3,045 research outputs found

    New methods in conformal partial wave analysis

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    We report on progress concerning the partial wave analysis of higher correlation functions in conformal quantum field theory.Comment: 16 page

    Tree species driving functional properties of mobile organic matter in throughfall and forest floor solutions of beech, spruce and pine forests

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    The chemical nature of mobile organic matter is a prerequisite for advancing our understanding of the C and nutrient cycling and other forest ecosystem processes. Tree species differ in leaf composition (e.g. nutrient, polyphenol content) and leaf litter quality, which in turn affects a variety of ecosystem processes. However, the composition of OM derived from living plant material via throughfall (TF) and its compositional fate traversing the forest floor (FF) is insufficiently understood. Are there tree-species specific differences in functional properties (e.g. aromaticity) of OM in TF and FF solutions collected from pine, spruce and different beech stands? And if yes- how do functional properties change with tree species and ecosystem compartment (throughfall vs. forest floor)? We addressed these questions by applying solid-state C-13 NMR spectroscopy to TF and FF solutions from European beech forests of the three DFG “Biodiversity Exploratories”, from Norway spruce sites of the Hainich-Dün-Exploratory and Scots pine stands in East-Thuringia. C-13 NMR spectroscopy revealed a homogeneous composition of TF-DOM under beech between the three Exploratories and exhibited remarkable tree-species related differences in DOM composition: Compared to spruce and pine, TF-DOM under beech showed higher intensities of aromatic and phenolic C (beech > pine > spruce) and lower ones of alkyl-C (pine ≈ spruce > beech). Consequently, beech TF exhibited higher aromaticity values and lower alkyl/O-alkyl ratios (i.e. extent of decomposition) in comparison to coniferous TF-DOM. FF-DOM under beech was very similar between the three “Biodiversity Exploratories” and surprisingly analog to FF-DOM under spruce, while under pine higher intensities of aromatic and phenolic C and alkyl-C (pine > beech ≈ spruce) and lower O-alkyl-C signals were observed. Thus, pine FF-DOM exhibited the highest values for both aromaticity (28%) and decomposition (0.87). In essence, tree-species effects became most notable for the composition and functionality of DOM in TF exhibiting consistently the highest aromatic and phenolic C signals for the beech sites. In view of the allelopathic effectiveness of phenolic compounds, the results might point to an increased allelopathic potential of beech TF, which successfully impairs competing plants and organisms and hence alter ecosystem processes and functioning. In the end, the ecological functions of DOM in ecosystems are still imperfectly understood

    New Measurements of Fine-Scale CMB Polarization Power Spectra from CAPMAP at Both 40 and 90 GHz

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    We present new measurements of the cosmic microwave background (CMB) polarization from the final season of the Cosmic Anisotropy Polarization MAPper (CAPMAP). The data set was obtained in winter 2004-2005 with the 7 m antenna in Crawford Hill, New Jersey, from 12 W-band (84-100 GHz) and 4 Q-band (36-45 GHz) correlation polarimeters with 3.3' and 6.5' beamsizes, respectively. After selection criteria were applied, 956 (939) hours of data survived for analysis of W-band (Q-band) data. Two independent and complementary pipelines produced results in excellent agreement with each other. A broad suite of null tests as well as extensive simulations showed that systematic errors were minimal, and a comparison of the W-band and Q-band sky maps revealed no contamination from galactic foregrounds. We report the E-mode and B-mode power spectra in 7 bands in the range 200 < l < 3000, extending the range of previous measurements to higher l. The E-mode spectrum, which is detected at 11 sigma significance, is in agreement with cosmological predictions and with previous work at other frequencies and angular resolutions. The BB power spectrum provides one of the best limits to date on B-mode power at 4.8 uK^2 (95% confidence).Comment: 19 pages, 17 figures, 2 tables, submitted to Ap

    Line defects in epitaxial silicon films grown at 560 C

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    We present an investigation of line defects in epitaxially grown silicon layers using Secco defect etching and transmission electron microscopy TEM . 1 m thick layers were deposited onto Si 100 wafers at a substrate temperature of 560 C using electron cyclotron resonance chemical vapour deposition ECRCVD . Defect etching reveals a variety of etch pits related to extended defects. A detailed analysis of the orientations and shapes of etch pits related to line defects is carried out. Using this information it is then possible to assign different types of etch pits to line defects observed by TEM. The investigations show, that one type of defect are extended dislocations parallel to lt;112 gt;, while the direction of two other types are lt;110 gt; as well as lt;314 gt;, a direction uncommon for line defects in silico

    The QUIET Instrument

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    The Q/U Imaging ExperimenT (QUIET) is designed to measure polarization in the Cosmic Microwave Background, targeting the imprint of inflationary gravitational waves at large angular scales (~ 1 degree). Between 2008 October and 2010 December, two independent receiver arrays were deployed sequentially on a 1.4 m side-fed Dragonian telescope. The polarimeters which form the focal planes use a highly compact design based on High Electron Mobility Transistors (HEMTs) that provides simultaneous measurements of the Stokes parameters Q, U, and I in a single module. The 17-element Q-band polarimeter array, with a central frequency of 43.1 GHz, has the best sensitivity (69 uK sqrt(s)) and the lowest instrumental systematic errors ever achieved in this band, contributing to the tensor-to-scalar ratio at r < 0.1. The 84-element W-band polarimeter array has a sensitivity of 87 uK sqrt(s) at a central frequency of 94.5 GHz. It has the lowest systematic errors to date, contributing at r < 0.01. The two arrays together cover multipoles in the range l= 25-975. These are the largest HEMT-based arrays deployed to date. This article describes the design, calibration, performance of, and sources of systematic error for the instrument

    Osteoporosis drug treatment: duration and management after discontinuation. A position statement from the SVGO/ASCO.

