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Berdeu, Anthony, Ferréol Soulez, Loïc Denis, Maud Langlois und Éric Thiébaut. „PIC: a data reduction algorithm for integral field spectrographs“. Astronomy & Astrophysics 635 (März 2020): A90. http://dx.doi.org/10.1051/0004-6361/201936890.
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Context. The improvement of large size detectors permitted the development of integral field spectrographs (IFSs) in astronomy. Spectral information for each spatial element of a two-dimensional field of view is obtained thanks to integral field units that spread the spectra on the 2D grid of the sensor. Aims. Here we aim to solve the inherent issues raised by standard data-reduction algorithms based on direct mapping of the 2D + λ data cube: the spectral cross-talk due to the overlap of neighbouring spectra, the spatial correlations of the noise due to the re-interpolation of the cube on a Cartesian grid, and the artefacts due to the influence of defective pixels. Methods. The proposed method, Projection, Interpolation, and Convolution (PIC), is based on an “inverse-problems” approach. By accounting for the overlap of neighbouring spectra as well as the spatial extension in a spectrum of a given wavelength, the model inversion reduces the spectral cross-talk while deconvolving the spectral dispersion. Considered as missing data, defective pixels undetected during the calibration are discarded on-the-fly via a robust penalisation of the data fidelity term. Results. The calibration of the proposed model is presented for the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE). This calibration was applied to extended objects as well as coronagraphic acquisitions dedicated to exoplanet detection or disc imaging. Artefacts due to badly corrected defective pixels or artificial background structures observed in the cube reduced by the SPHERE data reduction pipeline are suppressed while the reconstructed spectra are sharper. This reduces the false detections by the standard exoplanet detection algorithms. Conclusions. These results show the pertinence of the inverse-problems approach to reduce the raw data produced by IFSs and to compensate for some of their imperfections. Our modelling forms an initial building block necessary to develop methods that can reconstruct and/or detect sources directly from the raw data.
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Smentek, Lidia, und Andrzej Ke¸dziorski. „Efficiency of the energy transfer in lanthanide-organic chelates; spectral overlap integral“. Journal of Luminescence 130, Nr. 7 (Juli 2010): 1154–59. http://dx.doi.org/10.1016/j.jlumin.2010.02.013.
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Langlois, Adam, und Pierre D. Harvey. „Maple™-assisted calculations of the J-integral: a key parameter for the understanding of excited state energy transfer in porphyrins and other chromophores“. Journal of Porphyrins and Phthalocyanines 18, Nr. 08n09 (August 2014): 666–74. http://dx.doi.org/10.1142/s1088424614500400.
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The spectral overlap between the emission of a donor molecule and the absorption of an acceptor molecule, quantifiable using the J-integral calculation, is a parameter of extreme importance when studying the excited state energy transfer by either the Főrster or Dexter mechanism. Despite its extreme importance in both mechanisms, it is often misinterpreted, approximated or incorrectly calculated. The calculation of the J-integral is not trivial especially when one wishes to carry out the calculation on measured spectroscopic data. A detailed description for the correct calculation of the J-integral is herein reported and presents a Maple™ assisted template that is capable of performing this calculation in the two different energy scales (nm and cm-1) to yield the value of the J-integral in given units. Specific examples using porphyrin-containing compounds are provided. This Maple™ program is flexible and can be easily adapted to the needs of a researcher. A call for the standardization of the calculation of the J-integral for the facile comparison with other overlap integrals found in the literature is made.
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Stark, Pauline, Caroline Zab, Andrea Porzel, Katrin Franke, Paride Rizzo und Ludger A. Wessjohann. „PSYCHE—A Valuable Experiment in Plant NMR-Metabolomics“. Molecules 25, Nr. 21 (04.11.2020): 5125. http://dx.doi.org/10.3390/molecules25215125.
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1H-NMR is a very reproducible spectroscopic method and, therefore, a powerful tool for the metabolomic analysis of biological samples. However, due to the high complexity of natural samples, such as plant extracts, the evaluation of spectra is difficult because of signal overlap. The new NMR “Pure Shift” methods improve spectral resolution by suppressing homonuclear coupling and turning multiplets into singlets. The PSYCHE (Pure Shift yielded by Chirp excitation) and the Zangger–Sterk pulse sequence were tested. The parameters of the more suitable PSYCHE experiment were optimized, and the extracts of 21 Hypericum species were measured. Different evaluation criteria were used to compare the suitability of the PSYCHE experiment with conventional 1H-NMR. The relationship between the integral of a signal and the related bin value established by linear regression demonstrates an equal representation of the integrals in binned PSYCHE spectra compared to conventional 1H-NMR. Using multivariate data analysis based on both techniques reveals comparable results. The obtained data demonstrate that Pure Shift spectra can support the evaluation of conventional 1H-NMR experiments.
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Takakusa, Hideo, Kazuya Kikuchi, Yasuteru Urano, Hirotatsu Kojima und Tetsuo Nagano. „A Novel Design Method of Ratiometric Fluorescent Probes Based on Fluorescence Resonance Energy Transfer Switching by Spectral Overlap Integral“. Chemistry - A European Journal 9, Nr. 7 (04.04.2003): 1479–85. http://dx.doi.org/10.1002/chem.200390167.
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Koç, Hüseyin. „Analytical Evaluation for Calculation of Two-Center Franck–Condon Factor and Matrix Elements“. Journal of Chemistry 2018 (15.11.2018): 1–6. http://dx.doi.org/10.1155/2018/3147981.
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The Franck–Condon (FC) factor is defined as squares of the Franck–Condon (FC) overlap integral and represents one of the principle fundamental factors of molecular physics. The FC factor is used to determine the transition probabilities in different vibrational levels of the two electronic states and the spectral line intensities of diatomic and polyatomic molecules. In this study, new analytical formulas were derived to calculate Franck–Condon integral (FCI) of harmonic oscillators and matrix elements (xη, e−2cx, and e−cx2) including simple finite summations of binomial coefficients. These formulas are valid for arbitrary values. The results of formulas are in agreement with the results in the literature.
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Alamiry, Mohammed A. H., Effat Bahaidarah, Anthony Harriman, Jean-Hubert Olivier und Raymond Ziessel. „Influence of applied pressure on the probability of electronic energy transfer across a molecular dyad“. Pure and Applied Chemistry 85, Nr. 7 (20.02.2013): 1349–65. http://dx.doi.org/10.1351/pac-con-12-09-04.
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A pair of covalently linked molecular dyads is described in which two disparate boron dipyrromethene dyes are separated by a tolane-like spacer. Efficient electronic energy transfer (EET) occurs across the dyad; the mechanism involves important contributions from both Förster-type coulombic interactions and Dexter-type electron exchange processes. The energy acceptor is equipped with long paraffinic chains that favor aggregation at high concentration or at low temperature. The aggregate displays red-shifted absorption and emission spectral profiles, relative to the monomer, such that EET is less efficient because of a weaker overlap integral. The donor unit is insensitive to applied pressure but this is not so for the acceptor, which has extended π-conjugation associated with appended styryl groups. Here, pressure reduces the effective π-conjugation length, leading to a new absorption band at higher energy. With increasing pressure, the overall EET probability falls but this effect is nonlinear and at modest pressure there is only a small recovery of donor fluorescence. This situation likely arises from compensatory phenomena such as restricted rotation and decreased dipole screening by the solvent. However, the probability of EET falls dramatically over the regime where the π-conjugation length is reduced owing to the presumed conformational exchange. It appears that the pressure-induced conformer is a poor energy acceptor.
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Puls, Joachim. „FASTWIND reloaded: Complete comoving frame transfer for “all” contributing lines“. Proceedings of the International Astronomical Union 12, S329 (November 2016): 435. http://dx.doi.org/10.1017/s1743921317000229.
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AbstractFASTWIND is a unified NLTE atmosphere/spectrum synthesis code originally designed (and frequently used) for the optical/IR spectroscopic analysis of massive stars with winds. Until the previous version (v10), the line transfer for background elements (mostly from the iron-group) was performed in an approximate way, by calculating the individual line-transitions in a single-line Sobolev or comoving frame approach, and by adding up the individual opacities and source functions to quasi-continuum quantities that are used to determine the radiation field for the complete spectrum (see Puls et al. 2005, A&A 435, 669, and updates).We have now updated this approach (v11) and calculate, for all contributing lines (from elements H to Zn), the radiative transfer in the comoving frame, thus also accounting for line-overlap effects in an “exact” way. Related quantities such as temperature, radiative acceleration and formal integral have been improved in parallel. For a typical massive star atmospheric model, the computation times (from scratch, and for a modern desktop computer) are 1.5 h for the atmosphere/NLTE part, and 30 to 45 minutes (when not parallelized) for the formal integral (i.e., SED and normalized flux) in the ranges 900 to 2000 and 3800 to 7000 Å(Δλ = 0.03 Å).We compare our new with analogous results from the alternative code CMFGEN (Hillier & Miller 1998, ApJ 496, 407, and updates), for a grid consisting of 5 O-dwarf and 5 O-supergiant models of different spectral subtype. In most cases, the agreement is very good or even excellent (i.e., for the radiative acceleration), though also certain differences can be spotted. A comparison with results from the previous, approximate method shows equally good agreement, though also here some differences become obvious. Besides the possibility to calculate the (total) radiative acceleration, the new FASTWIND version will allow us to investigate the UV-part of the spectrum in parallel with the optical/IR domain.
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BAEK, NAM SEOB, YONG HEE KIM und HWAN KYU KIM. „RECENT PROGRESS IN ERBIUM(III)-CORED COMPLEXES BASED ON DENDRITIC LIGANDS FOR ADVANCED PHOTONICS APPLICATIONS“. Journal of Nonlinear Optical Physics & Materials 15, Nr. 03 (September 2006): 369–79. http://dx.doi.org/10.1142/s0218863506003360.
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We present that the stable and inert Er(III) -encapsulated complexes based on naphthalene and anthracene ligands bearing a Fréchet aryl-ether dendron exhibit much stronger near-IR emission bands bands at 1530 nm, originated from the 4f–4f electronic transition of the first excited state (4 I 13/2) to the ground state (4 I 15/2) of the partially-filled 4f shell. A strong decrease in the fluorescence of G n-aryl ether dendron (n = 0 or 2) is accompanied by strongly increasing the fluorescence intensity of the luminescent anthracene or naphthalene ligand with the generation number of the dendrons. The strong decrease of fluorescence intensity of luminescent ligand such as naphthalene and anthracene units is accompanied by strongly increasing the near infrared (IR) emission of the Er 3+ ions in Er(III) -encapsulated complexes. It could be attributed to the efficient energy transfer process occurring between the aryl-ether dendron and anthracene moiety as well as between dendritic anthracene ligand and Er 3+ ion. Thus, the emission intensity of the lanthanide complexes, upon photoexcitation of aryl-ether dendrons at 290 nm, was dramatically enhanced with an increase in the generation number n of dendrons, due to the site-isolation and light-harvesting effects. In addition, Er 3+-[ G 2- An ]3(terpy) exhibits the stronger PL intensity than Er 3+-[ G 2- Na ]3(terpy)) by 2.5 times, upon photoexcitation of aryl-ether dendrons at 290 nm. It may be due to the fact that the anthracene ligand in Er 3+-[ G 2- An ]3(terpy)) has higher spectral overlap integral (J) value than the naphthalene ligand in Er 3+-[ G 2- Na ]3(terpy) by 1.5 times. Surprisingly, all Er(III) -cored dendrimer complexes have excellent thermal- and photo-stability as well as good solubility.
