International Nuclear Information System (INIS)
Bouquet, A.; Salati, P.
1988-01-01
We present the results of an analytic approximation to compute the effects of WIMPs on stellar structures in a self-consistent way. We examine in particular the case of the Sun and of horizontal branch stars
International Nuclear Information System (INIS)
Goldsmith, Donald.
1995-01-01
In the rush to account for the missing ''dark matter'' in the universe, many teams of cosmologists are setting up experiments to prove the existence of a hypothetical form of matter called weakly interacting massive particles, or WIMPS. The innovative research ideas developed by these teams are described and compared briefly. (UK)
The WIMP Paradigm: Current Status
International Nuclear Information System (INIS)
Feng, Jonathan
2011-01-01
The WIMP paradigm is the glue that joins together much of the high energy and cosmic frontiers. It postulates that most of the matter in the Universe is made of weakly-interacting massive particles, with implications for a broad range of experiments and observations. I will review the WIMP paradigm's underlying motivations, its current status in view of rapid experimental progress on several fronts, and recent theoretical variations on the WIMP paradigm theme.
Planck-scale effects on WIMP dark matter
Directory of Open Access Journals (Sweden)
Sofiane M Boucenna
2014-01-01
Full Text Available There exists a widely known conjecture that gravitational effects violate global symmetries. We study the effect of global-symmetry violating higher-dimension operators induced by Planck-scale physics on the properties of WIMP dark matter. Using an effective description, we show that the lifetime of the WIMP dark matter candidate can satisfy cosmological bounds under reasonable assumptions regarding the strength of the dimension-five operators. On the other hand, the indirect WIMP dark matter detection signal is significantly enhanced due to new decay channels.
Craig, Nathaniel
2015-01-01
We identify and analyze thermal dark matter candidates in the fraternal twin Higgs model and its generalizations. The relic abundance of fraternal twin dark matter is set by twin weak interactions, with a scale tightly tied to the weak scale of the Standard Model by naturalness considerations. As such, the dark matter candidates benefit from a "fraternal WIMP miracle," reproducing the observed dark matter abundance for dark matter masses between 50 and 150 GeV. However, the couplings dominantly responsible for dark matter annihilation do not lead to interactions with the visible sector. The direct detection rate is instead set via fermionic Higgs portal interactions, which are likewise constrained by naturalness considerations but parametrically weaker than those leading to dark matter annihilation. The predicted direct detection cross section is close to current LUX bounds and presents an opportunity for the next generation of direct detection experiments.
Cosmological radio emission induced by WIMP Dark Matter
International Nuclear Information System (INIS)
Fornengo, N.; Regis, M.; Lineros, R.; Taoso, M.
2012-01-01
We present a detailed analysis of the radio synchrotron emission induced by WIMP dark matter annihilations and decays in extragalactic halos. We compute intensity, angular correlation, and source counts and discuss the impact on the expected signals of dark matter clustering, as well as of other astrophysical uncertainties as magnetic fields and spatial diffusion. Bounds on dark matter microscopic properties are then derived, and, depending on the specific set of assumptions, they are competitive with constraints from other indirect dark matter searches. At GHz frequencies, dark matter sources can become a significant fraction of the total number of sources with brightness below the microJansky level. We show that, at this level of fluxes (which are within the reach of the next-generation radio surveys), properties of the faint edge of differential source counts, as well as angular correlation data, can become an important probe for WIMPs
Cosmological radio emission induced by WIMP Dark Matter
Energy Technology Data Exchange (ETDEWEB)
Fornengo, N.; Regis, M. [Dipartimento di Fisica Teorica, Università di Torino, via P. Giuria 1, I-10125 Torino (Italy); Lineros, R.; Taoso, M., E-mail: fornengo@to.infn.it, E-mail: rlineros@ific.uv.es, E-mail: regis@to.infn.it, E-mail: mtaoso@phas.ubc.ca [IFIC, CSIC-Universidad de Valencia, Ed. Institutos, Apdo. Correos 22085, E-46071 Valencia (Spain)
2012-03-01
We present a detailed analysis of the radio synchrotron emission induced by WIMP dark matter annihilations and decays in extragalactic halos. We compute intensity, angular correlation, and source counts and discuss the impact on the expected signals of dark matter clustering, as well as of other astrophysical uncertainties as magnetic fields and spatial diffusion. Bounds on dark matter microscopic properties are then derived, and, depending on the specific set of assumptions, they are competitive with constraints from other indirect dark matter searches. At GHz frequencies, dark matter sources can become a significant fraction of the total number of sources with brightness below the microJansky level. We show that, at this level of fluxes (which are within the reach of the next-generation radio surveys), properties of the faint edge of differential source counts, as well as angular correlation data, can become an important probe for WIMPs.
Constraints on WIMP masses and interactions
International Nuclear Information System (INIS)
Enqvist, K.
1991-01-01
It is shown that cosmology, experiments and unitarity considerations limit the mass and coupling g' of a generic, heavy WIMP from the above as well as from the below. There are absolute lower limits of 4x10 -5 g and 6x10 -5 g for the couplings of Diracn and Majorana WIMPs, respectively. In U(1)' models cosmology implies an upper limit of about 1 TeV on the Z' and on the WIMP masses, but only in the absence of Z-Z' mixing. (orig.)
Readout technologies for directional WIMP Dark Matter detection
International Nuclear Information System (INIS)
Battat, J.B.R.; Irastorza, I.G.; Aleksandrov, A.; Asada, T.; Baracchini, E.; Billard, J.; Bosson, G.; Bourrion, O.; Bouvier, J.; Buonaura, A.; Burdge, K.; Cebrián, S.
2016-01-01
The measurement of the direction of WIMP-induced nuclear recoils is a compelling but technologically challenging strategy to provide an unambiguous signature of the detection of Galactic dark matter. Most directional detectors aim to reconstruct the dark-matter-induced nuclear recoil tracks, either in gas or solid targets. The main challenge with directional detection is the need for high spatial resolution over large volumes, which puts strong requirements on the readout technologies. In this paper we review the various detector readout technologies used by directional detectors. In particular, we summarize the challenges, advantages and drawbacks of each approach, and discuss future prospects for these technologies.
Joint Rome Workshop "Challenges in the Dark Sector: Alternatives to the WIMP paradigm”
2015-01-01
Identifying what Dark Matter (DM) is, as well as its nature and properties, remains a major challenge for both theoretical and experimental astroparticle physics communities. In the past decades, WIMP DM has been the most hunted candidate, with the result that nowadays WIMPS are cornered by large amounts of experimental data from Direct Detection, Indirect Detection, and Collider Experiments. If no WIMP signal is detected in the next few years, the possibility that this very appealing theoretical idea is not what Nature has chosen will become even more compelling and will boost theoretical studies and experimental searches for non-WIMP alternatives for DM. The aim of this 3-day meeting is to convene experts on alternatives to the WIMP paradigm to stimulate informal discussions on different possibilities (dark photons, axion-like particles, Majorons, self-interacting dark sectors, just to mention a few). We plan to have only three or four talks each day, and plenty of time to discuss implications of these DM s...
Boffins go underground searching for Wimps
2003-01-01
In a bid to identify the prime suspect for Dark Matter known as Weakly Interacting Massive Particles, or Wimps, British scientists have installed detectors 1100m down a salt mine at Boulby on the North Yorkshire moors (1/2 page).
A precision search for WIMPs with charged cosmic rays
Reinert, Annika; Winkler, Martin Wolfgang
2018-01-01
AMS-02 has reached the sensitivity to probe canonical thermal WIMPs by their annihilation into antiprotons. Due to the high precision of the data, uncertainties in the astrophysical background have become the most limiting factor for indirect dark matter detection. In this work we systematically quantify and—where possible—reduce uncertainties in the antiproton background. We constrain the propagation of charged cosmic rays through the combination of antiproton, B/C and positron data. Cross section uncertainties are determined from a wide collection of accelerator data and are—for the first time ever—fully taken into account. This allows us to robustly constrain even subdominant dark matter signals through their spectral properties. For a standard NFW dark matter profile we are able to exclude thermal WIMPs with masses up to 570 GeV which annihilate into bottom quarks. While we confirm a reported excess compatible with dark matter of mass around 80 GeV, its local (global) significance only reaches 2.2 σ (1.1 σ) in our analysis.
Working Group Report: WIMP Dark Matter Direct Detection
International Nuclear Information System (INIS)
Cushman, P.; Galbiati, C.; McKinsey, D. N.; Robertson, H.; Tait, T. M.P.
2013-01-01
As part of the Snowmass process, the Cosmic Frontier WIMP Direct Detection subgroup (CF1) has drawn on input from the Cosmic Frontier and the broader Particle Physics community to produce this document. The charge to CF1 was (a) to summarize the current status and projected sensitivity of WIMP direct detection experiments worldwide, (b) motivate WIMP dark matter searches over a broad parameter space by examining a spectrum of WIMP models, (c) establish a community consensus on the type of experimental program required to explore that parameter space, and (d) identify the common infrastructure required to practically meet those goals.
Working Group Report: WIMP Dark Matter Direct Detection
Energy Technology Data Exchange (ETDEWEB)
Cushman, P.; Galbiati, C.; McKinsey, D. N.; Robertson, H.; Tait, T. M.P.
2013-10-30
As part of the Snowmass process, the Cosmic Frontier WIMP Direct Detection subgroup (CF1) has drawn on input from the Cosmic Frontier and the broader Particle Physics community to produce this document. The charge to CF1 was (a) to summarize the current status and projected sensitivity of WIMP direct detection experiments worldwide, (b) motivate WIMP dark matter searches over a broad parameter space by examining a spectrum of WIMP models, (c) establish a community consensus on the type of experimental program required to explore that parameter space, and (d) identify the common infrastructure required to practically meet those goals.
WIMP search and a Cherenkov detector prototype for ILC polarimetry
Energy Technology Data Exchange (ETDEWEB)
Bartels, Christoph
2011-10-15
The planned International Linear Collider (ILC) will be an essential experiment to precisely determine the properties and structure of physics at the TeV scale. An important feature of the ILC is the possibility to use polarized electrons and positrons. In part 1 of this thesis, a model independent search for Weakly Interacting Massive Particles (WIMPs) at ILC is presented. The signal channel under study is direct WIMP pair production with associated Initial State Radiation (ISR), e{sup +}e{sup -} {yields} {chi}{chi}{gamma}, where the WIMPs leave the detector without any further interaction, and only the emitted photon is detected. From the energy spectrum of the detected photons the coupling structure, cross sections, masses and the quantum number of the dominant partial wave in the production process can be inferred. The analysis includes the dominant SM, as well as machine-induced backgrounds, and is performed using a full simulation of the ILD detector concept. For an integrated luminosity of L=500 fb{sup -1}, the signal cross sections can be measured to a precision of 3%, dominated by systematic uncertainties on the polarization measurement of the initial electrons and positrons. Masses can be measured to a precision of up to 2% by a comparison of the data photon spectrum to parametrized template spectra. In part 2 of this thesis, a Cherenkov detector prototype for Compton polarimetry at ILC is presented. For the polarization measurement a systematic uncertainty of {delta} P/P = 0.25% or better is envisioned. To achieve this goal, the Cherenkov detector has to be precisely aligned with the fan of Compton scattered electrons and its signal response needs to be highly linear. For the detector prototype data driven alignment strategies have been developed by comparing data recorded at the Elsa accelerator in Bonn, Germany, with detailed Geant4 simulations. With the use of multi-anode photomultipliers, data driven alignment strategies promise to provide the
WIMP search and a Cherenkov detector prototype for ILC polarimetry
International Nuclear Information System (INIS)
Bartels, Christoph
2011-10-01
The planned International Linear Collider (ILC) will be an essential experiment to precisely determine the properties and structure of physics at the TeV scale. An important feature of the ILC is the possibility to use polarized electrons and positrons. In part 1 of this thesis, a model independent search for Weakly Interacting Massive Particles (WIMPs) at ILC is presented. The signal channel under study is direct WIMP pair production with associated Initial State Radiation (ISR), e + e - → χχγ, where the WIMPs leave the detector without any further interaction, and only the emitted photon is detected. From the energy spectrum of the detected photons the coupling structure, cross sections, masses and the quantum number of the dominant partial wave in the production process can be inferred. The analysis includes the dominant SM, as well as machine-induced backgrounds, and is performed using a full simulation of the ILD detector concept. For an integrated luminosity of L=500 fb -1 , the signal cross sections can be measured to a precision of 3%, dominated by systematic uncertainties on the polarization measurement of the initial electrons and positrons. Masses can be measured to a precision of up to 2% by a comparison of the data photon spectrum to parametrized template spectra. In part 2 of this thesis, a Cherenkov detector prototype for Compton polarimetry at ILC is presented. For the polarization measurement a systematic uncertainty of δ P/P = 0.25% or better is envisioned. To achieve this goal, the Cherenkov detector has to be precisely aligned with the fan of Compton scattered electrons and its signal response needs to be highly linear. For the detector prototype data driven alignment strategies have been developed by comparing data recorded at the Elsa accelerator in Bonn, Germany, with detailed Geant4 simulations. With the use of multi-anode photomultipliers, data driven alignment strategies promise to provide the required precision. At ILC, these
Viscoelastic property identification from waveform reconstruction
Leymarie, N.; Aristégui, C.; Audoin, B.; Baste, S.
2002-05-01
An inverse method is proposed for the determination of the viscoelastic properties of material plates from the plane-wave transmitted acoustic field. Innovations lie in a two-step inversion scheme based on the well-known maximum-likelihood principle with an analytic signal formulation. In addition, establishing the analytical formulations of the plate transmission coefficient we implement an efficient and slightly noise-sensitive process suited to both very thin plates and strongly dispersive media.
Identifying WIMP dark matter from particle and astroparticle data
Bertone, Gianfranco; Bozorgnia, Nassim; Kim, Jong Soo; Liem, Sebastian; McCabe, Christopher; Otten, Sydney; Ruiz de Austri, Roberto
2018-03-01
One of the most promising strategies to identify the nature of dark matter consists in the search for new particles at accelerators and with so-called direct detection experiments. Working within the framework of simplified models, and making use of machine learning tools to speed up statistical inference, we address the question of what we can learn about dark matter from a detection at the LHC and a forthcoming direct detection experiment. We show that with a combination of accelerator and direct detection data, it is possible to identify newly discovered particles as dark matter, by reconstructing their relic density assuming they are weakly interacting massive particles (WIMPs) thermally produced in the early Universe, and demonstrating that it is consistent with the measured dark matter abundance. An inconsistency between these two quantities would instead point either towards additional physics in the dark sector, or towards a non-standard cosmology, with a thermal history substantially different from that of the standard cosmological model.
Looking for the WIMP next door
Evans, Jared A.; Gori, Stefania; Shelton, Jessie
2018-02-01
We comprehensively study experimental constraints and prospects for a class of minimal hidden sector dark matter (DM) models, highlighting how the cosmological history of these models informs the experimental signals. We study simple `secluded' models, where the DM freezes out into unstable dark mediator states, and consider the minimal cosmic history of this dark sector, where coupling of the dark mediator to the SM was sufficient to keep the two sectors in thermal equilibrium at early times. In the well-motivated case where the dark mediators couple to the Standard Model (SM) via renormalizable interactions, the requirement of thermal equilibrium provides a minimal, UV-insensitive, and predictive cosmology for hidden sector dark matter. We call DM that freezes out of a dark radiation bath in thermal equilibrium with the SM a WIMP next door, and demonstrate that the parameter space for such WIMPs next door is sharply defined, bounded, and in large part potentially accessible. This parameter space, and the corresponding signals, depend on the leading interaction between the SM and the dark mediator; we establish it for both Higgs and vector portal interactions. In particular, there is a cosmological lower bound on the portal coupling strength necessary to thermalize the two sectors in the early universe. We determine this thermalization floor as a function of equilibration temperature for the first time. We demonstrate that direct detection experiments are currently probing this cosmological lower bound in some regions of parameter space, while indirect detection signals and terrestrial searches for the mediator cut further into the viable parameter space. We present regions of interest for both direct detection and dark mediator searches, including motivated parameter space for the direct detection of sub-GeV DM.
WIMP dark matter candidates and searches—current status and future prospects
Roszkowski, Leszek; Sessolo, Enrico Maria; Trojanowski, Sebastian
2018-06-01
We review several current aspects of dark matter theory and experiment. We overview the present experimental status, which includes current bounds and recent claims and hints of a possible signal in a wide range of experiments: direct detection in underground laboratories, gamma-ray, cosmic ray, x-ray, neutrino telescopes, and the LHC. We briefly review several possible particle candidates for a weakly interactive massive particle (WIMP) and dark matter that have recently been considered in the literature. We pay particular attention to the lightest neutralino of supersymmetry as it remains the best motivated candidate for dark matter and also shows excellent detection prospects. Finally we briefly review some alternative scenarios that can considerably alter properties and prospects for the detection of dark matter obtained within the standard thermal WIMP paradigm.
WIMP dark matter candidates and searches-current status and future prospects.
Roszkowski, Leszek; Sessolo, Enrico Maria; Trojanowski, Sebastian
2018-06-01
We review several current aspects of dark matter theory and experiment. We overview the present experimental status, which includes current bounds and recent claims and hints of a possible signal in a wide range of experiments: direct detection in underground laboratories, gamma-ray, cosmic ray, x-ray, neutrino telescopes, and the LHC. We briefly review several possible particle candidates for a weakly interactive massive particle (WIMP) and dark matter that have recently been considered in the literature. We pay particular attention to the lightest neutralino of supersymmetry as it remains the best motivated candidate for dark matter and also shows excellent detection prospects. Finally we briefly review some alternative scenarios that can considerably alter properties and prospects for the detection of dark matter obtained within the standard thermal WIMP paradigm.
Science plumbs new depths in hunt for Wimps
Benfield, C
2003-01-01
Lord Sainsbury has officially opened a laboratory in the salt mine at Boulby near Whitby. The lab is searching for WIMPs and was recently awarded 3.1 millions pounds by PPARC to upgrade the facility (1 page).
Understanding WIMP-baryon interactions with direct detection: a roadmap
International Nuclear Information System (INIS)
Gluscevic, Vera; Peter, Annika H.G.
2014-01-01
We study prospects of dark-matter direct-detection searches for probing non-relativistic effective theory for WIMP-baryon scattering. We simulate a large set of noisy recoil-energy spectra for different scattering scenarios (beyond the standard momentum-independent contact interaction), for Generation 2 and futuristic experiments. We analyze these simulations and quantify the probability of successfully identifying the operator governing the scattering, if a WIMP signal is observed. We find that the success rate depends on a combination of factors: the WIMP mass, the mediator mass, the type of interaction, and the experimental energy window. For example, for a 20 GeV WIMP, Generation 2 is only likely to identify the right operator if the interaction is Coulomb-like, and is unlikely to do so in any other case. For a WIMP with a mass of 200 GeV or higher, success is almost guaranteed. We also find that, regardless of the scattering model and the WIMP parameters, a single Generation 2 experiment is unlikely to successfully discern the momentum dependence of the underlying operator on its own, but prospects improve drastically when experiments with different target materials and energy windows are analyzed jointly. Furthermore, we examine the quality of parameter estimation and degeneracies in the multi-dimensional parameter space of the effective theory. We find in particular that the resulting WIMP mass estimates can be severely biased if data are analyzed assuming the standard (momentum-independent) operator while the actual operator has momentum-dependence. Finally, we evaluate the ultimate reach of direct detection, finding that the prospects for successful operator selection prior to reaching the irreducible backgrounds are excellent, if the signal is just below the current limits, but slim if Generation 2 does not report WIMP detection
WIMP-nucleus scattering in chiral effective theory
Cirigliano, Vincenzo; Graesser, Michael L.; Ovanesyan, Grigory
2012-10-01
We discuss long-distance QCD corrections to the WIMP-nucleon(s) interactions in the framework of chiral effective theory. For scalar-mediated WIMP-quark interactions, we calculate all the next-to-leading-order corrections to the WIMP-nucleus elastic cross-section, including two-nucleon amplitudes and recoil-energy dependent shifts to the single-nucleon scalar form factors. As a consequence, the scalar-mediated WIMP-nucleus cross-section cannot be parameterized in terms of just two quantities, namely the neutron and proton scalar form factors at zero momentum transfer, but additional parameters appear, depending on the short-distance WIMP-quark interaction. Moreover, multiplicative factorization of the cross-section into particle, nuclear and astro-particle parts is violated. In practice, while the new effects are of the natural size expected by chiral power counting, they become very important in those regions of parameter space where the leading order WIMP-nucleus amplitude is suppressed, including the so-called "isospin-violating dark matter" regime. In these regions of parameter space we find order-of-magnitude corrections to the total scattering rates and qualitative changes to the shape of recoil spectra.
Optimizing EDELWEISS detectors for low-mass WIMP searches
Arnaud, Q.; Armengaud, E.; Augier, C.; Benoît, A.; Bergé, L.; Billard, J.; Broniatowski, A.; Camus, P.; Cazes, A.; Chapellier, M.; Charlieux, F.; de Jésus, M.; Dumoulin, L.; Eitel, K.; Foerster, N.; Gascon, J.; Giuliani, A.; Gros, M.; Hehn, L.; Jin, Y.; Juillard, A.; Kleifges, M.; Kozlov, V.; Kraus, H.; Kudryavtsev, V. A.; Le-Sueur, H.; Maisonobe, R.; Marnieros, S.; Navick, X.-F.; Nones, C.; Olivieri, E.; Pari, P.; Paul, B.; Poda, D.; Queguiner, E.; Rozov, S.; Sanglard, V.; Scorza, S.; Siebenborn, B.; Vagneron, L.; Weber, M.; Yakushev, E.; EDELWEISS Collaboration
2018-01-01
The physics potential of EDELWEISS detectors for the search of low-mass weakly interacting massive particles (WIMPs) is studied. Using a data-driven background model, projected exclusion limits are computed using frequentist and multivariate analysis approaches, namely, profile likelihood and boosted decision tree. Both current and achievable experimental performances are considered. The optimal strategy for detector optimization depends critically on whether the emphasis is put on WIMP masses below or above ˜5 GeV /c2 . The projected sensitivity for the next phase of the EDELWEISS-III experiment at the Modane Underground Laboratory (LSM) for low-mass WIMP search is presented. By 2018 an upper limit on the spin-independent WIMP-nucleon cross section of σSI=7 ×10-42 cm2 is expected for a WIMP mass in the range 2 - 5 GeV /c2 . The requirements for a future hundred-kilogram-scale experiment designed to reach the bounds imposed by the coherent scattering of solar neutrinos are also described. By improving the ionization resolution down to 50 eVe e , we show that such an experiment installed in an even lower background environment (e.g., at SNOLAB) together with an exposure of 1 000 kg .yr , should allow us to observe about 80 B 8 neutrino events after discrimination.
Proceedings of the 4th Patras workshop on axions, WIMPs and WISPs
Energy Technology Data Exchange (ETDEWEB)
Lindner, Axel; Redondo, Javier; Ringwald, Andreas [eds.
2008-08-15
The following topics were dealt with: Physical foundations for WIMPs, axions, and WISPS, signals from astrophysical sources, direct searches for dark matter WIMPs, new theoretical developments, new experimental approaches. (HSI)
Proceedings of the 4th Patras workshop on axions, WIMPs and WISPs
International Nuclear Information System (INIS)
Lindner, Axel; Redondo, Javier; Ringwald, Andreas
2008-08-01
The following topics were dealt with: Physical foundations for WIMPs, axions, and WISPS, signals from astrophysical sources, direct searches for dark matter WIMPs, new theoretical developments, new experimental approaches. (HSI)
6th Patras workshop on axions, WIMPs and WISPs (PATRAS 2010). Proceedings
Energy Technology Data Exchange (ETDEWEB)
Baudis, Laura; Schumann, Marc (eds.)
2010-11-15
The following topics were dealt with: Axions, WIMPs, WISPs, and neutrinos in the universe, laboratory experimental searching for WISPs, astrophysical experimental searching for WISPs, direct and indirect detection of WIMPs, new ideas and developments, visions, large laboratories. (HSI)
6th Patras workshop on axions, WIMPs and WISPs (PATRAS 2010). Proceedings
International Nuclear Information System (INIS)
Baudis, Laura; Schumann, Marc
2010-11-01
The following topics were dealt with: Axions, WIMPs, WISPs, and neutrinos in the universe, laboratory experimental searching for WISPs, astrophysical experimental searching for WISPs, direct and indirect detection of WIMPs, new ideas and developments, visions, large laboratories. (HSI)
First low WIMP mass results in EDELWEISS III experiment
Energy Technology Data Exchange (ETDEWEB)
Scorza, Silvia [Karlsruher Institut fuer Technologie, Institut fuer Experimentelle Kernphysik, Postfach 3640, Karlsruhe (Germany); Collaboration: EDELWEISS-Collaboration
2016-07-01
The EDELWEISS-III collaboration is operating an experiment for the direct detection of Weakly Interacting Massive Particle (WIMPs) dark matter in the low radioactivity environment of the Modane Underground Laboratory. It consists of twenty-four advanced high purity germanium detectors operating at 18 mK in a dilution refrigerator in order to identify rare nuclear recoils induced by elastic scattering of WIMPs from our Galactic halo. The current EDELWEISS-III program, including improvements of the background, data-acquisition and the configuration is detailed. Sources of background along with the rejection techniques are discussed. Detector performances and a first low WIMP mass analysis of data acquired in a long-term campaign are presented as well.
The WIMP Forest: Indirect Detection of a Chiral Square
Energy Technology Data Exchange (ETDEWEB)
Bertone, Gianfranco; Jackson, C.B.; Shaughnessy, Gabe; Tait, Tim M.P.; Vallinotto, Alberto
2009-04-01
The spectrum of photons arising from WIMP annihilation carries a detailed imprint of the structure of the dark sector. In particular, loop-level annihilations into a photon and another boson can in principle lead to a series of lines (a WIMP forest) at energies up to the WIMP mass. A specific model which illustrates this feature nicely is a theory of two universal extra dimensions compactified on a chiral square. Aside from the continuum emission, which is a generic prediction of most dark matter candidates, we find a 'forest' of prominent annihilation lines that, after convolution with the angular resolution of current experiments, leads to a distinctive (2-bump plus continuum) spectrum, which may be visible in the near future with the Fermi Gamma-Ray Space Telescope (formerly known as GLAST).
No WIMP mini-spikes in dwarf spheroidal galaxies
Wanders, M.; Bertone, G.; Volonteri, M.; Weniger, C.
2015-01-01
The formation of black holes inevitably affects the distribution of dark and baryonic matter in their vicinity, leading to an enhancement of the dark matter density, called spike, and if dark matter is made of WIMPs, to a strong enhancement of the dark matter annihilation rate. Spikes at the center
WIMP detection and slow ion dynamics in carbon nanotube arrays
Cavoto, G.; Cocina, F.; Ferretti, J.; Polosa, A.D.
2016-06-24
Large arrays of aligned carbon nanotubes (CNTs), open at one end, could be used as target material for the directional detection of weakly interacting dark matter particles (WIMPs). As a result of a WIMP elastic scattering on a CNT, a carbon ion might be injected in the body of the array and propagate through multiple collisions within the lattice. The ion may eventually emerge from the surface with open end CNTs, provided that its longitudinal momentum is large enough to compensate energy losses and its transverse momentum approaches the channeling conditions in a single CNT. Therefore, the angle formed between the WIMP wind apparent orientation and the direction of parallel carbon nanotube axes must be properly chosen. We focus on very low ion recoil kinetic energies, related to low mass WIMPs (~ 10 GeV) where most of the existing experiments have low sensitivity. Relying on some exact results on two-dimensional lattices of circular obstacles, we study the low energy ion motion in the transverse plane with ...
WIMP detection and slow ion dynamics in carbon nanotube arrays
International Nuclear Information System (INIS)
Cavoto, G.; Cirillo, E.N.M.; Cocina, F.; Ferretti, J.; Polosa, A.D.
2016-01-01
Large arrays of aligned carbon nanotubes (CNTs), open at one end, could be used as target material for the directional detection of weakly interacting dark matter particles (WIMPs). As a result of a WIMP elastic scattering on a CNT, a carbon ion might be injected in the body of the array and propagate through multiple collisions within the lattice. The ion may eventually emerge from the surface with open end CNTs, provided that its longitudinal momentum is large enough to compensate energy losses and its transverse momentum approaches the channeling conditions in a single CNT. Therefore, the angle formed between the WIMP wind apparent orientation and the direction of parallel carbon nanotube axes must be properly chosen. We focus on very low ion recoil kinetic energies, related to low mass WIMPs (∼ 11 GeV) where most of the existing experiments have low sensitivity. Relying on some exact results on two-dimensional lattices of circular obstacles, we study the low energy ion motion in the transverse plane with respect to CNT directions. New constraints are obtained on how to devise the CNT arrays to maximize the target channeling efficiency. (orig.)
WIMP detection and slow ion dynamics in carbon nanotube arrays
Energy Technology Data Exchange (ETDEWEB)
Cavoto, G. [INFN Sezione di Roma, Rome (Italy); Cirillo, E.N.M. [Sapienza Universita di Roma, Dipartimento SBAI, Rome (Italy); Cocina, F. [Sapienza Universita di Roma, Dipartimento di Fisica, Rome (Italy); Ferretti, J. [Sapienza Universita di Roma, Dipartimento di Fisica (Italy); INFN Sezione di Roma, Rome (Italy); Polosa, A.D. [Sapienza Universita di Roma, Dipartimento di Fisica (Italy); CERN, Theory Division, Geneva (Switzerland); INFN Sezione di Roma, Rome (Italy)
2016-06-15
Large arrays of aligned carbon nanotubes (CNTs), open at one end, could be used as target material for the directional detection of weakly interacting dark matter particles (WIMPs). As a result of a WIMP elastic scattering on a CNT, a carbon ion might be injected in the body of the array and propagate through multiple collisions within the lattice. The ion may eventually emerge from the surface with open end CNTs, provided that its longitudinal momentum is large enough to compensate energy losses and its transverse momentum approaches the channeling conditions in a single CNT. Therefore, the angle formed between the WIMP wind apparent orientation and the direction of parallel carbon nanotube axes must be properly chosen. We focus on very low ion recoil kinetic energies, related to low mass WIMPs (∼ 11 GeV) where most of the existing experiments have low sensitivity. Relying on some exact results on two-dimensional lattices of circular obstacles, we study the low energy ion motion in the transverse plane with respect to CNT directions. New constraints are obtained on how to devise the CNT arrays to maximize the target channeling efficiency. (orig.)
WIMP detection and slow ion dynamics in carbon nanotube arrays.
Cavoto, G; Cirillo, E N M; Cocina, F; Ferretti, J; Polosa, A D
2016-01-01
Large arrays of aligned carbon nanotubes (CNTs), open at one end, could be used as target material for the directional detection of weakly interacting dark matter particles (WIMPs). As a result of a WIMP elastic scattering on a CNT, a carbon ion might be injected in the body of the array and propagate through multiple collisions within the lattice. The ion may eventually emerge from the surface with open end CNTs, provided that its longitudinal momentum is large enough to compensate energy losses and its transverse momentum approaches the channeling conditions in a single CNT. Therefore, the angle formed between the WIMP wind apparent orientation and the direction of parallel carbon nanotube axes must be properly chosen. We focus on very low ion recoil kinetic energies, related to low mass WIMPs ([Formula: see text] GeV) where most of the existing experiments have low sensitivity. Relying on some exact results on two-dimensional lattices of circular obstacles, we study the low energy ion motion in the transverse plane with respect to CNT directions. New constraints are obtained on how to devise the CNT arrays to maximize the target channeling efficiency.
ZEPLIN-II limits on WIMP-nucelon interactions
International Nuclear Information System (INIS)
Alner, G. J.; Bungau, C.; Camanzi, B.; Durkin, T.; Edwards, B.; Lewin, J. D.; Luescher, R.; Preece, R. M.; Smith, N. J. T.; Smith, P. F.; Sumner, T. J.; Thorne, C.; Araujo, H. M.; Bewick, A.; Davidge, D.; Dawson, J.; Howard, A. S.; Jones, W. G.; Joshi, M.; Lebedenko, V. N.
2009-01-01
ZEPLIN II is a two-phase xenon detector designed to detect dark matter in the form of Weakly Interacting Massive Particles (WIMPs). Following the first 31-day underground run in Boulby Mine, UK, the collaboration published dark matter limits in January 2007; the first such limits using two-phase xenon technology. We outline the key detector design, performance and results here.
Dark Matter: Looking for WIMPs in the Galactic Halo
International Nuclear Information System (INIS)
Akerib, Daniel S.
2006-01-01
Overwhelming observational evidence indicates that most of the matter in the Universe consists of non-baryonic dark matter. One possibility is that the dark matter is Weakly-Interacting Massive Particles (WIMPs) that were produced in the early Universe. These relics could comprise the Milky Way's dark halo and provide evidence for new particle physics, such as Supersymmetry. After reviewing some of the evidence for dark matter and the WIMP hypothesis, I will describe the strategy for searching for WIMPs, along with a survey of the current status and outlook. In particular, dark matter searches have begun to explore the region of parameter space where SUSY particles could provide dark matter candidates. I will also mention some of the recent theoretical work on dark matter candidates which is being done in anticipation of the turn-on of the LHC and as part of the active R and D on the ILC. Finally, a vigorous detector development program promises significant advances in WIMP sensitivity in the coming years
Helioseismic and neutrino data-driven reconstruction of solar properties
Song, Ningqiang; Gonzalez-Garcia, M. C.; Villante, Francesco L.; Vinyoles, Nuria; Serenelli, Aldo
2018-06-01
In this work, we use Bayesian inference to quantitatively reconstruct the solar properties most relevant to the solar composition problem using as inputs the information provided by helioseismic and solar neutrino data. In particular, we use a Gaussian process to model the functional shape of the opacity uncertainty to gain flexibility and become as free as possible from prejudice in this regard. With these tools we first readdress the statistical significance of the solar composition problem. Furthermore, starting from a composition unbiased set of standard solar models (SSMs) we are able to statistically select those with solar chemical composition and other solar inputs which better describe the helioseismic and neutrino observations. In particular, we are able to reconstruct the solar opacity profile in a data-driven fashion, independently of any reference opacity tables, obtaining a 4 per cent uncertainty at the base of the convective envelope and 0.8 per cent at the solar core. When systematic uncertainties are included, results are 7.5 per cent and 2 per cent, respectively. In addition, we find that the values of most of the other inputs of the SSMs required to better describe the helioseismic and neutrino data are in good agreement with those adopted as the standard priors, with the exception of the astrophysical factor S11 and the microscopic diffusion rates, for which data suggests a 1 per cent and 30 per cent reduction, respectively. As an output of the study we derive the corresponding data-driven predictions for the solar neutrino fluxes.
Energy Technology Data Exchange (ETDEWEB)
Manungu Kiveni, Joseph [Syracuse Univ., NY (United States)
2012-12-01
This dissertation describes the results of a WIMP search using CDMS II data sets accumulated at the Soudan Underground Laboratory in Minnesota. Results from the original analysis of these data were published in 2009; two events were observed in the signal region with an expected leakage of 0.9 events. Further investigation revealed an issue with the ionization-pulse reconstruction algorithm leading to a software upgrade and a subsequent reanalysis of the data. As part of the reanalysis, I performed an advanced discrimination technique to better distinguish (potential) signal events from backgrounds using a 5-dimensional chi-square method. This dataanalysis technique combines the event information recorded for each WIMP-search event to derive a backgrounddiscrimination parameter capable of reducing the expected background to less than one event, while maintaining high efficiency for signal events. Furthermore, optimizing the cut positions of this 5-dimensional chi-square parameter for the 14 viable germanium detectors yields an improved expected sensitivity to WIMP interactions relative to previous CDMS results. This dissertation describes my improved (and optimized) discrimination technique and the results obtained from a blind application to the reanalyzed CDMS II WIMP-search data.
Reconstruction of negative hydrogen ion beam properties from beamline diagnostics
Energy Technology Data Exchange (ETDEWEB)
Ruf, Benjamin
2014-09-25
For the experimental fusion reactor ITER, which should show the feasibility of sustaining a fusion plasma with a positive power balance, some technology still has to be developed, amongst others also the plasma heating system. One heating technique is the neutral beam injection (NBI). A beam of fast deuterium atoms is injected into the fusion plasma. By heavy particle collisions the beam particles give their energy to the plasma. A NBI system consists of three major components. First, deuterium ions are generated in a low temperature, low pressure plasma of an ion source. At ITER, the requirements on the beam energy of 1 MeV cause the necessity of negative charged deuterium ions. Secondly, the ions are accelerated within an acceleration system with several grids, where the plasma grid is the first grid. The grids are on different descending high voltage potentials. The source itself is on the highest negative potential. Thirdly, the fast deuterium ions have to be neutralised. This thesis deals with the second step in the mentioned beam system, the ion acceleration and beam formation. The underlying experiments and measurements were carried out at the testbeds BATMAN (BAvarianTest MAchine for Negative ions) and ELISE (Extraction from a Large Ion Source Experiment) at the Max-Planck-Institut fuer Plasmaphysik Garching (IPP Garching). The main goal of this thesis is to provide a tool which allows the determination of the beam properties. These are beam divergence, stripping losses and beam inhomogeneity. For this purpose a particle trajectory code has been developed from scratch, namely BBC-NI (Bavarian Beam Code for Negative Ions). The code is able to simulate the whole beam and the outcome of several beam diagnostic tools. The data obtained from the code together with the measurements of the beam diagnostic tools should allow the reconstruction of the beam properties. The major beam diagnostic tool, which is used in this thesis, is the beam emission spectroscopy
NEWSdm: Nuclear Emulsions for WIMP Search with directional measurement
Directory of Open Access Journals (Sweden)
Di Crescenzo A.
2017-01-01
Full Text Available Direct Dark Matter searches are nowadays one of the most exciting research topics. Several experimental efforts are concentrated on the development, construction, and operation of detectors looking for the scattering of target nuclei with Weakly Interactive Massive Particles (WIMPs. The measurement of the direction of WIMP-induced nuclear recoils is a challenging strategy to extend dark matter searches beyond the neutrino floor and provide an unambiguous signature of the detection of Galactic dark matter. Current directional experiments are based on the use of gas TPC whose sensitivity is strongly limited by the small achievable detector mass. We present an innovative directional experiment based on the use of a solid target made by newly developed nuclear emulsions and read-out systems reaching a position resolution of the order of 10 nm.
Neutrino astronomy and search for WIMPs with MACRO
Bernardini, P
2000-01-01
Upward-going muons, induced primarily by atmospheric neutrinos, are used to search for neutrinos of astrophysical origin. No evidence has been found looking at the event direction and flux limits are obtained on candidate sources. A space-time correlation between gamma ray bursts and upward-going muons has been also investigated. Furthermore the search for a neutrino signal from the Earth and the Sun induced by weakly interacting massive particles (WIMP) has been updated. The number of events from the Sun and from the Earth is compatible with the background from atmospheric neutrinos. Therefore flux limits for different search cones have been estimated. Here we concentrate on neutralinos as WIMP candidates and limits depending on the neutralino mass are given and compared with the prediction of supersymmetric models. (11 refs).
NEWSdm: Nuclear Emulsions for WIMP Search with directional measurement
Di Crescenzo, A.
2017-12-01
Direct Dark Matter searches are nowadays one of the most exciting research topics. Several experimental efforts are concentrated on the development, construction, and operation of detectors looking for the scattering of target nuclei with Weakly Interactive Massive Particles (WIMPs). The measurement of the direction of WIMP-induced nuclear recoils is a challenging strategy to extend dark matter searches beyond the neutrino floor and provide an unambiguous signature of the detection of Galactic dark matter. Current directional experiments are based on the use of gas TPC whose sensitivity is strongly limited by the small achievable detector mass. We present an innovative directional experiment based on the use of a solid target made by newly developed nuclear emulsions and read-out systems reaching a position resolution of the order of 10 nm.
Choice of reconstructed tissue properties affects interpretation of lung EIT images.
Grychtol, Bartłomiej; Adler, Andy
2014-06-01
Electrical impedance tomography (EIT) estimates an image of change in electrical properties within a body from stimulations and measurements at surface electrodes. There is significant interest in EIT as a tool to monitor and guide ventilation therapy in mechanically ventilated patients. In lung EIT, the EIT inverse problem is commonly linearized and only changes in electrical properties are reconstructed. Early algorithms reconstructed changes in resistivity, while most recent work using the finite element method reconstructs conductivity. Recently, we demonstrated that EIT images of ventilation can be misleading if the electrical contrasts within the thorax are not taken into account during the image reconstruction process. In this paper, we explore the effect of the choice of the reconstructed electrical properties (resistivity or conductivity) on the resulting EIT images. We show in simulation and experimental data that EIT images reconstructed with the same algorithm but with different parametrizations lead to large and clinically significant differences in the resulting images, which persist even after attempts to eliminate the impact of the parameter choice by recovering volume changes from the EIT images. Since there is no consensus among the most popular reconstruction algorithms and devices regarding the parametrization, this finding has implications for potential clinical use of EIT. We propose a program of research to develop reconstruction techniques that account for both the relationship between air volume and electrical properties of the lung and artefacts introduced by the linearization.
Choice of reconstructed tissue properties affects interpretation of lung EIT images
International Nuclear Information System (INIS)
Grychtol, Bartłomiej; Adler, Andy
2014-01-01
Electrical impedance tomography (EIT) estimates an image of change in electrical properties within a body from stimulations and measurements at surface electrodes. There is significant interest in EIT as a tool to monitor and guide ventilation therapy in mechanically ventilated patients. In lung EIT, the EIT inverse problem is commonly linearized and only changes in electrical properties are reconstructed. Early algorithms reconstructed changes in resistivity, while most recent work using the finite element method reconstructs conductivity. Recently, we demonstrated that EIT images of ventilation can be misleading if the electrical contrasts within the thorax are not taken into account during the image reconstruction process. In this paper, we explore the effect of the choice of the reconstructed electrical properties (resistivity or conductivity) on the resulting EIT images. We show in simulation and experimental data that EIT images reconstructed with the same algorithm but with different parametrizations lead to large and clinically significant differences in the resulting images, which persist even after attempts to eliminate the impact of the parameter choice by recovering volume changes from the EIT images. Since there is no consensus among the most popular reconstruction algorithms and devices regarding the parametrization, this finding has implications for potential clinical use of EIT. We propose a program of research to develop reconstruction techniques that account for both the relationship between air volume and electrical properties of the lung and artefacts introduced by the linearization. (paper)
5th Patras workshop on axions, WIMPs and WISPs (PATRAS 2009). Proceedings
Energy Technology Data Exchange (ETDEWEB)
Jaeckel, Joerg; Lindner, Axel; Redondo, Javier [eds.
2010-06-15
The following topics were dealt with: Direct searches for dark matter, indirect searches for WIMPS, photon generation and laser polarization experiments, direct axion signals, theoretic WISP developments. (HSI)
5th Patras workshop on axions, WIMPs and WISPs (PATRAS 2009). Proceedings
International Nuclear Information System (INIS)
Jaeckel, Joerg; Lindner, Axel; Redondo, Javier
2010-06-01
The following topics were dealt with: Direct searches for dark matter, indirect searches for WIMPS, photon generation and laser polarization experiments, direct axion signals, theoretic WISP developments. (HSI)
Supersymmetry with Radiatively-Driven Naturalness: Implications for WIMP and Axion Searches
Directory of Open Access Journals (Sweden)
Kyu Jung Bae
2015-05-01
Full Text Available By insisting on naturalness in both the electroweak and quantum chromodynamics (QCD sectors of the minimal supersymmetric standard model (MSSM, the portrait for dark matter production is seriously modified from the usual weakly interacting massive particle (WIMP miracle picture. In supersymmetry (SUSY models with radiatively-driven naturalness (radiative natural SUSY or radiative natural SUSY (RNS which include a Dine–Fischler–Srednicki–Zhitnitsky (DFSZ-like solution to the strong charge-conjugation-parity (CP and SUSY \\(\\mu\\ problems, dark matter is expected to be an admixture of both axions and higgsino-like WIMPs. The WIMP/axion abundance calculation requires simultaneous solution of a set of coupled Boltzmann equations which describe quasi-stable axinos and saxions. In most of parameter space, axions make up the dominant contribution of dark matter although regions of WIMP dominance also occur. We show the allowed range of Peccei-Quinn (PQ scale \\(f_a\\ and compare to the values expected to be probed by the axion dark matter search experiment (ADMX axion detector in the near future. We also show WIMP detection rates, which are suppressed from usual expectations, because now WIMPs comprise only a fraction of the total dark matter. Nonetheless, ton-scale noble liquid detectors should be able to probe the entirety of RNS parameter space. Indirect WIMP detection rates are less propitious since they are reduced by the square of the depleted WIMP abundance.
International Nuclear Information System (INIS)
Qi, Jinyi; Klein, Gregory J.; Huesman, Ronald H.
2000-01-01
A positron emission mammography scanner is under development at our Laboratory. The tomograph has a rectangular geometry consisting of four banks of detector modules. For each detector, the system can measure the depth of interaction information inside the crystal. The rectangular geometry leads to irregular radial and angular sampling and spatially variant sensitivity that are different from conventional PET systems. Therefore, it is of importance to study the image properties of the reconstructions. We adapted the theoretical analysis that we had developed for conventional PET systems to the list mode likelihood reconstruction for this tomograph. The local impulse response and covariance of the reconstruction can be easily computed using FFT. These theoretical results are also used with computer observer models to compute the signal-to-noise ratio for lesion detection. The analysis reveals the spatially variant resolution and noise properties of the list mode likelihood reconstruction. The theoretical predictions are in good agreement with Monte Carlo results
An intermediate framework between WIMP, FIMP, and EWIP dark matter
International Nuclear Information System (INIS)
Yaguna, Carlos E.
2012-01-01
WIMP (Weakly Interacting Massive Particle), FIMP (Feebly interacting Massive Particle) and EWIP (Extremely Weakly Interacting Particle) dark matter are different theoretical frameworks that have been postulated to explain the dark matter. In this paper we examine an intermediate scenario that combines features from these three frameworks. It consists of a weakly interacting particle — à la WIMP — that does not reach thermal equilibrium in the early Universe — à la FIMP — and whose relic density is determined by the reheating temperature of the Universe — à la EWIP. As an example, an explicit realization of this framework, based on the singlet scalar model of dark matter, is analyzed in detail. In particular, the relic density is studied as a function of the parameters of the model, and the new viable region within this intermediate scenario is determined. Finally, it is shown that this alternative framework of dark matter allows for arbitrarily heavy dark matter particles and that it suggests a connection between dark matter and inflation
Hobbs, Joanne K; Prentice, Erica J; Groussin, Mathieu; Arcus, Vickery L
2015-10-01
Ancestral sequence reconstruction has been widely used to study historical enzyme evolution, both from biochemical and cellular perspectives. Two properties of reconstructed ancestral proteins/enzymes are commonly reported--high thermostability and high catalytic activity--compared with their contemporaries. Increased protein stability is associated with lower aggregation rates, higher soluble protein abundance and a greater capacity to evolve, and therefore, these proteins could be considered "superior" to their contemporary counterparts. In this study, we investigate the relationship between the favourable in vitro biochemical properties of reconstructed ancestral enzymes and the organismal fitness they confer in vivo. We have previously reconstructed several ancestors of the enzyme LeuB, which is essential for leucine biosynthesis. Our initial fitness experiments revealed that overexpression of ANC4, a reconstructed LeuB that exhibits high stability and activity, was only able to partially rescue the growth of a ΔleuB strain, and that a strain complemented with this enzyme was outcompeted by strains carrying one of its descendants. When we expanded our study to include five reconstructed LeuBs and one contemporary, we found that neither in vitro protein stability nor the catalytic rate was correlated with fitness. Instead, fitness showed a strong, negative correlation with estimated evolutionary age (based on phylogenetic relationships). Our findings suggest that, for reconstructed ancestral enzymes, superior in vitro properties do not translate into organismal fitness in vivo. The molecular basis of the relationship between fitness and the inferred age of ancestral LeuB enzymes is unknown, but may be related to the reconstruction process. We also hypothesise that the ancestral enzymes may be incompatible with the other, contemporary enzymes of the metabolic network.
Thermalization time scales for WIMP capture by the Sun in effective theories
Energy Technology Data Exchange (ETDEWEB)
Widmark, A., E-mail: axel.widmark@fysik.su.se [The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, SE-106 91 Stockholm (Sweden)
2017-05-01
I study the process of dark matter capture by the Sun, under the assumption of a Weakly Interacting Massive Particle (WIMP), in the framework of non-relativistic effective field theory. Hypothetically, WIMPs from the galactic halo can scatter against atomic nuclei in the solar interior, settle to thermal equilibrium with the solar core and annihilate to produce an observable flux of neutrinos. In particular, I examine the thermalization process using Monte-Carlo integration of WIMP trajectories. I consider WIMPs in a mass range of 10–1000 GeV and WIMP-nucleon interaction operators with different dependence on spin and transferred momentum. I find that the density profiles of captured WIMPs are in accordance with a thermal profile described by the Sun's gravitational potential and core temperature. Depending on the operator that governs the interaction, the majority of the thermalization time is spent in either the solar interior or exterior. If normalizing the WIMP-nuclei interaction strength to a specific capture rate, I find that the thermalization time differs at most by 3 orders of magnitude between operators. In most cases of interest, the thermalization time is many orders of magnitude shorter than the age of the solar system.
Constraints on low-mass WIMPs from the EDELWEISS-III dark matter search
Energy Technology Data Exchange (ETDEWEB)
Armengaud, E.; De Boissière, T. [CEA Saclay, DSM/IRFU, Gif-sur-Yvette Cedex, 91191 France (France); Arnaud, Q.; Augier, C.; Benoît, A.; Billard, J.; Cazes, A.; Charlieux, F. [Institut de Physique Nucléaire de Lyon-UCBL, IN2P3-CNRS, 4 rue Enrico Fermi, Villeurbanne Cedex, 69622 France (France); Benoît, A.; Bres, G.; Camus, P. [Institut Néel, CNRS/UJF, 25 rue des Martyrs, BP 166, Grenoble, 38042 France (France); Bergé, L.; Broniatowski, A.; Chapellier, M.; Dumoulin, L. [CSNSM, Université Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, 91405 France (France); Bergmann, T. [Karlsruher Institut für Technologie, Institut für Prozessdatenverarbeitung und Elektronik, Postfach 3640, Karlsruhe, 76021 Germany (Germany); Blümer, J. [Karlsruher Institut für Technologie, Institut für Experimentelle Kernphysik, Gaedestr. 1, Karlsruhe, 76128 Germany (Germany); Brudanin, V.; Filosofov, D. [JINR, Laboratory of Nuclear Problems, Joliot-Curie 6, Dubna, Moscow Region, 141980 Russian Federation (Russian Federation); Eitel, K., E-mail: eric.armengaud@cea.fr [Karlsruher Institut für Technologie, Institut für Kernphysik, Postfach 3640, Karlsruhe, 76021 Germany (Germany); and others
2016-05-01
We present the results of a search for elastic scattering from galactic dark matter in the form of Weakly Interacting Massive Particles (WIMPs) in the 4–30 GeV/ c {sup 2} mass range. We make use of a 582 kg-day fiducial exposure from an array of 800 g Germanium bolometers equipped with a set of interleaved electrodes with full surface coverage. We searched specifically for ∼ 2.5–20 keV nuclear recoils inside the detector fiducial volume. As an illustration the number of observed events in the search for 5 (resp. 20) GeV/ c {sup 2} WIMPs are 9 (resp. 4), compared to an expected background of 6.1 (resp. 1.4). A 90% CL limit of 4.3 × 10{sup −40} cm{sup 2} (resp. 9.4 × 10{sup −44} cm{sup 2}) is set on the spin-independent WIMP-nucleon scattering cross-section for 5 (resp. 20) GeV/ c {sup 2} WIMPs. This result represents a 41-fold improvement with respect to the previous EDELWEISS-II low-mass WIMP search for 7 GeV/ c {sup 2} WIMPs. The derived constraint is in tension with hints of WIMP signals from some recent experiments, thus confirming results obtained with different detection techniques.
Generalized spin-dependent WIMP-nucleus interactions and the DAMA modulation effect
Energy Technology Data Exchange (ETDEWEB)
Scopel, Stefano; Yoon, Kook-Hyun; Yoon, Jong-Hyun, E-mail: scopel@sogang.ac.kr, E-mail: koreasds@naver.com, E-mail: pledge200@gmail.com [Department of Physics, Sogang University, Seoul (Korea, Republic of)
2015-07-01
Guided by non-relativistic Effective Field Theory (EFT) we classify the most general spin-dependent interactions between a fermionic Weakly Interacting Massive Particle (WIMP) and nuclei, and within this class of models we discuss the viability of an interpretation of the DAMA modulation result in terms of a signal from WIMP elastic scatterings using a halo-independent approach. We find that, although several relativistic EFT's can lead to a spin-dependent cross section, in some cases with an explicit, non-negligible dependence on the WIMP incoming velocity, three main scenarios can be singled out in the non-relativistic limit which approximately encompass them all, and that only differ by their dependence on the transferred momentum. For two of them compatibility between DAMA and other constraints is possible for a WIMP mass below 30 GeV, but only for a WIMP velocity distribution in the halo of our Galaxy which departs from a Maxwellian. This is achieved by combining a suppression of the WIMP effective coupling to neutrons (to evade constraints from xenon and germanium detectors) to an explicit quadratic or quartic dependence of the cross section on the transferred momentum (that leads to a relative enhancement of the expected rate off sodium in DAMA compared to that off fluorine in droplet detectors and bubble chambers). For larger WIMP masses the same scenarios are excluded by scatterings off iodine in COUPP.
Simultaneous Generation of WIMP Miracle-like Densities of Baryons and Dark Matter
International Nuclear Information System (INIS)
McDonald, John
2012-01-01
The observed density of dark matter is of the magnitude expected for a thermal relic weakly-interacting massive particle (WIMP). In addition, the observed baryon density is within an order of magnitude of the dark matter density. This suggests that the baryon density is physically related to a typical thermal relic WIMP dark matter density. We present a model which simultaneously generates thermal relic WIMP-like densities for both baryons and dark matter by modifying a large initial baryon asymmetry. Production of unstable scalars carrying baryon number at the LHC would be a clear signature of the model.
Gravitationally induced particle production and its impact on the WIMP abundance
Directory of Open Access Journals (Sweden)
I. Baranov
2015-12-01
Full Text Available A large set of independent astronomical observations have provided a strong evidence for nonbaryonic dark matter in the Universe. One of the most investigated candidates is an unknown long-lived Weakly Interacting Massive Particle (WIMP which was in thermal equilibrium with the primeval plasma. Here we investigate the WIMP abundance based on the relativistic kinetic treatment for gravitationally induced particle production recently proposed in the literature (Lima and Baranov, 2014 [16]. The new evolution equation is deduced and solved both numerically and through a semi-analytical approach. The predictions of the WIMP observables are discussed and compared with the ones obtained in the standard approach.
Beyond WIMPs: the Quark (Anti Nugget Dark Matter
Directory of Open Access Journals (Sweden)
Zhitnitsky Ariel
2017-01-01
Full Text Available We review a testable dark matter (DM model outside of the standard WIMP paradigm. The model is unique in a sense that the observed ratio Ωdark ≃ Ωvisible for visible and dark matter densities finds its natural explanation as a result of their common QCD origin when both types of matter (DM and visible are formed during the QCD phase transition and both are proportional to single dimensional parameter of the system, Λqcd. We argue that the charge separation effect also inevitably occurs during the same QCD phase transition in the presence of the CP odd axion field a(x. It leads to preferential formation of one species of nuggets on the scales of the visible Universe where the axion field a(x is coherent. A natural outcome of this preferential evolution is that only one type of the visible baryons (not anti- baryons remain in the system after the nuggets complete their formation. Unlike conventional WIMP dark matter candidates, the nuggets and anti-nuggets are strongly interacting but macroscopically large objects. The rare events of annihilation of the anti-nuggets with visible matter lead to a number of observable effects. We argue that the relative intensities for a number of measured excesses of emission from the centre of galaxy (covering more than 11 orders of magnitude are determined by standard and well established physics. At the same time the absolute intensity of emission is determined by a single new fundamental parameter of the theory, the axion mass, 10−6eV ≲ ma ≲ 10−3eV. Finally, we comment on implications of these studies for the axion search experiments, including microwave cavity and the Orpheus experiments.
Directory of Open Access Journals (Sweden)
Jacob J Setterbo
Full Text Available Racetrack surface is a risk factor for racehorse injuries and fatalities. Current research indicates that race surface mechanical properties may be influenced by material composition, moisture content, temperature, and maintenance. Race surface mechanical testing in a controlled laboratory setting would allow for objective evaluation of dynamic properties of surface and factors that affect surface behavior.To develop a method for reconstruction of race surfaces in the laboratory and validate the method by comparison with racetrack measurements of dynamic surface properties.Track-testing device (TTD impact tests were conducted to simulate equine hoof impact on dirt and synthetic race surfaces; tests were performed both in situ (racetrack and using laboratory reconstructions of harvested surface materials. Clegg Hammer in situ measurements were used to guide surface reconstruction in the laboratory. Dynamic surface properties were compared between in situ and laboratory settings. Relationships between racetrack TTD and Clegg Hammer measurements were analyzed using stepwise multiple linear regression.Most dynamic surface property setting differences (racetrack-laboratory were small relative to surface material type differences (dirt-synthetic. Clegg Hammer measurements were more strongly correlated with TTD measurements on the synthetic surface than the dirt surface. On the dirt surface, Clegg Hammer decelerations were negatively correlated with TTD forces.Laboratory reconstruction of racetrack surfaces guided by Clegg Hammer measurements yielded TTD impact measurements similar to in situ values. The negative correlation between TTD and Clegg Hammer measurements confirms the importance of instrument mass when drawing conclusions from testing results. Lighter impact devices may be less appropriate for assessing dynamic surface properties compared to testing equipment designed to simulate hoof impact (TTD.Dynamic impact properties of race surfaces
Nilsen, T.; Divine, D.; Rypdal, M.; Werner, J.; Rypdal, K.
2016-12-01
A modified two-dimensional stochastic-diffusive energy balance model (EBM) defined on a sphere was used for generating pseudoproxy/instrumental data and target data for surface temperature. The EBM is described in Rypdal et al. (2015). The target field has prescribed long-range memory (LRM) properties in time, and a frequency-dependent autocorrelation function in space. The Bayesian hierarchical model BARCAST, was used to generate surface temperature field reconstructions of an area corresponding to the European landmass for the past millennium. BARCAST has a built-in multivariate AR(1) model for the evolution of the temperature field, with an exponential, spatial covariance function, (Tingley & Huybers, 2010). The AR(1) process has a short-range memory, and we seek to find out how the competing spatiotemporal models influence the persistence of the reconstruction. A number of pseudoproxy experiments were performed with a fixed proxy network, using different signal-to-noise ratios (SNR) and colors of noise, (white/red). To study the persistence properties, the power-law relation of the power spectral density for LRM processes was used: S(f) f-β. The spectral exponent β was estimated both for local data and the spatial mean of the full region. The local β for the target varies between (0.1, 0.4), and for the spatial mean β 0.6. Results for the reconstructions show that the local and global memory is influenced by the noise color and level. Low noise levels or absence of noise results in reconstructions that exhibit similar properties as the target, while for higher noise levels the reconstructions have memory properties of a white/red character, (SNR=0.3 by standard deviation). Since an SNR of 0.5-0.25 is considered realistic for real proxy records, this implies that estimates of temporal persistence from proxy-based reconstructions reflect the proxy noise to a high degree, and not the signal as desired. Rypdal et al., 2015: Spatiotemporal Long-Range Persistence
Limits on Spin-Dependent WIMP-Nucleon Cross Section Obtained from the Complete LUX Exposure
Akerib, D. S.; Alsum, S.; Araújo, H. M.; Bai, X.; Bailey, A. J.; Balajthy, J.; Beltrame, P.; Bernard, E. P.; Bernstein, A.; Biesiadzinski, T. P.; Boulton, E. M.; Brás, P.; Byram, D.; Cahn, S. B.; Carmona-Benitez, M. C.; Chan, C.; Chiller, A. A.; Chiller, C.; Currie, A.; Cutter, J. E.; Davison, T. J. R.; Dobi, A.; Dobson, J. E. Y.; Druszkiewicz, E.; Edwards, B. N.; Faham, C. H.; Fallon, S. R.; Fiorucci, S.; Gaitskell, R. J.; Gehman, V. M.; Ghag, C.; Gilchriese, M. G. D.; Hall, C. R.; Hanhardt, M.; Haselschwardt, S. J.; Hertel, S. A.; Hogan, D. P.; Horn, M.; Huang, D. Q.; Ignarra, C. M.; Jacobsen, R. G.; Ji, W.; Kamdin, K.; Kazkaz, K.; Khaitan, D.; Knoche, R.; Larsen, N. A.; Lee, C.; Lenardo, B. G.; Lesko, K. T.; Lindote, A.; Lopes, M. I.; Manalaysay, A.; Mannino, R. L.; Marzioni, M. F.; McKinsey, D. N.; Mei, D.-M.; Mock, J.; Moongweluwan, M.; Morad, J. A.; Murphy, A. St. J.; Nehrkorn, C.; Nelson, H. N.; Neves, F.; O'Sullivan, K.; Oliver-Mallory, K. C.; Palladino, K. J.; Pease, E. K.; Reichhart, L.; Rhyne, C.; Shaw, S.; Shutt, T. A.; Silva, C.; Solmaz, M.; Solovov, V. N.; Sorensen, P.; Stephenson, S.; Sumner, T. J.; Szydagis, M.; Taylor, D. J.; Taylor, W. C.; Tennyson, B. P.; Terman, P. A.; Tiedt, D. R.; To, W. H.; Tripathi, M.; Tvrznikova, L.; Uvarov, S.; Velan, V.; Verbus, J. R.; Webb, R. C.; White, J. T.; Whitis, T. J.; Witherell, M. S.; Wolfs, F. L. H.; Xu, J.; Yazdani, K.; Young, S. K.; Zhang, C.; LUX Collaboration
2017-06-01
We present experimental constraints on the spin-dependent WIMP-nucleon elastic cross sections from the total 129.5 kg yr exposure acquired by the Large Underground Xenon experiment (LUX), operating at the Sanford Underground Research Facility in Lead, South Dakota (USA). A profile likelihood ratio analysis allows 90% C.L. upper limits to be set on the WIMP-neutron (WIMP-proton) cross section of σn=1.6 ×10-41 cm2 (σp=5 ×10-40 cm2 ) at 35 GeV c-2 , almost a sixfold improvement over the previous LUX spin-dependent results. The spin-dependent WIMP-neutron limit is the most sensitive constraint to date.
Model-independent determination of the WIMP mass from direct dark matter detection data
International Nuclear Information System (INIS)
Drees, Manuel; Shan, Chung-Lin
2008-01-01
Weakly interacting massive particles (WIMPs) are one of the leading candidates for dark matter. We develop a model-independent method for determining the mass m χ of the WIMP by using data (i.e. measured recoil energies) of direct detection experiments. Our method is independent of the as yet unknown WIMP density near the Earth, of the form of the WIMP velocity distribution, as well as of the WIMP–nucleus cross section. However, it requires positive signals from at least two detectors with different target nuclei. In a background-free environment, m χ ∼50 GeV could in principle be determined with an error of ∼35% with only 2 × 50 events; in practice, upper and lower limits on the recoil energy of signal events, imposed to reduce backgrounds, can increase the error. The method also loses precision if m χ significantly exceeds the mass of the heaviest target nucleus used
An H(∞) approach for elasticity properties reconstruction.
