect of about 20%. Finally, as byproducts of the experiments, data on backstreaming positive ions and the temperature of the plasma grid have been obtained.

  20. Two oppositely localised frizzled RNAs as axis determinants in a cnidarian embryo.

    Directory of Open Access Journals (Sweden)

    Tsuyoshi Momose

    2007-04-01

    Full Text Available In phylogenetically diverse animals, including the basally diverging cnidarians, "determinants" localised within the egg are responsible for directing development of the embryonic body plan. Many such determinants are known to regulate the Wnt signalling pathway, leading to regionalised stabilisation of the transcriptional coregulator beta-catenin; however, the only strong molecular candidate for a Wnt-activating determinant identified to date is the ligand Wnt11 in Xenopus. We have identified embryonic "oral-aboral" axis determinants in the cnidarian Clytia hemisphaerica in the form of RNAs encoding two Frizzled family Wnt receptors, localised at opposite poles of the egg. Morpholino-mediated inhibition of translation showed that CheFz1, localised at the animal pole, activates the canonical Wnt pathway, promotes oral fates including gastrulation, and may also mediate global polarity in the ectoderm. CheFz3, whose RNA is localised at the egg vegetal cortex, was found to oppose CheFz1 function and to define an aboral territory. Active downregulation mechanisms maintained the reciprocal localisation domains of the two RNAs during early development. Importantly, ectopic expression of either CheFz1 or CheFz3 was able to redirect axis development. These findings identify Frizzled RNAs as axis determinants in Clytia, and have implications for the evolution of embryonic patterning mechanisms, notably that diverse Wnt pathway regulators have been adopted to initiate asymmetric Wnt pathway activation.

  1. Somatostatin receptor scintigraphy and intraoperative gamma probe detection in the localisation and treatment of pancreatic insulinoma

    International Nuclear Information System (INIS)

    Full text: Aims: We report a case of insulinoma that was successfully enucleated under radio-guidance after an initial unsuccessful laparotomy. This case highlights the utility of Somatostatin Receptor Scintigraphy (SRS) and gamma probe in the localisation and treatment of neuroendocrine tumours. Methods: The patient presented with recurrent hypoglycaemia. An abdominal CT scan identified a lesion in the uncinate process of the pancreas, however, laparotomy with use of intraoperative ultrasound failed to localise the lesion. SRS with SPECTICT was then requested by the surgical team with a view to radio-guided surgery. Results: SRS demonstrated an octreotide-avid tumour in the posterior uncinate process of the pancreas, and confirmed suitability for radio-guided surgery. At re-exploration, the surgeon was again unable to palpate the lesion or localise it with intraoperative ultrasound, however, the lesion was successfully detected and removed with the use of a gamma probe. A postoperative SRS confirmed complete excision and histopathology was diagnostic of insulinoma. Conclusion: This case highlights the utility of SRS in the intraoperative localisation and surgical excision of neuroendocrine tumours. The lesion was unable to be localised clinically or with intraoperative ultrasound but was successfully detected with scintigraphic techniques. The surgical team acknowledge that the use of a gamma probe enabled enucleation of the insulinoma, which obviated the need for an invasive Whipple's procedure.

  2. Fast-neutron, coded-aperture imager

    Energy Technology Data Exchange (ETDEWEB)

    Woolf, Richard S., E-mail: richard.woolf@nrl.navy.mil; Phlips, Bernard F., E-mail: bernard.phlips@nrl.navy.mil; Hutcheson, Anthony L., E-mail: anthony.hutcheson@nrl.navy.mil; Wulf, Eric A., E-mail: eric.wulf@nrl.navy.mil

    2015-06-01

    This work discusses a large-scale, coded-aperture imager for fast neutrons, building off a proof-of concept instrument developed at the U.S. Naval Research Laboratory (NRL). The Space Science Division at the NRL has a heritage of developing large-scale, mobile systems, using coded-aperture imaging, for long-range γ-ray detection and localization. The fast-neutron, coded-aperture imaging instrument, designed for a mobile unit (20 ft. ISO container), consists of a 32-element array of 15 cm×15 cm×15 cm liquid scintillation detectors (EJ-309) mounted behind a 12×12 pseudorandom coded aperture. The elements of the aperture are composed of 15 cm×15 cm×10 cm blocks of high-density polyethylene (HDPE). The arrangement of the aperture elements produces a shadow pattern on the detector array behind the mask. By measuring of the number of neutron counts per masked and unmasked detector, and with knowledge of the mask pattern, a source image can be deconvolved to obtain a 2-d location. The number of neutrons per detector was obtained by processing the fast signal from each PMT in flash digitizing electronics. Digital pulse shape discrimination (PSD) was performed to filter out the fast-neutron signal from the γ background. The prototype instrument was tested at an indoor facility at the NRL with a 1.8-μCi and 13-μCi 252Cf neutron/γ source at three standoff distances of 9, 15 and 26 m (maximum allowed in the facility) over a 15-min integration time. The imaging and detection capabilities of the instrument were tested by moving the source in half- and one-pixel increments across the image plane. We show a representative sample of the results obtained at one-pixel increments for a standoff distance of 9 m. The 1.8-μCi source was not detected at the 26-m standoff. In order to increase the sensitivity of the instrument, we reduced the fastneutron background by shielding the top, sides and back of the detector array with 10-cm-thick HDPE. This shielding configuration led

  3. Safety margins of RBMK-1500 accident localisation system at Ignalina NPP

    International Nuclear Information System (INIS)

    Accident localisation system (ALS) at Ignalina NPP forms the last barrier against release of radioactive material to environment. According to functional principle the ALS could be attributed to so called 'pressure suppression' type containment. It means, that ALS uses condensing pools, which condense the released steam in order to reduce the peak pressures that can be reached during any loss of coolant accident. The main safety function for ALS is to contain the radioactive materials released in the course of accident and to limit the releases within specified limits. The ALS performance during the accidents relies upon the ALS structure capability to withstand the loads. The maximal pressure, which can be reached during accident, is one of the most important parameters, defining ALS capability to remain intact and to perform its safety function. The maximal loads on ALS could be reached during the maximum design basis accident (MDBA). The MDBA is defined as the guillotine (i.e. complete) rupture of the pressure header of the main circulation pumps. The pressure header is a sizable element of the RBMK-1500 piping: the length of this component is ∼18.5 m, the inner diameter is 900 mm. Other important design basis event is the break of a Group Distribution Header (GDH). This break represents a medium size LOCA (internal diameter of GDH - 0.295 m), but it is important from the point of view of ALS performance, because GDH piping is located in a restricted space below the reactor core. The GDHs are fed from the pressure header and distribute coolant to fuel channels. There are 20 GDH units in a circulation loop, or a total of 40 in the plant.The behaviour of main thermal hydraulic parameters in ALS is presented in this paper for both of these LOCAs (MDBA and GDH break). The release rates through the breaks were calculated by applying the RELAP5 code. A number of calculations variants were performed in order to evaluate ALS response to MDBA as well as to GDH break

  4. Divergent RNA Localisation Patterns of Maternal Genes Regulating Embryonic Patterning in the Butterfly Pararge aegeria.

    Directory of Open Access Journals (Sweden)

    Jean-Michel Carter

    Full Text Available The maternal effect genes responsible for patterning the embryo along the antero-posterior (AP axis are broadly conserved in insects. The precise function of these maternal effect genes is the result of the localisation of their mRNA in the oocyte. The main developmental mechanisms involved have been elucidated in Drosophila melanogaster, but recent studies have shown that other insect orders often diverge in RNA localisation patterns. A recent study has shown that in the butterfly Pararge aegeria the distinction between blastodermal embryonic (i.e. germ band and extra-embryonic tissue (i.e. serosa is already specified in the oocyte during oogenesis in the ovariole, long before blastoderm cellularisation. To examine the extent by which a female butterfly specifies and patterns the AP axis within the region fated to be the germ band, and whether she specifies a germ plasm, we performed in situ hybridisation experiments on oocytes in P. aegeria ovarioles and on early embryos. RNA localisation of the following key maternal effect genes were investigated: caudal (cad, orthodenticle (otd, hunchback (hb and four nanos (nos paralogs, as well as TDRD7 a gene containing a key functional domain (OST-HTH/LOTUS shared with oskar. TDRD7 was mainly confined to the follicle cells, whilst hb was exclusively zygotically transcribed. RNA of some of the nos paralogs, otd and cad revealed complex localisation patterns within the cortical region prefiguring the germ band (i.e. germ cortex. Rather interestingly, otd was localised within and outside the anterior of the germ cortex. Transcripts of nos-O formed a distinct granular ring in the middle of the germ cortex possibly prefiguring the region where germline stem cells form. These butterfly RNA localisation patterns are highly divergent with respect to other insects, highlighting the diverse ways in which different insect orders maternally regulate early embryogenesis of their offspring.

  5. Optimization of synthetic aperture image quality

    Science.gov (United States)

    Moshavegh, Ramin; Jensen, Jonas; Villagomez-Hoyos, Carlos A.; Stuart, Matthias B.; Hemmsen, Martin Christian; Jensen, Jørgen Arendt

    2016-04-01

    Synthetic Aperture (SA) imaging produces high-quality images and velocity estimates of both slow and fast flow at high frame rates. However, grating lobe artifacts can appear both in transmission and reception. These affect the image quality and the frame rate. Therefore optimization of parameters effecting the image quality of SA is of great importance, and this paper proposes an advanced procedure for optimizing the parameters essential for acquiring an optimal image quality, while generating high resolution SA images. Optimization of the image quality is mainly performed based on measures such as F-number, number of emissions and the aperture size. They are considered to be the most contributing acquisition factors in the quality of the high resolution images in SA. Therefore, the performance of image quality is quantified in terms of full-width at half maximum (FWHM) and the cystic resolution (CTR). The results of the study showed that SA imaging with only 32 emissions and maximum sweep angle of 22 degrees yields a very good image quality compared with using 256 emissions and the full aperture size. Therefore the number of emissions and the maximum sweep angle in the SA can be optimized to reach a reasonably good performance, and to increase the frame rate by lowering the required number of emissions. All the measurements are performed using the experimental SARUS scanner connected to a λ/2-pitch transducer. A wire phantom and a tissue mimicking phantom containing anechoic cysts are scanned using the optimized parameters for the transducer. Measurements coincide with simulations.

  6. Multibeam synthetic aperture radar for global oceanography

    Science.gov (United States)

    Jain, A.

    1979-01-01

    A single-frequency multibeam synthetic aperture radar concept for large swath imaging desired for global oceanography is evaluated. Each beam iilluminates a separate range and azimuth interval, and images for different beams may be separated on the basis of the Doppler spectrum of the beams or their spatial azimuth separation in the image plane of the radar processor. The azimuth resolution of the radar system is selected so that the Doppler spectrum of each beam does not interfere with the Doppler foldover due to the finite pulse repetition frequency of the radar system.

  7. Tissue Harmonic Synthetic Aperture Ultrasound Imaging

    DEFF Research Database (Denmark)

    Hemmsen, Martin Christian; Rasmussen, Joachim; Jensen, Jørgen Arendt

    2014-01-01

    Synthetic aperture sequential beamforming (SASB) and tissue har- monic imaging (THI) are combined to improve the image quality of medical ultrasound imaging. The technique is evaluated in a compar- ative study against dynamic receive focusing (DRF). The objective is to investigate if SASB combined...... with THI improves the image qual- ity compared to DRF-THI. The major benet of SASB is a reduced bandwidth between the probe and processing unit. A BK Medical 2202 Ultraview ultrasound scanner was used to acquire beamformed RF data for oine evaluation. The acquisition was made interleaved between...

  8. Cancellation of singularities for synthetic aperture radar

    Science.gov (United States)

    Caday, Peter

    2015-01-01

    In a basic model for synthetic aperture radar (SAR) imaging, one wishes to recover a function or distribution f from line integrals over circles whose centers lie on a given curve γ. In this paper, we consider the problem of recovering the singularities (wavefront set) of f given its SAR data, and specifically whether it is possible to choose a singular f whose singularities are hidden from γ, meaning that its SAR data is smooth. We show that f 's singularities can be hidden to leading order if a certain discrete reflection map is the identity, and give examples where this is the case. Finally, numerical experiments illustrate the hiding of singularities.

  9. Development of large aperture composite adaptive optics

    Czech Academy of Sciences Publication Activity Database

    Kmetík, Viliam; Vítovec, Bohumil; Jiran, L.; Němcová, Š.; Zicha, J.; Inneman, A.; Mikuličková, L.; Pavlica, R.

    Vol. 9442. Bellingham: SPIE-INT SOC OPTICAL ENGINEERING, 2015 - (Kovačičinová, J.; Vít, T.), 94420L-94420L. (SPIE). ISBN 978-1-62841-557-5. ISSN 0277-786X. [Optics and Measurement Conference 2014 (OaM 2014). Liberec (CZ), 07.10.2014-10.10.2014] R&D Projects: GA TA ČR TA01010878 Institutional support: RVO:61389021 Keywords : Large aperture * adaptive optics * deformable mirror * bimorph deformable mirror * composite optics Subject RIV: BH - Optics, Masers, Lasers http://dx.doi.org/10.1117/12.2175713 .

  10. Digital exploitation of synthetic aperture radar

    Science.gov (United States)

    Wagner, H. L.; Shuchman, R. A.

    1977-01-01

    A digital processing and analysis scheme for use with digitized synthetic aperture radar data was developed. Using data from a four channel system, the imagery is preprocessed using specially designed software and then analyzed using preexisting facilities originally intended for use with MSS type data. Geometric and radiometric correction may be performed if desired, as well as classification analysis, Fast Fourier transform, filtering and level slice and display functions. The system provides low cost output in real time, permitting interactive imagery analysis. System information flow diagrams as well as sample output products are shown.

  11. Cancellation of singularities for synthetic aperture radar

    International Nuclear Information System (INIS)

    In a basic model for synthetic aperture radar (SAR) imaging, one wishes to recover a function or distribution f from line integrals over circles whose centers lie on a given curve γ. In this paper, we consider the problem of recovering the singularities (wavefront set) of f given its SAR data, and specifically whether it is possible to choose a singular f whose singularities are hidden from γ, meaning that its SAR data is smooth. We show that f 's singularities can be hidden to leading order if a certain discrete reflection map is the identity, and give examples where this is the case. Finally, numerical experiments illustrate the hiding of singularities. (paper)

  12. Association between PSA kinetics and cancer-specific mortality in patients with localised prostate cancer

    DEFF Research Database (Denmark)

    Thomsen, F B; Brasso, K; Berg, K D;

    2016-01-01

    with localised PCa managed on watchful waiting. PATIENTS AND METHODS: Patients with clinically localised PCa managed observationally, who were randomised to and remained on placebo for minimum 18 months in the SPCG-6 study, were included. All patients survived at least 2 years and had a minimum of...... three PSA determinations available. The prognostic value of PSA kinetics was analysed and patients were stratified according to their PSA at consent: ≤10, 10.1-25, and >25 ng/ml. Cumulative incidences of PCa-specific mortality were estimated with the Aalen-Johansen method. RESULTS: Two hundred and sixty...

  13. A comparative evaluation of CAT tools during the localisation of HTML5 files

    OpenAIRE

    Castro Hernandez, Laura

    2015-01-01

    The new version of HTML5 introduced in 2014 includes ten new structural elements. The aim of this research project is to discover whether CAT tools are prepared to localise HTML5 or not, and to determine which of the two tools studied, MemoQ 2013 and SDL Trados Studio 2014, is the most suitable when localising a HTML5 website with HTML5 new structural elements. With this purpose, an experiment was designed and implemented at the University of Geneva (UNIGE). Fourteen students of the Faculty o...

  14. An evaluation of focal therapy in the treatment of localised prostate cancer

    OpenAIRE

    Ahmed, H. U.

    2014-01-01

    In this doctoral thesis I am proposing a paradigm shift in the management of men with localised prostate cancer involving destroying areas of prostate cancer alone – so-called focal therapy. By doing so, I propose that side-effects of whole-gland therapies will be reduced whilst maintaining cancer control. I have carried out a phased and structured programme of work to test this hypothesis. First, I review the literature to define the current problem faced by men with localised prostate cance...

  15. Strain localisation in mechanically layered rocks beneath detachment zones: insights from numerical modelling

    Directory of Open Access Journals (Sweden)

    L. Le Pourhiet

    2013-04-01

    Full Text Available We have designed a series of fully dynamic numerical simulations aimed at assessing how the orientation of mechanical layering in rocks controls the orientation of shear bands and the depth of penetration of strain in the footwall of detachment zones. Two parametric studies are presented. In the first one, the influence of stratification orientation on the occurrence and mode of strain localisation is tested by varying initial dip of inherited layering in the footwall with regard to the orientation of simple shear applied at the rigid boundary simulating a rigid hanging wall, all scaling and rheological parameter kept constant. It appears that when Mohr–Coulomb plasticity is being used, shear bands are found to localise only when the layering is being stretched. This corresponds to early deformational stages for inital layering dipping in the same direction as the shear is applied, and to later stages for intial layering dipping towards the opposite direction of shear. In all the cases, localisation of the strain after only γ=1 requires plastic yielding to be activated in the strong layer. The second parametric study shows that results are length-scale independent and that orientation of shear bands is not sensitive to the viscosity contrast or the strain rate. However, decreasing or increasing strain rate is shown to reduce the capacity of the shear zone to localise strain. In the later case, the strain pattern resembles a mylonitic band but the rheology is shown to be effectively linear. Based on the results, a conceptual model for strain localisation under detachment faults is presented. In the early stages, strain localisation occurs at slow rates by viscous shear instabilities but as the layered media is exhumed, the temperature drops and the strong layers start yielding plastically, forming shear bands and localising strain at the top of the shear zone. Once strain localisation has occured, the deformation in the shear band becomes

  16. Localised sarcoptic mange in dogs: a retrospective study of 10 cases.

    Science.gov (United States)

    Pin, D; Bensignor, E; Carlotti, D-N; Cadiergues, M C

    2006-10-01

    The authors report 10 cases of localised sarcoptic mange in dogs. In each case, lesions were localised to one precise area of the skin. Pruritus was present in nine cases and absent in one. Affected areas were the feet (one case), the face and/or the pinnae (six cases), the abdominal skin (one case), the flank (one case) and the lumbar area (one case). The types of lesions were erythema, papules, lichenification, scales, crusts and alopecia. Parasites were found in all cases except one, in which anti-immunoglobulin G Sarcoptes serology was positive. The acaricidal treatments given were lindane, ivermectin or selamectin and were all successful. PMID:17004955

  17. Calorie restriction and stroke

    Directory of Open Access Journals (Sweden)

    Manzanero Silvia

    2011-09-01

    Full Text Available Abstract Stroke, a major cause of disability and mortality in the elderly, occurs when a cerebral blood vessel is occluded or ruptured, resulting in ischemic damage and death of brain cells. The injury mechanism involves metabolic and oxidative stress, excitotoxicity, apoptosis and inflammatory processes, including activation of glial cells and infiltration of leukocytes. In animal models, dietary energy restriction, by daily calorie reduction (CR or intermittent fasting (IF, extends lifespan and decreases the development of age-related diseases. Dietary energy restriction may also benefit neurons, as suggested by experimental evidence showing that CR and IF protect neurons against degeneration in animal models. Recent findings by our group and others suggest the possibility that dietary energy restriction may protect against stroke induced brain injury, in part by inducing the expression of neurotrophic factors, such as brain-derived neurotrophic factor (BDNF and basic fibroblast growth factor (bFGF; protein chaperones, including heat shock protein 70 (Hsp70 and glucose regulated protein 78 (GRP78; antioxidant enzymes, such as superoxide dismutases (SOD and heme oxygenase-1 (HO-1, silent information regulator T1 (SIRT1, uncoupling proteins and anti-inflammatory cytokines. This article discusses the protective mechanisms activated by dietary energy restriction in ischemic stroke.

  18. Bilinear Fourier restriction theorems

    CERN Document Server

    Demeter, Ciprian

    2012-01-01

    We provide a general scheme for proving $L^p$ estimates for certain bilinear Fourier restrictions outside the locally $L^2$ setting. As an application, we show how such estimates follow for the lacunary polygon. In contrast with prior approaches, our argument avoids any use of the Rubio de Francia Littlewood--Paley inequality.

  19. Neuroaesthetics: range and restrictions.

    Science.gov (United States)

    Chatterjee, Anjan

    2013-04-01

    Bullot & Reber (B&R) should be commended for highlighting tensions between scientific aesthetics and art history. The question of how each tradition can learn from the other is timely. While I am sympathetic to their views, their diagnosis of the problem appears exaggerated and their solution partial. They underestimate the reach of scientific aesthetics while failing to identify its inherent restrictions. PMID:23507092

  20. Training Restricted Boltzmann Machines

    DEFF Research Database (Denmark)

    Fischer, Asja

    Restricted Boltzmann machines (RBMs) are probabilistic graphical models that can also be interpreted as stochastic neural networks. Training RBMs is known to be challenging. Computing the likelihood of the model parameters or its gradient is in general computationally intensive. Thus, training...

  1. Coded aperture optimization using Monte Carlo simulations

    International Nuclear Information System (INIS)

    Coded apertures using Uniformly Redundant Arrays (URA) have been unsuccessfully evaluated for two-dimensional and three-dimensional imaging in Nuclear Medicine. The images reconstructed from coded projections contain artifacts and suffer from poor spatial resolution in the longitudinal direction. We introduce a Maximum-Likelihood Expectation-Maximization (MLEM) algorithm for three-dimensional coded aperture imaging which uses a projection matrix calculated by Monte Carlo simulations. The aim of the algorithm is to reduce artifacts and improve the three-dimensional spatial resolution in the reconstructed images. Firstly, we present the validation of GATE (Geant4 Application for Emission Tomography) for Monte Carlo simulations of a coded mask installed on a clinical gamma camera. The coded mask modelling was validated by comparison between experimental and simulated data in terms of energy spectra, sensitivity and spatial resolution. In the second part of the study, we use the validated model to calculate the projection matrix with Monte Carlo simulations. A three-dimensional thyroid phantom study was performed to compare the performance of the three-dimensional MLEM reconstruction with conventional correlation method. The results indicate that the artifacts are reduced and three-dimensional spatial resolution is improved with the Monte Carlo-based MLEM reconstruction.

  2. Aperture determination by long term and multiparticle tracking

    International Nuclear Information System (INIS)

    Apertures determined by long term tracking for 106 turns at β* = 2m and 6m and tracking of 100 particles for 1,000 turns at β* = 2m are reported. The multiparticle results are consistent with the aperture determined from 106 turn runs. Finally, the 106 turn results are extrapolated to 3 x 109 turns to obtain an estimate of the aperture for which particles survive for 10 hours in RHIC

  3. Magnetically tunable broadband transmission through a single small aperture

    OpenAIRE

    Ke Bi; Wenjun Liu; Yunsheng Guo; Guoyan Dong; Ming Lei

    2015-01-01

    Extraordinary transmission through a small aperture is of great interest. However, it faces a limitation that most of approaches can not realize the tunable transmission property, which is not benefit for the miniaturization of the microwave system. Here, we demonstrate a magnetically tunable broadband transmission through a small aperture. By placing two ferrite rods symmetrically on both sides of a single small aperture, the strongly localized electromagnetic fields are effectively coupled ...

  4. An Introduction of Aperture Coupled Microstrip Slot Antenna

    OpenAIRE

    Zarreen Aijaz; S.C Shrivastava

    2010-01-01

    A microstrip slot antenna is very small and lightweight still it has the problem of back radiation due to which power loss occurs and the SAR increases. To reduce the back lobe a technique introduces i.e. aperture coupled microstrip slot antenna which reduces the back lobe as well as increases the bandwidth of the antenna. Aperture coupled microstrip slot antenna couples the patch antenna with microstripline through an aperture.

  5. Optical Phase Imaging Using Synthetic Aperture Illumination and Phase Retrieval

    CERN Document Server

    Lee, Dennis J

    2016-01-01

    We perform quantitative phase imaging using phase retrieval to implement synthetic aperture imaging. Compared to digital holography, the developed technique is simpler, less expensive, and more stable.

  6. Jacobi-Bessel analysis of reflector antennas with elliptical apertures

    Science.gov (United States)

    Rahmat-Samii, Yahya

    1987-01-01

    Although many reflector antennas possess circular projected apertures, there are recent satellite and ground antenna applications for which it is desirable to employ reflectors with elliptical apertures. Here a modification of the Jacobi-Bessel expansion is presented for the diffraction analysis of reflectors with elliptical apertures. A comparative study is also performed between this modified Jacobi-Bessel algorithm and the one which uses the Jacobi-Bessel expansion over a circumscribing circular region. Numerical results are presented for offset reflectors with elliptical and circular apertures and the improved convergence properties of the modified algorithm are highlighted.

  7. Pinch and swell structures: evidence for strain localisation by brittle-viscous behaviour in the middle crust

    Science.gov (United States)

    Gardner, R. L.; Piazolo, S.; Daczko, N. R.

    2015-09-01

    The flow properties of middle crustal rocks are commonly represented by viscous flow. Examples of pinch and swell structures found in a high strain zone at St. Anne Point (Fiordland, New Zealand) and Wongwibinda (N.S.W., Australia) suggest pinch and swell structures may be initiated by brittle failure of the more competent layer in conjunction with subsequent material softening. On this basis we develop a numerical model where Mohr-Coulomb constitutive strain localising behaviour is utilised to initiate pinch and swell structure development. Results show that pinch and swell structures develop in a competent layer in both Newtonian and non-Newtonian flow, provided the competent layer has sufficient viscosity contrast and can localise strain to form shear bands. The flow regime and strain localising characteristics of the surrounding country rock appear not to impact pinch and swell structure formation. The degree of material softening after the initial strain localising behaviour is shown to impact pinch and swell characteristics, while extensive material softening causes the formation of thick necks between swells by limiting the focused localisation of strain into shear bands. To aid analysis of the structures and help derive the flow properties of rocks in the field, we define three stages of pinch and swell development and offer suggestions for measurements to be made in the field. Our study suggests that Mohr-Coulomb strain localising behaviour combined with viscous flow is a viable alternative representation of the heterogeneous rheological behaviour of rocks seen in the middle crust. This type of mid-crustal rheological behaviour can have significant influence on the localisation of strain at all scales. For example, inclusion of Mohr-Coulomb strain localising behaviour with viscous flow in just some mid-crustal layers within a crustal-scale model can result in significant strain localisation, extending from the upper crust into the middle crust. This

  8. Aesthetic Proximity: the Role of Stylistic Programme Elements in Format Localisation

    NARCIS (Netherlands)

    van Keulen, Jolien

    2016-01-01

    abstractImplications of the transnationalisation of television are often studied by focusing on the localisation of the content of formatted programmes. Although television is essentially an audio-visual medium, little attention has been paid to the aesthetic aspects of television texts in relation

  9. Unprecedented spin localisation in a metal-metal bonded dirhenium complex

    OpenAIRE

    Yan, Yong; Mague, Joel T.; Donahue, James; Sproules, Stephen

    2015-01-01

    he molecular and electronic structure of edge-sharing bioctahedral [N(n-Bu)4]3[Re2(mnt)5] is reported here. Despite the short intermetal bond length of 2.6654(2) Å with computed bond order of 1.2, the unpaired electron is localised by the asymmetric ligand distribution, as demonstrated by its remarkable EPR spectrum.