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Ma, Tao, und R. A. Serota. „Spectral and parametric averaging for integrable systems“. International Journal of Modern Physics B 29, Nr. 17 (23.06.2015): 1550109. http://dx.doi.org/10.1142/s021797921550109x.
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We analyze two theoretical approaches to ensemble averaging for integrable systems in quantum chaos, spectral averaging (SA) and parametric averaging (PA). For SA, we introduce a new procedure, namely, rescaled spectral averaging (RSA). Unlike traditional SA, it can describe the correlation function of spectral staircase (CFSS) and produce persistent oscillations of the interval level number variance (IV). PA while not as accurate as RSA for the CFSS and IV, can also produce persistent oscillations of the global level number variance (GV) and better describes saturation level rigidity as a function of the running energy. Overall, it is the most reliable method for a wide range of statistics.
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Annenkov, S. Y., und V. I. Shrira. „Evaluation of Skewness and Kurtosis of Wind Waves Parameterized by JONSWAP Spectra“. Journal of Physical Oceanography 44, Nr. 6 (28.05.2014): 1582–94. http://dx.doi.org/10.1175/jpo-d-13-0218.1.
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Abstract The authors consider the deviations of wave height statistics from Gaussianity, manifested in higher statistical moments of random wind-wave fields, namely, in the nonzero values of the skewness and the kurtosis. These deviations are examined theoretically under the standard set of assumptions used in the established statistical theory of water waves, in particular in the derivation of the Hasselmann kinetic equation. P. Janssen proposed integral representations of the skewness and the kurtosis in terms of multidimensional integrals of wave spectra. However, the use of these representations for broadband wind-wave fields proved to be challenging; it requires substantial computational resources, which is unsuitable for applications. Using specially designed parallel algorithms to evaluate the integrals, the authors provide a comprehensive picture of the behavior of the kurtosis and the skewness of wind waves in the multidimensional parameter space of the most commonly used Joint North Sea Wave Project (JONSWAP) parameterizations of wind-wave spectra. Except for very narrow angular distributions where the overall picture is qualitatively different, the behavior of the higher moments proved to be not sensitive to the particular form of the directional spectrum. On this basis for the broad angular spectra typical of the ocean, the study puts forward simple parameterizations of the skewness and the kurtosis in terms of the JONSWAP peakedness parameter γ and in terms of the inverse wave age. These parameterizations can be used in operational wave forecasting and other applications.
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Baranov, V. I., und D. Yu Zelent'sov. „Methods for calculation of electronic—vibrational spectra of polyatomic molecules Part I. Overlap integrals of vibrational wave functions“. Journal of Molecular Structure 328 (Dezember 1994): 179–88. http://dx.doi.org/10.1016/0022-2860(94)08372-x.
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Hannoun, Imad A., und E. John List. „Turbulent mixing at a shear-free density interface“. Journal of Fluid Mechanics 189 (April 1988): 211–34. http://dx.doi.org/10.1017/s0022112088000977.
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The interaction of a sharp density interface with oscillating-grid-induced shear-free turbulence was experimentally investigated. A linear photodiode array was used in conjunction with laser-induced fluorescence to measure the concentration of dye that was initially only in the less dense layer. A laser-Doppler velocimeter was used to measure the vertical velocity in and above the density interface at a point where the dye concentration was also measured. Potential refractive-index-fluctuation problems were avoided using solutes that provided a homogeneous optical environment across the density interface. Internal wave spectra, amplitudes and velocities, as well as the vertical mass flux were measured. The results indicate that mixing occurs in intermittent bursts and that the gradient (local) Richardson number remains constant for a certain range of the overall Richardson number Rj, defined in terms of an integral lengthscale, buoyancy jump and turbulence intensity. The spectra of the internal waves decay as f−3 at frequencies below the maximum Brunt-Väisälä frequency. These findings give support to a model for oceanic mixing proposed by Phillips (1977) in which the internal waves are limited in their spectral density by sporadic local instabilities and breakdown to turbulence. The results also indicate that, for a certain Rj range, the thickness of the interfacial layer (normalized by the integral lengthscale of the turbulence) is a decreasing function of Rj. At sufficiently high Rj the interfacial thickness becomes limited by diffusive effects. Finally, we discuss a simple model for entrainment at a density interface in the presence of shear-free turbulence.
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Baranov, V. I., und D. Yu Zelentsov. „A new method to calculate overlap integrals of vibrational wave functions in the theory of vibronic spectra of polyatomic molecules“. Journal of Structural Chemistry 35, Nr. 2 (März 1994): 161–68. http://dx.doi.org/10.1007/bf02578303.
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DelSole, Timothy, und Michael K. Tippett. „Average Predictability Time. Part I: Theory“. Journal of the Atmospheric Sciences 66, Nr. 5 (01.05.2009): 1172–87. http://dx.doi.org/10.1175/2008jas2868.1.
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Abstract This paper introduces the average predictability time (APT) for characterizing the overall predictability of a system. APT is the integral of a predictability measure over all lead times. The underlying predictability measure is based on the Mahalanobis metric, which is invariant to linear transformation of the prediction variables and hence gives results that are independent of the (arbitrary) basis set used to represent the state. The APT is superior to some integral time scales used to characterize the time scale of a random process because the latter vanishes in situations when it should not, whereas the APT converges to reasonable values. The APT also can be written in terms of the power spectrum, thereby clarifying the connection between predictability and the power spectrum. In essence, predictability is related to the width of spectral peaks, with strong, narrow peaks associated with high predictability and nearly flat spectra associated with low predictability. Closed form expressions for the APT for linear stochastic models are derived. For a given dynamical operator, the stochastic forcing that minimizes APT is one that allows transformation of the original stochastic model into a set of uncoupled, independent stochastic models. Loosely speaking, coupling enhances predictability. A rigorous upper bound on the predictability of linear stochastic models is derived, which clarifies the connection between predictability at short and long lead times, as well as the choice of norm for measuring error growth. Surprisingly, APT can itself be interpreted as the “total variance” of an alternative stochastic model, which means that generalized stability theory and dynamical systems theory can be used to understand APT. The APT can be decomposed into an uncorrelated set of components that maximize predictability time, analogous to the way principle component analysis decomposes variance. Part II of this paper develops a practical method for performing this decomposition and applies it to meteorological data.
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Sánchez-Fernández, C., J. J. E. Kajava, J. Poutanen, E. Kuulkers und V. F. Suleimanov. „Burst-induced coronal cooling in GS 1826–24“. Astronomy & Astrophysics 634 (Februar 2020): A58. http://dx.doi.org/10.1051/0004-6361/201936599.
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Type I X-ray bursts in GS 1826–24, and in several other systems, may induce cooling of the hot inner accretion flow that surrounds the bursting neutron star. Given that GS 1826–24 remained persistently in the hard state over the period 2003–2008 and presented regular bursting properties, we stacked the spectra of the X-ray bursts detected by INTEGRAL (JEM-X and ISGRI) and XMM-Newton (RGS) during that period to study the effect of the burst photons on the properties of the Comptonizing medium. The extended energy range provided by these instruments allows the simultaneous observation of the burst and persistent emission spectra. We detect an overall change in the shape of the persistent emission spectrum in response to the burst photon shower. For the first time, we observe simultaneously a drop in the hard X-ray emission, together with a soft X-ray excess with respect to the burst blackbody emission. The hard X-ray drop can be explained by burst-induced coronal cooling, while the bulk of the soft X-ray excess can be described by fitting the burst emission with an atmosphere model, instead of a simple blackbody model. Traditionally, the persistent emission was assumed to be invariant during X-ray bursts, and more recently to change only in normalization but not in spectral shape; the observed change in the persistent emission level during X-ray bursts may thus trigger the revision of existing neutron star mass-radius constraints, as the derived values rely on the assumption that the persistent emission does not change during X-ray bursts. The traditional burst fitting technique leads to up to a 10% overestimation of the bolometric burst flux in GS 1826–24, which significantly hampers the comparisons of the KEPLER and MESA model against this “textbook burster”.
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Monreal-Ibero, A., P. M. Weilbacher und M. Wendt. „Diffuse interstellar bands λ5780 and λ5797 in the Antennae Galaxy as seen by MUSE“. Astronomy & Astrophysics 615 (Juli 2018): A33. http://dx.doi.org/10.1051/0004-6361/201732178.
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Context. Diffuse interstellar bands (DIBs) are faint spectral absorption features of unknown origin. Research on DIBs beyond the Local Group is very limited and will surely blossom in the era of the Extremely Large Telescopes. However, we can already start paving the way. One possibility that needs to be explored is the use of high-sensitivity integral field spectrographs. Aims. Our goals are twofold. First, we aim to derive reliable mapping of at least one DIB in a galaxy outside the Local Group. Second, we want to explore the relation between DIBs and other properties of the interstellar medium (ISM) in the galaxy. Methods. We use Multi Unit Spectroscopic Explorer (MUSE) data for the Antennae Galaxy, the closest major galaxy merger. High signal-to-noise spectra were created by co-adding the signal of many spatial elements with the Voronoi binning technique. The emission of the underlying stellar population was modelled and substracted with the STARLIGHT spectral synthesis code. Flux and equivalent width of the features of interest were measured by means of fitting to Gaussian functions. Results. To our knowledge, we have derived the first maps for the DIBs at λ5780 and λ5797 in galaxies outside the Local Group. The strongest of the two DIBs (at λ5780) was detected in an area of ~0.6□′, corresponding to a linear scale of ~25 kpc2. This region was sampled using >200 out of ~1200 independent lines of sight. The DIB λ5797 was detected in >100 independent lines of sight. Both DIBs are associated with a region of high emission in the H I 21 cm line, implying a connection between atomic gas and DIBs, as the correlations in the Milky Way also suggest. Conversely, there is mild spatial association between the two DIBs and the molecular gas, in agreement with results for our Galaxy that indicate a lack of correlation between DIBs and molecular gas. The overall structures for the DIB strength distribution and extinction are comparable. Within the system, the λ5780 DIB clearly correlates with the extinction, and both DIBs follow the relationship between equivalent width and reddening when data for several galaxies are considered. This relationship is tighter when comparing only with galaxies with metallicities close to solar. Unidentified infrared emission bands (UIBs, likely caused by polycyclic aromatic hydrocarbons PAHs) and the λ5780 and λ5797 DIBs show similar but not identical spatial distributions. We attribute the differences to extinction effects without necessarily implying a radically different nature of the respective carriers. Conclusions. The results illustrate the enormous potential of integral field spectrographs for extragalactic DIB research.
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Häckl, Martina, Philipp Tauber, Frank Schweda, Helena U. Zacharias, Michael Altenbuchinger, Peter J. Oefner und Wolfram Gronwald. „An R-Package for the Deconvolution and Integration of 1D NMR Data: MetaboDecon1D“. Metabolites 11, Nr. 7 (13.07.2021): 452. http://dx.doi.org/10.3390/metabo11070452.
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NMR spectroscopy is a widely used method for the detection and quantification of metabolites in complex biological fluids. However, the large number of metabolites present in a biological sample such as urine or plasma leads to considerable signal overlap in one-dimensional NMR spectra, which in turn hampers both signal identification and quantification. As a consequence, we have developed an easy to use R-package that allows the fully automated deconvolution of overlapping signals in the underlying Lorentzian line-shapes. We show that precise integral values are computed, which are required to obtain both relative and absolute quantitative information. The algorithm is independent of any knowledge of the corresponding metabolites, which also allows the quantitative description of features of yet unknown identity.
