825 research outputs found

    Visually localizing design problems with disharmony maps

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    Assessing the quality of software design is difficult, as “design” is expressed through guidelines and heuristics, not rigorous rules. One successful approach to assess design quality is based on de-tection strategies, which are metrics-based composed logical condi-tions, by which design fragments with specific properties are de-tected in the source code. Such detection strategies, when exe-cuted on large software systems usually return large sets of arti-facts, which potentially exhibit one or more “design disharmonies”, which are then inspected manually, a cumbersome activity. In this article we present disharmony maps, a visualization-based approach to locate such flawed software artifacts in large systems. We display the whole system using a 3D visualization technique based on a city metaphor. We enrich such visualizations with the results returned by a number of detection strategies, and thus render both the static structure and the design problems that affect a subject system. We evaluate our approach on a number of open-source Java systems and report on our findings

    Initial results from a multiple monoenergetic gamma radiography system for nuclear security

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    The detection of assembled nuclear devices and concealed special nuclear materials (SNM) such as plutonium or uranium in commercial cargo traffic is a major challenge in mitigating the threat of nuclear terrorism. Currently available radiographic and active interrogation systems use-1-10 MeV bremsstrahlung photon beams. Although simple to build and operate, bremsstrahlung-based systems deliver high radiation doses to the cargo and to potential stowaways. To eliminate problematic issues of high dose, we are developing a novel technique known as multiple monoenergetic gamma radiography (MMGR). MMGR uses ion-induced nuclear reactions to produce two monoenergetic gammas for dual energy radiography. This allows us to image the areal density and effective atomic number (Z(eff)) of scanned cargo. We present initial results from the proof-of-concept experiment, which was conducted at the MIT Bates Research and Engineering Center. The purpose of the experiment was to assess the capabilities of MMGR to measure areal density and Z(eff) of container cargo mockups. The experiment used a 3.0 MeV radiofrequency quadrupole accelerator to create sources of 4.44 MeV and 15.11 MeV gammas from the ¹¹B(d,n gamma)¹²C reaction in a thick natural boron target; the gammas are detected by an array of Nal (TI) detectors after transmission through cargo mockups. The measured fluxes of transmitted 4.44 MeV and 15.11 MeV gammas were used to assess the areal density and Zeff. Initial results show that MMGR is capable of discriminating the presence of high-Z materials concealed in up to 30 cm of iron shielding from low-and mid-Z materials present in the cargo mockup. Published by Elsevier B.V.Domestic Nuclear Detection Office of the United States Department of Homeland Security (ARI-LA Award, ECCS-1348328

    First measurements of high frequency cross-spectra from a pair of large Michelson interferometers

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    Measurements are reported of the cross-correlation of spectra of differential position signals from the Fermilab Holometer, a pair of co-located 39 m long, high power Michelson interferometers with flat, broadband frequency response in the MHz range. The instrument obtains sensitivity to high frequency correlated signals far exceeding any previous measurement in a broad frequency band extending beyond the 3.8 MHz inverse light crossing time of the apparatus. The dominant but uncorrelated shot noise is averaged down over 2×1082\times 10^8 independent spectral measurements with 381 Hz frequency resolution to obtain 2.1×1020 m/Hz2.1\times 10^{-20} \ \mathrm{m}/\sqrt{\mathrm{Hz}} sensitivity to stationary signals. For signal bandwidths Δf>11\Delta f > 11 kHz, the sensitivity to strain hh or shear power spectral density of classical or exotic origin surpasses a milestone PSDδh<tpPSD_{\delta h} < t_p where tp=5.39×1044/Hzt_p= 5.39\times 10^{-44}/\mathrm{Hz} is the Planck time.Comment: 5 pages, 3 figure

    Interferometric Constraints on Quantum Geometrical Shear Noise Correlations

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    Final measurements and analysis are reported from the first-generation Holometer, the first instrument capable of measuring correlated variations in space-time position at strain noise power spectral densities smaller than a Planck time. The apparatus consists of two co-located, but independent and isolated, 40 m power-recycled Michelson interferometers, whose outputs are cross-correlated to 25 MHz. The data are sensitive to correlations of differential position across the apparatus over a broad band of frequencies up to and exceeding the inverse light crossing time, 7.6 MHz. By measuring with Planck precision the correlation of position variations at spacelike separations, the Holometer searches for faint, irreducible correlated position noise backgrounds predicted by some models of quantum space-time geometry. The first-generation optical layout is sensitive to quantum geometrical noise correlations with shear symmetry---those that can be interpreted as a fundamental noncommutativity of space-time position in orthogonal directions. General experimental constraints are placed on parameters of a set of models of spatial shear noise correlations, with a sensitivity that exceeds the Planck-scale holographic information bound on position states by a large factor. This result significantly extends the upper limits placed on models of directional noncommutativity by currently operating gravitational wave observatories.Comment: Matches the journal accepted versio