  10. Sestamibi scintigraphy for parathyroid localisation: a reminder of the dangers of false positives

    OpenAIRE

    Whitcroft, Katherine Lisa; Sharma, Anup

    2014-01-01

    Surgical parathyroidectomy is the only curative treatment for primary hyperparathyroidism. As minimally invasive parathyroidectomy increases in popularity, so does reliance on preoperative parathyroid localisation techniques. One such technique is sestamibi scintigraphy. We report a case of false-positive sestamibi scintigraphy caused by follicular variant of papillary thyroid carcinoma. Subsequent completion thyroidectomy was not possible due to widespread postoperative fibrosis. This case, ...

  11. Organic molecules showing the characteristics of localised corrosion aggravation and inhibition

    Energy Technology Data Exchange (ETDEWEB)

    Tan Yongjun, E-mail: yj.tan@curtin.edu.a [Department of Chemistry, Curtin University, GPO Box U1987, Perth (Australia); Mocerino, Mauro; Paterson, Tristan [Department of Chemistry, Curtin University, GPO Box U1987, Perth (Australia)

    2011-05-15

    Research highlights: {yields} Novel experiment for the discovery of localised corrosion inhibitors. {yields} New method of identifying inhibitors promoting random distribution of anodic currents. {yields} Discovery of resorcinarene acid as an effective localised corrosion inhibitor. - Abstract: The behaviour of imidazoline and an acid functionalised resorcinarene as steel corrosion inhibitors in carbon dioxide (CO{sub 2})-saturated brine solutions has been studied using an electrochemically integrated multi-electrode array namely the wire beam electrode (WBE). Both imidazoline and resorcinarene acid provided excellent inhibition to general CO{sub 2} corrosion; however imidazoline was found to aggravate localised corrosion by creating a small number of major anodes that focused on a small area of the WBE surface, leading to highly concentrated anodic dissolution. The resorcinarene acid showed distinctively different behaviour by generating a large number of minor anodes randomly distributing over the WBE surface, leading to insignificant general anodic dissolution. These results indicate that resorcinarene acid provided effective localised corrosion inhibition by promoting a random distribution of insignificant anodic currents.

  12. Immuno-localisation of anti-thyroid antibodies in adult human cerebral cortex.

    Science.gov (United States)

    Moodley, Kogie; Botha, Julia; Raidoo, Deshandra Munsamy; Naidoo, Strinivasen

    2011-03-15

    Expression of thyroid-stimulating hormone receptor (TSH-R) has been demonstrated in adipocytes, lymphocytes, bone, kidney, heart, intestine and rat brain. Immuno-reactive TSH-R has been localised in rat brain and human embryonic cerebral cortex but not in adult human brain. We designed a pilot study to determine whether anti-thyroid auto-antibodies immuno-localise in normal adult human cerebral cortex. Forensic samples from the frontal, motor, sensory, occipital, cingulate and parieto-occipito-temporal association cortices were obtained from five individuals who had died of trauma. Although there were no head injuries, the prior psychiatric history of patients was unknown. The tissues were probed with commercial antibodies against both human TSH-R and human thyroglobulin (TG). Anti-TSH-R IgG immuno-localised to cell bodies and axons of large neurones in all 6 regions of all 5 brains. The intensity and percentage of neurones labelled were similar in all tissue sections. TSH-R immuno-label was also observed in vascular endothelial cells in the cingulate gyrus. Although also found in all 5 brains and all six cortical regions, TG localised exclusively in vascular smooth muscle cells and not on neurones. Although limited by the small sample size and number of brain areas examined, this is the first study describing the presence of antigenic targets for anti-TSH-R IgG on human cortical neurons, and anti-TG IgG in cerebral vasculature. PMID:21196016

  13. Localisation of Sensor Nodes with Hybrid Measurements in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Muhammad W. Khan

    2016-07-01

    Full Text Available Localisation in wireless networks faces challenges such as high levels of signal attenuation and unknown path-loss exponents, especially in urban environments. In response to these challenges, this paper proposes solutions to localisation problems in noisy environments. A new observation model for localisation of static nodes is developed based on hybrid measurements, namely angle of arrival and received signal strength data. An approach for localisation of sensor nodes is proposed as a weighted linear least squares algorithm. The unknown path-loss exponent associated with the received signal strength is estimated jointly with the coordinates of the sensor nodes via the generalised pattern search method. The algorithm’s performance validation is conducted both theoretically and by simulation. A theoretical mean square error expression is derived, followed by the derivation of the linear Cramer-Rao bound which serves as a benchmark for the proposed location estimators. Accurate results are demonstrated with 25%–30% improvement in estimation accuracy with a weighted linear least squares algorithm as compared to linear least squares solution.

  14. Growth patterns in Onychophora (velvet worms: lack of a localised posterior proliferation zone

    Directory of Open Access Journals (Sweden)

    Landman Kerry A

    2010-11-01

    Full Text Available Abstract Background During embryonic development of segmented animals, body segments are thought to arise from the so-called "posterior growth zone" and the occurrence of this "zone" has been used to support the homology of segmentation between arthropods, annelids, and vertebrates. However, the term "posterior growth zone" is used ambiguously in the literature, mostly referring to a region of increased proliferation at the posterior end of the embryo. To determine whether such a localised posterior proliferation zone is an ancestral feature of Panarthropoda (Onychophora + Tardigrada + Arthropoda, we examined cell division patterns in embryos of Onychophora. Results Using in vivo incorporation of the DNA replication marker BrdU (5-bromo-2'-deoxyuridine and anti-phospho-histone H3 immunolabelling, we found that a localised posterior region of proliferating cells does not occur at any developmental stage in onychophoran embryos. This contrasts with a localised pattern of cell divisions at the posterior end of annelid embryos, which we used as a positive control. Based on our data, we present a mathematical model, which challenges the paradigm that a localised posterior proliferation zone is necessary for segment patterning in short germ developing arthropods. Conclusions Our findings suggest that a posterior proliferation zone was absent in the last common ancestor of Onychophora and Arthropoda. By comparing our data from Onychophora with those from annelids, arthropods, and chordates, we suggest that the occurrence of a "posterior growth zone" currently cannot be used to support the homology of segmentation between these three animal groups.

  15. How active ingredient localisation in plant tissues determines the targeted pest spectrum of different chemistries

    DEFF Research Database (Denmark)

    Buchholz, Anke; Trapp, Stefan

    2016-01-01

    information sets revealed that the intracellular localisation of active ingredients determines the performance of test compounds against different target pests because of different feeding behaviours: mites feed on mesophyll, and aphids and whiteflies mostly in the vascular system. Polar compounds have a slow...

  16. Globalisation and Localisation in Music Education in Hong Kong and Taiwan

    Science.gov (United States)

    Ho, Wai-Chung

    2013-01-01

    The purpose of the study is to analyse and discuss the influences of globalisation and localisation on music education in Hong Kong and Taiwan. It argues that the reform of music education concerns changes to the contents of the curriculum that envisage the cultural and political developments that arise from processes of globalisation and…

  17. Semi-Classical Localisation Properties of Quantum Oscillators on a Noncommutative Configuration Space

    Science.gov (United States)

    Benatti, Fabio; Gouba, Laure

    2015-11-01

    When dealing with the classical limit of two quantum mechanical oscillators on a noncommutative configuration space, the limits corresponding to the removal of configuration-space noncommutativity and position-momentum noncommutativity do not commute. We address this behaviour from the point of view of the phase-space localisation properties of the Wigner functions of coherent states under the two limits.

  18. Quantum resonance, Anderson localisation and selective rotational excitation in periodically kicked molecules

    Directory of Open Access Journals (Sweden)

    Averbukh I. Sh.

    2013-03-01

    Full Text Available We show that molecules kicked periodically by laser pulses currently used in molecular alignment experiments allow to observe effects of the periodically kicked quantum rotor in a real rotational system. Among these effects are Anderson localisation in angular momentum and the scaling of the quantum resonance. Based on this, we propose a new scheme for selective molecular rotational excitation.

  19. Localisation of Sensor Nodes with Hybrid Measurements in Wireless Sensor Networks.

    Science.gov (United States)

    Khan, Muhammad W; Salman, Naveed; Kemp, Andrew H; Mihaylova, Lyudmila

    2016-01-01

    Localisation in wireless networks faces challenges such as high levels of signal attenuation and unknown path-loss exponents, especially in urban environments. In response to these challenges, this paper proposes solutions to localisation problems in noisy environments. A new observation model for localisation of static nodes is developed based on hybrid measurements, namely angle of arrival and received signal strength data. An approach for localisation of sensor nodes is proposed as a weighted linear least squares algorithm. The unknown path-loss exponent associated with the received signal strength is estimated jointly with the coordinates of the sensor nodes via the generalised pattern search method. The algorithm's performance validation is conducted both theoretically and by simulation. A theoretical mean square error expression is derived, followed by the derivation of the linear Cramer-Rao bound which serves as a benchmark for the proposed location estimators. Accurate results are demonstrated with 25%-30% improvement in estimation accuracy with a weighted linear least squares algorithm as compared to linear least squares solution. PMID:27455268

  20. Localisation of brain functions : stimuling brain activity and source reconstruction for classification/

    OpenAIRE

    Noirhomme, Quentin

    2006-01-01

    A key issue in understanding how the brain functions is the ability to correlate functional information with anatomical localisation. Functional information can be provided by a variety of techniques like positron emission tomography (PET), functional MRI (fMRI), electroencephalography (EEG), magnetoencephalography (MEG) or transcranial magnetic stimulation (TMS). All these methods provide different, but complementary, information about the functional areas of the brain. ...

  1. In vivo fluorescence kinetics and localisation of aluminium phthalocyanine disulphonate in an autologous tumour model

    NARCIS (Netherlands)

    Witjes, MJH; Speelman, OC; Nikkels, PGJ; Nooren, CAAM; Nauta, JM; vanderHolt, B; vanLeengoed, HLLM; Roodenburg, JLN

    1996-01-01

    Sulphonated phthalocyanines are studied as photosensitisers for photodynamic therapy of cancer. Their strong fluorescence and tumour-localising properties make them also potentially useful for detection of cancer by fluorescence. For this purpose, we have studied the fluorescence kinetics and locali

  2. Localisation of Sensor Nodes with Hybrid Measurements in Wireless Sensor Networks †

    Science.gov (United States)

    Khan, Muhammad W.; Salman, Naveed; Kemp, Andrew H.; Mihaylova, Lyudmila

    2016-01-01

    Localisation in wireless networks faces challenges such as high levels of signal attenuation and unknown path-loss exponents, especially in urban environments. In response to these challenges, this paper proposes solutions to localisation problems in noisy environments. A new observation model for localisation of static nodes is developed based on hybrid measurements, namely angle of arrival and received signal strength data. An approach for localisation of sensor nodes is proposed as a weighted linear least squares algorithm. The unknown path-loss exponent associated with the received signal strength is estimated jointly with the coordinates of the sensor nodes via the generalised pattern search method. The algorithm’s performance validation is conducted both theoretically and by simulation. A theoretical mean square error expression is derived, followed by the derivation of the linear Cramer-Rao bound which serves as a benchmark for the proposed location estimators. Accurate results are demonstrated with 25%–30% improvement in estimation accuracy with a weighted linear least squares algorithm as compared to linear least squares solution. PMID:27455268

  3. Characterisation of a novel proteolytic enzyme localised to goblet cells in rat and man

    DEFF Research Database (Denmark)

    Poulsen, Steen Seier

    1984-01-01

    A proteolytic enzyme, ingobsin , purified from rat duodenal extracts is shown to be localised to intestinal goblet cells of both man and rat. Enzyme positive cells decrease in number from duodenum to colon. The enzyme is a 33 000 Mr protein with an isoelectric point of 5.1. The pH optimum for...

  4. Local characterisation of fluid flow in sandstone with localised deformation features through fast neutron imaging

    Directory of Open Access Journals (Sweden)

    Rowe S.

    2010-06-01

    Full Text Available Understanding fluid flow through rocks is of key interest in hydrocarbon production and CO2 sequestration, amongst other applications. Such fluid injection or extraction from subsurface reservoirs can be significantly modified (increased or decreased by deformation and in particular by localised deformation features (fractures, shear bands and compaction bands. How such deformation alters fluid flow is however not well characterised experimentally. Measurement of fluid-flow distributions throughout a specimen requires techniques that can, first, see inside a test specimen and, second, see the fluid distinctly from the solid part. Therefore, neutron absorption imaging is well adapted to fluid flow monitoring in rocks as water is largely opaque to neutrons (i.e., it is highly absorbing and rocks are generally less absorbing. In this paper we present initial results of neutron radiography monitoring of fluid-flow through samples of a sandstone containing localised deformation features (shear-bands. A comparison of flow through an intact specimen and flow through samples containing localised deformation features is presented that provides insight into the effect of localised deformation on the flow properties.

  5. Restriction of Helmholtz Model

    Directory of Open Access Journals (Sweden)

    V.M. Polunin

    2014-07-01

    Full Text Available The results of the experimental studies of physical mechanisms of energy dissipation in the oscillating system in which air cavity held by the forces of magnetic levitation is used as the elastic element, and magnetic fluid prepared on the basis of dispersing media with different viscosity level is used as the inertial element are considered in the article. Based on the obtained results the conclusion on the restriction of the applicability of Helmholtz equation, caused by boundary effects is made.

  6. License restrictions at Barnwell

    Energy Technology Data Exchange (ETDEWEB)

    Autry, V.R. [S.C. Dept. of Health and Environmental Control, Columbia, SC (United States). Bureau of Radiological Health

    1991-12-31

    The State of South Carolina was delegated the authority by the US Nuclear Regulatory Commission to regulate the receipt, possession, use and disposal of radioactive material as an Agreement State. Since 1970, the state has been the principal regulatory authority for the Barnwell Low-Level Waste Disposal Facility operated by Chem-Nuclear Systems, Inc. The radioactive material license issued authorizing the receipt and disposal of low-level waste contains numerous restrictions to ensure environmental protection and compliance with shallow land disposal performance criteria. Low-level waste has evolved from minimally contaminated items to complex waste streams containing high concentrations of radionuclides and processing chemicals which necessitated these restrictions. Additionally, some waste with their specific radionuclides and concentration levels, many classified as low-level radioactive waste, are not appropriate for shallow land disposal unless additional precautions are taken. This paper will represent a number of these restrictions, the rationale for them, and how they are being dealt with at the Barnwell disposal facility.

  7. Strain field of a buried oxide aperture

    Science.gov (United States)

    Kießling, F.; Niermann, T.; Lehmann, M.; Schulze, J.-H.; Strittmatter, A.; Schliwa, A.; Pohl, U. W.

    2015-02-01

    The strain field of an AlOx current aperture, fabricated by selective oxidation of an AlAs/GaAs layer buried in a circular GaAs mesa, is studied. Components of the strain tensor for a thin cross-section lamella cut out of such a structure are evaluated from dark-field electron holography, proving the validity of simulations based on linear elasticity. Simulation of the entire structure is utilized to prepare mesa surfaces with tailored strain fields for controlling the nucleation site of InGaAs quantum dots. The experimental proof of strain simulations allows estimating the magnitude of piezoelectricity, yielding for the studied mesa structures a piezoelectric potential up to 50 mV.

  8. Wind energy applications of synthetic aperture radar

    DEFF Research Database (Denmark)

    Badger, Merete

    planning as a supplement to on site measurements, which are costly and sparse, and model wind fields, which are not fully validated. Two applications of SAR measurements in offshore wind energy planning areaddressed here: the study of wind farm wake effects and the potential of using SAR winds in offshore......Synthetic aperture radars (SAR), mounted on satellites or aircraft, have proven useful for ocean wind mapping. Wind speeds at the height 10 m may be retrieved from measurements of radar backscatter using empirical model functions. The resulting windfields are valuable in offshore wind energy...... offshore wind resource assessment isinvestigated. The resource assessment is made through Weibull fitting to frequency observations of wind speed and requires at least 100 satellite observations per year for a given site of interest. Predictions of the energy density are very sensitive tothe wind speed and...

  9. Synthetic aperture tissue and flow ultrasound imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav

    simultaneously at every emission, which makes it possible to average over a large number of lines. This makes stationary echo canceling easier and significantly improves the velocity estimates. Only 8 emissions per plane are necessary to create the color flow map. Scanning 12 cm in depth, up to 800 planes can be......This Ph.D. project was carried out at the Center for Fast Ultrasound Imaging, Technical University of Denmark. The goal was to improve existing imaging techniques in order to make them suitable for real-time three-dimensional ultrasound scanning. This dissertation focuses on the synthetic aperture...... and beamformation methods are adequate for the imaging modalities in clinical use - the B-mode imaging of tissue structures, and the color mapping of blood flow. The acquisition time, however, is too long, and these methods fail to perform real-time three-dimensional scans. The synthetic transmit...

  10. Mathematical Problems in Synthetic Aperture Radar

    CERN Document Server

    Klein, Jens

    2010-01-01

    This thesis is concerned with problems related to Synthetic Aperture Radar (SAR). The thesis is structured as follows: The first chapter explains what SAR is, and the physical and mathematical background is illuminated. The following chapter points out a problem with a divergent integral in a common approach and proposes an improvement. Numerical comparisons are shown that indicate that the improvements allow for a superior image quality. Thereafter the problem of limited data is analyzed. In a realistic SAR-measurement the data gathered from the electromagnetic waves reflected from the surface can only be collected from a limited area. However the reconstruction formula requires data from an infinite distance. The chapter gives an analysis of the artifacts which can obscure the reconstructed images due to this problem. Additionally, some numerical examples are shown that point to the severity of the problem. In chapter 4 the fact that data is available only from a limited area is used to propose a new invers...

  11. Ultrasonic synthetic aperture imaging of defects

    International Nuclear Information System (INIS)

    Current reactor systems have been generally designed with limited facility for in-service inspection. Where ultrasonic crack detection and sizing techniques have been applied they appear to be functioning adequately. The purpose of this paper is to introduce a modification to conventional ultrasonic defect sizing which yields acoustic measurements of the dimensions of the defect in its plane parallel to the inspection surface. The technique retains the simplicity of a single probe to collect data, but achieves the effect of multidepth focussing by a particular signal processing procedure. The subject is discussed under the headings: ultrasonic focussing procedures; the basic principle of linear synthetic aperture focussing; the mechanics of the system; the capability of the system; comments and conclusion. (U.K.)

  12. High Contrast Imaging with an Arbitrary Aperture: Active Correction of Aperture Discontinuities

    CERN Document Server

    Pueyo, Laurent

    2012-01-01

    We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of Deformable Mirror Surfaces that yield high contrast Point Spread Functions is not linear, and non-linear methods are needed to find the true minimum in the optimization topology. We solve the highly non-linear Monge-Ampere equation that is the fundamental equation describing the physics of phase induced amplitude modulation. We determine the optimum configuration for our two sequential Deformable Mirror system and show that high-throughput and high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries si...

  13. Operational Ship Monitoring System Based on Synthetic Aperture Radar Processing

    Directory of Open Access Journals (Sweden)

    Antonio Tabasco

    2009-08-01

    Full Text Available This paper presents a Ship Monitoring System (SIMONS working with Synthetic Aperture Radar (SAR images. It is able to infer ship detection and classification information, and merge the results with other input channels, such as polls from the Automatic Identification System (AIS. Two main stages can be identified, namely: SAR processing and data dissemination. The former has three independent modules, which are related to Coastline Detection (CD, Ship Detection (SD and Ship Classification (SC. The later is solved via an advanced web interface, which is compliant with the OpenSource standards fixed by the Open Geospatial Consortium (OGC. SIMONS has been designed to be a modular, unsupervised and reliable system that meets Near-Real Time (NRT delivery requirements. From data ingestion to product delivery, the processing chain is fully automatic accepting ERS and ENVISAT formats. SIMONS has been developed by GMV Aerospace, S.A. with three main goals, namely: 1 To limit the dependence on the ancillary information provided by systems such as AIS. 2 To achieve the maximum level of automatism and restrict human manipulation. 3 To limit the error sources and their propagation. Spanish authorities have validated SIMONS. The results have been satisfactory and have confirmed that the system is useful for improving decision making. For single-polarimetric images with a resolution of 30 m, SIMONS permits the location of ships larger than 40 m with a classification ratio around 50% of positive matches. These values are expected to be improved with SAR data from new sensors. In the paper, the performance of SD and SC modules is assessed by cross-check of SAR data with AIS reports.

  14. Shadow Enhancement in Synthetic Aperture Sonar Using Fixed Focusing

    NARCIS (Netherlands)

    Groen, J.; Hansen, R.E.; Callow, H.J.; Sabel, J.C.; Sæbø, T.O.

    2009-01-01

    Abstract—A shadow cast by an object on the seafloor is important information for target recognition in synthetic aperture sonar (SAS) images. Synthetic aperture imaging causes a fundamental limitation to shadow clarity because the illuminator is moved during the data collection. This leads to a blen

  15. Increasing the Dynamic Range of Synthetic Aperture Vector Flow Imaging

    DEFF Research Database (Denmark)

    Villagómez Hoyos, Carlos Armando; Stuart, Matthias Bo; Jensen, Jørgen Arendt

    2014-01-01

    presented using synthetic aperture which increases the frame-to-frame signal correlation of the scatterer displacement while providing continuous data. In this paper, recursive synthetic aperture acquisition, directional beamforming, and cross-correlation are used to produce B-mode and vector velocity...

  16. Synthetic Aperture Sequential Beamformation applied to medical imaging

    DEFF Research Database (Denmark)

    Hemmsen, Martin Christian; Hansen, Jens Munk; Jensen, Jørgen Arendt

    2012-01-01

    Synthetic Aperture Sequential Beamforming (SASB) is applied to medical ultrasound imaging using a multi element convex array transducer. The main motivation for SASB is to apply synthetic aperture techniques without the need for storing RF-data for a number of elements and hereby devise a system...

  17. Velocity estimation using synthetic aperture imaging [blood flow

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2001-01-01

    Presented an approach for synthetic aperture blood flow ultrasound imaging. Estimates with a low bias and standard deviation can be obtained with as few as eight emissions. The performance of the new estimator is verified using both simulations and measurements. The results demonstrate that a fully...... functioning synthetic aperture scanner can be made...

  18. Apparatus and method for velocity estimation in synthetic aperture imaging

    DEFF Research Database (Denmark)

    2003-01-01

    The invention relates to an apparatus for flow estimation using synthetic aperture imaging. The method uses a Synthetic Transmit Aperture, but unlike previous approaches a new frame is created after every pulse emission. In receive mode parallel beam forming is implemented. The beam formed RF data...

  19. Second harmonic imaging using synthetic aperture sequential beamforming

    DEFF Research Database (Denmark)

    Du, Yigang; Rasmussen, Joachim; Jensen, Henrik;

    2011-01-01

    The paper investigates Second Harmonic Imaging (SHI) using Synthetic Aperture Sequential Beamforming (SASB). The investigation is made by an experimental Synthetic Aperture Real-time Ultrasound System (SARUS). A linear array transducer is used to scan 4 wires at the image depths of f22.5, 47.5, 72...

  20. Velocity estimation using synthetic aperture imaging [blood flow

    OpenAIRE

    Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2001-01-01

    Presented an approach for synthetic aperture blood flow ultrasound imaging. Estimates with a low bias and standard deviation can be obtained with as few as eight emissions. The performance of the new estimator is verified using both simulations and measurements. The results demonstrate that a fully functioning synthetic aperture scanner can be made

  1. The nature of carrier localisation in polar and nonpolar InGaN/GaN quantum wells

    Science.gov (United States)

    Dawson, P.; Schulz, S.; Oliver, R. A.; Kappers, M. J.; Humphreys, C. J.

    2016-05-01

    In this paper, we compare and contrast the experimental data and the theoretical predictions of the low temperature optical properties of polar and nonpolar InGaN/GaN quantum well structures. In both types of structure, the optical properties at low temperatures are governed by the effects of carrier localisation. In polar structures, the effect of the in-built electric field leads to electrons being mainly localised at well width fluctuations, whereas holes are localised at regions within the quantum wells, where the random In distribution leads to local minima in potential energy. This leads to a system of independently localised electrons and holes. In nonpolar quantum wells, the nature of the hole localisation is essentially the same as the polar case but the electrons are now coulombically bound to the holes forming localised excitons. These localisation mechanisms are compatible with the large photoluminescence linewidths of the polar and nonpolar quantum wells as well as the different time scales and form of the radiative recombination decay curves.

  2. Subcellular localisation of Medicago truncatula 9/13-hydroperoxide lyase reveals a new localisation pattern and activation mechanism for CYP74C enzymes

    Directory of Open Access Journals (Sweden)

    Hughes Richard K

    2007-11-01

    Full Text Available Abstract Background Hydroperoxide lyase (HPL is a key enzyme in plant oxylipin metabolism that catalyses the cleavage of polyunsaturated fatty acid hydroperoxides produced by the action of lipoxygenase (LOX to volatile aldehydes and oxo acids. The synthesis of these volatile aldehydes is rapidly induced in plant tissues upon mechanical wounding and insect or pathogen attack. Together with their direct defence role towards different pathogens, these compounds are believed to play an important role in signalling within and between plants, and in the molecular cross-talk between plants and other organisms surrounding them. We have recently described the targeting of a seed 9-HPL to microsomes and putative lipid bodies and were interested to compare the localisation patterns of both a 13-HPL and a 9/13-HPL from Medicago truncatula, which were known to be expressed in leaves and roots, respectively. Results To study the subcellular localisation of plant 9/13-HPLs, a set of YFP-tagged chimeric constructs were prepared using two M. truncatula HPL cDNAs and the localisation of the corresponding chimeras were verified by confocal microscopy in tobacco protoplasts and leaves. Results reported here indicated a distribution of M.truncatula 9/13-HPL (HPLF between cytosol and lipid droplets (LD whereas, as expected, M.truncatula 13-HPL (HPLE was targeted to plastids. Notably, such endocellular localisation has not yet been reported previously for any 9/13-HPL. To verify a possible physiological significance of such association, purified recombinant HPLF was used in activation experiments with purified seed lipid bodies. Our results showed that lipid bodies can fully activate HPLF. Conclusion We provide evidence for the first CYP74C enzyme, to be targeted to cytosol and LD. We also showed by sedimentation and kinetic analyses that the association with LD or lipid bodies can result in the protein conformational changes required for full activation of the enzyme

  3. Coded Aperture Imaging for Fluorescent X-rays-Biomedical Applications

    Energy Technology Data Exchange (ETDEWEB)

    Haboub, Abdel; MacDowell, Alastair; Marchesini, Stefano; Parkinson, Dilworth

    2013-06-01

    Employing a coded aperture pattern in front of a charge couple device pixilated detector (CCD) allows for imaging of fluorescent x-rays (6-25KeV) being emitted from samples irradiated with x-rays. Coded apertures encode the angular direction of x-rays and allow for a large Numerical Aperture x- ray imaging system. The algorithm to develop the self-supported coded aperture pattern of the Non Two Holes Touching (NTHT) pattern was developed. The algorithms to reconstruct the x-ray image from the encoded pattern recorded were developed by means of modeling and confirmed by experiments. Samples were irradiated by monochromatic synchrotron x-ray radiation, and fluorescent x-rays from several different test metal samples were imaged through the newly developed coded aperture imaging system. By choice of the exciting energy the different metals were speciated.