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Manickam, Surendar, und Ana Barros. „Parsing Synthetic Aperture Radar Measurements of Snow in Complex Terrain: Scaling Behaviour and Sensitivity to Snow Wetness and Landcover“. Remote Sensing 12, Nr. 3 (03.02.2020): 483. http://dx.doi.org/10.3390/rs12030483.
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This study investigates the spatial signatures of seasonal snow in Synthetic Aperture Radar (SAR) observations at different spatial scales and for different physiographic regions. Sentinel-1 C-band (SAR) backscattering coefficients (BSC) were analyzed in the Swiss Alps (SA), in high elevation forest and grasslands in Grand Mesa (GM), Colorado, and in North Dakota (ND) croplands. GM BSC exhibit 10 dB sensitivity to wetness at small scales (~100 m) over homogeneous grassland. Sensitivity decreases to 5 dB in the presence of trees, and it is demonstrated that VH BSC sensitivity enables wet snow mapping below the tree-line. Area-variance scaling relationships show minima at ~100 m and 150–250 m, respectively, in barren and grasslands in SA and GM, increasing up to 1 km and longer in GM forests and ND agricultural fields. The spatial organization of BSC (as described by 1D-directional BSC wavelength spectra) exhibits multi-scaling behavior in the 100–1000 m range with a break at (180–360 m) that is also present in UAVSAR L-band measurements in GM. Spectral slopes in GM forested areas steepen during accumulation and flatten in the melting season with mirror behavior for grasslands reflecting changes in scattering mechanisms with snow depth and wetness, and vegetation mass and structure. Overall, this study reveals persistent patterns of SAR scattering variability spatially organized by land-cover, topography and regional winds with large inter-annual variability tied to precipitation. This dynamic scaling behavior emerges as an integral physical expression of snowpack variability that can be used to model sub-km scales and for downscaling applications.
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KUNDU, RUPALI. „SOME FACTORS LEADING TO ASYMMETRY IN ELECTRONIC SPECTRA OF BILAYER GRAPHENE“. International Journal of Modern Physics B 25, Nr. 14 (10.06.2011): 1877–88. http://dx.doi.org/10.1142/s0217979211100060.
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We have investigated the effects of in-plane and interplane nearest neighbor overlap integrals (s0 and [Formula: see text]) and the site energy difference (Δ) between atoms in two different sublattices in the same graphene layer on the electronic dispersion of bilayer graphene within tight binding model. We then extended the calculation to include the in-plane next nearest neighbor interactions (γ1, s1) and next to next nearest neighbor interactions (γ2, s2) for bilayer graphene bands. It is observed that [Formula: see text] introduces further asymmetry in energy values of top conduction band and bottom valence band at the K point in addition to the asymmetry due to Δ. In general there is noticeable electron–hole asymmetry in the slope of the bands away from the K point, and also the changes in band widths due to [Formula: see text] as well as the other in-plane coupling parameters. The density of states of bilayer graphene has also been calculated within the same model.
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Scudder, Jillian M., Sara L. Ellison, Loubna El Meddah El Idrissi und Henry Poetrodjojo. „Conversions between gas-phase metallicities in MaNGA“. Monthly Notices of the Royal Astronomical Society 507, Nr. 2 (13.08.2021): 2468–87. http://dx.doi.org/10.1093/mnras/stab2339.
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ABSTRACT We present polynomial conversions between each of 11 different strong line gas-phase metallicity calibrations, each based on ∼1.1 million star-forming spaxels in the public Sloan Digital Sky Survey (SDSS) Data Release 15 (DR15) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. For this sample, which is ∼20 times larger than previous works, we present fifth-order polynomial fits for each of 110 possible calibration conversions, for both Small Magellanic Cloud-type and Milky Way-type dust corrections. The typical 2σ scatter around our polynomial fits is 0.1 dex; we present the range over which the metallicities are valid. Conversions between metallicities which rely on the same set of line ratios, or a heavily shared set of emission lines, have reduced scatter in their conversions relative to those conversions with little overlap in required emission lines. Calibration conversions with less consistent sets of emission lines also have increased galaxy-to-galaxy variability, and this variability can account for up to 35 per cent of the total scatter. We also compare our conversions to previous work with the single fibre SDSS DR7 spectra along with higher spatial resolution data from the TYPHOON Integral Field Spectroscopy survey, resulting in comparison samples with spatial resolutions from several kpc down to ∼100 pc. Our metallicity conversions, obtained with the large sample of MaNGA, are robust against the influence of diffuse ionized gas, redshift, effective radius, and spatial blurring, and are therefore consistent across both integrated spectra and the high-resolution integral field spectroscopy data.
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Cao, Qing, und Guifu Zhang. „Errors in Estimating Raindrop Size Distribution Parameters Employing Disdrometer and Simulated Raindrop Spectra“. Journal of Applied Meteorology and Climatology 48, Nr. 2 (01.02.2009): 406–25. http://dx.doi.org/10.1175/2008jamc2026.1.
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Abstract There have been debates and differences of opinion over the validity of using drop size distribution (DSD) models to characterize precipitation microphysics and to retrieve DSD parameters from multiparameter radar measurements. In this paper, simulated and observed rain DSDs are used to evaluate moment estimators. Seven estimators for gamma DSD parameters are evaluated in terms of the biases and fractional errors of five integral parameters: radar reflectivity (ZH), differential reflectivity (ZDR), rainfall rate (R), mean volume diameter (Dm), and total number concentration (NT). It is shown that middle-moment estimators such as M234 (using the second-third-fourth moments) produce smaller errors than lower- and higher-moment estimators if the DSD follows the gamma distribution. However, if there are model errors, the performance of M234 degrades. Even though the DSD parameters can be biased in moment estimators, integral parameters are usually not. Maximum likelihood (ML) and L-moment (LM) estimators perform similarly to low-moment estimators such as M012. They are sensitive to both model error and the measurement errors of the low ends of DSDs. The overall differences among M234, M246, and M346 are not substantial for the five evaluated parameters. This study also shows that the discrepancy between the radar and disdrometer observations cannot be reduced by using these estimators. In addition, the previously found constrained-gamma model is shown not to be exclusively determined by error effects. Rather, it is equivalent to the mean function of normalized DSDs derived through Testud’s approach, and linked to precipitation microphysics.
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Seidl, Regina, Stephanie Weiss, Rudolf W. Kessler, Waltraud Kessler, Edith M. Zikulnig-Rusch und Andreas Kandelbauer. „Prediction of Residual Curing Capacity of Melamine-Formaldehyde Resins at an Early Stage of Synthesis by In-Line FTIR Spectroscopy“. Polymers 13, Nr. 15 (31.07.2021): 2541. http://dx.doi.org/10.3390/polym13152541.
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Melamine-formaldehyde (MF) resins are widely used as surface finishes for engineered wood-based panels in decorative laminates. Since no additional glue is applied in lamination, the overall residual curing capacity of MF resins is of great technological importance. Residual curing capacity is measured by differential scanning calorimetry (DSC) as the exothermic curing enthalpy integral of the liquid resin. After resin synthesis is completed, the resulting pre-polymer has a defined chemical structure with a corresponding residual curing capacity. Predicting the residual curing capacity of a resin batch already at an early stage during synthesis would enable corrective measures to be taken by making adjustments while synthesis is still in progress. Thereby, discarding faulty batches could be avoided. Here, by using a batch modelling approach, it is demonstrated how quantitative predictions of MF residual curing capacity can be derived from inline Fourier Transform infrared (FTIR) spectra recorded during resin synthesis using partial least squares regression. Not only is there a strong correlation (R2 = 0.89) between the infrared spectra measured at the end of MF resin synthesis and the residual curing capacity. The inline reaction spectra obtained already at the point of complete dissolution of melamine upon methylolation during the initial stage of resin synthesis are also well suited for predicting final curing performance of the resin. Based on these IR spectra, a valid regression model (R2 = 0.85) can be established using information obtained at a very early stage of MF resin synthesis.
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Farrell, W. E., J. Berger, J. R. Bidlot, M. Dzieciuch, W. Munk, R. A. Stephen und P. F. Worcester. „Wind Sea behind a Cold Front and Deep Ocean Acoustics“. Journal of Physical Oceanography 46, Nr. 6 (Juni 2016): 1705–16. http://dx.doi.org/10.1175/jpo-d-15-0221.1.
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AbstractA rapid and broadband (1 h, 1 < f < 400 Hz) increase in pressure and vertical velocity on the deep ocean floor was observed on seven instruments comprising a 20-km array in the northeastern subtropical Pacific. The authors associate the jump with the passage of a cold front and focus on the 4- and 400-Hz spectra. At every station, the time of the jump is consistent with the front coming from the northwest. The apparent rate of progress, 10–20 km h−1 (2.8–5.6 m s−1), agrees with meteorological observations. The acoustic radiation below the front is modeled as arising from a moving half-plane of uncorrelated acoustic dipoles. The half-plane is preceded by a 10-km transition zone, over which the radiator strength increases linearly from zero. With this model, the time derivative of the jump at a station yields a second and independent estimate of the front’s speed, 8.5 km h−1 (2.4 m s−1). For the 4-Hz spectra, the source physics is taken to be Longuet-Higgins radiation. Its strength depends on the quantity , where Fζ is the wave amplitude power spectrum and I the overlap integral. Thus, the 1-h time constant observed in the bottom data implies a similar time constant for the growth of the wave field quantity behind the front. The spectra at 400 Hz have a similar time constant, but the jump occurs 25 min later. The implications of this difference for the source physics are uncertain.
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Leckler, Fabien, Fabrice Ardhuin, Charles Peureux, Alvise Benetazzo, Filippo Bergamasco und Vladimir Dulov. „Analysis and Interpretation of Frequency–Wavenumber Spectra of Young Wind Waves“. Journal of Physical Oceanography 45, Nr. 10 (Oktober 2015): 2484–96. http://dx.doi.org/10.1175/jpo-d-14-0237.1.
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AbstractThe energy level and its directional distribution are key observations for understanding the energy balance in the wind-wave spectrum between wind-wave generation, nonlinear interactions, and dissipation. Here, properties of gravity waves are investigated from a fixed platform in the Black Sea, equipped with a stereo video system that resolves waves with frequency f up to 1.4 Hz and wavelengths from 0.6 to 11 m. One representative record is analyzed, corresponding to young wind waves with a peak frequency fp = 0.33 Hz and a wind speed of 13 m s−1. These measurements allow for a separation of the linear waves from the bound second-order harmonics. These harmonics are negligible for frequencies f up to 3 times fp but account for most of the energy at higher frequencies. The full spectrum is well described by a combination of linear components and the second-order spectrum. In the range 2fp to 4fp, the full frequency spectrum decays like f−5, which means a steeper decay of the linear spectrum. The directional spectrum exhibits a very pronounced bimodal distribution, with two peaks on either side of the wind direction, separated by 150° at 4fp. This large separation is associated with a significant amount of energy traveling in opposite directions and thus sources of underwater acoustic and seismic noise. The magnitude of these sources can be quantified by the overlap integral I(f), which is found to increase sharply from less than 0.01 at f = 2fp to 0.11 at f = 4fp and possibly up to 0.2 at f = 5fp, close to the 0.5π value proposed in previous studies.
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Abdalla, H., F. Aharonian, F. Ait Benkhali, E. O. Angüner, M. Arakawa, C. Arcaro, C. Armand et al. „The starburst galaxy NGC 253 revisited by H.E.S.S. and Fermi-LAT“. Astronomy & Astrophysics 617 (September 2018): A73. http://dx.doi.org/10.1051/0004-6361/201833202.