Liu, Huafeng; Hu, Hongjie; Sinusas, Albert J; Shi, Pengcheng
2012-01-01
Quantification of object elasticity properties has significant technical implications as well as important practical applications, such as medical disease diagnosis. In general, given noisy measurements on the kinematic states of the objects from imaging data, the aim is to recover the elasticity parameters for assumed material constitutive models of the objects. The implementation is complicated caused by the large dimensionality of the parameters. Various versions of the least-square (LS) methods have been widely used, which, however, do not perform well under reasonably realistic levels of disturbances. Another popular strategy, based on the extended Kalman filter (EKF), is also far from optimal and subject to divergence if either the initializations are poor or the noises are not Gaussian. In this paper, the authors propose a robust system identification paradigm for the quantitative analysis of object elasticity. It is derived and extended from the H(∞) filtering principles and is particularly powerful for real-world situations where the types and levels of the disturbances are unknown. Using synthetic data, the authors investigate the sensitivity of the strategies toward different types (Gaussian and Poisson) and levels of noises, as well as various initializations. The experimental results show consistently superior performance of the proposed method over the LS and EKF algorithms in reliably identifying object elastic modulus distributions. Results from phase contrast imaging data of canine hearts and human MRI data are also presented, which demonstrate the power of the framework.
Optical properties reconstruction using the adjoint method based on the radiative transfer equation
Addoum, Ahmad; Farges, Olivier; Asllanaj, Fatmir
2018-01-01
An efficient algorithm is proposed to reconstruct the spatial distribution of optical properties in heterogeneous media like biological tissues. The light transport through such media is accurately described by the radiative transfer equation in the frequency-domain. The adjoint method is used to efficiently compute the objective function gradient with respect to optical parameters. Numerical tests show that the algorithm is accurate and robust to retrieve simultaneously the absorption μa and scattering μs coefficients for lowly and highly absorbing medium. Moreover, the simultaneous reconstruction of μs and the anisotropy factor g of the Henyey-Greenstein phase function is achieved with a reasonable accuracy. The main novelty in this work is the reconstruction of g which might open the possibility to image this parameter in tissues as an additional contrast agent in optical tomography.
Projected WIMP Sensitivity of the LUX-ZEPLIN (LZ) Dark Matter Experiment
Energy Technology Data Exchange (ETDEWEB)
Akerib, D.S.; et al.
2018-02-16
LUX-ZEPLIN (LZ) is a next generation dark matter direct detection experiment that will operate 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. Using a two-phase xenon detector with an active mass of 7 tonnes, LZ will search primarily for low-energy interactions with Weakly Interacting Massive Particles (WIMPs), which are hypothesized to make up the dark matter in our galactic halo. In this paper, the projected WIMP sensitivity of LZ is presented based on the latest background estimates and simulations of the detector. For a 1000 live day run using a 5.6 tonne fiducial mass, LZ is projected to exclude at 90% confidence level spin-independent WIMP-nucleon cross sections above $1.6 \\times 10^{-48}$ cm$^{2}$ for a 40 $\\mathrm{GeV}/c^{2}$ mass WIMP. Additionally, a $5\\sigma$ discovery potential is projected reaching cross sections below the existing and projected exclusion limits of similar experiments that are currently operating. For spin-dependent WIMP-neutron(-proton) scattering, a sensitivity of $2.7 \\times 10^{-43}$ cm$^{2}$ ($8.1 \\times 10^{-42}$ cm$^{2}$) for a 40 $\\mathrm{GeV}/c^{2}$ mass WIMP is expected. With construction well underway, LZ is on track for underground installation at SURF in 2019 and will start collecting data in 2020.
arXiv Uncertainties in WIMP Dark Matter Scattering Revisited
Ellis, John; Olive, Keith A.
We revisit the uncertainties in the calculation of spin-independent scattering matrix elements for the scattering of WIMP dark matter particles on nuclear matter. In addition to discussing the uncertainties due to limitations in our knowledge of the nucleonic matrix elements of the light quark scalar densities , we also discuss the importances of heavy quark scalar densities , and comment on uncertainties in quark mass ratios. We analyze estimates of the light-quark densities made over the past decade using lattice calculations and/or phenomenological inputs. We find an uncertainty in the combination that is larger than has been assumed in some phenomenological analyses, and a range of that is smaller but compatible with earlier estimates. We also analyze the importance of the {\\cal O}(\\alpha_s^3) calculations of the heavy-quark matrix elements that are now available, which provide an important refinement of the calculation of the spin-independent scattering cross section. We use for illustration a benchmar...
Results and status of the Edelweiss Wimp search experiment
International Nuclear Information System (INIS)
Benoit, A.; Berge, L.; Blumer, J.; Broniatowski, A.; Censier, B.; Chabert, L.; Chambon, B.; Chapellier, M.; Chardin, G.; Charvin, P.; Jesus, M. de; Drain, D.; Di Stefano, P.; Dumoulin, L.; Eitel, K.; Fesquet, M.; Firucci, S.; Gascon, J.; Gerbier, G.; Gerlic, E.; Goldbach, C.; Goyot, M.; Gros, M.; Habermahl, F.; Horn, M.; Hadjout, J.P.; Herve, S.; Juillard, A.; Kikuchi, C.; Lesquen, A. de; Luca, M.; Mallet, J.; Marnieros, S.; Martineau, O.; Mosca, L.; Navick, X.F.; Nollez, G.; Pari, P.; Riccio, C.; Sanglard, V.; Stern, M.; Vagneron, L.; Villard, V.
2005-01-01
In the Edelweiss experiment, nuclear recoils induced by elastic collisions with WIMPs (weakly interacting massive particle) from the galactic halo are identified in low-temperature Ge detectors where the ratio of the heat and ionization signals provide an event-by-event discrimination of nuclear recoils from the dominant background coming from γ-rays interactions. The Edelweiss experiment is located in the Modane underground facility in order to cut the muon flux drastically. We present here the results obtained during the first part of the experiment named Edelweiss-I that ended in the beginning of 2004. Since october 2002, 3 optimized 320 grams detectors have been simultaneously operated at a regulated temperature of 0.017 K and about 50 kg*day were added to the previous published data. These data are still under analysis but preliminary results concerning the upper limit at 90% CL (confidence level) confirm the limit already published in 2002. The first run of Edelweiss-II is due to begin during summer 2005, we are expecting to gain 2 orders of magnitude in terms of detector sensitivity and reach 0.002 events/day*kg. (A.C.)
Bioengineered human IAS reconstructs with functional and molecular properties similar to intact IAS
Singh, Jagmohan
2012-01-01
Because of its critical importance in rectoanal incontinence, we determined the feasibility to reconstruct internal anal sphincter (IAS) from human IAS smooth muscle cells (SMCs) with functional and molecular attributes similar to the intact sphincter. The reconstructs were developed using SMCs from the circular smooth muscle layer of the human IAS, grown in smooth muscle differentiation media under sterile conditions in Sylgard-coated tissue culture plates with central Sylgard posts. The basal tone in the reconstructs and its changes were recorded following 0 Ca2+, KCl, bethanechol, isoproterenol, protein kinase C (PKC) activator phorbol 12,13-dibutyrate, and Rho kinase (ROCK) and PKC inhibitors Y-27632 and Gö-6850, respectively. Western blot (WB), immunofluorescence (IF), and immunocytochemical (IC) analyses were also performed. The reconstructs developed spontaneous tone (0.68 ± 0.26 mN). Bethanechol (a muscarinic agonist) and K+ depolarization produced contraction, whereas isoproterenol (β-adrenoceptor agonist) and Y-27632 produced a concentration-dependent decrease in the tone. Maximal decrease in basal tone with Y-27632 and Gö-6850 (each 10−5 M) was 80.45 ± 3.29 and 17.76 ± 3.50%, respectively. WB data with the IAS constructs′ SMCs revealed higher levels of RhoA/ROCK, protein kinase C-potentiated inhibitor or inhibitory phosphoprotein for myosin phosphatase (CPI-17), phospho-CPI-17, MYPT1, and 20-kDa myosin light chain vs. rectal smooth muscle. WB, IF, and IC studies of original SMCs and redispersed from the reconstructs for the relative distribution of different signal transduction proteins confirmed the feasibility of reconstruction of IAS with functional properties similar to intact IAS and demonstrated the development of myogenic tone with critical dependence on RhoA/ROCK. We conclude that it is feasible to bioengineer IAS constructs using human IAS SMCs that behave like intact IAS. PMID:22790596
International Nuclear Information System (INIS)
Michel, Eric; Hernandez, Daniel; Cho, Min Hyoung; Lee, Soo Yeol
2014-01-01
Purpose: To validate the use of adaptive nonlinear filters in reconstructing conductivity and permittivity images from the noisy B 1 + maps in electrical properties tomography (EPT). Methods: In EPT, electrical property images are computed by taking Laplacian of the B 1 + maps. To mitigate the noise amplification in computing the Laplacian, the authors applied adaptive nonlinear denoising filters to the measured complex B 1 + maps. After the denoising process, they computed the Laplacian by central differences. They performed EPT experiments on phantoms and a human brain at 3 T along with corresponding EPT simulations on finite-difference time-domain models. They evaluated the EPT images comparing them with the ones obtained by previous EPT reconstruction methods. Results: In both the EPT simulations and experiments, the nonlinear filtering greatly improved the EPT image quality when evaluated in terms of the mean and standard deviation of the electrical property values at the regions of interest. The proposed method also improved the overall similarity between the reconstructed conductivity images and the true shapes of the conductivity distribution. Conclusions: The nonlinear denoising enabled us to obtain better-quality EPT images of the phantoms and the human brain at 3 T
Energy Technology Data Exchange (ETDEWEB)
Solomon, Justin, E-mail: justin.solomon@duke.edu [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 (United States); Samei, Ehsan [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 and Departments of Biomedical Engineering and Electrical and Computer Engineering, Pratt School of Engineering, Duke University, Durham, North Carolina 27705 (United States)
2014-09-15
Purpose: Quantum noise properties of CT images are generally assessed using simple geometric phantoms with uniform backgrounds. Such phantoms may be inadequate when assessing nonlinear reconstruction or postprocessing algorithms. The purpose of this study was to design anatomically informed textured phantoms and use the phantoms to assess quantum noise properties across two clinically available reconstruction algorithms, filtered back projection (FBP) and sinogram affirmed iterative reconstruction (SAFIRE). Methods: Two phantoms were designed to represent lung and soft-tissue textures. The lung phantom included intricate vessel-like structures along with embedded nodules (spherical, lobulated, and spiculated). The soft tissue phantom was designed based on a three-dimensional clustered lumpy background with included low-contrast lesions (spherical and anthropomorphic). The phantoms were built using rapid prototyping (3D printing) technology and, along with a uniform phantom of similar size, were imaged on a Siemens SOMATOM Definition Flash CT scanner and reconstructed with FBP and SAFIRE. Fifty repeated acquisitions were acquired for each background type and noise was assessed by estimating pixel-value statistics, such as standard deviation (i.e., noise magnitude), autocorrelation, and noise power spectrum. Noise stationarity was also assessed by examining the spatial distribution of noise magnitude. The noise properties were compared across background types and between the two reconstruction algorithms. Results: In FBP and SAFIRE images, noise was globally nonstationary for all phantoms. In FBP images of all phantoms, and in SAFIRE images of the uniform phantom, noise appeared to be locally stationary (within a reasonably small region of interest). Noise was locally nonstationary in SAFIRE images of the textured phantoms with edge pixels showing higher noise magnitude compared to pixels in more homogenous regions. For pixels in uniform regions, noise magnitude was
International Nuclear Information System (INIS)
Solomon, Justin; Samei, Ehsan
2014-01-01
Purpose: Quantum noise properties of CT images are generally assessed using simple geometric phantoms with uniform backgrounds. Such phantoms may be inadequate when assessing nonlinear reconstruction or postprocessing algorithms. The purpose of this study was to design anatomically informed textured phantoms and use the phantoms to assess quantum noise properties across two clinically available reconstruction algorithms, filtered back projection (FBP) and sinogram affirmed iterative reconstruction (SAFIRE). Methods: Two phantoms were designed to represent lung and soft-tissue textures. The lung phantom included intricate vessel-like structures along with embedded nodules (spherical, lobulated, and spiculated). The soft tissue phantom was designed based on a three-dimensional clustered lumpy background with included low-contrast lesions (spherical and anthropomorphic). The phantoms were built using rapid prototyping (3D printing) technology and, along with a uniform phantom of similar size, were imaged on a Siemens SOMATOM Definition Flash CT scanner and reconstructed with FBP and SAFIRE. Fifty repeated acquisitions were acquired for each background type and noise was assessed by estimating pixel-value statistics, such as standard deviation (i.e., noise magnitude), autocorrelation, and noise power spectrum. Noise stationarity was also assessed by examining the spatial distribution of noise magnitude. The noise properties were compared across background types and between the two reconstruction algorithms. Results: In FBP and SAFIRE images, noise was globally nonstationary for all phantoms. In FBP images of all phantoms, and in SAFIRE images of the uniform phantom, noise appeared to be locally stationary (within a reasonably small region of interest). Noise was locally nonstationary in SAFIRE images of the textured phantoms with edge pixels showing higher noise magnitude compared to pixels in more homogenous regions. For pixels in uniform regions, noise magnitude was
Placing the pieces: Reconstructing the original property mosaic in a warrant and patent watershed
Bain, D.J.; Brush, G.S.
2005-01-01
Recent research shows that land use history is an important determinant of current ecosystem function. In the United States, characterization of land use change following European settlement requires reconstruction of the original property mosaic. However, this task is difficult in unsystematically surveyed areas east of the Appalachian Mountains. The Gwynns Falls watershed (Baltimore, MD) was originally surveyed in the 1600-1700s under a system of warrants and patents (commonly known as 'metes and bounds'). A method for the reconstruction and mapping of warrant and patent properties is presented and used to map the original property mosaic in the Gwynns Falls watershed. Using the mapped mosaic, the persistence of properties and property lines in the current Gwynns Falls landscape is considered. The results of this research indicate that as in agricultural areas, the original property lines in the Gwynns Falls watershed are persistent. At the same time, the results suggest that the property mosaic in heavily urbanized/suburbanized areas is generally 'reset.' Further, trends in surveying technique, parcel size, and settlement patterns cause property line density and property shape complexity to increase in the less urbanized upper watershed. The persistence of original patterns may be damping expression of heterogeneity gradients in this urban landscape. This spatial pattern of complexity in the original mosaic is directly opposite of hypothesized patterns of landscape heterogeneity arising from urbanization. The technique reported here and the resulting observations are important for landscape pattern studies in areas settled under unsystematic survey systems, especially the heavily urbanized areas of the eastern United States. ?? 2004 Kluwer Academic Publishers.
Energy Technology Data Exchange (ETDEWEB)
Benoit, A.; Berge, L.; Blumer, J.; Broniatowski, A.; Censier, B.; Chabert, L.; Chambon, B.; Chapellier, M.; Chardin, G.; Charvin, P.; Jesus, M. de; Drain, D.; Di Stefano, P.; Dumoulin, L.; Eitel, K.; Fesquet, M.; Firucci, S.; Gascon, J.; Gerbier, G.; Gerlic, E.; Goldbach, C.; Goyot, M.; Gros, M.; Habermahl, F.; Horn, M.; Hadjout, J.P.; Herve, S.; Juillard, A.; Kikuchi, C.; Lesquen, A. de; Luca, M.; Mallet, J.; Marnieros, S.; Martineau, O.; Mosca, L.; Navick, X.F.; Nollez, G.; Pari, P.; Riccio, C.; Sanglard, V.; Stern, M.; Vagneron, L.; Villard, V
2005-07-01
In the Edelweiss experiment, nuclear recoils induced by elastic collisions with WIMPs (weakly interacting massive particle) from the galactic halo are identified in low-temperature Ge detectors where the ratio of the heat and ionization signals provide an event-by-event discrimination of nuclear recoils from the dominant background coming from {gamma}-rays interactions. The Edelweiss experiment is located in the Modane underground facility in order to cut the muon flux drastically. We present here the results obtained during the first part of the experiment named Edelweiss-I that ended in the beginning of 2004. Since october 2002, 3 optimized 320 grams detectors have been simultaneously operated at a regulated temperature of 0.017 K and about 50 kg*day were added to the previous published data. These data are still under analysis but preliminary results concerning the upper limit at 90% CL (confidence level) confirm the limit already published in 2002. The first run of Edelweiss-II is due to begin during summer 2005, we are expecting to gain 2 orders of magnitude in terms of detector sensitivity and reach 0.002 events/day*kg. (A.C.)
International Nuclear Information System (INIS)
Han, Zhaolong; Li, Jiasong; Singh, Manmohan; Wu, Chen; Liu, Chih-hao; Wang, Shang; Idugboe, Rita; Raghunathan, Raksha; Sudheendran, Narendran; Larin, Kirill V; Aglyamov, Salavat R; Twa, Michael D
2015-01-01
We present a systematic analysis of the accuracy of five different methods for extracting the biomechanical properties of soft samples using optical coherence elastography (OCE). OCE is an emerging noninvasive technique, which allows assessment of biomechanical properties of tissues with micrometer spatial resolution. However, in order to accurately extract biomechanical properties from OCE measurements, application of a proper mechanical model is required. In this study, we utilize tissue-mimicking phantoms with controlled elastic properties and investigate the feasibilities of four available methods for reconstructing elasticity (Young’s modulus) based on OCE measurements of an air-pulse induced elastic wave. The approaches are based on the shear wave equation (SWE), the surface wave equation (SuWE), Rayleigh-Lamb frequency equation (RLFE), and finite element method (FEM), Elasticity values were compared with uniaxial mechanical testing. The results show that the RLFE and the FEM are more robust in quantitatively assessing elasticity than the other simplified models. This study provides a foundation and reference for reconstructing the biomechanical properties of tissues from OCE data, which is important for the further development of noninvasive elastography methods. (paper)
Accelerating image reconstruction in dual-head PET system by GPU and symmetry properties.
Directory of Open Access Journals (Sweden)
Cheng-Ying Chou
Full Text Available Positron emission tomography (PET is an important imaging modality in both clinical usage and research studies. We have developed a compact high-sensitivity PET system that consisted of two large-area panel PET detector heads, which produce more than 224 million lines of response and thus request dramatic computational demands. In this work, we employed a state-of-the-art graphics processing unit (GPU, NVIDIA Tesla C2070, to yield an efficient reconstruction process. Our approaches ingeniously integrate the distinguished features of the symmetry properties of the imaging system and GPU architectures, including block/warp/thread assignments and effective memory usage, to accelerate the computations for ordered subset expectation maximization (OSEM image reconstruction. The OSEM reconstruction algorithms were implemented employing both CPU-based and GPU-based codes, and their computational performance was quantitatively analyzed and compared. The results showed that the GPU-accelerated scheme can drastically reduce the reconstruction time and thus can largely expand the applicability of the dual-head PET system.
Nanduri, Vibudha; Tattikota, Surendra Mohan; T, Avinash Raj; Sriramagiri, Vijaya Rama Rao; Kantipudi, Suma; Pande, Gopal
2014-06-01
Articular cartilage (AC) injuries and malformations are commonly noticed because of trauma or age-related degeneration. Many methods have been adopted for replacing or repairing the damaged tissue. Currently available AC repair methods, in several cases, fail to yield good-quality long-lasting results, perhaps because the reconstructed tissue lacks the cellular and matrix properties seen in hyaline cartilage (HC). To reconstruct HC tissue from 2-dimensional (2D) and 3-dimensional (3D) cultures of AC-derived human chondrocytes that would specifically exhibit the cellular and biochemical properties of the deep layer of HC. Descriptive laboratory study. Two-dimensional cultures of human AC-derived chondrocytes were established in classical medium (CM) and newly defined medium (NDM) and maintained for a period of 6 weeks. These cells were suspended in 2 mm-thick collagen I gels, placed in 24-well culture inserts, and further cultured up to 30 days. Properties of chondrocytes, grown in 2D cultures and the reconstructed 3D cartilage tissue, were studied by optical and scanning electron microscopic techniques, immunohistochemistry, and cartilage-specific gene expression profiling by reverse transcription polymerase chain reaction and were compared with those of the deep layer of native human AC. Two-dimensional chondrocyte cultures grown in NDM, in comparison with those grown in CM, showed more chondrocyte-specific gene activity and matrix properties. The NDM-grown chondrocytes in 3D cultures also showed better reproduction of deep layer properties of HC, as confirmed by microscopic and gene expression analysis. The method used in this study can yield cartilage tissue up to approximately 1.6 cm in diameter and 2 mm in thickness that satisfies the very low cell density and matrix composition properties present in the deep layer of normal HC. This study presents a novel and reproducible method for long-term culture of AC-derived chondrocytes and reconstruction of cartilage
Halo-independent determination of the unmodulated WIMP signal in DAMA: the isotropic case
Energy Technology Data Exchange (ETDEWEB)
Gondolo, Paolo [Department of Physics, University of Utah, 115 South 1400 East #201, Salt Lake City, Utah 84112-0830 (United States); Scopel, Stefano, E-mail: paolo.gondolo@utah.edu, E-mail: scopel@sogang.ac.kr [Department of Physics, Sogang University, Seoul 121-742 (Korea, Republic of)
2017-09-01
We present a halo-independent determination of the unmodulated signal corresponding to the DAMA modulation if interpreted as due to dark matter weakly interacting massive particles (WIMPs). First we show how a modulated signal gives information on the WIMP velocity distribution function in the Galactic rest frame from which the unmodulated signal descends. Then we describe a mathematically-sound profile likelihood analysis in which the likelihood is profiled over a continuum of nuisance parameters (namely, the WIMP velocity distribution). As a first application of the method, which is very general and valid for any class of velocity distributions, we restrict the analysis to velocity distributions that are isotropic in the Galactic frame. In this way we obtain halo-independent maximum-likelihood estimates and confidence intervals for the DAMA unmodulated signal. We find that the estimated unmodulated signal is in line with expectations for a WIMP-induced modulation and is compatible with the DAMA background+signal rate. Specifically, for the isotropic case we find that the modulated amplitude ranges between a few percent and about 25% of the unmodulated amplitude, depending on the WIMP mass.
Experimental research of vehicle traction properties for reconstruction of traffic accidents
Directory of Open Access Journals (Sweden)
Dudziak Marian
2018-01-01
Full Text Available In order to broaden the database of motor vehicle traction properties in unusual conditions, the research team has performed experimental studies: on wet and snow-covered surfaces. Tests of vehicles equipped with winter tyres with non-skid snow chains have been performed on snow-covered surfaces. It has been shown that on snowy surface chains affect vehicle traction properties, mostly during acceleration. They increase the rate of acceleration up to 50% compared to a vehicle with winter tyres without chains. The results of the performed research can be the basis for the full reconstruction of road accidents under these conditions. Knowledge of traction properties of cars in difficult and unusual conditions is an important cognitive factor and serves to improve road safety.
Beyond WIMP: From Theory to Detection of Sub-GeV Dark Matter
CERN. Geneva
2014-01-01
The existence of dark matter has been well established with overwhelming evidence, but its particle identity is still unknown. For more than three decades, significant theoretical and experimental efforts have been directed towards the search for a Weakly Interacting Massive Particle (WIMP), often overlooking other possibilities. The lack of an unambiguous positive WIMP signal, at both indirect- and direct-detection experiments and at the LHC, stresses the need to expand dark matter research into additional theoretical scenarios and, more importantly, to develop new experimental capabilities that go beyond the limitations of WIMP detection. In this talk I will discuss new theoretical ideas and experimental avenues for searching for light, sub-GeV dark matter. Some emphasis will be given to direct detection experiments, where several new strategies to directly detect dark matter particles with MeV to GeV mass, far below standard direct detection capabilities, are developed.
Accurate calculations of the WIMP halo around the Sun and prospects for its gamma-ray detection
International Nuclear Information System (INIS)
Sivertsson, Sofia; Edsjoe, Joakim
2010-01-01
Galactic weakly interacting massive particles (WIMPs) may scatter off solar nuclei to orbits gravitationally bound to the Sun. Once bound, the WIMPs continue to lose energy by repeated scatters in the Sun, eventually leading to complete entrapment in the solar interior. While the density of the bound population is highest at the center of the Sun, the only observable signature of WIMP annihilations inside the Sun is neutrinos. It has been previously suggested that although the density of WIMPs just outside the Sun is lower than deep inside, gamma rays from WIMP annihilation just outside the surface of the Sun, in the so-called WIMP halo around the Sun, may be more easily detected. We here revisit this problem using detailed Monte Carlo simulations and detailed composition and structure information about the Sun to estimate the size of the gamma-ray flux. Compared to earlier simpler estimates, we find that the gamma-ray flux from WIMP annihilations in the solar WIMP halo would be negligible; no current or planned detectors would be able to detect this flux.
Power corrections to the universal heavy WIMP-nucleon cross section
Energy Technology Data Exchange (ETDEWEB)
Chen, Chien-Yi; Hill, Richard J.; Solon, Mikhail P.; Wijangco, Alexander M.
2018-06-01
WIMP-nucleon scattering is analyzed at order $1/M$ in Heavy WIMP Effective Theory. The $1/M$ power corrections, where $M\\gg m_W$ is the WIMP mass, distinguish between different underlying UV models with the same universal limit and their impact on direct detection rates can be enhanced relative to naive expectations due to generic amplitude-level cancellations at leading order. The necessary one- and two-loop matching calculations onto the low-energy effective theory for WIMP interactions with Standard Model quarks and gluons are performed for the case of an electroweak SU(2) triplet WIMP, considering both the cases of elementary fermions and composite scalars. The low-velocity WIMP-nucleon scattering cross section is evaluated and compared with current experimental limits and projected future sensitivities. Our results provide the most robust prediction for electroweak triplet Majorana fermion dark matter direct detection rates; for this case, a cancellation between two sources of power corrections yields a small total $1/M$ correction, and a total cross section close to the universal limit for $M \\gtrsim {\\rm few} \\times 100\\,{\\rm GeV}$. For the SU(2) composite scalar, the $1/M$ corrections introduce dependence on underlying strong dynamics. Using a leading chiral logarithm evaluation, the total $1/M$ correction has a larger magnitude and uncertainty than in the fermionic case, with a sign that further suppresses the total cross section. These examples provide definite targets for future direct detection experiments and motivate large scale detectors capable of probing to the neutrino floor in the TeV mass regime.
Power corrections to the universal heavy WIMP-nucleon cross section
Chen, Chien-Yi; Hill, Richard J.; Solon, Mikhail P.; Wijangco, Alexander M.
2018-06-01
WIMP-nucleon scattering is analyzed at order 1 / M in Heavy WIMP Effective Theory. The 1 / M power corrections, where M ≫mW is the WIMP mass, distinguish between different underlying UV models with the same universal limit and their impact on direct detection rates can be enhanced relative to naive expectations due to generic amplitude-level cancellations at leading order. The necessary one- and two-loop matching calculations onto the low-energy effective theory for WIMP interactions with Standard Model quarks and gluons are performed for the case of an electroweak SU(2) triplet WIMP, considering both the cases of elementary fermions and composite scalars. The low-velocity WIMP-nucleon scattering cross section is evaluated and compared with current experimental limits and projected future sensitivities. Our results provide the most robust prediction for electroweak triplet Majorana fermion dark matter direct detection rates; for this case, a cancellation between two sources of power corrections yields a small total 1 / M correction, and a total cross section close to the universal limit for M ≳ few × 100GeV. For the SU(2) composite scalar, the 1 / M corrections introduce dependence on underlying strong dynamics. Using a leading chiral logarithm evaluation, the total 1 / M correction has a larger magnitude and uncertainty than in the fermionic case, with a sign that further suppresses the total cross section. These examples provide definite targets for future direct detection experiments and motivate large scale detectors capable of probing to the neutrino floor in the TeV mass regime.
International Nuclear Information System (INIS)
Zhao, Shuyuan; Zhang, Wenjiao; He, Xiaodong; Li, Jianjun; Yao, Yongtao; Lin, Xiu
2015-01-01
To probe thermal degradation behavior of fibrous insulation for long-term service, an inverse analysis model was developed to simultaneously reconstruct thermal degradation properties of fibers after thermal exposures from the experimental thermal response data, by using the measured infrared spectral transmittance and X-ray phase analysis data as direct inputs. To take into account the possible influence of fibers degradation after thermal exposure on the conduction heat transfer, we introduced a new parameter in the thermal conductivity model. The effect of microstructures on the thermal degradation parameters was evaluated. It was found that after high temperature thermal exposure the decay rate of the radiation intensity passing through the material was weakened, and the probability of being scattered decreased during the photons traveling in the medium. The fibrous medium scattered more radiation into the forward directions. The shortened heat transfer path due to possible mechanical degradation, along with the enhancement of mean free path of phonon scattering as devitrification after severe heat treatment, made the coupled solid/gas thermal conductivities increase with the rise of heat treatment temperature. - Highlights: • A new model is developed to probe conductive and radiative properties degradation of fibers. • To characterize mechanical degradation, a new parameter is introduced in the model. • Thermal degradation properties are reconstructed from experiments by L–M algorithm. • The effect of microstructures on the thermal degradation parameters is evaluated. • The analysis provides a powerful tool to quantify thermal degradation of fiber medium
Painlevé equations, topological type property and reconstruction by the topological recursion
Iwaki, K.; Marchal, O.; Saenz, A.
2018-01-01
In this article we prove that Lax pairs associated with ħ-dependent six Painlevé equations satisfy the topological type property proposed by Bergère, Borot and Eynard for any generic choice of the monodromy parameters. Consequently we show that one can reconstruct the formal ħ-expansion of the isomonodromic τ-function and of the determinantal formulas by applying the so-called topological recursion to the spectral curve attached to the Lax pair in all six Painlevé cases. Finally we illustrate the former results with the explicit computations of the first orders of the six τ-functions.
The waning of the WIMP? A review of models, searches, and constraints
Arcadi, Giorgio; Dutra, Maíra; Ghosh, Pradipta; Lindner, Manfred; Mambrini, Yann; Pierre, Mathias; Profumo, Stefano; Queiroz, Farinaldo S.
2018-03-01
Weakly Interacting Massive Particles (WIMPs) are among the best-motivated dark matter candidates. No conclusive signal, despite an extensive search program that combines, often in a complementary way, direct, indirect, and collider probes, has been detected so far. This situation might change in near future due to the advent of one/multi-TON Direct Detection experiments. We thus, find it timely to provide a review of the WIMP paradigm with focus on a few models which can be probed at best by these facilities. Collider and Indirect Detection, nevertheless, will not be neglected when they represent a complementary probe.
Impacts of WIMP dark matter upon stellar evolution: main-sequence stars
Scott, Pat; Edsjo, Joakim
2008-01-01
The presence of large amounts of WIMP dark matter in stellar cores has been shown to have significant effects upon models of stellar evolution. We present a series of detailed grids of WIMP-influenced stellar models for main sequence stars, computed using the DarkStars code. We describe the changes in stellar structure and main sequence evolution which occur for masses ranging from 0.3 to 2.0 solar masses and metallicities from Z = 0.0003-0.02, as a function of the rate of energy injection by WIMPs. We then go on to show what rates of energy injection can be obtained using realistic orbital parameters for stars near supermassive black holes, including detailed considerations of dark matter halo velocity and density profiles. Capture and annihilation rates are strongly boosted when stars follow elliptical rather than circular orbits, causing WIMP annihilation to provide up to 100 times the energy of hydrogen fusion in stars at the Galactic centre.
Detector Simulation and WIMP Search Analysis for the Cryogenic Dark Matter Search Experiment
Energy Technology Data Exchange (ETDEWEB)
McCarthy, Kevin [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
2013-06-01
Astrophysical and cosmological measurements on the scales of galaxies, galaxy clusters, and the universe indicate that 85% of the matter in the universe is composed of dark matter, made up of non-baryonic particles that interact with cross-sections on the weak scale or lower. Hypothetical Weakly Interacting Massive Particles, or WIMPs, represent a potential solution to the dark matter problem, and naturally arise in certain Standard Model extensions. The Cryogenic Dark Matter Search (CDMS) collaboration aims to detect the scattering of WIMP particles from nuclei in terrestrial detectors. Germanium and silicon particle detectors are deployed in the Soudan Underground Laboratory in Minnesota. These detectors are instrumented with phonon and ionization sensors, which allows for discrimination against electromagnetic backgrounds, which strike the detector at rates orders of magnitude higher than the expected WIMP signal. This dissertation presents the development of numerical models of the physics of the CDMS detectors, implemented in a computational package collectively known as the CDMS Detector Monte Carlo (DMC). After substantial validation of the models against data, the DMC is used to investigate potential backgrounds to the next iteration of the CDMS experiment, known as SuperCDMS. Finally, an investigation of using the DMC in a reverse Monte Carlo analysis of WIMP search data is presented.
Simultaneous generation of WIMP miracle-like densities of baryons and dark matter
International Nuclear Information System (INIS)
McDonald, John
2011-01-01
The observed density of dark matter is of the magnitude expected for a thermal relic weakly-interacting massive particle (WIMP). In addition, the observed baryon density is within an order of magnitude of the dark matter density. This suggests that the baryon density is physically related to a typical thermal relic WIMP dark matter density. We present a model which simultaneously generates thermal relic WIMP-like densities for both baryons and dark matter by modifying a large initial baryon asymmetry. Dark matter is due to O(100) GeV gauge singlet scalars produced in the annihilation of the O(TeV) colored scalars which are responsible for the final thermal WIMP-like baryon asymmetry. The requirement of no baryon washout implies that there are two gauge singlet scalars. The low-temperature transfer of the asymmetry to conventional baryons can be understood if the long-lived O(TeV) colored scalars have large hypercharge, |Y|>4/3. Production of such scalars at the LHC would be a clear signature of the model.
Ultra-cold WIMPs relics of non-standard pre-BBN cosmologies
Gelmini, Graciela B
2008-01-01
We point out that in scenarios in which the Universe evolves in a non-standard manner during and after the kinetic decoupling of weakly interacting massive particles (WIMPs), these relics can be much colder than in standard cosmological scenarios (i.e. can be ultra-cold), possibly leading to the formation of smaller first objects in hierarchical structure formation scenarios.
Civitarese, O.; Fushimi, K. J.; Mosquera, M. E.
2016-12-01
Weakly interacting massive particles (WIMPs) are possible components of the Universe’s dark matter (DM). The detection of WIMPs is signaled by the recoil of the atomic nuclei which form a detector. CoGeNT at the Soudan Underground Laboratory (SUL) and DAMA at the Laboratori Nazionali del Gran Sasso (LNGS) have reported data on annual modulation of signals attributed to WIMPs. Both experiments are located in laboratories in the Northern Hemisphere. DM detectors are planned to operate (or already operate) in laboratories in the Southern Hemisphere, including SABRE at Stawell Underground Physics Laboratory (SUPL) in Australia, and DM-ICE in Antarctica. In this work we have analyzed the dependence of diurnal and annual modulation of signals, pertaining to the detection of WIMP, on the coordinates of the laboratory, for experiments which may be performed in the planned new Agua Negra Deep Experimental Site (ANDES) underground facility, to be built in San Juan, Argentina. We made predictions for NaI and Ge-type detectors placed in ANDES, to compare with DAMA, CoGeNT, SABRE and DM-ICE arrays, and found that the diurnal modulation of the signals, at the ANDES site, is amplified at its maximum value, both for NaI (Ge)-type detectors, while the annual modulation remains unaffected by the change in coordinates from north to south.
International Nuclear Information System (INIS)
Civitarese, O; Mosquera, M E; Fushimi, K J
2016-01-01
Weakly interacting massive particles (WIMPs) are possible components of the Universe’s dark matter (DM). The detection of WIMPs is signaled by the recoil of the atomic nuclei which form a detector. CoGeNT at the Soudan Underground Laboratory (SUL) and DAMA at the Laboratori Nazionali del Gran Sasso (LNGS) have reported data on annual modulation of signals attributed to WIMPs. Both experiments are located in laboratories in the Northern Hemisphere. DM detectors are planned to operate (or already operate) in laboratories in the Southern Hemisphere, including SABRE at Stawell Underground Physics Laboratory (SUPL) in Australia, and DM-ICE in Antarctica. In this work we have analyzed the dependence of diurnal and annual modulation of signals, pertaining to the detection of WIMP, on the coordinates of the laboratory, for experiments which may be performed in the planned new Agua Negra Deep Experimental Site (ANDES) underground facility, to be built in San Juan, Argentina. We made predictions for NaI and Ge-type detectors placed in ANDES, to compare with DAMA, CoGeNT, SABRE and DM-ICE arrays, and found that the diurnal modulation of the signals, at the ANDES site, is amplified at its maximum value, both for NaI (Ge)-type detectors, while the annual modulation remains unaffected by the change in coordinates from north to south. (paper)
Improved EDELWEISS-III sensitivity for low-mass WIMPs using a profile likelihood approach
Energy Technology Data Exchange (ETDEWEB)
Hehn, L. [Karlsruher Institut fuer Technologie, Institut fuer Kernphysik, Karlsruhe (Germany); Armengaud, E.; Boissiere, T. de; Gros, M.; Navick, X.F.; Nones, C.; Paul, B. [CEA Saclay, DSM/IRFU, Gif-sur-Yvette Cedex (France); Arnaud, Q. [Univ Lyon, Universite Claude Bernard Lyon 1, CNRS/IN2P3, Institut de Physique Nucleaire de Lyon, Lyon (France); Queen' s University, Kingston (Canada); Augier, C.; Billard, J.; Cazes, A.; Charlieux, F.; Jesus, M. de; Gascon, J.; Juillard, A.; Queguiner, E.; Sanglard, V.; Vagneron, L. [Univ Lyon, Universite Claude Bernard Lyon 1, CNRS/IN2P3, Institut de Physique Nucleaire de Lyon, Lyon (France); Benoit, A.; Camus, P. [Institut Neel, CNRS/UJF, Grenoble (France); Berge, L.; Chapellier, M.; Dumoulin, L.; Giuliani, A.; Le-Sueur, H.; Marnieros, S.; Olivieri, E.; Poda, D. [CSNSM, Univ. Paris-Sud, CNRS/IN2P3, Universite Paris-Saclay, Orsay (France); Bluemer, J. [Karlsruher Institut fuer Technologie, Institut fuer Kernphysik, Karlsruhe (Germany); Karlsruher Institut fuer Technologie, Institut fuer Experimentelle Kernphysik, Karlsruhe (Germany); Broniatowski, A. [CSNSM, Univ. Paris-Sud, CNRS/IN2P3, Universite Paris-Saclay, Orsay (France); Karlsruher Institut fuer Technologie, Institut fuer Experimentelle Kernphysik, Karlsruhe (Germany); Eitel, K.; Kozlov, V.; Siebenborn, B. [Karlsruher Institut fuer Technologie, Institut fuer Kernphysik, Karlsruhe (Germany); Foerster, N.; Heuermann, G.; Scorza, S. [Karlsruher Institut fuer Technologie, Institut fuer Experimentelle Kernphysik, Karlsruhe (Germany); Jin, Y. [Laboratoire de Photonique et de Nanostructures, CNRS, Route de Nozay, Marcoussis (France); Kefelian, C. [Univ Lyon, Universite Claude Bernard Lyon 1, CNRS/IN2P3, Institut de Physique Nucleaire de Lyon, Lyon (France); Karlsruher Institut fuer Technologie, Institut fuer Experimentelle Kernphysik, Karlsruhe (Germany); Kleifges, M.; Tcherniakhovski, D.; Weber, M. [Karlsruher Institut fuer Technologie, Institut fuer Prozessdatenverarbeitung und Elektronik, Karlsruhe (Germany); Kraus, H. [University of Oxford, Department of Physics, Oxford (United Kingdom); Kudryavtsev, V.A. [University of Sheffield, Department of Physics and Astronomy, Sheffield (United Kingdom); Pari, P. [CEA Saclay, DSM/IRAMIS, Gif-sur-Yvette (France); Piro, M.C. [CSNSM, Univ. Paris-Sud, CNRS/IN2P3, Universite Paris-Saclay, Orsay (France); Rensselaer Polytechnic Institute, Troy, NY (United States); Rozov, S.; Yakushev, E. [JINR, Laboratory of Nuclear Problems, Dubna, Moscow Region (Russian Federation); Schmidt, B. [Karlsruher Institut fuer Technologie, Institut fuer Kernphysik, Karlsruhe (Germany); Lawrence Berkeley National Laboratory, Berkeley, CA (United States)
2016-10-15
We report on a dark matter search for a Weakly Interacting Massive Particle (WIMP) in the mass range m{sub χ} element of [4, 30] GeV/c{sup 2} with the EDELWEISS-III experiment. A 2D profile likelihood analysis is performed on data from eight selected detectors with the lowest energy thresholds leading to a combined fiducial exposure of 496 kg-days. External backgrounds from γ- and β-radiation, recoils from {sup 206}Pb and neutrons as well as detector intrinsic backgrounds were modelled from data outside the region of interest and constrained in the analysis. The basic data selection and most of the background models are the same as those used in a previously published analysis based on boosted decision trees (BDT) [1]. For the likelihood approach applied in the analysis presented here, a larger signal efficiency and a subtraction of the expected background lead to a higher sensitivity, especially for the lowest WIMP masses probed. No statistically significant signal was found and upper limits on the spin-independent WIMP-nucleon scattering cross section can be set with a hypothesis test based on the profile likelihood test statistics. The 90 % C.L. exclusion limit set for WIMPs with m{sub χ} = 4 GeV/c{sup 2} is 1.6 x 10{sup -39} cm{sup 2}, which is an improvement of a factor of seven with respect to the BDT-based analysis. For WIMP masses above 15 GeV/c{sup 2} the exclusion limits found with both analyses are in good agreement. (orig.)
Exclusion limits on the WIMP-nucleon cross section from the Cryogenic Dark Matter Search
International Nuclear Information System (INIS)
Abrams, D.; Baudis, L.; Brink, P.L.; Cabrera, B.; Castle, J.P.; Chang, C.L.; Clarke, R.M.; Saab, T.; Akerib, D.S.; Bolozdynya, A.; Driscoll, D.; Kamat, S.; Perera, T.A.; Schnee, R.W.; Wang, G.; Armel-Funkhouser, M.S.; Golwala, S.R.; Hellmig, J.; Mandic, V.; Meunier, P.
2002-01-01
The Cryogenic Dark Matter Search (CDMS) employs low-temperature Ge and Si detectors to search for weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei while discriminating against interactions of background particles. For recoil energies above 10 keV, events due to background photons are rejected with >99.9% efficiency, and surface events are rejected with >95% efficiency. The estimate of the background due to neutrons is based primarily on the observation of multiple-scatter events that should all be neutrons. Data selection is determined primarily by examining calibration data and vetoed events. Resulting efficiencies should be accurate to ∼10%. Results of CDMS data from 1998 and 1999 with a relaxed fiducial-volume cut (resulting in 15.8 kg days exposure on Ge) are consistent with an earlier analysis with a more restrictive fiducial-volume cut. Twenty-three WIMP candidate events are observed, but these events are consistent with a background from neutrons in all ways tested. Resulting limits on the spin-independent WIMP-nucleon elastic-scattering cross section exclude unexplored parameter space for WIMPs with masses between 10-70 GeV/c 2 . These limits border, but do not exclude, parameter space allowed by supersymmetry models and accelerator constraints. Results are compatible with some regions reported as allowed at 3σ by the annual-modulation measurement of the DAMA Collaboration. However, under the assumptions of standard WIMP interactions and a standard halo, the results are incompatible with the DAMA most likely value at >99.9% confidence level (C.L.), and are incompatible with the model-independent annual-modulation signal of DAMA at 99.99% C.L. in the asymptotic limit
Neutrinos from WIMP annihilations obtained using a full three-flavor Monte Carlo approach
International Nuclear Information System (INIS)
Blennow, Mattias; Ohlsson, Tommy; Edsjö, Joakim
2008-01-01
Weakly interacting massive particles (WIMPs) are one of the main candidates for making up the dark matter in the Universe. If these particles make up the dark matter, then they can be captured by the Sun or the Earth, sink to the respective cores, annihilate, and produce neutrinos. Thus, these neutrinos can be a striking dark matter signature at neutrino telescopes looking towards the Sun and/or the Earth. Here, we improve previous analyses on computing the neutrino yields from WIMP annihilations in several respects. We include neutrino oscillations in a full three-flavor framework as well as all effects from neutrino interactions on the way through the Sun (absorption, energy loss, and regeneration from tau decays). In addition, we study the effects of non-zero values of the mixing angle θ 13 as well as the normal and inverted neutrino mass hierarchies. Our study is performed in an event-based setting which makes these results very useful both for theoretical analyses and for building a neutrino telescope Monte Carlo code. All our results for the neutrino yields, as well as our Monte Carlo code, are publicly available. We find that the yield of muon-type neutrinos from WIMP annihilations in the Sun is enhanced or suppressed, depending on the dominant WIMP annihilation channel. This effect is due to an effective flavor mixing caused by neutrino oscillations. For WIMP annihilations inside the Earth, the distance from source to detector is too small to allow for any significant amount of oscillations at the neutrino energies relevant for neutrino telescopes
GENIUS and the Genius TF: A New Observatory for WIMP Dark Matter and Neutrinoless Double Beta Decay
Klapdor-Kleingrothaus, H. V.; Majorovits, B.
2001-01-01
The GENIUS proposal is described and some of it's physics potential is outlined. Also in the light of the contradictive results from the DAMA and CDMS experiments the Genius TF, a new experimental setup is proposed. The Genius TF could probe the DAMA evidence region using the WIMP nucleus recoil signal and WIMP annual modulation signature simultaneously. Besides that it can prove the long term feasibility of the detector technique to be implemented into the GENIUS setup and will in this sense...
Energy Technology Data Exchange (ETDEWEB)
Cao, Huajie [Princeton Univ., NJ (United States)
2014-11-01
Robust results of WIMP direct detection experiments depend on rm understandings of nuclear recoils in the detector media. This thesis documents the most comprehensive study to date on nuclear recoils in liquid argon - a strong candidate for the next generation multi-ton scale WIMP detectors. This study investigates both the energy partition from nuclear recoil energy to secondary modes (scintillation and ionization) and the pulse shape characteristics of scintillation from nuclear recoils.
The Diurnal Variation of the Wimp Detection Event Rates in Directional Experiments
Vergados, J D
2009-01-01
The recent WMAP data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. Modern particle theories naturally provide viable cold dark matter candidates with masses in the GeV-TeV region. Supersymmetry provides the lightest supersymmetric particle (LSP), theories in extra dimensions supply the lightest Kaluza-Klein particle (LKP) etc. The nature of dark matter can only be unraveled only by its direct detection in the laboratory. All such candidates will be called WIMPs (Weakly Interacting Massive Particles). In any case the direct dark matter search, which amounts to detecting the recoiling nucleus, following its collision with WIMP, is central to particle physics and cosmology. In this work we briefly review the theoretical elements relevant to the direct dark matter detection experiments, paying particular attention to directional experiments. i.e experiments in which, not only the energy but the direction of the recoiling nucleus is ob...
Halo-independent analysis of direct detection data for light WIMPs
International Nuclear Information System (INIS)
Nobile, Eugenio Del; Gelmini, Graciela B.; Huh, Ji-Haeng; Gondolo, Paolo
2013-01-01
We present a halo-independent analysis of direct detection data on ''light WIMPs'', i.e. weakly interacting massive particles with mass close to or below 10 GeV/c 2 . We include new results from silicon CDMS detectors (bounds and excess events), the latest CoGeNT acceptances, and recent measurements of low sodium quenching factors in NaI crystals. We focus on light WIMPs with spin-independent isospin-conserving and isospin-violating interactions with nucleons. For these dark matter candidates we find that a low quenching factor would make the DAMA modulation incompatible with a reasonable escape velocity for the dark matter halo, and that the tension among experimental data tightens in both the isospin-conserving and isospin-violating scenarios. We also find that a new although milder tension appears between the CoGeNT and DAMA annual modulations on one side and the silicon excess events on the other, in that it seems difficult to interpret them as the modulated and unmodulated aspects of the same WIMP dark matter signal
WIMP-nucleon cross-section results from the second science run of ZEPLIN-III
Energy Technology Data Exchange (ETDEWEB)
Akimov, D.Yu. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Araujo, H.M., E-mail: h.araujo@imperial.ac.uk [High Energy Physics Group, Blackett Laboratory, Imperial College London (United Kingdom); Barnes, E.J. [School of Physics and Astronomy, SUPA University of Edinburgh (United Kingdom); Belov, V.A. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Bewick, A. [High Energy Physics Group, Blackett Laboratory, Imperial College London (United Kingdom); Burenkov, A.A. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Chepel, V. [LIP-Coimbra and Department of Physics of the University of Coimbra (Portugal); Currie, A. [High Energy Physics Group, Blackett Laboratory, Imperial College London (United Kingdom); DeViveiros, L. [LIP-Coimbra and Department of Physics of the University of Coimbra (Portugal); Edwards, B. [Particle Physics Department, STFC Rutherford Appleton Laboratory, Chilton (United Kingdom); Ghag, C.; Hollingsworth, A. [School of Physics and Astronomy, SUPA University of Edinburgh (United Kingdom); Horn, M.; Jones, W.G. [High Energy Physics Group, Blackett Laboratory, Imperial College London (United Kingdom); Kalmus, G.E. [Particle Physics Department, STFC Rutherford Appleton Laboratory, Chilton (United Kingdom); Kobyakin, A.S.; Kovalenko, A.G. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Lebedenko, V.N. [High Energy Physics Group, Blackett Laboratory, Imperial College London (United Kingdom); Lindote, A. [LIP-Coimbra and Department of Physics of the University of Coimbra (Portugal); Particle Physics Department, STFC Rutherford Appleton Laboratory, Chilton (United Kingdom); Lopes, M.I. [LIP-Coimbra and Department of Physics of the University of Coimbra (Portugal); and others
2012-03-13
We report experimental upper limits on WIMP-nucleon elastic scattering cross sections from the second science run of ZEPLIN-III at the Boulby Underground Laboratory. A raw fiducial exposure of 1344 kg Dot-Operator days was accrued over 319 days of continuous operation between June 2010 and May 2011. A total of eight events was observed in the signal acceptance region in the nuclear recoil energy range 7-29 keV, which is compatible with background expectations. This allows the exclusion of the scalar cross-section above 4.8 Multiplication-Sign 10{sup -8} pb near 50 GeV/c{sup 2} WIMP mass with 90% confidence. Combined with data from the first run, this result improves to 3.9 Multiplication-Sign 10{sup -8} pb. The corresponding WIMP-neutron spin-dependent cross-section limit is 8.0 Multiplication-Sign 10{sup -3} pb. The ZEPLIN programme reaches thus its conclusion at Boulby, having deployed and exploited successfully three liquid xenon experiments of increasing reach.
WIMP-nucleon cross-section results from the second science run of ZEPLIN-III
International Nuclear Information System (INIS)
Akimov, D.Yu.; Araújo, H.M.; Barnes, E.J.; Belov, V.A.; Bewick, A.; Burenkov, A.A.; Chepel, V.; Currie, A.; DeViveiros, L.; Edwards, B.; Ghag, C.; Hollingsworth, A.; Horn, M.; Jones, W.G.; Kalmus, G.E.; Kobyakin, A.S.; Kovalenko, A.G.; Lebedenko, V.N.; Lindote, A.; Lopes, M.I.
2012-01-01
We report experimental upper limits on WIMP-nucleon elastic scattering cross sections from the second science run of ZEPLIN-III at the Boulby Underground Laboratory. A raw fiducial exposure of 1344 kg⋅days was accrued over 319 days of continuous operation between June 2010 and May 2011. A total of eight events was observed in the signal acceptance region in the nuclear recoil energy range 7-29 keV, which is compatible with background expectations. This allows the exclusion of the scalar cross-section above 4.8×10 -8 pb near 50 GeV/c 2 WIMP mass with 90% confidence. Combined with data from the first run, this result improves to 3.9×10 -8 pb. The corresponding WIMP-neutron spin-dependent cross-section limit is 8.0×10 -3 pb. The ZEPLIN programme reaches thus its conclusion at Boulby, having deployed and exploited successfully three liquid xenon experiments of increasing reach.
Vibrational properties of the Au-(√{3 }×√{3 } )/Si(111) surface reconstruction
Halbig, B.; Liebhaber, M.; Bass, U.; Geurts, J.; Speiser, E.; Räthel, J.; Chandola, S.; Esser, N.; Krenz, M.; Neufeld, S.; Schmidt, W. G.; Sanna, S.
2018-01-01
The vibrational properties of the Au-induced (√{3 }×√{3 })R 30∘ reconstruction of the Si(111) surface are investigated by polarized surface Raman spectroscopy and density-functional theory. The Raman measurements are performed in situ at room temperature as well as 20 K, and they reveal the presence of vibrational eigenmodes in the spectral range from 20 to 450 cm-1. In particular, two peaks of E symmetry at 75 and 183 cm-1 dominate the spectra. No substantial difference between room- and low-temperature spectra is observed, suggesting that the system does not undergo a phase transition down to 20 K. First-principles calculations are performed based on the structural models discussed in the literature. The thermodynamically stable conjugate honeycomb-chained-trimer model (CHCT) [Surf. Sci. 275, L691 (1992), 10.1016/0039-6028(92)90785-5] leads to phonon eigenvalues compatible with the experimental observations in the investigated spectral range. On the basis of the phonon eigenfrequencies, symmetries, and Raman intensities, we assign the measured spectral features to the calculated phonon modes. The good agreement between measured and calculated modes provides a strong argument in favor of the CHCT model.
Energy Technology Data Exchange (ETDEWEB)
Golwala, Sunil Ramanlal [UC, Berkeley
2000-01-01
Extensive evidence indicates that a large fraction of the matter in the universe is nonluminous, nonbaryonic, and “cold” — nonrelativistic at the time matter began to dominate the energy density of the universe. Weakly Interacting Massive Particles (WIMPs) are an excellent candidate for nonbaryonic, cold dark matter. Minimal supersymmetry provides a natural WIMP candidate in the form of the lightest superpartner, with a typical mass Mδ ~ 100 GeV c-2 . WIMPs are expected to have collapsed into a roughly isothermal, spherical halo within which the visible portion of our galaxy resides. They would scatter off nuclei via the weak interaction, potentially allowingtheir direct detection. The Cryogenic Dark Matter Search (CDMS) employs Ge and Si detectors to search for WIMPs via their elastic-scatteringinteractions with nuclei while discriminatingagainst interactions of background particles. The former yield nuclear recoils while the latter produce electron recoils. The ionization yield (the ratio of ionization production to recoil energy in a semiconductor) of a particle interaction differs greatly for nuclear and electron recoils. CDMS detectors measure phonon and electron-hole-pair production to determine recoil energy and ionization yield for each event and thereby discriminate nuclear recoils from electron recoils. This dissertation reports new limits on the spin-independent WIMP-nucleon elastic-scattering cross section that exclude unexplored parameter space above 10 GeV c-2 WIMP mass and, at > 75% CL, the entire 3σ allowed region for the WIMP signal reported by the DAMA experiment. The experimental apparatus, detector performance, and data analysis are fully described.
A Search for WIMP Dark Matter Using the First Five-Tower Run of the Cryogenic Dark Matter Search
Energy Technology Data Exchange (ETDEWEB)
Filippini, Jeffrey Peter [UC, Berkeley
2008-01-01
In recent decades astronomers and physicists have accumulated a vast array of evidence that the bulk of the universe's matter is in some non-baryonic form that remains undetected by electromagnetic means. This \\dark matter" resides in diuse halos surrounding galaxies and other cosmic structures. Particle theorists have proposed a wide array of candidates for its nature. One particularly promising class of candidates are Weakly Interacting Massive Particles (WIMPs): quanta with masses of order 100 GeV/c2 and interactions characteristic of the weak nuclear force. The Cryogenic Dark Matter Search (CDMS) experiment seeks to directly detect the rare elastic interactions of galactic WIMPs with terrestrial nuclei. To this end, CDMS operates an array of crystalline Ge and Si particle detectors in Soudan Underground Laboratory in northern Minnesota. These crystals are operated at millikelvin temperatures and instrumented to measure the ionization and athermal phonons generated by each particle interaction. This combination provides a powerful two-fold discrimination against the interactions of particles generated by radioactive decay and cosmogenic showers. This dissertation describes the commissioning, analysis, and results of the rst WIMP-search data runs of the CDMS experiment with its full complement of 5 \\Towers" of detectors. These data represent a substantial increase in target mass and exposure over previous CDMS results. The results of this work place the most stringent limits yet set upon the WIMP-nucleon spin-independent cross section for WIMP masses above 44 GeV/c2 , as well as setting competitive limits on spin-dependent WIMP-nucleon interactions. This work also outlines the larger context of this and other probes of the WIMP theory of dark matter, as well as some current development eorts toward a larger cryogenic experiment.
International Nuclear Information System (INIS)
Tong, S; Alessio, A M; Kinahan, P E
2010-01-01
The addition of accurate system modeling in PET image reconstruction results in images with distinct noise texture and characteristics. In particular, the incorporation of point spread functions (PSF) into the system model has been shown to visually reduce image noise, but the noise properties have not been thoroughly studied. This work offers a systematic evaluation of noise and signal properties in different combinations of reconstruction methods and parameters. We evaluate two fully 3D PET reconstruction algorithms: (1) OSEM with exact scanner line of response modeled (OSEM+LOR), (2) OSEM with line of response and a measured point spread function incorporated (OSEM+LOR+PSF), in combination with the effects of four post-reconstruction filtering parameters and 1-10 iterations, representing a range of clinically acceptable settings. We used a modified NEMA image quality (IQ) phantom, which was filled with 68 Ge and consisted of six hot spheres of different sizes with a target/background ratio of 4:1. The phantom was scanned 50 times in 3D mode on a clinical system to provide independent noise realizations. Data were reconstructed with OSEM+LOR and OSEM+LOR+PSF using different reconstruction parameters, and our implementations of the algorithms match the vendor's product algorithms. With access to multiple realizations, background noise characteristics were quantified with four metrics. Image roughness and the standard deviation image measured the pixel-to-pixel variation; background variability and ensemble noise quantified the region-to-region variation. Image roughness is the image noise perceived when viewing an individual image. At matched iterations, the addition of PSF leads to images with less noise defined as image roughness (reduced by 35% for unfiltered data) and as the standard deviation image, while it has no effect on background variability or ensemble noise. In terms of signal to noise performance, PSF-based reconstruction has a 7% improvement in
Li, Hechao
An accurate knowledge of the complex microstructure of a heterogeneous material is crucial for quantitative structure-property relations establishment and its performance prediction and optimization. X-ray tomography has provided a non-destructive means for microstructure characterization in both 3D and 4D (i.e., structural evolution over time). Traditional reconstruction algorithms like filtered-back-projection (FBP) method or algebraic reconstruction techniques (ART) require huge number of tomographic projections and segmentation process before conducting microstructural quantification. This can be quite time consuming and computationally intensive. In this thesis, a novel procedure is first presented that allows one to directly extract key structural information in forms of spatial correlation functions from limited x-ray tomography data. The key component of the procedure is the computation of a "probability map", which provides the probability of an arbitrary point in the material system belonging to specific phase. The correlation functions of interest are then readily computed from the probability map. Using effective medium theory, accurate predictions of physical properties (e.g., elastic moduli) can be obtained. Secondly, a stochastic optimization procedure that enables one to accurately reconstruct material microstructure from a small number of x-ray tomographic projections (e.g., 20 - 40) is presented. Moreover, a stochastic procedure for multi-modal data fusion is proposed, where both X-ray projections and correlation functions computed from limited 2D optical images are fused to accurately reconstruct complex heterogeneous materials in 3D. This multi-modal reconstruction algorithm is proved to be able to integrate the complementary data to perform an excellent optimization procedure, which indicates its high efficiency in using limited structural information. Finally, the accuracy of the stochastic reconstruction procedure using limited X
Chaudhury, Soumini; Bhattacharjee, Pijushpani; Cowsik, Ramanath
2010-09-01
Direct detection of Weakly Interacting Massive Particle (WIMP) candidates of Dark Matter (DM) is studied within the context of a self-consistent truncated isothermal model of the finite-size dark halo of the Galaxy. The halo model, based on the ``King model'' of the phase space distribution function of collisionless DM particles, takes into account the modifications of the phase-space structure of the halo due to the gravitational influence of the observed visible matter in a self-consistent manner. The parameters of the halo model are determined by a fit to a recently determined circular rotation curve of the Galaxy that extends up to ~ 60 kpc. Unlike in the Standard Halo Model (SHM) customarily used in the analysis of the results of WIMP direct detection experiments, the velocity distribution of the WIMPs in our model is non-Maxwellian with a cut-off at a maximum velocity that is self-consistently determined by the model itself. For our halo model that provides the best fit to the rotation curve data, the 90% C.L. upper limit on the WIMP-nucleon spin-independent cross section from the recent results of the CDMS-II experiment, for example, is ~ 5.3 × 10-8 pb at a WIMP mass of ~ 71 GeV. We also find, using the original 2-bin annual modulation amplitude data on the nuclear recoil event rate seen in the DAMA experiment, that there exists a range of small WIMP masses, typically ~ 2-16 GeV, within which DAMA collaboration's claimed annual modulation signal purportedly due to WIMPs is compatible with the null results of other experiments. These results, based as they are on a self-consistent model of the dark matter halo of the Galaxy, strengthen the possibility of low-mass (lsim10 GeV) WIMPs as a candidate for dark matter as indicated by several earlier studies performed within the context of the SHM. A more rigorous analysis using DAMA bins over smaller intervals should be able to better constrain the ``DAMA regions'' in the WIMP parameter space within the context of
A low error reconstruction method for confocal holography to determine 3-dimensional properties
Energy Technology Data Exchange (ETDEWEB)
Jacquemin, P.B., E-mail: pbjacque@nps.edu [Mechanical Engineering, University of Victoria, EOW 548,800 Finnerty Road, Victoria, BC (Canada); Herring, R.A. [Mechanical Engineering, University of Victoria, EOW 548,800 Finnerty Road, Victoria, BC (Canada)
2012-06-15
A confocal holography microscope developed at the University of Victoria uniquely combines holography with a scanning confocal microscope to non-intrusively measure fluid temperatures in three-dimensions (Herring, 1997), (Abe and Iwasaki, 1999), (Jacquemin et al., 2005). The Confocal Scanning Laser Holography (CSLH) microscope was built and tested to verify the concept of 3D temperature reconstruction from scanned holograms. The CSLH microscope used a focused laser to non-intrusively probe a heated fluid specimen. The focused beam probed the specimen instead of a collimated beam in order to obtain different phase-shift data for each scan position. A collimated beam produced the same information for scanning along the optical propagation z-axis. No rotational scanning mechanisms were used in the CSLH microscope which restricted the scan angle to the cone angle of the probe beam. Limited viewing angle scanning from a single view point window produced a challenge for tomographic 3D reconstruction. The reconstruction matrices were either singular or ill-conditioned making reconstruction with significant error or impossible. Establishing boundary conditions with a particular scanning geometry resulted in a method of reconstruction with low error referred to as 'wily'. The wily reconstruction method can be applied to microscopy situations requiring 3D imaging where there is a single viewpoint window, a probe beam with high numerical aperture, and specified boundary conditions for the specimen. The issues and progress of the wily algorithm for the CSLH microscope are reported herein. -- Highlights: Black-Right-Pointing-Pointer Evaluation of an optical confocal holography device to measure 3D temperature of a heated fluid. Black-Right-Pointing-Pointer Processing of multiple holograms containing the cumulative refractive index through the fluid. Black-Right-Pointing-Pointer Reconstruction issues due to restricting angular scanning to the numerical aperture of the
A low error reconstruction method for confocal holography to determine 3-dimensional properties
International Nuclear Information System (INIS)
Jacquemin, P.B.; Herring, R.A.
2012-01-01
A confocal holography microscope developed at the University of Victoria uniquely combines holography with a scanning confocal microscope to non-intrusively measure fluid temperatures in three-dimensions (Herring, 1997), (Abe and Iwasaki, 1999), (Jacquemin et al., 2005). The Confocal Scanning Laser Holography (CSLH) microscope was built and tested to verify the concept of 3D temperature reconstruction from scanned holograms. The CSLH microscope used a focused laser to non-intrusively probe a heated fluid specimen. The focused beam probed the specimen instead of a collimated beam in order to obtain different phase-shift data for each scan position. A collimated beam produced the same information for scanning along the optical propagation z-axis. No rotational scanning mechanisms were used in the CSLH microscope which restricted the scan angle to the cone angle of the probe beam. Limited viewing angle scanning from a single view point window produced a challenge for tomographic 3D reconstruction. The reconstruction matrices were either singular or ill-conditioned making reconstruction with significant error or impossible. Establishing boundary conditions with a particular scanning geometry resulted in a method of reconstruction with low error referred to as “wily”. The wily reconstruction method can be applied to microscopy situations requiring 3D imaging where there is a single viewpoint window, a probe beam with high numerical aperture, and specified boundary conditions for the specimen. The issues and progress of the wily algorithm for the CSLH microscope are reported herein. -- Highlights: ► Evaluation of an optical confocal holography device to measure 3D temperature of a heated fluid. ► Processing of multiple holograms containing the cumulative refractive index through the fluid. ► Reconstruction issues due to restricting angular scanning to the numerical aperture of the beam. ► Minimizing tomographic reconstruction error by defining boundary
WIMP dark matter and supersymmetry searches with neutrino telescopes
International Nuclear Information System (INIS)
Fornengo, N.