  4. Microfabricated high-bandpass foucault aperture for electron microscopy

    Science.gov (United States)

    Glaeser, Robert; Cambie, Rossana; Jin, Jian

    2014-08-26

    A variant of the Foucault (knife-edge) aperture is disclosed that is designed to provide single-sideband (SSB) contrast at low spatial frequencies but retain conventional double-sideband (DSB) contrast at high spatial frequencies in transmission electron microscopy. The aperture includes a plate with an inner open area, a support extending from the plate at an edge of the open area, a half-circle feature mounted on the support and located at the center of the aperture open area. The radius of the half-circle portion of reciprocal space that is blocked by the aperture can be varied to suit the needs of electron microscopy investigation. The aperture is fabricated from conductive material which is preferably non-oxidizing, such as gold, for example.

  5. Synthetic aperture radar imaging with motion estimation and autofocus

    International Nuclear Information System (INIS)

    We introduce from first principles a synthetic aperture radar (SAR) imaging and target motion estimation method that is combined with compensation for radar platform trajectory perturbations. The main steps of the method are (a) segmentation of the data into properly calibrated small apertures, (b) motion or platform trajectory perturbation estimation using the Wigner transform and the ambiguity function of the data in a complementary way and (c) combination of small aperture estimates and construction of high-resolution images over wide apertures. The analysis provides quantitative criteria for implementing the aperture segmentation and the parameter estimation process. X-band persistent surveillance SAR is a specific application that is covered by our analysis. Detailed numerical simulations illustrate the robust applicability of the theory and validate the theoretical resolution analysis. (paper)

  6. Do Economic Restrictions Improve Forecasts?

    OpenAIRE

    Murphy, Elizabeth A.; Norwood, F. Bailey; Wohlgenant, Michael K.

    2003-01-01

    A previous study showed that imposing economic restrictions improves the forecasting ability of food demand systems, thus warranting their use even when they are rejected in-sample. This article evaluates whether this result is due to economic restrictions enhancing degrees of freedom or containing nonsample information. Results indicate that restrictions improve forecasting ability even when they are not derived from economic theory, but theoretical restrictions forecast best.

  7. Deconfinement from action restriction

    International Nuclear Information System (INIS)

    The effect of restricting the plaquette to be greater than a certain cutoff value is studied. The action considered is the standard Wilson action with the addition of a plaquette restriction, which should not affect the continuum limit of the theory. In this investigation, the strong coupling limit is also taken. It is found that a deconfining phase transition occurs as the cutoff is increased, on all lattices studied (up to 204). The critical cutoff on the infinite lattice appears to be around 0.55. For cutoffs above this, a fixed point behavior is observed in the normalized fourth cumulant of the Polyakov loop, suggesting the existence of a line of critical points corresponding to a massless gluon phase, not unlike the situation in compact U(1). The Polyakov loop susceptibility also appears to be diverging with lattice size at these cutoffs. A strong finite volume behavior is observed in the pseudo-specific heat. It is discussed whether these results could still be consistent with the standard crossover picture which precludes the existence of a deconfining phase transition on an infinite symmetric lattice. (orig.)

  8. 47 CFR 25.134 - Licensing provisions of Very Small Aperture Terminal (VSAT) and C-band Small Aperture Terminal...

    Science.gov (United States)

    2010-10-01

    ... Terminal (VSAT) and C-band Small Aperture Terminal (CSAT) networks. 25.134 Section 25.134 Telecommunication...) and C-band Small Aperture Terminal (CSAT) networks. (a)(1) VSAT networks operating in the 12/14 GHz bands. All applications for digital VSAT networks granted on or before September 15, 2005, with...

  9. Phase retrieval from a high-numerical-aperture intensity distribution by use of an aperture-array filter.

    Science.gov (United States)

    Nakajima, Nobuharu

    2009-10-01

    Almost all noninterferometric phase-retrieval methods used in coherent diffractive imaging have been based on the measurement system with low numerical aperture, in which Fresnel or Fraunhofer approximation is valid to express the wave propagation between an object and a detector. In microscopy, which is a typical application of coherent diffractive imaging, the measurement of the diffraction intensity with high numerical aperture is required for object reconstruction at high spatial resolution. We here propose an extension procedure to apply the previous phase-retrieval method using an aperture-array filter [J. Opt. Soc. Am. A25, 742 (2008)] to the system with high numerical aperture, in which the first Rayleigh-Sommerfeld integral for spherical waves is utilized instead of the Fresnel integral for parabolic waves. Computer-simulated examples in the high-numerical-aperture system demonstrate object reconstruction at high lateral resolution and retrieval of information in the depth direction of an object. PMID:19798394

  10. Stereoscopic full aperture imaging in nuclear medicine

    Directory of Open Access Journals (Sweden)

    Sergio G. Strocovsky

    2011-06-01

    Full Text Available Images of planar scintigraphy and single photon emission computerized tomography (SPECT used in nuclear medicine are often low quality. They usually appear to be blurred and noisy. This problem is due to the low spatial resolution and poor sensitivity of the acquisition technique with the gamma camera (GC. Other techniques, such as coded aperture imaging (CAI reach higher spatial resolutions than GC. However, CAI is not frequently used for imaging in nuclear medicine, due to the decoding complexity of some images and the difficulty in controlling the noise magnitude. Summing up, the images obtained through GC are low quality and it is still difficult to implement CAI technique. A novel technique, full aperture Imaging (FAI, also uses gamma ray-encoding to obtain images, but the coding system and the method of images reconstruction are simpler than those used in CAI. In addition, FAI also reaches higher spatial resolution than GC. In this work, the principles of FAI technique and the method of images reconstruction are explained in detail. The FAI technique is tested by means of Monte Carlo simulations with filiform and spherical sources. Spatial resolution tests of GC versus FAI were performed using two different source-detector distances. First, simulations were made without interposing any material between the sources and the detector. Then, other more realistic simulations were made. In these, the sources were placed in the centre of a rectangular prismatic region, filled with water. A rigorous comparison was made between GC and FAI images of the linear filiform sources, by means of two methods: mean fluence profile graphs and correlation tests. Finally, three-dimensional capacity of FAI was tested with two spherical sources. The results show that FAI technique has greater sensitivity (>100 times and greater spatial resolution (>2.6 times than that of GC with LEHR collimator, in both cases, with and without attenuating material and long and

  11. X-ray lenses with large aperture

    International Nuclear Information System (INIS)

    Up to now, most X-ray imaging setups are based on absorption contrast imaging. There is a demand for focused X-rays in many X-ray analysis applications, either to increase the resolution of an imaging system, or, to reduce the time effort of an experiment through higher photon flux. For photon energies higher than 15 keV refractive X-ray optics are more efficient in comparison to non-refractive X-ray optics. The aim of this work was to develop X-ray lenses with large apertures and high transparency. By increasing the number of refracting surfaces while removing unnecessary lens material such lenses have been developed. Utilizing this approach the overall beam deflection angle is large with respect to the lens material it propagates through and so the transparency of the lens is increased. Within this work, X-ray lenses consisting of several thousands of prisms with an edge length in the range of micrometers have been developed and fabricated by deep X-ray lithography. Deep X-ray lithography enables high precision microstrucures with smooth sidewalls and large aspect ratios. The aperture of high-transparency X-ray lenses made this way is greater than 1 mm. They are suitable for photon energies in the range of 8 keV to 24 keV and offer a focal width of smaller than 10 μm at a transparency of around 40%. Furthermore, rolled X-ray lenses have been developed, that are made out of a microstructured polyimide film, which is cut according to the requirements regarding focal length and photon energy. The microstructured film is fabricated by molding, using an anisotropically etched silicon wafer as molding tool. Its mean roughness is in the range of nanometers. The film features prismatic structures, its surface topology is similar to an asparagus field. The measured diameter of the point focus was 18 μm to 31 μm, the calculated opticla efficiency was 37%. Future work will concentrate on increasing the aspect ratio of Prism Lenses and on increasing the rolling accuracy

  12. An investigation into a suitable scintillator for localising neutron capture within a detector

    International Nuclear Information System (INIS)

    Using Monte-Carlo modelling, an investigation into a suitable loaded scintillator for localising neutron capture in a novel neutron survey meter has been undertaken. A comparison of estimated neutron capture location in a scintillator with Geant4 and MCNP simulations was undertaken and a good general agreement between the two models was observed. The interactions of γ emissions from neutron capture in the scintillator are investigated. The results show that the γ emission from neutron capture will not aid neutron capture localisation and will only inhibit it. It is observed that the lithium-loaded scintillator has the lowest neutron capture efficiency when compared with boron and gadolinium scintillators. However, it is the most promising of the detectors investigated in this research for use in a novel neutron survey meter design

  13. Critical Factors in Transnational Oil Companies Localisation Decisions - Clusters and Portfolio Optimisation

    International Nuclear Information System (INIS)

    Enhanced understanding of the factors determining trans national companies' localisation decisions is important for regulators and other stake holders concerned about maintaining current activity levels in a petroleum producing country. This article discusses localisation decisions in the context of theories of industrial clusters and real portfolio optimisation theory (materiality), which we argue are two fruitful lines of explanation for trans national companies' behaviour. The industrial cluster literature is concerned about the level of positive externalities associated with geographic clustering of related production activities. The concept of materiality, implying that investment projects in an oil province must be of a certain minimum size in order to be interesting for oil companies, is evaluated empirically and compared to predictions of mainstream economic theory. (author)

  14. THE PERITONEAL HYDATIC CYST – THE RARE PRIMARY LOCALISATION. CASE REPORT

    Directory of Open Access Journals (Sweden)

    L. Dubei

    2010-05-01

    Full Text Available Primary peritoneal localisation of hydatic cyst is exceptional, because the first filter is the liver, the second is the lung and disemination is realised by haematogen way. Another particular situation is the breaking of univesicular hydatic cyst with migration of intact proligera and inseminations of Douglas peritoneum. In this last case is a not true primitive peritoneal localisation. We present a case of a 30 years old patient who comes to physician for hypogastric pains, polakiuria, disuria, rectal tenesma and “pencil-like” stools. Physical examination revealed an abdominal tumor in the hipogastrum and extrinsic compression of rectum superior at the rectal tact. An abdominal ultrasound scan showed a large cystic mass in the pelvis and bilateral ureterohidronefrosis. We realized an open intervention and found and resolved a hydatic cyst of Douglas recessus. The optimal approach – laparoscopic - was not possible because of technical conditions and the desire of patient.

  15. Critical Factors in Transnational Oil Companies Localisation Decisions - Clusters and Portfolio Optimisation

    Energy Technology Data Exchange (ETDEWEB)

    Kind, Hans Jarle; Osmundsen, Petter; Tverteraas, Ragnar

    2001-10-01

    Enhanced understanding of the factors determining transnational companies' localisation decisions is important for regulators and other stakeholders concerned about maintaining current activity levels in a petroleum producing country. This article discusses localisation decisions in the context of theories of industrial clusters and real portfolio optimisation theory (materiality), which we argue are two fruitful lines of explanation for transnational companies' behaviour. The industrial cluster literature is concerned about the level of positive externalities associated with geographic clustering of related production activities. The concept of materiality, implying that investment projects in an oil province must be of a certain minimum size in order to be interesting for oil companies, is evaluated empirically and compared to predictions of mainstream economic theory. (author)

  16. Numerical modelling of bifurcation and localisation in cohesive-frictional materials

    Science.gov (United States)

    de Borst, René

    1991-12-01

    Methods are reviewed for analysing highly localised failure and bifurcation modes in discretised mechanical systems as typically arise in numerical simulations of failure in soils, rocks, metals and concrete. By the example of a plane-strain biaxial test it is shown that strain softening and lack of normality in elasto-plastic constitutive equations and the ensuing loss of ellipticity of the governing field equations cause a pathological mesh dependence of numerical solutions for such problems, thus rendering the results effectively meaningless. The need for introduction of higher-order continuum models is emphasised to remedy this shortcoming of the conventional approach. For one such a continuum model, namely the unconstrained Cosserat continuum, it is demonstrated that meaningful and convergent solutions (in the sense that a finite width of the localisation zone is computed upon mesh refinement) can be obtained.

  17. CONGENITAL LOCALISED ABSENCE OF SKIN (BART’S SYNDROME RARE CASE REPORT

    Directory of Open Access Journals (Sweden)

    Garima

    2014-12-01

    Full Text Available It is defined as congenital localised absence of skin associated with epidermolysis bullosa. It may be associated with any type of epidermolysis bullosa. Three cutaneous manifestation are characteristics of Bart syndrome: congenital localised absence of skin (CLAS, mucocutaneous blistering and nail abnormalities. It present as raw beefy areas of denuded skin on trauma prone site; extremity like hands and feet, also perioral area. Diagnosis is obvious clinically but requires ultrastructural microscopy. We describe here a case of newborn baby in our OPD who presented with raw beefy red areas of denuded skin on the hands, feet, neck area with few flaccid bulla near thigh. The patient was treated with antibiotic and steroid (fusidic acid + hydrocortisone cream and emollients. Thus, Clinical appearance was sufficiently distinct to suggest the diagnosis of Bart’s syndrome.

  18. Bringing order through disorder: Localisation of errors in topological quantum memories

    CERN Document Server

    Wootton, James R

    2011-01-01

    The ability to reliably store quantum states is an essential element for any task in quantum information. Topological systems promise to protect quantum information by topological and energetic considerations. If undesired anyonic excitations are propagated at large distances, either through coherent or probabilistic processes, they can cause logical errors in the topologically encoded information. Here we show that Anderson localisation induced by disorder in the system can successfully protect topological quantum memories from the coherent propagation of anyons. For concreteness we employ the toric code model at zero temperature. It is known that in the absence of a magnetic field it can tolerate a finite initial density of anyonic errors. In the presence of a spurious magnetic field anyonic quantum walks are induced and the tolerable density becomes zero. We demonstrate that disorder in the couplings of the model can successfully localise anyons. This allows the topological quantum memory to tolerate a fin...

  19. Towards quantification of the interplay between strain weakening and strain localisation in granular material

    Science.gov (United States)

    Ritter, Malte C.; Rosenau, Matthias; Leever, Karen; Oncken, Onno

    2014-05-01

    Strain weakening is the major agent of localisation of deformation into shear zones and faults at various scales in brittle media. Physical analogue models using granular material are especially apt to investigate both phenomena, because they are able to reproduce them without the need of any assumptions concerning the physics behind. Several attempts have been made to quantify either strain weakening (e. g. Lohrmann et al., 2003, using Ring-Shear tests) or strain localisation (e. g. Schrank et al., 2008, using a variation of the classical Riedel-experiment). While Ring-Shear tests yield excellent data on strain weakening through measuring shear stress during localisation, they do not allow monitoring the process of strain localisation in-situ because of experimental inaccessibility of the small scale kinematics. In Riedel-type strike-slip experiments, on the other hand, no direct measurements of shear stresses have been available so far. Furthermore, they contain a strong boundary condition in form of a pre-defined linear discontinuity at the base. This forces the formation of Riedel-Shears, i. e. a complex fault system, that makes it difficult to define strain localisation on single faults. We developed a new experimental set-up, in which the formation of a strike-slip shear zone in granular material is induced using an ndenter with stress and strain monitored at high accuracy and resolution. In a first set of experiments we used a horizontal sand layer indented by a vertical wall. The sand layer is laterally unconfined and rests on low-viscosity silicone oil in order to minimize basal shear strength. Compared to the Riedel experiments, this avoids the boundary condition of a pre-existing basal discontinuity allowing one single, hrough-going shear crack to form and propagate. The indenter moves at a constant rate and is equipped with a force sensor that measures the applied push, which integrates over shear stresses along the fault and the base of the sand pack

  20. Modelling impacts and recovery in benthic communities exposed to localised high CO2.

    Science.gov (United States)

    Lessin, Gennadi; Artioli, Yuri; Queirós, Ana M; Widdicombe, Stephen; Blackford, Jerry C

    2016-08-15

    Regulations pertaining to carbon dioxide capture with offshore storage (CCS) require an understanding of the potential localised environmental impacts and demonstrably suitable monitoring practices. This study uses a marine ecosystem model to examine a comprehensive range of hypothetical CO2 leakage scenarios, quantifying both impact and recovery time within the benthic system. Whilst significant mortalities and long recovery times were projected for the larger and longer term scenarios, shorter-term or low level exposures lead to reduced projected impacts. This suggests that efficient monitoring and leak mitigation strategies, coupled with appropriate selection of storage sites can effectively limit concerns regarding localised environmental impacts from CCS. The feedbacks and interactions between physiological and ecological responses simulated reveal that benthic responses to CO2 leakage could be complex. This type of modelling investigation can aid the understanding of impact potential, the role of benthic community recovery and inform the design of baseline and monitoring surveys. PMID:27289279

  1. Photon counting imaging and centroiding with an electron-bombarded CCD using single molecule localisation software

    Science.gov (United States)

    Hirvonen, Liisa M.; Barber, Matthew J.; Suhling, Klaus

    2016-06-01

    Photon event centroiding in photon counting imaging and single-molecule localisation in super-resolution fluorescence microscopy share many traits. Although photon event centroiding has traditionally been performed with simple single-iteration algorithms, we recently reported that iterative fitting algorithms originally developed for single-molecule localisation fluorescence microscopy work very well when applied to centroiding photon events imaged with an MCP-intensified CMOS camera. Here, we have applied these algorithms for centroiding of photon events from an electron-bombarded CCD (EBCCD). We find that centroiding algorithms based on iterative fitting of the photon events yield excellent results and allow fitting of overlapping photon events, a feature not reported before and an important aspect to facilitate an increased count rate and shorter acquisition times.

  2. Localisation of Information and Communication Technologies in Cameroonian Languages and Cultures:Experience and Issues

    Directory of Open Access Journals (Sweden)

    Mathurin Soh

    2015-12-01

    Full Text Available In this paper, we tackle the problem of adapting Information and Communication Technologies (ICTs in local languages of Cameroon. The objectives are to reduce the digital and language divides, and to pave the way for the usage of such technologies to local populations who don’t understand this technological language. We first discuss and highlight several concerns about the localisation of ICTs. Afterwords, we address some challenges and issues to computerize cultural and linguistic features, and indigenous knowledge (IK for national languages and cultures in Cameroon. As case study, we describe our experience in localising an open source editor for the Yemba language, within the of Rural Electronic Schools in African Languages Project. Because Cameroonian languages are based on the same basic alphabet, this qualitative research is extensible to other languages.

  3. MRI of restrictive cardiomyopathy

    International Nuclear Information System (INIS)

    Objective: To evaluate the diagnostic value of MRI in combination of delayed gadolinium-enhanced MR imaging for the identification of restrictive cardiomyopathy (RCM). Methods: One hundred sixteen patients with RCM underwent ECG, thoracic radiography, echocardiography and MRI. The final diagnosis was made on comprehensive evaluation in consideration of patient history, clinical symptoms and imaging appearances. Fifty-five normal subjects were used as the controls. All patients were divided into two groups according to contrast-enhanced MRI patterns: RCM with delayed enhancement (RCM with DE, n=35) and RCM without delayed enhancement (RCM without DE, n=81). Bi-atrial and bi-ventricular size, ventricular septal and left free wall thickness were measured. A paired t-test was used for statistic analysis. Results: Bi-atrial size, right ventricular diastolic diameter (RVDD), ventricular septal and left free wall thickness were significantly larger in RCM patients than in normal subjects (P0.05). Visual observation showed mild mitral regurgitation (50 cases), moderate mitral regurgitation (24 cases ), mild tricuspid regurgitation (32 cases) and severe tricuspid regurgitation (46 cases). Thirty-five RCMs with DE presented diffuse (15 cases) or segmental (20 cases) enhancement. Twelve RCMs with diffuse delayed enhancement showed powdery, enhancement, and 3 showed petaline enhancement. Three cases with powdery enhancement were histologically proven as myocardial amyloidosis. Ventricular septum was the most vulnerable segment in patients with segmental enhancement. Six cases presented subendocardial enhancement that corresponded to apical obliteration, of which one case was confirmed as hypereosinophilia by bone marrow biopsy and the other 14 cases didn't present any regular enhancement. In 81 RCMs without DE, marked bi-atrial dilation, near-normal ventricular chambers and near-normal ventricular thickness were presented. Conclusion: MRI is an excellent imaging modality for

  4. Eyeglass: A Very Large Aperture Diffractive Space Telescope

    Energy Technology Data Exchange (ETDEWEB)

    Hyde, R; Dixit, S; Weisberg, A; Rushford, M

    2002-07-29

    Eyeglass is a very large aperture (25-100 meter) space telescope consisting of two distinct spacecraft, separated in space by several kilometers. A diffractive lens provides the telescope's large aperture, and a separate, much smaller, space telescope serves as its mobile eyepiece. Use of a transmissive diffractive lens solves two basic problems associated with very large aperture space telescopes; it is inherently fieldable (lightweight and flat, hence packagable and deployable) and virtually eliminates the traditional, very tight, surface shape tolerances faced by reflecting apertures. The potential drawback to use of a diffractive primary (very narrow spectral bandwidth) is eliminated by corrective optics in the telescope's eyepiece. The Eyeglass can provide diffraction-limited imaging with either single-band, multiband, or continuous spectral coverage. Broadband diffractive telescopes have been built at LLNL and have demonstrated diffraction-limited performance over a 40% spectral bandwidth (0.48-0.72 {micro}m). As one approach to package a large aperture for launch, a foldable lens has been built and demonstrated. A 75 cm aperture diffractive lens was constructed from 6 panels of 1 m thick silica; it achieved diffraction-limited performance both before and after folding. This multiple panel, folding lens, approach is currently being scaled-up at LLNL. We are building a 5 meter aperture foldable lens, involving 72 panels of 700 {micro}m thick glass sheets, diffractively patterned to operate as coherent f/50 lens.

  5. Motion Measurement for Synthetic Aperture Radar.

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin W.

    2015-01-01

    Synthetic Aperture Radar (SAR) measures radar soundings from a set of locations typically along the flight path of a radar platform vehicle. Optimal focusing requires precise knowledge of the sounding source locations in 3 - D space with respect to the target scene. Even data driven focusing techniques (i.e. autofocus) requires some degree of initial fidelity in the measurements of the motion of the radar. These requirements may be quite stringent especially for fine resolution, long ranges, and low velocities. The principal instrument for measuring motion is typically an Inertial Measurement Unit (IMU), but these instruments have inherent limi ted precision and accuracy. The question is %22How good does an IMU need to be for a SAR across its performance space?%22 This report analytically relates IMU specifications to parametric requirements for SAR. - 4 - Acknowledgements Th e preparation of this report is the result of a n unfunded research and development activity . Although this report is an independent effort, it draws heavily from limited - release documentation generated under a CRADA with General Atomics - Aeronautical System, Inc. (GA - ASI), and under the Joint DoD/DOE Munitions Program Memorandum of Understanding. Sandia National Laboratories is a multi - program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of En ergy's National Nuclear Security Administration under contract DE - AC04 - 94AL85000.

  6. Real-time beamforming synthetic aperture radar

    Science.gov (United States)

    Rincon, Rafael; Hildebrand, Peter; Hilliard, Lawrence; Bradley, Damon; Krnan, Luko; Sheikh, Salman; Lucey, Jared

    2006-09-01

    This paper discusses the concept and design of a real-time Digital Beamforming Synthetic Aperture Radar (DBSAR) for airborne applications which can achieve fine spatial resolutions and wide swaths. The development of the DBSAR enhances important scientific measurements in Earth science, and serves as a prove-of-concept for planetary exploration missions. A unique aspect of DBSAR is that it achieves fine resolutions over large swaths by synthesizing multiple cross-track beams simultaneously using digital beamforming techniques. Each beam is processed using SAR algorithms to obtain the fine ground resolution without compromising fine range and azimuth resolutions. The processor uses an FPGA-based architecture to implement digital in-phase and quadrature (I/Q) demodulation, beamforming, and range and azimuth compression. The DBSAR concept will be implemented using the airborne L-Band Imaging Scatterometer (LIS) on board the NASA P3 aircraft. The system will achieve ground resolutions of less than 30 m and swaths of 10 km from an altitude of 8 km.

  7. Oceanic eddies in synthetic aperture radar images

    Indian Academy of Sciences (India)

    Andrei Yu Ivanov; Anna I Ginzburg

    2002-09-01

    Continuous observations since 1991 by using synthetic aperture radar (SAR) on board the Almaz-1, ERS-1/2, JERS-1, and RADARSAT satellites support the well-known fact that oceanic eddies are distributed worldwide in the ocean. The paper is devoted to an evaluation of the potential of SAR for detection of eddies and vortical motions in the ocean. The classification of typical vortical features in the ocean detected in remote sensing images (visible, infrared, and SAR) is presented as well as available information on their spatial and temporal scales. Examples of the Almaz-1 and ERS-1/2 SAR images showing different eddy types, such as rings, spiral eddies of the open ocean, eddies behind islands and in bays, spin-off eddies and mushroom-like structures (vortex dipoles) are given and discussed. It is shown that a common feature for most of the eddies detected in the SAR images is a broad spectrum of spatial scales, spiral shape and shear nature. It is concluded that the spaceborne SARs give valuable information on ocean eddies, especially in combination with visible and infrared satellite data.

  8. Synthetic aperture radar imaging exploiting multiple scattering

    International Nuclear Information System (INIS)

    In this paper, we consider an imaging scenario, where a bi-static synthetic aperture radar (SAR) system is used in a multiple scattering environment. We consider a ray-theoretic approximation to the Green function to model a multiple scattering environment. This allows us to incorporate the multiple paths followed by the transmitted signal, thereby providing different views of the object to be imaged. However, the received signal from the multiple paths and additive thermal noise may interfere and produce artifacts when standard backprojection-based reconstruction algorithms are used. We use microlocal analysis in a statistical setting to develop a novel filtered-backprojection type image reconstruction method that not only exploits the multi-paths leading to enhancement of the reconstructed image but also suppresses the artifacts due to interference. We assume a priori knowledge of the second-order statistics of the target and noise to suppress the artifacts due to interference in a mean-square error sense. We present numerical simulations to demonstrate the performance of our image reconstruction method. While the focus of this paper is on radar applications, our image formation method is also applicable to other problems arising in fields such as acoustic, geophysical and medical imaging

  9. Confocal and conventional immunofluorescence and ultrastructural localisation of intracellular strength-giving components of human amniochorion.