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Context. NGC 253 is one of only two starburst galaxies found to emit γ-rays from hundreds of MeV to multi-TeV energies. Accurate measurements of the very-high-energy (VHE; E > 100 GeV) and high-energy (HE; E > 60 MeV) spectra are crucial to study the underlying particle accelerators, probe the dominant emission mechanism(s) and to study cosmic-ray interaction and transport. Aims. The measurement of the VHE γ-ray emission of NGC 253 published in 2012 by H.E.S.S. was limited by large systematic uncertainties. Here, the most up to date measurement of the γ-ray spectrum of NGC 253 is investigated in both HE and VHE γ-rays. Assuming a hadronic origin of the γ-ray emission, the measurement uncertainties are propagated into the interpretation of the accelerated particle population. Methods. The data of H.E.S.S. observations are reanalysed using an updated calibration and analysis chain. The improved Fermi–LAT analysis employs more than 8 yr of data processed using pass 8. The cosmic-ray particle population is evaluated from the combined HE–VHE γ-ray spectrum using NAIMA in the optically thin case. Results. The VHE γ-ray energy spectrum is best fit by a power-law distribution with a flux normalisation of (1.34 ± 0.14stat ± 0.27sys) × 10−13 cm−2 s−1 TeV1 at 1 TeV – about 40% above, but compatible with the value obtained in Abramowski et al. (2012). The spectral index Γ = 2.39 ± 0.14stat ± 0.25sys is slightly softer than but consistent with the previous measurement within systematic errors. In the Fermi energy range an integral flux of F(E > 60 MeV) = (1.56 ± 0.28stat ± 0.15sys) × 10−8 cm−2 s−1 is obtained. At energies above ∼3 GeV the HE spectrum is consistent with a power-law ranging into the VHE part of the spectrum measured by H.E.S.S. with an overall spectral index Γ = 2.22 ± 0.06stat. Conclusions. Two scenarios for the starburst nucleus are tested, in which the gas in the starburst nucleus acts as either a thin or a thick target for hadronic cosmic rays accelerated by the individual sources in the nucleus. In these two models, the level to which NGC 253 acts as a calorimeter is estimated to a range of fcal = 0.1 to 1 while accounting for the measurement uncertainties. The presented spectrum is likely to remain the most accurate measurements until the Cherenkov Telescope Array (CTA) has collected a substantial set of data towards NGC 253.
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Fedorova, Elena, B. I. Hnatyk, V. I. Zhdanov und A. Del Popolo. „X-ray Properties of 3C 111: Separation of Primary Nuclear Emission and Jet Continuum“. Universe 6, Nr. 11 (21.11.2020): 219. http://dx.doi.org/10.3390/universe6110219.
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3C111 is BLRG with signatures of both FSRQ and Sy1 in X-ray spectrum. The significant X-ray observational dataset was collected for it by INTEGRAL, XMM-Newton, SWIFT, Suzaku and others. The overall X-ray spectrum of 3C 111 shows signs of a peculiarity with the large value of the high-energy cut-off typical rather for RQ AGN, probably due to the jet contamination. Separating the jet counterpart in the X-ray spectrum of 3C 111 from the primary nuclear counterpart can answer the question is this nucleus truly peculiar or this is a fake “peculiarity” due to a significant jet contribution. In view of this question, our aim is to estimate separately the accretion disk/corona and non-thermal jet emission in the 3C 111 X-ray spectra within different observational periods. To separate the disk/corona and jet contributions in total continuum, we use the idea that radio and X-ray spectra of jet emission can be described by a simple power-law model with the same photon index. This additional information allows us to derive rather accurate values of these contributions. In order to test these results, we also consider relations between the nuclear continuum and the line emission.
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Adegoke, Oluwashina, Banibrata Mukhopadhyay und Ranjeev Misra. „Correlating the non-linear time series and spectral properties of IGR J17091–3624: is it similar to GRS 1915+105?“ Monthly Notices of the Royal Astronomical Society 492, Nr. 3 (28.01.2020): 4033–42. http://dx.doi.org/10.1093/mnras/staa071.
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ABSTRACT Using the correlation integral method, we explore the non-linear properties of IGR J17091–3624 by comparing the underlying behaviour to GRS 1915+105. We find that while GRS 1915+105 is known to reveal a combination of fractal (or even chaotic) and stochastic behaviours depending on its temporal class, IGR J17091–3624 mostly shows stochastic behaviour. Therefore, although several observations find that IGR J17091–3624 is similar to GRS 1915+105, and that they have temporal classes in common, the underlying non-linear time series analyses offer a different view. Nevertheless, the ratio of the Poisson noise to rms variation for IGR J17091–3624 turns out to be high, suggesting that it is dominated by Poisson noise. Hence it might plausibly lead to the suppression of its non-linear properties, if there is any. Indeed, IGR J17091–3624 is a very faint source compared with GRS 1915+105. However, by increasing the time bin, some of the temporal classes of IGR J17091–3624 show deviation from stochasticity, indicating the plausibility of a higher fractal dimension. Along with spectral analysis, overall IGR J17091–3624 seems to reveal three different accretion classes: slim, Keplerian and advective accretion discs.
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Bueler, Ed, Craig S. Lingle und Jed Brown. „Fast computation of a viscoelastic deformable Earth model for ice-sheet simulations“. Annals of Glaciology 46 (2007): 97–105. http://dx.doi.org/10.3189/172756407782871567.
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AbstractThe model used by Lingle and Clark (1985) to approximate the deformation of the Earth under a single ice stream is adapted to the purposes of continent-scale ice-sheet simulation. The model combines a layered elastic spherical Earth (Farrell, 1972) with a viscous half-space overlain by an elastic plate lithosphere (Cathles, 1975). For the half-space model we identify a new mathematical formulation, essentially a time-dependent partial differential equation, which generalizes and improves upon the standard elastic plate lithosphere with relaxing asthenosphere model widely used in ice-sheet simulation. The new formulation allows a significantly faster numerical strategy, a spectral collocation method based directly on the fast Fourier transform. We verify this method by comparing to an integral formula for a disk load. We also demonstrate that the magnitudes of numerical errors made in approximating coupled ice-flow/Earth-deformation systems are significantly smaller than pairwise differences between several Earth models. Our implementation of the Lingle and Clark (1985) model offers important features of spherical, layered, self-gravitating, viscoelastic Earth models without the computational expense.
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KLAASSEN, Corné H. W., Petra H. M. BOVEE-GEURTS, Godelieve L. J. DECALUWÉ und Willem J. DEGRIP. „Large-scale production and purification of functional recombinant bovine rhodopsin with the use of the baculovirus expression system“. Biochemical Journal 342, Nr. 2 (24.08.1999): 293–300. http://dx.doi.org/10.1042/bj3420293.
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Here we describe a generic procedure for the expression and purification of milligram quantities of functional recombinant eukaryotic integral membrane proteins, exemplified by hexahistidine-tagged bovine rhodopsin. These quantities were obtained with the recombinant baculovirus/Sf9 insect cell-based expression system in large-scale bioreactor cultures with the use of a serum-free and protein-free growth medium. After optimization procedures, expression levels up to 4 mg/l were established. The recombinant rhodopsin could be purified with high overall yield by using immobilized-metal-affinity chromatography on Ni2+-agarose. After reconstitution into a native lipid environment, the purified protein was functionally indistinguishable from native rhodopsin with regard to the following parameters: spectral absorbance band, structural changes after photoactivation, and G-protein activation. The procedures developed can be adapted to other membrane proteins. The ability to produce and purify tens of milligrams of functional recombinant eukaryotic membrane protein meets the ever-increasing demand of material necessary to perform detailed biochemical and structural biophysical studies that are essential in unravelling their working mechanism at a molecular level.
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Gómez, Celina, und Cary A. Mitchell. „Growth Responses of Tomato Seedlings to Different Spectra of Supplemental Lighting“. HortScience 50, Nr. 1 (Januar 2015): 112–18. http://dx.doi.org/10.21273/hortsci.50.1.112.
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Seedlings of six tomato (Solanum lycopersicum) cultivars (‘Maxifort’, ‘Komeett’, ‘Success’, ‘Felicity’, ‘Sheva Sheva’, and ‘Liberty’) were grown monthly for 2-week treatment periods to determine photomorphogenic and developmental responses to different light-quality treatments from supplemental lighting (SL) across changing solar daily light integrals (DLIs). Seedlings were grown in a glass-glazed greenhouse at a midnorth latitude (lat. 40° N, long. 86° W) under one of five lighting treatments: natural solar light only (control), natural + SL from a 100-W high-pressure sodium (HPS) lamp, or natural + SL from arrays of red and blue light-emitting diodes (LEDs) using 80% red + 20% blue, 95% red + 5% blue, or 100% red. Varying solar DLI occurred naturally for all treatments, whereas constant DLI of 5.1 mol·m−2·d−1 was provided for all SL treatments. Supplemental lighting increased hypocotyl diameter, epicotyl length, shoot dry weight, leaf number, and leaf expansion relative to the control, whereas hypocotyl elongation decreased when SL was applied. For all cultivars tested, the combination of red and blue in SL typically increased growth of tomato seedlings. These results indicate that blue light in SL has potential to increase overall seedling growth compared with blue-deficient LED SL treatments in overcast, variable-DLI climates.
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Fiorito, Luca, James Dyrda und Michael Fleming. „JEFF-3.3 covariance application to ICSBEP using SANDY and NDAST“. EPJ Web of Conferences 211 (2019): 07003. http://dx.doi.org/10.1051/epjconf/201921107003.
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Providing reliable estimates of the nuclear data contribution to the uncertainty of well-known integral benchmarks is fundamental to the validation and verification process for a nuclear data library. The Nuclear Energy Agency has produced and maintains the NDaST sensitivity tool, which integrates the DICE sensitivities and nuclear data covariances. This system has been used to rigorously and efficiently provide direct feedback to evaluators and streamline validation. For its future evolution and to identify high-priority development areas, NDaST is continuously compared against state-of-the-art codes that use different uncertainty propagation methodologies. In this work, NDaST was compared to the nuclear data sampling code SANDY for several ICSBEP criticality benchmarks using the JEFF-3.3 evaluated data. Despite excellent overall agreement for cross sections and fission neutron multiplcities, discrepancies due to processed covariance descriptions for angular distributions and prompt fission neutron spectra have identified areas where coordinated development of nuclear data covariance descriptions should be prioritised.
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Hammock, Hunter A., Dean A. Kopsell und Carl E. Sams. „Supplementary Blue and Red LED Narrowband Wavelengths Improve Biomass Yield and Nutrient Uptake in Hydroponically Grown Basil“. HortScience 55, Nr. 12 (Dezember 2020): 1888–97. http://dx.doi.org/10.21273/hortsci15267-20.