    Looking for pulsations in HgMn stars through CoRoT lightcurves

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    HgMn Chemically Peculiar stars are among the quietest stars of the main-sequence. However, according to theoretical predictions, these stars could have pulsations related to the very strong overabundances of iron peak elements, which are produced by atomic diffusion in upper layers. Such pulsations have never been detected from ground based observations. Our aim is to search for signatures of pulsations in HgMn stars using the high quality lightcurves provided by the CoRoT satellite. We identified three faint stars (V>12), from VLT-GIRAFFE multiobject spectrograph survey in a field which was planned for observation by CoRoT. They present the typical characteristics of HgMn stars. They were observed by the CoRoT satellite during the long run (131 days) which started from the 24th of October 2007, with the exoplanets CCD's (Additional Programme). In the present work, we present the analysis of the ground based spectra of these three stars and the analysis of the corresponding CoRoT lightcurves. Two of these three HgMn candidates show low amplitude (less than 1.6 mmag) periodic variations (4.3 and 2.53 days respectively, with harmonics) which are compatible with periods predicted by theoretical models.Comment: Accepted paper in A&A (7 May 2009

    MHz gravitational wave constraints with decameter Michelson interferometers

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    A new detector, the Fermilab Holometer, consists of separate yet identical 39-meter Michelson interferometers. Strain sensitivity achieved is better than 10[superscript -21]/√Hz between 1 to 13 MHz from a 130-h data set. This measurement exceeds the sensitivity and frequency range made from previous high frequency gravitational wave experiments by many orders of magnitude. Constraints are placed on a stochastic background at 382 Hz resolution. The 3σ upper limit on Ω[subscript GW], the gravitational wave energy density normalized to the closure density, ranges from 5.6×10[superscript 12] at 1 MHz to 8.4×10[superscript 15] at 13 MHz. Another result from the same data set is a search for nearby primordial black hole binaries (PBHB). There are no detectable monochromatic PBHBs in the mass range 0.83–3.5×10[superscript 21]  g between the Earth and the Moon. Projections for a chirp search with the same data set increase the mass range to 0.59-2.5×10[superscript 25]  g and distances out to Jupiter. This result presents a new method for placing limits on a poorly constrained mass range of primordial black holes. Additionally, solar system searches for PBHBs place limits on their contribution to the total dark matter fraction.United States. Dept. of Energy (Contract DE-AC02-07CH11359)United States. Dept. of Energy (Early Career Research Program FNAL FWP 11-03)Templeton FoundationNational Science Foundation (U.S.) (Grants PHY- 1205254 and DGE-1144082)National Aeronautics and Space Administration (Grant NNX09AR38G)Fermi Research AllianceUniversity of Chicago. Kavli Institute for Cosmological PhysicsUniversity of Chicago. Fermilab Strategic Collaborative InitiativesScience Support ConsortiumNational Science Foundation (U.S.). Graduate Research Fellowship Program (Grant DGE-0638477)Universities Research Association (U.S.). Visiting Scholars Progra

    Salvage high-dose chemotherapy in female patients with relapsed/refractory germ-cell tumors: A retrospective analysis of the European Group for Blood and Marrow Transplantation (EBMT)

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    Background: High-dose chemotherapy (HDC) with hematopoietic progenitor cell transplantation is a standard option for relapsed/refractory testicular germ-cell tumor (GCT), but only few data have been reported in female patients with GCT. We conducted a retrospective analysis of female patients with GCT treated with HDC and registered with the European Society for Blood and Marrow Transplantation. Patients and methods: Between 1985 and 2013, 60 registered female patients with GCT, median age 27 years (range 15-48), were treated with salvage HDC. Forty patients (67%) had primary ovarian GCT, 8 (13%) mediastinal, 7 (12%) retroperitoneal and 5 (8%) other primary sites/unknown. Twenty-two patients (37%) received HDC as second-line therapy, 29 (48%) as third-line, and 9 (15%) as fourth- to sixth-line. Nine of 60 patients (15%) received HDC as late-intensification with no evidence of metastasis before HDC. The conditioning HDC regimens comprised carboplatin in 51 of 60 cases (85%), and consisted of a single HDC cycle in 31 cases (52%), a multi-cycle HDC regimen in 29 (48%). Results: Nine cases who underwent late intensification HDC were not evaluable for response. Of the other 51 assessable patients, 17 (33%) achieved a complete response (CR), 8 (16%) a marker-negative partial remission (PRm-), 5 (10%) a marker-positive partial remission, 5 (10%) stable disease, and 13 (25%) progressive disease. There were 3 toxic deaths (6%). With an overall median follow-up of 14 months (range 1-219), 7 of 9 (78%) patients with late intensification and 18 of the 25 patients (72%) achieving a CR/PRm- following HDC were free of relapse/progression. In total, 25 of 60 patients (42%) were progression-free following HDC at a median follow-up of 87 months (range 3-219 months). Conclusions: Salvage HDC based on carboplatin represents a therapeutic option for female patients with relapsed/refractory GCT
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