36,428 research outputs found
Time variations of the narrow FeII and HI spectral emission lines from the close vicinity of Eta Carinae during the spectral event of 2003
The spectrum of Eta Carinae and its ejecta shows slow variations over a
period of 5.5 years. However, the spectrum changes drastically on a time scale
of days once every period called the 'spectral event'. We report on variations
in the narrow emission line spectrum of gas condensations (the Weigelt blobs)
close to the central star during a spectral event. The rapid changes in the
stellar radiation field illuminating the blobs make the blobs a natural
astrophysical laboratory to study atomic photoprocesses. The different
responses of the HI Paschen lines, fluorescent lines and forbidden
[FeII] lines allow us to identify the processes and estimate physical
conditions in the blobs. This paper is based on observations from the Pico dos
Dias Observatory (LNA/Brazil) during the previous event in June 2003.Comment: Accepted for publication in A&
Forage legume silage and cold-pressed rapeseed cake for dairy bull calves
Rearing of organic dairy bull calves can be contradictory, using calves with a high need for quality protein at the same time as a high intake of forage (>60% up to 6 months of age) is required. Forage legumes contain more crude protein than grass, but with high rumen degradability of the protein. When legume forage is fed together with energy-rich cold-pressed rapeseed cake (CRC) the protein in the feeds can be utilized to a higher extent and a satisfactory calf weight gain can be achieved as shown. Using locally produced protein feeds instead of the often used soya bean meal (SBM) is of great interest not only in organic but also in conventional feeding because of environmentally advantages
Theory of ultrathin films at metal-ceramic interfaces
A theoretical model for understanding the formation of interfacial thin films
is presented, which combines density functional theory calculations for
interface energies with thermodynamic modeling techniques for multicomponent
bulk systems. The theory is applied to thin film formation in VC-doped WC-Co
cemented carbides. It is predicted that ultrathin VC films may exist in WC/Co
interfaces at the high temperature sintering conditions where most of the WC
grain growth occurs, which provides an explanation of the grain growth
inhibiting effect of VC additions in the WC-Co system
Undoing measurement-induced dephasing in circuit QED
We analyze the backaction of homodyne detection and photodetection on
superconducting qubits in circuit quantum electrodynamics. Although both
measurement schemes give rise to backaction in the form of stochastic phase
rotations, which leads to dephasing, we show that this can be perfectly undone
provided that the measurement signal is fully accounted for. This result
improves upon that of Phys. Rev. A, 82, 012329 (2010), showing that the method
suggested can be made to realize a perfect two-qubit parity measurement. We
propose a benchmarking experiment on a single qubit to demonstrate the method
using homodyne detection. By analyzing the limited measurement efficiency of
the detector and bandwidth of the amplifier, we show that the parameter values
necessary to see the effect are within the limits of existing technology
Strategic Investments in the Pulp and Paper Industry: A Count Data Regression Analysis
This paper analyses the effects of price and market size variables on the investment propensities in the pulp and paper industry. A panel of 15 European countries in the time period 1984 - 1997 is used in the regression analysis. We find the wages, the US/ECU exchange rate, the price of paper and the installed production capacity to be the main determinants of strategic investments in this industry. Our measure of market size have no - or only very small - effects.Lumpy investments; Prices; Market size; Agglomeration; Distance; Investment determinants
The Inflection Point of the Speed-Density Relation and the Social Force Model
It has been argued that the speed-density digram of pedestrian movement has
an inflection point. This inflection point was found empirically in
investigations of closed-loop single-file pedestrian movement. The reduced
complexity of single-file movement does not only allow a higher precision for
the evaluation of empirical data, but it occasionally also allows analytical
considerations for micosimulation models. In this way it will be shown that
certain (common) variants of the Social Force Model (SFM) do not produce an
inflection point in the speed-density diagram if infinitely many pedestrians
contribute to the force computed for one pedestrian. We propose a modified
Social Force Model that produces the inflection point.Comment: accepted for presentation at conference Traffic and Granular Flow
201
Maximal Unitarity for the Four-Mass Double Box
We extend the maximal-unitarity formalism at two loops to double-box
integrals with four massive external legs. These are relevant for higher-point
processes, as well as for heavy vector rescattering, VV -> VV. In this
formalism, the two-loop amplitude is expanded over a basis of integrals. We
obtain formulas for the coefficients of the double-box integrals, expressing
them as products of tree-level amplitudes integrated over specific complex
multidimensional contours. The contours are subject to the consistency
condition that integrals over them annihilate any integrand whose integral over
real Minkowski space vanishes. These include integrals over parity-odd
integrands and total derivatives arising from integration-by-parts (IBP)
identities. We find that, unlike the zero- through three-mass cases, the IBP
identities impose no constraints on the contours in the four-mass case. We also
discuss the algebraic varieties connected with various double-box integrals,
and show how discrete symmetries of these varieties largely determine the
constraints.Comment: 25 pages, 3 figures; final journal versio
An Overview of Maximal Unitarity at Two Loops
We discuss the extension of the maximal-unitarity method to two loops,
focusing on the example of the planar double box. Maximal cuts are
reinterpreted as contour integrals, with the choice of contour fixed by the
requirement that integrals of total derivatives vanish on it. The resulting
formulae, like their one-loop counterparts, can be applied either analytically
or numerically.Comment: 7 pages, presented at Loops & Legs 2012, Wernigerode, German
Two-Loop Maximal Unitarity with External Masses
We extend the maximal unitarity method at two loops to double-box basis
integrals with up to three external massive legs. We use consistency equations
based on the requirement that integrals of total derivatives vanish. We obtain
unique formulae for the coefficients of the master double-box integrals. These
formulae can be used either analytically or numerically.Comment: 41 pages, 7 figures; small corrections, final journal versio
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