2011-01-01
The particle physics interpretation of the missing-mass, or dark-matter, a problem of cosmological and astrophysical nature, is going to be placed under strong scrutiny in the next years. From the particle physics side, accelerator physics will deeply test theoretical ideas about new physics beyond the Standard Model, where a particle physics candidate to dark matter is often naturally obtained. From the astrophysical side, many probes are already providing a great deal of independent information on signals which can be produced by the galactic or extra-galactic dark matter. The current and new-generation experimental efforts are therefore going to place under deep scrutiny the theoretical explanations of the relevant signals. The ultimate hope is in fact to be able to disentangle a dark matter signal from the various sources of backgrounds. Neutrino telescopes are one of the prominent tools for looking at dark matter and search for a signal, the neutrino flux from Earth and Sun. In this neutrino dark matter searches share properties with both direct dark matter searches and cosmic-ray indirect dark matter searches, and therefore complement these different detection techniques.
Search for WIMP dark matter produced in association with a Z boson with the ATLAS detector
Basalaev, Artem; The ATLAS collaboration
2016-01-01
The search for weakly interacting dark matter particle (WIMP) candidates produced in association with a Z boson is presented. Events with large missing transverse momentum and consistent with the decay of a Z boson into oppositely charged electron or muon pairs were selected in analysis. Background estimates and corresponding systematic uncertainties are shown. The limits on the mass scale of the contact interaction as a function of the dark matter particle mass and the limits on the coupling and scalar particle mediator mass for 8 TeV proton-proton collisions data are presented. Prospects for analysis using 13 TeV proton-proton collisions data are discussed.
Further results on the WIMP annual modulation signature by DAMA/NaI
International Nuclear Information System (INIS)
Bernabei, R.; Belli, P.; Cappella, F.
2005-01-01
The ≅ 100 kg highly radiopure NaI(Tl) set-up of the DAMA project (DAMA/NaI) has investigated the model- independent WIMP annual modulation signature over seven annual cycles for a total exposure of 107731 kg x day, obtaining a model-independent evidence for the presence of a dark matter particle component in the galactic halo at 6.3 σ C.L.. Some of the many possible corollary model-dependent quests for the candidate particle have been investigated with the total exposure as well
CPN/Tools: A Post-WIMP Interface for Editing and Simulating Coloured Petri Nets
DEFF Research Database (Denmark)
Andersen, Peter; Beaudouin-Lafon, Michel; Mackay, Wendy E.
2001-01-01
traditional ideas about user interfaces, getting rid of pull-down menus, scrollbars, and even selection, while providing the same or greater functionality. It also uses the new and much faster CPN simulator and features incremental syntax checking of the nets. CPN/Tools requires an OpenGL graphics accelerator......CPN/Tools is a major redesign of the popular Design/CPN tool from the University of Aarhus CPN group. The new interface is based on advanced, post-WIMP interaction techniques, including bi-manual interaction, toolglasses and marking menus and a new metaphor for managing the workspace. It challenges...
The use of twin-screen-based WIMPS in spacecraft control
Klim, R. D.
1990-10-01
The ergonomic problems of designing a sophisticated Windows Icons Mouse Pop-up (WIMP) based twin screen workstation are outlined. These same problems will be encountered by future spacecraft controllers. The design of a modern, advanced workstation for use on a distributed multicontrol center in a multisatellite control system is outlined. The system uses access control mechanisms to ensure that only authorized personnel can undertake certain operations on the workstation. Rules governing the use of windowing features, screen attributes, icons, keyboard and mouse in spacecraft control are discussed.
Development of low-background CsI(Tl) crystals for WIMP search
International Nuclear Information System (INIS)
Lee, H.S.; Bhang, H.; Hahn, I.S.; Hwang, M.J.; Kim, H.J.; Kim, S.C.; Kim, S.K.; Kim, S.Y.; Kim, T.Y.; Kim, Y.D.; Kwak, J.W.; Kwon, Y.J.; Lee, J.; Lee, J.I.; Lee, M.J.; Li, J.; Myung, S.S.; Park, H.; Zhu, J.J.
2007-01-01
Search for weakly interacting massive particles (WIMPs) is being carried out at the underground laboratory, Yangyang, Korea. Characteristics and internal background of CsI(Tl) crystal have been investigated. In our extensive R and D, we reduced internal background in the CsI(Tl) crystal. With the latest, we have achieved 5.50+/-0.10cpd (counts/keV/kg/day) at 10-15keV low-energy region. Further reduction of internal background is foreseen with the CsI powder lately produced
Klos, P.; Menéndez, J.; Gazit, D.; Schwenk, A.
2013-01-01
We perform state-of-the-art large-scale shell-model calculations of the structure factors for elastic spin-dependent WIMP scattering off 129,131Xe, 127I, 73Ge, 19F, 23Na, 27Al, and 29Si. This comprehensive survey covers the non-zero-spin nuclei relevant to direct dark matter detection. We include a pedagogical presentation of the formalism necessary to describe elastic and inelastic WIMP-nucleus scattering. The valence spaces and nuclear interactions employed have been previously used in nucl...
Reconstruction Effects on Surface Properties of Co/Mg/Al Layered Double Hydroxide
Directory of Open Access Journals (Sweden)
Denis SOKOL
2017-08-01
Full Text Available Layered double hydroxides having different cationic (Mg2+, Co2+, Al3+ composition were successfully synthesized by the low supersaturation method. The samples were thermally decomposed and reconstructed using water and nitrate media at different temperatures. X-ray powder diffraction analysis, X-ray fluorescence analysis, thermogravimetry and BET/BJH methods were used to investigate the differences between the directly obtained layered materials and those after the reconstruction process.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.15184
WIMP search in the mono-photon channel at the international linear collider
Energy Technology Data Exchange (ETDEWEB)
Habermehl, Moritz [Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22607 Hamburg (Germany); Universitaet Hamburg, Institut fuer Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg (Germany); List, Jenny [Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22607 Hamburg (Germany)
2016-07-01
The International Linear Collider (ILC) is a planned electron-positron collider with √(s) tunable from 250 to 500 GeV, with a possible upgrade to 1 TeV. Besides precision measurements of the Higgs boson its physics goals comprise searches for physics beyond the Standard Model, e.g. searches for Dark Matter. This collider search assumes the production of WIMPs in pairs. They are not visible in the detector but the energy carried away can be observed via an additional (''tag'') particle. Photon emission from the initial state leads to the almost model independent signature: e{sup +}e{sup -} → χχγ. As this analysis tests couplings between WIMPs and leptons it is complementary to analogues searches at the LHC. A precise study is facilitated by the clean environment of lepton colliders with small systematics of electroweak backgrounds. While the conceptual feasibility and the sensitivity reach of the ILC have been shown in the past, this talk focusses on the consequences for the detector design. The requirements for the central detector as well as for the instrumentation of the forward region are discussed in the context of the ILD detector concept.
Constraints on light WIMP candidates from the isotropic diffuse gamma-ray emission
International Nuclear Information System (INIS)
Arina, Chiara; Tytgat, Michel H.G.
2011-01-01
Motivated by the measurements reported by direct detection experiments, most notably DAMA, CDMS-II, CoGeNT and Xenon10/100, we study further the constraints that might be set on some light dark matter candidates, M DM ∼ few GeV, using the Fermi-LAT data on the isotropic gamma-ray diffuse emission. In particular, we consider a Dirac fermion singlet interacting through a new Z' gauge boson, and a scalar singlet S interacting through the Higgs portal. Both candidates are WIMP (Weakly Interacting Massive Particles), i.e. they have an annihilation cross-section in the pbarn range. Also they may both have a spin-independent elastic cross section on nucleons in the range required by direct detection experiments. Although being generic WIMP candidates, because they have different interactions with Standard Model particles, their phenomenology regarding the isotropic diffuse gamma-ray emission is quite distinct. In the case of the scalar singlet, the one-to-one correspondence between its annihilation cross-section and its spin-independent elastic scattering cross-section permits to express the constraints from the Fermi-LAT data in the direct detection exclusion plot, σ n 0 −M DM . Depending on the astrophysics, we argue that it is possible to exclude the singlet scalar dark matter candidate at 95% confidence level. The constraints on the Dirac singlet interacting through a Z' are comparatively weaker
Asymmetric WIMP Dark Matter in the presence of DM/anti-DM oscillations
International Nuclear Information System (INIS)
Zaharijas, G.
2014-01-01
The general class of 'Asymmetric Dark Matter (DM)' scenarios assumes the existence of a primordial particle/anti-particle asymmetry in the dark matter sector related to the asymmetry in the baryonic one, as a way to achieve the observed similarity between the baryonic and dark matter energy densities today. Focusing on this framework we study the effect of oscillations between dark matter and its anti-particle on the re-equilibration of the initial asymmetry. We calculate the evolution of the dark matter relic abundance and show how oscillations re-open the parameter space of asymmetric dark matter models, in particular in the direction of allowing large (WIMP-scale) DM masses. We found in particular that a typical WIMP with a mass at the EW scale (about 1 TeV) having a primordial asymmetry of the same order as the baryon asymmetry, naturally gets the correct relic abundance if the δm mass term is in the ∼ meV range. This turns out to be a natural value for fermionic DM arising from the higher dimensional operator H 2 DM 2 /Λ where H is the Higgs field and Λ ∼ M Pl . Finally, we constrain the parameter space in this framework by applying up-to-date bounds from indirect detection signals on annihilating DM
Consequences of DM/antiDM Oscillations for Asymmetric WIMP Dark Matter
Cirelli, Marco; Servant, Geraldine; Zaharijas, Gabrijela
2012-01-01
Assuming the existence of a primordial asymmetry in the dark sector, a scenario usually dubbed Asymmetric Dark Matter (aDM), we study the effect of oscillations between dark matter and its antiparticle on the re-equilibration of the initial asymmetry before freeze-out, which enable efficient annihilations to recouple. We calculate the evolution of the DM relic abundance and show how oscillations re-open the parameter space of aDM models, in particular in the direction of allowing large (WIMP-scale) DM masses. A typical wimp with a mass at the EW scale (\\sim 100 GeV - 1 TeV) presenting a primordial asymmetry of the same order as the baryon asymmetry naturally gets the correct relic abundance if the DM-number-violating Delta(DM) = 2 mass term is in the \\sim meV range. The re-establishment of annihilations implies that constraints from the accumulation of aDM in astrophysical bodies are evaded. On the other hand, the ordinary bounds from BBN, CMB and indirect detection signals on annihilating DM have to be consi...
Volozhin, A. I.; Pavlova, M. P.; Muradov, I. S.; Stupakov, G. P.; Korzhenyants, V. A.
1980-01-01
Ca45 incorporation into the bones of the limbs, particularly in the area of the muscle attachment increased in dogs as a result of 6 month hypokinesia. There were no phenomena of osteoporosis in the cortical layer of the diaphyses; however, changes in the form of osteons, an increase in the number of anastomoses between the channels and the thinning of the subperiosteal layer pointed to disturbances of the bone tissue reconstruction. Mineral saturation of the bone microstructures of the experimental dogs had a tendency to rise. No changes in the mechanical properties of the long bones occurred as a result of hypokinesia in dogs.
International Nuclear Information System (INIS)
Mackay, C; Hayward, D; Mulholland, A J; McKee, S; Pethrick, R A
2005-01-01
An inverse problem motivated by the nondestructive testing of adhesively bonded structures used in the aircraft industry is studied. Using transmission line theory, a model is developed which, when supplied with electrical and geometrical parameters, accurately predicts the reflection coefficient associated with such structures. Particular attention is paid to modelling the connection between the structures and the equipment used to measure the reflection coefficient. The inverse problem is then studied and an optimization approach employed to recover these electrical and geometrical parameters from experimentally obtained data. In particular the approach focuses on the recovery of spatially varying geometrical parameters as this is paramount to the successful reconstruction of electrical parameters. Reconstructions of structure geometry using this method are found to be in close agreement with experimental observations
Carpenter, Janet S; Heit, Michael; Rand, Kevin L
2017-04-01
Catheter burden after pelvic reconstructive surgery is an important patient-reported quality of life outcome in research and clinical practice. However, existing tools focus on long-term catheter users rather than short-term postoperative patients. The study aim was to evaluate the psychometric properties of a modified version of the intermittent self-catheterization questionnaire (ISC-Q) in postoperative pelvic reconstructive patients. After experts convened to discuss and modify the ISC-Q items based on their knowledge of women's experiences and clinical practices, 178 women (108 with transurethral and 70 with suprapubic catheters) completed the modified scale and other measures as part of a larger parent study designed to assess health-related quality of life (HRQoL) following pelvic reconstructive surgery requiring bladder drainage. During psychometric testing, the modified ISC-Q was reduced to six items encompassing two factors: a three-item difficulty of use factor and a 3-item embarrassment factor. The new scale was named the short-term catheter burden questionnaire (STCBQ). The two-factor model was robust in both subsamples. Only scores within and not between subsamples can be meaningfully compared due to a lack of scalar invariance. Correlations among STCBQ total scores, subscores, and a single satisfaction item indicated good construct validity. Correlations with patient demographics provided further information about the scale. The STCBQ is a short, efficient assessment of short-term catheter burden following pelvic reconstructive surgery. The scale can be used as an important patient reported outcome measure in clinical practice and research. Neurourol. Urodynam. 36:1140-1146, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.
A Bio-Inspired Model-Based Approach for Context-Aware Post-WIMP Tele-Rehabilitation
Directory of Open Access Journals (Sweden)
Víctor López-Jaquero
2016-10-01
Full Text Available Tele-rehabilitation is one of the main domains where Information and Communication Technologies (ICT have been proven useful to move healthcare from care centers to patients’ home. Moreover, patients, especially those carrying out a physical therapy, cannot use a traditional Window, Icon, Menu, Pointer (WIMP system, but they need to interact in a natural way, that is, there is a need to move from WIMP systems to Post-WIMP ones. Moreover, tele-rehabilitation systems should be developed following the context-aware approach, so that they are able to adapt to the patients’ context to provide them with usable and effective therapies. In this work a model-based approach is presented to assist stakeholders in the development of context-aware Post-WIMP tele-rehabilitation systems. It entails three different models: (i a task model for designing the rehabilitation tasks; (ii a context model to facilitate the adaptation of these tasks to the context; and (iii a bio-inspired presentation model to specify thoroughly how such tasks should be performed by the patients. Our proposal overcomes one of the limitations of the model-based approach for the development of context-aware systems supporting the specification of non-functional requirements. Finally, a case study is used to illustrate how this proposal can be put into practice to design a real world rehabilitation task.
TREX-DM: a low-background Micromegas-based TPC for low-mass WIMP detection
Energy Technology Data Exchange (ETDEWEB)
Iguaz, F.J.; Garza, J.G.; Castel, J.F.; Cebrian, S.; Dafni, T.; Garcia, J.A.; Irastorza, I.G.; Lagraba, A.; Luzon, G.; Peiro, A. [Universidad de Zaragoza, Grupo de Fisica Nuclear y Astroparticulas, Zaragoza (Spain); Aznar, F. [Universidad de Zaragoza, Grupo de Fisica Nuclear y Astroparticulas, Zaragoza (Spain); Universidad de Zaragoza, Centro Universitario de la Defensa, Zaragoza (Spain)
2016-10-15
If Dark Matter is made of Weakly Interacting Massive Particles (WIMPs) with masses below ∝20 GeV, the corresponding nuclear recoils in mainstream WIMP experiments are of energies too close, or below, the experimental threshold. Gas Time Projection Chambers (TPCs) can be operated with a variety of target elements, offer good tracking capabilities and, on account of the amplification in gas, very low thresholds are achievable. Recent advances in electronics and in novel radiopure TPC readouts, especially micro-mesh gas structure (Micromegas), are improving the scalability and low-background prospects of gaseous TPCs. Here we present TREX-DM, a prototype to test the concept of a Micromegas-based TPC to search for low-mass WIMPs. The detector is designed to host an active mass of ∝0.300 kg of Ar at 10 bar, or alternatively ∝0.160 kg of Ne at 10 bar, with an energy threshold below 0.4 keVee, and is fully built with radiopure materials. We will describe the detector in detail, the results from the commissioning phase on surface, as well as a preliminary background model. The anticipated sensitivity of this technique may go beyond current experimental limits for WIMPs of masses of 2-8 GeV. (orig.)
Reconstruction of 3D Micro Pore Structure of Coal and Simulation of Its Mechanical Properties
Directory of Open Access Journals (Sweden)
Guang-zhe Deng
2017-01-01
Full Text Available This article takes the low permeability coal seam in the coalfield of South Judger Basin in Xinjiang, as a research object. The pore structure characteristics of coal rock mass in low permeability coal seam were analyzed quantitatively using scanning electron microscopy (SEM through the methods of statistics and digital image analysis. Based on the pore structure parameters and the distribution function of the coal rock mass, a three-dimensional porous cylinder model with different porosity was reconstructed by FLAC3D. The numerical simulation study of reconstructed pore model shows that (1 the porosity and the compressive strength have obvious nonlinear relation and satisfy the negative exponential relation; (2 the porosity significantly affects the stress distribution; with the increase of micro porosity, the stress distribution becomes nonuniform; (3 the compressive failures of different models are mainly shear failures, and the shape of fracture section is related to porosity; (4 the variation of seepage coefficient of the pore reconstruction model is consistent with the development of micro cracks. The micro mechanism of the deformation and failure of coal and the interaction of multiphase flow with porosity are revealed, which provides a theoretical reference for the clean development of the low permeability coal seam.
Herbort, Mirco; Heletta, Sebastian; Raschke, Michael J; Schliemann, Benedikt; Osada, Nani; Petersen, Wolf; Zantop, Thore
2012-03-01
The aim of this study was to evaluate the mechanical properties of anterior cruciate ligament (ACL) reconstruction using the medial portal technique with cortical fixation and hybrid fixation after penetration of the lateral cortex by use of different drill sizes. In this biomechanical study a porcine in vitro model was used. The testing protocol consisted of a cyclic loading protocol (1,000 cycles, 50 and 250 N) and subsequent ultimate failure testing. Number of cyclic loadings survived, stiffness, yield load, maximum load, and graft elongation, as well as failure mode, were analyzed after ACL reconstruction with 5- to 9-mm soft-tissue grafts. In the control group, conventional penetration of the lateral cortex with a 4.5-mm drill and cortical fixation were performed. In the tested groups, the lateral cortex was penetrated with a drill matching the graft size. In the first part of the study, we used cortical fixation. In the second part, we used hybrid fixation with an interference screw. In the first part of the study, ACL reconstruction with 5- to 6-mm perforation of the lateral cortex showed no significant differences in ultimate failure load after cyclic loading compared with the control group (P > .05). Specimens with reconstruction with 7- to 9-mm perforation of the lateral cortex and cortical fixation did not survive the cyclic loading protocol. In the second part of the study, with a hybrid fixation technique, ultimate failure testing after cyclic loading of specimens with 7- to 9-mm penetration showed no significant differences in tested parameters compared with the control group (P > .05). After penetration of the lateral cortex with a drill size of more than 6 mm, cortical ACL fixation results in poor mechanical properties. Hybrid fixation increases the mechanical properties significantly after penetration with a 7- to 9-mm drill. We advise caution to avoid penetration of the lateral femoral cortex when using cortical flip-button fixation. In case of
DEFF Research Database (Denmark)
Rose, Sean; Andersen, Martin S.; Sidky, Emil Y.
2015-01-01
Purpose: The authors develop and investigate iterative image reconstruction algorithms based on data-discrepancy minimization with a total-variation (TV) constraint. The various algorithms are derived with different data-discrepancy measures reflecting the maximum likelihood (ML) principle......: An incremental algorithm framework is developed for this purpose. The instances of the incremental algorithms are derived for solving optimization problems including a data fidelity objective function combined with a constraint on the image TV. For the data fidelity term the authors, compare application....... Simulations demonstrate the iterative algorithms and the resulting image statistical properties for low-dose CT data acquired with sparse projection view angle sampling. Of particular interest is to quantify improvement of image statistical properties by use of the ML data fidelity term. Methods...
Search for WIMP dark matter produced in association with a Z boson with the ATLAS detector
AUTHOR|(INSPIRE)INSPIRE-00399337; The ATLAS collaboration
2016-01-01
The search for weakly interacting dark matter particle (WIMP) candidates produced in association with a Z boson with the ATLAS detector at the LHC is presented. Events with large missing transverse momentum and consistent with the decay of a Z boson into oppositely charged electron or muon pairs were selected in analysis. Background estimates and corresponding systematic uncertainties are shown. The limits on the mass scale of the contact interaction as a function of the dark matter particle mass and the limits on the coupling and scalar particle mediator mass for 8 TeV proton-proton collisions data are presented. Prospects for analysis using 13 TeV proton-proton collisions data are discussed.
Complementarity of WIMP Sensitivity with direct SUSY, Monojet and Dark Matter Searches in the MSSM
Arbey, Alexandre; Mahmoudi, Farvah
2014-01-01
This letter presents new results on the combined sensitivity of the LHC and underground dark matter search experiments to the lightest neutralino as WIMP candidate in the minimal Supersymmetric extension of the Standard Model. We show that monojet searches significantly extend the sensitivity to the neutralino mass in scenarios where scalar quarks are nearly degenerate in mass with it. The inclusion of the latest bound by the LUX experiment on the neutralino-nucleon spin-independent scattering cross section expands this sensitivity further, highlighting the remarkable complementarity of jets/$\\ell$s+MET and monojet at LHC and dark matter searches in probing models of new physics with a dark matter candidate. The qualitative results of our study remain valid after accounting for theoretical uncertainties.
7th Patras workshop on axions, WIMPs and WISPs (PATRAS 2011). Proceedings
Energy Technology Data Exchange (ETDEWEB)
Zioutas, Konstantin; Schumann, Marc (eds.)
2011-12-15
The year 2011 was an exciting period to work on the ''dark side'' of the Universe. Several experimental claims of the direct detection of WIMP dark matter were challenged by the restrictive limits of several others. Dedicated experiments searching for axions, another well motivated dark matter candidate, and for axion-like particles continued to improve their limits and got an additional boost by puzzling astrophysical observations and new developments in theory. The LHC collected an unexpectedly large amount of data and started to produce results at an amazing speed. And finally, this year's Nobel price of physics was awarded to the observation of the accelerating expansion of the Universe, an effect which might be related to dark energy, whose nature remain among the biggest mysteries in physics. These exciting topics and many more important aspects of particle- and astroparticle physics were discussed between experimentalists and theorists at the 7th Patras Workshop on Axions, WIMPs, and WISPs. The workshop took place from June 27 - July 1, 2011, in the Royal Myconian and Myconian Imperial Resorts Hotels on the Greek island of Mykonos. As in the previous years, it was a very fruitful and lively meeting in an inspiring and open atmosphere, which allowed for many open and constructive discussions also on controversial topics. The scientific exchange, the beautiful scenery of the island, the venue itself, the food, an excursion to the ancient ruins of Delos, and finally an amazing conference dinner made this meeting really unique. The ''spirit'' of the workshop and its atmosphere cannot be brought to paper, but many of its scientific highlights are collected in these proceedings. We are looking forward to the 8th Patras Workshop, which will be held in Chicago (USA) July 18-22, 2012. It will be organized jointly by our US colleagues Andrei Afanasev (JLAB), Oliver Baker (Yale), and William Wester (FNAL).
7th Patras workshop on axions, WIMPs and WISPs (PATRAS 2011). Proceedings
International Nuclear Information System (INIS)
Zioutas, Konstantin; Schumann, Marc
2011-12-01
The year 2011 was an exciting period to work on the ''dark side'' of the Universe. Several experimental claims of the direct detection of WIMP dark matter were challenged by the restrictive limits of several others. Dedicated experiments searching for axions, another well motivated dark matter candidate, and for axion-like particles continued to improve their limits and got an additional boost by puzzling astrophysical observations and new developments in theory. The LHC collected an unexpectedly large amount of data and started to produce results at an amazing speed. And finally, this year's Nobel price of physics was awarded to the observation of the accelerating expansion of the Universe, an effect which might be related to dark energy, whose nature remain among the biggest mysteries in physics. These exciting topics and many more important aspects of particle- and astroparticle physics were discussed between experimentalists and theorists at the 7th Patras Workshop on Axions, WIMPs, and WISPs. The workshop took place from June 27 - July 1, 2011, in the Royal Myconian and Myconian Imperial Resorts Hotels on the Greek island of Mykonos. As in the previous years, it was a very fruitful and lively meeting in an inspiring and open atmosphere, which allowed for many open and constructive discussions also on controversial topics. The scientific exchange, the beautiful scenery of the island, the venue itself, the food, an excursion to the ancient ruins of Delos, and finally an amazing conference dinner made this meeting really unique. The ''spirit'' of the workshop and its atmosphere cannot be brought to paper, but many of its scientific highlights are collected in these proceedings. We are looking forward to the 8th Patras Workshop, which will be held in Chicago (USA) July 18-22, 2012. It will be organized jointly by our US colleagues Andrei Afanasev (JLAB), Oliver Baker (Yale), and William Wester (FNAL).
On the properties of energy stable flux reconstruction schemes for implicit large eddy simulation
Vermeire, B. C.; Vincent, P. E.
2016-12-01
We begin by investigating the stability, order of accuracy, and dispersion and dissipation characteristics of the extended range of energy stable flux reconstruction (E-ESFR) schemes in the context of implicit large eddy simulation (ILES). We proceed to demonstrate that subsets of the E-ESFR schemes are more stable than collocation nodal discontinuous Galerkin methods recovered with the flux reconstruction approach (FRDG) for marginally-resolved ILES simulations of the Taylor-Green vortex. These schemes are shown to have reduced dissipation and dispersion errors relative to FRDG schemes of the same polynomial degree and, simultaneously, have increased Courant-Friedrichs-Lewy (CFL) limits. Finally, we simulate turbulent flow over an SD7003 aerofoil using two of the most stable E-ESFR schemes identified by the aforementioned Taylor-Green vortex experiments. Results demonstrate that subsets of E-ESFR schemes appear more stable than the commonly used FRDG method, have increased CFL limits, and are suitable for ILES of complex turbulent flows on unstructured grids.
The phenomenology of superWIMP dark matter scenariow with long-lived sleptons
Energy Technology Data Exchange (ETDEWEB)
Heisig, Jan
2013-08-15
We study the phenomenology of a supersymmetric scenario where the next-to-lightest superparticle (NLSP) is the charged slepton and is long-lived due to a lightest superparticle (LSP) which is a super weakly interacting massive particle (superWIMP), like the gravitino. This has far-reaching consequences for the cosmological history of the universe on the one hand and for the signatures at colliders on the other hand. We do not assume any high-scale model for the mediation of SUSY breaking to the MSSM but work along the lines of simplified models and the phenomenological MSSM (pMSSM). In a first part, we investigate the LHC sensitivity and its dependence on the superparticle spectrum with an emphasis on strong production and decay. We formulate appropriate simplified models that allow to conservatively approximate the signal efficiencies of arbitrary spectra from a small number of decisive parameters. We found that the application of simplified models is especially suitable in the considered scenario. Devising cuts that yield a large detection efficiency in the whole parameter space, we determine the discovery and exclusion potential of the LHC. We found that the prominent signature of long-lived sleptons allows to extract more robust constraints on the parameter space than for the widely studied case of a neutralino LSP scenario. In addition, we study the implications of the recent LHC results on the cosmological validity of a superWIMP Dark Matter scenario with a long-lived stau NLSP. Therefore, we work in a pMSSM framework and perform a Monte Carlo scan over the pMSSM parameter space highlighting the implications of a Higgs around 125 GeV and the nullsearches for heavy stable charged particles at the 7 and 8TeV LHC. Further, we consider bounds from MSSM Higgs searches, from flavor and precision observables as well as from the theoretical requirement of vacuum stability. In particular we work out the impact on the allowed range for the stau yield after freeze
The phenomenology of superWIMP dark matter scenariow with long-lived sleptons
International Nuclear Information System (INIS)
Heisig, Jan
2013-08-01
We study the phenomenology of a supersymmetric scenario where the next-to-lightest superparticle (NLSP) is the charged slepton and is long-lived due to a lightest superparticle (LSP) which is a super weakly interacting massive particle (superWIMP), like the gravitino. This has far-reaching consequences for the cosmological history of the universe on the one hand and for the signatures at colliders on the other hand. We do not assume any high-scale model for the mediation of SUSY breaking to the MSSM but work along the lines of simplified models and the phenomenological MSSM (pMSSM). In a first part, we investigate the LHC sensitivity and its dependence on the superparticle spectrum with an emphasis on strong production and decay. We formulate appropriate simplified models that allow to conservatively approximate the signal efficiencies of arbitrary spectra from a small number of decisive parameters. We found that the application of simplified models is especially suitable in the considered scenario. Devising cuts that yield a large detection efficiency in the whole parameter space, we determine the discovery and exclusion potential of the LHC. We found that the prominent signature of long-lived sleptons allows to extract more robust constraints on the parameter space than for the widely studied case of a neutralino LSP scenario. In addition, we study the implications of the recent LHC results on the cosmological validity of a superWIMP Dark Matter scenario with a long-lived stau NLSP. Therefore, we work in a pMSSM framework and perform a Monte Carlo scan over the pMSSM parameter space highlighting the implications of a Higgs around 125 GeV and the nullsearches for heavy stable charged particles at the 7 and 8TeV LHC. Further, we consider bounds from MSSM Higgs searches, from flavor and precision observables as well as from the theoretical requirement of vacuum stability. In particular we work out the impact on the allowed range for the stau yield after freeze
Ajduković, Zorica R; Mihajilov-Krstev, Tatjana M; Ignjatović, Nenad L; Stojanović, Zoran; Mladenović-Antić, Snezana B; Kocić, Branislava D; Najman, Stevo; Petrović, Nenad D; Uskoković, Dragan P
2016-02-01
In the field of oral implantology the loss of bone tissue prevents adequate patient care, and calls for the use of synthetic biomaterials with properties that resemble natural bone. Special attention is paid to the risk of infection after the implantation of these materials. Studies have suggested that some nanocontructs containing metal ions have antimicrobial properties. The aim of this study was to examine the antimicrobial and hemolytic activity of cobalt-substituted hydroxyapatite nanoparticles, compared to hydroxyapatite and hydroxyapatite/poly-lactide-co-glycolide. The antibacterial effects of these powders were tested against two pathogenic bacterial strains: Escherichia coi (ATCC 25922) and Staphylococcus aureus (ATCC 25923), using the disc diffusion method and the quantitative antimicrobial test in a liquid medium. The quantitative antimicrobial test showed that all of the tested biomaterials have some antibacterial properties. The effects of both tests were more prominent in case of S. aureus than in E coli. A higher percentage of cobalt in the crystal structure of cobalt-substituted hydroxyapatite nanoparticles led to an increased antimicrobial activity. All of the presented biomaterial samples were found to be non-hemolytic. Having in mind that the tested of cobalt-substituted hydroxyapatite (Ca/Co-HAp) material in given concentrations shows good hemocompatibility and antimicrobial effects, along with its previously studied biological properties, the conclusion can be reached that it is a potential candidate that could substitute calcium hydroxyapatite as the material of choice for use in bone tissue engineering and clinical practices in orthopedic, oral and maxillofacial surgery.
B1-based SAR reconstruction using contrast source inversion-electric properties tomography (CSI-EPT)
Balidemaj, Edmond; van den Berg, Cornelis A T; van Lier, A.L.H.M.W.; Nederveen, Aart J; Stalpers, Lukas J A; Crezee, Hans; Remis, Rob F
Specific absorption rate (SAR) assessment is essential for safety purposes during MR acquisition. Online SAR assessment is not trivial and requires, in addition, knowledge of the electric tissue properties and the electric fields in the human anatomy. In this study, the potential of the recently
B1-based SAR reconstruction using contrast source inversion–electric properties tomography (CSI-EPT)
Balidemaj, E.; van den Berg, CAT; van Lier, ALHMW; Nederveen, AJ; Stalpers, LJA; Crezee, H; Remis, R.F.
2016-01-01
Specific absorption rate (SAR) assessment is essential for safety purposes during MR acquisition. Online SAR assessment is not trivial and requires, in addition, knowledge of the electric tissue properties and the electric fields in the human anatomy. In this study, the potential of the recently
Bruce, Iain P.; Karaman, M. Muge; Rowe, Daniel B.
2012-01-01
The acquisition of sub-sampled data from an array of receiver coils has become a common means of reducing data acquisition time in MRI. Of the various techniques used in parallel MRI, SENSitivity Encoding (SENSE) is one of the most common, making use of a complex-valued weighted least squares estimation to unfold the aliased images. It was recently shown in Bruce et al. [Magn. Reson. Imag. 29(2011):1267–1287] that when the SENSE model is represented in terms of a real-valued isomorphism, it assumes a skew-symmetric covariance between receiver coils, as well as an identity covariance structure between voxels. In this manuscript, we show that not only is the skew-symmetric coil covariance unlike that of real data, but the estimated covariance structure between voxels over a time series of experimental data is not an identity matrix. As such, a new model, entitled SENSE-ITIVE, is described with both revised coil and voxel covariance structures. Both the SENSE and SENSE-ITIVE models are represented in terms of real-valued isomorphisms, allowing for a statistical analysis of reconstructed voxel means, variances, and correlations resulting from the use of different coil and voxel covariance structures used in the reconstruction processes to be conducted. It is shown through both theoretical and experimental illustrations that the miss-specification of the coil and voxel covariance structures in the SENSE model results in a lower standard deviation in each voxel of the reconstructed images, and thus an artificial increase in SNR, compared to the standard deviation and SNR of the SENSE-ITIVE model where both the coil and voxel covariances are appropriately accounted for. It is also shown that there are differences in the correlations induced by the reconstruction operations of both models, and consequently there are differences in the correlations estimated throughout the course of reconstructed time series. These differences in correlations could result in meaningful
Directory of Open Access Journals (Sweden)
husen hendriyana
2017-10-01
Full Text Available Along with recent rapid development of science, technology, art and culture, through research institutions from the central to the local level, the government seriously activates enhancement and protection of the intellectual products of the nation. Such as protection of intellectual property rights against irresponsible plagiarism. This is due to that the appearance, process, or invention steps of the creative furniture designer in the society or in the academic environment have the potential and the opportunity to be registered as Intellectual Properties (IP or gain Intellectual Property Rights (IPR. Besides aiming to lift up the state or institutions achievement and attainment of intellectual property rights internationally, the added value also can be developed in the direction of economic upgrade. Research on furniture products designs have been numerously carried out with various objects and cases, yet the diversity of the subject character and creative processes still have not well defined so they enrich the model of creative process design. This study aims to identify, classify and formulate a potential furniture design model of creative process and IPR standard, through methods PAR. The results of this study are (1 prototype of furniture design products, (2 the creative process model and the construction methods process of furniture design with a concept or a specific theme; (3 Registration of IPR; (4 Scientific manuscript. Seiring dengan perkembangan ilmu pengetahuan, teknologi, seni dan budaya yang marak dewasa ini, melalui lembaga penelitian dari tingkat pusat sampai ketingkat daerah, pemerintah semakin serius menggalangkan peningkatan dan perlindungan terhadap produk intelektual anak bangsa. Salah satu contoh di antaranya adalah perlindungan terhadap hak kekayaan intelektual dari perilaku plagiarism yang tidak bertanggung jawab. Hal ini tiada lain bahwa, bentuk, proses, maupun invention steps dari para pelaku kreatif desain mebel
Niu, Chun-Yang; Qi, Hong; Huang, Xing; Ruan, Li-Ming; Wang, Wei; Tan, He-Ping
2015-11-01
A hybrid least-square QR decomposition (LSQR)-particle swarm optimization (LSQR-PSO) algorithm was developed to estimate the three-dimensional (3D) temperature distributions and absorption coefficients simultaneously. The outgoing radiative intensities at the boundary surface of the absorbing media were simulated by the line-of-sight (LOS) method, which served as the input for the inverse analysis. The retrieval results showed that the 3D temperature distributions of the participating media with known radiative properties could be retrieved accurately using the LSQR algorithm, even with noisy data. For the participating media with unknown radiative properties, the 3D temperature distributions and absorption coefficients could be retrieved accurately using the LSQR-PSO algorithm even with measurement errors. It was also found that the temperature field could be estimated more accurately than the absorption coefficients. In order to gain insight into the effects on the accuracy of temperature distribution reconstruction, the selection of the detection direction and the angle between two detection directions was also analyzed. Project supported by the Major National Scientific Instruments and Equipment Development Special Foundation of China (Grant No. 51327803), the National Natural Science Foundation of China (Grant No. 51476043), and the Fund of Tianjin Key Laboratory of Civil Aircraft Airworthiness and Maintenance in Civil Aviation University of China.
Gogorza, C. G.; Orgeira, M. J.; Ponce, F.; Fernández, M.; Laprida, C.; Coronato, A.
2013-05-01
We report preliminary results obtained from a multi-proxy analysis including paleomagnetic and rock-magnetic studies of two sediment cores of Laguna Carmen (53°40'60" S 68°19'0" W, ~83m asl) in the semiarid steppe in northern Tierra del Fuego island, Southernmost Patagonia, Argentina. Two short cores (115 cm) were sampled using a Livingstone piston corer during the 2011 southern fall. Sediments are massive green clays (115 to 70 cm depth) with irregularly spaced thin sandy strata and lens. Massive yellow clay with thin sandy strata continues up to 30 cm depth; from here up to 10 cm yellow massive clays domain. The topmost 10 cm are mixed yellow and green clays with fine sand. Measurements of intensity and directions of Natural Remanent Magnetization (NRM), magnetic susceptibility, isothermal remanent magnetization, saturation isothermal remanent magnetization (SIRM), back field and anhysteretic remanent magnetization at 100 mT (ARM100mT) were performed and several associated parameters calculated (ARM100mT/k and SIRM/ ARM100mT). Also, as a first estimate of relative magnetic grain-size variations, the median destructive field of the NRM (MDFNRM), was determined. Additionally, we present results of magnetic parameters measured with vibrating sample magnetometer (VSM). The stability of the NRM was analyzed by alternating field demagnetization. The magnetic properties have shown variable values, showing changes in both grain size and concentration of magnetic minerals. It was found that the main carrier of remanence is magnetite with the presence of hematite in very low percentages. This is the first paleomagnetic study performed in lakes located in the northern, semiarid fuegian steppe, where humid-dry cycles have been interpreted all along the Holocene from an aeolian paleosoil sequence (Orgeira et el, 2012). Comparison between paleomagnetic records of Laguna Carmen and results obtained in earlier studies carried out at Laguna Potrok Aike (Gogorza et al., 2012
International Nuclear Information System (INIS)
Lebedenko, V. N.; Bewick, A.; Currie, A.; Davidge, D.; Dawson, J.; Horn, M.; Howard, A. S.; Jones, W. G.; Joshi, M.; Liubarsky, I.; Lyons, K.; Quenby, J. J.; Sumner, T. J.; Thorne, C.; Walker, R. J.; Araujo, H. M.; Edwards, B.; Barnes, E. J.; Ghag, C.; Murphy, A. StJ.
2009-01-01
We present new experimental constraints on the WIMP-nucleon spin-dependent elastic cross sections using data from the first science run of ZEPLIN-III, a two-phase xenon experiment searching for galactic dark matter weakly interacting massive particles based at the Boulby mine. Analysis of ∼450 kg·days fiducial exposure allow us to place a 90%-confidence upper limit on the pure WIMP-neutron cross section of σ n =1.9x10 -2 pb at 55 GeV/c 2 WIMP mass. Recent calculations of the nuclear spin structure based on the Bonn charge-dependent nucleon-nucleon potential were used for the odd-neutron isotopes 129 Xe and 131 Xe. These indicate that the sensitivity of xenon targets to the spin-dependent WIMP-proton interaction could be much lower than implied by previous calculations, whereas the WIMP-neutron sensitivity is impaired only by a factor of ∼2.
Romzaikina, Olga; Vasenev, Viacheslav; Khakimova, Rita
2017-04-01
On-going urbanization stresses a necessity for structural and aesthetically organized urban landscapes to improve citizen's life quality. Urban soils and vegetation are the main components of urban ecosystems. Urban greenery regulates the climate, controls and air quality and supports biodiversity in urban areas. Soils play a key role in supporting urban greenery. However, soils of urban parks also perform other important environmental functions. Urban soils are influenced by a variety of environmental and anthropogenic factors and, in the result, are highly heterogeneous and dynamic. Reconstructions of green zones and urban parks, usually occurring in cities, alter soil properties. Analyzing spatial variability and dynamics of soil properties is important to support decision-making in landscaping. Therefore, the research aimed to analyze the spatial distribution of the key soil properties (acidity, soil organic carbon (SOC) and nutrient contents) in the urban park before and after reconstruction to support decision-making in selecting ornamental plants for landscaping. The research was conducted in the urban park named after Artyom Borovik in Moscow before (2012) and after (2014) the reconstruction. Urban soil's properties maps for both periods were created by interpolation of the field data. The observed urban soils included recreazems, urbanozems and constuctozems. Before the reconstruction soils were sampled using the uniform design (the net with 100 m side and key plots with 50m size). After the reconstructions the additional samples were collected at locations, where the land cover and functional zones changed in a result of the reconstruction.We sample from the depths 0-30, 30-50 and 50-100 cm. The following soil properties were measured: pH, SOC, K2O and P2O5. The maps of the analyzed properties were developed using open QGIS2.4 software by IDW. The vegetation in the park was examined using the scale of the visual assessment. The results of the visual
From superWIMPs to decaying dark matter. Models, bounds and indirect searches
Energy Technology Data Exchange (ETDEWEB)
Weniger, Christoph
2010-06-15
Despite lots of observational and theoretical efforts, the particle nature of dark matter remains unknown. Beyond the paradigmatic WIMPs (Weakly Interacting Massive Particles), many theoretically well motivated models exist where dark matter interacts much more weakly than electroweak with Standard Model particles. In this case new phenomena occur, like the decay of dark matter or the interference with the standard cosmology of the early Universe. In this thesis we study some of these aspects of superweakly coupled dark matter in general, and in the special case of hidden U(1){sub X} gauginos that kinetically mix with hypercharge. There, we will assume that the gauge group remains unbroken, similar to the Standard Model U(1){sub em}. We study different kinds of cosmological bounds, including bounds from thermal overproduction, from primordial nucleosynthesis and from structure formation. Furthermore, we study the possible cosmic-ray signatures predicted by this scenario, with emphasis on the electron and positron channel in light of the recent observations by PAMELA and Fermi LAT. Moreover we study the cosmic-ray signatures of decaying dark matter independently of concrete particle-physics models. In particular we analyze in how far the rise in the positron fraction above 10 GeV, as observed by PAMELA, can be explained by dark matter decay. Lastly, we concentrate on related predictions for gamma-ray observations with the Fermi LAT, and propose to use the dipole-like anisotropy of the prompt gamma-ray dark matter signal to distinguish exotic dark matter contributions from the extragalactic gamma-ray background. (orig.)
From superWIMPs to decaying dark matter. Models, bounds and indirect searches
International Nuclear Information System (INIS)
Weniger, Christoph
2010-06-01
Despite lots of observational and theoretical efforts, the particle nature of dark matter remains unknown. Beyond the paradigmatic WIMPs (Weakly Interacting Massive Particles), many theoretically well motivated models exist where dark matter interacts much more weakly than electroweak with Standard Model particles. In this case new phenomena occur, like the decay of dark matter or the interference with the standard cosmology of the early Universe. In this thesis we study some of these aspects of superweakly coupled dark matter in general, and in the special case of hidden U(1) X gauginos that kinetically mix with hypercharge. There, we will assume that the gauge group remains unbroken, similar to the Standard Model U(1) em . We study different kinds of cosmological bounds, including bounds from thermal overproduction, from primordial nucleosynthesis and from structure formation. Furthermore, we study the possible cosmic-ray signatures predicted by this scenario, with emphasis on the electron and positron channel in light of the recent observations by PAMELA and Fermi LAT. Moreover we study the cosmic-ray signatures of decaying dark matter independently of concrete particle-physics models. In particular we analyze in how far the rise in the positron fraction above 10 GeV, as observed by PAMELA, can be explained by dark matter decay. Lastly, we concentrate on related predictions for gamma-ray observations with the Fermi LAT, and propose to use the dipole-like anisotropy of the prompt gamma-ray dark matter signal to distinguish exotic dark matter contributions from the extragalactic gamma-ray background. (orig.)
International Nuclear Information System (INIS)
Pan Xiaochuan; Yu Lifeng
2003-01-01
In computed tomography (CT), the fan-beam filtered backprojection (FFBP) algorithm is used widely for image reconstruction. It is known that the FFBP algorithm can significantly amplify data noise and aliasing artifacts in situations where the focal lengths are comparable to or smaller than the size of the field of measurement (FOM). In this work, we propose an algorithm that is less susceptible to data noise, aliasing, and other data inconsistencies than is the FFBP algorithm while retaining the favorable resolution properties of the FFBP algorithm. In an attempt to evaluate the noise properties in reconstructed images, we derive analytic expressions for image variances obtained by use of the FFBP algorithm and the proposed algorithm. Computer simulation studies are conducted for quantitative evaluation of the spatial resolution and noise properties of images reconstructed by use of the algorithms. Numerical results of these studies confirm the favorable spatial resolution and noise properties of the proposed algorithm and verify the validity of the theoretically predicted image variances. The proposed algorithm and the derived analytic expressions for image variances can have practical implications for both estimation and detection/classification tasks making use of CT images, and they can readily be generalized to other fan-beam geometries
International Nuclear Information System (INIS)
Akerib, D.S.; Bailey, C.N.; Dragowsky, M.R.; Driscoll, D.D.; Hennings-Yeomans, R.; Kamat, S.; Perera, T.A.; Schnee, R.W.; Wang, G.; Armel-Funkhouser, M.S.; Daal, M.; Filippini, J.; Lu, A.; Mandic, V.; Meunier, P.; Mirabolfathi, N.; Issac, M.C. Perillo; Rau, W.; Seitz, D.N.; Serfass, B.
2005-01-01
The Cryogenic Dark Matter Search (CDMS-II) employs low-temperature Ge and Si detectors to seek weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei. Simultaneous measurements of both ionization and phonon energy provide discrimination against interactions of background particles. For recoil energies above 10 keV, events due to background photons are rejected with >99.99% efficiency. Electromagnetic events very near the detector surface can mimic nuclear recoils because of reduced charge collection, but these surface events are rejected with >96% efficiency by using additional information from the phonon pulse shape. Efficient use of active and passive shielding, combined with the 2090 m.w.e. overburden at the experimental site in the Soudan mine, makes the background from neutrons negligible for this first exposure. All cuts are determined in a blind manner from in situ calibrations with external radioactive sources without any prior knowledge of the event distribution in the signal region. Resulting efficiencies are known to ∼10%. A single event with a recoil of 64 keV passes all of the cuts and is consistent with the expected misidentification rate of surface electron recoils. Under the assumptions for a standard dark matter halo, these data exclude previously unexplored parameter space for both spin-independent and spin-dependent WIMP-nucleon elastic scattering. The resulting limit on the spin-independent WIMP-nucleon elastic-scattering cross section has a minimum of 4x10 -43 cm 2 at a WIMP mass of 60 GeVc -2 . The minimum of the limit for the spin-dependent WIMP-neutron elastic-scattering cross section is 2x10 -37 cm 2 at a WIMP mass of 50 GeVc -2
Directory of Open Access Journals (Sweden)
Oleg Kikhtyanin
2018-05-01
Full Text Available MgGa layered double hydroxides (Mg/Ga = 2–4 were synthesized and used for the preparation of MgGa mixed oxides and reconstructed hydrotalcites. The properties of the prepared materials were examined by physico-chemical methods (XRD, TGA, NH3-TPD, CO2-TPD, SEM, and DRIFT and tested in aldol condensation of furfural and acetone. The as-prepared phase-pure MgGa samples possessed hydrotalcite structure, and their calcination resulted in mixed oxides with MgO structure with a small admixture phase characterized by a reflection at 2θ ≈ 36.0°. The interaction of MgGa mixed oxides with pure water resulted in reconstruction of the HTC structure already after 15 s of the rehydration with maximum crystallinity achieved after 60 s. TGA-MS experiments proved a substantial decrease in carbonates in all rehydrated samples compared with their as-prepared counterparts. This allowed suggesting presence of interlayer hydroxyls in the samples. Acido-basic properties of MgGa mixed oxides determined by TPD technique did not correlate with Mg/Ga ratio which was explained by the specific distribution of Ga atoms on the external surface of the samples. CO2-TPD method was also used to evaluate the basic properties of the reconstructed MgGa samples. In these experiments, an intensive peak at T = 450°C on CO2-TPD curve was attributed to the decomposition of carbonates newly formed by CO2 interaction with interlayer carbonates rather than to CO2 desorption from basic sites. Accordingly, CO2-TPD method quantitatively characterized the interlayer hydroxyls only indirectly. Furfural conversion on reconstructed MgGa materials was much larger compared with MgGa mixed oxides confirming that Brønsted basic sites in MgGa catalysts, like MgAl catalysts, were active in the reaction. Mg/Ga ratio in mixed oxides influenced product selectivity which was explained by the difference in textural properties of the samples. In contrast, Mg/Ga ratio in reconstructed catalysts had
Kikhtyanin, Oleg; Čapek, Libor; Tišler, Zdeněk; Velvarská, Romana; Panasewicz, Adriana; Diblíková, Petra; Kubička, David
2018-01-01
MgGa layered double hydroxides (Mg/Ga = 2-4) were synthesized and used for the preparation of MgGa mixed oxides and reconstructed hydrotalcites. The properties of the prepared materials were examined by physico-chemical methods (XRD, TGA, NH 3 -TPD, CO 2 -TPD, SEM, and DRIFT) and tested in aldol condensation of furfural and acetone. The as-prepared phase-pure MgGa samples possessed hydrotalcite structure, and their calcination resulted in mixed oxides with MgO structure with a small admixture phase characterized by a reflection at 2θ ≈ 36.0°. The interaction of MgGa mixed oxides with pure water resulted in reconstruction of the HTC structure already after 15 s of the rehydration with maximum crystallinity achieved after 60 s. TGA-MS experiments proved a substantial decrease in carbonates in all rehydrated samples compared with their as-prepared counterparts. This allowed suggesting presence of interlayer hydroxyls in the samples. Acido-basic properties of MgGa mixed oxides determined by TPD technique did not correlate with Mg/Ga ratio which was explained by the specific distribution of Ga atoms on the external surface of the samples. CO 2 -TPD method was also used to evaluate the basic properties of the reconstructed MgGa samples. In these experiments, an intensive peak at T = 450°C on CO 2 -TPD curve was attributed to the decomposition of carbonates newly formed by CO 2 interaction with interlayer carbonates rather than to CO 2 desorption from basic sites. Accordingly, CO 2 -TPD method quantitatively characterized the interlayer hydroxyls only indirectly. Furfural conversion on reconstructed MgGa materials was much larger compared with MgGa mixed oxides confirming that Brønsted basic sites in MgGa catalysts, like MgAl catalysts, were active in the reaction. Mg/Ga ratio in mixed oxides influenced product selectivity which was explained by the difference in textural properties of the samples. In contrast, Mg/Ga ratio in reconstructed catalysts had practically
Song, Zhongchang; Zhang, Yu; Berggren, Per; Wei, Chong
2017-02-01
Computed tomography (CT) imaging and ultrasound experimental measurements were combined to reconstruct the acoustic properties (density, velocity, and impedance) of the head from a deceased Indo-Pacific humpback dolphin (Sousa chinensis). The authors extracted 42 soft forehead tissue samples to estimate the sound velocity and density properties at room temperature, 25.0 °C. Hounsfield Units (HUs) of the samples were read from CT scans. Linear relationships between the tissues' HUs and velocity, and HUs and density were revealed through regression analyses. The distributions of the head acoustic properties at axial, coronal, and sagittal cross sections were reconstructed, suggesting that the forehead soft tissues were characterized by low-velocity in the melon, high-velocity in the muscle and connective tissues. Further, the sound velocities of melon, muscle, and connective tissue pieces were measured under different temperatures to investigate tissues' velocity response to temperature. The results demonstrated nonlinear relationships between tissues' sound velocity and temperature. This study represents a first attempt to provide general information on acoustic properties of this species. The results could provide meaningful information for understanding the species' bioacoustic characteristics and for further investigation on sound beam formation of the dolphin.
International Nuclear Information System (INIS)
Armengaud, E.; Augier, C.; Benoit, A.; Berge, L.; Bluemer, J.; Broniatowski, A.; Brudanin, V.; Censier, B.; Chardin, G.; Chapellier, M.; Charlieux, F.; Coulter, P.; Cox, G.A.; Defay, X.; De Jesus, M.; Dolgorouki, Y.; Domange, J.; Dumoulin, L.
2011-01-01
The EDELWEISS-II Collaboration has completed a direct search for WIMP dark matter with an array of ten 400-g cryogenic germanium detectors in operation at the Laboratoire Souterrain de Modane. The combined use of thermal phonon sensors and charge collection electrodes with an interleaved geometry enables the efficient rejection of γ-induced radioactivity as well as near-surface interactions. A total effective exposure of 384 kg d has been achieved, mostly coming from fourteen months of continuous operation. Five nuclear recoil candidates are observed above 20 keV, while the estimated background is 3.0 events. The result is interpreted in terms of limits on the cross-section of spin-independent interactions of WIMPs and nucleons. A cross-section of 4.4x10 -8 pb is excluded at 90%CL for a WIMP mass of 85 GeV. New constraints are also set on models where the WIMP-nucleon scattering is inelastic.
Yang, Li-Tao; Li, Hau-Bin; Yue, Qian; Kang, Ke-Jun; Cheng, Jian-Ping; Li, Yuan-Jing; Tsz-King Wong, Henry; Aǧartioǧlu, M.; An, Hai-Peng; Chang, Jian-Ping; Chen, Jing-Han; Chen, Yun-Hua; Deng, Zhi; Du, Qiang; Gong, Hui; He, Li; Hu, Jin-Wei; Hu, Qing-Dong; Huang, Han-Xiong; Jia, Li-Ping; Jiang, Hao; Li, Hong; Li, Jian-Min; Li, Jin; Li, Xia; Li, Xue-Qian; Li, Yu-Lan; Lin, Fong-Kay; Lin, Shin-Ted; Liu, Shu-Kui; Liu, Zhong-Zhi; Ma, Hao; Ma, Jing-Lu; Pan, Hui; Ren, Jie; Ruan, Xi-Chao; Sevda, B.; Sharma, Vivek; Shen, Man-Bin; Singh, Lakhwinder; Singh, Manoj Kumar; Tang, Chang-Jian; Tang, Wei-You; Tian, Yang; Wang, Ji-Min; Wang, Li; Wang, Qing; Wang, Yi; Wu, Shi-Yong; Wu, Yu-Cheng; Xing, Hao-Yang; Xu, Yin; Xue, Tao; Yang, Song-Wei; Yi, Nan; Yu, Chun-Xu; Yu, Hai-Jun; Yue, Jian-Feng; Zeng, Xiong-Hui; Zeng, Ming; Zeng, Zhi; Zhang, Yun-Hua; Zhao, Ming-Gang; Zhao, Wei; Zhou, Ji-Fang; Zhou, Zu-Ying; Zhu, Jing-Jun; Zhu, Zhong-Hua; CDEX Collaboration
2018-01-01
We report results of a search for light weakly interacting massive particle (WIMP) dark matter from the CDEX-1 experiment at the China Jinping Underground Laboratory (CJPL). Constraints on WIMP-nucleon spin-independent (SI) and spin-dependent (SD) couplings are derived with a physics threshold of 160 eVee, from an exposure of 737.1 kg-days. The SI and SD limits extend the lower reach of light WIMPs to 2 GeV and improve over our earlier bounds at WIMP mass less than 6 GeV. Supported by the National Key Research and Development Program of China (2017YFA0402200, 2017YFA0402201), the National Natural Science Foundation of China (11175099, 11275107, 11475117, 11475099, 11475092, 11675088), the National Basic Research Program of China (973 Program) (2010CB833006). We thank the support of grants from the Tsinghua University Initiative Scientific Research Program (20121088494, 20151080354) and the Academia Sinica Investigator Award 2011-15, contracts 103-2112-M-001-024 and 104-2112-M-001-038-MY3 from the Ministry of Science and Technology of Taiwan.
Ghebes, C.A.; Kelder, C.; Schot, T.; Renard, A.J.S.; Pakvis, D.F.M.; Fernandes, H.; Saris, Daniël B.F.
2015-01-01
Anterior cruciate ligament (ACL) reconstruction involves the replacement of the torn ligament with a new graft, often a hamstring tendon (HT). Described as similar, the ACL and HT have intrinsic differences related to their distinct anatomical locations. From a cellular perspective, identifying
International Nuclear Information System (INIS)
La Riviere, Patrick J.; Pan Xiaochuan
2002-01-01
Volumes reconstructed by standard methods from single-slice helical computed tomography (CT) data have been shown to have noise levels that are highly nonuniform relative to those in conventional CT. These noise nonuniformities can affect low-contrast object detectability and have also been identified as the cause of the zebra artifacts that plague maximum intensity projection (MIP) images of such volumes. While these spatially variant noise levels have their root in the peculiarities of the helical scan geometry, there is also a strong dependence on the interpolation and reconstruction algorithms employed. In this paper, we seek to develop image reconstruction strategies that eliminate or reduce, at its source, the nonuniformity of noise levels in helical CT relative to that in conventional CT. We pursue two approaches, independently and in concert. We argue, and verify, that Fourier-based longitudinal interpolation approaches lead to more uniform noise ratios than do the standard 360LI and 180LI approaches. We also demonstrate that a Fourier-based fan-to-parallel rebinning algorithm, used as an alternative to fanbeam filtered backprojection for slice reconstruction, also leads to more uniform noise ratios, even when making use of the 180LI and 360LI interpolation approaches
International Nuclear Information System (INIS)
Collar, J.I.; Girard, T.A.; Miley, H.S.; Waysand, G.
2000-01-01
The Superheated Instrument for Massive Particle searches (SIMPLE 2000) will consist of an array of 8-16 large active mass (approx. 15 g) superheated droplet detectors (SDDs) to be installed in the new underground laboratory of Rustrel-Pays d'Apt. Several factors make the use of SDDs an attractive approach for the detection of weakly interacting massive particles (WIMPs), namely their intrinsic insensitivity to minimally ionizing particles, high fluorine content, low cost and operation at near ambient pressure and temperature. We comment here on the fabrication, calibration and already-competitive first limits from prototype SDDs for SIMPLE, as well as on the expected immediate increase in sensitivity of the programme, which aims at an exposure of > 25 kg day during 2000. The ability of modest-mass fluorine-rich detectors to investigate regions of neutralino parameter space beyond the reach of the most ambitious cryogenic projects is pointed out. (author)
International Nuclear Information System (INIS)
Collar, J I; Puibasset, J; Girard, T A; Limagne, D; Miley, H S; Waysand, G
2000-01-01
The Superheated Instrument for Massive Particle searches (SIMPLE 2000) will consist of an array of 8-16 large active mass (≅15 g) superheated droplet detectors (SDDs) to be installed in the new underground laboratory of Rustrel-Pays d'Apt. Several factors make the use of SDDs an attractive approach for the detection of weakly interacting massive particles (WIMPs), namely their intrinsic insensitivity to minimally ionizing particles, high fluorine content, low cost and operation at near ambient pressure and temperature. We comment here on the fabrication, calibration and already-competitive first limits from prototype SDDs for SIMPLE, as well as on the expected immediate increase in sensitivity of the programme, which aims at an exposure of > 25 kg day during 2000. The ability of modest-mass fluorine-rich detectors to investigate regions of neutralino parameter space beyond the reach of the most ambitious cryogenic projects is pointed out
International Nuclear Information System (INIS)
Gunda, Naga Siva Kumar; Mitra, Sushanta K
2012-01-01
A well-known approach to develop a high efficiency solid-oxide fuel-cell (SOFC) consists of extracting the microstructure and transport properties such as volume fractions, internal surface area, geometric connectivity, effective gas diffusivity, effective electronic conductivity and geometric tortuosities from three-dimensional (3D) microstructure of the SOFC electrodes; thereafter, performing the SOFC efficiency calculations using previously mentioned quantities. In the present work, dual-beam focused ion beam - scanning electron microscopy (FIB-SEM) is applied on one of the SOFC cathodes, a lanthanum strontium manganite (LSM) electrode, to estimate the aforementioned properties. A framework for calculating transport properties is presented in this work. 3D microstructures of LSM electrode are reconstructed from a series of two-dimensional (2D) cross-sectional FIB-SEM images. Volume percentages of connected, isolated and dead-ends networks of pore and LSM phases are estimated. Different networks of pore and LSM phases are discretized with tetrahedral elements. Finally, the finite element method (FEM) is applied to calculate effective gas diffusivity and electronic conductivity of pore and LSM phases, respectively. Geometric tortuosities are estimated from the porosity and effective transport properties. The results obtained using FEM are compared with the finite volume method (FVM) results obtained by Gunda et al. [J. Power Sources, 196(7), 35929(2011)] and other numerical results obtained on randomly generated porous medium. Effect of consideration of dead-ends and isolated-ends networks on calculation of effective transport properties is studied.
International Nuclear Information System (INIS)
Arnaud, Quentin
2015-01-01
The EDELWEISS-III experiment is dedicated to direct dark matter searches aiming at detecting WIMPS. These massive particles should account for more than 80% of the mass of the Universe and be detectable through their elastic scattering on nuclei constituting the absorber of a detector. As the expected WIMP event rate is extremely low ( 20 GeV). Finally, a study dedicated to the optimization of solid cryogenic detectors to low mass WIMP searches is presented. This study is performed on simulated data using a statistical test based on a profiled likelihood ratio that allows for statistical background subtraction and spectral shape discrimination. This study combined with results from Run308, has lead the EDELWEISS experiment to favor low mass WIMP searches ( [fr
Sommer, Gerhard; Eder, Maximilian; Kovacs, Laszlo; Pathak, Heramb; Bonitz, Lars; Mueller, Christoph; Regitnig, Peter; Holzapfel, Gerhard A
2013-11-01
A preoperative simulation of soft tissue deformations during plastic and reconstructive surgery is desirable to support the surgeon's planning and to improve surgical outcomes. The current development of constitutive adipose tissue models, for the implementation in multilayer computational frameworks for the simulation of human soft tissue deformations, has proved difficult because knowledge of the required mechanical parameters of fat tissue is limited. Therefore, for the first time, human abdominal adipose tissues were mechanically investigated by biaxial tensile and triaxial shear tests. The results of this study suggest that human abdominal adipose tissues under quasi-static and dynamic multiaxial loadings can be characterized as a nonlinear, anisotropic and viscoelastic soft biological material. The nonlinear and anisotropic features are consequences of the material's collagenous microstructure. The aligned collagenous septa observed in histological investigations causes the anisotropy of the tissue. A hyperelastic model used in this study was appropriate to represent the quasi-static multiaxial mechanical behavior of fat tissue. The constitutive parameters are intended to serve as a basis for soft tissue simulations using the finite element method, which is an apparent method for obtaining promising results in the field of plastic and reconstructive surgery. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Yvon, D
2000-06-01
The author reviews his contributions to the use of bolometers (cryogenic detectors) for the detection of wimps (weakly interactive massive particles). Wimps are detected through their elastic scattering on the nuclei of the detector, a heat signal, luminescence or ionization can be simultaneously detected (at least 2 signals are necessary to discard photon interactions). Bolometers operate at low temperatures (< 50 mK) so they allow very low detection threshold and resolution (< keV) with a full energy conversion for recoiling nuclei. In Saclay the technology of bolometers based on simultaneous detection of heat and ionisation has been developed and improvements have been studied (NbSi thin films bolometers). The first results obtained in the framework of the Edelweiss collaboration are presented. Other developments based on infra-red bolometry (Planck surveyor and Archeops projects) are briefly described. In an appendix the operating principle of a bolometer is presented. (A.C.)
