1,625 research outputs found
Linking partial and quasi dynamical symmetries in rotational nuclei
Background: Quasi dynamical symmetries (QDS) and partial dynamical symmetries
(PDS) play an important role in the understanding of complex systems. Up to now
these symmetry concepts have been considered to be unrelated. Purpose:
Establish a link between PDS and QDS and find an emperical manifestation.
Methods: Quantum number fluctuations and the intrinsic state formalism are used
within the framework of the interacting boson model of nuclei. Results: A
previously unrecognized region of the parameter space of the interacting boson
model that has both O(6) PDS (purity) and SU(3) QDS (coherence) in the ground
band is established. Many rare-earth nuclei approximately satisfying both
symmetry requirements are identified. Conclusions: PDS are more abundant than
previously recognized and can lead to a QDS of an incompatible symmetry.Comment: 5 pages, 4 figures, 1 tabl
Elasticity-Dependent Self-assembly of Micro-Templated Chromonic Liquid Crystal Films
We explore micropatterned director structures of aqueous lyotropic chromonic
liquid crystal (LCLC) films created on square lattice cylindrical-micropost
substrates. The structures are manipulated by modulating the LCLC mesophases
and their elastic properties via concentration through drying. Nematic LCLC
films exhibit preferred bistable alignment along the diagonals of the micropost
lattice. Columnar LCLC films, dried from nematics, form two distinct director
and defect configurations: a diagonally aligned director pattern with local
squares of defects, and an off-diagonal configuration with zig-zag defects. The
formation of these states appears to be tied to the relative splay and bend
free energy costs of the initial nematic films. The observed nematic and
columnar configurations are understood numerically using a Landau-de Gennes
free energy model. Among other attributes, the work provide first examples of
quasi-2D micropatterning of LC films in the columnar phase and lyotropic LC
films in general, and it demonstrates alignment and configuration switching of
typically difficult-to-align LCLC films via bulk elastic properties.Comment: 9 pages; 9 figures; accepted for publication in Soft Matte
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Efficient palladium-catalyzed synthesis of 2-aryl propionic acids
A flexible two-step, one-pot procedure was developed to synthesize 2-aryl propionic acids including the anti-inflammatory drugs naproxen and flurbiprofen. Optimal results were obtained in the presence of the novel ligand neoisopinocampheyldiphenylphosphine (NISPCPP) (9) which enabled the efficient sequential palladium-catalyzed Heck coupling of aryl bromides with ethylene and hydroxycarbonylation of the resulting styrenes to 2-aryl propionic acids. This cascade transformation leads with high regioselectivity to the desired products in good yields and avoids the need for additional purification steps. © 2020 by the authors. Licensee MDPI, Basel, Switzerland
Inâsitu characterization of deposits in ceramic hollow fiber membranes by compressed sensing RAREâMRI
Ultrafiltration with ceramic hollow fiber membranes was investigated by compressed sensing rapid acquisition relaxation enhancement (CS-RARE) magnetic resonance imaging (MRI) to characterize filtration mechanisms. Sodium alginate was used as a model substance for extracellular polymeric substances. Dependent on the concentration of divalent ions like Ca21 in an aqueous alginate solution, the characteristics of the filtration change from concentration polarization to a gel layer. The fouling inside the membrane lumen could be measured by MRI with a CS-RARE pulse sequence. Contrast agents have been used to get an appropriate contrast between deposit and feed. The lumen was analyzed quantitatively by exploring the membraneâs radial symmetry, and the resulting intensity could be modeled. Thus, different fouling mechanisms could be distinguished. CS-RARE-MRI was proven to be an appropriate in situ tool to quantitatively characterize the deposit formation during in-out filtration processes. The results were underlined by flux interruption experiments and length dependent studies, which make it possible to differentiate between gel layer or cake filtration and concentration polarization filtration processes
Mining for Process Improvements: Analyzing Software Repositories in Agile Retrospectives
Software Repositories contain knowledge on how software engineering teams
work, communicate, and collaborate. It can be used to develop a data-informed
view of a team's development process, which in turn can be employed for process
improvement initiatives. In modern, Agile development methods, process
