Search

This paper presents an analytical model of an asymmetric junctionless double-gate (asymmetric DGJL) silicon-on-nothing metal-oxide-semiconductor field-effect transistor (MOSFET). Solving the 2-D Poisson’s equation, the expressions for center potential and threshold voltage are calculated. In addition, the response of the device toward the various short-channel effects like hot carrier effect, drain-induced barrier lowering and threshold voltage roll-off has also been examined along with subthreshold swing and drain current characteristics. Performance analysis of the present model is also demonstrated by comparing its short-channel behavior with conventional DGJL MOSFET. The effect of variation of the device features due to the variation of device parameters is also studied. The simulated results obtained using 2D device simulator, namely ATLAS, are in good agreement with the analytical results, hence validating our derived model. [ABSTRACT FROM AUTHOR]

The distributions of transverse momentum and longitudinal momentum fraction of charged particles in jets are measured in Pb+Pb and pp collisions with the ATLAS detector at the LHC. The distributions are measured as a function of jet transverse momentum and rapidity. The analysis utilises an integrated luminosity of 0.14 nb $$^{-1}$$ of Pb+Pb data and 4.0 pb $$^{-1}$$ of pp data collected in 2011 and 2013, respectively, at the same centre-of-mass energy of 2.76 TeV per colliding nucleon pair. The distributions measured in pp collisions are used as a reference for those measured in Pb+Pb collisions in order to evaluate the impact on the internal structure of jets from the jet energy loss of fast partons propagating through the hot, dense medium created in heavy-ion collisions. Modest but significant centrality-dependent modifications of fragmentation functions in Pb+Pb collisions with respect to those in pp collisions are seen. No significant dependence of modifications on jet $$p_\mathrm{T}$$ and rapidity selections is observed except for the fragments with the highest transverse momenta for which some reduction of yields is observed for more forward jets. [ABSTRACT FROM AUTHOR]

High-precision measurements by the ATLAS Collaboration are presented of inclusive $$W^+ \rightarrow \ell ^+\nu $$ , $$W^- \rightarrow \ell ^-\bar{\nu }$$ and $$Z/\gamma ^* \rightarrow \ell \ell $$ ( $$\ell =e,\mu $$ ) Drell-Yan production cross sections at the LHC. The data were collected in proton-proton collisions at $$\sqrt{s} = 7\,\text {TeV}$$ with an integrated luminosity of $$4.6\,\mathrm {fb}^{-1}$$ . Differential $$W^+$$ and $$W^-$$ cross sections are measured in a lepton pseudorapidity range $$|\eta _{\ell }|<2.5$$ . Differential $$Z/\gamma ^*$$ cross sections are measured as a function of the absolute dilepton rapidity, for $$|y_{\ell \ell }| < 3.6$$ , for three intervals of dilepton mass, $$m_{\ell \ell }$$ , extending from 46 to $$150\,\,\text {GeV}$$ . The integrated and differential electron- and muon-channel cross sections are combined and compared to theoretical predictions using recent sets of parton distribution functions. The data, together with the final inclusive $$e^{\pm }p$$ scattering cross-section data from H1 and ZEUS, are interpreted in a next-to-next-to-leading-order QCD analysis, and a new set of parton distribution functions, ATLAS-epWZ16, is obtained. The ratio of strange-to-light sea-quark densities in the proton is determined more accurately than in previous determinations based on collider data only, and is established to be close to unity in the sensitivity range of the data. A new measurement of the CKM matrix element $$\vert V_{cs} \vert $$ is also provided. [ABSTRACT FROM AUTHOR]

We present high-performance simulations of global seismic wave propagation with an unprecedented accuracy of 1.2 s seismic period for a realistic three-dimensional Earth model using the spectral element method on the K computer. Our seismic simulations use a total of 665.2 billion grid points and resolve 1.8 trillion degrees of freedom. To realize these large-scale computations, we optimize a widely used community software code to efficiently address all hardware parallelization, especially thread-level parallelization to solve the bottleneck of memory usage for coarse-grained parallelization. The new code exhibits excellent strong scaling for the time stepping loop, that is, parallel efficiency on 82,134 nodes relative to 36,504 nodes is 99.54%. Sustained performance of these computations on the K computer is 1.24 petaflops, which is 11.84% of its peak performance. The obtained seismograms with an accuracy of 1.2 s for the entire globe should help us to better understand rupture mechanisms of devastating earthquakes. [ABSTRACT FROM AUTHOR]

In the last centuries the experimental particle physics began to develop thank to growing capacity of computers among others. It is allowed to know the structure of the matter to level of quark gluon. Plasma in the strong interaction. Experimental evidences supported the theory to measure the predicted results. Since its inception the researchers are interested in the track reconstruction. We studied the jet browser model, which was developed for 4π calorimeter. This method works on the measurement data set, which contain the components of interaction points in the detector space and it allows to examine the trajectory reconstruction of the final state particles. We keep the total energy in constant values and it satisfies the Gauss law. Using GPUs the evaluation of the model can be drastically accelerated, as we were able to achieve up to 223 fold speedup compared to a CPU based parallel implementation. [ABSTRACT FROM AUTHOR]