FIRST STUDY OF DARK MATTER PROPERTIES WITH DETECTED SOLAR GRAVITY MODES AND NEUTRINOS
Energy Technology Data Exchange (ETDEWEB)
Turck-Chieze, S.; Garcia, R. A. [CEA/DSM/IRFU/SAp-AIM, CE Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette (France); Lopes, I. [Centro Multidisciplinar de Astrofisica, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Ballot, J. [Institut de Recherche en Astrophysique et Planetologie, CNRS, 14 avenue Edouard Belin and Universite de Toulouse, UPS-OMP, IRAP, 31400 Toulouse (France); Couvidat, S. [W.W. Hansen. E. P. L., Stanford University, Stanford, CA 94305 (United States); Mathur, S. [High Altitude Observatory, NCAR, P.O. Box 3000, Boulder, CO 80307 (United States); Salabert, D. [CNRS, Observatoire de la Cote d' Azur, Universite de Nice Sophia-Antipolis, BP 4229, 06304 Nice Cedex 4 (France); Silk, J., E-mail: Sylvaine.Turck-Chieze@cea.fr [UPMC-CNRS, UMR7095, Institut d' Astrophysique de Paris, F-75014 Paris (France)
2012-02-10
We derive new limits on the cold dark matter properties for weakly interacting massive particles (WIMPs), potentially trapped in the solar core by using for the first time the central temperature constrained by boron neutrinos and the central density constrained by the dipolar gravity modes detected with the Global Oscillations at Low Frequency/Solar Helioseismic Observatory instrument. These detections disfavor the presence of non-annihilating WIMPs for masses {<=}10 GeV and spin dependent cross-sections >5 Multiplication-Sign 10{sup -36} cm{sup 2} in the solar core but cannot constrain WIMP annihilation models. We suggest that in the coming years helio- and asteroseismology will provide complementary probes of dark matter.
Directory of Open Access Journals (Sweden)
Kristýna Šimůnková
2018-03-01
Full Text Available At present, many historical artefacts and furniture are only reconstructed and not restored. They are preserved in terms of material reparation, but their historical value decreases significantly. This work is focused on the comparison of the resistance of high-gloss polyurethane varnish with traditional shellac varnish. The varnishes were applied to oak wood and exposed to interior artificial accelerated ageing in Xenotest. Before and after ageing, cold liquid-resistance tests were performed on the tested specimens and gloss, colour, and adhesion were also evaluated. The structures of the surfaces were also analysed using a confocal laser scanning microscope. As expected, polyurethane varnish was much more durable than shellac varnish. Interestingly, shellac varnish was fairly resistant to water at the beginning, but this resistance was greatly reduced after artificial accelerated ageing. This illustrates the importance of sheltering the shellac treated artefacts in stable temperature-humidity conditions with the least possible effect of solar radiation.
Hybrid spectral CT reconstruction.
Directory of Open Access Journals (Sweden)
Darin P Clark
Full Text Available Current photon counting x-ray detector (PCD technology faces limitations associated with spectral fidelity and photon starvation. One strategy for addressing these limitations is to supplement PCD data with high-resolution, low-noise data acquired with an energy-integrating detector (EID. In this work, we propose an iterative, hybrid reconstruction technique which combines the spectral properties of PCD data with the resolution and signal-to-noise characteristics of EID data. Our hybrid reconstruction technique is based on an algebraic model of data fidelity which substitutes the EID data into the data fidelity term associated with the PCD reconstruction, resulting in a joint reconstruction problem. Within the split Bregman framework, these data fidelity constraints are minimized subject to additional constraints on spectral rank and on joint intensity-gradient sparsity measured between the reconstructions of the EID and PCD data. Following a derivation of the proposed technique, we apply it to the reconstruction of a digital phantom which contains realistic concentrations of iodine, barium, and calcium encountered in small-animal micro-CT. The results of this experiment suggest reliable separation and detection of iodine at concentrations ≥ 5 mg/ml and barium at concentrations ≥ 10 mg/ml in 2-mm features for EID and PCD data reconstructed with inherent spatial resolutions of 176 μm and 254 μm, respectively (point spread function, FWHM. Furthermore, hybrid reconstruction is demonstrated to enhance spatial resolution within material decomposition results and to improve low-contrast detectability by as much as 2.6 times relative to reconstruction with PCD data only. The parameters of the simulation experiment are based on an in vivo micro-CT experiment conducted in a mouse model of soft-tissue sarcoma. Material decomposition results produced from this in vivo data demonstrate the feasibility of distinguishing two K-edge contrast agents with
Hybrid spectral CT reconstruction
Clark, Darin P.
2017-01-01
Current photon counting x-ray detector (PCD) technology faces limitations associated with spectral fidelity and photon starvation. One strategy for addressing these limitations is to supplement PCD data with high-resolution, low-noise data acquired with an energy-integrating detector (EID). In this work, we propose an iterative, hybrid reconstruction technique which combines the spectral properties of PCD data with the resolution and signal-to-noise characteristics of EID data. Our hybrid reconstruction technique is based on an algebraic model of data fidelity which substitutes the EID data into the data fidelity term associated with the PCD reconstruction, resulting in a joint reconstruction problem. Within the split Bregman framework, these data fidelity constraints are minimized subject to additional constraints on spectral rank and on joint intensity-gradient sparsity measured between the reconstructions of the EID and PCD data. Following a derivation of the proposed technique, we apply it to the reconstruction of a digital phantom which contains realistic concentrations of iodine, barium, and calcium encountered in small-animal micro-CT. The results of this experiment suggest reliable separation and detection of iodine at concentrations ≥ 5 mg/ml and barium at concentrations ≥ 10 mg/ml in 2-mm features for EID and PCD data reconstructed with inherent spatial resolutions of 176 μm and 254 μm, respectively (point spread function, FWHM). Furthermore, hybrid reconstruction is demonstrated to enhance spatial resolution within material decomposition results and to improve low-contrast detectability by as much as 2.6 times relative to reconstruction with PCD data only. The parameters of the simulation experiment are based on an in vivo micro-CT experiment conducted in a mouse model of soft-tissue sarcoma. Material decomposition results produced from this in vivo data demonstrate the feasibility of distinguishing two K-edge contrast agents with a spectral
Collar, J I; Girard, T A; Limagne, D; Miley, H S; Waysand, G
2000-01-01
SIMPLE 2000 ({\\underline S}uperheated {\\underline I}nstrument for {\\underline M}assive {\\underline P}artic{\\underline {LE}} searches) will consist of an array of eight to sixteen large active mass ($\\sim15$ g) Superheated Droplet Detectors(SDDs) to be installed in the new underground laboratory of Rustrel-Pays d'Apt. Several factors make of SDDs an attractive approach for the detection of Weakly Interacting Massive Particles (WIMPs), namely their intrinsic insensitivity to minimum ionizing particles, high fluorine content, low cost and operation near ambient pressure and temperature. We comment here on the fabrication, calibration and already-competitive first limits from SIMPLE prototype SDDs, as well as on the expected immediate increase in sensitivity of the program, which aims at an exposure of $>$25 kg-day during the year 2000. The ability of modest-mass fluorine-rich detectors to explore regions of neutralino parameter space beyond the reach of the most ambitious cryogenic projects is pointed out.
Energy Technology Data Exchange (ETDEWEB)
Hennings-Yeomans, Raul [Case Western Reserve Univ., Cleveland, OH (United States)
2009-02-01
Non-baryonic dark matter makes one quarter of the energy density of the Universe and is concentrated in the halos of galaxies, including the Milky Way. The Weakly Interacting Massive Particle (WIMP) is a dark matter candidate with a scattering cross section with an atomic nucleus of the order of the weak interaction and a mass comparable to that of an atomic nucleus. The Cryogenic Dark Matter Search (CDMS-II) experiment, using Ge and Si cryogenic particle detectors at the Soudan Underground Laboratory, aims to directly detect nuclear recoils from WIMP interactions. This thesis presents the first 5 tower WIMP-search results from CDMS-II, an estimate of the cosmogenic neutron backgrounds expected at the Soudan Underground Laboratory, and a proposal for a new measurement of high-energy neutrons underground to benchmark the Monte Carlo simulations. Based on the non-observation of WIMPs and using standard assumptions about the galactic halo [68], the 90% C.L. upper limit of the spin-independent WIMPnucleon cross section for the first 5 tower run is 6.6 × 10^{-44}cm^{2} for a 60 GeV/c^{2} WIMP mass. A combined limit using all the data taken at Soudan results in an upper limit of 4.6×10^{-44}cm^{2} at 90% C.L.for a 60 GeV/c2 WIMP mass. This new limit corresponds to a factor of ~3 improvement over any previous CDMS-II limit and a factor of ~2 above 60 GeV/c ^{2} better than any other WIMP search to date. This thesis presents an estimation, based on Monte Carlo simulations, of the nuclear recoils produced by cosmic-ray muons and their secondaries (at the Soudan site) for a 5 tower Ge and Si configuration as well as for a 7 supertower array. The results of the Monte Carlo are that CDMS-II should expect 0.06 ± 0.02+0.18 -0.02 /kgyear unvetoed single nuclear recoils in Ge for the 5 tower configuration, and 0.05 ± 0.01+0.15 -0.02 /kg-year for the 7 supertower configuration. The systematic error is based on the available
National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Paleoclimatology Program archives reconstructions of past climatic conditions derived from paleoclimate proxies, in addition to the Program's large holdings...
International Nuclear Information System (INIS)
Chabanat, E.; D'Hondt, J.; Estre, N.; Fruehwirth, R.; Prokofiev, K.; Speer, T.; Vanlaer, P.; Waltenberger, W.
2005-01-01
Due to the high track multiplicity in the final states expected in proton collisions at the LHC experiments, novel vertex reconstruction algorithms are required. The vertex reconstruction problem can be decomposed into a pattern recognition problem ('vertex finding') and an estimation problem ('vertex fitting'). Starting from least-squares methods, robustifications of the classical algorithms are discussed and the statistical properties of the novel methods are shown. A whole set of different approaches for the vertex finding problem is presented and compared in relevant physics channels
Chabanat, E; D'Hondt, J; Vanlaer, P; Prokofiev, K; Speer, T; Frühwirth, R; Waltenberger, W
2005-01-01
Because of the high track multiplicity in the final states expected in proton collisions at the LHC experiments, novel vertex reconstruction algorithms are required. The vertex reconstruction problem can be decomposed into a pattern recognition problem ("vertex finding") and an estimation problem ("vertex fitting"). Starting from least-square methods, ways to render the classical algorithms more robust are discussed and the statistical properties of the novel methods are shown. A whole set of different approaches for the vertex finding problem is presented and compared in relevant physics channels.
Energy Technology Data Exchange (ETDEWEB)
Miramonti, L. [CEA/Saclay, Dept. d' Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l' Instrumentation Associee (DAPNIA), 91 - Gif-sur-Yvette (France)]|[Paris-11 Univ., 91 - Orsay (France)
1999-11-01
This thesis is dedicated to the detection of black matter in the form of WIMPs (weakly interacting massive particle). The characteristics of the interaction of WIMPs with matter are recalled. The very low number of expected events (<1 event/day.Kg) implies a radioactive background noise as weak as possible, furthermore the exponential decrease of the interacting rate with increasing energy calls for detectors with very low thresholds. Bolometers present advantages in WIMPs detection: i) very good resolution and very low thresholds, ii) very broad range of materials that can be used as absorber, the only requirements are: a crystal structure, to be a diamagnetic isolator and to have a convenient Debye temperature, iii) the possibility of detecting ionizing or non-ionizing particles, iv) the possibility of identifying the incident particle by measuring both temperature and another parameter such as ionization or scintillation, and v) the possibility of localizing the interaction inside the absorber by detecting ballistic phonons. The problematic of radioactive background noise is presented and the answers to the different sources (cosmic radiation,natural and artificial radioactivity) generating the background noise are examined. The materials used in the building of the detector and cryostat must be carefully chosen, they should be as little radioactive as possible. The test benches used to select materials for the Edelweiss experiment are described. The first measurements concerning the detectors Ge-4 and Ge-7 are presented. (A.C.)
International Nuclear Information System (INIS)
Lesavoy, M.A.
1985-01-01
Vaginal reconstruction can be an uncomplicated and straightforward procedure when attention to detail is maintained. The Abbe-McIndoe procedure of lining the neovaginal canal with split-thickness skin grafts has become standard. The use of the inflatable Heyer-Schulte vaginal stent provides comfort to the patient and ease to the surgeon in maintaining approximation of the skin graft. For large vaginal and perineal defects, myocutaneous flaps such as the gracilis island have been extremely useful for correction of radiation-damaged tissue of the perineum or for the reconstruction of large ablative defects. Minimal morbidity and scarring ensue because the donor site can be closed primarily. With all vaginal reconstruction, a compliant patient is a necessity. The patient must wear a vaginal obturator for a minimum of 3 to 6 months postoperatively and is encouraged to use intercourse as an excellent obturator. In general, vaginal reconstruction can be an extremely gratifying procedure for both the functional and emotional well-being of patients
... in moderate exercise and recreational activities, or play sports that put less stress on the knees. ACL reconstruction is generally recommended if: You're an athlete and want to continue in your sport, especially if the sport involves jumping, cutting or ...
Adam, Frank; Pape, Dietrich; Schiel, Karin; Steimer, Oliver; Kohn, Dieter; Rupp, Stefan
2004-01-01
Reliable fixation of the soft hamstring grafts in ACL reconstruction has been reported as problematic. The biomechanical properties of patellar tendon (PT) grafts fixed with biodegradable screws (PTBS) are superior compared to quadrupled hamstring grafts fixed with BioScrew (HBS) or Suture-Disc fixation (HSD). Controlled laboratory study with roentgen stereometric analysis (RSA). Ten porcine specimens were prepared for each group. In the PT group, the bone plugs were fixed with a 7 x 25 mm BioScrew. In the hamstring group, four-stranded tendon grafts were anchored within a tibial tunnel of 8 mm diameter either with a 7 x 25 mm BioScrew or eight polyester sutures knotted over a Suture-Disc. The grafts were loaded stepwise, and micromotion of the graft inside the tibial tunnel was measured with RSA. Hamstring grafts failed at lower loads (HBS: 536 N, HSD 445 N) than the PTBS grafts (658 N). Stiffness in the PTBS group was much greater compared to the hamstring groups (3500 N/mm versus HBS = 517 N/mm and HSD = 111 N/mm). Irreversible graft motion after graft loading with 200 N was measured at 0.03 mm (PTBS), 0.38mm (HBS), and 1.85mm (HSD). Elasticity for the HSD fixation was measured at 0.67 mm at 100 N and 1.32 mm at 200 N load. Hamstring graft fixation with BioScrew and Suture-Disc displayed less stiffness and early graft motion compared to PTBS fixation. Screw fixation of tendon grafts is superior to Suture-Disc fixation with linkage material since it offers greater stiffness and less graft motion inside the tibial tunnel. Our results revealed graft motion for hamstring fixation with screw or linkage material at loads that occur during rehabilitation. This, in turn, may lead to graft laxity.
Directory of Open Access Journals (Sweden)
Brown James
2007-12-01
Full Text Available This article aims to discuss the various defects that occur with maxillectomy with a full review of the literature and discussion of the advantages and disadvantages of the various techniques described. Reconstruction of the maxilla can be relatively simple for the standard low maxillectomy that does not involve the orbital floor (Class 2. In this situation the structure of the face is less damaged and the there are multiple reconstructive options for the restoration of the maxilla and dental alveolus. If the maxillectomy includes the orbit (Class 4 then problems involving the eye (enopthalmos, orbital dystopia, ectropion and diplopia are avoided which simplifies the reconstruction. Most controversy is associated with the maxillectomy that involves the orbital floor and dental alveolus (Class 3. A case is made for the use of the iliac crest with internal oblique as an ideal option but there are other methods, which may provide a similar result. A multidisciplinary approach to these patients is emphasised which should include a prosthodontist with a special expertise for these defects.
Primary vertex reconstruction with the ATLAS detector
International Nuclear Information System (INIS)
Meloni, F.
2016-01-01
Efficient and precise reconstruction of the primary vertex in a LHC collision is essential for determining the full kinematic properties of a hard-scatter event and of soft interactions as a measure of the amount of pile-up. The reconstruction of primary vertices in the busy, high pile-up environment of Run-2 of the LHC is a challenging task. The algorithms developed by the ATLAS experiments to reconstruct multiple vertices with small spatial separation are presented.
International Nuclear Information System (INIS)
O'Sullivan, F.; Pawitan, Y.; Harrison, R.L.; Lewellen, T.K.
1990-01-01
In statistical terms, filtered backprojection can be viewed as smoothed Least Squares (LS). In this paper, the authors report on improvement in LS resolution by: incorporating locally adaptive smoothers, imposing positivity and using statistical methods for optimal selection of the resolution parameter. The resulting algorithm has high computational efficiency relative to more elaborate Maximum Likelihood (ML) type techniques (i.e. EM with sieves). Practical aspects of the procedure are discussed in the context of PET and illustrations with computer simulated and real tomograph data are presented. The relative recovery coefficients for a 9mm sphere in a computer simulated hot-spot phantom range from .3 to .6 when the number of counts ranges from 10,000 to 640,000 respectively. The authors will also present results illustrating the relative efficacy of ML and LS reconstruction techniques
Energy Technology Data Exchange (ETDEWEB)
Gasperi, Patricia Martins Silva de
1999-07-01
The aim of this work is to investigate and apply a method for predicting petrophysical properties from bidimensional petrographic image data. Based on the assumption of statistical homogeneity, the method uses stochastic simulation to reconstruct the porous media tridimensional structure. The geometrical characterization of the simulated media allows the construction of a network model to simulate fluid flow and estimate permeability, formation factor, mercury capillary pressure curves and resistivity index as function of water saturation. This method is applied to four porous systems with different heterogeneity levels. The results demonstrate that good predictions depend on the appropriate image acquisition resolution, which identifies pores and throats that effectively control the flow properties of the system. The capillary pressure curves suggest the necessity of scale composition. The electrical properties are affected by samples porosity, with reliable estimates being restricted to water-wet systems. (author)
Breast Reconstruction After Mastectomy
... Cancer Prevention Genetics of Breast & Gynecologic Cancers Breast Cancer Screening Research Breast Reconstruction After Mastectomy On This Page What is breast reconstruction? How do surgeons use implants to reconstruct a woman’s breast? How do surgeons ...
Breast reconstruction - implants
Breast implants surgery; Mastectomy - breast reconstruction with implants; Breast cancer - breast reconstruction with implants ... harder to find a tumor if your breast cancer comes back. Getting breast implants does not take as long as breast reconstruction ...
Simulation and Track Reconstruction for Beam Telescopes
Maqbool, Salman
2017-01-01
Beam telescopes are an important tool to test new detectors under development in a particle beam. To test these novel detectors and determine their properties, the particle tracks need to be reconstructed from the known detectors in the telescope. Based on the reconstructed track, its predicted position on the Device under Test (DUT) are compared with the actual hits on the DUT. Several methods exist for track reconstruction, but most of them do not account for the effects of multiple scattering. General Broken Lines is one such algorithm which incorporates these effects during reconstruction. The aim of this project was to simulate the beam telescope and extend the track reconstruction framework for the FE-I4 telescope, which takes these effects into account. Section 1 introduces the problem, while section 2 focuses on beam telescopes. This is followed by the Allpix2 simulation framework in Section 3. And finally, Section 4 introduces the Proteus track reconstruction framework along with the General Broken ...
Quadriceps Tendon Autograft Medial Patellofemoral Ligament Reconstruction.
Fink, Christian; Steensen, Robert; Gföller, Peter; Lawton, Robert
2018-06-01
Critically evaluate the published literature related to quadriceps tendon (QT) medial patellofemoral ligament (MPFL) reconstruction. Hamstring tendon (HT) MPFL reconstruction techniques have been shown to successfully restore patella stability, but complications including patella fracture are reported. Quadriceps tendon (QT) reconstruction techniques with an intact graft pedicle on the patella side have the advantage that patella bone tunnel drilling and fixation are no longer needed, reducing risk of patella fracture. Several QT MPFL reconstruction techniques, including minimally invasive surgical (MIS) approaches, have been published with promising clinical results and fewer complications than with HT techniques. Parallel laboratory studies have shown macroscopic anatomy and biomechanical properties of QT are more similar to native MPFL than hamstring (HS) HT, suggesting QT may more accurately restore native joint kinematics. Quadriceps tendon MPFL reconstruction, via both open and MIS techniques, have promising clinical results and offer valuable alternatives to HS grafts for primary and revision MPFL reconstruction in both children and adults.
Adaptive algebraic reconstruction technique
International Nuclear Information System (INIS)
Lu Wenkai; Yin Fangfang
2004-01-01
Algebraic reconstruction techniques (ART) are iterative procedures for reconstructing objects from their projections. It is proven that ART can be computationally efficient by carefully arranging the order in which the collected data are accessed during the reconstruction procedure and adaptively adjusting the relaxation parameters. In this paper, an adaptive algebraic reconstruction technique (AART), which adopts the same projection access scheme in multilevel scheme algebraic reconstruction technique (MLS-ART), is proposed. By introducing adaptive adjustment of the relaxation parameters during the reconstruction procedure, one-iteration AART can produce reconstructions with better quality, in comparison with one-iteration MLS-ART. Furthermore, AART outperforms MLS-ART with improved computational efficiency
Polaron-Driven Surface Reconstructions
Directory of Open Access Journals (Sweden)
Michele Reticcioli
2017-09-01
Full Text Available Geometric and electronic surface reconstructions determine the physical and chemical properties of surfaces and, consequently, their functionality in applications. The reconstruction of a surface minimizes its surface free energy in otherwise thermodynamically unstable situations, typically caused by dangling bonds, lattice stress, or a divergent surface potential, and it is achieved by a cooperative modification of the atomic and electronic structure. Here, we combined first-principles calculations and surface techniques (scanning tunneling microscopy, non-contact atomic force microscopy, scanning tunneling spectroscopy to report that the repulsion between negatively charged polaronic quasiparticles, formed by the interaction between excess electrons and the lattice phonon field, plays a key role in surface reconstructions. As a paradigmatic example, we explain the (1×1 to (1×2 transition in rutile TiO_{2}(110.
Lorbach, O; Pape, D; Raber, F; Busch, L C; Kohn, D; Kieb, M
2012-11-01
Influence of the initial rotator cuff tear size and of different subregions of the SSP tendon on the cyclic loading behavior of a modified single-row reconstruction compared to a suture-bridging double-row repair. Artificial tears (25 and 35 mm) were created in the rotator cuff of 24 human cadaver shoulders. The reconstructions were performed as a single-row repair (SR) using a modified suture configuration or a suture-bridge double-row repair (DR). Radiostereometric analysis was used under cyclic loading (50 cycles, 10–180 N, 10–250 N) to calculate cyclic displacement in three different planes (anteroposterior (x), craniocaudal (y) and mediolateral (z) level). Cyclic displacement was recorded, and differences in cyclic displacement of the anterior compared to the posterior subregions of the tendon were calculated. In small-to-medium tears (25 mm) and medium-to-large tears (35 mm), significant lower cyclic displacement was seen for the SR-reconstruction compared to the DR-repair at 180 N (p ≤ 0.0001; p = 0.001) and 250 N (p = 0.001; p = 0.007) in the x-level. These results were confirmed in the y-level at 180 N (p = 0.001; p = 0.0022) and 250 N (p = 0.005; p = 0.0018). Comparison of the initial tear sizes demonstrated significant differences in cyclic displacement for the DR technique in the x-level at 180 N (p = 0.002) and 250 N (p = 0.004). Comparison of the anterior versus the posterior subregion of the tendon revealed significant lower gap formation in the posterior compared to the anterior subregions in the x-level for both tested rotator cuff repairs (p ≤ 0.05). The tested single-row repair using a modified suture configuration achieved superior results in three-dimensional measurements of cyclic displacement compared to the tested double-row suture-bridge repair. The results were dependent on the initial rupture size of the rotator cuff tear. Furthermore, significant differences were found between tendon subregions of the rotator cuff with
Esmaeilzadeh, Javad; Hesaraki, Saeed; Hadavi, Seyed Mohammad-Mehdi; Ebrahimzadeh, Mohammad Hosein; Esfandeh, Masoud
2017-08-01
In this paper, different nanocomposites made of a polymer blend (80% of PDLLA and 20% of PCL in w/w) and various amounts of a sol-gel derived bioactive glass nanoparticles (0, 1, 3 and 6wt%) were prepared using a solvent-evaporation technique. The morphology, mechanical properties and osteoblastic cell behaviors of the nanocomposites were evaluated. According to the early results, addition of bioactive glass nanoparticles to the polymer matrix reduced the tensile and flexural strength because of a non-uniform distribution of the nanoparticles. Thus, a homogeneous dispersion was obtained by surface modification of the glass nanoparticles using (3-aminopropyl)triethoxysilane as a coupling agent. The results showed that the tensile and flexural strength of the nanocomposite were improved by the nanoparticle functionalization, however the glass content was a crucial factor. The maximum tensile and flexural strength values of 38MPa and 94MPa were obtained for the polymer matrix loaded with 3wt% of the modified nanofiller and further increase of filler content led to sever agglomeration and hence a reduction of the mechanical properties. The obtained mechanical properties are favorable for anterior cruciate ligament reconstruction screws. Besides, the results of cell culture using human osteoblastic cells illustrated better cell attachment and cell growth of the nanocomposites compared to the neat polymer blend. Copyright © 2017 Elsevier B.V. All rights reserved.
Breast reconstruction - natural tissue
... flap; TRAM; Latissimus muscle flap with a breast implant; DIEP flap; DIEAP flap; Gluteal free flap; Transverse upper gracilis flap; TUG; Mastectomy - breast reconstruction with natural tissue; Breast cancer - breast reconstruction with natural tissue
Breast reconstruction after mastectomy
Directory of Open Access Journals (Sweden)
Daniel eSchmauss
2016-01-01
Full Text Available Breast cancer is the leading cause of cancer death in women worldwide. Its surgical approach has become less and less mutilating in the last decades. However, the overall number of breast reconstructions has significantly increased lately. Nowadays breast reconstruction should be individualized at its best, first of all taking into consideration oncological aspects of the tumor, neo-/adjuvant treatment and genetic predisposition, but also its timing (immediate versus delayed breast reconstruction, as well as the patient’s condition and wish. This article gives an overview over the various possibilities of breast reconstruction, including implant- and expander-based reconstruction, flap-based reconstruction (vascularized autologous tissue, the combination of implant and flap, reconstruction using non-vascularized autologous fat, as well as refinement surgery after breast reconstruction.
Clinical applications of iterative reconstruction
International Nuclear Information System (INIS)
Eberl, S.
1998-01-01
Expectation maximisation (EM) reconstruction largely eliminates the hot and cold streaking artifacts characteristic of filtered-back projection (FBP) reconstruction around localised hot areas, such as the bladder. It also substantially reduces the problem of decreased inferior wall counts in MIBI myocardial perfusion studies due to ''streaking'' from high liver uptake. Non-uniform attenuation and scatter correction, resolution recovery, anatomical information, e.g. from MRI or CT tracer kinetic modelling, can all be built into the EM reconstruction imaging model. The properties of ordered subset EM (OSEM) have also been used to correct for known patient motion as part of the reconstruction process. These uses of EM are elaborated more fully in some of the other abstracts of this meeting. Currently we use OSEM routinely for: (i) studies where streaking is a problem, including all MIBI myocardial perfusion studies, to avoid hot liver inferior wall artifact, (ii) all whole body FDG PET, all lung V/Q SPECT (which have a short acquisition time) and all gated 201 TI myocardial perfusion studies due to improved noise characteristics of OSEM in these studies; (iii) studies with measured, non-uniform attenuation correction. With the accelerated OSEM algorithm, iterative reconstruction is practical for routine clinical applications and we have found OSEM to provide clearly superior reconstructions for the areas listed above and are investigating its application to other studies. In clinical use, we have not found OSEM to introduce artifacts which would not also occur with FBP, e.g. uncorrected patient motion will cause artifacts with both OSEM and FBP
DEFF Research Database (Denmark)
Paradowski, Przemysław T; Witoński, Dariusz; Kęska, Rafał
2013-01-01
Knee Injury and Osteoarthritis Outcome Score (KOOS) is available in over 30 languages and a commonly used Patient-Reported Outcome (PRO) for assessment of treatment effects following knee surgery. The aim of the study was to report the linguistic translational process and evaluate the psychometri...... properties of the Polish version of the KOOS questionnaire....
International Nuclear Information System (INIS)
Dolgorouky, Y.W.
2008-09-01
The EDELWEISS experiment aims at the direct detection of WIMPs as possible candidates for dark matter. It uses heat-and-ionization detectors that can discriminate these particles from the radioactive background. To date, this method is limited by events with incomplete charge collection that occur just beneath the detectors electrodes. In order to identify and reject these undesirable events, we have developed detectors equipped with thin films used both as thermometers - and hence sensitive to the transient athermal regime - and as electrodes for the charge collection. This thesis focuses on the optimization of such thin films regarding surface events rejection and on the modelling of the physical processes enabling this identification. The optimization must both maximize the fiducial volume and conserve an energy resolution such that the recoil energy threshold is of the order of 30 keV. Our work explores four generations of detectors each of which corresponds to successive evolutions in their conception. In all cases, the electrode-thermometer is an amorphous Anderson insulator NbSi thin film polarized by two interleaved comb-shaped niobium electrodes. In spite of constant progress in the successive detectors performances, the latest generation does not display the performances required for the EDELWEISS II experiment. Our work has shown the difficulty of the transient thermal signal modelling due to the complex contribution of the charge collection. This works has lead to new ideas regarding the detectors configuration, so that the athermal regime can be optimized to enhance both the rejection capability and the resolution. (author)
Garcia-March, Jose Rafael; Surge, Donna; Tena-Medialdea, Jose; Torres, Javi; Garcia-Martinez, Micaela
2017-04-01
We analysed the stable isotope ratios (δ18O and δ13C) from the calcite of the outer prismatic layer of 8 Pinna nobilis shells at a rate of c. 12-16 samples/year for years between 1997 and 2013. These produced 8 time series between 4 and 16 years long. The empty shells had been collected in two Spanish marine protected areas, Tabarca Island in Alicante and Columbretes Islands in Castellón (4 specimens each). For all shells we constrained the time of death within at least a halve year window. The present study completes previous calibrations by using recorded seawater temperature data during at least two years for each site, coinciding with part of the analysed periods in the shells. Our preliminary results clearly reflect the seasonality of the signal in δ18O values for the entire ontogeny of the individuals studied. However, one specimen from Tabarca Island sampled between years 4 and 11 (corresponding to real age) shows a clear ontogenetic change, with an abrupt reduction in the amplitude of the signal from age 6 to 11 for both δ18O and δ13C values. We hypothesize this pattern relates to the onset of first gonad maturation. Values of δ13C track δ18O values in most individuals, but 3 specimens show low amplitude. For all time series, δ13C values show a decreasing slope with ontogeny similar to previous observations in P. nobilis and other bivalves. Estimated seawater temperature from our δ18O time series reveals the potential of P. nobilis shells as valuable archives of Mediterranean temperature reconstructions in the context of climate change.
An analytical statistical approach to the 3D reconstruction problem
Energy Technology Data Exchange (ETDEWEB)
Cierniak, Robert [Czestochowa Univ. of Technology (Poland). Inst. of Computer Engineering
2011-07-01
The presented here approach is concerned with the reconstruction problem for 3D spiral X-ray tomography. The reconstruction problem is formulated taking into considerations the statistical properties of signals obtained in X-ray CT. Additinally, image processing performed in our approach is involved in analytical methodology. This conception significantly improves quality of the obtained after reconstruction images and decreases the complexity of the reconstruction problem in comparison with other approaches. Computer simulations proved that schematically described here reconstruction algorithm outperforms conventional analytical methods in obtained image quality. (orig.)
Piele, Philip K.
Numerous cases in this year's chapter dealt with the same topics of previous years--contracts and bids for building construction, and detachment and annexation of a portion of a school district. The courts continued to attribute board discretionary authority to school boards in school property matters. Intergovernmental disputes over ownership or…
Atmospheric muons reconstruction with Antares
International Nuclear Information System (INIS)
Melissas, M.
2007-09-01
The ANTARES collaboration is building a neutrino telescope in the Mediterranean Sea. This detector contains 900 photomultiplier tubes, dispatched on 12 lines, in order to detect Cerenkov light from muon induced by neutrino interactions in the the vicinity of the detector. Currently the first 5 lines have been deployed. A first task consists in studying the stability of the detector calibration, which is a necessary step to understand the detector response. Then we studied optical properties of water, for this we developed a reconstruction method dedicated to LED Beacon. The extracted parameters are compatible with earlier measurements. A quality criteria to reject badly reconstructed track has been developed based on the likelihood of the tracks fit versus point fit. This has been applied to real data and a preliminary analysis of atmospheric muons with a 5-lines detector is performed. (author)
Vertex Reconstruction and Performance in ATLAS
Whitmore, Ben William; The ATLAS collaboration
2017-01-01
Efficient and precise reconstruction of the primary vertices in LHC collisions is essential in both the reconstruction of the full kinematic properties of a hard-scatter event and of soft interactions as a measure of the amount of pile-up. The reconstruction of the primary vertices in the busy, high pile up environment of the LHC is a challenging task. The challenges and novel methods developed by the ATLAS experiment to reconstruct vertices in such environments will be presented. The performance of the current vertexing algorithms using Run-2 data will be presented and compared to results from simulation. Additionally, data-driven methods to evaluate vertex resolution, and details of upgrades to the ATLAS inner detector will be presented.
DD4Hep based event reconstruction
AUTHOR|(SzGeCERN)683529; Frank, Markus; Gaede, Frank-Dieter; Hynds, Daniel; Lu, Shaojun; Nikiforou, Nikiforos; Petric, Marko; Simoniello, Rosa; Voutsinas, Georgios Gerasimos
The DD4HEP detector description toolkit offers a flexible and easy-to-use solution for the consistent and complete description of particle physics detectors in a single system. The sub-component DDREC provides a dedicated interface to the detector geometry as needed for event reconstruction. With DDREC there is no need to define an additional, separate reconstruction geometry as is often done in HEP, but one can transparently extend the existing detailed simulation model to be also used for the reconstruction. Based on the extension mechanism of DD4HEP, DDREC allows one to attach user defined data structures to detector elements at all levels of the geometry hierarchy. These data structures define a high level view onto the detectors describing their physical properties, such as measurement layers, point resolutions, and cell sizes. For the purpose of charged particle track reconstruction, dedicated surface objects can be attached to every volume in the detector geometry. These surfaces provide the measuremen...
An Intelligent Actuator Fault Reconstruction Scheme for Robotic Manipulators.
Xiao, Bing; Yin, Shen
2018-02-01
This paper investigates a difficult problem of reconstructing actuator faults for robotic manipulators. An intelligent approach with fast reconstruction property is developed. This is achieved by using observer technique. This scheme is capable of precisely reconstructing the actual actuator fault. It is shown by Lyapunov stability analysis that the reconstruction error can converge to zero after finite time. A perfect reconstruction performance including precise and fast properties can be provided for actuator fault. The most important feature of the scheme is that, it does not depend on control law, dynamic model of actuator, faults' type, and also their time-profile. This super reconstruction performance and capability of the proposed approach are further validated by simulation and experimental results.
Directory of Open Access Journals (Sweden)
Kuhbier, Jörn W.
2015-08-01
Full Text Available The isolation and expansion of multipotent mesenchymal stem cells (MSCs could be demonstrated from bone marrow, peripheral blood, skin, umbilical cord blood and adipose issue. They can be differentiated to different mesodermal cell lines like bone, cartilage, muscle or adipose tissue cells as well as . Thus MSCs represent an attractive cell population for the substitution of mesenchymal tissues via tissue engineering due to their potential of differentiation and their favourable expansion properties. In contrast to embryonic stem cells (ESCs they have the advantage that they can be autologously harvested in high numbers. Besides, there are fewer ethical issues in the use of MSCs. Another advantage of MSCs is the highly regenerative secretion profile of cytokines and growth factors, in particular supporting angiogenesis. A plethora of studies describe the morphological and phenotypical characterization of this cell type as well as regulatory mechanisms lying the differentiation into specific tissues aiming to optimize conditions for differentiation and thus clinical application. This review describes the definition of a mesenchymal stem cell, methods for isolation and phenotypical characterization, possibilities of differentiation and possible therapeutical applications of MSCs.
Image Reconstruction. Chapter 13
Energy Technology Data Exchange (ETDEWEB)
Nuyts, J. [Department of Nuclear Medicine and Medical Imaging Research Center, Katholieke Universiteit Leuven, Leuven (Belgium); Matej, S. [Medical Image Processing Group, Department of Radiology, University of Pennsylvania, Philadelphia, PA (United States)
2014-12-15
This chapter discusses how 2‑D or 3‑D images of tracer distribution can be reconstructed from a series of so-called projection images acquired with a gamma camera or a positron emission tomography (PET) system [13.1]. This is often called an ‘inverse problem’. The reconstruction is the inverse of the acquisition. The reconstruction is called an inverse problem because making software to compute the true tracer distribution from the acquired data turns out to be more difficult than the ‘forward’ direction, i.e. making software to simulate the acquisition. There are basically two approaches to image reconstruction: analytical reconstruction and iterative reconstruction. The analytical approach is based on mathematical inversion, yielding efficient, non-iterative reconstruction algorithms. In the iterative approach, the reconstruction problem is reduced to computing a finite number of image values from a finite number of measurements. That simplification enables the use of iterative instead of mathematical inversion. Iterative inversion tends to require more computer power, but it can cope with more complex (and hopefully more accurate) models of the acquisition process.
Update on orbital reconstruction.
Chen, Chien-Tzung; Chen, Yu-Ray
2010-08-01
Orbital trauma is common and frequently complicated by ocular injuries. The recent literature on orbital fracture is analyzed with emphasis on epidemiological data assessment, surgical timing, method of approach and reconstruction materials. Computed tomographic (CT) scan has become a routine evaluation tool for orbital trauma, and mobile CT can be applied intraoperatively if necessary. Concomitant serious ocular injury should be carefully evaluated preoperatively. Patients presenting with nonresolving oculocardiac reflex, 'white-eyed' blowout fracture, or diplopia with a positive forced duction test and CT evidence of orbital tissue entrapment require early surgical repair. Otherwise, enophthalmos can be corrected by late surgery with a similar outcome to early surgery. The use of an endoscope-assisted approach for orbital reconstruction continues to grow, offering an alternative method. Advances in alloplastic materials have improved surgical outcome and shortened operating time. In this review of modern orbital reconstruction, several controversial issues such as surgical indication, surgical timing, method of approach and choice of reconstruction material are discussed. Preoperative fine-cut CT image and thorough ophthalmologic examination are key elements to determine surgical indications. The choice of surgical approach and reconstruction materials much depends on the surgeon's experience and the reconstruction area. Prefabricated alloplastic implants together with image software and stereolithographic models are significant advances that help to more accurately reconstruct the traumatized orbit. The recent evolution of orbit reconstruction improves functional and aesthetic results and minimizes surgical complications.
Permutationally invariant state reconstruction
DEFF Research Database (Denmark)
Moroder, Tobias; Hyllus, Philipp; Tóth, Géza
2012-01-01
Feasible tomography schemes for large particle numbers must possess, besides an appropriate data acquisition protocol, an efficient way to reconstruct the density operator from the observed finite data set. Since state reconstruction typically requires the solution of a nonlinear large-scale opti...... optimization, which has clear advantages regarding speed, control and accuracy in comparison to commonly employed numerical routines. First prototype implementations easily allow reconstruction of a state of 20 qubits in a few minutes on a standard computer.......-scale optimization problem, this is a major challenge in the design of scalable tomography schemes. Here we present an efficient state reconstruction scheme for permutationally invariant quantum state tomography. It works for all common state-of-the-art reconstruction principles, including, in particular, maximum...
Energy Technology Data Exchange (ETDEWEB)
Dolgorouky, Y.W.
2008-09-15
The EDELWEISS experiment aims at the direct detection of WIMPs as possible candidates for dark matter. It uses heat-and-ionization detectors that can discriminate these particles from the radioactive background. To date, this method is limited by events with incomplete charge collection that occur just beneath the detectors electrodes. In order to identify and reject these undesirable events, we have developed detectors equipped with thin films used both as thermometers - and hence sensitive to the transient athermal regime - and as electrodes for the charge collection. This thesis focuses on the optimization of such thin films regarding surface events rejection and on the modelling of the physical processes enabling this identification. The optimization must both maximize the fiducial volume and conserve an energy resolution such that the recoil energy threshold is of the order of 30 keV. Our work explores four generations of detectors each of which corresponds to successive evolutions in their conception. In all cases, the electrode-thermometer is an amorphous Anderson insulator NbSi thin film polarized by two interleaved comb-shaped niobium electrodes. In spite of constant progress in the successive detectors performances, the latest generation does not display the performances required for the EDELWEISS II experiment. Our work has shown the difficulty of the transient thermal signal modelling due to the complex contribution of the charge collection. This works has lead to new ideas regarding the detectors configuration, so that the athermal regime can be optimized to enhance both the rejection capability and the resolution. (author)
Simulation and track reconstruction for beam telescopes
Maqbool, Salman
2017-01-01
Beam telescopes are used for testing new detectors under development. Sensors are placed and a particle beam is passed through them. To test these novel detectors and determine their properties, the particle tracks need to be reconstructed from the known detectors in the telescope. Based on the reconstructed track, it’s predicted hits on the Device under Test (DUT) are compared with the actual hits on the DUT. Several methods exist for track reconstruction, but most of them don’t account for the effects of multiple scattering. General Broken Lines is one such algorithm which incorporates these effects during reconstruction. The aim of this project was to simulate the beam telescope and extend the track reconstruction framework for the FE-I4 telescope, which takes these effects into account. Section 1 introduces the problem, while section 2 focuses on beam telescopes. This is followed by the Allpix2 simulation framework in Section 3. And finally, Section 4 introduces the Proteus track reconstruction framew...
Overview of image reconstruction
International Nuclear Information System (INIS)
Marr, R.B.
1980-04-01
Image reconstruction (or computerized tomography, etc.) is any process whereby a function, f, on R/sup n/ is estimated from empirical data pertaining to its integrals, ∫f(x) dx, for some collection of hyperplanes of dimension k < n. The paper begins with background information on how image reconstruction problems have arisen in practice, and describes some of the application areas of past or current interest; these include radioastronomy, optics, radiology and nuclear medicine, electron microscopy, acoustical imaging, geophysical tomography, nondestructive testing, and NMR zeugmatography. Then the various reconstruction algorithms are discussed in five classes: summation, or simple back-projection; convolution, or filtered back-projection; Fourier and other functional transforms; orthogonal function series expansion; and iterative methods. Certain more technical mathematical aspects of image reconstruction are considered from the standpoint of uniqueness, consistency, and stability of solution. The paper concludes by presenting certain open problems. 73 references
The evolving breast reconstruction
DEFF Research Database (Denmark)
Thomsen, Jørn Bo; Gunnarsson, Gudjon Leifur
2014-01-01
The aim of this editorial is to give an update on the use of the propeller thoracodorsal artery perforator flap (TAP/TDAP-flap) within the field of breast reconstruction. The TAP-flap can be dissected by a combined use of a monopolar cautery and a scalpel. Microsurgical instruments are generally...... not needed. The propeller TAP-flap can be designed in different ways, three of these have been published: (I) an oblique upwards design; (II) a horizontal design; (III) an oblique downward design. The latissimus dorsi-flap is a good and reliable option for breast reconstruction, but has been criticized...... for oncoplastic and reconstructive breast surgery and will certainly become an invaluable addition to breast reconstructive methods....
Forging Provincial Reconstruction Teams
National Research Council Canada - National Science Library
Honore, Russel L; Boslego, David V
2007-01-01
The Provincial Reconstruction Team (PRT) training mission completed by First U.S. Army in April 2006 was a joint Service effort to meet a requirement from the combatant commander to support goals in Afghanistan...
Breast Reconstruction with Implants
... your surgical options and discuss the advantages and disadvantages of implant-based reconstruction, and may show you ... Policy Notice of Privacy Practices Notice of Nondiscrimination Advertising Mayo Clinic is a not-for-profit organization ...
Multicore Performance of Block Algebraic Iterative Reconstruction Methods
DEFF Research Database (Denmark)
Sørensen, Hans Henrik B.; Hansen, Per Christian
2014-01-01
Algebraic iterative methods are routinely used for solving the ill-posed sparse linear systems arising in tomographic image reconstruction. Here we consider the algebraic reconstruction technique (ART) and the simultaneous iterative reconstruction techniques (SIRT), both of which rely on semiconv......Algebraic iterative methods are routinely used for solving the ill-posed sparse linear systems arising in tomographic image reconstruction. Here we consider the algebraic reconstruction technique (ART) and the simultaneous iterative reconstruction techniques (SIRT), both of which rely...... on semiconvergence. Block versions of these methods, based on a partitioning of the linear system, are able to combine the fast semiconvergence of ART with the better multicore properties of SIRT. These block methods separate into two classes: those that, in each iteration, access the blocks in a sequential manner...... a fixed relaxation parameter in each method, namely, the one that leads to the fastest semiconvergence. Computational results show that for multicore computers, the sequential approach is preferable....
Systems biology: properties of reconstructed networks
National Research Council Canada - National Science Library
Palsson, Bernhard
2006-01-01
... between the mathematical ideas and biological processes are made clear, the book reﬂects the irreversible trend of increasing mathematical content in biology education. Therefore to assist both teacher and student, Palsson provides problem sets, projects, and PowerPoint slides in an associated web site and keeps the presentation in the book concrete with illustrat...
Interval-based reconstruction for uncertainty quantification in PET
Kucharczak, Florentin; Loquin, Kevin; Buvat, Irène; Strauss, Olivier; Mariano-Goulart, Denis
2018-02-01
A new directed interval-based tomographic reconstruction algorithm, called non-additive interval based expectation maximization (NIBEM) is presented. It uses non-additive modeling of the forward operator that provides intervals instead of single-valued projections. The detailed approach is an extension of the maximum likelihood—expectation maximization algorithm based on intervals. The main motivation for this extension is that the resulting intervals have appealing properties for estimating the statistical uncertainty associated with the reconstructed activity values. After reviewing previously published theoretical concepts related to interval-based projectors, this paper describes the NIBEM algorithm and gives examples that highlight the properties and advantages of this interval valued reconstruction.
Industrial dynamic tomographic reconstruction
International Nuclear Information System (INIS)
Oliveira, Eric Ferreira de
2016-01-01
The state of the art methods applied to industrial processes is currently based on the principles of classical tomographic reconstructions developed for tomographic patterns of static distributions, or is limited to cases of low variability of the density distribution function of the tomographed object. Noise and motion artifacts are the main problems caused by a mismatch in the data from views acquired in different instants. All of these add to the known fact that using a limited amount of data can result in the presence of noise, artifacts and some inconsistencies with the distribution under study. One of the objectives of the present work is to discuss the difficulties that arise from implementing reconstruction algorithms in dynamic tomography that were originally developed for static distributions. Another objective is to propose solutions that aim at reducing a temporal type of information loss caused by employing regular acquisition systems to dynamic processes. With respect to dynamic image reconstruction it was conducted a comparison between different static reconstruction methods, like MART and FBP, when used for dynamic scenarios. This comparison was based on a MCNPx simulation as well as an analytical setup of an aluminum cylinder that moves along the section of a riser during the process of acquisition, and also based on cross section images from CFD techniques. As for the adaptation of current tomographic acquisition systems for dynamic processes, this work established a sequence of tomographic views in a just-in-time fashion for visualization purposes, a form of visually disposing density information as soon as it becomes amenable to image reconstruction. A third contribution was to take advantage of the triple color channel necessary to display colored images in most displays, so that, by appropriately scaling the acquired values of each view in the linear system of the reconstruction, it was possible to imprint a temporal trace into the regularly
Alternative reconstruction after pancreaticoduodenectomy
Directory of Open Access Journals (Sweden)
Cooperman Avram M
2008-01-01
Full Text Available Abstract Background Pancreaticoduodenectomy is the procedure of choice for tumors of the head of the pancreas and periampulla. Despite advances in surgical technique and postoperative care, the procedure continues to carry a high morbidity rate. One of the most common morbidities is delayed gastric emptying with rates of 15%–40%. Following two prolonged cases of delayed gastric emptying, we altered our reconstruction to avoid this complication altogether. Subsequently, our patients underwent a classic pancreaticoduodenectomy with an undivided Roux-en-Y technique for reconstruction. Methods We reviewed the charts of our last 13 Whipple procedures evaluating them for complications, specifically delayed gastric emptying. We compared the outcomes of those patients to a control group of 15 patients who underwent the Whipple procedure with standard reconstruction. Results No instances of delayed gastric emptying occurred in patients who underwent an undivided Roux-en-Y technique for reconstruction. There was 1 wound infection (8%, 1 instance of pneumonia (8%, and 1 instance of bleeding from the gastrojejunal staple line (8%. There was no operative mortality. Conclusion Use of the undivided Roux-en-Y technique for reconstruction following the Whipple procedure may decrease the incidence of delayed gastric emptying. In addition, it has the added benefit of eliminating bile reflux gastritis. Future randomized control trials are recommended to further evaluate the efficacy of the procedure.
A clinical perspective of accelerated statistical reconstruction
International Nuclear Information System (INIS)
Hutton, B.F.; Hudson, H.M.; Beekman, F.J.
1997-01-01
Although the potential benefits of maximum likelihood reconstruction have been recognised for many years, the technique has only recently found widespread popularity in clinical practice. Factors which have contributed to the wider acceptance include improved models for the emission process, better understanding of the properties of the algorithm and, not least, the practicality of application with the development of acceleration schemes and the improved speed of computers. The objective in this article is to present a framework for applying maximum likelihood reconstruction for a wide range of clinically based problems. The article draws particularly on the experience of the three authors in applying an acceleration scheme involving use of ordered subsets to a range of applications. The potential advantages of statistical reconstruction techniques include: (a) the ability to better model the emission and detection process, in order to make the reconstruction converge to a quantitative image, (b) the inclusion of a statistical noise model which results in better noise characteristics, and (c) the possibility to incorporate prior knowledge about the distribution being imaged. The great flexibility in adapting the reconstruction for a specific model results in these techniques having wide applicability to problems in clinical nuclear medicine. (orig.). With 8 figs., 1 tab
Dynamic dual-tracer PET reconstruction.
Gao, Fei; Liu, Huafeng; Jian, Yiqiang; Shi, Pengcheng
2009-01-01
Although of important medical implications, simultaneous dual-tracer positron emission tomography reconstruction remains a challenging problem, primarily because the photon measurements from dual tracers are overlapped. In this paper, we propose a simultaneous dynamic dual-tracer reconstruction of tissue activity maps based on guidance from tracer kinetics. The dual-tracer reconstruction problem is formulated in a state-space representation, where parallel compartment models serve as continuous-time system equation describing the tracer kinetic processes of dual tracers, and the imaging data is expressed as discrete sampling of the system states in measurement equation. The image reconstruction problem has therefore become a state estimation problem in a continuous-discrete hybrid paradigm, and H infinity filtering is adopted as the estimation strategy. As H infinity filtering makes no assumptions on the system and measurement statistics, robust reconstruction results can be obtained for the dual-tracer PET imaging system where the statistical properties of measurement data and system uncertainty are not available a priori, even when there are disturbances in the kinetic parameters. Experimental results on digital phantoms, Monte Carlo simulations and physical phantoms have demonstrated the superior performance.
Primary Vertex Reconstruction at the ATLAS Experiment
Grimm, Kathryn; The ATLAS collaboration
2016-01-01
Efficient and precise reconstruction of the primary vertex in an LHC collision is essential in both the reconstruction of the full kinematic properties of a hard-scatter event and of soft interactions as a measure of the amount of pile-up. The reconstruction of primary vertices in the busy, high pile-up environment of Run-2 of the LHC is a challenging task. New methods have been developed by the ATLAS experiment to reconstruct vertices in such environments. Advances in vertex seeding include methods taken from medical imaging, which allow for reconstruction of multiple vertices with small spatial separation. The adoption of this new seeding algorithm within the ATLAS adaptive vertex finding and fitting procedure will be discussed, and the first results of the new techniques from Run-2 data will be presented. Additionally, data-driven methods to evaluate vertex resolution will be presented with special focus on correct methods to evaluate the effect of the beam spot constraint; results from these methods in Ru...
International Nuclear Information System (INIS)
Yeong, C.L.; Torquato, S.
1998-01-01
We formulate a procedure to reconstruct the structure of general random heterogeneous media from limited morphological information by extending the methodology of Rintoul and Torquato [J. Colloid Interface Sci. 186, 467 (1997)] developed for dispersions. The procedure has the advantages that it is simple to implement and generally applicable to multidimensional, multiphase, and anisotropic structures. Furthermore, an extremely useful feature is that it can incorporate any type and number of correlation functions in order to provide as much morphological information as is necessary for accurate reconstruction. We consider a variety of one- and two-dimensional reconstructions, including periodic and random arrays of rods, various distribution of disks, Debye random media, and a Fontainebleau sandstone sample. We also use our algorithm to construct heterogeneous media from specified hypothetical correlation functions, including an exponentially damped, oscillating function as well as physically unrealizable ones. copyright 1998 The American Physical Society
Delayed breast implant reconstruction
DEFF Research Database (Denmark)
Hvilsom, Gitte B.; Hölmich, Lisbet R.; Steding-Jessen, Marianne
2012-01-01
We evaluated the association between radiation therapy and severe capsular contracture or reoperation after 717 delayed breast implant reconstruction procedures (288 1- and 429 2-stage procedures) identified in the prospective database of the Danish Registry for Plastic Surgery of the Breast during...... of radiation therapy was associated with a non-significantly increased risk of reoperation after both 1-stage (HR = 1.4; 95% CI: 0.7-2.5) and 2-stage (HR = 1.6; 95% CI: 0.9-3.1) procedures. Reconstruction failure was highest (13.2%) in the 2-stage procedures with a history of radiation therapy. Breast...... reconstruction approaches other than implants should be seriously considered among women who have received radiation therapy....
HEEL BONE RECONSTRUCTIVE OSTEOSYNTHESIS
Directory of Open Access Journals (Sweden)
A. N. Svetashov
2010-01-01
Full Text Available To detect the most appropriate to heel bone injury severity variants of reconstructive osteosynthesis it was analyzed treatment results of 56 patients. In 15 (26.8% patients classic methods of surgical service were applied, in 41 (73.2% cases to restore the defect porous implants were used. Osteosynthesis without heel bone plastic restoration accomplishment was ineffective in 60% patients from control group. Reconstructive osteosynthesis method ensures long-term good functional effect of rehabilitation in 96.4% patients from the basic group.
Reconstructing Neutrino Mass Spectrum
Smirnov, A. Yu.
1999-01-01
Reconstruction of the neutrino mass spectrum and lepton mixing is one of the fundamental problems of particle physics. In this connection we consider two central topics: (i) the origin of large lepton mixing, (ii) possible existence of new (sterile) neutrino states. We discuss also possible relation between large mixing and existence of sterile neutrinos.
Position reconstruction in LUX
Akerib, D. S.; Alsum, S.; Araújo, H. M.; Bai, X.; Bailey, A. J.; Balajthy, J.; Beltrame, P.; Bernard, E. P.; Bernstein, A.; Biesiadzinski, T. P.; Boulton, E. M.; Brás, P.; Byram, D.; Cahn, S. B.; Carmona-Benitez, M. C.; Chan, C.; Currie, A.; Cutter, J. E.; Davison, T. J. R.; Dobi, A.; Druszkiewicz, E.; Edwards, B. N.; Fallon, S. R.; Fan, A.; Fiorucci, S.; Gaitskell, R. J.; Genovesi, J.; Ghag, C.; Gilchriese, M. G. D.; Hall, C. R.; Hanhardt, M.; Haselschwardt, S. J.; Hertel, S. A.; Hogan, D. P.; Horn, M.; Huang, D. Q.; Ignarra, C. M.; Jacobsen, R. G.; Ji, W.; Kamdin, K.; Kazkaz, K.; Khaitan, D.; Knoche, R.; Larsen, N. A.; Lenardo, B. G.; Lesko, K. T.; Lindote, A.; Lopes, M. I.; Manalaysay, A.; Mannino, R. L.; Marzioni, M. F.; McKinsey, D. N.; Mei, D.-M.; Mock, J.; Moongweluwan, M.; Morad, J. A.; Murphy, A. St. J.; Nehrkorn, C.; Nelson, H. N.; Neves, F.; O'Sullivan, K.; Oliver-Mallory, K. C.; Palladino, K. J.; Pease, E. K.; Rhyne, C.; Shaw, S.; Shutt, T. A.; Silva, C.; Solmaz, M.; Solovov, V. N.; Sorensen, P.; Sumner, T. J.; Szydagis, M.; Taylor, D. J.; Taylor, W. C.; Tennyson, B. P.; Terman, P. A.; Tiedt, D. R.; To, W. H.; Tripathi, M.; Tvrznikova, L.; Uvarov, S.; Velan, V.; Verbus, J. R.; Webb, R. C.; White, J. T.; Whitis, T. J.; Witherell, M. S.; Wolfs, F. L. H.; Xu, J.; Yazdani, K.; Young, S. K.; Zhang, C.
2018-02-01
The (x, y) position reconstruction method used in the analysis of the complete exposure of the Large Underground Xenon (LUX) experiment is presented. The algorithm is based on a statistical test that makes use of an iterative method to recover the photomultiplier tube (PMT) light response directly from the calibration data. The light response functions make use of a two dimensional functional form to account for the photons reflected on the inner walls of the detector. To increase the resolution for small pulses, a photon counting technique was employed to describe the response of the PMTs. The reconstruction was assessed with calibration data including 83mKr (releasing a total energy of 41.5 keV) and 3H (β- with Q = 18.6 keV) decays, and a deuterium-deuterium (D-D) neutron beam (2.45 MeV) . Within the detector's fiducial volume, the reconstruction has achieved an (x, y) position uncertainty of σ = 0.82 cm and σ = 0.17 cm for events of only 200 and 4,000 detected electroluminescence photons respectively. Such signals are associated with electron recoils of energies ~0.25 keV and ~10 keV, respectively. The reconstructed position of the smallest events with a single electron emitted from the liquid surface (22 detected photons) has a horizontal (x, y) uncertainty of 2.13 cm.
Application of iterative reconstruction in dynamic studies
International Nuclear Information System (INIS)
Meikle, S.R.
1998-01-01
Full text: The conventional approach to analysing dynamic tomographic data (SPECT or PET) is to reconstruct projections corresponding to each time interval separately and then fit a suitable tracer kinetic model to the dynamic sequence (method 1 ) . This approach assumes that the tracer distribution remains static during any given time interval and, for practical reasons, filtered back-projection (FBP) is the preferred reconstruction algorithm. However, alternative approaches exist which lend themselves to iterative algorithms, such as EM. One approach is to fit the model directly to the projection data, followed by EM reconstruction of the parameter estimates (method 2). This requires that the tracer model can be expressed as a linear function of the unknown model parameters. A third alternative is to incorporate the tracer model into the reconstruction algorithm (method 3). Such an extension was described during the early development of the EM algorithm, referred to as the EM parametric image reconstruction algorithm (EM-PIRA). We have investigated these various strategies for analysing dynamic data and their relative pros and cons. Tracer modelling was performed using a general model, referred to as spectral analysis, which makes no restriction on the number of physiological compartments and satisfies the linearity requirement of method 2. A kinetic software phantom was created and used to test the convergence and noise properties of the different approaches. In summary, method 2 is the most practical as it reduces the number of reconstructions by at least an order of magnitude and provides improved signal-to-noise ratios compared with method 1. EM-PIRA allows greater flexibility in the choice of parametric images and appears to have a regularising effect on convergence. Methods 2 and 3 are also better suited to dynamic scanning with a rotating camera, as they can potentially account for changes in tracer distribution between projections
Algebraic reconstruction techniques for spectral reconstruction in diffuse optical tomography
International Nuclear Information System (INIS)
Brendel, Bernhard; Ziegler, Ronny; Nielsen, Tim
2008-01-01
Reconstruction in diffuse optical tomography (DOT) necessitates solving the diffusion equation, which is nonlinear with respect to the parameters that have to be reconstructed. Currently applied solving methods are based on the linearization of the equation. For spectral three-dimensional reconstruction, the emerging equation system is too large for direct inversion, but the application of iterative methods is feasible. Computational effort and speed of convergence of these iterative methods are crucial since they determine the computation time of the reconstruction. In this paper, the iterative methods algebraic reconstruction technique (ART) and conjugated gradients (CGs) as well as a new modified ART method are investigated for spectral DOT reconstruction. The aim of the modified ART scheme is to speed up the convergence by considering the specific conditions of spectral reconstruction. As a result, it converges much faster to favorable results than conventional ART and CG methods
Liquid Argon TPC Signal Formation, Signal Processing and Hit Reconstruction
Energy Technology Data Exchange (ETDEWEB)
Baller, Bruce [Fermilab
2017-03-11
This document describes the early stage of the reconstruction chain that was developed for the ArgoNeuT and MicroBooNE experiments at Fermilab. These experiments study accelerator neutrino interactions that occur in a Liquid Argon Time Projection Chamber. Reconstructing the properties of particles produced in these interactions requires knowledge of the micro-physics processes that affect the creation and transport of ionization electrons to the readout system. A wire signal deconvolution technique was developed to convert wire signals to a standard form for hit reconstruction, to remove artifacts in the electronics chain and to remove coherent noise.
Arctic Sea Level Reconstruction
DEFF Research Database (Denmark)
Svendsen, Peter Limkilde
Reconstruction of historical Arctic sea level is very difficult due to the limited coverage and quality of tide gauge and altimetry data in the area. This thesis addresses many of these issues, and discusses strategies to help achieve a stable and plausible reconstruction of Arctic sea level from...... 1950 to today.The primary record of historical sea level, on the order of several decades to a few centuries, is tide gauges. Tide gauge records from around the world are collected in the Permanent Service for Mean Sea Level (PSMSL) database, and includes data along the Arctic coasts. A reasonable...... amount of data is available along the Norwegian and Russian coasts since 1950, and most published research on Arctic sea level extends cautiously from these areas. Very little tide gauge data is available elsewhere in the Arctic, and records of a length of several decades,as generally recommended for sea...
Herrera, Ramón
2018-03-01
The reconstruction of a warm inflationary universe model from the scalar spectral index n_S(N) and the tensor to scalar ratio r( N) as a function of the number of e-folds N is studied. Under a general formalism we find the effective potential and the dissipative coefficient in terms of the cosmological parameters n_S and r considering the weak and strong dissipative stages under the slow roll approximation. As a specific example, we study the attractors for the index n_S given by nS-1∝ N^{-1} and for the ratio r∝ N^{-2}, in order to reconstruct the model of warm inflation. Here, expressions for the effective potential V(φ ) and the dissipation coefficient Γ (φ ) are obtained.
Jet Vertex Charge Reconstruction
Nektarijevic, Snezana; The ATLAS collaboration
2015-01-01
A newly developed algorithm called the jet vertex charge tagger, aimed at identifying the sign of the charge of jets containing $b$-hadrons, referred to as $b$-jets, is presented. In addition to the well established track-based jet charge determination, this algorithm introduces the so-called \\emph{jet vertex charge} reconstruction, which exploits the charge information associated to the displaced vertices within the jet. Furthermore, the charge of a soft muon contained in the jet is taken into account when available. All available information is combined into a multivariate discriminator. The algorithm has been developed on jets matched to generator level $b$-hadrons provided by $t\\bar{t}$ events simulated at $\\sqrt{s}$=13~TeV using the full ATLAS detector simulation and reconstruction.