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Light emitting diodes (LEDs) can produce a wide range of narrowband wavelengths with varying intensities. Previous studies have demonstrated that supplemental blue (B) and red (R) wavelengths from LEDs impact plant development, physiology, and morphology. High-pressure sodium (HPS) lighting systems are commonly used in greenhouse production, but LEDs have gained popularity in recent years because of their improved energy efficiency and spectral control. Research is needed to determine the efficacy of supplementary B and R LED narrowband wavelengths compared with traditional lighting systems like HPS in terms of yield, quality, and energy consumption for a variety of greenhouse-grown high-value specialty crops. The objective of this study was to determine the impact of LED and HPS lighting on greenhouse hydroponic basil (Ocimum basilicum var. ‘Genovese’) biomass production and edible tissue nutrient concentrations across different growing seasons. Basil was chosen because of its high demand and value among restaurants and professional chefs. A total of eight treatments were used: one nonsupplemented natural light (NL) control; one HPS treatment; and six LED treatments (peaked at 447 nm/627 nm, ±20 nm) with progressive B/R ratios (10B/90R; 20B/80R; 30B/70R; 40B/60R; 50B/50R; and 60B/40R). Each supplemented light (SL) treatment provided 8.64 mol·m−2·d−1 (100 µmol·m−2·s−1, 24 h·d−1). The daily light integral (DLI) of the NL control averaged 9.5 mol·m−2·d−1 across all growing seasons (ranging from 4 to 18 mol·m−2·d−1). Relative humidity averaged 50%, with day/night temperatures averaging 27.4 °C/21.8 °C, respectively. LED treatments had the greatest total fresh biomass (FM) and dry biomass (DM) accumulation; biomass for LED treatments were 1.3 times greater on average than HPS, and 2 times greater than the NL control. Biomass partitioning revealed that the LED treatments had more FM and DM for the individual main stem, shoots, and leaves of each plant at varying levels. LED treatments resulted in greater height and main stem diameter. Some essential nutrient concentrations were impacted by SL treatments and growing season. An energy analysis revealed that on average, narrowband B/R LED treatments were 3 times more energy efficient at increasing biomass over HPS. LED treatments reduced SL energy cost per gram FM increase by 95% to 98% when compared with HPS. In addition, the rate of electricity consumption to biomass increase varied across LED treatments, which demonstrates that basil uses different B/R narrowband ratios at varying efficiencies. This experiment shows that spectral quality of both supplemental sources and natural sunlight impacts primary metabolic resource partitioning of basil. The application of LED lighting systems to supplement natural DLI and spectra during unfavorable growing seasons has the potential to increase overall biomass accumulation and nutrient concentrations in a variety of high-value specialty crops.
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Stern, Frederick, Robert Ettema und Javier Lazaro. „Dynamics of Continuous-Mode Icebreaking by a Polar-Class Hull—Part 2: Spectral Analysis“. Journal of Ship Research 33, Nr. 03 (01.09.1989): 236–51. http://dx.doi.org/10.5957/jsr.1989.33.3.236.
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Part 2 of this two-part paper presents additional results from an ice towing-tank study of a Polar-Class hull for two conditions: for one, the hull was free to pitch, heave, and undergo limited roll (free hull); for the other, the hull was restrained from motions (fixed hull). Measurements were made of resistance as well as motions and restraining forces and moments for the free-and fixed-hull conditions, respectively. In Part 1, the values of the mean and standard deviation for both conditions are compared and related to observed patterns of icebreaking. In Part 2, the spectral densities are examined with regard to the natural frequencies of hull motions and frequencies associated with icebreaking pattern to determine the dominant cycles of resistance and motions. A series of experiments was conducted to determine values of zero-speed natural frequencies and added-mass and damping coefficients for ice-covered conditions. The presence of an ice sheet significantly reduces the natural frequencies and increases the added-mass and damping coefficients. It was found that hull motions and icebreaking pattern determined the dominant cycles of resistance for the free hull. Icebreaking frequency, the frequency of individual breaking events, was significant only for thin ice such that significant heave and pitch did not occur. When w b was less than the natural frequencies of coupled heave and pitch amid ice, w the dominant frequency of resistance and motions occurred at integral fractions of usually b/2. The frequencies, (b/n, are associated with the icebreaking pattern, that is, cyclic manner by which hull trim changed as the hull broke and cleared a track through an ice sheet. When b equaled or exceeded to„, the dominant frequency of resistance coincided with The fixed hull responded at higher frequencies than the free hull, usually at u>0. Also, available full-scale data are shown to be in reasonable agreement with the present results for the free hull. Lastly, the principal conclusions of the overall study are summarized and the implications of the present work with regard to the development of prediction methods are discussed.
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Hertkorn, N., M. Harir, B. P. Koch, B. Michalke, P. Grill und P. Schmitt-Kopplin. „High field NMR spectroscopy and FTICR mass spectrometry: powerful discovery tools for the molecular level characterization of marine dissolved organic matter from the South Atlantic Ocean“. Biogeosciences Discussions 9, Nr. 1 (19.01.2012): 745–833. http://dx.doi.org/10.5194/bgd-9-745-2012.
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Abstract. Non target high resolution organic structural spectroscopy of marine dissolved organic matter (DOM) isolated on 27 November 2008 by means of solid phase extraction (SPE) from four different depths in the South Atlantic Ocean off the Angola coast (3.1° E; −17.7° S; Angola basin) provided molecular level information of complex unknowns with unprecedented coverage and resolution. The sampling was intended to represent major characteristic oceanic regimes of general significance: 5 m (FISH; near surface photic zone), 48 m (FMAX; fluorescence maximum), 200 m (upper mesopelagic zone) and 5446 m (30 m above ground). 800 MHz proton (1H) nuclear magnetic resonance (NMR) 1H NMR, spectra were least affected by fast and differential transverse NMR relaxation and produced at first similar looking, rather smooth bulk NMR envelopes reflecting intrinsic averaging from massive signal overlap. Visibly resolved NMR signatures were most abundant in surface DOM but contributed at most a few percent to the total 1H NMR integral and were mainly limited to unsaturated and singly oxygenated carbon chemical environments. The relative abundance and variance of resolved signatures between samples was maximal in the aromatic region; in particular, the aromatic resolved NMR signature of the deep ocean sample at 5446 m was considerably different from that of all other samples. When scaled to equal total NMR integral, 1H NMR spectra of the four marine DOM samples revealed considerable variance in abundance for all major chemical environments across the entire range of chemical shift. Abundance of singly oxygenated CH units and acetate derivatives declined from surface to depth whereas aliphatics and carboxyl-rich alicyclic molecules (CRAM) derived molecules increased in abundance. Surface DOM contained a remarkably lesser abundance of methyl esters than all other marine DOM, likely a consequence of photodegradation from direct exposure to sunlight. All DOM showed similar overall 13C NMR resonance envelopes typical of an intricate mixture of natural organic matter with noticeable peaks of anomerics and C-aromatics carbon whereas oxygenated aromatics and ketones were of too low abundance to result in noticeable humps at the S/N ratio provided. Integration according to major substructure regimes revealed continual increase of carboxylic acids and ketones from surface to deep marine DOM, reflecting a progressive oxygenation of marine DOM, with concomitant decline of carbohydrate-related substructures. Isolation of marine DOM by means of SPE likely discriminated against carbohydrates but produced materials with beneficial NMR relaxation properties: a substantial fraction of dissolved organic molecules present allowed the acquisition of two-dimensional NMR spectra with exceptional resolution. JRES, COSY and HMBC NMR spectra were capable to depict resolved molecular signatures of compounds exceeding a certain minimum abundance. Here, JRES spectra suffered from limited resolution whereas HMBC spectra were constrained because of limited S/N ratio. Hence, COSY NMR spectra appeared best suited to depict organic complexity in marine DOM. The intensity and number of COSY cross peaks was found maximal for sample FMAX and conformed to about 1500 molecules recognizable in variable abundance. Surface DOM (FISH) produced a slightly (~25%) lesser number of cross peaks with remarkable positional accordance to FMAX (~80% conforming COSY cross peaks were found in FISH and FMAX). With increasing water depth, progressive attenuation of COSY cross peaks was caused by fast transverse NMR relaxation of yet unknown origin. However, most of the faint COSY cross peak positions of deep water DOM conformed to those observed in the surface DOM, suggesting the presence of a numerous set of identical molecules throughout the entire ocean column even if the investigated water masses belonged to different oceanic regimes and currents. Aliphatic chemical environments of methylene (CH2) and methyl (CH3) in marine DOM were nicely discriminated in DEPT HSQC NMR spectra. Classical methyl groups terminating aliphatic chains represented only ~15% of total methyl in all marine DOM investigated. Chemical shift anisotropy from carbonyl derivatives (i.e. most likely carboxylic acids) displaced aliphatic methyl 1H NMR resonances up to δH ~1.6 ppm, indicative of alicyclic geometry which furnishes more numerous short range connectivities for any given atom pairs. A noticeable fraction of methyl (~2%) was bound to olefinic carbon. The comparatively large abundance of methyl ethers in surface marine DOM contrasted with DOM of freshwater and soil origin. The chemical diversity of carbohydrates as indicated by H2CO-groups (δC ~ 62 ± 2 ppm) and anomerics (δC ~ 102 ± 7 ppm) exceeded that of freshwater and soil DOM considerably. HSQC NMR spectra were best suited to identify chemical environments of methin carbon (CH) and enabled discrimination of olefinic and aromatic cross peaks (δC > 110 ppm) and those of doubly oxygenated carbon (δC < 110 ppm). The abundance of olefinic protons exceeded that of aromatic protons; comparison of relative HSQC cross peak integrals indicated larger abundance of olefinic carbon than aromatic carbon in all marine DOM as well. A considerable fraction of olefins seemed isolated and likely sterically constrained as judged from small nJHH couplings associated with those olefins. High S/N ratio and fair resolution of TOCSY and HSQC cross peaks enabled unprecedented depiction of sp2-hybridized carbon chemical environments in marine DOM with discrimination of isolated and conjugated olefins as well as α, β-unsaturated double bonds. However, contributions from five-membered heterocycles (furan, pyrrol and thiophene derivatives) even if very unlikely from given elemental C/N and C/S ratios and upfield proton NMR chemical shift (δH < 6.5 ppm) could not yet been ruled out entirely. In addition to classical aromatic DOM, like benzene derivatives and phenols, six-membered nitrogen heterocycles were found prominent contributors to the downfield region of proton chemical shift (δH > 8 ppm). Specifically, a rather confined HSQC cross peak at δH/δC = 8.2/164 ppm indicated a limited set of nitrogen heterocycles with several nitrogen atoms in analogy to RNA derivatives present in all four marine DOM. Appreciable amounts of extended HSQC and TOCSY cross peaks derived from various key polycyclic aromatic hydrocarbon substructures suggested the presence of previously proposed but NMR invisible thermogenic organic matter (TMOC) in marine DOM at all water depths. Eventually, olefinic unsaturation in marine DOM will be more directly traceable to ultimate biogenic precursors than aromatic unsaturation of which a substantial fraction originates from an aged material which from the beginning was subjected to complex and less specific biogeochemical reactions like thermal decomposition. The variance in molecular mass as indicated from Fourier transform ion cyclotron resonance (FTICR) mass spectra was limited and could not satisfactorily explain the observed disparity in NMR transverse relaxation of the four marine DOM samples. Likewise, the presence of metal ions in isolated marine DOM remained near constant or declined from surface to depth for important paramagnetic ions like Mn, Cr, Fe, Co, Ni and Cu. Iron in particular, a strong complexing paramagnetic ion, was found most abundant by a considerable margin in surface (FISH) marine DOM for which well resolved COSY cross peaks were observed. Hence, facile relationships between metal content of isolated DOM (which does not reflect authentic marine DOM metal content) and transverse NMR relaxation were not observed. High field (12 T) negative electrospray ionization FTICR mass spectra showed at first view rather conforming mass spectra for all four DOM samples with abundant CHO, CHNO, CHOS and CHNOS molecular series with slightly increasing numbers of mass peaks from surface to bottom DOM and similar fractions (~50%) of assigned molecular compositions throughout all DOM samples. The average mass increased from surface to bottom DOM by about 10 Dalton. The limited variance of FTICR mass spectra probably resulted from a rather inherent conformity of marine DOM at the mandatory level of intrinsic averaging provided by FTICR mass spectrometry, when many isomers unavoidably project on single nominal mass peaks. In addition, averaging from ion suppression added to the accordance observed. The proportion of CHO and CHNO molecular series increased from surface to depth whereas CHOS and especially CHNOS molecular series markedly declined. The abundance of certain aromatic CHOS compounds declined with water depth. For future studies, COSY NMR spectra appear best suited to assess organic molecular complexity of marine DOM and to define individual DOM molecules of yet unknown structure and function. Non-target organic structural spectroscopy at the level demonstrated here covered nearly all carbon present in marine DOM. The exhaustive characterization of complex unknowns in \\mbox{marine} DOM will reveal a meaningful assessment of individual marine biogeosignatures which carry the holistic memory of the oceanic water masses (Koch et al., 2011).