In this paper, analog/RF performance and small signal behavior of Transparent Gate Recessed Channel (TGRC) MOSFET has been investigated in terms of transconductance, DIBL, channel resistance parasitic capacitances, cut-off frequency and maximum oscillator frequency. Results so obtained are compared with Conventional Recessed Channel (CRC) MOSFET at THz frequency range, using ATLAS-3D device simulator. Furthermore, the impact of technology parameter variations in terms of gate length ( L g ) has also been evaluated. Result shows that there is 42% enhancement in cut-off frequency, 132% increment in maximum oscillator frequency and significant improvement in parasitic capacitances for TGRC-MOSFET due to reduced short channel effects (SCEs) and enhanced on-current driving capabilities thus, reflecting its significance in high-frequency THz range applications. [ABSTRACT FROM AUTHOR]

This Letter presents a search at the LHC for s -channel single top-quark production in proton–proton collisions at a centre-of-mass energy of 8 TeV. The analyzed data set was recorded by the ATLAS detector and corresponds to an integrated luminosity of 20.3 fb −1 . Selected events contain one charged lepton, large missing transverse momentum and exactly two b -tagged jets. A multivariate event classifier based on boosted decision trees is developed to discriminate s -channel single top-quark events from the main background contributions. The signal extraction is based on a binned maximum-likelihood fit of the output classifier distribution. The analysis leads to an upper limit on the s -channel single top-quark production cross-section of 14.6 pb at the 95% confidence level. The fit gives a cross-section of σ s = 5.0 ± 4.3 pb , consistent with the Standard Model expectation. [ABSTRACT FROM AUTHOR]

A measurement of the total pp cross section at the LHC at s = 7 TeV is presented. In a special run with high- β ⋆ beam optics, an integrated luminosity of 80 μb −1 was accumulated in order to measure the differential elastic cross section as a function of the Mandelstam momentum transfer variable t . The measurement is performed with the ALFA sub-detector of ATLAS. Using a fit to the differential elastic cross section in the | t | range from 0.01 GeV 2 to 0.1 GeV 2 to extrapolate to | t | → 0 , the total cross section, σ tot ( p p → X ) , is measured via the optical theorem to be: σ tot ( p p → X ) = 95.35 ± 0.38 ( stat. ) ± 1.25 ( exp. ) ± 0.37 ( extr. ) mb , where the first error is statistical, the second accounts for all experimental systematic uncertainties and the last is related to uncertainties in the extrapolation to | t | → 0 . In addition, the slope of the elastic cross section at small | t | is determined to be B = 19.73 ± 0.14 ( stat. ) ± 0.26 ( syst. ) GeV − 2 . [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) is the most common form of joint disease and often characterized by cartilage changes. Accurate quantitative methods are needed to rapidly screen large image databases to assess changes in cartilage morphology. We therefore propose a new automatic atlas-based cartilage segmentation method for future automatic OA studies. Atlas-based segmentation methods have been demonstrated to be robust and accurate in brain imaging and therefore also hold high promise to allow for reliable and high-quality segmentations of cartilage. Nevertheless, atlas-based methods have not been well explored for cartilage segmentation. A particular challenge is the thinness of cartilage, its relatively small volume in comparison to surrounding tissue and the difficulty to locate cartilage interfaces – for example the interface between femoral and tibial cartilage. This paper focuses on the segmentation of femoral and tibial cartilage, proposing a multi-atlas segmentation strategy with non-local patch-based label fusion which can robustly identify candidate regions of cartilage. This method is combined with a novel three-label segmentation method which guarantees the spatial separation of femoral and tibial cartilage, and ensures spatial regularity while preserving the thin cartilage shape through anisotropic regularization. Our segmentation energy is convex and therefore guarantees globally optimal solutions. We perform an extensive validation of the proposed method on 706 images of the Pfizer Longitudinal Study. Our validation includes comparisons of different atlas segmentation strategies, different local classifiers, and different types of regularizers. To compare to other cartilage segmentation approaches we validate based on the 50 images of the SKI10 dataset. [ABSTRACT FROM AUTHOR]

Abstract: Semiregular models are now ubiquitous in computer graphics. These models are constructed by refining a model with an arbitrary initial connectivity. Due to the regularity enforced by the refinement, the vertices of semiregular models are mostly regular. To benefit from this regularity, it is desirable to have a data structure specifically designed for such models. We discuss how to design such a data structure, which we call the atlas of connectivity maps (ACM) for semiregular models. In an ACM, semiregular models are divided into regular patches. The connectivity between patches is captured at the coarsest resolution. In this paper, we discuss how to find these patches in a given semiregular model and how to set up the ACM. We also show some of the benefits of this data structure in applications such as the multiresolution framework. ACM can support a variety of different multiresolution frameworks including compact and smooth reverse subdivision methods. The efficiency of ACM is also compared with a standard implementation of half-edge. [Copyright &y& Elsevier]