Electron and Photon Reconstruction with the ATLAS Detector
Mitrevski, J
2014-01-01
An excellent performance of the reconstruction of electrons and photons with the ATLAS detector at the LHC is a key component to realize the full physics potential of ATLAS, both in searches for new physics and in precision measurements. For instance, all these played a critical role in the discovery of a Higgs boson, announced by the ATLAS Collaboration in 2012, and in the measurement of its properties. This paper highlights the reconstruction of electrons and photons.
3D Reconstruction of NMR Images by LabVIEW
Directory of Open Access Journals (Sweden)
Peter IZAK
2007-01-01
Full Text Available This paper introduces the experiment of 3D reconstruction NMR images via virtual instrumentation - LabVIEW. The main idea is based on marching cubes algorithm and image processing implemented by module of Vision assistant. The two dimensional images shot by the magnetic resonance device provide information about the surface properties of human body. There is implemented algorithm which can be used for 3D reconstruction of magnetic resonance images in biomedical application.
Fast algorithm of track reconstruction for the Delphy TPC
International Nuclear Information System (INIS)
Maillard, J.
1984-01-01
We describe a simple geometrical method (polar inversion) to reconstruct tracks. When the magnetic field is constant in magnitude and direction. This method uses geometrical properties of the trajectories. In the case of the DELPHI apparatus, the track reconstruction is done using TPC informations. After explaining the algorithm, we give results on ''GEANT'' simulated events using the ''Lund'' generator. Today we get a computer time of the order of 1.2 milliseconds on a CDC 7600 and an efficiency of 98% [fr
Alternative method for reconstruction of antihydrogen annihilation vertices
Amole, C; Andresen , G B; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jonsell, S; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki,Y
2012-01-01
The ALPHA experiment, located at CERN, aims to compare the properties of antihydrogen atoms with those of hydrogen atoms. The neutral antihydrogen atoms are trapped using an octupole magnetic trap. The trap region is surrounded by a three layered silicon detector used to reconstruct the antiproton annihilation vertices. This paper describes a method we have devised that can be used for reconstructing annihilation vertices with a good resolution and is more efficient than the standard method currently used for the same purpose.
Alternative method for reconstruction of antihydrogen annihilation vertices
Energy Technology Data Exchange (ETDEWEB)
Amole, C., E-mail: chanpreet.amole@cern.ch [York University, Department of Physics and Astronomy (Canada); Ashkezari, M. D. [Simon Fraser University, Department of Physics (Canada); Andresen, G. B. [Aarhus University, Department of Physics and Astronomy (Denmark); Baquero-Ruiz, M. [University of California, Department of Physics (United States); Bertsche, W. [Swansea University, Department of Physics (United Kingdom); Bowe, P. D. [Aarhus University, Department of Physics and Astronomy (Denmark); Butler, E. [CERN, Physics Department (Switzerland); Cesar, C. L. [Universidade Federal do Rio de Janeiro, Instituto de Fisica (Brazil); Chapman, S. [University of California, Department of Physics (United States); Charlton, M.; Deller, A.; Eriksson, S. [Swansea University, Department of Physics (United Kingdom); Fajans, J. [University of California, Department of Physics (United States); Friesen, T.; Fujiwara, M. C. [University of Calgary, Department of Physics and Astronomy (Canada); Gill, D. R. [TRIUMF (Canada); Gutierrez, A. [University of British Columbia, Department of Physics and Astronomy (Canada); Hangst, J. S. [Aarhus University, Department of Physics and Astronomy (Denmark); Hardy, W. N. [University of British Columbia, Department of Physics and Astronomy (Canada); Hayano, R. S. [University of Tokyo, Department of Physics (Japan); Collaboration: ALPHA Collaboration; and others
2012-12-15
The ALPHA experiment, located at CERN, aims to compare the properties of antihydrogen atoms with those of hydrogen atoms. The neutral antihydrogen atoms are trapped using an octupole magnetic trap. The trap region is surrounded by a three layered silicon detector used to reconstruct the antiproton annihilation vertices. This paper describes a method we have devised that can be used for reconstructing annihilation vertices with a good resolution and is more efficient than the standard method currently used for the same purpose.
Assessing the Accuracy of Ancestral Protein Reconstruction Methods
Williams, Paul D; Pollock, David D; Blackburne, Benjamin P; Goldstein, Richard A
2006-01-01
The phylogenetic inference of ancestral protein sequences is a powerful technique for the study of molecular evolution, but any conclusions drawn from such studies are only as good as the accuracy of the reconstruction method. Every inference method leads to errors in the ancestral protein sequence, resulting in potentially misleading estimates of the ancestral protein's properties. To assess the accuracy of ancestral protein reconstruction methods, we performed computational population evolu...
Segmentation-DrivenTomographic Reconstruction
DEFF Research Database (Denmark)
Kongskov, Rasmus Dalgas
such that the segmentation subsequently can be carried out by use of a simple segmentation method, for instance just a thresholding method. We tested the advantages of going from a two-stage reconstruction method to a one stage segmentation-driven reconstruction method for the phase contrast tomography reconstruction......The tomographic reconstruction problem is concerned with creating a model of the interior of an object from some measured data, typically projections of the object. After reconstructing an object it is often desired to segment it, either automatically or manually. For computed tomography (CT...
International Nuclear Information System (INIS)
Francisco, Oscar; Rangel, Murilo; Barter, William; Bursche, Albert; Potterat, Cedric; Coco, Victor
2012-01-01
Full text: The Large Hadron Collider (LHC) is the most powerful particle accelerator in the world. It has been designed to collide proton beams at an energy up to 14 TeV in the center of mass. In 2011, the data taking was done with a center of mass energy of 7 TeV, the instant luminosity has reached values greater than 4 X 10 32 cm -2 s -1 and the integrated luminosity reached the value of 1,02fb -1 on the LHCb. The jet reconstruction is fundamental to observe events that can be used to test perturbative QCD (pQCD). It also provides a way to observe standard model channels and searches for new physics like SUSY. The anti-kt algorithm is a jet reconstruction algorithm that is based on the distance of the particles on the space ηX φ and on the transverse momentum of particles. To maximize the energy resolution all information about the trackers and the colorimeters are used on the LHCb experiment to create objects called particle flow objects that are used as input to anti-kt algorithm. The LHCb is specially interesting for jets studies because its η region is complementary to the others main experiments on LHC. We will present the first results of jet reconstruction using 2011 LHCb data. (author)
Energy Technology Data Exchange (ETDEWEB)
Francisco, Oscar; Rangel, Murilo [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Barter, William [University of Cambridge, Cambridge (United Kingdom); Bursche, Albert [Universitat Zurich, Zurich (Switzerland); Potterat, Cedric [Universitat de Barcelona, Barcelona (Spain); Coco, Victor [Nikhef National Institute for Subatomic Physics, Amsterdam (Netherlands)
2012-07-01
Full text: The Large Hadron Collider (LHC) is the most powerful particle accelerator in the world. It has been designed to collide proton beams at an energy up to 14 TeV in the center of mass. In 2011, the data taking was done with a center of mass energy of 7 TeV, the instant luminosity has reached values greater than 4 X 10{sup 32} cm{sup -2}s{sup -1} and the integrated luminosity reached the value of 1,02fb{sup -1} on the LHCb. The jet reconstruction is fundamental to observe events that can be used to test perturbative QCD (pQCD). It also provides a way to observe standard model channels and searches for new physics like SUSY. The anti-kt algorithm is a jet reconstruction algorithm that is based on the distance of the particles on the space {eta}X {phi} and on the transverse momentum of particles. To maximize the energy resolution all information about the trackers and the colorimeters are used on the LHCb experiment to create objects called particle flow objects that are used as input to anti-kt algorithm. The LHCb is specially interesting for jets studies because its {eta} region is complementary to the others main experiments on LHC. We will present the first results of jet reconstruction using 2011 LHCb data. (author)
Advances in thermographic signal reconstruction
Shepard, Steven M.; Frendberg Beemer, Maria
2015-05-01
Since its introduction in 2001, the Thermographic Signal Reconstruction (TSR) method has emerged as one of the most widely used methods for enhancement and analysis of thermographic sequences, with applications extending beyond industrial NDT into biomedical research, art restoration and botany. The basic TSR process, in which a noise reduced replica of each pixel time history is created, yields improvement over unprocessed image data that is sufficient for many applications. However, examination of the resulting logarithmic time derivatives of each TSR pixel replica provides significant insight into the physical mechanisms underlying the active thermography process. The deterministic and invariant properties of the derivatives have enabled the successful implementation of automated defect recognition and measurement systems. Unlike most approaches to analysis of thermography data, TSR does not depend on flawbackground contrast, so that it can also be applied to characterization and measurement of thermal properties of flaw-free samples. We present a summary of recent advances in TSR, a review of the underlying theory and examples of its implementation.
[Reconstructive methods after Fournier gangrene].
Wallner, C; Behr, B; Ring, A; Mikhail, B D; Lehnhardt, M; Daigeler, A
2016-04-01
Fournier's gangrene is a variant of the necrotizing fasciitis restricted to the perineal and genital region. It presents as an acute life-threatening disease and demands rapid surgical debridement, resulting in large soft tissue defects. Various reconstructive methods have to be applied to reconstitute functionality and aesthetics. The objective of this work is to identify different reconstructive methods in the literature and compare them to our current concepts for reconstructing defects caused by Fournier gangrene. Analysis of the current literature and our reconstructive methods on Fournier gangrene. The Fournier gangrene is an emergency requiring rapid, calculated antibiotic treatment and radical surgical debridement. After the acute phase of the disease, appropriate reconstructive methods are indicated. The planning of the reconstruction of the defect depends on many factors, especially functional and aesthetic demands. Scrotal reconstruction requires a higher aesthetic and functional reconstructive degree than perineal cutaneous wounds. In general, thorough wound hygiene, proper pre-operative planning, and careful consideration of the patient's demands are essential for successful reconstruction. In the literature, various methods for reconstruction after Fournier gangrene are described. Reconstruction with a flap is required for a good functional result in complex regions as the scrotum and penis, while cutaneous wounds can be managed through skin grafting. Patient compliance and tissue demand are crucial factors in the decision-making process.
Assessing the accuracy of ancestral protein reconstruction methods.
Directory of Open Access Journals (Sweden)
Paul D Williams
2006-06-01
Full Text Available The phylogenetic inference of ancestral protein sequences is a powerful technique for the study of molecular evolution, but any conclusions drawn from such studies are only as good as the accuracy of the reconstruction method. Every inference method leads to errors in the ancestral protein sequence, resulting in potentially misleading estimates of the ancestral protein's properties. To assess the accuracy of ancestral protein reconstruction methods, we performed computational population evolution simulations featuring near-neutral evolution under purifying selection, speciation, and divergence using an off-lattice protein model where fitness depends on the ability to be stable in a specified target structure. We were thus able to compare the thermodynamic properties of the true ancestral sequences with the properties of "ancestral sequences" inferred by maximum parsimony, maximum likelihood, and Bayesian methods. Surprisingly, we found that methods such as maximum parsimony and maximum likelihood that reconstruct a "best guess" amino acid at each position overestimate thermostability, while a Bayesian method that sometimes chooses less-probable residues from the posterior probability distribution does not. Maximum likelihood and maximum parsimony apparently tend to eliminate variants at a position that are slightly detrimental to structural stability simply because such detrimental variants are less frequent. Other properties of ancestral proteins might be similarly overestimated. This suggests that ancestral reconstruction studies require greater care to come to credible conclusions regarding functional evolution. Inferred functional patterns that mimic reconstruction bias should be reevaluated.
Assessing the accuracy of ancestral protein reconstruction methods.
Williams, Paul D; Pollock, David D; Blackburne, Benjamin P; Goldstein, Richard A
2006-06-23
The phylogenetic inference of ancestral protein sequences is a powerful technique for the study of molecular evolution, but any conclusions drawn from such studies are only as good as the accuracy of the reconstruction method. Every inference method leads to errors in the ancestral protein sequence, resulting in potentially misleading estimates of the ancestral protein's properties. To assess the accuracy of ancestral protein reconstruction methods, we performed computational population evolution simulations featuring near-neutral evolution under purifying selection, speciation, and divergence using an off-lattice protein model where fitness depends on the ability to be stable in a specified target structure. We were thus able to compare the thermodynamic properties of the true ancestral sequences with the properties of "ancestral sequences" inferred by maximum parsimony, maximum likelihood, and Bayesian methods. Surprisingly, we found that methods such as maximum parsimony and maximum likelihood that reconstruct a "best guess" amino acid at each position overestimate thermostability, while a Bayesian method that sometimes chooses less-probable residues from the posterior probability distribution does not. Maximum likelihood and maximum parsimony apparently tend to eliminate variants at a position that are slightly detrimental to structural stability simply because such detrimental variants are less frequent. Other properties of ancestral proteins might be similarly overestimated. This suggests that ancestral reconstruction studies require greater care to come to credible conclusions regarding functional evolution. Inferred functional patterns that mimic reconstruction bias should be reevaluated.
Photometric Lunar Surface Reconstruction
Nefian, Ara V.; Alexandrov, Oleg; Morattlo, Zachary; Kim, Taemin; Beyer, Ross A.
2013-01-01
Accurate photometric reconstruction of the Lunar surface is important in the context of upcoming NASA robotic missions to the Moon and in giving a more accurate understanding of the Lunar soil composition. This paper describes a novel approach for joint estimation of Lunar albedo, camera exposure time, and photometric parameters that utilizes an accurate Lunar-Lambertian reflectance model and previously derived Lunar topography of the area visualized during the Apollo missions. The method introduced here is used in creating the largest Lunar albedo map (16% of the Lunar surface) at the resolution of 10 meters/pixel.
Penile surgery and reconstruction.
Perovic, Sava V; Djordjevic, Miroslav L J; Kekic, Zoran K; Djakovic, Nenad G
2002-05-01
This review will highlight recent advances in the field of penile reconstructive surgery in the paediatric and adult population. It is based on the work published during the year 2001. Besides the anatomical and histological studies of the penis, major contributions have been described in congenital and acquired penile anomalies. Also, a few new techniques and modifications of old procedures are described in order to improve the final functional and aesthetic outcome. The techniques for penile enlargement present a trend in the new millennium, but are still at the stage of investigation.
Progressive Reconstruction: A Methodology for Stabilization and Reconstruction Operations
National Research Council Canada - National Science Library
Rohr, Karl C
2006-01-01
... these nations in accordance with stated United States' goals. The argument follows closely current and developing United States military doctrine on stabilization, reconstruction, and counterinsurgency operations...
Synchronized dynamic dose reconstruction
International Nuclear Information System (INIS)
Litzenberg, Dale W.; Hadley, Scott W.; Tyagi, Neelam; Balter, James M.; Ten Haken, Randall K.; Chetty, Indrin J.
2007-01-01
Variations in target volume position between and during treatment fractions can lead to measurable differences in the dose distribution delivered to each patient. Current methods to estimate the ongoing cumulative delivered dose distribution make idealized assumptions about individual patient motion based on average motions observed in a population of patients. In the delivery of intensity modulated radiation therapy (IMRT) with a multi-leaf collimator (MLC), errors are introduced in both the implementation and delivery processes. In addition, target motion and MLC motion can lead to dosimetric errors from interplay effects. All of these effects may be of clinical importance. Here we present a method to compute delivered dose distributions for each treatment beam and fraction, which explicitly incorporates synchronized real-time patient motion data and real-time fluence and machine configuration data. This synchronized dynamic dose reconstruction method properly accounts for the two primary classes of errors that arise from delivering IMRT with an MLC: (a) Interplay errors between target volume motion and MLC motion, and (b) Implementation errors, such as dropped segments, dose over/under shoot, faulty leaf motors, tongue-and-groove effect, rounded leaf ends, and communications delays. These reconstructed dose fractions can then be combined to produce high-quality determinations of the dose distribution actually received to date, from which individualized adaptive treatment strategies can be determined
Augusto, O
2012-01-01
The Large Hadron Collider (LHC) is the most powerful particle accelerator in the world. It has been designed to collide proton beams at an energy up to 14 TeV in the center of mass. In 2011, the data taking was done with a center of mass energy of 7 TeV, the instant luminosity has reached values greater than $4 \\times 10^{32} cm^{-2} s^{-1}$ and the integrated luminosity reached the value of 1.02 $fb^{-1}$ on the LHCb. The jet reconstruction is fundamental to observe events that can be used to test pertubative QCD (pQCD). It also provides a way to observe standard model channels and searches for new physics like SUSY. The anti-kt algorithm is a jet reconstruction algorithm that is based on the distance of the particles on the space $\\eta \\times \\phi$ and on the transverse momentum of particles. To maximize the energy resolution all information about the trackers and the calo...
Three-dimensional ICT reconstruction
International Nuclear Information System (INIS)
Zhang Aidong; Li Ju; Chen Fa; Sun Lingxia
2005-01-01
The three-dimensional ICT reconstruction method is the hot topic of recent ICT technology research. In the context, qualified visual three-dimensional ICT pictures are achieved through multi-piece two-dimensional images accumulation by, combining with thresholding method and linear interpolation. Different direction and different position images of the reconstructed pictures are got by rotation and interception respectively. The convenient and quick method is significantly instructive to more complicated three-dimensional reconstruction of ICT images. (authors)
Three-dimensional ICT reconstruction
International Nuclear Information System (INIS)
Zhang Aidong; Li Ju; Chen Fa; Sun Lingxia
2004-01-01
The three-dimensional ICT reconstruction method is the hot topic of recent ICT technology research. In the context qualified visual three-dimensional ICT pictures are achieved through multi-piece two-dimensional images accumulation by order, combining with thresholding method and linear interpolation. Different direction and different position images of the reconstructed pictures are got by rotation and interception respectively. The convenient and quick method is significantly instructive to more complicated three-dimensional reconstruction of ICT images. (authors)
Virtual 3-D Facial Reconstruction
Directory of Open Access Journals (Sweden)
Martin Paul Evison
2000-06-01
Full Text Available Facial reconstructions in archaeology allow empathy with people who lived in the past and enjoy considerable popularity with the public. It is a common misconception that facial reconstruction will produce an exact likeness; a resemblance is the best that can be hoped for. Research at Sheffield University is aimed at the development of a computer system for facial reconstruction that will be accurate, rapid, repeatable, accessible and flexible. This research is described and prototypical 3-D facial reconstructions are presented. Interpolation models simulating obesity, ageing and ethnic affiliation are also described. Some strengths and weaknesses in the models, and their potential for application in archaeology are discussed.
Entropy and transverse section reconstruction
International Nuclear Information System (INIS)
Gullberg, G.T.
1976-01-01
A new approach to the reconstruction of a transverse section using projection data from multiple views incorporates the concept of maximum entropy. The principle of maximizing information entropy embodies the assurance of minimizing bias or prejudice in the reconstruction. Using maximum entropy is a necessary condition for the reconstructed image. This entropy criterion is most appropriate for 3-D reconstruction of objects from projections where the system is underdetermined or the data are limited statistically. This is the case in nuclear medicine time limitations in patient studies do not yield sufficient projections
Liquid argon TPC signal formation, signal processing and reconstruction techniques
Baller, B.
2017-07-01
This document describes a reconstruction chain that was developed for the ArgoNeuT and MicroBooNE experiments at Fermilab. These experiments study accelerator neutrino interactions that occur in a Liquid Argon Time Projection Chamber. Reconstructing the properties of particles produced in these interactions benefits from the knowledge of the micro-physics processes that affect the creation and transport of ionization electrons to the readout system. A wire signal deconvolution technique was developed to convert wire signals to a standard form for hit reconstruction, to remove artifacts in the electronics chain and to remove coherent noise. A unique clustering algorithm reconstructs line-like trajectories and vertices in two dimensions which are then matched to create of 3D objects. These techniques and algorithms are available to all experiments that use the LArSoft suite of software.
Iterative image reconstruction in ECT
International Nuclear Information System (INIS)
Chintu Chen; Ordonez, C.E.; Wernick, M.N.; Aarsvold, J.N.; Gunter, D.L.; Wong, W.H.; Kapp, O.H.; Xiaolong Ouyang; Levenson, M.; Metz, C.E.
1992-01-01
A series of preliminary studies has been performed in the authors laboratories to explore the use of a priori information in Bayesian image restoration and reconstruction. One piece of a priori information is the fact that intensities of neighboring pixels tend to be similar if they belong to the same region within which similar tissue characteristics are exhibited. this property of local continuity can be modeled by the use of Gibbs priors, as first suggested by German and Geman. In their investigation, they also included line sites between each pair of neighboring pixels in the Gibbs prior and used discrete binary numbers to indicate the absence or presence of boundaries between regions. These two features of the a priori model permit averaging within boundaries of homogeneous regions to alleviate the degradation caused by Poisson noise. with the use of this Gibbs prior in combination with the technique of stochastic relaxation, German and Geman demonstrated that noise levels can be reduced significantly in 2-D image restoration. They have developed a Bayesian method that utilizes a Gibbs prior to describe the spatial correlation of neighboring regions and takes into account the effect of limited spatial resolution as well. The statistical framework of the proposed approach is based on the data augmentation scheme suggested by Tanner and Wong. Briefly outlined here, this Bayesian method is based on Geman and Geman's approach
Analyzing direct dark matter detection data with unrejected background events by the AMIDAS website
International Nuclear Information System (INIS)
Shan, Chung-Lin
2012-01-01
In this talk I have presented the data analysis results of extracting properties of halo WIMPs: the mass and the (ratios between the) spin-independent and spin-dependent couplings/cross sections on nucleons by the AMIDAS website by taking into account possible unrejected background events in the analyzed data sets. Although non-standard astronomical setup has been used to generate pseudodata sets for our analyses, it has been found that, without prior information/assumption about the local density and velocity distribution of halo Dark Matter, these WIMP properties have been reconstructed with ∼ 2% to ∼< 30% deviations from the input values.
Energy Technology Data Exchange (ETDEWEB)
Barrera, Barbara
2000-10-13
The two B{sup 0} decay processes B{sup 0} {yields} D*{sup -} {pi}{sup +} and B{sup 0} {yields} D*{sup -} {ell}{sup +} {nu}{sub {ell}} have been studied by means of a partial reconstruction technique using a data sample collected with the BABAR detector at the PEP-II storage ring. To increase statistics, only the soft {pi}{sup -} from the decay D*{sup -} {yields} {pi}{sup -} D{sup 0} was used in association with either an oppositely-charged high-momentum pion or lepton. Events were then identified by exploiting the constraints from the simple kinematics of {Upsilon}(4S) decays. A clear signature is obtained in each case. The position of the B{sup 0} decay point was obtained from the reconstructed {pi}{sup +} ({ell}{sup +}){pi}{sup -} vertex. The position of the other {bar B}{sup 0} in the event was also determined. Taking advantage of the boost given to the {Upsilon}(4S) system by the asymmetric beam energies of PEP-II, the lifetime of the B{sup 0} meson has been measured from the separation distance between the two vertices along the beam direction.
International Nuclear Information System (INIS)
Cook, G.O. Jr.; Knight, L.
1979-07-01
The question of optimal projection angles has recently become of interest in the field of reconstruction from projections. Here, studies are concentrated on the n x n pixel space, where literative algorithms such as ART and direct matrix techniques due to Katz are considered. The best angles are determined in a Gauss--Markov statistical sense as well as with respect to a function-theoretical error bound. The possibility of making photon intensity a function of angle is also examined. Finally, the best angles to use in an ART-like algorithm are studied. A certain set of unequally spaced angles was found to be preferred in several contexts. 15 figures, 6 tables
CRUCIATE LIGAMENT RECONSTRUCTION
Directory of Open Access Journals (Sweden)
A. V. Korolev
2016-01-01
Full Text Available Purpose: To evaluate long-term results of meniscal repair during arthroscopic ACL reconstruction.Materials and methods: 45 patients who underwent meniscal repair during arthroscopic ACL reconstruction between 2007 and 2013 by the same surgeon were included in the study. In total, fifty meniscus were repaired (26 medial and 24 lateral. Procedures included use of one up to four Fast-Fix implants (Smith & Nephew. In five cases both medial and lateral meniscus were repaired. Cincinnati, IKDC and Lysholm scales were used for long-term outcome analysis.Results: 19 male and 26 female patients were included in the study aging from 15 to 59 years (mean age 33,2±1,5. Median time from injury to surgical procedure was zero months (ranging zero to one. Mean time from surgery to scale analysis was 55,9±3 months (ranged 20-102. Median Cincinnati score was 97 (ranged 90-100, with excellent results in 93% of cases (43 patients and good results in 7% (3 patients. Median IKDC score was 90,8 (ranged 86,2-95,4, with excellent outcomes in 51% of cases (23 patients, good in 33% (15 patients and satisfactory in 16% (7 patients. Median Lysholm score was 95 (ranged 90-100, with excellent outcomes in 76% of cases (34 patients and good in 24% (11 patients. Authors identified no statistical differences when comparing survey results in age, sex and time from trauma to surgery.Conclusions: Results of the present study match the data from orthopedic literature that prove meniscal repair as a safe and efficient procedure with good and excellent outcomes. All-inside meniscal repair can be used irrespectively of patients' age and is efficient even in case of delayed procedures.
Universal Spatial Correlation Functions for Describing and Reconstructing Soil Microstructure
Skvortsova, Elena B.; Mallants, Dirk
2015-01-01
Structural features of porous materials such as soil define the majority of its physical properties, including water infiltration and redistribution, multi-phase flow (e.g. simultaneous water/air flow, or gas exchange between biologically active soil root zone and atmosphere) and solute transport. To characterize soil microstructure, conventional soil science uses such metrics as pore size and pore-size distributions and thin section-derived morphological indicators. However, these descriptors provide only limited amount of information about the complex arrangement of soil structure and have limited capability to reconstruct structural features or predict physical properties. We introduce three different spatial correlation functions as a comprehensive tool to characterize soil microstructure: 1) two-point probability functions, 2) linear functions, and 3) two-point cluster functions. This novel approach was tested on thin-sections (2.21×2.21 cm2) representing eight soils with different pore space configurations. The two-point probability and linear correlation functions were subsequently used as a part of simulated annealing optimization procedures to reconstruct soil structure. Comparison of original and reconstructed images was based on morphological characteristics, cluster correlation functions, total number of pores and pore-size distribution. Results showed excellent agreement for soils with isolated pores, but relatively poor correspondence for soils exhibiting dual-porosity features (i.e. superposition of pores and micro-cracks). Insufficient information content in the correlation function sets used for reconstruction may have contributed to the observed discrepancies. Improved reconstructions may be obtained by adding cluster and other correlation functions into reconstruction sets. Correlation functions and the associated stochastic reconstruction algorithms introduced here are universally applicable in soil science, such as for soil classification
Reconstruction of electric systems (ELE)
International Nuclear Information System (INIS)
Kohutovic, P.
2001-01-01
The original design of WWER-230 units consisted of a single common system EEPS (essential electric power supply system) per unit. The establishment of redundancy 2 x 100% EEPS was a global task. The task was started during the 'Small reconstruction' - MR V1, continued in 'Gradual reconstruction' and finished in the year 2000. (author)
Breast Reconstruction Following Cancer Treatment.
Gerber, Bernd; Marx, Mario; Untch, Michael; Faridi, Andree
2015-08-31
About 8000 breast reconstructions after mastectomy are per - formed in Germany each year. It has become more difficult to advise patients because of the wide variety of heterologous and autologous techniques that are now available and because of changes in the recommendations about radiotherapy. This article is based on a review of pertinent articles (2005-2014) that were retrieved by a selective search employing the search terms "mastectomy" and "breast reconstruction." The goal of reconstruction is to achieve an oncologically safe and aestically satisfactory result for the patient over the long term. Heterologous, i.e., implant-based, breast reconstruction (IBR) and autologous breast reconstruction (ABR) are complementary techniques. Immediate reconstruction preserves the skin of the breast and its natural form and prevents the psychological trauma associated with mastectomy. If post-mastectomy radiotherapy (PMRT) is not indicated, implant-based reconstruction with or without a net/acellular dermal matrix (ADM) is a common option. Complications such as seroma formation, infection, and explantation are significantly more common when an ADM is used (15.3% vs. 5.4% ). If PMRT is performed, then the complication rate of implant-based breast reconstruction is 1 to 48% ; in particular, Baker grade III/IV capsular fibrosis occurs in 7 to 22% of patients, and the prosthesis must be explanted in 9 to 41% . Primary or, preferably, secondary autologous reconstruction is an alternative. The results of ABR are more stable over the long term, but the operation is markedly more complex. Autologous breast reconstruction after PMRT does not increase the risk of serious complications (20.5% vs. 17.9% without radiotherapy). No randomized controlled trials have yet been conducted to compare the reconstructive techniques with each other. If radiotherapy will not be performed, immediate reconstruction with an implant is recommended. On the other hand, if post-mastectomy radiotherapy
Biofabrication and biomaterials for urinary tract reconstruction
Directory of Open Access Journals (Sweden)
Elsawy MM
2017-05-01
Full Text Available Moustafa M Elsawy,1–3 Achala de Mel1 1Division of Surgery and Interventional Science, Royal Free Hospital, NHS Trust, University College London (UCL, 2Division of Reconstructive Urology, University College London Hospitals (uclh, London, UK; 3Urology Department, School of Medicine, Alexandria, University, Alexandria, EgyptAbstract: Reconstructive urologists are constantly facing diverse and complex pathologies that require structural and functional restoration of urinary organs. There is always a demand for a biocompatible material to repair or substitute the urinary tract instead of using patient’s autologous tissues with its associated morbidity. Biomimetic approaches are tissue-engineering tactics aiming to tailor the material physical and biological properties to behave physiologically similar to the urinary system. This review highlights the different strategies to mimic urinary tissues including modifications in structure, surface chemistry, and cellular response of a range of biological and synthetic materials. The article also outlines the measures to minimize infectious complications, which might lead to graft failure. Relevant experimental and preclinical studies are discussed, as well as promising biomimetic approaches such as three-dimensional bioprinting. Keywords: reconstruction, biofunctionalization, tissue engineering, urinary tract
Strategies of reconstruction algorithms for computerized tomography
International Nuclear Information System (INIS)
Garderet, P.
1984-10-01
Image reconstruction from projections has progressively spread out over all fields of medical imaging. As the mathematical aspects of the problem become more and more comprehensively explored a great variety of numerical solutions have been developed best suited to such-and-such imaging medical application and taking into account the physical phenomena related to data collection (a priori properties for signal and noise). The purpose of that survey is to present the general mathematical frame and the fundamental assumptions of various strategies; Fourier methods approximate explicit deterministic inversion formula for the Radon transform. Algebraic reconstruction techniques set up an a priori discrete model through a series expansion approach of the solution. The numerical system to be solved is huge when a fine grid of pixels is to be reconstructed; iterative solutions may then be found. Recently some least square procedures have been shown to be tractable which avoid the use of iterative methods. Finally maximum like hood approach incorporates accurately the Poisson nature of photon noise and are well adapted to emission computed tomography. The various strategies will be analysed from both aspects of theoretical assumptions needed for suitable use and of computing facilities, actual performance and cost. In the end we take a glimpse of the extension of the algorithms from two dimensional imaging to fully three dimensional volume analysis in preparation of the future medical imaging technologies
Hongbo Guo; Xiaowei He; Muhan Liu; Zeyu Zhang; Zhenhua Hu; Jie Tian
2017-06-01
Cerenkov luminescence tomography (CLT) provides a novel technique for 3-D noninvasive detection of radiopharmaceuticals in living subjects. However, because of the severe scattering of Cerenkov light, the reconstruction accuracy and stability of CLT is still unsatisfied. In this paper, a modified weight multispectral CLT (wmCLT) reconstruction strategy was developed which split the Cerenkov radiation spectrum into several sub-spectral bands and weighted the sub-spectral results to obtain the final result. To better evaluate the property of the wmCLT reconstruction strategy in terms of accuracy, stability and practicability, several numerical simulation experiments and in vivo experiments were conducted and the results obtained were compared with the traditional multispectral CLT (mCLT) and hybrid-spectral CLT (hCLT) reconstruction strategies. The numerical simulation results indicated that wmCLT strategy significantly improved the accuracy of Cerenkov source localization and intensity quantitation and exhibited good stability in suppressing noise in numerical simulation experiments. And the comparison of the results achieved from different in vivo experiments further indicated significant improvement of the wmCLT strategy in terms of the shape recovery of the bladder and the spatial resolution of imaging xenograft tumors. Overall the strategy reported here will facilitate the development of nuclear and optical molecular tomography in theoretical study.
International Nuclear Information System (INIS)
Verhaeghe, Jeroen; D'Asseler, Yves; Vandenberghe, Stefaan; Staelens, Steven; Lemahieu, Ignace
2007-01-01
The use of a temporal B-spline basis for the reconstruction of dynamic positron emission tomography data was investigated. Maximum likelihood (ML) reconstructions using an expectation maximization framework and maximum A-posteriori (MAP) reconstructions using the generalized expectation maximization framework were evaluated. Different parameters of the B-spline basis of such as order, number of basis functions and knot placing were investigated in a reconstruction task using simulated dynamic list-mode data. We found that a higher order basis reduced both the bias and variance. Using a higher number of basis functions in the modeling of the time activity curves (TACs) allowed the algorithm to model faster changes of the TACs, however, the TACs became noisier. We have compared ML, Gaussian postsmoothed ML and MAP reconstructions. The noise level in the ML reconstructions was controlled by varying the number of basis functions. The MAP algorithm penalized the integrated squared curvature of the reconstructed TAC. The postsmoothed ML was always outperformed in terms of bias and variance properties by the MAP and ML reconstructions. A simple adaptive knot placing strategy was also developed and evaluated. It is based on an arc length redistribution scheme during the reconstruction. The free knot reconstruction allowed a more accurate reconstruction while reducing the noise level especially for fast changing TACs such as blood input functions. Limiting the number of temporal basis functions combined with the adaptive knot placing strategy is in this case advantageous for regularization purposes when compared to the other regularization techniques
Tau Reconstruction, Identification Algorithms and Performance in ATLAS
DEFF Research Database (Denmark)
Simonyan, M.
2013-01-01
identification of hadronically decaying tau leptons is achieved by using detailed information from tracking and calorimeter detector components. Variables describing the properties of calorimeter energy deposits and track reconstruction within tau candidates are combined in multi-variate discriminants...... by investigating single hadron calorimeter response, as well as kinematic distributions in Z¿ tt events....
Evidence-Based ACL Reconstruction
Directory of Open Access Journals (Sweden)
E. Carlos RODRIGUEZ-MERCHAN
2015-01-01
Full Text Available There is controversy in the literature regarding a number of topics related to anterior cruciate ligament (ACLreconstruction. The purpose of this article is to answer the following questions: 1 Bone patellar tendon bone (BPTB reconstruction or hamstring reconstruction (HR; 2 Double bundle or single bundle; 3 Allograft or authograft; 4 Early or late reconstruction; 5 Rate of return to sports after ACL reconstruction; 6 Rate of osteoarthritis after ACL reconstruction. A Cochrane Library and PubMed (MEDLINE search of systematic reviews and meta-analysis related to ACL reconstruction was performed. The key words were: ACL reconstruction, systematic reviews and meta-analysis. The main criteria for selection were that the articles were systematic reviews and meta-analysesfocused on the aforementioned questions. Sixty-nine articles were found, but only 26 were selected and reviewed because they had a high grade (I-II of evidence. BPTB-R was associated with better postoperative knee stability but with a higher rate of morbidity. However, the results of both procedures in terms of functional outcome in the long-term were similar. The double-bundle ACL reconstruction technique showed better outcomes in rotational laxity, although functional recovery was similar between single-bundle and double-bundle. Autograft yielded better results than allograft. There was no difference between early and delayed reconstruction. 82% of patients were able to return to some kind of sport participation. 28% of patients presented radiological signs of osteoarthritis with a follow-up of minimum 10 years.
Reconstructing human evolution
AUTHOR|(CDS)2074069
1999-01-01
One can reconstruct human evolution using modern genetic data and models based on the mathematical theory of evolution and its four major factors : mutation, natural selection, statistical fluctuations in finite populations (random genetic drift), and migration. Archaeology gives some help on the major dates and events of the process. Chances of studying ancient DNA are very limited but there have been a few successful results. Studying DNA instead of proteins, as was done until a few years ago, and in particular the DNA of mitochondria and of the Y chromosome which are transmitted, respectively, by the maternal line and the paternal line, has greatly simplified the analysis. It is now possible to carry the analysis on individuals, while earlier studies were of necessity based on populations. Also the evolution of ÒcultureÓ (i.e. what we learn from others), in particular that of languages, gives some help and can be greatly enlightened by genetic studies. Even though it is largely based on mechanisms of mut...
Fast Dictionary-Based Reconstruction for Diffusion Spectrum Imaging
Bilgic, Berkin; Chatnuntawech, Itthi; Setsompop, Kawin; Cauley, Stephen F.; Yendiki, Anastasia; Wald, Lawrence L.; Adalsteinsson, Elfar
2015-01-01
Diffusion Spectrum Imaging (DSI) reveals detailed local diffusion properties at the expense of substantially long imaging times. It is possible to accelerate acquisition by undersampling in q-space, followed by image reconstruction that exploits prior knowledge on the diffusion probability density functions (pdfs). Previously proposed methods impose this prior in the form of sparsity under wavelet and total variation (TV) transforms, or under adaptive dictionaries that are trained on example datasets to maximize the sparsity of the representation. These compressed sensing (CS) methods require full-brain processing times on the order of hours using Matlab running on a workstation. This work presents two dictionary-based reconstruction techniques that use analytical solutions, and are two orders of magnitude faster than the previously proposed dictionary-based CS approach. The first method generates a dictionary from the training data using Principal Component Analysis (PCA), and performs the reconstruction in the PCA space. The second proposed method applies reconstruction using pseudoinverse with Tikhonov regularization with respect to a dictionary. This dictionary can either be obtained using the K-SVD algorithm, or it can simply be the training dataset of pdfs without any training. All of the proposed methods achieve reconstruction times on the order of seconds per imaging slice, and have reconstruction quality comparable to that of dictionary-based CS algorithm. PMID:23846466
Prospects of linear reconstruction in atomic resolution electron holographic tomography
International Nuclear Information System (INIS)
Krehl, Jonas; Lubk, Axel
2015-01-01
Tomography commonly requires a linear relation between the measured signal and the underlying specimen property; for Electron Holographic Tomography this is given by the Phase Grating Approximation (PGA). While largely valid at medium resolution, discrepancies arise at high resolution imaging conditions. We set out to investigate the artefacts that are produced if the reconstruction still assumes the PGA even with an atomic resolution tilt series. To forego experimental difficulties the holographic tilt series was simulated. The reconstructed electric potential clearly shows peaks at the positions of the atoms. These peaks have characterisitic deformations, which can be traced back to the defocus a particular atom has in the holograms of the tilt series. Exchanging an atom for one of a different atomic number results in a significant change in the reconstructed potential that is well contained within the atom's peak. - Highlights: • We simulate a holographic tilt series of a nanocrystal with atomic resolution. • Using PGA-based Holographic Tomography we reconstruct the atomic structure. • The reconstruction shows characteristic artefacts, chiefly caused by defocus. • Changing one atom's Z produces a well localised in the reconstruction
Prospects of linear reconstruction in atomic resolution electron holographic tomography
Energy Technology Data Exchange (ETDEWEB)
Krehl, Jonas, E-mail: Jonas.Krehl@triebenberg.de; Lubk, Axel
2015-03-15
Tomography commonly requires a linear relation between the measured signal and the underlying specimen property; for Electron Holographic Tomography this is given by the Phase Grating Approximation (PGA). While largely valid at medium resolution, discrepancies arise at high resolution imaging conditions. We set out to investigate the artefacts that are produced if the reconstruction still assumes the PGA even with an atomic resolution tilt series. To forego experimental difficulties the holographic tilt series was simulated. The reconstructed electric potential clearly shows peaks at the positions of the atoms. These peaks have characterisitic deformations, which can be traced back to the defocus a particular atom has in the holograms of the tilt series. Exchanging an atom for one of a different atomic number results in a significant change in the reconstructed potential that is well contained within the atom's peak. - Highlights: • We simulate a holographic tilt series of a nanocrystal with atomic resolution. • Using PGA-based Holographic Tomography we reconstruct the atomic structure. • The reconstruction shows characteristic artefacts, chiefly caused by defocus. • Changing one atom's Z produces a well localised in the reconstruction.
Fast dictionary-based reconstruction for diffusion spectrum imaging.
Bilgic, Berkin; Chatnuntawech, Itthi; Setsompop, Kawin; Cauley, Stephen F; Yendiki, Anastasia; Wald, Lawrence L; Adalsteinsson, Elfar
2013-11-01
Diffusion spectrum imaging reveals detailed local diffusion properties at the expense of substantially long imaging times. It is possible to accelerate acquisition by undersampling in q-space, followed by image reconstruction that exploits prior knowledge on the diffusion probability density functions (pdfs). Previously proposed methods impose this prior in the form of sparsity under wavelet and total variation transforms, or under adaptive dictionaries that are trained on example datasets to maximize the sparsity of the representation. These compressed sensing (CS) methods require full-brain processing times on the order of hours using MATLAB running on a workstation. This work presents two dictionary-based reconstruction techniques that use analytical solutions, and are two orders of magnitude faster than the previously proposed dictionary-based CS approach. The first method generates a dictionary from the training data using principal component analysis (PCA), and performs the reconstruction in the PCA space. The second proposed method applies reconstruction using pseudoinverse with Tikhonov regularization with respect to a dictionary. This dictionary can either be obtained using the K-SVD algorithm, or it can simply be the training dataset of pdfs without any training. All of the proposed methods achieve reconstruction times on the order of seconds per imaging slice, and have reconstruction quality comparable to that of dictionary-based CS algorithm.
Adaptive wavelet tight frame construction for accelerating MRI reconstruction
Directory of Open Access Journals (Sweden)
Genjiao Zhou
2017-09-01
Full Text Available The sparsity regularization approach, which assumes that the image of interest is likely to have sparse representation in some transform domain, has been an active research area in image processing and medical image reconstruction. Although various sparsifying transforms have been used in medical image reconstruction such as wavelet, contourlet, and total variation (TV etc., the efficiency of these transforms typically rely on the special structure of the underlying image. A better way to address this issue is to develop an overcomplete dictionary from the input data in order to get a better sparsifying transform for the underlying image. However, the general overcomplete dictionaries do not satisfy the so-called perfect reconstruction property which ensures that the given signal can be perfectly represented by its canonical coefficients in a manner similar to orthonormal bases, resulting in time consuming in the iterative image reconstruction. This work is to develop an adaptive wavelet tight frame method for magnetic resonance image reconstruction. The proposed scheme incorporates the adaptive wavelet tight frame approach into the magnetic resonance image reconstruction by solving a l0-regularized minimization problem. Numerical results show that the proposed approach provides significant time savings as compared to the over-complete dictionary based methods with comparable performance in terms of both peak signal-to-noise ratio and subjective visual quality.
Reconstructing Topological Graphs and Continua
Gartside, Paul; Pitz, Max F.; Suabedissen, Rolf
2015-01-01
The deck of a topological space $X$ is the set $\\mathcal{D}(X)=\\{[X \\setminus \\{x\\}] \\colon x \\in X\\}$, where $[Z]$ denotes the homeomorphism class of $Z$. A space $X$ is topologically reconstructible if whenever $\\mathcal{D}(X)=\\mathcal{D}(Y)$ then $X$ is homeomorphic to $Y$. It is shown that all metrizable compact connected spaces are reconstructible. It follows that all finite graphs, when viewed as a 1-dimensional cell-complex, are reconstructible in the topological sense, and more genera...
Tomographic reconstruction of binary fields
International Nuclear Information System (INIS)
Roux, Stéphane; Leclerc, Hugo; Hild, François
2012-01-01
A novel algorithm is proposed for reconstructing binary images from their projection along a set of different orientations. Based on a nonlinear transformation of the projection data, classical back-projection procedures can be used iteratively to converge to the sought image. A multiscale implementation allows for a faster convergence. The algorithm is tested on images up to 1 Mb definition, and an error free reconstruction is achieved with a very limited number of projection data, saving a factor of about 100 on the number of projections required for classical reconstruction algorithms.
Optical image reconstruction using DC data: simulations and experiments
International Nuclear Information System (INIS)
Huabei Jiang; Paulsen, K.D.; Oesterberg, U.L.
1996-01-01
In this paper, we explore optical image formation using a diffusion approximation of light propagation in tissue which is modelled with a finite-element method for optically heterogeneous media. We demonstrate successful image reconstruction based on absolute experimental DC data obtained with a continuous wave 633 nm He-Ne laser system and a 751 nm diode laser system in laboratory phantoms having two optically distinct regions. The experimental systems used exploit a tomographic type of data collection scheme that provides information from which a spatially variable optical property map is deduced. Reconstruction of scattering coefficient only and simultaneous reconstruction of both scattering and absorption profiles in tissue-like phantoms are obtained from measured and simulated data. Images with different contrast levels between the heterogeneity and the background are also reported and the results show that although it is possible to obtain qualitative visual information on the location and size of a heterogeneity, it may not be possible to quantitatively resolve contrast levels or optical properties using reconstructions from DC data only. Sensitivity of image reconstruction to noise in the measurement data is investigated through simulations. The application of boundary constraints has also been addressed. (author)
Practical algorithms for simulation and reconstruction of digital in-line holograms.
Latychevskaia, Tatiana; Fink, Hans-Werner
2015-03-20
Here we present practical methods for simulation and reconstruction of in-line digital holograms recorded with plane and spherical waves. The algorithms described here are applicable to holographic imaging of an object exhibiting absorption as well as phase-shifting properties. Optimal parameters, related to distances, sampling rate, and other factors for successful simulation and reconstruction of holograms are evaluated and criteria for the achievable resolution are worked out. Moreover, we show that the numerical procedures for the reconstruction of holograms recorded with plane and spherical waves are identical under certain conditions. Experimental examples of holograms and their reconstructions are also discussed.
Atmospheric muons reconstruction with Antares; Reconstruction de muons atmospheriques avec ANTARES
Energy Technology Data Exchange (ETDEWEB)
Melissas, M
2007-09-15
The ANTARES collaboration is building a neutrino telescope in the Mediterranean Sea. This detector contains 900 photomultiplier tubes, dispatched on 12 lines, in order to detect Cerenkov light from muon induced by neutrino interactions in the the vicinity of the detector. Currently the first 5 lines have been deployed. A first task consists in studying the stability of the detector calibration, which is a necessary step to understand the detector response. Then we studied optical properties of water, for this we developed a reconstruction method dedicated to LED Beacon. The extracted parameters are compatible with earlier measurements. A quality criteria to reject badly reconstructed track has been developed based on the likelihood of the tracks fit versus point fit. This has been applied to real data and a preliminary analysis of atmospheric muons with a 5-lines detector is performed. (author)
Penalized maximum likelihood reconstruction for x-ray differential phase-contrast tomography
International Nuclear Information System (INIS)
Brendel, Bernhard; Teuffenbach, Maximilian von; Noël, Peter B.; Pfeiffer, Franz; Koehler, Thomas
2016-01-01
Purpose: The purpose of this work is to propose a cost function with regularization to iteratively reconstruct attenuation, phase, and scatter images simultaneously from differential phase contrast (DPC) acquisitions, without the need of phase retrieval, and examine its properties. Furthermore this reconstruction method is applied to an acquisition pattern that is suitable for a DPC tomographic system with continuously rotating gantry (sliding window acquisition), overcoming the severe smearing in noniterative reconstruction. Methods: We derive a penalized maximum likelihood reconstruction algorithm to directly reconstruct attenuation, phase, and scatter image from the measured detector values of a DPC acquisition. The proposed penalty comprises, for each of the three images, an independent smoothing prior. Image quality of the proposed reconstruction is compared to images generated with FBP and iterative reconstruction after phase retrieval. Furthermore, the influence between the priors is analyzed. Finally, the proposed reconstruction algorithm is applied to experimental sliding window data acquired at a synchrotron and results are compared to reconstructions based on phase retrieval. Results: The results show that the proposed algorithm significantly increases image quality in comparison to reconstructions based on phase retrieval. No significant mutual influence between the proposed independent priors could be observed. Further it could be illustrated that the iterative reconstruction of a sliding window acquisition results in images with substantially reduced smearing artifacts. Conclusions: Although the proposed cost function is inherently nonconvex, it can be used to reconstruct images with less aliasing artifacts and less streak artifacts than reconstruction methods based on phase retrieval. Furthermore, the proposed method can be used to reconstruct images of sliding window acquisitions with negligible smearing artifacts
Watson, Andrew William
2017-08-01
One of the most enduring questions in modern physics is the dark matter problem. Measurements of galactic rotation curves taken in the middle of the twentieth century suggest that there are large spherical halos of unseen matter permeating and surrounding most galaxies, stretching far beyond their visible extents. Although some of this mass discrepancy can be attributed to sources like primordial black holes or Massive Astrophysical Compact Halo Objects (MACHOs), these theories can only explain a small percentage of this "missing matter". One approach which could account for the entirety of this missing mass is the theory of Weakly Interacting Massive Particles, or "WIMPs". As their name suggests, WIMPs interact only through the weak nuclear force and gravity and are quite massive (100 GeV/c2 to 1 TeV/c2). These particles have very small cross sections ( ≈ 10-39 cm2) with nucleons and therefore interact only very rarely with "normal" baryonic matter. To directly detect a dark matter particle, one needs to overcome this small cross-section barrier. In many experiments, this is achieved by utilizing detectors filled with liquid noble elements, which have excellent particle identification capabilities and are very low-background, allowing potential WIMP signals to be more easily distinguished from detector noise. These experiments also often apply uniform electric fields across their liquid volumes, turning the apparatus into Time Projection Chambers or "TPCs". TPCs can accurately determine the location of an interaction in the liquid volume (often simply called an "event") along the direction of the electric field. In DarkSide-50 ("DS-50" for short), the electric field is aligned antiparallel to the z-axis of the detector, and so the depth of an event can be determined to a considerable degree of accuracy by measuring the time between the first and second scintillation signals ("S1" and "S2"), which are generated at the interaction point itself and in a small gas
Study of DNA reconstruction enzymes
Energy Technology Data Exchange (ETDEWEB)
Sekiguchi, M [Kyushu Univ., Fukuoka (Japan). Faculty of Science
1976-12-01
Description was made of the characteristics and mechanism of 3 reconstructive enzymes which received from M. luteus or E. coli or T4, and of which natures were clarified as reconstructive enzymes of DNA irradiated with ultraviolet rays. As characteristics, the site of breaking, reaction, molecular weight, electric charge in the neutrality and a specific adhesion to DNA irradiated with ultraviolet rays were mentioned. As to mutant of ultraviolet ray sensitivity, hereditary control mechanism of removal and reconstruction by endo-nuclease activation was described, and suggestion was referred to removal and reconstruction of cells of xedoderma pigmentosum which is a hereditary disease of human. Description was also made as to the mechanism of exonuclease activation which separates dimer selectively from irradiated DNA.
Quantum Logic and Quantum Reconstruction
Stairs, Allen
2015-01-01
Quantum logic understood as a reconstruction program had real successes and genuine limitations. This paper offers a synopsis of both and suggests a way of seeing quantum logic in a larger, still thriving context.
International Nuclear Information System (INIS)
Ibarra, Alejandro
2007-01-01
In this talk we discuss the prospects to reconstruct the high-energy see-saw Lagrangian from low energy experiments in supersymmetric scenarios. We show that the model with three right-handed neutrinos could be reconstructed in theory, but not in practice. Then, we discuss the prospects to reconstruct the model with two right-handed neutrinos, which is the minimal see-saw model able to accommodate neutrino observations. We identify the relevant processes to achieve this goal, and comment on the sensitivity of future experiments to them. We find the prospects much more promising and we emphasize in particular the importance of the observation of rare leptonic decays for the reconstruction of the right-handed neutrino masses
Breast Reconstruction with Flap Surgery
... augmented with a breast implant to achieve the desired breast size. Surgical methods Autologous tissue breast reconstruction ... as long as a year or two before feeling completely healed and back to normal. Future breast ...
Rational reconstructions of modern physics
Mittelstaedt, Peter
2013-01-01
Newton’s classical physics and its underlying ontology are loaded with several metaphysical hypotheses that cannot be justified by rational reasoning nor by experimental evidence. Furthermore, it is well known that some of these hypotheses are not contained in the great theories of Modern Physics, such as the theory of Special Relativity and Quantum Mechanics. This book shows that, on the basis of Newton’s classical physics and by rational reconstruction, the theory of Special Relativity as well as Quantum Mechanics can be obtained by partly eliminating or attenuating the metaphysical hypotheses. Moreover, it is shown that these reconstructions do not require additional hypotheses or new experimental results. In the second edition the rational reconstructions are completed with respect to General Relativity and Cosmology. In addition, the statistics of quantum objects is elaborated in more detail with respect to the rational reconstruction of quantum mechanics. The new material completes the approach of t...
Miéville, Frédéric A.; Bolard, Gregory; Benkreira, Mohamed; Ayestaran, Paul; Gudinchet, François; Bochud, François; Verdun, Francis R.
2011-03-01
The noise power spectrum (NPS) is the reference metric for understanding the noise content in computed tomography (CT) images. To evaluate the noise properties of clinical multidetector (MDCT) scanners, local 2D and 3D NPSs were computed for different acquisition reconstruction parameters. A 64- and a 128-MDCT scanners were employed. Measurements were performed on a water phantom in axial and helical acquisition modes. CT dose index was identical for both installations. Influence of parameters such as the pitch, the reconstruction filter (soft, standard and bone) and the reconstruction algorithm (filtered-back projection (FBP), adaptive statistical iterative reconstruction (ASIR)) were investigated. Images were also reconstructed in the coronal plane using a reformat process. Then 2D and 3D NPS methods were computed. In axial acquisition mode, the 2D axial NPS showed an important magnitude variation as a function of the z-direction when measured at the phantom center. In helical mode, a directional dependency with lobular shape was observed while the magnitude of the NPS was kept constant. Important effects of the reconstruction filter, pitch and reconstruction algorithm were observed on 3D NPS results for both MDCTs. With ASIR, a reduction of the NPS magnitude and a shift of the NPS peak to the low frequency range were visible. 2D coronal NPS obtained from the reformat images was impacted by the interpolation when compared to 2D coronal NPS obtained from 3D measurements. The noise properties of volume measured in last generation MDCTs was studied using local 3D NPS metric. However, impact of the non-stationarity noise effect may need further investigations.
Petz recovery versus matrix reconstruction
Holzäpfel, Milan; Cramer, Marcus; Datta, Nilanjana; Plenio, Martin B.
2018-04-01
The reconstruction of the state of a multipartite quantum mechanical system represents a fundamental task in quantum information science. At its most basic, it concerns a state of a bipartite quantum system whose subsystems are subjected to local operations. We compare two different methods for obtaining the original state from the state resulting from the action of these operations. The first method involves quantum operations called Petz recovery maps, acting locally on the two subsystems. The second method is called matrix (or state) reconstruction and involves local, linear maps that are not necessarily completely positive. Moreover, we compare the quantities on which the maps employed in the two methods depend. We show that any state that admits Petz recovery also admits state reconstruction. However, the latter is successful for a strictly larger set of states. We also compare these methods in the context of a finite spin chain. Here, the state of a finite spin chain is reconstructed from the reduced states of a few neighbouring spins. In this setting, state reconstruction is the same as the matrix product operator reconstruction proposed by Baumgratz et al. [Phys. Rev. Lett. 111, 020401 (2013)]. Finally, we generalize both these methods so that they employ long-range measurements instead of relying solely on short-range correlations embodied in such local reduced states. Long-range measurements enable the reconstruction of states which cannot be reconstructed from measurements of local few-body observables alone and hereby we improve existing methods for quantum state tomography of quantum many-body systems.
Animated Reconstruction of Forensic Animation
Hala, Albert; Unver, Ertu
1998-01-01
An animated accident display in court can be significant evidentiary tool. Computer graphics animation reconstructions which can be shown in court are cost effective, save valuable time and illustrate complex and technical issues, are realistic and can prove or disprove arguments or theories with reference to the perplexing newtonian physics involved in many accidents: this technology may well revolutionise accident reconstruction, thus enabling prosecution and defence to be more effective in...
Equilibrium Reconstruction in EAST Tokamak
International Nuclear Information System (INIS)
Qian Jinping; Wan Baonian; Shen Biao; Sun Youwen; Liu Dongmei; Xiao Bingjia; Ren Qilong; Gong Xianzu; Li Jiangang; Lao, L. L.; Sabbagh, S. A.
2009-01-01
Reconstruction of experimental axisymmetric equilibria is an important part of tokamak data analysis. Fourier expansion is applied to reconstruct the vessel current distribution in EFIT code. Benchmarking and testing calculations are performed to evaluate and validate this algorithm. Two cases for circular and non-circular plasma discharges are presented. Fourier expansion used to fit the eddy current is a robust method and the real time EFIT can be introduced to the plasma control system in the coming campaign. (magnetically confined plasma)
Urogenital Reconstructive Surgery
DEFF Research Database (Denmark)
Jakobsen, Lotte Kaasgaard
bladder to those of the bladder from young pigs used in the animal model. Results: By further characterising the effect of congenital obstruction, regarding urodynamic properties of the bladder and structural changes in the bladder tissue and comparing the results after relief of obstruction by continous...... of the lower urinary tract causes voiding disabilities, renal failure and chronic bladder changes. Children with such malformations often require extensive treatment, and will experience side effects and not always satisfactory results. Aim: To develop an animal model of congenital infravesical obstruction...... will be collected. To supplement the experimental studies we will evaluate patients with posterior urethral valves, and compare the effects of obstruction seen in these patients with the effects observed in the animal model. Bladder tissue from fetal pigs will be investigated, comparing the properties of the fetal...
Secondary reconstruction of maxillofacial trauma.
Castro-Núñez, Jaime; Van Sickels, Joseph E
2017-08-01
Craniomaxillofacial trauma is one of the most complex clinical conditions in contemporary maxillofacial surgery. Vital structures and possible functional and esthetic sequelae are important considerations following this type of trauma and intervention. Despite the best efforts of the primary surgery, there are a group of patients that will have poor outcomes requiring secondary reconstruction to restore form and function. The purpose of this study is to review current concepts on secondary reconstruction to the maxillofacial complex. The evaluation of a posttraumatic patient for a secondary reconstruction must include an assessment of the different subunits of the upper face, middle face, and lower face. Virtual surgical planning and surgical guides represent the most important innovations in secondary reconstruction over the past few years. Intraoperative navigational surgery/computed-assisted navigation is used in complex cases. Facial asymmetry can be corrected or significantly improved by segmentation of the computerized tomography dataset and mirroring of the unaffected side by means of virtual surgical planning. Navigational surgery/computed-assisted navigation allows for a more precise surgical correction when secondary reconstruction involves the replacement of extensive anatomical areas. The use of technology can result in custom-made replacements and prebent plates, which are more stable and resistant to fracture because of metal fatigue. Careful perioperative evaluation is the key to positive outcomes of secondary reconstruction after trauma. The advent of technological tools has played a capital role in helping the surgical team perform a given treatment plan in a more precise and predictable manner.
Technical basis for dose reconstruction
International Nuclear Information System (INIS)
Anspaugh, L.R.
1996-01-01
The purpose of this paper is to consider two general topics: Technical considerations of why dose-reconstruction studies should or should not be performed and methods of dose reconstruction. The first topic is of general and growing interest as the number of dose-reconstruction studies increases, and one asks the question whether it is necessary to perform a dose reconstruction for virtually every site at which, for example, the Department of Energy (DOE) has operated a nuclear-related facility. And there is the broader question of how one might logically draw the line at performing or not performing dose-reconstruction (radiological and chemical) studies for virtually every industrial complex in the entire country. The second question is also of general interest. There is no single correct way to perform a dose-reconstruction study, and it is important not to follow blindly a single method to the point that cheaper, faster, more accurate, and more transparent methods might not be developed and applied. 90 refs., 4 tabs
Technical basis for dose reconstruction
International Nuclear Information System (INIS)
Anspaugh, L.R.
1996-01-01
The purpose of this paper is to consider two general topics: technical considerations of why dose-reconstruction studies should or should not be performed and methods of dose reconstruction. The first topic is of general and growing interest as the number of dose-reconstruction studies increases, and one asks the question whether it is necessary to perform a dose reconstruction for virtually every site at which, for example, the Department of Energy (DOE) has operated a nuclear-related facility. And there is the broader question of how one might logically draw the line at performing or not performing dose-reconstruction (radiological and chemical) studies for virtually every industrial complex in the entire country. The second question is also of general interest. There is no single correct way to perform a dose-reconstruction study, and it is important not to follow blindly a single method to the point that cheaper, faster, more accurate, and more transparent methods might not be developed and applied
Anterior Cruciate Ligament Reconstruction in Ehlers-Danlos Syndrome
Directory of Open Access Journals (Sweden)
John Williams
2015-01-01
Full Text Available This report details the reconstruction of the anterior cruciate ligament in an 18-year-old man with Ehlers-Danlos syndrome (EDS. The reduced mechanical properties of the tissue in EDS can pose a challenge to the orthopaedic surgeon. In this case, we describe the use of a hamstring autograft combined with a Ligament Advanced Reinforcement System (LARS. There was a good radiographical, clinical, and functional outcome after two years. This technique gave a successful outcome in the reconstruction of the ACL in a patient with EDS and therefore may help surgeons faced with the same clinical scenario.
Visualization and Analysis-Oriented Reconstruction of Material Interfaces
Energy Technology Data Exchange (ETDEWEB)
Childs, Henry R.
2010-03-05
Reconstructing boundaries along material interfaces from volume fractions is a difficult problem, especially because the under-resolved nature of the input data allows for many correct interpretations. Worse, algorithms widely accepted as appropriate for simulation are inappropriate for visualization. In this paper, we describe a new algorithm that is specifically intended for reconstructing material interfaces for visualization and analysis requirements. The algorithm performs well with respect to memory footprint and execution time, has desirable properties in various accuracy metrics, and also produces smooth surfaces with few artifacts, even when faced with more than two materials per cell.
Epitaxial graphene-encapsulated surface reconstruction of Ge(110)
Campbell, Gavin P.; Kiraly, Brian; Jacobberger, Robert M.; Mannix, Andrew J.; Arnold, Michael S.; Hersam, Mark C.; Guisinger, Nathan P.; Bedzyk, Michael J.
2018-04-01
Understanding and engineering the properties of crystalline surfaces has been critical in achieving functional electronics at the nanoscale. Employing scanning tunneling microscopy, surface x-ray diffraction, and high-resolution x-ray reflectivity experiments, we present a thorough study of epitaxial graphene (EG)/Ge(110) and report a Ge(110) "6 × 2" reconstruction stabilized by the presence of epitaxial graphene unseen in group-IV semiconductor surfaces. X-ray studies reveal that graphene resides atop the surface reconstruction with a 0.34 nm van der Waals (vdW) gap and provides protection from ambient degradation.
On the Complexity of Reconstructing Chemical Reaction Networks
DEFF Research Database (Denmark)
Fagerberg, Rolf; Flamm, Christoph; Merkle, Daniel
2013-01-01
The analysis of the structure of chemical reaction networks is crucial for a better understanding of chemical processes. Such networks are well described as hypergraphs. However, due to the available methods, analyses regarding network properties are typically made on standard graphs derived from...... the full hypergraph description, e.g. on the so-called species and reaction graphs. However, a reconstruction of the underlying hypergraph from these graphs is not necessarily unique. In this paper, we address the problem of reconstructing a hypergraph from its species and reaction graph and show NP...
