51,134 research outputs found
Mixed d-f Block Single-Molecule Toroics
No full textSingle Molecule Toroics pp 15–66Cite as
Mixed d-f Block Single-Molecule Toroics
Keith S. Murray, Stuart K. Langley, Kuduva R. Vignesh, Gopalan Rajaraman, Kieran Hymas & Alessandro Soncini
Chapter
First Online: 24 November 2022
3 Accesses
Abstract
In this chapter, we focus on the single-molecule toroidal (SMT) behaviour of a family of “double dysprosium triangle” heptanuclear species which contain a bridging d-block M(III) or a p-block M(III) ion. They are of general formula [MIIIDyIII 6(OH)8(o-tol)12(NO3)(MeOH)5]∙3MeOH, labelled MDy 6, where o-tol = o-toluate. The parent compound has M = Cr, with subsequent family members having M = Mn, Fe, Co and Al, the latter two having diamagnetic M(III) centres. This heptanuclear family could also be made using chloride as counter-anion rather than nitrate, the molecular structures being similar to the nitrates though the unit cells are different. The LnIII ion could also be varied to include Tb, Ho and Er and, thus, allow exploration of SMT behaviour in non-Dy analogues. The syntheses, structures and magnetic and EPR properties are described, starting with the parent CrDy 6. Theoretical calculations are described in detail, with MOLCAS methods employed to determine anisotropy directions, blocking barriers and relaxation effects and a newly developed model used to calculate magnetically coupled toroidal states and the role of these states in spin dynamics. The direct simulation of the micro-Squid magnetic hysteresis loops of all family members is described as well as that of the original Dy 3 material. Toroido-structural correlations are presented with strategies developed to optimize the important ferrotoroidic coupling between Dy3 triangles in these heptanuclear toroidal species. Finally, we give a brief summary of SMT behaviour in ring-shaped 3d-4f toroidal species
The astrochemical observatory: Computational and theoretical focus on molecular chirality changing torsions around O – O and S – S bonds
No full textThe observation of hydrogen peroxide in the interstellar medium represents a remarkable discovery for the astrochemistry community. The prototypical role that this molecule, arguably the simplest chiral molecule, plays in the evolution of life in biospheres, is related to the chirality change transitions associated with the torsional motions around the O - O and the S - S bonds. In this paper, we present an overview on the state-of-art of possible experiments to demonstrate chiral effects discrimination and computational tools applied to peroxides and persulfides
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Observations of Bºs→ψ(2S)η and Bº(s)→ψ(2S)π+π- decays
No full textFirst observations of the B0s
→ψ(2S)η, B0 →ψ(2S)π
+
π
− and B0s
→ψ(2S)π
+
π
− decays are made
using a dataset corresponding to an integrated luminosity of 1.0 fb−1 collected by the LHCb experiment in
proton–proton collisions at a centre-of-mass energy of
√
s = 7 TeV. The ratios of the branching fractions
of each of the ψ(2S) modes with respect to the corresponding J/ψ decays are
B(B0s
→ψ(2S)η)
÷
B(B0s
→J/ψη)
= 0.83± 0.14 (stat)±0.12 (syst) ±0.02 (B),
;
B(B0→ψ(2S)π
+
π
−
)
÷
B(B0→J/ψπ
+
π
−
)
= 0.56± 0.07 (stat)±0.05 (syst)± 0.01 (B),
;
B(B0s
→ψ(2S)π
+
π
−
)
÷
B(B0s
→J/ψπ
+
π
−
)
= 0.34± 0.04 (stat)±0.03 (syst)± 0.01 (B),
where the third uncertainty corresponds to the uncertainties of the dilepton branching fractions of the J/ψ
and ψ(2S) meson decays
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Pattern Line Object(s)
No full textHet afstudeerproject Pattern_Line_Object(s) beslaat het inrichten van een restgebied gelegen tussen het spoor en de snelweg (A20). Beide infrastructurele banen zijn op een talud gelegen. Het gat in het stedelijke weefsel wordt opgevuld met een weloverwogen compositorische samenstelling: Pattern Line Object(s). Deze compositie maakt gebruik van de banaliteit van het perifere landschap en versterkt deze op verscheidene momenten. De bereikbaarheid van het gebied wordt uitgebuit, op een wijze waarbij een omschrijving als park & ride of transferium een understatement zouden zijn. Het gebied doorgaat een transformatie van een onbereikbaar en verwaarloosd stuk stadsrand tot entree gebied voor Schiedam en Rotterdam. Dit wordt niet alleen op infrastructureel maar ook op visueel niveau bewerkstelligd.Architectur
Dibenzyl ferrocene-1,1′-dicarboxylate
No full textIn the title compound, [Fe(C13H11O2)2], there are markedly different orientations of the two phenylmethoxycarbonyl substituents [O—C—C—C torsion angles = 84.5 (3) and 139.6 (2)°]. These orientations are mediated by a number of intermolecular C—H...O interactions, which result in a one-dimensional hydrogen-bonded network of molecules
Measurement of the CP-violating phase \phi s in Bs->J/\psi\pi+\pi- decays
No full textMeasurement of the mixing-induced CP-violating phase phi_s in Bs decays is of prime importance in probing new physics. Here 7421 +/- 105 signal events from the dominantly CP-odd final state J/\psi pi+ pi- are selected in 1/fb of pp collision data collected at sqrt{s} = 7 TeV with the LHCb detector. A time-dependent fit to the data yields a value of phi_s=-0.019^{+0.173+0.004}_{-0.174-0.003} rad, consistent with the Standard Model expectation. No evidence of direct CP violation is found
Thermal boundary layer equation for turbulent Rayleigh-Benard convection
No full textWe report a new thermal boundary layer equation for turbulent Rayleigh-Benard convection for Prandtl number P>1that takes into account the effect of turbulent fluctuations. These fluctuations are neglected in existing equations, which are based on steady-state and laminar assumptions. Using this new equation, we derive analytically the mean temperature profiles in two limits: Pr~1 and Pr>>1. These two theoretical predictions are in excellent agreement with the results of our direct numerical simulations for Pr=4.38 and Pr=2547.9, respectively
Enzymatic S-Methylation of Thiols Catalyzed by Different O-Methyltransferases
No full textS-Adenosyl-l-methionine (SAM)-dependent methyltransferases (MTs) are highly chemoselective enzymes grouped in C-, N-, O-, S- and halide MTs, depending on the (hetero) atom that acts as the methyl group acceptor. So far, OMTs present the largest group, including many well investigated candidates. The catechol OMT from mammals such as from Rattus norvegicus (RnCOMT) is involved in the metabolism of neurotransmitters like dopamine. It is known to methylate the hydroxyl of the catechol ring in the 3 position. There are also reports showing that the regioselectivity of different COMTs can vary leading to different products with methyl groups in the 3 and or 4 positions. Nevertheless, there was only O-methylation reported for COMTs. Another related MT, the caffeate OMT involved in the lignin biosynthesis of plants has also been reported as a chemoselective enzyme. In nature, S-methylation is a rare phenomenon with different methyl donors being involved in the methyl transfer onto sulfur atoms. Several SAM-dependent MTs are identified as S-methyltransferases (SMTs), these are involved in salvaging pathways and xenobiotic metabolism of cells. Here, we report a new function of three OMTs; RnCOMT, a COMT from Myxococcus xanthus (MxSafC), and a CaOMT from Prunus persica (PpCaOMT) with acceptance towards different aromatic thiol substrates with up to full conversion.BT/Biocatalysi
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