612 research outputs found
Combined vertical-velocity observations with Doppler lidar, cloud radar and wind profiler
Case studies of combined vertical-velocity measurements of Doppler lidar, cloud radar and wind profiler are presented. The measurements were taken at the Meteorological Observatory, Lindenberg, Germany. Synergistic products are presented that are derived from the vertical-velocity measurements of the three instruments: a comprehensive classification mask of vertically moving atmospheric targets and the terminal fall velocity of water droplets and ice crystals corrected for vertical air motion. It is shown that this combination of instruments can up-value the measurement values of each single instrument and may allow the simultaneous sensing of atmospheric targets and the motion of clear air
Organofluorine chemistry : difluoromethylene motifs spaced 1,3 to each other imparts facial polarity to a cyclohexane ring
This work was supported by the Engineering and Physical Sciences Research Council (EPSRC) and the European Research Council (ERC). The authors acknowledge the EPSRC National Mass Spectrometry Facility (Swansea). D.OâH. thanks the Royal Society for a Wolfson Research Merit Award.2,2-Dimethyl-5-phenyl-1,1,3,3-tetrafluororocyclohexane has been prepared and characterised as an example of a facially polarised cyclohexane containing 1,3 related CF2 groups. The dipolar nature of the ring arises from the axial orientation of two of the C-F bonds pointing in the same direction, and set by the chair conformation of the cyclohexane. This electrostatic profile is revealed experimentally both in the solid-state (X-ray) packing of the rings and by solution (NMR) in different solvents. A computationally derived electrostatic profile of this compound is consistent with a more electronegative and a more electropositive face of the cyclohexane ring. This placing of CF2 groups 1,3 to each other in a cyclohexane ring is introduced as a new design strategy which could be applicable to the preparation of polar hydrophobic cyclohexane motifs.Publisher PDFPeer reviewe
Identification and Environmental Assessments for Different Scenarios of Repurposed Decommissioned Wind Turbine Blades
The rapidly growing wind industry poses a fundamental problem for wind turbine blade (WTB) disposal in many areas of
the world. WTBs are primarily manufactured from composites consisting of a thermoset matrix and reinforcing fibers. Currently,
there are no economically viable recycling technologies available for such large-scale composite products. Thus, other
treatment strategies for disposed WTBs have to be considered. This study explores the repurpose of WTBs as a promising
alternative approach from a processual and technological point of view. For this purpose, the study is guided by the categorization
into four different types of repurposed applications: high-loaded complete structure (T1), low-loaded complete
structure (T2), high-loaded segmented structure (T3), and low-loaded segmented structure (T4). A three-dimensional CAD
model of an Enercon-40/500 (E40) wind turbine blade is derived in a reverse engineering procedure to obtain knowledge
about the actual geometry of the WTB. Based on the design, three ecosystems of product scenarios (S) with different
manufacturing technologies involved are investigated: a climbing tower (S1), a playground (S2) and the combination of a
photovoltaic (PV)-floating pontoon, and a lounger (S3). A screening life cycle assessment (LCA) is conducted to evaluate
the three repurposed scenarios according to environmental aspects. It is shown that the repurpose of E40 WTB composite
material can reduce the environmental impact and leads to significant resource savings in relation to a reference product
of similar quality. A particularly high saving potential is identified for the substitution of emission-intensive materials in
construction applications. Furthermore, it is found that transport processes are the primary contributor to the environmental
impact of repurposed applications
Effect of ligand backbone on the selectivity and stability of rhodium hydroformylation catalysts derived from phospholane-phosphites
We thank the Eastman Chemical Company for funding and permission to publish. M.B. thanks the School of Chemistry and EaStCHEM for support.A study on how ligand backbone structure has an impact on selectivity, rate, and catalyst stability of hydroformylation catalysts was prompted by some longer-term stability issues being discovered for a phospholane-phosphite with a [âCH2Oâ] backbone. A series of phospholane-phosphite ligands were synthesized. Catalysts made in situ from these ligands and [Rh(acac)(CO)2] were found to give iso-butanal selectivities up to 75% at temperatures between 75 and 105 °C: the latter being a benchmark for iso-selectivity in reactions conducted at industrially meaningful temperatures. A racemic rhodium complex of a bidentate phospholane-phosphite from a tropos-biphenol with an extended backbone showed unusually high stability at high temperatures, combined with even better iso-selectivity in propene hydroformylation relative to the original complex. A related ligand with an electron-withdrawing group maintained the unusually high stability and improved activity. Characterization of the precatalysts of type [RhH(CO)2(L)] was accomplished using in situ HPIR spectroscopy and backed up by density functional theory calculations (B3PW91-D3 level) and by NMR studies; the latter showed that the variation of the backbone also had a pronounced impact on the precatalyst structure. A key finding is that it is now possible to prepare phospholane-phosphite ligands that deliver high iso-butanal selectivity and that show no signs of degradation after several days even above typical reaction temperatures. In one stability test, several kilograms of aldehydes were produced with TOF and selectivity being consistent over several days.PostprintPeer reviewe
Combining cloud radar and radar wind profiler for a value added estimate of vertical air motion and particle terminal velocity within clouds
Vertical-stare observations from a 482âMHz radar wind profiler and a