Energy Technology Data Exchange (ETDEWEB)
Van Eyndhoven, G., E-mail: geert.vaneyndhoven@uantwerpen.be [iMinds-Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium); Kurttepeli, M. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Van Oers, C.J.; Cool, P. [Laboratory of Adsorption and Catalysis, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium); Bals, S. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Batenburg, K.J. [iMinds-Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium); Centrum Wiskunde and Informatica, Science Park 123, NL-1090 GB Amsterdam (Netherlands); Mathematical Institute, Universiteit Leiden, Niels Bohrweg 1, NL-2333 CA Leiden (Netherlands); Sijbers, J. [iMinds-Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium)
2015-01-15
Electron tomography is currently a versatile tool to investigate the connection between the structure and properties of nanomaterials. However, a quantitative interpretation of electron tomography results is still far from straightforward. Especially accurate quantification of pore-space is hampered by artifacts introduced in all steps of the processing chain, i.e., acquisition, reconstruction, segmentation and quantification. Furthermore, most common approaches require subjective manual user input. In this paper, the PORES algorithm “POre REconstruction and Segmentation” is introduced; it is a tailor-made, integral approach, for the reconstruction, segmentation, and quantification of porous nanomaterials. The PORES processing chain starts by calculating a reconstruction with a nanoporous-specific reconstruction algorithm: the Simultaneous Update of Pore Pixels by iterative REconstruction and Simple Segmentation algorithm (SUPPRESS). It classifies the interior region to the pores during reconstruction, while reconstructing the remaining region by reducing the error with respect to the acquired electron microscopy data. The SUPPRESS reconstruction can be directly plugged into the remaining processing chain of the PORES algorithm, resulting in accurate individual pore quantification and full sample pore statistics. The proposed approach was extensively validated on both simulated and experimental data, indicating its ability to generate accurate statistics of nanoporous materials. - Highlights: • An electron tomography reconstruction/segmentation method for nanoporous materials. • The method exploits the porous nature of the scanned material. • Validated extensively on both simulation and real data experiments. • Results in increased image resolution and improved porosity quantification.
Beard reconstruction: A surgical algorithm.
Ninkovic, M; Heidekrueger, P I; Ehrl, D; von Spiegel, F; Broer, P N
2016-06-01
Facial defects with loss of hair-bearing regions can be caused by trauma, infection, tumor excision, or burn injury. The presented analysis evaluates a series of different surgical approaches with a focus on male beard reconstruction, emphasizing the role of tissue expansion of regional and free flaps. Locoregional and free flap reconstructions were performed in 11 male patients with 14 facial defects affecting the hair-bearing bucco-mandibular or perioral region. In order to minimize donor-site morbidity and obtain large amounts of thin, pliable, hair-bearing tissue, pre-expansion was performed in five of 14 patients. Eight of 14 patients were treated with locoregional flap reconstructions and six with free flap reconstructions. Algorithms regarding pre- and intraoperative decision making are discussed and long-term (mean follow-up 1.5 years) results analyzed. Major complications, including tissue expander infection with the need for removal or exchange, partial or full flap loss, occurred in 0% (0/8) of patients with locoregional flaps and in 17% (1/6) of patients undergoing free flap reconstructions. Secondary refinement surgery was performed in 25% (2/8) of locoregional flaps and in 67% (4/6) of free flaps. Both locoregional and distant tissue transfers play a role in beard reconstruction, while pre-expansion remains an invaluable tool. Paying attention to the presented principles and considering the significance of aesthetic facial subunits, range of motion, aesthetics, and patient satisfaction were improved long term in all our patients while minimizing donor-site morbidity. Copyright © 2016 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.
Real-time quasi-3D tomographic reconstruction
Buurlage, Jan-Willem; Kohr, Holger; Palenstijn, Willem Jan; Joost Batenburg, K.
2018-06-01
Developments in acquisition technology and a growing need for time-resolved experiments pose great computational challenges in tomography. In addition, access to reconstructions in real time is a highly demanded feature but has so far been out of reach. We show that by exploiting the mathematical properties of filtered backprojection-type methods, having access to real-time reconstructions of arbitrarily oriented slices becomes feasible. Furthermore, we present , software for visualization and on-demand reconstruction of slices. A user of can interactively shift and rotate slices in a GUI, while the software updates the slice in real time. For certain use cases, the possibility to study arbitrarily oriented slices in real time directly from the measured data provides sufficient visual and quantitative insight. Two such applications are discussed in this article.
Energy reconstruction and calibration algorithms for the ATLAS electromagnetic calorimeter
Delmastro, M
2003-01-01
The work of this thesis is devoted to the study, development and optimization of the algorithms of energy reconstruction and calibration for the electromagnetic calorimeter (EMC) of the ATLAS experiment, presently under installation and commissioning at the CERN Large Hadron Collider in Geneva (Switzerland). A deep study of the electrical characteristics of the detector and of the signals formation and propagation is conduced: an electrical model of the detector is developed and analyzed through simulations; a hardware model (mock-up) of a group of the EMC readout cells has been built, allowing the direct collection and properties study of the signals emerging from the EMC cells. We analyze the existing multiple-sampled signal reconstruction strategy, showing the need of an improvement in order to reach the advertised performances of the detector. The optimal filtering reconstruction technique is studied and implemented, taking into account the differences between the ionization and calibration waveforms as e...
Titanium template for scaphoid reconstruction.
Haefeli, M; Schaefer, D J; Schumacher, R; Müller-Gerbl, M; Honigmann, P
2015-06-01
Reconstruction of a non-united scaphoid with a humpback deformity involves resection of the non-union followed by bone grafting and fixation of the fragments. Intraoperative control of the reconstruction is difficult owing to the complex three-dimensional shape of the scaphoid and the other carpal bones overlying the scaphoid on lateral radiographs. We developed a titanium template that fits exactly to the surfaces of the proximal and distal scaphoid poles to define their position relative to each other after resection of the non-union. The templates were designed on three-dimensional computed tomography reconstructions and manufactured using selective laser melting technology. Ten conserved human wrists were used to simulate the reconstruction. The achieved precision measured as the deviation of the surface of the reconstructed scaphoid from its virtual counterpart was good in five cases (maximal difference 1.5 mm), moderate in one case (maximal difference 3 mm) and inadequate in four cases (difference more than 3 mm). The main problems were attributed to the template design and can be avoided by improved pre-operative planning, as shown in a clinical case. © The Author(s) 2014.
Practical implementation of tetrahedral mesh reconstruction in emission tomography
Boutchko, R.; Sitek, A.; Gullberg, G. T.
2013-05-01
This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio
Practical implementation of tetrahedral mesh reconstruction in emission tomography
International Nuclear Information System (INIS)
Boutchko, R; Gullberg, G T; Sitek, A
2013-01-01
This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio
Energy Technology Data Exchange (ETDEWEB)
Ramirez, Diego [Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz (Germany)
2016-07-01
XENON1T is the 3rd stage of a series of experiments performed by the XENON collaboration for the direct detection of dark matter candidates, such as WIMPs. Its projected spin-independent WIMP-nucleon elastic scattering cross-section entails an improvement of two orders of magnitude with respect to Xenon100 and requires, for a fiducial mass of the detector of about 1 ton liquid xenon, a similar reduction in background. In order to minimize the neutron background induced by cosmic ray muons, the XENON1T TPC is placed in the center of a 750 m{sup 3} water tank acting as an active Cherenkov muon veto, the walls of which are clad with the high reflective DF2000MA foil by 3M. The improved setup and results of a dedicated study of the reflective properties of the foil is presented, as well as a measurement of its possible wavelength shifting (WLS) properties. The analysis yields a specular reflectance of ∼ 100% for wavelengths larger than 400 nm, while ∼ 90% of the incoming light with wavelengths smaller than 370 nm is absorbed by the foil. The emission spectra of the WLS are dependent on the absorbed wavelength and show Gaussian shapes, with highest intensities at mean values of ∼ 450 nm emission wavelength.
Fan-beam filtered-backprojection reconstruction without backprojection weight
International Nuclear Information System (INIS)
Dennerlein, Frank; Noo, Frederic; Hornegger, Joachim; Lauritsch, Guenter
2007-01-01
In this paper, we address the problem of two-dimensional image reconstruction from fan-beam data acquired along a full 2π scan. Conventional approaches that follow the filtered-backprojection (FBP) structure require a weighted backprojection with the weight depending on the point to be reconstructed and also on the source position; this weight appears only in the case of divergent beam geometries. Compared to reconstruction from parallel-beam data, the backprojection weight implies an increase in computational effort and is also thought to have some negative impacts on noise properties of the reconstructed images. We demonstrate here that direct FBP reconstruction from full-scan fan-beam data is possible with no backprojection weight. Using computer-simulated, realistic fan-beam data, we compared our novel FBP formula with no backprojection weight to the use of an FBP formula based on equal weighting of all data. Comparisons in terms of signal-to-noise ratio, spatial resolution and computational efficiency are presented. These studies show that the formula we suggest yields images with a reduced noise level, at almost identical spatial resolution. This effect increases quickly with the distance from the center of the field of view, from 0% at the center to 20% less noise at 20 cm, and to 40% less noise at 25 cm. Furthermore, the suggested method is computationally less demanding and reduces computation time with a gain that was found to vary between 12% and 43% on the computers used for evaluation
Parametric image reconstruction using spectral analysis of PET projection data
International Nuclear Information System (INIS)
Meikle, Steven R.; Matthews, Julian C.; Cunningham, Vincent J.; Bailey, Dale L.; Livieratos, Lefteris; Jones, Terry; Price, Pat
1998-01-01
Spectral analysis is a general modelling approach that enables calculation of parametric images from reconstructed tracer kinetic data independent of an assumed compartmental structure. We investigated the validity of applying spectral analysis directly to projection data motivated by the advantages that: (i) the number of reconstructions is reduced by an order of magnitude and (ii) iterative reconstruction becomes practical which may improve signal-to-noise ratio (SNR). A dynamic software phantom with typical 2-[ 11 C]thymidine kinetics was used to compare projection-based and image-based methods and to assess bias-variance trade-offs using iterative expectation maximization (EM) reconstruction. We found that the two approaches are not exactly equivalent due to properties of the non-negative least-squares algorithm. However, the differences are small ( 1 and, to a lesser extent, VD). The optimal number of EM iterations was 15-30 with up to a two-fold improvement in SNR over filtered back projection. We conclude that projection-based spectral analysis with EM reconstruction yields accurate parametric images with high SNR and has potential application to a wide range of positron emission tomography ligands. (author)
Time-Dependent-Asymmetric-Linear-Parsimonious Ancestral State Reconstruction.
Didier, Gilles
2017-10-01
The time-dependent-asymmetric-linear parsimony is an ancestral state reconstruction method which extends the standard linear parsimony (a.k.a. Wagner parsimony) approach by taking into account both branch lengths and asymmetric evolutionary costs for reconstructing quantitative characters (asymmetric costs amount to assuming an evolutionary trend toward the direction with the lowest cost). A formal study of the influence of the asymmetry parameter shows that the time-dependent-asymmetric-linear parsimony infers states which are all taken among the known states, except for some degenerate cases corresponding to special values of the asymmetry parameter. This remarkable property holds in particular for the Wagner parsimony. This study leads to a polynomial algorithm which determines, and provides a compact representation of, the parametric reconstruction of a phylogenetic tree, that is for all the unknown nodes, the set of all the possible reconstructed states associated with the asymmetry parameters leading to them. The time-dependent-asymmetric-linear parsimony is finally illustrated with the parametric reconstruction of the body size of cetaceans.
Reconstructing a general inflationary action
International Nuclear Information System (INIS)
Bean, Rachel; Chung, Daniel J. H.; Geshnizjani, Ghazal
2008-01-01
If inflation is to be considered in an unbiased way, as possibly originating from one of a wide range of underlying theories, then observations need not be simply applied to reconstructing the inflaton potential V(φ) or a specific kinetic term, as in Dirac-Born-Infeld inflation, but rather to reconstruct the inflationary action in its entirety. We discuss the constraints that can be placed on a general single field action from measurements of the primordial scalar and tensor fluctuation power spectra and non-Gaussianities. The analytic form of the action that is consistent with data turns out to be surprisingly simple and easy to categorize. We also present the flow equation formalism for reconstructing a general inflationary Lagrangian L(X,φ), with X=(1/2)∂ μ φ∂ μ φ, in a general gauge, that reduces to canonical and DBI inflation in the specific gauge L X =c s -1 .
Avoiding Complications with MPFL Reconstruction.
Smith, Marvin K; Werner, Brian C; Diduch, David R
2018-05-12
To discuss the potentially significant complications associated with medial patellofemoral ligament (MPFL) reconstruction. Additionally, to review the most current and relevant literature with an emphasis on avoiding these potential complications. Multiple cadaveric studies have characterized the anatomy of the MPFL and the related morphologic abnormalities that contribute to recurrent lateral patellar instability. Such abnormalities include patella alta, excessive tibial tubercle to trochlear grove (TT-TG) distance, trochlear dysplasia, and malalignment. Recent studies have evaluated the clinical outcomes associated with the treatment of concomitant pathology in combination with MPFL reconstruction, which is critical in avoiding recurrent instability and complications. Although there remains a lack of consensus regarding various critical aspects of MPFL reconstruction, certain concepts remain imperative. Our preferred methods and rationales for surgical techniques are described. These include appropriate work up, a combination of procedures to address abnormal morphology, anatomical femoral insertion, safe and secure patellar fixation, appropriate graft length fixation, and thoughtful knee flexion during fixation.
CURRENT CONCEPTS IN ACL RECONSTRUCTION
Directory of Open Access Journals (Sweden)
Freddie H. Fu
2008-09-01
Full Text Available Current Concepts in ACL Reconstruction is a complete reference text composed of the most thorough collection of topics on the ACL and its surgical reconstruction compiled, with contributions from some of the world's experts and most experienced ACL surgeons. Various procedures mentioned throughout the text are also demonstrated in an accompanying video CD-ROM. PURPOSE Composing a single, comprehensive and complete information source on ACL including basic sciences, clinical issues, latest concepts and surgical techniques, from evaluation to outcome, from history to future, editors and contributors have targeted to keep the audience pace with the latest concepts and techniques for the evaluation and the treatment of ACL injuries. FEATURES The text is composed of 27 chapters in 6 sections. The first section is mostly about basic sciences, also history of the ACL, imaging, clinical approach to adolescent and pediatric patients are subjected. In the second section, Graft Choices and Arthroscopy Portals for ACL Reconstruction are mentioned. The third section is about the technique and the outcome of the single-bundle ACL reconstruction. The fourth chapter includes the techniques and outcome of the double-bundle ACL reconstruction. In the fifth chapter revision, navigation technology, rehabilitation and the evaluation of the outcome of ACL reconstruction is subjected. The sixth/the last chapter is about the future advances to reach: What We Have Learned and the Future of ACL Reconstruction. AUDIENCE Orthopedic residents, sports traumatology and knee surgery fellows, orthopedic surgeons, also scientists in basic sciences or clinicians who are studying or planning a research on ACL forms the audience group of this book. ASSESSMENT This is the latest, the most complete and comprehensive textbook of ACL reconstruction produced by the editorial work up of two pioneer and masters "Freddie H. Fu MD and Steven B. Cohen MD" with the contribution of world
Recovery after abdominal wall reconstruction
DEFF Research Database (Denmark)
Jensen, Kristian Kiim
2017-01-01
Incisional hernia is a common long-term complication to abdominal surgery, occurring in more than 20% of all patients. Some of these hernias become giant and affect patients in several ways. This patient group often experiences pain, decreased perceived body image, and loss of physical function......, which results in a need for surgical repair of the giant hernia, known as abdominal wall reconstruction. In the current thesis, patients with a giant hernia were examined to achieve a better understanding of their physical and psychological function before and after abdominal wall reconstruction. Study...... was lacking. Study II was a case-control study of the effects of an enhanced recovery after surgery pathway for patients undergoing abdominal wall reconstruction for a giant hernia. Sixteen consecutive patients were included prospectively after the implementation of a new enhanced recovery after surgery...
Fast group matching for MR fingerprinting reconstruction.
Cauley, Stephen F; Setsompop, Kawin; Ma, Dan; Jiang, Yun; Ye, Huihui; Adalsteinsson, Elfar; Griswold, Mark A; Wald, Lawrence L
2015-08-01
MR fingerprinting (MRF) is a technique for quantitative tissue mapping using pseudorandom measurements. To estimate tissue properties such as T1 , T2 , proton density, and B0 , the rapidly acquired data are compared against a large dictionary of Bloch simulations. This matching process can be a very computationally demanding portion of MRF reconstruction. We introduce a fast group matching algorithm (GRM) that exploits inherent correlation within MRF dictionaries to create highly clustered groupings of the elements. During matching, a group specific signature is first used to remove poor matching possibilities. Group principal component analysis (PCA) is used to evaluate all remaining tissue types. In vivo 3 Tesla brain data were used to validate the accuracy of our approach. For a trueFISP sequence with over 196,000 dictionary elements, 1000 MRF samples, and image matrix of 128 × 128, GRM was able to map MR parameters within 2s using standard vendor computational resources. This is an order of magnitude faster than global PCA and nearly two orders of magnitude faster than direct matching, with comparable accuracy (1-2% relative error). The proposed GRM method is a highly efficient model reduction technique for MRF matching and should enable clinically relevant reconstruction accuracy and time on standard vendor computational resources. © 2014 Wiley Periodicals, Inc.
Graft fixation in cruciate ligament reconstruction.
Brand, J; Weiler, A; Caborn, D N; Brown, C H; Johnson, D L
2000-01-01
Cruciate ligament reconstruction has progressed dramatically in the last 20 years. Anatomic placement of ligament substitutes has fostered rehabilitation efforts that stress immediate and full range of motion, immediate weightbearing, neuromuscular strength and coordination, and early return to athletic competition (3 months). This has placed extreme importance on secure graft fixation at the time of ligament reconstruction. Current ligament substitutes require a bony or soft tissue component to be fixed within a bone tunnel or on the periosteum at a distance from the normal ligament attachment site. Fixation devices have progressed from metal to biodegradable and from far to near-normal native ligament attachment sites. Ideally, the biomechanical properties of the entire graft construct would approach those of the native ligament and facilitate biologic incorporation of the graft. Fixation should be done at the normal anatomic attachment site of the native ligament (aperture fixation) and, over time, allow the biologic return of the histologic transition zone from ligament to fibrocartilage, to calcified fibrocartilage, to bone. The purpose of this article is to review current fixation devices and techniques in cruciate ligament surgery.
Non-Cartesian parallel imaging reconstruction.
Wright, Katherine L; Hamilton, Jesse I; Griswold, Mark A; Gulani, Vikas; Seiberlich, Nicole
2014-11-01
Non-Cartesian parallel imaging has played an important role in reducing data acquisition time in MRI. The use of non-Cartesian trajectories can enable more efficient coverage of k-space, which can be leveraged to reduce scan times. These trajectories can be undersampled to achieve even faster scan times, but the resulting images may contain aliasing artifacts. Just as Cartesian parallel imaging can be used to reconstruct images from undersampled Cartesian data, non-Cartesian parallel imaging methods can mitigate aliasing artifacts by using additional spatial encoding information in the form of the nonhomogeneous sensitivities of multi-coil phased arrays. This review will begin with an overview of non-Cartesian k-space trajectories and their sampling properties, followed by an in-depth discussion of several selected non-Cartesian parallel imaging algorithms. Three representative non-Cartesian parallel imaging methods will be described, including Conjugate Gradient SENSE (CG SENSE), non-Cartesian generalized autocalibrating partially parallel acquisition (GRAPPA), and Iterative Self-Consistent Parallel Imaging Reconstruction (SPIRiT). After a discussion of these three techniques, several potential promising clinical applications of non-Cartesian parallel imaging will be covered. © 2014 Wiley Periodicals, Inc.
WIMP Dark Matter interpretation of Higgs results
Wang, Renjie; The ATLAS collaboration
2017-01-01
The results from searching for dark matter either directly from invisible decay of Higgs bosons or in association with a Higgs boson at the LHC are presented. No significant excess is found beyond the Standard Model prediction, and upper limits are set on the production cross section times branching fraction using data collected in proton-proton collisions at center-of-mass energies of 13 TeV by the ATLAS and CMS detectors. An interpreted upper limit is presented on the allowed dark matter-nucleon scattering cross section.
International Nuclear Information System (INIS)
Choi, Joonsung; Kim, Dongchan; Oh, Changhyun; Han, Yeji; Park, HyunWook
2013-01-01
In MRI (magnetic resonance imaging), signal sampling along a radial k-space trajectory is preferred in certain applications due to its distinct advantages such as robustness to motion, and the radial sampling can be beneficial for reconstruction algorithms such as parallel MRI (pMRI) due to the incoherency. For radial MRI, the image is usually reconstructed from projection data using analytic methods such as filtered back-projection or Fourier reconstruction after gridding. However, the quality of the reconstructed image from these analytic methods can be degraded when the number of acquired projection views is insufficient. In this paper, we propose a novel reconstruction method based on the expectation maximization (EM) method, where the EM algorithm is remodeled for MRI so that complex images can be reconstructed. Then, to optimize the proposed method for radial pMRI, a reconstruction method that uses coil sensitivity information of multichannel RF coils is formulated. Experiment results from synthetic and in vivo data show that the proposed method introduces better reconstructed images than the analytic methods, even from highly subsampled data, and provides monotonic convergence properties compared to the conjugate gradient based reconstruction method. (paper)
Optically stimulated luminescence of common plastic materials for accident dose reconstruction
Energy Technology Data Exchange (ETDEWEB)
Chang, I.; Lee, J. I.; Kim, J. L. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Chung, K. S. [Gyeongsang National Univ., Jinju (Korea, Republic of)
2014-05-15
Optically stimulate luminescence(OSL) has many applications in a variety of radiation dosimetry fields, including personal dosimetry, environmental radiation level monitor, retrospective dosimetry for dating, and reconstruction of radiation doses from radiation accident. In the reconstruction of radiation doses from radiation accident, OSL technique has been used to estimate the doses exposed to public area through analysis of housewares or house construing materials. Recently, many efforts have been carried out for dose reconstruction using personal electronic devices such as mobile phones and USB memory chips. Some of natural minerals such as quartz and feldspar have OSL properties. Quartz is the second most abundant mineral in continental crust of the Earth. In some of common plastics, inorganic fillers (quartz, alumina etc.) are added to make strengthen of their properties depends on applications areas. The aim of this research is to explore a possibility of use of the common plastic materials for dose reconstruction in radiation accident case. In this research the OSL dose response-curve and fading characteristics of the common plastics were tested and evaluated. Finally, we expect this work contribute to elevate the possibility of the dose reconstruction. The general conclusion of this work is that the possibility of dose reconstruction using common plastic materials is showed using the OSL characteristics of the materials. However, the tested common plastic materials have relatively low sensitivities. Further work is required to establish a database of OSL properties of common plastic materials for emergency dose reconstruction by using housewares.
Method of reconstructing a moving pulse
Energy Technology Data Exchange (ETDEWEB)
Howard, S J; Horton, R D; Hwang, D Q; Evans, R W; Brockington, S J; Johnson, J [UC Davis Department of Applied Science, Livermore, CA, 94551 (United States)
2007-11-15
We present a method of analyzing a set of N time signals f{sub i}(t) that consist of local measurements of the same physical observable taken at N sequential locations Z{sub i} along the length of an experimental device. The result is an algorithm for reconstructing an approximation F(z,t) of the field f(z,t) in the inaccessible regions between the points of measurement. We also explore the conditions needed for this approximation to hold, and test the algorithm under a variety of conditions. We apply this method to analyze the magnetic field measurements taken on the Compact Toroid Injection eXperiment (CTIX) plasma accelerator; providing a direct means of visualizing experimental data, quantifying global properties, and benchmarking simulation.
International Nuclear Information System (INIS)
Hofmann, Christian; Sawall, Stefan; Knaup, Michael; Kachelrieß, Marc
2014-01-01
Purpose: Iterative image reconstruction gains more and more interest in clinical routine, as it promises to reduce image noise (and thereby patient dose), to reduce artifacts, or to improve spatial resolution. Among vendors and researchers, however, there is no consensus of how to best achieve these aims. The general approach is to incorporatea priori knowledge into iterative image reconstruction, for example, by adding additional constraints to the cost function, which penalize variations between neighboring voxels. However, this approach to regularization in general poses a resolution noise trade-off because the stronger the regularization, and thus the noise reduction, the stronger the loss of spatial resolution and thus loss of anatomical detail. The authors propose a method which tries to improve this trade-off. The proposed reconstruction algorithm is called alpha image reconstruction (AIR). One starts with generating basis images, which emphasize certain desired image properties, like high resolution or low noise. The AIR algorithm reconstructs voxel-specific weighting coefficients that are applied to combine the basis images. By combining the desired properties of each basis image, one can generate an image with lower noise and maintained high contrast resolution thus improving the resolution noise trade-off. Methods: All simulations and reconstructions are performed in native fan-beam geometry. A water phantom with resolution bar patterns and low contrast disks is simulated. A filtered backprojection (FBP) reconstruction with a Ram-Lak kernel is used as a reference reconstruction. The results of AIR are compared against the FBP results and against a penalized weighted least squares reconstruction which uses total variation as regularization. The simulations are based on the geometry of the Siemens Somatom Definition Flash scanner. To quantitatively assess image quality, the authors analyze line profiles through resolution patterns to define a contrast
Energy Technology Data Exchange (ETDEWEB)
Diogenes, Alysson N.; Santos, Luis O.E. dos; Fernandes, Celso P. [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil); Appoloni, Carlos R. [Universidade Estadual de Londrina (UEL), PR (Brazil)
2008-07-01
The reservoir rocks physical properties are usually obtained in laboratory, through standard experiments. These experiments are often very expensive and time-consuming. Hence, the digital image analysis techniques are a very fast and low cost methodology for physical properties prediction, knowing only geometrical parameters measured from the rock microstructure thin sections. This research analyzes two methods for porous media reconstruction using the relaxation method simulated annealing. Using geometrical parameters measured from rock thin sections, it is possible to construct a three-dimensional (3D) model of the microstructure. We assume statistical homogeneity and isotropy and the 3D model maintains porosity spatial correlation, chord size distribution and d 3-4 distance transform distribution for a pixel-based reconstruction and spatial correlation for an object-based reconstruction. The 2D and 3D preliminary results are compared with microstructures reconstructed by truncated Gaussian methods. As this research is in its beginning, only the 2D results will be presented. (author)
Ulysses S. Grant and Reconstruction.
Wilson, David L.
1989-01-01
Discusses the role played by Ulysses S. Grant during the four years of Reconstruction before he became President of the United States. Describes the dynamics of the relationship between Grant and Andrew Johnson. Points out that Grant's attitude of service to the laws created by Congress submerged his desire to create a new South. (KO)
ASME method for particle reconstruction
International Nuclear Information System (INIS)
Ierusalimov, A.P.
2009-01-01
The method of approximate solution of motion equation (ASME) was used to reconstruct the parameters for charged particles. It provides a good precision for momentum, angular and space parameters of particles in coordinate detectors. The application of the method for CBM, HADES and MPD/NICA setups is discussed
A Survey of Urban Reconstruction
Musialski, P.
2013-05-10
This paper provides a comprehensive overview of urban reconstruction. While there exists a considerable body of literature, this topic is still under active research. The work reviewed in this survey stems from the following three research communities: computer graphics, computer vision and photogrammetry and remote sensing. Our goal is to provide a survey that will help researchers to better position their own work in the context of existing solutions, and to help newcomers and practitioners in computer graphics to quickly gain an overview of this vast field. Further, we would like to bring the mentioned research communities to even more interdisciplinary work, since the reconstruction problem itself is by far not solved. This paper provides a comprehensive overview of urban reconstruction. While there exists a considerable body of literature, this topic is still under active research. The work reviewed in this survey stems from the following three research communities: computer graphics, computer vision and photogrammetry and remote sensing. Our goal is to provide a survey that will help researchers to better position their own work in the context of existing solutions, and to help newcomers and practitioners in computer graphics to quickly gain an overview of this vast field. Further, we would like to bring the mentioned research communities to even more interdisciplinary work, since the reconstruction problem itself is by far not solved. © 2013 The Eurographics Association and John Wiley & Sons Ltd.
A Survey of Urban Reconstruction
Musialski, P.; Wonka, Peter; Aliaga, D. G.; Wimmer, M.; van Gool, L.; Purgathofer, W.
2013-01-01
This paper provides a comprehensive overview of urban reconstruction. While there exists a considerable body of literature, this topic is still under active research. The work reviewed in this survey stems from the following three research communities: computer graphics, computer vision and photogrammetry and remote sensing. Our goal is to provide a survey that will help researchers to better position their own work in the context of existing solutions, and to help newcomers and practitioners in computer graphics to quickly gain an overview of this vast field. Further, we would like to bring the mentioned research communities to even more interdisciplinary work, since the reconstruction problem itself is by far not solved. This paper provides a comprehensive overview of urban reconstruction. While there exists a considerable body of literature, this topic is still under active research. The work reviewed in this survey stems from the following three research communities: computer graphics, computer vision and photogrammetry and remote sensing. Our goal is to provide a survey that will help researchers to better position their own work in the context of existing solutions, and to help newcomers and practitioners in computer graphics to quickly gain an overview of this vast field. Further, we would like to bring the mentioned research communities to even more interdisciplinary work, since the reconstruction problem itself is by far not solved. © 2013 The Eurographics Association and John Wiley & Sons Ltd.
Solutions for autonomy and reconstruction
Energy Technology Data Exchange (ETDEWEB)
Wilming, Wilhelm
2011-07-01
Stand-alone systems, whether solar home or pico solar systems, have reached a cost level at which they are an increasingly interesting option for wide-area development in grid-remote regions or for reconstruction where the previous grid infrastructure has been destroyed. (orig.)
Poethical: Breaking Ground for Reconstruction
Krojer, Jo; Holge-Hazelton, Bibi
2008-01-01
Departing from a methodological experiment performed by the authors, this article reflects on and discusses issues of ethics and politics in poetic strategies of "representation". In relation to the experiment the article questions how to conceive the notion of connectedness between empirical time and the reconstruction of it in poststructuralist…
Regional absolute conductivity reconstruction using projected current density in MREIT
International Nuclear Information System (INIS)
Sajib, Saurav Z K; Kim, Hyung Joong; Woo, Eung Je; Kwon, Oh In
2012-01-01
Magnetic resonance electrical impedance tomography (MREIT) is a non-invasive technique for imaging the internal conductivity distribution in tissue within an MRI scanner, utilizing the magnetic flux density, which is introduced when a current is injected into the tissue from external electrodes. This magnetic flux alters the MRI signal, so that appropriate reconstruction can provide a map of the additional z-component of the magnetic field (B z ) as well as the internal current density distribution that created it. To extract the internal electrical properties of the subject, including the conductivity and/or the current density distribution, MREIT techniques use the relationship between the external injection current and the z-component of the magnetic flux density B = (B x , B y , B z ). The tissue studied typically contains defective regions, regions with a low MRI signal and/or low MRI signal-to-noise-ratio, due to the low density of nuclear magnetic resonance spins, short T 2 or T* 2 relaxation times, as well as regions with very low electrical conductivity, through which very little current traverses. These defective regions provide noisy B z data, which can severely degrade the overall reconstructed conductivity distribution. Injecting two independent currents through surface electrodes, this paper proposes a new direct method to reconstruct a regional absolute isotropic conductivity distribution in a region of interest (ROI) while avoiding the defective regions. First, the proposed method reconstructs the contrast of conductivity using the transversal J-substitution algorithm, which blocks the propagation of severe accumulated noise from the defective region to the ROI. Second, the proposed method reconstructs the regional projected current density using the relationships between the internal current density, which stems from a current injection on the surface, and the measured B z data. Combining the contrast conductivity distribution in the entire imaging
Stability indicators in network reconstruction.
Directory of Open Access Journals (Sweden)
Michele Filosi
Full Text Available The number of available algorithms to infer a biological network from a dataset of high-throughput measurements is overwhelming and keeps growing. However, evaluating their performance is unfeasible unless a 'gold standard' is available to measure how close the reconstructed network is to the ground truth. One measure of this is the stability of these predictions to data resampling approaches. We introduce NetSI, a family of Network Stability Indicators, to assess quantitatively the stability of a reconstructed network in terms of inference variability due to data subsampling. In order to evaluate network stability, the main NetSI methods use a global/local network metric in combination with a resampling (bootstrap or cross-validation procedure. In addition, we provide two normalized variability scores over data resampling to measure edge weight stability and node degree stability, and then introduce a stability ranking for edges and nodes. A complete implementation of the NetSI indicators, including the Hamming-Ipsen-Mikhailov (HIM network distance adopted in this paper is available with the R package nettools. We demonstrate the use of the NetSI family by measuring network stability on four datasets against alternative network reconstruction methods. First, the effect of sample size on stability of inferred networks is studied in a gold standard framework on yeast-like data from the Gene Net Weaver simulator. We also consider the impact of varying modularity on a set of structurally different networks (50 nodes, from 2 to 10 modules, and then of complex feature covariance structure, showing the different behaviours of standard reconstruction methods based on Pearson correlation, Maximum Information Coefficient (MIC and False Discovery Rate (FDR strategy. Finally, we demonstrate a strong combined effect of different reconstruction methods and phenotype subgroups on a hepatocellular carcinoma miRNA microarray dataset (240 subjects, and we
Genital reconstruction in exstrophy patients
Directory of Open Access Journals (Sweden)
R B Nerli
2012-01-01
Full Text Available Introduction: Surgery for bladder exstrophy has been evolving over the last four to five decades. Because survival has become almost universal, the focus has changed in the exstrophy-epispadias complex to improving quality of life. The most prevalent problem in the long-term function of exstrophy patients is the sexual activity of the adolescent and adult males. The penis in exstrophy patients appears short because of marked congenital deficiency of anterior corporal tissue. Many patients approach for genital reconstruction to improve cosmesis as well as to correct chordee. We report our series of male patients seeking genital reconstruction following exstrophy repair in the past. Materials and Methods: Fourteen adolescent/adult male patients attended urology services during the period January 2000-December 2009 seeking genital reconstruction following exstrophy repair in the past. Results: Three patients underwent epispadias repair, four patients had chordee correction with cosmetic excision of skin tags and seven patients underwent chordee correction with penile lengthening. All patients reported satisfaction in the answered questionnaire. Patients undergoing penile lengthening by partial corporal dissection achieved a mean increase in length of 1.614 ± 0.279 cm dorsally and 1.543 ± 0.230 cm ventrally. The satisfactory rate assessed by the Short Form-36 (SF-36 showed that irrespective of the different genital reconstructive procedures done, the patients were satisfied with cosmetic and functional outcome. Conclusions: Surgical procedures have transformed the management in these patients with bladder exstrophy. Bladders can be safely placed within the pelvis, with most patients achieving urinary continence and cosmetically acceptable external genitalia. Genital reconstruction in the form of correction of chordee, excision of ugly skin tags and lengthening of penis can be performed to give the patients a satisfactory cosmetic and functional
Nuclear data compression and reconstruction via discrete wavelet transform
Energy Technology Data Exchange (ETDEWEB)
Park, Young Ryong; Cho, Nam Zin [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)
1997-12-31
Discrete Wavelet Transforms (DWTs) are recent mathematics, and begin to be used in various fields. The wavelet transform can be used to compress the signal and image due to its inherent properties. We applied the wavelet transform compression and reconstruction to the neutron cross section data. Numerical tests illustrate that the signal compression using wavelet is very effective to reduce the data saving spaces. 7 refs., 4 figs., 3 tabs. (Author)
Nuclear data compression and reconstruction via discrete wavelet transform
Energy Technology Data Exchange (ETDEWEB)
Park, Young Ryong; Cho, Nam Zin [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)
1998-12-31
Discrete Wavelet Transforms (DWTs) are recent mathematics, and begin to be used in various fields. The wavelet transform can be used to compress the signal and image due to its inherent properties. We applied the wavelet transform compression and reconstruction to the neutron cross section data. Numerical tests illustrate that the signal compression using wavelet is very effective to reduce the data saving spaces. 7 refs., 4 figs., 3 tabs. (Author)
Error Propagation dynamics: from PIV-based pressure reconstruction to vorticity field calculation
Pan, Zhao; Whitehead, Jared; Richards, Geordie; Truscott, Tadd; USU Team; BYU Team
2017-11-01
Noninvasive data from velocimetry experiments (e.g., PIV) have been used to calculate vorticity and pressure fields. However, the noise, error, or uncertainties in the PIV measurements would eventually propagate to the calculated pressure or vorticity field through reconstruction schemes. Despite the vast applications of pressure and/or vorticity field calculated from PIV measurements, studies on the error propagation from the velocity field to the reconstructed fields (PIV-pressure and PIV-vorticity are few. In the current study, we break down the inherent connections between PIV-based pressure reconstruction and PIV-based vorticity calculation. The similar error propagation dynamics, which involve competition between physical properties of the flow and numerical errors from reconstruction schemes, are found in both PIV-pressure and PIV-vorticity reconstructions.
Mandibular reconstruction in adults: a review.
Goh, B.T.; Lee, S.; Tideman, H.; Stoelinga, P.J.W.
2008-01-01
Mandibular defects may result from trauma, inflammatory disease and benign or malignant tumours. Mastication, speech and facial aesthetics are often severely compromised without reconstruction. The goal of mandibular reconstruction is to restore facial form and function, implying repair of
Discrete Wigner Function Reconstruction and Compressed Sensing
Zhang, Jia-Ning; Fang, Lei; Ge, Mo-Lin
2011-01-01
A new reconstruction method for Wigner function is reported for quantum tomography based on compressed sensing. By analogy with computed tomography, Wigner functions for some quantum states can be reconstructed with less measurements utilizing this compressed sensing based method.
Climate reconstruction from borehole temperatures influenced by groundwater flow
Kurylyk, B.; Irvine, D. J.; Tang, W.; Carey, S. K.; Ferguson, G. A. G.; Beltrami, H.; Bense, V.; McKenzie, J. M.; Taniguchi, M.
2017-12-01
Borehole climatology offers advantages over other climate reconstruction methods because further calibration steps are not required and heat is a ubiquitous subsurface property that can be measured from terrestrial boreholes. The basic theory underlying borehole climatology is that past surface air temperature signals are reflected in the ground surface temperature history and archived in subsurface temperature-depth profiles. High frequency surface temperature signals are attenuated in the shallow subsurface, whereas low frequency signals can be propagated to great depths. A limitation of analytical techniques to reconstruct climate signals from temperature profiles is that they generally require that heat flow be limited to conduction. Advection due to groundwater flow can thermally `contaminate' boreholes and result in temperature profiles being rejected for regional climate reconstructions. Although groundwater flow and climate change can result in contrasting or superimposed thermal disturbances, groundwater flow will not typically remove climate change signals in a subsurface thermal profile. Thus, climate reconstruction is still possible in the presence of groundwater flow if heat advection is accommodated in the conceptual and mathematical models. In this study, we derive a new analytical solution for reconstructing surface temperature history from borehole thermal profiles influenced by vertical groundwater flow. The boundary condition for the solution is composed of any number of sequential `ramps', i.e. periods with linear warming or cooling rates, during the instrumented and pre-observational periods. The boundary condition generation and analytical temperature modeling is conducted in a simple computer program. The method is applied to reconstruct climate in Winnipeg, Canada and Tokyo, Japan using temperature profiles recorded in hydrogeologically active environments. The results demonstrate that thermal disturbances due to groundwater flow and climate
Graft infections after surgical aortic reconstructions
Berger, P.
2015-01-01
Prosthetic vascular grafts are frequently used to reconstruct (part) of the aorta. Every surgical procedure caries a certain risk for infection and when a prosthetic aortic graft is implanted, this may lead to an aortic graft infection (AGI). Endovascular techniques have gradually replaced open surgical reconstructions as first line of treatment for aorto-iliac diseases. Nowadays, open reconstructions are primarily reserved for patients unsuitable for endovascular reconstructions or for redo ...
Craniofacial Reconstruction Evaluation by Geodesic Network
Zhao, Junli; Liu, Cuiting; Wu, Zhongke; Duan, Fuqing; Wang, Kang; Jia, Taorui; Liu, Quansheng
2014-01-01
Craniofacial reconstruction is to estimate an individual’s face model from its skull. It has a widespread application in forensic medicine, archeology, medical cosmetic surgery, and so forth. However, little attention is paid to the evaluation of craniofacial reconstruction. This paper proposes an objective method to evaluate globally and locally the reconstructed craniofacial faces based on the geodesic network. Firstly, the geodesic networks of the reconstructed craniofacial face and the or...
REGEN: Ancestral Genome Reconstruction for Bacteria
Yang, Kuan; Heath, Lenwood S.; Setubal, João C.
2012-01-01
Ancestral genome reconstruction can be understood as a phylogenetic study with more details than a traditional phylogenetic tree reconstruction. We present a new computational system called REGEN for ancestral bacterial genome reconstruction at both the gene and replicon levels. REGEN reconstructs gene content, contiguous gene runs, and replicon structure for each ancestral genome. Along each branch of the phylogenetic tree, REGEN infers evolutionary events, including gene creation and deleti...
Top reconstruction and boosted top experimental overview
Skinnari, Louise
2015-01-01
An overview of techniques used to reconstruct resolved and boosted top quarks is presented. Techniques for resolved top quark reconstruction include kinematic likelihood fitters and pseudo- top reconstruction. Many tools and methods are available for the reconstruction of boosted top quarks, such as jet grooming techniques, jet substructure variables, and dedicated top taggers. Different techniques as used by ATLAS and CMS analyses are described and the performance of different variables and top taggers are shown.
MRI isotropic resolution reconstruction from two orthogonal scans
Tamez-Pena, Jose G.; Totterman, Saara; Parker, Kevin J.
2001-07-01
An algorithm for the reconstructions of ISO-resolution volumetric MR data sets from two standard orthogonal MR scans having anisotropic resolution has been developed. The reconstruction algorithm starts by registering a pair of orthogonal volumetric MR data sets. The registration is done by maximizing the correlation between the gradient magnitude using a simple translation-rotation model in a multi-resolution approach. Then algorithm assumes that the individual voxels on the MR data are an average of the magnetic resonance properties of an elongated imaging volume. Then, the process is modeled as the projection of MR properties into a single sensor. This model allows the derivation of a set of linear equations that can be used to recover the MR properties of every single voxel in the SO-resolution volume given only two orthogonal MR scans. Projections on convex sets (POCS) was used to solve the set of linear equations. Experimental results show the advantage of having a ISO-resolution reconstructions for the visualization and analysis of small and thin muscular structures.
Vertex Reconstruction in ATLAS Run II
Zhang, Matt; The ATLAS collaboration
2016-01-01
Vertex reconstruction is the process of taking reconstructed tracks and using them to determine the locations of proton collisions. In this poster we present the performance of our current vertex reconstruction algorithm, and look at investigations into potential improvements from a new seed finding method.
Mandibular reconstruction using bone allografts
International Nuclear Information System (INIS)
Chang Joon Yim
1999-01-01
Further understanding of bone healing mechanisms, bone physiology and bone biology, transplantation immunology, and development of Tissue Banking procedures has enabled oral and maxillofacial surgeons to reconstruct even the most difficult bony defects successfully with the preserved allogeneic bone implant. Although it had been known that bone allografts were clinically effective, its application has not been widespread until the reports of Inclan (I 942), Hyatt and Butler (I 950), and Wilson (I 95 1). Tissue Banking provides the surgeon with a readily available, relatively inexpensive, and relatively safe selection of allogeneic bone for clinical use. Now autogenous bone and allogeneic bone implants present a wide variety of surgical options to surgeons, whether used separately or in combination. The surgeons are able to make judicious and fruitful choices, only with a thorough knowledge of the above-mentioned biological principles and skillful techniques. Many kinds of bone grafting techniques have been tried for reconstructing defective osseous tissues of the oral and maxillofacial region, though they have varying degrees of success. The osseous defects which require grafting include those of various size, shape, position, or amount. Unlike autogenous grafts, whose function is to provide osteogenic cells, allografts are purely passive, offering only a matrix for the inductive phase of bone healing. The condition of the recipient bed is of primary importance, because the host must produce all of the essential elements for the bone allograft to become incorporated. Depending on the processing methods of the allogeneic bone, the bone graft materials have different qualities, different healing potentials and different indications. Proper selection of grafts and surgical techniques requires an understanding of graft immunology and the mechanisms of graft healing. The surgeons should know about the biological principles to raise the clinical success rate
International Nuclear Information System (INIS)
Nielsen, Tim; Brendel, Bernhard; Ziegler, Ronny; Beek, Michiel van; Uhlemann, Falk; Bontus, Claas; Koehler, Thomas
2009-01-01
Diffuse optical tomography (DOT) is a potential new imaging modality to detect or monitor breast lesions. Recently, Philips developed a new DOT system capable of transmission and fluorescence imaging, where the investigated breast is hanging freely into the measurement cup containing scattering fluid. We present a fast and robust image reconstruction algorithm that is used for the transmission measurements. The algorithm is based on the Rytov approximation. We show that this algorithm can be used over a wide range of tissue optical properties if the reconstruction is adapted to each patient. We use estimates of the breast shape and average tissue optical properties to initialize the reconstruction, which improves the image quality significantly. We demonstrate the capability of the measurement system and reconstruction to image breast lesions by clinical examples
Energy Technology Data Exchange (ETDEWEB)
Baniassadi, Majid; Mortazavi, Behzad; Hamedani, Amani; Garmestani, Hamid; Ahzi, Said; Fathi-Torbaghan, Madjid; Ruch, David; Khaleel, Mohammad A.
2012-01-31
In this study, a previously developed reconstruction methodology is extended to three-dimensional reconstruction of a three-phase microstructure, based on two-point correlation functions and two-point cluster functions. The reconstruction process has been implemented based on hybrid stochastic methodology for simulating the virtual microstructure. While different phases of the heterogeneous medium are represented by different cells, growth of these cells is controlled by optimizing parameters such as rotation, shrinkage, translation, distribution and growth rates of the cells. Based on the reconstructed microstructure, finite element method (FEM) was used to compute the effective elastic modulus and effective thermal conductivity. A statistical approach, based on two-point correlation functions, was also used to directly estimate the effective properties of the developed microstructures. Good agreement between the predicted results from FEM analysis and statistical methods was found confirming the efficiency of the statistical methods for prediction of thermo-mechanical properties of three-phase composites.
Towards easy and reliable AFM tip shape determination using blind tip reconstruction
International Nuclear Information System (INIS)
Flater, Erin E.; Zacharakis-Jutz, George E.; Dumba, Braulio G.; White, Isaac A.; Clifford, Charles A.
2014-01-01
Quantitative determination of the geometry of an atomic force microscope (AFM) probe tip is critical for robust measurements of the nanoscale properties of surfaces, including accurate measurement of sample features and quantification of tribological characteristics. Blind tip reconstruction, which determines tip shape from an AFM image scan without knowledge of tip or sample shape, was established most notably by Villarrubia [J. Res. Natl. Inst. Stand. Tech. 102 (1997)] and has been further developed since that time. Nevertheless, the implementation of blind tip reconstruction for the general user to produce reliable and consistent estimates of tip shape has been hindered due to ambiguity about how to choose the key input parameters, such as tip matrix size and threshold value, which strongly impact the results of the tip reconstruction. These key parameters are investigated here via Villarrubia's blind tip reconstruction algorithms in which we have added the capability for users to systematically vary the key tip reconstruction parameters, evaluate the set of possible tip reconstructions, and determine the optimal tip reconstruction for a given sample. We demonstrate the capabilities of these algorithms through analysis of a set of simulated AFM images and provide practical guidelines for users of the blind tip reconstruction method. We present a reliable method to choose the threshold parameter corresponding to an optimal reconstructed tip shape for a given image. Specifically, we show that the trend in how the reconstructed tip shape varies with threshold number is so regular that the optimal, or Goldilocks, threshold value corresponds with the peak in the derivative of the RMS difference with respect to the zero threshold curve vs. threshold number. - Highlights: • Blind tip reconstruction algorithms have been implemented and augmented to determine the optimal input parameters. • We demonstrate the capabilities of the algorithms using a simulated AFM
A variational study on BRDF reconstruction in a structured light scanner
DEFF Research Database (Denmark)
Nielsen, Jannik Boll; Stets, Jonathan Dyssel; Lyngby, Rasmus Ahrenkiel
2017-01-01
Time-efficient acquisition of reflectance behavior together with surface geometry is a challenging problem. In this study, we investigate the impact of system parameter uncertainties when incorporating a data-driven BRDF reconstruction approach into the standard pipeline of a structured light...... setup. Results show that while uncertainties in vertex positions and normals have a high impact on the quality of reconstructed BRDFs, object geometry and light source properties have very little influence on the reconstructed BRDFs. With this analysis, practitioners now have insight in the tolerances...... required for accurate BRDF acquisition to work....
The Algebraic Reconstruction Technique (ART)
International Nuclear Information System (INIS)
Raparia, D.; Alessi, J.; Kponou, A.
1997-01-01
Projections of charged particle beam current density (profiles) are frequently used as a measure of beam position and size. In conventional practice only two projections, usually horizontal and vertical, are measured. This puts a severe limit on the detail of information that can be achieved. A third projection provides a significant improvement. The Algebraic Reconstruction Technique (ART) uses three or more projections to reconstruct 3-dimensional density profiles. At the 200 MeV H-linac, we have used this technique to measure beam density, and it has proved very helpful, especially in helping determine if there is any coupling present in x-y phase space. We will present examples of measurements of current densities using this technique
Septal graft in laryngeal reconstruction
International Nuclear Information System (INIS)
Bahannan, Abdulrahman; Slavicek, A.; Taudy, M.; Chovanec, M.
2006-01-01
A 62-year-old woman presented with symptoms of dyspnea. Ultrasonography and computed tomography examinations revealed mass extending from the cricoid cartilage to the left lobe of thyroid gland and thyroid cartilage. Cytology revealed possibility of cartilaginous origin, which was proven to be chondrosarcoma (Grade 1) from the biopsy specimen obtained during panendosopy. She underwent one stage radical resection and immediate reconstruction of laryngeal skeleton defect by mucocartilaginous graft from the nasal septum. Her postoperative course was optimal with preservation of the laryngeal functions. Twenty-eight months postoperatively, she had to undergo total laryngectomy as a salvage procedure for the advanced local recurrence. We report on the relatively easy technique for functional reconstruction of the large laryngeal defect with the employment cartilage graft from the nasal septum. (author)
Phylogenetic reconstruction methods: an overview.
De Bruyn, Alexandre; Martin, Darren P; Lefeuvre, Pierre
2014-01-01
Initially designed to infer evolutionary relationships based on morphological and physiological characters, phylogenetic reconstruction methods have greatly benefited from recent developments in molecular biology and sequencing technologies with a number of powerful methods having been developed specifically to infer phylogenies from macromolecular data. This chapter, while presenting an overview of basic concepts and methods used in phylogenetic reconstruction, is primarily intended as a simplified step-by-step guide to the construction of phylogenetic trees from nucleotide sequences using fairly up-to-date maximum likelihood methods implemented in freely available computer programs. While the analysis of chloroplast sequences from various Vanilla species is used as an illustrative example, the techniques covered here are relevant to the comparative analysis of homologous sequences datasets sampled from any group of organisms.
Direct reconstruction of dark energy.
Clarkson, Chris; Zunckel, Caroline
2010-05-28
An important issue in cosmology is reconstructing the effective dark energy equation of state directly from observations. With so few physically motivated models, future dark energy studies cannot only be based on constraining a dark energy parameter space. We present a new nonparametric method which can accurately reconstruct a wide variety of dark energy behavior with no prior assumptions about it. It is simple, quick and relatively accurate, and involves no expensive explorations of parameter space. The technique uses principal component analysis and a combination of information criteria to identify real features in the data, and tailors the fitting functions to pick up trends and smooth over noise. We find that we can constrain a large variety of w(z) models to within 10%-20% at redshifts z≲1 using just SNAP-quality data.
Structure Assisted Compressed Sensing Reconstruction of Undersampled AFM Images
DEFF Research Database (Denmark)
Oxvig, Christian Schou; Arildsen, Thomas; Larsen, Torben
2017-01-01
reconstruction algorithms that enables the use of our proposed structure model in the reconstruction process. Through a large set of reconstructions, the general reconstruction capability improvement achievable using our structured model is shown both quantitatively and qualitatively. Specifically, our...
A simulation of portable PET with a new geometric image reconstruction method
Energy Technology Data Exchange (ETDEWEB)
Kawatsu, Shoji [Department of Radiology, Kyoritu General Hospital, 4-33 Go-bancho, Atsuta-ku, Nagoya-shi, Aichi 456 8611 (Japan): Department of Brain Science and Molecular Imaging, National Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, 36-3, Gengo Moriaka-cho, Obu-shi, Aichi 474 8522 (Japan)]. E-mail: b6rgw@fantasy.plala.or.jp; Ushiroya, Noboru [Department of General Education, Wakayama National College of Technology, 77 Noshima, Nada-cho, Gobo-shi, Wakayama 644 0023 (Japan)
2006-12-20
A new method is proposed for three-dimensional positron emission tomography image reconstruction. The method uses the elementary geometric property of line of response whereby two lines of response, which originate from radioactive isotopes in the same position, lie within a few millimeters distance of each other. The method differs from the filtered back projection method and the iterative reconstruction method. The method is applied to a simulation of portable positron emission tomography.
International Nuclear Information System (INIS)
Zhao-Jiang, Chen; Shu-Yi, Zhang
2010-01-01
A new hybrid inversion method for depth profiling reconstruction of thermal conductivities of inhomogeneous solids is proposed based on multilayer quadrupole formalism of thermal waves, particle swarm optimization and sequential quadratic programming. The reconstruction simulations for several thermal conductivity profiles are performed to evaluate the applicability of the method. The numerical simulations demonstrate that the precision and insensitivity to noise of the inversion method are very satisfactory. (condensed matter: structure, mechanical and thermal properties)
Sue, Gloria R; Lee, Gordon K
2018-05-01
Mastectomy skin necrosis is a significant problem after breast reconstruction. We sought to perform a comparative analysis on this complication between patients undergoing autologous breast reconstruction and patients undergoing 2-stage expander implant breast reconstruction. A retrospective review was performed on consecutive patients undergoing autologous breast reconstruction or 2-stage expander implant breast reconstruction by the senior author from 2006 through 2015. Patient demographic factors including age, body mass index, history of diabetes, history of smoking, and history of radiation to the breast were collected. Our primary outcome measure was mastectomy skin necrosis. Fisher exact test was used for statistical analysis between the 2 patient cohorts. The treatment patterns of mastectomy skin necrosis were then analyzed. We identified 204 patients who underwent autologous breast reconstruction and 293 patients who underwent 2-stage expander implant breast reconstruction. Patients undergoing autologous breast reconstruction were older, heavier, more likely to have diabetes, and more likely to have had prior radiation to the breast compared with patients undergoing implant-based reconstruction. The incidence of mastectomy skin necrosis was 30.4% of patients in the autologous group compared with only 10.6% of patients in the tissue expander group (P care in the autologous group, only 3.2% were treated with local wound care in the tissue expander group (P skin necrosis is significantly more likely to occur after autologous breast reconstruction compared with 2-stage expander implant-based breast reconstruction. Patients with autologous reconstructions are more readily treated with local wound care compared with patients with tissue expanders, who tended to require operative treatment of this complication. Patients considering breast reconstruction should be counseled appropriately regarding the differences in incidence and management of mastectomy skin
International Nuclear Information System (INIS)
Son, J.H.
1979-01-01
Because of much attractiveness, digital reconstruction of image from ultrasonic hologram by computer has been widely studied in recent years. But the method of digital reconstruction of image is displayed in the plain only, so study is done mainly of the hologram obtained from bidimensional objects. Many applications of the ultrasonic holography such as the non-distructive testing and the ultrasonic diagnosis are mostly of the tridimensional object. In the ordinary digital reconstruction of the image from the hologram obtained from tridimensional object, a question of hidden-image problem arises, and the separated reconstruction of the image for the considered part of the object is required. In this paper, multi-diffraction by tridimensional object is assumed to have linearity, ie. superposition property by each diffraction of bidimensional objects. And a new algorithm is proposed here, namely reconstructed image for considered one of bidimensional objects in tridimensional object obtained by means of operation from the two holograms tilted in unequal angles. Such tilted holograms are obtained from the tilted linear array receivers by scanning method. That images can be reconstructed by the operation from two holograms means that the new algorithm is verified. And another new method of the transformation of hologram, that is, transformation of a hologram to arbitrarily tilted hologram, has been proved valid. The reconstructed images obtained with the method of transformation and the method of operation, are the images reconstructed from one hologram by the tridimensional object and more distinctly separated that any images mentioned above. (author)
Reconstruction of Attosecond Pulse Trains
Mairesse, Y.; Agostini, P.; Breger, P.; Carre, B.; Merdji, A.; Monchicourt, P.; Salieres, P.; Varju, K.; Gustafsson, E.; Johnsson, P.; Mauritsson, J.; Remetter, T.; L'Huillier, A.; Frasinski, L. J.
2006-11-01
We show that it is possible to completely reconstruct the intensity profile of the attosecond bursts emitted as a superposition of high harmonics from a series of RABBIT measurements carried out at different infrared intensities. The electric field can be recovered from a measurement of the central harmonic chirp. Timing, chirp and variations of the carrier-to-envelope phase of the attosecond bursts are accessible to the proposed method.
Hanford Environmental Dose Reconstruction Project
International Nuclear Information System (INIS)
Cannon, S.D.; Finch, S.M.
1992-10-01
The objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation doses that individuals and populations could have received from nuclear operations at Hanford since 1944. The independent Technical Steering Panel (TSP) provides technical direction. The project is divided into the following technical tasks. These tasks correspond to the path radionuclides followed from release to impact on humans (dose estimates):Source Terms, Environmental Transport, Environmental Monitoring Data, Demography, Food Consumption, and Agriculture, and Environmental Pathways and Dose Estimates
Computed laminography and reconstruction algorithm
International Nuclear Information System (INIS)
Que Jiemin; Cao Daquan; Zhao Wei; Tang Xiao
2012-01-01
Computed laminography (CL) is an alternative to computed tomography if large objects are to be inspected with high resolution. This is especially true for planar objects. In this paper, we set up a new scanning geometry for CL, and study the algebraic reconstruction technique (ART) for CL imaging. We compare the results of ART with variant weighted functions by computer simulation with a digital phantom. It proves that ART algorithm is a good choice for the CL system. (authors)
Colour reconstruction of underwater images
Hoth, Julian; Kowalczyk, Wojciech
2017-01-01
Objects look very different in the underwater environment compared to their appearance in sunlight. Images with correct colouring simplify the detection of underwater objects and may allow the use of visual SLAM algorithms developed for land-based robots underwater. Hence, image processing is required. Current algorithms focus on the colour reconstruction of scenery at diving depth where different colours can still be distinguished. At greater depth this is not the case. In this study it is i...
A Reduction of the Graph Reconstruction Conjecture
Directory of Open Access Journals (Sweden)
Monikandan S.
2014-08-01
Full Text Available A graph is said to be reconstructible if it is determined up to isomor- phism from the collection of all its one-vertex deleted unlabeled subgraphs. Reconstruction Conjecture (RC asserts that all graphs on at least three vertices are reconstructible. In this paper, we prove that interval-regular graphs and some new classes of graphs are reconstructible and show that RC is true if and only if all non-geodetic and non-interval-regular blocks G with diam(G = 2 or diam(Ḡ = diam(G = 3 are reconstructible
BES-II fast data reconstruction
International Nuclear Information System (INIS)
Rong Gang; Zhang Jiawen; Guo Yiqing; Zhang Shaoqiang; Zhao Dixin
2002-01-01
The BES-II fast data reconstruction is reported. Based on PC FARM and/or a 'Distributed Clustered Linux PC System', BES-II fast data reconstruction system is set up. With this system the BES-II data can be fully reconstructed in about 20 minutes after data collection. It takes only 12 minutes to fully reconstruct 30000 events, collected with BES-II detector at BEPC Collider, with a P III-800 PC. The detector performance can be examined based on fully reconstructed data in about 20 minutes after data taking in the BES-II experiment
Reconstruction of FXR Beam Conditions
International Nuclear Information System (INIS)
Nexen, W E; Scarpetti, R D; Zentler, J
2001-01-01
Beam-envelope radius, envelope angle, and beam emittance can be derived from measurements of beam radius for at least three different transport conditions. We have used this technique to reconstruct exit parameters from the FXR injector and accelerator. We use a diamagnetic loop (DML) to measure the magnetic moment of the high current beam. With no assumptions about radial profile, we can derive the beam mean squire radius from the moment under certain easily met conditions. Since it is this parameter which is required for the reconstruction, it is evident that the DML is the ideal diagnostic for this technique. The simplest application of this technique requires at least three shots for a reconstruction but in reality requires averaging over many more shots because of shot to shot variation. Since DML measurements do not interfere with the beam, single shot time resolved measurements of the beam parameters appear feasible if one uses an array of at least three DMLs separated by known transport conditions
Network reconstruction via graph blending
Estrada, Rolando
2016-05-01
Graphs estimated from empirical data are often noisy and incomplete due to the difficulty of faithfully observing all the components (nodes and edges) of the true graph. This problem is particularly acute for large networks where the number of components may far exceed available surveillance capabilities. Errors in the observed graph can render subsequent analyses invalid, so it is vital to develop robust methods that can minimize these observational errors. Errors in the observed graph may include missing and spurious components, as well fused (multiple nodes are merged into one) and split (a single node is misinterpreted as many) nodes. Traditional graph reconstruction methods are only able to identify missing or spurious components (primarily edges, and to a lesser degree nodes), so we developed a novel graph blending framework that allows us to cast the full estimation problem as a simple edge addition/deletion problem. Armed with this framework, we systematically investigate the viability of various topological graph features, such as the degree distribution or the clustering coefficients, and existing graph reconstruction methods for tackling the full estimation problem. Our experimental results suggest that incorporating any topological feature as a source of information actually hinders reconstruction accuracy. We provide a theoretical analysis of this phenomenon and suggest several avenues for improving this estimation problem.
Three-Dimensional Reconstruction of Sandpile Interiors
Seidler, G. T.
2001-03-01
The granular bed, or sandpile, has become one of the condensed matter physicist's favorite systems. In addition to conceptual appeal, the simplest sandpile of monodisperse hard spheres is a valuable model system for understanding powders, liquids, and metallic glasses. Any fundamental approach to the transport and mechanical properties of three-dimensional mesoscale disordered materials must follow from a thorough understanding of their structure. However, in the overwhelming majority of cases, structure measurements have been limited to the mean filling fraction and the structural autocorrelation function. This is particularly unfortunate in the ongoing sandpile renaissance, where some of the most interesting questions concern structure and the relationship between structure and dynamics. I will discuss the combination of synchrotron x-ray microtomography and computer vision algorithms to perform three-dimensional virtual reconstructions of real sandpiles. This technique is rapid and noninvasive, and is applicable to samples large enough to separate bulk and boundary properties. The resulting complete knowledge of structure can be used to calculate otherwise inaccessible correlation functions. I will present results for several measures of the bond-orientational order in three-dimensional sandpiles, including fabric tensors and nematic order parameters.
Garg, Rishi; Javidan, Pooya; Lee, Thay Q.
2013-01-01
Background Several different surgical techniques have been described to address the coracoclavicular (CC) ligaments in acromioclavicular (AC) joint injuries. However, very few techniques focus on reconstructing the AC ligaments, despite its importance in providing stability. The purpose of our study was to compare the biomechanical properties of two free-tissue graft techniques that reconstruct both the AC and CC ligaments in cadaveric shoulders, one with an extramedullary AC reconstruction and the other with an intramedullary AC reconstruction. We hypothesized intramedullary AC reconstruction will provide greater anteroposterior translational stability and improved load to failure characteristics than an extramedullary technique. Methods Six matched cadaveric shoulders underwent translational testing at 10 N and 15 N in the anteroposterior and superoinferior directions, under AC joint compression loads of 10 N, 20 N, and 30 N. After the AC and CC ligaments were transected, one of the specimens was randomly assigned the intramedullary free-tissue graft reconstruction while its matched pair received the extramedullary graft reconstruction. Both reconstructed specimens then underwent repeat translational testing, followed by load to failure testing, via superior clavicle distraction, at a rate of 50 mm/min. Results Intramedullary reconstruction provided significantly greater translational stability in the anteroposterior direction than the extramedullary technique for four of six loading conditions (p < 0.05). There were no significant differences in translational stability in the superoinferior direction for any loading condition. The intramedullary reconstructed specimens demonstrated improved load to failure characteristics with the intramedullary reconstruction having a lower deformation at yield and a higher ultimate load than the extramedullary reconstruction (p < 0.05). Conclusions Intramedullary reconstruction of the AC joint provides greater stability in the
Image reconstruction technique using projection data from neutron tomography system
Directory of Open Access Journals (Sweden)
Waleed Abd el Bar
2015-12-01
Full Text Available Neutron tomography is a very powerful technique for nondestructive evaluation of heavy industrial components as well as for soft hydrogenous materials enclosed in heavy metals which are usually difficult to image using X-rays. Due to the properties of the image acquisition system, the projection images are distorted by several artifacts, and these reduce the quality of the reconstruction. In order to eliminate these harmful effects the projection images should be corrected before reconstruction. This paper gives a description of a filter back projection (FBP technique, which is used for reconstruction of projected data obtained from transmission measurements by neutron tomography system We demonstrated the use of spatial Discrete Fourier Transform (DFT and the 2D Inverse DFT in the formulation of the method, and outlined the theory of reconstruction of a 2D neutron image from a sequence of 1D projections taken at different angles between 0 and π in MATLAB environment. Projections are generated by applying the Radon transform to the original image at different angles.