In 1964, a new particle was proposed by several groups to answer the question of where the masses of elementary particles come from; this particle is usually referred to as the Higgs particle or the Higgs boson. In July 2012, this Higgs particle was finally found experimentally, a feat accomplished by the ATLAS Collaboration and the CMS Collaboration using the Large Hadron Collider at CERN. It is the purpose of this review to give my personal perspective on a brief history of the experimental search for this particle since the '80s and finally its discovery in 2012. Besides the early searches, those at the LEP collider at CERN, the Tevatron Collider at Fermilab, and the Large Hadron Collider at CERN are described in some detail. This experimental discovery of the Higgs boson is often considered to be the most important advance in particle physics in the last half a century, and some of the possible implications are briefly discussed. This review is partially based on a talk presented by the author at the conference "Higgs Quo Vadis," Aspen Center for Physics, Aspen, CO, USA, March 10-15, 2013. [ABSTRACT FROM AUTHOR]

An understanding of early maps is best achieved through an analysis that seeks to integrate a scientific approach to map history with the idea that maps are also subject to socio-economic and political influences prevailing at the time. An analytical framework that uses such an integrated approach is applied here to William Petty's atlas of Ireland, published in 1685 under the title Hiberniae Delineatio, in an effort to deepen our understanding of this landmark in the mapping of Ireland. The atlas emerges as an incomplete and sometimes flawed document which, nevertheless, made Ireland the first country in Europe to be mapped from accurately measured surveys and provided the definitive shape of Ireland for the next century. It also gives testimony to the reciprocal relationships between maps and society and illustrates the role of the map itself in the historical process. [ABSTRACT FROM AUTHOR]

Abstract: Polymicrogyria (PMG) is a cortical malformation characterized by multiple small gyri and altered cortical lamination, which may be associated with disrupted white matter connectivity. However, little is known about the topological patterns of white matter networks in PMG. We examined structural connectivity and network topology using individual primary gyral pattern-based nodes in PMG patients, overcoming the limitations of an atlas-based approach. Structural networks were constructed from structural and diffusion magnetic resonance images in 25 typically developing and 14 PMG subjects. The connectivity analysis for different fiber groups divided based on gyral topology revealed severely reduced connectivity between neighboring primary gyri (short U-fibers) in PMG, which was highly correlated with the regional involvement and extent of abnormal gyral folding. The patients also showed significantly reduced connectivity between distant gyri (long association fibers) and between the two cortical hemispheres. In relation to these results, gyral node-based graph theoretical analysis revealed significantly altered topological organization of the network (lower clustering and higher modularity) and disrupted network hub architecture in cortical association areas involved in cognitive and language functions in PMG patients. Furthermore, the network segregation in PMG patients decreased with the extent of PMG and the degree of language impairment. Our approach provides the first detailed findings and interpretations on altered cortical network topology in PMG related to abnormal cortical structure and brain function, and shows the potential for an individualized method to characterize network properties and alterations in connections that are associated with malformations of cortical development. [Copyright &y& Elsevier]

Diffusion tensor imaging has become an important modality in the field of neuroimaging to capture changes in micro-organization and to assess white matter integrity or development. While there exists a number of tractography toolsets, these usually lack tools for preprocessing or to analyze diffusion properties along the fiber tracts. Currently, the field is in critical need of a coherent end-to-end toolset for performing an along-fiber tract analysis, accessible to non-technical neuroimaging researchers. The UNC-Utah NA-MIC DTI framework represents a coherent, open source, end-to-end toolset for atlas fiber tract based DTI analysis encompassing DICOM data conversion, quality control, atlas building, fiber tractography, fiber parameterization, and statistical analysis of diffusion properties. Most steps utilize graphical user interfaces (GUI) to simplify interaction and provide an extensive DTI analysis framework for non-technical researchers/investigators.We illustrate the use of our framework on a small sample, cross sectional neuroimaging study of eight healthy 1-year-old children from the Infant Brain Imaging Study (IBIS) Network. In this limited test study, we illustrate the power of our method by quantifying the diffusion properties at 1 year of age on the genu and splenium fiber tracts. [ABSTRACT FROM AUTHOR]

Abstract: Label fusion multi-atlas approaches for image segmentation can give better segmentation results than single atlas methods. We present a multi-atlas label fusion strategy based on probabilistic weighting of distance maps. Relationships between image similarities and segmentation similarities are estimated in a learning phase and used to derive fusion weights that are proportional to the probability for each atlas to improve the segmentation result. The method was tested using a leave-one-out strategy on a database of 21 pre-segmented prostate patients for different image registrations combined with different image similarity scorings. The probabilistic weighting yields results that are equal or better compared to both fusion with equal weights and results using the STAPLE algorithm. Results from the experiments demonstrate that label fusion by weighted distance maps is feasible, and that probabilistic weighted fusion improves segmentation quality more the stronger the individual atlas segmentation quality depends on the corresponding registered image similarity. The regions used for evaluation of the image similarity measures were found to be more important than the choice of similarity measure. [Copyright &y& Elsevier]

Abstract: This Letter reports a search for a heavy particle that decays to WW using events produced in pp collisions at . The data were recorded in 2011 by the ATLAS detector and correspond to an integrated luminosity of 4.7 fb−1. ( or μ) final states are considered and the distribution of the transverse mass of the WW candidates is found to be consistent with Standard Model expectations. Upper limits on the production cross section times branching ratio into W boson pairs are set for Randall–Sundrum and bulk Randall–Sundrum gravitons, which result in observed 95% CL lower limits on the masses of the two particles of 1.23 TeV and 0.84 TeV, respectively. [Copyright &y& Elsevier]