35âGHz cloud radar are combined on the level of individual Doppler
spectra to measure vertical air motions in clear air, clouds and
precipitation. For this purpose, a separation algorithm is proposed to remove
the influence of falling particles from the wind profiler Doppler spectra and
to calculate the terminal fall velocity of hydrometeors. The remaining error
of both vertical air motion and terminal fall velocity is estimated to be
better than 0.1âmâsâ1 using numerical simulations. This
combination of instruments allows direct measurements of in-cloud vertical
air velocity and particle terminal fall velocity by means of ground-based
remote sensing. The possibility of providing a profile every 10âs
with a height resolution of â<â100âm allows further insight into the
process scale of in-cloud dynamics. The results of the separation algorithm
are illustrated by two case studies, the first covering a deep frontal cloud
and the second featuring a shallow mixed-phase cloud.</p
Static dipole polarizability of C70 fullerene
The electronic and vibrational contributions to the static dipole
polarizability of C70 fullerene are determined using the finite-field method
within the density functional formalism. Large polarized Gaussian basis sets
augmented with diffuse functions are used and the exchange-correlation effects
are described within the Perdew-Burke-Ernzerhof generalized gradient
approximation (PBE-GGA). The calculated polarizability of C70 is 103
Angstrom^3, in excellent agreement with the experimental value of 102
Angstrom^3, and is completely determined by the electronic part, vibrational
contribution being negligible. The ratio of polarizabilities of C70 and C60 is
1.26. The comparison of polarizability calculated with only local terms (LDA)
in the PBE functional to that obtained with PBE-GGA shows that LDA is
sufficient to determine the static dipole polarizability of C70.Comment: IOP style, 1 figur
Der virtuelle Raum als Double - oder: zur Persistenz hierarchischer Gesellschaftsstruktur im Netz
Der raumsoziologische Beitrag diskutiert, was die mit der Technologie des Internets einhergehende Virtualisierung fĂŒr eine sich Ă€ndernde Gesellschaftsordnung bedeuten kann. Anhand ihres methodologischen RaumZeit-Modells zeigt die Autorin, dass die virtuelle RealitĂ€t des Internets eine doppelte materiale Gestalt hervorbringt. Als Double ergĂ€nzt der virtuelle Raum den realen. Die Ausgangsannahme lautet, dass die bĂŒrgerlich-moderne Gesellschaft Raum als ZweidimensionalitĂ€t und als BehĂ€lter sowie Zeit als messbar und linear hervorgebracht hat. Entgegen vielfach geĂ€uĂerter EinschĂ€tzungen revolutioniert das Internet nicht Vorstellungen und Praxis von Raum und Zeit, sondern es perfektioniert die bĂŒrgerliche Konstruktion des ideal beherrschbaren Lebens. Der Hypothese folgend, dass die neuen virtuellen RealitĂ€ten verĂ€nderte MaterialitĂ€ten etablieren, werden verschiedene Zukunftsszenarien am Beispiel des GeschlechterverhĂ€ltnisses durchgespielt
Global hybrids from the semiclassical atom theory satisfying the local density linear response
We propose global hybrid approximations of the exchange-correlation (XC)
energy functional which reproduce well the modified fourth-order gradient
expansion of the exchange energy in the semiclassical limit of many-electron
neutral atoms and recover the full local density approximation (LDA) linear
response. These XC functionals represent the hybrid versions of the APBE
functional [Phys. Rev. Lett. 106, 186406, (2011)] yet employing an additional
correlation functional which uses the localization concept of the correlation
energy density to improve the compatibility with the Hartree-Fock exchange as
well as the coupling-constant-resolved XC potential energy. Broad energetical
and structural testings, including thermochemistry and geometry, transition
metal complexes, non-covalent interactions, gold clusters and small
gold-molecule interfaces, as well as an analysis of the hybrid parameters, show
that our construction is quite robust. In particular, our testing shows that
the resulting hybrid, including 20\% of Hartree-Fock exchange and named hAPBE,
performs remarkably well for a broad palette of systems and properties, being
generally better than popular hybrids (PBE0 and B3LYP). Semi-empirical
dispersion corrections are also provided.Comment: 12 pages, 4 figure
DFT investigation of 3d transition metal NMR shielding tensors in diamagnetic systems using the gauge-including projector augmented-wave method
We present a density functional theory based method for calculating NMR
shielding tensors for 3d transition metal nuclei using periodic boundary
conditions. Calculations employ the gauge-including projector augmented-wave
pseudopotentials method. The effects of ultrasoft pseudopotential and induced
approximations on the second-order magnetic response are intensively examined.
The reliability and the strength of the approach for 49Ti and 51V nuclei is
shown by comparison with traditional quantum chemical methods, using benchmarks
of finite organometallic systems. Application to infinite systems is validated
through comparison to experimental data for the 51V nucleus in various vanadium
oxide based compounds. The successful agreement obtained for isotropic chemical
shifts contrasts with full estimation of the shielding tensor eigenvalues,
revealing the limitation of pure exchange-correlation functionals compared to
their exact-exchange corrected analogues.Comment: 56 page
The DACAPO-PESO campaign: Dynamics, Aerosol, Cloud and Precipitation Observations in the Pristine Environment of the Southern Ocean: An overview
This article gives an overview of the DACAPO-PESO field experiment,
which has taken place in Punta Arenas, Chile, from November 2018 to November 2021,
and showcases first exciting research results that have already emerged from it.In diesem Artikel wird ein Ăberblick ĂŒber das DACAPO-PESO
Experiment gegeben, welches von November 2018 bis November 2021 in Punta Arenas,
Chile, stattgefunden hat. AuĂerdem werden erste spannende Forschungsergebnisse
vorgestellt, die bereits daraus gewonnen wurden
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