Evaluation of reconstruction algorithms in SPECT neuroimaging: Pt. 1
International Nuclear Information System (INIS)
Heejoung Kim; Zeeberg, B.R.; Reba, R.C.
1993-01-01
In the presence of statistical noise, an iterative reconstruction algorithm (IRA) for the quantitative reconstruction of single-photon-emission computed tomographic (SPECT) brain images overcomes major limitations of applying the standard filtered back projection (FBP) reconstruction algorithm to projection data which have been degraded by convolution of the true radioactivity distribution with a finite-resolution distance-dependent detector response: (a) the non-uniformity within the grey (or white) matter voxels which results even though the true model is uniform within these voxels; (b) a significantly lower ratio of grey/white matter voxel values than in the true model; and (c) an inability to detect an altered radioactivity value within the grey (or white) matter voxels. It is normally expected that an algorithm which improves spatial resolution and quantitative accuracy might also increase the magnitude of the statistical noise in the reconstructed image. However, the noise properties in the IRA images are very similar to those in the FBP images. (Author)
Mizuno, Mitsuru; Kobayashi, Shinji; Takebe, Takanori; Kan, Hiroomi; Yabuki, Yuichiro; Matsuzaki, Takahisa; Yoshikawa, Hiroshi Y; Nakabayashi, Seiichiro; Ik, Lee Jeong; Maegawa, Jiro; Taniguchi, Hideki
2014-03-01
In healthy joints, hyaline cartilage covering the joint surfaces of bones provides cushioning due to its unique mechanical properties. However, because of its limited regenerative capacity, age- and sports-related injuries to this tissue may lead to degenerative arthropathies, prompting researchers to investigate a variety of cell sources. We recently succeeded in isolating human cartilage progenitor cells from ear elastic cartilage. Human cartilage progenitor cells have high chondrogenic and proliferative potential to form elastic cartilage with long-term tissue maintenance. However, it is unknown whether ear-derived cartilage progenitor cells can be used to reconstruct hyaline cartilage, which has different mechanical and histological properties from elastic cartilage. In our efforts to develop foundational technologies for joint hyaline cartilage repair and reconstruction, we conducted this study to obtain an answer to this question. We created an experimental canine model of knee joint cartilage damage, transplanted ear-derived autologous cartilage progenitor cells. The reconstructed cartilage was rich in proteoglycans and showed unique histological characteristics similar to joint hyaline cartilage. In addition, mechanical properties of the reconstructed tissues were higher than those of ear cartilage and equal to those of joint hyaline cartilage. This study suggested that joint hyaline cartilage was reconstructed from ear-derived cartilage progenitor cells. It also demonstrated that ear-derived cartilage progenitor cells, which can be harvested by a minimally invasive method, would be useful for reconstructing joint hyaline cartilage in patients with degenerative arthropathies. © AlphaMed Press.
Cosmological constraints on the properties of weakly interacting massive particles
International Nuclear Information System (INIS)
Steigman, G.; Turner, M.S.
1984-10-01
Considerations of the age and density of, as well as the evolution of structure in, the Universe lead to constraints on the masses and lifetimes of weakly interacting massive particles (WIMPs). 26 references
Cosmological constraints on the properties of weakly interacting massive particles
Energy Technology Data Exchange (ETDEWEB)
Steigman, G.; Turner, M.S.
1984-10-01
Considerations of the age and density of, as well as the evolution of structure in, the Universe lead to constraints on the masses and lifetimes of weakly interacting massive particles (WIMPs). 26 references.
Ekofisk chalk: core measurements, stochastic reconstruction, network modeling and simulation
Energy Technology Data Exchange (ETDEWEB)
Talukdar, Saifullah
2002-07-01
This dissertation deals with (1) experimental measurements on petrophysical, reservoir engineering and morphological properties of Ekofisk chalk, (2) numerical simulation of core flood experiments to analyze and improve relative permeability data, (3) stochastic reconstruction of chalk samples from limited morphological information, (4) extraction of pore space parameters from the reconstructed samples, development of network model using pore space information, and computation of petrophysical and reservoir engineering properties from network model, and (5) development of 2D and 3D idealized fractured reservoir models and verification of the applicability of several widely used conventional up scaling techniques in fractured reservoir simulation. Experiments have been conducted on eight Ekofisk chalk samples and porosity, absolute permeability, formation factor, and oil-water relative permeability, capillary pressure and resistivity index are measured at laboratory conditions. Mercury porosimetry data and backscatter scanning electron microscope images have also been acquired for the samples. A numerical simulation technique involving history matching of the production profiles is employed to improve the relative permeability curves and to analyze hysteresis of the Ekofisk chalk samples. The technique was found to be a powerful tool to supplement the uncertainties in experimental measurements. Porosity and correlation statistics obtained from backscatter scanning electron microscope images are used to reconstruct microstructures of chalk and particulate media. The reconstruction technique involves a simulated annealing algorithm, which can be constrained by an arbitrary number of morphological parameters. This flexibility of the algorithm is exploited to successfully reconstruct particulate media and chalk samples using more than one correlation functions. A technique based on conditional simulated annealing has been introduced for exact reproduction of vuggy
DEFF Research Database (Denmark)
Thornton, Katsuyo; Poulsen, Henning Friis
2008-01-01
The recent development of experimental techniques that rapidly reconstruct the three-dimensional microstructures of solids has given rise to new possibilities for developing a deeper understanding of the evolution of microstructures and the effects of microstructures on materials properties. Comb...... an overview of this emerging field of materials science, as well as brief descriptions of selected methods and their applicability.......The recent development of experimental techniques that rapidly reconstruct the three-dimensional microstructures of solids has given rise to new possibilities for developing a deeper understanding of the evolution of microstructures and the effects of microstructures on materials properties....... Combined with three-dimensional (3D) simulations and analyses that are capable of handling the complexity of these microstructures, 3D reconstruction, or tomography, has become a powerful tool that provides clear insights into materials processing and properties. This introductory article provides...
Spiral scan long object reconstruction through PI line reconstruction
International Nuclear Information System (INIS)
Tam, K C; Hu, J; Sourbelle, K
2004-01-01
The response of a point object in a cone beam (CB) spiral scan is analysed. Based on the result, a reconstruction algorithm for long object imaging in spiral scan cone beam CT is developed. A region-of-interest (ROI) of the long object is scanned with a detector smaller than the ROI, and a portion of it can be reconstructed without contamination from overlaying materials. The top and bottom surfaces of the ROI are defined by two sets of PI lines near the two ends of the spiral path. With this novel definition of the top and bottom ROI surfaces and through the use of projective geometry, it is straightforward to partition the cone beam image into regions corresponding to projections of the ROI, the overlaying objects or both. This also simplifies computation at source positions near the spiral ends, and makes it possible to reduce radiation exposure near the spiral ends substantially through simple hardware collimation. Simulation results to validate the algorithm are presented
Reconstructive options in pelvic tumours
Directory of Open Access Journals (Sweden)
Mayilvahanan N
2005-01-01
Full Text Available Background: Pelvic tumours present a complex problem. It is difficult to choose between limb salvage and hemipelvectomy. Method: Forty three patients of tumours of pelvis underwent limb salvage resection with reconstruction in 32 patients. The majority were chondrosarcomas (20 cases followed by Ewing sarcoma. Stage II B was the most common stage in malignant lesions and all the seven benign lesions were aggressive (B3. Surgical margins achieved were wide in 31 and marginal in 12 cases. Ilium was involved in 51% of cases and periacetabular involvement was seen in 12 patients. The resections done were mostly of types I &II of Enneking′s classification of pelvic resection. Arthrodesis was attempted in 24 patients. Customized Saddle prosthesis was used in seven patients and no reconstruction in 12 patients. Adjuvant chemotherapy was given to all high-grade malignant tumours, combined with radiotherapy in 7 patients. Results: With a mean follow up of 48.5 months and one patient lost to follow up, the recurrence rate among the evaluated cases was 16.6%. Oncologically, 30 patients were continuously disease free with 7 local recurrences and 4 deaths due to disseminated disease and 2 patients died of other causes. During the initial years, satisfactory functional results were achieved with prosthetic replacement. Long-term functional result of 36 patients who were alive at the time of latest follow up was satisfactory in 75% who underwent arthrodesis and in those where no reconstruction was used. We also describe a method of new classification of pelvic resections that clarifies certain shortcomings of the previous systems of classification. Conclusion: Selection of a procedure depends largely on the patient factors, the tumour grade, the resultant defect and the tissue factors. Resection with proper margins gives better functional and oncological results
The reconstruction property in Banach spaces and a perturbation theorem
DEFF Research Database (Denmark)
Casazza, P.G.; Christensen, Ole
2008-01-01
Perturbation theory is a fundamental tool in Banach space theory. However, the applications of the classical results are limited by the fact that they force the perturbed sequence to be equivalent to the given sequence. We will develop a more general perturbation theory that does not force...
Bayes reconstruction of missing teeth
DEFF Research Database (Denmark)
Sporring, Jon; Jensen, Katrine Hommelhoff
2008-01-01
contains two major parts: A statistical model of a selection of tooth shapes and a reconstruction of missing data. We use a training set consisting of 3D scans of dental cast models obtained with a laser scanner, and we have build a model of the shape variability of the teeth, their neighbors...... or equivalently noise elimination and for data analysis. However for small sets of high dimensional data, the log-likelihood estimator for the covariance matrix is often far from convergence, and therefore reliable models must be obtained by use of prior information. We propose a natural and intrinsic...
Hanford Environmental Dose Reconstruction Project
International Nuclear Information System (INIS)
Finch, S.M.; McMakin, A.H.
1991-04-01
The objective of the Hanford Environmental Dose Reconstruction Project is to estimate the radiation doses that populations could have received from nuclear operations at Hanford since 1944. The project is being managed and conducted by the Pacific Northwest Laboratory (PNL) under the direction of an independent Technical Steering Panel (TSP). The project is divided into the following technical tasks. These tasks correspond to the path radionuclides followed, from released to impact on humans (dose estimates): source terms; environmental transport; environmental monitoring data; demographics, agriculture, food habits; and, environmental pathways and dose estimates
Economics of abdominal wall reconstruction.
Bower, Curtis; Roth, J Scott
2013-10-01
The economic aspects of abdominal wall reconstruction are frequently overlooked, although understandings of the financial implications are essential in providing cost-efficient health care. Ventral hernia repairs are frequently performed surgical procedures with significant economic ramifications for employers, insurers, providers, and patients because of the volume of procedures, complication rates, the significant rate of recurrence, and escalating costs. Because biological mesh materials add significant expense to the costs of treating complex abdominal wall hernias, the role of such costly materials needs to be better defined to ensure the most cost-efficient and effective treatments for ventral abdominal wall hernias. Copyright © 2013 Elsevier Inc. All rights reserved.
Cartilage grafting in nasal reconstruction.
Immerman, Sara; White, W Matthew; Constantinides, Minas
2011-02-01
Nasal reconstruction after resection for cutaneous malignancies poses a unique challenge to facial plastic surgeons. The nose, a unique 3-D structure, not only must remain functional but also be aesthetically pleasing to patients. A complete understanding of all the layers of the nose and knowledge of available cartilage grafting material is necessary. Autogenous material, namely septal, auricular, and costal cartilage, is the most favored material in a free cartilage graft or a composite cartilage graft. All types of material have advantages and disadvantages that should guide the most appropriate selection to maximize the functional and cosmetic outcomes for patients. Copyright © 2011 Elsevier Inc. All rights reserved.
Hanford Environmental Dose Reconstruction Project
International Nuclear Information System (INIS)
Finch, S.M.; McMakin, A.H.
1992-06-01
The objective of the Hanford Environmental Dose Reconstruction Project is to estimate the radiation doses that individuals and populations could have received from nuclear operations at Hanford since 1944. The project is being managed and conducted by the Battelle Pacific Northwest Laboratories under contract with the Centers for Disease Control. The independent Technical Steering Panel (TSP) provides technical direction. The project is divided into the following technical tasks. These tasks correspond to the path radionuclides followed, from release to impact on humans (dose estimates): source terms; environmental transport; environmental monitoring data; demography, food consumption, and agriculture; environmental pathways and dose estimates
Virtual resistive network and conductivity reconstruction with Faraday's law
International Nuclear Information System (INIS)
Lee, Min Gi; Ko, Min-Su; Kim, Yong-Jung
2014-01-01
A network-based conductivity reconstruction method is introduced using the third Maxwell equation, or Faraday's law, for a static case. The usual choice in electrical impedance tomography is the divergence-free equation for the electrical current density. However, if the electrical current density is given, the curl-free equation for the electrical field gives a direct relation between the current and the conductivity and this relation is used in this paper. Mimetic discretization is applied to the equation, which gives the virtual resistive network system. Properties of the numerical schemes introduced are investigated and their advantages over other conductivity reconstruction methods are discussed. Numerically simulated results, with an analysis of noise propagation, are presented. (paper)
Strain-activated edge reconstruction of graphene nanoribbons
Cheng, Yingchun
2012-02-17
The edge structure and width of graphene nanoribbons (GNRs) are crucial factors for the electronic properties. A combination of experiment and first-principles calculations allows us to determine the mechanism of the hexagon-hexagon to pentagon-heptagon transformation. GNRs thinner than 2 nm have been fabricated by bombardment of graphene with high-energetic Au clusters. The edges of the GNRs are modified in situ by electron irradiation. Tensile strain along the edge decreases the transformation energy barrier. Antiferromagnetism and a direct band gap are found for a zigzag GNR, while a fully reconstructed GNR shows an indirect band gap. A GNR reconstructed on only one edge exhibits ferromagnetism. We propose that strain is an effective method to tune the edge and, therefore, the electronic structure of thin GNRs for graphene-based electronics.
Model-based microwave image reconstruction: simulations and experiments
International Nuclear Information System (INIS)
Ciocan, Razvan; Jiang Huabei
2004-01-01
We describe an integrated microwave imaging system that can provide spatial maps of dielectric properties of heterogeneous media with tomographically collected data. The hardware system (800-1200 MHz) was built based on a lock-in amplifier with 16 fixed antennas. The reconstruction algorithm was implemented using a Newton iterative method with combined Marquardt-Tikhonov regularizations. System performance was evaluated using heterogeneous media mimicking human breast tissue. Finite element method coupled with the Bayliss and Turkel radiation boundary conditions were applied to compute the electric field distribution in the heterogeneous media of interest. The results show that inclusions embedded in a 76-diameter background medium can be quantitatively reconstructed from both simulated and experimental data. Quantitative analysis of the microwave images obtained suggests that an inclusion of 14 mm in diameter is the smallest object that can be fully characterized presently using experimental data, while objects as small as 10 mm in diameter can be quantitatively resolved with simulated data
Retrospective reconstruction of personal doses using mobile phones
International Nuclear Information System (INIS)
Ekendahl, Daniela
2011-01-01
Mobile phones are among objects usable for retrospective reconstruction of doses received by persons irradiated from serious radiation accidents or terrorist acts involving radioactivity. In this respect, it is an advantage of mobile phones that they are often worn close to the body and are used by the majority of population. Like other portable electronic devices, mobile phones contain electronic components which can include ceramic materials exhibiting radiation induced luminescence. Aluminium oxide (Al2O3) is an example; its layers are often used in chip resistors. This work summarizes the results of a pilot study investigating the dosimetric potential of Al2O3 measured via thermoluminescence (TL) and optically stimulated luminescence (OSL). A trial dose reconstruction performed with two mobile phones is described. It is shown that the material exhibits favourable dosimetric properties and the method is sufficiently accurate and operative for personal accident dosimetry purposes. (orig.)
Strain-activated edge reconstruction of graphene nanoribbons
Cheng, Yingchun; Han, Yu; Schwingenschlö gl, Udo; Wang, H. T.; Zhang, Xixiang; Zhu, Y. H.; Zhu, Zhiyong
2012-01-01
The edge structure and width of graphene nanoribbons (GNRs) are crucial factors for the electronic properties. A combination of experiment and first-principles calculations allows us to determine the mechanism of the hexagon-hexagon to pentagon-heptagon transformation. GNRs thinner than 2 nm have been fabricated by bombardment of graphene with high-energetic Au clusters. The edges of the GNRs are modified in situ by electron irradiation. Tensile strain along the edge decreases the transformation energy barrier. Antiferromagnetism and a direct band gap are found for a zigzag GNR, while a fully reconstructed GNR shows an indirect band gap. A GNR reconstructed on only one edge exhibits ferromagnetism. We propose that strain is an effective method to tune the edge and, therefore, the electronic structure of thin GNRs for graphene-based electronics.
Sediment core and glacial environment reconstruction - a method review
Bakke, Jostein; Paasche, Øyvind
2010-05-01
Alpine glaciers are often located in remote and high-altitude regions of the world, areas that only rarely are covered by instrumental records. Reconstructions of glaciers has therefore proven useful for understanding past climate dynamics on both shorter and longer time-scales. One major drawback with glacier reconstructions based solely on moraine chronologies - by far the most common -, is that due to selective preservation of moraine ridges such records do not exclude the possibility of multiple Holocene glacier advances. This problem is true regardless whether cosmogenic isotopes or lichenometry have been used to date the moraines, or also radiocarbon dating of mega-fossils buried in till or underneath the moraines themselves. To overcome this problem Karlén (1976) initially suggested that glacial erosion and the associated production of rock-flour deposited in downstream lakes could provide a continuous record of glacial fluctuations, hence overcoming the problem of incomplete reconstructions. We want to discuss the methods used to reconstruct past glacier activity based on sediments deposited in distal glacier-fed lakes. By quantifying physical properties of glacial and extra-glacial sediments deposited in catchments, and in downstream lakes and fjords, it is possible to isolate and identify past glacier activity - size and production rate - that subsequently can be used to reconstruct changing environmental shifts and trends. Changes in average sediment evacuation from alpine glaciers are mainly governed by glacier size and the mass turnover gradient, determining the deformation rate at any given time. The amount of solid precipitation (mainly winter accumulation) versus loss due to melting during the ablation-season (mainly summer temperature) determines the mass turnover gradient in either positive or negative direction. A prevailing positive net balance will lead to higher sedimentation rates and vice versa, which in turn can be recorded in downstream
Biomechanical Comparison of Five Posterior Cruciate Ligament Reconstruction Techniques.
Nuelle, Clayton W; Milles, Jeffrey L; Pfeiffer, Ferris M; Stannard, James P; Smith, Patrick A; Kfuri, Mauricio; Cook, James L
2017-07-01
No surgical technique recreates native posterior cruciate ligament (PCL) biomechanics. We compared the biomechanics of five different PCL reconstruction techniques versus the native PCL. Cadaveric knees ( n = 20) were randomly assigned to one of five reconstruction techniques: Single bundle all-inside arthroscopic inlay, single bundle all-inside suspensory fixation, single bundle arthroscopic-assisted open onlay (SB-ONL), double bundle arthroscopic-assisted open inlay (DB-INL), and double bundle all-inside suspensory fixation (DB-SUSP). Each specimen was potted and connected to a servo-hydraulic load frame for testing in three conditions: PCL intact, PCL deficient, and PCL reconstructed. Testing consisted of a posterior force up to 100 N at a rate of 1 N/s at four knee flexion angles: 10, 30, 60, and 90 degrees. Three material properties were measured under each condition: load to 5 mm displacement, maximal displacement, and stiffness. Data were normalized to the native PCL, compared across techniques, compared with all PCL-intact knees and to all PCL-deficient knees using one-way analysis of variance. For load to 5 mm displacement, intact knees required significantly ( p < 0.03) more load at 30 degrees of flexion than all reconstructions except the DB-SUSP. At 60 degrees of flexion, intact required significantly ( p < 0.01) more load than all others except the SB-ONL. At 90 degrees, intact, SB-ONL, DB-INL, and DB-SUSP required significantly more load ( p < 0.05). Maximal displacement testing showed the intact to have significantly ( p < 0.02) less laxity than all others except the DB-INL and DB-SUSP at 60 degrees. At 90 degrees the intact showed significantly ( p < 0.01) less laxity than all others except the DB-SUSP. The intact was significantly stiffer than all others at 30 degrees ( p < 0.03) and 60 degrees ( p < 0.01). Finally, the intact was significantly ( p < 0.05) stiffer than all others except the DB
Effects of Piecewise Spatial Smoothing in 4-D SPECT Reconstruction
Qi, Wenyuan; Yang, Yongyi; King, Michael A.
2014-02-01
In nuclear medicine, cardiac gated SPECT images are known to suffer from significantly increased noise owing to limited data counts. Consequently, spatial (and temporal) smoothing has been indispensable for suppressing the noise artifacts in SPECT reconstruction. However, recently we demonstrated that the benefit of spatial processing in motion-compensated reconstruction of gated SPECT (aka 4-D) could be outweighed by its adverse effects on the myocardium, which included degraded wall motion and perfusion defect detectability. In this work, we investigate whether we can alleviate these adverse effects by exploiting an alternative spatial smoothing prior in 4-D based on image total variation (TV). TV based prior is known to induce piecewise smoothing which can preserve edge features (such as boundaries of the heart wall) in reconstruction. However, it is not clear whether such a property would necessarily be beneficial for improving the accuracy of the myocardium in 4-D reconstruction. In particular, it is unknown whether it would adversely affect the detectability of perfusion defects that are small in size or low in contrast. In our evaluation study, we first use Monte Carlo simulated imaging with 4-D NURBS-based cardiac-torso (NCAT) phantom wherein the ground truth is known for quantitative comparison. We evaluated the accuracy of the reconstructed myocardium using a number of metrics, including regional and overall accuracy of the myocardium, accuracy of the phase activity curve (PAC) of the LV wall for wall motion, uniformity and spatial resolution of the LV wall, and detectability of perfusion defects using a channelized Hotelling observer (CHO). For lesion detection, we simulated perfusion defects with different sizes and contrast levels with the focus being on perfusion defects that are subtle. As a preliminary demonstration, we also tested on three sets of clinical acquisitions. From the quantitative results, it was demonstrated that TV smoothing could
REGEN: Ancestral Genome Reconstruction for Bacteria
Directory of Open Access Journals (Sweden)
João C. Setubal
2012-07-01
Full Text Available Ancestral genome reconstruction can be understood as a phylogenetic study with more details than a traditional phylogenetic tree reconstruction. We present a new computational system called REGEN for ancestral bacterial genome reconstruction at both the gene and replicon levels. REGEN reconstructs gene content, contiguous gene runs, and replicon structure for each ancestral genome. Along each branch of the phylogenetic tree, REGEN infers evolutionary events, including gene creation and deletion and replicon fission and fusion. The reconstruction can be performed by either a maximum parsimony or a maximum likelihood method. Gene content reconstruction is based on the concept of neighboring gene pairs. REGEN was designed to be used with any set of genomes that are sufficiently related, which will usually be the case for bacteria within the same taxonomic order. We evaluated REGEN using simulated genomes and genomes in the Rhizobiales order.
Computer Based Road Accident Reconstruction Experiences
Directory of Open Access Journals (Sweden)
Milan Batista
2005-03-01
Full Text Available Since road accident analyses and reconstructions are increasinglybased on specific computer software for simulationof vehicle d1iving dynamics and collision dynamics, and forsimulation of a set of trial runs from which the model that bestdescribes a real event can be selected, the paper presents anoverview of some computer software and methods available toaccident reconstruction experts. Besides being time-saving,when properly used such computer software can provide moreauthentic and more trustworthy accident reconstruction, thereforepractical experiences while using computer software toolsfor road accident reconstruction obtained in the TransportSafety Laboratory at the Faculty for Maritime Studies andTransport of the University of Ljubljana are presented and discussed.This paper addresses also software technology for extractingmaximum information from the accident photo-documentationto support accident reconstruction based on the simulationsoftware, as well as the field work of reconstruction expertsor police on the road accident scene defined by this technology.
REGEN: Ancestral Genome Reconstruction for Bacteria.
Yang, Kuan; Heath, Lenwood S; Setubal, João C
2012-07-18
Ancestral genome reconstruction can be understood as a phylogenetic study with more details than a traditional phylogenetic tree reconstruction. We present a new computational system called REGEN for ancestral bacterial genome reconstruction at both the gene and replicon levels. REGEN reconstructs gene content, contiguous gene runs, and replicon structure for each ancestral genome. Along each branch of the phylogenetic tree, REGEN infers evolutionary events, including gene creation and deletion and replicon fission and fusion. The reconstruction can be performed by either a maximum parsimony or a maximum likelihood method. Gene content reconstruction is based on the concept of neighboring gene pairs. REGEN was designed to be used with any set of genomes that are sufficiently related, which will usually be the case for bacteria within the same taxonomic order. We evaluated REGEN using simulated genomes and genomes in the Rhizobiales order.
Method for position emission mammography image reconstruction
Smith, Mark Frederick
2004-10-12
An image reconstruction method comprising accepting coincidence datat from either a data file or in real time from a pair of detector heads, culling event data that is outside a desired energy range, optionally saving the desired data for each detector position or for each pair of detector pixels on the two detector heads, and then reconstructing the image either by backprojection image reconstruction or by iterative image reconstruction. In the backprojection image reconstruction mode, rays are traced between centers of lines of response (LOR's), counts are then either allocated by nearest pixel interpolation or allocated by an overlap method and then corrected for geometric effects and attenuation and the data file updated. If the iterative image reconstruction option is selected, one implementation is to compute a grid Siddon retracing, and to perform maximum likelihood expectation maiximization (MLEM) computed by either: a) tracing parallel rays between subpixels on opposite detector heads; or b) tracing rays between randomized endpoint locations on opposite detector heads.
Multiscale reconstruction for MR fingerprinting.
Pierre, Eric Y; Ma, Dan; Chen, Yong; Badve, Chaitra; Griswold, Mark A
2016-06-01
To reduce the acquisition time needed to obtain reliable parametric maps with Magnetic Resonance Fingerprinting. An iterative-denoising algorithm is initialized by reconstructing the MRF image series at low image resolution. For subsequent iterations, the method enforces pixel-wise fidelity to the best-matching dictionary template then enforces fidelity to the acquired data at slightly higher spatial resolution. After convergence, parametric maps with desirable spatial resolution are obtained through template matching of the final image series. The proposed method was evaluated on phantom and in vivo data using the highly undersampled, variable-density spiral trajectory and compared with the original MRF method. The benefits of additional sparsity constraints were also evaluated. When available, gold standard parameter maps were used to quantify the performance of each method. The proposed approach allowed convergence to accurate parametric maps with as few as 300 time points of acquisition, as compared to 1000 in the original MRF work. Simultaneous quantification of T1, T2, proton density (PD), and B0 field variations in the brain was achieved in vivo for a 256 × 256 matrix for a total acquisition time of 10.2 s, representing a three-fold reduction in acquisition time. The proposed iterative multiscale reconstruction reliably increases MRF acquisition speed and accuracy. Magn Reson Med 75:2481-2492, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
Stereo reconstruction from multiperspective panoramas.
Li, Yin; Shum, Heung-Yeung; Tang, Chi-Keung; Szeliski, Richard
2004-01-01
A new approach to computing a panoramic (360 degrees) depth map is presented in this paper. Our approach uses a large collection of images taken by a camera whose motion has been constrained to planar concentric circles. We resample regular perspective images to produce a set of multiperspective panoramas and then compute depth maps directly from these resampled panoramas. Our panoramas sample uniformly in three dimensions: rotation angle, inverse radial distance, and vertical elevation. The use of multiperspective panoramas eliminates the limited overlap present in the original input images and, thus, problems as in conventional multibaseline stereo can be avoided. Our approach differs from stereo matching of single-perspective panoramic images taken from different locations, where the epipolar constraints are sine curves. For our multiperspective panoramas, the epipolar geometry, to the first order approximation, consists of horizontal lines. Therefore, any traditional stereo algorithm can be applied to multiperspective panoramas with little modification. In this paper, we describe two reconstruction algorithms. The first is a cylinder sweep algorithm that uses a small number of resampled multiperspective panoramas to obtain dense 3D reconstruction. The second algorithm, in contrast, uses a large number of multiperspective panoramas and takes advantage of the approximate horizontal epipolar geometry inherent in multiperspective panoramas. It comprises a novel and efficient 1D multibaseline matching technique, followed by tensor voting to extract the depth surface. Experiments show that our algorithms are capable of producing comparable high quality depth maps which can be used for applications such as view interpolation.
Voting based object boundary reconstruction
Tian, Qi; Zhang, Like; Ma, Jingsheng
2005-07-01
A voting-based object boundary reconstruction approach is proposed in this paper. Morphological technique was adopted in many applications for video object extraction to reconstruct the missing pixels. However, when the missing areas become large, the morphological processing cannot bring us good results. Recently, Tensor voting has attracted people"s attention, and it can be used for boundary estimation on curves or irregular trajectories. However, the complexity of saliency tensor creation limits its applications in real-time systems. An alternative approach based on tensor voting is introduced in this paper. Rather than creating saliency tensors, we use a "2-pass" method for orientation estimation. For the first pass, Sobel d*etector is applied on a coarse boundary image to get the gradient map. In the second pass, each pixel puts decreasing weights based on its gradient information, and the direction with maximum weights sum is selected as the correct orientation of the pixel. After the orientation map is obtained, pixels begin linking edges or intersections along their direction. The approach is applied to various video surveillance clips under different conditions, and the experimental results demonstrate significant improvement on the final extracted objects accuracy.
Reconstruction of abstract quantum theory
International Nuclear Information System (INIS)
Drieschner, M.; Goernitz, T.; von Weizsaecker, C.F.
1988-01-01
Understanding quantum theory as a general theory of prediction, we reconstruct abstract quantum theory. Abstract means the general frame of quantum theory, without reference to a three-dimensional position space, to concepts like particle or field, or to special laws of dynamics. Reconstruction is the attempt to do this by formulating simple and plausible postulates on prediction in order to derive the basic concepts of quantum theory from them. Thereby no law of classical physics is presupposed which would then have to be quantized. We briefly discuss the relationship of theory and interpretation in physics and the fundamental role of time as a basic concept for physics. Then a number of assertions are given, formulated as succinctly as possible in order to make them easily quotable and comparable. The assertations are arranged in four groups: heuristic principles, verbal definitions of some terms, three basic postulates, and consequences. The three postulates of separable alternatives, indeterminism, and kinematics are the central points of this work. These brief assertions are commented upon, and their relationship with the interpretation of quantum theory is discussed. Also given are an outlook on the further development into concrete quantum theory and some philosophical reflections
Stochastic Optical Reconstruction Microscopy (STORM).
Xu, Jianquan; Ma, Hongqiang; Liu, Yang
2017-07-05
Super-resolution (SR) fluorescence microscopy, a class of optical microscopy techniques at a spatial resolution below the diffraction limit, has revolutionized the way we study biology, as recognized by the Nobel Prize in Chemistry in 2014. Stochastic optical reconstruction microscopy (STORM), a widely used SR technique, is based on the principle of single molecule localization. STORM routinely achieves a spatial resolution of 20 to 30 nm, a ten-fold improvement compared to conventional optical microscopy. Among all SR techniques, STORM offers a high spatial resolution with simple optical instrumentation and standard organic fluorescent dyes, but it is also prone to image artifacts and degraded image resolution due to improper sample preparation or imaging conditions. It requires careful optimization of all three aspects-sample preparation, image acquisition, and image reconstruction-to ensure a high-quality STORM image, which will be extensively discussed in this unit. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.
Outcome of different facial nerve reconstruction techniques
Mohamed, Aboshanif; Omi, Eigo; Honda, Kohei; Suzuki, Shinsuke; Ishikawa, Kazuo
2016-01-01
Abstract Introduction: There is no technique of facial nerve reconstruction that guarantees facial function recovery up to grade III. Objective: To evaluate the efficacy and safety of different facial nerve reconstruction techniques. Methods: Facial nerve reconstruction was performed in 22 patients (facial nerve interpositional graft in 11 patients and hypoglossal-facial nerve transfer in another 11 patients). All patients had facial function House-Brackmann (HB) grade VI, either caused by...
Considerations on Xi- reconstruction in LHCb
Brochu, F.M.
2016-01-01
This paper describes an alternative method of charged hyperon reconstruction applicable to the LHCb experiment. It extends the seminal work of the FOCUS collaboration to the specific detector layout of LHCb and addresses the reconstruction ambiguities reported in their earlier work, leading to improvements in the reconstruction efficiency for the specific cases of Xi- and Omega- baryon decays to a charged meson and a Lambda baryon.
The Theory of Variances in Equilibrium Reconstruction
International Nuclear Information System (INIS)
Zakharov, Leonid E.; Lewandowski, Jerome; Foley, Elizabeth L.; Levinton, Fred M.; Yuh, Howard Y.; Drozdov, Vladimir; McDonald, Darren
2008-01-01
The theory of variances of equilibrium reconstruction is presented. It complements existing practices with information regarding what kind of plasma profiles can be reconstructed, how accurately, and what remains beyond the abilities of diagnostic systems. The σ-curves, introduced by the present theory, give a quantitative assessment of quality of effectiveness of diagnostic systems in constraining equilibrium reconstructions. The theory also suggests a method for aligning the accuracy of measurements of different physical nature
Prosthetic breast reconstruction: indications and update
Quinn, Tam T.; Miller, George S.; Rostek, Marie; Cabalag, Miguel S.; Rozen, Warren M.
2016-01-01
Background Despite 82% of patients reporting psychosocial improvement following breast reconstruction, only 33% patients choose to undergo surgery. Implant reconstruction outnumbers autologous reconstruction in many centres. Methods A systematic review of the literature was undertaken. Inclusion required: (I) Meta-analyses or review articles; (II) adult patients aged 18 years or over undergoing alloplastic breast reconstruction; (III) studies including outcome measures; (IV) case series with more than 10 patients; (V) English language; and (VI) publication after 1st January, 2000. Results After full text review, analysis and data extraction was conducted for a total of 63 articles. Definitive reconstruction with an implant can be immediate or delayed. Older patients have similar or even lower complication rates to younger patients. Complications include capsular contracture, hematoma and infection. Obesity, smoking, large breasts, diabetes and higher grade tumors are associated with increased risk of wound problems and reconstructive failure. Silicone implant patients have higher capsular contracture rates but have higher physical and psychosocial function. There were no associations made between silicone implants and cancer or systemic disease. There were no differences in outcomes or complications between round and shaped implants. Textured implants have a lower risk of capsular contracture than smooth implants. Smooth implants are more likely to be displaced as well as having higher rates of infection. Immediate breast reconstruction (IBR) gives the best aesthetic outcome if radiotherapy is not required but has a higher rate of capsular contracture and implant failure. Delayed-immediate reconstruction patients can achieve similar aesthetic results to IBR whilst preserving the breast skin if radiotherapy is required. Delayed breast reconstruction (DBR) patients have fewer complications than IBR patients. Conclusions Implant reconstruction is a safe and popular
Algorithms for reconstructing images for industrial applications
International Nuclear Information System (INIS)
Lopes, R.T.; Crispim, V.R.
1986-01-01
Several algorithms for reconstructing objects from their projections are being studied in our Laboratory, for industrial applications. Such algorithms are useful locating the position and shape of different composition of materials in the object. A Comparative study of two algorithms is made. The two investigated algorithsm are: The MART (Multiplicative - Algebraic Reconstruction Technique) and the Convolution Method. The comparison are carried out from the point view of the quality of the image reconstructed, number of views and cost. (Author) [pt
A systematic review of acelluar dermal matrices in head and neck reconstruction.
Shridharani, Sachin M; Tufaro, Anthony P
2012-11-01
The use of acellular dermal matrices has been well described in the scientific literature since the early 1990 s and has been utilized for multiple applications in the head and neck for both aesthetic and reconstructive efforts. After systematically searching the PubMed database and following further refinement (based on the authors' inclusion and exclusion criteria), the authors identified 30 studies that provided information about patients who had undergone head and neck reconstruction with the use of acellular dermal matrix. Studies had to report quantifiable objective results in patients who were older than 1 year and younger than 90 years. The authors excluded single case reports, studies with fewer than 10 patients, and studies not published in English. The optimal material used as an implant for reconstruction possesses the following properties: facilitation of vascular ingrowth, decreased propensity to incite inflammation, biologic inertness, resistance to infection, and ease of handling. Acellular dermal matrix possesses many of these properties and is utilized in reconstructing nasal soft tissue and skeletal support, tympanic membrane, periorbital soft tissue, extraoral and intraoral defects, oropharyngeal defects, dura mater, and soft-tissue deficits from parotidectomy. Furthermore, it is used to assist in preventing Frey syndrome following parotidectomy and surgical treatment of facial paralysis. Use of acellular dermal matrix for head and neck reconstruction has expanded exponentially and is validated in many studies. Further prospective randomized control trials are warranted to further investigate the efficacy of acellular dermal matrix in head and neck reconstruction.
Directory of Open Access Journals (Sweden)
Berrak Akşam
2016-06-01
Full Text Available Objective: Most of the malignant cutaneous carcinomas are seen in the nasal region. Reconstruction of nasal defects is challenging because of the unique anatomic properties and complex structure of this region. In this study, we present our algorithm for the nasal skin defects that occurred after malignant skin tumor excisions. Material and Methods: Patients whose nasal skin was reconstructed after malignant skin tumor excision were included in the study. These patients were evaluated by their age, gender, comorbities, tumor location, tumor size, reconstruction type, histopathological diagnosis, and tumor recurrence. Results: A total of 130 patients (70 female, 60 male were evaluated. The average age of the patients was 67.8 years. Tumors were located mostly at the dorsum, alar region, and tip of the nose. When reconstruction methods were evaluated, primary closure was preferred in 14.6% patients, full thickness skin grafts were used in 25.3% patients, and reconstruction with flaps were the choice in 60% patients. Different flaps were used according to the subunits. Mostly, dorsal nasal flaps, bilobed flaps, nasolabial flaps, and forehead flaps were used. Conclusion: The defect-only reconstruction principle was accepted in this study. Previously described subunits, such as the dorsum, tip, alar region, lateral wall, columella, and soft triangles, of the nose were further divided into subregions by their anatomical relations. An algorithm was planned with these sub regions. In nasal skin reconstruction, this algorithm helps in selection the methods for the best results and minimize the complications.
Reconstructions of the sulfur-passivated InSb (100) surface
Energy Technology Data Exchange (ETDEWEB)
Ciochoń, Piotr, E-mail: piotr.ciochon@doctoral.uj.edu.pl; Olszowska, Natalia; Wróbel, Sonia; Kołodziej, Jacek
2017-04-01
Highlights: • Two new surface reconstructions of a S-passivated InSb (001) surface are reported. • The reconstructions are obtained through partial loss of surface sulfur. • They are characterized by the thickness of ∼4 Å and good crystallographic ordering. • The reconstructions provide adequate electronic passivation of the surface. - Abstract: We have studied the properties of the InSb (100) surface passivated with sulfur dimers emitted by the solid-state electrochemical cell in ultra-high vacuum. Annealing the passivated surface in the temperature equal to T = 326 °C led to the formation of the c(4 × 8) surface reconstruction, while increasing the temperature to T = 348 °C resulted in the transition to c(4 × 12) reconstruction. To the best of our knowledge these reconstructions have not been reported to date and are characterized by the exceptionally good crystallographic order. XPS studies revealed that there are at least 4 different chemical species of sulfur present on the surface and the estimated thickness of the sulfur layers is equal to around 4 Å. The surface reconstructions are characterized by the lowered intensity of the surface electronic states and resonances near the Fermi level, compared to the clean InSb surface, making them potentially very useful for the fabrication of InSb-based electronic and optoelectronic devices.
Reconstruction of convex bodies from surface tensors
DEFF Research Database (Denmark)
Kousholt, Astrid; Kiderlen, Markus
We present two algorithms for reconstruction of the shape of convex bodies in the two-dimensional Euclidean space. The first reconstruction algorithm requires knowledge of the exact surface tensors of a convex body up to rank s for some natural number s. The second algorithm uses harmonic intrinsic...... volumes which are certain values of the surface tensors and allows for noisy measurements. From a generalized version of Wirtinger's inequality, we derive stability results that are utilized to ensure consistency of both reconstruction procedures. Consistency of the reconstruction procedure based...
Boomerang flap reconstruction for the breast.
Baumholtz, Michael A; Al-Shunnar, Buthainah M; Dabb, Richard W
2002-07-01
The boomerang-shaped latissimus dorsi musculocutaneous flap for breast reconstruction offers a stable platform for breast reconstruction. It allows for maximal aesthetic results with minimal complications. The authors describe a skin paddle to obtain a larger volume than either the traditional elliptical skin paddle or the extended latissimus flap. There are three specific advantages to the boomerang design: large volume, conical shape (often lacking in the traditional skin paddle), and an acceptable donor scar. Thirty-eight flaps were performed. No reconstruction interfered with patient's ongoing oncological regimen. The most common complication was seroma, which is consistent with other latissimus reconstructions.
Jini service to reconstruct tomographic data
Knoll, Peter; Mirzaei, S.; Koriska, K.; Koehn, H.
2002-06-01
A number of imaging systems rely on the reconstruction of a 3- dimensional model from its projections through the process of computed tomography (CT). In medical imaging, for example magnetic resonance imaging (MRI), positron emission tomography (PET), and Single Computer Tomography (SPECT) acquire two-dimensional projections of a three dimensional projections of a three dimensional object. In order to calculate the 3-dimensional representation of the object, i.e. its voxel distribution, several reconstruction algorithms have been developed. Currently, mainly two reconstruct use: the filtered back projection(FBP) and iterative methods. Although the quality of iterative reconstructed SPECT slices is better than that of FBP slices, such iterative algorithms are rarely used for clinical routine studies because of their low availability and increased reconstruction time. We used Jini and a self-developed iterative reconstructions algorithm to design and implement a Jini reconstruction service. With this service, the physician selects the patient study from a database and a Jini client automatically discovers the registered Jini reconstruction services in the department's Intranet. After downloading the proxy object the this Jini service, the SPECT acquisition data are reconstructed. The resulting transaxial slices are visualized using a Jini slice viewer, which can be used for various imaging modalities.
Optimizing Aesthetic Outcomes in Delayed Breast Reconstruction
Directory of Open Access Journals (Sweden)
Wojciech Dec, MD
2017-08-01
Conclusions:. Optimal aesthetic results can be achieved with: (1 restoration of breast skin envelope with tissue expansion when possible, (2 optimal positioning of a small skin paddle to be later incorporated entirely into a nipple areola reconstruction when adequate breast skin surface area is present, (3 limiting the reconstructed breast mound to 2 skin tones when large area skin resurfacing is required, (4 increasing breast volume by deepithelializing, not discarding, the inferior mastectomy flap skin, (5 eccentric division of abdominal flaps when an immediate and delayed bilateral breast reconstructions are performed simultaneously; and (6 performing second-stage breast reconstruction revisions and fat grafting.
Reconstructing Nearly Simple Polytopes from their Graph
Doolittle, Joseph
2017-01-01
We present a partial description of which polytopes are reconstructible from their graphs. This is an extension of work by Blind and Mani (1987) and Kalai (1988), which showed that simple polytopes can be reconstructed from their graphs. In particular, we introduce a notion of $h$-nearly simple and prove that 1-nearly simple and 2-nearly simple polytopes are reconstructible from their graphs. We also give an example of a 3-nearly simple polytope which is not reconstructible from its graph. Fu...
Breast Reconstruction After Solid Organ Transplant.
Koonce, Stephanie L; Giles, Brian; McLaughlin, Sarah A; Perdikis, Galen; Waldorf, James; Lemaine, Valerie; TerKonda, Sarvam
2015-09-01
Solid organ transplant patients frequently develop posttransplant malignancies including breast cancer. They may desire breast reconstruction after mastectomy, which could potentially be complicated by their transplant status, immunosuppressive regimen, and previous operations. We review our experience with patients who have undergone solid organ transplant and subsequent breast reconstruction after mastectomy After institutional review board approval, we queried our prospective breast reconstruction and solid organ transplant databases for corresponding patients. Inclusion criteria comprised breast reconstruction after solid organ transplant. A chart review was conducted of identified patients. Seventeen patients were identified: 1 pulmonary transplant, 4 cardiac transplants, 2 liver transplants, 1 pancreas transplant, 2 combined kidney/pancreas transplants, and 7 kidney transplants. Indications for mastectomy included posttransplant malignancy and prophylaxis. Median time from transplant to completion of reconstruction was 186 months (range, 11-336 months). Median age at transplant was 34.5 years (range, 21-65 years) with the median age of the patients at reconstructive surgery 51.5 years (range, 34-71 years). Median body mass index was 25.3 (range, 21.3-46.5). No significant complications were noted after reconstructive surgery. All patients were on full immunosuppression at time of reconstruction. Breast reconstruction is a viable option for transplant patients after mastectomy and should not be refused based on their transplant status. Close coordination with the transplant team and careful preoperative planning is essential for optimal outcomes.
Sparse Image Reconstruction in Computed Tomography
DEFF Research Database (Denmark)
Jørgensen, Jakob Sauer
In recent years, increased focus on the potentially harmful effects of x-ray computed tomography (CT) scans, such as radiation-induced cancer, has motivated research on new low-dose imaging techniques. Sparse image reconstruction methods, as studied for instance in the field of compressed sensing...... applications. This thesis takes a systematic approach toward establishing quantitative understanding of conditions for sparse reconstruction to work well in CT. A general framework for analyzing sparse reconstruction methods in CT is introduced and two sets of computational tools are proposed: 1...... contributions to a general set of computational characterization tools. Thus, the thesis contributions help advance sparse reconstruction methods toward routine use in...
Tomographic image reconstruction using Artificial Neural Networks
International Nuclear Information System (INIS)
Paschalis, P.; Giokaris, N.D.; Karabarbounis, A.; Loudos, G.K.; Maintas, D.; Papanicolas, C.N.; Spanoudaki, V.; Tsoumpas, Ch.; Stiliaris, E.
2004-01-01
A new image reconstruction technique based on the usage of an Artificial Neural Network (ANN) is presented. The most crucial factor in designing such a reconstruction system is the network architecture and the number of the input projections needed to reconstruct the image. Although the training phase requires a large amount of input samples and a considerable CPU time, the trained network is characterized by simplicity and quick response. The performance of this ANN is tested using several image patterns. It is intended to be used together with a phantom rotating table and the γ-camera of IASA for SPECT image reconstruction
Optoelectronic Computer Architecture Development for Image Reconstruction
National Research Council Canada - National Science Library
Forber, Richard
1996-01-01
.... Specifically, we collaborated with UCSD and ERIM on the development of an optically augmented electronic computer for high speed inverse transform calculations to enable real time image reconstruction...
Theoretical interpretation of experimental data from direct dark matter detection
Energy Technology Data Exchange (ETDEWEB)
Chung-Lin, Shan
2007-10-15
I derive expressions that allow to reconstruct the normalized one-dimensional velocity distribution function of halo WIMPs and to determine its moments from the recoil energy spectrum as well as from experimental data directly. The reconstruction of the velocity distribution function is further extended to take into account the annual modulation of the event rate. All these expressions are independent of the as yet unknown WIMP density near the Earth as well as of the WIMP-nucleus cross section. The only information about the nature of halo WIMPs which one needs is the WIMP mass. I also present a method for the determination of the WIMP mass by combining two (or more) experiments with different detector materials. This method is not only independent of the model of Galactic halo but also of that of WIMPs. (orig.)
Theoretical interpretation of experimental data from direct dark matter detection
International Nuclear Information System (INIS)
Shan Chung-Lin
2007-10-01
I derive expressions that allow to reconstruct the normalized one-dimensional velocity distribution function of halo WIMPs and to determine its moments from the recoil energy spectrum as well as from experimental data directly. The reconstruction of the velocity distribution function is further extended to take into account the annual modulation of the event rate. All these expressions are independent of the as yet unknown WIMP density near the Earth as well as of the WIMP-nucleus cross section. The only information about the nature of halo WIMPs which one needs is the WIMP mass. I also present a method for the determination of the WIMP mass by combining two (or more) experiments with different detector materials. This method is not only independent of the model of Galactic halo but also of that of WIMPs. (orig.)
DEFF Research Database (Denmark)
Zhu, Yansong; Jha, Abhinav K.; Dreyer, Jakob K.
2017-01-01
Fluorescence molecular tomography (FMT) is a promising tool for real time in vivo quantification of neurotransmission (NT) as we pursue in our BRAIN initiative effort. However, the acquired image data are noisy and the reconstruction problem is ill-posed. Further, while spatial sparsity of the NT...... matrix coherence. The resultant image data are input to a homotopy-based reconstruction strategy that exploits sparsity via ℓ1 regularization. The reconstructed image is then input to a maximum-likelihood expectation maximization (MLEM) algorithm that retains the sparseness of the input estimate...... and improves upon the quantitation by accurate Poisson noise modeling. The proposed reconstruction method was evaluated in a three-dimensional simulated setup with fluorescent sources in a cuboidal scattering medium with optical properties simulating human brain cortex (reduced scattering coefficient: 9.2 cm-1...
A deep learning-based reconstruction of cosmic ray-induced air showers
Erdmann, M.; Glombitza, J.; Walz, D.
2018-01-01
We describe a method of reconstructing air showers induced by cosmic rays using deep learning techniques. We simulate an observatory consisting of ground-based particle detectors with fixed locations on a regular grid. The detector's responses to traversing shower particles are signal amplitudes as a function of time, which provide information on transverse and longitudinal shower properties. In order to take advantage of convolutional network techniques specialized in local pattern recognition, we convert all information to the image-like grid of the detectors. In this way, multiple features, such as arrival times of the first particles and optimized characterizations of time traces, are processed by the network. The reconstruction quality of the cosmic ray arrival direction turns out to be competitive with an analytic reconstruction algorithm. The reconstructed shower direction, energy and shower depth show the expected improvement in resolution for higher cosmic ray energy.
Reconstruction of Novel Viewpoint Image Using GRNN
Institute of Scientific and Technical Information of China (English)
李战委; 孙济洲; 张志强
2003-01-01
A neural-statistical approach to the reconstruction of novel viewpoint image using general regression neural networks(GRNN) is presented. Different color value will be obtained by watching the same surface point of an object from different viewpoints due to specular reflection, and the difference is related to the position of viewpoint. The relationship between the position of viewpoint and the color of image is non-linear, neural network is introduced to make curve fitting, where the inputs of neural network are only a few calibrated images with obvious specular reflection. By training the neural network, network model is obtained. By inputing an arbitrary virtual viewpoint to the model, the image of the virtual viewpoint can be computed. By using the method presented here, novel viewpoint image with photo-realistic property can be obtained, especially images with obvious specular reflection can accurately be generated. The method is an image-based rendering method, geometric model of the scene and position of lighting are not needed.
Last Glacial Maximum Salinity Reconstruction
Homola, K.; Spivack, A. J.
2016-12-01
It has been previously demonstrated that salinity can be reconstructed from sediment porewater. The goal of our study is to reconstruct high precision salinity during the Last Glacial Maximum (LGM). Salinity is usually determined at high precision via conductivity, which requires a larger volume of water than can be extracted from a sediment core, or via chloride titration, which yields lower than ideal precision. It has been demonstrated for water column samples that high precision density measurements can be used to determine salinity at the precision of a conductivity measurement using the equation of state of seawater. However, water column seawater has a relatively constant composition, in contrast to porewater, where variations from standard seawater composition occur. These deviations, which affect the equation of state, must be corrected for through precise measurements of each ion's concentration and knowledge of apparent partial molar density in seawater. We have developed a density-based method for determining porewater salinity that requires only 5 mL of sample, achieving density precisions of 10-6 g/mL. We have applied this method to porewater samples extracted from long cores collected along a N-S transect across the western North Atlantic (R/V Knorr cruise KN223). Density was determined to a precision of 2.3x10-6 g/mL, which translates to salinity uncertainty of 0.002 gms/kg if the effect of differences in composition is well constrained. Concentrations of anions (Cl-, and SO4-2) and cations (Na+, Mg+, Ca+2, and K+) were measured. To correct salinities at the precision required to unravel LGM Meridional Overturning Circulation, our ion precisions must be better than 0.1% for SO4-/Cl- and Mg+/Na+, and 0.4% for Ca+/Na+, and K+/Na+. Alkalinity, pH and Dissolved Inorganic Carbon of the porewater were determined to precisions better than 4% when ratioed to Cl-, and used to calculate HCO3-, and CO3-2. Apparent partial molar densities in seawater were
BREAST RECONSTRUCTIONS AFTER BREAST CANCER TREATING
Directory of Open Access Journals (Sweden)
Erik Vrabič
2018-02-01
Full Text Available Background. Breasts are an important symbol of physical beauty, feminity, mothering and sexual desire through the entire history of mankind. Lost of the whole or part of the breast is functional and aesthetic disturbance for woman. It is understandable, that the woman, who is concerned over breast loss, is as appropriate as another person´s concern over the loss of a limb or other body part. Before the 1960, breast reconstruction was considered as a dangerous procedure and it was almost prohibited. Considering the psychological importance of the breast in modern society, the possibility of breast reconstruction for the woman about to undergo a mastectomy is a comforting alternative. We can perform breast reconstruction with autologous tissue (autologous reconstruction, with breast implants and combination of both methods. For autologous reconstruction we can use local tissue (local flaps, or tissue from distant parts of the body (free vascular tissue transfer. Tissue expansion must be performed first, in many cases of breast reconstructions with breast implants. Conclusions. Possibility of breast reconstruction made a big progress last 3 decades. Today we are able to reconstruct almost every defect of the breast and the entire breast. Breast reconstruction rise the quality of life for breast cancer patients. Breast reconstruction is a team work of experts from many medicine specialites. In Slovenia we can offer breast reconstruction for breast cancer patients in Ljubljana, where plastic surgeons from Clinical Department for Plastic Surgery and Burns cooperate with oncologic surgeons. Ten years ago a similar cooperation between plastic surgeons and surgeons of the Centre for Breast Diseases was established in Maribor.
Neural Network for Sparse Reconstruction
Directory of Open Access Journals (Sweden)
Qingfa Li
2014-01-01
Full Text Available We construct a neural network based on smoothing approximation techniques and projected gradient method to solve a kind of sparse reconstruction problems. Neural network can be implemented by circuits and can be seen as an important method for solving optimization problems, especially large scale problems. Smoothing approximation is an efficient technique for solving nonsmooth optimization problems. We combine these two techniques to overcome the difficulties of the choices of the step size in discrete algorithms and the item in the set-valued map of differential inclusion. In theory, the proposed network can converge to the optimal solution set of the given problem. Furthermore, some numerical experiments show the effectiveness of the proposed network in this paper.
Hanford Environmental Dose Reconstruction Project
International Nuclear Information System (INIS)
McMakin, A.H.; Cannon, S.D.; Finch, S.M.
1992-07-01
The objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation doses that individuals and populations could have received from nuclear operations at Hanford since 1944. The TSP consists of experts in environmental pathways, epidemiology, surface-water transport, ground-water transport, statistics, demography, agriculture, meteorology, nuclear engineering, radiation dosimetry, and cultural anthropology. Included are appointed technical members representing the states of Oregon, Washington, and Idaho, a representative of Native American tribes, and an individual representing the public. The project is divided into the following technical tasks. These tasks correspond to the path radionuclides followed from release to impact on humans (dose estimates): Source terms, environmental transport, environmental monitoring data, demography, food consumption, and agriculture, and environmental pathways and dose estimates. Progress is discussed
Rational approximations for tomographic reconstructions
International Nuclear Information System (INIS)
Reynolds, Matthew; Beylkin, Gregory; Monzón, Lucas
2013-01-01
We use optimal rational approximations of projection data collected in x-ray tomography to improve image resolution. Under the assumption that the object of interest is described by functions with jump discontinuities, for each projection we construct its rational approximation with a small (near optimal) number of terms for a given accuracy threshold. This allows us to augment the measured data, i.e., double the number of available samples in each projection or, equivalently, extend (double) the domain of their Fourier transform. We also develop a new, fast, polar coordinate Fourier domain algorithm which uses our nonlinear approximation of projection data in a natural way. Using augmented projections of the Shepp–Logan phantom, we provide a comparison between the new algorithm and the standard filtered back-projection algorithm. We demonstrate that the reconstructed image has improved resolution without additional artifacts near sharp transitions in the image. (paper)
Data acquisition, reconstruction, and display
International Nuclear Information System (INIS)
Huesman, R.H.
1981-01-01
A special emphasis of the Research Medicine program is the development of methods for acquiring and manipulating data from the Donner 280-crystal positron emission tomograph. This past year, development of a system capable of taking 1 million events per second while simultaneously correcting for unwanted accidental coincidence events was completed. The system permits the simultaneous acquisition of data for eight different time-slices of the cardiac cycle. A microprocessor responds to the patient's electrocardiogram (EKG) signal, routing data to the histogram memory corresponding to the phase of the cardiac cycle indicated by the signal. Additional work completed this year includes quantitation of the signal-to-noise ratio to be expected when imaging the human head. Effort is continuing on the more complicated problem of noise propagation in reconstructions of the human thorax
Bayesian tomographic reconstruction of microsystems
International Nuclear Information System (INIS)
Salem, Sofia Fekih; Vabre, Alexandre; Mohammad-Djafari, Ali
2007-01-01
The microtomography by X ray transmission plays an increasingly dominating role in the study and the understanding of microsystems. Within this framework, an experimental setup of high resolution X ray microtomography was developed at CEA-List to quantify the physical parameters related to the fluids flow in microsystems. Several difficulties rise from the nature of experimental data collected on this setup: enhanced error measurements due to various physical phenomena occurring during the image formation (diffusion, beam hardening), and specificities of the setup (limited angle, partial view of the object, weak contrast).To reconstruct the object we must solve an inverse problem. This inverse problem is known to be ill-posed. It therefore needs to be regularized by introducing prior information. The main prior information we account for is that the object is composed of a finite known number of different materials distributed in compact regions. This a priori information is introduced via a Gauss-Markov field for the contrast distributions with a hidden Potts-Markov field for the class materials in the Bayesian estimation framework. The computations are done by using an appropriate Markov Chain Monte Carlo (MCMC) technique.In this paper, we present first the basic steps of the proposed algorithms. Then we focus on one of the main steps in any iterative reconstruction method which is the computation of forward and adjoint operators (projection and backprojection). A fast implementation of these two operators is crucial for the real application of the method. We give some details on the fast computation of these steps and show some preliminary results of simulations
International Nuclear Information System (INIS)
Knesaurek, K.; Machac, J.; Vallabhajosula, S.; Buchsbaum, M.S.
1996-01-01
A new interative reconstruction technique (NIRT) for positron emission computed tomography (PET), which uses transmission data for nonuniform attenuation correction, is described. Utilizing the general inverse problem theory, a cost functional which includes a noise term was derived. The cost functional was minimized using a weighted-least-square maximum a posteriori conjugate gradient (CG) method. The procedure involves a change in the Hessian of the cost function by adding an additional term. Two phantoms were used in a real data acquisition. The first was a cylinder phantom filled with uniformly distributed activity of 74 MBq of fluorine-18. Two different inserts were placed in the phantom. The second was a Hoffman brain phantom filled with uniformly distributed activity of 7.4 MBq of 18 F. Resulting reconstructed images were used to test and compare a new interative reconstruction technique with a standard filtered backprojection (FBP) method. The results confirmed that NIRT, based on the conjugate gradient method, converges rapidly and provides good reconstructed images. In comaprison with standard results obtained by the FBP method, the images reconstructed by NIRT showed better noise properties. The noise was measured as rms% noise and was less, by a factor of 1.75, in images reconstructed by NIRT than in the same images reconstructed by FBP. The distance between the Hoffman brain slice created from the MRI image was 0.526, while the same distance for the Hoffman brain slice reconstructed by NIRT was 0.328. The NIRT method suppressed the propagation of the noise without visible loss of resolution in the reconstructed PET images. (orig.)
Modern approach to facial skin defects reconstruction
Directory of Open Access Journals (Sweden)
Mateusz Kister
2017-10-01
Full Text Available Reconstruction of a facial defect is usually a challenging endeavor. The article aims to describe different types of flaps that might be used to restore such deformities- including their characteristics, indications and guidelines that should be followed in the reconstructive procedures.
Seismic interferometry : Reconstructing the earth's reflection response
Draganov, D.S.; Wapenaar, C.P.A.; Thorbecke, J.W.
2006-01-01
In 1968, Jon Claerbout showed that the reflection response of a 1D acoustic medium can be reconstructed by autocorrelating the transmission response. Since then, several authors have derived relationships for reconstructing Green's functions at the surface, using crosscorrelations of (noise)
Oral cavity reconstruction with the masseter flap
Mahieu, R.; Russo, S.; Gualtieri, T.; Colletti, G.; Deganello, A.
The purpose of this report is to highlight how an unusual, outdated, unpopular and overlooked reconstructive method such as the masseter flap can be a reliable, straightforward and effective solution for oral reconstruction in selected cases. We report the transposition of the masseter crossover
RECONSTRUCTION OF THE SOUND CONDUCTING MECHANISM ...
African Journals Online (AJOL)
In this progress report on a new tympanoplastic procedure for reconstructing a disrupted sound conducting mechanism characterized by destruction of the handle of the malleus, it is shown that by reconstructing a tympanic membrane and a handle of the malleus from a patient's own tissue and by utilizing a prosthesis for ...
Anatomic Double-bundle ACL Reconstruction
Schreiber, Verena M.; van Eck, Carola F.; Fu, Freddie H.
2010-01-01
Rupture of the anterior cruciate ligament (ACL) is one of the most frequent forms of knee trauma. The traditional surgical treatment for ACL rupture is single-bundle reconstruction. However, during the past few years there has been a shift in interest toward double-bundle reconstruction to closely
Advances in bioprinting technologies for craniofacial reconstruction
Visscher, D.O.; Farré-Guasch, E.; Helder, M.N.; Gibbs, S.; Forouzanfar, T.; van Zuijlen, P.P.; Wolff, J.
2016-01-01
Recent developments in craniofacial reconstruction have shown important advances in both the materials and methods used. While autogenous tissue is still considered to be the gold standard for these reconstructions, the harvesting procedure remains tedious and in many cases causes significant donor
Parallel Algorithm for Reconstruction of TAC Images
International Nuclear Information System (INIS)
Vidal Gimeno, V.
2012-01-01
The algebraic reconstruction methods are based on solving a system of linear equations. In a previous study, was used and showed as the PETSc library, was and is a scientific computing tool, which facilitates and enables the optimal use of a computer system in the image reconstruction process.
Labral reconstruction: when to perform and how
Directory of Open Access Journals (Sweden)
Brian J White
2015-07-01
Full Text Available Over the past decade, the understanding of the anatomy and function of the hip joint has continuously evolved, and surgical treatment options for the hip have significantly progressed. Originally, surgical treatment of the hip primarily involved resection of damaged tissue. Procedures that maintain and preserve proper hip anatomy, such as labral repair and femoroacetabular impingement (FAI correction, have shown superior results, in terms of pain reduction, increased function, and ability to return to activities. Labral reconstruction is a treatment option that uses a graft to reconstruct the native labrum. The technique and outcomes of labral reconstruction have been described relatively recently, and labral reconstruction is a cutting edge procedure that has shown promising early outcomes. The aim of this article is to review the current literature on hip labral reconstruction. We will review the indications for labral reconstruction, surgical technique and graft options, and surgical outcomes that have been described to date. Labral reconstruction provides an alternative treatment option for challenging intra-articular hip problems. Labral reconstruction restores the original anatomy of the hip and has the potential to preserve the longevity of the hip joint. This technique is an important tool in the orthopaedic surgeon’s arsenal for hip joint treatment and preservation.