Abstract: A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results. [Copyright &y& Elsevier]

Abstract: AnoverviewoftheATLAS detectorattheLHCatCERNis presented, followedbya brief discussiononthe present status. ATLAS is studying upgrade scenarios in order to be prepared to the LHC luminosity upgrade. ATLAS upgrade plans and ideas behind are discussed. [Copyright &y& Elsevier]

Abstract: The Micro Pixel Chamber(μ-PIC)isbeingdevelopedasacandidateforthe muonsystemoftheATLAS detectorfor upgrading in LHC experiments. The μ-PICisa micro-patterngaseous detector that doesn’thave floating structure such as wires, mesh, or foil. This detector can be made by printed-circuit-board (PCB) technology, which is commercially available and suited for mass production. Operation tests have been performed under high flux neutrons under similar conditions to theATLAS cavern. Spark rates are measured using severalgas mixtures under7MeV neutron irradiation, andgoodpropertieswereobservedusingneon,ethane,andCF4mixtureofgases.Usingresistivematerialsas electrodes, we are also developing a new μ-PIC, which is not expected to damage the electrodes in the case of discharge sparks. [Copyright &y& Elsevier]

Abstract: The ATLAS muon spectrometer consists of a system of precision tracking and trigger chambers embedded in a 2T magnetic field generated by three large aircore superconducting toroids. The precision Monitored Drift Tube (MDT) chambers measure the track sagitta up to a pseudorapidity of 2.7 with a 50 μm uncertainty yielding a design muon transverse momentum resolution of 10% at 1 TeV. Muon tracking is augmented in the very forward region by Cathode Strip Chambers (CSC). The calibration program, essential to achieve the spectrometer design performance and physics reach, is conducted at three worldwide computing centers. These centers each receive a dedicated High Level Trigger data stream that enables high statistics based determination of t0 and drifttime to driftspace relations. During the first year of data taking a system of periodic calibration updates has been established. The calibration algorithms, methods and tools and performance results using LHC collision data are discussed. [Copyright &y& Elsevier]

Abstract: Monitored drift tube chambers are used as precision tracking detectors in the muon spectrometer of the ATLAS experiment at the LHC at CERN. These chambers provide a spatial resolution of 35μm and a tracking efficiency of close to 100% up to background rates of 0.5kHz/cm2, the former being limited at higher rates mainly due to space-charge effects and the latter due to the maximum drift time of 700ns. For LHC upgrades, a faster drift tube chamber has been developed, using drift tubes with a diameter of 15mm instead of 30mm. The increased channel density and shorter drift time of about 200ns raise the rate capability to about 10kHz/cm2, while retaining the spatial resolution. A prototype chamber with trapezoidal shape consisting of 2 x 8 layers of 15mm diameter drift tubes with an active surface of 0.8 m2 has been constructed. The prototype chamber has been tested at CERN with a 180GeV muon beam at a SPS beam line and with cosmic ray muons at the Gamma Irradiation Facility (GIF) at high γ radiation rates. [Copyright &y& Elsevier]

Abstract: The ATLAS Transition Radiation Tracker (TRT) is the outermost of the three sub-systems of the ATLAS Inner Detector at the Large Hadron Collider at CERN. It consists of close to 300000 thin-wall drift tubes (straws) providing ∼30 measurements with position resolution of about 120μm for charged particle tracks with |η| < 2 and pT > 0.5GeV. Along with continuous tracking, it provides particle identification capability through the detection of transition radiation, X-ray photons generated by high momentum particles in the many polymer fibers or films that fill the spaces between the straws. Custom-built analog and digital electronic read-out are optimized to operate at the LHC design luminosity. In this article, a review of the commissioning and first operational experience of the TRT detector will be presented. Emphasis will be given to performance studies based on the reconstruction and analysis of proton-proton collision data collected at the LHC. In addition, the response of the TRT detector to the extremely high track density conditions encountered during the first heavy ion LHC collisons will be presented. [Copyright &y& Elsevier]

Abstract: Even though the LHC is still in an early phase of operation, plans are being developed to operate the machine and its detectors at up to 10 times the original design luminosity. This has a major impact on the Forward Calorimeter (FCal), which is exposed to some of the highest radiation rates in ATLAS. The FCal detector and its associated components were designed for operation at the maximum LHC luminosity of 1034 cm-2s-1. However at the higher luminosities projected for the HL-LHC, operation of the FCal may be compromised. Beam heating in the FCal could lead to the formation of argon bubbles in the detector, the ionization rate will result in space charge effects that will reduce the signal and the current draw will result in a voltage drop across the HV current limiting resistors. Two possible solutions are being considered to maintain FCal operation at HL-LHC. One is a complete replacement of the FCal system. A replacement FCal would have a similar design to the current calorimeter except for the addition of cooling loops, lower value HV protection resistors and the use of smaller ionization gaps, as small as 100 microns in the first compartment. The second solution is the installation of a small warm calorimeter, referred to as the Mini-FCal, to be placed in front of the FCal. This addition would reduce the ionization load in the first FCal compartment, which would keep a larger region of the FCal active and reduce the heat load to an acceptable level. The current concept for the Mini-FCal is a standard parallel plate calorimeter with copper absorbers and diamond sensors, which were chosen for their inherent radiation resistance. It is anticipated that neutrons will be the major cause of damage to the diamond sensors and the integrated flux of neutrons in the Mini-FCal after 3000 fb-1 at the HL-LHC will be up to 2 x 1017 neutrons/cm2. Recent irradiation tests carried out by members of the ATLAS Liquid Argon group show that these sensors can still operate after irradiation up to these levels although with a large reduction in signal. [Copyright &y& Elsevier]