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    Antiosteoporotic drugs are recommended in patients with fragility fractures and in patients considered to be at high fracture risk on the basis of clinical risk factors and/or low bone mineral density. As first-line treatment most patients are started with an antiresorptive treatment, i.e. drugs that inhibit osteoclast development and/or function (bisphosphonates, denosumab, oestrogens or selective oestrogen receptor modulators). In the balance between benefits and risks of antiresorptive treatment, uncertainties remain regarding the optimal treatment duration and the management of patients after drug discontinuation. Based on the available evidence, this position statement will focus on the long-term management of osteoporosis therapy, formulating decision criteria for clinical practice

    First Season QUIET Observations: Measurements of CMB Polarization Power Spectra at 43 GHz in the Multipole Range 25 <= ell <= 475

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    The Q/U Imaging ExperimenT (QUIET) employs coherent receivers at 43GHz and 95GHz, operating on the Chajnantor plateau in the Atacama Desert in Chile, to measure the anisotropy in the polarization of the CMB. QUIET primarily targets the B modes from primordial gravitational waves. The combination of these frequencies gives sensitivity to foreground contributions from diffuse Galactic synchrotron radiation. Between 2008 October and 2010 December, >10,000hours of data were collected, first with the 19-element 43GHz array (3458hours) and then with the 90-element 95GHz array. Each array observes the same four fields, selected for low foregrounds, together covering ~1000deg^2. This paper reports initial results from the 43GHz receiver which has an array sensitivity to CMB fluctuations of 69uK sqrt(s). The data were extensively studied with a large suite of null tests before the power spectra, determined with two independent pipelines, were examined. Analysis choices, including data selection, were modified until the null tests passed. Cross correlating maps with different telescope pointings is used to eliminate a bias. This paper reports the EE, BB and EB power spectra in the multipole range ell=25-475. With the exception of the lowest multipole bin for one of the fields, where a polarized foreground, consistent with Galactic synchrotron radiation, is detected with 3sigma significance, the E-mode spectrum is consistent with the LCDM model, confirming the only previous detection of the first acoustic peak. The B-mode spectrum is consistent with zero, leading to a measurement of the tensor-to-scalar ratio of r=0.35+1.06-0.87. The combination of a new time-stream double-demodulation technique, Mizuguchi-Dragone optics, natural sky rotation, and frequent boresight rotation leads to the lowest level of systematic contamination in the B-mode power so far reported, below the level of r=0.1Comment: 19 pages, 14 figures, higher quality figures are available at http://quiet.uchicago.edu/results/index.html; Fixed a typo and corrected statistical error values used as a reference in Figure 14, showing our systematic uncertainties (unchanged) vs. multipole; Revision to ApJ accepted version, this paper should be cited as "QUIET Collaboration et al. (2011)

    Simulating the Mammalian Blastocyst - Molecular and Mechanical Interactions Pattern the Embryo

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    Mammalian embryogenesis is a dynamic process involving gene expression and mechanical forces between proliferating cells. The exact nature of these interactions, which determine the lineage patterning of the trophectoderm and endoderm tissues occurring in a highly regulated manner at precise periods during the embryonic development, is an area of debate. We have developed a computational modeling framework for studying this process, by which the combined effects of mechanical and genetic interactions are analyzed within the context of proliferating cells. At a purely mechanical level, we demonstrate that the perpendicular alignment of the animal-vegetal (a-v) and embryonic-abembryonic (eb-ab) axes is a result of minimizing the total elastic conformational energy of the entire collection of cells, which are constrained by the zona pellucida. The coupling of gene expression with the mechanics of cell movement is important for formation of both the trophectoderm and the endoderm. In studying the formation of the trophectoderm, we contrast and compare quantitatively two hypotheses: (1) The position determines gene expression, and (2) the gene expression determines the position. Our model, which couples gene expression with mechanics, suggests that differential adhesion between different cell types is a critical determinant in the robust endoderm formation. In addition to differential adhesion, two different testable hypotheses emerge when considering endoderm formation: (1) A directional force acts on certain cells and moves them into forming the endoderm layer, which separates the blastocoel and the cells of the inner cell mass (ICM). In this case the blastocoel simply acts as a static boundary. (2) The blastocoel dynamically applies pressure upon the cells in contact with it, such that cell segregation in the presence of differential adhesion leads to the endoderm formation. To our knowledge, this is the first attempt to combine cell-based spatial mechanical simulations with genetic networks to explain mammalian embryogenesis. Such a framework provides the means to test hypotheses in a controlled in silico environment
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