[Pelvic reconstructions after bone tumor resection].
Anract, Philippe; Biau, David; Babinet, Antoine; Tomeno, Bernard
2014-02-01
The three more frequent primitive malignant bone tumour which concerned the iliac bone are chondrosarcoma, following Ewing sarcoma and osteosarcoma. Wide resection remains the most important part of the treatment associated with chemotherapy for osteosarcoma and the Ewing sarcoma. Iliac wing resections and obdurate ring don't required reconstruction. However, acetabular resections and iliac wing resection with disruption of the pelvic ring required reconstruction to provide acceptable functional result. Acetabular reconstruction remains high technical demanding challenge. After isolated acetabular resection or associated to obdurate ring, our usual method of reconstruction is homolateral proximal femoral autograft and total hip prosthesis but it is possible to also used : saddle prosthesis, Mac Minn prosthesis with auto or allograft, modular prosthesis or custom made prosthesis, massive allograft with or without prosthesis and femoro-ilac arthrodesis. After resection of the iliac wing plus acetabulum, reconstruction can be performed by femoro-obturatrice and femora-sacral arthrodesis, homolateral proximal femoral autograft and prosthesis, femoral medialisation, massive allograft and massive allograft. Carcinological results are lesser than resection for distal limb tumor, local recurrence rate range 17 to 45%. Functional results after Iliac wing and obdurate ring are good. However, acetabular reconstruction provide uncertain functional results. The lesser results arrive after hemipelvic or acetabular and iliac wing resection-reconstruction, especially when gluteus muscles were also resected. The most favourable results arrive after isolated acetabular or acetabular plus obturateur ring resection-reconstruction.
Reconstruction of sound fields with a spherical microphone array
DEFF Research Database (Denmark)
Fernandez Grande, Efren; Walton, Tim
2014-01-01
waves traveling in any direction. In particular, rigid sphere microphone arrays are robust, and have the favorable property that the scattering introduced by the array can be compensated for - making the array virtually transparent. This study examines a recently proposed sound field reconstruction...... method based on a point source expansion, i.e. equivalent source method, using a rigid spherical array. The study examines the capability of the method to distinguish between sound waves arriving from different directions (i.e., as a sound field separation method). This is representative of the potential...
Hierarchical Bayesian sparse image reconstruction with application to MRFM.
Dobigeon, Nicolas; Hero, Alfred O; Tourneret, Jean-Yves
2009-09-01
This paper presents a hierarchical Bayesian model to reconstruct sparse images when the observations are obtained from linear transformations and corrupted by an additive white Gaussian noise. Our hierarchical Bayes model is well suited to such naturally sparse image applications as it seamlessly accounts for properties such as sparsity and positivity of the image via appropriate Bayes priors. We propose a prior that is based on a weighted mixture of a positive exponential distribution and a mass at zero. The prior has hyperparameters that are tuned automatically by marginalization over the hierarchical Bayesian model. To overcome the complexity of the posterior distribution, a Gibbs sampling strategy is proposed. The Gibbs samples can be used to estimate the image to be recovered, e.g., by maximizing the estimated posterior distribution. In our fully Bayesian approach, the posteriors of all the parameters are available. Thus, our algorithm provides more information than other previously proposed sparse reconstruction methods that only give a point estimate. The performance of the proposed hierarchical Bayesian sparse reconstruction method is illustrated on synthetic data and real data collected from a tobacco virus sample using a prototype MRFM instrument.
Recent advances in 3D SEM surface reconstruction.
Tafti, Ahmad P; Kirkpatrick, Andrew B; Alavi, Zahrasadat; Owen, Heather A; Yu, Zeyun
2015-11-01
The scanning electron microscope (SEM), as one of the most commonly used instruments in biology and material sciences, employs electrons instead of light to determine the surface properties of specimens. However, the SEM micrographs still remain 2D images. To effectively measure and visualize the surface attributes, we need to restore the 3D shape model from the SEM images. 3D surface reconstruction is a longstanding topic in microscopy vision as it offers quantitative and visual information for a variety of applications consisting medicine, pharmacology, chemistry, and mechanics. In this paper, we attempt to explain the expanding body of the work in this area, including a discussion of recent techniques and algorithms. With the present work, we also enhance the reliability, accuracy, and speed of 3D SEM surface reconstruction by designing and developing an optimized multi-view framework. We then consider several real-world experiments as well as synthetic data to examine the qualitative and quantitative attributes of our proposed framework. Furthermore, we present a taxonomy of 3D SEM surface reconstruction approaches and address several challenging issues as part of our future work. Copyright © 2015 Elsevier Ltd. All rights reserved.
Sparse/Low Rank Constrained Reconstruction for Dynamic PET Imaging.
Directory of Open Access Journals (Sweden)
Xingjian Yu
Full Text Available In dynamic Positron Emission Tomography (PET, an estimate of the radio activity concentration is obtained from a series of frames of sinogram data taken at ranging in duration from 10 seconds to minutes under some criteria. So far, all the well-known reconstruction algorithms require known data statistical properties. It limits the speed of data acquisition, besides, it is unable to afford the separated information about the structure and the variation of shape and rate of metabolism which play a major role in improving the visualization of contrast for some requirement of the diagnosing in application. This paper presents a novel low rank-based activity map reconstruction scheme from emission sinograms of dynamic PET, termed as SLCR representing Sparse/Low Rank Constrained Reconstruction for Dynamic PET Imaging. In this method, the stationary background is formulated as a low rank component while variations between successive frames are abstracted to the sparse. The resulting nuclear norm and l1 norm related minimization problem can also be efficiently solved by many recently developed numerical methods. In this paper, the linearized alternating direction method is applied. The effectiveness of the proposed scheme is illustrated on three data sets.
Track reconstruction in CMS high luminosity environment
AUTHOR|(CDS)2067159
2016-01-01
The CMS tracker is the largest silicon detector ever built, covering 200 square meters and providing an average of 14 high-precision measurements per track. Tracking is essential for the reconstruction of objects like jets, muons, electrons and tau leptons starting from the raw data from the silicon pixel and strip detectors. Track reconstruction is widely used also at trigger level as it improves objects tagging and resolution.The CMS tracking code is organized in several levels, known as iterative steps, each optimized to reconstruct a class of particle trajectories, as the ones of particles originating from the primary vertex or displaced tracks from particles resulting from secondary vertices. Each iterative step consists of seeding, pattern recognition and fitting by a kalman filter, and a final filtering and cleaning. Each subsequent step works on hits not yet associated to a reconstructed particle trajectory.The CMS tracking code is continuously evolving to make the reconstruction computing load compat...
Track reconstruction in CMS high luminosity environment
Goetzmann, Christophe
2014-01-01
The CMS tracker is the largest silicon detector ever built, covering 200 square meters and providing an average of 14 high-precision measurements per track. Tracking is essential for the reconstruction of objects like jets, muons, electrons and tau leptons starting from the raw data from the silicon pixel and strip detectors. Track reconstruction is widely used also at trigger level as it improves objects tagging and resolution.The CMS tracking code is organized in several levels, known as iterative steps, each optimized to reconstruct a class of particle trajectories, as the ones of particles originating from the primary vertex or displaced tracks from particles resulting from secondary vertices. Each iterative step consists of seeding, pattern recognition and fitting by a kalman filter, and a final filtering and cleaning. Each subsequent step works on hits not yet associated to a reconstructed particle trajectory.The CMS tracking code is continuously evolving to make the reconstruction computing load compat...
Reconstruction of convex bodies from surface tensors
DEFF Research Database (Denmark)
Kousholt, Astrid; Kiderlen, Markus
2016-01-01
We present two algorithms for reconstruction of the shape of convex bodies in the two-dimensional Euclidean space. The first reconstruction algorithm requires knowledge of the exact surface tensors of a convex body up to rank s for some natural number s. When only measurements subject to noise...... of surface tensors are available for reconstruction, we recommend to use certain values of the surface tensors, namely harmonic intrinsic volumes instead of the surface tensors evaluated at the standard basis. The second algorithm we present is based on harmonic intrinsic volumes and allows for noisy...... measurements. From a generalized version of Wirtinger's inequality, we derive stability results that are utilized to ensure consistency of both reconstruction procedures. Consistency of the reconstruction procedure based on measurements subject to noise is established under certain assumptions on the noise...
Reconstructing baryon oscillations: A Lagrangian theory perspective
International Nuclear Information System (INIS)
Padmanabhan, Nikhil; White, Martin; Cohn, J. D.
2009-01-01
Recently Eisenstein and collaborators introduced a method to 'reconstruct' the linear power spectrum from a nonlinearly evolved galaxy distribution in order to improve precision in measurements of baryon acoustic oscillations. We reformulate this method within the Lagrangian picture of structure formation, to better understand what such a method does, and what the resulting power spectra are. We show that reconstruction does not reproduce the linear density field, at second order. We however show that it does reduce the damping of the oscillations due to nonlinear structure formation, explaining the improvements seen in simulations. Our results suggest that the reconstructed power spectrum is potentially better modeled as the sum of three different power spectra, each dominating over different wavelength ranges and with different nonlinear damping terms. Finally, we also show that reconstruction reduces the mode-coupling term in the power spectrum, explaining why miscalibrations of the acoustic scale are reduced when one considers the reconstructed power spectrum.
Additive manufacturing technology in reconstructive surgery.
Fuller, Scott C; Moore, Michael G
2016-10-01
Technological advances have been part and parcel of modern reconstructive surgery, in that practitioners of this discipline are continually looking for innovative ways to perfect their craft and improve patient outcomes. We are currently in a technological climate wherein advances in computers, imaging, and science have coalesced with resulting innovative breakthroughs that are not merely limited to improved outcomes and enhanced patient care, but may provide novel approaches to training the next generation of reconstructive surgeons. New developments in software and modeling platforms, imaging modalities, tissue engineering, additive manufacturing, and customization of implants are poised to revolutionize the field of reconstructive surgery. The interface between technological advances and reconstructive surgery continues to expand. Additive manufacturing techniques continue to evolve in an effort to improve patient outcomes, decrease operative time, and serve as instructional tools for the training of reconstructive surgeons.
Innovations in diabetic foot reconstruction using supermicrosurgery.
Suh, Hyun Suk; Oh, Tae Suk; Hong, Joon Pio
2016-01-01
The treatment of diabetic foot ulceration is complex with multiple factors involved, and it may often lead to limb amputation. Hence, a multidisciplinary approach is warranted to cover the spectrum of treatment for diabetic foot, but in complex wounds, surgical treatment is inevitable. Surgery may involve the decision to preserve the limb by reconstruction or to amputate it. Reconstruction involves preserving the limb with secure coverage. Local flaps usually are able to provide sufficient coverage for small or moderate sized wound, but for larger wounds, soft tissue coverage involves flaps that are distantly located from the wound. Reconstruction of distant flap usually involves microsurgery, and now, further innovative methods such as supermicrosurgery have further given complex wounds a better chance to be reconstructed and limbs salvaged. This article reviews the microsurgery involved in reconstruction and introduces the new method of supermicrosurgery. Copyright © 2016 John Wiley & Sons, Ltd.
Sensation Following Immediate Breast Reconstruction with Implants.
Lagergren, Jakob; Wickman, Marie; Hansson, Per
2010-01-01
Sensation is a neglected aspect of the outcome of breast reconstructions with implants. The aim of this prospective study was to evaluate the cutaneous somatosensory status in breasts following mastectomy and immediate reconstruction with permanent adjustable prostheses and to analyze the patients' subjective experience of the sensation. Twenty-four consecutive patients diagnosed with invasive or in situ breast carcinoma were examined preoperatively and 2 years after mastectomy and reconstruction, for assessment of perception thresholds for touch, cold, warmth, and heat pain above and below the areola. Von Frey filaments and a Peltier element-based thermode were used. The patients completed a questionnaire concerning their experienced sensation in the reconstructed breast. Using quantitative somato-sensory testing, the sensation to all the examined modalities was significantly impaired compared to preoperatively. Most affected was the area above the areola. Patients given postoperative radiotherapy (n = 9) did not differ from those without radiotherapy (n = 15) regarding any of the modalities. All patients reported reduced sensation in the reconstructed breast compared to that preoperatively. Twenty-three patients stated that the reconstructed breast felt different from the other breast; nevertheless 16 reported that the reconstructed breast felt like a real breast. The study revealed sensation impairment following mastectomy and immediate reconstruction with implants. Patients should be informed about this effect preoperatively to allow adequate expectations regarding the sensation outcome. However, two-thirds of the study patients considered that the reconstructed breast felt like a real breast, which must be one of the main purposes of a breast reconstruction.
Influence of rebinning on the reconstructed resolution of fan-beam SPECT
International Nuclear Information System (INIS)
Koole, M.; D'Asseler, Y.; Staelens, S.; Vandenberghe, S.; Eede, I. van den; Walle, R. van de; Lemahieu, I.
2002-01-01
Aim: Fan-beam projection data can be rebinned to a parallel-beam geometry. This rebinning operation allows these data to be reconstructed with algorithms for parallel-beam projection data. The advantage of such an operation is that a dedicated projection/backprojection step for fan-beam geometry doesn't need to be developed. In clinical practice bilinear interpolation is often used for this rebinning operation. The aim of this study is to investigate the influence of the rebinning operation on the resolution properties of the reconstructed SPECT-image. Materials and methods: We have simulated the resolution properties of a fan-beam collimator, used in clinical routine, by means of a dedicated projector operation which models the distance dependent sensitivity and resolution of the collimator. With this projector, we generated noise-free sinograms for a point source located at various distances from the center of rotation. The number of angles of these sinograms varied from 60 to 180, corresponding to a step angle of 6 to 2 degrees. These generated fan-beam projection data were reconstructed directly with a filtered backprojection algorithm for fan-beam projection data, which consists of weighting and filtering the projection data with a ramp filter and of a weighted backprojection. Next, the generated fan-beam projection data were rebinned by means of bilinear interpolation and reconstructed with standard filtered backprojection for parallel-beam data. A two-dimensional Gaussian was fitted to the two point sources, one reconstructed with FBP for fan-beam and one reconstructed with FBP for parallel-beam after rebinning, yielding an estimate for the reconstructed Full Width at Half Maximum (FWHM) in the radial and tangential direction, for different locations in the field of view. Results: Results show little difference in resolution degradation in the radial direction between direct reconstruction and reconstruction after rebinning. However, significant loss in
Partial volume correction in SPECT reconstruction with OSEM
Energy Technology Data Exchange (ETDEWEB)
Erlandsson, Kjell, E-mail: k.erlandsson@ucl.ac.uk [Institute of Nuclear Medicine, University College London and University College London Hospital, London NW1 2BU (United Kingdom); Thomas, Ben; Dickson, John; Hutton, Brian F. [Institute of Nuclear Medicine, University College London and University College London Hospital, London NW1 2BU (United Kingdom)
2011-08-21
SPECT images suffer from poor spatial resolution, which leads to partial volume effects due to cross-talk between different anatomical regions. By utilising high-resolution structural images (CT or MRI) it is possible to compensate for these effects. Traditional partial volume correction (PVC) methods suffer from various limitations, such as correcting a single region only, returning only regional mean values, or assuming a stationary point spread function (PSF). We recently presented a novel method in which PVC was combined with the reconstruction process in order to take into account the distance dependent PSF in SPECT, which was based on filtered backprojection (FBP) reconstruction. We now present a new method based on the iterative OSEM algorithm, which has advantageous noise properties compared to FBP. We have applied this method to a series of 10 brain SPECT studies performed on healthy volunteers using the DATSCAN tracer. T1-weighted MRI images were co-registered to the SPECT data and segmented into 33 anatomical regions. The SPECT data were reconstructed using OSEM, and PVC was applied in the projection domain at each iteration. The correction factors were calculated by forward projection of a piece-wise constant image, generated from the segmented MRI. Images were also reconstructed using FBP and standard OSEM with and without resolution recovery (RR) for comparison. The images were evaluated in terms of striatal contrast and regional variability (CoV). The mean striatal contrast obtained with OSEM, OSEM-RR and OSEM-PVC relative to FBP were 1.04, 1.42 and 1.53, respectively, and the mean striatal CoV values are 1.05, 1.53, 1.07. Both OSEM-RR and OSEM-PVC results in images with significantly higher contrast as compared to FBP or OSEM, but OSEM-PVC avoids the increased regional variability of OSEM-RR due to improved structural definition.
Krishnan, Neeraja M; Seligmann, Hervé; Stewart, Caro-Beth; De Koning, A P Jason; Pollock, David D
2004-10-01
flexibility. To determine whether biased reconstructions using optimization methods might affect inferences of functional properties, ancestral primate mitochondrial tRNA sequences were inferred and helix-forming propensities for conserved pairs were evaluated in silico. For ambiguously reconstructed nucleotides at sites with high base composition variability, ancestral tRNA sequences from Bayesian analyses were more compatible with canonical base pairing than were those inferred by other methods. Thus, nucleotide bias in reconstructed sequences apparently can lead to serious bias and inaccuracies in functional predictions.
36 CFR 294.23 - Road construction and reconstruction in Idaho Roadless Areas.
2010-07-01
... 36 Parks, Forests, and Public Property 2 2010-07-01 2010-07-01 false Road construction and..., DEPARTMENT OF AGRICULTURE SPECIAL AREAS Idaho Roadless Area Management § 294.23 Road construction and... Significance, or Primitive. Road construction and reconstruction are prohibited in Idaho Roadless Areas...
Friedman, C D; Costantino, P D; Takagi, S; Chow, L C
1998-01-01
BoneSource-hydroxyapatite cement is a new self-setting calcium phosphate cement biomaterial. Its unique and innovative physical chemistry coupled with enhanced biocompatibility make it useful for craniofacial skeletal reconstruction. The general properties and clinical use guidelines are reviewed. The biomaterial and surgical applications offer insight into improved outcomes and potential new uses for hydroxyapatite cement systems.
Maxillary reconstruction: Current concepts and controversies
Directory of Open Access Journals (Sweden)
Subramania Iyer
2014-01-01
Full Text Available Maxillary reconstruction is still an evolving art when compared to the reconstruction of the mandible. The defects of maxilla apart from affecting the functions of the speech, swallowing and mastication also cause cosmetic disfigurement. Rehabilitation of the form and function in patients with maxillary defects is either by using an obturator prosthesis or by a surgical reconstruction. Literature is abundant with a variety of reconstructive methods. The classification systems are also varied, with no universal acceptance of any one of them. The oncologic safety of these procedures is still debated, and conclusive evidence in this regard has not emerged yet. Management of the orbit is also not yet addressed properly. Tissue engineering, that has been hyped to be one of the possible solutions for this vexing reconstructive problem, has not come out with reliable and reproducible results so far. This review article discusses the rationale and oncological safety of the reconstructing the maxillary defects, critically analyzes the classification systems, offers the different reconstructive methods and touches upon the controversies in this subject. The management of the retained and exenterated orbit associated with maxillectomy is reviewed. The surgical morbidity, complications and the recent advances in this field are also looked into. An algorithm, based on our experience, is presented.
Maxillary reconstruction: Current concepts and controversies
Iyer, Subramania; Thankappan, Krishnakumar
2014-01-01
Maxillary reconstruction is still an evolving art when compared to the reconstruction of the mandible. The defects of maxilla apart from affecting the functions of the speech, swallowing and mastication also cause cosmetic disfigurement. Rehabilitation of the form and function in patients with maxillary defects is either by using an obturator prosthesis or by a surgical reconstruction. Literature is abundant with a variety of reconstructive methods. The classification systems are also varied, with no universal acceptance of any one of them. The oncologic safety of these procedures is still debated, and conclusive evidence in this regard has not emerged yet. Management of the orbit is also not yet addressed properly. Tissue engineering, that has been hyped to be one of the possible solutions for this vexing reconstructive problem, has not come out with reliable and reproducible results so far. This review article discusses the rationale and oncological safety of the reconstructing the maxillary defects, critically analyzes the classification systems, offers the different reconstructive methods and touches upon the controversies in this subject. The management of the retained and exenterated orbit associated with maxillectomy is reviewed. The surgical morbidity, complications and the recent advances in this field are also looked into. An algorithm, based on our experience, is presented. PMID:24987199
Photoacoustic image reconstruction via deep learning
Antholzer, Stephan; Haltmeier, Markus; Nuster, Robert; Schwab, Johannes
2018-02-01
Applying standard algorithms to sparse data problems in photoacoustic tomography (PAT) yields low-quality images containing severe under-sampling artifacts. To some extent, these artifacts can be reduced by iterative image reconstruction algorithms which allow to include prior knowledge such as smoothness, total variation (TV) or sparsity constraints. These algorithms tend to be time consuming as the forward and adjoint problems have to be solved repeatedly. Further, iterative algorithms have additional drawbacks. For example, the reconstruction quality strongly depends on a-priori model assumptions about the objects to be recovered, which are often not strictly satisfied in practical applications. To overcome these issues, in this paper, we develop direct and efficient reconstruction algorithms based on deep learning. As opposed to iterative algorithms, we apply a convolutional neural network, whose parameters are trained before the reconstruction process based on a set of training data. For actual image reconstruction, a single evaluation of the trained network yields the desired result. Our presented numerical results (using two different network architectures) demonstrate that the proposed deep learning approach reconstructs images with a quality comparable to state of the art iterative reconstruction methods.
Updates in Head and Neck Reconstruction.
Largo, Rene D; Garvey, Patrick B
2018-02-01
After reading this article, the participant should be able to: 1. Have a basic understanding of virtual planning, rapid prototype modeling, three-dimensional printing, and computer-assisted design and manufacture. 2. Understand the principles of combining virtual planning and vascular mapping. 3. Understand principles of flap choice and design in preoperative planning of free osteocutaneous flaps in mandible and midface reconstruction. 4. Discuss advantages and disadvantages of computer-assisted design and manufacture in reconstruction of advanced oncologic mandible and midface defects. Virtual planning and rapid prototype modeling are increasingly used in head and neck reconstruction with the aim of achieving superior surgical outcomes in functionally and aesthetically critical areas of the head and neck compared with conventional reconstruction. The reconstructive surgeon must be able to understand this rapidly-advancing technology, along with its advantages and disadvantages. There is no limit to the degree to which patient-specific data may be integrated into the virtual planning process. For example, vascular mapping can be incorporated into virtual planning of mandible or midface reconstruction. Representative mandible and midface cases are presented to illustrate the process of virtual planning. Although virtual planning has become helpful in head and neck reconstruction, its routine use may be limited by logistic challenges, increased acquisition costs, and limited flexibility for intraoperative modifications. Nevertheless, the authors believe that the superior functional and aesthetic results realized with virtual planning outweigh the limitations.
Iterative reconstruction reduces abdominal CT dose
International Nuclear Information System (INIS)
Martinsen, Anne Catrine Trægde; Sæther, Hilde Kjernlie; Hol, Per Kristian; Olsen, Dag Rune; Skaane, Per
2012-01-01
Objective: In medical imaging, lowering radiation dose from computed tomography scanning, without reducing diagnostic performance is a desired achievement. Iterative image reconstruction may be one tool to achieve dose reduction. This study reports the diagnostic performance using a blending of 50% statistical iterative reconstruction (ASIR) and filtered back projection reconstruction (FBP) compared to standard FBP image reconstruction at different dose levels for liver phantom examinations. Methods: An anthropomorphic liver phantom was scanned at 250, 185, 155, 140, 120 and 100 mA s, on a 64-slice GE Lightspeed VCT scanner. All scans were reconstructed with ASIR and FBP. Four readers evaluated independently on a 5-point scale 21 images, each containing 32 test sectors. In total 672 areas were assessed. ROC analysis was used to evaluate the differences. Results: There was a difference in AUC between the 250 mA s FBP images and the 120 and 100 mA s FBP images. ASIR reconstruction gave a significantly higher diagnostic performance compared to standard reconstruction at 100 mA s. Conclusion: A blending of 50–90% ASIR and FBP may improve image quality of low dose CT examinations of the liver, and thus give a potential for reducing radiation dose.
EIT image reconstruction with four dimensional regularization.
Dai, Tao; Soleimani, Manuchehr; Adler, Andy
2008-09-01
Electrical impedance tomography (EIT) reconstructs internal impedance images of the body from electrical measurements on body surface. The temporal resolution of EIT data can be very high, although the spatial resolution of the images is relatively low. Most EIT reconstruction algorithms calculate images from data frames independently, although data are actually highly correlated especially in high speed EIT systems. This paper proposes a 4-D EIT image reconstruction for functional EIT. The new approach is developed to directly use prior models of the temporal correlations among images and 3-D spatial correlations among image elements. A fast algorithm is also developed to reconstruct the regularized images. Image reconstruction is posed in terms of an augmented image and measurement vector which are concatenated from a specific number of previous and future frames. The reconstruction is then based on an augmented regularization matrix which reflects the a priori constraints on temporal and 3-D spatial correlations of image elements. A temporal factor reflecting the relative strength of the image correlation is objectively calculated from measurement data. Results show that image reconstruction models which account for inter-element correlations, in both space and time, show improved resolution and noise performance, in comparison to simpler image models.
[Reconstructive surgery of cranio-orbital injuries].
Eolchiian, S A; Potapov, A A; Serova, N K; Kataev, M G; Sergeeva, L A; Zakharova, N E; Van Damm, P
2011-01-01
The aim of study was to optimize evaluation and surgery of cranioorbital injuries in different periods after trauma. Material and methods. We analyzed 374 patients with cranioorbital injuries treated in Burdenko Neurosurgery Institute in different periods after trauma from January 1998 till April 2010. 288 (77%) underwent skull and facial skeleton reconstructive surgery within 24 hours - 7 years after trauma. Clinical and CT examination data were used for preoperative planning and assessment of surgery results. Stereolithographic models (STLM) were applied for preoperative planning in 89 cases. The follow-up period ranged from 4 months up to 10 years. Results. In 254 (88%) of 288 patients reconstruction of anterior skull base, upper and/or midface with restoration of different parts of orbit was performed. Anterior skull base CSF leaks repair, calvarial vault reconstruction, maxillar and mandibular osteosynthesis were done in 34 (12%) cases. 242 (84%) of 288 patients underwent one reconstructive operation, while 46 (16%)--two and more (totally 105 operations). The patients with extended frontoorbital and midface fractures commonly needed more than one operation--in 27 (62.8%) cases. Different plastic materials were used for reconstruction in 233 (80.9%) patients, of those in 147 (51%) cases split calvarial bone grafts were preferred. Good functional and cosmetic results were achieved in 261 (90.6%) of 288 patients while acceptable were observed in 27 (9.4%). Conclusion. Active single-stage surgical management for repair of combined cranioorbital injury in acute period with primary reconstruction optimizes functional and cosmetic outcomes and prevents the problems of delayed or secondary reconstruction. Severe extended anterior skull base, upper and midface injuries when intracranial surgery is needed produced the most challenging difficulties for adequate reconstruction. Randomized trial is required to define the extent and optimal timing of reconstructive surgery
Additive manufacturing in maxillofacial reconstruction
Directory of Open Access Journals (Sweden)
Dincă Luciana Laura
2017-01-01
Full Text Available In this paper the benefits of using additive manufacturing technologies in maxillofacial reconstruction are highlighted. Based on a real clinical case, the paper describes the manufacture of an implant prototype replacing the right zygomatic bone and a part of maxilla using additive manufacturing technologies. The face is the most expressive part of the human body that makes us unique. It was shown that the maxillofacial prostheses help to improve the psychological state of patients affected by, because low self esteem feeling appears commonly to this patients with the facial defects. The aim of this paper is to show how using additive manufacturing technologies methods within this research, the producing a surgical model will help surgeon to improve the pre-operative planning. For this we used additive manufacturing technologies such as Stereolitography to achieve the biomodel and FDM-fused deposition modelling to obtain a prototype model because these technologies make it possible to obtain prosthesis according to the physical and mechanical requirements of the region of implantation.
High-Performance Phylogeny Reconstruction
Energy Technology Data Exchange (ETDEWEB)
Tiffani L. Williams
2004-11-10
Under the Alfred P. Sloan Fellowship in Computational Biology, I have been afforded the opportunity to study phylogenetics--one of the most important and exciting disciplines in computational biology. A phylogeny depicts an evolutionary relationship among a set of organisms (or taxa). Typically, a phylogeny is represented by a binary tree, where modern organisms are placed at the leaves and ancestral organisms occupy internal nodes, with the edges of the tree denoting evolutionary relationships. The task of phylogenetics is to infer this tree from observations upon present-day organisms. Reconstructing phylogenies is a major component of modern research programs in many areas of biology and medicine, but it is enormously expensive. The most commonly used techniques attempt to solve NP-hard problems such as maximum likelihood and maximum parsimony, typically by bounded searches through an exponentially-sized tree-space. For example, there are over 13 billion possible trees for 13 organisms. Phylogenetic heuristics that quickly analyze large amounts of data accurately will revolutionize the biological field. This final report highlights my activities in phylogenetics during the two-year postdoctoral period at the University of New Mexico under Prof. Bernard Moret. Specifically, this report reports my scientific, community and professional activities as an Alfred P. Sloan Postdoctoral Fellow in Computational Biology.
Optimization of PET image quality by means of 3D data acquisition and iterative image reconstruction
International Nuclear Information System (INIS)
Doll, J.; Zaers, J.; Trojan, H.; Bellemann, M.E.; Adam, L.E.; Haberkorn, U.; Brix, G.
1998-01-01
The experiments were performed at the latest-generation whole-body PET system ECAT EXACT HR + . For 2D data acquisition, a collimator of thin tungsten septa was positioned in the field-of-view. Prior to image reconstruction, the measured 3D data were sorted into 2D sinograms by using the Fourier rebinning (FORE) algorithm developed by M. Defrise. The standard filtered backprojection (FBP) method and an optimized ML/EM algorithm with overrelaxation for accelerated convergence were employed for image reconstruction. The spatial resolution of both methods as well as the convergence and noise properties of the ML/EM algorithm were studied in phantom measurements. Furthermore, patient data were acquired in the 2D mode as well as in the 3D mode and reconstructed with both techniques. At the same spatial resolution, the ML/EM-reconstructed images showed fewer and less prominent artefacts than the FBP-reconstructed images. The resulting improved detail conspicuously was achieved for the data acquired in the 2D mode as well as in the 3D mode. The best image quality was obtained by iterative 2D reconstruction of 3D data sets which were previously rebinned into 2D sinograms with help of the FORE algorithm. The phantom measurements revealed that 50 iteration steps with the otpimized ML/EM algorithm were sufficient to keep the relative quantitation error below 5%. (orig./MG) [de
RECONSTRUCTING WOMANHOOD IN TONY MORRISON'S BELOVED
Directory of Open Access Journals (Sweden)
Setefanus Suprajitno
2000-01-01
Full Text Available Tony Morrison's fifth novel, Beloved (1987, explores the degradation of slavery imposed upon slaves, even when they were owned by a "humane" slave master. The novel is set in the Reconstruction period, the period after the American civil war. The word reconstruction may be used for the Afro-Americans, especially for the Afro-American women who face double discrimination for being black and women. In dealing with women's oppression, Afro-American women have to reconstruct themselves as an act of survival, and to be aware of the horrors of the experiences which their ancestors had to go through.
High-speed reconstruction of compressed images
Cox, Jerome R., Jr.; Moore, Stephen M.
1990-07-01
A compression scheme is described that allows high-definition radiological images with greater than 8-bit intensity resolution to be represented by 8-bit pixels. Reconstruction of the images with their original intensity resolution can be carried out by means of a pipeline architecture suitable for compact, high-speed implementation. A reconstruction system is described that can be fabricated according to this approach and placed between an 8-bit display buffer and the display's video system thereby allowing contrast control of images at video rates. Results for 50 CR chest images are described showing that error-free reconstruction of the original 10-bit CR images can be achieved.
Vertex Reconstruction for AEGIS’ FACT Detector
Themistokleous, Neofytos
2017-01-01
My project dealt with the development of a vertex reconstruction technique to discriminate antihydrogen from background signals in the AEGIS apparatus. It involved the creation of a Toy Monte-Carlo to simulate particle annihilation events, and a vertex reconstruction utility based on the Bayesian theory of probability. The ﬁrst results based on 107 generated events with single track in the detector are encouraging. For such events, the algorithm can reconstruct the z-coordinate accurately , while for the r-coordinate the result is less accurate.
An iterative reconstruction from truncated projection data
International Nuclear Information System (INIS)
Anon.
1985-01-01
Various methods have been proposed for tomographic reconstruction from truncated projection data. In this paper, a reconstructive method is discussed which consists of iterations of filtered back-projection, reprojection and some nonlinear processings. First, the method is so constructed that it converges to a fixed point. Then, to examine its effectiveness, comparisons are made by computer experiments with two existing reconstructive methods for truncated projection data, that is, the method of extrapolation based on the smooth assumption followed by filtered back-projection, and modified additive ART
Arthroscopic-Assisted Triangular Fibrocartilage Complex Reconstruction.
Chu-Kay Mak, Michael; Ho, Pak-Cheong
2017-11-01
Injury of the triangular fibrocartilage complex (TFCC) is a common cause of ulnar-sided wrist pain. Volar and dorsal radioulnar ligaments and their foveal insertion are the most important stabilizing components of the TFCC. In irreparable tears, anatomic reconstruction of the TFCC aims to restore normal biomechanics and stability of the distal radioulnar joint. We proposed a novel arthroscopic-assisted technique using a palmaris longus tendon graft. Arthroscopic-assisted TFCC reconstruction is a safe and effective approach with outcomes comparable to conventional open reconstruction and may result in a better range of motion from minimizing soft tissue dissection and subsequent scarring. Copyright © 2017 Elsevier Inc. All rights reserved.
International Nuclear Information System (INIS)
Jeon, Min-Gyu; Deguchi, Yoshihiro; Kamimoto, Takahiro; Doh, Deog-Hee; Cho, Gyeong-Rae
2017-01-01
Highlights: • The measured data were successfully used for generating absorption spectra. • Four different reconstruction algorithms, ART, MART, SART and SMART were evaluated. • The calculation speed of convergence by the SMART algorithm was the fastest. • SMART was the most reliable algorithm for reconstructing the multiple signals. - Abstract: Recent advent of the tunable lasers made to measure simultaneous temperature and concentration fields of the gases. CT-TDLAS (computed tomography-tunable diode laser absorption spectroscopy) is one the leading techniques for the measurements of temperature and concentration fields of the gases. In CT-TDLAS, the accuracies of the measurement results are strongly dependent upon the reconstruction algorithms. In this study, four different reconstruction algorithms have been tested numerically using experimental data sets measured by thermocouples for combustion fields. Three reconstruction algorithms, MART (multiplicative algebraic reconstruction technique) algorithm, SART (simultaneous algebraic reconstruction technique) algorithm and SMART (simultaneous multiplicative algebraic reconstruction technique) algorithm, are newly proposed for CT-TDLAS in this study. The calculation results obtained by the three algorithms have been compared with previous algorithm, ART (algebraic reconstruction technique) algorithm. Phantom data sets have been generated by the use of thermocouples data obtained in an actual experiment. The data of the Harvard HITRAN table in which the thermo-dynamical properties and the light spectrum of the H_2O are listed were used for the numerical test. The reconstructed temperature and concentration fields were compared with the original HITRAN data, through which the constructed methods are validated. The performances of the four reconstruction algorithms were demonstrated. This method is expected to enhance the practicality of CT-TDLAS.
Theoretical evaluation of the detectability of random lesions in bayesian emission reconstruction
International Nuclear Information System (INIS)
Qi, Jinyi
2003-01-01
Detecting cancerous lesion is an important task in positron emission tomography (PET). Bayesian methods based on the maximum a posteriori principle (also called penalized maximum likelihood methods) have been developed to deal with the low signal to noise ratio in the emission data. Similar to the filter cut-off frequency in the filtered backprojection method, the prior parameters in Bayesian reconstruction control the resolution and noise trade-off and hence affect detectability of lesions in reconstructed images. Bayesian reconstructions are difficult to analyze because the resolution and noise properties are nonlinear and object-dependent. Most research has been based on Monte Carlo simulations, which are very time consuming. Building on the recent progress on the theoretical analysis of image properties of statistical reconstructions and the development of numerical observers, here we develop a theoretical approach for fast computation of lesion detectability in Bayesian reconstruction. The results can be used to choose the optimum hyperparameter for the maximum lesion detectability. New in this work is the use of theoretical expressions that explicitly model the statistical variation of the lesion and background without assuming that the object variation is (locally) stationary. The theoretical results are validated using Monte Carlo simulations. The comparisons show good agreement between the theoretical predications and the Monte Carlo results
Hosseinbor, A. Pasha; Chung, Moo K.; Wu, Yu-Chien; Alexander, Andrew L.
2012-01-01
The ensemble average propagator (EAP) describes the 3D average diffusion process of water molecules, capturing both its radial and angular contents. The EAP can thus provide richer information about complex tissue microstructure properties than the orientation distribution function (ODF), an angular feature of the EAP. Recently, several analytical EAP reconstruction schemes for multiple q-shell acquisitions have been proposed, such as diffusion propagator imaging (DPI) and spherical polar Fourier imaging (SPFI). In this study, a new analytical EAP reconstruction method is proposed, called Bessel Fourier orientation reconstruction (BFOR), whose solution is based on heat equation estimation of the diffusion signal for each shell acquisition, and is validated on both synthetic and real datasets. A significant portion of the paper is dedicated to comparing BFOR, SPFI, and DPI using hybrid, non-Cartesian sampling for multiple b-value acquisitions. Ways to mitigate the effects of Gibbs ringing on EAP reconstruction are also explored. In addition to analytical EAP reconstruction, the aforementioned modeling bases can be used to obtain rotationally invariant q-space indices of potential clinical value, an avenue which has not yet been thoroughly explored. Three such measures are computed: zero-displacement probability (Po), mean squared displacement (MSD), and generalized fractional anisotropy (GFA). PMID:22963853
Breast reconstruction following mastectomy: current status in Australia.
Sandelin, Kerstin; King, Elizabeth; Redman, Sally
2003-09-01
Although breast reconstruction provides some advantages for women following mastectomy, few Australian breast cancer patients currently receive reconstruction. In Australia, the routine provision of breast reconstruction will require the development of specific health service delivery models. The present paper reports an analysis of the provision of breast reconstruction in eight sites in Australia. A semi-structured telephone interview was conducted with 10 surgeons offering breast reconstruction as part of their practice, including nine breast or general surgeons and one plastic surgeon. Surgeons reported offering breast reconstruction to all women facing mastectomy; the proportion of women deciding to have breast reconstruction varied between sites with up to 50% of women having a reconstruction at some sites. Most sites offered three types of reconstruction. Two pathways emerged: either the breast surgeon performed the breast surgery in a team with the plastic surgeon who undertook the breast reconstruction or the breast surgeon provided both the breast surgery and the reconstruction. Considerable waiting times for breast reconstruction were reported in the public sector particularly for delayed reconstruction. Surgeons reported receiving training in breast reconstruction from plastic surgeons or from a breast surgery team that performed reconstructions; a number had been trained overseas. No audits of breast reconstruction were being undertaken. Breast reconstruction can be offered on a routine basis in Australia in both the private and public sectors. Women may be more readily able to access breast reconstruction when it is provided by a breast surgeon alone, but the range of reconstruction options may be more limited. If access to breast reconstruction is to be increased, there will be a need to: (i) develop effective models for the rural sector taking account of the lack of plastic surgeons; (ii) address waiting times for reconstruction surgery in the
Markov Random Field Surface Reconstruction
DEFF Research Database (Denmark)
Paulsen, Rasmus Reinhold; Bærentzen, Jakob Andreas; Larsen, Rasmus
2010-01-01
) and knowledge about data (the observation model) in an orthogonal fashion. Local models that account for both scene-specific knowledge and physical properties of the scanning device are described. Furthermore, how the optimal distance field can be computed is demonstrated using conjugate gradients, sparse...
Statistical Reconstruction of Gas Oil Cuts Reconstruction statistique de coupes gazoles
Directory of Open Access Journals (Sweden)
Hudebine D.
2009-11-01
Full Text Available Gas oil cuts are extremely complex mixtures of several thousands of different chemical species. Consequently, conventional petroleum analyses do not allow to obtain the molecular detail that is required for the development of robust and predictive kinetic models. Recently, two-dimensional Gas Chromatographic techniques (GC2D have greatly improved the knowledge in the field of characterization of gas oils. However, they remain R&D tools and are hardly utilized in the refining industry. Hence, the goal of the statistical reconstruction of gas oils is to provide a surrogate for this GC2D analysis. To this aim, the gas oil cuts are characterized by means of matrices of molar fractions of pseudo-compounds, which are classified by chemical family and by carbon atom number. The input analyses are the Fitzgerald mass spectrometry, the sulfur speciation (one-dimensional gas chromatography coupled to a specific sulfur chemiluminescence detector and the total nitrogen and basic nitrogen contents, and allow to quantify the proportions of all the chemical families present in the matrix. The simulated distillation is also used in order to introduce information on the volatility of the gas oil cut. The reconstruction method proposed in this paper is mainly based on a reference statistical distribution of the number of carbon atoms for the side chains connected to the naphtheno-aromatic cores. For each chemical family, the knowledge of the number of potential side chains and the estimation of the maximum length of these alkyl chains allow to determine the carbon number distribution by adjusting of the reference distribution. After reconstruction, the properties of the resulting molar fractions matrix are very close to the analyses used for the reconstruction. Moreover, the method allows to predict, with a high precision, complementary analyses such as the hydrogen content, the aromatic carbon content and the density at 15 ˚C. Finally, the matrix can be
Michalski, Andrew S; Edwards, W Brent; Boyd, Steven K
2017-10-17
Quantitative computed tomography has been posed as an alternative imaging modality to investigate osteoporosis. We examined the influence of computed tomography convolution back-projection reconstruction kernels on the analysis of bone quantity and estimated mechanical properties in the proximal femur. Eighteen computed tomography scans of the proximal femur were reconstructed using both a standard smoothing reconstruction kernel and a bone-sharpening reconstruction kernel. Following phantom-based density calibration, we calculated typical bone quantity outcomes of integral volumetric bone mineral density, bone volume, and bone mineral content. Additionally, we performed finite element analysis in a standard sideways fall on the hip loading configuration. Significant differences for all outcome measures, except integral bone volume, were observed between the 2 reconstruction kernels. Volumetric bone mineral density measured using images reconstructed by the standard kernel was significantly lower (6.7%, p kernel. Furthermore, the whole-bone stiffness and the failure load measured in images reconstructed by the standard kernel were significantly lower (16.5%, p kernel. These data suggest that for future quantitative computed tomography studies, a standardized reconstruction kernel will maximize reproducibility, independent of the use of a quantitative calibration phantom. Copyright © 2017 The International Society for Clinical Densitometry. Published by Elsevier Inc. All rights reserved.
Reconstruction of a Broadband Spectrum of Alfvenic Fluctuations
Vinas, Adolfo F.; Fuentes, Pablo S. M.; Araneda, Jaime A.; Maneva, Yana G.
2014-01-01
Alfvenic fluctuations in the solar wind exhibit a high degree of velocities and magnetic field correlations consistent with Alfven waves propagating away and toward the Sun. Two remarkable properties of these fluctuations are the tendencies to have either positive or negative magnetic helicity (-1 less than or equal to sigma(sub m) less than or equal to +1) associated with either left- or right- topological handedness of the fluctuations and to have a constant magnetic field magnitude. This paper provides, for the first time, a theoretical framework for reconstructing both the magnetic and velocity field fluctuations with a divergence-free magnetic field, with any specified power spectral index and normalized magnetic- and cross-helicity spectrum field fluctuations for any plasma species. The spectrum is constructed in the Fourier domain by imposing two conditions-a divergence-free magnetic field and the preservation of the sense of magnetic helicity in both spaces-as well as using Parseval's theorem for the conservation of energy between configuration and Fourier spaces. Applications to the one-dimensional spatial Alfvenic propagation are presented. The theoretical construction is in agreement with typical time series and power spectra properties observed in the solar wind. The theoretical ideas presented in this spectral reconstruction provide a foundation for more realistic simulations of plasma waves, solar wind turbulence, and the propagation of energetic particles in such fluctuating fields.
Least Square NUFFT Methods Applied to 2D and 3D Radially Encoded MR Image Reconstruction
Song, Jiayu; Liu, Qing H.; Gewalt, Sally L.; Cofer, Gary; Johnson, G. Allan
2009-01-01
Radially encoded MR imaging (MRI) has gained increasing attention in applications such as hyperpolarized gas imaging, contrast-enhanced MR angiography, and dynamic imaging, due to its motion insensitivity and improved artifact properties. However, since the technique collects k-space samples nonuniformly, multidimensional (especially 3D) radially sampled MRI image reconstruction is challenging. The balance between reconstruction accuracy and speed becomes critical when a large data set is processed. Kaiser-Bessel gridding reconstruction has been widely used for non-Cartesian reconstruction. The objective of this work is to provide an alternative reconstruction option in high dimensions with on-the-fly kernels calculation. The work develops general multi-dimensional least square nonuniform fast Fourier transform (LS-NUFFT) algorithms and incorporates them into a k-space simulation and image reconstruction framework. The method is then applied to reconstruct the radially encoded k-space, although the method addresses general nonuniformity and is applicable to any non-Cartesian patterns. Performance assessments are made by comparing the LS-NUFFT based method with the conventional Kaiser-Bessel gridding method for 2D and 3D radially encoded computer simulated phantoms and physically scanned phantoms. The results show that the LS-NUFFT reconstruction method has better accuracy-speed efficiency than the Kaiser-Bessel gridding method when the kernel weights are calculated on the fly. The accuracy of the LS-NUFFT method depends on the choice of scaling factor, and it is found that for a particular conventional kernel function, using its corresponding deapodization function as scaling factor and utilizing it into the LS-NUFFT framework has the potential to improve accuracy. When a cosine scaling factor is used, in particular, the LS-NUFFT method is faster than Kaiser-Bessel gridding method because of a quasi closed-form solution. The method is successfully applied to 2D and
From 2D PET to 3D PET. Issues of data representation and image reconstruction
International Nuclear Information System (INIS)
Gundlich, B.; Musmann, P.; Weber, S.; Nix, O.; Semmler, W.
2006-01-01
Positron emission tomography (PET), intrinsically a 3D imaging technique, was for a long time exclusively operated in 2D mode, using septa to shield the detectors from photons emitted obliquely to the detector planes. However, the use of septa results in a considerable loss of sensitivity. From the late 1980s, significant efforts have been made to develop a methodology for the acquisition and reconstruction of 3D PET data. This paper focuses on the differences between data acquisition in 2D and 3D mode, especially in terms of data set sizes and representation. Although the real time data acquisition aspect in 3D has been mostly solved in modern PET scanner systems, there still remain questions on how to represent and how to make best use of the information contained in the acquired data sets. Data representation methods, such as list-mode and matrix-based methods, possibly with additional compression, will be discussed. Moving from 2D to 3D PET has major implications on the way these data are reconstructed to images. Two fundamentally different approaches exist, the analytical one and the iterative one. Both, at different expenses, can be extended to directly handle 3D data sets. Either way the computational burden increases heavily compared to 2D reconstruction. One possibility to benefit from the increased sensitivity in 3D PET while sticking to high-performance 2D reconstruction algorithms is to rebin 3D into 2D data sets. The value of data rebinning will be explored. An ever increasing computing power and the concept of distributed or parallel computing have made direct 3D reconstruction feasible. Following a short review of reconstruction methods and their extensions to 3D, we focus on numerical aspects that improve reconstruction performance, which is especially important in solving large equation systems in 3D iterative reconstruction. Finally exemplary results are shown to review the properties of the discussed algorithms. (orig.)
Wang, J.; Emile-Geay, J.; Guillot, D.; Smerdon, J. E.; Rajaratnam, B.
2014-01-01
Pseudoproxy experiments (PPEs) have become an important framework for evaluating paleoclimate reconstruction methods. Most existing PPE studies assume constant proxy availability through time and uniform proxy quality across the pseudoproxy network. Real multiproxy networks are, however, marked by pronounced disparities in proxy quality, and a steep decline in proxy availability back in time, either of which may have large effects on reconstruction skill. A suite of PPEs constructed from a millennium-length general circulation model (GCM) simulation is thus designed to mimic these various real-world characteristics. The new pseudoproxy network is used to evaluate four climate field reconstruction (CFR) techniques: truncated total least squares embedded within the regularized EM (expectation-maximization) algorithm (RegEM-TTLS), the Mann et al. (2009) implementation of RegEM-TTLS (M09), canonical correlation analysis (CCA), and Gaussian graphical models embedded within RegEM (GraphEM). Each method's risk properties are also assessed via a 100-member noise ensemble. Contrary to expectation, it is found that reconstruction skill does not vary monotonically with proxy availability, but also is a function of the type and amplitude of climate variability (forced events vs. internal variability). The use of realistic spatiotemporal pseudoproxy characteristics also exposes large inter-method differences. Despite the comparable fidelity in reconstructing the global mean temperature, spatial skill varies considerably between CFR techniques. Both GraphEM and CCA efficiently exploit teleconnections, and produce consistent reconstructions across the ensemble. RegEM-TTLS and M09 appear advantageous for reconstructions on highly noisy data, but are subject to larger stochastic variations across different realizations of pseudoproxy noise. Results collectively highlight the importance of designing realistic pseudoproxy networks and implementing multiple noise realizations of PPEs
Reconstruction of convex bodies from surface tensors
DEFF Research Database (Denmark)
Kousholt, Astrid; Kiderlen, Markus
. The output of the reconstruction algorithm is a polytope P, where the surface tensors of P and K are identical up to rank s. We establish a stability result based on a generalization of Wirtinger’s inequality that shows that for large s, two convex bodies are close in shape when they have identical surface...... that are translates of each other. An algorithm for reconstructing an unknown convex body in R 2 from its surface tensors up to a certain rank is presented. Using the reconstruction algorithm, the shape of an unknown convex body can be approximated when only a finite number s of surface tensors are available...... tensors up to rank s. This is used to establish consistency of the developed reconstruction algorithm....
Structure-based bayesian sparse reconstruction
Quadeer, Ahmed Abdul; Al-Naffouri, Tareq Y.
2012-01-01
Sparse signal reconstruction algorithms have attracted research attention due to their wide applications in various fields. In this paper, we present a simple Bayesian approach that utilizes the sparsity constraint and a priori statistical
Social consciousness in post-conflict reconstruction.
Gans, Ben; Rutkowski, Anne; Kaminski, B.; Kersten, G.E.; Szapiro, T.
This paper sheds light on the complexities intergovernmental organizations are facing during post-conflict reconstruction. The article discusses the added-value of Social Responsibility in the context of the Comprehensive Approach, involving collaboration amongst defense, diplomacy and development.
Tissue Engineering in Vesical Reconstruction | Morsi | African ...
African Journals Online (AJOL)
TE) and describes the possible future clinical application in bladder reconstruction. Material and Methods: This review is based on an electronic search of the PubMed database and recently published presentations between November 2008 and ...
Simulation and reconstruction of the BESIII EMC
International Nuclear Information System (INIS)
He Miao
2011-01-01
The simulation and reconstruction software of the BES III Electromagnetic Calorimeter (EMC), are developed based on the object-oriented language C++, in the framework of Gaudi. Performance of EMC are studied with data and compared with Monte Carlo samples.
Maximum Likelihood Reconstruction for Magnetic Resonance Fingerprinting.
Zhao, Bo; Setsompop, Kawin; Ye, Huihui; Cauley, Stephen F; Wald, Lawrence L
2016-08-01
This paper introduces a statistical estimation framework for magnetic resonance (MR) fingerprinting, a recently proposed quantitative imaging paradigm. Within this framework, we present a maximum likelihood (ML) formalism to estimate multiple MR tissue parameter maps directly from highly undersampled, noisy k-space data. A novel algorithm, based on variable splitting, the alternating direction method of multipliers, and the variable projection method, is developed to solve the resulting optimization problem. Representative results from both simulations and in vivo experiments demonstrate that the proposed approach yields significantly improved accuracy in parameter estimation, compared to the conventional MR fingerprinting reconstruction. Moreover, the proposed framework provides new theoretical insights into the conventional approach. We show analytically that the conventional approach is an approximation to the ML reconstruction; more precisely, it is exactly equivalent to the first iteration of the proposed algorithm for the ML reconstruction, provided that a gridding reconstruction is used as an initialization.
Advances in Bioprinting Technologies for Craniofacial Reconstruction.
Visscher, Dafydd O; Farré-Guasch, Elisabet; Helder, Marco N; Gibbs, Susan; Forouzanfar, Tymour; van Zuijlen, Paul P; Wolff, Jan
2016-09-01
Recent developments in craniofacial reconstruction have shown important advances in both the materials and methods used. While autogenous tissue is still considered to be the gold standard for these reconstructions, the harvesting procedure remains tedious and in many cases causes significant donor site morbidity. These limitations have subsequently led to the development of less invasive techniques such as 3D bioprinting that could offer possibilities to manufacture patient-tailored bioactive tissue constructs for craniofacial reconstruction. Here, we discuss the current technological and (pre)clinical advances of 3D bioprinting for use in craniofacial reconstruction and highlight the challenges that need to be addressed in the coming years. Copyright © 2016 Elsevier Ltd. All rights reserved.
Template Assembly for Detailed Urban Reconstruction
Nan, Liangliang; Wonka, Peter; Ghanem, Bernard; Jiang, Caigui
2015-01-01
Structure from Motion and Multi View Stereo, and we model a set of 3D templates of facade details. Next, we optimize the initial coarse model to enforce consistency between geometry and appearance (texture images). Then, building details are reconstructed
Medical image reconstruction. A conceptual tutorial
International Nuclear Information System (INIS)
Zeng, Gengsheng Lawrence
2010-01-01
''Medical Image Reconstruction: A Conceptual Tutorial'' introduces the classical and modern image reconstruction technologies, such as two-dimensional (2D) parallel-beam and fan-beam imaging, three-dimensional (3D) parallel ray, parallel plane, and cone-beam imaging. This book presents both analytical and iterative methods of these technologies and their applications in X-ray CT (computed tomography), SPECT (single photon emission computed tomography), PET (positron emission tomography), and MRI (magnetic resonance imaging). Contemporary research results in exact region-of-interest (ROI) reconstruction with truncated projections, Katsevich's cone-beam filtered backprojection algorithm, and reconstruction with highly undersampled data with l 0 -minimization are also included. (orig.)
Extended Reconstructed Sea Surface Temperature (ERSST)
National Oceanic and Atmospheric Administration, Department of Commerce — The Extended Reconstructed Sea Surface Temperature (ERSST) dataset is a global monthly sea surface temperature analysis derived from the International Comprehensive...
Speeding up image reconstruction in computed tomography
CERN. Geneva
2018-01-01
Computed tomography (CT) is a technique for imaging cross-sections of an object using X-ray measurements taken from different angles. In last decades a significant progress has happened there: today advanced algorithms allow fast image reconstruction and obtaining high-quality images even with missing or dirty data, modern detectors provide high resolution without increasing radiation dose, and high-performance multi-core computing devices are there to help us solving such tasks even faster. I will start with CT basics, then briefly present existing classes of reconstruction algorithms and their differences. After that I will proceed to employing distinctive architectural features of modern multi-core devices (CPUs and GPUs) and popular program interfaces (OpenMP, MPI, CUDA, OpenCL) for developing effective parallel realizations of image reconstruction algorithms. Decreasing full reconstruction time from long hours up to minutes or even seconds has a revolutionary impact in diagnostic medicine and industria...
Model-centric software architecture reconstruction
Stoermer, C.; Rowe, A.; O'Brien, L.; Verhoef, C.
2006-01-01
Much progress has been achieved in defining methods, techniques, and tools for software architecture reconstruction (SAR). However, less progress has been achieved in constructing reasoning frameworks from existing systems that support organizations in architecture analysis and design decisions.
Parallel CT image reconstruction based on GPUs
International Nuclear Information System (INIS)
Flores, Liubov A.; Vidal, Vicent; Mayo, Patricia; Rodenas, Francisco; Verdú, Gumersindo
2014-01-01
In X-ray computed tomography (CT) iterative methods are more suitable for the reconstruction of images with high contrast and precision in noisy conditions from a small number of projections. However, in practice, these methods are not widely used due to the high computational cost of their implementation. Nowadays technology provides the possibility to reduce effectively this drawback. It is the goal of this work to develop a fast GPU-based algorithm to reconstruct high quality images from under sampled and noisy projection data. - Highlights: • We developed GPU-based iterative algorithm to reconstruct images. • Iterative algorithms are capable to reconstruct images from under sampled set of projections. • The computer cost of the implementation of the developed algorithm is low. • The efficiency of the algorithm increases for the large scale problems
Language distance and tree reconstruction
International Nuclear Information System (INIS)
Petroni, Filippo; Serva, Maurizio
2008-01-01
Languages evolve over time according to a process in which reproduction, mutation and extinction are all possible. This is very similar to haploid evolution for asexual organisms and for the mitochondrial DNA of complex ones. Exploiting this similarity, it is possible, in principle, to verify hypotheses concerning the relationship among languages and to reconstruct their family tree. The key point is the definition of the distances among pairs of languages in analogy with the genetic distances among pairs of organisms. Distances can be evaluated by comparing grammar and/or vocabulary, but while it is difficult, if not impossible, to quantify grammar distance, it is possible to measure a distance from vocabulary differences. The method used by glottochronology computes distances from the percentage of shared 'cognates', which are words with a common historical origin. The weak point of this method is that subjective judgment plays a significant role. Here we define the distance of two languages by considering a renormalized edit distance among words with the same meaning and averaging over the two hundred words contained in a Swadesh list. In our approach the vocabulary of a language is the analogue of DNA for organisms. The advantage is that we avoid subjectivity and, furthermore, reproducibility of results is guaranteed. We apply our method to the Indo-European and the Austronesian groups, considering, in both cases, fifty different languages. The two trees obtained are, in many respects, similar to those found by glottochronologists, with some important differences as regards the positions of a few languages. In order to support these different results we separately analyze the structure of the distances of these languages with respect to all the others
Language distance and tree reconstruction
Petroni, Filippo; Serva, Maurizio
2008-08-01
Languages evolve over time according to a process in which reproduction, mutation and extinction are all possible. This is very similar to haploid evolution for asexual organisms and for the mitochondrial DNA of complex ones. Exploiting this similarity, it is possible, in principle, to verify hypotheses concerning the relationship among languages and to reconstruct their family tree. The key point is the definition of the distances among pairs of languages in analogy with the genetic distances among pairs of organisms. Distances can be evaluated by comparing grammar and/or vocabulary, but while it is difficult, if not impossible, to quantify grammar distance, it is possible to measure a distance from vocabulary differences. The method used by glottochronology computes distances from the percentage of shared 'cognates', which are words with a common historical origin. The weak point of this method is that subjective judgment plays a significant role. Here we define the distance of two languages by considering a renormalized edit distance among words with the same meaning and averaging over the two hundred words contained in a Swadesh list. In our approach the vocabulary of a language is the analogue of DNA for organisms. The advantage is that we avoid subjectivity and, furthermore, reproducibility of results is guaranteed. We apply our method to the Indo-European and the Austronesian groups, considering, in both cases, fifty different languages. The two trees obtained are, in many respects, similar to those found by glottochronologists, with some important differences as regards the positions of a few languages. In order to support these different results we separately analyze the structure of the distances of these languages with respect to all the others.
Software Architecture Reconstruction Method, a Survey
Zainab Nayyar; Nazish Rafique
2014-01-01
Architecture reconstruction belongs to a reverse engineering process, in which we move from code to architecture level for reconstructing architecture. Software architectures are the blue prints of projects which depict the external overview of the software system. Mostly maintenance and testing cause the software to deviate from its original architecture, because sometimes for enhancing the functionality of a system the software deviates from its documented specifications, some new modules a...
Reconstructing weak values without weak measurements
International Nuclear Information System (INIS)
Johansen, Lars M.
2007-01-01
I propose a scheme for reconstructing the weak value of an observable without the need for weak measurements. The post-selection in weak measurements is replaced by an initial projector measurement. The observable can be measured using any form of interaction, including projective measurements. The reconstruction is effected by measuring the change in the expectation value of the observable due to the projector measurement. The weak value may take nonclassical values if the projector measurement disturbs the expectation value of the observable
3D Reconstruction of NMR Images
Directory of Open Access Journals (Sweden)
Peter Izak
2007-01-01
Full Text Available This paper introduces experiment of 3D reconstruction NMR images scanned from magnetic resonance device. There are described methods which can be used for 3D reconstruction magnetic resonance images in biomedical application. The main idea is based on marching cubes algorithm. For this task was chosen sophistication method by program Vision Assistant, which is a part of program LabVIEW.
Medial canthal reconstruction with multiple local flaps
Directory of Open Access Journals (Sweden)
Akihiro Ogino
2018-03-01
Conclusion: This method is somewhat complicated compared to reconstruction with a single flap, but it is a combination of standard local flaps and is a simple reconstructive procedure. By adding additional resection, the suture line is consistent with the border of the facial unit, so postoperative scarring is inconspicuous. This technique is aesthetically useful because of the continuity of colour and texture resulting from the use of adjacent flaps.
Reconstructions in ultrasound modulated optical tomography
Allmaras, Moritz; Bangerth, Wolfgang
2011-01-01
We introduce a mathematical model for ultrasound modulated optical tomography and present a simple reconstruction scheme for recovering the spatially varying optical absorption coefficient from scanning measurements with narrowly focused ultrasound signals. Computational results for this model show that the reconstruction of sharp features of the absorption coefficient is possible. A formal linearization of the model leads to an equation with a Fredholm operator, which explains the stability observed in our numerical experiments. © de Gruyter 2011.
Upgrade trigger & reconstruction strategy: 2017 milestone
Albrecht, Johannes; Campora Perez, Daniel Hugo; Cattaneo, Marco; Marco, Clemencic; Couturier, Ben; Dziurda, Agnieszka; Fitzpatrick, Conor; Fontana, Marianna; Grillo, Lucia; Hasse, Christoph; Hill, Donal; Jones, Christopher Rob; Lemaitre, Florian; Lupton, Olli; Matev, Rosen; Pearce, Alex; Polci, Francesco; Promberger, Laura; Ponce, Sebastien; Quagliani, Renato; Raven, Gerhard; Sciascia, Barbara; Schiller, Manuel Tobias; Stahl, Sascha; Szymanski, Maciej Pawel; Chefdeville, Maximilien
2018-01-01
The LHCb collaboration is currently preparing an update of the experiment to take data in Run 3 of the LHC. The dominant feature of this upgrade is a trigger-less readout of the full detector followed by a full software trigger. To make optimal use of the collected data, the events are reconstructed at the inelastic collision rate of 30 MHz. This document presents the baseline trigger and reconstruction strategy as of the end of 2017.
Electron Reconstruction in the CMS Electromagnetic Calorimeter
Meschi, Emilio; Seez, Christopher; Vikas, Pratibha
2001-01-01
This note describes the reconstruction of electrons using the electromagnetic calorimeter (ECAL) alone. This represents the first step in the High Level Trigger reconstruction and selection chain. By making "super-clusters" (i.e. clusters of clusters) much of the energy radiated by bremsstrahlung in the tracker material can be recovered. Representative performance figures for energy and position resolution in the barrel are given.
Developments on jet reconstruction by DELPHI
Kiskinen, A
2002-01-01
The most relevant techniques used by DELPHI to identify jets in multihadronic final states are reviewed. The performance of jet reconstruction algorithms is analysed together with the additional use of energy and momentum conservation in order to allow for a precise reconstruction of the event kinematics. Also jet flavour tagging methods are summarised. Applications in some analyses like searches for new particles such as Higgs bosons, W mass physics and QCD studies are presented. (9 refs).
The Temporalis Muscle Flap in Maxillofacial Reconstruction
International Nuclear Information System (INIS)
ElSheikh, M; Zeitoun, I; ElMassry, M A K
1991-01-01
The temporalis muscle flap is a very versatile and valuable axial flap, which could be used in various reconstructive procedures in and around the oro-maxillofacial region. The surgical anatomy, vascular pattern and technique of elevation of the flap are described, together with our experience in different reconstructive situations. The advantages and disadvantages of the use of this flap are thoroughly discussed taking into consideration the potentiality of cancer recurrence under cover of the flap. (author)