2,867 research outputs found

    Performance data of US Naval Observatory VLG-11 hydrogen masers since September, 1983

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    In 1983, two VLC-11 masers were delivered to the U.S. Naval Observatory by the Smithsonian Astrophysical Observatory. Last year the short-term stability of these masers was reported and the effect of this short-term stability on timekeeping performance was examined. Since the date of installation, 13 September 1983, data on the masers' long-term performance have been accumulated. The Allan variance, agma(tau), of the relative frequency between the masers reaches a minimum of about 4 parts in 10 to the 16th power at averaging times 5,000 seconds and rises at longer averaging times due, at least partly, to systematic frequency drift. The systematic frequency drifts, expressed in units of fractional frequency difference per day are discussed

    Forecast, observation and modelling of a deep stratospheric intrusion event over Europe

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    A wide range of measurements was carried out in central and southeastern Europe within the framework of the EU-project STACCATO (Influence of Stratosphere-Troposphere Exchange in a Changing Climate on Atmospheric Transport and Oxidation Capacity) with the principle goal to create a comprehensive data set on stratospheric air intrusions into the troposphere along a rather frequently observed pathway over central Europe from the North Sea to the Mediterranean Sea. The measurements were based on predictions by suitable quasi-operational trajectory calculations using ECMWF forecast data. A predicted deep Stratosphere to Troposphere Transport (STT) event, encountered during the STACCATO period on 20-21 June 2001, could be followed by the measurements network almost from its inception. Observations provide evidence that the intrusion affected large parts of central and southeastern Europe. Especially, the ozone lidar observations on 20-21 June 2001 at Garmisch-Partenkirchen, Germany captured the evolution of two marked tongues of high ozone with the first one reaching almost a height of 2 km, thus providing an excellent data set for model intercomparisons and validation. In addition, for the first time to our knowledge concurrent measurements of the cosmogenic radionuclides <sup>10</sup>Be and <sup>7</sup>Be and their ratio <sup>10</sup>Be/<sup>7</sup>Be are presented together as stratospheric tracers in a case study of a stratospheric intrusion. The ozone tracer columns calculated with the FLEXPART model were found to be in good agreement with water vapour satellite images, capturing the evolution of the observed dry streamers of stratospheric origin. Furthermore, the time-height cross section of ozone tracer simulated with FLEXPART over Garmisch-Partenkirchen captures with many details the evolution of the two observed high-ozone filaments measured with the IFU lidar, thus demonstrating the considerable progress in model simulations. Finally, the modelled ozone (operationally available since October 1999) from the ECMWF (European Centre for Medium-Range Weather Forecasts) atmospheric model is shown to be in very good agreement with the observations during this case study, which provides the first successful validation of a chemical tracer that is used operationally in a weather forecast model. This suggests that coupling chemistry and weather forecast models may significantly improve both weather and chemical forecasts in the future

    Time decay of the remanent magnetization in the ±J\pm J spin glass model at T=0

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    Using the zero-temperature Metropolis dynamics, the time decay of the remanent magnetization in the ±J\pm J Edward-Anderson spin glass model with a uniform random distribution of ferromagnetic and antiferromagnetic interactions has been investigated. Starting from the saturation, the magnetization per spin mm reveals a slow decrease with time, which can be approximated by a power law:m(t)=m+(ta0)a1m(t)=m_{\infty}+ ({t\over a_{0}})^{a_{1}}, a1<0a_{1} < 0. Moreover, its relaxation does not lead it into one of the ground states, and therefore the system is trapped in metastable isoenergetic microstates remaining magnetized. Such behaviour is discussed in terms of a random walk the system performs on its available configuration space.Comment: 9 pages, 3 figure

    Microtiming patterns and interactions with musical properties in Samba music

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    In this study, we focus on the interaction between microtiming patterns and several musical properties: intensity, meter and spectral characteristics. The data-set of 106 musical audio excerpts is processed by means of an auditory model and then divided into several spectral regions and metric levels. The resulting segments are described in terms of their musical properties, over which patterns of peak positions and their intensities are sought. A clustering algorithm is used to systematize the process of pattern detection. The results confirm previously reported anticipations of the third and fourth semiquavers in a beat. We also argue that these patterns of microtiming deviations interact with different profiles of intensities that change according to the metrical structure and spectral characteristics. In particular, we suggest two new findings: (i) a small delay of microtiming positions at the lower end of the spectrum on the first semiquaver of each beat and (ii) systematic forms of accelerando and ritardando at a microtiming level covering two-beat and four-beat phrases. The results demonstrate the importance of multidimensional interactions with timing aspects of music. However, more research is needed in order to find proper representations for rhythm and microtiming aspects in such contexts

    16th IHIW: Immunogenetics of Aging

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    Ageing is a process characterised by progressive loss of function in multiple different organ systems, such as the nervous, endocrine and immune systems. Current data showing that ageing processes may be associated with alterations in the immune system suggest that some of the genetic determinants of senescence might be polymorphic genes that regulate immune responses. The ‘Immunogenetics of Aging’ programme was a component introduced in the 14th International HLA and Immunogenetics Workshop (IHIWS) and developed further within the 15th and 16th. The aim of this component was to determine the contribution of immune genes to successful ageing and an increased capacity to reach the extreme limits of lifespan. Within the 16th IHIWS, new populations were included, and the number of samples analysed was increased. Analysis was focused on innate immunity genes (KIR and MBL2) and their correlation with CMV serostatus. Collaborative studies suggested that both activating and inhibitory KIR and functionally relevant MBL2 haplotypes are important factors for control of CMV infection in the elderly and therefore for chronic low-grade inflammation. Results showed that these genes might be predictive biomarkers in ageing and longevity. Prevalence of MBL2 haplotypes determining absence of the protein (LYPB, LYQC and HYPD) was observed in elderly people with a higher CMV antibody titre. The high CMV titre was also associated with a decreased frequency of the activatory KIR2DS5 and A1B10 haplotypes in elderly. Due to the role of KIR and low or deficient MBL haplotypes in viral infections, these genetic markers could be considered as indicators of a need for CMV prophylaxis at younger age and therefore increased probability of longer lifespan

    First International Consensus Conference on lesions of uncertain malignant potential in the breast (B3 lesions).