    OpenAIRE

    Ockleford, C; Malak, T; A. Hubbard; Bracken, K; Burton, S A; Bright, N.; Blakey, G; Goodliffe, J; Garrod, D; d'Lacey, C

    1993-01-01

    Key cytoskeletal polypeptides of human fetal membranes have been localised at subcellular level using confocal and conventional indirect immunofluorescence microscopy. Correlation with electron microscope data has allowed us to examine how cellular compartments of this multilaminar tissue maintain their mechanical integrity until the time of membrane rupture at parturition. Evidence is presented for myofibroblastic characteristics of cells in both the fibroblast and reticular layers which may...

  10. Early maize root and phosphorus uptake responses to localised application of sewage sludge derived fertilisers

    OpenAIRE

    Lemming, Camilla; Oberson, Astrid; Hund, Andreas; Stoumann Jensen, Lars; Magid, Jakob

    2015-01-01

    Background: Phosphorus recycling from waste and localised placement of fertilisers can be means to improve sustainable P management in agriculture. However, knowledge about root and plant P uptake responses to placement of complex waste- derived fertilisers is lacking. Methods: Sewage sludge (SS) and sewage sludge ash (ASH) were tested against triple superphosphate (TSP) in a rhizobox setup where shoot and root growth of maize was followed for 30 days. The three P sources were either mixed...

  11. Space–time and hybrid algorithms for the passive acoustic localisation of sperm whales and vessels

    OpenAIRE

    Houégnigan, Ludwig; Zaugg, Serge Alain; Van der Schaar, Mike Connor Roger Malcolm; André, Michel

    2010-01-01

    In the frame of the European Sea-floor Observatory Network (ESONET) and in preparation of the Demonstration Mission Listening to the Deep-Ocean Environment (LIDO) algorithms for the automated real-time detection, classification and localisation of cetaceans have been developed. Such Passive Acoustic Monitoring techniques have the potential to play a key role in cetaceans’ conservation for they allow a non-invasive study of their behaviour, a better knowledge of their population ...

  12. An investigation into a suitable scintillator for localising neutron capture within a detector

    OpenAIRE

    Balmer, Matthew; Gamage, Kelum; Taylor, Graeme

    2014-01-01

    Using Monte-Carlo modelling, an investigation into a suitable loaded scintillator for localising neutron capture in a novel neutron survey meter has been undertaken. A comparison of estimated neutron capture location in a scintillator with Geant4 and MCNP simulations was undertaken and a good general agreement between the two models was observed. The interactions of γ emissions from neutron capture in the scintillator are investigated. The results show that the γ emission from neutron capture...

  13. Immunohistochemical Localisation of PDE5 in Rat Lung during Pre- and Postnatal Development

    OpenAIRE

    Angela Scipioni; Mauro Giorgi; Valeria Nuccetelli; Stefania Stefanini

    2009-01-01

    In mammalian lung, at the transition to extrauterine life, NO/cGMP signal transduction system is known to play crucial roles in the regulation of vascular resistance and is supposed to act in angiogenesis. PDE5, which is the most abundant cGMP metabolizing enzyme within the lung, is highly expressed in the perinatal period, but its localisation in the different pulmonary cells is still poorly known. In our research, PDE5 immunohistochemical distribution was investigated in foetal and neonatal...

  14. Localised lymphoma of bone: prognostic factors and treatment recommendations. The Princess Margaret Hospital Lymphoma Group.

    OpenAIRE

    Rathmell, A. J.; Gospodarowicz, M K; Sutcliffe, S.B.; Clark, R.M.

    1992-01-01

    Twenty seven adult patients with newly diagnosed non-Hodgkin's lymphoma localised to either bone (Stage IE) or bone and regional lymph nodes (Stage IIE) were treated between 1967 and 1988. Median age was 53 years and the commonest histology (21 patients) was diffuse histiocytic lymphoma. Twenty-four patients were treated radically: 15 with radiation therapy (XRT) alone and nine with chemotherapy plus radiation therapy (CMT). The cause specific survival for these patients was 56% at 5 years an...

  15. Local characterisation of fluid flow in sandstone with localised deformation features through fast neutron imaging

    OpenAIRE

    Rowe S.; Hughes D.; Hall S.A.

    2010-01-01

    Understanding fluid flow through rocks is of key interest in hydrocarbon production and CO2 sequestration, amongst other applications. Such fluid injection or extraction from subsurface reservoirs can be significantly modified (increased or decreased) by deformation and in particular by localised deformation features (fractures, shear bands and compaction bands). How such deformation alters fluid flow is however not well characterised experimentally. Measurement of fluid-flow distributi...

  16. Localised Skin Hyperpigmentation as a Presenting Symptom of Vitamin B12 Deficiency Complicating Chronic Atrophic Gastritis

    OpenAIRE

    Kawther El-Shafie; Nafisa Samir; Ritu Lakhtakia; Robin Davidson; Ahmed Al-Waili; Muna Al-Mamary; Mohammed Al-Shafee

    2015-01-01

    Vitamin B12 deficiency is common in developing countries and should be suspected in patients with unexplained anaemia or neurological symptoms. Dermatological manifestations associated with this deficiency include skin hyper- or hypopigmentation, angular stomatitis and hair changes. We report a case of a 28-year-old man who presented to the Sultan Qaboos University Hospital in Muscat, Oman, in November 2013 with localised hyperpigmentation of the palmar and dorsal aspects of both hands of two...

  17. In planta localisation patterns of MADS domain proteins during floral development in Arabidopsis thaliana

    OpenAIRE

    Urbanus, S.L.; Folter, de, S.; Shchennikova, A.; Kaufmann, K.; Immink, G.H.; Angenent, G.C.

    2009-01-01

    Background: MADS domain transcription factors play important roles in various developmental processes in flowering plants. Members of this family play a prominent role in the transition to flowering and the specification of floral organ identity. Several studies reported mRNA expression patterns of the genes encoding these MADS domain proteins, however, these studies do not provide the necessary information on the temporal and spatial localisation of the proteins. We have made GREEN FLUORESCE...

  18. Localisation binaurale active de sources sonores en robotique humanoïde

    OpenAIRE

    Portello, Alban

    2013-01-01

    This thesis deals with the definition of algorithms for the localisation of still or moving sound sources from a mobile binaural sensor in robotics. The aim is to develop active strategies, combining left-right perceived signals with the sensor motor commands so as to overcome usual limitations in the case of a static world : resolve ambiguities (e.g. front-back), recover observability of variables, etc. The study focuses on two-step strategies : (1) extraction of spatial information and sour...

  19. Technological change and industry competitiveness through the evolution of localised comparative advantages - The case of Italy

    OpenAIRE

    Palma, Daniela; Zini, Alessandro

    2005-01-01

    The influence of technological change on industry performances is nowadays being increasingly investigated under the broad category of "national systemic competitiveness". Moreover theoretical works have shown that the relationship between technology and economic performance not only takes different forms in different socio-economic contexts, but is also powerfully influenced by the way that innovation processes evolve over time along strongly localised patterns. The present study is focused ...

  20. Localised low velocity impact performance of short glass fibre reinforced polyamide 66 oil pans

    OpenAIRE

    Mouti, Zakaria

    2012-01-01

    This thesis focuses on the mechanical properties of short glass fibre reinforced polyamide 66 material used in automotive composite structures, and its impact resistance under localised low velocity impact. The main application of this research concerns the impact performance of an oil pan component susceptible to stone impact damage. The thesis reviews the current state-of-the-art of thermoplastic polyamide materials with an overview of the glass fibre reinforced polyamide ...

  1. Localisation pattern of Foxp3+ regulatory T cells is associated with clinical behaviour in gastric cancer

    OpenAIRE

    Mizukami, Y.; Kono, K; Kawaguchi, Y; Akaike, H.; Kamimura, K.; Sugai, H.; Fujii, H.

    2007-01-01

    It has been reported that the population of regulatory T cells (T regs) is increased in tumour-infiltrating lymphocytes in cancer-bearing hosts. Recently, forkhead/winged helix transcription factor p3, Foxp3, is thought to be the most reliable marker of T regs. In the present study, we investigated the prevalence and localisation pattern of Foxp3+ cells in gastric cancer (n=80) by immunohistochemistry, in relation to the clinical outcome of gastric cancer patients. Immunohistochemical stainin...

  2. Ureteric angioplasty balloon placement to increase localised dosage of BCG for renal pelvis TCC.

    LENUS (Irish Health Repository)

    Forde, J C

    2012-03-01

    Endoscopic percutaneous resection of a renal pelvis transitional cell carcinoma (TCC) is a viable treatment option in those who would be rendered dialysis dependent following a nephroureterectomy. We report endoscopic percutaneous resection of an upper tract TCC recurrence in a single functioning kidney followed by antegrade renal pelvis BCG instillation with novel placement of inflated angioplasty balloon in the ureter to help localise its effect.

  3. Robust localisation of automated guided vehicles for computer-integrated manufacturing environments

    OpenAIRE

    Dixon, R. C.; Bright, G.; Harley, R.

    2013-01-01

    As industry moves toward an era of complete automation and mass customisation, automated guided vehicles (AGVs) are used as material handling systems. However, the current techniques that provide navigation, control, and manoeuvrability of automated guided vehicles threaten to create bottlenecks and inefficiencies in manufacturing environments that strive towards the optimisation of part production. This paper proposes a decentralised localisation technique for an automated guided vehicle ...

  4. Cellular localisation of type XIII collagen, and its induced expression in human neoplasias and corneal diseases

    OpenAIRE

    Väisänen, T. (Teemu)

    2005-01-01

    Abstract Type XIII collagen belongs to the group of transmembrane collagens. In this thesis the plasma membrane localisation and function of type XIII collagen have been studied using cell biological methods. Type XIII collagen was found to reside in focal adhesions. It appeared in these structures at a very early stage of their assembly and disappeared from them concurrently with focal adhesion proteins talin and vinculin. Insect cells expressing type XIII collagen showed an enhanced ...

  5. Auditory localisation of conventional and electric cars : laboratory results and implications for cycling safety

    OpenAIRE

    Stelling-Konczak, A. & Hagenzieker, M.P.

    2016-01-01

    When driven at low speeds, cars operating in electric mode have been found to be quieter than conventional cars. As a result, the auditory cues which pedestrians and cyclists use to assess the presence, proximity and location oncoming traffic may be reduced, posing a safety hazard. This laboratory study examined auditory localisation of conventional and electric cars including vehicle motion paths relevant for cycling activity. Participants (N = 65) in three age groups (16–18, 30–40 and 65–70...

  6. Morphoea (localised scleroderma) in a patient with mixed connective tissue disease.

    OpenAIRE

    Golding, D. N.

    1986-01-01

    An 18 year old girl concurrently developed skin lesions of morphoea (localised scleroderma) and pain and swelling of the hands and fingers. There were no dermatological or systemic signs of systemic sclerosis. The immunological features (high titred speckled antinuclear antibody, negative DNA binding, high titred positive anti-RNP and negative anti-Sm antibodies, speckled nuclear Ig fluorescence in the epidermis of the skin lesions) were consistent with mixed connective tissue disease, and it...

  7. Localisation of primary food production in Finland: production potential and environmental impacts of food consumption patterns

    OpenAIRE

    Risku-Norja, Helmi; Hietala, Reija; Virtanen, Hanna; Ketomäki, Hanna; Helenius, Juha

    2008-01-01

    The potential for and environmental consequences of localising primary production of food were investigated by considering different food consumption patterns, based on conventional and organic production. Environmental impact was assessed according to agricultural land use and numbers of production animals, both of which depend on food consumption. The results were quantified in terms of nutrient balances, greenhouse gas and acid emissions and the diversity of crop cultivation, which indicat...

  8. Application of multiple-wireless to a visual localisation system for emergency services

    OpenAIRE

    Efthymiou, C; Gormus, S; Fan, Zhong; Calway, AD; Mayol-Cuevas, WW; Doufexi, A

    2010-01-01

    In this paper we discuss the application of multiplewireless technology to a practical context-enhanced service system called ViewNet. ViewNet develops technologies to support enhanced coordination and cooperation between operation teams in the emergency services and the police. Distributed localisation of users and mapping of environments implemented over a secure wireless network enables teams of operatives to search and map an incident area rapidly and in full coordination with each other ...

  9. A Unified Scalable Model of User Localisation with Uncertainty Awareness for Large-scale Pervasive Environments

    OpenAIRE

    Aksenov, Petr; Luyten, Kris; Coninx, Karin

    2011-01-01

    Localisation has become a standard feature in many mobile applications. Numerous techniques for both indoor and outdoor location tracking are available today, providing a diversity of ways positioning information can be delivered to a mobile application (e.g., a location-based service). Such factors as the variation of precision over time and covered areas or the difference in quality and reliability make the adoption of several techniques for one application cumbersome. ...

  10. Multiple-input multiple-output synthetic aperture ladar system for wide-range swath with high azimuth resolution.

    Science.gov (United States)

    Tang, Yu; Qin, Bao; Yan, Yun; Xing, Mengdao

    2016-02-20

    For the trade-off between the high azimuth resolution and the wide-range swath in the single-input single-output synthetic aperture ladar (SAL) system, the range swath of the SAL system is restricted to a narrow range, this paper proposes a multiple-input multiple-output (MIMO) synthetic aperture ladar system. The MIMO system adopts a low pulse repetition frequency (PRF) to avoid a range ambiguity for the wide-range swath and in azimuth adopts the multi-channel method to achieve azimuth high resolution from the unambiguous azimuth wide-spectrum signal, processed through adaptive digital beam-forming technology. Simulations and analytical results are presented. PMID:26906593

  11. Human perception of indoor environment generated by chilled ceiling combined with mixing ventilation or localised chilled beam under cooling mode

    DEFF Research Database (Denmark)

    Bolashikov, Zhecho Dimitrov; Nygaard, Linette; Uth, Simon C.;

    2014-01-01

    Experiments with 24 subjects were performed to study and compare the human perception of the indoor environment under summer conditions generated by a chilled ceiling combined with overhead mixing ventilation and localised chilled beam. The experiments were performed in an experimental chamber (4...... simulate direct solar load on the floor (270 W). The total heat load in the room was 56 W/m2. The air temperature around the workstation by the window was kept either 26 or 28 oC. The supplied air by the overhead mixing ventilation and the primary supply air of the localised chilled beam was kept at 13 L....../s and 16 0C. The localised chilled beam was installed over the workstation placed by the simulated window. During the experiment the subjects were delegated control over the primary flow rate supplied by the localised chilled beam. The whole exposure lasted 2 hours with 30 min of acclimatisation before...

  12. Genetic optimisation of a plane array geometry for beamforming. Application to source localisation in a high speed train

    Science.gov (United States)

    Le Courtois, Florent; Thomas, Jean-Hugh; Poisson, Franck; Pascal, Jean-Claude

    2016-06-01

    Thanks to its easy implementation and robust performance, beamforming is applied for source localisation in several fields. Its effectiveness depends greatly on the array sensor configuration. This paper introduces a criterion to improve the array beampattern and increase the accuracy of sound source localisation. The beamwidth and the maximum sidelobe level are used to quantify the spatial variation of the beampattern through a new criterion. This criterion is shown to be useful, especially for the localisation of moving sources. A genetic algorithm is proposed for the optimisation of microphone placement. Statistical analysis of the optimised arrays provides original results on the algorithm performance and on the optimal microphone placement. An optimised array is tested to localise the sound sources of a high speed train. The results show an accurate separation.

  13. Weakly nonlinear analysis and localised structures in nonlinear cavities with metamaterials

    Science.gov (United States)

    Slimani, N.; Makhoute, A.; Tlidi, M.

    2016-04-01

    We consider an optical ring cavity filled with a metamaterial and with a Kerr medium. The cavity is driven by a coherent radiation beam. The modelling of this device leads to the well known Lugiato-Lefever equation with high order diffraction term. We assume that both left-handed and right-handed materials possess a Kerr focusing type of nonlinearity. We show that close to the zero-diffraction regime, high-order diffraction effect allows us to stabilise dark localised structures in this device. These structures consist of dips or holes in the transverse profile of the intracavity field and do not exist without high-order diffraction effects. We show that high order diffraction effects alter in depth the space-time dynamics of this device. A weakly nonlinear analysis in the vicinity of the first threshold associated with the Turing instability is performed. This analysis allows us to determine the parameter regime where the transition from super- to sub-critical bifurcation occurs. When the modulational instability appears subcritically, we show that bright localised structures of light may be generated in two-dimensional setting. Close to the second threshold associated with the Turing instability, dark localised structures are generated.

  14. On The Role of MHD Waves in Heating Localised Magnetic Structures

    Science.gov (United States)

    Erdélyi, R.; Nelson, C. J.

    2016-04-01

    Satellite and ground-based observations from e.g. SOHO, TRACE, STEREO, Hinode, SDO and IRIS to DST/ROSA, IBIS, CoMP, STT/CRISP have provided a wealth of evidence of waves and oscillations present in a wide range of spatial scales of the magnetised solar atmosphere. Our understanding about localised solar structures has been considerably changed in light of these high spatial and time resolution observations. However, MHD waves not only enable us to perform sub-resolution magneto-seismology of magnetic waveguides but are also potential candidates to carry and damp the necessary non-thermal energy in these localised waveguides. First, we will briefly outline the basic recent developments in MHD wave theory focussing on linear waves. Next, we discuss the role of the most frequently studied wave classes, including the Alfven, and magneto-acoustic kink and sausage waves. The current theoretical (and often difficult) interpretations of the detected solar atmospheric wave and oscillatory phenomena within the framework of MHD will be shown. Last, the latest reported observational findings of potential MHD wave flux, in terms of localised plasma heating, in the solar atmosphere is discussed, bringing us closer to solve the coronal heating problem.

  15. Counterintuitive electron localisation from density-functional theory with polarisable solvent models

    International Nuclear Information System (INIS)

    Exploration of the solvated electron phenomena using density-functional theory (DFT) generally results in prediction of a localised electron within an induced solvent cavity. However, it is well known that DFT favours highly delocalised charges, rendering the localisation of a solvated electron unexpected. We explore the origins of this counterintuitive behaviour using a model Kevan-structure system. When a polarisable-continuum solvent model is included, it forces electron localisation by introducing a strong energetic bias that favours integer charges. This results in the formation of a large energetic barrier for charge-hopping and can cause the self-consistent field to become trapped in local minima thus converging to stable solutions that are higher in energy than the ground electronic state. Finally, since the bias towards integer charges is caused by the polarisable continuum, these findings will also apply to other classical polarisation corrections, as in combined quantum mechanics and molecular mechanics (QM/MM) methods. The implications for systems beyond the solvated electron, including cationic DNA bases, are discussed

  16. Counterintuitive electron localisation from density-functional theory with polarisable solvent models.

    Science.gov (United States)

    Dale, Stephen G; Johnson, Erin R

    2015-11-14

    Exploration of the solvated electron phenomena using density-functional theory (DFT) generally results in prediction of a localised electron within an induced solvent cavity. However, it is well known that DFT favours highly delocalised charges, rendering the localisation of a solvated electron unexpected. We explore the origins of this counterintuitive behaviour using a model Kevan-structure system. When a polarisable-continuum solvent model is included, it forces electron localisation by introducing a strong energetic bias that favours integer charges. This results in the formation of a large energetic barrier for charge-hopping and can cause the self-consistent field to become trapped in local minima thus converging to stable solutions that are higher in energy than the ground electronic state. Finally, since the bias towards integer charges is caused by the polarisable continuum, these findings will also apply to other classical polarisation corrections, as in combined quantum mechanics and molecular mechanics (QM/MM) methods. The implications for systems beyond the solvated electron, including cationic DNA bases, are discussed. PMID:26567651

  17. An Autonomous Wearable System for Predicting and Detecting Localised Muscle Fatigue

    Directory of Open Access Journals (Sweden)

    Martin Colley

    2011-01-01

    Full Text Available Muscle fatigue is an established area of research and various types of muscle fatigue have been clinically investigated in order to fully understand the condition. This paper demonstrates a non-invasive technique used to automate the fatigue detection and prediction process. The system utilises the clinical aspects such as kinematics and surface electromyography (sEMG of an athlete during isometric contractions. Various signal analysis methods are used illustrating their applicability in real-time settings. This demonstrated system can be used in sports scenarios to promote muscle growth/performance or prevent injury. To date, research on localised muscle fatigue focuses on the clinical side and lacks the implementation for detecting/predicting localised muscle fatigue using an autonomous system. Results show that automating the process of localised muscle fatigue detection/prediction is promising. The autonomous fatigue system was tested on five individuals showing 90.37% accuracy on average of correct classification and an error of 4.35% in predicting the time to when fatigue will onset.

  18. Counterintuitive electron localisation from density-functional theory with polarisable solvent models

    Energy Technology Data Exchange (ETDEWEB)

    Dale, Stephen G., E-mail: sdale@ucmerced.edu [Chemistry and Chemical Biology, School of Natural Sciences, University of California, Merced, 5200 North Lake Road, Merced, California 95343 (United States); Johnson, Erin R., E-mail: erin.johnson@dal.ca [Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia B3H 4R2 (Canada)

    2015-11-14

    Exploration of the solvated electron phenomena using density-functional theory (DFT) generally results in prediction of a localised electron within an induced solvent cavity. However, it is well known that DFT favours highly delocalised charges, rendering the localisation of a solvated electron unexpected. We explore the origins of this counterintuitive behaviour using a model Kevan-structure system. When a polarisable-continuum solvent model is included, it forces electron localisation by introducing a strong energetic bias that favours integer charges. This results in the formation of a large energetic barrier for charge-hopping and can cause the self-consistent field to become trapped in local minima thus converging to stable solutions that are higher in energy than the ground electronic state. Finally, since the bias towards integer charges is caused by the polarisable continuum, these findings will also apply to other classical polarisation corrections, as in combined quantum mechanics and molecular mechanics (QM/MM) methods. The implications for systems beyond the solvated electron, including cationic DNA bases, are discussed.

  19. Illumination-invariant image matching for autonomous UAV localisation based on optical sensing

    Science.gov (United States)

    Wan, Xue; Liu, Jianguo; Yan, Hongshi; Morgan, Gareth L. K.

    2016-09-01

    This paper presents an UAV (Unmanned Aerial Vehicle) localisation algorithm for its autonomous navigation based on matching between on-board UAV image sequences to a pre-installed reference satellite image. As the UAV images and the reference image are not necessarily taken under the same illumination condition, illumination-invariant image matching is essential. Based on the investigation of illumination-invariant property of Phase Correlation (PC) via mathematical derivation and experiments, we propose a PC based fast and robust illumination-invariant localisation algorithm for UAV navigation. The algorithm accurately determines the current UAV position as well as the next UAV position even the illumination condition of UAV on-board images is different from the reference satellite image. A Dirac delta function based registration quality assessment together with a risk alarming criterion is introduced to enable the UAV to perform self-correction in case the UAV deviates from the planned route. UAV navigation experiments using simulated terrain shading images and remote sensing images have demonstrated a robust high performance of the proposed PC based localisation algorithm under very different illumination conditions resulted from solar motion. The superiority of the algorithm, in comparison with two other widely used image matching algorithms, MI (Mutual Information) and NCC (Normalised Correlation Coefficient), is significant for its high matching accuracy and fast processing speed.

  20. Quantitative Evaluation of Stereo Visual Odometry for Autonomous Vessel Localisation in Inland Waterway Sensing Applications

    Directory of Open Access Journals (Sweden)

    Thomas Kriechbaumer

    2015-12-01

    Full Text Available Autonomous survey vessels can increase the efficiency and availability of wide-area river environment surveying as a tool for environment protection and conservation. A key challenge is the accurate localisation of the vessel, where bank-side vegetation or urban settlement preclude the conventional use of line-of-sight global navigation satellite systems (GNSS. In this paper, we evaluate unaided visual odometry, via an on-board stereo camera rig attached to the survey vessel, as a novel, low-cost localisation strategy. Feature-based and appearance-based visual odometry algorithms are implemented on a six degrees of freedom platform operating under guided motion, but stochastic variation in yaw, pitch and roll. Evaluation is based on a 663 m-long trajectory (>15,000 image frames and statistical error analysis against ground truth position from a target tracking tachymeter integrating electronic distance and angular measurements. The position error of the feature-based technique (mean of ±0.067 m is three times smaller than that of the appearance-based algorithm. From multi-variable statistical regression, we are able to attribute this error to the depth of tracked features from the camera in the scene and variations in platform yaw. Our findings inform effective strategies to enhance stereo visual localisation for the specific application of river monitoring.

  1. Performance characteristics of a polyethylene collimator with an EJ-426 detector in neutron source localisation

    Energy Technology Data Exchange (ETDEWEB)

    Gamage, K.A.A., E-mail: k.gamage@lancaster.ac.uk; Crompton, A.J.; Joyce, M.J.

    2014-08-01

    In this paper, characteristics of neutron source localisation using an EJ-426 detector with a polyethylene collimator are presented. The detector is placed inside of the polyethylene collimator, where the collimator has a constant internal diameter and external diameter gradually increases towards the back end. The combined detector-collimator unit was mounted onto an equatorial mount and, data were collected from an ultra-fast mixed-field analyser. Neutron images have been produced to characterise the area investigated in real-time. Radiation images are fundamentally related to the detector efficiency and to the collimator geometry. In order to characterise the neutron source localisation capability of the polyethylene collimator, with an EJ-426 detector, experiments have been carried out using three different neutron sources. Results indicate that the existing design of the polyethylene collimator is suitable for localisation of low energy neutron sources. The measurements were performed in the low-scatter facility of the Neutron Metrology, National Physical Laboratory, Teddington, UK.

  2. Electromagnetic Formation Flight (EMFF) for Sparse Aperture Arrays

    Science.gov (United States)

    Kwon, Daniel W.; Miller, David W.; Sedwick, Raymond J.

    2004-01-01

    Traditional methods of actuating spacecraft in sparse aperture arrays use propellant as a reaction mass. For formation flying systems, propellant becomes a critical consumable which can be quickly exhausted while maintaining relative orientation. Additional problems posed by propellant include optical contamination, plume impingement, thermal emission, and vibration excitation. For these missions where control of relative degrees of freedom is important, we consider using a system of electromagnets, in concert with reaction wheels, to replace the consumables. Electromagnetic Formation Flight sparse apertures, powered by solar energy, are designed differently from traditional propulsion systems, which are based on V. This paper investigates the design of sparse apertures both inside and outside the Earth's gravity field.

  3. Adjustable off-focal aperture for x-ray tubes

    International Nuclear Information System (INIS)

    This patent describes an x-ray tube assembly for radiographic scanners. It comprises: an evacuated envelope; an anode rotatably mounted within the envelope; a housing surrounding the envelope to define a cooling fluid reservoir therebetween, the housing defining an aperture therein and having a collar surrounding the aperture; an x-ray permeable, fluid impermeable window mounted to the housing to seal the aperture; an x-ray beam defining means, an off-focal radiation attenuating means, a flexible cable means, and a first stop means

  4. Coherent processing for ISAR imaging with sparse apertures

    Institute of Scientific and Technical Information of China (English)

    SHENG JiaLian; ZHANG Lei; XU Gang; XING MengDao; BAO Zheng

    2012-01-01

    To implement target detection,tracking and imaging in a multifunctional radar system,the wideband measurements for inverse synthetic aperture radar (ISAR) imaging are usually sparsely recorded.Considering the incoherence problem in such sparse-aperture ISAR (SA-ISAR) systems,we concentrate on the study of a coherent processing method in this work.Based on an all-pole model,the incoherence parameters between abutting sub-apertures can be effectively estimated.After coherence compensation,an optimization-based SA-ISAR imaging approach is provided from the view of statistics.Simulation and real data experiments validate the feasibility and effectiveness of the proposals.