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Stephanie, Margareta Vania, Alexander A. Iskandar und May-On Tjia. „Bonding state energy of metal nanoparticle dimer and its dependence on nanosphere size and interparticle separation“. Journal of Nonlinear Optical Physics & Materials 27, Nr. 02 (Juni 2018): 1850018. http://dx.doi.org/10.1142/s0218863518500182.
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A study is conducted regarding the effects of particle size [Formula: see text] and interparticle separation [Formula: see text] on the electromagnetic (plasmon) coupling in a dimer of two identical metal nanospheres. The dimer states are modeled as the hybridized bonding and antibonding states of two isolated plasmon states, with the associated energies given in terms of the isolated plasmon energy ([Formula: see text], the coupling energy ([Formula: see text] and the overlap integral ([Formula: see text] of the constituent plasmonic fields. The resonance absorption energies of the isolated plasmon and the dimer in certain dielectric medium are calculated according to the Mie theory for incident light of parallel polarization along the dimer axis. The results are fitted with the bonding state energies of both Au and Ag nanosphere dimers for [Formula: see text] ranging within 10–20[Formula: see text]nm and x varied within [Formula: see text]–200[Formula: see text]nm in compliance with the restricted consideration of dipole absorption spectra. The excellent fits of the bonding state energies [Formula: see text] for the ranges of [Formula: see text] and [Formula: see text] variations are consistently achieved with [Formula: see text] around 0.99 by a single function of the form [Formula: see text] where [Formula: see text] and [Formula: see text] vary with the nanosphere materials and the surrounding media considered. This result suggests the possible relation of the best fitted functional form [Formula: see text] with the underlying physical mechanism.
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KORRES, G., A. PAPADOPOULOS, P. KATSAFADOS, D. BALLAS, L. PERIVOLIOTIS und K. NITTIS. „A 2-year intercomparison of the WAM-Cycle4 and the WAVEWATCH-III wave models implemented within the Mediterranean Sea“. Mediterranean Marine Science 12, Nr. 1 (18.04.2011): 129. http://dx.doi.org/10.12681/mms.57.
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In this work we present the implementation of a wave forecast/hindcast system for the Mediterranean Sea at a 1/10º horizontal resolution and we show a first assessment of its performance by inter-comparing model results to observational data time series at selected points for the period 2000-2001. The system which is part of the POSEIDON-II operational system includes the WAM – Cycle4 and the WAVEWATCH-III wave forecast models (implemented within the same region) one way coupled with the non-hydrostatic version of the ETA atmospheric model which provides at 3-hour intervals the necessary wind velocity fields to the wave models. The same system but based on the WAM-Cycle4 wave model, has been used in the past for the production of the Aegean Sea wind and wave Atlas. Overall, the inter-comparison shows that both wave models are rather skilful in predicting the integral wave parameters with significant wave height skill scores in the range 0.85-0.90 and mean period scores in the range 0.77-0.83. It is also evident that WAM model has a tendency to overestimate mean wave periods while the opposite is true for WAVEWATCH-III model. Differences between the two models simulated spectra exist along the main passage of cyclonic systems over the Mediterranean Sea while in the wind seas dominated areas of the basin (the Aegean Sea for example) the two models show almost the same behavior.
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Corcho-Caballero, P., J. Casado, Y. Ascasibar und R. García-Benito. „Galaxy evolution on resolved scales: ageing and quenching in CALIFA“. Monthly Notices of the Royal Astronomical Society 507, Nr. 4 (04.09.2021): 5477–91. http://dx.doi.org/10.1093/mnras/stab2503.
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ABSTRACT This work investigates the fundamental mechanism(s) that drive galaxy evolution in the local Universe. By comparing two proxies of star formation sensitive to different time-scales, such as EW($\rm H\,\alpha$) and colours like g − r, one may distinguish between smooth secular evolution (ageing) and sudden changes (quenching) in the recent star formation history of galaxies. Building upon the results obtained from a former study based on 80 000 Sloan Digital Sky Survey (SDSS) single-fibre measurements, we now focus on spatially resolved (on kpc scales) galaxies, comparing with a sample of 637 nearby objects observed by the Calar Alto Legacy Integral-Field Area survey. In general, galaxies cannot be characterized in terms of a single ‘evolutionary stage’. Individual regions within galaxies arrange along a relatively narrow ageing sequence, with some intrinsic scatter possibly due to their different evolutionary paths. These sequences, though, differ from one galaxy to another, although they are broadly consistent with the overall distribution found for the (central) SDSS spectra. We find evidence of recent quenching episodes (relatively blue colours and strong $\rm H\,\alpha$ absorption) in a small fraction of galaxies (most notably, low-mass ellipticals), on global scales and individual regions (particularly at high metallicity). However, we argue that most of the systems, over their entire extent, are compatible with a secular inside-out scenario, where the evolutionary stage correlates with both global (mass, morphology, and environment) and local (surface brightness and metallicity) properties.
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Ferreras, Ignacio, Nicholas Scott, Francesco La Barbera, Scott Croom, Jesse van de Sande, Andrew Hopkins, Matthew Colless et al. „The SAMI galaxy survey: stellar population radial gradients in early-type galaxies“. Monthly Notices of the Royal Astronomical Society 489, Nr. 1 (06.08.2019): 608–22. http://dx.doi.org/10.1093/mnras/stz2095.
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ABSTRACT We study the internal radial gradients of the stellar populations in a sample comprising 522 early-type galaxies (ETGs) from the SAMI (Sydney-AAO Multi-object Integral field spectrograph) Galaxy Survey. We stack the spectra of individual spaxels in radial bins, and derive basic stellar population properties: total metallicity ([Z/H]), [Mg/Fe], [C/Fe] and age. The radial gradient (∇) and central value of the fits (evaluated at Re/4) are compared against a set of six observables that may act as drivers of the trends. We find that velocity dispersion (σ) – or, equivalently gravitational potential – is the dominant driver of the chemical composition gradients. Surface mass density is also correlated with the trends, especially with stellar age. The decrease of ∇[Mg/Fe] with increasing σ is contrasted by a rather shallow dependence of ∇[Z/H] with σ (although this radial gradient is overall rather steep). This result, along with a shallow age slope at the massive end, imposes a substantial constraint on the progenitors of the populations that contribute to the formation of the outer envelopes of ETGs. The SAMI sample is split, by design, between ‘field’ and cluster galaxies. Only weak environment-related differences are found, most notably a stronger dependence of central total metallicity ([Z/H]e4) with σ, along with a marginal trend of ∇[Z/H] to steepen in cluster galaxies, a result that is not followed by [Mg/Fe]. The results presented here serve as stringent constraints on numerical models of the formation and evolution of ETGs.
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Lutz, K. A., V. Kilborn, B. Catinella, L. Cortese, T. H. Brown und B. Koribalski. „The H IX galaxy survey“. Astronomy & Astrophysics 635 (März 2020): A69. http://dx.doi.org/10.1051/0004-6361/201936556.
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Context. This paper presents the analysis of optical integral field spectra for the H I eXtreme (H IX) galaxy sample. H IX galaxies host at least 2.5 times more atomic gas (H I) than expected from their optical R-band luminosity. Previous examination of their star formation activity and H I kinematics suggested that these galaxies stabilise their large H I discs (radii up to 94 kpc) against star formation due to their higher than average baryonic specific angular momentum. A comparison to semi-analytic models further showed that the elevated baryonic specific angular momentum is inherited from the high spin of the dark matter host. Aims. In this paper we now turn to the gas-phase metallicity as well as stellar and ionised gas kinematics in H IX galaxies to gain insights into recent accretion of metal-poor gas or recent mergers. Methods. We compare the stellar, ionised, and atomic gas kinematics, and examine the variation in the gas-phase metallicity throughout the stellar disc of H IX galaxies. Results. We find no indication for counter-rotation in any of the components, the central metallicities tend to be lower than average, but as low as expected for galaxies of similar H I mass. Metallicity gradients are comparable to other less H I-rich, local star forming galaxies. Conclusions. We conclude that H IX galaxies show no conclusive evidence for recent major accretion or merger events. Their overall lower metallicities are likely due to being hosted by high spin halos, which slows down their evolution and thus the enrichment of their interstellar medium.
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Scheu, Patrick D., Yun-Feng Liao, Julia Bauer, Holger Kneuper, Thomas Basché, Gottfried Unden und Wolfgang Erker. „Oligomeric Sensor Kinase DcuS in the Membrane of Escherichia coli and in Proteoliposomes: Chemical Cross-linking and FRET Spectroscopy“. Journal of Bacteriology 192, Nr. 13 (07.05.2010): 3474–83. http://dx.doi.org/10.1128/jb.00082-10.
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ABSTRACT DcuS is the membrane-integral sensor histidine kinase of the DcuSR two-component system in Escherichia coli that responds to extracellular C4-dicarboxylates. The oligomeric state of full-length DcuS was investigated in vitro and in living cells by chemical cross-linking and by f luorescence r esonance e nergy t ransfer (FRET) spectroscopy. The FRET results were quantified by an improved method using background-free spectra of living cells for determining FRET efficiency (E) and donor fraction {fD = (donor)/[(donor) + (acceptor)]}. Functional fusions of cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) variants of green fluorescent protein to DcuS were used for in vivo FRET measurements. Based on noninteracting membrane proteins and perfectly interacting proteins (a CFP-YFP fusion), the results of FRET of cells coexpressing DcuS-CFP and DcuS-YFP were quantitatively evaluated. In living cells and after reconstitution of purified recombinant DcuS in proteoliposomes, DcuS was found as a dimer or higher oligomer, independent of the presence of an effector. Chemical cross-linking with disuccinimidyl suberate showed tetrameric, in addition to dimeric, DcuS in proteoliposomes and in membranes of bacteria, whereas purified DcuS in nondenaturing detergent was mainly monomeric. The presence and amount of tetrameric DcuS in vivo and in proteoliposomes was not dependent on the concentration of DcuS. Only membrane-embedded DcuS (present in the oligomeric state) is active in (auto)phosphorylation. Overall, the FRET and cross-linking data demonstrate the presence in living cells, in bacterial membranes, and in proteoliposomes of full-length DcuS protein in an oligomeric state, including a tetramer.
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San Roman, I., A. J. Cenarro, L. A. Díaz-García, C. López-Sanjuan, J. Varela, R. M. González Delgado, P. Sánchez-Blázquez et al. „The ALHAMBRA survey: 2D analysis of the stellar populations in massive early-type galaxies at z < 0.3“. Astronomy & Astrophysics 609 (22.12.2017): A20. http://dx.doi.org/10.1051/0004-6361/201630313.