improvement takes place in Retrospective meetings, in which the last
development iteration is discussed. However, previously proposed activities
that take place in these meetings often do not rely on project data, instead
depending solely on the perceptions of team members. We propose new
Retrospective activities, based on mining the software repositories of
individual teams, to complement existing approaches with more objective,
data-informed process views.Comment: In IEEE/ACM 42nd International Conference on Software Engineering
Workshops (ICSEW'20
Being in front is goodâbut where is in front? Preferences for spatial referencing affect evaluation
Speakers of English frequently associate location in space with valence, as in moving up and down the âsocial ladder.â If such an association also holds for the sagittal axis, an object âin front ofâ another object would be evaluated more positively than the one âbehind.â Yet how people conceptualize relative locations depends on which frame of reference (FoR) they adoptâand hence on crossâlinguistically diverging preferences. What is conceptualized as âin frontâ in one variant of the relative FoR (e.g., translation) is âbehindâ under another variant (reflection), and vice versa. Do such diverging conceptualizations of an object's location also lead to diverging evaluations? In two studies employing an implicit association test, we demonstrate, first, that speakers of German, Chinese, and Japanese indeed evaluate the object âin front ofâ another object more positively than the one âbehind.â Second, and crucially, the reversal of which object is conceptualized as âin frontâ involves a corresponding reversal of valence, suggesting an impact of linguistically imparted FoR preferences on evaluative processes.publishedVersio
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Highly active and selective photochemical reduction of CO2 to CO using molecular-defined cyclopentadienone iron complexes
Herein, we report highly active (cyclopentadienone)ironâtricarbonyl complexes for CO2 photoreduction using visible light with an Ir complex as photosensitizer and TEOA as electron/proton donor. Turnover numbers (TON) of ca. 600 (1 h) with initial turnover frequencies (TOF) up to 22.2 minâ1 were observed. Operando FTIR measurements allowed for the proposal of a plausible mechanism for catalyst activation
The maximum modulus of a trigonometric trinomial
Let Lambda be a set of three integers and let C_Lambda be the space of
2pi-periodic functions with spectrum in Lambda endowed with the maximum modulus
norm. We isolate the maximum modulus points x of trigonometric trinomials T in
C_Lambda and prove that x is unique unless |T| has an axis of symmetry. This
permits to compute the exposed and the extreme points of the unit ball of
C_Lambda, to describe how the maximum modulus of T varies with respect to the
arguments of its Fourier coefficients and to compute the norm of unimodular
relative Fourier multipliers on C_Lambda. We obtain in particular the Sidon
constant of Lambda
<i>In vitro</i> Characterization of Phenylacetate Decarboxylase, a Novel Enzyme Catalyzing Toluene Biosynthesis in an Anaerobic Microbial Community
Anaerobic bacterial biosynthesis of toluene from phenylacetate was reported more than two decades ago, but the biochemistry underlying this novel metabolism has never been elucidated. Here we report results of in vitro characterization studies of a novel phenylacetate decarboxylase from an anaerobic, sewage-derived enrichment culture that quantitatively produces toluene from phenylacetate; complementary metagenomic and metaproteomic analyses are also presented. Among the noteworthy findings is that this enzyme is not the well-characterized clostridial p-hydroxyphenylacetate decarboxylase (CsdBC). However, the toluene synthase under study appears to be able to catalyze both phenylacetate and p-hydroxyphenylacetate decarboxylation. Observations suggesting that phenylacetate and p-hydroxyphenylacetate decarboxylation in complex cell-free extracts were catalyzed by the same enzyme include the following: (i) the specific activity for both substrates was comparable in cell-free extracts, (ii) the two activities displayed identical behavior during chromatographic separation of cell-free extracts, (iii) both activities were irreversibly inactivated upon exposure to O2, and (iv) both activities were similarly inhibited by an amide analog of p-hydroxyphenylacetate. Based upon these and other data, we hypothesize that the toluene synthase reaction involves a glycyl radical decarboxylase. This first-time study of the phenylacetate decarboxylase reaction constitutes an important step in understanding and ultimately harnessing it for making bio-based toluene
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