  5. Experimental Study of Convex Coded Synthetic Transmit Aperture Imaging

    DEFF Research Database (Denmark)

    Gammelmark, Kim; Jensen, Jørgen Arendt

    . For synthetic aperture imaging an 11 element transmit aperture is used with a 20 μs linear FM signal as excitation. For both methods, 128 elements are used on receive. Measurements are done using our experimental multi-channel ultrasound scanner, RASMUS. Wire phantom measurements show an improvement......Synthetic transmit aperture imaging is investigated using a convex array transducer. To increase the signal-to-noise ratio, a multi-element subaperture is used to emulate the spherical wave transmission, and the conventional short excitation pulse is replaced by a linear FM signal. The approach is...

  6. Motion compensated beamforming in synthetic aperture vector flow imaging

    DEFF Research Database (Denmark)

    Oddershede, Niels; Jensen, Jørgen Arendt

    2006-01-01

    In synthetic aperture imaging the beamformed data from a number of emissions are summed to create dynamic focusing in transmit. This makes the method susceptible to motion, which is especially the case for the synthetic aperture flow estimation method, where large movements are expected. In this....... Here the SNR is -10 dB compared to the stationary scatterer. A 2D motion compensation method for synthetic aperture vector flow imaging is proposed, where the former vector velocity estimate is used for compensating the beamforming of new data. This method is tested on data from an experimental flow...

  7. Multi element synthetic aperture transmission using a frequency division approach

    DEFF Research Database (Denmark)

    Gran, Fredrik; Jensen, Jørgen Arendt

    2003-01-01

    In synthetic aperture imaging an image is created by a number of single element defocused emissions. A low resolution image is created after every emission and a high resolution image is formed when the entire aperture has been covered. Since only one element is used at a time the energy...... can therefore be used for flow imaging, unlike with Hadamard and Golay coding. The frequency division approach increases the SNR by a factor of N2 compared to conventional pulsed synthetic aperture imaging, provided that N transmission centers are used. Simulations and phantom measurements are...

  8. High-contrast imaging with an arbitrary aperture: Active compensation of aperture discontinuities

    International Nuclear Information System (INIS)

    We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential deformable mirrors (DMs) to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of DM surfaces that yield high-contrast point-spread functions is not linear, and nonlinear methods are needed to find the true minimum in the optimization topology. We solve the highly nonlinear Monge-Ampere equation that is the fundamental equation describing the physics of phase-induced amplitude modulation. We determine the optimum configuration for our two sequential DM system and show that high-throughput and high-contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to the James Webb Space Telescope, ACAD can attain at least 10–7 in contrast and an order of magnitude higher for both the future extremely large telescopes and on-axis architectures reminiscent of the Hubble Space Telescope. We show that the converging nonlinear mappings resulting from our DM shapes actually damp near-field diffraction artifacts in the vicinity of the discontinuities. Thus, ACAD actually lowers the chromatic ringing due to diffraction by segment gaps and struts while not amplifying the diffraction at the aperture edges beyond the Fresnel regime. This outer Fresnel ringing can be mitigated by properly designing the optical system. Consequently, ACAD is a true broadband solution to the problem of high-contrast imaging with segmented and/or on-axis apertures. We finally show that once the nonlinear solution is found, fine tuning with linear methods used in wavefront control can be applied to further contrast by another order of magnitude. Generally speaking, the

  9. Photoletter to the editor: Dermatitis herpetiformis co-localised with vitiligo in a patient with autoimmune polyglandular syndrome

    OpenAIRE

    Macbeth, Abby E.; Lee, Kevin Y. C.; Levell, Nick J.; Igali, Laszlo; Millington, George W.M.

    2013-01-01

    We report a case of dermatitis herpetiformis co-localised with segmental vitiligo in a 37-year-old woman with a background history of autoimmune polyglandular syndrome type 2. We propose genetic mosaicism as a possible mechanism. There has only been one previous case report in which dermatitis hepetiformis co-localised in close proximity but not exclusively within vilitigo in a patient with autoimmune thyroiditis. To our knowledge, this is the first case report of dermatitis herpetiformis co-...

  10. Development of a prototype of the tele-localisation system in radiotherapy using personal digital assistant via wireless communication

    International Nuclear Information System (INIS)

    In localisation of radiotherapy treatment field, the oncologist is present at the simulator to approve treatment details produced by the therapist. Problems may arise if the oncologist is not available and the patient requires urgent treatment. The development of a tele-localisation system is a potential solution, where the oncologist uses a personal digital assistant (PDA) to localise the treatment field on the image sent from the simulator through wireless communication and returns the information to the therapist after his or her approval. Our team developed the first tele-localisation prototype, which consisted of a server workstation (simulator) for the administration of digital imaging and communication in medicine localisation images including viewing and communication with the PDA via a Wi-Fi network; a PDA (oncologist's site) installed with the custom-built programme that synchronises with the server workstation and performs treatment field editing. Trial tests on accuracy and speed of the prototype system were conducted on 30 subjects with the treatment regions covering the neck, skull, chest and pelvis. The average time required in performing the localisation using the PDA was less than 1.5 min, with the blocked field longer than the open field. The transmission speed of the four treatment regions was similar. The average physical distortion of the images was within 4.4% and the accuracy of field size indication was within 5.3%. Compared with the manual method, the tele-localisation system presented with an average deviation of 5.5%. The prototype system fulfilled the planned objectives of tele-localisation procedure with reasonable speed and accuracy.

  11. Pre-treatment nomogram for biochemical control after neoadjuvant androgen deprivation and radical radiotherapy for clinically localised prostate cancer

    OpenAIRE

    Parker, C C; Norman, A R; Huddart, R A; Horwich, A; Dearnaley, D P

    2002-01-01

    Phase III studies have demonstrated the clinical benefit of adding neo-adjuvant androgen deprivation to radical radiotherapy for clinically localised prostate cancer. We have developed a nomogram to describe the probability of PSA control for patients treated in this way. Five hundred and seventeen men with clinically localised prostate cancer were treated with 3–6 months of neo-adjuvant androgen deprivation and radical radiotherapy (64 Gy in 32#) between 1988 and 1998. Median presenting PSA ...

  12. CRITICAL RESOURCE DIMENSIONS FOR DEVELOPMENT OF PATENTS — AN ANALYSIS OF 131 NEW TECHNOLOGY-BASED FIRMS LOCALISED IN INCUBATORS

    OpenAIRE

    HANS LÖFSTEN

    2015-01-01

    The purpose of this study is to analyse critical resource dimensions for development of patents for these new technology-based firms. The empirical base is 131 new technology-based firms in five high-tech industries: Software/information technology, technology consultants, electronics/electrical, pharmacology and pharmaceutical preparation and mechanics, localised on 16 incubators in Sweden. The incubators in this study are all affiliated to a university. The 131 localised new technology-base...

  13. Carcinoma of the breast wire localisation post nuclear medicine sentinel lymph node imaging. Are radiologists receiving a significant dose?

    Energy Technology Data Exchange (ETDEWEB)

    Meades, R.T.; Frank, J.W.; Gada, V.; Ralleigh, G.; Satchithananda, K.; Barrett, N.; Nijran, K.S. [Imperial College Healthcare NHS Trust, London (United Kingdom); Svensson, W.E. [Imperial College Healthcare NHS Trust, London (United Kingdom); Charing Cross Hospital, Department of Nuclear Medicine, London (United Kingdom)

    2010-03-15

    To assess the radiation dose received by the radiologist when performing wire localisation for axillary radio-isotope sentinel node imaging-guided biopsy in patients with impalpable breast cancers treated with breast-preserving excision. When wire placement follows radio-isotope sentinel node imaging (RSNI) the radiologist is exposed to a radiation risk that has never been previously assessed. Radiation doses to radiologists performing ultrasound-guided localisation following nuclear medicine sentinel node imaging were measured for procedures on the day of surgery (20 MBq) and also on the day before surgery (40 MBq). These measurements were compared with theoretically calculated doses. Twelve patients showed comparable results between measurements and estimated doses. The mean measured dose was 1.8{mu}Sv (estimated 1.8{mu}Sv) for same-day and 4.8{mu}Sv (estimated 3.4{mu}Sv) for next-day surgery cases. At worst, radiologists who perform 36 wire localisations per year immediately following RSNI receive a radiation dose of 0.17 mSv. This study highlights the need to inform radiologists of the relative risk when performing pre-surgical localisation after RSNI. This risk should be justified locally in accordance with the total dose received by the localising radiologist. Particular consideration should be given to pregnant staff and the possibility of performing wire localisations before radio-isotope injection. (orig.)

  14. Optical Transmission Properties of Dielectric Aperture Arrays

    Science.gov (United States)

    Yang, Tao

    Optical detection devices such as optical biosensors and optical spectrometers are widely used in many applications for the functions of measurements, inspections and analysis. Due to the large dimension of prisms and gratings, the traditional optical devices normally occupy a large space with complicated components. Since cheaper and smaller optical devices are always in demand, miniaturization has been kept going for years. Thanks to recent fabrication advances, nanophotonic devices such as semiconductor laser chips have been growing in number and diversity. However, the optical biosensor chips and the optical spectrometer chips are seldom reported in the literature. For the reason of improving system integration, the study of ultra-compact, low-cost, high-performance and easy-alignment optical biosensors and optical spectrometers are imperative. This thesis is an endeavor in these two subjects and will present our research work on studying the optical transmission properties of dielectric aperture arrays and developing new optical biosensors and optical spectrometers. The first half of the thesis demonstrates that the optical phase shift associated with the surface plasmon (SP) assisted extraordinary optical transmission (EOT) in nano-hole arrays fabricated in a metal film has a strong dependence on the material refractive index value in close proximity to the holes. A novel refractive index sensor based on detecting the EOT phase shift is proposed by building a model. This device readily provides a 2-D biosensor array platform for non-labeled real-time detection of a variety of organic and biological molecules in a sensor chip format, which leads to a high packing density, minimal analyte volumes, and a large number of parallel channels while facilitating high resolution imaging and supporting a large space-bandwidth product (SBP). Simulation (FDTD Solutions, Lumerical Solutions Inc) results indicate an achievable sensitivity limit of 4.37x10-9 refractive index

  15. Morphometric analysis of septal aperture of humerus

    Directory of Open Access Journals (Sweden)

    Raghavendra K, Anil kumar Reddy Y, Shirol VS, Daksha Dixit, Desai SP

    2014-04-01

    Full Text Available Introduction: Lower end of humerus shows olecranon and coronoid fossae separated by a thin bony septum, sometimes it may deficient and shows foramen which communicates both the fossae called Septal aperture, which is commonly referred as supratrochlear foramen (STF. Materials & Methods: We have studied 260 humeri (126 right side and 134 left side, measurements were taken by using vernier caliper, translucency septum was observed by keeping the lower end of humerus against the x-ray lobby. Results: A clear cut STF was observed in 19.2% bones, translucency septum was observed in 99 (91.6% humeri on the right side and 95 (93.1% humeri on the left sides respectively (Table – 1. Clinical significance: The presence of STF is always associated with the narrow medullary canal at the lower end of humerus, Supracondylar fracture of humerus is most common in paediatric age group, medullary nailing is done to treat the fractures in those cases the knowledge about the STF is very important for treating the fractures. It has been observed in x-ray of lower end of the humerus the STF is comparatively radiolucent, it is commonly seen as a type of ‘pseudolesions’ in an x-ray of the lower end of humerus and it may mistake for an osteolytic or cystic lesions. Conclusion: The present study can add data into anthropology and anatomy text books regarding STF and it gives knowledge of understanding anatomical variation of distal end of the humerus, which is significant for anthropologists, orthopaedic surgeons and radiologists in habitual clinical practice.

  16. The LASS [Larger Aperture Superconducting Solenoid] spectrometer

    International Nuclear Information System (INIS)

    LASS is the acronym for the Large Aperture Superconducting Solenoid spectrometer which is located in an rf-separated hadron beam at the Stanford Linear Accelerator Center. This spectrometer was constructed in order to perform high statistics studies of multiparticle final states produced in hadron reactions. Such reactions are frequently characterized by events having complicated topologies and/or relatively high particle multiplicity. Their detailed study requires a spectrometer which can provide good resolution in momentum and position over almost the entire solid angle subtended by the production point. In addition, good final state particle identification must be available so that separation of the many kinematically-overlapping final states can be achieved. Precise analyses of the individual reaction channels require high statistics, so that the spectrometer must be capable of high data-taking rates in order that such samples can be acquired in a reasonable running time. Finally, the spectrometer must be complemented by a sophisticated off-line analysis package which efficiently finds tracks, recognizes and fits event topologies and correctly associates the available particle identification information. This, together with complicated programs which perform specific analysis tasks such as partial wave analysis, requires a great deal of software effort allied to a very large computing capacity. This paper describes the construction and performance of the LASS spectrometer, which is an attempt to realize the features just discussed. The configuration of the spectrometer corresponds to the data-taking on K+ and K- interactions in hydrogen at 11 GeV/c which took place in 1981 and 1982. This constitutes a major upgrade of the configuration used to acquire lower statistics data on 11 GeV/c K-p interactions during 1977 and 1978, which is also described briefly

  17. RADARSAT-1 synthetic aperture radar analysis

    International Nuclear Information System (INIS)

    The M/V Selendang Ayu grounded off Unalaska Island in Alaska on December 8, 2004, and spilled over 1270 m3 of oil and an unknown quantity of soybeans. The freighter grounded nearshore in a high-wave energy zone along a remote and rugged coastline, a terrain which can cause difficulties for remote sensors in detecting oil slicks. In addition, guano, kelp beds, whale and fish sperm, and releases from fishing activities generated biogenic films on the sea surface that had a signature similar to that of petroleum films. RADARSAT-1 synthetic aperture radar (SAR) imagery was used as part of the response effort to assist in the pollution monitoring effort. This paper described the methodology and results of the RADARSAT-1 analysis. Detailed information on the spill response was reported daily, and provided an opportunity to compare field observations with RADARSAT-1 SAR imagery. Observers recorded observations onto electronic maps during 35 aerial surveillance flights. Fifty-seven incident reports describing the vessel status were also used for comparison. Using screening criteria for the favorable wind and wave conditions, 37 images were available for viewing the wreck, and 22 images were acceptable for oil slick viewing. Image analysis for the wreck suggested that the sensor has the resolution and capability to monitor a grounded freighter. Visual inspection of the images showed that SAR can capture changes in vessel status, such as the gradual sinking of the bow. However, SAR's oil slick detection capability was disappointing due to the significant number of biogenic films in the nearshore areas of Alaska. It was concluded that future work should concentrate on developing a ranking system to indicate analysis confidence that a particular image does in fact contain a petroleum pocket. 25 refs., 2 tabs., 10 figs

  18. Restricting retrotransposons: a review.

    Science.gov (United States)

    Goodier, John L

    2016-01-01

    Retrotransposons have generated about 40 % of the human genome. This review examines the strategies the cell has evolved to coexist with these genomic "parasites", focussing on the non-long terminal repeat retrotransposons of humans and mice. Some of the restriction factors for retrotransposition, including the APOBECs, MOV10, RNASEL, SAMHD1, TREX1, and ZAP, also limit replication of retroviruses, including HIV, and are part of the intrinsic immune system of the cell. Many of these proteins act in the cytoplasm to degrade retroelement RNA or inhibit its translation. Some factors act in the nucleus and involve DNA repair enzymes or epigenetic processes of DNA methylation and histone modification. RISC and piRNA pathway proteins protect the germline. Retrotransposon control is relaxed in some cell types, such as neurons in the brain, stem cells, and in certain types of disease and cancer, with implications for human health and disease. This review also considers potential pitfalls in interpreting retrotransposon-related data, as well as issues to consider for future research. PMID:27525044

  19. An Adaptive Homomorphic Aperture Photometry Algorithm for Merging Galaxies

    CERN Document Server

    Huang, Jen-Chao

    2016-01-01

    We present a novel automatic adaptive aperture photometry algorithm for measuring the total magnitudes of merging galaxies with irregular shapes. First, we use a morphological pattern recognition routine for identifying the shape of an irregular source in a background-subtracted image. Then, we extend the shape of the source by using the Dilation image operation to obtain an aperture that is quasi-homomorphic to the shape of the irregular source. The magnitude measured from the homomorphic aperture would thus have minimal contamination from the nearby background. As a test of our algorithm, we applied our technique to the merging galaxies observed by the Sloan Digital Sky Survey (SDSS) and the Canada-France-Hawaii Telescope (CFHT). Our results suggest that the adaptive homomorphic aperture algorithm can be very useful for investigating extended sources with irregular shapes and sources in crowded regions.

  20. Photonic spin-controlled multifunctional shared-aperture antenna array

    Science.gov (United States)

    Maguid, Elhanan; Yulevich, Igor; Veksler, Dekel; Kleiner, Vladimir; Brongersma, Mark L.; Hasman, Erez

    2016-06-01

    The shared-aperture phased antenna array developed in the field of radar applications is a promising approach for increased functionality in photonics. The alliance between the shared-aperture concepts and the geometric phase phenomenon arising from spin-orbit interaction provides a route to implement photonic spin-control multifunctional metasurfaces. We adopted a thinning technique within the shared-aperture synthesis and investigated interleaved sparse nanoantenna matrices and the spin-enabled asymmetric harmonic response to achieve helicity-controlled multiple structured wavefronts such as vortex beams carrying orbital angular momentum. We used multiplexed geometric phase profiles to simultaneously measure spectrum characteristics and the polarization state of light, enabling integrated on-chip spectropolarimetric analysis. The shared-aperture metasurface platform opens a pathway to novel types of nanophotonic functionality.

  1. Synthetic aperture radar signal processing: Trends and technologies

    Science.gov (United States)

    Curlander, John C.

    1993-01-01

    An overview of synthetic aperture radar (SAR) technology is presented in vugraph form. The following topics are covered: an SAR ground data system; SAR signal processing algorithms; SAR correlator architectures; and current and future trends.

  2. Preliminary comparison of 3D synthetic aperture imaging with Explososcan

    DEFF Research Database (Denmark)

    Rasmussen, Morten Fischer; Hansen, Jens Munk; Ferin, Guillaume;

    2012-01-01

    Explososcan is the 'gold standard' for real-time 3D medical ultrasound imaging. In this paper, 3D synthetic aperture imaging is compared to Explososcan by simulation of 3D point spread functions. The simulations mimic a 32x32 element prototype transducer. The transducer mimicked is a dense matrix...... phased array with a pitch of 300 μm, made by Vermon. For both imaging techniques, 289 emissions are used to image a volume spanning 60 in both the azimuth and elevation direction and 150mm in depth. This results for both techniques in a frame rate of 18 Hz. The implemented synthetic aperture technique...... cystic resolution, which expresses the ability to detect anechoic cysts in a uniform scattering media, at all depths except at Explososcan's focus point. Synthetic aperture reduced the cyst radius, R20dB, at 90mm depth by 48%. Synthetic aperture imaging was shown to reduce the number of transmit channels...

  3. Foamed Antenna Support for Very Large Apertures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Large aperture antennas are of interest to NASA for applications in establishing high-speed communication relays for interplanetary missions. Design goals include...

  4. Ultra-Lightweight Large Aperture Support Structures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Ultra-lightweight membranes may prove to be very attractive for large aperture systems, but their value will be fully realized only if they are mated with equally...

  5. Electronic aperture control devised for solid state imaging system

    Science.gov (United States)

    Anders, R. A.; Callahan, D. E.; Mc Cann, D. H.

    1968-01-01

    Electronic means of performing the equivalent of automatic aperture control has been devised for the new class of television cameras that incorporates a solid state imaging device in the form of phototransistor mosaic sensors.

  6. Foamed Antenna Support for Very Large Apertures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed Phase I program will demonstrate the feasibility of the in-space production of large aperture antenna structures. The use of a novel open cell foam,...

  7. Stitching interferometry for cylindrical optics with large angular aperture

    International Nuclear Information System (INIS)

    Stitching interferometry is an attractive method for measuring optics with large apertures. However, existing stitching algorithms are not suitable for measuring cylindrical optics, because the misalignment aberrations in cylindrical interferometry are more complicated than those in plane, spherical and aspherical measurements. This paper presents a stitching algorithm for measuring cylindrical optics with large angular apertures. With it, we use five aberrations (i.e. piston, tilt, tip, defocus and twist) to describe the possible misalignments of the tested cylindrical surface and to build the cylindrical stitching model. Using this model allows us to calculate the relative misalignment aberrations of subapertures from their overlapped areas, so that the full aperture map of a cylindrical surface is obtained by compensating for these misalignment aberrations. In experiment, a cylindrical lens with an angular aperture over 150° is measured, thus demonstrating the feasibility and validity of the proposed method. (paper)

  8. Stellwagen Bank National Marine Sanctuary - Synthetic Aperture Radar (SAR) Imagery

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This geodatabase contains Synthetic Aperture Radar images (SAR), which consist of a fine resolution (12.5-50m), two-dimensional radar backscatter map of the...

  9. Detection of small, slow ground targets using Synthetic Aperture Radar

    Science.gov (United States)

    Chen, Curtis; Chapin, Elaine; Rosen, Paul

    2005-01-01

    Synthetic aperture radar (SAR) along-track interferometry (ATI) is a technique for sensing Earth-surface motion. The technique involves interferometrically combining data from two radar images acquired from phase centers separated along the platform flight track.

  10. Autofocus algorithm for synthetic aperture radar imaging with large curvilinear apertures

    International Nuclear Information System (INIS)

    An approach to autofocusing for large curved synthetic aperture radar (SAR) apertures is presented. Its essential feature is that phase corrections are being extracted not directly from SAR images, but rather from reconstructed SAR phase-history data representing windowed patches of the scene, of sizes sufficiently small to allow the linearization of the forward- and back-projection formulae. The algorithm processes data associated with each patch independently and in two steps. The first step employs a phase-gradient-type method in which phase correction compensating (possibly rapid) trajectory perturbations are estimated from the reconstructed phase history for the dominant scattering point on the patch. The second step uses phase-gradient-corrected data and extracts the absolute phase value, removing in this way phase ambiguities and reducing possible imperfections of the first stage, and providing the distances between the sensor and the scattering point with accuracy comparable to the wavelength. The features of the proposed autofocusing method are illustrated in its applications to intentionally corrupted small-scene 2006 Gotcha data. The examples include the extraction of absolute phases (ranges) for selected prominent point targets. They are then used to focus the scene and determine relative target–target distances. (paper)

  11. Property Rights, Restrictions and Responsibilities

    DEFF Research Database (Denmark)

    Enemark, Stig

    more to a social, ethical commitment or attitude to environmental sustainability and good husbandry. This paper provides an overall understanding of the concept of land administration systems for dealing with rights, restrictions and responsibilities in future spatially enabled government. Finally the......Land Administration Systems are the basis for conceptualizing rights, restrictions and responsibilities related to people, policies and places. Property rights are normally concerned with ownership and tenure whereas restrictions usually control use and activities on land. Responsibilities relate...

  12. Antiretroviral Restriction Factors in Mice

    OpenAIRE

    Nair, Smita; Rein, Alan

    2014-01-01

    One of the most exciting areas in contemporary retrovirus research is the discovery of “restriction factors”. These are cellular proteins that act after virus entry to inhibit infection by or replication of retroviruses (and other viruses and intracellular pathogens). We briefly discuss here three antiretroviral restriction factors in mice: Fv1, APOBEC3, and tetherin, touching on both biological and molecular aspects of these restriction systems.

  13. Dynamic Aperture Of The Heavy Ion Collider Nica

    International Nuclear Information System (INIS)

    Dynamic aperture of the heavy ion collider NICA which is under construction at the Joint Institute for Nuclear Research in Dubna has been studied. Both nonlinearities in the magnetic elements and beam-beam forces have been taken into account in the numerical simulations. The obtained values of the dynamic aperture and the nonlinear acceptance are close to those in other heavy ion accelerators. Key words: particle accelerators, collider, beam dynamics

  14. Coded aperture imaging in nuclear medicine: review and update

    International Nuclear Information System (INIS)

    Since mid-1972, a number of investigators have been studying the properties of coded apertures as applied to imaging distributions of gamma-emitting radiotracers in the human body. Aperture codes including the zone plate, annulus, stationary and time modulated random hole patterns and the rotating slit have been employed with a variety of detectors ranging from X-ray film to multi-wire proportional counters. These methods are described and discussed

  15. Transmission of High-Power Electron Beams Through Small Apertures

    CERN Document Server

    Tschalär, C; Balascuta, S.; Benson, S.V.; Bertozzi, W.; Boyce, J.R.; Cowan, R.; Douglas, D.; Evtushenko, P.; Fisher, P.; Ihloff, E.; Kalantarians, N.; Kelleher, A.; Legg, R.; Milner, R.G.; Neil, G.R.; Ou, L.; Schmookler, B.; Tennant, C.; Williams, G.P.; Zhang, S.

    2013-01-01

    Tests were performed to pass a 100 MeV, 430 kWatt c.w. electron beam from the energy-recovery linac at the Jefferson Laboratory's FEL facility through a set of small apertures in a 127 mm long aluminum block. Beam transmission losses of 3 p.p.m. through a 2 mm diameter aperture were maintained during a 7 hour continuous run.

  16. Shallow Water Height Mapping With Interferometric Synthetic Aperture Sonar

    OpenAIRE

    Sergio Rui Silva; Sergio Cunha; Anibal Matos; Nuno Cruz

    2008-01-01

    Height mapping of shallow water areas is an important task for many commercial and scientific applications like river navigability, infrastructure maintenance or natural resource monitoring. The use of an autonomous boat presents several advantages that case the use of synthetic aperture images to create three-dimensional topographic maps through interferometric techniques. Sample data obtained during test trials illustrate how synthetic aperture can be used to generate imagery and bathymetry...

  17. Synthetic aperture single-exposure on-axis digital holography

    OpenAIRE

    Martínez León, Lluís; Javidi, Bahram

    2008-01-01

    We present a system for reconstructing single-exposure on-line (SEOL) digital holograms with improved resolution using a synthetic aperture. Several recordings are made in order to compose the synthetic aperture, shifting the camera within the hologram plane. After processing the synthetic hologram, an inverse Fresnel transformation provides an enhanced resolution reconstruction. We show that recognition capacity for high frequency details is increased. Experimental results ...

  18. Radiometric resolution of motion-induced synthetic aperture radiometer

    OpenAIRE

    Hyuk, Park; Camps Carmona, Adriano José; Choi, Min Gyu; Kim, Yong-Hoon

    2011-01-01

    The radiometric resolution of a motion-induced synthetic aperture radiometer (MISAR) is analytically obtained from the standard deviation of a baseline response, an observation scenario, and the imaging method of the MISAR. The intrinsic long integration time given by the whole dwell time on moving platforms improves the radiometric resolution compared with the snapshot resolution of other nominal synthetic aperture radiometers. In addition, it is illustrated that the MISAR imaging hold...