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We present a technique that permits the analysis of stellar population gradients in a relatively low-cost way compared to integral field unit (IFU) surveys. We developed a technique to analyze unresolved stellar populations of spatially resolved galaxies based on photometric multi-filter surveys. This technique allows the analysis of vastly larger samples and out to larger galactic radii. We derived spatially resolved stellar population properties and radial gradients by applying a centroidal Voronoi tessellation and performing a multicolor photometry spectral energy distribution fitting. This technique has been successfully applied to a sample of 29 massive (M⋆ > 1010.5M⊙) early-type galaxies at z < 0.3 from the ALHAMBRA survey. We produced detailed 2D maps of stellar population properties (age, metallicity, and extinction), which allow us to identify galactic features. Radial structures were studied, and luminosity-weighted and mass-weighted gradients were derived out to 2–3.5 Reff. We find that the spatially resolved stellar population mass, age, and metallicity are well represented by their integrated values. We find the gradients of early-type galaxies to be on average flat in age (∇log AgeL = 0.02 ± 0.06 dex/Reff) and negative in metallicity (∇[Fe/H]L = −0.09 ± 0.06 dex/Reff). Overall,the extinction gradients are flat (∇Av = −0.03 ± 0.09 mag/Reff ) with a wide spread. These results are in agreement with previous studies that used standard long-slit spectroscopy, and with the most recent IFU studies. According to recent simulations, these results are consistent with a scenario where early-type galaxies were formed through major mergers and where their final gradients are driven by the older ages and higher metallicity of the accreted systems. We demonstrate the scientific potential of multi-filter photometry to explore the spatially resolved stellar populations of local galaxies and confirm previous spectroscopic trends from a complementary technique.
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Hertkorn, N., M. Harir, B. P. Koch, B. Michalke und P. Schmitt-Kopplin. „High-field NMR spectroscopy and FTICR mass spectrometry: powerful discovery tools for the molecular level characterization of marine dissolved organic matter“. Biogeosciences 10, Nr. 3 (08.03.2013): 1583–624. http://dx.doi.org/10.5194/bg-10-1583-2013.
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Abstract. High-performance, non-target, high-resolution organic structural spectroscopy was applied to solid phase extracted marine dissolved organic matter (SPE-DOM) isolated from four different depths in the open South Atlantic Ocean off the Angola coast (3° E, 18° S; Angola Basin) and provided molecular level information with extraordinary coverage and resolution. Sampling was performed at depths of 5 m (Angola Current; near-surface photic zone), 48 m (Angola Current; fluorescence maximum), 200 m (still above Antarctic Intermediate Water, AAIW; upper mesopelagic zone) and 5446 m (North Atlantic Deep Water, NADW; abyssopelagic, ~30 m above seafloor) and produced SPE-DOM with near 40% carbon yield and beneficial nuclear magnetic resonance (NMR) relaxation properties, a crucial prerequisite for the acquisition of NMR spectra with excellent resolution. 1H and 13C NMR spectra of all four marine SPE-DOM showed smooth bulk envelopes, reflecting intrinsic averaging from massive signal overlap, with a few percent of visibly resolved signatures and variable abundances for all major chemical environments. The abundance of singly oxygenated aliphatics and acetate derivatives in 1H NMR spectra declined from surface to deep marine SPE-DOM, whereas C-based aliphatics and carboxyl-rich alicyclic molecules (CRAM) increased in abundance. Surface SPE-DOM contained fewer methyl esters than all other samples, likely a consequence of direct exposure to sunlight. Integration of 13C NMR spectra revealed continual increase of carboxylic acids and ketones from surface to depth, reflecting a progressive oxygenation, with concomitant decline of carbohydrate-related substructures. Aliphatic branching increased with depth, whereas the fraction of oxygenated aliphatics declined for methine, methylene and methyl carbon. Lipids in the oldest SPE-DOM at 5446 m showed a larger share of ethyl groups and methylene carbon than observed in the other samples. Two-dimensional NMR spectra showed exceptional resolution and depicted resolved molecular signatures in excess of a certain minimum abundance. Classical methyl groups terminating aliphatic chains represented ~15% of total methyl in all samples investigated. A noticeable fraction of methyl (~2%) was bound to olefinic carbon. Methyl ethers were abundant in surface marine SPE-DOM, and the chemical diversity of carbohydrates was larger than that of freshwater and soil DOM. In all samples, we identified sp2-hybridized carbon chemical environments with discrimination of isolated and conjugated olefins and α,β-unsaturated double bonds. Olefinic proton and carbon atoms were more abundant than aromatic ones; olefinic unsaturation in marine SPE-DOM will be more directly traceable to ultimate biogenic precursors than aromatic unsaturation. The abundance of furan, pyrrol and thiophene derivatives was marginal, whereas benzene derivatives, phenols and six-membered nitrogen heterocycles were prominent; a yet unassigned set of six-membered N-heterocycles with likely more than one single nitrogen occurred in all samples. Various key polycyclic aromatic hydrocarbon substructures suggested the presence of thermogenic organic matter at all water depths. Progressive NMR cross-peak attenuation from surface to deep marine SPE-DOM was particularly strong in COSY NMR spectra and indicated a continual disappearance of biosignatures as well as entropy gain from an ever increased molecular diversity. Nevertheless, a specific near-seafloor SPE-DOM signature of unsaturated molecules recognized in both NMR and Fourier transform ion cyclotron mass spectrometry (FTICR/MS) possibly originated from sediment leaching. The conformity of key NMR and FTICR/MS signatures suggested the presence of a large set of identical molecules throughout the entire ocean column even though the investigated water masses belonged to different oceanic regimes and currents. FTICR/MS showed abundant CHO, CHNO, CHOS and CHNOS molecular series with slightly increasing numbers of mass peaks and average mass from surface to bottom SPE-DOM. The proportion of CHO and CHNO negative ions increased from surface to depth, whereas CHOS and especially CHNOS molecular series markedly declined. While certain rather aliphatic CHOS and CHNOS ions were observed solely in the surface, deep marine SPE-DOM was enriched in unique unsaturated and rather oxygenated CHO and CHNO molecular series. With the exception of abyssopelagic SPE-DOM at 5446 m, which showed a peculiar CHOS chemistry of unsaturated carbon and reduced sulphur (black sulphur), CHO and CHNO molecular series contributed ~87% to total positive electrospray ionization FTICR mass peak integral, with a near constant ratio of CHNO / CHO molecular compositions near 1.13 ± 0.05. In case of all four marine SPE-DOM, remarkably disparate average elemental compositions as determined from either MS and NMR spectra were observed, caused by a pronounced ionization selectivity in electrospray ionization FTICR/MS. The study demonstrates that the exhaustive characterization of complex unknowns in marine DOM will enable a meaningful classification of individual marine biogeosignatures. Future in-depth functional biodiversity studies with a clear understanding of DOM structure and function might eventually lead to a novel, unified perception of biodiversity and biogeochemistry.
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Woo, Sangbeom, und Andrea Vacca. „Experimental Characterization and Evaluation of the Vibroacoustic Field of Hydraulic Pumps: The Case of an External Gear Pump“. Energies 13, Nr. 24 (16.12.2020): 6639. http://dx.doi.org/10.3390/en13246639.
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This paper presents the experimental characterization of the vibroacoustic fields and the evaluation of noise performances of hydraulic pumps. Research on hydraulic pump noise has traditionally focused on the fluid-borne noise sources, and very often the analyses of vibration and noise have been performed focusing on a few local points. This trend results in the lack of investigation on the overall behaviors of vibroacoustic fields of hydraulic pumps, and it has been one of the obstacles to understand the complete mechanisms of noise generation. Moreover, despite the existence of the ISO standards for the determination of noise levels, diverse metrics have been used for the evaluation of noise performances of the pumps, but the adequacy of these metrics has not been carefully examined. In this respect, this paper aims at introducing a way to characterize and interpret the measured vibroacoustic field and providing proper methods which are also capable of applying the ISO standards for the fair assessment of pump noise performances. For the characterization of the vibroacoustic field, operational deflection shapes (ODS) and corresponding radiated sound fields are visualized at harmonics of the pumping frequency by using a spectral analysis. Observations are made regarding the motions of the pump and its mounting plate and the resultant radiated noise, depending on the frequency, as well as their correlation. A numerical analysis using the Rayleigh integral equation is also performed to further investigate the contribution of the mounting plate motion on the noise radiation. For the evaluation of noise performance, two different units are tested at multiple operating conditions, and comparisons are made based on their measured sound power levels (SWLs) and sound pressure levels (SPLs). The results emphasize the importance of SWL measurement for the fair noise performance evaluation, and the two methods are proposed as practices to determine the minimum number of measurement points for practicability and to have reliable sound power determination for hydraulic pumps.
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Kamliya Jawahar, Hasan, Yujing Lin und Mark Savill. „Large eddy simulation of airfoil self-noise using OpenFOAM“. Aircraft Engineering and Aerospace Technology 90, Nr. 1 (02.01.2018): 126–33. http://dx.doi.org/10.1108/aeat-05-2015-0130.
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Purpose The purpose of this paper is to investigate airfoil self-noise generation and propagation by using a hybrid method based on the large-eddy simulation (LES) approach and Curle’s acoustic analogy as implemented in OpenFOAM. Design/methodology/approach Large-eddy simulation of near-field flow over a NACA6512-63 airfoil at zero angle of attack with a boundary layer trip at Rec = 1.9 × 105 has been carried out using the OpenFOAM® computational fluid dynamics (CFD) code. Calculated flow results are compared with published experimental data. The LES includes the wind tunnel installation effects by using appropriate inflow boundary conditions obtained from a RANS κ – ω SST model computation of the whole wind tunnel domain. Far-field noise prediction was achieved by an integral method based on Curle’s acoustic analogy. The predicted sound pressure levels are validated against the experimental data at various frequency ranges. Findings The numerical results presented in this paper show that the flow features around a NACA6512-63 airfoil have been correctly captured in OpenFOAM LES calculations. The mean surface pressure distributions and the local pressure peaks for the step trip setup agree very well with the experimental measurements. Aeroacoustic prediction using Curle’s analogy shows an overall agreement with the experimental data. The sound pressure level-frequency spectral analysis produces very similar data at low to medium frequency, whereas the experimentally observed levels are slightly over predicted at a higher frequency range. Practical implications This study has achieved and evaluated an alternative aeroacoustic simulation method based on the combination of LES with a simple Smagorinsky SGS model and Curle’s analogy, as implemented in the OpenFOAM CFD code. The unsteady velocity/pressure source data produced can be used for any simpler analytically based far-field noise prediction scheme. Originality/value A complete integration of the LES and Curle’s acoustic analogy for aeroacoustic simulations has been achieved in OpenFOAM. The capability and accuracy of the hybrid method are fully evaluated for high-camber airfoil self-noise predictions. Wind tunnel installation effects have been incorporated properly into the LES.
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Díaz, Argüelles K. M., Oro J. M. Fernández, E. Blanco Marigorta und C. Santolaria Morros. „Numerical prediction of tonal noise generation in an inlet vaned low-speed axial fan using a hybrid aeroacoustic approach“. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, Nr. 9 (02.06.2009): 2081–98. http://dx.doi.org/10.1243/09544062jmes1426.