Abstract: TileCal is the central hadronic calorimeter of the ATLAS detector operating at LHC. It is a sampling calorimeter whose active material is made of scintillating plastic tiles. Scintillation light is read by photomultipliers. A Laser system is used to monitor their gain stability. During dedicated calibration runs the Laser system sends via long optical fibers, a monitored amount of light simultaneously to all the ≈10000 photomultipliers of TileCal. This note describes two complementary methods to measure the stability of the photomultipliers gain using the Laser calibration runs. The results of validation tests are presented for both methods and theirrespective performances and limitations are discussed. [Copyright &y& Elsevier]

Abstract: The ATLAS experiment is designed to study the proton-proton collisions produced at the LHC with a centre-of-mass energy of 14 TeV. Liquid Argon (LAr) sampling calorimeters are used in ATLAS for all electromagnetic calorimetry covering the pseudorapidity region |η| <3.2, as well as for hadronic calorimetry from η = 1.4 to η = 4.8. An overview of the system is shown as well as a discussion of its operation and performance at √s=900 GeV and 7 TeV since the start of LHC running. The latest status of the detector as well as problems and solutions addressed during the last years are also discussed. [Copyright &y& Elsevier]

Abstract: TileCal is the Barrel hadronic calorimeter of the ATLAS experiment at LHC/CERN. To equalize the response of individual TileCal cells with a precision better than 1% and to monitor the response of each cell over time, a calibration and monitoring system based on a Cs 137 radioactive source driven through the calorimeter volume by liquid flow has been implemented. This calibration system relies on a dedicated readout chain based on slow integrators that read currents from the TileCal photomultipliers integrating over milliseconds during the calibration runs. Moreover, during the LHC collisions the TileCal integrator based readout provides the signal coming from inelastic proton-proton collisions at low momentum transfer. This is used to monitor in ATLAS the instantaneous luminosity as well as the response of all calorimeter cells during data-taking. [Copyright &y& Elsevier]

Abstract: The ATLAS iron-scintillator hadronic calorimeter (TileCal) provides precision measurements of jets and missing transverse energy produced in the LHC proton-proton collisions. Results assessing the calorimeter calibration obtained using cosmic ray muons collected in 2008, 2009 and 2010 are presented. The analysis was based on the comparison between experimental and simulated data, and addresses three issues. First the average non-uniformity of the response of the cells within a layer was estimated to be about ±2%. Second, the average response of different layers was found to be not inter-calibrated, considering the sources of error. The largest difference between the responses of two layers was 4%. Finally, the differences between the energy scales of each layer obtained in this analysis and the value set at test beams using electrons was found to range between -3% and +1%. The sources of uncertainties in the response measurements were strongly correlated, including the uncertainty in the simulation. The total error of each layer determinations was 2%. Stable response values were obtained for the three data-taking periods. The uncertainties on the comparisons were less than ±1% for the Long Barrel layers and less than ±3% for the Extended Barrel ones. [Copyright &y& Elsevier]

Abstract: The ATLAS muon spectrometer is designed to measure the momentum of a 1 TeV/c muon to an accuracy of 10%. A muon of this momentum bends, on average, 500μm in the toroidal field of ATLAS. Therefore, the position of the muon chambers within a tower and along the precision coordinate must be known to better than 50μm. ATLAS uses a combination of an optical and track-based alignment to achieve such a precise alignment. Several analyses to monitor and validate the alignment were undertaken in the first year of LHC operation. This report provides a brief overview of the motivation, building and commissioning of the optical system, performance, and validation of the alignment of the muon spectrometer. [Copyright &y& Elsevier]

Abstract: This paper describes the mechatronic design concept of a motion simulation platform called Atlas capable of delivering unlimited rotational motion. Atlas’ novel actuation system uses three actuated omni-directional wheels to rotate a spherical capsule that houses the occupant, the cockpit, and the simulator equipment. The unique actuation system allows the spherical capsule to be rotated with a continuously variable angular velocity about a continuously variable axis of rotation. The design process and challenges involved in the development and control of the Atlas simulator are discussed in this paper. To date, an incremental three-phase development approach of the Atlas simulator has resulted in desktop, half-scale, and full-scale prototypes of the simulator. The desktop proof-of-concept model and the focus of this paper, Atlas Lite, is used to test the basics of Atlas’s novel actuation, sensing, and control technologies. This paper introduces the actuation system concept and its implementation on Atlas Lite and a unique vision-based sensing system based on color markers used to estimate the orientation of the spherical capsule. This paper also describes a new nonlinear kinematic controller that allows the spherical capsule to track an arbitrary trajectory. Results from the implementation on Atlas Lite indicate the orientation controller and actuation system allow the spherical capsule to track representative aircraft motions from traditional flight simulation software. [Copyright &y& Elsevier]