  19. Harmonic ultrasound imaging using synthetic aperture sequential beamforming

    DEFF Research Database (Denmark)

    2012-01-01

    A method includes generating an ultrasound image based on the harmonic components in the received echoes using multi-stage beam forming and data generated therefrom. An ultrasound imaging system (100, 200) includes a transducer array (108) including a plurality of transducer elements configured t...... ultrasound imaging system further includes a synthetic aperture processor (128), including a second beam former (130) configured to process the stored intermediate scan lines, based on a synthetic aperture algorithm, generating a focused image....

  20. The synthetic aperture method in the environment microwave interferometer radiometry

    OpenAIRE

    Kutuza, B.G.; Zagorin, G. K.

    2003-01-01

    The basic principles of space-borne two dimensional synthetic aperture microwave polarimetric interferometer function are considered. The main advantages of these systems over the well-known systems ESMR, SMMR and SSM/I are: a high rate of the observation scene image construction; the finite angular resolution; besides, they have no movable onboard construction elements on the spacecraft board, like the scanning antenna, and etc. The advantages of the synthetic aperture systems with hexagonal...

  1. Water Level Detection Using Synthetic Aperture Radar Imagery

    International Nuclear Information System (INIS)

    Reservoir water levels are of interest for international safeguards and domestic monitoring because they can be used as indicators of processing activity, uranium mine tailings protection status, or power generation for clandestine operation. Monitoring of water levels using satellite technology, especially civilian synthetic aperture radar (SAR) for remote or restricted-access sites worldwide has the potential to be a valuable tool for national/international safeguards as well as environmental monitoring applications. Unlike optical sensors, SAR is capable of reliable repeat monitoring regardless of cloud cover or solar illumination, i.e. it can image the target through clouds and darkness. Because of this ability, quick turn around for a SAR image is almost always guaranteed. SAR is very sensitive to the land/water interface and can be used to extract detailed elevation models. SAR is also sensitive to metallic structures or objects and can thus be useful in detection of heavy equipment or undeclared construction at decommissioned facilities. Although spaceborne SAR cannot match the resolution of optical satellites, future SAR satellites will offer much better resolution (e.g., approximately 3 metres for RADARSAT-2). Furthermore, future SAR satellites will offer different polarization and frequency channels to provide terrain and vegetation classification. The objective is to investigate the use of SAR for water level detection using Canada's RADARSAT-1 imagery. Three Canadian sites were chosen for our study: Niagara Area Hydro Reservoir; Quirke Lake uranium tailings management facility (TMF); and JEB Pit TMF. Initial results, using RADARSAT-1 data acquired over a three year period, show dramatic changes in both the total water surface area and markers (natural or man-made) becoming visible as the water level decreases. These very promising results indicated that SAR imagery can be used as an excellent tool for mapping remote location (which is useful for

  2. Transport of Particle Swarms Through Variable Aperture Fractures

    Science.gov (United States)

    Boomsma, E.; Pyrak-Nolte, L. J.

    2012-12-01

    Particle transport through fractured rock is a key concern with the increased use of micro- and nano-size particles in consumer products as well as from other activities in the sub- and near surface (e.g. mining, industrial waste, hydraulic fracturing, etc.). While particle transport is often studied as the transport of emulsions or dispersions, particles may also enter the subsurface from leaks or seepage that lead to particle swarms. Swarms are drop-like collections of millions of colloidal-sized particles that exhibit a number of unique characteristics when compared to dispersions and emulsions. Any contaminant or engineered particle that forms a swarm can be transported farther, faster, and more cohesively in fractures than would be expected from a traditional dispersion model. In this study, the effects of several variable aperture fractures on colloidal swarm cohesiveness and evolution were studied as a swarm fell under gravity and interacted with the fracture walls. Transparent acrylic was used to fabricate synthetic fracture samples with (1) a uniform aperture, (2) a converging region followed by a uniform region (funnel shaped), (3) a uniform region followed by a diverging region (inverted funnel), and (4) a cast of a an induced fracture from a carbonate rock. All of the samples consisted of two blocks that measured 100 x 100 x 50 mm. The minimum separation between these blocks determined the nominal aperture (0.5 mm to 20 mm). During experiments a fracture was fully submerged in water and swarms were released into it. The swarms consisted of a dilute suspension of 3 micron polystyrene fluorescent beads (1% by mass) with an initial volume of 5μL. The swarms were illuminated with a green (525 nm) LED array and imaged optically with a CCD camera. The variation in fracture aperture controlled swarm behavior. Diverging apertures caused a sudden loss of confinement that resulted in a rapid change in the swarm's shape as well as a sharp increase in its velocity

  3. Phase errors in diffraction-limited imaging: contrast limits for sparse aperture masking

    Science.gov (United States)

    Ireland, M. J.

    2013-08-01

    Bispectrum phase, closure phase and their generalization to kernel phase are all independent of pupil-plane phase errors to first order. This property, when used with sparse aperture masking behind adaptive optics, has been used recently in high-contrast observations at or inside the formal diffraction limit of large telescopes. Finding the limitations to these techniques requires an understanding of spatial and temporal third-order phase effects, as well as effects such as time-variable dispersion when coupled with the non-zero bandwidths in real observations. In this paper, formulae describing many of these errors are developed, so that a comparison can be made to fundamental noise processes of photon noise and background noise. I show that the current generation of aperture-masking observations of young solar-type stars, taken carefully in excellent observing conditions, are consistent with being limited by temporal phase noise and photon noise. This has relevance for plans to combine pupil remapping with spatial filtering. Finally, I describe calibration strategies for kernel phase, including the optimized calibrator weighting as used for LkCa15, and the restricted kernel phase POISE (phase observationally independent of systematic errors) technique that avoids explicit dependence on calibrators.

  4. Spatio-temporal Compressed Sensing with Coded Apertures and Keyed Exposures

    CERN Document Server

    Harmany, Zachary T; Willett, Rebecca M

    2011-01-01

    Optical systems which measure independent random projections of a scene according to compressed sensing (CS) theory face a myriad of practical challenges related to the size of the physical platform, photon efficiency, the need for high temporal resolution, and fast reconstruction in video settings. This paper describes a coded aperture and keyed exposure approach to compressive measurement in optical systems. The proposed projections satisfy the Restricted Isometry Property for sufficiently sparse scenes, and hence are compatible with theoretical guarantees on the video reconstruction quality. These concepts can be implemented in both space and time via either amplitude modulation or phase shifting, and this paper describes the relative merits of the two approaches in terms of theoretical performance, noise and hardware considerations, and experimental results. Fast numerical algorithms which account for the nonnegativity of the projections and temporal correlations in a video sequence are developed and appl...

  5. Synthetic aperture in terahertz in-line digital holography for resolution enhancement.

    Science.gov (United States)

    Huang, Haochong; Rong, Lu; Wang, Dayong; Li, Weihua; Deng, Qinghua; Li, Bin; Wang, Yunxin; Zhan, Zhiqiang; Wang, Xuemin; Wu, Weidong

    2016-01-20

    Terahertz digital holography is a combination of terahertz technology and digital holography. In digital holography, the imaging resolution is the key parameter in determining the detailed quality of a reconstructed wavefront. In this paper, the synthetic aperture method is used in terahertz digital holography and the in-line arrangement is built to perform the detection. The resolved capability of previous terahertz digital holographic systems restricts this technique to meet the requirement of practical detection. In contrast, the experimental resolved power of the present method can reach 125 μm, which is the best resolution of terahertz digital holography to date. Furthermore, the basic detection of a biological specimen is conducted to show the practical application. In all, the results of the proposed method demonstrate the enhancement of experimental imaging resolution and that the amplitude and phase distributions of the fine structure of samples can be reconstructed by using terahertz digital holography. PMID:26835956

  6. Wind energy applications of synthetic aperture radar

    Energy Technology Data Exchange (ETDEWEB)

    Bruun Christiansen, M.

    2006-11-15

    Synthetic aperture radars (SAR), mounted on satellites or aircraft, have proven useful for ocean wind mapping. Wind speeds at the height 10 m may be retrieved from measurements of radar backscatter using empirical model functions. The resulting wind fields are valuable in offshore wind energy planning as a supplement to on site measurements, which are costly and sparse, and model wind fields, which are not fully validated. Two applications of SAR measurements in offshore wind energy planning are addressed here: the study of wind farm wake effects and the potential of using SAR winds in offshore wind resource assessment. Firstly, wind wakes behind two large offshore wind farms in Denmark Horns Rev and Nysted are identified. A region of reduced wind speed is found downstream of both wind farms from the SAR wind fields. The wake extent and magnitude depends on the wind speed, the atmospheric stability, and the fraction of turbines operating. Wind farm wake effects are detected up to 20 km downwind of the last turbine. This distance is longer than predicted by state-of-the art wake models. Wake losses are typically 10-20% near the wind farms. Secondly, the potential of using SAR wind maps in offshore wind resource assessment is investigated. The resource assessment is made through Weibull fitting to frequency observations of wind speed and requires at least 100 satellite observations per year for a given site of interest. Predictions of the energy density are very sensitive to the wind speed and the highest possible accuracy on SAR wind retrievals is therefore sought. A 1.1 m s{sup -1} deviation on the mean wind speed is found through comparison with mast measurements at Horns Rev. The accuracy on mean wind speeds and energy densities found from satellite measurements varies with different empirical model functions. Additional uncertainties are introduced by the infrequent satellite sampling at fixed times of the day. The accuracy on satellite based wind resource

  7. Oil Slick Characterization Using Synthetic Aperture Radar

    Science.gov (United States)

    Jones, C. E.; Breivik, O.; Brekke, C.; Skrunes, S.; Holt, B.

    2015-12-01

    Oil spills are a hazard worldwide with potential of causing high impact disasters, and require an active oil spill response capability to protect personnel, the ecosystem, and the energy supply. As the amount of oil in traditionally accessible reserves decline, there will be increasing oil extraction from the Arctic and deep-water wells, both new sources with high risk and high cost for monitoring and response. Although radar has long been used for mapping the spatial extent of oil slicks, it is only since the Deepwater Horizon spill that synthetic aperture radar (SAR) has been shown capable of characterizing oil properties within a slick, and therefore useful for directing response to the recoverable thicker slicks or emulsions. Here we discuss a 2015 Norwegian oil-on-water spill experiment in which emulsions of known quantity and water-to-oil ratio along with a look-alike slick of plant oil were released in the North Sea and imaged with polarimetric SAR (PolSAR) by NASA's UAVSAR instrument for several hours following release. During the experiment, extensive in situ measurements were made from ship or aircraft with meteorological instruments, released drift buoys, and optical/IR imagers. The experiment was designed to provide validation data for development of a physical model relating polarization-dependent electromagnetic scattering to the dielectric properties of oil mixed with ocean water, which is the basis for oil characterization with SAR. Data were acquired with X-, C-, and L-band satellite-based SARs to enable multi-frequency comparison of characterization capabilities. In addition, the data are used to develop methods to differentiate mineral slicks from biogenic look-alikes, and to better understand slick weathering and dispersion. The results will provide a basis for modeling oil-in-ice spills, currently a high priority for nations involved in Arctic oil exploration. Here we discuss the Norwegian experiment, the validation data, and the results of

  8. Deployable Wide-Aperture Array Antennas

    Science.gov (United States)

    Fink, Patrick W.; Dobbins, Justin A.; Lin, Greg Y.; Chu, Andrew; Scully, Robert C.

    2005-01-01

    Inexpensive, lightweight array antennas on flexible substrates are under development to satisfy a need for large-aperture antennas that can be stored compactly during transport and deployed to full size in the field. Conceived for use aboard spacecraft, antennas of this type also have potential terrestrial uses . most likely, as means to extend the ranges of cellular telephones in rural settings. Several simple deployment mechanisms are envisioned. One example is shown in the figure, where the deployment mechanism, a springlike material contained in a sleeve around the perimeter of a flexible membrane, is based on a common automobile window shade. The array can be formed of antenna elements that are printed on small sections of semi-flexible laminates, or preferably, elements that are constructed of conducting fabric. Likewise, a distribution network connecting the elements can be created from conventional technologies such as lightweight, flexible coaxial cable and a surface mount power divider, or preferably, from elements formed from conductive fabrics. Conventional technologies may be stitched onto a supporting flexible membrane or contained within pockets that are stitched onto a flexible membrane. Components created from conductive fabrics may be attached by stitching conductive strips to a nonconductive membrane, embroidering conductive threads into a nonconductive membrane, or weaving predetermined patterns directly into the membrane. The deployable antenna may comprise multiple types of antenna elements. For example, thin profile antenna elements above a ground plane, both attached to the supporting flexible membrane, can be used to create a unidirectional boresight radiation pattern. Or, antenna elements without a ground plane, such as bow-tie dipoles, can be attached to the membrane to create a bidirectional array such as that shown in the figure. For either type of antenna element, the dual configuration, i.e., elements formed of slots in a conductive

  9. Programmable Aperture with MEMS Microshutter Arrays

    Science.gov (United States)

    Moseley, Samuel; Li, Mary; Kutyrev, Alexander; Kletetschka, Gunther; Fettig, Rainer

    2011-01-01

    A microshutter array (MSA) has been developed for use as an aperture array for multi-object selections in James Webb Space Telescope (JWST) technology. Light shields, molybdenum nitride (MoN) coating on shutters, and aluminum/aluminum oxide coatings on interior walls are put on each shutter for light leak prevention, and to enhance optical contrast. Individual shutters are patterned with a torsion flexure that permits shutters to open 90 deg. with a minimized mechanical stress concentration. The shutters are actuated magnetically, latched, and addressed electrostatically. Also, micromechanical features are tailored onto individual shutters to prevent stiction. An individual shutter consists of a torsion hinge, a shutter blade, a front electrode that is coated on the shutter blade, a backside electrode that is coated on the interior walls, and a magnetic cobalt-iron coating. The magnetic coating is patterned into stripes on microshutters so that shutters can respond to an external magnetic field for the magnetic actuation. A set of column electrodes is placed on top of shutters, and a set of row electrodes on sidewalls is underneath the shutters so that they can be electrostatically latched open. A linear permanent magnet is aligned with the shutter rows and is positioned above a flipped upside-down array, and sweeps across the array in a direction parallel to shutter columns. As the magnet sweeps across the array, sequential rows of shutters are rotated from their natural horizontal orientation to a vertical open position, where they approach vertical electrodes on the sidewalls. When the electrodes are biased with a sufficient electrostatic force to overcome the mechanical restoring force of torsion bars, shutters remain latched to vertical electrodes in their open state. When the bias is removed, or is insufficient, the shutters return to their horizontal, closed positions. To release a shutter, both the electrode on the shutter and the one on the back wall where

  10. Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures

    Science.gov (United States)

    Epstein, Ariel; Wong, Joseph P. S.; Eleftheriades, George V.

    2016-01-01

    One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators.

  11. Stroke and restricted sensory syndromes

    International Nuclear Information System (INIS)

    There have been sporadic case reports of a restricted sensory syndrome caused by stroke, most often as a cheiro-oral syndrome. We describe 14 patients with stroke who showed various restricted sensory syndromes and correlated their symptoms with the radiological findings. (orig./MG)

  12. Experimental Investigation of an L-Shaped Very-Small-Aperture Laser

    Institute of Scientific and Technical Information of China (English)

    XU Ji-Ying; WANG Jia; GAI Hong-Feng; TIAN Qian; WANG Bo-Xiong; HAO Zhi-Biao; HAN Shuo

    2006-01-01

    @@ An L-shaped very-small-aperture laser (VSAL) with high power output and field enhancement effect is fabricated and characterized. As a comparison, a conventional rectangular VSAL and a double-aperture VSAL containing one L-aperture and one rectangular aperture are also fabricated and measured.

  13. Localisation of sentinel lymph nodes: Will it influence the management of penis carcinoma?

    International Nuclear Information System (INIS)

    Aim: Patients in developing countries often present with advanced penis carcinoma and palpable inguinal lymph nodes. Since secondary infection is almost invariably present, distinguishing clinically between reactive nodes and metastasis can be difficult. The aim of our study was to evaluate dynamic sentinel node localisation for the detection of inguinal metastases in patients with penile carcinoma, in order to avoid the morbidity of full inguinal block dissection. Material and Methods: Patients with penis carcinoma presenting at the Department of Urology were included in the study. All patients underwent a scintigraphic sentinel node localisation procedure one day prior to surgery. Blue dye was injected immediately prior to surgery. Aided by a gamma probe and/or by visualising a blue node, the sentinel nodes were identified and removed. In patients with a small, well differentiated primary lesion and non-palpable nodes only the sentinel nodes were removed. In those with locally advanced or poorly differentiated primary lesions and/or clinically palpable nodes, a full inguinal block dissection was performed immediately after sentinel node biopsy and penectomy. Results: Seventeen patients with a mean age of 55 years (range 33-83 years) were included in the study. Sentinel nodes were detected bilaterally in ten patients and unilaterally in six. In one patient no sentinel node could be detected scintigraphically. Tumour involvement of sentinel nodes was found in only 1 patient, in whom malignancy was also found in other ipsilateral nodes removed at block dissection. In two patients the sentinel nodes were tumour negative, but metastases were shown in other inguinal nodes removed at block dissection. Conclusion: In this evaluation dynamic sentinel lymph node localisation followed by immediate inguinal block dissection was true positive in 1 and false negative in 2 of 17 patients with penile carcinoma. Further study and follow-up is required before routine use of the

  14. EphB4 localises to the nucleus of prostate cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Mertens-Walker, Inga, E-mail: inga.mertenswalker@qut.edu.au [Institute of Health and Biomedical Innovation, Queensland University of Technology, Woolloongabba, QLD (Australia); Australian Prostate Cancer Research Centre—Queensland, Translational Research Institute, 37 Kent Street, Woolloongabba 4102, QLD (Australia); Lisle, Jessica E. [Institute of Health and Biomedical Innovation, Queensland University of Technology, Woolloongabba, QLD (Australia); Australian Prostate Cancer Research Centre—Queensland, Translational Research Institute, 37 Kent Street, Woolloongabba 4102, QLD (Australia); Nyberg, William A. [Institute of Health and Biomedical Innovation, Queensland University of Technology, Woolloongabba, QLD (Australia); Stephens, Carson R. [Institute of Health and Biomedical Innovation, Queensland University of Technology, Woolloongabba, QLD (Australia); Australian Prostate Cancer Research Centre—Queensland, Translational Research Institute, 37 Kent Street, Woolloongabba 4102, QLD (Australia); Burke, Leslie [Institute of Health and Biomedical Innovation, Queensland University of Technology, Woolloongabba, QLD (Australia); Rutkowski, Raphael; Herington, Adrian C.; Stephenson, Sally-Anne [Institute of Health and Biomedical Innovation, Queensland University of Technology, Woolloongabba, QLD (Australia); Australian Prostate Cancer Research Centre—Queensland, Translational Research Institute, 37 Kent Street, Woolloongabba 4102, QLD (Australia)

    2015-04-10

    The EphB4 receptor tyrosine kinase is over-expressed in a variety of different epithelial cancers including prostate where it has been shown to be involved in survival, migration and angiogenesis. We report here that EphB4 also resides in the nucleus of prostate cancer cell lines. We used in silico methods to identify a bipartite nuclear localisation signal (NLS) in the extracellular domain and a monopartite NLS sequence in the intracellular kinase domain of EphB4. To determine whether both putative NLS sequences were functional, fragments of the EphB4 sequence containing each NLS were cloned to create EphB4NLS-GFP fusion proteins. Localisation of both NLS-GFP proteins to the nuclei of transfected cells was observed, demonstrating that EphB4 contains two functional NLS sequences. Mutation of the key amino residues in both NLS sequences resulted in diminished nuclear accumulation. As nuclear translocation is often dependent on importins we confirmed that EphB4 and importin-α can interact. To assess if nuclear EphB4 could be implicated in gene regulatory functions potential EphB4-binding genomic loci were identified using chromatin immunoprecipitation and Lef1 was confirmed as a potential target of EphB4-mediated gene regulation. These novel findings add further complexity to the biology of this important cancer-associated receptor. - Highlights: • The EphB4 protein can be found in the nucleus of prostate cancer cell lines. • EphB4 contains two functional nuclear localisation signals. • Chromatin immunoprecipitation has identified potential genome sequences to which EphB4 binds. • Lef1 is a confirmed target for EphB4-mediated gene regulation.

  15. EphB4 localises to the nucleus of prostate cancer cells

    International Nuclear Information System (INIS)

    The EphB4 receptor tyrosine kinase is over-expressed in a variety of different epithelial cancers including prostate where it has been shown to be involved in survival, migration and angiogenesis. We report here that EphB4 also resides in the nucleus of prostate cancer cell lines. We used in silico methods to identify a bipartite nuclear localisation signal (NLS) in the extracellular domain and a monopartite NLS sequence in the intracellular kinase domain of EphB4. To determine whether both putative NLS sequences were functional, fragments of the EphB4 sequence containing each NLS were cloned to create EphB4NLS-GFP fusion proteins. Localisation of both NLS-GFP proteins to the nuclei of transfected cells was observed, demonstrating that EphB4 contains two functional NLS sequences. Mutation of the key amino residues in both NLS sequences resulted in diminished nuclear accumulation. As nuclear translocation is often dependent on importins we confirmed that EphB4 and importin-α can interact. To assess if nuclear EphB4 could be implicated in gene regulatory functions potential EphB4-binding genomic loci were identified using chromatin immunoprecipitation and Lef1 was confirmed as a potential target of EphB4-mediated gene regulation. These novel findings add further complexity to the biology of this important cancer-associated receptor. - Highlights: • The EphB4 protein can be found in the nucleus of prostate cancer cell lines. • EphB4 contains two functional nuclear localisation signals. • Chromatin immunoprecipitation has identified potential genome sequences to which EphB4 binds. • Lef1 is a confirmed target for EphB4-mediated gene regulation

  16. Localisation of breast lesions with MR mammography (work-in-progress)

    International Nuclear Information System (INIS)

    While working with dynamic MR mammography (MRM) the need for an MR-guided localisation technique became obvious, because certain lesions were only detectable with dynamic MRM. We developed a technique to mark small breast lesions with MR guidance. Contrast-enhanced MRI was performed in a second examination, and with the use of markers on the skin a needle was placed next to the lesion. A charcoal mixture was injected around the lesion. We performed this procedure in five patients. Follow-up examinations have shown that the procedure was successful. (orig.)

  17. Localisation d'un bruit blanc en fonction de son azimut, en ecoute binaurale vs. monaurale

    OpenAIRE

    Mazo, Vincent; Paquier, Mathieu; Carriou, Célia; Jantzem, Brice; Marianovski, Rémi

    2016-01-01

    Lorsque l'information d'une seule oreille est disponible (normo-entendant avec une oreille bouchée ou malentendant atteint d'une cophose unilatérale), seuls les indices monauraux sont disponibles. L'objectif de cette étude était d'observer dans quelle mesure la localisation de sources en azimut, généralement rendue possible par l'exploitation des différences interaurales de temps et de niveau, était possible uniquement grâce à des indices monauraux. Un bruit blanc a été diffusé par différente...

  18. Localised agri-food systems: concept development and diversity of situations

    OpenAIRE

    Muchnik, José

    2010-01-01

    Localised agri-food systems (syal: from the French systèmes agroalimentaires localisés) are a type of organisation of agri-food activities, in which territorial dynamics play a decisive role in terms of the coordination between stakeholders and the development of production activities. The aim of this paper is to analyse: (i) the construction and evolution of the syal concept, (ii) the integrated character of the syal concept and its conceptual basis, (iii) how agri-food activities are linked...

  19. Saturation mechanism in clarinet-like instruments, the effect of the localised non-linear losses

    OpenAIRE

    Atig, Merouane; Dalmont, Jean-Pierre; Gilbert, Joël

    2004-01-01

    The question of what limits the amplitude of the oscillations of clarinet-like instruments is investigated. The study is based on numerical simulations in which two kind of losses are taken into account: linear losses and non-linear losses localised at the open end of the tube. The influence of the amount of losses on the saturation process and on the playing range of clarinet-like instruments is shown. Results are confirmed by experiments using an artificial mouth in which the non-linear los...

  20. Fibre Tip Sensors for Localised Temperature Sensing Based on Rare Earth-Doped Glass Coatings

    Directory of Open Access Journals (Sweden)

    Erik P. Schartner

    2014-11-01

    Full Text Available We report the development of a point temperature sensor, based on monitoring upconversion emission from erbium:ytterbium-doped tellurite coatings on the tips of optical fibres. The dip coating technique allows multiple sensors to be fabricated simultaneously, while confining the temperature-sensitive region to a localised region on the end-face of the fibre. The strong response of the rare earth ions to changing temperature allows a resolution of 0.1–0.3 °C to be recorded over the biologically relevant range of temperatures from 23–39 °C.

  1. Conception d'un capteur sonore pour la localisation de source en robotique mobile

    OpenAIRE

    Argentieri, Sylvain

    2006-01-01

    Le système auditif de l'homme fournit de nombreuses informations sur son environnement sonore. Nous sommes par exemple capables de localiser précisément l'origine d'un son et d'en interpréter sa signification, si bien qu'il parait aujourd'hui extrêmement difficile de se passer de ces informations sonores dans un monde dynamique et imprévisible. Pourtant, la robotique mobile n'a que très peu intégré cette modalité auditive, bien qu'elle apparaisse indispensable pour compléter les informations ...

  2. Common mathematical framework for real and synthetic aperture by interferometry radiometers

    OpenAIRE

    Bosch Lluís, Xavier; Ramos Pérez, Isaac; Camps Carmona, Adriano José; Rodríguez Álvarez, Nereida; Valencia Domènech, Enric; Hyuk, Park

    2014-01-01

    This work focuses on the relationship between real and synthetic aperture radiometers giving a general and common mathematical framework for both of them. It will be demonstrated that a real aperture radiometer array can be understood as a synthetic aperture one, with a high level of redundancy. Therefore, all the recent results from synthetic aperture radiometry can be translated to real aperture radiometer arrays. This fact can be used to create beamforming arrays in a ...

  3. Vision aided inertial navigation system augmented with a coded aperture

    Science.gov (United States)

    Morrison, Jamie R.