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This work presents a numerical prediction of the tonal noise generation in a single-stage, axial flow fan, using a hybrid approach that first calculates the noise sources (generation) using conventional computational fluid dynamics (CFD) techniques, and then estimates the noise level in the blower far-field region (propagation) by means of an aeroacoustic analogy. As a starting point, an unsteady three-dimensional full-annulus simulation of the internal flow is carried out, using a wall-modelled large eddy simulation (WMLES) scheme for the turbulence closure to identify the acoustic sources. A well-tested commercial CFD package, FLUENT, was employed for that purpose, so a complete set of unsteady forces exerted over the blades was calculated. Following, a generalization of Lighthill's aeroacoustic analogy, the so-called Ffowcs Williams and Hawkings (FFWH) aeroacoustic analogy, was numerically implemented using a C++algorithm to resolve an integral formulation of the free-field FFWH wave equation, where CFD data are included in the source terms. The major contribution was expected to be found in the estimation of the tonal noise levels, directly linked to the intensity of the stator—rotor interaction phenomena. Additionally, intensive experimental measurements in the noise propagation region of the fan were conducted, in order to validate the numerical study. A reasonable agreement was found in the tonal noise spectra, although important discrepancies appeared due to the attenuation produced by the fan casing, not considered in the numerical model. Although limitations in the current computational resources led to the use of a relatively coarse mesh in the CFD modelling, the numerical study provided valuable information about the particular influence of the tonal noise sources, estimating accordingly overall experimental trends, and showing the potentiality of numerical tools to deal with noise control for designers and researchers.
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Zentkova, Maria, und Marian Mihalik. „The Effect of Pressure on Magnetic Properties of Prussian Blue Analogues“. Crystals 9, Nr. 2 (20.02.2019): 112. http://dx.doi.org/10.3390/cryst9020112.
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We present the review of pressure effect on the crystal structure and magnetic properties of Cr(CN)6-based Prussian blue analogues (PBs). The lattice volume of the fcc crystal structure space group Fm 3 ¯ m in the Mn-Cr-CN-PBs linearly decreases for p ≤ 1.7 GPa, the change of lattice size levels off at 3.2 GPa, and above 4.2 GPa an amorphous-like structure appears. The crystal structure recovers after removal of pressure as high as 4.5 GPa. The effect of pressure on magnetic properties follows the non-monotonous pressure dependence of the crystal lattice. The amorphous like structure is accompanied with reduction of the Curie temperature (TC) to zero and a corresponding collapse of the ferrimagnetic moment at 10 GPa. The cell volume of Ni-Cr-CN-PBs decreases linearly and is isotropic in the range of 0–3.1 GPa. The Raman spectra can indicate a weak linkage isomerisation induced by pressure. The Curie temperature in Mn2+-CrIII-PBs and Cr2+-CrIII-PBs with dominant antiferromagnetic super-exchange interaction increases with pressure in comparison with decrease of TC in Ni2+-CrIII-PBs and Co2+-CrIII-PBs ferromagnets. TC increases with increasing pressure for ferrimagnetic systems due to the strengthening of magnetic interaction because pressure, which enlarges the monoelectronic overlap integral S and energy gap ∆ between the mixed molecular orbitals. The reduction of bonding angles between magnetic ions connected by the CN group leads to a small decrease of magnetic coupling. Such a reduction can be expected on both compounds with ferromagnetic and ferrimagnetic ordering. In the second case this effect is masked by the increase of coupling caused by the enlarged overlap between magnetic orbitals. In the case of mixed ferro–ferromagnetic systems, pressure affects μ(T) by a different method in Mn2+–N≡C–CrIII subsystem and CrIII–C≡N–Ni2+ subsystem, and as a consequence Tcomp decreases when the pressure is applied. The pressure changes magnetization processes in both systems, but we expect that spontaneous magnetization is not affected in Mn2+-CrIII-PBs, Ni2+-CrIII-PBs, and Co2+-CrIII-PBs. Pressure-induced magnetic hardening is attributed to a change in magneto-crystalline anisotropy induced by pressure. The applied pressure reduces saturated magnetization of Cr2+-CrIII-PBs. The applied pressure p = 0.84 GPa induces high spin–low spin transition of cca 4.5% of high spin Cr2+. The pressure effect on magnetic properties of PBs nano powders and core–shell heterostructures follows tendencies known from bulk parent PBs.
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Koppelman, Helmer H., Amina Helmi, Davide Massari, Adrian M. Price-Whelan und Tjitske K. Starkenburg. „Multiple retrograde substructures in the Galactic halo: A shattered view of Galactic history“. Astronomy & Astrophysics 631 (November 2019): L9. http://dx.doi.org/10.1051/0004-6361/201936738.
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Aims. Several kinematic and chemical substructures have been recently found amongst Milky Way halo stars with retrograde motions. It is currently unclear how these various structures are related to each other. This Letter aims to shed light on this issue. Methods. We explore the retrograde halo with an augmented version of the Gaia DR2 RVS sample, extended with data from three large spectroscopic surveys, namely RAVE, APOGEE, and LAMOST. In this dataset, we identify several structures using the HDBSCAN clustering algorithm. We discuss their properties and possible links using all the available chemical and dynamical information. Results. In concordance with previous work, we find that stars with [Fe/H] < −1 have more retrograde motions than those with [Fe/H] > −1. The retrograde halo contains a mixture of debris from objects like Gaia-Enceladus, Sequoia, and even the chemically defined thick disc. We find that the Sequoia has a smaller range in orbital energies than previously suggested and is confined to high energy. Sequoia could be a small galaxy in itself, but since it overlaps both in integrals-of-motion space and chemical abundance space with the less bound debris of Gaia-Enceladus, its nature cannot yet be fully settled. In the low-energy part of the halo, we find evidence for at least one more distinct structure: Thamnos. Stars in Thamnos are on low-inclination, mildly eccentric retrograde orbits, moving at vϕ ≈ −150 km s−1, and are chemically distinct from the other structures. Conclusions. Even with the excellent Gaia DR2 data, piecing together all the fragments found in the retrograde halo remains challenging. At this point, we are very much in need of large datasets with high-quality high-resolution spectra and tailored high-resolution hydrodynamical simulations of galaxy mergers.
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Torres, Benjamin, und David Fuertes. „Characterization of aerosol size properties from measurements of spectral optical depth: a global validation of the GRASP-AOD code using long-term AERONET data“. Atmospheric Measurement Techniques 14, Nr. 6 (17.06.2021): 4471–506. http://dx.doi.org/10.5194/amt-14-4471-2021.
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Abstract. A validation study is conducted regarding aerosol optical size property retrievals from measurements of the direct sun beam only (without the aid of diffuse radiation). The study focuses on using real data to test the new GRASP-AOD application, which uses only spectral optical depth measurements to retrieve the total column aerosol size distributions, assumed to be bimodal lognormal. In addition, a set of secondary integral parameters of aerosol size distribution and optical properties are provided: effective radius, total volume concentration and fine-mode fraction of aerosol optical depth (AOD). The GRASP-AOD code is applied to almost 3 million observations acquired over 20 years (1997–2016) at 30 AERONET (Aerosol Robotic Network) sites. These validation sites have been selected based on known availability of an extensive data record, significant aerosol load variability throughout the year, wide worldwide coverage and diverse aerosol types and source regions. The output parameters are compared to those coming from the operational AERONET retrievals. The retrieved fine-mode fractions at 500 nm (τf(500)) obtained by the GRASP-AOD application are compared to those retrieved by the spectral deconvolution algorithm (SDA) and by the AERONET aerosol retrieval algorithm. The size distribution properties obtained by the GRASP-AOD are compared to their equivalent values from the AERONET aerosol retrieval algorithm. The analysis showed the convincing capacity of the GRASP-AOD approach to successfully discriminate between fine- and coarse-mode extinction to robustly retrieve τf(500). The comparisons of 2 million results of τf(500) retrieval by the GRASP-AOD and SDA showed high correlation with a root mean square error (RMSE) of 0.015. Also, the analysis showed that the τf(500) values computed by the AERONET aerosol retrieval algorithm agree slightly better with the GRASP-AOD (RMSE = 0.018, from 148 526 comparisons) than with the SDA (RMSE = 0.022, from 127 203 comparisons). The comparisons of the size distribution retrieval showed agreement for the fine-mode median radius between the GRASP-AOD and AERONET aerosol retrieval algorithm results with an RMSE of 0.032 µm (or 18.7 % in relative terms) for the situations when τ(440)>0.2 occur for more than 80 000 pairs of the study. For the cases where the fine mode is dominant (i.e., α>1.2), the RMSE is only of 0.023 µm (or 13.9 % in relative terms). Major limitations in the retrieval were found for the characterization of the coarse-mode details. For example, the analysis revealed that the GRASP-AOD retrieval is not sensitive to the small variations of the coarse-mode volume median radius for different aerosol types observed at different locations. Nonetheless the GRASP-AOD retrieval provides reasonable agreement with the AERONET aerosol retrieval algorithm for overall coarse-mode properties with with RMSE = 0.500 µm (RMSRE = 20 %) when τ(440)>0.2. The values of effective radius and total volume concentration computed from the GRASP-AOD retrieval have been compared to those estimated by the AERONET aerosol retrieval algorithm. The RMSE values of the correlations were 30 % for the effective radius and 25 % for the total volume concentration when τ(440)>0.2. Finally, the study discusses the importance of employing the assumption of bimodal lognormal size distribution. It also evaluates the potential of using ancillary data, in particular aureole measurements, for improving the characterization of the aerosol coarse-mode properties.
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Kalita-de Croft, Priyakshi, Jasmin Straube, Malcolm Lim, Fares Al-Ejeh, Sunil R. Lakhani und Jodi M. Saunus. „Proteomic Analysis of the Breast Cancer Brain Metastasis Microenvironment“. International Journal of Molecular Sciences 20, Nr. 10 (22.05.2019): 2524. http://dx.doi.org/10.3390/ijms20102524.
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Patients with brain-metastatic breast cancer face a bleak prognosis marked by morbidity and premature death. A deeper understanding of molecular interactions in the metastatic brain tumour microenvironment may inform the development of new therapeutic strategies. In this study, triple-negative MDA-MB-231 breast cancer cells or PBS (modelling traumatic brain injury) were stereotactically injected into the cerebral cortex of NOD/SCID mice to model metastatic colonization. Brain cells were isolated from five tumour-associated samples and five controls (pooled uninvolved and injured tissue) by immunoaffinity chromatography, and proteomic profiles were compared using the Sequential Window Acquisition of All Theoretical Mass Spectra (SWATH-MS) discovery platform. Ontology and cell type biomarker enrichment analysis of the 125 differentially abundant proteins (p < 0.05) showed the changes largely represent cellular components involved in metabolic reprogramming and cell migration (min q = 4.59 × 10−5), with high-throughput PubMed text mining indicating they have been most frequently studied in the contexts of mitochondrial dysfunction, oxidative stress and autophagy. Analysis of mouse brain cell type-specific biomarkers suggested the changes were paralleled by increased proportions of microglia, mural cells and interneurons. Finally, we orthogonally validated three of the proteins in an independent xenograft cohort, and investigated their expression in craniotomy specimens from triple-negative metastatic breast cancer patients, using a combination of standard and fluorescent multiplex immunohistochemistry. This included 3-Hydroxyisobutyryl-CoA Hydrolase (HIBCH), which is integral for gluconeogenic valine catabolism in the brain, and was strongly induced in both graft-associated brain tissue (13.5-fold by SWATH-MS; p = 7.2 × 10−4), and areas of tumour-associated, reactive gliosis in human clinical samples. HIBCH was also induced in the tumour compartment, with expression frequently localized to margins and haemorrhagic areas. These observations raise the possibility that catabolism of valine is an effective adaptation in metastatic cells able to access it, and that intermediates or products could be transferred from tumour-associated glia. Overall, our findings indicate that metabolic reprogramming dominates the proteomic landscape of graft-associated brain tissue in the intracranial MDA-MB-231 xenograft model. Brain-derived metabolic provisions could represent an exploitable dependency in breast cancer brain metastases.