Purpose: This work aims to develop a methodology for automated atlas-guided analysis of small animal positron emission tomography (PET) data through deformable registration to an anatomical mouse model. Methods: A non-rigid registration technique is used to put into correspondence relevant anatomical regions of rodent CT images from combined PET/CT studies to corresponding CT images of the Digimouse anatomical mouse model. The latter provides a pre-segmented atlas consisting of 21 anatomical regions suitable for automated quantitative analysis. Image registration is performed using a package based on the Insight Toolkit allowing the implementation of various image registration algorithms. The optimal parameters obtained for deformable registration were applied to simulated and experimental mouse PET/CT studies. The accuracy of the image registration procedure was assessed by segmenting mouse CT images into seven regions: brain, lungs, heart, kidneys, bladder, skeleton and the rest of the body. This was accomplished prior to image registration using a semi-automated algorithm. Each mouse segmentation was transformed using the parameters obtained during CT to CT image registration. The resulting segmentation was compared with the original Digimouse atlas to quantify image registration accuracy using established metrics such as the Dice coefficient and Hausdorff distance. PET images were then transformed using the same technique and automated quantitative analysis of tracer uptake performed. Results: The Dice coefficient and Hausdorff distance show fair to excellent agreement and a mean registration mismatch distance of about 6 mm. The results demonstrate good quantification accuracy in most of the regions, especially the brain, but not in the bladder, as expected. Normalized mean activity estimates were preserved between the reference and automated quantification techniques with relative errors below 10 % in most of the organs considered. Conclusion: The proposed automated quantification technique is reliable, robust and suitable for fast quantification of preclinical PET data in large serial studies. [ABSTRACT FROM AUTHOR]

The article focuses on the Surface Ocean Carbon Dioxide (CO2) Atlas (SOCAT) project. The project was pioneered by the international marine carbon science community in 2007 with the goal to give a comprehensive and updated global data set of marine surface CO2, which have been subject to quality control (QC). It discusses the gridded SOCAT, the second data product from the project, which provide robust regularly spaced fCO2 product with minimal interpolation.

Abstract: Cardiovascular disease is the leading cause of death worldwide and for this reason computer-based diagnosis of cardiac diseases is a very important task. In this article, a method for segmentation of aortic outflow velocity profiles from cardiac Doppler ultrasound images is presented. The proposed method is based on the statistical image atlas derived from ultrasound images of healthy volunteers. The ultrasound image segmentation is done by registration of the input image to the atlas, followed by a propagation of the segmentation result from the atlas onto the input image. In the registration process, the normalized mutual information is used as an image similarity measure, while optimization is performed using a multiresolution gradient ascent method. The registration method is evaluated using an in-silico phantom, real data from 30 volunteers, and an inverse consistency test. The segmentation method is evaluated using 59 images from healthy volunteers and 89 images from patients, and using cardiac parameters extracted from the segmented image. Experimental validation is conducted using a set of healthy volunteers and patients and has shown excellent results. Cardiac parameter segmentation evaluation showed that the variability of the automated segmentation relative to the manual is comparable to the intra-observer variability. The proposed method is useful for computer aided diagnosis and extraction of cardiac parameters. [Copyright &y& Elsevier]

Abstract: This paper presents a fully automated method for atlas-based whole-body segmentation in non-contrast-enhanced Micro-CT data of mice. The position and posture of mice in such studies may vary to a large extent, complicating data comparison in cross-sectional and follow-up studies. Moreover, Micro-CT typically yields only poor soft-tissue contrast for abdominal organs. To overcome these challenges, we propose a method that divides the problem into an atlas constrained registration based on high-contrast organs in Micro-CT (skeleton, lungs and skin), and a soft tissue approximation step for low-contrast organs. We first present a modification of the MOBY mouse atlas (Segars et al., 2004) by partitioning the skeleton into individual bones, by adding anatomically realistic joint types and by defining a hierarchical atlas tree description. The individual bones as well as the lungs of this adapted MOBY atlas are then registered one by one traversing the model tree hierarchy. To this end, we employ the Iterative Closest Point method and constrain the Degrees of Freedom of the local registration, dependent on the joint type and motion range. This atlas-based strategy renders the method highly robust to exceptionally large postural differences among scans and to moderate pathological bone deformations. The skin of the torso is registered by employing a novel method for matching distributions of geodesic distances locally, constrained by the registered skeleton. Because of the absence of image contrast between abdominal organs, they are interpolated from the atlas to the subject domain using Thin-Plate-Spline approximation, defined by correspondences on the already established registration of high-contrast structures (bones, lungs and skin). We extensively evaluate the proposed registration method, using 26 non-contrast-enhanced Micro-CT datasets of mice, and the skin registration and organ interpolation, using contrast-enhanced Micro-CT datasets of 15 mice. The posture and shape varied significantly among the animals and the data was acquired in vivo. After registration, the mean Euclidean distance was less than two voxel dimensions for the skeleton and the lungs respectively and less than one voxel dimension for the skin. Dice coefficients of volume overlap between manually segmented and interpolated skeleton and organs vary between 0.47±0.08 for the kidneys and 0.73±0.04 for the brain. These experiments demonstrate the method’s effectiveness for overcoming exceptionally large variations in posture, yielding acceptable approximation accuracy even in the absence of soft-tissue contrast in in vivo Micro-CT data without requiring user initialization. [Copyright &y& Elsevier]