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    The purpose of this study is to obtain a consensus for the therapy of B3 lesions. The first International Consensus Conference on lesions of uncertain malignant potential in the breast (B3 lesions) including atypical ductal hyperplasia (ADH), flat epithelial atypia (FEA), classical lobular neoplasia (LN), papillary lesions (PL), benign phyllodes tumors (PT), and radial scars (RS) took place in January 2016 in Zurich, Switzerland organized by the International Breast Ultrasound School and the Swiss Minimally Invasive Breast Biopsy group-a subgroup of the Swiss Society of Senology. Consensus recommendations for the management and follow-up surveillance of these B3 lesions were developed and areas of research priorities were identified. The consensus recommendation for FEA, LN, PL, and RS diagnosed on core needle biopsy or vacuum-assisted biopsy (VAB) is to therapeutically excise the lesion seen on imaging by VAB and no longer by open surgery, with follow-up surveillance imaging for 5 years. The consensus recommendation for ADH and PT is, with some exceptions, therapeutic first-line open surgical excision. Minimally invasive management of selected B3 lesions with therapeutic VAB is acceptable as an alternative to first-line surgical excision

    Staging of uterine cervical cancer with MRI: guidelines of the european society of urogenital radiology

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    Objective: To design clear guidelines for the staging and follow-up of patients with uterine cervical cancer, and to provide the radiologist with a framework for use in multidisciplinary conferences. Methods: Guidelines for uterine cervical cancer staging and follow-up were defined by the female imaging subcommittee of the ESUR (European Society of Urogenital Radiology) based on the expert consensus of imaging protocols of 11 leading institutions and a critical review of the literature. Results: The results indicated that high field Magnetic Resonance Imaging (MRI) should include at least two T2-weighted sequences in sagittal, axial oblique or coronal obliqu

    SPT-3G: A Next-Generation Cosmic Microwave Background Polarization Experiment on the South Pole Telescope

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    We describe the design of a new polarization sensitive receiver, SPT-3G, for the 10-meter South Pole Telescope (SPT). The SPT-3G receiver will deliver a factor of ~20 improvement in mapping speed over the current receiver, SPTpol. The sensitivity of the SPT-3G receiver will enable the advance from statistical detection of B-mode polarization anisotropy power to high signal-to-noise measurements of the individual modes, i.e., maps. This will lead to precise (~0.06 eV) constraints on the sum of neutrino masses with the potential to directly address the neutrino mass hierarchy. It will allow a separation of the lensing and inflationary B-mode power spectra, improving constraints on the amplitude and shape of the primordial signal, either through SPT-3G data alone or in combination with BICEP-2/KECK, which is observing the same area of sky. The measurement of small-scale temperature anisotropy will provide new constraints on the epoch of reionization. Additional science from the SPT-3G survey will be significantly enhanced by the synergy with the ongoing optical Dark Energy Survey (DES), including: a 1% constraint on the bias of optical tracers of large-scale structure, a measurement of the differential Doppler signal from pairs of galaxy clusters that will test General Relativity on ~200 Mpc scales, and improved cosmological constraints from the abundance of clusters of galaxies.Comment: 21 pages, 9 figures. To be published in Proceedings of SPIE Volume 9153. Presented at SPIE Astronomical Telescopes + Instrumentation 2014, conference 915

    A First Order Predicate Logic Formulation of the 3D Reconstruction Problem and its Solution Space

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    This paper defines the 3D reconstruction problem as the process of reconstructing a 3D scene from numerous 2D visual images of that scene. It is well known that this problem is ill-posed, and numerous constraints and assumptions are used in 3D reconstruction algorithms in order to reduce the solution space. Unfortunately, most constraints only work in a certain range of situations and often constraints are built into the most fundamental methods (e.g. Area Based Matching assumes that all the pixels in the window belong to the same object). This paper presents a novel formulation of the 3D reconstruction problem, using a voxel framework and first order logic equations, which does not contain any additional constraints or assumptions. Solving this formulation for a set of input images gives all the possible solutions for that set, rather than picking a solution that is deemed most likely. Using this formulation, this paper studies the problem of uniqueness in 3D reconstruction and how the solution space changes for different configurations of input images. It is found that it is not possible to guarantee a unique solution, no matter how many images are taken of the scene, their orientation or even how much color variation is in the scene itself. Results of using the formulation to reconstruct a few small voxel spaces are also presented. They show that the number of solutions is extremely large for even very small voxel spaces (5 x 5 voxel space gives 10 to 10(7) solutions). This shows the need for constraints to reduce the solution space to a reasonable size. Finally, it is noted that because of the discrete nature of the formulation, the solution space size can be easily calculated, making the formulation a useful tool to numerically evaluate the usefulness of any constraints that are added
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