    Navigation through a three-dimensional indoor environment is a formidable challenge for an autonomous micro air vehicle. A main obstacle to indoor navigation is maintaining a robust navigation solution (i.e. air vehicle position and attitude estimates) given the inadequate access to satellite positioning information. A MEMS (micro-electro-mechanical system) based inertial navigation system provides a small, power efficient means of maintaining a vehicle navigation solution; however, unmitigated error propagation from relatively noisy MEMS sensors results in the loss of a usable navigation solution over a short period of time. Several navigation systems use camera imagery to diminish error propagation by measuring the direction to features in the environment. Changes in feature direction provide information regarding direction for vehicle movement, but not the scale of movement. Movement scale information is contained in the depth to the features. Depth-from-defocus is a classic technique proposed to derive depth from a single image that involves analysis of the blur inherent in a scene with a narrow depth of field. A challenge to this method is distinguishing blurriness caused by the focal blur from blurriness inherent to the observed scene. In 2007, MIT's Computer Science and Artificial Intelligence Laboratory demonstrated replacing the traditional rounded aperture with a coded aperture to produce a complex blur pattern that is more easily distinguished from the scene. A key to measuring depth using a coded aperture then is to correctly match the blur pattern in a region of the scene with a previously determined set of blur patterns for known depths. As the depth increases from the focal plane of the camera, the observable change in the blur pattern for small changes in depth is generally reduced. Consequently, as the depth of a feature to be measured using a depth-from-defocus technique increases, the measurement performance decreases. However, a Fresnel zone

  4. Co-localisation studies of Arabidopsis SR splicing factors reveal different types of speckles in plant cell nuclei

    International Nuclear Information System (INIS)

    SR proteins are multidomain splicing factors which are important for spliceosome assembly and for regulation of alternative splicing. In mammalian nuclei these proteins localise to speckles from where they are recruited to transcription sites. By using fluorescent protein fusion technology and different experimental approaches it has been shown that Arabidopsis SR proteins, in addition to diffuse nucleoplasmic staining, localise into an irregular nucleoplasmic network resembling speckles in mammalian cells. As Arabidopsis SR proteins fall into seven conserved sub-families we investigated co-localisation of members of the different sub-families in transiently transformed tobacco protoplast. Here we demonstrate the new finding that members of different SR protein sub-families localise into distinct populations of nuclear speckles with no, partial or complete co-localisation. This is particularly interesting as we also show that these proteins do interact in a yeast two-hybrid assay as well as in pull-down and in co-immunopreciptiation assays. Our data raise the interesting possibility that SR proteins are partitioned into distinct populations of nuclear speckles to allow a more specific recruitment to the transcription/pre-mRNA processing sites of particular genes depending on cell type and developmental stage

  5. Adjustable liquid aperture to eliminate undesirable light in holographic projection.

    Science.gov (United States)

    Wang, Di; Liu, Chao; Li, Lei; Zhou, Xin; Wang, Qiong-Hua

    2016-02-01

    In this paper, we propose an adjustable liquid aperture to eliminate the undesirable light in a holographic projection. The aperture is based on hydrodynamic actuation. A chamber is formed with a cylindrical tube. A black droplet is filled in the sidewall of the cylinder tube and the outside space is the transparent oil which is immiscible with the black droplet. An ultrathin glass sheet is attached on the bottom substrate of the device and a black shading film is secured to the central area of the glass sheet. By changing the volume of the black droplet, the black droplet will move to the middle or sidewall due to hydrodynamic actuation, so the device can be used as an adjustable aperture. A divergent spherical wave and a solid lens are used to separate the focus planes of the reconstructed image and diffraction beams induced by the liquid crystal on silicon in the holographic projection. Then the aperture is used to eliminate the diffraction beams by adjusting the size of the liquid aperture and the holographic projection does not have undesirable light. PMID:26906784

  6. Aperture referral in dioptric systems with stigmatic elements

    Directory of Open Access Journals (Sweden)

    W. F. Harris

    2012-12-01

    Full Text Available A previous paper develops the general theory of aperture referral in linear optics and shows how several ostensibly distinct concepts, including the blur patch on the retina, the effective cornealpatch, the projective field and the field of view, are now unified as particular applications of the general theory.  The theory allows for astigmatism and heterocentricity.  Symplecticity and the generality of the approach, however, make it difficult to gain insight and mean that the material is not accessible to readers unfamiliar with matrices and linear algebra. The purpose of this paper is to examine whatis, perhaps, the most important special case, that in which astigmatism is ignored.  Symplecticity and, hence, the mathematics become greatly simplified. The mathematics reduces largely to elementary vector algebra and, in some places, simple scalar algebra and yet retains the mathematical form of the general approach.  As a result the paper allows insight into and provides a stepping stone to the general theory.  Under referral an aperture under-goes simple scalar magnification and transverse translation.  The paper pays particular attention to referral to transverse planes in the neighbourhood of a focal point where the magnification may be positive, zero or negative.  Circular apertures are treated as special cases of elliptical apertures and the meaning of referred apertures of negative radius is explained briefly. (S Afr Optom 2012 71(1 3-11

  7. Adaptive coded aperture imaging: progress and potential future applications

    Science.gov (United States)

    Gottesman, Stephen R.; Isser, Abraham; Gigioli, George W., Jr.

    2011-09-01

    Interest in Adaptive Coded Aperture Imaging (ACAI) continues to grow as the optical and systems engineering community becomes increasingly aware of ACAI's potential benefits in the design and performance of both imaging and non-imaging systems , such as good angular resolution (IFOV), wide distortion-free field of view (FOV), excellent image quality, and light weight construct. In this presentation we first review the accomplishments made over the past five years, then expand on previously published work to show how replacement of conventional imaging optics with coded apertures can lead to a reduction in system size and weight. We also present a trade space analysis of key design parameters of coded apertures and review potential applications as replacement for traditional imaging optics. Results will be presented, based on last year's work of our investigation into the trade space of IFOV, resolution, effective focal length, and wavelength of incident radiation for coded aperture architectures. Finally we discuss the potential application of coded apertures for replacing objective lenses of night vision goggles (NVGs).

  8. Numerical Simulation of Transient Gauss pulse Coupling through Small Apertures

    Directory of Open Access Journals (Sweden)

    Jinshi Xiao

    2011-08-01

    Full Text Available Transient electromagnetic pulse (EMP can easily couple into equipments through small apertures in its shells. To study the coupling effects of transient Gauss pulse to a cubic cavity with openings, coupling course is simulated using sub-gridding finite difference in time domain (FDTD algorithm in this paper. A new grid partition approach is provided to simulate each kind of apertures with complex shapes. With this approach, the whole calculation space is modeled, and six kinds of aperture with different shapes are simulated. Coupling course is simulate in the whole time domain using sub-gridding FDTD approach. Selecting apertures with dimension of several millimeters to research, coupled electric field waveform, power density and coupling coefficient are calculated. The affect on coupling effects by varied incident angle and varied pulse width are also analyzed. The main conclusion includes interior resonance phenomenon, increase effect around rectangle aperture and several distributing rules of coupled electric field in the cavity. The correctness of these results is validated by comparing with other scholars’ results. These numerical results can help us to understand coupling mechanism of the transient Gauss pulse.

  9. Ecosystem Service Potentials, Flows and Demands – Concepts for Spatial Localisation, Indication and Quantification

    Directory of Open Access Journals (Sweden)

    Benjamin Burkhard

    2014-06-01

    Full Text Available The high variety of ecosystem service categorisation systems, assessment frameworks, indicators, quantification methods and spatial localisation approaches allows scientists and decision makers to harness experience, data, methods and tools. On the other hand, this variety of concepts and disagreements among scientists hamper an integration of ecosystem services into contemporary environmental management and decision making. In this article, the current state of the art of ecosystem service science regarding spatial localisation, indication and quantification of multiple ecosystem service supply and demand is reviewed and discussed. Concepts and tables for regulating, provisioning and cultural ecosystem service definitions, distinguishing between ecosystem service potential supply (stocks, flows (real supply and demands as well as related indicators for quantification are provided. Furthermore, spatial concepts of service providing units, benefitting areas, spatial relations, rivalry, spatial and temporal scales are elaborated. Finally, matrices linking CORINE land cover types to ecosystem service potentials, flows, demands and budget estimates are provided. The matrices show that ecosystem service potentials of landscapes differ from flows, especially for provisioning ecosystem services.

  10. Chemical shift imaging and localised magnetic resonance spectroscopy in full-term asphyxiated neonates

    International Nuclear Information System (INIS)

    Diagnosis of brain lesions after birth anoxia-ischemia is essential for appropriate management. Clinical evaluation is not sufficient. MRI has been proven to provide useful information. To compare abnormalities observed with MRI, including diffusion-weighted imaging (DWI), localised magnetic resonance spectroscopy (MRS) and chemical shift imaging (CSI) and correlate these findings with the clinical outcome. Fourteen full-term neonates with birth asphyxia were studied. MRI, MRS and CSI were performed within the first 4 days of life. Lesions observed with DWI were correlated with outcome, but the apparent diffusion coefficient (ADC) did improve diagnostic confidence. The mean value of Lac/Cr for the neonates with a favourable outcome was statically lower than for those who died (0.22 vs 1.04; P = 0.01). The same results were observed for the Lac/NAA ratio (0.21 vs 1.23; P = 0.01). Data obtained with localised MRS and CSI were correlated for the ratio N-acetyl-aspartate/choline, but not for the other metabolites. No correlation was found between the ADC values and the metabolite ratios. Combination of these techniques could be helpful in our understanding of the physiopathological events occurring in neonates with asphyxia. (orig.)

  11. Subcritical monitoring studies in BZD/2 using alternative absorber compositions and a localised neutron source

    International Nuclear Information System (INIS)

    A series of supplementary subcritical monitoring studies has been carried out in the Single Annular Core BZD/2. The first part concerned the use of alternative absorber compositions: 40 % enriched B4C and Eu2O3. The worth of the 40 % enriched B4C absorber relative to the naturally enriched one was found to be significantly lower than for the corresponding measurements in the conventional core BZB (1.197 versus 1.259). Although an influence of the harder spectrum in BZD is likely, the results of similar studies in BZC seem to contradict this assumption. Within the experimental errors, the worth of the Eu2O3 absorber relative to natural B4C agrees with that found in BZB. As in previous investigations, diffusion theory calculations were found to overestimate the worth of the 40 % enriched B4C absorber relative to the natural one by several percent. The worth of Eu2O3 relative to B4C-nat was again severely underpredicted. In a second series of experiments, a localised neutron source (Cf-252) was introduced into the core. For the two absorber arrays established in the presence of the source, the MSM analysis produced reactivities, which agree within about 0.5 % relative with those, obtained from previous measurements of these arrays without the localised source. This confirms the satisfactory performance of the MSM technique even in a strongly decoupled annular system with very irregular source distribution

  12. Organisation as a key factor in Localised Agri-Food Systems (LAFS

    Directory of Open Access Journals (Sweden)

    Corrado Giacomini

    2015-05-01

    Full Text Available Most studies of Localised Agri-Food Systems (LAFS focus on the localised concentration of members and firms, and pay less attention to organisational factors, particularly those of an exogenous nature. This paper focuses on the role of organisation in a LAFS, assessing the efficacy of EU organisational measures aimed at strengthening the concentration of supply from the recent CAP reform 2014-2020. The paper has three sections. Part One describes the evolution of the concept of LAFS. Part Two examines the leading role played by institutions in organising relationships between firms in a LAFS. The example provided is that of the measures affecting the organisation of supply introduced by the recent CAP reform, 2014-2020. It makes particular reference to the Distretto del pomodoro da industria – Nord Italia (‘Industrial Tomato District – Northern Italy’. Part Three describes how organisational factors can lead to the creation of a LAFS, while the criterion of proximity is necessary but not sufficient.

  13. Functional MRI of the brain: localisation of eloquent cortex in focal brain lesion therapy

    Energy Technology Data Exchange (ETDEWEB)

    Dymarkowski, S.; Sunaert, S.; Oostende, S. van; Hecke, P. van; Wilms, G.; Demaerel, P.; Marchal, G. [Department of Radiology, University Hospitals, Leuven (Belgium); Nuttin, B.; Plets, C. [Department of Neurosurgery, University Hospitals, Leuven (Belgium)

    1998-12-01

    The aim of this study was to assess the feasibility of functional MRI (fMRI) in a clinical environment on a large patient group, and to evaluate the pretherapeutic value of localisation of eloquent cortex. Forty patients with focal brain lesions of different origin were studied using fMRI. Functional information was obtained using motor, somatosensory, auditory and phonological stimuli depending on the localisation of the lesions. To obtain information about the spatial accuracy of fMRI, the results were compared with postoperative electrocortical stimulation. Two patients with secondary trigeminal neuralgia were scanned using a motor protocol and were implanted with an extradural plate electrode. Imaging was successful in 40 of 42 patients (including the 2 with trigeminal neuralgia). These patients were analysed for strength of activation, the relation of the lesion to activation sites and the presence of mass effect. The correlation between these data and surgical findings provided significant additional clinical information. Functional MRI can be accurately performed in patients with focal brain lesions using a dedicated approach. Functional MRI offers important clinical information as a contribution to a decrease in posttherapeutic morbidity. The accuracy of the technique can be confirmed by other modalities, including invasive cortical electrostimulation. (orig.) With 7 figs., 2 tabs., 25 refs.

  14. Detection and cellular localisation of the synthetic soluble macromolecular drug carrier pHPMA

    International Nuclear Information System (INIS)

    Synthetic macromolecules such as copolymers of N-(2-hydroxypropyl)methacrylamide (pHPMA) are potential carriers for the delivery of drugs owing to their ability to passively accumulate in solid tumours [enhanced permeation and retention (EPR) effect]. To gain further knowledge about the biodistribution and the cellular localisation, poly(HPMA) was prepared for labelling by introducing biotin molecules. Biotinylated pHPMA (5 mol%) was intravenously injected into tumour-bearing rats and the accumulation of biotin-pHPMA was visualised using a streptavidin-alkaline phosphatase technique at day 7 post injection. In spite of the high solubility of pHPMA copolymers and the lack of attachment to cell structures, the biotinylated polymer could be easily detected in tissues fixed in 10% paraformaldehyde-phosphate buffer at 4 C for 48 h. While biotin-pHPMA could be detected intracytoplasmically in liver and spleen, a predominantly interstitial localisation was observed within the anaplastic prostate carcinoma (Dunning R3327-AT1). How biotin as a label influences the biodistribution of poly(HPMA) was assessed by scintigraphy, autoradiography and histology comparing homopolymer poly(HPMA) with biotin-pHPMA. The organ distribution patterns of the two polymers correlated well, except with respect to kidney. It is assumed that the accumulation of biotin-pHPMA in the distal tubuli is due to a biotin transporter in the brush border membrane. The technique presented is useful for a more comprehensive understanding of the biodistribution of soluble macromolecules. (orig.)

  15. Treatment of localised prostate cancer with transrectal high intensity focused ultrasound.

    Science.gov (United States)

    Chapelon, J Y; Ribault, M; Vernier, F; Souchon, R; Gelet, A

    1999-03-01

    With the advent of PSA dosing, an increasing number of prostate cancers are being detected at a local stage. Since 1989, our group has been developing a research project with the aim of establishing treatment of localised prostate cancer by means of HIFU. The treatment is performed transrectally, using ultrasound imaging guidance only. The quality of HIFU treatment depends on four factors: the intensity of the transmitted pulse, the exposure time, the signal frequency, and the time between two firing bursts. The lesions are created by a thermal effect. Their slightly conical form is due to the absorption of ultrasound by tissue, enhanced by cavitation bubbles. Results obtained since 1993 demonstrate that transrectally administered HIFU treatment achieves local control of localised prostate cancer in 80% of cases, with 70% complete success and 30% partial response. The use of an annular array probe with variable focus and frequency should significantly improve results in the future. Finally, real time visual display of the damaged tissue via differential imaging of the attenuation coefficient should give the surgeon an instant appreciation of the result of the sequence. It would thus be possible to repeat treatment of insufficiently covered zones in the same session. PMID:10099164

  16. Rare events statistics of random walks on networks: localisation and other dynamical phase transitions

    Science.gov (United States)

    De Bacco, Caterina; Guggiola, Alberto; Kühn, Reimer; Paga, Pierre

    2016-05-01

    Rare event statistics for random walks on complex networks are investigated using the large deviation formalism. Within this formalism, rare events are realised as typical events in a suitably deformed path-ensemble, and their statistics can be studied in terms of spectral properties of a deformed Markov transition matrix. We observe two different types of phase transition in such systems: (i) rare events which are singled out for sufficiently large values of the deformation parameter may correspond to localised modes of the deformed transition matrix; (ii) ‘mode-switching transitions’ may occur as the deformation parameter is varied. Details depend on the nature of the observable for which the rare event statistics is studied, as well as on the underlying graph ensemble. In the present paper we report results on rare events statistics for path averages of random walks in Erdős–Rényi and scale free networks. Large deviation rate functions and localisation properties are studied numerically. For observables of the type considered here, we also derive an analytical approximation for the Legendre transform of the large deviation rate function, which is valid in the large connectivity limit. It is found to agree well with simulations.

  17. Functional MRI of the brain: localisation of eloquent cortex in focal brain lesion therapy

    International Nuclear Information System (INIS)

    The aim of this study was to assess the feasibility of functional MRI (fMRI) in a clinical environment on a large patient group, and to evaluate the pretherapeutic value of localisation of eloquent cortex. Forty patients with focal brain lesions of different origin were studied using fMRI. Functional information was obtained using motor, somatosensory, auditory and phonological stimuli depending on the localisation of the lesions. To obtain information about the spatial accuracy of fMRI, the results were compared with postoperative electrocortical stimulation. Two patients with secondary trigeminal neuralgia were scanned using a motor protocol and were implanted with an extradural plate electrode. Imaging was successful in 40 of 42 patients (including the 2 with trigeminal neuralgia). These patients were analysed for strength of activation, the relation of the lesion to activation sites and the presence of mass effect. The correlation between these data and surgical findings provided significant additional clinical information. Functional MRI can be accurately performed in patients with focal brain lesions using a dedicated approach. Functional MRI offers important clinical information as a contribution to a decrease in posttherapeutic morbidity. The accuracy of the technique can be confirmed by other modalities, including invasive cortical electrostimulation. (orig.)

  18. Axial super-localisation using rotating point spread functions shaped by polarisation-dependent phase modulation.

    Science.gov (United States)

    Roider, Clemens; Jesacher, Alexander; Bernet, Stefan; Ritsch-Marte, Monika

    2014-02-24

    We present an approach for point spread function (PSF) engineering that allows one to shape the optical wavefront independently in both polarisation directions, with two adjacent phase masks displayed on a single liquid-crystal spatial light modulator (LC-SLM). The set-up employs a polarising beam splitter and a geometric image rotator to rectify and process both polarisation directions detected by the camera. We shape a single-lobe ("corkscrew") PSF that rotates upon defocus for each polarisation channel and combine the two polarisation channels with a relative 180° phase-shift on the computer, merging them into a single PSF that exhibits two lobes whose orientation contains information about the axial position. A major advantage lies in the possibility to measure and eliminate the aberrations in the two polarisation channels independently. We demonstrate axial super-localisation of isotropically emitting fluorescent nanoparticles. Our implementation of the single-lobe PSFs follows the method proposed by Prasad [Opt. Lett.38, 585 (2013)], and thus is to the best of our knowledge the first experimental realisation of this suggestion. For comparison we also study an approach with a rotating double-helix PSFs (in only one polarisation channel) and ascertain the trade-off between localisation precision and axial working range. PMID:24663724

  19. Low-frequency variability in idealised GCM experiments with circumpolar and localised storm tracks

    Directory of Open Access Journals (Sweden)

    W. Müller

    2002-01-01

    Full Text Available Idealised global circulation model simulations with circumpolar and localised (one and two storm tracks are re-analysed to determine scaling, intermittency and phase-space structures. In a hundred year experiment with a circumpolar storm track, the spectrum S(f of the first principal component of the zonal wind fluctuations shows the following power law regimes: (a a short-term memory between f- -4 and f  -2 up to 50 days and (b a long-term memory f -1 from 50 to 400 days and f -0.24 beyond 400 days, similar to observed maritime single station near-surface air temperature data. In the presence of localised storm tracks, the wave number two dominates the dynamics and a long-term memory cannot be detected. The recurrence plot is introduced as a novel tool to comprehensively visualise the evolution of the dynamical system in terms of state separations (distances in phase space. The patterns allow for a qualitative interpretation of the underlying local phenomena in phase space, such as waves, analogs, extremes, and global regimes. Attractor dimensions are, in general, larger than 10, but they appear to be lower in the wave-dominated regimes of the double storm track experiment.

  20. Apodized Pupil Lyot Coronagraphs for Arbitrary Telescope Apertures

    CERN Document Server

    Soummer, R

    2004-01-01

    In the context of high dynamic range imaging, this study presents a breakthrough for the understanding of Apodized Pupil Lyot Coronagraphs, making them available for arbitrary aperture shapes. These new solutions find immediate application in current, ground-based coronagraphic studies (Gemini, VLT) and in existing instruments (AEOS Lyot Project). They also offer the possiblity of a search for an on-axis design for TPF. The unobstructed aperture case has already been solved by Aime et al. (2002) and Soummer et al. (2003). Analytical solutions with identical properties exist in the general case and, in particular, for centrally obscured apertures. Chromatic effects can be mitigated with a numerical optimization. The combination of analytical and numerical solutions enables the study of the complete parameter space (central obstruction, apodization throughput, mask size, bandwidth, and Lyot stop size).

  1. Optimized baffle and aperture placement in neutral beamlines

    Science.gov (United States)

    Stone, R.; Duffy, T.; Vetrovec, J.

    1983-11-01

    Most neutral beamlines contain an iron-core ion-bending magnet that requires shielding between the end of the neutralizer and this magnet. This shielding allows the gas pressure to drop prior to the beam entering the magnet and therefore reduces beam losses in this drift region. The beam losses are reduced even further by eliminating the iron-core magnet and the magnetic shielding altogether. The required bending field is supplied by current coils without the iron poles. In addition, placement of the baffles and apertures affects the cold gas entering the plasma region and the losses in the neutral beam due to re-ionization. The placement of the baffles which, determine the amount of pumping in each chamber, and the apertures, which determine the beam loss were varied. A baffler/aperture configuration is for either minimum cold gas into the plasma region or minimum beam losses, but not both.

  2. Measurement of the atmospheric primary aberrations by 4-aperture DIMM

    CERN Document Server

    Shomali, Ramin; Darudi, Ahmad

    2011-01-01

    The present paper investigates and discusses the ability of the Hartmann test with 4-aperture DIMM to measure the atmospheric primary aberrations which, in turn, can be used for calculation of the atmospheric coherence time. Through performing numerical simulations, we show that the 4-aperture DIMM is able to measure the defocus and astigmatism terms correctly while its results are not reliable for the coma. The most important limitation in the measurement of the primary aberrations by 4-aperture DIMM is the centroid displacements of the spots which are caused by the higher order aberrations. This effect is negligible in calculating of the defocus and astigmatisms, while, it cannot be ignored in the calculation of the coma.

  3. Central obscuration effects on optical synthetic aperture imaging

    Science.gov (United States)

    Wang, Xue-wen; Luo, Xiao; Zheng, Li-gong; Zhang, Xue-jun

    2014-02-01

    Due to the central obscuration problem exists in most optical synthetic aperture systems, it is necessary to analyze its effects on their image performance. Based on the incoherent diffraction limited imaging theory, a Golay-3 type synthetic aperture system was used to study the central obscuration effects on the point spread function (PSF) and the modulation transfer function (MTF). It was found that the central obscuration does not affect the width of the central peak of the PSF and the cutoff spatial frequency of the MTF, but attenuate the first sidelobe of the PSF and the midfrequency of the MTF. The imaging simulation of a Golay-3 type synthetic aperture system with central obscuration proved this conclusion. At last, a Wiener Filter restoration algorithm was used to restore the image of this system, the images were obviously better.

  4. Synthetic aperture integration (SAI) algorithm for SAR imaging

    Science.gov (United States)

    Chambers, David H; Mast, Jeffrey E; Paglieroni, David W; Beer, N. Reginald

    2013-07-09

    A method and system for detecting the presence of subsurface objects within a medium is provided. In some embodiments, the imaging and detection system operates in a multistatic mode to collect radar return signals generated by an array of transceiver antenna pairs that is positioned across the surface and that travels down the surface. The imaging and detection system pre-processes the return signal to suppress certain undesirable effects. The imaging and detection system then generates synthetic aperture radar images from real aperture radar images generated from the pre-processed return signal. The imaging and detection system then post-processes the synthetic aperture radar images to improve detection of subsurface objects. The imaging and detection system identifies peaks in the energy levels of the post-processed image frame, which indicates the presence of a subsurface object.

  5. Field of view for near-field aperture synthesis imaging

    CERN Document Server

    Buscher, David F

    2015-01-01

    Aperture synthesis techniques are increasingly being employed to provide high angular resolution images in situations where the object of interest is in the near field of the interferometric array. Previous work has showed that an aperture synthesis array can be refocused on an object in the near field of an array, provided that the object is smaller than the effective Fresnel zone size corresponding to the array-object range. We show here that, under paraxial conditions, standard interferometric techniques can be used to image objects which are substantially larger than this limit. We also note that interferometric self-calibration and phase-closure image reconstruction techniques can be used to achieve near-field refocussing without requiring accurate object range information. We use our results to show that the field of view for high-resolution aperture synthesis imaging of geosynchronous satellites from the ground can be considerably larger than the largest satellites in Earth orbit.

  6. Coronagraph-Integrated Wavefront Sensing with a Sparse Aperture Mask

    CERN Document Server

    Subedi, Hari; Kasdin, N Jeremy; Cavanagh, Kathleen; Riggs, A J Eldorado

    2015-01-01

    Stellar coronagraph performance is highly sensitive to optical aberrations. In order to effectively suppress starlight for exoplanet imaging applications, low-order wavefront aberrations entering a coronagraph such as tip-tilt, defocus and coma must be determined and compensated. Previous authors have established the utility of pupil-plane masks (both non-redundant/sparse-aperture and generally asymmetric aperture masks) for wavefront sensing. Here we show how a sparse aperture mask (SAM) can be integrated with a coronagraph to measure low-order, differential phase aberrations. Starlight rejected by the coronagraph's focal plane stop is collimated to a relay pupil, where the mask forms an interference fringe pattern on a subsequent detector. Our numerical Fourier propagation models show that the information encoded in the fringe intensity distortions is sufficient to accurately discriminate and estimate Zernike phase modes extending from tip-tilt up to radial degree $n=5$, with amplitude up to $\\lambda/20$ RM...

  7. Permeability and dispersivity of variable-aperture fracture systems

    Energy Technology Data Exchange (ETDEWEB)

    Tsang, Y.W.; Tsang, C.F.

    1990-01-01

    A number of recent experiments have pointed out the need of including the effects of aperture variation within each fracture in predicting flow and transport properties of fractured media. This paper introduces a new approach in which medium properties, such as the permeability to flow and dispersivity in tracer transport, are correlated to only three statistical parameters describing the fracture aperture probability distribution and the aperture spatial correlation. We demonstrate how saturated permeability and relative permeabilities for flow, as well as dispersion for solute transport in fractures may be calculated. We are in the process of examining the applicability of these concepts to field problems. Results from the evaluation and analysis of the recent Stripa-3D field data are presented. 13 refs., 10 figs.