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The ATLAS detector at CERN's Large Hadron Collider (LHC) will be exposed to proton-proton collisions from beams crossing at 40 MHz. A three-level trigger system will select potentially interesting events in order to reduce the read-out rate to about 200 Hz. The first trigger level is implemented in custom-built electronics and makes an initial fast selection based on detector data of coarse granularity. It has to reduce the rate by a factor of 104 to less than 100 kHz. The other two consecutive trigger levels are in software and run on PC farms. We present an overview of the first-level central trigger and the muon barrel trigger system and report on the current installation status. Moreover, we show analysis results of cosmic-ray data recorded in situ at the ATLAS experimental site with final or close-to-final hardware. [ABSTRACT FROM AUTHOR]

Event data from proton-proton collisions at the LHC will be selected by the ATLAS experiment by a three level trigger system, which reduces the initial bunch crossing rate of 40 MHz at its first two trigger levels (LVL1+LVL2) to ∼3 kHz. At this rate the Event-Builder collects the data from all Read-Out system PCs (ROSs) and provides fully assembled events to the the Event-Filter (EF), which is the third level trigger, to achieve a further rate reduction to ∼200 Hz for permanent storage. The Event-Builder is based on a farm of 0(100) PCs, interconnected via Gigabit Ethernet to 0(150) ROSs. These PCs run Linux and multi-threaded software applications implemented in C++. All the ROSs and one third of the Event-Builder PCs are already installed and commissioned. Performance measurements have been exercised on this initial system, which show promising results that the required final data rates and bandwidth for the ATLAS event builder are in reach. [ABSTRACT FROM AUTHOR]

The ATLAS experiment at the Large Hadron Collider (LHC) will face the challenge of efficiently selecting interesting candidate events in pp collisions at 14 TeV centre-of-mass energy, whilst rejecting the enormous number of background events. The High-Level-Trigger (HLT = second level trigger and Event Filter), which is a software based trigger will need to reduce the first level trigger output rate of ∼75 kHz to ∼200 Hz written out to mass storage. In this paper an overview of the steering mechanism of the HLT is given. The HLT Steering is responsible for the schedulling of algorithms and for the global event trigger decision evaluation. The concept of step-wise and seeded selection strategy implemented by the steering will be presented. Integration of large number of trigger menus and sophisticated physics selection strategies will also be discussed. The electron and photon menus will be described to demonstrate that the trigger is well adapted for the physics program at the LHC. [ABSTRACT FROM AUTHOR]

TileCal is the hadronic tile calorimeter of the ATLAS experiment at LHC/CERN. The central element of the back-end system of the TileCal detector is the Read-Out Driver (ROD).The main components of the TileCal ROD are the Digital Signal Processors (DSPs) placed on the Processing Unit (PU) daughterboards. This paper presents a detailed description of the code developed for the DSPs. The code is divided into two different parts: the first part contains the core functionalities and the second part the reconstruction algorithms. The core acts as an operating system and controls configuration, data reception and transmission and synchronization between front-end data and the Timing, Trigger and Control (TTC) information. The reconstruction algorithms implemented on the DSP are the Optimal Filtering (OF), Muon Tagging (MTag) and Missing ET calculation. The OF algorithm reconstructs the deposited energy and the phase of the signal for every calorimeter channel within a front-end module. This reconstructed energy is used by the MTag algorithm to tag low transverse momentum muons that may escape the ATLAS muon spectrometer Level 1 trigger whereas the Missing ET algorithm computes the total transverse energy and the projection on X and Y axis for the entire module that will be used by the Level 2 trigger system. [ABSTRACT FROM AUTHOR]

The Fast Track processor (FTK) has been proposed for high-quality track finding at very high rates (Level-i output rates) for the LHC experiments. Fast, efficient and precise pattern recognition has been studied using a silicon 7-layer sub-detector, including a subset of the pixel and SCT layers. We tested the FTK algorithms using the ATLAS full simulation. We compare the FTK reconstruction quality with the tracking capability of the offline iPatRec algorithm. We show that similar resolutions and efficiencies are reached by FTK at a speed higher than iPatRec by orders of magnitude. With FTK full events are reconstructed at the Level-1 output rate. Bso μ +μ- events are fully simulated together with background samples. We show that a low Level-2 rate is allowed by FTK, even using a single 6 GeV Level-1 muon selection trigger. FTK provides the full-resolution track list ready for the Level-2 Bso identification. All selection cuts performed by the Event Filter can be easily anticipated at Level-2. We present the Bso μ +μ- efficiency gain and related Level-2 rates. [ABSTRACT FROM AUTHOR]

The ATLAS experiment at the Large Hadron Collider (LHC) will face the challenge of selecting interesting candidate events in proton-proton collisions at 14 TeV center of mass energy, while rejecting the enormous number of background events. The trigger system architecture is organized in three levels. From a bunch crossing rate of 40 MHz, the First Level trigger, hardware implemented, will reduce this rate to around ∼ 75 kHz. Then the software based High Level Trigger (HLT), composed by the Second Level Trigger and the Event Filter reduces the rate to ∼ 200 Hz. In this paper, we will present the implementation of the muon trigger "slice," signal efficiencies, background rejection rates, and system performances (execution time, memory consumption, etc.) for online muon selection based on Monte Carlo simulations and results obtained on real events collected during cosmic data taking runs. [ABSTRACT FROM AUTHOR]

During 2006 and spring 2007, integration and commissioning of trigger and data acquisition (TDAQ) equipment in the ATLAS experimental area has progressed. Much of the work has focused on a final prototype setup consisting of around eighty computers representing a subset of the full TDAQ system. There have been a series of technical runs using this setup. Various tests have been run including those where around 6 k Level-1 preselected simulated proton-proton events have been processed in a loop mode through the trigger and dataflow chains. The system included the readout buffers containing the events, event building, second level and third level trigger processors. Aspects critical for the final system, such as event processing times, have been studied using different trigger algorithms as well as the different dataflow components. [ABSTRACT FROM AUTHOR]

ATLAS is one of the four experiments under construction along the Large Hadron Collider (LHC) ring at CERN. The LHC will produce interactions at a center-of-mass energy equal to √s = 14 TeV with a frequency of 40 MHz. The detector consists of more than 140 million electronic channels. The challenging experimental environment and the extreme detector complexity impose the necessity of a common, scalable, distributed monitoring frame- work, which can be tuned for optimal use by different ATLAS sub-detectors at the various levels of the ATLAS data flow. This paper presents the architecture of this monitoring software frame- work and describes its current implementation, which has already been used at the ATLAS beam test activity in 2004. Preliminary performance results, obtained on a computer cluster consisting of 700 nodes, will also be presented, showing that the performance of the current implementation is within the range of the final ATLAS requirements. [ABSTRACT FROM AUTHOR]

In order to meet the requirements of ATLAS experiment data taking, the Trigger-DAQ (TDAQ) system is composed of O(10000) of applications running on more than 2600 computers in a network. With such a system size, software and hardware failures are quite frequent. To minimize system downtime, the Trigger-DAQ control system shall include advance verification and diagnostics facilities. The operator shall use tests and expertise of the TDAQ and detectors developers in order to diagnose and recover from errors, if possible automatically. The TDAQ control system is built as a distributed tree of controllers, where the behavior of each controller is defined in a rule-based language allowing easy customization. The control system also includes a verification framework which allows users to develop and configure tests for any component in the system with different levels of complexity. It can be used as a stand-alone test facility for a small detector installation, as part of the general TDAQ initialization procedure, and for diagnosing problems which may occur during run time. The system is currently being used in TDAQ commissioning at the ATLAS experimental zone and by subdetectors for stand-alone verification of the detector hardware before it is finally installed. [ABSTRACT FROM AUTHOR]

This paper introduces the Log Service, developed at CERN within the ATLAS TDAQ/DCS framework. This package remedies the long standing problem of centralizing log messages produced by TDAQ applications in order to ease later access and maintenance. One or multiple Log Servers form the system's archival container, based on the MySQL database engine. A C++ interface is provided to access the Log Servers in a transparent manner. Furthermore, a user-friendly web-based tool intended for developers is available to easily browse and/or remove Log Messages. The outline of these software components are herein explained. Performance testing has been conducted within a controllable environment to observe the behaviour of the Log Service. [ABSTRACT FROM AUTHOR]

Objectives: This paper evaluates a semi-automatic segmentation procedure to enhance utilizing atlas based treatment plans. For this application, it is crucial to provide a collection of ‘reference’ organs, restorable from the atlas so that they closely match those of the current patient. To enable assembling representative organs, we developed a semi-automatic procedure using an active contour method. Method: The 3D organ volume was identified by defining contours on individual slices. The initial organ contours were matched to patient volume data sets and then superimposed on them. These starting contours were then adjusted and refined to rapidly find the organ outline of the given patient. Performance was evaluated by contouring organs of different size, shape complexity, and proximity to surrounding structures. We used representative organs defined on CT volumes obtained from 12 patients and compared the resulting outlines to those drawn by a radiologist. Results: A strong correlation was found between the area measures of the delineated liver (r=0.992), lung (r=0.996) and spinal cord (r=0.81), obtained by both segmentation techniques. A paired Student''s t-test showed no statistical difference between the two techniques regarding the liver and spinal cord (p>0.05). Conclusion: This method could be used to form ‘standard’ organs, which would form part of a whole body atlas (WBA) database for radiation treatment plans as well as to match atlas organs to new patient data. [Copyright &y& Elsevier]

Deals with a study which detailed the Level-2 Trigger (LVL2) Pilot Project of ATLAS, one of the two general purpose LHC experiments, which is part of the on-going program to develop the ATLAS high-level triggers. Features of the project; Task of a LVL2 processor; Functions of the Region of Interest Builder and Supervisor; Use of a field-programmable gate array as co-processor.