  8. Permeability and dispersivity of variable-aperture fracture systems

    International Nuclear Information System (INIS)

    A number of recent experiments have pointed out the need of including the effects of aperture variation within each fracture in predicting flow and transport properties of fractured media. This paper introduces a new approach in which medium properties, such as the permeability to flow and dispersivity in tracer transport, are correlated to only three statistical parameters describing the fracture aperture probability distribution and the aperture spatial correlation. We demonstrate how saturated permeability and relative permeabilities for flow, as well as dispersion for solute transport in fractures may be calculated. We are in the process of examining the applicability of these concepts to field problems. Results from the evaluation and analysis of the recent Stripa-3D field data are presented. 13 refs., 10 figs

  9. Frequency division transmission imaging and synthetic aperture reconstruction

    DEFF Research Database (Denmark)

    Gran, Fredrik; Jensen, Jørgen Arendt

    2006-01-01

    In synthetic transmit aperture imaging only a few transducer elements are used in every transmission, which limits the signal-to-noise ratio (SNR). The penetration depth can be increased by using all transmitters in every transmission. In this paper, a method for exciting all transmitters in every...... transmission, and the information from the different transmitters can be separated instantaneously. Compared to traditional synthetic transmit aperture (STA) imaging, in which the different transmitters are excited sequentially, more energy is transmitted in every transmission, and a better signal......-to-noise-ratio is attained. The method has been tested in simulation, in which the resolution arid contrast was compared to a standard synthetic transmit aperture system with a single sinusoid excitation. The resolution and contrast was comparable for the two systems. The method also has been tested using the...

  10. Experimental investigation of synthetic aperture flow angle estimation

    DEFF Research Database (Denmark)

    Oddershede, Niels; Jensen, Jørgen Arendt

    2005-01-01

    Currently synthetic aperture flow methods can find the correct velocity magnitude, when the flow direction is known. To make a fully automatic system, the direction should also be estimated. Such an approach has been suggested by Jensen (2004) based on a search of the highest cross-correlation as a...... function of velocity and angle. This paper presents an experimental investigation of this velocity angle estimation method based on a set of synthetic aperture flow data measured using our RASMUS experimental ultrasound system. The measurements are performed for flow angles of 60, 75, and 90 deg. with...... respect to the axial direction, and for constant velocities with a peak of 0.1 m/s and 0.2 m/s. The implemented synthetic aperture imaging method uses virtual point sources in front of the transducer, and recursive imaging is used to increase the data rate. A 128 element linear array transducer is used...

  11. Synthetic aperture flow imaging using dual stage beamforming

    DEFF Research Database (Denmark)

    Li, Ye; Jensen, Jørgen Arendt

    2013-01-01

    A method for synthetic aperture flow imaging using dual stage beamforming has been developed. The main motivation is to increase the frame rate and still maintain a beamforming quality sufficient for flow estimation that is possible to implement in a commercial scanner. This method can generate...... continuous high frame rate flow images with lower calculation demands than the full synthetic aperture flow imaging. The performance of the approach was investigated using Field II simulations and measurements with the experimental scanner SARUS. A laminar flow with a parabolic profile was generated by a.......6% (2.1% and 3.2% for the simulations). A parameter study revealed that emission spacing, number of cross-correlation functions used for averaging, and the length of the velocity searching range influence the performance. Compared to the full synthetic aperture flow imaging the total number of...

  12. A new method of aperture synthetizing in digital holography

    Institute of Scientific and Technical Information of China (English)

    Zhang Qing-Sheng; Lü Xiao-Xu; Yu Qing-Ting; Liu Gan-Yong

    2009-01-01

    This paper proposes a new method of aperture synthetizing in digital holography based on the principle of holography. In the new method aperture synthetizing is achieved by reconstructing each sub-hologram respectively, firstly,moving each reconstructed wave field referred to the benchmark reconstructed wave field according to the relationship between spacial motion and frequency shift, and finally splicing them by using superposition. Two different recording ways, using plane wave to record and using spherical wave to record, are analyzed, and their moving formula is deduced,too. Simulation and experiment are done. The results show that in comparison with the traditional method of aperture synthetizing in digital holography, the new method can decrease calculation and save reconstructed time obviously which has better applicability.

  13. Dynamic aperture and transverse proton diffusion in HERA

    International Nuclear Information System (INIS)

    The dynamic aperture caused by persistent-current nonlinear field errors is an important concern in the design of superconducting hadron storage rings. The HERA proton ring is the second superconducting accelerator in operation. In this lecture note, its measured dynamic aperture is compared with that inferred from comprehensive trackig studies. To understand the difference between prediction and measurement, a semi-analytical method is developed for evaluating transverse diffusion rates due to various processes, such as modulational diffusion or sweeping diffusion this analysis makes use of parameters for high-order resonances in the transverse phase space, which are obtained by normal-form algorithms using differential-algebra software. This semi-analytical results are consistent wit the measurements, and suggest that the actual dynamic aperture is caused by an interplay of tune modulation and nonlinear magnetic fields

  14. Extended model of restricted beam for FSO links

    Science.gov (United States)

    Poliak, Juraj; Wilfert, Otakar

    2012-10-01

    Modern wireless optical communication systems in many aspects overcome wire or radio communications. Their advantages are license-free operation and broad bandwidth that they offer. The medium in free-space optical (FSO) links is the atmosphere. Operation of outdoor FSO links struggles with many atmospheric phenomena that deteriorate phase and amplitude of the transmitted optical beam. This beam originates in the transmitter and is affected by its individual parts, especially by the lens socket and the transmitter aperture, where attenuation and diffraction effects take place. Both of these phenomena unfavourable influence the beam and cause degradation of link availability, or its total malfunction. Therefore, both of these phenomena should be modelled and simulated, so that one can judge the link function prior to the realization of the system. Not only the link availability and reliability are concerned, but also economic aspects. In addition, the transmitted beam is not, generally speaking, circularly symmetrical, what makes the link simulation more difficult. In a comprehensive model, it is necessary to take into account the ellipticity of the beam that is restricted by circularly symmetrical aperture where then the attenuation and diffraction occur. General model is too computationally extensive; therefore simplification of the calculations by means of analytical and numerical approaches will be discussed. Presented model is not only simulated using computer, but also experimentally proven. One can then deduce the ability of the model to describe the reality and to estimate how far can one go with approximations, i.e. limitations of the model are discussed.

  15. How harmful are adaptation restrictions

    OpenAIRE

    Bruin, de, B.; Dellink, R.B.

    2009-01-01

    The dominant assumption in economic models of climate policy remains that adaptation will be implemented in an optimal manner. There are, however, several reasons why optimal levels of adaptation may not be attainable. This paper investigates the effects of suboptimal levels of adaptation, i.e. adaptation restrictions, on the composition and level of climate change costs and on welfare. Several adaptation restrictions are identified and then simulated in a revised DICE model, extended with ad...

  16. X-ray lenses with large aperture; Roentgenlinsen mit grosser Apertur

    Energy Technology Data Exchange (ETDEWEB)

    Simon, Markus

    2010-07-01

    Up to now, most X-ray imaging setups are based on absorption contrast imaging. There is a demand for focused X-rays in many X-ray analysis applications, either to increase the resolution of an imaging system, or, to reduce the time effort of an experiment through higher photon flux. For photon energies higher than 15 keV refractive X-ray optics are more efficient in comparison to non-refractive X-ray optics. The aim of this work was to develop X-ray lenses with large apertures and high transparency. By increasing the number of refracting surfaces while removing unnecessary lens material such lenses have been developed. Utilizing this approach the overall beam deflection angle is large with respect to the lens material it propagates through and so the transparency of the lens is increased. Within this work, X-ray lenses consisting of several thousands of prisms with an edge length in the range of micrometers have been developed and fabricated by deep X-ray lithography. Deep X-ray lithography enables high precision microstrucures with smooth sidewalls and large aspect ratios. The aperture of high-transparency X-ray lenses made this way is greater than 1 mm. They are suitable for photon energies in the range of 8 keV to 24 keV and offer a focal width of smaller than 10 {mu}m at a transparency of around 40%. Furthermore, rolled X-ray lenses have been developed, that are made out of a microstructured polyimide film, which is cut according to the requirements regarding focal length and photon energy. The microstructured film is fabricated by molding, using an anisotropically etched silicon wafer as molding tool. Its mean roughness is in the range of nanometers. The film features prismatic structures, its surface topology is similar to an asparagus field. The measured diameter of the point focus was 18 {mu}m to 31 {mu}m, the calculated opticla efficiency was 37%. Future work will concentrate on increasing the aspect ratio of Prism Lenses and on increasing the rolling

  17. Radio Astronomy Transformed: Aperture Arrays - Past, Present & Future

    OpenAIRE

    Garrett, Michael A.

    2012-01-01

    I review the early development of Aperture Arrays and their role in radio astronomy. The demise of this technology at the end of the 1960's, and the reasons for the rise of parabolic dishes is also considered. The parallels with the Antikythera mechanism (see these proceedings) as a lost technology are briefly presented. Aperture Arrays re-entered the world of radio astronomy as the idea to build a huge radio telescope with a collecting area of one square kilometre (the Square Kilometre Array...

  18. The baffle aperture region of an ion thruster

    International Nuclear Information System (INIS)

    During the period of this research project, electron bombardment ion thrusters have passed from an advanced state of development to highly successful flight demonstrations (e.g. Deep Space 1). Such advances made by NASA have been quickly followed in the commercial sector (e.g. NSSK of communications satellites). In the next few years, these early successes will be followed by many new electric propulsion missions, planned by the world's space agencies and commercial space organisations. These early successes will spawn more ambitious and demanding missions, necessitating thrusters of different power demands, thrusts and sizes. Scaling of the UK series of electron bombardment ion thrusters has previously been carried out by semi- empirical scaling laws. These scaling laws have worked well within a certain range of thruster sizes with some iterative redesign necessary to produce acceptable efficiencies. However, when scaling beyond the ranges of the T5, T6 and UK25, the current scaling laws cannot be used due to the conflicting requirements of magnetic field strength in the discharge chamber and baffle aperture region. The baffle aperture region contains a plasma double layer that accelerates primary electrons into the discharge chamber and thus controls ionisation in the ion thruster. Previously, the baffle aperture region was poorly understood. An extensive and unique experimental investigation of the plasma properties around this critical baffle aperture region has been carried out using Langmuir probes. The externally applied magnetic field has been mapped and the Langmuir probe results have been validated using emissive probes. Results are presented on both argon and xenon propellant and high- resolution maps of an extensive range of plasma properties are plotted over a continuous area from the coupling plasma, through the baffle aperture and into the discharge plasma. Maps were taken over a unique and wide range of thruster operating conditions in which all

  19. Intracavity frequency doubling in a wide-aperture argon laser

    International Nuclear Information System (INIS)

    The four-mirror cavity with a BBO crystal for frequency doubling in a wide-aperture argon laser is optimised. The dependences of the second-harmonic power on the displacement of a focusing mirror, the displacement of the crystal, and the discharge current are measured. These dependences are in good agreement with calculations. After optimisation, ∼1 W of UV laser radiation at 244 nm was obtained with the conversion efficiency twice as large as that for the known similar lasers. It is shown that the increase in the efficiency was achieved mainly due to the increase in the discharge-tube aperture. (nonlinear optical phenomena)

  20. Synthetic aperture radar system design for random field classification

    Science.gov (United States)

    Harger, R. O.

    1973-01-01

    An optimum design study is carried out for synthetic aperture radar systems intended for classifying randomly reflecting areas (such as agricultural fields) characterized by a reflectivity density spectral density. The problem solution is obtained, neglecting interfield interference and assuming areas of known configuration and location, as well as a certain Gaussian signal field property. The optimum processor is nonlinear, but includes conventional matched filter processing. A set of summary design curves is plotted, and is applied to the design of a satellite synthetic aperture radar system.

  1. A fast autofocus algorithm for synthetic aperture radar processing

    DEFF Research Database (Denmark)

    Dall, Jørgen

    1992-01-01

    High-resolution synthetic aperture radar (SAR) imaging requires the motion of the radar platform to be known very accurately. Otherwise, phase errors are induced in the processing of the raw SAR data, and bad focusing results. In particular, a constant error in the measured along-track velocity or...... the cross-track acceleration leads to a phase error that varies quadratically over the synthetic aperture. The process of estimating this quadratic phase error directly from the radar data is termed autofocus. A novel autofocus algorithm with a computational complexity which is at least an order of...

  2. In-vivo evaluation of convex array synthetic aperture imaging

    DEFF Research Database (Denmark)

    Pedersen, Morten Høgholm; Gammelmark, Kim Løkke; Jensen, Jørgen Arendt

    2007-01-01

    This paper presents an in-vivo study of synthetic transmit aperture (STA) imaging in comparison to conventional imaging, evaluating whether STA imaging is feasible in-vivo, and whether the image quality obtained is comparable to traditional scanned imaging in terms of penetration depth, spatial...... element aperture was used in transmit and receive with a 1.5 cycle sinusoid excitation pulse. Conventional and STA images were acquired interleaved ensuring that the exact same anatomical location was scanned. Image sequences were recorded in real-time and processed off-line. Seven male volunteers were...

  3. Performance of Synthetic Aperture Compounding for in-vivo imaging

    DEFF Research Database (Denmark)

    Hansen, Jens Munk; Jensen, Jørgen Arendt

    2011-01-01

    A method for synthetic aperture compounding (SAC) is applied to data from water tank measurements, data from a tissue-mimicking phantom, and clinical data from the abdomen of a healthy 27 year old male. Further, using this method compounding can be obtained without any loss in temporal resolution....... The water tank measurements reveal an improved detail resolution of 45% when comparing SAC to conventional compounding and an improvement of 22%, when comparing to synthetic aperture (SA) imaging. The cystic resolution at 12 dB is improved by 50% and 12% when comparing SAC to conventional compounding...

  4. Synthetic Aperture Sequential Beamformation applied to medical imaging.

    OpenAIRE

    Hemmsen, Martin Christian; Hansen, Jens Munk; Jensen, Jørgen Arendt

    2012-01-01

    Synthetic Aperture Sequential Beamforming (SASB) is applied to medical ultrasound imaging using a multi element convex array transducer. The main motivation for SASB is to apply synthetic aperture techniques without the need for storing RF-data for a number of elements and hereby devise a system with a reduced system complexity. Using a 192 element, 3.5 MHz, λ-pitch transducer, it is demonstrated using tissue-phantom and wire-phantom measurements, how the speckle size and the detail resolutio...

  5. Improving the performance of monocular visual simultaneous localisation and mapping through the use of a gimballed camera

    Science.gov (United States)

    Playle, Nicholas

    In this thesis modern vision based localisation methods are discussed and contrasted with existing satellite based approaches. Shortcomings are noted and potential solutions are highlighted. A novel method of using a gimballed camera to perform visual Simultaneous Localisation and Mapping (SLAM) is proposed, along with a control algorithm to point the camera toward feature dense regions. This method is then modularly coupled with existing visual SLAM techniques allowing seamless integration across different platforms. Ground tests are performed to verify operation of the gimbal controller and rotation inverser. Results from experimental flight tests are incorporated as a final means of obtaining information to verify gimbal operation.

  6. Intérêt du guidage 3D et de la localisation des biopsies de prostate par voie endorectale

    OpenAIRE

    Mozer, Pierre; Chevreau, Grégoire; Troccaz, Jocelyne; Renard-Penna, Raphaëlle

    2011-01-01

    International audience La réalisation de biopsies de prostate, le plus souvent par voie endorectale, est primordiale pour le diagnostic et l'évaluation du pronostic du cancer. La précision de la localisation des biopsies est sujette à caution. Le développement de systèmes informatiques permet d'enregistrer avec précision leur localisation et de les guider pour améliorer leur distribution. Ces mêmes dispositifs permettent de fusionner images échographiques et images IRM et de fusionner diff...

  7. Organization of crop and animal production in dairy farms localised in three chosen regions of lubelskie voivodeship

    Directory of Open Access Journals (Sweden)

    Jolanta Bojarszczuk

    2010-01-01

    Full Text Available The evaluation of organization of crop and animal production in dairy farms localised in three regions in Lubelskie voivodeship was presented in the paper. The data source was questionnaire research. The study was trained in 145 farms. The provided analysis showed that cereals had significantly share in pattern system in tested farms. Researched farms are differentiated of occupied differentiation of cropping pattern and density livestock between farms localised in different regions of Lubelskie voivodeship caused different level of intensity of organization animal and crops production. The differentiation of indicators was especially significant between farms in Krasnystaw and Ryki.

  8. Basolateral localisation of KCNQ1 potassium channels in MDCK cells: molecular identification of an N-terminal targeting motif

    DEFF Research Database (Denmark)

    Jespersen, Thomas; Rasmussen, Hanne B; Grunnet, Morten; Jensen, Henrik S.; Angelo, Kamilla; Dupuis, Delphine S; Vogel, Lotte K; Jorgensen, Nanna K; Klaerke, Dan A; Olesen, Søren-Peter

    channels are located basolaterally when expressed in polarised MDCK cells. The basolateral localisation of KCNQ1 is not affected by co-expression of any of the five KCNE beta-subunits. We characterise two independent basolateral sorting signals present in the N-terminal tail of KCNQ1. Mutation of the...... tyrosine residue at position 51 resulted in a non-polarized steady-state distribution of the channel. The importance of tyrosine 51 in basolateral localisation was emphasized by the fact that a short peptide comprising this tyrosine was able to redirect the p75 neurotrophin receptor, an otherwise apically...

  9. Genetics Home Reference: familial restrictive cardiomyopathy

    Science.gov (United States)

    ... Home Health Conditions familial restrictive cardiomyopathy familial restrictive cardiomyopathy Enable Javascript to view the expand/collapse boxes. ... All Open All Close All Description Familial restrictive cardiomyopathy is a genetic form of heart disease. For ...

  10. Study of the possibility of localising a channel instability in Forsmark-1

    International Nuclear Information System (INIS)

    A special type of instability occurred in the Swedish BWR Forsmark 1 in 1996. In contrast to the better known global or regional instabilities, the decay ratio appeared to be very high in one half of the core and quite low in the other half. A more detailed analysis showed that the most likely reason for the observed behaviour is a local perturbation of thermohydraulic character induced by the incorrect positioning of a fuel assembly. In such a case it is of importance to determine the position of the unseated assembly already during operation so that it can be easily found during reloading. The subject of this paper is to report on development and application of a method by which the position of such a local perturbation can be determined. The method can be separated into two parts that support and complement each other. First a visualisation technique was elaborated which displays the space-time behaviour of the neutron flux oscillations in the core. This visualisation expedites a very good qualitative comprehension of the situation and can be useful for the operators. It also gives a basis for the application of the localisation algorithm. Second, a quantitative localisation method, based on reactor physical models of the perturbation and of the transfer function between the perturbation and the flux oscillations, was elaborated. This latter takes noise spectra from selected detectors as input and yields the perturbation position as output. The strength of the method lies in its potentially high spatial resolution, which is smaller than the typical distance between two adjacent LPRM detectors. The method was tested on simulated data, and then applied to the Forsmark measurements. The location of the disturbance, found by the algorithm, is in accordance with independent judgements for the case, and close to a position where an unseated assembly was found during refuelling. The purpose of this study was to develop and test the localisation method. To apply the

  11. Gliadin peptide P31-43 localises to endocytic vesicles and interferes with their maturation.

    Directory of Open Access Journals (Sweden)

    Maria Vittoria Barone

    Full Text Available BACKGROUND: Celiac Disease (CD is both a frequent disease (1:100 and an interesting model of a disease induced by food. It consists in an immunogenic reaction to wheat gluten and glutenins that has been found to arise in a specific genetic background; however, this reaction is still only partially understood. Activation of innate immunity by gliadin peptides is an important component of the early events of the disease. In particular the so-called "toxic" A-gliadin peptide P31-43 induces several pleiotropic effects including Epidermal Growth Factor Receptor (EGFR-dependent actin remodelling and proliferation in cultured cell lines and in enterocytes from CD patients. These effects are mediated by delayed EGFR degradation and prolonged EGFR activation in endocytic vesicles. In the present study we investigated the effects of gliadin peptides on the trafficking and maturation of endocytic vesicles. METHODS/PRINCIPAL FINDINGS: Both P31-43 and the control P57-68 peptide labelled with fluorochromes were found to enter CaCo-2 cells and interact with the endocytic compartment in pulse and chase, time-lapse, experiments. P31-43 was localised to vesicles carrying early endocytic markers at time points when P57-68-carrying vesicles mature into late endosomes. In time-lapse experiments the trafficking of P31-43-labelled vesicles was delayed, regardless of the cargo they were carrying. Furthermore in celiac enterocytes, from cultured duodenal biopsies, P31-43 trafficking is delayed in early endocytic vesicles. A sequence similarity search revealed that P31-43 is strikingly similar to Hrs, a key molecule regulating endocytic maturation. A-gliadin peptide P31-43 interfered with Hrs correct localisation to early endosomes as revealed by western blot and immunofluorescence microscopy. CONCLUSIONS: P31-43 and P57-68 enter cells by endocytosis. Only P31-43 localises at the endocytic membranes and delays vesicle trafficking by interfering with Hrs

  12. Entanglement with restricted measurement setups

    CERN Document Server

    Meznaric, Sebastian

    2010-01-01

    We consider what is the effective amount of entanglement when the measurement operators one has at their disposal are restricted. Such a scenario occurs when superselection rules are in effect or when there are imperfections in our measurement setup. Given a quantum state and the restrictions on measurements, we consider the following scenario. Imagine we have an ideal, or non-restricted, measurement setup and a state $\\rho_1$ and a non-ideal, or restricted, measurement setup and a state $\\rho_2$. Then the minimum amount of entanglement in $\\rho_1$ so that all quantum communication protocols still perform with the same fidelity as with $\\rho_2$ is effectively the entanglement with restricted measurement setup. For indistinguishable particles, we find that any quantum communication protocol that can be performed with indistinguishable particles, can thus be performed with a ``normal'' state of no more than $E_P$ of entanglement. For the imperfect measurement apparatus we find an upper bound for the effective e...

  13. High numerical aperture all-dielectric metasurface micro-lenses

    NARCIS (Netherlands)

    Silvestri, F.; Gerini, G.; Pisano, E.; Galdi, V.

    2015-01-01

    In this paper, the design principles and the sensitivity analysis needed for the realization of a high numerical aperture metasurface micro-lens are presented. The metasurface micro-lens is realized defining a surface with spatially-variant dielectric resonators embedded in a dielectric bulk. The de

  14. Wind retrieval from synthetic aperture radar - an overview

    DEFF Research Database (Denmark)

    Dagestad, Knut-Frode; Horstmann, Jochen; Mouche, Alexis;

    2013-01-01

    This paper represents a consensus on the state-of-the-art in wind retrieval using synthetic aperture radar (SAR), after the SEASAR 2012 workshop “Advances in SAR Oceanography” hosted by the European Space Agency (ESA) and the Norwegian Space Centre in Tromsø, Norway 18–22 June 2012. We document t...... conditions near cyclones and complex coastal topography....

  15. Characterization of a dense aperture array for radio astronomy

    CERN Document Server

    Torchinsky, S A; Censier, B; Karastergiou, A; Serylak, M; Picard, P; Renaud, P; Taffoureau, C

    2016-01-01

    EMBRACE@Nancay is a prototype instrument consisting of an array of 4608 densely packed antenna elements creating a fully sampled, unblocked aperture. This technology is proposed for the Square Kilometre Array and has the potential of providing an extremely large field of view making it the ideal survey instrument. We describe the system,calibration procedures, and results from the prototype.

  16. Investigation of the feasability for 3D synthetic aperture imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2003-01-01

    This paper investigates the feasibility of implementing real-time synthetic aperture 3D imaging on the experimental system developed at the Center for Fast Ultrasound Imaging using a 2D transducer array. The target array is a fully populated 32 × 32 3 MHz array with a half wavelength pitch. The...

  17. Aperture alignment in autocollimator-based deflectometric profilometers.

    Science.gov (United States)

    Geckeler, R D; Artemiev, N A; Barber, S K; Just, A; Lacey, I; Kranz, O; Smith, B V; Yashchuk, V V

    2016-05-01

    During the last ten years, deflectometric profilometers have become indispensable tools for the precision form measurement of optical surfaces. They have proven to be especially suitable for characterizing beam-shaping optical surfaces for x-ray beamline applications at synchrotrons and free electron lasers. Deflectometric profilometers use surface slope (angle) to assess topography and utilize commercial autocollimators for the contactless slope measurement. To this purpose, the autocollimator beam is deflected by a movable optical square (or pentaprism) towards the surface where a co-moving aperture limits and defines the beam footprint. In this paper, we focus on the precise and reproducible alignment of the aperture relative to the autocollimator's optical axis. Its alignment needs to be maintained while it is scanned across the surface under test. The reproducibility of the autocollimator's measuring conditions during calibration and during its use in the profilometer is of crucial importance to providing precise and traceable angle metrology. In the first part of the paper, we present the aperture alignment procedure developed at the Advanced Light Source, Lawrence Berkeley National Laboratory, USA, for the use of their deflectometric profilometers. In the second part, we investigate the topic further by providing extensive ray tracing simulations and calibrations of a commercial autocollimator performed at the Physikalisch-Technische Bundesanstalt, Germany, for evaluating the effects of the positioning of the aperture on the autocollimator's angle response. The investigations which we performed are crucial for reaching fundamental metrological limits in deflectometric profilometry. PMID:27250378

  18. A system of gamma ray imaging devices with coded apertures

    Directory of Open Access Journals (Sweden)

    Papadimitropoulos Christos

    2016-01-01

    Full Text Available We describe a system consisting of two CdTe based gamma cameras with coded apertures and a video camera. The system is used for the localization of radioactive sources with the aid of triangulation. The methods used and the performance of the system are analyzed.

  19. Multielement Synthetic Transmit Aperture Imaging Using Temporal Encoding

    DEFF Research Database (Denmark)

    Gammelmark, Kim; Jensen, Jørgen Arendt

    2003-01-01

    A new method to increase the signal-to-noise ratio (SNR) of synthetic transmit aperture imaging is investigated. The approach utilizes multiple elements to emulate a spherical wave, and the conventional short excitation pulse is replaced by a linear frequency-modulated (FM) signal. The approach is...

  20. Radio Astronomy Transformed: Aperture Arrays - Past, Present & Future

    CERN Document Server

    Garrett, Michael A

    2012-01-01

    I review the early development of Aperture Arrays and their role in radio astronomy. The demise of this technology at the end of the 1960's, and the reasons for the rise of parabolic dishes is also considered. The parallels with the Antikythera mechanism (see these proceedings) as a lost technology are briefly presented. Aperture Arrays re-entered the world of radio astronomy as the idea to build a huge radio telescope with a collecting area of one square kilometre (the Square Kilometre Array, SKA) arose. Huge ICT technology advances had transformed Aperture Arrays in terms of their capability, flexibility and reliability. In the mid-1990s, ASTRON started to develop and experiment with the first high frequency aperture array tiles for radio astronomy - AAD, OSMA, THEA & EMBRACE. In the slipstream of these efforts, Phased Array Feeds (PAFs) for radio astronomy were invented and LOFAR itself emerged as a next generation telescope and a major pathfinder for the SKA. Meanwhile, the same advantages that apertu...